TIG Method Research Articles

Ultrasonic-vibration assisted arc-welding of aluminum alloys

Abstract The structure and hardness of the surface-welds and fusion-welds made on a 2017A aluminum alloy waveguide using the MIG and TIG methods with and without the participation of ultrasonic vibrations were examined. Cross-sections of the fusions and surface-welds thus obtained were observed in a microscope and the hardness distributions were determined. The aim of the study was to analyze the effects of the ultrasonic vibrations applied to the melted metal pool by a vibrating substrate which in our experiments was a waveguide. The interactions of the ultrasonic vibrations with the molten metal during its solidification and also with the heat-affected zone were examined at various phases of the vibration wave. The ultrasonic vibrations affected the structure of a weld. These changes are strongly depended on the wave phase.

Creep Resistance of WE43 Magnesium Alloy Joints

Magnesium alloys of Mg-Y-RE-Zr series are characterized by creep resistance up to a temperature of 250 ° C, and can work up to a temperature of 300oC. These properties allow for the application of alloys of Mg-Y-RE-Zr series for the elements of racing car engines operating in the conditions of high loads and temperatures. The requirement of high reliability components of aircraft propulsion system, with high strength and corrosion resistance, also led to the use of these alloys in the aerospace industry. Welding technologies in cast magnesium alloys are applied in order to repair defects in castings, occurring in the casting process, as well as to regenerate worn out castings. Joints made of magnesium alloys should have at least the same properties as a finished casting. The literature lacks information on the properties of joints welded of cast magnesium alloys.This work includes examination of influence of heat treatment on creep resistance of alloy WE43. Material for the study comprised joints made by the TIG method, welded in the cast state. Creep tests were carried out on joints without heat treatment and joints after heat treatment. The tests were performed at the temperatures of 200 ° C and 250 ° C during 100h. It was found that there is an increase in creep resistance of the joints after heat treatment.

Single-layer bronze hardfacing with the TIG method

This article presents an assessment of TIG pad welding technology as applied to a steel shaft with a thin single-layer coating of bronze CuSn6. Recommended technological parameters for avoidance of welding imperfections are given. Filled CuSn6 bronze layers were assessed for hardness and consumption volume in terms of friction.

Study of the law between the weld pool shape variations with the welding parameters under two TIG processes

A double-shielded TIG method was proposed to improve weld penetration and has been compared with the traditional TIG welding method under different welding parameters (i.e., speed, arc length and current). The strength of the Marangoni convection was calculated to estimate the influence of the welding parameters on the variations in weld pool shapes. The results show that the changes in the welding parameters directly impact the oxygen concentration in the weld pool and the temperature distribution on the pool surface. The oxygen content and heat distribution on the weld pool surface are determinants of the pattern and strength of the Marangoni convection. For a negative temperature coefficient of surface tension (∂σ/∂T<0), an outward Marangoni convection leads to a wide and shallow weld pool shape. The narrow and deep weld pool shape occurs when the Marangoni convection flows along an inward direction (∂σ/∂T>0). The oxide layer that may appear with the relatively high oxygen content in the weld pool is harmful for the heat flow along the pool surface so as to reduce the welding efficiency especially in the double shielded TIG process.

Analysis of possible shipbuilding application of friction stir welding (FSW) method to joining elements made of AlZn5Mg1 alloy

Analysis of possible shipbuilding application of friction stir welding (FSW) method to joining elements made of AlZn5Mg1 alloy In industrial practice the welding of Al- alloys is usually performed under pure argon shielding by means of MIG or TIG methods. In recent years new joining techniques such as friction stir welding (FSW) have appeared. Joints of EN AW-7020 T6 alloy elements welded by using FSW method have been tested. Results of static tensile tests, transverse bending tests as well as tests on stress corrosion susceptibility are presented. Parameters of friction welding (FSW) applied to joints of plates made of AlZn5Mg1[7020] alloy are given. Stress corrosion tests have been performed by using slow-strain-rate testing method (SSRT) in compliance with PN-EN ISO 7539-7 standard. The tests were conducted in air and 3.5% NaCl water solution. The following parameters have been measured during the tests: time to failure - T [h], maximum failure load - F [N], fracture energy (area under stress-elongation curve) - E [MJ/m3], relative elongation of specimen - A10 [%], maximum tensile stress - R [MPa], as well as percentage reduction of area - Z [%]. On the basis of the obtained test results it was concluded that the joints welded by means of FSW method show good resistance to stress corrosion at satsifactory strength properties, which indicates that application of friction welding by using FSW method in shipbuilding industry is purposeful.

