TY - JOUR

T1 - Process Integrated Heat Treatment of a Microalloyed Medium Carbon Steel

T2 - Microstructure and Mechanical Properties

AU - Herbst, Sebastian

AU - Schledorn, Mareike

AU - Maier, Hans Jürgen

AU - Milenin, Andrij

AU - Nürnberger, Florian

N1 - Funding information: The authors thank the German Research Foundation (DFG) for financial support within the Project NU297/2-1 and the Institut für Umformtechnik und Umformmaschinen (IFUM) of the Leibniz Universität Hannover for supplying the material.

PY - 2016/4

Y1 - 2016/4

N2 - Air-water spray cooling was employed during a heat treatment to enhance the mechanical properties of microalloyed medium carbon steel test cylinders (38MnVS6, 88 mm diameter). Using appropriate cooling times and intensities, the test cylinders’ surfaces could be quenched and subsequently self-tempered by the residual heat of the core. Simultaneously, it was possible to keep the core regions of the cylinders in the bainitic regime and carry out a quasi-isothermal holding. The resulting microstructures consisted of tempered martensite (near-surface) and bainite with pearlite and ferrite (core). Compared to the standard heat treatment (controlled air cooling), the tensile properties (proof stress and ultimate tensile strength) could be improved for both near-surface and core regions with the adapted spray cooling. A hardness profile with 450 HV10 surface hardness and a hardening depth of more than 11 mm could be realized. In addition, an increase of the impact toughness for the core was achieved, resulting in approximately 25 J charpy impact energy. This is a substantial improvement compared to standard heat treatment procedure and values reported in the literature and can be attributed to the reduced pearlite volume fraction and the increased amount of fine bainite.

AB - Air-water spray cooling was employed during a heat treatment to enhance the mechanical properties of microalloyed medium carbon steel test cylinders (38MnVS6, 88 mm diameter). Using appropriate cooling times and intensities, the test cylinders’ surfaces could be quenched and subsequently self-tempered by the residual heat of the core. Simultaneously, it was possible to keep the core regions of the cylinders in the bainitic regime and carry out a quasi-isothermal holding. The resulting microstructures consisted of tempered martensite (near-surface) and bainite with pearlite and ferrite (core). Compared to the standard heat treatment (controlled air cooling), the tensile properties (proof stress and ultimate tensile strength) could be improved for both near-surface and core regions with the adapted spray cooling. A hardness profile with 450 HV10 surface hardness and a hardening depth of more than 11 mm could be realized. In addition, an increase of the impact toughness for the core was achieved, resulting in approximately 25 J charpy impact energy. This is a substantial improvement compared to standard heat treatment procedure and values reported in the literature and can be attributed to the reduced pearlite volume fraction and the increased amount of fine bainite.

KW - 38MnVS6

KW - heat treatment

KW - mechanical properties

KW - microstructure

KW - phase transformation

KW - spray cooling

UR - http://www.scopus.com/inward/record.url?scp=84961208873&partnerID=8YFLogxK

U2 - 10.1007/s11665-016-2004-9

DO - 10.1007/s11665-016-2004-9

M3 - Article

AN - SCOPUS:84961208873

VL - 25

SP - 1453

EP - 1462

JO - Journal of Materials Engineering and Performance

JF - Journal of Materials Engineering and Performance

SN - 1059-9495

IS - 4

ER -