本文關鍵詞： 貝氏體鋼軌 再結(jié)晶 馬氏體 貝氏體　出處：《內(nèi)蒙古科技大學》2015年碩士論文　論文類型：學位論文

【摘要】：作為國民經(jīng)濟發(fā)展的重要組成，鐵路的發(fā)展對國家的工業(yè)化進程有著重要的作用。貝氏體鋼軌與其他鋼軌相比具有更優(yōu)越的塑性和韌性，因而此類鋼軌的研發(fā)與制備成為各國爭相研究的重點。但是貝氏體鋼軌在使用過程中仍會出現(xiàn)裂紋傷損等問題。因此在充分利用貝氏體鋼軌優(yōu)點的同時，解決此類問題是根據(jù)試驗鋼的CCT圖，鋼軌的終軋溫度，鋼軌精軋后的冷卻速度等參數(shù)制定生產(chǎn)工藝，控制貝氏體鋼軌鋼的組織變化。從熱軋過程中的再結(jié)晶行為、相變行為、冷卻控制行為三方面著手，研究不同的軋后余熱淬火工藝對貝氏體鋼軌鋼組織變化的影響。 本課題是以某鋼廠貝氏體鋼軌為研究對象主要從這兩個方面進行分析，首先通過ZEISS金相顯微鏡和Zeiss SUPRA55型掃描電子顯微鏡對熱處理后的組織進行觀察與分析。另一方面采用Gleeble-1500D熱模擬實驗機研究了貝氏體鋼軌在不同條件下熱變形時的再結(jié)晶行為，多道次壓縮實驗分析了變形工藝參數(shù)對再結(jié)晶行為的影響。 結(jié)果表明：不同的冷卻方式的熱處理工藝對試驗鋼的組織有很大的影響。貝氏體鋼軌油冷時，得到的組織為板條馬氏體+殘余奧氏體。緩慢冷卻時，得到的組織為鐵素體加粒狀貝氏體。在鹽浴爐350℃等溫淬火15min，30min，60min時得到的是條片狀貝氏體。在回火時得到的是無碳貝氏體加殘余奧氏體。在熱模擬單道次實驗中貝氏體鋼軌在1100℃時發(fā)生動態(tài)再結(jié)晶，900℃-1050℃只是發(fā)生了少量的動態(tài)回復，沒有發(fā)生動態(tài)再結(jié)晶；在間隔時間為20s時，就可以辨別出900℃為未再結(jié)晶區(qū)，950℃為部分再結(jié)晶區(qū)，1000℃-1050℃為完全再結(jié)晶區(qū)。多道次壓縮中，方案一二是在第一道次發(fā)生了動態(tài)再結(jié)晶，二三道次之間是應變積累的過程，第四道次是在910℃發(fā)生了18%的壓下，有再結(jié)晶的趨勢。壓下量較大時就容易發(fā)生動態(tài)再結(jié)晶。方案三中前兩道次是在完全再結(jié)晶區(qū)域內(nèi)進行軋制，后兩道次在未再結(jié)晶區(qū)域內(nèi)進行軋制，避開部分再結(jié)晶區(qū)可以使晶粒更加細化。研究發(fā)現(xiàn)：貝氏體鋼中存在冶金缺陷，存在明顯的帶狀組織及MnS夾雜物；在冷卻過程中易于產(chǎn)生馬氏體組織，，這些是引起鋼軌開裂的原因。
[Abstract]:As an important component of national economic development, the development of railway plays an important role in the industrialization process of the country. Bainite rail has better plasticity and toughness than other rails. Therefore, the research and preparation of this kind of rail has become the focus of many countries. However, the bainitic rail will still have crack damage in the process of use. Therefore, the advantages of bainite rail can be fully utilized at the same time. To solve this problem, the production process is determined according to the CCT diagram of the test steel, the final rolling temperature of the rail, and the cooling rate of the rail after finishing rolling. In order to control the microstructure of bainitic rail steel, the recrystallization behavior, transformation behavior and cooling control behavior during hot rolling are discussed. The effect of different afterheat quenching processes on the microstructure of bainitic rail steel was studied. In this paper, the bainitic rail in a steel plant is taken as the research object, which is mainly analyzed from these two aspects. First, through ZEISS metallographic microscope and Zeiss. The microstructure after heat treatment was observed and analyzed by SUPRA55 scanning electron microscope. On the other hand, the bainite rail under different conditions was studied by Gleeble-1500D thermal simulation machine. Recrystallization behavior during hot deformation. The effect of deformation parameters on recrystallization behavior was analyzed by multi-pass compression experiment. The results show that different cooling processes have great influence on the microstructure of the test steel. When the bainite rail oil is cooled, the microstructure obtained is lath martensite retained austenite. The microstructure obtained is ferrite with granular bainite and isothermal quenching at 350 鈩

本文編號：1482876