Automatic Welding Process Research Articles

Friction Stir Welding and Hybrid Laser Welding Applied to 6056 Alloy

Innovative welding processes are continuously gaining industrial interest. Both friction stir welding (FSW) and hybrid laser welding (HLW) are automated welding processes which allow achieving high quality joints in aluminium alloys, in combination with a high productivity. The EN AW-6056-T4 alloy is a relatively recent high strength weldable AlMgSiCu alloy, which is used in aviation. This alloy was subjected to FSW and HLW. The optimisation procedures which were used for FSW and HLW to assess the most appropriate welding parameters are discussed. A comparison is made between the mechanical properties in the as-welded and in the T78 post-weld heat treated (PWHT) temper. Concerning the friction stir welds, the PWHT only caused a decrease of the elongation after fracture; the thermal treatment had no effect on the minimal hardness zones of the weld, hence the tensile strength did not change. The hybrid laser welds however showed a significantly higher tensile strength after PWHT, but this was also accompanied by a ductility loss. Fatigue testing was performed on the PWHT welds. Friction stir welds clearly possessed better fatigue properties than hybrid laser welds.

Evaluation of cold metal transfer (CMT) process for welding aluminium alloy

Cold metal transfer (CMT) is an automated welding process based on dip transfer welding, characterised by controlled material deposition during the short circuit of the wire electrode to the workpiece. Preliminary results are presented examining the suitability of this process for welding aluminium alloy. Trials show that in comparison with pulsed metal inert gas (MIG) welding, CMT exhibits a higher electrode melting coefficient. By adjusting the short circuit duration penetration can be controlled with only a small change in electrode deposition. Furthermore, by mixing pulsed MIG welding with CMT welding the working envelope of the process is greatly extended allowing thicker material sections to be welded with improved weld bead aesthetics.

Intelligent systems for welding process automation

This paper presents and evaluates the concept and implementation of two distinct multi-sensor systems for the automated manufacturing based on parallel hardware. In the most sophisticated implementation, 12 processors had been integrated in a parallel multi-sensor system. Some specialized nodes implement an Artificial Neural Network, used to improve photogrammetry-based computer vision, and Fuzzy Logic supervision of the sensor fusion. Trough the implementation of distributed and intelligent processing units, it was shown that parallel architectures can provide significant advantages compared to conventional bus-based systems. The paper concludes with the comparison of the main aspects of the transputer and the DSP-based implementation of sensor guided robots.

縦向き大入熱溶接法 ８電極エレクトロガスアーク溶接工法―外ダイヤフラム形式鋼管柱（ＥＧコラム）の開発―

縦向き大入熱溶接法 ８電極エレクトロガスアーク溶接工法―外ダイヤフラム形式鋼管柱（ＥＧコラム）の開発―

Optimising residual stresses at a repair in a steam header to tubeplate weld

Following the discovery of incorrect weld metal in the steam side shell to tubeplate weld in a type 316H stainless steel superheater steam header, a repair strategy had to be determined. The strategy adopted was to remove the incorrect weld material, which extended around the full circumference, by machining from the inside of the header, followed by rewelding from the inside using an automatic welding process and localised post-weld heat treatment. Due to concern over potential reheat cracking of the repair after return to service, a considerable amount of residual stress modelling was carried out to support the development and optimisation of a successful repair and heat treatment strategy and thus underwrite the safety case for return to service.

Large-scale manufacturing of nickel aluminide transfer rolls for steel austenitizing furnaces

This paper describes the first large-scale manufacturing of nickel aluminide IC-221M into roll bodies for the production of steel hardening furnace. One hundred and ten roll bodies were produced at Duraloy Technologies using the conventional foundry practice. Since it was the first manufacturing of this magnitude, foundry personnel were given special training with the melting of IC-221M by the Exo-Melt™ process and hands-on training with the welding process. Large-scale manufacturing produced 220 automated welds between nickel aluminide and H-Series trunnions, which is the largest number of welds ever produced in an intermetallic alloy. The manufacturing process for 110 rolls was completed in nearly four months and the rolls have been operating successfully in the production furnace for six months. Use of the Exo-Melt™ process for melting, automatic welding process, and successful completion of this project opens the opportunity for broader application of nickel aluminide rolls for steel hardening furnaces.

