Akademik Veri Yönetim Sistemi
MATERIALS RESEARCH EXPRESS, cilt.10, sa.8, ss.1-14, 2023 (SCI-Expanded)
Quenched and tempered S960QL (yield strength ≥ 960 MPa)
ultra-high strength steel (UHSS) thick plates were joined by multi-pass robotic
gas metal arc welding (GMAW) using weaving and stringer bead techniques. The
effects of microstructural changes in heat-affected zone (HAZ) of the joint on
toughness and hardness were examined. Weaving and stringer bead techniques
applied for the multi-pass welding procedure altered average peak temperatures
and exposure time to those temperatures. Mechanical properties of HAZs were
evaluated by utilizing notch impact and hardness tests, and these results were
correlated with microstructural characterizations using optical (OM) and
scanning electron microscopes (SEM). Prior austenite grain (PAG) coarsening
occurred because of increased exposure time to peak temperature in
coarse-grained HAZ (CGHAZ) of the W-5 (weaving pass) joint. CGHAZs at the face
pass, which have not been subjected to a second thermal cycle, have the highest
hardness in both joints. Hardness of SCHAZ and CGHAZ of S-12 joint was 7% and
1% higher compared with W-5 joint, respectively. Weld metal hardness of W-5
joint was 15% lower than that of S-12 joint. Both joints not only fulfilled the
requirements of minimum 50 J per EN ISO 10025-6 at −20 °C but exceeded this
limit by 50% (W-5) and 200% (S-12). Lateral expansions for impact toughness
specimens were around 17.5% for S-12 joint, whereas it was 4% for W-5 joint.
Since HAZ in the S-12 (stringer bead) joint is narrow compared with the one in
the W-5 joint, impact toughness values were higher with the S-12 joint due to
the locations of the notches of the impact specimens.