低屈强比SPCC钢板热处理工艺及夹杂物探究
发布时间：2019-07-10 10:41
【摘要】：优质碳素结构钢SPCC冷轧钢板因其具有良好的深冲性能、较低的屈服强度、良好的延展性和光洁平整的表面状态在汽车、农用机械、电子产品、仪器仪表及家电领域得到了越来越广泛的应用。薄板材的性能严重影响着成品的工艺性能,因而优质的冲压板材是获得性能优异、表面光洁成品的保证。因此生产较低屈强比、力学性能优异的薄钢板对于企业具有重要意义。本课题选取泰山钢铁集团生产的两种不同规格的冷轧板作为研究对象。分别对其进行4小时热处理,温度区间为440℃-760℃,步长为40℃。通过金相显微镜分析恒时热处理的金相组织,利用维氏硬度计测量不同温度热处理后试样的硬度。根据金相显微组织和硬度值选取较为合适的热处理温度;随后对其进行恒温不同保温时间的热处理,通过金相显微组织和硬度观察分析保温时间的影响。从恒温和恒时热处理结果中选定较为合适的几组热处理工艺制度,对950产线和1780产线的冷轧板进行热处理,测定其力学性能,并利用SEM扫描电子显微镜对其拉伸断口形貌进行观察。随后通过SEM配合能谱仪对金相试样中的夹杂物形貌及其成分、分布等观察分析。为获得较低屈强比、力学性能良好的SPCC钢板提出改善工艺。研究发现泰钢生产的两种规格的冷轧薄钢板均存在屈强比过高,冲压变形抗力过大的问题。分析其金相显微组织发现退火后的晶粒过于细小,晶粒度等级在9-10,晶粒度等级过高。恒时热处理结果显示,950产线和1780产线的SPCC钢板再结晶的温度在520℃左右,在520℃以下退火时,SPCC冷轧薄钢板金相组织中呈现纤维状的拉长晶粒,在520℃退火后金相组织中开始出现无畸变的新晶粒,随着退火温度的升高,无畸变的新晶粒开始增多并逐渐吞噬变形组织进行长大,在680℃时材料的再结晶过程基本完成,晶粒较为均匀。晶粒度随着温度升高而呈现降低的趋势。680℃和720℃恒温热处理后发现,SPCC钢板退火后的晶粒度和硬度随着保温时间的增加呈现缓慢波动变化,总体来说保温时间相比于退火温度对SPCC钢板组织性能的影响较小。拉伸断口形貌分析显示宏观断口均为无金属光泽的暗灰色,属于韧性断口。在微观断口形貌上,随着温度的升高,950产线拉伸断口的韧窝尺寸和数量逐渐减小,韧窝的尺寸由均匀性向差异性发展,韧窝的深度变得越来越浅。1780产线680℃4小时退火后的拉伸断口韧窝的大小相对均匀,720℃4小时退火后拉伸断口平均尺寸跟680℃时相差不大,但韧窝尺寸大小不均,温度在760℃时,韧窝尺寸增大,平均韧窝尺寸在12μm左右且大小更加不均匀。拉伸断口中的韧窝越均匀,韧窝深度较深且尺寸越小,材料的力学性能越好。从夹杂物方面分析来看,夹杂物对SPCC冷轧薄钢板力学性能的影响主要表现在夹杂物的含量、尺寸和分布上,夹杂物的含量越多,尺寸越大,则其韧性越差。950和1780产线的夹杂物总体来说尺寸较为均匀,大尺寸的环状外来夹杂物相对较少。夹杂物以链状的Al2O3和长条状的MnS以及不变形的硅酸盐居多,Al2O3和MnS常以复合的蝌蚪状存在于基体之中。1780产线的夹杂物相比950产线数量更少,因而其延伸率更高,塑性相对更好。
[Abstract]:The high-quality carbon structural steel SPCC cold-rolled steel plate has been widely used in the fields of automobile, agricultural machinery, electronic products, instruments and electrical appliances because of its excellent deep drawing performance, lower yield strength, good ductility and smooth and smooth surface state. The performance of the thin plate greatly influences the process performance of the finished product, so the high-quality stamped sheet material is a guarantee of excellent performance and smooth surface finish. Therefore, the thin steel sheet with low yield ratio and excellent mechanical property is of great significance to the enterprise. In this paper, two kinds of graphite plates with different specifications produced by Taishan Iron and Steel Group are selected as the research object. The heat treatment is carried out for 4 hours respectively, and the temperature range is 440-760 DEG C and the step length is 40 DEG C. The hardness of the specimen after heat treatment at different temperatures was measured by means of the Vickers hardness meter by means of the metallographic structure of the heat treatment at constant time by means of a metallographic microscope. The proper heat treatment temperature is selected according to the metallographic microstructure and the hardness value, and then the heat treatment of the constant temperature and different heat preservation time is carried out, and the influence of the thermal insulation time is analyzed through the metallographic microstructure and the hardness observation. A suitable group of heat treatment process systems were selected from the results of constant-temperature and constant-time heat treatment. The mechanical properties of 950 and 1780 wire-producing plates were measured and their tensile fracture morphology was observed by means of SEM. The morphology, composition and distribution of the inclusions in the metallographic sample were then analyzed by means of the SEM. In ord to obtain a SPCC steel plate with a lower yield ratio and a good mechanical property, an improvement process is proposed. It has been found that the two kinds of cold-rolled steel sheets produced by Tae Steel have the problems of high yield ratio and excessive punching deformation resistance. The results show that the grain size is too small, the grain size is 9-10, and the grain size is too high. The results of the constant-time heat treatment show that the