烧结机尾固定筛篦条的消失模铸造

烧结机尾固定筛篦条上的条形孔具有长、窄、深的特点。文中从泡沫塑料模样的制作、涂料配方、涂料涂敷及干燥方法、浇注位置及浇注系统的确定、装箱振实操作步骤、浇注、打箱等方面介绍了消失模铸造生产固定筛篦条的工艺方案。实践表明，采用消失模铸造生产的固定筛篦条产品表面质量、性能指标均能保证使用要求。     

一种真空消失模铸造生产线专用的全液压浇注机

分析了真空消失模铸造生产线浇注过程的特点,针对其特殊要求,设计制造了全液压专用浇注机,该设备已用于本公司真空消失模铸造生产线上,生产应用效果良好,能满足真空消失模铸造浇注过程要求.     

机尾滚筒消失模铸造凝固过程模拟及工艺优化

分析了机尾滚筒的结构特点,建立机尾滚筒的三维实体模型,并对机尾滚筒消失模铸造工艺进行部分改进。运用华铸CAE软件对原浇注工艺方案和改进后的工艺方案进行凝固过程模拟分析。结果表明,改进后的工艺不但能简化制模过程及冒口去除过程,且对铸件进行有效的补缩,缩孔缩松等缺陷得到明显的改善。     

消失模铸造生产方法及其在汽车工业上的应用

作为一种精密铸造生产方法，消失模铸造生产方法对于生产汽车铸件已逐步显示出优点，例如降低铸件重量，减少铸件机械加工余量等。本文简要介绍消失模铸造生产方法、浇注机理、常见铸造缺陷及其防止方法，并简要介绍其在汽车工业中的应用。近几年来，铸造业对消失模铸造非常感兴趣，消失模铸造法是将散砂充填到塑料聚苯乙烯模周围的钢砂箱里，通过震动或锤击进行紧实，然后浇注金属液，金属液凝固成消失模形状。在SO年代初期，美国的大型汽车制造公司，如福特公司和通用公司把消失模铸造法实用化，用于生产汽车铸件。消失模铸造法与传统的…     

不同浇注方式对消失模铸造充型的影响

运用ProCAST软件研究了铝合金铸件的消失模铸造充型过程,考察了不同浇注方式对铸件消失模铸造过程的影响。研究表明,底注式浇注系统的充型相对平稳,是一种比较好的消失模铸造浇注系统方案。浇注系统、浇注速度和界面气隙压力对消失模铸造的充型有很大影响。     

大型热风炉炉箅子的消失模铸造技术

一种用消失模生产高质量要求炉箅子的铸造技术,该技术通过优化模具设计,研制消失模铸造方案,采用四块白模对接技术,设计白模拼接工装、最佳刷涂料厚度及涂刷次数、最佳浇注系统及浇注温度范围,获得了尺寸准确、表面光洁的致密铸件。     

连接筒的消失模铸造工艺设计及数值模拟

通过对连接筒的结构、尺寸分析,确定采用消失模铸造连接筒。根据消失模铸造生产的特点、经验及实际生产条件设计了连接筒铸件的消失模铸造工艺。通过ViewCast对铸造凝固过程进行了数值模拟,并分析了铸造缺陷产生的原因。根据模拟结果,优化冒口和浇注位置,提出新工艺,从而降低了铸件废品率,提高了产品质量。     

电机机座铸件的消失模铸造

针对出口电机座铸件、简要介绍了其消失模模具设计、成型发泡及铸件的浇注试验情况,确定了合适的铸造工艺参数,生产出了合格的铸件,证消失模铸造工艺生产电机机座铸件的可行性。     

消失模铸造生产不锈钢阀门铸件

介绍了利用消失模工艺生产阀门铸件的试制过程。对不锈钢阀门消失模铸造的浇注位置选择、浇注工艺的设计、模样组合、涂料涂挂、装箱浇注和过程控制等方面进行了论述。     

贝氏体磨球的消失模铸造

针对传统铸造工艺生产Φ60mm贝氏体磨球的生产效率低、质量差、成品合格率低、磨后失因及耐磨性差等问题,试样采用了消失模铸造工艺进行生产,解决了这些问题,并通过选择合适的EPS模样密度、干砂粒度、初始负压度、浇注温度和浇注速度等各项参数来进行严格控制,使消失模铸造生产的铸铁磨球耐磨性良好,从而显著提高了生产效率和经济效益。     

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.     

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.