Electric Resistance Welding Research Articles

Development of a Model to Support the Management of the Resistance Welding Process

The work was carried out as part of a project to improve the corrosion resistance of welded joints. The optimal selection of input parameters reduces the consumption of welded material as well as the negative impact on the environment. The samples were welded by electrical resistance welding, more precisely by cross-wire welding. Electric resistance welding is a process for welding with electricity in which of high electrical resistance is used to generate heat at the contact point of the welded parts. Steel wire S235 with a diameter of 4 and 3 mm was used. The article shows the creation of the model to predict the percentage of setdown and weld strength as a function of the input parameters, welding current and welding time. The first task was to create a Design of experiments in which the process parameters or the range of input parameters are determined. The Design of the experiments was created for both wire diameters. This covers the range of parameters with which a welded joint of wires can be realised. A statistical analysis of the process follows, where it was found that for 4 and 3 mm diameter wires the percentage setdown increases with increasing welding current and time. An increase in strength as a function of welding current and welding time is also observed, but the results overlap in most cases and the range of their values is greater than that of setdown. The appearance of the weld was analysed for each sample. The visual inspection revealed seven categories of welds, which were divided into two groups, i.e. good and poor welds. All results were listed in a table with the percentage of expectation for a particular category of weld appearance. Based on the analysis, a model for determining the welding result parameters depending on the specified input parameters was developed, which can be used in practise to support the management of the electric resistance welding process.

Role of residual stress in the failure of HF-ERW welded tubes

High-frequency electric resistance welding is used for manufacturing hydro formable tubes. Tube forming and welding results in the formation of residual stress. The hole drilling technique was used to evaluate the residual stress of the welded tube. Tensile residual stress of varying magnitude was observed at different locations on the tube. The weld, heat affected zone was observed to have the highest residual stress as a result of phase transformation, forming and gradually reduced towards the parent material. The generated tensile residual stress led to failure of the tube during mechanical evaluation. Additionally, electron backscattered diffraction studies (EBSD) of the fusion line and the thermo-mechanically heat-affected zone were found to have goss and cube texture. These detrimental textures can lead to easy crack propagation in the presence of defects along the fusion line. A post-weld heat treatment (PWHT) was carried out to alleviate the tensile residual stress and alter the weld microstructure. PWHT helped transform the bainite in the weld to ferrite and pearlite. The inter-critical annealing significantly reduced the tensile residual stress along the circumferential direction resulting in improved formability.

Experimental characterisation and statistical modelling of woven carbon fibre weld conductors for electrical resistance welding of thermoplastic composites

Resistance welding of high-performance thermoplastic composites is a promising joining technique for the structural assembly of aerospace components. Knowledge of the weld conductor resistance as a function of its dimensions, as well as external boundary conditions such as contact preparation and pressure, can be used to scale welding parameters. This paper presents a comprehensive review on the weld conductor contact preparation, length, width and contact pressure dependent resistance with respect to the Toray 5HS T300JB carbon woven prepreg 281 gsm fibre architecture. The study is based on a 4-wire resistance measurement of the carbon fibre fabric weld conductors and was conducted to provide a solid basis for defining the weld conductor’s resistance, considering the dependence on length, width and contact pressure. The experimentally determined resistance values were approximated using linear and non-linear regression functions and combined into a general formulation with respect to the investigated carbon fibre fabric architecture. The least squares fit of experimental versus model data confirmed a very high model confidence. Thus, the model allows a simplified transfer of electrical properties for process pre-design and scaling considering weld conductors with the same fibre architecture.

Numerical Study on Residual Stresses and Plastic Strains in Cold-Formed High-Strength Steel Circular Hollow Sections.

