电渣重熔大型板坯的质量控制

电渣重熔大型板坯的内部质量问题主要是氢含量的控制和偏析的控制;电渣重熔大型板坯的表面质量问题主要为波纹、重皮或漏渣以及凹陷或铸锭不饱满等表面缺陷.本文旨在总结前人工作的基础上,结合生产实际探讨电渣重熔大型板坯的质量控制方法.     

电渣重熔大型板坯的质量控制

电渣重熔大型板坯的内部质量问题主要是氢含量的控制和偏析的控制;电渣重熔大型板坯的表面质量问题主要为波纹、重皮或漏渣以及凹陷或铸锭不饱满等表面缺陷.本文旨在总结前人工作的基础上,结合生产实际探讨电渣重熔大型板坯的质量控制方法.     

无氟渣电渣重熔及铸锭的凝固组织

采用不含氟组元的无氟渣;CaO 50％,Al_2O_350％及CaO48％,Al_2O_348％,MgO 4％的渣系进行电渣重熔,由于渣比电阻高,可以提高电效率,降低电耗,消除氟的污染。通过对铸锭组织结构的检测,证明无氟渣电渣重熔铸锭的二次枝晶间距与AHΦ—6渣相比略有减小。所以,无氟渣电渣重熔铸锭偏析程度小,组织致密、均匀。     

舞钢板坯电渣钢锭表面渣沟现象浅析

结合舞钢板坯电渣锭的生产实际,针对生产中出现的表面渣沟现象,从熔速、渣系、锭体冷却等方面进行了简单的剖析,并采取了相应的预防措施,取得了显著的效果。     

舞钢大型板坯电渣钢探伤不合综述与解析

从结晶器规格、钢种、季节等方面,对近3年舞钢大型板坯电渣钢探伤不合问题进行了综述和解析,并据此提出了工艺改进措施,取得了良好效果。     

板坯电渣锭双边缺陷的成因分析及解决途径

根据舞钢公司实际生产中遇到的电渣锭双边缺陷问题,探讨其产生机理,分析磁场力强弱、渣池深度、熔炼功率控制、自耗电极处理、渣系选择等主要影响因素,并提出解决途径。     

板坯电渣重熔炉结晶器报废原因分析及改进措施

着重对舞钢公司40 t板坯电渣重熔炉结晶器的报废原因进行了分析研究,阐述了针对该类型结晶器所制定的维护、修复与报废标准,同时提出了延长结晶器使用寿命和降低结晶器使用成本方面的一些措施和设想展望。     

本钢板坯连铸结晶器保护渣国产化研究

本文从连铸结晶器保护渣的实际出发，对保护渣使用条件及最终的确定做了全面阐述，并对结果做了认真的分析。     

新钢板坯连铸用保护渣的开发

介绍了新钢板坯连铸的凝固特点及对保护渣性能的要求。研制开发出了板坯连铸用保护渣。工业试验表明：研制的保护渣具有良好的使用效果。     

电渣重熔板锭的温度场计算

建立了电渣重熔板锭过程的非稳态模型,计算了板锭重熔过程中的温度场,得到不同熔速、不同重熔时刻的熔池深度;分析了影响熔池深度的主要因素及板锭的凝固规律,计算表明:熔速是影响熔池深度的最大因素,当铸锭到达一定高度时,系统处于准稳定状态,熔池深度不再变化.同时铸锭底部的冷却条件对熔池深度影响不大.     

电渣重熔工艺对GH4169脱硫的影响

 为进一步降低GH4169中的硫含量,进行了大气下、氩气氛保护及氩气氛保护下向渣池加钙精炼3种工艺条件对脱硫效果影响的电渣重熔试验。结果表明,大气下重熔时脱硫效果明显,硫含量(质量分数,下同)由18×10-6降低到6×10-6,渣中的硫通过气化反应脱除;氩气氛保护不利于电渣重熔工艺的脱硫,硫含量降低到7×10-6后提高到9×10-6,熔渣中的硫不断富集;硫分配比的计算值与实测值的对比研究表明,电渣重熔脱硫热力学条件优越,动力学条件是限制实际脱硫效率进一步提高的主要因素;氩气氛保护下通过向渣池加钙后,熔渣中钙元素能够对合金进行脱硫且脱硫率有较大幅度的提升,合金中硫含量随钙含量的增加而减少,重熔结束时硫含量降至3×10-6。     

Mathematical Model for Electroslag Remelting Process

 A mathematical model, including electromagnetic field equation, fluid flow equation, and temperature field equation, was established for the simulation of the electroslag remelting process. The distribution of temperature field was obtained by solving this model. The relationship between the local solidification time and the interdendritic spacing during the ingot solidification process was established, which has been regarded as a criterion for the evaluation of the quality of crystallization. For a crucible of 950 mm in diameter, the local solidification time is more than 1 h at the center of the ingot with the longest interdendritic spacing, whereas it is the shortest at the edge of the ingot according to the calculated results. The model can be used to understand the ESR process and to predict the ingot quality.     

