PURPOSE: To make micro structure fine without adding new process and to improve material characteristic by hot-rolling a steel ingot of maraging steel under specifying the temp. and the work strain quantity and executing solution heat treatment and aging treatment after controlling cooling.
CONSTITUTION: To the steel ingot of 18 Ni maraging steel produced, the hot- working making the total work strain rate to 1.20 is executed in the temp. range of 950-1,150°C, This is cooled with water under limiting the average cooling velocity (v) (°C/min) to in the range of 2.0≤v≤10.0 from finish temp. of the hot working to 850°C. Successively, the solution heat treatment and the aging treatment are executed. By this method, the micro structure after hot- working is made to fine, and the maraging steel having excellent mechanical property and cold workability, is obtd.
SUENAGA HIROYOSHI
MINAGAWA KUNINORI
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