Argon Tungsten-arc Welding Research Articles

Study on welding process of stainless steel/superalloy dissimilar materials

Abstract In this study, dissimilar materials of 321 stainless steel, S-03 stainless steel, and GH3030 superalloy were selected and the argon tungsten-arc welding method was used to explore the welding parameters. The microstructure and properties of three materials after welding were studied. The main mechanism of welding cracks was analyzed by optical microscope and scanning electron microscope. Reasonable welding parameters were established and the dissimilar welding process was realized. The experimental results show that the cracks produced by welding of the three materials are typical welding hot cracks. The crack source originated from the bottom layer and extended to the surface of the welded joint. The main reason for cracking is the formation of low melting point compounds by the segregation of S and Ti elements during the process of self-melting. The welding process of the dissimilar materials can be realized by multi-pass filling welding. Increasing welding speed and reducing heat input are effective ways to improve weld mechanical properties of the welded joint.

Penetration state recognition for tungsten inert gas welding via an alternating cusp-shaped magnetic field-assisted molten pool-oscillation

To ensure optimal penetration in direct current (DC) argon tungsten arc welding, a method was proposed to recognize the molten pool penetration during molten pool oscillation under alternating cusp-shaped magnetic field (ACSMF). An arc discharge model is established to analyze the oscillation mechanism of the molten pool under ACSMF. The periodic variation of arc shape induces the periodic oscillation to establish a mapping relationship with the fluctuation of arc voltage waveform. At the excitation current of 3 A and frequency of 10 Hz, the arc voltage waveform undergoes abrupt changes at 1.26 V and 1.37 V, corresponding to the critical and the full penetration states, respectively. The errors in identifying moving penetration are 0.8 % and 0.7 %, with a full penetration weld, demonstrating a penetration rate of 100 %, indicating effective penetration recognition. Arc sensing technology for tungsten inert gas (TIG) welding under ACSMF is poised for gradual application in single-side welding and double-side forming of medium and thick plates. It is anticipated to evolve towards real-time identification technology for molten pool penetration monitoring.

The Influence and Mechanism Analysis of the Longitudinal Magnetic Field on the Microstructure Evolution and Properties of AZ40 Welds

This paper studied the effect of the longitudinal magnetic field (LMF) on the microstructure evolution and mechanical properties of AZ40 argon tungsten arc welding joints. Magnetic field-assisted argon tungsten arc welding technology was used to achieve butt welding of an AZ40 Mg alloy sheet with a thickness of 1.5 mm. The microstructure of the Mg alloy weld was studied by using metallographic microscopy and scanning electron microscopy. Mechanical performance of the Mg alloy weld was evaluated by using a hardness tester and universal tensile machine. The experimental results revealed that the average crystallite dimension of the weld zone of the Mg alloy joint reached 43 μm without an LMF. By introducing LMF-assisted technology, the weld structure was significantly refined and the average crystallite dimension of the weld seam was reduced by 39.5% to 26 μm with a coil current of 1.2 A. For the joint without magnetic field assistance, the optimum tensile strength of the AZ40 weldment was 225 MPa under a welding current of 80 A, and fracture occurred in the center of joint welding seam. Under an LMF coil current of 1.2 A, the joint strength increased from the initial 225 MPa to 254 MPa, and fracture occurred at the weld edge with obvious plastic fracture characteristics. It can be confirmed that the LMF-assisted welding process effectively improved the microstructure characteristics of the weld seam and strengthened the microhardness and mechanical performance of the AZ40 joint.

Research on Welding Process of Duplex Stainless Steel S31803

The welding test of duplex stainless steel S31803 pipe was carried out by means of argon tungsten arc welding as backing, hot welding, and manual arc welding as filling and covering. The mechanical properties, microstructure, phase ratio, and corrosion resistance of the welded joint were studied and analyzed through the test method. The results show that the appropriate welding parameters can control the proportion of ferrite and austenite, the mechanical properties, ferrite content, and pitting resistance of welded joints to meet the relevant requirements of the standard, and the established welding process has a good guiding role for the welding of duplex stainless steel in gathering and transmission pipelines.

Study on TIG Process of AZ31 Magnesium Alloy

In this paper, manual argon tungsten arc welding is used to weld AZ31 magnesium alloy plate with thickness of 2.5mm on both sides. The welding current parameters are changed. The best welding current is explored by analyzing the performance of welding joint; The corrosion resistance of welded joint was studied in the same medium. The results show that the microstructure of base metal zone is α- Mg solid solution, and the microstructure of the weld seam is mg solid solution α- Mg solid solution and β- Mg17Al12 intermetallic compound. When the welding current increases from 80A to 120A, the welding heat input increases gradually, and the grain size of HAZ increases gradually. The results of microhardness test show that the microhardness of weld zone is the largest, that of base metal is moderate, and that of heat affected zone is the lowest. The corrosion resistance of AZ31 magnesium alloy welded joint shows that the corrosion resistance of the weld zone is better than that of the base metal zone.

