Abstract: Sampling of burned coal residue directly from the raceway of two Chinese BF reveals that at the current rate of anthracite injection up to 140 kg/tHM or 27% of the total fuel coal could not be burned completely in the raceway although devolatilization and combustion take place early in the blowpipe. This does not interrupt the smooth running of the furnaces. From laboratory study on kinetics of coal powder combustion in two bench-scale combustion furnaces, one of which preheats the air blast by electrical resistance, the other by plasma torch, rate of combustion is found almost inversely proportional to grain size of coal; it increases with increaseof blast temperature up to 1475℃; oxygen enrichment up to 40% of the blast is very effective;with decrease of coefficient of surplus air to less than. 1.2-1.3 the rate of combustion decreases abruptly, while whirling or rotation of the blast accelerates the combustion rate. Melting behavior of dropping zone slag mixed with ash of injected coal or partially burned coal residue seems not to be the limiting bottle-neck to high rate of coal injection. Investigation on effect of injection position, angle and shape of coal lance on the two phase gas-solid distribution by shock-wave tube and schlieren method reveals remarkable influence of these factors on uniform distribution of injected coal particles in the combution air stream.
Abstract: In a brasion resistant low alloy white cast iron just as in unalloyed white cast iron, ledeburitic carbide morphology can be changed by RE modification to platelike carbide morphology having discontinuous distribution. The toughness of the alloy can thus be increased (Table I and Fig.1 and 2). Experiments showed that the effects of RE modification on the crystallization of white cast iron include the following. Most of RE is concentrated, in sulfide inclusions (Fig. 3), which can serve as the substrate for the crystallization of primary austenite and thus volumetric nucleation of austenite is effected (Fig. 4).When crystallized in RE enriched melt, the order of austenitic dendrite axis can be increased thru the effect of constitutional undercooling(Fig. 5). Both effects cause obstruction to the continuous growth of eutectic carbide.RE modification causes the lowering of eutectic freezing temperature which favors the growth of divorced auste nite-carbide eutectic(fig.6) and it also enlarges the eutectic freezing temperature range, favoring volumetric nucleation of eutectics.(Fig.7). Selective absorption of RE on eutectic carbide obstructs the continuous preferential edgewise growth of carbide and favors its more or less uniform growth in different directions as platelike carbide.Based on the above assumption of RE modification mechanism, the effect of RE modification can be improved by the following techniques. Lowering of C content causes the lowering of carbide content and the incresing of primary austenite in white iron(Fig. 8).Slight increase of Si content causes the lowering of eutectic freezing temperature.Inoculation treatment before RE modification can help nucleate primary austenite,which is called duplex treatment. Use of complex inoculant and complex modifier can develop their advantageous effects with less unfavorable by effects.with this duplex modification technology,better and more reproducible results of changing carbide morphology in low alloy white cast iron can be obtained with much less RE modifier addition (Fig. 9).
Abstract: The elementary morphology of c/v graphite has been studied with unidirectional solidification specimens.The results indicate that the basic part of the branches of c/v graphite is essentialy a compound prism.The "spine line"often revealed under polarized light as the microstructure of the c/v graphite could be explained through our analysis of the structure on the transverse section of the c/v graphite branches by means of polarized light microscopy and TEM.
Abstract: A series of fatigue-creep fracture life curves for a big ESR-Cast-toShape gas turbine disc(ECD) were obtained from tests called fatigue-creepnteraction test which was performed at constant temperature and fixed max stress with various value of min stress The shape of interaction curve was different from that of the normal S-N curve and creep curve.It could be envisaged as a combination of pure fatigue and pure creep curves.On the ground of the different stress being dependent of fracture lives,the whole interaction curve could be classified into three parts:fatigue(F),creep(C), and mixed(FC) regions. The larger the max strss the stronger the interaction,the shorter the life.According to the fracture mechanisms and experimental observation of the appearance of fracture surfaces,five distinct fracture mechanism regions (i.e.FF,FCF,CFF,CFC,CC,regions) were occured. On the basic of macro-micro analysis of fracture a new fatigue-creep interaction map called first type of interaction map was constructed.It provided the basic information of fracture lives and fracture mechanisms. Discussing several features of interaction,a unified competi tive and cumulative model was suggested to show the nature of fatigue-creep interaction.
