JPS583787B2 - How to change slab width during continuous casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for rapidly reducing and expanding the slab width during continuous casting without waste.

The width of continuous cast slabs, such as slabs, is determined based on the equipment specifications of the hot strip mill, plate mill, etc. to which the slab is supplied, as well as requirements regarding rolling technology, finished coil weight, etc. While there is a large demand for standard-sized slabs for commercial use, recently there has been a tendency for the demand for various slabs with widths other than the standard size to increase.
For inch hot strips, the width is 900mm~
Dimension difference of 50mm to 100mm between 1500mm is about 2
The reality is that there are as many as 0 types.

However, in continuous casting, the width of the slab was changed until now after the molten steel injected into the continuous casting mold was pulled out as a slab. When changing the width of the mold, loosen the clamp of the mold and move one or both of the mold walls (usually the short side for slab molds) to move along the inner surface of the fixed wall, and change the width of the mold. Next, the tip of a dummy par corresponding to this width is brought to the bottom of the mold and the injection of molten steel into the mold is started.

Therefore, it takes at least 40 to 80 minutes to change the width.
If width changes are required frequently, the inherent productivity of continuous casting will be significantly hindered, and in the case of small-scale demand of less than one charge, continuous casting will increase surplus inventory that cannot be allocated to orders, making it uneconomical. This was a problem because it was also disadvantageous.

In view of this current situation, research has recently been conducted on the possibility of changing the width of the mold during continuous casting and connecting and pulling out the slab after the width change to the slab currently in progress, and several examples of these attempts are presented. Although proposals have already been made, most of these have only been considered for expanding the slab width, and there are still problems with the expansion of the width, such as safety against solidified shell breakage, leakage, and operability when changing the width. is left behind.

The present invention aims to solve these problems and provide a method that is safe, easy and quick, and allows not only the expansion but also the reduction of the slab width.

In the method of the present invention, when expanding or contracting a slab during continuous casting, the method includes at least two opposing walls that are parallel to the movable wall of the mold, and the outer surface of the required range up to the upper end approximately matches the width of the slab after the width is changed. A partition is formed in a vertical plane with a width interval between two surfaces, and the lower end thereof forms a charging part whose lower end can be positioned below the surface of the current slab molten steel in the mold with the width of the current slab, and is fixed to the mold. It is characterized by the provision of a temporary mold inserted between the walls, which is an effective means for preventing accidents such as breakage of the slab solidified shell on the side of width change, which is the most concern when changing width during casting, and the above-mentioned It is also an object of the invention to provide a temporary mold suitable for the method.

Other objects of the invention will become apparent in the following specification.

1 to 5 show step by step the progress of the method of the present invention in reducing the slab width, and each figure schematically represents a vertical cross-sectional front view of a mold portion of a continuous casting device.

Figures 6 to 8 are the same diagrams as above showing step by step the progress of the method of the present invention when expanding the slab width, and Figure 9 is a perspective view of an example of a temporary mold when reducing the slab width; FIG. 10 is a perspective view showing an example of a temporary mold for expanding the slab width.

First, a method for reducing the slab width during continuous casting according to the present invention will be explained with reference to FIGS. 1 to 5.

Figure 1 shows a slab 1 with a slab width of 11 being continuously cast. 2 is a movable wall of the mold set to the slab width of 11, 3 is a fixed wall of the mold, and 4 is an immersion nozzle for pouring molten steel. , 5 is the molten steel part of the slab, 6 is the solidified shell (shell) being formed, and 7 is the powder flux on the surface of the molten steel.

In order to reduce the width of the slab 1' to the slab 1' having a width of 12, first 1) the injection of molten steel is temporarily stopped and the nozzle 4 is pulled up above the surface of the molten steel being cast.

However, the drawing of the slab 1 by the pinch rolls continues as it is, and when the surface of the molten steel approaches the lower end of the mold, for example, when it reaches 100 to 200 mm from the lower end of the mold, the pulling out of the slab 1 is temporarily stopped.

FIG. 2 shows this state. At this point, the solidified shell 6 of the slab has grown considerably, but the upper surface of the slab remains in a molten steel state due to the heat retention effect of the powder flux 7.

■ In this state, a temporary mold is installed in the mold as shown in Fig. 3. In other words, the two opposing walls 8, 8 are inserted from above the mold, and parallel to the movable walls 2, 2, between the fixed walls 3, 3. Attach it tightly.

