Role of Steel Tube Heat Treatment

Heat treatment is mainly used to change the properties of the metal material, one of the modified process of animal performance, exhibit a metallic material in a thermal processing performance: the second is to improve the practical performance, under conditions of use of metal materials performance properties, the first material "annealing" is conducive to reducing the hardness of the steel cutting: After processing into rasp, it must be "hardened" and "tempered" in order to improve the hardness and wear resistance. Ensure the use of rasp, the heat treatment can improve and strengthen the performance of metallic materials. Ensure product quality, improve processing conditions, saving metal material, so the vast majority of machine parts to be heat treated to improve the product quality is to meet the requirements to extend the working life, if the pre-heat treatment of metallic materials are included, almost All parts requiring heat treatment. Therefore, with the rapid development of modern industry, heat treatment will play a greater role.Workpiece in the heating and cooling process, the cooling rate is inconsistent and the central portion of the surface and time to form a temperature, volume expansion and contraction can lead to uneven stress, the thermal stress. Under thermal stress, the surface temperature is lower core section, leaving the central portion is larger than the contraction of the heart portion is pulled when the cooling is completed, the final cooling unit volume of the heart contraction can freely leaving the center portion of the pressure receiving surface tension. That is the role of thermal stress eventually the workpiece surface tension pressure and heart department. This phenomenon is cooled velocity, material composition and heat treatment process and other factors. When cooled, the faster, the higher the carbon content and alloy composition, uneven cooling process of plastic deformation under thermal stress generated by the larger, the final form of the residual stress it gets. Seamless steel pipe in the heat treatment process on the other hand due to tissue changes in the austenite to martensite transformation i.e., the specific volume is increased due to the volume expansion accompanied by the workpiece, the workpiece has a phase change portion, causing inconsistency in the volume brought up produce tissue stress. The end result is that the surface tissue stress tensile stress, the center compressive stress, thermal stress and the opposite happens. The size of the stress in the workpiece cooling rate of change martensitic area, shape, chemical composition of the material. Practice proved that no seamless steel workpiece during the heat treatment, as long as the phase change, the stress and thermal stress occurs. Thermal stress in the past but it has generated organizational change, and organizational stress is generated in the process of organizational change in the whole cooling process, thermal stress and the results of the combined effects of the stress that is actually present in the work stress. The results of these two combined effects of stress is very complex, being affected by many factors, such as composition, shape, heat treatment and so on. Only two types, i.e., thermal stress and the stress, the direction of offset on its two opposite development, the role of the two mutually superimposed in the same direction. Whether or cancel each other mutual superposition of two seamless pipe stress should be a dominant factor, the role of the dominant thermal stress results when the central portion of the workpiece is pulled, the surface pressure. The results stress the role of the dominant organization at the Ministry of pressure on the workpiece surface tension heart.