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English for Material Science and Engineering Ex.1

In order to improve the efficiency of existing precipitators, research has been done in Germany into conditioning the waste gas by injecting SO3 . The research has indicated that an injection of about 20 ppm (volume basis) should be sufficient to get the emission level down to below 50 mg/Nm3 which will be the statutory requirement in

Germany (TA-Luft) from 1994. Similar requirements may flow on to the rest of Europe. Lungen etal. Estimated that to comply with the new regulations, gas cleaning could make up 35% of the cost of a new sinter plant. Ex. 2

There is no doubt that the blast furnace will remain the mainstay of iron production although problems with the quantity or cost and quality of coke, as discussed earlier, may have some effect. The first tendency will be further elimination of small, inefficient units and their partial replacement by large furnaces. Recall that the average production of the 263 operating blast furnaces in the

United States in 1960 was only 860 tons/day, while soon it is expected to reach 2,350 tons/day from only 150 units. Ex. 3

The converter technology can be characterized by two processes which occur continuously and in parallel in the converter bath:(a) intensive supply of oxygen and (b) slag formation. The melting process in an oxygen converter may be divided into two periods: in the first period, the concentrations of impurities (C, Si, Mn, P) in the bath are stilt rather high; in the second period, there remain almost no impurities in the bath. During the first period, the

intensity rate of oxidation of impurities is determined by the rate of oxygen supply. With a higher rate of blowing, impurities are oxidized more quickly. Thus, it may be said that the first period is limited by external diffusion. Ex. 4

The metallurgical differences between the basic and acid processes indicate that none of the advantages of one process over the other is sufficient to justify the selection of one or the other process without full consideration of all factors. Many of these factors have already been discussed, and explain the present preference for the

basic process in the majority of applications. The next two subsections more fully describe the processes involved in basic-and acid-lined electric-arc furnaces. Ex. 5

The maximum powder injection rate is 150kg per minute. By making the injection while under vacuum, the flux

powder can be injected with a lower pressure drop, larger solid-to-gas ratio and faster speed than a conventional ladle injection. The nozzles can last as long as the lower vessel refractories and they can be utilized maintenance free throughout one campaign. Ex. 6

At the casting machine, two steps are involved in

transferring the liquid steel from the ladle to the molds. Liquid steel is first fed continuously or semi-continuously from the ladle to the tundish which, in turn, distributes the liquid steel through nozzles in a continuous flow to the individual molds. Metal flow through the ladle nozzle into the tundish is controlled by a stopper rod mechanism or by hydraulically or electrically controlled slide-gate systems.