| A new type,
hot-dip galvanized steel sheet (GI) with excellent
press formability, weldability, and surface
appearance was developed for automotive outer
panels. The sliding characteristics of GI
in press forming were improved by optimizing
surface roughness by texture control in skinpass
rolling and use of a high-lubricity anti-rust
oil, while spot welding electrode life was
extended by selecting a suitable substrate
chemistry. Many process improvements were
also adopted to improve the surface quality
of GI for use of automotive outer panels.
They included adjustment of wiping conditions
to prevent bath wrinkle pattern, adoption
of an exclusive bath for GI with an appropriate
Al content to prevent dross adherence, and
control of the cooling rate after galvanizing
to produce a stable minimum spangle coating.
The developed GI is now in commercial production. |
