Search1998 Vol. 5, No. 1
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1998, vol. 5, no. 1, pp.
1-4.
Abstract:
In order to extract gold fines from pyrite slag, the hydrophobic flocculation flotation (HFF) was studied and compared with conventional flotation. The main parameters of HFF such as flotation reagent, surfactant dosage. the duration of agitation and the amount of non-polar oil were investigated, and the effect of non-polar oil was analyzed particularly. It is demonstrated that the HFF is better for gold extraction from pyrite slag than the conventional flotation, and the non-polar oil and the intensive agitation are the key to improve the Au contents and recovery in the concentrate. HFF was used to treat the pyrite slag from the west of Jiangxi province, whose gold contents are 2.949/t and the size of which are smaller than 10μm. The gold concentrate with gold grade 126.3 g/t and 51.35% recovery was obtained. Thus, a new method of extracting gold fines from pyrite slag is developed using HFF.
In order to extract gold fines from pyrite slag, the hydrophobic flocculation flotation (HFF) was studied and compared with conventional flotation. The main parameters of HFF such as flotation reagent, surfactant dosage. the duration of agitation and the amount of non-polar oil were investigated, and the effect of non-polar oil was analyzed particularly. It is demonstrated that the HFF is better for gold extraction from pyrite slag than the conventional flotation, and the non-polar oil and the intensive agitation are the key to improve the Au contents and recovery in the concentrate. HFF was used to treat the pyrite slag from the west of Jiangxi province, whose gold contents are 2.949/t and the size of which are smaller than 10μm. The gold concentrate with gold grade 126.3 g/t and 51.35% recovery was obtained. Thus, a new method of extracting gold fines from pyrite slag is developed using HFF.
1998, vol. 5, no. 1, pp.
5-8.
Abstract:
The kinetics of nitrogen removal from molten steel under vacuum and gas-blowing conditions has been studied during the VIM process. The experimental results indicated that vacuum affected the kinetics of nitrogen removal in the range of 67~5 360 Pa. At 67 Pa, the rate of nitrogen removal is controlled by the liquid phase mass transfer of nitrogen in molten steel. At 2 680Pa, the limited step for nitrogen removal from molten steel is the chemical reaction at the metal/gas interface. Under the present experimental conditions, the type (Ar, CO, CO2) and quantity of gas flowed have no evident influences on the rate of nitrogen removal. The ratio of nitrogen removal of gas bubbles is less than 3%. Based on the experimental results, the mechanism of nitrogen removal during the VD process with argon blowing and the other melting or secondary refining processes with carbon-oxygen reaction have been discussed. Some new viewpoints are proposed.
The kinetics of nitrogen removal from molten steel under vacuum and gas-blowing conditions has been studied during the VIM process. The experimental results indicated that vacuum affected the kinetics of nitrogen removal in the range of 67~5 360 Pa. At 67 Pa, the rate of nitrogen removal is controlled by the liquid phase mass transfer of nitrogen in molten steel. At 2 680Pa, the limited step for nitrogen removal from molten steel is the chemical reaction at the metal/gas interface. Under the present experimental conditions, the type (Ar, CO, CO2) and quantity of gas flowed have no evident influences on the rate of nitrogen removal. The ratio of nitrogen removal of gas bubbles is less than 3%. Based on the experimental results, the mechanism of nitrogen removal during the VD process with argon blowing and the other melting or secondary refining processes with carbon-oxygen reaction have been discussed. Some new viewpoints are proposed.
1998, vol. 5, no. 1, pp.
9-12.
Abstract:
A micro-modeling method (MM) for the quantitative prediction of the shrinkage cavity formation in SG iron castings is proposed. The mathematical models describing the volume changes during the solidification of spheroidal graphite cast iron are established based on the models of solidification kinetics. The shrinkage cavity formation of T-shaped SG iron castings is calculated with MM method. The calculated results are compared with the experimental results. It is shown that the predicted size, shape and distribution of shrinkage cavity by MM method are in good agreement with the measured results.
