Showing papers on "Submerged arc welding published in 2001"

Fuel cell operated welder

Abstract: An electric arc welder powered by a plurality of liquid organic fuel cells The fuel cells use a methanol/water mixture as the organic feed The fuel cells produce carbon dioxide as a reactive product which is used an a shielding gas during the arc welding process The fuel cells are stacked together to produce the desired arc voltage and current between an electrode and the workpiece The arc welder includes a welding current to control the current wave shape through the electrode and to control or increase the voltage through the electrode

Computer Simulation of Residual Stress and Distortion of Thick Plates in Multielectrode Submerged Arc Welding : Their Mitigation Techniques

Abstract: Welding is the main joining method used in shipbuilding. A multi-electrode submerged arc welding is usually applied to long joints of massive components since the early 1950s.The problem of welding ...

Laser/arc hybrid welding process with appropriate gas mixture

Abstract: Process for welding one or more metal workpieces to be joined together by producing at least one welded joint between the edges to be welded of the said metal workpiece or workpieces, the said welded joint being obtained by using at least one laser beam and at least one electric arc, in which process, during welding of the joint, at least one part of the welding zone comprising at least one part of said welded joint is shielded during the operation with at least one shielding atmosphere formed by a gas mixture consisting of argon and/or helium with a content greater than or equal to 70% by volume; and at least one additional compound chosen from H 2 , O 2 , CO 2 and N 2 with a content of 0 to 30% by volume.

Application of a hybrid arc/laser process to the welding of pipe

Abstract: Process for manufacturing a welded pipe from a metal strip having two longitudinal edges approximately parallel to each other, which are brought together so as to come approximately into contact with each other and thus form an unwelded pre-tube, the said pre-tube then being welded in order to join the said edges together. According to the invention, the two edges are welded together to obtain a welded metal pipe by using, approximately simultaneously, at least one laser beam and at least one electric arc, that is to say using a hybrid arc/laser, preferably plasma/laser, welding process. This process can be used to produce weld seams of rectilinear, helicoidal or spiralled shape.

Welding electrode and method for reducing manganese in fume

Abstract: A cored electrode for arc welding, said electrode having a core in which the fill material incudes a manganese-containing composite particle.

Assessing metal transfer stability and spatter severity in flux cored arc welding

Abstract: Five experimental basic type flux cored arc welding consumable wire electrodes were manufactured from the same base formulation. The composition of these electrodes was adjusted in an attempt to improve the operating performance. This involved additions of various ratios of alkali oxides, namely, lithium, magnesium, sodium, and potassium containing ingredients, in the flux formulations. The operating behaviours of these experimental electrodes and two reference products (i.e. one commercial basic T–5 and one commercial rutile T–1 electrode) were thoroughly investigated by recording welding arc signals using a high speed data acquisition system. By comparing these electrodes among themselves, the experimental electrodes were reported to exhibit extremely stable arcs, some showing electrical arc signals even smoother than those for the reference rutile grade electrode. Despite their improved metal transfer consistency, however, basic electrodes were characterised by somewhat higher spatter levels.

Laser-assisted gas metal arc welding of 25-mm-thick HY-80 plate

Abstract: Laser-assisted gas metal arc welding of HY-80 steel was investigated. The effect of welding parameters was studied and optimum welding conditions were identified. Welding using Lincoln LA-100 wire on 25-mm-thick HY-80 plate with a four-pass technique, a double 45-deg groove preparation, 9.5 mm deep with no root opening, a heat input of 1.6 kJ/mm and a 50% Ar-50% He gas shield produced a predominately martensitic weld metal microstructure. An acicular ferrite weld metal microstructure could not be produced for any set of processing conditions investigated. This is believed to be a result of the high levels of dilution. The toughness of the laser-assisted gas metal arc welds was assessed with dynamic tear testing and explosion bulge testing. Toughness was found to be low but highly variable. Optimum electrode chemistry would probably allow the toughness to be improved.

Effect of shield gas composition on surface tension of steel droplets in a gas-metal-arc welding arc

Abstract: A technique for in-situ measurement of the surface tension of molten steel droplets in a gas-metal-arc welding plasma is described. Surface tension measurements obtained using this method are reported for ER 70S-6 wire, with varying shielding gas compositions, and compared with previously reported results. The in-situ technique is found to produce results consisten with values found in the literature, while incorporating the effects of alloy composition and arc atmosphere.

Development of an Intelligent System for Selection of the Process Variables in Gas Metal Arc Welding Processes

Abstract: Gas metal arc (GMA) welding is extensively employed in the metal industries for a variety of ferrous and non-ferrous metals because of its potential for increasing the productivity and quality of welding which is controlled by the process parameters. The objective of this paper is to develop an algorithm that enables the determination of process variables for optimised bead geometry for robotic GMA welding. It depends on the inversion of empirical Eq. derived from multiple regression analysis of the relationships between the process variables and the bead dimensions using the least-squares method. The method determines directly those variables which will give the desired set of bead geometry. This avoids the need to iterate by a succession of guesses which are employed in the finite element method (FEM). These results suggest that process variables from experimental equations for robotic GMA welding may be employed to monitor and control the bead geometry in real-time.

