DEFORM模拟支撑辊的锻造

轧机中的关键零件之一支撑辊在轧制设备运行的过程中承受轧辊传来的交变应力。大型支撑辊由大型钢锭锻造而成,但大型钢锭中存在种种缺陷,给支撑辊的质量带来很多问题。针对此问题,采用WHF法能够锻合锻件内部组织缺陷,可改善锻件质量。采用DEFORM软件,模拟WHF法拔长,研究WHF法在锻造拔长过程中对锻件心部的作用。实验研究表明,WHF法在拔长的第3道次时,锻件心部的应力状态由拉应力完全转变为压应力。同时,到第6道次后,锻件心部等效应变达到1.2。通过锻件心部压应力和等效应变值可知,WHF法能够完全破碎锻件内部的组织缺陷,生产出质量合格的支撑辊锻件。     

RP120-80大型挤压辊锻件缺陷修复研究

新产品RP120-80挤压辊是典型的大型短粗轴类锻件,在冷加工后易出现超声波探伤超标现象.通过低倍酸洗、断口试验、扫描电镜及能谱分析等手段,确定了缺陷为夹杂性裂纹,夹杂物的主要成分是Al2O3、 Fe2O3及少量CaO,并分析了缺陷的成因、影响因素及控制措施,提出采用两次镦拔锻造新工艺.试制结果表明,采用新工艺可以控制大型锻件中的夹杂物形态,修复裂纹,改善锻件内在质量.     

大型挤压辊锻件两次镦拔工艺锻前加热研究

采用两次镦拔锻造工艺,可以在大型水压机上利用小钢锭锻造大型挤压辊锻件.由于锻件尺寸大,两次镦粗和两次拔长相结合,锻造过程历时较长,需要三次锻前加热.加热不当会造成资源和时间的浪费,甚至造成锻件的报废.本文通过理论分析,考虑到材质和锻件尺寸及生产条件,制定了RP170-110挤压辊锻件两次镦拔锻造前的加热工艺,包括锻造温度范围、装炉温度、加热速度以及保温时间等.结果表明,该加热工艺具有良好效果.     

大锻件两次镦拔锻造的工艺优化

总结的两次镦拔锻造新工艺具有可靠性高，锻透效果好，可控制钢中夹杂物的形态和对坯料内部缺陷进行修复的独特作用，是一种新颖的大锻件锻造工艺。特别是明确了两次镦拔新工艺中砧宽比W／H和料宽比B／H的控制、每趟压下率△H/H的安排原则等，是对WHF法锻造的重要补充。     

改进的WHF法在大型整锻支承辊上的应用

本文介绍了用改进的WHF法锻造φ1400mm整锻支承辊的生产过程。文中通过用改进的WHF法,取消镦粗,直接拔长1.6t钢锭的中间模拟试验结果,探讨了改进的WHF法在实际生产应用中的有关参数的选择问題。     

宽厚板P20塑料模具钢成形仿真分析与试验研究北大核心CSCD

P20塑料模具钢锻件属于异形截面(中心凹槽),且吨位重、厚度和展宽尺寸大,采用传统的镦拔下料、压扁出成品的成形方法很难保证技术标准、锻透压实效果和金属纤维流线的延续性要求。通过综合分析宽厚板锻件成形方法和控制难点,提出“首次WHF法拔长(10趟)+二次WHF法拔长(6趟)+宽砧拔扁下料(6趟)+锻制凹槽”的压实成形方案和近净成形控制新方法;并结合工艺控制和难点分析,建立有限元分析模型,全流程仿真WHF法、宽砧拔扁法和心部凹槽锻制过程,预测工艺参数设计和过程控制成形效果和质量;最后,通过生产试制验证了工艺参数及成形工艺的合理性。     

基于Deform-3D的齿轮箱输出轴锻造成形研究

大型齿轮箱输出轴属于大型轴类锻件.针对某齿轮箱输出轴锻造质量不高的问题,提出了两次镦拔成形工艺,并运用有限元软件Deform-3D对其锻造工艺进行了数值模拟.结果表明,采用两次镦拔工艺,可以得到质量更佳的输出轴锻件.     

大型管板锻件夹杂性裂纹分析及锻造工艺改进

在分析夹杂性裂纹形成机理的基础上,从控制锻造过程中夹杂物形状变化的角度出发,通过有限元模拟管板锻件成形过程,力求减小镦粗时的不均匀变形,提出了WHF法拔长+预镦粗+旋压成形的大型管板锻件锻造工艺。生产实践证明,采用该工艺可有效控制夹杂性裂纹的形成,提高锻件内部质量。     

大型短粗挤压辊锻后的热处理工艺

通过分析大型42CrMo钢的挤压辊锻件的特征形状、晶粒遗传的防治及钢的去氢处理工艺,制定了适合该产品的热处理工艺,包括1次前处理、2次预热处理、2次正火、3次贝氏体等温处理和1次去氢处理的锻后热处理工艺.试用结果表明,热处理的8个锻件,晶粒得到细化,超声波探伤合格,符合质量要求,适用于大型短粗轴类锻件,可推广应用.     

大规格SAE4130锻件白点缺陷分析

对SAE4130大型锻件心部白点缺陷进行了分析,认为钢锭心部区域铸造缺陷未能有效锻合,氢在未锻合缺陷处的富集是导致白点缺陷产生的主要原因。通过调整锻造工艺,增加一次镦粗拔长工序,未再出现超标缺陷和白点。     

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。