本文選題：鎳鉻鉬鑄鐵　切入點(diǎn)：顯微組織　出處：《陜西理工學(xué)院》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著研磨技術(shù)的發(fā)展,各種大型設(shè)備不斷涌現(xiàn),需要使用各種大型軋輥,因此對(duì)軋輥的要求越來越高。軋輥是各種研磨、破碎、壓片等機(jī)械設(shè)備的主要部件,其質(zhì)量優(yōu)劣關(guān)系到研磨、破碎、壓片等產(chǎn)品的質(zhì)量以及設(shè)備的使用和安全。耐磨材料具有較高的硬度但常伴隨著脆性,導(dǎo)致沖擊韌性不理想,因而在使用過程中會(huì)出現(xiàn)外層局部剝落、斷輥等重大事故。所以,在維持原有的高硬度條件下,改善其沖擊韌性一直都是材料領(lǐng)域關(guān)注的熱點(diǎn)。本文主要以軋輥用鎳鉻鉬鑄鐵為研究對(duì)象,用釩合金化和稀土復(fù)合變質(zhì)處理兩種處理方法,用金屬型鑄造模擬離心復(fù)合鑄造,來研究釩元素及稀土復(fù)合變質(zhì)劑對(duì)鎳鉻鉬鑄鐵顯微組織和性能的影響。合金化處理主要的添加元素為V,復(fù)合變質(zhì)處理時(shí)主要添加RE-Al和RE-Al-V。分析并討論了不同加入量的合金對(duì)鎳鉻鉬鑄鐵顯微組織和力學(xué)性能的影響。實(shí)驗(yàn)研究結(jié)果表明:(1)在鎳鉻鉬鑄鐵中加入釩進(jìn)行合金化處理,可使得鎳鉻鉬鑄鐵中的奧氏體與碳化物得到明顯的細(xì)化效果,有效地改善了碳化物組織的形態(tài)及分布,基體的連續(xù)性顯著地增強(qiáng),使其沖擊韌性得到提高,并在顯微組織細(xì)化過程中,釩促使了奧氏體向馬氏體轉(zhuǎn)變,同時(shí)生成了新的釩碳化合物V4C3相。(2)經(jīng)過RE-Al復(fù)合變質(zhì)處理后,鎳鉻鉬鑄鐵顯微組織在尺寸與形貌有了明顯的改觀,細(xì)化了奧氏體晶粒,碳化物由網(wǎng)狀變?yōu)閴K條狀同時(shí)分布更加均勻,有效地增強(qiáng)了基體的連續(xù)性,提高了鑄鐵本身的塑韌性;并通過檢測(cè)變質(zhì)處理前后組成相并未有明顯變化,進(jìn)一步說明RE-Al變質(zhì)主要在于通過促進(jìn)異質(zhì)形核作用及變質(zhì)劑元素產(chǎn)生界面富集,從而改善顯微組織的形態(tài)與分布。(3)經(jīng)過RE-Al-V復(fù)合變質(zhì)處理后,顯著改變了顯微組織中的粗大化,聚集態(tài)等萊氏體特征,細(xì)化了晶粒,使得細(xì)小的等軸晶奧氏體增多,改善了碳化物的形態(tài)與分布。同時(shí)RE-Al-V多元復(fù)合變質(zhì)與V合金化和RE-Al復(fù)合變質(zhì)相比,結(jié)合了后兩者的優(yōu)點(diǎn),并且變質(zhì)的作用更好,對(duì)鎳鉻鉬鑄鐵韌性的提高更有效果。
[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.
【學(xué)位授予單位】：陜西理工學(xué)院
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG143

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