In this case, the two walls 8, 8 of the temporary mold are for moving the movable walls 2, 2 of the mold to that position according to the process sequence described below, and the outer surfaces reaching the upper ends of the two opposing walls are moved. The part where the inner surface of the movable wall comes into contact must form at least a vertical plane parallel to the movable wall, and the width interval between the outer surfaces should be set to approximately correspond to the target slab width l2 to be changed in width, The lower ends of the two opposing walls are inserted so as to reach 100 to 200 mm below the surface of the molten steel of the existing slab 1.

The one shown in the figure has a hook part 9 on the lower end of a flat plate made of mild steel plate with a thickness of 6 mm to 10 mm, which has two opposing walls, and a hook part 9 on the opposite inner side to firmly connect the slab after restarting casting. This is an example in which a temporary mold is formed from a pair of flat plates with protrusions 10 for locking.

In this way, the hot water level in the mold should be 100 to 20 m below the bottom of the mold.
The reason why a temporary mold is provided at the point of 0 mm is to prevent molten steel from leaking, and even if molten metal leaks between the two opposing walls and the fixed wall that make up the temporary mold, it will immediately solidify and be used safely. This is to prevent this from happening.

In order to ensure complete safety during actual operation, it is recommended to further sprinkle a cold material such as powder on the surface of the molten steel between the temporary mold wall and the movable wall of the mold.

Further, as illustrated in FIG. 9, the temporary mold has two opposing walls 8,
8 are connected by tie rods 11 or side plates, etc., to form a frame shape in advance, making it convenient to handle when inserting and mounting into the mold.

After the temporary mold has been installed, the nozzle 4 is lowered into the temporary mold to resume pouring the molten steel, as shown in Figure 4, and when the molten metal level in the temporary mold reaches a height of 100 to 200 mm from the bottom end. Then, the end shoulder of the current width of the slab passes the lower edge of the movable mold walls 2, 2, and the movable walls 2, 2 are moved in the horizontal arrow direction as shown in FIG. From the broken line position of slab width l1 to the vertical plane position of the temporary mold, that is, slab width 12 after width change
Move it to the position shown by the solid line.

During this time, the slab is also pulled out and moved downward, so the upper H range of the outer surfaces of the two opposing walls of the temporary mold must be at least a vertical plane parallel to the movable wall.

The movement of the movable walls 2, 2 is generally configured to be remotely controlled using hydraulic pressure or an electric motor as a drive source, but in the case of implementing this method, for example, a celsin mechanism or the like is incorporated into this to control the movement of the movable walls by a predetermined amount. It is recommended to make it so that the operator can distinguish it, or to automatically stop the movement by setting a predetermined amount of movement.

In addition, the moving speed of the movable wall is as follows: two opposing walls of the temporary mold 8, a movable wall 2,
2 moves are determined to be completed.

■After the mold width has been reduced, the temporary mold is passed under the mold together with the slab as shown in Figure 5, and continuous casting can be continued as usual. One part is cut off using a cutting machine on the output side of the pinch roll.

Another feature of this method is that the truncation range is only the above-mentioned portion, which is extremely small compared to other width changing methods.

Next, the case of expanding the slab width during continuous casting will be explained with reference to FIGS. 6 to 8.

When expanding the slab width from the previously explained continuous casting slab having the slab width 11 in the state shown in Fig. 1 to the slab 1' having the slab width 13, there is no difference from the procedure for reducing the slab width already explained. .

That is, first, (1) injection of molten steel is temporarily stopped, and when the nozzle 4 is pulled up and the molten metal level in the mold reaches 100 to 200 mm from the lower end of the mold, drawing out of the slab is temporarily stopped.

(2) In this state, a temporary mold is placed in the mold as shown in FIG.

In this case, since the intended slab width l3 for width change is larger than the current slab width l1, the two opposing walls 8', 8' forming the temporary mold are
The point is that the width interval between the vertical surfaces of the outer surface of the upper part up to the upper end is larger than the facing width interval of the lower part inserted into the mold, and therefore the two walls 8', 8' naturally take a bent or curved shape. The only difference from the above-mentioned case for width reduction is that the width interval between the outer surfaces of the upper opposing width enlarged portions is set to approximately match the target slab width, and the lower end of the insertion is set to the molten steel of the current slab 1. There is no difference from the above point in that it is located below the surface.

Fig. 10 shows an example in which the two opposing walls 8', 8' are connected by a side plate 12 to form a frame shape in advance to facilitate operation, but of course the two walls 8', 8' can be individually molded into a mold. A temporary mold may be provided by inserting and fixing the molds so as to face each other between the fixed walls of the molds.