Numerical Study on the Effect of Low-Frequency Power Supply on Desulfurization in the Electroslag Remelting Process

In the electroslag remelting (ESR) process, low-frequency power supply can significantly reduce power consumption and achieve three-phase balance of power supply. Therefore, a transient coupling model of fluid flow, heat transfer, and component transport in the ESR process, which is coupled to the electromagnetic field calculated using Maxwell 3D software, is established to study the influence of low-frequency power supply on desulfurization. When a 50 Hz power supply is used, a skin effect is observed in the metal, and the direction of the Lorentz force at the slag/metal interface changes. However, this effect becomes less pronounced with decreasing current frequency. Sulfur is mainly transferred at the electrode tip, and the desulfurization rate is approximately 50%. Electrochemical reactions mainly occur at the electrode tip/slag interface and the metal pool/slag interface. The removal rate of sulfur using direct current (DC) power supply is less than that using an alternating current power supply. The DC reverse polarity power supply leads to higher desulfurization rate than DC straight polarity, which is 74% and 31%, respectively. The sulfur removal rate increases from 81.37% to 84.59% as the frequency decreases from 50 to 2 Hz because of the longer electrochemical reaction time at this lower frequency.     

Hydrogen Pick-Up During Electroslag Remelting Process

  The pick up of hydrogen during electroslag remelting process for several slags consisting of CaF2 Al2O3 CaO SiO2 MgO had been investigated. The laboratory scale remelting experiments had been carried out in open air and water free argon atmosphere, and then the influencing factors were analyzed. It had been found that the hydrogen content in steel varied with different slag compositions. The compositions and state of slag had significant effect on the hydrogen level in steel. Partial return slag and premelted slag could avoid the hydrogen pick up especially in the early stages of the process. However, premelted slag was the optimum state to control the hydrogen pick up in steel. Experimental results indicated that water free argon atmosphere was very favorable to the control of hydrogen in steel in the normal remelting period.     

电渣连铸技术的开发

在结合电渣重熔和连铸技术优点的基础上。东北大学钢铁冶金研究所采用双极串联、交换电极及在线切割等技术，在国内首次成功地开发了电渣连铸（ESCC）技术；解决了电渣重熔钢锭直径小于300mm时熔速很慢、冶炼费用很高的难题。通过对重熔方坯质量的低倍、高倍、夹杂物检验等分析表明，该技术生产的方坯表面质量和内部质量良好，具有广泛应用前景和经济价值。     

Segregation of Niobium During Electroslag Remelting Process

 Experiment was carried out after the process parameters were calculated by the model previously established. The relationship between interdendritic spacing and local solidification time (LST) mainly determined by process parameters was exposed. Furthermore, the extent of segregation was studied. The results indicate that LST and interdendritic spacing are the largest and the amount of Laves phase as a result of the niobium segregation is the highest in the center of the ingot, whereas the opposite results are obtained at the edge of ingot. The extent of element segregation and the amount of Laves phase can be reduced when appropriate parameters are used. Therefore, the duration of subsequent homogenization treatments for 718 is shortened and the alloy quality is improved.     

Mechanism of Slag Composition Change During Electroslag Remelting Process

 The mass loss rate of CaF2-CaO-Al2O3-SiO2-MgO slag system originated from ANF-6 was studied with CaF2, CaO, Al2O3, SiO2 or MgO content as variables. The method of quadratic regression orthogonal design was used for the design and analysis of the experiment. The experimental results indicated that mass loss rate of slag can be increased by 6% with CaF2 changing from 50% to 65%. Mass loss increases with SiO2, Al2O3 and MgO adding and decreases with CaO content increasing. Because of the reaction between oxide and fluoride in the slag pool, apparent mass loss of CaF2-Al2O3-CaO-SiO2-MgO slag system appears at melting point. This will cause obvious composition change of electroslag. In addition, the segregation occurs in the slag skin forming process. This is another reason causing the composition change of electroslag.     

Effect of Low-Frequency AC Power Supply During Electroslag Remelting on Qualities of Alloy Steel

The effect of frequencies of AC power supply on the quality of the electroslag-melted ingot is studied. The results show that with a decrease in the frequency, electromagnetic force becomes more violent, and the temperature in the slag bath becomes more homogeneous, and therefore, the depth of molten metal pool is decreased; electrochemical reactions occur with the decrease in the frequency, and the atomic oxygen electrolyzed dissolves in the molten metal pool; the nonmetallic inclusions, which are distributed dispersively in the ingot, have an increased content,and their size is approximately in the range of 2-3 μm.