A new weld repair technique for friction stir welded aluminium structure:inertia friction pull plug welding

The paper gives an analysis on technical characteristics of repair techniques for friction stir welding defects. To overcome the defects,a new repair technique, inertia friction pull plug welding( IFPPW), was researched and its equipment was developed as well. Elementary datum was achieved by investigating the influences of technological parameters on mechanical properties and by analyzing the structural characteristics of repair joint with IFPPW. The study shows that the stability and reliability of welding process of IFPPW can be guaranteed through the constant energy from the flywheel.Integrated with the advantages of friction pull plug welding,the IFPPW,free from back anvil,is considered as a promising technique in repair of termination keyhole of bobbin tool friction stir welding and point-like defects in aluminum alloy welding.

Residual Stress and Fracture Toughness Study in A516 Gr70 Steel Joints Welded and Repaired by Arc Processes

Structural components made of steel are used in several areas and require welding for assembly. In some situations, repair of the weld bead, also performed by electric arc welding, can be used to correct, and eliminate any discontinuities. However, electric arc welding causes the presence of residual stresses in the joint, which can impair its performance and not meet specific design requirements. In this paper, welded joints made of ASTM A 516 GR 70 steel plates, with a thickness of 30.5 mm, welded by the MAG—Metal Active Gas process (20% CO2) and using a “K” groove were analysed. The joints were manufactured with seven welding passes on each side of the groove. After welding, one batch underwent repair of the bead by TIG welding (Tungsten Insert Gas) and another batch underwent two repairs by TIG welding. Were presented results of the behaviour of the residual stress profile measured by X-ray diffraction and the Vickers microhardness profile in the joints as well the fracture toughness in the conditions only welded and submitted to repairs. The results indicated that the greater number of repair passes reduced the residual compressive stress values obtained in the material manufacturing process and caused a stabilization on the Vickers hardness values. It was concluded that compressive residual stresses did not play a major role in the R-curve results. The presence of discontinuities in the welded joint caused greater influence on the behaviour of the R curve.

Effect of Conventional and Pulsed TIG Welding on Microstructural and Mechanical Characteristics of AA 6082-T6 Repair Welds

Repair welding of AA 6082-T6 joints was carried out using ER 4043 filler through the TIG welding process with or without pulsed current.Microstructure and mechanical characteristics of the joints before and after repairing were investigated by examining macrostructure,microstructure,and distributions of porosity in the weld metal(WM),and by hardness,tensile,and bending tests.We observed that the welding current,phase transformations in heat-affected zone(HAZ)and porosity introduced in the WM during welding influence on its mechanical properties in sequence.The experimental results showed that the bead width and penetration as well as size of pores in the joints were mainly influenced by the welding currents.The sound joints were obtained at a welding current of 140 A with or without pulsed current when welding speed and gas flow rate were set at 20 cm·min-1 and 15 L·min-1,respectively.Among them,the decrease in mechanical properties of repair weld(RW)was directly related to the phase transformations in the over-ageing zone due to the double welding thermal cycles and elevated distribution of porosity in the WM.In addition,it was observed that the comparatively smaller grain size and lower porosity in WM of the RW produced by pulsed TIG welding gave a positive effect on its mechanical properties.

Microstructure and mechanical properties of repair welds of low-pressure sand-cast Mg?Y?RE?Zr alloy by tungsten inert gas welding

The sand castings of Mg-Y-RE-Zr series alloys are widely utilized in the large scales and complex shapes in the aerospace industry,as a result of which there are always some cast defects in the products. In this study, the feasibility of repair welding of sand-cast Mg-4 Y-3 RE-0.5 Zr alloy by tungsten inert gas(TIG) welding was scrutinized with different welding currents from 150 to 210 A. The results indicated that defect-free repaired joints with good appearance could be acquired at 170 and 190 A. Interestingly, the grain size of the fusion zone(FZ) was refined initially and then increased with the linear increment of welding current. Because at the higher heat inputs, although the cooling rate of the molten pool was reduced, substantial constitutional supercooling for the grain refinement was attained after the Zr particles were transformed into Zr solutes. The tensile strength of the repaired joint at 170 A was 195 MPa with the maximum joint efficiency of 87.8%, and the elongation reached to 124.4% of the sand-cast base material(BM). However, serious grain coarsening and continuous eutectic structures generated in heat-affected zone(HAZ) above 190 A resulted in the weakening of the joint due to the brittle intergranular fracture.

