Numerical process design for hot forging of steel encased titanium workpieces
Janina Siring, Donik Brahimi, Jytte Möckelmann, Hendrik Wester, Johanna Uhe, Bernd-Arno Behrens
Abstract. This paper presents the numerical design of a hot forging process for titanium Ti-6Al-4V. A steel-encasing made of AISI 316L is used to enclose the titanium and protect it from the surrounding gases and excessive cooling. Oxidation by the ambient gases can lead to a reduction in the mechanical properties of the titanium in the near surface regions. At the same time, costs and resources can be saved, as time-consuming reworking of the titanium and therefore the amount of reworking required can be reduced. Finite element simulation was carried out for efficient process design. For a realistic depiction of the process the coefficient of thermal expansion as well as the flow curves were determined in experimental tests. A numerical parameter study was carried out by varying process boundary conditions such as the starting temperature of the billet, the ram velocity and the thickness of the steel-encasing. The numerical results indicate that a steel-encasing of two millimetres at the top area of the billet, compared to four millimetres, is not recommended for the process due to a fracture in the steel-encasing. Overall, it was revealed that an increasing billet temperature results in a higher final temperature in the titanium and greater local thinning of the steel. The same tendency was also determined with increasing ram velocity. For the variants investigated here, the combination of a billet temperature of 1,100 °C and a medium ram velocity of 20-40 mm/s with a thickness of four millimetres of the steel-encasing at the top is recommended.
Keywords
Titanium, Steel, Hot Forging, Material Characterisation
Published online 5/7/2025, 10 pages
Copyright © 2025 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA
Citation: Janina Siring, Donik Brahimi, Jytte Möckelmann, Hendrik Wester, Johanna Uhe, Bernd-Arno Behrens, Numerical process design for hot forging of steel encased titanium workpieces, Materials Research Proceedings, Vol. 54, pp 859-867, 2025
DOI: https://doi.org/10.21741/9781644903599-92
The article was published as article 92 of the book Material Forming
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
References
[1] Z.X. Zhang, S.J. Qu, A.H. Feng, J. Shen, Achieving grain refinement and enhanced mechanical properties in Ti–6Al–4V alloy produced by multidirectional isothermal forging, Materials Science & Engineering A. 692 (2017) 127-138. https://doi.org/10.1016/j.msea.2017.03.024
[2] B.-A. Behrens, T. Prüß, Keramische Werkzeuge für das Isothermschmieden von Titanlegierungen, Bamberg, Verlag Meisenbach GmbH, 2012.
[3] J. Möckelmann, J. Siring, J. Peddinghaus, H. Wester, K. Brunotte, B.-A. Behrens, Study on the isothermal and oxygen-free forming of encapsulated semi-finished titanium parts, wt Werkstatttechnik online. 114 (2024) 578-587. https://doi.org/10.37544/1436-4980-2024-10-6
[4] G. Lütjering, J.C. Williams, Titanium, Second Edition, Springer Berlin, Heidelberg, 2007. https://doi.org/10.1007/978-3-540-73036-1
[5] C. Leyens, M. Peters, Titanium and Titanium Alloys: Fundamentals and Applications, John Wiley & Sons, 2003. https://doi.org/10.1002/3527602119
[6] C.C. Chen, Recent Advancement in Titanium Near-Net-Shape Technology, JOM. 34(11) (1982) 30-35. https://doi.org/10.1007/BF03338136
[7] S. L. Semiatin, V. Seetharaman, I. Weiss, The thermomechanical processing of alpha/beta titanium alloys, JOM. 49(6) (1997) 33-39. https://doi.org/10.1007/BF02914711
[8] C.C. Chen, Recent Advancement in Titanium Near-Net-Shape Technology, JOM. 34(11) (1982), 30-35. https://doi.org/10.1007/BF03338136
[9] S.L. Semiatin, V. Seetharaman, I. Weiss, The thermomechanical processing of alpha/beta titanium alloys, JOM. 49 (1997) 33-39. https://doi.org/10.1007/BF02914711
[10] J. Zhang, A. Kutzsche, K. Rosenberg, C. Leyens, B. Viehweger, A Novel Canning Technology for Forging of Gamma-TiAl Alloys, Materials Science Forum. 546-549 (2007) 1421-1426. https://doi.org/10.4028/www.scientific.net/MSF.546-549.1421
[11] S. Germain Careau, B. Tougas, E. Ulate-Kolitsky, Effect of Direct Powder Forging Process on the Mechanical Properties and Microstructural of Ti-6Al-4V ELI, Materials. 14(16) (2021) 4499. https://doi.org/10.3390/ma14164499
[12] J.D. James, J.A. Spittle, S.G.R. Brown, R.W. Evans, A review of measurement techniques for the thermal expansion coefficient of metals and alloys at elevated temperatures, Measurement Science and Technology. 12(3) (2001) R1-R5. https://doi.org/10.1088/0957-0233/12/3/201
[13] B.-A. Behrens, J. Uhe, H. Wester, T. Matthias, C. Büdenbender, FE-based Layer Design of Deposition-Welded Semi-finished Parts for the Production of Hybrid Bevel Gear, Procedia Manufacturing. 47 (2020) 309-314. https://doi.org/10.1016/j.promfg.2020.04.235
[14] Y. Zhu, W. Zeng, X. Ma, Q. Tai, Z. Li, X. Li, Determination of the friction factor of Ti-6Al-4V titanium alloy in hot forging by means of ring-compression test using FEM, Tribology International. 44(12) (2011) 2074-2080. https://doi.org/10.1016/j.triboint.2011.07.001
[15] G. Shen, S.L. Semiatin, E. Kropp, T. Altan, A technique to compensate for termperature history effects in the simulation of non-isothermal forging processes, Journal of Materials Processing Technology. 33 (1992) 125–139. https://doi.org/10.1016/0924-0136(92)90315-J
[16] J. Siring, C. Heine, M. Till, H. Wester, J. Uhe, B.-A. Behrens, K. Brunotte, Numerical process design for the production of a hybrid die made of tool steel X38CrMoV5.3 and inconel 718, Materials Research Proceedings. 41 (2024) 812-821. https://doi.org/10.21741/9781644903131-89
[17] R.R. Boyer, G. Welsch, E. W. Collings, Materials Properties Handbook: Titanium Alloys, ASM International, 1994. ISBN: 978-0-87170-481-8
[18] S. M. Ji, S. M. Jang, Y.S. Lee, H.M. Kwak, J. Muk Choi, M.S. Joun, Characterization of Ti-6Al-4V alloy in the temperature range of warm metal forming and fracture analysis of the warm capping process, Journal of Materials Research and Technology. 18 (2022) 1590-4606. https://doi.org/10.1016/j.jmrt.2022.03.066