铸造和热轧高铝304、316L、310S不锈钢组织演化及铝元素作用机制

发布时间：2018-02-16 22:47

本文关键词： 304、316L、310S不锈钢铸造组织固溶组织轧制温度轧制变形量　出处：《兰州理工大学》2016年博士论文　论文类型：学位论文

【摘要】：近年来,含Al奥氏体不锈钢因其良好的耐腐蚀、抗高温氧化、耐高温蠕变性而受到广泛关注。本课题组前期利用真空电弧炉制备了不同铝含量304、316L、310S铸锭、板材,发现通过调控Al含量,不锈钢在满足力学性能不出现明显下降的同时,耐蚀性、抗氧化性显著提高。为了使此类钢能实现工业化应用,本文采用中频感应炉制备了不同Al含量(1.5、2、3wt%)304、316L、310S不锈钢,研究了不同Al含量304、316L、310S不锈钢铸造、固溶、轧制组织演变规律及组织对性能的作用机制。研究发现,Al元素的添加,使得304不锈钢基体由单相奥氏体转变为奥氏体+铁素体双相,Al含量为3wt%时,基体转变为完全的铁素体相。铁素体形貌也由最初的骨骼状转变为条状。含Al304不锈钢凝固模式均为F模式。Al元素主要以固溶的形式存在,其在铁素体相内出现偏析。固溶处理改变了不同Al含量304不锈钢中铁素体/奥氏体相的比例及形貌,消除了Al元素在铁素体相内的偏析。分析了轧制温度、轧制变形量、Al含量对304不锈钢热轧态组织的影响,当轧制变形量为50%时,调控轧制温度、Al含量可以获得形态、尺寸不同的奥氏体、铁素体相。轧制温度升高或Al含量增加,均有助于细化组织,其中轧制温度1200℃,2wt%Al 304不锈钢中铁素体、奥氏体相细化最明显,最小的奥氏体相大约长4μm,宽3μm。轧制温度为1100℃时,随轧制变形量的增加,1.5wt%Al 304不锈钢奥氏体相形貌、尺寸无明显变化,而铁素体相内亚结构数目增多。轧制温度为1150℃时,随轧制变形量的增加,2wt%Al304不锈钢中铁素体、奥氏体相细化。然而,变形量增加到70%时,组织发生粗化。Al元素对316L不锈钢相组成、凝固模式的影响与其对304不锈钢的影响规律相似。所不同的是,随Al含量的增加,316L不锈钢中铁素体相依次以短杆、长条+岛状分布在奥氏体基体上;Al含量为3wt%时,铁素体相转变为基体相;Al元素主要固溶在基体中,Al含量为3wt%时,其在铁素体相内才出现明显偏析。固溶处理后,相同Al含量316L不锈钢中铁素体体积分数增加,Al元素在铁素体、奥氏体相内分布趋于平衡。分析了轧制温度、轧制变形量、Al含量对316L不锈钢热轧态组织的影响发现,轧制变形量为50%时,调控轧制温度、Al含量可以获得形态、尺寸不同的奥氏体、铁素体相。轧制温度提高或Al含量增加,有利于1.5、2wt%Al 316L不锈钢中铁素体相内亚结构的形成;轧制温度为1150℃时,2wt%Al 316L不锈钢中铁素体、奥氏体两相晶粒细化,最小的奥氏体尺寸大约长10μm,宽5μm。轧制温度为1200℃时,随轧制变形量的增加,1.5wt%Al 316L不锈钢中奥氏体相有新的再结晶晶粒形成。轧制温度为1150℃时,随轧制温度的升高,2wt%Al 316L不锈钢中铁素体、奥氏体相细化,当变形量增加到70%时,铁素体、奥氏体相明显粗化。Al元素的添加,使得310S不锈钢基体由单相奥氏体转变为奥氏体+铁素体双相;1.5、2wt%Al 310S不锈钢的凝固模式为FA模式,3wt%Al 310S不锈钢的凝固模式为F模式。铁素体相依次以枝晶状、枝晶+网格状、杆状+小岛状存在于奥氏体基体。大部分Al元素以固溶的形式存在于310S不锈钢中。Al含量为3wt%时,其在铁素体相内出现明显的偏析现象。固溶处理改变了铁素体、奥氏体两相的形貌及相比例,Al元素在铁素体、奥氏体相内分布趋于平衡。Al含量为2、3wt%时,沿奥氏体/铁素体相界处有碳化物析出。不同轧制温度,50%轧制变形量1.5、2wt%Al310S不锈钢中,铁素体相局部被拉长并发生粗化。前者铁素体相内有针状、长条状二次奥氏体相析出;3wt%Al310S不锈钢中,部分区域内奥氏体相破碎,以小块状、短杆状分布在基体上。
[Abstract]:In recent years, including Al austenitic stainless steel due to its good corrosion resistance, oxidation resistance, high temperature creep and attracted widespread attention. Ourprevious 304316L, different aluminum content were prepared by vacuum arc furnace for 310S ingot, plate, found by regulating Al content in stainless steel to meet the mechanical properties do not appear significantly lower at the same time, corrosion resistance, oxidation resistance is improved significantly. In order to make such steel can realize the industrial application, the different contents of Al were prepared by medium frequency induction furnace system (1.5,2,3wt%) 304316L, 310S stainless steel, 304316L was studied with different content of Al, 310S stainless steel casting, solid solution, rolling mechanism of microstructure evolution and structure on the performance. The study found that the addition of Al, the 304 stainless steel substrate changed from single-phase austenitic AUSTENITIC FERRITIC duplex, Al content is 3wt%, the matrix into full ferrite ferrite phase. Appearance has changed from the initial skeleton strip. Al304 containing stainless steel solidification mode is F mode.Al elements mainly exist in the form of solid solution, the ferrite phase segregation. Solid solution changed with different content of Al 304 stainless steel ferrite / austenite phase ratio and morphology, eliminate segregation the Al element in the ferrite phase. Analysis of the rolling temperature, rolling deformation, the influence of Al content on Microstructure of 304 stainless steel hot rolling, when the rolling deformation is 50%, control of the rolling temperature, the content of Al can obtain different morphology, size of austenite, ferrite rolling temperature or Al content. Increase, all contribute