Plastic mold steel plate and method for producing same

A method for producing a plastic mold steel plate, comprising the following processes,

• first heating:
• sending a billet to a heating furnace for three-stage heating, a temperature of a preheating section being 850~950° C., a residence time of the preheating section being ≥60 min, a temperature of a heating section being 1100~1220° C., a temperature of a soaking section being 1210~1250° C., and an in-furnace time being ≥240 min;
• second heating:
• reheating the billet discharged from the furnace in the first heating process, a temperature of a soaking section being 1140~1170° C., and an in-furnace time being ≥200 min;
• rolling:
• rolling the billet discharged from the furnace in the second heating process into a steel plate, an initial rolling temperature being 1060~1140° C., and a final rolling temperature being 980~1050° C.;
• cooling after rolling:
• moving the steel plate obtained by the final rolling to a cooling bed and cooling the steel plate to 200° C. or lower;
• normalizing:
• normalizing the steel plate cooled in the cooling after rolling process, and a normalizing temperature TN being Ac3+60° C.≤TN≤Ac3+90° C.;
• cooling after normalizing:
• moving the steel plate produced by the normalizing process to the cooling bed for air cooling to TF, Bf−50° C.≤TF≤Bf−20° C.;
• and
• cross-stacking self-tempering:
• cross-stacking the steel plate and a ferritic pearlitic steel plate with a temperature of 450~550° C., and self-tempering the steel plate during the stacking period until the temperature of the steel plate is reduced to TM again, Bf−50° C.≤TM≤Bf−20° C.;
• after that, unstacking and naturally air cooling the steel plate to room temperature,
• wherein the cross stacking is that bottom and top layers are ferritic pearlitic steel plates, and steel plates and ferritic pearlitic steel plates are alternately stacked layer by layer.