电渣液态浇注空心钢锭的数值模拟

建立了电渣液态浇注空心钢锭体系三维准稳态数学模型,利用商业软件ANSYS与CFX进行顺序耦合求解,得到了电渣液态浇注空心钢锭过程的电场、磁场、温度场与流场.计算结果表明,由于采用了导电结晶器技术,渣池电位、焦耳热分布、磁场分布、流场分布与温度场分布等均有别于传统电渣重熔过程.渣池高温区位于外结晶器壁附近,远离渣金界面,最高温度为2 113 K.渣池流场存在两个漩涡,浮力为主要的驱动力,熔渣最大速度为0.068m.s-1.金属熔池呈浅平状,有利于提高空心钢锭的凝固质量.     

Growth characteristics of directionally solidified Al2O3/YAG/ZrO2 ternary hypereutectic in situ composites under ultra-high temperature gradient

Oxide eutectic ceramic in situ composites have attracted significant interest in the application of high-temperature structural materials because of their excellent high-temperature strength,oxidation and creep resistance,as well as outstanding microstructural stability.The directionally solidified ternary Al2O3/YAG/ZrO2 hypereutectic in situ composite was successfully prepared by a laser zone remelting method,aiming to investigate the growth characteristic under ultra-high temperature gradient.The microstructures and phase composition of the as-solidified hypereutectic were characterized by using scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and X-ray diffraction(XRD).The results show that the composite presents a typical hypereutectic lamellar microstructure consisting of fine Al2O3 and YAG phases,and the enriched ZrO2 phases with smaller sizes are randomly distributed at the Al2O3/YAG interface and in Al2O3 phases.Laser power and scanning rate strongly affect the sample quality and microstructure characteristic.Additionally,coarse colony microstructures were also observed,and their formation and the effect of temperature gradient on the microstructure were discussed.     

电渣重熔1Mn18Cr18N护环钢补缩过程的温度变化规律

以电渣重熔准稳态过程的温度场为初始条件,采用ANSYS与CFX商业软件相结合的方法,研究分析了电渣重熔补缩过程中的温度分布,考察了无补缩操作、直线降流方式和阶梯降流方式三种条件下电渣锭热节的最终位置.结果表明:在无补缩操作条件下,电渣锭热节附近糊状区离渣-金界面的最远距离为162 mm,直线降流方式距离为130 mm,大阶梯降流方式距离为70 mm,而小阶梯降流方式的热节位置几乎保持不变.因此,阶梯降流方式更有利于1Mn18Cr18N护环钢电渣重熔补缩工艺的顺利进行.     

电极插入深度对电渣重熔过程影响的数模研究

以电渣重熔系统电极、渣池和钢锭为研究对象,利用有限元分析软件求得稳定电渣重熔过程电磁场和焦耳热场分布,并通过计算流体动力学软件模拟分析了耦合电磁场和焦耳热场的三维电渣重熔过程在不同电极插入深度下温度场、速度场和电磁场的变化.结果表明:当电极插入深度为15 mm时,渣池两侧的逆时针方向旋转涡流之间出现一个顺时针方向旋转涡流,其尺寸随着电极插入深度的增加而增加;电极插入深度每增加15 mm,湍流动能的降幅约为21%,而最大温度值的降幅约为1%.     

钢筋电渣压力焊接头质量问题分析

分析了钢筋电渣压力焊接头的质量问题及其发生原因：通过因果分析， 获得了影响电渣压力焊不合格的因素，提出了解决方法，同时，系统地分析了产生的原因，并指出施工现阶段现场质量监理工程师预防质量缺陷发生应采取的预防措施。     

Characteristics of Al2O3, MnS,and TiN inclusions in the remelting process of bearing steel

The Al2O3, MnS, and TiN inclusions in bearing steel will deteriorate the steel's mechanical properties. Therefore, elucidating de-tailed characteristics of these inclusions in consumable electrode during the electroslag remelting process is important for achieving a subse-quently clean ingot. In this study, a confocal scanning violet laser microscope was used to simulate the remelting process and observe, in real time, the behaviors of inclusions. The obtained images show that, after the temperature exceeded the steel solidus temperature, MnS and TiN inclusions in the specimen began to dissolve. Higher temperatures led to faster dissolution, and the inclusions disappeared before the steel was fully liquid. In the case of an observed Al2O3 inclusion, its shape changed from angular to a smooth ellipsoid in the region where the solid and liquid coexisted and it began to dissolve as the temperature continued to increase. This dissolution was driven by the difference in oxygen potential between the inclusion and the liquid steel.     

