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Grade AH36 ship steel plate, frequently used in offshore applications, was joined underwater by shielded metal arc welding (SMAW) using two different types of electrodes (E6013 and E7014). The ship steel plate was also joined under atmospheric conditions in order to compare both joints in terms of mechanical and metallurgical properties. The E6013 rutile electrode was isolated by wrapping before use, and the underwater welding process was carried out at a depth of 8 m under the sea. The joints were first subjected to visual inspection and then liquid penetrant, ultrasonic, and radiographic tests were performed. In order to determine the mechanical properties of the joints, tensile, bending, and impact toughness tests were also carried out. In addition to the microhardness test on the weld zones, microstructural examination was also performed on the joints. As a result of the nondestructive tests, weld defects like slag remaining between the passes, gas porosities, burn-through, and lack of penetration were seen on the joints welded underwater with the two different electrodes. The study determined that these defects had significantly influenced the mechanical properties and width of the weld zone of the joints.

The high-pressurized zinc vapor, which was developed at the interface of the two metal sheets due to the lower boiling point of zinc (around 906 °C) than the melting point of steel (over 1500 °C), led to the formation of macro-blowholes. Vacuum-assisted laser welding was a powerful approach to obtain a defect-free weld bead. The laser welding process was simulated to observe the dynamic or zinc vapor. The stability of laser welding was analyzed according to simulated results. The zinc distribution which was measured by EDS experiment also represented the influence of ambient pressure on welding stability. The bearing load for weld beads under different ambient pressure was measured by shear strength test. A defect-free continuous laser weld bead could be obtained under 3 kPa ambient pressure.

MIG-TIG double arc welding of magnesium alloy was studied in this paper. The effects of different welding process parameters (bypass current, wire extension, distance between the tungsten electrode, and the workpiece) on weld forming were analyzed, and the craft parameters were obtained through the technology experiment. The favorable forming weld was obtained at the total current of 225 A, bypass current of 140 A, welding voltage of 21 V, welding speed of 2.8 m/min, distance between end of tungsten electrode, and the workpiece of 5 mm. The effect of the process parameters on welding process and weld was analyzed to provide a theoretical basis for further improving the stability of double arc welding of magnesium alloy and obtaining the weld which was in high quality and good forming.

Fusion welding processes such as shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) are used extensively and economically in fabrication of critical engineering structures and components across varied industries and applications throughout the world. By-product inherent with these welding processes consists of varied discrete lengths of unused welding rod remaining at the end of the weld thermal cycle. These residuals are typically considered spent or scrap material with minimal engineering value. This paper, however, presents an experimental investigation to further process such materials into commodities and components of enhanced economic and engineering value. A novel prototype system identified as indexing equal channel angular pressing (IX-ECAP) was developed using modifications to traditional equal channel angular pressing (ECAP) to transform welding residuals into nanostructured or ultra-fine grained materials. Such materials with significantly enhanced performance characteristics can then be used as feed stock for potential uses as composite matrix reinforcements, micro-machine elements, and micro-fasteners. Micro-hardness conversions from processed material allowed theoretical determination of grain sizes employing Hall-Petch relationships. Analysis of variance (ANOVA) using a five-factor two-level fractional factorial split plot design (FFSP) studied significance of number of passes, pressing speed, temperature, back pressure, and vibration on material properties. IX-ECAP provided significant improvements in mechanical properties and offered a viable solution whereby processing of discrete variable length aluminum 4043 welding rod residuals proved very successful.

This study introduces a novel approach to produce hardfaced alloys via pre-placement technique using the shielded metal arc welding process. The comparison between the microstructural, mechanical, and tribological properties of the Nb-free and Nb-additive hardfacings was characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray mapping, dry sliding wear, and hardness measurements. From the optical microscopy results, it was observed that the hardfacing alloys obtained by pre-placement technique with premixed powders are free of pores or cracks and show good metallurgical bonding with the substrate. SEM images revealed that the Nb-additive alloys are comprised of net-like carbides in interdendritic region and NbC particles in the matrix with a grain size ranges from 0.5–2 μm, which were found to be beneficial for enhanced hardness and wear resistance. Nb-additive alloy showed 2.63% increase in wear resistance in comparison with the Nb-free hardfacing. It has shown possible to obtain the high hardness and wear-resistant hardfacings with pre-placement technique.

