Showing papers on "Shielded metal arc welding published in 1995"
TL;DR: The mass distributions for all four consumables were unimodal and well described by a lognormal distribution; with the exception of the GMAW-MS and GMAw-SS comparison, they were statistically different.
Abstract: Particle size distributions were measured for fumes from mild steel (MS) and stainless steel (SS); shielded metal arc welding (SMAW)and gas metal arc welding (GMAW) consumables. Up to six samples of each type of fume were collected in a test chamber using a micro-orifice uniform deposit (cascade) impactor. Bulk samples were collected for bulk fume density and specific surface area analysis. Additional impactor samples were collected using polycarbonate substrates and analyzed for elemental content. The parameters of the underlying mass distributions were estimated using a nonlinear least squares analysis method that fits a smooth curve to the mass fraction distribution histograms of all samples for each type of fume. The mass distributions for all four consumables were unimodal and well described by a lognormal distribution; with the exception of the GMAW-MS and GMAW-SS comparison, they were statistically different. The estimated mass distribution geometric means for the SMAW-MS and SMAW-SS consumables we...
58 citations
TL;DR: In this article, a comparative evaluation of the low-cycle fatigue (LCF) behavior of type 316LN base metal, 316 weld metal, and 316 ln/316 weld joints was carried out at 773 and 873 K.
Abstract: A comparative evaluation of the low-cycle fatigue (LCF) behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld joints was carried out at 773 and 873 K. Total strain-controlled LCF tests were conducted at a constant strain rate of 3 × 10−3 s−1 with strain amplitudes in the range ±0.20 to ±1.0 pct. Weld pads with single V and double V configuration were prepared by the shielded metal-arc welding (SMAW) process using 316 electrodes for weld-metal and weld-joint specimens. Optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) of the untested and tested samples were carried out to elucidate the deformation and the fracture behavior. The cyclic stress response of the base metal shows a very rapid hardening to a maximum stress followed by a saturated stress response. Weld metal undergoes a relatively short initial hardening followed by a gradual softening regime. Weld joints exhibit an initial hardening and a subsequent softening regime at all strain amplitudes, except at low strain amplitudes where a saturation regime is noticed. The initial hardening observed in base metal has been attributed to interaction between dislocations and solute atoms/complexes and cyclic saturation to saturation in the number density of slip bands. From TEM, the cyclic softening in weld metal was ascribed to the annihilation of dislocations during LCF. Type 316LN base metal exhibits better fatigue resistance than weld metal at 773 K, whereas the reverse holds true at 873 K. The weld joint shows the lowest life at both temperatures. The better fatigue resistance of weld metal is related to the brittle transformed delta ferrite structure and the high density of dislocations at the interface, which inhibits the growth rate of cracks by deflecting the crack path. The lower fatigue endurance of the weld joint was ascribed to the shortening of the crack initiation phase caused by surface intergranular crack initiation and to the poor crack propagation resistance of the coarse-grained region in the heat-affected zone.
38 citations
Journal Article•
TL;DR: In this paper, the roles of welding procedure, material composition and postweld heat treatment are examined in relation to producing the minimum hardness levels in the weld zone, and the NACE MR0175 standard limits 13%Cr-4%Ni alloys to HRC 23 for sour service.
Abstract: For many years, the petroleum industry has employed martensitic stainless steels for wellhead and valve applications, and increasing use has been made of 13%Cr-4%Ni alloys. This material type was originally developed as a cast alloy (e.g., ASTM A487/A487M-89a Grade CA6NM). The combination of a low-carbon content and the addition of 3.5 to 4.5% nickel produces a fine, lath martensite structure which, after a tempering heat treatment, can exhibit superior mechanical properties. Thus, CA6NM and its forged variant ASTM A182/A182M-91 F6NM find application for production fluids containing CO{sub 2} and H{sub 2}S environments, particularly when hardening occurs, as is the case with fusion welds. Sensitivity to sulfide SCC increases at high material hardness levels, and the NACE MR0175 standard limits 13%Cr-4%Ni alloys to HRC 23 maximum for sour service. Attainment of such a hardness level requires careful consideration of tempering procedure. In this paper, the roles of welding procedure, material composition and postweld heat treatment are examined in relation to producing the minimum hardness levels in the weld zone.
37 citations
TL;DR: A subject is described who developed late and dual asthmatic reactions after occupational-type challenge exposure to gas metal arc welding on uncoated mild steel.
Abstract: Occupational asthma has been documented in electric arc welders exposed to manual metal arc welding on stainless steel. A subject is described who developed late and dual asthmatic reactions after occupational-type challenge exposure to gas metal arc welding on uncoated mild steel.
