Refining effect of hydrogen plasma arc melting on hafnium metal

Removal of metallic impurities from Hf metal by hydrogen plasma arc melting (HPAM) has been examined. Several impurities such as Al, Ti, Cr, Fe, and Cu were efficiently removed when only Ar plasma gas was used. Furthermore, the addition of H₂ to Ar plasma gas remarkably improved the removal degrees of Si, Ni, Ge, and Sn as well as above impurities. It was found that HPAM has an excellent effect to eliminate impurities with higher vapor pressures than that of Hf metal.     

Hydrogen effect on refining of Mo metal by Ar-H2 plasma arc melting

The refining effect of Ar/Ar-H₂ plasma arc melting (PAM) was investigated and the purity of Mo metals was evaluated by glow discharge mass spectrometry (GDMS). Most impurities in the Mo metals except for W were removed by Ar/Ar-H₂ PAM down to a few mass ppm levels, and the purities of respective Mo metals refined by Ar/Ar-20%H₂ PAM were improved up to 4N(99.9943%) and 5N(99.9996%). It is also found that Ar-H₂ PAM provides excellent decarburization, deoxidation, and denitrogenization. This confirmed that the refining effect is chemically induced by activated hydrogen atoms during Ar-H₂ PAM.     

多晶硅真空电磁感应熔炼除磷及其过程研制

磷是多晶硅中的主要杂质元素之一,目前采用的酸洗以及定向凝固工艺无法将其含量降低到太阳能级多晶硅所要求的范围之内。采用自行设计的真空电磁感应熔炼炉及定向凝固炉研究了真空度、精炼时间和精炼温度对除磷效果的影响。研究结果表明当炉内压强为5.0×10-1 Pa时,精炼温度和时间分别为1723K和60min时,精炼后硅中磷含量由原来的2.0×10-5（质量分数）降低到1.8×10-6（质量分数）;研究推导出了在压强为5×10-1Pa下磷的含量随精炼时间和精炼温度的关系式如下：XP=X0Pexp[（-1.43×10-4-3.1×10-7T）t]同时还对真空感应熔炼除磷过程进行了热力学与动力学分析。     

Oxidation refining of iron using plasma-arc melting

Oxidation refining of Fe using plasma arc melting, by the addition of iron oxide as an oxidizing agent, has been carried out. In this refining process, an impurity element which has higher affinity for oxygen than iron was expected to be eliminated. As the result, decreases in Si, Mn, Al, Ca, Ga, and Zr were observed and 99.996 mass% of iron could be obtained from 99.93 mass% of electrolytic iron by plasma arc melting under oxidizing conditions followed by argon–hydrogen plasma arc melting. Specifically, the removal of Si was found to proceed by the distribution between in the liquid Fe phase and in the oxide phase. In addition, the relation of Si and oxygen concentration in liquid iron was consistent with the data in the literature.     

Comparative study on microstructure and homogeneity of NiTi shape memory alloy produced by copper boat induction melting and conventional vacuum arc melting

A comparative study was carried out on the microstructures of NiTi shape memory alloy produced by two techniques of copper boat induction melting and vacuum arc melting. The as-solidified and homogenized specimens were characterized by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with EDS, and differential scanning calorimetry (DSC). The results showed that the microstructure formed in the copper boat method was free of segregation (Ti or Ni-rich precipitates) with a low scatter (<5 K) in phase transition temperatures within the ingot at different positions. Unlike the multi-stage vacuum arc remelting process, a homogeneous microstructure was achieved only after one melting procedure.     

电热还原法制备V-Ti-Cr-Fe储氢合金

采用电热还原热法制备了V-Ti-Cr-Fe合金,考察了CaO加入量、Al-Ca还原剂用量及精炼剂成分对制备效果的影响。结果表明,CaO和Al-Ca合金用量对Ti的收得率和合金中杂质含量影响显著,m(CaO)/m(Al)为0.9、m(Al-Ca)/m(Al)为0.5时的熔炼效果较好,Ti的收得率可达66%,Al、O杂质含量可分别达到3.66%和0.75%(质量分数)。以90%(3CaF_2-CaO)-10%V_2O_5(质量分数)渣体为精炼剂,采用喷吹造渣的精炼方法,可较有效地去除合金中的Al杂质,并能起到一定的预脱O作用,精炼后Al和O含量可分别降到1.23%和0.59%(质量分数)。SEM分析表明,未精炼的合金除了含有固溶体主相外,还含有很多氧化物夹杂相,而通过喷吹造渣精炼,夹杂相明显减少。     

