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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.

Stainless preserves Tasmania's heritage

Hastings Caves, one of Tasmania’s major tourist attractions situated a scenic two hours’ drive south of Hobart, has received a major upgrade.

According to the Site Co-ordinator Keith Vanderstaay, the caves "have been reinvented with the completion of a state of the art, computer-controlled lighting system which will change the way everybody will see the cave."

New stainless steel handrails allow visitors to navigate the cave in safety, and are designed to last for generations, minimising the need for maintenance in the caves' sensitive environment.

Tasmania’s Parks and Wildlife Service, as part of a safety review of structures used by the public, identifed the 1930s galvanised pipe handrails as substandard to the new AS2156.2 Walking Track: Infrastructure Design and decided to replace them.

Another primary concern was the environmental damage being caused by the breakdown of the galvanise.

The Service looked at using stainless steel or aluminium for the project and after all considerations, including cost, the decision was made to use grade 304 stainless for the posts and rails.

The job consisted of 263m of rail along around 90m of walkways, stairs, ramps and viewing platforms which snake through the cave.

Sinclair Knight Merz was engaged to design, seek tenders and supervise construction. The project presented some unusual and physically demanding challenges for the fabricator, Prins
Metalwork of Kingston.

COLD, DARK WORK

Adrian Prins and his firm worked on the project for two and half months, with a team of four or five people living at the caves for half that period.

All of the installation work, which was carried out in winter, had to take place at night so that the caves could stay open to visitors during the day. For the same reason, no voids were allowed to remain at the end of each session. The workers had to carry out all the old carbon steel balustrades by hand, just as they had to carry in all the new rails and their equipment, down 200+ steps into the cave.

Once inside they had to be very careful not to touch any of the formations, which are extremely fragile.

Because no angle grinding was allowed inside the cave for environmental reasons, they used a reciprocating saw to remove some 190 old posts.

The stubs were capped and the new posts installed. MIG welding was allowed, but kept to a minimum. There was only 240V, 10 amp power supply throughout the cave.

Where possible, fabrication took place at the workshop and was fine-tuned on site. The nature of the project meant that there were many adjustments to be made as few of the
balustrades have consistent angles. The concrete steps and landings, which were boxed in situ to adapt to the contours for the caves’ public opening in 1939, are quite irregular.

Sitework was carried out at the cave entrance, under artificial lights, in an area 400m from the carpark. It took the workers six trips along a boardwalk every night just to set up equipment
and they then had to carry materials and equipment up to 400m from the cave entrance.

While those who worked on the project recall the cold and the dark conditions, visitors can now safely enjoy the beauty of the cave in the knowledge that the new stainless steel infrastructure is protecting the caves and its visitors.

This article featured in Australian Stainless magazine - Issue 21, June 2002.

Stainless for power generation

At a time when so many industrial processes are computer-driven, there is still a place for human knowledge and experience in the highly specialised area of hydro-turbine manufacturing.

Steel Castings Pty Ltd, situated in Port Melbourne, has a reputation for precision moulding which has secured the firm contracts to produce two 'Pelton Runners' – the heart of the turbine – for a Victorian Hydro Power Station, working with the Norwegian designers, GE Australia and Acron Engineering.

Steel Castings have been making Peltons since the mid-90s. Measuring 2m in diameter and weighing in at 3.5 tonnes, these units are the largest so far. They are designed to withstand water cascading onto them from 400m above for 20 to 30 years to generate about five megawatts of electricity.

Despite their complex shape, the Peltons were cast in a single pour.

Technical Director Jim West explains the steps involved in achieving such a feat of engineering.

First a wooden pattern is made from drawings. Thousands of measurements must be checked. For example, there are 64 measurements for each of the Pelton Runner's 21 buckets. The pattern took about five weeks to make followed by a week of refinements.

One of the skills involved in pattern manufacture is estimating the contraction allowances for the shrinkage and distortions that occur during cooling and heat treatment. With only a 3mm tolerance window, this is something that can't be done by a computer, says Mr West. Once the pattern is complete, the mould and cores are produced from sand combined with a bonding agent – 17 tonnes of sand were required for this mould. The stainless steel used is CA6NM, a modified grade 410, poured at a temperature of nearly 1600ºC.

