Abstract: Through the heat treatment experiment of the low cost-made 29Mn5 steel,the P110 casing as per applicable requirements under API Spec 5CT is obtained.Analyses of the microstructure morphology and the mechanical properties,and the magnetic particle detection result are conducted to the samples as taken from pipes undergone different quenching and tempering processes.The experimental results show that more than 95% of martensite can be obtained after quenching at 920 ℃ and 880 ℃ for 15 min,and then water quenching;quench-caused cracks are apt to be develop,in case of quenching at 920 ℃;and the P110 casing with proper comprehensive performance can be produced by means of the process of quenching at 880 ℃ + tempering at 540 ℃.