Abstract: According to the eutccticum content of the Fe-Mg system,the standard free energy change of the following reaction is calculated.The result is as follows Mg(g)=[Mg]1%(Fe) △G°=-108,993 + 63.25 T,J/g-at It is then impossible to produce or retain Mg content ≥ 0.002% by means of Si or Mn in the GH36 alloy while ESR is conducted with slag containing MgO or MgF2.The necessity of containing a few Al in consumanle-electrode during ESR has been proposed.The effect of the original contents of Al,Mg and the the composition of slag system CaF2-MgO-Al2O3-CaO on the content of Mg in ingot is investigated.At temperature of the slag pool is about 1690±10℃, 0·32 ≤ [Al]o ≤ 0.62wt%,0.0035 ≤ [Mg]o ≤ 0.014 0 wt% and in the mole concentration range of the slag. 0.10 ≤ NMgo ≤ 0.30,0.05 ≥ NAt2O3 ≤ 0.21, NCaO ≤ 0.15, the Mg content in the GH36A alloy after ESR may be controled. It is found that the smooth and notched stress rupture life of the GH36A alloy contained suitable Mg and Al contents may be substantialy improved,and the notch sensitivity of the alloy may be eliminated under esting temperature of 650℃ and stress of 372.65Mpa
Abstract: This paper deals with the effects of cobalt on the microstructures of Fe-Cr-Ni-Co base superalloy Refractoloy26, cobalt is replaced by nickel to produce versions of alloy containing 0, 7, 14, and standard 20 pct.cobaltr espectively.The microstructures of these alloys arc examined by optical and electron microscope,X-ray diffractionand chemical phase analysis technique. As cobalt decreases, the weight fraction ofγ'phase as well as the average diameter of γ' particles increase,while theγ' lattice mismatch decreases. It is found that removing cobalt destabilizes MC carbide in the alloys so that t more grain boundaries M23C6 and M6 C carbide form during ageing treatment,and the amount of carbides increase.The results of X-ray diffr-action analysis illustrate that the M23C6 carbide disappears but μ-phase forms in the alloys with 14 and 20 pct.cobalt.Optical quantative analysis re-suits show that as cobalt content increases, the amount of twin increases, the morpholoy of twin boundary is changed.It is directly depended on the effect of cobalt morphloy on the stacking fault energy of matrices.
Abstract: Asymmetric rolling is a new method of plasticworking. Recently it is one of obvious features that the subject is made study of by a device (the chief about mechanics) with compressing and shearing deformation. From the viewpoint of stressing main factors and of simplifying the process, it is necessary and significant to use this device.But, with respect to the deformation features of sample on above device and the significancy of above compressing and shearing device for studying asymmetric rolling, it has rarely been considered. This paper shows the results of the compressing and shearing deformation with the Fringe technique and Spline function smoothing the experimental data. Experiment was made on compressing and shearing device simulating asymmetric rolling designed by ourselves.It is proved that analysing the deformation under the compressing and shearing state has important significance of theory and practice for revealing the nature of asymmetric rolling and choosing the appropriate type of plasticworking.
Abstract: Great progress has been made in the study of asynchronous rolling, but these studies are rather rough because the method used are not so suitable. It is difficult to describe the deformation in detail without the analysis of stress-strain fields. In this paper the roll force,specific pressure distribution, stress-strain-strainrate fields are obtained using RFEM. After analyzing the results, we obtained the following conclusions:In strip rolling the friction exerts a great influence on the pressure distribution.Comparing the asynchronous rolling with the normal rolling, the characteristics of them are different. The stress distribution in the deformation zone, and the direction and value of shear stress have been changed during asychronous rolling, this change makes the roll force decreasing, it is known as action of "cutting peak". The behaviour in asynchronous rolling(such as "bending"of rolled-piece etc.) is explained using the calculating results yet.
