Upset Welding Research Articles

Interface and microstructural characteristics of titanium and 304 stainless steel dissimilar joints by upset butt welding using a gleeble thermo mechanical simulator

This work discusses joining dissimilar material combinations of commercial pure titanium and 304 stainless steel utilizing an upset butt welding process. The process involves rapid heating to a temperature of 1150 °C at a heating rate of 200 °C/s with simultaneous application of pressure at a level of 1.5 MPa to achieve fusion. Then, the joints are post-heated to 850 °C during the soaking period for 90 min to relieve the welding residual stresses and achieve good bond strength. The upset welding experiments are conducted with the help of a Gleeble thermomechanical simulator. This process does not require the conventional severe metallographic preparation generally used for the typical diffusion bonding process. The weld joint achieves an ultimate tensile strength of 274 MPa, approximately 60% of the strength of commercial pure titanium. Moreover, intermetallic compounds occurred at the interfaces, which were attributed to significant changes in the microhardness of the Ti/SS alloy.

Hydrogenation Behavior of Cr-Coated Resistance Upset Welds of E110 Zirconium Alloy

The hydrogenation behavior of Cr-coated resistance upset welds (RUW) of E110 zirconium alloy was investigated at 360, 450 and 900 °C and a hydrogen pressure of 2 bar. The deposition of Cr coating, via magnetron sputtering, can decrease the hydrogen absorption rate of an RUW Zr alloy. The activation energy for the hydrogen absorption of Cr-coated specimens (84 kJ/mol) is higher in comparison with uncoated ones (71 kJ/mol), which indicates the deceleration of the hydriding of welded Zr alloys in the case of Cr coating deposition. A Cr coating can limit the formation of radially oriented hydrides and the hardening of RUW specimens at 360 and 450 °C. No significant difference in the hydrogen absorption rate was found at 900 °C. The application of Cr coating deposition to protect resistance-upset-welded Zr alloys in a hydrogen atmosphere is discussed.

Results of the Archaeometallographic Study of the Collection of Forged Pieces from the Shcherbet Settlement on the Lower Kama

The purpose of the paper is to present the features of the development of ironworking of the Volga-Kama periphery of the Eastern European part of the Barbarikum on the basis of data obtained during the metallographic study of forged pieces related to the materials of the Imenkovo culture (V–VII centuries), that were found in different years (mainly by P.N. Starostin in the 1960s–80s) on the part of the Shcherbet I settlement destroyed by the reservoir. Schemes and methods of making 31 items made of ferrous metal were determined: a ploughshare, a chisel, 2 axes, 4 sickles, 13 knives, 4 awls, 2 rings for fastening, two fishhooks and two rod-shaped items. It was found that forging welding and local carburizing were often used in their manufacture. Half of the objects had traces of heat treating in the tempering mode or in a soft temper milieu. As a characteristic technological feature of this collection, a combination of iron and steel forgings (usually low-carbon) components is noted in the design, mainly in the form of upset welding or welding of a strip bent in half. A significant mass of items have distinct signs of multi-layer packing. The degree of using of blacksmithing skills and the quality of the studied items on the example of the examined samples give reason to believe that the ironworking of the Imenkovo culture had a deep-seated tradition.

Investigation and Optimization of Resistance Implant Welding of Polypropylene Sheets

Recently, the use of resistance welding in the joining of polymeric materials and polymer composites in the aviation, marine, and automotive industries has been gradually increasing. However, challenges continue in regard to improving product quality as affected by several parameters. This study focused on the effects of wire geometries and wire diameters on the characteristics of polypropylene (PP) sheets united by resistance implant welding. Here, PP sheets manufactured by the injection molding method were joined via the resistance upset welding method with three different wire geometries, including spiral, wavy, and M-shaped, and two different wire diameters of 0.3 and 0.5 mm. Mechanical properties, morphological properties, and heating characteristics were examined. The results showed that wire diameter and wire geometry affected amount of heat formation in the weld zone and, therefore, weld performance in terms of the mechanical properties. The results obtained from the study can be used as a reference in similar applications.

High-Temperature Oxidation of Cr-Coated Resistance Upset Welds Made from E110 Alloy

The resistance upset welds (RUW) made from E110 alloy without and with Cr coatings were oxidized in air atmosphere at 1100 °C for 2, 10 and 30 min. The cross-section microstructure, elemental composition and hardness were studied before and after oxidation using optical and scanning electron microscopy, and indentations in welding region. The RUW welding does not noticeably change oxidation kinetics of E110 alloy. The most crucial effect has surface non-regularities formed after welding, which prevent uniform coating deposition on full surface of welded cladding tube and end plug. Cr coating deposition can strongly reduce oxidation of welded E110 alloy, while additional post-processing treatment should be applied to improve surface morphology after RUW welding. Several suggestions favorable to development of ATF Zr-based claddings using Cr coating deposition on welded nuclear rods were discussed.

