Showing papers on "Shielded metal arc welding published in 1993"

Investigation of the effect of welding parameters on weld quality of plasma arc keyhole welding of structural steels

Abstract: In the present investigation, the individual and interactive effects of the main welding parameters on weld quality of plasma arc keyhole welding of conventional structural steel, high strength microalloyed steel and strong formable microalloyed steel have been examined using welding of butt joints with a square groove in various welding positions, and welding of joint roots with a single-V-groove and the root face in the flat position. The most important welding parameters are welding current, welding speed and welding gases, especially plasma gas flow rate. Welding parameter combinations producing the best quality welds are presented. It is shown that it is possible to achieve defect-free high-quality welds with good strength and toughness properties, but the allowable range of variation of welding parameters, especially for the highest weld quality, is narrow. An argonhydrogen mixture for the plasma gas together with argon as shielding and backing gases give the best results with respect to weld quality.

Flux cored arc welding electrode

Abstract: A flux cored arc welding electrode of the type used with external shielding gas wherein the electrode comprises an outer ferrous sheath and a particulate fill material comprising an acidic flux system and alloying agents with the fill material including an arc stabilizer, titanium dioxide, calcium fluoride, an alloying system of 0-4.0 percent by weight of electrode selected from the class consisting of aluminum, silicon, titanium, carbon and manganese. Iron powder controls the percentage of the fill of the electrode and 0.2-1.0 percent by weight of electrode is polytetrafluoroethylene powder.

The effects of process variables on the weld deposit area in submerged arc welds

Abstract: The results of bead-on-plate submerged arc welding experiments are presented to determine the effects of process variables on the weld deposit area at a constant heat input of 2kj/mm. It is found that the deposit area is a function of the welding current, welding voltage, welding speed, electrode polarity, electrode diameter and electrode extension. In general, welds made using direct current electrode negative (DCEN) polarity, a small-diameter electrode, long electrode extension, high welding current, low welding voltage and high welding speed have large deposit areas. The weld deposit area is, however, not affected significantly by the power source or the flux type used in this investigation.

Shielding Gases for Arc Welding

Abstract: A shielding gas for flux cored arc welding. The specific gas combination is intended to promote significantly lower fume emission levels while providing equivalent or better welding performance.

Corrosion resistant welding of stainless steel

Abstract: A process for welding stainless steel tubing in the presence of an inert gas comprising a silicon base gas, in particular silane SiH₄. During the welding operation, a suitable quantity of silicon is deposited by chemical vapor deposition at the weld joint to significantly improve the corrosion resistance of the weld.

Study of gas tungsten arc welding in space (1st report)

Abstract: In the present paper, a new type GTA welding system using a hollow tungsten electorode is proposed to ignite and sustain a welding arc in a vacuum like the open space. In the developed system, Ar gas for discharge is supplied to arc space through the hollow tungsten electrode.The results of the present work are summarized as follows, (1) Even in a low pressure condition, a small quantity of Ar gas flow can ignite and sustain an arc discharge and the arc can melt the base metal.(2) In a low pressure condition, a stationary arc follows a transient arc. The period of the transient arc discharge increases with the decrease of Ar gas flow rate.(3) With the decrease of Ar gas flow rate, the arc voltage increases and the penetration of base metal (stainless steel) increases in size.

Chemical composition variations in shielded metal arc welds

Abstract: The use of shielded metal arc (SMA) welding can result in chemical composition variations along the weld length. Manganese and silicon, commonly found in low-carbon steel welds, change in composition with weld position. This research was performed to better characterize the composition variations observed in structural steel welds and to understand the controlling factors that determine the extent of these composition changes. Single bead-on-plate and multipass welds were performed and analyzed. Manganese, silicon, and oxygen contents showed significant variation along the weld length. To determine the cause of such composition variations, additional experiments were carried out with the welding arc established between the electrode and a water-cooled copper pipe. The individual metal droplets were collected in water and processed using standard particulate materials processing techniques to remove the slag covering. The droplet size distribution was determined and related to the composition variation and position along the weld length.

