Studying sources of acoustic emission during the cooling of a weld seam with the use of cluster analysis

Acoustic-emission (AE) signals localized during cooling of a weld seam were analyzed. The hazard degree of flaws (faulty fusions, cracks in the root of a weld seam, etc.) was studied using cluster analysis in the parameters of AE signals. Flaws were simulated via introduction of titanium and duralumin inserts into a weld seam. The results of metallographic investigations of specimens with artificial and actual flaws were analyzed. Localization of AE signals was performed for the specimens studied, and a time distribution taking into account the clustering of the total count and energy of AE signals was constructed.     

基于"生死单元"技术的焊缝缺陷模拟

应用有限元方法，计算分析带几何缺陷焊接接头力学性能。通过杀死焊接接头有限元模型中相应位置的单元，模拟存在的几何缺陷。计算分析带有气孔或咬边缺陷的焊接接头应力分布特性和应力集中程度，验证了应用生死单元模拟几何缺陷的有效性。通过对建模方法的比较，表明生死单元技术能够灵活模拟缺陷。     

Studying the correlation of the informative parameters of acoustic-emission signals with the destruction processes in specimens with welding flaws

The results of acoustic-emission (AE) testing of flaws in steel specimens during welding and subsequent loading until destruction in MTS-50 and MTS-250 electrohydraulic machines are presented. Flaws were simulated via faulty fusions or the introduction of titanium and duralumin inserts. During loading, some specimens were broken along the weld seam and the other specimens were broken in the near-seam zone. A comparative analysis of the distributions of the informative parameters of AE signals, which are recorded during different types of specimen fracture, is presented.     

Clustering of sources of acoustic-emission signals by the leading-edge rise rate

It is shown that the method of clustering by the leading-edge rise rate of the envelope of an acoustic-emission (AE) signal makes it possible to reduce the time of calculation of the coordinates of flaws as compared to the clustering by shape. The developed technique realizes the on-line localization of massive flows of AE signals with an accuracy sufficient for practical application. The practical parameters of using the method for operation on a steel sheet with a simulator obtained for a statically loaded duralumin specimen and for welding of steel specimens with aluminum and titanium inserts are considered.     

低温分离器用钢板及其焊接接头性能的试验研究

介绍西气东输源头的关键设备（低温分离器）用钢及其焊接接头性能的试验研究。试验结果表明：虽然某些炉批号的09MnNiDR钢板沿厚度方向的组织和性能存在明显的差异，且冲击功有较低的值出现；此外，焊接时要获得没有超标缺陷的焊缝也有难度，但其钢板及没有超标缺陷的焊接接头的性能是可以满足设备的使用要求。     

焊后热处理对BHW35钢焊接接头组织性能的影响

对采用E7015-D2焊条焊制的BHW35钢厚壁对接焊接接头分别采取不同冷却速度的焊后热处理制度,进行了弯曲、拉伸、冲击韧性等力学性能、金相组织及扫描电镜断口分析对比,指出采用正火＋回火空冷＋消应力退火热处理能使焊接接头组织及强韧性满足使用要求,而缓冷工艺使母材性能不能很好恢复,接头横向拉伸强度低于母材规定值的下限,冲击韧性低于空冷工艺,抗裂纹扩展能力下降。断口特征佐证了上述结果。     

Determination of the magnetic properties of separate zones of welds and the width of welded joints based on magnetic measurements

The magnetic characteristics of pipe steel specimens containing welded joints of different widths were investigated, both under the conditions of a closed magnetic circuit and using overlaid transducers in the form of a half-closed magnetic circuit. The parameters correlating with the welded joint width were determined. The possibility of using the measured magnetic characteristics for deter-mining magnetic properties of separate zones of a welded joint and the welded joint width was demonstrated.     

某发动机动力涡轮轴承座氩弧焊工艺研究

动力涡轮轴承座是某航空发动机的重要部件,在对其上的各种安装座氩弧焊后出现了焊接裂纹,严重影响了产品质量和交付进度.本文通过荧光检查和冶金分析,确定了氩弧焊焊接裂纹的性质为结晶裂纹,并针对结晶裂纹的产生机理和预防措施,调整了焊接参数.试验验证表明,采用增设焊接接头坡口、采用分段式焊接、改进焊缝收弧方式以及控制焊接速度等工艺措施,能够有效地防止结晶裂纹的产生,提高产品的质量.     

