Laser forming of Dual Phase Steel

Laser Forming (LF) is an advanced manufacturing technique that shapes sheet metals by inducing thermal stress using a defocused laser beam. It can be used in forming, straightening, and precision adjustment, LF offers significant advantages for applications in aerospace, automotive, and other industries. This research investigates the LF of Advanced High Strength Steels (AHSS) for automotive applications, focusing on Dual Phase Steel (DP1000), which contains hard martensite islands in a soft ferrite matrix. Ensuring minimal impact on material properties is critical for industrial acceptance. Both 2D and 3D LF of DP1000 have been investigated, with comparative studies against CR2 mild Steel. To investigate the 3D laser forming of DP1000 representative geometries for automotive precision adjustment applications have been devised. Process parameters such as power, speed, spot size, dwell time, number of passes with different irradiation paths, beam shape and mode structure have been studied to investigate the effect of laser forming process parameters on the material both experimentally and by numerical modelling. Key findings in this study reveal that laser forming of DP1000 is possible without significant impact on material properties providing that optimised process parameters used. In addition, it was found that LF can enhance the formability of AHSS, though LF under certain conditions can reduce post-forming hardness due to martensite tempering. This reduction poses potential risks as it may create stress concentration zones. However, a slower laser speed and higher temperatures promote a laser hardening effect, enabling recovery of hardness through martensite regeneration during self-quenching. This re-hardening effect offers a useful post-forming treatment, mitigating undesirable side effects. Consequently, the research broadens the process window for LF of DP1000, minimising metallurgical impact for potential industrial applications.