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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.


Posted 17 May 2001

Two 2205 duplex stainless steel elution columns over 12 metres long have been installed in a replacement project at Kalgoorlie Consolidated Gold Mines in Western Australia.

Elution columns are used in the mettalurgical process of extracting gold from carbon.

Carbon impregnated with gold is hot washed with caustic cyanide in the elution columns to dissolve the gold out of the carbon. The gold solution is pumped away while the barren carbon remains in the columns and then is removed for reuse.

The columns hold temperatures of 140°C and operate under pressures of 550 kilopascals (KPa).

he previous columns, constructed from grade 304 stainless steel, were beginning to fail due to pitting corrosion caused by chlorides carried over in the process water, combined with erosion corrosion on the internal surface. The tanks were in service for a total of five years.

Stainless steel supplier, ASSDA member Sandvik Australia, worked with a consultant to find a more suitable grade of stainless steel for the job.

2205 was chosen for its ability to provide a higher resistance to chloride attack. The grade also has improved hardness over grade 304, thereby offering better resistance to the erosion effect of the activated carbon.

Kalgoorlie Consolidated Gold Mines Mechanical Engineer Adrian Rowell, said the grade change was made to try to ensure the columns lasted the life of the mine.

"The plant is planned to operate for another 15 to 20 years," Mr Rowell said . "By shifting to 2205 we anticipate that the columns will last that long."

Fabricated by ASSDA member Specialised Engineering Services (WA) Pty Ltd, the columns were constructed from 2205 duplex stainless steel
8 millimetre plate, which offered a significant weight saving over the original 10 millimetre grade 304 vessel. The columns were fabricated to AS 1210 class 28 Pressure Vessels with a maximum design temperature of 150°C.

Each elution column is 12.4 metres long, 1.7 metres in diameter and positioned vertically.

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


Posted 17 May 2001

Nearly four tonnes of stainless steel has been used to extend and upgrade facilities at Cape Clairault Winery in Western Australia's Margaret River region.

The project involved the installation of four 5 000 litre red wine hopper fermenters, four 12 000 litre and one 4 500 litre white wine storage tanks and the upgrade of 15 existing tanks of 1 000 -12 000 litre capacities.

Each hopper has a 20 degree sloping bottom to allow complete drainage after service. The design reduces the need for manual cleaning, a potentially dangerous practice due to the build-up of carbon dioxide in the enclosed tank space.

The white wine storage tanks have a conical bottom, also for drainage, and a two piece controllable heating/cooling system constructed from grade 316 stainless steel high pressure cavity plate. If the tank is only half full, refrigeration can be pumped through just the bottom cavity plate.

The cavity plate, constructed by ASSDA member Simcraft Products also features off-centre dimples for greater distribution of the cooling brine.

To convert the winery's existing tanks from storage to fermentation, high pressure cavity plate and temperature probes were added for cold stabilisation, while one of the 5 000 litre tanks was converted to a fermentation hopper.

The tanks were fabricated or upgraded with grade 316 stainless steel in coil, with all welds acid cleaned with post-fabrication polishing to ensure greater corrosion resistance.

The tanks were fabricated in sections then joined together, stacked one on top of the other. Plug welds were used to reduce the risk of cracking at contact points and for improved corrosion resistance.

Simcraft Products undertook all fabrication for the project. Stainless steel and stainless steel components for the tanks were supplied by ASSDA member Austral Wright Metals.

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


Posted 17 May 2001

Stainless steel spiral handrails provide a stunning support for climbers of Perth's new Bell Tower complex.

Grade 316 stainless steel tube was used to construct handrails for an internal spiral staircase and for an observation platform on the building's sixth floor.

170 metres of tube was used for the staircase, which was spiralled and fixed to the mild steel structure of the building. Washers and neoprene gaskets were used to separate the stainless steel from the mild steel, avoiding corrosion issues caused by dissimilar metal contact.

The handrails were fabricated by Tubelok Metals Australia in their Cannington (Western Australia) workshop and brought into the Bell Tower in six metre lengths.

Handrails on the sixth floor observation platform were secured to the structure with patch fittings through toughened glass, with 40 metres of stainless steel pipe used in total.

All handrail for the project was polished to a AWBP finish (as welded buff polished)_ Stainless steel for the project was supplied by ASSDA member Austral Wright Metals.

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


Posted 28 February 2002

A combination of grades 304 and 316L stainless steel has been utilised for all contact surfaces in Murray Goulburn's milk processing plant in Rochester, Victoria, which was upgraded in 2000.

