Heat treatment method for improving low-temperature toughness of super martensitic stainless steel

The invention relates to a heat treatment method for improving the low-temperature toughness of super martensitic stainless steel, which comprises the following steps: carrying out high-temperature heat preservation austenitizing and quenching cooling on the super martensitic stainless steel, and then carrying out tempering treatment twice. Compared with the prior art, the method can effectively regulate and control the enrichment degree of alloy elements in reversion austenite formed in the tempering process, the thermal stability of the reversion austenite is greatly improved, and the material has excellent low-temperature toughness. After the super martensitic stainless steel is subjected to heat treatment, the impact toughness of the material at the room temperature is larger than or equal to 140 J/cm < 2 >, the impact toughness at the liquid nitrogen temperature is larger than or equal to 80 J/cm < 2 >, the toughness loss is smaller than 50% compared with that at the room temperature, and the super marte