Combination Of Welding Parameters Research Articles

Metallurgy and mechanical performance of AZ31 magnesium alloy friction spot welds

Microstructural features were studied along the cross-section of AZ31 magnesium alloy friction spot welded joints made using different combinations of welding parameters. Static lap shear testing was performed to evaluate the mechanical properties of the welded joints, and the resulting fracture mechanisms and crack propagation paths were fully examined. Failure load is optimized when the welding procedure is performed with the combination of parameters that maximizes the material mixing, the size of fully metallurgical bonding and simultaneously minimizes the vertical displacement of hook region. The welds demonstrate three failure modes during lap shear testing: through the weld and non-circumferential pull-out modes, in which crack propagation crosses the recrystallized zone, and circumferential pull-out mode, around this zone.

Optimization of weld bead geometry in laser welding with filler wire process using Taguchi’s approach

In the present work, laser welding with filler wire was successfully applied to joining a new-type Al–Mg alloy. Welding parameters of laser power, welding speed and wire feed rate were carefully selected with the objective of producing a weld joint with the minimum weld bead width and the fusion zone area. Taguchi approach was used as a statistical design of experimental technique for optimizing the selected welding parameters. From the experimental results, it is found that the effect of welding parameters on the welding quality decreased in the order of welding speed, wire feed rate, and laser power. The optimal combination of welding parameters is the laser power of 2.4kW, welding speed of 3m/min and the wire feed rate of 2m/min. Verification experiments have also been conducted to validate the optimized parameters.

Using the welding parameters to improve the mechanical properties of Liquefied Natural Gas storage tank welded joint

The increase demand for LNG as alternative of conventional oil fuel and due to the risk assessment of LNG tank . The increase of focus has been put on the performance of welded LNG tank . Where the improvement of 9%Ni steel plates mechanical properties is still continued by steel making to reduce the cost of fabrication of LNG storage tank and to give more safe structure. These applied by development of heat treatment process that change from quenched till reach to double quenched and tempered . The problem in welded joint is to be more match to mechanical properties of base metal especially with no facility of applying PWHT process . The only way to enhanced the mechanical properties of welded joint by controlling the parameters of using welding process. From the main variables of the arc welding process are the heat input and interpass temperature where the two variables control the thermal cycle of welding process. But there are limitations on the heat input and interpass temperature. The limitations of the welding parameters are greater as the strength of the parent metal increases. Where using the too high heat input as well as high interpass temperature that produce welded joint with low tensile strength, low hardness and low toughness mechanical properties. Although the low heat input or low interpass temperature increase the susceptibility of existing hydrogen crack. The combination of welding parameters, notably interpass temperature, are identified for SMAW process of a 9% Ni steel plates to improve the zones of welded joint strength and toughness properties. Results showed that for thin test specimen , the heat input range from 1.4 to 2 Kj/mm and controlling interpass temperature within 80° C give high tensile strength and improve the toughness properties of welded joint and the ductility improve reduce the probability of brittle fracture happened.

Decoupling control scheme for pulsed GMAW process of aluminum

A double-variable decoupling control scheme was proposed for GMAW-P process of aluminum helping to efficiently develop welding procedure. Weld pool width and arc length were both measured through vision sensing in welding process. Weld bead shape was improved by changing the current waveforms to adjust the heat input while the arc length was controlled to stabilize the welding process. An experimental system was developed to sense, observe and control the welding process real-timely. Experiments were conducted to verify the effectiveness of the scheme. The results show that good weld bead shape and stable welding process can be obtained through the double-variable decoupling control scheme without complex metal transfer control and considerable trial and error to identify suitable combinations of welding parameters in GMAW-P. This control scheme provides an alternative to obtain proper weld quality for GMAW-P.

Modeling and analysis of simultaneous laser transmission welding of polycarbonates using an FEM and RSM combined approach

In this paper, simultaneous laser transmission welding process is systematically investigated via process modeling, using an FEM and RSM combined approach. The objective of the present research is to study the effects of process parameters on the temperature field and weld bead dimensions. The thermal field is simulated by solving a three dimensional transient heat diffusion equation with temperature dependent material properties using the ANSYS ® multi-physics. Response surface methodology is then applied for developing mathematical models based on simulation results. The second order equations developed by RSM can predict the values of the responses with significant accuracy. The effect of parameters and their interactions on the responses are studied using the developed response surface models. The mathematical models are further used in search of the optimal process window for obtaining an acceptable weld. The graphical optimization results into a couple of overlay contours plots, which allow quick visual inspection of the area of feasible response values in the factor space to choose the favorable welding parameter combination.

