一种Cu基自蔓延焊笔焊接Q235和45钢焊缝的组织与性能

利用研制的一种可焊接6～10 mm厚钢结构件的Cu基自蔓延焊笔,焊接了10 mm厚的Q235钢和45钢,研究了其焊缝的组织形貌和性能,发现焊缝与基体间存在熔合区,焊缝属于熔焊焊接.焊缝的拉伸强度达282 MPa,弯曲强度达628 MPa,冲击韧度为46.43 J/cm2;焊缝显微硬度达HV0.1230,熔合区显微硬度达HV0.1255.6,高于基体热影响区的硬度.     

铝青铜水下湿法激光焊接焊缝成形与力学性能

为解决湿法焊接焊缝质量不高的问题,对铝青铜材料展开水下湿法激光焊接实验,利用扫描电子显微镜(Scanning Electron Microscope,SEM)、显微硬度仪、万能试验机分别检测和分析了焊接接头的微观组织和力学性能。结果表明:铝青铜水下湿法焊接会出现大量气孔,水深增加会导致气孔增多,提高焊接速度可以改善焊缝成形质量,通过在基体表面预置自蔓延粉末能够有效减少气孔;焊缝中上部为胞状晶组织,底部为发达的树枝晶;焊缝平均硬度为240 HV,与基体相比提高了50%;拉伸试验试件均断裂在焊缝处,平均拉伸强度为235 MPa,为基体的43%。     

2A12铝合金焊接接头超声冲击处理前后拉伸性能分析

为克服铝合金薄板焊接接头强度偏低、韧性不足的缺点,用ER5356焊丝对不同厚度的2A12铝合金板材进行了手工氩弧焊接,并采用超声冲击处理对焊接接头进行全覆盖强化处理。采用金相显微镜观察了处理和未处理焊接接头的显微组织结构,对接头的力学性能进行了测试分析,分析了超声冲击处理改善2A12铝合金焊接接头力学性能的机理。结果表明：铝合金焊接接头经超声冲击强化处理后,6 mm和4 mm厚板材对接接头的抗拉强度分别提高了17.4%和23.7%,延伸率分别提高了28%和44%,焊缝表层组织得到明显细化。分析认为：晶粒大幅细化、组织致密化和缺陷减少,是超声冲击处理改善铝合金焊接接头抗拉伸性能的主要原因。     

非均匀焊接接头的力学建模与断裂分析

建立了非均匀焊接接头"4区连接"的新模型,并利用积分变换-奇异积分方程的方法,研究了焊缝区的反平面断裂问题。数值计算表明:增大界面区的刚度或者适当地增大焊缝区、热影响区和界面区的宽度都有利于降低焊缝区裂纹的应力强度因子;相对于高匹配情形而言,低匹配焊接接头焊缝区的抗断裂能力明显较高。     

铝热焊接工艺参数优化研究

为获得最佳铝热焊接工艺参数,对拉伸试件进行了正交试验和二次通用旋转组合试验,研究预热温度、加压时间和预留焊缝3因素对接头强度的影响,进而寻求一组使焊接接头强韧性最高的焊接工艺参数组合。利用电子显微镜等对试件拉伸断口进行了分析,通过对比2种开始加压时间下试件的显微组织和性能,研究了这2种方法对接头强韧性的影响。结果表明:采用设计的铝热焊接试验装置和优化出的随焊加压致密化工艺参数,可使焊接接头获得大变形组织,从而获得高的强度和韧性。该项研究可为提高铝热焊接质量提供基础数据。     

7A52铝合金便携式搅拌摩擦焊接头的组织与性能分析

采用便携式搅拌摩擦焊设备,对3mm厚的7A52铝合金薄板进行了焊接,对焊接头的显微组织和机械性能进行了观察测试。研究结果表明:焊接头可分为动态再结晶区、热-机影响区和母材3个区域,而没有明显的热影响区。动态再结晶区组织发生再结晶,生成细小的等轴晶粒;热-机影响区有塑性变形流线,且范围较窄;母材区保持着原来的轧制组织。接头硬度的最薄弱环节在热-机影响区。接头抗拉强度达到母材的70%左右,能够满足战场应急抢修的需求。     

环氧树脂/CTBN/无机颗粒高分子合金修补剂材料的制备与性能分析

通过端羧基丁腈液态橡胶(Carboxyl Terminated Butadiene Acrylonitrile,CTBN)协同纳米Al2O3、SiO2颗粒与微米MoS2颗粒共混改性环氧树脂,制备了双组分的耐磨高分子合金修补剂材料。采用拉伸、摩擦磨损等试验及SEM等方法测试和分析了该高分子合金修补剂的拉伸强度、显微硬度等基本性能及摩擦学性能,并对其耐磨减摩机理进行了分析。结果表明:该材料的拉伸强度为42.3MPa,拉伸剪切强度为13.8MPa,显微硬度为231.1MPa,摩擦因数为0.17,耐磨性比LY12铝合金提高了50%。     

