GMAW Welding Research Articles

Laser Beam Welding of Nitride Steel Components

Laser beam welding is a joining technique that has many advantages over conventional GMAW welding, such as low heat input, short cycle time as well as good cosmetic welds. Laser beam welding has been widely used for welding powertrain components in automotive industry. When welding nitride steel components, however, laser beam welding faces a great challenge. The difficulty lies in the fact that the nitride layer in the joint releases the nitrogen into the weld pool, resulting in a porous weld. This research presents an industrial ready solution to prevent the nitrogen from forming gas bubbles in the weld.

Study on qualification of GMAW welding faults based on the digital signal

Study on qualification of GMAW welding faults based on the digital signal

Utilização do ensaio erichsen para a avaliação do desempenho de juntas soldadas

Para aprovação de uma junta soldada é comum a realização de testes mecânicos para avaliar seu desempenho em comparação com o metal base ou outra junta soldada. Entre os diversos ensaios que podem ser usados, o ensaio Erichsen tem sido utilizado para avaliar juntas em chapas de pequena espessura. A utilização deste ensaio nesta aplicação específica não está ainda bem estabelecida e a interpretação dos resultados obtidos muitas vezes gera controvérsia. Neste contexto, o presente trabalho compara os resultados de três tipos de ensaio mecânico (tração, dobramento e Erichsen) na avaliação de cordões de solda depositados em chapas de aço inoxidável ferrítico de 1,5 mm de espessura. Na primeira etapa deste trabalho, usando soldas obtidas com o processo de soldagem GTAW, foram selecionadas as condições para a realização do ensaio Erichsen. Para isto, foram comparados os resultados deste ensaio em diferentes condições e a distribuição de deformações na região de ensaio foi avaliada quantitativamente com um programa de computador específico. Na segunda etapa, juntas soldadas pelo processo GMAW foram avaliadas pelos ensaios de tração, dobramento e Erichsen e seus resultados comparados. Mostrou-se que o ensaio Erichsen foi mais efetivo para detectar uma menor ductilidade em juntas soldadas em condições para as quais se esperava um pior comportamento mecânico.

The synchronized tandem wire welding process applied to the welding of structural plates*

As part of a European research project, partially funded by the Steel Research Fund (RFS-CR-03049), the potential benefits derived from the use of synchronized tandem wire welding (STW) technology applied to structural plates, in place of the currently used arc techniques, have been evaluated. In particular, two welded joint types have been investigated: T joints and butt joints in S355 grade structural plate, 6 and 12 mm thick. Considering the variables that characterize the process, also depending on the type of tandem torch, i.e. variable or fixed electrode configuration, the influence of the distance between the electrodes, stick-out, the type of arc and weld speed on the process characteristics have been examined. The joints obtained have been compared with those produced using traditional technology in terms of overall joint deformation, structural integrity, microstructural analysis and mechanical performance (toughness and fatigue strength). The results have demonstrated that the STW process is an effective technology for increasing both the weld speed, at the same penetration and the quantity of metal deposited, by about 50% compared to GMAW welding, with only slightly higher but relatively modest heat input (1 kJ/mm). These operating conditions have allowed the preservation of a level of joint quality (EN ISO 5817 quality level B) and structural integrity, comparable with those of GMAW and SAW welded joints, in addition to significant reductions in distortion. Furthermore, the fatigue strength of STW joints has also been in compliance with the reference class (butt joint, FAT class 100). The objective of the project (RFS-CR-03049), partially supported by the Research Fund for Coal and Steel, was to explore and quantify the benefits of STW applied to structural steels as an alternative technology to established arc welding technologies. T joints and butt joints of 6 and 12 mm steel grade S355 plates have been investigated using two different types of welding gun configuration, i.e. fixed electrodes and variable electrodes configuration. The influence of electrodes distance, stick-out, arc types and welding speed have been examined. The optimized joints have been characterized in terms of structural integrity, microstructure, mechanical performance (impact fracture toughness and fatigue resistance), total deformation and compared to traditional arc welding joints. STW technology allowed an increase of about 50% in both the welding speed, at the same penetration and deposited metal compared to GMAW with a not much greater heat input (1 kJ/mm) maintaining the same level of joint quality (EN ISO 5817 quality level B) and structural integrity with a reduction of joint distortion. In addition, fatigue resistance of STW joints was in compliance with the requirement (FAT Class 100 MPa).

