TY - JOUR

T1 - Mechanical and Thermal Influences on Microstructural and Mechanical Properties during Process-Integrated Thermomechanically Controlled Forging of Tempering Steel AISI 4140

AU - Behrens, Bernd Arno

AU - Brunotte, Kai

AU - Petersen, Tom

AU - Diefenbach, Julian

N1 - Funding Information: Acknowledgments: The results presented in this paper were obtained within the research project “Im-provement and identification of mechanical properties in forged parts by immediate post-forming after hot forging on different temperature levels by influencing microstructure of tempering steel” (359921546). The authors would like to thank the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG) for the financial and organizational support of this project.

PY - 2020/12/17

Y1 - 2020/12/17

N2 - Thermomechanical treatment (TMT) describes the effect of thermal and mechanical conditions on the microstructure of materials during processing and offers possible integration in the forging process. TMT materials exhibit a fine-grained microstructure, leading to excellent mechanical properties. In this study, a two-step TMT upsetting process with intermediate cooling is used to demonstrate possibilities for a process-integrated treatment and corresponding properties. A water–air-based cooling system was designed to adjust different phase configurations by varying the target temperature and cooling rate. Four different thermal processing routes and four combinations of applied plastic strains are investigated in standardized mechanical tests and metallographic analyses. The applied TMT results in a finely structured bainitic microstructure of the investigated tempering steel AISI 4140 (42CrMo4) with different characteristics depending on the forming conditions. It can be shown that the demands of the standard (DIN EN ISO 683) in a quenched and tempered state can be fulfilled by means of appropriate forming conditions. The yield strength can be enhanced up to 1174 MPa while elongation at break is about 12.6% and absorbed impact energy reaches 58.5 J without additional heat treatment when the material is formed after rapid cooling.

AB - Thermomechanical treatment (TMT) describes the effect of thermal and mechanical conditions on the microstructure of materials during processing and offers possible integration in the forging process. TMT materials exhibit a fine-grained microstructure, leading to excellent mechanical properties. In this study, a two-step TMT upsetting process with intermediate cooling is used to demonstrate possibilities for a process-integrated treatment and corresponding properties. A water–air-based cooling system was designed to adjust different phase configurations by varying the target temperature and cooling rate. Four different thermal processing routes and four combinations of applied plastic strains are investigated in standardized mechanical tests and metallographic analyses. The applied TMT results in a finely structured bainitic microstructure of the investigated tempering steel AISI 4140 (42CrMo4) with different characteristics depending on the forming conditions. It can be shown that the demands of the standard (DIN EN ISO 683) in a quenched and tempered state can be fulfilled by means of appropriate forming conditions. The yield strength can be enhanced up to 1174 MPa while elongation at break is about 12.6% and absorbed impact energy reaches 58.5 J without additional heat treatment when the material is formed after rapid cooling.

KW - Forging

KW - Mechanical properties

KW - Tempering steel

KW - Thermomechanical treatment

UR - http://www.scopus.com/inward/record.url?scp=85098256722&partnerID=8YFLogxK

U2 - 10.3390/ma13245772

DO - 10.3390/ma13245772

M3 - Article

AN - SCOPUS:85098256722

VL - 13

SP - 1

EP - 13

JO - MATERIALS

JF - MATERIALS

SN - 1996-1944

IS - 24

M1 - 5772

ER -