Obtaining flaw images by the SAFT method taking the variable velocity of sound in a test object into account

A modification of the SAFT method for obtaining flaw images in test objects containing three regions with different velocities of sound (SV) is proposed. Complex composite welded joints and repair welds are classified as objects in which the SV in a welded joint may differ from the velocity in a parent metal by >5%; therefore, a high-quality image of flaws can be obtained by taking different SVs into account. To solve this problem, a method for obtaining a test object with three regions with different SVs is proposed. The delays of propagating ultrasonic pulses were calculated using the Fermat principle. The results of reconstructing flaw images in a 300 welded joint from echo signals obtained as a result of numerical simulation by the finite-element method are presented. The images obtained by the SAFT method without taking different SVs into account are displaced from their true position, thus they do not allow determination of their coordinates and location. Consideration of different SVs allows one to obtain unshifted reflections of flaw images and, hence, evaluate the types and dimensions of flaws more accurately.     

Determination of Welded Joint Flaw Dimensions on the Basis of Scanned X-Ray Images

A method of calculating the depth of incomplete fusion of a welded joint root on the basis of its X-ray image is outlined. The results of approbation of the method using artificial and natural flaws are given.     

Ti-6Al-4V钛合金板与304L不锈钢网的扩散焊

分别在800℃、825℃、850℃焊接温度、30 m in保温时间,3 MPa焊接压力下,进行Ti-6A l-4V钛合金板与304L不锈钢网的真空扩散焊接。对接头组织结构与化学元素扩散进行了扫描电镜与能谱分析,并测试了接头的剪切强度。结果表明:不添加中间过渡层金属,可以成功地实现钛合金板与不锈钢网的扩散焊接,并使接头的剪切强度达到90 MPa以上。不锈钢网中的Fe、N、iCr扩散并固溶到钛合金中,稳定了β相,使钛合金在一定深度上,其组织由原来的α+β双相结构转变为单相的β相。不锈钢中的Cr,由于钛合金中Ti的扩散进入,而在界面发生了上坡扩散现象。这种Cr在不锈钢一定深度内的富集,形成窄长的富Cr区域,冷却后转变为硬脆的σ相。但在焊接接头中没有发现明显其它的金属间化合物或氧化物相的生成,使得接头的机械性能得到了很好的保证。     

Low-cycle fatigue of a friction stir welded 2219-T62 aluminum alloy at different welding parameters and cooling conditions

Strain-controlled low-cycle fatigue tests and microstructural evaluation were performed on a friction stir welded 2219-T62 aluminum alloy with varying welding parameters and cooling conditions. Cyclic hardening of friction stir welded joints was appreciably stronger than that of the base material. The cyclic stress amplitude increased, and plastic strain amplitude and fatigue lifetime slightly decreased with increasing welding speed from 60 to 200 mm/min but were only weakly dependent of the rotational rate between 300 and 1,000 rpm with air cooling. Friction stir welded joints with water cooling had higher stress amplitude and fatigue life than that with air cooling. Fatigue failure of the joint occurred in the HAZ where the soft zone was present, with crack initiation from the specimen surface or near-surface defect and crack propagation characterized by typical fatigue striations.     

焊接接头J积分断裂参量的有限元数值分析

对中心裂纹和单边裂纹板远场均匀拉伸条件下的焊接接头试件做了有限元计算和分析，得出了一些适合不同焊接接头的J积分测试方法和计算公式。     

The UMD-101M plant for automated bulk magnetic nondestructive testing of quality of electric-welded pipes

The optimal structural scheme and special features of the new automated plant for magnetic nondestructive testing of electric-welded pipes in a technological industrial line, which meets contemporary demands, are considered. It has been shown that the use of computer technologies and thin-filmed high-resolution transducers provides significant improvement of operating possibilities of a flaw detector and makes it possible to detect, not only such flaws as discontinuities in metal and displacement of edges, but also flaws caused by failures in welding regimes, such as burns and cohesion of edges near a welded joint.     

力学性能不均匀性对焊接接头三点弯曲试样塑性区发展规律的影响

利用弹塑性有限元方法对焊接接头试样在三点弯曲试验中塑性区的发展情况进行了计算。分析了不同的裂纹深度、强度组配，焊缝宽度以及不同位置裂纹的焊接接头试样对塑性区形状发展的影响规律。分析结果显示，不同强度组配和几何特征的焊接接头试样对裂纹尖端塑性区的发展规律有较大的影响，由于裂纹尖端拘束程度的不同会造成塑性区的形状和尺寸的改变，因此在做焊接接头试样三点弯曲试验时，可能会得出与均质材料试样不同的驱动力曲线     

Fatigue analysis of spot welded joints in suspension mounting part

Experimental and numerical analyses were performed to characterize the fatigue behavior of spot welded joints in suspension mounting of a passenger car body. Static and fatigue tests were carried out for the tensile-shear and cross-tension specimens. S-N curve and fatigue strengths were obtained from the fatigue test of various specimens. Nonlinear finite element analysis showed that fatigue behavior of spot welded joints could be well estimated in terms of Von Mises stress at the nugget edge. Fatigue behavior of spot welded joint was represented by Von Mises stress better than the fatigue load.     

