Abstract: According to the fact that there are some vacuoles and mosaic structures in meagre coal and anthracite in Yuxian-Xinggong coalfield of Henan province, a series of high temperature and pressure experiments were carried out on the fat coal from southern Pingdingshan coalfield. After heating at different temperature under pressure 1.5 kbar for one week, the vitrinites have been changed to some extent. The following conclusions are drawn on the basis of the experiments:vacuoles in coal form from 250-350℃, mosaic structures 350-500℃, anisotropy increases slightly when temperature is elevated. And comparing with the coal in nature, the reflectance of the heated samples with vacuoles and mosaic structures is evidently lower.
Abstract: Cu-Ni-Cr-Mn cast steel is a kind of low alloyed high tensile steel, which is used in ship industry. It often become worthless due to the crack defect. An investigation on the particularity and the causes of crack formation in this steel has been carried out with optical microscope, scanning electric microscope, microprobe and Auger spectroscope. Results show that the crack is a intergranular brittle fracture caused by eutectic phases γ Fe+ (Fe, Cr, Mn) 3C precipiting at the austinite grain boundaries because of solidification microsegregation. With broadening solidification interval and decreasing the partition coefficient, caused by arbon, segregation index Cmax/Cmin of the alloying element, such as Cr. ncrease consequently In presence of sulfur, the segregation index of Cr is increased by sulphide formation. In order to prevent the precipitation ofeUtectic phase and eliminate the crack,the concentration of carbon and sulfurmust be decreased and the increase of cooling rateof castings will be helpful.
Abstract: The Saturation Level of Carbon (A) is defined as Cs/Cp.Cs-carbon content of steel; Cp-a parameter of carbon in proportion to the contents of carbide forming elements in steel, presented by G.Steven[2].The relationship between three factors are established in this paper, i.e. saturation level of carbon (A), quenching temperature (TQ) and secondary hardness (HRCT).This work confirms that the value of A can be used as a composition parameter to evaluate the secondary hardening ability of steel, and that A can also be used to choice the quenching temperature of individual heat for certain object of selected secondary hardness. Furthermore, the influence of several alloying elements on secondary hardening ability of steels containing W12, Mo3, Cr4 and V3 had been investigated, and the interchange ability between elements in high speed steel had also been discussed.
Abstract: This paper dealt with the effect of dwell time at max. stress on the fatigue-creep interaction behavior of superalloy ECD. The results indicated that the cycle number of fracture decreased as the time of dwell at max. stress increased, However, the shape of interaction curve was not changed.The dwell at max stress intensified the creep effect resulting in the expansion of the interaction regions with predominant creep fracture (i, e.CC, CFC regions), and the FC mixed region moved to the area with high alternative stress, even the FCC region appeared instead of CFF region. On the basis of macro-microanalysis of fracture the fatigue-creep interaction map for the tests with dwell time was constructed.It provided the basic information of fracture mechanisms and fracture cycles for the tests with hold time. However, the influence of hold time on the total rupture time was different:the total rupture time was increased for tests in F region, and for tests in C region it was decreased till a saturated value which is larger than that for the pure creep test at max. stress.
