Welding electrodes too large for the parameters or position slag inclusion a discontinuity consisting of slag entrapped in weld metal or at the weld interface welds in joint too narrow a joint angle or initial joint gap. Modeling and validation of multiple joint reflections for. This yields a weld with a high ratio of depth to width. The welding head hng multi has been designed around the flat, welding nozzle. Kjoint, positioning aids, tabs, bayonets, interlocking joints, tolerance compensation planes, etc.
Structural steel design, fabrication, and construction. Figure 2 shows the design of the round bar and flat bar tension specimens which were machined after welding. Application of narrow gap welding process with high speed. You can use the narrow gap welding process if you demonstrate it will produce the required results.
The effects of multiple internal reflections within a laser weld joint as a function of joint geometry and processing conditions have been characterized. A two axis remote controlled motorized wire manipulator is available with the ami ngt torch. Mo and nb that produce long living radioactive isotopes in the. Although the merits of narrow gap welding for thick plate in large structures are well known, its application is still relatively rare. So much higher wire deposition rate can be obtained. Laser multipass narrowgap welding a promising technology for joining thickwalled components of future power plants. Rafm steels have a chemical composition similar to modified 9cr1mo steel. Grinding grit and residue enter the final weld and weaken its properties.
At present, the narrow gap submerged arc welding is an advanced welding technology. When root pass welding with a narrow or closed gap, stiff settings can be beneficial. Experience gained from user contact and welding training of crewmembers showed that. Pdf narrow gap laser welding of thick section stainless. Excellent display of filler wire position and entry point. A narrow gap tigwelding tool including two cascade welding nozzles was developed for the study. Narrowgroove ng welding is defined, in part, by the american welding society aws as a variation of a multiplepass welding process with filler metal, using a small root opening and a vgroove with a small groove angle. Us5900167a us08928,895 us92889597a us5900167a us 5900167 a us5900167 a us 5900167a us 92889597 a us92889597 a us 92889597a us 5900167 a us5900167 a us 5900167a authority us united states prior art keywords contact tip gas supply machine barrel supply tubes apparatus prior art date 19970912 legal status the legal status is an. Vijayan m g background rafm steels are the candidate structural materials for tbm to be installed in the iter fusion reactor. Narrow gap welding, electrogas and electroslag welding. In comparison to the conventional weld seam preparation, the weld seam volume. The heat input for nglw is much lower than that of arc welding, as are the expected levels of residual stress and distortion. Realize there are several ways to bridge the gap, but dont start there consider the variety of design features when designing for laser welding e. Separate systems for the horizontal and the vertical joint tracking.
Qualify the wps in accordance with clause 4 parts a and b. Avc, aea, osc control welding with combined parameters easy processing of all materials deposition rate up to 5,5 kgh lowest energy per unit environmental friendly, no spatter, low emission, no arc noise narrow gap welding technologies possible smaller aperture angles, less weld preparation time less welding time application advantages. In this study, butt joints with narrow gap were welded using a highpower co2 laser. The multipass laser welding technique, based on the narrow gap approach, is an emerging welding technology which can be applied to thicksection welds using a relatively lowpower laser, but the process is more.
The reciprocating movement of the nozzle is accomplished by means of a pneumatic three position cylinder and is transferred from cylinder to nozzle through a shaft transmission system. It was found out, that the narrow gap arc welding of. The narrow gap system space is also equipped with a protection cap made of a high quality boron nitride ceramic. Narrow gap welding aws welding code issues engtips. The narrowgap welding system ng is typically designed to fit on torch sb400w500w or identical. Narrowgap welding with vision a video system for remote operation and observation of the weld zone from leading and trailing directions. In practice several types of welding units for narrow gap welding are known at present. Pdf narrow gap laser welding of thick section stainless steel.
Top tig process filler wire is fed directly to arc through shielding nozzle. However, it has recently been shown that the narrow gap laser welding nglw technique can be used to join materials with thicknesses that are well beyond the. This article evaluates the performance of the coldwire gas metal arc welding cwgmaw process for narrow gap girth welding. However, manual fine tuning of the welding speed in response to changes in the groove width is necessary.
The spa narrow gap welding system innershield is available in the length 90 mm 3. It is consisted of welding walking tractor, height adjuster. Characteristics of welding and arc pressure in tig narrow gap. The required current decreases as the gap size increases. A number of stations also including joint preparation. Weld inspection checklist american welding society. The coldwire is melted by using the surplus heat available at the arc and molten metal.
