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Stainless Takes Flight

Lightweight stainless steel sheet, polished to a high level of reflectivity, has been chosen to interpret the layered feathers of one of Australia's national icons, the dancing brolga. 

Designing and creating a trio of life-size sculptures has occupied much of Allen Minogue's time since his retirement as an engineer and designer.

The birds, inspired by a visit to the Northern Territory, have cast grade 316 legs and heads and feathers made from 2B finish 316 sheet in four
thicknesses, from 0.55mm to 1.2mm.

The feathers are all individually shaped using a hand guillotine and other hand tools. They are then screwed into a fibreglass body moulded from a wooden carving. The first figure, which took 700 hours to complete, has 700 feathers. The poses are realistic, with the central male bird
captured at the moment of taking flight.

This article featured in Australian Stainless magazine - Issue 22, September 2002.

 

Stainless Memorial to Rail Workers

Stainless steel responds admirably to the strength and durability imperatives of public art at the Ipswich Workshops Rail Museum, opened to the public earlier this month.

The Workshops began operations in the 1860s and initially assembled components imported from England, but by the early 1900s railway stock was being manufactured from the ground up. During the peak employment period of the 1950s there were over 3 000 workers. To reflect the Workshops’ importance in shaping the identity of the town of Ipswich, west of Brisbane, the design brief called for a monument concentrating on the social history of the Workshops and the contribution of the vast number of workers, interpreted in a contemporary framework.

In response, Brisbane sculptor Brad Nunn designed MARKER, a curving stainless steel column bearing the words spirit and presence,studded with numbered discs representing individual workers.

Each worker had a disc resembling a dog tag known as a check, which he collected from the foreman on arrival at work. He used the check throughout the day, for example to borrow tools, and returned it when clocking off. Railway authorities calculated the workers’ pays by seeing which checks had been collected each day.

Nunn obtained a first-hand account of life at the Workshops from his father, an apprentice there in the late 1940s. He chose the text to communicate the strong spirit of place he felt when touring the Workshops and selected a photo of payday, 16 July 1924, which was reproduced at eye-level using laser marking to retain tonal variations.

Nunn, who has been practicing artist since graduating from the Queensland College of Arts in 1990, has previously designed public artworks
using aluminium. He chose stainless steel for this project because it fulfilled the brief’s requirements for durability, longevity and vandal-resistance.

Fabrication of the sculpture was carried out over 300 hours by two staff members of ASSDA member Stoddart Metal Fabricators. The 3m high structure weighs about 1 tonne. Grade 316 plate in 10mm thickness was used; the hundreds of round recesses were milled out and the column bead-blasted and finished with a no.4 vertical polish. Approximately 600 checks are attached to the sculpture and another 600 appear to have been dislodged and are glued to the concrete base around MARKER.

This article featured in Australian Stainless magazine - Issue 22, September 2002.

New Technology for Design Excellence

The overwhelming response from the architecture community to our earlier article on precision folding of stainless steel sheet using vee-cutting technology has prompted a more in-depth look at the process. 

Thanks to vee-cut technology, stainless steel sheet can be formed into angles as precise as those obtained by extrusion. This technology is now being carried out in Sydney, allowing the local manufacture of a whole range of stainless steel architectural products. The technique is particularly suited to elements such as door fronts, window frames, shopfronts, showcases, elevator doors as well as all forms of cladding.

In a completely new method of manufacture, vee-cutting can also be used to make flat products such as tread plates for lifts and escalators by removing strips of material to the required width and depth.

CLEAN LINES COMPLEMENT SPECIAL FINISHES
Ordinary bends made on a brake press typically produce a corner radius twice the thickness of the sheet, resulting in a finished product with soft, blurred lines. But with the introduction to Australia of vee-cut technology, it is now possible to produce stainless steel with corners as precise as an extruded angle, such as those found on aluminium window frames.

The method is particularly useful when working with textured and patterned stainless sheet. Such finishes are distorted by the traditional bending method. Using the vee-cut machine, the feature finish is preserved without loss of quality. This makes it the manufacturing method of choice for items such as bar fronts, display cases, door furnishings and a myriad of other uses where appearance counts.

THE VEE-CUTTING PROCESS
The machine cuts a continuous vee-shaped notch in the sheet using a series of five tools, which make repeated passes across the surface. The number of passes required varies depending on the thickness of the metal; generally three or four are needed, but up to 15 can be required for thicker product.

The machine can handle thicknesses in the range of 0.6mm to 6.0mm and is capable of cutting to a minimum depth of 0.4mm and processing sheet up to 4m in length. The sheet is then folded along the groove in a brake press. The depth of the groove can be set for acute angles down to 15°.

When used for cladding, up to 70% of the thickness of the sheet can be removed; however, care needs to be taken not to weaken structural components by removing too much of the thickness. One option is to remove material to obtain a tight corner and then stitch weld to restore strength – it is a matter of weighing up cost and other considerations.

A TYPICAL APPLICATION - ENTRANCE DOORS
An example of the finish available can be seen in the revolving doors of the McKell Building in Sydney (pictured). Byrnes Entrance Technology Pty Ltd (BET) worked with ASSDA member the Townsend Group to produce profiles and folded panel sections to clad the central steel and aluminium core of the triple door. The final effect is the appearance of a solid, triangular-shaped central column with lightly inward-curving sides.

This article featured in Australian Stainless magazine - Issue 22, September 2002.

Stainless, Sun and Air

Stainless steel is well-known as a versatile and attractive medium for large scale public artworks. Two recent projects by Perth’s Stusha Studio make use of different treatments of the material to deliver attention-grabbing results.

INSPIRED BY NATURE
The Armadale Kelmscott Memorial Hospital in WA commissioned shade structures in two courtyards and Stusha Studio responded with four elements, representing a flower, a seed, a leaf and a fruit, inspired by the orchards of the area and the seasons. The structures provide a shadow-play on the courtyard floors and walls, blushing the areas with shade.

The elements are made of stainless steel mesh, rod and square tube and are suspended at 4.4m. The material supply of grades 316 and 304 and support from ASSDA member Stirling Stainless Steel was crucial to the production of the work, fabricated at Stusha Studio and Art Engineering.

As the shades were installed after the hospital was complete, they were made in sections and re-assembled like a kite inside the courtyards. Because the rib-work for the shade structures was garnet-blasted, installation required care to avoid scuffing and this was provided in ample amounts by Damien Costello at Tension Structures.

COLOUR AND MOVEMENT
Hale School in Wembley, WA commissioned a sculptural interpretation of the theme ‘young hearts run free’. Stusha Studio created four stainless steel winged figures, grounded in four points but able to move with the wind, suggesting freedom no matter what the conditions.

The figures are on internal bearings that allow the whole structure to respond to the breeze. Because of their different dimensions the figures move at varying rates, producing an ever-changing kinetic sculpture.

The wings are made entirely of grade 304 stainless steel, cold forged under the largest hammer in the southern hemisphere at Ferrous Forging in Sunshine, Victoria. The sheets were heated by torch, rippled and fabricated by Kevin Burnett at Red Falcon in collaboration with Stusha Studio, in Melbourne. The wings were then shipped to Perth and combined with the rotating shaft, designed by Michael Ong and machined by Medical Engineering.

STAINLESS FOR PUBLIC ART
In carrying out these and other commissions, Stusha Studio has chosen to use stainless steel to deliver artistic concepts because of its robust quality and the easy access to technical advice and expertise. As an artistic material, stainless steel is versatile in the decorative treatments it supports. Text and graphics can be etched into the surface and paint filled if desired, while forging opens up a whole range of colours and effects.

This article featured in Australian Stainless magazine - Issue 22, September 2002.

