When welding thin wall stainless steel, the technical level requirements are very high, because in the welding of this kind of material, will face many problems, such as construction site problems, heat treatment problems, thermal expansion and cold contraction problems, the following to tell the solution to these problems.
First of all, the construction capacity, welding is a relatively strong professional activities, generally after welding can not be demolished, in the actual construction site for a long time, because it is necessary to change, resulting in very inconvenient. Because of the need for specialized equipment and argon arc welding of thin wall stainless steel tube, the thickness is very thin, there must be a high level of welders operation, but in the actual construction site personnel mobility, if no welding operation certificate of personnel of electric welding, argon flow, the adjustment will not be reasonable, and the influence of construction site space and human factors, often produce weld and weld welding pipe even wear phenomenon, although Water Leakage problem does not appear in the pressure test, but there is a great risk in construction, after a certain period of time, because of the effect of thermal expansion and contraction and other factors, will lead to future Water Leakage.
The second is the problem of heat treatment, as for thin wall stainless steel pipe and socket fittings to place for welding solution treatment at the factory, but in the construction site, restricted construction site welding pipes and pipe fittings, is unlikely to do solid solution treatment of austenitic stainless steel, due to slow after 450~800 degrees. The carbon precipitation generated by the precipitation of chromium carbide in grain boundary material, chromium content in the vicinity and therefore lower generation lack of chromium, lead to corrosion resistance drop. Long time use is usually late, will produce in the weld of stainless steel materials most worried about intergranular corrosion, if the high carbon content of stainless steel materials, in the weld will lead to failure of stainless steel pipe in advance, and this is certainly flawed will appear in the use of a certain period of time after the test is not on the spot.
The third point is the expansion and contraction of the problem, the stainless steel plate material with the change of temperature and the formation of destructive force is very strong, so the expansion and contraction of stainless steel material is critical. The influence of thermal expansion is not simply in the products produced by pulling force to determine the value, such as the original thread connection with much more easily affected by thermal expansion and contraction, because the stainless steel pipes and pipe fittings have no way to extend or shorten the occurrence of fatigue and often burst, if the temperature the greater the damage the greater the.
So the connection of thin wall stainless steel pipes and pipe fittings if buried installation, must fully consider the material thermal properties, and by argon arc welding of the socket type pipe, is difficult to achieve the parent pipe and pipe fittings and welding, to eliminate stress, especially in the north of the buried pipeline is mostly in the summer season, resulting in water and when the maximum buried negative temperature difference of 35 degrees, especially when the temperature drops sharply, the pipeline expansion joint is not installed under the condition of axial tension will cause the pipe and pipe welding crack, once the treatment is not good, there are pores, weld damage is thermal expansion and contraction of the defect, with the passage of time will be completely unmasked, so we must pay attention to the use of the installation process is reasonable in the case of buried.
Source: China Stainless Steel Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)