Evaluation of sheet metal covers to improve tool life in forging
Final Report Abstract
The die cover concept is a concept aiming to prolong tool life and decrease tooling costs in closed-die forging processes. The basic idea is to replace the surface of a forging die by an inexpensive and easy-to-exchange sheet metal part: a die cover. The die cover protects the forging die from the high-level thermal and mechanical loads during the process and can be easily exchanged after being worn out. The goal of this project is the development and evaluation of the die cover concept. In the first funding period, the general knowledge that is necessary for the application of the concept was built by studying material selection, boundary conditions such as heat transfer coefficient and friction coefficient and the application on simple twodimensional geometries. The results within this period generally proved that the tool life could be prolonged by applying a die cover, but also revealed the challenge that deformation of the die cover occurred in the experimental validation. This resulted e.g. in not achieving the final geometry of the part if a flat sheet was placed above the die, as wrinkling occurred and the folds of the die cover were imprinted on the part. In the second period of this project, the factors influencing the deformation of die covers were analyzed, such as the friction coefficient on the two contact surfaces between billet, die cover and forging die. Here, to prevent die cover movement, the condition is low friction between the billet and the die cover and large friction between the die cover and the forging die. To additionally prevent deformation and movement of the die cover, different fixation methods were considered and a mechanical fixation by using screws was experimentally investigated. Besides investigating boundary conditions, three application-oriented geometries were proposed and validated in experiments as geometries suitable for applying die covers. The service life of a single die cover made from hardened 22MnB5 was up to 100 forging cycles. The protective effects of the die cover were also proven in regards to temperature and wear by experimental validation, in which the temperature shock was reduced more than 40 % as measured in experiments. The wear of the forging dies was decreased by up to 98% by applying the die cover. In a last step, a two-stage process was investigated to produce tie rod ends from round billets. For 50 and 80 forging cycles, two die covers wear tested and the wear of the dies after the total 130 cycles was investigated by contact measurements. In experiments as well as in simulation, the die cover showed protective effects in terms of temperature shock as well as stresses, especially in the critical areas, i.e. the transition radii. This lead to an overall reduction of die wear by more than 95 % and once again underlines the strong protective effects of die covers. This project proved the feasibility of the die cover concept, identified the boundary conditions suitable for applying die cover, validated six geometries in experiments with die cover and specified the application range of the die cover concept. It proved that the die cover concept is a feasible and effective approach for prolonging tool life in closed-die forging.
Publications
- (2015), First experimental and numerical study on the use of sheet metal die covers for wear protection in closed-die forging, Key Engineering Materials, 651, pp. 266-271
D. Rosenstock, E.T. Segebade, G. Hirt
(See online at https://doi.org/10.4028/www.scientific.net/KEM.651-653.266) - (2017), Estudo da aplicabilidade de máscaras metálicas de DP600 em superfícies de matrizes de forjamento, Revista Ferramental., 66, pp. 27-32
T.M. Ivaniski
- (2017), Forjamento a quente com Máscaras Metálicas como Revestimento Superficial, Revista Ferramental, ed. 71, pp. 27 -33
J. Zottis, L.D.L. de Costa, A.d.S. Rocha, L. Schaeffer
- (2019), Avaliação do Retorno Elástico em Tiras de Aco 22MnB5 estampadas a quente em diferentes temperaturas, Revista Ferramental
C.P. Lisboa, L.D.L. de Costa, R.d.S. Ramalho, L. Schaeffer
- (2019), Desenvolvimento de Ferramental para Ensaio de compressão a quente em discos empilhados. Revista Ferramental
A. Rosiak, L.D.L. de Costa, A.M.G. Brito, L. Schaeffer
- (2019), Experimental evaluation of wear protection ability of sheet metal die covers in closed-die forging, Production Engineering, 13(5), pp. 627-634
Y. Yu, D. Alba, L. Schaeffer, G. Hirt
(See online at https://doi.org/10.1007/s11740-019-00917-z) - (2019), Investigation of applying protective sheet metal die covers for hot forging dies on a cross-forging geometry, The International Journal of Advanced Manufacturing Technology, 102 (1-4), pp. 999-1007
Y. Yu, J. Zottis, M. Wolfgarten, G. Hirt
(See online at https://doi.org/10.1007/s00170-018-03250-4) - (2020), Study of the applicability of 22MnB5 sheet metal as protective masks to improve tool life in hot forging process, The International Journal of Advanced Manufacturing Technology
L.D.L. de Costa, A.M.G. Brito, A. Rosiak, L. Schaeffer
(See online at https://doi.org/10.1007/s00170-020-05010-9)
