JP2012086233A - Bottom pouring type teeming tube and teeming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the flow speed of the molten metal in the molten metal surface direction (vertical direction) within a mold that is being teemed, by a simple method that is not associated with reduction in productivity or increase in cost due to installation of a complex equipment, without lowering the teeming speed and without any variation under the condition in which the teeming speed varies, in a bottom pouring type teeming method for molten metal.SOLUTION: The shape of an inner hole 2 of a teeming tube 1 within a region from an outlet 3 provided on the bottom of a mold 4 downward along a length L is formed such that the radius of the lateral cross-section is reduced with a gradual curve downward from the outlet 3 as a starting point, and the curve of the radius that is gradually reduced is represented by a specific formula in the vertical cross-section passing the center axis of the teeming tube.

Description

  The present invention relates to a pouring method and a pouring pipe of a pouring method for producing a metal ingot by discharging / injecting molten metal from a discharge port at the bottom of a mold, and more specifically, from a discharge port at the bottom of a mold. The present invention relates to an inner hole structure of a pouring pipe and a pouring method using the pouring pipe.

  As a casting method for producing a metal ingot, there is a method in which molten metal is poured into a mold and cooled and solidified.

  This casting method includes an upper pouring method and a lower pouring method. Among these, the pouring method of the pouring method connects the tip of the pouring pipe through which the molten metal passes to the discharge port provided at the bottom of the mold, The molten metal in a molten metal container such as a ladle is discharged / injected from the discharge port at the bottom of the mold via the pouring pipe.

  Compared to other methods such as top pouring, this bottom pouring method can make the molten metal flow in the mold gentler when pouring the molten metal into the mold. It has been adopted for the purpose of suppressing deterioration of the quality of metal ingots such as suspension due to objects.

  FIG. 5 is a longitudinal sectional view of a mold provided with a conventional pouring pipe by a pouring method of pouring. As shown in the figure, a pouring pipe 1 is connected to the discharge port 3 provided at the bottom of the mold 4, and the molten metal passes through the inner hole 2 of the pouring pipe 1 and rises, and the discharge port 3. Are discharged into the mold 4 and injected. Conventionally, as the pouring pipe 1, a cylindrical pipe having a generally constant inner diameter has been used.

  When the molten metal is discharged / injected into the mold 4 (hereinafter also referred to as “pouring”), the shape of the pouring pipe 1 directly below the discharge port 3 is such a general cylindrical shape. In the initial stage, the speed (energy) in the upward direction at the front end (discharge port) of the pouring pipe 1, that is, in the pouring pipe axis direction, increases. Therefore, a flow (six parts in FIG. 5) is formed in which the upper end surface (hereinafter referred to as “molten surface”) of the molten metal (5 in FIG. 5) rises in a raised shape. At the raised portion of the molten metal surface directly above the discharge port, slag and antioxidant (powder) floating on the upper surface of the molten metal 5 are pushed away to the surroundings, and the molten metal is An exposed portion, that is, an eyeball 6 is generated, which causes oxidation of the molten metal. Further, the flow of the molten metal having a large velocity (energy) immediately above the discharge port forms a violent flow in the lateral direction or the downward direction around the upper axis of the discharge port after reaching the molten metal surface. This lateral or downward flow causes a more intense rotational flow due to collision with the inner wall of the mold 4 or the like. At this time, the molten metal 5 in the mold 4 is vigorously stirred to entrain the slag 7 and the slag is diffused and suspended throughout the molten metal in the mold. As a result, the quality of the metal ingot is lowered.

  As a countermeasure, for example, Patent Document 1 discloses that the ratio of the inner diameter of the end of the runner (pouring pipe) to the inner diameter of the main body is 1.1 or more and the inner hole diameter is increased upward, By applying a pouring pipe having an inner hole taper shape in which the length of the hole diameter enlarged portion is 0.2 to 2.0 times the tip inner diameter, the discharge pressure of the molten metal is dispersed and the hot water rises in the center. A technique for stabilizing the molten metal surface in the mold by reducing the flow rate is disclosed.

  However, in the technique of Patent Document 1, the maximum speed of the central portion in the directly upward direction of the molten metal discharge flow can be reduced to some extent, but the degree is not sufficient. Further, the high-velocity flow of the molten metal is still concentrated in the vicinity of the vertical axis immediately above the discharge port, and diffusion to the outer peripheral side (periphery) of the shaft and the reduction in speed cannot be realized.

  As a result, the molten metal bath protrudes onto the molten metal surface at a shallow depth before the molten metal bath reaches a predetermined depth in the mold, or is stirred at a high speed. It is difficult to suppress this. Such a phenomenon becomes more remarkable as the depth of the molten metal bath is relatively shallow, particularly in the initial stage of pouring. In the technique of Patent Document 1, a sufficient effect for solving the above problems cannot be obtained.

