Abstract: The relation between atmospheric corrosion resistance and the composition and microstructure of scales of weathering steel is discussed The scale of cold-rolled plates consists of lepidocrocites,iron hydroxides and dispersed iron particles. Comparing with that of carbon steel, the atmospheric resistance of weathering steel is very good, as lepidocrocites grow just adjacent to iron matrix. For the scales of carbon steel the iron matrix was not protected fron atmospheric corrosion for iron hydroxide was made as "harbour" between scale and metal. Magnetites and hematites were formed on the surface of hot-rolled plates. The scale with developed magnetite and a sawtooth structure connected with matrix coule provide a good protection to the matrix.The rare earth added made the steel cleaner and inclusions more g ranular. It seems that rare earth in the steel inhibited the decomposition of magnetite under the reaction with water and air. The steel treated by rare earth had better atmospheric corrosion resistance.
Abstract: In order to understand the air oxidation of molten steel during teeming the model experiments on the oxygen absorption of pouring stream were carried out.A theoretical formula of gas absorption is given. The results show that the content of oxygen came from air is calculated by using the relationship between the absorption rate of[N] and [O].
Abstract: A mathematical model of two-dimensional unsteady solidification heat transfer has been developed to simulate the square billiet continuous casting.Due to the ratio of length to cross section of the billets is about 102, an integral on line is used to complate the simulation with a common computer (IBM-PC).As a result, application of this model to engineering has been made satisfactory.
Abstract: The morphologies and crystallographic features of bainite/austenite interface structure formed isothermally in an Fe-C-Si-Mn-Mo alloy have been studied by means of STEM(a Vacuum Generators HB5).These observations are interpreted in terms of current ideas concerning the structure migration characteristics of FCC/BCC interfaces.It is concluded that the bainite/austenite interface is probably closely similar to Widmanstatten ferrite described by Rigsbee and Aaronson. The differentia between bainite and lath martensite,Widmanstatten ferrite interface structure and migration mechanism, are discussed.
Abstract: The maraging alloys series containing copper but cobalt free have been investigated. It was found that during solid solution treatment, the temperature for the second phase Fe2Mo dissolving completely could not lower than 950℃, and for the alloys containing 6% Mo or less,the recrystallization treatment temperature for high temperature reversed auste-nite was 950℃.For the alloys containing more than 6% Mo, the recrystallization treatment temperature raised with increasing Mo%.Under opi-tical microscopy the morphology after recrystallization was rectangular block shape while it was fine packet shape before recrystallization. After solid solution and recrystallization treatments at 950℃ and aging at 540℃ for 3 h, the general mechanical properties of Fe-Nil5-Mo6-Cu4-Ti alloy were as follow: σb=1893.3MPa, σ0.2=1784.5MPa.δ5=9.5%, (ψ)=46%,HRC=52.5.
Abstract: Grain size and magnesium effects on stress rupture and notched cyclic stress rupture properties have been investigated.A minute amount addition of Mg and grain refinement can successfully improve high temperature stress rupture notch sensitivity.The failure lives of iron-nickel base superalloy GH169 with high temperature stress rupture notch sensitivity or low stress rupture ductility decrease dramatically at creep and fati-que interaction conditions. The notched cyclic stress rupture lives are emarkably enhanced by addition microalloying of magnesium and grain refinement even the presence of duplex structure with certain of small grains and large grains.
Abstract: The dynamics of phase transformation of the ternary alloy which consists of 69.40wt% Mn, 29.86wt%Al, 0.58wt% C, and constant temperature for three types of Mn-Al-C have been researched.The critical temperature of base transformation of the alloys were measured by DTA.It indicated that the transformation temperature for these alloy varied with the different compositions.In the sub-eutectic composition, phase decomposed, γ-Phase precipitated first. But in over-eutectic composition,β-Mn phase precipitated from τ-phase.When the content of C was constant,the stability of τ-phase decreased with the increase of Mn content.
Abstract: The effect of additional some elements on the structure and electric properties of internal oxidized Ag-4-8.5 wt% Zn alloys has been investis gated. Three kinds of experiments has been done, e. g. (1) adding Te, Al, and Ni; (2) adding Te, In and Sn; (3) adding Al and Ni. Both cases (1) and(2) have shown the improvement of the structure of oxides, but the case (3) has not. The results indicate that adding a small amount of available lements and controlling the content of ZnO can improve the such performance of switch in electric contact materials as to gain high resistance to welding adhesion, high resistance to erosion and low contact resis-etance.
Abstract: Rigid-plastic Finite Element Method (RFEM) is non-linear,so it is necessary to give a good initial velocity field and to ensure for evaluation. Ori K. I. proposed "function G" to determine the initial velocity field, but he didn't make a through analysis. Newton-Raphson method is generally used in RFEM, but it has some drawbacks: 1) it is possible to deverge during itterating;and 2) the step is difficult to determine, so that the calculating time is increased. In order to Overcome the drawbacks above mentioned,we advanced a new method-penality method of function G and carried on a detail analysis. As iteration method the Gill-Murrary mothod (improved Newton method) is used instead of Newton-Raphson method and the linear search is made by 0.618 method. The RFEM program is worked out for calculating parameters of plastic working processes. The calculating results obtained in studying roll-ing process coincide with the experimental data. The research shows clearly that the improved RFEM method is satisfactory for analysing plastic working problems.
