Showing papers on "Filler metal published in 2014"

Study on microstructure and mechanical characteristics of low-carbon steel and ferritic stainless steel joints

Abstract: In this work, examinations on the microstructure and mechanical properties of plain carbon steel and AISI 430 ferritic stainless steel dissimilar welds are carried out. Welding is conducted in both autogenous and using ER309L austenitic filler rod conditions through gas tungsten arc welding process. The results indicate that fully-ferritic and duplex ferritic–martensitic microstructures are formed for autogenous and filler-added welds, respectively. Carbide precipitation and formation of martensite at ferrite grain boundaries (intergranular martensite) as well as grain growth occur in the heat affected zone (HAZ) of AISI 430 steel. It is found that weld heat input can strongly affect grain growth phenomenon along with the amount and the composition of carbides and intergranular martensite. Acquired mechanical characteristics of weld in the case of using filler metal are significantly higher than those of autogenous one. Accordingly, ultimate tensile strength (UTS), hardness, and absorbed energy during tensile test of weld metal are increased from 662 MPa to 910 MPa, 140 Hv to 385 Hv, and 53.6 J m −3 to 79 J m −3 , respectively by filler metal addition. From fracture surfaces, predominantly ductile fracture is observed in the specimen welded with filler metal while mainly cleavage fracture occurs in the autogenous weld metal.

Strength development versus process data in ultrasonic welding of thermoplastic composites with flat energy directors and its application to the definition of optimum processing parameters

Abstract: Ultrasonic welding of thermoplastic composites is a very interesting joining technique as a result of good quality joints, very short welding times and the fact that no foreign material, e.g. a metal mesh, is required at the welding interface in any case. This paper describes one further advantage, the ability to relate weld strength to the welding process data, namely dissipated power and displacement of the sonotrode, in ultrasonic welding of thermoplastic composite parts with flat energy directors. This relationship, combined with displacement-controlled welding, allows for fast definition of optimum welding parameters which consistently result in high-strength welded joints.

Evaluation of Microstructure and Mechanical Properties in Dissimilar Austenitic/Super Duplex Stainless Steel Joint

Abstract: To study the effect of chemical composition on microstructural features and mechanical properties of dissimilar joints between super duplex and austenitic stainless steels, welding was attempted by gas tungsten arc welding process with a super duplex (ER2594) and an austenitic (ER309LMo) stainless steel filler metal. While the austenitic weld metal had vermicular delta ferrite within austenitic matrix, super duplex stainless steel was mainly comprised of allotriomorphic grain boundary and Widmanstatten side plate austenite morphologies in the ferrite matrix. Also the heat-affected zone of austenitic base metal comprised of large austenite grains with little amounts of ferrite, whereas a coarse-grained ferritic region was observed in the heat-affected zone of super duplex base metal. Although both welded joints showed acceptable mechanical properties, the hardness and impact strength of the weld metal produced using super duplex filler metal were found to be better than that obtained by austenitic filler metal.

Evaluation of Surface Crack in Resistance Spot Welds of Zn-Coated Steel

Abstract: The development of the automotive industry is now focused not only on improving basic vehicle performance but also on reducing weight and enhancing safety and durability. Various automotive high-strength steels are being developed, and Zn-coated steels are being manufactured to prevent corrosion of the external white vehicle body. The most commonly used welding method in the car body assembly process is resistance spot welding (RSW), which has been extensively studied worldwide. In this process, the work piece is basically heated according to the contact resistivity of the interfacial between the electrode and the material as well as the bulk resistivity of the material itself. At this point, if the meta li s Zn, which has a lower melting point than the Fe base metal on the surface, it is mainly melted in the temperature range of 400­900°C. It becomes easy to penetrate the grain boundary of the HAZ during welding. Also, the tensile stress in such a state decreases the ductility of the grain boundary and causes liquid metal embrittlement (LME). Cu5Zn8, an intermetallic compound, can be formed from the reaction of the alloy with the Cu material electrode in the expulsion current range at a high temperature. Its formation is likely to be facilitated by LME or a surface crack. In this study, the fatigue characteristics of a tensile shear specimen during spot welding was investigated with the welding parameters that occur in the surface crack of welds on Zn-coated steel. Finally, a controlled spot welding condition was suggested to prevent surface cracks. [doi:10.2320/matertrans.M2013244]

