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Posted 19 November 2012

This is an abridged version of a story that first appeared under the same title in Stainless Steel Focus No. 07/2012.

The Nickel Institute's director of promotion, Peter Cutler, and consultant Gary Coates, reveal some of the reasons for the continuing popularity of nickel in stainless steels.

Stainless steel is everywhere in our world and contributes to all aspects of our lives. We find stainless steel in our homes, in our buildings and offices, in the vehicles we travel in and in every imaginable industrial sector. Yet the first patents for stainless steel were issued only 100 years ago.

How did this metal become so desirable over the past century that more than 32 million tonnes was produced in 2011? And how does nickel, a vital alloying element in most stainless steel alloys, contribute to the high demand for stainless steel?

THE 'CREATION' OF STAINLESS STEEL
By definition, a ‘stainless’ steel has a minimum level of about 10.5% chromium, so the discovery of chromium in 1799 by Nicolas Louis Vauquelin in France was the first key event in the creation of stainless steel. In 1821 another Frenchman, Pierre Berthier, published research that showed a correlation between increasing chromium content and increasing corrosion resistance, but the high carbon content of his alloys prevented them from showing a true ‘stainless’ behaviour.

Still in France, in 1904 Leon Guillet first published his metallographic work on alloys that today would be classified as ferritic and martensitic stainless steel. In 1906 Guillet published his work on the nickel-containing austenitic stainless steel family, but his studies did not include corrosion resistance. Albert Portevin then continued to build on Guillet’s work.

In 1911, a German scientist named Philip Monnartz reported that as the chromium content neared 12% in a steel with a relatively low carbon content, the alloy exhibited ‘stainless’ properties. Further developments then rapidly occurred in many other countries. In the United States, Elwood Haynes started working with martensitic alloys while Becket and Dantsizen were developing a ferritic stainless steel as lead-in wires for electric light bulbs. In 1912, Great Britain’s Harry Brearley worked on a 13% chromium martensitic alloy, initially for high temperature service in exhaust valves for aeroplane engines.

Meanwhile in Germany, Eduard Maurer and Benno Strauss were testing nickel-containingalloys and, in 1912, two patents were awarded. One of these grades, containing about 20% chromium and 7% nickel, was called V2A, and was found to have exceptional corrosion resistance in nitric acid. That grade had a relatively high carbon content compared to today’s stainless steel, and would be
similar to a Type 302 (EN 1.4317) stainless steel. 100 years later, the most commonly used alloy for nitric acid is 304L (EN 1.4307) with approximately 18.5% chromium and 8.5% nickel, quite similar to the V2A composition other than having a much lower carbon content.

Brearley’s martensitic stainless steel alloy would not rust when wet. He worked with Sheffield cutlery manufacturers to forge it into knife blades and then harden it, replacing the carbon steel blades they were then making. Stainless steel knives rapidly became a common household item. However, for forks and spoons, where high hardness was not so important, the 18-8 (302) composition became the most commonly used alloy.

300 SERIES
We normally think of the austenitic or 300 series family of stainless steels as the ‘nickel stainless steels’, but many other families contain nickel. One of the prime reasons for using nickel in the 300 series alloys is that nickel is an austenite former, but other reasons include:

  • Nickel adds corrosion resistance, especially in certain aqueous environments, and in certain high temperature environments.
  • Nickel can retard the formation of embrittling intermetallic phases at elevated temperatures, a major downfall of the non-austenitic families.
  • The austenitic structure can mean high toughness at cryogenic temperatures.
  • The advantages of the 300 series extend to welding and forming operations.

A fuller discussion of these topics can be found in 'The Nickel Advantage - Nickel in Stainless Steels', available on the Nickel Institute website.

200 SERIES
The 200 series stainless steels are also austenitic in structure. The standardised 200 series grades, which have chromium contents close to the level of a 304L alloy (about 18%), have an intermediate level of nickel. The ‘non-standardised’ 200 series not only have lower contents of nickel, but also lower contents of chromium, with the net effect of significantly reduced corrosion resistance, although still an improvement over the 11-13% chromium ferritic stainless steels.

DUPLEX
The duplex (austenitic-ferritic) family of alloys also need some nickel as well as nitrogen to ensure proper austenite formation. Most ‘matching’ duplex filler metals are actually over-alloyed with nickel to ensure that the welds have the required properties.

PRECIPITATION HARDENABLE
The precipitation hardenable (PH) stainless steel family contain nickel, which increases their corrosion resistance, ductility and weldability compared with hardenable non-nickel-containing stainless steel alloys. One of the other major advantages of the PH grades is that, unlike the martensitic grades, they do not need a quenching operation, which considerably reduces risk of distortion. Some of the martensitic grades also contain a small nickel addition. In the higher chromium types, the nickel is needed for the martensitic transition. In all nickel containing martensitic grades, nickel improves their corrosion resistance, ductility and weldability.

Some of the lower alloyed ferritic grades such as UNS S41003 (EN 1.4001) and S40975 contain a small intentional nickel alloying addition that allows for grain size control, which aids especially in welded constructions. A few of the higher alloyed ferritic grades also have a small nickel addition to increase toughness and ductility, which is beneficial during both hot rolling and in their end use.

Clearly, it is important for each specific application to select the appropriate alloy or alloys to give the desired properties.

GROWTH IN DEMAND FOR STAINLESS STEEL
According to the ISSF, 300 series stainless steel still dominates the worldwide production figures, as shown in Figure 1.

The properties of the various 300 series grades - created by the addition of nickel - are clearly valued by users, both in industry and the general public. Upwards of two thirds of all stainless steel produced in 2011 fell within the 300 series and close to three quarters of all stainless steel produced contains nickel.

The growth of worldwide production of stainless steel over the past 100 years has been steady, if not spectacular. This has meant that the demand for new nickel has steadily increased along with the demand for stainless steel, as shown in Figure 2. Recycled stainless steel is also a very important component in the alloy supply chain.

EFFICIENCY AND 'GREEN' CREDENTIALS
Resource efficiency is a recurring theme as the global economy faces economic challenges. Stainless steel not only contributes towards efficiency in many applications, it also shows continuous improvement in the resource efficiency related to stainless steel itself.

There are three important factors:

  1. Stainless steel’s long service life, which might average 15 to 20 years, although much longer in prestigious buildings.
  2. The extent of recycling: The percentage recovered and recycled at end-of-life - around 90% - is amongst the highest of all materials. Moreover, this recycling can be repeated many times without loss of quality. While the recycled content may appear to be relatively low, this is simply a result of stainless steel’s long service life (15 to 20 years) coupled with much lower global production 15 to 20 years ago.
  3. Continual production improvements for stainless steel and its raw materials. For example, whilst the ores being processed today are of lower grade than before, the extraction and recovery processes are more efficient.

THE FUTURE
The history of stainless steel would be incomplete without celebrating the extent to which it has enabled innovation not just in the area of improved performance, but also in the more intangible, aesthetic aspects. From chemical plants to medical equipment to iconic stainless steel-clad buildings, stainless steel has made - and will continue to make - a major contribution to almost every aspect of our lives.

With durability, recyclability, versatility and aesthetic appeal at the core of its appeal, stainless steel - with nickel as one of its trusted alloys - is well placed to continue to innovate and expand its applications.

STAINLESS STEEL IN USE

FOOD AND BEVERAGE INDUSTRY
The popularity of stainless steels in kitchens did not go unnoticed in the food and beverage industry.

If we take milk, we know of an early stainless steel bulk milk tank truck from 1927 in the USA. A paper entitled ‘The Corrosion of Metals by Milk’ from the January 1932 Journal of Dairy Science by Fink and Rohrman states: ‘It has long been known that milk in contact with iron and copper will not only acquire a metallic taste, but corrode these metals readily’. At that time, tin-coated metals were commonly used. It went on to say that ‘High chromium nickel (18-8) iron alloys … are very resistant to corrosion by milk and are satisfactory for dairy equipment …’. The modern milk processing industry is filled with stainless steel equipment, mostly of Type 304 (EN 1.4301) or 304L.

