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Posted 17 May 1999

When the United States Navy required 35 lightweight transportable recompression chambers in the late 1980s, Cowan Manufacturing took up the challenge of developing the units.

Cowan Manufacturing developed a prototype out of a virtually unknown material. It was duplex 2205 (UNS 31803) stainless steel.

No other manufacturer in the world was producing chambers out of 2205 and, after six years of negotiations, Cowan was sourced as the sole supplier of the chambers.

Cowan chose 2205 for its high strength, light weight and corrosion resistant properties. This enabled them to meet the Navy's requirements without the weight and corrosion problems of other materials.

Traditionally, recompression chambers have been made out of carbon steel and required high maintenance because of the severe marine environment in which they are used (on ships at sea). Chamber walls had to be thick to combat the effects of corrosion and so were very heavy.

The strength and corrosion resistance of 2205 over other materials enabled the chamber shell thickness to be reduced to 3mm. The thinner chamber walls effectively halved the weight of the units and corrosion resistance lengthened their service life.

However, Cowan faced some difficulties with the material because it was new on the market at the time. Staff had to be specially trained in welding techniques for the 2205 which had to be approved by Navy certification teams. (2205 is now a common material that is used for many industrial applications.)

The 2205 material was supplied by Sandvik Australia. The 3mm x 2000mm wide coil material was sized on its cut to length line and plasma arc cut the conical sections and the end cap discs which were then formed by Dome Engineering.

The strict quality requirements specified by the US Navy resulted in all material being ultrasonically examined and charpy tested before processing.

The chambers were produced at the Cowan Manufacturing facility at Warners Bay in New South Wales. Cowan has since become a specialist
in its field, supplying recompression chambers to 12 countries including the United States and Australia.

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


Posted 17 May 1999

Queensland Rail has achieved international recognition for its use of stainless steel in coal wagons by winning the ferritic stainless steel category in the Stainless Steel Awards in South Africa recently.

Entrants were judged on criteria including usage, application, substitution, growth, fitness for purpose, cost saving and effectiveness of solutions.

The award recognised Queensland Rail's use of weldable UNS S41 003 stainless steel as the preferred material for coal wagons. These wagons have performed successfully for 10 years.

According to Queensland Rail, the stainless has proven to be long lasting and low maintenance in comparison to aluminium and carbon steel wagons which were previously used. They intend to replace 55% of their fleet (3079 wagons) with stainless wagons by 2001.

The main advantage of using stainless steel over other materials is its resistance to corrosion.

All coal in Queensland is washed at the mine and transported wet. Wagons made out of materials susceptible to corrosion deteriorate very quickly under these conditions. For example, carbon steel wagons need to be coated with hot zinc every 1 0 years to protect against corrosion. Because this is not necessary with stainless, dramatic lifecycle cost savings can be achieved. Additional cost savings are made with stainless because improved design has resulted in reduced tare mass which reduces the number of wagons needed to carry the same amount of coal. This leads to lower operating costs per tonne of coal hauled and less demand on the infrastructure as fewer trains are running.

Until recently the application of stainless to coal wagons had been disregarded due to perceived high cost. However with the development of low cost, weldable ferritic grades of stainless, its use for coal wagons was reassessed and found to be effective.

The durability of stainless steel had previously been recognised in the railway industry in passenger trains (grade 301) and wagons carrying water to isolated regions (small amount of grade 304).

Stainless steel is now being considered for other freight wagons, with small numbers of wagons that haul aggressive material concentrates being built in grade 316.

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


Posted 17 May 1999

The Regency Institute of TAFE (Elizabeth Campus) in Adelaide has developed an exciting new course that will 'bridge the gap' in knowledge about the welding and fabrication of stainless steel.

Until now there have been only three fabrication and welding training modules available in Australia and they have all applied to light sheet metal. The need for a practical course to teach skills for heavier gauge stainless steel was identified by the Regency Institute of TAFE.

After close consultation with industry, the Regency Institute developed new modules that will fill this need by teaching skills appropriate for upskilling of existing workers and training new ones. Unlike existing courses, which focus on teaching skills to new workers (apprentices) only, this course also targets existing workers.

Three stainless steel welding modules, TIG (tungsten inert gas) welding, MIG (metal inert gas) welding and MMA (manual metal arc) welding have been developed to assist to address the skill shortage.

The modules have been nationally accredited. This allows them to be taken up by learning institutions and organisations Australia-wide and to be accepted as training towards a recognised qualification.

John Coudraye of the Regency Institute of TAFE (Elizabeth Campus) explained the campus was fortunate to have received a capital grant from the South Australian government to purchase capital equipment for the course.

"The grant was given as part of the government's strategic development plan for training," John said.

"Ten of our staff were also sent to Cigweld in Victoria to train for four days in technology and consumables in stainless steel and welding."

The program commences on 3 May, with 12 workers from the Barossa Valley being upskilled. The participants will complete the three modules developed by the Regency Institute of TAFE as well as an additional three light fabrication modules with an emphasis on heavy gauge material.

In addition to its upskilling focus, the course will also be incorporated into apprenticeship training.

Although apprenticeship training is currently available in Melbourne, the Regency Institute of TAFE's course will make a significant contribution to the development of a skilled workforce of stainless steel specialists, particularly important to the growing wine industry in South Australia.

The need for apprentice training in stainless steel was confirmed in 1996 by research conducted by NIETL in conjunction with Melbourne based ASTEP (Alignment of Skills Training to Employment).

At that time, apprentice training focused on various materials (such as carbon steel) and was not meeting the skills needs of stainless steel employers, including the large conglomerate of stainless steel industry in the northern region of Melbourne.

ASTEP conducted a survey which identified a need for full skilling, semiskilling and upgrading of skills in the stainless steel industry.

They chose to focus on full-skilling (apprenticeship) as the underpinning issue. A stainless steel apprentice course was developed with the Northern Melbourne Institute of TAFE and launched in 1997.

Now in its third year, ongoing improvements to the course have seen it develop increased understanding between training providers and participants and their employers, especially through its mentor scheme.

Australia's stainless steel industry employs between 7,000 to 1 0,000 people nationally and adds more than $1.1 billion to the economy each year. These two courses pave the way for further developments in the challenge to provide adequate training to establish a skilled workforce of stainless steel specialists.

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


Posted 28 February 2000

15 million dollars worth of stainless steel has been used to construct the largest rotary fermentation area in Australia.

The facility at Southcorp's Karadoc Winery in Victoria comprises 88 stainless steel red grade processing tanks, pipes and tubes, brine jackets and rotary fermenters.

Southcorp Wines Engineering Manager (Eastern Region) Geoff Leighton said stainless steel was preferred by the wine industry because it is "corrosion resistant, provides a stable environment for the wine, is easy to clean and maintain and has a long service life."

Grade 304 stainless steel was used for the tanks, with a thickness range of 2mm - 6mm, with the highest tank 1 5 metres tall. An extensive amount of 304 and 316 tube was also used.

ASSDA members Atlas Steel (SA), Alfa Laval, APV Valves and James Contract Supplies were all involved in the project.

The expansion brings the Karadoc site's total storage capacity to approximately 93 million litres.

The winery, which produces known brands Lindemans, Queen Adelaide, Kaiser Stuhl and Matthew Lang exports approximately 60% of its bottled wine production.

