Abstract
The effect of Mo additions on the development of bainitic ferrite in hot rolled low carbon (0·05 wt-%C) Nb containing steel strips has been studied. The steel strips were fabricated by a combined process of controlled rolling and accelerated cooling. Microstructural characterisation and mechanical testing for the corresponding strips were investigated. The results indicated that a small amount of Mo addition (0·1–0·3 wt-%) causes the production of a high volume fraction of bainite, which undergoes significant secondary hardening after tempering treatment at 600°C for 1 h. It is noticeable that the secondary hardening effect provides an additional way to significantly increase the strength of low carbon Nb–Mo containing bainitic steels.
Highlights
The structure of steel can be influenced by processing and alloying in many different ways
The conventional microstructure of Nb containing high strength low alloy steels is a mixture of allotriomorphic ferrite and pearlite
Through the suitable addition of microalloying elements and an accelerated cooling process, it is possible to produce a high quantity of bainitic structures in low carbon steels
Summary
The structure of steel can be influenced by processing and alloying in many different ways. The conventional microstructure of Nb containing high strength low alloy steels is a mixture of allotriomorphic ferrite and pearlite. Through the suitable addition of microalloying elements and an accelerated cooling process, it is possible to produce a high quantity of bainitic structures in low carbon steels. The development of low carbon bainitic steels originates from the idea that an extremely low carbon concentration can reduce or eliminate the interplate cementite in the bainitic ferrite matrix, thereby further improving the steel’s toughness.[1] With higher amounts of bainite, higher strengths can be achieved due to the fine size of bainitic ferrite subunit platelets and their high dislocation density. A low carbon bainitic structure offers an excellent combination of toughness, strength and weldability
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