Study of the Diffusible Hydrogen in Aluminized Boron Steel
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The proportion of high strength steels in modern cars increases continuously. In this framework, boron steel with Al-Si coating experiences a rapid growth in anti-intrusion applications thanks to its superior mechanical properties. However, such very hard microstructures can be sensitive to delayed fracture. Diffusible hydrogen is then the key parameter to control for safety improvement. In this paper, we study the parameters governing absorption and desorption of diffusible hydrogen in aluminized boron steel. We demonstrate that the dew point and the austenitizing holding time have a large influence on the diffusible hydrogen content. Simultaneously, four-point bending test was used to determine acceptable limits of diffusible hydrogen and to propose delayed fracture maps, aiming to determine safe process areas.