METHOD OF MAKING STEEL DOUBLE-LAYER HOT-ROLLED SHEETS Russian patent published in 2020 - IPC C21D8/04 B23K20/04 C21D9/48 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, particularly, to production of steel sheets consisting of main layer and plating layer of corrosion-resistant steel intended for production of large-diameter pipes, equipment for oil processing, chemical industry, as well as other industries. To ensure high quality of joining layers – continuity and increase impact strength of the base layer of the sheet at a negative test temperature, a steel two-layer workpiece having a plating layer of corrosion-resistant steel is stepped heated in a furnace, wherein at first the workpiece is heated to a temperature of not less than 450 °C at a heating rate N₁ (°C/min) corresponding to expression N₁=(k₁⋅h)±0.5, where k₁ is an empirical coefficient equal to 0.006÷0.010, h is a nominal value thickness of workpiece (mm), after which workpiece is heated at rate N₂ (°C/min) to temperature not less than T₂ (°C), wherein N₂=(k₂⋅h)±5, where k₂ is empirical coefficient equal to 0.06–0.10, T₂=(T₃-150)±50, where T₃ – minimum temperature of this workpiece, required by the moment of its dispensing from furnace (°C), then billet is heated with rate N₃ (°C/min) to temperature corresponding to range from T₃ to (T₃+20), wherein N₃=(k₁⋅h)±0.5, after which billet while maintaining its temperature in range from T₃ to (T₃+20) is held in furnace for at least 120 minutes, then hot rolling of workpiece is carried out, at this operation is completed at temperature of rolled stock not over 920 °C, after which the obtained sheet is cooled with water.

EFFECT: high quality of joining layers.

4 cl, 1 tbl