Showing papers on "Shielded metal arc welding published in 1998"

A theoretical model for gas metal arc welding and gas tungsten arc welding. I.

Abstract: A recently developed theory for predicting arc and electrode properties in gas metal arc welding (GMAW) has been generalized to include arc–electrode interfaces, variation of surface tension pressure with temperature, Marangoni forces and handling of weld pool development in stationary gas tungsten arc welding (GTAW). The new theory is a unified treatment of the arc, the anode, and the cathode, and includes a detailed account of sheath effects near the electrodes. The electrodes are included as dynamic entities and the volume of fluid method is used to handle the movement of the free surface of the molten metal at one electrode. Predictions can be made of the formation and shape of the welding droplets as a function of time in GMAW and also of weld pool development in GTAW, accounting for effects of surface tension, inertia, gravity, arc pressure, viscous drag force of the plasma, Marangoni effect and magnetic forces, and also for wire feed rate in GMAW. Calculations are made of current densities, electric potential, temperatures, pressures and velocities in two dimensions, both in the arc and also within the molten metal and solid electrodes. Calculations are presented for GMAW and GTAW for an arc in argon and the results are compared with experimental temperature measurements for the plasma and the electrodes.

Chromium, nickel and manganese in shipyard welding fumes

Abstract: Tests were conducted to determine the effects of base metal and welding electrode composition on welding fume. Materials included HY-100 and HSLA-100 high-strength, low-alloy steels. Shielded metal arc welding (SMAW) was performed with E1 1018-M electrodes and gas metal arc welding (GMAW) with MIL-100S-1 electrode wire. These tests included measurement of fume composition, fume generation rates and worker breathing zone fume. Sampling of welding fume also was conducted in a shipyard. This study concludes that some shipyard welding and cutting operations, materials and processes will be impacted by the recent and anticipated reductions in exposure limits. Additional controls will be required to comply with these reductions. Results indicate: . Exposure to hexavalent chromium can be expected when welding or cutting materials that contain chromium or chromates. These materials include stainless steels, high-chromium nickel alloys and some low-alloy steels. . The highest nickel levels occurred during SMAW and GMAW of stainless steels and nickel alloys. However, only the samples in enclosed spaces exceeded the proposed limit for nickel. . SMAW, GMAW and flux cored arc welding (FCAW) of stainless steels, carbon steels and low-alloy steels produced the highest manganese levels. . Eight-hour TWA levels of hexavalent chromium of up to 1-2 μg/m 3 were found during shipyard and laboratory sampling of SMAW of HY-100 using E11018-M and E12018-M electrodes. Similar levels also may be possible when welding with these electrodes on other materials.

Predictions of metal droplet formation in gas metal arc welding. II.

Abstract: Predictions of metal droplet formation in gas metal arc welding (GMAW) are made for mild steel wires with argon as a shielding gas, using a generalized theory for predictions of arc and electrode properties in arc welding The theory is a unified treatment of the arc and the electrodes and includes a detailed analysis of the anode sheath region, together with a free surface treatment for the molten metal at the tip of the welding wire Results of calculations made for a mild steel wire of 012 and 016 cm diameters are in good agreement with experimental measurements of droplet diameter and droplet detachment frequency at currents between 150 and 330 A The results indicate that the anode sheath region and the effects due to variation of surface tension with temperature have an important influence on the dynamics of droplet growth at the tip of the wire in GMAW Predictions are made for the transition from the globular to the spray mode of metal transfer, in agreement with experimental observations in arc welding

Occupational asthma caused by aluminium welding

Abstract: Work-related asthma has been documented in workers employed in the primary aluminium industry and in the production of aluminium salts. The role of aluminium in the development of occupational asthma has, however, never been convincingly substantiated. We investigated a subject who experienced asthmatic reactions related to manual metal arc welding on aluminium. Challenge exposure to aluminium welding with flux-coated electrodes, as well as with electrodes without flux, elicited marked asthmatic reactions. Manual metal arc welding on mild steel did not cause significant bronchial response. The results of inhalation challenges combined with exposure assessments provided evidence that aluminium can cause asthmatic reactions in the absence of fluorides. Awareness of this possibility may be relevant to the investigation of asthma in workers exposed to aluminium.

