JPS63203250A - Continuous casting apparatus for metal - Google Patents

Abstract

PURPOSE:To improve casting surface of a casting billet by arranging one part either projected part or recessed part adjoining with flat face on an inner wall face of molten metal flow-in hole in a molten metal basin. CONSTITUTION:The projected part 4c or the recessed part 4d is formed on the inner wall face 4a of the molten metal receiving vessel 4 for hot-top casting device and the range except the projected part 4c and the recessed part 4d is made to the flat face 4b. Then, the projected part 4c or the recessed part 4d is formed around the whole circumference of the molten metal basin 4 and the shape and dimension of the height or depth, etc., is suitably formed, so as to be able to catch oxide in the molten metal at any part. By this method, at the time of supplying the molten metal in the molten metal basin 4, as the flowing velocity of the molten metal flow is sharply changed at the projected or recessed part 4c, 4d, oxide, etc., having high viscosity and low fluidity is caught at the projected or recessed part 4c, 4d.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a continuous metal casting apparatus, and more specifically, a molten metal reservoir is installed above the mold during continuous casting of non-ferrous metals such as aluminum. The present invention relates to the improvement of so-called hot top casting snow protection.

[Conventional technology]

In continuous casting of non-ferrous metals, a molten metal reservoir made of an insulating refractory material called a hesogu, molten metal receiving tank, etc. is installed above the through-mold to hold molten metal with high molten metal hydrostatic pressure above the solidified part of the metal. The so-called hot-nod top casting method is widely adopted.

FIG. 13 is a conceptual diagram of a hot top continuous casting device in which the molten metal reservoir has an overhang. In such a continuous casting apparatus, the ingot 6 is cooled by the wall surface of the through mold 1 itself and the cooling water discharged from the cooling water channel 2 formed inside the mold through the injection port 3, and the molten metal 8 is The molten metal is temporarily held in a molten sump 4 having an overhang 5, and then continuously supplied to a solidification section 7.

When continuously casting aluminum and its alloys, a molten metal sump 4 made of a heat-insulating or refractory material mainly composed of asbestos-silica or calcium silicate is generally used. Such constituent materials are commercially available in the form of plates, and are produced at foundries by cutting the plates into appropriate shapes after purchase, and then polishing the surfaces that will become the molten metal inlet holes.

In the hot top casting method, there is a problem in that if the cooling by the through mold 1 or the lubrication between the through mold 1 and the ingot 6 are not maintained in a good state, the ingot 6 will have a poor casting surface. Therefore, measures have been taken to make the casting surface of the ingot beautiful, and many methods are known.

The main points of some of the representative ones will be explained below.

According to the casting apparatus disclosed in Japanese Patent Publication No. 48-44607, a thin thermally conductive insert plate is inserted into the horizontal contact surface between the through mold and the molten metal reservoir, and the inner end surface of the insert plate is attached to the inner peripheral surface of the upper end of the through mold. The overhang formed by the insert plate, which protrudes from the molten metal but retracts from the inner circumferential surface of the lower end of the molten metal pool, performs a pre-cooling action to cool the molten metal prior to forced cooling by the inner wall surface of the mold. By doing so, the surface of the ingot is improved.

According to the aluminum ingot manufacturing method disclosed in Japanese Patent Publication No. 50-79429, smooth casting can be achieved by optimally controlling the relationships among casting speed, vertical length of the lower part of the mold (vertical length of the mold wall), and pressure head. It is said to yield skin ingots.

According to a proposal for improving the shape of a through mold disclosed in U.S. Pat. It is said that increasing the forced cooling effect is more effective in improving casting surface than in other cases.

According to the continuous casting method and apparatus disclosed in Japanese Patent Publication No. 54-42827, the casting surface is improved by introducing gas directly under the overhang formed by the molten metal pool and applying gas pressure to the outer peripheral surface of the molten metal. has been done.

As can be seen from the conventional technology explained above, the conventional method for improving the casting surface by controlling the influence of the through-hole mold on the solidification and cooling of molten metal has been the mainstream technology for countermeasures against the casting surface of the ingot. .