24 citations
TL;DR: The particle size distributions and bulk fume densities for mild steel and stainless steel welding fumes generated using two welding processes were used in mathematical models to estimate regional pulmonary deposition and regional pulmonary exposure and it is likely that for equal exposure concentrations GMAW fumes deliver nearly three times the particle surface area to the lungs as S MAW fumes.
Abstract: The particle size distributions and bulk fume densities for mild steel and stainless steel welding fumes generated using two welding processes (shielded metal arc welding [SMAW] and gas metal arc welding [GMAW]) were used in mathematical models to estimate regional pulmonary deposition (the fraction of each fume expected to deposit in each region of the pulmonary system) and regional pulmonary exposure (the fraction of each fume expected to penetrate to each pulmonary region and would be collected by a particle size-selective sampling device) Total lung deposition for GMAW fumes was estimated at 60% greater than that of SMAW fumes Considering both the potential for deposition and the fume specific surface areas, it is likely that for equal exposure concentrations GMAW fumes deliver nearly three times the particle surface area to the lungs as SMAW fumes This leads to the hypothesis that exposure to GMAW fumes constitutes a greater pulmonary hazard than equal exposure to SMAW fumes The implications of t
24 citations
TL;DR: In this article, the influence of titanium additions and interpass temperature on microstructures and properties in low carbon-15Mn-3Ni-05Mo multiple pass steel weld metals produced using the shielded metal arc welding (SMAW) process was studied.
Abstract: The influence of titanium additions and interpass temperature on the microstructures and properties in low carbon-15Mn-3Ni-05Mo multiple pass steel weld metals produced using the shielded metal arc welding (SMAW) process was studied Robust weld metals with high strength (>690 MPa) and toughness (100 J at -70°C) were produced when titanium concentrations of 180 to 400 ppm were added to a base chemical composition of low carbon-15Mn-3Ni-05Mo steels High toughness was measured in weld metals containing either 30 to 90 ppm titanium or 180 to 400 ppm titanium while deteriorated weld metal toughness was observed when weld metal titanium concentrations were less than 10 ppm, 90 to 180 ppm, or more than 400 ppm The microstructures of these low carbon weld metals were complex The difference between the classification systems used for weld metals and base metals was addressed
21 citations
TL;DR: In this article, a theoretical model of a gas metal arc welding system was developed to make predictions of the anode temperature profile, welding arc length and arc current, for spray transfer.
Abstract: A theoretical model of a gas metal arc welding system has been developed to make predictions of the anode temperature profile, welding arc length and arc current. The model incorporates a one-dimensional thermal model of the moving consumable anode and a two-dimensional model for the arc plasma. The model makes possible the calculation of the relationship between the welding arc current, wire feed rate and the supply voltages, for various wire diameters and shielding gases. The predicted welding current for a given wire feed rate shows good agreement with our experimental observation for operation in the spray transfer mode, for steel wire of two different diameters, assuming a workpiece sheath voltage of 15 V.
20 citations
Journal Article•
TL;DR: In this article, the effect of powder particle density and size distribution on the dispersion of particulates in the weld deposit was investigated, and critical welding criteria for the production of uniform particle distributions were identified.
Abstract: Weld metal consisting of particulate-reinforced metal matrix composite structure was produced with ceramic or refractory metal powder filled cored wire. Results are presented for both gas tungsten arc and gas metal arc weldments on Type 304 stainless steel. The effect of powder particle density and size distribution on the dispersion of particulates in the weld deposit was investigated. The motion and final distribution of particulates in the weld pool were evaluated with a fluid mechanics-based model, and critical welding criteria for the production of uniform particle distributions were identified. With particulates of optimum size and density in powder-filled cored wire it was possible to produce arc welding particulate-reinforced metal matrix weld deposits having uniform spatial particle distributions.
17 citations
Patent•
02 Jul 1995
TL;DR: In this article, a weld bead is formed which has a penetration depth ratio (aspect ratio) of 0.9 or less against the bead width, and a material having a large thickness, an upper plate is used which is provided with a groove that enlarges the penetration depth.
Abstract: PROBLEM TO BE SOLVED: To obtain through laser welding a sound weld zone with blowhole defects suppressed. SOLUTION: In the laser welding of an aluminum alloy in which molten metal is unexposed in the rear surface in a weld zone, a weld bead is formed which has a penetration depth ratio (aspect ratio) of 0.9 or less against the bead width. In welding a material having a large thickness, an upper plate is used which is provided with a groove that enlarges a penetration depth. Residual foams are reduced by minimizing the aspect ratio to 0.9 or less, enabling a weld zone to be obtained with a satisfactory mechanical characteristics.
