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齒輪鋼氧含量及夾雜物控制技術研究

Control technology for oxygen content and inclusions of gear steel

  • 摘要: 利用熱力學軟件計算了齒輪鋼氧含量與夾雜物成分控制、夾雜物轉變條件.結果表明,20CrMoH鋼中具有較高塑性的非金屬夾雜物成分(質量分數)為:SiO2 0%~10%、Al2O3 22%~55%、CaO 42%~60%、MgO 5%~10%,與之平衡的鋼液中鋁的質量分數大于0.020%,鈣的質量分數大于0.7×10-6,aO為0.0005%左右;選擇組成為CaO>40%、Al2O3 ≤ 37%、MgO 10%、(% CaO+% MgO)/% SiO2為10、SiO2含量盡量低的渣系,鋼中Al2O3、MgO·Al2O3夾雜物可轉變為低熔點的鈣鋁酸鹽.試驗發現LF和RH精煉結束時鋼液TO含量均隨爐渣堿度增加而降低,采用高Al2O3含量的爐渣對降低TO含量有利;精煉過程鋼液中夾雜物按"Al2O3系夾雜物→MgO-Al2O3系夾雜物→CaO-MgO-Al2O3系夾雜物"順序發生轉變,其中MgO-Al2O3系夾雜物向CaO-MgO-Al2O3系夾雜物的轉變是由外向內逐步進行的,轉變速度相對較慢;降低TO含量有利于生成較低熔點的CaO-MgO-Al2O3系夾雜物.

     

    Abstract: The control of oxygen content and composition and the transformation conditions of non-metallic inclusions in gear steel are calculated with the thermodynamic calculation software Factsage. The results show that the composition of non-metallic inclusions with high plasticity in 20CrMoH steel is as follows (mass fraction):SiO2 0% to 10%,Al2O3 22% to 55%,CaO 42% to 60%,and MgO 5% to 10%. Under this condition,the mass fraction of aluminum in molten steel is above 0.020%,that of calcium is above 0.7×10-6,and the activity of oxygen in molten steel is about 0.000 5%. If the compositions of refining slag with CaO > 40%, Al2O3 ≤ 37%, MgO 10%, (% CaO +% MgO)/% SiO2=10,and the SiO2 content as low as possible are selected,Al2O3 and MgO·Al2O3 in molten steel can transform into calcium aluminates with low melting point. It is found that the contents of TOat the end of LF and RH refining both decrease with the increase in slag basicity,and the content of TOdecreases with increasing the content of Al2O3 in the slag. In the refining process,the composition of the non-metallic inclusions changes in order of "inclusions of the Al2O3 system→inclusions of the MgO-Al2O3 system→inclusions of the CaO-MgO-Al2O3 system",among which the change of inclusions of the MgO-Al2O3 system to inclusions of the CaO-MgO-Al2O3 system is inwardly from the outside surface and the reaction speed is relatively slower. Thus,at the end of the ladle furnace refining (LF),there are still many unchanged MgO-Al2O3 system inclusions. The TOcontent of the steel significantly affects the composition change of the inclusions and decreasing TOcontent favors the change of inclusions.

     

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