Cooling process for controlling structure transformation of large-specification medium-carbon CrMo steel

Abstract

The invention discloses a cooling process for controlling structure transformation of large-specification medium-carbon CrMo steel. The cooling process comprises the following steps: performing air cooling on a long rolled piece on a transverse moving rack for temperature waiting; outputting the long rolled piece to a long cooling bed input roller way through the transverse moving rack, and controlling and actually measuring the temperature when the long roller piece enters the long cooling bed input roller way, namely the transformation initial temperature; enabling the long rolled piece to enter a long cooling bed heat preservation cover from the long cooling bed input roller way and be conveyed in the cover, and controlling the retention time, namely the conveying speed of the long cooling bed heat preservation cover, of the long rolled piece in the long cooling bed heat preservation cover according to the needed transformation ending temperature in combination with the transformation initial temperature and the temperature drop rate of the long rolled piece in the long cooling bed heat preservation cover; and conveying the long rolled piece out of the heat preservation cover, and taking the actually measured temperature as the transformation ending temperature. By adopting the cooling process, more pearlites (P) and ferrites (F) can be obtained, so that the hardness of the steel is less than or equal to 260 HB, and the problems of more procedures, long production period, high production cost and uncontrolled hardness in a pit-entering slow cooling process are solved.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and in particular relates to a cooling process for controlling microstructure transformation of large-scale medium-carbon CrMo steel. Background technique [0002] The post-rolling cooling process of the steel rolling production line is the basic technical means to control the structural transformation of high-temperature rolled pieces, and the starting temperature and ending temperature of the rolled piece structure transformation are the key control parameters, and the large-scale medium-carbon CrMo (such as 42CrMoA, 42CrMo- The cooling process of N2, SCM440, etc.) bars is difficult. At present, the cooling process adopted for this kind of steel at home and abroad is mainly the method of high-temperature slow cooling in the pit. If the microstructure transformation is to be realized during the pit cooling process, the surface temperature of the steel should be at least above 680°C when enter...

AI Technical Summary

Problems solved by technology

[0009] Purpose of the invention: the purpose of the invention is to provide a cooling process for controlling the structural transformation of large-scale medium-carbon CrMo steel, so as to obtain more pearlite (P) and ferrite (F), so that the hardness of the steel is ≤ 260HB, so as to solve the problem of pitting There are many processes in the slow cooling process, the production cycle is long, the production cost is high, and the hardness is not controlled.