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Katayama T.,Osaka University | Tashiro S.,Osaka University | Tanaka M.,Japan Research and Development Center for Metals
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society | Year: 2011

In plasma MIG welding process, because shielding gas is ionized in advance by a plasma electrode before supply, the shape of arc is easily controlled through electromagnetic force. Therefore the controllability of the arc is remarkably enhanced compared with that in a conventional MIG welding process. Because of this advantage, it can be employed for MIG welding in pure inert gas atmosphere. Although experimental results on plasma MIG welding in pure argon atmosphere were reported, further improvement of the welding process is required because it is difficult to form bead stably due to lack of the wettability. We have developed a new torch for plasma MIG welding which has shorter distance between a contact tip and the top of a nozzle than that of the conventional torch. In this paper, experimental results on welding of steel plates with V groove in pure argon atmosphere employing the new torch are discussed compared with those for the conventional torch. As a result, it was found that the bead formation was improved due to high wettability in case of the new torch, because melting volume of the base metal increased due to increase in averaged MIG current and heat flux.


Komazaki S.-I.,Muroran Institute of Technology | Komazaki S.-I.,Japan Research and Development Center for Metals | Kato T.,Muroran Institute of Technology
Materials at High Temperatures | Year: 2010

The small punch (SP) creep test using a TEM disk-type specimen (φ 3 × t0.25 mm) was applied to the fusion zone (FZ), the coarsened grain heat-affected zone (CGHAZ), the fine grain HAZ (FGHAZ), the tempered HAZ (THAZ) and the base metal (BM), respectively, which were removed from the joint of 8Cr-2W-VTa steel welded by an electron beam welding, in order to investigate the creep properties of such local regimes. Experimental results revealed that the SP creep rupture of the FGHAZ was accompanied by creep void formation even if the rupture time was relatively short and its creep rupture strength was inferior to those of the other regimes. This reduction in rupture strength seemed to be attributable to the microstructural changes during the welding thermal cycles, which were represented by the annihilation of clear lath martensitic structure and the change in precipitate distribution. © 2010 Science Reviews 2000 Ltd.


Tada M.,Jfe Holdings | Nakagawa Y.,Jfe Holdings | Kojima K.,Jfe Holdings | Nakamaru H.,Jfe Holdings | Nakamaru H.,Japan Research and Development Center for Metals
Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan | Year: 2016

When the welding body is expanded, it shrinks in the direction of can height. The change of height of can is influenced by r-value. The effect of cold rolling reduction on the r-value of niobium (Nb) and boron (B) combined added extra low-carbon steel was investigated by using commercial steels. Ferrite grain size of annealed sheet decreased with the increase of cold rolling reduction. At the same time, the intensity of {001} <110> increased and the r90°-value decreased. The behavior of the decrease of r-value was dependent on the ferrite grain size of hot-rolled sheet. The intensity of {001} <110> of annealed sheet was large for the hot-rolled sheet of grain size of 8.4 μm comparing with 10.8 μm and the r90°-value decreased.


Inomoto T.,Nippon Steel & Sumitomo Metal Corporation | Matsuo M.,Japan Research and Development Center for Metals | Yano M.,Nippon Steel & Sumitomo Metal Corporation
ISIJ International | Year: 2015

For the mass production of ultra-low-carbon steel, application of the chemical vacuum method was examined in depth. In the present study, based on the results of 600-kg-scale experiments and theoretical analysis of them, the possibility of innovative creation producing ultra-low-carbon products without using a vacuum degasser was obtained. To confirm the effect, a 60-t-scale AOD plant test was carried out. As a result, by using the chemical vacuum effect, the carbon content is reduced to 9 ppm in normal steel because of its much higher CO partial pressure than that of stainless steel. The results of the examination show that, theoretically, the reaction rate can be further enhanced. However, it is necessary to construct a dispersion condition in a large-scale metal vessel with small argon bubbles because applying the current technique of small bubble production cannot produce a sufficiently high argon injection flow rate. For the construction of an innovative secondary refining process in the future steelmaking process, the gas dispersion technique is strongly preferred. © 2015 ISIJ.


Ide N.,Kyoto Institute of Technology | Morita T.,Kyoto Institute of Technology | Maeda T.,Nippon Steel & Sumitomo Metal Corporation | Maeda T.,Japan Research and Development Center for Metals | Seto H.,Nippon Steel & Sumitomo Metal Corporation
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2014

This study was conducted to investigate the relationship of rolling reduction with the microstructure and mechanical properties of cold-rolled Ti-20V-4Al-1Sn alloy. Cold rolling was performed under the rolling reduction between 10-50%. The microstructure was compressed by cold rolling, and became finer. Plastic deformation was partially inhomogeneous in the thickness direction of the cold-rolled material. The preferred orientation of the formed crystallographic texture was {112}<110>∼ {001}<110> which is typical in metals possessing the bcc structure. The texture evolved with increasing rolling reduction. Hardness and static strength were increased by increase in rolling reduction because of work hardening and microstructural refinement. Anisotropy was induced in yield strength and work hardening exponent by cold rolling: however, it was not marked in hardness and tensile strength. © 2014 The Japan Institute of Metals and Materials.

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