钛及钛合金熔炼技术发展现状

目前生产钛及钛合金铸锭最主要的方法是真空自耗电弧熔炼以及冷床炉熔炼方法。详细介绍了真空自耗电弧熔炼、电子束冷床炉熔炼以及等离子束冷床炉熔炼技术的原理、特点和发展现状。     

冷轧纯钛带分层缺陷分析

利用宏观观察、金相、显微硬度测试等方法,对冷轧纯钛带分层缺陷进行了总结分析。分析结果表明,冷轧纯钛带分层缺陷,是由铸锭真空自耗电弧熔炼(VAR)过程中形成的中心缩孔缩松、气孔及硬α相缺陷引起的。     

真空自耗电弧炉真空系统的检漏

主要论述了用于生产钛及钛合金铸锭的真空自耗电弧炉真空系统的组成与特点,针对钛、钛合金的冶金特点及生产实际,阐述真空系统漏率对于生产钛、钛合金的意义;应用最新技术的莱宝300型检漏仪,对真空系统进行了测漏,总结了检漏方法,此法对真空白耗电弧炉真空系统或类似的真空设备测点的设计、检漏具有指导意义.     

钛合金VAR熔炼自耗电极破断原因分析

主要对钛合金VAR熔炼过程导致自耗电极破断的各种因素进行了分析.通过大量生产试验,探索出在现有装备条件下,通过控制原料的搭配、混合的均匀化程度和填料的充实性,以及改进自耗电极焊接技术、转运过程的抗震防护技术和熔炼控制技术使熔炼过程稳定,自耗电极无破断现象发生,为工业化批量生产大规格钛合金铸锭提供了技术保障.     

钛与钛合金(续)

(三)钛合金的熔炼 由钛矿石还原制成的海绵钛不能直接用作结构材料,必须进行进一步的熔炼或烧结,使成为致密的铸锭或烧结块。 我们知道金属钛与氢、氧、氮和碳的化合力很强,这样就造成了钛与钛合金在熔炼和加工中的复杂性,它们的熔炼和烧结操作都要求在高度的真空或纯化的惰性气氛(如氩、氦等)中进行。此外,由于钛对一般的耐火材料均发生蚀侵作用,到目前为止还没有寻找到一种适合于工业生产应用的坩埚材料。 现行的生产致密钛的主要方法就是电弧熔炼法,即使用自耗式电极或非自耗电极在水冷     

高性能轴承钢真空自耗熔炼过程组织演变规律与控制研究

通过Pro-CAST有限元软件模拟了高性能轴承钢真空自耗熔炼过程的温度场、熔池形貌和微观组织,研究了真空自耗铸锭组织演变规律,探究了温度场、熔池形貌对组织生长的影响。熔炼结束后,对真空自耗铸锭进行解剖酸洗以验证模拟结果。研究表明:模拟结果与实验结果吻合,铸锭组织形貌为贯穿铸锭中心的细长柱状晶,真空自耗铸锭的底部、边部和凝固末端有小面积等轴晶。柱状晶的生长带有明显的择优取向,底部柱状晶取向为垂直向上,中上部为斜向上。熔池深度越大,斜向上角度越小;熔池形貌对铸锭组织形貌影响显著,通过控制熔炼参数控制好熔池形貌能有效提高铸锭质量。     

Ti-V-Cr系阻燃钛合金厚板组织与力学性能对比研究

研究了WSTi3515S合金和TB12合金的大型铸锭成分和组织均匀性,对比分析了两种Ti-V-Cr系阻燃钛合金厚板的力学性能。结果表明:采用真空自耗电弧熔炼技术制备的Ti-V-Cr系阻燃钛合金3t级大型铸锭成分均匀;利用大型挤压机和大型快锻机制备的阻燃钛合金大尺寸厚板组织和性能均匀;两种合金的室温拉伸、硬度、冲击和540℃高温拉伸等性能相当,WSTi3515S合金在540℃条件下的热强性能较好;V和C元素有利于提高合金的热强性能,且C元素还能细化组织。     

真空自耗电弧炉恒熔速控制系统改造

为真空自耗电弧炉设备由恒电压控制升级改造至恒熔速控制系统。通过对2000kg真空自耗电弧炉熔炼钛合金的生产工艺、过程参数、产品要求进行了详细分析,选取恰当的数据采样算法,为更好的掌握真空弧电压、真空弧电流、钛合金熔炼速度等工艺参数间的耦合关系提供了良好的依据。同时对真空自耗电弧炉的控制系统现状及熔炼技术发展做了综述。在PLC中建立弧电压、弧电流,熔炼速率等的计算公式来实现设定各级控制回路的设定值。     

钒基贮氢合金的公斤级熔炼工艺与性能改善

研究了V-60%(TiCrFeMn)贮氢合金的公斤级熔炼工艺和热处理工艺,采用真空中频感应和非自耗真空电弧熔炼两种不同的熔炼方法制备公斤级钒基贮氢合金,采用高温退火方法改善合金的性能.结果表明,采用真空中频感应熔炼的合金由于熔炼过程中合金液与坩埚反应,致使合金含氧量过高,合金性能恶化,而采用非自耗真空电弧熔炼的合金表现...     

TC11钛合金铸锭表面质量和电压关系的研究

以海绵钛和中间合金压制的电极经两次熔化得到的TC11合金铸锭为原材料,采用真空自耗电弧炉,在不同的电压下熔炼3次TC11合金铸锭,研究熔化电压、弧长与TC11合金铸锭扒皮深度和扒皮量的关系.结果表明,熔化电压控制在35～38 V之间,可得到合理的电弧弧长,熔炼出的TC11合金铸锭表面质量好,扒皮深度为10～12 mm,扒皮量为2.75%～3.31%.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。