JP2009090323A - Continuous casting machine and continuous casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous casting machine which can attain both reduction of inclusions in a continuous casting product and flow control of a spout by a stopper. <P>SOLUTION: The stopper 2 is formed to be a circular type in cross section, and a throughhole 11 which penetrates an axial core portion of the stopper 2 is provided along a flowing direction of molten metal in a trough 6, by which the molten metal passes through the throughhole 11 and flows. In a region α at a downstream side of the stopper 2 of a diameter 2r, flow of a direction which is parallel to the flowing direction of the molten metal is forcedly generated along the flowing direction of the molten metal, by which generation of a harmful vortex is suppressed, and invasion of an oxide film on a molten metal surface is prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a continuous casting apparatus and a continuous casting method for controlling a molten metal surface in continuous casting of a non-ferrous metal, particularly aluminum, particularly a stopper / float control when pouring from a trough to a mold.

  As a casting method for aluminum plate materials or aluminum alloy plates used for thin plate materials for automobiles and home appliances, a continuous casting device was used to continuously draw the molten metal injected into the melting furnace or holding furnace to the lower part by a dummy bar through a trough. