【作者】 靳星；

【导师】 文光华；

【作者基本信息】 重庆大学 ， 冶金工程， 2007， 硕士

【摘要】 连铸二次冷却在连铸生产中占有非常重要的地位,不但关系到铸坯质量,而且还与铸机产量密切相关。因此,建立合理的二冷制度(包括喷嘴选型、布置方式和配水控制模型)具有重要的意义。本文提出了现有喷嘴检测设备的不足,通过对喷嘴检测系统的完善与改进,开发了新一代连铸喷嘴性能检测设备。对现有测试系统进行一系列改进,有效地提高了测试系统对水流密度测试的准确性,减小了系统的测试误差,提高了喷嘴测试精度。对南钢方坯铸机使用的水喷嘴和气水喷嘴进行了冷态性能测试,得到了喷嘴的流量特性、喷射角、水流密度和冲击压力分布曲线,对四种不同类型的气水喷嘴进行了比较,根据测试结果给出了气水喷嘴在一定工作条件下的最佳气水比,得到了喷嘴的水流密度分布与二冷水量的关系式。建立了方坯凝固传热数学模型,结合南钢方坯实际情况对模型边界条件进行了优化,并进行了测温和铸坯坯壳厚度验证,结果表明模型的计算与实测结果能够很好地吻合。二冷水量动态控制模型根据拉速的变化来实现二冷段动态配水,在非稳态条件下为了保证配水的合理性,采用矫直点温度反馈的方法,即每隔△t时间将矫直点温度与目标温度进行比较,产生反馈信号,调节水量变化,直至矫直点温度控制在目标温度范围内,从而保证了较好的铸坯质量。本文结合南钢方坯易切削钢种、中、高、低碳钢铸坯质量缺陷,分析了南钢现有二冷制度存在的问题,根据不同钢种比水量的冷却要求和矫直点目标温度,提出了二冷配水优化方案,并针对低碳钢钢种进行了测温验证和铸坯低倍质量观察,结果表明二冷配水优化后,铸坯质量得到明显改善,有效地解决了与二冷有关的质量问题。更多还原

【Abstract】 The secondary cooling system has an important status during continuous casting process, it not only relates to the product quality directly, but also affects caster output. Therefore, establishing a proper secondary cooling system (including choice of nozzle type, arrangement manner and control model for water distribution) has a significant role in continuous casting.This paper introduced the new equipment developed for testing characteristic of nozzle by improving the existing testing system. Through a series of improvement, the testing system has increased the accuracy of the water flow density testing, and decreased the testing error of system. The cold state characteristics of water nozzles and air-water nozzles from NanGang billet caster were tested. The flux characteristic, spraying angle, water flow density and impacting force distribution of the nozzles were present. Through the comparison of four different type air-mist nozzles, the best air water ratio in a condition and the relation of water flow density and water flow were obtained based on the testing results.The solidifying heat transfer model of billet has been established, and its boundary conditions have been optimized according to the circumstances of NanGang billet caster. The results of temperature and billet shell thickness testing indicate that the calculating results of model were in good agreement with testing results, and the solidifying heat transfer model was feasible. The dynamic control model of secondary cooling water adjusts the water distribution by casting speed, uses the straightening point temperature to feed back in order to make proper water adjustment in unsteady state condition. Through the comparison of the straightening point temperature and target temperature, there is a feed back signal to adjust the water distribution so as to guarantee better quality of the billet, until the straightening point temperature in a range of target temperature.In addition, the paper analyzed the problem of the existing secondary cooling system according to the billet quality defects of different types of steel which contains free-cutting steel, high-carbon steel, medium-carbon steel, low-carbon steel at NanGang. Optimizing scheme of secondary cooling water distribution has been put forward on the basic of water rate cooling request of different types of steel and the straightening point target temperature. Then low-carbon steel has been chosen for temperature proof and macroscopic billet quality survey. The results indicate that the quality of billet has improved greatly, and the optimizing scheme has effectively settled the quality problem related to the secondary cooling.更多还原