JP2013091072A - System for semi-continuous casting of aluminum and method for semi-continuous casting of aluminum using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system for semi-continuous casting of aluminum, using a bottom block which can effectively restrain deformation on a bottom section even though casting a slab having a cross section in which the ratio of (length of a long side/length of a short side) is large.SOLUTION: The system for semi-continuous casting of aluminum includes a water-cooled mold opened at up and down directions, and the bottom block for blocking a lower part of the mold at the time of starting casting, in which a solidified ingot is descended together with the bottom block by pouring molten metal to the top face of the bottom block in the mold in casting. In the system, the bottom block in which the horizontal cross section is a rectangle, and in the periphery of the top face of the bottom block, the long side is formed at a mountain shape having an inclined section gradually increasing its height rather than a corner angle section intersected between the long side section and a short side section and each point of the long side section excluding the corner angle section is higher than each point of the short side section, is applied as a bottom block.

Description

  The present invention relates to a semi-continuous casting apparatus for aluminum (including an aluminum alloy, the same shall apply hereinafter) and a method for semi-continuous casting of aluminum using the apparatus.

  Semi-continuous casting of aluminum ingots, for example, aluminum slabs for rolling with a rectangular horizontal cross section, has a water-cooled mold that is opened up and down, and a bottom block that closes the bottom of the mold at the start of casting. Using a casting device configured to inject molten metal into the top surface of the block and lower the solidified ingot together with the bottom block, applying a rectangular water-cooled mold and a bottom block with a rectangular horizontal section Although it has been carried out, there is a problem that the cast slab is liable to have a shape defect such as warping or constriction. These shape defects are likely to occur at the beginning of casting, as will be described below.

  That is, the semi-continuous casting of the aluminum slab is started by setting the bottom block 2 in the mold 1, injecting the molten metal 4, and lowering the solidified slab 3 together with the bottom block 2 as shown in FIG. 8. Then, after casting starts, the descending speed of the bottom block 2 is sequentially increased, the descending speed of the bottom block 2, the pouring speed, and the molten metal level (from the lower end (P) of the mold shown in FIG. 9 to the molten metal surface (Q Casting is performed in a steady state in which the height Y) is kept constant. 8 and 9, 5 is a refrigerant (usually cooling water) supplied to the mold 1, 1a is an opening (slit) provided at the lower end of the mold 1, and the refrigerant 5 flows out of the opening 1a. Then, it is supplied to the side surface of the slab 3 that has left the mold 1. 3a is a solidified shell and 2b is a top surface of the bottom block.

  After the start of casting, the slab 3 drawn downward together with the bottom block 2 is rapidly cooled by coming into contact with the refrigerant 5 discharged from the opening 1a when it comes out of the mold 1 and large solidification shrinkage occurs. Since the solidification shrinkage amount is different between the long side portion and the short side portion of the slab 3, as shown in FIG. 10, the bottom portion of the slab 3 is warped toward the long side portion. It deforms from the original solidified shell 3b and falls away from the mold 1 and falls inward (this deformation is referred to as “sledge”). By forming the warp, as shown in FIG. 11, the long side of the bottom of the slab 3 is warped upward by a distance S, and the outermost part of the solidified shell 3 a is deformed inward by a distance K (this deformation is referred to as “ Called “Cubire”).

  Since the molten metal 4 is stored on the solidified shell 3a, if the warp is large, the amount of deformation K of the constriction increases, and there is a risk that the molten metal 4 leaks from the gap of the mold 1 and so-called hot water leakage occurs. Therefore, preventing the leakage of hot water is a problem in the semi-continuous casting method, and the shape of the bottom block has been changed so far in order to suppress the formation of constrictions due to warping (hereinafter referred to as “bottom deformation”). There have been attempts to do so.

  In recent years, aluminum slabs have been increased in size for the purpose of improving yield, etc., and there are many slabs with a longer cross-sectional shape than the conventional one (the ratio of the length of the long side / the length of the short side is large) It has become to. For this reason, the difference in solidification shrinkage between the long side and the short side in the slab cross section becomes larger and the bottom deformation tends to increase accordingly, and the conventional bottom block has the effect of suppressing the bottom deformation. Is not enough.

