【摘要】：316L不銹鋼是一種能適應于諸多環(huán)境的奧氏體不銹鋼鋼種。因其優(yōu)良的耐蝕性,可加工性和良好的焊接性能在石化、海洋、造紙等領(lǐng)域發(fā)揮著重要的作用。但由于其具有面心立方結(jié)構(gòu)和碳含量低的特點,316L不銹鋼的強度和硬度較低,因而限制了其在更多重要的領(lǐng)域的應用。為提高316L不銹鋼的強度,同時保證其良好的塑性,本課題通過鋁熱反應法制備得到了微納結(jié)構(gòu)316L不銹鋼。但由于鋁熱反應未完全,少量剩余的鋁元素熔進了不銹鋼中,使得不銹鋼中出現(xiàn)了鐵素體組織。本課題研究:為消除不銹鋼中的鐵素體組織,往反應物料中添加不同過量比例的氧化鐵使鋁粉能充分反應,研究其對制得的316L不銹鋼組織、成分和微納結(jié)構(gòu)的影響,并探究了軋制和退火對微納組織結(jié)構(gòu)、耐蝕性和力學性能的影響規(guī)律,為其實現(xiàn)工業(yè)化生產(chǎn)奠定理論和實驗基礎(chǔ)。最后,通過一系列表征分析和總結(jié),得出以下幾條結(jié)論:1、反應物料中過量的Fe_2O_3能降低鋁熱法制得的不銹鋼中的鋁含量。當Fe_2O_3過量2.5%時,不銹鋼中的鋁含量降低為1.74%,鐵素體含量降至4.1%;當Fe_2O_3過量5%時,鋼中的鋁含量為1.3%,且鐵素體消失。當Fe_2O_3過量7.5%時,鋼中的鋁含量降為0.99%,鐵素體仍然沒有,但是出現(xiàn)了較多的FeCrMo金屬間化合物相。故Fe_2O_3過量5%為鋁熱法制備全奧氏體316L不銹鋼的最佳制備參數(shù)。通過TEM表征其微觀結(jié)構(gòu)發(fā)現(xiàn)不同F(xiàn)e_2O_3過量比例制得的316L不銹鋼都仍然具有微納結(jié)構(gòu)。2、為優(yōu)化制得的316L不銹鋼的微納結(jié)構(gòu),本課題對其采用了800℃-40%+600℃-80%的軋制處理。將軋制后的不銹鋼進行組織結(jié)構(gòu)和各項性能的表征,得到如下結(jié)果:軋制后,不銹鋼中出現(xiàn)了體積分數(shù)為8.4%鐵素體,此為應變誘導奧氏體向鐵素體轉(zhuǎn)變的結(jié)果。且晶粒有了一定幅度增長:平均尺寸由鑄態(tài)時的23nm增長到軋制后的47nm。納米晶和微米晶體積分數(shù)的比例也得到了改善:微米晶體積分數(shù)由鑄態(tài)8.9%的增長至軋制后的15.6%。相比軋制前的不銹鋼,軋制后其強度得到大幅提升,屈服強度從207MPa提升至1007MPa,增幅約為400%;抗拉強度由376MPa提升至1030MPa,增幅為174%。但軋制后不銹鋼的塑形卻降至2.4%,對此將采用高溫退火提升其塑性。另外,用電化學工作站對軋制前后兩種狀態(tài)下不銹鋼的耐蝕性進行了表征,腐蝕介質(zhì)為0.5M H2SO4溶液,表征形式有開位電路、動電位極化曲線和電化學阻抗譜。表征結(jié)果顯示:軋制后不銹鋼的耐蝕性優(yōu)于軋制前,說明軋制處理提升了不銹鋼的耐腐性能。3、為進一步優(yōu)化微納結(jié)構(gòu)316L不銹鋼的力學性能和其在高溫下的結(jié)構(gòu)穩(wěn)定性,本課題將對軋制后的微納結(jié)構(gòu)316L不銹鋼在800℃下分別進行20min、40min、60min和80min的退火處理。對其組織結(jié)構(gòu)表征發(fā)現(xiàn):退火20min后,不銹鋼中的鐵素體的體積分數(shù)由8.4%降至3.6%,平均晶粒尺寸由47nm增長至57nm,且仍然保留了其微納結(jié)構(gòu)。隨后,隨著退火時間的延長,鐵素體體積分數(shù)又呈現(xiàn)上升趨勢。退火80min后,不銹鋼內(nèi)的鐵素體為6.9%。晶粒尺寸方面,隨著退火時間的延長,晶�？焖匍L大。在退火40min后,不銹鋼的平均晶粒尺寸為107nm,已屬于亞微米晶范疇。說明不銹鋼退火超過40min后,其微納結(jié)構(gòu)消失。隨后又對800℃退火后的316L不銹鋼進行了拉伸試驗,得到了其強度和塑性的參數(shù)。拉伸結(jié)果顯示:退火20min后,不銹鋼的屈服強度及抗拉強度分布為464MPa和770MPa,相比軋制后的不銹鋼其強度有一定程度的下降,但其塑性有很大的提升:由軋制態(tài)的2.4%上升至21.5%,大大提升了其綜合力學性能。但隨著退火時間的延長,強度呈微小下降趨勢,延伸率有較大幅度的增長,最終延伸率達30.4%。
[Abstract]:316L stainless steel is a kind of austenitic stainless steel which can adapt to many environments. Because of its excellent corrosion resistance, processability and good welding performance, it plays an important role in the fields of petrochemical, ocean and paper making. However, because of its low-core cubic structure and low carbon content, the strength and hardness of 316L stainless steel are low, thus limiting its application in more important fields. In order to improve the strength of 316L stainless steel and to ensure its good plasticity, this paper prepared the microstructure 316L stainless steel by the aluminum thermal reaction method. However, due to the incomplete thermal reaction of the aluminum, a small amount of the remaining aluminum elements are fused into the stainless steel, so that the ferritic structure is present in the stainless steel. In order to eliminate the ferrite structure in stainless steel, add iron oxide with different excess proportion to the reaction material to make the aluminum powder fully react, study its influence on the microstructure, composition and micro-nano structure of 316L stainless steel, and explore the microstructure of the micro-nano-structure by rolling and annealing. The effect of corrosion resistance and mechanical properties is the theoretical and experimental basis for the realization of industrial production. Finally, through a series of characterization analysis and conclusion, the following conclusions are drawn: 1. The excess Fe _ 2O _ 3 in the reaction material can reduce the aluminum content in the stainless steel obtained by the aluminum thermal process. When the excess of Fe _ 2O _ 3 is 2.5%, the Al content in the stainless steel is reduced to 1. 74%, the ferrite content is reduced to 4. 1%, when Fe _ 2O _ 3 is 5% excess, the aluminum content in the steel is 1. 3%, and the ferrite disappears. When the excess of Fe _ 2O _ 3 is 7.5%, the aluminum content in the steel drops to 0. 99%, the ferrite is still not, but there are more Fe _ 2O _ 3 intermetallic compound phases. Therefore, 5% of Fe _ 2O _ 3 was used to prepare the optimum preparation parameters of austenitic 316L stainless steel by aluminum thermal method. The microstructure of 316L stainless steel with different Fe _ 2O _ 3 excess ratio was found by TEM. The microstructure of 316L stainless steel was optimized by TEM, and 800 鈩，

本文編號：2293324