冷轧变形对316LN奥氏体不锈钢组织和性能的影响
发布时间：2018-11-05 15:01
【摘要】：奥氏体不锈钢由于具有优良的韧塑性、抗高温氧化性以及耐腐蚀性等,被广泛用于食品、化工等领域,但固溶态奥氏体不锈钢的强度比较低,因而奥氏体不锈钢很少作为结构材料使用,通常需要借助加工硬化的方式来提高其综合性能,以满足其使用要求,冷轧作为一种有效的加工硬化方式,也常常被人们用作改善不锈钢性能的手段。近些年来,国内外有许多关于室温冷轧对奥氏体不锈钢性能影响的研究文献,但鲜有人系统地研究室温冷轧与深冷轧制对316 LN奥氏体不锈钢组织和性能的影响,且国内外深冷轧制研究的对象也都基本局限在有色金属方面。鉴于上述情况,本文将全面地研究冷轧变形对316 LN奥氏体不锈钢组织和性能的影响,为316 LN奥氏体不锈钢的开发和应用提供实验依据和技术支撑。本文以316 LN奥氏体不锈钢为研究对象,随后分别进行室温状态和深冷状态(液氮)下的轧制,并对轧制后316 LN奥氏体不锈钢力学性能的变化进行详细研究,借助金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)等微观组织分析手段对其组织演变过程进行系统表征,结果表明:奥氏体不锈钢在轧制变形过程中均发生了形变诱导马氏体相变,且随着轧制变形量的增大,形变诱导马氏体所占的体积分数也越大。室温轧制状态下,形变诱导马氏体的体积分数由11.1%(30%)上升到72.3%(90%)。深冷轧制状态下,轧制变形量为30%时,形变诱导马氏体的体积分数为58.7%,变形量为50%时,其体积分数为78.7%,当轧制变形量继续增大为70%时,奥氏体组织已完全转变成马氏体。经同一轧制状态下各变形量间的比较以及两种不同轧制状态下不同变形量的对比可知:深冷轧制状态下形变诱导马氏体相变的速率远远高于室温轧制状态,且深冷轧制下奥氏体组织能100%转化成马氏体。室温轧制过程中,在变形量较小的情况下,变形的组织中主要是以位错的增殖和缠结为主,同时有少量的形变孪晶和板条马氏体生成;当变形量较大时,变形组织则以形变孪晶为主,并伴随有少量高密度位错墙和位错胞,同时形变诱导马氏体大量出现。深冷轧制过程中,在变形量较小时,已出现大量形变诱导马氏体,当变形量进一步增大到70%时,组织内部已完全发生形变诱导马氏体相变。随着变形量的增大,奥氏体不锈钢的硬度值和强度值也随之增大,前期呈迅速上升状态,后期逐渐趋于平稳,且同一变形量,深冷轧制后奥氏体不锈钢的硬度值和强度值均明显高于室温冷轧:变形量为90%时,深冷轧制后奥氏体不锈钢的硬度值约为原始试样的3倍,屈服强度和抗拉强度约为原始试样的7倍和3倍;室温冷轧后试样硬度值约为原始试样的2.6倍,屈服强度和抗拉强度为原始试样的4.9倍和2.2倍。试样拉伸断口形貌均由韧性断裂向韧性和准解理混合型断裂转变。延伸率随着轧制变形量的增大而迅速降低,与力学性能指标变化趋势相反:室温轧制时,试样的延伸率由3.5%(30%)下降至2.5%(90%);深冷轧制状态,延伸率由2.3%(30%)下降至1.5%(90%)。
[Abstract]:The austenitic stainless steel is widely used in the fields of food, chemical industry and the like due to the excellent toughness, high temperature oxidation resistance, corrosion resistance and the like, but the strength of the solid soluble austenitic stainless steel is low, so that the austenitic stainless steel is rarely used as a structural material, it is often necessary to improve its comprehensive performance by means of a cold rolling to meet its use requirements, cold rolling as an efficient cold rolling method, and often used as a means of improving the performance of the stainless steel. In recent years, there are many studies on the effect of cold rolling on the properties of austenitic stainless steel at room temperature, but few have systematically studied the effect of cold rolling and cryogenic rolling on the microstructure and properties of 316LN austenitic stainless steel. And the object of cryogenic rolling research both at home and abroad is also limited to non-ferrous metals. In view of the above situation, this paper will comprehensively study the effect of cold rolling deformation on microstructure and properties of 316LN austenitic stainless steel, and provide experimental basis and technical support for the development and application of 316LN austenitic stainless steel. In this paper, 316 LN austenitic stainless steel was used as the research object, then the rolling at room temperature and cryogenic state (liquid nitrogen) were carried out respectively, and the mechanical properties of 316L austenitic stainless steel after rolling were studied in detail. The microstructure evolution of austenitic stainless steel is characterized by means of microstructure analysis such as transmission electron microscope (TEM). The results show that the deformation induced martensite transformation in the process of rolling deformation of austenitic stainless steel, and with the increase of rolling deformation, The larger the volume fraction of the deformation-induced martensite. In the condition of room temperature rolling, the volume fraction of deformation-induced martensite increased from 11.1% (30%) to 72.3% (90%). In the state of cryogenic rolling, when the rolling deformation amount is 30%, the volume fraction of deformation-induced martensite is 58. 7%, and when the deformation amount is 50%, its volume fraction is 77.8%, and when the rolling deformation continues to increase to 70%, the austenite structure has completely transformed into martensite. The comparison between the deformation amounts in the same rolling state and the comparison of different deformation amounts in two different rolling states shows that the rate of deformation induced martensite transformation in deep cooling rolling state is much higher than that of the room temperature rolling state, and the austenite structure can be converted into martensite by 100% under the deep cooling rolling state. In the process of rolling at room temperature, under the condition that the deformation amount is small, the deformation is mainly caused by the propagation and entanglement of dislocations, and at the same time, a small amount of the deformed columnar crystal and the lath martensite are generated, and when the deformation amount is large, the deformation structure mainly takes the deformed columnar crystal as the main structure, It is accompanied by a small number of high density dislocation walls and dislocation cells, and deformation induces a great deal of martensite. In the process of deep cooling, a large number of deformation-induced martensite has occurred during low deformation. When the deformation amount is further increased to 70%, the deformation-induced martensite transformation is completely induced inside the structure. With the increase of the deformation amount, the hardness value and the strength value of the austenitic stainless steel are also increased, the early stage is in a rapidly rising state, the later stage gradually becomes stable, and the same deformation amount, the hardness value and the strength value of the austenitic stainless steel after the deep cooling rolling are obviously higher than that of the room temperature cold rolling: When the deformation amount is 90%, the hardness value of the austenitic stainless steel after the deep cooling rolling is about 3 times of the original sample, the yield strength and the tensile strength are about 7 times and 3 times of the original sample, the hardness value of the sample after cold rolling at room temperature is about 2.6 times of the original sample, Yield strength and tensile strength were 4. 9 and 2. 2 times the original sample. The tensile fracture morphology of specimen was changed from ductile fracture to ductile fracture and quasi-cleavage mixed fracture. The elongation of the specimen decreases rapidly with the increase of rolling deformation and the change trend of mechanical property index is opposite: the elongation of the specimen decreases from 3.5% (30%) to 2.5% (90%) when rolling at room temperature. The elongation of cryogenic rolling decreases from 2.3% (30%) to 1.5% (90%).
