New developments in advanced welding

Future trends

There are a number of misconceptions and genuine limitations relating to GTAW and these must be addressed if the process is to retain its relevance in the future. The ‘basic’ GTAW process has been hampered by its low penetration and consequent poor productivity. As a production tool it tends to be used when quality or other overriding issues demand it. This chapter has argued that the process has much more to offer and has illustrated this with the detailed description of two of its many variants. It is suggested that this realisation that GTAW has ‘more to offer’ will be increasingly appreciated, particularly as fabrication operations become more integrated and mechanised. One of the historical impediments to the seamless integration of welding into production lines has been poor joint fitup and the consequent need for a degree of adaptability that was only available with manual intervention. This impediment is rapidly being removed as component tolerances improve, welding processes become more tolerant, and control systems are made more intelligent and responsive. This trend will suit the lower deposition welding processes such as GTAW and should renew the search for innovative ways of exploiting this very elegant process.

Many of the changes to GTAW over recent times have been forecast correctly to be in the area of the equipment used to implement the process (Lucas, 1990; Muncaster, 1991). This area covers power sources, control systems, monitoring, viewing and data acquisition (Muncaster, 1991). This trend is expected to continue in the future, with the increasing availability of significant computational power driving the process in the direction of greater adaptability and user friendliness. Occupational health and safety as well as environmental issues are also becoming more important and concerns about electromagnetic radiation and its potential to interfere with computerised equipment, metal fume and overall power requirements, will all lead to further changes in equipment and practices.

However, the opportunity for new variants is expected to continue and to produce some very productive processes. One example of this is the recent research into hybrid processes and particularly laser plus GTAW (Dilthey and Keller, 2001; Ishide et al., 2002). Hybrid welding refers to a situation where two processes (in this case, laser welding and GTAW) are coupled together to act at a single point. The coupling between the laser beam and the gas tungsten arc produces a number of synergistic effects that enhance the best features of each process. For example, the laser not only provides deep penetration but also stabilises the anode spot of the arc. As one result the gas tungsten arc then can be operated in the more efficient DCEN mode, even when welding aluminium. At the same time the arc broadens the weld pool at the plate surface, improves the laser to material coupling, and relaxes the very high joint tolerances required for laser welding. It also provides additional heat input and an improved weld profile with reduced notch angles. In one set of trials on a 2mm aluminium 3% magnesium alloy, Dilthey and Keller (2001) reported an increase in welding speed from 5m/min for the laser, to 8m/min with the hybrid process. The GTAW operated alone could only be operated in the ac mode at 2 m/min.

Another innovation, in GTAW is the newly reported guided GTAW or GGTAW process (Zhang et al., 2003). In this variant the main arc is established between a short, hollow tungsten electrode and the workpiece. However, a separately powered electrode positioned above the main electrode provides a lower current ‘pilot arc’. This arc is constricted in passing through the hollow main electrode. The result is two concentric arcs, the inner of which has a high energy density and is relatively stiff. The inner arc has the effect of stiffening or ‘guiding’ the main arc, hence the name of the process. This process is anticipated to have some advantages over both GTAW and plasma arc.

In summary, GTAW is a particularly elegant welding process because of its apparent simplicity and appeal to fundamental physical principles. It is also becoming far more productive and versatile than popular images of the process suggest. The likely scenario is that this process will continue to be developed in new and imaginative ways for many years to come.

