冷拉型鋼在拉伸過程中會出現(xiàn)塑性變形,從而產(chǎn)生位錯和局部的殘余應(yīng)力,由此可見,殘余應(yīng)力是由于工件在制備過程中,在構(gòu)件內(nèi)部產(chǎn)生的應(yīng)力。在無外力作用下,以平衡狀態(tài)存在于物體內(nèi)部的應(yīng)力。它不只存在壓應(yīng)力或拉應(yīng)力,而是同時存在與之平衡的拉應(yīng)力或壓應(yīng)力,理論上其數(shù)值不應(yīng)該超過材料的屈服強(qiáng)度。
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.
冷拉型鋼之所以存在殘余應(yīng)力,原因是多方面的,一方面是不均勻變形引起的,塑性變形后,載荷去除后內(nèi)部由于變形形成的應(yīng)力;另一方面是熱作用的結(jié)果,冷卻過程中外部冷卻快,內(nèi)部冷卻慢,因而外部呈現(xiàn)拉應(yīng)力,內(nèi)部呈現(xiàn)壓應(yīng)力狀態(tài);還有因為相變等等原因產(chǎn)生的熱殘余應(yīng)力。還有一方面則是因為化學(xué)作用產(chǎn)生的應(yīng)力。
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.
為了能消除冷拉型鋼中的殘余應(yīng)力,首先需要調(diào)整制備工藝參數(shù),因為在冷拉型鋼制備工藝過程中,大多階段都可以引入殘余應(yīng)力,包括合金熔煉、鍛造,軋制,焊接,切削等加工過程、熱處理冷卻等都會導(dǎo)致殘余應(yīng)力產(chǎn)生,因此首先要做的就是調(diào)整工藝參數(shù)。 然后是通過低溫?zé)崽幚?,消除?nèi)部殘余應(yīng)力,也就是我們常說的去應(yīng)力退火;或者是振動消除,用便攜式強(qiáng)力激振器,使金屬結(jié)構(gòu)產(chǎn)生一個或多個振動狀態(tài),從而產(chǎn)生如同機(jī)械加載時的彈性變形,使零件內(nèi)某些部位的殘余應(yīng)力與振動載荷疊加后,超過材料的屈服應(yīng)力引起塑性應(yīng)變,從而引起內(nèi)應(yīng)力的降低和重新分布。
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.