TA23合金不同焊接方法接头组织性能研究

采用CMT、TIG和EBW焊对TA23合金进行焊接,对比分析了不同焊接方法下接头微观组织和力学性能的差异。结果表明,焊接热输入直接影响焊缝晶粒尺寸和焊接接头宽度,TIG焊缝晶粒尺寸最大,CMT次之,EBW最小;EBW接头宽度为5 mm,CMT接头宽度为7 mm,TIG接头达14 mm;3种焊接方法焊缝区域组织均由马氏体α相、片层状α相和残余β相组成,热影响区组织形态介于焊缝和母材组织形态之间;3种焊接方法焊缝区显微硬度和接头抗拉强度均大于母材,其中EBW焊缝区显微硬度值最大,TIG焊接头抗拉强度最高,CMT焊缝显微硬度和接头抗拉强度均居中。     

Q960E超高强钢焊接接头组织和性能研究

目的 对Q960E超高强钢的焊接工艺进行研究以获得高强高韧的焊接接头。方法 选择超高强钢Q960E作为母材、FK1000ER120S–G焊丝作为填充材料进行MAG焊,采用改变焊接电流的方式来研究焊接热输入对焊接接头组织和性能的影响。结果 当焊接电流为155～230 A时,均获得了全焊透无明显缺陷的焊缝。随着焊接热输入的增大,焊接接头中各亚区宽度增大,其中焊缝区变化最为显著,在最小热输入条件下焊缝宽度为3.98 mm,在最大热输入条件下焊缝宽度增至5.53 mm。对焊接接头进行组织分析发现,焊缝组织主要为针状铁素体和板条马氏体;完全相变区组织主要为板条马氏体;未完全相变区组织主要为回火马氏体和部分重结晶形成的马氏体。硬度测试表明,在热影响区的回火区发生了软化现象,最低硬度仅为290HV;在完全相变区发生了硬化现象,硬度最大值可达500HV。在不同热输入条件下,焊接接头各亚区硬度变化趋势一致,焊接接头抗拉强度为995～1 076 MPa,拉伸试验均断裂在热影响区,断后伸长率为9.33%～10.21%,断裂时存在颈缩现象,为韧性断裂。随着热输入的增加,粗晶区马氏体板条束宽度增大,未完全相变区...     

薄壁3003铝合金管高频感应焊焊接接头微观组织及力学性能研究

采用高频感应焊接技术对壁厚为0.28 mm的3003铝合金进行焊接，研究了焊接接头的微观组织和力学性能。结果表明，焊接接头晶粒细小，是焊接过程中感应加热与挤压同步进行，局部晶粒发生塑性变形从而抑制了晶粒长大所致；焊接接头熔合区呈上下宽、中间窄的窄腰状，宽度为6～10μm,熔融区呈细腰鼓形，单侧宽度为24～49μm,其相邻两侧的热影响区部分发生再结晶，宽度为115～127μm;断口形貌显示焊接接头断裂类型为以韧性断裂为主的韧脆混合型断裂，其抗拉强度为242 MPa,达到带材的91%,伸长率为15%,略低于带材(23%);焊接接头各区域硬度值呈M形对称分布，熔融区与热影响区硬度值明显高于母材区，熔融区最高，达到85.27HV,热影响区约为79.33HV,熔合区硬度值最低，为55.85HV。与母材相比，焊接接头强度和硬度分布规律与各区域晶粒大小和第二相种类及分布有关。     

Q345D钢结构梁腹板对接接头裂纹分析

Q345D钢结构梁腹板对接接头热影响区出现了长约100mm的裂纹。采用金相方法观察了接头热影响区和母材的组织以及裂纹的宏观形貌，采用扫描电镜观察了裂纹的微观形貌以及对微区的化学成分分析。分析结果表明，焊接接头热影响区没有形成淬硬组织。裂纹两侧出现了一定宽度的脱碳层，脱碳层内部出现了二次氧化产物。该裂纹并不是焊接过程产生的裂纹，而是钢坯轧制以前其表面已存在微裂纹所致。     

X70大变形管环焊接头及断裂机制研究

目的基于应变设计大变形管线环焊接头热影响区的软化问题,解决制约管线安装质量和服役寿命等难题。方法通过显微硬度测试、微观组织分析,研究了X70大变形管接头热影响区的软化原因,并利用数字相关法研究了焊接接头拉伸过程中的断裂机制,还对焊接接头热影响区进行了激光增强探索。结果 X70焊接接头热影响区粗晶区的最大硬度损失达HV0.239;软化区最大应变达到37%以上;经过热影响区激光重熔后,X70钢焊接接头抗拉强度可提高10%以上,断裂位置均位于母材。结论 X70焊接接头热影响区粗晶区存在明显的软化;拉伸过程中在软化区出现了明显的应变集中,是X70焊接接头断裂于近缝区的主要原因;焊接接头热影响区粗晶区粗大的粒状贝氏体和铁素体导致了焊接接头热影响区的软化。     