Residual stresses analysis of ND-YAG laser welded joints

Laser deposit welding based on modern ND-YAG lasers is a new mould repair process with advantages relatively to the traditional methods (micro-plasma and TIG methods), namely deposition of small volumes of the filler material without distortion. Residual stresses play a major role on the fatigue and thermal–mechanical fatigue behaviour of welds. This paper presents the experimental results and numerical predictions of the residual stresses in joints manufactured with two hot-working tool steels: X.40.CrMoV.5.1 and 40.CrMnNiMo.8.6.4, in the laser-deposited layer and in the heat-affected zone. Welded specimens were prepared with U notches and filled with ND-YAG laser welding deposits. Trough-depth residual stresses evaluation after laser deposit welding were performed in order to analyse the influence of the residual stress state on fatigue behaviour of mould steels. Both X-ray diffraction sin 2γ method (XRD) and incremental hole-drilling technique (IHD) were used in residual stress measurement. Numerical predictions of the residual stress distributions were obtained for several values of the technologic parameters, compared with experimental results and discussed based on the assumptions stated.

Fracture toughness of the heat affected zone on Nd-YAG laser welded joints

Laser deposit welding based on modern Nd-YAG lasers is a new mould repair process with advantages relatively to the traditional methods (Micro-plasma and TIG methods). For moulds steels there are no research studies about the laser deposit welding process effects in respect to fracture toughness, hardness and residual stresses variations in the laser-deposited layer and in the heat affected zone. These variations will have an important influence in the thermal–mechanical fatigue strength of the moulds parts. This paper is concerned on the study of the fracture toughness of transient microstructure regions in Nd-YAG laser welded joints performed in mould steels. Fracture toughness tests were performed in two hot-working tool steels: AISI H13 and AISI P20. Small welded specimens were prepared with U notches and filled with laser welding deposits. The hardness profiles were obtained at the middle cross-section of specimens against distance to the surface in order to identify the microstructures present at the crack tip region. Fracture toughness was evaluated and plotted against the Vickers hardness measured at the fatigue crack tip. Depending of the crack tip depth two very different toughness levels were observed in the H13 steel, while a lower variation of toughness was observed for the P20 steel. The values of fracture toughness observed in each specimen are consistent with the correspondent crack tip microstructure hardness.

Fatigue and microstructure of welded joints of metal sheets for automotive exhaust system

Fillet or butt welded joints were prepared, so that the sheets of low carbon or stainless steels such as 18Cr–1Mo–Ti were welded by MIG or TIG method with the ferritic or austenitic welding wires, followed with or without heat treatment. The geometry of deposited zone, element distribution, crystal structure, microstructure, stress and fatigue of the joints, was tested with the tensile and fatigue tests, EPMA composition analysis, X-ray diffraction, microscopic examination, computer simulation etc.

Corrosion and mechanical strength of welded joints of downcomers for RBMK reactors

In the process of operation of RBMK reactors damage took place on welded pipings produced from austenitic stainless steel of the type 08X18H10T. The inspection of damaged sections in pipings has shown that in most cases crack-like defects were of corrosion and mechanical character. This paper considers in detail the reasons for the damage appearance and their development for this type of welded joints of downcomers ∅325×16 mm, which were fabricated from austenitic stainless steel using TIG and MAW welding methods.

