Influence of cooling rate on tensile behaviour of S690Q high strength steel butt joint

Systematic experimental and numerical investigations were conducted in this study to quantify the impact of cooling rate of the Heat Affected Zone (HAZ) on the post-weld strengths of S690Q High Strength Steel (HSS) butt joint. Five butt joints were fabricated by using 8, 12 and 16 mm HSS plates with different welding heat inputs and cooling times. Direct tensile tests were conducted to obtain their failure modes and stress-strain curves. Based on the test data, a new finite element modelling approach which considers the influence of peak temperature and cooling rate on the material property of HAZ was proposed. After validated with experimental results, the proposed approach was then employed to conduct a parametric study to examine the effects of cooling rate on the joint's post-weld strengths. Parametric study results showed that the strengths of the joints were adversely affected as the cooling time increased. Furthermore, when compared with the ultimate tensile strength, the yield strength deterioration was more seriously affected by a long cooling rate.