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Casting/mold thermal contact heat transfer during solidification of Al-Cu-Si alloy (LM 21) plates in thick and thin molds 总被引:1,自引:0,他引:1
K. Narayan Prabhu Bheemappa Chowdary N. Venkataraman 《Journal of Materials Engineering and Performance》2005,14(5):604-609
Heat flow at the casting/mold interface was assessed and studied during solidification of Al-Cu-Si (LM 21) alloy in preheated
cast iron molds of two different thicknesses, coated with graphite and alumina based dressings. The casting and the mold were
instrumented with thermocouples connected to a computer controlled temperature data acquisition system. The thermal history
at nodal locations in the mold and casting obtained during experimentation was used to estimate the heat flux by solving the
one-dimensional inverse heat conduction problem. The cooling rate and solidification time were measured using the computer-aided
cooling curve analysis data. The estimated heat flux transients showed a peak due to the formation of a stable solid shell,
which has a higher thermal conductivity compared with the liquid metal in contact with the mold wall prior to the occurrence
of the peak. The high values of heat flux transients obtained with thin molds were attributed to mold distortion due to thermal
stresses. For thin molds, assumption of Newtonian heating yielded reliable interfacial heat transfer coefficients as compared
with one-dimensional inverse modeling. The time of occurrence of peak heat flux increased with a decrease in the mold wall
thickness and increase in the casting thickness. 相似文献
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通过对活塞式压缩机缸体底注方式和顶注雨淋两种工艺方案的充型和凝固过程的数值模拟,揭示了缸体的液相分布和温度场分布及凝固顺序和冷铁的特殊作用,冷铁使顶注雨淋方式的下低上高的温度场分布趋势得到明显的加强,改善了缸体在凝固过程中的液相分布,改变了先中间后两头的凝固顺序,缸体从总体上形成了从下往上的有利于补缩的凝固顺序。从而得出了压缩机缸体的最佳铸造工艺方案是顶注雨淋浇注系统+硕部压力冒口+底部冷铁+阀孔冷铁+缸径冷铁(下部),并预测了压缩机缸体缩孔缩松产生的部位和大小。实际生产验证了模拟结果的正确性。 相似文献
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1. IntroductionSince the 1960's, there have been 3 progressive periodsfor modeling and simulation of the technological processof castings. In 1988, 3-D temperature fields were calculatedsuccessfully during the solidification process of steelcastings in many countries [1-4]. In 1995, 3-D velocityfields calculations of metal flow in mold filling were alsoachieved by advanced researchers [5-8]. From 1990 untilnow, the new task has been to model and simulate themicrostructure and morphology of cr… 相似文献
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Fluid flow, heat transfer and solidification of steel in the mold are so complex but crucial, determining the surface quality of the continuous casting slab. In the current study, a 2D numerical model was established by Fluent software to simulate the fluid flow, heat transfer and solidification of the steel in the mold. The VOF model and k-ε model were applied to simulate the flow field of the three phases(steel, slag and air), and solidification model was used to simulate the solidification process. The phenomena at the meniscus were also explored through interfacial tension between the liquid steel and slag as well as the mold oscillation. The model included a 20 mm thick mold to clarify the heat transfer and the temperature distribution of the mold. The simulation results show that the liquid steel flows as upper backflow and lower backflow in the mold, and that a small circulation forms at the meniscus. The liquid slag flows away from the corner at the meniscus or infiltrates into the gap between the mold and the shell with the mold oscillating at the negative strip stage or at the positive strip stage. The simulated pitch and the depth of oscillation marks approximate to the theoretical pitch and measured depth on the slab. 相似文献
