焊接方法对Q235钢焊接接头缺陷、组织和力学性能的影响

通过微观组织表征、显微硬度试验和拉伸试验等研究了CO2气体保护焊和焊条电弧焊两种焊接方法对Q235钢焊接接头缺陷、组织和力学性能的影响.结果表明:采用CO2气体保护焊焊接时焊缝容易出现气孔,采用焊条电弧焊焊接时焊缝容易出现夹渣;由于焊条电弧焊焊接热输入相对较大,接头组织比较粗大,在过热区还存在魏氏体过热组织,硬度和抗拉强度较低;由于CO2气体保护焊焊接热输入较低,接头的组织晶粒细小,过热区未发现过热的魏氏组织,硬度和抗拉强度较高.两种焊接方法焊接时接头的断裂方式均为韧性断裂.     

不同焊接方法下316L不锈钢焊接接头组织性能研究

采用20%CO2+80%Ar气体保护MAG焊和焊条电弧焊对316L不锈钢进行焊接,通过对焊接接头进行拉伸、弯曲、硬度试验和显微组织观察,研究了焊接接头组织性能。结果表明,焊条电弧焊接头的抗拉强度和显微硬度比MAG焊接头的抗拉强度和显微硬度高;焊条电弧焊焊缝金属中δ铁素体含量比MAG焊焊缝金属中δ铁素体含量高;MAG焊焊缝金属含有少量的MC型碳化物;拉伸时,焊条电弧焊接头断裂在热影响区,而MAG焊接头断裂在焊缝中心位置;焊接接头的弯曲试验均合格。     

Incoloy 825镍基高温合金电子束焊工艺及接头组织与力学性能分析

采用电子束焊,对空冷器管箱Incoloy 825镍基高温合金进行对接焊试验. 通过对焊接接头的组织观察,并结合拉伸力学性能以及接头的冲击韧性等试验,分析镍基高温合金电子束焊接头的组织和力学性能. 结果表明, 采用电子束焊焊接镍基高温合金可以得到良好的焊接接头,焊缝区组织由大片等轴晶和少量柱状晶组成;焊缝区没有出现明显的元素烧损现象;焊缝、热影响区硬度达到母材硬度值;焊缝接头抗拉强度达到600 MPa,接近母材抗拉强度,接头断裂形式为韧性断裂;焊缝和热影响区的冲击吸收能量高于母材区,其中焊缝区的冲击吸收能量达到了262 J,冲击断口形貌为韧窝状.     

S355管板相切T形接头残余应力数值模拟与试验验证

管板T形接头是轨道车辆转向架构架中应用较多的接头形式之一,各类吊座等均通过该接头形式与横梁进行连接,其焊接质量直接影响着转向架的稳定性和承载能力。文中以S355低合金钢作为试验材料,利用SYSWELD有限元软件,并结合多层焊的热力耦合特征,对管板相切T形接头焊后残余应力进行了耦合计算;采用X射线衍射法对管板相切多层焊T形接头的焊后残余应力进行了测试。对比分析模拟和试验结果表明:二者结果吻合良好,为实现工艺优化设计提供了基础。对于横向残余应力,最大残余应力出现在焊趾附近,且在垂直于焊缝方向的横向应力呈现出焊缝中心受拉应力和远离焊缝的管表面一侧承受压应力;对于纵向残余应力,最大残余应力也出现在焊趾附近,并在焊缝的中心位置处出现最大值,然后沿着垂直于焊缝方向逐渐减小。     

细丝CO_2气体保护焊在JS661A客车骨架上的试验和运用

JS661A客车骨架是全焊结构,过去经常发生焊缝接头早期断裂,影响车身使用寿命。从78年开始,将CO_2气体保护焊应用到客车骨架的焊接中,现在,骨架焊接已全部应用CO_2气体保护焊。数年来,通过实践总结,先后制定了“骨架焊接工艺”、“CO_2保护焊焊缝质量标准”、     

