锌合金表带链型材挤压模设计与挤压过程数值模拟

通过对单孔挤压模和双孔挤压模挤压过程的数值模拟和实际挤压实验,实现了锌合金表带链型材的挤压成形,用2种不同结构的模具挤压时,相同挤压速度下,型材的温升基本相同,最大挤压力相差不大;随着挤压速度的增大,型材温度升高显著,最大挤压力增大。采用双孔模挤压时,挤压过程更平稳,挤压效率更高。     

镁合金挤压变形工艺的研究进展

镁合金是目前金属结构材料中最轻的材料,挤压变形是镁合金变形最常用的方法,在提高镁合金综合性能方面具有显著的作用。综述了镁合金挤压变形的传统挤压方法和非传统挤压方法,其中传统挤压方法包括正挤压、反挤压、等通道转角挤压等,非传统挤压方法包括等通道转角膨胀挤压、复合挤压、连续变截面直接挤压等;介绍了挤压变形在制备铝/镁合金复合材料等方面取得的研究进展;分析了不同挤压变形方法在细化镁合金晶粒、提高力学性能等方面的作用和机理。提出采用创新的挤压变形方法,制备出不仅具有优异的力学性能,而且兼备较高的抗腐蚀性能的铝/镁合金复合材料,将是镁合金挤压变形技术未来发展的趋势。     

反向挤压时的挤压力变化规律

利用正、反向挤压对比实验研究了反向挤压铝合金时 ,在基本挤压阶段 ,挤压力的变化规律以及其最大挤压力与正向挤压时的差异 ,以便为合理制订反向挤压工艺和进行工具设计提供依据。研究表明 :挤压棒材时 ,随着挤压过程的进行 ,挤压力呈现上升趋势 ,在挤压结束时达到最大值 ,这与正向挤压时是相反的 ,其最大挤压力比正向挤压时小 10 %左右 ;挤压管材时 ,在基本挤压阶段开始时的挤压力最大 ,随着挤压过程的进行 ,挤压力呈现下降趋势 ,与正向挤压时相似 ,而当挤压过程进行到一定程度时 ,挤压力基本保持稳定 ,其最大挤压力比正向挤压时小 30 %左右。     

基于有限元的铝合金反向挤压技术研究

根据铝合金反向挤压技术特点,分析了反向挤压时铝合金挤压出口温度的变化趋势,采用有限元数值模拟的方法模拟了铝合金反向挤压过程,得到了不同挤压速度情况下铝合金挤压出口温度的变化趋势,根据出口温度的变化情况,提出了采用挤压速度逐渐减小的速度曲线来实现反向挤压的等温挤压技术路线。     

第一讲 挤压筒的优化设计（1）

第一讲　挤压筒的优化设计（１）沈阳新光模具制造公司赵云路西南铝加工厂刘静安编者按语：本讲座从提高铝合金挤压工艺水平，提高挤压生产效率，提高挤压工具寿命的角度出发，全面而系统地总结了铝合金挤压工具（挤压筒，挤压轴，挤压针，挤压垫等）优化设计的实践经验。...     

挤压剪切与正挤压对AZ31镁合金塑性变形的影响

借鉴正挤压与多道次等通道挤压的特点提出了挤压(Extrusion)-剪切(Shear)复合挤压工艺(简称ES),制造了多副适合工业卧式挤压机的ES变形组合凹模,进行了ES挤压和普通挤压实验。构建了ES挤压和普通挤压的三维有限元热力耦合模型及数值模拟条件,对ES挤压过程的挤压力、累积应变演化进行了计算机模拟仿真。通过对坯料的应力状态进行了计算机模拟分析,发现ES挤压过程局部坯料受到四向压应力,ES挤压与普通正挤压相比可以显著提高镁合金变形过程的累积应变,因此可以更有效的细化晶粒。针对ES挤压和普通挤压棒料的不同位置进行了微观组织观察,发现在挤压温度为370℃、挤压比为12时ES挤压可以有效的细化晶粒,不仅可以细化棒材表层晶粒,心部也得到了细化。     

丝锥头数对内螺纹冷挤压成形质量的影响

为了研究大导程内螺纹的挤压成形过程及挤压丝锥的结构参数对其成形质量的影响,建立了3种头数的挤压丝锥模型,通过数值模拟得到了内螺纹冷挤压过程中的应力分布、金属流动规律以及挤压温度和挤压扭矩,获得了内螺纹成形质量,并通过内螺纹冷挤压试验验证了仿真结果。研究结果表明:内螺纹冷挤压过程中应力主要集中在工件与挤压棱齿接触区域,金属沿挤压棱齿表面流动,逐渐形成螺纹廓形;单头挤压丝锥加工的内螺纹质量最好,挤压温度与挤压扭矩最高;三头挤压丝锥加工的内螺纹质量最差,挤压温度与挤压扭矩最低;双头挤压丝锥兼有单头和三头丝锥的优点,内螺纹加工过程中的挤压温度和挤压扭矩较低,同时内螺纹的成形质量较好,试验结果与数值模拟结果基本吻合。     

