RU2397042C2 - Method and device for manufacturing of metal hot-rolled strips and device for manufacturing of metal hot-rolled strips - Google Patents

Abstract

FIELD: technological processes. ^ SUBSTANCE: invention relates to metallurgy, in particular for production of light structural steel strips. Device comprises reservoir (6) with melt (9), horizontally arranged casting tray (8), primary cooling zone with two guide rolls and rotary cooled casting belt (1), secondary zone of cooling with roller bed arranged in body and the first stand of rolling mill. Under casting belt in area, where strip has strong shell, there is an electromagnet device (10) installed to impart local oscillating motion to casting belt in order to reduce contact between strip and casting belt. On casting belt there are grooves and ledges arranged, reducing heat exchange between hardening strip and casting belt. Hardened strip with thickness from 6 to 20 mm cast in atmosphere of protective gas is exposed to hot rolling. ^ EFFECT: improved quality of cast hot-rolled strips. ^ 14 cl, 4 dwg

Description

The invention relates to a method for manufacturing hot rolled metal strips, in particular strips of light structural steel according to the preamble of claim 1, as well as to a device according to the preamble of claim 7.

A generic concept for manufacturing hot rolled strips of light structural steel is known (steel research 74 (2003), No. 11/12, p.724-731).

According to this known method, the melt from the supply tank through the injection tray is fed to a rotating injection tape of a horizontal strip casting plant. As a result of intensive cooling of the casting tape, the fed melt, hardening, turns into a blank strip with a thickness of 6 to 20 mm. After complete solidification, the strip-billet is subjected to a hot rolling process.

During hardening as a result of material stresses, the blank strip may become defective, which adversely affects the quality of the hot rolled strip. In particular, in some steels, too fast cooling leads to the formation on the underside of the strip located without a specific system of extensive weights.

In addition, too much friction between the injection tape and the hardened strip results in too much difference in synchronous speed between the speed of the injection tape and the rolling speed, resulting in the worst case rupture of the tape.

This problem of ensuring synchronous speeds always occurs in cases where casting and rolling are carried out in the same production line.

The present invention is to develop a method and device, the use of which for the manufacture of hot-rolled metal strips, in particular strips of light structural steel, the above problems do not arise.

This problem is solved in accordance with the restrictive part and the hallmarks of claim 1 of the claims. Preferred embodiments of the invention, as well as a device for manufacturing hot rolled strips, are the subject of the remaining items.

In accordance with the invention, heat transfer is reduced, as well as the contact (area, duration in time) between the strip that hardens into the preform strip and the casting tape. This can be achieved through various events, and each individual event is effective not only in itself, but also in a combination of events. The method according to the invention is suitable in principle for the manufacture of hot-rolled strips of various metallic materials, including strips of light structural steel.

The first proposal is aimed at reducing the contact between the injection tape and the hardened strip. This is achieved due to the fact that the oscillating motion is locally imparted to the injection belt using an electromagnetic system. For this, an electromagnetic system is installed under the casting tape, which functions similarly to a loudspeaker. It is important for the functioning of the system that it be installed in the place where a sufficiently strong shell has already formed at the strip.

Another proposal is to reduce heat transfer. For this, a gas, in particular a mixture of inert and reducing gases, is fed into the melt supply area between the casting tray and the casting tape. Preferably, the reducing gas is hydrogen.

Preferably, the gas coating occurs over the entire width of the injection tape. The volumetric gas flow is small and more consistent with light blowing. If the volume flows are too large, the uniform formation of the lower side of the strip would be disrupted. The supplied gas mixture acts in such a way that there is practically no scale on the surface of the lower side of the plate. With a clean surface, thermal radiation is less, so the heat transfer between the hardened strip and the casting tape is significantly attenuated.

The third proposal, aimed at structuring the injection tape, was also very effective. Preferably create grooves extending in the longitudinal direction of the casting. Alternatively, protrusions distributed over the surface of the injection tape can also be created. The use of longitudinally directed grooves provides the advantage that their creation is relatively simple and is achieved by pulling a smooth strip through a pair of profiled rollers.

Any type of structuring of the injection tape is guaranteed to reduce heat transfer between the hardened strip and the injection tape. The formation of groove imprints in the melt leads, as a result of shrinkage during hardening, to a local raising of the strip shell and thereby to a decrease in the contact area. This means reducing heat transfer and friction between the strip and the casting tape and can be used to increase the reliability of the process during casting and rolling in one production line.

When produced in a single production line, the casting speed should ideally be synchronous with respect to the rolling speed. In reality, however, there are often deviations, which, of course, cannot be too large, since in this case the strip-blank breaks. For example, synchronous speed deviations of more than 0.5 m / s are considered problematic. If such deviations cannot be eliminated, a buffer, the so-called looper, must be installed in front of the cage of the rolling mill.

