EFFECT OF Zr ADDITION TO Ti-KILLED STEEL ON INCLUSION FORMATION AND MICROSTRUCTURAL EVOLUTION IN WELDING INDUCED COARSE-GRAINED HEAT AFFECTED ZONE
来源期刊：Acta Metallurgica Sinica2008年第3期
论文作者：Z.Xu H.Su C.F.Yang Y.H.Yang Y.Q.Zhang F.Chai
Key words：Nonmetallic inclusions; Zirconium; Acicular ferrite; Coarse-grain heat affected zone (CGHAZ);
Abstract: Effects of Zirconium on the chemical component and size distribution of Ti-bearing inclusions, favored the grain refinement of the welding induced, coarse-grained heat affected zone (CGHAZ) with enhanced impact toughness in Ti-killed steels, which were examined based on experimental observations and thermodynamic calculations.It indicated that the chemical constituents of inclusions gradually varied from the TiO oxide to the Ti-O+Zr-O compound oxide and a single phase of the ZrO2 oxide,as the Zr content increased from zero to 0.0100%. A trace of Zr (0.0030%-0.0080%,depending on the oxygen content in liquid steel) provided a large amount of nucleating core for Ti oxide because of the larger specific density of ZrO2 oxide, and produced a small size distribution of the inclusions favorable for aeieular ferrite transformation with a high nucleation rate in the CGHAZ, and a high volume fraction of aeicular ferrite was obtained in the CGHAZ, with enhanced impact toughness. Otherwise, a high content of Zr (～0.0100%) produced a single phase ZrO2, which was impotent to nucleate acicular ferrite, and a microstructure composed of ferrite side plate and grain boundary ferrite developed in the CGHAZ. The experimental results were confirmed by thermodynamic calculations.
Z.Xu1，H.Su2，C.F.Yang2，Y.H.Yang3，Y.Q.Zhang2，F.Chai2
(1.School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200030, China;
2.Institute for Structural Materials, Central Iron and Steel Research Institute, Beijing 100081, China;
3.School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China)
Abstract:Effects of Zirconium on the chemical component and size distribution of Ti-bearing inclusions, favored the grain refinement of the welding induced, coarse-grained heat affected zone (CGHAZ) with enhanced impact toughness in Ti-killed steels, which were examined based on experimental observations and thermodynamic calculations.It indicated that the chemical constituents of inclusions gradually varied from the TiO oxide to the Ti-O+Zr-O compound oxide and a single phase of the ZrO2 oxide,as the Zr content increased from zero to 0.0100%. A trace of Zr (0.0030%-0.0080%,depending on the oxygen content in liquid steel) provided a large amount of nucleating core for Ti oxide because of the larger specific density of ZrO2 oxide, and produced a small size distribution of the inclusions favorable for aeieular ferrite transformation with a high nucleation rate in the CGHAZ, and a high volume fraction of aeicular ferrite was obtained in the CGHAZ, with enhanced impact toughness. Otherwise, a high content of Zr (～0.0100%) produced a single phase ZrO2, which was impotent to nucleate acicular ferrite, and a microstructure composed of ferrite side plate and grain boundary ferrite developed in the CGHAZ. The experimental results were confirmed by thermodynamic calculations.
Key words:Nonmetallic inclusions; Zirconium; Acicular ferrite; Coarse-grain heat affected zone (CGHAZ);
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