What is the difference between SA335 P22 steel and 15CrMo material?

SA335 P22 steel is a grade of American standard boiler tube. The executive standard is American standard ASME SA335/SA335M. SA335 P22 steel is chromium-molybdenum high-temperature ferritic steel for boilers and superheaters. SA335 P22 alloy steel pipes are mainly used for heating surface pipes of low and medium pressure boilers (the working pressure is generally not greater than 5.88 Mpa, and the working temperature is below 450℃); for high-pressure boilers (the working pressure is generally above 9.8 Mpa and the working temperature is 450℃- 650℃) heating surface pipe, economizer, superheater, reheater, petrochemical industry pipe, etc.

15CrMo material belongs to the heat-resistant steel with pearlite structure. 15CrMo material has high thermal strength (δb≥440MPa) and oxidation resistance at high temperature (generally no more than 600℃), and has certain resistance to hydrogen corrosion. 15CrMo material is used in petrochemical industry, etc. The applications in the industry are becoming more extensive. However, due to the high content of Cr, C and other alloying elements in the steel, the hardening tendency of the15CrMo material is obvious and the weldability is poor. The main problem is the hardening of the heat-affected zone, cold cracks and reheat cracks during post-weld heat treatment.