本文選題：鈦微合金鋼　切入點：動態(tài)再結晶　出處：《江蘇大學》2016年碩士論文

【摘要】：中國鈦資源非常豐富,價格相對便宜,且鈦在鋼中能產(chǎn)生沉淀強化和細晶強化效果,具有開發(fā)出高強韌鋼的潛力。本課題參考珠鋼鈦微合金鋼的生產(chǎn)工藝,在普通低碳鋼的基礎上添加適量的Ti元素,在實驗室利用Gleeble-3800熱模擬機,結合控制軋制和控制冷卻工藝,模擬了不同變形工藝下高溫奧氏體再結晶、不同冷卻工藝過程中組織的演變和等溫過程中碳氮化物在鐵素體中的析出行為。另外,借助光學顯微鏡、顯微硬度儀、透射電鏡、Matlab等手段,研究分析了不同工藝下鈦微合金鋼組織的再結晶、演變規(guī)律和碳氮化物在鐵素體中的析出機理,實驗結果表明:(1)鈦微合金鋼奧氏體化的合理加熱溫度為1200℃,保溫時間為5min,在850~1100℃的溫度范圍內,以不同的應變速率(0.025~1.0s-1)對試樣進行50%單道次壓縮變形,結果顯示應力-應變曲線呈現(xiàn)兩種形式,即動態(tài)回復型和動態(tài)結晶型。在低溫和低應變速率下,應變速率對變形抗力的作用不大,變形溫度則對其起決定作用。動態(tài)再結晶晶粒隨變形程度的增加而明顯細化,達到穩(wěn)態(tài)應變后,細化作用減弱。當變形溫度為1050℃,應變速率為0.1s-1時,發(fā)生完全再結晶后,晶粒尺寸由固溶條件下的99.5um減小到17.4um。(2鈦微合金鋼的熱變形激活能Q=427.85k J mol-1。峰值應力、峰值應變和臨界應變與成線性關系,且都隨的增大而增大。根據(jù)變形程度、變形溫度和應變速率對變形抗力的影響作用,回歸建立了鈦微合金鋼的變形抗力模型,通過模型計算結果和實驗結果良好吻合。(3無論變形還是未變形條件下,增大冷卻速率(V3℃/s),都會出現(xiàn)貝氏體組織,說明鈦微合金鋼相變過程容易獲得貝氏體組織。隨著冷速的提高,相變組織由粒狀貝氏體向板條貝氏體轉變。變形促進貝氏體形核,使貝氏體板條變短,細化貝氏體組織。(4)變形使奧氏體的連續(xù)冷卻轉變曲線向上移動,提高了相變的開始溫度并加快了相變的轉變速度;變形擴大了先共析鐵素體的相變區(qū)域并且可以誘發(fā)珠光體轉變,使得冷速1℃/s時,變形奧氏體的相變組織為先共析鐵素體+珠光體而不發(fā)生貝氏體轉變,但未變形的相變組織為鐵素體+少量粒狀貝氏體。(5)600℃保溫時,碳氮化物析出為平面型相間析出,析出的粒子呈現(xiàn)兩種尺寸范圍,粒子直徑分別為10~20nm的應變誘導析出和5nm左右沉淀析出,在保溫5~10min左右時具有最大的形核率。(6)在600℃保溫1h后獲得最大沉淀效果,貢獻值為114MPa,繼續(xù)保溫,沉淀強化效果減弱。
[Abstract]:China is rich in titanium resources and relatively cheap in price, and titanium can produce precipitation strengthening and fine grain strengthening effect in steel, which has the potential to develop high strength and toughness steel. The austenite recrystallization at high temperature under different deformation conditions was simulated by adding appropriate amount of Ti on the basis of common low carbon steel, using Gleeble-3800 thermal simulator in laboratory, combined with controlled rolling and controlled cooling process. The evolution of microstructure in different cooling processes and the precipitation behavior of carbon and nitride in ferrite during isothermal process. In addition, by means of optical microscope, microhardness instrument, transmission electron microscope (TEM) and Matlab, etc. The recrystallization and evolution of microstructure of titanium microalloyed steel under different processes and the mechanism of carbonitride precipitation in ferrite are studied. The experimental results show that the reasonable heating temperature of austenitization of titanium microalloyed steel is 1200 鈩，

本文編號：1654805