[Problem that the invention seeks to solve]

Through the above-described attempts to improve the surface of an ingot, the surface of an ingot obtained by hot-top casting has been improved to a certain extent. However, the current hot top casting method does not solve the problem of poor casting surface of the ingot.

In order to further improve the hot top casting method, the present inventors
In the process of conducting this research, we focused on the influence of the molten metal pool on the casting surface, which had previously been understood only from the perspective of level feed. In order to study this effect, we investigated the effects of the molten metal inlet hole wall and overhang lower surface of the hot top casting mold on the ingot casting surface. As a result, a considerable portion of the oxide film formed on the surface of the molten metal that was continuously poured onto the bottom block at the start of casting was captured by the molten metal inflow hole wall surface due to friction with the molten metal inflow hole inner wall surface. Then, a new surface is formed on the surface of the molten metal at the interface with the wall surface of the molten metal inlet hole, and this is brought to the surface of the ingot, resulting in a beautiful ingot surface. It was confirmed that the molten metal sump has a function that makes it possible to obtain molten metal. Not only at the start of casting but also during stable casting, a part of the oxide film formed on the upper surface of the molten metal reservoir is captured on the wall surface of the molten metal inlet hole and gradually accumulates to form a build-up portion.

In conventional hot top molds, a portion of the oxide film may not be sufficiently collected in the build-up area, and may be taken from the molten metal pool onto the surface of the molten metal.

In particular, when the metal level in the molten metal reservoir fluctuates due to unavoidable fluctuations in the amount of poured metal, or when the molten metal temperature changes, the oxide film on the build-up area that was in contact with the molten metal may be removed at once. It often flowed onto the surface of the molten metal.

When oxides are taken into the molten metal surface from the build-up area in this way, the oxides are carried in groups onto the surface of the ingot that has solidified as a product, not only impairing the surface appearance but also causing As a result of the mass adhering to the overhang, which is the lower surface of the molten metal pool, and the surface of the mold, a twitching phenomenon occurs in the ingot, which upsets the overall balance of the casting, causing uneven cooling and local concentration of the drawing force. In particular, in the case of hot-top casting, in which gas is introduced below the overhang to improve the casting surface, if oxides are taken into the molten metal surface from the build-up area, the balance of the gas addition effect around the entire circumference of the ingot is affected. Lost,
This also caused damage to the overall appearance of the ingot.

[Means for solving problems]

In order to solve the above-mentioned problems, the present inventor conducted research to improve the ability of the wall surface of the molten metal inlet hole of the molten metal reservoir to capture the oxide film, and as a result, the portion of the inner wall surface of the molten metal inlet hole that comes into contact with the molten metal It has been found that oxides can be effectively captured by forming one or more protrusions or depressions and rapidly changing the angle of the protrusions or depressions. The configuration of the unevenness will be explained in detail below.The protrusion protrudes toward the molten metal side when viewed from the molten metal pool, and the inner wall surface of the molten metal pool other than the protrusion is substantially flat. On the other hand, the recess is formed by recessing a part of the molten metal pool, and the inner wall surface of the molten metal pool other than the recess is substantially flat. When the molten metal that has flowed down along such a flat surface reaches the concave or convex portion, the flow of the molten metal is abruptly changed, resulting in the effect of trapping a group of oxides. Next, the angle of the convex part and the concave part is determined by the inclination of the upper and lower surfaces that substantially form the convex part and the concave part, and the angle of the convex part is determined by the angle of the convex part when viewed from the molten metal pool side.
Preferably the upper surface is 135 degrees or less and the lower surface is 70 degrees or more with respect to the vertical plane, and each is more preferably 120 or less 90 degrees.
The upper surface of the concave portion is 70° or more, preferably 90° or more.
0° or more and the bottom surface is 135° or less, preferably 120°
It is as follows. The angle between the top surface of the convex part and the bottom surface of the concave part is 135
If the temperature exceeds 100°, the effect of the concavities and convexities will be reduced, and the oxide mass will be sent into the mold in the same way as if the molten metal were flowing down along the flat surface of the molten metal pool. If the lower surface of the convex part and the upper surface of the recessed part are smaller than 70", the processing of the molten metal receiving tank will not only be complicated and expensive, but also air pockets will be formed during casting, causing stagnation of the molten metal and the molten metal surface. As the oxidation progresses, an oxide film is formed, resulting in the formation of an extra film, which does not produce good results in terms of the quality of the ingot.

