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Steel
Thursday | 23 April, 2009 | 8:42 am

Big thinking near the Arctic Circle

By Lauren Duensing

April 2009 - Deeply rooted in shipbuilding applications, SSAB’s heavy plate division in Sweden, is no stranger to the potential of steel products. In fact, all of SSAB?has built its business around high-strength steel. Its operations consist of three divisions: SSAB Strip Products, Borlänge, Sweden; SSAB Plate, Oxelösund, Sweden; and SSAB North America, which includes the company’s Mobile and Montpelier steelworks. In total, the company employs 10,000 people in more than 45 countries.

The heavy plate mill was built on the shores of the Baltic Sea to support the Swedish shipbuilding industry. However, when that industry collapsed in the 1970s, the company had to change its focus. "Our mill was the backbone of our local economy," says Christer Offerman, business area manager, tool steel. "We had to find a way to survive."

As a result, the company developed a strategy to become a world leader in producing quenched and tempered plate for construction machinery, heavy-equipment manufacturers and high-wear applications.

"We basically took the ship plate, changed the chemistry, quenched and tempered it," says Offerman. "What we got was steel that was two to three times as strong as the not-quenched steel. We came from the weldable ship-building plates to weldable, wear-resistant and high-strength quenched and tempered steel plate. Eventually, that led us to tool steel and engineering steel."

Along the way, as with any type of research and development, there was trial and error. "Of course, we made some mistakes," Offerman says. In the beginning, one of the company’s immediate needs was a new, larger blast furnace.

"The board of directors and the banks didn’t want to invest in new equipment," he says. "We were only allowed to rebuild our existing furnace, but a mistake was made. The engineer in charge of the project inadvertently sent the plans for the new blast furnace to the construction company. By the time we caught the error, the new furnace was well under construction. The board and the banks felt that, under the circumstances, we should complete the new furnace."

From quenched and tempered to tool steel
For the past 30 years, the heavy plate division has built a presence in the quenched and tempered market. "Because we’re a mill situated close to the Arctic Circle, we needed to have a product that could carry the transportation costs down to the big markets," says Offerman. Quenched and tempered steel was the answer because it was a niche product: small enough not to create a ruckus among the market giants but "big enough that we could be a world player in it."

As those who work with high-tech products know, great ideas are often stumbled upon. "I was working on developing Hardox 600, 55 HRC wear-resistant steel, and, in a conversation with a former employee of a Swedish tool steel mill, it was pointed out that Hardox 600 was more or less a cold-forming tool steel," Offerman says. "He asked, ‘Why don’t you make tool steel?’"

This passing comment caught the interest of the team at SSAB. "We knew we produced exceptionally clean steel," he says. "In fact, our steel is as clean as the conventional tool steel mills’ ESR double melting, but our methods are more efficient. We use the same production facility that we use use for the Hardox and Weldox steels. Our existing production machinery is sufficient also for tool steel."

So, in 2000, SSAB decided that rather than try and produce conventional tool steel, the company would use these technological advantages to produce a fully martensitic, pre-hardened quenched and tempered HRC 45 steel with exceptional toughness. The alloy design was low-carbon and low-alloy additives.

"We kid that we alloy with water," Offerman says. "Our phenomenal quench rate gives us the hardness, strength and grain structure we want with the added benefit of low residual stress. The low-carbon, low-carbide content allows Toolox 44 to machine well without free-machining additives, which would be detrimental to the mechanical properties."

Expanding horizons
The foundation was laid, but before moving out of the European market, the company wanted to ensure the product was the best it could be.

"We learned that you should do your homework in your hometown," Offerman says. "If you can be a prophet in your hometown, then you have something. We stayed in Europe and Sweden for quite a while to understand and develop the material, so we were pleased and secure that it really worked. There are three big markets for tool steel: Europe, America and Asia. We know we have an interesting product, and if it works in Europe, it should work in America."

Toolox 44 was introduced to the North American market by International Mold Steel, Florence, Ky. The company has a previous relationship with Carrs Tool Steels Ltd., West Midlands, U.K.

"We have a great deal of respect and a close working relationship with Carrs," says Tom Schade, executive vice president of International Mold Steel. "On a visit here in 2005, Andrew Eastwood, director of sales, gave me some literature and told me why Carrs decided to carry Toolox. His enthusiasm was infectious, so I asked him to send me some. Based on the cleanliness, 0.003 [percent] maximum sulfur, I assumed it would be a bear to a machine." However, the steel machined well and performed under both drilling and tapping applications. "We were impressed," Schade says.

IMS stocks a pre-hardened H11 modified at 37/42 HRC. "The modification is the addition of sulfur," Schade says. "We kept the hardness low, so we didn’t have to put too much sulfur in. Sulfur exacerbates heat check in die cast dies, so the applications for re-sulfurized steels are limited in die casting. Sulfur is also detrimental to impact and fatigue strength. Toolox doesn’t have those restrictions; it’s clean."

Successes aren’t limited to hot-work applications. "The draw temperature for Toolox 44 is 1,094 degrees Fahrenheit, so it’s a great, tough substrate for PVD or ion nitride," Schade says. "Die shops are making forming dies, avoiding the time loss and cost of heat treat, running tryouts at 45 HRC, then coating and putting the die into production."

Entering overseas markets allows SSAB to build its reputation. The tool steel market complements the Hardox and Weldox products the company has been running for the last 30 years, Offerman says. "It’s not competition with these grades. Weldox and Hardox are optimized for weldability. When you weld, you need to have a low-alloy product, but you accept residual stresses. Toolox is the other way around. It’s not that good for welding, but it’s important to have low residual stresses."

The company’s existence is built around doing things right the first time. "We deliver our products ready to use. We measure the mechanical properties. That’s how we were brought up. When we made plate for ships, if the plate was no good, it would break, and the ships would go under. We supply all plate with a mix of hardness and toughness. The customer knows exactly what he’s getting, and we guarantee the quality all the way out.

"That’s the way we do things--full stop," Offerman says. "We don’t go to the market with anything that’s not ready to use. We have 30 years’ experience of trial and terror in developing quenched and tempered steel, and that’s really what we use now in the new segment." MM

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