ボロン含有制御圧延鋼の強度・靱性におよぼす炭素量の影響

概要

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An influence of carbon content on the strength and toughness of Nb-Ti-B steel, which contains 1.5%Mn or 1.7%Mn finish-rolled at 720℃ after heating at 1050℃ then air-cooled or acceleratedly-cooled, was studied. The strength of air-cooled plates after the controlled-rolling increases as carbon content increases at C=0.001∿0.015%, because ferrite becomes fine and TiC, Nb (C, N) precipitate, then decreases at C=0.015∿0.048%, because microstructure changes from fine-ferrite to coarse-ferrite+pearlite, then increases again at C=0.048∿0.170%, because the amount of pearlite increases. The change of microstructure and strength decreasing at C=0.015∿0.048% results from a decrease of the amount of free boron and free niobium. The toughness decreases at C=0.015∿0.048%, because the number of separation decreases by a decrease of austenite/ferrite transformation temperature. The strength and toughness increase, because ferrite becomes fine and pearlite changes to bainite by an increase of manganese. The strength of acceleratedly-cooled plates after the controlled-rolling increases monotonously with an increase of carbon. Because the microstructure becomes fine, and the secondary phase changes from pearlite to martensite by the increase of cooling rate.
社団法人日本鉄鋼協会の論文
1989-06-01