Abstract:Laser welded Transformation-induced plasticity (TRIP) steels are known to generate martensite in the fusion (FZ) and the heat-affected (HAZ) zones. To solve this issue, the present study proposes a high temperature (HT) welding to avoid decay below the martensite start temperature after laser welding. Therefore, an inductive heating has been used to reach 500 °C before laser weld of superposed 1.6mm thick TRIP steel class 750. After welding the temperature was kept constant at 500 °C for more 10 minutes in ord… Show more
“…One thermocouple welded to the bottom surface of the plate recorded the temperature profile. The furnace and laser setup were reported elsewhere (Braga et al, 2018).…”
“…One thermocouple welded to the bottom surface of the plate recorded the temperature profile. The furnace and laser setup were reported elsewhere (Braga et al, 2018).…”
“…In the RT case, the specimen is welded in the usual way, but the HT case requires an external heating source. This was accomplished by an induction furnace specially conceived for the current experiment and reported elsewhere 11 . The temperature evolution of the specimen was recorded by a thermocouple (TC) soldered to the lower surface of the workpiece.…”
Section: Methodsmentioning
confidence: 99%
“…In previous studies, the present authors proved the usefulness of an in-situ inductive heating of the base material during and after the laser beam interaction for controlling the volume fraction of martensite in FZ and HAZ. Braga et al 11 produced a bainitic fusion zone instead of a martensitic one when transformation-induced plasticity (TRIP) steels were laser welded at 500 °C and keeping isothermal for 10 minutes. These in-situ austempered welded sheets presented an outstanding behavior in cup-drawing tests.…”
It was verified that SAE 4130 steel plates crack when laser beam welded at room temperature (RT). To overcome this problem, this work proposes a high temperature (HT) laser welding in order to reduce the residual stresses and create a bainitic structure instead of a martensitic one. A conventional post-welding heat treatment (PWHT) had been used as a comparison for HT. The centerline crack disappeared after a heat treatment of both in-situ (HT) or after inserting in a furnace (PWHT) at 500 °C for 10 minutes. The finite element analyses indicated a residual stress reduction from 163.70 to 3.72 MPa in the fusion zone (FZ) of the welds from RT to HT. The hardness obtained in FZ depends on the thermal cycle induced microstructure of the welds as 400 HV, 340 HV and 250 HV, for martensite (RT), tempered martensite (PWHT) and bainite (HT) micro-constituents. The proposed in-situ high-temperature laser beam welding method proved its usefulness to solve the center crack issue in SAE 4130 joints.
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