JP-A-8-215803 Japanese Patent Laid-Open No. 9-308944

  The present invention has been made as a result of repeated tests and examinations on the relationship between the bottom deformation of the continuously cast aluminum slab and the shape of the bottom block. The purpose of the present invention is (length of long side / A semi-continuous casting apparatus for aluminum using a bottom block capable of effectively suppressing bottom deformation even with a slab having a cross-sectional shape with a large ratio of the length of the short side part, and the apparatus The object is to provide a semi-continuous casting method of aluminum.

  In order to achieve the above object, an aluminum semi-continuous casting apparatus according to claim 1 is provided with a water-cooled mold opened up and down and a bottom block that closes the lower part of the mold at the start of casting. In the aluminum semi-continuous casting machine configured to inject molten metal into the top surface of the steel and to lower the solidified ingot together with the bottom block, the bottom block has a rectangular horizontal cross section, at the outer periphery of the top surface of the bottom block The long side portion is formed in a mountain shape having an inclined portion whose height gradually increases from the corner portion where the long side portion intersects with the short side portion, and any portion of the long side portion excluding the corner portion is short. A bottom block that is higher than the side portion is applied.

  The semi-continuous casting apparatus for aluminum according to claim 2 is characterized in that, in claim 1, the length of the inclined portion in the long side portion of the outer peripheral portion of the top surface of the bottom block is D (mm), and the length of the short side portion is W ( mm), the relation of W / 2 ≦ D is satisfied.

  According to a third aspect of the present invention, there is provided the semi-continuous casting apparatus for aluminum according to the first or second aspect, wherein the length of the long side portion of the outer peripheral portion of the top surface of the bottom block is L (mm) and the length of the short side portion is W (mm). ), The relationship of L / W ≧ 1.7 is satisfied.

  A method for semi-continuous casting of aluminum according to claim 4 is a method for semi-continuously casting an aluminum slab having a rectangular horizontal section using the casting apparatus according to any one of claims 1 to 3, wherein the top surface of the bottom block Casting is started by placing the bottom block so that the corner (A) where the long side intersects with the short side is positioned above the lower end (P) of the mold by a distance of O (mm) in the outer periphery of The difference between the height of the highest part (B) of the long side part formed in the mountain shape and the height of the corner part (A) is H (mm), and the mold from the lower end part (P) of the mold in the steady state Casting is performed so as to satisfy the relationship of Y ≦ H + O, where Y (mm) is the height of the molten metal surface (Q). However, the steady state refers to a state where semi-continuous casting is performed with the bottom block descending speed constant.

  According to the present invention, the problem of bottom deformation is solved, and even in the case of a slab having a cross-sectional shape having a large ratio of (long side length / short side length), bottom deformation is effectively suppressed. An aluminum semi-continuous casting apparatus and a method of semi-continuous casting of aluminum using the apparatus are provided.

It is a schematic perspective view which shows the Example of the bottom block used with the semi-continuous casting apparatus of aluminum by this invention. It is explanatory drawing which shows the state which set the bottom block of FIG. 1 to the casting_mold | template at the time of casting start. It is a schematic perspective view which shows the Example of the bottom block used with the semi-continuous casting apparatus of aluminum by this invention. It is a schematic perspective view which shows the Example of the bottom block used with the semi-continuous casting apparatus of aluminum by this invention. It is a schematic perspective view which shows the Example of the bottom block used with the semi-continuous casting apparatus of aluminum by this invention. It is a schematic perspective view which shows the Example of the bottom block used with the semi-continuous casting apparatus of aluminum by this invention. It is a schematic perspective view which shows the Example (The form by which the inclination part was formed in circular arc shape in FIG. 6) of the bottom block used with the semi-continuous casting apparatus of aluminum by this invention. It is a partial longitudinal cross-sectional view which shows the time of the casting start in the semi-continuous casting of aluminum. It is a partial longitudinal cross-sectional view which shows the steady state in the semi-continuous casting of aluminum. It is a figure explaining generation | occurrence | production of the warp in the semi-continuous casting of aluminum. It is a figure explaining generation | occurrence | production of the constriction in the semi-continuous casting of aluminum.

  As shown in FIG. 9, the semi-continuous casting apparatus for aluminum according to the present invention comprises a water-cooled mold 1 opened up and down and a bottom block 2 that closes the lower part of the mold at the start of casting. It is assumed that the molten metal 4 is poured into the top surface of the block 2 and the solidified ingot (slab) 3 is lowered together with the bottom block 2.

