GB241038A - Improvements in and relating to processes for making composite cutter blades - Google Patents

Abstract

241,038. Simonds Saw & Steel Go., and Davis, A. W. Nov. 18, 1924. Cased or compound forms; tools.-A composite cutter for paper-cutting machine, planers, leather splitters, wood chippers, &c., having a backing of mild steel and a facing of high speed steel, is made by superposing the facing and backing, heating to welding temperature, and then uniting by a single pass through rolls, the rolling being completed substantially within the critical range of temperatures corresponding to the permissible ductility ratios for the union of the metals. A bar 1 of soft steel of thickness greater than the finished cutter may first be provided with a bevelled recess 2. Its upper surface is then sprinkled with flux such as borax and the bar is then heated to 1800‹ F. On withdrawal from the furnace the surface is cleaned, fine chips of steel and borax applied thereto, and a high-speed steel bar 4, preferably with a bevelled edge 5 and of size corresponding to the recess 2, is then placed on the bar 1. The whole is then heated to welding temperature between 2010‹ and 2025‹ F. On withdrawal from the furnace the bar 4 is given a series of light hammer blows to stick the parts together and the whole is then again heated to welding temperature. It is then flattened by a few blows of a drop hammer and again heated to welding temperature. It is then passed quickly between a pair of rolls under heavy pressure so as to weld the parts together and reduce them to size in a single pass into the form shown in Fig. 4 before the temperature drops to 1600‹ F., below which the differences in the ductility of the high speed steel and soft steel due to the decrease in the ductility of the former would cause internal strains and cracks in the high speed steel during rolling. If the bar warps during rolling it is straightened by a flattening hammer. The bar is then heated to 1500‹ F. in an annealing furnace and allowed to cool gradually. It is then cut transversely into a series of blanks which are then preferably heat treated and the edge ground off to produce a cutting edge. In a modification, Fig. 8, the bar 1 may be initially formed with a bevelled shoulder 11 into which the bevelled bar 4 is placed. As a modification of this form, the bar 1 may consist of a flat bar and a bevelled bar welded thereto either before or during the welding of the bar 4 thereto. In a further form the bars may be initially shaped in a manner similar to that shown in Fig. 4. A high speed steel containing the following percentage of non- ferrous ingredients may be used :-Carbon. 0.6 to 0.75, phosphorus 0.02, sulphur 0.02, manganese 0.25, silicon 0.2, chromium 3.5 to 4, vanadium 0.6 to 1 tungsten 18 to 19.5.