690 MPa级低合金高强钢焊接接头组织性能

为探讨690 MPa级低合金高强钢焊接接头组织与性能的关系,采用手工电弧焊(SMAW)和埋弧焊(SAW)获得成形良好的焊接接头,经过拉伸、冲击、弯曲试验及光学显微镜、扫描电镜和透射电镜分析,对两种焊接方法的接头组织性能进行研究.结果表明:两种焊接方法的焊缝组织主要为板条状贝氏体和少量针状铁素体,粗晶区为粗大贝氏体和少量马氏体;焊缝中含有大量分布均匀的微小球形夹杂物;两种焊接方法所得焊接接头都具有较高力学性能,-50℃的冲击断口形貌为韧窝、准解理混合型;埋弧焊焊缝冲击韧性低于手工电弧焊,手工电弧焊熔合线处冲击吸收功小于埋弧焊,但随距熔合线距离增加其值增加更快.显微组织和夹杂物是影响接头性能的主要因素.     

X70管线钢焊缝金属弯曲脆断分析

用光学显微镜、扫描电镜和能谱仪分析了X70管线钢焊缝金属弯曲脆断的原因。结果表明，焊缝金属中存在的非金属夹杂物，在低应力作用下形成微裂纹成为裂源，加之焊缝组织中存在大量的M-A结构群，从而发生焊缝金属在室温下的解理断裂。     

S135钻杆摩擦焊焊缝区冲击韧性低的原因

为找到S135钻杆焊缝冲击韧性低、不符合要求的原因,对焊缝进行了冲击试验、力学性能试验、金相检验、化学成分分析、非金属夹杂物检验等,并对冲击试样断口进行了宏观及微观分析.结果表明:钻杆接头材料硫元素含量高,A类非金属夹杂物级别高、含量多,造成摩擦焊焊接时焊缝区形成较多A类非金属夹杂物,影响了组织的连续性,受到冲击力时,...     

钛-铝异种合金电子束焊接接头组织与性能研究

采用电子束焊接方法对厚度为2.5 mm的Ti6321钛合金板材和5083铝合金板材进行了对接焊接试验,并进行了力学性能、显微组织测试。结果表明,焊缝的钛侧及其热影响区组织主要是α'相和原始α相混合形成的马氏体组织,铝侧主要为粗大柱状晶组织,钛铝焊缝交界处析出少量Ti Al金属间化合物;焊接接头的拉伸强度约为219 MPa,接头断裂位置主要在铝侧焊缝位置,部分在钛铝两侧焊缝交界处的Ti-Al金属间化合物上。     

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...     

线能量对铝/钢双光束激光焊接接头组织及性能的影响

为了研究线能量对铝钢异种金属双光束激光焊接接头组织和性能的影响,本工作通过激光双光束铝钢搭接焊工艺优化实验,获取了焊接工艺窗口,研究了焊接线能量与焊缝成形、显微组织和接头性能的关系.结果表明:不同焊接速度下,线能量过大或过小将导致焊缝出现坑洞或未连接,焊接速度超过0.05 m/s时,线能量的最高值和最低值基本维持不变,且线能量与熔深成正比,与熔宽无相关性.低线能量的焊接接头的抗剪切力为130.70 N/mm,断裂位置位于铝合金焊缝,而高线能量的焊接接头的抗剪切力仅有35.76 N/mm,断裂位置位于铝钢界面焊缝.低线能量接头的显微组织为板条马氏体,显微硬度的最高和最低值分别位于热影响区和焊缝中心,而高线能量接头的显微组织为粗大柱状晶或片状马氏体,显微硬度的最低值位于熔合区.在低线能量和高线能量接头处,主、辅助光束共同作用面积分别占整个焊缝截面积的1/3和2/3.     

