High magnetism was found in austenitic heat resistant steel boiler tubes after service at high temperatures. To solve this problem

the magnetic properties(such as magnetic equivalent

magnetic induction intensity

magnetization

saturation magnetization

remanence

coercivity and magnetic hysteresis loop) of TP304 H steel

TP347 H steel

S30432 steel and other new samples of austenitic heat-resistant steel

samples after service at high temperatures and their carbides were investigated

through magnetic induction intensity measuring instrument

detector for carbides of austenitic steel

integrated physical property measurement system(VSM)

heat treatment and metallographic analysis. The results show that

the ferromagnetic α′-martensite

high internal stress caused by transformation expansion and weak ferromagnetic carbides lead to high magnetism in the austenitic heat resistant steel boiler tubes after service at high temperatures. The magnetism caused by weak ferromagnetic carbides can be ignored.