热输入对3Cr耐候钢MAG焊缝金属组织和性能的影响

采用三种热输入进行3Cr耐候钢MAG焊,借助金相显微镜、扫描电子显微镜及透射电子显微镜分析了热输入对焊缝金属组织和性能的影响.结果表明,三种热输入焊缝金属组织主要由板条贝氏体、粒状贝氏体和M-A组元组成.随着焊接热输入的增加,焊缝组织中粒状贝氏体含量增加;M-A组元含量增加且尺寸增大.随着热输入的增加,焊缝金属冲击韧性降低.组织粗化、M-A组元含量增加尺寸增大是导致其韧性降低的主要原因.接头不同区域耐蚀性能相当,腐蚀产物主要由α-FeOOH组成.热输入为8~12 kJ,采用所选焊丝焊接高强耐候钢能够获得强韧性、耐蚀性匹配良好的焊接接头.热输入为8 kJ,接头综合性能最佳.     

焊接热输入对Q890钢焊缝金属组织及韧性的影响

采用熔化极气体保护焊对Q890调质钢进行不同热输入的对接焊试验。利用金相显微镜、扫描电子显微镜、透射电镜和电子背散射衍射技术研究热输入对焊缝组织及冲击性能的影响。结果表明,3种热输入焊缝金属组织主要由板条马氏体和板条贝氏体及少量的粒状贝氏体和残留奥氏体组成。随着热输入的增加,焊缝组织中板条粗化,而粒状贝氏体逐渐增多,部分板条内析出细小针状碳化物;随着热输入的增加,焊缝分析区域内残留奥氏体量逐渐减少分别为1.2%、0.53%、0.41%。焊缝金属冲击断口形貌呈从韧脆混合型断裂特征向脆性断裂特征的变化趋势,与焊缝金属冲击吸收能量变化趋势一致。     

热输入对800MPa级超厚板窄间隙焊缝金属组织和性能的影响

采用三种热输入进行超厚板窄间隙熔化极气体保护焊,借助金相显微镜、扫描电子显微镜及附带EDS系统和透射电子显微镜研究了热输入对焊缝金属组织和性能的影响.结果表明,三种热输入焊缝金属组织主要由板条马氏体、无碳化物贝氏体、M-A组元和残余奥氏体组成.随着焊接热输入的增加,焊缝组织中马氏体含量减少;也使无碳化物贝氏体形核率降低,造成无碳化物贝氏体粗化.并且当贝氏体相变时热输入的增加使碳原子扩散距离变远,促使残余奥氏体形状由膜状向块状转变.另外随着热输入的增加,焊缝金属强度下降,而冲击韧性对热输入不敏感.     

结构钢焊缝金属在低温和动载条件下的脆断本质

研究了结构钢焊缝金属在低温和高加载速率条件下的断裂韧度与断口形貌变化规律,讨论了沿晶脆性断裂的本质。研究指出,降低温度和提高加载速率都导致断裂韧度降低和沿晶脆性断裂倾向增加,表现出一定的低温效应和高加载速率效应,降低试验温度和提高加载速率的作用是相互促进的。焊缝金属沿晶脆性断裂是特定的材料因素、结构因素和环境因素共同作用的结果,沿晶脆性断裂倾向决定于晶界协调相邻晶粒塑性变形的能力,在晶界不足以协调其两侧晶粒的变形时便出现沿晶断裂。     

Effects of Ni and Co on the Acl temperature of P92 steel weld metal

The effects of the addition of 0-1.2wt.％ Ni and 0-2wt.％ Co in P92 steel weld metal on its Acl temperature was analyzed using computational thermodynamic software ( Thermo-CalcTM ) in this paper.The res...     

800 MPa级高强钢焊缝金属热处理组织与性能

在10Ni5CrMoV高强结构钢焊接中,为了获得良好的强韧性匹配,焊后需要进行热处理来改善焊缝金属的组织和性能.试验采用富氩气体保护焊焊接10Ni5CrMoV钢,分析了不同调质热处理工艺下焊缝组织、性能的变化规律.结果表明,焊缝金属焊态的组织主要是贝氏体、少量马氏体和残余奥氏体组织,调质热处理后焊缝组织主要为回火马氏体,随着回火温度的升高,焊缝中残余奥氏体减少,马氏体中碳化物析出长大并有球化趋势.调质态焊缝金属的强度随着回火温度的升高而逐渐降低,而韧性随着回火温度的升高而显著提高.     

焊接规范对14MnNbq钢焊接接头低温韧性的影响

对国产新型桥梁用钢14MnNbp进行了焊接工艺性研究。分别就焊接线能量、层间温度变化对焊接接头的-30℃冲击韧性的影响进行了试验，并用光学显微镜和电子显微镜观察了接头组织，结果表明，中、小线能量焊接时，层间温度在80～200℃之间变化，焊接接头-30℃冲击韧性较好；线能量超过40kJ/cm时，接头冲击韧性明显下降。     

Effect of copper on mechanical properties of high strength SMAW weld-metal

Mechanical properties of SMA W （shielded metal arc welding） weld metal （ yield strength higher than 900 MPa ） with systemazic additions of copper （ up to 1.48 wt% ） were tested, The microstructure and precipitates in different regions were analyzed by optical microscope and transmission electron microscope, The results indicate that copper improves the low temperature toughness of weld metal when the copper content is low and reaches the peak value 48 J （ at - 50℃ ） with 0. 2 wt% copper additions. When the content is high the copper precipitates as 8-Cu phase in the reheat zone of middle beads. These precipitates improve the strength of the weld metal evidently （ yield strength up to 975 MPa） without obvious effect on the low temperature toughness. The copper within 1.1 wt% content can improve the strength without toughness loss.     