1Cr17与1Cr18Ni9Ti异种钢的焊接

在分析1Cr17与ICr18Ni9Ti各自焊接性的基础上,根据异种钢接接头焊缝金属成分与组织,选择不同焊接材料进行工艺试验,依据试验结果成功地焊接了异种钢接头。     

补焊工艺对30CrMnSiA接头微观组织及性能的影响研究

为了降低企业成本、避免检修过程中大型结构件直接更换造成的资源浪费,针对30CrMnSiA焊接件服役过程中出现的裂纹缺陷开展了补焊试验。试验过程中的焊缝填充金属分别选用HTJ-3、HTG-1焊条,并采用金相、扫描电镜、电子背散射衍射、拉伸、冲击、弯曲等试验对补焊前后接头的组织和性能进行表征分析,建立微观组织与力学性能之间的依存关系,为结构钢钢补焊工艺的优化提供一定的理论支撑。结果表明：补焊前后焊缝底部区域的组织均以马氏体+铁素体为主。补焊过程采用HTG-1作为填充金属,使得补焊区沿垂直于熔合线方向形成了粗大的柱状晶。另外,补焊前后接头原始焊缝区均以大角度晶界为主,使得该区域金属对裂纹扩展的阻碍能力增强。补焊后,焊接接头的抗拉强度及塑性指标都有明显的下降,但冲击韧性有所提高。     

CMT+P焊接电流对5083铝合金焊接接头组织及力学性能的影响

采用不同焊接电流,对3 mm厚5083-H116铝合金板材进行CMT+P焊接试验,并对接头显微组织、拉伸性能、弯曲性能等进行检测。结果表明,焊接电流对接头力学性能和焊缝中心晶粒尺寸有显著影响;焊接电流增大,抗拉强度降低,焊缝中心晶粒尺寸增加。通过对CMT+P焊接参数进行调整,可以获得满足使用要求的焊接接头,抗拉强度281 MPa,达到母材的84.38%;屈服强度163 MPa,达到母材的67.92%;伸长率13.5%,达到母材的75%;焊缝中心为等轴晶,熔合线内侧为柱状晶。      

非金属夹杂物对纯镍N6焊接接头组织性能的影响

以纯镍N6为主要研究对象,借助光学显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)、X射线衍射仪(XRD)及电解萃取装置等手段分析了非金属夹杂物对纯镍N6焊接接头结构及性能的影响.结果表明:纯镍N6试样断裂与非金属夹杂物尺寸、形貌、数量等因素有直接的关系;非正常断裂试样的断口表现为沿晶断裂,断口上夹杂物主要由Al、Si、Ca、Mg、O、Fe等元素组成;对试样的金相组织与夹杂物进行分析发现非正常断裂试样中夹杂物数量及尺寸均大于正常试样,杂物数量大于50个/mm2且夹杂物尺寸大于10 μm的试样均发生断裂;夹杂物主要为氧化铝类(Al2O3、SiO2)、硅酸盐类、氮化物类(AlN、TiN、Ti(C,N))及复相夹杂物;原位拉伸试验表明,断裂的主要原因是在金属基体中存在的夹杂物诱发裂纹源,在应力的作用下裂纹扩展导致断裂.综合分析表明,纯镍N6焊接接头在生产中的断裂是由脆性夹杂物的存在而引起的.     

Microstructure and Fracture Morphology in the Welding Zone of T91 Heat—resisting Steel Used in Power Station

Microstructure performance in the welding zone of T91 heat-resistant steel under the condition of TIG welding was researched by means of metallography, X-ray diffraction and scanning electron microscope (SEM). Experimental results indicated that microstructure of T91 weld metal was austenite + a little amount of S ferrite when using TGS-9cb filler wire. Substructure inside the austenite grain was crypto-crystal lath martensite, on which some Cr23C6 blocky carbides were distributed. The maximum hardness (HRC44) in the welding zone is near the fusion zone. There existed no obvious softening zone in the heat-affected zone (HAZ). For T91 steel tube of $63 mmx5 mm, when increasing welding heat input (E) from 4.8 kJ/cm to 12 5 kJ/cm, fracture morphology in the fusion zone and the HAZ changed from dimple fracture into quasi-cleavage fracture (QC). Controlling the welding heat input of about 9.8 kJ/cm is suitable in the welding of T91 heat-resistant steel.     