Walking on Water

Pedestrians using Brisbane’s scenic RiverWalk when it opens next March will be strolling across 150 tonnes of stainless steel reinforcing, embedded in 287 concrete pontoons linked to form an 875 metre long walkway from the CBD along the river to New Farm Park.

Although the 5.4 metre wide walkway will feel like a single solid structure, it is actually made up of a series of 13.5 tonne concrete blocks, half of their bulk floating below the water level.

Stainless steel balustrades will preserve open views across to Southbank and back to the CBD while ensuring public safety. These combine subtly curved 600 grit electropolished handrails which give a wave effect and 320 grit polished end-posts and staunchions with an art deco feel.

An overall Ra of 0.5 mm was specified not just for the aesthetics but to provide maximum corrosion resistance for grade 316 stainless in a marine environment and to minimise tea-staining.

Stainless steel wire strung horizontally between the posts will provide a strong safety barrier while fading to invisibility from just a few metres away. Customised tamper-proof electropolished turnbuckles developed by ASSDA member Ronstan International Pty Ltd and the posts inward-curving profile will ensure that RiverWalk meets stringent safety standards.

Night-time illumination will come from Y-shaped light poles placed at 30 metre intervals and spot lighting will highlight decorative elements such as mosaics.

Each section of the balustrade runs the length of an individual pontoon. Sections are joined with a tapered stainless steel sleeve to absorb the small amount of movement from wave action, expected be around 20mm.

AN INNOVATIVE BASE FOR A SCENIC WALKWAY
Assembly of the concrete pontoons involves advanced construction methods modelled on the latest overseas developments and a similar, but much smaller, floating walkway which was successfully built on Melbourne’s Yarra River.

To obtain the necessary strength and buoyancy, high strength 50mPa concrete is reinforced with grade 316 stainless steel. The 10mm and 12mm diameter rebar is fashioned into a cage around a polystyrene core which takes up 85% of the pontoon’s volume. The corrosion-resistant properties of stainless steel reinforcing enable the pontoon to be built with narrower walls than would be the case with conventional reinforcing creating savings in the amount of concrete required.

With stainless steel reinforcing an impressive lifespan is assured, making it the best long-term option in building assets where longevity is desired. The design life of this structure is 100 years.

Funded by the Brisbane City Council (BCC) and developed by a BCC and consultant design team led by project architect Jan Jensen, RiverWalk is one of the city’s most ambitious and forward looking projects. It uses techniques which are new to Australia and draws on the expertise of many construction professionals including stainless steel materials experts, suppliers and fabricators.

ASSDA’s role in the project included detailed specification advice on all aspects of the stainless steel work and provision of detailed answers to technical issues in design and prototyping.

Construction contractor Smithbridge Australia Pty Ltd heads the project team which also includes a number of ASSDA members, including Pryde Fabrication, Arminox Australia Pty Ltd and Stoddart Metal Fabricators.

This article featured in Australian Stainless magazine - Issue 22, September 2002.

Stainless Braves the Elements

Advanced engineering solutions are required to handle conditions found on offshore drilling and processing platforms. The saltwater environment is highly corrosive, the flare presents extremes of temperature and the force of winds and currents is constant. The most durable and reliable materials need to be employed, which is why stainless steel plays and important part.

An impressive project making use of stainless' strength and corrosion-resistance is the Bayu Undan Gas Project in the Timor Sea, 5OOkm north of Darwin (pictured). Here, stainless steel is used to line the 18" pipelines between the processing platform and the wellhead platform 8km distant and in thousands of metres of pipes throughout the installation.

SPECIALIST BRIDGE BEARINGS
Stainless steel and high nickel alloy bearings support various bridges, including a 225m long bridge from the drilling platform to the flare. The bearings have been designed by specialist engineering and manufacturing firm Ludowici Ltd of Sydney, working closely with the project consultants TIGA JV of Perth. The bearing shown above is mirror polished to slide ±600mm while supporting a 900 tonne load, with operating temperatures up to 220°C due to the flare. In addition to continuous wave action, the bearing is designed to withstand 160 tonnes of transverse load due to gale force winds during tropical cyclones, as well as "bumps" during installation.

Bayu Undan is a project of Phillips Petroleum Company Australia Pty Ltd. Gas and liquid hydrocarbon reserves were discovered in 1995. It is estimated that the 25km by 15km field has a 25 year life and reserves of 350-400 million barrels of hydrocarbon liquids and 3.4 trillion cubic feet of gas. Work on the site is proceeding with full commercial production due by 2004. The first phase of the development, representing a US$1.4 billion investment, involves production and processing of wet gas. A second phase is planned to harvest the field's gas reserves.

Ludowici became involved in Bayu Undan in mid 2001, when it was chosen to design, manufacture, test and supply eight highly complex stainless steel pot-type bearings.

The design team drew on technical expertise of the Australian Stainless Steel Development Association and the Nickel Development Institute to produce a suitable design.

BUILT TO WITHSTAND WIND, WAVES AND WATER
The brief presented some unique challenges including massive steel superstructures requiring high-strength low-friction supports, to be left maintenance-free in a remote, aggressive tropical marine environment. Some were required to have uplift capacity, all were to be resistant to salt build-up, and all were required to be virtually maintenance free for a 25 year life. Whilst the majority of the bearing components ('pot' cylinders and pistons) were made from 316 and 316L stainless steel, the large-movement slide plates were made from grade 2205 duplex stainless steel, with a facing of polished Inconel 625, fully TIG welded around its perimeter. Thermal coefficients of expansion of mating parts were matched. Assembled bearings were tested in overload and friction, both at ambient temperature at 140°C.

The bearings were fabricated at the firm's Castle Hill, Sydney factory and transported to Batam, Indonesia where they were incorporated into the structure for the final trip to site.

The bearings measure up to 2m long and weigh up to 3 tonne each with attachments plates. They were also designed to withstand severe impact during installation.

The various bridges, platforms and piping are currently bring assembled.

For more information on Bayu Undan, visit www.offshore-technology.com/projects/bayu-undan

This article featured in Australian Stainless magazine - Issue 23, December 2002.

Sheer Delight

Stainless Steel Mesh

Woven metal fabrics are a popular architectural product in Europe, where stainless steel mesh is used for a high-level finish in many internal and external settings, such as wall and ceiling panelling, space dividers, external cladding and facades.

Now Sydney firm Interspace Manufacturing Pty Ltd is making and installing woven stainless steel wire mesh screens using metal fabrics from iO Metal Fabrics Pty Ltd, a German firm with an Australian presence and a member of ASSDA.

ASSDA member Interspace has been designing and manufacturing store fittings and custom fixtures for displays and exhibitions since 1970. The firm began utilising stainless steel mesh two years ago and has produced partitions for a number of interiors, including the AMP Building in Sydney and the office of medical supply firm B. Braun, designed by Leffler Simes Architects. Another project is Space 207 in St Leonards, Sydney, which is being billed as "the North Shore's finest office building, so advanced it is destined to lead the way in business premises for a long time to come." The designers of Space 207 set out to create an environment representing "style, sophistication and elegance" and chose stainless steel mesh to complement the building's hi-tech, ultra-modern decor.

Woven stainless steel fabrics are versatile and reliable. Made from corrosion-resistant grade 316 stainless, they are equally at home in hostile external locations requiring stainless steel's hard-wearing capability and in internal spaces where aesthetic values come to the fore. They can be put to a variety of uses, including partitions, wall and ceiling cladding, awnings and sunscreens. In Germany they are also employed in roadside noise reduction barriers.

Stainless mesh is lightweight but strong and it is extremely resilient when subjected to environmental threats such as heavy weather, fire and chemicals.

Like textiles generally, metal fabrics are woven on a loom, producing an attractive array of patterns and textures in a varying degrees of weight and flexibility.