Experiments and numerical simulations on joint formation and material flow during resistance upset welding of WC-10Co and B318 steel

Joints of WC-10Co and B318 steel were obtained using resistance upset welding for the application of carbide-tipped sawblades. Research concerning resistance upset welding of WC-Co and steel is rare, and the joint formation evolution and material flow phenomenon have not been studied. The welding current was the research parameter to study the joint formation evolution and the material flow phenomenon during welding by analysing high-speed photography, numerical simulation results, macro and micro morphologies, mechanical properties, and the fracture morphology of welded joints. The results showed that with an increased heat input, the shear strength of the joint had an initial increasing trend before decreasing. The maximum shear strength under a suitable welding current (850 A) was 678 MPa. The joint formation process as captured with a high-speed camera was consistent with the numerical simulation results, which verifies the model. The simulation results revealed that a larger heat input gave a faster material flow. The thickness of the reaction layer at the centre of the interface was the smallest and increased from the centre to the periphery as related to the material flow. Compared with other welding approaches, resistance upset welding of cemented carbide and steel generates extrudates on the steel side. As the welding current increased, the extrudates shifted from the centre of the interface to the edges.

Effect of In Situ Post Weld Heat Treatment on Mechanical Behavior and Austenite–Ferrite Phase Balance of Fe-Cr-Ni/Fe-Cr Stainless Steels Upset Resistance Dissimilar Weld

Abstract Effect of the in situ post weld heat treatment (PWHT) was investigated on the flash profile, austenite/ferrite phase balance, and mechanical properties of the upset resistance dissimilar weld between Fe-Cr-Ni and Fe-Cr stainless steels rods. In order to explore the effect of the heat treatment on the joint strength, two as-welded samples with low strength (116 MPa) and high strength (372 MPa) were used. The results showed that in situ PWHT was beneficial for both welded samples, though in different ways. For the weld with low strength, PWHT improved the joint strength (∼130% increase in the optimum condition compared with the as-welded sample) due to the increase in the size of the flash and the related bonded area at the joint interface. However, ferrite percent in the weld zone increased from ∼50% up to ∼70%. For the sample with the high strength, ferrite/austenite phase balance was restored at an optimum condition of PWHT. However, the joint strength decreased slightly (less than 5%) due to the grain growth in the Fe-Cr rod, i.e., the fracture location. Fracture analysis was used for justification of the variations in the joint strength. For both Fe-Cr-Ni side and Fe-Cr side of the welds, in situ PWHT generally reduced the hardness. This observation is discussed in light of the simultaneous effects of the grain growth and formation of little martensite.

Ferritic and martensitic ODS steel resistance upset welding of fuel claddings: Weldability assessment and metallurgical effects

Development and characterization of clad-to-plug resistance upset welds is presented for two oxide dispersion strengthened steels candidates for sodium-cooled fast reactors fuel cladding: 9Cr ferrito-martensitic steel and 14Cr ferritic steel. A comparative approach is adopted regarding these two materials implying weldability studies and weld mechanical strength tests. A special attention is paid on welding metallurgical effects on the specific microstructure of these materials. Among others, some major grain property modifications by dynamic recrystallization and a slight modification of precipitate sizes and volume fraction are found and discussed.

Upset-resistance welding of aluminium to copper rods: effect of interface on performance

ABSTRACTUpset resistance dissimilar welding of aluminium and copper narrow rods was performed. Effect of the interface characteristics was studied on the joint mechanical and electrical properties. Upset resistance welding (URW) was successful for production of joints with high strength and electrical conductivity between aluminium and copper rods. Reaction layer at the joint interface was composed of the Al2Cu cellular phase and lamellar eutectic structure of α-Al and Al2Cu. Enhancement of the welding current and decrease in the upset force increased the reaction layer thickness and strength of the joint. URW had no significant detrimental effect on the electrical conductivity of the weld zone. Neither the joint strength nor the joint electrical conductivity was improved by in situ post weld heat treatment.

