JPH09239494A - Spouting runner in bottom pouring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the development of bare molten metal surface without lowering casting speed and to reduce the consumption of an oxidation inhibitor by forming the inner diameter at the tip part of a spouting runner to larger than the inner diameter of a main body. SOLUTION: Spouting pressure is dispersed by forming the tip part diameter D1 of the runner 40 to >=1.1 times of the main body part diameter D2 and also, the molten metal surface is stabilized by lowering the flowing speed of the molten metal rising at the center part, and the development of cold shot is restrained and the entrapment of the oxidation inhibitor is reduced. Therefore, since the development of the bare molten metal is prevented by stabilizing the molten metal surface without lowering the casting speed, the oxidation inhibitor is scarcely needed to use and is sufficient in only the necessary quantity to cover the molten metal surface. Further, since the molten metal rising is stabilized and the molten metal is formed as laminated flow state to reduce the entrapment of the oxidation inhibitor into the molten metal, the quality of a produced steel ingot, etc., is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge runner which serves as a passage for feeding a molten metal when a steel ingot or the like is manufactured by a down pouring method and finally discharges the molten metal into a mold.

[0002]

2. Description of the Related Art Generally, in the production of steel ingots, an ingot making method in which molten steel is solidified in a mold is generally used. In this method, there are two methods, a top pouring method and a bottom pouring method, depending on the method of pouring the molten steel into the mold. Separated. Of these methods, the pour method is
It has the advantage that a good ingot surface can be obtained, and is applied to the production of high-grade steel where quality is important. In the above-mentioned bottom pouring method, as shown in FIG.
And a mold 3 is arranged on the base 2 to form a ingot-making device. A through hole for a runner is formed from the surface plate 1 to the base 2, and an inner wall of the through hole is formed. A heat-resistant brick 5 is lined inside to form a round hole-shaped runner 4. Molten steel 6 supplied from a ladle or the like is sent through this runner 4,
The molten steel 6 is discharged and supplied into the molten steel 60 in the mold 3 from the tip end of the runner 4.

[0003]

By the way, in the above ingot making apparatus, the surface of the molten steel 60 in the mold 3 is protected by the antioxidant 7.
However, in the conventional device, since the discharge pressure of the molten steel is large, the above-mentioned antioxidant 7 is driven to the inner peripheral edge of the mold and the vicinity of the center of the surface portion of the molten steel 60 is covered. In addition, there is a problem that the hot water zone 8 called "eyeball" appears to rise. Since the molten steel is discharged on the basis of the casting speed in consideration of manufacturing efficiency, it is difficult to reduce the casting speed to lower the discharge pressure itself in terms of manufacturing efficiency. Therefore, a large amount of the antioxidant is added to the molten steel to prevent the formation of the bare hot water zone, and there is a problem that the amount of the antioxidant used is significantly increased. In addition, since the discharge pressure is large, upflow tends to be a turbulent flow, and there is also a problem that a steel ingot solidified by the antioxidant being entrained in molten steel has a sand flaw or a defective casting surface.

The present invention has been made in view of the above circumstances, and makes it possible to stabilize the molten metal surface of the molten steel in the mold without lowering the casting speed and to reduce the amount of the antioxidant to be used, and It is an object of the present invention to provide a discharge runner in the lower pouring method, which can prevent an antioxidant from being caught in the steel ingot and obtain a steel ingot of excellent quality.

[0005]

In order to solve the above problems, the first invention of the discharge runner in the lower pouring method of the present invention is such that the inner diameter of the tip of the discharge runner is larger than the inner diameter of the main body. It is characterized in that the ratio (D1 / D2) of the inner diameter D1 of the tip of the discharge runner and the inner diameter D2 of the main body is 1.1 or more. A second invention is characterized in that, in the first invention, the tip end length L is 0.2 to 2.0D1. A third aspect of the invention is characterized in that, in the first or second aspect, the inner peripheral surface of the tip portion has a tapered surface shape whose diameter gradually increases toward the tip.

