多炉连浇大钢锭中间包内流体流动行为研究
|
摘要
大型钢锭一般指其重量大于400吨的钢锭。百万千瓦级核电常规岛整锻低压转子的重量约为170~180吨,是目前世界上所需钢锭体积最大、锻件毛坯重量最大、截面尺寸最大、技术要求最高的实心锻件,需浇注约580~650吨大型钢锭。为解决低压转子在工作温度条件下的回火脆性问题,要求该类钢需进行超纯净控制。目前,国内外转子钢的生产多采用EAF—LF—VD—VCD多炉连浇工艺,通过上注法真空浇注而成。
大型钢锭的浇注受冶炼炉容量的限制,须采用多炉连浇技术,但由于浇注速度大(通钢量是连铸的1.5-2.5倍),故既同于常规连铸又有别于常规连铸。在多炉连浇大型钢锭过程中,中间包是连接钢包与钢锭模之间的中间容器,其主要功能为贮存一定量的钢水,以保证在更换钢包时实现多炉连续浇注。随着中间包冶金技术的发展,常规连铸中间包的去夹杂功能成为了冶金工业洁净钢生产的一个关键技术。即,采用大容量、深熔池、设置挡墙挡坝中间包来提高钢水在中间包内的平均停留时间,从而促使夹杂物在中间包内聚合上浮、排除。目前国内重型机械行业大型钢锭生产为满足浇注速度的要求,使用的圆形中间包虽然具有大容量、深熔池的特点,但由于其大包注点到注流出口的距离短,浇注流量大,导致钢液在包内的停留时间较短,夹杂物来不及上浮就直接进入钢锭模,没能发挥中间包去夹杂的冶金功能,降低了大型铸锻件的质量。因此,正确设计满足模铸过程多炉连浇、保证大通钢量和高去除夹杂物能力的中间包几何尺寸,对提高低压转子锻件及大型钢锭洁净度具有重要意义。
本文以第一重型机械厂多炉连浇大钢锭中间包为研究对象,通过物理模拟和数理模拟实验,对不同熔池深度(H)的圆形中间包和不同中间包长度(L)的槽型中间包内钢水流动模式和夹杂物上浮状况进行了研究。针对大流量、深熔池的特点,结合现场的安装、砌墙和吊浇等因素,首次提出了有效提高多炉连浇大钢锭质量的中间包的合理几何尺寸(即L/H),设计了新型椭圆形中间包及控流装置。现场应用证明,采用本研究结果设计的多炉连浇大钢锭新型椭圆形中间包能有效地去除钢水中非金属夹杂物,较大提高钢水洁净度,确保了低压转子锻件的成品质量。本文还通过不同湍流模型对多炉连浇大钢锭中间包内钢液流动行为和状况的预测能力的讨论和研究,建立了大钢锭圆形和椭圆形中间包的三维稳态计算模型,提出了最优湍流模型流场数值模拟方案,提高了预测能力和效果。
主要的研究内容和成果如下:
1、现用圆形多炉连浇大钢锭中间包的评估
采用数理模拟对某重型机械厂多炉连浇大钢锭圆形中间包内钢液流动状况和夹杂物去除情况进行了评估比较,结果表明:
①圆形中间包无任何控流装置时,中间包内钢液的平均停留时间较短,死区大,夹杂物上浮率较低。
②安装控流装置后,中间包内钢液的平均停留时间虽然有所增加,但是由于大包注点至中间包出口距离过近,夹杂物来不及上浮,仍然不能达到提高钢水洁净度的要求。因此,需要对圆形中间包进行优化。
2、多炉连浇大钢锭中间包结构尺寸研究
首次进行了多炉连浇大钢锭中间包不同熔池深度和长高比对中间包内钢液流动行为和夹杂物上浮率的影响研究,并提出了针对大流量多炉连浇大钢锭的中间包合理的几何尺寸(论文的第一个创新点)。
①增大熔池深度和延长中间包长度都有利于夹杂物的上浮,但中间包体积相同时,延长中间包长度更有利于夹杂物上浮。
②结合钢液在中间包内的流动模式和夹杂物上浮率的结构分析认为,多炉连浇大钢锭中间包液位熔池深度应在1500mm～2000mm,长度与熔池深度之比应控制在2.0～2.7之间。
3、多炉连浇大钢锭椭圆形中间包内控流装置研究
结合现场实际生产情况和中间包吊运、砌砖、安放等因素设了一种新型的深熔池、大容量的椭圆形中间包,并对其控流装置进行了优化,提出了最优挡墙挡坝的安装距离和挡墙的开口位置(论文的第二个创新点)。
①通过对18组控流装置设计方案的研究,从钢液流动停留时间、流动模式和夹杂物上浮率分析研究,挡墙距离中间包底部为300mm、挡坝高度为400mm,大包注点与挡墙距离为1500mm、挡墙与挡坝距离为490mm为最优控流装置安装位置方案。
②根据前文研究结果和现场实际情况,在设计的中间包长度与熔池深度比为2.0的椭圆形中间包中对挡墙开孔位置进行了优化分析,研究结果表明,开孔位于中间包对称轴上的方案为最优方案。
③相同容量的椭圆形中间包与圆形中间包模拟结果相比可知,安装控流装置后,椭圆形中间包的开始响应时间是圆形中间包的2.5倍,钢水平均停留时间和活塞流停留时间分别延长了6%和24%,其混合流体积增大了30%;死区体积减小了28%, Vp/Vd之比增大了68%,并且没有短路流存在,夹杂物上浮率增加了17%,有效提高了钢水洁净度。
4、湍流模型在大钢锭中间包内流场数值模拟中的适应性研究
本文采用标准k-ε模型和Realizable k-ε模型模拟的圆形多炉连浇中间包内空况和加挡墙挡坝后的钢液流动状况,并结合物理模拟结果进行了验证,提出Realizable k-ε模型更适合深熔池、大流量的多炉连浇大钢锭中间包流场的模拟(论文的第三个创新点):
①两种湍流模型都能用于圆形和椭圆形中间包内钢液流动状况模拟。但标准k-ε模型中粘度系数为常数,对中间包内漩涡模拟效果差;模拟圆形中间包时与物理模拟结果最大误差达50%,模拟椭圆形中间包时最大误差为56.3%。而在Realizable k-ε模型中粘度系数是一个变化量,能更准确地模拟中间包内钢液流动行为,模拟圆形中间包时与物理模拟结果最大误差减小到了9.6%,模拟椭圆形中间包时最大误差减小为16.5%。
②对比Realizable k-ε模型与物理模拟结果的比较可知,与空况相比Realizable k-ε模型对加控流装置的模拟结果与物理模拟结果更接近,其中模拟圆形中间包空况时最大误差为50%,安装控流装置后的最大误差为9.6%;模拟椭圆形中间包空况时最大误差为56.3%,安装控流装置后的最大误差为16.5%。
5、椭圆形中间包现场应用
根据前文研究结果,将椭圆形中间包应用到实际生产过程中。现场试验结果表明,与圆形中间包生产的钢锭相比,采用椭圆形中间包后相同材质和体积的钢锭内氧含量得到了明显减少;还对两种形状中间包生产的钢锭所制造的百万千低压转子锻件进行了无损检测和氧含量分析,结果表明:
①使用椭圆形中间包浇注后,中间包内全氧量减小了25%～33%。
②锻件单个缺陷的当量直径从2.5mm减小到了1.6mm,并不存在密集性缺。
③百万千瓦低压转子全氧量减小了30%。
这说明采用椭圆形中间包大大提高了锻件的质量,更适合用于浇注超纯低压转子锻件。
Generally, the weight of a heavy steel ingot is bigger than 400 tonne. Due to the limitation on the volume of smelting furnace, the multi-heat teeming is usually used as that in traditional continuous casting by flow rate 1.5 to 2.5 times. In the present study, the steel ingot is made for the 1000MW nuclear conventional island integral solid rotor forgings. It is one of the most important parts with the biggest weight of forging blank, which is the biggest of section size and the highest technical requirements in the world. Since the weight of rotor is 170 to 180 tonne, it requires the weight of ingot as large as 580 to 650 tonne. This kind of steel demands a super pure control in order to solve the problem of the temper brittleness. So, the multi-heat teeming of EAF—LF—VD—VCD, up-pour technology and vacuum casting are commonly used both at home and abroad. In the process of multi-heat teeming in heavy ingot, the tundish acts as an intermediate vessel which connecting the ladle and ingot mold, storing liquid steel to ensure the multi-heat teeming when ladle is changing. With the development of tundish metallurgical technology, the function of inclusions removal in a tundish of conventional continuous casting has turned into a key technology for the clean steel production of metallurgy industry. Large capacity tundish, high bath depth and flow control devices were used to enhance the residence time of liquid steel in a tundish, and to promote inclusions aggregation and floatation. In China, round tundish with large-capacity and deep bath is mainly used in the production of heavy ingot to meet the requirement of a high casting flow rate. However, the short residence time of liquid steel and the low inclusions floatation rate in the round tundish caused by the short distance from the zone of ladle injection to the outlet and large flow rate, weakened the inclusions removal. Therefore, it is quite significant to design a proper geometry size of tundish for the multi-heat teeming and the function of inclusions removal in heavy ingot casting processes, which will largely improve the cleanliness of low pressure rotor forging.
