Hydroforming High Strength Steel Tube for Automotive Structural Applications Using Expansion

The need for lighter, stronger, more rigid vehicle structures will increasingly require complex hydroformed structural tubes to increase strength, and decrease weight, cost and part count. This effort will increase the use of high strength, low alloy (HSLA) steel, in place of SAE 1006/1008 or 1010 steel. Traditional hydroforming techniques require the higher elongation of the latter materials. An alternative tube hydroforming process has been developed to successfully use these, and HSLA grades from 310 (945XF) to 552 (980XF) MPa minimum yield stress. This paper concentrates on hydroforming steel with a focus on HSLA. It will demonstrate to automotive designers available features such as local section expansion and reduction, hole piercing, achievable cross sectional shapes and the relationship between tube size, corner radii, and wall thickness.