The strength of steel sheets used in tailored blanks of the automotive body has been increasing. In this study, weldability of high strength steel sheets and formability of tailored blanks were investigated. This study has two aims. First is to obtain a guideline to determine appropriate welding conditions. Second is to clarify the effects of steel strength and welding methods on the formability of tailored blanks. Four steel sheets, whose nominal tensile strength is ranging from 290MPa to 590MPa were used. They were welded with laser welding, mash seam welding and gas shield tungsten arc welding. Formability was evaluated with tensile test, stretch dome test and hole expanding test. In fusion welding such as laser welding and arc welding, welding conditions have no relationship to steel grade, any steel can be welded at the same welding condition. In the mash seam weld, on the other hand, the appropriate welding condition depends on steel strength; for example higher strength steels require higher electrode force. In general, tailored blanks using higher strength steel show lower formability. In the dome test, difference in formability by welding methods was observed. However mash seam welded retained austenite steels show an exceptional high dome height. In the hole expanding test, laser welded steel sheets exhibit a higher hole expansion ratio compared to other methods in any grade steel. In summary, although there might be any difficulties in use, it was concluded that 590MPa-grade high strength steel could be applied in tailored blanks.
Tailored blanks of high strength steel sheets - Weldability and formability
1998
7 Seiten, 12 Bilder, 3 Tabellen, 2 Quellen
Conference paper
English
Tailored Blanks of High Strength Steel Sheets - Weldability and Formability
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