Elevated-temperature, plasma-transferred arc welding of nickel-base superalloy articles

Abstract: A nickel-base superalloy article which is susceptible to strain-age cracking and has a directionally oriented, single crystal, or equiaxed grain structure is repaired with minimal welding heat input into the article. The article is first heated to a welding temperature of from about 1650° F. to about 2000° F. in an inert atmosphere. A damaged area of the article is weld repaired using a plasma-transferred arc welder which vaporizes a filler metal in a plasma arc and deposited the vaporized metal onto the article to form a weld overlay. Minimal additional heat is added to the article during welding, as the weldment metal is vaporized remotely from the article.

Double-sided arc welding increases weld joint penetration : Aluminium welding

Abstract: Connecting two torches to the two terminals of a single power supply achieves more concentrated arcs that increase weld joint penetration.

An electronic welder control circuit

Abstract: This paper presents a 6 kW electronic welder control circuit. The DC welding current is controlled with a simple and robust control circuit. Fast dynamic performance and low current ripple are achieved. Paralleled IGBTs are used with a switching frequency of 50 kHz. The welder machine with this control stage can be applied to shielded metal arc welding and gas tungsten arc welding processes. The welding DC voltage is also controlled with an outer controller acting in the current reference value. Fast dynamic is also obtained for the DC voltage control without steady state error. With this control level, gas metal arc welding and flux-cored arc welding can be applied. The current control and the DC voltage control can also be applied in different cycles depending on a external signal. In the peak and background current cycles. the current control and DC voltage control are applied, respectively, enabling the use of the electronic welder for pulsed gas metal arc welding. In the paper, the system modelling is also realised. Some modelling and experimental results are presented. The annoying problems caused by this type of equipment in low voltage networks are also shown.

Method and apparatus for spot welding a work having a plurality of welding materials placed on top of each other by boring a hole to release vapors

Abstract: A plasma arc welding for effectively letting gases of low boiling point substances for coating a steel sheet escape, ensuring the escape of a molten metal into gaps between the steel sheets and eventually accomplishing satisfactory plasma arc welding. A hole (31) is first bored in an upper sheet (21)(or both upper and lower sheets (21 and 22)) quickly by using a plasma arc (20) having greater power than an appropriate welding value, and a vapor of coating substances is allowed to escape through the hole (31). Subsequently, power of the plasma arc (20) is lowered to the appropriate welding value, and the upper sheet (21) and the lower sheet (22) are welded together while a filler (9) is being supplied to fill the hole (31) and the gap (23). While boring is made or immediately after boring is finished, the size of the gap (23) is measured on the basis of the plasma arc voltage, and the feed quantity of the filler (9) is controlled in accordance with the size of the gap (23).

Electrochemical oxygen transfer during direct current arc welding

Abstract: The electrochemical transfer of oxygen was investigated for electrode negative and electrode positive polarities in the submerged arc, shielded metal arc and gas tungsten arc welding processes. Analysis of the welds showed that electrochemical reactions as well as thermochemical reactions are significant in altering the oxygen content of the weld metal. The oxygen transfer in the submerged and shielded metal arc welding processes is strongly influenced by electrochemical reactions at the slag/metal interface, and oxygen transfer in gas tungsten arc welding is strongly influenced by electrochemical reactions at the plasma/metal interface. The electrochemical oxygen reactions at the slag/metal interface include oxygen pickup at the anode and oxygen refining at the cathode. Electrochemical oxygen reactions at the plasma/metal interface include the refining of oxygen at the anode and pickup at the cathode. Electrochemical reactions have the greatest influence on weld metal chemistry at high welding currents and at slow weld travel speeds.

