Influence of Oxidation Temperature and Cr Content on the Adhesion and Microstructure of Scale on Low Cr Steels

Descalability of steels during hot rolling processes is essential in order to maintain the surface quality of steel products, because the remaining scale can be impressed into the steel, producing surface defects. Therefore, a quantitative evaluation of scale adhesion at high temperature is needed in order to find suitable heating conditions for hot rolling processes that promote the formation of scale that easily detach. Round bar shape specimens of low Cr steels were oxidized in a fuel combustion environment, and then compressed at high temperature to detach the scale. The area fraction of the remaining scale was evaluated by image analysis. Under a thick outer oxide scale, a thin continuous inner oxide layer, which consisted of Cr and Si oxides, strongly adhered to the substrate, resulting in poor descalability. On the other hand, if this inner scale changed into a discontinuous layer with a porous FeO layer beneath, the descalability improved. It was found that scales with greater descalability formed on steels containing less Cr and for oxidation at higher temperatures.     

The conversion of methane with silica-supported platinum catalysts: the effect of catalyst preparation method and platinum particle size

The particle size distribution of platinum in silica prepared by the complexing agent-assisted sol–gel method and impregnation method and also in MCM-41 has been compared and its influence on the product distribution in the non-oxidative dehydrogenation of methane has been investigated. The sol–gel method gives a narrow range of platinum particle size distribution compared to the impregnation method. It was found that as the particle size increases, the selectivity for the higher hydrocarbons increases though the yield decreases.     

商业车辆第二代EE传动自动机械变速箱(AMT)的优越性

自动机械变速箱在1985年起由Hino开发的EE－传动,其特点是气动冲程控制、油喷射螺旋弹簧型离合器[1][2]^*。由于在日本自动变速器（AT）市场扩大而为城市大客车建造了该装置。本文介绍了装于中型货车的第二代EE传动,其特微是采用液压控制、油喷射离合器。该装置直接通过离合器片压力使起动平稳。同时能快速换档,变速不带离合冲击而使压力降低。它将在市场与1990年出现的完善的电子控制（ECT）具有变扭器的自动变速器（AT）相竞争。在日本商业车辆的自动变速器开始发展于1990年前半期。1985年Hino EE传动投放市场。同时期在日本自动变速器的轿车超过总轿车数量的一半达到57％。应为AT用于商业车辆准备市场。已经扩大市场主要在城市大客车中采用EE传动。许多公共运输服务的客户支持把AT延伸至自动机械变速器（AMT）[3]。在这种意义上,装有EE传动的城市客车仍占主导地位。在1987年,另外的制造商的一种AMT投放市场。伴随着由于较低的燃油经济性使液压自动变速器（HAT）不能实现商业用途。随着大众化的AT轿车采用电子控制自动变速器（ECT）的出现而快速发展的同时,一种真正的商业车辆的AT时代当用于商业车辆的HAT也用电子控制改进时,HAT和AMT竞争共存。HAT和AMT的优点将在竞争中显示。Hino EE传动的第2代的目的在于造成商业车辆的AT时代即将到。本文概括了该装置的市场状况,新型装置的要求,结构、操作运行、新装置的性能控制软件以及今后的建议。     

Effect of Organic Nitrogen Sources on Raw Starch‐Digesting Glucoamylase Production of Rhizopus sp. MKU 40

In a liquid cultivation of Rhizopus sp. MKU 40, supplementation of the medium with 1.5% (w/v) organic nitrogen sources (neopeptone, casein from milk, and meat extract) had a slightly positive effect on glucoamylase (GA) (EC 3.2.1.3) activity compared with the medium lacking organic nitrogen sources. The addition of organic nitrogen sources induced production of protease. Supplementation of the medium with 1.5% (w/v) organic nitrogen sources resulted in an acid and neutral protease activity of 11 — 25 U/mL and 12 — 20 U/mL, respectively. The co‐existence of GA‐I [a highly raw starch‐digesting glucoamylase (RSDG)] and protease in the same medium leads to the production of Ga‐II (an extremely weak RSDG) from GA‐I. As a result the RSDG activity in the medium decreases. Raw starch adsorption rates of a medium without organic nitrogen sources were 100%, because the medium contained only GA‐I. In contrast, the media supplemented with organic nitrogen sources had low starch adsorption rates because the media contained both GA‐I and GA‐II. The results presented in this paper indicate that supplementation of the culture medium of Rhizopus strains with organic nitrogen sources negatively affects GA‐I production.     

