Causes and control of welding cracks in electron-beam-welded superalloy GH4169 joints

Welding joint of GH4169 alloy with a good formation was obtained. No macroscopic defects occurred in the joint. The weld had mainly a dendritic structure; the base metal was a solid solution of Ni, Cr, and Fe, and the strengthening-phase particles such as Ni3Nb were dispersively distributed along the grain boundary. The average tensile strength of the joint reached 743.7 MPa, and the Vickers hardness of the weld exceeded HV 300. Because of the segregation of the low-melting compound Ni3Nb at the grain boundary of the fusion zone, liquid cracks tended to occur as a result of welding stress. The formation of liquid cracks was inhibited by adding an alloying element, Mn, to the welding bath, because Mn diffused to the fusion zone and the high-melting phase Mn2Nb formed, and thus the overall properties of the joint were improved.

Equalization of Ti 6Al 4V alloy welded joint by scanning electron beam welding

The equalization of Ti 6Al 4V alloy welded joint with base metal on corrosion resistance, strength and ductility was studied. The solidification microstructure is transformed from 650 μm columnar grains to 100 μm equiaxed grains by scanning electron beam welding. The anodic polarization curve of 150 μm equiaxed grains coincides with that of base metal. Equal corrosion resistance between weld metal and base metal was obtained. Uniform microstructure and solute distribution are the basis of equalization. Corrosion rate of weld with 150 μm equiaxed grains is the lowest, 2.45 times lower than that of 650 μm columnar grains. Weld strength is 98% as much as that of base metal, yield strength ratio is 99.5%, which is 3.6% higher than that of base metal.

Detection and processing of molten-pool image of electron-beam deep-penetration welding based on visual sensing

A visual sensing system was developed. The system is suitable for titanium-alloy electron-beam welding, and senses and detects molten-pool dynamic processes. A suite of processing programs for colored molten-pool images in titanium-alloy electron-beam welding was developed using Matlab software; molten-pool edge images are completely obtained using the program. The Matlab software was used to write a program which could extract the molten-pool width. The functional relationship between the molten-pool width and penetration under the experimental conditions was obtained by a curve-fitting method, and provided the theoretical basis for further penetration control.

Analysis of ultrasonic C-scan image features and image processing for spot welding

A focused ultrasonic transducer is used for precise, step-by-step, surface ultrasonic svanuing iusgection of spot welds. Two methods for generating characteristic data matrices of ultrasonic echo signals of the spot welds are established. One is based on the ultrasonic echo amplitude and the other is based on frequency spectrum. Both methods generate scamping inspection data arrays and provide clear C-scan images. Based on C-scan noise reduction, the Krisch edge detection operator for edge detection-a gray window transform-reflects the shapes of the spot welds and allows quantitative determination of their size. The method based on the ultrasonic echo amplitude provides a greater quantitative detection accuracy.

Feature Extraction of Sectorial Scan Image of Thick-Walled Electron Beam Welding Seam Based on Principal Component Analysis

A feature extraction method was proposed to sectorial scan image of Ti-6Al-4V electron beam welding seam based on principal component analysis to solve problem of high-dimensional data resulting in timeconsuming in defect recognition. Seven features were extracted from the image and represented 87. 3% information of the original data. Both the extracted features and the original data were used to train support vector machine model to assess the feature extraction performance in two aspects: recognition accuracy and training time. The results show that using the extracted features the recognition accuracy of pore,crack,lack of fusion and lack of penetration are 93%,90.7%,94.7% and 89.3%,respectively,which is slightly higher than those using the original data. The training time of the models using the extracted features is extremely reduced comparing with those using the original data.

The Application of Electron-Beam Welding in Pellet Mold Preparation

This paper provides insight into the application of electron-beam welding in pellet mold preparation,highlighting the importance of the combination of electron-beam welding and pellet mold preparation in the fields of microstructure joining and micro-and nanostructure preparation.Precise material joining and microstructure fabrication can be achieved by the precise control of electron-beam welding and the shape adjustment of pellet molds.These applications hold significant potential in the modern industrial field,providing robust support for the development of new materials and the growth of the petrochemical industry.This paper asserts that in the future,the ongoing development of electron-beam welding and pelletizing template technology will unlock new possibilities in the field of petrochemicals,fostering progress in science and technology.

