Showing papers on "Shielded metal arc welding published in 2002"

The welding of aluminium and its alloys

Abstract: Introduction to the Welding of Aluminium. Welding metallurgy. Material Standards, Designations and Alloys. Preparation for Welding. Welding Design. TIG Welding. MIG Welding. Other Welding Processes. Resistance Welding Processes. Welding procedure and welder approval. Weld Defects and Quality Control. Appendices.

Rapid prototyping of 5356-aluminum alloy based on variable polarity gas tungsten arc welding: process control and microstructure

Abstract: This paper concentrates on rapid prototyping of a 5356-aluminum alloy based on a new deposition process of variable polarity gas tungsten arc welding (VPGTAW), and describes the microstructure and ...

Weldability and Microstructural Aspects of Shielded Metal Arc Welded HSLA-100 Steel Plates

Abstract: HSLA-100 steel with 14 mm thickness in quenched and tempered condition was shielded metal arc welded (SMAW) with 2 kJ/mm heat input using basic flux coated filler rods without any pre or post welding heat treatments. The steel was found to be welded satisfactorily in this condition without developing any defect. Optical microscopy studies revealed typical cast dendritic structure in the weld metal and coarse bainite in grain-coarsened area of the heat-affected zone (HAZ). Transmission electron microscopy (TEM) study confirmed incidence of mixed structure of martensite laths and bainite in weld metal, while, it was mainly of bainite laths in HAZ with evidence of martensite–austenite (M–A) constituent and massive ferrite. The yield strength (YS), ultimate tensile strength (UTS) and Charpy V-notch (CVN) impact energy of the weld metal (YS-695 MPa, UTS-842 MPa and CVN-105 J at –50°C) and HAZ (YS-790 MPa, UTS-891 MPa and CVN-130 J at –50°C) were found satisfactory although HAZ properties were inferior to the base metal properties. The hardening of HAZ was not very significant in this steel under the present welding condition.

Magnetically Impelled Arc Butt Welding of Hollow and Solid Parts

Abstract: Magnetically Impelled Arc Butt (MIAB) welding is mainly used in the automotive industry for butt welding of tubes and tubular parts 8–100mm in diameter and 0.8–6mm wall thickness. To extend the range of MIAB welding applications research work was conducted on different hollow and solid parts, special attention being given to welding of parts, the cross section of which is commensurable with of the active spot diameter of the rotating arc.

The effect of ferro-alloy additions and depth on the quality of underwater wet welds

Abstract: Underwater wet welding offers significant cost savings over other repair techniques for submerged structures, but the weld metal mechanical properties are not equal to those of surface welds. The problems of porosity and oxidation of the weld pool as underwater depths increased were addressed by additions of manganese, titanium, boron, and rare earth metals (REM) to the coating of a rutile-based SMAW electrode. A test matrix of 60 coating formulations was prepared and test welds were made at four depths: 70, 140, 200, and 300 ft (21, 43, 61, 91 m). With the addition of titanium, a strong deoxidant, it was possible to control weld metal chemical composition. Low porosity was associated with electrodes that deposited a slag with a basicity index approaching neutral (1.0). Slag basicity may influence transfer of hydrogen to the weld pool and, thus, influence porosity. Addition of titanium and boron produced a microstructure of 60 to 90 vol-% acicular ferrite. Tensile strength increased with the combined addition of manganese, titanium, and boron. The results of this investigation demonstrated some of the adverse effects of increasing underwater depth on weld metal quality can be mitigated by modifications to the electrode coatings.

Theoretical and Experimental Assessment of Chloride Effects in the A-TIG Welding of Magnesium

