铸态QT600-10的生产工艺

介绍了汽车铸件的结构以及技术要求,根据技术要求将球化处理后的化学成分控制在:w(C)3.6%~3.8%,w(Si)2.6%~2.9%,w(Mn)0.25%~0.45,w(P)≤0.030%,w(S)≤0.015%,w(Mg残)0.03%~0.04%,w(RE残)0.01%~0.02%,采用5 t中频炉熔炼,原铁液出炉温度控制在1 480~1 520℃,采用冲入法进行球化处理,选用低RE的FeSiMg6RE2球化剂,粒度为10~25mm,加入量为每包铁液量的1.1%;采用粒度为3~8 mm的CaBa复合孕育剂进行一次孕育,浇注时使用粒度为0.3~1 mm的高CaBa复合孕育剂进行二次随流孕育。最终生产铸件的球化等级控制在2~3级,石墨球大小6级,抗拉强度不低于600MPa,伸长率不低于10%,且珠光体体积分数及力学性能波动均在10%以内。     

低Mg球化剂在汽车球铁件生产中的应用

采用w(Mg)量为7%~9%的球化剂生产汽车球铁件,为确保浇注温度,出铁温度为1 550℃以上,采用冲入法进行球化处理,反应剧烈,Mg吸收率只有30%~40%,铁液温度降低严重。改用w(Mg)量4%~4.5%的球化剂,出铁温度降低20~30℃,试验结果显示:球化反应平稳,Mg吸收率提高到50%~60%,球化剂的加入量减少了0.2%,孕育剂加入量从1.0%降为0.7%,覆盖剂加入量从1.5%降为1.3%,回炉料加入量从40%增加到60%,降低了生产成本。     

高镍奥氏体球墨铸铁涡轮增压器壳体材质及工艺研究

对高镍球铁涡轮增压器壳铸件的开发和研究进行了系统总结,包括高镍奥氏体球铁材质成分和铸件工艺设计,球化剂、孕育剂的选择和制备,高镍球铁涡壳铸件表面气孔缺陷和缩孔缩松缺陷的消除,高镍奥氏体球铁铸造性能的测试以及高镍球铁涡轮增压器壳铸件理化检测问题.     

铸态QT550-10工作锚板的生产

采用覆砂铁型铸造工艺试制了铸态QT550-10工作锚板。采用废钢增C工艺熔炼原铁液,铁液出炉温度1 500～1 520℃;采用低Mg低RE球化剂冲入法进行球化处理,球化剂加入量为1%,球化处理时间不超过60 s;采用含Ca、Ba、Bi的孕育剂进行多次复合孕育处理。生产结果:铸件球化率为2级,铸态抗拉强度605 MPa,伸长率15.6%,满足要求。     

高镍奥氏体球墨铸铁涡壳的开发

针对D-3.5和D-5S两种材质的高镍奥氏体球铁涡壳进行了试验研究,认为奥氏体枝晶发达才是高镍球铁出现碎块状石墨和显微缩松难以消除的根本原因.通过MAGMA模拟软件进行了铸造工艺模拟分析,优化了铸造工艺,缩短了开发周期,降低了成本.采用长效的Si-Ba和Si-Sr孕育剂的多次孕育,并加入微量的Sn和Sb元素,同时严格控制化学成分、出铁温度等关键参数,解决了球化不稳定、碎块石墨和显微缩松等问题,成功完成了高镍奥氏体球铁涡壳的开发,掌握了高镍奥氏体球铁的批量生产技术.     

汽车用铸态高韧性中小球铁铸件的试验研究

采用中频感应电炉熔炼获得了高温、低硫、低氧化的优质铁液。合理地设计了铁液化学成分,选用低稀土低镁FeSiMg6RE2球化剂进行盖包法球化处理,用含Ba的多元微量复合孕育剂进行孕育处理,稳定生产出了铸态高韧性QT450-18球铁。结果表明,铸件本体的抗拉强度达到456.3~500.6 MPa,伸长率达到18.4%~19.2%。     

球墨铸铁QT850-4多缸曲轴的研制

使球铁曲轴材料的性能达到QT850-4要求,采取了下列技术措施:①采用电炉熔化铁液,进行吹氮脱硫获得高温、低氧化、低硫的优质铁液;②严格控制铁液的化学成分,在铁液中适当加入Cu、Mo合金元素,有利于改善曲轴的金相组织,细化晶粒;③选用低稀土球化剂FeSiMg8RE3;④使用盖包法球化处理工艺,用多元微量复合孕育剂进行孕育处理;⑤进行部分奥氏体化热处理工艺,研制出了高强度且具有一定韧性的球铁曲轴.     

QT850-4球铁曲轴的试制

通过合理选择铁液的化学成分,严格控制铁液的硫、磷含量,在球铁中添加Cu、Mo元素,选用低稀土球化剂,采用盖包法球化处理工艺及复合孕育工艺,并且进行部分奥氏体化热处理工艺,研制出了高品质的球墨铸铁件,其抗拉强度和伸长率分别超过850MPa和4%.     

球化处理后w(C)量降低原因分析

采用冲入法在500 kg的堤坝包中进行球化处理,用RESiFeMg合金作球化剂,球化反应时间>40 s;用SiBa合金作孕育剂,在180 kg的浇包内进行孕育处理;用直读光谱仪分析球化处理前后铁液的激冷试样。发现:(1)球化处理后w(C)量比原铁液的w(C)量低;(2)石墨漂浮是导致球化处理后w(C)量降低的主要原因。     

高综合性能球铁的研制

通过选用合理的化学成分，严格控制铁液硫、磷的含量，在铁液中适当加入Cu、Mo合金元素，选用低稀土球化剂．并使用盖包法球化处理工艺，采用复合孕育处理工艺，进行部分奥氏体化热处理，成功研制出高强度且具有较高韧性的球铁曲轴。     

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。