METHOD FOR PREPARING HOT-ROLLED STEEL IN THE MANUFACTURE OF AUTOMOTIVE FASTENERS BY COLD DIE FORGING Russian patent published in 2021 - IPC C21D8/06 C21D1/26 

FIELD: thermomechanical processing.

SUBSTANCE: invention relates to the field of thermomechanical processing of hot-rolled and calibrated rolled products from structural alloy steel of the pearlite class and can be used for the manufacture of fasteners (bolts, nuts) and hardware products (ladders, traction, etc.) for cars, tractors and various special equipment. The method of preparing hot-rolled steel for cold forging in the manufacture of fasteners includes double annealing and double drawing on a drawing mill, characterized in that the first annealing is carried out in a furnace at a temperature of 760-780°С with holding for 3-4 hours, followed by cooling to a temperature of 660-680°C and holding at this temperature for 3-4 hours, followed by cooling to a temperature of 170-180°C and holding at this temperature for 1-2 hours, after which, air cooling is carried out, then the first drawing is carried out with a reduction rate of 22-23%, then the second annealing of rolled products in coils is carried out by induction heating by means of high frequency current (HFC) at a temperature of 660-680^οС, after which the second drawing is carried out with a reduction rate of 12-13 %.

EFFECT: obtaining the required mechanical characteristics of finished calibrated rolled products due to the required structure with fine-grained pearlite along the cross-section and length of the rolled product while maintaining the required strength and plasticity before cold forging of fasteners and hardware products.

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