钒合金化与稀土复合变质处理镍铬钼铸铁组织与性能的研究

发布时间：2018-03-22 23:29

本文选题：镍铬钼铸铁　切入点：显微组织　出处：《陕西理工学院》2015年硕士论文　论文类型：学位论文

【摘要】：随着研磨技术的发展,各种大型设备不断涌现,需要使用各种大型轧辊,因此对轧辊的要求越来越高。轧辊是各种研磨、破碎、压片等机械设备的主要部件,其质量优劣关系到研磨、破碎、压片等产品的质量以及设备的使用和安全。耐磨材料具有较高的硬度但常伴随着脆性,导致冲击韧性不理想,因而在使用过程中会出现外层局部剥落、断辊等重大事故。所以,在维持原有的高硬度条件下,改善其冲击韧性一直都是材料领域关注的热点。本文主要以轧辊用镍铬钼铸铁为研究对象,用钒合金化和稀土复合变质处理两种处理方法,用金属型铸造模拟离心复合铸造,来研究钒元素及稀土复合变质剂对镍铬钼铸铁显微组织和性能的影响。合金化处理主要的添加元素为V,复合变质处理时主要添加RE-Al和RE-Al-V。分析并讨论了不同加入量的合金对镍铬钼铸铁显微组织和力学性能的影响。实验研究结果表明:(1)在镍铬钼铸铁中加入钒进行合金化处理,可使得镍铬钼铸铁中的奥氏体与碳化物得到明显的细化效果,有效地改善了碳化物组织的形态及分布,基体的连续性显著地增强,使其冲击韧性得到提高,并在显微组织细化过程中,钒促使了奥氏体向马氏体转变,同时生成了新的钒碳化合物V4C3相。(2)经过RE-Al复合变质处理后,镍铬钼铸铁显微组织在尺寸与形貌有了明显的改观,细化了奥氏体晶粒,碳化物由网状变为块条状同时分布更加均匀,有效地增强了基体的连续性,提高了铸铁本身的塑韧性;并通过检测变质处理前后组成相并未有明显变化,进一步说明RE-Al变质主要在于通过促进异质形核作用及变质剂元素产生界面富集,从而改善显微组织的形态与分布。(3)经过RE-Al-V复合变质处理后,显著改变了显微组织中的粗大化,聚集态等莱氏体特征,细化了晶粒,使得细小的等轴晶奥氏体增多,改善了碳化物的形态与分布。同时RE-Al-V多元复合变质与V合金化和RE-Al复合变质相比,结合了后两者的优点,并且变质的作用更好,对镍铬钼铸铁韧性的提高更有效果。
[Abstract]:With the development of grinding technology, a variety of large-scale equipment is constantly emerging, which requires the use of a variety of large rollers, so the requirements for rollers are becoming more and more high. Roller is the main part of various mechanical equipment such as grinding, crushing, pressing and so on. Its quality is related to the quality of grinding, crushing, pressing and other products, as well as the use and safety of equipment. Wear-resistant materials have high hardness but are often accompanied by brittleness, resulting in poor impact toughness. As a result, major accidents such as partial exfoliation of the outer layer and breaking of rollers will occur in the course of use. Therefore, under the condition of maintaining the original high hardness, Improving its impact toughness has always been the focus of attention in the field of materials. In this paper, nickel chromium-molybdenum cast iron used in roll is mainly studied. Two treatment methods, vanadium alloying and rare earth compound modification, are used to simulate centrifugal composite casting by metal mold casting. The effect of vanadium and rare earth compound modifier on microstructure and properties of nickel-chromium-molybdenum cast iron was studied. The main addition elements in alloying treatment were V, and RE-Al and RE-Al-V were mainly added in composite modification. The different addition amounts were analyzed and discussed. The experimental results show that: 1) adding vanadium to Ni-Cr-Mo cast iron for alloying, The austenite and carbides in Ni-Cr-Mo cast iron can be refined obviously, the morphology and distribution of carbides are improved effectively, the continuity of matrix is enhanced significantly, and the impact toughness is improved. In the process of microstructure refinement, vanadium promoted the transformation of austenite to martensite, and a new vanadium carbohydrate, V4C3 phase, was formed at the same time. The microstructure of Ni-Cr-Mo cast iron changed obviously in size and morphology after RE-Al compound modification. The austenitic grain is refined, the carbide is distributed more evenly from mesh to strip, the continuity of matrix is enhanced effectively, the ductility of cast iron is improved, and the phase composition does not change obviously before and after modification. It is further explained that RE-Al metamorphism mainly depends on improving the morphology and distribution of microstructure by promoting heterogeneous nucleation and interfacial enrichment of modifier elements. The morphology and distribution of carbides are improved because of the fine equiaxed austenite, and the morphology and distribution of carbides are improved. Meanwhile, compared with V alloying and RE-Al complex modification, RE-Al-V multicomponent modification combines the advantages of the latter two. And the effect of modification is better and the toughness of nickel-chromium-molybdenum cast iron is improved more effectively.
【学位授予单位】：陕西理工学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG143

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