This article featured in Australian Stainless magazine - Issue 23, December 2002.

Coated Abrasives for Surface Finishing - Part 2

The last issue of Australian Stainless contained an overview of coated abrasives and guidelines for achieving the desired surface finish. This technical series continues with a comparison of grit size and hardness. Read Part 1. Read Part 3.

Early versions of abrasive sheets and rolls were made by sprinkling naturally occurring grit, such as sand or emery, onto cloth or paper coated with animal hide glue. The resulting 'sandpaper' was used for surface finishing in woodwork or preparing a surface for paint or varnish. Because the application of the grit was random the product soon became dull and lost its cut.

Not long after the development of paper products, the flexible emery cloth roll made its appearance in metal working workshops as a standard tool for rust removal and light finishing. By contrast, solid bonded grinding wheels were developed for heavy stock removal in foundries.

3 Elements: Backing, Bond and Grain
Modern coated abrasives allow stock removal up to 30 times faster than with a bonded grinding wheel. This superior performance has been brought about by improvements to all three elements of coated abrasives: backing, bond and grain.

Backing
The type of backing used sets the basic design parameters, being: strength, safety, shape, geometry, tolerance and coolant resistance.

Paper - available in various weights up to 300 gsm (grams per square metre) in widths up to 1650mm.

Cloth - cotton, polyester or a mixture, in widths up to 1550mm.

Fibre - 0.7mm (30 thou) vulcanised fibre.

Combination - linen scrim cloth plus paper in widths up to 1000mm.

Polyester film - flexible consistent thickness.

Bond
Natural glues can be used for the matrix supporting the abrasive grain but modern abrasives generally use synthetic thermosetting resins which are stronger, tougher and more heat resistant.

Grain
Abrasive grain provides the cutting edges for surface generation. Common types are:

> Aluminium oxide AI203 available with various surface treatments
> Silicon carbide SiC
> Zirconia Zr02
> Ceramic aluminium oxide SG (seeded gel).

The important characteristics of grain are hardness, friability, toughness and shape.

The graph below shows the hardness of selected materials including abrasives.


Relative Comparison of Grit Size
The selection of the correct grit size and sequence is vitally important in achieving the desired surface finish. The most common grading system in use today is the FEPA or 'P' series (Federation of European Producers of Abrasives).

However, certain products made in the US or Japan may be graded differently. Equivalents are provided in Table 1.

Abrasive Production
The majority of abrasive manufacturers employ a reel to reel process to combine the backing, adhesive bond and grit into an efficient cutting tool.

As shown below, he grain is propelled into the wet adhesive by means of an electrostatic force. This critical part of the manufacturing process ensures a sharp, long lasting product. In order to further secure the abrasive grain, an additional coat of adhesive, known as a 'size' coat, is applied and the whole product is dried and cured. Certain products (called multi-bond or super-sized) have a further coating applied in order to minimise heat build up and subsequent welding action. This feature is particularly important in the case of stainless steel grinding because non-oxidised steels are very reactive at interface grinding temperatures and they combine readily with the aluminium oxide grain. This phenomenon is visible as a silvery sheen on the surface of an abrasive belt. Once the grain has been 'capped' with metal it can perform no further cutting action and merely increases frictional heat and subsequent degradation.


Using Abrasives Economically

There are a number of factors to be considered to obtain best value from coated abrasives. If obtaining a specified, repeatable finish is an important consideration it may be most economical to limit the abrasive belt to a set amount of polishing, for example a certain number of metres of coil. If specific finish is not a criteria the abrasive can be used to the very end of its life. Saving time or power usage and utilising the most technically advanced product can be as significant overall as the amount of abrasive consumed.

 

Table 1 - Relative Comparison of Grit Size

Particle size inches Particle size microns All product other than emery Emery
Grading system Comparable grit symbol Polishing paper Cloth
CAMI FEPA
0.00026 6.5 1200 - - 4/0 -
0.00035 9.0 - - - - -
0.00036 9.2 1000 - - 3/0 -
0.00047 12.0 - - - - -
0.00048 12.2 800 - - - -
0.00059 15.0 - - - - -
0.00060 15.3 - P1200 - - -
0.00062 16.0 600 - - 2/0 -
0.00071 18.3 - P1000 - - -
0.00077 19.7 500 - - 0 -
0.00079 20.0 - - - - -
0.00085 21.8 - P800 - - -
0.00092 23.6 400 - 10/0 - -
0.00098 25.0 - - - - -
0.00100 25.75 - P600 - - -
0.00112 28.8 360 - - - -
0.00118 30.0 - P500 - - -
0.00137 35.0 - P400 - - -
0.00140 36.0 320 - 9/0 - -
0.001575 40.0 - - - - -
0.00158 40.5 - P360 - - -
0.00172 44.0 280 - 8/0 1 -
0.00177 45.0 - - - - -
0.00180 46.2 - P320 - - -
0.00197 50.0 - - - - -
0.00204 52.5 - P280 - - -
0.00209 53.5 240 - 7/0 - -
0.00217 55.0 - - - - -
0.00228 58.5 - P240 - - -
0.00230 60.0 - - - - -
0.00254 65.0 - P220 - - -
0.00257 66.0 220 - 6/0 2 -
0.00304 78.0 180 P180 5/0 3 -
0.00363 93.0 150 - 4/0 - Fine
0.00378 97.0 - P150 - - -
0.00452 116.0 120 - 3/0 - -
0.00495 127.0 - P120 - - -
0.00550 141.0 100 - 2/0 - Medium
0.00608 156.0 - P100 - - -
0.00749 192.0 80 - 0 - Coarse
0.00768 197.0 - P80 - - -
0.01014 260.0 - P60 - - -
0.01045 268.0 60 - 1/2 - -
0.01271 326.0 - P50 - - -
0.01369 351.0 50 - 1 - Ex. Coarse
0.01601 412.0 - P40 - - -
0.01669 428.0 40 - 1-1/2 - -
0.02044 524.0 - P36 - - -
0.02087 535.0 36 - 2 - -
0.02426 622.0 - P30 - - -
0.02488 638.0 30 - 2-1/2 - -
0.02789 715.0 24 - 3 - -
0.02886 740.0 - P24 - - -
0.03530 905.0 20 - 3-1/2 - -
0.03838 984.0 - P20 - - -
0.05148 1320.0 16 - 4 - -
0.05164 1324.0 - P16 - - -
0.06880 1764.0 - P12 - - -
0.07184 1842.0 12 - 4-1/2 - -

Words by Charles Fenton. Charles E. Fenton is Managing Director of Kongspor Abrasive Technologies, Australia. The next article will look at specific finishes and their generation using coated abrasives.

This technical article featured in Australian Stainless magazine - Issue 23, December 2002.

Stainless Enclosures Built to Last

Australian-made weighing technology is the first choice for global giant Caterpillar Inc., the world's leading manufacturer of construction and mining equipment.

Local firm Transcale, designers and manufacturers of electronic weighing equipment specifically for the mining and transport industries, exports its equipment worldwide to over 11 countries in North and South America, Southern Africa and South East Asia.

Transcale's focus on the mining sector means that cutting edge technology needs to be protected from some of the harshest environments in the world. Extremes of heat and clod, record rainfalls, drought, high salt or other corrosive minerals are just a few of the considerations in the design process. Transcale's equipment is housed in stainless steel enclosures.

Over the last six years Transcale has used both 'off the shelf' boxes from companies such as ASSDA member B & R Enclosures, and custom-built stainless steel enclosures. One of the custom-built enclosures manufactured by MT Sheet Metal in Archerfield, Brisbane uses a 316 N4 brush finish stainless steel supplied to MT by ASSDA member Atlas Steels. B & R Enclosures also manufactures its high performance enclosures using grade 316 stainless with an N4 finish and fully welded body to withstand corrosive atmospheric conditions.