钢筋混凝土柱-钢梁混合构造节点(RCS)制作工艺

设计了一个集平台、定位、夹具于一体的新型工装,解决了一种钢筋混凝土柱-钢梁混合构造节点(RCS)制作上的难题,保证了制作精度,同时采取合理的坡口形式,降低了钢板对接的角变形。在制作质量上,根据焊丝特性规定焊接道间温度、焊接摆弧宽度、焊接热输入,有效保障了钢板对接焊缝的综合力学性能,顺利完成了RCS节点的制作。     

低合金高强度钢焊缝金属中针状铁素体的微观组织

利用光学显微镜,扫描电子显微镜及EBSD(electron backscattering diffraction)分析技术对800MPa级低碳微合金高强度钢的焊缝金属进行了分析.结果表明,焊缝金属组织主要为针状铁素体和贝氏体.针状铁素体以夹杂物为核心形核,该夹杂物主要是以Al2O3为核心形成的钛氧化物.针状铁素体以夹杂物为核心多维形核呈放射状生长,仅某些方向的针状铁素体晶核迅速长大,生长方向存在取向择优.EBSD分析同样表明针状铁素体晶粒存在取向择优.观察到由同一夹杂物生长,沿同一直线方向背向生长的针状铁素体取向相同,沿不同方向生长的针状铁素体取向不同,说明其沿原奥氏体惯习面生长,并非与夹杂物共格.     

EH36钢埋弧焊焊缝金属组织临界断裂韧性

通过对典型海洋结构用钢EH36埋弧焊焊缝金属进行单边缺口拉伸试验(single edge notched tensile,SENT)研究焊缝金属中针状铁素体(acicular ferrite,AF)和先共析铁素体(proeutectoid ferrite,PF)的临界断裂韧性. 结果表明,AF的断裂韧性要高于PF,主要原因在于AF内部具有较高密度的位错及位错能,在外力作用下,裂纹尖端极易发生塑性变形而钝化;相反,PF组织较纯且均匀,位错密度较小,裂纹尖端并未发生钝化. 这种组织的不均匀性导致了焊缝金属断裂韧性较大的分散性,主要归结于试样预制裂纹尖端位置的微观组织性能.     

铌和钒在高碳钢质焊缝金属中的行为

利用能谱(EDS)及电子探针(EPMA)、透射电镜(TEM)分析了高碳钢质焊缝金属中铌和钒及其碳化物的行为特点，结果表明，Nb可以强烈地改变C的分布和存在状态，导致C在基体固溶体中的显著贫化和高密度NbC质点的析出。改变Nb／C比，可使弥散的碳化物分布在板条马氏体、索氏体、铁素体等不同的基体组织上，与此同时，与Nb共存的Cr失去形成碳化物的倾向，成为固溶强化元素。V有与Nb类似的作用，但其碳化物易沿晶界析出。     

Microstructure evolution in the weld metal region of a Ni-based Inconel 718 superalloy produced by tungsten inert gas welding

The microstructure evolution of the weld metal (WM) region in a Ni-based 718 superalloy is discussed. The superalloy sheets were welded using the tungsten inert gas process at different heat inputs. The precipitates and dendrites in the WM of each joint were analyzed by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy (EDS). Statistics on the dendrite arm spacing and precipitates were obtained from the metallographs. Using the alloy composition determined by EDS and the phase diagram obtained using ThermoCalc, the equilibrium distribution coefficient of Nb, the temperature range of solid/liquid coexistence, and the distribution and morphology of Laves phase in different subregion of the WM were analyzed. There is lamellar segregation, regional segregation, and microsegregation in the WM. As the heat input increases, the arm spacing and the microsegregation increase. At a fixed heat input, the microsegregation rate is smallest in the crater, but with the macrosegregation seriously.     

低合金钢焊缝的针状铁素体微观组织

针对X70管线钢多道焊焊缝金属,利用Gleeble1500热模拟机进行了热模拟试验,对焊缝金属中初生针状铁素体组织及其与非金属夹杂物之间的关系以及经历二次热循环后感生形核的针状铁素体组织进行了SEM及TEM分析.结果表明,针状铁素体边界存在着一层富碳的薄膜,其长大既存在切变转变的特征,同时也伴随着C原子的扩散过程.共感生成的二次针状铁索体是在初生针状铁索体基体的高密度位错处形核并以一定的速度迅速长大到有限的尺寸.初生针状铁素体和共感形核针状铁素体都是在奥氏体晶内形核、长大,都具有细化奥氏体晶粒、提高多道焊焊缝金属和焊接热影响区韧性的作用.     