The report also went on to state that some materials that are otherwise suitable for processing of milk ‘…do not stand up well to the action of cleaning compounds that are commonly used in dairies’, but that the 18-8 alloy was suitable for those cleaning compounds. Today, the typical cleaning acids and hypochlorite sanitising compounds that are used not only in the dairy industry but also in most food and beverage plants worldwide, require that same 18-8 alloy as a minimum. A correctly chosen stainless steel alloy will not change the taste or appearance
of the food product. However, it is the ability to withstand repeated use of the sanitising chemicals over the lifetime of the equipment that has led to the widespread use of stainless steel in all sectors of the food and beverage industry. Producers are then able to guarantee the
safety of their food products.

ARCHITECTURE
Another area of quick acceptance was in architecture. The first recorded use for that purpose was in 1929 in London at the Savoy Hotel where a sidewalk canopy and a sign were erected with the 18-8 alloy. These were soon followed by two iconic skyscrapers in New York that used stainless steel as a dominant element on their exteriors: the Chrysler Building in 1930 and the Empire State Building in 1931.

Since then, many prestigious buildings around the world have used stainless steel, including the Petronas Tower in Kuala Lumpur, the Trump Tower in Chicago, and the Jin Mao Tower in Shanghai. Related to architecture is sculpture, and Isamu Noguchi convinced the Associated Press in 1940 to approve stainless steel instead of bronze for his sculpture above the entrance to its building in New York. Since then, artists around the world have been using stainless steel, mostly either 304L or 316L (EN 1.4404), in their works. The St Louis Arch in the USA, Frank Gehry’s Peis (Fish) in Barcelona, Spain, and more recently Genghis Khan in Mongolia are examples of what can be done with stainless steel.

TRANSPORTATION
During the Great Depression in the USA, Edward Budd realised the untapped potential for stainless steels. Although their use in aeroplanes was his first application, his legacy remains the building of more than 10,000 passenger railcars, some of them still in use today.

Around the world, stainless steel is used extensively for passenger rail cars for subways, commuter trains and long distance trains, ensuring safety plus long life and low maintenance costs. In addition, stainless steels are used to transport cargoes such as food products, petroleum products and corrosive chemicals by rail, road, water and even air, both domestically and internationally.

ENERGY
In the broad field of energy, stainless steels have been used to extract oil and gas containing hazardous substances as well as for use in the refining stages. For power plants, stainless steel is used extensively at both low and high temperatures, whether the fuel is coal, oil, gas, uranium or waste products. Hydroelectric stations use stainless steel for dam gates as well as turbines. Many of the established sustainable
energy technologies such as solar and geothermal are using stainless steel, as well as the present biofuels industry with corn or sugar cane as feed stock.

WATER
Fresh water is an essential commodity for mankind, and stainless steel is used extensively in treatment plants for potable water as well as for wastewater. Cost effectively producing fresh water from seawater or brackish water by desalination also requires the use of stainless steel. In some countries, underground stainless steel pipe is used to deliver potable water to homes to prevent leakage, or in other special cases to protect either the environment outside the pipe or the water inside the pipe. Stainless steel plumbing is also common in certain countries and offers a long lasting, low maintenance option.

SURGERY
The first recorded example of an austenitic stainless steel surgical implant is from 1926. Medical instruments are also known from that time period. The ability to easily and repeatedly sterilise components that come in contact with the human body or are used in hospitals and clinics contributed to the early acceptance of stainless steel. Today, there are well-established international specifications for materials used in this industry. For example, stainless steel alloys for implants must meet stringent metallurgical cleanliness requirements and be completely non-magnetic so that the patient can safely undergo diagnosis by Magnetic Resonance Imaging.

FUTURE USES OF STAINLESS STEEL
Strong growth in the use of stainless steel has continued in the past decades despite the rapid and diverse developments in other materials and the more recent economic turmoil. The nickel-containing alloys in the 300 series still account for nearly two thirds of current stainless steel production worldwide, and there is nickel in the 200 series, duplex and precipitation hardening families, as well as in some of the martensitic and ferritic alloys. The reason for this is the great value that is placed on the properties which nickel provides.

Society is rapidly evolving and facing challenges on a global scale. Population is increasing, expectations are growing and resources are limited. Therefore we must use those resources more efficiently. This is particularly apparent for energy where stainless steel, and especially the nickel-containing alloys, already plays a major role in the more difficult to extract fossil fuels. Stainless steel’s corrosion and heat resisting properties are key to more cost-efficient operations. This also applies to the renewable sources that are now being developed, such as wave power and biofuels from new organic sources.

The worldwide need for higher quality, safe food and beverages and water will only increase, especially as food products can come from anywhere in the world. Stainless steel has evolved as the material of choice in this industry, both industrially and domestically, and it is likely to continue to meet the demands of a global population that is predicted to increase to nine billion by 2050.

This growing population, combined with a rapid movement to urbanisation, requires an expanded and more efficient transport infrastructure. The characteristics of stainless steel enable it to deliver lightweight and durable designs, leading to more efficient performance, safety, lower energy requirements and reduced emissions while giving lower life-cycle costs.

Image of Trump Tower (Chicago, USA) pictured above courtesy of C.Houska.

This article is featured in Australian Stainless magazine, issue 52.


Posted 3 May 2012

The Fibonacci spiral and the intersecting spines of a nautilus shell have inspired an impressive 23m high stainless steel sculpture at Kangaroo Point Park overlooking Brisbane's river.

Designed by UK public space artist Wolfgang Buttress, Venus Rising features 10,790 individual welds and over 7km of grade 316 and 2205 duplex stainless steel tube, pipe and round bar supplied by ASSDA Sponsor, Sandvik.

Having worked with stainless steel for over 25 years, Buttress said that the material’s strength, ability to look good over time with minimal maintenance, and the flexibility of finishes works well both practically and aesthetically.

“The variety of finishes which can be achieved with stainless steel through polishing, glass blasting and heat treatment is great. The material needs to be strong, resilient and look as good in 50 years as it does on installation,” Buttress said.

Initial fabrication works took place in the UK before being transported to Brisbane for final assembly. D&R Stainless, an ASSDA member and Accredited Fabricator, continued the fabrication of the 11.5 tonne spire-like sculpture over a period of six weeks. It used the artistic vision of Buttress, as well as renders and 3D models to guide the assembly of the sculpture.

The central design of the sculpture was to create a piece of artwork that was visibly prominent and exemplified strength, elegance and weightlessness. The sculpture features a criss cross ladder-type construction with heavy wall pipes that gently twist to create a hollow spiral. Visitors can enter the sculpture at the base level and gaze up at the sky through an opening at the top.

“I wanted to make connections between the Brisbane River and the sky above. It was important to me that the sculpture works on an intimate scale as well as being seen from afar,” Buttress said.

“Visually, the most challenging part of the project was to try and maintain harmony between form and sculpture. I wanted the piece to have a delicacy but also be strong.”

The main structure of the sculpture features 2205 duplex stainless with cladding tubes at the bottom of the structure starting at 12mm, ascending to 8mm and 10mm tube through the middle and 6mm and 8mm solid round bar at the top. Tubes were supplied in 6m lengths and welded together to create continuous lines of tubing for the stretch of the sculpture.

12mm thick stainless steel tubes in the skeleton of the structure extend about half way up and were heat treated in a stress relieving oven. This transformed the colour of the steel into a golden hue to create a contrast effect in the sculpture.

“We cut 30 to 40 small lengths of stainless steel at various thicknesses and baked them at different temperatures from 100˚ C up to 400˚ C. After comparing the various shades and hues, I chose the golden colour in the end which required heating to around 300˚ C,” Buttress said.
Grade 316 polished stainless steel tubing was used for the middle cladding on the exterior of the structure.

Stainless steel rings were laser cut from LDX 2101 plate in various thicknesses from 20mm down to 3mm, and welded to the body of the sculpture to create an intricate lace-like effect.

The main structure was bead blasted to create a uniform finish and all tubes were chemically cleaned.

Both TIG and MIG welding processes were used, with both solid wire and flux cord used in the MIG welding technique. Di-penetration testing was conducted offsite on the welding of the body of the sculpture to ensure structural integrity.

D&R Stainless director Karl Manders said that while fabricating stainless steel was familiar territory, the application was different and stimulating.
“We found the project intriguing because while we were producing a delicate structure, the core components of the fabrication were quite complex. Our business focuses on heavy industrial applications, and the materials we used for Venus Rising are those used in the heart of the mining and petrochemical industries,” Manders said.

“The experience of this project was intense but satisfying. We made Wolfgang’s vision come to life.”

Buttress said D&R Stainless was a perfect fit for the project and they will also be on board for an upcoming sculpture for The University of Canberra.

