The twin roll caster for aluminum alloys has many a dv antages. For example, rapid solidification, low equipment cost, and low running cost, etc. However, the twin roll caster has some disadvantages. They are slow c a...The twin roll caster for aluminum alloys has many a dv antages. For example, rapid solidification, low equipment cost, and low running cost, etc. However, the twin roll caster has some disadvantages. They are slow c asting speed and limitation of alloys. In the conventional twin roll caster, the casting speed is slower than 10 m/min. Aluminum alloys, which freezing range is wide, can not be cast. In the present study, break through of these problems wa s tried, and a new type twin roll caster was devised. A vertical type twin roll caster equipped with a nozzle was devised in order to cast aluminum strips at the speeds higher than 60 m/min. Characteristic features of this caster were vertical type, use of copper rolls, low separating force (n o operation of rolling), no use of lubricant, and equipment of the nozzle. In th e high speed roll casting, feed of molten metal of the vertical type twin roll c aster was easier than that of the conventional horizontal type caster. The use o f the copper rolls made cooling rate higher. The low separating force and the us e of the copper rolls prevented sticking of the strip to the roll. The lubricant was not needed, as the sticking of the strip to the roll did not occur. No use of the lubricant was useful to increase the cooling rate and casting speed of th e strip. The nozzle was used in order to improve contact condition (heat transfe r) between the melt and the rolls by hydrostatic pressure. In the twin roll cast er of the present study, many devices were done to improve the cooling condition of the strip in order to increase the casting speed. It was said that the roll casting of A5182 was very difficult, as freezing zone of A5182 was very wide. However, A5182 strip could be cast at high speeds up to 120 m/min using the twin roll caster of the present study. The microstructure of the strip cast using the conventional type twin roll caster is columnar structu re. The microstructure of the strip cast using the twin roll caster of the prese nt study was not columnar but equiaxed structure. It is said that mechanical pro perties of the strip cast using the twin roll caster is cheaper than that of the strip made from DC casting. However, the mechanical properties of the strip cas t using the twin roll caster in the present study were almost same as the proper ties of the strip made from DC casting. The thickness of the strip cast using th e twin roll caster of the present study was from 1.5 mm to 2.5 mm, and this thic kness was thinner than that of the strip cast using the conventional twin roll c aster. Semisolid roll casting was tried in order to increase the roll speed more and mo re. The twin roll caster of the present study was equipped with a cooling slope in order to make semisolid slurry. The cooling slope was the simplest process to make the semisolid slurry. Solid rate of the semisolid slurry was about 10%. Th e casting speed increased up to 180 m/min by the effect of semisolid casting. Me chanical properties were improved by the semisolid casting, too.展开更多
为了在普通微机上实现对医学体数据场的实时清晰绘制,给出了一种多种因素融合的光学属性赋值方法,进而提出一种新的医学体绘制算法。将医学体数据场进行分类,对于前景体素集采用LOD(Layer of Detail)技术进行重采样;然后用定义的光学属...为了在普通微机上实现对医学体数据场的实时清晰绘制,给出了一种多种因素融合的光学属性赋值方法,进而提出一种新的医学体绘制算法。将医学体数据场进行分类,对于前景体素集采用LOD(Layer of Detail)技术进行重采样;然后用定义的光学属性赋值方法对采样点赋值,从而将物体距离视点的距离与物体距离光源的距离有效地结合起来。最后,采用基于空间跳跃的加速技术显示背景体素。实验结果表明:对于512×512×482×2 Byte大小的体数据在减少至原来大小2/3的情况下,在普通微机上能够达到2.5 frame/s的清晰绘制。本算法能够实现一般大小体数据场的实时绘制,而且组织器官显示清晰,符合人的视觉特征。展开更多
With the experiment and finite element simulation, the influences of power ultrasonic on the solidification structure of 7050 aluminum alloy ingot in semi-continuous casting were researched, and the effects of casting...With the experiment and finite element simulation, the influences of power ultrasonic on the solidification structure of 7050 aluminum alloy ingot in semi-continuous casting were researched, and the effects of casting speed on solidification structure in ultrasonic field were also analyzed. The experiment and simulation results show that the solidification structure of the ingot is homogeneously distributed, and its grain size is obviously refined at ultrasonic power of 240 W. The average grain sizes, which can be seen from the Leica microscope, are less than 100 μm. When the casting speed is 45-50 mm/min, the best grain refinement is obtained.展开更多
Cantilever casting concrete arch bridge using form traveller has a broad application prospect.However,it is difficult to obtain reasonable initial cable force in construction stage.In this study,stress balance and inf...Cantilever casting concrete arch bridge using form traveller has a broad application prospect.However,it is difficult to obtain reasonable initial cable force in construction stage.In this study,stress balance and influence matrix methods were developed to determine the initial cable force of cantilever casting concrete arch bridge.The stress balance equation and influence matrix of arch rib critical section were established,and the buckle cable force range was determined by the allowable stress of arch rib critical section.Then a group of buckle cable forces were selected and substituted into the stress balance equation,and the reasonable initial buckle cable force was determined through iteration.Based on the principle of force balance,the initial anchor cable force was determined.In an engineering application example,it is shown that the stress balance and influence matrix methods for the determination of initial cable force are feasible and reliable.The initial cable forces of arch rib segments only need to be adjusted once in the corresponding construction process,which improves the working efficiency and reduces the construction risk.It is found that the methods have great advantages for determining initial cable force in cantilever casting construction process of concrete arch bridge.展开更多
