AT509895A1 - continuous casting - Google Patents

Description

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The invention relates to a continuous casting device for the production of billet or bloom strands, essentially comprising a mold, a device with preferably spaced rollers for guiding the strand, Strangrichtmittel and / or strand withdrawal means, consisting of a arranged in a straightening and / or withdrawal line respectively drivable and mutually engageable pairs of rollers and a sub-device and discharge for cutting and moving the strands.

Continuous casting equipment, in which liquid metal is poured vertically and horizontally substantially continuously into strands and allowed to solidify, are known. Casting machines are also known for producing substantially continuous curved strands with a straightening during or after a solidification thereof.

The skilled worker is familiar with the many achievable advantages in the production of semi-finished material by means of modern continuous casting.

However, the strands may contain glaring defects, which may require improvements in terms of plant and process engineering to reduce or avoid them.

Basically, solidification of liquid metal takes place on a crystallization front, through which heat is removed from the melt. If the liquid melt now has a temperature above that of the quenching temperature of the alloy, solidification thereof will take place exclusively at the crystallization front. When the temperature drops below the uquidus temperature, that is to say in the solidus liquidus region of the alloy, dendrites are formed even in the liquid region at a distance from the crystallization front, which continue to develop with increasing temperature to form larger dendrite formations and sink in the melt due to their higher density. For a solidifying strand, this means that dendrite formations can sink into the pointed conical region of the solidification of the melt, crystallize on the solidification front or on the strand shell, form a bridge, and thus prevent subsequent delivery of liquid metal to the tip of the pool leads to a centric often coarse voids formation.

In order to reduce the formation of centering dances and segregations in the strand core or to improve the metallurgical strand quality, it has already been proposed to carry out a rolling pass with caliber rolls during the final solidification of the strand or to carry out multiple rolling operations each with small thickness decreases with free expansion of the rolling cross section.

Solid metallic materials have extremely low tensile strength in a temperature range close to the solidus temperature, so that local, often only low tensile stresses in the solidifying strand can lead to tearing or cracking. In these cracks, which are weak points, in many cases residual melt is introduced with a higher concentration of Seiger elements, whereby a metallurgical strand quality is reduced.

The problems of coarse voids formation and high local segregation intensity as well as the formation of stress cracks are increased with increasing dimensions, in particular increasing thicknesses of the strand.

The invention is an object of the invention to provide a continuous casting of the type mentioned for the production of billets or Bloomsträngen with which the metallurgical quality of the products is improved.

This object is achieved by the characterizing features of claim 1. Advantageous embodiments of the device are characterized in the subclaims.

The continuous casting device according to the invention has the advantage that in the strand layering means and / or strand removal means can be achieved by minimizing the local tensile stresses in the strand shell by the mutually engageable pairs of rollers and the associated adjoining side rollers reduction or avoiding Lunkerbildung and thus the strand quality is improved. 2

The invention will be explained in more detail below with reference to sketches, which represent only one embodiment.

In a schematic representation:

1 shows a deformation unit in a straightening section and / or a withdrawal section for a strand with a square cross-section. FIG. 2 shows a deformation unit for a strand with a polygon cross-section FIG. 3 shows a deformation unit for a strand with a round cross-section

In Fig. 1 is a cross section of a square strand S is shown in a passage through a deformation unit.

By means of a pair of rollers 1,1 'is a strand S in its thickness of an output format, which is shown in dashed lines, reduced in the arrow direction. Employed side rollers 2,2 'prevent by support a free expansion of the strand S, whereby tensile stresses are minimized in the strand interior. It may also be advantageous for the metallurgical strand quality, if an additional deformation of the strand takes place by means of the side rollers 2,2 '.

The axes 11,11 'of the roller pair 1,1' and the axes 21,21 'of the side rollers ck 2,2' have to Strangaye X a vertical orientation.

The side rollers 2, 2 'associated with the roller pair 1, 1' can each also be designed as so-called tandem rollers (not illustrated) consisting of two individual rollers.

Fig. 2 shows a strand S with an octagonal cross-sectional format.

The structure of a deformation unit and its mode of action corresponds to the statements in the description of FIG. 1.

In a deformation of a polygon strand S with a low reduction in thickness, it may be advantageous if the pairs of rollers 1,1 'and / or the side rollers 2,2' with a 3

I * * · * * · profiled or adapted to the strand cross-section working surface are formed.

FIG. 3 shows a strand S with a circular cross-section in a deformation unit 5.

If profound compressive stresses are to be formed in the case of a round strand in a deformation unit during straightening and / or removal with a small reduction in cross-section, it may be advantageous if a profiled roll pair io 1, 1 * and profiled side rolls 2, 2 'can be set and driven relative to one another are executed. 15 4

Claims (5)

1. Continuous casting device for the production of billet or Bloomsträngen, essentially comprising a mold, a device with preferably spaced rollers for guiding the strand, strand directing means and / or Strand removal means, consisting of arranged in a straightening and / or withdrawal line respectively drivable and mutually engageable pairs of rollers and a sub-device and discharge device for cutting and dispensing the strands, characterized in that the strand directing means and / or strand withdrawal means of at least three, substantially horizontal, respectively drivable and mutually engageable pairs of rollers (1, T) is formed and each roller pair engageable side rollers (2,2 ') are assigned, wherein the roller axes (11,11') and the Seitenrollenachsen (21,2V) to Stranga \ e (X) have a vertical orientation. 2. continuous casting device according to claim 1, characterized in that the axes (11.1V) of each pair of rollers (1,1 ') and the axes (21,2V) of the associated side rollers (2,2') lie on one level. 3. continuous casting device according to claim 1 or 2, characterized in that the side rollers (2,2 ') at least one pair of rollers (1,1') are mutually adjustable and driven. 4. Continuous casting device according to one of claims 1 to 3, characterized in that in the first pair of rollers (1,1 ') incoming cast strand (S) has a thickness of greater than 400 mm, preferably greater than 500 mm. 5. continuous casting device according to one of claims 1 to 4, characterized in that the mold has a round cross section, a square cross section or a polygonal cross section. Vienna, 17 May 2010 5