Patent GB-683085-A (GB)
Title: Method of fabricating machine parts such as crankshafts and other assemblies built up of ferrous components
Inventor: PROCTOR THOMAS EMERSON
IPC: B23K35/00
Filed: 1950-07-26
Abstract: 683,085. Making shafts and shafting; soldering; powder metallurgy. ISTHMIAN METALS, Inc. July 26, 1950, No. 18675/50. Classes 83 (ii) and 83 (iv). Component parts of a machine part, such as a crank-shaft, having ferrous surfaces to be joined, are assembled with a preformed shaperetaining connector element, comprising a powdered metal compact of from 5-30 parts of a low melting constituent selected from copper, bronze and copper-tin mixtures in which copper predominates and 95-70 parts of a high melting constituent which provides the shape-retaining structure, interposed between the ferrous surfaces and are subjected to a bonding temperature which is higher than the melting point of the low melting point constituent and lower than that of the high melting point constituent to unite the ferrous surfaces. The connector element 5 made by mixing electrolytic iron having up to 0.1 per cent carbon with preferably 20 per cent of bronze (pre-alloyed) powder (90 per cent Cu, 10 per cent Su) with a lubricant, e.g. stearic acid in a ball mill or conical blender, the mixture being poured into a die and then compressed between punches at a pressure of approximately 30 tons/inch<SP>2</SP>. The pressed compact is then sintered at approximately 1500‹ F. for 1-3 hours in an atmosphere of hydrogen, cracked ammonia, &c. to drive off the lubricant and relieve work hardness. The sintered element is then re-pressed at 50-100 tons/inch<SP>2</SP> to provide e.g. a washer 40 (Fig. 4) of unalloyed powdered metal. The washer 40 is then formed with an eccentric hole 42 and is between 0.005 and 0.25 inches thick. In one example of a built-up crank-shaft, Fig. 2, a steel crank-pin 12, crank 26 and main bearing part 10 are temporarily assembled with brazing elements 40 between the surfaces to be joined by means of nuts and bolts 52, 50. The initially radially oversize pin 12 and bearing 10, each having flanges 16 and fillets 20 between the flanges 16 and body part are bored to provide holes 24, 22 respectively, for lubricant and to house the bolts 50, the pin 12 being bored eccentrically while the bearing 10 is bored concentrically to allow a large mass M of overlapped metal. The elements 40 are placed between the flanges 16 and the crank 26 to extend slightly beyond the flanges, washers 48 on the bolts 50 securing the parts together. Packing pieces 54 are used between the washers 48 and the crank 26. The bolts may be screwed into adjacent counterweights &c. instead of passing through the parts. Tack welding of the flange 16 may be used to temporarily secure the parts. The assembled parts are mounted on a nickelchrome-iron alloy jig 46 and are placed in a furnace in which an atmosphere of hydrogen, cracked ammonia, &c. is maintained at a' temperature of approximately 1990‹ F. or 2050‹ F. when the non-ferrous components are bronze or copper respectively. After bonding, the assembly is slowly cooled to below the critical temperature of the steel, is reheated to 1550-1750‹ F. and is again cooled. The shaft may then be tempered. In an embodiment in which crank-pins are joined to cranks and counterweights to complete a crank-shaft, cylindrical connector elements are push-fitted into holes in the cranks &c. to closely surround the pins. Alternatively, the elements may be shrunk on the pins. In another embodiment, cylindrical parts are joined by a cylindrical sleeve element fitting within the parts or by a sleeve element having a radial flange against which the ends of the parts abut. Bolts may be used to hold the parts temporarily together. A further example shows cylindrical crank pins 70, Fig. 11, and bearing parts joined to cranks 72 by means of cylindrical flanged connector elements 74, the former abutting the plain face of the crank while the latter enters a recess 82 in the crank. The element 74 may be provided with nuts which engage similar recesses on the crank. The parts are held together by tubes 88 which have their ends peened over or bolts may be used. Specification 676,345 is referred to.