The experiment of ultrasonic treatment of roll casting aluminum strip on plane twin-roll cast-roller with double-heads ultrasonic tools was carried out, and the metallographic structure of the roll casting aluminum st...The experiment of ultrasonic treatment of roll casting aluminum strip on plane twin-roll cast-roller with double-heads ultrasonic tools was carried out, and the metallographic structure of the roll casting aluminum strip treated by ultrasonic was studied. The results show that ultrasonic treatment can refine the grain of the roll casting aluminum strips and make the structure of the strips more homogeneous. The effect is the best when the power of ultrasonic is 300 W and the incident angle of the guide rod is 45、. The mechanism of acoustic cavitations and acoustic flow on grain refinement was also discussed. The heat effect of intensity ultrasonic was studied. The present problems during ultrasonic roll casting process, such as the imperfect cooling system, the inaccurate calculation of ultrasonic energy, and the shape and position of the guide rod to be improved were pointed out.展开更多
In order to increase productivity and reduce energy consumption of steelmaking-continuous casting(SCC) production process, especially with complicated technological routes, the cross entropy(CE) method was adopted to ...In order to increase productivity and reduce energy consumption of steelmaking-continuous casting(SCC) production process, especially with complicated technological routes, the cross entropy(CE) method was adopted to optimize the SCC production scheduling(SCCPS) problem. Based on the CE method, a matrix encoding scheme was proposed and a backward decoding method was used to generate a reasonable schedule. To describe the distribution of the solution space, a probability distribution model was built and used to generate individuals. In addition, the probability updating mechanism of the probability distribution model was proposed which helps to find the optimal individual gradually. Because of the poor stability and premature convergence of the standard cross entropy(SCE) algorithm, the improved cross entropy(ICE) algorithm was proposed with the following improvements: individual generation mechanism combined with heuristic rules, retention mechanism of the optimal individual, local search mechanism and dynamic parameters of the algorithm. Simulation experiments validate that the CE method is effective in solving the SCCPS problem with complicated technological routes and the ICE algorithm proposed has superior performance to the SCE algorithm and the genetic algorithm(GA).展开更多
An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface ar...An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significantly refined.In the center area of the copper,the grains are bigger than those at the boundary.On the surface of the deformable body,the grain size is the smallest,but with irregular grain morphology.After the product is entirely extruded,all the copper and aluminum grains are refined with small and uniform morphology.In the center area,the average diameter of aluminum grains is smaller than 5 μm,and the copper grain on the surface is about 10 μm.At the interface,the grain size is very small,with a good combination of copper and aluminum.The thickness of interface is in the range of 10-15 μm.Energy spectrum analysis shows that CuAl3 phase presents at the interface.展开更多
A high speed steel composite roll billet was fabricated, which is regular in shape, smooth in surface, slight in trace, compact in internal structure, free of slag inclusion, shrinkage cavity, cracks and other flaws, ...A high speed steel composite roll billet was fabricated, which is regular in shape, smooth in surface, slight in trace, compact in internal structure, free of slag inclusion, shrinkage cavity, cracks and other flaws, and good in macro quality of junction surface using a vertical continuous casting machine. The interface zone microstructure of bimetallic in billet of high speed steel composite roll was analyzed by metallurgical microscope(OM), X-ray diffractmeter(XRD), scanning electron microscopy(SEM) and energy-dispersive X-ray analysis(EDS). The results indicate that the microstructure of roll billet is composed of chilled solidified layer, dendrite zone, interfacial zone of bimetal and core material zone. The microstructure of outer shell material is composed of martensite + bainite + residual austenite + some small labyrinth-shape, small-short lath-shape, or dollop-shape eutectic carbides. The microstructure of core material is slice-shape pearlite and a little ferrite along boundary of cells. The interface region microstructure of bimetallic composite roll consists of diffusion region, chilled solidified layer and columnar grain region.展开更多
Deformation behavior of slab at the straightening stage during continuous casting was simulated by the explicit dynamic finite element method,and the stress distribution along the width direction of the slab and its c...Deformation behavior of slab at the straightening stage during continuous casting was simulated by the explicit dynamic finite element method,and the stress distribution along the width direction of the slab and its change regularity at slab center during continuous casting were obtained.The influence of distribution and change of stress on the propagation of longitudinal cracks on slab surface was discussed.The results show that the tensional stress appears on slab surface at the inner arc side and the compressive stress appears on slab surface at the outer arc side at stages 6-8 in straightening zone during continuous casting.Longitudinal cracks generally appear on slab top surface and do not appear on slab bottom surface,which are also observed in industry.展开更多
