Influence of Modification of 38khN3MFa Steel on the Structural-Phase State and Cutting Products under Variable Technolog
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INFLUENCE OF MODIFICATION OF 38KhN3MFA STEEL ON THE STRUCTURAL-PHASE STATE AND CUTTING PRODUCTS UNDER VARIABLE TECHNOLOGICAL CONDITIONS О. І. Balyts’kyi,1,2,3 V. О. Kolesnikov,1, 4 and М. R. Havrylyuk1
UDC 621.892.8
We study the influence of modification on the structural-phase state of 38KhN3MFA steel and the morphology of chips formed in the course of turning of billets at a rotation speed of 315 rpm under dry conditions, in the presence of water, and with lubricoolants. It is shown that, in the case of application of lubricoolants, the sizes of chips decrease, their shape becomes more compact and folded, and the roughness of the treated surface becomes ten times lower than after dry turning. Keywords: lubricoolant, machining, steel, chips, damage, turning.
Introduction Cutting products in the form of chips formed in the course of machining are quite informative from the viewpoint of correction of the technological processes. The investigations of the specific features of chip formation focus attention on the fracture processes in steels. Moreover, the results of these investigations can be used for the modification of steels with required operating properties [1–6]. The 38KhN3MFA steel (its European analogs are 34NiCrMoV14-5 and 35NiCrMoV12-5 steels) is used in the power-generating industry for the production of the most critical components of turbine units and compressor machines (rotors and shafts) [2]. Rotor blanks are first mechanically and then thermally treated. As a result of long-term operation and the influence of hydrogen-containing working media, the metal degrades and its structural and phase composition changes, which should be taken into account in the case of repeated turning of the rotor performed as a part of scheduled or emergency maintenance of steam and nuclear power plants. The aim of the present work is to study the influence of modification on the structural and phase state of 38KhN3MFA steel and the morphology of cutting products under variable conditions of lubrication in the process of turning. Materials and Methods of the Experiment We studied 38KhN3MFA steel in the as-delivery state (without heat treatment) with a hardness of 35 HRС [1]. Chips were obtained in the process of cutting of a blank on a screw-cutting machine into cylinders 28 mm in diameter and 4 mm in thickness. The cutter was equipped with a plate made of VK-6 hard alloy. To create 1 2 3 4
Karpenko Physicomechanical Institute, Ukrainian National Academy of Sciences, Lviv, Ukraine. West Pomeranian University of Technology, Szczecin, Poland. Corresponding author; e-mail: [email protected].
T. Shevchenko Lugansk National University, Starobilsk, Ukraine.
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 55, No. 6, pp. 125–130, November–December, 2019. Original article submitted August 28, 2018. 1068-820X/20/5506–0915
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Springer Science+Business Media, LLC
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О. І. BALYTS’KYI, V. О. KOLESNIKOV,
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М. R. HAVRYLYUK
Table 1 Chemical Composition of the Investigated Steels Contents of elements,
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