大型灰铸铁汽轮机缸体的铸造工艺设计

针对大型HT250汽轮机缸体的壁厚差别大,尺寸精度和表面粗糙度要求高等诸多难点,进行了砂型和制芯工艺方案设计,对两种工艺方案进行了分析和选定,并就选定的造型工艺进行了浇口、冒口、冷铁工艺设计.结合缸体铸造工艺设计要求,给出了合箱、熔炼、浇注和热处理等工艺的控制要点.按照工艺方案成功地生产出了大型HT250汽轮机缸体铸件,铸件品质达到工艺设计要求.     

缸体缸盖类铸件气孔缺陷的讨论

以汽车发动机缸体和缸盖等铸件为例,论述了气孔缺陷的特点和分布。经过大量试验,并结合多年的实践经验,从工艺设计中的浇注系统、铸型排气、型砂温度、制芯材料、铁液浇注速度、铁液浇注温度、铁液气体含量等方面分析了铸件气孔缺陷的主要原因和防止措施。     

WD618气缸体气孔缺陷分析及对策

通过对缺陷位置的解剖切割制样,利用扫描电镜和能谱分析了WD618气缸体裂隙状气孔的类型和成因。针对WD618气缸体的实际生产工艺,分别从熔炼工艺、浇包、浇注温度、型砂水分及制芯等方面分析了引起铸件裂隙状气孔缺陷的原因。结果表明,通过控制原材料质量、改进熔炼工艺和制芯工艺,裂隙状气孔缺陷被消除了。     

耐高压易溶芯的研制与应用

根据水溶材料和耐火材料的性质 ,研究了耐高压易溶芯的材料配比及制造工艺 ,对浇注成形及压制成形所制得的易溶芯性能进行了分析 ,确定了获得耐高温高压易溶芯材料的最佳值。用复合料制得的水溶芯 ,具有足够的机械强度 ,能承受高比压压力的液态金属的冲击 ;投入水中可在较短时间内溶解 ,并完全溃散。     

蠕墨铸铁NE840V8柴油机缸体铸造工艺研究与试制

介绍了蠕墨铸铁NE840V8柴油机缸体铸件试制过程,通过合理设计缸体毛坯铸造造型、制芯及砂芯组装工艺,合理使用炉料配比,同时根据生产条件正确选择和控制化学成分、蠕化剂及蠕化处理方法,使紧凑的蠕化处理、合理的浇注温度和浇注速度工艺过程相匹配,可得到缸体铸件的蠕化率达到80%以上,满足相关技术和质量控制要求。     

4G1发动机缸体的铸造工艺

介绍了4G1气缸体的铸件结构及技术要求,详细阐述了该铸件的生产工艺:一箱2件造型,采用覆膜砂制芯,2个缸体由10个砂芯组合而成;组芯夹具由4个夹紧气缸带动4个活动定位块,防止砂芯损坏,下芯夹具设置限位块和自由活动框,保证了下芯精度和缸体生产的尺寸稳定性;采用底注、阶梯式浇注系统,实现了顺序凝固,并设计了相应的排气系统,增加了排气通道,防止了气孔缺陷的产生;采用合理的熔炼工艺、孕育工艺及浇注工艺,保证了铸件的材料要求。生产结果显示:缸体铸件合格率已达到80%,机械加工合格率已达到90%。     

汽车缸体缸盖砂芯用热芯盒射芯机适宜性浅评

简述了汽车发动机缸体、缸盖砂芯的制芯工艺，分析了目前国产热芯盒射芯机的基本特点、工艺性能及经济性，提出了制造汽车发动机缸体缸盖砂芯适宜的国产热芯盒射芯机和配用的树脂砂种类。     

N485气缸体铸造工艺的改进

N485气缸体由于原工艺设计的浇注系统尺寸偏小，而产生了大量的浇不足和冷隔等铸造缺陷，其铸件合格率仅为30／～40％。我们对原工艺的浇注系统作了全面改进后，使该气缸体的合格率达到了95％以上。1原铸造工艺分析1．1原铸造工艺N485气缸体由于为中等批量，在我厂未上铸造线生产。采用的生产方式是：一箱一件，震击式造型机造型，湿型砂，油砂手工制芯。原铸造工艺方案的特点是：底注式浇注系统，小孔进铁水（浇注系统各组元断面积均较小），浇注时间长等，其工艺方案大致如图1所示。用图1所示的原铸造工艺方案生产N485气缸体，在凸轮室…     

发动机缸体缸盖的铸造

对国内外发动机缸体、缸盖铸造生产进行了总结,其材质主要以C（质量分数,下同）：3.15%～3.3%,CE：3.95%～4.05%,Si/C：0.6%～0.7%的灰铸铁为主。一般选择冲天炉-有芯工频电炉进行熔炼,孕育剂仍普遍采用75SiFe,立浇底注式浇注系统和保温冒口有利于获得优质缸体、缸盖,冷芯制芯工艺已逐渐取代热芯工艺。通过提高浇注温度、型砂紧实率等措施可减少缸体、缸盖常见缺陷渗漏的出现。     

3CR缸盖铸造工艺

介绍了3CR灰铸铁缸盖的结构特点、技术要求,以及铸造工艺设计详细情况,包括铸造工艺参数的确定、浇注及排气系统的设计、制芯和组芯方案、造型工艺等.采用冲天炉和感应电炉双联熔炼铁液,浇注温度控制在1 350～1 390℃,浇注时间10～16s.分析了3CR缸盖常见的气孔和碎芯缺陷产生的原因,并提出了防止措施,使其综合废品率控制在10％左右.     

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.     

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。     

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.     

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.