Recovering aluminum from aluminum dross in a DC electric-arc rotary furnace

The recycling of aluminum scrap and dross yields significant economic and energy savings, as well environmental benefits. The recovery of aluminum depends on many factors. The aim of this work is to experimentally investigate aluminum recovery under different conditions. In this study, aluminum dross was processed in a direct-current electric-arc rotary furnace. The presence of crushing refractory bodies during processing was found to increase the degree of aluminum recovery by about ten percent.     

Nanopowder synthesis of aluminum doped cadmium oxide via sol-gel calcination processing

The structural, optical and electrical properties of undoped and Al-doped CdO powder nanostructures prepared by sol-gel calcinations method have been investigated. X-ray diffraction (XRD) results revealed that pure and Al-doped CdO have the polycrystalline with face centered cubic (FCC) structure. The crystallite size for undoped and 5, 10, 15, 20% of Al-doped CdO samples were found to be 17.2, 15.9, 16.1, 16.3 and 16.8 nm, respectively. The optical band gap of the samples were determined from the diffused reflectance spectra and E_g values for undoped and 5, 10, 15, 20% of Al-doped CdO samples were found to be 1.89, 2.07, 2.03, 2.07 and 2.12 eV, respectively. The electrical conductivities of pure and Al-doped CdO were measured in the temperature range (290-420 K) and their temperature dependence was analyzed according to Arrhenius relation. The electrical conductivity results indicate that the electrical conductivity mechanism is controlled by thermally activated processes. The results showed that sol-gel calcinations technique can be effectively used to produce undoped and doped nanopowders.     

Al-SiC powder preparation for electronic packaging aluminum composites by plasma spray processing

Powders of pure aluminum (Al) with 55 and 75 vol.% SiC particles were ball milled in a conventional rotating ball mill with stainless steel and ZrO₂ balls for 1–10 h. The morphology and microstructure of the milled powders have been observed and analyzed by scanning electron microscopy (SEM) and energy dispersive x-ray (EDX). The milled powders were plasma sprayed onto a graphite substrate to obtain Al matrix composites with high SiC volume fraction. SiC particles in the milled powders existed in two forms; i.e., the combination of Al into composite powder and individual. Plastic Al particles were broken during ball milling, and fine Al particles can be coated onto the surface of SiC particles. Iron contamination in the milled powders occurred when stainless steel balls were used. The iron level can be effectively controlled by using ZrO₂ ball media. The milling efficiency by ZrO₂ balls is inferior to that by stainless steel balls. Longer milling time was required with ZrO₂ balls to achieve the same effect as obtained with stainless steel balls. SiC particles in the sprayed composites from the milled powders exhibited a reasonably uniform distribution and high volume fraction.     

Recovering plastics for recycling by mineral processing techniques

Patents and other literature on recycling post-consumer plastics from various sources (e.g., municipal solid waste) indicate that unit operations common to minerals processing have been seriously considered at various times. A review of the available literature and statistics on recoverable plastics reveals that only 2.4 percent is recycled. This article presents a flowsheet that we developed and tested in a bench-scale pilot plant. It shows that a combination of mineral processing techniques, including comminution, heavy media separation, and flotation, can be successfully adapted to the recycling of post-consumer plastics. The gamma flotation process, which operates on the basis of solution surface tension control to facilitate the separation of inherently hydrophobic solids, combined with the alkali-treatment of a mixed polyvinal chloride-polyethylene terephthalate feedstock generates clean polymer concentrates at high recoveries.     

Pressure-infiltration processing of reinforced aluminum

Pressure infiltration of liquid metal is one of the most important processing routes for the production of aluminum-matrix composites having a self-supporting reinforcement phase. This article briefly examines the physical phenomena governing infiltration processes, to present practical guidelines derived from their analysis for optimization of the process and the materials produced. Engineering aspects that are pertinent to infiltration techniques, including preform preparation, process configurations, flow control, and innovative processes, are summarized.     