Study for TIG–MIG hybrid welding process

Abstract: Tungsten inert gas (TIG) and metal inert gas (MIG) welding are the most popular gas-shielded arc-welding processes used in many industrial fields. MIG welding is a high-efficiency process compared to TIG welding. However, improvements are needed to reduce spatter and improve weld metal toughness. Although pure argon shielding gas is desirable for weld metal toughness, MIG arcs are unstable in pure Ar to the extent that executing welding is difficult. We have found that MIG arcs become stable even using pure argon by simply using a hybrid TIG and MIG system. This process has the possibility of becoming a new welding process giving high quality and efficiency. In this study, we investigate the influence of the balance of current between the TIG and MIG arcs, which is most important in determining arc stability and arc penetration. We have confirmed the suitable range of conditions both experimentally and through numerical simulation and have applied this process for butt and fillet joints. We show that the welding time can be reduced to 17 ~ 44 % of the time required using a conventional TIG process.

Effect of welding speed on microstructural and mechanical properties of laser lap weld joints in dissimilar Al and Cu sheets

Abstract: Conventional fusion welding of aluminium and copper dissimilar materials is difficult because of poor weldability arising from the formation of brittle intermetallic compounds on the weld zone as well as different chemical, mechanical and thermal properties of welded joints. Joining of Al and Cu plates or sheets offers a metallurgical challenge due to unavoidable formation of brittle intermetallic compounds. Therefore, it is necessary to effectively suppress the formation and growth of Al–Cu intermetallic compounds. For welding of dissimilar Al and Cu sheets, no systematic work has been conducted to reduce these defects. Thus, this paper focuses on the effect of welding speed on the quality of a lap weld joint in the Al and Cu sheets with a single mode fibre laser. It was found that consequently sound strong weld joints could be produced by suppressing the formation of intermetallic compounds in the interface zone at extremely high speeds.

Hybrid laser arc welding of X80 and X120 steel grade

Abstract: The aim of the present work was to investigate the possibilities of hybrid laser arc welding regarding reliable production of longitudinal welds of high strength pipe steels X80 and X120 and to evaluate achievable mechanical properties of laser hybrid welds. The study focused on weld toughness examination in low temperature range up to −60°C. Suitable filler materials were identified in the context of this task. It could be shown that metal cored electrodes guaranteed sufficient Charpy impact toughness at low temperature for both investigated materials. Modern arc welding technologies such as modified pulsed spray arc were used to promote deeper penetration of the filler material into the narrow laser welding gap. Edge preparation with a 14 mm deep root face was considered as optimum, because no penetration of the filler material could be detected beyond this depth limit, and therefore, any metallurgical influences on the weld metal properties through the welding wire could be excluded.

Reducing bubbles in friction lap welded joint of magnesium alloy and polyamide

Abstract: The direct joining between AZ31B Mg alloy and MC Nylon 6 using friction lap welding (FLW) was performed over a wide range of welding parameters to clarify the effect of welding parameters on bubble formation for the purpose of obtaining high strength hybrid joints without bubbles. The volume of bubbles in the FLW joints was influenced by the amount of gases generated due to the pyrolysis of Nylon 6 and the amount of gases squeezed out of the joints during welding. An appropriate increase in welding speed, tool rotation rate and plunge depth can reduce the volume of bubbles. Strong FLW joint with area fraction of bubbles <8% was obtained after welding process optimisation.

Feedback from a welding torch of a welding system

Abstract: A method includes displaying, on a display of a welding torch, a welding parameter in relation to a predetermined threshold range for the welding parameter, a target value for the welding parameter, or some combination thereof as a position of the welding torch changes, an orientation of the welding torch changes, a movement of the welding torch changes, or some combination thereof, to enable a welding operator to perform a welding operation with the welding parameter within the predetermined threshold range, at the target value, or some combination thereof. The welding parameter is associated with the position of the welding torch, the orientation of the welding torch, the movement of the welding torch, or some combination thereof.