This paper presents a numerical investigation on the residual stresses and co-existent equivalent plastic strains in cold-formed high-strength steel (CFHSS) circular hollow sections (CHS) by using an advanced finite element (FE)-based method. In this method, the entire manufacturing process of the CFHSS CHS was modeled numerically. The accuracy of the numerical predictions of equivalent plastic strains and residual stresses in the CFHSS CHS was verified by comparing the predictions with the existing test results of both the residual stress measurement and load-end shortening response of the stub column. By using the FE-based method, the effects of high-frequency electric resistance welding on the residual stresses and the stub column response were investigated. The through-thickness variations of both the equivalent plastic strains and residual stresses in CFHSS CHS, which are difficult to measure in the laboratory, were explored numerically. Finally, the effect of cold work (which is quantified by the equivalent plastic strains and residual stresses) on the stub column response of CFHSS CHS tubes was evaluated. It can be found that the equivalent plastic strains and longitudinal residual stresses are generally uniform around the cross-section of CFHSS CHS. The transverse and longitudinal residual stresses are generally uniform across each half-thickness, with the inner half-thickness under compression and the outer half-thickness under tension. The results also demonstrate that both the plastic strains and residual stresses may significantly affect the cross-section capacities of CFHSS CHS.

Merged Mode TFM with Mode Conversion Artifact Suppression

The objective of the paper is to compare the merits of the multiplication and max value schemes for producing a total focusing method (TFM) representation that combines multiple acoustic modes. We have chosen to compound phase coherence imaging (PCI) images because it eliminates the difficulties associated with handling vastly different acoustic sensitivities across different propagation modes. We also introduce an apodization-based algorithm that can filter out unwanted mode-conversion artifacts that are caused by similarities in time of flights. Experimental data were gathered on an electric resistance welding (ERW) hook crack and a natural bottom-surface-connected vertical crack. Experimental results indicate the multiplication scheme suppresses defect echoes that can only be imaged by a subset of acoustic modes. This can potentially lead to false negatives or underestimation of the extent of the defect. In contrast, the max value scheme retains all indications that appear in a subset of acoustic modes. For the vertical crack configuration imaged by shear wave acoustic modes, the max value scheme retains all mode-conversion artifacts and therefore complicates the defect analysis. The apodization-based filtering method significantly suppressed mode-conversion artifacts without affecting the imaging of the vertical crack. The combination of PCI with max value merging and apodization-based mode-conversion filtering is a promising methodology for merged mode TFM in shear wave weld inspections.

Microstructure formation and fatigue performance of duplex stainless steel 2205 welded joints by electric resistance welding

Microstructure formation and fatigue performance of duplex stainless steel 2205 welded joints by electric resistance welding

Cracking failure analysis on a high-frequency electric resistance welding pipe in buried fire water pipeline

Leakage of a buried fire water pipeline occurred after in service of 15 years. It was manufactured from a Q235B carbon structural steel plate by high-frequency electric resistance welding. The water pressure increased from 0.8 MPa at a normal operating condition to 1.2 MPa at the tube burst moment. Cracks propagate along the weld and incomplete fusion defects are observed. This paper aims to explore the cracking failure through a combination method of experimental tests and theoretical analysis. The metallographic analysis clearly shows that the crack is located in the fusion zone and grains are coarse in that zone. Mechanical property tests indicate tensile properties of the anti-corrosion layer meet requirements. Finite element analysis reveals that the pipeline with an incomplete fusion can safely operate under a pressure of 0.8 MPa, while fracture occurs under the pressure of 1.2 ∼ 1.3 MPa. The results indicated that the deep unfused defect of the welded joint was the root cause of cracking, and selective seam weld corrosion also played an important role. The failure progress and mechanism were discussed in details.

Study of Melting Methods by Electric Resistance Welding of Rails

An analysis of the results of rail operation shows that up to a third of all rail breaks in the railway line and up to 12.9% of all withdrawn acute defective rails are associated with welded joints. This is largely explained by the formation of structures with martensite sections in the welded joints of rails and the formation of burns. This work presents the results of studying welded joints, obtained under three welding modes (continuous flash welding, pulsating flash welding and combined flash welding). The conducted studies have shown that the flash welding mode significantly influences both the cooling rate value and the very nature of the thermal cycle of the welded joint as a whole. Changes in the cooling rate under different modes exert a significant influence on the structure and properties of the weld. Resistance welding of rails from the steel grade E76HGF by pulsating flash welding can result in the appearance of needle martensite areas, which is the reason for increased embrittlement of the weld and a decrease in its properties. The conducted field experiments have reliably shown that in the conditions of the combined welding mode it becomes possible to avoid these problems. Moreover, a slight increase in the mechanical properties of the weld in the range of 2–4% has been experimentally recorded, and the destructive load of the welded joint of the rail increases by 2–3% at high values of the bending deflection. In turn, these factors allow a significant reduction in the number of cases of rail welded-joint failures in real conditions of their operation.