The present applicant has filed a patent application dated December 11, 1986.
In No. 293507, a method was proposed in which the inner surface of a molten metal receiving tank was roughened with a brush or the like to form fine irregularities. This method differs from the method of the previous application in that the inner surface of the molten metal receiving tank is flat in areas where no concavities (convexities) are formed, that is, the surface is unique to refractories available under trade names such as Marinite. The difference lies in the structure of the molten metal receiving tank. In addition, in the previous application, oxides, etc. are captured by the fine irregularities, but the flow of the molten metal is hardly affected by the irregularities, but oxides are captured by the irregularities, whereas in the case of the present application, the molten metal flow is As a sudden change in the flow rate occurs at the irregularities, and perhaps a significant change in flow velocity occurs at the irregularities, oxides, etc., which have a substantially higher viscosity than aluminum and have poor fluidity, are left behind in the irregularities, and the oxides are trapped. There are functional differences between the two. However, the method of the prior application may be applied to surfaces other than the formation of concave/convex portions of the present application.

Further explanation will be given below with reference to drawings showing specific examples of the concave portions or convex portions.

In FIG. 1, a convex portion 4C is formed on the inner wall surface 4a of the molten metal receiving tank 4,
A specific example is shown in which the areas other than 4C are flat surfaces 4b. Similarly, FIG. 2 shows the recess 4d.

If the formation heights of the protrusions 4c (Fig. 1) and the recesses 4d (Fig. 2) are extremely high, and the protrusions 4c and the recesses 4d are formed near the inflow side end of the molten metal reservoir 4, It is only effective in capturing oxides flowing down an extremely narrow section, and the convex portion 4
This is not preferable because the oxide will freely flow into the mold below C and the recess 4d. The convex portion 4C and the concave portion 4d are formed around the entire circumference of the molten metal pool 4, so that oxides and the like can be captured anywhere around the molten metal pool 4. Convex portion 4
If the height of C and the depth of the recess 4d are too small, the effect of trapping oxides, etc. will be lost, and if they are too large, the cooling effect of the molten metal will occur, which will have an adverse effect on the solidification behavior in the mold. It is necessary to determine the height and depth. The height of the convex portion 4C and the depth of the concave portion 4d are preferably 2 to 50 m5, more preferably 5 to 20 m5.

Two convex portions 4C may be formed as shown in FIG. 3, or more convex portions 4C may be formed. In this case, oxides, etc. are first captured by the upper protrusion 40', and oxides etc. that are not captured here are captured by the lower protrusion 40', and extremely clean molten metal is sent into the mold. It turns out. However, when the distance between the convex portions 4C and 4 c / is narrow, there is a risk that the molten metal will solidify due to this distance, and a steady flow flowing on the flat surface 4b will not be formed, so that the lower convex portion 4C will not be captured. This is not preferable because it weakens the effect. The distance between the convex portions 4C and 4cI is preferably 5 fins or more, more preferably 15 m or more. In addition, although the convex part 4C was illustrated and explained in FIG. 3, two or more concave parts 4d can be similarly formed, and furthermore, the convex part 4C and the concave part 4d may be formed in one molten metal reservoir.

The shapes of the convex portion 4C and the concave portion 4d, which have the effect of trapping oxides and the like, will be further explained. Specifying the shapes of the convex portion 4C and the concave portion 4d, α is the upper surface and lower surface of 4C, the lower surface of 4d, and the angle between the upper surface and the vertical plane, respectively.

β, as shown in FIGS. 4 and 5. When we investigated the shape of the trapping part for separating only oxides from the molten metal containing oxides and the like from the molten metal flow in the convex part 4C and the concave part 4d (collectively referred to as the trapping part), we found that the angle is It was found that the angle α mentioned above is the most dominant. These angles are preferably 135° or less
At 20 degrees or less, there is a remarkable effect of trapping oxides, etc. angle β
Although it has no direct relation to the trapping effect, if it is extremely small, it is undesirable as it may disturb the flow of the molten metal or entrain air. 70” or more, preferably 90°
That's all.

