电力铁塔厚板防层状撕裂焊接工艺

在厚板焊接中层状撕裂是一种低温脆性断裂，一般出现在钢板厚度大干40mm的十字型接头、T型接头和角接接头焊接中。本文对电力铁塔塔脚焊接中层状撕裂问题进行了研究，对层状撕裂产生的机理进行分析，从焊接工艺上制定了防止层状撕裂的方案，对电力铁塔厚板焊接中层状撕裂问题有一定指导意义。     

转炉托圈层状撕裂预防措施

针对转炉托圈焊接时产生层状撕裂问题，从产品结构、焊接工艺等方面入手，分析了撕裂原因，并制定了相应的工艺措施，避免了层状撕裂产生。     

特厚Q390NBZ35钢板焊接工艺

120 mm厚Q390NBZ35钢板为特厚、低合金高强度结构钢,钢材自身淬硬倾向性大,焊接性较差,厚度方向受到较大的拉伸力,易于产生层状撕裂。文中通过评价核电站常用的特厚板(120 mm)Q390NBZ35钢焊接性,分析冷裂纹及层状撕裂产生的原因,制订并验证焊接工艺措施的有效性,包括明确钢材交货状态、选用超低氢型焊材、焊前预热、后热及保温、抗裂性及层状撕裂的验算、优化焊接工艺设计与加强工艺管理,以保证该低合金高强钢特厚板的焊接质量。     

T型焊接接头层状撕裂超声波检测技术的研究

钢板层状撕裂是T型焊接接头一种非常危险的缺陷,本文以AP1000蒸汽发生器横向支撑与CA01墙体T型焊接接头为研究对象,在CA01母材上堆焊模拟产生拉伸应力,采用超声波检测技术通过堆焊层对母材层状撕裂进行检测,较好的解决母材侧检测位置受限问题。     

海洋钻井平台升降腿焊接工艺及抗层状撕裂性能的研究

针对屈服强度为690 MPa的Z向钢制造的海洋平台升降腿,研究了二氧化碳气体保护焊和焊条电弧焊这两种不同焊接方法焊接工艺及焊接变形、焊接接头的组织及力学性能、母材的层状撕裂敏感性等.通过试验对比,选择合理的焊接方法和焊接材料,制订合理的焊接工艺,为海洋平台升降腿的制造提供了理论和试验依据.     

水轮发电机转子支架焊接裂纹问题的探讨

本文根据75MW 水轮发电机转子中心体和5MW 灯泡式贯流发电机转(?)支架产生的焊接冷裂纹和层状撕裂的情况,详细分析了产生裂纹的各种影响因素,并提出了一些行之有效的防止措施和合理建议。     

大厚度Z向钢CO2气体保护焊的立焊工艺

针对焊接大厚度正火钢Q420C-Z15时出现的层状撕裂问题,采用Z向钢,运用高效、优质实芯焊丝CO2气体保护焊的立焊焊接工艺,正确选材,优化规范,合理布置焊缝层道,把握合适的预热温度和层间温度,经焊接工艺评定,各项指标符合规定要求,取得了满意的焊接效果。     

焊接修复中易产生的焊接缺陷及防止方法

[接上期 ]2　内部缺陷手工电弧焊在焊接修复时 ,产生的外观缺陷易被发现和修复。而内部的焊接缺陷 ,是要采用着色探伤、磁粉探伤、超声探伤、射线探伤、密封水压试验等检测手段才能发现。对于重要的焊接修复部件 ,根据要求还要作力学性能试验、化学成分分析和金相检验等。内部产生的焊接缺陷是与被修复构件焊接修复的材质、结构形状、焊接材料的选择及焊接工艺的制定等相关的。焊接修复中易产生的内部焊接缺陷主要有 :夹渣、气孔、未熔合和裂纹。裂纹又分为热裂纹、冷裂纹、再热裂纹、应力裂纹和层状撕裂。以上各种焊接缺陷 ,在焊接修复中是…     

海洋平台焊接接头层状撕裂的分析

层状撕裂主要是指焊接导致的母材沿厚度方向开裂,在海洋平台制造过程中属于比较严重的质量问题。从层状撕裂产生的机理、应对措施进行了深入地分析,并对文中的3种层状撕裂案例提出了解决方案,为后续海洋平台建造过程中层状撕裂的有效预防提供了指导建议。     

ZG270-500与Q345B异种钢的焊接裂纹研究

以单柱立式车铣中心的部件横梁的组装、焊接为契机,针对复杂受力的高拉伸应力、厚板高拘束度下ZG270-500与Q345B的焊接易出现焊接裂纹的问题进行了研究;结合生产实践中的实验对比,从材料的力学性能、受力情况、焊接性能等方面综合分析了ZG270-500与Q345B异种钢焊接因焊接接头的受力情况复杂、厚板拘束度大,如果在焊接接头中存在微裂纹、非金属夹杂物、未熔合等缺陷作为裂纹源时极易产生层状撕裂。针对这种情况提出了相应的工艺措施,较好地解决了裂纹缺陷的发生。     

Study on lamellar tearing generated by corner joint welding in box column of ultrathick plate

Abstract

In an attempt to reduce the risk of lamellar tearing during welding of ultrathick plates, the present study has evaluated the susceptibility to lamellar tearing of steel structures in relation to welding stress rather than metallurgical properties, and eventually attempted to determine the optimum groove shape and welding procedure by computer simulation based on the finite element method. Based on the simulation, it has been identified that controlling the shape of the deposited weld metal in the anticipated position of the occurrence of lamellar tearing is the most favourable method of preventing lamellar tearing by minimising welding residual stress and strain. Owing to the difference in weld deposited area, the cooling rate for the partial penetration condition is more rapid than for full penetration. Furthermore, in terms of welding residual stress, the full penetration condition is preferable to the partial penetration condition.     