In this paper, focused on the heavy steel ingot, physical modeling was performed on the research of the flow field pattern and inclusions removal efficiency in the different types of multi-heat teeming tundishs, the round tundishs with different bath depths (H) and the groove tundishs with different lengths (L). And a reasonable geometry size (L/H) of the multi-heat teeming with a large flow rate was obtained. A new ellipse tundish was designed by a comprehensive consideration of industrial field installation, walling.The trial results showed that the modified multi-heat teeming tundish of heavy ingot can effectively remove the nonmetal inclusions in liquid steel, improve the cleanliness of liquid steel and ensure the product quality of low pressure rotor. Study on the fluid flow in a multi-heat teeming tundish for the heavy steel ingot by using different turbulence models in numerical simulation.
There are four main contents and results of the dissertation as follows:
1、The evaluation of fluid flow in the round for multi-heat teeming tundishs
The flow condition of the molten steel and the inclusion floatation efficiency were evaluated in the round shape tundish for heavy steel ingot. The results showed that:
①Without flow control devices, the residence time of molten steel was short, the dead volume was big and the inclusion floatation efficiency was low.
②After installing the flow control devices, the mean residence time slightly increased,the inclusions has no time to float due to the short distance from the pouring point to the outlet of the tundish.
Thus, the purpose of improving the molten steel cleanliness cannot be achieved.
2、Study on the geometric dimension design in a multi-heat teeming tundish for heavy steel ingot
Effect of fluid flow and inclusion motion on different bath depth and the ratio length and bath depth in a multi-heat teeming tundish for heavy steel ingot were firstly studied. The geometric dimension was afforded for a multi-heat teeming tundish of large flow rate. This is the first innovation in the dissertation.
①Increasing the bath depth and tundish length was beneficial to the inclusions floatation. When the tundish volume was the same, prolonging the tundish length was more advantageous to inclusions floatation.
②Considering the flow field patterns of liquid steel in the tundish and the inclusions floatation efficiency, the bath depth of the multi-heat teeming tundish for heavy steel ingot should be between 1500 mm and 2000 mm, and the L/H should be controlled between 2.0 to 2.7.
3、Study on the flow control device in a multi-heat teeming tundish for heavy steel ingot
Considering the tundish hoisting, brickwork and placing, a new elliptical tundish of deep bath and large flow rate was designed. And the flow control device was optimized. This is the second innovation in the dissertation.
①According to the study of 18 design schemes of flow control devices and the residence time of molten steel, flow pattern and inclusion floatation efficiency, the optimal installation position of the flow control device is that, the distance from the weir to the bottom of tundish is 300mm, the height of the dam is 400mm,,the distance from pouring point to the weir is 1500 mm, and the distance from the weir to the dam is 490 mm.
②Based on the research above and the site actual conditions, a new ellipse tundish with the ratio of length and bath depth is 2.0 was designed, and an optimization analysis was performed on the position of the weir exit, the results indicate that the scheme that the outlet locates on the axis of symmetry is the optimal one.
③The comparison of simulation results between the two shapes of tundishs with the same capacity showed that, in the elliptical shape tundish with the flow control devices, the response time was 2.5 times longer than that in the round shape tundish, the mean residence time and the residence time of the plug increased by 6% and 24% respectively, the mixed volume increased by 30%, the dead volume decreased by 28%, the ratio of the plug volume to the dead volume increased by 68%, and no short -circuiting flow, the inclusion flotation efficiency increased 17%.
4、Applicability of turbulence models in numerical simulation of flow field in a tundish for heavy steel ingot
The flow field of molten steel in a multi-heat teeming tundish for heavy steel ingot was simulated by using the standard k-εmodel and Realizable k-εmodel. And the accuracy of simulation was validated by the comparison between the results of physical modeling and numerical simulation. For the flow field simulation of the tundish with deep molten pool, large flow rate and vortex, the adoption of the Realizable k-εModel was more suitable than the Standard k-εModel. This is the three innovation in the dissertation The results indicate that:
①Both two turbulence models can be applied in the simulation of flow conditions of molten steel inside the round and elliptical shape tundishs. In the Standard k-εModel, the viscosity coefficient was a constant, and it has a poor effect of vortex simulation inside the tundish, the maximum deviation of the round tundish reached 50% while the maximum deviation of the elliptical tundish reached 56.3% compared to the results of physical modeling. In the Realizable k-εModel, the viscosity coefficient was a variable, the flowing behavior of molten steel inside the tundish can be simulated more accurately, the maximum deviation of the round tundish was reduced to 9.6%, and the maximum deviation of the elliptical tundish was reduced to 16.5%.
②It can be known from the comparison between the Realizable k-εModel and physical modeling that, as for the Realizable k-εModel, the simulation results of molten steel flowing condition inside the two tundishs with flow control device was even closer to that of physical modeling than that without flow control device. The maximum deviation was 50% in the round tundish without flow control device, and 9.6% in the round tundish with flow control device. The maximum deviation was 56.3% in the elliptical tundish without flow control device, and 16.5% in the elliptical tundishs with flow control device.
5、The trial application of the elliptical tundish
According to the research results mentioned above, the elliptical tundish was used in trial application. The trial results indicated that after using the elliptical tundish,
①The content of the total oxygen in the elliptical was decreased by 25%～33%.
②The equivalent diameter of single defect decreased from 2.5 mm to 1.6 mm, and no intensity defect observed.
③The content of the total oxygen in the rotor was 21 ppm, which was decreased by 30%.
Therefore, the quality of rotor forgings was improved greatly by using the elliptical shape tundishs.
大型钢锭的浇注受冶炼炉容量的限制,须采用多炉连浇技术,但由于浇注速度大(通钢量是连铸的1.5-2.5倍),故既同于常规连铸又有别于常规连铸。在多炉连浇大型钢锭过程中,中间包是连接钢包与钢锭模之间的中间容器,其主要功能为贮存一定量的钢水,以保证在更换钢包时实现多炉连续浇注。随着中间包冶金技术的发展,常规连铸中间包的去夹杂功能成为了冶金工业洁净钢生产的一个关键技术。即,采用大容量、深熔池、设置挡墙挡坝中间包来提高钢水在中间包内的平均停留时间,从而促使夹杂物在中间包内聚合上浮、排除。目前国内重型机械行业大型钢锭生产为满足浇注速度的要求,使用的圆形中间包虽然具有大容量、深熔池的特点,但由于其大包注点到注流出口的距离短,浇注流量大,导致钢液在包内的停留时间较短,夹杂物来不及上浮就直接进入钢锭模,没能发挥中间包去夹杂的冶金功能,降低了大型铸锻件的质量。因此,正确设计满足模铸过程多炉连浇、保证大通钢量和高去除夹杂物能力的中间包几何尺寸,对提高低压转子锻件及大型钢锭洁净度具有重要意义。
本文以第一重型机械厂多炉连浇大钢锭中间包为研究对象,通过物理模拟和数理模拟实验,对不同熔池深度(H)的圆形中间包和不同中间包长度(L)的槽型中间包内钢水流动模式和夹杂物上浮状况进行了研究。针对大流量、深熔池的特点,结合现场的安装、砌墙和吊浇等因素,首次提出了有效提高多炉连浇大钢锭质量的中间包的合理几何尺寸(即L/H),设计了新型椭圆形中间包及控流装置。现场应用证明,采用本研究结果设计的多炉连浇大钢锭新型椭圆形中间包能有效地去除钢水中非金属夹杂物,较大提高钢水洁净度,确保了低压转子锻件的成品质量。本文还通过不同湍流模型对多炉连浇大钢锭中间包内钢液流动行为和状况的预测能力的讨论和研究,建立了大钢锭圆形和椭圆形中间包的三维稳态计算模型,提出了最优湍流模型流场数值模拟方案,提高了预测能力和效果。
主要的研究内容和成果如下:
1、现用圆形多炉连浇大钢锭中间包的评估
采用数理模拟对某重型机械厂多炉连浇大钢锭圆形中间包内钢液流动状况和夹杂物去除情况进行了评估比较,结果表明:
①圆形中间包无任何控流装置时,中间包内钢液的平均停留时间较短,死区大,夹杂物上浮率较低。
②安装控流装置后,中间包内钢液的平均停留时间虽然有所增加,但是由于大包注点至中间包出口距离过近,夹杂物来不及上浮,仍然不能达到提高钢水洁净度的要求。因此,需要对圆形中间包进行优化。
2、多炉连浇大钢锭中间包结构尺寸研究
首次进行了多炉连浇大钢锭中间包不同熔池深度和长高比对中间包内钢液流动行为和夹杂物上浮率的影响研究,并提出了针对大流量多炉连浇大钢锭的中间包合理的几何尺寸(论文的第一个创新点)。
①增大熔池深度和延长中间包长度都有利于夹杂物的上浮,但中间包体积相同时,延长中间包长度更有利于夹杂物上浮。
②结合钢液在中间包内的流动模式和夹杂物上浮率的结构分析认为,多炉连浇大钢锭中间包液位熔池深度应在1500mm～2000mm,长度与熔池深度之比应控制在2.0～2.7之间。
3、多炉连浇大钢锭椭圆形中间包内控流装置研究
结合现场实际生产情况和中间包吊运、砌砖、安放等因素设了一种新型的深熔池、大容量的椭圆形中间包,并对其控流装置进行了优化,提出了最优挡墙挡坝的安装距离和挡墙的开口位置(论文的第二个创新点)。
①通过对18组控流装置设计方案的研究,从钢液流动停留时间、流动模式和夹杂物上浮率分析研究,挡墙距离中间包底部为300mm、挡坝高度为400mm,大包注点与挡墙距离为1500mm、挡墙与挡坝距离为490mm为最优控流装置安装位置方案。
②根据前文研究结果和现场实际情况,在设计的中间包长度与熔池深度比为2.0的椭圆形中间包中对挡墙开孔位置进行了优化分析,研究结果表明,开孔位于中间包对称轴上的方案为最优方案。
③相同容量的椭圆形中间包与圆形中间包模拟结果相比可知,安装控流装置后,椭圆形中间包的开始响应时间是圆形中间包的2.5倍,钢水平均停留时间和活塞流停留时间分别延长了6%和24%,其混合流体积增大了30%;死区体积减小了28%, Vp/Vd之比增大了68%,并且没有短路流存在,夹杂物上浮率增加了17%,有效提高了钢水洁净度。
4、湍流模型在大钢锭中间包内流场数值模拟中的适应性研究
本文采用标准k-ε模型和Realizable k-ε模型模拟的圆形多炉连浇中间包内空况和加挡墙挡坝后的钢液流动状况,并结合物理模拟结果进行了验证,提出Realizable k-ε模型更适合深熔池、大流量的多炉连浇大钢锭中间包流场的模拟(论文的第三个创新点):
①两种湍流模型都能用于圆形和椭圆形中间包内钢液流动状况模拟。但标准k-ε模型中粘度系数为常数,对中间包内漩涡模拟效果差;模拟圆形中间包时与物理模拟结果最大误差达50%,模拟椭圆形中间包时最大误差为56.3%。而在Realizable k-ε模型中粘度系数是一个变化量,能更准确地模拟中间包内钢液流动行为,模拟圆形中间包时与物理模拟结果最大误差减小到了9.6%,模拟椭圆形中间包时最大误差减小为16.5%。
