Precipitation thermodynamics analysis and control of titanium nitride inclusions in extra-low oxygen wheel steel
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摘要: 通過對高速車輪鋼中TiN夾雜物析出進行熱力學分析,得到了車輪鋼的液相線和固相線溫度及1873K時Ti、N的活度.對TiN生成反應和鋼中Ti、N溶度積進行了計算.結果表明:TiN只能在固相中生成,但在本車輪鋼Ti、N含量下,固相中也沒有TiN生成的條件,只有在鋼液凝固前沿,由于Ti、N在兩相區的富集,TiN夾雜物的生成反應得以進行.因此,在生產中,適當提高連鑄二冷的冷卻速率,使鋼液快速凝固,減少凝固前沿Ti、N的富集時間,可減少純TiN的析出.對本實驗車輪鋼中TiN夾雜的檢測結果進行計算分析可知,在正常生產時鑄坯冷卻速率條件下,將鋼中Ti的質量分數控制在3.5×10-5以下、N的質量分數控制在3.1×10-5以下,理論上可以消除TiN夾雜物的析出,改善車輪鋼的疲勞性能,提高車輪的使用壽命.Abstract: The liquidus and solidus temperatures and the Ti and N activities of high speed wheel steel at 1 873 K were obtained by thermomechanically analyzing the precipitation of TiN inclusions.The formation reaction of TiN and the solubility product of Ti and N in the steel were calculated,and the results show that TiN inclusions only form in solid phase,but under the chemical composition of this wheel steel,TiN inclusions can not be produced in solid phase.Only in a solidification front,the formation reaction of TiN can take place owing to the enrichment of Ti and N in the two-phase region.During an engineering process,properly increasing the cooling rate of the secondary cooling zone in a continuous caster to make the rapid solidification of molten steel and shorten the enrichment time of Ti and N in a solidification front can decrease the precipitation of pure TiN inclusions.The calculations and analysis on detection results of TiN inclusions in the experimental wheel steel show that the best way of removing the precipitation of pure TiN inclusions in theory and improving the fatigue properties and service life of the wheel steel is controlling the content of Ti below 3.5×10-5 and the content of N below 3.1×10-5 in the steel under the condition of normal cooling rate.
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Key words:
- railway wheels /
- steelmaking /
- titanium nitride /
- inclusions /
- thermodynamics /
- solubility product
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