铝液净化的关键限制因素

从Al2O3杂膜和液态金属结构分析入手，阐述了气体在铝-杂H2系统中形核长大的全过程，提出“寄生机制”，并被试验和实践所证实，杂的存在是气体难以除净的关键限制因素，杂吸附着气，气寄生于杂，杂多气多，除气必排杂，排杂是除气的基础。     

提高铝熔体净化效果的理论基础及途径

铝熔体中Al2O3夹杂与氢的行为及相互作用关系的实质，是改善和提高铝液净化效果的理论基础，对于铝液净化工艺的合理设计极为重要。从定关键入手进行了分析讨论，提出杂与气相互作用的“寄生机制”观点；同时针对目前净化方法主要从除气角度进行设计，忽视杂气相互关系及对净化效果的影响等现状，在杂气关系分析的基础上，突破传统净化思路的束缚，首次明确提出了“排杂是除气的基础，排杂为主、除气为辅”的铝液净化原则，据此研究开发出熔剂过渡净化方法及相应的高效排杂净化熔剂，并指出了提高铝熔体净化效果的技术途径。     

铝熔体高效净化的理论及净化处理技术的现状分析

在杂气关系分析的基础上,提出"排杂是除气的基础,排杂为主,除气为辅"的铝液净化原则,根据此研究开发出熔剂过滤净化方法及相应的高效排杂净化熔剂,分析讨论国内、国外净化处理技术的发展现状及存在问题,提出提高铝熔体净化效果的技术途径.     

铝熔体中夹杂物与气体相互作用的关系

分析了夹杂物（Ａｌ２Ｏ３等）的结构特性和气体（氢）在铝凝固过程中的行为,阐述了铝熔体中夹杂与氢的相互依存关系,提出了夹杂与氢相互作用的“寄生机制”观点。指出了夹杂的存在是气体难以除净的关键限制因素,排杂是除气的基础,并通过实验得到证实,对铝液净化实践具有实际指导作用,是提高铝材冶金质量的关键。     

熔炼温度与静置时间对A356铝合金净化效果的影响

在对比不同熔剂对A356铝合金净化效果的基础上,研究了熔炼温度与保温静置时间对净化效果的影响。结果表明,排杂熔剂具有较好的除气除杂效果,随着净化处理温度的升高,排杂熔剂净化处理后的铝合金含杂量与含气量变化比较平稳,保持在一个较低水平;随着保温静置时间的延长,铝液中的含杂含气量保持比较稳定。     

铝熔体中夹杂物与氢相互关系的分子动力学模拟探索

运用分子动力学模拟方法对铝熔体中夹杂物与氢气关系进行研究,从径向分布函数、均方位移、配位数等方面分析Al_2O_3对铝熔体中氢扩散行为的影响。模拟结果表明,Al_2O_3夹杂物会破坏铝熔体中铝原子的有序排列,形成空位,大量的氢在空位上聚集,为氢气泡的形成创造条件,且在一定范围内,铝熔体中Al_2O_3原子含量越高,氢的聚集程度越大。A356铝屑再生试验进一步表明杂气是相互依存和作用的,排杂是除气的基础。     

川气东送金陵支线杂散电流干扰的检测与防护

随着机动轨车及电力网络的快速发展,其引起的杂散电流给埋地钢质管道造成的腐蚀已严重危害管道安全。本文介绍了川气东送金陵支线杂散电流检测判断方法,杂散电流干扰防护措施,并提出了利用锌带排流针对埋地钢制管道直流腐蚀进行防护的方法。     

直流杂散电流对煤气管道的腐蚀及排流保护

沈阳某煤矿，由于煤层浅而采用露天开采，并在矿床四周铺设直流电气化铁路，该电铁产生的直流杂散电流，直接干扰腐蚀其平行埋设的气管道。为消除干扰腐蚀而进行大量现场调查工作，最后确定采用接地排流法和物牲阳极阴极保护法，使煤气管道处于良好的保护状态。本文主要介绍现场调查内容及方法，排流装置的选择、安装及效果。     

