Search1999 Vol. 6, No. 4
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1999, vol. 6, no. 4, pp.
237-241.
Abstract:
Laboratory and industrial experiments were carried out to study the possibility of producing high purity purity mullite-corundum thermal insulating firebricks. The results show that by using industrial alumina, natural powder power, coal gangues and a small amount of additives. high purity mullite-corundum thermal insulating firebricks can be produced The service. temperature of these brick can be up to 1780℃ with low. thermal conductivity and good thermal shock resistance.
Laboratory and industrial experiments were carried out to study the possibility of producing high purity purity mullite-corundum thermal insulating firebricks. The results show that by using industrial alumina, natural powder power, coal gangues and a small amount of additives. high purity mullite-corundum thermal insulating firebricks can be produced The service. temperature of these brick can be up to 1780℃ with low. thermal conductivity and good thermal shock resistance.
1999, vol. 6, no. 4, pp.
242-245.
Abstract:
In mining industries no mines are identical and each mine has its own unique set of mining conditions. In order to study the condition of mines for efficiency, safety and economy reasons, a fuzzy model is presented based on fuzzy evaluation. Relevant data from five mines were collected and the model was used to evaluate the mining condition of these mines. The evaluation results are in conformity with the real situation.
In mining industries no mines are identical and each mine has its own unique set of mining conditions. In order to study the condition of mines for efficiency, safety and economy reasons, a fuzzy model is presented based on fuzzy evaluation. Relevant data from five mines were collected and the model was used to evaluate the mining condition of these mines. The evaluation results are in conformity with the real situation.
1999, vol. 6, no. 4, pp.
246-249.
Abstract:
The basic method for designing and calculating reasonable jig cycle of movable screen jig was presented. The reasonability and reliability of designed jig cycle were verified by means of the test on artificial mixed materials. An iron ore (12-100 mm) was treated in tile TJD-75 model movable screen jig with the jig cycle. The good results were achieved. This would provide a reliable basis for design of commercial movable-screen jig.
The basic method for designing and calculating reasonable jig cycle of movable screen jig was presented. The reasonability and reliability of designed jig cycle were verified by means of the test on artificial mixed materials. An iron ore (12-100 mm) was treated in tile TJD-75 model movable screen jig with the jig cycle. The good results were achieved. This would provide a reliable basis for design of commercial movable-screen jig.
1999, vol. 6, no. 4, pp.
250-252.
Abstract:
By continuous quenching process, the effect of austenitizing temperature and time on the structure and hardness of bainite ductile cast iron was studied. It was found that (l) low austenitizing temperature would result in scrap ferrite existing in matrix, which reduces the macro-hardness of bainite ductile cast iron; (2) high austenitizing temperature would make carbide decomposed, which also induces the macro-hardness of bainite cast iron, and (3) austenitizing time has little effect on the structure of bainite ductile cast iron, but as it increases, the macro-hardness of bainite ductile cast iron and micro-hardness of bainite increases. To the ductile cast iron, as a result,the suitable austenitizing temperature and time are recommended as 880℃ and 120 min respectively.
By continuous quenching process, the effect of austenitizing temperature and time on the structure and hardness of bainite ductile cast iron was studied. It was found that (l) low austenitizing temperature would result in scrap ferrite existing in matrix, which reduces the macro-hardness of bainite ductile cast iron; (2) high austenitizing temperature would make carbide decomposed, which also induces the macro-hardness of bainite cast iron, and (3) austenitizing time has little effect on the structure of bainite ductile cast iron, but as it increases, the macro-hardness of bainite ductile cast iron and micro-hardness of bainite increases. To the ductile cast iron, as a result,the suitable austenitizing temperature and time are recommended as 880℃ and 120 min respectively.
1999, vol. 6, no. 4, pp.
253-258.
Abstract:
In non-equilibrium nonlinear region, the nonlinear equations of time dependence of perturbation amplitude at the solid/liquid interface during solidification of a dilute binary alloy are established on the base of assuming that there is local equilibrium at the solid/liquid interface and considering that curvature, temperature and composition at the solid/liquid interface which are related to the perturbation amplitude are nonlinear. As a result, patterns at the solid/liquid interface during solidification process, which is from nonsteady state to steady state can be controlled by these nonlinear equations.
In non-equilibrium nonlinear region, the nonlinear equations of time dependence of perturbation amplitude at the solid/liquid interface during solidification of a dilute binary alloy are established on the base of assuming that there is local equilibrium at the solid/liquid interface and considering that curvature, temperature and composition at the solid/liquid interface which are related to the perturbation amplitude are nonlinear. As a result, patterns at the solid/liquid interface during solidification process, which is from nonsteady state to steady state can be controlled by these nonlinear equations.
