废旧铅锡合金真空蒸馏的研究

本文针对日益增多的铅锡合金废科,对含铅量在4%～76%的铅锡合金采用真空蒸馏分离工艺进行了系统研究,最终得到的:铅的纯度为99%,锡中含铅量为0.01%.     

废旧铅锡合金真空蒸馏的研究

本文针对日益增多的铅锡合金废料,对含铅量在4％～76％的铅锡合金采用真空蒸馏分离工艺进行了系统研究,最终得到的铅的纯度为99％,锡中含铅量为001％。     

分子相互作用体积模型在真空蒸馏分离铅-锡-锑三元合金中的应用

基于分子相互作用体积模型(MIVM),计算Pb?Sn?Sb三元合金体系的活度,并使用活度系数计算真空蒸馏过程中Pb?Sn?Sb三元合金体系的气液相平衡。结果表明：随着蒸馏温度和液相中锡含量的增加,气相中锡含量也不断增加;然而,在1100°C液相中锡含量为97%(质量分数)时,气相中锡含量仅为0.45%,分离效果较好。在真空(10 Pa)条件下,在1100~1300°C蒸馏温度范围内进行真空蒸馏分离Pb?Sn?Sb三元合金实验。结果表明：在1100°C时,当液相中锡含量为97%时,气相中锡含量为0.54%。最后对比分析了实验结果和预测值,分析表明实验结果和预测值吻合较好。     

二元锡铅合金电镀工艺实践

锡和铅都是低熔点金属,锡的熔点231.9℃,铅的熔点327.4℃。锡铅二元合金,是低熔点合金,锡铅合金镀层是低熔点功能性二元合金镀层,锡铅合金镀层在空气中有良好的化学稳定性,可焊性能优于锡镀层,也不会象锡镀层那样容易在其表面形成针状晶须,所以锡铅二元合金电镀广泛应用于电子元器件工业领域。 锡铅合金镀层的结晶较锡或铅单金属的结晶都细致,并具有抗蚀性等多种优异性能,二元合金镀层中锡铅含量比例不同,锡铅二元合金镀层的用途有所区别。如含锡4％～10％的锡铅合金镀层可作为钢铁制件的防腐层用于特定的环境中,含锡6％～10％的锡铅合金镀层,由于防蚀和减摩作用优良,广泛用于高速发动机滑动轴承摩擦面的减磨镀层。含锡40％～60％的铅锡合金镀层有熔点低、焊接性能优良等性能,大量应用于电子元器件工业,本文就低熔铅锡二元合金电镀实践提些肤浅看法,与电镀界同行共商。     

分子相互作用体积模型在真空蒸馏分离Pb-Sb、Pb-Ag和Sb-Cu合金中的应用

基于分子相互作用体积模型(MIVM),使用牛顿迭代方法结合无限稀活度系数实验数据γ∞计算对势能相互作用参数Bij和Bji;然后使用参数Bij和Bji计算Pb-Sb、Pb-Ag及Sb-Cu二元合金体系的活度α和活度系数γ,并与实验值进行比较分析;最后计算Pb-Sb、Pb-Ag及Sb-Cu二元合金体系的气液相平衡组成。气液相平衡组成计算结果表明:活度计算值和实验值吻合较好;Pb-Ag和Sb-Cu体系中的组元均能通过真空蒸馏实现良好分离,而Pb-Sb体系中的组元不能通过一次真空蒸馏实现完全分离。分子相互作用体积模型用于预测二元合金体系的活度及真空蒸馏分离效果具有很高的可靠性,为真空蒸馏分离二元合金提供良好的理论依据。     

高砷焊锡真空蒸馏脱铅砷

研究了真空蒸馏法处理高砷焊锡,探讨了温度、真空度和蒸馏时间对蒸馏过程的影响。结果表明:在温度为1151℃,真空度为13.33～26.66 Pa,蒸馏时间为60 min 的条件下,脱砷率达94.09%,脱铅率超过99%,所得粗锡的含锡量在98 wt.-%以上。     

