EP0070493B1 - Dummy bar for a continuous casting plant - Google Patents

Abstract

1. A stopping and withdrawing head for a continuous casting installation with an openended mould, the stopping and withdrawing head (2, 38) having a permanent coupling part (5, 5') which is provided with a ridge and forms, with the cast bar (30) and in the withdrawal direction (25), a shape-locking, hook-shaped connection which can be uncoupled by a tilting movement of the stopping and withdrawing head (2, 38) or of the cast bar (30), the stopping and withdrawing head (2, 38) comprising a sealing edge (11) at its periphery, characterized in that the hook-shaped coupling part (5, 5') lies with all its faces at a distance (6) from the lateral boundary faces (7) abutting the sealing edge (11) of the stopping and withdrawing head (2, 38) and projects beyond the substantially flat end-face (10, 10'), the peripheral sealing edge (11) being provided only at this flat end-face (10, 10').

Description

The invention relates to a start-up head for a continuous caster with a continuous mold, the start-up head having a permanent coupling part provided with a bead, which forms a form-fitting hook-shaped connection with the cast strand in the pull-out direction, which can be uncoupled by a tilting movement of the start-up head or the cast strand and which Starting head has a sealing edge on its circumference and an operating mode for this starting head.

To start up a continuous caster with a continuous mold, a start-up line with a start-up head is required. Such starting heads are matched to the cross sections of the mold cavities and fit into them with only a small amount of side play. Before the start of pouring, gaps between the start-up head and the mold walls are sealed to prevent start-up breakthroughs. The steel cast into the mold cavity at the start of casting solidifies on contact with the cooled mold walls and the cold start-up head. Due to its shape, after the metal has solidified, a positive connection is formed between it and the cast strand, which makes it possible to pull the cast strand out of the mold with the help of the starting strand. After the drive rollers, the starting strand is separated from the cast strand.

It is known (US Pat. No. 2,079,644) to provide a starting head with an insertable coupling element before the start of casting. This coupling element, which is releasably connected to the start-up head, is cast around when melt is poured on, as a result of which a connection is formed. After the separating cut, the coupling element remains cast in the hot strand and cannot be used again for further castings. This leads to additional costs, both for the procurement of the coupling elements and for their insertion into the start-up head. Automatic decoupling is usually only possible with the appropriate mechanical and control-related effort.

A significant improvement was brought about by permanent start-up heads which, thanks to their shape, create a coupling with the cast strand, can automatically disengage with little effort and can be used for a large number of castings.

From DE-AS 1'921'312 a permanent start-up head for a continuous casting plant with a continuous mold is known, the start-up head having a reusable coupling part provided with a bead. The part of the head that seals the mold cavity has an extension on one side, which lies on the outside of the mold wall and on the opposite side carries the said bead as a permanent coupling part. This coupling part, which can be used multiple times, forms a positive connection with the cast strand in the pull-out direction, which can be uncoupled by a tilting movement of the start-up head or the cast strand. The start-up head is furthermore provided on its circumferential line facing the pouring side with a sealing edge which, depending on the shape of the coupling part, lies on different levels. This starting head has proven itself well in slab systems with an uninterrupted support between the mold and the decoupling point. This permanent start head cannot be used for billet, bloom or sinker strands that require much shorter support guides in the secondary cooling zone or can even be cast without a support guide, because unwanted decoupling is possible in sections without support guides in front of the intended decoupling point. The risk of uncoupling increases accordingly in the case of continuous casters without supports with an arcuate strand guide.

The invention has for its object to provide a permanent start-up head that is suitable for all strand formats and does not allow unwanted decoupling in a secondary cooling zone with few or no strand guiding devices, can be sealed in the mold with little effort and a safe, automatic uncoupling the intended decoupling point guaranteed. In addition, trouble-free pouring should also be ensured in the case of a non-controllable metal flow into the mold which is matched to high casting speeds.

According to the invention, this object is achieved in that the hook-shaped coupling part is arranged on all sides at a distance from the lateral boundary surfaces abutting the sealing edge of the start-up head and above the essentially flat end face, and the all-round sealing edge is provided exclusively on this flat end face.

The hook-shaped coupling part protruding from the front side enables this starting head to be used advantageously for small stick formats as well as for bloom and slab formats. The all-round molded hook also prevents unwanted decoupling in guide-free cooling zones. This start-up head offers a further significant advantage due to the all-round sealing edge provided on one level. This start-up head also allows a failed strand to be restarted while casting continues on adjacent strands because the sealing work can be carried out without looking into the mold. Furthermore, a safe automatic automatic uncoupling can be carried out at the point at which the start-up strand is removed from the run-out roller table. As a result, no additional mechanical engineering effort is required for the automatic uncoupling operation. The shrinking process of the cast strand onto the coupling part, which begins shortly after the casting, enables rapid cooling and solidification of the undercut coupling part, so that after the start of pouring without interruption of the inflow through the emergency channel, even with non-controllable pouring systems and high pouring speeds, trouble-free start-up is ensured.