After the temporary mold was installed, the nozzle 4 was lowered into the temporary mold to resume injection of molten steel, as shown in Figure 7, and the molten metal level in the temporary mold reached a height of 100 to 200 mm from the top. At this point, the drawing of the mold 1 is resumed, and the movable walls 2, 2 of the mold are
is moved in the horizontal arrow direction from the position shown by the broken line of the current slab width l1 to the vertical plane position above the temporary mold, that is, the position shown by the solid line of the slab width l3 after width change.

In this case, the movement of the movable wall must be completed before the upwardly expanding portion of the temporary mold, which descends together with the slab, reaches the upper end of the movable walls 2, 2.

■After expanding the mold width in this way, the temporary mold is passed under the mold together with the slab, and after being pulled out as already described in the case of reducing the slab width, the slab with the temporary mold attached Cut off the connected part.

As described above, the method of the present invention allows for safe and easy width change during continuous casting while protecting slabs in a temporary mold, where the shell formed in the mold is not yet strong enough and there is an extremely high risk of breakout. It is unique in that it allows both expansion and reduction of the slab width, and the time required to stop drawing the slab during continuous casting to change the width is extremely short, about 30 seconds.

In other words, according to actual results, in S-type continuous casting equipment, 0.
09%C, 0.15%Si, 0.61%Mn steel 11
Casting speed 0.9m into a 50mm wide x 27Qmt thick slab
The drawing stop time required to change the slab width to 1350 mm during continuous casting at a rate of 1,350 mm was 30 seconds;
1200m from the slab width of 250mm width x 270mm thickness
The drawing stop time required to reduce the width to m width was 35 seconds.

There were no accidents such as breakouts or leaks, and the desired slab width change could be completed quickly.

As described above, according to this method, it is possible to meet various demands for different slab widths without reducing the productivity inherent in continuous casting, and the equipment cost required for implementing this method is extremely low.

[Brief explanation of drawings]

1 to 5 are longitudinal sectional front views for explaining step-by-step the process of reducing the slab width during continuous casting by carrying out this method. Figures 6 to 8 are the same views when the slab width is similarly enlarged. FIG. 9 is a perspective view showing an example of a temporary mold for reducing the slab width. FIG. 10 is a perspective view showing an example of a temporary mold for expanding the slab width. Symbols in the drawings: 1... Slab (slab), 2... Movable wall of the mold, 3... Fixed wall of the mold, 4... Nozzle for injecting molten steel, 5... To the molten steel part of the slab 6... ...Solidified shell (shell) of the slab, 7... Powder flux on the surface of molten steel, 8... Wall plate of the temporary mold facing the movable wall of the mold, 9... Hook for locking,
10... Locking protrusion, 11... Tie rod, 12... Temporary mold side plate.

Claims (1)

[Scope of Claims] 1. The injection of molten steel is temporarily stopped, the drawing of the slab is continued, and when the surface of the molten steel in the mold approaches the lower end of the mold, the drawing of the slab is temporarily stopped, and then at least the movement of the mold is stopped. It has two opposing sides that are parallel to the wall, and the outer surface of the required range up to the upper end is formed into a vertical plane with a width interval between two surfaces that approximately corresponds to the width of the slab after width replacement, and the lower end is the same as the current slab. A temporary mold is prepared by inserting a steel partition that reaches below the surface of the molten steel in a wide mold between the fixed walls of the mold, and in this state, the injection of molten steel into the temporary mold is resumed until the molten metal level is When the height of the slab reaches 100 to 200 mm from the lower end of the mold, the drawing of the slab is restarted, and the movable wall of the mold is moved to the vertical plane position of the temporary mold to change the width of the mold, and the temporary mold is removed from the slab. A method for changing the width of a slab during continuous casting, characterized by passing the width of the slab along with the cast slab to the bottom of the mold. 2. It can be inserted closely between the fixed walls of the mold for changing the width of the slab, and it has at least two opposing walls 8, 8 parallel to the movable wall of the mold, and the outer surface reaching the upper end of the required range above the mold can be inserted tightly between the fixed walls of the mold for changing the width of the slab. A vertical plane is formed with a width interval between two surfaces that approximately corresponds to the width of the slab, and the lower part of the two opposing walls forms a charging part whose lower end can be inserted under the surface of the molten steel of the existing slab. Temporary steel mold for changing slab width during continuous casting. 3 At least two opposing walls 8 of the temporary mold parallel to the movable wall of the mold
, 8 have locking protrusions 10 on their inner surfaces, the steel temporary mold for changing the slab width during continuous casting according to claim 2. 4. Continuous casting according to claims 2 and 3, characterized in that the two opposing walls 8, 8 of the temporary mold parallel to the movable wall of the mold have locking hooks 9, 9 at the lower ends of the insertion mold. Temporary steel mold for changing the width of the slab inside.