②对比Realizable k-ε模型与物理模拟结果的比较可知,与空况相比Realizable k-ε模型对加控流装置的模拟结果与物理模拟结果更接近,其中模拟圆形中间包空况时最大误差为50%,安装控流装置后的最大误差为9.6%;模拟椭圆形中间包空况时最大误差为56.3%,安装控流装置后的最大误差为16.5%。
5、椭圆形中间包现场应用
根据前文研究结果,将椭圆形中间包应用到实际生产过程中。现场试验结果表明,与圆形中间包生产的钢锭相比,采用椭圆形中间包后相同材质和体积的钢锭内氧含量得到了明显减少;还对两种形状中间包生产的钢锭所制造的百万千低压转子锻件进行了无损检测和氧含量分析,结果表明:
①使用椭圆形中间包浇注后,中间包内全氧量减小了25%～33%。
②锻件单个缺陷的当量直径从2.5mm减小到了1.6mm,并不存在密集性缺。
③百万千瓦低压转子全氧量减小了30%。
这说明采用椭圆形中间包大大提高了锻件的质量,更适合用于浇注超纯低压转子锻件。
Generally, the weight of a heavy steel ingot is bigger than 400 tonne. Due to the limitation on the volume of smelting furnace, the multi-heat teeming is usually used as that in traditional continuous casting by flow rate 1.5 to 2.5 times. In the present study, the steel ingot is made for the 1000MW nuclear conventional island integral solid rotor forgings. It is one of the most important parts with the biggest weight of forging blank, which is the biggest of section size and the highest technical requirements in the world. Since the weight of rotor is 170 to 180 tonne, it requires the weight of ingot as large as 580 to 650 tonne. This kind of steel demands a super pure control in order to solve the problem of the temper brittleness. So, the multi-heat teeming of EAF—LF—VD—VCD, up-pour technology and vacuum casting are commonly used both at home and abroad. In the process of multi-heat teeming in heavy ingot, the tundish acts as an intermediate vessel which connecting the ladle and ingot mold, storing liquid steel to ensure the multi-heat teeming when ladle is changing. With the development of tundish metallurgical technology, the function of inclusions removal in a tundish of conventional continuous casting has turned into a key technology for the clean steel production of metallurgy industry. Large capacity tundish, high bath depth and flow control devices were used to enhance the residence time of liquid steel in a tundish, and to promote inclusions aggregation and floatation. In China, round tundish with large-capacity and deep bath is mainly used in the production of heavy ingot to meet the requirement of a high casting flow rate. However, the short residence time of liquid steel and the low inclusions floatation rate in the round tundish caused by the short distance from the zone of ladle injection to the outlet and large flow rate, weakened the inclusions removal. Therefore, it is quite significant to design a proper geometry size of tundish for the multi-heat teeming and the function of inclusions removal in heavy ingot casting processes, which will largely improve the cleanliness of low pressure rotor forging.
In this paper, focused on the heavy steel ingot, physical modeling was performed on the research of the flow field pattern and inclusions removal efficiency in the different types of multi-heat teeming tundishs, the round tundishs with different bath depths (H) and the groove tundishs with different lengths (L). And a reasonable geometry size (L/H) of the multi-heat teeming with a large flow rate was obtained. A new ellipse tundish was designed by a comprehensive consideration of industrial field installation, walling.The trial results showed that the modified multi-heat teeming tundish of heavy ingot can effectively remove the nonmetal inclusions in liquid steel, improve the cleanliness of liquid steel and ensure the product quality of low pressure rotor. Study on the fluid flow in a multi-heat teeming tundish for the heavy steel ingot by using different turbulence models in numerical simulation.
There are four main contents and results of the dissertation as follows:
1、The evaluation of fluid flow in the round for multi-heat teeming tundishs
The flow condition of the molten steel and the inclusion floatation efficiency were evaluated in the round shape tundish for heavy steel ingot. The results showed that:
①Without flow control devices, the residence time of molten steel was short, the dead volume was big and the inclusion floatation efficiency was low.
②After installing the flow control devices, the mean residence time slightly increased,the inclusions has no time to float due to the short distance from the pouring point to the outlet of the tundish.
Thus, the purpose of improving the molten steel cleanliness cannot be achieved.
2、Study on the geometric dimension design in a multi-heat teeming tundish for heavy steel ingot
Effect of fluid flow and inclusion motion on different bath depth and the ratio length and bath depth in a multi-heat teeming tundish for heavy steel ingot were firstly studied. The geometric dimension was afforded for a multi-heat teeming tundish of large flow rate. This is the first innovation in the dissertation.
①Increasing the bath depth and tundish length was beneficial to the inclusions floatation. When the tundish volume was the same, prolonging the tundish length was more advantageous to inclusions floatation.
②Considering the flow field patterns of liquid steel in the tundish and the inclusions floatation efficiency, the bath depth of the multi-heat teeming tundish for heavy steel ingot should be between 1500 mm and 2000 mm, and the L/H should be controlled between 2.0 to 2.7.
3、Study on the flow control device in a multi-heat teeming tundish for heavy steel ingot
Considering the tundish hoisting, brickwork and placing, a new elliptical tundish of deep bath and large flow rate was designed. And the flow control device was optimized. This is the second innovation in the dissertation.
①According to the study of 18 design schemes of flow control devices and the residence time of molten steel, flow pattern and inclusion floatation efficiency, the optimal installation position of the flow control device is that, the distance from the weir to the bottom of tundish is 300mm, the height of the dam is 400mm,,the distance from pouring point to the weir is 1500 mm, and the distance from the weir to the dam is 490 mm.
②Based on the research above and the site actual conditions, a new ellipse tundish with the ratio of length and bath depth is 2.0 was designed, and an optimization analysis was performed on the position of the weir exit, the results indicate that the scheme that the outlet locates on the axis of symmetry is the optimal one.
③The comparison of simulation results between the two shapes of tundishs with the same capacity showed that, in the elliptical shape tundish with the flow control devices, the response time was 2.5 times longer than that in the round shape tundish, the mean residence time and the residence time of the plug increased by 6% and 24% respectively, the mixed volume increased by 30%, the dead volume decreased by 28%, the ratio of the plug volume to the dead volume increased by 68%, and no short -circuiting flow, the inclusion flotation efficiency increased 17%.
4、Applicability of turbulence models in numerical simulation of flow field in a tundish for heavy steel ingot
The flow field of molten steel in a multi-heat teeming tundish for heavy steel ingot was simulated by using the standard k-εmodel and Realizable k-εmodel. And the accuracy of simulation was validated by the comparison between the results of physical modeling and numerical simulation. For the flow field simulation of the tundish with deep molten pool, large flow rate and vortex, the adoption of the Realizable k-εModel was more suitable than the Standard k-εModel. This is the three innovation in the dissertation The results indicate that:
①Both two turbulence models can be applied in the simulation of flow conditions of molten steel inside the round and elliptical shape tundishs. In the Standard k-εModel, the viscosity coefficient was a constant, and it has a poor effect of vortex simulation inside the tundish, the maximum deviation of the round tundish reached 50% while the maximum deviation of the elliptical tundish reached 56.3% compared to the results of physical modeling. In the Realizable k-εModel, the viscosity coefficient was a variable, the flowing behavior of molten steel inside the tundish can be simulated more accurately, the maximum deviation of the round tundish was reduced to 9.6%, and the maximum deviation of the elliptical tundish was reduced to 16.5%.
②It can be known from the comparison between the Realizable k-εModel and physical modeling that, as for the Realizable k-εModel, the simulation results of molten steel flowing condition inside the two tundishs with flow control device was even closer to that of physical modeling than that without flow control device. The maximum deviation was 50% in the round tundish without flow control device, and 9.6% in the round tundish with flow control device. The maximum deviation was 56.3% in the elliptical tundish without flow control device, and 16.5% in the elliptical tundishs with flow control device.
