Made of steel

Högbo Stål & Jernwerks was established near Sandviken in 1862. A small fishing community on the edge of Lake Storsjön was soon turned into a thriving and large ‘company town’ where just about everybody worked for Sandvik, or owed their livelihood to the company. Little has changed as Sandvik employs over 11,000 people in Sweden today (and over 47,000 worldwide). The name Sandvik actually translates as ‘Sandy Bay’.
Other major milestones for the company included producing stainless steel in 1921 and cemented carbide – still providing the tips for tools used in high wear applications such as rock drilling – in 1942.
The company was actually producing drill steel for rock drilling as early as the 1860s and today this business sector is handled by Sandvik Mining and Construction.
As far as the wood based panel industry is concerned, of course the fame of Sandvik stems from those two words ‘stainless steel’. As one of only two major producers of large endless stainless steel belts worldwide, the enormous proliferation of continuous presses in the panel industry has provided a major market for the company and is a significant and profitable part of the diverse range of speciality steels. However, there is more to this story than meets the eye, as Jan Ola Jonsson, former general manager press belt sales, until his semi-retirement in 2007 (he is succeeded by Johan Sjögren), is quick to point out. Many people do not appreciate that Sandvik developed the first successful continuous double-belt press in 1966 (the earlier Bartrev press, developed in the UK, was not a success).
“At that time, we did not see a future in wood based panels, but supplied the press to other industries such as the glass reinforced plastic (GRP) sector,said Mr Jonsson. “Also, Bison was supplying Mende-type continuous belt presses to the panel industry at that time, utilising our stainless steel belts. “However, we have built about 40 double-belt presses for the chemical industry. We gave up production of presses for the wood based panel industry and licensed the process to Siempelkamp and Dieffenbacher of Germany in the 1980s and 90s, both of whom are of course specialist heavy continuous press manufacturers.”
The Sandvik continuous press had a two-temperature-zone principle seen again in the Metso Contipress (formerly Küsters press) in recent years. Sandvik does still manufacture smaller double-belt presses for lower pressure processes such as plastic components, artificial stone marble manufacture and acrylic ‘glass’, the latter employing belts which are highly polished by Sandvik. The belt production section of Sandvik comes under product area Process Systems. It does not only produce belts for presses, or indeed stainless steel belts: another important market sector is in process belts for bake ovens, chemical and pharmaceutical factories, meat cutting; belts for cooling, drying and of course pressing. They may be made from various specific grades of carbon or stainless steel and can also be perforated, for the drying of fruit and vegetables for example.
Belt running speeds can vary from use in a wind tunnel for testing Formula One cars at up to 300 kilometres per hour to belts for use in extracting nickel out of slurry at 0.1 metres a minute. The temperature range is from 80 to 8000C-plus.
However, wood based panels is the largest of these many markets for Sandvik’s steel belts. “There are approximately 400 continuous presses worldwide, running or under installation, and generally they are not scrapped; older presses are moved to new locations, often in eastern Europe. So there is a big market just for replacement belts,said Mr Jonsson. About 20-30% of the company’s stainless steel press belts go to the press manufacturers to go out with new machines, while the rest are ordered by the panel makers themselves. Sandvik says it is not just the supply of belts, but application advice as well, that it offers to the panel and other industries.
Sandvik ceased to produce raw steel when it closed its foundry in 1960 so its stainless steel belt stock is bought in from specialist producers in Sweden and Japan, in precipitation-hardened stainless steel and other grades. Press belt thicknesses vary from 1mm to 3.5mm, but 60-70 % are 2.7mm. Belt material arrives in rolls and is first cut to length, welded into a loop and mounted on one of Sandvik’s machines where it is quality-checked and then ‘levelled’. Levelling is a process in which the belt is flattened by a combination of tension and multiple rollers and the flatness and straightness is read by the machine and corrected accordingly.
The belt is cut to width, straightening it as necessary in the process (belts come in over-width to allow for this) and one edge is prepared for the longitudinal welding necessary to make a wider belt, while the outer edge is rounded. Dressing the outer edge in this way makes it less liable to cracking and damage in use. The longitudinal weld joint is prepared by cutting with carbide inserts supplied by Sandvik Coromant and welding is then carried out, from both sides of the belt, and the weld line is ground and levelled in a customised production line. The belt loop is then cut and the belt coiled up.
Heat treatment follows, which hardens the steel and increases its strength by around 50%. This heat treatment is carried out in a flat condition, not coiled, which Sandvik says produces a belt with less in-built stresses.
The belt then receives its final grinding, is trimmed to width, and the outer edges rounded. Levelling and tracking is also tested at this point to ensure the belt runs true in the continuous press. Finally, the belt’s outer edges are dressed again and the belt is cut to the customer’s required length, coiled and packaged in a substantial wooden crate. A one-metre off-cut is always supplied to the customer to be used in later repairs, although most customers buy an extra three-metre length for this purpose. Damage to the stainless steel belts in the harsh environment of a hot continuous press running at anything up to 2,000mm/second is inevitable and, given the high cost of the belts, repair systems for them are essential. Sandvik thus offers a selection of repair and maintenance tools.