Both Transcale and its customers report that they are impressed with the long-term performance of these enclosures. According to Transcale, investing just a few extra dollars up front by choosing stainless for their enclosures produces tangible rewards by way of repeat business and an enhanced reputation.

For example, one of Transcale's major clients, US-based Caterpillar Inc., recently stated its intention to use Transcale truck scales exclusively for all replacement systems in its mining departments globally. Caterpillar's considerations for choice of product were quality and reliability along with appearance and after sales support.

In Australia, a major interstate line haul company has just taken delivery of a third Transcale dynamic axle weighing system, giving it a unit in Melbourne, Sydney and now Brisbane. In Brisbane the system has been installed at the Port of Brisbane facility, where salt air was one of the considerations. This system is protected from the elements by an MT Sheet Metal enclosure.

This article featured in Australian Stainless magazine - Issue 23, December 2002.

Walsh Bay

A Style Statement in Stainless

The transformation of Sydney's Walsh Bay from derelict wharves and sheds into a prestigious residential complex, complete with cultural, retail and commercial facilities, provides a stage for Australian innovation in design and technology, including some of the finest examples of stainless steel structural and architectural applications.

Located amid Sydney's landmarks -the Opera House, Circular Quay, The Rocks and Sydney Harbour Bridge -the Walsh Bay Precinct is said to be "the most significant urban renewal of heritage Sydney to be undertaken for many years."

According to developers Walsh Bay Partnership (WBP), a joint venture project between Mirvac and Transfield, "the redevelopment captures an exceptional balance between Walsh Bay's rich heritage, sympathetic contemporary design, and the vision to revitalise Walsh Bay as Australia's finest new residential address."

The development features 350 luxury apartments, 140 of them located on Pier 6f7, one of the five "finger wharves" constructed between 1906 and 1922 to serve Sydney's expanding commercial shipping activity. But the area's history goes back much further: Walsh Bay was one of Sydney's first industrial ports, dating back to 1820. Like many other city ports around the world, Walsh Bay ceased operations in the '70s and by the late '90s much of the area was unused and neglected.

 

New Technology Preserves Authentic Feel
WBP was formed in '97 to undertake restoration, with an emphasis on conservation strategies such as salvaging the old hardwood timbers and historical artefacts. Over 80% of the original buildings are being retained and the style of new construction is required to evoke and interpret Walsh Bay's rich heritage. Preserving its historic appeal, unique operable louvres which mimic the original timber planks face the 200m long refurbished pier. These are made from aluminium and supported by grade 316 stainless steel brackets. The louvres pivot on stainless steel supports, allowing them to withstand winds up to 130krnlh. As a safety measure, they close automatically if the weather worsens. They were designed by Architectural Glass Projects Pty Ltd, a Sydney firm which specialises in building components such as glass facades, operable louvres, balustrading and specialised glazing.

 

Stainless to Resist Sea Spray
To take best advantage of its Sydney Harbour location, a marina with private boat moorings accessible from ground-level apartments runs along both sides of the pier and features     stainless steel steps, gates and balustrades.

Starting with the right materials and selecting the most appropriate surface finish are key factors for ensuring the quality and life-cycle of the finished project, particularly in harsh marine environments. A surface roughness (Ra) under O.SJ.Jm using 320 grit abrasives was specified for the stainless steel used in this project. Mechanical grinding was followed by electropolishing, a chemical process which smooths and levels the surface, to produce the best protection against tea staining and contamination.

Surface treatments were carried out by two ASSDA members, MME Surface Finishing and Metaglo Pty Ltd. A large proportion of the stainless steel material used was imported large extruded T and 'L' sections up to 150mm deep. MME, which has the capacity to process elements up to 6.5m long by either mechanical means or electropolishing, modified machines and developed new techniques to produce a consistent O.SJ.Jm finish throughout. Components were returned to MME after fabrication for immersion pickling and electropolishing.

An Asset for Sydney
The revitalised Walsh Bay precinct is set to become an attraction for residents and visitors when it opens next year. As well as offices and apartments, the development includes a new cultural centre, an 850 seat theatre, parks, restored bridges and walkways. A promenade will link Walsh Bay to The Rocks and Circular Quay, opening up the foreshore to the public for the first time in over a century.

This article featured in Australian Stainless magazine - Issue 23, December 2002.


Posted 1 July 2003

John Hodgkinson is mad about hams! The managing director of ASSDA member Smo-King Ovens really loves his products and is passionate about helping butchers generate more business through their use.

You may not have noticed these stainless steel ovens that are an important element of nearly every quality butcher shop in Australia. Just as you can tell a good patisserie by their éclairs, you can tell a good butcher by their smoked hams!

Of 304 stainless steel construction, Smo-King ovens are used extensively for smoking and cooking hams, bacon, roast meats, poultry, fish and a wide range of smallgoods. Cakes and pastries can also be made in one oven which can operate at temperatures high enough to allow baking.

“The 304 stainless steel ensures that the ovens are corrosion and stain resistant”, says Hodgkinson. “It also means they are very durable, easy to clean and many health and food safety authorities insist that stainless steel is used in all food processing applications if the equipment comes into contact with the food as it does in a smoke oven – plus it fulfills our requirement for high quality while still providing acceptable cost.

“I’ve been longing to make my own smoked products”, says Wally Dafter. Dafter’s Quality Meats is located in Charmhaven on the NSW Central Coast. “We have one Smo-King oven which operates at least four days a week and currently we produce 10 different types of smoked goods”, he says.

“We reckon our smoked foods are really good”, enthuses Dafter who is planning to enter them in the 2004 Royal Easter Show.

John Hodgkinson believes Smo-King ovens are about 70%-80% of the price of European ovens with similar features. “These ovens definitely allow our customers to add value to their products and their business”, says Hodgkinson.

This article featured in Australian Stainless magazine - Issue 25, July 2003.


Posted 1 July 2003

Consumers expect processed foods to be tasty and nutritious, affordable and safe. To meet these expectations, food contact equipment has to be hygienic and productive.

A manufacturer’s wish list for its food processing components might read like this:

>    durable, with easy release and easy-to-clean surface
>    inert, non-toxic and non-contaminating
>    corrosion-resistant and non-degrading
>    suited to continuous, in-line sanitation and cleaning
>    impervious and non-absorbent to food products, odours, stains and colourings
>    economical, reliable and safe over its entire working life
>    temperature versatile and highly conductive, eg from cooking to cryogenic temperatures
>    smooth, seamless, one-piece construction
>    removable and replaceable
>    repairable/maintainable by existing technologies.

At first sight this seems too much to ask of any single product, but stainless steel conveyor belts fit the bill.

Unique Belting for the Food Industry
Continuous carbon steel belts were introduced into US and European bakeries in the 1920s and are today used primarily for processing baked goods. ASSDA member Sandvik launched a stainless steel belt in 1931 to withstand wet or corrosive conditions in the food and chemical industries.

The product found a foothold in the market and increasingly since the 1960s, the stainless steel belt has moved from being a simple food conveying medium to a processing platform. Now ranging in width from 200mm up to several metres and in solid or perforated forms, stainless belts are used in cooling (chilling, freezing, pastillating, freeze drying), heating (drying, roasting, blanching, steaming) and mass transfer (dehydrating, aeration, dewatering) for value added processing of foods. Stainless provides superb temperature versatility, from -200ºC (in cryo-freezing belt tunnels) up to +300ºC (high-temperature cooking tunnels). It can be continuously sanitised during operation using zoned washing boxes fitted to the lower strand of the belt.

