Showing papers on "Submerged arc welding published in 2004"

A unified model of transport phenomena in gas metal arc welding including electrode, arc plasma and molten pool

Abstract: This paper presents a theoretical model for describing globular transfer in gas metal arc welding. The heat and mass transfer in the electrode, arc plasma and molten pool are considered in one unified model. Using the volume of fluid method, the transport phenomena are dynamically studied in the following processes: droplet formation and detachment, droplet flight in arc plasma, impingement of droplets on the molten pool and solidification after the arc extinguishes. The simulation of heat and mass transfer in the arc plasma considers the developing surface profile of the electrode and molten pool and also the effect of the flying droplet inside the arc plasma. Furthermore, the heat inputs to the electrode and the molten pool result from the simulation of the arc plasma. In addition, a He–Ne laser in conjunction with the shadow-graphing technique is used to observe the metal-transfer process. The theoretical predictions and experimental results are shown to be in good agreement.

Electrode evaporation and its effects on thermal arc behavior

Abstract: In circuit breakers, arc heaters and arc welding apparatus, metal vapor resulting from electrode erosion is inevitably injected into the arc plasma. The arc then burns in a mixture of the working gas (SF/sub 6/ in the case of circuit breakers) and electrode vapor, whose properties are substantially different from those of pure SF/sub 6/. The present work is a computational investigation into the effects of electrode vapor on the behavior of a supersonic nozzle arc under dc conditions. The arc and electrodes are treated as a coupled system. The arc plasma is assumed to be in local thermodynamic equilibrium (LTE). The thin non-LTE layer between the electrode and the arc is not included in the computation but its effects are taken into account in the energy balance at the electrode surface. A conservation equation for the electrode vapor is solved together with the governing equations for mass, momentum, and energy of the gas mixture. Comparisons were made between the results with and without electrode vaporization. Results show that vaporization of the electrode material (copper in the present investigation) has a cooling effect at the arc center and broadens the arc column. The arc voltage is, however, not sensitive to the presence of electrode vapor for the gas discharge conditions investigated.

Three-dimensional finite element analysis to predict the different zones of microstructure in submerged arc welding

Abstract: The temperature distribution and cooling rate during the welding process have significant effects on the mechanical and metallurgical properties of a weldment. The change in microstructure,...

Diffusible Hydrogen Content in Rutile Flux-Cored Arc Welds as a Function of the Welding Parameters

Abstract: The objective of the current work was to establish the effect of flux-cored arc welding (FCAW) parameters, such as welding current, contact-tip to workpiece distance (CTWD) and shielding gas type, on diffusible hydrogen content for single run, horizontal position, bead-on-plate welds using seamed and seamless rutile consumable wires. The work included an investigation of arc characteristics under typical welding conditions, using high-speed digital imaging and laser backlighting, in order to provide information on metal transfer and arc length. The work has shown that under most conditions investigated, the hydrogen levels for the seamed rutile wire were above the 10 ml/100 g specified by the consumable’s classification (H10). In contrast, the seamless wire met the requirements of the H5 classification for all welding conditions investigated. In general, lower diffusible hydrogen levels were achieved when using CO2 shielding gas, although the effect is less significant with the H5 seamless rutile wire. It is further concluded that the time that the wire resides in the resistive heating zone, tRHZ, and the arc length are important factors in determining diffusible hydrogen content.

A Comprehensive Model on the Transport Phenomena During Gas Metal Arc Welding Process

Abstract: A comprehensive mathematical model and the associated numerical technique have been developed to simulate the coupled, interactive transport phenomena between the electrode (droplets), the arc plasma, and the workpiece (weld pool) during a stationary axisymmetric gas metal arc welding process The simulation involves arc plasma generation, electrode melting, droplet formation, detachment, transfer, and impingement onto the workpiece, and weld pool dynamics During transfer from the tip of the electrode to the workpiece, the droplet subjects to gravity, electromagnetic force, surface tension, and arc plasma drag force Transient temperature and velocity distributions of the arc plasma, shapes of the electrode, droplet, and weld pool, and heat transfer and fluid flow in the weld pool are all calculated in a single, unified model The predicted solidified weld bead shape compares favourably with the experimental result

Development of hardfacing material in Fe-Cr-Nb-C system for use under highly abrasive conditions

Abstract: The present paper summarises theoretical and experimental work undertaken to develop a hardfacing product designated '167Nb-S'. This material, which is based on the Fe-Cr-Nb-C system, was designed for cladding components subjected to severe abrasive wear by submerged arc welding. The work undertaken includes microstructural characterisation, solidification modelling and abrasion testing. The microstructure of 167Nb-S consists of a large volume fraction of primary niobium carbides, surrounded by a martensitic matrix containing fine quasi-eutectic niobium carbides. Some retained austenite is found along grain boundaries, together with small amounts of intermetallic phase. Alloy development enabled a reduction in the amount of retained austenite and intermetallic phase present in early versions of the alloy, which is beneficial in terms of abrasive wear resistance and weld cracking susceptibility. Standard three body abrasion tests showed that 167Nb-S exhibits wear rates comparable to those of high c...