Sintering of Iron Powders by Resistance Heating Technique

In this study, powder metal samples of 15x15x4 mm dimensions of Fe powders were produced at different pressures (650,850,1050 MPa). They were sintered in atmospheric environment with the help of resistance sintering method applied for the first time using electric resistance welding machine. The sintered and green densities of the powder metal samples were determined and their sinterability in the unprotected environment was examined. In addition, the effects of electric resistance heating technique on sintering were investigated by performing hardness measurement and microscopic examination of sintered samples. As a conclusion, powder metal samples were sintered successfully with the electric resistance welding technique in an unprotected environment and high-density values such as 98% were obtained.

Improving the thermal performance of thin vapor chamber by optimizing screen mesh wick structure

• Effect of mesh layer and mesh number on the thermal performance of TVCs are investigated. • Thermal performance of the singular mesh wicked TVCs is dependent on effective capillary radius and wick thickness. • Larger thickness and smaller effective capillary radius of mesh wick can enhance the thermal performance of TVCs with wick thickness below 0.12 mm. • The multilayer composite mesh wick can improve the thermal performance of TVCs with a 0.4 mm thick mesh wick. Due to the booming of portable electronic devices, thin vapor chambers (TVCs) have been used to effectively transfer high heat flux in narrow space. In this study, various-layer singular meshes and multilayer composite mesh whose thicknesses are below 0.4 mm are developed by electrical resistance welding. For improving the thermal performance of TVCs, the various-layer singular mesh wicked TVCs are investigated to reveal the effects of mesh layer (mesh thickness) and mesh number (effective capillary radius of pores) on the thermal performance of TVCs, and the multilayer composite mesh wicked TVC is also studied as a comparison. The results show that the thermal performance of various-layer singular mesh wicked TVCs is mainly dependent on effective capillary radius along height direction and mesh thickness. Among the mesh wicks whose thicknesses are below 0.12 mm, the mesh wick with a larger thickness and smaller effective capillary radius can enhance the thermal performance of TVCs. The multilayer composite mesh wick with larger pores on top of smaller pores can improve the thermal performance of TVCs with 0.4 mm-thick mesh wick. In addition, three-layer 350 in -1 singular mesh wicked TVC shows the best performance, the maximum heat transfer capacity is 240 W and the lowest thermal resistance is 0.115 K/W.

강 파이프의 고주파 전기저항 용접공정에 대한 수치 해석

The high-frequency electric resistance welding (HF-ERW) process is widely used in the steel pipes production because it can weld at a high speed, has excellent weldability, and attains clean and precise shapes. However, for process improvement, analytic studies on electromagnetic field and temperature distributions, and selection of appropriate process variables are required. In this study, finite element analysis models that can analyze the electromagnetic field distribution and temperature distribution in the HF-ERW of a steel pipe were proposed, in consideration of the characteristics of the process, including electromagnetic phenomena localized to the workpiece surface and fast welding speed. By applying the proposed analysis models, changes in current density, magnetic flux density, generated heat density, and fused width in the pipe could be predicted according to changes in process variables such as the V angle of the strip, the electrode position, and the source voltage. Through comparison with the analysis and the limited-case experiment, the analysis result predicted the actual fused width fairly well, and the validity of the proposed model could be verified.

Pipe Spatter Detection and Grinding Robot

This paper proposes a robotic system that automatically identifies and removes spatters generated while removing the back-bead left after the electric resistance welding of the outer and inner surfaces during pipe production. Traditionally, to remove internal spatters on the front and rear of small pipes with diameters of 18–25 cm and lengths of up to 12 m, first, the spatter locations (direction and length) are determined using a camera that is inserted into the pipe, and then a manual grinder is introduced up to the point where spatters were detected. To optimize this process, the proposed robotic system automatically detects spatters by analyzing the images from a front camera and removes them, using a grinder module, based on the spatter location and the circumferential coordinates provided by the detection step. The proposed robot can save work time by reducing the required manual work from two points (the front and back of the pipe) to a single point. Image recognition enables the detection of spatters with sizes between 0.1 and 10 cm with 94% accuracy. The internal average roughness, Ra, of the pipe was confirmed to be 1 µm or less after the spatters were finally removed.