Quickdisc is a tool designed to patch larger areas of damage and the latest version is light, pneumatic and safe, says Sandvik. The patching tool is clamped to the belt surface by four or six suction pads and a rotating tipped cutter cuts out a circular area of belt containing the damage. An identical-size disc, cut from the belt off-cut supplied, is then welded in place and the join is ground until it is virtually invisible. Apart from the obvious sources of damage to a belt, such as foreign bodies in the panel mat, belts do become curved across their width due to the heat and pressure applied in the press. The old trick was to cut the continuous belt, remove it from the press, turn it inside out and re-weld the join.
Sandvik developed a simpler system, to repair the belt in situ. This employs shot peening with minute hardened steel balls to ‘hammer’ the ‘short’ side of the belt as it travels around the press during normal panel production, in a completely closed system. Different sizes of shot can be employed for different degrees of deformation. Since endless belts are now supplied in thicknesses up to 3.5mm, hand shears are no longer sufficient to cut the belt and so special cutting technology is required for creating the joints to be welded. Sandvik offers a cemented carbide-tipped circular saw for this purpose.
When it comes to welding the belt back together into an endless loop (a process carried out within the press), the company offers a portable TIG welding jig. Made of aluminium alloy, the jig is easily portable by hand. Sandvik is currently working on a belt cleaning system. Dry ice systems have been developed by others in the past, but have seen little uptake, while increasing the amount of melamine in the panel glue mix, though effective in reducing dirt accumulation, is expensive these days. Sandvik says it hopes to market an environmentally-friendly, completely new system in the near future. All these repair tools are available for Sandvik’s customers to purchase and their staff can be trained in their use, or the customer can call in a Sandvik engineer to operate them on his premises.
Very few continuous presses have the facility to insert and remove continuous belts in one piece from the side of the press. The majority are cut in situ and then removed from one end of the press for repair or replacement and reinserted in the same way. Joining of the replacement/repaired belt within the press is sometimes carried out by the customer, but more often is done by Sandvik engineers. It is this need to be on hand for service, installation and repair that has led Sandvik to establish a global presence of wholly-owned sales and service centres, manned by its own trained staff, rather than trusting such work to general machinery agents or sub-contractors. The company also offers on-site customer and staff training and recently held such a session for Panel Plus and Siam Fibreboard in Hat Yai, Thailand, with 30 customer staff and 20 from Sandvik.
Research & Development has a very high priority in the company and it invested a total of SEK2,739m (US$460m and 4% of invoiced sales) in this and Quality Assurance in 2007 throughout the company.
Scanning electron microscopes for metallurgical analysis at the molecular level are among the specialist tools employed here. This, says Sandvik, is the largest such centre for materials technology research in northern Europe and employs over 2,300 people throughout the company’s areas of activity. Belts for wood based panels of course benefit from this attention to R&D as well. There is a fatigue testing laboratory at the Sandviken factory, where computer-controlled machines can run tests on steel belts for maybe two or three weeks and these machines can be enclosed for temperature-controlled testing as required.
The surge in demand for belts for the panel industry in recent years, particularly with the expansion in China, eastern Europe, Turkey and South America, has put some strains on Sandvik’s facilities and it now has to invest to ensure it keeps up with demand.
“Currently all belts for longitudinal welding – carbon steel and stainless steel – have to go through one machine and we need that machine just for stainless steel belts,said Mr Jonsson. “Therefore we are investing between e20-30m in a ‘ground-breaking’ new levelling line, designed and coordinated in-house, but supplied from an outside specialist.
“We will also continue to invest in the production of belts for the paper making industry to meet additional capacity in that market. “The belt market is very strong at the moment. It was always a good business but the volume has increased a lot in recent years and we now need to invest in additional capacity.A major step for Sandvik in the decorative panels and laminate market came with the takeover, in 2000, of Hindrichs-Auffermann of Ennepetal, Germany. This company has a long history in the production of smooth, mirror-finish and textured press plates for short cycle pressing, but also offers a wide range of chromed endless press belts for double belt presses with textures such as smooth, mirror and wood grain.
Sandvik of course makes the raw stainless steel belts, which are pre-ground and given a special heat treatment at Sandviken for lifetime and performance reasons. Sandvik Laminates Hindrichs-Auffermann then has to produce the endless press belt by welding it before it can start the texturing process and apply various surface treatment processes.
Maximum belt dimensions here are 21m long and approximately 2.5m wide. Most of these belts are used in the flooring industry.
To maximise the lifetime of the belt, Sandvik Laminates also offers various services for endless press belts, such as refurbishment, cleaning and belt handling workshops.
A visit to the Sandviken exhibition of products amply illustrates the wide range of highly specialised applications for the company’s products – it is not in the business of commodity steel products at all. Current and past products include: the balls for ball-point pens; studs for winter tyres; cutters to produce finished dyes without the need for grinding (the dyes are used in car door panel production, Coke bottle moulding and many other uses); fine wires of smaller diameter than a human hair, umbilical cords for offshore oil drilling rigs; cemented carbide drilling and industrial tool tips; the list goes on and on.
Meanwhile the Mining and Construction division makes heavy drilling machinery, which includes robotic drilling machines for use in confined spaces and those areas particularly hazardous to humans. The Sandvik philosophy is only to be in markets in which it can be a world leader – or a very good second. Many people still associate the company with garden and workshop hand tools, but this division was sold to Snap-On Tools of the US some years ago; the market did not suit the philosophy any more.