The effect of welding parameters including the relative position between the laser beam and the filler wire, welding speed, and the distance from the intersection of the beam and wire to root of the groove on the weld bead geometry and welding defects was studied. Narrow gap welding ngw, also called narrow groove welding, is a term applied to arc weld made in thick plates using a square groove weld joint or a v groove weld joint with a groove angle less than 10 and utilizing it for 9 to 12 mm wide gap. Throughout this time key plant has continued to supply, develop and revise their equipment from the sales of new and refurbished equipment to key plants large rental department and service centre through to more recent. The basis of the narrow gap technology is the rectangular narrow gap blade with a length of up to 300 mm, which guides the wire electrode, the shielding gas and the water coolant. The projected three year program focused on the development of geometric optical models which predict the trapping of laser energy within the weld joint and experimental validation of these models. A narrow gap tig welding tool including two cascade welding nozzles was developed for the study. It covers gas tungsten arc welding gtaw, gas metal arc welding gmaw, high energy density processes like laser welding, and narrow gap welding methods. This paper was presented at the aws annual meeting, philadelphia, pa. Therefore, a new kind of narrow gap submerged arc welding slag cleaning device is designed to clean the welding slag. Narrow gap arc welding experiments of thick copper sections.
Narrow gap tig welding and development of filler wires of. Narrow gap laser welding of 316l stainless steel for. Narrow gap arc welding experiments of thick copper sections pdf. Joint strength of heavy plates with lower strength weld metal. Key plants association, the number 1 when it comes to the welding automation equipment market, traces back over 55 years. Narrowgap laser welding using filler wire of thick steel. Applications requirements and process variants weld preparation filler wire diameter one pass per layer welding multipass per layer welding high deposition rate. Bridging of welding gaps in welding with a multiplewire electrode multiple wires. The hng multi meets the demands for a fully automatic welding process with accurate controlling of all parameters for reduced welding times and perfect weld metal when welding hightensile material. Narrow gap electroslag welding welding time approx. The widest range of orbital welding equipment in the world. A computer model utilizing optical ray tracing is used to predict the reflective propagation of laser beam energy focused into the narrow gap of a metal joint for the purpose of predicting the location of melting and coalescence which form.
Highspeed cinematography of the phenomena revealed that molten metal bridges, which formed between neighboring strip edges near the apex point, travel along a narrow gap toward the welding point at a speed much faster than that of the strip. In this paper we report an investigation into multipass laser welding of 316l stainless steel sheets of 510 mm thickness, based on narrow gap 1. Jun 01, 2015 the art of narrowgroove welding june 1, 2015 narrowgroove ng welding is defined, in part, by the american welding society aws as a variation of a multiplepass welding process with filler metal, using a small root opening and a vgroove with a small groove angle. In comparison to the conventional weld seam preparation, the weld seam. Feasibility of narrow gap welding using the coldwire gas. Laser welding 101 american iron and steel institute. Lincoln electric supplies electrodes, power sources, automatic and semiautomatic wire feeders, submerged arc wire and flux, which are the industry standards for pipeline construction around the world. The original scope of the project was to develop a method to enhance the laser welding of beal alloys by the use of weld joint designs based on the principals of nonimaging optics. Thicksection austenitic stainless steels have widespread industrial applications, especially in nuclear power plants. The joining methods used in the nuclear industry are primarily based on arc welding processes. As the weld is very deep and narrow, the slag is difficult to clean and will have impact on the quality of welding seam. Scribd is the worlds largest social reading and publishing site. Design on cleaning device for slag of narrow gap submerged. However, narrow gap welding does require specialised equipment, because of the limited accessibility to the root of the preparation.
The cmf submerged arc narrow gap welding heads are featuring state of the art technologies. Addition of filler wire while welding in either direction. I i welding would typically be outofposition welding and situations where the end user wants to carry a larger puddle. Tungsten inert gas tig narrow gap welding using magnetic arc oscillation is one of the most important methods for joining thick components.
The ultra narrow gap welding is a multilayer welding where the gap is designed with the specific shape to create one layer by the maximum of two welds the ultra narrow gap width is chosen between 10 15 mm. Narrow gap techniques have been applied when welding using submerged arc welding saw, gas shielded metal arc welding migmag, gmaw and tungsten inert gas welding tig, gtaw processes. Narrow gap welding, electrogas and electroslag welding 76 nique is the high crystal restructuring rate in the weld metal and in the basemetal adjacent to the fusion line an advantage that gains good toughness properties. The arc machines ngt torch oscillating electrode is ideal.