锡基合金体系组元活度及气-液平衡的模型预测

采用正规溶液模型、亚正规溶液模型以及简化的分子相互作用体积模型(Simplifiedmolecularinteraction volume model, SMIVM)预测Pb-Sn、Sb-Sn、Bi-Sn合金组元的活度,并计算模型的预测偏差。结果表明:SMIVM的平均标准偏差最小,分别为0.0050和0.0046,表明采用SMIVM预测锡基合金组元的活度是可靠的。在此基础上,采用SMIVM,结合真空冶金及气液平衡理论,建立二元合金体系的气-液平衡(Vapor-liquid equilibrium, VLE)预测模型。采用该模型计算上述锡基合金的VLE数据,并绘制VLE相图(包括T-x(y)和p-x(y)相图),最后采用VLE实验数据检验其可靠性。结果表明:采用该方法预测锡基合金体系的气-液相平衡具有较高的可靠性。依据气-液平衡相图,分析真空蒸馏分离锡基合金的实验条件以及不同蒸馏条件下的产物成分,可为真空蒸馏设备的改进及蒸馏过程优化提供理论依据。     

化学浸镀铅锡合金

为提高电子部件的可靠性,采用铅锡镀层代替锡镀层,铅锡镀层中含50%铅就能防止锡须产生.化学浸镀铅锡合金其作用同电镀铅锡合金,而且还具有节省电能与电气设备,操作比较简单.     

废弃锡合金真空分离回收金属（英文）

以废弃锡合金的回收利用为目标,计算绘制了Sn-Pb、Sn-Sb及Sn-Zn二元合金的气-液相平衡成分图。结果表明:Pb、Sb及Zn能够有效地与Sn分离。以此为指导,对不同成分的Sn-Pb合金、Sn-Pb-Sb合金、Sn-Pb-Sb-As合金、粗Pb合金以及Sn-Zn合金开展真空蒸馏工业化实验研究。实验结果表明:Sn-Pb合金在1323K条件下经真空蒸馏可获得含Pb99%的粗Pb和含Pb≤0.003%的Sn;Sn-Pb-Sb合金经一次真空蒸馏,可得到含Sn量90%、含Pb量≤2%、含Sb量≤6%的粗Sn和含Sn≤2%的粗Pb;粗Sn经过真空蒸馏后,产品中Pb和Bi含量达到Sn锭GB/T 728—2010中Sn99.99A级标准,超过50%的As和Sb得到脱除;Sn-Pb合金在1173 K。体系压力20-30 Pa条件下真空蒸馏8-10 h,得到的产品Zn中含Sn0.002%,Sn中含Zn约3%。     

粗铅真空蒸馏精炼杂质脱除的热力学(英文)

采用纯物质饱和蒸气压、分离系数和Pb-i系气-液相平衡成分图从热力学上分析粗铅真空蒸馏精炼脱除杂质的可行性。探讨粗铅中常见的杂质铜、锡、银、锌、砷、锑、铋在真空蒸馏精炼过程中的行为规律。结果表明:粗铅低温(923~1023 K)真空蒸馏时,锌和砷挥发进入气相而被除去,大部分锑挥发进入气相而实现与铅的分离,而铋则随铅残留于液相中无法除去。粗铅高温(1323~1423 K)真空蒸馏时,铅挥发进入气相冷凝,铜、锡、银不挥发而富集于残留物中被除去,铅挥发的同时铋也随着铅一起挥发进入气相无法除去。此理论为真空蒸馏脱除粗铅中的杂质提供新的思路,并能有效富集贵金属银等,对粗铅采用真空蒸馏精炼除杂具有一定的指导意义和实用价值。     

Electrodeposition of alloys XIX: Electrodeposition of lead-tin alloys

Pb-Sn alloys containing from 1.2 to 94.3 wt.% Sn were electrodeposited from aqueous solutions prepared from diethylenetriaminepentaacetates of the two metals. The effects of current density and the solution composition on the composition of deposits and cathodic current efficiencies were investigated. Pb-Sn alloy deposition was of irregular type. At current densities equal to or less than 2.0 A dm^-2, lead deposited preferentially. At current densities of more than 2.0 A dm^-2 and in solutions containing more than 50.0 met.% Sn (the percentage weight of the total metal content), preferential deposition of tin occured. An increased in the tin content of the bath increased the percentage of tin in the deposit. The presence of chloride ions in the bath did not seem to affect the composition of the deposit.     

