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1.
A three-dimentional thermal elastoplastic contact FE analysis model of solidifiedshell in moulds for continuous casting of thin slabs is set up, based on the known geometry of theshell and the temperature distribution in the shell. We in turn obtain the stress and Strain distributions of the solidified shells formed in lSP and CSP moulds,the gap distributions between the Shellsand the mould walls,as well as the curves of cracking index [1] in the shells,which provides afoundation for the design and control of technical parameturs for continuous casting of thin slabs. 相似文献
2.
The mathematic model of solidification heat transfer process in continuous casting strand is useful for quantitatively analyzing heat transfer in continuous casting process, quality control and process control. The heat transfer in continuous cast strand in crystallizer and secondary cooling zone have been analyzed. The attention has been paid to basic logic and methodology in model building up. Typical methods determing solution condition and parameters for the model have been discussed. Some numerical methods at the present time for solving solidification heat transfer model, such as finite difference method, finite-element method and boundary element, have been investigated comparatively. In the future, working on solidification heat transfer model, which is more practical, and the integration of the control model will play an important role in the development of high efficiency continuous casting technology. 相似文献
3.
In the established model,
the cooling differences are considered between the surface of inner radius and that of
outer radius, and in the transverse direction of thin slab. And the conception for the
effective coefficient of spraying water in continuous casting is firstly put forward.
According to different casting speeds and different cooling zones, different time step
lengths are adopted. In this model the heat transfer differences are thought over among
vertical and curved zones, wide and narrow surfaces an well as angular zone of mould. The
method of the corrected equivalent specific heat is used to deal with latent heat. The
influence of forced convection is considered on heat transfer. Therefore, the model has
higher accuracy and is consistent with the practice. 相似文献
4.
In order to increase decision accuracy of the intermixing slab length and position, and decrease the slabs which are offgraded or scrapped. Water model experiments were conducted to simulate the continuous casting grade transition process of No. 2 continuous caster at Bao Steel. The dimensionless concentration profiles along slab length with different continuous casting conditions were measured. Based on the profiles a mathematical model was developed to predict the final composition distributions and length of intermixing slab. Comparison of predicted dimensionless concentration profile with plant data shows that the precision of the model is considerably satisfied to meet the need of steel grade transition evaluation. 相似文献
5.
Based on the existing research on nozzle arrangement method in secondary cooling zone of continuous casting, the method of superposed water flow density is put forward to optimize the nozzle arrangement at casting direction and transverse section of slab according to the optimization principle. The two-dimension heat transfer model is established. The solidification morphology of cross-section at casting direction is simulated with consideration of the influence of water flow density inhomogeneity on solidification process at transversal section, and the temperature distribution of slab, solidification process, and quality of slab are compared between before and after optimization. The results indicate that the surface temperature of slab is dropped equably after optimization, and the casting blank is cooling uniformly in the water springing zone so as to ensure better quality of the casting blank. 相似文献
6.
A dynamic control model for the secondary cooling of slab casting is presented to reduce the difference between the actual temperature and the goal surface temperature of slab. The model, which is based on the BP neural networks for forecasting the temperature and the fuzzy neural networks for dynamically controlling the water in the secondary cooling in the continuous casting, could timely adjust and allocate the water according to the speed and temperature of slab. A series of tests have been conducted based on inputs of the No. 2 slab caster in a steel plant. It has been shown that the model, which integrate the charateristics of water controlling problem in secondary cooling into the temperature status of slab during the cooling process, can control the water in secondary cooling efficiently and dynamically according to the situation of actual production. 相似文献
7.
On the core concepts that the distributing of temperature and solidified slab shell in mold are a stable process, a new method to calculate the temperature field in mold has been promoted. Consequently, a coupling model on fluid filed and temperature field in stable state has also been established. The concept of effective heat capacity is introduced to deal with the latent heat source term from phase transformation. During the programming for computation, the dynamic updating method is also applied to simulate the influence of solidification on physical properties. The resolution results of this model are analyzed and compared with the tested thickness of solidified shell from casting broke out slab, which demonstrates the correctness and applicability of this model to the practical continuous casting process. Additionally, the thickness distribution of solidified shell in slab mold are also studied in detail. 相似文献
8.
