R.P. García, L.B. Peral, F.J. Belzunce
International Journal of Advanced Manufacturing Technology
https://doi.org/10.1007/S00170-025-16083-9
Resumen
The mechanical properties of heat-affected zone (HAZ) and weld metal (WM) of S690QL steel joints performed with a shielded metal arc welding (SMAW) process were determined. Three heat inputs (0.8, 1.7, and 2.5 kJ/mm) were applied, and properties were determined in the as-welded (AW) and after post weld heat treatment (PWHT). Tensile, hardness profiles, Charpy V impact toughness, and crack tip opening displacement (CTOD) tests with cracks located at the HAZ and fusion line (FL) were performed, along with microstructural analysis using optical and scanning electron microscopes and X-ray diffraction. A fine self-tempered martensite microstructure was produced in the coarse-grained HAZ when a low heat input was applied, achieving a high transversal tensile strength, high HAZ hardness, and excellent toughness at low temperatures (− 40 °C). Under high heat inputs (1.7 and 2.5 kJ/mm), prior austenite grain size increases, favoring brittle unstable (cleavage) fractures near to the FL. Acicular ferrite with isolated M-A constituent was obtained in the WM region. Increasing heat input, the stability of this last brittle component enhances, decreasing its toughness. The application of PWHT did not provide any significant change in the mechanical properties of these welds. The use of low heat input is recommended to weld S690QL steel offshore structures, and PWHT is not necessary.