りん添加極低炭素高強度冷延鋼板の耐二次加工脆性におよぼす Nb, Ti 複合添加の効果

概要

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The present work deals with the resistance to deep drawing-induced brittleness. The materials used in this study are 40∿45kgf/mm^2 grade extra-low-carbon high strength steel sheets containing P and Si as strengthening elements. Though the resistance to the brittleness is improved by B addition in any steel, it is more remarkable in Nb and Ti containing steel than in Nb or Ti containing one. The difference of the effects of B between Nb and Ti containing steel and Nb containing one is attributable to the difference of existing state of B. In Nb and Ti containing steel, B exists as solute atom because N is precipitated as TiN, thus acting to inhibit the segregation of P to grain boundaries. Solute B also enhances the grain boundary strength by itself. On the other hand, solute B content is quite small because a considerable portion of B precipitates as BN in Nb containing steel. The reason why Nb and Ti containing steel is superior to Ti containing steel in resistance to the brittleness is that a small amount of solute C coexists with B only in the former. Solute C also inhibits the segregation of P to grain boundaries and enhances the grain boundary strength.
社団法人日本鉄鋼協会の論文
1987-06-01