Korean Journal of Materials Research (한국재료학회지)

Materials Research Society of Korea (한국재료학회)
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Effects of Tempering Treatment on Microstructure and Mechanical Properties of Cu-Bearing High-Strength Steels

템퍼링에 따른 Cu 첨가 고강도강의 미세조직과 기계적 특성

  • Lee, Sang-In (Department of Materials Science and Engineering, Seoul National University of Science and Technology) ;
  • Hwang, Byoungchul (Department of Materials Science and Engineering, Seoul National University of Science and Technology)
  • 이상인 (서울과학기술대학교 신소재공학과) ;
  • 황병철 (서울과학기술대학교 신소재공학과)
  • Received : 2014.08.27
  • Accepted : 2014.09.22
  • Published : 2014.10.27
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Abstract

The present study deals with the effects of tempering treatment on the microstructure and mechanical properties of Cu-bearing high-strength steels. Three kinds of steel specimens with different levels of Cu content were fabricated by controlled rolling and accelerated cooling, ; some of these steel specimen were tempered at temperatures ranging from $350^{\circ}C$ to $650^{\circ}C$ for 30 min. Hardness, tensile, and Charpy impact tests were conducted in order to investigate the relationship of microstructure and mechanical properties. The hardness of the Cu-added specimens is much higher than that of Cu-free specimen, presumably due to the enhanced solid solution hardening and precipitation hardening, result from the formation of very-fine Cu precipitates. Tensile test results indicated that the yield strength increased and then slightly decreased, while the tensile strength gradually decreased with increasing tempering temperature. On the other hand, the energy absorbed at room and lower temperatures remarkably increased after tempering at $350^{\circ}C$; and after this, the energy absorbed then did not change much. Suitable tempering treatment remarkably improved both the strength and the impact toughness. In the 1.5 Cu steel specimen tempered at $550^{\circ}C$, the yield strength reached 1.2 GPa and the absorbed energy at $-20^{\circ}C$ showed a level above 200 J, which was the best combination of high strength and good toughness.

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References

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