S1100Q钢窄间隙熔化极气体保护焊

S1100Q细晶高强钢成功地采用窄间隙熔化极气体保护焊实施焊接。在相同焊接速度时,用药芯焊丝和实心焊丝焊接的接头机械性能无明显区别,热影响区的冲击韧性大于焊缝金属,但焊接接头均在热影响区断裂。采用药芯焊丝焊的焊缝金属中,合金元素Cr、Mo和Ni的含量高于采用实心焊丝焊的。焊接速度成倍增加后,焊接接头和焊缝金属的屈服强度和拉伸强度升高,而冲击韧性和断后伸长率则降低。冲击韧性和断后伸长率满足欧盟标准要求。     

硅对304不锈钢GMAW高速焊接头组织性能的影响

以不锈钢焊丝中Si元素含量不同对高速焊焊后焊缝成形以及接头组织性能为研究目的,采用GMAW焊接工艺方法,借助扫描电镜、XRD衍射图谱、拉伸以及微观硬度等力学性能测试作为分析手段,深入研究Si元素在焊缝内部空间分布规律,及其对焊后成形焊缝组织和力学性能的影响规律. 结果表明,焊丝中存在特定含量的Si元素,不仅能够增加熔池金属流动性,提高焊接过程稳定性,改善焊后焊缝成形;同时焊接速度可以大幅提高至120 cm/min;由于Si元素的存在,GMAW高速焊焊后接头组织主要为奥氏体+δ铁素体,焊缝组织得到优化. XRD衍射图谱中发现焊后接头组织中存在马氏体和渗碳体,焊后接头微观硬度有所增加,拉伸性能基本持平,且在拉伸断裂前有明显的颈缩,塑性及抗拉强度良好.     

根部间隙对高强钢焊接接头组织和性能的影响

采用富氩混合气体保护焊对高强钢钢板进行焊接,研究了焊缝根部间隙对焊接接头显微组织和力学性能的影响。结果表明:焊缝区的显微组织主要为铁素体和珠光体;焊接接头抗拉强度随着焊缝根部间隙的增大先升高后降低,焊缝根部间隙为2 mm时焊接接头拉伸性能最好;焊缝断口微观表面布满了大小不一的韧窝,属于典型的韧性断裂。     

铝薄板高速DP-GMAW焊接性能的研究

双脉冲熔化极气体保护焊(DP-GMAW)是对传统的熔化极气体保护焊(GMAW)的高频脉冲进行低频调制,是一种可实现高速焊接的高效焊接方法。论文以1070铝薄板为试验母材进行平板堆焊,通过与焊接速度0.6m/min下的焊接接头性能质量的对比,进行外观、显微维氏硬度试验和金相分析得出高速焊接接头性能质量。结果表明,高速DP-GMAW焊接接头没有出现高速焊接下常会出现的驼峰焊道;高速下焊缝周围低于母材硬度的区域变窄,宽度减少了约25%,焊缝硬度比焊接速度0.6 m/min下的焊缝硬度提高近30%;高速焊接的焊缝区晶粒更加细化,融合区晶粒长大的现象不明显。     

焊接工艺对5A66铝合金接头组织与性能的影响

分别采用钨极惰性气体保护焊(TIG焊)和冷金属过渡焊(CMT)焊接5A66铝合金。为研究焊接方法对接头的影响,使用光学显微镜、扫描电子显微镜、显微硬度测试仪和万能试验机对焊接接头进行了测试。试验结果表明,CMT接头强度达到母材的93%,高于TIG焊接头强度7%;CMT接头断裂在热影响区位置,TIG焊接头断裂在焊缝位置。另外,CMT热输入小,热影响区软化程度低,力学性能与母材相差不大。在试验条件下CMT焊工艺焊接接头的性能优于TIG焊接头。     

喷瓷管道焊接接头的自熔覆防护

通过分析焊接对喷瓷管道焊接接头处瓷层的影响，提出了用自熔覆法对焊接接头进行防护。试验结果表明，在合适的电流下采用TIG焊打底能够使焊口附近的瓷层重熔并向焊缝流布、熔覆，在焊缝区形成保护层，起到自熔覆防护作用；焊前管端预涂釉浆能有效增加焊后接头区自熔覆瓷层的厚度，提高瓷层的防护效果；焊后采用火焰加热对接头区进行重熔处理，可以消除瓷层中气泡、裂纹等缺陷。采用焊前管端预涂釉浆、TIG焊打底、焊条电弧焊填充、焊后接头区瓷层重熔处理等配套措施能够有效解决喷瓷管道焊接接头的防护问题，焊后不用进行内补口。     

