【作者】 李小蕴；

【导师】 祖方遒；

【作者基本信息】 合肥工业大学 ， 材料加工工程， 2005， 硕士

【摘要】 大量国内外文献表明,在高锰钢加工硬化规律及机理研究中,一般采用小能量多次冲击和静载荷拉伸压缩的方法来获得加工硬化。但是小能量多次冲击和静载荷拉伸压缩的方法毕竟与实际的工况条件不同,未必能反映在实际工况条件下高锰钢的加工硬化规律及机制。针对这一现状,本文主要研究了在模拟实际工况条件下,冲击功、碳锰的含量、变质处理及热处理工艺对加工硬化规律及机制的影响。本文根据对球磨机及锤式破碎机两类最典型应用高锰钢的不同机型实际工况的分析,选择50、 80、 100和200J/cm2四种不同的‘相对冲击功’,采用自行设计、制造的冲击落锤试验装置,探索了在模拟实际工况的条件下各因素对加工硬化的影响规律。结果表明,高锰钢的加工硬化能力和所加冲击功关系密切,对于给定成分的高锰钢,存在一定的临界‘相对冲击功’,只有相对冲击功高于临界值时才能达到最佳的加工硬化效果;锰量的降低、碳量的升高有利于加工硬化能力的提高;稀土变质处理可以提高加工硬化速率,但不能改变最终的硬化效果;合适的沉淀强化处理可以在一定范围内提高高锰钢的加工硬化能力。采用光学金相和透射电镜分析、研究高锰钢加工硬化后的组织变化规律。结果表明,在不同硬化条件下高锰钢中的硬化组织不同,其加工硬化的机制也不相同。对于本文涉及的高锰钢试件,在‘相对冲击功’为50J/cm2的情况下,高锰钢的组织主要由大量的位错和层错及少量的孪晶组成,加工硬化机制主要为位错滑移机制;在冲击功高于100J/cm2的情况下,其组织主要由位错和孪晶组成,加工硬化以孪生硬化机制为主。由于普通高锰钢在中、低应力下往往难以达到最佳加工硬化效果,常常需采取合金化或改性处理。因此本文探讨了SG变质剂对于含有较多碳化物形成元素的高锰钢铸态及热处理状态下的组织影响规律。研究结果表明,SG变质处理有效抑制柱状枝晶的生长,降低铸态组织中珠光体数量,细化了组织,并在一定程度上缩短高锰钢水韧处理的保温时间或降低水韧处理的温度。更多还原

【Abstract】 A mass of scientific and technical literatures show small energy impact or static load compress/tension deformation is used to gain work hardening in research on work hardening ability and mechanism of high manganese steel. Small energy impact and static load compress/tension deformation are different from actual working condition, so both two methods may not show work hardening ability and mechanism of actual working condition. For this reason, this paper studied effect of impact energy , C content, Mn content, modification and heat treatment on work hardening ability and mechanism of high manganese steel by simulating actual working condition.According to the analysis of actual working condition, four ’relative impact energies’ of 50, 80, 100, 200J/ cm~2 were selected in this experiment. The effect of the factors on work hardening ability of high manganese steel were studied under four ’relative impact energies’ with dropping impact hammer designed on our own. The results show that the best work hardening effect could only be obtained when ’relative impact energy’ exceeds the critical value; work hardening ability could benefit from the reduction of Mn content and increase of C content; RE-modification can improve work hardening velocity, but it can’t improve the final work hardening effect; Proper precipitate reinforcement treatment could improve work hardening ability to some degree.Furthermore, in order to study the microstructure of high manganese steel, the samples after work hardening were investigated with optics metallographic microscope and transmission electron microscope, and also work hardening mechanism is analyzed. The research results show that the microstructure and work hardening mechanism are distinguishing under different work hardening effect; For the given specimens of high manganese steel, with the relative impact energy of 50J/cm~2 , vast dislocation , stacking fault and few twinning exist in the microstructure, therefore work hardening mechanism could be considered as dislocation hardening mechanism; With the relative impact energy more than 100 J/cm~2, dislocation and twins exist, where work hardening mechanism could be considered as twinning hardening mechanism.It’s difficult to reach the best work hardening effect for high manganese steel under low and medium stress, so alloying and modification are adopted to improvethe wearing property. In this paper, we investigated the effect of SG modification on as-cast and heat-treated microstructure of high manganese steel with carbide forming element (e.g. Cr, V). The research results show SG modification could restrain the growth of columnar crystals, reduce the content of pearlite in as-cast microstructure and refine the grain and also SG modification reduces holding time or temperature of quenching.更多还原