The hook-shaped coupling part can have different geometric shapes within the scope of the invention, provided that the uncoupling feature is ensured by tilting movement. An advantageous design results if the hook-shaped coupling part is delimited on one side by an arched undercut surface, on the opposite side by an essentially arched roof surface and by two side walls diverging towards the front side.

An acceleration of the solidification of the arcuate undercut coupling part, which essentially has to transmit the pull-out forces at the start of casting, can be achieved if the undercut coupling part is provided with at least one cooling fin. With such a cooling fin, the metal volume between the undercut coupling part and the adjacent mold wall can be significantly reduced.

As a further measure against start-up breakthroughs, especially in the case of non-controllable intermediate vessel pouring and high pouring speeds, it is recommended to limit the distance between the undercut on the cooling fin and the opposite mold wall to a third to a quarter of the strand dimension measured in the same direction.

In the case of rectangular strand cross sections, the base area of the hook is advantageously rectangular and a uniformly small distance is selected between the base area and the all-round sealing edge. Even with round or octagonal strands etc., it is easily possible to design the base area of the hook and the base area of the end face of the start-up head in a similar manner. The distance between the base of the hook and the all-round sealing edge should be chosen to be substantially uniform even in such formats.

To accelerate the solidification in the area of the all-round sealing edge, according to a characteristic of the invention, the base area of the hook should cover 50-80%, preferably 70-80%, of the end face area.

The tilt angle for decoupling the start-up head from the cast strand can be freely selected within a certain range and can be adapted to the management conditions in the secondary cooling zone. For strands that have sections without support guides in the secondary cooling area, the invention proposes a tilting angle of 45 ° -90 °, preferably 60 ° -90 °, for uncoupling.

When inserting the seal, in particular when restarting a failed strand during the casting operation, there are additional advantages if the flat end face is arranged transversely to the direction of the strand. The end face can also, if desired, be at an angle to the strand axis.

The tilting movement can be supported on a tilting edge at the start of a decoupling process between the starting head and the cast strand. In the subsequent further tilting movement, the play between the coupling part and the cast strand increases continuously, and a defined tilting movement around a tilting edge is no longer necessary. However, if a defined tilting or rotating movement is desired during a major part of the uncoupling, the transition line between the cooling fin and the curved undercut hook shape can be designed as a guide for the cast coupling part during the tilting movement, according to a further characteristic.

In continuous sheet caster systems, there are additional advantages if the hook of the coupling part is directed towards the inside of the arcuate strand guide and when the coupling point between the starting head and the cast strand is plastically deformed by the straightening unit through the straightening unit.

• Figur 1 einen vertikalen Schnitt durch eine teilweise dargestellte Kokille mit teilweise dargestelltem Anfahrkopf,
• Figur 2 eine Draufsicht auf Fig. 1,
• Figur 3 einen Schnitt nach der Linie 111-111 in Fig.1,
• Figur 4 eine Draufsicht auf einen Anfahrkopf für ein Rundformat,
• Figur 5 eine Ansicht auf den Anfahrkopf nach Fig. 3 und
• Figur 6 eine Seitenansicht auf eine Entkupplungsstelle in einer teilweise dargestellten Stranggiessanlage.

Examples of the subject matter of the invention are explained below with reference to figures. Show it :

• FIG. 1 shows a vertical section through a partially shown mold with a partially shown starting head,
• FIG. 2 shows a top view of FIG. 1,
• 3 shows a section along the line 111-111 in FIG. 1,
• FIG. 4 shows a plan view of a start-up head for a round format,
• Figure 5 is a view of the start head of Fig. 3 and
• FIG. 6 shows a side view of a decoupling point in a continuous casting installation which is partially shown.

1 to 3, 2 shows a starting head in a continuous mold 3, preferably in a continuous steel casting plant. The starting head 2 is provided with a hook-shaped permanent coupling part 5, which forms a positive connection with the cast strand (not shown) in the pull-out direction 4. This form-fitting connection can be uncoupled at a predetermined decoupling point by a tilting movement of the starting head or the cast strand.