Ti40阻燃钛合金电子束焊接头组织与力学性能

采用不同工艺参数对2 mm厚Ti40阻燃钛合金进行电子束焊接(EBW),通过金相分析、电子探针(EPMA)、室温拉伸以及显微硬度测试对Ti40阻燃钛合金电子束焊接接头的显微组织和力学性能进行分析.结果表明,焊缝中分布着晶粒内部有片层状组织析出的β柱状晶和少量等轴β晶粒,熔合线到焊缝中心晶粒逐渐细化,无明显热影响区.接头中易产生气孔、裂纹等缺陷,通过添加直线扫描波形能够有效地控制焊缝气孔缺陷,从而提高接头的强度.添加直线扫描波形电子束焊的Ti40阻燃钛合金的抗拉强度仍可达到917 MPa,断口呈现出脆性断裂与韧性断裂的混合特征,焊缝区的硬度高于母材,其最大值为376HV.     

X65管线钢管闪光对焊工艺参数对焊接接头力学性能和缺陷的影响

利用正交试验法,研究了焊接工艺参数对X65管线钢管闪光对焊焊接接头力学性能的影响。正交试验中选择激发闪光阶段烧化量、稳定闪光阶段烧化量、稳定闪光阶段焊接电流、加速闪光阶段闪光速度作为试验因素,焊接接头抗拉强度、塑性和低温冲击韧性作为焊接工艺的评价指标,得到了最优的焊接工艺参数。接头的金相分析表明,焊接的高热输入使接头焊缝区和部分热影响区的晶粒粗化,形成魏氏组织,降低了接头的冲击韧性。刻槽锤断试验表明,灰斑缺陷内部和边缘的密集裂纹导致接头脆性解理断裂。加速闪光阶段优化的闪光速度有利于减少焊缝区内的缺陷并提高接头的力学性能。     

On the weldability of grey cast iron using nickel based filler metal

Shielded metal arc welding process using nickel based filler metal was used to join grey cast iron. The effect of post weld heat treatment (PWHT) on the microstructure and hardness was studied. PWHT included heating up to 870 °C, holding for 1 h at 870 °C and then furnace cooling. By using nickel based filler metal, formation of hard brittle phase (e.g. carbides and martensite) in the fusion zone is prevented. Before PWHT, heat affected zone exhibited martensitic structure and partially melted zone exhibited white cast iron structure plus martensite. Applied PWHT resulted in the dissolution of martensite in heat affected zone and graphitization and in turn the reduction of partially melted zone hardness. Results showed that welding of grey cast iron with nickel based filler metal and applying PWHT can serve as a solution for cast iron welding problems.     

Microstructure and mechanical properties of resistance spot welded dissimilar thickness DP780/DP600 dual-phase steel joints

In this study, resistance spot welding (RSW) experiments were performed in order to evaluate the microstructure and mechanical properties of single-lap joints between DP780 and DP600. The results show that the weld joints consist of three regions including base metal (BM), heat affected zone (HAZ) and fusion zone (FZ). The grain size and martensite volume fractions increase in the order of BM, HAZ and FZ. The hardness in the FZ is significantly higher than hardness of base metals. Tensile properties of the joints were described in terms of the failure modes and static load-carrying capabilities. Two distinct failure modes were observed during the tensile shear test of the joints: interfacial failure (IF) and pullout failure (PF). The FZ size plays a dominate role in failure modes of the joints.     

Influence of peak temperature during simulation and real thermal cycles on microstructure and fracture properties of the reheated zones

