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平头搅拌针调修是指在原有焊缝背面用无搅拌针的搅拌头对焊缝再次进行搅拌摩擦焊,使焊缝温度升高,改善FSW接头性能.对平头搅拌针不同调修次数的高速列车用6082-T6铝合金搅拌摩擦焊接头进行脉动拉伸疲劳试验,利用扫描电镜观察分析疲劳断口,试验结果表明:铝合金搅拌摩擦焊接头指定寿命为1×107次的中值疲劳极限随着搅拌针调修次数的增加而升高.平头搅拌针调修两次时焊接接头的疲劳极限强度较高,焊缝背面边缘是本次试验集中产生裂纹的部位.启裂区和扩展区疲劳纹清晰;终断区为深韧窝状花样的韧性断口. 相似文献
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使用回填式搅拌摩擦点焊设备,对6系列铝合金弧焊焊接接头进行了搅拌摩擦点焊补焊试验,点焊补焊后试样表面平整光滑。对搅拌摩擦点焊补焊、MIG焊焊接接头进行了疲劳性能试验,研究发现,搅拌摩擦点焊补焊接头的疲劳寿命高于MIG焊焊接接头,断口组织更为致密。 相似文献
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对采用双轴肩搅拌摩擦焊的两种不同焊前表面状态6005A-T6铝合金型材焊接接头进行脉动拉伸疲劳试验。断口疲劳断裂分析结果表明:焊前打磨时接头疲劳强度略高;焊前打磨状态对6005A-T6铝合金型材双轴肩搅拌摩擦焊接头疲劳强度影响不大。电镜扫描结果显示:两种类型接头试件宏观断裂形貌均为纤维状,启裂位置均集中在热影响区(焊核边缘),未出现明显缺陷;启裂区断口齐平光滑、疲劳源清晰;扩展区可观察到相互平行的塑性疲劳条带;终断区断口表现为韧性断裂,呈明显的等轴韧窝型。 相似文献
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针对搅拌摩擦单面焊两侧热输入不均匀性导致疲劳强度低的问题,采用双面对称搅拌摩擦焊方法对10 mm厚的AZ31镁合金板材进行焊接,并研究其疲劳性能. 结果表明,双面对称搅拌摩擦焊接头的屈服强度为130 MPa,与单面焊的屈服强度123 MPa相比提高了5%;其疲劳极限为88 MPa,比单面焊接头的50 MPa提高了76%;双面对称接头疲劳裂纹萌生在上/下侧的前进侧位置,并跨越上/下侧焊缝交界面,最终在下/上侧焊缝的后退侧RS区域瞬断,其疲劳断口均为以解理特征为主的脆性断裂. 双面对称焊接头其中一面应变范围与单面搅拌摩擦焊的应变较高的后退侧接近. 通过双面搅拌摩擦焊接的镁合金接头疲劳强度得到了大幅度提升,疲劳寿命得到了延长. 相似文献
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《热加工工艺》2015,(13)
针对6005A-T6铝合金型材搅拌摩擦焊接头缺陷,分别采用搅拌摩擦焊(FSW)和熔化极气体保护焊(MIG)进行补焊,对补焊后的接头疲劳性能进行了研究。结果表明,在循环次数N107时,FSW补焊接头的疲劳强度为100MPa,可达母材疲劳强度的84.53%,MIG补焊接头的疲劳强度为80 MPa,可达母材疲劳强度的67.62%。FSW补焊接头的疲劳断口裂纹源位于焊缝底部,裂纹扩展区有典型的疲劳辉纹,瞬断区为剪切型断口,为撕裂棱和韧窝组合形貌。MIG补焊接头疲劳断口的断面有微气孔,裂纹源位于夹杂气孔缺陷处,扩展区为准解理断裂,瞬断区为韧性断裂和脆性断裂的复合形式。 相似文献
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Fatigue properties of friction stir welded butt joint and base metal of MB8 magnesium alloy 下载免费PDF全文
The fatigue properties of friction stir welded(FSW) butt joint and base metal of MB8 magnesium alloy were investigated.The comparative fatigue tests were carried out using EHF-EM200K2-070-1A fatigue testing machine for both FSW butt joint and base metal specimens.The fatigue fractures were observed and analyzed using a scanning electron microscope of JSM-6063 LA type.The experimental results show that the fatigue performance of the FSW butt joint of MB8 magnesium alloy is sharply decreased.The conditional fatigue limit(2 × 10~6) of base metal and welded butt joint is about77.44 MPa and 49.91 MPa,respectively.The conditional fatigue limit(2 × 10~6) of the welded butt joint is 64.45%of that of base metal.The main reasons are that the welding can lead to stress concentration in the flash area,tensile welding residual stress in the welded joint(The residual stress value was 30.5 MPa),as well as the grain size is not uniform in the heat-affected zone.The cleavage steps or quasi-cleavage patterns present on the fatigue fracture surface,the fracture type of the FSW butt joint belongs to a brittle fracture. 相似文献
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The characteristics of fatigue crack propagation in welds produced in conventional conditions (welds made out of water) and in underwater repair welding conditions (underwater wet welding) were evaluated out of water. The fatigue crack growth rates da/dN showed considerable dependence on pore density and distribution, factors that vary significantly with the welding process and the environment. Variations in the fatigue crack propagation rate were correlated with analysis of the fracture surface in the zone of stable crack propagation. The results of this study show that the underwater wet welding procedure produces weld metal resistant to fatigue, which is suitable for use at low applied stresses in offshore structures. 相似文献
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In the area of heavy construction, welding processes are vital in the production and maintenance of pipelines and power plants.
