本科毕业论文---连铸的发展外文翻译.doc
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1、The Development of Continuous Casting【连铸】中英文对照Continuous CastingFrom the Making, Shaping and Treating of Steel by William,McGrawHill Companies, Inc., 2002The Development of Continuous CastingContinuous casting was developed very rapidly after the Second World War. Steel-producers arc today generally
2、 convinced that continuous casting is at least as economical as ingot production and can match the quality of the latter across much of the production spectrum for high-quality steels. Continual development of the technique aimed at improved steel characteristics is leading to increasing adoption of
3、 the process in works producing special high-grade steels. The reasons for continuous-casting systems are: (1) lower investment outlay compared with that for a blooming train (mini-steelworks); (2) about 10% more productivity than with conventional ingot-casting; (3) high degree of consistency of st
4、eel composition along the whole length of the strand; better core quality, especially with flat strands; high inherent surface quality, leading to savings on an otherwise expensive surfacing process; (4) high degree of automation; (5) friendlier to the environment; (6) better working conditions. Typ
5、es of Installation The first continuous-casting plants were aligned vertically; however, with larger cross-sections, increasing strand-length, and, above all, with increasing pouring-rates this type of construction leads to unreasonable building-heights. These factors also lead to a considerable inc
6、rease in the length of the liquid phase which has metallurgical effects. The length of the liquid phase in a continuously-cast strand is determined by the following formula: L=D2/4x2Vc Where D =strand thickness (mm) x = solidification characteristic (mm / min1/2) These values amount to 2633 for the
7、whole cooling length. Vc = casting rate (m /min) Efforts to reduce building-height first led to continuous-casting systems in which molten metal passed into a vertical mould and solidified completely before being bent or where the strand has been in the liquid phase and later to the bow-type install
8、ation which has a curved mould and is the system most used today. Vertical systems and those in which the strand is bent when completely solidified have long straight liquid phases and can lead to unacceptably high capital outlay. However, these systems have metallurgical advantages from the point o
9、f view of maintenance. A vertical system in which the strand is bent while still in the liquid phase has the advantage that the building need not be as tall as when the strand is bent after solidification; however, the liquid-phase bending system requires higher initial outlay and greater maintenanc
10、e costs. The bow-type system represents a compromise between the costs of capital outlay and of maintenance and what can be achieved metallurgic ally. Continuous-casting is suitable for the production of almost any cross-section imaginable; square, rectangular, polygonal, round, and oval sections ar
11、e all available. There are also some instances of preliminary sections for tubes and slabs, blooms, and billets. Sections with a breadth /thickness ratio greater than 1.6 are normally described as slabs. Billet-machines produce square or nearly-square, round, or polygonal cross-sections up to 160mm
12、across. Larger sections and those with a breadth /thickness ratio less than 1.6 are cast in bloom-machines. Billets nowadays normally produced in this way range from 80 x80 to 300 x300 mm, and slabs are 50 - 350mm thick and 300 - 2500 mm wide. Continuous-casting output-rates have risen sharply, espe
13、cially in the last few years. This is essentially because of increase in the breadth of the strand and in casting rate. The following outputs have been exceeded per section per minute: slabs 5 tones blooms 1 tones billets 350 kg Finally, we should mention horizontal continuous-casting systems which
14、are already used for non-ferrous metals and cast iron and which are being further developed for steel. R. Thieimann and R. Steffen have produced a comprehensive report about the state of development of horizontal continuous-casting systems for producing billets from unalloyed and alloy steels. Horiz
15、ontal continuous-casting systems have three important advantages over conventional continuous-casting system: (1) low height and cost of building; (2) simple means of protecting the melt against reoxidatioin; (3) no strand deformation because the ferrostatic pressure is much lower. Casting Technique
16、 Molten steel is poured from a casting ladle via a tundish into an open water-cooled copper mould. At first the bottom of the mould is closed off by a starting-bar, which then leads transport of the hot strand from the mould into the continuous withdrawing rolls. The strand, which starts to solidify
17、 in the mould, passes through a cooling system before it finally reaches the withdrawing rolls, whereupon the hot strand takes over transport. The starting-bar is separated from the hot strand before or after it reaches the parting device. The latter, which may either be a flame-cutter or hot shears
18、, moves at the same rate as the hot strand and cuts it into the lengths required. The purpose of the tundish is to feed a defined quantity of molten steel into one or more moulds. This can be done by using nozzles controlled by stoppers, slide-gates, or other means. The tundish may initially be cold
19、, warm, or hot according to the nature of its refractory lining. Where difficult steels are processed the pouring stream is protected against oxidation between the submerged boxes. The mould not only forms the strand section but also extracts a defined quantity of heat, so that the strand shell is s
20、trong enough for transport by the time it reaches the mould-outlet. The mould may be made from copper tube or hard enable copper alloy, depending on the shape and size of the strand to be cast. As a rule, tubular moulds tire used for smaller sections. The interior surface of the mould may be coated
21、with chronic or molybdenum to reduce wear and to suit heat-transfer from the alloy being cast. The mould is tapered to match steel-shrinkage and casting-rate and the type of steel concerned. Moulds used today range from 400 to 1200 mm in length overall, but their usual length is between 700 and 800
22、mm. The problem of steel adhering to the mould-sides is usually countered by oscillating the mould sinusoidally relative to the strand and by adding lubricant (oil or casting flux in an attempt to cut friction between the mould and the steel. The lubricant, particularly casting-flux, has an addition
23、al metallurgical function. The choice of lubricant depends on the qualities required and the casting conditions; it is particularly important that casting-flux should be chosen to match the quality-programme precisely. The level of steel in the mould may be controlled manually or by an automatic sys
24、tem. Either method may be used to keep the level constant or to match the incoming molten steel, i. e. to accommodate variations in casting rate. Manual control is affected via the stopper in the tundish or by varying the output rate. An automatic control system may meter radioactivity or infrared r
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