Hybrid laser welding of dual phase steel DP600: Microstructural and mechanical properties

Welding of Ultra High Strength Steels

“…2 Effect of welding current on the minimum hardness in the HAZ of DP 980 [15] Studies of the weld ability of UHSS have shown, for the most part, that maximum softening occurs in the microstructures area of the HAZ where the peak temperature during welding reaches the lower critical temperature (Ac 1 ) of the steel [8,37]. This is typically referred to as HAZ softening in the subcritical area (SCHAZ), i.e., the zone in which the temperature is too low to cause ferrite-austenite transformation but high enough to temper the martensite present in the base material microstructure [37]. Decomposition of martensite due to high-tempering causes the soft area in the HAZ [28].…”

“…In spite of the susceptibility to cracking and softening phenomena in the HAZ and weld metal of UHSS, these steels can be welded effectively, but the linear energy of the welding must be precisely adjusted, in order to avoid excessive hardening and subsequent cold cracking in the case of short cooling time, and reduced strength properties, especially in the HAZ, in the case of excessively high linear energy of welding or slow cooling rates [8,12,27,28,37,40,41]. It should be emphasized that when welding UHSS, the heat input in the welding process must be kept as low as possible to avoid excessive softening [8,12,27,28,37]. Filler Material.…”

“…Another key parameter in welding of UHSS is correct selection of a filler material with respect to the base metal to obtain sufficient weld strength. Although, when welding UHSS with a yield point higher than 800 MPa, it is recommended to select a deposited weld metal with a yield point that is not lower than the yield point of the base metal, some studies have shown that the required strength of welded joints made of quenched and tempered UHSS can be obtained when weld metal deposits with a lower yield point are used (under-matching filler material) [8,37].In such cases, in addition to lower costs, the propensity of joints for cold cracking can be reduced as well.…”

Effect of Welding Position and Gap between Samples on Hybrid Laser-Arc Welding Efficiency

“…Comparative analyze of laser, arc and laser-arc welding [1], research of HLAW with different type of lasers [2] were considering of some publications. Other publications describe influence voltage, frequency and ripple arc time [3], distance between axis of laser beam and electrode [4], type of edge preparation [5], type of treatment edge preparation [6], type of welding seal and composition of protective gas [7] on mechanical properties and geometry of welding seam. Some researchers describe of influence frequency responses at laser beam scanning on internal defects of welded joint [8] and also influence of HLAW parameters on distribution alloys and mechanical properties of welding joint [9,10].…”