高级别管线钢夹杂物控制研究

Study on inclusion control of high grade pipeline steel

针对管线钢夹杂不合的问题,提出了管线钢夹杂物控制目标为Al2O3-CaS系固态夹杂物,并系统研究了钢液成分对此类夹杂物生成的影响与定量关系。研究结果表明,钙处理后Al2O3-CaS夹杂物存在两种形成机理,通过调整Ca、S、T[O]成分可实现对不同类型夹杂的精确控制。随着钢中Ca/T[O]质量分数比的增加,夹杂物中Al2O3含量显著降低;当Ca/T[O]质量分数比小于0.5时,钢中夹杂物主要以Al2O3夹杂为主;当Ca/T[O]质量分数比介于0.5~1.5之间时,夹杂物主要以Al2O3-CaS复合夹杂物为主;当Ca/T[O]质量分数比大于1.5时,夹杂物主要以CaO-CaS复合夹杂物为主。工艺优化后,高级别管线钢夹杂物初检不合格率由3.12%降低至1.54%,高级别管线夹杂物评级全部不大于1.5的比例由90%提高至95.4%。

Based on the comparative analysis of inclusions control of pipeline steel at home and abroad, the objective of inclusion control of pipeline steel is proposed to be solid inclusions of Al2O3-CaS system, and the influence and quantitative relationship of liquid steel composition on the formation of such inclusions are systematically studied. The results show that there are two formation mechanisms of Al2O3-CaS inclusions after calcium treatment. The precise control of different types of inclusions can be achieved by adjusting the composition of Ca, S, T[O]. With the increase of Ca/T[O] ratio in steel, the content of Al2O3in inclusions decreases significantly. When the Ca/T[O] ratio is less than 0.5, the inclusions in steel are mainly composed of Al2O3. When the Ca/T[O] ratio is between 0.5 and 1.5, the inclusions are mainly composed of Al2O3-CaS. When the Ca/T[O] ratio is greater than 1.5, the inclusions are mainly composed of CaO-CaS. After the process optimization, the unqualified rate of inclusions in high grade pipeline steel is reduced from 3.12% to 1.54%, and the proportion of inclusions in all high-level pipeline steel less than 1.5 level is increased from 90% to 95.4%.