JPH0999344A - Mold for vertical semi-continuous casting of non-ferrous metallic slab - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a metallic slab at a low cost, facilitating the control and thinning the thickness of surface skin structure by sufficiently thinning the wall thickness of a lower step mold at solidified metal side, flowing secondary cooling water in the lower step mold from a short wall side of the mold and radiant-cooling into the solidified metal from the inner part in the lower part of the mold. SOLUTION: The water-cooling mold 30 is made tow-step structure of the upper step mold 31 and the lower step mold 32, and the upper step mold 31 is made a slow cooling mold and the lower step mold 32 is made a rapid cooling mold. Then, a heat insulating material 33 is interposed between the upper step mold 31 and the lower step mold 32. The upper step mold 31 sufficiently thickness the wall thickness 31a at the molten metal side and cooling water is flowed from the short wall side of the rectangular mold and discharged to the outer part from many flow-out holes 31d on the whole periphery of the rectangular mold through a primary cooling chamber 31b. Further, the lower step mold 32 sufficiently thins the wall thickness 32a at the solidified metal side, and secondary cooling water is flower from the short wall side of the rectangular mold and radiated 32d from secondary cooling water discharging nozzle 32c at the whole periphery of the inner part in the lower part of the mold through a secondary cooling chamber 32b to cool the solidified metal 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical semi-continuous casting of a non-ferrous metal, in particular aluminum and an aluminum alloy, for rolling slabs (square ingots). The present invention relates to a mold having a structure in which a chill layer and a coarse cell layer are combined and which has a reduced thickness (described later).

[0002]

2. Description of the Related Art Conventionally, DC casting (direct chill casting) has been widely used as a continuous casting method for rolling slabs of nonferrous metals such as aluminum and aluminum alloys. In this DC casting, as shown in FIG. 3, a molten metal 1 is poured from above into a water-cooled mold 3 made of metal such as a rectangular copper-based or aluminum-based mold having an open bottom, and a solidified metal 2 is poured from the bottom of the mold. It is known as semi-continuous casting because it is continuously taken out to obtain an ingot of a predetermined length. The rectangular cross-section slab for rolling produced by this DC casting is subjected to hot rolling after chamfering the upper and lower surfaces.

As shown in FIG. 4, the cross-sectional structure of the rectangular slab manufactured by DC casting has a chill layer 211 at the outermost periphery, a coarse cell layer (columnar crystal) 212 next, and an internal portion. It is a uniform and fine cell layer (granular crystal) 22. The outermost chill layer 211 and the coarse cell layer 212
Is very different from the internal structure and causes surface defects and internal defects of the plate, and is thus scalped before being subjected to rolling.
The structure in which the outermost chill layer 211 and the coarse cell layer 212 are combined looks like a frame when the cross section of the slab is etched, and is therefore referred to as a frame structure 21 for convenience in this specification. Depending on the conditions of the DC casting method, the frame structure 21 grows to a thickness of 15 to 20 mm.

As described above, the frame structure 21 is surface-removed before hot rolling, but this surface-removal is a factor that greatly reduces the yield of ingots. Especially for large rolling slabs (eg thickness 500 mm x width 1800 mm x length 100
In the case of (00 mm), this effect is large. Therefore, how to reduce the thickness of the frame structure 21 is an issue. On the other hand, as an improvement of the conventional DC casting shown in FIG. 3, hot top casting method (for example, Japanese Patent Publication No. 54-42847) and gas pressure casting method (for example, Japanese Patent Laid-Open Publication No. 54-13243).
No. 0, Japanese Patent Laid-Open No. 61-37352), electromagnetic casting method, and the like, all of which have a problem that the frame structure is relatively thin, but the equipment is complicated and management is difficult. Further, the electromagnetic casting method has a problem that the initial equipment cost and running cost are high.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a casting mold for manufacturing a non-ferrous metal rolling slab which is low in cost, easy to manage, and capable of reducing the thickness of the frame structure. is there.