“Their understanding of the properties of stainless steel was second to none and their craftsmanship exemplary. It was great to witness such pride in their workmanship,” Buttress said.

Commissioned by the Queensland Government, Venus Rising was selected in a public vote as the winning design from over 60 submissions and was unveiled in late January 2012.

Photographer: David Sandison. Images courtesy of The State of Queensland, Department of Housing and Public Works.

This article is featured in Australian Stainless magazine, issue 51.

The Go-Between Bridge


Posted 3 May 2012

With 14,000 vehicles crossing Brisbane's Go-Between Bridge every day, stainless reinforcement is playing a vital structural role on Brisbane's first inner city bridge in over 40 years.

Formerly known as the Hale Street Link, the Go-Between Bridge connects Merivale and Montague Streets in West End to Coronation Drive and the Inner City Bypass in Milton.

Constructed as part of the Brisbane City Council’s TransApex plan, the Go-Between Bridge was designed to improve cross-river accessibility, reduce inner city traffic congestion, increase accessibility to Brisbane’s recreational and cultural precincts and cater for future residential developments in West End and South Brisbane.

The $338 million project commenced in 2008 and was built by the Hale Street Link Alliance (Bouygues Travaux Publics, MacMahon Holdings, Seymour Whyte Holding and Hyder Consulting).

The cantilever, box girder bridge stretches 274 metres over the Brisbane River and was built using stainless steel reinforcement with concrete foundations. Featuring a dedicated pedestrian and cyclist pathway, the Go-Between Bridge is 27 metres wide, with the main span measuring 117 metres.

ASSDA sponsor Valbruna Australia supplied 80 tonnes of grade 316L/1.4462 Reval® stainless steel in 12mm, 16mm, and 24mm reinforcement bar, which was used for the two major pile caps and north abutment of the bridge.

Valbruna Australia’s Managing Director, Ian Moffat, said stainless steel was specified for the critical elements of the bridge to minimise life cycle costs, improve structural integrity and corrosion resistance.

“Particularly being located in a marine environment, Reval® stainless in reinforced concrete is ideal to resist chlorides and pitting corrosion; it has an expected service life of 100 years in concrete,” Moffat said.

By specifying stainless, the designers were able to reduce the area in which stainless rebar was used in the structure because of its tensile strength being higher than carbon steel. In addition, using stainless steel reinforcement in concrete structures is stronger than carbon steel and will prevent material fatigue ensuring longevity for public infrastructure.

Moffat said Valbruna had 30% of stainless rebar already in stock, with the rest of the material having been shipped from their warehouse in Dubai and direct from their mill in Vicenza, Italy.

“Between the three locations, we were able to supply the stainless steel early and well within the specified timeframe,” Moffat said.
All Reval® stainless steel was produced and tested on site at the Acciaierie Valbruna S.p.A mill in Italy and manufactured to ISO 9001:2008 norms as certified by Lloyd’s Register Quality Assurance.

The Reval® stainless rebar was delivered to Neumann Steel in Currumbin for scheduling, cutting and bending.

A cut-to-length shear line machine was used, as well as a level off-coil machine to cut and bend the material into the finished product. All machines were cleaned before use to remove dust and carbon steel residue to avoid contamination of the stainless steel.

Neumann Steel’s Reinforcing Scheduler, Greg Prider, said the project was extremely complex and difficult to schedule.
“As the precast concrete units were manufactured at another site, we had tight tolerances to work with. It was critical to be precise in cutting and bending the stainless rebar to avoid unnecessary additional costs,” Prider said.

Following six weeks of scheduling, the stainless rebar was sent to the Brisbane Barge Berth, where precasting of the concrete units were assembled before transporting the modules direct to site by barge for installation.

Named after iconic Brisbane rock band The Go-Betweens, the Go-Between Bridge was completed and officially opened to traffic in July 2010.

This article is featured in Australian Stainless magazine, issue 52.


Posted 3 May 2012

Stainless is a key feature in the urban design and revamp of one of the Gold Coast's most iconic and vibrant tourist destinations.

The $25 million Surfers Foreshore Project was commissioned by the Gold Coast City Council (GCCC) to redevelop the beachfront area between Laycock Street and View Avenue in Surfers Paradise.

Aimed at improving infrastructure and visitor recreation, the new promenade features new lifeguard towers, amenity blocks, beach shelters, picnic areas with barbeques, and increased pedestrian and disability access to the beach.

Managing Contractor Abigroup Contractors Pty Ltd appointed ASSDA member and Accredited Fabricator J&T Mechanical Installation to fabricate and install the stainless steel architectural handrails and balustrades across stages 1, 2 and 3.

Trent Todd, J&T Mechanical Installation’s Director, said that with the handrails and balustrades being installed less than 30m from the shoreline, stainless steel was the only choice to withstand the harsh coastal environment to help resist tea staining and ensure long-term durability and performance.

A 2009 GCCC study in affiliation with Griffith University saw the GCCC adopt stainless steel as the default specification for structures with a design life of more than 19 years in foreshore zones.

This followed research results showing the material required lower maintenance and was the most effective in life cycle costs when compared with hot dipped galvanized (HDG) steel, paint systems and duplex systems using both HDG and paint.

At a total cost of approximately $80,000, the stainless steel handrails and balustrades span 1300m across the esplanade that fronts Surfers Paradise Beach.

Grade 316L stainless steel was specified for these elements of the project, which included 36 sheets of 10mm thick plate measuring 1500mm x 3000mm supplied by ASSDA member Allplates. ASSDA Sponsor STM Tube Mills Pty Ltd supplied 1300m of 50.8mm x 1.6mm thick tube. Another 3500m of 1/4” wire was also sourced for the balustrading.

All the flat and tube components including 124 stanchions were laser cut and folded by Allplates.

Stanchions and base plates were machine polished to 600 grit by ASSDA member and Accredited Fabricator Minnis & Samson to give the stainless steel an even polish and the stanchions a square edge. The stanchions were electropolished before being delivered back to J&T Mechanical Installation’s workshop for assembly.

J&T Mechanical Installation fabricated the top (50.8mm x 1.6mm tube) and bottom (folded channel, 4mm thick) rail frames with two vertical 16mm diameter solid round bar intermediate supports. Infill wires at 6.4mm diameter were positioned with swage fittings and lock nuts on each end to construct the vertical balustrades.

On site, J&T Mechanical Installation completed civil works prior to installation, including pre-drilling with the fasteners for the base plates to which the stanchions were then bolted. The rail frames were welded to the stanchions in 2.1m sections.

Following installation, a proprietary stainless steel cleaner was applied to remove any oxides, and a mild cleaner was followed to provide surface protection and inhibit corrosion.

Architectural feature lighting was installed to illuminate the pedestrian walkways at night.

The Surfers Foreshore Project was completed in April 2011 and today continues to thrive as the Gold Coast’s most popular entertainment precinct where city meets the surf.

Images courtesy of Allplates.

This article is featured in Australian Stainless magazine, issue 51.


Posted 3 May 2012

Stainless steel can provide excellent service underground. It is stronger than polymers and copper and its resistance to chlorides and acidic acids is significantly better than carbon or galvanised steels.

The performance of stainless steel buried in soil depends on the nature of the buried environment. If the soil has a high resistivity and is well drained, performance can be excellent even in conditions where other unprotected materials suffer degradation.

BASIC RULES

The Nickel Institute guidelines for burial of bare stainless steel in soil require:

  • No stray currents (see below) or anaerobic bacteria
  • pH greater than 4.5
  • Resistivity greater than 2000 ohm.cm.

Additional recommendations include the absence of oxidising manganese or iron ions, avoidance of carbon-containing materials and ensuring a uniform, well drained fill. If the guidelines are breached, then either a higher resistivity is required, i.e. measures to lower moisture or salts and ensure resistivity exceeds 10,000 ohm.cm, or else additional protective measures may be required.
In comparison, the piling specification (AS 2159) guidelines for mild steel require a pH greater than 5 and resistivity greater than 5000 ohm.cm for soils to be non-aggressive. It is rare for bare mild steel to be buried, i.e. typical specifications include a wrap or coating possibly with a cathodic protection system.