10 citations
Journal Article•
TL;DR: Astro Arc Polysoude, an orbital welding equipment manufacturer based in Sun Valley, Calif., and Nantes, France, has combined the hot wire GTAW process with a narrow-groove weld joint design as discussed by the authors.
Abstract: Heavy-wall pipe welding for the power and petrochemical industry must meet code requirements. Contractors strive to meet these requirements in the most productive way possible. The challenge put to orbital welding equipment manufacturers is to produce pipe welding equipment that cost-effectively produces code-quality welds. Orbital welding equipment using the GTA process has long produced outstanding quality results but has lacked the deposition rate to compete cost effectively with other manual and semiautomatic processes such as SMAW, FCAW and GMAW. In recent years, significant progress has been made with the use of narrow-groove weld joint designs to reduce weld joint volume and improve welding times. Astro Arc Polysoude, an orbital welding equipment manufacturer based in Sun Valley, Calif., and Nantes, France, has combined the hot wire GTAW process with orbital welding equipment using a narrow-groove weld joint design. Field test results show this process and procedure is a good alternative for many heavy-wall-pipe welding applications.
Patent•
23 Feb 1995
TL;DR: In this article, a gas shielded metal-arc welding device of a two torches and three wires system in which welding wires 1, 2, 3 are used as consumable electrodes, and a shield gas is supplied to a welding arc part through pipes 13, 14 arranged in the front and rear of welding.
Abstract: PURPOSE: To carry out a high-speed fillet welding by arranging a twin wire welding torch in which two wires are electrically insulated and another torch with a succeeding wire and providing three welding wires with an independent power source and a wire feeding means. CONSTITUTION: In a gas shielded metal-arc welding device of a two torches and three wires system in which welding wires 1, 2, 3 are used as consumable electrodes, the twin wire welding torch 4 which feeds a preceding wire 1 and an intermediate wire 2 to power feeding tips 10, 11 is arranged in a welding direction and in the front of another welding torch 5 having a succeeding wire 3. The preceding wire 1 and the intermediate wire 2 are electrically insulated, the three welding wires 10, 11, 12 are respectively provided with an independent power source and a wire feeding means, and a shield gas is supplied to a welding arc part through pipes 13, 14 arranged in the front and rear of welding. Thus, since the welding current is distributed into the three wires, the arc power per one wire is suppressed, and the retreat of a welding pool is prevented to enable the high-speed fillet welding. COPYRIGHT: (C)1996,JPO
Patent•
19 Sep 1995
TL;DR: In this article, the authors proposed a method and equipment capable of welding with less spatter, bringing economic merit due to the reduction of wire consumption, and mitigating a spatter removing operation thereby enhancing welding efficiency.
Abstract: PROBLEM TO BE SOLVED: To provide the method and equipment capable of welding with less spatter, bringing economic merit due to the reduction of wire consumption, and mitigating a spatter removing operation thereby enhancing welding efficiency. SOLUTION: In the case of performing gas shielded welding by feeding a consumable electrode wire 5 from a welding torch 3 and supplying a shielding gas, the feeding speed of the wire 5 is pulsatively increased from a fixed speed by means of a wire feeding nozzle oscillating in the welding torch 3. Simultaneously, in accordance with the pulse period of the high speed feeding of the wire 5, the pulse welding current I is superposed, moving in the short-circuit a droplet 23 formed at the tip end of the wire 5 to a welding material 1 side.
01 May 1995
TL;DR: Underwater wet welding is conducted directly in water with the shielded metal arc (SMA) and flux cored arc (FCA) welding processes as discussed by the authors, but wet welds have been attempted on carbon steel structures down to 200 meters (650 ft).
Abstract: Underwater wet welding is conducted directly in water with the shielded metal arc (SMA) and flux cored arc (FCA) welding processes. Underwater wet welding has been demonstrated as an acceptable repair technique down to 100 meters (325 ft.) in depth, but wet welds have been attempted on carbon steel structures down to 200 meters (650 ft.). The primary purpose of this interpretive report is to document and evaluate current understanding of metallurgical behavior of underwater wet welds so that new welding consumables can be designed and new welding practices can be developed for fabrication and repair of high strength steel structures at greater depths. First the pyrometallurgical and physical metallurgy behaviors of underwater weldments are discussed. Second, modifications of the welding consumables and processes are suggested to enhance the ability to apply wet welding techniques.
