EP1214996B1 - Thin-strip continuous casting machine - Google Patents

Abstract

A thin-strip casting device (1) assures across the entire selected range of the width an about constant production of thin-strip (12) without requiring artificially extended charging times of the steel plant installed upstream. A multitude of interchangeable pairs of casting rollers (2) having different casting roller diameters "D" depending on the strip width "B" to be cast, are associated with the thin-strip casting device (1).

Description

The invention relates to a thin strip caster including a pair opposite and approximately equal executed casting rolls, in turn form a funnel for receiving the molten steel by means of side seals.

In practice, thin-strip casters, in particular two-roll casters, for the production of warm broadband in the usual width range of about 800 up to 1,400 mm and thickness range of about 2 to 5 mm, using casting rolls with Constant diameter and variable bale lengths are used as the Bandwidth is essentially determined by the bale length of the same.

When planning, for example, a steel mill in the form of a mini-hut with an annual output of about 400,000 to 500,000 t, which is usually upstream of the thin-strip casting plant and this supplied continuously with molten steel, but there is the problem that the production of the steel mill is practically constant and this only works economically, if at least three to five batches are shed as a conti-konti casting.
This means that the steelworks should be designed and laid out in such a way that it can still supply the thin-strip caster at the desired maximum bandwidth, although it must be accepted that the steelworks must be operated at lower belt widths with artificially extended batch times , However, this fact affects the economy of the entire system.

This is where the invention described below begins.

The object of the invention is to improve the performance of existing thin-strip casters, which may already be operating in their marginal areas, with low mechanical engineering use and reasonable capital expenditure to increase, d. h., The disadvantages of the above-described prior art to avoid that a thin-strip caster is provided, the over the entire selected width range an approximately constant production of Thin strip ensured without artificially prolonged batch times of the upstream steelworks are required.

According to the invention, the object in connection with the features in the preamble of claim 1 achieved in that the thin-strip caster a plurality associated with each other interchangeable pairs of casting rolls, in Depending on the bandwidths to be cast "B" different casting rolls diameter Have "D".

In an advantageous embodiment of the invention, each pair of casting rolls one Bale length defined by the bandwidth "B" and a defined casting roll diameter "D" on, with the product of the bale length and the casting roll diameter "D" of the casting rolls of all interchangeable pairs of Casting rolls is approximately equal.

An expedient development of the invention provides that the pairs of Casting rolls are each pre-installed in a removable frame.

The proposed thin-strip casting plant has with regard to known systems the main advantage that they are consistent without great technical effort Production of thin strip in every usual width range and thus one economic utilization of the upstream steelworks guaranteed.

The invention will be described below with reference to a drawing in the drawings illustrated embodiment explained in more detail.

Figur 1a

die Seitenansicht einer Dünnband-Gießanlage in Form einer Zweirollen-Gießanlage,

Figur 1b

die Ansicht A nach Fig. 1a,

Figur 2a

die Dünnband-Gießanlage nach Fig. 1a in zwei schematisch angedeuteten Varianten, unter Verwendung von unterschiedlich gestalteten Gießrollen,

Figur 2b

die Ansicht B nach Fig. 2a,

Figur 3

die Seitenansicht einer Seitendichtung für ein Paar Gießrollen,

Figur 4

den Schnitt C-C nach Fig. 3.

Show it:

FIG. 1a

the side view of a thin strip casting plant in the form of a two-roll casting plant,

FIG. 1b

the view A of Fig. 1a,

FIG. 2a

1a in two schematically indicated variants, using differently shaped casting rolls, the thin-strip caster according to FIG.

FIG. 2b

the view B of Fig. 2a,

FIG. 3

the side view of a side seal for a pair of casting rolls,

FIG. 4

the section CC of FIG. 3.

1a and 1b show a thin-strip caster 1 in the form of a known Zweirollen-casting plant, which in turn has a pair of opposing and approximately equal executed casting rolls 2, with a certain predetermined bale length, the approximately the bandwidth "B" corresponds, and a certain predetermined casting roll diameter "D" are provided.
By means of associated side seals 3, which are each arranged in holders 4, the casting rolls 2 form a funnel 5.
This funnel 5 is used to hold the molten steel 6, which in turn is continuously provided by a upstream, not shown steelworks via an intermediate container 7 with so-called dip tube 8.
The molten steel 6 is filled into the funnel 5 formed by the casting rolls 2 and the side seals 3 up to a specific bath level 9, the height of which is also referred to as the solidification length "I" and defined by the bath level angle "α".