A Lagrangian relaxation(LR) approach was presented which is with machine capacity relaxation and operation precedence relaxation for solving a flexible job shop(FJS) scheduling problem from the steelmaking-refining-co...A Lagrangian relaxation(LR) approach was presented which is with machine capacity relaxation and operation precedence relaxation for solving a flexible job shop(FJS) scheduling problem from the steelmaking-refining-continuous casting process. Unlike the full optimization of LR problems in traditional LR approaches, the machine capacity relaxation is optimized asymptotically, while the precedence relaxation is optimized approximately due to the NP-hard nature of its LR problem. Because the standard subgradient algorithm(SSA) cannot solve the Lagrangian dual(LD) problem within the partial optimization of LR problem, an effective deflected-conditional approximate subgradient level algorithm(DCASLA) was developed, named as Lagrangian relaxation level approach. The efficiency of the DCASLA is enhanced by a deflected-conditional epsilon-subgradient to weaken the possible zigzagging phenomena. Computational results and comparisons show that the proposed methods improve significantly the efficiency of the LR approach and the DCASLA adopting capacity relaxation strategy performs best among eight methods in terms of solution quality and running time.展开更多
The 2024/3003 aluminum gradient alloys are prepared by semi continuous casting. The influences of throttle bore diameter of embedded nozzle and temperature of internal melt on composition distribution, macrostructure,...The 2024/3003 aluminum gradient alloys are prepared by semi continuous casting. The influences of throttle bore diameter of embedded nozzle and temperature of internal melt on composition distribution, macrostructure, hardness are analyzed, and the stability of gradient distribution of composition, macrostructure and hardness along the axial direction of the ingot is also studied. The results show that diffe rent composition profiles can be achieved by adjusting the processing parameters; the volume fraction of inner alloy in the ingot can be increased by enlarging the throttle bore diameter and elevating the temperature of inner melt; quasi steady solidification can be realized within 20 s during cast processing, and consistent quality ingot is obtained by controlling the casting speed and liquid height of inner melt.展开更多
To understand the solidification behavior of austenitic stainless steel in rotary electromagnetic-field, the influence of low-frequency rotary electromagnetic-field on solidification structure of austenitic stainless ...To understand the solidification behavior of austenitic stainless steel in rotary electromagnetic-field, the influence of low-frequency rotary electromagnetic-field on solidification structure of austenitic stainless steel in horizontal continuous casting was investigated based on industrial experiments. The results show that the solidification structure of austenitic stainless steel can be remarkably refined, the central porosity and shrinkage cavity can be remarkably decreased, and the equiaxed grains zone are enlarged by means of application of appropriate low-frequency electromagnetic-field parameters. The industrial trials verify that the stirring intensity of austenitic stainless steel should be higher compared with that of plain carbon steel. Electromagnetic stirring affects the macrostructure even if the average magnetic flux density of the electromagnetic stirring reaches 90 mT (amplitude reaches 141 mT) with the frequency of 3-4 Hz. Due to a higher viscosity, rotating speed of molten stainless steel is 20%-30% lower than that of molten carbon steel in the same magnetic flux density.展开更多
The dispersion, stabilization and rheological properties of the slurry with various relative molecular masses of PVB were studied. The sintering properties, microstructure and dielectric properties of borosilicate gla...The dispersion, stabilization and rheological properties of the slurry with various relative molecular masses of PVB were studied. The sintering properties, microstructure and dielectric properties of borosilicate glass/Al203 composites were also investigated. The intensities of the typical vibrating bands decrease with the decrease of the relative molecular mass of PVB, which demonstrates that the content of butyral groups in PVB binders decreases correspondingly, leading to a rapid decrease in the viscosity of the mixed slurry. The solid content of samples increases with the decrease of the relative molecular mass of PVB, and this further leads to the increase of tape thickness, bulk density and dried-shrinkage coefficient of tapes. The bulk density, relative density, three-point strength and dielectric constant of sintered samples increase with the increase of the solid content, and the shrinkage and dielectric loss decrease. By contrast, samples for PVB-5s exhibit better properties of a bulk density of 3.10 g/cm3, a relative density of 98.1%, a three-point strength of 208 MPa, aεt value of 8.01, a tanδ value of 7.6× 10^-4 at 10 MHz and a well matching with Ag electrodes.展开更多
