直齿圆柱齿轮冷挤压可控运动凹模成形工艺

为降低直齿圆柱齿轮冷挤压成形载荷和改善齿形角隅部分充填性,在分析直齿圆柱齿轮成形过程中金属流动特性基础上,提出了采用可控运动凹模的成形工艺。利用Deform-3D软件对此成形工艺过程中的金属流动规律、成形载荷、成形缺陷进行了数值模拟分析,并对该工艺进行了优化。分析结果表明,当凹模速度为冲头速度的1/2时,成形过程中齿形充填均匀、齿形角隅部分充填饱满,成形载荷最小,较传统单向挤压成形载荷降低了约20%。对优化后的成形工艺进行了成形试验研究,试验成形齿轮齿形饱满,无塌角缺陷,试验结果与模拟结果基本吻合。     

带运动可控式凹模的直齿轮精锻成形研究

为了改善直齿圆柱齿轮冷精锻成形时齿形上下角部充填情况,本文在对精锻成形阻力分析的基础上,提出了一种新的齿形凹模运动可控的直齿圆柱齿形精锻成形装置,通过弹性元件和定位销实现了精锻成形过程中齿形凹模不动、齿形凹模随冲头一起运动、齿形凹模先不动而后再运动以及齿形凹模先运动而后不动等多种运动方式。有限元模拟和实验研究表明:通过控制齿形凹模的运动方式,形成齿形凹模对成形角部充填的积极摩擦,有利于促进齿腔角部充填。     

高精度直齿圆柱齿轮冷锻成形加工方法的研究

针对真齿圆柱齿轮冷成形难度大的问题,提出了闭式镦挤－－约束孔分流两步成形实用化工艺方案和基于变位理论的齿形凹模修正设计方法,并对１５、４５、２０ＣｒＭｎＴｉ钢质直齿圆柱齿轮冷精锻工艺进行了系统研究。研究结果表明,两步成形法是降低直齿圆柱齿轮冷精锻成形力的有效方法,提出的齿形凹模修正设计方法可获得较高的齿形精度。     

基于凹模强度的圆柱直齿轮温精锻工艺分析

运用三维刚塑性有限元计算软件Defrom-3D,对直齿圆柱齿轮温精锻成形过程进行模拟和变形抗力计算;将模腔充满度为99%时的单位成形力作为凹模载荷,利用Lame公式对组合凹模进行应力计算,比较了几种不同凹模结构对凹模受力的影响。     

直齿圆柱齿轮精锻过程的实验研究

针对直齿圆柱齿轮冷成形难度大的问题，列举了一种可用于直齿圆柱齿轮的精密成型方案，通过模拟实验从齿形的填充和所需变形力等方面进行了研究。本文设计了带浮动凹模的模拟实验模具装置。提出了一种直齿圆柱齿轮精锻模结构。     

直齿圆柱齿轮冷锻成型技术研究

金属流动性差导致齿形填充困难并且成形所需压力大,是直齿圆柱齿轮冷锻成型需要解决的突出问题.本文从改进凹模型腔、凸模结构和整个工艺过程入手,提出流线型凹模型腔设计方案,通过改变凸、凹模的形状来改善金属的塑性流动;提出镦挤压的工艺方案并对模具结构进行了合理的设计,提高金属的填充能力并降低成形压力.     

直齿圆柱齿轮温挤压数值模拟

数值模拟可以有效地节省人力物力，免去大量的物理模拟，在设计阶段即可对不同的设计方案及时进行评价，筛选出最优方案。本文用优化后的凹模结构对直齿圆柱齿轮的温挤压成形进行数值模拟，并对模拟结果进行分析，为现实生产提供理论依据。     

直齿圆柱齿轮净形成形技术研究

研究了高精度直齿圆柱齿轮净形成形的若干相关技术,提出了钢质直齿圆柱齿轮冷精锻约束分流两步成形工艺,并对净形成形中的凹模修正设计方法、模具材料和结构、软化及润滑等实际应用关键技术问题进行了探索,冷精锻２０ Ｃｒ Ｍｎ Ｔｉ钢直齿圆柱齿轮具有较高精度。     

约束分流精锻成形直齿圆柱齿轮

基于约束分流原理,以某厂生产的减速小齿轮为例,采用数值模拟和物理试验相结合的方法,对直齿圆柱齿轮精锻成形工艺进行了深入研究。通过分析小芯棒约束分流和凸缘分流两种方案下坯料孔径的大小对直齿圆柱齿轮成形过程的影响,确定出可以改善充填性与降低工作载荷的最佳工艺方案:浮动凹模下坯料尺寸为直径38 mm、孔径16 mm、高度27.3 mm的小芯棒约束分流与固定凹模下坯料尺寸为直径38 mm、孔径18 mm、高度25.5 mm的凸缘分流。由小芯棒约束分流浮动凹模形式下的力-行程曲线可知,试验结果与有限元数值模拟结果能很好地吻合。     

驱动齿轮冷挤压成形研究

分析了驱动齿轮的冷挤压成形工艺特征,确定其成形方式为齿轮与内花键同步挤压成形。利用Deform-3D有限元分析软件对驱动齿轮挤压成形过程进行数值模拟,分析了毛坯尺寸、凹模入口角对其挤压成形特性的影响。研究结果表明:当毛坯的外径尺寸大于齿顶圆直径尺寸2 mm、毛坯的内径尺寸为花键小径及凹模入口角为50°时,齿轮和内花键的齿形填充效果较好,同步挤压成形力相对较小。采用模拟得到的优化工艺参数进行挤压成形工艺试验,得到了符合成形精度要求的驱动齿轮成形件。     

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.