The purpose of the heat treatment of the slitter blade after forging is to eliminate the internal stress of forging, refine the crystal grain, improve the forging structure, and reduce the hardness at the same time, which is beneficial to the cutting process. Since the steel used for cold-rolling work rolls is a steel with high sensitivity to white spots, preventing the formation of white spots has become one of the important tasks.
The heat treatment process specification of the slitting machine blade after forging is shown in Figure 7-4: If the spherical pearlite is required to be obtained after heat treatment, the isothermal temperature should be from 650 to 670 to 700 to 720 °C; if there is network carbonization in the structure Existence of materials, the holding time of heating at 790~810°C should be extended or the heating temperature should be increased to 820~840°C; if the roll diameter is over 600mm or the forging condition is not good, it should be added before isothermal annealing. The fire treatment process is shown in Figure 7-5. There are also two normalizing and tempering treatments. In this case, the subsequent quenching and tempering process can be cancelled, except for the cold-rolled work roll of the leveler.
9Cr2MoV steel large-scale cold rolls have a long time for isothermal spheroidizing annealing after forging. If continuous cooling spheroidizing annealing is used, the production cycle can be greatly shortened and gas consumption can be saved:
The original process uses isothermal spheroidizing annealing, as shown in Figure 7-6. The process can meet the technical requirements, that is, the spheroidization structure is 1 to 4, no white spots, but the production cycle is long and the gas consumption is large. Change to continuous cooling spheroidizing annealing process, as shown in Figure 7-7, each furnace can shorten the production cycle by 30h and save 38,000 square meters of gas.
