Патент USA US2404157код для вставки
Jul)’ 15, 1946- ' _ _ F. w. AHALT 2,404,157 METHOD OF BONDING STRUCTURES Filed Sept. 8; 1943 INVENTOR. BY [WA/MAT ATTO/PA/f)’ 2,404,157 Patented July 16, i946 UNITED STATES PATENT OFFICE 2,404,157 METHOD OF BONDING STRUCTURES Frank W. Ahalt, Downers Grove, Ill., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application September 8, 1943, Serial No. 501,544 6 Claims. (01. 219-10) 1 This invention relates to a method of bonding structures, and more particularly to a method of bonding structures comprising a plurality of parts formed of tungsten. In the manufacture of incandescent lamps and of electronic emission devices, such as may be positioned in‘ a vacuum tube, it is sometimes the practice to employ a ?lament of tungsten, which is capable of withstanding considerable 2 Referring to the drawing, and particularly to Fig. 1, an apparatus is there shown which may be employed in following the method of this in vention. As shown in Fig. l, a hood 5, or bell, is positioned on a table 6 and may be supplied with hydrogen through a port 1 formed in the upper portion of the hood 5, it being desirable that the bonding operation take place in a non oxidizing atmosphere, such as hydrogen, in order heat over long periods of operation. This ?la 10 to reduce so far as possible oxidation of the me tallic elements. Positioned within the hood 5 ment may be mounted between a pair of spaced and mounted on the table 6 is a base plate 8 tungsten lead wires which serve as electrodes which serves as a support for a base member 9 and supporting elements and the ?lament may of an assembly to be welded. As shown in this be attached to the upper ends of the lead wires drawing, two spaced parallel glass tubes H) ex 15 by welding. tend vertically through the assembly base 9 and One method of welding has been to arc weld two lead wires H, which are made of tungsten, the tungsten ?lament to the tungsten lead wires are positioned in these tubes and extend sub in a hydrogen atmosphere using a carbon elec trode. However, because of the high tempera stantially beyond the ends thereof. The glass tubes, which may be fused to the lead wires, ture present in a carbon arc and necessary to 20 serve to insulate the lead wires from the base melt the tungsten, both the tungsten ?lament member 9. The upper end of each lead wire II and lead wires were sometimes embrittled in the is provided with a notch l5, as shown in Fig, 2, areas adjacent the joints due to the formation and the ends of a tungsten ?lament wire 16 rest of tungsten carbide in that area because of car these notches, the ?lament being positioned bon mixing with the tungsten, the carbon being 2-5 in between and supported by the lead wires which supplied from the carbon electrode, and also due are substantially thicker than the ?lament wire to crystallization of the tungsten caused by the l6. excessive heat, which is on the order of 7000° F., An electrode holder I8 is universally supported generated during the welding process. Since the in a ball and socket joint l9 mounted in the hood 30 welded assembly may be employed in lamps or 5 and serves as a support for an electrode 20 tubes which may be subjected to considerable which is made of nickel. In changing from a shocks and vibrations during use, this embrit carbon-type electrode to a metallic electrode, a tlement of the ?lament and lead wires tends to metal must be selected which will itself with reduce their useful life. An object of the present invention is to pro 35 stand the high temperatures encountered when the tungsten ?lament becomes incandescent dur vide an improved and an efficient and effective ing operation, as well as a metal which will form method of bonding structures. a mechanically strong joint between the tung In accordance with the present invention, a sten lead wires and the tungsten ?lament. tungsten ?lament may be bonded to a tungsten lead wire by using a nickel electrode and a cur rent su?icient to cause the nickel to be deposited over the juncture of the tungsten elements to form in effect a brazed union between the ele ments, the union being made at a temperature 40 Nickel, as used in accordance with this inven tion, meets these requirements fully. It will be noted that the electrode holder I8 is so positioned that the end of the nickel elec trode 20 may be moved into contact with the substantially lower than the melting temperature 45 upper end of the lead wire I I. In some cases, the of the tungsten. Other objects and advantages of the present invention will be apparent from the following de tailed description taken in conjunction with the accompanying drawing, wherein ‘ Fig. 1 shows diagrammatically an apparatus which may be used in accordance with the pres bonding operation may be expedited by making the supporting plate 8 rotatable and providing a mechanism (not shown) operable from outside of the hood 5 to rotate the table to bring each 50 lead wire into position adjacent the electrode 20. The electrode 20 is connected to one side of a source ‘2| of direct current, such as a direct cur rent generator, and each lead wire II is con ent invention; and nected to the other side of the same source. As Fig. 2 is an enlarged sectional view along the 55 may be seen in Fig. 1, the mounting plate 8 is line 2-2 of Fig. 1 showing a. completed joint. 