Weld joint structure of high cr ferrite steel

Abstract: PROBLEM TO BE SOLVED: To provide a weld joint structure which is capable of forming weld metal high in toughness without lowering welding efficiency and which enables such corrosion resistance of a weld zone to be obtained as is comparable to that of a basic material, and to improve reliability of the weld zone through the reduction of danger against brittle fracture, in the welding of a high Cr ferritic heat resistant steel containing 8.5-13 wt.% Cr. SOLUTION: The initial layer is constructed by TIG welding using a welding material having the same component base as that of a high Cr ferritic heat resistant steel; and, the next and subsequent layers are constructed by at least one welding method selected from shielded metal arc welding, submerged arc welding, inert gas metal arc welding, and CO 2 gas shielded arc welding, using a high strength welding material which contains 1.9-2.6 wt.% Cr, with W added for a prescribed quantity. Otherwise, after the initial layer 2 and the subsequent layers are successively welded, the last layer is laminated with weld metal using a welding material which has the same component base as that of the base material containing 8.5-13% Cr. COPYRIGHT: (C)1999,JPO

Portable holding oven for welding electrodes utilizing exhaust heat from welding machine

Abstract: A portable oven for holding shielded metal arc welding electrodes prior to their use. The holding oven utilizes the heated exhaust gases of a welding machine engine to maintain welding electrodes at an elevated temperature to prevent the absorption of moisture, which would adversely affect the quality of welds. The holding oven includes an insulated outer housing, which is positioned on or near an engine-driven welding machine. An interior rack for the electrodes is mounted in the upper portion of the housing and is accessible through a hinged door. A heat exchanger in the lower part of the housing is coupled to the exhaust pipe of the welding machine and radiates the exhaust heat into the interior of the housing before transferring the exhaust gases to a directional exhaust port. The holding oven may include means for measuring and regulating the interior temperature of the housing to keep the electrodes within a predetermined temperature range. In an alternative embodiment, the holding oven is integral with the welding machine housing.

The effect of welding parameters on high-strength SMAW all-weld-metal - Part 2: AWS E10018-M and E12018-M

Abstract: Three AWS A5.5-81 all-weld-metal test assemblies were welded, each with one of E10018-M and E1201 8-M type electrodes from standard production batches, varying the welding parameters, in such a way as to use high heat input and high interpass temperature (hot), medium heat input and medium interpass temperature (medium) and low heat input and low interpass temperature (cold). Mechanical properties and metallographic studies were performed in the as-welded condition. The following results were achieved: the three all-weld-metals from E10018-M electrodes satisfied the AWS requirements, despite the fact that the measured properties varied slightly. With the E12018-M electrodes, the medium test specimen was the only one that fulfilled the AWS requirements. The cold test specimen showed a yield strength that exceeded the maximum requirement of the norm and the hot specimen did not achieve the minimal value of tensile strength. All the test specimens satisfied elongation and toughness requirements. Metallographic studies showed that as the heat input increased, the percentages of recrystallized zones increased, the grain size became larger and, in the columnar regions, there was a small increment of acicular ferrite and ferrite with second phase at the expense of primary ferrite. These results showed the E10018-M alloy to be markedly less sensitive to the variations of heat input than the E12018-M. With the E12018-M electrode, it is necessary to weld under strict control and with precise conditions, as found for E11018-M electrodes in Part 1 of this work, in which the same study was performed with the latter type of electrode.

Protective gas for tig welding

Abstract: The invention relates to a protective gas for TIG welding of metals, especially high alloy or low alloy steel, whose thermal conductivity is lower than that of aluminium. The inventive gas consists of argon, helium and hydrogen and enables significant improvements to be made in electric arc stability, welding speed, oxidation of weld surface and adjacent area, flow-on performance and weld appearance.

Weldability and toughness evaluation of pressure vessel quality steel using the shielded metal arc welding (SMAW) process