Abstract: In order to eliminate the shortcomings of onerousness of calculation and of too many memory spaces needed in the practical calculation of establishing the heat transfer mathematical model of flame furnace by the zone method, "furnace section imaginary area" zone method has been developed in this paper. The predicated calculation of two oil-fired continuous reheating furnaces has been carried out using this method. The radiant direct exchange areas have been solved by applying Dunkle's concept of geometric mean beam length of travel. The solution of the non-linear zone energy coupled equations is obtained by Broyden method. The calculating results show that in comparison with the conventional zone method, "furnace section imaginary area" zone method has the ad-vantage of simplicity, more accuracy, rapid convengency and occupying less memory space.
Abstract: An new optimimzation algorithm and program of mixed discrete variables are described in this paper. This program applied to solve the optimal problems that involves all or some discrete, integer and continuous variables, and give normalized optimal solution in keeping with engineering requirements. This algorithm and program has stood the test of 30 problems of engineering design and mathematics. Tne results indicate that the composite algorithm and program have, with some of different reseach function in superior both in reliabilty and efficiency. The reliablity of soultion is 100% according to accuracy under 0.001 of objective function vaule. Two examples used in mechanical engieering are given.
Abstract: This paper analyses elastic shell-bending problems by means of the least-square collocation method.The mixed method of MWR has been used in which the trial function-a double power series with unknown coefficients can meet the requirements of neither the differential equation of deflection in the interior of shell nor the boundary conditions. The computational results of cylindrical shells with 4 hinged edges show the errors less than 1.5 percent as compared with results of classical solutions,When analysing cantilever plate problems-a special case of cantilever cylindrical shell, the errors are also small. The calculation of all shell-bending problems can be generaly programmed by means of the method presented in this paper.
Abstract: This paper describes the method of constructing the model for thyri-stor device which used for power electric circuits and presents a nonlinear lumped equivalent circuit model for it. In modelling of the thyristors, it is based on the analog of the physical process of carriers moyement inside the device. The following facts are also analysed: (1) Injection of minority carriers in device. (2) Generation and recombination of carriers in space charge region. (3) The effects due to the avalanche multiplication basewidth modulation, and charge storage. The mathematical formulas describing these physical process are replaced by corresponding nonlinear elements and an equivalent circuit model for a thyristor is formed which consists of nonlinear resistors, nonlinear capacitors and controlled current sources. Using this model, it is possible to analyse the dynamic nonlinear characteristics of thyristor's ON-OFF process.
Abstract: On the basis of macroeconomy of China, the paper deals with the methods of mathematics economic model-its construction, development and application. In addition to the establishment of the model for money demand forecast and supply control. The author probes into the principles of the model's mathematic nature, structure decomposing and police implication simulation and work out all the algorithms and computer software concerned. All the achivement above can serve as a powerful auxiliary tool for the decision making of the macroeconomy of pur country.
Abstract: The equilibrium of gaseous CO-CO2 mixture with liquid iron-Niobium-Carbon alloys and NbO2(s) contained in Al2O3 or ZrO2 crucible is discribed. It shows that the deposition of carbon is inevitable in the low temperature zone(from 1073 to 1273K). The equilibrium partial pressure of oxygen in gaseous on the surface of the melt has been determined with the solid electrolyte cell.The oxide in equilibrium with the niobium in the melt is considered to be NbO2 (s). The equilibrium constant for the reaction[Nb] + O2=NbO2 (s)at 1823K is:K=6.31×1010 therefore the standard free energy is △G°=-377150 (J/mol) The interaction coefficients of activity evaluated, are ${\rm{e}}\frac{{\rm{C}}}{{{\rm{Nb}}}}$=-0.74;${\rm{e}}\frac{{\rm{C}}}{{{\rm{Nb}}}}$=-0.092.
Abstract: New formulae have been derived for the void fraction and density ofthe two phase regions in flow fields of the liquid bath in bottom blowingsystems.Certain improvements have been proceeded to them odels developedby previous investigators. The resultant predictions have been shown insatisfactory agreements with the experimental data in present study.
Abstract: After analyzing the factors such as the presence of the contaminants containing free chloride, the presence of the stresses, the incomplete Au-plating on the Kovar and the entrance of hydrogen into the Kovar, it is found that the discontinuity of cathodic plating is bound to create the galvanic corrosion in the presence of the appropriate electrolyte, and the extent of corrosion of substrate Kovar exposed at such discontinuities depends on Cl-concentration and pH, etc. Especially when the pores in the plating exceed a certain critical diametre, it is possible to form constantly growing pitting, which is the most harmful. Thus in the presence of applied stress, remained stress or wedging action of corrosion product it can lead to scc. The mechanism of corrosion fracture of Au-plated Kovar transistor leads caused by the coordinated actions of galvanic corrosion, pitting (or crevice corrosion) and scc can better explain the facts observed in the practice. The ways to improve the resistance to corrosion of Au-plated Kovar transistor leads are also proposed.
Abstract: The relationship between cathode potential with Ni-P amorphous alloy formed during the process of electrolytic deposition was studied. The result indicates that it is often formed at the terrace of cathode polarization curve. The effect of electroplating conditions on forming Ni-P amorphous alloy was also researched.When the content of H3PO3 in the bath amounts to a certain ratio an amorphous deposition can be easily formed at higher temperature, lower pH and proper current density The higher content of H3PO3 in bath, the higher the content of P in deposit.When the content of P in deposit exceeds 9% the amorphous are formed. The resistance to corrosion for the deposition increases with an increase in phosphor content. The effect of annealed temperature on the properties of Ni-P amorphous was examined.
Abstract: The paper deals with the decoupling and stable decoupling of non-square systems on the state feedback and input transformation. Using the specific property of the matrix on the state feedback and input transformation, we give necessary and sufficient condition for the existence of solutions to the decoupling problem. Moreover by utilizing the property of the Yokoyama standard patten, we obtained necessary and sufficient conditions for the existence of solutions to the stable decoupling problem of non-square systems.
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
