本文選題：軸承鋼GCr15SiMn　切入點(diǎn)：CCT曲線　出處：《江蘇大學(xué)》2017年碩士論文

【摘要】：軸承被譽(yù)為工業(yè)的心臟,隨著現(xiàn)代工業(yè)的突飛猛進(jìn),對(duì)軸承鋼的要求越來(lái)越嚴(yán)格。本文以軸承鋼GCr15SiMn為對(duì)象,基于控軋控冷的工藝,采用熱模擬實(shí)驗(yàn)方法,系統(tǒng)研究了軸承鋼生產(chǎn)過(guò)程中的相變和組織演變規(guī)律,并采用軋后兩階段冷卻工藝有效降低了網(wǎng)狀碳化物的級(jí)別。論文的主要研究?jī)?nèi)容與結(jié)果如下:(1)軸承鋼GCr15SiMn在連續(xù)冷卻過(guò)程中,珠光體析出溫度區(qū)間為600~700℃。隨冷速的增加,相變溫度降低,室溫組織中珠光體量減少,馬氏體量增加;和靜態(tài)相比,動(dòng)態(tài)變形會(huì)提高珠光體相變溫度,使珠光體相變溫度沿CCT曲線向左上方移動(dòng);變形會(huì)促進(jìn)珠光體轉(zhuǎn)變量增加,并使組織明顯細(xì)化;完全發(fā)生珠光體相變的臨界冷卻速度由靜態(tài)2℃/s提高到動(dòng)態(tài)變形3℃/s;變形使馬氏體相變溫度由204℃降低到166℃。(2)以0.3℃/s冷卻時(shí),二次碳化物沿晶界大量析出、聚集,形成彼此相連的網(wǎng)狀碳化物,隨冷速的增加,碳化物的析出逐漸減少;相比于靜態(tài),動(dòng)態(tài)變形會(huì)促進(jìn)二次碳化物的析出,使明顯抑制網(wǎng)狀碳化物生成的臨界冷速由靜態(tài)3℃/s提高到5℃/s,但由于冷速較高,室溫組織中均有馬氏體組織產(chǎn)生。(3)隨冷速的增加,試驗(yàn)鋼顯微硬度不斷提高,當(dāng)冷速小于2℃/s時(shí),與靜態(tài)相比,變形促進(jìn)了再結(jié)晶的發(fā)生,細(xì)化了晶粒,顯微硬度更大;冷速增大到2℃/s及以上時(shí),靜態(tài)組織中領(lǐng)先生成了馬氏體,顯微硬度大幅增加,冷速相同時(shí),高于變形條件下的顯微硬度。(4)變形速率和變形量對(duì)網(wǎng)狀碳化物的析出無(wú)明顯影響;終軋溫度越低,對(duì)碳化物網(wǎng)狀破碎作用越強(qiáng),但溫度越低對(duì)軋機(jī)要求越高,易使軋機(jī)斷輥;相比于變形速率、變形量、終軋溫度,軋后冷速對(duì)軸承鋼GCr15SiMn組織形貌的影響顯著,軋后冷速的增加,二次碳化物的析出減弱明顯,碳化物厚度減小,能有效的抑制網(wǎng)碳,但高冷速下,室溫組織中會(huì)產(chǎn)生大量的馬氏體組織。(5)結(jié)合實(shí)際生產(chǎn),終軋后采用分段冷卻的工藝,在高溫階段,快速穿過(guò)二次碳化物大量析出溫度范圍,快冷到合理的終冷溫度,隨后緩冷至室溫,奧氏體充分發(fā)生珠光體相變,在抑制網(wǎng)狀碳化物析出的同時(shí)避免產(chǎn)生馬氏體�？炖潆A段的冷速與終冷溫度是該工藝的關(guān)鍵,快冷冷速增大到5℃/s冷卻到610℃時(shí),隨后以1℃/s緩冷至室溫,可有效地抑制網(wǎng)狀碳化物的形成,獲得理想的珠光體組織。
[Abstract]:Bearing is known as the heart of industry. With the rapid development of modern industry, the requirement of bearing steel becomes more and more strict.In this paper, based on the controlled rolling and controlled cooling process, the phase transformation and microstructure evolution of bearing steel during production are systematically studied by means of thermal simulation experiment based on GCr15SiMn.The two-stage cooling process after rolling can effectively reduce the grade of reticulated carbides.With the increase of cooling rate, the transformation temperature decreases, the amount of pearlite decreases and the amount of martensite increases at room temperature, compared with static state, the dynamic deformation will increase the transformation temperature of pearlite, and make the temperature of pearlite phase transition move along the CCT curve to the upper left.Deformation will increase the amount of pearlite transformation and make the microstructure thinning obviously.When the critical cooling rate of pearlite phase transformation is increased from static 2 鈩，

本文編號(hào)：1686685