SPECIFIC ISSUES

  • Uniform soil packing is required as variable compaction can induce differential aeration effects.
  • Avoid organic materials in the fill around buried stainless steel as they can encourage microbial attack.
  • Avoid carbon-containing ash in contact with metals in soils. Localised galvanic attack of the metal can occur.
  • Oxygen access is critical. Having good drainage and sand backfill provides this. A sand-filled trench dug through clay may become a drain and it is not appropriate. Stainless steels generally retain their passive film provided there is at least a few ppb of oxygen, i.e. 1000 times less than the concentration in water exposed to air.
  • Chlorides are the most frequent cause of problems with stainless steels. In soils, the level of chlorides vary with location, depth and, in areas with rising salinity, with time.  High surface chlorides may also occur with evaporation. This is a problem for all metals although stainless steels are not usually subject to structural failure.

The general guidelines for immersed service are that in neutral environments at ambient temperatures and without crevices, 304/304L may be used up to chloride levels of 200ppm, 316/316L up to about 1000ppm chloride and duplex (2205) up to 3600ppm chloride. The super duplex alloys (PRE>40) and the 6% molybdenum super austenitic stainless steels are resistant to seawater levels of chloride, i.e. approximately 20,000ppm. These guidelines are easy to apply in aqueous solutions.

Soil tests for chlorides may not exactly match actual exposure conditions in the soil. Actual conditions may be more (or less) severe than shown by the tests. The difference is calculable but in practice, the aqueous limits can be used as general guidelines. More specific recommendations, based on published guidelines, are provided in Table 1.

 

 

It may seem redundant to assess both chlorides and resistivity. Both are required as the resistivity is primarily affected by water content and if it is low, then quite high chlorides could be tolerated – as seen by the choice of 304/304L in high chloride/high resistivity conditions.  Despite these recommendations, most Australian practice is to use 316/316L or equivalent, primarily because of variable soils.

  • Good drainage and uniform, clean backfill are essential for bare stainless.
  • Duplex or super duplex could be replaced with appropriate austenitics and 304/304L could be replaced with a lean duplex.
  • Ferritic stainless steels of similar corrosion resistance (usually classified by Pitting Resistance Equivalent [PRE]) could also be used underground.

Potential acid sulphate soils are widespread, particularly in coastal marine areas as described in http://www.derm.qld.gov.au/land/ass/index.html. Once disturbed and drained, which also allows oxygen access, such soils typically become more acidic than pH 4 and will attack metals (although stainless steels will be less readily attacked than other metals). Detailed assessment is required if using metals in such an environment as the effect of other aggressive ions is likely to be more severe at low pH.

  1. Properly specified stainless steel can provide the longest service underground. It is strong compared to plastics and copper, and is more reliably corrosion resistant than carbon steel.
  2. Table 1 guides grade choice for soil conditions.
  3. Normal fabrication practices apply: welds must be pickled and carbon steel contamination avoided.
  4. Pipelines must be buried in clean sand or fine, uniform fill in a self-draining trench that avoids stagnant water. Organic or carbonaceous fill must be avoided.

CASE STUDIES

The Nickel Institute published a five year Japanese study in 1988 (#12005) showing 304 and 316 gave good service in buried soil, although vertically buried pipes did suffer some minor pitting and staining apparently due to differential aeration effects.

  • NI #12005 describes a five year burial exposure in Japan at 25 sites with highly varied corrosivity. After five years in marine sites, horizontal 304 pipes showed no pitting but some crevice attack under vinyl wrap. Only one 316 pipe showed any attack.
  • Vertical 304 pipe suffered attack near the base at some sites apparently due to differential aeration effects.
  • An Idaho study of a 33-year NIST burial found 12% Cr martensitics perforated. The ‘lake sand’ site had high ground water with pH 4.7 at recovery. Sensitised 304 was attacked worse than annealed but both suffered attack along the rolling direction from edges.
  • 316 was not attacked even if sensitised.

As noted, duplex stainless steel of similar corrosion resistance (PRE) to 304 and 316, respectively, would be expected to provide similar results when buried.

On a more practical level, there are several common approaches that are used when burying stainless steel:

  • Wrap the stainless steel pipe in a protective material, such as a petrolatum tape, prior to burial. If the wrapping is effective (typically an overlap no less than 55% of the wrap width is specified), then the nature of the external surface of the buried pipe is of no consequence. In this case, stainless steel is only used for its internal corrosion resistance, i.e. its resistance to corrosion by the fluid which the pipe is carrying. Some authorities prohibit this practice because of concerns that damage to the wrap could cause a perforating pit in severe environments.
  • Ensure that the soil environment surrounding the buried stainless steel is suitable for this application. In this case, the trench is dug so that it is self-draining, without there being areas where stagnant water can accumulate in contact with the buried pipe. The stainless steel pipe is then placed on a sand or crushed aggregate bed and covered by similar material. Under these circumstances,  316 grade stainless steel can be quite a suitable choice. US practice is to use 304 but Australian soils are quite variable and there have been mixed experiences with 304.
  • Above ground sections of pipework are often stainless steel as they are at risk of mechanical damage while underground pipework is polymeric - polyethylene (PE) or fibre reinforced plastic (FRP) - despite the risk of damage due to soil movement.

In all of these cases, the assumption is that the stainless steel has been fabricated to best practice. This includes pickling of welds (or mechanical removal of heat tint and chromium depleted layer followed by passivation to dissolve sulphides) and ensuring that contamination by carbon steel has been prevented. It is also assumed that the buried stainless steel does not have stickers or heavy markings that could cause crevices and lead to attack.

STRAY CURRENTS

All buried metals, including stainless steels, are at risk if there are stray currents from electrically driven transport, incorrectly installed or operated cathodic protection systems, or earthing faults in switchboards. Stray current corrosion can be identified as it causes localised general loss rather than pitting. It is also very rapid.

WHAT TEST METHODS ARE USED?

There are Australian and ASTM standards giving basic measurements of resistivity on site with 4 pin Wenner probes or in a soil box in the laboratory. More detailed checking includes water content, chlorides, organic carbon or Biological Oxygen Demand (BOD), pH and redox (or Oxidation Reduction Potential [ORP]) potential – which assess microbial attack risk but also captures the effect of oxidising ions and dissolved oxygen. Most of these test methods are covered in “Soil Chemical Methods: Australasia” written by George E Rayment and David J Lyons and published by CSIRO.

 

SOIL

Natural soils are a mixture of coarse pebbles, sand of increasing fineness through to silts and clays where the particles are less than 5 µm in diameter.  Some of the particles contain soluble salts that, if mixed with water, are likely to be corrosive. Normally, soils also contain organic material from decaying plants or ash, which can provide nutrients for microbial activity or galvanic effects, respectively.

If water is present in the soil, corrosion can take place. Metals below the water table can corrode (following the rules for immersed service). However if the soil is well compacted so oxygen cannot gain access or corrosion products cannot diffuse away, then corrosion would be stifled - even for carbon steel. Above the water table, moisture comes from percolating rain, which will, over time, leach away soluble corrosives and make the soil less aggressive. This also means that in dry climates, salts may accumulate and when there is rain, the run-off or percolating water is very aggressive.  Deposited salts can also be a problem in marine zones almost regardless of rainfall.

Most of the moisture above the water table is bound to particles but if there is sufficient water content, typically more than about 20%, enough water is free to wet buried metals.

Image pictured is the Appin Sewerage Treatment Plant, NSW. Fabricated and installed by ASSDA member and Accredited Fabricator Roladuct Spiral Tubing Pty Ltd using 316 grade stainless steel. Image courtesy of Roladuct Spiral Tubing Pty Ltd.

This technical article is featured in Australian Stainless magazine, issue 51.


Posted 3 May 2012

As bottled water continues to gain popularity in Australia, maintaining the quality and purity of the water extracted from natural springs is paramount.

This is just one example within the food and beverage sector where hygiene is vitally important and, therefore, stainless steel continues to be the material of choice for processing and storage facilities.

In 2011, Coca-Cola Amatil (CCA) commissioned ‘Project Flint’ to upgrade three spring water storage tanks for their Moorabbin plant in Victoria plus an additional two tanks for their Thebarton plant in South Australia.

GEA Process Engineering Australia engaged Byford Equipment on behalf of CCA to fabricate and install the five storage tanks.

GEA Engineering’s General Manager Operations, Andrew Fillery, said stainless steel was an important specification as the tanks had to cope with the chemical and thermal rigours of cleaning processes.

