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다층용접한 저합금 용접금속의 강도와 인성에 미치는 입열량 및 예열/패스간 온도의 영향
방국수(Kook-soo Bang),정호신(Ho-shin Jung),박찬(Chan Park) 한국해양공학회 2015 韓國海洋工學會誌 Vol.29 No.6
The effects of the heat input and preheat/interpass temperatures on the tensile strength and impact toughness of multipass welded weld metal were investigated and interpreted in terms of the recovery of the alloying elements and microstructure. Increases in both the heat input and preheat/interpass temperatures decreased the tensile strength of the weld metal. A lower recovery of alloying elements, especially Mn and Si, and smaller area fraction of acicular ferrite in the weld metal were observed in higher heat input welding, resulting in a lower tensile strength. In contrast, only a microstructure difference was observed at a higher preheat/interpass temperature. The impact toughness of the weld metal gradually increased with an increase in the heat input because of the lower tensile strength. However, it decreased again when the heat input was larger than 45 kJ/cm because of the much smaller area fraction of acicular ferrite. No effect of the preheat/interpass temperature on the impact toughness was observed. The formation of a weld metal heat-affect zone showed little effect on the impact toughness of the weld metal in this experiment.
Ti/Al/STS 클래드재의 접합특성에 미치는 예비 열처리의 영향
배동현 ( Dong Hyun Bae ),정수정 ( Su Jung Jung ),조영래 ( Young Rae Cho ),정원섭 ( Won Sup Jung ),정호신 ( Ho Shin Jung ),강창룡 ( Chang Yong Kang ),배동수 ( Dong Su Bae ) 대한금속·재료학회 2009 대한금속·재료학회지 Vol.47 No.9
Titanium/aluminum/stainless steel(Ti/Al/STS) clad materials have received much attention due to their high specific strength and corrosion-resisting properties. However, it is difficult to fabricate these materials, because titanium oxide is easily formed on the titanium surface during heat treatment. The aim of the present study is to derive optimized cladding conditions and thereupon obtain the stable quality of Ti/Al/STS clad materials. Ti sheets were prepared with and without pre-heat treatment and Ti/Al/STS clad materials were then fabricated by cold rolling and a post-heat treatment process. Microstructure of the Ti/ Al and STS/Al interfaces was observed using a Scanning Electron Microscope(SEM) and an Energy Dispersed X-ray Analyser(EDX) in order to investigate the effects of Ti pre-heat treatment on the bond properties of Ti/ Al/STS clad materials. Diffusion bonding was observed at both the Ti/Al and STS/Al interfaces. The bonding force of the clad material with non-heat treated Ti was higher than that with pre-heat treated Ti before the cladding process. The bonding force decreased rapidly beyond 400℃, because the formed Ti oxide inhibited the joining process between Ti and Al. Bonding forces of STS/Al were lower than those of Ti/Al, because brittle Fe3Al, Al3Fe intermetallic compounds were formed at the interface of STS/Al during the cladding process. In addition, delamination of the clad material with pre-heat treated Ti was observed at the Ti/Al interface after a cupping test.