Hydrogen damage in a power boiler: A study of damage selectivity and conditions

We report two evaporator tube failures that took place in the same boiler owing to hydrogen damage within an interval of approximately one year. Notably, hydrogen damage occurred selectively on recently repaired tubes. In contrast, some of the original tubes that had been operating for 18 years or longer remained intact under the same environment. Comprehensive metallurgical investigation and chemical analysis revealed that the older tubes slowly developed a thin film of evaporation residue on their inner surface, which had a protective effect and suppressed the progress of corrosion. Hydrogen damage is more likely to proceed in the electric resistance welding (ERW) part than in the other parts. Kinetic consideration proved the rapid (within 18 hours) progression of hydrogen damage in evaporator tubes. Moreover, it confirmed that the hydrogen damage could be stemmed by instantaneous shutdown without improving the water quality immediately. The cleaning test suggested that tubes that already suffered hydrogen damage may be further damaged during acid cleaning. These results can help identify the cause of hydrogen damage in evaporator tubes due to poor water quality and determine the area of tube renewal/repair.

Cylindrical interfaces repair technique using electric resistance welding of metal powder materials

The study aims to increase the manufacturability of cylindrical interfaces repair by restoring the outside surface geometry using electric resistance powdered welding. The paper presents the technique of coating a worn outside cylinder surface using metal powders and mesh by giving the results of the quality indicators study. The research allowed identifying optimal parameters for the metal powder supply depending on the metal mesh size and the powder's technological properties. Theoretical studies have been undertaken to substantiate the technological process parameters. The nomographic chart developed to determine the angle of powder supply to the electric resistance welding zone allows predicting the coating thickness and varying within 0.3 … 1.5 mm. The powder brand, the diameter of the electrode roller, part and mesh are considered when developing the chart. Due to the triaxial compression under the electrode rollers' force and the mesh deformation, the powder layer experiences additional compaction and is practically sintered to a compact state. The coating obtained under optimal conditions has a porosity of 2 … 6%. Laboratory and operational tests allowed justifying the applicability of coatings in interfaces operating using lubrication and experiencing moderate loads. The electric resistance welding provides high anti-friction properties of resulting metal coatings (1.9 times higher than hardened steel 45, and HD80 (high duty) cast iron by 1.6 times). The developed technology makes it possible to restore cylinder parts worn to 1 mm with wear resistance higher than that of new parts such as the support surfaces of drive shafts, screw rotors, mould guides, etc.

Non-metallic inclusions and quality of pipe joints obtained by high-frequency electric resistance welding

An incisive analysis of studies of the most frequent defects of pipe joints obtained by high-frequency electric resistance welding (HFW) is included herein with particular focus on nonmetallic inclusions (NMIs), which are the cause of defects in such welded joints. Their composition, origin and methods of elimination under industrial conditions are discussed. In order to validate the nature of defects the interpretation procedure of the composition of NMIs detected in the discontinuities of welded joints has been developed. Examples of its application on the low-carbon line pipe steels of different grades X52–X56 are presented. The compositions of NMIs found in 64 defects of welded joints of A 516-55 (09G2S) steel pipes are summarized. These compositions significantly differ from each other and correspond to the different nature of NMIs: indigenous deoxidation products based on spinel MgO∙Al2O3 (8 %), products of steel modification by calcium (62 %), exo-indigenous NMIs with residuals of mould flux (4 %) or MgO (8 %) and indi-exogenous NMIs based on MgO (18 %). The unique variation ranges of the main elements included in these groups of NMIs are used for automated determination of their origin when carrying out metallographic examination of defects by means of the Thixomet image analyzer in the conditions of factory practice. The detailed origin of NMIs makes it possible to indicate the exact location in the technology of ladle treatment and steel casting for their improvement and to enhance on this basis the quality of line pipe joints obtained by HFW.

