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Effect of Coating Thickness on Microstructures and Tensile Properties in Yb:YAG Disk Laser Welds of Al-Si Coated Boron Steel

Al-Si 용융 도금된 보론강의 Yb:YAG 디스크 레이저 용접부의 미세조직과 인장성질에 미치는 도금두께의 영향

  • Cao, Wei-Ye (Dept. of Material Science and Engineering, Pusan National University) ;
  • Kong, Jong-Pan (Dept. of Material Science and Engineering, Pusan National University) ;
  • Ahn, Yong-Nam (Advanced Welding & Joining Department, Korea Institute of Industrial Technology) ;
  • Kim, Cheol-Hee (Advanced Welding & Joining Department, Korea Institute of Industrial Technology) ;
  • Kang, Chung-Yun (Dept. of Material Science and Engineering, Pusan National University)
  • Received : 2013.05.18
  • Accepted : 2013.06.27
  • Published : 2013.06.30

Abstract

In this study, the effect of coating thickness($20{\mu}m$ and $30{\mu}m$) on microstructure and tensile properties in Yb:YAG disk laser welds of Al-Si-coated boron steel (1.2mmt) was investigated. In the case of as welds, the quantity of ferrite was found to be higher in base metal than that in HAZ (Heat Affected Zone) and fusion zone, indicating, fracture occurrs in base metal, and the fracture position is unrelated to the coating thickness. Furthermore, yield strength, tensile strength of base metal and welded specimens showed similar behavior whereas elongation was decreased. On the other hand, base metal and HAZ showed existence of martensite after heat treatment, the fusion zone indicated the presence of full ferrite or austenite and ferrite during heat treatment ($900^{\circ}C$, 5min), After water cooling, austenite was transformed to martensite, and the quantity of ferrite in fusion zone was higher as compared with in base metal, resulting in sharply decrease of yield strength, tensile strength and elongation, which leads to fracture occured at fusion zone. In particular, results showed that because the concentration of Al was higher in 30um coating layer specimen than that of 20um coating specimen, after heat treatment, producing a higher quantity of ferrite was higher after heat treatment in the fusion zone; howevers, it leads to a lower tensile property.

Keywords

Acknowledgement

Supported by : 한국연구재단

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