Obrabotka Metallov 2014 No. 1

ОБРАБОТКА МЕТАЛЛОВ № 1 (62) 2014 31 МАТЕРИАЛОВЕДЕНИЕ Received 28 October 2013 Revised 20 December 2013 Accepted 10 January 2014 Abstract The possibility of obtaining high-purity steels 65С2А and 65С2ВА melted in a vacuum induction furnace, with the level of strength of about 2500 MPa is studied. It is shown that without the use of special processing methods this level of strength can’t be achieved. Using high-temperature thermomechanical treatment (HTMT) and treatment to ultrafine grain gives the opportunity to get tensile strength σ B ≈ 2600 MPa, ψ = 20-35% and КСU= 0.25-0.4 MJ/m 2 . Upon alloying mild steel by carbide-forming elements (65С2А steel) the ductility КСU= 0.4 MJ/m 2 is provided , but plasticity is relatively low ψ < 20%. Without the carbide-forming elements (65С2А steel) value of КСU is 0.25-0.30 MJ/m 2 , but the value of plasticity is ψ = 35-40%. Study of the fracture structure showed that due to HTMT the dimensions of the chipping surfaces are reduced, intergranular fracture sites are disappeared and the most important thing is that the area of the fracture occupied pits is increased. It can be assumed, that this is a consequence of the general dispersion structure in HTMT. Keywords: high- purity low-alloy siliceous steel, high-strength state, HTMT, treatment to ultrafine grain. References 1. Vylezhnev V.P., Kokovjakina S.A., Simonov Yu.N. Suhih A.A. Povyshenie harakteristik nadezhnosti marten- sitno-starejushhej stali 03N18K9M5T putem sozdanija struktury tipa «Nanotripleks» [Elevation of reliability char- acteristics of maraging steel 03N18K9M5T by creating a “nanotriplex” – type structure]. Metallovedenie i termi- cheskaja obrabotka metallov - Metal Science and Heat Treatment , 2010, no. 11, pp. 39–47. 2. Antolovich S., Saxena A., Chanani G.R. Increased Fracture Toughness in a 300 Grade Maraging Steel as Re- sult of Thermal Cycling. Metallurgical Transactions. 1974, Vol. 5, pp. 623–632. 3. Dement'ev V.B. Perspektivy primenenija sovmeshhennyh processov deformacii i termicheskoj obrabotki dlja obespechenija jekspluatacionnoj nadezhnosti detalej [Prospects of application of the combined processes of defor- mation and heat treatment to ensure the operational reliability of parts]. Sbornik nauchnyh trudov OKTB «Voshod» [Proceedings of the Experimental - Design and Technological Bureau “ Voshod “]. Izhevsk, Izhevskij Mehanicheskij institute, 1989, no.1, pp. 3–16. 4. Bykova P.O., Zajac L.C., Panov D.O. Zavodskaja laboratorija. Diagnostika materialov , 2008, no. 6, pp. 42–45. 5. Kurdjumov G.V., Utevskij L.M., Jentin R.I. Prevrashhenija v zheleze i stali [Transformation in iron and steel]. Moscow, Nauka, 1977. 236 p. 6. Bernshtejn M.L., Zajmovskij V.A., Kaputkina L.M. Termomehanicheskaja obrabotka stali [Thermomechani- cal processing of steel]. Moscow, Metallurgija, 1983. 480 p. 7. Kidin I.N. Fizicheskie osnovy jelektrotermicheskoj obrabotki metallov [Physical basis of electrothermal treat- ment of metals]. Moscow, Metallurgija, 1969. 375 p.