A three-dimensional finite-element model of slab continuous casting mold was conducted to clarify the effect of cooling structure on thermal behavior of copper plates. The results show that temperature distribution of...A three-dimensional finite-element model of slab continuous casting mold was conducted to clarify the effect of cooling structure on thermal behavior of copper plates. The results show that temperature distribution of hot surface is mainly governed by cooling structure and heat-transfer conditions. For hot surface centricity, maximum surface temperature promotions are 30 ℃and 15 ℃ with thickness increments of copper plates of 5 mm and nickel layers of 1 ram, respectively. The surface temperature without nickel layers is depressed by 10 ℃ when the depth increment of water slots is 2 mm and that with nickel layers adjacent to and away from mold outlet is depressed by 7℃ and 5 ℃, respectively. The specific trend of temperature distribution of transverse sections of copper plates is nearly free of cooling structure, but temperature is changed and its law is similar to the corresponding surface temperature.展开更多
Contrastive research was carried out to study the thermal properties of open-celled aluminum foams prepared by counter-gravity infiltration casting system and the traditional process respectively.The experimental resu...Contrastive research was carried out to study the thermal properties of open-celled aluminum foams prepared by counter-gravity infiltration casting system and the traditional process respectively.The experimental results show that the thermal conductivity coefficients of aluminum foams prepared by two different infiltration methods have similar increasing trend with the increase of particle size;along with the reducing porosity,the thermal conductivity coefficients will be enhanced oppositely.However,with the same particle size,the open-celled aluminum foam prepared by the former method has a higher thermal conductivity coefficient obviously.It is largely because that the sample prepared by counter-gravity infiltration casting has a lower void content and better dense crystallization of metal-matrix after the constant pressure process.展开更多
Unequal diameter twin-roll casting(UDTRC)can improve the formability,surface conditions,and production efficiency during the fabrication of clad strips.Using Fluent software,a numerical simulation is used to study the...Unequal diameter twin-roll casting(UDTRC)can improve the formability,surface conditions,and production efficiency during the fabrication of clad strips.Using Fluent software,a numerical simulation is used to study the asymmetric heat transfer characteristics of Cu/Al clad strips fabricated by UDTRC.The effects of roller velocity ratio,Cu strip thickness,and inclination angle on the kissing point position,as well as the entire temperature distribution are obtained.The heat transfer model is established,and the mechanism is discussed.The Cu strip and rollers are found to be the main causes of asymmetric heat transfer,indicating that the roller velocity ratio changes the liquid zone proportion in the molten pool.The Cu strip thickness determines the heat absorption capacity and the variations in thermal resistance between the molten Al and the big roller.The inclination angle of the small roller changes the cooling time of big roller to molten Al.Moreover,the microstructure of Al cladding under different roller velocity ratios is examined.The results show significant grain refinement caused by the shear strain along the thickness direction of Al cladding and the intense heat transfer at the moment of contact between the metal Al cladding and Cu strip.展开更多
In order to use the cast method to replace forge method in producing the load bearing wheel used in certain heavy duty vehicle, simplified and reduced size load bearing wheels were squeeze cast and studied using Al Cu...In order to use the cast method to replace forge method in producing the load bearing wheel used in certain heavy duty vehicle, simplified and reduced size load bearing wheels were squeeze cast and studied using Al Cu alloy. Tensile properties, hardness, microstructures and morphologies of the squeeze cast wheels were investigated. The results show that the finer microstructure, higher density, strength, toughness and hardness were achieved through the squeeze casting. Ultimate tensile strength of 428 MPa, yield strength of 360 MPa, elongation of 13.1% were achieved for T5 heat treated squeeze cast wheels. The Brinell hardness of squeeze cast wheels is from HB 120 to HB 137.展开更多
The influence and signification of casting parameters on the solidification process of steel ingot were discussed based on the finite element method (FEM) results by orthogonal experiment method. The range analysis, a...The influence and signification of casting parameters on the solidification process of steel ingot were discussed based on the finite element method (FEM) results by orthogonal experiment method. The range analysis, analysis of variance (ANOVA) and optimization project were used to investigate the FEM results. In order to decrease the ingot riser head and improve the utilization ratio of ingot, the casting parameters involved casting temperature, pouring velocity and interface heat transfer were optimized to decrease shrinkage pore and microporosity. The results show that the heat transfer coefficient between melt and heated board is a more sensitive factor. It is favor to decrease the shrinkage pore and microporosity under the conditions of low temperature, high pouring velocity and high heat transfer between melt and mold. If heat transfer in the ingot body is quicker than that in the riser, the position of shrinkage pore and microporosity will be closer to riser top. The results of optimization project show that few of shrinkage pore and microporosity reach into ingot body with the rational parameters, so the riser size can be reduced.展开更多
