70CrMnMo拉丝碰焊接头脆断的解决方法

70CrMnMo马氏体钢焊接材料常用于同类工模具钢表面或工作面堆焊修复。针对70CrMnMo拉丝碰焊过程中大量脆性断裂情况,运用热处理原理分析材料组织特性,计算Ac1相变点,通过试验验证了从马氏体组织分解为回火索氏体组织相变点的准确性。据此制定了合理的回火工艺参数,利用自制的便携式热处理设备,快速高效地获得了理想的组织和性能,解决了70CrMnMo材料拉丝生产中碰焊脆断的难题。     

Cr3轧辊局部堆焊修复工艺研究

Cr3铜是目前广泛使用的轧辊材料,其局部修复有重要意义.研究了不同预热温度和焊后缓冷对Cr3钢轧辊局部堆焊修复质量的影响.通过焊接工艺试验、无损探伤、焊接热模拟试验及金相分析,证明了在Cr3铜轧辊局部修复中,焊接热影响区的最大焊接收缩量△L、马氏体含量均随预热温度的下降而增加;在预热温度相同时,△L随冷速降低而降低.在350℃保温缓冷即可明显改善Cr3钢组织.通过缓冷可将常规400℃以上的预热温度降低到200℃而保证不裂.     

半钢轧辊堆焊修复用隔离层材料的研制

依据半钢轧辊的成分特点和服役工况,设计开发半钢轧辊堆焊修复用的隔离层材料,研究采用隔离层材料打底,配合工作层材料修复半钢轧辊的可能性。结果表明,在半钢轧辊表面堆焊隔离层材料后,脆性高碳马氏体周围析出了韧性的珠光体组织,增加了隔离层的韧性储备,隔离层中无裂纹等冶金缺陷,且隔离层材料与工作层材料具有良好的相容性,解决了半钢轧辊不可堆焊修复的技术难题。     

Cr3轧辊局部修复工艺的焊接热模拟分析

利用焊接工艺试验和热模拟试验研究了预热温度和冷速对高碳含量的轧辊材料Cr3钢焊接性的影响.通过金相分析、X射线衍射分析及温度-体积变化关系的分析,研究了预热温度和冷速影响Cr3钢焊接性的机理.确定了Cr3钢在焊接冷速下的组织,得到了冷却速度与焊后组织、加热区最大收缩量和焊接残余应力的关系.研究表明,控制焊接时的冷却速度是保证这类轧辊材料堆焊修复质量的关键.     

大模数齿轮磨损后的堆焊修复工艺研究

通过试板的工艺试验，探索选用适当的焊条、采用适当的焊接工艺和焊后热处理工艺来修复ＺＧ４５钢大模数齿轮磨损齿面的可能性。试验结果表明，联合使用Ｄ１３２＋Ｄ１１２或Ｄ１３２＋Ｊ４２２进行堆焊，均可满足堆焊修复工艺的要求。     

飞剪转鼓斜齿轮的焊接修复

飞剪转鼓斜齿轮是热轧剪刀转鼓大型承载零件之一,主要承受180°回转冲击载荷.在长期运行过程中,齿轮内孔磨损严重,与装配轴之间存在着轴向窜动使剪刃无法连续正常工作,最终决定采用焊接修复加工成型的方法来解决.对于40NiCrMoA钢,为了避免产生冷裂必须进行严格的工艺控制,焊前必须预热,控制输入的线能量,焊后及时进行热处理.但是,需要修复的斜齿轮齿面不允许受到损伤,故决定采用对齿轮内孔局部预热,进行堆焊修复,焊后对内孔及时进行局部后热处理.     

带钢热连轧机支承辊堆焊修复工艺研究

通过对轧辊母材的分析,选择合适的堆焊材料。研制支承辊堆焊专用夹具,并确定埋弧焊机类型。通过模拟辊的制作与检测,确定并优化堆焊工艺及热处理工艺。分阶段完成了两支支承辊的堆焊修复。     

冷轧辊耐磨堆焊修复工艺

从轧辊局部堆焊修复入手,介绍了Cr3型冷轧工作辊耐磨堆焊参数及试验过程,进行了堆焊层耐磨试验及堆焊焊缝的显微观察,结合母材和堆焊焊接材料的成分特点及2种不同的堆焊工艺试验,对试验结果及工艺参数的选取进行了分析说明.     

钢轧辊局部冷焊实用工艺设计与分析

全面介绍了钢轧辊局部缺陷修复的实用冷焊工艺。结合工程应用,分析了“分区孤立堆焊”、“周边熔合区最后形成”、“焊缝整体硬—软结合”等工艺要点,对降低焊接区内应力,提高焊缝工作寿命有独特作用。该工艺是近百条轧辊局部修复的实践总结,特别是在降低焊接内应力和保证熔合区质量方面的措施,对高硬度构件的堆焊工艺设计,有一定的参考价值。     

短流程堆焊修复轧辊

<正>短流程堆焊修复工艺具有修复周期短、堆焊工序少、修复效率高的特点。具体做法如下:(1)利用磨辊装配车间的设备,在车间内设立一个小型的堆焊工位,以避免周转环节多的问题。(2)应用堆焊和热处理一体化轧辊堆焊装置进行修复。工作原理是综合堆焊机床和热处理炉的基本结构和功能,使轧辊堆焊过程中的预热、堆焊、热处理三个工序集中操作。     

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。