共查询到19条相似文献,搜索用时 171 毫秒
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结合连铸机实际操作参数,本文建立了二维非稳态传热的数学模型,采用数值实验,通过计算机研究和模拟板坯结晶器铜板的温度分布。研究结果表明影响结晶器铜壁温度场的两个主要参数是铸坯拉速和冷却水流速。 相似文献
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通过建立结晶器内钢液和水的二维对流-传热耦合模型过程,研究了小方坯结晶器冷却水入口温度和流速对铜管温度和结晶器内平均热流的影响.该模型使用Fluent进行求解,模拟了钢液和冷却水的流动和传热,凝固坯壳的生长,以及热量以辐射和导热两种通过保护渣和气隙.通过将坯壳厚度和铜管温度与其他研究的结果进行对比来验证模型准确性.研究结果表明,结晶器冷却水的温度显著影响铜管的冷面温度,水温超过313 K会导致铜管冷面最高温度超过水的沸点.水流速升高0.49 m·s-1能够消除水温升高4 K带来的不利影响. 相似文献
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运用有限元软件ANSYS热分析模块对浇铸0.2%C钢水的10 mm铜结晶器壁面的温度场、应力场及位移场的分布状况进行数值模拟,比较得出在不同换热系数工况下结晶器壁面的恶劣服役部位的安全性。结果表明,结晶器热面峰值温度为525 K,冷面的峰值温度为475 K;结晶器外壁圆角变形值为0.789 mm,较内壁变形大;结晶器最大等效应力和最大应变均出现在钢液与空气接触的内壁圆角处,分别为218 MPa和0.002 079。结晶器温度、变形和应力均满足连铸安全性要求。 相似文献
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连铸结晶器内冷却水的流动、传热和金属液的传热、凝固全耦合计算时,模型计算效率低、收敛性差,而不考虑真实冷却水流场只进行金属液传热-凝固耦合时,模型计算精度较低,可将冷却水流动-传热和金属液传热-凝固过程分别建模,并基于二次开发的温度场量原位传递程序,将模型串联耦合。结果表明,通过耦合流场计算得到的真实冷却边界替代传统均匀界面换热系数的边界条件施加方式,在保证模型计算效率和计算精度的前提下,可准确模拟铸坯晶粒的尺寸、取向和数量,经试验验证,模拟结果与试验结果高度吻合。 相似文献
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连铸板坯结晶器温度场数学模型 总被引:6,自引:0,他引:6
建立了结晶器铜板二维非稳态传热数学模型,研究了结晶器铜板温度场。利用工厂实例对模型进行了验证。讨论了拉速、冷却水流速、铜板厚、水垢和铜板镀层对结晶器温度分布的影响。 相似文献
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板坯连铸结晶器铜板温度场研究 总被引:4,自引:0,他引:4
本文建立了结晶器铜板二维非稳态传热数学模型,研究了板坯结晶器铜板温度场。利用工厂实测数据对模型进行了验证。讨论了拉速、冷却水流速、铜板厚度、水垢和铜板镀层对铜板温度分布的影响。 相似文献
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Extensive experimental studies were conducted to quantify the effect of different parameters that can affect the heat transfer from the metal to the mold during the steady-state phase of DC casting. In the first part previously published, the experimental technique was established and results were reported for the effect of gas type (atmosphere within the mold) and the gap between the metal and the mold. The results showed the significant effect of gas thermal conductivity and the metal-mold gap on the mold wall heat transfer coefficient. In this second publication on heat transfer in the mold wall region of a DC casting mold, the results from the effect of casting temperature, gas flow rate, casting alloy, mold material, and the mold insert material on the mold wall heat transfer coefficient are described. The experiments reported in the current paper show that these additional factors tested do not affect the heat flux through the mold wall to the same extent as the gap size or the gas type. The heat transfer coefficient changes by less than 5 pct when casting temperature is changed by ±25 K, less than 15 pct when the gas flow rate within the metal-mold gap flows at up to 3 LPM, and approximately 30 pct when the mold material is changed from stainless steel to AA601 to copper. Similar results were obtained when different insert materials were used. These results are explained with the help of an electrical analogy of heat transfer and are consistent with the heat transfer theory. 相似文献
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To produce castings of titanium, nickel, copper, aluminum, and zinc alloys, graphite molds can be used, which makes it possible to provide a high cooling rate. No die coating and lubricant are required in this case. Computer simulation of casting into graphite molds requires knowledge of the thermal properties of the poured alloy and graphite. In addition, in order to attain adequate simulation results, a series of boundary conditions such as heat transfer coefficients should be determined. The most important ones are the interface heat transfer coefficient between the casting and the mold, the heat transfer coefficient between the mold parts, and the interface heat transfer coefficient into the environment. In this study, the interface heat transfer coefficient h between the cylindrical aluminum (99.99%) casting and the mold made of block graphite of the GMZ (low ash graphite) grade was determined. The mold was produced by milling using a CNC milling machine. The interface heat transfer coefficient was found by minimizing the error function reflecting the difference between the experimental and simulated temperatures in a mold and in a casting during pouring, solidification, and cooling of the casting. The dependences of the interface heat transfer coefficient between aluminum and graphite on the casting surface temperature and time passed from the beginning of pouring are obtained. It is established that, at temperatures