Bar And Wire Rod Direct Rolling Technology without Heating

The technology of direct rolling without heating of bar and wire refers to the technology of directly sending the slab with residual heat after continuous casting into the rolling mill line for rolling. When the heating-free process is used, the billet does not need to be heated in the furnace, and it does not need to be reheated (some of which replenishes the corner parts through the electromagnetic induction device), completely eliminating the fuel consumption of the heating furnace, which can greatly save energy and reduce carbon dioxide of emissions.

Feature

The start rolling temperature is between the conventional rolling and the low-temperature rolling, and the final rolling temperature is not much different from the conventional rolling; the center temperature of the workpiece is high, and the surface temperature is low, which is conducive to the deep deformation; because of the different time to reach the cut-off point, the temperature of the front section of the slab is low, and the temperature of the rear end is high. 

Limited by the speed of drawing billet, the running speed of casting billet before cutting is low, and it is possible to increase the speed after cutting; the rolling force of roughing rolling mill is higher than that of conventional rolling.

Key technology

The technology needs to adopt the following key technologies to ensure the smooth progress of production: 

1) Through comprehensive control of the cooling water flow, distribution and billet drawing speed of the crystallizer and secondary cooling zone, measures such as shortening the connection time from continuous casting to rolling are achieved continuous casting process optimization to increase the temperature of the slab. 

2) Establish a continuous casting slab solidification and temperature prediction model and a slab temperature feedback control system to make an online prediction of the safe distance from the solidification endpoint to the slab cutting point to prevent steel leakage accidents. 

3) Take measures such as increasing the conveying roller speed, reducing waiting time, and covering the thermal insulation cover, etc., to quickly transfer the cut billet from the continuous casting machine to the rough rolling unit, to reduce the temperature loss of the billet and ensure the open rolling temperature. 

4) Optimize the load distribution of the roughing rolling unit, improve the cooling rolling capacity of the roughing mill, and avoid the implementation of the heating-free rolling process due to the overload of individual passes.

Advantage

1) The heating furnace is omitted, and energy-saving and emission reduction are realized. Compared with conventional hot-feeding and hot-loading and cold-rolling furnace heating and rolling, energy-saving per ton of steel can reach 20 and 40 kg of standard coal respectively. According to the calculation of 2.6t carbon dioxide and 8.5Kg sulfur dioxide emission per ton of standard coal, the annual production line of rod and wire rod with an annual output of 1 million tons can save more than 20000 tons of standard coal, reduce more than 50000 tons of carbon dioxide and reduce more than 8500t sulfur dioxide, which has huge economic and environmental benefits. 

2) The heating-free process avoids the long stay of the cast slab in the heating furnace, the burning loss is reduced, and the yield rate can be increased by 0.5-1.5%. Based on the average value of 1%, the production line with an annual output of 1 million tons can save 10,000 tons of materials. 

3) After the heating-free process is implemented, the rolling temperature can be between 920-980℃, and rolling within this temperature range is beneficial to improve the strength of the product. According to statistics, the yield strength of the product can be increased by 10-15 MPa after the heating-free process is implemented. At the same time, it is beneficial to avoid the appearance of the Wei’s structure and improve the internal quality of the product. 

4) In addition, the technology has the advantages of saving the cooling water for continuous casting, reducing the maintenance and operation costs of the heating furnace, and avoiding the overhaul and shutdown of the heating furnace.