挤压铸造设备现状及发展分析

挤压铸造工艺因能生产高性能铸件在在近年获得快速发展，挤压铸造设备决定了挤压铸造工艺的推广和优势的发挥。论文从挤压铸造方式、浇注系统、合模力规格、挤压过程控制4个方面分析了当前挤压铸造设备的现状，介绍了我国挤压铸造设备的研究和应用情况，针对我国挤压铸造设备的差距，提出在挤压铸造设备总体虚拟优化设计技术、实时挤压机构、合模机构及设备系统集成方面开展研究的建议。     

1050铝合金扭转挤压加工的3D有限元分析(英文)

研究了扭转挤压做为一种大塑性变形加工技术的可行性,并将其与普通的正挤压进行比较。在室温下对AA1050铝合金成功进行了扭转挤压和正挤压。采用商用有限元软件ABAQUS/Explicit模拟挤压过程。结果表明,在扭转挤压中,所需的载荷要比正挤压所需的小。有限元分析结果表明,在扭转挤压中,试样承受了较高的等效塑性应变,在挤压的最后阶段扭转挤压试样中的应变分布较之正挤压更为平滑,均匀。     

基于伺服压力机的AZ31镁合金反挤压成形

为探讨挤压速度模式对AZ31镁合金杯形件反挤压成形的影响,对伺服压力机反挤压成形进行有限元分析与实验,并与普通曲柄压力机和液压机反挤压成形进行比较。有限元分析结果表明,反挤压终了阶段,伺服挤压和液压挤压最大损伤值分别为3.41和3.30,远低于普通挤压的最大损伤值6.08;挤压过程中杯形件最大温差伺服挤压为45℃,而普通挤压和液压挤压分别为127℃和70℃。实验结果表明,在1100kN伺服压力机上,采用伺服挤压模式,可成功获得壁厚为3mm的AZ31镁合金反挤压杯形件,而采用普通挤压模式,在杯形件边缘则出现破裂。实验与有限元分析结果基本吻合。     

高速开关阀位置控制方法

阐述了脉宽调制(PWM)控制的基本原理以及PWM信号的驱动方式，并以变量泵的排量控制为研究对象，通过对高速开关阀位置控制系统控制方法的理论分析和仿真研究，得出了一种基于常规控制手段的可提高高速开关阀位置控制系统精度的方法。     

Asymmetry of the yield strength in single crystals of titanium nickelide

Based on the results of the experimental studies of the temperature dependence of the yield stress of single crystals of TiNi alloys and of the mechanism of the mechanical twinning of the B2 phase as a martensite-type local reversible phase transformation, the asymmetry of the mechanical behavior of these materials during tension and compression in the [001] direction has been investigated. It is shown that a specific feature of this mechanism is the fact that the critical mode of distortion which determines stresses during mechanical twinning is a homogeneous deformation of transformation of the Bain-deformation type. To analyze the asymmetry of these stresses during tension and compression, a concept of the factor of normal stresses reduced to the principal axes of the tensor of the homogeneous deformation of transformation is introduced. It is shown that this factor can be used for analyzing the asymmetry of the mechanical behavior of single crystals of TiNi alloys.     

Corrosion Monitoring of Pipelines of Heat-Supply Systems Based on Gravimetric and Electrochemical Methods of Analysis

The aim of this work is to investigate the possibility of the application of the procedure for the prediction of the rate of corrosion for internal surfaces of the pipes of heat-supply systems. As a basis of the system for the evaluation of protective properties of oxide films, gravimetric studies and evaluation of the phase composition of films and their permittivity are chosen. The results of investigations of films show that it is possible to predict the rate of corrosion using not only gravimetric studies, but also the determination of the fraction of free surface and identification of the type and number of phases of the film. These procedures, being involved in the general system, make it possible not only to predict the corrosion process, but also to analyze reasons for its further development.     

Ten Years of the Russian Metallurgists Association and the 3rd Lakhtin Readings

The report is devoted to the 10th anniversary of the Russian Metallurgists Association (RASMET). The history of the appearance of the society of metallurgists in Russia is presented and the role of professor of Yu. M. Lakhtin, one of the creators of the theory and technology of nitriding in Russia, in the formation of the society is described. Lakhtin Readings are a scientific forum of specialists working in the field of thermochemical treatment. The role of IFHTSE in the organization and popularization of the Readings and the results of the 10-years work of RASMET are presented.     

