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Coil Processing
Tuesday | 24 March, 2015 | 9:38 am

Flexing muscle

By Corinna Petry

Above: A Tata Steel employee measures the gauge of material that’s been through the flying cutoff shear (pictured at rear) at the Llanwern, Wales, service center.

U.K. service center processes HSS using a tough but elegant Italian solution

March 2015 - When a British steel producer wanted to attach a high-volume, heavy-gauge coil processing operation to the front end of its steelworks, it found the perfect partner in an Italian equipment manufacturer.

Tata Steel’s operations in Llanwern, Wales, are 17 miles northeast of Cardiff near the mouth of the River Severn. The facilities house a hot strip mill, pickling line, a cold mill, annealing, continuous galvanizing and other downstream operations, according to Rodney Rice, marketing manager for the United Kingdom and Ireland. 

In mid-2013, Tata began to construct a service center that would straighten, flatten, edge trim and cut to length thick sheet and plate. The £11 million (U.S. $16.7 million) project involved lengthy ground preparation because the site is reclaimed marshland and the footprint for this expansion is substantial.

“This line is almost twice the length of our previous coil processing lines. We wanted to be able to produce cut sheet or plate up to 17 meters long,” says Rice. 

The material range—3 mm to 25 mm thick steel—led FIMI Group of Italy to recommend placing “two large leveling stations next to each other. Depending on the thickness of each coil, we use one or the other.”

Most coil processing centers employ a single leveler so when material thickness changes, the line must be stopped to modify the rollers. “In our case, two leveling stations help productivity and throughput. There is less downtime, more operating time,” Rice says.

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Equipment deliveries occurred in January 2014, with mechanical installation completed in March. Commissioning began in April and deliveries in May. “There has since been a steady increase in our output as the operators familiarize themselves with the process and we optimize the logistics of getting product through the facility.”

Why build such a massive facility? “Customers want flatter product made from wider, thicker plate and particularly in higher strengths, and the market needs a bigger, more powerful line to decoil and flatten that product,” Rice explains.

Within a few months of ramping up, Tata Steel closed other U.K. plate leveling shops and moved all processing to Llanwern. The attached hot strip mill—along with Tata plants at Port Talbot, South Wales, and Ijmuiden, the Netherlands—feed the new operation with coils up to 34 metric tons.

“By moving from three separate regional sites to a larger national hub, we optimized our line loading and stock arrangements and reduced lead times,” Rice continues.

Products & customers

The new service center predominantly processes dry hot-rolled coil with a smaller proportion of pickled and oiled material. “This includes products such as our Ympress range of high-strength steels and Durbar flooring plate.”

Tata supplies a diverse customer base with cut plate. Lifting and excavating equipment builders comprise one major sector, with manufacturers of truck trailers, tanks, weigh bridges, communication towers, general engineering fabricators and other service centers consuming the remainder.

Tata’s Steelpark plant near Wolverhampton—northwest of Birmingham, England—houses a plate profiling facility, flat-rolled decoiling and slitting operations and doubles as a producer of automotive quality blanks. Tata also operates long product processing and distribution centers in the U.K. All together, Tata’s European service center business annually processes and distributes 3 million metric tons of steel.

Appearances matter

Having worked with FIMI Group before, Tata Steel believed the equipment manufacturer to be the best vendor to assemble and install the entire line. Novel features include in-line surface brushing to enhance plate appearance, in-line side-trimming for improved dimensional accuracy, the potential to supply customer-specific sizes from stock, and the ability to cut and handle long plates, all of which may reduce the amount of fabrication customers must do.

The line’s width, thickness and strength capability allows Tata to supply plate that historically could only come from a reversing mill. “Several developments are under way to create new sheet products that would not have been processable on previous decoiling lines,” says Rice.

The service center industry is very competitive in Europe, he concedes, but “the Tata product coming off this line is consistently superior in flatness, surface appearance and overall appearance in stacking and presentation.

“When the guys manufacturing and selling this material enter a customer site, they see that our product tends to stick out visually among the others. Customer response has been extremely positive,” Rice adds, based on the dimensional accuracy, straightness and surface condition achieved. Fabricators cutting smaller parts from large plates are especially gratified by not having to combat deflection, says Rice. Other customers indicated they are able to eliminate shot blasting because the surface is so clean, and skip profiling because the edges are so perfect.

“People will talk about how thick and strong the steel is they can process, and how flat they can get it. The smart bit is being able to process thick, wide, strong material and still be flat. The mechanical loads are so much greater. That’s why our levelers are so enormous. The drives have the power, the torque, to flatten the steel.”

High-strength steels (HSS) are becoming a higher proportion of Tata’s sold product mix every year because lightweighting efforts are expanding from passenger cars to commercial trucks and off-road equipment. “We are future proofing the business by possessing capabilities in excess of current needs,” says Rice.

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Flattening philosophy

Tata Steel’s goal is to cut and flatten high-strength and ultra-high strength steel. “The task is so challenging because the plate has to retain 1,400 megapascals (Mpa) of yield strength from 4 to 13 mm thick and up to 2,100 mm wide,” FIMI Group General Sales Manager Filippo Tagliabue says.

“Our philosophy of flattening this steel is to use multileveling, which distributes the work and applies tension between the pre-leveler and levelers,” he says. In the past it was common to use a skin pass mill or temper mill before leveling. “To avoid building such huge, costly machines that are heavy consumers of energy, we developed technology to exceed the mechanical limits of the torque necessary (transmitted at each leveler working roll) to flatten and stress relieve this high-strength material to laser cutting quality,” Tagliabue says.

FIMI does it by building the leveler frames with a great deal of rigidity, which provides a highly calibrated elastic deformation, says Tagliabue. “We used string gauges—electronic sensors that measure micrometer movements—during our factory tests to demonstrate the machinery met Tata’s contractual requirements.”

The most important feature, he continues, is “the way we apply the torque to each of the levelers. Each leveler’s rolls penetrate each other while the material flowing through is deflected up and down between them. The two-dimensional plastic area is flattened and stress relieved in such a way that the material is totally dead and not moving anymore. There will be no springback during downstream processes to compromise the quality of the cutting or damage the laser machines.”

Patented technology

FIMI Group also had to design the motors and all other components to handle the stresses. Its levelers include a mechanical transmission system, motor, gear reducer, distributor, shaft, couplings and rolls.

“The mechanical distributor wants to move at one speed, and obliges each roll to move at the same speed. Due to the geometry of the machine, the speed of each roll varies and the torque is very high. The first roll works hard but at the exit end, they are less loaded with internal stress,” says Tagliabue, who notes that FIMI won a patent for its design of a self-regulating torque speed converter for surpassing the mechanical limits for HSS.

To get the optimum surface quality on the finished product, FIMI installed several stations that remove scale and buff out imperfections. 

FIMI placed the first brushing machine between the decoiler and pre-leveler. “Now you don’t have scale in pre-leveler backup rolls damaging the surface of the material down the line,” Tagliabue says. A second brushing unit sits after the pre-leveler and before the edge trimmer and first leveler, then a third brushing machine follows the second leveler.

After the last leveler, FIMI used a flying shear “because it is a faster solution for heavy gauge material. It gets the best quality in terms of cut and geometry.” After the flying shear there is a layout table and a stacking machine, which feeds two platforms so operators don’t have to stop the coil.

With the FIMI line, Tata can cut a 30-ton coil in 15 to 25 minutes to 12-foot lengths. The annual 250,000-metric-ton line is highly automated with drives and controls by Siemens, and FIMI’s own software. “Two operators can easily handle the whole line by themselves,” Tagliabue says. MM

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