共查询到19条相似文献,搜索用时 187 毫秒
1.
以相同的冷却强度、拉速、浇注温度、钢种等板坯连铸条件为模拟初始参数,采用相同的凝固潜热处理方式,针对两种常用的板坯连铸二冷边界条件处理方法FCA法和MCA法,分别采用四种不同的传热经验公式,计算了板坯连铸的热过程。得到这两种处理方式四种不同二冷传热经验公式的八组计算结果,并将计算结果与实测值相比较,结果证明,采用FCA法处理边界条件,得到的模拟计算结果与实测值相对误差均小于5%,而利用MCA法处理边界条件,得到的模拟计算结果与实际测量值相对误差在8%左右。因此,采用FCA法处理板坯连铸二冷边界条件得到的模型能更加准确地模拟板坯连铸的热过程。 相似文献
2.
基于DEFORM反传热模型表面换热系数的确定 总被引:1,自引:0,他引:1
以7075铝合金厚板淬火过程为对象,研究DEFORM反传热模型中控制参数对表面换热系数计算和温度预测精度的影响规律。结果表明,当选择实测温度曲线上的拐点温度作为温度控制点,且表面换热系数初始值接近平均换热系数时,采用反传热模型确定的表面换热系数所预测的冷却曲线与实测曲线吻合较好。在此基础上选取合理的控制参数,并确定了7075铝合金厚板淬火过程的表面换热系数,经冷却曲线预测结果与实测值对比表明,采用DEFORM反传热模型确定的表面换热系数所预测的温度场有较高精度,可以满足工程应用需要。 相似文献
3.
根据试验获得的钢板内部冷却曲线,采用DEFORM反传热模型计算出低合金钢板高压水除鳞对流换热系数。在计算中考虑了水压、除鳞喷嘴距钢板表面距离、钢板表面温度对换热系数的影响。为了便于应用,对不同工况计算得到的高压水除鳞换热系数进行归纳整理,然后采用非线性回归方法回归出高压水除鳞对流换热系数模型。为了验证回归的换热系数模型正确性,将国内某钢厂现场生产实际工况的参数代入换热系数模型,计算得到对应工况下的高压水除鳞对流换热系数。根据此换热系数采用有限元软件模拟连铸坯除鳞温度场,通过有限元模拟温度和现场实测温度曲线的比较,两者吻合度较高,证明了回归的高压水除鳞换热系数模型合理。 相似文献
4.
不同冷却方式下换热系数的测量与计算 总被引:9,自引:0,他引:9
为了研究不同冷却方式下的换热系数,设计了一套可以测量空冷、水淬以及不同压力下喷气淬火下冷却曲线的试验装置,试验中测量的探头采用120mm×120mm×20mm奥氏体不锈钢方板。该探头经有限元(FEM)计算验证了其一维传热特性后,用来测量上述几种冷却方式下的冷却曲线,并用反传热法(IHCM)和集中热容法(LHCM)进行换热系数的计算与分析,比较了不同压力下喷气淬火的换热系数。实验结果表明,当毕欧数Bi<0.1时集中热容法是适用的,反之则不适用;在喷气淬火时,压力越大,表面换热系数也越大。 相似文献
5.
端淬实验是研究材料冷却速率与组织性能之间关系的高通量方法,而工件表面综合换热系数则是端淬数值模拟研究的必要边界条件。采用经验公式法、传热反问题法及流-固耦合分析法,计算了CSU-A1型镍基高温合金工件在空气端淬实验中的各表面综合换热系数;结合工件实验温度测点的冷却曲线及平均冷却速率对三种方法进行了比较。结果表明:实验温度范围内工件底端、侧部以及顶端的综合换热系数分别在323~555、16~30、58~184W/(m~2·K)之间。三种方法中,经验公式法获得的冷却曲线误差较大;传热反问题法的冷却曲线误差最小,但对实验数据及其他边界条件的依赖性强;流-固耦合分析法获得的平均冷却速率准确度最高,且不需要通过实验即可获取工件任意位置的换热系数,是研究气体端淬过程表面综合换热系数的有效方法。 相似文献
6.
7.
大断面轴承钢棒材超快速冷却过程温度场模拟 总被引:2,自引:0,他引:2
对大断面轴承钢棒材高温保温后超快速冷却过程温度场进行模拟,分析超快速冷却过程中棒材断面不同部位温度和冷却速度的变化。利用ANSYS软件,采用计算超快速冷却终冷温度与实测值一致时停止计算的途径,确认换热系数的较精确值,不断修改传热模型,并对其温度场进行求解。结果表明,对于直径Φ≥60mm棒材,运用分段式二次超快速冷却,可在不延长超快速冷却总时间的前提下,提高棒材内部的冷却速度,使棒材断面不同部位的冷却速度均达到抑制网状碳化物析出?过冷奥氏体完全发生珠光体转变的冷却速度要求。 相似文献
8.
9.