“Stainless steel was chosen for process and hygienic reasons, and the vessels needed to withstand the process and cleaning conditions where mild caustic and acid CIP solutions were used,” said Fillery.

Strength and durability was key for the 200,000L capacity silos, which measured 4.7m in diameter by 14.5m high for the Moorabbin site and 5.5m in diameter by 10m high for the Thebarton plant.

ASSDA Sponsor Midway Metals supplied 27 tonnes of grade 304 stainless steel coil with a 2B finish in 2mm, 2.5mm, 3mm and 4mm thicknesses. The coil widths were 1219mm and 1500mm.

With a team of five fabricators on the project, the tanks were welded together using a semi-automatic MIG welding process. The welds were then pickled to restore the chromium oxide layer and abstain from rusting.

Byford Equipment’s Project Manager Geoff Smallwood said coordinating the delivery of the tanks was a challenge, given the logistics of travelling through three states by road.

The delivery of the vessels was critical added Fillery, as there were specific installation windows to work within.

The storage tanks were delivered from Byford’s workshop in New South Wales to Moorabbin in March 2011. The two remaining tanks were delivered to Thebarton a month later for installation. It took one day and one crane to install each tank on site.

The connecting pipework was positioned on site, which was grade 304 polished tube in diameters ranging from 38mm to 150mm and purge welded prior to installation.

Images courtesy of Byford Equipment.

This article is featured in Australian Stainless magazine, issue 51.

Where Strength Meets Style


Posted 9 December 2011

Innovation in zoo enclosure design is a key feature of the recently completed $7.5 million makeover of the Chimpanzee Sanctuary at Sydney’s Taronga Zoo.

The project brief was to create a chimpanzee habitat akin to their native home that would encourage social interaction and allow the zoo’s primate keepers to manage animal husbandry and the group’s changing demographic. The enclosure’s transparency and the ability to withstand the chimpanzee’s remarkable strength and intelligence were essential.

ASSDA member Ronstan Tensile Architecture was contracted by the builder, the Lipman Group, to be the specialist contractor for the technical design and installation of a mesh enclosure and non-climbable wall. Ronstan’s unique capability in tensile architecture and their technical expertise were a natural fit for this challenging project designed by Jackson Teece Architects.

The Sanctuary features the mesh separation paddock (similar to an aviary), at one end of the main exhibit. A non-climbable wall with a removable curtain, allows both spaces to function as one large paddock. This enables introductions of new chimpanzees into the compound and helps manage the apes’ complex behaviour patterns.

Ronstan Tensile Architecture’s General Manager, Rowan Murray, said the non-climbable wall structure was one of the most the challenging design aspects.

“The architect’s greatest challenge was to separate the chimpanzees physically, but still have them all in view in the paddock. We had to build a wall that was transparent, had openings of no more than 5mm to avoid chimpanzees putting their fingers in and climbing, and could withstand the strength of chimpanzees.” Mr Murray said.

The structural complexity of the non-climbable wall required 3D modelling to analyse design configurations and ensure structural integrity. Test panels of the non-climbable wall were fabricated and assessed in the chimpanzees’ temporary enclosure to determine which would offer the safest containment of the site and minimise visibility.

Mr Murray said the primary structure for the wall consists of a Ronstan supplied tensile cable net that supports semi-transparent perforated stainless steel panels.

“Most materials can be damaged, but the durability of stainless steel panels of certain perforation proved to be the right solution and important in the development of the overall design,” he said.

“The non-climbable wall had been designed with wall panels clamped directly to the enclosure mesh face. In a collaborative effort, we changed this to an independent cable net structure to remove the risk of having the final wall shape differ from that modelled, and in doing so, avoided the risk of panel geometry differing from the complex 10 degree incline necessary for non-climbability. This also ensured uniform set out and fixing methods, more consistent panel shapes and allowed the panel geometry to drive the wall structure rather than this being determined by other elements.”

ASSDA member, Locker Group, supplied the grade 304 stainless steel panels, which were perforated to 50%. A black painted finish was applied before installation.

With stringent performance characteristics to adhere to, including long-term corrosion resistance and aesthetics, Carl Stahl X-Tend stainless steel mesh was specified for the separation enclosure and the removable curtain within the non-climbable wall. The stainless steel mesh was blackened using an electrolytic process to increase transparency of the enclosure.

Trevor Williams, Lead Consultant of Jackson Teece and Project Architect for the development, said materials selection was critical in delivering the aesthetic appeal and longevity of the enclosure.

“We spoke with Ronstan Tensile Architecture for technical design advice in the early stages of the project. There were various other types of meshes that were a possibility but, being a dynamic structure, alternate materials were far too rigid and not as flexible as the Carl Stahl X-Tend stainless steel mesh. I don’t think we could have achieved this outcome with any other mesh,” Mr Williams said.

“The stainless steel will have a longer life in the aggressive south-facing coastal environment. The blackened mesh has a fantastic form and from an architectural point of view, has achieved an organic appearance.”

Ronstan Tensile Architecture’s contribution to the project, including the tensile mesh enclosure and non-climbable wall, cost about $1.2 million and took 16 weeks to construct.

Mr Murray said the stainless steel demonstrates a great mix of strength and transparency, and the end tensile result is very forgiving.

“Achieving the architectural intent involved complex modelling and finite analysis of the mesh form to ensure the surrounding structures could be designed to support the enclosure loads. Ronstan is absolutely rapt with the state-of-the-art structure,” he said.

The paddock was completely re-landscaped and the impressive exhibit also now features several climbing platforms at varying heights of up to 12 metres, and a 180 kilogram hammock for the chimpanzees to enjoy.

The 17 lucky Taronga Zoo chimpanzees moved in to their renovated home in late September 2011.

QUANTITIES AND GRADES OF STAINLESS STEEL USED

›    Mesh enclosure 770m² of 3mm Ø x 60mm blackened stainless steel, grade 316 Carl Stahl X-Tend mesh.
›    Non-climbable wall facade 140m² of grade 304 stainless steel perforated to 50%, with a black painted finish.
›    Cables 1x19 construction 8mm, 12mm and 22mm diameter, grade 316 stainless steel cables. The stainless steel cable end fittings and  components were polished and passivated prior to installation.

Images courtesy of Ronstan Tensile Architecture.

This article features in Australian Stainless magazine - Issue 50, Summer 2011/12.


Posted 9 December 2011

Fabricating equipment for the chemical sector requires solid high quality materials and superior workmanship. In April 2011, ASSDA member and Accredited Fabricator U-Neek Bending Co Pty Ltd put the finishing touches on a radiant helical coil at their factory in Dandenong, Victoria.

 

The coil, designed as a heater for Titanium Tetrachloride (TiCl4) production, is 11.4 metres long with a diameter of 3.05 metres and required more than 7 tonnes of high grade Inconel Alloy.

U-Neek’s Business Development Manager, John Lovell, said the client chose to have this material shipped from America.
“At around US$1000 a metre, Inconel Alloy is a very expensive option but it has great heat transfer properties and is completely non-corrosive,” Mr Lovell said.

The Western Australian client, who declined to be named, were looking for a fabricator that, in addition to having a proven record in metal bending, could work to their particular requirements for this critical process componet.

“U-Neek weren’t just competitive in pricing,” said Greg, a project engineer with the client. “They succeeded with all the trial projects we sent them.”

“To ensure total quality control, we provided a comprehensive report that detailed every step of the process, including the names of every person who worked on the individual stages,” Mr Lovell said.

U-Neek Engineer Dale Theobold said  the coil was manufactured to exacting tolerances using a range of Inconel Alloy materials.
“We used 150NB Schedule 40 seamless 600 for the pipes and flanges, 366-04 WPNCI-S for the elbows, B168-08 for the plate and 253MA for the high temperature pieces,” he said.

Once completed, the coil then had to undergo a rigorous series of tests. The butt welds were verified with full radiography, the attachment welds were submitted to liquid penetrant inspection (LPI), and a full hydro exam was done on the coil itself.

“The coil was filled with distilled water to test its heating capabilities. Then the coil was pressurised with nitrogen, to a dew point of -12°, to remove all traces of water and moisture prior to transporting,” Mr Lovell said.

The transport frame and mounting jigs were manufactured from mild steel. To ensure no cross contamination, Inconel strips were fitted to the mounting points. The coil was lifted onto the back of a semi-trailer for final transportation to Perth, using U-Neek’s 16 tonne travelling overhead cranes.

