镁系合金在钢水精炼中作用的研究

STUDY ON THE POTENTIAL OF MAGNESIUM-CONTAINING ALLOYS IN REFINING TREATMENT OF LIQUID STEEL

在实验室条件下,研究了镁在钢水精炼中的作用。探讨了含镁合金(NiMg、MgAl、CaMgRE和MgRE)在脱硫,去气及非金属夹杂物变性等方面的冶金规律,并与SiCa合金的精炼效果进行了对比。结果表明,镁合金对钢水有良好的净化效果。转子钢经镁处理后钢中全氧量可达5 ppm的超低水平。在α_(?)/α_0。值较高时,镁在脱氧的同时也有一定的脱硫作用。在中性气氛下用镁精炼钢水有明显的脱氮效果,氮的去除与镁气泡的上浮有密切关系。镁处理后钢中夹杂物形态及分布基本得到控制,典型的夹杂物为细小,弥散分布的球形氧硫复合夹杂物。实验证实镁有固磷,固氮及细化二次枝晶臂的作用。一定冷却条件下二次枝晶间距与钢中残镁量的关系可用幂函数表示。镁处理对改善钢材的高温塑性有益。

Refining experiment was carried out in laboratory to study the potential of magnesium as a refining agent in liquid steel and the metallurgical effects of magnesium-containing alloys in deoxidation, desulphuri-zation and inclusion modification. Some comparision with SiCa was also given. Results indicate that magnesium has a good effect on purifying liquid steel. 5ppm of total oxygen in rotor steel was obtained after magnesium treatment. At higher ratio of S content to O content, a reasonable effect of magnesium on desulphurization was obtained simultaneously with deoxidization. Under inert atmosphere, the average efficiency of denitrogenation was 52%. The removal of nitrogen from steel was closely related to the floatingup action of magnesium bubbles. The distribution and morphology of in elusions were essentially controlled by the addition of magnesium. Typic inclusions after magnesium treatment were small, discrete and globular complex inclusions. The role of magnesium in nitrogen fixation, phosphorus fixation and refining second dendrite arm was also proved experimentally. And a regression equation in the form of power function was obtained to express the relationship between the second dendrite arm and the residual magnesium content. After magnesium treatment the ductility of steel was increased at high temperature.