铜加工连续挤压工装模具的改进

连续挤压技术属于一种金属性的塑性加工技术,具有明显的优势,将其与传统的挤压技术对比就可以发现,连续挤压技术具有节约资源、提高利用率与降低成本的优势,将其用于铜加工中可以更好地发挥作用。在对铜加工连续挤压工装模具的工艺改进中,通过设计不同长度的挤压模具进行分析,其中包括偏心结构的挤压模具设计,从而增加延伸槽的面积,并在此期间安装夹紧环,在初始阶段进行预热。该文通过比较铜加工连续挤压工装模具工艺改进前后的材料性能对比设计一种新型的连续挤压工具模具,用于加工铜材,在铜材使用期间能节约铜材、降低成本、提升模具的实际使用寿命,取得良好的经济效益。     

连续往复式等通道转角挤压装置的研究

目前常见的等通道转角挤压是用"L"形通道结构模具配合压力机来进行非连续挤压的,该模具结构存在不足之处,特别是在实现连续往复挤压方面存在极大的困难。通过改进模具结构和压力机工作台的结构,提出把模具中的"L"形通道改进成"U"形通道,并在常见液压机的固定工作台上增设移动工作台装置和工作台运动控制系统的方式来实现挤压模具在工作台上的精确移动和位置的改变,从而可以在不取出试样的条件下实现连续往复式多道次挤压块体材料,挤压后的材料可得到超细晶结构。     

高温软钎料材料

为强化地球环境保护，采用不含铅的软钎焊材料。其中，作为熔化温度200～250℃的Sn-Pb软钎焊材料的替代材料，促进了Sn-Ag系、及Sn-Cu系的软钎焊材料等不含铅的软钎焊材料的实用化。另外，对于谋求高耐热性的高温软钎焊材料，还未见到替代材料，目前离实用化还很远。作为熔化温度达到250～300℃的高温软钎焊材料，提出了以铋（Bi）为主体的材料。     

H13铝型材挤压模具失效分析及改进

以H13铝型材挤压模具开裂失效严重的分流桥为研究对象,采用金相组织观察、断面形貌等物化试验,结合挤压条件分析,探讨了模具材料组织、模具结构和挤压强度及模具预热强度对模具开裂失效的影响。对失效模具进行了分析,改进了热处理工艺及选材方案,模具平均使用寿命提高了17%以上。     

差速器行星齿轮新工艺及新型模具设计

针对汽车差速器行星齿轮原挤压模具结构存在的问题,改进了挤压工艺,设计了新型预成型挤压模和精压模。工艺试验表明:新工艺可显著降低挤压变形力、材料消耗和生产成本,提高模具寿命和生产效率。     

铝挤压的PSA氮气保护

硬铝合金和软铝合金的挤压已广泛采用氮气保护[1、2]。氮气保护的好处在于它能消除氧化物的粘结,进而改进挤压件表面质量,增加模具寿命,延长坯锭行程,减少模具抛光次数,并在不降低表面质量的情况下提高挤压速度。自70年代初期,大气产品公司就首先采用     

铝及其合金软钎焊技术的研究现状

本文综述了铝及铝合金软钎焊近年来的研究动态。指出了钎剂在铝质材料软钎焊中的重要作用,分析了无铅钎料成分的优缺点,并讨论一些新出现的钎料配方和钎焊工艺以及目前的发展趋势。还阐述了一些较新型的钎焊加热工艺,并指出其优点和应用前景。     

H13铝型材挤压模具早期开裂失效分析

根据铝型材挤压模具早期开裂失效形式 ,对模具进行了强度校核 ,并通过化学成分、显微组织及断口分析等试验方法 ,对模具材料进行分析 ,探讨了模具早期失效的原因 ,并提出了改进建议。     

连续挤压大宽厚比产品的物理模拟实验研究

针对连续挤压大宽厚比产品中易出现的裂边等产品质量问题,进行模具设计。传统塑性加工实验易造成材料浪费且不易操作,实验采用橡皮泥作为模拟材料,对所设计模具进行物理模拟,并依据模拟结果对模具进行改进。结果表明,改进后的模具具有良好的材料成形性,产品裂边问题得到有效控制。     

钎焊基本知识讲座

(一)概说一、钎焊及其与熔焊比较钎焊和熔焊一样,是连接金属的一种方法。钎焊是依靠熔融的液体钎料填满固态基体金属的间隙,并靠其熔融钎料与基体金属的相互扩散、溶解作用而形成牢固连接,这种连接金属的方法称为钎焊。钎焊材料根据其熔点的高低不同分为软钎料(熔点低于450℃)和硬钎料(熔点高于450℃)。使用软钎料来钎焊连接     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。