X80管线钢LF-RH二次精炼过程夹杂物行为及控制

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、0.039～0.047Al]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、20～25Al₂O₃、4～7SiO₂、0.5～1.4TFe),炉渣和钢液反应活跃,使得钢中Al₂O₃夹杂物很快向液态钙铝酸盐和部分液态CaO-MgO-Al₂O₃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TO]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。

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

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 F Al] s) produced by 210 t BOF-LF-RH-slab CC flow sheet during refining process has been studied. With adding Al during BOF tapping for intensifying deoxidation (0. 01 % ? 0. 02% Al] s) and using high basicity and reducibility refining slag (ingredient /%: 50 ?58CaO, 7 ~ l0MgO, 20 ~ 25Al₂O₃, 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) x 10 ^-6, the size range of inclusions in steel is 3 ~ 5 μm and the large-scale low melting point calcium aluminate stringer inclusion doesn^,t be found in hot rolled plate of test heats.