As a good deformation compensation element, corrugated expansion joint has been widely used in electric power, petroleum, chemical industry, shipbuilding and other fields. Driven by the development of science and technology, the application of thick wall expansion joint in engineering is more and more. From the engineering application, there are many cases of expansion joint failure caused by large residual stress due to cold work hardening. The heat treatment of thick wall corrugated expansion joint is explained to you.

　　Heat treatment is a process that changes the internal structure of a solid metal and obtains the required properties by heating and cooling the solid metal. According to its main purpose, heat treatment in the process of product manufacturing can be divided into post weld heat treatment, hydrogen elimination treatment, heat treatment to recover or reach the specified mechanical properties, and solution treatment and stabilization treatment for austenitic stainless steel. For carbon steel and low alloy steel products, due to the large amount of cold forming deformation, there will be obvious cold work hardening, which is the improvement of material strength and hardness, the reduction of plasticity and toughness, and the generation of larger internal stress. In practical production, the product is heated to 50-150 ℃ and cooled slowly with furnace after proper heat preservation, and stress relief annealing. As the activity of atoms increases with the increase of temperature, the grains broken, elongated or flattened during cold deformation become uniform and fine equiaxed grains through the nucleation and nucleation growth of new crystals, thus eliminating the internal stress and cold work hardening of the product, reducing the strength and hardness of the material, and restoring its plasticity and toughness.

　　At present, the manufacturing technology of integral cold forming thick wall expansion joint is becoming more and more mature, which makes the heat treatment of thick wall corrugated expansion joint more critical. After forming stainless steel bellows, metal hose and stainless steel compensator, a large amount of deformation martensite structure will be produced, which will increase the hardness of the material, reduce the toughness, and produce larger internal stress. If the product works in the stress corrosion environment, it will be very dangerous, so the necessary solution treatment is also indispensable

　　Definition of corrugated expansion joint:

　　If there is no metal wire or metal belt braided net cover on the outer surface of the corrugated expansion joint, the corrugated expansion joint is equipped with tie rod, hinge, reinforcing ring and other restraint devices, which is an annular bellows assembly with a ratio of less than 3. Corrugated expansion joint is commonly called corrugated expansion joint in the West. Generally, the bellows expansion joint compensates the position movement of pipeline system caused by temperature difference by its axial expansion and contraction or angle change ratio, and absorbs the vibration of equipment under the condition of starting, stopping or normal operation.

　　There are several kinds of classification methods for corrugated compensators

　　1. According to the structural characteristics

　　2. According to performance characteristics

　　3. According to traditional habits

　　However, no matter which method is used to classify bellows expansion joints, in fact, the products of bellows expansion joints are still various. They will not be increased or decreased due to different classification methods, but the name has changed.

　　Corrugated expansion joint, also known as corrugated expansion joint and corrugated compensator, is mainly used to ensure the safe operation of the pipeline. It has a number of cylindrical thin-walled folded shell with transverse waves. The bellows is elastic and can produce displacement under the action of pressure, axial force, transverse force or bending moment. Corrugated pipe materials should meet the following conditions: high elastic limit, tensile strength and fatigue strength to ensure the bellows work; good plasticity to facilitate molding and processing, and through the subsequent treatment process (work hardening, heat treatment, etc.) to obtain sufficient hardness and strength; good corrosion resistance to meet the requirements of bellows in different environments. The working principle is mainly to use its own elastic deformation function to compensate the axial, angular, lateral and combined displacement of the pipeline due to thermal deformation, mechanical deformation and various mechanical vibration. The compensation function has the functions of pressure resistance, sealing, corrosion resistance, temperature resistance, impact resistance, vibration reduction and noise reduction, which can reduce the pipeline deformation and improve the service life of the pipeline.

　　Metal hose mainly refers to a kind of spiral corrugated pipe. It is a kind of flexible pressure pipe fitting installed in the liquid transportation system, which is used to compensate the mutual displacement of pipe or machine and equipment connection ends, absorb vibration energy, and play the role of vibration reduction and noise elimination. It has good flexibility, light weight, corrosion resistance, fatigue resistance, high and low temperature resistance, flexible pitch, and good flexibility There is no obstruction and rigidity.