JPH04270035A - Dummy sheet in twin roll type strip continuous casting - Google Patents

Abstract

PURPOSE:To stably take-up a cast strip to a take-up machine without breaking a dummy sheet to the cast strip by forming an end part in the connecting side of the cast strip so as to make a cross sectional area smaller as it approaches to the tip part. CONSTITUTION:The end-part of the dummy sheet 13 is formed by cutting so as to become protruded shape. Therefore, as it approaches to the tip part, the width of the strip becomes narrower and the cross sectional area become smaller. By this method, in the joining part between the dummy sheet 13 and the cast strip 6, the gentle deflection is generated but sharp breakage does not occurr.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of thin sheet slabs using a twin-roll continuous sheet casting apparatus.

0002

BACKGROUND OF THE INVENTION Twin-roll continuous sheet metal casting produces thin metal sheet slabs with a thickness of 1 to 3 mm. Therefore, thin metal sheets that are difficult to roll can be manufactured. Furthermore, when producing a thinner metal sheet by rolling, the rolling process can be greatly simplified because the reduction amount is small.

FIG. 2 is an explanatory diagram of the production of slabs using a twin-roll type continuous thin plate casting machine. In FIG. 2(A), the molten metal 5 is
Twin rolls 1-1, 1-2 rotating in the direction of arrow 8 and side weir 1
Pour into the pool 2 formed in step 5. The molten metal is cooled by twin rolls to form solidified shells 3-1 and 3-2. These solidified shells 3-1 and 3-2 are combined to form a slab 6,
It is taken out from the minimum gap part 4 of the twin rolls.

The solidified shells 3-1 and 3-2 are brought together near the minimum gap 4. Figure 2(B) shows the solidified shell 3-1
This is an example in which 3-2 and 3-2 are combined at 7 before reaching the minimum gap 4. When combined at 7, the thickness is t2mm, which is larger than t1.
However, the solidified part with a thickness of t2 mm is
It is not easy to perform routine work to pass through the minimum gap between the two rolls, which is t1 mm, which is narrower than mm.

As mentioned above, in the twin-roll type continuous thin plate casting machine, in order to combine the solidified shells at the minimum gap 4,
Immediately before the minimum gap 4, the center of the thickness of the slab is in a molten state. Therefore, immediately after coming out of the minimum gap 4, the slab 6 is scattered with micro-segregation in a liquid state and is at an extremely high temperature. This makes it extremely vulnerable. FIG. 3 shows an example of a track for conveying the manufactured slab 6 to the winding machine 9. FIG. 3A shows an example in which the loop 10 is formed and then wound. In this case, loop 1
The dead weight of the slab 6 of 0 is equal to the part of the slab directly below the minimum gap 4. However, as already mentioned, the slab directly below the minimum gap 4 is extremely fragile. Therefore, the slab directly below the minimum gap 4 cannot withstand the weight of the loop 10, and the slab is likely to break immediately below the minimum gap 4.

FIG. 3(B) shows an example in which a descending slab is supported by a slide 11. At this time, the slab slides on the slide 11 and is guided to the transport roll group 14. The weight of most of the cast slab is on the slide. Therefore, the slab is prevented from breaking immediately below the minimum gap portion 4. Although FIG. 3B shows an example of the slide 11 having a smooth inclined surface, it may be a slide that uses a large number of horizontal rollers to support the slab from below and guide it incline.

In FIG. 3(C), pinch rolls 12 press and support both sides of the slab. At this time, most of the dead weight of the slab is applied to the pinch rolls 12. Therefore, the slab is prevented from breaking immediately below the minimum gap portion 4.

FIG. 3 shows the running path for conveying the slab, but at the start of casting, a dummy sheet 13 is stretched in advance along the running path between the minimum gap 4 and the take-up roll 9 shown in FIG. The dummy sheet 13 has one end attached to the double roll 1-1.
and 1-2 and arranged in the tundish 2, extending along the running path of the slab, and the other end is fitted into the winding machine 9. When starting casting, after pouring the molten metal into the trough 2 shown in FIG. 2(A), the twin rolls 1-1 and 1-2 are rotated in the direction of arrow 8, and at the same time the dummy sheet is wound up by the winding machine 9. . Hot water pool 2
The molten metal melts and solidifies at the end of the dummy sheet inside, forming the tip of the slab, but when the twin rolls are rotated and the dummy sheet is wound up by the winder 9, the tip of the slab is Guided by the dummy sheet, it runs along the running path shown in FIGS. 3(B) and 3(C), and reaches the winding machine 9. That is, the winding machine 9 first winds up the dummy sheet, and then successively winds up the slab.

