Effect of Different Intercritical Annealing Treatments without and with Overaging on the Mechanical Material Behavior

• Published in: Steel research international Vol. 89; no. 10
• Main Authors: Wolf, Lars Oliver, Cordebois, Jean‐Pierre, Rodman, Dmytro, Nürnberger, Florian, Maier, Hans Jürgen
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.10.2018
• Subjects: Automotive bodies; Boron steels; Elastic limit; Energy absorption; Ferritic stainless steels; Heat treatment; low‐alloyed steel (22MnB5); Manganese; Martensitic stainless steels; Material properties; Mathematical models; mechanical characterization; microscopy; Microstructure; Multiphase; optical metallography; Overaging; partial martensitic steel; Tensile tests; Yield stress
• ISSN: 1611-3683; 1869-344X
• DOI: 10.1002/srin.201800196

In the last decade, press‐hardening of manganese‐boron steels for the manufacturing of safety‐relevant components has become a well‐established industrial process. Thereby, very high strengths are achieved with pure martensitic microstructures. However, in certain areas of the car body structure more ductile components are necessary to absorb crash energy. For tailoring the material properties, two‐ or multiphase microstructures can be induced by rolling and heat treatment processes. The press‐hardening steel 22MnB5 which is employed in the present study, is used to manufacture three different ferritic‐martensitic microstructures. These different materials are characterized by classical mechanical models, based on experimental results. For the mechanical description of the initial yield stress depending on the stress state of different multiphase steels, the Hill model is calibrated. The elastic limit and the kinematic hardening of three various heat treatment conditions are determined using conventional tensile tests and the Galimel test, respectively. Therefore, the applied mathematical relations are derived and adapted for the performed investigations. The relationship between the load conditions and the proper application of the equations are explained. The resulting microstructures are characterized and the ramifications with respect to their energy absorption capability are discussed. The press‐hardening steel 22MnB5 is used to manufacture different ferritic‐martensitic microstructures. These materials are characterized by classical mechanical models, based on experimental results. For the mechanical description of the initial yield stress, the Hill model is calibrated. The elastic limit and the kinematic hardening of various heat treatment conditions are determined using conventional tensile tests and the Galimel test.