  Further, in Patent Document 2, when the molten metal is discharged into the mold by the down-pour method from the discharge port provided at the bottom of the mold, a part of the coating agent is caught if the hot water flow is suddenly upward. It has been proposed to cause the molten steel flow to slowly flow out in the lateral direction by using an ascending brick having an opening toward the short side of the mold as a solution to the cause of inclusions.

  However, the “rising brick having an opening toward the short side of the mold” in Patent Document 2 has a wall shape with the top end closed, and the opening for discharging the molten steel in the lateral direction is formed on the lower part on the circumference. 2-4 places are provided, and the shape of the space (hole) that becomes the molten steel path toward the opening is “Y-shaped”, and the molten steel is 2-4 places on the circumference. In this case, the ink is discharged only in the direction from the opening provided at the position of only the portion having the opening.

  In the case of such a structure, the molten steel flow velocity in the direction directly above the discharge port can be reduced, but the molten steel cannot be diffused uniformly and widely in the lateral direction. In this case, since the molten steel flow is discharged in a lateral direction from a limited narrow portion, the speed of the discharged molten steel flow is increased. This partial high-speed molten steel flow may cause the entrained flow of non-metallic inclusions in the molten steel, particularly when the head at the beginning of molten steel pouring is shallow.

  Patent Document 3 proposes that one or a plurality of swirl flow forming means (twist plate for swirl flow formation) for forming a swirl flow in the molten metal is provided in the pouring pipe. This is because a swirl flow is formed in the molten metal in the pouring pipe, which is a path of the molten metal, and a swirl flow centered on the central axis in the discharge port is formed in the molten metal discharged from the discharge port. It is intended to reduce the maximum velocity at the central portion in the direction directly above the flow, and to achieve diffusion to the outer peripheral side (periphery) of the shaft and a reduction in velocity.

  However, in the technique of Patent Document 3, although the maximum speed of the central portion directly above the molten metal discharge flow can be reduced to some extent, the swirl flow forming means (in the swirl flow forming means) installed in the pouring pipe which is the path of the molten metal. For example, a torsion plate or the like) becomes a large resistance of the molten metal flow, and there is a possibility that the pouring speed (referring to the amount of molten metal injected into the mold per unit time, the same applies hereinafter) is greatly reduced. Further, if the pouring speed is not reduced or the pouring speed is increased, the inner diameter of the pouring pipe needs to be increased.

  Furthermore, in order to install the swirling flow forming means of Patent Document 3 in the pouring pipe, it is necessary to produce highly accurate swirling flow forming means (such as a torsion plate for swirling flow formation). Special pouring pipe structures and construction techniques are also required for installation. For this reason, problems such as generation of new costs and reduction of productivity may occur.

  In addition, since there is no container that floats nonmetallic inclusions such as alumina before pouring into a mold such as a tundish in the continuous casting method, most of these nonmetallic inclusions are in the molten metal. It flows into the mold while being diffused. These fine non-metallic inclusions are unlikely to float and stay in a dispersed state in the metal ingot, often reducing the quality.

JP-A-9-239494 JP-A-51-037035 JP 2007-216295 A

  Occurrence of `` eyeball '' that causes deterioration of the quality of the metal ingot in the pouring method, entrainment of slags and non-metallic inclusions in the molten metal, dispersion and retention in the molten metal in the mold, etc. The main reason for this is that the molten metal flow rate from the molten metal discharge port to the molten metal surface, that is, the molten metal flow rate directly upward from the discharge port is relatively large.

  The generation of such eyeballs, the turbulence of the molten metal flow in the mold, and the deterioration of the quality of the metal ingot due to these fluctuate depending on individual operation conditions such as the mold shape, the pouring speed, and the steel type.

  However, the occurrence of “eyeball”, which is a direct cause of quality deterioration, and the occurrence and extent of slags and non-metallic inclusions in the molten metal are caused by the flow of molten metal flowing into the mold at the discharge port. Is almost determined by. That is, the greatest or fundamental factor is the degree of flow velocity in the direction directly above the molten metal flowing from the discharge port. Therefore, it is necessary to solve a common problem that can solve these problems even under operating conditions that vary individually.

  Therefore, the present invention provides a molten metal pouring method in a pouring method without reducing the pouring speed or even under conditions in which the pouring speed fluctuates (in particular, regardless of fluctuations in individual operating conditions). Similarly, when the pouring speed is increased in the same equipment, etc.) Similarly, the molten metal in the mold during pouring can be reduced by a simple method that does not lead to a decrease in productivity or an increase in cost, such as installation of complicated equipment. It is an object to reduce the flow velocity in the hot water surface direction (directly upward direction). As a result, it aims at reducing the deterioration of the quality of the metal ingot accompanying nonmetallic inclusions and oxidation.

  In the present invention, the shape of the inner hole of the pouring pipe at the bottom of the mold and the pouring pipe immediately below (that is, the region immediately before the pouring outlet of the mold at the tip of the pouring pipe) is made a specific shape.

