JP3166517B2 - Electromagnetic casting apparatus and method for casting Al or Al alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic field configured to pull out an ingot while holding a molten metal of Al or Al alloy in a column shape by an electromagnetic force generated by the electromagnetic coil. The present invention relates to a casting apparatus and method, and more particularly to an electromagnetic field casting apparatus and method of Al or Al alloy for improving the quality of an ingot surface.

[0002]

2. Description of the Related Art As one of the methods for casting Al or an Al alloy (hereinafter, may be represented by Al), a semi-continuous casting method called an electromagnetic field casting method is performed. In this method, a pouring nozzle from which the molten aluminum flows out and an electromagnetic coil surrounding the pouring nozzle are arranged, and the molten aluminum flowing out of the pouring nozzle is brought into non-contact with the electromagnetic force generated by the electromagnetic coil. The side surface of the columnar molten metal (hereinafter, sometimes referred to as a “molten column”) is cooled by a cooling medium and the ingot is drawn downward while holding the columnar molten metal in a columnar shape. In such an electromagnetic field casting method, a relatively smooth ingot surface is obtained,
It is said that the omission of the facing step before rolling and the reduction of the facing amount can be achieved, and that an ingot excellent in structure can be obtained.

When an ingot is cast from molten Al by the above-mentioned electromagnetic field casting method, an oxide film layer is formed on the upper surface of the molten aluminum column, and this oxide film layer constantly moves to the periphery during casting, and the ingot is cast. Is formed. However, particularly in the case of manufacturing a rectangular ingot, since the distance from the pouring nozzle is not equal over the entire circumference, the movement of the surface oxide film layer is not always uniformly and smoothly achieved. , Tend to grow locally thick. The oxide film layer thus grown thickly moves intermittently to the periphery, and the oxide tends to stagnate below the oxide film. Therefore, not only does the appearance of the obtained ingot deteriorate, but also the surface quality is unfavorable, and the advantage of the electromagnetic field casting method that the omission of the facing step before rolling and reduction of the facing amount can be achieved cannot be exhibited. There is.

[0004] For these reasons, various electromagnetic field casting techniques for improving the quality of the surface of the ingot have been proposed. As such a method, for example, a method of disposing a frame dam near the outer periphery of the surface of the Al molten metal to control the movement of the oxide film (for example, Japanese Patent Publication No. 54-40210),
A method of covering the upper surface of the molten metal column with conductive slag or flux and placing a shell weir near the outer peripheral surface to make the molten metal column hermetically closed, thereby suppressing the generation and growth of oxides on the molten metal column (for example, , Tokiko Sho 59-35
No. 708), a method of disposing a cover member so as to surround the upper portion and side portions of the molten metal column, and introducing an inert gas into the inside of the cover member to suppress oxide generation and growth on the surface of the molten metal column (for example, JP-A-1-127143).

[0005]

However, each of the above techniques has the following problems. First, in the above method, the movement of the oxide film from the inside of the frame dam to the outside cannot be completely suppressed and controlled, and the unevenness of the oxide film generated outside the frame dam cannot be eliminated. . Further, in the above method, the apparatus configuration becomes complicated, the maintenance becomes complicated, the cost is increased, and a new problem that slag or flux is involved in the ingot occurs. Further, in the above-mentioned method, unless an inert gas having a considerably high purity is used, the sealing effect on the surface of the molten metal column cannot be exhibited, and an increase in cost due to the use of the inert gas having a high purity cannot be avoided.

The present invention has been made to solve the technical problems in the prior art, and has as its object to reduce the thickness of the oxide film formed on the surface of the molten metal column and to reduce the thickness of the oxide film. An electromagnetic field casting method of Al or an Al alloy capable of preventing entrainment in an ingot and improving the surface quality of the ingot with good productivity and workability, and a relatively simple configuration of such a method. An object of the present invention is to provide an electromagnetic field casting apparatus that can be implemented.

[0007]

According to the present invention, which has attained the above objects, there is provided a pouring nozzle through which a molten metal of Al or an Al alloy flows out, and an electromagnetic coil arranged so as to surround the pouring nozzle. In an Al or Al alloy electromagnetic casting apparatus configured to pull out an ingot downward while holding the molten Al or Al alloy flowing out of the hot water nozzle in a columnar shape by the electromagnetic force generated by the electromagnetic coil, In addition to providing a frame-shaped external weir along the upper peripheral edge of the molten metal,
The point is that a frame-shaped submerged weir is provided in the columnar molten metal, the columnar molten metal is divided into an internal molten metal region and an external molten metal region, and at least one auxiliary pouring nozzle is provided in the external molten metal region. It is an electromagnetic field casting apparatus of Al or Al alloy having the following.