5、The trial application of the elliptical tundish
According to the research results mentioned above, the elliptical tundish was used in trial application. The trial results indicated that after using the elliptical tundish,
①The content of the total oxygen in the elliptical was decreased by 25%～33%.
②The equivalent diameter of single defect decreased from 2.5 mm to 1.6 mm, and no intensity defect observed.
③The content of the total oxygen in the rotor was 21 ppm, which was decreased by 30%.
Therefore, the quality of rotor forgings was improved greatly by using the elliptical shape tundishs.
引文
[1]王凤喜.大锻件的生产与发展[J].锻压机械. 1999, 5:5-9.
[2]王凤喜.大锻件生产行业与锻造技术发展[J].锻压机械. 2002, 4:3-6.
[3]郭会光,曲宗实.我国大锻件制造业的发展[J].大型铸锻件. 2003, 1: 42-45.
[4]曾祖良.国外大型锻件用钢锭的生产水平[J].工程建设与设计. 1987, 1 (2):10-13.
[5]蒋梦龙.优质大型转子钢锭的冶金技术[J].上海金属. 1994, 16 (5): 23-27.
[6] Sanjib Chakraborty, Yogeshwar Sahai. Effect of Varying Ladle Stream Temperature on the Melt Flow and Heat Transter in Continuous Casting Tundishe [J]. ISIJ International. 1991(9): 960-967.
[7] A. Vargas-Zamora, R.D. Morales.Heat and mass transfer of a convective-stratified flow in a trough type tundish[J]. InternationalJournal of Heat and Mass Transfer. 2003:3029–3039.
[8] C. M. Fan, R. J. Shie and W. S. Hwang. Studies by mathematical and physical modelling of fluid flow and inclusion removal phenomena in slab tundish for casting stainless steel using various flow control device designs[J]. Ironmaking and Steelmaking. 2003 (5): 341-347.
[9] Marcela B. Goldschmit. Sergio P. Ferro. Guillermo F. Walter, Virginia G. Aranda, Jorge A.Tena Morelos. Numerical model for the minimization of intermixed round bars in a four line continous caster[J]. Metallurgical and materials transactions B, 2001, 32(3): 537-546.
[10] P. Gardin, M. Brunet, J. F. Domgin, K. Pericleous. An experimental and numerical CFD study of turbulence in a tundish container[J]. Applied mathematical modeling, 2002, 26(2): 323-336.
[11] J.舍克里著.彭一川徐匡迪樊养颐译.冶金中的流体流动现象[M].北京.冶金工业出版社.1985.
[12] S.V.帕坦卡著.张政译.传热与流体流动的数值计算[M].北京.科学出版社.1980.
[13] K. M. Godiwalla, S.K. Sinha, C.S. Sivaramakrishnan. Statistical analysis of residence time distribution of fluid elements in continuous casting water model tundish with one side entry[J]. Steelmaking conference proceedings, 1994, 77: 703-712.
[14] Manfred M. Wolf. Slab caster tundish configuration and operation a review[C]. Steelmaking conference proceedings, 1996: 367-381.
[15]盛东源,倪满森,邓开文,刘家奇,干勇,肖泽强.中间包内钢液流动、温度控制和夹杂物行为的数学模拟[J].金属学报.1996(7):742-747.
[16]王建军,包燕平.中间包冶金学[M].北京:冶金工业出版社,2001.
[17] http://www.fibretech.com/refactories_steel_continuous_datasheet.htm
[18]江友波,孙晓光.炼钢、铸锭过程中产生非金属夹杂物的原因[J].一重技术, 2003,(3):31-32.
[19]戴云阁,蔡锡年,郭仲文.连铸坯中的非金属夹杂物[J].钢铁钒钛. 1997, 18(3):35-39.
[20]张全新.非金属夹杂物对锻造裂纹形成的影响[J].四川冶金, 2009, 31(5):66-67.
[21]蔡开科.浇注与凝固[M].北京:冶金工业出版社,1987.
[22]蔡开科,程士富.连续铸钢原理与工艺[M].北京:冶金工业出版社. 1994.
[23] Nakashima J, Miyazawa K, Imoto K .Origin of Nonmetallic Inclusions in Ladle Transition Part of Continuously Cast Slab[J]. Tetsu to Hagane-Journal of the Iron and Steel Institute of Japan. 2007, 93(5): 348-354.
[24] Lind, Minna, Holappa, Lauri. Transformation of Alumina Inclusions by Calcium Treatment. Metalurgcal and Meterials Transactions B-process Metallurgy and Materials Processing Science, 2010, 41(2): 359-366.
[25] Doostmohammadi H, Jonsson PG, Komenda J. Inclusion Characteristics of Bearing Steel in a Runner after Ingot Casting. Steel Research International. 2010, 81(2): 142-149.
[26]张文奇.中间包塞棒吹氩在钢锭真空浇注中的应用[J].大型铸锻件, 2009, 9(5): 36-37.
[27]王建军,包燕平.中间包冶金学[M].北京:冶金工业出版社,2001.
[28] ZHONG LIANG-CAI, LI BAO-KUANGB, ZHU YING-XIONG, et al. Fluid flow in a four-strand bloom continuous casting tundishs with different flow modifiers[J]. ISIJ International. 2007, 47(1):88-94.
[29] ZHENG SHU-GUO, ZHU MIAO-YONG. Optimization of baffles in a six-strand round bloom continuous casting tundish: a physical modeling study [J]. Ironmaking and Steelmaking, 2006, 33(5): 398.
[30] SAHAI Y, EMI T. Flow characterization in continuous casting tundishs[J]. ISIJ International, 1996, 36(6): 667-672.
[31] Liu Jingang, Yan Huicheng. Water Modeling of Optimizing Tundish Flow Field [J]. Journal of iron and steel research, International. 2007, 14 (3): 13-19.
[32] Sahai, Y, Emi, T. Physical Modeling of Melt Flow in Continuous Casting Tundishes[C]. Proceedings of the International Conference on Modelling and Simulation in Metallurgical Engineering and Materials Science. 1996, 1:11-13
[33] R. Dekkers, B. Blanpain, P. Wollants. Steel Sampling to Study Inclusions[C]. ISSTech 2003 Conference Proceedings. Warrandale, PA: ISS, 2003:19-209.
[34]王焕洋.漩流中间包的夹杂物模拟试验研究[J].宽厚板. 2008, 14(3):4-6.
[35]王立涛,张乔英,李正邦.中间包内流体流动及夹杂物去除的研究[J].炼钢. 2005, 21(2)
[36] Yuji Miki, Brian G.,Thomas. Modeling of Inclusion Removal in a Tundish[J]. Metallurgical and Materials Transactions. 1999,9(30): 639-654.
[37] Bessho N, Yamasaki H, Fujii T, et al. Removal of Inclusion from Molten Steel in Continuous Casting Tundish [J]. ISIJ International. 1992,32(1):157-163.
[38]张立峰,蔡开科.连铸中间包钢液流动和夹杂的去除[C].第五届连铸铸术会议论文选集. 1995.35-43.
[39]张胜军,朱苗勇.连铸中间包内夹杂物去除机理的水模型研究[J].金属学报, 2007, 43(9): 1104-1108.
[40]李东辉,李宝宽,赫冀成.中间包双板多孔挡墙流动控制去除夹杂物效果的模拟研究[J].金属学报, 1999, 35(10): 1107-1111.
[41]张胜军,郑淑国,朱苗勇.连铸中间包内夹杂物去除行为的水模型研究[J].北京科技大学学报, 2007, 29(8): 781-786,826.
[42]黄永锋,文光华,唐萍,祝明妹,张宁.中间包湍流控制器结构优化的水力学模拟[J].炼钢, 2011, 27(1):31-35.
[43] Ruchert A, Warzecha M, Koitzsch R, et al. Particle distribution and separation in continuous casting tundish[J]. Steel Research International, 2009, 80(8): 568-574.
[44] Liu J.G, Yan H. C. Water modeling of optimizing tundishs flow field[J]. Journal of iron and steel research, international, 2007, 14(3): 13-19.
[45] Miki Y, Thomas B. G. Modeling of inclusion removal in a tundish[J]. Metallurgical and materials transactions, 1999, 30B(4): 639-654.
[46] Zhang L. F, et al. Fluid flow and inclusion removal in continuous casting tundish[J]. Metallurgical and materials transactions, 2000, 31(2):253-266.
[47]郑淑国,朱苗勇,王颖.连铸中间包内夹杂物出去行为的物理模拟[J].东北大学学报, 2010, 31(5): 677-680.
[48] Minoru.S. Recent Japanese Studies on Control of Non-metallic Inclusions in Steel[C]. The 1st International Congress on Science and Technology of Steelmaking. Chiba, Japan. 1996: 68.
[49] Eck H, Syracuse G.. Adanced Reticulated Ceramic Metal Filters and Performance Result[C]. Electric Furnace Conference Proceedings, 1988(46):435-443.
[50]张华书,梁友.在中间罐内去除钢水中夹杂物技术发展[J].连铸. 2000(4):36-38.
[51]张立峰,菜开科.连铸中间包钢液流动和夹杂物的去除[C].第五届连铸铸术会议论文选集, 1995: 35-43.
[52]王建军,戴朝珊,周俐.板坯中间包钢水流动的热态水模[J].金属学报, 1997, 5: 509-514.
[53] Launder B E, B G.Thomas. Application of Mathematical Model to the CC Mould[C]. Steelmaking conference proceedings, 1990: 473-480.
