ALLOY ELECTROPLATED STEEL SHEET HAVING SUPERIOR CHIPPING RESISTANCE AT LOW TEMPERATURE

摘要

PURPOSE:To improve chipping resistance at low temp. by forming recesses of a specified depth and shape in the surface of a steel sheet and forming a Zn alloy film by electroplating. CONSTITUTION:The surface of a cold rolled steel sheet is temper-rolled to irregularly or regularly form recesses of 1-10mum depth in the surface of the steel sheet at =5% space factor to the total surface area. The peripheral walls of the recesses make =60 deg. angle to a perpendicular plane of the steel sheet. The surface of the steel sheet is then electroplated with a Zn alloy such as Zn-Ni. The electroplated steel sheet has superior chipping resistance at low temp., undergoes no deterioration of the press formability and is suitable for use as a steel sheet for the exterior coated steel sheet of an automobile body.