Mechanical Properties of Domestic Super304H Tube in Original and Service State for Ultra Supercritical Unit

The domestic Super304H tube in original and service state(approx.12 000 h and 34 000 h) was researched through the tensile test,impact test,hardness test and metallographic examination.The test results indicate that the mechanical properties of domestic Super304H tube fulfilled the requirements of related standards.With the service time passing,the tensile strength and hardness had little change,while the impact toughness declined obviously.The impact toughness of welding seam was much lower than that of base material.The steep decline in impact toughness was related closely to the precipitation and accumulation of carbide along the grain boundary.