Search2003 Vol. 10, No. 4
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2003, vol. 10, no. 4, pp.
1-6.
Abstract:
The solidification structure, microstructure evolution during rolling and precipitates with nanometers in dimension of thelow carbon steels produced by CSP process with thin slabs have been studied in recent years. Important differences in microstructureand mechanical properties between the CSP products and the conventional one were observed. These differences may arise from themuch rapider solidification rate and cooling rate after casting of the thin slabs. Some aspects of the microstructure for the low carbonsteels of the CSP thin slabs are summarized and compared with the conventional one.
The solidification structure, microstructure evolution during rolling and precipitates with nanometers in dimension of thelow carbon steels produced by CSP process with thin slabs have been studied in recent years. Important differences in microstructureand mechanical properties between the CSP products and the conventional one were observed. These differences may arise from themuch rapider solidification rate and cooling rate after casting of the thin slabs. Some aspects of the microstructure for the low carbonsteels of the CSP thin slabs are summarized and compared with the conventional one.
2003, vol. 10, no. 4, pp.
7-11.
Abstract:
Four reactors of up-flow anaerobic sludge blanket (UASB) were concurrently operated to examine the effects of the xonotlite secondary particles on promoting the sludge granulation during the starting-up stage at room temperature. The results show that the putting of the xonotlite secondary particles into the UASB reactors can increase the basicity of the reacting liquid significantly. The particles can act as the media for biomass accumulation. Thus, the granulation process of the sludge within the reactor can be largely promoted by the special performances of the particles both in physical and chemical aspects.
Four reactors of up-flow anaerobic sludge blanket (UASB) were concurrently operated to examine the effects of the xonotlite secondary particles on promoting the sludge granulation during the starting-up stage at room temperature. The results show that the putting of the xonotlite secondary particles into the UASB reactors can increase the basicity of the reacting liquid significantly. The particles can act as the media for biomass accumulation. Thus, the granulation process of the sludge within the reactor can be largely promoted by the special performances of the particles both in physical and chemical aspects.
2003, vol. 10, no. 4, pp.
12-15.
Abstract:
Time interval of short delay ignition is an important factor to affect the efficiency of blasting cuts. The motion process of rock pieces in the cut cavity is analyzed, a mechanical model to calculate the delay time of parallel hole cuts is presented for tunnel blasting, and a theoretical method to determine the volume ratio (the clearage rate) of the rock pieces within the cut cavity at different moments is proposed for the blasting cut with an empty hole. Numerical analysis results show that the optimal delay interval is proportional to the borehole depth. The suggested results are of practical value to the optimal design of the delay interval in millisecond blasting related to the parallel hole cuts with an empty hole.
Time interval of short delay ignition is an important factor to affect the efficiency of blasting cuts. The motion process of rock pieces in the cut cavity is analyzed, a mechanical model to calculate the delay time of parallel hole cuts is presented for tunnel blasting, and a theoretical method to determine the volume ratio (the clearage rate) of the rock pieces within the cut cavity at different moments is proposed for the blasting cut with an empty hole. Numerical analysis results show that the optimal delay interval is proportional to the borehole depth. The suggested results are of practical value to the optimal design of the delay interval in millisecond blasting related to the parallel hole cuts with an empty hole.
2003, vol. 10, no. 4, pp.
16-19.
Abstract:
The fact that the amount of the mold flux components differs at different locations on the cracking surface indicates that the longitudinal surface cracks are initially formed in the mold and are enlarged in the secondary cooling zone. Based on the hot ductility measurement of two typical container used steels, it is known that the steels are in severe embrittlement state in the temperature range of 825-775℃. By means of increasing Cr/Ni plating thickness on the upper part of the mold, reducing mold heat flux, adopting new secondary cooling pattern, etc., the occurrence of the surface longitudinal cracks on the steel CC (continuous casting) slabs has been significantly reduced.
The fact that the amount of the mold flux components differs at different locations on the cracking surface indicates that the longitudinal surface cracks are initially formed in the mold and are enlarged in the secondary cooling zone. Based on the hot ductility measurement of two typical container used steels, it is known that the steels are in severe embrittlement state in the temperature range of 825-775℃. By means of increasing Cr/Ni plating thickness on the upper part of the mold, reducing mold heat flux, adopting new secondary cooling pattern, etc., the occurrence of the surface longitudinal cracks on the steel CC (continuous casting) slabs has been significantly reduced.
2003, vol. 10, no. 4, pp.
20-23.