Development of High HAZ Toughness Steel Plates for Box Columns with High Heat Input Welding

Abstract: For safety against earthquakes and for highly efficient welding in high-rise building constructions, high HAZ toughness steel plates have been developed. Based on the new technology for HAZ microstructure refinement, HTUFF ® , and by optimizing chemical compositions of steel, BT-HT355C-HF and BT-HT440C-HF steel plates possessing high-performance of HAZ toughness have been commercialized. High heat input welded joints of box columns made of the developed steel plates, joined by electroslag welding or submerged arc welding with high efficiency, had excellent HAZ toughness of more than 70J at 0°C. The weld metal had also good toughness by using newly developed welding materials matched to the developed steel plates.

Prediction of submerged arc weld‐metal composition from flux ingredients with the help of statistical design of mixture experiment

Abstract: A prediction model has been developed for submerged arc weld-metal chemical composition in terms of flux ingredients with the help of statistical experiments for mixture (extreme vertices design). Bead-on-plate weld deposits as per statistical mixture design experiments were performed at the following welding parameters: current (400 A), voltage (26 V), speed (4.65 mm/s) and electrode extension (30 mm) using CaO-MgO-CaF 2 -Al 2 O 3 flux system. The results show that some of the individual flux ingredients and their binary mixtures have a predominant effect on weld-metal oxygen, manganese, silicon, sulphur, nickel and carbon content. The predicted results show a reasonably good agreement with the experimental results, which were obtained by performing the actual experiments based on a randomly designed flux. Analysis of the experimental data indicate that several mechanisms such as basicity index, oxygen potential, oxide stability, viscosity, electrode chemical reaction, kinetics of slag-metal reaction, etc. are operating simultaneously to yield the final weld-metal composition.

Sensing of weld pool surface using non-transferred plasma charge sensor

Abstract: Gas tungsten arc welding (GTAW) is the primary process for precision joining of metals due to its capability for accurate control of heat input. As a close relative and modification of GTAW, plasma arc welding (PAW) has higher energy density and can penetrate thicker workpieces while maintaining the desired capability for accurate control of heat input. In order to produce quality welds consistently using PAW, in addition to accurate control of heat input, the sensing and control of the weld pool surface are also critical. It has been found that the non-transferred plasma arc, in the absence of the transferred arc or the main plasma arc for welding, can establish a plasma charge potential which is indicative of the arc length. In order to take good advantage of this intrinsic characteristic of the non-transferred arc and eliminate the influence of the transferred arc in a normal PAW process, a power module is used to cut off the main arc current periodically for a very short period of time to acquire accurate information for monitoring the weld pool surface. A non-transferred plasma charge sensor is proposed based on this mechanism and experiments verified its effectiveness.

Method and apparatus for composite YAG laser/arc welding

Abstract: A combined YAG laser/arc welding apparatus is disclosed which performs a welding operation with a large depth of fusion and a deep fusion at a high efficiency. The welding apparatus includes an arc electrode which targets a point on a welded member where a laser beam from a YAG laser is focused. While an arc power supply is connected between the arc electrode and the welded member, the welded member is irradiated by the YAG laser to produce plasmoid gasses and metal vapors or a plume which is effective to start an arc from the arc electrode. A combined YAG laser/arc welding operation takes place while keeping the plume within and without a keyhole. Welded surface is covered by a hood, and a shielded gas passed through a commutation metal network surrounds the welded focus to prevent an oxidation and keeps the plume maintained. A filler wire is fed to a molten pool.

