GB761752A - Improvements in and relating to the working of materials by arc discharge - Google Patents

Abstract

761,752. Removing metal by arc discharge. HEIDENREICH, R., and GROSS, K. Dec. 6, 1951 [Dec. 6, 1950; Nov. 12, 1951], No. 28662/51. Class 83 (4). In working the surface of a ferrous, non- ferrous or cemented carbide workpiece, an arc is produced between the workpiece and an electrode, moved relatively thereto, such that material is transferred only from the workpiece to the electrode or is transferred alternately in both directions with the transference from the workpiece predominant in volume, the electrode having at least a surface layer of material similar to that of the workpiece but which when deposited on the latter by the arc improves the hardness and/or toughness thereof. The current may be alternating or periodically reversed direct current. In an embodiment two disc electrodes 11, 12, Fig. 1, mounted on a shaft 9 for rotation by a motor 2 through belt 8 and pulleys 7, 10 are insulated from the shaft and are supplied with current from brushes 24, 26 engaging rings 16, 16 connected to the discs 11, 12. Workpieces 31, 32 are supported on adjustable tables 29, 30 and are connected to conductors 27, 28. The workpieces 31, 32 and discs 11, 12 may be supplied with A.C. from a transformer 17 or with D.C. from a rectifier 38. A polarity change switch 41 allows the polarity of the workpieces 31, 32 and discs 11, 12 to be changed. The discs 11,12 may have raised conducting inserts for guiding the arc, coated mechanically, galvanically or by spraying with material similar to that of the workpieces and free of abrasive particles, in their circumferential or side faces. A projection 48, Fig. 2, a series of projections 49, Fig. 4 (not shown), or projections 51, Fig. 6, may be provided to guide the arc on the workpiece. The surface of the discs may be coated, the inserts being omitted. In operation with the discs 11, 12 rotating each of the workpieces 31, 32 is brought into contact with the discs 11, 12 and withdrawn to produce arcs therebetween. The arc may be started by blowing powdered metal between the workpieces and the electrodes, the metal having a composition similar to that of the workpieces, or by employing radio-active substances or ionized gases. The electrodes may be moved relatively to a moving workpiece.