Analysis of Reason for Low Toughness of Super 13Cr Martensitic Stainless Steel Pipe and Relevant Countermeasures

Aiming at the event that the post-heat treatment toughness of a certain batch of the super 13Cr seamless steel pipe, based on the manufacturing process, all the tests are conducted to the pipe in terms of microstructure, nonmetallic inclusion, tensile property, impact energy and chemical composition. It is revealed via the analysis that after being quenched, the pipe's hardness is rather low, and due to quenching and tempering treatment, its microstructure is not homogeneous enough, and there exist many coarse ferrite phases as parallel to the axis of the steel pipe, and distributed between the phases, which breaks the continuity of the matrix structure, and leads to the low transverse impact energy. The corresponding countermeasures are put forward and taken for the said batch of pipes and the remaining raw materials, including increasing the deformation amount of the steel pipe, and changing the quenching and the tempering processes so as to optimize the metallographic structure, and thus improve the performance of the product.