In the above apparatus, (a) the area ratio of the upper surface of the columnar molten metal in the inner molten metal region and the outer molten metal region is 1: 1 to 1: 2; The gap between the weir and the dive weir is arranged so as to be equal or substantially equal over the entire circumference, and (c) the distance between the solidification interface between the columnar molten metal and the ingot and the lower end of the dive weir is 2 mm.
It is preferable to add requirements such as a configuration of 0 to 60 mm in order to further improve the effects of the present invention.

On the other hand, the method of the present invention, which has achieved the above-mentioned object, refers to the following (1) using various electromagnetic field casting apparatuses as described above.
This is an electromagnetic field casting apparatus method for Al or an Al alloy, which is characterized in that the operation is performed with the ratio of the pouring amount per unit surface area in the internal molten metal region and the external molten metal region represented by the formula being 5.0 to 7.0. (Amount of molten metal in the internal molten metal area / Area of the internal molten metal area) / (Amount of molten metal in the external molten metal area / Area of the external molten metal area) ... (1)

[0010]

The operation of each component of the present invention will be explained while
The present invention will be described. First, in the electromagnetic field casting apparatus of the present invention, a frame-shaped submerged weir is provided in a molten metal pillar. The basic function of this submerged weir is an oxide film layer formed near the center of the upper surface of the molten metal pillar. Is prevented from moving to the side of the molten metal column. Therefore, the upper end of the descent weir protrudes from the upper surface of the molten pillar. However, there is an optimum value for the immersion depth of the dive weir. If the distance from the lower end portion (immersed portion) of this dive weir to the solidification interface (the interface between the molten metal pillar and the ingot) becomes too large, it moves from the inner molten metal region to below the dive weir to the outer molten metal region. The flow is generated in the upper layer of the molten metal, and the surface downward flow (described later) in the external molten metal region is not suppressed, and the oxide film layer formed near the central portion of the upper surface of the molten metal moves to the side of the molten metal column. And the basic function of the dive weir cannot be achieved. As a result, the quality of the surface of the ingot is reduced. For this reason, the distance from the lower end of the dive weir to the solidification interface is preferably 60 mm or less. In consideration of the above-described operation of the descent weir, it can be said that the lower end of the dive weir is preferably as close as possible to the solidification interface. However, if the distance from the lower end to the solidification interface becomes too small and becomes less than 20 mm, solidification will occur. If the solidification interface reaches the lower end of the internal weir due to instability due to the fluctuation of the interface position, the dive weir may be damaged.
From the above, the distance from the lower end of the dive weir to the solidification interface is preferably 20 to 60 mm.

On the other hand, the external weir provided along the outer peripheral edge of the upper part of the molten pillar suppresses the movement of the oxide film layer generated in the external molten region to the side of the molten pillar. However, the movement of the oxide film layer to the side surface of the molten metal column cannot be completely suppressed. This is because a downward flow is constantly generated on the surface of the molten pillar due to the distribution of the electromagnetic force acting on the molten pillar, and the oxide film layer generated in the external molten metal region is moved to the side surface of the molten pillar.

Therefore, in the present invention, the balance between the electromagnetic force and the static pressure of the molten metal is broken by providing at least one auxiliary pouring nozzle also in the external molten metal region and directly pouring the molten metal into the external molten metal region. Quickly recovered, and succeeded in improving the properties of the molten metal column side surface.

When the molten metal is not poured into the external molten metal area, the molten metal is supplied to the external molten metal area from the internal molten metal area by passing below the submerged weir. As a result, the downward flow on the surface of the molten metal column is suppressed, and the molten metal is constantly supplied to the solidification interface from the internal molten metal region, so that an ingot with excellent surface quality free of surface defects due to the oxide film layer is produced. It is expected to be possible. However, when such a configuration is adopted, the following inconveniences become apparent when the volume or shape of the outer molten metal portion changes due to disturbance or the like. In other words, when the volume and shape of the external molten metal region change, the balance between the electromagnetic force and the molten metal static pressure on the side surfaces of the molten metal column is lost. However, since the supply of the molten metal is performed from below the dive weir, the imbalance is quickly recovered. Therefore, it is impossible to obtain an ingot having a uniform surface shape.