Vacuum Carbothermal Reduction for Treating Tin Anode Slime

In this work, a process of vacuum carbothermal reduction was proposed for treating tin anode slime containing antimony and lead. During vacuum carbothermal reduction, the antimony and lead were selectively removed simultaneously by reducing and decomposing the less volatile mixed oxide of lead and antimony into the more volatile Sb₂O₃ and PbO. Then the tin was enriched in the distilland and primarily present as SnO₂. Crude tin was obtained via vacuum reduction of the residual SnO₂. The results showed that 92.85% by weight of antimony and 99.58% by weight of lead could be removed at 850°C for 60 min with 4 wt.% of reductant and air flow rate at 400 mL/min corresponding to the residual gas pressure of 40 Pa–150 Pa. Under these conditions, an evaporation ratio of 52.7% was achieved. Crude tin with a tin content of 94.22 wt.% was obtained at temperature of 900°C, reduction time of 60 min, reductant dosage of 12.5 wt.%, and a residual gas pressure of 40 Pa–400 Pa. Correspondingly, the direct recovery of tin was 94.35%.     

An AES study of the oxidation of a 97Pb3Sn alloy

A 97Pb-3Sn alloy was oxidized at oxygen pressures below 10 mPa and temperatures from 20°C to 200°C. The reaction was monitored by Auger electron spectroscopy (AES). The oxide film formed most likely is SnO and is less than 2 nm thick. Lead is oxidized only if there is no tin at the surface. If tin can diffuse to the alloy surface sufficiently fast, lead will not be oxidized. Oxidized lead is reduced by metallic tin.     

Electrodeposition of lead–tin alloy from methanesulphonate bath containing organic surfactants

The article discusses the process of electrodeposition of lead-tin alloy (tin content in the deposit up to 10–12 wt %) from methanesulfonate electrolytes. A composition was proposed of organic additives to the electrolyte providing attainment of high quality microcrystalline coatings with the alloy of predetermined composition at relatively low content of Sn²⁺ in the solution. It has been shown that the tin content in the deposit increases at an increase in current density and decrease in the electrolyte temperature. For production of anti-frictional Pb-Sn alloys with the tin content of about 10% the electrolysis should be performed at a current density of about 4 A/dm² and the temperature not exceeding 25°C. The effect of a decrease in the discharge rate of the Sn²⁺ ions into the alloy at deposition from electrolyte without organic additives was discovered, that is stipulated by deceleration of crystallization stage of tin on foreign substrate. When the alloy is deposited from electrolyte containing a composition of organic additives, the effect of super-polarization of discharge of Sn²⁺ ions is reduced.     

Preparation of high-purity bismuth by sulphur deleadization in vacuum distillation

The feasibility of separation of impurities in refined bismuth and sulphur deleadization with vacuum distillation was studied theoretically. Experimental studies on sulphur deleadization were carried out under vacuum. The influences of amount of sulphur, distillation temperature, vacuum degree and distillation time on deleadization were investigated and an optimal technical condition was achieved. The content of lead in refined bismuth can be decreased from 30μg/g to 0.21 μg/g, which has reached the level of“5N” high-purity bismuth. Other impurities in refined bismuth can be also removed effectively under certain conditions.     

Thermodynamics of removing impurities from crude lead by vacuum distillation refining

A novel technique was developed to remove impurities from crude lead by vacuum distillation. The thermodynamics on vacuum distillation refining process of crude lead was studied by means of saturated vapor pressure of main components of crude lead, separation coefficients and vapor-liquid equilibrium composition of Pb-i (i stands for an impurity) system at different temperatures. The behaviors of impurities in the vacuum distillation refining process were investigated. The results show that the vacuum distillation should be taken to obtain lead from crude lead, in which Zn, As and partial Sb are volatilized at lower temperature of 923-1023 K. Lead is distilled from the residue containing Cu, Sn, Ag and Bi at higher temperature of 1323-1423 K, but the impurity Bi is also volatilized along with lead and cannot be separated from lead.     

