汽车制动钳体冒口颈缩孔工艺改进

汽车制动钳体是制动系统的关键零件,其铸件品质要求高,在生产中易产生缩孔缺陷。通过分析铸件冒口颈缩孔产生的原因,结合计算机凝固数值模拟,优化浇注系统和冒口设计,实现浇注液流均匀,冒口充分补缩,有效地解决了铸件冒口颈缩孔问题。     

用亚共晶成分生产厚大断面铸态球铁油缸

金相、硬度、机械性能测试分析表明，在生产厚大断面油缸类球墨铸件时，用亚共晶成分（CE＝4．0％～4．2％）并加入合金化元素（Cu、Sn），能完全满足铸态QT600－2的材质要求，并消除了铸件中心或热节部位的组织疏松、石墨漂浮等缺陷，解决了长期以来油缸类铸件渗漏问题，并取得了良好的经济和社会效益。     

浇注温度对铝合金制动泵体流变挤压铸造的影响

高强度铝合金代替钢铁零件已成为汽车轻量化的一个重要发展方向。半固态流变挤压铸造生产的铸件,成品率高、力学性能好,有着广阔的发展空间。使用半固态流变挤压铸造工艺生产了汽车铝合金制动泵体,并通过金相实验和拉伸实验研究了浇注温度对铝合金制动泵体流变挤压铸造的影响。结果表明,在600~620℃浇注可获得金相组织呈近球状的制动泵体,且质量良好;随着浇注温度降低,铸件的晶粒尺寸变小,抗拉强度和伸长率增大。     

基于ProCAST的汽车制动鼓消失模铸造工艺优化

针对汽车制动鼓铸件在实际生产中存在的缩孔、缩松问题,通过ProCAST软件对制动鼓消失模铸造工艺进行数值模拟,分析了铸件温度场对铸件缩松缩孔缺陷的影响,并对消失模铸造汽车制动鼓工艺方案进行了优化。结果表明,采用底部注入式浇注系统,液态金属在充型过程中均匀平稳并且能够充满铸型型腔,通过在铸件顶部加环形冒口以及增加铸件顶部内壁壁厚,可以有效地改善凝固过程中的温度场,降低铸件出现缩松、缩孔的几率,使缩松、缩孔缺陷基本出现在直浇道中。对铸件进行X射线检测,实际生产汽车制动鼓铸件内部无缩松、缩孔缺陷,提高了铸件的合格率。     

制动卡钳铸件皮下气孔缺陷的防止

介绍了球墨铸铁制动卡钳的铸件结构和技术要求。693制动钳和812制动钳铸件均在DISA垂直分型挤压造型线上生产,原工艺生产的制动钳铸件经常由于皮下气孔报废。为查明废品原因,对2种制动钳铸件结构及皮下气孔废品率进行了对比,随后在不改变铸件结构的情况下,通过降低型砂水分和提高灼烧减量,消除了皮下气孔反复发生的现象,废品率稳定控制在1.5%以下,提高了铸件质量稳定性,降低了铸件生产成本。试验证明:选择适当的型砂水分并适当提高型砂灼烧减量,是防止制动卡钳皮下气孔反复发生的有效措施。     

国内中小汽车配件铸造厂的发展改造方向和途径

1国内中小汽车配件铸造企业的现状与问题汽车铸造业是我国汽车制造行业的主要支撑之一，一辆整车约有10．5％的零件是铸铁件，6．4％的铝铸件。2002年以来，我国汽车产量持续增加，2006年汽车产销双双突破700万辆，分别达到727．97万辆和721．6万辆，已成为继美国和日本之后的第3大汽车生产大国。同时，国外汽车用铸件全球采购，逐步向中国转移。我国汽车铸件市场呈现出需求强劲，     

涂料对轴承座铸件内表面废品率的影响

1铸件技术要求轴承座是微型汽车传动轴与后桥连接处的连接件，重9kg，灰铸铁，铸造采用合脂油芯，装配后内部有几个传动的伞齿轮及差速器等零件。由于这些齿轮的磨损会直接影响到汽车的性能，轴承座内腔清洁度要求很高．内表面不允许有粘砂、夹渣、砂孔和气孔等，因此，型芯徐（浸）涂料是生产中必不可少的一道工序。2涂料对铸件质量的影响2．1涂料涂覆工艺对废品率的影响GM牌醇基涂料为例，各种涂覆工艺对内表面废品率的影响如表1所示。由表1可知，涂料对铸件内表面废品率的影响是相当明显的。同时，涂覆工艺不同，铸件内腔表面质量不合格…     

杯状壳体类零件压铸模具改为挤压压铸模锻模具的方案

杯状壳体类零件是一种典型结构的零件,占压铸件(低压铸件)相当大的比例,如各种汽车水泵机油泵体、制冷机壳体、减振器壳体等,这种铸件未必结构复杂,但多是壁厚件,归类为"功能件"(与"结构件"相对),要求有良好的气密性及较高的强度,很多时还有材质方面(如高强度使用低流动性的ZL203、LY12)、热处理和表面处理(如固溶强化、阳极氧化)的要求.因此,它是出现缩孔缩松问题最多的压铸件.     

油缸二工位冷挤压工艺及模具设计

结合油缸二工位冷挤压(光)工艺及模具设计实践 ,论述了冷挤压 ,特别是二工位冷挤压的优越性及工艺特点 ,并对该工艺及模具设计作了较详细的介绍 ,可供千斤顶行业及其它内孔要求较高的长筒形零件加工参考。     

铝合金导轨的铸造工艺

铝合金导轨长度长、壁厚簿且不均匀,铸件的技术及质量要求较高,给导轨铸件的生产带来了较大的难度.通过对导轨的铸件结构进行充分的分析,制定了合理的铸造工艺,对主要部位采取了相应的工艺措施,严格控制熔炼及浇注操作,经过多次试制,完成了导轨铸件的生产试制任务,经加工检验符合零件的使用要求,为铸件批量生产奠定了基础.     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.