A study of an arc sensor model for gas metal arc welding with rotating arc Part 1: Dynamic simulation of wire melting

Abstract: A dynamic wire melting phenomenon is found in rotating arc welding since self-regulation of the arc length is not fully performed. Consequently welding current and electrode extension vary rapidly in high speed rotating arc operation. This paper presents the dynamic simulation of wire melting by using the variable space network method and by modelling the heat flux from the molten end of the wire into the electrode. The simulations are compared with experimental results from other references to show a fairly good agreement. By using simulation analyses, it is clarified how the characteristics of the welding power source affect the sensitivity of the arc sensor.

A study of an arc sensor model for gas metal arc welding with rotating arc Part 2: Simulation of an arc sensor in mechanically rotating gas metal arc welding:

Abstract: The high-speed rotating arc process forms a flat bead surface and decreased penetration depth. It can be effectively applied to automatic seam tracking, because the sensitivity of this type of arc sensor is greater than that of the conventional torch weaving method. In this study, a new rotation mechanism was developed by using a hollow shaft motor designed to be installed in the electrode nozzle. By rotating the welding arc, the amplitude of the current waveform increases remarkably since self-regulation of the arc is not fully performed. This paper presents a mathematical model for the dynamic behaviour of the electrode melting rate and arc length to simulate the welding signals in rotating arc welding. A simplified weld pool shape is considered with the dynamic wire melting model, because the welding arc rotates above the preformed weld pool.

Consumable electrode gas shielded arc welding method and apparatus

Abstract: A gas having an arc current-voltage property that is different from a shielding gas is intermittently added to the shielding gas, an arc current is intermittently changed in proportion to an intermittent chemical composition change of the shielding gas at an arc generation region, and an arc generation point situated at a tip of a welding wire is displaced upwardly or downwardly along a groove of a base metal.

Modeling of a DC Electric Arc Furnace-Mixing in the Bath

Abstract: A mathematical model was developed to describe fluid flow, heat transfer and electromagnetic phenomena in the bath region of a Direct Current Electric Arc Furnace (DC-EAF). The different effects on the steel bath from the arc, a layer of slag on the top of the steel, and the injection of argon gas from the bottom, are represented using three different numeric approaches and analyzed in terms of fluid flow, heat transfer, and temperature stratification in the steel bath. Additionally, a sensitivity analysis was performed to explore the effect of the main process parameters and design variables of the process, such as furnace dimensions, arc conditions, and anode configurations. It was found that in the absence of gas injection, the electromagnetic body forces dominate the fluid flow in the bath region overcoming the opposite effects of buoyancy and shear from the arc. Injection of gases homogenizes the melt improving mixing, while the effect of the slag is to decrease mixing in the bath. Regarding the process analysis, the model showed that the best mixing and the best energy optimization from the arc are achieved when the geometry of the furnace presents the highest aspect ratio. Similarly, short arc lengths and high arc currents are beneficial for mixing. However, these improvements in mixing could be detrimental for the bottom refractory of the furnace because of the direct exposure of the hot metal coming from the arc attachment zone at the bottom wall. Then, the anode configuration can be designed to avoid excessive damage to the refractory.

Hybrid arc/laser welding with earth contactor position control

Abstract: Hybrid welding process using a laser beam and an electric arc to produce a weld bead. The electric arc is established between an electrode connected to a first pole of a current source and at least one workpiece to be welded and connected to a second pole of a current source via at least one electrically conducting earth contactor in contact with the workpiece to be welded. To obtain effective welding, a contact is made between the earth contactor and the workpiece to be welded laterally and/or upstream of the point of impingement of the electric arc on the workpiece(s) to be welded, and considering the direction of formation of the welded joint, so as to balance the forces associated with the induced electromagnetic field acting on the puddle of liquid metal.

Consumable electrode arc welding method and welder

Abstract: A consumable electrode wire (1) serving as a preceding wire in the direction of the welding is placed generally parallel to a filler wire (2) serving as a succeeding wire. A current is supplied from a welding power supply and flows through a feeding terminal (4a), the consumable electrode wire (1), an arc (12), a molten pool (8), a base metal (3), and a ground wire (7) to the ground terminal. An electric resistor (20) is connected between the base metal (3) and the ground terminal of the welding power supply (5). Therefore the current Ib flowing through the base metal to the ground terminal is limited by the electric resistor (20). The voltage difference caused across the electric resistor (20) results in an increase the ratio of the current If branching into the filler wire (2) to the welding current Iw, and the increase of the branching current increases the heat generated by the filler wire (2). As a result, even if the amount of movement of the filler (2) increases, the Joule heat is sufficiently generated, and the fusion mixing of the filler wire (2) in the molten pool is complete.