Investigations into the phenomena of high speed one-sided welding of thin sheet, paying attention to arc force

Paying special attention to the arc force, the welding phenomenon of high speed one-side welding of thin sheet was investigated.In high speed and high current one-side welding method, the arc force becomes very strong. The solid surface is produced at the front part of the molten pool by this strong arc force and others. But the high speed one-side welding of thin sheet is possible using high current TIG and plasma arc welding method because the strong arc force effects to this solid surface. However, in the case of these welding, the face bead becomes undercut bead.In spite of high welding current, the arc force holding forward torch angle keeps lower level. So this method is more effective for high speed one-side welding. Especially, using the knife-edge electrode with forward torch angle, these tendency becomes more effective.

アーク力に着目した薄板の高速片面溶接現象の検討

Paying special attention to the arc force, the welding phenomenon of high speed one-side welding of thin sheet was investigated.In high speed and high current one-side welding method, the arc force becomes very strong. The solid surface is produced at the front part of the molten pool by this strong arc force and others. But the high speed one-side welding of thin sheet is possible using high current TIG and plasma arc welding method because the strong arc force effects to this solid surface. However, in the case of these welding, the face bead becomes undercut bead.In spite of high welding current, the arc force holding forward torch angle keeps lower level. So this method is more effective for high speed one-side welding. Especially, using the knife-edge electrode with forward torch angle, these tendency becomes more effective.

The thermal history of a composite cylinder girth welded by TIG

AbstractA mathematical model for the calculation of the three‐dimensional thermal history of a composite cylinder, during girth welding by the TIG method, is presented. The solution is obtained by the alternating direction implicit finite difference method. The model takes into consideration the distribution of the heat input from the welding arc, the heat losses from the cylinder by radiation and convection, the dependence of the physical properties of the metal on the temperature and the solid‐liquid phase transformation. The effects of the efficiency coefficient of the welding arc, of the effective arc radius and of heat transfer coefficients on the thermal history are presented.

希土類元素添加による高純度30Cr-2Mo鋼溶接金属のじん性改善

Effect of REM addition on the toughness in the weld metal of high purity 30Cr-2Mo steel was investigated. Welding was carried out by TIG method using deliberately contaminated argon with various ratio of nitrogen or air as shielding gas in order to vary the toughness of weld metals. The toughness of weld metals was evaluatedd using sub-size Charpy V-notch specimens with thickness of 3 mm. The main results obtained in this study are as follows;1) The toughness of the weld metal is significantly improved by addition of REM. Effective content of REM ranges from about 50 ppm to 200 ppm when nitrogen content in shielding gas being less than 1%.2) The quantity of absorbed nitrogen decreases in the REM bearing weld metal, which yields the improvement of toughness in it.3) It was deduced that the decrease of nitrogen in the REM bearing weld metal was attributed to the decrease of its absorption rate due to the formation of REM oxide film or absorbed layer of REM on the surface of the molten pool.

低温材料の研究 ＩＩ ＳＵＳ３０４，３１６ステンレス鋼溶接部の極低温における機械的性質と加工による強磁性化

SUS 304 and 316 austenitic stainless steel plates were welded by filler wires of Y308 and Y316 using TIG method, and the strength and the toughness of the weldments were evaluated at cryogenic temperatures (77K and 4.2K). The change in magnetic properties due to the strain-induced martensite (α′) were also examined.The yield strength of 304 (parent metals and weld metals) are greater than those of 316 at room temperature, but at 77K and 4.2K, the yield strength of 316 overcomes those of 304. The elongation of both weld metals are smaller than those of their parent metals at room temperature, but become equal to those of their parent metals at 77K and 4.2K.The tensile tests of the notched specimens of weld metals show that the notch yield strength ratios of 304/Y308 and 316/Y316 weld metals keep 2.4 and 1.9 at 4.2K respectively, and both fracture modes correspond to the ductile manner, although the notch sensitivities decrease with decreasing temperature.The relations of the volume pct of γ, e′ and α′ to the amount of strain at 77K and 4.2K were obtained. The amount of martensite (α′) formed in the fractured specimens at 4.2K were 95% for 304/Y308 weld metal and 70% for 316/Y316 weld metal. An austenitic phase of 316/Y316 weld metal is more stable than that of 304/Y308 weld metal.It was found that the weld metals showed similar mechanical and magnetic properties to their parent metals at 77K and 4.2K because of the dominant effect of strain-induced martensitic transformation on those properties.

