To improve strength as well as corrosion resistance, particularly intergranular stress corrosion cracking resistance, in a base material and a heat-affected zone by subjecting an Ni-Cr alloy, having respectively specified chemical composition and impurity content, to two-stage heat treatment under specific conditions.

The Ni-Cr alloy has a chemical composition consisting of, by weight, 0.015-0.04% C, 0.2-1% Si, 0.05-1% Mn, 25-35% Cr, 40-70% Ni, ≤0.1% Al, 0.1-0.4% Zr, 0-0.3% Ti, 0-0.3% Nb, 0-2% Mo, 0-2% W, 0.005-0.010% N, and the balance Fe with inevitable impurities. Further, the contents of P and S among the impurities are controlled to ≤0.015%, respectively. This Ni-Cr alloy is subjected to a first heat treatment consisting of holding at a temp. in the range between the heating temp. T1°C, represented by equation I, and [T1+50]°C for 1-5min and then to a second heat treatment consisting of holding at the temp. T2°C satisfying the condition of inequality II for 0.1-100hr. By this heat treatment, a structure in which Cr carbides are continuously precipitated in crystalline grain boundaries can be obtained.