A Comparative Study of Abbreviated Heat Treatments for SAE 4130 Steel After Laser Welding

Abstract

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.

Reduced Coefficient of Friction of Laser Surface Hardened AISI 4130 Steel Substrates

“…Considering an isotherm at 1000 °C, the cooling rates at 40 and 100 μm were 32'280 and 21'434 °C/s, respectively. These rates are high enough to inhibit any long-range diffusional phase transformation, which promotes martensite formation [18]. However, as seen before, there was a small fraction of allotriomorphic ferrite in the FZ, both in condition B and in C. This ferrite must be a residue of the original BM that did not have time to dissolve in the austenitic matrix.…”

The effects of oil-quenching and over-tempering heat treatments on the dry sliding wear behaviours of 25CrMo4 steel

“…Finite element analysis revealed a significant reduction in residual stress from 163.70 MPa to 3.72 MPa in the fusion zone (FZ) of the welds when transitioning from RT to HT. The study concludes that the hardness in the FZ is influenced by the microstructure resulting from the thermal cycle, with values of 400 HV for martensite (RT), 340 HV for tempered martensite (PWHT), and 250 HV for bainite (HT) [ 11 ].…”