1、外文资料In the past decade, there were many studies of high speed slab casting in order to improve productivity and save energy.However,high casting speed may decrease the powder consumption and increase the disturbance of the meniscus, which leads directly to poor lubrication and therefore the liquid s
2、lag is unable to flow uniformly into the gap between the strand and the mould, and subsequently more surface defects would occur.Therefore, online measurement and proper control of mould process, frictional behavior and thermal behavior are essential for strand surface quality.In the present work th
3、e measurements of mould friction (MDF) for an electrohydraulic servo oscillation system were made.Through measuring the hydraulic force of cylinders at empty and casting state with different oscillating parameters,the friction force between slab and mould was calculated. In addition,the periodic var
4、iations of MDF were analysed, and the fluctuation characteristics of other parameters were also discussed.In the present work,the measurements of MDF were performed on a continuous slab caster with hydraulic oscillators.The sampling rate of 1250 Hz was high enough to calculate MDF instantaneously,an
5、d a large quantity of MDF data had been collected for subsequent analysis.The following conclusions were drawn.（1）Transient MDF is explicitly displayed which varies regularly and periodically following the relative velocity between mould and strand.The tensile and compressive friction forces acting
6、on strand surface caused by MDF appear alternatively,and the waveforms of friction tend to be a rectangular or trapeziform shape at different oscillating frequencies.（2）The friction and relative velocity between mould and strand do not vary synchronously.The time is defined, during which the compres
7、sive force acts on the strand surface, as shell compressed time.The shell compressed time is less than the negative strip time, and the correlation between them can be expressed as a linear function.In addition,the maximum friction is proportional to the maximum relative velocity between mould and s
8、trand.（3）In plant trials, the maximum friction decreases gradually and the minimum friction maintains at a stable value during the decrease in casting speed.A proper relationship between casting speed and oscillat oscillating frequencies could contribute to alleviate the friction fluctuations during
9、 the changes of casting speed.This article is devoted to the problem of separating different grades of steel cast in succession on sectionand slab-type continuous casters,the goal being to reduce the incidence of rejection of steel for incorrect chemical composition.With this as their objective,rese
10、archers found that it is necessary to determine the optimum length of the specific semifinished products which serve to separate successive heats of dissimilar steels.A mathematical model was constructed to help determine the optimum lengths of the semifinished products. The model, based on material
11、 balance equations, makes it possible to determine the changes that take place in the constituent chemical elements when different grades of steel are cast back-to-back.Having been refined through the use of actual production data to describe those elements distributions in the continuous-cast semif
12、inished product,the model was then used to develop an efficient method for extracting and pattern-shearing ingots that function as separators when different grades of steel are cast in a series.The production of continuous-cast semifinished products in steelmaking shops is currently based on casting
13、 of successive heats.Different grades of steel may be cast within a given series of heats,including grades differing significantly from one another in chemical composition.The result is the formation of cast semifinished products with a mixed chemical composition that may have to be relegated to low
14、er quality categories or rejected altogether.In 2005, the oxygen converter shop at the Magnitogorsk Metallurgical Combine (MMK) performed 5073 casts of different grades of steel on its continuous casters.18886 slabs (total weight 289,381 tons) had to be assigned to lower quality categories and 2353
15、slabs (total weight 37149 tons) were rejected for further use.To minimize the loss of ingots due to incorrect chemical composition, it is necessary to restrict the size of the regionin which steels of different compositions mix with one another over the length of a given semifinished product.Several
16、 methods have been developed to separate heats of different chemical compositions in continuous casting: simultaneously replace the steel-pouring ladle (SPL) and the tundish; use a separating plate inside the mold; open the nozzle of the ladle holding a new heat only when the level (mass) of the steel in the tundish from the previous heat is as low as possible. The effectiveness of each of these methods depends on the type of equipment and method of casting tha
