铸铁件打箱时间设计的影响因素研究

针对铸铁件打箱时间设计的影响因素,从凝固时间、组织结构转变、冷却速率、材料的高温性能进行了研究,并给出了铸铁件打箱时间设计的原则和方法,提出以下建议:(1)须在铸件完全凝固后再考虑移动铸件,完成凝固时间可以根据经验公式进行估算;(2)为保证铸件基本性能,须等到组织转变完成后再考虑打箱,对于铸铁件,不建议高于550℃打箱;(3)铸铁件高温打箱时,须设法避免铸件发生较大受力或撞击;(4)对于结构复杂、壁厚差异大的铸件,须进行炉内热时效处理才能发货,对于不进行热时效的铸件,球墨铸铁件不建议高于300℃,灰铸铁件不建议高于200℃打箱。     

重载铁路货车摇枕的铸造工艺

介绍了30t轴重摇枕铸件的结构特点和铸造工艺难点,确定了摇枕铸件的工艺方案,包括主要工艺参数、浇冒口系统、造型及制芯工艺、浇注温度和打箱时间、清理及热处理规范,利用华铸CAE铸造数值模拟软件对充型过程流场和凝固过程温度场进行了模拟分析.试生产结果表明,利用整体芯技术和新型酯硬化水玻璃砂工艺,可获得符合重载要求的优质铸件产品.     

大型铸钢托轮温裂的形成及防止

本文探讨了大型铸钢托轮温裂的形成机理及影响因素。应用铸件形成理论和传热学理论，对托轮温裂的形成进行了定性、定量的热应力分析。从调整挂砂层厚度，控制铸件打箱时间，合理安排托轮在热处理窑中的摆放，控制加热升温速度方面提出了防止措施     

锁条铸件硬度控制的技术措施

为满足铸态锁条灰铁铸件对硬度的要求,对铸件化学成分、炉料成分、孕育处理、浇注温度以及出箱时间等工艺过程进行了分析和理论探讨.通过严格执行熔炼工艺操作,高度重视应用孕育措施,强化生产各个环节的工艺控制,使锁条铸件的硬度满足了技术要求,并得到锁具生产企业的认可.     

大型铸型的打箱设备

把打箱工序分成两个工序的大型铸型打箱设备的新结构已得到应用。基洛夫工厂的大型铸钢车间,机械化流水线上用2700×3000×450～600毫米、箱挡尺寸为300×313毫米的砂箱制造铸件;地面造型用4000×4500×550毫     

铸造模拟在大型复杂铸铁件上的实用研究

使用计算机进行铸造模拟有助于复杂铸铁件的铸造工艺设计,流动和凝固解析的结果可以作为日常确定方案时的重要参考.利用凝固解析功能确立了独特的使用方法,可以预测和优化大型铸铁件的打箱时机,预测铸件热处理时的铸件温度分布,以及采用简易模型进行铸件内部应力的估算.这些方法对铸铁件生产是行之有效的.     

大型铸钢件强制冷却

冶金、轧钢、发电等工业的重大设备,浇注后一般需要几天的冷却时间才能打箱,有些铸件甚至需要一个月的时间,长期占据着作业面积,阻碍了生产率的提高与翻番。     

机床床身铸件的数值模拟及残余应力研究

采用数值模拟软件JSCAST对精密车削加工中心HTC2050和精密卧式加工中心HMC50e灰铸铁床身铸件的充型、凝固过程、温度场、应力及变形进行模拟分析;采用盲孔法测量不同打箱温度下的灰铸铁床身铸件和粗加工前后的球铁滑枕箱体铸件的残余应力。结果表明:铸件下箱床身凝固慢,导致床身容易产生残余应力,且横导轨的应力比竖导轨大;导轨及节点处有缩松缺陷,易引起收缩应力;床身在长度方向的变形量比宽度和高度方向的变形量大;灰铸铁件的残余应力比球墨铸铁件大,较低的打箱温度有利于减小残余应力,粗加工后残余应力明显增大。     

铸件湿法开箱作业

铸件打箱是铸造车间最繁重、条件最恶劣、硅尘浓度最大的工作之一。过去我厂铸造车间第一班造型、合箱,第二班开炉浇注,并由浇注工人打箱落砂。一般他们下午     

大型发动机缸体铸件清理工艺概述

现阶段大型发动机机体清理过程中，由于其结构复杂，重量、体积均较大，难以实现自动化。结合现场工作现状对大型发动机机体打箱工艺、粗清工艺、抛丸工艺、细清工艺以及铸件清理设备进行介绍，并对未来铸件清理情况进行展望。     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。