Abstract: The present study was carried out to assess the weldability properties of ASTM A 537 Cl. 1 pressure-vessel quality steel using the shielded metal arc welding (SMAW) process. Implant and elastic restraint cracking (ERC) tests were conducted under different welding conditions to determine the cold cracking susceptibility of the steel. The static fatigue limit values determined for the implant test indicate adequate resistance to cold cracking even with unbaked electrodes. The ERC test, however, established the necessity to rebake the electrodes before use. Lamellar tearing tests carried out using full-thickness plates under three welding conditions showed no incidence of lamellar tearing upon visual examination, ultrasonic inspection, and four-section macroexamination. Lamellar tearing tests were repeated using machined plates, such that the central segregated band located at the midthickness of the plate corresponded to the heat-affected zone (HAZ) of the weld. Only in one (no rebake, heat input: 14.2 kj cm-1, weld restraint load: 42 kg mm-2) of the eight samples tested was lamellar tearing observed. This was probably accentuated due to the combined effects of the presence of localized pockets of a hard phase (bainite) and a high hydrogen level (unbaked electrodes) in the weld joint. Optimal welding conditions were formulated based on the above tests. The weld joint was subjected to extensive tests and found to exhibit excellent strength (tensile strength: 56.8 kg mm-2, or 557 MPa), and low temperature impact toughness (7.4 and 4.5 kg-m at-20 °C for weld metal, WM, and HAZ) properties. Crack tip opening displacement tests carried out for the WM and HAZ resulted in δm values 0.36 and 0.27 mm, respectively, which indicates adequate resistance to brittle fracture.

Gas shielded metal arc welding method for circumferential joint of steel tube, and wire for gas shielded metal arc welding

Abstract: PROBLEM TO BE SOLVED: To prevent generation of defective arc which is caused by slag inclusion and generation of defective fusion, to provide the weld metal which is excellent in cracking resistance and excellent in conformability to a steel tube of the base metal, and to improve the welding efficiency. SOLUTION: A wire for gas shield metal-arc welding to be used in the welding of a circumferential joint of steel tubes has the composition consisting of, by weight, 0.02-0.08% C, 0.70-1.00% Si, 0.80-1.60% Mn, 0.005-0.025% S and 0.002-0.015% S, and at least two kinds of elements to be selected from the group consisting of 0.10-0.40% Mo, 0.010-0.100% N, 0.015-0.500% Cr, and 0.004-0.050%, and the balance Fe with inevitable impurities. In the inevitable impurities, P is limited to be <=0.020%, Ti <=0.15%, Nb <=0.03%, V <=0.03%, and B <=0.0010%.

Metal and method for gas-shielded metal arc welding of high strength chromium-molybdenum steel

Abstract: PROBLEM TO BE SOLVED: To improve the strength, toughness and SR crack resistance or the like at the room temperature and high temperature after SR treatment. SOLUTION: The weld metal 3 to be formed by the gas-shielded metal arc welding in which the mixed gas of Ar gas with either of CO2 gas or O2 gas is used as the shielding gas for welding, has the composition consisting of, by weight, 0.04-0.15% C, 0.10-0.50% Si, 0.30-1.40% Mn, 2.00-3.25% Cr, 0.90-1.20% Mo, 0.20-0.70% V, and the balance Fe with inevitable impurities. The inevitable impurities contain =10% V.

Gas shielded consumable electrode welding with rotating arc

Abstract: A gas shielded, consumable electrode, rotating arc welding process employs a wire electrode of ferromagnetic material and a shielding gas of 1-8 (more than 5, especially 5.5-8) vol.% O2, optionally 10-40 (15-35, especially 20-30) vol.% He and balance Ar. The wire electrode is a copper coated solid wire.

Controlling formation of foam slag in an electric arc furnace

Abstract: The invention relates to a method and device for controlling the formation of foamed slag in an arc furnace (5) to which the carbon is fed in such a way that the arc is at least partially enveloped in the arc furnace (5) and an over abundant feeding of carbon is avoided. The quantity of the carbon which is fed to the arc furnace is thus determined by means of a foamed slag model (25) according to the quantity of at least one of the coating materials comprised of scrap metal, steel, alloy material or admixtures.

Gas shielded metal arc welding method of small leg length high-speed horizontal fillet type

Abstract: PROBLEM TO BE SOLVED: To provide a small leg length, high-speed horizontal fillet gas shielded metal-arc welding method free from any defective welds and capable of obtaining excellent bead shape even when the leg length is small to reduce the distortion of a welded structure in the horizontal fillet welding of two- electrode one-pool system. SOLUTION: In a horizontal fillet gas shielded metal-arc welding method of two-electrode and one-pool system to be performed using the flux-cored wire, the wire projection length (WL1 ) of a preceding electrode and the projection length (WL2 ) of a succeeding electrode satisfy the inequalities of (WL1 +5 mm) =1.0mm/min to obtain the small leg length high-speed horizontal fillet gas shielded metal-arc welding to form the bead of 3-4 mm in leg length.