Electron-Beam Welding Joint Strength of Dissimilar Materials

This paper provides an in-depth discussion of the joint strength of electron beam welding of dissimilar materials.The effect of welding parameters and material properties on the joint strength was analyzed,and an argument for the optimal parameter combination is presented.Electron-beam welding technology offers several advantages,including high energy density and the ability to create fine weld seams.However,it also presents certain challenges,such as the complexity of welding parameters and the potential generation of brittle phases.The analysis conducted in this paper holds significant importance in enhancing the quality and efficiency of dissimilar material welding processes.

Rapid ultrasonic C-scan on image test for spot welding based interpolation

In this paper, ultrasonic C-scan test of spot welds for stainless steel has been studied. It is concluded that large scanning step length contributes to high testing efficiency, however, the low-resolution C-scan image generated cannot be used to assess spot welding quality reliably. Based on bicubic image interpolation, the C-scan image in low resolution with the large step length 1 000 ~xm is subdivided and reconstructed. By this means, the C-scan image resolution is greatly enhanced and testing results obtained are satisfactory, realizing rapid assessment of spot welds. The results of rapid ultrasonic C-scan test fit the actual metallographic measured value well. Mean value of normal distribution of error statistics is O. 006 67, and the standard deviation is O. 087 11. Rapid ultrasonic C-scan test based on image interpolation is of high accuracy and excellent stability.

Microstructures and Plane Energy Spectra of X80 Pipeline Steel Welded Joints by Submerged Arc Automatic Welding

X80 pipeline steel was welded with submerged arc automatic welding, the microstructures, cavity sizes, fusion depths and plane scanning of chemical elements in the welded zone, fusion zone, heat affected zone and base steel were observed with OM（optical microscope） and SEM（scanning electron microscope）, respectively. The experimental results show that there is main acicular ferrite in the base steel and welded zone, the microscopic structure of fusion zone is a blocked bainite, and the heat affected zone is composed of multilateral ferrite and pearlite. M-A unit of the welded zone is the main factor to strengthen the welded zone, composed of acicular ferrites. The percentage of cavities in the welded joint is less than that in the base steel, which is beneficial to increasing its mechanical performance and corrosion resistance. The fusion depth in the fusion zone and welded zone is 101.13 μm and 115.85 μm, respectively, and the distribution of chemical elements in the welded zone is uniform, no enrichment phenomena.

Joining of hybrid AA6063-6SiCp-3Grp composite and AISI1030 steel by friction welding

Joining of metals and aluminium hybrid metal matrix composites has significant applications in aviation,ship building and automotive industries. In the present work, investigation is carried out on Friction Welding of AISI 1030 steel and hybrid AA6063-6 SiC_p-3 Gr_pcomposite, that are difficult to weld by fusion welding technique. Silicon carbide and graphite particle reinforced AA6063 matrix hybrid composite was developed successfully using stir casting method and the joining feasibility of AISI1030 steel with AA6063-6 SiC_p-3 Gr_p hybrid composite was tried out by friction stud welding technique. During friction stage of welding process, the particulates(SiC & Graphite) used for reinforcement, tend to increase the viscosity and lead to improper mixing of matrix and reinforcement. This eventually results in lower strength in dissimilar joints. To overcome this difficulty AA1100 interlayer is used while joining hybrid composite to AISI 1030 steel. Experimentation was carried out using Taguchi based design of experiments(DOE) technique. Multiple regression methods were applied to understand the relationship between process parameters of the friction stud welding process. Micro structural examination reveals three separate zones namely fully plasticized zone, partially deformed zone and unaffected base material zone. Ultra fine dynamically recrystallized grains of about 341 nm were observed at the fully plasticized zone. EDX analysis confirms the presence of intermetallic compound Fe_2 Al_5 at the joint interface. According to the experimental analysis using DOE, rotational speed and interlayer sheet thickness contribute about 39% and 36% respectively in determining the impact strength of the welded joints. It is found that joining with 0.5 mm interlayer sheet provides efficient joints. Developed regression model could be used to predict the axial shortening distance and impact strength of the welded joint with reasonable accuracy.

