JPS5923899B2 - Mold for semi-continuous metal casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold for semi-continuous casting of metal,
More specifically, the present invention relates to a semi-continuous casting mold for producing billets and slabs as ingots for plastic working of nonferrous metals such as aluminum and copper, and alloys.

Such a mold has an external shape suitable for contacting the circumferential surface of the molten metal to give it a columnar or cylindrical shape, and also has a shape suitable for giving the molten metal a columnar or cylindrical shape, and a mold through which a cooling liquid flows in order to inject the cooling liquid onto the metal having such a shape. It consists of a casing with a hollow part and an injection hole.

In other words, once the mold is placed in the hollow part and cooled, it is usually filled with water,
is injected onto the metal at a position directly below the lower end surface of the mold through a through hole drilled in the wall of the hollow body.

Cooling of metal by this injection is called primary cooling.

In order to increase the productivity of semi-continuous casting of metals, it is a predominant requirement to increase the casting speed, ie the speed of movement of the metal mass drawn from the annular mold.

In order to increase the casting speed, it is necessary to strengthen the injection of coolant, but as the casting speed increases, the difference in cooling rate between the surface and center of the ingot increases, which can cause cracks in the ingot. The tensile stress in the central part increases.

Therefore, increasing the casting speed is mainly hindered by defects called casting cracks.

The maximum casting speed that does not cause casting cracks (hereinafter referred to as critical casting speed) is determined by factors such as the dimensions of the ingot, the alloy composition, and the degree of grain refinement by grain refinement elements added to the alloy.

For example, it is a known fact that the smaller the size of the ingot and the finer the casting structure, the higher the limit casting speed.

The ingot cooling method, which increases the critical casting speed by improving the cooling conditions when the above factors are kept constant, was developed in the 4th year of the Special Publication.
It is publicly known from No. 9-48045, Japanese Unexamined Patent Publication No. 47-27836, and the like.

In each of these methods, a secondary cooling zone is provided using an injection ring or the like further below the primary cooling zone using water injected from a normal water-cooled mold, and the end of solidification of the molten metal (
The feature is that cooling water is used from the secondary cooling zone to reduce the difference in cooling rate between the center and surface of the ingot (at the bottom of the sump).

However, in this method, since two or more cooling devices are provided above and below, the structure of the metal semi-continuous casting apparatus becomes complicated.

In particular, all cooling equipment except for the top one is located on the back side of the foundry's work floor, which is lower than the work floor, making maintenance difficult and once a casting accident such as hot water leaking occurs, cooling The equipment is extremely difficult to maintain.

The present invention aims to provide simple improvements to conventional semi-continuous casting molds to increase the critical cooling rate over that achieved by conventional molds.

The present invention has an injection hole formed in the lower part of the casing for injecting the cooling liquid flowing inside the casing constituting the mold around the metal ingot formed into a predetermined shape by the mold,
In a metal semi-continuous casting mold in which the injection hole is directed toward a portion of the metal ingot immediately below the lower end surface of the casing as a primary cooling means, the injection hole is directed toward a portion of the metal ingot directly below the lower end surface of the casing. In addition to the primary cooling means, by configuring the slit as a slit whose width gradually increases in the direction of injection, it is possible to inject the cooling liquid around the metal ingot at a level where the solidification of the molten metal is almost completed. The second cooling means is formed in one mold.

By making a simple modification to a conventional general housing mold, the present invention provides a single cooling system that performs not only the primary cooling directly under the mold but also the secondary cooling at the level where the solidification of the molten metal is completed (the bottom of the sump). What makes it possible is that it is made possible using a mold.

Specifically, since the injection hole of the present invention gradually increases in width toward the injection direction, the primary cooling water and the secondary cooling water diverge within the injection hole and collide with the ingot surface. .

Of both walls of the slit whose width has been expanded, the one closer to the ingot, that is, the upper (inner) wall, is extended directly below the mold, and the lower (outer) wall of the slit is extended vertically, or It was found that if the inclination was made slightly toward the ingot from the same direction, the cooling water would clearly diverge.

The angle at which the upper and lower wall surfaces of the slit intersect (hereinafter referred to as the intersection angle) is 15° to 35°, preferably 30°.
In this case, the cooling water branches under all practical cooling conditions.