Creep properties of austenitic stainless-steel weld metals

Abstract: The creep behavior of two austeitic stainless-steel weld metals was investigated. Two AISI 316L stainless-steel base plates were welded together using the submerged arc-welding process. Creep tests were carried out on the welds at constant load, over a stress range of 100 to 400 MPa, and in the temperature range of 600 to 700 °C. The relationships between stress and minimum secondary creep rate at a constant temperature were obtained with Norton’s law. The results showed that AISI 347 weld metal presented a higher creep resistance with lower values of the minimum strain rate, and, consequently, it exhibited a longer life before rupture than AISI 316L weld metal. However, this weld metal showed a lower ductility value than AISI 316L weld metal. The weld-metal microstructure survey, performed before and after the creep testing, has shown different amounts of delta ferrite, which was strongly dependent on time, temperature, and stress level.

High transmittance alumina for ceramic metal halide lamps

Abstract: A high transmittance polycrystalline alumina arc tube for a metal halide discharge lamp is formed by treating an alumina arc tube material having a few percent of closed porosity in a two step process, which provides a high-transmittance arc tube. An initially porous arc tube is formed by extruding or die pressing individual components of the tube from a mixture which includes powdered alumina, assembling the components into an arc tube body, and then partially sintering the components to seal them together. The two step process includes hot isostatic pressing of the partially sintered arc tube and then chemically polishing the surface of the tube. The first, pressing step involves heating the alumina arc tube in an inert atmosphere, such as argon, at a temperature of 1600 to 1900° C. and a pressure of about 700 to 2100 kg/sq.cm. for from about one to three hours. This reduces porosity in the crystalline structure. In the second step, the surface of the tube is immersed in a flux comprising a molten alkali metal borate at moderately elevated temperatures, or coated with a flux material which is heated to form the flux, to remove surface imperfections. The finished arc tube has transmittance values which approach those of single crystal sapphire arc tubes.

Effects of a postweld heat treatment on a submerged arc welded ASTM A537 pressure vessel steel

Abstract: Postweld heat treatment (PWHT) is frequently applied to steel pressure vessels, following the requirements of the ASME code (section VIII), which establishes the parameters of the PWHT based on the thickness and chemical composition of the welded section. This work shows the results of an analysis undertaken on a sample of ASTM A537 C1 steel subjected to qualifying welding procedure tests including PWHT (650°C/5 h). The results obtained showed that this PWHT practice promoted a reduction in the mechanical properties of the base metal and the heat-affected zone (HAZ).

High deposition submerged arc welding system

Abstract: The present invention relates to a high deposition submerged arc welding system, comprising a gantry fixture, a weldhead, an operator control module and a modular control system. The gantry fixture is configured to receive a first plate and a second plate. The weldhead is operatively coupled to the gantry fixture and welds the first plate and second plate together with a metal powder, a welding wire and a flux. The operator control module is configured to receive a program for welding the first plate and the second plate together. The modular control system has a common bus which communicates the program to a plurality of control modules.

Submerged arc welding application method and welding material for austenitic stainless steel

Abstract: PROBLEM TO BE SOLVED: To provide a submerged arc welding application method for austenitic stainless steel which gives the same tensile strength as base metal; 600 N/mm2 and over, to the submerged arc weld of austenitic steel which has tensile strength: 600 N/mm2 and over, giving excellent hot-crack resistant property and bending resistant property, thereby enables to carry out double-sided one pass submerged arc welding to the plate thickness: 12-25 mm. SOLUTION: The chemical composition of weld is controlled to be the composition which includes in weight %, Cr: 19-23%, Ni: 11-15%, Mo: 1.0-1.4% N: 0.10-0.20%, C: 0.06% and below, Si: 1.00% and below, Mn: 0.5-2.50%, P: 0.040% and below, S: 0.03% and below, satisfying quantity of ferrite: 3-20% and below, and the residue consisting of substantially Fe. In double-sided one pass welding, gas metal arc welding(GMAW) is carried out after backside gouging, after that, backside submerged arc welding is carried. Otherwise before right side submerged arc welding, welding by GMAW in a groove for sealing is carried, after that right side submerged arc welding is carried out. Right side welding heat input shall be larger than backside welding heat input.

