Post-forging heat treatment process for 45Cr4NiMoV alloy steel large back-up rolls of rolling mills

Abstract

The invention belongs to the technical field of large forging heat treatment processes, and mainly relates to a post-forging heat treatment process for 45Cr4NiMoV alloy steel large back-up rolls of rolling mills. A forged back-up roll is cooled to 400 DEG C to 500 DEG C by the air and put into a furnace, and the material temperature in the heat treatment furnace is not lower than 600 DEG C; a high-temperature normalizing plus low-temperature normalizing plus spheroidizing annealing plus high-temperature tempering process is adopted, and air cooling is carried out. The adopted post-forging heat treatment process disclosed by the invention is characterized in that: crystalline grains are thinned; the structure is regulated, so that the network structure is removed; the carbon segregation ofthe upper part of the large steel ingot is considerable, temperature higher than Ac1 is kept for a long time, consequently, part of carbide is remelted, the remaining unmelted carbide is spheroidized, and a granular pearlite structure is obtained during cooling; consequently, the structure toughness is high, and structure preparation is done for the next step of heat treatment; and fish eyes are prevented.

Description

technical field [0001] The invention belongs to the technical field of heat treatment process for large forgings, and mainly relates to a post-forging heat treatment process for large backing rolls of 45Cr4NiMoV alloy steel in rolling mills. Background technique [0002] Large back-up rolls are generally used in the key and core parts of large-scale strip rolling equipment. They are important parts used to support work rolls or intermediate rolls in rolling mills to prevent deflection and deformation of work rolls during rolling and affect the quality of the plate. , is the basic part of large-scale cold rolling and hot rolling equipment. [0003] With the development of rolling mills in the direction of automation, high precision, and high-quality shape control, rolling conditions are becoming more and more stringent. Improving rolling efficiency, reducing rolling costs, and ensuring product quality have become prominent issues. [0004] Due to the long-term heavy load dur...

AI Technical Summary

Problems solved by technology

[0018] (1) Putting into the furnace after forging is usually kept at 600-650°C and then heated up directly, so that the cooling of the core is very slow, and the austenite transformation is not sufficient

[0019] (2) After forging, a heat treatment method of normalizing (normalizing + spheroidizing annealing + tempering) is adopted, which is not sufficient for refining the grain of the backup roll