The mould is constructed so that the metal flows into all areas of the shape in less than 30 seconds of pouring time. The casting has to cool for seven days before it can be inspected. Then
the 'plumbing', the additional pieces which enable pouring the casting, is removed and the Pelton is heat treated at 1020ºC over a 23 hour cycle to strengthen the structure of the metal before final tempering and machining.

From drawing to installation the procedure takes about five months. The resulting finished technical marvel is worth hundreds of thousands of dollars.

ASSDA member Steel Castings Pty Ltd has its roots in the 19th century. It has operated in Port Melbourne since it was founded and employs a workforce of around 30 depending on current projects. The company's main business is manufacturing stainless steel and nickel-based alloy valves for the oil, gas and petrochemical industry. The firm also makes stainless steel ingots for the forging industry.

This article featured in Australian Stainless Issue 21 - June 2002.

Images:

Main image: mould nearing completion

Above right: cast detail of buckets

Large tube now made in Australia

The Australian construction and food processing sectors can specify stainless steel tube in large sizes with confidence in its quality and timely delivery, now that local production has commenced at a Victorian plant.

Manufacturing by an Australian firm will also make it easier for specificiers to communicate their special requirements.

Stainless Tube Mills' special purpose factory in Melbourne’s outer east is producing longitudinally welded tube in diameters up to 300mm and wall thicknesses up to 8mm – the largest seamwelded stainless steel tube available in Australia. Tube in this size range has always been imported.

The recently commissioned draw mill, designed in house by ASSDA member STM in conjunction with CSIRO, joins twelve other mills on site which produce welded tube up to 101.6mm outside diameter.

While a conventional mill uses a drive mechanism to feed the strip through the mill and produce welded tube, in the draw mill strip (1) is drawn through the mill with the forming rolls idling (2 & 3). This has the effect of producing a tube with minimal roll forming marks, as well as precise tolerances. The internal weld bead (4) is rolled to merge with the parent metal producing a smooth bore. Externally, the polished finish renders the seam all but invisible.

The smooth interior finish means tube produced on the draw mill is ideal for transfer of processing fluids, particularly food products, where the clean internal bore is mandatory.

Large diameter tube is also finding application architecturally for balustrades, barriers and structural column formers. As formers they make an attractive alternative to brick or concrete,
delivering a superlative appearance and impressive structural strength, which can be further bolstered by filling with concrete. STM used 300mm columns in T304 alloy to dramatically enhance its own office façade (left).

The draw mill has only been in operation commercially for a short time, however STM reports there has already been considerable demand. The firm's future plans include production of heavy walled large diameter sectional tubes for architectural applications.

This article featured in Australian Stainless Issue 21 - June 2002.

New winery development

 A major new development project at the Jindalee Winery at Moorabool near Geelong utilises over 100 tonnes of grade 304 2B finish stainless steel.

Shepparton’s J Furphy & Sons fabricated 95 wine storage and fermentation tanks, ranging in size from 75,000 to 1,200 litres.

The new tanks provide almost three million litres of temperature-controlled storage capacity for grapes processed from the adjoining vineyard and a much larger vineyard which Jindalee’s owners, Vince and David Littore, operate in the Murray Darling region near Mildura.

Three years ago the Littore Brothers acquired the former Idyll Vineyard and winery at Geelong which they are now using as the production centre for their wines produced under the Jindalee and Fettlers Rest labels for both local and export markets.

In addition to the tankage, most of which features the new Furphy Laser Welded Dimple Plate design which provides the cooling jackets to the tanks for circulation of refrigerants, Furphy’s have also completed more than 350 lineal metres of galvanised walkway and tank access systems.

Jindalee’s winemaker Scott Ireland describes the project as a state of the art winery facility designed to produce wines which will appeal to the most discerning palates as well as capitalising on and growing the export market success already achieved under the Jindalee label.