Resistance upset welding of Zr-based bulk metallic glasses

Zr-based bulk metallic glasses represent an emerging important class of structural materials with interesting properties due to its amorphous nature. In this study, the structural and microstructural transformations to the heat-affected zone of a Zr-based bulk metallic glass welded by the resistance upset technology were investigated. X-ray diffraction, optical and scanning electron microscopy were used to characterize the base metal and the heat-affected zone. Vickers microhardness testing was performed to assess the mechanical response of the welded joints. The amorphous phase volume fraction measured along the welded joints shows no difference between the base metal and the heat-affected zone. It was possible to achieve a sound weld with no crystallization of the base metal.

Resistance Upset Welding of ODS Steel Fuel Claddings—Evaluation of a Process Parameter Range Based on Metallurgical Observations

Resistance upset welding is successfully applied to Oxide Dispersion Strengthened (ODS) steel fuel cladding. Due to the strong correlation between the mechanical properties and the microstructure of the ODS steel, this study focuses on the consequences of the welding process on the metallurgical state of the PM2000 ODS steel. A range of process parameters is identified to achieve operative welding. Characterizations of the microstructure are correlated to measurements recorded during the welding process. The thinness of the clad is responsible for a thermal unbalance, leading to a higher temperature reached. Its deformation is important and may lead to a lack of joining between the faying surfaces located on the outer part of the join which can be avoided by increasing the dissipated energy or by limiting the clad stick-out. The deformation and the temperature reached trigger a recrystallization phenomenon in the welded area, usually combined with a modification of the yttrium dispersion, i.e., oxide dispersion, which can damage the long-life resistance of the fuel cladding. The process parameters are optimized to limit the deformation of the clad, preventing the compactness defect and the modification of the nanoscale oxide dispersion.

Study on the Upset Welding of Shear Reinforcement with Large Diameter

Study on the Upset Welding of Shear Reinforcement with Large Diameter

Numerical simulation of resistance upset welding in rod to tube configuration with contact resistance determination

A 2-D axisymmetric finite element model of upset resistance welding on tube to rod configuration is developed. It is based on an electrical-thermal-mechanical analysis and developed on commercial software MARC for nuclear fuel pin cladding welding application. It allows to assess local temperature and strain fields during welding. A parameter influence study reveals, among others, the importance of contact resistances between samples and electrodes. Some contact resistance models are proposed and a specific calibration method of those models, which implies experimental tests and numerical simulations, is developed. This calibration method allows to obtain a good agreement between the welding simulation and the relevant instrumented experiment for two different studied geometries.

A Study of Fatigue Properties of Steel AISI4130 (30KhMF) After Upset Welding

The microstructure, microhardness, tensile strength, fatigue resistance, and fracture surfaces of welded joints of steel AISI4130 (30KhMF) are studied after annealing and after quenching and tempering. Resistance upset welding is used to create the welds. The fractograms of the welded joints after tensile and fatigue tests exhibit fracture over the middle of the surface of the weld.

Study of Fatigue Properties of AISI4130 Steel Joined by Upset Welding in Heat Treated Condition

Resistance upset welding (UW) is a widely used for joining metals parts. In this research, the fatigue properties of AISI4130 steel joined by upset welding in annealed and quenched-tempered heat treated condition are investigated. Microstructure of weld and base metals was studied using optical microscopy. Tensile, impact and fatigue tests were performed and the final fracture surface was studied by scanning electron microscopy (SEM). The fatigue resistance is better for tempered martensite base metal than for the ferrite-pearlite and upset welded specimens. Results shows during the welding, proeutectoid ferrite phase forms at the interface which reduce the fatigue strength of welded specimens. Fractography of fatigue and tension welded samples indicated that in all samples fracture occurred in the middle of weld interface. Study of fracture surface of fatigue samples shows that the final fracture mode for welded samples is cleavage.

Phenomena Leading to a Modification of the Nano-Sized Structure during Resistance Upset Welding of ODS Steel Cladding

ODS steels (Oxide Dispersion Strengthened) are candidate materials for fuel cladding in Sodium Fast Reactors (SFR). These materials have good mechanical properties at high temperature due to a dispersion of nanometer-sized oxides into the matrix. Previous studies have shown that melting can induce a decrease of the mechanical properties at high temperatures due to modifications of the nanometer-sized oxide dispersion. Therefore the fusion welding techniques are not recommended and the solid state boundings has to be evaluated. This study is focused on resistance upset welding. Welding experiments and numerical simulations are coupled. The numerical simulation is developed in order to have a better understanding of the thermal and the mechanical phenomena occurring during the welding process. The simulation shows that the welding steps can be divided in two stages. First, the temperature of the contact between pieces increases. Second, the heat generation is mainly located in the cladding leading to the collapse and forging the pieces. The microstructural observations confirm that the major deformation is located in the cladding. Oxide dispersion modification and dynamical recrystallisation has been found for welds achieved with a non optimized process parameter set. The deformation and the temperature seem to be of prime importance in the modification of the oxide dispersion.

