成形性のすぐれたニオブ添加フェライトベイナイト組織高強度熱延鋼板(成形性)(<特集>高強度薄鋼板)

概要

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Dual phase steels are known not to have superior characteristics in such properties as hole expanding property, Charpy impact property and especially in flash butt welding property which has a great influence on wheel rim fabrication. Through the investigation of the quality and volume fraction of second phase and alloying elemets, it has been clarified that Nb-added steels composed of ferrite and 10 to 20% bainite eliminate these problems in dual phase steels and exhibit excellent characteristics. In this paper, the effects of the quality of second phase such as martensite, bainite, and pearlite which are produced by changing the coiling temperature from room temperature to 650℃ and the volume fraction of bainite on the mechanical properties and so on are investigated. As far as flash butt welding property is concerned, Nb-added steel composed of ferrite plus bainite dose not show a remarkable softening and localized necking in the heat affected zone which usually occur in dual phase steel because of the tempering of martensite. The superiority of the hole expanding property of Nb added ferrite plus bainite steel is due to the superior ductility of bainite compared to that of martensite or pearlite.
社団法人日本鉄鋼協会の論文
1982-07-01