Hardenability of alloy cold drawn seamless steel pipe after quenching and tempering

Most of the quenched and tempered cold drawn seamless steel pipes bear a variety of working loads, and the stress situation is complex, which requires high comprehensive mechanical properties, i.e. high strength, good plasticity and toughness. Alloy quenched and tempered cold drawn seamless steel pipe also requires good hardenability. However, the requirements for hardenability of cold drawn seamless steel pipes are different due to different stress conditions of different parts.

Composition characteristics
(1) Medium carbon cold drawn seamless steel pipe: the carbon content is generally between 0.25% and 0.50%, most of which is 0.4%;

(2) The alloying elements Cr, Mn, Ni, Si are added to improve the hardenability. These alloying elements can not only improve the hardenability, but also form alloy ferrite and improve the strength of steel. For example, the performance of 40Cr cold drawn seamless steel pipe after tempering treatment is much higher than that of 45# cold drawn seamless steel pipe;

(3) The second kind of tempering brittleness is easy to be produced when the alloying quenched and tempered steel containing Ni, Cr and Mn is added. The second kind of temper embrittlement can be prevented by adding Mo and W into the cold drawn seamless steel pipe. The suitable content of Mo is 0.15% - 0.30%, or W is 0.8% - 1.2%.