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Stainless Steel for  High Performance Enclosures

Stainless steel is the ultimate materials solution for electrical enclosures in safeguarding the network and communications technology invested in underground mining sites.

Olympic Dam is a large polymetallic underground mine located in South Australia, approximately 550km northwest of Adelaide.

Home to a major source of oxide copper gold deposit, Olympic Dam produces combined quantities of copper, gold, uranium and silver through an underground mining system integrated with a metallurgical processing plant. The large deposit was discovered in 1975 and in 1988, the mine was opened by WMC Resources. Today, Olympic Dam is owned and operated by BHP, following its acquisition of WMC Resources in 2005. 

ASSDA Member and Accredited Fabricator B&R Enclosures was contracted by MPS Building & Electrical to assist with finding a solution to a fibre enclosure hub capable of linking four mining shafts to the surface.

B&R’s design and engineering team worked closely with MPS Building & Electrical to design and fabricate an enclosure specific to BHP’s requirements. The customised solution was supplied through Auslec Electrical and Data located in Wingfield.

The outcome was a double door stainless steel field cabinet, 1000mm deep and capable of housing electrical and monitoring equipment. Due to the remote location of the project and the type of equipment installed, stainless steel sunshades and lockable handles were included to reduce heat within the enclosure and prevent vandalism.

Grade 316 stainless steel with a No. 4 surface finish was specified for the custom-designed enclosures, with material supplied by ASSDA Member Outokumpu in 1.5mm thick sheet. 

Underground communication networks are a critical link between operations below ground and at the surface to ensure efficiencies in production and personnel safety. Protecting the equipment that delivers these communication networks is vital and stainless steel offers the durability and longevity required to deliver a robust structure to ensure preservation of the internal hardware.

In addition, grade 316 stainless steel offers excellent corrosion resistance, particularly to pitting corrosion which can occur in inland Australia due to high salinity in the ground water. 

B&R have worked alongside BHP and MPS Building & Electrical on past projects, installing enclosure solutions into a variety of different applications. B&R’s ability to design custom solutions along with their reliable service meant MPS Building & Electrical could confidently deliver this project and supply an enclosure suitable for harsh mining environments and extreme weather conditions.

As a result of good collaboration and local technical expertise, the project’s stainless steel enclosure design is now a standard specification for future installations across Olympic Dam.

This article featured in Australian Stainless magazine - Issue 64, Summer 2018/19.

Stainless Shines in Darling Harbour

Mirror finished stainless steel sign blades can be found scattered along the central boulevard of Sydney’s revitalised Darling Harbour.

Through a recent $3.4 billion transformation, Darling Harbour has become Australia’s largest entertainment and events precinct boasting world class facilities, including over 40,000 square metres of exhibition space. This urban rejuvenation builds on the success of Darling Harbour and in turn, will generate $200 million annually in economic benefit for the NSW economy.

The Harbour is ringed by attractions, entertainment and extraordinary waterfront restaurants. The Boulevard creates an active north-south pedestrian connection between Central Station and Cockle Bay. Its prime location is within walking distance of most points in the Sydney CBD therefore wayfinding signage is pivotal in navigating people through and around the precinct.

ASSDA Member and Accredited Fabricator Stoddart were engaged by Lend Lease to manufacture and install 19 stainless steel wayfinding sign blades for Darling Harbour’s ‘once in a generation’ re-development. The sign blades are featured in groups of two and three, each standing seven metres tall and two metres wide.

258 panels of grade 316 stainless steel were used for the sign blades in order to provide housing for LED display screens throughout the precinct. The structural stainless steel frame also mounts speakers and power outlets. All stainless steel used in this project was supplied by ASSDA Member, Fagersta Steels

Featuring a mirror profile finish, the stainless steel signs create a stunning visual effect through the reflection of the countless city lights and surrounds of the bustling tourist and entertainment mecca.

Stainless steel was specified by landscape architects, Hassell, for its aesthetic appeal and high-quality attributes. The Harbour’s salt water environment and location was also a consideration in the materials specification, being adjacent to the city centre.

It is only fitting for quality material such as stainless steel to be showcased in one of the world’s most desirable entertainment and event destinations.

This article featured in Australian Stainless magazine - Issue 64, Summer 2018/19.

Pickling and Passivation of Stainless Steel

One of the most common misunderstandings in specifications for stainless steel fabrication relates to the post-fabrication treatments to restore or enhance the corrosion resistance. 

The surface treatment processes invoked vary between pickle and passivate, passivate, or sometimes simply pickle. Needless to say, whilst pickling and passivation are two distinct processes, a lack of clarity can cause some confusion between the owner and the builder/fabricator about what is expected and required. 

This article briefly outlines the factors that affect the corrosion resistance of stainless steels, what surface treatments can be used and how they affect the steel’s surface to improve corrosion resistance.

Corrosion Resistance and its Controls

Stainless steel is resistant to aggressive environments because of a very thin, self-repairing, chromium-rich complex, oxide film present on the surface of the steel. It is not completely impervious, but it dissolves many orders of magnitude more slowly than it reforms. The passive layer is more resistant for alloys with more chromium, molybdenum and nitrogen. This is the reason for the empirical, composition based Pitting Resistant Equivalent (PRE(N)) index which is often used as a ranking tool in selecting which stainless steel will be used in new applications. However, the alloy composition is not the only control of the passive film’s strength, and hence its corrosion resistance. There must also be an adequate supply of oxygen and moisture to maintain the integrity of the passive film. This requires either good design or a maintenance program – and preferably both.  

For a specific alloy, i.e. a specific PRE(N), the passive film (and hence the corrosion resistance) can be improved by chemically oxidising the steel’s surface. Air and water are good and the ASTM standard dealing with passivation (A967 Standard Practice for Chemical Passivation Treatments for Stainless Steel Parts) advises that for many environments, no further treatment is required for satisfactory service. However, oxidising or chelating chemical treatments will provide better corrosion resistance.

Roughness

Corrosion resistance is indirectly improved if the surface is smooth and clean (free of contaminants) to facilitate the self-renewal of the passive film. For abraded surfaces there is also a critical surface roughness of 0.5μm Ra that should not be exceeded. This is recognised in surface finish 2K in EN 10088.2. It seems that for steels, the size of abrasives causing this roughness is too large to cut the surface cleanly and leaves rough edges and metal debris which can accumulate dirt and corrosives – hence more rapid corrosion with coarser polishing.

Contamination

The bête noir of stainless steel: carbon steel contamination. If it is not removed, the stainless steel will rust. In marine environments, it will collect chlorides and cause large rust stains and small pits in the stainless steel. If it is mechanically removed, it is likely that the smeared steel will leave a larger rust stain, although it may be less intense. Acid treatments can remove carbon steel deposits and have the added advantage that they can also remove surface breaking manganese sulphide (MnS) inclusions. These MnS inclusions do not have a passive film and act as initiating points for corrosion.

Welding

If you have welded your fabrication and there are rainbow coloured bands along the welds, they are zones where the passive film has been destroyed. Under the darker colours, there will be a wedge-shaped layer with a lower chromium content than the bulk stainless steel. Corrosion will initiate in these coloured bands. The weld tint colours can be mechanically removed provided the grinding is not too rough. Chemical removal by pickling is often a better option.

Pickling

Pickling uses a mixture of nitric and hydrofluoric (HF) acids. The wide range of concentrations and exposure times are described in ASTM A380 Standard Practice for Cleaning, Descaling and Passivation of Stainless Steel Parts, Equipment and Systems. Typically the nitric concentration is up to 10 times the HF concentration, but pickling is slow unless the HF is more than about 3%. Longer pickling times are required at lower temperatures or if a high alloy is being used, i.e. super duplex takes longer than duplex which requires longer than 304. If a paste is used, the contact area acid gets exhausted unless it is stirred, e.g. with the application brush. Thorough washing is needed to remove all residue even from crevices and, to avoid stains, it is important not to allow acid or rinse water to dry on the surfaces.  

OHS and environmental considerations mean that using a pickling contractor is easier, safer and ensures the appropriate disposal of acid and pickled heavy metals. Contractors will often use a temperature-controlled, stirred tank or, sometimes, a spray pickling solution in an acid-proof and bunded bay. Unless an additional level of passivation is required for a very aggressive environment, the outcome is a pickled item that is passive.

Chemical Passivation

The traditional and very effective acid is nitric, typically between 15% and 25% for about two hours, although it is not uncommon to drop machined parts into a bucket of nitric acid for half a shift. The passive film is significantly strengthened and the ratio of chromium to iron in the surface layers can exceed 1 – compared to <0.4 in the bulk. Nitric acid will also remove rust stains and sulphide inclusions plus, more slowly, carbon steel smears. Phosphoric acid will remove rust and sulphide inclusions, but it is not oxidising and will not strengthen the passive film. Another method of strengthening the passive film of a chemically-clean surface is to use a hydrogen peroxide solution – lots of free oxygen and only water residue.