[54] Yogeshwar Sahai, Toshihiko Emi. Criteria for Water Modeling of Melt Flow and Inclusion Removal in Continuous Casting Tundishes [J]. ISIJ International, 1996, 36 (9): 1166-1173.
[55]牛光源,黄杰.水力学模拟固体夹杂物制备[J].锦州工学院学报, 1989, (8): 95-99.
[56] Wen Guanghua, Zhang Lifeng,Ping Tang etc. Modeling Study on Fluid Flow and Inclusion Mmotion in 6-strand Bloom Caster Tundishes [J]. Journal of University of Science and Technology Beijing. 2004,11(4):310-314.
[57] Zhang S J, Zhu M Y. Water Model Study of Removal Mmechanism of Inclusion in Continuous Casting Tundish [J]. Acta Metallurgica Sinica. 2007, 43(9): 1004-1008.
[58] Zhang S J, Zheng S G, Zhu M Y. Water Model Study on the Mechanism of Inclusion Removal in a Continuous Casting Tundish [J]. Journal of University of Science and Technology Beijing. 2007, 29(8): 781-784.
[59] Launder B E, Spalding D B. The Numerical Computation of Turbulent Flows [J]. Computer Metheods in Applied Mechanics and Engineering. 1974, 3: 268-289.
[60]朱苗勇,肖泽强.连铸中间内三维流动的数学模拟[J].东北大学学报(自然科学版).1995, 16(4): 352-355.
[61] Pradeep K. Jha and Sukanta K. Dash. Effect of Outlet Positions and Various Turbulence Models on Mixing in a Single and Multistrand Tundish [J]. International Journal of Numerical Methods for Heat & Fluid flow. 2002,12 (5):560-584.
[62]张美杰,汪厚植,顾华志等.连铸中间包内钢液速度场数值模拟的研究进展[J].武汉科技大学学报, 2004, 27(3): 245-249.
[63] Ye F. Numerical simulations of the hydraulic charateristics of side inlet/outlets [J]. Journal of Hydrodynamics, 2011, 23(1): 48-54.
[64] Ely M J, Jubran B A. A numerical evaluation on the effect of sister holes on film cooling effectiveness and the surrounding flow field[J]. Heat Mass Transfer, 2009, 45:1435-1446.
[65]茅晓慧.中间包控流装置优化的物理模拟和数值模拟[学位论文].北京:北京科技大学, 2008:54.
[66]刘耀林.基于Ansys的中间包流场和温度场的模拟研究[学位论文].武汉:武汉科技大学, 2005:30
[67]朱苗勇.连铸中间包内三维湍流流动的数值模拟[J],金属学报, 1997, 33(11): 1215-1221.
[68] S.JOO, RI.L.Guthrie.Can. MEET.Quarterly, 1991, 30(4):261-269.
[69] S.Chakraborty, Y.Sahai. Role of Near-wall Node Location on the Prediction of Melt Flow and Residence Time Distribution in Tundish by Mathematical Modeling. Metallurgical Transactions B, 1991, 22B (4):429-437.
[70]朱苗勇.连铸中间包内钢液流动与传热耦合过程的计算机模拟[J].金属学报. 1997.(9):933～938.
[71]程乃良,朱苗勇,萧泽强.非等温双流连铸中间包内钢液的流动与传热特征[J].钢铁.2001, 36(10): 23-25.
[72]彭世恒.中间包等温和非等温过程的基础研究和数值模拟[D].长沙:中南大学, 2000: 66-68.
[73] M. Hashio, M. Tokuda, M. Kawasaki, and T. Watanabe. 2nd Process Technology Conference, ISS-AIME, 1981, 65-73.
[74] T. Nakaoka, T. Miyake, T. Mimura and H. Tai, Testu-to-Hagane. 2000, 86, 231-238.
[75]贺有多,Y. Sahai.不同因素对连铸机中间包流场的影响.金属学报. 1989, 25 (4): 272-276.
[76] Y. Tozaki, T. Saito, T. Yasui, K. Matsuo, M. Yokoyama, and H. Fujimoto: Steelmaking Conference Processdings, ISS-AIME, 1990,115-121.
[77] Dipak Mazumdar, Roderick I.L.Guthrie.The Physical and Mathematical Modeling of Continuous Casting Tundish Systems. ISIJ International, 1999,39(6):524-547.
[78] Hiraki S,Kanazawa T, Kumakura S etc. Influence of Tundish Operation on the Quality of Hot Coils during High Speed Continuous Casting. I&SM, 1999,(3):47-52.
[79] McPherson N A. The Effect of Tundish Design on the Quality of Continuously Cast Steel Slabs. MPT International, 1986(3):40-51.
[80]贺友多,Y.Sahai.不同因素对连铸中间包流场的影响.金属学报,1989,25(4):B272-276.
[81]吴永生,喻承欢,骆忠汉等.扩容中间包冶金效果研究.炼钢, 2001,17(1): 38-42.
[82] R. D. Morales, J. de J. Barreto, S. Lopez-ramirez, J. Palafox-Ramosm and D. Zacharias. Melt flow control in a multistrand tundish using a turbulence inhaibor. Metallurgical and Materials Transaction B. 2000, 31B: 1505-1515.
[83]文光华,唐萍等.六流大方坯连铸中间包选型和控流装置研究[J].钢铁钒钛.2002(2):19-22.
[84] Chih-Ming FAN and Weng-Sing Hwang. Mathematical Modeling of Fluid Flow Phenomena during Tundish Filling and Subsequent Initial Casting Operation in Steel Continuous Casting Process[J].ISIJ International. 2000(11):1105–1114.
[85]戴朝珊,王建军,朱立本.马钢六流小方坯连铸机中间包内型优化水模试验[J].华东冶金学院学报.1997 (4):381-386.
[86]王建军,戴朝珊,朱立本.六流小方坯中间包内型优化数模研究[J].炼钢.1995(10):16-20.
[87]刘旭峰,周俐,王建军等.六流小方坯连铸中间包内型优化设计水模研究[J].安徽工业大学学报.2002(1):26-28.
[88]唐继山,谢长川,于学斌等.六流连铸中间包的物理模拟[J]. 2002 (1):52-54.
[89]于学斌,唐继山,谢长川.六流连铸机型中间包内流场的数学模拟[J].武汉科技大学学报(自然科学版).2005 (2):122-125.
[90] S. K. Das. Mathematical Modeling of Flow Field in a Continuous Slab Caster TundishInclusion near Wall Turbluence Effect. Trans. Indian Inst. Met, 2001, 54 (1): 21-26.
[91] M. M. Wolf. History of continuous casting [C]. Iron & Steel Society, Steelmaking Conferences, Warren dale PA: 1992:83-137.
[92] J. J. Kim, S. K. Kim, S. D. Shim et al. Numerical an experimental study of tundishs flow during continuous casting of stainless steel [C]. Phoenix AZ. 59th Electric Furnace Conference and 19th Process Technology Conference [C]. USA: 2001, 396-406.
[93] Sahay S K, De T K, Basu D S et al. Strand performance improvement through use of asymmetric baffles in tundishs of six strand billet caster at DSP [J]. I&SM, 2001, 7:71-74.
[94]张立峰.纯净钢水钢水洁净度的工艺及理论研究[D].博士学位论文,北京:北京科技大学,1998.
[95] K. H. Tacke. Steel flow and inclusion separation in continuous casting tundishes[J]. Steel Research, 1987, 58(6):262-270.
[96] F. Kemeny, Harris D. J., Mclean A. Fluid flow studies in the tundishs of a slab caster [C], Continuous Casting of Steel, Proc. 2nd Process Technology Conference, Chicago, 1981: 232-245.
[97] Singh S, Koria. S. C. Physical modeling of steel flow in continuous casting tundish [J]. Ironmaking and Steelmaking. 1993 (3): 221-230.
[98] Koria S C, Singh S. Physical modeling of the effect of the flow modifier on the dynamics of molten steel flow in a tundish [J]. ISIJ International. 1994 (10): 784-793.
[99] Steal S P, Suzwkj Y, Bullock R. A. Improving steel cleanliness through tundish baf technology [J]. I&SM. 1991 (8): 17-18.
[100] K. J. Craig, D. J de Kock, K. W. Makgata and G. J. de Wet. Design Optimization of a Single- Strand Continuous Caster Tundish Using Residence Time Distribution Data [J]. ISIJ International, 2001,41(10): 1194-1200.
[101] Tacke K-H, etal. Steel flow and inclusion separation in continuous casting tundish [J], Steel Reasearch, 1987, 58 (6): 262-270.
[102] Nakajima H, Sebo F, Tanaka S, Dumitru L, Harris D J, and Guthrie R I L. Steelmaking Conference Proceedings, ISS-AIME, 1986, 69: 705-716.
[103] Tolve P, Praitoni A, and Ramacciotti A. Steelmaking Conference Proceedings, ISS-AIME, 1986, 69, 689-697.
[104] Sarbjit Singh and Satush C. KORIA. Model Study of the Dynamics of Flow of Steel in Tundish ISIJ International, 1993, 33(12):1226-1237.
[105] A. Tripathi and S. K. Ajmani. Numerical investigation of fluid flow phenomenon in a curved shape tundish of billet caster ISIJ International, 2005, 45(11): 1616-1625.
[106]薛伟峰,文光华,唐萍等.薄板坯连铸中间包控流装置的数理模拟[J].特殊钢, 2005, 26(3):19-21.
[107]金忠青. N-S方程的数值解和湍流模型[M].河海大学出版社. 1989
[108] Kolmogorov A N. Turbulent flow equation of incompressible fluid. Bulletin of Academic of Science of Soviet Union, Physics Series, 1942.