[0006]

According to the invention of claim 1 for solving the above-mentioned problems, molten metal is poured from above into a rectangular water-cooled mold having an open bottom, and solidified metal is continuously supplied from the bottom of the mold. In the semi-continuous casting metal water-cooled mold to be taken out to, the water-cooled mold has a two-stage structure of an upper mold and a lower mold, and the upper mold has a sufficiently thick wall thickness on the molten metal side and primary cooling water in the upper mold. Is introduced from the short side of the mold and discharged outward from a large number of outlets around the entire circumference of the mold.The lower mold has a sufficiently thin wall on the solidified metal side, and the secondary cooling water in the lower mold is the mold. A vertical semi-continuous casting mold for a non-ferrous metal slab, characterized in that it flows in from the shorter side and is radiatively cooled to the solidified metal from the entire inner circumference of the lower part of the mold.
The invention according to claim 1 is a mold for vertical semi-continuous casting of a non-ferrous metal slab according to claim 1, wherein the metal is aluminum and an aluminum alloy, and the invention according to claim 3 is that the upper mold is molten. The wall thickness on the metal side is 40-60 mm
The lower mold is a vertical semi-continuous casting mold for a non-ferrous metal slab according to claim 1 or 2, wherein the wall thickness on the solidified metal side is 5 to 10 mm. The invention is characterized in that the angle for radiatively cooling the secondary cooling water to the solidified metal is 20 to 30 ° with respect to the surface of the solidified metal. Is a mold for vertical semi-continuous casting of non-ferrous metal slabs.

[0007]

DETAILED DESCRIPTION OF THE INVENTION A mold according to the present invention is shown in FIGS.
This will be described with reference to FIG. In the present invention, as shown in FIGS. 1 and 2, the water-cooled mold 30 is replaced by an upper mold 31 and a lower mold 32.
The upper mold 31 is a slow cooling mold and the lower mold 32 is a quenching mold. The upper mold 3
A heat insulating material 33 is interposed between 1 and the lower mold 32. The upper mold 31 has a sufficiently thick wall 31a on the molten metal side, and cooling water flows in from the short side 31c of the rectangular mold, passes through the primary cooling chamber 31b, and has a large number of outlets 31d around the entire circumference of the rectangular mold. To the outside. Further, the lower mold 32 is
The wall thickness 32a on the solidified metal side is made sufficiently thin, and the secondary cooling water flows in from the short side (not shown) of the rectangular mold, passes through the secondary cooling chamber 32b, and the secondary cooling water around the inner circumference of the lower part of the mold. Radiation 32d is emitted from the radiation nozzle 32c to cool the solidified metal 2 .

The reason why the wall thickness 31a of the upper mold 31 on the molten metal side is made sufficiently thick is to gradually cool the molten metal 1 , and the wall thickness 32a of the lower mold 32 on the solidified metal side is made sufficiently thin. This is because the solidified metal 2 is rapidly cooled to suppress the growth of the frame structure 21 composed of the chill layer 211 and the coarse cell layer 212, particularly the coarse cell layer (columnar crystal) 212, and reduce the thickness thereof. By configuring the present invention as described above, the length of the air gap 7 in the vertical direction can be shortened, and the thickness of the frame structure can be reduced.

The mold 30 of the present invention is suitable for non-ferrous metals, but is particularly suitable for casting aluminum and aluminum alloys. Further, in the mold 30 of the present invention, in the case of aluminum and aluminum alloy, the upper mold 31
It is preferable that the wall thickness on the molten metal side is 40 to 60 mm, and the wall thickness on the solidified metal side of the lower mold is 5 to 10 mm.
This is because the effect of gradual cooling or rapid cooling is not appropriate when the amount is less than the lower limit or exceeds the upper limit.

Further, in the mold 30 of the present invention, the angle for radiatively cooling the secondary cooling water of the lower mold 32 to the solidified metal 32d is preferably 20 to 30 ° with respect to the solidified metal surface 2a. This angle is about 15 ° in the conventional mold of FIG. 3, but by setting it to 20 to 30 °, the length of the air gap 7 in the longitudinal direction can be shortened, and the thickness of the frame structure can be reduced. This is because it can be made thinner.

[0011]

EXAMPLES The present invention will be described below based on examples. Using the two-stage water-cooled mold 30 according to the present invention shown in FIG. 1, Al alloy 5182 (Al-4.5 wt% Mg-0.
A molten metal (3 wt% Mn alloy) was supplied from the upper part of the mold to cast a rolling slab having a thickness of 500 mm × a width of 1820 mm × a length of 10000 mm. This mold 30 (total height 17
0 mm, the height of the upper mold 31 is about 120 mm, the height of the lower mold is about 50 mm) is made of an aluminum alloy, the molten metal side thickness 31a of the upper mold 31 is 75 mm, and the water temperature of the primary cooling water is 50 ° C. there were. The thickness 32a of the lower mold 32 on the solidified metal side is 8 mm, the temperature of the secondary cooling water is 30 ° C., and the angle of the secondary cooling water radiating nozzle 32c is 25 ° with respect to the solidified outer surface 2a of the slab. The solidified outer surface 2a of the slab was cooled with the secondary cooling water radiation 32d. The temperature of the molten metal poured into the mold was 690 ° C and the casting speed was 50 mm.
It was / min. In this case, the height of the head (height from the molten metal surface to the bottom of the mold) was 70 mm. Frame structure of the rolling slab obtained by casting as described above (Figs. 4 and 2).
The thickness of 1) was 12 mm.

