High-performance tungsten-based materials make casting processes more cost-effective and improve quality
With the Triamet A product series, Bayerische Metallwerke GmbH offers various tungsten-based alloys that can avoid these problems. Tools made of Triamet A are highly resistant to liquid aluminium and magnesium. This can increase the service life by 10 to 500 times compared to conventional materials, depending on the field of application and the type of casting process. The negligibly small alloy formation tendency and the formation of a natural separating layer counteract sticking of the work piece to the casting mould, which has a positive impact on product quality as well.
Low thermal expansion coefficient prevents fire cracks
Fire cracks in casting moulds are caused mainly by thermal fatigue due to alternating compressive and tensile stress on the tools. The lower the thermal conductivity and the higher the thermal expansion coefficient of a material, the greater this stress will be. Compared to the commonly used steel, the thermal conductivity of Triamet A at 70 to 105 W/mK is about 3 to 5 times higher while the thermal expansion coefficient at 5.2-6.5 [10-6 K-1] is simultaneously only about 50 percent. This greatly reduces stresses in the tool. The high resistance to temperature changes significantly reduces the fire cracking tendency and therefore greatly increases the service life.
Sintering process at 1,500 °C thanks to nickel and iron binder phase
Bayerische Metallwerke GmbH uses a nickel and iron binder phase for the production of Triamet A, added to the tungsten powder at the rate of two to ten percent. Nickel acts as a catalyst that accelerates diffusion processes on the surface of the tungsten power and thereby reduces the sintering temperature by about 1,000 °C. Subsequently the Triamet green parts are sintered at about 1,500 °C – in contrast to the 2,500 °C required for pure tungsten – so that a unique microstructure with a spherical tungsten phase encased by the binder phase is formed. All Triamet A series products set themselves apart with a very high density from 17.0 ± 0.15 g/cm3 for Triamet A17 to about 18.8 ± 0.2g/cm3 for A19.