Cold roll bonding of tin-coated steel sheets with subsequent heat treatment

One possibility to increase the interface strength of cold roll bonded materials is the application of a thin intermediate layer. In the present study, a tin coating was employed to strengthen the interface formed between cold roll bonded steel sheets, and the impact of subsequent heat treatment on the resulting bonding strength was investigated. To increase the bond strength by diffusion, the tin-coated steel bonds underwent heat post-treatment between temperatures of 150◦ C and 300◦ C for different dwell times. The results demonstrate that the use of tin as an active intermediate layer increases the bond area established. Moreover, the thin tin coating results in the formation of an active intermediate layer that directly takes part in the joining process by establishing a reactive link between the two substrates. A subsequent heat treatment further affects the bond strength by diffusion of tin at the interface. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Phase transformations in a boron-alloyed steel at high heating rates

Products or semi-finished products featuring tailored properties are highly relevant for many industrial applications. Hence, new technologies that allow to locally adapt mechanical properties are of key interest. For example, tailoring properties in profiles or tubes by a local heat-treatment appear to be promising in combination with subsequent forming operations requiring locally adapted material strength to realize complex shapes. To implement an inline process of tube forming and local heat treatment by inductive heating and spray quenching, dilatometric investigations were carried out for a heat treatable boron-alloyed steel 1.5528 (22MnB5). In particular, focus was on the effect of high inductive heating rates on the austenite formation. The influence of heating rates in the range from 500 K/s to 2500 K/s on the austenitization was evaluated and a continuous time-temperature-austenitization diagram proposed. The results can be used to compute the decomposition of ferrite and pearlite due to inductive heating