Abstract:
Fine bubbles will create when the inert gas is introduced to the high rapid steel stream within the shroud nozzle between ladle and tundish. The collision and attachment among the bubbles and fine inclusions will promote the floatation efficiency of inclusions in the tundish. The behaviors of the bubbles, such as the dispersion in shroud, coalescence and floatation in tundish, are studied.The results show that the maximum sizes of the bubbles in the water and steel flow within the shroud in the length of 1.2 m are 0.70-1.44mm and 1.53-3.16mm respectively when the flow rates are 0.006-0.016 m3/s; the terminal velocities of fine bubbles in the water and molten steel within the tundish are 0.02-0.2 and 0.05-0.6 m/s.
Fine bubbles will create when the inert gas is introduced to the high rapid steel stream within the shroud nozzle between ladle and tundish. The collision and attachment among the bubbles and fine inclusions will promote the floatation efficiency of inclusions in the tundish. The behaviors of the bubbles, such as the dispersion in shroud, coalescence and floatation in tundish, are studied.The results show that the maximum sizes of the bubbles in the water and steel flow within the shroud in the length of 1.2 m are 0.70-1.44mm and 1.53-3.16mm respectively when the flow rates are 0.006-0.016 m3/s; the terminal velocities of fine bubbles in the water and molten steel within the tundish are 0.02-0.2 and 0.05-0.6 m/s.
2003, vol. 10, no. 4, pp.
24-28.
Abstract:
Generally, the cooler life can determine the blast furnace life. The slag-metal skull frozen on the cooler can separate the cooler from the hot gas flow in blast furnace. The key problem is how to freeze liquid slag-metal on the cooler, and the main measure is to decrease the hot surface temperature of the cooler. The computational technology of heat transfer was practically used for long campaign blast furnace design. The optimum design of the cast iron stave, copper stave, plate-stave combined system and flangestave was given by the computing results. According to the results, the optimum arrangement of different coolers (cast iron or copper stave, flange stave and plate-stave combined system) on different height of blast furnace wall can be found through all these temperature fields.
Generally, the cooler life can determine the blast furnace life. The slag-metal skull frozen on the cooler can separate the cooler from the hot gas flow in blast furnace. The key problem is how to freeze liquid slag-metal on the cooler, and the main measure is to decrease the hot surface temperature of the cooler. The computational technology of heat transfer was practically used for long campaign blast furnace design. The optimum design of the cast iron stave, copper stave, plate-stave combined system and flangestave was given by the computing results. According to the results, the optimum arrangement of different coolers (cast iron or copper stave, flange stave and plate-stave combined system) on different height of blast furnace wall can be found through all these temperature fields.
2003, vol. 10, no. 4, pp.
29-32.
Abstract:
A second order heat equation with convection in an infinite medium is studied. Suitable similarity transformations are used to reduce the parabolic heat equation to a class of singular nonlinear boundary value problems. Numerical solutions are presented for different representations of heat conduction, heat convection, heat flux, and power law parameters by utilizing the shooting technique. The results reveal the heat transfer characteristic and the effect of parameters on the solutions.
A second order heat equation with convection in an infinite medium is studied. Suitable similarity transformations are used to reduce the parabolic heat equation to a class of singular nonlinear boundary value problems. Numerical solutions are presented for different representations of heat conduction, heat convection, heat flux, and power law parameters by utilizing the shooting technique. The results reveal the heat transfer characteristic and the effect of parameters on the solutions.
2003, vol. 10, no. 4, pp.
33-37.
Abstract:
Based on the electric-spark principle, a new kind of cavitation damage testing apparatus was designed, which could produce the bubble. Bubbles collapsed and acted on a small surface area of the alloy surface, so an intensive electrochemical inhomogenous state would be induced and lead to the existence of surface galvanic effect on the alloy. The galvanic effect of 1Crl3 SS during cavitation damage has been quantitatively investigated in NaCl solution. The results show that intensive galvanic effect of 1Crl3 SS during cavitation damage appears the potential of the damaged area shifting negatively with the bubble collapse and simultaneously the galvanic current generates, The mass loss of alloy due to cavitation increases with the bubble quantity, and increases with the increasing of Cl- content. And both the total mass loss and the mass loss due to galvanic corrosion increase linearly with the area ratio of cavitation damaged to undamaged area. Such surface galvanic effects speed up the dissolution rate of the alloy, which, in turn, accelerates the mechanical damage, and aggravates the mass loss of the alloy. It has been further confirmed that the mass loss due to the surface galvanic effect can be decreased by catholic protection.