"The project has provided infrastructure to the district and significant employment opportunities in the areas of viticulture, transport and production facilities," Mr Leighton said.

Mr Leighton said while stainless steel met the needs of the wine industry, there was room for improvement.

"Stainless steel demand exceeds supply on occasions," he said. "It is not totally corrosion resistant and requires diligence in the specification and fabrication process."

The Karadoc project is one example of current growth in the Australian wine industry, which has brought with it exciting opportunities for the stainless steel industry.

Domestic wine production has increased five fold since 1966, from 156 million litres to over 800 million litres.

Vision 2025, a strategic plan by the Australian wine industry, aims to make the industry a global force by achieving $4.5 billion in annual sales of wine and 6.5% of the value of world production by 2025.

Results to date have been positive, with 1999 total sales estimated to be approximately $2.4 billion and 3.5% of the world export volume.

The number and size of fabrication firms in wine growing regions is expanding and as such, real opportunities to explore new applications and methods of design, fabrication and maintenance exist.

To assist the wine and stainless industries meet their objectives, ASSDA is conducting "Using Stainless Steels in the Food Industry" seminar in May and June which will cover fabrication, corrosion, welding, cleaning and sanitation issues for stainless steel use in the food industries as well as issues specific to the wine industry.

For more information on ASSDA's "Using Stainless Steels in the Food Industry" Seminars, please contact ASSDA on (07) 3220 0722.

REFERENCES
1. Australian Wine Foundation (1996) Strategy 2025 - The Australian Wine Industry.

This article featured in Australian Stainless magazine - Issue 15, February 2000.


Posted 28 February 2000

When the Gold Coast City Council was seeking a stable and visually stunning medium for use on their Kirra Point board walk project, they looked no further than stainless steel!

Geoff Clemence, Design Coordinator, said Council engineers chose stainless steel for the upright posts and moveable hand rail system for safety, corrosion resistance and aesthetic reasons.

"Stainless is far superior to wooden handrails in terms of safety and lasting life and will require far less maintenance," Mr Clemence said.

"From an aesthetic point of view, the stainless steel fits in beautifully with both the concrete pavement and the timber board walk that we will be installing in the near future," Mr Clemence said.

"Once the board walk is built, there will be a vertical drop to the beach below - an important safety issue met by using stainless steel handrailing.

"We had to choose what the best solution would be to the issue of safety that the steep drop off on the side of the walkway would cause," Mr Clemence said.

"Stainless steel was the safest option."

The board walk project is being undertaken in two stages, the first of which involved constructing a cement walkway and handrails along the Kirra Point foreshore.

The second stage will see the construction of a timber board walk out over the foreshore onto the beach.

ASSDA Sustaining Members Tom Stoddart Pty Ltd supplied 186 custom made upright posts and supplied and installed 326 metres of stainless steel tubular handrails.

Both were made from 316 grade stainless steel with a number 4 finish.

The upright posts were passivated in nitric acid after manufacture to ensure a clean surface and promote corrosion resistance.

During the installation, the welds in the posts were fully grounded and polished on site to stop sand and salt deposit build-up.

The hand railing is made up of 6 metre segments of tubular stainless steel welded on site.

Expansion joints are included every 7.2 metres.

The expansion joint allows for thermal movement and the inclusion of additional railings when a timber board walk is built in 2001.

The Gold Coast City Council engineers acknowledged the assistance provided by the Australian Stainless Steel Development Association in highlighting the possibilities and advantages of stainless applications, in meetings leading up to specification in the project.

This article featured in Australian Stainless magazine - Issue 15, February 2000.


Posted 28 February 2000

75 tonnes of stainless steel has been used to replace the floor in an enormous tank at QNI Limited's Yabulu Refinery near Townsville in North Queensland.

The tank is one of a series of seven thickener tanks, each of which is 50 metres in diameter. The purpose of the tanks is to form a counter current decant wash circuit for leached ore. Solid tailings are separated from liquor streams in the tanks which act as large settling devices, separating leached ore from a leached solution for the recovery of nickel and cobalt.

When the floor plate of one of the tanks was due to be replaced in June this year, QNI chose stainless steel for the job.

According to QNI's Deputy General Manager lan Skepper, the deciding factors in the choice of stainless were that it was relatively inexpensive and offered increased service life.

"The tanks have been in service for 25 years and the floor plates require replacement on a rolling basis," Mr Skepper said.

"They operate in a harsh environment, holding a solution which consists of strong ammonium hydroxide with up to 15 grams of sulphate per litre heated to 50 degrees celsius. This harsh chemical composition means that the floor plates suffer from severe corrosion and need to be replaced every 10 to 12 years.

"Traditionally we have used mild steel, but chose to use stainless this time because the material cost was not substantially higher particularly when the life expectancy of the floor will double due to the corrosion resistant properties of stainless."

Stainless steel was chosen also for its mechanical robustness and because it can be repaired or modified by workers who possess relatively standard trade skills.

To replace the floor plate, the tank had to be taken offline for six weeks resulting in reduced washing efficiencies and reduced metal recoveries at the refinery during this period.

"Future disruptions to the refinery due to replacements of thickener tank floor plates will now be reduced, because we expect the floor of this tank to last for at least 25 years," Mr Skepper said.

The job involved insitu welding of 5mm sheets of grade 304 stainless laid onto a sand bed.

The stainless steel for the project was supplied by Atlas Steels (Australia) Pty Ltd, Australian Stainless Steel Development Association Levy-paying members.

This article featured in Australian Stainless magazine - Issue 15, February 2000.


Posted 28 February 2000

As we pack up our Christmas decorations, vow to lose those extra kilos gained over the holidays and make plans for the new year, the festive season seems so long ago - not so far for travellers and pedestrians on St Kilda Road in Melbourne.

Perched in front of Central Equity's three new apartment buildings are 12 three metre tall stainless steel trees which, although not specifically designed as Christmas trees, have stylised conical shapes that have a distinctly Christmas 'feel' about them.

Central Equity commissioned Phillip Naughton of Design Inferno to design the trees to complement the prestigious $123 million complex.

"Trees were specifically chosen for the design to reflect the living trees on the boulevard in front of the building," Mr Naughton said.

"They also add a human element to the complex. Because the buildings are 24 stories high, the architects, the Span Group, paid close attention to the surrounding landscape to ensure that they would not be imposing.

"We worked closely with the Span Group when designing the trees so that they would add to the feel of the complex," Mr Naughton said "In fad, unless you look straight up, you don't realise the scale of the buildings because their surrounds are so comfortable."

Stainless steel was chosen for the design for its inherent qualities.

"The design brief specified that the trees had to be low maintenance. Stainless steel fitted this brief as well as adding other qualities such as simplicity and the sense of movement that could be achieved through different surface finishes," Mr Naughton said.

"As one side of each tree is mirror finished, with the other side satin finished, they reflect the seasonal colours of the living trees on the boulevard. They have changed from reflecting little colour through the winter months when the deciduous trees were without leaves, to reflecting the lush green growth of spring."

According to Joe Delacruz of DBM Industries, the trees' fabricator, welding was the most difficult aspect of the fabrication.

"The design of the trees made them susceptible to buckling during welding," Mr Delacruz said.

"To add to the difficulty, the welds had to be invisible."

As part of the careful planning for the job, DBM first built scale models of the trees from timber.