A $1 million bottling hall and packaging facility will be added providing a fully integrated facility.

This article featured in Australian Stainless Issue 21 - June 2002.

Cleaning your indoor stainless steel

Quick and easy tips for keeping that shine

Retaining a sparkling finish on stainless steel surfaces is just a matter of a few simple steps. And you don't need expensive products or special equipment - ordinary household cleaners are usually all that's required. You just need to bear in mind a few easy DOs and DON'Ts...

It'll come out in the wash

Stainless steel looks best if it's cleaned regularly with plenty of water. Drying afterwards makes sure streaky marks aren't left behind.

Remember that simply wiping with a damp cloth is not as effective as it can smear dirt without removing it.

Routine cleaning prevents any stubborn stains building up.

So what will you need?

You don't need any fancy equipment. For day to day cleaning, plenty of water, some mild detergent and a cloth or soft brush will do the job. You can use a 1% ammonia solution but don't use bleach? it's just too easy to make the solution too strong and too hard to rinse it properly afterwards.

After washing, rinse in clean water and wipe the surface dry with a soft absorbent cloth. On brushed stainless steel, follow the direction of the polish for best results.

An excellent cloth to use is 3M's Scotch-Brite high performance cleaning cloth.

Watch out for scratches!

The important thing to remember is that stainless steel can be scratched by careless handling or aggressive scrubbing. Just like you would take care of a polished timber finish, avoid dragging rough items across the surface and be aware that grit trapped under other objects can be the culprit.

Avoid bad chemistry

Stainless steel may discolour if left in contact with salts or acids for extended periods. Also avoid leaving carbon steel items in contact with stainless steel, particularly if wet. But if you observe ordinary hygiene measures, like timely cleaning-up in food preparation areas, you won't have any problems.

How to handle the tough customers

Sometimes you need a tougher approach. Here's how to get rid of the most common offenders:

Fingerprints, oil & grease marks

If a mild detergent or dishwashing detergent doesn't shift unsightly fingermarks, get rid of them with a bit of glass cleaner on a soft cloth. You can also use a small amount of alcohol, methylated spirits, acetone or mineral turpentine. Then rinse with clean water and dry.

You can give longer protection to high traffic areas by lightly rubbing with olive oil or baby oil followed by a polish and shine using a soft cloth.

Tea & coffee stains

Discolouration from tea and coffee stains can be removed by soaking in a solution of boiling water and baking powder. Remember to rinse well and wipe dry.

Sticky labels

Remove sticky labels as soon as possible. Gentle heat from a hair dryer or a glue gun generally softens the glue for easy removal, or you can warm stainless steel pots and pans in the oven before peeling off the labels. Eucalyptus oil based cleaners (or eucalyptus oil on its own) often work well to remove adhesives.

Ensure you don't leave any glue on the surface ? it could trap dirt or break down and cause staining.

Rust marks

Apply cream cleanser with a soft damp cloth and rub gently.

If the mark still won't shift, it might be necessary to use a proprietary stainless steel cleaner. These are usually based on dangerous chemicals (such as phosphoric, oxalic or sulphamic acids) and must be handled with care according to the manufacturer's directions.

After cleaning it is important to neutralise the acid with a 1% ammonia or baking powder solution, rinse with clean water and wipe dry. If the rust has worn away the surface, don't despair! Bad rusting can be repaired with professional polishing but you will need to get expert advice.

Paint

Apply paint stripper, taking care to follow the safety instructions. You may need to use a nylon brush or scouring pad, but avoid metal scrapers at all costs - they will damage the surface.

Hard water scale

Heavy limescale from hard water can be loosened by soaking in a hot water and 25% vinegar solution. Rinse well with a solution of baking powder or 1% ammonia and then with clean water. Always wipe dry.

Cement and mortar

Cement and mortar splashes should be washed off before they set. Mild acids such as vinegar may be needed but not those using chloride rich chemicals. Never use brick cleaning liquids which contain hydrochloric acid. Be very careful that loosened particles don't scratch the steel surface.

