According to a 2025 review in Welding in the World, heat-affected zone (HAZ) softening remains a critical challenge when welding advanced high-strength steels (AHSS), particularly dual-phase (DP) steels used in automotive and structural applications.
The softened zone occurs in the subcritical HAZ, where the martensite phase tempers and loses strength. This local strength drop can reduce joint performance under static and fatigue loading. The degree of softening depends on peak temperature, cooling rate, and the initial martensite fraction.
Key factors influencing HAZ softening include:
• Heat input: Higher heat input broadens the softened region.
• Pre-existing martensite: Steels with higher martensite content show more pronounced softening.
• Post-weld heat treatment: PWHT can partially restore strength, but process control is essential.
For welding engineers, selecting appropriate heat input, using low-temperature filler metals, and optimizing weld sequencing are practical mitigation strategies. Finite element modeling can predict softening zones before production.
How do you manage HAZ softening in your DP steel welds?
Source: Welding in the World, 2025