  As shown in FIG. 1, in the present invention, as shown in FIG. 1, in the present invention, the horizontal cross section is a rectangle having a vertical L and a horizontal W, and the long side portion is the long side portion in the outer peripheral portion of the top surface of the bottom block. Is formed in a mountain shape having an inclined part (length D) whose height gradually increases from the corner A intersecting the short side, and any part of the long side excluding the corner A is shorter than the short side. It is characterized by applying a raised bottom block. In the bottom block shown in FIG. 1, the long side portion is composed of an inclined portion (length D) and a horizontal portion (length C), and the height of the chevron, that is, the highest part of the long side formed in the chevron. The difference between the height of B and the height of the corner A is H.

  As described above, at the initial stage of casting, when the refrigerant (cooling water) directly collides with the slab, the solidified shell grows rapidly, which causes the bottom deformation. However, the aluminum slab using the bottom block of the present invention is used. In this semi-continuous casting, the timing of rapid solidified shell growth can be made different between the long side portion and the short side portion of the slab. That is, when the bottom block of FIG. 1 is used, when the molten metal injected into the top surface of the bottom block is solidified at the beginning of casting, first, the short side portion and the corner portion A of the bottom block are used as a coolant (cooling water). Because of contact, coagulation is first initiated at that site. At that time, the long side is still in the mold, and after the solidification at the short side and the corner A is completed, the long side comes into contact with the coolant (cooling water). Solidification is delayed, and there is a shift in the timing of solidified shell growth at the long side and short side of the slab, and the bottom deformation can be effectively suppressed.

  In the present invention, the length L (mm) of the long side portion of the outer peripheral portion of the top surface of the bottom block, the length D (mm) of the inclined portion in the long side portion, and the length W (mm) of the short side portion It is desirable to make the relationship W / 2 ≦ D ≦ L / 2 in order to effectively suppress bottom deformation. In the case of W / 2> D, since the change in the height of the long side portion and the short side portion is too rapid, cracks are likely to occur at the corners of the slab.

  In addition, the bottom block illustrated in FIG. 1 is effective for suppressing the deformation of the bottom of the slab. In particular, the ratio of the length L of the long side to the length W of the short side, L / W is If the bottom block of 1.7 or more is used, the bottom deformation of the slab can be more effectively suppressed.

  As shown in FIG. 1, the bottom block 2 applied in the present invention has only a slope portion as shown in FIG. 3 in addition to a slope portion and a horizontal portion (length C) provided on the long side portion. However, it may be one that does not have a horizontal portion, and as shown in FIGS. 4 and 5, the inclined portion may be formed in an arc shape. Moreover, as shown in FIG. 6, FIG. 7, what formed the digging part in the center part of the top face of a bottom block is also applicable.

  A semi-continuous casting method of an aluminum slab having a rectangular horizontal cross section for obtaining the effect of suppressing the deformation of the bottom using the above semi-continuous casting apparatus will be described. At the time of casting preparation, as shown in FIG. The bottom block 2 is arranged so that the corner A where the long side intersects with the short side is positioned above the lower end P of the mold 1 by a distance of O (mm) in the outer peripheral portion of the top surface of the mold. The difference between the height of the highest portion B of the long side formed in the chevron and the height of the corner A is H (mm), and the molten metal surface Q in the mold from the lower end P of the mold 1 in a steady state. When the height (molten metal level) is Y (mm) (see FIG. 9), casting is performed so as to satisfy the relationship of Y ≦ H + O. As described above, the steady state refers to a state where semi-continuous casting is performed with the lowering speed of the bottom block 2 being constant.

  In the case of Y> H + O, since the timing of the rapid solidified shell growth at the long side portion, the short side portion, and the corner portion A is too close, the effect of suppressing the bottom portion deformation cannot be sufficiently obtained. It is desirable that H + O <M when the length of the mold is M (mm). When H + O ≧ M, when the bottom block is set in the mold at the time of casting preparation, the bottom block protrudes from the mold to cause an inconvenience such as poor workability.

  Examples of the present invention will be described below in comparison with comparative examples to demonstrate the effects of the present invention. In addition, these Examples show one embodiment of the present invention, and the present invention is not limited to these.

