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Diverse improvements

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Steelmakers continue to turn to a diversified mix of technological improvements to help them achieve such goals as better meeting customer specifications, reducing costs, increasing production efficiencies, being more energy efficient and protecting their workers.
“No one is looking to reinvent the wheel, but everyone is looking to produce steel more cost effectively, more efficiently and quicker,” without necessarily adding more production capacity, Alberto Voltolina, vice-president of sales for Danieli North America, Cranberry Township, Pennsylvania, points out. “Doing so will make steelmakers more competitive,” he explains.

Because of this, steelmakers are very interested in technologies that are automation-related as much as, or more than, those related to physical equipment components, according to Bill Emling, vice-president of steelmaking and continuous casting for SMS group Inc. This includes the use of certain process models to meet such goals as improving plant productivity, cost effectiveness, product quality and energy efficiency.

But while the overwhelming belief that technologies relating to automation, including digitalization, are going to result in a profound change upon the steel industry in coming years, that is not to say that there have not been, nor that there will not continue to be, several other types of cutting-edge technologies taking hold.

Higher grades
There has been a big push for new high-strength steel grades for both automotive and energy tubular applications – many of which contain expensive micro-alloys. According to Francesco Memoli, executive vice-president of Coraopolis, Pennsylvania-based Tenova Inc, this could be said to be the latest and most important recent change in the steel industry and one that has resulted in the development of both new production and processing equipment specifically for these new steel grades, including the third-generation advanced high strength steels (AHSS) about to enter the market.

Keith Watson, vice-president of SMS group’s flat rolling division, says that one area of particular interest related to this is technologies being developed to support new hot rolled steel, cold rolled steel and galvanized steel cooling strategies. This, Watson says, includes selectively cooling different sections of the steel strip differently with the aim of changing the microstructure of the steel to get such properties as much higher strength levels and better formability without having to add expensive micro-alloys to the steel. He explains that this could be accomplished through high-intensity, high-pressure water cooling for certain sections of the strip and much less intense air cooling for other sections of the steel. “If you could get the same results from water cooling as from adding micro-alloys, it is much cheaper,” he explains.

Watson notes that this could be used both to produce AHSS for automotive applications with tensile strengths of 980 to 1,200 megapascals (MPa) and beyond, and API pipe with yield strengths of 70,000, 80,000 or even 100,000 pounds per square inch. The equipment used to produce and process these higher strength steel grades must be more robust – heavier, with greater horsepower, with stronger coilers and larger rolling mill stands, shears and other cutting tools – than traditional equipment producing conventional steel grades. Watson says that feasibility studies can help steel producers and processors to decide whether they need new equipment or if upgrading or retrofitting existing equipment will suffice.

Endless and continuous
Another big technology push has been in endless, or continuous, steelmaking processes, which has been occurring both for steel long products – largely with the emergence of micro-mills – and for flat steel.

“The use of a micro-mill to produce 200,000 to 500,000 tonnes per year of such commodity-grade steel long products as straight and spool coiled reinforcing bar (rebar) and wire rod has been a winning concept,” given the ability for these super-compact production units to provide a fast turnaround and to control production costs without compromising quality, says Voltolina.

Not only does the micro-mill have a very compact footprint, almost 150 metres shorter than a traditional mini-mill, but it also allows the steelmaker to have endless, or uninterrupted, production through the casting and rolling of the steel, enabling the achievement of 32 continuous heats per day with its very fast turnaround – going from scrap melting to liquid casting to steel rolling in less than two hours. This, Voltolina says, could represent 10 to 30% cost savings – about $40 to $50 per ton – by comparison with a traditional mini-mill for steelmakers operating in local markets with limited competition.

The micro-mill concept has been gaining momentum. Commercial Metals Co is currently ramping up its second micro-mill in Durant, Oklahoma. Also, Nucor Corp recently announced plans to build two micro-mills – in Sedalia, Missouri, and Frostproof, Florida. Based on recent inquiries, Voltolina predicts that within the next two to three years at least two more micro-mills will be under construction in the United States.