Repair welding process of friction stir welding groove defect

The groove defect formed in the friction stir welding dramatically deteriorates weld appearances and mechanical properties of the joints owing to its larger size and penetration. Therefore, the friction stir repair welding was utilized to remove such a groove defect, and the focus was placed on the mechanical properties and microstructural characteristics of the repair joints so as to obtain an optimum repair welding process. The experimental results indicate that the groove defect can be removed by friction stir repair welding, and the offset repair welding process is superior to the symmetrical repair welding process. In the symmetrical repair welding process, a large number of fine cavity defects and an obvious aggregation of hard-brittle phase Al2Cu occur, accordingly the mechanical properties of the repair joint are weakened, and the fracture feature of repair joint is partially brittle and partially plastic. A good-quality repair joint can be obtained by the offset repair welding process, and the repair joint is fractured near the interface between the weld nugget zone and thermal-mechanically affected zone.

The development and design of the repair welding procedure of the thick wall duplex stainless steel piping

In this paper,the performance characteristics of ASTM A790 S31803 and ASTM A182 F51 duplex stainless steel were introduced,and the weldabilities were analyzed. The welding repair procedures of thick wall duplex stainless steel were developed by welding procedure qualification. Research shows that the repair welding has less effect on mechanical properties of welded joint, and great influence on phase proportions and pitting corrosion resistance. The test results meet the requirements of project specifications. The repair welding procedure can be used in project,and only one time repair shall be used.

Formation mechanism of transverse crack in repair welding for thick plate of Q345 high strength steel

Transverse cracks occur usually in repair welding for thick plate of high strength steel. It needs multiple times of repair welding. The quality of production and deliver deadline will be influenced. Therefore, it is very significant to investigate the cause and control of transverse crack in repair welding. In this paper, both ends restraint crack experiment is developed to produce delay transverse crack for high strength steel. Metallographic results show that four types of cracks are found in repair welding metal zone and heat affected zone. Large chevron transverse cracks are found in repair welding zone. Lots of micro transverse cracks are found in inter-layer repair welding metal zone, root HAZ and two ends of repair welding individually. The distribution character and formation mechanism of the transverse crack are further analyzed through hardness testing and residual stress measurement.

X80钢补焊残余应力模拟与试验验证

X80管线钢在铺设或者使用过程中会产生裂纹、气孔等缺陷而需要进行补焊修复。利用ABAQUS有限元分析软件建立了X80钢平板补焊模型,模拟分析了补焊前后X80钢焊接残余应力的变化情况,同时研究了3种不同补焊热输入量对焊接残余应力的影响。为验证模拟结果的准确性,开展了3种对应热输入量的补焊试验。模拟及试验研究结果表明,补焊残余应力高于初始焊残余应力,补焊后横向残余应力峰值较初始焊增加55.52%,补焊后纵向残余应力峰值已超过材料屈服强度。随着补焊热输入量的增大,Mises等效残余应力峰值和纵向残余应力无明显改变,但不同路径的横向残余应力变化规律有所不同。试验测量的残余应力值与模拟结果接近,两者的变化趋势一致。

通流改造机组高压主汽联合阀焊缝开裂分析及处理建议

针对某机组通流改造后高压主汽阀和高压调节阀的R337对接焊缝出现的横向裂纹问题进行深入分析。通过观察现场裂纹、分析样品以及评估材料性能,确定裂纹形成的主要原因。首先,焊材R337的选用不当导致了焊缝脆性的增加,其次,结构应力和交变应力的叠加作用加速了裂纹的扩展;ZG15Cr1Mo1V钢的碳当量较高,具有较大的淬硬倾向,容易产生冷裂纹,而Nb元素的加入则增加了再热裂纹的敏感性。针对裂纹形成的原因提出了处理建议,首先彻底清除原有的R337焊缝,并采用低匹配的R317焊条进行修复;在焊接过程中,严格控制预热温度、层间温度和焊接线能量,以减少焊接应力;焊后进行中频感应热处理,以均匀温度场并充分消减应力;考虑到ZG15Cr1Mo1V钢的再热裂纹倾向,建议在修复过程中采取适当的预防措施。

水下激光修复研究现状与发展趋势

海洋装备的维修养护与事故抢修技术既是人类进行远洋探索与资源开发的重要保障,又是核电站、水利工程等重要基础设施在役运维的有力技术支撑,而水下激光修复正是这一领域中极具前景的解决方案之一.激光修复技术作为陆地上常规环境中的优势技术,近年来也在水下环境中有了长足的发展,已在海洋油气资源的开采与运输、船舶应急维修、船坞港口装备、水利工程、核动力工程等领域得到了广泛的关注与研究.为了进一步总结并分析水下激光修复技术所面对的问题与现有解决方案,从水下激光修复技术的研究现状入手,综述了水下湿法、高压干法和局部干法激光修复技术的工艺问题及其产生机理,并分析对比了多种对应主流解决方案的改善效果与研究进展,最后对水下激光修复技术的发展趋势进行了总结与展望.