HPAM/St的固相力化学合成及产物表征

利用磨盘型力化学反应器对部分水解聚丙烯酰胺(HPAM)和疏水单体苯乙烯进行固相力化学共碾磨。产物红外谱图分析表明,接枝产物既有HPAM的结构,同时含有苯环,说明两者发生聚合。差示扫描量热结果显示,未碾磨的HPAM的熔融温度为209.4℃,碾磨10次后下降为206.7℃,而碾磨10次的共聚产物为256.2℃,说明发生共聚反应后使聚合物的热稳定性明显改善。热重分析表明,未碾磨的HPAM的Ti为233.9℃,碾磨10次后Ti降低为233.1℃,碾磨10次的共聚产物的Ti没有降低反而升高为281.6℃,提高了47.5℃,进一步说明聚合物的热稳定性提高。     

Mechanism of Fe-Mn-Al alloy steel ingot failure from MgO-C refractory corrosion

Fe-Mn-Al alloy steel was melted in a mass production tonnage arc furnace equipped with ladle refining facilities. The ingots were cracked and torn apart on hot rolling. Blue flames erupted from the cracks and became red. A white powder was observed adjacent to the cracks in ingots. The white powder was identified as magnesia. Concentrations of Mg and Ca were high in the centre of the ingot, implying the segregation of impurities. Quantitative elemental analysis and microstructural investigation revealed Mg, Si, Ca and S containing impurities and Cr, Mo and Si carbides were segregated within grain boundaries. The segregation was the main cause of ingot cracking. The 1600°C static cup test for carbon containing MgO-C refractories exhibited the reduction reaction, which raised the Mg concentration up to 0.017 wt% in Fe-Mn-Al alloy steel, whereas the pure MgO refractory cup test showed inertness to Fe-Mn-Al alloy.     

Ar-O2气体去除硅铁合金中金属杂质研究

硅铁合金在炼钢过程中被广泛用作合金剂和脱氧剂,其中含有的金属杂质Al,Ca,Ti会直接影响钢液的洁净度,因此采用顶吹Ar-O2气体的方法去除硅铁合金中的金属杂质。借助自动扫描电镜统计精炼前后硅铁合金中杂质相的形貌、成分、面积分数,通过ICP-AES测试金属杂质的含量变化。结果表明:硅铁合金原料中含有大量的金属杂质相,Al,Ca,Ti杂质含量分别为1.11%(质量分数,下同),0.31%,0.11%;吹气精炼5min时,Al和Ca的含量分别急剧降低至0.66%和0.13%;吹气精炼45min后,杂质元素去除速率变缓,精炼反应趋于平衡;吹气精炼120min时,Al,Ca,Ti含量分别降低至0.42%,0.014%,0.094%,去除率分别为62.16%,95.48%,14.54%。吹气精炼方法能有效去除硅铁合金中Al和Ca杂质,Ti杂质去除效果不明显。     

部分水解聚丙烯酰胺的固相力化学活化

利用磨盘型力化学反应器对部分水解聚丙烯酰胺(HPAM)进行固相力化学碾磨。随着碾磨次数的增加,特性黏度先降低,后上升,表明在碾磨过程中HPAM主链断裂,产生大分子自由基,继而发生重新聚合;平均粒径由碾磨10次的0.822μm减小到碾磨30次的0.436μm,说明碾磨后HPAM活性增强;碾磨前起始分解温度为233.9℃,碾磨10次、30次后分别为233.1℃和232.4℃,碾磨前熔融温度为209.4℃,碾磨10次、30次后分别为206.7℃和205.4℃,说明固相力化学作用使HPAM的热稳定性降低。     

Effects of boron,carbon, and silicon additions on microstructure and properties of a Ti–15Mo based beta titanium alloy

