102 Prakt. Met. Sonderband 52 (2018)
CONCLUSIONS a
The annealing of fine carbide-free lower bainite has proven a successful means of
obtaining microstructures with superior machinability performance. This was achieved
without the introduction of particles or phases which could lead to the degradation of
mechanical properties or polishability. A fully annealed microstructure was obtained after :
reasonably short annealing times, very short if viewed from the perspective of graphite
formation. It can be seen that bainite and martensite behave differently upon annealing
as the prior martensitic regions are clearly identifiable after annealing in the High C-Al
steel. Further work should be conducted on a more detailed study on the fraction and
morphology of graphite and the exact ratios required for a transition from cementite. ABSTR
ACKNOWLEDGEMENT pis
The authors would like to thank dr. Henrik Kaker for performing the XRD measurements, ® “
and dr. Peter Majeri€ for his help with FESEM characterization. Am
REFERENCES VE
[11 J.P. Davim, Machinability of advanced materials, vol. 53, no. 9. John Wiley & Sons, rts
Inc., 2013. on
[2] P. Wright, Edward Trent, Metal cutting 4th edition, 4th ed., vol. 1. Butterworth-
Heinemann, 2000.
[3] V.P. Astakhov, Metal Cutting Mechanics, 1st ed. CRC Press, 1998. { NTR
[4] N.E. Luiz and A. R. Machado, “Development trends and review of free-machining Co
steels,” Proc. Inst. Mech. Eng. Part B J. Eng. Manuf., vol. 222, no. 2, pp. 347-360, re -
2008. Lr
[6] D.V. Edmonds, “The * Silicon Age ’ of Steel : How Alloying With Silicon Is Playing oie :
a Crucial Role in Modern Steel Developments,” Iron Steel Technol., no. October, Rae
pp. 157-176, 2015. the finist
[6] C.K. Syn, D. R. Lesuer, and O. D. Sherby, “Influence of microstructure on tensile we
properties of spheroidized ultrahigh-carbon (1.8 Pct C steel,” Metall. Mater. Trans. Cos
A, vol. 25, no. 7, pp. 1481-1493, 1994. I
[7] H.S. Hasan, M. J. Peet, and H. K. D. H. Bhadeshia, “Severe tempering of bainite
generated at low transformation temperatures,” Int. J. Mater. Res., vol. 103, no. 11,
pp. 1319-1324, 2012. MOU
[8] M.N. Lunika, “Effect of alloying on the quench hardness and transformation during Cold mo
tempering of graphitized steels.” Metalloved. i Termicheskaya Obrab. Met., no. 3, m .
pp. 166-168, 1982. ra
[9] A.Inam, R.Brydson, and D. V Edmonds, “Effect of starting microstructure upon the Ure Sa
nucleation sites and distribution of graphite particles during a graphitising anneal of Fas
an experimental medium-carbon machining steel,” Mater. Charact., vol. 1086, pp. MS
86-92. 2015. We
[10] M. a. Neri, R. Colas, and S. Valtierra, “Effect of deformation on graphitization “rn
kinetics in high carbon steels,” J. Mater. Process. Technol., vol. 83, no. 1-3, pp. Dreterab
142-150, 1998. nee