That is, the present invention is used in a pouring method of a pouring method in which molten metal is discharged into a mold from a discharge port provided at the bottom of the mold, and in a pouring pipe whose tip is in communication with the discharge hole, The shape of the inner hole of the pouring pipe in the region extending downward from the discharge port to the length L is the diameter of the cross section in the lateral direction (the cross section in the direction perpendicular to the molten metal traveling direction; the same applies hereinafter). The diameter gradually decreases in the downward direction from the starting point as the outlet, and the gradually decreasing diameter has a shape represented by the following formula 1 in a longitudinal section passing through the central axis of the pouring pipe. We provide a pouring pipe pouring pipe characterized by


Here, H is represented by Equation 2 below.


In Equation 2,


Moreover, in Formula 1 and Formula 2,
n is 1.5 ≦ n ≦ 5.0,
L is (Do × 1.1) ≦ L ≦ (Do × 4.0).

Here, each character symbol of Formula 1 and Formula 2 shows the following matters.
L: Length of change area of pouring pipe inner hole diameter downward from discharge port Di: Diameter of discharge port Do: Diameter of transverse cross section of pouring pipe inner hole at position L Z: Arbitrary downward from discharge port Length to the position of Dz: Diameter of the transverse cross section of the pouring pipe inner hole at the position of Z

  Moreover, this invention provides the pouring method of the pouring method which reduces the flow velocity of the molten metal of a discharge port upper direction using the said pouring pipe.

  Hereinafter, the present invention will be described in detail.

  Prior to the present invention, the inventors of the present invention flow the molten metal in the direction opposite to the downward pouring method that is the subject of the present invention, that is, downward from the discharge port provided at the bottom of the molten metal container. It has been found that the rectifying effect can be obtained by making the inner hole of the discharge port into a specific shape when flowing out.

  In this case, the molten metal flow is determined by the position in the flow direction in the inner hole of the discharge port and the pressure distribution at each position. In other words, it is determined by the state of transition of the energy loss of the molten steel flow between the discharge port starting point and the position below it.

  First, the shape in the case of flowing out this molten metal downward from the discharge port provided in the bottom part of the molten metal container is demonstrated.

Since the energy that supports the flow velocity of the molten metal flowing out from the discharge port of the molten metal container basically depends on the pressure of the molten metal at the discharge port (in this case, the range from the discharge port starting point to the lower small diameter side), the discharge port The flow velocity V (z) of the molten steel at a distance Z from the starting point (on the same horizontal plane as the lower end surface of the container, on the large diameter side) is g, acceleration is H, the molten metal head is H, and the flow coefficient is k. Then
V (z) = k (2g (H + Z)) ^1/2 ............ Formula 3
It is represented by

Since the flow rate Q of the molten metal passing through the discharge port is a product of the flow velocity v and the cross-sectional area A, the length from the discharge port to the lower portion of the discharge port is L, and the melting at the position below the discharge port starting point L is L. When the flow velocity of the metal is v (L) and the cross-sectional area at the position below the discharge port origin L is A (L),
Q = V (L) × A (L) = k (2 g (H + L)) ^1/2 × A (L).
It is represented by

Further, since the flow rate Q is constant regardless of the position perpendicular to the central axis in the molten metal traveling direction at any position in the inner hole of the discharge port, the cross-sectional area A (z) at the position of the distance Z downward from the discharge port starting point. Is the flow velocity of the molten steel at point Z, V (z),
A (z) = Q / V (z) = k (2 g (H + L)) ^1/2 × A (L) / k (2 g (H + Z)) ^1/2
...... Formula 5
When both sides are divided by A (L),
A (z) / A (L) = ((H + L) / (H + Z)) ^1/2 ...
It becomes.

Here, the circumference is π, the diameter (diameter) of the discharge port is Di, the diameter (diameter) of the position L below the discharge port is Do, and the discharge port at the position of the distance Z from the discharge port to the lower position direction. If the diameter of the inner hole of the (diameter) and Dz, a (z) = πDz 2/4, a (L) = from πDo a ^2/4,
A (z) / A (L ) = (πDz 2/4) / (πDo 2/4) = ((H + L) / (H + Z)) 1/2 ... Equation 7
Dz ² / Do ² = ((H + L) / (H + Z)) ^1/2 Formula 8
Dz = ((H + L) / (H + Z)) ^1/4 × Do ... Formula 9
Thus, the following relationship holds.
ln (Dz) = (1/4) × ln ((H + L) / (H + Z)) + ln (Do)

  That is, the energy loss (pressure loss) can be minimized by setting the cross-sectional shape of the inner hole of the discharge port to a shape that satisfies Equation 9 (Equation 10).

  Here, H can be expressed (deformed) as the above-described formula 2 based on the above-described formula relating to flow (where n = 4).

