複合組織鋼의 摩擦 熔接部의 疲勞破壞特性에 관한 硏究 = A Study on the Characteristic of Fatigue Crack of Welded Zone of Friction-Welded Dual Phase Steel

다국어 초록 (Multilingual Abstract)

This study has been carried out to investigate the characteristics of fatigue crack of welded zone and heat affected zone of friction welded dual phase steel.
The results obtained from the experiments are summarized as follows.
Microstructure of welded zone is changed to ferrite and pearlite from ferrite and martensite by wel-ding heat. Micro-vickers hardness of welded zone is higher than that of base metal zone and heat affec-ted zone.
Micro-vickers hardness of heat affected zone is lower than that of welded zone and microstructure of heat affected zone is changed to fine martensite and ferrite by heating cycle of welding.
Fatigue limits of heat affected zone is a little higher than that of welded zone and base metal zone. There are no difference of fatigue limit of base metal zone and welded zone. Fatigue strength of welded zone is similar to that of base metal zone.
At high △K region(△K＞19MPa·??), fatigue crack propagation velocity of heat affected zone is slower than that of welded zone and base metal zone, and the difference of fatigue crack propagation velocity is smaller than that of high △K region.
The crack occurs to the notch in heat affected zone first, but the final fracture surface is the surface of welded zone.
It is abvious that heat affected zone of friction welded dual phase steel superior to welded zone and base metal zone in fatigue strength and resistance of fatigue crack propagation. The above mentioned facts are contrary to theory that heat affected zone of general metals is weaker than welded zone and base metal zone.

목차 (Table of Contents)

• Ⅰ. 緖 論
• Ⅱ. 實驗裝置 및 方法
• Ⅲ. 實驗結果 및 考察
• １. 摩擦熔接部의 組織變化 및 硬度分布
• ２. 疲勞强度 및 疲勞크랙傳播 特性
• ３. 疲勞破斷面 考察
• Ⅳ. 結 論
• 參考文獻
• Summary