电弧超声对SiC_p/AlMMCs焊缝组织与性能的影响

以Ti合金作为填加材料,以氮氩混合气作为离子气,对SiCp/6061Al基复合材料进行电弧超声等离子弧原位合金化焊接,研究了电弧超声对等离子弧焊接头组织和性能的影响.结果表明,在不加超声时,焊缝中新生AlN相呈细长条状,Al3Ti相粗大,TiC,TiN等新生增强颗粒分布不均匀;在加入超声后,焊缝组织细密,TiC,TiN,AlN等增强相呈细小颗粒状存在,数量增加,且分布均匀,Al3Ti相尺寸减小,数量减少,从而有效改善了焊接接头的组织和性能,使焊接接头抗拉强度最大值达到225MPa,比不加超声时提高了约7%.     

Ti-Al-Si-Mg对SiCp/Al基复合材料等离子弧原位焊接焊缝组织和性能的影响

以填充自制药芯铝焊丝的形式向熔池内部直接添加Ti,Al,Si,Mg等金属元素,用氩氮混合等离子气体对SiCp/Al基复合材料进行等离子弧原位焊接.分析了Ti-Al-Si-Mg以及它们的氧化物对焊缝组织和性能的影响.结果表明,以Ti-Al-Si-Mg作为原位反应填充材料,可以有效抑制针状脆生相Al4C3的生成,改善熔池流...     

超声频电弧对SiCp/6061Al等离子弧焊缝微观组织的影响

应用高通滤波器原理设计了一台隔离耦合装置,实现了交流弧焊电源与高频 激励源的隔离与耦合,成功在交流电弧中激励出超声波.以自主研制的A1-5Ti-5Si药芯焊丝为填充材料对SiCp/6061A1基复合材料进行等离子弧原位合金化焊接,在不同频率电弧超声作用下研究了电弧超声频率对焊缝组织的影响.对比0(不加超声),30,40...     

钛/铝异种合金电弧熔钎焊接头界面特征及力学性能

采用AlSi5焊丝和交流TIG电弧实现了TC4钛合金和6056铝合金的熔钎焊连接,通过金相显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)和拉伸试验等方法评价了接头界面微观组织特征和力学性能.结果表明,当焊接电流为30,40和60 A时,界面反应层分别呈棒状、块状和锥状分布,过大的热输入使界面产生了粗大柱状金属间化合物层,冷却时在焊接内应力作用下产生了冷裂纹.金属间化合物主要为TiAl3相,Si元素偏聚其内形成过饱和固溶体.接头强度-焊接电流曲线出现了两次峰值强度.焊接电流为30 A时,熔钎焊接头平均抗拉强度为103 MPa.焊接电流为60 A时,电弧形态扩张使能量密度降低,接头强度出现第二次峰值.     

不平衡因子对药芯焊丝CO2气体保护焊焊缝金属韧度的影响

研究了由氮化物形成元素Al,Ti等控制的不平衡因子B对低合金药芯焊丝CO2气体保护焊缝金属韧度的作用.结果表明,在药芯具有氧化性的条件下,不平衡因子B对焊缝金属韧度的作用仍然明显.并且相比实心焊丝CO2气体保护焊而言,不平衡因子B的最佳值增大了.分析表明,药芯焊丝自身的氧化性是不平衡因子B增大的原因.在不平衡因子B由小增加到最佳值的过程中,焊缝金属组织由粒状贝氏体 板条铁素体逐渐向以夹杂物为核心的针状铁素体组织发展,由此其韧度逐渐改善;而当不平衡因子B超过最佳值较多时,过剩的氮化物形成元素进入铁素体固溶而导致脆化.     

等离子弧焊接SiCp/Al基复合材料焊缝“原位”合金化分析

采用等离子弧焊焊接SiCp／Al基复合材料,以Ar＋N2为离子气,并以Ti作为合金化填充材料,研究了焊缝“原位”合金化元素Ti对焊缝显微组织的影响。结果表明,采用焊缝原位合金化方法焊接SiC颗粒增强铝基复合材料（sicp／A1MMCs）,可以有效抑制焊缝中针状脆性相Al4C3的形成,并且由于耶的加入,改善了增强相和Al基体之间的润湿性,形成了稳定的熔池,得到以均匀分布的TiN、AlN等为增强相的新型铝基复合材料焊缝,焊接性能得到有效提高。同时还研究了Ti的添加量对焊缝显微组织的影响,结果发现,随着耶含量的增加,焊缝中还生成如Ti5Si3等新的增强相。焊缝“原位”合金化等离子弧焊接是焊接SiCp／Al基复合材料的一种新方法。     