490MPa급 고장력강 탄뎀 가스메탈아크 용접부에 대한 기계적 성질과 미세조직 비교

Tandem GMAW is one of the high performance welding process and used in many industries to increase the productivity. An evaluation is presented of the mechanical properties and microstructural characteristics of the Tandem GMAW and conventional Single GMAW welds in 30mm thickness 490MPa grade steel by comparison method. Welding sequence and bead with and hight was kept, avoiding the effect of the bead shape and welding sequence. Tension, bending, hardness and Charpy impact test results of Tandem GMAW met the requirement of specification and showed similar distribution with conventional Single GMAW. Volume fraction of ferrite phase in weld metal showed little difference between Tandem GMAW and Single GMAW

Stability of Double Wires Narrow-gap Gas Metal Arc Welding

Some special parameters of double wires narrow gap GMAW (NG-GMAW) welding can be adjusted individually, such as the angle and distance between the two wires along the welding direction and the distance between the wire and the sidewall of the groove. These parameters have great influence on the welding stability. Experiments results show that when the distance between the two wires is less than 15 mm or greater than 50 mm, the two welding arcs are in one molten pool or two independent molten pools, and the welding process is very stable. When the distance is 20～30 mm, the molten pool is transforming from single one to two independent one. Under the action of unbalanced electromagnetic force, the arc is compelled to break frequently and the stable welding process is destroyed. When the two wires are parallel along the welding direction, the welding process is stable; if the front wire is inclined to the rear wire, the wandering of the front arc is aggravated. The distance between the wire and the groove sidewall has great influence on the arc modality. When the distance is 2.5 mm, the arc burns stably between the wire and the sidewall as well as the bottom of the groove. But if the distance is less than 1.5 mm, the arc burns between the sidewall or bottom randomly, and the welding stability deteriorates.

Cost estimation of joints preparation for GMAW welding process using feature model

The cost estimation is important in structural design. Thus recent advances achieved in technology such as integrated engineering, provide a new concept in the cost estimation starting from the design phase. In this paper we propose a method, based on the feature model, to estimate the manufacturing cost of welding joints. The approach uses the manufacturing knowledge in the design phase of a welded structure. It helps to provide the best economical choice of different design alternatives of a product. Two types of information have been structured in this work: information of economical type defining the relationship between parameters of the feature and manufacturing cost; technical information relating to the manufacturing process of the preparation feature. In the first step, we present the preparation feature, which will consist of the welding achievement, considering the type of assembly, feature geometry and parameters of welding process. The focus is only on butt-welded assembly using a gas metal arc welding process (GMAW) in which the choice of preparation feature is made only according to thickness, electric current intensity and electrode diameter. Then, we will set in details the generating method of the manufacturing process for different preparation features. Finally, we propose a calculation model for manufacturing cost to prepare the welding joint.

The influence of arc transfer mode in hybrid laser-mig welding

Abstract In the recently developed welding process, a Laser beam and an electric arc are coupled in order to combine the positive aspects of each technology: high speed, low thermal load and high seam depth, all typical features of the Laser; low cost and ability to withstand poor edge preparation, typical of GMAW arc welding. In particular hybrid Laser Nd:Yag-GMAW welding has been widely studied for thin sheet welding in the automotive industry. On the other hand hybrid Laser CO 2 -GMAW welding, which is nowadays one of the most promising solutions for optimum power/cost ratio, has significant advantages over Nd:Yag-GMAW in the welding of thick sheets, where high power sources are required. This paper investigates the stability condition of a hybrid Laser CO 2 -GMAW welding process by analyzing the influence of several process parameters. A first set of experiments was carried out in order to determine the optimal position of the two sources. A second set of trials made it possible to investigate the importance of the filler metal transfer mode on the stability of the whole process. The obtained specimens are I-butt joints of AISI 304 stainless steel sheet 8 mm thick. The depths, widths and reinforcements of the weld beads were measured, related to the controlled process parameters and analyzed by means of a statistical approach.

Effect of preheating temperature and filler metal type on the microstructure, fracture toughness and fatigue crack growth of stainless steel welded joints

It is known that the main problem related with the welding of low carbon 12% Cr stainless steels is its hydrogen induced cracking susceptibility. Thus, it is common practice to perform welding with two alternative ways, preheating the welded parts and using similar filler material or using an austenitic stainless steel filler metal without preheating. This research work consists in identifying and comparing, for these two alternatives, the effect on microstructure, fracture toughness and fatigue crack growth rate of the welded joint. On the first alternative, using a GMAW welding process and similar filler metal, the variable is preheating temperature, with the purpose of minimizing internal residual stresses and the level of diffusible hydrogen. On the second alternative, also using a GMAW welding process and austenitic stainless steel filler metal (greater hydrogen solubility), the variable is hydrogen concentration in the argon shielding gas with the purpose of diffusing hydrogen to the heat affected zone. The results indicate how the thermal cycle, different hydrogen levels and hydrogen trapping sites affect the mechanical properties.