Images courtesy of U-Neek Bending Co Pty Ltd.

This article features in Australian Stainless magazine - Issue 50, Summer 2011/12.


Posted 9 December 2011

The greatest challenge we face is the control of our own success. With 7 billion people on earth, all with an insatiable appetite for a high standard of living, the newest dimension of materials competition is sustainability.

Sustainability is development that meets the needs of the present without compromising the ability of future generations to meet their own needs (UN World Commission on Environment and Development, 1987). In real terms, that means making choices that do minimum damage to our environment, but support a high level of human development.

The built environment is an excellent place to start. Buildings last for a long time, locking up the energy used in making their materials, requiring maintenance and consuming the energy used for heating and air-conditioning. They consume a large proportion of our resources. The choice of materials affects all 3 aspects of consumption, and, a number of building evaluation systems have been created around the world to assist in rating buildings for sustainability. Materials are scored for their energy content reuse during major refurbishment, waste management, recycled content and contribution to the overall design and running costs.

The Green Building Council of Australia rates green buildings for sustainability. The pace of registration and certification is increasing. Of the 368 certified projects, 96 were certified in the last 12 months. The push towards sustainable development in the building sector is strong and accelerating. City of Melbourne’s Council House 2 (CH2) is Australia’s first Green Star rated building to be awarded 6 Stars, which carries an international leadership status. Stainless steel was used to support screening walls of living green plants that shade the building and, required no maintenance or painting, working with the environment to keep good working conditions. Such membranes, containing plants or actively or passively screening the sun, allow the use of a smaller capacity air-conditioning plant, with lower capital costs and ongoing running costs and energy demand.

The only Gold LEED® (Leadership in Energy and Environmental Design) certified meeting venue in the world is the Pittsburgh Convention Centre in the United States. Its grade 316 stainless steel roof is used to harvest rainwater, reducing water demand on th

e city system - another example of the special properties of stainless steel.

Stainless steel roofing and rainwater goods give extremely low levels of run-off. See Table 1. But this is not the only reason to use stainless steel in the built environment. It contributes to sustainability because of its long service life, excellent corrosion resistance, clean and unchanging appearance and its exceptional hygiene characteristics. Stainless steel is reusable, entirely recyclable, and probably the most recycled product in the world. On top of that, it needs very little cleaning or short or long term maintenance, and makes no contribution to indoor pollution as materials emitting volatile organic compounds (VOCs) do.

There is considerable history and experience of stainless steel service life in the built environment. The Chrysler Building (1930) and Empire State Building (1931) in New York demonstrate the material’s durability, excellent appearance and resistance to corrosion. This extraordinary functionality has been played out many times with a number of examples here in Australia, including the Fujitsu Building in Brisbane, which is clad with 445M2 ferritic stainless steel. Located in a marine industrial environment, this building looks as good as it did on completion in 2002. The long life of stainless steel in these atmospheric applications shows its very high corrosion resistance. The corrosion rate of grade 316 for instance in most atmospheres is is more than 5000 times slower than the rate of carbon steel. See Figure 1 (below).

There is a considerable industry devoted to the collection and recycling of stainless steel products at the end of their life and, scrap is the standard feedstock for making stainless steel. In any stainless steel object, there is an average of 60% recycled content. New production would virtually all be made from recycled stainless steel if it were available, but the growth in the use of stainless steel and its long life in service limit the supply. Table 2 compares the recycled content and end of life capture rate of the industrial metals, and demonstrates that stainless steel is the most recycled industrial metal.

Sustainability is about much more than recycling. The energy used to make the material has a direct impact on sustainability, and all metals are energy intensive. Energy is a scarce resource, generates greenhouse gases and creates specific demands on land use likely to impact on future generations. Longevity and extraordinary recyclability will not be helpful if stainless steels’ energy consumption is much higher than other materials. Figure 2 describes the embodied energy in terms of CO2 equivalent for some of the industrial metals, and shows that stainless has a comparatively high level of embodied energy. In kilogram of CO2  per kilogram of metal, the austenitic grades are over double the footprint of carbon steel, although the ferritic grades are a little less. The footprint of stainless steel is caused by the production of alloying elements nickel and chromium, which are needed to give stainless steel its special properties, including extremely long life. Even so, efforts are ongoing in the stainless steel industry to reduce the energy content.

But in the real world, kilogram CO2  per kilogram metal comparisons are misleading. Take a typical application; a box gutter on a building. The metals have different strength, so are used with different thickness. Stainless steel gives a relatively light weight gutter (see Table 3), and hence the lowest footprint as installed. Coupled with its extended durability without maintenance, stainless comes out as the most sustainable option. Painted galvanised or Zincalume® coated carbon steel has not been included in the table as the calculation of the contributions of the components were too complex, but these materials are highly unlikely to beat the sustainability of stainless steel, even as-installed, and they have a much shorter life.

In summary, stainless steel has excellent recyclability, energy content as-installed (at least as good as other metals), extraordinary longevity and next to no need for maintenance, ever. Add to that the benefits of their special properties, which allow for the construction and operation of buildings at a lower cost. The contribution of stainless steel to sustainability is obvious and considerable.

This article was prepared by ASSDA Technical Committee member, Alex Gouch from Austral Wright Metals.

This technical article is featured in Australian Stainless magazine - Issue 50, Summer 2011/12.


Posted 9 December 2011

Stainless steel’s star has ascended in the public’s conscience as thousands of Westfield Sydney shoppers enjoy the world-class design and materials on show in its newest retail development.

Covering 103,000m2, the $1.2 billion Westfield Sydney development is bound by the Pitt Street Mall and Market and Castlereagh Streets in the heart of Sydney’s CBD. It integrates Westfield Centrepoint, the Centrepoint Convention Centre, Imperial Arcade and Skygarden, plus a new office tower at 85 Castlereagh Street and an extensively modified and refurbished tower at 100 Market Street.

While the size of the project is enormous, it’s the design that’s turning heads. With a nod to lauded international developments in Paris and Frankfurt, the architects of Westfield Sydney have created a stunning environment that makes extensive use of mirror and hairline finished stainless steel in the interior spaces.

Stainless steel was chosen by Westfield’s architects to create a very upmarket, stylish environment for shoppers. In addition to meeting the design intent, stainless steel also offers durability and ease-of-use during construction.

ASSDA Accredited Townsend Group was chosen to design, fabricate and install stainless steel elements throughout the complex, a task it was confident to undertake due to its experience delivering exceptional quality products to exacting clients, such as Apple Inc.

Townsend was awarded the following elements using only 316 grade stainless steel:

›    8,500m2 of mirror-finished stainless steel troughs and particle board infills in the feature ceilings on levels 3 and 4
›    Composite stainless steel panel cladding of the escalators on all levels
›    Black glass and mirror-finished stainless steel on the escalator soffits in void 4
›    Hairline-finished stainless steel composite panel cladding in voids 1 to 10
›    Mirror-finished stainless steel cladding of the elliptical column in void 1 from levels 1 to 5.

The project’s innovative design and engineering required the use of Townsend’s Vee-Cutter, the only one of its type in Australia, to create a very tight radii on the corners on some of the architectural elements. No additional services or treatments were required before or after installation as the stainless steel was procured with a protective film that remained on the product through the manufacturing process until the installation was complete.

Townsend Managing Director and CEO Russ Hill stated that the company was excited when selected for this prestigious development. The complexity of the project presented many challenges which Townsend was able to meet through its skill and experience, resulting in a finish which met the brief set by Westfield and its architects.

Images courtesy of Townsend Group.

This article is featured in Australian Stainless magazine - Issue 50, Summer 2011/12.

Synergy of Lightness and Strength


Posted 9 December 2011

Artist Wendy Mills’ interest in an ancient Sumerian myth helped bring her vision to reality for a stainless steel sculpture at Willoughby City Council’s new cultural centre.

Described as the cultural home of the North Shore, The Concourse (Chatswood, NSW) incorporates a concert hall, theatre, library, outdoor urban screen, restaurants and retail stores.

Council worked through Pamille Berg Consulting to commission Ms Mills to create an artwork for the library’s water court, which is located below ground level. The 6.1m sculpture, fabricated by ASSDA Accredited Fabrications Australia, is visible from above as well as from within the library.

Fabrications Australia fabricated the sculpture from 50mm x 50mm x 3mm square hollow sections of grade 316 stainless steel and applied a mirror polish. The joins were TIG welded and carefully ground smooth to ensure a high quality finish.

