Ultra-high-strength steels are used in the automobile industry primarily for bumper beam and door beam applications. Over the past few years, the industry has begun demanding economical sacrificial corrosion protection for these components, especially for bumper beams. The need for this type of protection has arisen out of two major factors; first, consumers are demanding an ever greater degree of corrosion protection in the cars they buy; and second, collision sensors located inside the bumper beam (for triggering air bags) preclude the use of effective electro-coat protection.
In response to this challenge, we have developed a new product, hot-dip galvanized ultra-high-strength sheet steel. This product provides a high degree of corrosion protection at a tensile strength as high as 1200 MPa. A patent application has been filed for this new product. For this product, the ultra-high-strength steel is made at Inland's No. 3 CAL, and the coil is hot-dip galvanized at an outside toll-coater.
The feasibility of electrogalvanizing of ultra-high strength steel coils has also been demonstrated. This approach must be used in place of hot-dip galvanizing when tensile strength levels in excess of 1200 MPa are required.