1999, vol. 6, no. 4, pp.
259-261.
Abstract:
An investigation was made on the influences of mechanical stirring on microstructure of hyper-eutectic Al-30%Si alloy (in mass fraction) during solidification. The primary Si crystals formed in the alloy melt were gradually changed from elongated platelets to near-spherical shapes by mechanical stirring. The spheroidization of primary St crystals occurs by the mechanism of bending and fracture of Si platelets, wear and collision between Si crystals, and coalescence of small Si particles. The influence of under-cooling and cooling rate of the alloy melt on primary Si crystals of semi-solid processed alloys is investigated as well. The increase of under-cooling and cooling rate decreases the size of primary Si crystals.
An investigation was made on the influences of mechanical stirring on microstructure of hyper-eutectic Al-30%Si alloy (in mass fraction) during solidification. The primary Si crystals formed in the alloy melt were gradually changed from elongated platelets to near-spherical shapes by mechanical stirring. The spheroidization of primary St crystals occurs by the mechanism of bending and fracture of Si platelets, wear and collision between Si crystals, and coalescence of small Si particles. The influence of under-cooling and cooling rate of the alloy melt on primary Si crystals of semi-solid processed alloys is investigated as well. The increase of under-cooling and cooling rate decreases the size of primary Si crystals.
1999, vol. 6, no. 4, pp.
262-267.
Abstract:
Castex of AS wire is a new technology of near net shape. To study the variation of temperature and velocity of liquid (or semisolid) aluminum during dynamic solidification the numerical simulation was carried out with the theory of heat-transfer and hydrodynamics by means of 3-dimensional finite element method. From simulation results, it is found that the variation of temperature and velocity is mainly influenced by the casting temperature of aluminum, rotating speed of Castex wheel and flow of cooling water. Among these influencing factors, the casting temperature distributes most to the length of liquid phase metal. Moreover, the faster the metal solidifies,the higher the metal there moves with the overall trend of descending from the bottom of the wheel to the shoe wall as well as from sidewalls to the center of wheel groove. In comparison with the practical value, the simulation is reliable.
Castex of AS wire is a new technology of near net shape. To study the variation of temperature and velocity of liquid (or semisolid) aluminum during dynamic solidification the numerical simulation was carried out with the theory of heat-transfer and hydrodynamics by means of 3-dimensional finite element method. From simulation results, it is found that the variation of temperature and velocity is mainly influenced by the casting temperature of aluminum, rotating speed of Castex wheel and flow of cooling water. Among these influencing factors, the casting temperature distributes most to the length of liquid phase metal. Moreover, the faster the metal solidifies,the higher the metal there moves with the overall trend of descending from the bottom of the wheel to the shoe wall as well as from sidewalls to the center of wheel groove. In comparison with the practical value, the simulation is reliable.
1999, vol. 6, no. 4, pp.
268-271.
Abstract:
The internal cracks in continuously cast slabs are attributed to the excessive tensile strain occurring at the solidifying front during the continuous casting process. Based on the understanding, a model for diagnosing the formation of the internal cracks was established, in which the strains at the solidifying front caused by bulging, straightening or unbending, and roll misalignment were calculated and compared with a critical strain value to estimate whether the internal cracks form. Moreover, the established model was applied to a real slab caster to reveal the distribution of the strains in casting direction and its effect on the internal cracks. It was proved that the model was reliable and useful for optimizing the operation of continuous casting.
The internal cracks in continuously cast slabs are attributed to the excessive tensile strain occurring at the solidifying front during the continuous casting process. Based on the understanding, a model for diagnosing the formation of the internal cracks was established, in which the strains at the solidifying front caused by bulging, straightening or unbending, and roll misalignment were calculated and compared with a critical strain value to estimate whether the internal cracks form. Moreover, the established model was applied to a real slab caster to reveal the distribution of the strains in casting direction and its effect on the internal cracks. It was proved that the model was reliable and useful for optimizing the operation of continuous casting.
1999, vol. 6, no. 4, pp.
272-276.
Abstract:
The effect of lamellar orientation on crack paths in PST crystals of y-TiAl based alloys was investigated by in-situ SEM technique. The results indicate that the crack paths in PST crystals of y-TiAl based alloys are strongly dependent on lamellar orientation of PST crystals, and the differently oriented PST crystals show different nucleation and propagation mechanisms of crack, resulting in different levels of fracture toughness.
The effect of lamellar orientation on crack paths in PST crystals of y-TiAl based alloys was investigated by in-situ SEM technique. The results indicate that the crack paths in PST crystals of y-TiAl based alloys are strongly dependent on lamellar orientation of PST crystals, and the differently oriented PST crystals show different nucleation and propagation mechanisms of crack, resulting in different levels of fracture toughness.
