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Study on Microstructures and Properties of Bimetal Composites by the Addition of Particles

Author: LiXiuQing
Tutor: SongYanPei
School: Henan University of Science and Technology
Course: Materials Processing Engineering
Keywords: Centrifugal Casting Carbon ferrochrome Bimetal composite material Microstructure and Properties Friction and wear
CLC: TB331
Type: Master's thesis
Year: 2011
Downloads: 43
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Abstract

This article desired hot metal smelting the surface of the composite roll of the working layer and the core portion using a furnace, and by applying a high-carbon ferrochromium particle method and centrifugal casting, the high-carbon ferrochromium granules added directly to the mold of rotation of the centrifuge, the preparation of the roll barrel again using gravity casting casting roll core made size Φ180mm × 500mm high chromium cast iron / ductile iron bimetallic composite roll casting. HR-150D type Rockwell hardness tester and JB-300B type pendulum impact testing machine, mechanical properties testing equipment testing different heat treatment conditions, the mechanical properties of the sample; With MH-3 digital microhardness of high chromium cast iron combined with ductile iron near the interface of the microhardness measurements; using an optical microscope equipped with EDAX spectrometer JSM-5610LV type scanning electron microscopy and Germany Bruker D8 X-ray diffraction (XRD) and other micro-analytical instruments to observe and analyze the sample microstructure; MMS-1G high-speed pin - disc friction and wear testing machine to study the high-speed friction and wear characteristics of the sample under different heat treatment conditions, and by means of scanning electron microscopy analysis of the wear mechanism. The above test results show that: 1. Additional particles prepared by high-chrome cast iron - ductile iron bimetallic composite roll, heat treatment process on the mechanical properties of the surface layer has a certain impact. In 900 ^{1 000 ℃ the austenitization temperature range, with the austenitization temperature rise, the trend of the macro hardness first increases and then decreases, while the impact toughness decreased slightly match the mechanical properties of in 950 ℃ austenitizing, good. Its mechanical properties can be achieved: the impact toughness of 5.2 ^{6 .6J/cm ^{2 ; hardness HRC56.7 ^{6 4.8. 2. Composite roll surface chromium cast iron cast under the layer microstructure: the alloy carbides pearlite residual austenite. After heat treatment, the microstructure becomes: tempered martensite Cr ₇ C ₃ of residual austenite small amount of Cr ₂₃ C ₆ and Cr3C, bars, cakes and daisy-like morphology of the primary carbides were a large number of granular tempering carbides; distribution in the martensitic matrix by EDS analysis, these carbides containing Fe, C and Cr and other elements of the composite carbide. 3. Prepared bimetallic composite roll, high chromium cast iron and ductile iron connection interface is clear, two alloys were intertwined canines like junction porosity, inclusions, casting defects such as cracks and voids; from ductile iron side of the layer to the high chromium cast iron, spheroidal graphite number fewer, smaller and smaller dimensions; iron layer to the ball from one side of the high chromium cast iron, as amended, the number of massive carbides fewer dimensions increasingly smaller. Approximately 800HV combination of the microhardness of the interface side of high chromium cast iron, ductile iron side microhardness of about 350 HV seen, the difference between both sides of the microhardness of the composite interface is relatively large, but at the bonding interface microhardness lower more relaxed. Shows that the alloying elements diffusion occurs at the bonding interface, the two metals to achieve a good metallurgical bond. 4 high-speed friction and wear tests austenitizing temperature, plus the normal load and friction line speed has a significant impact on high-speed friction and wear properties of the composite roll wear layer materials. Within the test temperature range, the grinding weight loss with increasing austenitizing temperature changes, austenitizing at 950 ℃ grinding minimize weight loss, the abrasion best; the friction line speed constant to the increase of the load with the applied method, the composite roll wear layer sample wire wear rate gradually increases, while the coefficient of friction gradually decreases; outer adder to the load constant, the With the friction line speed increases, the composite the sample line of the wear-resistant layer of the roll wear rate is gradually increased, and the friction coefficient decreases. According to the analysis, the wear layer wear mechanism to abrasive wear, oxidation wear and adhesive wear. Under the same experimental conditions, the prepared composite roll wear layer material grinding pin specimen weight loss, wire wear rates and friction coefficients are smaller than the grinding weight loss of the wear-resistant high-alloy steel, wire wear rate and coefficient of friction, that prepared by the high-speed friction and wear properties of the composite roll wear layer material is superior to high wear-resistant alloy steel.}}}}

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