安装工程常用热处理工艺基础知识（Basic knowledge of heat treatment process in installation engineering）.docVIP

安装工程常用热处理工艺基础知识（Basic knowledge of heat treatment process in installation engineering） Basic knowledge of heat treatment process in installation engineering I. overview Heat treatment is a process that changes the internal structure of metals by heating and cooling solid metals, and obtains the physical, chemical, and mechanical properties of the desired metals. There are many ways to heat treatment, but any kind of heat treatment is made up of three stages: heating, holding and cooling. The welding residual stress relaxation and harden zone softening can be improved by the heat treatment process, the internal structure is improved, the hydrogen content is decreased, and the corrosion resistance, impact toughness and creep limit are improved. Two, commonly used heat treatment method The heat treatment in the construction of the installation project is divided into two parts, pre welding preheating and post welding heat treatment. (1) preheating before welding; Preheating of the weldment before welding can prevent or reduce the occurrence of stress. The preheating effect is to improve the welding temperature, reducing the temperature of weld metal and base metal, reduce weld cooling rate, change the control of steel organization, to avoid the formation of brittle martensite in the heat affected zone, reducing local hardening, improve the welding quality, at the same time as the preheating slow cooling rate, is conducive to the exhaust, slag, it can reduce pores, slag and other defects. Whether you need welding preheating and preheating temperature is how much, according to the chemical composition of steel (hardening), plate thickness, vessel structural rigidity, welding form, welding method and welding material and environmental temperature and other factors to consider. Under normal circumstances, when the ambient temperature is below 0 degrees, it should be properly preheated except for non-ferrous metals. The preheating temperature of 35# and 45# steel can be sel