A micro-modeling method (MM) for the quantitative prediction of the shrinkage cavity formation in SG iron castings is proposed. The mathematical models describing the volume changes during the solidification of spheroidal graphite cast iron are established based on the models of solidification kinetics. The shrinkage cavity formation of T-shaped SG iron castings is calculated with MM method. The calculated results are compared with the experimental results. It is shown that the predicted size, shape and distribution of shrinkage cavity by MM method are in good agreement with the measured results.
1998, vol. 5, no. 1, pp.
13-15.
Abstract:
Based on Miedema's semiempirical formation enthalpy model for binary alloys, free volume theory and a general solution model, a new model for prediction of activity interaction coefficient ε11 is proposed. The calculated results are better in agreement with the experimental values than the two previous models. The related theories and models are discussed according to the degree of agreement with experimental values.
Based on Miedema's semiempirical formation enthalpy model for binary alloys, free volume theory and a general solution model, a new model for prediction of activity interaction coefficient ε11 is proposed. The calculated results are better in agreement with the experimental values than the two previous models. The related theories and models are discussed according to the degree of agreement with experimental values.
1998, vol. 5, no. 1, pp.
16-19.
Abstract:
A mathematical and physical model was adopted to compute the fluid flow distribution in case of local gas holdup in mold. The photography was used to show the fluid field. The predicted flow patterns show. reasonable agreement with experiment observations using actual water model.
A mathematical and physical model was adopted to compute the fluid flow distribution in case of local gas holdup in mold. The photography was used to show the fluid field. The predicted flow patterns show. reasonable agreement with experiment observations using actual water model.
1998, vol. 5, no. 1, pp.
20-22.
Abstract:
By altering the electrochemical properties of slag, the decarburization reaction of Fe3+-based slag with Fe-C droplet was studied. The results showed that a lot of free electrons and holes exist in the slag containing transition metal oxides (such as TiO2 and Fe2O3). So electronic conduction in the slag increases. Finally, it led to the increment of the decarburization reaction rate between slag and Fe-C droplet, and mass fraction of carbon remaining in droplet decreases to a lower level.
By altering the electrochemical properties of slag, the decarburization reaction of Fe3+-based slag with Fe-C droplet was studied. The results showed that a lot of free electrons and holes exist in the slag containing transition metal oxides (such as TiO2 and Fe2O3). So electronic conduction in the slag increases. Finally, it led to the increment of the decarburization reaction rate between slag and Fe-C droplet, and mass fraction of carbon remaining in droplet decreases to a lower level.
1998, vol. 5, no. 1, pp.
23-25.
Abstract:
Electrochemical behavior of hypophosphite was studied with cyclic voltammogram in acidic solution(pH = 4.6) at 80℃. Two anodic peaks were observed on gold electrode at -0.44V and -0.59 V (SCE),respectively, and no corresponding cathodic peaks were obtained. The one at -0.44 V wits ascribed to the oxidation of tautomeric form of hypophosphite, the other at -0.59 V was due to the oxidation of absorbed form of hypophosphite. The two oxidation reactions were believed to be the electron source of nickel ion reduction in electroless nickel processes.
Electrochemical behavior of hypophosphite was studied with cyclic voltammogram in acidic solution(pH = 4.6) at 80℃. Two anodic peaks were observed on gold electrode at -0.44V and -0.59 V (SCE),respectively, and no corresponding cathodic peaks were obtained. The one at -0.44 V wits ascribed to the oxidation of tautomeric form of hypophosphite, the other at -0.59 V was due to the oxidation of absorbed form of hypophosphite. The two oxidation reactions were believed to be the electron source of nickel ion reduction in electroless nickel processes.
1998, vol. 5, no. 1, pp.
26-30.
