钢制压力容器焊接残余应力分析与研究

应用小孔释放法对系列钢制压力容器手弧焊接接头的焊接残余应力进行测试，讨论了焊接残余应力的分布规律及其相关影响因素，对加载法消除焊接残余应力的效果进行了初步的验证。结果表明，焊接接头的应力不均匀性和不确定性是影响钢制压力容器安全性的关键，采用加载法可以有效地改善这种非均匀应力分布状况。     

焊接电流对Q235钢焊接接头残余应力的影响

对12 mm厚Q235试板进行手工电弧焊试验研究。采用3种不同焊接电流参数对3组试板进行焊接,以研究不同焊接电流下焊接接头所产生的残余应力。3组试板均采用双面焊。分别对正面填充焊和盖面层焊采用155 A、165 A、175 A三种焊接电流。焊完后采用残余应力测试方法对焊接接头进行分析。研究结果表明,Q235钢在175 A电流下焊接接头残余应力比165 A电流下大,155 A电流下最小。随着焊接电流的增大,焊接残余应力升高。     

钢制压力容器焊接残余应力测试分析

应用小孔释放法对系列钢制压力容器手弧焊接接头的焊接残余应力进行测试 ,讨论了焊接残余应力的分布规律及其相关影响因素 ,对加载法消除焊接残余应力的效果进行了初步的验证。结果表明 ,焊接接头的应力不均匀性和不确定性是影响钢制压力容器安全性的关键 ,采用加载法可以有效地改善这种非均匀应力分布状况。     

焊缝返修引起残余应力变化的研究

经焊接加工制成的压力容器或化工设备,在制造过程中不可避免地要产生残余应力。此应力对构件的静载荷承受能力看不出明显影响,但对焊接接头的疲劳承载能力的影响是明显的。特别是在腐蚀性介质中极大地降低了构件抗应力腐蚀开裂的能力。在焊接接头产生了焊接缺陷进行返修时,由于构件的刚性很大,焊缝返修是在很大的外约束条件下进行,其结果是在返修部位造成了更大的、分布更加复杂的残余应力。     

预热措施对焊接残余应力影响的数值模拟

首先采取试验验证的方法证明了高斯热源方案模拟手工电弧焊的准确性。对于石油化工装置中经常出现的复杂构件,以管板角接头为例,利用ANSYS分析软件对焊接残余应力进行建模计算,得到焊接残余应力数值分布。有限元分析结果表明,采用预热与不预热两种不同的焊接参数对模拟结果进行了对比。合理的预热措施使最大径向向焊接残余应力降低20%左右。本文对工程设计公司了解管道焊接过程中焊接接头产生的残余应力及分布引进了一个可行方法。可作为工程设计过程中的参考依据。同时也可用来检验焊接工艺,为现场施工提供建议。     

陶瓷金属扩散焊接的残余应力及其缓和措施

采用热弹塑性有限元法分析了热压氧化硅和Ｋ－５００合金的散焊接引起的残余应力状态。比较了方棒试件三维残余就力和圆棒试件二维轴对残余应力的特征，探讨了不同过渡层的影响。结果表明，在靠近连接界面际近的陶恣外表面存在轴向最大拉伸应力，它是导致接头开裂和强度降低的关键因素。     

焊管残余应力及其测试

由成型及焊接过程造成的残余应力对焊管的质量及服役可靠性有重要影响,降低焊管的承压能力、易造成焊管的耐腐蚀能力降低、使焊管易产生疲劳破坏。本文对焊管残余应力的研究方法进行了综述,并采用盲孔法对螺旋焊管的残余应力进行了测试。其内表面为低值拉应力,外表面为低值压应力,峰值环向应力在焊缝附近外表面,整个焊管范围内残余应力的分布较均匀。     

内伸入式接管焊接接头应力的有限元分析

本文应用Ansys有限元应力分析软件,根据钢制化工容器结构设计规定(HG20583-1998),分别建立内部施焊和外部施焊的内伸入式接管与壳体间焊接接头的模型,分析焊接接头处应力分布的情况,并对焊接接头处的应力进行对比。对比结果表明:a类焊接接头所受应力最大;c类焊接接头应力相对较小;b类焊接接头受力效果最好。若可以对焊缝的坡口连接拐点附近进行优化,可以大大的减小应力水平,改善焊缝的受力情况。     