Study on microstructures and mechanical properties of laser–arc hybrid welded S355J2W+N steel

Abstract: The technology of laser–MAG hybrid welding was used on 16 mm thick plate of weathering steel S355J2W+N. Under the welding parameters used in the experiment, full penetration weld without flaws such as pores, cracks and lack of fusion was obtained by a three-layer and three-pass welding technique. In this study, the outstanding advantages of laser–arc hybrid welding were summarized by comparison with welded joint of traditional MAG welding. The microstructure of hybrid welded joint has also been detailed investigated. Besides, the mechanical property tests were performed according to corresponding European standards. Furthermore, the tensile and impact strength of laser–MAG hybrid welded joint turned out to be almost as good as base metal. Most of the hybrid welded joints had a good bending property, but for some sample, there was a micro-crack with the length of 0.9 mm emerging within the transition region where contraction stress would accumulate and remain, being one of the most vulnerable zones in weld metal. The results show that laser–MAG hybrid welding technology is appropriate for S355J2W+N thick plate welding, in favor of not only improving the product performance, but also lowering the production cost and improving the productivity.

Effects of wire feed conditions on in situ alloying and additive layer manufacturing of titanium aluminides using gas tungsten arc welding

Abstract: An additive layer manufacturing (ALM) process based on gas tungsten arc welding (GTAW) was used to produce simple 3-dimensional titanium aluminide components, which were successfully in situ alloyed by separately delivering elemental Al and Ti wires to the weld pool. The difference in microstructure, chemical composition, and microhardness of four wall components built with four different wire-feeding conditions has been evaluated. There was no significant change in the microstructure of the four walls. The composition and microhardness values were comparatively homogeneous throughout each wall except the near-substrate zone. However, with increasing the ratio of Al to Ti wire feed rates from 0.80 to 1.30, an increase of Al concentration and γ phases were observed. The situation was reversed for the effect of the Al:Ti ratio on microhardness. Additionally, an unexpected increase in the α2 phase was produced when the ratio was increased to 1.30.

Modern fiber laser beam welding of the newly-designed precipitation-strengthened nickel-base superalloys

Abstract: In the present research, the modern fiber laser beam welding of newly-designed precipitation-strengthened nickel-base superalloys using various welding parameters in constant heat input has been investigated. Five nickel-base superalloys with various Ti and Nb contents were designed and produced by Vacuum Induction Melting furnace. The fiber laser beam welding operations were performed in constant heat input (100 J mm−2) and different welding powers (400 and 1000 W) and velocities (40 and 100 mm s−1) using 6-axis anthropomorphic robot. The macro- and micro-structural features, weld defects, chemical composition and mechanical property of 3.2 mm weldments were assessed utilizing optical and scanning electron microscopes equipped with EDS analysis and microhardness tester. The results showed that welding with higher powers can create higher penetration-to-width ratios. The porosity formation was increased when the welding powers and velocities were increased. None of the welds displayed hot solidification and liquation cracks in 400 and 1000 W welding powers, but liquation phenomenon was observed in all the heat-affected zones. With increasing the Nb content of the superalloys the liquation length was increased. The changing of the welding power and velocity did not alter the hardness property of the welds. The hardness of welds decreased when the Ti content declined in the composition of superalloys. Finally, the 400 and 1000 W fiber laser powers with velocity of 40 and 100 m ms−1 have been offered for hot crack-free welding of the thin sheet of newly-designed precipitation-strengthened nickel-base superalloys.

Microstructure and joining mechanism of Ti/Al dissimilar joint by pulsed gas metal arc welding

Abstract: Butt joining of titanium alloy Ti–2Al–Mn to aluminum 1060 using AlSi5 filler wire was conducted using pulsed gas metal arc welding. Joining mechanism of Ti–2Al–Mn/Al 1060 dissimilar joint with different welding heat input was investigated. Formations of precipitation and Ti/Al interface were discussed in detail. Fusion zone near aluminum is composed of α-Al dendrites and Al–Si hypoeutectic structures. A few TiAl3 precipitations appear in the weld metal owing to metallurgical reactions of Al with dissolved Ti. When the welding heat input was in the range of 1.87–2.10 kJ/cm, titanium alloy Ti–2Al–Mn and Al 1060 were joined together by the formation of a complex Ti/Al interface. With a low welding heat input, a serrate TiAl3 interfacial reaction layer was formed near Ti/Al interface. With the increasing of the welding heat input, α-Ti, Ti7Al5Si12, and TiAl3 layers were formed orderly from Ti–2Al–Mn to weld metal.