Increasing Welding Speed Research Articles

Study of the microstructure and impact properties of the heat-affected zone of high nitrogen steel for laser-arc hybrid welding

The effect of different heat inputs on the microstructure and impact properties in the heat affected zone (HAZ) for laser-arc hybrid welding of high nitrogen steel are studied in this paper. The microstructure and impact properties were investigated using optical microscopy, scanning electron microscopy, and other methodologies. The results showed that the HAZ consists of massive amounts of austenite with small amounts of δ-ferrites. The combination of laser and arc causes the high nitrogen steel to absorb more energy, and the area of the heat affected zone increases as the heat input increases. At an identical heat input, the upper grain size of the HAZ is larger than the lower grain size, and the grain size of the HAZ increases as the laser power and welding current increase, and decreases as the welding speed increases. The impact energy decreases as the laser power and welding electric current increase, and the impact performance decreases as the welding speed increases. The experimental impact specimens showed obvious ductile fracture characteristics, with many dimples distributed on it.

EFFECT OF FRICTION STIR WELDING PROCESS PARAMETERS AND POST-WELD HEAT TREATMENT ON THE CORROSION BEHAVIOUR OF AA6061-O ALUMINUM ALLOYS

The aim of the present work is to study the effect of rotation and welding speeds as well as the T4 and T6 post-weld heat treatments (PWHT) on the corrosion behavior of AA6061-O aluminum plates joined using friction stir welding (FSW). The corrosion properties of welded joints were studied by Potentiodynamic polarization and Immersion tests. The results showed that both T4 and T6 PWHT improves the corrosion resistance of stirred zones compared to base alloy. However, joints of T4 showed lower corrosion resistance compared to T6. Increasing welding speed or reducing rotation speed increased the corrosion resistance of joints.

Effect Of Welding Speed On Weld Bead Geometry And Percentage Dilution In Gas Metal Arc Welding Of SS409L

Abstract Welding process parameters are the controlling factor for percentage dilution and weld bead geometry (bead width, bead height and penetration). Percentage dilution and weld bead geometry are very important factors to determine the quality of the joints. Present work aims to investigate the effect of welding speed (300, 400 and 500 mm/minute) on percentage dilution and weld bead geometry. Gas metal arc welding of ferritic stainless steel SS409L with austenitic stainless steel filler wire ER304L using pure argon gas has been done. The study of percentage dilution and weld bead geometry has been carried out. It has been found out that with increasing welding speed, bead width, bead height and penetration decreases but percentage dilution first increases with the welding speed parameter and then decreases with further increase in these values.

Study on connection and properties of green assembled building steel structures

Abstract In order to meet the research and industrialization application needs of green building integration technology and key technology of green building envelope structure in affordable housing projects, the effects of laser power and welding speed on the forming quality, microstructure and hardness of welded joints of heterogeneous steels with unequal thickness in steel structures were studied. The results showed that, for the front weld width, the influence of laser power on the back weld width is more obvious, and the influence of welding speed on the back weld width is greater than that of the front weld width. With the increase of laser power, coarse lath martensite and ferrite are formed in laser welded joints; with the increase of welding speed, heat input decreases, heat dissipation speed increases, grain growth time shortens, and grain refinement occurs. With the increase of laser power and welding speed, the tensile strength of laser welded joint has little change compared with base metal, but the elongation of welded joint is lower than that of base metal. With the increase of laser power, the fracture position of welded joint will shift from base metal to heat-affected softening zone. With the increase of welding speed, the fracture position of welded joint will shift from heat-affected softening zone to base metal. The suitable laser power for HC550/DP780 heterogeneous steel plate is 1.2 KW and the welding speed is 2400 mm/min. At this time, the welded joint has good welding forming quality, the hardness of weld zone is high and there is no softening point in heat affected zone.

