CO_(2)/CO替代H_(2)O/H_(2)气氛制备高牌号硅钢可行性

Feasibility of CO_(2)/CO substitute for H_(2)O/H_(2) atmosphere for preparation of high-grade silicon steel

在国家“双碳”背景下,清洁能源发电得到了快速发展,高牌号无取向硅钢是发电机组应用最普遍的铁芯材料,其生产制备主要依赖长流程工艺。提出面向电炉短流程工艺,并以CO_(2)/CO替代H_(2)O/H_(2)作为固态脱碳气氛制备高牌号无取向硅钢,试验以硅质量分数为3.5%、碳质量分数为0.18%薄带钢为研究对象,利用热力学分析和实验室试验开展CO_(2)/CO和H_(2)O/H_(2)2种气氛制备硅钢对比研究。热力学分析结果表明,在CO_(2)/CO和H_(2)O/H_(2)2种气氛下存在生成Fe_(2)SiO_(4)的临界pH_(2)O/pH_(2)(H_(2)O与H_(2)的分压比)或pCO_(2)/pCO(CO_(2)与CO的分压比)值,将气氛条件控制在这一临界分压值以下可避免铁元素大量氧化。XRD测试结果表明,在1 423 K的脱碳温度下pH_(2)O/pH_(2)应控制为0.34以下、pCO_(2)/pCO应控制为0.22以下,可避免氧化层生成Fe_(2)SiO_(4);通过对钢带氧化层显微结构观察发现,脱碳气氛pCO_(2)/pCO=0.10时,氧化层厚度可控制为10μm,且氧化层可分为3层,为表面和靠近集体一侧的SiO_(2)层以及中间的Fe与圆球状SiO_(2)层,这是由于CO_(2)/CO气氛氧势相对较低,脱碳过程伴随着气氛中氧向基体内扩散和硅向基体外扩散;CO_(2)/CO气氛与H_(2)O/H_(2)气氛脱碳效果对比发现,由于CO_(2)/CO气氛氧化性弱于H_(2)O/H_(2)气氛,使得相同脱碳温度CO_(2)/CO气氛可以维持较高脱碳速率,在pCO_(2)/pCO=0.10气氛下,温度为1 423 K时,5 min可将0.3 mm厚钢带碳质量分数由0.18%脱至0.002 9%,在573 K回火1 h后,硅钢铁损P1.5/50为1.713 W/kg,磁感应强度B50为1.892 T,采用CO_(2)/CO作为固态脱碳气氛可制备出与H_(2)O/H_(2)气氛磁性能相当的硅钢,具有深入研究价值。

Under the background of the national"double carbon",clean energy power generation has been rapidly developed,high grade non-oriented silicon steel is the most common core material used in generator sets,and its production and preparation mainly rely on long process technology.In this paper,a short process oriented to electric furnace is proposed,and CO_(2)/CO is substituted for H_(2)O/H_(2) as a solid decarburization atmosphere to prepare high grade non-oriented silicon steel.The test takes the thin strip steel with silicon content of 3.5%and carbon content of 0.18%as the research object.A comparative study on the preparation of silicon steel under CO_(2)/CO and H_(2)O/H_(2) atmospheres was carried out using thermodynamic analysis and laboratory tests.The thermodynamic analysis results show that there is a critical pH_(2)O/pH_(2) or pCO_(2)/pCO value for the formation of Fe_(2)SiO_(4) in CO_(2)/CO and H_(2)O/H_(2) atmospheres,and a large amount of iron oxidation can be avoided if the atmosphere conditions are controlled below this critical partial pressure value.XRD test results show that at 1423 K decarburization temperature,pH_(2)O/pH_(2) should be controlled below 0.34,pCO_(2)/pCO should be controlled below 0.22,which can avoid the formation of Fe_(2)SiO_(4) oxide layer.According to the observation of the microstructure of the oxide layer of the steel strip,when the decarburization atmosphere pCO_(2)/pCO=0.10,the thickness of the oxide layer can be controlled to 10μm,and the oxide layer can be divided into three layers,namely the SiO_(2) layer on the surface and near the collective side,and the Fe and spherical SiO_(2) layer in the middle,because the oxygen potential of the CO_(2)/CO atmosphere is relatively low.The decarburization process is accompanied by the diffusion of oxygen and silicon into the matrix in the atmosphere.The comparison of the decarbonization effect between CO_(2)/CO atmosphere and H_(2)O/H_(2) atmosphere shows that due to the weaker oxidation of CO_(2)/CO atmosphere than H_(2)O/H_(2) atmosphere,the CO_(2)/CO atmosphere can maintain a higher decarbonization rate at the same decarbonization temperature.In the atmosphere pCO_(2)/pCO=0.10,the temperature is 1423 K.The carbon content of 0.3 mm thick steel strip can be removed from 0.18%to 0.0029%in 5 minutes.After 573 K tempering for 1 h,the loss of silicon steel P1.5/50=1.713 W/kg,magnetic induction intensity B50=1.892 T,using CO_(2)/CO as a solid state decarburization atmosphere can be prepared from silicon steel with magnetic properties equivalent to H_(2)O/H_(2) atmosphere,which has the value of further research.