变极性等离子弧焊换向过程控制方法研究

通过试验证实了变极性等离子弧焊换向过程中存在电弧电流谐振现象,且不同极性的电流谐振峰值不同,依据电弧理论分析发现换向期间等效电弧电阻是一个时变量。对换向电路建模分析和仿真结果表明,在换向期间系统阻尼比为时变量,调整系统阻尼比是降低电流谐振峰值的有效途径。又根据变结构控制思想提出了新的换向控制方法,并重新设计了换向电路,显著降低了电流谐振峰值,改善了大电流焊接时换向器件的工作状态,为大功率变极性等离子弧焊电源的研制和开发提供了依据。     

Effect of post weld heat treatment on tensile properties and microstructure characteristics of friction stir welded armour grade AA7075-T651 aluminium alloy

This paper reports the effects of post weld heat treatments, namely artificial ageing and solution treatment followed by artificial ageing, on microstructure and mechanical properties of 12 mm thick friction stir welded joints of precipitation hardenable high strength armour grade AA7075-T651 aluminium alloy. The tensile properties, such as yield strength, tensile strength, elongation and notch tensile strength, are evaluated and correlated with the microhardness and microstructural features. The scanning electron microscope is used to characterie the fracture surfaces. The solution treatment followed by ageing heat treatment cycle is found to be marginally beneficial in improving the tensile properties of friction stir welds of AA7075-T651 aluminium alloy.     

22SiMn2TiB装甲钢异种焊接接头超声波探伤探头设计

用常规探头对22SiMn2TiB装甲钢与TWE312异种钢焊接接头进行缺陷检测,杂波和伪缺陷波导致灵敏度、信噪比不高。用扫描电镜观察到这种异种钢焊接接头主要为奥氏体+铁素体组织,其中奥氏体是主体组织。根据焊缝的组织特点,设计出了2.5P13×13K1.5型专用探头。在预制缺陷的焊接接头上进行了验证试验,结果表明2.5P13×13K1.5探头对接头内部的缺陷具有较高的检出率。     

8031单片机在氩气自动焊接过程中的应用

在焊接流水线过程中,应用单片机进行控制,目前国内尚不多见。本文介绍了使用单片机控制氩气焊枪的方法,实现了焊接过程自动化,提高了产品质量和工作效率。本文对于单片机在工业上的实际应用具有一定的参考价值。     

激光——等离子弧复合焊铝锂合金熔化过程的分析

为了研究激光-等离子弧复合焊熔化过程中的传热和流动特性，建立了针对1420铝锂合金的数值分析模型。在同时考虑表面张力、电磁力和热浮力作用的情况下，利用有限控制容积法求解该模型，得到熔池流场和温度场的数值解，从而直观地反映熔池形状的变化过程，并采用无量纲分析法对不同作用力对熔池传热和流动过程的影响进行定量化研究。分析结果表明：熔深的增长快于熔宽，因为熔深增加的主要机理是小孔效应，而熔宽增加的机理为对流传热作用；表面张力对熔池流动的影响最大，比电磁力的作用大1个数量级，比热浮力的作用大3个数量级；在熔化过程中，对流传热的作用大于热传导作用，心数最大值达7．6。     

火药复合焊条焊接接头的微观组织及性能

为提高战场装备的应急抢修能力,以火药和2Al/3CuO系高热剂为焊接热源,开发了一种新型的便携式焊接材料——火药复合焊条,对其焊缝的组织形貌及性能进行研究.试验结果表明,火药复合焊条的焊接属于熔化焊,焊缝与基体之间存在明显的过渡区,焊缝成形良好,焊缝的抗拉强度大于400MPa,高于母材本身强度,能够满足战场应急抢修能力的需要.     