An experimental study of the fracture properties of oil pipeline girth welds

The application of fracture mechanics to the "Fitness For Purpose" assessment of the fracture properties of pipeline girth welds is generally essential for the safe operation of oil pipeline systems. Based on the analysis of the fracture toughness requirements of the oil pipeline girth weld, a systematic study has been conducted on the fracture behavior of the API 5L X65 steel pipelin egirth weld made by two welding materials. The critical COD values of the pipe line girth weld under the different temperatures are tested. In the paper other influential factors on fracture behavior are also discussed, such as the welding materials, the welding positions (flat welding, vertical welding, overhead welding), the welded joint area (weld, heat-affected zone, fusion line and base metal) and the experiment temperature. The result shows that the welding material, the welded joint area and the experiment temperature have considerable influence on the fracture behavior of pipeline girth welds. It is also concluded that t he effect of the welding position is related to the welding process. The study provides a scientific basis for the welding of oil pipelines.     

Experimental and numerical investigation on combined girth welding of API X80 pipeline steel

Abstract

API X80 pipeline steel is widely used in natural gas and oil transportation. In this study, X80 pipeline steels with 18.4?mm thickness and 1219?mm diameter, made in China, were welded by a combined girth welding technology. Experimental results showed that microstructures in weld metal and coarse grain heat affected zone are mainly composed of coarsening bainite grains with dimensions of 20–50?μm, and Vickers hardness in weld seam is lowered by the seven-pass welding process. Simulated results illustrated that repeatedly thermal cycles imposed by the combined multipass girth welding process easily result in softened weld joints. The predicted microstructures, phase compositions and hardness in weld metal are in agreement with the measured ones. The results could be applied to optimise this combined girth welding process and improve the weld quality of API X80 pipeline steel and even higher grade pipeline steels.     

环焊接头强度对高应变海洋管道轴向承载能力的影响

基于应变设计的油气输送管道,环焊接头的强度对管道轴向变形能力起着至关重要的作用。以OD559×31.8 mm L485高应变海洋管道环缝为研究对象,采用有限元方法和数字图像相关法(DIC)拉伸试验及宽板拉伸试验,研究了GMAW环焊接头不同区域的强度变化对管道轴向承载能力的影响。结果表明,随焊缝金属强度的升高,管道轴向极限载荷和轴向平均应变增大,失效位置由焊缝向热影响区和母材转移;根焊金属占比小,热影响区很窄,高强匹配时根焊金属和热影响区强度对管道轴向极限载荷和轴向平均应变影响较小;在轴向载荷下,低强匹配环焊接头的母材、热影响区和焊缝的轴向应力和轴向应变分布极不均匀。受母材的拘束作用和焊缝金属自身的形变强化,低强匹配焊接接头的抗拉强度高于全焊缝金属,但变形和屈服主要集中在焊缝区域,容易导致管道环焊缝断裂失效。     

X60/625镍基合金复合管环缝焊接工艺及应用

X60/625双金属复合管环缝焊接时,由于2种材料化学成分和物理性能差异太大,易引起镍基合金层氧化、稀释等问题,从而影响覆层耐腐蚀性和管道完整性.针对该问题,文中通过对X60/625双金属复合管焊接性的分析和焊接工艺的研究,制定出适用于X60/625双金属复合管环缝焊接工艺.经过焊缝无损检验、理化性能检验、耐腐蚀性能检...     

装配条件对X80钢外根焊接头成分与性能的影响

摘要： X80钢管道铜衬垫外根焊全自动焊接过程中,装配条件的改变对铜衬垫熔化导致的Cu元素向焊缝扩散及接头的力学性能具有一定影响。系统地分析了不同对口间隙与错边量对X80钢管道铜衬垫外根焊全自动电弧焊接接头的Cu元素含量和力学性能的影响。通过能谱分析和化学成分分析对焊缝中的Cu元素含量进行表征,利用拉伸试验、常温冲击试验及背弯和侧弯试验测量不同装配条件下接头的力学性能。结果表明,对口间隙大于1.0 mm或错边量大于3.0 mm的装配条件下焊缝成形质量差;在保证获得良好焊缝成形的条件下,对口间隙和错边量的增大会导致根焊层底部Cu含量的增加,但不同条件下焊缝的Cu元素含量均低于0.5%(质量分数),铜衬垫的使用对焊缝Cu元素含量影响不大。接头的力学性能测试结果显示,不同装配条件下得到的接头抗拉强度和冲击韧性差异较小,且拉伸试样均断裂在母材位置,热影响区的冲击韧性优于焊缝,而对口间隙和错边量的增加会降低接头的弯曲性能。 创新点： 研究了不同装配条件对X80钢管道铜衬垫外根焊接头的Cu元素含量和力学性能的影响,发现对口间隙和错边量的增大会导致根焊层底部Cu元素含量的少量增加及接头弯曲性能的下降,而对接头的抗拉强度及冲击韧性无显著影响。     