There are other acids that will strengthen the passive film and dissolve carbon steel and inclusions, but by a different method. Citric and oxalic acids and EDTA all have a carboxylic acid [O-C-OH] atomic structure, and once the acid dissolves the unwanted metal, the positive ion is trapped by the negative oxygen atoms in a process called chelating or sequestering. This process is used in wastewater treatment to remove metals. In passivation, it is important to rinse thoroughly. Chelating treatments are widely used in the food industry as formulations which include biocides, so the citric acid does not contribute as a food source.

There are a number of special cases detailed in ASTM A380 which require care when pickling:

• Sensitised or hardened (nitrided or carburised) areas may suffer intergranular attack.

• Free machining stainless steels requires an inhibitor or it will pit.

• Martensitic stainless steels can suffer hydrogen embrittlement.

All of the above methods are chemical treatments which are quite traditional and generally well applied. Further information is provided in ASTM A380, which also details test and inspection methods to confirm surface cleanliness.

Three Definitions

CLEANING Removal of contaminants such as soil, grease, oil, etc. using low-chloride detergents and/or solvents to allow free access for water and oxygen to grow the passive film.

The bulk material is not affected and the surface looks brighter. Chlorinated solvents may be a risk as residues can degrade if heated and may cause pitting. In vessels or pipework, it is important to drain and dry the surfaces.

PICKLING The removal of any high temperature scale and any adjacent low chromium layer of metal from the surface of stainless steel by chemical means.

It also removes embedded or smeared carbon steel, inclusions and loose flakes of stainless steel left from abrasives.

It will leave a matt finish, which may be paler if the pickling is extended. It provides a passive surface immediately on rinsing – hence you pickle and get a passive surface.

PASSIVATION The treatment of the surface of stainless steel, often with acid solutions (or gels), to remove contaminants and promote the formation of the passive film on a surface that was freshly created, e.g. through grinding, machining or mechanical damage. It will remove acid soluble inclusions such as MnS.

Clean humid air will form a passive film on clean stainless steel and the appearance will not change.

Chemical passivation strengthens the passive film and typically takes an hour or so at ambient temperatures. Air passivation is adequate unless the environment is very aggressive for the grade.

1. Rusting steel contamination from shearing stainless sheet. Photo courtesy of Graham Sussex.

2. Rainbow oxide from poor gas shielding during welding. Photo courtesy of HERA.
3.Before (left) and after (right) pickling of welded fitting. Photo courtesy of Graham Sussex. 4. Welded components after pickling to remove heat tint and possible steel contamination. Photo courtesy of Australian Pickling & Passivation Service.

This article featured in Australian Stainless magazine - Issue 64, Summer 2018/19.


Stainless Opulence

Exemplary stainless steel craftmanship has delivered a sophisticated and lavish cocktail lounge in the heart of the Gold Coast’s entertainment hub.

Cocktail connoisseurs have been flocking to Cherry, The Star Gold Coast to experience the designer drinks on offer in the grandeur of the lounge featuring a 22m long bar. Refurbished in 2017 as part of the first stage of the property’s major transformation, its upmarket look and feel was inspired by its sister venue at The Star Sydney.

Central to Cherry’s luxury design is the intricate, gold metalwork featured in the VIP booth screens, lounge surrounds and balustrades. ASSDA Member and Accredited Fabricator Minnis & Samson fabricated these elements using grade 316 stainless steel tube and flat bar supplied by ASSDA Member Australian Stainless Distributors

The stainless steel was mirror polished prior to the electrostatic application of a special coating to achieve the gold colour finish. Crystal hardware and lush red velvet furnishings complement the gold stainless steel to deliver the opulent design and vision of the cocktail lounge.

Stainless steel is a high quality and high strength material, and was specified for its longevity, hygienic properties and aesthetic appeal. In addition, stainless steel offered better weldability to achieve the detail in the metalwork’s curvature design.

This article featured in Australian Stainless magazine - Issue 63, Spring 2018

The Emerging Dragon

A stainless steel masterpiece

Michael Van Dam’s award-winning stainless steel dragon sculpture plays a major part in Chinese culture dating several thousand years. 

The dragon is a symbol of prosperity, strength, courage and resolve. The designer himself was born in the year of the Dragon (1964). As a result of welding thousands of stainless steel links together, alongside Van Dam’s creativity, a durable and aesthetically pleasing piece of art came to life – The ‘Emerging Dragon’. 

The Emerging Dragon has been showcased at various locations and shows on the Gold Coast. This stainless steel masterpiece was originally created for the 2015 Swell Sculpture Festival held on Currumbin Beach which attracted 250,000 visitors over ten days, winning both Kid’s and People’s Choice Awards. 

The 3m high by 5m long sculpture was created from more than 4000m of 4mm 316 stainless steel chain and weighs an impressive 700kg. Following fabrication the sculpture was electropolished. All stainless steel chain used for Michael’s sculptures is supplied by ASSDA Member BRIDCO

Van Dam’s stainless steel art pieces are well equipped to face the rigours of outdoor display. This led to grade 316 stainless steel chain being his choice of material for all his sculptures. He believes the use of stainless steel for his pieces makes for a unique use of the material, it feels great to the touch, can withstand various environments and will outlast most other materials. 

This article featured in Australian Stainless magazine - Issue 63, Spring 2018

Stainless Steel: Sustainability and Life Cycle Costing

Humanity’s use of materials has progressed over the millennia from natural resources such as plants and stone to manufactured materials such as ceramics, metals and plastics with a corresponding increase in consumption of energy and materials – and increasing waste production. In parallel, the world’s consumers have grown exponentially from about 1 billion in 1800, to 7.6 billion in 2018 and a predicted 9.8 billion in 2050 – all demanding more infrastructure, facilities and resources to support the expectations of higher standards of living. This has led to an increasing realisation that green production, recycling, waste reduction and more efficient use of resources are essential.  

The green or sustainable credentials of stainless steels largely derive from their corrosion resistance and consequent long life, without the need for more than cleaning by rain washing or routine water and detergent cleaning. A good example is the Chrysler Building in New York which was built in 1930. It has only been washed twice in 1961 and 1995 using low impact detergents and yet it still retains its bright appearance partly because of good drainable design, although the inherently smooth surface from its manufacture was also a factor.

In comparison, the Eiffel Tower in Paris is painted every seven years using 60 tonnes of paint in a 15-month campaign with 25 painters and their consumable equipment. Closer to home, the constant repainting of the Sydney Harbour Bridge provides a similar contrast to the penetration of stainless steel into the building and construction industry without the ongoing labour required for repainting and maintenance of carbon steel structures. At a smaller scale, current practice minimises maintenance in more aggressive environments by processing the surface after fabrication as shown by the bright surface of the electropolished railings beside the Brisbane River.

It is difficult to compare any corrosion (and therefore lifetime) of stainless steel with carbon steel or zinc because of the different mode of attack, i.e. stainless steel pitting vs. the general loss of copper or zinc. However, a South African 20-year atmospheric corrosion study of lifetimes used carbon steel as a baseline of 1 and found that zinc, copper, aluminium and 316 stainless steel had lifetimes of 25, 90, 170 and >5000 years respectively. 

A secondary benefit of the long life of stainless steel is that the carbon dioxide emissions and the embodied energy required in manufacture are amortised over a much longer period of time. Raw CO2/kg metal and MegaJoule/kg metal data is given in Table 1 for these materials. Stainless steel is not the lowest or highest in absolute terms of carbon dioxide emissions or energy required per kilogram of stainless steel produced, but when its long life is considered, its performance on these criteria is outstanding.

Stainless steel does not use volatile organic solvents in its production or use and does not contain lead, mercury or other leachable heavy metals. Stainless steel is routinely used in pharmaceutical, food and beverage processing because of this chemical stability due to the hydrated chromium-oxide passive layer.

In a confirmation study of the stability of stainless steel with water, a 3.5-year testing program of the hot and cold water in 316 pipework of a Scottish hospital found the chromium content was less than 1% of the 0.5ppb permitted for potable water and nickel content (a trace food requirement) was less than 3% of the 0.2ppb permitted.Looking at environmental issues, Table 2 shows the results of a Scandinavian run-off study, commissioned because of concerns about heavy metals in environmentally sensitive areas. The zinc and copper values will obviously vary with time as the oxide layers form and leach. However, the passive film of stainless steel is substantially stable so that run-off can be used for potable water. A first flush discard system may also be used.