【学位授予单位】：河南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.71;TG337.5
[Abstract]:The austenitic stainless steel is widely used in the fields of food, chemical industry and the like due to the excellent toughness, high temperature oxidation resistance, corrosion resistance and the like, but the strength of the solid soluble austenitic stainless steel is low, so that the austenitic stainless steel is rarely used as a structural material, it is often necessary to improve its comprehensive performance by means of a cold rolling to meet its use requirements, cold rolling as an efficient cold rolling method, and often used as a means of improving the performance of the stainless steel. In recent years, there are many studies on the effect of cold rolling on the properties of austenitic stainless steel at room temperature, but few have systematically studied the effect of cold rolling and cryogenic rolling on the microstructure and properties of 316LN austenitic stainless steel. And the object of cryogenic rolling research both at home and abroad is also limited to non-ferrous metals. In view of the above situation, this paper will comprehensively study the effect of cold rolling deformation on microstructure and properties of 316LN austenitic stainless steel, and provide experimental basis and technical support for the development and application of 316LN austenitic stainless steel. In this paper, 316 LN austenitic stainless steel was used as the research object, then the rolling at room temperature and cryogenic state (liquid nitrogen) were carried out respectively, and the mechanical properties of 316L austenitic stainless steel after rolling were studied in detail. The microstructure evolution of austenitic stainless steel is characterized by means of microstructure analysis such as transmission electron microscope (TEM). The results show that the deformation induced martensite transformation in the process of rolling deformation of austenitic stainless steel, and with the increase of rolling deformation, The larger the volume fraction of the deformation-induced martensite. In the condition of room temperature rolling, the volume fraction of deformation-induced martensite increased from 11.1% (30%) to 72.3% (90%). In the state of cryogenic rolling, when the rolling deformation amount is 30%, the volume fraction of deformation-induced martensite is 58. 7%, and when the deformation amount is 50%, its volume fraction is 77.8%, and when the rolling deformation continues to increase to 70%, the austenite structure has completely transformed into martensite. The comparison between the deformation amounts in the same rolling state and the comparison of different deformation amounts in two different rolling states shows that the rate of deformation induced martensite transformation in deep cooling rolling state is much higher than that of the room temperature rolling state, and the austenite structure can be converted into martensite by 100% under the deep cooling rolling state. In the process of rolling at room temperature, under the condition that the deformation amount is small, the deformation is mainly caused by the propagation and entanglement of dislocations, and at the same time, a small amount of the deformed columnar crystal and the lath martensite are generated, and when the deformation amount is large, the deformation structure mainly takes the deformed columnar crystal as the main structure, It is accompanied by a small number of high density dislocation walls and dislocation cells, and deformation induces a great deal of martensite. In the process of deep cooling, a large number of deformation-induced martensite has occurred during low deformation. When the deformation amount is further increased to 70%, the deformation-induced martensite transformation is completely induced inside the structure. With the increase of the deformation amount, the hardness value and the strength value of the austenitic stainless steel are also increased, the early stage is in a rapidly rising state, the later stage gradually becomes stable, and the same deformation amount, the hardness value and the strength value of the austenitic stainless steel after the deep cooling rolling are obviously higher than that of the room temperature cold rolling: When the deformation amount is 90%, the hardness value of the austenitic stainless steel after the deep cooling rolling is about 3 times of the original sample, the yield strength and the tensile strength are about 7 times and 3 times of the original sample, the hardness value of the sample after cold rolling at room temperature is about 2.6 times of the original sample, Yield strength and tensile strength were 4. 9 and 2. 2 times the original sample. The tensile fracture morphology of specimen was changed from ductile fracture to ductile fracture and quasi-cleavage mixed fracture. The elongation of the specimen decreases rapidly with the increase of rolling deformation and the change trend of mechanical property index is opposite: the elongation of the specimen decreases from 3.5% (30%) to 2.5% (90%) when rolling at room temperature. The elongation of cryogenic rolling decreases from 2.3% (30%) to 1.5% (90%).
【学位授予单位】：河南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.71;TG337.5
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