TC4真空电子束焊后热处理对接头组织性能影响

<正>采用真空电子束焊接不等厚TC4钛环,焊后对接头进行整体退火、电子束局部退火、不退火方式获得3个接头。采用X射线测残余应力、通过拉伸、弯曲试验以及光学显微镜对焊接接头组织和性能进行研究。结果表明:焊后局部退火与整体退火能降低接头残余应力且使接头区域残余应力变化稳定,其作用效果相当;真空电子束局部退火能细化焊缝针状组织,改善热影响区组织。三种状态下接头都具有较高的抗拉强度并表现出良好的弯曲性能。在无法进行整     

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。     

LD10CS铝合金箱体材料焊接区断裂韧性研究

本文叙述用表面裂纹法测试LD10铝合金箱底手工氩弧焊焊接接头焊肉和热影响区各个部位的断裂韧性,通过显微分析和断口形貌分析,对接头各部位的热循环和组织变化作了较详细的探讨,指出焊接接头各个部位常规力学性能与断裂韧性不同的变化规律,提出了改进焊接接头断裂韧性的意见。     

焊接过程对焊接残余应力及残余变形的影响

采用热弹塑性有限元法 ,对直通焊和多人同时分段焊两种焊接过程的平板对接焊时焊接应力变形和圆柱壳板环缝的焊接变形进行比较 ,认为多人同时分段焊较直通焊无论在降低焊接残余应力还是焊接残余变形都具有非常显著的效果     

焊接工艺对熔敷金属韧性的影响

探讨了改变焊接工艺对焊条熔敷金属冲击韧性的影响．研究表明：改变焊接工艺,将通过改变熔敷金属的化学成分,影响熔敷金属的强度和韧性;降低焊接线能量时,将降低熔敷金属中的氧含量及其氧化夹杂物的数量和大小,从而提高熔敷金属的韧性     

Gas tungsten arc welding of ZrB_2-SiC based ultra high temperature ceramic composites

The difficulty in fabricating the large size or complex shape limits the application of ZrB2-SiC composites. Joining them by fusion welding without or with preheating, controlled cooling under protective gas shield leads to thermal shock failure or porosity at the weld interface. In the present work, a filler material of(ZrB2-SiC-B4C-YAG) composite with oxidation resistance and thermal shock resistance was produced in the form of welding wire. Using the filler, gas tungsten arc welding(GTAW) was performed without employing preheating, post controlled cooling and extraneous protective gas shield to join hot pressed ZrB2-SiC(ZS), and pressureless sintered ZrB2-SiC-B4C-YAG(ZSBY) composites to themselves. The fusion welding resulted in cracking and non-uniform joining without any filler material. The weld interfaces of the composites were very clean and coherent. The Vickers micro-hardness across the weld interface was found to increase due to the increase in the volume % of both SiC and B4C in the filler material. The shear strength of the weld was about 50% of the flextural strength of the parent composite.     

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.     

Experimental investigation of Tie6Ale4V titanium alloy and 304L stainless steel friction welded with copper interlayer

The basic principle of friction welding is intermetallic bonding at the stage of super plasticity attained with self-generating heat due to friction and finishing at upset pressure. Now the dissimilar metal joints are especially popular in defense, aerospace, automobile, bio-medical,refinery and nuclear engineerings. In friction welding, some special alloys with dual phase are not joined successfully due to poor bonding strength. The alloy surfaces after bonding also have metallurgical changes in the line of interfacing. The reported research work in this area is scanty. Although the sound weld zone of direct bonding between Tie6Ale4 V and SS304 L was obtained though many trials, the joint was not successful. In this paper, the friction welding characteristics between Tie6Ale4 V and SS304 L into which pure oxygen free copper(OFC) was introduced as interlayer were investigated. Boxe Behnken design was used to minimize the number of experiments to be performed. The weld joint was analyzed for its mechanical strength. The highest tensile strength between Tie6Ale4 V and SS304 L between which pure copper was used as insert metal was acquired. Micro-structural analysis and elemental analysis were carried out by EDS, and the formation of intermetallic compound at the interface was identified by XRD analysis.     