Methods to Obtain Weld Discontinuities in Spot-Welded Joints Made of Advanced High-Strength Steels

Resistance spot welding is the major joining technique in mass car production. This applies in particular to high-strength steel and advanced high-strength steel (AHSS) joining of thin sheet steel components for lightweight body shell structures. Joining of AHSS in mass production might lead to weld discontinuities under certain circumstances. Those discontinuities in form of cracks might be an initial start of cracking in the spot-welded joints regarding fatigue loads. It is of great interest to figure out, if, in comparison to specimens without weld discontinuities, the crack initiating point changes and if the fatigue resistance might be reduced by the discontinuities. In this contribution, an overview of potential discontinuities is given. Their possible causes are discussed and means for their detection are highlighted. Among the possible causes of weld discontinuities, two major groups are distinguished: the welding parameters as primary influences in the welding process, and the production-specific influences as secondary ones. With emphasis on major cracks penetrating the weld nugget, these influences are analysed. Finally, a combination of extreme welding parameters with production-specific influences is chosen in order to establish a method which enables the preparation of fatigue test specimens with reproducible major cracks in different locations of the spot-welded joints. This method is then applied in order to prepare spot weld specimens for fatigue tests.

Bead-on-Plate Welding on Q235A Steel by Underwater Wet Welding Process with Flux-Cored Wire

Bead-on-plate welds was made by underwater wet welding with flux-cored wire in a tailor-made pentrough. The effect of welding parameters such as welding speeds, welding currents and welding voltages on welds surface appearances and microstructure were studied. Orthogonal experiment method was used to optimize combination of different welding parameters. The results showed that the hardness (HV) of welds fusion zone ranged between 515 and 670 while the hardness (HV) of base metal was only 350. The fusion zone of the welds was mainly composed of columnar grain structure.

Temperature Distribution during Friction Stir Spot Welding of Magnesium Alloy AM60B

Abstract This study investigated the effects of welding parameters on temperature distribution of magnesium alloy AM60B during Friction Stir Spot Welding (FSSW). The welding parameters included tool rotational velocity, plunge depth, and holding time. These parameters were selected from previous test results. The temperature distributions were measured with type-K thermocouples during FSSW with various welding parameter combinations. The measurement locations were placed along the centerline in longitudinal direction of the coupons. The temperature distributions during FSSW were also calculated with finite element analysis (FEA) for each combination of the welding parameters. The experimental results were compared with those obtained from FEA.

Friction Welding Studies on SiCp Reinforced Aluminium Alloy AA 2124 Metal Matrix Compositie

Continuous drive friction welding studies were carried out on AA 2124 SiCp metal matrix particulate composite. Taguchi technique was employed to select the best combination of friction welding parameters. Studied the influence of main friction welding process parameters such as friction force, forge force and burn off on tensile properties. Low friction force, high forge force and high burn-off yielded maximum tensile strength. Friction welds of metal matrix composite with higher volume fraction of SiCp yielded high tensile strength. It was observed that tensile strength of the welds were stronger than the corresponding parent material. The higher tensile strength of the welds is thought to be due to the break down of the reinforcement particle.

Characteristics of Laser Welded Joints of HDT580X Steel

In the present study, the characteristics of Nd:YAG laser welded joints of 600 MPa DP steel (HDT580X), 2.4 mm in thickness, in respect of hardness, microstructures and mechanical properties were investigated. The test joints have been welded under a shielding gas on the stand for robotic Nd:YAG laser welding at the beam power of 1.5 kW and 2.0 kW. Three combinations of welding parameters were used: 2.0 kW - 2.1 m/min, 2.0 kW - 1.5 m/min and 1.5 kW - 1.2 m/min. Detailed examinations were performed on the joint welded at the highest speed. The microstructure was examined by the optical-, scanning- and transmission electron microscope. The heat affected zone (HAZ) was composed of ferrite, bainite and lath martensite, the weld contained lath martensite. The maximum hardness in the HAZ did not exceed 343 HV. The tensile strength of the welded joint was at the same level as that of the base material. The results of fatigue tests and residual stress measurement of laser welded DP steel joints are also presented. The fatigue strength of the welded joint is lower than that of the base material. The fatigue class FAT was determined, which is equal to 284 MPa - for the base material and 150 MPa – for the welded joint. By means of the modified hole drilling method the following residual stresses were measured: σmax = 573 MPa and σmin= -126 MPa.

