JPH0128665B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides mold cooling water for preventing explosion phenomena and other various troubles caused by the reaction between molten steel flowing into the mold and dew condensation water at the start of casting in horizontal continuous casting equipment. Relating to a control supply device.

In horizontal continuous casting, a mold with a water-cooled jacket is directly connected to the side wall of a tundish, and the molten steel flowing from one end of the tundish into the mold through the nozzle of the tundish is indirectly cooled to form a solidified shell, which is then turned into a slab from the other end. are continuously pulled out. In order for this process to take place, it is necessary for the molten steel to start forming a solidified shell at a desired position downstream from the inlet end of the mold, and therefore the mold has a large water cooling capacity and is easy to control. It is desirable that the

By the way, to start casting, the tundish is preheated and a dummy bar is inserted from the other end of the mold to guide the drawing of the slab. In horizontal continuous casting, the inside of the mold is closed, and the water vapor in the tandate preheating exhaust gas is cooled by the water-cooled mold and dummy bar, condenses, and remains as moisture, which reacts with the molten steel when it flows in and causes an explosion. There is a fear that the molten steel inside the tank will blow up. As one of the countermeasures, it has been proposed to not allow cooling water to flow through the mold when preheating the tundish, but the timing between the start of molten steel flowing into the mold and the start of the flow of cooling water is extremely difficult. Because it has to be done at delicate timing and involves sudden changes in temperature, there is a high risk of an accident.

The present invention has been made to solve these problems, and when preheating the tundish, heat is applied to the mold to an extent that does not cause moisture condensation. To achieve this objective, the present invention is a mold cooling water supply device for horizontal continuous casting, in which a mold is directly connected to the side wall of a tundish and is formed by cooling molten steel that flows from the tundish into the mold through a nozzle provided on the side wall. In a horizontal continuous casting machine that draws slabs horizontally, cooling water is supplied to the mold from a hot water tank equipped with a heating device.
There are two lines: a hot water supply line with a temperature of 40℃ or more and less than 100℃, and a low-temperature cooling water supply line.A temperature detector is installed on the mold wall, and the detected temperature automatically switches from hot water supply to cold water supply. It is characterized by being able to switch water supply.

For the same purpose, heating the mold from the outside is generally difficult due to the complicated structure of the jacket cooling channels in the mold for horizontal continuous casting, and it is extremely difficult to eliminate the accumulation of cooling water due to the horizontal arrangement. Therefore, steam is generated locally due to external heating, and it is necessary to provide mold strength to withstand it, which poses a risk of steam explosion.

Furthermore, since O-rings with a heat resistance of about 100° C. are often used as seals inside the mold, they can burn out due to external heating, causing water leakage, and there is a risk of an explosion similar to condensation inside the mold.

Hereinafter, the present invention will be explained specifically and in detail with reference to the accompanying drawings. FIG. 1 shows one embodiment of the present invention in the form of a system diagram.

Mold 1 of horizontal continuous casting is tandate 2
The molten steel 6 injected into the tundish 2 from the ladle 5 flows into the mold 1 from the nozzle 3 through the plate ring 4. The mold 1 is a slab 7 that can be drawn by starting solidification by indirect heat exchange and water cooling heat removal from the molten steel.
A water cooling jacket 8 is provided in order to
Cooling water is circulated from the outlet toward the outlet 10.

The cooling water supply source is a water cooling tower 11 that holds a relatively large amount of low-temperature cooling water to enable rapid and continuous removal of a large amount of heat from the molten steel in the mold 1, and generally a heat exchanger. The cold water receiving tank 12 is used. Hot water from the outlet 10 of the water cooling jacket of the mold passes through a return pipe 15 having a stop valve 13 and an electric switching valve 14 to the water cooling tower 11.
The water returns to the cold water tank 12, where it dissipates heat and becomes low-temperature cooling water, which is collected in the cold water tank 12, from which it is passed through the filter 1.
6, the inlet 9 via a supply pipe 23 having a stop valve 17, a water supply pump 18, a flow meter 19, an electric switching valve 20, a check valve 21, and a stop valve 22.
Cooling water is supplied to and circulated through the jacket 8, forming a low-temperature cooling water supply system.

