提高26t中间包覆盖剂碱度改善管坯质量的生产实践

Production Practice for Improvement of Quality of Tube Bloom by Increasing Basicity of 26 t Tundish Covering Powder

生产试验钢种26CrMo4,30Mn5和30Mn6V的冶金流程为150 t EAF-LF-VD-Φ210~310 mm管坯连铸。从6炉钢使用原低碱度中间包覆盖剂和15炉高碱度覆盖剂(/%:9.2MgO,0.87Fe_2O_3,44.03CaO,7.53SiO_2,18.68Al_2O_3)冶炼的钢中夹杂物的分析结果表明,使用现有低碱度中间包覆盖剂钢中Al含量从VD弱搅结束后到中间包衰减5×10^(-6)~35×10^(-6),平均Al含量减少25×10^(-6),而使用碱度为6中间包覆盖剂衰减10×10^(-6)~20×10^(-6),使用原覆盖剂VD到中间包300 mm^2钢样上1~10μm夹杂物明显增多,>10μm夹杂物减少,而使用碱度为6覆盖剂VD到中间包相同面积钢样上1~10μm夹杂物减少,>10μm夹杂物明显减少,表明碱度为6的中间包覆盖剂比原覆盖剂更适合纯净钢生产。

The metallurgy flowsheet of tested production steel grades 26CrMo4, 30Mn5 and 30Mn6V is 150 t EAF- LF-VD-Ф210 -310 mm tube bloom casting. The results of analysis on inclusions in steels steelmaking by 6 heats using o- riginal low basicity tundish covering powder and by 15 heats using high basieity tundish coveting powder （/% ： 9. 2MgO, O. 87Fe203,44.03CaO, 7.53SiO2, 18.68Al2O3 ） show that with using original low basicity tundish covering powder, the A1 content in liquid from end VD soft stirring to tundish decreases by 5× 10 -6 - 35 ×10 -6, average A1 content decreases by 25 × 10 -6, but that with using basieity 6 tundish covering powder decreases by 10 ×10 -6 - 20 × 10 -6 ; with using origi- nal covering powder the amount of 1- 10μm inclusions in steel sample at 300 mm2 area increases obviously from VD to tundish and that of 〉 10 μm inclusions decreases, but with using basicity 6 tundish coveting powder the amount of 1 -10 μm inclusions in steel sample at same area decreases from VD to tundish and that of 〉 10μm inclusions decreases obviously, it indicates that as compared with original covering powder the basicity 6 tundish coveting powder is more suitable for steelmaking of clean steel.