Cold rolling is not exactly back on a roll, but the sentiment at the Iron & Steel Technology Conference in Nashville, Tennessee last month was upbeata distinct improvement on the beat-up mood of the past few years.
Equipment makers tell AMM that commissions from mills for evaluations and analysis are strong, and resulting orders for both rebuilds and new equipment are also showing signs of life.
This comes as good news to both mills and suppliers, which have been battered literally and figuratively. The figurative has been financial. Many steelmakers, especially in North America, have not had the capital available to invest in upgrades; sometimes not even in maintenance. The physical battering has come from the strong demand for advanced high-strength steels (AHSS) that are tough on equipment that was not designed to deal with such hardness.
This year the industry has been avidly watching the final flowering of the landmark Big River steel complex in Osceola, Ark., the first greenfield mill in North America in years. SMS supplied much of the rolling equipment and is justifiably proud of the initial reports.
With Big River now in operation, attention turns to major upcoming projects, one of the most notable of which is the new cold-rolling line being built by Andritz Metals for Nucors complex in Hickman, Arkansas. The new line is scheduled to begin service late next year.
The 650,000 ton a year expansion project will increase Nucor Hickmans production of specialty grades, including third-generation, advanced high-strength steels, high-strength low-alloy steels, and high-efficiency electrical steels.
We are in the design phase together with Nucor, says Bjorn Bahr, head of sales for North America at Andritz. Procurement should start by the end of the year.
Bahr notes that it was at the end of last year that inquires started to pick up, especially for the AHSS stuff, the kind of materials that Nucor wants to produce. It is difficult to upgrade existing rolling equipment to deal with that material because it is so hard, he said. Mostly you need to buy new. You cannot trick the physics. And you cant roll big diameters on smaller equipment.
That realization, as well as an improved market has opened more than a few checkbooks. We have been getting more inquiries after Nashville, Bahr said. The mood there was definitely better than in Pittsburgh last year.
Andritzs approach is to put small work rolls on six-high mills, which it calls S-6 for support. That gives flexibility in both maintenance and operations, Bahr explained. The same applies to temper, or four-high mills.
Focus on throughput
As much as mill suppliers would love to fill the world with brand new rolling equipment, they understand the fiscal realities. There is extensive installed capital out there already, Joe Dzierzawski, president and chief executive officer of Pittsburgh-based SMS USA, a subsidiary of SMS Group, Düsseldorf, Germany, points out The focus for most mills is optimizing throughput, not replacing their equipment. The larger and older facilities are not out there looking at all-new mills. They are looking to modernize.
SMS is offering its SieFlex drive spindle to increase torqueby as much as 100 percent Dzierzawski saidand that allows for smaller work-roll diameter and lighter grades of AHSS to be produced. Compact cooling, a complimentary technology, provides for increased strength from improved crystalline structure through cooling, eliminating the need to produce alloys. Process upgrades such as these are linked by sensors to adjust operations in real time.
Before anything new is built or installed, most major suppliers conduct a thorough process analysis. Equipment is designed to specific grades, Dzierzawski noted. If mills are trying to roll new grades, then yes there will be more frequent maintenance or breakdowns. But we are finding our customers recognize this and they call us to do a study. We go step by step to identify how to improve the mix. Each step is more expensive, so we determine what is prudent.
The move to modernize is somewhat of a mandate, Dzierzawski notes. Mills cant just crank through increased tons of less sophisticated steels. Historically, the added value has been in higher-quality grades. he said. All of our customers realize they cant really make money on simpler commodities.
Similarly, there is a shift to cold rolling. The spread between hot- and cold-rolled sheet historically was $100 a ton, and now it is closer to $200, Dzierzawski pointed out. Mills need to recognize that they need cold-rolled or coated.
Endless strip production is also growing as an alternative approach to conventional rolling. We truly believe that in the future conventional hot rolling might be substituted with our Arvedi Endless Strip Production (ESP) system, says Andreas Flick, head of the casting and ESP business segment of Primetals Technologies, a joint venture teaming Siemens, Mitsubishi Heavy Industries and other partners.
Almost the same grade mix can be produced with this leap-frogging technology as on conventional hot-strip mills at lower costs, higher speeds, more efficiently and in a more environmentally friendly way, Flick claimed.
Another key consideration is the ability ESP allows to produce much thinner, hot-rolled coil, Flick noted. For many applications, no extra cold-rolling is required, he added.
The first ESP, installed at Arvedi in Italy, operates extremely efficiently and the properties and tolerances of the hot bands are extremely good, he said.
For reference, records on this mill at press time were:
Highest amounts on thin-gauge production-like sequences with 50 percent below 1 mm or six- month average with 45 percent below 1.2 mm and 84 percent below 2 mm.
Lowest energy consumption 131 kWh/t for 2-mm strip.
Most stable operation conditions resulting in 2.5 deg. C finishing temperature over four hours.
Endless Strip finds its niche
The latest installations of the endless strip production technology are at Rizhao Steel in China, which ordered five ESP lines at one location for the production of more than 10-million tonnes of hot-rolled coil. Three lines are already in operation, producing about 500,000 tonnes per month.
Rizhao Steel wanted to increase capacity and at the same time outperform their competition in a saturated and competitive market like China, Flick said. The key is that they are able to omit cold rolling completely; they dont even have a cold rolling mill at their plant, he pointed out.
The hot-rolled coils from the ESP lines are first pickled and then processed directly at annealing and galvanizing lines without cold rolling, Flick said. The output is then sold directly as cold-rolled substitute material.