Recovering gold from thiosulfate leach pulps via ion exchange

Increasing environmental and occupational safety concerns about the use of cyanide in gold processing has increased interest in more acceptable alternative lixiviants, the most promising of which is thiosulfate. However, the thiosulfate process lacks a proven inpulp method of recovering the dissolved gold because activated carbon is not effective for the absorption of the gold-thiosulfate complex. This paper describes work aimed at evaluating the effectiveness of commercially available anion exchange resins for the recovery of gold from thiosulfate leach liquors and pulps.     

Recovering gold from copper concentrate via the HydroCopper™ process

HydroCopper? technology comprises a chloride-leaching method for copper sulfide concentrates and copper production up to semi-products. As compared with the commonly used sulfate solutions, brine solutions offer aggressiveness and stability of the copper(I) ion and, consequently, a lower energy consumption in leaching. Copper(II) ions and oxygen are used as oxidants. Iron reports to the leaching residue as oxide and sulfur as elemental sulfur. Gold is dissolved and recovered in the third stage of the counter-current leaching when the redox potential reaches higher levels.     

铝合金的超常铸轧制备

铝合金连续铸轧以其短流程、高效、节能等突出的优势成为铝板带热轧坯的主要生产模式之一,特别是在我国其产量已大于热轧板.因此,提高其产品质量和生产效率成为十分突出的普遍问题.提出"超常铸轧"技术思路,通过强化铸轧环境,改变铸轧工艺,使铝合金铸轧组织发生新的演变,板材性能全面改善,成型性有显著提高."超常铸轧"的核心技术是:1)基于高能量密度输运的热传导技术;2)基于外加瞬时随机变化磁场的铸轧区熔体强微扰动技术.研究了两种新技术的科学原理和技术要素.     

The environmental management of selenium in aluminum processing

To identify the environmental fate and exposures with respect to selenium compounds in aluminum processing, total particulates and selenium concentrations at three U.S. aluminum facilities were assessed in October 2002. Site A was a reduction facility that utilized manganese alloys containing selenium, Site B was a rolling mill facility that used manganese alloys free of selenium, and Site C was a recycling facility that received aluminum dross and scrap from both Site A and Site B. Total selenium concentrations in process materials and waste materials were measured. Simultaneously, furnace stack emissions and occupational airborne exposures were monitored at each of the three facilities. Results indicated that the major environmental management issues were selenium particulates in the stack emissions from Site A and baghouse dusts classified as hazardous due to selenium from the rotary furnaces at Site C. For more information, contact K. Hagelstein, TIMES Limited, 1604 Leopard Street, Sheridan, WY 82801; (307) 674-4844; fax (307) 674-4843; e-mail aircaredoc@aol.com.     

Electrochemical magnesium sensors for Use in aluminum processing

Improvements in process control during the production and reclamation of aluminum alloys can be achieved through in-situ measurement of the magnesium content in the molten alloy. Electrochemical sensors are compact, can be inserted directly into molten aluminum, and produce a continuous direct current voltage proportional to the logarithm of the magnesium content. This article describes and compares electrochemical magnesium sensors based on three different electrolytes— MgCl₂-CaCl₂, MgF₂, and β″ alumina.     

铝合金涂层搅拌摩擦加工的作用机制

为研究搅拌摩擦加工作用机理,对铝合金表面热喷涂铝基涂层进行了4道次搅拌摩擦加工。应用SEM、EDS、TEM和显微硬度测试对加工前后的涂层进行分析。结果表明,涂层经过搅拌摩擦加工后,原本层叠状、有孔隙组织通过形变诱导位错切割机制,首先形成滑移带,同时位错密度不断增加并聚集成小角度晶界,然后逐渐转变成大角度晶界,将晶粒分解细化,最终演变成致密的超细等轴晶,尺寸达到200 nm以下。涂层和基体之间发生了相互融合,涂层和基体间的间隙消失。基体中的合金元素向涂层扩散。搅拌摩擦加工后,涂层显微硬度从62 HV上升到269 HV。     

铝合金加工过程中含铬废水的处理

在铝合金加工过程中产生的含铬废水中六价铬离子对人体危害很大,铁氧体法处理六价铬离子是一种无中间二次污染物,能达到一步无害化处理,处理后的废水达到了国家规定的排放标准,有显著的经济效益和环境效益。     

