焊接工艺对GMAW堆焊焊缝区温度场影响的数值模拟

为了探索焊接工艺对熔化极气体保护堆焊快速成形零件组织性能的影响，根据材料热物理性能参数以及相变潜热与温度的非线性关系，建立了熔化极气体保护堆焊成形过程的数学模型和有限元模型，利用ANSYS软件的APDL语言编写程序，实现了高斯移动热源载荷下的熔化极气体保护堆焊成形温度场计算，分析对比了不同焊接工艺对焊缝区温度场热循环的影响。结果表明：在其他因素一定的条件下，热输入和焊接速度对焊缝区热循环影响显著，而基板厚度对其影响较小；选择厚度约为16mm的基板，采用小于120×20J的热输入和大于10mm／s的焊接速度有望成形出性能优良的零件。     

添加剂对无电焊接脱渣性及焊缝成形的影响

针对焊接熔渣严重影响无电焊接焊缝成形的问题,通过添加造渣剂组分,研究了添加剂对无电焊接熔渣脱渣性及焊缝成形的影响。测试结果表明:添加剂的加入,使得无电焊接熔渣体系中形成多种多元化合物,并均匀、弥散地分布在Al2O3基体之中,形成规则的片层状组织,具有较好的相容性,而且通过形成多种多元化合物,使得无电焊接熔渣中的Al2O3相含量明显降低,从而显著地改善了无电焊接的脱渣性和焊缝成形性能,焊接接头的拉伸强度得到明显提高。     

无电焊接中厚度钢板焊接接头的组织结构与性能研究

采用无电焊接方法对12mm厚度钢板进行了焊接。分析了满足中厚度钢板焊接能量要求的技术途径;利用SEM,EDS,XRD等手段观察、分析了焊缝的组织成分与显微结构;测试了焊接接头的拉伸强度、弯曲强度、显微硬度等力学性能。结果表明:在选择高放热体系基础上,通过增大焊接笔直径、减小反应物料粒径、提高压坯密度等方法,可以有效增大焊接热效率,从而满足中厚度钢板焊接能量需求;焊缝组织分为热影响区、熔合区与合金区,焊缝合金与母材间通过熔合区形成了冶金结合;焊接接头因固溶强化和析晶强化的作用,具有良好的力学性能,拉伸强度、平均显微硬度与弯曲强度分别为357MPa、186HV0.2与644MPa,达到了野战应急抢修技术要求。     

简析回流焊的温度曲线

通过对回流焊温度曲线的分段描述,理解焊膏各成分在回流炉中不同阶段所发生的变化,给出获得最佳温度曲线的一些基本数据,并分析不良温度曲线可能造成的回流焊接缺陷。     

无电焊接材料的燃烧速度和燃烧温度研究

采用高放热性的铝热剂（CuO＋Al）并加入适当的添加剂,制备了便携式的无电焊接笔材料,其燃烧速度可控,且具有高的燃烧温度。研究了反应剂颗粒大小、混料均匀性等对无电焊接笔材料的燃烧性能的影响。结果表明：反应剂粒径对无电焊接笔的燃烧速度具有显著影响,随着反应剂粒径的增大,燃烧速度明显减慢。反应剂粒径和混料时间是影响单位时间放热量和混料均匀度的主要因素,因而对无电焊接笔的燃烧温度具有明显影响。在一定的混料时间下,反应物粉末具有最佳的混料均匀性。反应物粒径小且混料均匀性好的无电焊接笔材料,其燃烧温度高。     

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     

不同射流状态下射流气体与高超声速主流相互作用影响

为研究不同射流状态对高超声速飞行器气动加热的影响,对高超声速来流条件下方孔和圆孔横向射流模型进行数值模拟,讨论射流压强、射流速度及射流方向对主流流场的影响,得到了不同射流状态下流场结构、壁面温度热流分布及壁面中心线温度热流变化。结果表明:射流在一定程度上能缓解壁面气动加热情况,壁面引射效果更好,壁面引射速度1 m·s~(-1)时壁面热流降低接近三分之二。在高速(Ma1)射流情况下,适当增大压强和速度,均会使得射流下游的冷却效果加强;在中低速(Ma0.6)射流情况下,射流基本上不改变主流流场而在边界层内流动,流速越大,冷却范围越大,冷却效果也相对较好。射流方向与主流方向夹角为锐角时,利于射流孔下游降温;夹角为钝角时,利于射流孔上游降温。     

一种临界速度估算方法及其对潜艇隐蔽作战的影响

考虑到潜艇航行速度对其隐蔽作战具有重要影响,提出了一种可行的临界速度估算方法,在螺旋桨以及潜艇的外形已经确定的前提下,计算出潜艇在不同航行深度时适用于隐蔽攻击的航行速度范围,并给出了两型潜艇临界速度随深度变化的曲线.计算分析结果表明:临界速度主要与潜艇所在深度有关,航行深度越大,潜艇进行隐蔽攻击的允许速度也越大;潜艇可...     