REUSE AND RECYCLING

In a well designed and executed project, stainless steel will not degrade and therefore it is probable that the process or application will become outdated while the stainless steel is still operational as a pipe or vessel or tank or other component. Such repurposing may be on the same site or elsewhere in the same industry, e.g. from milk to wine or water or fruit juices or for a radically different process. However, it is rare for repurposing to move from chemical to hygienic industries. Since stainless steel has an inherently high value, there are multiple examples of building refurbishment where the stainless steel has suffered mechanical damage or the layout must be changed. The William Penn Place (Pittsburgh) rejuvenation shown was after 50 years of use but did not require material replacement.

Recycling may occur as part of the life cycle, e.g. re-melting of scrap, or at end-of-life. Table 3 indicates significant variations depending on the material and its proposed use.  A study of the recycling at 14 European mills covered 18 products across two ferritic, two austenitic and one duplex grade, i.e. all but the small volume of specialised, niche grades of stainless steel. For each of the 18 products, the mean recycled stainless steel content was significantly greater than 65%. The six ferritic products were all above 90%, the nine austenitic products were between 68% and 78% while the three duplex product forms had between 69% and 76% recycled steel input.

While some mills show significantly higher percentages, a nominal 30-year life of stainless steel combined with the almost 6% compound growth of stainless steel use means there is insufficient scrap available now to substantially increase the recycled content from general use.

LIFE CYCLE COSTING AND SAVINGS FROM DURABILITY 

The minimal maintenance required on stainless steel buildings and structures is a significant direct cost saving, and increased availability of equipment is also important. For example, in a waste water processing plant, a decision to replace the wetted parts of a galvanised distributor with 316 and the notionally dry parts with 304, reduced maintenance costs by 92% and increased availability from 76% to 98%.

A civil engineering example is the Progresso Pier as shown below where the original pier with carbon steel reinforcement is in ruins after 32 years exporsure. A Nickel Institute funded comparison between the 1940s construction using 304 reinforcement (right pier) and a theoretical pier constructed with carbon steel showed that the carbon steel would have contributed to a 44% greater overall life cost until 2020. It also showed that using stainless steel reinforcement had between 20% and 80% less environmental impact. This low figure was due to the predominance of the mass of concrete compared to the 240 tonne of stainless steel.

GREEN AND SUSTAINABLE

Green projects minimise energy use and one option is to reduce solar loading by installing perforated sunscreens or fixed slats in locations where insolation is high and ambient temperatures are not extreme. Design of perforated sunscreens is a sophisticated but well understood process with standard programs available. There are multiple examples that use stainless steel because it does not require more than rain or simple water washing to retain a bright appearance.  

Finally, increasingly the “green” label means growing plants or other flora along stainless steel wires or supports either in public places as a visual softening or as a deciduous sun screen where stainless steel is required because of the lack of maintenance access to the supports once the vegetation is mature.

In summary, the durability of stainless steel provides substantial reductions in maintenance costs, supports a considerable recycling and reuse process, and provides control mechanisms for energy use.

This article featured in Australian Stainless magazine - Issue 63, Spring 2018

Stainless Steel for 100 Year+ Design Life

Stainless steel has delivered the confidence it will provide the structural performance and meet the 100-year life-cycle of a new marina development on the New South Wales’ South Coast.

The Waterfront, Shell Cove, is a joint residential and mixed-use development between Shellharbour City Council and Frasers Property Australia located 22km south of Wollongong.

Central to the development is its waterfront location and world-class marina that will offer pontoon berthing for approximately 270 vessels, direct access to the Pacific Ocean, charter boat operations, a public boat ramp and a variety of marina facilities and services.

Stainless steel reinforcement has played a significant role in the structural design and construction of the marina, with over 318 tonnes of grade 2304 lean duplex stainless steel reinforcement bar (rebar) supplied by ASSDA Member Valbruna Australia. Ranging in diameters from 8mm to 25mm, stainless steel rebar was used in all pre-cast elements to form the marina sea walls, marina steps and boat ramps and installed by Coastwide Civil.

The original project specification was for alternative materials and products with cathodic protection and sacrificial anodes that struggled to exceed a 50-year life-cycle guarantee. This specification was superseded by a requirement for a 100-year life span, and the use of stainless steel provided the best solution, as well substantial cost savings around constructability and man hours per tonne required.

Stainless steel rebar offers structural longevity in many environments with exceptional corrosion resistance in harsh marine developments. Its specification in this landmark waterfront development meets the expected minimum 100-year life and was also critical to minimising ongoing maintenance costs. This was an important consideration to avoid future maintenance closures due to corrosion issues and to ensure continued public accessibility to the waterfront promenade for all residents and tourists.

In addition, the use of stainless steel rebar significantly reduced the amount of concrete cover required, also minimising costs and resulting in a more lightweight and higher tensile strength structure.

Valbruna Australia’s commitment to stock large volumes of stainless steel rebar on the floor in Australia meant no delays were experienced during the project’s supply term, including meeting the 20% increase in supply quantity during installation. Coordinated supply was critical to the on-time completion of the project, which was further impacted by narrow site delivery windows and limited set down holding areas.

The scheduling, cutting and bending of the stainless steel rebar to tight precast tolerances was completed by Mesh & Bar, and performed at a dedicated stainless steel facility to prevent contamination risks.

All stainless steel welds were completed in a controlled environment, and pickled and passivated by Waeger Constructions.

Construction of the residential and mixed-use infrastructure will continue into next year, with the marina due to take water by the end of 2019. Once completed, Shell Cove will also boast a vibrant town centre and retail precinct, community centre and library, foreshore dining and waterfront tavern, and boutique accommodation.

This article featured in Australian Stainless magazine - Issue 63, Spring 2018.
 

Grand Reflections

Innovative Melbournian architecture has delivered a striking stainless steel feature in the city’s latest commercial mixed-use development.

Melbourne is setting the benchmark for world-class design with Collins Square now one of Australia’s largest CBD commercial precincts, covering an entire city block on Collins Street. Already home to a number of leading global corporations and the revitalised heritage-listed Southern Goods Shed, the $2.5 billion project will at completion comprise of five commercial towers and over 10,000sqm of retail space.

Black mirror finish stainless steel columns are the focal point in the lobbies and food precincts of Towers Two and Four of Collins Square. Soaring an impressive 10m to 12m tall at a diameter of 1300mm, the stainless steel-clad columns are complemented by floor-to-ceiling window glass and natural stone masonry walls and floors.

ASSDA Member Fabmetal Specialists supplied, fabricated and installed the grade 304 stainless steel circular columns, using its own patented column cladding system. Twenty stainless steel clad columns were installed across the two towers.

Fabmetal Specialists’ pre-fabricated the customised stainless steel column panels from 1.2mm sheet, and using a modular cladding method, installed the panels with a unique fixing system allowing no visible fixings or caulked joints.

Coloured stainless steel in a No. 8 mirror finish from the company’s TiVox range was used for the project and specified for its upmarket appeal and elegant aesthetics. In addition, stainless steel also offers durability and ease-of-use during construction.

Providing a true mirror reflection, the black chromatic colour (known as ‘Jet Mirror’ in the TiVox range) was achieved with a titanium film using a Physical Vapour Deposition (PVD) coating process. The coating technology offers a number of high chemical and technical features, including resistance to abrasion, scratches and corrosion, and overall minimal maintenance.

The end result is an innovatory, high quality stainless steel finish, bringing life to the surrounding activity of Melbourne’s place-to-be for business and leisure.

This article featured in Australian Stainless magazine - Issue 62 Winter 2018.

 

Stainless and Sand Go Hand-In-Hand

With the use of stainless steel, indigenous artist Kylie Graham’s interest in Whadjuk Noongar customs and culture has helped bring a symbolic sculpture to life at Perth’s recently revitalised Scarborough beach. 

The people of Whadjuk Noongar are the traditional owners of Perth. The Ethereal Welcome Hand sculpture represents a hand casting sand which acknowledges the custodians, the people of Whadjuk and their enduring spiritual connection to the land and sea. 

In respect to Noongar cultural customs, visitors are to throw a handful of sand into the water as an introduction of themselves to the spirits and ancestors. It was only fitting for the 3D sculpture to cast its presence near water and is primarily constructed from grade 316 stainless steel supplied by ASSDA Members Midway Metals and Stirlings Australia

The 6.5m tall sculpture uses 5mm stainless steel plate throughout the entire wire frame hand spanning 4m long. The finish is 2B and all the welds are TIG welded, cleaned and passivated. The four support columns are also fabricated from 316 stainless steel. 

Illustrated in the palm of the stainless steel hand, pouring down to the ground is gold anodised aluminium cladding, with perforations backlit with LED lights which can be programmed for multiple occasions.

At the back of the hand, the design of a dolphin and three fish is laser cut through the stainless steel, to reflect the importance of the relationship between Noongars and mammals.