Voltolina also says he expects that over the next two to three years several EAF-based long product steelmakers are likely to, little by little, replace their reheating furnaces (at the entry side of the rolling mill) by induction heating furnaces, like those used in micro-mills, thereby avoiding the decarburization of their steel products. He says that doing so could allow them to increase productivity and improve quality while consistently reducing carbon dioxide emissions by up to 80%.

There are also some new technologies to enable endless, continuous production of flat steel products. One example, Voltolina says, is his company’s new Danieli Universal Endless (DUE) technology, which works in conjunction with its Quality Strip Production (QSP) vertical thin-slab production technology. What makes this new concept different is the ability to have “universal” rolling modes thanks to the fact that now, within one single plant, it is possible to perform coil-to-coil and endless rolling modes, which Voltolina says makes this plant a major technology innovation compared with the previous generation. The first DUE plant was recently installed in China as a greenfield project, but Voltolina says this technology could also be installed into an existing plant.

Scrap charging
Memoli says that there have also been advances in technologies aimed at increased interest in continuous charging and pre-heating of scrap, especially as the percentage of EAF versus integrated steelmaking grows. For example, he notes that Tenova’s Consteel technology is now 30-40% more energy efficient than when it was first developed in 1989.

He says this is because the newest generation of that technology utilizes many sensors and other instruments to control the combustion in the furnace that is used to preheat the scrap and the rate at which the scrap is fed into the furnace. Also, through a combination of design, software and automation, the electric arc in the EAF has been optimized. For the latest new-generation technology the scrap goes into the furnace faster and hotter. Memoli says that electrode consumption is also much lower with the upgraded Consteel technology, which, with current high electrode prices, could give steelmakers a competitive edge.

Digital developments
As part of steelmakers’ increased interest in incorporating automation throughout the steel production process – including the use of process controls, robotics and real-time communications – Voltolina says Danieli has developed its Digimet platform, which it sees as the means of providing digitalization to enable steelmakers to increase the reliability and efficiency of machines, mechanical components and metallurgical processes. He says that this solution, which could be applied to any process at a low capital investment cost, provides measurable cost reduction.

“I truly believe that over the next several years digitalization is going to change the steel industry,” Memoli says, noting that already a lot of data is being collected in steel mills and that amount is growing. “The big question is what companies are going to do with that huge amount of data,” he says, adding that currently only a very small percentage is being used. However, there is a growing number of models and algorithms that are being designed to increase that utilization.

SMS group’s Emling says that it is important for the people who design automation packages for the steel industry to understand the steelmaking process so they know what steelmakers are trying to achieve and to ensure that their customers get a quick return on their investment.

Franck Adjogble, chief engineer of process control and production planning systems for SMS group, says that his company has produced several computer models aimed at specific steelmaking processes. For example, besides the well-known process models, its newly developed Material Properties Model (MPM) allows steelmakers to calculate the mechanical properties, the yield and tensile strength, elongation and grain size of the steel products they produce before they are even rolled – with an eye to limit sub-prime steel production and to know if they need to reschedule additional steel rollings.

This, he says, is accomplished by considering such factors as plant data, hot strip data, reheating, rolling and cooling conditions, as well as the furnace temperature, coiling temperature, pass schedule, the cooling strategy, steel grades and chemical compositions. Speed, roll force, reduction and thickness for specific steel grades and chemical compositions are further factors. The calculation is based on thermodynamic data, numerical approaches for solving differential equations and regression formulas. Then, once the company begins to roll the steel, the system can collect the actual information and compare it to the desired preset values for adaptation and optimization.

This, notes Emling, is especially helpful when the steelmaker is developing new steel grades, such as advanced high-strength steels or high-strength pipe grades that use a lot of expensive micro-alloys.