The discharge runner of the present invention can be used for ingot casting of various steel ingots and other metals, and the temperature and pouring speed of molten metal, the length and diameter of the entire runner (the main body portion and the tip portion). (Excluding relative relationships) is not particularly limited. Further, the material forming the runner is not particularly limited, but generally heat-resistant brick is used. The inner diameter of the tip of the runner is larger than the inner diameter of the main body, and it is desirable that the inner diameter of the tip be larger on the tip side than on the same diameter. As shown in the third aspect of the invention, it can be tapered.

[0007]

According to the present invention, by making the tip diameter D1 of the runner 1.1 times or more the main body diameter D2, the discharge pressure is dispersed and the flow velocity of the molten metal in the central portion is reduced to lower the molten metal surface. Is stable, the generation of eyeballs is suppressed, and the inclusion of the antioxidant is reduced. Therefore, the action of lowering the discharge pressure and the like can be obtained without lowering the casting speed. Since the surface of the molten metal is stabilized in this way, it is almost unnecessary to use an antioxidant to prevent the generation of bare hot water, and therefore the amount of the antioxidant is sufficient to cover the surface of the molten metal. Therefore, the amount of antioxidant used can be significantly reduced. Further, since the molten metal is stably brought into a laminar flow state, the inclusion of the antioxidant in the molten metal is reduced, and the quality of the manufactured steel ingot or the like is improved.

In order to obtain the above effect, the above ratio (D
1 / D2) must be 1.1 or more, and 1.
If it is less than 1, the above effect cannot be sufficiently obtained. For the same reason, the ratio (D1 / D2) is preferably 1.3 or more. If the ratio exceeds 1.8, the discharge pressure will be excessively dispersed, causing problems such as hot water leak and mold melting loss. Therefore, the ratio is preferably 1.8 or less, and for the same reason, 1.5 or less. Is more desirable.

Further, the discharge runner preferably has a tip end length L within a predetermined range in relation to the tip inner diameter D1 of the tip end, whereby the discharge pressure is appropriately dispersed. If the length of the tip is less than 0.5D1, the discharge pressure is not sufficiently dispersed, and the above effect cannot be obtained sufficiently. on the other hand,
When the tip length exceeds 2.0D1, the discharge pressure is not sufficiently dispersed. Therefore, the tip end length L is 0.5
It is desirable to be in the range of 2.0 D1. Further, it is desirable that the tip of the runner has a larger diameter on the tip side as described above. This is because a rapid change in the diameter has a great effect on the molten metal discharge behavior, and a turbulent flow is likely to occur particularly in the molten metal, so that the rapid change in the diameter is preferably as small as possible. For this reason, it is most desirable that the inner peripheral surface of the tip portion has a tapered surface shape.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
A description will be given with reference to FIG. In the ingot making apparatus of this embodiment, the base 2 is arranged on the surface plate 1, and the wide mold 3 is arranged on the base 2. A runner 4 is formed from the surface plate 1 to the base plate 2, and the wall surface of the runner 4 is made of refractory bricks 5. The discharge runner 40 located on the bed of the runner 4 is composed of a main body portion 40a and a tip end portion 40b. The tip portion 40a is formed in a tapered shape whose diameter gradually increases toward the tip, and the inner diameter of the tip is 1.1 times or more the inner diameter of the body portion 40a (optimally 1.5). Times). Further, the length of the tip portion 40a is in the range of 0.2 to 2.0 with respect to the inner diameter of the tip, and it is optimally the same as the inner diameter of the tip.

When the molten steel 6 is fed to the runner 4 from a ladle (not shown), the molten steel 6 is discharged into the molten steel 60 in the mold through the main body 40a and the tip 40b of the discharge runner 40. The applied antioxidant 7 floats on the surface of the molten steel 60 and covers the entire surface of the molten steel 60. The discharge pressure of the molten steel 6 described above is dispersed by the change in shape from the main body portion 40a of the discharge runner 40 to the tip portion 40b, and a stable molten steel molten metal surface can be obtained without causing eyeballs.
In addition, the boiling water is stable, and it flows in a laminar flow state. An antioxidant 7 is additionally added to the molten steel 60 as needed, and a desired steel ingot can be obtained by solidifying the molten steel in the mold.

