Patent ID: 7718014

Claim:
A weld joint of a low alloy steel excellent in hydrochloric acid corrosion resistance and sulfuric acid corrosion resistance, characterized in that: said weld joint comprises a base material containing, in mass, C: 0.001 to 0.2%, Si: 0.01 to 2.5%, Mn: 0.1 to 2%, Cu: 0.1 to 1%, Mo: 0.001 to 0.12%, Sb: 0.01 to 0.2%, Ni: 0.1 to 1%, P: 0.05% or less, S: more than 0.005% to 0.012%, N: 0.001 to 0.007%, and Cr: less than 0.5%, with the balance being Fe and unavoidable impurities and a weld metal containing, in mass, C: 0.005 to 0.2%, Si: 0.01 to 2.5%, Mn: 0.1 to 2%, Cu: 0.1 to 1%, Mo: 0.001 to 0.12%, Sb: 0.01 to 0.2%, Ni: 0.1 to 1%, P: 0.03% or less, S: more than 0.005% to 0.012%, N: 0.001 to 0.02%, and Cr: less than 0.5%, with the balance being Fe and unavoidable impurities; and the acid corrosion resistance indexes AI, which are calculated from the following expression <1>, of said base material and weld metal are zero to 75, AI/ 10,000=0.0005+0.045 ×Sb %−C %×Mo % <1>, where % means mass %.