Optimisation of regenerative heat treatment parameters of G21CrMoV4-6 cast steel

• Autorzy: Golański, G. , Stachura, S. , Gajda-Kucharska, B. , Kupczyk, J.
• Języki publikacji: EN

Abstrakty

EN

Purpose: of the paper was to design the optimal parameters of regenerative heat treatment of G21CrMoV4-6 (L21HMF) cast steel after long-term serviced at elevated temperature. Design/methodology/approach: The data obtained from dilatometric curves were used to determine the optimal cooling rates leading to acquire the bainite microstructure with the ferrite amount lower than 10%. Structures were investigated using light optical microscopy and scanning electron microscopy. In order to determine stability of carbide precipitates the equilibrium temperatures of precipitates dissolving were defined using thermodynamic databases of Thermo-Calc software. Findings: The tempered bainitic microstructure of the Cr-Mo-V cast steel has the very good mechanical properties and impact energy. The optimal bainite or bainite with a small amount of ferrite (<10%) structure can be obtained after cooling with the cooling rates 13.64 K/s ≥ v _8-5 ≤ 33. 33K/s. The optimal tempering temperature range of the bainitic G21CrMoV4–6 cast steel equals 710-720 °C and ensures high mechanical properties and impact energy. Practical implications: The above mentioned heat treatment is the new type of regenerative heat treatment of elements long term serviced at elevated temperatures. Heat treatment leads to the obtaiment of very good mechanical properties and high impact energy. Originality/value: The paper shows the possibilities of regenerative heat treatment long term serviced cast steels for lifetime extension.

Słowa kluczowe

PL

stopy metaliczne; plastyczność; obróbka termiczna

EN

metallic alloys; ductility; heat treatment

• Czasopismo: Archives of Materials Science and Engineering
• Rocznik: 2007
• Tom: Vol. 28, nr 6
• Strony: 341-344
• Opis fizyczny: Bibliogr. 14 poz., il., wykr.

Twórcy

autor

Golański, G.

autor

Stachura, S.

autor

Gajda-Kucharska, B.

autor

Kupczyk, J.

• Institute of Materials Engineering, Częstochowa University of Technology, ul. Armii Krajowej 19, 42-200 Częstochowa, Poland,

Bibliografia

• [1] O. I. Balyts’kyi, I. V. Ripei, Kh. A. Protsakh, Degradation of the cast elements of steam turbines of thermal power plants made of 20KhMFL steel in the course of long-term operation, Materials Science 41 (2005) 423-426.
• [2] D. Renowicz, A. Hernas, M. Cieśla, K. Mutwil, Degradation of the cast steel parts working in power plant pipelines, Journal of Achievements in Materials and Manufracturing Engineering 18 (2006) 219-222.
• [3] W. Brunne, Material fatigue degradation of cast HP pipe cross, Energetic 2 (1999) 103-109 (in Polish).
• [4] J. Okrajni, K. Mutwil, M. Cieśla, Chemical pipelines material fatigue, Proceedings of the 13th Scientific International Conference on Achievements in Mechanical and Mechanical Properties 2005, 497-502.
• [5] Z. Lu, R. G. Faulkner, P. E. J. Flewitt, The role of irradation-induced phosphorus segregation in the DBTT temperature iun ferritic steel, Materials Science and Engineering A 437 (2006) 306-312.
• [6] M. A. Islam, J. F. Knott, P. Bowen, Kinetics of phosphorus segregation and its effect on low temperature fracture behaviour in 2.25Cr-1Mo pressure vessel steel, Materials Science and Technology 21 (2005) 76-84.
• [7] S. Stachura, J. Kupczyk, M. Gucwa, Optimization of structure and properties of Cr-Mo and Cr- Mo-V cast steel intended for use at increased temperature, Foundry Review 54 (2004) 402-408.
• [8] G. Golański, S. Stachura, B. Gajda, J. Kupczyk, Influence of the cooling rate on structure and mechanical properties of L21HMF cast steel after regenerative heat treatment, Archives of Foundary 6 (2006) 143-150 (in Polish).
• [9] J. Trzeszczyński, E. Grzesiczek, W. Brunne, Effectiveness of solutions extending operation time of long operated cast steel elements of steam turbines and steam pipelines, Energetic 3 (2006) 179-184 (in Polish).
• [10] J. Dobosiewicz, Present experience connected with the revitalization of steam turbine cylinders, Energetic 1 (1996) 39-41 (in Polish).
• [11] A. Rehmus-Forc, Change of structure after revitalizatrion cylinders of a steam turbine, Materials Science and Engineering 3 (2006) 265-267 (in Polish).
• [12] K. Dudziński, K. Dudziński, L. Pękalska, G. Pękalski, Welding and regenerative heat treatment of steam turbine castings, Materials Science and Engineering 6 (2003) 712-715 (in Polish).
• [13] PN-89/H-83157-Steel castings creep resistant at elevated temperatures. Grades (in Polish).
• [14] G. Golański, J. Kupczyk, S. Stachura, B. Gajda, Regenerative heat treatment of Cr-Mo-V cast steel after long term serviced, Materials Science and Engineering 3 (2006) 147-150 (in Polish).