of the metal surface contacting with a mold of 1000, 660, 619, and 190°C, the h is 1100, 4700, 700, and 100 W/(m2 K), respectively; i.e., when cooling the melt from 1000°C (pouring temperature) to 660°C (aluminum melting point), the h rises from 1100 to 4700 W/(m2 K), and after forming the metal solid skin on the mold surface and decreasing its temperature, the h decreases. In our opinion, a decrease in the interface heat transfer coefficient at casting surface temperatures lower than 660°C is associated with the air gap formation between the surfaces of the mold and the casting because of the linear shrinkage of the latter. The heat transfer coefficient between mold parts (graphite–graphite) is constant, being 1000 W/(m2 K). The heat transfer coefficient of graphite into air is 12 W/(m2 K) at a mold surface temperature up to 600°C. 相似文献
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Etienne J. F. R. Caron Amir R. Baserinia Harry Ng Mary A. Wells David C. Weckman 《Metallurgical and Materials Transactions B》2012,43(5):1202-1213
Thermal modeling of the direct-chill casting process requires accurate knowledge of (1) the different boundary conditions in the primary mold and secondary direct water-spray cooling regimes and (2) their variability with respect to process parameters. In this study, heat transfer in the primary cooling zone was investigated by using temperature measurements made with subsurface thermocouples in the mold as input to an inverse heat conduction algorithm. Laboratory-scale experiments were performed to investigate the primary cooling of AA3003 and AA4045 aluminum alloy ingots cast at speeds ranging between 1.58 and 2.10 mm/s. The average heat flux values were calculated for the steady-state phase of the casting process, and an effective heat-transfer coefficient for the global primary cooling process was derived that included convection at the mold surfaces and conduction through the mold wall. Effective heat-transfer coefficients were evaluated at different points along the mold height and compared with values from a previously derived computational fluid dynamics model of the direct-chill casting process that were based on predictions of the air gap thickness between the mold and ingot. The current experimental results closely matched the values previously predicted by the air gap models. The effective heat-transfer coefficient for primary cooling was also found to increase slightly with the casting speed and was higher near the mold top (up to 824 W/m2·K) where the molten aluminum first comes in contact with the mold than near the bottom (as low as 242 W/m2·K) where an air gap forms between the ingot and mold because of thermal contraction of the ingot. These results are consistent with previous studies. 相似文献
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喷淋结晶器是一种新型结晶器,它是用特殊的喷嘴将水喷淋到结晶器的铜板表面上进行铸坯冷却的,这种冷却方式具有较高的传热速度,便于调节结晶器的热流密度,可以提高拉坯速度和铸坯质量,喷淋结晶器的传热现象是很复杂的,本文通过建立传热实验台,对喷淋冷却过程进行较细致的实验研究,找出喷水量和换热系数的关系等,为设计喷淋冷却结晶器提供必要的参数。 相似文献
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基于国内某钢厂CSP漏斗结晶器铜板结构,建立了考虑铜板水槽冷却水流动的薄板坯结晶器铜板三维热/力耦合计算模型,研究分析了典型连铸工艺下结晶器铜板水槽内冷却水的传热特点和铜板温度场与热应力场分布规律,并探讨了冷却水流速及铜板厚度对铜板热/力行为的影响。结果表明,铜板宽面热面与窄面热面最高温度均位于弯月面下约15 mm处,分别达436.5、379.2 ℃。宽面和窄面铜板的最大热应力均位于弯月面下方约25 mm处,分别达876.7、867.8 MPa。宽面铜板的热应力总体比窄面高且分布更为不均匀,螺栓处热面的热应力整体低于其两侧水槽处热面的热应力。增加冷却水流速、减小铜板厚度可减小铜板热面温度与热应力。将螺栓处冷却水缝延长到距结晶器下口30 mm处,可显著改善宽面铜板中下部横向温度分布的均匀性,使其热面横向最大温差减少约19.6 ℃。 相似文献
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Klaus Schwerdtfeger 《国际钢铁研究》2006,77(12):911-920
Two principal methods are used to investigate the heat transfer in the continuous casting mold. The direct way is to measure cooling water temperatures, mold wall temperatures, strand temperatures and shell thickness in actual operation, and then deduce from these data the correlations for heat flux densities. The other way is to investigate the “unit operations” of heat transfer theoretically or experimentally in the laboratory, viz. heat transfer through a layer of casting flux or of gas, and heat transfer in a copper wall cooled on one side by water. The results obtained in this approach can then be used to explain the data determined with the direct method and to optimize the heat transfer behaviour of the mold in the machine. In the first part of this paper some unit operations are discussed and engineering formulae are given for computation of the heat resistances of the gap and the copper/water system. In the second part of the paper the available operational data on heat flux density are analysed. Algorithms are presented for computation of local and average heat flux density as functions of casting speed, carbon content of the steel and composition of the casting flux. Finally, values of shell thickness are computed with the correlation for heat flux density and are compared with the measured data. 相似文献
