Zr对Ti微合金钢奥氏体中析出相与再结晶的影响

发布时间：2018-02-05 01:20

  本文关键词： Ti微合金钢 Zr 奥氏体 固溶度 析出相 静态再结晶　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着国家工业化水平的日益提高,对综合性能优异的钢材需求越来越广。Ti微合金钢因其本身所具有的优良性能以及相对低廉的价格,受到越来越多的关注。但是,由于Ti比较活泼,易与O、S等杂质元素结合形成夹杂物,从而降低了Ti在钢中作用的发挥;此外,TiC的析出具有较高的温度敏感性,可能导致钢板性能出现波动。针对这些问题,研究者普遍采用Ti与Nb、V、Mo等复合微合金化的方式去改善。但同属于微合金化元素,Zr对Ti微合金钢影响方面的研究报道还很少。因此,本文针对Ti、Zr-Ti两种微合金钢,通过理论计算和热处理、热模拟的实验方法,利用金相显微镜(OM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等,研究Zr对Ti微合金钢奥氏体化及Ti的碳氮化物固溶的影响、Zr对形变奥氏体中析出与再结晶的影响规律。通过热力学模型计算得到Zr-Ti钢中相互作用系数为,εZrTI =-0.976 +166.15/T、εZrZr=-1.07 + 190.06/T、εCZR=-0.387-2.08/T、εNZr=18.9-184.41/T;说明Zr可以降低Ti、C在铁基体中的活度,提高其在奥氏体中的固溶度;升高了 N在铁基体中的活度,降低其在奥氏体中的固溶度。不同均热温度下Zr对Ti微合金钢奥氏体化及Ti的碳氮化物固溶的影响实验结果表明,在1150℃时,Ti钢中的TiC可能仍处于溶解阶段,1200～1250℃时,两种试验钢中的TiC均完全溶解于奥氏体中,Zr·的加入促进了试验钢的奥氏体均匀化,同时也细化了奥氏体晶粒。Ti钢中存在着Ti4C2S2,Zr-Ti钢中存在着(Mn,Zr)S等硫化物;两种试验钢中均存在着大、小尺寸的氮化物;大尺寸氮化物导致试验钢的塑性、韧性及成形性能恶化,要避免形成;小尺寸的氮化物则对细化奥氏体晶粒有重要作用。应力松弛实验的结果表明,两种试验钢奥氏体中微合金碳氮化物的析出-时间-温度(PTT)曲线均呈典型的“C”曲线;最快析出温度均在925℃左右;低温下Zr延迟了含Ti的碳化物析出。双道次压缩实验结果表明,两种试验钢的静态再结晶动力学模型分别为,Ti钢:X =1-exp[-0.693(t/t0.5)0.715]、r-Ti钢:Xs=1-exp(-0.693(t/t0.5)0.786];两种试验钢的静态再结晶激活能分别为,Ti钢:142.292KJ/mol,Zr-Ti钢:115.052KJ/mol;形变奥氏体组织与软化分数—时间曲线保持较好的吻合性;Zr的加入可以提高Ti钢的变形抗力,有效的抑制奥氏体变形。应变诱导析出相的分析结果表明,Ti钢中的应变诱导析出相为TiC,Zr-Ti钢中的应变诱导析出相为(Zr,Ti)C;应变诱导析出相以晶界形核为主,部分会在未溶相周围形核长大,应变诱导析出相的存在阻碍再结晶的进行;Zr加入到Ti钢中得到尺寸较大的(Zr,Ti)C颗粒,相对于Ti钢来说,静态再结晶更易进行。
[Abstract]:With the increasing industrialization of the country, the demand for the steel with excellent comprehensive properties is becoming wider and wider, because of its own excellent performance and relatively low price. More and more attention has been paid to it. However, because Ti is active, it is easy to form inclusions by combining with impurities such as OFS, thus reducing the role of Ti in steel. In addition, the precipitation of tic is highly temperature-sensitive, which may lead to the fluctuation of the properties of the steel plate. In view of these problems, Ti and NB V are widely used by researchers. The method of composite microalloying such as Mo has been improved. However, there are few reports on the effect of Zr on Ti microalloying steel. Therefore, this paper focuses on Ti. Two kinds of Zr-Ti microalloyed steels were studied by means of theoretical calculation, heat treatment, thermal simulation, metallographic microscope and scanning electron microscope (SEM). The effect of Zr on austenitization of Ti microalloyed steel and the solution of Ti carbonitride were studied by transmission electron microscope (TEM). The effect of Zr on precipitation and recrystallization in deformed austenite was studied. The coefficient of interaction in Zr-Ti steel was calculated by thermodynamic model. 蔚 ZrTI + -0.976 166.15 / T, 蔚 ZrZr=-1.07 190.06 / T, 蔚 CZR=-0.387-2.08/T. 蔚 NZr18.9-184.41 / T; The results show that Zr can decrease the activity of TiOC in iron matrix and increase its solution in austenite. The effect of Zr on the austenitization of Ti microalloyed steel and the solution of Ti carbides at different soaking temperatures were investigated. The results show that the effect of Zr on the austenitization of Ti microalloyed steel and the solid solution of Ti carbides. At 1150 鈩，

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