Abstract:
The effect of temperature, soak times, carbon and addition on composites was discussed in the process of synthesizing O'-sialon-SiC by carbonthermal reduction-nitration from nature kaolin. It showed that the fracture strength (MOR) of composites sintered under certain conditions can be up to 140MPa at room temperature. The target parameter optima regions with good mechanical properties of this material were also indicated by using computer pattern recognition program.
The effect of temperature, soak times, carbon and addition on composites was discussed in the process of synthesizing O'-sialon-SiC by carbonthermal reduction-nitration from nature kaolin. It showed that the fracture strength (MOR) of composites sintered under certain conditions can be up to 140MPa at room temperature. The target parameter optima regions with good mechanical properties of this material were also indicated by using computer pattern recognition program.
1998, vol. 5, no. 1, pp.
31-35.
Abstract:
Compacts of α-Al2O3 and Mo powder were heated in radio-frequency (RF) induced low pressure N2, H2, Ar, and their mixture plasma. An optical pyrometer, a radiation pyrometer, and a system called Accufiber Model 310 were used to measure the temperature of compacts heated in the plasma. The results indicate that there are different heat transfer mechanisms from plasma to specimens of different physical properties. The Ar plasma showed the highest heating ability among N2, H2, and Ar plasma for Al2O3 specimens, whereas the H2 plasma could heat Mo specimens to a higher temperature than the Ar plasma did, even under the same generating conditions.
Compacts of α-Al2O3 and Mo powder were heated in radio-frequency (RF) induced low pressure N2, H2, Ar, and their mixture plasma. An optical pyrometer, a radiation pyrometer, and a system called Accufiber Model 310 were used to measure the temperature of compacts heated in the plasma. The results indicate that there are different heat transfer mechanisms from plasma to specimens of different physical properties. The Ar plasma showed the highest heating ability among N2, H2, and Ar plasma for Al2O3 specimens, whereas the H2 plasma could heat Mo specimens to a higher temperature than the Ar plasma did, even under the same generating conditions.
1998, vol. 5, no. 1, pp.
36-38.
Abstract:
The surface of a compact disk is analyzed by using SPM and the quantitative micromorphology analysis software SPMIAS developed by the author. Images at the same position but with different scanning ranges are obtained under the same experimental conditions. Micromorphology parameters are calculated and compared, and the relationship between the changing of the scanning range and the changing of micromorphology parameters is summarized.
The surface of a compact disk is analyzed by using SPM and the quantitative micromorphology analysis software SPMIAS developed by the author. Images at the same position but with different scanning ranges are obtained under the same experimental conditions. Micromorphology parameters are calculated and compared, and the relationship between the changing of the scanning range and the changing of micromorphology parameters is summarized.
1998, vol. 5, no. 1, pp.
39-40.
Abstract:
Based on considering both negative effect of compacting pressure on glass temperature (Tg) and positive effect of plasticizer added into organic binder, a mathematical equation for adjusting Tg of binder used for warm compaction processing is given. The equation shows that mass fraction of plasticizer need for lowering Tg is function of compacting plessure. The rationality of the equation for warm compaction processing is also discussed.
Based on considering both negative effect of compacting pressure on glass temperature (Tg) and positive effect of plasticizer added into organic binder, a mathematical equation for adjusting Tg of binder used for warm compaction processing is given. The equation shows that mass fraction of plasticizer need for lowering Tg is function of compacting plessure. The rationality of the equation for warm compaction processing is also discussed.
1998, vol. 5, no. 1, pp.
41-43.
Abstract:
The microhardness and modulus changes of the interface between U-0.75Ti alloy and TiC before and after heat treatment were studied by SEM and Nano Indenter II, and the results show that the hardness and modulus of the interface are greatly increased after 820℃, 2 h water quenching and 450℃, 6 h aging. This result probably comes from much more U2Ti and U6Ni precipitates along the interface.