  When the above equation 10 is shown in a graph, a quartic curve is drawn. In the case of the cross-sectional shape of the inner hole in the region from the discharge port to the lower length L, which corresponds to the graph of Expression 10, the pressure loss of the molten metal can be minimized. In addition, in the shape that matches this equation 10, the pressure gradually decreases (slowly) at every arbitrary distance Z from the discharge port starting point to become a rectified state.

  The inventors of the present invention have the effect of rectification due to the cross-sectional shape of the inner hole in the region from the discharge port to the lower length L based on the above-described formula in the fluid analysis by computer simulation and the actual operation based on the result. It has already been confirmed along with reproducibility and correlation.

  However, even if the method of flowing the molten metal downward from such a molten metal container through the discharge port (the shape whose diameter is expanded upward) as described above is applied directly to the downward pouring method, the present invention We cannot solve the problem of the pouring method.

  This “applying as it is” means that in the down-pour method, an inner hole shape that expands to the lower (upstream) side of the pouring pipe is applied near the tip of the pouring pipe just below the mold, In this case, the molten metal is discharged upward (see FIG. 12). In this case, the effect of improving (reducing) the flow velocity at the center of the pouring pipe inner hole cannot be obtained (see Experimental Example F below).

  The present inventors have applied the inner hole shape corresponding to the above-mentioned formula 9 (formula 10) based on the above-mentioned theory so that the diameter is increased in the mold side (that is, upward) direction in the pouring pipe, that is, the pouring pipe. The shape of the inner hole is a shape that satisfies the above formulas 1 and 2, and the molten metal is allowed to flow from the small diameter side to the large diameter side of the pouring pipe inner hole of the above shape (in other words, when flowing out downward from the aforementioned container) It was found that the flow rate in the upper direction of the center of the pouring pipe immediately below the discharge port can be remarkably reduced. This is because the molten metal that flows through the inner hole of the pouring pipe of the present invention and flows out into the mold flows smoothly in the diameter expansion direction without causing a portion where the energy loss is locally large. it is conceivable that. Furthermore, the present inventors have found that the variables of the formulas 1 and 2 can be changed within a certain range and the specific range thereof.

  ADVANTAGE OF THE INVENTION According to this invention, the following effects can be acquired by diffusing the molten metal flow which passes the inner hole of a pouring pipe and flows out into a casting_mold | template from a discharge outlet.

1. The flow velocity of the molten metal at the top of the pouring pipe (discharge port) decreases, and the fluctuation of the molten metal surface becomes smaller and stable due to diffusion of the molten metal, and the molten metal springs up to the center of the mold. Such a phenomenon is greatly reduced, and the occurrence of eyeballs is suppressed.

2. Entrainment of slags above the hot water surface is also reduced. As a result, mixing and dispersion of slag as inclusions in the molten metal can be reduced, and the quality of the metal ingot can be improved.

3. Stabilization of the molten metal surface reduces the amount of slag entrained in the molten metal, reduces the tendency for antioxidants, etc. to be introduced to the molten metal surface to be unevenly distributed, greatly reducing the amount used. be able to.

4). There is no need to install complicated equipment that tends to cause flow resistance of molten metal flow in the pouring pipe, and there is no increase in improvement costs or running costs, and drastic changes in pouring technology, methods, conditions, etc. The problem can be solved without being accompanied.

5. As a result, the molten metal pouring (supplying) rate is easy (without reducing productivity) and without increasing production cost (or while making it possible to reduce production cost). In addition, the quality of the metal ingot can be improved.