The objective of this paper is to study the influence of the second peak temperature during real and simulated welding on properties of the subcritically (S), intercritically (IC) and supercritically (SC) reheated coarse grained heat affected (CGHAZ) zones. The X80 high strength pipeline microalloyed steel was subject to processing in a double-pass tandem submerged arc welding process with total heat input of 6.98 kJ/mm and thermal cycles to simulate microstructure of reheated CGHAZ zones. This involved heating to a first peak temperature (T_P1) of 1400 °C, then reheating to different second peak temperatures (T_P2) of 700, 800 and 900 °C with a constant cooling rate of 3.75 °C/s. Toughness of the simulated reheated CGHAZ regions were assessed using Charpy impact testing at 0 °C, −25 °C and −50 °C. The microstructure of the real and simulated reheated CGHAZ regions was investigated using an optical microscope and field emission scanning electron microscope. Morphology of the martensite/austenite (MA) constituent was obtained by the use of a field emission scanning electron microscope. The blocky and connected MA particles, along prior-austenite grain boundaries, act as a brittle phase for the initiation site of the brittle fracture. Charpy impact results indicated that IC CGHAZ had less absorbed energy with higher transition temperature and hardness. The SC CGHAZ region showed higher absorbed impact energy with lower hardness. Design of multipass weld joints with less IC CGHAZ regions can result in a higher toughness property.     

汽车高强钢SG1000激光复合焊接力学性能研究

目的 针对汽车高强钢SG1000焊接接头恶化等问题,研究了SG1000激光复合焊接的力学性能。方法 选用等强匹配焊丝MG90-G对高强钢SG1000进行激光复合焊接,对焊接接头进行拉伸和低温冲击韧性试验,并结合扫描和硬度监测等手段对焊缝组织和断口形貌进行分析。结果 由于激光的预热作用,高强钢SG1000激光复合焊接成形件的焊缝美观,焊接过程稳定可靠,焊接熔池深度较大,有效改善了传统焊接的咬边、飞溅、气孔等缺陷。焊缝组织主要由板条马氏体和奥氏体晶粒组成,热影响区的过热区内部板条马氏体和奥氏体晶粒比较粗大,而焊接母材主要为细小的板条马氏体和奥氏体晶粒。焊接拉伸断口主要为细小且较浅的韧窝,且韧窝底部存在第二相粒子及夹杂物,焊接拉伸断口断裂于热影响区且微观形貌为韧性断裂;冲击微观形貌主要由准解理小平面及河流花样组成,且存在一定数量大小不一的韧窝交错分布,焊接冲击断口断裂于热影响区且微观形貌也为韧性断裂。结论 焊缝热影响区的晶粒比非热影响区的晶粒粗大,拉伸和冲击断裂均发生于热影响区;随着激光功率的增大,复合焊接接头的力学性能呈现逐渐增强的趋势;随着焊接速度的增大,复合焊接接头的力学性能呈现先增强后削弱的趋势。高强钢SG1000激光复合焊接最佳工艺参数如下:激光功率为9.5 kW,焊接速度为0.8 m/min,对应屈服强度为1 072 MPa,抗拉强度为1 175 MPa,断裂伸长率为13.5%,冲击断裂吸收的能量为30.8 J、焊缝中心显微硬度为342 HV。     

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.     

Study on cold metal transfer welding–brazing of titanium to copper

3 mm Pure titanium TA2 was joined to 3 mm pure copper T2 by Cold Metal Transfer (CMT) welding–brazing process in the form of butt joint with a 1.2 mm diameter ERCuNiAl copper wire. The welding–brazing joint between Ti and Cu base metals is composed of Cu–Cu welding joint and Cu–Ti brazing joint. Cu–Cu welding joint can be formed between the Cu weld metal and the Cu groove surface, and the Cu–Ti brazing interface can be formed between Cu weld metal and Ti groove surface. The microstructure and the intermetallic compounds distribution were observed and analyzed in details. Interfacial reaction layers of brazing joint were composed of Ti₂Cu, TiCu and AlCu₂Ti. Furthermore, crystallization behavior of welding joint and bonding mechanism of brazing interfacial reaction were also discussed. The effects of wire feed speed and groove angle on the joint features and mechanical properties of the joints were investigated. Three different fracture modes were observed: at the Cu interface, the Ti interface, and the Cu heat affected zone (HAZ). The joints fractured at the Cu HAZ had higher tensile load than the others. The lower tensile load fractured at the Cu interface or Ti interface was attributed to the weaker bonding degree at the Cu interface or Ti interface.