Abstract: The phases of tungsten blue oxides produced by the light reduction of ammonium paratungstatc (APT) with hydrogen vary with the reduction temperature. The product reduced at 275℃ is noncrystalline ammonium tungsten bronze (ATB) and at 325℃ is crystalline ATB. The content of ATB in the reduced product gradually decreases with increasing the reduction temperature. There is no ATB in the product reduced at 575℃. The phase W20O58 appears above 325℃. Its content increases with the reduction temperature and reaches its maximum at 525℃, and then it decreases sharply above 525℃. The phases WO2 and β-W appear at 525℃. The phase α-W appears between 525℃and 575℃.The phases of the products reduced at 525-575℃change remarkably from ATB andW20O58 to WO2, β-W and α-W. The quantitative relationship between the phases of tungsten blue oxide and the reduction temperature of APT has been studied in this paper. When WO3 is lightly reduced by hydrogen, W20O58 appears at certain temperature between 425℃ and 525℃; W18O49 appears between 475℃ and 525℃; A little β-W appears at 625℃. When the reduction temperature is higher than 625℃, the content of α-W in the reduction product rapidly increases with the reduction temperature. When APT is lightly reduced by hydrogen, β-W can be obtained at a very wide temperature range, compared with WO3also reduced by hydrogen. The content of β-W obtained from APT is more than that obtained from WO3. When APT is reduced by hydrogen at 450℃ for five minutes, the product is crystalline ATB.If the reduction time is longer than five minutes, W20O58 phase will appear. The content of W20O58 increases gradually with the reduction time and at the same time the content of ATB decreases gradually. When the reduction of APT with hydrogen is carried out at 450℃, the relationship between the phases of tungsten blue oxide and the reduction time has been experimentally investigated in this article.
Abstract: In order to reduce the Production cost for making Nd-Fe-B magnets, which has record magnetic Properties, a new production technology, reduction-diffusion process, was studied.In which Nd2O3 is used as start ing material to work out Nd-Fe-B permanent magnets directly. The effecte of the contents of Nd, as basic constituent, and Al, Co, as substitute constituents, and some technologic factors on permanent magnetic properties are studied. The practical permanent magnets of Nd-Fe-B and Nd-Fe-Co-B are made out.The optimum magnetic properties are Br=13.7 T,MHc=0. 46 MA/m, (BH)max=286.5 KJ/m3 The experimental result shows that oxygen is harmful to magnet properties, so it must be controlled below 0.8%.
Abstract: Cubic Boron Nitride (CBN) cutting tools have been found to exhibit brittle fracture serious during machining alloy cast iron(HRc 58).This pa per introduces the results of metal cutting and photoelastic tests performed to determine optimum rake angle, in accordance with the stresas distribution analyzed by using the theory of elasticity.The theoretical analysis is basical agreement with the experimental results.The maximum stress point moves to compressive stress, depended on the experimental data, when negative rake angle substituted for positive one and other cutting conditions kept fixed. Besides, tool life is longer and fracture of tools is improved as well.On stress analysis and experiments, the optimum rake angle is defined and necessity of negative first face land has been discussed briefly for brittle tools.
Abstract: It is summarized that a microcomputer M24 is used for English auxiliary education,defined as the English Automatic Test Making Sustem (ATMS). It describes elemental principle of ATMS and gives out some main frameworks.
Abstract: The behaviour of grain boundary segregation and precipitation of boron in low carbon MO-B steels (with or without Mn) and Fe-30%Ni (B) alloys during isothermal holding have been investigated with Particle Tracking Au-toradiography (PTA).Specimens heated to 1350 or 120013 are quenched and isothermally held at 550-1000℃ for different periods.It is shown that the nonequilibrium grain boundary segregation of boron occurs as a dynamic Process and the magnitude of nonequilibrium grain boundary segregation of boron may be many times of that of equilibrium segregation. After cooling, the boron segregation at grain boundaries,on isothermal holding at a relatively high temperature, probably bring there by complex of boron atoms with supersaturated vacances, and increases with time to the annihilation of vacancies,then it becomes supersaturated with respect to equilibrium segregation concentration. Thus it decrease by diffusing back into the grain interior, giving a peak On the segregaton degree-isothermal holding time curve.The height and position of the peak depend on the initial heating and subsequent holding temperature.On the other hand,when the holding temperature is low, the nonequilibriumly segregated boron becomes supersaturating and will be Precipitated at the grain boundaries, owing to the difficulty in the back diffusion at low temperature. Thus a curve increasing at the first stage and then reaching a steady segregation (including Precipitated boron) is given.
