GB949979A - Method and apparatus for joining or welding materials - Google Patents

Abstract

<PICT:0949979/C1/1> <PICT:0949979/C1/2> Workpieces are bonded with inter-diffusion of their atoms or molecules by pressing together at 0.4-2 kg. per sq. mm. in a vacuum of at least 10-2 mm. Hg. The workpieces are heated during bonding to a temperature greater than <PICT:0949979/C1/3> <PICT:0949979/C1/4> the recrystallization temperature of one or more of the workpieces. Workpiece materials specified are steel, cast iron, copper, tungsten, aluminium, non-ferrous alloys, rare earth metals, beryllium, tellurium, uranium, platinum and their alloys, metallic-ceramics and ceramics. The working temperatures may be up to 1000 DEG C. The workpieces are mounted in a fixture and heated by an induction heating coil in a vacuum chamber, Fig. 1, having a water-cooled upper part screened from the work-pieces. The vacuum is created by hot oil diffusion and backing pumps 3, 2, and an hydraulic system operates push rods 9 applying the pressure to the workpieces and arms 11 for lifting the chamber 1. In a modification, four vacuum chambers 13, Fig. 3, are mounted as a common assembly rotatable on a pedestal to facilitate servicing. Each is provided with an hydraulic pressure-applying device, an air inlet valve 15, an induction heater 16 and a valve-controlled connection to a common receiver 18 evacuated by the pumps 3, 2. The bonding is automatically controlled in a sequence of four operations, viz. unloading and loading temperature raising at a vacuum of up to 10-3 mm. Hg, bonding at up to 10-5 mm. Hg and cooling. In another modification, five vacuum chambers 13, Fig. 4, and an hydraulic system for producing the bonding pressure are mounted on a rotary valve disc 28 co-operating with and supported by a fixed valve disc 27 having connections at the appropriate stations to the atmosphere and to vacuum pumps 3, 2. The chambers 13 are each provided with induction heaters 31. The chambers 13 are indexed to five stations at which a sequence of operations similar above but with the addition of an intermediate high vacuum station enabling a higher vacuum of up to 10-9 mm. Hg at the bonding station. In a further modification a machine has a single transparent vacuum chamber 34, Fig. 5, in which is a fixed electrode 35. The work is sandwiched between the electrode 35 and a movable cooled electrode 32 on an hydraulic ram 8. Heating is derived from contact resistance by passing A.C. between the electrodes.