Mechanism governing nitrogen absorption by steel weld metal during laser welding

Abstract: The existence of monatomic nitrogen in the plasma just over the keyhole during CO2 laser welding was confirmed by the monochromatic image of a specific spectrum line emitted by monatomic nitrogen. The smaller reaction area of the molten pool with monatomic nitrogen is considered to lead to less nitrogen absorption during CO2 laser welding than that during arc welding. The effect of the penetration mode shows that the nitrogen absorption during CO2 laser welding mainly occurs on the upper surface of the molten pool. The nitrogen content in a reduced-pressure nitrogen atmosphere during CO2 laser welding is in good agreement with that obtained during yttrium aluminum garnet (YAG) laser welding within the range of low nitrogen (partial) pressures. This result supports the supposition that the different behaviors of nitrogen absorption between CO2 laser welding and YAG laser welding can be reasonably attributed to the lesser amount of monatomic nitrogen during YAG laser welding.

An introduction to physical phenomena in arc welding processes

Abstract: As is well known, arc discharges have been applied to various processes such as welding, cutting, spray coating, melting and refining. Unlike electrodeless discharge methods such as high frequency discharge of inductive coupling type (eg. RF discharge), arc discharge is a polarized discharge in which the arc is generated between the positive and negative electrodes.1 Accordingly, when the arc discharge is applied to welding processes, the material becomes one of the electrodes. In TIG welding, the material, that is, the molten pool, generally acts as the anode to the tungsten cathode. As shown in Fig. 1, TIG welding processes are based on the close energy balance between the ‘electrode–arc plasma–molten pool’. On the other hand, for the formation of the molten pool, energy transfer from the arc is also important, but energy transfer in the molten pool after that is extremely important, too. In TIG welding of steels, in which energy transfer by convection current becomes dominant rather than therm...

Contact welding influenced by anode arc and cathode arc, respectively

Abstract: Under certain conditions surprisingly shorter bounce arcs cause stronger welds than the much longer lasting arcs, if the shorter lasting arcs, also shorter in length, are of the anode arc mode while the longer arcs are of the cathode arc mode. The different welding behaviour can be explained in terms of the corresponding arc roots. Thus it appeared that the different arc modes during the stages of the contact bouncing are influencing not only the material transfer but also the contact welding.

Prevention of weld metal hydrogen cracking in high-strength multipass welds

Abstract: Welding modern high-strength steel with low carbon and impurity contents, preheat may be dictated by cracking sensitivity of the weld metal instead of the HAZ. Standard EN 1011 does not provide the user with any unified methodology for the calculation of safe preheat for weld metal. The few calculation formulae that apply to multipass welds can give greatly varying predictions. This article studies controlling factors that govern transverse hydrogen cracking in high-strength multipass weld metal. The experiments comprised heavily restrained Y- and U-groove multipass cracking tests of SMAW and SAW welds. The objectives were the assessment of hydrogen cracking risk by defining the Crack — No Crack boundaries in terms of safe line description giving the desired lower-bound estimates, and to derive predictive equations capable of giving reliable estimates of the required preheat/interpass temperature T 0/T i for the avoidance of cracking. Equations were derived to assess the weld critical hydrogen content H cr corresponding to the Crack — No Crack conditions as a function of either weld metal P cm, yield strength R p0.2 or maximum hardness HV 5(max). For the calculation of safe T 0/T i estimates, a formula incorporating weld metal strength as linear functions of either CET or weld HV 5(max), weld build-up thickness a w in the form of tanh expression and weld diffusible hydrogen H d in terms of combined [In / powerlaw] expression, was found descriptive.

Passage built-in mount and its production method

Abstract: PROBLEM TO BE SOLVED: To provide a passage built-in mount with a constitution where the generation of cracks in a welding line surrounding a groove and the corrosion of the welding line are prevented, and the sealing function of the welding line can be maintained, and to provide its production method. SOLUTION: A plate 22 and a plate 23 are welded in such a manner that a groove 24 is surrounded by friction stir welding to form a welding line 28, and, in the space between the groove 24 and the welding line 28, a brazing filler metal 30 provided between the plate 22 and the plate 23 is melted with friction heat at the time when the welding line 28 is formed by the friction stir welding, thus the plate 22 and the plate 23 are brazed. Alternatively, a thermosetting adhesive is used instead of the brazing filler metal, and the thermosetting adhesive is set by the friction heat. Alternatively, a plurality of grooves 24 are surrounded by the welding line 28, and the plate 22 and the plate 23 are spot-welded at the central part within the welding line. COPYRIGHT: (C)2006,JPO&NCIPI

Manufacturing and Use of Spiral Welded Pipes for High Pressure Service: State of the Art

