Showing papers on "Shielded metal arc welding published in 1983"

Fibrogenic potential of welding fumes.

Abstract: A search of 3600 indexed pathology cases has disclosed pulmonary fibrosis in 29 welders. Scanning electron microscopy of biopsy material revealed macrophages laden with inorganic particulates which have characteristics compatible with welding aerosols. In order to establish a possible relationship between fibrotic reaction and welding-fume exposure, the fibrogenic potential fo some 11 different welding fumes and metallic aerosols, considered to be reference standard surrogates for the commonly used welding technologies and applications responsible for 70% of welders exposure, were screened using the Rat Peritoneal Macrophage in vitro bioassay. Only one class of fumes, that from the manual metal arc welding of stainless steel, showed distinct fibrogenic potential. This fume is, however, not common to more than four or five of the heretofore 90 cases of pulmonary fibrosis reported among welders. Thus, although insoluble Cr(VI) is probably the active fibrogen in stainless steel fumes, an etiological factor common to all fibrogenic welding exposures must be sought. It is tentatively proposed to be NO2, a potential experimental in vivo fibrogen copiously produced by certain welding processes and ubiquitous at low concentrations in the welding environment.

Urine chromium as an estimator of air exposure to stainless steel welding fumes

Abstract: Welding stainless steel with covered electrodes, also called manual metal arc welding, generates hexavalent airborne chromium. Chromium concentrations in air and post-shift urine samples, collected the same arbitrarily chosen working day, showed a linear relationship. Since post-shift urine samples reflect chromium concentrations of both current and previous stainless steel welding fume exposure, individual urine measurements are suggested as approximate although not exact estimators of current exposure. This study evaluates the practical importance of such measurements by means of confidence limits and tests of validity.

The Metallurgy of Underwater Welding

Abstract: Wet and dry welding processes are surveyed in terms of compositional changes, cooling programme and weld joint performance. Introduction of hydrogen and oxygen in wet welding may lead to porosity and slag inclusions. High cooling rates, mainly controlled by convection, may cause cracking. Significant improvements can be achieved by local protection of the site of welding. Effects of pressure predominates in dry welding, leading to increased absorption of hydrogen, oxygen and carbon and to reduced contents of silicon and manganese in MMA welding. The increased impurity level limits the application of hyperbaric MMA welding to about 300m depth. Inert-gas protected processes are shown to be much less affected by pressure. Examples of performance and methods of predicting the chemistry and properties are given.

Development of mma electrodes for offshore fabrication

Abstract: The development of nickel-containing electrodes for manual metal arc welding to meet high-toughness requirements in offshore structures is described. Results of related COD and Charpy tests are included, and comparisons are made between Mn-Ni systems and previously-investigated C-Mn systems.

Resistance welding of zinc-coated steel

Abstract: A method for resistance welding zinc-coated steel members is described wherein at least one member comprises a copper layer intermediate the steel and the zinc coating. The copper layer melts during welding and seals fissures within the fused steel to produce a hermetic weld. The copper layer also protects exterior surfaces where the zinc coating is disrupted by the welding operation.

Prediction of weld-metal composition during flux-shielded welding

Abstract: It is well known that the slag and metal do not reach equilibrium during fluxshielded welding, due to the short reaction times and large thermal gradients inherent in the process. Nonetheless, many investigators have attempted to define the effective equilibrium by empirical analysis of experimental data. The results of these analyses have generally been contradictory and, in most cases, have lacked a firm scientific basis.

Stainless steel manual metal arc welding fumes in rats.

Abstract: Forty two male Wistar rats were exposed to manual metal arc (MMA) stainless steel (SS) welding fumes generated by an automatic welding device for "nose-only" exposure. The exposure simulated an actual MMA/SS welding environment as closely as possible. For the retention study, the duration of exposure was one hour per workday for one, two, three, of four weeks and for the clearance study four weeks. The retention and clearance of the chromium, nickel, and iron found in MMA/SS welding fumes in the rats' lungs were studied as was the distribution of the metals to other organs. Instrumental neutron activation analysis (INAA) was used for the multi-element chemical activation analyses. The concentrations of chromium and nickel in the blood and the urine were determined by atomic absorption method (AAS). The retention of exogenous iron was determined by a magnetic measuring method. The results indicated that the lungs were the target organs of soluble hexavalent chromates. The half times of lung clearance for Cr, Ni, and Fe were 40 +/- 4 d, 20 +/- d, and 50 +/- 10 d. When the lung clearance curves are compared, the half times of Cr and Fe lung clearance are similar but nickel disappears faster. The distribution and clearance patterns of chromium to other organs differ from those obtained after single intravenous or intratracheal injections of alkaline chromates.