Abstract: Active fluxes that are deposited on the TIG torch path before alloy melting can significantly increase weld penetrations. Several mechanisms (arc constriction, surface-tension-driven flow) for the active-TIG or A-TIG welding process have been postulated. The A-TIG welding of magnesium is discussed here using a simple model for the surface tension over the weld pool, real-time monitoring data, and measured characteristics from the fusion zone region. The chlorides selected for this investigation incorporated simple-metal elements from different group numbers (LiiaCl, CaiiaCl2, CdiibC12, PbivbCl2 and CeCl3) so that correlations between their chemistry and their effects during A-TIG welding could be established. Video recordings showed that chlorides intensified the visible light emission from the arc and affected its profile. Measurements during arc welding at a constant current demonstrated that all chlorides increased the arc voltage (thus the heat input) and the arc temperature. A-TIG weld cross sections revealed that chlorides increased fusion zone dimensions, as could be expected from greater heat inputs. While calculations suggested that surface tension might have altered weld pool circulation, specially designed experiments with low-energy-density laser beams were inconclusive. Among all tested chlorides, cadmium chloride was the most effective during A-TIG welding due to the high first ionization potential of cadmium, which correlated to several observations such as: low chloride melting, boiling, and dissociation temperatures, high welding voltage, augmented arc temperature, increased fusion zone penetration, and greater depth-to-width ratio.

Weldability characteristics of shielded metal arc welded high strength quenched and tempered plates

Abstract: High strength, quench and tempered (Q&T) plates having yield strength of a minimum of 670 MPa and conforming to SA 517 Gr. F specification were successfully developed at Rourkela Steel Plant in plates up to 40 mm thickness. The plates are used extensively for the fabrication of impellers, penstocks, excavators, dumpers, and raw material handling devices, where welding is an important processing step. SA 517 Gr. F plates, characterized by a relatively high carbon equivalent (CE: ∼0.6) and alloyed with Ni, Cr, Mo, Cu, and V, are susceptible to a crack-sensitive microstructure and cold cracking during welding. In view of the above, the present study investigated the weldability properties of 20 mm thick plates using the shielded metal arc welding (SMAW) process. Implant and elastic restraint cracking (ERC) tests were carried out to assess the cold cracking resistance of the weld joint under different welding conditions. Preheat of 100 °C, partial or full rebake, and a heat input of 14.9 to 15.4 KJ/cm resulted in static fatigue limit (SFL) values well in excess of the minimum specified yield strength (MSYS) of 670 MPa and a critical restraint intensity (K cr) value of 34,650 MPa, indicating adequate cold cracking resistance. Lamellar tear tests conducted using full thickness plates at heat input levels ranging from 9.7 to 14.4 KJ/cm and weld restraint loads (WRL) of 510 to 685 MPa showed no incidence of lamellar tear upon visual, ultrasonic, and four-section macroexamination. The weld joint, based on optimized welding parameters, exhibited adequate tensile strength (812.4 MPa) and low temperature impact toughness 88.3 and 63.4 J (9.2 and 6.6 kg-m) at −40 °C for weld metal (WM), and heat-affected zone (HAZ) properties, respectively. The crack tip opening displacement (CTOD) values of WM and HAZ (0.40 and 0.36 mm, respectively) were superior to that of the parent metal (0.29 mm), indicating adequate resistance of weld joint to brittle fracture. It was concluded that the weld joint conforms to the requirements of SA 517 Gr. F specification and ensures a high integrity of the fabricated products.

Explosion Welding of Steel with Aluminum

Abstract: An analysis is made of the main kinematic parameters that determine the beginning of weld formation near the lower boundary of the region of explosion welding. The welding of aluminum with steel is considered. The paper reports experimental results for the flow of material in the gap under oblique collision of metal plates. Key words: oblique collision, particle flow, explosion welding.

Alloying and Microstructural Management in Developing SMAW Electrodes for HSLA-100 Steel To determine the optimal composition of SMA W electrodes for use with HSLA- 100 steel, three sets of experimental welding electrodes were developed

