Transactions of the Korean Society of Mechanical Engineers A (대한기계학회논문집A)

The Korean Society of Mechanical Engineers (대한기계학회)
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Optimization of Resistance Spot Weld Condition for Single Lap Joint of Hot Stamped 22MnB5 by Taking Heating Temperature and Heating Time into Consideration

핫스템핑 공정에서 가열온도 및 유지시간을 고려한 22MnB5의 단일겹치기 저항 점용접 조건 최적화

  • Choi, Hong-Seok (Division of Precision and Manufacturing Systems, Pusan Nat'l Univ.) ;
  • Kim, Byung-Min (School of Mechanical Engineering, Pusan Nat'l Univ.) ;
  • Park, Geun-Hwan (Division of Precision and Manufacturing Systems, Pusan Nat'l Univ.) ;
  • Lim, Woo-Seung (Division of Precision and Manufacturing Systems, Pusan Nat'l Univ.) ;
  • Lee, Sun-Bong (School of Mechanical and Automotive Engineering, Keimyung Univ.)
  • 최홍석 (부산대학교 정밀가공시스템) ;
  • 김병민 (부산대학교 기계공학부) ;
  • 박근환 (부산대학교 정밀가공시스템) ;
  • 임우승 (부산대학교 정밀가공시스템) ;
  • 이선봉 (계명대학교 기계자동차공학부)
  • Received : 2010.03.12
  • Accepted : 2010.07.23
  • Published : 2010.10.01
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Abstract

In this study, optimization of the process parameters of the resistance spot welding of a sheet of aluminum-coated boron alloyed steel, 22MnB5, used in hot stamping has been performed by a Taguchi method to increase the strength of the weld joint. The process parameters selected were current, electrode force, and weld time. The heating temperature and heating time of 22MnB5 are considered to be noise factors. It was known that the variation in the thickness of the intermetallic compound layer between the aluminum-coated layer and the substrate, which influences on the formation of nugget, was generated due to the difference of diffusion reaction according to heating conditions. From the results of spot weld experiment, the optimum weld condition was determined to be when the current, electrode force, and weld time were 8kA, 4kN, and 18 cycles, respectively. The result of a test performed to verify the optimized weld condition showed that the tensile strength of the weld joint was over 32kN, which is considerably higher than the required strength, i.e., 23kN.

본 연구에서는 핫스템핑 소재로 사용되는 보론합금강판 22MnB5의 단일 겹치기 점용접에서 용접부의 강도 향상을 위한 최적화를 수행하였다. 최적화 과정은 다구찌 실험계획법에 의해 행해졌으며 공정변수는 전류, 가압력 및 통전시간으로 선정하였고, 잡음인자로서 핫스템핑 시 소재의 가열온도와 유지시간을 고려하였다. 가열조건에 따라 22MnB5 표면의 알루미늄 도금층과 모재 간의 확산반응에 의해 화합물층 두께에 산포가 발생하였으며 이러한 산포는 너겟의 형성에 영향을 미치는 것을 알 수 있었다. 한편 용접부의 인장전단강도를 목적함수로 하였을 때, 이러한 가열조건에 강건한 최적의 용접 조건은 전류 8kA, 가압력 4kN, 통전시간 18cycle로 선정되었다. 최적 조건의 검증 결과 용접부의 인장전단강도 는 32kN으로서 요구되는 규격인 23kN보다 크게 증가되었다.

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