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The programme, filmed on location at two light bulb manufacturers, Lamp Metals in Gateshead and Osram Lamps in Wembley, examines the metallurgy and the processes by which tungsten powder is manufac...tured into filaments for electric light bulbs.
Metadata describing this Open University video programme
Module code and title: T352, Materials processing
Item code: T352; 13
First transmission date: 28-08-1979
Published: 1979
Rights Statement:
Restrictions on use:
Duration: 00:24:00
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Producer: Colin Robinson
Contributors: Tony Leach; Mike Wise
Publisher: BBC Open University
Keyword(s): Doping; Ductility; Filament; Heat treatment; Industry; Lamps; Powder metallurgy; Sintering; Tungsten; Wire drawing
Footage description: Film of light bulbs on a conveyor belt during manufacture. Commentary by Mike Wise introduces the programme. Mike Wise and Tony Leach, technical manager at Lamp Metals, explain the first stage in the production of light bulb filaments, that of compacting tungsten powder into a bar. Film of the powder being compacted under great pressure while they talk. Wise and Leach go on to explain the process of sintering by which the porous tungsten bar produced above is made more dense by solid state diffusion at high temperature. Film of this process. Film of the sintered bar undergoing further treatment, this time by hot rolling, to reduce porosity further. Micrographs before and after hot rolling illustrate the porosity of the metal. Commentary by Mike Wise. Tony Leach breaks a tungsten bar after hot rolling to demonstrate that it is still very brittle. In order to discover how the tungsten bar can be made more ductile, Mike Wise examines an animated graph which plots fracture energy at various temperatures. He points out the ductile brittle transition temperature at which the tungsten will be tough and exhibit typically ductile behaviour. Film of the swaging process in which the tungsten bar is rolled down to a size suitable for wire drawing at the ductile brittle transition temperature. Commentary by Mike West. Film of wire being drawn and coiled from the tungsten bar. Commentary by Wise explains the process. An animated diagram with commentary by Mike Wise and Tony Leach explains why the ductile brittle transition temperature is lowered considerably during the wire drawing operation. Film of a fine tungsten wire being coiled for use as a lamp filament. Commentary by Wise. An animated graph shows the process of creep due to grain boundary sliding in the tungsten filament. Mike Wise lists one traditional metallurgical methods for preventing creep. Wise goes on to explain another method, that of doping the tungsten with silicon, aluminium and potassium to prevent creep. An animated diagram illustrates how this doping works to prevent creep. Film of light bulbs on the assembly line.
Master spool number: 6HT/72627
Production number: 00525_5337
Videofinder number: 1440
Available to public: no