Automatic Welding of High Carbon Hoop Steels

At Chita Plant of Daido Steel Co. the butt welding of hoop steels, as the preparatory process, is being done aiming at improvement of efficiency and yield of cold rolling work of hoop steels.The welding has been done manually up to now under TIG method, but the raw material was such a high carbon steel whose weldability was poor and therefore, it was inclined to grow weld defects and there occured breaking accident very often around the weld zone during rolling.Therefore, we have made an investigate on automation of welding for the purpose of quality stabilization of weld zone.Considering that the part to be welded is, before rolling, to be made smooth after removing the reinforcement, the thickness of plate for welding, the most positive trial of making the weld zone into product, the processing at Chita Plant etc. We have come to adopt TIG method without using filler metal.If the plate thickness is up to 4.2mm the automation of a one side welding of I-butt by Ar or Ar plus H2 atmosphere is possible. For the plate thicker than the above mentioned, the double side welding method whose first pass is flat position is preferable.The above written method is now being tried experimentally at present and our purpose seems to be achieved efficiently.

チタンおよびチタン合金の溶接部におよぼす超高波振動および磁気撹拌の影響

Pure Ti and Ti alloy are generally welded by TIG or MIG welding method. Sometimes fine porosities are detected in these welds by a X-ray examination. It seems that these porosities decrease the fatigue strength in some case. So it is important to protect the pure Ti and Ti alloy welds from these porosities. A study was carried out to make clear the effect of the ultrasonic vibration and the electromagnetic stirring on the porosities. At the same time, the effect of these two methods on the grain refinement, the bead shape, the penetration and the spatter were investigated. It was concluded that :(1) the ultrasonic vibration(i) The porosities of the TIG Welds were reduced by the ultrasonic vibration (9KC, 0.5-2 KW out put)(ii) The grains of the MIG Welds were made finer by the ultrasonic vibration (9KC, 0.5-2 KW out put)(2) the electromagnetic stirring(i) The porosities of the TIG Welds were reduced by the electromagnetic stirring. (DC or 60c/s AC and 2000 AT.)(ii) When using the coarse surface welding wire or with the machine oil on the groove surface, the porosities increase. But even in these cases by the electromagnetic stirring the porosities were considerably reduced.(iii) The grain of the TIG or MIG welds made finer by the electromagnetic stirring, especially in the Ti alloy MIG Welds.(iv) The frequency of the coil current was changed between DC and 60c/s AC The most effective frequency was around 8c/s.(v) In case of MIG Welding, the spatter increased with the intensity of the magnetic field.(vi) The bead shape was changed according to the frequency of the electromagnetic stirring. The bead was the concave type around 30 c/s, but tended to chahge into the convex type gradually with a decrease of the frequency.(vii) The penetration decreased with the intensity of the magnetic field, especially in case of MIG Welding.

電子ビーム溶接の利用に関する研究(第2報)

There are several advantages of electron beam welding as widely known and it is necessary to develop fully the application technique of this process, making good use of its merit.Some works on the applicability of the electron beam process to the welding of the nuclear fuel element and some heat resisting alloys were carried out. Discussion on the problem concerning the development work of the electron beam welding are also described.The conclusions obtained in this study are as follows.(1) From the experimental end-plug welding of nuclear fuel sheathing by electron beam, excellent joint design and weld penetration which are not expected by ordinary welding method were obtained. A smaller and simpler end-plug can be used for fuel element welding and this means a considerable widening of fuel element design. Weldability of such micro-welding was generally better by electron beam than by TIG method.(2) With electron beam, new joint design and welding procedure are applicable for various types of specimen. So it seems likely that the electron beam welding process has many fields of application in industries.(3) The results from the electron beam welding of some heat resisting alloys show a narrow and deep penetration in welds which reduces the heat affected zone and hardened area. Working efficiency on welding is rather superior with electron beam to that with ordinary arc welding.