In view of the process characteristics of thin slab casting with a vertical-arcmould and super thin submerged nozzles, the fluid flow laws in a mould and in scarch of reasonablesu bmerged nozzle patterns have been physieally simulated. The fluid flow states of several typiealnozzleS in moulds were studied through water model experimen ts. The shape and dimensions of asuitable submerged nozzle have heen optimized for industry trials. 相似文献
9.
10.
Several long term creep and cyclic creep tests of Shanghai soft clay are performed in the laboratory. Test results have been obtained under various combinations of confining stresses, deviation static stress ratios and deviation cyclic stress ratios. The results reveal that the axial creep strain increases with the increase of deviation static stress ratio under a constant confining stress, while it also increases with the increase of confining stress under a constant deviation stress ratio. Such a phenomenon is similar to that from the cyclic creep tests, but the following creep strain increase will be significantly reduced after a period of cyclic loading. The results will benefit the expressway, railroad and underground constructions. 相似文献
11.
A genetic algorithm was used for coding the volume of cooling water in the secondary cooling zone based on the heat transfer model in real time production. This was done to improve the dynamic control of the secondary cooling water in high efficiency continuous casting. The fitness function of multi objective optimization in the algorithm is in accordance with the distribution of metallurgical criteria. The genetic algorithm was integrated with the metallurgical criteria and the heat transferring model to optimize the water distribution. These steps increase the distribution adaptability and improve its efficiency compared to the traditional optimization methods of solving multi objective optimization and other non linear problems. Simulation using the process data of the No.2 slab caster in the Steelmaking Plant of Panzhihua Iron and Steel and on site testing were carried out. The results show that the optimized distribution saves 2% of water than without optimization, while water distribution along the slab to the water gradually decreases in accordance with requirements for slab quality control. 相似文献
12.
CCD radiation temperature measurement method for hot continuous casting billet surface 总被引：2，自引：0，他引：2
According to the present research status and existing problems of hot continuous billet surface temperature non contact measurement technology, a real time temperature measurement model, which combines two-color(R,G) and monochrome (B) of surface radiation image, is established. The surface image is collected through tricolor charge coupled device (CCD) sensor, at the same time, the temperature dynamic response range of CCD can be improved by controlling integrated time and setting different apertures. Through computer image process technology, multi-point temperature can be measured simultaneously, and 2-D temperature field distribution on continuous casting billet surface can be realized. It is be proved by theory and application that the model and method can provide a theory and technology support for realizing surface temperature field on-line measurement for continuous casting billet. 相似文献
13.
The cellular automaton (CA) method is coupled with finite difference method to establish a stochastic nucleation and growth model. According to the actual production conditions, the solidification structure of continuous casting slab is simulated and the evolution law of the inner structure is reconstructed. It is showed that grain transformation is from equiaxed crystal to columnar crystal and then to equiaxed crystal. Thickness of three crystal layers are different in various production technological systems, thickness of surface equiaxed crystal and inner equiaxed crystal are reduced, and the results of the columnar crystal thickness are contrary, while casting speed and superheat are increasing. The results show well agreement with the stochastic nucleation, preferred growth, competitive growth and random orientation of grain. 相似文献
14.
A new model is proposed to analyze the strain/stress transfer relation between host materials and piezoceramic sensors/actuators under bending and axial stress loading. The finite thickness of the adhesive is taken into account. The physical layers of the piezoceramic, adhesive and structure material are further subdivided into thinner layers as fine as necessary in order to improve the accuracy of stress analysis. In each thin layer the in-plane stresses are assumed to vary linearly across the thickness. By satisfying equilibrium equations, constitutive equations and displacement-strain relations, all components of stress, strain and displacement can be expressed as functions of the in-plane forces and the moments of the thin layers. The differential equations governing the in-plane forces and the moments are obtained. Then, this analytical model is used to predict strain transfer from the structure material to the sensor. It is found, both experimentally and theoretically, that the axial strain of the host material is considerably larger than the strain of the sensor, which is directly related to the output voltage. By introducing the so-called strain transfer factor, a relationship between the output voltage of the sensor and the strain of the measured material is derived. The model is used to predict interlayer stress distributions and strain transfer, which are induced by actuator strain. The result was compared with existing experiments and FEM. There is stress concentration between the actuator and adhesive around the edge of the smart structures, which may cause debonding under high stress loading. 相似文献
15.