文摘The twin roll caster for aluminum alloys has many a dv antages. For example, rapid solidification, low equipment cost, and low running cost, etc. However, the twin roll caster has some disadvantages. They are slow c asting speed and limitation of alloys. In the conventional twin roll caster, the casting speed is slower than 10 m/min. Aluminum alloys, which freezing range is wide, can not be cast. In the present study, break through of these problems wa s tried, and a new type twin roll caster was devised. A vertical type twin roll caster equipped with a nozzle was devised in order to cast aluminum strips at the speeds higher than 60 m/min. Characteristic features of this caster were vertical type, use of copper rolls, low separating force (n o operation of rolling), no use of lubricant, and equipment of the nozzle. In th e high speed roll casting, feed of molten metal of the vertical type twin roll c aster was easier than that of the conventional horizontal type caster. The use o f the copper rolls made cooling rate higher. The low separating force and the us e of the copper rolls prevented sticking of the strip to the roll. The lubricant was not needed, as the sticking of the strip to the roll did not occur. No use of the lubricant was useful to increase the cooling rate and casting speed of th e strip. The nozzle was used in order to improve contact condition (heat transfe r) between the melt and the rolls by hydrostatic pressure. In the twin roll cast er of the present study, many devices were done to improve the cooling condition of the strip in order to increase the casting speed. It was said that the roll casting of A5182 was very difficult, as freezing zone of A5182 was very wide. However, A5182 strip could be cast at high speeds up to 120 m/min using the twin roll caster of the present study. The microstructure of the strip cast using the conventional type twin roll caster is columnar structu re. The microstructure of the strip cast using the twin roll caster of the prese nt study was not columnar but equiaxed structure. It is said that mechanical pro perties of the strip cast using the twin roll caster is cheaper than that of the strip made from DC casting. However, the mechanical properties of the strip cas t using the twin roll caster in the present study were almost same as the proper ties of the strip made from DC casting. The thickness of the strip cast using th e twin roll caster of the present study was from 1.5 mm to 2.5 mm, and this thic kness was thinner than that of the strip cast using the conventional twin roll c aster. Semisolid roll casting was tried in order to increase the roll speed more and mo re. The twin roll caster of the present study was equipped with a cooling slope in order to make semisolid slurry. The cooling slope was the simplest process to make the semisolid slurry. Solid rate of the semisolid slurry was about 10%. Th e casting speed increased up to 180 m/min by the effect of semisolid casting. Me chanical properties were improved by the semisolid casting, too.
文摘为了在普通微机上实现对医学体数据场的实时清晰绘制,给出了一种多种因素融合的光学属性赋值方法,进而提出一种新的医学体绘制算法。将医学体数据场进行分类,对于前景体素集采用LOD(Layer of Detail)技术进行重采样;然后用定义的光学属性赋值方法对采样点赋值,从而将物体距离视点的距离与物体距离光源的距离有效地结合起来。最后,采用基于空间跳跃的加速技术显示背景体素。实验结果表明:对于512×512×482×2 Byte大小的体数据在减少至原来大小2/3的情况下,在普通微机上能够达到2.5 frame/s的清晰绘制。本算法能够实现一般大小体数据场的实时绘制,而且组织器官显示清晰,符合人的视觉特征。
基金Project(2010CB731700) supported by the National Basic Research Program of China
文摘With the experiment and finite element simulation, the influences of power ultrasonic on the solidification structure of 7050 aluminum alloy ingot in semi-continuous casting were researched, and the effects of casting speed on solidification structure in ultrasonic field were also analyzed. The experiment and simulation results show that the solidification structure of the ingot is homogeneously distributed, and its grain size is obviously refined at ultrasonic power of 240 W. The average grain sizes, which can be seen from the Leica microscope, are less than 100 μm. When the casting speed is 45-50 mm/min, the best grain refinement is obtained.
基金Projects(51478049,51778068)supported by the National Natural Science Foundation of ChinaProject(14JJ2075,2019JJ40301)supported by the Hunan Natural Science Foundation of China+1 种基金Project(17A010)supported by the Scientific Research Fund of Hunan Provincial Education Department of ChinaProject(2017GK4034)supported by the Major Technological Achievements Transformation Program of Hunan Strategic Emerging Industries of China
文摘Cantilever casting concrete arch bridge using form traveller has a broad application prospect.However,it is difficult to obtain reasonable initial cable force in construction stage.In this study,stress balance and influence matrix methods were developed to determine the initial cable force of cantilever casting concrete arch bridge.The stress balance equation and influence matrix of arch rib critical section were established,and the buckle cable force range was determined by the allowable stress of arch rib critical section.Then a group of buckle cable forces were selected and substituted into the stress balance equation,and the reasonable initial buckle cable force was determined through iteration.Based on the principle of force balance,the initial anchor cable force was determined.In an engineering application example,it is shown that the stress balance and influence matrix methods for the determination of initial cable force are feasible and reliable.The initial cable forces of arch rib segments only need to be adjusted once in the corresponding construction process,which improves the working efficiency and reduces the construction risk.It is found that the methods have great advantages for determining initial cable force in cantilever casting construction process of concrete arch bridge.
