Weld Geometry Investigation on Dissimilar Boron Steel Laser Welded for TWB Application

Abstract

The pulse wave (PW) mode is an excellent replacement for continuous wave (CW) mode f laser welding in the tailor-welded blank (TWB) application for the automotive ndustry. Due to its ability to produce higher peak power in low power laser pulse mode, he weld penetration and high weld quality can be achieved similarly to the utilization of very high power laser of CW mode. This present work was carried out to investigate the ffect of pulse laser welding parameters of a dissimilar thickness of boron steel for the TWB application. Low power fibre laser with 200 W average power was chosen in this xperimental work. Response surface method (RSM) was used for the design of xperiment (DOE) by applying Box-behnken design (BBD) since there were three rocess factors involved. The process factors are peak power (PP), welding speed (WS) nd focal position (FP) and tensile strength is the response for the weld joint. The metallurgical analysis was conducted at the cross section of sample possessing highest nd lowest tensile strength. Boron steel was successfully welded by using low power fibre aser with PW mode in butt joint configuration. It was found that the highest tensile trength possessed fracture located at the base metal, which is convincing the strength of he joint. For microstructure, finer grain produced at the centre of the fusion zone (FZ) ompared to the FZ near the transition line which produced coarser and medium grain. Finer grain size in FZ contributes to the higher microhardness value and tensile strength f the joint compared to the BM region.

Pulsed Nd: YAG Laser Parameters Effect on Welding Uncoated Advance High Strength Steel (AHSS) for Automotive

“…A slight increment was observed as the defocus position was in the positive region. For a better weld size analysis, smaller bead width with high penetration depth was considered a better weld characteristic as possessing a lower aspect ratio, where a lower aspect ratio indicating that the weld geometry produced was more toward the keyhole characteristics [12]. The positive defocus position produced a weld pool geometry with high penetration depth and a smaller weld width compared to the negative defocus position.…”

“…The application of laser welding was practically used in joining the AHSS for these recent years such as Dual-phase (DP) steel, transformation-induced plasticity (TRIP) steel, boron steel, etc [10][11][12]. The application of PW mode to weld AHSS is truly needed to produce deep penetration weld with free defects, resulting in high strength joining product.…”

Process Parameters Optimisation and Numerical Simulation of Laser Beam Welded Butt Joints of Maraging Steel

“…The main features of laser beam welding include very low heat input, deep penetration, little heat-affected zone, very tiny fusion zone and high flexibility. In the past, many researchers [10][11][12][13] studied the laser beam welding process. Numerous examinations have been done on the use of laser welding of different compounds, for example, Ti-6Al-4V titanium alloy and 18% Ni maraging steel [14].…”

“…The poor strength and toughness of the joints of the weld are normally assigned to the separation of the elements and to the formation of titanium and nitride inclusion. The cases where the heat treatment temperature goes above 820 ℃, the precipitates may have a greater impact on the mechanical properties of the maraging steels [26][27][28][29].…”

An Overview of Laser Welding of High Strength Steels for Automotive Application

“…In the automotive sector, minimum heat-affected zone, deep penetration, and excellent seam welding are required. A great number of studies have been conducted for laser welding for tailor welded blank applications using boron steel [15]. The superb quality intersection is obtained by a few numbers of processing parameters associated with the CW mode.…”