基于Jmat-pro计算的Q345级别耐火钢焊接工艺评定

通过测定焊接热影响区连续冷却转变(SH-CCT)曲线图评定两种Q345级别低Mo(约0.25wt.%)耐火钢焊接工艺。试验结果表明,Q1钢当实际冷却时间t8/5>43s时,焊接的热影响区以及熔合区附近不会产生开裂,而当t8/5<43s时,热影响区或熔合区有开裂的可能;Q2钢当实际冷却时间t8/5>44s时,焊接热影响区和熔合区附近不会产生开裂,而当t8/5<44s时,热影响区或熔合区有开裂的可能。此外,Jmat-pro软件对Ac3的计算有一定的准确性,但对连续冷却转变(CCT)曲线误差较大,特别是Q2钢的计算值与实测值差距更大,只具有参考价值。     

铝中间层对TA2/5083爆炸焊接影响的数值模拟

为研究添加中间层对TA2/5083爆炸焊接的影响,分别选取0.3 mm和0.5 mm厚度的1060铝中间层,利用ANSYS/LS-DYNA软件结合ALE算法建立三维数值模型,分别模拟出添加0.3 mm和0.5 mm厚度1060铝中间层的焊接过程,与直接爆炸焊接TA2和5083复合板进行对比。模拟结果表明：选择适当厚度的1060铝中间层,能有效减少基板所受碰撞压力,让爆炸焊接过程更加平稳;结合建立的爆炸复合窗口,添加中间层能大大扩展可焊接窗口,减小碰撞速度,模拟结果更加接近理论碰撞速度,使复板以更佳的飞行速度与基板结合;0.3 mm厚度中间层复合板的焊接质量高于0.5 mm厚度中间层高于无中间层的,模拟与实验吻合较好,添加合适厚度的中间层1060能大程度提高TA2/5083复合质量。     

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.     

Effect of fusion welding processes on tensile properties of armor grade,high thickness,non-heat treatable aluminium alloy joints

AA5059 is one of the high strength armor grade aluminium alloy that finds its applications in the military vehicles due to the higher resistance against the armor piercing (AP) threats. This study aimed at finding the best suitable process among the fusion welding processes such as gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) by evaluating the tensile properties of AA5059 aluminium alloy joints. The fracture path was identified by mapping the low hardness distribution profile (LHDP) across the weld cross section under tensile loading. Optical and scanning electron microscopies were used to characterize the microstructural features of the welded joints at various zones. It is evident from the results that GTAW joints showed superior tensile properties compared to GMAW joints and this is primarily owing to the presence of finer grains in the weld metal zone (WMZ) and narrow heat-affected zone (HAZ). The lower heat input associated with the GTAW process effectively reduced the size of the WMZ and HAZ compared to GMAW process. Lower heat input of GTAW process results in faster cooling rate which hinders the grain growth and reduces the evaporation of magnesium in weld metal compared to GMAW joints. The fracture surface of GTAW joint consists of more dimples than GMAW joints which is an indication that the GTAW joint possess improved ductility than GMAW joint.     

LD10cs 铝合金焊接接头疲劳裂纹扩展速率的研究

本文研究用表面裂纹法测试LD10cs铝合金板材焊接接头各部位疲劳裂纹扩展速率。结果表明:焊接接头各部位疲劳裂纹扩展速率随焊接热循环引起的金属组织变化而变化,有一定规律性。熔合线和焊趾处疲劳裂纹扩展速率较其他部位大。焊缝加强高的存在,引起焊趾处应力集中,使该处疲劳性能进一步恶化,成为焊接接头疲劳性能最差的部位。结合金相组织和扫描电镜分析,对影响焊接接头各部位疲劳裂纹扩展速率的各种因素作了较详细的探讨,并提出了改进焊缝质量的建议。     

Pulsed current and dual pulse gas metal arc welding of grade AISI: 310S austenitic stainless steel

The transverse shrinkage, mechanical and metallurgical properties of AISI: 310 S ASS weld joints prepared by P-GMAW and DP-GMAW processes were investigated. It was observed that the use of the DP-GMAW process improves the aforementioned characteristics in comparison to that of the P-GMAW process. The enhanced quality of weld joints obtained with DP-GMAW process is primarily due to the combined effect of pulsed current and thermal pulsation(low frequency pulse). During the thermal pulsation period, there is a fluctuation of wire feed rate,which results in the further increase in welding current and the decrease in arc voltage. Because of this synchronization between welding current and arc voltage during the period of low frequency pulse, the DP-GMAW deposit introduces comparatively more thermal shock compared to the P-GMAW deposit, thereby reducing the heat input and improves the properties of weld joints.     

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.