An ultra high-strength steel which plays a vital role in the automotive industry is boron steel. Anti-intrusion systems and structural components are manufactured with boron steel since it allows them to create lighter cars which are strong, high strength and increase safety of passengers.
Several welds are made on a car and the most common method is that of spot welding. It causes exposure of the boron steel to high temperatures which cause the metal to rise above their melting point temperatures. These solidify soon on cooling. Microstructures are changed amd surrounding metal contracts.
However this method on boron steel leads to reduction in strength and thereby its lifetime. ILL, Tata Steel , WMG at the university of Warwick and the Engineering and Physical Science Research Council (EPSRC) performed a study to find the correlation between boron steel hardness and residual stress. The boron steel sheets were provided by Tata Steel, experiments were carried out by WMG researchers at the ILL’s SALSA (Stress Analyser for Large-Scale Applications) beamline. Owing to the fine resolution that neutron diffraction provides and its ability to penetrate through heavy metals like boron steel it was chosen as the method for measuring residual stress. The same welds were used to measure the hardness distribution.
Reduced hardness in heat-affected zones of boron steel spot welds and increased residual stress have a strong correlation between them. This was found out for the first time from this study. Magnetic pulse welding and post-welding heat methods will be looked into by evading these issues with boron steel and reduced hardness. Avoiding the usage of heat and the fact that magnetic pulse welding does not cause a heat-affected zone is what brings this technique into consideration. The other method causes a reversal in the reduction of hardness due to spot welding process. This will be of prominent importance in farming and automotive industries. Also for those who use destructive simulations in their own work and materials developers would find them pretty useful.