During the hot stamping process a blank is first heated up 900 °C for 6 min 30 s. Then, the blank is transferred to the press where it is hot stamped. During the transfer, the blank is slowly cooled down by convection and radiation with the ambient air and metallurgical transformations can occur and modify the mechanical properties after hot stamping. Using samples with welded thermocouples, a method is presented to estimate the kinetic of the metallurgical transformations. The results are compared with the metallurgical analysis of samples that are quenched in the water after different transfer times. The influence of the thickness of the blank is also investigated. It is highlighted that using different thicknesses leads to different cooling rates and different resulting microstructures. The influence of the transfer time on the mechanical properties after hot stamping is highlighted with hardness measurements and tensile tests. Finally, a coupled heat transfer/metallurgical model is built to simulate the kinetic of the transformations and a diagram can be plotted that presents the evolution of the metallurgy as a function of the thickness and the transfer time. These results show the high importance of the transfer time from the furnace to the press and a tool is proposed to help the engineers to define a process window.

References

References
1.
Neugebauer
,
R.
,
Schieck
,
F.
,
Polster
,
S.
,
Mosel
,
A.
,
Rautenstrauch
,
A.
,
Schönherr
,
J.
, and
Pierschel
,
N.
,
2012
, “
Press Hardening—An Innovative and Challenging Technology
,”
Arch. Civ. Mech. Eng.
,
12
(
2
), pp.
113
118
.10.1016/j.acme.2012.04.013
2.
Karbasian
,
H. H.
, and
Tekkaya
,
A.
,
2010
, “
A Review on Hot Stamping
,”
J. Mater. Process. Technol.
,
210
(
15
), pp.
2103
2118
.10.1016/j.jmatprotec.2010.07.019
3.
Naderi
,
M.
,
2007
, “
Hot Stamping of Ultra High Strength Steels
,” Ph.D. thesis,
RWTH Aachen University, Aachen, Germany
.
4.
Grigorieva
,
R.
,
Drillet
,
P.
,
Mataigne
,
J.
, and
Barges
,
P.
,
2011
, “
Study of Phase Transformations in Al-Si Coating During the Austenitization Step
,” 8th Intl' Conference on Zinc and Zinc Alloy Coated Steel Sheet, Galvatech 2011, Genova, Italy, June 21–24.
5.
Blaise
,
A.
,
Abdulhay
,
B.
,
Bourouga
,
B.
, and
Dessain
,
C.
,
2012
, “
Latent Heat Estimation of the Martensite Transformation Through Inverse Methods During Hot Stamping Process
,”
ASME
11th Biennial Conference on Engineering Systems Design and Analysis
, Nantes, France, July 2–4, pp.
741
747
. 10.1115/ESDA2012-82969
6.
Blaise
,
A.
,
Bourouga
,
B.
,
Abdulhay
,
B.
, and
Dessain
,
C.
,
2013
, “
Thermal Contact Resistance Estimation and Metallurgical Transformation Identification During the Hot Stamping
,”
Appl. Therm. Eng.
,
61
(
2
), pp.
141
148
.10.1016/j.applthermaleng.2013.07.041
7.
Bardelcik
,
A.
,
Worswick
,
M. J.
,
Winkler
,
S.
, and
Wells
,
M. A.
,
2012
, “
A Strain Rate Sensitive Constitutive Model for Quenched Boron Steel With Tailored Properties
,”
Int. J. Impact Eng.
,
50
, pp.
49
62
.10.1016/j.ijimpeng.2012.06.007
8.
Blaise
,
A.
,
Bourouga
,
B.
, and
Dessain
,
C.
,
2012
, “
Metallurgical Model Fitted to Experimental Data Using a Genetic Algorithm
,”
Key Eng. Mater.
,
504–506
, pp.
1079
1084
.10.4028/www.scientific.net/KEM.504-506.1079
9.
McAdams
,
W. H.
,
1954
,
Heat Transmission
,
3rd ed.
,
McGraw-Hill
,
New York
.
10.
Levenberg
,
K.
,
1944
, “
A Method for the Solution of Certain Problems in Least
,”
Q. Appl. Math.
,
2
, pp.
164
168
.
11.
Marquardt
,
D.
,
1963
, “
An Algorithm for Least-Squares Estimation of Nonlinear
,”
SIAM J. Appl. Math.
,
11
(2)
, pp.
431
441
.10.1137/0111030
12.
Avrami
,
M.
,
1941
, “
Kinetics of Phase Change. III. Granulation, Phase Change, and Microstructure
,”
J. Chem. Phys.
,
9
, pp.
177
184
.10.1063/1.1750872
13.
Fernandes
,
F.
,
1985
, “
Modélisation et Calcul de l’évolution de la Temperature et de la Microstructure au Cours du Refroidissement des Aciers
,” Nancy.
You do not currently have access to this content.