This welding procedure uses joint preparations with small, included angles, typically. Welding research penetrator formation mechanisms during high. The projected three year program focused on the development of geometric optical models which predict the trapping of laser energy within the weld joint and experimental validation of these. The purpose of the welding handbook for maritime welders is to provide guidance in modern welding and related processes and to provide the welder with a source of practical information on the right solution to specific onboard welding problems. Jul 10, 2017 in this study, butt joints with narrow gap were welded using a highpower co2 laser. This process allows very thick plates to be joined using fewer weld passes as compared to. Oct 05, 2015 the migmag narrow gap technology offers a particular economic efficiency for welding thickwalled component parts. A copper welding station, which is an insulated cell, was also developed for the welding trials. Structural steel design, fabrication, and construction jamie f. Narrow gap gtaw process welding power supply hstig system supplied by bub hitachi industrial co. Preprogrammed number of beads at different joint width.
The preferred choice for automated heavy wall, pipe. They are divided regard ing the welding process tungsten inertgas. Remotecontrolled motorized wire guide manipulators. In multipass welds, improper bead spacing can result in a valley, between beads with too narrow a gap or side walls. Narrowgroove welding techniques are wellestablished for submerged arc welding. Series iv by metalarc narrow gap welding an ht 80 structural steel 25 mm thick with an electrode of 50 kgmm2 nomina tensile strength level. If notch toughness is a requirement, you must also comply with part d. Tig hot wire narrow gap the process equipment competes primarily with other solutions for orbital pipe line welding, but also in prefab of pipe to pipe and pipe to fitting, when set up as a production line with fixed stations. Narrow gap tig welding and development of filler wires of rafms for welding free download as powerpoint presentation. Ahw atomic hydrogen welding caw constricted arc welding tig tungsten inertgas arc welding mig metal inertgas arc welding mag metal activegas arc welding pjw plasma jet welding paw plasma arc welding pjpw plasma jet plasma arc welding gmgmma gasmixture shielded metalarc welding magm magc co2shielded metalarc welding ngw narrow gap welding. The amplitude of this movement is set by means of screws located on the upper part of the welding head. Pdf narrowgap welding is a low distortion welding process. Due to an easy handling and quick interchangeable single components a. Pdf analysis of welding distortion due to narrowgap welding of.
The coldwire is melted by using the surplus heat available at the arc and molten metal at the weld pool. This booklet is a guide to welding pipe with shielded metal arc welding smaw and double ending pipe using automatic welding. Ngiesw major improvements three major improvements included 1 consistent defectfree welds, 2 fatigue performance, and 3 impact toughness in the weld and heataffected zones. Mar 09, 2016 narrow gap welding also called narrow groove welding was developed to weld thick sections more economically. We are acquainted with processes, such as multiplewire welding, multiplehead welding and weld ing with an additional hot and cold wire 1216.
The innershield system is designed for a fluxe cored wire electrode of o 2. This book introduces the range of advanced welding techniques currently in use. It is a submerged arc process designed to weld thick walled steel plate from 2 in. The preferred choice for automated heavy wall, pipe, vessel.
The lincoln electric narrow gap welding process is designed to meet the quality, mechanical properties and overall cost requirements of heavy wall fabrication. If the gap is too narrow, it is not unusual to push so hard on the electrode that a. The migmag narrow gap technology offers a particular economic efficiency for welding thickwalled component parts. The cwgmaw process is characterized by the introduction of a continuously fed nonenergized wire coldwire into the electric arcweld pool region. Two narrowgap welding variations with a rotating arc movement are shown in fig. While wide gap brazing should not be the first choice solution, it is. While widegap brazing should not be the first choice solution, it is. Narrow gap welding also called narrow groove welding was developed to weld thick sections more economically. Ahw atomic hydrogen welding caw constricted arc welding tig tungsten inertgas arc welding mig metal inertgas arc welding mag metal activegas arc welding pjw plasma jet welding paw plasma arc welding pjpw plasma jet plasma arc welding gmgmma gasmixture shielded metalarc welding magm magc co2shielded metalarc welding ngw narrowgap welding.
1257 451 1015 949 1126 40 1522 1503 724 1405 28 38 1050 851 1308 248 487 1414 1444 1410 206 948 880 150 189 1279 949 650 1431 1 1467 1409