It is a longitudinal cross-sectional view (image) which shows the pouring pipe of this invention, (a) is the whole figure containing a casting_mold | template, (b) is an enlarged view of a discharge outlet and its direct lower part (a part). It is the longitudinal cross-sectional view (image) which shows the example (inner hole is cylindrical = straight pipe) of a prior art, (a) is the whole figure including a casting_mold | template, (b) is a discharge port and its direct under ( It is an enlarged view of a part a). It is a longitudinal cross-sectional view (image) which shows the example of the pouring pipe of a prior art (inner hole is taper shape = patent document 1), (a) is the whole figure including a casting_mold | template, (b) is a discharge port and its direct bottom It is an enlarged view of (a part). It is a longitudinal cross-sectional view (image) which shows the example (inner hole is R = spherical shape) of the pouring pipe of a comparative example, (a) is the whole figure including a casting_mold | template, (b) is a discharge port and its direct bottom (a FIG. The state of the molten metal and slag in a casting_mold | template in the example of the pouring pipe | tube of the prior art near a casting_mold | template and a casting_mold | template just under a casting_mold | template is shown typically. (However, the inclusions are dispersed in the molten metal at the same time, but this state is not shown in this figure.) Experimental example A (Table 1), that is, a simulation result regarding the comparison of the shape of the pouring pipe between the present invention and the prior art. Shows the transition. It is a simulation result of Experimental example A (Table 1), and shows the upward direction speed of the molten steel center portion at a position 250 mm directly above the discharge port. It is a simulation result of Experimental Example A (Table 1), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 1 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example A (Table 1), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port upstream of Comparative Example 1 to 250 mm directly above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example A (Table 1), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port upstream of Comparative Example 2 to 250 mm directly above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example A (Table 1), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port upstream of Comparative Example 3 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). Experimental example B (Table 2), that is, in the pouring pipe shape of the present invention, is a simulation result on the influence of the value of n in the formulas 1 and 2 on the speed of the molten steel, about the upstream side just below the discharge port The transition of the speed in the upward direction of the molten steel center from about 400 mm to 250 mm immediately above the discharge port is shown. It is a simulation result of Experimental example B (Table 2), and shows the speed in the direction directly above the molten steel center at the position 250 mm directly above the discharge port. It is a simulation result of Experimental example B (Table 2), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 2 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example B (Table 2), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 3 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example B (Table 2), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 4 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example B (Table 2), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port in Example 5 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example B (Table 2), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port upstream of Comparative Example 4 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). Experimental example C (Table 3), that is, in the shape of the pouring pipe of the present invention, is a simulation result on the effect of the Di / Do ratio value in Equation 2 on the speed of the molten steel, about 400 mm upstream immediately under the discharge port The transition of the speed in the directly upward direction of the molten steel center from the vicinity to 250 mm immediately above the discharge port is shown. It is a simulation result of Experimental example C (Table 3), and shows the speed in the direction directly above the molten steel center at a position 250 mm directly above the discharge port. It is a simulation result of Experimental example C (Table 3), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port upstream of Comparative Example 5 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example C (Table 3), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port upstream of Comparative Example 6 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example C (Table 3), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 6 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example C (Table 3), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 7 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example C (Table 3), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 8 to 250 mm directly above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example C (Table 3), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 9 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). Experimental example D (Table 4), that is, in the shape of the pouring pipe of the present invention, is a simulation result on the effect of the value of L in Formula 1 and Formula 2 on the speed of the molten steel, about the upstream side just below the discharge port The transition of the speed in the upward direction of the molten steel center from about 400 mm to 250 mm immediately above the discharge port is shown. It is a simulation result of Experimental example D (Table 4), and shows the speed in the direction directly above the molten steel center at the position 250 mm directly above the discharge port. It is a simulation result of Experimental example D (Table 4), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port upstream of Comparative Example 7 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example D (Table 4), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 12 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example D (Table 4), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 13 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example D (Table 4), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 14 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result regarding the influence which the value of the flow rate (t / min.) Of molten steel has on the speed of molten steel in Experimental Example E (Table 5), ie, the pouring pipe shape of the present invention, about 400 mm upstream immediately under the discharge port. The transition of the speed in the directly upward direction of the molten steel center from the vicinity to 250 mm immediately above the discharge port is shown. It is a simulation result of Experimental example E (Table 5), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 15 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is a simulation result of Experimental example E (Table 5), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port of Example 16 to 250 mm immediately above the discharge port (white to black portion. This portion has a deep color tone. High speed). Experiment F (Table 6), that is, the pouring pipe shape of the present invention of Example 1 of Experiment A was installed in the upside down direction of Example 1 (Comparative Example 9), and the speed of the molten steel was investigated. It is a simulation result, and shows the transition of the speed in the direction directly above the molten steel center from about 400 mm upstream immediately below the discharge port to 250 mm directly above the discharge port. It is a simulation result of Experimental example F (Table 6), and shows the velocity distribution of the molten steel flow from about 400 mm upstream of the discharge port upstream of Comparative Example 9 to 250 mm directly above the discharge port (white to black portion. This portion has a deep color tone. High speed). It is the longitudinal cross-sectional view (image) at the time of installing the pouring pipe of the inner-hole shape which satisfies the said Formula 1 and the said Formula 2 of this invention upside down (Comparative Example 9 of Experimental Example F), (a) Is an overall view including the mold, and (b) is an enlarged view of the discharge port and directly below (portion a).

  The present invention will be described using the results of analysis by computer simulation.

For this simulation, fluid analysis software manufactured by Fluent, trade name “Fluent Ver. 6.3.26” was used. The input parameters in this fluid analysis software are as follows.
Number of calculation cells: Approximately 120,000 (However, there are variations depending on the model.)
Viscous Model: K-omega calculation Fluid (molten metal): Molten steel ・ Molten steel temperature: 1580 (° C.)
・ Molten steel density: 6.0 (g / cm ³ )
・ Pouring speed: 1.3 t / min.
・ Mold diameter: 1000mm
-Calculated molten steel depth: 250 mm (assuming a pouring method in which the molten steel depth is 2000 mm and the maximum amount of molten steel in the mold is about 10 t, and an initial state of pouring is assumed.)
L: Length (arbitrary length) of the change area (reduced diameter area) of the hole diameter in the pouring pipe downward from the discharge port
Di: Diameter of the discharge port Do: Diameter of the transverse cross section of the pouring pipe inner hole at the position L,

  FIG. 5 schematically shows the state of the molten metal and slag in the mold in the example of the casting pipe of the prior art near the mold and immediately below the mold. Moreover, FIG. 6D shows the molten steel flow velocity distribution by the computer simulation of this conventional shape (in which the pouring pipe inner diameter change is linear, ie, a cylinder. FIG. 2).

