Korean Journal of Materials Research (한국재료학회지)

Materials Research Society of Korea (한국재료학회)
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Prediction of Jominy Hardness Curves Using Multiple Regression Analysis, and Effect of Alloying Elements on the Hardenability

다중 회귀 분석을 이용한 보론강의 조미니 경도 곡선 예측 및 합금 원소가 경화능에 미치는 영향

  • Wi, Dong-Yeol (Department of Materials Science and Engineering, Inha University) ;
  • Kim, Kyu-Sik (Department of Materials Science and Engineering, Inha University) ;
  • Jung, Byoung-In (POSCO) ;
  • Lee, Kee-Ahn (Department of Materials Science and Engineering, Inha University)
  • 위동열 (인하대학교 신소재공학과) ;
  • 김규식 (인하대학교 신소재공학과) ;
  • 정병인 (포스코 기술연구소) ;
  • 이기안 (인하대학교 신소재공학과)
  • Received : 2019.09.27
  • Accepted : 2019.10.27
  • Published : 2019.12.27
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Abstract

The prediction of Jominy hardness curves and the effect of alloying elements on the hardenability of boron steels (19 different steels) are investigated using multiple regression analysis. To evaluate the hardenability of boron steels, Jominy end quenching tests are performed. Regardless of the alloy type, lath martensite structure is observed at the quenching end, and ferrite and pearlite structures are detected in the core. Some bainite microstructure also appears in areas where hardness is sharply reduced. Through multiple regression analysis method, the average multiplying factor (regression coefficient) for each alloying element is derived. As a result, B is found to be 6308.6, C is 71.5, Si is 59.4, Mn is 25.5, Ti is 13.8, and Cr is 24.5. The valid concentration ranges of the main alloying elements are 19 ppm < B < 28 ppm, 0.17 < C < 0.27 wt%, 0.19 < Si < 0.30 wt%, 0.75 < Mn < 1.15 wt%, 0.15 < Cr < 0.82 wt%, and 3 < N < 7 ppm. It is possible to predict changes of hardenability and hardness curves based on the above method. In the validation results of the multiple regression analysis, it is confirmed that the measured hardness values are within the error range of the predicted curves, regardless of alloy type.

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