PROBLEM TO BE SOLVED: To provide a manufacturing method to forge a large parts of a 718 alloy so as not to allow any abnormal grain growth. ;SOLUTION: The manufacturing method includes a) process to prepare a billet 14 having the average grain size of ASTM0-ASTM3, b) a process to heat the billet 14 to the temperature of 1,750-1,800°F, c) a process to upset the billet 14 to obtain a parts 24 having the minimum strain of 0.125 at least in a predetermined area, d) a process to re-heat the parts 24 to the temperature of 1,750-1,800°F, e) a process to upset the parts 24 to the final shape so that the predetermined area is not subjected to the strain of 0.01 to 0.125, f) a process to achieve the solution treatment of the parts 24 at the temperature of 1,725-1,750°F, and g) a process to achieve the aging treatment of the parts 24 for a predetermined time at diversified temperature. Abnormal grain growth occurs in the predetermined area of the parts by modified methods of this method.;COPYRIGHT: (C)2001,JPO
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