In the present invention, a hot water tank 25 equipped with a temperature raising device 24 and having a relatively small amount of water is provided separately from the cooling water supply system, and from there, a filter 26, a water supply pump 27, a flow meter 28, an electric switching valve 29, 40°C or higher via the check valve 30 and the stop valve 22 mentioned above.
A conduit 31 is provided for supplying hot water of less than 100° C. to the water cooling jacket 8. From the outlet 10, a pipe line 33 is provided which passes through a stop valve 13, branches off from a pipe line 15, and returns to the hot water tank 25 via an electric switching valve 32, so that hot water circulates through the jacket 8.

Reference numeral 34 denotes an emergency cooling water supply route, and when a pressure drop occurs in the water supply lines 23, 31 to either mold or in the event of a power outage, the emergency cooling water valve 3 is supplied via a pressure switch 35 and a pilot switching valve 36.
7 is opened so that cooling water can be supplied to the mold from an elevated tank (not shown).

In the present invention, a temperature detector 38 consisting of a thermocouple for temperature measurement is provided on the mold wall, and the detection signal is sent to a converter 39, thereby controlling the electric switching valves 14, 20,
The opening and closing of 29 and 32 is controlled. The converter 39 also serves as a temperature indicator. 40, 41, 42 indicate thermometers.

The apparatus of the present invention having the above configuration is operated in the following order.

() Energize the temperature raising device 24 to raise the temperature of the water in the hot water tank 25 to 40°C or more and less than 100°C. The hot water in the hot water tank is automatically controlled to maintain a constant temperature and level.

() Open the electric switching valves 29 and 32, and
4 is closed, and the water supply pump 27 is started to circulate and warm the hot water inside the mold 1.

() After confirming the temperature rise of the mold using the temperature detector 38, attach the break ring 4, connect the mold 1 to the tundish 2, and insert the dummy bar. The dummy bar is heated by hot water circulating through the mold 1. Preheating of the tandice is also carried out during this time. Condensation inside the heated mold 1 is completely prevented.

It is better to heat the dummy bar beforehand outside the mold 1 before attaching it, but in the case of a small cross section, it may be left as is.

() After completing the casting preparations as described above, ideally after 5 minutes of installing the dummy bar, pour molten steel from the ladle 5 into the tundish 2.

() The inflow of molten steel into the mold 1 is automatically detected by the temperature detector 38, and the electric switching valves 29, 32 are closed based on the signal, and the electric switching valves 20, 1 are closed.
4 is opened to circulate low-temperature cooling water from the cold water tank 12 to perform continuous casting in a stable state.

As a result of experiments, it was found that 60 to 80 degrees Celsius is the best setting temperature for hot water due to the risk of condensation and problems with cavitation of the water supply pump.

FIG. 3A shows time on the horizontal axis and flow rate on the vertical axis, and shows the change in flow rate of hot water X and the change in flow rate of low-temperature cooling water Y. As shown in the figure, if the supply of low-temperature cooling water is started 5 to 10 seconds before the hot water circulation is stopped, and the water flow is overlapped so that the low-temperature cooling water is in a full flow state when the hot water circulation is stopped, as shown in Figure 3. As shown in FIG. 2, with temperature on the vertical axis and time on the horizontal axis, sudden changes in the temperature of water flowing into the mold jacket can be avoided.
Regarding the balance between the pressure and water volume of hot water and low-temperature cooling water, if the pressures are the same, no flow from one path to the other occurs, making switching control easier and smooth switching possible.

As described above, according to the present invention, condensation not only on the mold but also on the surface of the dummy bar can be prevented by heating the mold by flowing hot water of 40°C or more and less than 100°C into the mold jacket until the start of casting. . Furthermore, since there is no sudden temperature change when the molten steel flows in, and the strain that occurs in the mold can be reduced, the chances of water leakage due to mold distortion can be reduced. Furthermore, by raising the temperature of the mold to an appropriate amount before mounting, the amount of push-in of the break ring etc. can be reduced, making it easier to manage it. Furthermore, by providing a temperature detector on the mold wall to detect when molten steel flows in, it is possible to easily switch between hot water and low-temperature cooling water.