Based on the electric-spark principle, a new kind of cavitation damage testing apparatus was designed, which could produce the bubble. Bubbles collapsed and acted on a small surface area of the alloy surface, so an intensive electrochemical inhomogenous state would be induced and lead to the existence of surface galvanic effect on the alloy. The galvanic effect of 1Crl3 SS during cavitation damage has been quantitatively investigated in NaCl solution. The results show that intensive galvanic effect of 1Crl3 SS during cavitation damage appears the potential of the damaged area shifting negatively with the bubble collapse and simultaneously the galvanic current generates, The mass loss of alloy due to cavitation increases with the bubble quantity, and increases with the increasing of Cl- content. And both the total mass loss and the mass loss due to galvanic corrosion increase linearly with the area ratio of cavitation damaged to undamaged area. Such surface galvanic effects speed up the dissolution rate of the alloy, which, in turn, accelerates the mechanical damage, and aggravates the mass loss of the alloy. It has been further confirmed that the mass loss due to the surface galvanic effect can be decreased by catholic protection.
2003, vol. 10, no. 4, pp.
38-41.
Abstract:
An autonatic surface quality inspection system installed on a finishing line of cold rolled strips is introduced. The system is able to detect surface defects on cold rolled strips, such as scratches, coil breaks, rusts, roll imprints, and so on. Multiple CCD area scan canteras were equipped to capture images of strip surface simultaneously. Defects were detected through "Dark-field illumination" which is generated by LED illuminators. Parallel computation technique and fast processing algorithms were developed for real-time data processing. The application to the production line shows that the system is able to detect defects effectively.
An autonatic surface quality inspection system installed on a finishing line of cold rolled strips is introduced. The system is able to detect surface defects on cold rolled strips, such as scratches, coil breaks, rusts, roll imprints, and so on. Multiple CCD area scan canteras were equipped to capture images of strip surface simultaneously. Defects were detected through "Dark-field illumination" which is generated by LED illuminators. Parallel computation technique and fast processing algorithms were developed for real-time data processing. The application to the production line shows that the system is able to detect defects effectively.
2003, vol. 10, no. 4, pp.
42-45.
Abstract:
Mechanical properties and microstructure changes have been investigated on a new nickel-base superalloy after long-term aging at 700℃. It is found that the major precipitates of the tested alloy are MC, M23C6, M6C and γ' in the course of long-term aging at 700℃. The carbides maintain good thermal stability with the aging time up to 5008 h. The growth rate of gamma prime precipitates is relatively high in the early aging period and then slows down. The coarsening behavior of gamma prime follows a diffusion-controlled growth procedure. The room temperature Rockwell hardness of the alloy aged at 700℃ increases slightly at the initial stage of aging, but it decreases with the prolonged time. It mainly depends on the size of gamma prime. In comparison with Nimonic lloy 263, the new alloy characterizes with higher tensile and stress-rupture strengths at high temperatures. The new nickel-base superalloy offers a combination of microstructure stability, strength, ductility and toughness at 700℃.
Mechanical properties and microstructure changes have been investigated on a new nickel-base superalloy after long-term aging at 700℃. It is found that the major precipitates of the tested alloy are MC, M23C6, M6C and γ' in the course of long-term aging at 700℃. The carbides maintain good thermal stability with the aging time up to 5008 h. The growth rate of gamma prime precipitates is relatively high in the early aging period and then slows down. The coarsening behavior of gamma prime follows a diffusion-controlled growth procedure. The room temperature Rockwell hardness of the alloy aged at 700℃ increases slightly at the initial stage of aging, but it decreases with the prolonged time. It mainly depends on the size of gamma prime. In comparison with Nimonic lloy 263, the new alloy characterizes with higher tensile and stress-rupture strengths at high temperatures. The new nickel-base superalloy offers a combination of microstructure stability, strength, ductility and toughness at 700℃.
2003, vol. 10, no. 4, pp.
46-49.
Abstract:
Ni/Co bimetallic nano-cluters have been prepared from the aqueous solution by reducing their corresponding metal salts under suitable conditions. The experimental conditions including the type and concentration of protective agent, feeding order and the pH of the solution that influence the average particle size have been studied in detail. Transmission electron microscopy (TEM)indicates that the shape of those bimetallic nano-cluster particles is spheroid. The alloy structure has been shown by X-ray powder diffraction (XRD). The X-ray photoelectron spectroscopic (XPS) data have confirmed that the nickel and cobalt in the bimetallic nano-clusters are in the zero-valence state.
Ni/Co bimetallic nano-cluters have been prepared from the aqueous solution by reducing their corresponding metal salts under suitable conditions. The experimental conditions including the type and concentration of protective agent, feeding order and the pH of the solution that influence the average particle size have been studied in detail. Transmission electron microscopy (TEM)indicates that the shape of those bimetallic nano-cluster particles is spheroid. The alloy structure has been shown by X-ray powder diffraction (XRD). The X-ray photoelectron spectroscopic (XPS) data have confirmed that the nickel and cobalt in the bimetallic nano-clusters are in the zero-valence state.