Method for welding very low carbon steel

Abstract: A method for arc welding a very low carbon steel containing 0005-006% C characterized by employing a welding material with nickel together with high carbon so as to form weld metal containing nickel Solidification cracking on the thus welded metal can be prevented

Process Variables and Properties of Underwater Wet Shielded Metal Arc Laboratory Welds

Abstract: Hydrogen pick up and HAZ hardness increase with coating thickness of rutile electrodes in underwater wet SMA welding but decrease with heat input. Multilayer welding of 15 mm thick, 0,14 % C, 0,90 % Mn grade D-steel, provides weld metal CVN-toughness of 35–40 J at 0 °C, applying a total of 14–15 low heat input stringer beads.

Shielding gas for electric arc welding

Abstract: A shielding gas for use in electric arc welding is disclosed. The gas comprises a mixture of helium, argon, 1.75% to 2.25% carbon dioxide and 0.25% to 1.0% oxygen (by volume). Use of the gas enables slag-free welds which accept readily paint applied by an electrostatic deposition process.

Technologies and Practices of Underwater Welding

Abstract: This paper describes the present state-of-the-art of technologies and practices of underwater welding. The first part of this paper presents a review of various underwater welding technologies. The techniques currently in use may be classified depending upon the environment in which the welding takes place—dry chamber technique, portable dry spot technique, and wet technique. Shielded metal arc (SMA), gas tungsten arc (GTA), and gas metal arc (GMA) processes are the most widely used in underwater application. Stud welding has been used to a limited degree. Studies have been made of underwater applications of various processes including submerged arc, plasma arc, etc. Although all practical applications and most of the studies so far have been on manual welding, limited efforts have been made to automate welding operations by use of remotely controlled manipulators. The later parts of this paper discuss the practical aspects of two techniques which are widely used—hyperbaric dry chamber habitat welding and wet shielded metal arc welding. The second part of this paper, on hyperbaric dry welding, is based on actual experiences obtained at the Taylor Diving and Salvage Co. The third part, on wet welding process, is based on actual experiences obtained at Sea-Con Services, Inc.

Joining method of aluminum-titanium by arc welding

Abstract: PURPOSE:To obtain a defectless joint part by combining specifically a welding power source, heat source, shielding gas and welding rod or electrode wire so that only the Al base metal side and welding rod are melted and that the Ti base metal side is hardly melted. CONSTITUTION:An arc 5 is generated between an electrode 6 of a torch 7 and base metals 1, 2 for the butt parts of the base metal 1 consisting of an Al alloy and the base metal 2 consisting of Ti. The TIG arc by a DC power source of a straight polarity or AC power source AC as a welding power source P or the MIG arc by a DC power source of a reversel polarity is used as a heat source for the arc 5. Al or the alloy thereof, phosphor copper solder or silver alloy contg. >=20% (by weight) Al is used as the welding rod or electrode wire. Gaseous Ar 8 is used as the shielding gas. The weld metal 3 formed in the joint parts between the base metals 1 and 2 has the compsn. in which the Al base metal 1 and the welding rod 4 are mixed.

New approach would help control weld fumes at source. part three: mma fumes

Abstract: Parts one and two of this series dealt with the biochemical effects of welding fume and howfume formation could be minimised at source in Metal-Inert-Gas welding. This article considers how to minimise fume from manual metal arc welding, where an important factor is found to be the flux coating of the electrode. The results of controlled MMA welding experiments are given and the effect of welding parameters on fume formation and toxicity is discussed. This study suggests a number of ways in which the hazards of particulate fume emissions from MMA welding can be reduced by modifying the welding electrode.

Ni-containing wire for mig arc welding of low temperature use steel

Abstract: PURPOSE:To obtain high toughness by adding a specific amt. of a rare earth element, Al and B to a titled wire and using pure gaseous argon as a shielding gas thereby decreasing the content of oxygen in the weld metal and forming the finer structure. CONSTITUTION:A rare earth element is added at 0.02-0.30wt% to a titled wire to stabilize an arc and Al is added thereto at 0.010-0.080wt% and B at 0.0004- 0.0015wt% to form the finer structure. The wire for pure gaseous argon shielded MIG arc welding for low temp. use steel contains, by weight %, <=0.05% C, 0.1- 0.60% Si, 0.4-1.5% Mn, 2-6% Ni and 0.05-0.25% Mo as the other components and consists of the balance Fe and unavoidable impurities.

Comparison of the behavior of stainless and mild steel manual metal arc welding fumes in rat lung.

Abstract: The lung retention and clearance of manual metal arc (MMA) stainless steel and mild steel welding fumes were determined in the rat. The exposure simulated the actual welding situation. The duration of exposure in the "nose-only" exposure chamber was 1 h/workday for one, two, three, or four weeks in the retention study and for four weeks in the clearance study. The concentration of exogenous iron was determined by the magnetic measuring method. Instrumental neutron activation analysis was applied to determine the concentration of total iron, chromium, and nickel in the lungs. The results indicated that the lung retention and clearance patterns for the two types of welding fumes were different. A linear relationship was observed between the amount of stainless steel MMA welding fume retained in the lungs and the duration of exposure, whereas the retention of mild steel MMA welding fume in the lung was saturated as a function of the cumulative exposure time rates. The maximum amount of lung-retained contaminants was 880 micrograms for stainless steel MMA welding fume and 220 micrograms for mild steel MMA fume.

