基于LabVIEW的焊接过程多信息分析平台

基于焊接多信息同步采集系统,采用LabVIEW图形化语言,以熔化极气保焊的焊接电流、电弧电压、电弧光谱为信号源,构建了包括电信号参数设置、电信号数据分析模块、光信号参数设置与自动选择、光信号数据分析的焊接过程多信息分析平台。可实时显示焊接电流波形、电弧电压波形、电弧辐射光谱等;系统还通过数据分析处理得到U-I相图、焊接电流和电弧电压概率密度、短路时间频次图、电弧辐射光强与波长对应图、计算焊接温度的玻尔兹曼图等,通过上述信息分析,检测电弧状态和信息,可用于焊接过程诊断和焊接电弧物理研究等。     

GMAW-P频率特性复合弧长适应控制法

为了提高GMAW-P焊接弧长控制的调节速度,减少弧长调节过程中脉冲频率、焊接电流的波动范围,提出了基于DSP数字控制脉冲熔化极气体保护焊接电源采用频率一特性复合弧长适应控制法.在焊接过程中通过实时采集电弧电压信号、焊接电流信号,当弧长发生扰动时,在当前脉冲周期内,以基值时间和给定电压为控制量,从而保证在弧长调节过程中脉冲频率的变化较小.台阶试验和爬坡试验表明,此控制方法的弧长调节过程快速、稳定,焊接电流、脉冲频率波动范围小,焊机具有良好的弧长调节性能.     

低碳钢熔化极等离子弧焊接工艺

对Q235低碳钢进行熔化极等离子弧焊接工艺试验,并研究其工艺参数对焊缝成形和熔滴过渡的影响.结果表明,与常规的熔化极惰性气体保护焊相比熔化极等离子弧焊接在提高焊接效率、减少飞溅和气孔等方面具有优越性.当其它条件不变时,焊缝熔宽随等离子电流增大而变宽,而对熔深和熔滴过渡类型影响不大;熔化极等离子弧焊接电流增大时,U - I相图的线簇随着电流增大而集中,熔滴过渡依次为短路过渡、大滴过渡和射流过渡.     

U-I模式脉冲MAG焊脉冲参数对熔滴过渡影响规律

研制了一种以80C196KC16位单片机为核心,采用U-I模式控制的逆变熔化极脉冲气体保护焊机.通过采集焊接过程中的电弧电压和电流信号,在峰值期间保持电压恒定,在基值期间保持电流恒定,脉冲参数依据一个脉冲过渡一个熔滴的原则选取.在焊接过程中脉冲频率保持不变,通过峰值电流的变化来实现弧长调节.结果表明,该系统工作稳定,焊机具有良好的焊接工艺性能.     

金属粉末再压缩等离子弧焊接工艺

提高电弧穿透能力是等离子弧焊接领域的重要课题.自主设计并搭建了金属粉末再压缩等离子弧焊接新工艺试验平台,采集焊接过程电信号、视觉信号、弧光光谱信号等,并从焊缝成形、电弧电压、熔融金属过渡、弧光光谱等方面对金属粉末再压缩等离子弧焊接过程进行了初步的研究.在相同焊接电流195 A条件下,与常规等离子弧焊接工艺相比,金属粉末再压缩等离子弧焊接焊缝熔深增加1.29 mm、熔宽减少1.65 mm、电弧电压升高0.63 V.在波长为230 ~ 270 nm范围内,与常规等离子弧焊接相比,金属粉末再压缩等离子弧焊接中Fe和Cr元素的特征谱线明显增多. 结果表明,在相同电流条件下,与常规等离子弧焊接相比,金属粉末再压缩等离子弧焊接电弧穿透能力增强.     

等离子-MIG复合焊接熔滴过渡及电弧耦合特性研究

通过电信号采集系统和高速摄像采集系统对等离子-MIG复合焊接的电流信号、电压信号和熔滴过渡过程进行了同步采集,研究了等离子-MIG复合焊在不同焊接规范下最佳的熔滴过渡方式,对等离子电流对熔滴过渡的影响及复合焊接电弧耦合关系进行了分析。结果表明,等离子-MIG在不同焊接规范下均能实现良好的射滴过渡。在等离子-MIG复合焊接过程中,等离子电流对MIG焊的焊丝伸出长度和熔滴过渡有影响,随着等离子电流增加,MIG焊焊丝伸出长度逐渐缩短,直至由一脉一滴转化为一脉多滴;等离子弧与MIG弧相互耦合,MIG弧的加入使得等离子弧的电压升高,而等离子弧对MIG弧几乎没有影响。     

熔化极气体保护焊电流与电压调节

在应用熔化极气体保护焊的基础上,分析焊接电流和电弧电压对焊缝成形的影响,探究焊接电流与电弧电压匹配对焊接电弧特性的影响规律,总结正确调节焊接电流与电弧电压的基本方法和操作技能,正确调节焊接电流与电弧电压是熔化极气体保护焊技术推广与应用的关键因素。     

三熔化极MIG焊的燃弧形式及共有导电通道的建立

试验中搭建了单电源三熔化极MIG焊系统,利用电信号采集系统检测焊接电流和电弧电压,借助高速摄像系统同步拍摄电弧形态及熔滴过渡过程.通过改变不同的预设电压值,观察到了三种基本的燃弧形式,以此分析三电弧共有导电通道的建立.结果表明,三种基本的燃弧形式依次为单丝燃弧、双丝燃弧及三丝燃弧.共有导电通道的建立分三个阶段,首先三个电极与母材之间形成各自的导电通道,其次三个导电通道在电磁引力的作用下彼此倾斜,打破各自原有导电通道建立共同的导电通道,最后新的导电通道调整至稳定状态.共有导电通道的建立更有利于电弧稳定燃烧.     

等离子-熔化极气体保护焊电弧特性研究现状

等离子-熔化极气体保护焊的电弧形态和熔滴过渡方式直接关系到焊缝质量,采用不同的电极连接形式,如直流正接、直流反接,电弧形态及熔滴过渡方式均不同;主要介绍了目前等离子-熔化极气体保护焊在采用不同的电极连接形式下,不同的电弧形态和熔滴过渡方式,以及电弧成分组成和温度分布;通过对熔化极等离子弧静特性等方面的研究发现,熔化极电流的大小不是由焊丝与工件间的电压决定的,而是由导电嘴与焊丝端部处的等离子弧电位差决定的,并决定电流的方向.     

高速电弧焊工艺的研究现状

分析了在实际生产中实现高速焊接的必要性以及常规焊接方法在实现高速焊时断遇到的问题.然后主要从双丝或多丝电弧焊工艺和双焊炬组合焊接工艺两个大的方面着重介绍了纵列式熔化极气体保护焊、等离子弧-熔化极气体保护焊和双电极熔化极气体保护焊等高速弧焊工艺.另外还介绍了其他实现高速焊的方法及其存在的问题,并对高速电弧焊工艺的发展和应用进行了展望.     

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。