3 2,404,157 4 provided with recesses 23 through which the lower portions of the lead wires ll extend, the table 6 being similarly apertured, and a pair of clips 24 of electrically conductive material is at is deposited on the parts acts as a reinforcement to the wires in that area, Results obtained by following this process have been exceptionally satisfactory and have resulted in an appreciable tached to the lower ends of the lead Wires 1 l and reduction of failures as a result of breaking of the connected to the direct current source 2|. ?lament wires, which is largely due to embrittle In the operation of this apparatus, it is general ment of the tungsten adjacent the welding areas ly preferable to strike the arc between the elec during subsequenthandling of the welded assem trode 2i] and the lead wire l I rather than between bly. the electrode 20 and the ?lament it‘ since the fila 10 What is claimed is: ment is usually formed from a substantially 1. A method of uniting tungsten parts compris smaller diameter wire than the lead wire and, ing assembling the parts in the desired relation, consequently, is more likely to be burned through and applying an are from a nickel electrode to the than are the lead wires, In practice, an arc junction of the parts to deposit nickel thereon voltage of 25 to 30 volts at from 12 to 15 amperes 15 and unite the parts. may be used and the are is held for a short period 2. A method of uniting tungsten parts com of time, generally less than a second. Under prising assembling the parts in the desired rela these conditions, and using as an electrode a wire tion, applying an are from a nickel electrode to having a diameter of approximately .03", a read the junction of the parts, and depositing nickel ily visible deposit 25 of nickel will be formed at 20 on the junction of the parts to reinforce the junc the junction of the lead wire and the ?lament tion. wire and will provide a mechanically strong joint 3. A method of uniting tungsten parts compris therebetween. ing assembling the parts, and. applying an are In uniting the parts, in accordance with this from a nickel electrode to the junction of the invention, an are having a temperature substan tially below the melting point of tungsten, which is approximately 61000 F., but considerably‘ above the melting point of nickel, which is approxi 25 parts to deposit nickel‘ thereon and unite thev parts, the are being applied in a hydrogen at, mosphere. ‘i. A method of’ uniting tungsten parts compris mately 2645" is used. The speed of the opera ing assembling the parts, and applying an are tion is such that substantially no nickel is lost in 30 from anickelv electrode to the junction of the parts spite of the relatively high temperature, while to deposit nickel thereon and unite the parts, the on the other hand, the high temperature is suf? are being applied in a non-oxidizing- atmosphere. cient to cause the surface of the tungsten lead 5. A method of’ uniting tungsten parts com wire and the tungsten ?lament wire to soften prising assembling the parts, and applying an somewhat inv the area of the joint, thus forming are from a nickel electrode to the junction of the a joint very similar to that obtained by brazing. parts to cause nickel to be deposited on the junc By using an arc having a temperature below the tion of the parts to reinforce the junction, the melting point of tungsten, crystallization of the are being applied in a hydrogen atmosphere. tungsten is kept at a minimum since very little 6. A method of uniting tungsten parts com grain growth occurs in the tungsten when ex prising assembling the parts, drawing an arcfrom posed to the temperature used for the short weld a nickel electrode at a temperature below the. ing period required in accordance with this inven melting point of tungsten and above the melting tion. At the same time, ‘by eliminating the car point of nickel, and depositing nickel over the bon electrode, the formation of tungsten carbide, which is very brittle, in the area of the joint is 45 completely avoided. In addition, the nickel which juncture of said parts, ‘ FRANK: W.v AI-IALT.