JPS6224845A - Method and apparatus for continuous casting of thin ingot - Google Patents

Abstract

PURPOSE:To draw a solidified shell by horizontally or downward inclining paper and lower belts in tight contact therewith and to uniformly cool an ingot by forming said in such a manner that the space therebetween can be gradually adjusted by supporting rolls after a bending roll and that the space can also be adjusted by the supporting roll on the ingot side. CONSTITUTION:The endless belts 1, 3 held respectively to the horizontally or downward inclining pulleys 2, 4 are supported by the supporting rolls 6A, 8A between dam blocks 15. The belts are supported by supporting rolls 8B and 6B interposed with backup rolls 10 having belleville spring mechanisms 11 of movable frames 9 held by shafts 12 after the bending roll 5 and the space between the belts is made adjustable by a cylinder 13 so as to be gradually decreased. The space is also made adjustable by a cylinder 18 with the supporting roll 21 of a short side supporting frame 17 pressed to the belt 1, 3 surfaces by a spring-energized 19 centering roll 21 on the short side of the ingot as well. The solidified shell of the ingot is drawn by the belts 1, 3 in tight contact therewith, by which the ingot is uniformly cooled and the quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a continuous casting method for thin slabs and an apparatus for carrying out the method.

(Prior Art) Conventionally, as shown in Fig. 10, a twin-belt type continuous casting machine for thin slabs has a pair of belts on the long sides of the slab, which are disposed horizontally or inclined to face each other, and a belt between the belt sides. A mold consisting of a dam block on the short side of the slab that is closely arranged and moved in synchronization, or a pair of long sides of the slab that are arranged opposite each other so as to widen upward and narrow downward, although not shown. A narrow-type type in which a mold is made up of a side belt and a support plate on the short side of the cast strip that is closely arranged between the sides of the belt (Japanese Patent Laid-Open No. 6
0-9553 and Japanese Patent Laid-Open No. 60-9554) are known.

(Problem to be Solved by the Invention) However, in continuous casting machines that use horizontal or inclined molds, the thickness of the slab may be changed in-machine during casting, or the thickness of the slab may be changed by the cooling shrinkage of the slab. I can't narrow it down. When changing the thickness of the slab, it is necessary to stop the operation and replace it with a dam block corresponding to the thickness, which takes time and reduces productivity. In addition, since cooling shrinkage of the slab cannot be squeezed out, the slab separates from the upper belt, creating a gap, making it impossible to cool the slab evenly, and causing dents and cracks on the slab surface. Furthermore, there is a problem in that uneven thickness of the slab occurs, which is a difference in thickness at a predetermined position at the end of the slab in the width direction.

On the other hand, in the narrowing type continuous casting machine, the mold entrance is widened to allow the use of an immersion nozzle (because squeezing is performed in the molten metal state, the mold entrance dimension 2D is 1'20 mm).
It is necessary to make it as large as 711 JW or more, and it also requires a large reduction ratio of D/d=2 to 16, assuming the mold exit dimension is 2 d. Furthermore, a large-scale electromagnetic stirrer or the like is required to suppress the formation of solidified slab shells near the mold entrance.

Furthermore, even if the molten metal is stirred at the mold entrance, a thin solidified shell is formed on the short side of the slab, so a large reduction ratio like the one described above increases the drawing resistance, making stable casting difficult. There was an inconvenience.

(Means for Solving the Problem) The method for continuous casting of thin cast slabs of the present invention involves arranging upper and lower belts facing each other horizontally or with downward inclinations, and placing the upper and lower belts in the casting direction between the ends of the upper and lower belts on the entrance side of the mold. A bending roll is arranged along a direction perpendicular to the bending roll, side guides are provided between the upper and lower belt side portions in front and behind the roll, and the space between the upper and lower belts behind the bending roll is configured to gradually narrow toward the casting direction, In the process of drawing out the molten metal poured into the mold, the thickness of the slab is continuously reduced while crushing the solidified shell generated on the mold entrance side. This method enables stable drawing casting of slabs without suppressing the formation of solidified shells.

Further, the thin slab continuous casting device of the present invention is a twin belt type thin slab continuous casting machine in which upper and lower belts are disposed horizontally or downwardly inclined to face each other and are supported by belt support rolls. A bending roll along the direction perpendicular to the casting direction is arranged between the upper and lower belt ends on the side, and a support frame on which the upper belt support roll is attached is connected to an adjacent fixed frame near the bending roll and the fixed frame. It consists of a movable frame that can be tilted up and down about a side end, and an upper belt support roll behind the bending roll is provided so as to be movable in a downward direction via the movable frame, and between the upper and lower belt sides in front of the bending roll. A dam block is disposed at the top and bottom of the belt, and a support roll on the short side of the cast strip is disposed between the upper and lower belt sides behind the bending roll, and the short side support roll is movable in a direction perpendicular to the casting direction. This makes it possible to effectively implement the method of the present invention described above.

