J Mater Sci Technol ›› 2008, Vol. 24 ›› Issue (01): 41-44.

• Research Articles • Previous Articles     Next Articles

Hot-Dip Coating of Lead-free Aluminum on Steel Substrates with Ultrasonic Vibration

Y.Tsunekawa, S.Tamura, M.Okumiya, N.Ishihara   

  1. Toyota Technological Institute, Tempaku, Nagoya 468-8511, Japan
  • Received:2007-09-03 Revised:1900-01-01 Online:2008-01-28 Published:2009-10-10
  • Contact: Y.Tsunekawa

Abstract: Hot-dip coating has been practically employed in manufacturing zinc alloy coated steel sheets. However, it is difficult to coat aluminum alloy on a bulky steel substrate without sufficient preheating, because a rapidly solidified layer containing gas babbles is formed on a substrate surface. A variety of iron-aluminides are also formed at the interface of a steel and aluminum hot-dip coating system, which is the main difficulty in joining of steel with aluminum. Ultrasonic vibration was applied to a steel substrate during hot-dip coating of aluminum alloy to control a rapidly solidified layer and a brittle reaction layer. Hot dipping of columnar steel substrates into molten aluminum alloy (Al-2.7 mass fraction Si-4.6 mass fraction Sn) was carried out through the use of a Langevin oscillator with resonant frequency of 19.5 kHz. The application of ultrasonic vibration is quite effective to control a rapidly solidified layer and a surface oxide layer from a substrate surface by the sonocapillary effect based on a cavitation phenomenon, so that the intimate contact is achieved at the beginning of hot-dip coating. The application of ultrasonic vibration to hot-dipping is effective to control a reaction layer with less than 5 μm in thickness. An impact test exhibits that the good adhesive strength is approved in hot-dipped aluminum coatings with a thin reaction layer of approximately 5 μm.

Key words: Ultrasonic vibration, Cavitation, Sono-Capillary effect, Hot-dip coating