Laser welding of tailored blanks made of Al-Si-coated 22MnB5 steel using a filler wire and a variable energy distribution laser optics

Abstract

Laser welding of Al-Si-coated steels for hot stamping in automotive applications is problematic due to the mixing of the coating layers inside the molten pool that weakens the resulting weld seam. In this case, the most common welding procedure to overcome this issue consists in removing the Al-Si layer through laser ablation prior to the joining. This method continues to be the most widely used by major producers of tailor welded blanks, although in situ ablation of the Al-Si coating can be costly and time consuming. In this work, a novel approach consisting in joining as-received (i.e., not decoated) materials using a filler wire and an innovative variable energy distribution laser optics is introduced and tested on tailor welded blanks made of 22MnB5. Tensile tests of specimens obtained from a 33 full factorial design of experiment have shown an average value of ultimate tensile strength of 1523 MPa, which is much higher than the one usually observed in as-received welded then hot-stamped conditions and aligned with hot-stamped base material values. Hardness test results (494–543 HV0.5) were in the typical hot-stamped base material range of values as well, while SEM–EDS analyses detected no ferrite inclusions inside the fusion zone. Variations of the main process parameters have been considered on an iso-thickness and iso-material configuration, empirically demonstrating the stability and reliability of the proposed methodology as well as its suitability for production purposes.

Recent advances in mitigating fusion zone softening during laser welding of Al-Si coated 22MnB5 press-hardened steels

“…This increased C-alloying had the potential to induce excessive brittleness in the weld [48]. Other research on the subject has attempted to provide alternative methods to the colloidal graphite coating solution, like using a filler wire and a variable energy distribution laser optics [82] or modifying the laser welding processing parameters [83] but the results are underwhelming either due to the complexity of the setup or due to inadequate mechanical properties of the FZ. Therefore, an alternative approach to achieve in situ alloying in the FZ was adopted in which electro-spark deposition (ESD) was used to modify the as-received Al-Si coating on 22MnB5 PHS prior to laser welding [45].…”

Microstructure and properties of magnetic field assisted laser wire-filled welded 22MnB5 steel joints

“…Before welding, the surface of the test board is ground with sandpaper, the parts to be welded are cleaned with acetone, and both sides of the test board are fixed to the 304 stainless steel workbench with stainless steel clamps. Although most researchers used high power in laser welding experiments [6][7][8][11][12][13][14][15], it is equally important to investigate the laser welding process at low power to reduce the manufacturing cost. In this laser welding experiment, a YLS-1000W low-power fiber laser supplied by IPG company is used as a welding heat source, Ar is used as a shielding gas, and a YJ-105 wire feeder produced by Panasonic company is used to supply filler welding wire.…”

“…Only a few scholars have studied the laser filler wire welding of 22MnB5 steel, and their work primarily focuses on the welding materials and process parameters and their influence on the surface coating, microstructure, and properties of the joint [11]. For example, Lin et al [12] performed a comparative analysis of laser filler wire welding and laser welding to weld 22MnB5 steel with 1.5 mm thick Al-Si coating on its surface.…”