Welding Process Of Welded Stainless Steel Pipe

Update:28 Dec
Abstract:When buckling, under the action of external moment M, the outer arm wall of the neutral layer is thinned by tensile stress, and the inner side is subj

When buckling, under the action of external moment M, the outer arm wall of the neutral layer is thinned by tensile stress, and the inner side is subjected to compressive stress. The effect is thickened, and the combined forces N1 and N2 make the cross-section of the stainless steel pipe change. Based on this factor, the main reason for the quality decline of stainless steel pipes is RX and SX. Therefore, in GBJ235-82, the RX value and the thinning amount of the outside under various pressure levels are clearly stipulated, the purpose is to curb The values of RX and SX therefore determine the quality.

The principle of welded stainless steel pipes is gas shielded arc welding, referred to as gas shielded welding or gas electric welding, which uses the arc as the heat source and the gas as the protective medium for melting welding; during the welding process, the shielding gas forms a gas protective layer around the arc, and the arc and molten pool Separated from the air to prevent the influence of harmful gases and ensure the stable combustion of the arc; due to the different types of stainless steel, it needs to be determined according to the actual situation.

Commonly used stainless steel fusion welding methods include manual arc welding, submerged arc automatic welding, tungsten inert gas shielded welding, molten gas shielded welding, ion arc welding, etc. The welding spot of seamless laser welding is small, the welding seam is narrow, neat and beautiful, and no post-welding treatment is required or only a simple treatment process is required. The weld structure is uniform, with few pores and defects, which can reduce and optimize the impurities of the base material, and the mechanical strength of the weld is often higher than that of the base material. The mechanical properties, corrosion resistance and electromagnetic properties of laser welding are superior to conventional welding methods.

In order to reduce the heat loss of the stainless steel pipe and prevent thermal deformation, the buried depth of the pipe should be greater than 1.2 meters. (calculated from the top of the pipe). The burial in alpine areas should be properly deepened. At the same time, all pipelines should avoid laying below the groundwater table. For areas with high groundwater levels or where it is difficult to dig deep for other reasons, thermal insulation measures should be taken as much as possible before the pipe is buried.

If the conditions are not met, shallow excavation and deep burial can also be used, that is, pipe trenches are excavated 20 cm above the groundwater level, and then covered with soil to form an earth embankment. For stainless steel pipes, in order to improve the anti-corrosion performance and weldability, appropriate amount of stable elements Ti, Nb, Mo, etc. are added appropriately, and the weldability is better than that of stainless steel pipes. When using the same type of chromium stainless steel electrode, it should be preheated above 200 ℃ and tempered at about 800 ℃ after welding. If the weldments cannot be heat treated, chrome-nickel stainless steel electrodes should be used.

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