For alloy pipe fittings, heat treatment is a necessary process, compared with other material pipe fittings, alloy pipe fittings need to be heat treated. Heat treatment process generally includes three processes: heating, heat preservation and cooling, sometimes only heating and cooling. These processes connect with each other and are uninterrupted. Heating is one of the important processes of heat treatment. There are many heating methods of metal heat treatment, the earliest is to use charcoal and coal as heat source, and to use liquid and gas fuel. The application of electricity makes heating easy to control and no environmental pollution. These heat sources can be used to heat directly, or through molten salt or gold, or even floating particles. The children are heated indirectly. When the metal is heated, the work-piece is often oxidized and decarbonized (that is, the surface carbon content of iron and steel parts is reduced) when the work-piece is exposed to air, which has a very negative effect on the surface properties of the parts after heat treatment. Therefore, metals should usually be heated in controllable atmosphere or protective atmosphere, molten salt and vacuum, or by coating or packaging. Heating temperature is one of the important process parameters of heat treatment process. Selecting and controlling heating temperature is the main problem to ensure the quality of heat treatment. The heating temperature varies with the purpose of the treated metal material and the heat treatment, but it is generally heated above the phase transition temperature. To obtain high temperature micro-structure. In addition, it takes a certain time to change, so when the surface of the metal work-piece reaches the required heating temperature, it is necessary to keep the temperature at this temperature for a certain period of time, so that the internal and external temperatures are consistent and the micro-structure is completely transformed. This period of time is called holding time. When high energy density heating and surface heat treatment are used, the heating speed is very fast, and generally there is no holding time, but the holding time of chemical heat treatment is often longer.
Metal heat treatment process can be divided into three categories: integral heat treatment, surface heat treatment and chemical heat treatment. According to the different heating medium, heating temperature and cooling method, each category can be divided into several different heat treatment processes. Different microstructure can be obtained by using different heat treatment processes of the same metal, so it has different properties. Iron and steel is the most widely used metal in industry, and the microstructure of iron and steel is the most complex, so there are many kinds of heat treatment process of iron and steel. Integral heat treatment is the metal heat that heats the workpiece as a whole and then cools at an appropriate rate to obtain the metallographic structure needed to change the overall mechanical properties of the workpiece. Treatment process. There are four basic processes of overall heat treatment of iron and steel: annealing, normalizing, quenching and tempering.
Carbon steel A234WPB butt welded pipe fittings and A 105 flanges also need heat treatment under certain circumstances. The material is restored to the most important purpose.