Creep crack growth properties of type 308 austenitic stainless steel weld metals

Abstract: Using Type 308 austenitic stainless steel weld metal made by the SMAW and FCAW processes, creep tests and creep crack growth tests were carried out at a temperature of 650 C. Creep crack growth rate tests were conducted using CT-type specimens and the data derived were arranged according to parameter C{sup *}. With regard to the flux cored arc weld metal, Bi{sub 2}O{sub 3} (melting point 820 C) was intentionally added to the flux for easy slag peeling and enhanced welding operability. The bismuth segregated (segregation depth approximately 15 {angstrom}) at the grain boundaries and, due to the presence of this bismuth, fracturing occurred intergranularly, with marked reduction in creep ductility. Further, the creep crack growth rate of the flux cored arc weld metal, which contained large amounts of bismuth, was exceedingly rapid compared with that of SMA and FCA weld metal not containing bismuth. Bismuth that has segregated at the grain boundaries is extremely harmful with respect to creep ductility and creep crack growth properties.

Manufacture of high strength welded joint having excellent crack resistance

Abstract: PROBLEM TO BE SOLVED: To provide a method capable of manufacturing the high strength welded joint sufficiently exceeding the strength required for the welded joint and having the tensile strength of >=950 MPa without generating cracks in the deposited metal even by pre-heating in lower temperature zone than the conventional one. SOLUTION: The butt multi-layer welding by a shielded metal arc welding method using the welding consumable electrode containing, by wt., >=0.07% C, 3.0-4.0% Ni, 0.030-0.050% O and 0.6-0.9% carbon equivalent in the chemical composition of the deposited metal is applied to the steel having hardness of 310-360 HV and composing of, by wt., 0.07-0.16% C, =15 KJ/cm to =75 deg.C to =100 deg.C to <=250 deg.C in temperature between paths, whereby the joined part is formed with the deposited metal of 290-340 HV in hardness.

Flat one side gas shielded metal arc welding method

Abstract: PROBLEM TO BE SOLVED: To reduce the working time, to improve the safety in the working, and to provide a joint of high strength with an excellent bead shape. SOLUTION: Plate members 1, 2 are arranged in a substantially horizontal manner while slightly separated from each other, and a non-consumable butt strap 4 is arranged on a back side of a groove part 3, and the butt strap 4 can be moved in the welding direction. A recessed part having an arcuate or flat bottom surface of 0.5-20mm depth is formed in the non-consumable butt strap 4. The arc is generated at the tip of a welding wire 6 by butting a welding torch 5 to the groove part 3 with the torch 5 downward from an upper part and the plate members 1, 2 are welded to each other by slidingly moving the butt strap 4 in the same direction as the welding direction as the welding torch 5 is moved. The flux-cored wire in which the quantity of the slag generating agent based on the total weight of the wire is 1-11wt.% is used for the welding wire to be used.

Arc ignition arrangement

Abstract: The invention relates to an arrangement for contact arc ignition in manual TIG welding and to a method for welding with this arrangement. The arc is established by lifting the welding torch (12) after contact between electrode (13) and workpiece (14) under low ignition current. When the arc length is sufficient, the welder orders a change-over to welding current via an operating device (11). The invention can also be used for controlling the supply of heat to the workpiece both during continuous bead application and during the crater filling time at the end of welding. The invention creates reliable ignitions without extensive use of control electronics, and it substantially reduces the electrode wear in manual TIG welding.

A guide to GMA welding of aluminum : Aluminium welding

Abstract: For welding aluminum, GMAW offers advantages that include high welding speeds, narrow heat-affected zones and all-position welding.

Method and apparatus for welding plastic sheets, particularly sheets made from polyolefin

Abstract: For the welding of plastic, preferably of polyolefin films (12,13) ​​is supplied to the films in their compressed, area to be welded, the welding heat. To establish firm welds, in which the material is not displaced in the welding operation from the region of the welding seams, and to prevent the plastic material stuck to the sealing jaws during opening of the welding device, the area that is plasticized at will, the weld joint forming portion adjoined, cooled at the same time during the feeding of the welding heat.