The hook-shaped coupling part 5 is arranged in a projecting manner above the essentially flat end face 10 facing a mold cavity 9. There is a distance 6 on all sides from lateral boundary surfaces 7, which abut sealing edges 11 of the starting head 2. The sealing edge 11 surrounding the start-up head 2 is provided exclusively on this flat end face 10.

The hook-shaped coupling part 5 is undercut in an arc on one side 13 and delimited on the opposite side 14 by an essentially convex, curved roof surface. The two side walls 15 and 16 diverge towards the end face 10. The undercut side 13 of the coupling part 5 is provided with a cooling fin 18, which also forms an undercut. It is dimensioned such that the distance 20 between the undercut on the cooling fin 18 and the opposite mold wall is one fourth to one third of the strand dimension 21 measured in the same direction. A further dimensioning criterion is the size ratio of the base area of the hook to the base area of the end face. The base area of the hook a · b) should cover 50-80%, preferably 70-80%, of the total end face area (c. D).

The transition line 23 that forms between the cooling fin 18 and the curved undercut hook shape can serve as a guide for the cast strand during the tilting movement.

4 and 5, the coupling part 5 'is adapted to a round strand cross section. The base area (a ') 2. In this example, w / 4 of the coupling part 5 'is similar to the base area of the end face 10', as in FIGS. 1 and 2. The flat end face 10 'is also arranged essentially transversely to the strand running direction 25.

In Fig. 30, a curved strand is designated, which is straightened in a straightening unit 31. After the straightening machine 31, a separation point 32 is shown for decoupling a starting strand 33 from the cast strand 30. The start-up line 33 is raised in the direction of an arrow 35 by a lifting device, not shown. This stroke, which at the same time represents the removal of the starting strand 33 from an outfeed roller table 36, automatically causes the tilting movement for the uncoupling. The necessary tilt angle for the separation is generated in each case by the stroke and by the subsequent strand 30.

In the case of strand guides with a curved track, it must be noted for the operating mode that the hook-shaped coupling part 5 is directed towards the inside 39 of the curved strand guide and, when the coupling point passes between the starting head 38 and the cast strand 30 through the straightening unit 31, the cast positive connection part is plastically deformed becomes. These measures can destroy the shrinkage of the cast coupling part onto the hook-shaped part of the starting head 38.

Claims (9)

1. A stopping and withdrawing head for a continuous casting installation with an openended mould, the stopping and withdrawing head (2, 38) having a permanent coupling part (5, 5') which is provided with a ridge and forms, with the cast bar (30) and in the withdrawal direction (25), a shape-locking, hook-shaped connection which can be uncoupled by a tilting movement of the stopping and withdrawing head (2, 38) or of the cast bar (30), the stopping and withdrawing head (2, 38) comprising a sealing edge (11) at its periphery, characterized in that the hook-shaped coupling part (5, 5') lies with all its faces at a distance (6) from the lateral boundary faces (7) abutting the sealing edge (11) of the stopping and withdrawing head (2, 38), and projects beyond the substantially flat end-face (10, 10'), the peripheral sealing edge (11) being provided only at this flat end-face (10, 10').

2. A stopping and withdrawing head according to Claim 1, characterized in that the hook-shaped coupling part (5, 5') is bounded on one side (13) by an arcuately undercut face, and on the opposite side (14) by a substantially arcuate convex face and by two side walls (15, 16) which slope towards each other in the direction of the side wall (10, 10').

3. A stopping and withdrawing head according to Claim 1 or 2, characterized in that the undercut coupling part (5, 5') is provided with a cooling rib (18).

4. A stopping and withdrawing head according to any one of Claims 1-3, characterized in that the distance (20) between the undercut on the cooling rib (18) and the opposite wall of the mould is one-third to one-quarter of the bar dimension (21) measured in the same direction.

5. A stopping and withdrawing head according to any one of Claims 1-4, characterized in that the face surface (a. b) of the hook and the base surface (c - d) of the end face (10, 10') are similar.

6. A stopping and withdrawing head according to any one of Claims 1-5, characterized in that the base surface (a - b) of the hook covers 50-80 % and preferably 70-80 % of the base surface (c - d) of the end face.

7. A stopping and withdrawing head according to any one of Claims 1-6, characterized in that a tilt angle of 45°-90° and preferably 60°-90° is provided for uncoupling.

8. A stopping and withdrawing head according to any one of Claims 1-7, characterized in that the flat end-face (10, 10') is disposed substantially transversely of the direction of travel (4, 25) of the bar.

9. A stopping and withdrawing head according to any one of Claims 1-8, characterized in that the transition line (23) between the cooling rib and the arcuately undercut hook shape is designed as a guide for the cast bar during the tilting movement.

Images