A novel pulsed metal active gas-tungsten inert gas (PMAG-TIG) twin-arc tandem welding process is applied to make stable back beads in the first layer weld during one-side multilayer welding without backing plate. The effect of different arc distances on the arc plasma behavior, molten pool flow pattern, and back appearance of root welding during the twin-arc tandem welding was studied. Results indicated that when arc distance is about 22 mm during the welding process, about 30% heat energy of the arc heat is utilized to melt the root face of base metal, and the rest heat energy acts on the molten pool. In this condition, the temperature distribution of the molten pool is appropriate, the flow of the front edge of the molten pool is suitable, the back appearance is continuous, stable, and uniform, and the back reinforcement and weld width is moderate. When arc distance is about 17 mm, more arc heat energy is utilized to melt the root face, the fluidity of the front edge of the molten pool is stronger, which leading to the back reinforcement is relatively larger. While arc distance is about 27 mm, less arc heat acts on the root face, the fluidity of the front edge of the weld pool is weak, resulting that in the back reinforcement is relatively small. This twin-arc tandem welding process is a new welding process giving high quality and efficiency in root welding for medium or thick plates.

In this study, AISI 2304 duplex stainless steel sheets were joined with AISI 430 ferritic stainless steel sheets via resistance spot welding using various welding parameters. Welding processes were carried out at electrode forces of 0.6 and 0.8 MPa, welding currents of 2 and 3 kA, and welding times of 10, 20, and 30 cycles, and the effects of the welding parameters on the welded joints were investigated. In order to determine the strength of the welded zones, tensile-shearing tests were applied. The weld nugget diameters were measured using a digital caliper, while a micrometer was used to measure the electrode penetration depth values. In addition, hardness tests and scanning electron microscopy (SEM) studies were done on the welded regions of the joined samples. From the measured weld nugget diameters and electrode penetration depth values, it was determined that the changes in the welding parameters affected the weld nugget diameter and electrode penetration depth. The results of the tensile-shearing experiments showed that the increases in the welding parameters were effective on the tensile-shearing strength and weld nugget rupture form. Increasing the welding parameters also resulted in increased weld zone hardness. The microstructural examination indicated in particular that the increases in the welding parameters caused the ferrite grains to grow due to the rise in heat input.

Keyhole gas tungsten arc (K-TIG) welding with water cooling system was used to weld high-strength low-alloy steel of mid-thickness (thickness ranging 6–13 mm). Q345 plates of 8-mm thickness were jointed in a single pass without filler metal. The weld properties, including mechanical properties and microstructure, were analyzed. The maximum tensile strength of the weld was similar with that of the base metal, while the elongation and impact property of the weldment were decreased compared with the base metal. The numerical simulation result revealed that water cooling method used in K-TIG welding is greatly helpful in reducing the volume of the welding pool due to the enhanced cooling effect. Additionally, improved holding power of the welding pool can be obtained due to the increased surface tension.

External magnetic field (EMF) has a strong effect on the welding arc shape, droplet transfer, weld forming, microstructure, and properties of joint metal. This paper defines the types of external magnetic field and reviews the development of magnetically controlled arc welding process, particularly, the effect of external magnetic field parameters on the welding process. It is found that the welding productivity, the weld formation, the ductility, and toughness of welded metal can be improved; and the welding residual stresses, the chemical inhomogeneity, and the welding defects can be reduced. Finally, the development trend is discussed in the later sections of the paper.

In this paper, ultrasonic echo signals of four kinds of stainless steel resistance spot welds, namely failed weld, stick weld, good weld, and defective weld with gas pore, are analyzed in the time domain, frequency domain, and time-frequency domain based on wavelet packet transform. Fourteen ultrasonic characteristic signals which can reflect the different kinds of spot welds are extracted and can be automatically identified and classified by back-propagation (BP) neural network. The method of this paper can realize the intelligent identification of resistance spot welding defects, and the feasibility of this method has been verified in the experiment.

This study investigated the influence of oxide with a more negative Gibbs free energy (ΔG) on the surface appearance, geometry size, and delta-ferrite (δ-Fe) content of AISI 316LN stainless steel subjected to flux-aided tungsten inert gas (TIG) welding. Powdered ZrO2 of various particle sizes mixed with 80 % water/20 % acetone solution was used as flux. The potential advantages of ZrO2-aided TIG welding were also demonstrated. The results show that nanoscale ZrO2 flux produces a TIG weld with a slag-free surface, but it did not significantly increase the depth-to-width ratio of the weld. The present work also found that ZrO2 flux slag influences the δ-Fe content of AISI 316LN stainless steel weld. ZrO2-aided TIG welding has low tendency to form undercut ting and allows high-speed welding. The potential advantages of the ceramic slag created by the ZrO2 flux are a small tem-perature difference between the center and edges of welding pool surface, a low solidified rate of liquid metal at the rear of the welding pool, as well as alleviation of the arc pressure at the front of the welding pool.