Stainless steel was chosen as the main sculptural material for its durability, excellent corrosion resistance and aesthetically-pleasing properties. This stunning work-of-art was designed, fabricated and installed by local art consultant Forever Shining.

The Ethereal Welcome Hand is one of six pieces of artwork along the redeveloped foreshore and can be found between the surf club and swimming pool. It has been welcoming the public since March 2018 and will continue to do so for many years to come thanks to the durable life span of stainless steel.

This article featured in Australian Stainless magazine - Issue 62 Winter 2018.

Ferritic Stainless Steels

Ferritics account for approximately 25% of stainless steel use worldwide. The name arises because these alloys have similar properties to carbon steels when they are bent or cut and, unlike the well-known 304 and 316 austenitic grades, ferritics are strongly attracted to a magnet.

There is a major misconception that ferritic stainless steels are less corrosion resistant than austenitic alloys. On the contrary, for any required level of corrosion resistance (or Pitting Resistance Equivalent [PRE]), you can select a specific stainless steel from either the austenitic or ferritic family depending on the physical properties desired. Another similarity of these two families of stainless steel is that neither can be hardened by heat treatment. However, a significant difference is that, in common with carbon steels, ferritic stainless steels become brittle when used in sub-zero temperatures. The actual transition temperature depends on the specific alloy, but it increases for welded fabrications.

Often regarded as the simplest stainless steel alloy, ferritics are steels (iron and a small addition of carbon) with at least 11% chromium added to produce the passive chromium oxide film. This self-repairing chromium oxide layer gives stainless steel its corrosion resistance. The first stainless steels developed in 1913 were ferritics with a high carbon content. Today, those alloys are called martensitics and are used for high hardness blades or wear resistant surfaces. The alloys now known as ferritic stainless steels have been used commercially for many decades, primarily as sheet cladding up to about 3mm that do not require welding. The Fujitsu building in Brisbane for example is clad in profiled ferritic stainless steel sheet, and the use of perforated and solid ferritic stainless steel sheeting is featured in the ceiling and fascia paneling in Sydney’s Wynyard Walk.

Apart from the 12% chromium utility alloys, the sheet thickness limits for the supply and welding of ferritics are due to its metallurgical structure. Unlike austenitic stainless steels, the microstructure does not transform during welding, and so the initially microscopic ferrite grains can grow and embrittle the metal.

Ferritics have gained wider acceptance since changes in its alloy design and production methods allowed welding. The adoption of the Argon Oxygen Decarburisation (AOD) refining process in the 1970s also assisted, allowing both the reduction of impurity levels and, critical for welding, good control of both carbon and nitrogen content.

Table 1: Selected Ferritic Alloys

Common name

UNS

C%

Cr%

Mo%

Others

PRED

Main uses

409

S40900

0.03

11

-

0.3Ti

11

Car exhausts

4003, 3/5Cr12A

S40977

0.02

11

-

0.5Ni

11

Rail wagons, non-cosmetic structures

430B

S43000

0.03

17

-

-

17

Cladding – not marine

444

S44400

0.02

18

2

0.4(Ti+Nb)

25

Instant hot water units

446

S44600

0.15

24

-

-

24C

High temperature

447

S44700

0.01

29

3.8

0.1Cu,0.1Ni

42

Seawater tubing

Notes:
A. Balance of composition important to avoid welding corrosion issues
B. Also derivative grades with low carbon and Ti/Nb to allow welding
C. Not good indicator of corrosion resistance especially if welded because of high carbon
D. For comparison, the PRE of 304 is ~18.5 and 316  ~23.5.

Available Ferritic Alloys and Applications
The Ferritic Solution (TFS), published by the International Stainless Steel Forum, lists 71 ferritic alloys in ASTM, EN and JSA standards, although most are in sheet form. For example, A240 lists 26 alloys as flat product while ASTM A276 only has nine alloys listed as bar or shape. TFS classifies ferritic alloys into five groups based on chromium content:

- Chromium (10.5% to 14%)
- Chromium 14% to 18%)
- Titanium and/or niobium added to avoid sensitisation with welding
- Molybdenum additions for corrosion resistance
- Weldable group of alloys with higher corrosion resistance and chromium >18%, added molybdenum and low impurity content.  

Table 1 lists common names, UNS numbers, typical compositions and applications of representative alloys. There are also families of alloys derived from the same root UNS numbers. In addition, a growing number of proprietary ferritic alloys have been and are being developed especially in Japan. The PRE column is a measure of corrosion resistance based on composition, i.e. PRE = %Cr + 3.3% Mo. The 16%N term used for austenitic and duplex grades is omitted because nitrogen is virtually insoluble in ferritic alloys. 

Corrosion and Heat Resistance
These are not the same. Oxidation (or scaling) resistance of stainless steels in air depends on the stability of the oxide layer (or scale) on the surface. This is not the thin (nanometres) passive film formed in water but the thicker, high temperature oxide formed above about 250oC. Its protective properties depend on its bond to the metal surface below. In turn, this depends on the relative expansion of the oxide and the metal surface. 

As shown in Table 3, ferritic alloys have low thermal expansion compared to austenitics, which means the adhesion of their protective scale is better in thermal cycling conditions. In practical terms, this means that ferritic alloys have higher scaling temperature limits for intermittent service than in continuous service, whereas the reverse is true for austenitic alloys.

At temperatures in the high hundreds (oC), the relatively low strength of most ferritic alloys limits their use, although the niobium-treated ferritics have similar strength to the austentic alloys. Ferritic (and duplex) grades should not be used in the band around 475oC as metallurgical phase transformations cause embrittlement during extended exposures.

In oxygen-rich environments, the simple wet corrosion resistance of ferritic, austenitic and duplex alloys is well-described by the PRE index as given in Table 1. The predictions are for a passive surface and will be unreliable if the surface has been contaminated by carbon steel or if welding heat tint has not been removed.

PRE does not influence the spidery cracking that occurs in austenitic alloys that are stressed and exposed to warm or hot chloride solutions. Ferritic and duplex grades are effectively immune to this stress corrosion cracking attack and it is the reason why instant hot water tanks used in kitchens are ferritic alloys, usually 444.

Left: Fujitsu Building in Brisbane is clad in profiled ferritic stainless steel sheet. Right: Ferritic stainless steel sheeting featured in the ceiling and fascia paneling in Sydney's Wynyard Walk.

Mechanical and Fabrication Properties
Because of their microstructure, ferritic stainless steels behave very similarly to carbon steels in bending, roll forming, spinning and shaping. Fabricators can use the same techniques for ferritics when forming roofs or couplings.

Ferritics do not cold-work like austenitics and so, for the same thickness, they have less springback. Although deep drawing is easier for ferritics than austenitics, the higher chromium ferritics can suffer from ridging, so there are not many deep drawing applications. Stretch forming can only be to about 50% of that achieved with austenitics, as might be expected from the difference in ductility. Table 2 compares the mechanical properties of several ferritics with 304 and carbon steel. In broad outline, ferritic stainless steels have a higher yield (or strictly 0.2% proof stress) than austenitic stainless steels, lower tensile strength and about half the elongation at fracture. The modulus of elasticity is similar to carbon steels, so deflections under loading will be comparable.

Table 2: Typical room temperature mechanical properties

Common name

Yield MPa

Tensile

MPa

Elongation at break %

Modulus

GPa

409

170

380

20

220

4003, 3/5Cr12

L:320

T:360

480

18

220

430

205

450

22

220

444

275

415

20

220

304

270

650

57

200

Carbon steel

300

430

25

215

Welding

With the exception of the 12% chromium utility grades, welding of ferritics requires more skill than welding austenitics because of their sensitivity to impurities, which may cause cracking in the heat-affected zone. Very thorough attention to cleanliness is required as well as the use of high purity shielding gas and care in gas shielding – particularly outside the workshop where drafts can be a problem. Because of the risk of grain growth (and consequent low toughness) with extended periods at high temperatures, low heat input is required and pulsed welding equipment is a useful tool. This metallurgical sensitivity is the reason why ferritics are rarely available in thicknesses greater than 3mm. However, the low thermal expansion and better thermal conductivity of ferritics compared to austenitics means that welding distortion is less critical for all ferritics (refer to Table 3).

Like all stainless steels, the corrosion resistance of welded ferritics is restored if all heat tint is removed after welding, preferably by pickling. Mechanical abrasion is a good second best provided the surface roughness is not excessive.

The 12% chromium utility ferritics are widely used in welded thick structural sections in coal wagons, heavy vehicle chassis, high temperature exhaust ducting, fire proof fencing, low corrosion wear locations and multiple structures where aesthetics are not the primary consideration, i.e. where a brown adherent cosmetic haze is not considered a problem. The 12% utility ferritics are discussed in more detail in Australian Stainless #52 (available at www.assda.asn.au).