Abstract: Due to the excellent mechanical properties of high-strength, low-alloy (HSLA) plate steels, fabricators and manufacturers have great interest in the development of high-performance welding electrodes for these steels. Three sets of experimental welding electrodes were designed and manufactured for this research. The first iteration of electrodes was targeted to vary copper from 0.0 to 3.7 wt-%. In the second iteration, chromium was removed and the Ni and Cu contents were adjusted to the ranges of 1.0-3.0 and 1.0-1.5 wt-%, respectively. Niobium was added at 0.03 wt-%. The third iteration lowered the carbon content to 0.03 wt-% and reduced the nitrogen content to 100 ppm maximum. Nickel and copper contents were fine-tuned to 1.0 to 2.3 and 0.8 to 1.0 wt-%, respectively. Standard light and electron metallographic techniques were used to examine the weld metal microstructural evolution. Electron diffraction patterns from the different phases were analyzed. Mechanical testing was performed to characterize the resulting welds. The optimal composition for the HSLA-100 steel weld metals was determined as 0.04 wt-% C, 1.3 wt-% Mn, 2.3 wt-% Ni, 0.55 wt-% Mo, 0.8 wt-% Cu, 90 ppm N, and 270 ppm O. The 0.03 wt-% Nb worked well with Cu to develop synergistic precipitation, which uniformized the hardness fluctuations on weld cross sections. The weld metals that exhibited a predominantly acicular ferrite (AF) structure with some coarse granular bainite presented the best toughness properties. Weld metals with the above composition easily met the U.S. Navy requirement for HSLA-100 steel welds in this work.

Welding process effects in weldability testing of steels : Welding aluminium

Abstract: This work was part of a nationwide program for the development of new high-performance steels with 70 ksi (485 MPa) minimum yield strength, improved toughness, and lower manufacturing costs through the elimination of preheat for welding. The purpose of the present work was to evaluate the fusion zone hydrogen-induced cracking susceptibility of single-pass weld deposits made using four different welding processes at equivalent diffusible hydrogen levels. The gapped bead-on-plate test was used to compare shielded metal arc (SMAW), submerged arc (SAW), gas metal arc (GMAW), and flux cored arc (FCAW) welding processes. Equivalent net heat inputs were produced and the weld cross-sectional areas were normalized at different arc energies, including the heat transfer efficiency for each process. The minimum predicted preheats were different, lower for SAW than for GMAW, FCAW, and SMAW at similar diffusible hydrogen levels and heat inputs. This difference was attributed to the different solidification microstructures and weld bead geometries. Preheating guidelines based on the SMAW process remained the most conservative, confirming the validity of the past practice of using SMAW to find minimum preheats. It was concluded that preheat recommendations should not be extrapolated from one welding process to another. The information generated was used for manufacturing recommendations for welding high-performance steels.

Steel wire for gas shielded arc welding

Abstract: PROBLEM TO BE SOLVED: To provide a welding wire which can maintain a stable feeding performance even in such critical working conditions that the feeding speed of the welding wire increases or the temperature of the welding wire increases as is the case with the gas shielded arc welding under a high heat input and high interpass temperature. SOLUTION: The steel wire material of the welding wire comprises C:0.005-0.09 mass%, Si:0.50-1.2 mass%, Mn:1.50-2.2 mass%, Ti:0.15-0.30 mass%, B:0.0005-0.0035 mass%, Cu:≤0.50 mass%, S:0.005-0.025 mass% and the balance Fe with unavoidable impurities. The surface of the welding wire is covered by a solid lubricant layer of 0.2-1.0 g per the steel wire material of 10 kg, and the surface of the solid lubricant layer is coated with a lubricant of 0.2-1.8 g per the steel wire material of 10 kg. COPYRIGHT: (C)2004,JPO&NCIPI

Work welding method

Abstract: A laser light L is emitted from a laser light source 6 to works 1, 2, to form a laser molten weld pool 3, and immediately thereafter, an arc molten weld pool 4 is formed using an arc welding machine 7; thereby plates 1, 2 are welded. The arc welding machine 7 is provided with a filler wire to form a bead 5 on the plate 1. With the welding process according to the present invention, works can be efficiently and securely welded regardless of shape and material of the works.

Hydrogen embrittlement properties of heat affected zone of high strength steel in shielded metal arc welding

Abstract: Corrosion resistance, mechanical properties and hydrogen embrittlement were investigated from an electrochemical view, with the slow strain rate test (SSRT) method with applied constant cathodic potential. Fracture surface was analyzed by SEM. Corrosion resistance and mechanical properties were increased by post-weld heat treatment (PWHT) compared to those in the as-welded condition. Elongation and time-to-fracture were decreased with shifting cathodic polarization potential to the low potential direction. On analysis of SEM fractography, the quasi-cleavage (Q.C) fracture mode was also observed with an increase of susceptibility to hydrogen embrittlement. At the applied cathodic potential between −770 mV and −875 mV (SCE; saturated calomel electrode), the fracture morphology was of the dimple pattern with ductile fracture, while it changed to the transgranular pattern at under −900 mV (SCE). Eventually it is suggested that an optimum cathodic protection potential range was from −770 mV to −875 mV (SCE) without regard to PWHT condition.