Arcing-wire gas tungsten arc welding is an innovative process developed as a variant of gas tungsten arc welding to reinforce the deposition rate by utilizing bypass arc energy. After establishing an experimental platform, the experiments were conducted to study the arc characteristics, interaction of the main and bypass arcs, and metal transfer behavior. Magnetic arc blow, location of the bypass arc root, and shielding gas flow were found to cause arc deflection and an invisible obstacle between the arcs in arcing-wire gas tungsten arc welding. The bypass arc voltage should be controlled carefully to maintain the stability of the welding process. Globular transfer, short-circuiting transfer, and continuous bridging transfer could be obtained, which were determined by wire feed speed (the melting current) and the distance from the wire tip to the workpiece as well as the welding direction.

In this paper, Pulse on Pulse metal inert gas (MIG) welding–brazing of 6061 aluminum alloy to 304 stainless steel in a lap configuration was developed to investigate the effect of torch position and angle on the welding quality and welding process stability. Images of arc, electrical signals of welding current, and welding voltage were acquired in synchronous modes by a high-speed camera and electrical signal acquisition system, respectively. The obtained results demonstrate that arc shape, macrostructure, microstructure, and mechanical properties are sensitive to torch aiming position when torch travel angle is 20° and work angle is 0°. However, when travel angle is 20° and work angle is 20°, the effect of torch aiming position is insignificant. It is easier to strike arc and maintain it on the surface of aluminum alloy compared to stainless steel. High-strength joints, whose fracture occurred at heat-affected zones of Al alloys at 89 MPa up to 72 % of the tensile strength of Al alloys, have been obtained. Moreover, a comprehensive evaluation method for the welding process stability based on statistical techniques has been proposed. This method can be easily and quickly integrated in real-time control of the welding process, which provides a quantitative guidance in MIG welding–brazing of aluminum alloy to stainless steel.

An intelligent welding procedure qualification system has been developed in the current study. In this system, the welding procedure of Q345R is intelligently designed based on GBT25343.3-2010 welding standard. By setting the initial welding parameters including welding methods, base metal, and thickness, the welding procedure results will be launched after four steps reasoning of inference engine. To predict the mechanical properties and complete the welding procedure qualification, these initial welding procedure parameters are taken as the input values by artificial neural networks (ANN). Since the hyperbolic tangent function (tanh) is used in ANN, it performs well in dealing with nonlinear problem and controlling the prediction errors accuracy. To reasonably judge the qualification of the Welding Procedure Specifications, the mechanical properties as the output values are compared with the experimental results. Therefore, the ANN are imported to the expert system to control welding procedure design. Furthermore, the mutually beneficial relationship between them has been established. Artificial neural network provides a new approach to resolve the class of experience knowledge for the expert system. In turn, the expert system with a powerful knowledge base and dynamic database provides a lot of training samples for artificial neural networks.

Double-sided arc horizontal welding is a new process for high-strength steel thick plate. This study aims at studying thermal cycle and microstructure of backing weld. The special heating cycle with two peaks in double-sided double-arc welding is beneficial to the generation of microstructure with good strength and toughness, due to the effect of preheating and postheating. The microstructure was a mixture of ferrite and lath martensite. The heat-affected zone (HAZ) in the root area was overheated, owing to the shape of groove in the horizontal welding, resulting in meshes in the grain boundary. The meshes were analyzed to be the tempered martensite. Hardness tests showed that there were some softened regions in the HAZ on account of high-temperature tempering.

Based on the difference in melting point between aluminum alloy and steel, metal inert gas (MIG) arc brazing-fusion welding process was developed to join thin 6013 aluminum alloy plate to galvanized steel plate. A finite element model for lap joint was established to study its thermal process. In modeling, MIG arc was treated as the double ellipse Gaussian plane heat source and the overheated metal droplet was considered as the uniform body heat source. The effects of the zinc coating and the overlap gap were taken into consideration. The brazed seam width and the width of heat-affected zinc coating on the back side of galvanized steel plate were used to validate the calculated results. The results show that the calculated results are in good agreement with experimental results. The calculation results indicate that the temperature is not uniformly distributed in the brazing-fusion welded joint. There is a great difference in the reaction temperature and time at different positions on the brazed interface. In order to satisfy the energy condition in which aluminum plate is fully penetrated and steel plate is not melted, a corresponding relationship that the welding current and welding speed are synchronized to be increased must be followed.

