The invention discloses an improved 21 / 4Cr-1Mo-1 / 4V steel
forging which is characterized by comprising the following components in percent by weight: 0.11-0.15 percent of carbon, not more than 0.10 percent of
silicon, 0.30-0.60 percent of
manganese, not more than 0.01 percent of
phosphorus, not more than 0.01 percent of
sulfur, 2-2.5 percent of
chromium, 0.9-1.10 percent of
molybdenum, not more than 0.20 percent of
nickel, not more than 0.15 percent of
copper, 0.25-0.35 percent of
vanadium, not more than 0.30 percent of
titanium, not more than 0.002 percent of
boron, not more than 0.07 percent of
niobium, not more than 0.015 percent of
calcium and the balance of iron. The invention also discloses an automatic temperature-control inflation three-dimensional circulating water rapid cooling
thermal treatment method of the steel
forging, which comprises the steps of: 1, an after-
forging thermal treatment process: normalizing at a temperature of 890-990 DEG C, air-cooling after constant temperature is not less than 1h / 100mm,
tempering at a temperature of 680-720 DEG C, furnace-cooling after constant temperature, and cooling at a limited speed at a temperature of below 400 DEG C; 2, a thermal refining process:
quenching at a temperature of 900-980 DEG C, carrying out constant temperature with 1h / 100mm, rapidly cooling and
quenching and
tempering at a temperature of 680-720 DEG C, carrying out constant temperature with 1h / 100mm and air-cooling thickness of the forging, wherein the
water temperature of thickness of the forging is not more than 10 DEG C; and 3, adopting a three-dimensional
automatic control circulating water periphery inflation method. The forging has higher tension strength, temper
brittleness resistance,
hydrogen damage resistance and lower long-term high-temperature damage sensitivity.