Patent•
03 Oct 1995
TL;DR: In this paper, the authors provided the wire for the gas shielded metal arc welding of the high tensile steel where no short-circuit shifting phenomenon is generated, the droplet shifting phenomenon can be stabilized, the generation of spatter is extremely small, and the strength of the weld metal can be secured.
Abstract: PURPOSE:To provide the wire for the gas shielded metal arc welding of the high tensile steel where no short-circuit shifting phenomenon is generated, the droplet shifting phenomenon can be stabilized, the generation of spatter is extremely small, and the strength of the weld metal can be secured. CONSTITUTION:The wire for the MAG and pulsed MAG welding of the high tensile steel has a composition consisting of 0.05-0.15% C, 0.1-0.8% Si, 1.0-2.0% Mn, 0.01-0.25% Ti, 0.1-0.9% Mo, <=0.030% P, and <=0.030% S, and as required, one or two kinds of <=0.08% Cr and #3.5% Ni, and the balance Fe with inevitable impurities. In the inevitable impurities, O and N are <=80ppm in total, and the potassium compound is present in the vicinity of the surface layer of the welding wire by the amount of 0.2-10ppm per total amount of the welding wire in terms of K.
Patent•
03 May 1995TL;DR: A gas mixt. used as protective atmosphere during arc welding stainless steel contains 2-16% He; 1-2.5% CO2; 1 -2.8% N; balance Ar as mentioned in this paper.
Abstract: A gas mixt. used as protective atmosphere during arc welding stainless steel contains 2-16% He; 1-2.5% CO2; 1-2.8% N; balance Ar.
Journal Article•
TL;DR: In this article, four rutile electrodes with iron powder in the coating, E7024 type, adequate for manual and gravity welding, were produced in such a way as to obtain nominal carbon contents of 0.03, 0.10 and 0.13%.
Abstract: Four rutile electrodes with iron powder in the coating, E7024 type, adequate for manual and gravity welding, were produced in such a way as to obtain nominal carbon contents of 0.03, 0.06, 0.10 and 0.13% in the deposited metals, while the rest of the alloying elements remained constant. The all-weld-metal mechanical properties were evaluated according to AWS requirements, and it was found, as a general tendency, that as the carbon content increased, the tensile and yield strengths increased and the ductility and toughness decreased. It is possible to obtain a Grade 3 weld metal (with minimum 47 J at -20°C) with up to 0.10% carbon. Metallographic studies with the optical microscope and hardness measures were also carried out.
TL;DR: In this paper, the authors used TIG arc welding methods for hardfacing of aluminium products using TIG-based methods and found that the results were better than those obtained using conventional arc welding.
Abstract: (1995). Hardfacing of aluminium products using TIG arc welding methods. Welding International: Vol. 9, No. 2, pp. 94-99.
01 Jan 1995
TL;DR: In this article, the influence of weld surface finish, and in particular the surface roughness value Ra, as produced by different welding processes on the hygiene requirements of the food processing industry was determined.
Abstract: To achieve optimal hygiene conditions currently specified for the food processing industry requires a surface finish of welds equivalent to that of the parent plate. This is achieved by grinding and polishing adding substantially to the fabrication cost, and also representing a serious health hazard as a result of the substantial grinding dust. With the aim of reducing fabrication costs and health hazards, the research programme described in this paper determined the influence of weld surface finish, and in particular the surface roughness value Ra, as produced by different welding processes on the hygiene requirements of the food processing industry. The project has been carried out in two stages - one examining the correlation between welding process variations of MMAW, GMAW, FCAW, SAW, GTAW and PAW and achievable surface finish, the other examining the correlation between surface finish and hygiene requirements by investigating the biofilm development of the different pickled and passivated weld surface finishes and ground and polished welds.
TL;DR: In this article, a new method of arc welding with pulsed supply of shielding gases was proposed, and the method was shown to work well in the case of arc welders.
Abstract: (1995). A new method of arc welding with pulsed supply of shielding gases. Welding International: Vol. 9, No. 6, pp. 479-481.
Patent•
22 Aug 1995
TL;DR: In this article, the authors proposed a groove shape that feeds the lubricant containing K compound to the arc part without loss, and the width of the opening part on the surface of the groove is determined by satisfying the relationship of w/h =n>=0.1pi/h.
Abstract: PURPOSE:To improve the wire feedability and the welding operability by provid ing a groove where the depth of the groove and the width of the opening part are specified in the outer circumferential surface of the wire for welding, and by keeping the feeding lubricant in this groove. CONSTITUTION:The groove is provided in the outer circumferential surface of the wire by the cold rolling, the die drawing, the brushing, the shot-blasting or the roller die working, etc., in manufacturing welding wire. The depth (h) of the groove is 1--100mum, and the width (w) of the groove of the opening part on the surface of the groove is determined to satisfy the relationship of w/h =n>=0.1pi/h, where (d) is the diameter of the wire. This groove shape feeds the lubricant containing K compound to be kept in the groove to the arc part without loss.