with the purpose of improving weld joint quality and productivity, the oscillating arc narrow gap gas metal arc (GMA) welding was employed in welding quenched and tempered high-strength low-alloy thick steel. The microstructure and mechanical properties of weld joints were evaluated, namely micro-hardness, tensile strength, and low-temperature impact toughness. The test results indicated that mechanical properties of weld joints with oscillating arc narrow gap GMA welding were excellent and found to meet stipulated requirements. Oscillating arc narrow gap GMA welding is a promising process for welding quenched and tempered HSLA thick steels due to the low energy input and narrow square-butt groove.

Resistance spot welding is an essential welding mechanism for joining two or more metal sheets together in automotive industries. The mechanical assemblies are easily joined at discrete spots using high current flow through the area of concentration. It is easily achieved by compressing the base metals together to a certain pressure using copper electrode caps and allow the high current to flow through the concerned areas. The heat generation due to the current flow causes the metal sheets to be fused and consequently form bonds between base metals. The molten areas of base metals undergo solidification process by itself when the current flow is utterly stopped. Basically, the weld growth in any joint is determined by its process-controlling parameters, particularly the welding current, weld time, electrode force, and electrode tip. In these experiments, the welding current and weld time variations were carried out to characterize the weld growth for three types of joints mainly for stainless steel, mild steel, and both steel mixed joint. A pneumatically driven 75-kVA spot welder was used to accomplish the entire welding processes, and the welded samples were later subjected to tensile, hardness, and metallurgical tests to relate the diameter growth, loading force during tensile test, failure crack initiation, post-failure crack propagation direction, macro and microstructural changes, and also the hardness changes due to solidification process. Assessing the experimental results of 2-mm thickness of materials revealed that the welded areas’ characteristics have been varied from its original states to enriched states, in terms of shearing strength and hardness distribution as well as the microstructural orientation.

This study presents a new double-gas tungsten arc welding heat source, with two arcs serially arranged on the same side of a workpiece. During welding, a tungsten tube and inert gas are additionally used to help the rear electric arcs burn at the bottom of the existing weld pool formed by the fore arc. Bead-on-plate welding experiments using this heat source are carried out to investigate the heating efficiency of the heat source and the influences of the arc current, the gas flow rate in the tube on the welding process. Results show that the heat source presents higher melting efficiency and stronger heat penetrability compared with normal double-gas tungsten arc welding. The interactions of the forces near the weld pool in the welding process are also analyzed. Observation of the arc behavior by a high-speed camera proves that the electromagnetic force between the two burning arcs stabilizes the burning arcs and thus the welding process.

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.

Double-electrode gas metal arc welding (DE-GMAW) was developed to control the heat input to the work piece when the filler wire deposition rate was increased. Consumable DE-GMAW was developed to enhance the welding productivity by replacing the non-consumable electrode in DE-GMAW with a consumable electrode. However, the process of consumable DE-GMAW was unstable without a particular control system. In order to improve the stability of the welding process on condition of keeping the main characteristics of DE-GMAW, a novel welding method named consumable double electrode with a single arc (DESA)-GMAW was proposed. In this welding system, there were two consumable electrodes but only one arc. The distance between the tips of the main wire and the bypass wire mainly determined whether the welding method was consumable DESA-GMAW or consumable DE-GMAW. The welding process could be very stable with appropriate welding parameters: one filler wire kept arcing stably with regular metal transfer process, and the other filler wire was kept short-circuited with workpiece all through the time and was fed into the welding pool stably and smoothly. The transverse section of the weld bead was analyzed, and it was found that the penetration could be effectively decreased with high metal deposition rate by using consumable DESA-GMAW.

Manufacturing productivity can be improved by increasing the welding speed. However, humping bead will occur when welding speed is beyond a certain value. An experimental system of double-electrode gas metal arc welding (DE-GMAW) was developed to implement high speed welding and prevent from humping bead formation. The DE-GMAW appropriately partition the heat energy between the wire and the base metal so that higher deposition rate of filler wire and suitable shape and size of weld pool are ensured. The arc images captured during DE-GMAW process were used to optimize the geometric parameters between the gas tungsten arc welding and the gas metal arc welding (GMAW) torches. The main arc and bypass arc integrated well and satisfactory weld bead formation was obtained. Through observing the weld pool behaviors from side view during DE-GMAW process, it was found that the height of both solidified and molten region at the pool tail is almost flat so that no humping bead was formed during DE-GMAW with the welding speed up to 1.7 m/min. The side view images of weld pool in DE-GMAW were compared with those in conventional GMAW, and the reason why DE-GMAW can suppress humping bead is shortly discussed.

