Improvement on Formability of Galvannealed Steel Sheets with Fe rich-Zn Alloy Electrocoated Uppermost Layer

This report describes a study of 2-layer galvannealed steel sheets with an Fe rich-Zn alloy electrocoated layer (E-layer) on both sides from the viewpoint of formability improvement.

As a result of this study the following effects were confirmed.

1. 1)
   The lubricity of the galvannealed sheets is improved by applying E-layer at a coating weight of about 3g/m² on both sides.
2. 2)
   The lubricity of the E-layer is good even when low viscosity lubricant is used, and the lubricating effect of the E-layer is equal or superior to that of solid lubricant.
3. 3)
   The available range of forming widens even in parts difficult to form, and the sheets permit stable stamping.
4. 4)
   The exfoliation of the coating layer can be decreased even under high contact pressure conditions.

This paper further refers to the mechanism of improving lubricity and the mechanism of decreasing coating exfoliation.