本文選題：高強抗震鋼筋 + 貝氏體��； 參考：《昆明理工大學》2015年碩士論文

【摘要】：高強度抗震鋼筋在各種大型、高層建筑的復雜結構中承擔著重要作用,高強度、高韌性和高強屈比的鋼筋能夠更大限度的吸收地震能量,是保障建筑物結構安全的最重要材料之一。本文采用萬能試驗機、金相顯微鏡、顯微硬度計、高溫試驗機、掃描電鏡(SEM)、透射電子顯微鏡(TEM)等,對試驗鋼筋進行室溫和高溫拉伸變形,探討了不同溫度下顯微結構與抗震性能的變化規(guī)律。針對5種不同貝氏體含量(3%、8%、15%、20%和50%)的試驗鋼筋,進行室溫拉伸試驗。研究表明,不同貝氏體含量的試驗鋼筋的各項抗震指標符合500MPa抗震鋼筋的要求,隨著貝氏體含量的增加,強屈比呈現升高趨勢。分析貝氏體含量對屈服平臺的影響,結果顯示,當貝氏體含量達到20%時,試驗鋼筋屈服平臺消失：導致無屈服現象的主要原因有兩個：(1)溶質原子在位錯上的偏聚,起釘扎位錯的作用,位錯運動受阻,派納力增大,進一步運動需要應力增大,在曲線上表現為上升的趨勢。(2)貝氏體中的板條鐵素體中含有較高的位錯密度,在變形過程中高的位錯密度使得位錯之間容易發(fā)生纏結,需要增大應力才能使位錯運動,實現繼續(xù)變形。通過對比貝氏體含量為8%和50%的試驗鋼筋的顯微結構在不同變形階段的變化。研究結果表明,貝氏體含量50%的鋼筋,貝氏體承擔主要的變形,貝氏體中的亞板條中的位錯密度隨變形的進行先增大后減��；貝氏體含量為8%的試驗鋼筋中鐵素體的位錯密度隨變形的進行急劇增大,珠光體發(fā)生較大的變形,甚至斷裂,鐵素體和珠光體承擔主要的變形。五種貝氏體含量的試驗鋼筋在200～600℃高溫拉伸試驗。研究結果表明,在200～400℃,試驗鋼筋均出現明顯的加工硬化現象,并隨溫度的升高加工硬化現象越發(fā)不明顯。當溫度上升到500～600℃,試驗鋼筋的加工硬化現象基本消失,應力應變曲線甚至趨于水平直線。高溫拉伸試驗中的屈服強度和抗拉強度在不同溫度下的變化規(guī)律,結果表明：在200～600℃,試驗鋼筋的屈服強度和抗拉強度都隨溫度升高呈下降趨勢；在400～600℃,屈服強度和抗拉強度下降的程度比200～400℃內劇烈得多。在200～600℃,抗拉強度隨溫度的升高而下降的幅度比屈服強度的大。高溫試驗鋼筋的強屈比,研究結果顯示：當溫度不超過500℃時,試驗鋼筋的強屈比都高于1.25,滿足抗震要求；不同貝氏體含量的試驗鋼筋的強屈比都隨溫度的升高呈現先升高后降低的規(guī)律。試驗鋼筋的高溫抗震性能是通過與室溫性能的對比來確定,對比發(fā)現,試驗鋼筋具有較高的強屈比；而且不超過500℃時,高溫下的屈服強度都高于室溫屈服強度2/3,試驗鋼筋具有較好的高溫抗震性能。
[Abstract]:High-strength aseismic reinforcement plays an important role in complex structures of large and high-rise buildings. The reinforcement with high strength, high toughness and high yield ratio can absorb seismic energy to a greater extent. It is one of the most important materials to ensure the safety of building structure. In this paper, a universal testing machine, a metallographic microscope, a microhardness tester, a high temperature tester, a scanning electron microscope (SEM), a transmission electron microscope (TEM), etc, were used to deform the tested steel bars at room and high temperature. The variation of microstructure and seismic performance at different temperatures is discussed. Tensile tests at room temperature were carried out for 5 kinds of test steel bars with different bainite content of 20% and 50% respectively. The results show that the seismic indexes of the tested steel bars with different bainite content meet the requirements of 500MPa seismic reinforcement. With the increase of bainite content, the ratio of strength to yield increases. The effect of bainite content on the yield platform is analyzed. The results show that when the bainite content reaches 20%, the yield platform of the tested steel bar disappears. The main cause of the non-yielding phenomenon is the segregation of solute atoms on dislocation. As a result of pinning dislocation, the dislocation movement is blocked, the Pina force increases, and the further movement requires an increase in stress. In the curve, the lath ferrite in the bainite has a higher dislocation density, and the lath ferrite in the bainite has a higher density of dislocation. In the process of deformation, the high density of dislocation makes it easy to tangle between the dislocations, and it needs to increase the stress to make the dislocation move and continue to deform. The microstructure of steel bars with bainite content of 8% and 50% was compared in different deformation stages. The results show that when the bainite content is 50%, the bainite bears the main deformation, and the dislocation density in the bainite sublath increases first and then decreases with the deformation. When the bainite content is 8%, the dislocation density of ferrite increases sharply with the deformation, and the pearlite is deformed, even fracture, and the ferrite and pearlite bear the main deformation. Five kinds of bainite content test steel bar at 200 鈩，

本文編號：1870647