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利用Factsage软件,对20CrMnTiH1齿轮钢中(CaO)m(Al2O3)n与CaS夹杂形成进行了热力学分析。结果表明:当钢中w(Al)S=0.035%时,要使钢中夹杂物完全转变为液态(CaO)12(Al2O3)7,应控制钢中w(S)低于0.006 7%,w(Ca)/w(Al)高于0.12;本钢液成分条件下,在炼钢温度下不会自发生成CaS夹杂,当钢液温度下降到1 739.8 K时,凝固前沿的w(S)达到0.015 9%,此时会与低熔点(CaO)12(Al2O3)7夹杂表面的CaO反应析出CaS夹杂。通过对某钢厂生产的20CrMnTiH1齿轮钢铸坯中夹杂物的检验发现,实际情况与热力学计算相符合。同时,通过硫偏析方程计算得到:20CrMnTiH1齿轮钢在凝固过程中不析出CaS夹杂的条件为将硫的初始质量分数控制在0.000 318%以下。
Thermodynamic analysis of inclusions of (CaO) m (Al2O3) n and CaS in 20CrMnTiH1 gear steel was performed with Factsage software. The results show that when the content of w (s) is equal to or less than 0.035%, the inclusions in the steel should be completely transformed into liquid (CaO) 12 (Al2O3) 7. (Ca) / w (Al) is higher than 0.12; CaS inclusions will not spontaneously occur at the steelmaking temperature under the conditions of the steel composition. When the molten steel temperature drops to 1739.8K, the w (S) at the solidification front reaches 0.015 9%. In this case, CaS will be precipitated by CaO reaction with CaO 12 (Al 2 O 3) 7 inclusion surface. The test of inclusions in 20CrMnTiH1 gear steel slab produced by a steel mill found that the actual situation is consistent with the thermodynamic calculation. At the same time, calculated by the sulfur segregation equation: 20CrMnTiH1 gear steel in the solidification process does not precipitate CaS inclusions in the condition of the initial sulfur content of 0.000 318% or less.