(Example) Hereinafter, an example of an apparatus for carrying out the method for continuously casting thin slabs according to the present invention will be described with reference to FIGS. 1 to 7.

In the figure, reference numeral 1 denotes a horizontal or downwardly inclined lower belt which is wound around two lower nip pulleys 2 and supported by a casting machine frame (not shown) via these.

Reference numeral 3 denotes an upper belt that is inclined downward more than the lower belt 1, and is wound around two upper nip pulleys 4 and supported by the casting machine frame via these, and is disposed opposite to the lower belt 1.

A bending roll 5 is fixed to the casting machine frame and arranged between the ends of the upper and lower belts 1 and 3 on the mold entry side (left side in the first figure) along a direction perpendicular to the casting direction (arrow direction in the first figure). ing. By the bending roll 5 and the valve, the mold entry side end of the upper and lower belts 1.degree. 3 is held parallel, and the portion behind the end is tapered to widen toward the mold entry side.

6A and 6B are lower belt support rolls, which are mounted on a support frame 7 fixed to the casting machine frame.

8A and 8B are upper belt support rolls, which are attached to a fixed frame and a movable frame 9 (not shown) that constitute a support frame provided separately on the casting machine frame.

Upper and lower belt support rolls 6A on the mold entry side.

8A are arranged in close contact with the back surfaces of the parallel portions of the upper and lower belts 1 and 3 so as to be rotatable therewith.

Upper and lower belt support rolls 6B on the exit side of the mold.

8B is arranged in close contact with the back surfaces of the tapered portions of the upper and lower belts 1 and 3 so as to be rotatable therewith, and movable in the opposite direction of the belts. is supported. The backup roll IO is mounted on the support frame 7.9 so as to be movable in the direction opposite to the belt. The disc spring mechanism 11 is provided to press the bearing portion of the backup roll 10 against the belt 1°3 side.

The movable frame 9 is adjacent to the fixed frame in the vicinity of the bending roll 5, and is pivotally attached to the casting machine frame at the end on the side of the fixed frame, and can be tilted up and down about a shaft 12 by a reduction cylinder 13. ing. In this case, the upper belt support roll 8B on the mold exit side performs a lowering operation to push the upper belt 3 downward by the extension operation of the lowering cylinder 13 via the movable frame 9.

Reference numeral 14 denotes a reduction amount detector (a differential transformer in the embodiment), which is connected to a control device for the reduction cylinder 13. The control device is configured to perform feedback control of the reduction cylinder 13 while detecting the amount of reduction with the detector 14 so that a predetermined amount of reduction is obtained at the mold exit end of the movable frame 9.

A dam block 15 is fixedly supported by the casting machine frame and is disposed in front of the bending roll 5 between the sides of the upper and lower belts 1 and 3 so as to be close to or in contact with the roll 5. A cooling water passage 16 is provided in the dam block 15, and a cooling water supply source (not shown) for supplying and discharging cooling water thereto is connected to the passage 16.

Reference numeral 17 denotes a short side support frame, which is disposed between the tapered side portions of the upper and lower belts 1 and 3 so as to be movable in a direction perpendicular to the casting direction by means of a width holding cylinder 18.

At the upper and lower portions of this short side support frame 17, centering rollers 20 resiliently supported by springs 19 are provided in contact with the upper and lower belts 1 and 3 so as to be rotatable. Therefore, the short side support frame 17 is held by the centering roll 20 with a slight gap between the upper and lower belts 1 and 3.

Reference numeral 21 denotes support rolls for the short side of the slab, which are rotatably attached to the short side support frame 17 and arranged in a row in the casting direction, so that the center between the sides of the tapered portions of the upper and lower belts 1 and 3 is It is located in

Reference numeral 22 denotes a slab width detector (differential transformer in the embodiment), which is connected to a control device for the width holding cylinder 18. The control device uses a detector 22 to call a position that coincides with the opposing surface of the dam block 15 in the casting direction as the forward end position of the guide surface of the support roll 21 on the short side of the slab, so that a predetermined slab width is obtained. The configuration is such that each width holding cylinder 18 can be feedback-controlled while detecting the amount of retraction of the cylinder 21.

Reference numeral 23 denotes a cooling nozzle, which is installed in the short side support frame 1 so as to pass between each slab short side support roll 21 and open facing the side surface of the slab.
It is located at 7. This cooling nozzle 23 has piping 2
4 is connected to a cooling water supply source via a flexible hose (not shown) or the like.

25 is a pinch roll, which is arranged on the exit side of the mold.

During the casting operation, molten metal from the tundish 26 is poured into the mold entrance space formed by the parallel parts of the upper and lower belts 1 and 3 and the left and right dam blocks 15, cooled from the surroundings, and then poured into the mold entrance space. As shown in FIG. 6, the cast slab moves into the mold exit side space formed by the tapered portions of the upper and lower belts 1 and 3 and the left and right short side support rolls 21 while producing a solidified shell S.