Ti700sr高温钛合金TIG焊接接头组织及性能研究

采用TIG焊接方法对Ti700sr高温钛合金板材进行了焊接,研究了接头的组织形貌、硬度分布及力学性能。结果表明,Ti700sr高温钛合金板材焊接后的接头成形良好,焊缝区组织由粗大的柱状晶及细长的针状α相构成,热影响区组织由细针状α和残余β相构成,热影响区析出相得到有效控制,相边界上无明显硅化物析出;焊接热影响区的硬度相对较高,焊缝的硬度相对较低;接头室温抗拉强度约为903 MPa, 700℃高温抗拉强度为397 MPa,焊缝强度低于母材的。      

Al-Zn-Mg合金焊接接头性能分析

对研制的Al-Zn-Mg合金和焊丝施焊后的焊接接头进行了宏、微观组织分析以及力学性能测试。结果表明，焊接系数可达76．6％。焊接接头最薄弱的环节是焊缝区，其次是焊接热影响区的软化区。提高焊接接头的力学性能关键是焊丝成分进一步优化。另外，焊接接头留有余高可以在一定程度上提高其承载能力。     

高强低合金钢电子束焊接接头的组织与性能研究

采用电子束焊接了厚度为9 mm的15CrNi3MoV高强低合金钢试板,焊接接头成形良好,无内部缺陷,经热处理后焊接系数达到0.98以上。通过研究焊接接头组织和力学性能,发现热处理后,接头组织以贝氏体组织为主,在焊缝和热影响区粗晶区中出现索氏体组织,热影响区的细晶区存在粒状贝氏体组织,焊接接头的冲击韧性与母材相比得到提升;散焦修饰使原始焊缝的柱状晶碎化,能够改善焊缝处的显微硬度。     

TC4钛合金热丝钨极氩弧焊接头组织性能研究

对TC4钛合金热丝钨极氩弧焊(hot-wire-TIG)焊接接头组织与性能进行研究,采用金相显微镜观察焊接接头各区域的微观组织特点,并对接头显微硬度和力学性能进行了测定。结果表明,钛合金热丝TIG焊接接头内部无焊接缺陷,焊缝性能优良;焊缝为典型的铸造组织,由粗大的柱状晶和少量等轴晶组成,晶粒内部可以看到细长的针状α′相;热影响区形成粗大的等轴晶粒,其组织主要有细针状α相和残余β相构成;焊接接头的抗拉强度均值为924 MPa,与母材相当;热丝TIG焊缝冲击功较母材提升明显,基本达到母材的1.5倍以上,最大达到66 J;焊缝冷弯角度达到指标要求。     

激光焊接工艺参数对30CrMnSiNi2A钢组织和性能的影响EI北大核心

利用CO2激光对超高强度钢30CrMnSiNi2A进行了焊接处理。采用OM、显微硬度仪和电子万能试验机等对激光焊接接头的显微组织、硬度、拉伸强度进行了研究。结果表明,固定激光功率,扫描速度从60~220mm/min变化时,随着扫描速度的增加,焊缝区和热影响区(H.A.Z)宽度变窄,焊缝区组织就越细小,硬度值明显增大,抗拉强度变化不大;固定扫描速度,激光功率从2.6~3.2kW变化时,随着功率的增加,焊缝区和H.A.Z宽度变宽,焊缝组织变得粗大,硬度值有所减小,抗拉强度变化不大。当激光功率为2.8kW、扫描速度为180mm/min时,焊接接头组织细小、均匀,性能优良,抗拉强度最高值达到819.9MPa。     

Improvement of weld temperature distribution and mechanical properties of 7050 aluminum alloy butt joints by submerged friction stir welding

Submerged friction stir welding (FSW) in cold and hot water, as well as in air, was carried out for 7050 aluminum alloys. The weld thermal cycles and transverse distributions of the microhardness of the weld joints were measured, and their tensile properties were tested. The fracture surfaces of the tensile specimens were observed, and the microstructures at the fracture region were investigated. The results show that the peak temperature during welding in air was up to 380 °C, while the peak temperatures during welding in cold and hot water were about 220 and 300 °C, respectively. The temperature at the retreated side of the joint was higher than that at the advanced side for all weld joints. The distributions of microhardness exhibited a typical “W” shape. The width of the low hardness zone varied with the weld ambient conditions. The minimum hardness zone was located at the heat affected zone (HAZ) of the weld joints. Better tensile properties were achieved for joint welded in hot water, and the strength ratio of the weld joint to the base metal was up to 92%. The tensile fracture position was located at the low hardness zone of the weld joints. The fracture surfaces exhibited a mixture of dimples and quasi-cleavage planes for the joints welded in cold and hot water, and only dimples for the joint welded in air.     