基金Projects(IRT0549) supported by Program for Changjiang Scholars and Innovative Research Team in University, China
文摘The experiment of ultrasonic treatment of roll casting aluminum strip on plane twin-roll cast-roller with double-heads ultrasonic tools was carried out, and the metallographic structure of the roll casting aluminum strip treated by ultrasonic was studied. The results show that ultrasonic treatment can refine the grain of the roll casting aluminum strips and make the structure of the strips more homogeneous. The effect is the best when the power of ultrasonic is 300 W and the incident angle of the guide rod is 45、. The mechanism of acoustic cavitations and acoustic flow on grain refinement was also discussed. The heat effect of intensity ultrasonic was studied. The present problems during ultrasonic roll casting process, such as the imperfect cooling system, the inaccurate calculation of ultrasonic energy, and the shape and position of the guide rod to be improved were pointed out.
基金Project(ZR2014FM036)supported by Shandong Provincial Natural Science Foundation of ChinaProject(ZR2010FZ001)supported by the Key Program of Shandong Provincial Natural Science Foundation of China
文摘In order to increase productivity and reduce energy consumption of steelmaking-continuous casting(SCC) production process, especially with complicated technological routes, the cross entropy(CE) method was adopted to optimize the SCC production scheduling(SCCPS) problem. Based on the CE method, a matrix encoding scheme was proposed and a backward decoding method was used to generate a reasonable schedule. To describe the distribution of the solution space, a probability distribution model was built and used to generate individuals. In addition, the probability updating mechanism of the probability distribution model was proposed which helps to find the optimal individual gradually. Because of the poor stability and premature convergence of the standard cross entropy(SCE) algorithm, the improved cross entropy(ICE) algorithm was proposed with the following improvements: individual generation mechanism combined with heuristic rules, retention mechanism of the optimal individual, local search mechanism and dynamic parameters of the algorithm. Simulation experiments validate that the CE method is effective in solving the SCCPS problem with complicated technological routes and the ICE algorithm proposed has superior performance to the SCE algorithm and the genetic algorithm(GA).
基金Project(60806006) supported by the National Natural Science Foundation of China
文摘An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significantly refined.In the center area of the copper,the grains are bigger than those at the boundary.On the surface of the deformable body,the grain size is the smallest,but with irregular grain morphology.After the product is entirely extruded,all the copper and aluminum grains are refined with small and uniform morphology.In the center area,the average diameter of aluminum grains is smaller than 5 μm,and the copper grain on the surface is about 10 μm.At the interface,the grain size is very small,with a good combination of copper and aluminum.The thickness of interface is in the range of 10-15 μm.Energy spectrum analysis shows that CuAl3 phase presents at the interface.
基金Project(200809123) supported by the National Natural Science Foundation of China
文摘A high speed steel composite roll billet was fabricated, which is regular in shape, smooth in surface, slight in trace, compact in internal structure, free of slag inclusion, shrinkage cavity, cracks and other flaws, and good in macro quality of junction surface using a vertical continuous casting machine. The interface zone microstructure of bimetallic in billet of high speed steel composite roll was analyzed by metallurgical microscope(OM), X-ray diffractmeter(XRD), scanning electron microscopy(SEM) and energy-dispersive X-ray analysis(EDS). The results indicate that the microstructure of roll billet is composed of chilled solidified layer, dendrite zone, interfacial zone of bimetal and core material zone. The microstructure of outer shell material is composed of martensite + bainite + residual austenite + some small labyrinth-shape, small-short lath-shape, or dollop-shape eutectic carbides. The microstructure of core material is slice-shape pearlite and a little ferrite along boundary of cells. The interface region microstructure of bimetallic composite roll consists of diffusion region, chilled solidified layer and columnar grain region.
基金Project(50634030) supported by the National Natural Science Foundation of ChinaProject(20090042120005) supported by the Doctorate Foundation of the Ministry of Education of ChinaProject(2006CB605208-1) supported by the State Basic Research Program of China
文摘Deformation behavior of slab at the straightening stage during continuous casting was simulated by the explicit dynamic finite element method,and the stress distribution along the width direction of the slab and its change regularity at slab center during continuous casting were obtained.The influence of distribution and change of stress on the propagation of longitudinal cracks on slab surface was discussed.The results show that the tensional stress appears on slab surface at the inner arc side and the compressive stress appears on slab surface at the outer arc side at stages 6-8 in straightening zone during continuous casting.Longitudinal cracks generally appear on slab top surface and do not appear on slab bottom surface,which are also observed in industry.