加载消除焊接残余应力的研究

经焊接加工的化工设备及压力容器，在其内部要产生焊接残余应力。残余应力的峰值往往达到材料的屈服极限，当这些设备投入运行后，所受的载荷引起的应力与内部的残余应力叠加要严重影响设备的疲劳强度和抵抗腐蚀开裂及脆性断裂的能力，采用加载的办法来消除部分焊接残余应力是简便易行的方法，对我区的中小设备制造厂具有实际意义。     

压力容器焊接接头疲劳裂纹萌生寿命的探讨

本文对16MnR焊接接头进行了控制应变幅条件下的疲劳试验，获得其疲劳特性参数以及恒变变愠载荷下的疲劳－寿命关系，建立了焊接接头低周疲劳寿命曲线方程，并将试验结果同局部应力应变法计算的结晶进行了比较，为该焊接接头应变疲劳提供了理论依据。     

应力腐蚀开裂的断裂参量研究

根据焊接接头应力腐蚀开裂行为的特点,采用焊接接头力学不均匀性模拟试样,用断裂力学的 K 因子方法和 COD 方法进行研究。结果表明,焊接接头区域硬化层宽度 h 增加时,应力腐蚀裂纹扩展速率 da/dt 显著增加。     

钛制压力容器的焊缝应力研究

通过试验证明钛容器的破坏都是从焊缝开始的，其焊缝应力以离焊根５～１０ｍｍ处最大，达到了筒体按双向强化计算值２．２８～３．５１倍，并在此基础上提出了加强钛容器焊缝强度研究和如何降低焊缝应力峰值研究的新课题     

Effect of different welding parameters on residual stress and deformation of 20/0Cr18Ni9 dissimilar metal arc-welding joint

Abstract

Pipelines used for the petrochemical, energy, and other industries contain 20 steel and 0Cr18Ni9. This paper based on the finite element simulation software Simufact Welding, the residual stress field and deformation results for 6-mm-thick 20/0Cr18Ni9 plates were examined by combining numerical simulation with experimental verification and performing an orthogonal experiment of three factors on different welding parameters. Herein, the thermodynamic coupling, isotropic hardening model, viscoplastic model, moving heat source are considered, and the experiments confirm the welding residual stress and deformation. The experimental results show that the stress distribution of each model is similar and the maximum stress appears in the fusion zone. Furthermore, the longitudinal residual stress is substantially greater than the transverse residual stress, whereas the minimum stress distribution is observed in paramaters of heat input 13493?J (welding layer 1) and 22400?J (welding layer 2), interpass temperature 50?°C, ambient temperature 65?°C. The minimum deformation occurred in paramaters of heat input 5913?J (welding layer 1) and 9200?J (welding layer 2), interpass temperature 250?°C, ambient temperature 65?°C, whereas the maximum deformation occurred in paramaters of heat input 13493?J (welding layer 1) and 22400?J (welding layer 2), interpass temperature 250?°C, ambient temperature 20?°C. Finally, the paramaters of heat input 7077?J (welding layer 1) and 11440?J (welding layer 2), interpass temperature 50?°C, ambient temperature 20?°C were selected to conduct the actual experiment and verify the residual stress and deformation. The results showed that the simulation results agreed with the actual results, thereby confirming the model’s reliability.     

HDPE焊接三通管件壁厚数值优化设计

输气焊接HDPE三通管道,由于焊接使材料性能下降,并产生应力集中,因此必须对管道连接处增加壁厚.基于对HDPE材料性能和焊接处HDPE材料拉伸强度的试验,对HDPE材料三通管道壁厚进行数值优化设计.有限元模型中采用理想弹塑性和Ramberg-Osgood两种材料本构模型,计算得到管道等应力线以及壁厚优化曲线,对管道设计具有实际意义.     

