The effect of surface layer properties on bendability of ultra-high strength steel

Bendability is an important property for ultra-high strength steel because air-bending is the most common forming process for the material. In this paper the bendability of two ultra-high strength steels with similar mechanical properties but different bendability was investigated using tensile testing with optical strain measurements. The tensile tests were conducted also for specimens cut from the surface layer and the middle layer of the sheet. It was discovered that the mechanical properties of the surface of the sheet affect the bendability in great manner.