Effect of self-reacting friction stir welding on microstructure and mechanical properties of Mg-Al-Zn alloy joints

The 5 mm-thick Mg-6Al-1Zn alloy was self-reacting friction stir welded (SR-FSW) at various welding speeds. Sound joints were achieved with welding speed ranging from 300 to 400 mm/min. At lower welding speed, pore defect formed in the weld nugget zone (WNZ) due to the inadequate mixing of the plastic materials. The thermo-mechanically affected zone (TMAZ) consisted of fine equiaxed dynamic recrystallized grains instead of the elongated and rotated grains formed in the TMAZs of FSWed Mg alloys and SR-FSWed Al alloys. Finer grains were obtained in the WNZ, TMAZ and heat affected zone (HAZ) at higher welding speed due to the lower heat input. Both the TMAZ and WNZ have grains with a high density of dislocations due to the straining exerted by the tool. Hardness profiles show slight variation throughout the weld with the hardness values fluctuated between 50 to 68 HV. Results of tensile tests revealed that the tensile strength increased with increasing welding speed with the maximal strength efficiency reached 77%. Fracture elongations were lower than that of the base metal due to the inhomogeneous microstructure throughout the joint. The impact energy of both the WNZ and HAZ increased with increasing welding speed.

Effects of welding speed on bubble dynamics and process stability in mechanical constraint-assisted underwater wet welding of steel sheets

Dynamic behavior of the bubble was investigated by high-speed camera and using the dysprosium lamp method for welding speed ranging from 1.0 mm/s to 6.0 mm/s during conventional underwater wet welding and mechanical constraint-assisted underwater wet welding. Process stability analysis was conducted by welding electric signal to predict the evolution of bubble features. For conventional underwater wet welding, the variation in bubble geometry over time is visually observed and its track morphology changes from a vertically upward track to a deflected track with increasing welding speed. The stable and sustained bubble with its structural integrity benefits from mechanical constraint for all welding speeds. Mechanical constraint can compensate for the insufficient bubble protection and successfully prevent further bubble-induced perturbation on welding arc. In comparison to onshore welding and underwater wet welding with mechanical constraint, conventional underwater wet welding indicates the most variation of welding electric signal. The variation coefficient exhibits similar result with welding speed for the exertion of mechanical constraint, whereas the difference in variation coefficient exists for conventional underwater wet welding. The direct observation over weld morphology is also demonstrated to show the feasibility of bubble control using the developed process. Discernible difference in weld penetration appears, displaying higher value with mechanical constraint than without mechanical constraint.

Experimental and numerical investigations of bonding interface behavior in stationary shoulder friction stir lap welding

Stationary shoulder friction stir lap welding (SSFSLW) was employed to weld 2024 aluminum alloy. A coupled Eulerian-Lagrangian (CEL) model was developed to investigate the lap interface behavior during SSFSLW. Numerical results of material movement and equivalent plastic strain were in good agreement with the experimental work. With increasing welding speed, the distances from the hook tip to the top surface of the upper workpiece on the retreating side (RS) and the advancing side (AS) increase, while the distance between two wave-shaped alclads decreases. A symmetric interface bending is observed on the AS and the RS during plunging, while the interface bending on the AS is bigger than that on the RS during welding. The peak temperature of the interface on the AS is higher than that on the RS. The equivalent plastic strain gradually increases as the distance to the weld center decreases, and its peak value is obtained near the bottom of the weld.

Microstructures and mechanical properties of micro friction stir welding (μFSW) of 6061-T4 aluminum alloy

Micro friction stir welding (μFSW) was successfully performed to join the ultra-thin 6061-T4 sheet with the thickness of 0.5mm. The optimum plunging depth of 0.05mm was obtained and reduction ratio was lower than 0.2%. Based on better dynamic flow induced by the triflat pin, the good surface appearance at the wider process window was obtained, while the grain size at the nugget zone was finer than that by the taper pin. Increasing welding speed caused that tensile property increased firstly and then decreased with high welding speed than 500mm/min. The maximum values of tensile strength and elongation of the μFSW joint using the triflat pin reached 220.3MPa and 11.7%, which were 91.9% and 54.4% of base material, respectively.