Role of Boundary Strengthening on Prevention of Type IV Failure in High Cr Ferritic Heat-Resistant Steels

Microstructure evolution of newly developed 9Cr-3W-3Co-V, Nb steel with boron addition (B steel) has been analyzed during HAZ thermal cycle at the peak temperature of around A_c3 (A_c3 HAZ) and post-weld heat treatment (PWHT) to elucidate the prevention mechanism of type IV failure by boron addition. It was found that enhancement of the boundary strengthening by precipitates is the main reason for prevention of type IV failure by boron addition. In B steel HAZ, original austenite is reconstituted through martensitic α to γ reverse transformation during the heating and original martensite is reconstituted through martensitic transformation during cooling of the A_c3 HAZ thermal cycle. This process allows M₂₃C₆ carbides to precipitate at the prior austenite grain (PAG) and block boundaries during PWHT even if the chemical segregation of carbide forming elements exists. The effect of boundary strengthening on the creep property has also been investigated. Microstructure evolution during creep was compared among Gr.92 with different A_c3 HAZ microstructures prepared by three kinds of heat treatments and B steel. The results revealed that both the boundary length and kernel average misorientation value decreased in all samples during creep. However, this process occurred very rapidly in A_c3 HAZ simulated Gr.92, whereas it was significantly retarded in the other samples with sufficient boundary strengthening by precipitates. This result confirms that the precipitates formed at PAG and block boundaries play the most important role to stabilize the microstructure of A_c3 HAZ simulated samples during creep and prolong the creep life.     

Application of integrated computational chemistry system to the design of inorganic membranes

Today inorganic membranes attract a lot of interest as a growing field. Main focus of those activities is on the development of membrane materials, which can offer high permselectivities with acceptable high permeances. The need for high permselectivity beyond those limited by Knudsen flow requires the estimation of the factors, which determine the permselectivity. Plausible theoretical models based on physical or chemical reasoning is desirable to guide systematic development efforts for designing next generation inorganic membranes. Here we reviewed our attempts to generate theoretical models based on the molecular dynamics method for this purpose. As a first attempt, simulation was performed at specific conditions where the Knudsen theory can be applied and can be reproduced well by our simulation methodology. Molecular dynamics simulation at 373 K of the permeation of iso- and n-butanes through ZSM-5 type silicalite membrane are presented. After 200 ps of simulation time the permeation of n-butane was observed whereas the permeation of iso-butane was not observed. The calculated permeability of n-butane, which is close to experimental data, is also presented. A study on the affinity membrane for the separation of CO₂ at high temperature is presented and the prospect of permselectivity of CO₂ is demonstrated.     

用流动可视化技术研究混合器内研究简报流场及混合效果

引言 不同流体的混合是化工、生物制品、食品工业等工艺过程中一道重要的工序,仅依靠流体在输送过程中的自然湍流扩散不能进行有效的混合,因此必须使用混合器,使液体在短时间内获得均匀的特性,达到满意的混合效果,并使损失的能量较小.不同行业由于介质性能和混合要求不同,相应混合器的结构也不同.通常国内外多采用经验类比法设计混合器,用取样分析法检验混合效果.随着新技术的发展,深入研究流体混合机理对于高效节能混合器的设计具有重要意义.     

MOISTURE EVAPORATION AND MIGRATION IN THIN POROUS PACKED BED INFLUENCED BY AMBIENT AND OPERATING CONDITIONS

The present paper investigates moisture migration in a thin porous bed filled with unconsolidated sand, unsaturated with water, and examines its cooling effect by water evaporation when used as a cooling device for room air-conditioning. An analytical model has been developed to simulate heat and moisture transport phenomena numerically and calculate the evaporation rate of water on which its cooling performance is dependent. For the case of a horizontal thin bed problem, with very small height and a relatively larger surface that is exposed to atmosphere air, one-dimensional, steady-state computation results have been obtained by focusing on the influence of ambient and operating conditions on the physical quantity fields in the porous packed bed. © 1997 by John Wiley & Sons, Ltd.     

Effect of Longer Heating Time on Depolymerization of Low Moisturized Starches

Low moisturized potato, sweet potato, corn and wheat starches were treated with a flow tester under heated and heated-sheared conditions. The starches depolymerized into lower molecule by longer heating time at 150°C. With an increase in heating time, the cold water solubility of starches increased and the degree of depolymerization progressed. Comparing heated treatment with longer heating time and heated-sheared treatment, 60—120min heating was necessary for heated specimens to obtain similar cold water solubility and degree of depolymerization of heated-sheared specimens. These results conducted that heated-sheared treatment strongly promoted the depolymerization of low moist starches under high temperature as compared with heated treatment only. From the results of λ_max of iodine-polysaccharide complex, there was almost same molecular state between heated for longer time and heated-sheared treatment. Both amylose and amylopectin depolymerized into lower molecule by both treatments.