The smooth, continuous stainless belt is also versatile in the types of food product it can convey and process – powdery, granular, fragile, bacterially-sensitive, sticky, viscous, sharp, pasty, slurry, runny, chunky, awkward, hot, oily … you name it, chances are it can be handled by the stainless belt. Accordingly, the stainless belt has found application over wide areas of wet food processing – for dairy, confectionary, meats, seafoods, pet foods, beverages, snack foods, frozen foods, fruit, vegetables and nuts.

Quality stainless belts for the food industry are solid, continuous, smooth and seamless and free of links, hinges, pins, weaves or anything that could trap food residues, dirt and bacteria.

Textured Stainless Brings Increased Efficiency

Case Study 1 - GP Graders
Melbourne-based GP Graders has captured the attention of fresh fruit packers around the world with its innovative grading and packing lines which utilize textured stainless by ASSDA member Rimex Metals.

Its machines, exported to the US, Chile, Switzerland, Norway, Turkey and Spain, are predominantly fabricated from stainless steel sheet and square tube, incorporating textured stainless steel sheet.

Rimex textured 6WL is used under flat conveyor belts and in ‘dead’ areas to reduce friction (wet belt adhesion) and eliminate product build up. The increased rigidity has enabled the company to reduce sheet thickness and fabrication time, which previously required labor-intensive friction reduction techniques. The end result is a lighter and more cost effective product.

GP Graders was established in 1963 to design and manufacture grading and packing equipment for the cherry, pome fruit, citrus, stone fruit and mango industries.

Case Study 2 - Tripax Engineering
Melbourne-based Tripax Engineering has been a major supplier of industrial food processing machinery in Australia for over 30 years, servicing the fresh vegetable, fruit, salad, potato, cheese, cereal/snack food, and frozen food industries and more.

Its diverse client profile ranges from large multinationals to small vegetable growers, and current export markets include the UK, New Zealand, South Africa, and Denmark.

The majority of equipment is purpose designed and manufactured. During the design process, special attention is paid to matching the type of stainless to the product type, whether sticky, wet, powdery, warm and so on. Rimex textured 6WL pattern is often selected for its low adhesion which reduces the chance of product build-up. It also provides extra strength and rigidity in vibratory conveyor equipment.

From washing equipment for the salad industry, to cheese shredders, abrasive peelers and cutting equipment, all Tripax equipment is made to food industry standards and incorporates high-grade stainless steel, food grade plastics and ancillary parts.

Serving the Australian Food Industry
The multiple benefits of stainless belt technology have assisted the development of new food products and will doubtless continue to do so.

As well as making the stainless belts, Sandvik Process Systems also designs, builds and services complete steel belt equipment. In parallel, within Australia, services in stainless steel belt technologies are available from Process Systems Services (PSS) in Sydney and Industrial Marketing Services in Melbourne, with the former having design, light fabrication and maintenance capabilities. Rimex Metals textured product is distributed by ASSDA member Fagersta Steels.

Words by Russell Jackson and Neil Lyons.

Image on left courtesy of Sandvik Steel.

This article featured in Australian Stainless magazine - Issue 25, July 2003.


Posted 1 July 2003

Stainless steel combines structural strength with corrosion resistance to form a superior construction material which additionally supports a range of aesthetically pleasing finishes.

The austenitic grades, typically 304 and 316, are most common and comprise 70% to 80% of all stainless steel used. Their popularity is due to their excellent corrosion resistance and mechanical properties combined with their relatively low cost. Nevertheless, the use of stainless steel hollow sections in construction has been restricted in the past by the unavailability of product larger than 150mm x 150mm x 6mm.

Today, however, the stainless steel industry internationally has the capacity to produce hollow sections up to 300mm x 300mm OD (outside dimensions) in thicknesses up to 12.5mm, matching the size range of carbon steel.

Design Codes and Research
The new AS/NZS 4673 gives minimum design requirements for static load bearing stainless members cold formed from annealed or temper rolled materials. Eurocode 3: Design of steel structures, Part 1-4: General rules - supplementary rules for stainless steel is the draft European standard for structural stainless steel design.

According to AS/NZS 4763, pending the release of Eurocode 3 as a European standard, the National Building Code of Finland used in conjunction with the draft Eurocode 3 part 1.2: General rules, structural fire design contains the most specific guidance on fire design for stainless steel members.

Finnish supplier Stalatube Oy has a research program which has concentrated on maximising stainless steel’s advantages as a construction material – corrosion and fire resistance, mechanical strength, easy maintenance and clean aesthetic looks. Good results have been found particularly in relation to work-hardening, which can more than double yield strength, and hold the increased values at temperatures up to 800°C.

Work Hardening
Normal austenitic stainless steel grades cannot be hardened by heat treatment. Hardening is achieved through cold-forming which increases mechanical properties such as the yield and tensile strength. This is particularly desirable in situations where weight is critical, for example in vehicles, or in construction where the design is enhanced by reducing bulk. Enhanced properties result in cost savings as well. The savings potential can be roughly calculated by comparing the enhanced yield strength to the base yield strength.

According to the European standard EC3 part 1.4 the design is based on the strength values shown in the table below.

Grade 0.2% proof stress, MPa min Tensile strength MPa Elongation A80, % min
EN 1.4301 (closest to grade 304) 220 540-750 45
EN 1.4404 (closest to grade 316L) 230 530-680

40

Table 2 below compares the requirements of EC3 part 1.4 (the European standard for design) and ASTM A666 regarding proof stress (yield) and tensile strength values for austenitic stainless steel grades in cold worked state.

Strength class EN 0.2% proof stress, MPa min Tensile strength, MPa min ASTM A666 nearest temper
C700 350 700 1/8 Hard
C850 530 850 1/4 Hard

he Australian Standard AS/NZS 4673:2001
permits the mechanical properties used for designing with austenitic grades to be established by testing of the finished product, ie, instead of testing a sample of the original plate or sheet, a section of the tube can be stretched to failure in a tensile testing machine to find the proof stress and ultimate tensile strengths. This allows the benefits of increased strength due to work hardening to be included when designing structures to the Australian Standard.

 

Over a short period, austenitic stainless steel sustains its mechanical values at higher temperatures than carbon steel. The figure above shows the reduction factors for elastic-modulus for stainless and 0.2% proof stress for an austenitic stainless steel. The sustainability of mechanical values makes it possible to obtain 30 minute fire resistance in stainless steel structures without any additional fire protection. These mechanical values are accepted in Finland as the basis for fire design in structures made of austenitic stainless steel hollow sections. In Australia it is possible to take advantage of the high temperature properties of stainless steels by carrying out fire tests, or by using the results of fire tests in conjunction with appropriate calculations.

The high temperature properties of stainless steel means that in suitable locations the intumescent coatings or other fire protection materials which would need to be applied to carbon steel are not required, allowing the stainless steel framing to be exposed. This is simpler and results in a much improved appearance and could be more economical and environmentally acceptable.

Designing with Stainless Hollow Sections
The qualities of stainless steel favour lightweight, slender structures, with a modern, classy feel and futuristic overtones. The combination of higher mechanical strength at room temperature and fire resistance makes stainless suitable for glass facades and glass roofs, accessways, stairways and balcony structures. A major application area in Australia is air distribution tube in sewage treatment plants.

For those projects where structural loads are being carried and design strength is critical, structural tube with guaranteed mechanical properties can be obtained; this generally implies a minimum 0.2% proof stress of 350MPa.