Fatigue Behavior of a Dissimilar Aluminum Alloy Welding Joint With and Without Natural Defect

In order to investigate the influence of natural defect on the fatigue behavior of 5A06/7A05 dissimilar aluminum alloys welding joint,fatigue tests of two types of specimens with and without defects were carried out systematically under stress amplitude control conditions (stress ratio R=0.1) at normal temperature in laboratory air condition.Furthermore,a new parameter,i e,fatigue defect effect factor (FDEF) was introduced to assess the effect of defect on fatigue strength.The fatigue failure analysis was conducted as well to compare the fatigue and fracture behavior of the two types of specimens.The results show that:(1) natural defects have a strong effect on the fatigue lives of welding joint,and the differences between the specimens with and without defects can reach 80 times under a same theoretical net sectional stress;(2) the FDEF parameter introduced is effective to deal with the defect effect,and the FDEF decreases along with the increase of fatigue life.The mean relative error between the experimental data and predicted fatigue strength based on the FDEF is 10.2%;(3) the macro fracture of both types of specimens have three typical zones,i e,fatigue source zone,crack propagation zone and final fracture zone,while there are more than one fatigue sources for specimens with natural defects.The overall pattern of crack propagation zone and fracture zone are quite similar,but the morphologies are different in details.

Sensitization behavior of welded 304L austenitic stainless steel using scanning vibrating probe

The sensitization behavior of special structures such as weld seams reduces the resistance of materials to intergranular corrosion and intergranular stress corrosion cracking. How ever,the degree of sensitization in the seams could not be detected by the traditional electrochemical potentiokinetic reactivation（ EPR） measurement using the double loop method. Results based on non-effective tests bring risks to the application of these materials. In this study,the degree of sensitization in w eld seams are determined by using the scanning vibrating probe（ SVP）method.

超声F-Scan成像技术检测双金属复合材料的方法

随着技术和需求的发展,人们对检测的要求不再仅仅是判断缺陷的有无,而是希望能够通过直观的图像显示出缺陷的全貌,从中得到可靠的分析结果。对于一些较薄的金属复合材料,手工检测存在很大难度,甚至无法进行检测。针对小构件、异形构件、薄壁金属复合材料工件,提出利用超声特征扫描成像检测系统对金属复合材料的质量进行检测。通过对时域超声信号的分析,从超声信号本身以及材料缺陷两方面进行特征提取和分析成像,给出结合层连接质量的定量化直观结果,减少扩散焊缺陷的漏检和误检问题,实现对双金属复合材料扩散焊质量的无损检测与评价。

Ultrasonic testing for laser welded joint of stainless steel

Two dimensional scan for laser welded joint of stainless steel was implemented according to the reflection characteristics of ultrasonic. B-scan imaging technique was applied to characterize the fusion state in the joint and distinguish welding detects such as incomplete penetration. Calculation of weld width at the interface of the two plates and imaging of the weld cross section were accomplished. Experimental results show that rapid nondestructive testing can be achieved by this method with threshold value of 30% attenuation degree. The calculation error is less than 0. 25 mm.

Effects of Severe Plastic Deformation and Heat Treatment on Transformation Behavior of Explosively Welded Duplex TiNi-TiNi

The effects of severe plastic deformation and heat treatment on the transformation behavior of explosively welded duplex TiNi-TiNi shape memory alloys （SMAs） were investigated by differential scanning calorimeter （DSC） measurements. The explosively welded duplex TiNi-TiNi plate of 0.7 mm thickness was cold-rolled at room temperature to a 60% reduction in thickness and then annealed at different temperatures for different durations. The results showed that low temperature （623-723K） heat-treatment led to the crystallization of the amorphous region, and re-crystallization occurred in the specimens annealed at higher temperatures （over 873 K）. Research indicated that the change of martensitic transformation temperature is due to the change of internal stresses with increasing heat treatment temperature. The change of annealing time also led to a change in martensitic transformation temperature, which was associated with the precipitation and decomposition of Ti3Ni4 in TiNi-1.