Characteristics of fiber laser weldments of two phases (α+β) titanium alloy

Laser welding experiments are conducted at various welding conditions on Ti-6Al-4 V alloy plates by employing fiber laser. A special type of workpiece fixture having provision of supplying shielding gas is fabricated for the protection of weld bead efficiently from environmental contamination. The influence of process parameters i.e. welding speed on the development of non-homogeneous microstructure of the weld bead is investigated by conducting microstructural characterization in details. Different morphologies of martensitic phase such as α´martensite, massive αm, blocky α and basket-weave structure are observed in the fusion zone. The variation in amount of α´ martensite is observed within heat affected zone. The calculated cooling rate and microstructure evaluation in the fusion zone are consistent with the continuous cooling transformation curve of Ti-6Al-4 V alloy. Higher hardness is found in fusion zone of the weldments. At lower welding speeds (500 ̶ 600 mm/min), underfill weld defects and at higher welding speed (800 mm/min) the micro-pores are observed in the weld bead. However, sizes of micro-pores are within the acceptable range as per BSEN: 4678 European standard. The microhardness and tensile strength of weldments are increased with increasing welding speed due to the development of finer α´ martensite in the fusion zone. For a fixed beam power of 1200 W, the most favorable range of welding speed (700 ̶ 800 mm/min) is identified which produced consistently high quality welds without crack and acceptable pore size. Vickers microhardness and tensile test results indicate that the optimal process parameters obtained in the current study can be suitably used in industries.

In-situ micro-tensile testing of AA2024-T3 fibre laser welds with digital image correlation as a function of welding speed

In this paper, the influence of welding speed on tensile properties of AA2024-T3 fibre laser welds was investigated by monitoring the deformation behaviour during tensile loading. In-situ micro-tensile testing combined with a high-resolution optical microscope and DIC was used to measure strain distribution in narrow weld regions showing characteristics of fibre laser beam welding with limited metallurgical modifications. A chemical etching technique was used to generate a micro-scale random speckle pattern by revealing the weld microstructure. Such pattern enabled a sufficient spatial resolution of strain while keeping the weld seam visible during deformation. The results of microstructural and mechanical properties determined under numerous welding speeds indicated that increasing the welding speed led to the transition of weld pool shape from circular to elliptical to teardrop with a greater fraction of equiaxed dendrites. The weaker strength of the weld, as measured by local lower micro-hardness values, constrained significant plasticity development locally within the weld. Tensile tests revealed that increasing the welding speed resulted in greater yield strength and ultimate tensile strength, whereas, total elongation to failure dropped. The tensile properties improved with increasing welding speed as the fraction of equiaxed dendrites increased.

The effect of welding speed on mechanical and microstructural properties of 5754 Al (AlMg3) alloy joined by laser welding

5754 (AlMg3) alloys have advantages such as good strength, perfect corrosion resistance and cold forming in addition to the low specific density. Because of these advantages, they are commonly used in automotive, chemical and food industries, and especially in the vessel and yacht industry. However, in spite of having such important and common areas of usage, it is very difficult to join Al and its alloys by traditional welding methods. This study focused on joining of 5754 Al alloy materials, which are hard to be joined by the traditional welding methods but have common areas of usage, by using the laser welding method. Laser welding method has many advantages such as the low heat input, deep penetration, low residual stress, and distortion compared to traditional welding methods. For this purpose, 3 mm thick 5754 Al alloy sheets were joined by using the laser welding method. The welding processes was carried out selecting three welding speeds (3, 4.8, and 6 m min−1). The macrostructure, microstructure, hardness, tensile, and impact strength properties of the samples taken from the welded joints were examined. It was observed that micro-porosity and micro-void defects formed in the microstructure of the weld metal. The rate and size of these defects increased with increasing welding speed. The increase in the welding speed decreased the amount of the accumulated metal and the penetration rate. The mechanical properties were also negatively affected by the increase in the welding speed.