The trees were laser cut and mirror finished at DBM Industries' facility at Reservoir in Victoria. ASSDA members MME Surface Finishing of Seaford in Victoria did the satin finish.

Each tree is made from approximately 400 kilograms of grade 316 stainless steel sheet set into a concrete base which is covered with a 20mm base plate. They are capped with 10 x 30mm capping. ASSDA members Atlas Steels supplied the stainless for the job.

The trees are located on 150 metres of streetscape on St Kilda Road (near the intersection of Toorak Road).

This article featured in Australian Stainless magazine - Issue 15, February 2000.


Posted 29 August 2000

The common austenitic grades of stainless steel, 304 and 316, are also available with controlled low or high carbon contents, know as "L" and "H" variants, with particular applications.

Low carbon or "L" grades are used to prevent or delay sensitisation  of stainless steel at elevated temperatures and the resulting lower corrosion resistance. The problematic temperature zone is 450-850°C, encountered during welding or specific application environments. "L" grades are often available in thicker selection sizes, greater than about 5mm in flat products.

High carbon or "H" grades are used for higher strength.

Substitution between standard, "L" and "H" grades is often possible allowing many specifications to be met from existing stock.

WHAT "L" GRADES ARE AND WHY THEY ARE USED
The low carbon "L" grades are used where high temperature exposure will occur, including welding of medium or heavy sections. The low carbon is one way of delaying or preventing grain boundary carbide precipitation (often referred to as sensitisation) which can result in intergranular corrosion in corrosive service environments. As shown in the time-temperature-sensitisation curve (right), there is an incubation time before the precipitation of carbides at temperatures in the range of about 450-850°C. The time for precipitation to occur is highly dependent upon the amount of carbon present in the steel, so low carbon content increases resistance to this problem. Because of their application area the "L" grades are most readily available in plate and pipe, but often also in round bar. In the absence of heavy section welding, or of high temperature exposure, the corrosion resistances of the standard and "L" grades are usually identical.

WHAT "H" GRADES ARE AND WHY THEY ARE USED
"H" grades are higher carbon versions of standard grades and have increased strength, particularly at elevated temperatures (generally above 500°C). Long term creep strength is also higher. "H" grades are primarily available in plate and pipe. Applicable grades are most commonly 304H and 316H, but high carbon versions of 309, 310, 321, 347 and 348 are specified in ASTM A240/A240M. These grades are susceptible to sensitisation if held in the temperature range of 450-850°C. Once sensitised, impaired aqueous corrosion resistance and some reduction in ambient temperature ductility and toughness will result (usually irrelevant in high temperature applications).

WHAT THE DIFFERENCES ARE

  1. Composition limits for 304 and 304L are identical except for carbon content (304L does permit up to 12.0%Ni, compared to 10.5% max for 304 -but given the cost of nickel it is usual for both grades to have close to the minimum of 8.5%, so there is no practical difference). Neither grade has a minimum carbon content specified. A carbon content of 0.02% for example complies with both 304 and 304L specifications.
  2. 304H has the same composition specification as 304 except for the carbon range of 0.04-0.1 0% (note the minimum limit for carbon) and that the 304H does not have the 0.10% nitrogen maximum limit which applies to both standard and "L" grades. Also, all austenitic "H" grades must have a grain size of ASTM No. 7 or coarser.
  3. The relationship between 316, 316L and 316H is the same as that between the 304 series of stainless steels. Only the carbon contents differentiate 316, 316L and 316H grades (and the nitrogen and grain size limits mentioned above). Carbon contents are listed in Table 1 (from ASTM A240/A240M). Specifications for some other products, particularly tube and pipe, have a carbon limit of 0.035% or 0.040% maximum for 304L and 316L, but are otherwise the same.

    TABLE 1:
    Grade UNS Number Specified Carbon Content (%)
    304 S30400 0.08 max
    304L S30403 0.030 max
    304H S30409 0.04 - 0.10
    316 S31600 0.08 max
    316L S31603 0.030 max
    316H S31609 0.04 - 0.10


  4. Mechanical property specification differences are illustrated in Table 2 (from ASTM A240/A240M). In practice, steel mills generally ensure that the "L" grade heats meet the strength requirements of standard grades, ie all 304L will have yield/tensile properties above 205/515MPa, so will meet both standard and "L" grade requirements.

    TABLE 2:
    Grade UNS Strength (MPa) min Tensile Strength (MPa) min Yield (%) min Elongation Hardness (HB) max Brinell Hardness (HRB) max Rockwell
    304 S30400 515 205 40 201 92
    304L S30403 485 170 40 201 92
    304H S30409 515 205 40 201 92
    316 S31600 515 205 40 217 95
    316L S31603 485 170 40 217 95
    316H S31609 515 205 40 217 95
  5. Dimensional and other requirements are the same for standard, "L" and "H" grades.
  6. Pressure vessel codes (eg AS 121 O) and pressure piping codes (eg AS4041) give allowable working pressures for each of the grades at nominated elevated temperatures. These codes allow higher pressure ratings for standard grades than for "L" grades. The codes do not permit the use of "L" grades above 525"C (AS4041) or 425"C (AS1210). Both codes include a clause stating that for use above 550"C the standard grades must contain at least 0.04% carbon. 304 or 316 material with 0.02% carbon are therefore not permitted for these elevated  temperatures, whether called "L" or not. At temperatures from ambient up to this high temperature cut-off "L" grade heats with the standard grade pressure ratings would be permitted, so long as the material was in full compliance with the standard grade composition and mechanical property specifications. As discussed above, it is normal practice for this condition to be met.

    The pressure vessel codes give the same allowable pressure rating for "H" grades as for standard grades -this is logical as the "H" grades are simply the standard grades with their carbon contents controlled to the top half of the range, or slightly above.

ALTERNATIVE GRADE USAGE
Because of availability issues it is sometimes desirable to use a product labelled as a standard grade when an "L" or "H" grade has been specified, or vice versa. Substitution can be made under the following conditions:

  1. "L" grades can be used as standard grades so long as the mechanical properties (tensile and yield) conform to the standard grade requirements and high temperature strength is not a requirement. "L" grades usually comply with standard grade requirements, but Mills' test certificates need to be checked on a case by case basis. It is common for steel mills to supply "L" heats when standard grades have been ordered. The practice is legitimate and should  not present problems to fabricators or end users.
  2. Standard grades can be used as "L" grades as long as their carbon content meets the "L" grade maximum limits.
  3. It is increasingly common for "dual certified" products to be stocked - particularly in plate, pipe and bar. These materials fully comply with both 304 and 304L or 316/316L. Dual certified product is deliberately intended to fulfill requirements for both standard and "L" grades, but cannot be used in applications for "H" grade. If an application requires an "H" grade, this must be specified at time of order. Standard grades can often be used in place of "H" grades so long as their carbon contents meet the "H" limits (generally 0.04-0.1 0%). Grain size requirements may have to be satisfied by extra testing. The product and its test certificate may describe it as a standard 304 or 316 unless it was originally manufactured as an "H" grade. Details of the test certificate will confirm grade compliance.
  4. "H" grades can be used as standard grades so long as their carbon contents are 0.08% maximum, and nitrogen 0.10% maximum. This is likely, but would need to be checked.

