Temper mill operators are well positioned, as part-makers
increasingly demand truly flat steel.

By Corinna Petry,
Managing Editor

Sidebars and Tables:

• Temper Rolling vs. Leveling

Business is growing for the handful of temper mill operators in the United States and Canada, fueled by the proliferation of plasma and laser cutting systems, as well as other precision part-making machines, that require dead flat steel.

Steelmakers have been offering temper-passed (also called cold-reduced) products from hot-rolled and cold-rolled coils for decades. But when they recoil the material for shipment, it’s no longer flat. Even after uncoiling and leveling, the material may retain “coil memory” that causes it to buckle as parts are cut.

Beginning in the 1980s, several service-center companies and toll processors purchased their own temper mills, usually placed in-line with a pickling or cut-to-length operation, to provide their customers with higher quality steel. Using the temper mills, they could offer product with superior flatness and surface characteristics that would remain stable through most types of cutting operations.

Today, nine service center/processing companies and one plate and tube producer operate 28 temper-pass lines in the United States and Canada. Temper mills cold reduce steel by 1.5 to 2 percent, elongating the product and giving it added strength.

IPSCO Inc. has temper mills in Toronto, Houston and St. Paul, Minn. “We operate three coil processing lines that all include temper mills,” says Chuck Schmitt, general manager of Southern region product sales. “We make a temper leveled cut-to-length plate product, cut in line after temper leveling.”
Not only is the product flat, he says, but it stays flat.

“Temper processing equalizes the residual or internal stresses as opposed to conventional leveling. When you talk to people involved in burning and welding steel plate, stability is critical. With high-speed lasers and high-speed plasma machines that are cutting ever faster with greater precision, you cannot have the steel moving while it’s forming under intense speed and heat,” Schmitt explains.

As burning and cutting equipment progresses, he says, the material needs to advance along with the technology. “We certainly see more customers using lasers. We are seeing demand grow for higher productivity, and that means cutting faster and cleaner. They want a better surface quality and a flatter surface. That’s what the temper leveling process gives us—a showroom finish, something that’s very clean,” he says.

Laser and high-speed plasma machinery places burning heads extremely close to the surface of the steel. “Nothing gets a customer calling you faster than if your steel has started moving or deforming under the heat, and either raises and pops off a [torch] head, or it moves and now the shape is not as precise as it should be.”

The precise flatness and surface quality of temper-passed steel also help part-forming operations using dies or stamping presses to maintain better shape control.

Schmitt says IPSCO’s temper-rolled plate is qualified for high-strength applications such as transmission towers, crane booms, truck frames, and all manufactured goods that require yield strength of 65,000 to 100,000 psi.

“The flatness we can offer from our lines is one-quarter ASTM A6 tolerances, as opposed to mill plate. In lighter gauges like 0.25 and 3/16ths (0.1875) where most mills might be up to full ASTM tolerances, we can offer quarter and half flatness tolerances with temper mill product—much, much better performance.”

Using temper-passed steel speeds cycle times and lowers reject rates for manufacturers and fabricators. “The product is so much more consistent. There is very little variation from plate to plate that comes off a temper mill,” Schmitt says.

Worthington Steel operates two temper mills at the exit end of pickling lines at Porter, Ind., and Monroe, Ohio. Ted Armbruster, vice president of technical services, says the mills “produce good shape and improved surface over standard hot-rolled pickled and oiled. An added benefit of good shape is less camber if you’re going to slit the coil into narrower coils.”

Worthington temper rolls other companies’ steel on a toll basis, and produces temper-passed product for inventory. The company places the largest coils possible—up to 45 tons—on its mills “because coil size equals productivity. If we’re making slit coils, we try to get it [the master coil] as wide as possible.”

Worthington also operates nine narrow mills, with combined annual capacity of about 300,000 tons, to produce one-pass cold-rolled strip and tempered cold-rolled strip. “We also have two wider mills, 22 and 29 inches wide, for temper passing cold-rolled annealed strip [called dead-soft after annealing]. We temper roll it back to the desired hardness,” Armbruster says.

Cold-rolled strip goes into close-tolerance applications where the surface, the edge, the alloy and the temper are custom engineered. Such applications include automotive transmissions, seat belts and door closures, he says.
Worthington’s hot-rolled tempered product goes into a wide range of sheet applications where surface quality and flatness are critical.

The supply-demand balance for tempered products cycles with the rest of the flat-rolled steel market, Armbruster says, admitting that the market suffers from excess capacity. “Nobody is really full right now. Most temper mills are not usually at capacity.”

However, he believes temper rolling has become more important as minimill producers have developed lighter gauge hot-roll that usually needs shape correction.

Mike Lerman, president of Steel Warehouse Co. Inc., South Bend, Ind., agrees that the temper mill market is very competitive, but he sees strong growth potential. “[Our mills] are very busy. With more laser technology and more laser-cutting capacity, there will be a continuing demand for higher and higher quality in flatness and memory suppression.”

