X80管线钢LF-RH二次精炼过程夹杂物行为及控制

Behavior and Control of Nonmetallic Inclusions in X80 Pipeline Steel during LF-RH Secondary Refining Process

研究了210 t BOF-LF-RH-CC工艺流程生产X80管线钢(%:0.041～0.044C、0.15Si、1.78～1.80Mn、0.007～0.010P、0.000 8～0.001 2S、0.039～0.047[Al]s)时精炼过程中夹杂物的变化。在BOF出钢阶段采用加Al强脱氧(0.01%～0.02%[Al]s),LF精炼过程采用高碱度、强还原性精炼渣(精炼渣成分%:50～58CaO、7～10MgO、20～25Al_2O_3、4～7SiO_2、0.5～1.4TFe),炉渣和钢液反应活跃,使得钢中Al_2O_3夹杂物很快向液态钙铝酸盐和部分液态CaO-MgO-Al_2O_3复合夹杂物转变。液态夹杂物通过碰撞、聚合、长大及上浮去除,提高了钢液的洁净度。浇铸前T[O]降到(7～10)×10^(-6),钢中夹杂物尺寸在3～5μm,试验炉次的热轧板内未发现大尺寸的低熔点钙铝酸盐类长条夹杂物。

The change of nonmetallic inclusions in X80 pipeline steel （% ： 0. 041 - 0. 044C, 0. 15Si, 1.78 1.80Mn, 0. 007 - 0. 010P, 0.000 8 - 0. 001 2S, 0. 039 - 0. 047 1 All s） produced by 210 t BOF-LF-RH-slab CC flow sheet during refining process has been studied. With adding A1 during BOF tapping for intensifying deoxidation （0. 01% - 0.02% [ Al] s） and using high basicity and reducibility refining slag （ingredient/% ： 50 -58CAO, 7 - 10MgO, 20 25A12Oa, 4 -7SiO2, 0. 5 -1.4TFe） in LF refining process to activate the slag-metal reaction, the Al2O3 inclusions in steel are quickly transformed to liquid calcium aluminates and part-liquid CaO-MgO-Al2O3 complex compound inclusions. The cleanliness of steel liquid is improved by liquid and part-liquid inclusions colliding with one other, agglomerating, coarsening and floating removing. Before casting the T[ O] decreases to （7 - 10） × 10^-6, the size range of inclusions in steel is 3 - 5μm and the large scale low melting point calcium aluminate stringer inclusion doesn＇ t be found in hot rolled plate of test heats.