Microstructure and mechanical properties of resistance upset butt welded 304 austenitic stainless steel joints

Resistance upset welding (UW) is a widely used process for joining metal parts. In this process, current, time and upset pressure are three parameters that affect the quality of welded products. In the present research, resistance upset butt welding of 304 austenitic stainless steel and effect of welding power and upset pressure on microstructure, tensile strength and fatigue life of the joint were investigated. Microstructure of welds were studied using scanning electron microscopy (SEM). X-ray diffraction (XRD) analysis was used to distinguish the phase(s) that formed at the joint interface and in heat affected zone (HAZ). Energy dispersive spectroscopy (EDS) linked to the SEM was used to determine chemical composition of phases formed at the joint interface. Fatigue tests were performed using a pull–push fatigue test machine and the fatigue properties were analyzed drawing stress-number of cycles to failure ( S– N) curves. Also tensile strength tests were performed. Finally tensile and fatigue fracture surfaces were studied by SEM. Results showed that there were three different microstructural zones at different distances from the joint interface and delta ferrite phase has formed in these regions. There was no precipitation of chromium carbide at the joint interface and in the HAZ. Tensile and fatigue strengths of the joint decreased with welding power. Increasing of upset pressure has also considerable influence on tensile strength of the joint. Fractography of fractured samples showed that formation of hot spots at high welding powers is the most important factor in decreasing tensile and fatigue strengths.

Effect of Heat on the Soundness of Zircaloy-4 End Cap Closure Using a Resistance Upset Welding

The objective of this study is to investigate the effect of main heat on the soundness of Zircaloy-4 end cap welds and the process of weld line elimination in resistance upset welding for a Direct Use of spent PWR fuel In CANDU reactor (DUPIC) fuel fabrication. The weld current and amount of upset increased linearly with the main heat, from which two relations between them were derived. It was found that the threshold to obtain sound welds was 50% of the main heat in terms of upset size, mechanical strength, and weld line elimination. A microstructure of resistance upset welds of Zircaloy-4 comprised basketweave, Widmanstätten, and martensite depending on the alteration of the main heats. Dimples on the uniaxially fractured surface at the weld line in Zircaloy-4 welds were larger and deeper than those on a biaxially fractured surface. It was also found that the process of weld line elimination in the resistance upset weld of Zircaloy-4 could be divided into three stages in terms of the presence of many pores, their shrinkage and elimination, and the shrinkage of the original weld interface with increasing weld current.

Effect of Heat on the Soundness of Zircaloy-4 End Cap Closure Using a Resistance Upset Welding

The objective of this study is to investigate the effect of main heat on the soundness of Zircaloy-4 end cap welds and the process of weld line elimination in resistance upset welding for a Direct Use of spent PWR fuel In CANDU reactor (DUPIC) fuel fabrication. The weld current and amount of upset increased linearly with the main heat, from which two relations between them were derived. It was found that the threshold to obtain sound welds was 50% of the main heat in terms of upset size, mechanical strength, and weld line elimination. A microstructure of resistance upset welds of Zircaloy-4 comprised basketweave, Widmanstätten, and martensite depending on the alteration of the main heats. Dimples on the uniaxially fractured surface at the weld line in Zircaloy-4 welds were larger and deeper than those on a biaxially fractured surface. It was also found that the process of weld line elimination in the resistance upset weld of Zircaloy-4 could be divided into three stages in terms of the presence of many pores, their shrinkage and elimination, and the shrinkage of the original weld interface with increasing weld current.

Numerical simulation of tensile strength of upset welded joints with experimental verification

Resistance upset welding (UW) is a widely used process for joining metal parts. In this process current, time and upsetting force are three parameters that affect the quality of welded products. This paper considers numerical simulation and experimental investigation of UW process parameters. The investigated parameters include heating and post-weld heating current and their corresponding duration as well as interference of the part features that form the joint. In this study, evaluation of tensile strength of the welded joint with variation of the process parameters is also reported. For numerical analysis, a two-dimensional axisymmetric model using a coupled electro-thermal finite element method is developed to study the thermal behavior of the welded joints. The results of this numerical simulation are used to determine the status of the weldment and therefore evaluate the quality of the weld at the joint. Both numerical and experimental results suggest an optimum set of welding parameters, i.e. time and electrical current that yields a maximum value for the tensile strength of the joint. Also the effects of post-weld heating time and current on the tensile strength are evaluated and show that these parameters have a remarkable effect on improving tensile strength of the weldment.