Al-Zn-Mg系三元合金闪光对焊接头层状裂纹研究

层状裂纹是7003铝合金挤压材料对焊接头中最主要的缺陷之一。本文通过金相和断口观察,指出层状裂纹的性质和形貌特征,同时较深入地讨论了其产生与原材料状态、对焊温度场及应力场形态及变化规律的相互关系。提出通过提高顶锻速度、使用对口强迫成形模式完全可以消除层状裂纹。控制有电顶锻时间,没有层状裂纹的7003铝合金闪光对焊优质接头接近于母材塑性。     

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.     

核电站钢制安全壳SA738Gr.B钢焊缝裂纹产生原因分析及预防

针对国内某核电工程钢制安全壳闸门插入板与筒体之间的焊缝产生裂纹的实际情况,重点围绕焊接过程质量控制,焊接热裂纹、冷裂纹、层状撕裂、应力腐蚀裂纹以及再热裂纹产生的原因进行了详细分析,确定了SA738Gr.B钢焊缝裂纹产生的原因和制定了合理的预防措施,避免裂纹再次产生,为后续工程焊接工艺制定提供了参考。     

SA738Gr.B钢焊缝裂纹产生原因分析及处理

钢制安全壳是核电站的第三道安全屏障,其作用是在事故工况下,阻止放射性物质向环境逸散。焊接是钢制安全壳制作安装阶段的重要加工工艺方法,焊接裂纹缺陷的存在将影响钢制安全壳的质量,对核电站的安全运行造成极大的安全隐患。针对国内某核电工程钢制安全壳闸门插入板与筒体之间的焊缝产生了裂纹的实际情况,重点围绕焊接过程质量控制,详细分析了焊接热裂纹、冷裂纹、层状撕裂、应力腐蚀裂纹以及再热裂纹产生的原因,通过分析确认SA738钢Gr.B钢焊缝裂纹为再热裂纹,并结合工程实际提出了预防措施和裂纹缺陷处理方法,为后续工程焊接工艺制定提供了参考。     

三通护板裂纹失效分析

通过对施焊时开裂的三通护板进行渗透检测、宏微观断口形貌分析、金相检验、显微硬度检验以及力学分析,对三通下护板裂纹产生原因进行分析。结果表明：裂纹成锯齿状,具有层状撕裂特征,为穿晶＋沿晶（少量）混合断裂方式;断面上可见氧化皮,该裂纹为层状撕裂裂纹。裂纹附近存在带状粗大铁素体,裂纹沿带状铁素体扩展;三通下护板生产过程中的焊道没有完全切除,残留焊道处粗大带状铁素体力学性能差,是裂纹产生的直接原因。     

镁合金Az31B的电阻点焊

对镁合金AZ31B进行点焊研究，确定出合理的工艺参数，进行了力学性能试验，包括撕裂试验和拉剪试验，分析了个别试件缺陷产生的原因，为进一步工作提供了有益的指导。     

铝合金非熔化极直流正接氦弧焊氧化膜撕裂机理

采用高速摄影观察了不同气体流量下铝合金非熔化极直流正接氦弧焊焊接过程中电弧的形态及氧化膜撕裂过程. 观察测量结果表明,在试验参数范围内氦气流量的增加减弱了氧化膜的撕裂程度,但提升了焊缝深宽比及电弧能量效率. 氦弧焊阳极产热功率的提升削弱了氧化膜之间的化学键强度,产生了氧化膜撕裂现象. 在静力学平衡方程基础上推导得出了熔池液面与电极所在平面交线的微分方程,解释了熔池液面下凹程度随氦气流量增加而增加的原因,同时熔池中心指向熔池边缘表面张力也随气体流量增加而减小,两种因素共同作用使氧化膜撕裂程度随气体流量增加而减弱.     

Microstructure and mechanical properties of tungsten inert gas welded–brazed Mg/Ti lap joints

The tungsten inert gas (TIG) welding–brazing technology using Mg based filler was developed to join AZ31B Mg alloy to TA2 pure Ti in a lap configuration. The results indicate that robust joints can be obtained with welding current in the range of 60–70 A and welding speed of 0·2 m min^?1. The joints were found to be composed of the coarse grained fusion zone accompanied with the precipitated phase of Mg₁₇Al₁₂, and a distributed Mg–Ti solid solution zone at the interface of Mg/Ti, indicating that metallurgical bonding was achieved. The maximum tensile–shear strength of 193·5 N mm^?1, representing 82·3% joint efficiency relative to the Mg alloy base metal, was attained. The optimised Mg/Ti joint fractured at Mg fusion zone upon tensile–shear loading, mainly caused by grain coarsening. Moreover, the fracture surface practically consisted of scraggly areas, which was characterised by equiaxed dimple patterns accompanied with a few lamellar tearing.     

Lamellar tearing

Lamellar tearing is a type of weld cracking which occurs in a joint on which a large restraint stress acts in the direction of the plate thickness (hereafter referred to as Z-direction) of a steel plate. The term 'lamellar tear' was first used by J E Jubb¹, D M Nicholls² and others of Cranfield University, UK in 1968 and means tearing in a lamellar form.