Don't go against the grain

Always rub stainless steel in the same direction as the grain. Rubbing against the grain will spoil the finish and stainless will lose its shine. Worse, rubbing against the grain can damage the surface by creating microscopic crevices where dirt can collect. This can lead to corrosion spots.

Fortunately, it's usually easy to tell which is the right direction. You need to watch out for items like round handrails, which are often polished around their circumference when they're manufactured, rather than up and down the length of the tube.

If you have to scrub a stain to remove it, make sure you use a clean nylon scourer or a cloth with chalk-based cream cleaner. But test an inconspicuous area first as you could end up with a bright polished spot which doesn't match the rest of the surface.

NEVER EVER use steel wool (wire wool) to clean stainless steel.

It is usually made of carbon steel and any fragments left behind will rust onto the stainless steel surface. Using any kind of scourer which has previously been used on ordinary (carbon) steel is also a no-no for the same reason.

Stainless steel wool scouring pads are available for heavy duty work, like removing burnt food from stainless steel saucepans. These will scratch the stainless steel surface, but won't leave fragments to go rusty.

Download Technical FAQ 2

Important Disclaimer

The technical recommendations contained in this publication are necessarily of a general nature and should not be relied on for specific applications without first securing competent advice. Whilst ASSDA has taken all reasonable steps to ensure the information contained herein is accurate and current, ASSDA does not warrant the accuracy or completeness of the information and does not accept liability for errors or omissions.

This article featured in Australian Stainless Issue 21 - June 2002.

Stainless across a cultural spectrum

Melbourne's public life is populated with unique, strong and take-as-you-find personalities. Its culture – from high to mass – is influenced by figures like Jeff Kennett and Sam Newman, who shape Melbourne's view of itself and its environment.

While the former Premier's impact on the Victorian capital has been comprehensive, the refurbishment of Brighton Sea Baths as an upscale nightspot part-owned by Mr Newman has contributed a smaller scale landmark which is just as likely to provide visitors (male ones, anyway) with a memorable impression of the city.

The retired Geelong player and AFL Footy Show co-host, well-known in Melbourne for his flamboyant lifestyle, including a 5m high mural of pop icon Pamela Anderson at his Brighton home, came up with a quirky idea for the urinal: a built-in wide-screen TV (main image).

ASSDA member Britex, working with Buxton Constructions' Adrian Seymour and architects McGauran Soon Pty Ltd, were able to deliver the goods thanks to the versatility of stainless steel.

Melbourne's CBD has undergone a transformation in recent years, and everywhere stainless steel is playing a significant role. It’s proving its durability and appeal in major public facilities, such as Colonial Stadium (urinals) and Vodafone Arena (food preparation areas), both venues which showcase the city’s top sports events and attract many international visitors. The facilities must perform under the pressure of large crowds and yet look good.

Stainless steel fulfills these requirements here as it does at the Melbourne Convention Centre. The Centre, one of the country’s premier sites for international events, makes the most of its riverside location, with floor to ceiling windows framing views of the Yarra and one of Melbourne's best-known attractions, the Polly Woodside. Stainless steel benches in the foyer are in keeping with the clean lines and open spaces (see image, right).

Stainless works equally well in boutique refurbishments, such as Brighton Sea Baths and Retreat on Spring, an upmarket health resort tucked away near Melbourne’s gracious old Parliament buildings. The design language of Retreat on Spring is quiet, peaceful, harmonious.

Blond, polished floorboards, bamboo and stone set a tranquil tone. Stainless steel slips easily into this combination of natural elements and muted colours, while providing a practical surface in the health bar area and for the vanities in the individual therapy rooms.

From the intimate setting of Retreat on Spring to the high-traffic amenities at the city’s massive sports arenas, stainless steel is perfectly at home, providing both understated elegance and rugged performance.

This article featured in Australian Stainless Issue 21 - June 2002.

