The welding types are mainly divided into: 1, welding rod arc welding; 2, submerged arc welding (automatic welding); 3, carbon dioxide gas shielded welding (automatic or semi-automatic welding); 4, MIG / MAG welding (melting inert gas shielded welding; 5 TIG welding (tungsten inert gas shielded welding); 6, plasma arc welding six kinds of welding methods, the principle and application of each method are different, because it is not the focus of this article, so everyone can easily know, the following key points Welding ball valve welding technology processing:
Welding of welded ball valves is actually different from ordinary welding technology because the non-metallic sealing material rubber and PTFE plastic in the valve cavity cannot be heat treated after welding. The thick-walled multi-layer welding process of the welded ball valve is a repeated heating and cooling process of the metal material. Usually, the welded joints are designed to be narrow-gauge thick-wall submerged arc welding, and the other uses a fully welded valve body. It is an oversized tubular joint with a thick thickness. Therefore, the stress concentration in the root gap of the valve body welded joint, the residual stress, and the inferiority of the structure become the weak link in the valve body structure. The current two treatment methods are as follows: 1. It is treated by heat treatment technology; It is the joint treatment; these two treatment methods will produce stress concentration several times the normal working stress, which is also difficult for manufacturers engineers to deal with.
It can be seen that how to solve the stress concentration of the root gap of the welded ball valve body welded joint, residual stress, and tissue inferiority become the big problem of valve welding. Quanzhou brand all-welded ball valve manufacturer here gives everyone the technical points of valve body welding technology. As summarized below, I hope to help those who want to know the ball valve welding technology!
The welding process of the valve body is now described as follows.
1, the technical requirements of the valve body
(1) After the seam welding, the valve body has no deformation, including the upper and lower shaft flanges (45 steel).
(2) The heating area of ​​the valve body should not be too wide and the temperature should not be too high, otherwise the sealing device inside the valve body will be destroyed.
(3) No welds can occur.
(4) Ensure that the pressure is above 10 MPa.
2, weld structure
According to the above technical requirements, it is determined that the weld is not welded through the weld. Therefore, the butt joint form of the weld is required to ensure both assembly and penetration. After the test, the weld form was determined after the Zui.
3, the material of the valve body
Because the valve body is ZG15II, the chemical composition of the valve body is tested before processing, and the test results are consistent with the test results at the time of casting, which meets the design requirements.
4, assembly
The hydraulic tire is used to modify the position of the reversing tire, and the two halves are fastened with bolts to adjust the sealing test, and the design between the outer part of the sphere and the valve body is achieved.
5, welding process
Taking into account the technical requirements of the valve body, Zui finally chose MAG's CO2 welder.
The welding material is ER50-6 (Ø1.0) welding wire.
According to the principle of equal strength of the welding material, the selected ER50-6 (Ø1.0) welding wire is satisfied with the requirements of ZG15II.
The shielding gas is a mixture of 82% Ar + 18% CO 2 .
5.1 tack welding
Due to the severe hardening tendency of cast steel and 45 steel, it needs to be preheated before tack welding. The oxygen-acetylene flame is evenly heated to 75~100 °C in the range of 2 times the thickness of the weld on both sides of the weld. (biased to the 45 steel side), measured by the far infrared ray thermometer, without affecting the sealing device.
The scale and rust in the range of 20 mm on both sides of the weld are polished to a metallic luster before welding.
Positioning point 6 is made 50 mm from the edge of both sides of the weld, and the distance between the two points is measured with a caliper to measure the amount of contraction.
5.2 back cover welding
Due to the large rigidity and poor plasticity of ZG15II materials, small welding parameters, ie small welding heat input, should be adopted in the selection of welding specifications. Under the premise of ensuring the quality of the weld, the welding speed is increased as much as possible, the fusion ratio is reduced, and the multi-segment multi-segment 6-segment symmetrical welding method is adopted in the deformation; pay attention to measuring the positioning point with a caliper for each welding layer, and performing the shrinkage amount Control until welding is complete. In addition to the one after the * road and the Zui, the other methods are hammered to eliminate stress.
6, one step after zui
After the welding is completed, there is no leakage through the pressure test (airtight) weld. After the sealing surface meets the technical requirements, after X-ray inspection, the weld itself has no welding defects such as pores, slag inclusions, unfused, cracks, etc. Claim.
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