TY - GEN

T1 - Porosity in hot formed cast steel

AU - Behrens, Bernd Arno

AU - Ursinus, Jonathan

AU - Büdenbender, Christoph

AU - Brunotte, Kai

AU - Nürnberger, Florian

AU - Demler, Eugen

AU - Maier, Hans Jürgen

N1 - Funding Information: The present results were obtained in the research project “Precision Forging of Cast Preforms”, Project number 351032371. The authors thank the German Research Foundation (DFG) for the financial support.

PY - 2020

Y1 - 2020

N2 - In order to reduce the number of process steps of steel forging processes. and thus also tool wear and process costs, tailored preform geometries can be produced by casting. By only one subsequent forming operation it is possible to improve the casting microstructure, eliminate possible defects and achieve the required mechanical properties. To evaluate the properties of the cast microstructure and the closure of possible casting defects during warm/hot forming, cylindrical steel billets (C45/1.0503) were produced by sand casting and then upset in a hydraulic press. Global plastic strain f was varied between 0.3 and 0.7 while forging temperatures of 600 °C and 1,200 °C were applied to detect possible temperature effects. Conventional rolled bar material formed under the same conditions was used as a reference. After forming, the specimens were tempered and the mechanical properties were determined by tensile tests (ISO 6892-1) and notch impact tests (similar to ISO 148-1). The microstructures were examined by metallographic analysis while defects were characterised using an optical wide-area 3D measurement system and digital image processing. It could be observed that the ultimate tensile strength of the cast-forged specimens depends on the forming temperature and is about 15 % lower in comparison to the reference material at a forming temperature of 600 °C and 5 % lower at 1,200 °C, respectively. The impact energies show a strong dependence on plastic strain for both, the cast-forged and reference specimens. The values of the mechanical properties of the reference specimens were higher than those of the cast-forged specimens. These results allow a deeper understanding of the cast-forging of steel and will contribute to the cast-forging design of more complex steel parts.

AB - In order to reduce the number of process steps of steel forging processes. and thus also tool wear and process costs, tailored preform geometries can be produced by casting. By only one subsequent forming operation it is possible to improve the casting microstructure, eliminate possible defects and achieve the required mechanical properties. To evaluate the properties of the cast microstructure and the closure of possible casting defects during warm/hot forming, cylindrical steel billets (C45/1.0503) were produced by sand casting and then upset in a hydraulic press. Global plastic strain f was varied between 0.3 and 0.7 while forging temperatures of 600 °C and 1,200 °C were applied to detect possible temperature effects. Conventional rolled bar material formed under the same conditions was used as a reference. After forming, the specimens were tempered and the mechanical properties were determined by tensile tests (ISO 6892-1) and notch impact tests (similar to ISO 148-1). The microstructures were examined by metallographic analysis while defects were characterised using an optical wide-area 3D measurement system and digital image processing. It could be observed that the ultimate tensile strength of the cast-forged specimens depends on the forming temperature and is about 15 % lower in comparison to the reference material at a forming temperature of 600 °C and 5 % lower at 1,200 °C, respectively. The impact energies show a strong dependence on plastic strain for both, the cast-forged and reference specimens. The values of the mechanical properties of the reference specimens were higher than those of the cast-forged specimens. These results allow a deeper understanding of the cast-forging of steel and will contribute to the cast-forging design of more complex steel parts.

KW - Cast-forging

KW - Mechanical properties

KW - Porosity

KW - Steel

UR - http://www.scopus.com/inward/record.url?scp=85096793637&partnerID=8YFLogxK

U2 - 10.37904/metal.2020.3480

DO - 10.37904/metal.2020.3480

M3 - Conference contribution

AN - SCOPUS:85096793637

T3 - International Conference on Metallurgy and Materials, Conference Proceedings

SP - 283

EP - 288

BT - METAL 2020 - 29th International Conference on Metallurgy and Materials, Conference Proceedings

T2 - 29th International Conference on Metallurgy and Materials, METAL 2020

Y2 - 20 May 2020 through 22 May 2020

ER -