石油套管钢中镁铝尖晶石的形成与改性

Formation and Modification of MgO·Al_2O_3 Spinel in Oil Casing Steel

通过石油套管钢的工业试验及热力学分析,研究精炼过程中镁铝尖晶石的形成和改性机理。结果表明：当钢液中溶解铝分别为0.02%和0.05%时,溶解镁只要达到1.5×10-6和2.8×10-6,钢中便有镁铝尖晶石生成;钢液中溶解铝0.02%,镁含量为4×10-6~8×10-6时,钢中溶解钙含量只要分别达到0.21×10-6和0.42×10-6,钢液中的镁铝尖晶石便开始向液态钙铝酸盐转变;镁铝尖晶石比氧化铝更容易改性为液态夹杂物;钢液精炼过程中夹杂物受钢渣反应和钙处理的影响,按照Al2O3→MgO-Al2O3系夹杂物→Ca O-Al2O3-MgO或Ca O-Al2O3系液态复合夹杂物的过程演变。

The formation and modification mechanism of MgO·Al2O3 spinel in oil casing steel during secondary refining process was studied by industrial experiments and thermodynamic calculations.The results show that when dissolved Al are 0.02% and 0.05% respectively,the required amount of dissolved Mg for the formation of MgO · Al2O3 spinel are 1.5 × 10-6and 2.8 × 10-6accordingly.For molten steel with0.02% dissolved Al,When the dissolved Mg ranges from 4 × 10-6to 8 × 10-6,MgO·Al2O3inclusions would transform into Ca O-Al2O3-MgO system inclusions under dissolved Ca content of 0.21 × 10-6and 0.42 × 10-6respectively.MgO·Al2O3spinel inclusions could be easier modified than Al2O3 inclusions.Because of the influence of slag-metal reaction and calcium treatment,the evolution of inclusion could be roughly described as follows：Al2O3→MgO-Al2O3 system inclusions→Ca O-Al2O3-MgO or Ca O-Al2O3 system liquid complex inclusions.