飞轮壳消失模铸造的缺陷分析及防止

根据消失模铸造工艺原理和飞轮壳铸件的结构和工艺特性,通过控制EPS泡沫堆积密度和泡沫成形工艺操作、增设支撑筋、优化涂料配制工艺以及造型装箱工艺,改进浇注系统设计和浇注操作方法以及优化管理等措施,有效预防了飞轮壳铸件变形、夹渣、铁包砂、冷隔等缺陷的产生,提高了铸件的工艺出品率和合格率.     

大型矿山机械下机架铸件铸造工艺优化

针对超级旋回式矿石破碎机下机架铸件铸造工艺出品率较低和铸件缺陷较多等问题,对原铸造工艺进行了改进,采用大平面朝下的造型方案,调整了冒口、补贴和冷铁的设置,增加了内浇口数量,应用MAGMA软件对铸件的凝固过程进行了模拟,证实了改进后铸造工艺的有效性.生产结果表明,下机架铸件的铸造工艺出品率达到65％,铸件质量得到明显改进,彻底解决了铸件的疏松、裂纹和夹渣问题.     

DZ029转向器支架铸造工艺改进

陕西金鼎铸造有限公司是陕重汽的专业铸件生产厂,为了改善铸件外观质量和提高生产效率,公司在2010年年初新建成了静压造型线.在静压造型线建成的背景下,我们对一批批量性的铸件进行了工艺改进,依靠静压线的特点,实现了造型工艺的优化,最终节约了成本,大幅度提高了生产效率.     

年产1.5万t铸件的水平脱箱造型线工艺设计

为满足铸件生产的需求,选择采用先进的水平脱箱造型线,依据铸件产能及其工艺要求,设计了造型、砂处理、熔炼及其他配套工部的工艺参数,制定了合理的工艺流程.生产线实际运行结果表明,造型线所用设备先进,故障率小,工艺参数设计合理,工艺流程顺畅;生产的铸件质量达到CT8级,表面粗糙度Ra12.5 ～ 25 μm,综合废品率≤1％.     

小件造型生产线的改造

1991年宜昌纺织机械厂铸造车间对原有的小件造型生产线进行了移位更新改造。改进后的小件造型生产线布局先进,完善了压铁、推箱、落砂、铸件输送、除尘等配套装置。整个车间的送砂系统、回砂系统、铸件输送系统、造型浇注等,做到规范化和标准化,推动了生产的发展和质量的提高。 1小件造型线改造前的状况随着生产的发展,原小件造型线已远远不能适应生产的要求。该生产线的悬链压铁已不能使用,推箱装置的推力不足,砂斗严重腐蚀,落砂和输送铸件不甚理想,造型线距冲天炉又较远,防尘装置不佳。这些既给操作者增加了劳     

凝固模拟在球铁飞轮工艺优化上的应用

应用MAGMAsoft对四种不同结构球铁飞轮的不同工艺方案进行凝固模拟,根据凝固模拟结果和实际试生产铸件外观缺陷及内部缩松情况,提出不同改进工艺方案并对其进行凝固模拟,选择最佳方案应用于生产.优化后的工艺方案投入批量生产,球铁飞轮的缩孔、缩松缺陷达到用户要求.     

自动造型线型砂性能要求及其控制

在自动造型生产线生产过程中,型砂性能对铸件质量具有决定性的影响,型砂性能控制是保证铸件质量的重要工艺手段。合理选择原砂、膨润土、煤粉等原辅材料,控制好型砂的水分、紧实率、透气性、湿压强度、含泥量及有效膨润土含量、挥发份、灼减量和旧砂温度、旧砂水分等是自动造型生产线型砂性能控制的关键。应确定合适的型砂各项性能指标、控制参数和控制方法,严格型砂混制的工艺过程,保证自动造型生产线正常运行,充分发挥自动造型生产线的优越性。稳定了型砂性能,就为获得良好的铸件成品率提供了保障。     

电动机托架湿型砂铸造工艺

为采用湿型砂气冲造型工艺生产电动机托架铸件,基于铸件结构和生产条件,分析了分型面、浇注位置、浇注系统等工艺要素,确定了托架铸件的工艺方案；针对浇注后出现的铸件表面缩陷和夹砂缺陷,从熔炼、型砂、浇冒口设置等方面进行了改进和调整.改进后的工艺经生产验证,铸件表面缩陷和膨胀夹砂现象得以彻底消除,效果明显,系列铸件的工艺出品率可达85％以上.     

球墨铸铁飞轮壳的无冒口铸造工艺实践

对某球铁飞轮壳铸件的无冒口铸造工艺进行了分析,采用呋喃树脂自硬砂造型、控制铁液的化学成分、采用中间底注、铁液分散进入型腔的浇注方式以及四角设置出气孔等措施,使球铁飞轮壳的无冒口铸造工艺得到了实现,生产的球铁飞轮壳力学性能符合技术要求,且实现了批量生产.     

数值模拟在后桥壳体铸造工艺优化中的应用

采用三维造型软件对后桥壳体铸件进行造型,添加浇冒系统和铸型,用华铸CAE软件进行凝固过程的数值模拟,通过比较不同工艺条件下的凝固过程中的液相动态分布过程,预测了形成缩孔缺陷的不同倾向,并对比了不同工艺方案下铸件的缩孔分布及工艺出品率,对铸造工艺进行改进和优化,将改进后的铸造工艺应用于生产,既解决了铸件的铸造缺陷,又缩短了生产制造周期。     

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.     

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.     

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.