Abstract: A theoretic analysis is conducted relating to the corrosion-resistance of the Sweden-made hi-chromium-nickel alloy steel (904L) pipe as used on some kind of chemical industrial equipment. The conclusion is that the said 904L steel is in possession of rather high resistance against intergranular corrosion, corrosive pitting and stress corrosion-caused fracture. Described here in the paper is the welding process of the said steel pipes, covering the welding condition requirements, the bevel shape and related technological criteria as well as the welding tips and post-welding inspection, etc. The welding procedure as introduced by the author can be used as a guideline for welding operation of hi-Cr-Ni alloy pipes.