Process Window Definition to Predict Mechanical Properties of Press Hardened Parts of Boron Steel with Tailored Properties

Abstract

Tailored Tool Tempering (TTT) is an innovative method able to calibrate the strength and ductility characteristics of the components manufacture by means of Press-Hardening process. The process parameters that most influence the final mechanical properties of the soft zone are quenching time and temperature of the heated tools.In this work, with the aim of defining a process window to estimate the soft zone properties of an automotive B-pillar in Usibor®2000 steel using TTT Press-Hardening approach, the strength and ductility of the soft zone are studied varying the quenching time and the temperature of the heated tools. Using a numerical-experimental approach, a Finite Element (FE) model is firstly developed in AutoForm to simulate the TTT Press-Hardening process and to define thermo-mechanical cycles that are characteristics of the soft zone as a function of quenching parameters (quenching time and temperature of the heated tools). FE thermo-mechanical cycles are then physically simulated on Usibor®2000 specimens using Gleeble 3180 system. The treated specimens are subsequently subjected to micro-hardness and tensile tests. Experimental results are adopted to train an artificial neural network used to construct the process window.

Effect of heat treatment on microstructure and properties of 10B21 cold-heading steel for fasteners

“…The alloying elements can improve the hardenability of steel mainly because they prevent the transformation of austenite into proeutectoid ferrite, pearlite or upper bainite during quenching. Dong et al [7,[11][12] explored Trace B is isolated at the boundary, occupies the appropriate nucleation position in advance, reduces the austenite grain boundary energy, inhibits the ferrite nucleation and delays the ferrite formation. At the same time, the boron atom on the grain boundary also blocks the diffusion of the grain boundary atom, and slows down the ferrite nucleation on the grain boundary, thus improving the thermoplasticity of the material.…”