In carrying out the method of the present invention, if the amount of direct pouring into the external molten metal region is too large, a large amount of downward flow on the surface of the molten column will occur as described above. Need to adjust. The present inventors have confirmed by experiments that when the operation is performed with the ratio of the pouring amount per unit surface area in the internal pouring region and the external pouring region represented by the above formula (1) being 5.0 to 7.0, That is, by pouring the molten metal into the external pouring area by moving the molten metal from below the dive weir together with the direct pouring by the auxiliary pouring nozzle, the surface descent flow on the surface of the molten metal column is suppressed, and the electromagnetic force is reduced. It has become possible to achieve the stability of the balance between the molten metal static pressure.

The area ratio (area ratio in plan view) between the internal molten metal region and the external molten metal region divided by the dive weir and the external weir is not particularly limited, but is 1:
About 1-1: 2 is optimal. That is, when the area of the external molten metal region is too small, the balance between the electromagnetic force and the static pressure of the molten metal is reduced, causing a change in the thickness of the ingot, and it may be difficult to pour the molten metal into the external molten metal region. . Also, if the area of the external molten metal region becomes too large, the influence of the molten metal flow from the internal molten metal region to the external molten metal region below the dive dam becomes weak, and the surface descending flow in the external molten metal region becomes severe, so that the external molten metal region has The movement of the oxide film layer on the surface becomes remarkable, and the oxide film transferred to the surface of the ingot results in deterioration of the surface quality. Further, from the viewpoint of achieving uniform and smooth movement of the molten metal in the molten metal column, it is preferable that the distance between the external weir and the descent weir is set to be equal or substantially equal over the entire circumference. In addition, it is set as "substantially equal" because the diagonal part when manufacturing a rectangular ingot was considered.

Since the present invention has been made in consideration of the inconvenience in producing a rectangular ingot as described above, the effect is most exhibited when producing such a rectangular ingot. From the viewpoint that an excellent ingot having a columnar shape is obtained, the shape of the ingot targeted by the present invention is not limited to a rectangle, and the effects of the present invention are exerted even when manufacturing a cylindrical ingot. Needless to say. In carrying out the electromagnetic field casting method, it is common practice to arrange a magnetic field shielding screen on the outer peripheral portion of the upper portion of the molten metal column so as to adjust the upper shape of the molten metal column. A magnetic field shielding screen may be used in combination.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples are not intended to limit the present invention. It is included in the technical scope.

[0018]

FIG. 1 is a schematic plan view showing an embodiment of an electromagnetic field casting apparatus according to the present invention. FIG. 2 is a sectional view taken along line AA of FIG. 2 is a dive weir, 3 is an electromagnetic coil, 4a to 4e are pouring nozzles (4b to 4d are auxiliary pouring nozzles), 5a to 5e are stoppers, 6 is a pouring gutter, 7 is a cooling medium, and 8 is an inside. A molten metal region, 9 is an external molten metal region, 10 is a pouring column, 11 is an ingot, and 12 is a cooling medium jacket. The electromagnetic casting apparatus shown in FIGS. 1 and 2 is for producing a rectangular ingot. The cooling medium jacket 12 is not shown in FIG. 1 for convenience of explanation.

The Al molten metal that has been melted in a melting furnace (not shown) and passed through various steps such as adjustment of alloy components, degassing, and removal of inclusions is poured into a pouring gutter 6, and is placed below the pouring gutter 6. From the provided pouring nozzles 4 a to 4 e, pouring is performed into each region surrounded by the electromagnetic coil 3. At this time, the internal molten metal region 8 is configured to be individually poured from the pouring nozzle 4a, and the external molten region 9 is configured to be individually poured from the four auxiliary pouring nozzles 4b to 4e.

Electromagnetic force from the electromagnetic coil 3 acts on the Al molten metal poured into the area surrounded by the electromagnetic coil 3,
It is held in a non-contact manner in the region, a pouring column 10 is formed, and is cooled and solidified sequentially by a cooling medium 7 such as water,
It becomes an ingot 11. Stoppers 5a to 5e are arranged directly above the pouring nozzles 4a to 4e, respectively. By moving the stoppers 5a to 5e up and down, the upper openings of the pouring nozzles 4a to 4e are removed. It is configured such that the opening degree can be adjusted and the pouring amount ratio represented by the above equation (1) can be controlled, whereby the downward flow on the outer peripheral surface of the pouring column 10 (indicated by an arrow A in FIG. 2). ) And dive weir 2
The balance of the melt flow below (indicated by arrow B in FIG. 2) is maintained.