水下自蔓延焊接技术

基于自蔓延高温合成技术,研究水下构件的自蔓延快速焊接技术.所用焊料由高热剂(CuO+Cu₂O+Al)、造气剂(CaCO₃)、合金剂(FeSi+MnFe)及造渣剂(B₂O₃)四部分组成.焊块采用石墨坩埚/矩管复合结构设计,其中矩管的一端密封,另一端部分封接,留下开口,可实现对燃烧火焰加热方向的控制,同时采用低功率的钨丝/线圈点火方式,以KNO₃/Al-Mg为点火料,以石蜡对焊块开口处密封,解决了水下自蔓延快速焊接可行性难题.结果表明,该技术无需大功率电源和复杂操作,可在0.5 m水深环境下自行快速燃烧形成焊接接头,且接头抗拉强度经测试达到135 MPa,基本上达到了水下结构件应急抢修的目的.     

Welding experiments of aluminium pipe by space GHTA welding in aircraft-borne simulated space environment

The gas hollow tungsten arc (GHTA) welding experiments on aluminum pipe were carried out in a simulated space environment using an aircraft. A vacuum chamber and welding machine for GHTA welding test were placed in the cabin of the aircraft and the 10^? 2 G gravity environment was produced by a parabolic flight of the aircraft. The square butt welding joints with non root gap on aluminum pipe were made by orbital welding in the vacuum chamber without wire filler metal using DC or DC-pulsed power supply under the 10^? 2 and 1 G gravity conditions. The welding phenomenon during the aluminum GHTA welding recorded in the high-speed video image was analysed and also the macrostructure and mechanical properties of butt weld joints were investigated. The welding experiments under simulated space environment showed that the DC-pulsed GHTA process could make the welding joints without the weld defects such as a lack of fusion, oxide film inclusion and spattering, though throat thickness decreased by the impulsive arc pressure of pulsed current. It was also clarified that the arc discharge phenomenon and melting characteristic at the molten pool surface during the DC-pulsed GHTA welding were insensitive to the gravity condition. However, the sagging weld metal made at 1 G gravity condition increases a little more than that welded under the 10^? 2 G gravity condition.     

高铌X80管道不同强度匹配环焊接头性能及应变演化

为探究管道环焊缝断裂失效机理,测试了两种不同强度匹配的高铌X80环焊缝接头的组织和性能,并借助数字图像相关法(digital image correlation,DIC)观测了焊接接头在拉伸载荷下的应变行为.结果表明,低强匹配和高强匹配的高铌X80管道环焊接头均具有较好的冲击韧性,二者的夏比冲击吸收能量平均值相当,热影...     

Rupture locations of friction stir welded joints of AA2017-T351 and AA6061-T6 aluminum alloys

The tensile rupture locations of friction stir welded joints of AA2017-T351 and AA6061-T6 aluminum alloys were examined. The experiments show that the rupture locations of the joints are different for the two aluminum alloys, which are influenced by the welding parameters. When the joints are free of welding defects, the AA2017-T351 joints are ruptured in the weld nugget adjacent to the thermo-mechanically affected zone on the advancing side and the rupture surfaces appear as oval contours of the weld nugget, while the AA6061-T6 joints are ruptured in the heat affected zone on the retreating side and the rupture surfaces are inclined at a certain degree to the bottom surfaces of the joints. When welding defects are present in the joints, the AA2017-T351 joints are ruptured in the weld center, while the AA6061-T6 joints are ruptured on the retreating side near the weld center. The rupture locations of the joints are dependent on the internal structures of the joints and can be explained through them.