Abstract
BackgroundStructure and properties of welded joints of low-alloy thermomechanically processed (09G2FB) and quenched and tempered shipbuilding steels (10XN2MD, 08XN3MD, and 12XN3MF), welded with manual metal arc welding (MMA) and submerged arc welding (SAW), were studied.MethodsEffects of specific energy input on the microstructure, mechanical properties, and impact energy of the heat-affected zone (HAZ) have been investigated, and probable reasons for crack formation in welded joints have been found.ResultsIt was found that welding heat input increase leads to a significant increase in grain size near the fusion boundary and the formation of martensite with high hardness. Therefore, the heat input is recommended to be limited to 2.5–3.5 kJ/mm for these specific steel grades.ConclusionsThe study indicates that microalloying elements can be used to limit the grain growth when the steel is subjected to high temperatures during welding thermal cycle. Carbon content and alloying level reduction tend to increase the steel ductility and lower the HAZ toughness.
Highlights
Structure and properties of welded joints of low-alloy thermomechanically processed (09G2FB) and quenched and tempered shipbuilding steels (10XN2MD, 08XN3MD, and 12XN3MF), welded with manual metal arc welding (MMA) and submerged arc welding (SAW), were studied
Cold resistance of the weld joints is hard to achieve, as during welding, some irreversible structural changes occur in heat-affected zone (HAZ) caused by the influence of the welding thermal cycle (Lee et al 2012; Khaustov 2006; Østby et al 2012; Shin et al 2006)
quenching and tempering (QT) steel 10XN2MD with bainite-martensite structure welded by manual metal arc welding (MMA) and SAW
Summary
Structure and properties of welded joints of low-alloy thermomechanically processed (09G2FB) and quenched and tempered shipbuilding steels (10XN2MD, 08XN3MD, and 12XN3MF), welded with manual metal arc welding (MMA) and submerged arc welding (SAW), were studied. A wide range of high-strength coldresistant steels with high plasticity and toughness for shipbuilding were developed. Cold resistance of the weld joints is hard to achieve, as during welding, some irreversible structural changes occur in heat-affected zone (HAZ) caused by the influence of the welding thermal cycle (Lee et al 2012; Khaustov 2006; Østby et al 2012; Shin et al 2006). These changes may result in low impact toughness in the vicinity of the fusion line and significant increase or decrease of HAZ hardness. Rapid cooling is not desirable, as steel microstructure tends to convert to martensitic
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