1999, vol. 6, no. 4, pp.
277-280.
Abstract:
The effect of cooling rate and austenitizing condition on the mechanical properties of high carbon steel (SWRH82B) has been investigated. Specimens were made of high carbon steel rod and heat-treated by Gleeble-2000 to produce a wide variation in prior austenite size. Different cooling rates were carried out, and then pearlite interlaminar spacing and mechanical properties were measured and tested respectively. According to the results, it could be found that under the continuous cooling with the increase of cooling rate, tensile strength greatly increases and reduction in area exhibits a slightly increase for an equivalent value of prior austenite grain size. When prior austenite size increases, reduction in area decreases, and tensile strength increases slightly for an equivalent value of pearlite interlaminar spacing. It is concluded that prior austenite size primarily controls ductility and pearlite interlaminar spacing controls tensile strength. Mathematical formulae are given for these relations.
The effect of cooling rate and austenitizing condition on the mechanical properties of high carbon steel (SWRH82B) has been investigated. Specimens were made of high carbon steel rod and heat-treated by Gleeble-2000 to produce a wide variation in prior austenite size. Different cooling rates were carried out, and then pearlite interlaminar spacing and mechanical properties were measured and tested respectively. According to the results, it could be found that under the continuous cooling with the increase of cooling rate, tensile strength greatly increases and reduction in area exhibits a slightly increase for an equivalent value of prior austenite grain size. When prior austenite size increases, reduction in area decreases, and tensile strength increases slightly for an equivalent value of pearlite interlaminar spacing. It is concluded that prior austenite size primarily controls ductility and pearlite interlaminar spacing controls tensile strength. Mathematical formulae are given for these relations.
1999, vol. 6, no. 4, pp.
281-284.
Abstract:
Under optimal conditions free-standing high quality diamond films were prepared by DC arc plasma jet CVD method at a growth rate of 7-10 μm/h. Surface and cross section morphologies of the diamond films were observed by SEM. Raman spectrometer was used to characterize the quality of diamond films. The IR transmittivity measured by IR spectrometer is close to the theoretical value of about 71% in the far infrared band. The thermal conductivity measured by photothermal deflection exceeds 18 W/cm·K. <l 10> is the preferential growth orientation of the films detected by X-ray diffractometer. As s result, the extremely high temperature of DC arc plasma jet can produce supersaturated atomic hydrogen, which played an important role in the process for the deposition of high quality diamond films.
Under optimal conditions free-standing high quality diamond films were prepared by DC arc plasma jet CVD method at a growth rate of 7-10 μm/h. Surface and cross section morphologies of the diamond films were observed by SEM. Raman spectrometer was used to characterize the quality of diamond films. The IR transmittivity measured by IR spectrometer is close to the theoretical value of about 71% in the far infrared band. The thermal conductivity measured by photothermal deflection exceeds 18 W/cm·K. <l 10> is the preferential growth orientation of the films detected by X-ray diffractometer. As s result, the extremely high temperature of DC arc plasma jet can produce supersaturated atomic hydrogen, which played an important role in the process for the deposition of high quality diamond films.
1999, vol. 6, no. 4, pp.
285-288.
Abstract:
A novel technique for fabricating TiB2/Al composites in molten aluminum was introduced. The formation mechanism of brittle Al3Ti particulates up to 30 m in size produced in the composites was studied and a method of eliminating them was proposed. The results show that (1) the brittle Al3Ti particulates are always present in the composites when the molar ratio of Ti to B nTi:nB is 1:2; and (2) the formation of the brittle Al3Ti phase can be avoided entirely from the final product by using a proper nTi:nB of l:4 in the Ti-B-Al preforms.In the former case, the tensile elongation of the composite is only 4%, much lower than the value of pure aluminum (20%). In the later case, the tensile elongation of this composite is 10%, higher than the value of the composite with a lot of Al3Ti (4%), whereas the ultimate tensile strength of the former is nearly that of the later.
A novel technique for fabricating TiB2/Al composites in molten aluminum was introduced. The formation mechanism of brittle Al3Ti particulates up to 30 m in size produced in the composites was studied and a method of eliminating them was proposed. The results show that (1) the brittle Al3Ti particulates are always present in the composites when the molar ratio of Ti to B nTi:nB is 1:2; and (2) the formation of the brittle Al3Ti phase can be avoided entirely from the final product by using a proper nTi:nB of l:4 in the Ti-B-Al preforms.In the former case, the tensile elongation of the composite is only 4%, much lower than the value of pure aluminum (20%). In the later case, the tensile elongation of this composite is 10%, higher than the value of the composite with a lot of Al3Ti (4%), whereas the ultimate tensile strength of the former is nearly that of the later.
