Patent ID: 9574250
Date: 2017-02-21
CPC Classifications: B21J,B21K,C21D

Claim:
1. A method for producing a stepped forged material, comprising the steps of: obtaining a primary forged material, wherein an austenite stainless steel billet for forging is heated to 1000-1080° C., and, without any further heating, the material is forged into a round rod having a forging ratio of 1.5 or greater along the entire length of the material by means of reciprocal forging of repeating a forging operation in which the material is delivered from one end to the other end in the axial direction with respect to a forging apparatus and thereafter delivered in the opposite direction; obtaining a secondary forged material formed to have a large diameter flange portion and a small diameter shaft portion, wherein without reheating, forging is started at a temperature before a surface temperature of the primary forged material falls more than 200° C. lower than the material heating temperature, and the small diameter shaft portion is formed by means of reciprocal forging of repeating a forging operation in which the primary forged material is delivered from one end in the axial direction to a predetermined position with respect to the forging apparatus and thereafter delivered in the opposite direction, and the forging is completed before a surface temperature of a final forged portion falls more than 300° C. lower than the material heating temperature; and performing a solution heat treatment, wherein the secondary forged material is heated to 1040-1100° C. for 30 minutes or longer.