[0012]

EXAMPLE Using the ingot making apparatus shown in FIGS. 1 and 2,
Inner diameter D1 of the tip portion 40b and inner diameter D2 of the body portion 40a
The ratio (D1 / D2) was changed variously, and the length L of the tip portion 40b was similarly changed in relation to the tip inner diameter D1 to carry out the ingot-making test. Specifically, molten steel melted by a conventional method is put in a ladle, which is cast at a temperature of 1580 ° C.
It is supplied from the runner into the mold at a casting speed of 5 t / min,
About 20 tons of steel ingot was cast. The inner diameter of the casting mold at the molten metal surface position was about 1200 mm. For comparison, a discharge runner having the same diameter and an inner diameter equal to the inner diameter of the main body 40a was prepared, and casting was performed under the same conditions as above. In addition, in each of the examples, an antioxidant was appropriately charged into the mold so that bare molten metal was not generated during casting.

The results of the above test are shown in Table 1. As shown in Table 1, in the examples of the method of the present invention, bare hot water was scarcely generated, and even if an eyeball was generated, it was extremely small and had no swelling. Requires only a small amount. On the other hand, in the comparative method, a large eyeball (about 250 to 350 mm diameter) is generated without interruption,
The centerpiece also had a big swell. For this reason, it is necessary to additionally add an antioxidant at a constant pitch during casting, resulting in a large increase in the amount used. Further, the steel ingot obtained by the method of the invention does not have sand defects, and the casting surface is excellent, whereas the steel ingot obtained by the comparative method shows the occurrence of sand defects, and the casting surface is also an example. Was inferior to that of. In the invention method, D1 / D2 is 1.5 and L = D
The best results were obtained using the discharge runner of No. 1.

[0014]

[Table 1]

[0015]

As described above, according to the discharge runner in the lower pouring method of the present invention, the inner diameter of the tip of the discharge runner is formed larger than the inner diameter of the main body, and the inner diameter D1 of the tip of the runner is formed. Since the ratio (D1 / D2) of the inner diameter D2 of the body to 1.1 or more is set, the amount of the antioxidant used is reduced by stabilizing the molten metal surface during casting without lowering the casting speed. It is also possible to prevent the inclusion of antioxidants,
There is also an effect of improving the quality of the obtained steel ingot and the like.

Further, if the length L of the tip portion is within the range of 0.5D1 to 1.0D1 with respect to the inner diameter of the tip, the above effect is further secured. Further, if the inner peripheral surface of the tip portion is formed in a tapered surface shape in which the diameter gradually increases toward the tip, the molten metal is smoothly discharged, and the rising of the molten metal can be further stabilized.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view near a discharge runner showing an embodiment of the present invention.

FIG. 2 is a front sectional view of the ingot making device.

FIG. 3 is a front sectional view showing a molten steel discharge situation in a conventional ingot making apparatus.

[Explanation of symbols]

 1 surface plate 2 base plate 3 mold 4 runner 40 discharge runner 40a body 40b tip 5 refractory brick 6 molten steel 60 molten steel 8 naked bath zone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitohisa Yamada, No. 4, Chazu-cho, Muroran-shi, Hokkaido, Japan Steel Works, Inc. (72) Inventor, Koji Kikuchi No. 4, Chazu-cho, Muroran, Hokkaido, Japan, Japan Steel Works, Ltd.

Claims (3)

[Claims] 1. The inner diameter of the tip of the discharge runner is formed to be larger than the inner diameter of the main body, and the inner diameter D1 of the tip of the discharge runner is formed.
The discharge runner in the lower pouring method, characterized in that the ratio (D1 / D2) of the inner diameter D2 of the body to the inner diameter D2 is 1.1 or more. 2. The tip length L is 0.2D1 to 2.0D1.
The discharge runner in the lower pouring method according to claim 1, wherein 3. The discharge runner according to claim 1 or 2, wherein the inner peripheral surface of the tip portion has a tapered surface shape whose diameter gradually increases toward the tip.