METHOD OF HEAT TREATMENT OF FORGED PIECES FROM STRUCTURAL ALLOYED STEEL GRADE 4340 (VERSIONS) Russian patent published in 2025 - IPC C21D1/25 C21D1/02 C21D6/00 

FIELD: performing operations.

SUBSTANCE: invention relates to heat treatment of structural alloyed steels and can be used in heat treatment of steel forgings, which can be used in production of oil and gas, petrochemical equipment and in other areas where high resistance to impact wear is required. Method of heat treatment of forgings from structural alloyed steel grade 4340 includes quenching at temperature 860-880 °C with a holding time of 1.8 h per each 100 mm of forging thickness, then cooling is performed in oil for at least 40-50 minutes with oil temperature at the start in quenching tank of not more than 35 °C, followed by tempering at temperature of 510-560 °C for 2.5-3 hours for each 100 mm of forging thickness, then cooling is carried out in water for at least 20-25 minutes until metal surface temperature is below 50 °C, wherein water temperature in quenching tank is not more than 20-25 °C at the start, water temperature at the finish is not more than 40 °C, further cooling is carried out in air. Method of heat treatment of forgings from structural alloyed steel grade 4340 includes quenching at temperature 860-880 °C with a holding time of 1.8 h per each 100 mm of forging thickness, then cooling is performed in oil for at least 40-50 minutes with oil temperature at the start in quenching tank of not more than 35 °C, after which the first tempering is carried out at temperature of 510-560 °C for 2.5-3 hours for every 100 mm of forging thickness with subsequent cooling in air until metal surface temperature is below 300 °C, after which the second tempering is carried out at temperature of 490-530 °C for 2.5-3 hours for each 100 mm of forging thickness, then cooling is carried out in water for at least 20-25 minutes until metal surface temperature is below 50 °C, wherein water temperature in quenching tank is not more than 20-25 °C at the start, water temperature at the finish is not more than 40 °C, further cooling is carried out in air.

EFFECT: improved strength properties of steel products and increased level of impact operation at test temperature below 40 °C.

2 cl, 3 tbl