Ti75合金激光焊接接头的组织及力学性能

采用10 kW的连续光纤激光器对3 mm厚的Ti75合金板进行激光焊接,通过调整不同的激光功率来获得全熔透的焊接接头.同时,观察了不同热输入下焊接接头的宏观形貌、微观组织,测试了焊接接头的力学性能和显微硬度,对接头不同部位的组织特征及成形原因进行了分析.结果表明,随着焊接过程中激光功率的增加,焊缝的宽度逐渐变大,在不同...     

TiNiNb形状记忆合金丝精密脉冲电阻对焊工艺分析

使用自行研制的UMN -3型精密脉冲电阻对焊机对TiNiNb形状记忆合金丝的焊接性进行了研究 ,分析了焊接电流、焊接压力、顶锻压力和保护气体等焊接参数对焊接接头微观组织和力学性能的影响规律 ,并给出某些TiNiNb形状记忆合金丝获得优质接头的工艺条件 .研究结果表明 ,所研制的精密脉冲电阻对焊机可实现TiNiNb形状记忆合金丝的优质连接 ,这对于进一步研究、开发TiNi基形状记忆合金丝的潜能 ,具有重要的理论和实际应用价值 .     

Gas tungsten-arc filler welding of AZ31 magnesium alloy

Optical microscopy and scanning electron microscopy (SEM) were used to examine the microstructure and fracture of AZ31 magnesium alloy joint welded by automatic gas tungsten-arc filler (GTAF) welding process with AZ61 wire. More endeavors have been put on investigating the effect of filler wire on microstructure and performance of welded joint. The result showed that the grain size in heat-affected zone (HAZ) of GTAF welded joint holds significant variety compared with that of GTA welded joint (without filler wire). The modification of microstructure in HAZ has changed the fracture location as well as the ultimate tensile strength (UTS) of joint in tensile test.     

Mechanical properties characterisation of welded joint of austenitic stainless steel using instrumented indentation technique

The instrumented indentation test is a promising nondestructive technique for evaluating mechanical properties of metallic materials. In this study, the localised mechanical properties of welded joint of 304 austenitic stainless steel were characterised with the instrumented indentation test. The single V-groove welded joint was produced using the electric arc welding. A series of instrumented indentation tests were carried out at different regions, including base material, weld zone and heat-affected zone (HAZ). A soft zone regarding strength properties was found in the coarse-grain HAZ. The results show that the HAZ has the lowest yield strength and tensile strength (263.6 MPa, 652.5 MPa) compared with the base material (307.4 MPa, 807.9 MPa) and the weld zone (285.6 MPa, 702.1 MPa). In addition, characterisations of microstructure, microhardness and conventional tensile tests have been performed for comparison. The results reveal that the localised mechanical properties of welded joint of austenitic stainless steel can be represented effectively with the instrumented indentation technique.     

热处理对2519铝合金接头组织及性能的影响

研究了焊后时效及固溶＋时效热处理对2519铝合金焊接接头组织和力学性能的影响．结果表明,时效处理后,处于欠时效态的焊缝析出强化相增加,硬度升高,而过时效态的热影响区软化区组织和硬度没有明显变化,焊接接头的强度略微提高,塑性下降．固溶＋时效处理后,焊缝中网状共晶减少,焊缝和热影响区软化区内的析出相形态变为细小的针状,且数量增加,焊缝金属硬度明显提高,热影响区的软化现象消失,焊接接头的强度和塑性显著增加．     

焊后时效处理对6082-T6铝合金搅拌摩擦焊接头的影响

对6082-T6铝合金搅拌摩擦焊接头进行自然时效和人工时效处理,通过透射电子显微镜、扫描电子显微镜、拉伸实验机和显微硬度计对组织演变和力学性能进行研究。结果表明:人工时效处理后显微硬度比焊态和自然时效高10~25HV,提高焊核区和热机影响区硬度效果明显好于自然时效。经过焊后自然时效、人工时效的焊接接头力学性能得到一定程度的提升,人工时效析出相比自然时效析出相抗拉强度提高12%,延伸率降低9%,人工时效提高拉伸强度效果更明显。人工时效处理后,焊核区组织发生显著变化,NZ主要为GP区,经过人工时效后NZ强化效应随团簇和GP区尺寸增大及数量增多而加强。HAZ主要为粗大的β′,经过人工时效后变化不大,硬度基本保持不变。通过对微观组织进行研究发现析出物的形状由界面能和应变能决定。     

