微纳结构316L不锈钢的制备及其组织和性能
发布时间：2018-10-25 09:43
【摘要】：316L不锈钢是一种能适应于诸多环境的奥氏体不锈钢钢种。因其优良的耐蚀性,可加工性和良好的焊接性能在石化、海洋、造纸等领域发挥着重要的作用。但由于其具有面心立方结构和碳含量低的特点,316L不锈钢的强度和硬度较低,因而限制了其在更多重要的领域的应用。为提高316L不锈钢的强度,同时保证其良好的塑性,本课题通过铝热反应法制备得到了微纳结构316L不锈钢。但由于铝热反应未完全,少量剩余的铝元素熔进了不锈钢中,使得不锈钢中出现了铁素体组织。本课题研究:为消除不锈钢中的铁素体组织,往反应物料中添加不同过量比例的氧化铁使铝粉能充分反应,研究其对制得的316L不锈钢组织、成分和微纳结构的影响,并探究了轧制和退火对微纳组织结构、耐蚀性和力学性能的影响规律,为其实现工业化生产奠定理论和实验基础。最后,通过一系列表征分析和总结,得出以下几条结论:1、反应物料中过量的Fe_2O_3能降低铝热法制得的不锈钢中的铝含量。当Fe_2O_3过量2.5%时,不锈钢中的铝含量降低为1.74%,铁素体含量降至4.1%;当Fe_2O_3过量5%时,钢中的铝含量为1.3%,且铁素体消失。当Fe_2O_3过量7.5%时,钢中的铝含量降为0.99%,铁素体仍然没有,但是出现了较多的FeCrMo金属间化合物相。故Fe_2O_3过量5%为铝热法制备全奥氏体316L不锈钢的最佳制备参数。通过TEM表征其微观结构发现不同Fe_2O_3过量比例制得的316L不锈钢都仍然具有微纳结构。2、为优化制得的316L不锈钢的微纳结构,本课题对其采用了800℃-40%+600℃-80%的轧制处理。将轧制后的不锈钢进行组织结构和各项性能的表征,得到如下结果:轧制后,不锈钢中出现了体积分数为8.4%铁素体,此为应变诱导奥氏体向铁素体转变的结果。且晶粒有了一定幅度增长:平均尺寸由铸态时的23nm增长到轧制后的47nm。纳米晶和微米晶体积分数的比例也得到了改善:微米晶体积分数由铸态8.9%的增长至轧制后的15.6%。相比轧制前的不锈钢,轧制后其强度得到大幅提升,屈服强度从207MPa提升至1007MPa,增幅约为400%;抗拉强度由376MPa提升至1030MPa,增幅为174%。但轧制后不锈钢的塑形却降至2.4%,对此将采用高温退火提升其塑性。另外,用电化学工作站对轧制前后两种状态下不锈钢的耐蚀性进行了表征,腐蚀介质为0.5M H2SO4溶液,表征形式有开位电路、动电位极化曲线和电化学阻抗谱。表征结果显示:轧制后不锈钢的耐蚀性优于轧制前,说明轧制处理提升了不锈钢的耐腐性能。3、为进一步优化微纳结构316L不锈钢的力学性能和其在高温下的结构稳定性,本课题将对轧制后的微纳结构316L不锈钢在800℃下分别进行20min、40min、60min和80min的退火处理。对其组织结构表征发现:退火20min后,不锈钢中的铁素体的体积分数由8.4%降至3.6%,平均晶粒尺寸由47nm增长至57nm,且仍然保留了其微纳结构。随后,随着退火时间的延长,铁素体体积分数又呈现上升趋势。退火80min后,不锈钢内的铁素体为6.9%。晶粒尺寸方面,随着退火时间的延长,晶粒快速长大。在退火40min后,不锈钢的平均晶粒尺寸为107nm,已属于亚微米晶范畴。说明不锈钢退火超过40min后,其微纳结构消失。随后又对800℃退火后的316L不锈钢进行了拉伸试验,得到了其强度和塑性的参数。拉伸结果显示:退火20min后,不锈钢的屈服强度及抗拉强度分布为464MPa和770MPa,相比轧制后的不锈钢其强度有一定程度的下降,但其塑性有很大的提升:由轧制态的2.4%上升至21.5%,大大提升了其综合力学性能。但随着退火时间的延长,强度呈微小下降趋势,延伸率有较大幅度的增长,最终延伸率达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，
本文编号：2293324
[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，
本文编号：2293324
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