Numerical simulation of transport phenomena in continuous casting of steel plates with electromagnetic brake

The present work numerically investigates two-dimensional (2-D) solidification transport phenomena (EM-STP) during continuous casting (CC) process in the absence and the presence of static magnetic fields (SMFs), based on a unified numerical model. For the purpose of controlling vortexes, the electromagnetic brake (EMBR) effects of various SMFs under the given depth of submerged entry nozzle (SEN) and the same casting velocity V0 are investigated. ANSYS software is used to analyze the SMFs that applied to the EMCC process, and then a data-conversion program based on the principle of linear interpolation proposed previously is used to deal with the issue of data-format-matching between FEM and FVM. The simulation results indicate that, an appropriate SMF can effectively suppress the bulk liquid flow in CC-process of steel plate, and with increase of the intensity of applied magnetic fields, the vortexes become weaker and the oscillating amplitude of impinging jet decreases. Based on the knowledge gained from the EMCC-STP analysis and by comparing the results with the applied magnetic fields with those without magnetic fields, it is found that a SMF with |Bmax|=55×10-3 T can meet the need of braking, and consequently improve the quality of casting by reducing the penetration of non-metallic inclusions, as well as avoiding breakout, macro-segregation and crack ultimately.     

ZL205A合金铸件中偏析的形成机理与预防措施

通过对ZL205A合金圆筒形铸件的3种铸造工艺的比较,分析了ZL205A合金铸件中线性偏析的形成条件、形成机理、预防措施。经优化浇注系统后,采用中空的砂芯等方式消除铸件热节和应力,成功消除了铸件的线性偏析。     

A Mathematical Model for Determination of Lamellar Spacing in Materials of Poly-Grain Microstructures

基于多晶材料球形晶粒的假设合金相理论的基础上,建立了的计算两相片状组织表观值与真实值定量关系的数学模型。结果表明,对于多数多晶材料其晶粒尺寸远大于片间距,片间距的平均表观值与真实值的比可以由修正系数k表征。片间距与晶粒尺寸比值从0.05减小到0.0001,k从1.5391增加到1.5707,k值逐渐接近于π/2。当片间距与晶粒尺寸的比值小于0.001时,可以认为k为常数π/2。本模型比传统方法在得到真实片间距过程中减少了工作量。     

行波磁场励磁电流对薄壁件充型和表面缩陷的影响

通过使用ansoft软件对筒形薄壁件在不同励磁电流的行波磁场作用下的电磁力进行了分析,进一步研究了行波磁场的励磁电流对合金充型能力以及铸件外表面缩陷的影响。结果发现:行波磁场影响合金充型能力的同时也影响了铸件凝固表面质量;随着励磁电流强度的增加,合金充型能力成平方倍的提高,同时也成平方倍的增加了铸件表面缩陷发生的几率;相同励磁电流强度下,励磁电流频率对合金充型能力存在最优值;励磁电流频率在1000 Hz以下变化时,随着励磁电流频率的降低铸件表面缩陷发生的可能性不断减小。     

Al-Si-Mg-Cu铸造铝合金高温拉伸性能研究

研究了一种Al-Si-Mg-Cu铸造铝合金分别在200、250℃的瞬时拉伸性能以及经200℃和250℃稳定化处理不同时间后的高温瞬时拉伸性能,并和已有标准中常用的Al-Si系耐热铸造铝合金的高温拉伸性能进行了对比。结果表明,随着测试温度的升高,Al-Si-Mg-Cu铸造铝合金的瞬时拉伸性能呈下降趋势;随着稳定化处理温度的升高和时间的延长,强度都呈下降趋势,200℃时伸长率基本不变,250℃时伸长率显著升高。200℃时,Al-Si-Mg-Cu铸造铝合金表现出良好的拉伸性能,明显优于其他常用Al-Si系耐热铸造铝合金。     

行波磁场对ZL205A合金薄壁铸件凝固缺陷和力学性能的影响

研究了凝固过程中局部加载行波磁场对ZL205A合金薄壁件缩孔、缩松和力学性能的影响。利用扫描电子显微镜对制备试样的显微组织进行分析,采用电子万能材料试验机对铸件力学性能进行测试。结果表明:与相同条件下获得的未施加行波磁场的铸件进行对比,施加行波磁场的铸件缩孔、缩松缺陷得到大幅改善;经过T6热处理后,抗拉强度、屈服强度、延伸率分别由436.61 MPa、390.22 MPa、3.29%提高到470.24 MPa、416.97 MPa、4.15%,抗拉强度和屈服强度分别提高了33.63 MPa、26.75 MPa,延伸率提高了26.14%。