[0009]

[Problems to be Solved by the Invention] The present inventors have discovered that
In the twin roll continuous casting machine of type B) and (C),
Using an ordinary strip plate with its ends cut at right angles to the length direction as a dummy sheet, casting was started using the method described above to produce a thin plate slab. It was discovered that sharp bends frequently occur at the joint between the slab and the dummy sheet directly under the twin rolls. FIG. 4 is a diagram showing an example of folding of a joint.

[0010] When a bend 17 occurs at the joint, the joint between the slab 6 and the dummy sheet 13 is likely to break. This breakage frequently occurs when the broken joint 17 reaches the transport roll group 14 in FIG. 3 or the winding machine 9, and the shape of the fold 17 is corrected and smoothed. In addition, if the degree of bending is severe, it will break just below the twin rolls.

An object of the present invention is to provide a dummy sheet that prevents the occurrence of folding 17 at the joint between the slab and the dummy sheet at the start of casting.

0012

[Means for Solving the Problems] The present invention provides a dummy sheet for twin-roll continuous thin plate casting, in which the end on the side where the slabs are connected is formed so that the cross-sectional area becomes smaller as it approaches the tip. It is a feature.

FIG. 1 is an explanatory diagram of an example of the end of the dummy sheet on the side where slabs are connected, (A) and (B) are the conventional end shapes, (C), (D), (E) and (F) are examples of the ends of the dummy sheet of the present invention. Further, in the figure, 13 is a dummy sheet, 6 is a slab, and these are taken out in the direction of arrow 19.

According to the knowledge of the present inventors, in the conventional dummy sheet (A), the dummy sheet 13 ends at the arrow 17-1, and immediately after that, the entire moving object suddenly becomes only the slab 6. The sharp bend 17 mentioned in Fig. 4 is indicated by the arrow 17-1.
occurs. In FIG. 1A, 20 is a hole provided in the dummy sheet 13, and the molten metal enters the hole 20 and solidifies, thereby strengthening the connection between the dummy sheet and the slab. This hole 20 is shown in Figure 1.
Since it is obvious that the holes 20 can be provided as appropriate in the cases of (B) to (F), the description of the holes 20 is omitted in FIGS. 1(B) to (F).

The inventors used the dummy sheet shown in FIG. 1(B), but in this case too, a sharp fold occurred at the arrow 17-1 where the dummy sheet abruptly ended.

FIG. 1C shows an example of the dummy sheet of the present invention, in which the end of the dummy sheet 13 is cut and formed into a convex mountain shape. Therefore, the plate width becomes narrower toward the tip, and the cross-sectional area becomes smaller. According to the findings of the present inventors, when the dummy sheet shown in FIG. 17 does not occur. Note that the gentle deflection is within the range indicated by the arrow 16 in which the cross-sectional area of the dummy sheet 13 gradually decreases.

FIG. 1(D) shows another example of the dummy sheet of the present invention, in which the end of the dummy sheet 13 is provided with a large number of notches, and the entire dummy sheet is formed into a convex mountain shape. . Therefore, the cross-sectional area of the dummy sheet shown in FIG. 1(D) gradually decreases toward the tip. According to the findings of the present inventors, in the case of FIG. 1(D), gentle bending occurs within the range 16, but the sharp bend 17 shown in FIG. 4 does not occur.

FIG. 1(E) shows another example of the dummy sheet of the present invention, in which the end of the dummy sheet 13 is cut and formed into a concave valley shape. In this case as well, the cross-sectional area of the end of the dummy sheet decreases as it approaches the tip;
), no sharp bends occur. Although not shown in FIG. 1, the edges of the dummy sheet 13 shown in FIG.
Similar effects were obtained by providing a large number of cuts similar to those shown in FIG. 1(D) and forming the entire structure into the concave valley shape shown in FIG. 1(E).

FIG. 1(F) shows still another example of the dummy sheet of the present invention, in which (F-1) is a front view and (F-2) is a longitudinal sectional view. In the example of FIG. 1(F), the tip of the dummy sheet 13 is formed in the range indicated by the arrow 16 so that it becomes thinner toward the tip. Therefore, in this case as well, the cross-sectional area of the dummy sheet 13 decreases as it approaches the tip, but in this case as well, gentle bending occurs within the range 16, but the sharp fold 17 shown in FIG. 4 does not occur.

[0020]

[Operation] In Fig. 4, the sharp bend 17 at the joint between the slab 6 and the dummy sheet 13 is between the minimum gap 4 and the support portion 11' of the dummy sheet (slab) on the slide, or in Fig. 4 (B). ) is thought to be due to compressive stress acting on the material passing between the pinch roll 12 and the pinch roll 12.