During the rotational movement of the casting rolls 2, the molten steel 6 solidifies the same to two strand skins 10 of thickness "s" and are due to the Rotation of the casting rolls 2 moves down and at the so-called kiss point 11 to the thin strip 12 with the strip thickness d = 2 * s compressed.

The thin strip 12 leaves the thin strip caster 1 with the casting speed "V", which in turn corresponds to the peripheral speed of the casting rolls 2.

Furthermore, the following conditions for thin-strip casting must be observed:

The thickness "s" of the two strand skins 10 results approximately from the known relationship s = k * t n where "k" is a constant dependent on the cooling conditions and "t" is the solidification time.

For "n", a value of 0.5 to 1.0 can be assumed, where n = 0.5 for a constant surface temperature applies (conventional continuous casting) and n = 1.0 for a constant temperature gradient in the strand skin 10, so strongly sloping Surface temperature of the same.

Since thin strip casting has to be expected to have a very steep surface temperature of the strand skin 10, it has thus been found that in the thickness range up to approximately 5 mm, at least approximately n = 1, accordingly s = k * t

For "t" in seconds and "s" in mm, a constant "k" = 2.5 for the very rapid initial solidification of the strand skins 10 was also found in evaluation of extensive experiments and the specialist literature for thin strip casting in the thickness range up to 5 mm.
Thereafter, the conditions now apply: s = 2.5 * t d = 2 * s and accordingly d = 5 * t or t = d / 5

For the casting speed "v" applies known v = l / t wherein the solidification length "I" results at a bath level angle "α" of 45 ° as follows: l = (π * D * 45) / 360 = 0.39 * D

For t = d / 5, "v" is given in m / s ("D" in m and "d" in mm) v = (0.39 * D * 5) / d = (1.95 * D) / d therefore for "v" in dm / s as well as "D" and "d" in dm v = (1.95 * D) / (d * 100)

As demonstrated above, the casting speed is "v" of a thin strip caster 1 proportional to the casting roll diameter "D" and vice versa proportional to the strip thickness "d".

The production "P" of a thin-strip caster 1, measured in kg / s, results as a function of the bandwidth "B" and the strip thickness "d" (in each case in dm), the casting speed "v" (in dm / s) and the density for steel of 7.8 kg / dm ³ from the following relationship: P = B * d * v * 7,8

Further, in consideration of the above conditions regarding "v" for the production "P" P = B * 1.95 * D * 0.078

It was further found that the production of a thin strip casting machine 1 proportional to the bandwidth B "and the casting roll diameter D".

An almost constant production geared to an upstream steel mill According to the invention, "P" can now be evaluated by evaluating the above conditions be achieved, that the thin-strip caster 1 a plurality against each other exchangeable pairs of casting rolls 2 are assigned, wherein the same in each case in Depending on the bandwidths to be cast "B" different casting rolls diameter D "exhibit.

2a and 2b show in side view and plan view in comparison on the left side the casting roll 2 of a pair of casting rolls 2 for the production of a wide and right side the casting roll 2 of a pair of casting rolls 2 for the production of a narrow thin strip 12, since known the bale length the casting rolls 2 is defined or determined by the selected bandwidth "B".
Furthermore, the casting roll 2 drawn on the left side for wide thin strip 12 has a smaller casting roll diameter "D" than the casting roll 2 drawn on the right side.

This measure according to the invention results from the knowledge that the solution the task, namely over the entire selected width range one to ensure about constant production of thin strip 12 without being artificial extended batch times of the upstream steelworks become necessary, Bandwidth "B" and bale diameter and casting roll diameter "D" of each pair of Casting 2 are chosen so that the product of the bale length and the Casting roll diameter "D" of the casting rolls 2 of all interchangeable Pairs of casting rolls 2 is approximately equal.

The invention will be illustrated by way of example even more clearly.
For a miniature smelter for hot broadband with electric steel plant and thin strip casting plant 1 for approx. 500,000 t annual output in the width range of 800 to 1400 mm bandwidth "B", a steelworks with approx. 90 t hourly output and a thin strip Caster 1 with a casting roll diameter "D" of about 1.2 m are provided.
With a selected belt width "B" of 1,400 mm and the aforementioned casting roll diameter "D" of 1.2 m, the thin-strip casting plant also has an hourly output of 90 t.