Analysis by Modeling of Horizontal Coaxial Arc Welding Phenomena-Automatic Welding Process for Ship's Bottom Shell Plates-

New automatic arc welding process has been developed for welding ship's shell plates upwards from the ground. In this process, the axis of the leading welding gun corresponds to that of a weld bead, therefore it is called ‘Horizontal Coaxial Arc Welding’ (HCAW). In order to keep the welding process under control, the simplified numerical model expressing the static balance of forces on the leading molten pool has been designed. The model enables to estimate the weld bead height and the bead formation rate. As a result of analysis by the model, the wire extension length will reach its equilibrium state spontaneously in the case of using a constant voltage characteristic power source, and controlling of the wire feeding speed is effective to reduce the change of the wire extension length during welding in various root opening.

Improvements of Flux-Copper Backing Welding Quality

Flux-copper backing process welding is a high-speed, one-sided automatic welding process that is a type of submerged arc welding. Although it has been widely applied for the joining of flat skin plates in shipbuilding, a couple of problems with this process still exist: longitudinal cracks occur in the vicinity of the end point, and transverse cracks occur on the back surface. The data in this study were collected in the production site of Ishikawajima-Harima Heavy Industries Company Ltd, Kure Shipyard. The causes of failures were examined, and countermeasures were studied. Concerning the longitudinal cracks, the behavior of plate deformation during welding was investigated, and the end tab plates and the tack welding method were improved in order to reduce the rapidly increased transverse distortion of the joining plates. Concerning the transverse cracks, the dispersal figure of the reverse flux to form the backing bead was observed, the relation between the flux spraying height and the welding quality was investigated, and the height was standardized. In addition, welding heat input was also examined and regulated to avoid the transverse cracks.

Effects of thermocapillary forces during welding of 316L-type wrought, cast and powder metallurgy austenitic stainless steels

The Large Hadron Collider (LHC) is now under construction at the European Organisation for Nuclear Research (CERN). This 27 km long accelerator requires 1248 superconducting dipole magnets operating at 1.9 K. The cold mass of the dipole magnets is closed by a shrinking cylinder and two end covers at both extremities of the cylinder. The end covers are welded, cast or powder metallurgy (PM) dished-heads equipped with a number of protruding nozzles for the passage of the different cryogenic lines. Structural materials and welds must retain high strength and toughness at cryogenic temperature. AISI 316L-type austenitic stainless steel grades have been selected because of their mechanical properties, ductility, weldability and stability of the austenitic phase against low-temperature spontaneous martensitic transformation. 316LN is chosen for the fabrication of the end covers, while the interconnection components to be welded on the protruding nozzles will be fabricated from forged 316L or 316LN, and welded 316L tubes. Autogenous welds between the nozzles and the interconnection components will be performed by the automatic orbital TIG technique. Several thousands of welds are foreseen. When welding together grades of slightly different composition, or grades issued from different fabrication methods (cast, PM, cold or hot rolled, forged, etc.), phenomena such as variable weld penetration, “off-centre welding” and “arc wander” may possibly appear, resulting in uncontrolled formation of non-axisymmetric welds. Such deflections of the weld pool are difficult to correct for an automatic process and may affect the soundness of the weld. A large and systematic campaign of welding tests associated with video recording of the melt pool has been carried out. Hot metal deflections have been precisely quantified. The results are interpreted in terms of the different content of soluble surface-active elements of the various steel batches and the directions of the thermocapillary flow arising from these different contents. This interpretation gives a quantitative prevision of the hot metal deflections. Possible corrections applicable to automatic welding processes are discussed.