Structural-Phase State of Multicomponent Surfacing Weld Formed by Pulsed Argon Tungsten Arc Welding

Structural-Phase State of Multicomponent Surfacing Weld Formed by Pulsed Argon Tungsten Arc Welding

Digital visualization of thermal processes accompanying welding of small-diameter pipes

The work investigates the specificity of the thermal processes occurring during formation of a molten pool in curvilinear specimens. The process is exemplified by welding of small-diameter pipes. A numerical 3D-model of the interaction of a moving heating source and thick-walled pipes of various curvature was built. The material, diameter and thickness of pipes were selected as per active standards. The numerical calculations were performed. The practical experiment was performed using argon tungsten-arc welding. The results establish the effect of the welded part geometry on the dynamics of thermal processes in the molten pool.

Finite-Element Thermal Analysis and Grain Growth Behavior of HAZ on Argon Tungsten-Arc Welding of 443 Stainless Steel

This paper presents a numerical and infrared experimental study of thermal and grain growth behavior during argon tungsten arc welding of 443 stainless steel. A 3D finite element model was proposed to simulate the welding process. The simulations were carried out via the Ansys Parametric Design Language (APDL) available in the finite-element code, ANSYS. To validate the simulation accuracy, a series of experiments using a fully-automated welding process was conducted. The results of the numerical analysis show that the simulation weld bead size and the experiment results have good agreement. The grain growth in the heat-affected zone of 443 stainless steel is influenced via three factors: (1) the thermal cycle experienced; (2) grain boundary migration; and (3) particle precipitation. Grain boundary migration is the main factor. The modified coefficient k of the grain growth index is calculated. The value is 1.16. Moreover, the microhardness of the weld bead softened slightly compared to the base metal.

Microstructure and Mechanical Properties of Welded Joints of Cr18Ni30Mo2Al3Nb Alloy

In this present study, A comparative research on the mechanical properties of the dissimilar welded joints of 800H and Cr18Ni30Mo2Al3Nb was investigated. Butt joints were made using argon tungsten-arc welding (TIG). The TIG joint was made using well established welding parameters (i.e., current ampere of 110~120A, welding rate of 105~115mm/min, argon flow 8~10L/min and voltage of 12V). Mechanical behavior of joints was evaluated by room temperature and high temperature (650°C) tensile testing, and hardness testing, respectively. The microstructure of joint was characterized via optical microscopy, and the morphology of tensile fracture was observed by scaning electron microscopy. As can be seen from the experimental results, clearly shown that Cr18Ni30Mo2Al3Nb has better mechanical performance of welded joint than 800H.

The Microstructure and Properties of TIG Welded Joint of AZ31B/Cu Dissimilar Metal

AZ31B magnesium alloy and T2 Cu metal plates with the thickness of 2mm were bonded by argon tungsten arc welding (TIG) under the conditions that the welding current is 100A and the welding speed is 150 mm/min. The microstructure, phase composition and properties of welded joint were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-hardness test. The results show that AZ31B magnesium alloy and T2 Cu combined well with no cracks, porosities, incomplete penetration and other metallurgical defects. A transition zone composed of equiaxed and columnar crystals of α-Cu exists between the weld metal and base metal Cu, its width is about 80μm. The central area of the weld is made up of α-Mg matrix and Mg-Cu eutectic. The joint consists of α-Cu, α-Mg, Cu2Mg, Mg2Cu and little MgO, CuO phase. The micro-hardness of weld zone is significantly higher than that of the base metals, and its heat affected zone appears softening phenomenon.

Present Status and Development Tendency of Plasma Transferred Arc Welding

With the rapid development of manufacturing in china,the welding technology,especially plasma surfacing develops quickly.Plasma transferred arc welding technology has energy-saving,efficient and stable quality,it become one of important green manufacturing and remanufacturing technologies.The characteristics of plasma surfacing are summarized and compared with argon tungsten-arc welding,electrode welding and submerged arc welding.The present status and development trend of plasma surfacing equipment and methods are also reviewed.The problems and future developing orientation of plasma surfacing technology are proposed.

Characterization of TiC/Ti5Si3<i> In Situ</i> Synthesis Composite Materials on Ti-5Al-2.5Sn by Argon Tungsten-Arc Welding Deposition

TiC/Ti5Si3composite materials on Ti-5Al-2.5Sn were in-situ synthesized by argon tungsten-arc welding (GTAW) deposition from powder compacts with the molar ratio of Ti:Si:C=3:1:2. X-ray diffraction (XRD) techniques and scanning electron microscope (SEM) were employed to characterize the microstructure of the composites. The effects of depositing times on the surface microstructure of the tracks deposited were studied. From the products synthesized in this work, the content of TiC/Ti5Si3in-situ composites on the surface of the tracks differed from each other by depositing one, two, three, and four times, respectively. The minimum impurities were obtained and the distribution of TiC/Ti5Si3. In-situ composites were most homogeneous in the track surface by depositing three times.