[109] Carajilescov P, Todreas N E. Experimental and analytical study of axial turbulent flow in an interior subc hannel of abare rod bundle [J]. ASME J Heat Transfer. 1976, 98: 262-268.
[110] Gori F, E1Hadiy M A, Spalding D B. Numerical prediction of heat transfer to low-Prandtl fluids [J]. Numer Heat Transfer. 1979, 2: 441-454.
[111]陶文铨.数值传热学(第二版)[M].西安:西安交通大学出版社, 2001.
[112] Fu S, Launder B E, Leschziner M A. Modeling strongly swirling recirculating jet flow with Reynolds-stress transport closures[C]. In Sixth Symposium on Turbulent Shear Flows, Toulouse, France, 1987.
[113] Launder B E, Spalding D B. The numerical computation of turbulent flows [J]. Computer Methods in Applied Mechanicsand Engineering, 1974, 3(2):269-289.
[114]郭洪志.传输过程数值模拟[M].北京:冶金工业出版社, 1998.
[115] Yakhot V, Orszag S A, Thangam S, etal. Development of turbulence models for shear flows by a double expansion technique [J]. Physics of Fluids A (Fluid Dynamics), 1992, 4(7): 1510-1520.
[116] Yakhot V, Orszag S A. Renormalizaiton group analysis of turbulence: basic theory [J]. Journal of Scientific Computing, 1986, 1(1):1-11.
[117] Odenthal H-J, Boelling R, Pfeifer H. Numerical and physical simulation of tundish phenomenal [J]. Steel Research, 2003, 74(1):44-45.
[118] Demedices L D, Morales R D. Mathematical modeling of the geometry influence of a multi-strand tundish on the momentum, heat and mass transfer of steel flow [J]. Steel Reasearch, 2001, 72(9): 346-352.
[119]唐海燕,于满,李京社,等.连铸中间包内部结构优化的数理模拟及冶金效果[J].北京科技大学学报, 2009, 31(增1): 38-42.
[120] Morales R D, Barreto J de J, etal. Mathematical simulation of the influence of buoyancy forces on the molten steel flow in a continuous casting tundish [J]. Metallurgical Transaction, 2000, 31B:1505-1515.
[121] Mishra S. K. Numerical investigation of fluid flow and hear transfer in a multi-strand steelmaking tundishs with closed strands[J]. International Jounal of Engineering Science and Technology, 2011, 3(2): 1138-1146.
[122] Zhang L.Validation of the Numerical Simulation of Fluid Flow in the Continuous Casting Tundish[J].Journal of University of Science and Technoligy Bejing,2005 (2):116～122.
[123] Shih T H, Liou W W, Shabbir A, et al. A new k-εeddy viscosity model for high Reynolds number turbulent flows [J]. Computers & Fluids, 1995, 24(3): 227-238.
[124] Pradeep K J, Sukanta K D. Employment of different turbulence models to the design of optimum steel flows in a tundish [J]. International Journal of Numerical Methods for Heat&Fluid Flow, 2004, 14(8):953-979.
[125] Wang Y F, Wen G H, Tang P. Mathematical modeling of fluid flow, heat transfer and inclusion transport in a four strand tundish[J]. Journal of University of Science and Technology Beijing, 2007, 14(1): 22-26.
[126]朱苗勇.连铸中间包内钢液流动与传热耦合过程的计算机模拟[J].金属学报. 1997.(9): 933～938.
[127] Kumar A, Mazumdar D, Koria S C. Modeling of fluid flow and residence time distribution in a four-strand tundish for enhancing inclusion removal [J]. ISIJ International, 2008, 48(1):38-47.
[128]童秉纲,尹协远,朱克勤.涡运动理论[M].中国科学技术大学出版社,合肥, 1994.6-16.
[129] Tanaka Y, Sato I. Development of high purity large forgings for nuclear power plants [J]. Journal of Nuclear Materials, 2011, 1: 1-6.
[130]孙宝中,沈建中.合成孔径聚焦成像(一)[J].应用声学, 1993, 12(3): 43-48.
[131]王邓志,罗斌,罗宏建.合成孔径聚焦超声成像系统研究[J].东北电力技术, 2002, 23(12): 42-45.
[132]万芳. 6种无损检测[J].国外铁道车辆, 1999, 1:13.
[133]吴汉平,译机载雷达导论[M],电子工艺出版社. 2005.
[134]李养良,王邓志,陈大兵.合成孔径聚焦超声成像系统的计算机仿真[J].现代电子技术, 2004, 27(22): 74-75, 79.
[135]高道龙.超声波探伤仪的检定[M].成都市计量测试研究所,成都2001.
[136]环川建,张强,江向华.小径薄壁焊接头超声波探伤方法探讨[J].无损探伤, 2005, 29(6):34-36.
[137]陈卫华,李新德,赵兴群.数字超声波探伤仪的现状与展望[J].无损探伤检测, 1994, 16(6): 157-158.
[138] http://www.cfhi.com/yzjt/contents/1026/15073.aspx
[2]王凤喜.大锻件生产行业与锻造技术发展[J].锻压机械. 2002, 4:3-6.
[3]郭会光,曲宗实.我国大锻件制造业的发展[J].大型铸锻件. 2003, 1: 42-45.
[4]曾祖良.国外大型锻件用钢锭的生产水平[J].工程建设与设计. 1987, 1 (2):10-13.
[5]蒋梦龙.优质大型转子钢锭的冶金技术[J].上海金属. 1994, 16 (5): 23-27.
[6] Sanjib Chakraborty, Yogeshwar Sahai. Effect of Varying Ladle Stream Temperature on the Melt Flow and Heat Transter in Continuous Casting Tundishe [J]. ISIJ International. 1991(9): 960-967.
[7] A. Vargas-Zamora, R.D. Morales.Heat and mass transfer of a convective-stratified flow in a trough type tundish[J]. InternationalJournal of Heat and Mass Transfer. 2003:3029–3039.
[8] C. M. Fan, R. J. Shie and W. S. Hwang. Studies by mathematical and physical modelling of fluid flow and inclusion removal phenomena in slab tundish for casting stainless steel using various flow control device designs[J]. Ironmaking and Steelmaking. 2003 (5): 341-347.
[9] Marcela B. Goldschmit. Sergio P. Ferro. Guillermo F. Walter, Virginia G. Aranda, Jorge A.Tena Morelos. Numerical model for the minimization of intermixed round bars in a four line continous caster[J]. Metallurgical and materials transactions B, 2001, 32(3): 537-546.
[10] P. Gardin, M. Brunet, J. F. Domgin, K. Pericleous. An experimental and numerical CFD study of turbulence in a tundish container[J]. Applied mathematical modeling, 2002, 26(2): 323-336.
[11] J.舍克里著.彭一川徐匡迪樊养颐译.冶金中的流体流动现象[M].北京.冶金工业出版社.1985.
[12] S.V.帕坦卡著.张政译.传热与流体流动的数值计算[M].北京.科学出版社.1980.
[13] K. M. Godiwalla, S.K. Sinha, C.S. Sivaramakrishnan. Statistical analysis of residence time distribution of fluid elements in continuous casting water model tundish with one side entry[J]. Steelmaking conference proceedings, 1994, 77: 703-712.
[14] Manfred M. Wolf. Slab caster tundish configuration and operation a review[C]. Steelmaking conference proceedings, 1996: 367-381.
[15]盛东源,倪满森,邓开文,刘家奇,干勇,肖泽强.中间包内钢液流动、温度控制和夹杂物行为的数学模拟[J].金属学报.1996(7):742-747.
[16]王建军,包燕平.中间包冶金学[M].北京:冶金工业出版社,2001.
[17] http://www.fibretech.com/refactories_steel_continuous_datasheet.htm
[18]江友波,孙晓光.炼钢、铸锭过程中产生非金属夹杂物的原因[J].一重技术, 2003,(3):31-32.
[19]戴云阁,蔡锡年,郭仲文.连铸坯中的非金属夹杂物[J].钢铁钒钛. 1997, 18(3):35-39.
[20]张全新.非金属夹杂物对锻造裂纹形成的影响[J].四川冶金, 2009, 31(5):66-67.
[21]蔡开科.浇注与凝固[M].北京:冶金工业出版社,1987.
[22]蔡开科,程士富.连续铸钢原理与工艺[M].北京:冶金工业出版社. 1994.
[23] Nakashima J, Miyazawa K, Imoto K .Origin of Nonmetallic Inclusions in Ladle Transition Part of Continuously Cast Slab[J]. Tetsu to Hagane-Journal of the Iron and Steel Institute of Japan. 2007, 93(5): 348-354.
[24] Lind, Minna, Holappa, Lauri. Transformation of Alumina Inclusions by Calcium Treatment. Metalurgcal and Meterials Transactions B-process Metallurgy and Materials Processing Science, 2010, 41(2): 359-366.
[25] Doostmohammadi H, Jonsson PG, Komenda J. Inclusion Characteristics of Bearing Steel in a Runner after Ingot Casting. Steel Research International. 2010, 81(2): 142-149.
[26]张文奇.中间包塞棒吹氩在钢锭真空浇注中的应用[J].大型铸锻件, 2009, 9(5): 36-37.
[27]王建军,包燕平.中间包冶金学[M].北京:冶金工业出版社,2001.