Abstract: A math method calculating the surface tension, the volume of liquid drop and the contact angle of a liquid drop on a level substrate is worked out in this paper. The method is carried out by computer according to the projection sizes of the liquid drop which was measured by the Chatel's method. The BASIC program fitting in single board computer type ZX-48 is Compiled. The surface tensions of Hg, Cu, Cu (40%)-Sb, Sb have been calculated with this program and the feasibility and the reliability of this method have been proved.
Abstract: The LiCl-KCl-BaCl2-SrCl2quaternary system is of interest as a possible lectrolyte in the electroplating and electrochemical alloying of molten salt Up to now the phase diagram of the quaternary system and one of its subsystems LiCl-BaCl2-SrCl2 have not been measured,To obtain a better basis or understanding the LiCl-BaCl2-SrCl2-KCl system it is necessary to learn about the unknown ternary LiCl-BaCl2-BrCl2 system. In this paper the phase diagram of the LiCl-BaCl2-SrCl2 system has been measured and the liquidus curves of its three subsystems have been checked by the DTA method.The binary systems LiCl-BaCl2 and LiCl-SrCl2 are simple eutectic ones with the eutectic points E1 and E2 in 526℃, 33 mol%Ba-Cl2, 67mol%LiCl and 489℃, 38mol%SrCl2, 62mol%LiCl, respectively. The binary system BaCl2-SrCl2 is a continuous solid solution with a minimum temperature in 852℃, 35mol%BaCl2, 65mol%SrCl2. According to the present measurements of three subsystems and three ternary polythermal projections the phase diagram of LiCl-BaCl2-SrCl2at 1 atmosphere is drawn in Fig. 8. The uncertainty in the liquidus temperatures is estimated to be±6K. The ternary system LiCl-BaCl2-SrCl2 has a curve Ei-E-E2 running betweem binary eutectics E1 and E2 with a minimum temperature in E (482℃,58.4 mol%LiCl, 15.8mol%BaCl2 and 25.8mol%SrCl2). The curve E1-E-E2 divided the ternary system into two liquidus surfaces, the LiCl liquidus surface and the BaCl2-SrCl2 solid soluton one. It is noted that the minimum temperature in the LICl-BaCl2-SrCl 2 system is only a little lower than 489℃, the eutectic temperature of the LiCl-SrCl2 system.
Abstract: The pitting corrosion of the fresh stainless steel surface have been studied. The pitting critical potential of the fresh surface is lower than that of the surface covered by passive film. The pits on the fresh surface are primarily formed on grain boundaries and on inclusions. The morphology of pits are sharp streak pattern. According to the model of reaction steps of bare surface with chloride medium proposed by authors,the cours in which pits are formed on bare surface and the meaning of pit characteristic potentials have been discussed.
Abstract: The biaxial tension device is presented which can research the equibiaxial tension low cycle fatigue tests with uniaxial hydraulic fatigue testing machine and reference influencing factors are dicussed The tests make use of the low cycle fatigue test machine of loot. The device has been sustained fatigue loading about one million times concluding subjected alternative load amplitude of 5.5t about two hundred thousands times. These components which are assemblies of the device are good in use and suitable for requirement.The cruciform specimens for biaxial fatigue tests has been cracked successfully in internal hole. The primary results are obtained on the device to study impeller material properties under the condition of super velocity. The device is suitable to studying the low fatigue properties under concentration of plane stress. It is used to study the fatigue crack growth under biaxial load when it make use of high and intermediate cycle fatigue hydraulic fatigue testing machine. This paper pointed out that the device will require further improvement.
Abstract: Using Lagrange the second type equation of mechanics to set up computation of robot dynamics is an effective method that used frequently. But it is quite acomplicated one.It must be simplified being introduced differential translation and differential rotation by pual,and an approximate solution is obtained at last. In this paper,on the base of the Lagrange equation of the dynamics in the computation method,the concept of inner product in the linear space can be introduced and the law of inner product can be obtained too. The quite a simplicated equation can be apply to compute the dynamic equation of robot-1 in our university
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