Effect of hot dip aluminising on interfacial microstructure and mechanical properties of Ti/Al joint by TIG arc welding brazing

Abstract

The joint of Al 5A06 and aluminised Ti–6Al–4V dissimilar alloys was achieved by means of tungsten inert gas arc welding brazing. The effect of aluminized coating on the spreading behaviour of filler metal on Ti substrate was studied. The spreadability of liquid filler metal on the Ti substrate was enhanced obviously due to the presence of aluminised coating. The interfacial reaction layer was characterised by a uniform lamellar layer of TiAl₃ intermetallic, with a thickness of 1 μm. Sound joints with well appearance were obtained, and the optimised tensile strength of the joint reached 216 MPa. The failure initiated from the interfacial layer at the root face and then propagated within the weld seam at the upper part of the joint. Capable welding parameters were broadened by the presence of aluminised coating for dissimilar metal joining of Ti/Al.     

Influence of alloy elements on microstructure and mechanical property of aluminum–steel lap joint made by gas metal arc welding

5052 aluminum alloy sheets and galvanized mild steel sheets were joined in lap configuration by alternate-current double pulse gas metal arc welding with pure Al, Al–5Si, Al–12Si and Al–4.5Mg (wt%) filler wires. The effect of alloying elements on the microstructure of intermetallic compounds (IMC) layers formed between weld seam and steel, and tensile strength of the resultant joints were investigated. The thickness of IMC layer in all samples varied along the cross-section of the joint, the intermediate part of the IMC layer was thicker than the head and root parts. The diffusion of Si into Fe₂Al₅ sub-layer could restrain the growth of Fe₂Al₅ sub-layer and IMC layer, and joint's mechanical property improved with the increasing Si content in Fe₂Al₅ phase. Due to the high hot crack sensitivity of Al–4.5Mg alloy, cracks generated at the root of joint made with Al–4.5Mg filler, resulting in poor mechanical property.     

Gas tungsten arc welding of titanium using flux cored wire with magnesium fluoride

Abstract

Grade 2 Ti–CP was gas tungsten arc welded using flux cored (FC) wires and flux pastes that contained various MgF₂ contents. The effects of MgF₂ on bead morphology, chemical composition and hardness of weld bead were investigated and interpreted. With an increase of MgF₂ content in the flux paste, depth/width ratio of weld bead increased gradually with little variation in interstitial element contents and hardness. Weld bead made with cold FC wire feed showed even deeper and narrower bead, indicating the greater effectiveness of wire feed than flux paste on weld penetration. While the 50% MgF₂ FC wire produced complete slag coverage and smooth weld bead surface, 85% MgF₂ wire resulted in incomplete slag coverage and rough weld surface. Arc spectroscopy revealed that the 50% MgF₂ FC wire produced plasma spectrum with atomic and ionised titanium peaks, which is an indication of a high temperature arc and a larger amount of flux vapours in the arc. Therefore, it is believed that deep weld penetration associated with high MgF₂ fluxes in this experiment is caused by arc constriction, resulting from the greater amount of flux vapours owing to high arc temperature.     

Influence of shielding medium on deposition rate in arc welding

Abstract

The aim of this paper was to determine the influence of the shielding medium and the type of welding flux on the deposition rate in arc welding. Previous studies have stated that the shielding medium has no influence on deposition rate and a number of mathematical models derived by previous authors confirm this. In the present work it was found that a larger quantity of material was deposited when using helium, argon, or CO₂ as shielding. With constant wire feedrate and constant power, arc current was lowest with helium shielding and highest with argon shielding; with just wire feedrate constant, arc power was lowest with helium and CO₂ shielding and highest with basic flux. It was also found that arc welding efficiency was highest for helium shielding and lowest for submerged arc welding with basic flux.     

Effects of flux composition on the element transfer and mechanical properties of weld metal in submerged arc welding

Submerged arc welding was performed using metal-cored wires and fluxes with different compositions. The effects of wire/flux combination on the chemical composition, tensile strength, and impact toughness of the weld metal were investigated and interpreted in terms of element transfer between the slag and the weld metal, i.e., Δ quantity. Both carbon and manganese show negative Δ quantity in most combinations, indicating the transfer of the elements from the weld metal to the slag during welding. The amount of transfer, however, is different depending on the flux composition. More basic fluxes yield less negative Δ C and Δ Mn through the reduction of oxygen content in the weld metal and presumably higher Mn activity in the slag, respectively. The transfer of silicon, however, is influenced by Al₂O₃, TiO₂ and ZrO₂ contents in the flux. Δ Si becomes less negative and reaches a positive value of 0.044 as the oxides contents increase. This is because Al, Ti, and Zr could replace Si in the SiO₂ network, leaving more Si free to transfer from the slag to the weld metal. Accordingly, the Pcm index of weld metals calculated from chemical compositions varies from 0.153 to 0.196 depending on the wire/flux combination, and it almost has a linear relationship with the tensile strength of the weld metal.     

