Development of Sv‐18N5KhMF welding wire for welding high‐strength steel with mixed carbide‐intermetallic hardening

Abstract

To cite this article: V E Laz'ko , L L Starova & V I Lukin (2001) Development of Sv-18N5KhMF welding wire for welding high-strength steel with mixed carbide-intermetallic hardening, Welding International, 15:11, 907-911, Steels with mixed carbide-intermetallic hardening of the 9Ni-4Co system are superior to other steels with carbon hardening, in particular, Cr-Mo-Ni steels, in the parameters of fracture toughness, cold strength, stress corrosion resistance and the resistance to delayed fracture, which determine the reliability of operation of structures in the service conditions. 1 " 3 At the same time, the high nickel content of steel complicates the production of the dispersed structure of the weld metal and also increases the stability of the crystallisation texture. This result in the formation of 'woody' fracture on the fracture surface, accompanied by a decrease of impact toughness (by 30-40%) and endurance in low-cycle fatigue (by a factor 2-3). 4 The experimental results also show the formation of hot cracks in the welded joint (Fig. 1). Thus, to improve the weldability, it is necessary to improve the composition of the steel, in particular, when it is used as a filler metal.The aim of this work was to modernise Sv-18N8KhMF-VI wire (Author's certificate 859086, USSR) 5 in order to increase the hot cracking resistance in welding and prevent the formation of woody fracture on the fracture surface of the weld metal. The effect of the elements of the chemical composition was determined during consecutive variation of the content (%): 0.06-0.20 C, 2-14 Ni, 0.3-1.5 Mo, 0.25-0.57 Si, 0.78-1.08 Mn, 0.02-0.15 Ce and 0.025-0.45 Y and with the constant (mean) content of the other components.