[0012]

Comparative Example Conventional water-cooled mold 3 shown in FIG. 3 (total height 1
70 mm) and Al alloy 51
82 molten metal was supplied from the upper part of the mold to cast a rolling slab having a thickness of 500 mm × a width of 1820 mm × a length of 10000 mm. The mold 3 (total height 170 mm) is made of an aluminum alloy, and the thickness 3a of the mold 3 on the molten metal side is 2 mm.
It was 0 mm, and the water temperature of the cooling water was 30 ° C. Further, the angle of the cooling water radiating nozzle 3c is 15 ° with respect to the solidified outer surface 2a of the slab, and the cooling water radiation 3d is applied to the solidified outer surface 2a of the slab.
Cooled in. The temperature of the molten metal poured into the mold is 690
The casting speed at 50 ° C was 50 mm / min. The height of the head in this case (height from the molten metal surface to the bottom of the mold) is 7
It was 0 mm. The thickness of the frame structure (FIG. 4, 21) of the rolling slab obtained by casting as described above was 15 mm.

As is clear from the examples and comparative examples of the present invention, the thickness of the frame structure of the rolling slab manufactured using the mold of the present invention is 12 mm, and the frame structure of the slab manufactured by the conventional mold is It can be seen that the thickness is 3 mm thinner than the thickness. That is, the slab surface cutting depth is changed from the conventional 15 mm to 12 mm, which greatly contributes to the improvement of the yield of usable slabs from the area of the slab (both sides of width 1820 mm × length 10000 mm).

[0014]

As described in detail above, the mold for vertical semi-continuous casting of a non-ferrous metal rolling slab according to the present invention is low in cost, easy to manage, and has a thin frame structure. As a result, the production yield of the rolled slab can be remarkably improved, and industrially remarkable effects can be obtained.

[Brief description of drawings]

1 is a schematic explanatory view of a mold according to the present invention, and is a half sectional view taken along an arrow AA in FIG.

FIG. 2 is a plan view of a mold according to the present invention.

FIG. 3 is a schematic explanatory view (cross-sectional view) showing a relationship between a mold and a casting slab in conventional DC casting.

FIG. 4 is an explanatory diagram showing a relationship between a rolling slab and its internal structure.

[Explanation of symbols] 1 molten metal 2 solidified metal 21 frame structure 211 chill layer 212 coarse cell layer (columnar crystal) 22 fine cell layer (granular crystal) 2a solidified outer surface of slab 3 water-cooled mold 3a molten metal side thickness 3b water chamber 3c Water radiating nozzle 3d Radiant cooling water 7 Air gap 30 Two-stage water cooling mold 31 Upper mold 31a Molten metal side thickness 31b Primary cooling water chamber 31c Primary cooling water inlet 31d Primary cooling water outlet 32 Lower mold 32a Solidified metal side thickness 32b Two Secondary cooling water chamber 32c Secondary cooling water radiation nozzle 32d Secondary cooling water radiation 33 Insulation material

Claims (4)

[Claims] 1. A metal water-cooled mold for semi-continuous casting, in which molten metal is injected from above into a rectangular water-cooled mold having an open bottom, and solidified metal is continuously taken out from the bottom of the mold, wherein the water-cooled mold is an upper mold. The lower mold has a two-stage structure. The upper mold has a sufficiently thick wall on the molten metal side, and the primary cooling water in the upper mold flows from the short side of the mold and flows out from a large number of outlets all around the mold. Discharge to the outside, the lower mold has a sufficiently thin wall thickness on the solidified metal side, and the secondary cooling water in the lower mold flows in from the shorter side of the mold to radiatively cool the solidified metal from the entire inner circumference of the lower part of the mold. A mold for vertical semi-continuous casting of a non-ferrous metal slab, which is characterized in that 2. The vertical semi-continuous casting mold for a non-ferrous metal slab according to claim 1, wherein the metal is aluminum or an aluminum alloy. 3. The wall thickness of the upper mold is 40 to 40 on the molten metal side.
60 mm, the lower mold has a wall thickness on the solidified metal side of 5 to 10
mm, The mold for vertical semi-continuous casting of a non-ferrous metal slab according to claim 1 or 2, wherein 4. The angle of radiatively cooling the secondary cooling water to the solidified metal is 20 to 30 ° with respect to the surface of the solidified metal, according to any one of claims 1, 2 and 3. A mold for vertical semi-continuous casting of a non-ferrous metal slab described in.