Localized Heat Treatment
Direct diode sources for local softening of press-hardened steels
Press-hardened steels such as 22MnB5 reach strengths of around 1500 MPa after in-die quenching [1]. That strength is ideal for body areas that must protect the passenger compartment, but many parts also need local, more ductile zones: to absorb energy in a crash, in B-pillars and rails, or to ease joining and avoid weak heat-affected zones at spot welds [2].
Laser tempering creates these soft zones after stamping, by heating the martensite locally and under control until it transforms into tempered martensite. Because it is a post-forming process, the position and size of the soft zones can be adjusted for each vehicle variant sharing the same part, and it has been applied industrially since 2022 [2].
| Parameter | Reference value (22MnB5, laser tempering) |
|---|---|
| Power (CW) | 2,4 kW [1] |
| Irradiated area | ~40 × 40 mm [1] |
| Peak temperature | ~600 °C [1] |
| Tensile strength | From 1523 MPa to 920 MPa [1] |
| Hardness after tempering | 330 HV1 [1] |
| Width of softened zone | ~20 mm [1] |
Besides reducing strength, laser tempering markedly improves fracture toughness, with properties comparable to bainitic microstructures, which favors energy absorption in structural components [1]. Since the final properties depend on the temperature reached, precise control of the thermal cycle is key to obtaining reproducible soft zones [2].
Our sources
We have experience in local softening of press-hardened steel parts in the automotive sector. Our 2.4 kW direct diode sources generate square areas of perfectly homogeneous irradiance, sized to the zone to be treated and at the working distance the installation requires, well beyond the ~50 mm of VCSEL sources. Patterns can be combined to cover larger surfaces, and the source is delivered with its power and control electronics, including closed-loop temperature control with a pyrometer.
References
1. Garcia-Llamas E, Pujante J, Frómeta D, Corón D, Galceran L, Golling S, et al. Optimization of thick 22MnB5 sheet steel part performance through laser tempering. Metals. 2023;13(2):396. doi:10.3390/met13020396
2. WorldAutoSteel. AHSS Guidelines — Press hardening steels: soft zones. ahssinsights.org
Need to create soft zones in high-strength parts?
Tell us about the material, the thickness and the geometry of the zone to be treated, and we will work with you to define the most suitable source and pattern. We develop custom solutions for equipment manufacturers and integrators.
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