Precipitation-hardening-type austenitic alloy steel material and method for manufacturing same, and precipitation-hardening-type austenitic alloy heat-treated steel material and method for manufacturing same

Abstract

Provided is a method for manufacturing an austenitic alloy steel material that can improve mechanical properties even without improving a composition of a steel material and an increase in the service life of a component in a high-pressure hydrogen environment can be expected. A method for manufacturing a precipitation-hardening austenitic alloy steel material, the method including: a hot forging step of providing a material for forging having a composition of the precipitation-hardening austenitic alloy steel material, and performing hot forging several times so that a total forging forming ratio is 30 or more, to form a forged material. The method preferably includes a heat treatment step of additionally subjecting the forged material to a solution treatment and an aging treatment, to obtain a heat-treated steel material.

1 . A method for manufacturing a precipitation-hardening austenitic alloy steel material, the method comprising:
 providing a material for forging having a composition of a precipitation-hardening austenitic alloy, and performing hot forging several times so that a total forging forming ratio is 30 or more, to form a forged material, the forged material having a columnar shape and an equivalent area diameter of a cross section in a direction perpendicular to an axis of the forged material being 100 mm or more.   
     
     
         2 . A method for manufacturing a precipitation-hardening austenitic alloy heat-treated steel material, the method comprising:
 additionally subjecting the precipitation-hardening austenitic alloy steel material according to claim  1  to a solution treatment and an aging treatment, to obtain a heat-treated steel material.   
     
     
         3 . A precipitation-hardening austenitic alloy steel material,
 wherein an area ratio of grains having a GOS (Grain Orientation Spread) value of 1.0° or more is 50% or more,   wherein a shape of the precipitation-hardening austenitic alloy steel material is columnar, and an equivalent area diameter of a cross section in a direction perpendicular to an axis of the precipitation-hardening austenitic alloy steel material is 100 mm or more.   
     
     
         4 . A precipitation-hardening austenitic alloy heat-treated steel material, wherein
 when an equivalent area diameter of a cross section in a direction perpendicular to an axis of the heat-treated steel material is designated as D, the precipitation-hardening austenitic alloy heat-treated steel material has a grain size number of 4.0 or more, a 0.2% yield strength of 590 MPa or more, a tensile strength of 900 MPa or more, and an elongation of 15% or more at positions of depth D/4 and depth D/2 from a surface of the heat-treated steel material, and   a shape of the precipitation-hardening austenitic alloy heat-treated steel material is columnar, and an equivalent area diameter of a cross section in a direction perpendicular to an axis of the precipitation-hardening austenitic alloy heat-treated steel material is 100 mm or more.