Welding and Melting of SUS316LN Austenitic Stainless Steel under High Pressure Nitrogen Atmosphere(Materials, Metallurgy & Weldability)

概要

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Austenitic stainless steels of SUS316LN were melted by GTA and GMA in high pressure up to 6.1MPa nitrogen atmospheric arc. Melting condition, nitrogen absorption and microstructure of solidified metals have been investigated. In the case of GTA melting, it was impossible to starting of arc over 2.1MPa of nitrogen atmosphere, because the tungsten electrode was remarkable consumed in high pressure nitrogen. GMA melting is possible to perform up to 6.1MPa of nitrogen atmosphere at constant melting current of 200A and the arc length of 7mm. Arc voltage increased with increasing in pressure of nitrogen atmosphere. The solidified metals have no defect such as blow hole and crack. Nitrogen content of GMA solidified metal increased from 0.2 to 0.65 mass% with increasing in pressure from 0.1 to 6.1Mpa. Bending test indicated that there was no micro crack in solidified metal. Hardness (H_V) of solidified metal also increased from 200H_V to 350H_V with increasing the nitrogen content. The lattice parameters of solidified metal which were measured by means of the X-ray diffraction was increased from 3.60A to 3.62A with increasing in nitrogen content. It was considered that the absorbed nitrogen which existed as interstitial solid solution deform the lattice, which resulted to increase in hardness.
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