The plant comprises an evaporator to concentrate cow's milk and spray dryer to produce various milk powders. Approximately 100 000 litres of milk is processed per hour, with the majority of product for export to over 100 countries. The evaporator and dryer represent more than half of the total project, a capital investment of around A$50 million.

The stainless surfaces and components carry milk feed, evaporated vapour, milk concentrate, milk powder, hot drying gas and cleaning chemicals of alkali and acid.

Ardmona tomato processing plant constructed entirely in stainless steel using grade 304.All product contact surfaces are of austenitic stainless steel grade AISI 304, with the 12m long evaporator tubes being produced from strip then rolled with the seam welded and bead rolled; the tubes have a 2B internal finish.

Principal contractor Niro Australia received instructions to proceed in July 1999 and conducted the first powder trials 14 months later, with commercial production starting November 2000.

To carry out the project, Niro involved Victorian fabricators Stainless Technology and PLC Engineering, though some fabrication was also conducted in New Zealand.

ASSDA member Alfa Laval supplied food grade stainless steel pumps, process valves, tank equipment, fittings and tubing worth over $2.5 million. The total supply was in excess of 40 tonnes and included 40km of tubing in sizes 1" to 6".

Grade 316L stainless steel was used for wetted parts (parts in contact with process fluids) and 304 for non-wetted areas. Products were generally supplied with a no.4 external surface finish; AS 1528 was used as the guideline for component standards.

Many of the process pumps and valves were chosen for their product handling characteristics. Specialist mixproof valves, which allow two different products to travel through the same valve without fear of intermixing, and high efficiency pumps were selected. Spillage-free mixproof valves were specified to prevent accidental discharge onto process floors and ensure a clean process environment, and rotary lobe pumps were selected for their gentle handling of cream products.

Pre-fabrication of many of the valve and pipework assemblies was carried out off-site in controlled environments. Due to the critical nature of the process applications, importance was placed on welding techniques and subsequent cleaning of welds. Valve manifolds were pre-fabricated and transported to site on completion, minimising the number of critical welds performed on site.

TOMATO PROCESSING
Fifty thousand tonnes of tomatoes have passed through Ardmona's processing plant in Mooroopna, Victoria, since it began operation a year ago.

The $15 million plant, which produces whole peeled and crushed tomatoes, was constructed entirely in stainless steel using grade 304 for the structural components and 316 tube and fittings for the wetted parts. Stainless steel was specified for its corrosion resistance and low maintenance, and to meet the health and safety requirements of a food processing plant.

Designed with a life expectancy of 30 years, the plant is capable of processing 40 tonnes of tomatoes per hour.

Ardmona's Engineering and Production Department, in conjunction with Italian firm Sasib Foods, were responsible for the design, engineering and construction aspects of the nine-month installation.

This article featured in Australian Stainless magazine - Issue 20, February 2002.


Posted 28 February 2002

The first edition of Australian Stainless featured the flagpole which towers over the new Federal Parliament building in Canberra. Ten years on and fifteen years since it was erected, the flagpole is well on the way towards its planned 200 year life. A condition survey was recently carried out by an ASSDA member for the Joint Houses of Parliament Committee.

The statistics: the 81m high structure is constructed mainly from 16mm thick hot rolled 304L plate: the base plates are 321 and the clusters supporting the flagpole proper are unpolished, cast 304 equivalent (CF-8). The four triangular legs rise diagonally for 28m from the top of walls to the east and west, before curving to vertical 4m below the lower cluster. The legs continue for a further 15.5m to the upper cluster and terminate 5.1m above the upper cluster. The circular tapered flagpole extends 25.7m above the upper cluster.

The corner and face welds of the leg plate joins were ground using grits down to #120 to match the bold plate surfaces.

As the flagpole was assembled 18 months before Parliament House was completed, it was exposed to the dust and pollution of a construction site; since Parliament opened it has experienced air quality of a rural environment.

Although quite safe, the inspection required a good head for heights while using a "lie back and enjoy it" lift up one leg or the less steady 7m scissor lift to reach the lower plates of the legs. A 40 power theodolite lent by the ACT Survey Office completed the inspection of inaccessible areas.

SURVEY RESULTS
The overall appearance of the flagpole is outstanding. The rib marks, plate to plate welds and polishing patterns along the legs all add to the visual impact. The multiple heated weld joins are as bright as the rest of the surfaces. Slight deposits at drip points aren't obvious to the casual observer and were easily removed with a damp cloth. The location of these deposits was determined by the prevailing weather.

