| ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ KAWASAKI STEEL TECHNICAL REPORT No.42 ( May 2000 ) ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ |
| Development of 590 MPa Grade Galvannealed
Sheet Steels with Dual Phase Structure Yoichi Tobiyama, Kazunori Osawa, Motohiro Hirata |
| Synopsis: Kawasaki Steel has developed TS 590 MPa grade galvannealed sheet steels to reduce automobilie's weight and to improve anti-collision property of automotive bodies. Although the steels were heat-treated in the heat cycle of a continuous galvanizing line, in which quenching was difficult, favorable martensite phase was able to be obtained by Mo addition of 0.15% in conventional dual phase steels. Furthermore, the developed steels showed total elongation of 30%, apparent decrease in yield ratio and good spot weldability. Excellent surface quality of the coated steels was assured by good wettability by molten zinc during galvanizing, because no surface segregation of Mo occurred on the steel surface during recrystallization annealing. Powdering resistance of the galvannealed coatings was sufficient for automobile exterior panels. Low P content in steel, which did not retard galvannealing reaction, provided high productivity in continuous galvanizing lines. |
| TextiPDF: 5P/285kbj |