ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Mechanical and Corrosion Properties of High Strength 18% Cr Austenitic Stainless Steel Weldment for Boiler
Kazuhiro OgawaYoshiatsu SawaragiNobuo OtsukaHiroyuki HirataAtsushi NatoriShigeru Matsumoto
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1995 Volume 35 Issue 10 Pages 1258-1264

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Abstract

The properties of weld metal of 18Cr heat resistant austenitic steel containing high copper, niobium and nitrogen were investigated to obtain the matching filler metal for an austenitic stainless steel of 18Cr-9Ni-3Cu-Nb-N steel. This 18Cu-9Ni-3Cu-Nb-N steel tube has been registered as KA-SUS304HJ1TB in the Japanese official standard for fired power plant materials. This steel tube has a high temperature strength 1.4 times as high as the conventional 18Cr steel ASME TP347H. Welding material applicable to this steel is necessary in the fabrication. However, the weld metal consisting of the same chemistries as the base metal had a lower strength than that of the base metal. In this work, the effect of chemistries of molybdenum and nitrogen on the strength of weld metal was investigated. The addition of molybdenum up to 1 mass% was effective for improving the strength without a deterioration of the corrosion resistance. The nitrogen was also effective for improving the strength, but the nitrogen can be decreased by vaporizing during tungsten inert gas arc welding. For improving the solubility of nitrogen in the molten pool, the addition of manganese was effective. From these findings, the chemistry of welding material was determined as 18Cr-16Ni-3Cu-1Mo-3Mn-0.6Nb-0.2N and the tube weldment with that welding material was evaluated in terms of mechanical properties including creep rupture property. It was confirmed that the weldment had comparable properties to the base metal.

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