Tensile testing and digital image correlation of 22MnB5 press hardened steel (PHS)

Abstract

Spot welding is a widely used tool for joining sheets parts in the automotive industry. As 22MnB5 steel has the adequate mechanical strength to withstand lateral impact and rollover stresses, it was chosen for the use in B-pillar. It was observed the need to study the spot welded joints, due to the increased need of the automobile industry in reducing the weight vehicle and increasing the passengers' safety in compliance with Resolution of the National Traffic Council of Brazil - CONTRAN n° 751 on the lateral collision test. The microstructure of this steel, in the as fabricated condition, is basically formed by ferrite and perlite, with a tensile strength limit of 600 MPa. This steel is designed to undergo rapid cooling during hot stamping. After this process, this steel presents a completely martensitic microstructure and tensile strength close to 1500 MPa. This work aimed to investigate the strength of spot welded specimens under different experimental conditions, observing the deformations during the tensile tests. The tests were digitally recorded and the sequenced frames were analyzed using a method called digital image correlation (DIC).