Abstract: The HTS (Helical Seam Two Step) manufacturing process is used for the production of HSAW-pipes for high pressure service since 1987. The production process is split into pipe forming combined with continuous tack welding followed by submerged arc welding. The process has been continuously developed further. Details of this modern technology are described and qualitative and economical advantages over the conventional process are explained. The benefits of the existing network with steel plant and hot rolling mill as well as the quality controls, process automatisation and new NDT-equipment used in the pipe production are highlighted. Statistics on mechanical, chemical and dimensional properties of HTS pipes are presented to furnish proof of the uniform and well balanced profile of this product. Results from hot and cold bending on site, field weldability trials and tests related to the safety of spiral pipes are discussed. Results and experiences with the application of three-layer coatings (especially HDPE-high density polyethylene) on spiral pipes are also presented. Actual examples for the use and application of spiral welded pipes in international gas and oil projects are presented and an outlook on future development trends is given.Copyright © 2004 by ASME

Metal-base flux-cored wire for gas-shielded arc welding and gas-shielded arc welding method

Abstract: PROBLEM TO BE SOLVED: To provide metal based flux-containing wire for gas-shielded arc welding with which the amount of sputters to be generated is reduced and sufficient throat thickness can be secured even if an Ar-CO 2 gaseous mixture is used, and vertical downward welding is performed in d.c. straight polarity, and also welding operability is made satisfactory even if welding is performed in welding postures other than that of the vertical downward welding in d.c. straight polarity, and to provide a gas shielded arc welding method. SOLUTION: The metal based flux-cored wire is obtained by filling flux having a composition comprising, per the total mass of the wire, 0.07 to 0.22 mass% C, 1.10 to 2.50 mass% Mn, 0.40 to 1.50 mass% Si, 0.005 to 0.05 mass% F, 11 to 23 mass% Fe and a 0.020 to 0.090 mass% alkali metal compound, and in which the ratio of the content of Li to the total content of Na and K (=Li/(Na+K)) is 1.0 to 12.0 into an outer skin made of steel in which the content of C per mass of the outer skin is controlled to ≤0.02 mass%. COPYRIGHT: (C)2005,JPO&NCIPI

Gas metal arc welding of coated steels and shielding gas therefor

Abstract: This invention relates to a method for gas metal arc welding of coated steels, and a shielding gas therefor, in which the method comprises: (a) forming an arc between a consumable wire electrode and a coated steel workpiece; (b) maintaining a substantially constant arc voltage between said consumable wire electrode and the coated steel workpiece; (c) feeding the consumable wire electrode through a welding torch contact tube into said arc; (d) transferring metal from the consumable wire electrode to the coated steel workpiece; and (e) shielding the arc with a gas mixture consisting essentially of: (i) from 6 to 10 volume percent carbon dioxide; (ii) from 6 to 10 volume percent helium; and (iii) the balance argon.

Comparison of Metal Transfer Behavior in Electrodes for Shielded Metal Arc Welding

Abstract: Metal transfer behavior of three shielded metal arc welding electrodes, A WS Ell018, E6013 and E6010, were investigated through the characterization of size distribution of droplets and measurement of arc voltage signals. Of the three electrodes, E11018 electrode showed the largest droplet size with the smallest amount of spatter, while E6010 electrode showed the smallest droplet size with the largest amount of spatter. Even though E11018 electrode showed a good agreement between the frequencies of voltage drop in FFT processed voltage signals and the transfer rate of droplets, E6013 and E6010 electrodes showed weaker correlation because of their dominant explosive transfer behavior. The type of cathode used and electrode baking time also influenced the metal transfer behavior. Compared to bead-on-plate welding using steel plate as a cathode, welding on a water-cooled copper pipe showed less short-circuiting and higher melting rate in all electrodes because of higher arc potential and/or anode drop. When baked for a long time, E6010 electrode showed much more stable arc with less short-circuiting and explosion due to the loss of gas formation ingredients.