The microhardness and modulus changes of the interface between U-0.75Ti alloy and TiC before and after heat treatment were studied by SEM and Nano Indenter II, and the results show that the hardness and modulus of the interface are greatly increased after 820℃, 2 h water quenching and 450℃, 6 h aging. This result probably comes from much more U2Ti and U6Ni precipitates along the interface.
1998, vol. 5, no. 1, pp.
44-46.
Abstract:
The creep equation proposed in so called θ projection concept is developed in the concept of thermal activation of creep. The measured creep curves of A286 alloy are fitted by the equation. The activation energy in the equation is evaluated, and creep rupture lives are predicted. The results are confirmed by creep tests of up to 13 years.
The creep equation proposed in so called θ projection concept is developed in the concept of thermal activation of creep. The measured creep curves of A286 alloy are fitted by the equation. The activation energy in the equation is evaluated, and creep rupture lives are predicted. The results are confirmed by creep tests of up to 13 years.
1998, vol. 5, no. 1, pp.
47-50.
Abstract:
The variation regularity of dislocation densites of some deformed steel sheets under three kinds of strain paths as uniaxial tension, plane strain and equal biaxial stretching was investigated by means of positron lifetime spectrum and Doppler-broadening techniques. The results show that the increasing rate of dislocation densites is related to the plastic strain path. A relationship between the increasing rate of micro-defects, macro-instability and forming limits during the process of steel sheet forming was got based on analyzing the mechanism of dislocation density increasing under different stress-strain condihons.
The variation regularity of dislocation densites of some deformed steel sheets under three kinds of strain paths as uniaxial tension, plane strain and equal biaxial stretching was investigated by means of positron lifetime spectrum and Doppler-broadening techniques. The results show that the increasing rate of dislocation densites is related to the plastic strain path. A relationship between the increasing rate of micro-defects, macro-instability and forming limits during the process of steel sheet forming was got based on analyzing the mechanism of dislocation density increasing under different stress-strain condihons.
1998, vol. 5, no. 1, pp.
51-56.
Abstract:
Micro-crystalline coatings of 310S stainless steels were produced by unbalanced magnetron sputter deposition. Isothermal oxidation behavior of the coated and uncoated specimens has been studied using a thermogravimetric analysis (TGA) station. The oxidation time was 50h and the temperature was 1 000℃. The oxidation rates of the coated specimens was found to be much lower than the uncoated specimens after 50 h of oxidation. The oxidation kinetic curves of the coated specimens consisted of three stages: approximately parabolic at the first stage, speeding up at the second stage, and slow down at the third stage. The increase of the oxidation rate at the second stage nasattributed to the fast diffuison of Fe though the fine grained Cr2O3 layer formed on the micro-crystalline coatings.The top view and cross-section microstructures of the oxides formed on the coated and the uncoated specimens were studied with SEM and EDS. It was observed that the nucleation of oxide on the coated specimens was much enhanced at the initial oxidation stage. This was explained as the result of reduction in the critical free energy change and increase in the supply of chromium ions.
Micro-crystalline coatings of 310S stainless steels were produced by unbalanced magnetron sputter deposition. Isothermal oxidation behavior of the coated and uncoated specimens has been studied using a thermogravimetric analysis (TGA) station. The oxidation time was 50h and the temperature was 1 000℃. The oxidation rates of the coated specimens was found to be much lower than the uncoated specimens after 50 h of oxidation. The oxidation kinetic curves of the coated specimens consisted of three stages: approximately parabolic at the first stage, speeding up at the second stage, and slow down at the third stage. The increase of the oxidation rate at the second stage nasattributed to the fast diffuison of Fe though the fine grained Cr2O3 layer formed on the micro-crystalline coatings.The top view and cross-section microstructures of the oxides formed on the coated and the uncoated specimens were studied with SEM and EDS. It was observed that the nucleation of oxide on the coated specimens was much enhanced at the initial oxidation stage. This was explained as the result of reduction in the critical free energy change and increase in the supply of chromium ions.
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