Patent GB-550828-A (GB)
Title: Improvements in the coating of metal articles by deposition of metal by welding
IPC: B23K5/08
Filed: 1942-05-01
Abstract: 550,828. Coating valves &c. by welding. WAGNER, R. L. May 1, 1942, No. 5869. [Classes 83 (ii) and 83 (iv)] Uniting by fusion.-In welding annular coatings of wear-resistant or corrosion-resistant metals such as cobalt, chromium and tungsten on a metal article such as the seating surface of a poppet valve for airplane engines, the article is rapidly rotated on a vertical axis, at least two oxy-fuel gas flames are directed on the article to preheat it at and adjacent the annular zone to welding temperature and thereafter a pre-selected amount of the coating metal is progressively deposited within the annular zone during rotation of the article. A number of work supporting tables Ware carried by circular platforms P, p<SP>1</SP> mounted on a shaft 23 which is rotated step by step by ratchet and pawl mechanism 26, 27 from a cam 30 rotated by a motor 34 through reducing gear 35, the platform being locked in position by a spring-pressed pin 40 engaging a depression 39 in the platform P<SP>1</SP>. The tables each consist of a ring 55 supported by pins 54 from plates 51, 52 separated by heat insulating board 53, the plate 52 carrying a spindle 12, which is fixed to a collar 20 rotatable in ball bearings 17 and has the member 14 of a clutch for engagement with a member 13 on a spindle 11 mounted on the platform P<SP>1</SP>. The spindles 11 are rotated by a chain 38 driven by bevel gear 44, 43 and reduction gear 42 from a motor 41 carried by the platform P<SP>1</SP>. At certain of the stations, such as the loading station the clutches are disengaged by the portion 14 running up a curved angle iron member 47. The valve 63 is placed on a ledge on a refractory member 59 mounted on an annular member 56 supported in the ring 55. When the table is rotated the bevelled surface 67 to be coated is heated to welding temperature by two multi-jet torches 65, 66 disposed on opposite sides of the axis and having carburizing flames as described in Specification 368,605. At this stage a switch 86 is closed so that the coating metal 69 which is in rod form, is fed by rolls 71, 72 from a motor 73 and at the same time a valve 85 is opened so that a universally mounted torch 83 preheats the rod 69. The rate of feed is varied by a variable resistance 82. At the same time a valve 89 is partially closed so as to reduce supply to the torches 65, 66. The deposited metal passes beneath the torch 65 to spread the molten metal over the surface and weld it to the valve. After a time interval determined by a timer 87 the feed is stopped and the valve 89 reopened. The table may remain for a further period beneath the welding torches to smooth the deposit further. The platform P is then rotated by the motor 34 to bring the table under a torch 91 having a flame of low intensity so that slow regulated cooling is effected, the under surface of the cooler being submitted to a stream of cool air blown round the pins 54. At the same time the next table is brought into position under the welding torches. The parts may be fluxed prior to heating and in order to prevent flux running off the bevelled surface a vitreous flux such as a mixture of calcium or magnesium silicate with sodium silicate is used, the flow of flux being increased at the desired time by providing the rod 69 with a coating of low-melting flux such as borax, boric oxide, or borosilicate glass which thins out the viscous flux. The timing mechanism 87 may be replaced by means carried by the rod 69 for tripping a switch in the rod feeding circuit. If desired the articles to be coated may be previously preheated in a reducing or inert atmosphere.