The preparation technology and thermal treatment PT thin film used in infrareddetector and photo-electron devices are studied. The er thin film prepared by multi-ion-beam reac-tive co-sputtering apparams are analysised by x-ray , XPS and EPMA. The impurity of PbO,Pb2Ti2O6 in PT thin film is eleminated and PbTiO3 (001)preferred orientation is improved. The rea-sonable teperature of substrates is given in this paper. 相似文献
16.
早龄混凝土的拉伸、压缩徐变规律及其结构徐变应力计算方法是对早期裂缝进行有效预测并控制的关键。既有的徐变研究主要侧重于成熟混凝土,而早龄混凝土徐变相关的科学研究还有待进一步深入。对早龄混凝土的压缩和拉伸徐变研究成果、测试方法及其徐变应力计算方法进行了详细综述。研究表明：目前混凝土早龄期拉伸、压缩徐变试验测试尚无规范可循,相关试验数据较为缺乏;混凝土早龄期徐变预测模型基本未考虑其在低应力水平下的非线性性质;早龄混凝土结构非线性徐变应力理论分析方法亦不尽完善。基于系统试验研究和固化徐变理论建立混凝土非线性徐变理论模型,对早龄混凝土结构采用同时考虑受拉和受压不同应力松弛特性的非线性徐变应力理论计算方法,应可提高早龄结构的有限元仿真精度。 相似文献
17.
The heat transfer of steel fluid in continuous casting mould is a stable process and can be depicted with three-dimensional stable heat conduction equation depending on tension speed. The corresponding finite element equation, including the first, second and third boundary conditions, is deduced out with Galerkin residual method. The coded FEM program is used to analyze the temperature distribution of Q235 steel in continuous billet casting mould. The method proposed is a foundation of thermo-mechanical coupled analysis for the formation of solidified shells and stress in the shells in continuous casting. 相似文献
18.
WANG Yin-hui~ 《保鲜与加工》2004,(1):62-67
Different creep coefficients of concrete layers in composite beam will cause redistribution of stress and additional stress in section. Based on the concept of strain compatibility approach, in this paper,the authors deduced a differential equation of the additional inner forces resulted from creep. Thereafter, the authors proposed an equation to calculate stress redistribution of steel and concrete composite beam, concrete composite beam and concrete strengthening member. At last, the formulas of additional stress of the section were proposed. 相似文献
19.
When analysing the performance of casting powders in a specific casting machine, the thickness of liquid slag is a very important parameter. If the liquid slag thickness is not kept above a certain minimum value during the continuous casting operation,the surface and internal quality of the cast products will be jeopardised because lubrication between the strand and the mould is impaired . It is necessary, therefore , to choose the appropriate type of mould powder .In the industrial experiments, it is very difficult and expensive to study this sensitivity by introducing controlled variation in one parameter while keeping all the other constant. Numerical and computer simulation methods are used in the study .They can predict the liquid slag thickness developed above the liquid steel and distribution of the temperature. The sensitivity of the liquid slag thickness to variations can be determined in the material properties of the mould powders. 相似文献
20.
Employing the Gleeble-1500D thermal analogue machine and the STA449 synthesis thermal analyzer,the study on hot ductility and parts of thermology performance of 20CrMo steel has been carried out , many consulted foundation data has been obtained, the optimum ductility temperature arrange has been found, contraction of cross sectional area is only 30% between 600 degree and 775 degree, but contraction of cross sectional area is more than 80% between 800 degree and 1 250 degree, contraction of cross sectional area drops to under 60% rapidly between 1 350 degree and melting point,a curve is drawn showing the relationshi Pbetween heat capacity and the variation of temperature for the first time, the counting formulas of the heat capacity are regressed by disjunction. A curve is drawn showing the relationshi Pbetween the coefficient of thermal expansion and the variation of temperature, and their application in continuous casting is discussed herein. 相似文献