The primary cooling water is directly below the mold, preferably 0 to 3 Qmm,
Also, at the sump bottom position, secondary cooling water is injected onto the respective ingot surfaces to offset each other.

However, this does not mean that the cooling water will not collide with the ingot surface in the middle of these positions, and a small amount of the cooling water may collide with the ingot surface.

The extension direction of the inner (upper) wall surface of the slit is directed toward the primary cooling position, and the extension direction of the outer (lower) wall surface of the slit is directed toward the secondary cooling position or slightly above it.

The slits for injecting the primary cooling water are continuous annular holes when viewed from the bottom of the mold, while the slits for injecting the secondary cooling water are grooves cut into the mold wall at a distance from each other. Holes can be configured.

Contrary to this configuration, the injection holes may be configured such that the secondary cooling water injection slit is an annular continuous hole and the primary cooling water injection slit is a cut groove.

The cut grooves are evenly distributed on the circumference at appropriate intervals.

Both the primary cooling water slit and the secondary cooling water slit may be continuous annular slits.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Figure 1 is a partial vertical cross-sectional view of the mold, Figure 2 is from ■-■ in Figure 1.
It is a sectional view of a line.

The mold 1 defines a desired ingot shape by an inner wall surface 1a,
It has a housing method in which cooling water flows into the hollow part 2 inside.

The cooling water flows from the inlet 3 through the hollow part 2 and from the injection hole 4 to the ingot (
(not shown).

The injection hole 4 is made up of an annular slit 4a and a groove-like slit 4b that are continuous on the circumference.

The angle γ that the extension line of the annular slit 4a makes with the horizontal line
is between 92° and 95° and approximates 90°, thus creating a diversion of cooling water towards a level corresponding to the sump bottom of the ingot.

The angle β that the extension line of the cut groove-like slit 4b makes with respect to the horizontal line is 55 to 75 degrees, and causes a branch flow directed directly below the mold.

The angles β and γ are selected in such a way that the cooling water impinges on the sump bottom, preferably slightly above it, and that a shunt occurs, which varies depending on the desired casting speed.

In order to cause a split flow, the angle α that defines the degree of expansion of the slit width is 15°7. It is preferable that the angle is between i' and 35°.

The width of the slit 4a at the lower end of the mold is 0.5 to 1.5 m.
m, the width of the slit 4b is preferably 0.8 to 1.3 mm.

In order to prevent casting cracks from occurring due to branched cooling water flows, in known methods using two or more independent cooling means, the position of the secondary cooling is as described above, and the position of the secondary cooling is lower than that of the primary cooling. It is important to strengthen the subsequent cooling (see % Japanese Patent Publication No. 47-27336).

A similar tendency was observed when a casting experiment was conducted using the mold of the present invention.

That is, if the primary cooling is too strong, the effect of the secondary cooling is lost, and the cooling rate described above increases.

On the other hand, if the secondary cooling is too strong, the primary cooling water evaporates directly below the mold and pushes the secondary cooling shower outward away from the ingot. If it collides below, or in extreme cases, it may not hit the ingot.

In the end, even in the case of collapse, no improvement in the critical casting speed will be recognized.

In order to balance primary cooling and secondary cooling, it is desirable to adjust the amount of water to be balanced by changing the cross-sectional areas at the entrances of the slits 4a and 4b.

In Figure 3, the impaction continuous slit 4a is inside (upper side) of the mold 1.
4b is formed on the outside (lower side)
The mold differs from the mold shown in FIG. 1 in that it is formed in the mold.

Also in this mold, since the width of the slit is enlarged by the angle α, primary cooling and secondary cooling can be performed with one mold.

FIG. 4 shows a mold with an ejection hole 4 similar to that in FIG.
A groove-shaped slit 4b is cut from the middle of the annular continuous slit 4a.
This mold 1 differs from the mold shown in FIG. 1 in that the mold 1 is separated.

If the slit 4 is enlarged over a considerable section of its entire length, primary cooling and secondary cooling can be achieved with one mold.

In addition, in FIGS. 1 to 3, a specific example has been described in which one of the inner (upper) slit and the outer (lower) slit is continuous, and the other is in the shape of a cut groove.