The convex portion 4C having the above-mentioned angle can have various shapes, examples of which are shown in FIGS. 6 to 11. Although not shown, if the leading edge is rounded, there is a significant trapping effect when the R (radius of curvature) of that portion is 5u or less. Further, FIGS. 10 and 11 show an example in which the lower surface of the convex portion directly forms the overhang of the header.

Various shapes are also possible for the recess 4d having the above-mentioned angle, examples of which are shown in FIG. 12.

The present invention will be explained below with reference to Examples.

<Example 1> Contains AA standard 505 A billet with a diameter of 200 mm was cast under the following conditions.

■), thickness of the belly button 2), header protrusion amount 30■13), shape of header inner recess in Figure 5, α=90゛β=120.

Height of the lower surface of the concave from the bottom of the belly button 10 Depth of the dragon concave 10 Width of the deepest part of the fin concave 10 Tsuru4), Header molten metal level height 70mm5), Casting speed 100m/+win6), Lubricating oil type Castor oil7), Lubricating oil supply amount
3cc/win8), cooling water supply 1
801/win9), the pouring temperature in the header was 680°C. As a result, a smooth casting surface with no oxide film entrained over the entire length was obtained.

Comparative Example 1> The header was made under the same conditions as Example 1 except that no recesses were provided on the inner surface of the header and the inner surface was flat. A deep cast surface was obtained.

<Comparative Example 2> An AA standard 51-2 header was cast under the same conditions as in Example 2, except that no convex portion was provided on the inner surface of the header and the inner surface was in a flat state.

As a result, a defective skin containing oxide films was obtained throughout the ingot surface. Moreover, the smoothness was also impaired.

<Example 2> A slab having a cross-sectional shape of 300 mm x 500 mm was cast using the AA standard 51 x 2 cup casting method under the following conditions.

1), Hesogroove thickness: 10 (in2), Hesozoo protrusion amount: 50113), Header protrusion shape In Figure 10, α = 90° Protrusion amount from the inner surface of the header: 15mm Thickness: 10m 4) , molten metal level height in hesogou 70m5), casting speed 80m/5in6), lubricating oil type castor oil7), supply fi30
cc/5in8), gas introduction amount 21
/ll1n9), cooling water supply amount 2001
/akin10), temperature of pouring into the belly button 68
As a result, a smooth casting surface with no oxide film entrained over the entire length of the ingot was obtained.

〔Effect of the invention〕

The present invention further advances measures to improve the casting surface of ingots obtained by the true top casting method, and will greatly contribute to industry.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of the molten metal reservoir of the continuous metal casting apparatus according to the present invention, and is a drawing of the apparatus in which the trapping part for oxides, etc. is formed by a convex part. FIG. 3 is a drawing showing a plurality of convex portions; FIG. 4 and FIG. 5 are explanatory diagrams of angles of convex portions and concave portions, respectively; Figures 1 to 11 are drawings showing specific examples of the shapes of the convex portions. FIG. 12 is a drawing showing a specific example of the shape of the recess. FIG. 13 is a diagram showing a conventional hot top casting apparatus. l... Penetration mold, 2... Cooling water channel, 3...
・Injection hole, 4... Ingot, 4b... Flat part,
4cm: Convex portion, 4d: Concave portion. ,Mo34 Funeral figure 4・,-8,5,,λ drunkenness 7 i,,+,j 6W, 8 figure L~9 figure 13 figure 1 o view-shio 11 寞. cup 12

Claims (1)

[Scope of Claims] 1. A metal continuous casting apparatus in which a refractory molten metal reservoir having a molten metal inflow hole and an overhang projecting inward from the inner surface of the through mold is arranged at the upper part of the inlet side of the through mold, A continuous casting apparatus for metal, characterized in that at least one of a convex portion and a concave portion is provided adjacent to a flat surface in a portion of the inner wall surface of the molten metal inlet hole of the refractory material molten metal reservoir that comes into contact with the molten metal.