Method for combined welding with laser beam and arc

Abstract: PROBLEM TO BE SOLVED: To provide a method for a combined welding with a laser beam and an arc of a high quality and a high efficiency by which a deep penetration is available and an energy loss is suppressed. SOLUTION: The distance between the laser beam 4 and the arc is so adjusted that an arc plasma 6 does not interfere with a laser beam 4. Thus, the absorption of the laser beam 4 by the arc plasma 6 is prevented. Further, by adjusting the focusing position of the laser beam 4 during the welding the locate at a point above the bottom face of the V-shaped part of a Y-shaped groove and in the vicinity of the surface of a member 5 to be welded, while leaving a deep penetration energy given by the laser beam 4, a broad zone of the member to be welded is heated before an arc welding is performed, and the arc welding is realize as deep as the inside of the groove. Thus, the method for a combined welding with a laser beam and an arc of a high quality and a high efficiency is realized by which the deep penetration is available and the energy loss is suppressed.

狭開先化に伴うアーク溶接現象の基本的な特性把握と溶接安定化の提案 : 超狭開先gma溶接プロセスの開発(第1報)

Abstract: Narrow gap welding (NGW) joints offers many advantages over conventional welding methods, such as good mechanical properties of joints, high welding efficiency and low residual stress. As the groove gap width becomes narrower, the arc heat input can be reduced and the merits in narrow gap welding increases more.Generally, GMA welding method has been never applied to less than 5 mm groove gap, because it is guessed that it is arc instability and lack of fusion at the groove bottom area occur.In this paper, first of all, arc behavior under narrower gap joints is discussed, and it was concluded that the arc in MIG arc welding irregularly perturbates up-to-downwards along the groove wall under less than 5 mm gap, but CO2 arc was stable under narrower gap.Next, penetrations at the groove bottom area in CO2 arc welding were discussed. Characteristics of bead formation phenomena in CO2 buried arc welding of bead-on-plate were analyzed. From the results, the relationship between hydrostatic potential of molten metal and arc force corresponding with welding current was estimated. Furthermore, the width of gauging region of penetration by arc force was measured and the relationship between the melting width at groove bottom and welding conditions (welding current and welding speed) can be suggested.With these results, numerical simulation model was proposed and the optimum welding conditions to melt the groove bottom area sufficiently and to minimize heat input were searched by numerical simulation. And then narrow gap welding with 5 mm groove gap was carried out using these simulated welding conditions. In the experimental results, the weld bead was obtained without lack of fusion at groove bottom, but the convex surface bead was formed which is disagreeable in multi-pass welding.The new welding process was proposed from numerical simulations in order to prevent this convex bead and to obtain sufficient melting at bottom area. In the new process, the wire extension can be controlled by welding current waveform and then arc regularly oscillated up-to-downwards along the groove wall. In this arc oscillation, arc heating distribution along groove wall led to both sufficient penetration at groove bottom and concave surface bead shape.

Fatigue crack growth and fracture toughness properties of 304 stainless steel pipe for LNG transmission

Abstract: The fatigue crack growth rate and fracture toughness tests of type 304 stainless steel were studied over a temperature range of −162°C to room temperature. Girth weld metal specimens were fabricated using a combination of gas-tungsten-arc-welding and shielded-metal-arc-welding. The seam weld metal was made with submerged arc welding. Fatigue crack growth rate tests were conducted using compact tension specimens in accordance with ASTM E647. Fracture toughness was evaluated through CTOD tests with three point bend specimens. The CTOD values were affected by crack orientation with respect to the rolling direction, but orientation had no influence on fatigue crack growth rates. The fatigue crack growth rates and the CTOD values decreased with decreasing test temperature.

Numerical simulation of welds of thick steel sheets for some experimental models towards ITER TF coil case

Abstract: In order to set up the welding techniques to be utilized for ITER TF coil case, it was considered that the numerical simulations might be an important tool in order to give some information on deformations and residual stresses due to the different phases of welding. TIG and SAW with filler material are the welding techniques considered. By the numerical point of view, until 1998, the numerical simulation of these welding types was practically an uninvestigated problem. Studies, researches and developments have been carried out with the aim to single out the calculation tools and methodologies to be used. Reference has been made to some experimental models with simple geometry and reduced dimensions, which, however, consider a more complex experimental model. The welds of these models were followed by several measures for different physical quantities of interest to be compared with the corresponding numerical results. Subsequently, studies and researches, still in course, concerned simplifications of the numerical procedures, which, however, can produce equivalent results and are able to simulate the welds of more complex pieces, having big dimensions.

Pulsed-arc welding process and device

Abstract: Process for the arc welding in pulsed mode of one or more workpieces made of carbon steel, stainless steel, aluminum or aluminum alloy, with the use of a gas shield, in which an electric arc welding torch is supplied with at least one consumable wire at a wire feed speed (V wire ) and the consumable wire is subjected to current pulses, in order to melt the end of the consumable wire in which, for a given pulse frequency, a wire feed speed (F wire ), a mean current (I mean ) value and an rms current (I rms ) value are chosen, so as to detach one drop of molten metal per current pulse and to obtain a low degree of spatter.