再生器发生应力腐蚀开裂的探讨

针对炼油厂催化装置再生器下部件壁发生开裂的现象，通过分析催化装置近几年原料油田的变化、烟气露点测试结果与现场器壁温度对比，认为这是一种氢应力腐蚀开裂（SCC）。结合氢应力腐蚀特点制定了修复方案，特别是焊前预热、焊后热处理，选择合适的焊条及板材，降低了焊道和热影响区硬度，消除残余应力。并对再生器下部壁采取保温措施，确保再生器下部外壁温高于露点（137℃），使之无法在下部器壁形成水汽冷凝液，有效防止SCC的发生。     

圆筒环缝对接焊应力与变形的分析

利用柱壳理论的近似计算方法,对薄壁圆筒环向对接焊缝的应力与变形进行了分析讨论,定量地给出了焊后残余应力与变形随筒体尺寸及焊接条件而变化的规律     

Pitting and stress corrosion cracking behavior in welded austenitic stainless steel

The effect of microstructural changes in 304 austenitic stainless steel induced by the processes of gas tungsten arc welding (GTAW) and laser-beam welding (LBW) on the pitting and stress corrosion cracking (SCC) behaviors was investigated. According to the in situ observations with scanning reference electrode technique (SRET) and the breakdown potentials of the test material with various microstructures, the GTAW process made the weld metal (WM) and heat-affected zone (HAZ) more sensitive to pitting corrosion than base metal (BM), but the LBW process improved the pitting resistance of the WM. In the initiation stage of SCC, the cracks in the BM and HAZ propagated in a transgranular mode. Then, the crack growth mechanism changed gradually into a mixed transgranular + intergranular mode. The cracks in the WM were likely to propagate along the dendritic boundaries. The crack initiation rate, crack initiation lifetime and crack propagation rate indicated that the high-to-low order of SCC resistance is almost the same as that for pitting resistance. High heat-input (and low cooling rate) was likely to induce the segregation of alloying elements and formation of Cr-depleted zones, resulting in the degradation in the corrosion resistance.     

Experience with a full notch creep test in determining the stress crack performance of polyethylenes

A laboratory method to measure the stress crack resistance of polyethylenes was developed and has since been applied in our laboratory for more than twelve years. The experience gathered since our first paper is herewith reported. The creep rupture test of circumferentially notched specimens cut from plaques or pipes has proven to be a rapid and reliable method to evaluate the stress crack performance. Surfactant-assisted stress cracking was employed to accelerate testing. The stress crack resistance of several polyethylene samples was studied with respect to its dependence on stress, temperature, and environment. The creep rupture behavior at different temperatures could be superposed by horizontal shifting when the stresses were normalized in proportion to the respective bulk yield stresses. The notch tip radius turned out not to be very crucial, and variation of the nominal concentration of the surfactants, nonylphenolpolyglycolethers, scarcely affected slow crack growth. Acceleration of testing by surfactants equalized property differences to a noticeable extent but did not influence the ranking of the materials. The activation energy of crack growth was in the expected range. Defects introduced into the line by butt joint welding were precisely modeled by the full notch creep test.     

Behavior of NiTiNb SMA wires under recovery stress or prestressing

The recovery stress of martensitic shape-memory alloy [SMA] wires can be used to confine concrete, and the confining effectiveness of the SMA wires was previously proved through experimental tests. However, the behavior of SMA wires under recovery stress has not been seriously investigated. Thus, this study conducted a series of tests of NiTiNb martensitic SMA wires under recovery stress with varying degrees of prestrain on the wires and compared the behavior under recovery stress with that under prestressing of the wires. The remaining stress was reduced by the procedure of additional strain loading and unloading. More additional strains reduced more remaining stresses. When the SMA wires were heated up to the transformation temperature under prestress, the stress on the wires increased due to the state transformation. Furthermore, the stress decreased with a decreasing temperature of the wires down to room temperature. The stress of the NiTiNb wires was higher than the prestress, and the developed stress seemed to depend on the composition of the SMAs. When an additional strain was subsequently loaded and unloaded on the prestressed SMA wires, the remaining stress decreased. Finally, the remaining stress becomes zero when loading and unloading a specific large strain.     

Effect of welding parameters on the heat affected zone and the mechanical properties of friction stir welded poly(ethylene-terephthalate-glycol)

The bond strength and the heat affected zone (HAZ) of friction stir welded seams made of poly(ethylene-terephthalate-glycol) are analyzed in the article. The seams were prepared with various settings (rotation speed and feeding rate) and with various welding tools. Using the welding parameters (rotation speed, the feed rate, and the tool diameter) a K-factor characterizing the welding process was defined. The novel K factor is related to the welding heat input, which is in direct correlation with both the range of the HAZ and the mechanical properties of the seam. The HAZ formed was analyzed by stress optical method, the mechanical properties by flexural test. It has been demonstrated that the efficiency factor of the welded joint is closely related to the width of the HAZ and it depends on the welding parameters and the tools. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012