| Title |
Microstructure and Mechanical Properties of Direct Quenched Copper-Bearing High-Strength Steels |
| Authors |
황근철(Guen Chul Hwang) ; 이성학(Sung Hak Lee) ; 유장용(Jang Yong Yoo) ; 주웅용(Wung Yong Choo) |
| Abstract |
The present study is concerned with the processing of copper-bearing high strength steels by direct quenching and tempering (DQ&T) processes. Two DQ&T steels were rolled at different finish rolling temperatures, and their microstructures and mechanical properties such as strength and impact energy were compared with those of a reheat quenching and tempering(RQ&T) steel. The microstructural analyses indicated that the as-quenched microstructure of the DQ steels consisted of refined lath martensite including a number of dislocations, which acted as preferred precipitation sites for NbC or ε-Cu particles during tempering. These fine precipitates were not coarsened much up to the tempering temperature of about 650℃ and thus played a role in improving the tempering resistance. Especially in the DQ&T steel quenched at 760℃ and tempered at 660℃, yield strength reached 1050㎫ and Charpy impact energy at -18℃ showed 140J, indicating the potent effect of the DQ&T process. These findings suggest that copper-bearing low carbon alloy steels with high strength and toughness can be made by the DQ&T process. |