镁合金拉深成形模具结构研究

为了提高镁合金的冲压性能,通过分析镁合金板材性能及材料拉深过程中不同部分变化状况,得出提高镁合金薄板拉深成形性能模具结构上采取的应对措施.设计了镁合金拉深成形模具.采用电缆环形电阻丝线圈加热模具的压边圈和与坯料接触的凹模表面,以提高镁合金的塑性变形能力;采用热电偶控制模具温度;采用循环水对凸模和凹模进行冷却以保持镁合金的抗拉强度;设计了电缆环形电阻丝线圈的结构形式.提出了模具设计、制造和使用过程中的注意问题.     

防皱拉深胀形模

铝蒸锅是铝制品生产厂的主要产品之一,其中蒸锅盖(图1)是在双动拉深机上拉深成形。以往的拉深模具(图2)由四部分组成,即压边圈、凸模、凹模和顶盘。拉深成形时由压边圈和凹模平面压住坯料,凸模下降使坯料进入凹模中成形。当凸模下降到最低点时,利用凸模和顶盘间的挤压,成形拉深件表面的曲面轮廓。最后将拉深件从凹模中顶     

镁合金的冲压成形工艺研究

研究了在曲柄压力机上用镁合金板材冲压手机外壳的模具设计和工艺制度,研究了坯料温度、模具温度、润滑条件等工艺因素对镁合金手机外壳冲压质量的影响。试验表明,在应用正确的模具结构和适当的工艺条件下,当坯料温度在350℃左右,拉深凹模温度在350℃左右及良好润滑情况下,能够成功地在曲柄压力机上冲压出镁合金手机外壳。     

行李箱外板成形的温度影响分析及控制策略

某车型行李箱外板连续生产过程中存在稳定性问题。首先,总结了温度对热敏感的烘烤硬化钢板料性能的影响;然后,采用DYNAFORM软件分析了实际生产中模具的温度变化对材料成形阻力的影响,结果显示温度会使拉伸过程中的压边圈和凹模之间的间隙发生变化,从而产生稳定性问题;进一步分析了压边圈温度变化和坯料温度变化的主要原因,结果表明压边圈温度变化的主要影响因素是摩擦热,坯料的温度变化是变形热和摩擦热共同作用的结果;最后,分析了不同工艺参数条件下,压边圈和坯料的温度变化。根据分析结论,制定了针对性的控制策略,对凸模、凹模、压边圈进行镀铬处理以降低摩擦,增加吹气装置以快速散热,降低压边力以控制变薄率,最终成功将温度控制在可接受范围内,实现了稳定生产。     

AZ31B镁合金方盒形件拉深成形工艺参数研究

针对AZ31B镁合金方盒形件进行拉深成形工艺试验,分析了单个工艺参数的变化对盒形件拉深成形过程的影响,在其他因素不变的条件下,凹模温度在150~300℃范围内,成形深度随温度升高而增大,在300℃时成形深度达到最大值;凸模温度保持在120℃左右,差温拉深效果较为明显;压边间隙调整到1.3t(t为板材厚度)时,拉深深度最大;拉深速度在30 mm·min-1时成形深度最大。确定了影响拉深成形深度的各工艺参数的先后顺序为:压边间隙、凸模温度、凹模温度和拉深速度。运用正交试验方法进行各工艺参数优化组合,结果表明,采用最优工艺参数组合可以提高AZ31B镁合金方盒形件拉深成形的成形深度。     

镁合金板材的固体颗粒介质拉深工艺参数

提出基于固体颗粒介质成形(SGMF)工艺的镁合金板材差温拉深工艺,并展开试验研究。通过对AZ31B镁合金薄板进行差温拉深成形试验,研究了成形温度、拉深速度、压边力、压边间隙、凹模圆角和润滑条件对拉深性能的影响,确定AZ31B镁合金板料最佳成形工艺参数。结果表明:该工艺可显著提高镁合金板材的成形性能,成形温度及拉深速度对板料拉深性能影响较大,板料最佳成形温度区间为290～310℃,颗粒介质与板料理想温差为110～150℃;压边力和压边间隙对拉深性能产生联合影响;此外,凹模圆角和润滑条件也对拉深性能有一定的影响。当上述工艺参数达到最佳值时成功拉深出极限拉深比(LDR)为2.41的工件。     

双槽容器整体成形法

如图所示。首先将坯料7放置在凹模1上,压边圈6用预定的压边力将坯料7压紧。然后由液压装置将压力液体经孔13和12,流入压边圈6和坯料7之间,使坯料7在凹模1的模腔3a、3b内鼓起;同时坯料开始拉入凹模内。此时压料板14a、14b用预定的压料力,把容器底部压紧。在这种状态下,凸模5a、5b压入。当压力超过限定压力时,通过11a,11b和溢流阀将液体排出。成形过程中,压料板14a、     

镁合金板热拉深模具设计及应用

为测定镁合金的极限拉深比,根据圆筒拉深件成形的特点,设计了可实现差温变形的拉深模具。凹模与压边圈采用加热棒进行加热,最高温度可达300℃,以提高板坯的成形性能;凸模中通入冷却水,使完成弯曲变形进入到筒壁传力区的板料快速降温以提高其强度。利用该模具,分别对5083铝合金和AZ31镁合金进行了圆筒极限拉深比的测定试验,验证了该模具系统的可靠性。     

AZ31镁合金薄板手机外壳温冲模具设计及成形性能研究

设计并制造了AZ31镁合金薄板的手机外壳温冲模具,并对其成形性能进行试验研究。试验表明,eta/DYNAFORM有限元模拟软件能够较好的验证模具设计的合理性和分析AZ31镁合金薄板冲压成形性能,通过合理地选取模具参数,并对拉伸速度、润滑条件、坯料以及凸、凹模温度等主要影响因素的控制,可有效地解决AZ31镁合金拉伸生产过程中的拉裂缺陷,在普通液压机上能成功冲压出镁合金壳形件。     

拼焊板方盒件拉深成形的实验研究

本文对拼焊板方盒件的拉深成形进行了试验研究。试验中采用了整体压边圈和分瓣压边圈。凹模表面和型腔加工了台阶以补偿坯料的厚度差值。对压边力的控制采用了弹性橡胶控制法和刚性直接控制法。对压边力的分布采用了均匀压边力和局部改变压边力。通过调整模具结构和压边方法及压边力分布 ,对坯料不均匀变形规律及焊缝的移动规律、坯料的起皱规律及控制坯料不均匀变形的方法进行了探讨研究。     

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).     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.