[28] ZHONG LIANG-CAI, LI BAO-KUANGB, ZHU YING-XIONG, et al. Fluid flow in a four-strand bloom continuous casting tundishs with different flow modifiers[J]. ISIJ International. 2007, 47(1):88-94.
[29] ZHENG SHU-GUO, ZHU MIAO-YONG. Optimization of baffles in a six-strand round bloom continuous casting tundish: a physical modeling study [J]. Ironmaking and Steelmaking, 2006, 33(5): 398.
[30] SAHAI Y, EMI T. Flow characterization in continuous casting tundishs[J]. ISIJ International, 1996, 36(6): 667-672.
[31] Liu Jingang, Yan Huicheng. Water Modeling of Optimizing Tundish Flow Field [J]. Journal of iron and steel research, International. 2007, 14 (3): 13-19.
[32] Sahai, Y, Emi, T. Physical Modeling of Melt Flow in Continuous Casting Tundishes[C]. Proceedings of the International Conference on Modelling and Simulation in Metallurgical Engineering and Materials Science. 1996, 1:11-13
[33] R. Dekkers, B. Blanpain, P. Wollants. Steel Sampling to Study Inclusions[C]. ISSTech 2003 Conference Proceedings. Warrandale, PA: ISS, 2003:19-209.
[34]王焕洋.漩流中间包的夹杂物模拟试验研究[J].宽厚板. 2008, 14(3):4-6.
[35]王立涛,张乔英,李正邦.中间包内流体流动及夹杂物去除的研究[J].炼钢. 2005, 21(2)
[36] Yuji Miki, Brian G.,Thomas. Modeling of Inclusion Removal in a Tundish[J]. Metallurgical and Materials Transactions. 1999,9(30): 639-654.
[37] Bessho N, Yamasaki H, Fujii T, et al. Removal of Inclusion from Molten Steel in Continuous Casting Tundish [J]. ISIJ International. 1992,32(1):157-163.
[38]张立峰,蔡开科.连铸中间包钢液流动和夹杂的去除[C].第五届连铸铸术会议论文选集. 1995.35-43.
[39]张胜军,朱苗勇.连铸中间包内夹杂物去除机理的水模型研究[J].金属学报, 2007, 43(9): 1104-1108.
[40]李东辉,李宝宽,赫冀成.中间包双板多孔挡墙流动控制去除夹杂物效果的模拟研究[J].金属学报, 1999, 35(10): 1107-1111.
[41]张胜军,郑淑国,朱苗勇.连铸中间包内夹杂物去除行为的水模型研究[J].北京科技大学学报, 2007, 29(8): 781-786,826.
[42]黄永锋,文光华,唐萍,祝明妹,张宁.中间包湍流控制器结构优化的水力学模拟[J].炼钢, 2011, 27(1):31-35.
[43] Ruchert A, Warzecha M, Koitzsch R, et al. Particle distribution and separation in continuous casting tundish[J]. Steel Research International, 2009, 80(8): 568-574.
[44] Liu J.G, Yan H. C. Water modeling of optimizing tundishs flow field[J]. Journal of iron and steel research, international, 2007, 14(3): 13-19.
[45] Miki Y, Thomas B. G. Modeling of inclusion removal in a tundish[J]. Metallurgical and materials transactions, 1999, 30B(4): 639-654.
[46] Zhang L. F, et al. Fluid flow and inclusion removal in continuous casting tundish[J]. Metallurgical and materials transactions, 2000, 31(2):253-266.
[47]郑淑国,朱苗勇,王颖.连铸中间包内夹杂物出去行为的物理模拟[J].东北大学学报, 2010, 31(5): 677-680.
[48] Minoru.S. Recent Japanese Studies on Control of Non-metallic Inclusions in Steel[C]. The 1st International Congress on Science and Technology of Steelmaking. Chiba, Japan. 1996: 68.
[49] Eck H, Syracuse G.. Adanced Reticulated Ceramic Metal Filters and Performance Result[C]. Electric Furnace Conference Proceedings, 1988(46):435-443.
[50]张华书,梁友.在中间罐内去除钢水中夹杂物技术发展[J].连铸. 2000(4):36-38.
[51]张立峰,菜开科.连铸中间包钢液流动和夹杂物的去除[C].第五届连铸铸术会议论文选集, 1995: 35-43.
[52]王建军,戴朝珊,周俐.板坯中间包钢水流动的热态水模[J].金属学报, 1997, 5: 509-514.
[53] Launder B E, B G.Thomas. Application of Mathematical Model to the CC Mould[C]. Steelmaking conference proceedings, 1990: 473-480.
[54] Yogeshwar Sahai, Toshihiko Emi. Criteria for Water Modeling of Melt Flow and Inclusion Removal in Continuous Casting Tundishes [J]. ISIJ International, 1996, 36 (9): 1166-1173.
[55]牛光源,黄杰.水力学模拟固体夹杂物制备[J].锦州工学院学报, 1989, (8): 95-99.
[56] Wen Guanghua, Zhang Lifeng,Ping Tang etc. Modeling Study on Fluid Flow and Inclusion Mmotion in 6-strand Bloom Caster Tundishes [J]. Journal of University of Science and Technology Beijing. 2004,11(4):310-314.
[57] Zhang S J, Zhu M Y. Water Model Study of Removal Mmechanism of Inclusion in Continuous Casting Tundish [J]. Acta Metallurgica Sinica. 2007, 43(9): 1004-1008.
[58] Zhang S J, Zheng S G, Zhu M Y. Water Model Study on the Mechanism of Inclusion Removal in a Continuous Casting Tundish [J]. Journal of University of Science and Technology Beijing. 2007, 29(8): 781-784.
[59] Launder B E, Spalding D B. The Numerical Computation of Turbulent Flows [J]. Computer Metheods in Applied Mechanics and Engineering. 1974, 3: 268-289.
[60]朱苗勇,肖泽强.连铸中间内三维流动的数学模拟[J].东北大学学报(自然科学版).1995, 16(4): 352-355.
[61] Pradeep K. Jha and Sukanta K. Dash. Effect of Outlet Positions and Various Turbulence Models on Mixing in a Single and Multistrand Tundish [J]. International Journal of Numerical Methods for Heat & Fluid flow. 2002,12 (5):560-584.
[62]张美杰,汪厚植,顾华志等.连铸中间包内钢液速度场数值模拟的研究进展[J].武汉科技大学学报, 2004, 27(3): 245-249.
[63] Ye F. Numerical simulations of the hydraulic charateristics of side inlet/outlets [J]. Journal of Hydrodynamics, 2011, 23(1): 48-54.
[64] Ely M J, Jubran B A. A numerical evaluation on the effect of sister holes on film cooling effectiveness and the surrounding flow field[J]. Heat Mass Transfer, 2009, 45:1435-1446.
[65]茅晓慧.中间包控流装置优化的物理模拟和数值模拟[学位论文].北京:北京科技大学, 2008:54.
[66]刘耀林.基于Ansys的中间包流场和温度场的模拟研究[学位论文].武汉:武汉科技大学, 2005:30
[67]朱苗勇.连铸中间包内三维湍流流动的数值模拟[J],金属学报, 1997, 33(11): 1215-1221.
[68] S.JOO, RI.L.Guthrie.Can. MEET.Quarterly, 1991, 30(4):261-269.
[69] S.Chakraborty, Y.Sahai. Role of Near-wall Node Location on the Prediction of Melt Flow and Residence Time Distribution in Tundish by Mathematical Modeling. Metallurgical Transactions B, 1991, 22B (4):429-437.
[70]朱苗勇.连铸中间包内钢液流动与传热耦合过程的计算机模拟[J].金属学报. 1997.(9):933～938.
[71]程乃良,朱苗勇,萧泽强.非等温双流连铸中间包内钢液的流动与传热特征[J].钢铁.2001, 36(10): 23-25.
[72]彭世恒.中间包等温和非等温过程的基础研究和数值模拟[D].长沙:中南大学, 2000: 66-68.
[73] M. Hashio, M. Tokuda, M. Kawasaki, and T. Watanabe. 2nd Process Technology Conference, ISS-AIME, 1981, 65-73.
[74] T. Nakaoka, T. Miyake, T. Mimura and H. Tai, Testu-to-Hagane. 2000, 86, 231-238.
[75]贺有多,Y. Sahai.不同因素对连铸机中间包流场的影响.金属学报. 1989, 25 (4): 272-276.
[76] Y. Tozaki, T. Saito, T. Yasui, K. Matsuo, M. Yokoyama, and H. Fujimoto: Steelmaking Conference Processdings, ISS-AIME, 1990,115-121.
[77] Dipak Mazumdar, Roderick I.L.Guthrie.The Physical and Mathematical Modeling of Continuous Casting Tundish Systems. ISIJ International, 1999,39(6):524-547.
[78] Hiraki S,Kanazawa T, Kumakura S etc. Influence of Tundish Operation on the Quality of Hot Coils during High Speed Continuous Casting. I&SM, 1999,(3):47-52.
[79] McPherson N A. The Effect of Tundish Design on the Quality of Continuously Cast Steel Slabs. MPT International, 1986(3):40-51.
[80]贺友多,Y.Sahai.不同因素对连铸中间包流场的影响.金属学报,1989,25(4):B272-276.
[81]吴永生,喻承欢,骆忠汉等.扩容中间包冶金效果研究.炼钢, 2001,17(1): 38-42.
[82] R. D. Morales, J. de J. Barreto, S. Lopez-ramirez, J. Palafox-Ramosm and D. Zacharias. Melt flow control in a multistrand tundish using a turbulence inhaibor. Metallurgical and Materials Transaction B. 2000, 31B: 1505-1515.
