Abstract
Microstructure and mechanical performances of the coarse grain heat-affected-zone (CGHAZ) for oil tank steel with different Ti content were investigated through Gleeble-3500, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectrometer. The results show that the strength and low-temperature toughness of base material are significantly improved for the high titanium content steel, but the impact toughness of CGHAZ is seriously deteriorated after the high heat input welding and declined sharply with the heat input increasing, while the effects of heat input on impact toughness are very weak for the low titanium content steel, impact toughness of which is gradually larger than that of high titanium content steel with the welding heat input increasing because of the granular bainite increasing, TiN particle coarsening, and (Ti, Nb) N composition evolution during the high input welding for high titanium content steel.
Highlights
High-strength low-alloy steel has been widely applied to build the large-scale structures, such as oil tank, because it has a huge volume up to 10–20 million m3, wherein a lot of welding works are required in the construction [1,2,3]
The high heat input welding tends to cause a considerable reduction in the strength and toughness of HAZ, especially for the coarse grain heat-affected-zone (CGHAZ)
The CGHAZ is adjacent to the fusion line, where the peak temperature is close to the melting point of steel, which results in austenite grain obviously coarsening and occurrence of coarse grained embrittlement
Summary
High-strength low-alloy steel has been widely applied to build the large-scale structures, such as oil tank, because it has a huge volume up to 10–20 million m3, wherein a lot of welding works are required in the construction [1,2,3]. The toughness of CGHAZ is significantly improved by adding Ti, Nb, and other microalloyed elements in the lowalloy high strength steel; this is because of the action between Ti, Nb, and C, N in the steel to form the fine dispersed carbonitride. These carbonitrides block the growth of austenite grains and improve the secondary microstructure of CGHAZ. It is very important for us to study the effects of Ti content on the high-strength oil tank steel when they experience the high heat input welding. With different Ti content in the welding thermal cycle were investigated by metallographic microscope, scanning electron microscopy (SEM), and transmission electron microscope (TEM)
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