Heat-resistant martensitic steel and method of thermoplastic and heat treatment of heat-resistant martensitic steel

Abstract

The subject of the application is heat-resistant martensitic steel used for the production of power equipment components intended for operation in creep conditions in the temperature range of 630 - 650°C containing chromium and elements in percentage by weight determined according to the following ranges: carbon (C): 0.08 - 0.15% rhenium (Re): 0.21 - 1.50% manganese (Mn): 0.40 - 0.70%, copper (Cu): 1.00 - 2.00%, nickel (Ni): 0.70 - 1.50%, molybdenum (Mo): 0.70 - 1.50%, tungsten (W): 1.20 - 2.00%, cobalt (Co): 3.00 - 3.50%, vanadium (V): 0.40% - 0.50%, zirconium (Zr): 0.02 - 0.20%, niobium (Nb): 0.02 - 0.06%, titanium (Ti): 0.02 - 0.10%, boron (B): 0.001 - 0.005%, nitrogen (N): 0.02 - 0.04%, silicon (Si): ≤ 0.17%, phosphorus (P): 0.005 - 0.015%, sulfur (S): 0.005 — 0.015%, aluminum (Al): 0.02 — 0.04% and iron as a complement to 100% characterized in that the chromium (Cr) content in percent by weight is in the range of 13.5% to 15.5%, and the content of: molybdenum (Mo),tungsten (W) and rhenium (Re) satisfy the relationship: Re + (186 / 96)*Mo + (186 / 184)*W ≥ 2.78; while the contents of microadditions: vanadium (V), niobium (Nb), titanium (Ti) and zirconium (Zr) satisfy the relationship: 0.40 ≤ V+(51 / 48)*Ti+(51 / 93)*Nb+(51 / 91)*Zr ≤ 0.75. The application also covers a method of thermoplastic and heat treatment of heat-resistant martensitic steel used in the production of power equipment components intended for operation in the temperature range of 630 - 650°C, consisting of the following operations performed immediately one after the other: thermoplastic treatment carried out in the temperature range of 1200 - 800°C and heat treatment including solution heat treatment in the temperature range of 1100 - 1050°C for 30 to 60 minutes, intensive cooling, and tempering. The method is characterized in that intensive cooling is carried out at a rate of not less than 5°C / s in the temperature range of 800 - 500°C,and tempering is carried out in the temperature range of 700 - 650°C for 3 to 5 hours,