ESP-- strip headless continuous casting and rolling technology
ESP Steel rolling workshop of Hebei Taihang Iron & Steel Group Co., LTD., "The minimum thickness of sheet rolling is only 0.7 mm, the energy consumption is reduced by 40%, and the pollutant emission is reduced by 70%..." Zhang Kun, deputy general manager of the company, introduced that ESP is the world's leading ultra-short process steel rolling technology, which can complete full continuous production in 7 minutes, not only energy saving and land saving, but also the products have the advantages of pure steel, good strength and toughness, and can be customized. Taihang Iron and Steel is the second domestic iron and steel enterprise with ESP hot rolled strip production line, which has become a loud business card in Wuan iron and steel enterprises.
I. ESP process flow
This technology is developed on the basis of the ISP technology of Demark Company, the continuous casting machine in the production line adopts parallel plate straight-arc crystallizer, the casting blank guide adopts cast-rolling structure, the casting blank is directly rolled into the blooming mill by liquid core, and then it can be cut and sold off the line. The non-rolling slab is rolled into thin strip steel by five finishing mills after induction heating. It is cooled and curled into a strip. The ESP process line is compact, does not use a long heating furnace or Cremona furnace, and the total length of the production line is only 190m, which is the shortest continuous casting and rolling line in the world.
2. Main technical characteristics of ESP process
High casting speed. High casting speeds can be achieved by optimizing the configuration of the casting machine and by increasing the flexibility of thickness and casting speed changes. Through mathematical simulation of computer optimized fluid dynamics calculation and (physical) water model test, it is shown that the current pouring speed of 5-6 m/min can still be greatly improved.
Stable casting process control. In the last decade, the most significant improvements have been made in the stability control of billet forming and slab curing, and the protection slag required for different steel grades has also been optimized. By controlling the friction and the Angle arrangement of the mould, stability control at high casting speeds is now achieved.
The wide application of automation technology. Improvements in technical process control, sensor technology, data management and processes are key to success. In terms of thickness control, temperature control, plate shape control and flatness control of Siemens Voestalpine products, the central network enhances the flexibility and standardization of the process model. For example, the "microstructure target cooling" package can control the metallurgical parameters of the strip. In the ESP line, automation runs through the entire process step from casting to cooling.
3. Main advantages of ESP process
(1) Technical advantages
1.ESP production line is the first continuous hot rolling line with coil that can complete the process from molten steel to underground coiler in 7min, while the original ISP thin slab continuous casting and rolling line takes 15 min from molten steel pouring to finished strip steel.
2.ESP technology is rolled at high temperature to improve the uniformity of the product microstructure and improve the performance of the product;
3. The entire production line does not exceed 190m from the beginning of continuous casting to the finished product coiler, which is very compact and belongs to an ultra-short process, and the equipment investment and plant investment are reduced, and the revenue rate is relatively improved. The headless strip production process avoids the threading of the new strip coil in the finishing mill, so the thin gauge (0.8-1.0 mm) strip coil can be safely and reliably produced in large quantities. It is estimated that the yield of steel from molten steel to coil can reach 98.0%-98.5%, while the ISP process is only 96.5%.
4. Can produce high-quality ultra-thin strip steel, some can replace cold rolled products, directly pickling and galvanizing;
5. In terms of energy saving and environmental protection, ESP technology can make full use of the high temperature energy of continuous casting billet at high temperature, and the rolling force is low even if the larger reduction is implemented. Compared with conventional hot tandem rolling mill, 2-3 heating furnaces are reduced. Compared with CSP thin slab continuous casting and rolling, more than 200 meters long tunnel heating furnace is also reduced. Moreover, rolling at high temperature greatly reduces the power of the mill and the power consumption. ESP eliminates the Cremona furnace compared to the ISP process, but the power of its induction heating furnace is increased, with a maximum power of 20MW for the ISP induction heating furnace and 36MW for the ESP induction heating furnace. In addition, ESP, unlike other thin slab continuous casting and rolling processes, requires very little energy to increase the capacity and efficiency of the line. At the limit pulling speed, that is, 7.6m/ min (billet 70mm×1250mm) and 8.3m/ min (billet 55mm×1250mm), the induction heater energy input will drop to zero. ESP uses approximately 25% to 30% less energy than ISP and approximately 40% less energy than traditional tropical steel mills. Associated with the reduction in energy consumption is a reduction in direct or indirect greenhouse gas and harmful gas emissions, with a reduction of 40-50% for the production of general specification tape rolls and a reduction of 65-70% for the production of thinner specifications. In terms of water consumption, the water consumption is 80% lower than the best traditional production coil method.
(2) Advantages of variety structure
1. Full range of steel grades. ESP line design product outline from low carbon steel to high carbon steel, as well as a complete product range of alloy steel, including high grade quality steel (such as oriented and unoriented silicon steel, IF steel used in the manufacture of automotive body panels). Avidi ESP equipment can be used to produce hot-rolled products with cold-rolled surface quality (Class A) (which can be directly used in the manufacture of exposed automotive parts); Hot rolled products with the characteristics of IF steel can also be produced using converter steel.
2. Thin specification products. The ESP process uses a no-end rolling technology to reduce the number of belt passes, so the Avidi ESP process can be used to replace cold-rolled products in many areas of thin specifications (thickness 0.8-1.0mm) and Avidi patented hot rolled products, including the yield limit of 315MPa, 1mm thick steel grades; Steel grade with yield limit of 420MPa and thickness of 1.25mm; High strength steel with thickness below 2mm (strength 700-800MPa); The DP600-DP1000 steel grade with a thickness of 1.2-1.5mm can replace some cold-rolled products and improve the added value of products.
(3) Cost advantage
ESP production line has excellent process cost advantage because it adopts strip headless continuous casting and rolling process and compact short flow production. After analysis [3-5], it is concluded that the process cost of ESP process is about 55% of the traditional process cost, about 70% of other thin slab process cost, and about 77% of ISP process cost. It can be concluded that the full variety of ESP process product outline, is expected to 98% metal yield, production cost is about 30%-50% lower than the traditional tropical steel production process, compared with the two-roll thin strip casting and rolling production process, has a good comprehensive competitive advantage, is a worthy of attention and expectations of the new process.
In short, ESP is a representative of the environment-friendly production line with energy saving and consumption reduction. In the future, the steel industry continues to develop towards energy saving and environmental protection, high production efficiency and low consumption, and high quality products, the process has gradually highlighted its strong competitive advantages.
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