Material Properties of a Roll-Cladded Steel Composite Designed for Press Hardening With Rapid Heating

Abstract The characterization of the forming properties at elevated temperatures of a roll cladded steel composite material is presented. The composite consists of two layers of austenitic stainless steel (X5CrNi18-10 at the top and bottom side) and a boronmanganese steel (22MnB5 as the middle layer). This material enables more efficient and faster heating strategies for press hardening applications, which is not possible with the conventionally coated 22MnB5 due to the necessary time-intense diffusion phase. Previously, the manufacturability of these sheets in terms of bond formation has been demonstrated [1]. This works continues the investigations by analyzing the flow behavior under process-near conditions. Two different heating strategies, rapid heating (austenitization temperature Tγ = 1050 °C, heating rate rh = 50 °C/s, dwell time tγ = 5 s ) and slow heating (austenitization temperature Tγ = 950 °C, heating rate rh = 5 °C/s, dwell time tγ = 180 s ) are employed before forming the specimen to failure. The behavior of the base materials and composite are tested separately. The composite flow stress is lower than the higher-strength austenitic stainless steel and higher than the lower-strength 22MnB5 at all temperatures tested. In addition, the influence of different ratios between the outer and middle layers is investigated and compared with analytical predictions [1], whereby the composite strength can be calculated with an accuracy of 10%. To assess general useability of the material in actual press hardening conditions, a hat profile as a demonstrator is manufactured. Hardness values > 470 HV and flow stresses in line with predictions from the layer thickness ratio confirm the suitability and adjustability of the material for press hardening.