水轮机修复堆焊技术研究现状分析

传统能源逐渐枯竭,且对环境影响较大.国家大力推动绿色清洁能源的发展.水力发电占比也逐年提高,对水轮机相关技术的研究有了更高要求.我国河流泥沙含量大,泥沙含量越高,水轮机关键零部件磨损就越大.水轮机零部件修复技术存在成本高、效率低且质量难以保证等问题,因此亟需研究低成本高效率的智能堆焊修复技术.应用于轮机的先进堆焊技术可以促进绿色环保、提高能源利用率,同时也可促进国民经济发展和振兴机械工业.

铸造低合金钢回火焊道技术适用性判别分析

回火焊道技术是通过第二层焊道的热循环来改善第一层焊道的组织和性能的焊接技术,但目前尚无明确标准规定其适用范围。以A217 WC6和A217 WC9钢为对象,采用Gleeble热模拟试验判断二次回火对两种铸造低合金钢性能的影响规律,进而用回火焊道技术制造焊接试样,进行焊态、热处理态下的组织和性能对比试验。试验结果表明,A217 WC6钢在一次高温热循环后,冲击功从70 J提升至126 J,硬度值从154 HV10增至375 HV10。二次热循环后,A217 WC6钢的硬度整体降低,回火峰值温度对其性能有显著影响。相比之下,A217 WC9钢的冲击功从77 J降至52 J,硬度值从182 HV10增至364 HV10,二次热循环对其性能影响不显著。焊接试样的性能和硬度变化趋势与Gleeble热模拟试验一致。由此得到结论:Gleeble热模拟试验可以判断钢种是否适用于回火焊道技术;A217 WC6钢较A217 WC9钢更适合采用回火焊道技术进行修复。

BFe10-1-1摩擦塞补焊接头组织及性能研究

采用顶锻式摩擦塞补焊方法对5 mm厚的BFe10-1-1铜镍合金进行匙孔补焊实验,探讨了不同主轴转速下塞补焊接头的微观形貌、显微硬度、温度场分布及其力学性能。结果表明:主轴转速对铁白铜塞补焊成形有重要的影响,随着转速提高,接头底部缺陷逐渐缩小,塞棒区金属摩擦流线明显,晶粒呈破碎细化特征,接头从上到下,热影响区范围缩小明显。由于细晶强化作用,塞棒区显微硬度高于母材,且塞棒上侧显微硬度高于中下侧。在转速为2 100 r/min时得到接头拉伸强度最高,达到母材78%。接头表现出韧性断裂特征,随着转速提高,接头弱连接缺陷逐步下移,并不断缩小。

钨极氩弧焊与激光熔覆修复的K403镍基高温合金导向器叶片组织与性能

K403镍基高温合金具有优异的室温和高温综合性能,广泛用于航空发动机涡轮叶片及导向器的制造。针对涡轮叶片长期服役于复杂工况产生的裂纹缺陷等问题,本工作先对钨极氩弧(tungsten inert gas,TIG)焊和激光熔覆两种工艺修复后的组织与拉伸性能展开对比分析,而后使用激光熔覆工艺修复叶片,并进行无损检测。利用OM、SEM观察微观组织、断口形貌,利用EDS进行相的成分分析。结果表明:TIG焊修复工艺在修复界面区附近易产生微裂纹缺陷,主要碳化物相和低熔点共晶组织引起;激光熔覆工艺修复区域的晶粒与组织更加均匀,微裂纹缺陷更易得到控制;激光熔覆工艺修复的试样综合力学性能明显高于TIG焊修复工艺的试样,且激光熔覆工艺具有较好的工艺稳定性,TIG焊修复工艺的室温拉伸强度为K403母材强度的69.22%,激光熔覆修复工艺室温抗拉强度达到了母材的87.44%,断口形貌显示修复区域的室温拉伸断口呈现出混合断裂特征,高温拉伸断口呈现出沿晶断裂的特征。修复区域的微裂纹、局部液相不足缺陷和碳化物是拉伸断裂的主要原因。激光熔覆修复工艺具有热源集中、热影响区小的优势,能够有效抑制修复区缺陷并细化微观组织,在叶片修复方面具有更大优势。使用激光熔覆修复工艺完成了叶片试车过程产生的边缘板裂纹损伤修复,经过荧光检测及煤油-白垩检测,满足相关使用要求。

一种应用于二次平行封焊的工艺方法

实现二次平行封焊并达到气密性标准是气密性产品返修的关键。该文介绍了一种应用于二次平行封焊的工艺方法,通过对平行封焊后的气密性元器件进行激光开盖,在控制多余物产生后,利用机加工铣平壳体围框表面进行二次平行封焊。测试并分析了气密性元器件系统集成封装(SIP)模块二次平行封焊后的检漏。结果表明,细检漏率<1.01×10^(-8) Pa·m^(3)/s,粗检漏无连续气泡产生,气密性满足电子与电器元件试验方法(GJB 360B-2009)要求。根据该文介绍的工艺方法可为多余物可控的气密性元器件实现二次平行封焊提供一种有效的解决方案。