Abstract: In this paper, the numerical simulation of the coaxial swirling jet f low field in a cylindrical combustion chamber is introduced. Two vane-type swirlers with vane angle of 45°and 60° respectively arэ used in the experiments for study.The axial, radial and tangential velocity components of the flow field are measured with a five-hole pressure probe. A modified turbulent vorticity transport equation recently drived by o ne of the authors is used in carrying out this numerical simulation the predictions of the flow field are obtained by using ω-φ method and the turbulence K-e two equatipns model. The present investigation suggests that the calculation method intro-ueed by the authors is easy to handle for numerical simulation of strong-swirling and recirculating flows, therefore, this method is adequate for engineering purposes.
Abstract: Dearsenification of hot metal was studied on the bench scale with CaC2-CaF2 slag. Experiments were carried out in the Molybdenum-wound furnace under Ar atmosphere in the graphite crucible. Effects of temperature, composition and amount of slag, the initial As content and the Si content of hot metal on the degree of dearsenification were investigated. Thermodynamic analysis has shown that dearsenification in iron and steel melts is only accomplished under reducing conditions. It has been ascertained that it is impossible to carry out desulfurization, dephosphorization and dearsenifieation of hot metal with CaC2-CaF2 or CaO-CaF2 slag simultaneously.
Abstract: Hydrogen induced cracking (HIC) of austenitic stainless steel under Mode Ⅲ loading could occur during dynamic charging of hydrogen and the threshold stress intensity was KⅢH/KⅢX=0.62. The torsional angle, i·e·, the torsional plastic deformation, enlarged continuously during dynamic charging under a constant torque, which corresponded with increasing the external torque Continuously, until the specimen was twisted to failure. In the flat fracture surface of the delayed failure, however, there wera some secondary cracks propagating along the planes inclined at 45°. Stress corrosion cracking of austenitic stainless steel in a boiling MgCl2. so lution could occur under Mode Ⅲ loading and the threshold value was K Ⅲscc/K ⅢX=0.13. The cracks, however, initiate and propagate along the planes inclined at 45° instead of the original notched plane, where there is no shear stress but the maximum normal stress.
Abstract: IN this paper by means of potentialstatic method secondary passivity of the stainless steel 316 in NaCl solution,which occured while measuring anodic polarization curves is discussed. The range of Prazak's mechanism on secondary passivity is extended rom transpassive dissolution to pitting corrosion on the base of these experiments. this mechanism is then used in the discussion of secondary passivity in NaCl solution, The conclusion is that secondary passivity can only occu on certain conditions, i.e.on certain material, media and environment. The both mechanisms of the secondary passivity are like, though the process occurring in H2SO4 solution is the transpassive dissolution of the passive layer of stainless steel while the pitting corrosion of the same steel is taken place in NaCl solution.
Abstract: The effects of the twenty organic complexing agents on the absorbance of calcium in AAS by air-acetylene flame are examined. The atomic absorption signals for Ca are enhanced by all agents added except four ali-phatic acids,especially sulphosalicylic acid(SS) is the most remakable.The effects of SS on calcium absorption are investigated in detail. The mechanism of the enhancement and suppression effects are explored preliminarily. In the presence of 0.1M SS, with increasing the absorbance of Ca to about150%,the interference of some ions is suppressed partly, so that the linearity of calibration curves is improved. It is revealed that sulphosalicylic acid acts not only as an atomic absorption enhancer but also as an interference suppressor in the determination of calcium by air-acetylene flame AAS. The results obtained for artificial steel samples are satisfactory.
Abstract: A new PVC Au (111) ion-selective electrode is reported in this paper, The sensor membrane is composed of diantipyrylmethane (DAM)-Aucl4- (10 mg),dibutyl phthalate (DBP) (0.2ml), PVC (170mg). The electrode exhibited Nernstian response in the CAuCl4- ranging fnm 6×10-7 to 1×10-2M with a slope of 58±1mV/pM (22℃) in the medium 0.5M HC1. The limit of detection is 3.2×10-7M.The electrode that is used for three months continually remained good speciality. Trace gold in ores are collected and separated by foamed plastics, and are determined by this ion-selective electrode. The satisfactory results are obtained in determination of ores.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