The sculpture is mounted on a ‘blade’ made from 12mm grade 316 plate that was painted to reduce visibility within the water, so the sculpture appears to float on the surface. As the support structure is bolted into the floor immediately above a carpark, extensive water proofing was required.

Ms Mills said the sculpture was more than 2 years in the making from when it was first conceived. Fabrications Australia and Consulting Engineer, Bernie Davis from Opus, worked together with her design to overcome challenges such as the structural support and ensure a proper balance of geometry, constructability and aesthetics.

Mr Davis said it was the team focus on this total balance that ensured a happy client.

Fabrications Australia Director Shannon Molenaar said the project was a true collaboration that evolved over time. Key issues for the fabrication team were structural integrity and long-term durability.

Ms Mills said she chose to work with stainless steel because no coatings were required. She wanted a mirror finish as it requires very little maintenance and it reflects the environment, making the artwork seem lighter.

For this piece, she envisaged a form of transport halfway between a plane and a boat that would sit lightly on the surface of the water as if it is about to take off, yet from above it would appear like a winged insect that has just landed. Her goal was to create a ‘stillness’ – a space for reflection, transition and transformation.

She said her initial concepts of a sky boat and transition tied in beautifully with the Sumerian myth of Inanna and the location within the library water court in the cultural precinct. According to the myth, Inanna (the queen of heaven) travels in her sky-boat to visit Enki (the lord of wisdom) who lives in a watery abyss and gives Inanna divine decrees to transform her city into a new centre of civilisation and culture.

The end result of this successful collaboration is an artwork that purveys a sense of peacefulness while showcasing the versatility and durability of stainless steel in a water environment.

Images courtesy of Wendy Mills.

This article is featured in Australian Stainless magazine - Issue 50, Summer 2011/12.


Posted 9 December 2011

A worrying trend among Australia's major resource companies is the increasing amount of engineering, detailing and fabrication work being sent offshore - a move that has had significant impact on local fabrication. But there are some positive signs in the food and beverage sector that local fabricators are more than capable of meeting design and fabrication expectations.

When ASSDA member and Accredited Fabricator, A&G Engineering, put in a bid to build 10 x 100 hectolitre beer fermenters for Casella Estate - a company best known for their Yellowtail wine label - they had to compete against companies as far away as Europe for the coveted project.

But A&G had a few advantages over the offshore companies: they had worked with Casella before, fabricating 88 x 1.1 million litre wine tanks for the company’s tank farm in Yenda, NSW; they have supplied stainless steel tanks to Australia’s leading breweries, wineries and beverage companies; and they are one of the largest users of stainless steel in Australia.

A&G’s win is an important victory for the Australian industry as a whole and another milestone for A&G Engineering, which was founded in 1963.

The five-month Casella Brewery project, completed in August 2011, saw 25 of A&G’s 200 staff use 65 tonnes of 304 grade stainless steel (including 2-4mm coil and 8mm plate) to build the 10 vessels.

A&G’s Design Manager Heath Woodland said the tanks were designed to AS1210-2010 pressure vessel standards, in order to withstand a pressure rating of 115kPa.

The stainless was welded with A&G’s semi-automated welding process and the internal welds were polished to achieve a 0.6Ra surface finish, to meet beverage industry standards of a food grade finish.

A&G built the vessels at their Griffith and Irymple plants, before transporting them to Yenda. With the beer fermenters now in place, it is hoped the Casella Brewery will be operational by the end of 2011.

Images courtesy of A&G Engineering.

This article is featured in Australian Stainless magazine - Issue 50, Summer 2011/12.

 

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Posted 25th September 2009

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Posted 25th September 2009

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Australian Stainless is a leading industry magazine devoted to showcasing the unique diversity and durability of stainless steel. Since its inception in 1993, Australian Stainless has assisted and encouraged specifiers and end users of stainless steel, with a focus on local fabrication.

For 17 years, Australian Stainless has been enjoyed by more than 8,000 readers across the country. In October 2009, Australian Stainless Online was launched to provide a readily available live news feed to a wider audience around the world. Australian Stainless is published by the Australian Stainless Steel Development Association (ASSDA), a non-profit industry group that aims to increase the consumption of stainless steel in Australia, through publication, education, accreditation and more.

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Posted 17 May 1999

If a job requires greater corrosion resistance than grade 304 can provide, grade 316 is the 'next step up'. Grade 316 has virtually the same mechanical, physical and fabrication characteristics as 304 with better corrosion resistance, particularly to pitting corrosion in chloride environments.

Grade 316 (U NS S31600) is the second most popular grade accounting for about 20% of all stainless steel produced.

This article follows on from "304 -the place to start" in Issue 10 which is also available on ASSDA's website at www.assda.asn.au

COMPOSITION
Table 1 compares three related grades - 316, 316L and 31 6H.

Grade 316L is a low carbon 316 often used to avoid possible sensitisation corrosion in welded components.

Grade 316H has a higher carbon content than 316L, which increases the strength (particularly at temperatures above about 500°C), but should not be used for applications where sensitisation corrosion could be expected.

Both 316L and 316H are available in plate and pipe, but 316H is less readily available ex-stock. 316L and 316H are sometimes stocked as standard 316 (test certificates will confirm compliance with the 'L' or 'H' specification).

CORROSION RESISTANCE
Grade 316 has excellent corrosion resistance in a wide range of media. Its main advantage over grade 304 is its increased ability to resist pitting and crevice corrosion in warm chloride environments. It resists common rusting in virtually all architectural applications, and is often chosen for more aggressive environments such as seafront buildings and fittings on wharves and piers. It is also resistant to most food processing environments, can be readily cleaned, and resists organic chemicals, dye stuffs and a wide variety of inorganic chemicals.

In hot chloride environments, grade 316 is subject to pitting and crevice corrosion and to stress corrosion cracking when subjected to tensile stresses beyond about 50°C. In these severe environments duplex grades such as 2205 (UNS S31803) or higher alloy austenitic grades including 6% molybdenum (UNS S31254) grades are more appropriate choices.

The corrosion resistances of the high and low carbon versions of 316 (316L and 316H) are the same as standard 316.

HEAT RESISTANCE
Like grade 304, 316 has good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. Continuous use of 316 in the 425-860°C range is not recommended if subsequent exposure to room temperature aqueous environments is anticipated, but it often performs well in temperatures fluctuating above and below this range.

Grade 316L is more resistant to carbide precipitation than standard 316 and 316H and can be used in the above temperature range. However, where high temperature strength is important, higher carbon values are required. For example, AS 1210 Pressure Vessels Code limits the
operating temperature of 316L to 450°C and restricts the use of 316 to carbon values of 0.04% or higher for temperatures above 550°C. 316H or the titanium-containing version 316Ti can be specified for higher temperature applications.

316 has excellent toughness down to temperatures of liquefied gases and has application at these temperatures, although lower cost grades such as 304 are more usually selected for cryogenic vessels.

PHYSICAL AND MECHANICAL PROPERTIES (see Tables 2 and 3)
Like other austenitic grades, 316 in the annealed condition is virtually nonmagnetic (ie. very low magnetic permeability). While 304 can become significantly attracted to a magnet after being cold worked, grade 316 is almost always virtually totally non-responsive. This may be a reason for selecting grade 316 in some applications.

Annealing (also referred to as solution treating) is the main heat treatment carried out on grade 316. This is done by heating to 1,010-1,120°C and rapidly cooling - usually by water quenching.

FABRICABILITY
316 can be deep drawn without intermediate heat softening enabling it to be used in the manufacture of drawn stainless parts, such as sinks and saucepans. However, for normal domestic articles the extra corrosion resistance of grade 316 is not necessary. 316 is readily brake or roll formed into a variety of other parts for application in the industrial and architectural fields.

Grade 316 has outstanding weldability and all standards welding techniques can be used. Although post-weld annealing is often not required to restore 316's corrosion resistance (making it suitable for heavy gauge fabrication) appropriate post-weld clean-up is recommended.

Machinability of 316 is lower than most carbon steels. The standard austenitic grades like 316 can be readily machined if slower speeds and heavy feeds are used, tools are rigid and sharp, and cutting fluids are involved. An 'improved machinability' version of 316 also exists.