A novel double-electrode gas metal arc welding method to weld steel tubes was investigated in this paper. The new method combines two welding torches and current sensors with welding position and angel design. In addition, a new control system was designed to improve the quality of welding seams. Experiments showed that different positions of main torch and bypass torch had different influence on welding quality. With bypass arc voltage at 35 V and suitable main welding feeder speed (WFS) at 10.2 m/min (400 in/min, 195 A), double arcs were ignited well and metal transfer was in spray mode. When the bypass WFS was at 8.9 m/min (350 in/min, 195 amps), welding seam formation and welding seam penetration were good. High-speed photos had been provided to prove the experimental results.

Advanced creep-resistant steels have been developed to meet the demanding requirements of fossil power plants that strive to improve the generation efficiency by enhancing the steam temperature and pressure. These are ferritic steels with nominal chromium content ranging from 2% to 12% with significant addition of tungsten besides Nb, V, and N in small level. One of the candidate materials is 9Cr-0.5Mo-1.7W steel, developed for steam circuit components of tubes, and pipes of power plants for an operating temperature of 600°C. Hydrogen cracking is a major issue in welding of this steel, due to solid-state metallurgical transformations that lead to untempered martensite in the HAZ of weld joint. The hydrogen cracking does not occur below a threshold stress level called critical cracking stress. The critical stress for cracking in this steel was determined by carrying out implant weldability tests using shielded metal arc welding process for various levels of diffusible hydrogen in the weld metal and an empirical model relating levels of diffusible hydrogen and time taken for cooling from 800°C to 500°C to the critical stress has been developed. Results of current study also showed that residual diffusible hydrogen plays a major role in deciding hydrogen cracking than the initial diffusible hydrogen in the weld metal.

The present investigation is aimed at to study the effect of welding processes such as GTAW, GMAW and FSW on mechanical properties of AA6061 aluminium alloy. The preferred welding processes of these alloys are frequently gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) due to their comparatively easier applicability and better economy. In this alloy, the weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often causes inferior weld mechanical properties and poor resistance to hot cracking. Friction stir welding (FSW) is a solid phase welding technique developed primarily for welding metals and alloys that heretofore had been difficult to weld using more traditional fusion techniques. Rolled plates of 6 mm thickness have been used as the base material for preparing single pass butt welded joints. The filler metal used for joining the plates is AA4043 (Al-5Si (wt%)) grade aluminium alloy. In the present work, tensile properties, micro hardness, microstructure and fracture surface morphology of the GMAW, GTAW and FSW joints have been evaluated, and the results are compared. From this investigation, it is found that FSW joints of AA6061 aluminium alloy showed superior mechanical properties compared with GTAW and GMAW joints, and this is mainly due to the formation of very fine, equiaxed microstructure in the weld zone.

Weld hardfacing techniques are employed mainly to extend or improve the service life of engineering components either by rebuilding or by fabricating in such a way as to produce a composite wall section to combat wear, erosion, corrosion, etc. In this paper, an attempt has been made to determine the best welding process to hardface boiler grade steels based on quantitative factors (by measuring percentage of dilution) and qualitative factors (using the analytic hierarchy process [AHP]). Five different welding processes including shielded metal arc welding (SMAW), gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), submerged arc welding (SAW), and plasma transferred arc welding (PTAW) have been compared. Based on the quantitative and qualitative factors, the PTAW process is found to be the best method to hardface boiler grade steels.

The preferred process for welding titanium alloy is frequently gas tungsten arc (GTA) welding due to its comparatively easier applicability and better economy. Weld fusion zones of this alloy typically exhibit coarse columnar grains and lead to inferior mechanical and metallurgical properties. In the case of single pass GTA welding of a thinner section of this alloy, the pulsed current has been found to be beneficial primarily due to grain refinement of the weld fusion zone over the conventional continuous current process. Fusion zone grain refinement is controlled by pulsed current parameters such as peak current, back ground current, pulse frequency and pulse-on-time. In this investigation, a mathematical model has been developed to predict corrosion rate of gas tungsten arc welded titanium alloy by incorporating pulsed current parameters. Four factors, five level, central composite, rotatable design matrix has been used to minimize the experimental conditions. A mathematical model has been developed by response surface method (RSM). The developed model has been optimized using genetic algorithm (GA) and contour plots to attain minimum corrosion rate in the weld fusion zone.