TL;DR: In this paper, the influence of welding parameters on the delta ferrite content of austenitic weld metals was investigated by using Ferritescope measurements and fissure bend tests.
Abstract: The aim of the investigations was to study the influence of welding parameters on the delta ferrite content of austenitic weld metals. Different welding processes (shielded metal arc welding, gas tungsten arc welding, gas metal arc welding, submerged arc welding, electron beam welding, spot welding, flash butt welding and micro plasma arc welding) were used to prepare welds of AISI 316 L stainless steel. Process parameters like current, voltage, speed, polarity, gas additions etc. were varied. The weld metals were assessed microscopically, by Ferritescope measurements and fissure bend tests. The results showed that in the conventional melt welding processes, the ferrite content of the weld deposit is determined predominantly by the chemical composition. The variation of the gas composition by addition of oxygen, carbon dioxide or nitrogen to argon is therefore an effective way of reducing or controlling ferrite content.
Patent•
29 Sep 1995
TL;DR: In this paper, a contact tip used in gas shielded arc welding is provided with a first welding wire guide 1 arranged at the root part, welding wire feeder 2 at the tip end side of the first wire guide, and a second welding wire wire guide 3 placed at the end of the wire feeders, which is equipped with a hole diameter equal to that of the welding wires feeder.
Abstract: PROBLEM TO BE SOLVED: To provide such a contact tip for arc welding as greatly improves welding tolerance in sheet metal welding. SOLUTION: A contact tip used in gas shielded arc welding is provided with a first welding wire guide 1 arranged at the root part, welding wire feeder 2 at the tip end side of the first welding wire guide, and a second welding wire guide 3 arranged at the tip end side of the welding wire feeder, which is equipped with a hole diameter equal to that of the welding wire feeder and is formed with a heat resistant non-conductive material; consequently, a ratio of Joule's heat and arc heat by the projecting length of wire is changed.
Patent•
03 Feb 1995
TL;DR: In this paper, the manipulated variable of the output voltage to obtain the prescribed arc condition is inferred by a fuzzy controller 22 in accordance with the preset control rules by making the calculated results of computing elements 20, 21 as the input.
Abstract: PURPOSE:To provide constantly excellent welding results even by a non-skilled person by executing the fuzzy inference in accordance with the preset control rules to determine the manipulated variable to set the output voltage. CONSTITUTION:A wire 6 is fed to a part to be welded of the base metal 8 by a feeding equipment 7. The feeding speed of the wire 6 is set by a welding current setting device 9. The mean value and the standard deviation during the arc period to be measured during the welding are calculated. The manipulated variable of the output voltage to obtain the prescribed arc condition is inferred by a fuzzy controller 22 in accordance with the preset control rules by making the calculated results of computing elements 20, 21 as the input. Increase/decrease of the set value of the output voltage of the power source for welding is executed by a setting device 23 according to the output of the fuzzy controller 22. This constitution automatically changes the output voltage to an appropriate value even when the initial output voltage is set to any value.
Journal Article•
31 Mar 1995-Bulletin of the University of Osaka Prefecture, Series A Engineering and Natural Sciences
TL;DR: In this paper, the effect of the addition of iron powder to agglomerated flux on welding performance and the optimum welding conditions for high heat input welding were investigated, and the main conclusions obtained are as follows: the added of iron powders to flux increases the deposition rate and improves welding operability; the leading electrode was generated at a lower point in the molten metal, between the leading and the trailing electrodes, rather than at its top point.
Abstract: Summary The effect of the addition of iron powder to agglomerated flux on welding performance and the optimum welding conditions for high heat input welding were investigated. The main conclusions obtained are as follows: The addition of iron powder to flux increases the deposition rate and improves welding operability.The arc of the leading electrode was generated at a lower point in the molten metal, between the leading and the trailing electrodes, rather than at its top point. The penetration depth was influenced by the ratio of the area of the groove to that of the molten metal on which the leading arc is generated.The cross sectional profile of the bead was influenced by the current ratio of the trailing electrode to that of the leading. The optimum ratio for avoiding weld defects ranged between 0.70 and 0.80.The flux containing iron powder, together with the selection of optimum welding conditions, allowed tandem‐wire one‐pass submerged‐arc welding to be used for 60 mm thick plates.