本文選題：細晶高強IF鋼 + 奧氏體晶粒�。� 參考：《遼寧科技大學》2015年碩士論文

【摘要】：近年來,由于人們對環(huán)境污染和能源問題越來越重視,要求汽車生產向輕量化方向發(fā)展,汽車用鋼的高強度化是實現(xiàn)汽車生產輕量化的有效途徑。無間隙原子鋼(IF鋼)兼具較高的強度與優(yōu)異的深沖性能,在現(xiàn)代汽車生產中得到了大量的應用。隨著汽車產業(yè)的蓬勃發(fā)展,對IF鋼性能的要求也在不斷提高,因此對IF鋼做進一步的研發(fā)顯得尤為重要。本文以細晶高強IF鋼為研究對象,在不同的加熱溫度和保溫時間條件下對實驗鋼進行回溶實驗,然后利用光學顯微鏡觀察實驗鋼中顯微組織的變化規(guī)律,并采用透射電子顯微鏡對實驗鋼中第二相粒子的固溶析出規(guī)律與無沉淀析出區(qū)的形成機制進行研究,同時對實驗鋼進行力學性能檢測。主要研究結果如下:1.細晶高強IF鋼在加熱過程中,隨著加熱溫度的升高、保溫時間的延長,第二相粒子的數(shù)量逐漸減少且尺寸逐漸增大,同時奧氏體晶粒逐漸長大。對OM實驗數(shù)據進行非線性回歸,擬合得到加熱過程中奧氏體晶粒長大的數(shù)學模型為:2.由OM實驗結果可知,細晶高強IF鋼的奧氏體晶粒粗化溫度為1050℃,奧氏體晶粒粗化時間為40 min。因此,實際生產中最好將加熱溫度控制在1050℃~1100℃、保溫時間控制在30 min~40 min。3.TEM實驗結果顯示,實驗鋼中未溶的第二相粒子在低溫時主要是呈圓形、橢圓形的富Nb析出相,在高溫時主要是呈方形、長方形的富Ti析出相,當加熱溫度達到1150℃時,Nb元素基本完全固溶于鐵基體中。理論計算表明,含Nb第二相粒子的全固溶溫度為1130℃,理論計算結果與實驗現(xiàn)象基本吻合。4.實驗鋼中由于析出相粒子的固溶和粗大化與晶界遷移造成的掃動效應,導致僅在晶界遷移方向的后方,形成獨特的無沉淀析出區(qū),且在退火過程中無沉淀析出區(qū)優(yōu)先在晶界經過的區(qū)域形成。5.在退火過程中,隨著退火溫度的升高,細晶高強IF鋼的屈服強度逐漸降低,n值逐漸增加,無沉淀析出區(qū)的平均寬度逐漸增大。因此可以推測,無沉淀析出區(qū)的平均寬度是影響細晶高強IF鋼屈服行為和加工硬化行為的原因之一。
[Abstract]:In recent years, because people pay more and more attention to the environmental pollution and energy problems, the automobile production is required to develop to the direction of light weight. The high strength of automobile steel is an effective way to realize the light weight of automobile production.Non-gap atomic steel (if steel) has both high strength and excellent deep drawing performance, and has been widely used in modern automobile production.With the rapid development of automobile industry, the requirements of if steel properties are also increasing, so it is very important to further develop if steel.In this paper, the high-strength if steel with fine grain was used as the research object. The experimental steel was redissolved at different heating temperature and holding time, and the microstructure of the steel was observed by optical microscope.The rule of solid solution precipitation of the second phase particles and the formation mechanism of the precipitation zone without precipitation were studied by transmission electron microscope, and the mechanical properties of the experimental steel were tested.The main results are as follows: 1.With the increase of heating temperature and the prolongation of holding time, the number and size of the second phase of fine grained high strength if steel decrease gradually and the austenite grain grows gradually.The mathematical model of austenite grain growth during heating is obtained by nonlinear regression of OM experimental data.The results of OM experiment show that the austenite grain coarsening temperature is 1050 鈩，

本文編號：1772519