SUMMARY

Some ferritic grades have been in large scale commercial production for many years, but the variety of grades now available has only been possible because of new melting and refining technologies. A large number of grades now exist, and a great deal of active research and alloy development is continuing.

Ferritic stainless steels offer:
- Formability similar to carbon steels and can be readily bent, roll formed, pressed to shape or spun
- Higher yield strength and lower ductility than austenitics
- Comparable range of corrosion resistances to other stainless steel families
- A wide range of possible applications.

Table 3: Physical properties of Ferritic and Austenitic stainless steels

Property

Ferritic

Austenitic

Density (kg/m3)

7700

7900

Thermal expansion

(0-100oC μm/m/oC)

10.5

16.0

Thermal conductivity

(20oC, W/m.oC

25

15

Specific heat

(0-100oC, J/kg.oC

430-460

500

Electrical resisivity

(nΩ.m)

600

750-850

 

This article featured in Australian Stainless magazine - Issue 62 Winter 2018.

Stainless Delivers Success

World-class infrastructure demands high quality products and long-term asset performance, both of which have been delivered through superior workmanship and the use of stainless steel.

Fuchs Lubricants Australasia opened its new $33 million purpose-built plant at Beresfield, New South Wales in February 2018. Operating in Australia since 1979, Fuchs’ expanded and relocated from its original factory in Newcastle due to strong business growth, now being the only major lubricants company to still manufacture products in the country.

Fuchs’ new plant is a blending operation, features two highly-developed laboratories and is three times larger than the old factory, producing 10,000 lubricant products for applications in industries ranging from mining and automotive to transport and food.

Stainless steel has been integral to the plant expansion project design and construction, being the material of choice in demanding environments that involve high heat and aggressive substances. Offering structural integrity and excellent corrosion resistance in high temperature applications, stainless steel is vital in the construction of tanks, pressure vessels, valves and pipework. 

The Myriad Connections

ASSDA Member and Accredited Fabricator TFG managed the 12-month stainless steel installation project. This included 9km of 304L grade AS1528 tube ranging from 25mm to 101mm in diameter, 1km of pipe, 33 tanks, and the specialised fabrication of a blending platform and pipe racks for a purpose-designed traffic flow system to move and process raw through to final product oils and lubricants around the 25,000m2 plant. The stainless steel materials were supplied by ASSDA Members Prochem Pipeline Products and Stirlings Australia.

After receiving the process design and piping and instrumentation diagrams from Fuchs, TFG’s Foodline Projects division mechanically designed and installed the pipe routes and pipe racks, increasing production capacity from 30 million to 90 million litres per year. Foodline Projects was integral in the success of the project through designing and incorporating 3D models of the pipe routes and racks which improved performance and efficiencies. Foodline Projects also completed the piping and installation of a custom loading arm.

TFG’s Austline Fabrications division designed and completed 3D drawings of the 35-tonne blending platform and pipe racks, and included 40 per cent extra capacity for future expansion. The 40-metre-long and three-tier platform was pre-fabricated in their Perth workshop, then flat packed, transported, assembled and installed on site.

 

Processing and Vessels

ASSDA Member and Accredited Fabricator Furphy Engineering designed, fabricated and supplied 33 grade 304 stainless steel tanks ranging in size capacities of 16kL to 180kL, with material including processed plate supplied by ASSDA Member Vulcan Stainless.

The tank designs were produced by Furphy’s in-house engineering team, accommodating for both heat exchange and agitation requirements to ensure that Fuchs were confident in the ability of the tanks and vessels to perform the required manufacturing operations going forward, all of which were completed to AS1210.

The manufacture of the designs heavily utilised a range of innovative technologies in Furphy’s state-of-the-art workshop, including plasma welders, automated strake manufacturing and seam polishing systems, full undercover hydrotesting and QA/QC sign off, as well their own in-house laser welded cavity plate. While widely embraced in Europe, Furphy Engineering is currently the only manufacturer with laser welded cavity plate technology in Australia, a key part of the heat exchange design on this project.

The heat exchange loading on the pressure vessels was high given the materials and size of the equipment, and the laser welded cavity plate system enabled additional heat exchange surfaces to be included on the cones, increasing the active thermal exchange area and optimising the efficiency of the system to ensure effective operation.


The successful collaboration of TFG Group and Furphy Engineering resulted in the project being completed on time and within budget, each using their in-house stainless steel design and technical expertise to deliver a world-class facility supporting Fuchs’ continued expansion and investment in the Australian lubricants market.

  


This article featured in Australian Stainless magazine - Issue 62 Winter 2018.

Stainless Provides Strength and Style

Taking pride of place within Perth’s Optus Stadium Park is the Arbour featuring a stainless steel cable net canopy delivered by ASSDA Member Structural Dynamics.

The 60,000-capacity arena is the latest major development to hit Western Australia’s capital, boasting a world-class multi-purpose venue that combines innovative design with community infrastructure.

The impressive Arbour stands 10m tall and 20m wide, and stretches 450m around the south side of the Stadium. It connects a new six-platform railway station to the Swan River, over which the Matagarup Bridge is currently being constructed to provide pedestrian access to East Perth.

Over a thousand stainless steel cables were installed on the 43 arches that make up the Arbour to create a tensile structure in the form of a canopy. Suspended on the structure using bespoke fittings are 3,076 bronzed artwork panels reflecting Whadjuk and Noongar stories. 

Stadium Park was constructed on wetlands with cultural heritage significance to the Indigenous community, and its rich Aboriginal history was the inspiration behind the Arbour’s design.

More than 13 tonnes of grade 316 stainless steel was used, including in excess of 14km of 16mm and 8mm hammaTM X 1x19 wire rope supplied by ASSDA Member Arcus Wire Group, 20,000 bespoke fittings and over 34,000 screws.

Stainless steel was specified for the cable net canopy for its strength and durability to withstand the harsh Western Australian weather conditions, including powerful coastal winds driven from the Indian Ocean. The 16mm edge cables on the structure were tensioned to forces up to 52kN, with the 8mm longitudinal and transversal cables tensioned up to maximum of 11kN.

In addition, the high quality and aesthetical value of stainless steel complemented the Arbour’s design in creating an eye-catching structure for patrons.

Structural Dynamics provided value engineering and practical advice to the project engineer Maffeis Engineering and project architect Hassell on how to best integrate stainless steel tensile systems into the design.

Their in-house team of engineers used structural and finite element analysis as components of the detailed analysis and modelling on how the cable design would behave and interact within a tensile architecture installation.

Structural Dynamics also worked with engineering firm Partridge to undertake the final design, review, slip testing of the bespoke cable clamps and final sign off for the project. Each of the eight different types of cable edge clamps were sent to the National Association of Testing Authorities’ (NATA) accredited laboratory for slip testing under wet and dry conditions to ensure their strength and adequacy.

The cable fittings were designed to the AS 1170 series: Structural Design Action, AS 4100: Steel Structures and AS 2759: Steel Wire Rope – Use, Operation and Maintenance.

Structural Dynamics’ Project Manager Shaun Salmon explained the logistics of the assembly of the Arbour whilst maintaining safe and continued access to the Stadium for more than 1,000 workers. ‘It was important during the installation process that our team of skilled and qualified tradesmen and riggers followed the approved construction sequencing and quality management system processes whilst not impeding access to the Stadium from the primary entry point on the southern concourse. Both temporary and permanent bracing measures were used throughout construction along with sequential tightening and regular cable tension testing to achieve the design intent drape and sag of the cable net canopy and not applying adverse force to any single point on the structure.’

Structural Dynamics’ collaboration with the multiple stakeholders involved in the Arbour design and construction ensured the successful delivery of a custom-designed stainless steel cable net canopy providing the flexibility, tensile strength and structural performance required.  

Optus Stadium officially opened on 21 January 2018 and is the new home game venue of local Australian Football League teams Fremantle Football Club and the West Coast Eagles.

 

        

 

Arbour photos courtesy of Structural Dynamics. Photography by Abigail Harman.

Aerial photo of Optus Stadium Park courtesy of MakMax.

This article is featured in Australian Stainless Magazine #61.

Stainless Sustains Intricate Brick Facade

Stainless steel is playing a vital role in the structural integrity of a new state-of-the-art library at one of Brisbane’s most prestigious boys’ school.

The Centenary Library at Anglican Church Grammar School was designed by Brand + Slater Architects, and the ambitious project was part of the school’s master plan to provide a technology-rich, world-class centre for its 1800 students. Comprising four levels, the tertiary-inspired building features an extensive range of learning spaces including a 250-seat lecture theatre, teaching and meeting rooms and over 80 individual study areas.