Laser beam welding method and laser beam welding structure

Abstract: PROBLEM TO BE SOLVED: To provide a laser beam welding method which can firmly join a joining member and a laser beam welding structure. SOLUTION: A connection layer 4 formed from a nonwoven fabric of a thermoplastic resin material having a high laser beam absorption factor is formed between a substrate 21 formed from a thermoplastic resin material and the welding part 31 of a bracket 3. By irradiating with laser beams, the laser beams penetrating the welding part 31 are energy-absorbed by the connection layer 4 to heat and melt the connection layer 4. Heat generated in the connection layer 4 is propagated to the joining surfaces of the adjoining substrate 21 and the welding part 31 to melt the joining surfaces. The melted substrate 21, the connection layer 4, and the welding part 31, after being mixed with each other, are joined to each other. The deflectable connection layer 4, between the substrate 21 and the welding part 31, by being pressed, follows the shapes of the joining surfaces to be welded firmly without producing a clearance between the joining surfaces. COPYRIGHT: (C)2006,JPO&NCIPI

High heat input submerged-arc welding method excellent in toughness of weld metal

Abstract: PROBLEM TO BE SOLVED: To provide a welding method which provides weld metal having uniform toughness in the total thickness range from a face side to a back side thereof, and having high toughness when a steel plate is subjected to one-side high heat input submerged-arc welding of single pass at a welding heat input of ≤ about 600 kJ/cm. SOLUTION: The high heat input submerged-arc welding method is provided by which a steel plate 50 mm or more thick is subjected to one-side submerged-arc welding of single pass at welding heat input of ≥ 400 kJ/cm using flux of a specific composition and a welding wire, wherein the steel plate contains, by mass, 0.02-0.2% C, 0.01-1% Si, 0.1-2.5% Mn, 0.002-0.1% Al, and 0.001-0.015% N, and the welding wire contains 0.02-0.2% C, 0.01-1% Si, 0.5-2.5% Mn, 0.1-3% Mo, 1-6% Ni, 0.002-0.1% Al, 0.005-0.3% Ti, and 0.001-0.015% N. COPYRIGHT: (C)2006,JPO&NCIPI

Weld wire electrode for gas metal arc welding

Abstract: A weld wire electrode for use as a consumable in a gas-metal arc welding process comprises two or more strips wrapped around one another and drawn to a desired wire diameter.

Metal transfer in arc welding

Abstract: A double pulse welding current method is disclosed for the generation and transfer of droplets of welding metal from an electrode wire to a workpiece in an arc welding process. A suitable background direct current level is specified to deliver a desired number of droplets to the weld site. During each cycle of droplet formation and transfer, a first increased current pulse is applied to the electrode and arc to generate a droplet on the tip of and electrode and then a second further increased current pulse is applied to timely separate the droplet from the electrode for transport in the arc to the workpiece. This double-pulse current application reliably produces one droplet per cycle of pulses to deliver a specified number of droplets to the weld site for improved weld quality and reduced spatter or waste of weld metal.

Uoe steel tube manufacturing method

Abstract: PROBLEM TO BE SOLVED: To provide a method for manufacturing a UOE steel tube with excellent productivity SOLUTION: A butt weld joint of the submerged arc welding of a seam part of a stock UOE steel tube to be used for a pipeline or the like has a groove of an X-shaped section, and the sectional area of the groove on the outer surface side of the stock tube having the groove of the X-shaped section is set to be smaller than that on the inner side of the stock tube An outer face of the seam part of the stock tube is permanently welded by CO 2 welding which is also used for temporary welding, and an inner face thereof is permanently welded by the submerged arc welding COPYRIGHT: (C)2006,JPO&NCIPI

Solid wire for laser arc compound welding, and laser arc compound welding method

Abstract: PROBLEM TO BE SOLVED: To provide a solid wire for laser arc compound welding, and a laser arc compound welding method with which a sound weld whose bead shape is excellent can be formed even when the fillet welding is performed on a galvanized steel plate at high speed, by suppressing production of spatter, pits and blowholes. SOLUTION: A welding wire 5 has a composition composed of, by mass, 0.01-0.13% carbon (C), 0.1-1.2% silicon (Si), 0.5-2.5% manganese (Mn), and ≤ 0.3% one or two or more kinds selected from a group consisting of aluminum (Al), titanium (Ti) and zirconium (Zr) in total, and the balance Fe with inevitable impurities. The ratio (Si/Mn) is set to be larger than 0.2 and below 1.5, and satisfies the inequalities 4.5 COPYRIGHT: (C)2006,JPO&NCIPI

Method, apparatus and software for gas metal arc welding with a continuously fed electrode

Abstract: The invention relates to a welding method for gas metal arc welding with continuous electrode feeding with process control for short arc welding and/or spray arc welding, and also for short pulsing in which the process control according to the short pulse method is caused to alternate cyclically between this and the process control for short arc or spray arc welding and in which the time for at least one of these process control methods is determined by a time programmed in by the user. The invention also relates to a welding power source and software for carrying out said method.