TY - GEN

T1 - Manufacturing Of High-Performance Forging Dies By Ausforming

AU - Behrens, Bernd Arno

AU - Brunotte, Kai

AU - Till, Michael

N1 - Funding Information: The results presented were obtained in the research project „Development and Investigation of Mechanical Properties of Hot Forging Dies by Bulk Forming and Thermomechanical Treatment” financed under project number 318628894 by the German Research Foundation (DFG). The authors would like to thank the DFG for financial support.

PY - 2020/7/27

Y1 - 2020/7/27

N2 - During forging, dies are subject to a complex load collective caused by combined thermally and mechanically induced stresses. Crack formation and deformation on tool surfaces, as a result of low fatigue resistance, lead to tool failure and high process costs. Grain refinement is regarded as a method to improve fatigue resistance due to enhanced ductile material properties. To generate a fine-grained microstructure in the die material, increased deformation can be applied in the metastable austenite phase, also known as ausforming. In this study, the thermo-mechanical treatment ausforming will be used to form the final contour of forging dies. For this purpose, an analogy study was performed in which a preform is ausformed. It is investigated to what extent a fine-grained microstructure can be achieved in the final forming stage. The hot-working steel X37CrMoV5-1 (AISI H11) was used as specimen material. The developed sample geometry represents the inner contour of a highly mechanically loaded forging die. To achieve optimal properties, process routes with different cooling strategies and two defined true plastic strains were examined in metallographic analysis and hardness measurements according to EN ISO 6507-1 (HV1). It is shown that, after complete austenitisation, the highest hardness values can be achieved by applying a water-air spray cooling with subsequent forming. This could be demonstrated without material failure in the samples even with a high true plastic strain.

AB - During forging, dies are subject to a complex load collective caused by combined thermally and mechanically induced stresses. Crack formation and deformation on tool surfaces, as a result of low fatigue resistance, lead to tool failure and high process costs. Grain refinement is regarded as a method to improve fatigue resistance due to enhanced ductile material properties. To generate a fine-grained microstructure in the die material, increased deformation can be applied in the metastable austenite phase, also known as ausforming. In this study, the thermo-mechanical treatment ausforming will be used to form the final contour of forging dies. For this purpose, an analogy study was performed in which a preform is ausformed. It is investigated to what extent a fine-grained microstructure can be achieved in the final forming stage. The hot-working steel X37CrMoV5-1 (AISI H11) was used as specimen material. The developed sample geometry represents the inner contour of a highly mechanically loaded forging die. To achieve optimal properties, process routes with different cooling strategies and two defined true plastic strains were examined in metallographic analysis and hardness measurements according to EN ISO 6507-1 (HV1). It is shown that, after complete austenitisation, the highest hardness values can be achieved by applying a water-air spray cooling with subsequent forming. This could be demonstrated without material failure in the samples even with a high true plastic strain.

KW - Ausforming

KW - Cooling rate

KW - Metastable austenite

KW - True plastic strain

UR - http://www.scopus.com/inward/record.url?scp=85096764092&partnerID=8YFLogxK

U2 - 10.37904/metal.2020.3471

DO - 10.37904/metal.2020.3471

M3 - Conference contribution

AN - SCOPUS:85096764092

SP - 203

EP - 208

BT - Proceedings 29th International Conference on Metallurgy and Materials

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

Y2 - 20 May 2020 through 22 May 2020

ER -