Research On Composition, Structure And Property Of The High Alloy White Cast Iron Blade Used In Classifier

On the premise of analyzing the working condition and the working principle of the classifier blade, high chromium white cast iron were chosen for the material of classifier blade instead of gray cast iron. The microstructure and properties of the classifier blade were also researched by experiment. In the paper, stress analyzing and failure analysis of the classifier blade were carried, the composition and the process of smelting, casting and heat-treatment of high chromium cast iron were decided. The changes of matrix microstructure and carbide of high chromium cast iron and the effect on performance were studied with different heat treatment process. By means of microstructure observation, X-ray Difractometer (XRD), Scanning Electron Microscopy (SEM) with Energy Dispersive Spectrometer (EDS), rock well hardness test, impact-toughness test, abrasive wear test and observation of the wear surface and the as-cast morphology of impact fracture, mechanical properties and wear resistance were researched. The optimal heat treatment process was determined, preparate blade,then put it into manufacturability experiment.The chemical composition selected ultimately of the high alloy white cast iron blade: chromium 14.0%,carbon3.0%,vanadium0.1%,silicon1.3%,manganese1.3%,sulphur andphosphorus<0.05%. In the experimental temperature range, the sample after normalized at 850℃and tempering have best overall mechanical properties. The experimental results indicate that: Vanadium in the high chromium white cast iron blade is beneficial to refining microstructures; large distribution of the troostite in matrix structure of area appeared in the material of blade at as-cast. With normalized temperature increasing, troostite quantity and residual austenite both increasd, the strength decreased and the toughness improved. The fractographic features transferred brittle fracture to quasi-cleavage fracture and dimple fracture mixed features; After tempering, the amount of retained austenite decreased. Alloy has best wear resistance, when the amount of retained austenite is 21.67%. Moreover, the structure of the granular pearlite appeared at the bottom and lamellar pearlite on the top or middle of the blade were compared, and the forming reason of the former and the influence on the properties were also studied. The results show that the main cause of pearlite spheroidization is the macro-segregation of the matrix.. Both hardness and impact toughness of the granular pearlite are better than the lamellar pearlite's, but the lamellar wear resistance of pearlite is weaker. In the experimental temperature range, as normalized temperature rising, pearlite spheroidization process more absolutely. Sample at 900℃normalized whose wear resistance is weaker have spheroidized absolutely, and the sample at 850℃normalized have best wear resistance.