Abstract
The effect of peak temperature (TP) on the microstructure and impact toughness of the welding heat-affected zone (HAZ) of Q690 high-strength bridge steel was studied using a Gleeble-3500 thermal simulation testing machine. The results show that the microstructure of the inter critical heat-affected zone (ICHAZ) was ferrite and bainite. The microstructure of fine grain heat-affected zone (FGHAZ) and coarse grain heat-affected zone (CGHAZ) was lath bainite (LB), lath martensite (LM), and granular bainite (GB), but the microstructure of FGHAZ was finer. With the increase in peak temperature, the content of LB and GB decreased, the content of LM increased, and the lath bundles of LM and LB gradually became coarser. With the increase in peak temperature, the grain size of the original austenite increased significantly, and the impact toughness decreased significantly. When the peak temperature was 800 °C, the toughness was the best. For CGHAZ, the peak temperature should be less than 1200 °C to avoid excessive growth of grain and reduction of mechanical property.
Highlights
The effect of peak temperature (TP ) on the microstructure and impact toughness of the welding heat-affected zone (HAZ) of Q690 high-strength bridge steel was studied using a Gleeble3500 thermal simulation testing machine
Wen et al [11] thought that reasonable control of heat input is the key to preventing welding cold cracks by studying ultra-high-strength structural steel welding joint at different heat inputs
When the peak temperature was 800 ◦ C, the microstructures of simulated inter critical heat-affected zone (ICHAZ) were composed of bainite (B) and ferrite (F), and
Summary
The effect of peak temperature (TP ) on the microstructure and impact toughness of the welding heat-affected zone (HAZ) of Q690 high-strength bridge steel was studied using a Gleeble3500 thermal simulation testing machine. The main problems of high-strength steel welding include cold crack tendency, embrittlement, and softening in the heat-affected zone [5,6]. The heat-affected zone (HAZ) has a certain gradient distribution in the microstructure and performance and becomes the weakest part in the welding joint [7]. Wen et al [11] thought that reasonable control of heat input is the key to preventing welding cold cracks by studying ultra-high-strength structural steel welding joint at different heat inputs. It was pointed out that the heat input should be higher than 7.5 kJ/cm to avoid the formation of welding cold crack and twinned martensite in CGHAZ. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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