자율 주행 용접 로봇을 위한 시각 센서 개발과 환경 모델링

Automation of welding process in shipyards is ultimately necessary, since the welding site is spatially enclosed by floors and girders, and therefore welding operators are exposed to hostile working conditions. To solve this problem, a welding mobile robot that can navigate autonomously within the enclosure has been developed. To achieve the welding task in the closed space, the robotic welding system needs a sensor system for the working environment recognition and the weld seam tracking, and a specially designed environment recognition strategy. In this paper, a three-dimensional laser vision system is developed based on the optical triangulation technology in order to provide robots with 3D work environmental map. Using this sensor system, a spatial filter based on neural network technology is designed for extracting the center of laser stripe, and evaluated in various situations. An environment modeling algorithm structure is proposed and tested, which is composed of the laser scanning module for 3D voxel modeling and the plane reconstruction module for mobile robot localization. Finally, an environmental recognition strategy for welding mobile robot is developed in order to recognize the work environments efficiently. The design of the sensor system, the algorithm for sensing the partially structured environment with plane segments, and the recognition strategy and tactics for sensing the work environment are described and discussed with a series of experiments in detail.

Strategies for risk assessment and control in welding: challenges for developing countries

Metal arc welding ranges from primitive (manual) to increasingly complex automated welding processes. Welding occupies 1% of the labour force in some industrialised countries and increasing knowledge of health risks, necessitating improved assessment strategies and controls have been identified by the International Institute of Welding (IIW), ILO, WHO and other authoritative bodies. Challenges for developing countries need to be addressed. For small scale production and repair work, predominantly by manual metal arc on mild steel, the focus in developing economies has correctly been on control of obvious physical and acute health affects.Development introduces more sophisticated processes and hazards. Work pieces of stainless steel and consumables with chromium, nickel and manganese constituents are used with increasingly complex semi-manual or automated systems involving variety of fluxes or gasses. Uncritical adoption of new welding technologies by developing countries potentiates future health problems. Control should be integral at the design stage, otherwise substantive detriments and later costs can ensue. Developing countries need particular guidance on selection of the optimised welding consumables and processes to minimise such detriments.The role of the IIW and the MFRU are described. Applications of occupational hygiene principals of prevention and control of welding fume at source by process modification are presented.

Strategies for risk assessment and control in welding: challenges for developing countries

Metal arc welding ranges from primitive (manual) to increasingly complex automated welding processes. Welding occupies 1% of the labour force in some industrialised countries and increasing knowledge of health risks, necessitating improved assessment strategies and controls have been identified by the International Institute of Welding (IIW), ILO, WHO and other authoritative bodies. Challenges for developing countries need to be addressed. For small scale production and repair work, predominantly by manual metal arc on mild steel, the focus in developing economies has correctly been on control of obvious physical and acute health affects. Development introduces more sophisticated processes and hazards. Work pieces of stainless steel and consumables with chromium, nickel and manganese constituents are used with increasingly complex semi-manual or automated systems involving variety of fluxes or gasses. Uncritical adoption of new welding technologies by developing countries potentiates future health problems. Control should be integral at the design stage, otherwise substantive detriments and later costs can ensue. Developing countries need particular guidance on selection of the optimised welding consumables and processes to minimise such detriments. The role of the IIW and the MFRU are described. Applications of occupational hygiene principals of prevention and control of welding fume at source by process modification are presented.

３電極ＦＣＢ片面サブマージアーク溶接法の全自動制御システムの開発 １ 開先変動に対する溶接条件のアクティブ制御

To determine the correct welding current as function of the geometrical condition of groove incorporating deviations from prescribed standard groove shape, a quantity termed joint capacity was introduced, using which, linear expressions have been established relating the groove geometry to welding current and speed. The empirical relation thus derived gave results agreeing well with the expression given by A.A. Wells relating total heat input to quantity of electrode melting. These simple linear expressions enable active control of welding parameters for maintaining uniform reverse bead in automated welding process which produce defect free weld.

