铸铁拘束试件的拘束度计算及铸铁焊缝裂纹倾向定量评定

本文提出了一种试件拘束度分级可调的铸铁焊缝拘束裂纹定量新方法，采用有元元方法对铸铁试件拘束度进行了计算，并做了实测验证，应用本试验方法测定了石墨形态对铸铁焊缝裂纹倾赂的影响。     

铸铁拘束试件的拘束度计算及铸铁焊缝裂纹倾向定量评定

本文提出了一种试件拘束度分级可调的铸铁焊缝拘束裂纹定量试验新方法、采用有限元方法对铸铁试件拘束度进行了计算,并做了实测验证。应用本试验方法测定了石墨形态对铸铁焊缝裂纹倾向的影响。     

刚性对接裂纹试件和VRC试件拘束度有限元模拟

采用有限元方法研究了试件尺寸对刚性对接裂纹试件和可变拘束裂纹试件拘束度的影响规律.结果表明,两种试件的拘束度均随着厚度的增加而增大,随着厚度由20 mm增加至50 mm,刚性对接裂纹试件中心拘束度由14.87 kN/（mm·mm）增加至20.72 kN/（mm·mm）,可变拘束裂纹试件中心拘束度由10.46 kN/（mm·mm）增加至16.23 kN/（mm·mm）;对于40 mm厚的刚性对接裂纹试件,其拘束试件宽度由125 mm增加至275 mm时,试件的拘束度下降,但拘束试件宽度继续增加,试件的拘束度不再发生显著变化;对于40 mm厚可变拘束裂纹试件,随着拘束试件宽度由125 mm增加至575 mm,其拘束度呈连续下降趋势.     

大拘束度ZG20MnMo钢焊缝裂纹分析及处理

对ZG20MnMo钢大拘束度焊缝裂纹,采用插销试验方法,在不同的预热温度下,对试件进行临界断裂应力、金相与断口形貌分析,找出该钢焊缝产生裂纹的原因及主要影响因素,提出了防止ZG20MnMo钢大拘束度焊缝产生裂纹的措施.     

拘束应力对厚壁管焊接裂纹影响的实例分析

火力发电厂施工的现场大口径厚壁管焊接中，拘束应力过大往往是造成焊接裂纹产生的主要原因。本文以一具体实例分析了拘束应力使高温下焊缝残余塑性降低，导致焊接裂纹的产生，并就该例拘束应力的影响作了量的分析，同时提出了相应的改善措施。     

浮头式换热器浮头盖焊接冷裂纹的消除

钢材的淬硬倾向、焊接接头含氢量及其分布,以及接头所承受的拘束应力状态是产生焊接冷裂纹的三大主要因素.对于低淬硬倾向的钢材,采用低氢型焊材,合理设计焊接结构,降低接头的拘束应力状态,通过合理的焊接工艺,可以消除浮头式换热器浮头盖焊接时出现的焊接冷裂纹.     

高强度钢焊接区拘束应力的有限元分析

采用ANSYS有限元软件计算分析了HQ130高强钢焊接接头区拘束应力的分布。计算和分析结果表明，在气体保护焊线能量16kJ/cm条件下，HQ130钢焊缝表面的瞬时拉伸拘束应力最大达到800－1000MPa，焊缝底部的瞬时拉伸拘束应力达到500－600MPa。熔合区附近的应力梯度较大，这是高强度钢熔合区部位容易产生冷裂纹的重要原因之一。通过严格控制焊接线能量能减小焊接区的热应力，可防止焊接裂纹的产生。     

Numerical simulation and experimental verification of the restraint intensity of pipeline girth welding joint

The restraint intensity (RI) of the pipeline girth welding joint was investigated using finite element method and experimental method to predict the cold cracking susceptibility of pipeline steel. The distribution of RI along the girth weld was investigated to study the influence of welding position on the RI. Subsequently, the effects of outer diameter (OD) and wall thickness of pipeline on the RI were studied with ABAQUS software. The results show that the RI is almost independent of welding position. The RI increased with the increasing wall thickness but decreased with the increasing OD. A prediction model of RI was developed based on the effects of the OD and the wall thickness. It has been found that the predicted RIs were in good agreement with the experimental values. The maximum fractional error between the predicted RI and the experimental values was just about 10%. It was indicated that the errors were mainly caused by the heterogeneous of the weld bead.     

