| 摘要 |
PURPOSE:To give superplasticity by carrying out, prior to tempering, heating to a temp. of the A3 point or above and rapid cooling to form a martensite structure. CONSTITUTION:As steel, hypo-eutectoid steel containing alloying elements of 1 or >=2 kinds among 0.05-2wt% Nb, 0.1-2wt% V, and 0.05-1wt% Al is used. The hypo-eutectoid steel is heated to a temp. of the A3 point or above and cooled rapidly, which is subjected to tempering and cold working. Then the steel is heated to a temp. from the A3 point to the A3 point + 50 deg.C, held at the temp. and hardened to form martensite structure, which is heated to form a fine two-phase structure. |