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An experimental apparatus to determine the heat-transfer coefficient in the gap formed between the cast metal and the mold wall of a vertical direct chill (DC) casting mold is described. The apparatus simulates the conditions existing within the confines of the DC casting mold and measures the heat flux within the gap. Measurements were made under steady-state conditions, simulating the steady-state regime of the DC casting process. A range of casting parameters that may affect the heat transfer was tested using this apparatus. In the current article, the operation of the apparatus is described along with the results for the effect of gas type within the mold, and the size of the metal-mold gap formed during casting. The results show that the gas type and the gap size significantly affect the heat transfer within a DC casting mold. The measured heat fluxes for all the conditions tested were expressed as a linear correlation between the heat-transfer coefficient and the metal-mold gap size, and the fluxes can be used to estimate the heat transfer between the metal and the mold at any gap size. These results are compared to values reported in the literature and recommendations are made for the future reporting of the metal/mold heat-transfer coefficient for DC casting. The results for the effect of the other parameters tested are described in Part II of the article. 相似文献
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V. V. Stulov 《Steel in Translation》2018,48(2):78-81
Attention focuses on the processes in the mold of a continuous-casting machine when using a patented new cooling system. In particular, the temperature differences in the steel billet and in the wall over the mold height are of interest in modeling the casting processes, because those differences affect the quality of the billet produced. A literature review covers research on the slag-forming mixture, which affects the heat flux from the billet to the mold. Non-Russian authors highlight mild cooling of the mold in selecting the slagforming mixture. Improvement of billet cooling in the mold permits improvement in the surface quality of the slab, extension of mold life, and increase in productivity. According to numerous authors, that may be accomplished by mathematical modeling of the process. The mold cooling depends directly on the convective motion of liquid steel in the mold, a topic addressed by many non-Russian authors. Researchers have considered systems in which the heat pipes in the cooling system of the mold are based on porous material, with water and air as the working fluid, and those in which liquid droplets on nanostructured superhydrophilic surfaces are evaporated. Mold cooling at steel casting rates higher than 7 m/min, accompanied by increase in the heat-flux density, is of great importance, as reflected by the number of studies published. The relations between the basic process parameters are determined by means of Rayleigh dimensionality theory. The basic parameter selected is the temperature difference in the metal mold wall, which depends on the casting rate (the time that the billet is in the mold), the properties of the steel (specific heat, thermal diffusivity), the thermal conductivity of the mold wall, and the temperature difference in the cast steel. In determining the exponents in the dimensionless relations, the available experimental data regarding the dependence of the heatflux density on the casting rate and the parameter of the steel are taken into account. On the basis of the ratio Δtme/tme obtained (where Δtme is the mean temperature difference over the wall thickness and tme is the mean wall temperature) for molds with the existing and new (patented) cooling systems, the temperature difference in the steel billet may be determined. For the two cooling systems compared, Δtme1 = 450°C and Δtme2 = 231°C. Consequently, Δtme1/Δtme2 = 1.95. The smaller temperature difference Δtme2 indicates milder cooling of the mold with the new cooling system. 相似文献