鋼材に及ぼす溶接と冷間加工の重疊効果

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In the recent construction of steel ships, riveting has been largely replaced by welding. In welding ships, steels are frequently required to be welded in prestrained condition after cold working. One of the most important examples may be the joining of a gusset plate to the margin plate. In such a case it is usualy recommended by Ship Classification Societies that the prostrained area should not be welded in order to avoid deleterious effect of cold working upon welding. It is generaly cosidered that welding of a cold worked steel reduces impact strength and corrosion resistance of the steel.To investigate the problem, various kinds of tests were performed, that is, tensile, bending, fatigue, and corrosion tests as well as notch brittleness test.A rimmed steel, 13 mm thick and with the manganese-to-carbon ratio >2.5,was employed. After a stress relief heat treatment at 700℃ for one hour, specimens were prestrained in a 300 tons tensile testing machine to various amounts of cold working, 0,2.5,5,10%. Specimens were then bead welded with the submerged-arc welding process, and the following results were obtained.No effect of cold working upon welding was observed in the tensile and the bending tests. In the V-Charpy notch brittleness test, transition temperature seems to be raised with increasing prestrains.The fatigue test with repeated bending specimens in Schenk's fatigue testing machines, showed that the fatigue strength was increased with prestraining and welding.In the corrosion test, the steel was made less resistance to corrosion when it had mill scale unremoved, coldworked, while the effect of prestraining-and-welding seemed to be favourable to increase the corrosion resistance.Summarizing the test results, it may be concluded, that the effect of welding on a prestrained steel is not so deleterious as to be observable in tensile, bending, or fatigue tests, but rather effective to increase corrosion resistance. Therefore the said recommendation does not seem reasonable, and the gussets may be welded to the margin plate on cold worked corners.
社団法人日本船舶海洋工学会の論文

鋼材に及ぼす溶接と冷間加工の重疊効果

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