Molten metal processing of advanced cast aluminum alloys

Premium quality aluminum alloy castings are used extensively in various applications requiring a high strength-to-weight ratio, such as aerospace, automotive and other structural components. The mechanical properties in these structure-sensitive alloys are determined primarily by the secondary dendrite arm spacing and the morphology of interdendritic phases. In addition, the amount of porosity in the casting and the inclusion concentration have a strong influence on fracture, fatigue and impact properties. During the production of the casting, various molten metal processing techniques can be implemented to control these microstructural parameters. These melt treatments include grain refinement with Ti-B, eutectic modification with strontium or sodium, degassing with purge gases and filtration of inclusions. The efficiency of these treatments determines the quality of the cast component.     

铝合金型材深加工过程中的表面保护

介绍常用铝合金型材深加工的传统模具以及加工过程中对工件表面的保护方法,分析了传统深加工模式的缺点,阐述了现行铝合金型材深加工过程中对工件表面保护的先进方法.     

Constituents evolution of LFEC 7050 aluminum alloy during processing

The d 120 mm ingots of 7050 aluminum alloy were made by low frequency electromagnetic casting （LFEC） and conventional DC casting process, respectively. After homogenization treatment the ingots were extruded to rods and the solution and aging treatment were carried out for the rods. Constituents evolution during processing and effects of LFEC on constituents and remnant constituents were studied. The results show that 7050 aluminum alloy mainly contains Al-Zn-Mg-Cu type and Al-Cu-Fe type constituents. Al-Zn-Mg-Cu type constituents dissolve during homogenization, while Al-Cu-Fe type constituents could not dissolve. After homogenization treatment, the main remnant constituent is A17Cu2Fe which crushes and orients along the extrusion direction after extrusion. Compared with DC process, by the process of LFEC, the constituents or remnant constituents are smaller in size and less in content. The LFEC process shows significant improvement in elongation by LFEC in both as-cast state and final state.     

2618铝合金的热变形和加工图

在Gleeble-1500D热模拟仪上进行热压缩实验,研究了变形温度为573～773 K、应变速率为0.01～10s-1时2618铝合金的热变形行为.热变形过程中的稳态流变应力可用双曲正弦本构关系式来描述,平均激活能为181 kJ/mol,大于其自扩散激活能.根据材料动态模型,计算并分析了2618铝合金的加工图.利用加工图确定了热变形的流变失稳区,并且获得了试验参数范围内的热变形过程的最佳工艺参数,其热加工温度为623～723 K,应变速率为0.01 s-1,温加工温度为573 K左右,应变速率为0.01 s-1.     

The use of rotating-impeller gas injection in aluminum processing

The three major characteristics of liquid aluminum quality are hydrogen content, alkaline content, and inclusion content. The past 20 years have seen considerable development in rotating gas injectors processes, at different steps of liquid metal processing in the casthouses, designed to address these three quality factors. Simultaneously, a great deal of academic work has been done to understand and model these processes, using knowledge from the fields of chemical engineering, thermodynamics, and fluid dynamics. This article shows how very simple efficiency models can be used to represent the processes, combining first-order kinetics for batch treatment and residence time distribution for in-line systems, leading to realistic efficiency laws. These laws are valid for all quality factors under the same form and involve very few parameters.     

Atmospheric plasma deposition of glass coatings on aluminum

The deposition and properties of glass coatings on aluminum was investigated using atmospheric pressure plasma-enhanced chemical vapor deposition. The plasma, generated with radio frequency power at 27.12 MHz, was fed helium, oxygen and two types of silicon precursors, hexamethyldisilazane and tetraethylorthosilicate. After deposition, the coatings were analyzed for composition, adhesion and dielectric strength. X-ray photoelectron spectroscopy revealed that the glass coatings contained approximately 25% silicon, 50% oxygen and 25% carbon. Scratch tests indicated that the coatings were strongly adherent to the substrates. The glass coatings achieved DC dielectric strengths in between 50 and 250 V for a thickness range of 0.5 to 1.3 μm. The maximum breakdown voltage measured was 400 V. Scanning electron microscopy revealed that breakdown occurred at cracks and other defects in the coatings. These defects appeared to form around areas of surface roughness and contamination.