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通过Aspex全自动扫描电镜观察“电炉→LF→VD→连铸”工艺生产8620RH非调质钢的全流程夹杂物变化情况,结合钢水中T.O、氮含量的检测结果,分析了冶炼过程中钢液洁净度的变化趋势。研究表明:8620RH非调质钢样品中氧化物夹杂的主要成分是Al_2O_3-Mg O-Ca O,以Al_2O_3为主。增硫操作之后,夹杂物中CaO含量降低,硫化物和氧硫化物含量明显升高。冶炼过程夹杂物中MgO含量逐渐升高,每个工序冶炼后期的样品中含MgO夹杂物数量均明显高于该工序初期,未检测到大尺寸的镁铝尖晶石类夹杂物。采用铝脱氧方式生产的8620RH非调质钢铸坯中平均w(T.O)=10.1×10-6,达到了很高的洁净度,氧化物夹杂数量较少,尺寸较小。铸坯和轧材中氧化物类夹杂物数量均在10个/mm~2以下。轧材中硫化物多以包裹在氧化物外部的形式存在,有利于提高产品的综合性能,但轧材中存在较大尺寸的硫化物,可以适当提高钢中的氧含量,形成更多细小弥散的氧化物核心,利于硫化物的析出,改善硫化物的形态,使产品具备更好的切削性能。
Through the Aspex automatic scanning electron microscope observation, the change of inclusions in the whole process of 8620RH non-quenched and tempered steel produced by the process of “electric furnace → LF → VD → continuous casting” was studied. According to the test results of TO and nitrogen content in molten steel, Steel liquid cleanliness trends. The results show that the main component of oxide inclusions in 8620RH non-quenched and tempered steel samples is Al 2 O 3 -Mg O-Ca O, which is dominated by Al 2 O 3. After the sulfur addition operation, the content of CaO in inclusions decreased and the content of sulfide and oxysulfide increased obviously. During the smelting process, the content of MgO in inclusions gradually increased. The amount of inclusions containing MgO in the samples after each process smelting were significantly higher than those in the initial stage of the process. Large-size Mg-Al spinel inclusions were not detected. The average w (T.O) of 8620RH non-quenched and tempered steel slab produced by aluminum deoxidation method is 10.1 × 10-6, which achieves high cleanliness, less oxide inclusions and smaller size. Slab and rolling material in the number of oxide inclusions are 10 / mm ~ 2 or less. Sulfide in the rolled material is mostly in the form of wrapping in the outer part of the oxide, which helps to improve the comprehensive performance of the product. However, there is a larger size of the sulfide in the rolled material, which can appropriately increase the oxygen content in the steel to form more finely dispersed Of the oxide core, which is conducive to the precipitation of sulfide, improve the morphology of sulfide, so that products have better cutting performance.