Direct Rolling Technology without Heating
Direct rolling of continuous casting billet is that billet is heated by electromagnetic induction device at the opposite corner without reheating furnace, and then directly fed into the rolling mill for rolling. The technology of direct rolling without heating needs neither heating nor supplementary heating, which realizes an important innovation in the production process of bar and wire rod.
1. Technical Points:
1) Through the comprehensive control of cooling water flow, distribution and casting speed in the mold and secondary cooling zone, the continuous casting process is optimized and the slab temperature is increased.
2) Establishing the prediction model of solidification and temperature of continuous casting slab and the feedback control system of slab temperature, making the on-line prediction of the safe distance from solidification endpoint to slab cutting point, in order to prevent steel leakage accident.
3) Take measures such as increasing the speed of conveying roller, reducing waiting time and covering insulation cover to transport the cut-off slab from the continuous caster to the roughing mill quickly, so as to reduce the temperature loss of the slab and ensure the start-up temperature.
4) Optimizing the load distribution of roughing mill, improving the cooling rolling capacity of roughing mill, and avoiding the influence of overload of individual passes on the implementation of the heating-free rolling process.
2. The Main Advantages:
1) The reheating furnace is omitted to realize energy saving and emission reduction. Compared with conventional hot delivery, hot charging and cold charging furnace, energy saving per ton of steel can reach 20 kg and 40 kg standard coal respectively. According to the calculation of 2.6 tons of carbon dioxide and 8.5 kg of sulfur dioxide emissions per ton of standard coal, the production line of bar and wire rod with an annual output of 1 million tons can save more than 20,000 tons of standard coal every year, reduce more than 50,000 tons of carbon dioxide and reduce more than 8,500 tons of sulfur dioxide. The economic and environmental benefits are enormous.
2) The heating-free process avoids the slab staying in the heating furnace for a long time, reduces the burning loss, and improves the yield by 0.5-1.5%. According to the average value of 1%, the production line with an annual output of 1 million tons can save 10,000 tons of timber.
3) After exercising the heating-free process, the start-up temperature can be between 920 and 980 C, and the start-up rolling in this temperature range is conducive to improving the strength of the product. According to statistics, the yield strength of the product can be increased by 10-15 MPa after exercising the heating-free process, which is beneficial to avoid the appearance of Widmanstatten structure and improve the internal quality of the product.
4) In addition, the technology has the advantage of saving cooling water for continuous casting, reducing maintenance and operation cost of reheating furnace and avoiding overhaul and shutdown of the reheating furnace.
At present, China's bar and wire production capacity is seriously excessive, the whole industry has entered the era of marginal profits, energy-saving and environmental protection have become a hard indicator. Under the new normal conditions, direct rolling technology without heating can reduce costs, save energy and reduce emissions, which has positive significance.
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