Nb-Hf合金表面Si-Ti-Cr硅化物涂层在大气和真空中的高温热震性能

为了提高Nb-Hf合金的高温热震性能,采用浆料烧结和高温渗透法制备了Si-Ti-Cr硅化物涂层,对比分析了Si-Ti-Cr硅化物包覆的Nb-Hf合金样品在大气和真空条件下的高温热震性能。通过模拟在热冲击过程中涂层的温度场和热应力场分布,揭示了Si-Ti-Cr涂层在大气和真空条件下的热冲击失效机理。结果表明,在1300 ℃热震循环100次条件下,涂层的真空失重小于0.8 mg/cm²;在1600 ℃热震循环200次条件下,涂层的空气增重小于3 mg/cm²。硅化物涂层在1300 ℃真空环境下和1600 ℃空气环境下具有优异的抗热震性能。     

Die Feuerverzinkung siliziumhaltiger Stähle – Problem und Lösungsmöglichkeiten

Hot dip galvanizing of silicon containing steels – the problem and some attempts to its solution Hot dip galvanizing of silicon containing steels, which are increasingly used today, involves the danger of very thick, poorly adherent, unsightly zinc coatings forming on the steel surface. Quite a number of attempts have been made to prevent this drawback. Chemical surface treatments of the steels to be galvanized did not yield the desired success, whilst mechanical surface treatments by shot blasting gave positive results in certain cases only. Galvanizing in the upper temperature range of conventional working practice (475–485 °C) appears appropriate for steels containing 0.15–0.20% Si, whereas low-temperature galvanizing at 430–440 °C using conventional galvanizing baths should be universally applicable provided that suitable methods are found for pre-heating parts of larger dimensions. Galvanizing with inhibited attack of the zinc caused by small additions of aluminium (less than 0.2%) did not yield coating thicknesses independent of the Si content of the steel. High-temperature galvanizing at more than 530 °C gives satisfactory coatings irrespective of the Si content of the steel; saturation of the galvanizing bath with iron should, however, be avoided. Low-temperature galvanizing at less than 430 °C is possible on principle, provided that the melting point of the zinc is reduced by adding alloying elements such as tin (10–30%), magnesium (3%), or aluminium (4–5%). However, tin is expensive, magnesium deteriorates the wetting properties of the steel, and aluminium requires a very careful pre-treatment, the coatings obtained exhibiting low thicknesses and dependency on the Si content of the steel with iron-saturated baths. Galvanizing with reduced zinc concentrations in zinc-saturated lead baths gave zinc coatings independent of the Si content, while currentless galvanizing in zinc-saturated salt baths was not successful.     

Microstructures and Properties of W-Ti Alloys Prepared Under Different Cooling Conditions

W-(10 to 15) wt.% Ti alloys were sintered at 1400 or 1500 °C and cooled under different cooling conditions. The microstructures and properties of W-Ti alloys were affected by the cooling conditions. XRD, SEM, EBSD, and TEM were carried out to investigate the effects of cooling conditions and sintering temperature on the microstructures of W-Ti alloys. The nanohardness and elastic modulus of the alloys were also investigated. The results showed that when the temperature was 1500 °C, the content of Ti-rich phase in W-(10 to 15) wt.% Ti alloys decreased obviously with the increase of cooling rate (the average cooling rate of furnace cooling, air cooling and water cooling was 0.2, 10, and 280 °C/s, respectively). For the W-10 wt.% Ti alloy, the content decreased from 20.5 to 9.7%, and the grain size decreased from 2.33 to 0.67 μm. When the temperature decreased to 1400 °C, the grain size was also decreased sharply with the increase of cooling rate, but there was a little change in the microstructure. Meanwhile, the grain sizes were smaller than those of the alloys sintered at 1500 °C. The nanohardness and elastic modulus increased with the increase of cooling rate, and the alloys sintered at different temperatures had different nanohardness and elastic modulus which depended on the cooling conditions. Sintering at a proper temperature and then cooling at a certain cooling condition was a useful method to fabricate alloy with less Ti-rich phase and high properties.