高效排杂熔剂净化处理电工圆铝杆的试验研究

探讨了高效排杂熔剂净化处理对电工圆铝杆的冶金质量与性能的影响作用及规律。结果表明，用高效排杂熔剂净化处理明显提高了电工圆铝杆的冶金质量，其除杂率及气孔降低率分别达73．5％和92．1％，削弱了冶金缺陷的有害作用，明显提高了电工圆铝杆的力学性能，并使其电阻率有所降低；高效排杂熔剂净化后进行晶粒细化处理，充分发挥了细化处理效果，与常规处理相比，在强度提高的同时，伸长率仍得到明显提高（幅度达62．7％），电阻率降低了0．93％。     

铸造车间铝熔体的除气和净化

本文首先介绍铝熔体除气的一般方法，接着详细论述了旋转除气方法和各种旋转器的除气效果。含氢量采用熔体试样在真空中凝固的方法测量。利用所得到的铝合金的可比较气孔率，能测量出温度和时间对除气效果的影响。气孔率随旋转除气处理的时间增长呈指数下降，每隔１．５分钟下降一半。因此，能够控制除气量。本文最后对旋转除气处理的成本做了分析。     

铝熔体中氢和夹杂物的存在形态

阐述了铝熔体中氢和夹杂物的存在形态及其影响因素,介绍了控制铝熔体中氢和夹杂物的方法。     

铝的润湿行为以及Al2O3和SiC陶瓷过滤器的过滤行为

检测了工业用Al2O3过滤器和SiC过滤器与液态铝的润湿性并在工厂使用以上2种陶瓷过滤器过滤铝液。实验结果表明：Si C过滤器比Al2O3过滤器更易于润湿液态铝。提高液态铝与过滤器的润湿性有助于铝液透过过滤器,提高夹杂物的去除率,同时,易于去除与铝不浸润的杂质。     

纯铝与石墨、SiC和Al_2O_3的润湿性

纯铝与过滤材料和夹杂物之间的润湿性是影响铝的过滤性能的重要因素。在10-8bar真空条件下于1000~1300°C,研究液态铝与氧化铝、SiC和石墨之间的润湿角。为了描述铝的过滤和浇铸等在低温条件下铝与陶瓷的润湿行为,使用半经验模型进行研究。计算出的700°C的纯铝与氧化铝的润湿角为97°,与玻璃体石墨的为92°,与单晶和多晶石墨的为126°,与单晶的为SiC79°。结果表明：在浇铸温度下铝不能润湿氧化铝和石墨（或者Al4C3）,但可以润湿SiC。因此,为了让铝能够浸润过滤材料,在铝过滤时需要施加一个压力差作为推动力。提高温度也可以改善铝与陶瓷间的润湿性。     

The Variation of Hydrogen,Oxygen and Nitrogen Levels in Cast Iron with Varying Blast-air Moisture

Abstract

The effects of blast moisture on the gas content—hydrogen, oxygen and nitrogen—of molten iron derived from cupola melting have been studied, the dissolved oxygen content being measured by oxygen probes. It has been found that the hydrogen and oxygen contents of molten iron increase with rising levels of air moisture, although the nitrogen content remains almost the same. The rise in oxygen content is mainly the result of an increase in combined oxygen (oxide inclusions), the level of dissolved oxygen remaining almost unchanged.     

电解工艺对电解铝液质量的影响研究(上)

简介了铝电解机制对电解铝液中氢和Al2O3夹杂形成过程的影响,分析了铝液中Al2O3夹杂形成的机理,推算了CO2,对铝液扩散的质量传递方程,描述了效应处理期间铝液中氢和Al2O3夹杂的形成过程.利用Person-Waddington模型测算了铝液中可能形成的Al2O3夹杂最大值.电解液中的水份被电解成氢和氧,阴极析出的氢通过扩散和杂一气寄生机制进入铝液,是电解铝液中氢的主要来源.铝电解工艺对电解铝液具有一定的自净化作用.     

