Assessment of the Weldability of High-Strength Low-Alloyed Steels Considering the Manufacturing Routes

Abstract A welding process inevitably influences the base material in the heat-affected zone (HAZ) of the weld seam, which can critically alter the mechanical properties of high-strength low-alloyed (HSLA) steels. To account for this, weldability is commonly assessed using the carbon equivalent (CE), neglecting essential factors such as microalloying concepts and specific manufacturing routes. Since strengthening mechanisms respond differently to welding thermal cycles, CE alone offers limited reliability for evaluating the weldability of HSLA steels. To address this, thermophysical simulations using a TA Instruments DIL 805 dilatometer were carried out on quenched and tempered and thermomechanical-controlled processed steels with yield strength levels of ~ 700 MPa. Time–temperature cycles based on gas metal arc welding were applied using peak temperatures of 1,200 °C, 1,000 °C, 800 °C, and 600 °C and cooling times t 8/5 of 5–25 s. To evaluate the changes in material properties, tensile testing, hardness measurements, and microscopic analyses were conducted. The results demonstrate significant manufacturing-related differences of mechanical and microstructural properties, with strength reductions of up to 40% and hardness increases of up to 51%. Therefore, a new evaluation approach was discussed for HSLA steels, which incorporates specific manufacturing routes to enable a more reliable assessment of weldability.