GB629627A - Improved method of forming metal into shaped articles - Google Patents

Abstract

629,627. Forging-machines; dies. SALES, W. A. Feb. 14, 1947, No. 4372. [Class 83 (iv)] Making turbine blades.-Metal is forged in a die of refractory ceramic material by subjecting it to a relatively steady pressure while it or part of it is at a temperature at which it is in a plastic state. The dies may be formed from clays, silica, magnesite, dolomite, alumina, chromites, and in particular berrylia, zirconia, thoria, sillimanite and boron. In one form a die 11, 1<SP>11</SP>, split on a horizontal plane, is carried in steel covers 3<SP>1</SP>, 3<SP>11</SP> and mounted in a press, the upper cover 3<SP>1</SP> and die half 1<SP>1</SP> being vertically movable by the ram 2 of the press. A bar or partly preformed slug 4 extends through the die 1<SP>1</SP>, 1<SP>11</SP> and is held at each end by a split electrode 9, normally held closed by compression springs 10. In operation the upper die and electrode halves 1<SP>1</SP>, 9, are raised by the ram 2 and the work-piece 4 placed on the lower electrode halves, which are raised proud of the lower die half 1<SP>11</SP> by the springs 10, the upper die half 1<SP>1</SP> is lowered until the upper electrode halves grip the bar and electric current is switched on to heat the bar to a plastic state. The die-halves 1<SP>1</SP>, 1<SP>11</SP> are then brought firmly together and endwise pressure applied at each end, preferably by hydraulic rams, until the metal within the die upsets to fill cavities 8. Some preliminary forming may take place when the die-halves are brought together. In a modification, Figs. 3 and 4, (not shown), described as applied to the manufacture of turbine blades, the metal is forced into the die cavity by pressure applied to the upper die half, surplus metal being squeezed out and into a gap between the die halves, forming a flash which is subsequently removed. The current may be switched on and off during forming to control the temperature, and heating may be effected by either highfrequency induction or resistance heating, or a combination of both. The process may be performed under controlled atmosphere conditions to prevent scaling. In a modification, pre-heated bars or slugs may be used without recourse to electric heating to maintain the temperature.