REFERENCES FOR FURTHER READING
AS 1210
Pressure Vessels

AS 4041
Standard Specification for Pressure Piping

ASTM A240/A240M
Heat-resisting Chromium and Chromium-Nickel
Stainless Steel Plate, Sheet and Strip for Pressure Vessels

This technical article featured in Australian Stainless magazine - Issue 16, August 2000.


Posted 29 August 2000

New (and extended) life has been injected into a Brisbane landmark courtesy of a stainless make over worth about $1.2 million.

In an application believed to be the first of its kind in Queensland, engineers have used grade 316 stainless steel to replace the bearings on Brisbane's Victoria Bridge.

The transition from original carbon steel to stainless has increased the service life of the bearings to at least 50 years from 30 years, giving the Brisbane City Council at least 20 years before the enormous labour and logistical costs of servicing bearings is required.

he bridge, opened in 1969, spans the Brisbane River between the Central Business District and South Bank and is a major arterial link in the city's transport system. Any interruption to traffic flow is disruptive and costly.

Corrosion of the bridge bearings has always been an issue due to its proximity to tidal water and also from the corrosive influence of droppings by pigeons that nest around the bearings.

The Brisbane City Council hired an independent consultant, Dr Nick Stevens, to design the bearings and advise on technical issues associated with their replacement. After consultation with Hercules Engineering the use of stainless steel was recommended.

Principal Asset Officer, Structures, Brisbane City Council. Dr Peter Shaw said although the stainless steel bearings were marginally more expensive than carbon steel, the extended service life offered by stainless negated the Council's initial concerns.

"The initial outlay is completely negligible compared with the extended service life that stainless steel provides and the cost of installation," Dr Shaw said.

"We (the Council) can now wait at least an extra 20, hopefully 50 years before we need to plan such a major operation."

In future the bearings should suffer wear only and hence should require only replacement of the pot This operation should be far cheaper than complete bearing replacement.

Examination of the 30 year old carbon steel bearings showed severe overall corrosion, deep gouge marks and pitting corrosion where the PTFE (teflon) between some of the bearing plates had completely worn away.

Twin pot sliding bearings, and single pot fixed bearings were custom made for the project and installed on site. Grade 316 stainless steel was used for all steel components of the bearings, separated from the mild steel bolts and nuts by synthetic washers. The surfaces on the sliding components of the bearings were polished to a mirror finish to minimise friction.

Grade 304 stainless steel woven mesh was installed around the bearings to keep the pigeons out and further protect against corrosion.

The bearings were fabricated by Hercules Engineering in Sydney with stainless steel supplied by ASSDA member Sandvik Australia.

This article featured in Australian Stainless magazine - Issue 16, August 2000.

Stainless Blurs the Boundaries


Posted 29 August 2000

A Melbourne artist and designer is using stainless steel to blur the lines between form and functionality.

Colin Kirkpatrick from Modifie Designs adapts geometric shapes inspired by sculpture to create works that can transform from conversation pieces to coffee tables in seconds.

Cubes and three dimensional rectangular shapes are fabricated from grade 304 stainless steel sheeting welded to a timber subframe, then attached to castors for mobility and versatility.

The custom-sized shapes can be used as either furniture or sculpture and as a single unit or separated into individual pieces.

The Modifie range also includes coffee tables with stainless steel frames contrasted by glass, marble, sandstone or bluestone tops.

As versatile as the cubes, the coffee tables can also be stacked to form shelves and storage units.

Of crucial importance to Kirkpatrick is that as well as being aesthetically pleasing, his work be functional, a criteria met through design and the use of stainless steel.

'I love the cleanliness and exclusive look of stainless," Mr Kirkpatrick said.

"The material complements perfectly the angles, smooth surfaces and form of the furniture."

Each piece is designed and fabricated by Kirkpatrick in his Highett workshop using primarily grade 304 stainless steel, TlG welded top and bottom and polished with a No. 4 finish.

Kirkpatrick's work is available from a number of furniture stores in Sydney and Melbourne, including Orsson & Blake in Sydney, Blend Furniture in Collingwood, Urban Attitude in St Kilda, Crowded House Design in Malvern, Cochrane & Galloway in Hawthorn and Outhouse in Fitzroy.

He plans to extend the range to include multi-fundional, adaptable entertainment units and storage units, all made from stainless steel.

"In my opinion, not many other materials have the exclusivity of appearance and style that stainless steel has," Mr Kirkpatrick said.

Stainless steel used for the furniture is supplied by ASSDA member Dalsteel Stainless.

This article featured in Australian Stainless magazine - Issue 16, August 2000.


Posted 29 August 2000

When millions around the world watch the Sydney Olympic Games this September, they will also be experiencing the best of Australian architecture, with particular emphasis on stainless steel.

Stadium Australia, located at Homebush Bay in Sydney's inner city in the centrepiece of the Olympic site. Here, events such as the opening and closing ceremonies and the track and field program will be played out. Closer examination of the sit reveals the use of stainless steel in a myriad of applications, both aesthetic and functional. Perhaps more importantly, the use of stainless steel helps meet the organiser's "green" commitment: to use materials with minimal impact on the environment and designs that reduce waste and conserve resources.

THE STADIUM
Seating 110,000, Stadium Australia is the largest stadium in the history of the Olympic Games. To give an idea of its size, the two main curved trusses span 296 metres and four Boeing 747s would fit side by side under the span of the main arch.

The roofing material was supplied by ASSDA member Atlas Steels (Australia) Pty Ltd, the handrails by ASSDA member Sandvik Australia.

Nineteen lighting towers, representing the number of cities in which the Olympic Games have been held to date, stand like sentinels guarding the entrance to Stadium Australia.

The towers consist mostly of concrete and painted steel, but grade 316 stainless steel rods, 25 millimetres in diameter, provide tension in each corner, while 316 doors and infill panels, with a No. 4 finish, exist at ground level.

The names of each of the cities where the Games have been held are glass-bead blasted on to grade 316 sheet with a No. 4 finish.

These towers each carry solar panels that contribute to the public elecricity grid an amount of power equal to that consumed by the towers at night.

At the bottom of one of the towers is a Munich Memorial to honour the athletes who died at the 1972 Munich Olympics. The memorial consists of three plaques fabricated from grade 316 stainless steel and glass, the names being engraved and paint filled in a surface with a No. 4 finish. Stainless steel channel sections, glass bead blasted on the inside and mirror polished were used around some of the edges.

Spread over six levels, the kitchens at Stadium Australia will see almost as much action as the field! Anticipated to feed about 110,000 people every day during competition, the kitchens have been fitted out with stainless steel equipment including benches, exhaust hoods, 200 deep-fat fryers and 300 upright refrigerators. ASSDA members Curtin Foodservice Equipment Pty Ltd supplied a bulk of the equipment, including over four and a half kilometres of stainless steel benches, 145 stainless steel hi-velocity extraction hoods, 200 deep-fat fryers, bain maries, refrigeration equipment, bulk and plated hot food holding carts and more than 200 mobile trolleys. Grade 304 stainless steel for the equipment was provided by ASSDA member Fagersta Steel.

THE OLYMPIC VILLAGE
Home to 15,000 athletes, officials and coaches during competition, the Olympic Village reflects stainless steel's contribution to the "Green Games". 6,000 kilograms (10,500 square metres) of grade 316 stainless steel mesh were installed to provide a chemical-free termite barrier to over 500 houses in the Village.

