High-precision cold-drawn tubes have particularly high technical requirements in production and processing. Under the action of heat, high-precision cold-drawn tubes have a relatively high shrinkage speed due to the heat, and the condensation speed is also relatively high. Quickly, it is more susceptible to irritation during the setting process.
The faster the cooling rate, the higher the carbon content and alloy composition, the greater the uneven plastic deformation caused by the thermal stress during the cooling process, and the greater the final residual stress. On the other hand, during the heat treatment of steel, due to the change in the structure, that is, the transformation of austenite to martensite, the increase of the specific volume will accompany the expansion of the workpiece volume, and the various parts of the workpiece will phase change, resulting in inconsistent volume growth and microstructure stress. The ultimate result of the change of tissue stress is the tensile stress of the surface layer and the compressive stress of the core, which is just the opposite of thermal stress. The magnitude of the structural stress is related to the cooling rate, shape, and chemical composition of the material in the martensite transformation zone.