3.3 References

Adonyi Y., Richardson R. W. and Baeslack III W. A. (1992), ‘Investigation of arc force

effects in subsurface GTA welding’, Welding Journal, 71(9) 321s-30s Adonyi-Bucurdiu I. (1989), A Study of Arc Force Effects During Submerged Gas Tungsten-

arc Welding, PhD Dissertation, The Ohio State University Ohio

Anderson P. C.J. and Wiktorowicz R. (1996), ‘Improving productivity with A-TIG welding’, Welding and Metal Fabrication, (3/12) 108-9 Andrews J. G. and Atthey D. R. (1976), ‘Hydrodynamic limit to penetration of a material by a high-power beam’, Journal of Physics D: Applied Physics, 9 2181-94. Block-bolten A. and Eagar T. W. (1984), ‘Metal vaporization from weld pools’, Metallurgical Trans. B, 15B(9) 461-469 Converti J. (1981), Plasma Jets in Welding Arcs, PhD Thesis, Mechanical Engineering, MIT, Cambridge, MA Dilthey U. and Keller H. (2001), ‘Laser arc hybrid welding’, Proc. 7th Int. Welding Symposium, Kobe, Japan Welding Soc.

Erokhin A. A. (1979), ‘Force exerted by the arc on the metal being melted’, Avtom. Svarka, 7 21-6

Ferjutz K., Davis J. R. and Wheaton N. D. (eds) (1994), ASM Handbook, Volume 6, Welding Brazing and Soldering. ASM International, 195-9 Fujii H., Sogabe N., Kamai M. and Nogi K. (2001), ‘Effects of surface tension and gravity on convection in molten pool during electron beam welding’, Proc. 7th Int. Welding Symposium, Kobe, Japan Welding Soc., 131-6 Grimsehl E. (1947), A Textbook of Physics, Vol 1, Mechanics, London, Blackie & Son. Gurevich S. M. and Zamkov V. N. (1966), ‘Welding titanium with a non-consumable electrode using fluxes’, Automat. Welding, 12 13-16 Gurevich S. M., Zamkov V. N. and Kushnirenko N. A. (1965), ‘Improving the penetration of titanium alloys when they are welded by argon tungsten arc process’, Automat. Welding, 9 1-4

Halmoy E. (1994), ‘New applications of plasma keyhole welding’, Welding in the World, 34, 285-91

Heiple C. R. and Roper J. R. (1981), ‘Effects of selenium on GTA fusion zone geometry’, Welding Journal, 60 143s-5s Heiple C. R. and Roper J. R. (1982), ‘Mechanism for minor element on GTA fusion zone geometry’, Welding Journal, 61 97s-102s Howse D. and Lucas W. (2000), ‘Investigation into arc constriction by active fluxes for tungsten inert gas welding’, Sci. and Tech. Welding and Joining, 5(3) 189-93 Ishide T., Tsubbota S., Watanabe M. and Ueshiro K. (2002), Development of YAG Laser and Arc Hybrid Welding Method, Int. Inst. Welding Document Doc No. XII-1705-02 Jackson C. E. (1960), ‘The science of arc welding’, Welding Journal, 39(4), 129s-140s and 39(6), 225s-30s

Jarvis B. L. (2001), Keyhole Gas Tungsten Arc Welding: a novel process variant, PhD Thesis, Mechanical Engineering, University of Wollongong, Wollongong Kamo K., Nagura Y., Toyoda M., Matsubayashi K. and Miyake K. (2000), ‘Application of GTA welding with activating flux’, Intermediate Meeting of Comm. XIIof International Institute Welding, Ohio, Int. Inst. Welding, Doc. No. XII-1616-00 Katayama S., Mizutani M. and Matsunawa A. (2001), ‘Liquid flow inside molten pool during TIG welding and formation mechanism of bubble and porosity’, Proc. 7th Int. Welding Symp., Kobe, Japan Welding Soc., 125-30 Lancaster J. F. (1986), The Physics of Welding', 2nd ed., IIW publication, Oxford and New York etc., Pergamon Press Liptak J. A. (1965), ‘Gas tungsten arc welding heavy aluminium plate’, Welding Journal, 44(6) 276s-81s

Lorrain P. and Corson D. (1970), Electromagnetic fields and waves, 2nd ed., San Francisco, W. H. Freeman and Co.