Microstructure,mechanical and corrosion behavior of high strength AA7075aluminium alloy friction stir welds-Effect of post weld heat treatment

High strength aluminium alloy AA7075(Al-Zn-Mg-Cu) is a precipitate hardenable alloy widely used in the aerospace,defense,marine and automobile industries.Use of the heat treatable aluminium alloys in all these sectors is ever-increasing owing to their excellent strength-toweight ratio and reasonably good corrosion resistance.The shortage in corrosion resistance,however,usually poses negative concern about their reliability and lifetime when they service in the variable marine environments.These alloys also exhibit low weldability due to poor solidification microstructure,porosity in fusion zone and lose their mechanical properties when they are welded by fusion welding techniques.Friction stir welding(FSW) is a reliable technique to retain the properties of the alloy as the joining takes place in the solid state.The welds are susceptible to corrosion due to the microstructural changes in the weld nugget during FSW.In this work,the effect of post weld treatments,viz.,peak aging(T6) and retrogression reaging(RRA),on the microstructure,mechanical properties and pitting corrosion has been studied.Friction stir welding of 8 mm-thick AA7075 alloy was carried out.The microstructural changes of base metal and nugget zone of friction stir welds were studied using optical microscopy,scanning electron microscopy and transmission electron microscopy.Tensile and hardness test of base metal and welds has been carried out.Pitting corrosion resistance was determined through dynamic polarization test.It was observed that the hardness and strength of weld were observed to be comparatively high in peak aged(T6) condition but the welds showed poor corrosion resistance.The resistance to pitting corrosion was improved and the mechanical properties were maintained by RRA treatment.The resistance to pitting corrosion was improved in RRA condition with the minimum loss of weld strength.     

Comparative study on transverse shrinkage,mechanical and metallurgical properties of AA2219 aluminium weld joints prepared by gas tungsten arc and gas metal arc welding processes

Aluminium alloy AA2219 is a high strength alloy belonging to 2000 series. It has been widely used for aerospace applications, especially for construction of cryogenic fuel tank. However, arc welding of AA2219 material is very critical. The major problems that arise in arc welding of AA2219 are the adverse development of residual stresses and the re-distribution as well as dissolution of copper rich phase in the weld joint.These effects increase with increase in heat input. Thus, special attention was taken to especially thick section welding of AA2219-T87 aluminium alloy. Hence, the present work describes the 25 mm-thick AA2219-T87 aluminium alloy plate butt welded by GTAW and GMAW processes using multi-pass welding procedure in double V groove design. The transverse shrinkage, conventional mechanical and metallurgical properties of both the locations on weld joints were studied. It is observed that the fair copper rich cellular(CRC) network is on Side-A of both the weldments. Further, it is noticed that, the severity of weld thermal cycle near to the fusion line of HAZ is reduced due to low heat input in GTAW process which results in non dissolution of copper rich phase. Based on the mechanical and metallurgical properties it is inferred that GTAW process is used to improve the aforementioned characteristics of weld joints in comparison to GMAW process.     

Characterization of magnetically impelled arc butt welded T11 tubes for high pressure applications

Magnetically impelled arc butt(MIAB) welding is a pressure welding process used for joining of pipes and tubes with an external magnetic field affecting arc rotation along the tube circumference. In this work, MIAB welding of low alloy steel(T11) tubes were carried out to study the microstructural changes occurring in thermo-mechanically affected zone(TMAZ). To qualify the process for the welding applications where pressure could be up to 300 bar, the MIAB welds are studied with variations of arc current and arc rotation time. It is found that TMAZ shows higher hardness than that in base metal and displays higher weld tensile strength and ductility due to bainitic transformation. The effect of arc current on the weld interface is also detailed and is found to be defect free at higher values of arc currents. The results reveal that MIAB welded samples exhibits good structural property correlation for high pressure applications with an added benefit of enhanced productivity at lower cost.The study will enable the use of MIAB welding for high pressure applications in power and defence sectors.     

Effect of welding processes and consumables on fatigue crack growth behaviour of armour grade quenched and tempered steel joints

Quenched and Tempered (Q&T) steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking (HIC) in the heat affected zone (HAZ) after welding. The use of austenitic stainless steel (ASS) consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. The use of stainless steel consumables for a non-stainless steel base metal is not economical. Hence, alternate consumables for welding Q&T steels and their vulnerability to HIC need to be explored. Recent studies proved that low hydrogen ferritic steel (LHF) consumables can be used to weld Q&T steels, which can give very low hydrogen levels in the weld deposits. The use of ASS and LHF consumables will lead to distinct microstructures in their respective welds. This microstructural heterogeneity will have a drastic influence in the fatigue crack growth resistance of armour grade Q&T steel welds. Hence, in this investigation an attempt has been made to study the influence of welding consumables and welding processes on fatigue crack growth behaviour of armour grade Q&T Steel joints. Shielded metal arc welding (SMAW) and Flux cored arc welding (FCAW) were used for fabrication of joints using ASS and LHF consumables. The joints fabricated by SMAW process using LHF consumable exhibited superior fatigue crack growth resistance than all other joints.