Showing papers on "Filler metal published in 2012"

The Effect of Gas Metal Arc Welding (GMAW) Processes on Different Welding Parameters

Abstract: Gas Metal Arc Welding (GMAW) process is leading in the development in arc welding process which is higher productivity and good in quality. In this study, the effects of different parameters on welding penetration, microstructural and hardness measurement in mild steel that having the 6 mm thickness of base metal by using the robotic gas metal arc welding are investigated. The variables that choose in this study are arc voltage, welding current and welding speed. The arc voltage and welding current were chosen as 22, 26 and 30 V and 90, 150 and 210 A respectively. The welding speed was chosen as 20, 40 and 60 cm/min. The penetration, microstructure and hardness were measured for each specimen after the welding process and the effect of it was studied. As a result, it obvious that increasing the parameters value of welding current increased the value of depth of penetration. Other than that, arc voltage and welding speed is another factor that influenced the value of depth of penetration. The microstructure shown the different grain boundaries of each parameters that affected of the welding parameters.

Improving arc joining of Al to steel and Al to stainless steel

Abstract: Gas-tungsten arc welding (GTAW) with controlled heat input could avoid the formation of massive brittle Al–Fe intermetallics during solidification in dissimilar-metal joining of aluminum to steel. In the first part of the present study an Al–Mg alloy was joined to galvanized steel by GTAW with an Al–Si filler metal. The weld solidification microstructure was explained based on the Al–Mg–Si phase diagram. Ultrasonic vibration during GTAW increased the joint strength by 27%. Grain refinement, decreased Fe–Al intermetallics, and increased microhardness in both the heat-affected zone and the weld were observed, thus explaining the improved joint strength. In the second part, an Al–Mg alloy was joined to 304 stainless steel using a Zn-15Al filler metal with a noncorrosive flux core. The weld solidification microstructure was explained based on the Al–Zn–Mg phase diagram. Postweld heat treatment (PWHT) at 280 °C for 30 min doubled or even tripled the joint strength depending on the Al-sheet thickness. Dissolution of coarse Zn-rich particles at the weld/steel interface was observed after PWHT, thus eliminating these weak particles from the interface. The formation of Zn-rich particles near the interface and their dissolution by PWHT were explained based on the Al–Fe–Zn phase diagram.

Effect of Activated Flux on the Microstructure, Mechanical Properties, and Residual Stresses of Modified 9Cr-1Mo Steel Weld Joints

Abstract: A novel variant of tungsten inert gas (TIG) welding called activated-TIG (A-TIG) welding, which uses a thin layer of activated flux coating applied on the joint area prior to welding, is known to enhance the depth of penetration during autogenous TIG welding and overcomes the limitation associated with TIG welding of modified 9Cr-1Mo steels. Therefore, it is necessary to develop a specific activated flux for enhancing the depth of penetration during autogeneous TIG welding of modified 9Cr-1Mo steel. In the current work, activated flux composition is optimized to achieve 6 mm depth of penetration in single-pass TIG welding at minimum heat input possible. Then square butt weld joints are made for 6-mm-thick and 10-mm-thick plates using the optimized flux. The effect of flux on the microstructure, mechanical properties, and residual stresses of the A-TIG weld joint is studied by comparing it with that of the weld joints made by conventional multipass TIG welding process using matching filler wire. Welded microstructure in the A-TIG weld joint is coarser because of the higher peak temperature in A-TIG welding process compared with that of multipass TIG weld joint made by a conventional TIG welding process. Transverse strength properties of the modified 9Cr-1Mo steel weld produced by A-TIG welding exceeded the minimum specified strength values of the base materials. The average toughness values of A-TIG weld joints are lower compared with that of the base metal and multipass weld joints due to the presence of δ-ferrite and inclusions in the weld metal caused by the flux. Compressive residual stresses are observed in the fusion zone of A-TIG weld joint, whereas tensile residual stresses are observed in the multipass TIG weld joint.

Laser welding of Ti40Zr25Ni3Cu12Be20 bulk metallic glass

Abstract: Ti-based bulk metallic glass (BMG) plates have been successfully welded together by laser welding process. The tensile strength of the welded sample reaches up to 93% of the base material. Based on calculations and numerical simulations, the mechanism of successful welding of the BMG has been discussed in terms of the thermal history of weld fusion zone (WFZ) and heat affected zone (HAZ).

Effect of welding process on the microstructure and properties of dissimilar weld joints between low alloy steel and duplex stainless steel

Abstract: To obtain high-quality dissimilar weld joints, the processes of metal inert gas (MIG) welding and tungsten inert gas (TIG) welding for duplex stainless steel (DSS) and low alloy steel were compared in this paper. The microstructure and corrosion morphology of dissimilar weld joints were observed by scanning electron microscopy (SEM); the chemical compositions in different zones were detected by energy-dispersive spectroscopy (EDS); the mechanical properties were measured by microhardness test, tensile test, and impact test; the corrosion behavior was evaluated by polarization curves. Obvious concentration gradients of Ni and Cr exist between the fusion boundary and the type II boundary, where the hardness is much higher. The impact toughness of weld metal by MIG welding is higher than that by TIG welding. The corrosion current density of TIG weld metal is higher than that of MIG weld metal in a 3.5wt% NaCl solution. Galvanic corrosion happens between low alloy steel and weld metal, revealing the weakness of low alloy steel in industrial service. The quality of joints produced by MIG welding is better than that by TIG welding in mechanical performance and corrosion resistance. MIG welding with the filler metal ER2009 is the suitable welding process for dissimilar metals jointing between UNS S31803 duplex stainless steel and low alloy steel in practical application.