Effect of temperature on the charpy impact and CTOD values of type 304 stainless steel pipeline for LNG transmission

Abstract: Stainless steel pipe of type 304 the with a wall thickness of 26.9 mm and the outer diameter 406.4 mm is welded by manual arc welding process. Mechanical properties and fracture toughness of type 304 stainless steel are investigated in the temperature ranging from room temperature to — 162°C. The results obtained are summarized as follows. The tensile strength noticeably increases as the temperature becomes lower while the yield strength is relatively insensitive to temperature. The Charpy impact energy and CTOD values become higher in the case that crack propagation direction is aligned to the transverse axis upon the rolling direction than longitudinal direction. The drop of fracture toughness is associated with the noticeable diminution of plastic component as temperature seduces from room temperature to — 162°C.

Effect of material hardness on erosive wear behavior of some weld-deposited alloys

Abstract: This paper reports on solid particle erosive behavior of some weld-deposited alloys. Six different weld-deposited alloys were selected for the present investigation. These alloys were deposited on mild steel plate by a manual metal arc welding technique. The surface hardness of the selected alloys was in the range 300–800 Hv. The solid particle erosion experiments were performed to investigate the effect of material hardness on E–α characteristics of these alloys. Erosion tests were conducted with 100–150 μm silica sand and 125–150 μm alumina particles at a velocity of 50 m sec− 1 and at impingement angles in the range 15–90°. The maximum in erosion rate occurred at impingement angles of 30–90° depending upon the alloy. The peak in erosion rate shifted to higher impingement angles with increasing material hardness. The eroded surfaces were observed under scanning electron microscope to study the operating erosion mechanisms. At lower impingement angles, the erosion mechanisms involved were plowing and duc...

Investigation of the effect of a surface active flux on the microstructure and properties of gas tungsten arc welds made on a superaustenitic stainless steel

Abstract: The use ofa surface active flux during GTA welding has been shown to greatly increase penetration, thereby making the lower fume generating welding process more feasible for welding thicker materials. This lower fume generation is important in welding ofstainless steels because ofthe generation offumes containing the carcinogen hexavalent chromium. This research considers the effect ofa particular surface active flux on the microstructure and properties ofa superaustenitic stainless steel. The flux was composed of several oxides and applied to the metal prior to GTA welding. Conventional welds (made without flux) were also performed for comparison. The substantial effect ofthe flux on the shape and weld dimensions was confrrmed. This difference in shape resulted in differences in growth direction ofthe substructure. Copper sulfide particles were found to be heavily dispersed throughout the weld metal of the welds made with flux. It was discovered that the flux powder contained a significant amount ofsulfur, as well as oxides. This relatively high sulfur content was determined to be the reason for the copper sulfide particles. Hot cracking susceptibility was found to increase slightly due to the flux, especially at lower strains. Welds made with flux had to be polished to observe all the cracks on the surface due to the surface topography in the as-welded condition. Unexpectedly, pitting corrosion resistance was seen to increase slightly due to the flux. The surface topography ofthe welds made with flux, however, resulted in an increase in the number ofpits on the as-welded surface at the pitting initiation temperature due to the large number of initiation sites. The effect ofthe flux on the hot cracking susceptibility and pitting corrosion resistance could not be explained by microstructural differences between the welds. 1

シールドガス組成制御によるgma溶接プロセスの開発 : 超狭開先gma溶接プロセスの開発(第3報)

