Effect of chemical compositions on weldability of stainless steel tubes for high-purity gas supply system

摘要

The effect of chemical compositions on seldability of type 316L stainless steel tubes, which have been applied extensively for high- purity gas supply system in semiconductor manufacturing process, was investigated. The study was done on three kinds of tubes, conventional 316L, purified and the purest 316L, which include the different contents of Mn, Si and impurities such as Al, O. The circular butt welding was conducted on tubes using automatic gas tungsten arrc welding process. Then the properties of weldment, mainly the surface characteristics of inner bead were examined. The results showed that the range of proper welding condition became wider in order of conventional 316L< purified 316L< the purest 316L. The roughness of inner bead surface became larger in order of the purest 316L< purified 316L< conventional 316L. Then, by increase of MN and Si contents, the percentage of Cr included in the oxide film on inner bead surface was decreased and replaced by Mn. Additionally, there was a tendency to form a slag extensively on the weld bead surface in the material with high Mn, Si and Al. These results suggested that the tube including lower content of Mn, Si and impurities could be welded more easily. Further, the properties of welded joints such as the corrosion resistance would be superior in order of conventional 316L< purified 316L< the purest 316L since the cause to deteriorate a corrosion resistance such as the roughness of inner brad surface, the deterioration of oxide film and the slag formation was diminished. Therefore, the contents of Mn, Si and impurities such as Al, O should be reduced in the stainless stell tubes for high- purity gas supply system in semiconductor manufacturing process.