  In this simulation, the state at the time when molten steel exists at a depth of 250 mm is shown. As shown in FIG. 6D, it can be seen that the molten steel flow is concentrated in the upward direction with almost the same width as the diameter of the discharge port, the diffusion to the surroundings is small, and the molten steel flow flows out with little attenuation. Thus, it can be seen that the main item 6 as shown in FIG. 5 is mainly caused by the concentrated and high-speed molten metal flow in the upward direction.

  Such a concentrated and high-velocity molten metal flow immediately after reaching the molten metal surface is converted into a high-velocity flow in the direction along the molten metal surface (lateral direction). At this time, since the slag on the hot water surface (7 in FIG. 5) is swept away around the eyeball and moved, the hot water surface on the eyeball is exposed to the atmosphere with the molten metal exposed, and is oxidized. In an atmosphere, the molten metal is oxidized. Further, at this time, slags on the molten metal surface are wound into the molten metal. After that, the molten metal flow in the transverse direction collides with the inner wall surface of the mold while maintaining a high speed, and forms a complicated and intense stirring flow such as a downward direction and a vortex flow to further add a large amount of slag into the molten metal. It spreads while being caught. In this way, the concentrated and high-velocity molten metal flow directly causes a suspension state or contamination due to molten metal slags.

  The present invention reduces the occurrence of eyeballs and contamination of molten metal associated with such a concentrated and high-velocity molten metal flow. In other words, the molten metal flow discharged from the discharge port is reduced. While diffusing, the flow velocity in the direction immediately above is reduced. The diffusion of the molten metal flow discharged from the discharge port and the flow velocity in the directly upward direction can be evaluated based on the flow velocity in the directly upward direction of the central portion of the molten metal flow. That is, when the pouring speed (the amount of pouring per unit time, eg, t / min.) Is maintained and the flow velocity in the direction directly above the center of the molten metal flow is reduced, the flow velocity is dispersed in a direction other than the direction directly above. Will do. Here, the reason why the center portion is used is that the flow velocity in the transverse cross section of the molten metal flow becomes maximum at the center portion and gradually decreases as the distance from the center increases.

  For this reason, in the present invention, a specific target is set for the molten metal flow velocity in the direction directly above the center of the discharge port. Moreover, since the occurrence of eyeballs and contamination of the molten metal are particularly large when the molten metal depth in the mold at the beginning of pouring is shallow, a relative evaluation is performed based on the molten metal depth in the mold being 250 mm. The boundary value for solving the problem was determined.

  FIG. 1 shows an example of a pouring pipe of the present invention. The shape of the inner hole 2 of the pouring pipe 1 in the range from the discharge port 3 provided at the bottom of the mold 4 to the vicinity of the tip of the pouring pipe (length L) below the discharge port 3 is the diameter of the cross section in the lateral direction. From the starting point, the diameter is gradually reduced along a curve satisfying the above-described Expressions 1 and 2.

  In other words, the vertical cross section of the inner hole 2 of the pouring pipe 1 in the inner hole diameter changing region corresponding to the length L is discharged upward from the change start point of the region (a position below the discharge port 3 by the length L). A shape that gradually expands toward the outlet 3 while drawing a curve that satisfies the above-described equations 1 and 2.

  By adopting such a shape, the molten metal flowing out from the discharge port 3 does not concentrate in the upward direction, but flows into the mold 4 while diffusing in a direction according to the curve of the inner hole 2. In addition, a distribution state in which the upward flow velocity is averaged at a low level throughout the entire molten metal flow to be discharged is shown. This is considered to be because when the fluid moves according to the curves satisfying the above-mentioned formulas 1 and 2, the energy loss becomes small and the fluid can smoothly flow according to the curves.

  In the pouring pipe 1 of the present invention, it is only necessary that the longitudinal section of the inner hole 2 of the pouring pipe 1 in the inner hole diameter changing region corresponding to the length L has the aforementioned shape. Therefore, when manufacturing the pouring pipe of the present invention, there is no need to particularly limit the external shape of the pouring pipe, the method of dividing or connecting to the pouring pipe other than the target portion of the present invention, and the like.

  As a method for producing a pouring pipe of the present invention, a refractory earth material forming the pouring pipe is loaded into a mold having the above-mentioned inner hole shape and an arbitrary outer peripheral shape, and the longitudinal or lateral direction is used. A general method for producing a refractory (nozzle or the like) such as molding by pressing, drying, firing, processing, or the like can be employed. As a forming method in such a manufacturing method, an arbitrary method such as a friction press, an oil press, or an isostatic press can be selected. In addition, the refractory that constitutes the pouring pipe should be any refractory that is usually used for such a pouring type pouring pipe and that is designed for each operating condition. Can do.

