Ensuring uniform mechanical properties of wire rod 5.5-6.5 mm from steel grades 70-75

In 2019, the air-cooling line of Mill 170 of PJSC MMK was upgraded. It was aimed at obtaining sorbitized wire rod directly on the mill. The use of such products makes it possible to abandon one intermediate heat treatment operation in the wire production process, as well as to increase the stability of the mechanical properties of the finished wire produced from such wire rod. Taking into account the peculiarities of laying wire rod on the air cooling line behind the rolling mill, the hardware enterprises impose the following requirements on the uniformity of the mechanical properties of the resulting wire rod - no more than 40 N/mm2 along the length of the coil, 50 N/mm2 along the length of the coil, 60 N/mm2 for melting. When analyzing samples of rolled products from steel grades 70-75 with a diameter of 5.5-6.5 mm, it was found that full compliance with the requirements of hardware enterprises at existing rolling mills is difficult. By order of PJSC MMK, as part of scientific research on mastering the technology of wire rod production on an air cooling line, a mathematical model was developed, the adequacy of which was proved by developing rolling modes based on it, followed by evaluation of the resulting product. Upon further analysis of the obtained rolled products, it was found that the products produced according to the new modes meet the requirements for uneven mechanical properties along the length of the coil, coil and batch to a greater extent.