钛制容器设计中关于标准的两个问题

钛材标准升级后,设计标准与新材料标准中同一钛材牌号的力学性能已完全不同,实践中新旧钛材牌号易于混淆,可能因此导致受压元件强度不足,应引起重视。同时,还就新版压力容器焊接规程中钛-钢复合板对接接头的坡口形式展开讨论,针对确保基材焊透、防止钛-钢互熔及铁污染的坡口结构提出意见。     

Effect of Heat Sink and Cooling Mediums on Ferrite Austenite Ratio and Distortion in Laser Welding of Duplex Stainless Steel 2205

In order to control the ferrite and austenite percentage in duplex stainless steel welding, many researchers try to change the laser welding parameters and cooling medium, but ignore to study the influence of heat sink e ect on weld strength. In this work, the e ect of aluminium heat sink and varying cooling medium on the laser welding of duplex stainless steel(DSS) 2205 is studied. The 2 mm thick DSS sheets welded with pulsed Nd: YAG laser welding machine by varying the cooling medium(air and oil) and an aluminium plate used as a heat sink. The welded specimens tested for tensile strength, micro-hardness, distortion, microstructure and radiography analysis. The faster cooling rate in the oil quenching process enhances the ferrite percentage compared with air-cooled samples. But the faster cooling rate in oil quenching leads to more distortion and using aluminium as a heat sink influenced positively the distortion to a small extent. The lower cooling rate in air quenching leads to a higher tensile strength of the welded specimen. The objective of this work is to analyse experimentally the e ect of cooling medium and heat sink in the mechanical and metallurgical properties of laser welded duplex stainless steel.     

冷却方式对不锈钢板翅结构强度和微观组织的影响

对采用镍基钎料BNi-2的304不锈钢板翅结构进行真空钎焊试验,讨论冷却方式对结构强度和微观组织的影响。利用扫描电镜（SEM）对钎焊接头微观组织进行观察;利用能谱分析（EDS）对接头化学成分进行研究。研究结果表明,在其它钎焊工艺参数不变的情况下,冷却方式对304不锈钢板翅结构的强度影响很大。采用现有文献使用的充氮快速冷却的方式,导致钎焊接头产生了较多的裂纹和孔洞,绽得强度降低;采用改进的缓慢冷却方式,即从钎焊温度到620℃,让其自由冷却,当炉中温度降到620℃时,向炉内充氮气并同时启动风机快速冷却。利用高温蠕变松弛原理,释放部分钎焊残余应力,减少了裂纹等缺陷的产生,极大提高了304不锈钢板翅结构的强度。     

TC17-TC11异种钛合金线性摩擦焊接头弯曲性能分析与改善

分析了TC11和TC17异种钛合金线性摩擦焊接接头的弯曲性能,探寻了焊缝区弯曲塑性的薄弱区。通过测试焊接接头的硬度、分析焊缝区组织、断口形貌,特别是弯曲试样表面滑移线形态,研究了弯曲断裂机制。通过焊后超声冲击以及高温固溶+时效热处理,探索了改善焊接接头弯曲塑性的工艺方法。研究结果表明,采用接头弯曲性能试验,可以更好地表征TC11和TC17异种钛合金线性摩擦焊接接头焊缝区的宏观性能;经焊后时效热处理的线性焊接头的弯曲角度只有TC17母材的38%,TC11母材的30%。弯曲塑性是其力学性能的薄弱环节;焊合区及TC17侧变形区是接头弯曲塑性的薄弱区,弯曲断口均呈脆性断裂特征。焊合区断口为细小等轴晶粒的晶间断裂,焊接界面对TC17侧的滑移有明显的阻碍作用,容易在焊合区TC17侧形成微观裂纹;TC17变形区的弯曲起裂断口是大面积滑移剪切所形成的剪切韧窝,而TC17侧变形区晶粒大而长,有利于形成更长的滑移线和更集中的位错聚集,所以弯曲试验时TC17侧变形区最容易开裂。焊后进行超声冲击处理,在试件表面形成了约20 μm厚度的变形层,接头的弯曲角度相对提高34%;接头进行高温固溶+时效处理后,接头的弯曲塑性提高,最高平均弯曲角度达到31.2°,相对提高82%。为钛合金线性摩擦焊接接头的宏观塑性性能分析与改善提出了一个有意义的研究方向。