For bandwidths below 1,400 mm, however, the hourly output is lower. so that, as already demonstrated, the steel mill for the still required Continuous supply of the thin-strip caster 1 with artificial breaks between the batches must be driven. The annual output is at this interpretation of the average hourly output of the thin strip casting machine 1, the between about 52 t at 800 mm and, as above, about 90 t at 1,400 mm bandwidth "B" lies.

With the inventive measures, namely essentially for different belt widths "B" different casting rolls diameter "D" can use a mini hut for example, about 500,000 t annual output and to be produced bandwidths "B" from 800 to 1,400 mm and using a Electric steel plant with approx. 70 t hourly output and a thin-strip casting plant 1 with exemplarily selected casting roll diameters "D" of 1.4 m for Bandwidths "B" from 800 to 1,000 mm, 1.2 m for Bandwidths "B" from 1,000 to 1,200 mm and 1,0 m for bandwidths "B" from 1,200 to 1,400 mm. The hourly output of the thin strip caster 1 fits in this interpretation in entire width range for the hourly output of the steelworks.

Advantageously, artificial break times of the Steel mill between each batch no longer required to one to ensure continuous production "P".

As can further be seen from FIGS. 2 a and 2 b, for practical handling of the pairs of casting rolls 2, ie for exchanging the same according to the invention as a function of the selected bandwidth "B" to be cast, the respective pairs of casting rolls 2 can be preinstalled in a removable frame 13 be, in turn, on a non-illustrated basic framework of the thin-strip casting machine 1 fixed, but detachable, is arranged.
This change frame 13 can furthermore have the same external dimensions for all dimensions of the casting rolls 2 used (FIG. 2 b).

The removable frame 13 also carries known Anstellrahmen 14 for the bearings 15 of the casting rolls 2, for example by means of hydraulic or pneumatically actuated adjusting cylinder 16 to the desired strip thickness "d" can be hired.

On the support surfaces 17 of the removable frame 13, the brackets 4 not shown in Fig. 2a and 2b are provided for the known side seals 3 of the pairs of casting rolls 2.
In essence, these side seals 3 are known to be formed by an outer frame 18 which is filled with a refractory mass 19 (Figures 3 and 4).
In this refractory mass 19 are on both sides of the casting rolls 2 each deposits 20 made of special ceramic, such as boron nitride, embedded, which envelop the lying below the bath level 9 circumferential paths of the casting rolls 2.

It goes without saying for the person skilled in the art that correspondingly different side seals 3 can be assigned to the different casting roll diameters "D".
It is also possible to make the side seals 3 so that the different casting rolls diameter "D" having pairs of casting rolls 2 one and the same side seals 3 can be assigned by, for example, the deposits 20 at least in the region of the circumferential paths of the casting rolls 2, enveloping the same , are designed to change.
Likewise, it may behave with the holders 4 of the side seals 3, which in adaptation to changed casting roll diameter "D" and optionally variable executed side seals 3 and modified bale lengths of the casting rolls 2 vertically and / or horizontally and / or radially in not shown, However, known per se guide elements, such as rails, can be adjustably guided and locked.

As regards the removable frame 13, it is recommended that two removable frame 13 to provide, one of which with a corresponding pair of casting rolls 2 in Use is and the other with a corresponding pair of casting rolls 2 and new Side seals 3 is prepared for the next change.

Claims (3)

1. Thin-strip casting machine, comprising a pair of opposing casting rollers of an approximately identical configuration, which, by means of side seals, for their part form a funnel for receiving the steel melt, characterized in that the thin-strip casting machine (1) is assigned a plurality of mutually interchangeable pairs of casting rollers (2), which have different casting roller diameters "D" in accordance with the strip widths "B" to be cast.
2. Thin-strip casting machine according to Claim 1, characterized in that each pair of casting rollers (2) has a body length defined by the strip width "B" and a defined casting roller diameter "D", the product of the body length and the casting roller diameter "D" of the casting rollers (2) of all the mutually interchangeable pairs of casting rollers (2) being approximately equal.
3. Thin-strip casting machine according to either of Claims 1 and 2, characterized in that the pairs of casting rollers (2) are respectively preinstalled in a changing frame (13).

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