电渣熔铸-熔焊法生产大直径内燃机曲轴的工艺研究

介绍了采用电渣熔铸-熔焊法生产大直径内燃机曲轴毛坯的基本原理及熔铸、熔焊工艺.测定了铸件的化学成分分布,并对非金属夹杂和低倍组织进行了研究.结果表明:熔铸、熔焊工艺的要点是采用冷却能力较强的紫铜做结晶器工作面,冷却水层厚度为10mm,局部冷却速度≥2300℃/min,结晶器出水温度≤45℃;采用熔点低、流动性好的三元渣系(主要成分为CaF2 Al2O3 CaO)并对其进行熔化预处理.与锻件相比,整个电渣熔铸件(包括熔焊区)金属纯净,组织致密,成分均匀,硫、磷等有害元素含量低,夹杂物含量大幅度降低,疏松与偏析大为减少.     

电渣熔铸双金属复合斗齿

根据对挖掘机斗齿的失效分析,提出了采用电渣熔铸钢铁复合斗齿的合理性和可能性.文中着重说明了电渣熔铸双金属斗齿的工艺,包括结晶器、自耗电极、渣系、电制度等的选择和设计.还就钢、铁接合部过渡区的性能和组织进行了分析.现场应用表明,电渣熔铸法生产的双金属复合斗齿的使用寿命比高锰钢斗齿提高3倍以上.     

B30铜合金电渣重熔工艺实践

采用熔点比铜合金熔点低100～200℃的MgF2-CaF2渣系重熔B30铜合金,熔化速率(kg/h)控制在(1～1.3)×结晶器直径(mm),有利于改善电渣锭的表面质量,提高铜合金纯净度和电渣锭致密度,改善锻造性能。     

电渣重熔对Y-RAFM钢组织及力学性能的影响

通过30 kg真空感应炉+电渣重熔(ESR)工艺制备了Y-RAFM钢,研究了经过和未经过电渣重熔的Y-RAFM钢的组织及力学性能的变化。结果表明:经过电渣重熔的Y-RAFM钢的晶粒尺寸明显增大,微观组织仍为板条马氏体;室温下钢的抗拉强度和屈服强度分别降低了26. 15、39. 01 MPa,断后伸长率提高了4. 50%,冲击性能得到明显改善,室温冲击吸收能量提高了115 J,韧脆转变温度降低了14℃。     

电渣熔铸模具钢/低合金钢双金属平板件的制备与性能

采用电渣熔铸方法制备了Cr12MoV/40Cr双金属平板件,研究了熔铸及热处理工艺对双金属组织和性能的影响.结果表明:使电极与结晶器产生相对运动或增加电极数量可避免双金属U型界面、浇不足及冷隔等缺陷的产生,获得界面结合牢固、均匀平整且过渡层适当的双金属平板件.双金属Cr12MoV钢一侧的淬火和回火组织为回火马氏体 网状共晶碳化物 细小粒状二次碳化物 少量残余奥氏体.双金属的最佳热处理工艺为980℃淬火 230℃回火,其冲击韧性ak值可达25 J/cm2以上,工作层硬度HRC≥62.     

铸造工艺对B30合金铸锭组织及可锻性的影响

研究了不同工艺参数的半连续铸造工艺对铸锭组织及可锻性的影响,并将常用于改善铸钢组织性能的电渣重熔工艺引入B30铜合金铸造.研究表明,铸锭的晶粒生长方向及晶粒大小与铸造速度和冷却强度有关;低铸造速度(＜3m/h或停拉式)、大轴向冷却强度(冷却水量＞8m3/h)可在铸锭组织中形成较多的斜向柱状组织,斜向生长且与铸锭轴向间夹角小于30°的细长柱状组织对发挥B30铸锭的可锻性有利;电渣重熔B30铸锭,可锻性最好,B30合金电渣重熔的渣料及配比可选取CaF2、MgF2,比例:8/2.     

ESC中渣池热电耦合过程的数值模拟

电渣熔铸(ESC)过程中的渣池是一个集热场、电磁场、流场等于一体的复杂体系,各种场之间是相互影响的,且整个体系的边界条件非常复杂.本文对自耗电极、渣壳、结晶器、渣金界面等渣池热电传输边界条件作了合理的处理,同时借助于大型通用有限元分析软件ANSYS对渣池的热电场进行了模拟,获得了渣池的电场和温度场分布规律.并在此基础上研究了两种场的分布特点,提出作为熔铸过程中主要产热区的渣池是由高热源区和低热源区所组成的观点,对调整电渣熔铸过程中工艺参数、稳定熔铸过程具有一定的指导意义.     

高耐候钢板坯表面纵裂成因分析与控制

针对高耐候钢连铸板坯生产实践中遇到的表面纵裂纹问题,对钢的成分、结晶器保护渣、结晶器冷却及二冷区冷却等影响因素进行了讨论分析,提出了连铸工艺改进优化方向。生产实践表明,采取控制镍铜比大于0.3,选用高碱度、高熔点、低黏度耐候钢专用保护渣,调整结晶器倒锥度每米1.0%～1.1%,结晶器及二冷区弱冷却;控制非稳态浇铸,维持钢水过热度在20～30 ℃,稳定液面波动在2%以内、拉速波动在±0.2 m/min等技术措施,板坯表面纵裂发生率从50%以上降低到3%左右。     

电渣熔铸双金属复合材料界面的研究

采用电渣熔铸方法制备了Cr12MoV/20Cr双金属复合材料,研究了工艺参数对平板双金属界面结合状态及形状的影响.结果表明,在熔铸第一种合金后停留适当时间再熔铸第二种合金才能保证获得结合牢固且过渡层适量的平板双金属界面.增加电极数量或使电极与结晶器产生相对运动可避免双金属的U型界面、浇不足及冷隔等缺陷的产生.     

电渣熔铸异型件熔渣内溢现象

分析了异型电渣熔铸件生产过程中的熔渣内溢现象及形成因素.研究表明,更换电极中断功率操作后,供电工艺参数与结晶器冷却强度不匹配是导致结晶器内熔渣溢流的主要原因.从更换电极操作与熔铸工艺进行改进优化,改进后实际生产效果良好.     

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).     

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.     

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.     

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。