Manufacture of billets and blooms from a continuously cast steel

Details Manufacture of billets and blooms from a continuously cast steel Manufacture of billets and blooms from a continuously cast steel

1994-02-25

1996-03-12

Batten, Jr., J. Reed

Metal founding

Process

Shaping liquid metal against a forming surface

164417, 164424, B22D 1104, B22D 1112

Patent

active

054978211

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a process for the direct manufacture of billets and blooms from a continuously cast steel showing high or excellent quality, as well as an apparatus for the realization of such process.
It is known that the continuous casting is ever more utilized for the manufacture of steel, because of the clear and well known advantages therein involved, with respect to other kinds of casting. It is clear however that the thus obtained product, as it appears at the extracting machine at the end of the curvilinear casting route, shows the features of a typical casting piece, with all the qualitative drawbacks typical of these semifinished products. It is in fact possible to see, by a metallographic analysis, that the grain size and the structure isotropy are unsatisfactory and that the carbon percentage is not homogeneous but prevailingly concentrated in the central zone of the product, with consequent segregations which make the product, coming from the continuous casting, not directly exploitable for the rolling, when it is desirable to obtain end products consisting of high and excellent quality steel.
In the case of a high quality steel, the continuous casting can be exploited for obtaining blooms, which, after transit through an oven, are conveyed to a size-breaking rolling mill, in order to be converted into billets, which in their turn, optionally heated in a further oven, are eventually conveyed to a finishing rolling mill. In the case of an excellent quality steel, the casting is even occurring in the form of an ingot, and not in a continuous way, and in each ingot the cooling is adjusted by means of a predetermined cycle; therefore, the ingots, or the big size blooms, are conveyed to the size-breaking and subsequently to the pre-rolling or cogging and to the finishing rolling, wherein there are usually provided, between two subsequent operations, intermediate heatings in an oven, thus performing an extremely long and expensive operative cycle.
It is thus a purpose of the instant invention to supply a process allowing the direct manufacture, by means of a continuous casting, of billets or blooms showing such features as to be easily transferred, in a subsequent time and without any further operation, to the finishing rolling. Another object of the instant invention is residing in an apparatus for the realization of said process.
An advantage coming from the process according to the invention, described hereinbelow, is residing in that the consequent inner grain of the casting product is showing those features of fineness, homogeneity and isotropy, as well as of absolute absence of segregations, which are usually observed in a product ready for the finishing rolling, thus omitting the steps concerning size-breaking and pre-rolling, including the respective intermediate heatings, and thus reaching a considerable power saving.
The process according to the instant invention is characterized by a liquid core distortion of the casting product, obtained by means of a continuous casting, which causes a reduction of the product cross-section, the perimeter of the same cross- section being unchanged, in the route between the lowermost geometrical point on the casting axis, where it is still possible to find superheated liquid, and the end point of the metallurgical length, where the product is completely solidified.
According to a preferred embodiment of the instant invention, said distortion is made to occur in a zone where the concentration of the solid grains is from 10 to 80%.
The distortion hereinabove, from a practical point of view, can involve the conversion of the shape from round to square (i.e., billet), round to rectangular (i.e., bloom), billet to bloom, or bloom to a more flattened cross-section.
The apparatus for carrying out the process according to the invention is essentially comprising at least one of the sectors of the roller train along the curvilinear route, which is given the possibility of movement with respect to the opposite sector, and means fit for bringing said

REFERENCES:
patent: 3393727 (1968-07-01), Rys
patent: 3478809 (1969-11-01), Tarmann et al.
patent: 3638713 (1972-02-01), Knell et al.
patent: 4493363 (1985-01-01), Fredriksson et al.
Abstract of Japanese Patent Publication 63-171255 Published Jul. 15, 1988.

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