Effects of Zr addition on microstructure and toughness of simulated CGHAZ in high-strength low-alloy steels

• DOI: 10.1007/s42243-019-00319-6
• Publication Date: 2019-10-09T10:09:55Z
• Authors: Jin-wei Lei; Kai-ming Wu; Yu Li; Ting-ping Hou; Xing Xie; R.D.K. Misra
• Keywords: Acicular ferrite; Equiaxed crystals; High-strength low-alloy steel; Acicular

The effect of Zr addition (0.005, 0.013, and 0.054 wt.%) on the microstructure and toughness of simulated coarse-grained heat-affected zone in high-strength low-alloy steels was revealed using a Gleeble 2000 thermal simulator. It was observed that elongated MnS inclusions were formed in the lowest Zr-containing steel, while only pure equiaxed ZrO2 existed in the 0.054Zr steel (Zr content of 0.054 wt.%). Complex oxide–sulfide inclusions (ZrO2 + MnS) with size of (1.40 ± 0.25) μm were formed in 0.013Zr steel (Zr content of 0.013 wt.%). The complex inclusions refined the prior austenite grain, and the nucleation of acicular ferrite was promoted compared to those of 0.005Zr steel (Zr content of 0.005 wt.%) and 0.054Zr steel. Consequently, the 0.013Zr steel possessed superior low-temperature impact toughness in relation to 0.005Zr and 0.054Zr steels. Thus, moderate Zr addition can be considered as an effective method to refine the structure and improve the mechanical properties of the coarse-grained heat-affected zone.