In general, mills are emerging from a period during which many did little or no spending on equipment with some even deferring maintenance. Flick noted, however, that there are regional differences. In Europe and Japan, rolling mills have been kept in a much better conditionalso during difficult timescompared to the U.S., he observed.
That said, Flick also sees, a growing interest in ESP technology on the part of steelmakers still operating an outdated hot-strip mill and old slab casters. Investing in an ESP capable of producing 2.5- to 3-million tonnes annually could propel them back into a profitable situation, Flick said. Unfortunately, no one in the Western Hemisphere has taken a decision yet and I believe it will again be China or other Asian countries, which will invest in the latest innovations.
Primetals has also developed a new concept for producing AHSS called the Compact Cold Rolling System, Kasai Shunsaku, head of the companys cold rolling and processing business segment, points out. The key differentiator is ultra-low-speed rolling, reported to be one meter-per-minute. We have also developed a new type of cold-rolling mill, Hyper UCM, which is a six-high, universal crown control (UCM) mill with very small work-roll diameter, Shunsaku noted. It is especially designed for harder materials such as AHSS and non grain-oriented silicon steel.
Shunsaku added that the latest installation is an HZR, split-housing type, 20-high mill for grain-oriented silicon steel, which achieves high reduction with high gauge tolerance and automatic control for the hydraulic roll-positioning system. Broadly, he noted that tandem cold mills are being studied or planned for AHSS production in Japan, Korea, China, and the U.S. Reversing cold mills are favored for small-size production in the African market, and for AHSS and silicon steel in Japan, Korea, China, and the U.S.
Some like it hot
That is not to say that Primetals has given up on hot rolling. Some of our latest technologies are related to high-end steel production, such as AHSS and thick API grades, Yoichi Kira, head of the companys hot rolling business segment, pointed out. Those include a mill-stabilizing device that drastically mitigates vibration in finishing stands and is available for both new mills and for revamping. For strip cooling, we further developed the intensive strip cooling and transfer bar cooling technologies, under the brand Power Cooling, he said. That provides high cooling rates while maintaining the full control range. It may be common now, but we also have heavy-gauge coiling technology for API grades where inch thickness is essential.
Kira noted that installations keyed to modernization are following the trend towards higher quality and the development of high-strength steels. We supplied sixteen new hot-strip mills in the last 10 years, which corresponds to a yearly production of about 50 million tonnes, he calculated.
A number of equipment and service companies, such as Butech Bliss, focus on upgrades and rebuilds rather than new installations. We are not interested in chasing the billion-dollar projects, says Al Waigand, vice president of sales and marketing. One simple upgrade involves replacing electromagnetic screw downs with hydraulic.
Whether it is hot or cold, gauge control is essential, Waigand said. There is a lot of emphasis on productivity and hydraulics are simpler to open the roll stack for change outs. Both gauge control and faster changes count as a double benefit for HSS in automotive grades and also pipe for oil and gas.
Waigand noted that his firm has been conducting many assessments with findings ranging from overstressed housings to one strip mill that installed new shears to address higher-strength steels. We are working on lots of down coiler rebuilds. We bring them in, tear them down, inspect them, and offer advice not just on upgrades but also process improvements.
It seems there has been a mounting backlog of that type of work. When the bottom fell out of the market, we had one down coiler in our shop for about a year, Waigand recalled. A lot of people run two at a time to avoid delays in the process, and typically have one out for rework on a rotational basis. More than a few mills have been holding out on that for the last three or four years. Now we are getting them caught up.
Although full down-coiler assemblies are large and heavy, Butech Bliss is equipped with a 200-ton crane at its Salem, Ohio, facility, along with a rail spur that runs directly into the main shop.
Focus on control and sensing
Patrick Connell, president of Kocks Pittsburgh, says that his firm did not see much of a decrease in maintenance work coming in over the past few years. Our customer base is focused on special bar quality steel, and they know that they dont want to let the mill drift, he noted. Our parts and service business has been strong in SBQ and also in the seamless tube sector.
Kocks Pittsburgh is a subsidiary of Friedrich Kocks, based in Hilden, Germany. The firm recently introduced a new size-control system that can help insure quality even with less-experienced operating personnel. Our packages can start quickly and run different grades without tearing up the equipment, Connell said.
The challenge for the mills these days is that they have to maintain both quality and volume. They cant shut the mill to adjust too often. They have got to hit the spec on the first bar.
As reported in AMM, Kocks recently won a contract to supply Charter Steel in Cleveland. All of the factors quality, flexibility, and utilization were drivers for that award, Connell commented. To help meet future contract awards, Kocks Pittsburgh will be able to tap into increased manufacturing capacity at the parent companys facility in Bremen, Germany.
Other suppliers are increasing their focus on sensing and control equipment for duty on rolling mills. IMS Systems, based in Mars, Pennsylvania, outside Pittsburgh, has a new radar-based measurement system especially tailored for service on hot mills. With the water, steam and scaling, it is a tough environment for any measurement system, says Chris Lackinger, who was recently promoted to general manager and chief operating officer. Radar measurements are independent from those distractions. Even in a cold mill, the pickling acids and emulsions can affect light-based sensors. The radar sensors are a stand-alone system and can be customized to any equipment.
Still under development is a camera-cluster system that features multiple cameras tied into a computer and installed as a compact module. It is too early to provide any details, Lackinger said. But the high-resolution optical measurement will be used for width detection in slitting, also for edge crack and pinhole detection. That is very important in cans, he noted