Designers opting for stainless steel are discovering that there is a wide range of products on the market. For example, Stalatube’s hollow sections begin with 25mm x 25mm tubes used for decorative purposes and go up to 300mm x 300mm (or 400mm x 200mm) for heavy structures with high load-bearing requirements. Profiles above 100mm x 100mm can be manufactured to customers’ own dimensions for maximum cost effectiveness. Australian stock is generally limited to 150mm in square sections although rectangular sections to 200mm x 100mm are available. Smaller sections down to about 12.7mm are also readily available. In addition to the “direct off mill” tube external finish, which is essentially that of the 2B of HRAP strip from which the tube was manufactured, grit polished product is routinely stocked in most common sizes. The polished finish presents an attractive and cost-effective product for visually exposed building components. Grit polished surfaces not only look more attractive in appropriate applications, the finish is also such that welded joints can be blended in, giving a more finished presentation.

Image 1 A 15m high, 230m long copper wall surrounds the Nordic Embassies in Berlin. A load-bearing stainless steel frame inside the enclosure supports the copper panels. The welded frame is made of polished (grit 320) 316 austenitic stainless steel hollow sections measuring 120mm x 120mm x 5mm. Stainless steel was chosen to satisfy low maintenance requirements and to provide a surface which doesn't react with the copper.

Image 2 Nokia House, Helsinki, has a double facade with single glazing 70cm from the front wall. The double facade has many advantages. The air gap between the wall and glazing cover acts as insulation, reducing the need for heating in winter and cooling in summer. It blocks traffic noise when the internal windows are opened and allows ventilation during rainy weather and below zero temperatures.
The load-bearing structures of the double facade are made from 90mm x 45mm x 3mm austenitic hollow sections with the glass fixed on the narrow side. The dimensions were calculated to satisfy the load bearing needs whilst maintaining the deflection needed to avoid the light atmosphere required. The building is located close to both the sea and the main western suburbs of Helsinki where traffic pollution occurs. Grade 316 tubes were chosen for this harsh environment.
Architect Helin & Co Structural Design Matti Ollila & Co

Words by Pekka Yrjola. Pekka Yrjola is a Research & Development Engineer at Stalatube Oy's head office in Lahti, Finland.

This article featured in Australian Stainless magazine - Issue 25, June 2003.


Posted 1 July 2003

Architect Jan Jensen was a consultant to Brisbane City Council on the design of the Brisbane Riverwalk, currently under construction. The walk will take pedestrians from the CBD to the inner suburb of New Farm along the river.

At this proximity to Moreton Bay, the water is brackish and the air salt-laden - it is destructive to most construction materials. Corrosion-resistant stainless steel was chosen for this landmark project to deliver the 100 year service life required by the asset owner.

The structure consists of floating pontoons, reinforced with 316 stainless steel deformed bar. There are stainless steel balustrades and light poles and a suite of stainless street furniture.

Jensen describes the process of specifying the correct finish, including gaining a theoretical understanding and producing prototypes:

The Starting Point
As a key parameter of design responsibility 'value for money' the decision to use stainless steel was an easy one. Our rationale was: "It doesn't corrode and our work is in salt-affected air; it lasts forever; it is low maintenance; it will save us money and keep on looking good."

We needed a specification to let contracts for the manufacture of street and riverscape elements. Writing a specification required describing and reproducing the manufacturing process exactly to get reliable, predictable, consistent and economic results.

Our research took us to ASSDA's timely seminar on the fifty most frequently asked questions about stainless steel, where we were able to ask about tea-staining and how to avoid it.

Then we talked to manufacturers. The answers to our questions about surface roughness and the finishes available made us realise there were variations within the industry and we needed to define our requirements with scientific precision. Specifically, we needed to know the surface roughness (Ra) in microns (µm), as the labels 2B, No. 4 and so on refer to the method used to achieve the finish and comprise an Ra range.

Building Prototypes
We concluded that to write our specification we needed to build the product first to set it within the theory and the 'standard range of common industry manufacturing practice'. We commissioned prototypes of a balustrade and a light pole then the furniture suite for the Riverwalk: seats, bollards, bins, lights, sign posts and drinking fountain.

Forge Brothers Engineering produced the prototypes. It drew on the expertise of ASSDA and its members University of Queensland Materials Performance, 3M Australia, Heat & Control, Condamine Wellscreens, Ronstan International as well as AbrasiveFlex and Dana Ridge.

We soon realised that:

> The common system of finish grades is not a measure of surface roughness, eg the Ra of No. 4 finish products measures anywhere from 0.45 to 0.8µm depending on product form and supplier. Typical Ra for sheet is 0.3 to 0.4µm while it is not unusual for other products such as flat bar to be rougher. Thick plate, thin plate (sheet), tube, flat bar and hollow bar are manufactured by different processes which produce different finishes. The surface finish changes in hot rolled plate and gets smoother as the plate reduces in thickness.

> Ra meters were not commonly used in the industry although their use is growing.

> All abrasives aren't the same. Wear and tear and pressure make a difference. We tested non-woven abrasive belts, Trizact belts, air wheels and silicon carbide.

> The electro-polishing industry uses a variety of chemical baths and voltages.

Towards a Specification
In arriving at our specification we learned:

> Best practice calls for a finish below 0.5µm combined with electro-polishing to eliminate sulphides and increase the chromium content of the exposed surface.

> Wet blasting at low air pressure levels with a water and abrasive bead mix provides a consistent surface finish and economically removes surface variations ready for electro-polishing. This avoids the unexpected rise in roughness which can occur when electro-polishing removes microscopic peaks, previously flattened by mechanical polishing, to uncover underlying pits.

The proof that our specification works can be seen on the Brisbane River. After twelve months in a salt air environment our prototypes are still looking clean and new.

Words by Jan Jensen.

This article featured in Australian Stainless magazine - Issue 25, July 2003.


Posted 1 July 2003

The long-term cost effectiveness of stainless steel makes it a worthwhile proposition even though the initial outlay can be significant. The construction industry is realising that choosing a cheaper, but less durable material can be a false economy.

Eventually repairs need to be made and this can be at considerable expense. Further, there are likely to be logistical problems absent from the initial construction which add to the cost.

For example, when 101 Collins Street – a prestigious Melbourne high-rise office building – was completed twelve years ago, its two 80,000 litre fire water storage tanks were constructed out of bolted steel with a nylon-coated internal surface. Over time the coating had pitted and the steel was corroding, raising concerns about the future reliability of the system.

It was decided that replacement tanks should be fabricated from 4mm thick 316 stainless steel for long-term reliability.

Access was limited because the tanks had been placed in position with the attendant pumps and fire services system plumbing installed beneath them. In fact, a hatch in the floor above the tanks measuring just under a metre square was the only way in and out of the area.

ASSDA member, J Furphy & Sons of Shepparton, Victoria was the successful tenderer for the construction and installation of the new tanks.

The 7.4m long x 2.4m wide x 4.8m deep tanks were fabricated in individual panels, 4.8m x 900mm. With a hoist assembly above, the panels were lowered into position through the hatch and welded in situ. Other challenges to be overcome were creating adequate occupational health and safety conditions and providing welding power and services to the site.

The final step in the project was in situ hydrostatic testing for leaks which proved successful.

The owners of 101 Collins Street can now look forward to many years of worry-free service performance.

This article featured in Australian Stainless magazine - Issue 25, July 2003.

Sculpting Stainless Steel Mesh with Stone

When Canberra-based Artist, Anna Eggert began sculpting with stainless steel wire mesh two years ago she tried every tool to model the material with little success. 

Almost giving up on completing her installation, Eggert reached for a stone and began attacking the 316 mesh in frustration .... with extraordinary results.

The primitive stone became the perfect tool for modelling the wire mesh into soft folds to resemble drapery.

This modelling skill exploits the material to create smooth flowing lines of a garment pressed against a feminine body. It is an effect that effectively breathes life into material to create the illusion of steel 'blowing in the breeze'.