Encouragingly, neither design crevices nor minor fabrication anomalies have caused obvious corrosion in 15 years' exposure.

Occasional small round rust spots, probably caused by pollution during construction, were visible at a distance of about 30cm. There were fewer spots near the masthead probably due to better rain washing and less pollution. The spots were readily removed with water and a plastic scourer and when examined at X30 did not show pitting. Consistent with surface profile expectations, the unpolished top of the legs showed no signs of spots. Surface profile measurements around the base of the legs showed surface roughness between 1 and 1.5 micrometres with a vertical polish direction.

And the future? 304 is ideal for this environment and with the decision to clean off drip line deposits and monitor selected areas for changes in appearance, it is expected that the flagpole will still be brightly glistening in the sun in 2200.

This article featured in Australian Stainless magazine - Issue 20, February 2002.


Posted 28 February 2002

Polished stainless steel poles represent a barren wartime landscape at the Korean War Memorial in Canberra. The history of the conflict is etched in curved stainless steel panels.

ASSDA member MME Surface Finishing polished 1000 lineal metres of 25 nominal bore schedule 10, grade 316 pipe to make 260 poles standing 3.8m high. These were welded and gusseted to 12mm thick plates, chemically anchored to a concrete slab, by the fabricator, ACT Stainless Steel.

The other main components of the Memorial,also fabricated and installed by ACT and polished by MME, are the curved stainless steel panels inside a central viewing platform, which record the history of the war with maps and illustrations.

There are eight 3000 x 1200 x 3 mm sections and two 3000 x 3000 x 5 mm. The 5 mm sections were formed by TIG welding sheets together, then polishing, as joins were not desirable. The polished finish enabled the welded areas to be blended after joining. The sheets were coated with 80 micron polyethylene film to prevent damage to the polished surface during etching and fabrication.

MME also polished the stainless steel lettering provided by Waterjet Dynamics to a uniform roughness of 0.5 microns.

The whole project was completed under the $1.6million budget, which was raised by Korean War veterans and donations from the two countries.The construction time frame was 23 weeks, and practical completion was achieved 17 April 2000,the day before the dedication ceremony attended by then Governor-General Sir William Deane and Prime Minister John Howard.

The design was by ANKWM Design Group and documentation was completed in conjuction with architectural firm Daryl Jackson Pty Ltd. Manteena Pty Ltd was the project manager.

This article featured in Australian Stainless magazine - Issue 20, February 2002.

 

Principles of Mig Welding


Posted 28 February 2002

According to the AWS Welding Handbook volume 2, MIG welding is "an arc welding process that uses an arc between a continuous filler metal electrode and the weld pool. The process is used with shielding from an externally supplied gas and without the application of pressure". The wire is usually supplied in spools and fed through to the welding arc by an electric feed motor, with no manual control ofthe wire feeding process ie semiautomatic.

Most materials, except aluminium, use what is termed a ‘constant potential power source’, and this automatically regulates the arc gap by varying the burn off rate of the wire.

MODES OF METAL TRANSFER
There are four modes of metal transfer possible with the standard MIG welding system: short circuiting (or dip), globular, spray and pulsed modes.

Short circuiting transfer is the mode which uses the lowest amperage range, hence the lowest heat input of the four variants. Essentially the electrode contacts the molten weld pool, completing the electrical circuit. Resistance heating of the electrode takes place until the tip of the wire is melted off and transferred to the weld pool. The arc is then extinguished, until the tip of the wire comes back into contact with the weld pool, and the cycle begins again. This process is repeated between 20 to 200 per second.

Globular transfer uses slightly higher currents than for short circuit transfer, but lower than those used for the spray mode. The arc is continuous, but the molten metal is transferred across the arc in a characteristic globular fashion, with the globule diameter greater than that of the electrode.

Spray transfer uses the highest current ranges, having a continuous arc, and the weld metal transferred across the arc in many tiny droplets. The droplet diameter is equal to or less than the electrode diameter, and is also accompanied by an electric force propelling these droplets across the arc, hence the term spray transfer.

Pulsed transfer is achieved by using a lower welding current at which conventional spray transfer would not be possible, and then imposing background pulses of power through the system. Typical pulsing frequencies can be up to 40 kilohertz and this in turn transfers one droplet across the arc per pulse, thus achieving spray transfer at lower welding currents.

