Micro Structural Analysis of Damage Blade in Rice Milling Operation

  • O. D. Olakolegan
  • S. O. Ejiko


The blade is a component of a rice milling machine which performs the removal of husk from rice. This component usually gets damage within few months when in use. This has resulted in waste of resources and high production cost. This study aimed to proffer solution to the problem usually faced in rice milling. Samples of used and new common rice milling machine (Engelberg milling machine) components that are blade were obtained from different locations within Ekiti State and Ondo State. The chemical composition and micro structural analysis of the blades were determined using optical emission spectroscopy and optical microscopy method. The samples were machined to the required ASTM (American Society Testing and Materials) shapes and sizes for tensile, impact and hardness test. Three specimens of each blade were heat treated through annealing, hardening, normalising and tempering respectively. The results revealed that the blade made of low carbon steel contains 0.05-0.45% of carbon, chromium 0.001-0.05%, iron 98.5-99.5%, silicon 0.01-0.02% and manganese 0.20-0.90% respectively. The hardness test result also showed that hardening was best heat treatment to improve ultimate strength (blades: A1=119.7, B1=118.5, F1=168.1), (blades: HA1=177.3, HB1=172.0, HF1=164.5). The impact test result revealed that annealing was best method of heat treatment to increase toughness (blades: A1= 65.01J, B1=64.74J, F1=65.42J), (blades: AA1= 66.37J, AB1=66.82J, AF1=66.50J). Better ductility was obtained from the annealed specimens than other heat treatment specimen through the tensile test (blades: A1=0.07499mm, B1=0.1597mm, F1=0.1210mm), (blades: AA1=0.2467mm, AF1=0.1437mm, AB1=0.220mm). The least tensile extension at both maximum tensile stress and break up point was obtained from the hardened specimen that was the only one without ductility property among all the heat treatments.Key words: analysis, assessment, blade, heat treatment, microscopy, structural