Metal fibres filter, reinforce and quieten
1 min read
There are various occasions when it is useful to be able to turn metals into a fibrous form, whether to act as a high temperature fibre reinforcement, filtration medium or sound absorber.
Problem: Solution: Fibretech, based in Pinxton, Nottinghamshire, has a unique process which they call Melt Overflow, which they invented in 1984 but which continues to be developed. Metal is melted in an open vessel with a prominent lip. A plunger advances into the melt, until it displays a meniscus at the over flow point. A large water cooled drum, spinning counter to the potentially overflowing melt is advanced until it makes contact with the meniscus. Rapid air cooling takes place, typically at rates of around 50,000 deg K/s, and now solid fibres fly free from the drum in a similar manner to candy floss. The filaments have a kidney shaped cross section. If the drum is machine turned, it produces long fibres, but if it is grooved, it can be made to produce short filaments. Applications: Lee Marston, director of product development at Fibretech tells us that the company can make filaments out or stainless steel, fecralloys (iron-chromium-aluminium), aluminium and brass. Used to reinforce refractories, stainless steel and fecralloys extend working lives considerably. The different metal and alloy fibres improve heat removal from and durability of brake pads, as an alternative to copper, graded brass swarf, carbon steel or asbestos. They also find service as acoustic absorption and catalyst materials in automotive exhaust systems. Fibretech is working with Professor Bill Clyne in the Department of Materials Science and Metallurgy at the University of Cambridge on the joining and sintering of these materials, with a view to reducing the cost of the stainless steel sandwich materials described in our September 2001 notebook article, "Steel makes lightweight fibre sandwich." TS Fibretech Email Lee Marston