Microstructure and Corrosion Resistant Property Research of Super 304H and TP347H Heat-Resistant Steel Welding Joint

Microstructure of Super 304H and TP347H austenitic heat resistance steel welding joint by handwork argon tungsten-arc welding and electro-chemical corrosion property of weld metal and two base materials were investigated by SEM and M273 constant potential rectifier. The results shows that microstructure of the weld metalwere austenitic matrix + δ ferrite; In 5% HCl Solution, corrosion resistant capabilities were super 304H base material＞ weld metal＞TP347H base material; in 9.8% H2SO4 Solution, corrosion resistant capabilities were Super 304H base material＞TP347H base material＞ weld metal; Super 304H and TP347H austenitic heat resistance steel welding joint has better corrosion resistant property in HCl solution than in H2SO4 solution; Inter-crystalline corrosion results were consistence to results electro-chemical corrosion experiment in 9.8% H2SO4 solution.

Fretting Wear Resistance of ATW Cr<sub>3</sub>C<sub>2</sub>/Ni<sub>3</sub>Al Composite Hardfacing on IC6SX

The fretting wear performance of surface wear-resistant Cr3C2/Ni3Al composite deposited onto IC6SX alloy by manual argon tungsten-arc welding was investigated in this study. The results showed that the welded substrate exhibits a very good performance in comparison to the unwelded substrate at 500°C and 800°C, with 51.5% and 57.8% decrease of the fretting sectional area respectively. However, the fretting sectional area of the welded substrate is larger than that of the unwelded substrate at RT indicating poor fretting resistance as the reinforce phases of the welding layer is harder and more harmful to the sample surface. Examination of the fretting surfaces indicated that both the welded and unwelded samples undergo gross slip at RT and 500°C, and partial slip at 800°C. Coefficient of friction (COF) results were given by the SRV-4 tester which shows that as the temperature goes up, the COF of samples became lower and more stable. The results showed that the COF of welded substrate is lower than that of the unwelded substrate most of the time.

Mechanical and Galvano-chemistry Property Variation within Dissimilar Metal Weld between 1Cr18Ni9Ti and 1Cr13 Stainless Steel

The purpose of this study is to discuss the microstructure and properties variation of the weld metal in the dissimilar stainless steels during the argon tungsten-arc welding process. Because of the existence of different materials and chemistry variation within welds, properties, such as tensile and fracture properties and so on, are expected to show spatial variation. In the study, microstructures were observed by optical and electron microscopy. Good appearance and uniform structure and typical dendrite structure were observed in welding joint. The micro-hardness tester and electronic universal stretcher were used to measure the mechanical properties of the weldments and base metals. The heat affected zone (HAZ) near 1Cr13 hardness is up to peak value of 1150 HV, the strength of weldments is nearly same as austenite stainless steel. In addition, through seawater immersion test, polarization curves and AC impedance spectroscopy of the weldments and base metals are obtained. It was found that corrosion resistance at welding joint lies between 1C13 and 1Cr18Ni9Ti.

Developing mathematical models to predict grain size and hardness of argon tungsten pulse current arc welded titanium alloy

Abstract Titanium (Ti–6Al–4V) alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio, such as transportable bridge girders, military vehicles, road tankers and railway transport systems. The frequently preferred welding process of titanium alloy is argon tungsten arc welding due to its comparatively easier applicability and better economy. In case of single pass welding of thinner section of this alloy, pulse current was found beneficial due to its advantages over the conventional continuous current process. Many considerations have come into the picture and one need to carefully balance various pulse current parameters to arrive at an optimum combination. Hence, in this investigation an attempt has been made to develop mathematical models to predict grain size and hardness of argon tungsten pulse current arc welded titanium alloy weldments. Four factors, five level, central composite, rotatable design matrix is used to optimize the required number of experiments. The mathematical models were developed by response surface method (RSM). The adequacy of the models was checked by ANOVA technique. By using the developed mathematical models, grain size and hardness of the joints can be predicted with 99% confidence level.

The vanadium alloys technological and corrosion studies in construction and operation of liquid metal facilities for fusion reactor

The vanadium—lithium test facility has been constructed to carry out corrosion tests of vanadium alloys in lithium flow, to evaluate the welding procedures and to develop electrically insulating coatings for lithium self-cooled blanket application. The corrosion tests were performed in a nonisothermal lithium flow with the flow rate up to 1 m/s at temperatures in the range 450–700°C. The results of development of the electricity insulating coatings are presented. The achieved specific resistance of AlN based coatings is 30–40 Ω m. The results of electron-beam and argon tungsten-arc welding methods are presented for welding sheets, rods and pipes for VTiCr type alloys. Solution of the vanadium alloys and vanadium alloys—stainless steels welding problems enabled construction of a liquid metal system satisfying all the necessary requirements.