The fusion welding process generates formidable welding residual stresses and metallurgical change, which increase the crack
driving force and reduce the resistance of brittle fracture as well as environmental fracture. This is a serious problem with
many alloys as well as A106 Gr B steel pipe. This pipe, used in petrochemical and heavy chemical plants, either degrades due
to corrosive environments, e.g., chlorides and sulfides, and/or becomes damaged during service due to the various corrosion
damage mechanisms. Thus, in this study, the sulfide corrosion fatigue strength of multi-pass welded A106 Gr B steel pipe was
evaluated in a 5.0 wt.% NaCl solution that was saturated with H2S gas at room temperature on the basis of NACE TM 0177-90.
The crack growth characteristics of the welded pipe were then assessed at the low limit of sulfide corrosion fatigue strength,
which was previously obtained from the sulfide corrosion fatigue (SCF) tests. From the results, in terms of the SCF, all the
specimens failed at the heat-affected zone, where a high welding residual stress distributes. It was found that the fatigue
crack grew at the low corrosion fatigue limit (σ
SCFun-notched), which was 32 % (160MPa) of the ultimate tensile strength (502MPa) of the welded specimens. 相似文献
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利用MTS-810疲劳试验机测试了耐候钢SMA490BW对接接头原始焊件、一次焊补件、二次焊补件的疲劳性能. 分别拟合了三类接头的均值S-N曲线和存活率95%、置信度75%的P-C-S-N曲线. 分析了焊补对焊接接头疲劳性能的影响. 结果表明,三组疲劳数据点基本在允许的分散带内,焊补没有对焊接接头疲劳性能造成明显的影响. 将三组数据整合在一起作为一个样本,运用成组法和升降法数据处理思想获得疲劳曲线. 并通过八节点法绘制了疲劳极限图Goodman-Smith图,为转向架焊补后疲劳强度校核提供了依据. 相似文献
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《Science & Technology of Welding & Joining》2013,18(3):169-173
AbstractGas tungsten arc welding (GTAW) repair process and GTAW+FSW (friction stir welding) hybrid repair process are studied to remove the large size groove defect formed during FSW. The experimental results indicate that the groove defect can be removed by both the repair processes. The tensile strength of the GTAW repair joint is only 55% of that of the base metal. The tensile fracture occurs at the transition zone between the weld zone and the heat affected zone, and the fracture surface of the repair joint is characterised by clear brittleness. In contrast, the GTAW+FSW hybrid repair joint has a high tensile strength equivalent to 70% of that of the base metal. The tensile fracture occurs at the overlap thermomechanically affected zone between the two FSW nuggets, and the fracture feature of the hybrid repair joint is partially plastic and partially brittle. 相似文献
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P92钢是新型铁素体耐热钢,目前国内采用其匹配焊材进行返修,焊后需进行再次热处理,而多次热处理会造成管壁的性能下降,且需要花费大量的时间和成本。在临时性返修没有匹配焊材的情况下,采用镍基焊材进行P92钢管焊口返修,返修后免做热处理,避免多次热循环对管子性能的影响,然后进行各项性能试验。结果表明,返修后的焊接接头拉伸试验合格,断裂位置位于母材;焊缝、热影响区、母材的硬度值符合规定要求;焊缝、热影响区的冲击值符合规定要求;金相组织合格。试验证明,采用镍基焊材进行临时性返修试验是可行的,但对于高温时效性能及持久强度性能,还需要进一步研究。 相似文献
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以EH36高强度船板钢为研究对象,通过拉伸和冲击分析试验手段,对EH36船板钢不同热输入埋弧焊接头进行了力学性能测试,同时采用扫描电镜对冲击试样断口形貌进行分析.结果表明,所有断裂均发生在拉伸试样的母材区,EH36船板钢在大焊接热输入条件下,焊缝和焊接热影响区的强度好于母材,并没有出现热影响区软化现象;随着焊接热输入增加焊缝的冲击韧性降低,从焊缝和熔合区断口形貌来看,断裂类型为韧性断裂和准解理断裂的混合断裂.随着远离熔合线距离的增加,冲击吸收功有增加的趋势,在距离熔合线4 mm处的冲击吸收功跟母材接近,说明该位置处韧性基本不受焊接热循环的影响. 相似文献
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Kezhao Zhang Ming Liu Zhenglong Lei Yanbin Chen 《Journal of Materials Engineering and Performance》2014,23(10):3778-3785
The microstructure of laser-tungsten inert gas hybrid welded Ti2AlNb-based joints and their tensile properties at room temperature were investigated in this paper. The results showed that good-quality joints could be obtained by hybrid welding process. The microstructure evolution was identified by means of optical microscopy, scanning electron microscopy, x-ray diffraction, and transmission electron microscopy. The fusion zone mainly consisted of B2 phase due to the rapid cooling rate, as well as high Nb content. The phase compositions of the heat-affected zone were varied with different thermal cycles during the welding process. Tensile tests at room temperature showed that fracture tended to occur in the fusion zone, and the tensile strength and elongation were 950 MPa and 4.3%, respectively. The fracture mode was quasi-cleavage based on the observation of the fracture morphology. 相似文献