熔模铸造硅溶胶模壳制造工艺

介绍用石蜡-硬脂酸低温模料制作熔模,用硅溶胶作粘结剂制造模壳的工艺。包括熔模制造工艺、硅溶胶模壳工艺和焙烧工艺。生产实践证明,铸造硅溶胶模壳制造工艺是成熟的,为生产合格模壳和精密铸件提供了技术保障。     

精密铸造硅溶胶模壳的制造工艺

介绍用石蜡-硬脂酸低温模料，生产铸件的熔模和用精密铸造硅溶胶，作为制壳粘结刑，制造铸件的模壳的工艺要求。主要研究熔模制造工艺、硅溶胶模壳工艺和焙烧工艺。五年多来的生产实践充分证明精密铸造硅溶胶模壳制造工艺是成熟的。为生产合格模壳和精密铸件提供了技术保障。     

硅溶胶与硅酸乙酯复合型壳探讨：缩短硅溶胶制壳周期方法之一

探讨用硅溶胶与硅酸乙酯制造复合型壳的工艺，选择出层间干燥时间等参数，为生产使用提供了科学依据。复合型壳代替硅溶胶型壳可大大缩短制壳生产周期。     

硅溶胶型壳脱壳性能的改良方法

硅溶胶制壳是当前国内外精密铸造行业的主流生产工艺.为了改善硅溶胶型壳的脱壳性能,采取控制硅溶胶二氧化硅的含量、用快干硅溶胶做粘接剂、改进制壳工艺、控制焙烧温度的方法,在保证型壳有足够的高温强度下,尽量降低残留强度、提高脱壳性.实践证明效果较好,能在行业内推广使用.     

硅溶胶壳型的真空干燥工艺参数研究

经过大量实验发现采用胶态浇注成形技术和真空干燥方法可制备表面裂纹少的硅溶胶壳型。制备硅溶胶壳型用材料有JN-30硅溶胶、石英粉和NH4Cl。通过实验得到一组硅溶胶壳型的真空干燥工艺参数:干燥温度80~100℃,干燥时间5 h和真空度0.06~0.07 MPa。然后对此进行重复实验,得到硅溶胶壳型的收缩率(干燥收缩率和总收缩率)和抗压强度期望分别为0.97%、1.04%和5.05 MPa。     

SKP-27型快干硅溶胶在精密铸造中的应用

快干硅溶胶与普通硅溶胶比较，具有制壳周期短、型壳常温强度高、残留强度低的优点。经精密铸造企业大批量生产考核证明，用SKP-27型快干硅溶胶代替普通硅溶胶，型壳清砂容易，铸件尺寸符合公差要求，铸件成本略有下降。批生产证明，在干燥间风速、湿度控制合理时，型壳干燥时间可缩短50％以上。     

低温蜡-硅溶胶型壳的应用实践

分析了水玻璃型壳、复合型壳、中温蜡-硅溶胶型壳和低温蜡-硅溶胶型壳4种制壳工艺的优缺点,指出低温蜡-硅溶胶型壳工艺适用于质量要求一般的铸件,中温蜡-硅溶胶型壳工艺适用于高质量要求的小件、特小件。介绍了低温蜡-硅溶胶型壳的生产工艺要点。     

一种新型快干增强硅溶胶的试验

随着熔模铸造的不断发展,市场对硅溶胶型壳的强度及快干性能提出了更高的要求,发展快干增强硅溶胶成为必然趋势.目前国内硅溶胶型壳仍存在常温强度偏低及残留强度偏高的问题,因此,如何通过改善硅溶胶进而改善硅溶胶型壳的综合强度性能,则对提高硅溶胶型壳及铸件品质有着重要意义.本文重点介绍一种乳胶改性快干增强硅溶胶F,经与国内外硅溶胶比较,硅溶胶F在提高型壳常温强度、降低型壳残留强度方面有较明显的优势.     

聚乙烯蜡-硅溶胶熔模铸造工艺

介绍了用聚乙烯蜡低温模料制作熔模、用硅溶胶作粘结剂制造型壳的工艺.多年生产实践证明,采用聚乙烯蜡制模的硅溶胶型壳制造工艺是成熟的,可以达到减少污染、降低成本的效果.     

硅溶胶中二氧化硅含量对单晶型壳性能的影响

通过采用不同二氧化硅含量的硅溶胶制备单晶型壳,并测定型壳不同温度下的抗弯强度和自重变形,研究了硅溶胶中二氧化硅含量对单晶型壳性能的影响.研究结果表明:在1 350℃下,型壳中二次莫来石相的含量及型壳的抗弯强度随硅溶胶中二氧化硅含量的增大而提高;在1 550℃和1 600℃下,型壳中形成的二次莫来石相的强化作用与高温下玻璃相的软化作用相当,导致型壳的抗弯强度在某一数值附近波动.型壳自重变形表明,随硅溶胶中二氧化硅含量的增加,型壳的自重变形量减小.单晶型壳浇注试验表明,涂制型壳用硅溶胶中二氧化硅含量为15.65％～24.6％时,涂制出的型壳强度满足生产要求,未出现跑火现象.     

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.     

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。     

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.     

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.     

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.