Forgings

● Cold Rolling Mill Rolls directly affect strip quality and rolling stability. ● Material choice influences hardness, wear resistance, fatigue strength, and roll life. ● Forged rolls are valued for structural integrity and reliable performance. ● Quenching and tempering are critical for balancing hardness and toughness. ● Different mill positions require different rolls, such as work rolls, backup rolls, and intermediate rolls. ● Proper grinding, inspection, storage, and reconditioning extend service life. ● Applications vary across carbon steel, stainless steel, aluminum, copper, and precision strip processing.

Large forged steel backup rolls are critical components of rolling mills. However, surface defects dominated by forging cracks frequently occur during the forging process, which seriously hinders process implementation and even results in product scrap. This paper mainly analyzes the crack generation causes from the production process and implementation links of forged steel backup rolls, and discusses effective prevention and control measures.

Forged steel cold rolling rolls commonly use electric slag steel to manufacture roll blanks; Steel ingots are usually treated with high-temperature diffusion to improve the uniformity of the chemical composition of the rolling billet; The roller blank is deformed by forging, and the material has good density; After forging the roll blank, normalizing treatment is carried out to eliminate secondary network carbides, and spheroidization annealing treatment is performed to prepare the microstructure for the subsequent quenching and tempering treatment; Perform hydrogen expansion annealing to prevent the formation of white spots.

The problem of Grade 4 network carbides and a small amount of eutectic carbides in Cr5 forged steel caused by improper post-forging heat treatment design can be solved by optimizing the heat treatment process. High-temperature normalizing is adopted to dissolve most carbides into the matrix, followed by rapid cooling using water-based or oil-based quenching media to ensure full austenite transformation, reduce precipitation of secondary carbides, thereby sufficiently refining the microstructure and avoiding the formation of network carbides. Ultimately, zero defect echoes and favorable bottom echoes are achieved in testing.

Prior to roll quenching and tempering, appropriate heat treatment processes can improve the grass-like echo defects of roll blanks. Aiming at the grass-like echo defects detected by ultrasonic testing in 70Cr5Mo steel roll blanks, this paper adopts post-forging heat treatment processes such as normalizing and spheroidizing annealing to refine the microstructure morphology of 70Cr5Mo steel blanks, obtain favorable microstructural features, and reduce or eliminate grass-like echoes in the blanks, so as to ensure no adverse effects on inspection and service performance.

Due to prolonged friction and rolling contact between the work roll and the support roll, the support roll bears significant shear and contact stresses, resulting in deformation strengthening and wear. Therefore, its main failure modes are peeling and wear. The tonnage of forged steel support rollers is large, the production process is complex, and waste products are easily generated.