Examples 1-3, Comparative Examples 1-3
The bottom block of the shape shown in Table 2 was prepared, and the semi-continuous casting test of the aluminum alloy which has a composition shown in Table 1 was done using these bottom blocks. In addition, as a bottom block, about Example 1, 2, the shape shown in FIG. 7 (the center part of the top surface of the bottom block is provided with a digging portion of 400 mm × 50 mm), and Example 3 is a diagram. The thing of the shape shown in 1 was used.

  About the comparative example 1, in the shape shown in FIG. 7, the long side part of the outer peripheral part of the top surface of a bottom block is not formed in the mountain shape which has an inclination part, but all were formed in the horizontal part (boat shape), comparison Example 2 was formed in a flat plate shape, and Comparative Example 3 was shown in FIG. 1 of Patent Document 2, that is, an edge protruding upward at the peripheral edge of the top surface of the rectangular bottom block. The edge part formed in the long side part among this edge part was used higher than the edge part formed in the short side part.

The casting conditions are as follows.
Horizontal cross-sectional shape of slab: long side part 550mm, short side part 170mm
However, only Example 2 has a long side portion of 282 mm and a short side portion of 170 mm.
Casting temperature: 700 ± 15 ° C
Casting speed (bottom block lowering speed in steady state): 55 mm / min Mold cooling: Cooling water temperature 25 ° C., Cooling water amount 170 mm / min per 1 mm inner circumference of mold, mold length M: 105 mm
O value during casting preparation: 5 mm
Y value after casting starts (after pouring starts): 80mm

  Table 1 shows the results of measuring the amount of warpage of the cast slab. As shown in Table 1, the amount of warpage of the slabs of Examples 1 to 3 according to the present invention is remarkably improved as compared with the amount of warpage of the slabs of Comparative Examples 1 to 3, and the bottom deformation suppressing effect according to the present invention is improved. confirmed.

1 Mold 1a Opening (slit)
2 Bottom block 2b Top surface of bottom block 3 Slab (ingot)
3a Solidified shell 3b Original solidified shell 4 Molten metal 5 Refrigerant (cooling water)
A Bottom corner of the bottom block B The highest part of the long side of the bottom block H The difference between the height of B and the height of P P Lower end of the mold Q Molten surface position Y From the molten surface height OP, the bottom block is short Distance to the side M Mold height K Constriction amount S Sraft amount of slab bottom

Claims (4)

A water-cooled mold opened up and down and a bottom block that closes the lower part of the mold at the start of casting, and molten metal is injected into the top surface of the bottom block in the mold to lower the solidified ingot together with the bottom block. In the semi-continuous casting apparatus for aluminum (including aluminum alloy, the same shall apply hereinafter) configured as described above, the horizontal cross section is rectangular as the bottom block, and the long side is short on the outer periphery of the top surface of the bottom block. Applying a bottom block that is formed in a chevron with a slope that gradually increases in height from the corner that intersects the side, and that any part of the long side excluding the corner is higher than the short side A semi-continuous casting apparatus for aluminum. Satisfying the relationship of W / 2 ≦ D, where D (mm) is the length of the inclined portion at the long side portion of the outer peripheral portion of the top surface of the bottom block and W (mm) is the length of the short side portion. The semi-continuous casting apparatus for aluminum according to claim 1. When the length of the long side portion of the outer peripheral portion of the top surface of the bottom block is L (mm) and the length of the short side portion is W (mm), the relationship of L / W ≧ 1.7 is satisfied. The semi-continuous casting apparatus for aluminum according to claim 1 or 2. A method for semi-continuously casting an aluminum slab having a rectangular horizontal cross section using the casting apparatus according to any one of claims 1 to 3, wherein a long side portion is a short side portion in an outer peripheral portion of a top surface of a bottom block. Casting is started by placing the bottom block so that the intersecting corner (A) is positioned above the lower end (P) of the mold by a distance of O (mm), and the longest side formed in the chevron is the highest The difference between the height of the part (B) and the height of the corner (A) is H (mm), and the height of the molten metal surface (Q) in the mold from the lower end (P) of the mold in a steady state is Y. (Mm)
Y ≦ H + O
A semi-continuous casting method of aluminum, wherein casting is performed so as to satisfy the relationship of However, the steady state refers to a state where semi-continuous casting is performed with the bottom block descending speed constant.

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