Dissertation
Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Steel > All kinds of steel : use to distinguish between

Effect of Heat Treatment and Alloy Composition on Microstructure and Properties of Wear-resistant Casting Steel

Author SunGuangTing
Tutor ZhangGuoZhi
School Northeastern University
Course Materials Processing Engineering
Keywords Dual-phase wear-resistant steel Heat treatment Carbon content Alloying Abrasive wear
CLC TG142.4
Type Master's thesis
Year 2009
Downloads 200
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The wear-resistant high manganese steel, used as crawler board the traditionally, cannot be fully hardening and wear-resistant performance is weakened in the low stress abrasion conditions. Based on the performance shortcomings of this material, low-alloy martensite\ bainite dual-phase wear-resistant steel is developed to replace high manganese steel.In order to optimize chemical compositions of wear-resistant steel and obtain the heat optimal treatment processes, this thesis is mainly on the research of the following aspects:1-, The optimal composition was determined by comparing the effect of chromium and carbon content which is 0.26%,0.32%,0.37% respectively on microstructure, hardness, impact of room temperature on toughness, impact of low-temperature on toughness and tensile properties of three types of test steel.2、The test steel was quenched at temperature which was 900℃,950℃,1000℃respectively, and subsequently was tempered at temperature which was 220℃,280℃,320℃, 360℃respectively. The effect of heat treatment on comprehensive performance was studied by observing the microstructure of steel in different heat-treatment conditions and analyzing the tensile strength, hardness, impact of room temperature and low-temperature on toughness3、Combining with the practical application conditions, the wear-resistance of the steel was tested by two different abrasive wear ways. (One is the certain impact stress abrasion tester, the other is the low stress abrasion tester).The wear-resistances of the sample steel under two different wear conditions were compared with the high manganese steel, and the wear mechanism was analyzed.Through comprehensive analysis of the experimental results, following conclusions can be reached:1、By contrast of the comprehensive performance of different contents of carbon in steels, the one which contains carbon of 0.26% plays the best. Its hardness can be 48HRC, impact on toughness can reach 46J/cm2 of gaps specimens, tensile strength can reach1500MPa and elongation can achieve 8%. The hardness of test steel can not be affected after the chromium being put in. However, the impact on toughness is improved about 10J/cm2 after putting chromium in.2、When the sample was quenched and tempered, the microstructure are mainly lath martensite、needle-like bainite and a small amounts of austenite.Conclusion that hardness, intensity, toughness and combination property of the test steel are on the top under the condition of 950℃quenching and 280℃tempering can be gained after comparative analysis of comprehensive performance of different temperature in quenching and tempering.3、Under the low stress abrasion condition, the test steel which consists of 0.27%carbon and 0.621%chromium has the best wear-resisting property and improves 73% compared with high manganese steel. Observing the surface morphology mainly about isolated and short-range scraps pit after abrasion, it show that the abrasion mechanism is chiefly micro cutting wear in low profit abrasion wear condition. In addition, wear-resisting properties of the same material are distinct in different abrasion conditions. The wear-resisting property of test steel only improve 10% compared with that of high manganese steel in the environment of higher impact stress of abrasion. Therefore, this dual-phase wear-resistant steel is suitable for abrasive wear under the conditions of low stress

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