Microstructure and pitting corrosion of shielded metal arc welded high nitrogen stainless steel

The present work is aimed at studying the microstructure and pitting corrosion behaviour of shielded metal arc welded high nitrogen steel made of Cromang-N electrode. Basis for selecting this electrode is to increase the solubility of nitrogen in weld metal due to high chromium and manganese content. Microscopic studies were carried out using optical microscopy(OM) and field emission scanning electron microscopy(FESEM). Energy back scattered diffraction(EBSD) method was used to determine the phase analysis, grain size and orientation image mapping. Potentio-dynamic polarization testing was carried out to study the pitting corrosion resistance in aerated 3.5% NaCl environment using a GillAC electrochemical system. The investigation results showed that the selected Cr-Mn-N type electrode resulted in a maximum reduction in delta-ferrite and improvement in pitting corrosion resistance of the weld zone was attributed to the coarse austenite grains owing to the reduction in active sites of the austenite/delta ferrite interface and the decrease in galvanic interaction between austenite and delta-ferrite.

基于摆动激光扫描的GMAW焊缝成形调控

将摆动激光与GMAW工艺复合,利用“8”字形摆动激光扫描液态熔池,对其温度场和流场进行调控,以改变熔池温度梯度,主动调控熔池流动以改善焊缝成形.在6061铝合金板材表面进行堆焊试验,重点探究了光丝间距、摆动幅度、激光功率对于焊缝成形的影响,采用高速摄像机拍摄激光扫描熔池过程.结果表明,摆动激光扫描可以有效抑制成形缺陷的发生,当摆动激光扫描熔池中部时可以获得最佳的焊缝成形效果.摆动激光扫描降低了熔池温度梯度分布,同时激光扫描产生的激光蒸发反力可以驱动熔池流动,促进了液态熔池的流动铺展,从而有效抑制了不规则焊缝成形缺陷,减少焊缝内部气孔和裂纹缺陷.调节摆动激光摆幅可以在一定范围内对焊缝宽度进行调控.

高强低合金钢焊接接头在海水中的初期腐蚀行为

通过电化学方法和表面分析技术,研究了高强低合金钢焊接接头在海水中的初期腐蚀行为。结果表明:浸泡前母材区的初始电位较低,腐蚀倾向最大,浸泡后母材区电位波动最大;该焊接接头在初期腐蚀呈现阳极溶解速率由高向低转变的特征,其中母材区阳极溶解电流密度最大;焊接接头在海水中的初期腐蚀以全面腐蚀和点蚀两种形式发展,腐蚀产物主要成分为α-Fe_(2)O_(3),α-FeOOH和γ-FeOOH。在海水中浸泡初期,焊接接头各区域耐蚀性从低到高排序为母材区、热影响区、焊缝区。

海洋环境下高强钢及焊缝连接粗糙度参数分析

为研究海洋浪溅区环境下高强钢及焊缝连接的腐蚀形貌特征和时变效应,通过微观扫描测试Q690高强钢及焊缝连接表面粗糙度参数,得到表面峰最大高度(Sp)、表面谷最大深度(Sv)、表面轮廓偏斜度(Ssk)及表面轮廓峭度(Sku)随腐蚀时间的演化规律,并进行回归分析与对比.结果表明:通过分析粗糙度参数随腐蚀时间的变化过程,以及对比Q690高强钢母材与焊缝连接扫描区域的差异性,能准确地判断其腐蚀程度及特征,从而为海洋环境下国产高强钢损伤评估提供新的途径.

扫描路径对DP780双相钢激光点焊成形特征及组织性能的影响

为了探究激光焊接DP780双相钢的工艺特性,开展了不同扫描路径下激光点焊DP780双相钢的实验,对比不同摆动路径对焊缝成形、组织及剪切性能的影响。结果表明:不同扫描路径下激光点焊的焊缝组织相似:焊缝区组织为板条马氏体、贝氏体以及少量铁素体,热影响区组织为尺寸不均匀的块状铁素体、贝氏体以及少量马氏体。施加不同形式的扫描方式,使焊缝内铁素体和贝氏体在一定程度上有所增加,马氏体尺寸减小。扫描激光焊接头焊缝区的平均硬度有所降低,但软化区内最小硬度明显升高;扫描激光焊在一定程度上增大焊缝熔宽,降低焊缝熔深,可抑止气孔的形成;扫描激光焊接头的断口形貌主要由光滑界面和韧窝组成。