2003, vol. 10, no. 4, pp.
50-54.
Abstract:
A mathematical formulation is applied to represent the phenomena in the incremental melting and solidification process (IMSP), and the temperature and electromagnetic fields and the depth of steel liquid phase are calculated by a finite difference technique using the control volume method. The result shows that the predicted values are in good agreement with the observations. In accordance with the calculated values for different kinds of materials and different size of molds, the technological parameter of the IMS process such as the power supply and the descending speed rate can be determined.
A mathematical formulation is applied to represent the phenomena in the incremental melting and solidification process (IMSP), and the temperature and electromagnetic fields and the depth of steel liquid phase are calculated by a finite difference technique using the control volume method. The result shows that the predicted values are in good agreement with the observations. In accordance with the calculated values for different kinds of materials and different size of molds, the technological parameter of the IMS process such as the power supply and the descending speed rate can be determined.
2003, vol. 10, no. 4, pp.
55-60.
Abstract:
The coherent elastic strain-induced morphological transformation of a binary cubic model alloy was simulated with different strain energy parameters. The microscopic diffusion equation was combined with the theory of microscopic elasticity. The results show that when the strain energy is neglected, the randomly distributed equiaxed particles are obtained with isotropic characteristic.It is coarsening that follows the Ostwald ripening mechanism: smaller particles dwindle and larger particles grow; when the elastic strain is considered, plate precipitates tend to align along the elastically soft directions <01> with anisotropic characteristic. The particles grow in the soft directions and coarsen further; particles dwindle in out of the soft directions. While the coarsening of the particles localized in the same row or column follows the rule: smaller particles shrink and larger ones grow.
The coherent elastic strain-induced morphological transformation of a binary cubic model alloy was simulated with different strain energy parameters. The microscopic diffusion equation was combined with the theory of microscopic elasticity. The results show that when the strain energy is neglected, the randomly distributed equiaxed particles are obtained with isotropic characteristic.It is coarsening that follows the Ostwald ripening mechanism: smaller particles dwindle and larger particles grow; when the elastic strain is considered, plate precipitates tend to align along the elastically soft directions <01> with anisotropic characteristic. The particles grow in the soft directions and coarsen further; particles dwindle in out of the soft directions. While the coarsening of the particles localized in the same row or column follows the rule: smaller particles shrink and larger ones grow.
2003, vol. 10, no. 4, pp.
61-64.
Abstract:
The coherent-light-driven tunneling in double quantum wells has been studied. The electrons are coupled to a system of phonons and subjected to the two beams of coherently optical waves. By adopting a gauge to both the external field and the phonon field, the phonon field operators in the Schrodinger equations are eliminated. In this way, an expression of the tunneling current is conveniently derived considering the relaxation effect. It is shown that under the intense laser field, the tunneling current oscillates rapidly with time at low temperature. The duration of the oscillations is related to the temperature. By adjusting the phase difference of the two light-beams, the oscillation frequency can be modulated.
The coherent-light-driven tunneling in double quantum wells has been studied. The electrons are coupled to a system of phonons and subjected to the two beams of coherently optical waves. By adopting a gauge to both the external field and the phonon field, the phonon field operators in the Schrodinger equations are eliminated. In this way, an expression of the tunneling current is conveniently derived considering the relaxation effect. It is shown that under the intense laser field, the tunneling current oscillates rapidly with time at low temperature. The duration of the oscillations is related to the temperature. By adjusting the phase difference of the two light-beams, the oscillation frequency can be modulated.
2003, vol. 10, no. 4, pp.
65-68.
Abstract:
To overcome the disadvantages of conventional DGA (dissolved gas-in-oil) analysis using gas chromatography and other electrochemical sensors, initial researches were completed to realize on-line monitoring of dissolved gas-in-oil of power transformers using FTIR (Fourier Transform InfraRed) spectroscopy. Gas cell method is used to determine the characteristic absorption peaks of each diagnostic gas; simple and novel devices and procedures were designed in order to get measurable samples and spectra of mixed diagnostic gases with known concentration are taken using long optical path gas cell. The range of wavelength is estimated to be 3.0-13.9 μm from experimental spectra data. Hence the corresponding sampling frequency range should be in 536-4288 Hz and usable optical materials are suggested. It is concluded that a resolution of 10 cm-1 may well satisfy the monitoring of all diagnostic gases and water content except hydrogen, and the lowest detection limit may be as low as 2×10-8 to acetylene with a 2.4-meter-long optical length.
