梅山尾矿综合利用与无害化处置研究

梅山尾矿粒度细、含铁品位高,由于脱水困难,抑制了其在水泥中的应用。为解决梅山尾矿的堆存问题,结合梅山采选实际,提出梅山尾矿综合利用和无害化处置技术路径,开展了尾矿脱水工艺研究、微细粒级尾矿浓缩固化干堆研究。通过采用长锥旋流器和陶瓷过滤机联合脱水,可获得产率约70%的较粗粒尾矿用于水泥生产。旋流器溢流经超高压无耙浓密机处理,可获得浓度52%以上的膏体。固化剂MA和YX可以较好地固化膏体,固结体3、28 d的抗压强度分别超过0.20、0.70 MPa,且固结体不易泥化,可满足塌陷区的堆存要求。     

Improving the Solidified Structure by Optimization of Coil Configuration in Pulsed Magneto-Oscillation

Using both numerical and experimental methods, we studied the effect of coil configuration of pulsed magneto-oscillation (PMO) on distribution of electromagnetic field, flow field and solidification structure with the same pulse current parameters in Al ingots. We designed and constructed three types of coils: surface pulsed magneto-oscillation, hot-top pulsed magneto-oscillation (HPMO) and combined pulsed magneto-oscillation (CPMO). PMO treatment refined the solidification structure in all the ingots. The configuration of the PMO, however, introduced differences in magnetic field intensity, electromagnetic force, Joule heat, flow field, equiaxed grain zone, grain size and growth direction of columnar grains. The largest equiaxed grain zone was found in CPMO treated ingot, and the smallest grain size was found in both HPMO and CPMO treated ingots. Numerical simulation indicated that difference in electromagnetic field and flow field resulted in differences in solidification structure. HPMO is more advantageous over others for large ingot production.     

Dependency of eutectic spacings and microhardness on the temperature gradient for directionally solidified Sn–Ag–Cu lead-free solder

Sn–3.5 wt.%Ag–0.9 wt.%Cu alloy was directionally solidified upward at a constant growth rate (V = 7.20 μm s⁻¹) with different temperature gradients (G = 2.48–6.34 K mm⁻¹) by using a Bridgman type directional solidification furnace. The eutectic microstructures of directionally solidified Sn–3.5 wt.%Ag–0.9 wt.%Cu alloy were observed to be plate and rod structures from quenched samples. The values of eutectic spacings (λ) and microhardness (H_V) were measured from both transverse and longitudinal sections of the samples. The dependence of eutectic spacings (λ) and microhardness (H_V) on the temperature gradient (G) were determined by using linear regression analysis. According to these results, it has been found that, the value of λ decreases with the increasing the value of G and whereas, the value of H_V increases for a constant growth rate. The results obtained in the present work were also compared with the previous similar experimental results obtained for binary and ternary alloys.     

Enhanced heterogeneous nucleation in AZ91D alloy by intensive melt shearing

Intensive melt shearing was applied to the commercial AZ91D alloy melt to investigate its effects on grain refinement. Alloy melts with and without melt shearing were also filtered using a pressurized filtration technique to concentrate the potential nucleating particles for electron microscopic examination. The results showed that intensive melt shearing resulted in significant refinement of both the Al₈Mn₅ intermetallics and the primary α-Mg phase in the as-cast AZ91D alloy, and that this grain-refining effect is insensitive to the superheat and can persist even after prolonged isothermal holding. The pressurized filtration experiments showed for the first time that oxide films and skins consist of nano-sized MgO particles populated densely in a liquid matrix. Intensive melt shearing can effectively disperse such MgO particles throughout the alloy melt. The HRTEM investigation and detailed crystallographic analysis confirmed that dispersed MgO particles act as potent heterogeneous nucleation sites for both the Al₈Mn₅ and α-Mg phase.     

重轨钢连铸凝固末端位置研究及工艺优化

根据武钢第一炼钢厂重轨钢连铸生产条件,建立380 mm ×280 mm方坯凝固传热数学模型,并采用射钉法验证及修正。模拟结果表明,U71Mn和U75V钢的凝固末端各自位于距结晶器液面16.96～21.68 m和16.50～21.17 m;减弱二冷强度或增大拉速,U71Mn和U75V钢凝固终点均会明显后移。根据计算结果,二冷制度由弱冷(0.346 L/kg)改为超弱冷(0.218 L/kg),拉速采用0.7 m/min,应用1～4~#机架轻压下,压下量为5～7 mm,U71Mn和U75V钢凝固终点延长至21 m以上。连铸工艺优化后,重轨钢大方坯中心疏松Ⅰ级内平均合格率由89.64%提高到99.50%。     

The application of the homotopy perturbation method to one-phase inverse Stefan problem

In this paper, the application of the homotopy perturbation method for solving the inverse Stefan problem is presented. This problem consists in the calculation of temperature distribution in the domain, as well as in the reconstruction of the functions describing temperature and heat flux on the boundary, when the position of the moving interface is known.     

The Ag–Cu–Ge ternary phase diagram

The Ag–Cu–Ge phase diagram is not very well elaborated. In this work an attempt is made to validate the phase diagram in the area of the ternary eutectic and to decide whether it is a suitable model system for solidification experiments. The different steps in the solidification sequence are separately discussed and analysed. It is shown that an optimization of the system is necessary. The experiments in this work demonstrate that the transition reaction Ge is located closer to the ternary eutectic than assumed in earlier work.     

Application of mixture design to optimize cementation of simulated spent radioactive ion exchange resins

1 Introduction Cement solidification is a major immobilization technology for the treatment of radioactive waste like mining tails, evaporator concentrates, spent ion-exchange resins and so on. The current trend in cementation of wastes is toward maximizing waste loadings in resulting waste form on the premise of its performances meeting the acceptance criteria of in- terim storage or final disposal. For cement encapsula- tion of spent organic ion exchange resins, a consider- able amount of re…     

尾砂浓度对固化尾砂初始流动性和强度的影响

为更好地利用尾砂充填井下采空区,以南京铅锌银矿的尾砂为对象,研究了尾砂浓度对尾砂固化后初始流动性和强度的影响规律。结果表明：固化尾砂的初始流动性随尾砂浓度提高呈二次抛物线关系降低,固化尾砂的强度随尾砂浓度提高呈线性增长;在满足尾砂泵送能力的前提下,最大程度地提高尾砂的浓度可以有效减少水泥用量,降低固化成本。     

压力下凝固对真实压铸胀型力的影响

分析发现，在压力下凝固是影响真实压铸胀型力的主要因素，实际胀型力比金属完全处在液态条件下设备的额定胀型力要小得多，实验和批量生产证实了这一分析的正确性