ARC WELDING OF AUSTENITIC STEELS
FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO
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Conditions are given for welding heat-resistant Ni-base alloys by 1 Ar-shielded arc welding, 2 welding in CO2, 3 submerged-arc welding, and 4 manual welding. Precipitation-hardened stainless steels in the form of thin sheets are welded primarily by the Ar-shielded arc method with a W or fusing electrode. For ADS 17-7PH steel containing more than 1 Al, a film of aluminum oxide forms on the joint necessitating the use of alternating current or replacing the Ar with He when welding with direct current. Steel 17-7PH can be welded without cracks. The presence of aluminum nitride causes porosity along the fusion line. In order to prevent this porosity, small amounts of Ti and Zr are introduced into the steel these elements form nitrides more stable than the aluminum nitride. Preliminary hardening may be necessary before double heat-treatment in the case of welding thick 17-7PH steel in several passes when great structural alterations in the near-joint zone.