ROF爐內罩用鋼的成分優(yōu)化研究
發(fā)布時間：2018-12-13 19:27
【摘要】：ROF爐內罩用鋼是高鉻-鎳奧氏體耐熱不銹鋼。ROF爐內罩用鋼長期工作在高溫及還原性氣氛中,要求在高溫下具有一定的強度及良好的抗氧化性。本文通過對服役20850h后的進口 YUS701鋼鋼板與其供貨態(tài)鋼板進行對比發(fā)現,服役后鋼板中的奧氏體晶粒嚴重長大,發(fā)生了晶界氧化,室溫強度降低;位錯密度降低,晶界處析出大塊狀M23C6相;晶內析出長條狀的σ有害相,材料的高溫強度、塑性和韌性降低。現役ROF爐內罩用鋼主要存在高溫強度不足、密封處氧化嚴重及服役壽命不長的問題。為了改善和提高這些問題,本文在進口 YUS701鋼的成分基礎上添加合金元素進行成分優(yōu)化,得到優(yōu)化成分。通過熱力學模擬計算、熱處理實驗、氧化實驗,借助金相顯微鏡(OM)、掃描電子顯微鏡(SEM)及能譜分析(EDS)、透射電子顯微鏡(TEM)及X射線衍射(XRD)等顯微組織表征方法,研究了ROF內罩用鋼的高溫抗氧化性及經熱處理后的組織、性能,得出以下結論:1、加V、W的試驗鋼中,奧氏體晶粒粗大;力學性能沒有明顯提高,甚至略有降低。試驗鋼中加入Nb后,晶粒得以細化;且在室溫及高溫下的力學性能均較優(yōu);但因為σ相和Z相在650℃時的析出量隨著Nb含量的增加而增長,故本文將Nb含量控制在0.2 wt%左右即可。C含量由0.09 wt%降低為0.05 wt%時,有利于奧氏體晶粒細化及晶粒均勻化;同時減少了 M6C型碳化物及M2(C,N)相的析出。與此同時,Ni含量為14.00 wt%左右有利于進一步控制鋼中σ相、Z相及G相等有害相的析出。ROF爐內罩用鋼優(yōu)化后的成分為: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、隨著固溶溫度的升高,試驗鋼的晶粒尺寸逐漸增大,強度和硬度下降,而塑性和沖擊韌性則上升。在滿足所需晶粒尺寸要求(25～50μm)的條件下,試驗鋼在1070℃時的綜合力學性能較好。試驗鋼在1070℃保溫不同時間時,奧氏體晶粒隨著保溫時間的延長而逐漸均勻化。當固溶保溫時間為60min時,晶內碳氮化物基本完全溶解,在晶內僅有少量呈細小顆粒狀的富Cr碳化物析出,故經過成分優(yōu)化后的ROF爐內罩用鋼的熱處理工藝為:1070℃固溶60min,水冷。3、經過成分優(yōu)化后的試驗鋼在1100℃氧化100h后能夠形成較穩(wěn)定的氧化膜,氧化動力學曲線在各個階段的瞬時氧化速率最低,具有與進口料相當的高溫抗氧化性。4、試驗鋼經過成分優(yōu)化及熱處理工藝優(yōu)化后,高溫強度與進口料相當,同時,其室溫抗拉強度和屈服強度分別為823MPa和460MPa;室溫韌性為448J;室溫及高溫延伸率分別為55%及114%,均優(yōu)于進口料。
[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，
本文編號：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，
本文編號：2377087
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