What are the three main factors contributing to the deformation of thick-walled stainless steel pipes during heat treatment

It is well known that thick-walled stainless steel pipes exhibit better performance after heat treatment, better meeting the performance requirements of mechanical parts. However, during the heat treatment process, thick-walled stainless steel pipes may experience deformation. This deformation has a fatal impact on the machining of mechanical parts.

1. Quenching medium factors in the heat treatment of thick-walled stainless steel pipes.

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

2. Internal stress plastic deformation factors in the heat treatment of thick-walled stainless steel pipes.

In the heat treatment of thick-walled stainless steel pipes, uneven heating and cooling, as well as uneven phase transformation time, generate internal stress. Under certain plastic conditions, this internal stress plastic deformation occurs in the thick-walled stainless steel pipe. During heating and cooling, the heating and cooling rates of the inner and outer layers of the thick-walled stainless steel pipe differ, resulting in different temperatures and varying degrees of thermal expansion and contraction. The stress deformation generated in the thick-walled stainless steel pipe is called thermal stress plastic deformation. During heating and cooling, the internal structure of the thick-walled stainless steel pipe changes, and these changes occur at different times.

3. Factors affecting volumetric deformation during heat treatment of thick-walled stainless steel pipes.

During the heat treatment of thick-walled stainless steel pipes, the specific volume of various phase structures differs. The volume and dimensional changes during phase transformation constitute specific volumetric deformation. The specific volumetric deformation of thick-walled stainless steel pipes after heat treatment is generally only related to the content of carbon and gold elements in austenite, the amount of free carbides and ferrite, the difference in specific volume of the microstructure before and after quenching, and the amount of retained austenite.

Generally speaking, volumetric deformation is caused by changes in specific volume during phase transformation. The mass volume of martensite is greater than that of other constituent phases of steel. When thick-walled stainless steel pipes transform from other phases to martensite during heat treatment, their volume inevitably increases. The mass volume of austenite is smaller than that of other steel structures. Conversely, when thick-walled stainless steel pipes transform from other phases to austenite during heat treatment, their volume decreases.

From the above, we can understand that the main factors influencing the deformation of thick-walled stainless steel pipes during heat treatment include the quenching medium and its stirring speed; internal stress plastic deformation; and volume deformation. The deformation during heat treatment has a certain impact on efficiency. To ensure the precision of thick-walled stainless steel pipes, corresponding measures need to be taken to control the deformation of the workpiece within a minimum range during heat treatment.