Knowledge of welding defects and heat treatment of pressure vessels (1)

Pressure vessels occupy a very important position in petrochemical production. Pressure vessels can serve as petrochemical equipment for reaction, energy exchange, separation, tower, storage, and transportation. They have the danger of bombardment, and their safe operation is directly related to the production and personal safety of the enterprise. Therefore, the quality of pressure vessel products has always been highly valued by the state. In the past ten years or so, the design, manufacture, and management of pressure vessels in China have embarked on the legal management track, and product quality is steadily improving.

The welding quality is high and stable, and the weld surface is beautiful and flat. Welding has become a key process in the production of pressure vessels. The quality of welding is a very important link to ensure the quality of pressure vessels. The quality of single welding is affected by many factors: welder skills, chemical composition, mechanical properties, welding materials, welding process and equipment, environment, etc. can all affect the welding quality.

n order to improve the quality of pressure vessel products, the state can only produce by obtaining a manufacturing license. For manufacturers that have obtained manufacturing licenses, formulate welding procedures to allow production, welders to work with certificates, and strengthen the control and management of all aspects of the quality assurance system. The purpose is to try to avoid reducing quality risks and ensure the quality of pressure vessel products.

With the rapid development of the petrochemical industry, the pressure vessels are becoming larger and higher in strength, and higher quality requirements have been placed on pressure vessels, which promotes the continuous improvement of pressure vessel welding technology and processes.

Cracks in welded joints

The welded joint is a body with uneven structure and uneven mechanical properties. During the welding process, the temperature near the fusion line of the weld joint is between the solid phase and the liquid phase. After cooling, the structure is overheated, the grains are coarse, the chemical composition and structure are extremely uneven, the strength is increased, and the plasticity is reduced. The outer side of the fusion line is the "overheating zone", and the grains in this region are coarse. Weiss structure and sorbite often appear, so the toughness is significantly reduced.

Welding corrosion crack joints can cause cracks due to the hardenability of steel, cold cracks caused by hydrogen diffusion, reheat cracks, intergranular lines, and welding defects due to welding specifications and worker skills. Practice has proved that cracks have the most serious harm to the quality of pressure vessel products.

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