Dr. Irving Langtnuir, ~.ssistant Director of t h e Research Laboratory, General Electric Company.
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ATOMIC HYDROGEN FLAMES GUYBARYLEYT,GENERAL ELECTRIC COMPANY, SCHENBCTADY, N. Y. When Dr. Irving Langmuir, assistant director of the research laboratory of the General Electric Company, about fifteen years ago, started a series of experiments to determine the effects of different gases in incandescent
lamp bulbs, he was not thinking of poss~blefuture commercial applications of the results. He just wanted to see what would happen; it was a problem in pure research. And, even if he had thought of the possible outcome of those experiments, it is almost certain that he would not have foreseen that, years later, those experiments with traces of gases in incandescent bulbs would lead to the development of a method for producing welds as strong and ductile as the original'metals. Such, however, has been the case.
Previous to his work, it had been considered that a vacuum was necessary for efficient operation and long life of lamps, hut Dr. Langmuir found that the use of a coiled filament in a lamp containing an inert gas such as argon or nitrogen produced an even more efficient lamp in the larger sizes. In the course of his experiments on the heat loss of incandescent filaments in a gaseous atmosphere, Dr. Langmuir discovered that the heat loss increased a t a constant rate up to the melting point of the tungsten filament, except in the case of hydrogen. This gas behaved like other gases up to a
FIG.2.-Fan-sl1aprrl
Hydrogen Arc Flame.
certain temperature, but beyond that the heat loss increased much more rapidly. Up to slightly more than 1400°C. the heat loss increased with the l.9th power of the absolute temperature, hut above that temperature the rate of heat loss increased considerably. From 2300°C. to 31OO0C., for instance, the heat loss, with the gas a t atmospheric pressure, increased with the fifth power of the absolute temperature. The theory was advanced that the abnormal behavior of hydrogen was due to dissociation of the gas into atoms, with the absorption of considerable energy. Thus the hot tungsten filament dissociated the gas, more heat energy was absorbed from the filament, and the energy was liberated in the cooler portion of the bulb when the atoms recombined to the molecular state. Although this theory explained the phenomenon, there
was still the possibility that the action might be due to the temporary formation of molecules containing more than two atoms, but the law of mass action proved that dissociation was the correct explanation. Continuing the theoretical investigation, Dr. Langmuir found that large quantities of atomic hydrogen were formed in an electric arc between tungsten electrodes bv directing a jet of hydrogen from a small tube into the arc. The atomic bydrogen recombines to the molecularfom immediately beyond the arc, and in so doing liberates about half again as much heat as does the oxy-hydrogen flame. Molybdenum, one of the most refractoty of metals, meltswith ease in this flame. Quartz melts less easily, in spite of its lower melting point, indicating that the metal has a catalytic action. Iron can be melted or welded in the flame without contamination by carbon, oxygen, or nitrogen. Because of the powerful reducing action of the atomic hydrogen, alloys containing chromium, aluminum, silicon, or manganese can be welded without fluxes and without oxidation. The speed with which iron and similar metals can be melted seems to exceed that in the oxy-acetylene flame. Thetio electrodes of the FIG.3 -Laboratory Design of Hydrogen Arc Welding Torch, Type I.
atomic hydrogen torch are tungsten rods held at an acute angle with each other by means of lava insulators. The electrodes are in contact with each other when the equipment is not in use; they can be separated by pressing a lever on the handle. Slow adjustments of the electrodes are made with a set screw. Hydrogen, supplied by a tube through the handle, is used in sufficientquantity so that not only are the electrode tips surrounded by enough of the gas to form
the blast of atomic hydrogen, but by an additional quantity to surround the work with molecular hydrogen. Thus there is a flame within a flame. The atomic hydrogen, in recombining to the molecular form, gives an intensely hot flame which is surrounded by another of hydrogen burning in air. Since hydrogen is a reducing agent of the highest order, the formation of oxides within the flame is, therefore, impossible. Either alternating or direct current can be used, but alternating current has been found more convenient and electrodes of smaller diameter can be
FIG.4.-Laboratory
Design of Hydrogen Arc Welding Torch, Type 11.
used. A gas pressure of less than one pound per square inch was sufficient in the laboratory with short lengths of tubing, with metals up to one-half inch in thickness. The rate of gas consumption varies between 20 and 30 cubic feet per hour for ordinary welding. The torch is held close to the metal, and is inclined so that the blast of hydrogen from the torch passes over the molten metal in a direction opposite to that in which the torch is moved. Low carbon steels up to one-half inch in thickness have been welded without additional material, after being butted together tightly. Considerable work has also been done in connection with fully automatic welding using a butt joint, and with no metal added to the seam. Welds have beenmade on seamless tubing with a wall thickness of one-quarter inch and
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an outside diameter of four inches, and with boilerplate iron an inch thick. Welds on deoxidized copper, such as silicon-copper, have been made up to three-eighths inch thickmetal, giving unusually good sections. Welded portions have been twisted and bent double without cracking or otherwise being injured. Such a procedure has not been possible with the ordinary arc weld, since they are usually brittle due to the presence of nitrides or a thin film of oxide or scale, avoided in the atomic hydrogen flame. The technical develo~ment of this process has FIG.5.-Weld of Rectifier Seal, Joining Chromium been the work of several men and Low Carbon Steel. in the Schenectady laboratory, including R. A. Weinman and Robert Palmer. They have developed and
FIG.6.-Welded
Joint Subjected to %-Degree Ilcnd
experimented with many types of welding torches and with different welding methods. Experiments have also been conducted with several gas mixtures and various electrodes, and the best results have usually been obtained when tungsten electrodes and hydrogen alone are used. Considerable work has been done with this welding method in the laboratory, but commercial apparatus has not yet been developed.