温度对Super304H焊缝金属再热裂纹敏感性的影响

Super304H奥氏体不锈钢是超超临界火电机组中过热器与再热器管的重要材料,在高温长期服役条件下,管道焊接接头的装配处易产生再热裂纹。本文使用预压缩CT试样的方法系统的研究了温度对Super304H奥氏体不锈钢焊缝金属再热裂纹敏感性的影响。结果表明,650 ℃试验温度下的焊缝金属产生裂纹所需的时间比600 ℃试验温度下的焊缝金属所需要的时间更短,具有更高的再热裂纹敏感性。导致该现象的主要原因在于650 ℃试验温度下晶界强度随时间衰减更快,应力松弛速率更高,而不同温度下晶内强化差异带来的影响较小。     

10CrMo910钢焊缝焊接热循环的实时检测

针对10CrMo910钢焊后焊缝及近缝区常出现硬化和冷裂纹等问题,结合生产实际,采用合适的焊接工艺,对10CrMo910钢进行了成功焊接.焊接过程中将热电偶直接埋在焊缝里,实现了焊缝焊接热循环曲线的实时检测.检测到的热循环峰值温度最高为1701℃,较以往焊接热影响区热循环的研究结果提高了401℃.焊后的焊缝金属以不同的方式冷却,获得了10CrMo910钢油冷、空冷和砂冷后焊缝金属的焊接热循环曲线.     

Ni元素对Cr-Ni-Mo系高强焊缝组织演化的影响

主要利用金相显微镜(OM)、高分辨热场扫描电镜(FEGSEM)附带能谱仪(EDX)、透射电镜(TEM)等手段对不同Ni元素含量的高强钢焊缝组织及成分进行了观察分析,阐明了焊缝成分对组织的影响.利用Thermol-Calc热力学软件对两种焊缝的凝固模式进行了探讨.结果表明,随着Ni元素含量的提高,高强钢焊缝由板条贝氏体和马氏体为主的组织变为板条更细小的马氏体与粗大联合贝氏体的混合组织,而且焊缝硬度大大提高.Ni元素含量的增加提高了焊缝强度,并保持了良好的低温韧性.Ni元素含量的提高改变了焊缝的凝固模式,直接由液态转变为奥氏体,造成合金元素Mn和Ni在枝晶间偏析.     

Effects of evolution of nanoscale copper precipitation and copper content on mechanical properties of high-strength steel weld metal

Nanoscale copper precipitation in high-strength weld metal was characterised by using atom probe tomography (APT) and transmission electron microscopy. In as-deposited zone, there was no copper precipitation. During welding thermal cycling, nanoscale copper of 2–3?nm in radius precipitated with face-centred cubic (FCC) and body-centred cubic (BCC) structure. During post-weld heat treatment (PWHT), FCC copper precipitate became coarsen and BCC transformed into FCC. The highest hardness was in the reheated zone which subjected to the peak temperature below 500°C; while the lowest hardness was both in deposited zone and the reheated zone which subjected to the peak temperature greater than 810°C. After PWHT, the hardness became homogenous as well as decreased. With increasing copper content, the hardness was increased and the toughness was slightly decreased. After PWHT, the toughness decreased due to the change in the structure of copper precipitates.     

Experimental study on the shear strength of side fillet weld of Q235B steel post high temperatures

In order to learn the variation laws of shear strength of side fillet weld post high temperatures, the tension tests were conducted after the double-strapped side fillet welded joints which were cooled down from different high temperatures with different cooling patterns. The tests indicate that specimens appear brittle fracture at the side fillet weld during the tension tests after cooling down. The fracture su（face is located in the welding throat. The maximum temperatures undergone and the cooling pattern are major factors influencing shear strength of side fillet welded joint post high temperatures. The shear strength reduces by 24% at most within 900 ~C. Based on the experimental results, the calculation formulas of shear strength of side fillet weld post high temperatures were proposed. Conclusions supply references for evaluation damage and reinforcement of steel structure post fire.     

Comparative study of weld residual stress on steel pipes with different weld types

This study developed a sequential coupling finite element procedure to predict residual stresses of steel pipes with longitudinal wela\ circumferential weld and spiral weld.The results show that the residual stress in heat affected zone(HAZ)is higher than that in weld for spiral weld pipe.For the circumferential weld pipe and spiral weld pipe,the residual stress in inner surface is higher than that in outer surface.However,for the spiral weld pipe,the residual stress in inner surface is smaller than that in outer surface.The hoop residual stress of circumferential weld pipe is higher than that of longitudinal weld pipe,while the axial residual stress of circumferential weld pipe is smaller than that of longitudinal weld pipe.The hoop stresses for circumferential weld pipe and axial stress for longitudinal weld pipe have exceeded the yield strength of base metal.With the increase of helix angle,the hoop stress decreases while the axial stress increases.For the spiral pipe(α=30° to 50°),both the hoop stress and axial stress are relatively small.The spiral pipe(helix angle ranging from 30° to 50°) is helpful to reduce stress corrosion cracking(SCC) and it is recommended to manufacture the steel pipe.