Abstract: In previous reports, an ultra-narrow gap CO2 gas metal arc welding process has been developed in order to produce excellent welded joints. In the ultra-narrow gap (less than 5 mm gap) welding process, as the welding wire melting behavior was controlled by low frequency pulsated arc current waveform, the arc generating at the wire tip was widely oscillated in the direction of thickness and a good weld bead with large throat thickness was formed. In such a higher efficient welding process, the strong arc force of CO2 arc is essential to obtain sound beads without lack of fusion at a groove bottom, however, the oxygen content of weld metal in CO2 arc welding has to be reduced to obtain high-toughness at weld metal. In this report, a newly welding process is proposed in which an arc is widely oscillated along groove walls and oxygen content of welded metal is reduced as periodically controlling composition of CO2 gas in shielding gas. As an arc length between the wire tip and groove wall is held constant in ultra-narrow I type gap joint, arc current at stable operating point of CO2 arc essentially decreases less than that at stable operating point of Ar arc in constant potential characteristics of power source. It was confirmed from the numerical simulations on both wire melting and electric welding circuit that pulsated current waveform was produced as periodically alternating CO2 arc with MIG arc. Using the developed welding torch locally introducing CO2 gas into Ar+2%O2 shielding gas, the welding was carried out under V-type groove with less than 30 degree in the bevel angle. It was shown that the arc was widely oscillated along V groove walls and sound bead was formed in one side welding. Furthermore, it was confirmed that the oxygen content of weld metal in the proposed process was reduced to the level of that in MIG arc welding, and absorbed energy of weld metal was the same level as the MIG arc welding.

XRD and TEM analysis of microstructure in the welding zone of 9Cr-1Mo-V-Nb heat-resisting steel

Abstract: Under the condition of tungsten inert gas shielded welding (TIG) + shielded metal arc welding (SMAW) technology, the microstructure in the welding zone of 9Cr-1Mo-V-Nb (P91) heat-resisting steel is studied by means of X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The test results indicate that when the weld heat input (E) of TIG is 8.5 ∼ 11.7 kJ/cm and the weld heat input of SMAW is 13.3 ∼ 210 kJ/cm, the microstructure in the weld metal is composed of austenite and a little amount of δ ferrite. The substructure of austenite is crypto-crystal martensite, which included angle. There are some spot precipitates in the martensite base. TEM analysis indicates that the fine structure in the heat-affected zone is lath martensite. There are some carbides (lattice constant, 1.064 nm) at the boundary of grain as well as inside the grain, most of which are Cr23C6 and a little amount of (Fe, Me)23C6.

Investigation of effect of boronising on welding zone

Abstract: In the present study, AISI 1040 and AISI 8620 steels are joined by arc welding and gas metal arc welding, and then subjected to a solid boronising process at 850, 900, 950, and 1000°C using EKabor HM (tradename) for 4 h. The microhardness and thickness of the boride layers produced on the surfaces of the air cooled specimens are measured and the microstructures are photographed using optical microscopy. The effect of boronising in and around the welding zone is investigated.

Lump-Pass Welding Simulation Technology Development for Shipbuilding Applications

Abstract: A lump-pass welding simulation technology was developed for shipbuilding and ship repair applications based on Battelle and Caterpillar developed VFT™ weld modeling software. To develop this technology, we reanalyzed a 3D multi-pass model that was originally used in the NIST project where VFT™ was developed. In this model, good agreement was achieved between the moving arc simulation and the experimental data. By reanalyzing this model using lump-pass technology, the heat input calculation method was developed. To further establish the efficiency of the lump-pass technology, we performed analyses on a structural configuration common to the maritime industry. The structure consisted of many longitudinal and transverse stiffeners that were welded vertically at stiffener interface locations and welded horizontally to a one-inch thick base plate. These welds included numerous multi-pass tee and butt joints. For verifying the accuracy of the lump-pass weld simulation technology, an actual structural mock-up was built with FCAW and SMAW processes. Additionally, we performed a detailed moving arc solution to compare with the lump-pass solution of the same weld sequence to further evaluate the efficacy of the lump-pass approach. The simulation results show that the lump-pass approach is suitable for predicting weld-induced distortion in ship fabrication.Copyright © 2002 by ASME

Weldability characteristics of torr and corrosion-resistant TMT bars using SMAW process