Fabricated and installed by Termi-Mesh Sydney Pty Ltd, the stainless steel mesh provides a physical barrier around the building perimeter and is collar clamped to pipes and other entry points. The result is a permanent obstruction to termites that eliminates the use of potentially dangerous chemicals.

OLYMPIC BOULEVARD
Olympic Boulevard, which passes key venues such as Stadium Australia and the Aquatic Centre, features spectacular fountains with stainless steel components.

Water jets, each covered by a grade 316 stainless steel cowl, provide a cascading arch at Fig Grove.

Fabricated grade 316 stainless steel gratings, black chrome plated so they are almost invisible under water, are used as safety screens. Grade 316 sections are also used to ensure the water cascades evenly along the length of the feature and as structural supports.

At the far end of the Boulevard is a fountain featuring lines of tubular water jets. Each jet comprises an inner structure of grade 316 stainless steel tubes clad with 3 millimetre thick 316 sheet, formed into a tapered cylindrical section with a No. 4 finish.

The underground pump house receives fresh air through spiral, welded ducting consisting of 250 millimetre diameter grade 316 stainless steel. A nearby wooden viewing pier has 316 handrails on galvanised steel uprights.

THE TORCH
Perhaps the most evocative symbol of the Games is the Olympic Torch, which carries the flame from Olympia in Greece to Stadium Australia, via the Olympic Torch Relay.

he design of the approximately 1 kilogram, 72 centimetre tall torch includes three layers representing earth, fire and water. The inner layer is polished stainless steel, the middle layer anodized aluminium and the outer layer specially coated aluminium.

Thin grade 316 stainless steel strip was used to form a skin inside the grade 430 stainless steel tube inner layer, acting as a shield against heat, wind and rain. Also, very fine (25 micron opening) 316 stainless steel gauze was installed as a final filter to clean the liquid propane/butane gas mixture that fuels the torch, thereby preventing contaminants from extinguishing the flame.

The torch was fabricated by Sydney firm GA & L Harrington, who produced over 14,000 torches available for purchase by the 10,000 runners participating in the Torch Relay.

This article featured in Australian Stainless magazine - Issue 16, August 2000.


Posted 5 January 2001

Sports fans trekking to Melbourne's Colonial Stadium will enter the ground via a 200 metre long, 20 metre wide bridge shrouded in stainless.

The Bourke Street Pedestrian Bridge, which connects Spencer Street Station to the eastern entrance of the $460 million sporting arena, opened in March 2000, makes extensive use of stainless steel to stunning effect.

A 200 metre long canopy comprising 14 rolled cascading stainless steel sheets divided in sections by red coated curved steel antlers protects pedestrians queuing on the south side of the bridge. The antlers, made from carbon steel, provide lighting and primary support to the stainless steel canopy.

400 metres of stainless steel handrailing with balustrades run the length of each side of the bridge.

he bridge connects the Gateway to the east and adjacent Spencer Street Station and extends across the station to the West End Connection above North-South Road.

Pedestrians entering the 30 000 person capacity bridge on the station side are greeted by two red glass towers, large staircases and a crushed wall of stainless steel through which a ramp connects disabled access from street level to the bridge.

Wood Marsh, the firm commissioned to design the bridge, said stainless steel was chosen because of its appearance, low maintenance and longevity.

"With thousands of people expected to cross the bridge every time an event is on, we needed a material that would not only withstand this level of traffic, but would make an eye-catching entrance to the stadium."

"Stainless steel was the obvious material choice -it is durable, needs limited upkeep and achieved the look we were after."

The roof cladding consists of 20 tonnes of 1.6mm grade 316 stainless steel sheets rolled to a radius of approximately 325mm butt joined, with a No. 4 finish to both faces.

400 metres of 6 inch, Sched 40 grade 316 stainless steel pipe was used for the handrails, polished to a No. 4 finish.

The handrails were constructed at Shearform Industries' workshop and installed, invisibly fixed, on site. The roof cladding was fabricated and polished in the workshop and installed on site.

The roofing material was supplied by ASSDA member Atlas Steels (Australia) Pty Ltd, the handrails by ASSDA member Sandvik Australia.

This article featured in Australian Stainless magazine - Issue 17, January 2001.


Posted 5 January 2001

1,200 tonnes of stainless steel plate and coil and over 47,000 metres of stainless steel pipe and tube has been used in the construction of a new $400 million unbleached pulp and paper mill in Tumut, New South Wales.

The Visy Pulp and Paper Mill will produce 240,000 tonnes of unbleached kraft pulp and packaging paper annually, to be supplied to domestic and overseas markets.

Raw materials for the plant will come from local plantation timber sawmill residues and pulp materials from softwood plantations, and supplemented by domestic and commercially derived waste paper. The plant is being built using the latest technology, meeting the highest environmental standards.

Grades 304, 316 and 2507 stainless steel were used in pipes, storage tanks and vessels in the process area of the mill.

Approximately 1,200 tonnes of stainless steel plate and coil, ranging in thickness from three millimetres to 38 millimetres were used for the storage tanks. The storage tanks, 50 in total, have a capacity of nearly 30 000 cubic metres.

Grade 2507 stainless steel was used in smaller vessels that will contain highly concentrated liquids, sodium and potassium salts at high temperatures.

Visy Project Technical Manager Austin Davey said: "The combination of temperature and salt meant that 2507 was the only suitable material for the job."

304 stainless steel pipes will carry raw water, some chemicals and pulp used in the process.

Mr Davey said as well as its ability to deal with high temperatures and the corrosive environment of the plant, stainless steel was chosen for its cost-effectiveness and long life.

"We designed the mill to have at least a 30 year life, that's why we chose stainless," he said.

"We always look for the most cost-effective method for our projects.

"At the time of purchase, the price of stainless steel was very competitive and helped make the decision easy."

Fabrication was undertaken by a number of different companies in New South Wales, Queensland and Victoria.

Some of the piping for the mill was supplied by ASSDA member Skinner Engineering, with some storage tanks and vessels supplied by ASSDA members D&R Stainless and JC Butka Engineering Pty Ltd.

The majority of stainless steel used in the project was supplied by ASSDA member Sandvik Australia, with a proportion of the design work undertaken by ASSDA member Kvaerner.

Mr Davey said end users of stainless steel experience supply problems that he believes impact on the popularity of the material.

"Not all the materials or product forms are stocked in Australia. Lead times, availability and price movements must be watched."

The mill is expected to begin paper production in the middle of 2001.

This article featured in Australian Stainless magazine - Issue 17, January 2001.

 

 


Posted 5 January 2001

Reasons for using stainless steel threaded fasteners are the same as those for selecting other stainless steel components - generally resistance to corrosive or high temperature environments. In addition to the obvious benefits in improved aesthetics and longevity however, there can be significant cost savings if the joint will require disassembly and reassembly.

GRADES AND STANDARDS
Corrosion resistant fasteners are available 'off the shelf' in a variety of materials but by far the most comprehensive range is in stainless steel with more than 6 000 items available in Australia and many thousands more able to be sourced at short notice. Generally these are produced from grade 304 (A2), grade 316 (A4) or for less demanding applications, grade 303 (A 1 ). Grade classifications A 1, A2 and A4 are in accordance with International Standard ISO 3506; head markings often show this classification. It is common practice and legitimate to manufacture items labelled as grade 304 (or A2) from grades 302HQ or 304 depending on the type of fasteners and the manufacturing process. Less commonly, fasteners are available in hardened and tempered martensitic stainless steels, such as 410 (C 1) or in a higher molybdenum version of grade 316, often designated '2343'. An outline of the range of stainless steel fasteners available in Australia can be found in the Australian Stainless Reference Manual.