recrystallization temperature of the SPCC steel sheet at the 950-and 1780-producing lines is about 520.degree. C., and in the annealing at 520.degree. C., a fibrous elongated crystal grain is present in the metallographic structure of the SPCC cold-rolled steel sheet, and a new crystal grain with no distortion is started in the gold-phase structure after annealing at 520 DEG C, With the increase of the annealing temperature, the new crystal grain with no distortion started to increase and the deformed tissue was gradually engulfed to grow. The recrystallization process of the material was basically completed at 680 鈩，
本文编号：2512550
[Abstract]:The high-quality carbon structural steel SPCC cold-rolled steel plate has been widely used in the fields of automobile, agricultural machinery, electronic products, instruments and electrical appliances because of its excellent deep drawing performance, lower yield strength, good ductility and smooth and smooth surface state. The performance of the thin plate greatly influences the process performance of the finished product, so the high-quality stamped sheet material is a guarantee of excellent performance and smooth surface finish. Therefore, the thin steel sheet with low yield ratio and excellent mechanical property is of great significance to the enterprise. In this paper, two kinds of graphite plates with different specifications produced by Taishan Iron and Steel Group are selected as the research object. The heat treatment is carried out for 4 hours respectively, and the temperature range is 440-760 DEG C and the step length is 40 DEG C. The hardness of the specimen after heat treatment at different temperatures was measured by means of the Vickers hardness meter by means of the metallographic structure of the heat treatment at constant time by means of a metallographic microscope. The proper heat treatment temperature is selected according to the metallographic microstructure and the hardness value, and then the heat treatment of the constant temperature and different heat preservation time is carried out, and the influence of the thermal insulation time is analyzed through the metallographic microstructure and the hardness observation. A suitable group of heat treatment process systems were selected from the results of constant-temperature and constant-time heat treatment. The mechanical properties of 950 and 1780 wire-producing plates were measured and their tensile fracture morphology was observed by means of SEM. The morphology, composition and distribution of the inclusions in the metallographic sample were then analyzed by means of the SEM. In ord to obtain a SPCC steel plate with a lower yield ratio and a good mechanical property, an improvement process is proposed. It has been found that the two kinds of cold-rolled steel sheets produced by Tae Steel have the problems of high yield ratio and excessive punching deformation resistance. The results show that the grain size is too small, the grain size is 9-10, and the grain size is too high. The results of the constant-time heat treatment show that the recrystallization temperature of the SPCC steel sheet at the 950-and 1780-producing lines is about 520.degree. C., and in the annealing at 520.degree. C., a fibrous elongated crystal grain is present in the metallographic structure of the SPCC cold-rolled steel sheet, and a new crystal grain with no distortion is started in the gold-phase structure after annealing at 520 DEG C, With the increase of the annealing temperature, the new crystal grain with no distortion started to increase and the deformed tissue was gradually engulfed to grow. The recrystallization process of the material was basically completed at 680 鈩，
本文编号：2512550
本文链接：https://www.wllwen.com/kejilunwen/jiagonggongyi/2512550.html