However, the present invention is not limited to this specific example,
Primary cooling and secondary cooling may be realized in one mold by increasing the distance between the inner (upper) wall surface and outer (lower) wall surface of a kind of annular continuous slit in the cooling water injection direction.

Furthermore, unlike the above specific example in which one injection hole serves as both cooling means, another injection hole is bored in the lower part of the casing outside of the injection hole that performs primary cooling, and this injection hole The direction is set at the level where the solidification of the molten metal is almost completed (
In other words, the mold is characterized in that, in addition to the primary cooling means, a secondary cooling means is formed in one mold by directing the mold toward the bottom of the sump.

A specific example of this mold is shown in FIG.

In this mold 1, the primary cooling injection holes 5 and the secondary cooling injection holes 6 are formed as mutually independent through holes.

The through holes 5 and 6 may be continuous annular slits, groove-like slits, or pores.

It is preferable that the intersection angle δ of the injection holes is 10° or more so that the water flows flowing out from the respective injection holes do not interfere with each other.

The angle γ' of the primary cooling injection hole 5 with respect to the horizontal line is 55 to 7
5 degrees, and the similar angle of the secondary cooling injection hole 6 is 85 degrees.
It is 88°.

In order to make the secondary cooling stronger than the primary cooling, the amount of water flowing out from the injection holes 6 is set to 1.5 to 2.5 times the amount of water flowing out from the injection holes 5.
It needs to be tripled.

The main effects achieved by the present invention are as follows.

(a) The limit casting speed is increased by approximately 50% compared to the conventional case of using one mold.

Moreover, improving the mold for performing primary cooling and secondary cooling simultaneously is extremely simple and inexpensive.

(0) Since it is not necessary to arrange two or more cooling devices one above the other in order to improve the limit casting speed, maintenance and management of the cooling devices becomes extremely simple.

e→ There are fewer troubles when a casting accident occurs.

In other words, there is no need to carry out accident handling work below the foundry work floor.

(b) The balance between primary cooling and secondary cooling can be easily achieved by predetermining the shape of the injection hole in the mold.

That is, the hollow part of the mold, which is a direct supply source of cooling water, is common for both types of cooling, and there is no factor that disturbs the balance during water supply, so the balance is stable during casting.

The present invention will be explained in detail below.

Example 5 A 6063 alloy containing 142% iO, 0.52% Mg, and 20% FeO was cast into a 10-inch billet using a mold as shown in FIG.

The dimensions of the mold were as follows.

(1) Mold inner diameter 10 inches (2) Height 100ml (3) Width of slit 4a 0.9mm (4) Angle (γ) of slit 4a 93° (5) Maximum cutting width of Slin 1-4b 1mm (6) Cutting angle) 60° (7) Number of slits 4b: 90 (4° intervals) - The secondary cooling water collided with the billet in the form of spots and the secondary cooling water in the form of a wide curtain.

The casting conditions were as follows.

(1) Casting temperature 700°C (2) Cooling water amount 2001/min (primary cooling 70 minutes, secondary cooling 130 b minutes) (3) Water
Temperature: 20°G The following table shows the limit casting speeds for the cases where casting was performed using a conventional mold that performs only primary cooling and when casting was performed using the mold of the present invention.

The critical casting speed was determined by visually inspecting the cross section of the ingot.

From this table, it can be seen that the mold of the present invention increases the critical casting speed by about 50% compared to the conventional mold.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a specific example of the mold according to the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and FIGS. 3 to 5 are FIG. 1 showing other specific examples. This is a similar drawing. 1... Mold, 2... Cavity, 3...
...Cooling water inlet, 4...Injection hole, 5...
...Primary cooling injection hole, 6...Secondary cooling injection hole.

Claims (1)

[Claims] 1. An injection hole is formed in the lower part of the casing for injecting the cooling liquid flowing inside the casing constituting the mold around the metal ingot formed into a predetermined shape by the mold. In a mold for semi-continuous casting of metal, the injection hole is directed toward a portion of the metal ingot immediately below the lower end surface of the casing as a primary cooling means. By configuring at least a part of the section as a slit whose width gradually increases toward the injection direction, in addition to the above-mentioned secondary cooling means, a slit is formed around the metal ingot at a level where solidification of the molten metal is almost completed. A mold for semi-continuous casting of metal, characterized in that a secondary cooling means for injecting a cooling liquid is formed in one mold.