Microstructural and mechanical study of press hardening of thick boron steel sheet

• Press hardening has become a staple in the production of automotive safetycomponents, due to the combination of high mechanical properties and form complexity itoffers. However, the use of press hardened components has not spread to the truck industrydespite the advantages it confers, namely affordable weight reduction without the use of exoticmaterials, would be extremely attractive for this sector.The main reason for this is that application of press hardened components in trucks impliesadapting the process to the manufacture of thick sheet metal. This introduces an additionallayer of complexity, mainly due to the thermal gradients inside the material resulting inthough-thickness differences in austenitization and cooling, potentially resulting in complexmicrostructure and gradient of mechanical properties.This work presents a preliminary study on the press hardening of thick boron steel sheet.First of all, the evolution of the sheet metal during austenitization is studied by means ofdilatometry tests and by analysing the effect of furnace dwell time on grain size. Afterwards,material cooled using different cooling strategies, and therefore different effective cooling rates, isstudied in terms of microstructure and mechanical properties. Initial results from finite elementsimulation are compared to experimental results, focusing on the phase composition in throughthickness direction.Results show that industrial-equivalent cooling conditions do not lead to gradientmicrostructures, even in extreme scenarios involving asymmetrical cooling.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Teknisk mekanik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Applied Mechanics (hsv//eng)

Nyckelord

Boron steel

Microstructure

Properties

Press Hardening

Thick Sheet Metal

Hållfasthetslära

Solid Mechanics

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