[83]文光华,唐萍等.六流大方坯连铸中间包选型和控流装置研究[J].钢铁钒钛.2002(2):19-22.
[84] Chih-Ming FAN and Weng-Sing Hwang. Mathematical Modeling of Fluid Flow Phenomena during Tundish Filling and Subsequent Initial Casting Operation in Steel Continuous Casting Process[J].ISIJ International. 2000(11):1105–1114.
[85]戴朝珊,王建军,朱立本.马钢六流小方坯连铸机中间包内型优化水模试验[J].华东冶金学院学报.1997 (4):381-386.
[86]王建军,戴朝珊,朱立本.六流小方坯中间包内型优化数模研究[J].炼钢.1995(10):16-20.
[87]刘旭峰,周俐,王建军等.六流小方坯连铸中间包内型优化设计水模研究[J].安徽工业大学学报.2002(1):26-28.
[88]唐继山,谢长川,于学斌等.六流连铸中间包的物理模拟[J]. 2002 (1):52-54.
[89]于学斌,唐继山,谢长川.六流连铸机型中间包内流场的数学模拟[J].武汉科技大学学报(自然科学版).2005 (2):122-125.
[90] S. K. Das. Mathematical Modeling of Flow Field in a Continuous Slab Caster TundishInclusion near Wall Turbluence Effect. Trans. Indian Inst. Met, 2001, 54 (1): 21-26.
[91] M. M. Wolf. History of continuous casting [C]. Iron & Steel Society, Steelmaking Conferences, Warren dale PA: 1992:83-137.
[92] J. J. Kim, S. K. Kim, S. D. Shim et al. Numerical an experimental study of tundishs flow during continuous casting of stainless steel [C]. Phoenix AZ. 59th Electric Furnace Conference and 19th Process Technology Conference [C]. USA: 2001, 396-406.
[93] Sahay S K, De T K, Basu D S et al. Strand performance improvement through use of asymmetric baffles in tundishs of six strand billet caster at DSP [J]. I&SM, 2001, 7:71-74.
[94]张立峰.纯净钢水钢水洁净度的工艺及理论研究[D].博士学位论文,北京:北京科技大学,1998.
[95] K. H. Tacke. Steel flow and inclusion separation in continuous casting tundishes[J]. Steel Research, 1987, 58(6):262-270.
[96] F. Kemeny, Harris D. J., Mclean A. Fluid flow studies in the tundishs of a slab caster [C], Continuous Casting of Steel, Proc. 2nd Process Technology Conference, Chicago, 1981: 232-245.
[97] Singh S, Koria. S. C. Physical modeling of steel flow in continuous casting tundish [J]. Ironmaking and Steelmaking. 1993 (3): 221-230.
[98] Koria S C, Singh S. Physical modeling of the effect of the flow modifier on the dynamics of molten steel flow in a tundish [J]. ISIJ International. 1994 (10): 784-793.
[99] Steal S P, Suzwkj Y, Bullock R. A. Improving steel cleanliness through tundish baf technology [J]. I&SM. 1991 (8): 17-18.
[100] K. J. Craig, D. J de Kock, K. W. Makgata and G. J. de Wet. Design Optimization of a Single- Strand Continuous Caster Tundish Using Residence Time Distribution Data [J]. ISIJ International, 2001,41(10): 1194-1200.
[101] Tacke K-H, etal. Steel flow and inclusion separation in continuous casting tundish [J], Steel Reasearch, 1987, 58 (6): 262-270.
[102] Nakajima H, Sebo F, Tanaka S, Dumitru L, Harris D J, and Guthrie R I L. Steelmaking Conference Proceedings, ISS-AIME, 1986, 69: 705-716.
[103] Tolve P, Praitoni A, and Ramacciotti A. Steelmaking Conference Proceedings, ISS-AIME, 1986, 69, 689-697.
[104] Sarbjit Singh and Satush C. KORIA. Model Study of the Dynamics of Flow of Steel in Tundish ISIJ International, 1993, 33(12):1226-1237.
[105] A. Tripathi and S. K. Ajmani. Numerical investigation of fluid flow phenomenon in a curved shape tundish of billet caster ISIJ International, 2005, 45(11): 1616-1625.
[106]薛伟峰,文光华,唐萍等.薄板坯连铸中间包控流装置的数理模拟[J].特殊钢, 2005, 26(3):19-21.
[107]金忠青. N-S方程的数值解和湍流模型[M].河海大学出版社. 1989
[108] Kolmogorov A N. Turbulent flow equation of incompressible fluid. Bulletin of Academic of Science of Soviet Union, Physics Series, 1942.
[109] Carajilescov P, Todreas N E. Experimental and analytical study of axial turbulent flow in an interior subc hannel of abare rod bundle [J]. ASME J Heat Transfer. 1976, 98: 262-268.
[110] Gori F, E1Hadiy M A, Spalding D B. Numerical prediction of heat transfer to low-Prandtl fluids [J]. Numer Heat Transfer. 1979, 2: 441-454.
[111]陶文铨.数值传热学(第二版)[M].西安:西安交通大学出版社, 2001.
[112] Fu S, Launder B E, Leschziner M A. Modeling strongly swirling recirculating jet flow with Reynolds-stress transport closures[C]. In Sixth Symposium on Turbulent Shear Flows, Toulouse, France, 1987.
[113] Launder B E, Spalding D B. The numerical computation of turbulent flows [J]. Computer Methods in Applied Mechanicsand Engineering, 1974, 3(2):269-289.
[114]郭洪志.传输过程数值模拟[M].北京:冶金工业出版社, 1998.
[115] Yakhot V, Orszag S A, Thangam S, etal. Development of turbulence models for shear flows by a double expansion technique [J]. Physics of Fluids A (Fluid Dynamics), 1992, 4(7): 1510-1520.
[116] Yakhot V, Orszag S A. Renormalizaiton group analysis of turbulence: basic theory [J]. Journal of Scientific Computing, 1986, 1(1):1-11.
[117] Odenthal H-J, Boelling R, Pfeifer H. Numerical and physical simulation of tundish phenomenal [J]. Steel Research, 2003, 74(1):44-45.
[118] Demedices L D, Morales R D. Mathematical modeling of the geometry influence of a multi-strand tundish on the momentum, heat and mass transfer of steel flow [J]. Steel Reasearch, 2001, 72(9): 346-352.
[119]唐海燕,于满,李京社,等.连铸中间包内部结构优化的数理模拟及冶金效果[J].北京科技大学学报, 2009, 31(增1): 38-42.
[120] Morales R D, Barreto J de J, etal. Mathematical simulation of the influence of buoyancy forces on the molten steel flow in a continuous casting tundish [J]. Metallurgical Transaction, 2000, 31B:1505-1515.
[121] Mishra S. K. Numerical investigation of fluid flow and hear transfer in a multi-strand steelmaking tundishs with closed strands[J]. International Jounal of Engineering Science and Technology, 2011, 3(2): 1138-1146.
[122] Zhang L.Validation of the Numerical Simulation of Fluid Flow in the Continuous Casting Tundish[J].Journal of University of Science and Technoligy Bejing,2005 (2):116～122.
[123] Shih T H, Liou W W, Shabbir A, et al. A new k-εeddy viscosity model for high Reynolds number turbulent flows [J]. Computers & Fluids, 1995, 24(3): 227-238.
[124] Pradeep K J, Sukanta K D. Employment of different turbulence models to the design of optimum steel flows in a tundish [J]. International Journal of Numerical Methods for Heat&Fluid Flow, 2004, 14(8):953-979.
[125] Wang Y F, Wen G H, Tang P. Mathematical modeling of fluid flow, heat transfer and inclusion transport in a four strand tundish[J]. Journal of University of Science and Technology Beijing, 2007, 14(1): 22-26.
[126]朱苗勇.连铸中间包内钢液流动与传热耦合过程的计算机模拟[J].金属学报. 1997.(9): 933～938.
[127] Kumar A, Mazumdar D, Koria S C. Modeling of fluid flow and residence time distribution in a four-strand tundish for enhancing inclusion removal [J]. ISIJ International, 2008, 48(1):38-47.
[128]童秉纲,尹协远,朱克勤.涡运动理论[M].中国科学技术大学出版社,合肥, 1994.6-16.
[129] Tanaka Y, Sato I. Development of high purity large forgings for nuclear power plants [J]. Journal of Nuclear Materials, 2011, 1: 1-6.
[130]孙宝中,沈建中.合成孔径聚焦成像(一)[J].应用声学, 1993, 12(3): 43-48.
[131]王邓志,罗斌,罗宏建.合成孔径聚焦超声成像系统研究[J].东北电力技术, 2002, 23(12): 42-45.
[132]万芳. 6种无损检测[J].国外铁道车辆, 1999, 1:13.
[133]吴汉平,译机载雷达导论[M],电子工艺出版社. 2005.
[134]李养良,王邓志,陈大兵.合成孔径聚焦超声成像系统的计算机仿真[J].现代电子技术, 2004, 27(22): 74-75, 79.
[135]高道龙.超声波探伤仪的检定[M].成都市计量测试研究所,成都2001.
[136]环川建,张强,江向华.小径薄壁焊接头超声波探伤方法探讨[J].无损探伤, 2005, 29(6):34-36.
[137]陈卫华,李新德,赵兴群.数字超声波探伤仪的现状与展望[J].无损探伤检测, 1994, 16(6): 157-158.
[138] http://www.cfhi.com/yzjt/contents/1026/15073.aspx