Al-Si 도금된 보론강과 Zn 도금된 DP강 TWB 레이저 용접부내의 Al-편석부 미세조직에 미치는 핫스탬핑 열처리의 영향 (Effect of Hot-stamping Heat Treatment on the Microstructure of Al-Segregated Zone in TWB Laser Joints of Al-Si-coated Boron Steel and Zn-coated DP Steel)

서지정보

· 발행기관 : 대한금속·재료학회
· 수록지 정보 : 대한금속·재료학회지 / 50권 / 6호 / 455 ~ 462페이지
· 저자명 : 정병훈, 공종판, 강정윤

초록

Al-Si coated boron steel and Zn coated DP steel plates were laser-welded to manufacture a Tailor Welded Blank (TWB) for a car body frame. Hot-stamping heat treatment (900℃, 5 min) was applied to the TWB weld, and the microstructural change and transformation mechanism were investigated in the Al-rich area near the bond line of the Al-Si coated steel side. There was Al-rich area with a single phase, Fe_3(Al,Si), which was transformed to α-Fe (Ferrite) after the heat treatment. It could be explained that the Fe_3(Al,Si) phase was transformed to α-Fe during heat treatment at 900℃ for 5 min and the resultant α-Fe phase was not transformed by rapid cooling. Before the heat treatment, the microstructures around the Fe_3(Al,Si) phase consisted of martensite, bainite and α-Fe while they were transformed to martensite and δ-Fe after the heat treatment. Due to the heat treatment, Al was diffused to the Fe_3(Al,Si) and this resulted in an increase of Al content to 0.7 wt% around the Al-rich area. If the weld was held at 900℃ for 5 min it was transformed to a mixture of austenite (γ) and δ-Fe, and only γ was transformed to the martensite by water cooling while the δ-Fe was remained unchanged.

영어초록

Al-Si coated boron steel and Zn coated DP steel plates were laser-welded to manufacture a Tailor Welded Blank (TWB) for a car body frame. Hot-stamping heat treatment (900℃, 5 min) was applied to the TWB weld, and the microstructural change and transformation mechanism were investigated in the Al-rich area near the bond line of the Al-Si coated steel side. There was Al-rich area with a single phase, Fe_3(Al,Si), which was transformed to α-Fe (Ferrite) after the heat treatment. It could be explained that the Fe_3(Al,Si) phase was transformed to α-Fe during heat treatment at 900℃ for 5 min and the resultant α-Fe phase was not transformed by rapid cooling. Before the heat treatment, the microstructures around the Fe_3(Al,Si) phase consisted of martensite, bainite and α-Fe while they were transformed to martensite and δ-Fe after the heat treatment. Due to the heat treatment, Al was diffused to the Fe_3(Al,Si) and this resulted in an increase of Al content to 0.7 wt% around the Al-rich area. If the weld was held at 900℃ for 5 min it was transformed to a mixture of austenite (γ) and δ-Fe, and only γ was transformed to the martensite by water cooling while the δ-Fe was remained unchanged.

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