Adelaide Landmark Resplendent in Stainless

Pressed stainless steel cladding has been used to spectacular effect on the Dame Roma Mitchell Arts Building of Adelaide Institute of TAFE, the training ground for many of Australia’s future performing and visual artists.

The originality of the design complements the creative nature of the activities housed in the building, situated on the edge of Adelaide’s Light Square.

Completed in December 2001, the four-storey complex comprises an art gallery, basement workshop facilities for ceramics and sculpture, two theatre spaces, and various studios and workshops.

Stainless steel fulfils a dual function. Not only does it provide aesthetic appeal, the pressed surface combined with the choice of finish is strongly resistant to the type of damage likely to
occur in a public building.

This world-class facility occupies a site area of 3,785m2 and has a total floor space of 15,500m2, but in spite of its bulk, a striking feature is its apparent light and transparency. The uninterrupted flow of the stainless steel panels from the external feature walls into the main foyer through the window-wall area creates amplitude. Reflections from the polished and
textured panels generate a play of light.

CONSTRUCTION

Each 0.45mm thick panel was unique and had to be manufactured and pressed individually. The interlinking design made it critical for all work to be executed satisfactorily from the outset, as it could not be rectified later. The real construction challenge lay in resolving the myriad detailing issues at the interface between the stainless steel and other elements.

This achievement – an Australian construction first – was a key factor in head contractor Hansen Yuncken gaining a high commendation at the Australian Institute of Building Professional Excellence in Building Awards. The Dame Roma Mitchell Building project team also included architects Hassell Pty Ltd and engineering firm Wallbridge and Gilbert.

Fabrication, by Donato Steel Fabrications Pty Ltd, was carried out in the workshop and panels were delivered to the site in specially constructed crates to avoid physical damage. Most of the approximately 2,000m2 of grade 304 stainless steel sheet was supplied by ASSDA member Atlas Steels Pty Ltd.

FINISH

Using a minimalist colour palette, the interior design relies for interest on the contrasting essential qualities of the materials utilised – glass, concrete and stainless steel. A finish combining high lustre and surface roughness (2B) was chosen for the stainless panels, providing a rudimentary feel sympathetic to the overall design. This choice has proven highly successful from both the aesthetic and maintenance perspectives, as it does not attract surface contaminants.

The result for Adelaide TAFE is a unique Australian landmark.

This article appeared in Australian Stainless Issue 21 - June 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.

Hooked on Stainless

Grade 316 stainless steel offers superior corrosion resistance and has become the norm for architectural applications within 5km of the coastline. Another natural use for grade 316 stainless is in boating and marine sports gear, which has to withstand the corrosive effects of salt water.

Deck fittings and equipment made in 316 stainless are stronger and more durable than most alternatives. Their lifespan is further enhanced when kept clear of salt encrustations, grease and dirt. This is facilitated by a very smooth surface which doesn't present miniscule pits and crevices where corrosion can begin.

An example of grade 316 being used to good effect is the Cannon Rod Holder by ASSDA member Emro Products. For the benefit of the non-fisherperson, a rod holder is mounted onto the side or deck of the boat to hold the fishing rod and free up both hands for other tasks.

Using several rod holders when trolling allows more lures to be placed and the area covered is increased if the holders are angled at 90 degrees to the sides of the vessel.

The Cannon is made from highly polished grade 316 stainless steel, rigorously tested to ensure a durable and reliable product. It is fully adjustable so that the rod can be positioned as desired. Being detachable it can be easily cleaned and is less vulnerable to theft.

The D locking mechanism in the base of the shaft ensures that it attaches securely and cannot be accidentally released, losing both valuable fishing equipment and the catch.

The rod holder is manufactured in two lengths, 145mm long with rubber buffers on either end and 300mm long with a pin in the end to suit a gimbal.

This article featured in Australian Stainless magazine - Issue 24, March 2003.


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.

Stainless delivers the wow factor

A decor has to be unique to stand out among the trendy cafes and nightclubs in Park Road, Milton, one of Brisbane’s most fashionable locations, and it certainly has to possess the wow factor to compete with the multitude of sensory experiences which greet clubbers out to see the latest bands and DJs.

