METHOD OF HEAT TREATMENT OF CAST IRON TWO-PLY MILL ROLLS Russian patent published in 2017 - IPC C21D9/38 C21D5/00 

FIELD: metallurgy.

SUBSTANCE: method of heat treatment of cast-iron two-ply mill rolls includes carrying out drawing-back by way of heating to a temperature below Ac₁, holding and cooling, first determining the minimum temperature at which the bainite transformation occurs and the temperature of the graphite precipitation start in the cast iron of the roll working layer, and then calculating drawing-back temperature with the following relationship: T_d=T_gp-(10…20), °C, when the following condition is satisfied: T_d<T_{dbt min}; where T_d is the drawing-back temperature, °C; T_gp is the temperature of the graphite precipitation beginning, °C; T_{bt min} is the minimum temperature at which the bainitic transformation proceeds, °C; at that, the drawing-back cycle is repeated 3-4 times.

EFFECT: increased operational durability of mill rolls by creating conditions that ensure the formation of the optimal microstructure of the mill roll working layer cast iron.

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