Influence of the Process Input Parameters on the Cross-Wire Weld Breaking Force

Cross-wire welding is a type of electric resistance welding called projection welding that is used in the production of a variety of products. This paper deals with the case where steel wires of equal radii are joined together to form a reinforced steel mesh. The objective of the study is to determine the correlation between the welding parameters and the breaking force of the weld. Each weld is cut out from the given wire mesh and tested separately by destructive testing on the universal testing machine. A modular testing fixture was constructed for the tests. Although the tests are still in the initial stage, the results already give a good insight into the influence of the process input parameters on the breaking strength of the weld.

Analysis of the Cross-Wire Welding Process Stability

The research paper was prepared within the framework of a project whose aim is to improve the durability of the corrosion protection properties of the product by regulating the input parameters of the cross-wire welding process. Cross-wire welding is a subtype of electric resistance welding. Products made by the cross-wire welding process are widely used in everyday life and can be found in the form of grids, gratings, fencing systems, baskets, guards, etc. The subject of the research work is a preliminary analysis of the stability of the cross-wire welding process. The results of the performed analysis will serve as a starting point for the second phase of the project. Since the recorded values of the set down output parameter differ significantly from the expected values, this parameter is considered as an indicator of the process stability. From the specific trend of the results in the performed analysis, it was concluded that the position of the electrode has a significant influence on the result, which was confirmed by comparing the test results before and after the preliminary tests.

Experimental study on magnetic flaw detection of micro-defects in ERW tubes

Chassis lightweight is one of the implementation of vehicle lightweight, the use of Electric Resistance Welding(ERW)welded pipe by bending and internal high pressure molding from the parts are an important part of the chassis components. Due to the limitation of welded pipe size, thin wall, high temperature and continuous production, the conventional nondestructive testing method is difficult to meet the continuous dynamic testing requirements of ERW welded pipe. In view of the small defect of ERW welded pipe, a method for detection of welded pipe defects based on the principle of electromagnetic induction is presented. Firstly, the fuzzy evaluation model of weld quality was established based on the fuzzy mathematics principle. Secondly, the welding mechanism of ERW was analyzed, and the microstructure of the weld was observed by metallographic microscope, and the microstructure of the weld was obtained. Finally, eddy current method, the low-frequency electromagnetic scanning method and magnetic induction method were used to detect ERW welded pipes. The data analysis shows that the magnetic induction method can realize dynamic detection and accurate localization of welded pipe defects, and the comprehensive detection effect is the best.

Low Electric Power Resistance Welding of Chrome Steel by Inserting Low Boiling Point Compound

Automobile bodies are assembled by resistance spot welding of 3,000 to 6,000 points per car, mainly on pressed thin plate components. In this study, a low-power, high-strength joint was investigated by inserting a low boiling point compound into the joint interface and using the vaporization and volume expansion of the compound caused by heat during resistance welding to break down the oxide film and increase the area of strong joint. As a result，higher tensile strength was obtained than that of the non-inserted joint.

Case Study About Resistance Projection Welding of Aluminized Steel Parts

Resistance projection welding is a non-polluting mechanized process used to obtain an assembly between similar or dissimilar metallic materials. The main advantages of this welding process are the possibility to achieve many different welded points at the same time and the long life of the electrodes compared to the spot-welding process. The paper analyses the effects of thin aluminium coating existing on mild steel parts of on the correct formation of welding points when assembling moulds for the manufacture of baking bread. From optical and electron microscopy analyses it resulted that some adjacent welded points show an interrupted fusion line, sprinkled with elongated islands of aluminium-rich compounds. The paper presents the effect of changing the values ​​of the welding parameters on the weld spot size, in correlation with the Al-rich inclusions that appear on the weld fusion zone. The best results have been obtained when the welding parameters values were the follows: electrode pressure of 2.6 bar, welding power of 19.18kVA and welding time of 7ms. The problems that occur when electric resistance welding of parts with aluminium coating have been highlighted, being useful for specialists who make products using this welding process.