SWRCH22A冷镦钢脱氧过程中非金属夹杂物生成热力学及工业实践

A study on the thermodynamics and industrial practice of the formation of non-metallic inclusions in SWRCH22A cold heading steel during deoxidation process

文中通过热力学软件FactSage7.0和工业实践,对1873K下SWRCH22A冷镦钢脱氧过程中非金属夹杂物生成热力学进行研究.计算结果表明,当冷镦钢中[Al]含量增加到2×10-6以上时,平衡时钢中对应生成液态夹杂物、MnO·Al2O3和Al2O3,表明冷镦钢出钢过程应先加铝再加锰以降低精炼渣的氧化性.当冷镦钢中的[Mg]含量超过0.5×10-6时,钢中夹杂物由Al2O3转变为MgO·Al2O3;当钢中的[Mg]含量超过约9×10-6时,钢中夹杂物主要为MgO;随着钢中[Al]含量的提高,生成尖晶石夹杂物所需的最小[Mg]含量逐渐增大.当冷镦钢钢液中[Ca]含量超过约1.3×10-6时,钢中生成的夹杂物主要为液态钙铝酸盐;当钢液中的[Ca]超过约13×10-6时,钢中开始生成固态CaO夹杂物.冷镦钢中形成液态钙铝酸盐夹杂物所需的最小[Ca]含量随着钢中[Al]含量的提高逐渐增大.实验检测和热力学计算结果基本吻合,此外,研究发现,纯铁液的脱氧热力学与冷镦钢差异较大,因此,不能采用纯铁液的脱氧热力学指导冷镦钢生产实践.

Based on the thermodynamic software FactSage 7.0 and industrial practice, thermodynamics of the formation of non-metallic inclusions in SWRCH22A cold heading steel during deoxidation process at the temperature of 1 873 K was studied in this paper. The calculation results showed that when the [Al] content in cold heading steel increased to above 2×10-6, liquid inclusions, MnO·Al2O3 and Al2O3 were formed when the system reached equilibrium, which indicated that Al grains should be added before Mn during tapping process to lower the oxidation of refining slag;When the [Mg] content in cold heading steel exceeded 1.3×10-6, inclusions in steel shifted from Al2O3 to MgO·Al2O3;When the content of [Mg] exceeded 9×10-6, MgO became the main inclusions in steel;With the increase of [Al] content in steel, the minimum [Mg] content necessary for the formation of MgO·Al2O3 inclusions increased;When the [Ca] content in molten steel exceeded 1.3×10-6, liquid calcium aluminate became the main inclusions in steel;When the [Ca] content in molten steel exceeded 13×10-6, solid CaO inclusions began to form in the steel. With the increase of [Al] content in steel, the minimum [Ca] content necessary for the formation of liquid calcium aluminate inclusions increased. Experimental results were basically in agreement with thermodynamic results. Besides, it was found that the deoxidation thermodynamics of pure molten iron highly deviated from that of cold heading steel, indicating the former could not be applied to the industrial practice of cold heading steel.