Role of butter layer in low-cycle fatigue behavior of modified 9Cr and CrMoV dissimilar rotor welded joint

The present work aims at studying the role of butter layer (BL) in low-cycle fatigue (LCF) behavior of modified 9Cr steel and CrMoV steel dissimilar welded joint. The significant difference of the chemical composition of base metals (BMs) makes it a challenge to achieve sound welded joint. Therefore, buttering was considered to obtain a transition layer between the dissimilar steels. The LCF tests of two kinds of specimens without and with butter layer were performed applying strain-controlled cyclic load with different axial strain amplitudes. The test results indicated that the number of cycles at higher strain amplitudes of welded joint without butter layer was greatly higher than that of the joint with butter layer, while the fatigue lifetime to crack initiation (2N_f) became closer to each other at low and middle strain amplitudes. The failure was in the tempered heat affected zone (HAZ) at the CrMoV side for specimens without BL, while the fracture occurred at the tempered HAZ in the BL for specimens with BL. The microstructure details of BM, BL, HAZ and weld metals (WMs) were revealed by optical microscopy (OM). It was found that the tempered martensite was major microstructure for welded joint and much more carbides were observed in tempered HAZ than other parts due to the repeated tempering. Microhardness test indicated a softest zone existing tempered HAZ of BL and also there was a softer zone in tempered HAZ at the CrMoV side due to repeated tempering during welding and post weld heat treatment (PWHT). And scanning electron microscopy (SEM) was applied to observe the fractography. It was indicated that the fatigue crack initiation occurred from the specimen surface and all specimens were ductile–brittle mixed fractures. It is deemed that the softening behavior in BL caused by twice tempering correspondingly decreased the LCF lifetime at higher strain amplitudes. So suitable welding parameters and heat treatment processes became a key measure to ensure LCF property without losing other properties for welded joint with BL.     

Carbide precipitates and mechanical properties of medium Mn steel joint with metal inert gas welding

Medium Mn steel was metal inert gas(MIG)welded with NiCrMo-3 and 307Si filler wires.The effect of filler wires on the microstructure and mechanical properties of joint was investigated,and the carbide precipitates were contrastively discussed.The results revealed that the microstructure of weld metal,heat-affected zone and base metal are austenite.Obvious grain coarsening occurred in the heat-affected zone(HAZ),and the maximum grain size grew up to 160 pm.In HAZ,C and Cr segregated at grain boundaries,the carbides was identified as Cr7C3.The dispersive(Nb,Mo)C phase was also found in weld metal with NiCrMo-3 filler wire.All the welded joints failed in HAZ during tensile tests.The tensile strength of welded joint with NiCrMo-3 filler wire was 675 MPa,which is much higher than that with 307Si filler wire.In comparison to base metal,higher microhardness and lower impact toughness were obtained in HAZ for these two welded joints,which was attributed to the precipitation of Cr7C3 phase and grain coarsening.The impact toughness around the fusion line is the worst for these two welded joints.     

X90钢级管线钢预精焊接头的性能研究

为综合研究X90管线钢的焊接性,选用国内某钢厂轧制的X90管线钢卷板,利用预精焊工艺制备试验钢管4根,采用金相分析、扫描电镜(SEM)断口分析、夏比V型缺口冲击试验、拉伸、弯曲、硬度等试验,研究了焊接接头各个区域的组织和性能.试验结果表明:内外焊缝区组织均为针状铁素体,热影响区(HAZ)粗晶区晶粒粗化严重,主要组织为粒状贝氏体和贝氏体铁素体,在原奥氏体晶界和贝氏体板条内部存在块状或条状的(马氏体-奥氏体)M-A组元;HAZ冲击功离散性较大,出现了单值较低(45 J)的试样,SEM断口分析呈现典型的解理断裂特征;焊接接头抗拉强度805~815 MPa,断裂位置均在HAZ;焊接接头反弯试样易在HAZ出现裂纹和脆断现象;HAZ硬度在220~250 HV之间,较母材下降30 HV左右.HAZ是X90预精焊钢管焊接接头的薄弱环节,为提高X90管线钢的焊接稳定性,应重点研究精焊内外热循环双热影响亚区的组织转变和脆化机理.