COST COMPARISONS
The guidelines in Table 4 are approximate 'first cost' comparisons for sheet material in a standard mill finish suitable for construction projects. The appeal of stainless over its first cost competitors dramatically increases
when lifecycle costs are considered.

FORMS AVAILABLE
Grade 31 6 is available in virtually all stainless product forms including coil, sheet, plate, strip, tube, pipe, fittings, bars, angles, wire, fasteners and castings. 316L is also widely available, particularly in heavier products such as plate, pipe and bar. Most stainless steel surface finishes, from standard to special finishes, are available.

APPLICATIONS
Typical applications for 316 include boat fittings and structural members; architectural components particularly in marine, polluted or industrial
environments; food and beverage processing equipment; hot water systems; and plant for chemical, petrochemical, mineral processing, photographic and other industries.

Although 316 is often described as the 'marine grade', it is also seen as the first step up from the basic 304 grade.

Alternative grades to 316 should be considered in certain environments and applications including:

• strong reducing acids (alternatives might be 904L, 2205 or a super duplex grade),
• environments with temperatures above 50-60°C and with chlorides present (choose grades resistant to stress corrosion cracking and higher pitting resistance such as 2205 or a super duplex or super austenitic), and
• applications requiring heavy section welding (316L), substantial machining (an improved machinability version of 316), high strength or hardness (perhaps a martensitic or precipitation hardening grade).

 

This technical article featured in Australian Stainless magazine - Issue 13, May 1999.


Posted 17 May 1999

The devastation of the 1989 Newcastle earthquake resulted in a revision of standards specifying building materials and products to be used in differing environments.

One of the products that came under close scrutiny was wall ties (also known as brick ties).

Assessment of the damage after the earthquake found that many walls had 'peeled away' from building structures due to deteriorated wall ties.

A wall tie connects masonry to the structural backing which supports the wall. The most common wall ties are manufactured out of galvanised steel.

Australian Standard AS 3700 - 1998 revised the conditions under which wall ties are used and made recommendations about the types of material that should be used in different environments.

The Standard specifies that 316 or 316L stainless steel wall ties should be used in 'R4' category environments. These are severe marine environments, usually up to 1 00 metres from a nonsurf coast or one kilometre from a surf coast, where the highest airborne salinity level at the exterior of the masonry is 300 g/m2/day.

In such environments the chlorides in the air make it highly corrosive and not suitable for wall ties manufactured from materials that are susceptible to corrosion.

However this requirement is the subject of debate, with some specialists suggesting that corrosive environments stretch well beyond the distances specified in the Standard.

The use of stainless steel wall ties as suggested in the Standard will increase the safety and durability of buildings in corrosive environments for a very small increase in the overall cost. This again leads to the debate about what constitutes a corrosive environment, and whether the Standard should be more conservative.

The revised Standard has been incorporated into the Building Code of Australia and is mandatory for many provisions in the Code. The Australian Building Codes Board anticipates AS3700 - 1998 will become mandatory for the Housing Provisions in January 2000.

Thus, opportunities exist for the stainless industry to be proactive in its approach to such issues, as well as to investigate the use of stainless in other building applications, where durability and strength are principal concerns.

This article featured in Australian Stainless magazine - Issue 13, May 1999.


Posted 1 March 1998

Stainless steels are now cheaper than ever, but there is still room to minimise costs (see Table 1), which will improve the bottom line for individual companies, projects and the industry as a whole.

Flat productsAustralia is a relatively 'small fish' in the global stainless industry and, without the benefit of local stainless steel production, loses some flexibility on product availability. Unless you're a very large consumer of stainless steel to a single specification or Standard, ordering to common specifications will reduce costs and increase availability of products.

Flat Products - Table 1Suppliers are likely to have products to common specifications. Ordering them reduces the need for slow moving stock, increases stock turns, raises the size of single orders, and can substantially reduce costs. A similar mechanism works for mill or mill indent orders.

Flat products

Until recently, stainless steel flat products manufactured to Australian Standard 1449 were the most widely available in Australia. However, since the closure of BHP Stainless in 1997, products manufactured to this Standard are no longer commonly produced. More common international specifications will need to be recognised in Australia if economies are to be achieved (see Table 2).

Fortunately, the transition may not be difficult, because AS1449 was closely aligned with the ASTM Standards from the USA, which are also similar to the Japanese JIS Standards. Steels identical to AS1449 in nomenclature, chemical composition, mechanical properties and surface finish are readily available internationally.

Today the most commonly available stainless flat product in Australia is manufactured abroad to ASTM A2401A240M Standard specification for heat resisting chromium and chromium-nickel stainless steel plate, sheet and strip for pressure vessels, which nominates ASTM A4801A480M for additional general requirements of the steel ('M' designates the metric version, which is more appropriate in Australia).

European specifications are also emerging and EN 10088 Stainless steels has the potential to become a common specification in the Australian market. EN 10088 makes use of the established German names and numbers for stainless steel grades, Many grades in EN 10088 have close equivalents in the ASTM based Standards, but the nomenclature for grades and finishes is very different and replacements should be examined carefully. For example, in AS1449, ASTM A240M and JIS G4305, grade 304 (the most common stainless) has a minimum of European specifications are also emerging and EN 10088 Stainless steels has the potential to become a common specification in the Australian market. EN 10088 makes use of the established German names and numbers for stainless steel grades. Many grades in EN 10088 have close equivalents in the ASTM based Standards, but the nomenclature for grades and finishes is very different and replacements should be examined carefully. For example, in AS1449, ASTM A240M and JIS G4305, grade 304 (the most common stainless) has a minimum of Ordering at standard width and thickness is the best way to keep steel costs down. Each mill has equipment capable of a certain maximum width and running narrower steel is less productive.

The standard width varies from mill to mill (see Table 3), with most European mills manufacturing at 1,200mm or 1,250mm wide, with a few capable of 1,500mm and, for some thicker coil products, 2,000mm. Mills in Asia tend to standardise on the imperial widths 3', 4' and 5' (914mm, 1,219mm, 1,524mm).

Conclusions

An understanding of commonly used specifications can lead to more efficient and cheaper practices. If questions arise, your supplier or fabricator may have information on alternative Standards that are more commonly available and more suited to your requirements.

Flat Products - Table 2

 

This article featured in Australian Stainless Issue 11 - March 1998. More current information can be found in ASSDA's Australian Stainless Reference Manual.


Posted 1 March 1998

Stainless steel forms a significant part of a beef abattoir, including the conveyors, fixed and elevated platforms, sterilisers, chutes, hand wash basins and, of late, water supply and wastewater piping. The stainless component may now expand even further in new abattoirs with the recent development of cast stainless steel skids and forged hooks for use on dressing conveyors.

AbattoirDressing conveyors in beef abattoirs traditionally use rollers rather than a skid system or, in some cases, extruded aluminium skids and hooks are used. Both of these systems have limited service lives due to the weight of the beasts. They also result in downtime when cleaning and, in the case of rollers, lubrication is required. Hygiene is critical throughout the trimming process, as the carcass' meat is exposed to the environment.

G & B Stainless (Crestmead, Old) and Meateng (Melbourne, Vic) recognised the need to develop a dressing conveyor system which would allow a rapid turnaround of hooks while assuring a high level of hygiene.

Using stainless steel would provide sufficient strength to hold heavy carcasses (weighing up to 1,000kg), while allowing the skids and hooks to simply pass through a washbox for sterilisation on their return to the starting point of the conveyor.

The project has evolved over six months from a prototype fabricated skid, which did not provide enough strength, to the existing cast skid and forged hook. The cast skid also incorporates a high density polyethylene insert, which is the only component to experience wear during service. This insert can be replaced at low cost when required.

The skids are cast by Austcast Stainless (Northgate, Old) using a vertical joint automoulding sand casting system. Grade AS2074 H5A (equivalent to AISI 304) stainless is used and full traceability exists for the castings, The stainless hooks are forged by John Ure (Wacol, Qld). Production costs are comparable with extruded aluminium skids, but the low rate of replacement makes the lifecycle costs very attractive.

Over 1,000 stainless steel skids and hooks have been in service at Stockyard (Grantham, Qld) for six months and, according to site engineer, Roger Tocknell, they have been performing excellently.

The new skids are not interchangeable with existing mild steel rollers, but G & B Stainless' Director, John Van Koeverden, said the company's next goal is to develop stainless rollers which can be used on existing conveyors.

This article featured in Australian Stainless Issue 11 - March 1998.