Using the drawings, the method according to the invention is considered in more detail, they show:

figa is a front view of a molding tape according to the invention,

fig.1b is a cross section in the direction aa according to figa,

figure 2 - in longitudinal section corresponding to the invention, the placement of the electromagnetic system,

figure 3 - in longitudinal section, blowing the bottom side of the strip,

figure 4 is a top view according to figure 3.

Figure 1 shows a front view of the structure of the casting tape 1 according to the invention. You can see the rear guide roller 2 located in the transport direction, with the casting tape 1 running around it in the direction of arrow 3 shown. The side stops 4 located along the upper side of the tape are indicated , four'.

On the casting tape 1, grooves 5 running in the longitudinal direction are expanded. They are clearly visible in the partial image of FIG. 1b, a fragment of the cross section in direction AA according to FIG.

Figure 2 illustrates a second proposal for reducing heat transfer, wherein the image shows in longitudinal section the supply area of a horizontal strip casting plant.

The installation includes, as a main element, a melt container 6, a feeder 7 with an injection tray 8 connected to it. The melt 9 contained in the melt vessel 6 flows through the injection tray 8 and is fed to a rotating injection tape 1.

To excite local oscillatory motions of the injection belt 1, an electromagnetic system 10 is installed under the injection belt 1. It operates according to the loudspeaker principle and induces the injection belt 1 to oscillate. This leads to the fact that the duration of the contact time of the solidifying melt with the casting tape 1 is reduced. The excitation of oscillations, however, is only possible when the melt strip on the lower side has formed a sufficiently strong sheath of the strip. Therefore, the electromagnetic system 10 should be installed at a distance from the feed area.

A third suggestion for solving the problem is illustrated in FIG. It shows the same longitudinal section of the supply area of the strip casting installation as in FIG. 2, therefore, the same reference numbers are used to indicate identical parts of the installation.

The third proposal for solving the problem is characterized by the fact that before the melt 9 is fed to the injection belt 1, a mixture of gases is blown. For this, a hollow body 12 is installed under the injection tray 8 and above the front guide roller 11. For sealing and better distribution over the width of the injection tape 1, a brush 13 is installed in front of the hollow housing 12.

To provide gas, the hollow body 12 is connected to the inlet pipe 14 (figure 4). After turning on the gas supply, the gas mixture moves along the gap between the injection tape 1 and the bottom side of the injection tray 8 directly to the supply area. This prevents the formation of scale on the shell of the strip, which begins to harden on the casting tape 1. It remains almost clean.

List of Reference Items

1 Injection tape

2 Rear idler

3 Direction of rotation

4, 4 'Side guards

5 Longitudinal grooves

6 Melt tank

7 Feeder

8 Injection tray

9 Melt

10 Electromagnetic system

11 Front idler

12 Hollow body

13 Brush

14 Supply pipe

Claims (14)

1. A method of manufacturing a hot rolled metal strip, preferably a strip of light structural steel, comprising supplying melt through a casting tray to a rotating casting strip of a horizontal strip casting machine in a protective gas atmosphere, hardening strips from 6 to 20 mm thick on it and hot rolling after full hardening characterized in that in order to reduce heat transfer, area and contact time between the hardened strip and the casting tape, oscillatory movements in the region are locally imparted to the latter, in which the strip has a strong shell. 2. The method according to claim 1, characterized in that the injection tape is brought into vibrational motion by the electromagnetic method. 3. The method according to claims 1 and 2, characterized in that before supplying the melt between the injection tray and the injection tape, gas is supplied. 4. The method according to claim 3, characterized in that the gas is a mixture of an inert gas as a carrier and a reducing gas. 5. The method according to claim 4, characterized in that the reducing gas is hydrogen. 6. A device for the manufacture of hot rolled metal strips, preferably strips of light structural steel, containing a supply tank with a melt, a horizontally positioned casting tray, a primary cooling zone with two guide rollers and a rotating cooled casting tape, a secondary cooling zone with a roller table and a first stand placed in the housing rolling mill, characterized in that it is equipped with a device for exciting vibrational motion, installed under the injection tape in the area in which the first strip has a strong shell, while the injection tape is structured. 7. The device according to claim 6, characterized in that the structure has grooves extending in the longitudinal direction. 8. The device according to claim 6, characterized in that the structure has protrusions located on the surface. 9. The device according to claim 8, characterized in that the device for exciting vibrational movements is an electromagnetic device. 10. The device according to claim 9, characterized in that the location of the electromagnetic device is in the area where the tape already has a strong shell. 11. The device according to claim 6, characterized in that in the region of the front guide roller of the strip casting installation, a hollow body with a wide-cut slot connected to the gas supply pipe is installed across the injection belt across the injection tray. 12. The device according to claim 11, characterized in that the hollow body extends over the entire width of the injection tape. 13. The device according to PP.11 and 12, characterized in that under the outlet area of the hollow body is installed connected to the hollow body and adjacent to the injection tape seal. 14. The device according to item 13, wherein the seal is made in the form of a brush.

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