A survey of possible welding defects in steel sheets caused by shielding gases in GMAW and laser welding

A survey of possible welding defects in steel sheets caused by shielding gases in GMAW and laser welding

Development of closed‐loop control of robotic welding processes

PurposeThe purpose of this research is to develop closed‐loop control of robotic welding processes.Design/methodology/approachThe approach being developed is the creation of three‐dimensional models of the weld pool using stereo imagining. These models will be used in a model‐based feedback control system. Fusion of more than one sensor type in the controller is used.FindingsThree‐dimensional images can be produced from stereo images of GMAW‐p weld pools. This requires coordinating the image capture with the arc pulse to allow observation of the pool.Research limitations/implicationsThis is a work in progress. The imaging is not being done in real time at this point in time. Future work will address this issue. Also, how the image information is to be used to make corrections within the controller is future work.Practical implicationsClosing the loop on GMAW welding will allow robotic automation of welding to proceed to a much broader degree of application.Originality/valueThis paper demonstrates that stereo imaging of out‐of‐position GMAW‐p weld pools is possible and the useful information can be obtained from these images. It also provides insights into the analysis required within the model‐based controller if one is to close the loop on the process specifically with regard to weld pool stability.

Comparison between genetic algorithms and response surface methodology in GMAW welding optimization

The response surface methodology (RSM) is a traditional technique for experimental process optimization. Recently, a new approach to this problem has been tried with the genetic algorithm (GA), which is most known in the numerical field. The present paper compares these two techniques in the optimization of a GMAW welding process application. The situation was to choose the best values of three control variables (reference voltage, wire feed rate and welding speed) based on four quality responses (deposition efficiency, bead width, depth of penetration and reinforcement), inside a previous delimited experimental region. For the RSM, an experimental design was chosen and tests were performed in order to generate the proper models. In the GA case, the search for the optimal was carried out step by step, with the GA predicting the next experiment based on the previous, and without the knowledge of the modeling equations between the inputs and outputs of the GMAW process. Results indicate that both methods are capable of locating optimum conditions, with a relatively small number of experiments.

鉄鋼材料のアーク溶接およびレーザ溶接におけるシールドガスからみた欠陥防止・溶接性

鉄鋼材料のアーク溶接およびレーザ溶接におけるシールドガスからみた欠陥防止・溶接性

GMAW welding optimization using genetic algorithms

This article explores the possibility of using Genetic Algorithms (GAs) as a method to decide near-optimal settings of a GMAW welding process. The problem was to choose the near-best values of three control variables (welding voltage, wire feed rate and welding speed) based on four quality responses (deposition efficiency, bead width, depth of penetration and reinforcement), inside a previous delimited experimental region. The search for the near-optimal was carried out step by step, with the GA predicting the next experiment based on the previous, and without the knowledge of the modeling equations between the inputs and outputs of the GMAW process. The GAs were able to locate near-optimum conditions, with a relatively small number of experiments. However, the optimization by GA technique requires a good setting of its own parameters, such as population size, number of generations, etc. Otherwise, there is a risk of an insufficient sweeping of the search space.

Texture Evolution in Weld Regions of SUS-304 Stainless Steel and TRIP Steel

Electron back-scattered diffraction (EBSD) analysis has been conducted on the bead-on- plate GMAW welding of stainless steel SUS-304 and TRIP steel. The grain size, texture evolution, misorientation distributions and CSL grain boundary of weld metal (WM), HAZ and base metal (BM) have been observed at various welding conditions. With increasing heat input, the grain size in all cases increased at weld metal. With increasing heat input, no significant textural change was observed, but the characteristics of misorientation distributions and the CSL grain boundary decreased.

Numerical Simulation Of Droplets Formation In GMAW Welding

Numerical Simulation Of Droplets Formation In GMAW Welding

Computation of GMAW welding heat transfer with boundary element method

Based on the computation model for quasi-steady heat transfer problems of welding with the boundary element method, a computer program is developed and used for the computation of thermal cyles at heat affected zones with gas shielded metal arc (GMAW) welding on medium thickness plates. The computed results are in good agreement with those from experiments, showing the capabilities and versatilities of the boundary element method to deal with the computerized simulation of welding thermal processes.

Evaluation of the Usability and Benefits of Twist Wire GMAW and FCAW Narrow Gap Welding: 1984-1985

This paper is an interim report for the Puget Sound Naval Shipyard on the usability and benefits of twist wire narrow gap welding in the shipbuilding industry covering the period 1984 to 1985. It includes both the gas metal arc (GMAW) and flux cored arc (FCAW) welding processes. Various types of weld defects are discussed in terms of causes and effects. The ability of the twist wire process to produce high quality welds, with desired mechanical properties, over a wide range of gap widths and using a wide range of welding parameters, is also examined. The equipment used in this process is described.