Weld requirements and heat treatment for large diameter flanges

Large-diameter flanges have strict requirements for weld welds compared to standard flanges for the simple reason that the application environment for large flanges requires high strength. How to ensure the weld quality of large flanges? The answer is: strict testing methods. In terms of testing equipment, we usually use ultrasonic testing and radiation testing. For welds with large diameter flanges, 100% ultrasonic or ray inspection is required. The purpose of the test is to ensure that the surface of the flange is free of cracks or other defects that reduce the strength of the flange.

For the detection of long-diameter large-diameter flanges, the test is carried out under a large design working pressure exceeding 0.8 times the working pressure, and 100% inspection by X-ray film is required. When it comes to inspection ratings and standards, the large flange ultrasonic inspection class I is a qualified product, while the radiation inspection requirement is class II.

In the heat treatment of large diameter flanges and other flanged pipe fittings, the heating temperature is a very important indicator. The selection and control of the heating temperature involves the quality of the heat treatment and the final product quality. Therefore, in the pipe fittings such as large diameter flanges In the heat treatment process, how to choose the appropriate heating method and how to control the heating temperature is a problem that we need to pay special attention to.

In the early heat treatment of flanged pipe fittings, coal and charcoal are usually used as heating sources, and the heating effect is not mentioned. The pollution of the natural environment in this way is self-evident, with the emphasis on industrial pollution in recent years. Some new fuels are gradually being used in industrial heat treatments, such as some gas and liquid fuels. For the industrial heat treatment technology that pursues control, some heating methods such as induction heating can meet the demand, because this advanced heating method is easy to control, and the environmental pollution is small, and the product quality of the flange pipe fittings is also improved. The role.

Taking a marine flange as an example, its heat treatment process generally involves three processes, namely heating, heat preservation, and cooling. In the cooling process, the quenching cooling rate is faster than the normalizing cooling and annealing cooling. Note that the cooling rate required for different steel grades is different, only the technical details of each process can be mastered. Production of large diameter flange and pipe fittings.