Stainless steel fasteners available on the Australian market in the main are equal to or higher in tensile strength than the carbon and low alloy steel fasteners commercially used, and are higher strength than most other corrosion resistant fasteners. Table one shows the comparison between stainless steel fasteners and the various grades of carbon steel and low alloy steel fasteners and Figure one shows the strength comparison of various corrosion resistant materials.

The vast majority of stainless steel fasteners available are produced to ISO 3506 Class 70 (this designates a minimum tensile strength of 700 MPa) and are marked as such. If there is no marking it should be assumed the product is Class 50 (minimum tensile strength of 500 MPa).

If a stainless steel fastener with a higher tensile strength is required there are some products available in Class 80, these are usually produced in grade 316 stainless steel. There have recently become available some stainless steel products in Class 100, also in grade 316 material.

CORROSION CONSIDERATIONS
Where corrosion is an issue, an inexpensive olution is to specify steel fasteners with some form of plating or organic coating rather than to use products manufactured from corrosion resistant materials. Although painted, plated or galvanised fasteners are usually adequate in applications where corrosive conditions are not severe, consideration should also be given to the cost of possible failure and loss of aesthetic appearance when the protective coating becomes damaged or compromised, in comparison to the cost of stainless steel product. Damage to the coating on steel products can be easily caused by the wrench or driver used for tightening, poor plating practices or simply from the turning action of one thread against another in assembly.

TIGHTENING AND GALLING
As with all fasteners the proper installation of stainless steel products is critical to its performance; this is particularly so with respect to tightening and galling.

Galling occurs when the stainless steel oxide surface film breaks down as a result of direct metal contact. Solid-phase welding can then take place (whereby material is transferred from one surface to another). The symptoms of galling include surface damage and seizing and freezing up of equipment. Galling commonly occurs when using stainless steel nuts and bolts together, where the contact points are subjected to high tightening torques.

Fasteners made in accordance with internationally recognised standards should ensure the uniformity of threaded products. Reasonable care should be taken when handling stainless steel fasteners to avoid any thread damage and keep the threads clean and free from dirt, coarse grime or sand. If the threads are tightened on sand or dirt the possibility of galling or seizing is increased.

Ways to reduce galling include:

ROLLED THREADS
Rolled threads are less susceptible to galling than machined ones as they have a smoother surface and the grain lines follow the thread rather than cut across it, which IS the case with machined threads.

TIGHTENING TORQUE
Bolts should be tightened to the correct torque using a torque wrench as overtightening will promote galling.

LUBRICATION
It is recommended that some form of lubrication be applied to threads prior to assembly. Propriety grease-type lubricants, containing tenacious metals, oils etc are available. Some commonly used lubricants contain molybdenum disulphide or nickel powder (sometimes with graphite materials*).

HARDNESS MODIFICATION
Galling can also be reduced by using two different stainless steels, of significantly different hardnesses, on the mating surfaces. A Brinell hardness difference of 50HB may overcome galling.

A common belief that the use of grade 316 studs with grade 304 nuts (or vice versa) will avoid galling is a myth (there is a notable difference in galling).

Table two shows some suggested maximum torque values for various diameters of stainless steel fasteners. This table is a guide only based on industry tests that provide maximum clamping value with minimum risk of seizing. The values shown are based on fasteners that are dry - free of any lubricants - and wiped clean of any foreign matter. The addition of a lubricant can have a significant effect on the torque-tension relationship. A lubricated fastener requires less torque to achieve the same level of tension and also makes the torque-tension relationship more predictable. Different lubricants can also have different effects. Figure two shows that effect on the torque-tension relationship of adding a lubricant.

TABLE TWO: TORQUE GUIDE (Nm)
Bolt Size Grade 304 (A2) Grade 316 (A4)
1/4" - 20 8.5 9
1/4" - 28 11 11
5/16" - 18 15 16
5/16" - 24 16 17
3/8" - 16 27 28
3/8" - 24 29 31
7/16" - 14 42 44
7/16" - 20 45 47
1/2" - 13 58 61
1/2" - 20 61 64
9/16" - 12 77 81
9/16" - 18 85 89
5/8" - 11 125 131
5/8" - 18 141 147
3/4" - 10 173 179
3/4" - 16 168 176
7/8" - 9 263 275
7/8" - 14 262 273
1" - 8 389 406
1" - 14 351 367
1 1/8" - 7 560 586
1 1/8" - 12 529 553
1 1/4" - 7 709 740
1 1/4" - 12 651 683
1 1/2" - 6 1 204 1 261
1 1/2" - 12 953

993

Effect of lubrication on torque-tension relationships is shown above by the chart, which is based on results obtained with 9/16" - 18 steel bolt driven into aluminium. For a non-lubricated bolt, torques of 13Nm - 14Nm were required to develop tensions of 3.5kN to 6.2kN. For a lubricated bolt, torque values ranged from 7.3Nm to 8.5Nm for 4.4kN to 5.5kN tension range.

Torque values are affected in various ways by different types of lubricants. Wax on either the bolt or nut, or both, also acts to reduce the torque requirements.

Source: Skidmore-Wilhelm Mfg. Co.

NEW AUSTRALIAN STANDARD
he new Australian Standard Cold Formed Stainless Steel Structures is due to be published in early 2001. This will include sections giving specific design data for stainless steel fasteners produced to both ASTM and ISO specification systems, In addition an Appendix gives details of the grades and strength levels and their applicable markings, extracted from ISO 3506.

*Graphite is substantially more noble than stainless steel. Care in specification of graphite in contact with stainless steel is required to avoid corrosion.

This technical article featured in Australian Stainless magazine - Issue 17, January 2001.


Posted 5 January 2001

Sixty tonnes of stainless steel has been exported to Hong Kong as part of an innovative Australian-designed and manufactured kit form, large span skylight project worth three quarters of a million dollars.

The 42 gable trussed skylights and sub-frames in varying sizes up to four metres wide and eight metres long were installed in a $90 million dollar treatment plant commissioned by the Hong Kong Government.

Grade 316 stainless steel was used for the skylight's precision pre-cut sub-frame members, welded maintenance ladders, lntalok mechanism assemblies, special profiles, on sight assembly jigs, pivots and fixings.

The project specified that the skylights be easily removed from the roof to allow crane access to equipment in the building. However, the skylights also had to be strong enough to withstand Hong Kong's coastal gale force winds. Sky Roof International (Victoria) undertook the project.

Sky Roof Director, lan Howe, said the specifier's requirements and environmental concerns were met by adapting stainless steel to the company's lntalok cyclonic glazing frame system.

"The government specified that they wanted something striking, low maintenance and durable," Mr Howe said.

"As the frames had to be robust for lifting and withstand the conditions inherent in a coastal region, the obvious choice was stainless steel."

The skylight was designed to use wind uplift force to operate the lntalok hold down mechanism.