Inner surface welding method for clad steel tube

Abstract: PURPOSE: To reduce a rate of dilution of a low alloy steel and weld metal by arranging a groove of the specific depth and angle on the inner surface side of X shape groove and welding with suppressing the welding quantity of low alloy part to the specific height from the boundary with high alloy steel. CONSTITUTION: X shape groove is machined at a seam part of clad steel tube consisting of an outer surface of low alloy steel 1 and an inner surface of high alloy 2 of stainless steel, high Ni alloy, etc. The inner surface is subjected to one run welding of three electrodes, subsequently the outer surface side to four electrode submerged welding so as to weld clad steel tube. At this time, the groove of 8-10mm depth t 1 , 65-75° angle θ is arranged on the inner surface side of X shape groove. A low alloy part 1 of inner surface side is welded so that the welding metal quantity by low alloy welding wire is suppressed to the height t 2 1-2mm lower than the boundary with the high alloy steel 2. The inner surface side is subjected to MIG welding with a welding speed of 35-45cm/min. By this method, at welding the initial layer of low alloy steel of inner surface side, melting of the groove part of high alloy steel is prevented. COPYRIGHT: (C)1994,JPO

Rail repairing welding method

Abstract: PURPOSE:To provide the repair welding method of defects of a rail head for a railroad on which a metal having the hardness and the wear resistance of about the same grade as the rail base material is built up. CONSTITUTION:In the case many kinds of defects on the rail head are removed and the rail head is repaired with build up welding, a filler material for the shielded metal arc welding and a filler material for gas shield arc welding incorporating 0.5-1.5% C against the total weight of filler material are used, the portion from which many kinds of defects of rail head are removed is repaired with build up welding. The generation of high temperature crack in the vicinity of the molten boundary line of the rail base material which can be not avoided with the conventional cladding by welding at the welding part can be perfectly prevented, and the metallic padding excellent in pearlite composition and the wear resistance similar to the base material of rail can be obtained.

Cr-Mo steel pipe and welding method thereof

Abstract: A Cr-Mo steel pipe having a wall thickness of 5 to 25 mm consisting essentially of 0.03 to 0.10 wt. % C, 0.5 to 1.0 wt. % Si, 0.3 to 0.6 wt. % Mn, 0.02 wt. % or less P, 0.007 wt. % or less S, 1.0 to 1.5 wt. % Cr, 0.45 to 0.65 wt. % Mo, 0.002 to 0.1 wt. % Al, 0.002 to 0.01 wt. % N, and the balance being Fe and unavoidable impurities. In the method of welding the Cr-Mo steel pipe, the Cr-Mo steel pipe is welded by shielded metal arc welding without a preheat treatment and/or a post weld heat treatment.

Shielding-gas arc welding method and appertaining shielding gas

Abstract: The invention relates to shielding-gas arc welding methods making use of the melting (burning-off) electrode and also the non-melting electrode, which involve, during welding operations, continuously supplying the weld spot (welding point) adjacent to the electrode with a stream of shielding gas, the shielding gas being composed for a major part of argon and/or helium. Such welding methods are known in many versions, and quite generally they enable the most diverse materials (ferrous and non-ferrous materials) to be welded together satisfactorily. In a number of practical cases, e.g. with respect to aluminium welding, however, it is possible for welding to proceed in a non-optimal manner, not uncommonly particularly with respect to the important arc stability. This disadvantageous situation is improved markedly, according to the present invention, by the shielding gas being additionally mixed, in a proportion range of no more than from 20 to 5000 vpm, preferably from 50 to 3000 vpm (from 0.005 to 0.30 % by volume) with additions of heavy noble gases (Kr, Xe) and/or stable, simple biatomic or triatomic non-noble gases (H2,O2, CO2, N2O, NO2 and the like) and/or gaseous, stable organic compounds, preferably C1 to C4 hydrocarbons (CH4, C2H4), having ionisation energies between 8 and 17 eV, preferably 8 and 14.3 eV.

Friction welding of titanium and SUS304 stainless steel.