[Experiment A]
Experimental example A shows an experimental example using computer simulation in which the pouring pipe of the present invention is compared with the prior art.

  The test shape is the shape of the pouring pipe of the present invention as shown in FIG. 1 (Example 1), the pouring pipe of the comparative example is cylindrical (typical example, comparative example 1, FIG. 2), and the upward direction by a straight line. There are three types of diameter-expanded shapes (tapered in Patent Document 1, Comparative Example 2. FIG. 3), and discharge port inner holes are arc-shaped (R) (Comparative Example 3. FIG. 4). In Comparative Example 3, although the portion from the discharge port to the lower side is a curve, the comparison was performed as an example in the case where the above formulas 1 and 2 of the present invention were not satisfied. For these four samples, only the inner hole shape of the region from the discharge port to the lower position of the length L was different, and the other portions were the same.

  Table 1 shows the values of each shape and each element (variable) in Formula 1 and Formula 2 in the case of the present invention, and the results. FIG. 6A shows the discharge port from the vicinity of about 400 mm upstream immediately under the discharge port. The transition of the speed in the upward direction of the molten steel center up to 250 mm directly above (hereinafter simply referred to as “molten steel speed transition”) is shown in FIG. The speed in the direction directly above the center is shown. Further, FIGS. 6C to 6F are diagrams visualizing the state of the velocity distribution of the molten steel from about 400 mm upstream of the discharge port to 250 mm immediately above the discharge port in each example (hereinafter simply referred to as “molten steel velocity distribution”). This is indicated by a medium white to black portion, and this portion indicates a higher speed as the color tone is darker.

  From these results, it can be seen that in Comparative Example 1, the molten steel flow velocity reaches the reference molten metal surface with almost no attenuation. In contrast to Comparative Example 1, in Example 1 of the present invention, the index of the central flow velocity (hereinafter simply referred to as “flow velocity index”) on the reference hot water surface with Comparative Example 1 being 100 is 3.3, which is a very remarkable effect. Is obtained. On the other hand, Comparative Example 2 which is the technique of Patent Document 1 shows an improvement effect over Comparative Example 1, but the flow velocity index is only 16.6. Moreover, although the improvement effect with respect to the comparative example 1 is recognized by the comparative example 3, the flow velocity index has stopped at 36.3.

  From these results, it can be seen that the present invention provides a significantly more remarkable effect than any of the prior arts. In addition, even if the inner hole just below the discharge port is simply tapered or simply curved, and the diameter of the inner hole is expanded upward, the remarkable effect as in the case of the curved shape satisfying the above-described formulas 1 and 2 of the present invention can be obtained. I understand that there is no.

[Experiment B]
Experimental example B shows an experimental example using computer simulation about the influence of the value of n in the above-mentioned formulas 1 and 2 on the flow rate of the molten metal in the shape of the poured pipe of the present invention.

  Since the object of the present invention is to reduce the flow rate of the molten metal as compared with the prior art, the target value of the flow rate index of the present invention is smaller than that of Comparative Example 2, that is, less than 16.6 (the following experimental examples) The same).

  In this experimental example, the value of n was changed from 1.0 to 6.0 with reference to Example 1 of Experimental Example A.

  Table 2 shows the values of the elements (variables) of Formula 1 and Formula 2, and the results, FIG. 7A shows the transition of the molten steel speed, and FIG. 7B shows the direction directly above the center of the molten steel at the reference level relative to the value of n. Indicates speed. Further, FIGS. 7C to 7G show the molten steel velocity distribution of each example.

  From these results, it is understood that when the value of n is 1.5 or more and 5.0 or less, the target value is satisfied and a remarkable effect is obtained. In Comparative Example 4 where the value of n is 6.0, the improvement effect with respect to Comparative Example 1 is obtained, but the molten steel speed is higher than that of Comparative Example 2.

[Experiment C]
Experimental example C shows an experimental example using computer simulation on the influence of the value of the Di / Do ratio in the formula 2 on the flow rate of the molten metal in the pouring pipe shape of the present invention. Here, the value of the Di / Do ratio was changed from 1.5 to 4.0 with reference to Example 1 of Experimental Example A.

  Table 3 shows the values and results of each element (variable) of the above formulas 1 and 2, and FIG. 8A shows the change in the molten steel speed, and FIG. 8B shows the value at the reference level relative to the value of the Di / Do ratio. The speed in the direction directly above the molten steel center is shown. 8C to 8H show the molten steel velocity distribution of each example.

  From these results, when the value of the Di / Do ratio is 1.8 or more and the maximum value in this experiment is 4.0 or less, the target value is satisfied and a remarkable effect can be obtained, and Di / Do It can be seen that the most remarkable effect can be obtained when the ratio value is around 2.0.

