Structure and Properties of Bimetallic Centrifugally Cast Milling Rollers
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STRUCTURE AND PROPERTIES OF BIMETALLIC CENTRIFUGALLY CAST MILLING ROLLERS Zh. Zheng,1 A. P. Shatrava,2, 3 V. P. Likhoshva,2 O. A. Pelikan,2 and K. Zheng1
UDC 621.926.3:664.71-62-412
We propose a way to increase the wear and crack resistance of the main working tools for roller mills. Bimetallic rollers (with a diameter of 252 mm and a length of 1620 mm) are produced by sequential pouring of alloys with similar temperatures of phase transformations. The microstructure, phase composition, redistribution of alloying elements, and the properties of bimetallic materials are studied. The results are used as a basis for the development of a technological process for the production of bimetallic milling rollers by the method of centrifugal casting. The implementation of this method makes it possible to improve the reliability and durability of rollers in the course of their operation. Keywords: structural phase analysis, iron-carbon low alloys, method of centrifugal casting, transition area.
Introduction The increase in the performance and durability of grain-processing mill complexes makes it necessary to steadily increase the requirements to the materials and the design of modern equipment. The machines, such as roller mills, are used for the efficient grinding and milling of hard and soft wheat and are the most common machines for the processing of corn, wheat, rye, barley, or malt. The main working tools of these units aimed at grinding of grains are milling rollers operating in pairs, which have grooved or smooth surfaces. High requirements to the physical and mechanical properties of the rollers make it necessary to improve the durability of parts of the mill equipment of the leading manufacturers of plants, such as Bühler, Ocrim, Golfetto, MMW, etc. The roller mills are usually equipped with rollers with diameters of 250 or 300 mm. The design features and the operating conditions of milling rollers are determined by the need to have a wear-resistant working layer on the surface, while maintaining the viscosity and bearing properties of the cores of these products [1]. Therefore, the milling rollers with bimetallic structures are considered to perform well and have a number of advantages, namely, the combination of the best characteristics of two different materials, a wear-resistant working layer and a core providing the required stiffness and toughness, and the simultaneous increase of the wear resistance and durability of the product [2]. Iron-carbon alloys are commonly used for the manufacturing of rollers as wear-resistant materials. The austenitic manganese irons and steels were used as tribological materials [3, 4]. The relationship between the wear intensity and the structural-phase compositions of alloys and the load–speed characteristics are investigated. 1 2 3
Guangdong Institute of Materials and Processing, Guandong Academy of Sciences, Guangzhou, China. Physicotechnological Institute of Metals and Alloys, National Academy of Sciences, Kiev, Ukraine. Corresponding author; e-mail: [email protected].
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