SMS group has also developed its flexible analysis process model, aimed at limiting the amount of non-prime “transition” steel slabs that tend to be produced when two different grades are mixed in the caster tundish. Emling explains: “When different grades are mixed, the resulting transition slabs may not be within specification for either the first or the second grade.”

Adjogble says that this model could be used to adjust the chemical composition of both heats to be able to produce slabs that, while having different compositions, are within the ranges that are acceptable to both customers. Emling says that by using this model one of its US customers was able to reduce its transition slab production from about 5 % of its production to about 2%, which he estimates could equate to a $13.7 million per year saving for the steelmaker.

SMS group has also developed models to ensure that the width of coils remain within desired ranges and that the quality meets all customer requirements. Adjogble notes that the width optimization model makes adjustments in real time without operator intervention to optimize the product width. In addition, the company developed its product quality assessment (PQA) tool to analyze the product quality, documenting all the data necessary to produce that particular coil. All the information that was collected is saved long term, allowing for transparency between the steelmaker and its customers.

Robotics is another growing area of steel plant automation, which, according to Voltolina, could significantly reduce the risk of accidents and increase quality throughout the entire production process, while also providing a very fast return on investment. “It doesn’t mean that people will be leaving the steel plants, but rather robotics will be used in certain harsh, hostile environments, while humans will be located in safer areas of the plant,” he explains.

Adjogble says that while the steel industry is traditionally very conservative with regard to new developments and technologies, more recently it has been more open to embrace new ones. He believes that is because they are aware that if they do not do so they will fall behind their competitors. And when it comes to technologies aimed at safety, steelmakers are even more willing to invest, Watson says, explaining that safety has always been a top priority for steelmakers.

Additive manufacturing
Memoli says that another emerging technology, although perhaps a more niche one for the steel industry, is additive manufacturing, or 3D printing. He notes that, overall, 3D printing of metal parts has grown by about 60% over the last few years, with 3D printing of metals growing much faster than plastics. Expectations are that it will grow even faster, although, to date, the lion’s share has not been for steel, but for higher value metals such as titanium and nickel and cobalt alloys, given that much of the growth to date has been coming from the medical, dental and aerospace industries.

Several years ago it was predicted that by 2027 about 8,400 tonnes per year of steel would be used in additive manufacturing, which, Memoli admits, is a tiny amount. However, given that over the past five years 3D printing of other metals has taken off at a significantly higher rate than initial expectations, Memoli says that steel use in additive manufacturing could potentially be as much as ten times higher than these predicted volumes, especially given the growing interest by the automotive and energy sectors in 3D printing of certain hard-to-machine, complex-geometry parts, and given the potential to reduce scrap metal generation, labor costs and the carbon footprint of the manufacturing process.

Memoli says advances in printer technology could aid this. Until recently, owing to concerns about stress cracks with certain layers of the printed part being hotter than others, it was believed that only low carbon steels could be printed. But now with printers with four or more lasers working at the same time, he says that certain high carbon steels and tool steels are being successfully printed.
“It is not just that these printers are better than before thanks to research being done to come up with solutions for thermal stress,” he says, “But as demand for the printers increase they will become cheaper. This is a perfect recipe to enable the market to grow even faster.”

In the future there are likely to be improvements in sensor technologies that allow for further improvements in steelmaking processes. “Also, in the near future there will be a merging of soft industry, such as Amazon, Google and Uber, with heavy industry, including steel,” Adjogble predicts. “This will empower steelmaking companies to improve their way to make steel and will dramatically reduce their cost using technologies that certain other industries have already used for decades.”

In addition, Memoli says research to increase the availability of hydrogen, and other sources of gas in areas of the world where there is limited natural gas, could result in greater production of direct reduced iron (DRI). He says that on average a tonne of steel produced by an EAF steelmaker using DRI as well as scrap has about 30% of the carbon footprint of a tonne of steel produced using a blast furnace.

Written by Myra Pinkham

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