Effect of Surface Tension Anisotropy and Welding Parameters on Initial Instability Dynamics During Solidification: A Phase-Field Study

The effects of surface tension anisotropy and welding parameters on initial instability dynamics during gas tungsten arc welding of an Al-alloy are investigated by a quantitative phase-field model. The results show that the surface tension anisotropy and welding parameters affect the initial instability dynamics in different ways during welding. The surface tension anisotropy does not influence the solute diffusion process but does affect the stability of the solid/liquid interface during solidification. The welding parameters affect the initial instability dynamics by varying the growth rate and thermal gradient. The incubation time decreases, and the initial wavelength remains stable as the welding speed increases. When welding power increases, the incubation time increases and the initial wavelength slightly increases. Experiments were performed for the same set of welding parameters used in modeling, and the results of the experiments and simulations were in good agreement.

Cross touching behavior in arcing-wire gas tungsten arc welding

Continuous cross touching metal transfer in arcing-wire gas tungsten arc welding using a constant-current power supply is proposed. With increasing wire feed rate, the metal transfer behavior changed from critical touching to completely touching to over touching. In addition, the arc voltage waveform changed from an unstable to a stable state before reverting to an unstable state. With increasing welding speed, the weld pool moved away from the extension line of the tungsten electrode and the length of the preheated wire increased. With increasing main arc welding current, the weld pool began to close the extension line of the tungsten electrode, which allowed the wire tip to be easily inserted into the weld pool. Finally, the surface of the weld pool changed from convex to concave.

Establishing the Dependence of Output Parameters Depending on Local Process Conditions for Friction Stir Welding of Pure Copper Plates

Welding copper and its alloys is usually difficult to achieve by conventional fusion welding processes because of high thermal diffusivity of the copper, which is at least 10 times higher than most steel alloys, in addition to this, there are the well-known disadvantages of conventional fusion welding represented by necessity of using alloying elements, a shielding gas and a clean surface. To overcome these inconveniences, Friction Stir Welding (FSW), a solid state joining process that relies on frictional heating and plastic deformation, is being explored as a feasible welding process. In order to achieve an increased welding speed and a reduction in tool wear, this process is assisted by another one (TIG) which generates and adds heat to the process. The research includes two experiments for the FSW process and one experiment for tungsten inert gas assisted FSW process. The process parameters that varied were the rotational speed of the tool [rpm] and the welding speed [mm/min] while the compressive force remained constant. The purpose of this paper is to correlate the evolution of temperature, tensile strength, elongation and microscopic aspect with the linear position on the joint (local process parameters) for each experimental case and then make comparisons between them, and to identify and present the set of process parameters that has the best mechanical properties for this material.

Joining of aluminum alloy and polymer via friction stir lap welding

Sound hybrid joint was achieved with a sufficient mixture of 6061-T6 aluminum (Al) alloy and polyether ether ketone (PEEK) via friction stir lap welding (FSLW) by a tapered thread pin with the triple facets. The larger length ratio between the Al anchor and the rotating pin reached approximately 0.8 at low welding speeds due to the dynamic flow induced by the triple facets. The mechanical interlocking and adhesive bonding attributed to the high-quality joining. Increasing welding speed resulted in the reduction of the adhesion area and the decrease in the size of the Al anchor, deteriorating the mechanical interlocking. A high-quality with the maximum shear bond strength of 20 MPa was achieved through the big Al anchor with a high hardness value. The tapered thread pin with the triple facets has feasible and potential to FSLW of metal and polymer in terms of enhancing mechanical interlocking.

Modeling and Optimization of Bobbin Friction Stir Welding for AA6061-T6 alloy Utilizing Response Surface Methodology

Bobbin friction stir welding (BFSW) is special kind of friction stir welding. This investigation aims to develop empirical models through mathematical relationships between the welding process parameters and mechanical properties of Aluminum alloy AA6061-T6 welded joint created by using bobbin tool and to find the optimum welding parameters. The welding speed range (40-200 mm/min) and rotational speed range (340-930 rpm) were utilized (as the used input factors) to find their effects on elongation, tensile strength and maximum bending force as the main responses. These models were built using Design of Experiment (DOE) software ‘version 10’ with Response Surface Methodology (RSM) technique. The models adequacy were tested via the (ANOVA) analysis. The obtained models appeared that as the welding speed or rotational speed increases, the elongation, tensile strength and maximum bending force of the welded joint firstly rise to a maximum value and then drop. The optimum welding parameters were rotational speed (623.949 rpm) and welding speed (128.795 mm/min) with (6.33%), (204 MPa) and (6.216 KN) of elongation, tensile strength and maximum bending force, respectively. A proper harmonization was obtained between the models predicted results and the optimized ones with actual trial with 95% level of confidence.