Lerman believes the market is growing not because more steel is being consumed, but because the demands are getting greater on the steel itself. When one company buys a new laser, its competitors eventually follow suit, and they all need higher quality material to cut.

While he cannot predict how quickly demand will increase, he adds, “we have more customers interested in temper-passed cut-to-length product than before. The temper line is the busiest piece of equipment in all our facilities.”
Chicago-based Feralloy Corp. operates three temper mills, directly and through a joint venture. Each is in-line with cut-to-length operations.

“We are able to recoil the temper-passed product and cut it to length later, or we can cut it to length in-line as we temper pass it,” says Roger Sippey, executive vice president.

Feralloy sells its temper-passed plate and sheet primarily to capital goods markets: agricultural and construction equipment, truck trailers, pressure vessel tanks, as well as metal centers and plasma- and laser-cutting companies that supply those industries. Its joint venture, Oregon Feralloy Partners, also supplies temper-passed product for oil and gas pipeline production.

Robinson Steel Inc. operates three mills—which it calls cold-reduction mills—one in East Chicago, Ind., and two in Granite City, Ill.

President Paul Labriola says the lines take coils through cold reduction and corrective leveling before cutting to length. The lines can make steel up to a 100,000 psi yield. Robinson’s customer base consists of manufacturers in the transportation sector (trailers, railcars), plus metal buildings and conveyance systems, among others.

Robinson started up its first mill in July 1987, and has since evolved from just producing cold-reduced steel to laser cutting parts from that steel on a contract basis.

“Our goal is to maintain and increase our position in the marketplace, certainly in the realm of cold-reduced sheet and plate, a category that we created and popularized,” says Labriola. “We branded RPS (Robinson Processing System), which is the industry standard.”

More recently, Robinson has extended the brand to RPS Laser. “Over the last four or five years, we have invested a considerable amount of time, effort and money to building RPS Laser. We have 44 lasers in six locations, and we’ll soon have them in seven locations. That is a way for us to leverage the quality of RPS steel into laser cutting.”

Producing RPS Laser has “opened up the market more broadly for us, in terms of what kinds of customers we can call on,” Labriola says. “We laser-cut only product that we produce off our own lines. That gives us complete control of the process from start to finish. It makes us very, very cost efficient at producing laser-cut parts.”

Robinson makes RPS to one quarter of published mill ASTM quality. “We guarantee our product has no coil set, no edge wave, no crossbow. Our product will exhibit no shape abnormalities before, during or after processing,” Labriola says. He, too, is bullish on the prospects for temper-passed steel.

Although Novamerican Steel Inc. built the most recent in-line temper mill, started up in autumn 2004, numerous calls to company executives were not returned.

Temper Rolling vs. Leveling
As coil processing technology evolves, it is prompting a quiet little debate among the experts over the capacity of today’s new leveling machinery to truly flatten steel vs. the tried-and-true method of temper rolling.

Chuck Schmitt at IPSCO Inc. asserts that conventional leveling is not the answer for value-added processes such as high-speed plasma- and laser-cutting. “Conventional leveling has limitations with the higher strength materials.

“There are applications—whether it’s with Grade 65, Grade 80, Grade 100 and abrasion-resistant steels—where conventional leveling is incapable of processing it to the same consistency as a temper-passed product, just because of the amount of force you must use to reduce and flatten the product.”

On one hand, he doesn’t delineate the markets for conventional leveled cut plate and temper-rolled cut plate, because IPSCO readily supplies both. But on the other hand, he says, “if you take a high-strength coil and try to straighten that through a leveler, not to mention cutting it up, it is going to fight you every step of the way.”

Mike Lerman, president of Steel Warehouse Inc., expresses enthusiasm for the development of high-quality temper rolled product over the past 20 years.

He credits Robinson Steel with having “defied the laws of physics to come up with a process that was in violation of what the metallurgists and [temper mill builder] Mesta engineers said could be done. We felt Robinson was wrong until we saw the proof. And then we extended our own temper mill capacity.”

At the same time, he adds, Steel Warehouse has invested in some proprietary design of leveling technology to address the springback and memory issues associated with coiled steel. The company has installed two new levelers—one from Herr-Voss Stamco and one from Butech Inc.—in Decatur, Ala., and Charleston, S.C.

He acknowledges that productivity on a leveler is a bit lower than on a temper mill, since the leveler must run at slower speeds. Levelers also do not enhance the surface quality of the steel, and may not perform as well on high-yield material. But levelers require less capital investment, and can meet most customers’ needs. “In the normal range we ship every day from our lines in Decatur and Charleston to plasma-cutting operations, we have zero rejections,” Lerman says.

But most experts agree that for those who must use high-yield material (80,000 to 100,000 psi), temper rolling is the better choice. “You can’t go beyond flat, which is an absolute state,” remarks Robinson Steel’s Paul Labriola.