FIG. 5 is an explanatory diagram of deformation near the joint between the dummy sheet and the slab when this compressive stress is applied.
-1), (A-2), and (A-3) are examples using conventional dummy sheets. At this time, as shown in Figure (A-2), the strength of the joint decreases rapidly at 17-1, when the dummy sheet 13 ends and only the slab 6 remains. Therefore, the compressive stress causes a sharp bend in 17-1, as shown in Figure (A-3). In addition, P1 in the figure is the strength of the dummy sheet,
P2 is the strength of the slab.

(B-1), (B-2), (B-3) in FIG.
) is an example using the dummy sheet of the present invention. In this case, the dummy sheet should be placed at the arrow 16 as shown in figure (B-1).
Within this range, the width decreases toward the tip, and the cross-sectional area also decreases. Therefore, as shown in Figure (B-2), the strength of the joint changes gradually within the range of the arrow 16, and there is no place where the strength suddenly decreases near the joint between the dummy sheet 13 and the slab 6. Therefore, although a gentle bend 18 is formed in the joint due to the compressive stress, no sharp bend is formed. Furthermore, this gentle deflection 18
The joints will not break when the slab is transported or rolled up.

In FIG. 4, the reason why compressive stress is generated between the minimum gap 4 and the support portion 11' of the dummy sheet (slab) or between 4 and 12 is not necessarily clear, but it is roughly as follows. It is thought about.

FIG. 6 shows a twin-roll continuous casting operation immediately after the start of casting. The twin rolls 1-1, 1-2 rotate at a circumferential speed of V1, and at the same time, the winding machine 9 also rotates at a speed synchronized with the twin rolls, for example, V1. Therefore, at this time, the slab 6 is sent out from the twin rolls at a speed of V1. Further, the winding machine side 9' of the dummy sheet is wound up at a speed of V1. However, since the dummy sheet 13 has curls, twists, and warps, there is play as shown by the wave shape in FIG. For this reason, the twin roll side 21 of the dummy sheet has a speed of V1 after this play disappears by winding, but immediately after the winding machine is rotated, the speed is V1.
It moves at a speed of V2 which is less than . Therefore, compressive stress is generated between 4 and 21 in FIG. 6, but since the joint between the slab and the dummy sheet is weak, this compressive stress forms a sharp fold 17.

[0025] The dummy sheet can be placed under tension so that there is no play, but if the dummy sheet is placed under tension, tensile stress will be applied to the slab immediately after the start of casting, and the fragile slab will break. do. As described above, in FIG. 6, when the amount of play (sag) in the dummy sheet is large, the compressive stress is also large. The amount of play in the dummy sheet is mainly caused by curling, twisting, etc. of the dummy sheet, but it is difficult to control these with high precision. Therefore, it is difficult to control the compressive stress described in FIG. 6 with high accuracy. As described above, the magnitude of the compressive stress generated in objects passing between the minimum gap 4 and the support part of the dummy sheet varies and is difficult to control, but when the dummy sheet of the present invention is used, the compressive stress can be reduced. Even if there is fluctuation, no sharp creases will occur at or near the joint between the slab and the dummy sheet. Therefore, the joint between the slab and the dummy sheet is difficult to break.

[0026]

[Effects of the Invention] When the dummy sheet of the present invention is used, sharp bends will not occur at the joint between the slab and the dummy sheet directly under the twin rolls, and therefore the slab and the dummy sheet will not break. The slab can always be stably guided to the winding machine and wound up.

[Brief explanation of the drawing]

[Figure 1] is an explanatory diagram of the end of the dummy sheet on the side where the slabs are connected;

[Figure 2] is an explanatory diagram of the production of slabs by twin-roll continuous thin plate casting;

[Figure 3] is an explanatory diagram of the running path of slabs and dummy sheets,

[Figure 4] is an explanatory diagram of the bending of the joint between the slab and the dummy sheet.

FIG. 5 is an explanatory diagram of the action of the dummy sheet of the present invention;

FIG. 6 is an explanatory diagram of the cause of compressive stress.

[Explanation of symbols]

1-1, 1-2: Twin rolls, 2: Hot water pool, 3-
1, 3-2: Solidified shell, 4: Minimum gap, 5: Molten metal, 6: Slab, 8: Rotation direction of twin rolls,
9: Winding machine, 10: Loop, 11: Slide,
12: Pinch roll, 13: Dummy sheet,
14: Conveyance roll, 15: Side weir, 17: Bent joint, 18: Gentle deflection, 20: Hole provided in dummy sheet.

Claims (1)

[Claims] 1. A dummy sheet for twin-roll continuous thin plate casting, characterized in that the ends on the side where slabs are connected are formed so that the cross-sectional area becomes smaller toward the tip.