An unsteady,two-dimensional,explicitly solved finite difference heat transfer model of a billet caster was presented to clarify the influence of the thermal conductivity of steel on model accuracy.Different approaches were utilized for calculating the thermal conductivity of solid,mushy and liquid steels.Model results predicted by these approaches were compared,and the advantages of advocated approaches were discussed.It is found that the approach for calculating the thermal conductivity of solid steel notably influences model predictions.Convection effects of liquid steel should be considered properly while calculating the thermal conductivity of mushy steel.Different values of the effective thermal conductivity of liquid steel adopted could partly be explained by the fact that different models adopted dissimilar approaches for calculating the thermal conductivity of solid and mushy steels.
采用Netzsch DIL 402C热膨胀分析仪研究了GCr15钢在200～1 000℃温度范围内的热膨胀规律,通过取样、制样、试验测量得到试验数据,采用微分法进行数据运算与处理,得到瞬时热膨胀系数并发现一定规律。研究结果表明,GCr15钢的瞬时热膨胀系数在1.5×10-5～8.0×10-5之间,且在奥氏体转变点温度前后分别与温度呈三次方关系,符合Grüuneisen关系式和Debye模型的规律。
针对连铸小方坯的中心疏松等质量缺陷,建立了凝固传热数学模型,以研究二冷强度对连铸小方坯凝固过程的影响规律,优化二冷制度,改善铸坯质量.本文基于射钉和测温实验所建立的小方坯凝固传热模型精细度较高,用此模型深入研究二冷喷嘴的数量和喷射范围对小方坯凝固传热的影响;经验证,模拟结果与实测结果误差在1.7%以内.利用该模型定量分析了二冷强度对铸坯温度,凝固坯壳厚度和凝固终点的影响规律.结果表明,随着二冷强度的增大,二冷区内的铸坯表面中心温度降低,而进入空冷区后则逐渐趋于一致.二冷强度每增加10%,足辊段出口处温度平均降低8℃,二冷一段出口处温度平均降低10.75℃,二冷二段出口处温度平均降低10.75℃,二冷三段出口处温度平均降低9.75℃,铸坯凝固终点缩短约0.168 m.
A method for observing the three-dimensional morphologies of inclusions by deeply eroding a steel sample with a kind of organic solution composed of bromine water, acetone, and HCl (volume ratio, 45:45:10) was introduced. Four different kinds of inclusions in ultra low carbon steel were compared by metallographic observation and erosion observation. The results show that the three-dimensional morphologies of different kinds of inclusions could be observed clearly and simply after erosion. The method is useful for the observation and analysis of inclusions made by deep erosion. It also provides a new way to control and remove inclusions based on the true morphologies of inclusions.