The library stands 23.5m tall on a heritage-listed part of the school campus. Paying homage to the school’s history whilst appealing to a contemporary aesthetic, the library exterior features an intricate brick façade backed by a stainless steel support and restraint system custom-designed and manufactured by ASSDA Member and Accredited Fabricator, Ancon.

Grade 304 stainless steel was used and specified for its longevity, durability and performance properties to meet the building’s 50+ year design life.

Ancon’s specialist knowledge, manufacturing agility and project management service proved invaluable to the contractor when building the detailed façade of the decorative arches and corbelled brickwork with all structural steelwork now unseen.

Shelf Angle Brick Support

Ancon masonry support systems enabled the large-scale brick cladding installation on this impressive education facility to be completed to the highest safety standards, while showcasing its architectural brickwork features.

Ancon’s MDC and CFA continuous shelf angle support systems carry the intricate brick façade, consisting of freestanding archways and projected brickwork. The MDC stainless steel angles are fixed to the reinforced concrete frame, span a 40mm cavity, and create a horizontal shelf to provide the necessary support for up to 3 metres of brickwork.

Cast-In Channel

Ancon’s 30/20 cast-in horizontal channels were used to provide the fixing between the concrete frame and shelf angles. The channel enabled the necessary horizontal adjustment for the installer, and its compact size eliminated the issue of potential clashes with the reinforcement steel in floor slabs.

Nail holes aided the fixing of channels to timber framework and an infill prevented the ingress of concrete during casting. Cast-in fixings do not generate expansive forces in concrete. It can therefore be used at close centres and often used closer to the edges than expansion fittings.

Wall Ties and Restraint Fixings

To restrain the distinctive brickwork details to the reinforced concrete structure, stainless steel L-shaped SPB and SDB frame cramps were fixed into the reinforced concrete using 6mm FBN expansion bolts.

FBN single expansion bolts are a cost-effective anchor and fix into a hole similar to the diameter of the bolt. This allows the hole to be drilled through the hole in the item to be fixed.

Technical Expertise

As part of Ancon’s free design service, plans were produced illustrating the location and reference of all fixings required. Ancon’s early engagement with the project’s structural engineers, Bligh Tanner, enabled a workable and cost-effective design to be agreed upon prior to the build of the complex masonry features. Sharing their expertise with the clients at this stage of the project meant installation difficulties, site delays and unnecessary remedial measures were avoided.

  

 

Centenary Library photo (above); Copyright: Christopher Frederick Jones.

This article is featured in Australian Stainless Magazine #61.

Thermal Expansion and Design of Stainless Steel Fabrications

Either while being welded or glistening in the summer sun, the three major families of stainless steel behave differently to each other, carbon steels, aluminium and copper alloys because, as shown in the bar chart, the coefficient of thermal expansion and conductivity - and their ratio - varies.  

While alloys of copper and aluminium have equal or higher coefficients of expansion than austenitic stainless steels, it is the unique combination of high thermal expansion and low thermal conductivity that necessitates special precautions and procedures in the design and fabrication of the most commonly used 304/304L and 316/316L grades of austenitic stainless steel in structures and vessels. Information on handling other families of stainless steels is given in ASSDA’s Australian Stainless Reference Manual.

Distortion during welding

Failure to address thermal expansion and conductivity can result in severe distortion during welding, as differential expansion causes the heat generated by the welding process to remain localised, causing steep temperature gradients  and high localised stresses or surface distortion. Standard welding procedures should be adopted to minimise heat build-up in the weld zone. These include using minimum amperage consistent with good weld quality and controlling interpass temperatures using guidelines provided in Table 5.10 of AS/NZS 1554.6. Clamping jigs with copper or aluminium backing bars as heat sinks on the welds may also be feasible. Other precautions to minimise distortion during welding include efficient jigging or the use of an ends and middle sequence of closely spaced tack welds rather than a straight run. The wrinkled guttering below illustrates the shrinkage problems of poorly planned welding.

The Design Manual for Structural Stainless Steel2 indicates that austenitic stainless steels suffer from the same types of distortion during welding as carbon steel, but the higher coefficient of expansion (17 μm/m°C versus 12 μm/m°C for carbon steel) and the lower thermal conductivity (approximately 30% of carbon steel) increase distortion of austenitic stainless steel weldments. Duplexes are between carbon and austenitic stainless steels in thermal expansion coefficient, but the thermal conductivity is similar to austenitics so heat control is still important. Ferritic stainless steels have similar thermal welding properties to carbon steel but require more skilled welders for metallurgical reasons.

The Design Manual also suggests that a number of additional actions can be considered by both the designer and the fabricator to minimise welding distortion and mismatches such as illustrated in the manifold. These include designing with symmetrical joints, designing to accommodate wider dimensional tolerance, reducing cross-sectional area of welds in thick sections (e.g. replacing Single ‘V’ preparation by Double ‘V’ or Double ‘U’), ensuring that good fit-up and alignment are obtained prior to welding, and using balanced welding and appropriate sequences such as ‘backstepping’ and ‘block’ sequences.

Expansion problems after installation

Another problem arising from the high coefficient of expansion of austenitic stainless steels compared to plywood is differential expansion – although water uptake may also be an issue.  In the illustrated case of stainless steel bonded to plywood by adhesive, a maximum length of 3m is recommended to avoid failure of the adhesive bond during thermal cycling. 

Another problem is when panels (even quite small ones) are in full sun and do not have expansion room for the movement since they were installed at (say) 20°C to the 40°C day plus 30°C overheated metal.

In architectural applications with long runs such as profiled roofing, expansion clips should be used to permit thermal movement without localised buckling and failures. As with other metal roofing and cladding systems with runs 3-9m or longer, there are limits to the maximum width of formed profile for the thickness of stainless sheet used. The formed profile must have sufficient columnar rigidity and strength to transform thermal expansion stresses into sliding movement in the expansion clips. For longer runs, expansion joints should be provided every 7-12m, with clearances of 6mm at vertical faces and 12mm where a gutter end abuts a wall. The publication Stainless Steel in Architecture, Building and Construction - Guidelines for Roofs, Floors and Handrails3 illustrates roofing fixtures for roll-formed profiles and the traditional standing seam and batten roll types. In contrast, ferritic guttering and roofing have similar properties to carbon steels with about 62% of the expansion of an austenitic structure.

In stainless steel piping systems, thermal expansion stresses can cause rupture of the support points, buckling of the pipe, or breakage of equipment connected to the piping if the changes in dimensions are not absorbed by expansion joints or flexibility of the piping installation. The Piping Manual for Stainless Steel Pipes for Buildings4 provides a guide to assessing thermal stresses and reactions at supports and anchor points, as well as a guide to determining if the flexibility of piping can absorb its expansion. The latter involves an empirical formula which requires that the piping anchor points are at the pipe’s ends, the piping system has no branches, and there are no changes along the length of the pipe (e.g. diameter, thickness, material quality, temperature, etc.). If the flexibility cannot absorb the thermal expansion displacement, then expansion joints, flexible joints or ball joints should be used (after a computer stress analysis of the joint).

Conclusion

Thermal expansion and conductivity are critical determinants when designing and fabricating austenitic stainless steel products and are still important with duplex stainless steels. Early consideration of these elements will ensure a better and longer-lasting product, both aesthetically and structurally.

 

 

REFERENCES

  1. ASSDA’s Australian Stainless Reference Manual, see also:

    Avery, R.E. & Tuthill, A.H. (1992) Guidelines for the Welded Fabrication of Nickel-Containing Stainless Steels for Corrosion-Resistant Services (NI 11 007)

    IMOA’s Guidelines for the Welded Fabrication of Duplex Stainless Steels, 3rd Edition (2014)

  2. Design Manual for Structural Stainless Steel, 4th Edition (2017): www.steel-stainless.org/designmanual 

  3. Cochrane, D.J. (1994) Stainless Steel in Architecture, Building and Construction - Guidelines for Roofs, Floors and Handrails (NI 11 013)

  4. Nickel Institute and Japan Stainless Steel Association (1987) Piping Manual for Stainless Steel Pipes for Buildings (NI 12 008)

This article is featured in Australian Stainless Magazine #61.

 

Collaboration Brings Results

The new facility in Merrifield Estate on Melbourne's outer northern fringe will allow Dulux to step into the next generation of paint manufacturing technology and innovation. Dulux's aim was to design and construct a state-of-the-art facility, so using quality products was essential to achieve this. Stainless steel in 300 series grades was an integral part of the project design, including storage vessels and over 10,000m of food grade, quality tube complying with AS1528.

CONCEPT STAGE

In 2015, Dulux announced its decision to construct the new state-of-the-art, highly automated paint factory at an investment of $165m.