Wetting and oxidation during ultrasonic soldering of an alumina reinforced aluminum–copper–magnesium (2024 Al) matrix composite

Abstract: The effect of ultrasonic vibration on the solderability of a 30 vol% Al 2 O 3 reinforced Al–Cu alloy matrix composite in an air atmosphere was investigated. The results showed ultrasonic vibration gave the liquid filler an excellent ability to spread on the non-wetting base metal in both drop formation and soldering tests. Wetting was improved by removing the oxide film from the base metal, during which previous diffusion of the filler elements in the composite material producing partial melting played an important role. The joint strength increased significantly with soldering time, reaching a value equal to that of the filler metal after 3 s of ultrasonic vibration. The use of ultrasonic soldering is a possible solution to the problems in joining aluminum alloys highly reinforced with ceramic particles.

Effect of Activated Flux on the Microstructure and Mechanical Properties of 9Cr-1Mo Steel Weld Joint

Abstract: Tungsten inert gas (TIG) welding process is generally used to produce high quality weld joints of 9Cr-1Mo steel. However, there is limitation associated with the depth of penetration achievable in single pass autogenous welding. Specific activated flux has been developed in the present work to enhance the depth of penetration up to 6 mm in single pass by A-TIG welding. 9Cr-1Mo steel A-TIG weld joint using activated flux was made in single pass welding while the multipass TIG weld joint using modified 9Cr-1Mo filler wire was made in seven passes. The enhancement in depth of penetration during A-TIG welding process for this steel was attributed to arc constriction. The strength properties of the A-TIG weld joint was superior to that of the multipass TIG weld joint. The multipass TIG weld joint exhibited slightly improved impact toughness than the A-TIG weld joint in PWHT condition. Therefore, there was no degradation in the microstructure and mechanical properties of the weld joint produced by A-TIG welding...

Ultrasonic Welding of Hybrid Joints

Abstract: A central research field of the Institute of Materials Science and Engineering at the University of Kaiserslautern (WKK), Germany, is the realization of innovative hybrid joints by ultrasonic metal welding. This article gives an overview of suitable ultrasonic welding systems as well as of essential machine and material parameters, which influence the quality of the welds. Besides the ultrasonic welding of dissimilar metals such as Al to Cu or Al to steels, the welds between newly developed materials like aluminum foam sandwiches or flat flexible cables also can be realized. Moreover, the joining of glass and ceramic to sheet metals is a point of interest at the WKK. By using the ultrasonic metal welding process, it is possible to realize metal/glass welds with tensile shear strengths of 50 MPa. For metal/ceramic joints, the shear strengths values up to 150 MPa were measured. Finally, selected results about the occurring bonding mechanisms will be discussed.

Effect of zinc coatings on joint properties and interfacial reactions in aluminum to steel ultrasonic spot welding

Abstract: Dissimilar joining of aluminum to steel sheet in multimaterial automotive structures is an important potential application of ultrasonic spot welding (USW). Here, the weldability of different zinc-coated steels with aluminum is discussed, using a 2.5-kW USW welder. Results show that soft hot-dipped zinc (DX56-Z)-coated steel results in better weld performance than hard (galv-annealed) zinc coatings (DX53-ZF). For Al to hard galv-annealed-coated steel welds, lap shear strengths reached a maximum of ~80% of the strength of an Al-Al joint after a 1.0 s welding time. In comparison, welds between Al6111-T4 and hot dipped soft zinc-coated steel took longer to achieve the same maximum strength, but nearly matched the Al-Al joint properties. The reasons for these different behaviors are discussed in terms of the interfacial reactions between the weld members.

A Comparative Study on Direct and Pulsed Current Gas Tungsten Arc Welding of Alloy 617

Abstract: the aim of this article is to evaluate the mechanical and microstructure properties of Inconel 617 weldments produced by direct current electrode negative (DCEN) gas tungsten arc welding (GTAW) and pulse current GTAW. In this regard, the micro structural examinations, impact test and hardness test were performed. The results indicated that the joints produced by direct mode GTAW exhibit poor mechanical properties due to presence of coarse grains and dendrites. Grain refining in pulse current GTAW is reason of higher toughness and impact energy than DCEN GTAW. Further investigations showed that the epitaxial growth is existed in both modes that can strongly affect the mechanical behavior of the joints in heat affected zone (HAZ).