to the refinement of microstructure, the rolling temperature of 1200 DEG C, 2wt%Al 304 ferrite stainless steel, the most obvious refinement of austenite phase, minimum austenite phase about 4 m long, 3 m. wide rolling temperature is 1100 degrees centigrade with rolling deformation increase, 1.5wt%Al 304 The morphology of austenitic stainless steel, the size has no obvious change, but the ferrite phase sub structure increased. The rolling temperature is 1150 degrees centigrade, with the increase of rolling deformation, 2wt%Al304 ferrite, austenite phase refinement. However, the deformation increased to 70%, the organization coarsened.Al elements on the phase composition of 316L stainless steel the influence of solidification mode, and its influence on 304 stainless steel similar. The difference is that with the increase of Al content, 316L ferrite phase followed by a short rod, strip + island distribution in austenite; the content of Al is 3wt%, the ferrite phase transformation matrix; Al element dissolve in the matrix, the Al content is 3wt%, its apparent segregation in the ferrite phase. After solution treatment, the same Al content 316L ferrite volume fraction increases, the Al element in the ferrite phase distribution in austenite balance was analyzed. The rolling temperature, rolling deformation, influence of Al content on the microstructure of 316L stainless steel hot rolling, the rolling deformation is 50%, control of the rolling temperature, the content of Al can obtain different morphology, size of austenite, ferrite phase. Increasing rolling temperature or increasing the content of Al, 1.5,2wt%Al of 316L ferrite stainless steel is conducive to the formation of bulk the sub structure; the rolling temperature is 1150 degrees centigrade, 2wt%Al 316L ferrite, austenite grain refinement of austenite, the minimum size of approximately 10 m, width 5 m. rolling temperature is 1200 degrees centigrade, with the increase of rolling deformation, 1.5wt%Al 316L stainless steel in the austenite phase with new recrystallized grains formed. The rolling temperature is 1150 degrees centigrade with increasing rolling temperature, 2wt%Al 316L ferrite, austenite phase refinement, when the deformation rate increased to 70%, ferrite, add the austenite phase coarsening of.Al element, the 310S The stainless steel substrate by single phase austenite transformation for AUSTENITIC FERRITIC duplex stainless steel; solidification mode of 1.5,2wt%Al 310S for FA mode, 3wt%Al 310S stainless steel solidification mode is the F mode. The ferrite phase followed by dendrite, dendritic + grid, rod-shaped Island exists in austenite +. Most of the Al elements in the form of solid solution of.Al in 310S stainless steel 3wt%, the ferrite phase segregation phenomenon is obvious. The solution treatment changed the morphology of ferrite, austenite phase and phase ratio, Al elements in the ferrite, austenite phase distribution tends to balance the.Al content is 2,3wt%. Along the austenite / ferrite phase boundary carbide precipitates. Different rolling temperature and deformation of 1.5,2wt%Al310S stainless steel in 50% rolling, ferrite phase are partially coarsened and elongated. The ferrite phase in acicular, strip two austenite precipitates; In 3wt%Al310S stainless steel, the austenite is broken in part of the area and is distributed on the matrix with small block and short rod like shape.

【学位授予单位】：兰州理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG260;TG337.5

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