A unique interior, using stainless steel, which would wow the patrons, was the brief SOBAR NightClub owner Darren Perris gave Brisbane fabricator Klein Architectural, along with just 48 hours for concept, design and installation before opening night.

The mission was accomplished with patterned stainless surfaces to capitalise on the venue’s electric blue lighting and generate myriad shifting reflections, creating the perfect high-energy setting for the pounding beats and sinuous rhythms of the nightclub scene.

Working within a budget of around $8,000, Klein used 13 sheets of 0.9mm thick, grade 304 stainless with a 2B finish, supplied by ASSDA member Fagersta Steels, to line the bulkhead and square columns of the bar area. This was set off with 65mm round mirror polished tube at the rear of the bulkhead.

Following straightforward fabrication using glue and screwed fixings for the skinning, a heavy metal look was achieved by gluing the heads of cup bolts over counter-sunk screws.

Stainless panels on the columns were linished horizontally in a heavy grain and customised patterning was applied to the stainless steel skins of external and interior bulkheads and corners of the columns.

The end result is a shining example of stainless steel being used artistically and functionally without compromising either purpose.

This article featured in Australian Stainless Issue 24 - March 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.

Ingenious Design Serves Patrons Well

Lightweight stainless steel construction has allowed the proprietor of a Tasmanian cafe to expand operations without building new brick and mortar premises.

Page’s of the Mall is a stainless steel satellite to an existing cafe located in the busy Launceston Mall. Custom built for the site, it has proved popular and profitable since opening shortly before Christmas 2002.

The client, Mark Page, approached Launceston fabricator FAME Foley Industries with a particular brief: to construct a portable cafe catering to both take-away and sit-down trade which met standard refrigeration, food preparation and hygiene requirements. The unit had to conform to local Council guidelines and match the awnings recently installed in the Mall.

PACK UP AND MOVE

The challenge was to produce a design measuring just 2m high by 1.9m wide and 5.5m long to be wheeled into Page’s main shop at night.

The design evolved over the course of a year with input from a Launceston Council architect and took two months to build. The unit unpacks to a height of 2.5m when the roof is unfolded forming wing-like canopies above the serving areas, and the sides open out to 2.8m in width.

Concealed wheels at one end allow the unit to be moved using an electric pallet lifter. It is positioned over a pit with access via a hatch to water, power and drainage.

A seating area is enclosed by stainless steel barriers clad with laminex signs arranged in a zig zag shape for strength. These are also completely portable and have lockable castors.

Inside the cafe, which has garnered the nickname ‘coffee tram’, stainless steel pie heaters, fridges and washing facilities are built in as integral parts of the unit. Fully enclosed stainless steel trolleys are used to transport supplies from the main cafe.

PRACTICAL AND ECONOMICAL

Stainless steel was chosen for the project both for its clean style and for its appropriateness to the design and usage. The construction is simultaneously lightweight and strong, allowing it to be wheeled around daily and to withstand the mall traffic. Hygiene is readily maintained with easy to clean food preparation surfaces.

Most of the unit, including framework, walls, benches and supports are made from grade 304 stainless while grade 316 is used for the roof as it is exposed to the weather. The fridges, part of Foley’s range of kitchen and bathroom ware, are made from grade 430. Stainless steel was supplied by ASSDA member Atlas Steels.

Costs compare favourably with erecting a permanent building, at around $100,000 to construct and fit out, and the concept can be adapted to suit other locations.

The article featured in Australian Stainless Issue 24 - March 2003

Coated Abrasives for Surface Finishing - Part 3

Our three-part series on coated abrasives concludes with information on choosing the correct abrasive product for the desired finish. Read Part 1. Read Part 2.

THE IMPORTANCE OF SURFACE ROUGHNESS

The surface roughness of stainless steel is an important factor in determining corrosion resistance. Put simply, the smoother the finish the greater the corrosion resistance, whether in the form of sheet or coil or in welded components.