The Dulux plant, the first of its kind, is approximately 20,000m², built on 17 hectares of land and is due for completion towards the end of 2017. For a project of this large scale, it was crucial that a strong collaborative relationship was set up between Dulux and its chosen suppliers. In relation to the tubing, supply flexibility, reliability and quality was a key requirement and ASSDA Sponsor Prochem Pipeline Products stepped up to the mark and was the successful tenderer. At the outset the total amount of tube was unclear and would only become apparent as the building process unfolded.

Working together with the client, Prochem executed a strategy to provide more than 10,000 metres of stainless steel tube over a nine-month period to complete the project.

Whilst the original engineering design specified pharmaceutical standard ASME BPE, Prochem worked with the client and design team to have this changed to AS1528 due to its suitability for the application and also due to availability of this stainless steel standard compliant product in the Australian market.

THE DESIGN

The design included a number of large and small storage vessels which were fabricated locally and supplied by ASSDA Members and Accredited Fabricators A&G Engineering and J Furphy & Sons. 

A major part of the design involved the supply and fabrication of the AS1528 tubing and included stainless steel fitting and flanges. The fabrication work was contracted to ASSDA member John Beever Australia who worked closely with Prochem to ensure a continuous supply of materials was made available as required. 

The project consumed over 10,000 metres of AS1528 tubular products in a size range from ½” to 8” in outside diameter with the bulk being 2”, 3” and 4”. The fittings used in the project included BSM fittings, tri-clover ferrules and clamps and also a significant amount of ANSI flanges which were all supplied by Prochem and fabricated by John Beever. The overall project quantities were significant and as such a large degree of co-ordination and co-operation was required with numerous manufacturers to meet the project schedule. 

An innovative technique was designed to match the tri-clover ferrules and clamps to the tube and machinery to enable a correct fit-out at site. 

With good co-operation and education, the project also allowed the flexibility to use both stainless steel grades 304 and 316 if availability became an issue. 

With an innovative and co-operative approach involving many ASSDA members, this project was completed on time and within budget, and will support the Dulux paints business for decades to come.

 

This article is featured in Australian Stainless Magazine Issue 60 (Summer 2017/18).

Art Symbolises Community

You return home after a long journey. Imagine being greeted by a beautiful stainless steel sculpture surrounded by landscaped gardens on your return. One ASSDA Member has used stainless steel to symbolise everything we love about our communities: Security, comfort and home.

It’s easy to think of stainless steel in relation to tubes, panels and rolls in the construction industry, but Brisbane-based ASSDA member, Concept Stainless Design, has taken the product and crafted it into stunningly beautiful sculptures for developers Villa World at their new subdivision on the northern Gold Coast.

Located 70km south of Brisbane, Arundel Springs will provide 386 dwellings in a family-friendly environment adjacent to the Coombabah Lakelands Conservation Area and close to Griffith University and light rail services.

Villa World provided the concept design to reflect the organic growth of nature and symbolise the new families and children who will grow in the new suburb. 

The team at Concept Stainless Design adapted the design to match the size of available grade 316 stainless steel sheets. A small curve of 5mm radius was provided at the tip of the fronds to avoid sharp edges. Another small curve of 9mm was used at the gully between fronds to achieve a flawless polished finish.

The sculptures have been designed to withstand winds of up to 160km per hour, an important feature given Arundel Spring’s proximity to the ocean. An internal frame was built to secure the fronds in position, as well as a horizontal base beam hidden within the sculpture and two legs extending down from the base beam into a large buried concrete block. The structural design certification was completed by Concept Stainless Design’s in-house engineer.

The face of each sculpture was manufactured from grade 316 stainless steel sheet supplied by ASSDA Sponsor Dalsteel Metals.

The sculpture faces are joined along the centre line with an invisible polished butt weld, executed by Concept Stainless Design’s highly skilled tradesman at their Brisbane workshop. The faces were bonded to marine ply and “U” stiffeners were formed from grade 316 stainless steel strips then glued and screwed in. The second face was then placed over the stiffeners, glued and screwed to the ply-bonded face.

The entire project took eight weeks to construct and transported to their new home at Arundel Springs. The sculptures were secured in place by concrete blocks and steel bolts provided by Villa World’s civil contractor in under two hours.

Stainless steel was chosen for the sculptures because of its beautiful, smooth and highly polished finish, and for its low-maintenance properties. Surrounded by clear skies, new vegetation and lush grass, the sculptures welcome residents and visitors alike.

This article is featured in Australian Stainless Magazine Issue 60 (Summer 2017/18).

The Family of Duplex Stainless Steels

The use of duplex stainless steels has grown globally based on their strength, corrosion resistance and a range of properties that improve equipment life.

The name duplex is sometimes used to describe Alloy 2205 (UNS S31803 or UNS S32205), however duplex is a family of alloys ranging from lean duplex and standard duplex to super duplex stainless steel.

HISTORY

Duplex stainless steel was first developed in France and Sweden in the 1930’s, with the early grades becoming a forerunner for AISI 329, but a lack of control over the chemistry and lack of adequate welding products and techniques impeded development of the product.

Cast versions eventually became available and were subsequently used successfully in many industries where some corrosion, wear and strength were required.  

Areas such as pump components saw a raft of duplex grades developed in standard and super duplex. It should be noted that further work or welding was not required with these particular forms.

In the 1970’s Swedish manufacturers produced and marketed what could be described as a lean duplex called 3RE60 (UNS S31500) with lower chromium, nickel and nitrogen than grade 2205.

3RE60 had success with tubing and displayed excellent resistance in replacing 304 and 316 tubes that had previously failed due to chloride-induced stress corrosion cracking.  The use of 3RE60 in vessels was less successful due to issues such as inter-granular corrosion (IGC) from early welding techniques. The issue was not with the grade but with fabrication, as well as the melting technique to enable control of alloying elements to provide a consistent structure and provide predictable strength and corrosion control.

In the late 1970’s grade 2205 arrived in the market, initially as a tube, then in flat-rolled and other products. The point-of-difference from earlier attempts was well-documented welding technique control, which lead to the increased usage of duplex.

The grades displayed higher strength than standard austenitic grades, excellent resistance to stress corrosion cracking and improved pitting resistance. The other driver was the rising price of nickel, which added a commercial advantage over using a lower nickel duplex product.

GRADES OF DUPLEX

The grades are listed in three groups; standard, lean and super.

The major difference between each grade is corrosion resistance.  This is based on a Pitting Equivalent Number: 

(PREN) = %Cr + 3.3 x %Mo + 16 x %N.

This is a comparative rating that relates to the critical pitting and crevice corrosion temperatures in hi chloride environments (CPT and CCT respectively).

DUPLEX TYPE PREN
Standard Approximately 35
Lean 25-30
Duplex Above 40

USES OF DUPLEX STAINLESS STEELS

Stress corrosion cracking (SCC) is a form of corrosion that occurs with a particular combination of factors:

  • Tensile stress;
  • Corrosive environment; 
  • Sufficiently high temperatures: Normally above 60°C but can occur at lower temperatures (around 30°C in specific environments, notably unwashed atmospheric exposures above indoor chlorinated swimming pools). 

Unfortunately, the standard austenitic steels like 304 (1.4301) and 316 (1.4401) are the most susceptible to SCC. The following materials are much less prone to SCC:

  • Ferritic stainless steels;
  • Duplex stainless steels;
  • High nickel austenitic stainless steels;

 The resistence to SCC makes duplex stainless steels suitable for many processes operating at higher temperatures. Examples of the successful use of duplex stainless steel are hot water tanks, brewing tanks and thermal desalination vessels.

WHERE CARE IS REQUIRED WITH DUPLEX STAINLESS STEELS

Duplex stainless steels can also form a number of unwanted phases if steel is not given the correct processing, notably in heat treatment. Phases like sigma phase leads to embrittlement, meaning the loss of impact toughness, but sigma phase also reduces corrosion resistance.

The formation of sigma phase is most likely to occur when the cooling rate during manufacture or welding is not fast enough. The more highly alloyed the steel, the higher the probability of sigma phase formation. Therefore, super duplex stainless steels are most prone to this problem. Another form of embrittlement occurs above 475°C, and it can still form at temperatures as low as 300°C. This leads to the design limitations on the maximum service temperature for duplex stainless steels.

SUMMARY: DUPLEX CHARACTERISTICS

Compared to the austenitic and ferritic stainless steels, duplex can give:

  • Up to double the design strength;
  • Good corrosion resistance depending on the level required;
  • Good toughness down to -50°C;
  • Excellent resistance to stress corrosion cracking;
  • Welding in thin and thick sections with care;
  • Additional effort required due to high mechanical strength;
  • Up to 300°C maximum in service.

  

Author: Trent Mackenzie is a metallurgist with more than 35 years experience in the industry and General Manager of ASSDA.