Abstract: The optimum welding condition for brake type friction welding of titanium and SUS304 stainless steel was investigated using a response surface method. The optimum friction pressure, forging pressure, friction time and rotating speed of welding were determined as 91MPa, 195MPa, 0.8s and 1842rpm, respectively. The joint welded in CO2 gas had higher tensile strength than that welded in air. The transformation of α-Ti into β-Ti and γ-Fe(Cr) into α-Fe(Cr), and the formation of intermetallic compound (Fe(Ni)•Ti) were induced by the interdiffusion along the welding interface. The joint strength depends on the width of β-Ti and Fe(Ni)•Ti layer.

Exothermically assisted shielded metal arc welding

Abstract: Heat input, which is most often directly related to electrical energy input, controls weld bead morphology and the evolution of microstructure. Exothermic reactions have been found to increase the heat input available during shielded metal arc (SMA) welding. The work presented in this paper was performed to determine how much heat can be attained from exothermic reactions and determine the influence of this additional heat on weld deposition. Consumable SMA welding electrodes were produced with reagents added to the flux coating. The flux additions to promote exothermic reactions consisted of magnesium plus hermatite (Fe{sub 2}O{sub 3}), aluminum plus hermatite, and a 50-50 wt% aluminum-magnesium alloy plus hermatite. With calorimetry, increasing concentrations of exothermic promoting additions were found to produce an increase in the effective heat input. Electrodes with sufficient exothermic additions were found to product 25{emdash}30% of the heat necessary for welding. Finally, the efficiency of the shielded metal arc welding process was determined with and without the reagent. Analysis of energy generation and utilization was performed to evaluate the use of pyrochemical flux reactions to produce exothermically assisted consumables. A model ha been developed to assist in the formulation of exothermically assisted SMA electrodes.

Method and apparatus for thermal insulation of wet shielded metal arc welds

Abstract: A method for thermal insulation of a wet shielded metal arc welds including insulating a weld joint between workpieces to be welded with a synthetic insulator is provided. An apparatus for thermally insulating a wet shielded metal arc weld including a synthetic insulator is also provided.

Alloys for cryogenic service

Abstract: An alloy comprising nickel, chromium, molybdenum, manganese, nitrogen and iron in amounts such that a weld metal formed therefrom is austenitic, wherein nitrogen is present in a concentration of from about 01 to about 02% of the alloy in weight percent The weld metals prepared from the alloys of the present invention possess superior properties as compared to other stainless steels These properties include inter alia a superior tearing modulus, fracture toughness, and yield strength, even at cryogenic temperatures The present invention further provides a method for welding a metal part which is intended for exposure to cryogenic temperatures comprising welding the metal part using a welding electrode comprising nickel, chromium, molybdenum, manganese, nitrogen and iron in amounts such that a weld metal formed therefrom is austenitic, wherein nitrogen is present in the electrode in a concentration of from about 01 to about 02% of the electrode in weight percent Preferably, the welding comprises gas metal arc welding, wherein shielding gas used during welding contains no more than about 2% oxygen by volume

Effect of magnetic steering of the arc on clad quality in submerged arc strip cladding

Abstract: Submerged arc strip cladding is often used when thickness of clad material is required. The productivity of this process has been improved by the use of higher welding currents and wider strips. The associated problems were arc blow, increased penetration and poor bead characteristics. Dilution is the parameter that controls almost all qualities of cladding. Magnetic steering reduces penetration, and hence, dilution and arc blow control. Stainless steel cladding on mild steel is often used to impart corrosion resistance. In such situations, the clad quality is specified by corrosion resistance, ferrite content and good fusion between clad metal and base metal. This paper discusses results of an investigation on the effect of an oscillating magnetic field used to steer the arc in submerged arc strip cladding using 60 X 0.5-mm 309L stainless steel strips, with varying magnetizing flux intensity and dwell time. The resulting test pieces were evaluated for parameters that imparted the best clad quality.