In this mold exit side space, the upper and lower belts 1-3 are supported by upper and lower belt support rolls 6B and 8B in a state that gradually narrows toward the casting direction, and each belt support roll 8B is supported by a movable frame 9 and a disc spring. Mechanism 11. Since the equalized rolling blade is transmitted by the disc spring mechanism 11 via the backup roll 10, the slab 27 is transferred to each of the upper and lower belt support rolls 6B and 8 via the upper and lower belts 1°3.
It is gradually rolled down while being stably supported by B, and the solidified shell S is crushed and uniformly cooled by the close contact between the slab 27 and the upper and lower belts 1 and 3. On the other hand, the left and right slab short side support rolls 2
1, the slab 27 does not become wider as it is rolled down. Therefore, the slab 27 is stably drawn and cast.

The width dimension of this slab 27 is set by the left and right slab short side support rolls 21 whose position is adjusted by the control of the width holding cylinder 18, and the thickness dimension is set by the upper and lower belt support rolls whose reduction is adjusted by the control of the reduction cylinder 13. 6B and 8B are set via the upper and lower belts 1 and 3, and both can be changed as appropriate.

As is clear from the explanation of the operation of the apparatus, in the continuous thin slab casting method according to the present invention, in the process in which molten metal poured into the inlet space of the mold is drawn out to the mold outlet side, While crushing the solidified shell S generated in
The thickness is gradually and continuously reduced.

(Effects of the Invention) Since the present invention has the above configuration, the slab can be drawn and cast without suppressing the formation of solidified shells on the entrance side of the mold, and as a result, the slab and belt are brought into close contact and the slab is uniformly formed. Can be cooled.

According to experiments, as shown in Table 1, the ratio between the thickness of the slab at the entrance side of the mold (D in Figure 6) and the thickness of the upper and lower belts at the exit end of the mold (D in Figure 7) By setting D/d within the range of 1 (D/d≦lO), draw casting of carbon steel, stainless steel, and Hi-Mn steel can be carried out without problems. Cracks were significantly reduced.

Furthermore, as shown in FIGS. 9(A) and 9(B), the uneven thickness of the slab was significantly improved compared to the conventional method.

Therefore, according to the method of the present invention, the surface quality of the slab can be improved as a stable drawing casting effect of the slab.

Further, since the apparatus of the present invention has the above-described configuration, it is possible to effectively carry out the method of the present invention, and to draw and cast slabs to a predetermined thickness using a simple mechanism.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an apparatus for continuously casting thin slabs according to the present invention, FIG. 2 is a front view showing a belt supporting roll reduction device in the apparatus shown in FIG. 1, FIGS. 3 and 4. 2 are a plan view and a front view showing a short side support roll moving device in the apparatus shown in FIG. 1. FIG. FIG. 5 is a schematic diagram of the apparatus shown in FIG. 1, and FIGS. 6, 7, and 7 are sectional views taken along lines A-- and B-- in FIG. 5. Figure 8 is a diagram showing the rate of occurrence of defects on the slab surface; Figure 9 (5);
(E) shows the degree of uneven thickness of the cast slab compared to the present invention and the conventional method.
Upper belt, 4... Upper nip pulley 5... Bending rolls 6A, 6B... Lower belt support roll 7... Support frame 8A, 8B... Upper belt support roll 9... Movable frame 10... Backup roll 11... Dish Spring mechanism, 12... Shaft 13... Reduction cylinder, 14... Reduction amount detector 15...
Dam block, 16... Cooling water passage 17... Short side support frame 18... Width holding cylinder, 19... Spring 20... Centering roller 21... Slab short side support roll 22... Slab width detector , 23... Cooling nozzle 25... Pinch roll, 26... Tandish 27... Slab. Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (2)

[Claims] (1) The upper and lower belts are arranged horizontally or tilted downward to face each other, and a bending roll along the direction perpendicular to the casting direction is arranged between the ends of the upper and lower belts on the mold entry side, and the upper and lower belts are arranged in front and behind the roll. A side guide is provided between the sides, and the space between the upper and lower belts behind the bending rolls is configured to gradually narrow in the casting direction, and in the process of drawing out the molten metal poured into the mold, it A continuous casting method for thin slabs, characterized by continuously reducing the thickness of slabs while crushing the solidified shells produced. (2) In a twin-belt continuous casting machine in which the upper and lower belts are disposed horizontally or tilted downward to face each other and are supported by belt support rolls, the caster is placed between the ends of the upper and lower belts on the mold entry side. Bending rolls are arranged along a direction perpendicular to the bending direction, and a support frame to which an upper belt support roll is attached can be tilted up and down with respect to an adjacent fixed frame in the vicinity of the bending rolls, centering on the side edge of the fixed frame. A movable frame is provided so that an upper belt support roll behind the bending roll can be moved downwardly via the movable frame, and a dam block is arranged between the upper and lower belt sides in front of the bending roll. 1. A twin-belt type continuous casting machine for thin slabs, characterized in that a support roll on the short side of the slab, which is movable in a direction perpendicular to the casting direction, is disposed between the upper and lower belt sides behind the rolls.