Grain Mill Knife Wear Optimization
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RESISTANCE UDC 669.14.018.25:620.178.167
GRAIN MILL KNIFE WEAR OPTIMIZATION H. Ghafori,1 S. A. Khodarahmi,2 and M. Razazi3 Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 41 – 45, May, 2020.
The effect of heat treatment on the microstructure, hardness, and abrasive wear of the hammer mills knives made of steels EN 1.2080, 1.7225, 1.7131, and 1.1191 used in the grain crop processing into groats has been studied. The wear tests were performed using an “impeller-in-cup” type machine, and metallographic studies were performed using optical and scanning electron microscopy. A comparative analysis of the steel properties was performed. Steel EN 1.2080, which demonstrated the highest wear resistance, was recommended for knife manufacturing. The optimal heat treatment conditions for such steel were proposed.
Key words: knife, hammer mill, wear, hardness.
cient impact toughness and wear resistance. As the knife hardness increases, their rate of wear decreases significantly [6, 7]. However, materials featuring increased hardness and wear resistance have low impact resistance [8]. The required mechanical properties and wear resistance of the mill knives are achieved by properly choosing their heat treatment conditions [9]. The objective of this study is to determine the rate of wear of hammer mill knives made of different grades of steel after various thermal or thermochemical treatments for the purpose of selecting the optimal option, which would result in a decrease in knife wear, and ultimately, in a lower cost of grain products.
INTRODUCTION Hammer mills are commonly used to process wheat grains, barley, soybeans, etc. into groats. In such mills, grain breakdown occurs as a result of successive impacts of the mill knives. After a short period of use, such knives wear out significantly. The performance efficiency of the hammer mill knives depends on many parameters, including the properties of the material the knives are made of and their operating conditions. There are numerous studies of the grain grinding processes, which consider such aspects, as energy consumption, particle grinding and grinding quality, grain moisture content, screening parameters and (hammer) head thickness [1 – 4]. However, only few works are dedicated to studying the wear of hammer mill knives. Breakdowns as a result of equipment wear-out occur in various industries [5]. In the grain-processing industry, wear results from the interaction between grains and knives, which move at various speeds and have different temperatures and hardness. The environmental conditions also affect the wear processes. The knives of a hammer mill should possess suffi1 2 3
METHODS OF STUDY To determine the durability of the mill knives, a series of experiments were conducted during which grain were ground in a hammer mill equipped with a standard commercial grinder rated at 80 hp (59.3 kW). The knives were distributed over eight shafts, each holding 10 knifes. The rotation speed of the shaft was 3000 rpm. To select the optimal material
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