The present invention can also be operated to maintain the temperature of the cooling water fed to the mold during continuous casting at a desired temperature by combining hot water with low temperature cooling water.
FIG. 2 shows a system diagram of an embodiment that allows this operation to be carried out, and parts equivalent to those in the embodiment of FIG. Second
In the illustrated embodiment, in addition to the mold wall temperature detector 38, a low-temperature cooling water temperature detector 43 is provided in correspondence with the hot water temperature detector 40, and the water temperature signals detected by both detectors 40 and 43 are converted and processed by an arithmetic unit 39A. and controls the opening degrees of the electric switching valves 29, 32, 20, and 14 so that the temperature at the inlet of the cooling water to the inlet 9 and the temperature of the outflow water at the outlet 10 are kept constant depending on the merging ratio and flow rate. can do. These temperatures are detected by temperature detectors 41 and 42 and input as control data to converter and calculator 39A.

The cooling water inlet temperature can be controlled to be always constant at an optimum value of, for example, 30°C as a set value, and this optimum temperature is determined by converting the detected temperatures from the molten steel temperature detector 44 and the mold wall temperature detector 38 in the tundish 2 as data. and can be determined by inputting it to the calculator 39A.

In continuous casting, in many cases, as described above, cold water from a water cooling tower is used as cooling water for the mold.
Since a water cooling tower cools most of the hot water using large latent heat generated by evaporation of a portion of the hot water, the temperature of the cold water changes depending on the outside temperature.
Cooling towers are generally installed under outside air conditions in the summer, and tend to over-cool in the winter, so the mold cooling water temperature often becomes too low. Temperatures are extremely low, especially after long periods of rest or holidays. On the other hand, in the embodiment shown in Fig. 2, the data of the hot water temperature in the hot water tank and the low temperature cooling water temperature from the water cooling tower are converted and input into the calculator 39A, and the mold cooling water inlet temperature is controlled to be the specified value. Thus, continuous casting can be carried out under fixed conditions. Furthermore, by inputting data on the molten steel temperature in the tundish and the mold wall temperature and controlling the mold cooling water inlet and outlet temperatures to be constant, the continuous casting situation becomes more stable and slabs of good quality can be obtained.

[Brief explanation of drawings]

Fig. 1 is a system diagram of one embodiment of the device of the present invention, Fig. 2 is a system diagram of another embodiment of the device of the present invention, and Fig. 3 is a system diagram of one embodiment of the device of the present invention.
Figure A is a diagram showing changes in water flow rate, and Figure 3B is a diagram showing changes in water temperature. 1...Mold, 2...Tandatetsu, 3...
...Feed nozzle, 4...Break ring, 5...
... ladle, 6 ... molten steel, 7 ... slab, 8 ... water cooling jacket, 9 ... inlet, 10 ... outlet,
11...Water cooling tower, 12...Cold water tank, 13,1
7, 22...Stop valve, 14, 20, 2
9, 32...Electric switching valve, 15...Return pipe, 1
6, 26... Filter, 18, 27... Water supply pump, 19, 28... Flow meter, 21, 30... Check valve, 23... Supply pipe line, 24... Temperature raising device, 25
... Hot water tank, 31 ... Supply pipe, 33 ... Return pipe, 34 ... Emergency pipe, 35 ... Pressure switch, 36 ... Pilot valve, 37 ... Emergency valve, 38 ... Mold wall temperature detector, 39...Converter, 39A...Conversion and computing unit, 40,4
1, 42, 43, 44...Temperature detector, X, Y...
...flow curve.

Claims (1)

[Scope of Claims] 1. In a horizontal continuous casting machine in which a mold is directly connected to the side wall of a tundish, and molten steel is flowed from the tundish into the mold through a nozzle provided on the side wall, and a slab is horizontally drawn out. ,
Cooling water is supplied to the mold in two lines: a hot water supply line with a temperature of 40°C or more and less than 100°C from a hot water tank equipped with a temperature raising device, and a low-temperature cooling water supply line. 1. A mold cooling water supply device for horizontal continuous casting, characterized in that a temperature detector is provided so that the water supply can be automatically switched from hot water supply to cold water supply depending on the detected temperature. 2. The water in the hot water supply system line and the low temperature cooling water supply system line are combined so that water can be supplied to the mold, and a hot water temperature detector and a low temperature cooling water temperature detector are provided together with the temperature sensor on the mold wall, and The temperature of the combined water at the cooling water inlet of the mold is set to a desired value by controlling each flow rate of the hot water supply system line and the low temperature cooling water supply system line via a converter based on the detected temperature. A mold cooling water supply device for horizontal continuous casting according to claim 1.