Abstract

Additions of boron, carbon, and silicon have been made to a series of Ti–15Mo based β titanium alloys prepared by plasma arc melting and subjected to various processing and characterisation techniques. The purpose of these additions was to investigate their grain refining effect in the as cast, as forged, and heat treated states. The boron and carbon additions promoted dendritic solidification. Boride and carbide particles were present in the interdendritic regions. However, a fully equiaxed fine grained structure could not be obtained even at the highest levels of addition (1.0 wt-%). These additions resulted in substantial microstructural refinement after forging and the particles stimulated the nucleation of recrystallised grains. Significant retardation of grain growth was observed after solution treatment and attributed to the Zener pinning effects of the boride and carbide particles. Despite the microstructural refinement, the ductility of the alloys containing boron and carbon was severely impaired.     

Improvement in mechanical properties of C300 maraging steel by application of VAR process

The prime objective of this research was to improve the mechanical properties of C300 maraging steels originally cast in the vaccum induction melting (VIM) and AIM furnaces by application of vaccum arc remelting (VAR) process. For this purpose two sets of C300 maraging steel with different amounts of Ti were cast in two different types of furnaces. Three bars with 1, 1.5 and 2 wt% of Ti were produced in the argon induction melting (AIM) furnace and two bars with 0.65 and 1 wt% Ti in the VIM furnace. Then all of the bars were subjected to VAR process in order to study the effects of this process on the reduction of N and O gases and inclusions, hence improvement in the mechanical properties. The results show that the total reduction of N and O gases in the bars cast in the AIM furnace was up to 40%, the amounts of inclusions irrespective of their kind reduced up to 30% while ductility and impact energy increased up to 40%. However, these parameters in the bars cast in the VIM furnace changed as follows: total gas reduction decreased by 12%, ductility and impact energy increased by 30% and 47%, respectively. So this research provides a very informative data base for those who are interested in studying the effect of VAR process on the mechanical properties of this kind of cast steel.     

电渣重熔连续定向凝固FGH96合金非金属夹杂物研究

本文通过真空感应熔炼+惰性气氛保护电渣重熔连续定向凝固制备FGH96合金,对FGH96合金中的非金属夹杂物进行对比研究。结果表明,活泼元素Al、Ti、Zr、Ce、B等有轻微的烧损,主要元素含量都在合金要求的范围之内,氧含量略有降低,达到了真空熔炼的水平,氮含量有较大幅度的降低,主要存在两种类型的夹杂物,呈球形的夹杂物是Al、Ti、Mg的复合氧化物和TiN。图像统计分析结果表明,和传统电渣重熔相比,电渣重熔连续定向凝固工艺重熔后FGH96合金中的非金属夹杂物面积百分比、100个视场中的夹杂物个数降低了50%以上,夹杂物的最大尺寸由16μm降低到5.5μm,这主要是与熔池的形状、深度和结晶方式有较大关系,传统电渣重熔过程中金属熔池的形状是V字形,深度约占铸锭直径的50%左右,而电渣重熔连续定向凝固过程中形成的熔池呈扁平状,深度占直径10-20%。     

Production of semiconductor grade high-purity iron

Semiconductor grade high-purity Fe will be required in practical use of β-FeSi₂. However, high-purity Fe with more than 99.9999% in purity has not been produced commercially. Then, a process consisting of anion exchange in a HCl solution, hydrogen reduction and plasma arc melting has been developed for the production of high-purity Fe. All metallic impurities can be virtually removed from Fe by the two anion-exchange steps, in which some elements such as Cu and Mo are separated efficiently under reducing conditions by the addition of Fe powder at the 1st step, and the rest of impurities are surely separated under oxidizing conditions at the 2nd step. Non-metallic impurities such as oxygen, carbon and nitrogen also can be eliminated to very low levels by the hydrogen reduction and the hydrogen plasma arc melting steps.     

Analysis of the Thermodynamic Conditions of Refining during Electron Beam Melting of Refractory Metals

The electron beam melting and refining (EBMR) decreases the concentration of an impurity element through evaporation, removal of dissolved gases, lessening the size and density of the particulate impurities complexes by either flotation, either sedimentation (due to the difference in component densities) as well as by its dissolution in the liquid metal. The paper is focused on the analysis of the thermodynamic conditions for EB refining of wastes of the titanium, zirconium and hafnium with high oxygen contamination and other refractory metals using 60kW and 250kW EBMR plants.     