Using the electromagnetic field casting apparatus shown in FIGS.
The Al-Mg alloy (JIS 5182 alloy) was subjected to an area ratio (area of the inner molten metal area / area of the outer molten metal area), a distance (a distance from the lower end of the dive weir to the solidification interface), and the above (1).
Casting was performed while changing the conditions such as the pouring amount ratio defined by the formula to produce a rectangular ingot having a cross-sectional shape of 600 × 1200 (mm). At this time, the casting speed was constant at 50 mm / min and the pouring temperature was 750 ° C. The surface properties of the obtained ingot were evaluated by the number of wrinkle-like vertical streak defects formed on the surface. Table 1 shows the results.

[0022]

[Table 1]

The above Al—Mg alloy has an alloy component of M
Since the oxidizing power of g is large, it tends to form a thick oxide film on the surface of the molten metal. In the conventional electromagnetic field casting method, the unevenness of the thickness and moving speed of this oxide film causes a wrinkled vertical surface on the side of the ingot. Although there was a tendency for streak defects to occur, as is apparent from Table 1, according to the present invention, the occurrence of longitudinal streak defects was suppressed in this way, and in particular, the requirements (a) to (c) were satisfied. Satisfaction shows that the occurrence of vertical streak defects is significantly reduced.

[0024]

As described above, according to the method of the present invention, Al
Alternatively, the occurrence of surface defects of the Al alloy ingot is prevented, and an ingot with excellent surface quality can be manufactured by a simple apparatus configuration. This is expected to reduce the occurrence of ingot cracks due to vertical streak defects and the like, to achieve no surface grinding or reduction in the amount of surface grinding before rolling, and to greatly improve the yield.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing one embodiment of an electromagnetic field casting apparatus of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

[Description of Signs] 1 External weir 2 Internal weir 3 Electromagnetic coil 4a-4e Pouring nozzle 5a-5e Stopper 6 Pouring gutter 7 Cooling medium 8 Internal molten metal area 9 External molten metal area 10 Pouring column 11 Ingot

──────────────────────────────────────────────────続 き Continued on the front page (72) Katsuyuki Yoshikawa 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel, Ltd. Kobe Research Institute (72) Inventor Sumio Kaku Kobe City, Hyogo Prefecture 1-5-5 Takatsukadai, Nishi-ku Kobe Steel, Ltd. Kobe Research Institute (56) References JP-A-4-266453 (JP, A) JP-A-4-22539 (JP, A) JP JP-A-2-255246 (JP, A) JP-A-2-255245 (JP, A) JP-A-60-30553 (JP, A) JP-A-52-86926 (JP, A) JP-A-59-92146 (JP, A) A) JP-A-1-127143 (JP, A) JP-A-8-24995 (JP, A) JP-B-59-35708 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) B22D 11/01 B22D 11/00 B22D 11/103 B22D 11/18

Claims (5)

(57) [Claims] 1. A pouring nozzle through which a molten metal of Al or an Al alloy flows out, and an electromagnetic coil arranged so as to surround the pouring nozzle, wherein Al or Al flowing out of the pouring nozzle is provided.
In an Al or Al alloy electromagnetic casting device configured to pull out an ingot downward while holding the molten alloy in a columnar shape by the electromagnetic force generated by the electromagnetic coil, along the upper outer peripheral edge of the columnar molten metal In addition to providing a frame-shaped external weir and providing a frame-shaped submerged weir in the columnar molten metal, the columnar molten metal is divided into an internal molten metal region and an external molten metal region, and at least one auxiliary pouring nozzle is provided in the external molten metal region. An electromagnetic field casting apparatus for Al or an Al alloy, characterized in that: 2. An area ratio of an upper surface of the columnar molten metal in an inner molten metal region and an outer molten metal region is 1: 1 to 1:
2. The electromagnetic field casting apparatus according to claim 1, wherein the apparatus is configured to be 2. 3. An arrangement according to claim 1, wherein the distance between the outer weir and the dive weir is equal or substantially equal over the entire circumference.
2. The electromagnetic field casting apparatus according to claim 1. 4. The electromagnetic casting apparatus according to claim 1, wherein a distance between a solidification interface between the columnar molten metal and the ingot and a lower end of the dive is 20 to 60 mm. 5. The ratio of the pouring amount per unit surface area in the internal molten metal region and the external molten metal region represented by the following formula (1), using the electromagnetic casting apparatus according to claim 1. An electromagnetic field casting method for Al or an Al alloy, wherein the method is operated at 0 to 7.0. (Amount of molten metal in the internal molten metal area / Area of the internal molten metal area) / (Amount of molten metal in the external molten metal area / Area of the external molten metal area) ... (1)