ROF炉内罩用钢的成分优化研究
发布时间：2018-12-13 19:27
【摘要】：ROF炉内罩用钢是高铬-镍奥氏体耐热不锈钢。ROF炉内罩用钢长期工作在高温及还原性气氛中,要求在高温下具有一定的强度及良好的抗氧化性。本文通过对服役20850h后的进口 YUS701钢钢板与其供货态钢板进行对比发现,服役后钢板中的奥氏体晶粒严重长大,发生了晶界氧化,室温强度降低;位错密度降低,晶界处析出大块状M23C6相;晶内析出长条状的σ有害相,材料的高温强度、塑性和韧性降低。现役ROF炉内罩用钢主要存在高温强度不足、密封处氧化严重及服役寿命不长的问题。为了改善和提高这些问题,本文在进口 YUS701钢的成分基础上添加合金元素进行成分优化,得到优化成分。通过热力学模拟计算、热处理实验、氧化实验,借助金相显微镜(OM)、扫描电子显微镜(SEM)及能谱分析(EDS)、透射电子显微镜(TEM)及X射线衍射(XRD)等显微组织表征方法,研究了ROF内罩用钢的高温抗氧化性及经热处理后的组织、性能,得出以下结论:1、加V、W的试验钢中,奥氏体晶粒粗大;力学性能没有明显提高,甚至略有降低。试验钢中加入Nb后,晶粒得以细化;且在室温及高温下的力学性能均较优;但因为σ相和Z相在650℃时的析出量随着Nb含量的增加而增长,故本文将Nb含量控制在0.2 wt%左右即可。C含量由0.09 wt%降低为0.05 wt%时,有利于奥氏体晶粒细化及晶粒均匀化;同时减少了 M6C型碳化物及M2(C,N)相的析出。与此同时,Ni含量为14.00 wt%左右有利于进一步控制钢中σ相、Z相及G相等有害相的析出。ROF炉内罩用钢优化后的成分为:0.05 wt%C,14.00 wt%Ni,0.2 wt%Nb,0.30 wt%N,1.75 wt%Si,1.47 wt%Mn,0.67 wt%Mo。2、随着固溶温度的升高,试验钢的晶粒尺寸逐渐增大,强度和硬度下降,而塑性和冲击韧性则上升。在满足所需晶粒尺寸要求(25～50μm)的条件下,试验钢在1070℃时的综合力学性能较好。试验钢在1070℃保温不同时间时,奥氏体晶粒随着保温时间的延长而逐渐均匀化。当固溶保温时间为60min时,晶内碳氮化物基本完全溶解,在晶内仅有少量呈细小颗粒状的富Cr碳化物析出,故经过成分优化后的ROF炉内罩用钢的热处理工艺为:1070℃固溶60min,水冷。3、经过成分优化后的试验钢在1100℃氧化100h后能够形成较稳定的氧化膜,氧化动力学曲线在各个阶段的瞬时氧化速率最低,具有与进口料相当的高温抗氧化性。4、试验钢经过成分优化及热处理工艺优化后,高温强度与进口料相当,同时,其室温抗拉强度和屈服强度分别为823MPa和460MPa;室温韧性为448J;室温及高温延伸率分别为55%及114%,均优于进口料。
[Abstract]:ROF furnace cover steel is high chromium nickel austenitic heat resistant stainless steel. ROF furnace cover steel works in high temperature and reductive atmosphere for a long time and requires certain strength and good oxidation resistance at high temperature. In this paper, the austenitic grain of imported YUS701 steel plate after service 20850 h and its supplied steel plate are found to have grown seriously, resulting in grain boundary oxidation and decrease of room temperature strength. The dislocation density decreases and the bulk M23C6 phase is precipitated at the grain boundary, while the long stripe 蟽 harmful phase is precipitated in the crystal, and the high temperature strength, plasticity and toughness of the material decrease. The existing ROF furnace cover steel mainly has the problems of insufficient high temperature strength, serious oxidation in sealing area and short service life. In order to improve and improve these problems, the composition of imported YUS701 steel was optimized by adding alloying elements. Through thermodynamic simulation calculation, heat treatment experiment, oxidation experiment, (OM), scanning electron microscope (SEM) and energy spectrum analysis (EDS),). Transmission electron microscope (TEM) and X-ray diffraction (XRD) were used to characterize the microstructure of ROF inner cover steel. The oxidation resistance at high temperature and the microstructure and properties after heat treatment were studied. The following conclusions were obtained: 1. Coarse austenite grain; The mechanical properties were not obviously improved or even slightly decreased. After the addition of Nb into the test steel, the grain size can be refined, and the mechanical properties at room temperature and high temperature are better. But because the precipitation of 蟽 phase and Z phase increases with the increase of Nb content at 650 鈩，
本文编号：2377087
[Abstract]:ROF furnace cover steel is high chromium nickel austenitic heat resistant stainless steel. ROF furnace cover steel works in high temperature and reductive atmosphere for a long time and requires certain strength and good oxidation resistance at high temperature. In this paper, the austenitic grain of imported YUS701 steel plate after service 20850 h and its supplied steel plate are found to have grown seriously, resulting in grain boundary oxidation and decrease of room temperature strength. The dislocation density decreases and the bulk M23C6 phase is precipitated at the grain boundary, while the long stripe 蟽 harmful phase is precipitated in the crystal, and the high temperature strength, plasticity and toughness of the material decrease. The existing ROF furnace cover steel mainly has the problems of insufficient high temperature strength, serious oxidation in sealing area and short service life. In order to improve and improve these problems, the composition of imported YUS701 steel was optimized by adding alloying elements. Through thermodynamic simulation calculation, heat treatment experiment, oxidation experiment, (OM), scanning electron microscope (SEM) and energy spectrum analysis (EDS),). Transmission electron microscope (TEM) and X-ray diffraction (XRD) were used to characterize the microstructure of ROF inner cover steel. The oxidation resistance at high temperature and the microstructure and properties after heat treatment were studied. The following conclusions were obtained: 1. Coarse austenite grain; The mechanical properties were not obviously improved or even slightly decreased. After the addition of Nb into the test steel, the grain size can be refined, and the mechanical properties at room temperature and high temperature are better. But because the precipitation of 蟽 phase and Z phase increases with the increase of Nb content at 650 鈩，
本文编号：2377087
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