Determination of Optimum LASER Welding Parameters and the Development of a LASER Welding Technique to Enhance the Lateral Impact Strength of a Spacer Grid Assembly for a PWR Fuel Assembly

A spacer grid assembly, which is an interconnected array of slotted grid straps welded at the intersections to form an egg crate structure, is one of the core structural components of the nuclear fuel assemblies of a Pressurized light Water Reactor (PWR). The spacer grid assembly is structurally required to have enough buckling strength under lateral loads so that the nuclear fuel rods are maintained in a coolable geometry, and that control rods are able to be inserted. The ability of a spacer grid assembly to resist lateral loads is usually characterized in terms of its dynamic and static crush strengths. Since the crush strengths of a spacer grid assembly are known to depend on the weld qualities at the intersections of the slotted grid straps, high-tech welding methods, such as a TIG welding, LASER beam welding or Electron beam welding method, have been used recently in the nuclear fuel manufacturing fields. In this study, to meet the above requirements, two kinds of researches were carried out. First, by adjusting the LASER beam welding parameters, an optimum welding combination of the LASER beam welding parameters was obtained for welding a spacer grid assembly. Second, a new LASER beam welding technique was proposed to obtain a longer weld line and a smaller weld bead size by tilting the LASER beam. The buckling strength of the spacer grid welded by the new LASER beam welding technique was enhanced by up to 30 % when compared to that by the conventional LASER beam welding method.

Effect of the combination of different welding parameters on melting characteristics of grade 1 titanium with a pulsed Nd–Yag laser

The laser is a very attractive tool for joining dental metallic alloys. However, the choice of the setting parameters can hardly influence the welding performances. The aim of this research was to evaluate the impact of several parameters (pulse shaping, pulse frequency, focal spot size...) on the quality of the microstructure. Grade 1 titanium plates have been welded with a pulsed Nd-Yag laser. Suitable power, pulse duration, focal spot size, and flow of argon gas were fixed by the operator. Five different pulse shapes and three pulse frequencies were investigated. Two pulse shapes available on this laser unit were eliminated because they considerably hardened the metal. As the pulse frequency rose, the metal was more and more ejected, and a plasma on the surface of the metal increased the oxygen contamination in the welded area. Frequencies of 1 or 2 Hz are optimum for a dental use. Three pulse shapes can be used for titanium but the rectangular shape gives better results.

Study of friction stir welding of 01420 aluminum–lithium alloy

The 01420 Al–Li alloy plates were friction stir welded at different welding parameters. The effect of welding parameters on the quality of the 01420 Al–Li friction stir welded joints was investigated. As a result, the optimized combinations of various welding parameters (pin rotation speed, welding speed and welding pressure) were identified. By comparison of the heat inputs during welding process at different parameter combinations, the relationship between the grain size in the stirred zone (SZ) and the welding parameters was established. Furthermore, the mechanical properties of the defect-free joints under different heat inputs were investigated. The experimental results showed that the maximum ultimate strength of the joints is equivalent to 86% that of the base material and the maximum bending angle of the joints can reach 180°.

Preliminary studies on friction welding of sintered P/M steel preforms to wrought mild steel

Continuous drive friction welding studies on sintered powder metallurgical (P/M) steel preforms–wrought mild steel combination are reported in the present study. The work is a preliminary study to optimise the friction welding parameters and data generated by the present work is expected to contribute to friction welding of dissimilar and similar sintered P/M preforms to wrought metals or sintered P/M preforms – a planned future research work. Sound welds were obtained with all welding parameter combinations studied. The mechanical properties of welds were comparable to those of sintered P/M steel. Sintered P/M preforms deformed to a greater extent than wrought mild steel due to their low flow stress and thermal conductivity. The sintered density and other properties of the P/M preforms were found to dictate the deformation at the interface and consequently the weld strength. The results indicate that the current approach can be extended to other combinations of sintered P/M preforms.

Combined effect of flux and welding parameters on chemical composition and mechanical properties of submerged arc weld metal

Rotatable designs based on statistical experiments for mixtures have been developed to predict the combined effect of flux mixture and welding parameters on submerged arc weld metal chemical composition and mechanical properties. Bead-on-plate weld deposits on low carbon steel plates were made at different flux composition and welding parameter combinations. The results show that flux mixture related variables based on individual flux ingredients and welding parameters have individual as well as interaction effects on responses, viz. weld metal chemical composition and mechanical properties. In general, two factor interaction effect are higher than the individual effect of mixture related variables. Amongst welding parameters, polarity is found to be important for all responses under study.

