| Popis: |
In the present work, to improve the press formability of the combination of the TRIP steel and ferrite-martensite dual-phase (DP) steel, the mechanical properties and press formability (stretch-formability) of YAG laser welded TRIP/DP tailored blanks were investigated. An as-cold-rolled sheet steel with the chemical composition of (0.1-0.3)C-1.5Si-1.5Mn (mass%) was used in this study. For comparison, 0.14C-0.22Si-1.78Mn (mass%) DP steel was also prepared. The quenched DP steel is called MDPO, and the tempered MDPO steel is called MDP4. For butt welding, the blank obtained after the heat treatment was cut using a fine cutter, and YAG laser processing equipment was used. The press formability was evaluated from the maximum stretch-height (H max ). Tensile tests and stretch forming tests have been conducted for laser butt welded joints obtained from the combination of the different steel. The H max value of the MDPO steel was not controlled at the strength level of the DP steel, and was not different from the H max value of the MDP4 steel. It is thought that this was assisted to TRIP of the TDP steel because the tensile strength of the TDP steel is consequentially lower than that of the MDPO steel. High ductility and the high stretch-formability were able to be secured by the high strength TRIP/DP tailored blanks. |