Effect of alloying elements of steel wire on the structure and properties of coatings in electric arc spraying

This paper reports the results of a comparison between the mechanical characteristics of butt joints in 3.0 mm thick Ti6Al4V titanium alloy sheets, made by laser welding with no filler material and by laser–arc hybrid welding. Vickers hardness tests have been performed on cross-sections of the beads obtained. In particular, the influence of the gap between the sheets in test welds performed using CO₂ laser–MIG hybrid welding has been analysed. Cross-sections of the weld beads obtained with several different gap sizes have been analysed morphologically. The welded joints have been subjected to draw testing, and joint deformation behaviour has been analysed using an optical deformation measurement system based on stereoscopic image capture (ARAMIS 3D analysis system).     

Effect of lattice matching degree and intermetallic compound on the properties of Mg/Al dissimilar material welded joints

The welding of Mg/Al dissimilar materials with different filler metal was investigated, and the quantities and kinds of intermetallic compounds were discussed. In addition, the matching degrees between base metal and intermetallic compounds were defined and calculated, and the effect of different quantities of each intermetallic compound on the property of welded seam was investigated. The results indicated that the welded seam was composed of Al₃Mg₂ and Al₁₂Mg₁₇ by Mg/Al directly gas tungsten arc butt welding, and only one intermetallic compound of MgZn₂ formed in the welding seam using Zn and Zn–xAl filler metal. The tensile strengths of the joints increased with the increase of the matching degrees between the intermetallic compounds and the base metal when the welded seam contained different intermetallic compound. Meanwhile, the tensile strengths of the joints are decreased with the increase of intermetallic compound content when the welded seams contained the seam intermetallic compound.     

Investigation on TIG arc welding–brazing of Ti/Al dissimilar alloys with Al based fillers

Abstract

Dissimilar alloys of Ti–6Al–4V and 5A06 Al were butt joined by Al based fillers using a novel TIG welding process, referred to as keyhole arc welding–brazing. The flow behaviour of weld pool was introduced, which was characterised by the formation of a keyhole under the tungsten electrode. It was found that porosity tended to be produced in the middle of the fusion line, while adding elements prevented its formation. At brazing interface, interfacial reaction at root face was enhanced, and a uniform serrated layer, identified as TiAl₃, was obtained by pure Al fillers. When Al–Cu–La fillers were used, block Ti₂Al₂₀La phases appeared at the interface between the TiAl₃ layer and the brazed seam. Compared to joints brazed by pure Al fillers, the formation of Ti₂Al₂₀La reduced the hardness of the interfacial layer by more than half, while Al₂Cu increased that of the brazed seam by ～50%. The tensile strength of Ti/Al joints reached 270 MPa.     

焊丝成分对SiCp/6061Al复合材料MIG焊焊缝组织及性能的影响

采用Al-Mg及Al—Si两种焊丝分别对SiCp／6061Al复合材料进行了MIG焊及脉冲MIG焊，利用光学显微镜、电子显微镜及MTS-810试验机对焊缝的组织及性能进行了分析。结果表明，采用Al—Mg焊丝焊接时，无论是MIG焊还是脉冲MIG焊，熔池中Al-SiC间的界面反应程度均较大，生成了较多的针状Al4C3，且Al4C3的尺寸较大。采用Al-Si焊丝时，MIG焊熔池中的界面反应程度显著降低，仅生成了少量尺寸较小的针状Al4C3；而采用Al—Si焊丝的脉冲MIG焊焊缝中没有发现针状Al4C3。同时，利用Al—Si焊丝可有效地防止焊缝熄弧处的宏观结晶裂纹。力学性能试验表明，采用同样焊丝时，脉冲MIG焊接头的强度及伸长率比MIG焊接头的高，而用Al-Si焊丝焊接的接头强度比用Al—Mg焊丝焊接的接头强度高。     

Determination of the melting rate of coated electrodes in manual arc welding with modulated current

Summary

This study deals with shielded metal arc (manual metal arc, MMA) welding and CO₂ gas shielded arc welding, measuring the force required to remove adhering spatter from the surface of base metal by using different filler metals and by changing the conditions of the surface of the base metal. Rolled steel for general structural use (SS400) was used as base metal.