Photos courtesy of Outokumpu.

This article is featured in Australian Stainless Magazine Issue 60 (Summer 2017/18).

Wynyard Walk: Where Beauty Meets Function

New infrastructure in the heart of Sydney is set to transform the busy transport hub and provide a stylish new gateway to the Barangaroo development.

21 June 2017

A growing population in Australia's most populous city calls for innovative design, so when the NSW State Government commissioned construction of the Wynyard Walk, ASSDA Sponsor and Accredited Fabricator Stoddart stepped up to the challenge.

The Wynyard Walk forms one of several solutions to break congestion in the Sydney CBD, allowing pedestrians to move from the Wynyard transport hub to the new development at Barangaroo waterfront in six minutes, avoiding steep hills, busy intersections and inclement weather events.

With an estimated 75,000 commuters using the busy hub every day, traffic flow is expected to increase to 110,000 over the next seven years in what is traditionally Sydney's third busiest station.

The tunnel will become the main arterial connection between Barangaroo and the city's transport network and provides vital infrastructure into the future.

THE PROJECT

Alongside CPB Contractors, Stoddart incorporated over 1,600m2 of perforated and solid stainless steel sheeting fabricated into ceiling and fascia pannelling installed in the Clarence Street entrance facade and the tunnel lining. The new Clarance Street entry point is a multi-level portal descending to Wynyard Station via escalators and elevators.

ASSDA Sponsor Austral Wright Metals supplied the project with over 50 tonnes of 445M2 grade stainless steel sheet.

A major consideration for the design team was to ensure aesthetic value for commuters and visitors alike.

THE DESIGN

Inspired by nature and Sydney region geology, the design concept for Wynyard Station focused on flow, with all materials selected to create a sense of motion as part of a unified architectural expression.

The intricate patterns were all designed and executed within Stoddart's factory in Karawatha, Brisbane. The design work was completed wholly on CAD and Solidworks to ensure each panel fitted exactly into the patter and alongside adjacent panels. The Brisbane facility completed all aspects on the manufacture.

The external facade from Clarence Street to Wynyard Station was completed using perforated metal panels on the new access area via escalators and elevators down to the station several levels below.

The internal fitout, including the ceilings, walls and bulkheads, were all constructed from perforated stainless steel as well as solid stainless steel panels.

The complicated ceiling pattern proved challenging, but not insurmountable, resulting in a beautiful floating effect beckoning commuters along.

The project signalled the completion of Stage One of a $160 million upgrade to Wynyard Station.

 THE OUTCOME

The Kent Street level incorporates an extraordinary twenty-metre digital media screen which showcases flowing images of time, travel and places from all over Sydney throughout history, providing commuters with a far more entertaining commute than traditional toilet-block-tiled underground tunnels.

For tens of thousands of commuters who daily traverse the tunnel, Wynyard Walk is a time and energy saving alternative to the street level traffic roulette they once faced.

The added bonus is the stunning, aesthetically pleasing surrounds, the shiny panels and beautiful architecture, all of which was made possible by the use of stainless steel.

This article is featured in Australian Stainless Magazine Issue 59 (Winter 2017).

Disc Dryers Get a Makeover

Wave Discs Revolutionises Traditional Drying Process

In the search to find a more efficient way of manufacturing industrial disc dryers for the meat-rendering industry, Melbourne-based engineering company Pinches Group has developed a new technology called Wave Disc.

THE CHALLENGE

Traditional rotary discs comprise of a series of stainless steel discs, welded back-to-back and attached to a centre pipe. Together, the pipe and discs make up the shaft, which operates under steam pressure and rotates within a stainless steel shell.

Employed throughout the world in a wide range of industries, disc dryers are commonly used to dry materials such as coal, sand, sludge, paper pulp and animal waste.

There are significant inefficiencies in the manufacturing of disc dryers:

  • Discs are cut from industry standard rectangular plate, with the centres and corners of the donor material often wasted;
  • Flat discs rely on pressure-welded pins for structural support. A typical two-metre diameter disc requires ninety-six support pins pressure welded with full penetration on both sides of the disc. Pressure welds are not only labour intensive, but due to the proximity of discs with the drum, they are difficult to repair once the dryer is in operation.

ASSDA Member Pinches Group began investigating designs that could overcome the need for support pins and reduce raw materials waste. Rather than cutting the discs, Pinches discovered that using specific rectangular sections of material discs could be formed through a series of folds along one edge of the plate. This enable all supplied materials to be used in the formulation of the disc.

BENEFITS

Because folds occur consistently and consecutively around the disc, the folds reinforce the structure of the discs and eliminate the need for added support.

Removing the pins not only improves manufacturing time, it eliminates the chance of weld failure around the support pins, which can cause equipment faults in traditional disc dryers.

Additionally, the natural waves of the discs provide increased agitation to drying material, which can improve evaporation rates.

One design flaw with flat discs is a tendency for product to stick and build up between discs. With Wave Disc, the waves in the disc massage the product and keep it moving within the drum, preventing build up and ensuring that all raw materials are exposed to heat.

Wave Disc also provides greater surface area. Any indirect drying processes (where the heat source doesn't make direct contact with the product) is reliant on the surface area to transfer heat.

With the addition of the folds, Wave Disc provides a surface area at least thirteen per cent larger that conventional discs within the same footprint. This means that existing disc dryers can replace their current shaft with a Wave Disc shaft and increase the capacity of the dryer.

AWARD WINNING DESIGN

In 2012, the Wave Disc concept received top level funding from the Australian Federal Government's Commercialisation Australia program.

In 2014, the first Wave Disc unit was installed at animal by-product processor, Australian Tallow, in Brooklyn, Victoria. Since then, further units have been exported to by-product processors in New Zealand.

As Australia's leading supplier of processing equipment to the animal rendering industry, Pinches Group developed Wave Disc to overcome specific inefficiencies within the meat processing industry.

Now that this innovative new technology has been tested and proven in the rendering industry, Pinches has plans to expand their focus to heating and cooling processing technologies in the food and agricultural sector.

Pinches Group own and operate a testing facility in Melbourne which incorporates an operational Wave Disc pilot unit used by prospective clients and educational institutions for running trials on a range of raw materials.

Among other metrics, the pilot units can provide clients with evaporation rates and in-an-out moisture levels for specific products.

PATENT

The Wave Disc design is protected by Provisional Patent Number 593495.

This article in Australian Stainless Magazine Issue 59 (Winter 2017).

K-TIG: A Quantum Leap for Welding

Innovation Design Set to Transform the Industry

For the past six decades, the welding process has only been tweaked and modified, but one Adelaide company has developed a new process set to save millions of dollars and forever change the way welds are performed.

DEVELOPMENT

In 2000, Dr Laurie Jarvis and his associates at CSIRO Adelaide studied the effect of surface tension within an active weld. It was noted that under certain conditions, namely narrow gaps and increased process conditions, that far greater speeds could be obtained when welding clean materials.

The team developed a brand new process involving a high speed, single pass, full penetration welding technology that significantly reduces the need for wire or edge bevelling and is not required where autogenous welds are acceptable.

The result is a flawless finish at a speed up to 100 times faster than TIG welding in materials up to 16mm in thickness.

By definition, clean materials include stainless steels, nickel alloys, titanium and zirconium. Other materials with high impurities (such as alloy steels) cause the weld arc to become unstable and the process becomes unmanageable.

NEXT STEP

With Dr Jarvis as technical leader, a group of experienced materials experts formed K-TIG. Today K-TIG has progressed into many world markets with the system, winning a number of awards along the way.

The K-TIG process involves a specially controlled high current arc which opens a full penetration keyhole in the joint between the two welding surfaces.

Featuring extremely high stability and operating over a wide range of welding currents, K-TIG looks set to become the next big thing in fabrication.

Since its inception, K-TIG has achieved enormous growth in the market, with the technology being exported to eighteen countries. Customers using stainless steels are typiclaly saving 90% on production costs.

THE PROCESS 

The process ideally suits non-corrosive and exotic materials with a thickness range of 3mm to 16mm for single pass welding, however thicker metals can be welded by multiple passes.

K-TIG easily handles the traditionally difficult material, super duplex.

As for energy consumption, K-TIG consumes as little as 5% of the energy and gas consumed by TIG/GTAW for the same weld, dramatically reducing its carbon footprint.

A typical K-TIG weld is performed in a fraction of the time of a conventional weld, in a single full-penetration pass using just one welding gas.

The resulting weld is with multiple fusion lines, dramatically reducing the potential for inclusions, porosity and other defects typical of many welding processes.

The K-TIG system can monitor and control the addition of wire to a weld if that is desirable.

This article in Australian Stainless Magazine Issue 59 (Winter 2017).