Automatic narrow-gap submerged arc welding process for all-welded fixed ball valve with medium and large calibers

Abstract

The invention discloses an automatic narrow-gap submerged arc welding process for all-welded fixed ball valves with medium and large calibers. The process comprises the following steps of: performing general assembly of products; 2) performing pre-welding preparation; 3) selecting materials; 4) selecting a weld joint, wherein the weld joint used during welding is a 'U'-shaped groove; 5) selecting process parameters; and 6) welding, namely welding the integral annular weld joint continuously at one time by a left welding method. By the process, a production process is reasonable, welding is performed after the general assembly and performance tests of the products, the process parameters which can meet the key requirements of weld penetration, low linear energy, low interlayer temperature, ultra-low welding deformation and high accuracy are selected, the materials and a welding skill are selected, and the welding groove is improved, namely a V-shaped groove and the like are changed into the 'U'-shaped groove; and by the process, slag and convenient to discharge, the key requirements of heat crack prevention, high toughness, small welding deformation and high welding accuracy are met, and the safety of a valve seat seal ring in a valve is protected effectively in the welding process.

Description

technical field [0001] The invention relates to an automatic submerged arc welding technology with high precision, narrow gap and low line energy, especially for the key process of fully welded fixed ball valves with medium and large diameters. Background technique [0002] Traditional submerged arc welding is a welding method that uses flux for protection; it is a welding method with high deposition rate, high line energy and high production efficiency. The traditional narrow-gap submerged arc welding groove is basically a straight or V-shaped groove, with an inclination angle of about 1 degree on both sides. [0003] Although the existing technology is mature, it has high deposition rate, high production efficiency, good penetration, and high degree of automation. When the thickness of the welding base metal reaches hundreds of millimeters, one-time penetration forming can be realized. It can be seen that its production efficiency is high, but its line energy is also extr...

AI Technical Summary

Problems solved by technology

When the thickness of the welding base metal reaches hundreds of millimeters, one-time penetration forming can be realized. It can be seen that its production efficiency is high, but its line energy is also extremely high. Without bold innovation, it must not be used for medium and large diameter full welding fixation. Ball valve welding

Because the welding process parameters of traditional submerged arc welding are high current, high voltage, high welding speed, high line energy, high interlayer temperature of the weld, concentrated weld stress, large residual stress in the heat-affected zone, and weldment The thermal deformation is large, resulting in the following consequences: ①The most serious is that due to the high temperature of the weld or heat-affected zone (≥500°C, far higher than the allowable temperature of the sealing ring RTFE-165°C), the valve is bound to be burned The sealing ring makes the valve product completely scrapped

② Stress concentration and large residual stress will affect the strength of the shell, which may cause stress cracks and shorten the service life of the valve, or even make the valve scrapped

③The welding groove is not conducive to slag and steam exhaust, and the weld is prone to slag holes and steam holes, which will affect the strength of the weld

④ Welding is a process of metal smelting, and the welded parts deform greatly. Even if the sealing ring is not burned out, due to the large deformation, the valve sealing pair will produce a gap and cannot be sealed

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