Metal Mesh in Terry Hills, NSW supplied the sculptor with 0.56mm diameter wire mesh with an aperture of 1mm for strength and rigidity. However, various other sizes are often used to create different visual effects.

Two layers of different size mesh can produce a moire effect, with the lines shimmering in and around the material. In the shade, the mesh becomes transparent and in the sun it shines and glitters, it has a life of it's own.

"I was really lucky to stumble upon Wire Mesh Industries in North Ryde (Sydney). They knit stainless steel wire into all kinds of knitted things, car parts, filters and cables, which make beautiful ribbons and belts", says Eggert.

The works are all put together with 3mm stainless steel rivets supplied by Specialty Fasteners in Canberra.

Anna Eggert was recently a finalist in the National Sculpture Prize at the National Gallery of Australia, Canberra. Her latest work "Belinda's Wedding" features a five piece bridal party. The work will be on show until March 2004 as part of a major exhibition of Australian sculpture at the McClelland Gallery in Langwarrin, Victoria.

Photos by David Paterson and Anna Eggert.

This article featured in Australian Stainless magazine - Issue 26, November 2003.

Council Solves Fishy Problem with Stainless

Coastal areas are popular sites for recreational fun and fantastic fishing. However, the City of Albany in Western Australia had one major problem to deal with - fish waste in the nearby waterways 

Local fishermen were cleaning and filleting fish and disposing of the waste overboard. This waste not only stagnated in the water for days, but also attracted seals and stingrays that can become aggressive when feeding.

Faced with a situation of replacing what was a kitchen sink on rusty legs in the water, the Council turned to local ASSDA member, Austenitic Steel Products, to design and fabricate an innovative new stainless steel fish cleaning station for the Emu Point Boat Ramp.

The circular fish cleaning station is believed to be the first and only one of its design currently available in Australia and measures 1400mm in diameter and 1100mm high.

Produced in 316 stainless, the compact design allows six operators at a time and provides a safe environment with no corners or sharp edges.

All plumbing is internal with access only through a hatch on the face of the cone and fitted security locks. Waste water falls to the centre of the table and flows through a circular screen into a collection hopper before entering a two inch waste pipe concealed in the centre.

Initially, the station requires manual removal of offal, but when funding and municipal sewerage is available, the table can be modified to incorporate an automatic processor to pulverise offal into disposable liquid waste.

Albany City's $13,000 station project has generated interest from other Councils and looks set to appear in local boat launching areas, coastal caravan parks and seaside fishing locations throughout Australia.

This article featured in Australian Stainless magazine - Issue 26, November 2003.


Posted 30 November 2003

The humble stainless steel rail is set to become a visual feature with the introduction of an innovative new product that people just can't keep their hands off.

Decorative Tube or Deco Tube has already started making waves on Queensland's Sunshine Coast with a choice between six different patterns suitable for a whole range of applications.

Caboolture Wheelchairs' new Custom Stallion GT design made with stainless Deco Tube.An Expression of Individuality

Caboolture Wheelchairs manufactures a range of customised manual and electric wheelchairs made of stainless steel for disabled people, sporting wheelies, hospitals and nursing homes.

The company sought to transform an ordinary functional wheelchair frame into a stylish feature by using a Deco N8 tube pattern to create a unique, individualised look (pictured below - left).

Unlike most stainless steel applications, wheelchairs are not polished but powdercoated in a range of colours to overcome the stigmatic 'institutional' image.

Caboolture Wheelchairs applies clear blue or red colour powdercoat on the 1.2mm thickness tube supplied by ASSDA member, Tubesales (Qld) to retain the distinct pattern effect.

Ronca Sheetmetal's office foyer display feature fabricated using Rimex sign lettering and stainless Deco Tube.A Distinctive Foyer Display Feature

Caloundra-based ASSDA member, Ronca Sheetmetal wanted to show their interior design clients a myriad of options available to them using stainless steel materials.

Since the office foyer was due for minor refurbishment, the company opted to create a curved display feature wall that doubled as an internal company sign (pictured below - centre).

A Deco N8 tube was used for the feature rail to highlight the new product ... and to impress.

Manufactured in 304 stainless by ASSDA member, National Tube Mills, the feature rail measures 38.1mm in diameter with a thickness of 1.5mm.

This feature rail was complemented with sign lettering using a passivated 6WL stainless supplied by ASSDA member, Rimex Metals.

A feature rail made with stainless Deco Tube in the wine cellar of Sails Restaurant, NoosaA Wine Cellar with Function and Style

Lyndon Simmons, the owner of Sails Restaurant in Noosa loves stainless steel. Simmons has specified so much stainless steel at the popular restaurant location on Hastings Street that staff nickname him the 'Steel Man'.

So it was no surprise that Simmons jumped at the chance to use Deco Tube for a railing in the restaurant's wine cellar when told of the product by Sunrise Hills Welding and Mechanical.

The Noosaville company installed 304 stainless Deco N8 with a 31.8mm diameter and a thickness of 1.2mm.

The contrast of the timber wine racks combined with the stainless steel railings with minimal lighting creates a warm, alluring visual effect that highlights the quality wine collection.

The Deco N8 tube pattern available in six different patterns increasing to nine in the near future.Properties of Deco Tube

Deco Tube is suitable for bending, polishing and powder coating. Ductility does not change and due to the distinctive patern, tensile strength is increased dramatically. In fact, Deco Tube has approximately 70% higher tensile strength than standard tube, due to the cold working, which is required to produce the patterned surface.

Higher strength can result in weight savings by allowing designs in lighter wall thickness, which can be particularly important in the transportation industry.

Deco Tube is also suitable for use as accessories in bathrooms, marine environments or anywhere where safety is an issue.

The product is expected to be popular with Councils, architects, bending companies, boat manufacturers, home decorators and shopfitters.

Marketed by Tubesales (Qld), Deco Tube is designed and manufactured by National Tube Mills, Brisbane with material supplied by ASSDA member, AvestaPolarit (now trading as Outokumpu).

This article featured in Australian Stainless magazine - Issue 26, November 2003.

Chemical Surface Treatments

Successfully using stainless steel depends on environment, grade selected, surface finish, the expectations of the customer and the maintenance specified.

Stainless steels provide robust solutions, but in harsh or borderline environments with high expectations for durability, surface finish will have a substantial impact on performance. Surface finishes can be applied mechanically (usually with abrasives) and chemically.

Understanding how chemical and mechanical treatments will affect the characteristics of the surface and will enable the best possible outcome for the client and the structure. Chemical treatment can be used to improve the corrosion performance of the steel, and hence its appearance in service.

 

Stainless steels resist corrosion best if they are clean and smooth. Clean means being free of contaminants on or in the surface that can either react with the steel (like carbon steel or salt) or that create crevices or other initiation points where corrosion can start.

Smooth means having a low surface area at the 'micro' level. Mechanically abrading the surface can roughen the steel's surface and may also embed unwanted particles.

The common feature of chemical treatments is that they all clean the surface of the steel. They may also smooth or roughen the steel surface, or leave it unaffected depending on which process is chosen. But if carried out properly, they all increase the corrosion resistance.

Corrosion resistance improves as you go to the right of this graph. The graph shows the relative importance of the smoothness of the surface and chemical treatment of the surface. They can be used together to get the best corrosion resistance.

Corrosion resistance improves as you go to the right of this graph. The graph shows the relative importance of the smoothness of the surface and chemical treatment of the surface. They can be used together to get the best corrosion resistance. The study reported by G. Coates (Materials Performance - August 1990) looked at the effect of various methods of treating an artificial welding heat tint on grade 316, 2B surface.