Gas Tungsten Arc Welding Process for Surfacing Aluminum Alloys with Al-Cu Cored Wire : Surfacing on Aluminum Alloy (Report 2)

Abstract: The authors have investigated on surfacing technique on aluminum alloys by using gas tungsten arc welding (GTAW) process. The used filler metals were composite cored wire of seamless tube type and 1.2 mm in diameter. They were of Al-Cu composition with varied copper contents of 60, 70 and 80%. Each wire consisted of a copper tube sheath and an aluminum solid wire enclosed.The authors investigated the effects of arc current and weld cooling rate on microstructure, hardness distribution and porosity formation. They studied through chemical analysis the oxide film that covered the surfacing weld metal. They also analyzed the gases evolved in vacuum from machine cut porosities.The hardness in cross section of Al-70%Cu surfacing weld metal decreased from 270 HV to 170 HV with an increase of surfacing current in the case of helium shielding. Helium shielding drastically reduced the porosities that existed in the case of argon shielding. The remaining porosities became smaller than 0.2 mm in diameter. Moreover, the dual shielding by argon-helium gases was found to eliminate perfectly the porosity formation in the surfacing weld metal. Chromatography analysis revealed that the gas in porosities was dominantly hydrogen. The thickness of oxide film on the argon shielded weld metal surface was found to be remarkably greater than that of helium shielded weld metal, and thereby it might have caused more porosities in the case of argon shielding.

Method for welding high purity ferritic stainless steel thick plate

Abstract: PURPOSE:To perform welding without causing the embrittlement of a heat- affected zone with high efficiency by carrying out the weld pass for melting the base metal surface of the heat-affected zone by a TIG arc after piling up to a final layer CONSTITUTION:By weight, 16-21% Cr and 075-35% Mo are incorporated in the high purity ferritic stainless steel thick plate of base metal 1 In welding these, weld metals 2 are piled up to the final layer by multilayer sequence shielded metal arc welding Afterward, the weld pass for melting the base metal 1 surface of the heat-affected zone 3 by the TIG arc is carried out to form beads 4 and 5 by the TIG arc At least the weld pass of final layer between a first layer and the final layer is carried out by TIG welding, the weld pass of the other layer is carried out by shielding metal arc welding Consequently, the welding cost and the quality can be compatible with each other

Weldability of iron aluminides

Abstract: Corrosion-resistant, weldable iron-aluminide alloys with improved high-temperature strength are being developed for structural applications, and for weld overlay cladding of conventional structural steels and alloys. The weld hot cracking of iron-aluminide alloys is highly variable to over a wide range of aluminum content. In general, the higher aluminum content alloys are somewhat more resistant to hot cracking, and by careful choice of alloying additions (and balancing of multiple additions), cracking resistance equivalent to commercial austenitic stainless steels can be achieved. Improved weldability, however, often comes at the expense of high-temperature strength. Delayed cold cracking, presumed to be hydrogen-related, is also an important consideration in welding these alloys, either as monolithic materials, or as weld overlay cladding on stainless or low alloy steel substrates. The authors are employing various combinations of preheat and postweld stress relief heat treatments to assess the severity of this problem, and have determined that heat treatment in excess of 400 C following welding will be required to avoid delayed cracking. Due to the difficulties encountered in fabricating some of the alloy compositions into wire or rod, they are also pursuing the formulation of coated electrodes for use in shielded metal-arc (SMA) welding. Initial attempts have shownmore » very high aluminum losses in the welding arc, and additional batches of electrodes are being formulated and produced.« less

Effects of material properties on transient response in TIG welding

Abstract: Effects of thermal and physical properties of materials on the transient response of temperature to a step change in welding speed were investigated using TIG arc welding and FEM calculation of three-dimensional heat coduction. The materials used in this study were stainless steel, mild steel, aluminum alloy, brass and copper 9 mm in thickness.In TIG arc welding of low heat-conductive materials, large difference in maximum temperature appears in the period between former quasi-state and latter one. On the other hand, high heat-conductive materials indicate large difference in temperature gradient, but a little change in maximum temperature. In addition, the high heat-conductive materials require longer distance or time to be in latter quasi-state. The transient response from former to later quasi-state is characterized by the fraction of maximum temperature and temperature gradient to those at both quasi-states. These experimental results are confirmed by FEM calculations based on three-dimensional heat conduction. It is also clarified that although the maximum temperature mainly depend upon the thermal conductivity and thermal diffusivity, the transient response is dominated only on the thermal diffusivity. Therefore, the high thermal diffusive materials show slower response to a step change in welding speed.