《热加工工艺》2020,(18)
为了测量7A85铝合金表面换热系数以及优化反传热法计算表面换热系数的偏差,利用精密测温仪(GL900)对7A85铝合金片状试样进行了淬火冷却曲线测量,测量点A和B距端面间距为20 mm和40 mm。使用激光导热仪测量了在30~500℃之间试样的比热容,并进行了线性拟合。随后通过有限差分法外推得到端面冷却曲线,进而计算出表面换热系数。结果表明,使用室温比热容数据计算得到的端面淬火冷却曲线比实际曲线高,使用线性拟合后的比热容计算得到的端面淬火温度更准确。7A85铝合金端面换热系数随着温度降低,先增大后出现波动段,最终降低,在270℃时的最大表面换热系数为2250 W·m-2·℃-1。 相似文献
10.
铝合金厚板淬火表面换热系数的离散解析求法 总被引:4,自引:1,他引:3
为了快速准确求取铝合金厚板淬火过程的换热系数,对淬火热传导过程进行分析。首先,将换热系数解析过程假设为淬火温度离散化的,并且是相邻离散点可进行迭代优化的计算过程。然后,分步解析求解了各离散温度区间的换热系数,最后完成了数据修正和仿真计算还原。结果表明,该方法获得的换热系数,可以使实验冷却曲线与计算冷却曲线较好的吻合,从而证明这种计算方法的可行性,并在文末对该方法的误差来源和特点进行了分析。 相似文献
11.
The cooling efficiency of grinding fluids in deep grinding, at different material removal rates and grinding speeds, has been investigated. Two ‘inverse’ methods have been proposed to determine the level of convective heat transfer coefficients of grinding fluids, by matching the theoretical and experimental grinding fluid burn-out thresholds or matching the theoretical and measured grinding temperatures. Instead of using a constant chip melting temperature to estimate the energy partition to the grinding chips, the chip temperature and chip energy were calculated using the newly developed approach considering the variation of chip size, deformation and heat transfer at the abrasive/work interface. The variation of grinding heat taken away by the process fluids and grinding chips under different process parameters has been calculated, which shows the importance of cooling effects by the grinding fluids and the transition of thermal characteristics of deep grinding from cooling dominant to ‘dry’ grinding regime, where a large percentage of grinding heat is taken away by the grinding chips. 相似文献
12.
13.
14.
15.
16.
17.
Titanium alloys, as difficult-to-cut materials, have poor machinability due to their superior mechanical properties, heat resistance and corrosion resistance. High cutting temperature that will greatly accelerate tool wear often occurs in titanium alloy cutting process. In this paper, cold water mist jet (CWMJ) cooling method, an eco-friendly cooling method, was used to obtain a lower cutting temperature during TC9 titanium alloy turning process. The effects of CWMJ were mainly discussed as compared with cold air jet and flood cooling methods. A comprehensive evaluation on the cooling effects of CWMJ was carried out by hydrodynamic tests, heat transfer tests and turning tests, respectively. Experimental results indicated that CWMJ had better cooling effects as compared with other two cooling methods. Cutting temperature was greatly reduced, and tool life was improved with CWMJ during TC9 turning process. Machined surface quality and chip morphology were also acceptable. 相似文献
18.
Florent Chaffotte Linda Lefevre Didier Domergue Aymeric Goldsteinas Xavier Doussot 《材料热处理学报》2004,25(5)
AMONG the carburising and quenching technologieslow-pressure carburising in line with high pressure gasquenching knows a strong development[1],[2],[3].Thisprocess offers indeed an environmentally-friendlyalternative to standard atmosphere carburisingassociated to oil quenching.Gas quenching allows toeliminate parts washing and oil residues processingsteps.Besides low pressure carburising and quenchingprocesses allow more automation of the processFinally gas quenching offers process controopp… 相似文献
19.
EXPERIMENTAL RESEARCH AND NUMERICAL SIMULATION OF MOLD TEMPERATURE FIELD IN CONTINUOUS CASTING OF STEEL 总被引:1,自引:0,他引:1
X.S. Zheng M.H. Sha J.Z. Jin 《金属学报(英文版)》2006,19(3):176-182
Mold is the heart of the continuous casting machine. Heat transfer and solidification in a water cooled mold are the most important factors during the continuous casting of steel. For studying the temperature distribution of a mold wall, a simulated apparatus of mold was designed and experiments were performed by it. The measured results indicated that the mold wall temperature approaches the temperature of cooling-water. An equivalent thermal-conductivity coefficient was proposed and deduced on the basis of the conclusion of the experiments. This coefficient was applied to solve the heat transfer between the melt and cooling water, and to characterize the heat transfer capacity of the mold. By this equivalent thermal-conductivity coefficient, it is very easy and convenient to numerically simulate the solidification process of continuous casting. And the calculation results are in agreement with the experiments. The effects of casting speed and water flow rate on the mold temperature field were also discussed. 相似文献