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Kodama S.,Welding and Joining Research Center | Furusako S.,Welding and Joining Research Center | Miyazaki Y.,Welding and Joining Research Center | Ishida Y.,Kimitsu R and D Laboratory | And 2 more authors.
Nippon Steel Technical Report

Recent research progresses of arc welding techniques are described, focusing on the automotive chassis members or body members. As for welded joint performance, static strength and fatigue strength are improved with increasing of steel strength less than 780 MPa tensile strength. Additionally, galvanized steel sheets contribute to corrosion resistance of weld parts. Developed welding materials have made it possible to improve welding activities such as reducing spatters, gap allowance or weldability of galvanized steel sheets. In contrast, components of the steel sheet also effects on welding phenomenon, a flat bead geometry is obtained by increasing Si content of steel sheets. Low heat input welding such as CMT (Cold metal transfer) welding has begun to use for body welding and cross tension strength of advanced high tensile strength steel are improved by CMT applied arc spot welding. Source

Ohata M.,Osaka University | Ueno S.,Osaka University | Namekata T.,Nippon Steel and Sumikin Welding Co. | Satoh S.,Nippon Welding Rod Co. | And 4 more authors.
Welding in the World

A finite element (FE) analysis of tensile test for a welded joint of austenitic stainless steel for a building structure SUS304A predicts necking in the weld metal as well as lower tensile strength than that of the base metal, even though the joints has the strength-overmatched weld metal. The FE analytical studies also suggest that such an anticipated deformation behavior comes from large difference in uniform elongation between the base metal and the weld metal. Experimental works for overmatched welded joints using SUS 304A and welding wire TS308MoJ supports the joint strength and the necking behavior demonstrated by the FE analysis. On the basis of parametric FE analyses, mechanical parameters that should be controlled to ensure the base metal necking and the tensile strength of a base metal in tensile test of the overmatched joint are proposed. © 2014 International Institute of Welding. Source

Matsui H.,Toyota Motor Corporation | Matsui H.,Auto Parts Welding Laboratory Inc. | Chiba T.,Nippon Steel and Sumikin Welding Co. | Yamazaki K.,Kobe Steel
Welding International

In the pulsed MAG welding with highly precise periodic drop transfer, welding current was analysed by fast Fourier transform (FFT). By this analysis, peculiar frequency of the molten pool was detected by resonance phenomena with the base plate vibration and it was confirmed that peculiar frequency falls according to growth of the molten pool. Furthermore, natural frequency was detected at the natural welding state that is without vibration of the base plate and confirmed by the resonance method with the base plate vibration. To amplify natural vibration of the molten pool, drop transfer pulse was modulated consisting of regular pulse peak current and higher pulse peak current. The higher pulse peak current makes a change in the arc pressure and the molten pool is pushed down in the period of higher pulse. Because short circuit is apt to occur at the time that the molten pool is at the top of the front side, so it is effective for amplifying the molten pool oscillation that higher pulse phase begins at this time instantaneously or somewhat later. According to this, higher peak was gained at peculiar frequency by FFT analysis. It means that amplifying of the molten pool oscillation was successful. Appropriate period of higher pulse for maintaining stable oscillation is from about 1/4 to 1/2 of the oscillation cycle. © 2014 © 2013 Taylor & Francis. Source

Hashiba Y.,Nippon Steel & Sumitomo Metal Corporation | Sasaki K.,Nippon Steel and Sumikin Welding Co. | Kasuya T.,Nippon Steel & Sumitomo Metal Corporation | Inoue T.,Nippon Steel & Sumitomo Metal Corporation | Funatsu Y.,Nippon Steel & Sumitomo Metal Corporation
Welding in the World

Electrogas arc welding with high efficiency (Two-electrode Vibratory Electrogas Arc Welding, 2E-VEGA®process) and flux-cored wires for the 2E-VEGA process have been developed. They can be applied to YP460 MPa class extremely thick steel plates for very large container ships. The travel speed of the developed 2E-VEGA process is about twice as high as that of the ordinary 1E-VEGA process. Weld metal obtained with the present process and the present wires satisfied the target requirements of YP (yield point or proof stress) ≥ 460 MPa, TS (tensile strength) ≥ 570 MPa, vE -20 (-20 °C Charpy absorbed energy) ≥ 53 J and Hv (hardness number) ≤ 210 Hv in Vickers scale, even when 30 kJ/mm arc energy welding for 51 mm-thick plates was conducted. Using the present process and the present wires, sufficient fracture toughness of joints welded with high arc energy can be obtained. Source

Kodama S.,Nippon Steel & Sumitomo Metal Corporation | Ishida Y.,Nippon Steel & Sumitomo Metal Corporation | Asai K.,Nippon Steel & Sumitomo Metal Corporation | Mizumoto M.,Nippon Steel and Sumikin Welding Co. | And 2 more authors.
Rivista Italiana della Saldatura

Galvanized steel sheets are widely-used in the construction and automobile industriesto provide structural members with high corrosion resistance.When galvanized sheets are welded,zinc near a weld molten pool evaporates. As a result, the corrosion resistance is deteriorated and repair coating treatment is required after welding. The use ofaustenitic stainless steel welding materials with suitable ductility and high corrosion resistance appears to be beneficial. However, the conventional welding materials have such problems that zinc liquation cracking is likely to occur in the weld metal, a lot of welding spatter is generated and solidified slag is difficult to remove from the weld bead. To solve these problems, an austenitic stainless steel flux-cored wire was developed. Susceptibility to zinc liquation cracking was improved by increasing the ferrite content in the weld metal through the adjustment ofNi and Cr contents.The problems of the removal of solidified slag and the generation of welding spatter were solved by reducing the Tio2 content in flux to a level lower than that for a commercial wire.Thus, the weld appearance was improved, making repair coating treatment after welding unnecessary. The joints welded by the newly-developed welding material exhibited suitable mechanical properties and satisfactory corrosion resistance evaluated by salt spray testing. Source

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