Shielded metal arc welding method for pipe

Abstract: PURPOSE:To improve selective corrosion resistance, toughness and crack resistance of weld metal in circumferential welding of the pipe by regulating the difference between the weld metal and base metal, and Mo and welding conditions. CONSTITUTION:In circumferencial welding of the pipe, the pipe base metal, a high cellulose type electrode and the welding conditions are regulated. The inequality DELTAMo >=0.03% determined by the difference between the weld metal and the base metal, and Mo and the inequality PCM <=0.30% calculated from chemical composition of the weld metal are satisfied. Further, the welding conditions regulate the electrode diameter, a kind of a current, a welding current, the welding speed and the welding position.

Production of wire for arc welding

Abstract: PURPOSE: To provide the wire for arc welding which is smoothly drawn with high efficiency without generating flaws on the surface of the wire for arc welding and is good in wire feedability even in the case a long-sized conduit cable is used and welding is executed under welding conditions of a high current. CONSTITUTION: An ester consisting of a fatty acid and alcohol or animal or vegetable oil is applied on the wire surface and, thereafter, the wire is drawn by a dry process using a lubricant of an inorg. system or anhydrous system in the process for production of the wire for arc welding. Further, the amt. of the lubricant stuck in the dry drawing is adjusted by the water-soluble lubricant. This method does not require a baking treatment. COPYRIGHT: (C)1995,JPO

Investigation into the fatigue strength of fillet welded assemblies of E-36-4 steel as a function of the penetration of the weld subjected to tensile and bending loads

Abstract: This study is aimed at evaluating the effect of incomplete penetration on the fatigue behavior of fillet welded assemblies subjected to tension and bending Its purpose is to evaluate more precisely the conditions of slow extension of microcracks during the initiation stage The preferred sites for crack initiation at the weld root or the weld toe were determined by using the finite element method The experimental program, including 120 fatigue tests, was conducted on 10 mm and 30 mm thick E-36-4 steel plates welded with gas metal arc welding (GMAW) and shielded metal arc welding (SMAW) processes The results evidenced a propagation phase of short cracks, which may represent 30 to 90% of the fatigue life, and the existence of a critical size of incomplete joint penetration had no significant effect on the fatigue life of fillet welded assemblies subjected to tension and bending The numerical calculations, made with the finite element method, have permitted the modeling of the crack propagation paths as a function of the size of incomplete penetration and the determination of the relations Kl = f(a/t) for each zone of failure of the fillet weld

Arc welding burner - having protruding filler wire guide tube coated with insulation material

Abstract: Arc welding burner has a wire guiding tube (10) for the filter wire (26) that is provided with an extension tube (14) having an insulation layer (20) over the part protruding from the protection cap (16). The free length of the tube (14) is 50-300, pref. 100-250 mm. The tube may be made at least partly out of a non-conducting material such as ceramic or coated with a non-conductive material such as metal oxide. The coating may be made by chemical vapour deposition or thermal spraying. USE/ADVANTAGE - For welding together rails or build-up welding a seal in a ball valve, esp. in accessible positions. Ensures welding without fear of electrical contact between burner and parts to be welded.

Chamber free plasma welding root side purging method and apparatus

Abstract: A method and apparati are presented for non-chamber root side purging in fusion welding of oxygen reactive metals which require that the molten weld zone and local solid areas of the weld seam remaining at high temperatures be shielded from normal atmosphere to prevent degradation of the welded area. The apparatus provides an inert atmosphere to the root side of a weld joint through a porous medium whereby the jet-like thrust of the plasma arc actually draws the continuously supplied inert atmosphere into the path of the molten or high temperature solid weld zone. The porous medium is configured so it can be placed at the borders of the weld seam and substantially parallel to the seam without restricting the view of the root side of the seam. The inert gas is dispersed evenly through the porous media and across the weld seam, at the point of arc penetration and in front of and behind the arc. The apparatus can be constructed so as to limit the amount of inert gas flow and can be mobile and travel synchronously with the welding arc.