Influence of regenerative heat treatment on structure and properties of G20CrMo2-5 (L20HM) cast steel

• Autorzy: Golanski, G. , Kupczyk, J.
• Języki publikacji: EN

Abstrakty

EN

The paper presents results of research on the influence of regenerative heat treatment on the structure and properties (hardness, impact energy)of L20HM cast steel. lnvestigated material was taken from outer frame of a turbinę which was serviced for 167 424 hours at the temperature of 535 °C and pressure of 12.75 MPa. In post-operating condition the investigated cast steel was characterized by low impact ,energy of 13J and hardness of 139HV30. Analysis of the influence of austenitization parameters (temperature and time) has revealed that at the temperature range of 895 ÷ 955 °C (i.e. A_c3 + 10 ÷ 70 °C), for both 3 and 5 hours of hold time, the obtained grain size amounts to 20 ÷ 25μm. I has been proved that tempered bainitic-ferritic and ferritic-bainitic-pearlitic structure of the investigated cast steel ensures high t energy, i.e. KV > 100J, as well as hardness, i.e. HV30, just at the temperature of 680 °C. Temperature of 700 °C causes further of impact energy along with a slight decrease of hardness. Moreover, it has been concluded that applying of under-annealing of tempering, after standardization, guarantees required impact energy of KV > 27J.

Słowa kluczowe

PL

obróbka cieplna; właściwości mechaniczne; staliwo stopowe

EN

heat treatment; mechanical properties; cast steel

• Czasopismo: Archives of Foundry Engineering
• Rocznik: 2008
• Tom: Vol. 8, iss. 1 spec.
• Strony: 109--114
• Opis fizyczny: Bibliogr. 8 poz., rys., tab., wykr.

Twórcy

autor

Golanski, G.

• Institute of Materials Engineering, Częstochowa University of Technology, Armii Krajowej 19, Częstochowa, Poland,

autor

Kupczyk, J.

• Institute of Materials Engineering, Częstochowa University of Technology, Armii Krajowej 19, Częstochowa, Poland

Bibliografia

• [1] S. Stachura, G Golanski, Metallographic and mechanical properties of Steel and cast Steel after long term service at elevated temperatures, Report BZ - 202 - 1/01 researches unpublished.
• [2] A. Zieliński, J. Dobrzański, H. Krztoń, Structural changes In low alloy cast Steel Cr- Mo - v after long time creep service, JAMME, 25, (2007), 33.
• [3] S. Stachura, The changes of structure and mechanical properties of steels and cast steels after log term serviced at elevated temperatures, Energetic, 2, (1999), 109-115 (in Polish).
• [4] Molinie, R. Piques, A. Pineau, Behaviour of a lCr - lMo - 0.25V Steel after long - term exposure - I. Charpy impact toughness and creep properties, Fatique Fract. Engng Mater. Struct., 14, 5, (1991), 531.
• [5] 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, Przegląd Odlewnictwa 54, 5, (2004), 402-408.
• [6] G. Golański, S. Stachura, D. 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, 21, 2006, 143-150 (in Polish).
• [7] PN-89/H-83157 „Steel castings creep resistant at elevated temperatures. Grades.”
• [8] G. Golanski, S. Stachura, J. Kupczyk, D. Kucharska - Gajda, Heat treatment of cast steel using normalization and intercritical annealing, Arch. Foundry Eng., 7, (2007), 123.