1999, vol. 6, no. 4, pp.
289-291.
Abstract:
Based on experimental data, a nonlinear model about tensile strength and technical parameters such as Mn and St content, finishing rolling speed and finishing rolling temperature for deformed steel bars in the process of hot rolling was established by using artificial neural networks. The model can be optimized with a genetic algorithm. The optimum rolling parameters were obtained.
Based on experimental data, a nonlinear model about tensile strength and technical parameters such as Mn and St content, finishing rolling speed and finishing rolling temperature for deformed steel bars in the process of hot rolling was established by using artificial neural networks. The model can be optimized with a genetic algorithm. The optimum rolling parameters were obtained.
1999, vol. 6, no. 4, pp.
292-295.
Abstract:
Based on experimental data, the mathematical model of rolling force parameters of 3-roll mills was studied. The structure of the model was theoretically set up and the coefficients were determined by static analysis of the data. The torque in continuous rolling was measured, and the characteristics and efficiency of 3-roll mills are investigated.
Based on experimental data, the mathematical model of rolling force parameters of 3-roll mills was studied. The structure of the model was theoretically set up and the coefficients were determined by static analysis of the data. The torque in continuous rolling was measured, and the characteristics and efficiency of 3-roll mills are investigated.
1999, vol. 6, no. 4, pp.
296-298.
Abstract:
A new surface inspection system for cold rolled strips based on image processing is introduced. The system is equipped with two different illumination structures and CCD matrix cameras. The structure and image processing of the inspection system are described. Some efficient algorithms for image processing and classification are presented. The system is tested with strip samples from cold rolling plants. The results show that the system can detect and recognize six common defects of cold rolled strips successfully.
A new surface inspection system for cold rolled strips based on image processing is introduced. The system is equipped with two different illumination structures and CCD matrix cameras. The structure and image processing of the inspection system are described. Some efficient algorithms for image processing and classification are presented. The system is tested with strip samples from cold rolling plants. The results show that the system can detect and recognize six common defects of cold rolled strips successfully.
1999, vol. 6, no. 4, pp.
299-301.
Abstract:
Rigorous proofs are given for the representations of real and complex stability radii of 2-dimensional linear systems. This representations can be used to analyze the robustness of a nominal 2-dimensional linear system under pelturbation of the system parameters, in particular testing the effect of numerical algorithms which are used to calculate the real stability radii of higher dimensional piecewise-linear systems.
Rigorous proofs are given for the representations of real and complex stability radii of 2-dimensional linear systems. This representations can be used to analyze the robustness of a nominal 2-dimensional linear system under pelturbation of the system parameters, in particular testing the effect of numerical algorithms which are used to calculate the real stability radii of higher dimensional piecewise-linear systems.
1999, vol. 6, no. 4, pp.
302-305.
Abstract:
Inverse modeling is discussed based on neural networks. U-D factorization Kalman filter learning algorithm is introduced to train a feed forward multilayer neural network, which is used as inverse models. A scheme of Direct Current Electric Arc Furnace (DC EAF) control systems using Neural Networks (NN) is presented.
Inverse modeling is discussed based on neural networks. U-D factorization Kalman filter learning algorithm is introduced to train a feed forward multilayer neural network, which is used as inverse models. A scheme of Direct Current Electric Arc Furnace (DC EAF) control systems using Neural Networks (NN) is presented.
1999, vol. 6, no. 4, pp.
306-308.
Abstract:
Based on the analysis of weakness on the safety of traditional electric detonators, a BJ-l safety electric detonator initiating system and its corresponding safe examination technique were successfully developed. By leading false foot wires and taking advantage of the transmitting frequency band of Mo-Zn ferrite, detonators in this new system can completely impede the direct induction of outside crosstalk that may cause casual firing in the ordinary as well as eleclromagnetic ones. Possible causality by lightning was discussed. Results are presented, of its safety tests on resistance to direct and alternating current, electrostatic, and crosstalk induced by damp leakage in saturated salty water.
Based on the analysis of weakness on the safety of traditional electric detonators, a BJ-l safety electric detonator initiating system and its corresponding safe examination technique were successfully developed. By leading false foot wires and taking advantage of the transmitting frequency band of Mo-Zn ferrite, detonators in this new system can completely impede the direct induction of outside crosstalk that may cause casual firing in the ordinary as well as eleclromagnetic ones. Possible causality by lightning was discussed. Results are presented, of its safety tests on resistance to direct and alternating current, electrostatic, and crosstalk induced by damp leakage in saturated salty water.
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