Ultra large support roller forgings are prone to ultrasonic testing failure due to incomplete forging and compaction of the core. This time, the composite forging main deformation process of "upsetting WHF method for elongation+upsetting FM method for elongation" is adopted to achieve forging looseness and porosity, improve stress and inclusion distribution in the core of the steel ingot, and prevent the formation of new crack sources.
Slow cooling after forging will result in coarse structure and the appearance of network carbides, while high-temperature normalizing can improve the segregation of network carbides and materials. Therefore, efforts can be made to improve the annealed structure through two aspects: appropriate rapid cooling after forging, high-temperature normalizing, and finally spheroidization annealing.
H13 steel, as a widely used hot work die steel worldwide, can obtain a mixed microstructure of martensite and bainite after normal forging process. It has high hardness and is difficult to cut, so spheroidization annealing is necessary. Spheroidization annealing plays a significant role in eliminating residual stress in steel, reducing hardness, and evenly distributing alloy carbides. It also prepares the microstructure for final quenching and tempering heat treatment.
