Comparison between laser beam and gas tungsten arc tailored welded blanks via deep drawing

This paper aims at analyzing the deformation behavior of tailor welded blanks (TWBs), manufactured by laser beam welding (LBW) and gas tungsten arc welding (GTAW), through the deep drawing process. Dissimilar and similar steels with different thicknesses were used in the production of tailor welded blanks. The Nd: YAG laser welding method with nitrogen (N2) as the shielding gas was used to join TWBs. The effects of some significant process factors, namely welding speed, blank holder forces (BHF), material properties of base metals, dry/lubricated condition and laser spot size was experimentally investigated on the weld line movement and drawing depth. Results indicated that using LBW with optimum parameters for the production of dissimilar TWBs caused the control of failure in the weaker base metal. Results showed that the sound welds were produced in similar TWBs with a thickness ratio of 2 when using GTAW, but the weld quality was poor when using LBW. Moreover, it is observed that the critical stresses were taken place outside of the weld zone and rupture due to the high heat input of laser and metallurgical changes of the base metal that occur in the pre-softening zone. In addition, the weld line movement occurred as a result of plastic strain change of the weld joint that caused failure-prone zone creation as well as the adverse wrinkling.

Sustainability aspects in the warm forming of tailor welded blanks

Tailor welded blank (TWB) technology has been used in the manufacture of automobile body-in-white components since a long time. These components consist of different materials/thicknesses. Researchers and manufacturers involved with production of warm formed TWB components failed to address the sustainable issues related to warm forming. Rather they concentrated more on reducing the weld line movement (WLM). The WLM if not arrested shall lead to fracture, due to wrinkles, produced during forming. In this paper, the sustainability aspects involved in the warm forming of TWB were discussed with respect to energy and material savings. The results show a reduction of about 50% punch load in a hydraulic press during deep drawing under warm forming conditions. This paper addresses the questions related to the implications of thickness ratio on the weld line movement and further shows how material savings of nearly 33% has been obtained. It also discusses about the carbon emissions during manufacturing of raw materials and the recycling benefits of stainless steel, so as to minimize emissions at the production stage itself during raw materials production.

Minimization of weld line movement in heat-assisted forming of tailor welded blanks

In this work, the formability aspects in terms of desired cup height during stamping operation of tailor welded blanks have been studied along with minimizing the movement of weld line. Circular sheets were prepared by joining austenitic stainless steel (ASS 304 Grade) and drawing quality mild steel (AISI 1018) materials with tungsten inert gas welding. To reduce the undesirable weld line movement during stamping process, a novel heat-assisted forming method involving localized and controlled heating of the stronger material side (ASS 304 steel) has been carried out. The experimental setup developed for this purpose enabled heating and maintained the selected zone at the desired temperature during the stamping process. The entire process has been simulated using finite element method and the results obtained were in close agreement with the experimental results. The effect of selective heating of tailor welded blank also resulted in the overall improvement in the quality of the product.

Maximum Bulge Height and Weld Line Displacement in Hydroforming of Tailor Welded Blanks

Tailor welded blank (TWB) has many advantages over a traditional blank for manufacturing automobile sheet metal components, such as significant flexibility in product design, higher structural stiffness, and crash behavior. However, lower formability and weld line movement are some of the problems associated with forming of TWBs. Hydroforming is a potential technique to enhance formability. In this work, the effect of thickness ratio on maximum dome height and weld line movement in hydraulic bulging of laser welded interstitial-free (IF) steel blanks of different thickness combinations has been predicted using finite element (FE) simulations. The results are also validated with hydraulic bulging experiments on TWBs. It has been found that with increase in thickness ratio, the maximum bulge height decreased and weld line displacement toward thicker side increased. These results have been used to relocate the weld line toward the thinner side in the initial blanks and achieve a more uniform bulge profile of the dome. The peak pressure to achieve maximum safe dome height and percentage thinning has also been found out. The results showed huge improvement in uniformity of bulge profile with little reduction in dome height.