Lowke J. J., Kovitya P. and Schmidt H. P. (1992), ‘Theory of free-burning arc columns including the influence of the cathode’, Journal of Physics D: Applied Physics, 25 (11) 1600-6

Lu S.-P., Fujii H., Sugiyama H., Tanaka M. and Nogi K. (2002), ‘Weld penetration and marangoni convection with oxide fluxes in GTA welding’, Materials Trans. of Japan Institute of Metals, 43(11) 2926-31 Lucas W. (1990), TIG and Plasma Welding, Cambridge, UK, Woodhead Publishing Ltd Lucas W. (2000), ‘Activating flux - improving the performance of the TIG process’, Welding and Metal Fabrication, (2/12) 7-10 Lucas W. and Howse D. (1996), ‘Activating flux - increasing the performance and productivity of the TIG and plasma process’, Welding and Metal Fabrication, (1/12) 11-17

Lucas W., Howse D., Savitsky M. M. and Kovalenko I. V. (1996), ‘A-TIG flux for increasing the performance and productivity of welding processes’, Proc. 49th International Institute of Welding Annual Assembly, Budapest, Hungary, Int. Inst. Welding, Doc. No. XII-1448-96

Makara A. M., Savitskii M. M. and Kushnirenko B. N. et al. (1977), ‘The effect of refining on the penetration of metal in arc welding’, Automat. Welding, 9, 7-10 Matsuda F., Ushio M. and Sadek A. (1990), ‘Development of GTA electrode materials’.

The 5th International Symposium of the Japanese Welding Society. Tokyo, April 1990 Matsunawa A. (1992), ‘Modelling of heat and fluid flow in arc welding’, Keynote address, International Trends in Welding Conference, Gattlingburg, 1992 Matsunawa A., Kim J-D., Seto N., Mizutani M. and Katayama S. (1998), ‘Dynamics of keyhole and molten pool in laser welding’, Laser Applications, 10(6) 247-54 Muncaster P. (1991), Practical TIG (GTA) Welding, Cambridge, UK, Abington Publishing Norrish J. (1992), Advanced Welding Processes, Bristol, IOP Publishing Ltd Ogino K., Nogi K. and Hosoi C. (1983), ‘Surface tension of molten Fe-O-S Alloy’, Tetsu-to-Hagane (J. Iron Steel Inst. Japan), 69(16) 1989-94 Ohji T., Miyake A., Tamura M., Inoue H. and Nishiguchi K. (1990), ‘Minor element effect on weld penetration’, Q. J. Japan Welding Soc., 8(1) 54-8 Ohji T., Inoue H. and Nishiguchi K. (1991), ‘Metal flow in molten pool by defocused electron beam’, Q. J. Japan Welding Soc., 9(4) 501-6 Okazaki T. and Okaniwa T. (2002), ‘Application of active flux TIG welding’, J. Japan Welding Soc, 71(2) 100-3 Ootsuki M., Tsuboi R., Takahashi H., Asai S., Taki K. and Makino Y. (2000), ‘Study on high penetration welding using activated flux method’ (1), Preprints of the national meeting of Japan Welding Soc., 66 240-1 Ostrovskii O. E., Kryukovskii V. N., Buk B. B. et al. (1977), ‘The effect of activating fluxes on the penetration capability of the welding arc and the energy concentration in the anode spot’, Welding Production, 3 3-4 Papoular R. (1965), Electrical Phenomena in Gases, London, Iliffe Books Savitskii M. M. (1979), ‘The current density in the anode spot during the welding of standard and refined steels’, Automat. Welding, 7 17-20 Savitskii M. M. and Leskov G. I. (1980), ‘The mechanism of electrically-negative elements on the penetrating power of an arc with a tungsten cathode’, Automat. Welding, 9 17­22

Scriven L. E. and Sternling C V. (1960), ‘The marangoni effects’, Nature, 187(July) 186-8

Shaw Jr C. B. (1975), ‘Diagnostic studies of the GTAW arc, Part 1’ Welding Journal, 54(2) 33s-44s

Simonik A. G., Petviashvili V. I. and Ivanov A. A. (1976), ‘The effect of contraction of the arc discharge upon the introduction of electro-negative elements’, Welding Production, 3 49-51

