蠕墨铸铁缸体、缸盖的生产工艺

介绍了蠕墨铸铁缸体、缸盖的化学成分控制、铁液熔炼以及蠕化处理工艺.说明确保蠕化处理质量的主要措施是：（1）在蠕化的过程中应防止出铁断流,以减少蠕化剂蒸发损耗;（2）要经常更换蠕化处理包,或者处理后及时对包底蠕化剂安放坑吹风冷却;（3）蠕化剂顶面的孕育剂或者铁屑覆盖量要根据铁液反应的剧烈程度来控制;（4）蠕化处理前要对RESiFe合金进行过筛处理,将粉末去除,保证粒度均匀.最后指出：为防止气、缩孔缺陷,砂芯应留有足够的排气通道,并使用表面光洁的芯骨或者冷铁.     

浅谈砂型铸造排气系统的设计

砂型铸造排气系统的设计是铸造工艺设计中的重要环节,对铸件的质量影响很大。合理的排气系统可有效防止铸件产生气孔、粘砂、呛火和气缩孔等铸造缺陷,提高金属液的充型能力。本文介绍了砂型铸造工艺设计中各种排气系统的设计,包括砂芯排气及型腔排气措施,如排气孔、排气绳、排气通道、排气塞、出气孔、排气片、排气冒口、溢流冒口和点火引气等,可为业内同行提供经验及参考。     

GF线用大型球墨铸铁砂箱的铸造工艺

介绍了大型复杂球墨铸铁砂箱的铸造工艺.针对该铸件容易产生的缩孔、缩松、断芯及气孔缺陷采取了如下措施:(1)在铸件顶部设置多个热冒口,实现多点进铁补缩;(2)提高砂型和砂芯刚度;(3)使用冷铁,选择合理的浇注温度;(4)采用螺纹钢筋芯骨,提高侧面砂芯的刚度,并使用马鞍形组合芯撑防止砂芯变形;(5)砂箱内腔大砂芯采用钢板内衬,提高砂芯刚度,减少芯砂用量,从而减少发气量,并通过在钢板上钻排气眼,改善砂芯和型腔排气.生产结果表明,上述铸造缺陷均已消除.     

M3000蠕铁气缸盖气缩孔的成因及解决措施

对M3000蠕铁气缸盖气缩孔的成因进行了分析,并采取了加强型芯排气,严格控制浇注工艺;稳定过程控制,保证蠕化效果;加快热节部位冷却速度等工艺措施,使缸盖气缩孔缺陷基本消除,废品率由最高时的20%下降到1%以下.     

中硅钼耐热蠕墨铸铁排气歧管材质和工艺探讨

论述了蠕化率控制在50%左右的中硅钼蠕墨铸铁,由于在抗热疲劳和抗热变形性能方面大大优于灰铸铁和球墨铸铁,因而是在高温热循环条件下工作的排气歧管的理想材料.总结了在DISA高速造型线和自动塞杆气压浇注炉条件下,以稀土镁硅蠕化剂,采用包内冲入法和槽内喂丝法相结合的蠕化工艺的成功经验,以及从工艺设计上解决排气歧管缩孔缩松缺陷的办法.     

R6Z·03·0001气缸盖的生产试验

本文介绍了薄壁复杂的900马力蠕铁气缸盖的材质选择以及从浇注系统、冷铁使用、砂芯和型腔排气等方面采取的工艺措施,对防止铸件的缩松渗漏、气孔夹渣等缺陷取得了良好效果。     

铝合金缸盖渗漏原因分析及应对措施

阐述了采用重力铸造方式生产的GW4D20铝合金发动机缸盖,在气密性检测中发现的渗漏问题。采用金相显微观察及宏观分析等手段,研究了渗漏部位的组织与缺陷。结果表明,缩松及缩孔是导致缸盖渗漏的主要原因。浇注过程中砂芯挥发出来的气体及铝液氧化皮夹杂物增大了缸盖铸件在凝固过程中的缩松和缩孔倾向。针对上述铸造缺陷,加强了铸件缺陷部位的补缩,减少气体来源,保证模具型腔排气畅通,有效地控制了缸盖铸件在铸造凝固过程中缩松、缩孔及氧化皮的产生,降低了气缸盖的渗漏。     

大型铸件砂芯的排气措施

对于内腔形状复杂的大型铸件,砂芯的排气质量会影响到整个铸件的质量.为了保证砂芯排气畅通,在砂芯制作和造型时,加入了排气介质.当浇注时,埋在砂芯中的排气介质受热就会快速气化,形成一条完整的排气通道,从而保证砂芯排气畅通.     

VMC系列主轴箱气孔缺陷分析及其解决措施

介绍了主轴箱的铸件结构和铸造工艺,分析了铸件出现气孔缺陷的原因,指出由于砂芯排气不畅以及铁液阻塞砂芯的排气通道,使浇注过程中产生的大量气体无法排出而进入铁液形成气孔.为此,着重改进了砂芯的排气能力和铸件的浇冒口系统.生产结果表明,通过采取改进措施,铸件的废品率大幅降低,有效解决了VMC系列主轴箱的气孔缺陷.     

铸钢车轮的铸造工艺设计与生产

对车轮铸钢件的结构及铸造工艺性进行综合分析,针对其壁厚不均匀,易产生缩孔缩松、其砂芯阻碍收缩产生铸造应力易产生裂纹的现象,通过采用浇道通保温冒口及加覆盖剂、制作炮弹形砂芯、倾斜浇注加强补缩等工艺措施,有效地防止了裂纹和缩松的产生,生产出了合格铸件,为类似铸件的生产积累了经验.     

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。