SHIELDING GASES
A variety of shielding gases are available from many suppliers, which have been refined to suit various applications. A major effect that these gases have, is their ability to influence arc stability and mode of metal transfer.

The common MIG shielding gases are Argon and CO2. At all usable welding currents, CO2 will commonly produce a drip or globular transfer, whilst the full range of transfers can be obtained with Argon.

Mixtures of these two gases as well as a one or two percent addition of oxygen are also common when MIG welding the carbon and low alloy
steels. They have been designed to get the best characteristics of both gases, and improve arc stability, metal flow, sidewall fusion, wetability
etc.

PROBLEMS ASSOCIATED WITH MIG WELDING SHEET MATERIALS
It should not come as any surprise that welding sheet metals by the MIG process must have limits, especially on the thinner sections. MIG welding is a relatively high heat input process, and hence the rate of heat transfer away from the weld pool becomes important. The surrounding material must be able to support and maintain the weld pool until it solidifies. The final weld must also have an acceptable bead profile, with visual and surface quality within the specification requirements. Heat input must be kept to a minimum, and this in turn implies a
short circuit or globular transfer mode. Unfortunately, these modes are prone to spatter.

A compromise must be reached between heat input, travel speed, weldability and bead shape, which are all influenced by specific gas compositions.

The table shows some results of MIG welding austenitic stainless steel sheet using a one millimetre diameter wire, with a variety of gases. The volts and amps recorded indicate the lowest settings which achieved the stable transfer mode indicated.

The values of interest, and which formed the basis for the experiment, are the electrical settings, namely the amps and volts. Travel speed is obviously important in reducing heat input, but the effect of gas composition on the stable mode of transfer was the primary objective.

CONCLUSIONS
The results obtained not only confirmed the expected problems when welding thin stainless sheet, but also produced some interesting points
when using the pulsed transfer mode. As expected, spray transfer is not recommended for thin sheet.

Helium, as an alternative addition to shielding gases definitely has advantages in achieving an acceptable weld profile over the more common
gas mixtures, even in semi-automatic welding, but a greater degree of competency is required by the welder to be able to handle the necessary faster travel speeds.

Pulsing helps to overcome the problems associated with bead shape and burn-through, and if the equipment is available, it negates the advantages offered by a helium containing gas. Higher travel speeds in the pulsed mode are still necessary with the helium addition. The use of a helium-containing mixture with the pulsed mode should offer a combined benefit of a lower heat input and faster production rates, and, hopefully, less distortion as a result.

Words by Jim Henderson.

Reproduced with permission from the Australasian Welding Journal Volume 45 Fourth Quarter page 21.

This article featured in Australian Stainless magazine - Issue 20, February 2002.


Posted 28 February 2002

Sea World's latest attractions, polar bear cubs Lia and Lutik, have captured the public's attention since their arrival from Russia late last year. The one-year-old siblings join resident polar bears Kanook and Ping Ping, who have already given the park one of its most successful years since Polar Bear Shores was built in 2000.

The use of stainless steel in the construction of the polar bear enclosure contributes to giving park visitors a close look at the playful cubs and the adult bears. Large underwater viewing windows, supported by stainless steel frames, allow the public to watch the bears swimming and diving in a four-metre deep pool.

The health and well-being of the bears is a prime consideration in the design of their custom-built enclosure, which Sea World says "leads the world in providing a naturalistic and stimulating environment utilising the latest in polar bear technology, drawing on international research and knowledge."

The exhibit features natural landscaping, chilled water pools, shade cover, water misters and streams, wind generators and diving and climbing opportunities. Stainless steel plays a significant part. The larger bears are powerful animals, and strong stainless steel doors onto the exhibit ensure their security as well as the keepers'. The four air-conditioned den areas are made of grade 316 stainless, selected to withstand the corrosive effect of bear urine and daily hosing out.

Introducing the bears to one another had to be carefully managed. A specially designed stainless steel mesh screen known as the "howdy window" separated the older bears during the quarantine period, while allowing them to see and smell each other. Kanook, who was 16 when she was brought to the Gold Coast from Arizona, has taken the dominant role while Ping Ping, a young curious five-year-old when he arrived from China, is more submissive. The screen was a success with the two now getting along well together. The same method is being used to familiarise the bears and the new cubs without any risk to Lia and Lutik.

Bringing the polar bears to Australia was the culmination of three years of research and planning. Sea World says there has been overwhelming interest and support from the public which in turn can only assist conservation efforts for the polar bear.

This article featured in Australian Stainless magazine - Issue 20, February 2002.