Pb distribution in multistep bismuth refining products

Significant amounts of lead impurities have been removed from bismuth using a multistep refining process involving bismuth electrorefining in a hydrochloric acid solution, melting of a cathodic bismuth sponge, and pyrometallurgical processing of molten bismuth in an inert atmosphere. The Pb distribution between bismuth and the products forming in different refining steps has been studied.     

Purification of Cu by hydrogen plasma-arc zone melting and characterization of trace impurities by secondary ion mass spectrometry

Purification of 4N (99.99%) and 6N (99.9999%) purity Cu rods by hydrogen plasma-arc zone melting was carried out. Weight loss in the 4N and 6N Cu rods as a function of number of zone refined passes revealed a higher rate of impurity removal by vaporization in 4N Cu when compared to 6N Cu. Purification effect was studied by analyzing major impurities like Mg, Si, Ca, Ti, Cr, Ni and Fe by O₂⁺ ions and C, O, As, Cl, P and S by Cs⁺ ion sources using secondary ion mass spectrometry. A remarkable decrease of Si, Ti and Fe impurity concentrations in Cu at x/L = 0.03 after 10 zone passes was observed, but no similar purification effect along the remaining length of the zone refined copper rod was observed. Mg, Se and Ca in the Cu rods were reduced faster by a high evaporation effect due to P_i/P_Cu > 10². On the other hand, removal of O, C, S and Se was expectedly dominated by vaporization in the form of H₂O, CH_4, H₂S, and H₂Se through thermodynamically favored reactions. The overall segregation rate of the individual impurity elements was decreased with an increase in the purity from 4N to 6N of Cu rods. SIMS analysis of trace impurities was successfully carried out on HPZM Cu for quantitative estimation.     

矿化度影响HPAM溶液黏度机理

研究了矿化度对HPAM(部分水解聚丙烯酰胺)溶液流变性的影响,测定了电渗析器处理前后的油田污水、淡水、浓水配制的HPAM溶液的流变性,浓水对HPAM流变性影响最大;通过流变曲线拟合,确定了流变参数,矿化度越高,稠度系数越小,幂律指数越大。探讨了阴阳离子对HPAM溶液黏度的影响,阴离子对HPAM溶液黏度降低无贡献,阳离子是引起HPAM溶液黏度损失的主要原因,应用双电层理论深入探讨了阳离子浓度、电荷数及阳离子半径对HPAM分子构型的影响。得出了阳离子对HPAM分子构型的影响规律。     

部分水解聚丙烯酰胺在水溶液中的氧化降解

对各种还原性有机杂质如胺,酚和硫化物对ＨＰＡＭ水溶液稳定性的影响了研究,一般讲,大多数这些还原性杂质,对聚合物的氧化降解反应具有明显的促进作用,并使得溶液粘度大幅度降低。这种现象甚至发生在室温条件。这由于它们通过氧化还原作用,使聚合物降解过程中过氧分解活化能大幅度降低的缘故。     

Microstructure and mechanical properties of hot rolled TiNbSn alloys

Titanium alloys with lower elastic modulus and free from toxic elements such as Al and V have been studied for biomedical matters. Ti–Nb–Sn alloys showed up as presenting great potential for the aforementioned purpose. The current study got Ti–35Nb-XSn alloys (x = 2.5; 5.0; 7.5) by applying the following techniques: arc melting, homogenizing and cooling in furnace, homogenizing and water quenched, hot rolling and water quenched. According to each step of the study, the microstructures were featured by means of optical microscopy, by applying a scanning electron microscopy (SEM) analysis as well as X-ray diffraction. The mechanical properties were gotten by means of: Vickers microhardness, tensile and ultrasonic tests. Their ratio between tensile strength and elastic modulus as well as the ductility were compared to other biomedical alloys already available in the literature. The mechanical behavior of the Ti–Nb alloys directly depends on the Sn rates that constitutes the phases as well as on the thermomechanical background to which the alloy was submitted to. The hot rolled Ti–35Nb–2.5Sn alloy showed high ratio between strength and elastic modulus as well as high ductility, just as high as those of some cold rolled Ti alloys.