Peculiarities of the macroscopic investigation of multicomponent electrochemichal deposits on the basis of the comparison of relative deviations

The paper presents an analysis of the available indicators of the correlation of the macroscopic distribution of the multicomponent electrochemical deposits and offers new indicators based on the principle of the comparison of the relative deviations from the average values of the sets of measurements of the dispersed parameters of electrochemical objects. The elaborated indicators reflect the correlation between the dispersed parameters with regard to the share in an aggregate (at the cathode macrolevel) of the compared feature of the relative deviations and allow for the objective checking of their estimation by other indicators. In addition, they enable a thorough investigation of the formation process of the multicomponent electrochemical deposits at the cathode macrolevel and application of their values for the purpose of the control and prediction of the functional structure of the deposits.     

Relaxation of interphase stresses on the later stages of the heterogeneous decomposition of solid solutions. II. Variational problem

The study of relaxation processes upon the decomposition of solid solutions at the stage of coalescence in the regime of dislocation-matrix diffusion is performed using a “precipitated-phase-particle-feeding-dislocations” system as an example. Within the framework of the variational approach, the cases of the independent and interdependent variation of the fraction of the relaxed regions of the interphase surface and of the number of edge dislocations which supply the alloying component to the precipitated phase have been investigated. Under the assumption that implies the linearity of the possible connection between these parameters, the model approximation of the continuous nucleation of epitaxial defects, and the absence of free matrix dislocations near the particle in the initial state, it is shown that the decrease in the number of edge feeding dislocations in the process of relaxation of interphase stresses can occur only by means of “leakage” of dislocation segments localized in the precipitate outside the limits of the precipitate with the formation of structural dislocation loops on the interphase surface.     

Special Features of Vacuum Carburizing of Heat-Resistant Steel in Acetylene

The mechanism of formation of the diffusion layer due to vacuum carburizing of complexly alloyed steel 16Kh3NVFMB-Sh (VKS5) in a medium of acetylene is considered. It is shown that the process of carburizing occurs in a self-regulation mode without the danger of carbon black due to the high rate of arrival of carbon from the gas medium as a result of catalytic dissociation of acetylene molecules, intense process of carbide formation on the saturated surface, and absence of catalytic activity of carbides. The diffusion layer forms under a thin layer of the carbide phase in a kinetic regime, the intensity of which is determined by the rate of dissolution of carbides.     

Structure of two-dimensional domain walls in two-layer permalloy films with a nonmagnetic interlayer

Structure of domain walls in two-layer Permalloy films separated by a nonmagnetic interlayer has been studied by the numerical minimization of the functional of the total energy of the domain wall in terms of a two-dimensional model of the magnetization distribution with an exact allowance for basic interactions (including exchange, magnetoanisotropic, and dipole-dipole interactions). Differences between the structure of these walls and that of single-layer films of analogous thicknesses have been investigated. The total energy (and its exchange and dipole-dipole components) per unit area of the surface of domain walls in two-layer films has been calculated as functions of the thicknesses of the Permalloy layers and the interlayer. The dependence of the thickness of magnetic layers at which there occurs a transition from the walls of the same type as in single-layer films of the corresponding thickness to walls of another type on the thickness of the interlayer has also been constructed. A comparison of the curve of this dependence with the experimental data is carried out.     

Electroerosion treatment of dielectric materials

The authors worked out a new method of combined electric-erosion and electric-chemical processing of dielectrics in an electrolytic medium. This article is dedicated to the study of the process of passing an electric current through an aqueous solution of an electrolyte. With the help of measurements of the voltampere characteristics of the current passing through the electrolytes under study, the total character of the electrolytes’ dependence, which has 4 transition regimes, was determined. The characteristics of the transition regimes depend on both the electric regimes and the types of electrolytes and their concentration and don’t depend on the distance between the electrodes. It’s characteristic of characteristic third phase that a plasma envelope appears that is accompanied by distraction of the dielectric. It’s shown that the tension and corresponding current density at which the plasma envelope occurs exist for every type of electrolyte when the material of the cathode is not changed. The correlation between these parameters and the coefficient of the surface-tension of the studied electrolytes is determined. The results of the study include the dependence of the speed of the volumetric broaching upon such technological parameters as the electric power, the frequency of the revolution of the electrode device, the frequency of the relaxation of the generator, and the concentration of the electrolyte. The problem of the mechanisms of the influence of the electric discharge in the electrolyte upon dielectric is discussed.     

Mechanisms of the Influence of Nitrogen on the Structure and Properties of Steels (A Review)

Special features of the structure of nitrogen-containing steels and the role of nitrogen in their hardening are considered. The following mechanisms of the action of nitrogen on the structure and properties of steels are analyzed: change in the state of solid solutions, shifting of the temperature of phase equilibria, segregation of nitride particles, interaction between nitrogen atoms and defects of crystal structure, and effect of nitrogen on the electron subsystem of the metal.