Why does thick-walled stainless steel pipe deform during heat treatment?

　　The performance of thick-walled stainless steel pipes will be better after heat treatment, and it will be more in line with the performance requirements of mechanical parts. However, during the heat treatment process, metal materials will have problems such as deformation. The appearance of deformation of metal materials has a fatal impact on the processing of mechanical parts. Let’s take a look at the three major factors of heat treatment deformation of thick-walled stainless steel pipes.

　　1. Quenching medium factor

　　Relevant practical studies have shown that in the implementation of the heat treatment process, the selection of a quenching medium is related to the effect of the heat treatment process and is closely related to the occurrence of material deformation. In actual heat treatment, the selection of quenching medium quality affects the quenching effect of thick-walled stainless steel pipes, and its quenching stability is severely restricted. In addition, the stirring speed and method of the medium will also have a certain impact on the material. If the medium mixing method is unreasonable, the possibility of material deformation will increase.

　　2. Internal stress plastic deformation factor

　　In the heat treatment process of stainless steel product pipes, uneven heating and cooling and uneven phase change time will produce internal stress, and internal stress plastic deformation will occur under certain plastic conditions. During the heating and cooling process, the heating and cooling rates of the inner and outer layers of the steel pipe are different, resulting in different temperatures, resulting in different degrees of thermal expansion and cold contraction. The resulting stress deformation is called thermal stress plastic deformation. During the heating and cooling process, the internal structure of the thick-walled stainless steel pipe will change and change at different times.

　　3. Volume deformation factor

　　Volume deformation During the heat treatment of stainless steel welded pipes, the specific volumes of various phase structures are different, and the volume and size changes during the phase change process are specific volume deformation. Specific volume deformation is usually only related to the content of carbon and gold elements in austenite, the amount of free phase carbides and ferrite, the difference in the specific volume of the organization before and after quenching, and the amount of residual austenite. Generally speaking, volume deformation is caused by the change in specific volume during phase change. The mass volume of martensite is greater than that of other constituent phases of steel. When the thick-walled stainless steel pipe transforms from other constituent phases to martensite during heat treatment, the volume will inevitably increase. The mass volume of austenite is smaller than the mass volume of other steel structures. When it transforms from other constituent phases to austenite during heat treatment, the volume will decrease.

　　The main factors of heat treatment deformation of thick-walled stainless steel pipes are quenching medium and medium stirring speed; internal stress plastic deformation; and volume deformation. The deformation during heat treatment has a certain impact on efficiency. In order to ensure the accuracy of thick-walled stainless steel pipes, corresponding measures need to be taken to control the deformation of the workpiece during heat treatment to the minimum range.