4　Materials

4.1　General Requirement

4.1.1　Piping materials shall be selected according to the design pressure and temperature of piping，working medium，service conditions，economy，welding and processing of materials.All selected materials shall have satisfactory chemical and physical properties，fatigue resistance，and metallurgical stability，and meet the corresponding requirements in this code.

4.1.2　The specification and performance of piping materials shall comply with the relevant national standards in force.

4.1.3　Unlisted materials shall only be used if they meet the requirements in current national standards in respect of chemical composition，physical and mechanical properties，manufacturing process and method，heat treatment and test.