Activity coefficients of NiO and CoO in CaO-Al2O3-SiO2 slag and their application to the recycling of Ni-Co-Fe-based end-of-life superalloys via remelting

To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni–Co–Fe-based end-of-life (EoL) superalloys, knowledge of their activity coefficients in slags is essential. In this study, the activity coeffi-cients of NiO and CoO in CaO–Al2O3–SiO2 slag, a candidate slag used for the EoL superalloy remelting process, were measured using gas/slag/metal equilibrium experiments. These activity coefficients were then used to consider the recycling efficiency of nickel and cobalt by remelting EoL superalloys using CaO–Al2O3–SiO2 slag. The activity coefficients of NiO and CoO in CaO–Al2O3–SiO2 slag both show a positive deviation from Raoult’s law, with values that vary from 1 to 5 depending on the change in basicity. The activity coefficients of NiO and CoO peak in the slag with a composition near B = (%CaO)/(%SiO2) = 1, whereB is the basicity. We observed that controlling the slag composition at approximatelyB = 1 effectively reduces the cobalt and nickel oxidation losses and promotes the oxidation removal of iron during the remelting process of EoL superalloys.     

激光区熔定向凝固Al2O3/YAG/ZrO2共晶自生复合陶瓷的显微组织与断裂韧性

采用激光区熔定向凝固技术制备Al2O3/YAG/ZrO2共晶自生复合陶瓷,研究其在超高温度梯度、不同激光工艺条件下的快速凝固组织特征及其相互影响,并对其力学性能以及增韧机制进行了分析. 研究结果表明:(1)激光区熔定向凝固Al2O3/YAG/ZrO2共晶由α-Al2O3、YAG以及ZrO2三相组成,不存在其他相以及相间晶团. 各相均匀连续分布,耦合生长,呈网状结构,是典型的快速凝固层片状非规则共晶组织. (2)在一定的激光功率密度下,共晶间距随扫描速度的增大急剧减小,最小间距仅为0.2～0.3 μm. (3)Y2O3在ZrO2中具有一定的固溶度,固溶程度不同时,ZrO2呈现不同的形貌. (4)定向凝固Al2O3/YAG/ZrO2共晶陶瓷的硬度高达18.67 Gpa,室温断裂韧性为8.0 Mpa·m1/2. 第三组元ZrO2的加入、相的小尺寸效应以及裂纹分叉是韧性增强的主要原因.     

电渣重熔用无氟渣系设计中的一些问题

根据电渣重熔过程渣池-渣壳间平衡关系的特点,以相图为工具,讨论了国外无氟渣系设计中的一些问题,指出无氟渣的理想组成首先应考虑所形成的共晶或同份化合物的组成。     

电渣重熔对42 CrMo 钢中夹杂物的影响及 CCT 曲线研究

采用BX51M型金相显微镜和和Image Pro-Plus软件研究电渣重熔后优化成分的42CrMo钢中非金属夹杂物情况,并在Gleeble3000热模拟机上测定其连续冷却相转变( CCT)曲线.研究结果表明：电渣重熔后明显减少钢中夹杂物的数目,改善钢中夹杂物的尺寸,夹杂物去除率达到71.90%;同时根据热膨胀曲线和金相组织绘制出42CrMo钢的CCT曲线,冷却速度较低时组织为铁素体、珠光体和贝氏体,冷却速度较大时组织为马氏体和少量贝氏体.