Measuring Hydrogen Content in Molten Aluminium Alloys using the CHAPEL Technique

Abstract

A new method known as CHAPEL (Continuous Hydrogen Analysis by Pressure Evaluation in Liquids) for measuring hydrogen content in molten aluminium alloys has been developed and tested. The method relies on direct measurement of the hydrogen partial pressure in the melt. A number of interesting potential applications are indicated on the basis of laboratory and industrial experiences. The main advantage of the CHAPEL method, as compared to other techniques, is its ability to provide direct, continuous measurement of hydrogen in the melt, making it particularly suitable for process monitoring of aluminium melt quality. This paper systematically examines the influence of hydrogen content on porosity in aluminium-silicon cast alloys, taking solidification conditions and melt treatment into account. In this system, the greatest susceptibility to porosity is encountered with AlSi7Mg. An influence of the solidification rate on porosity, which varied with different hydrogen contents, was noted. The work describes a number of typical pore shapes and their distribution on the basis of metallographic studies.     

Influence of melt cleanliness on pore formation in aluminium—silicon alloys

Porosity and inclusions are the most serious problems encountered in the production of aluminium castings. The formation of porosity during solidification can be affected by several factors such as melt hydrogen, cooling rate, alloying elements, modification and melt cleanliness. Of all these factors, melt cleanliness (i.e. inclusion concentration) is the most difficult to control and is often considered as a key factor influencing the pore nucleation. In the present paper, the effect of melt cleanliness on porosity formation in two aluminium foundry alloys (A356 and 319) was investigated systematically. Melts with different inclusion levels were prepared and tested by the reduced pressure test, and the melt cleanliness was quantified using a pressure filtration technique. In addition, the influence of filtration by ceramic foam filters on the porosity was studied.

Results indicate that, at the same hydrogen level and with increased inclusion concentration, the density of reduced pressure samples decreases, and the amount of porosity and the number of pores increase. This trend is confirmed in both 356 and 319 alloys over a wide range of hydrogen levels. These results are discussed in the context of the nucleating effects of inclusions on pore formation during solidification. The practical application of the reduced pressure test for evaluation of both the melt cleanliness and the dissolved hydrogen level is outlined.     

Defects caused by precipitation of in liquid copper–nickel–aluminium–bronze alloys dissolved carbon and removal by treatment of melt

Castings made of copper–nickel–aluminium bronze (CuAl₁₀Fe₅Ni₅) alloys regularly show defects in the thick, slowly solidifying parts of the castings, which give rise to rejections. Metallographic examination has been made on material of scrap castings showing porosity accompanied with film-like inclusions located beside the iron rich κ_II phases. Investigations of large failed cast structures of copper–nickel–aluminium bronze show the same characteristic defects on which fatigue cracks initiate and grow. Investigation has been made to the nature and the cause of appearance of the film-like inclusions. Microanalysis indicates a high intensity of carbon at the place of the film-like inclusions. Hereafter, an investigation has been made into the solubility of carbon in liquid copper–nickel–aluminium bronze, and it is found that besides hydrogen, also carbon is soluble in copper–nickel–aluminium bronze alloys. The appearance of the carbon as flakes in the fracture surface of materials with defects does suspect there is a nucleating effect on the formation of microporosity causing the defects. To prevent the formation of the casting defects by the interaction between solved hydrogen and carbon, it is necessary to remove the carbon as far as possible by treatment of the melt.     

铝及铝合金在熔融纳中的腐蚀行为

研究了纯铝、Al-Si和AL-Mg合金在350～450℃熔融钠中的腐蚀行为。采用OM、XRD、EDAX和EPMA分析了腐蚀产物的组织形貌和合金元素的分布。实验结果表明高纯铝受到轻微的腐蚀,并非完全“免蚀”。工业纯铝的腐蚀较明显,主要发生在杂质偏聚的晶界附近。铝合金的腐蚀程度取决于杂质元素尤其是硅的含量。铝中添加一定量的镁并用微量锆细化晶粒可改善合金对熔融钠的耐蚀性。铝和铝合金的腐蚀产物经测定为AINaSi相。