基金Projects(51435009,51575212,61573249,61371200)supported by the National Natural Science Foundation of ChinaProjects(2015T80798,2014M552040,2014M561250,2015M571328)supported by Postdoctoral Science Foundation of ChinaProject(L2015372)supported by Liaoning Province Education Administration,China
文摘A Lagrangian relaxation(LR) approach was presented which is with machine capacity relaxation and operation precedence relaxation for solving a flexible job shop(FJS) scheduling problem from the steelmaking-refining-continuous casting process. Unlike the full optimization of LR problems in traditional LR approaches, the machine capacity relaxation is optimized asymptotically, while the precedence relaxation is optimized approximately due to the NP-hard nature of its LR problem. Because the standard subgradient algorithm(SSA) cannot solve the Lagrangian dual(LD) problem within the partial optimization of LR problem, an effective deflected-conditional approximate subgradient level algorithm(DCASLA) was developed, named as Lagrangian relaxation level approach. The efficiency of the DCASLA is enhanced by a deflected-conditional epsilon-subgradient to weaken the possible zigzagging phenomena. Computational results and comparisons show that the proposed methods improve significantly the efficiency of the LR approach and the DCASLA adopting capacity relaxation strategy performs best among eight methods in terms of solution quality and running time.
文摘The 2024/3003 aluminum gradient alloys are prepared by semi continuous casting. The influences of throttle bore diameter of embedded nozzle and temperature of internal melt on composition distribution, macrostructure, hardness are analyzed, and the stability of gradient distribution of composition, macrostructure and hardness along the axial direction of the ingot is also studied. The results show that diffe rent composition profiles can be achieved by adjusting the processing parameters; the volume fraction of inner alloy in the ingot can be increased by enlarging the throttle bore diameter and elevating the temperature of inner melt; quasi steady solidification can be realized within 20 s during cast processing, and consistent quality ingot is obtained by controlling the casting speed and liquid height of inner melt.
基金Project(CSTC2007BB4216) supported by the Natural Science Foundation of Chongqing,China
文摘To understand the solidification behavior of austenitic stainless steel in rotary electromagnetic-field, the influence of low-frequency rotary electromagnetic-field on solidification structure of austenitic stainless steel in horizontal continuous casting was investigated based on industrial experiments. The results show that the solidification structure of austenitic stainless steel can be remarkably refined, the central porosity and shrinkage cavity can be remarkably decreased, and the equiaxed grains zone are enlarged by means of application of appropriate low-frequency electromagnetic-field parameters. The industrial trials verify that the stirring intensity of austenitic stainless steel should be higher compared with that of plain carbon steel. Electromagnetic stirring affects the macrostructure even if the average magnetic flux density of the electromagnetic stirring reaches 90 mT (amplitude reaches 141 mT) with the frequency of 3-4 Hz. Due to a higher viscosity, rotating speed of molten stainless steel is 20%-30% lower than that of molten carbon steel in the same magnetic flux density.
基金Project(2007AA03Z455) supported by the National High Technology Research and Development Program of ChinaProjects(BE2009168)supported by Science&Technology Pillar Program of Jiangsu Province, China+2 种基金Project supported by the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions, ChinaProject(CXZZ12_0415) supported by the Innovation Foundation for Graduate Students of Jiangsu Province, ChinaProject(IRT1146) supported for Changjiang Scholars and Innovative Research Teamin University (PCSIRT) of China
文摘The dispersion, stabilization and rheological properties of the slurry with various relative molecular masses of PVB were studied. The sintering properties, microstructure and dielectric properties of borosilicate glass/Al203 composites were also investigated. The intensities of the typical vibrating bands decrease with the decrease of the relative molecular mass of PVB, which demonstrates that the content of butyral groups in PVB binders decreases correspondingly, leading to a rapid decrease in the viscosity of the mixed slurry. The solid content of samples increases with the decrease of the relative molecular mass of PVB, and this further leads to the increase of tape thickness, bulk density and dried-shrinkage coefficient of tapes. The bulk density, relative density, three-point strength and dielectric constant of sintered samples increase with the increase of the solid content, and the shrinkage and dielectric loss decrease. By contrast, samples for PVB-5s exhibit better properties of a bulk density of 3.10 g/cm3, a relative density of 98.1%, a three-point strength of 208 MPa, aεt value of 8.01, a tanδ value of 7.6× 10^-4 at 10 MHz and a well matching with Ag electrodes.
