Ga1lvannealed steel sheets (GA) have been used in large quantities especially for automobiles. The surface friction is one of the most important characteristics which influences the press formability of GA. Recently many surface modifications of GA have been developed to improve press formability. We developed a Ni-base inorganic lubricant film as a means to improve press formability of GA, and the new galvannealed product, "PZA-N", to meet the needs of the automotive industry for a low cost sheet with improved press formability. The "PZA-N" is comprised of GA coated with the Ni-base inorganic lubricant film(3). NKK started production of "PZA-N" for commercial applications in 1996, and "PZA-N" has a good reputation from our customers. Research has been done on the influence of the surface modification coating mentioned above on press formability of GA. This paper describes the effect of surface modification on coefficient of friction of GA. The coefficient of friction was measured on GA with Fe, Ni, Zn electroplated coatings. The mechanisms used in improving the lubricity of GA by the surface modifications are also discussed.
展开▼
