Obrabotka Metallov. 2016 no. 2(71)

ОБРАБОТКА МЕТАЛЛОВ № 2 (71) 2016 85 МАТЕРИАЛОВЕДЕНИЕ Abstract Thick-walled cylinders ( D/d ≥ 2) constitute a large group of parts with precise small diameter holes ( d = 1…10 mm). Improvement of surface finish and accuracy of small diameter holes is an actual task and requires the development of new methods of processing and cold expansion is one of the most effective methods of finish- ing and hardening of holes in such parts. Along with high productivity, cold expansion helps to increase accuracy, improve surface roughness, considerably work-harden surface layer and generate favorable compressive residual stresses. However, residual stresses generated during cold expansion of parts such as thick-walled cylinders can be undesirably high in some cases. It is supposed that in order to maintain high accuracy of holes and to reduce residual stresses after cold expan- sion of thick-walled cylinders, which undergo throughout plastic deformations, it is needed to perform axial plastic compression with subsequent cold expansion with small interferences. To test the hypothesis, the accuracy of holes as well as hoop, radial and axial residual stresses in cylinders made of steel grade 50 (0,5 % C, НВ 2170…2290 MPa) with hole diameter d = 5 mm, outer diameter D = 15 and length L = 30 mm by Sachs method is studied. It is found that double-cycle cold expansion with total interference а Σ /d = 5,1 % generates hoop residual stresses with largest absolute value equal to 284 MPa, which, after plastic compression with strain ∆L/L equal to 0.5% and 1% and single- cycle cold expansion with interference a/d = 0,9 %, changed to 177 MPa. It is shown that high hole accuracy (IT7) achieved through double-cycle expansion remained at the same high level after plastic compression and single-cycle expansion. Keywords thick-walled cylinders, cold expansion, plastic compression, residual stresses DOI: 10.17212/1994-6309-2016-2-80-86 References 1. Samsonov G.V., Upadkhaya G.Sh., Neshpor V.S. Fizicheskoe materialovedenie karbidov [Physical materials science of carbides]. Kiev, Naukova dumka Publ., 1974. 456 p. 2. Calik A., Taylan F., Sahin O., Ucaf N. Comparison of mechanical properties of boronized and vanadium car- bide coated AISI 1040 steels. Indian Journal of Engineering and Materials Sciences , 2009, vol. 16, pp. 326–330. 3. Dobrzanski L.A., Jonda E., Lukaszkowicz K., Labisz K., KlimpelA. Surface modification of the X40CrMoV5-1 steel by laser alloying and PVD coatings deposition. Journal of Achievements in Materials and Manufacturing Engi- neering , 2008, vol. 27, iss. 2, pp. 179–182. 4. Dobrzanski L.A., Jonda E., Labisz K. Structure and properties of surface layer of hot-work tool steels alloyed using high power diode laser. Journal of Achievements in Materials and Manufacturing Engineering , 2009, vol. 37, iss. 2, pp. 617–621. 5. Meletis E.I., Nie X., Wang F.L., Jiang J.C. Electrolytic plasma processing for cleaning and metal-coating of steel surfaces. Surface and Coatings Technology , 2002, vol. 150, iss. 2–3, pp. 246–256. doi: 10.1016/S0257- 8972(01)01521-3 6. Novakova A.A., Sizov I.G., Golubok D.S., Kiseleva T.Yu., Revokatov P.O. Electron-beam boriding of low- carbon steel. Journal of Alloys and Compounds , 2004, vol. 383, pp. 108–112. doi: 10.1016/j.jallcom.2004.04.017 7. Bataev I.A., Bataev A.A., Golkovski M.G., Krivizhenko D.S., Losinskaya A.A., Lenivtseva O.G. Structure of surface layers produced by non-vacuum electeon beam boriding. Applied Surface Science , 2013, vol. 284, pp. 472– 481. doi: 10.1016/j.apsusc.2013.07.121 8. Voroshnin L.G., Mendeleeva O.L., Smetkin V.A. Teoriya i tekhnologiya khimiko-termicheskoi obrabotki [The- ory and technology of chemical-thermal treatment]. Minsk, Novoe znanie Publ., 2010. 304 p. 9. Gur’ev A.M., Lygdenov B.D., Vlasova O.A. Intensifikatsiya protsessov khimiko-termicheskoi obrabotki metallov [Intensification of metals thermochemical treatment]. Fundamental’nye issledovaniya – Fundamental Re- search , 2008, no. 8, pp. 48–50. 10. Shmatov A.A. Modelirovanie protsessa formirovaniya karbidnogo sloya pri diffuzionnom khromovana- dirovanii stali U8 [Process modulation of forming diffusion Cr-V carbide coating on steel U8]. Vestnik Polotskogo gosudarstvennogo universiteta. Seriya B: Promyshlennost’. Prikladnye nauki – Herald of Polotsk State University. Series B. Industry. Applied Sciences , 2011, no. 11, pp. 113–123. (In Russian) 11. Butukhanov V.A., Greshilov A.D., Lygdenov B.D., Galaa O. Issledovanie protsessa diffuzionnogo nasysh- cheniya v smesi, soderzhashchei oksid vanadiya i alyuminii [Study of diffusion saturation in a mixture of vanadium oxide and aluminum]. Polzunovskii vestnik – Polzunov Bulletin , 2012, no. 1-1, pp. 51–55.