Optimising multiple qualities of Nd:YAG laser welding onto magnesium alloy via grey relational analysis

This work evaluates multiple quality optimisation of Nd:YAG laser welding onto magnesium alloy via grey relational analysis. The effectiveness of the grey relational grade lies in quantifying and judging the performance obtained using various combinations of laser welding parameters. The parameters are shielding gas, laser energy, travelling speed of workpiece, point at which the laser is focused, pulse frequency, and pulse shape in this work. Moreover, 18 combinations of these six essential welding parameters were set following Taguchi's method to evaluate the integrated performance. The welding parameters that govern the laser beam in thin plate butt welding were evaluated by measuring the ultimate tension stress, and both the depth and the width along the welding path. This integrated performance was then quantified and judged via grey relational analysis to obtain an optimised set-up for laser welding. The verifying test was proved to optimise the ultimate tension stress, depth and width along the welding path from 67·0 MPa, 0·50 mm and 0·77 mm to 142·3 MPa, 0·79 mm and 0·79 mm, respectively.

Thermomechanical Analysis of an Ultrasonic Rapid Manufacturing (URM) System

Ultrasonic rapid manufacturing (URM), a low-temperature solid freeform fabrication method capable of producing high-strength functional solid metal parts and multi-material composites, is based on ultrasonic welding (USW) of metals. The quality of the weld, a critical aspect of the URM process, depends on (a) the amount of mechanical energy applied, through an appropriate combination of welding parameters: vertical pressure, horizontal vibration frequency, amplitude, and welding time, (b) the resulting heat generation, and (c) temperature rise. This paper investigates the thermomechanical process aspects and provides insight into the heat generation and transient-temperature profile during a single weld cycle under the special welding conditions developed in this article and validated in the laboratory. The finite element model analysis of two layers of aluminum foil subjected to these welding conditions—with surface contact resistance calibrated by experiments—reveals a moderate temperature rise but one that is sufficient for metal bonding via vacancy diffusion.

Two-dimensional friction stir welding process model based on fluid mechanics

AbstractA two-dimensional friction stir welding (FSW) process model has been developed. The fully coupled model is based on fluid mechanics and handles the solid state material transport during welding as a laminar, viscous flow of a non-Newtonian fluid past a rotating circular cylinder. The heat necessary for the material softening is generated by deformation of the material. Material flow visualisation experiments agree very well with the predicted flow field. Accordingly, material within the pin diameter is transported only in the rotation direction around the pin. Owing to the simplifying assumptions inherent in the two-dimensional model, other experimental data such as forces on the pin, torque, and weld energy cannot be directly used for validation. However, the two-dimensional model predicts many of the trends observed in the experiments. The model also predicts a deviation from the 'normal' material flow for certain combinations of welding parameters, suggesting a possible mechanism for the occurr...

Prediction of steady state dilution in multipass hardfacing overlays deposited by self shielded flux cored arc welding

A method of predicting the steady state dilution of multipass hardfacing overlays deposited via self shielded flux cored arc welding is described. A new variable is defined and used to describe the steady state dilution of multipass overlays. A mathematical model for dilution is presented in terms of this variable. Eight multipass overlays were deposited, using different combinations of welding parameters in each instance. The steady state dilutions for these overlays were measured and compared with those predicted by the model for dilution. It is found that, with an empirical correction, it is possible to predict the dilution of multipass hardfacing overlays over a wide range of welding conditions. This predictive capability establishes a relationship between welding process variables and the steady state composition, and hence the microstructure, of high chromium white iron weld overlays. Microstructure–wear relationships can then be applied to complete the link between welding parameters and the wear performance of the overlay.

A Statistical Analysis of Expulsion Limits in Resistance Spot Welding

Expulsion is an important phenomenon in resistance spot welding. It involves loss of metal from the liquid nugget, which often results in the reduction of weld strength. Various models have been proposed to understand expulsion mechanisms. In these models the occurrence of expulsion is often treated as a deterministic event, and depicted by a line (boundary) in conventional lobe diagrams. In this study, statistical analysis is employed to explore expulsion with consideration of the influence of random factors. Models are built based on experimental data, and one steel and two aluminum alloys are used as examples. Expulsion probabilities are presented as a function of electrode force, welding current, and time. Analytical models and their graphical form of expression (contours and surfaces) are created to present expulsion limits under various combinations of welding parameters. This study provides not only quantitative model predictions on expulsion limits for the materials studied, but also a generic statistical methodology that can be used for analyzing expulsion in various material systems. [S1087-1357(00)00602-X]