SURFACE TOPOGRAPHY

Interaction between the abrasive belt and the workpiece is affected by surface topography (micro texture). Even a surface which appears perfectly flat to the naked eye has ‘asperities’, undulations between 0.05 μm and 50μm occurring 0.5μm to 5 mm apart.

A variety of instruments are available to measure surface micro texture. They work on the principle of moving a stylus over a representative length of the surface and recording the peaks and valleys.

In Australia, surface roughness is expressed in Ra. The measurement refers to the average variations of the undulations from the average surface of the sample.

Current density & surface roughnessTYPICAL FINISHES

Three stainless steel surface finishes are typically available from the mill:

  • #1 hot rolled, annealed and pickled (Ra 3 to 6μm)
  • 2B cold rolled (Ra 0.1 to 0.2μm)
  • BA bright annealed (Ra 0.06 to 0.2μm)

From these initial surfaces, a wide variety of finishes can be achieved with coated abrasives, satinising wheels and mops, buffing wheels and polishes. The type of finish generated depends on many variables: grit sequence, lubrication, raw material quality, machine type, abrasive type, pressure applied, through feed speed, abrasive belt speed and so on.

Because of all these factors, nominally identical finishes vary slightly from one producer to another. To ensure that the desired finish is delivered, specifiers should nominate the acceptable Ra (surface roughness) range and any other factors necessary for the application (for instance viewing angle or light conditions for architectural samples).

The common ASTM designations for stainless steel surfaces such as ‘No. 4’ specify a process to achieve a finish and not attributes of the surface itself. The result can fall outside the desired
surface roughness range. The Euronorm finishes of EN 10088, provide a larger number of specifications than ASTM A480 and include some which require particular Ra values.1

Although the measurements involved are microscopic, research indicates there is significantly higher resistance to corrosion in stainless surfaces with a roughness below 0.5μm Ra.

THE ROLE OF COATED ABRASIVES

Technically advanced coated abrasives are designed to optimise production by delivering consistent, measurable surface finishes. However, the operator must select the correct abrasives and the right product sequence.

Abrasive grainPolishing is hard work and even with machine operations, it takes time and care. The absolutely essential element is to remove all the polish lines from the previous stage before moving on to a finer grit. If this isn’t done, the final and finest buffing step will be marred by a streak on the surface. Although it is often impossible to rotate the work, removal of polish lines is readily
monitored by polishing at right angles for each new step.

The first grinding step should be as fine as possible. As #80 is usually the finest practicable size, it may require some time to smooth a large weld bead. An effective grit sequence for producing a mirror finish is 80, 120, 240, 320, 400, 600 and 800 before proceeding to mops.

Steps can be missed but at the cost of longer polishing times and the risk of stray scratches. Old abrasives will give a smoother finish but the results are less predictable and are operator dependent.

Lubricants may be necessary because of the poor conductivity of stainless steel. Lubricants also remove debris, improve the quality of the finish and increase the abrasive life. When buying abrasives it is important to choose a reputable product; an unknown quality could mean stray, coarse grit with its attendant final streaks which will mar the result and be especially obvious on a ‘mirror’ finish.

When silicon carbide abrasives are used a brighter, more highly reflective finish results, albeit at the expense of belt life. Other materials, for example aluminium oxide, zirconia or ceramic
grains, will give a significantly longer belt life but will produce a different overall finish.

A quality coated abrasive belt acts as a series of single point cutting tools. Each grain has the optimum shape and angle to accomplish the cutting action and subsequent chip removal. This is partly achieved through electrostatically orienting the grains in relation to the backing during manufacture. The rest comes from choosing the correct abrasive type for the job. A cutting facet which isn’t sharp enough results in random streaks on the stainless steel surface as the grain fails to cut cleanly and drags a chip along the surface. This effect is more prevalent with aluminium oxide belts.

