Maximizing Cross Tension Impact Properties of Spot Welds in 1.5mm Low Carbon, Dual-phase, and Martensitic Steels

Critical review of automotive steels spot welding: process, structure and properties

“…101 Gould et al 40 also used the phenomenological model of Bhadeshia 100 and thermodynamic based model of Li et al 102 to predict the critical cooling rate of steels. As a fast reference, the critical cooling rate to achieve martensite in the microstructure can be estimated using the following equation 18LogV~7 : 42{3 : 13C{0 : 71Mn{0 : 37Ni{0 : 34Cr{0 : 45Mo (6) where V is the critical cooling rate in K h 21 and the element symbols refer to their concentrations in weight percentage.…”

“…Adjusting the FZ chemical composition can be achieved through two techniques: (i) introducing an LCS shim insert between steels to be welded: 211 this can reduce carbon equivalent of FZ via dilution process. Peterson and Borchelt 6 showed that the weld dilution by inserting a low carbon shim at the faying interface 1330 MPa martensitic steel sheets led to producing pullout mode which dramatically improved the peak load by over 300%. However, it should be mentioned that an insert would be of limited practical applicability and the dilution technique does not reduce the HAZ hardening 211 (ii) dissimilar welding of high alloyed steel to lean alloyed steels: in automotive applications, AHSSs are seldom welded to themselves.…”

“…Current governmental regulations require vehicle crash tests at speeds up to 35 mph (15 m s 21 ) in frontal impact. 6 Therefore, impact strength is significant as this aspect of quality directly relates to the crashworthiness of the vehicle. 224 In a crash scenario, the strain rate sensitivity of mechanical performance of spot welds is most important.…”

DP780 dual-phase-steel spot welds: critical fusion-zone size ensuring the pull-out failure mode

“…total Void total (6) where A total is the total area of the fusion zone on the faying interface and A void is the projected area of the void in the fusion zone on the faying interface of the weld. Therefore, Equation (5) can be adjusted as follows:…”

“…Additionally, spot welds can act as fold-initiation sites to manage impact energy. 6 Vehicle crashworthiness, which is defined as the capability of a car structure to provide adequate protection to its passengers against injuries in the event of a crash, largely depends on the integrity and the mechanical performance of the spot welds. [7][8][9] Failure of spot welds may affect the vehicle's stiffness and NVH (noise, vibration and harshness) performance at the general level.…”