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采用大型商业软件ProCAST建立了钢锭凝固传热数值仿真,钢锭模在凝固过程中的温度场是空间和时间的变化量,属于三维不稳定态传热。为了验证钢锭凝固过程温度场变化对钢锭冶金缺陷的影响,本文采用24寸42CrMo钢种钢锭模进行数值仿真。采取钢锭浇注过热度、断面温度梯度、液相线和固相线的分析,模拟了钢锭凝固过程中温度场、凝固分数、缩松率及Niyama的分布。通过仿真与实际操作工艺相结合,以及钢锭的超声检测和解剖验证的低倍检验,证明了仿真技术和超声检测可以提高钢锭的冶金质量。 相似文献
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采用自制的计算机数据采集系统,测试了低压铸造薄壁件从开始充型到凝固结束全过程的温度变化,分析了薄板件的温度变化规律及分布特点。研究表明,薄壁件的充型形态对温度分面影响很大。测试结果反映了铸件的充填顺序及充型过程中的凝固现象。温度场测试结果可用于验证充型过程流场温度耦合程度的正确性。 相似文献
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连铸凝固传热全过程数值模拟与控制 总被引:1,自引:0,他引:1
基于传热学、凝固理论、熔渣理论,建立了凝固传热有限差分数值模型,对连铸全过程进行热状态、凝固状态分析及工艺控制,模型考虑了钢的热物性参数随温度变化的关系.并根据连铸冶金准则和目标温度控制进行二冷优化,获得合理的温度分布和二冷水量分布,实现最佳铸坯品质,同时针对不同钢种的凝固特点,对保护渣性能进行设计.计算值同现场实测数据进行对比,有较好的一致性.最后研究了浇注温度、拉坯速度、二冷配水等工艺参数对铸坯表面温度、液芯长度和凝固坯壳厚度的影响,以及浇注工艺对连铸保护渣指标的影响. 相似文献
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通过对活塞式压缩机缸体底注工艺方案的充型和凝固过程的数值模拟,揭示了缸体的液相分布、温度场分布及凝固顺序,通过及时补浇冒口和冷铁激冷等措施,使下高上低的温度场分布变为下低上高的分布趋势,从而改善了缸体在凝周过程中的液相分布,改变了先中间后两头的凝固顺序,缸体从总体上形成了从下往上的有利于补缩的凝固顺序,并预测了压缩机缸体缩孔、缩松产生的部位和大小。采用改进后的工艺进行生产,取得成功,从而验证了模拟结果的正确性。 相似文献
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The heat transfer during the casting solidification process includes the heat radiation of the high temperature casting and the mold, the heat convection between the casting and the mold, and the heat conduction inside the casting and from the casting to the mold. In this paper, a formula of time step in simulation of solidification is derived, considering the heat radiation, convection and conduction based on the conservation of energy. The different heat transfer conditions between the conventional sand casting and the permanent mold casting are taken into account in this formula. The characteristics of heat transfer in the interior and surface of the casting are also considered. The numerical experiments show that this formula can avoid computational dispersion, and improve the computational efficiency by about 20% in the simulation of solidification process. 相似文献
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随着国内高拉速连铸机日渐增多,结晶器铜板的失效已经变为以热疲劳裂纹形式为主。采用ANSYS数值模拟软件对结晶器铜板温度和热流密度分布规律进行了研究。计算结果表明,结晶器铜板的温度分布和生产中热疲劳裂纹的形式不相同;铜板弯月面区发生热裂失效的主要原因是在一定温度下,上下运动的热流密度的集中区即“能量流”撕裂了铜板,因此减小结晶器铜板弯月面处的热流密度,有可能减少铜板热裂纹的产生。设计均匀传热、减少铜板和连铸坯裂纹生成的结晶器是未来技术发展的方向。计算结果表明,沟槽结晶器铜板表面刻划沟槽后可以减弱弯月面区域热流密度,改善结晶器铜板的不均匀传热状况。 相似文献
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中空钢锭芯部压缩气体的冷却能力对于钢锭凝固过程有显著影响,也是凝固模拟的关键边界条件。用计算流体力学方法计算了芯部压缩气体湍流流动的速度、压力和换热系数的分布。分析了气体滞止压力、内套筒壁面温度和环隙宽度对换热系数的影响,并将数值模拟结果与解析模型的结果做了对比。计算结果可以用来指导芯子结构设计。 相似文献
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局部加压铝合金的凝固变化及其数值模拟 总被引:1,自引:0,他引:1
局部加压方法是压铸中用于消除铸件厚壁处缩孔缺陷的一种新工艺.该研究通过试验模型测量局部加压过程中金属型、铸件和加压杆的温度变化曲线,分析了传热与凝固现象.结果表明,局部加压使铸件的凝固时间大为缩短,加压杆前端的温度大幅上升,而金属型的温度则无明显变化.利用变网格技术,根据加压深度通过适时修改网格文件、初始条件和边界条件的方法,模拟了铝合金在局部加压过程中的凝固变化,并与试验结果进行了对比和讨论. 相似文献
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Inverse method was used in single crystal superalloy DD6 processing simulation during solidification. Numerical modeling coupled with experiments has been used to estimate the interface heat transfer coefficient (IHTC) between the surface of slab casting and inner mold. Calculated temperature dependent values of IHTC were obtained from a numerical solution. The calculated temperatures agreed well with the measurement of cooling profile. 相似文献
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在钢的连铸过程中,钢水在结晶器内的凝固对铸坯的产量和质量均有很大影响,几乎所有的铸坯表面缺陷均形成于结晶器内。近年来,随着连铸拉速的增加及对铸坯表面质量要求的提高,有关结晶器冷却、传热对钢水的初始凝固及表面纵裂纹影响的研究成为连铸科学研究的重点。结晶器壁热流不均是纵裂纹产生的有利环境,保护渣控制传热为常用的措施。薄板坯浇铸时由于拉速高,为获得表面无缺陷铸坯,对保护渣控制传热的要求更高,同时也需协调保护渣的润滑功能。通过生产试验,研究比较3种碱度保护渣(CaO/SiO2分别为1.06、1.26和1.48)对薄板坯结晶器平均热流量的影响,发现与低碱度保护渣相比,使用高碱度保护渣时,结晶器热流量最低,有利于实现弱冷却,形成均匀凝固坯壳,在一定拉速条件下浇铸裂纹敏感钢种时有助于获得良好表面质量的铸坯。 相似文献