电渣重熔过程电源频率对电渣锭洁净度的影响

 电渣重熔采用低频供电可以提高功率因数、降低电耗,并实现电力系统的三相平衡。然而,其对电渣锭冶金质量特别是洁净度的影响还缺乏足够的数据支撑。为了研究电源频率特别是低频操作对电渣重熔锭洁净度的影响,采用实验室小型低频电渣重熔炉,以304奥氏体不锈钢、GCr15轴承钢为研究对象,详细分析了不同的电源频率对电渣锭化学成分、气体含量、夹杂物分布的影响规律。研究结果发现,与工频电渣重熔相比,不论是不锈钢还是轴承钢,当采用低频电源(2、1、0.4、0.1 Hz)电渣重熔后(在其他工艺参数如渣系、渣量、电流、电压、气氛等完全相同的情况下), 电渣锭中的氧质量分数(0.010%～0.013%)大幅增加,对氮含量影响很小。电渣锭中的铝含量明显增加,而其他化学成分变化很小。与此相对应,低频电渣重熔锭的夹杂物数量也明显增加,且增加的夹杂物主要以氧化铝为主,但是夹杂物主要以小于10 μm的细小夹杂为主,大颗粒夹杂物略有增加,但是数量较少。氧含量增加的主要原因是低频电源的直流倾向增大,使重熔渣池中的氧化铝发生了电解(30%Al₂O₃+70%CaF₂渣系),在钢中氧含量增大的同时,铝含量也明显增加;氧化铝电解形成的铝和氧进入金属熔池造成电渣锭全氧含量增加。氧和铝随着金属熔池的降温及凝固形成氧化铝夹杂残留在电渣锭中。工业生产过程中低频电源的直流电解效应还有待进一步分析。

Influence of power frequency on cleanliness of electroslag ingot during electroslag remelting process

In the process of electroslag remelting, low-frequency power supply can improve power factor, reduce power consumption and realize three-phase balance of power system. However, the influence of power frequency on the metallurgical quality of electroslag ingot, especially the cleanliness, is still lack of sufficient data support. Based on the small-scale low-frequency electroslag remelting experiments in the laboratory, the effects of different power supply frequencies, especially low supply frequencies on the cleanliness of ingot were studied and the effect lows of power frequencies on chemical composition, oxygen and nitrogen content, inclusion distribution in the 304 austenitic stainless steel and GCr15 bearing steel electroslag ingots were analyzed in detail. The results show that compared with power frequency electroslag remelting, when low frequency (2, 1, 0.4, 0.1 Hz) electroslag remelting is adopted for both stainless steel and bearing steel (other experimental parameters such as the composition and weight of slag, smelting current and voltage, remelting atmosphere etc, are exactly the same), the oxygen content in electroslag ingots increases greatly, both between 0.010% and 0.013%. But the frequency variation has little effect on nitrogen content. The content of aluminum in electroslag ingot also increases significantly, while other chemical compositions change little. Correspondingly, the number of inclusions in low frequency electroslag ingot also increases significantly, and the increased inclusions are mainly alumina. However, the inclusions are mainly small inclusions less than 10 μm, the large inclusions increase slightly, but the number is very small. The main reason for increase of oxygen content is that the DC effect of low-frequency power supply causes the electrolysis of alumina in the remelting slag pool (30% Al₂O₃+70% CaF₂ slag system) which leads to the increase of aluminum and oxygen content. The total oxygen content of ESR ingot increases when the aluminum and oxygen formed by alumina electrolysis enter the molten metal pool. With the cooling and solidification of metal pool, oxygen and aluminum form alumina inclusions, which remain in the electroslag ingot. The DC electrolysis effect of low-frequency power supply in industrial production needs to be further analyzed.