Mechanical Properties and Micrstructure of Al-5083 by TIG

The current study deals with the parametric and micro-structural analysis and of Al5083 welded specimen with an automated TIG set up. TIG provides one of the most precise and quality welding fastest welding speed can be used in marine, aerospace and ship industries. Welding speed, current, gas flow rate are the important parameters which are directly affecting the tensile strength of welded specimen and plays an important role in metallurgical changes. Wire EDM cutting is used to cut the welded specimen as per ASTM standard. Tensile strength increases by increasing welding speed till an optimum value and further decreases by increasing the welding speed. Micro-Structural changes are investigated by X-ray diffraction (XRD) and Scanning electron microscopy (SEM) and Energy dispersive spectroscopy (EDS).

Comparative study on microhardness between friction stir welding and tungsten inert gas assisted friction stir welding of pure copper

Welding copper and its alloys is usually difficult to achieve by conventional fusion welding processes because of high thermal diffusivity of copper, which is at least 10 times higher than most steel alloys. In order to reduce the increased temperature loss, it would be advantageous to use a process that is carried out at lower temperatures. Friction Stir Welding (FSW) is a solid state joining process that involves the joining of two metal pieces at the molecular level without melting and was explored as a feasible welding process. In order to achieve an increased welding speed and a reduction in tool wear, this process is assisted by another one (TIG - tungsten inert gas) which generates and adds heat to the process. The research includes two experiments for the FSW process and two experiments for TIG assisted FSW process. It is presented the evolution of the temperature and of the axial force during the process and is determined the microhardness for each experimental case. The aim of this paper is to make known the effects of using TIG assisted FSW process on the microhardness of the pure copper joints and to present some conditions in which it is less affected.

Influence of welding speed on microstructures and mechanical properties of vacuum electron beam welded TZM alloy joints

Butt joints of molybdenum-titanium-zirconium (TZM) alloy were welded by electron beam welding (EBW) and the influence of welding speed on the microstructures and mechanical properties of TZM joints were investigated in this paper. The color etching method was performed to obtain the orientation and phase distribution on weld zones (WZs) of the joints welded at different welding speeds. The electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were conducted to further check the results of the color etching method. The results illustrated that the tensile strengths would reduce with the increasing welding speed within a certain range. When welding speed was 350 mm/min, the tensile strength was 403 MPa, while the tensile strength of the joint welded at the welding speed of 390 mm/min was 256 MPa. The segregation of the MoO2 particles on grain boundaries (GBs) was also promoted with the increase of the welding speed, leading to the decrease of tensile strength and formation of severe intergranular fracture in the WZ.

High-Speed Friction Stir Welding of AA7075-T6 Sheet: Microstructure, Mechanical Properties, Micro-texture, and Thermal History

Friction stir welding (FSW) is a cost-effective and high-quality joining process for aluminum alloys (especially heat-treatable alloys) that is historically operated at lower joining speeds (up to hundreds of millimeters per minute). In this study, we present a microstructural analysis of friction stir welded AA7075-T6 blanks with high welding speeds up to 3 M/min. Textures, microstructures, mechanical properties, and weld quality are analyzed using TEM, EBSD, metallographic imaging, and Vickers hardness. The higher welding speed results in narrower, stronger heat-affected zones (HAZs) and also higher hardness in the nugget zones. The material flow direction in the nugget zone is found to be leaning towards the welding direction as the welding speed increases. Results are coupled with welding parameters and thermal history to aid in the understanding of the complex material flow and texture gradients within the welds in an effort to optimize welding parameters for high-speed processing.