Roughness vs Abrasive Grit Size*

Grit
Ra(μm)
500# 0.10 - 0.25
320# 0.15 - 0.22
240# 0.30 - 0.67
180# 0.42 - 0.96
120# 0.29 - 0.81
60# 2.01

GETTING IT RIGHT

Supplying the desired surface is as much a part of filling a contract as other aspects of fabrication. There are a large number of variables which impact on the surface finish. The previous two issues of Australian Stainless presented an overview of modern coated abrasives and specific information on their composition and manufacture (issues 22 and 23). Data on the hardness of abrasive materials and a relative comparison of grit size was included.

An understanding of what makes a quality abrasive product and how coated abrasives interact with the workpiece helps ensure that the corrosion resistance and aesthetic requirements of
the client are met.

1. EN 10088-2 : 1995 specifies additional specific requirements to a ‘J’-type finish, in order to achieve adequate corrosion resistance for marine and external architectural applications. Transverse Ra < 0.5μm with clean cut surface finish.

This article featured in Australian Stainless Issue 24 - March 2003. It was written by Charles E. Fenton, Managing Director of Klingspor Abrasive Technologies, Australia and Graham Sussex, ASSDA’s technical specialist.

"Dancing Wall" - Colour & Movement in Stainless

To symbolise the wetlands landscape of the Nundah area in Brisbane’s north, sculptor Daniel Della Bosca sought out materials which best convey the fluidity and reflectivity of water and the reedy texture of waterside vegetation.

His choice was 316 stainless steel, finished with specialised surface treatments, combined with translucent blue glass and earthed in basalt.

“Dancing Wall” was commissioned by Brisbane City Council (BCC) as part of its program of Suburban Centre Improvement Projects (SCIPs) which aim to improve economic vitality, focus on community life and enrich local activity. The Nundah SCIP is one of the larger projects in the scheme with a budget of $2.5m.

The artwork is a sculptural balustrade set on the hilltop at the corner of Buckland Street and Sandgate Road. Its design symbolises the local environment which was once rich in waterholes and is now the focus of BCC and Wildlife Preservation Society rehabilitation initiatives.

According to Della Bosca, the piece is not just about the past: the materials and design provide an inspirational link to the future.

The client has expressed satisfaction with the completed project, with Deputy Mayor Councillor Quinn commenting that it fulfills the Council’s objectives of “good design and creative activity to build a prosperous city.”

FABRICATION

“Dancing Wall” was fabricated by Della Bosca in grade 316 stainless plate, flat bar and rod supplied by ASSDA member Austral Wright Metals. It houses five panels of slumped and toughened ‘azurelite’ glass, made by artist Shar Moorman, internally illuminated by concealed LED lighting.

Most of the structure was fabricated from rolled stock to bring an organic quality to the design. The intricate forming was carried out by local firm BJR Metal Rolling & Pressing who specialise in rolling compound curves.

SURFACE FINISH

Integral to the design are the surface treatments which suggest reed and water textures. ASSDA member Australian Industrial Abrasives helped to investigate the products, appropriate tooling and techniques to achieve the desired effects. The finishing on larger areas was completed with a Dynacushion on a variable speed sander polisher, using abrasive belts in a range from P80 to P150 Zirconia/Alox and finishing with 3M Blue Scotchbrite. The tighter, more intricate areas were finished using a Dynafile and various contact arms and the same range of abrasive belts.

An easily achievable, cost-effective maintenance schedule using an activated surfactant cleaner quarterly and a passivation gel as required has been implemented by Brisbane City Council.

The cleaning agent removes oil, grease and dirt, and also removes surface free iron which may cause discolouration or more serious corrosion.

This step is followed by a passivation gel which chemically generates the chrome oxide passive film on the surface to enhance corrosion resistance for stainless steel installed in high corrosion environments.

ARTISTIC POSSIBILITIES

Della Bosca says the qualities of stainless steel can best be conveyed by allowing the material to interact with light. “As fabricators well know it is easy to ‘muddy’ the surface of stainless, but if care is taken and correct procedures followed, the metal can give opportunities to a surface finisher.

“I work with the stainless to allow it to speak of more than itself. This is much more important to me than trying to force a finish.”

This article featured in Australian Stainless Issue 24 - March 2003.