連鋳-直送圧延プロセスによる Ti 添加高強度熱延鋼板の材質(組織と材質)(<特集>連続鋳造-熱間圧延の直結化)

概要

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Continuous-cast and hot direct-rolling processes (CC-HDR) have been under operation in Japan and contributed to saving energy and time. From a metallurgical point of view, some differences of mechanical properties of low alloyed steels may take place between CC-HDR and conventional reheat-rolling process (Reheat), because of its change in dissolution and precipitation behavior of the alloying elements. Mechanical properties of Ti-added high strength hot rolled steel sheets manufactured by CC-HDR in Sakai Works, Nippon Steel Corp., have been examined in comparison with those of conventional Reheat steels. Both of the tensile and yield strength of the HDR steel sheets, having 55 and 60kgf/mm^2 tensile strengths level, were 4∿5kgf/mm^2 higher than those of Reheat steels. The amount of H_3PO_4(2+1) soluble Ti of HDR steels were larger than that of Reheat steels and the number of relatively coarse Ti-precipitates measured by TEM were few in comparison with that of Reheat steels. Therefore it is concluded that the amount of very small size Ti-precipitates in HDR steels which contribute to the strength of steel may probably be larger than that of Reheat steels and so the strength of HDR steels are higher than that of Reheat steels. This difference of precipitation behavior between these processes was explained by their different thermal histories.
社団法人日本鉄鋼協会の論文
1988-07-01