Cold-drawn section steel will undergo plastic deformation during the stretching process, which will cause dislocations and local residual stress. It can be seen that the residual stress is due to the stress generated in the component during the preparation of the workpiece. In the absence of external force, the stress existing in the object in a balanced state. It not only exists compressive or tensile stress, but also tensile or compressive stress that is balanced with it. Theoretically, its value should not exceed the yield strength of the material.
There are many reasons for the residual stress of cold-drawn section steel. On the one hand, it is caused by uneven deformation. After plastic deformation, the internal stress caused by deformation after the load is removed; on the other hand, it is the result of thermal action and the cooling process. The internal and external cooling is fast, and the internal cooling is slow, so the tensile stress is present on the outside and the compressive stress is present on the inside; there is also thermal residual stress due to phase change and other reasons. On the other hand, it is due to the stress caused by chemical action.
In order to eliminate the residual stress in cold-drawn section steel, the preparation process parameters need to be adjusted first, because during the cold-drawn section steel preparation process, residual stress can be introduced in most stages, including alloy melting, forging, rolling, welding, cutting and other processing. Process, heat treatment and cooling will cause residual stress, so the first thing to do is to adjust the process parameters.Then, low-temperature heat treatment is used to eliminate internal residual stress, which is often referred to as stress relief annealing; or vibration elimination, using a portable powerful exciter, to make the metal structure generate one or more vibration states, so as to produce mechanical loading Due to the elastic deformation of the part, the residual stress in some parts of the part is superimposed with the vibration load, and the plastic strain is caused by the yield stress of the material, which causes the reduction and redistribution of the internal stress.