| 摘要 |
A surface-treated steel sheet comprising a galvanized steel sheet provided on its surface with a rustproof coating so as to exhibit a contact angle of lubricant of 51 to 69 mm2/s kinematic viscosity at 40°C and 11.1 to 14.9 mm2/s kinematic viscosity at 100°C of 10° or greater on at least the surface (A) of the rustproof coating applied to one major surface side of the steel sheet (providing that the contact angle is one exhibited at a steel sheet surface temperature of 30°C 30 seconds later than the formation of lubricant droplet on the surface of the rustproof coating). Preferably, on the surface-treated steel sheet, the contact angle of the lubricant on the rustproof coating surface (A) after plastic working of the surface-treated steel sheet at a draw ratio of 20% is 10° or greater. Still preferably, on the rustproof coating surface (A) and the rustproof coating surface (A) after plastic working of the surface-treated steel sheet at a draw ratio of 20%, the cracking density is 200 cracks or less per 100 µm. This surface-treated steel sheet excels in oil wet spread resistance, and in parts equipped with a bearing holder part, would ensure effective inhibition of lubricant ooze-out such as to cause lubricant shortage at the bearing part. |