Laser-Mig Hybrid Welding Of Aluminium To Steel — Effect Of Process Parameters On Joint Properties

Abstract: Laser MIG hybrid welding was recently suggested as a feasible process for joining of aluminium to steel for both structural as well as tailored blank applications. To promote an understanding of the process and the effect of process parameters on joint properties, laser MIG hybrid welding experiments were performed to join aluminium alloy AA6016 to DC05 zinc-coated steel sheets, in the thickness range of 1 mm, in a butt joint configuration. Among the process parameters varied were laser power, MIG arc power, wire feed rate, welding speed and arc position relative to the abutting edges. By metallographic cross-sections and tensile tests, the effect of these process parameters on joint properties such as wetting length, intermetallic phase layer thickness and tensile strength could be elucidated. Based on these results, a process parameter envelope resulting in adequate and reproducible joint properties (sound weld bead, sufficient and regular wetting, thin intermetallic phase layer, tensile strength exceeding 180 MPa) was established. Within this parameter envelope, corrosion behaviour was rated not critical, and forming behaviour showed promising results.

Influences of phosphorus and sulphur on ductility dip cracking susceptibility in multipass weld metal of alloy 690

Abstract: The influence of P and S on ductility dip cracking susceptibility in the reheated weld metal of alloy 690 was evaluated by the spot Varestraint test using different alloy 690 filler metals, while varying the contents of P and S The ductility dip cracking susceptibility was reduced with a decrease in the content of P and S in the filler metal; the amount of (P+1·2S) in the weld metal should be limited to 30 ppm in order to prevent microcracking in the multipass weld metal A numerical simulation of cosegregation behaviour of P and S revealed that both elements were segregated at the grain boundary in the ductility dip temperature range during multipass welding A molecular orbital analysis has suggested that ductility dip cracking can be attributed to grain boundary embrittlement due to grain boundary segregation of P and S

Interfacial microstructure and mechanical property of SiO2-BN ceramics and Invar joint brazed with Ag–Cu–Ti active filler metal

Abstract: SiO 2 -BN ceramics and Invar alloy were jointed by active brazing using Ag–21Cu–4.5Ti (wt.%) filler at 1113–1173 K for 5–30 min. Scanning and transmission electron microscopy studies revealed that the amorphous SiO 2 was not reacted during brazing while h-BN had strong tendency to react with Ti to formation a fine-grain layer adjacent to SiO 2 -BN ceramic. The composite TiN–TiB 2 fine-grain layer with the thickness of 100–150 nm was the key factor in achieving a good bond between SiO 2 -BN ceramic and Invar. Invar alloy dissolved into the molten filler and reacted with Ti to form Fe 2 Ti and Ni 3 Ti, which dispersed in Ag- and Cu-based solid solution. The shear strength of the joint decreases with the increase of Fe 2 Ti and Ni 3 Ti brittle compounds. The maximum shear strength reached 32 MPa when the joint brazed at 1153 K for 10 min. Cracks primarily propagated in the SiO 2 -BN ceramic and partially along the reaction layer.

Grain Refinement in Al-Mg-Si Alloy TIG Welds Using Transverse Mechanical Arc Oscillation

Abstract: Reduction in grain size in weld fusion zones (FZs) presents the advantages of increased resistance to solidification cracking and improvement in mechanical properties. Transverse mechanical arc oscillation was employed to obtain grain refinement in the weldment during tungsten inert gas welding of Al-Mg-Si alloy. Electron backscattered diffraction analysis was carried out on AA6061-AA4043 filler metal tungsten inert gas welds. Grain size, texture evolution, misorientation distribution, and aspect ratio of weld metal, PMZ, and BM have been observed at fixed arc oscillation amplitude and at three different frequencies levels. Arc oscillation showed grain size reduction and texture formation. Fine-grained arc oscillated welds exhibited better yield and ultimate tensile strengths and significant improvement in percent elongation. The obtained results were attributed to reduction in equivalent circular diameter of grains and increase in number of subgrain network structure of low angle grain boundaries.

Corrosion of AA6061 Brazed with an Al-Si Alloy: Effects of Si on Metallurgical and Corrosion Behavior

Abstract: Aluminum alloy (AA)6061 (UNS A96061) and AA4047 (UNS A94047) were brazed to construct a tapered model braze joint with variable braze clearances. Isolated AA6061-T6 was also exposed to the thermal cycle of a typical dip brazing process without applying filler metal. The braze, mixed, and heat-affected zones were modeled by thermochemical computations and characterized experimentally. Corrosion exposures were conducted in accordance with BS 11846 Method B for detection of intergranular corrosion (IGC). Each zone developed its own corrosion morphology traced to the unique chemical composition and metallurgical characteristics. The brazing thermal cycle promoted IGC of isolated AA6061. Moreover, the Al-Si braze and AA6061 joint promoted additional intergranular corrosion in the Si-enriched mixed zone exacerbated by grain boundary Q (Al4Cu2Mg8Si7) and β phases as well as eutectically formed Si needles at solidification boundaries. Pitting occurred in the Al-Si braze zone. Anodic and cathodic polarization scan...