Mass Transfer of Nickel-Base Alloy Covered Electrode During Shielded Metal Arc Welding
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well known that the INCONEL* 690 superalloy, *INCONEL is a trademark of Special Metals Corporation, New Hartford, NY.
a Ni-Cr-Fe ternary alloy, can maintain considerable strength and perdurability in the extremely harsh environment with high temperature, high pressure, high irradiation, and corrosive media. Because it is very resistant to attack from oxidizing chemicals or hot gases, this alloy has been widely used in some key industrial fields, e.g., chemical industry, nuclear power industry, and other energy industry.[1] For these applications, a welding process is frequently performed that often needs welding materials as filler metals for either nickel-base alloy welding or dissimilar metal welding such as nickel-base alloy joined to stainless steel, nickelbase alloy joined to or clad on high-strength low-alloy steel, etc.[2,3] Generally, the welding materials, especially the covered electrodes, are extremely important for welding process and weld quality. The stable arc welding depends on the flux coating covered on the core wire, which disintegrates during arc welding, giving off vapors that serve as a shielding gas and providing a layer of
RENYAO QIN, Postdoctoral Student, and GUO HE, Professor, are with the State Key Lab of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, P.R. China. Contact e-mail: [email protected] Manuscript submitted June 6, 2012. Article published online November 13, 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A
slag, both of which protect the weld area from atmospheric contamination.[4] The slag, the residue from the flux coating, must be chipped away after welding. Apart from these two profitable effects, the coating can also bring metals and some impurities into the weld. The former usually is purposive for regulating the chemical composition of the weld; the latter is inevitable and generally deleterious. The mass transfer from the coating and the core wire to the deposited metal during shielded metal arc welding (SMAW) is a result of metallurgical processing.[5] The metals in the covered electrode (in both the core wire and coating) partially transfer into the deposited metal and partially form oxides entering slag. Some metals are apt to burn off during arc welding. The electrode core itself acts as a filler material, which means that a separate filler material is not required. Though one can outline some chemical reactions in a specific welding process and estimate the possible products or elements entering into the deposited metal, it is difficult to exactly model and calculate the mass transfer during SMAW. However, the percentages of the metal or nonmetal mass transfer are very helpful for the welding material designers and the welding technicians when they develop a new covered electrode or adjust the welding parameters. In this study, we experimentally measured the main elements’ mass transfer during SMAW of a nickel-base alloy covered electrode that was developed especially for the welding of the INCONEL 690 superall
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