When the aluminium skylight structure is forced skyward by wind suction on the glazing, the small surface area of the stainless steel sub-frame is unaffected. This creates a differential force between the skylight and the sub-frame which is transmitted to the lntalok mechanism via the stainless steel ladders. The stronger the wind uplift on the skylight, the tighter the stainless steel lntalok engages the building.

All the prefabricated stainless steel components for the skylights were produced in a zircon glass bead blasted finish by ASSDA member Hart to Hart Fabrications (Dandenong, Victoria).

The skylights were then shipped to Hong Kong in fully fabricated kit form for easy on site assembly.

Mr Howe said ASSDA's Australian Stainless Reference Manual was vital in providing stainless steel technical and supply information.

"I found the Reference Manual and other pieces of information very useful in learning more about stainless steel and also in helping me find a fabricator for the job - Hart to Hart Fabrications," he said.

Following the success of the Hong Kong project, Sky Roof International is working on a design for a skylight featuring stainless steel glazing frames.

This article featured in Australian Stainless magazine - Issue 17, January 2001.


Posted 5 January 2001

A special grade of stainless steel is being used in an Australian-developed environmentally friendly energy production method.

Solid oxide fuel cells extract the energy from fuels such as natural gas by electrochemical rather than traditional combustion means. producing cheaper, cleaner and more convenient eledricity.

lnterconned material made from half to one millimetre thick SAS 'Self Aluminising Steel' sheet conneds individual fuel cells together, conduding eledricity and heat within the fuel cell stack. The fuel cells are the brainchild of Melbourne-based company Ceramic Fuel Cells Limited and have been in development for eight years.

Managing Diredor, Ceramic Fuel Cells Limited, Dr Bruce Godfrey said stainless steel was the most suitable interconned material in terms of performance and produdion.

"Because the fuel cells operate at 800°C we need high temperature steels that can withstand the rigours of increasing temperatures and the fuels that we put into them," he said.

"Stainless steel in this respect fitted the bill perfectly for the stage of development we are at.

"The material has also proven very efficient during the prototype - development stage because it can be laser cut to size rapidly."

The special grade of stainless steel was chosen because of its superior performance in stopping the emission of chromium oxides from the steel. This chromium loss from the interconnect material destroys the fuel cell cathode.

Using the SAS grade of stainless steel solved the problem as its properties ensure chromium remains within the stainless steel interconnect material.

The current prototype size for the cell is 90 millimetres x 110 millimetres with the company anticipating using a variety of different shapes in the production stage.

Ceramic Fuel Cells Limited has schedules commercial production of the fuel cells to begin in late 2003.

This article featured in Australian Stainless magazine - Issue 17, January 2001.


Posted 5 January 2001

A tranquil oasis has been created amid the bustle of Brisbane's Central Business District, with the help of stainless.

'a tree a rock a cloud', by Brisbane-based artist Barbara Heath, blends symbols of the innovation and achievement of business with images from the area's original landscape.

The five metre long, three and a half metre wide and tall sculpture, located outside Central Plaza Two, features 21 stainless steel 'fins' and a gold titanium-clad stainless steel cloud, all mounted on a stainless steel base plate. The base plate is hidden from view by stones in a pool of water.

The resulting sculpture provides a quiet corner for contemplation away from the noise of the busy inner city.

Ms Heath said she chose stainless steel because of its qualities in capturing the light and movement of the surrounding environment.

"The stainless strudure permits light and casts shadows. It has a shimmering quality that responds to movement and changes in the prevailing light," she said.

Stainless steel was also chosen for its physical qualities.

"I really like the precise engineering that can be achieved with stainless steel," Ms Heath said.

"The light feeling evoked by the appearance of the material makes something very heavy look evanescent."

The fins were constructed from grade 316 stainless steel flat bar, polished to a No.4 finish.

The cloud was fabricated from 5mm grade 316 stainless steel sheet, rolled top and bottom laser cut, joined and welded. Stainless steel pins were inserted in a series of holes throughout the cloud to give it structure and connect the two cloud pieces.

The gold titanium cladding, featuring a patterned sheet finish, was fitted to the top and underside of the cloud with double sided tape.

The base plate was constructed from 10mm grade 316 stainless steel sheet, which was profile cut using plasma technology.

All pieces for the five and a half tonne sculpture were fabricated by ASSDA member G&B Stainless Pty Ltd in their Brisbane workshop and installed on site with the aid of a crane.

Stainless steel flat bar and sheet for the sculpture was supplied by ASSDA member Atlas Steels (Australia) Pty Ltd and Sandvik Australia Pty Ltd.

Ms Heath acknowledged the assistance given by the Australian Stainless Steel Development Association during the project's 18 month duration.

This article featured in Australian Stainless magazine - Issue 17, January 2001.

The Workhorse of Hydrometallurgy


Posted 17 May 200

Stainless steel has earned a reputation as the material of choice for the mining and hydrometallurgical industries. This article discusses suitable grades and applications and the emerging opportunities for stainless steel in these industries.

Hydrometallurgy involves the extraction and refining of metals in aqueous solutions. It encompasses a range of processes such as leaching, solvent extraction, ion exchange, electrorefining, electrowinning, precipitation and solid/liquid separation for numerous metals including copper, zinc, nickel, cobalt, uranium, gold, silver, aluminium and rare earths. As stainless steel is the 'workhorse' material for many of these processes, especially those involving sulphuric acid solutions, hydrometallurgy is a significant market whose importance is growing as new processes are developed and applied.

HYDROMETALLURGY EXPANDING
Historically, metals extraction has been dominated by pyrometallurgical processes such as roasting and smelting, while hydrometallurgy has generally played a relatively minor role. However, since the 1950s, its role has expanded significantly, helped along by a string of new technical developments. These trends seem likely to continue as pyrometallurgical processes fall out of favour due to factors such as falling head grades, environmental pressure against gaseous emissions, the need to treat lower grades and impure ores, and the growing desire to add value by producing metals at the mine site. Significant growth areas for hydrometallurgy have been uranium ore processing in the 1950s, 1960s and 1970s, copper in the 1970s, 1980s and 1990s, and more recently nickel and cobalt.

TYPICAL APPLICATIONS
Uranium ores are almost exclusively treated by hydrometallurgy. The most common process is sulphuric acid leaching of finely ground material
at atmospheric pressure and temperatures up to about 800°C, followed by solid/liquid separation and solvent extraction or ion exchange. Stainless steels and high nickel alloys have been extensively used for tankage, pumps and piping.

Copper has traditionally been extracted from oxide ores by sulphuric acid leaching, either in agitated tanks or by spraying on heaps and dumps. Interest grew dramatically after the introduction of solvent extraction technology in the late sixties which, when coupled with electrowinning, enabled high grade copper cathode to be produced on site. More recently, this approach has been expanded to treat secondary sulphide ores such as chalcocite, and processes are now being developed for the treatment of chalcopyrite, the dominant copper mineral which is normally smelted. These new processes include pressure-oxidation, bio-oxidation and other novel leaching technology. Along with all of this has been the successful introduction of the use of stainless steel blanks for electrowinning and refining. Stainless steel is particularly suitable for copper in sulphuric acid solutions because of the inhibiting effect of copper in solution on corrosion.