FCAW焊接修复对AH36/2205不锈钢复合板接头性能的影响

由于减少了贵重合金元素的使用,AH36/2205不锈钢金属复合板在应用中有着巨大的经济效益。复层和基层金属间的物理、化学性质存在差异,焊接质量不稳定,因此焊接修复不可避免。为了研究焊接修复对于焊接接头性能的影响,针对14 mm+2 mm的AH36/2205不锈钢金属复合板,采用药芯焊丝气体保护焊(FCAW)进行1~3次焊接修复模拟试验。结果表明:AH36/2205不锈钢金属复合板不适合采用FCAW进行焊接修复,1次修复试板的点蚀率达到了167.7 mdd。随着修复次数的增加,不锈钢复合板接头的力学性能及耐晶间腐蚀性能良好,而点蚀率增加,接头的耐点蚀性能下降。

6082铝合金轴肩辅助加热摩擦塞补焊接头组织及温度分布

采用轴肩辅助加热方法实现了5 mm厚6082铝合金板匙孔类缺陷摩擦塞补焊修复,分析了摩擦塞补焊接头的组织和力学性能。结果表明:接头焊核区为细小等轴晶,结合面区为过渡区,轴肩影响区分层明显,热力影响区晶粒发生弯曲变形,热影响区保留了母材板条状组织。接头显微硬度均高于母材,在厚度方向上存在各层异性;抗拉强度最高达285.7 MPa,为母材的92.2%,断口呈韧性断裂特征。焊接热输入和材料热塑性变形,是接头不同区域显微组织存在明显差异的根本原因。

不同补焊次数对X2CrNi12铁素体不锈钢焊接接头耐点蚀性能的影响研究

以X2CrNi12铁素体不锈钢为研究对象,采用MAG焊进行不同次数的补焊,探讨了补焊次数对焊接接头组织及耐点蚀性能的影响。研究结果表明,一次补焊和二次补焊接头的焊缝区显微组织基本相似,主要由白色的奥氏体基体以及黑色的板条状和网状δ铁素体组成。与母材相比,焊接接头的晶粒尺寸明显增大。电化学测试结果显示,焊缝区的耐蚀性最好,其次是母材,而HAZ的耐蚀性最差。SEM观察发现,焊缝区无点蚀产生,而母材和HAZ出现了均匀分布的小点蚀坑。与一次补焊相比,二次补焊后的焊缝区耐蚀性更好。因此,二次补焊有利于提高X2CrNi12铁素体不锈钢焊接接头的耐点蚀性能。这一研究结果为根据焊接接头的电化学点蚀性能选择合适的补焊次数提供了理论依据。

G20Mn5铸钢件MAG焊焊补接头组织与力学性能研究

为研究G20Mn5铸钢件最优的焊补工艺,以提高铸钢件质量和降低生产成本。对G20Mn5铸钢件进行MAG焊焊补,比较了5种焊补工艺(包括焊前预热、焊后保温、热处理等条件)的接头显微组织和力学性能。试验结果显示,所有焊补工艺接头的焊缝区和热影响区粗晶区均未出现淬硬的马氏体组织和粗大的魏氏组织;焊补接头的抗拉强度均超过480 MPa,断后伸长率均大于20%,硬度峰值均低于250 HV,焊缝和热影响区的冲击功值均大于母材;各焊补接头的拉伸试样和疲劳试样均断裂于母材,疲劳裂纹源为铸钢件内部的显微缩松缺陷。试验证明,5种工艺焊补接头的显微组织和力学性能均满足使用要求,综合考虑各方面因素,焊补前不预热+焊补后覆盖保温缓冷+不热处理为最优焊补工艺。

焊趾工艺优化对压力管道对接接头残余应力的影响

为探讨焊趾工艺优化方案对压力管道对接接头残余应力分布的影响,以提高管道的疲劳寿命和整体性能。通过设计三种不同的焊趾工艺优化方案,利用有限元分析模拟了三种方案对X70管线钢对接接头周向和轴向残余应力的影响,并采用盲孔法对仿真结果进行了验证。仿真和试验结果表明,三种优化方案的周向和轴向残余应力变化趋势基本一致;焊趾位置凹形过渡(方案2)在减少应力峰值和平均应力方面表现最佳,其周向残余应力峰值为539.22 MPa,轴向应力峰值为204.57 MPa;盲孔法测量结果显示,残余应力仿真与试验结果趋势一致,误差控制在8.5%以内,该结果验证了仿真模型的可靠性。焊趾位置的凹形过渡设计能有效降低残余应力,提高压力管道的安全性和耐用性。