  In addition, when the value of Di / Do ratio exceeds 4.0, it can estimate from the result of FIG. 8B that it will remove | deviate from target value from 4.5 vicinity.

[Experiment D]
Experimental example D shows an experimental example using a computer simulation about the influence of the value of L in the formula 1 and the formula 2 on the flow rate of the molten metal in the shape of the pouring pipe of the present invention. Here, based on Example 1 of Experimental Example A, the value of L was changed from 1.0 to 4.0 (hereinafter, simply indicated by the value of magnification only) with respect to Do.

  Table 4 shows the values of the elements (variables) of Formula 1 and Formula 2, and the results, FIG. 9A shows the change in the molten steel speed, and FIG. 9B shows the direction directly above the center of the molten steel at the reference level relative to the value of L. Indicates speed. Further, FIGS. 9C to 9F show the molten steel velocity distribution of each example.

  From these results, when the value of L is 1.1 or more and the maximum value in this experiment is 4.0 or less, the target value is satisfied and a remarkable effect is obtained, and the value of L is 2. It can be seen that the most remarkable effect can be obtained in the vicinity of 0.

  In addition, when the value of L exceeds 4.0, it can be estimated that the value of L does not greatly exceed the effect in the vicinity of 4.0 because the lower part approaches a straight line. Therefore, it is not necessary to have a shape that satisfies the above formula 1 and the above formula 2 until the value of L exceeds 4.0, and there is no advantage. Therefore, the value of L is 1.1 or more. The maximum value may be 4.0 or less.

[Experiment E]
Experimental Example E shows an experimental example using computer simulation on the influence of the molten steel flow rate (t / min.) On the molten steel speed in the shape of the poured pipe of the present invention. Here, on the basis of Example 1 of Experimental Example A, the molten steel flow rate was changed by a factor of 1/2.

  Table 5 shows the values and results of the elements (variables) of the above formulas 1 and 2, and FIG. 10A shows the molten steel speed transition. Further, FIG. 10B and FIG. 10C show the molten steel velocity distribution of each example.

  From these results, it can be seen that, although the molten steel speed changes relatively with the change of the molten steel flow rate, a remarkable effect can be obtained with the pouring pipe of the present invention regardless of the magnitude of the molten steel flow rate.

[Experiment F]
Experimental Example F is an experimental example using computer simulation when the pouring pipe shape of the present invention of Example 1 of Experimental Example A is installed upside down from Example 1 (see FIG. 12). Show. The conditions are the same as in Experimental Example A.

  Table 6 compares the values and results of the elements (variables) of Formula 1 and Formula 2, the transition of the molten steel speed in FIG. 11A, and the molten steel speed distribution of Comparative Example 9 in FIG. Show.

  From this result, when the pouring pipe shape of the present invention is installed in the reverse direction, the substantial improvement effect with respect to the comparative example 1 (tubular shape) is not observed in both the central portion flow velocity and the velocity distribution. That is, even if it rectifies | straightens in a pouring pipe, it has shown that the diffusion effect is not acquired.

  INDUSTRIAL APPLICABILITY The present invention can be applied to casting of a steel ingot by molten steel pouring method and pouring into a mold by a pouring method of general castings and other molten metals.

1 Pouring pipe 2 Inner hole of the pouring pipe (space for molten metal passage)
3 Discharge port (opening of the mold bottom (lower end))
4 Mold 5 Molten metal in the mold (full state, but with inclusions suspended in the prior art)
6 Eyeball 7 Slag (inclusions, etc.)

Claims (2)

Used in a pouring method of a pouring method for discharging molten metal into a mold from a discharge port provided at the bottom of the mold, and in a pouring pipe whose tip is in communication with the discharge hole,
The shape of the inner hole of the pouring pipe in the region extending downward from the discharge port to the length L is the diameter of the cross section in the lateral direction (the cross section in the direction perpendicular to the molten metal traveling direction; the same applies hereinafter). The diameter gradually decreases in the downward direction from the starting point as the outlet, and the gradually decreasing diameter has a shape represented by the following formula 1 in a longitudinal section passing through the central axis of the pouring pipe. The pouring pipe of the down-pour method characterized by


Here, H is represented by Equation 2 below.


In Equation 2,


Moreover, in Formula 1 and Formula 2,
n is 1.5 ≦ n ≦ 5.0,
L is (Do × 1.1) ≦ L ≦ (Do × 4.0).

Here, each character symbol of Formula 1 and Formula 2 shows the following matters.
L: Length of change area of pouring pipe inner hole diameter downward from discharge port Di: Diameter of discharge port Do: Diameter of transverse cross section of pouring pipe inner hole at position L Z: Arbitrary downward from discharge port Length to the position of Dz: Diameter of the transverse cross section of the pouring pipe inner hole at the position of Z   A pouring method of pouring using the pouring pipe according to claim 1, wherein the pouring method is performed by using the pouring pipe to reduce the flow rate of the molten metal in the upward direction of the discharge port.