Nickel and cobalt hydrometallurgy has been significantly boosted by a number of recent developments including the installation of new pressure acid leaching (PAL) operations for laterites in Western Australia, the first application of tank bio-leaching for cobalt recovery, the development of pressure-oxidation and bio-heap leaching technology for nickel sulphides. Although the PAL operations have had difficult start-ups, the PAL process is likely to become a major force in the future treatment of laterites because of its relatively low energy consumption and high nickel and cobalt recoveries.

TYPICAL USES OF STAINLESS STEEL IN A NICKEL PAL PLANT
STAGE STAINLESS STEEL USED
Ore preparation and slurrying Grade 310 or super duplex grades
Pressure leach circuit Grade 310 or super duplex grades
Counter current decantation
(ccd) circuit
Tanks - grade 316
Rakes and rabble arms - grade 316
Refinery (separating nickel, cobalt
products, making metal)
Process piping - grade 316
TOTAL APPROXIMATE STAINLESS
STEEL USAGE (PER MAJOR PLANT)
6 000 TONNES


BRIGHT FUTURE

Current trends undoubtedly point to an expanding role and bright future for hydrometallurgy in the mining and metallurgical industries. Along with this should come increased opportunity for the use of stainless steels.

Image: Nickel Heap Leaching trial at Radio Hill, WA.

This article was written by Alan Taylor, Chairman of consulting company International Project Development Services and convener of the ALTA Nickel/Cobalt 2001 (Perth, WA, May 15 - 18).

This article featured in Australian Stainless magazine - Issue 18,  May 2001.


Posted 17 May 2001

Stainless steels are widely used in the food industries, including wine production, because of their corrosion resistance and ease of cleaning which result in negligible product contamination.

Long life can be expected from stainless steel equipment provided care is taken with:

> Vessel design
> Grade selection
> Fabrication procedures
> Maintenance practices.

The precautions to be taken are not complicated but are most important - neglecting to follow them can lead to rapid failure.

VESSEL DESIGN
Much can be done in the detailed design to improve corrosion resistance. The two cardinal rules are:

1. Design for complete and free drainage
2. Eliminate or seal weld crevices.

A series of drawings, with accompanying narrative, comparing good and bad design practices, are set out in Part Ill of Nickel Development Institute publication #11 007: Guidelines for the welded fabrication of nickel-containing stainless steels for corrosion resistant services.

GRADE SELECTION
Two stainless steel grades are particularly used in the wine industry, grades 304 and 316, and both 'standard' and 'low carbon (L)' versions are available. Their compositions are shown in Table One below.

Table One: Stainless Steel Grade Selection
GRADE CHROMIUM NICKEL MOLYBDENUM CARBON
304 18.0 - 20.0 8.0 - 10.5 - 0.08 max
304L 18.0 - 20.0 8.0 - 10.5 - 0.03 max
316 16.0 - 18.0 10.0 - 14.0 2.0 - 3.0 0.08 max
316L 16.0 - 18.0 10.0 - 14.0 2.0 - 3.0 0.03 max

The 'L grades are specified w here welding is to be carried out and there is concern that time-at-temperature may be sufficient to precipitate chromium carbides and hence cause sensitisation of the metal, resulting in susceptibility to intergranular corrosion.

The molybdenum content of grade 316 significantly improves its resistance to p1tting and crevice corrosion, particularly in the presence of chlorides. It also increases the material cost by about 20 to 25 percent.

For handling waters, grade 304 is satisfactory up to about 200 parts per million (ppm) chlorides, while grade 316 can be used up to 1 000 ppm chlorides.

Tartaric, acetic, tannic, malic and citric acids are not corrosive to stainless steel at the concentrations found in juices or wines. However, the level of su lphur dioxide is an issue. Grade 304 is generally regarded as resistant to corrosion when immersed in juice or wine at free SO2 levels up to 700 ppm. Above this, grade 316 is recommended. The problem is greater in the vapour space where sulphurcontaining acids can form. Grade 304 is not recommended for use in areas where there is more than 75 ppm SO2 in the liquid. This can lead to composite tanks using grade 316 in the ullage zone and grade 304 in the submerged zone.

FABRICATION PROCEDURES
Cracks and crevices in stainless steel welds can act as initiation points for pitting and crevice corrosion. They can also result in product contamination . The aim should be for smooth weld beads without porosity, slag inclusions or undercut.

During the welding of stainless steels, 'heat tint' is formed. This is a high temperature oxide, rich in chromium which has been drawn from the stainless steel. The result is a very thin low-chromium layer on the underlying stainless steel surtace. For best corrosion resistance, both the oxide film and underlying chromiumdeficient layer must be removed. This can be done by pickling using a nitric/hydrofluoric acid mix, either in a bath or as paste, or by mechanical removal.

Since stainless steel depends for its corrosion resistance on the presence of an extremely thin, continuous chromium oxide film, any contaminants which disrupt this film will reduce its corrosion performance and can initiate pitting. A common contaminant is embedded iron particles from nearby grinding of carbon steel fabrications or the use of iron-contaminated tools. Such contamination can be removed by passivating the stainless steel with nitric acid, followed by a thorough water rinse.

After hydrotesting and before being put into service, tanks should be drained and thoroughly dried. There are too many instances of new stainless steel systems failing due to pitting or crevice corrosion because either:

> Contaminated test water has been left stagnant in the system, or
> The system has been drained but not dried, leaving pools of water to evaporate, concentrating dissolved salts and resulting in corrosive attack.

MAINTENANCE
Stainless steel is inherently a low maintenance material - but it is not zero maintenance. The main requirements are:

> Deposits which build up on stainless steel surfaces should be regularly removed. This is because crevices exist under deposits and crevice corrosion can be initiated in such areas.
> Following cleaning, regular inspection is necessary to establish the condition of the equipment. This will ensure early detection of any developing problems so that steps can be taken to prevent further deterioration.

If guidelines such as these are followed, long and trouble free service can be expected from stainless steel equipment.

Words by David Jenkinson from the Nickel Development Institute.

This article featured in Australian Stainless magazine - Issue 18, May 2001.


Posted 17 May 2001

A stainless steel stackable wine storage and fermentation system has been adapted to carry water for use in hospitals.

STAKVATs feature internal temperature control tubes and a sloped design for complete drainage and radius corners for protection against crevice corrosion and bacteria collection.

Each vat has a storage capacity of 900 litres, can be stacked five high and easily transported on a tray truck. They are also fork-liftable four ways.

The vats are made from grade 316 stainless steel sheet and grade 304 tube. Standard BSM grade 316 fittings are used for the outlets, with door handles and locking pins made from grade 304.

The original STAKVAT design featured replaceable French and American Oak sides used for wine enhancement. The modified STAKVAT has a stainless steel side instead of oak, but maintains the cooling/heating tube system and sloped design.

Oxygenated water is created in the STAKVAT via the airspace in the top of the vat. The water will be circulated through a system of STAKVATs at approximately 30 litres per minute.

Managing Director of Ausvat, Peter Warren said the STAKVAT helped meet an industry need for efficiency in storage space.

"Stainless steel internal cooling systems and the space saved by using STAKVATS produces many cost-effective advantages," Mr Warren said.

Stainless steel for the STAKVATS were supplied by ASSDA member Stirling Stainless Steel, with fabrication by ASSDA members Simcraft Products and Unique Metal Works Pty Ltd.

This article featured in Australian Stainless magazine - Issue 18, May 2001.