Sire S. and Marya S. (2001), ‘New perspectives in TIG welding of aluminum through flux application FBTIG process’, Proc. 7th Int. Welding Symp., Kobe, Japan Welding Soc., 113-18

Taimatsu H., Nogi K. and Ogino K. J. (1992), ‘Surface tension of liquid Fe-O alloy’, High Temperature Soc. Japan, 18 14-19 Takahashi H., Asai S., Tsuboi R., Kobayashi M., Yasuda T., Ogawa T. and Takebayashi H. (2002), ‘Study on underwater GTAW with active flux cored wire (1)’, Preprints of the National Meeting of Japan Welding Soc., 70 24-5 Tanaka M. (2002), ‘Effects of activating flux on weld penetration in TIG welding’, J.

Japan Welding Soc, 71(2) 95-9 Tanaka M., Shimizu T., Terasaki H., Ushio M., Koshi-ishi F. and Yang C.-L. (2000), ‘Effects of activating flux on arc phenomena in gas tungsten arc welding’, Sci. and Tech. Welding and Joining, 5(6) 397-402 Tanaka M., Terasaki H., Ushio M. and Lowke J. J. (2003), ‘Numerical study of a free- burning argon arc with anode melting’, Plasma Chem. and Plasma Process., 23(3) 585-606

Thomson J. (1855), ‘On certain curious motions observable at the surfaces of wine and other alcoholic liquors’, Philosophical Magazine, 10 330-3 Tsuboi R., Asai S., Taki K., Ogawa T., Yasuda T. and Takebayashi H. (2002), ‘Study on underwater GTAW with active flux cored wire (2)’, Preprints of the National Meeting of Japan Welding Soc, 71 264-5 Winkler C., Amberg G., Inoue H., Koseki T. and Fuji M. (2000), ‘Effect of surfactant redistribution on weld pool shape during gas tungsten arc welding’, Sci. and Tech. Welding and Joining, 5(1) 8-20 Xiao Y. H. and den Ouden G. (1990), ‘A study of GTA weld pool oscillation’, Welding Journal, 69(8) 289s-293s Yamauchi N., Taka T. and Oh-I M. (1981), ‘Development and application of high current TIG process (SHOLTA) welding process’, The Sumitomo Search, 25 May 87-100 Zhang Y., Lu, W. and Liu Y. (2003), ‘Guided arc enhances GTAW’, Welding Journal, 12, 40-5

Zhu P., Lowke J. J. and Morrow R. (1992), ‘A unified theory of free burning arcs, cathode sheaths and cathodes’, Journal of Physics D: Applied Physics, 25 1221-30

New developments in advanced welding

Environmental issues

10.4.1 Introduction The last 30 or more years have seen a significant awakening of interest in the environment and a much greater understanding of how human activities in one geographical …

Recent and ongoing research

10.3.1 Fundamental difficulties Despite the labour figures indicating that around 400000 people in the USA are directly engaged in welding, it is difficult to research health effects and make positive …

Occupational health and safety

F. J. BLUNT, University of Cambridge, UK 10.1 Introduction The welding industry is a major player in manufacturing. It encompasses the traditional arc and gas processes as well as advanced …

Как с нами связаться:

Украина:
г.Александрия
тел./факс +38 05235  77193 Бухгалтерия

+38 050 457 13 30 — Рашид - продажи новинок
e-mail: msd@msd.com.ua
Схема проезда к производственному офису:
Схема проезда к МСД

Партнеры МСД

Контакты для заказов оборудования:

Внимание! На этом сайте большинство материалов - техническая литература в помощь предпринимателю. Так же большинство производственного оборудования сегодня не актуально. Уточнить можно по почте: Эл. почта: msd@msd.com.ua

+38 050 512 1194 Александр
- телефон для консультаций и заказов спец.оборудования, дробилок, уловителей, дражираторов, гереторных насосов и инженерных решений.