High strength aluminum alloys (Al-Zn-Mg-Cu alloys) have gathered wide acceptance in the fabrication of lightweight structures requiring high strength-to-weight ratio, such as transportable bridge girders, military vehicles, road tankers and railway transport systems. The preferred welding processes of high strength aluminum alloy are frequently the gas tungsten arc welding (GTAW) process and the gas metal arc welding (GMAW) process due to their comparatively easy applicability and better economy. Weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often results in inferior weld mechanical properties and poor resistance to hot cracking. In this investigation, an attempt has been made to refine the fusion zone grains by applying a pulsed current welding technique. Rolled plates of 6 mm thickness were used as the base material for preparing single pass welded joints. A single ‘V’ butt joint configuration was prepared for joining the plates. The filler metal used for joining the plates was AA 5356 (Al-5Mg (wt%)) grade aluminum alloy. Four different welding techniques were used to fabricate the joints: (1) continuous current GTAW (CCGTAW), (2) pulsed current GTAW (PCGTAW), (3) continuous current GMAW (CCGMAW) and (4) pulsed current GMAW (PCGMAW). Argon (99.99% pure) was used as the shielding gas. Tensile properties of the welded joints were evaluated by conducting tensile tests using a 100 kN electro-mechanical controlled universal testing machine. Current pulsing leads to relatively finer and more equi-axed grain structure in GTA and GMA welds. In contrast, conventional continuous current welding resulted in predominantly columnar grain structures. Grain refinement is accompanied by an increase in tensile strength and tensile ductility.

This paper describes an automatic welding control system developed for alternating current shielded metal arc welding (SMAW). This method could replace manual operations which require a well-trained technician. We have derived a mathematical model of the welding control system and identified the system’s parameters. The sliding surface is used as the input variable to reduce the number of fuzzy reasoning rules, in comparison with the conventional two-dimensional fuzzy logic control (FLC) algorithm. An adaptive fuzzy sliding mode controller (AFSMC) consists of an equivalent control part and a hitting control part. An adaptive law derived from a Lyapunov function is used to obtain the FLC’s parameters, and is applied to approximate the equivalent control part of the sliding mode control (SMC), so that the system states can be forced to zero. By using three-rules FLC, the control part that satisfies the hitting conditions of the SMC can force the system’s states to reach and remain on the sliding surface. Therefore, the stability of the AFSMC can be guaranteed and can be used to modulate the rate of the electrode feeding mechanism that regulates the arc current of the SMAW. The simulation and the experimental results both show that this automatic welding control system, based on the AFSMC, can perform effectively.

A new method to tune the gains of the proportional integral derivative (PID) controller for alternating current shield metal arc welding (SMAW) of automatic arc welding system using a SMAW process is presented in this paper. This method used the genetic algorithm (GA) approach to optimize the gains of the PID auto-tuner and considerably modulated the rate of an electrode feed mechanism that regulates arc current. The proposed controller was verified by simulation and experiments of the transient response in the automatic arc welding system. Finally, the performance indices of the proposed controller are compared with that based on Ziegler–Nichols tuning rules.

In this work, gas metal arc welding of high strength-low alloy (HSLA) steel with solid- and flux-cored arc welding wires using different shielding gas compositions was performed. The composition of filler wire and shielding gas in gas metal arc welds of HSLA steel determines the inclusion characteristics, microstructure and mechanical properties. Thus, acceptable weld metal properties in HSLA steel using gas metal arc welding (GMAW) process could be achieved with the proper combination of filler wire and shielding gas composition.

This paper describes a developed automatic welding control system for alternating current shield metal arc welding. It replaces manual operations which require a well-trained technician. We derived a mathematical model of the welding control system and identified the value of the system parameters thereof. A fuzzy gain scheduling PID controller modulates the rate of an electrode feed mechanism that regulates arc current. The electrode feed rate mechanism with this controller driven by an AC servomotor can both compensate for the molting part of the electrode and the undesirable fluctuation of the arc length during welding operation. It can also be easily applied to any welding system whose electrode is consumed during the welding process. By maintaining the magnitude of the arc current at the desired value and ensuring the stability of the arc length, excellent welding performance can be obtained. The simulation and experimental results both show that this automatic welding control system, based on the fuzzy gain scheduling PID controller, can perform effectively.