燃烧型焊条焊接A3钢的研究

基于燃烧合成技术的燃烧机理,结合焊接母材的材质,制备可用于手工施焊的燃烧型焊条焊接A3钢。对焊接试件进行力学性能测试和金相分析,结果表明:焊接试件的结合方式为冶金结合,焊缝合金在细晶强化和弥散强化的作用下,试件的抗拉强度(σb)达到370 MPa,抗弯强度(σf)达到1 100 MPa,成功实现了燃烧型焊条对A3钢的焊接。     

Investigation on the process parameters of TIG-welded aluminum alloy through mechanical and microstructural characterization

Multi-pass TIG welding was conducted on plates (15×300×180 mm3) of aluminum alloy Al-5083 that usually serves as the component material in structural applications such as cryogenics and chemical processing industries. Porosity formation and solidification cracking are the most common defects when TIG welding Al-5083 alloy, which is sensitive to the welding heat input. In the experiment, the heat input was varied from 0.89 kJ/mm to 5 kJ/mm designed by the combination of welding torch travel speed and welding current. Tensile, micro-Vicker hardness and Charpy impact tests were executed to witness the impetus response of heat input on the mechanical properties of the joints. Radiographic inspection was performed to assess the joint's quality and welding defects. The results show that all the specimens displayed inferior mechanical properties as compared to the base alloy. It was established that porosity was progressively abridged by the increase of heat input. The results also clinched that the use of me-dium heat input (1-2 kJ/mm) offered the best mechanical properties by eradicating welding defects, in which only about 18.26% of strength was lost. The yield strength of all the welded specimens remained unaffected indicated no influence of heat input. Partially melted zone (PMZ) width also affected by heat input, which became widened with the increase of heat input. The grain size of PMZ was found to be coarser than the respective grain size in the fusion zone. Charpy impact testing revealed that the absorbed energy by low heat input specimen (welded at high speed) was greater than that of high heat input (welded at low speed) because of low porosity and the formation of equiaxed grains which induce better impact toughness. Cryogenic (-196 C) impact testing was also performed and the results corroborate that impact properties under the cryogenic environment revealed no appreciable change after welding at designated heat input. Finally, Macro and micro fractured surfaces of tensile and impact specimens were analyzed using Stereo and Scanning Electron Microscopy (SEM), which have supported the experimental findings.     

微区脉冲电阻堆焊修复冷作模具研究

应用GM—3450(B)型工模具修补机及多种合金粉末,对冷作模具的棱边磨损或崩塌进行了修复试验,方便地实现了微区脉冲电阻堆焊.对修复部位进行了金相和SEM分析.证明这种修复技术具有结合强度高、HAZ小、无变形、无裂纹的特点,为冷作模具修复提供了一种新技术.     

Experimental and numerical investigations of interface properties of Ti6Al4V/CP-Ti/Copper composite plate prepared by explosive welding

Explosive welding technique is widely used in many industries. This technique is useful to weld different kinds of metal alloys that are not easily welded by any other welding methods. Interlayer plays an important role to improve the welding quality and control energy loss during the collision process. In this paper, the Ti6Al4V plate was welded with a copper plate in the presence of a commercially pure titanium interlayer. Microstructure details of welded composite plate were observed through optical and scanning electron microscope. Interlayer-base plate interface morphology showed a wavy structure with solid melted regions inside the vortices. Moreover, the energy dispersive spectroscopy analysis in the interlayer-base interface reveals that there are some identified regions of different kinds of chemical equilibrium phases of Cu–Ti, i.e. CuTi, Cu₂Ti, CuTi₂, Cu₄Ti, etc. To study the mechanical properties of composite plates, mechanical tests were conducted, including the tensile test, bending test, shear test and Vickers hardness test. Numerical simulation of explosive welding process was performed with coupled Smooth Particle Hydrodynamic method, Euler and Arbitrary Lagrangian-Eulerian method. The multi-physics process of explosive welding, including detonation, jetting and interface morphology, was observed with simulation. Moreover, simulated plastic strain, temperature and pressure profiles were analysed to understand the welding conditions. Simulated results show that the interlayer base plate interface was created due to the high plastic deformation and localized melting of the parent plates. At the collision point, both alloys behave like fluids, resulting in the formation of a wavy morphology with vortices, which is in good agreement with the experimental results.