罐车角焊缝裂纹的修复

近几年，在徐州市盛装液化石油气介质的汽车罐车检验中，经常发现罐内焊接接头出现裂纹等缺陷，其中在角接接头位置较多。主要原因为角焊缝易存在制造质量问题，且在使用中，在交变载荷的作用下，易产生疲劳裂纹缺陷。下面就罐车实例做出具体介绍。     

焊接钢结构角焊缝尺寸的探讨

随着焊接技术的日臻完善，焊接钢结构的产品不仅在铁路桥梁和建筑结构上得到了广泛的应用，在机械产品中所占的比例也在逐步增加。然而由于专业所限，有些结构在焊接坡口、焊缝尺寸的设计上，还存在着一些不甚合理之处，给焊接生产带来了困难或增加了制造成本。所以，设计工程师应了解和掌握一定的焊接及制造工艺方面的知识，以使焊接钢结构的设计更便于工厂的制造和焊接。     

焊接顺序对T型接头角焊缝残余变形的影响

为研究焊接顺序对T型接头角焊缝残余变形的影响,对平对接接头的焊接过程进行数值模拟和焊接实验,验证焊接模拟的合理性;建立T型接头双面角焊缝的有限元模型,采用生死单元技术和热结构耦合的方法对T型接头焊接过程中的温度场和应力场进行数值模拟,分析4种焊接顺序对其残余变形的影响。结果表明,模拟结果与残余应力测试结果吻合良好,说明焊接模拟过程合理有效。T型接头在焊后发生了挠曲变形,焊接顺序2的残余变形最小,变形量为0.61 mm,采用从两侧向中间的焊接顺序能够减小T型接头的残余变形。     

缝隙型焊接试件拘束应力的分析

缝隙型裂纹是一种最接近实际焊接结构受力状态的试件，研究其焊缝拘束应力的计算具有普遍的意义，本文以热弹塑性有限元分析计算作基础，建立了焊根间隙收缩曲线的数学模型，结合Ｓｌｉｔ试件拘束度的分布函数，首次提出了一个描述Ｓｌｉｔ试件拘束度与拘束应力关系的计算公式，计算与试验结果证明它能比较真实地反映实际焊接接头的应力水平，有重要的实用价值。     

低合金高强钢激光-电弧复合热源焊接冷裂纹敏感性分析

通过扩散氢含量测定,并利用经验公式计算JFE980S低合金高强钢冷裂纹敏感性和焊前预热温度,同时采用斜Y形坡口试验、金相试验以及残余应力测定等方法,研究低合金高强钢抗冷裂性能,对比分析了激光-电弧复合焊和MAG焊工艺对接头抗冷裂性能的影响.结果表明,激光复合焊抗冷裂性优于MAG焊方法.因复合焊加入了激光,使得焊缝熔深增加,拘束减小,并且激光在前,对焊接试板有一定的预热作用,使冷裂纹形成倾向进一步降低,特别是在无法预热的情况下,激光复合焊更能够体现出优势.     

Weldability and toughness evaluation of pressure vessel quality steel using the shielded metal arc welding (SMAW) process

The present study was carried out to assess the weldability properties of ASTM A 537 Cl. 1 pressure-vessel quality steel using the shielded metal arc welding (SMAW) process. Implant and elastic restraint cracking (ERC) tests were conducted under different welding conditions to determine the cold cracking susceptibility of the steel. The static fatigue limit values determined for the implant test indicate adequate resistance to cold cracking even with unbaked electrodes. The ERC test, however, established the necessity to rebake the electrodes before use. Lamellar tearing tests carried out using full-thickness plates under three welding conditions showed no incidence of lamellar tearing upon visual examination, ultrasonic inspection, and four-section macroexamination. Lamellar tearing tests were repeated using machined plates, such that the central segregated band located at the midthickness of the plate corresponded to the heat-affected zone (HAZ) of the weld. Only in one (no rebake, heat input: 14.2 kj cm^-1, weld restraint load: 42 kg mm^-2) of the eight samples tested was lamellar tearing observed. This was probably accentuated due to the combined effects of the presence of localized pockets of a hard phase (bainite) and a high hydrogen level (unbaked electrodes) in the weld joint. Optimal welding conditions were formulated based on the above tests. The weld joint was subjected to extensive tests and found to exhibit excellent strength (tensile strength: 56.8 kg mm^-2, or 557 MPa), and low temperature impact toughness (7.4 and 4.5 kg-m at-20 °C for weld metal, WM, and HAZ) properties. Crack tip opening displacement tests carried out for the WM and HAZ resulted in δ_m values 0.36 and 0.27 mm, respectively, which indicates adequate resistance to brittle fracture.