Application of large heat input automatic welding process to beam-to-column connections of steel framed structures (1st Report)

Summary Beam-to-column connections of construction steelwork have been conventionally welded by a CO2-based, semi-automatic, multi-layer welding process. Such welding processes, however, face the problems of limited efficiency and the fact that the welding quality often depends on the welder's workmanship. The electrogas arc welding process is generally considered difficult to apply to beam-to-column connections of construction steelwork because of the poor weld toughness it confers due to its conventional high heat input. Based on recent developments in structural steel plates for large heat input welding, the authors have developed a one-pass vertically upward large heat input electrogas arc welding process (referred to in this paper as large heat input welding process and in the diagrams as EGW) able to produce welds with a deposition rate of twice the conventional one without any loss of toughness and with far fewer weld defects. The proposed process can also be applied to new improved seismic details, such as non-scallop details, etc. A key characteristic of the newly developed welding process is that stable penetration can be obtained even when heavy-gauge plates are being welded through the welding torch being moved as a trapezoid within the groove formed by a water-cooled copper shoe. The heat input in the proposed welding process is some 5–20-fold greater than that conventionally applied, but the newly developed construction steel plates for large heat input welding show Charpy impact values in both the weld metal and the heat affected zone (HAZ) of not less than 150 J (zero °C). The Charpy impact test results further suggest that, even when the developed steel is welded by the proposed large heat input welding process at a plate thickness of 25 mm, the weld fracture toughness properties of 150 J at zero °C can be maintained, achieving a performance equivalent to that found during CO2 welding of conventional 25 mm thick steel.

Development of a high-speed automatic welding process for simultaneous use on inside and outside surfaces of pipes

Development of a high-speed automatic welding process for simultaneous use on inside and outside surfaces of pipes

An analysis of factors affecting the automatic MAG welding process

An analysis of factors affecting the automatic MAG welding process

Austenitic stainless steel surface cladding buffer layers produced by automatic submerged-arc welding

Abstract The influence of different types of buffer layer for type 308 austenitic stainless steel surface overlays with 19-21% chromium and 10-12% nickel contents was analysed. The cladding passes were deposited on carbon steel test samples by the automatic submerged-arc welding process. Experimental tests were conducted on buffer layers having seven different chemical compositions and the results obtained are reported and discussed in the article. The experimental results allow the selection of the most suitable buffer layer to be deposited in order to obtain the required cladding performance in service.

Flash-Butt Welding of Large-Diameter Oil and Gas Pipelines

Interest in developing a high-production automatic joining method for quality offshore pipelines led to full-scale evaluation of the flash-butt welding process. During the past five years, two separate flash-butt welding machines have been used to provide over 1100 welds in 914-mm (36-in.) o.d. pipe for test and evaluation. Increased speed and the quality inherent in a fully automatic welding process were the two major incentives for the development project. It is estimated that flash-butt welding can produce up to 377 joints per day in 914-mm (36-in.) o.d. × 25-mm wall thickness pipe—twice what can be produced by conventional manual (shielded metal arc) welding techniques. This paper describes the flash-butt welding process and plans to install production equipment aboard a semi-submersible laybarge in the near future.

Automatic Welding Process for Small Diameter Pipe of Aluminum Alloy

Automatic Welding Process for Small Diameter Pipe of Aluminum Alloy

Parameter Estimation Using Microprocessors and Adaptive Random Search Optimization

An optimization procedure is presented which can be used for off-line system parameter estimation. The technique utilizes a model reference adaptive control configuration and an adaptive random search to identify the parameter values for an arc voltage control system of an automatic welding process. An 8-bit microprocessor is used to acquire data from the system, and a microprocessor development system performs the optimization routine.