A high titanium oxide type electrode and a low hydrogen type electrode were used for shielded metal arc welding, a solid wire and a flux‐cored wire were used as filler metal for CO₂ gas shielded arc welding respectively. In order to examine the relationship between the condition of the surface of the base metal and the force required to remove spatter, a base metal whose surface was ground by an electric grinder, one which was not ground by an electric grinder, and another which was coated with an anti‐spatter compound were used for the experiments.

Whichever filler metal was used, the spatter which adhered to the surface of the base metal was located within 100 millimetres from the weld line. In those cases, the force required to remove the adhering spatter can be measured as mostly below 98 N. The spatter needing more than 98 N to remove was located mostly within 20 mm of the weld line.

No matter whether the scale was on the base metal or not, the difference of the force required to remove the spatter was small. When we used the base metal coated with anti‐spatter compound, in some cases we found spatter on the base metal, and in other cases we did not. When we found spatter, it was located within 40 millimetres of the weld line and the force required to remove it was below 20 N.     

Vision based seam tracking system for underwater flux cored arc welding

Abstract

Manual underwater welding is usually time consuming, expensive and hard to perform because of the rigorous underwater environment. Automatic underwater welding can be performed faster at less cost and with higher quality. An automatic seam tracking system for underwater flux cored arc welding has been developed. It consists of a vision sensing module, a seam recognition module, a fuzzy controller (FC) and an X–Y travel platform. The vision sensing module can capture clear seam images during welding, successfully resolving the problem of welding arc interference during underwater flux cored arc welding. The seam recognition module filters, enhances and thresholds the seam images and then recognises the seam deviation angle with a three layer back propagation neural network. The FC outputs the control parameters according to the seam deviation angle and then controls the X–Y platform to drive the torch to the centre of the seam. In this study, three different welds were considered: a straight line, a kinked straight line and an S curved line. These welds were tracked real timely during underwater flux cored arc welding. The results show that this seam tracking system can meet the requirements of the automatic underwater flux cored arc welding.     

Interface properties and thermodynamic analysis of laser–arc hybrid welded Al/steel joint

Abstract

Fibre laser–cold metal transfer hybrid welding was introduced to join AA 6061 aluminium alloy with AISI 304 stainless steel using Al–12Si filler wire. Interface properties and microstructure of welded joints were observed by optical microscope, scanning electron microscope, energy dispersive spectrometry and X-ray diffraction techniques. A serrated intermetallic compound (IMC) layer was found at the interface between fusion zone and stainless steel. The morphology of IMC layer was uniform from the top to the bottom, and its average thickness was 3 μm. The IMC layer consisted of two layers: Al₈(Fe,Cr)₂Si layer close to fusion zone and (Al,Si)₁₃Fe₄ layer close to stainless steel. The joint fractured at the IMC layer and presented a tensile strength of 165 MPa. The formation of the IMC layer was closely related with the thermodynamic and kinetic behaviours of the interface and fast cooling rate of hybrid welding.     

Visualization of gas metal arc welding on globular to spray transition current

The transfer modes in gas metal arc welding have important effects on welding quality. However, present study of metal transfer modes is not yet fully understood. In this study, welding arcs was visualised using the optical emission spectroscopy technique. The carbon steel wire electrode was used for welding with 80% Ar?+?20% CO₂ shielding gas. The results showed that the globular to spray transition current was 330–350?A. During globular to spray transition, argon,CO₂ and Fe plasma tended to gradually change from localising near the arc axis to a two-layer structure having 11,000?K in high-temperature region away from the arc axis and around 7000?K in low-temperature region near the arc axis.     

Effect of welding processes on joint characteristics of Ti–6Al–4V alloy

Abstract

Although Ti–6Al–4V alloys show reasonable weldability characteristics, the joint properties are greatly influenced by the welding processes. Microstructures and tensile and impact properties of welded Ti–6Al–4V alloy were evaluated for high vacuum electron beam welding, CO₂ laser beam welding and gas tungsten arc welding. The resultant tensile and impact properties of the welded joints are correlated with the weld metal microstructure and hardness. The results indicate that the electron beam welding is more suitable for Ti–6Al–4V sheet welding and the welding seam without defects can be obtained. The full penetration butt welds are obtained by gas tungsten arc welding process, but they have many drawbacks such as wide weld seam, big deformation and coarse grains. Laser beam welding has many advantages such as the narrowest weld seam, the least deformation and the finest grains, but it should be studied again for the reasons of unstable welding technologies and strict condition.