Plasma welding method

Abstract: PURPOSE:To form a stable keyhole and to obtain a satisfactory weld bead without sagging by using pulse current for welding current and pulsating a plasma jet. CONSTITUTION:The pulse current supplied from a pulse current generator 3 is used for welding current and an arc is projected between the bar-shaped tungsten cathode 4 in a torch 1 and a base metal 5. While a plasma jet 7 forms a keyhole in the state of penetrating through the metal 5, the base metal is arc- welded. The plasma jet 7 is therefore pulsated in synchronization with the pulsation by the pulse current of the welding current. The molten metal 9 trying to sag by the own weight is brown off as a small granular droplet 9' by such pulsation of the jet 7, by which the satisfactory weld bead having no sag is formed.

Gas shielded metal arc welding device

Abstract: PURPOSE:To stabilize arcs and to prevent the oxidation in the surfaces of weld beads by providing a succeeding nozzle for injection of an inert gas to a gas shielded metal arc welding device provided with a preceding nozzle which injects a gaseous mixture of an inert gas and an active gas. CONSTITUTION:In a gas shielded metal arc welding device which supplies a welding wire 1 through a welding tip 3 of a welding nozzle 2, generates arcs between the wire and materials 4 to be welded, supplies a gaseous mixture of an inert gas and an active gas through a preceding nozzle 5 to the weld zone and welding the materials while stabilizing the arc, a succeeding nozzle 6 is provided behind the nozzle 2 and an inert gas is injected from said nozzle. Since weld beads 7 are shut off from the atmospheric air by the inert gas in the cooling and solidifying stages thereof, the degradation in the quality of the weld beads by the oxidation of the surfaces of the beads 7 is prevented.

One-side arc welding method

Abstract: PURPOSE:To prevent the generation of a low-temp. crack in the welding of high tensile steel by specifying the content of a binder in back flux to be used on a one-side arc welding and specifying the grain size, bulk density and spraying thickness thereof. CONSTITUTION:The content of the binder in the back flux to be sprayed on a backing strip in the stage of one-side arc welding is limited to =70% of the total weight of the flux and and the thickness to be sprayed onto the backing strip is made 2-8mm.. The low-temp. cracking in the weld zone caused by diffusive hydrogen in welding of the high tensile steel is thus prevented and the excellent shape of a penetration bead is obtd.

Some effects of flux physical properties on weld-bead formation, in the SAW process

Abstract: The study of fundamental arc-welding process characteristics is important for controlling both the formation of and the mechanical properties in weld metals. Automated and semi-automated welding procedures require accurate knowledge of the effects on weld-bead dimensions of changes in process variables, in order to fill joints rapidly without defects. In the SAW process, one such variable is the type of flux used. Two classes of flux properties are important: flux chemistry and reactivity, which affect weld-metal composition and properties; and flux physical properties, which can be intrinsic, e.g., viscosity and surface tension, or extrinsic, e.g., particle size. Physical properties affect (or allegedly affect) bead dimensions, welding speed, and weldingcurrent capabilities. Much recent work on the SAW process has been concerned with the chemical composition and mechanical properties of weld metals.

Method for controlling welding machine

Abstract: PURPOSE:To form a wire to a sharp shape having no slag and to improve arc starting in arc welding of a consumable electrode by subjecting the wire to resistance heating with low voltage, increasing the voltage to perform arc welding and stopping the impression of the voltage when the arc is detected. CONSTITUTION:A wire in contact with base metal is first subjected to resistance heating with a low voltage in the stage of starting and the voltage is quickly increased to discharge the cut wire by the arc at the point of the time when the heated wire softens, by which the base metal is welded in automatic or semi- automatic arc welding using a consumable electrode. The impression of the voltage is quickly stopped in the stage of detecting the arc. The wire is melted to the sharp pointed shape having no slag so that the next arc starting is improved.

Process for the submerged arc welding of metallic materials in a narrow gap

Abstract: The invention relates to a process for the submerged arc welding of metallic materials in a narrow gap with a consumable wire electrode continuously fed through a nozzle. In this process, the nozzle is set with a curved outlet during the welding operation in a rotary pendulum movement, reciprocating from one flank of the weld to the other, with retention times in its end positions close to the flanks.

Damaged brace on offshore platform replaced using hyperbaric welding. part 1: preparation

Abstract: During routine inspection of a North Sea platform, a diagonal brace was found damaged in the splash zone; there was a crack in the area of a local dent and the brace was out of straightness. Computer analysis suggested that the brace be repaired to regain its original strength as closely as possible, and a clamp was fitted as a temporary measure. It was, however, decided to replace the brace with a new one, which would entail a combination of hyperbaric welding and surface welding. The Authors outline the planning for this replacement work and describe the several preparation procedures involved. These included establishing the welding procedure to be used and welder qualification requirements, the arrangements for quality assurance, and the design and construction of the welding habitat. A detailed specification for the welding procedure, which included both TIG and MMA welding, is included in the article.