Diffusible hydrogen characteristics of hybrid laser arc welding (HLAW)

Abstract

Preliminary diffusible hydrogen testing of the Hybrid Laser Arc Welding (HLAW) process has been performed. With increasing application of HLAW, the process will inevitably be applied to steels susceptible to Hydrogen Assisted Cracking (HAC,). Thus, it was deemed important to examine the diffusible hydrogen potential of HLAW in comparison to traditional Gas Metal Arc Welding (GMAW). This paper describes testing of a representative filler metal as might be used on quenched and tempered (Q&T) construction steels such as HY-80 and the newer high-strength, low-alloy (HSLA) steels. Many of the HSLA steels “have a much lower propensity for HAC in the heat-affected zone (HAZ) but there is still concern over HAC in the weld metals used to join them [1].”Also of interest is the fact that the laser portion of the total energy may constitute as much as half the energy in the molten pool, compared to the GMAW portion. If the susceptibility to hydrogen pickup is linked to the relative size of weld pool, then perhaps HLAW will have increased hydrogen pickup. Tests were made using HLAW, autogenous Laser Beam Welding (LBW) and conventional GMAW at several parameter sets. Testing was performed in accordance with AWS A4.3 using standard ASTM A-36 steel coupons. Results show that the HLAW process results in low levels of diffusible hydrogen, compared to conventional GMAW. Also, tests of the LBW process by itself demonstrated that at typical process welding speeds, the laser contributes little or no diffusible hydrogen to the weld.Preliminary diffusible hydrogen testing of the Hybrid Laser Arc Welding (HLAW) process has been performed. With increasing application of HLAW, the process will inevitably be applied to steels susceptible to Hydrogen Assisted Cracking (HAC,). Thus, it was deemed important to examine the diffusible hydrogen potential of HLAW in comparison to traditional Gas Metal Arc Welding (GMAW). This paper describes testing of a representative filler metal as might be used on quenched and tempered (Q&T) construction steels such as HY-80 and the newer high-strength, low-alloy (HSLA) steels. Many of the HSLA steels “have a much lower propensity for HAC in the heat-affected zone (HAZ) but there is still concern over HAC in the weld metals used to join them [1].”Also of interest is the fact that the laser portion of the total energy may constitute as much as half the energy in the molten pool, compared to the GMAW portion. If the susceptibility to hydrogen pickup is linked to the relative size of weld pool, then perhaps HL...