An experimental study was made on the spot welding of 18Cr-7Ni stainless steels containing high concentration of nitrogen up to about 0.6%, prepared by a high-pressure melting process in nitrogen atmosphere. Main results obtained were as follows.
(1) In the spot welding of high nitrogen 18Cr-7Ni stainless steels, if ordinary welding condition recommended for welding commercial austenitic stainless steels are adopted, we shall obtain usually-excellent and sound weld nuggets.
(2) The spot .weldability of, the steels scarcely depended upon nitrogen concentration. The weld defects such as weld cracking, welding distortion and large pit were not observed in any steels investigated.
(3) But, in the steel containing high concentration of nitrogen i.e., more than 0.5%, expulsion and blowhole in the weld nugget increase a little. Therefore, in case of welding high nitrogen steels, better properties of the nugget were obtained by taking electrode force comparatively high and weld time short with an increasing nitrogen content.
(4) It was confirmed that the nitrofien contained in base metals scarcely diffuses out of the nugget even in the steel containing about 0.6% nitrogen. Consequently, the spot weld shear strength rises in pro-portion to the increase in nitrogen content and any decrease of the strength does not occur on account of nitrogen diffusion.
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