大热输入焊接用钢冶炼过程Mg-Al-Ti类夹杂物的演变规律

Evolution Law of Mg-Al-Ti Inclusions in Smelting Process of High Heat Input Welding Steel

针对国内某钢厂生产的大热输入焊接用钢,对其精炼(钢包炉精炼、钢液真空循环脱气)及连铸工序节点钢液取样,采用ASPEX及JSM-6510LV型扫描电镜研究大热输入焊接用钢中Mg-Al-Ti类夹杂物的数量、尺寸、成分和类型的演变规律。结果表明:钢包炉精炼过程钢液夹杂物中Al2O3含量下降,MgO含量上升,夹杂物类型由硅锰氧化物转变为Mg-Al-Ti类复合夹杂;钢包炉精炼加Ca后,夹杂物中Al2O3含量上升,MgO含量下降;钢液真空循环脱气至连铸过程夹杂物类型无明显变化,夹杂物中Al2O3和MgO含量变化不大,CaO与CaS含量上升;连铸样中粒径在0.5~5μm的夹杂物占95%以上,夹杂物主要以Mg-Al-Ti类复合夹杂的形式存在。

In view of the high heat input welding steel produced by a domestic steel plant,the liquid steel samples of refining(ladle furnace refining,liquid steel vacuum circulation degassing)and continuous casting process nodes were taken.The evolution of quantity,size,composition and type of Mg-Al-Ti composite inclusions in high heat input welding steel were investigated with ASPEX and JSM-6510LV scanning electron mcroscopy.The results show that the content of Al2O3 in inclusions decreases,while the content of MgO increases,and the type of inclusions is changed from silicon manganese oxide toMg-Al-Ti composite inclusions in the process of ladle furnace refining.After adding Ca in ladle furnace refining,the content of Al2O3 in inclusions increases and the content of MgO decreases.There is no obvious change in inclusion types from vacuum degassing to continuous casting,and the contents of Al2O3 and MgO in inclusions has little obvious change,while the contents of CaO and CaS increases.The inclusions with particle size of 0.5-5μmaccount for more than 95%in the continuous casting,and the inclusions mainly exist in the form of Mg-Al-Ti composite inclusions.