To overcome the disadvantages of conventional DGA (dissolved gas-in-oil) analysis using gas chromatography and other electrochemical sensors, initial researches were completed to realize on-line monitoring of dissolved gas-in-oil of power transformers using FTIR (Fourier Transform InfraRed) spectroscopy. Gas cell method is used to determine the characteristic absorption peaks of each diagnostic gas; simple and novel devices and procedures were designed in order to get measurable samples and spectra of mixed diagnostic gases with known concentration are taken using long optical path gas cell. The range of wavelength is estimated to be 3.0-13.9 μm from experimental spectra data. Hence the corresponding sampling frequency range should be in 536-4288 Hz and usable optical materials are suggested. It is concluded that a resolution of 10 cm-1 may well satisfy the monitoring of all diagnostic gases and water content except hydrogen, and the lowest detection limit may be as low as 2×10-8 to acetylene with a 2.4-meter-long optical length.
2003, vol. 10, no. 4, pp.
69-74.
Abstract:
Reheating furnace is an important device with complex dynamic characteristics in steel plants. The temperature tracing control of reheating furnace has great importance both to the quality of slabs and energy saving. A model-based control strategy,multivariable constrained control (MCC) for the reheating furnace control is used. With this control method, the furnace is treated as a six-input-six-output general model with loops coupled in nature. Compared with the traditional control, the proposed control strategy gets better temperature tracing accuracy and exhibits some energy saving feature. The simulation results show that the performance of the furnace is greatly improved.
Reheating furnace is an important device with complex dynamic characteristics in steel plants. The temperature tracing control of reheating furnace has great importance both to the quality of slabs and energy saving. A model-based control strategy,multivariable constrained control (MCC) for the reheating furnace control is used. With this control method, the furnace is treated as a six-input-six-output general model with loops coupled in nature. Compared with the traditional control, the proposed control strategy gets better temperature tracing accuracy and exhibits some energy saving feature. The simulation results show that the performance of the furnace is greatly improved.
2003, vol. 10, no. 4, pp.
75-77.
Abstract:
The solid-solid phase transitions in the perovskite type layer materials (n-C12H25NH3)2ZnCl4 (C12Zn) and (n-C18H37NH3)2ZnCl4 (C18Zn) that are one kind of potential thermal storage material, were synthesized and, at the same time, a series of their mixtures C12Zn/C18Zn were prepared. The experimental binary phase diagram of C12Zn/C18Zn was established by means of differential scanning calorimetry (DSC) and X-ray diffraction. In the phase diagram a stable solid compound (n-C12H25NH3)(n-C18H37NH3)ZnCl4 (C12C18Zn) and two eutectoid invariants were observed. It is noticeable that the phase diagram contains solid solution ranges.
The solid-solid phase transitions in the perovskite type layer materials (n-C12H25NH3)2ZnCl4 (C12Zn) and (n-C18H37NH3)2ZnCl4 (C18Zn) that are one kind of potential thermal storage material, were synthesized and, at the same time, a series of their mixtures C12Zn/C18Zn were prepared. The experimental binary phase diagram of C12Zn/C18Zn was established by means of differential scanning calorimetry (DSC) and X-ray diffraction. In the phase diagram a stable solid compound (n-C12H25NH3)(n-C18H37NH3)ZnCl4 (C12C18Zn) and two eutectoid invariants were observed. It is noticeable that the phase diagram contains solid solution ranges.
2003, vol. 10, no. 4, pp.
78-80.
Abstract:
The aging precipitation behavior of β phase in two kinds of alloys with 7/3 and 9/1 nickel-to-iron ratios during aging at 800℃ after deformation was studied. The results show that there are two different kinds of aging hardness variation mechanisms (the softening mechanism and the hardening mechanism) deciding the hardness variations of the alloys. When Ni/Fe is smaller than 8/2, there is only the softening mechanism which results from the decreasing of dislocation density and recovery or re-crystallization.And when Ni/Fe is greater than 8/2 besides the softening mechanism there is still the hardening mechanism that is induced by the precipitation of β phase.
The aging precipitation behavior of β phase in two kinds of alloys with 7/3 and 9/1 nickel-to-iron ratios during aging at 800℃ after deformation was studied. The results show that there are two different kinds of aging hardness variation mechanisms (the softening mechanism and the hardening mechanism) deciding the hardness variations of the alloys. When Ni/Fe is smaller than 8/2, there is only the softening mechanism which results from the decreasing of dislocation density and recovery or re-crystallization.And when Ni/Fe is greater than 8/2 besides the softening mechanism there is still the hardening mechanism that is induced by the precipitation of β phase.
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