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An Investigation on Structure and Properties of CrNiMnMo Alloyed Lining Steel Modified by Rare Earth

Author: YangXiaoJuan
Tutor: DuXiaoDong
School: Hefei University of Technology
Course: Materials Science
Keywords: Rare earth modification CrNiMnMo alloyed lining steel Microstructure and properties Impact corrosion and wear wear mechanism
CLC: TG142.1
Type: Master's thesis
Year: 2009
Downloads: 108
Quote: 0
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Abstract


Lining board used in the wet-grinding machine at metallurgical mines works under very bad conditions. It has to bear impact, corrosion and wear. In recent years, It has became a hot spot to design and develop the alloyed lining steel instead of the high manganese steel. In order to improve the impact corrosion and wear properties of the alloy and make use of the rich rare earth in our country, a little of rare earth was added in the CrNiMnMo alloyed lining steel developed early in this paper. The subject is supported from Innovation Fund of Small and Medium-sized Enterprises of Anhui province and Natural Science Fund of Education Department of Anhui province.The article took the CrNiMnMo alloy lining steel modified by rare earth as the research object, investigated the influence of rare earth on the structure, mechanical properties, nonmetallic inclusion, corrosion resistance, impact corrosion of the alloy and wear resistance and its function mechanism. The way to further improve the performances and service life of CrNiMnMo alloy lining steel was investigated.The structure and properties of CrNiMnMo alloyed lining steel modified by rare earth and alloyed lining steel without Mo were researched through the methods of metallurgical microscope, SEM, EDS, X-ray and impact tester. The results show that the steel with little addition of rare earth element consists of the lath martensite and little residual austenite phase after quenching and tempering. The martensite laths are fine and uniform. Little rare earth changes the category, appearance, size and distribution of inclusion in the steel to reduce its damage to the properties. The impact toughness increases obviously in comparison with unmodified alloyed lining steel. The fracture mode is ductile under impact condition. The hardness of alloyed steel with addition of rare earth is enhanced slightly, and the corrosion resistance is also improved markedly. The hardness and the corrosion resistance of alloyed steel without Mo decline compared with alloy with Mo.The impact corrosion and wear behavior of CrNiMnMo alloyed lining steel modified by rare earth was tested by modified MLD-10 tester. Through SEM, optical microscope and microhardness tester, the worn surface morphology was observed, the subsurface metallographic microstructure and change of microhardness were analyzed, and the impact corrosion and wear mechanism was investigated. The results show that the CrNiMnMo alloyed lining steel modified by rare earth shows the best resistance to impact corrosion and wear, the wear mass loss curve is relatively flat and mass loss is the least. At impact energy of 0.8J, the impact corrosion and wear mechanism is mainly micro-cutting. With impact energy increasing to 2.0J, the mechanism has a transformation from micro-cutting in earlier stage to local shallow fatigue spalling later. For the modified alloyed lining steel without Mo, the impact corrosion and wear resistance declines, and corrosive traces appeare on the worn surface. The main wear mechanism is micro-cutting, extrusion deformation and corrosion wear interaction for this steel.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Steel > Microstructure and properties of steel
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