Abstract: Torr steel rebars, also known as cold twisted deformed (CTD) rebars, are used extensively for the construction of reinforced cement concrete (RCC) structures. These steels, which are characterized by a high carbon content and are subjected to a cold twisting operation to attain the desired strength level and bond strength, suffer from low ductility and poor bendability properties. Furthermore, these rebars are not suitable for coastal, humid, and industrial conditions where corrosion rates are very high. To combat these problems, recent efforts at the Steel Authority of India Limited (SAIL) have led to the successful development of corrosion-resistant thermomechanically treated (TMT) rebars with a minimum yield strength of 500 MPa. These rebars are characterized by a low carbon content, exhibit excellent strength-ductility-corrosion properties, and are rapidly replacing traditional torr rebars in corrosion-prone areas for a wide range of applications, namely, concrete reinforcement structures, bridges, flyovers on dams, etc. A comprehensive evaluation of the weldability properties of corrosion-resistant Cu-TMT rebars was carried out, and they were compared with those made of torr steel in order to assess their suitability for various structural applications. Implant and restraint cracking (RC) tests were carried out to assess the cold-cracking resistance of the weld joint under different welding conditions. The static fatigue limit (SFL) values were found to be similar, namely, 640 MPa (torr steel) and 625 MPa (Cu-TMT steel) under condition of no preheating and no rebaking using a heat input of 7.5 KJ/cm, indicating adequate cold-cracking resistance for both the steels. Restraint cracking tests yielded critical restraint intensities (Kcr) in excess of 16,800 MPa for both of the steels. Based on the weldability tests, the optimized conditions for welding were formulated and extensive tests were carried out on the welded joints. Both of the steels exhibited adequate strength levels (tensile strength (TS): torr rebars, 524 Mpa; Cu-TMT rebars, 630 MPa) and adequate low-temperature impact toughness properties, ensuring a high integrity of the fabricated products.

Welding of heat-resistant 20 % Cr - 5 % Al steels

Abstract: The paper treats welding of heat-resistant ferritic stainless steels alloyed with approximately 20% Cr and 5% Al. The major part of the paper is dedicated to welding of 20%Cr-5%Al steel with 3 mm in thickness. Welding was carried out with five different welding processes, i. e., manual metal-arc, MIG, TIG, plasma arc, and laser beam welding processes, using a filler material and using no filler material, respectively. The welded joints obtained were subjected to mechanical tests and the analysis of microstructure in the weld metal and the transition zone. The investigations conducted showed that heat-resistant ferritic stainless 20% Cr-5% Al steel can be welded with fusion welding processes using a Ni-based filler material.

Welding with two wire electrodes: Status and prospects of the optimisation of gas-shielded metal-arc welding

Abstract: A variant of high-productivity metal-active gas welding is presented below. It works with two wire electrodes which are electrically insulated from each other and is designated as "Time-Twin" at Fronius. Memories of the older T.I.M.E. process relate to the increases in productivity possible with it, achieved with standard shielding gases. The information provided ranges from the objectives, the status, the application, the process itself, the appliance-technology components and the options right up to the perspectives.

Ceramic weld insulator and metal weld gear combination for an improved micro weld head component of an orbital tube welding apparatus

Abstract: The invention is of an improvement to orbital welding heads and welding systems for welding pipe and tubing butt joints, consisting of a novel combination of materials, including a ceramic weld insulator and a metal weld gear. Such a combination, which has a greater dielectric strength than a plastic housing design, results in a more concentric tungsten travel path, increases the duty cycles of the weld head, minimizes erratic and wandering arcing, creates an electrical insulation yielding minimal expansion, allows for increased clamping surface for improved tube alignment, and provides a compact and very robust weld head.

Method used in gas-shielded metal-arc welding

Abstract: The invention relates to a method used in gas-shielded metal arc welding during the striking phase of welding. The aim of the invention is to provide a method which allows for an as low an energy input as possible in the short circuit phase. To this end, the method is characterized in that when the short circuit phase begins a control is activated and remains active for the duration of the short circuit. When a characteristic threshold value S1 is fallen short of, the control increases the energy input (phase A), and stops the energy input when a threshold value S2 is reached and then reduces the energy input (phase B).