基金Project(51004031) supported by the National Natural Science Foundation of ChinaProject(50925415) supported by the National Outstanding Young Scientist Foundation of China+1 种基金Project(20100042120012) supported by the Special Research Fund for Doctoral Programs of Ministry of Education of ChinaProject(N090402022) supported by the Fundamental Research Funds for the Central Universities of China
文摘A three-dimensional finite-element model of slab continuous casting mold was conducted to clarify the effect of cooling structure on thermal behavior of copper plates. The results show that temperature distribution of hot surface is mainly governed by cooling structure and heat-transfer conditions. For hot surface centricity, maximum surface temperature promotions are 30 ℃and 15 ℃ with thickness increments of copper plates of 5 mm and nickel layers of 1 ram, respectively. The surface temperature without nickel layers is depressed by 10 ℃ when the depth increment of water slots is 2 mm and that with nickel layers adjacent to and away from mold outlet is depressed by 7℃ and 5 ℃, respectively. The specific trend of temperature distribution of transverse sections of copper plates is nearly free of cooling structure, but temperature is changed and its law is similar to the corresponding surface temperature.
基金Project(51304254) supported by the National Natural Science Foundation of ChinaProject(2013GK4064) supported by the Strategic Emerging Industry Program of the Ministry of Science and Technology of Hunan Province,China
文摘Contrastive research was carried out to study the thermal properties of open-celled aluminum foams prepared by counter-gravity infiltration casting system and the traditional process respectively.The experimental results show that the thermal conductivity coefficients of aluminum foams prepared by two different infiltration methods have similar increasing trend with the increase of particle size;along with the reducing porosity,the thermal conductivity coefficients will be enhanced oppositely.However,with the same particle size,the open-celled aluminum foam prepared by the former method has a higher thermal conductivity coefficient obviously.It is largely because that the sample prepared by counter-gravity infiltration casting has a lower void content and better dense crystallization of metal-matrix after the constant pressure process.
基金Project(51974278)supported by the National Natural Science Foundation of ChinaProject(E2018203446)supported by the Natural Science Foundation of Hebei Province Distinguished Young Fund Project,ChinaProject(2018YFA0707303)supported by the National Key Research and Development Project of China。
文摘Unequal diameter twin-roll casting(UDTRC)can improve the formability,surface conditions,and production efficiency during the fabrication of clad strips.Using Fluent software,a numerical simulation is used to study the asymmetric heat transfer characteristics of Cu/Al clad strips fabricated by UDTRC.The effects of roller velocity ratio,Cu strip thickness,and inclination angle on the kissing point position,as well as the entire temperature distribution are obtained.The heat transfer model is established,and the mechanism is discussed.The Cu strip and rollers are found to be the main causes of asymmetric heat transfer,indicating that the roller velocity ratio changes the liquid zone proportion in the molten pool.The Cu strip thickness determines the heat absorption capacity and the variations in thermal resistance between the molten Al and the big roller.The inclination angle of the small roller changes the cooling time of big roller to molten Al.Moreover,the microstructure of Al cladding under different roller velocity ratios is examined.The results show significant grain refinement caused by the shear strain along the thickness direction of Al cladding and the intense heat transfer at the moment of contact between the metal Al cladding and Cu strip.
文摘In order to use the cast method to replace forge method in producing the load bearing wheel used in certain heavy duty vehicle, simplified and reduced size load bearing wheels were squeeze cast and studied using Al Cu alloy. Tensile properties, hardness, microstructures and morphologies of the squeeze cast wheels were investigated. The results show that the finer microstructure, higher density, strength, toughness and hardness were achieved through the squeeze casting. Ultimate tensile strength of 428 MPa, yield strength of 360 MPa, elongation of 13.1% were achieved for T5 heat treated squeeze cast wheels. The Brinell hardness of squeeze cast wheels is from HB 120 to HB 137.
基金Projects(50435010 50705080 50675187) supported by the National Natural Science Foundation of China
文摘The influence and signification of casting parameters on the solidification process of steel ingot were discussed based on the finite element method (FEM) results by orthogonal experiment method. The range analysis, analysis of variance (ANOVA) and optimization project were used to investigate the FEM results. In order to decrease the ingot riser head and improve the utilization ratio of ingot, the casting parameters involved casting temperature, pouring velocity and interface heat transfer were optimized to decrease shrinkage pore and microporosity. The results show that the heat transfer coefficient between melt and heated board is a more sensitive factor. It is favor to decrease the shrinkage pore and microporosity under the conditions of low temperature, high pouring velocity and high heat transfer between melt and mold. If heat transfer in the ingot body is quicker than that in the riser, the position of shrinkage pore and microporosity will be closer to riser top. The results of optimization project show that few of shrinkage pore and microporosity reach into ingot body with the rational parameters, so the riser size can be reduced.