Stainless Steel Products
During steel making, sulphur in the steel is controlled to very low levels. But even at these levels sulphide particles are left in the steel, and can become points of corrosion attack. This 'achilles heel' can be improved greatly by chemical surface treatment.

Most bar products will be slightly higher in sulphur when produced, so chemical treatment to remove inclusions in the surface of these products becomes more important.

Generally mill finishes for flat products (sheet, plate and strip) will be smoother as their thickness decreases.

A No 1 finish on a thick plate may have dimples or other imperfections and a surface roughness of 5 to 6 micrometres Ra.

A typical 2B cold rolled finish on 1.7mm thick sheet might have a surface roughness of 0.2 micrometres Ra or better as shown in Mill Forms.

New surfaces will be created during fabrication processes, (eg cutting, bending, welding and polishing). The corrosion performance of the new surfaces will generally be lower than the mill supplied product because the surface is rougher, or sulphide inclusions sitting just under the surface have been exposed or mild steel tooling contamination may have occurred.

Chemical treatments correctly performed can clean the surface and ensure the best possible corrosion performance.

Chemical surface treatments can be grouped into four categories:

  • Pickling - acids that remove impurities (including high temperature scale from welding or heat treatment) and etch the steel surface. 'Pickling' means some of the stainless steel surface is removed.
  • Passivation - oxidising acids or chemicals which remove impurities and enhance the chromium level on the surface.
  • Chelating agents are chemicals that can remove surface contaminants.
  • Electropolishing - electrochemical treatments that remove impurities and have the added beneficial effect of smoothing and brightening the surfaces.

Pickling
Mixtures of hydrofluoric (HF) and nitric acid are the most common and are generally the most effective. Acids are available as a bath, a gel or a paste.

Commercially available mixtures contain up to about 25% nitric acid and 8% hydrofluoric acid. These chemicals etch the stainless steel which can roughen and dull the surface.

Care is required with all these chemicals because of both occupational health and safety and environmental considerations. HF is a Schedule 7 poison which has implications for sale or use in most states. See ASSDA's Technical Bulletin on this subject.

Passivation
Nitric acid is most commonly used for this purpose. Passivation treatments are available as a bath, a gel or a paste. Available formulations contain up to about 50% nitric acid and may also contain other oxidisers such as sodium dichromate. Used correctly, a nitric acid treatment should not affect the appearance of the steel although mirror polished surfaces should be tested first.

Passivation works by dissolving any carbon steel contamination from the surface of the stainless steel, and by dissolving out sulphide inclusions breaking the surface.

Nitric acid may also enrich the proportion of chromium at the surface - some chelants are also claimed to do this.

Pickling and passivation: before treatment of fuel tanks for storing helicopter fuel on ships. Pickling and passivation (L-R): after treatment of fuel tanks for storing helicopter fuel on ships.
Pickling and passivation (L-R): before and after treatment of fuel tanks for storing helicopter fuel on ships. Photos courtesy of Alloy Engineers and MME Surface Finishing.

Chelants
Chelants have chemical 'claws' designed to selectively clean the surface.

The carboxylic acid group COOH is the basis for many chelants which are used in cleaners, water softening and lubricants. The pH and temperature must be correct for the chelant to do its job. Turbulent rinsing of pipes and vessels afterwards is important.

Cleaning by chelating agents tends to be based on proprietary knowledge and systems, and is less standardised than the other methods described.

The successful use of these systems needs to be established on a case by case basis.

Electropolishing
Most commonly phosphoric and sulphuric acids are used in conjunction with a high current density to clean and smooth (by metal removal) the surface of the steel.

The process preferentially attacks peaks and rounds valleys on the surface and raises the proportion of chromium at the surface.

The technique can have substantial effect on the appearance increasing lustre and brightness while only changing the measured roughness by about 30%.

Precautions
For chemical processes that etch the stainless steel, reaction times will increase with increasing grade.

More care is required with 'free machining' grades and these will usually require substantially less aggressive chemicals. The sulphur addition in these steels makes them readily attacked by chemical treatments. Care is also required when treating martensitic or low chromium ferritic stainless steels.

Detailed recommendations for each grade of stainless steel are given below.

The four categories of treatment are detailed in a number of Standards, but the most commonly used are:

  • ASTM A380 Cleaning, Descaling and Passivation of Stainless Steel Parts, Equipment and Systems.
  • ASTM A967 Chemical Passivation Treatments for Stainless Steel Parts.
  • ASTM B912 Passivation of Stainless Steels using Electropolishing.

These very useful documents give detailed recommendations on many aspects of selection, application and evaluation of these treatments. Highly recommended reading.

Dirt and grease will mask the surface from treatments outlined above. Therefore, the steel surfaces must be free of these agents before applying chemical treatments.

Many of the chemical treatments described contain strong acids. Before disposal they will require neutralisation. Check with your local authority concerning the requirements for trade waste, neutralisation and disposal.

Many of the chemicals described above will be classified as hazardous substances under State OHS legislation, with implications for purchasing, transport, storage and handling.

Chemical treatments are useful tools in cost effectively achieving peak performance with stainless steels. With appropriate training, hazards associated with their use can be managed.

This technical article featured in Australian Stainless magazine - Issue 26, November 2003.

Specifying Stainless for Suncorp Stadium

PDT Architects, Brisbane in association with HOK Sport, Venue and Event designed and documented the $280m Suncorp Stadium for the Queensland Government.

"It is the top grade material and that's what we wanted for the stadium...

When you take that the client is the people of Queensland, they expect the best to go into the stadium.

If they're paying $280 million for a stadium they want the thing to last and stainless will give you that longevity."

 

Director, John Brown of PDT Architects described the pros and cons of specifying stainless steel for the redevelopment of Lang Park (Suncorp Stadium).

Ticket Counters
When PDT Architects expressed concerns by Ticketek staff that stainless steel ticket counters would be too glary, ASSDA provided the necessary technical assistance required and prevented a switch to timber material.

JB: The client talked about changing from stainless to timber because Ticketek and others had commented that stainless steel would be too glary.

We found that we could use a brushed finish which wouldn’t throw up too much glare and we also did some sun shade diagrams and all sorts of diagrams to make sure the sun wasn’t hitting the ticket counters.

Full Stainless: Commercial Kitchens
JB: It was always going to be stainless steel, mainly because of the health reasons ... but also for cleaniness and ease of cleaning.

All the commercial kitchens at the stadium have them. All the finishing kitchens, all the food outlets, beverage and of course the main kitchen. All the food is prepared in that kitchen and taken up through the service lifts into the finishing kitchens, warming kitchens and then out into the public.

Stainless Wire Rope for Visibility
PDT Architects has recommended replacing the stadium’s flat bar rails with stainless steel wire rope to improve visibility.

JB: We've been able to convince the State Government code people that we can take a lot of the galvanising rails out and put in stainless steel wire rope which would give a better view.

We’ve put in a report to the Government whereby we can cut out a lot of these flat bars and put in stainless steel wire rope through them which will just open the whole place up.

Stadium Stainless Statistics
ASSDA member Fagersta supplied 60 tonnes of stainless steel coil of various widths and thicknesses to ASSDA member Tom Stoddart. A further 10 tonnes of stainless steel was supplied to Eziform for gutters and box gutters.

Tom Stoddart produced works at a cost of $11 million and approximately 50,000 man hours including full kitchen and bar fitouts, refrigeration units, cash register stations balustrading and some food service equipment.

Fagersta was also the main supplier of stainless steel for Colonial Stadium in Melbourne and Telstra Stadium in Sydney.

The Post Game Wrap-Up
JB: Firstly, it satisfied us as far as an architectural feature went, it satisfied us as far as life cycle went and most certainly it then satisfied us as far as safety issues went.

This article featured in Australian Stainless magazine - Issue 26, November 2003.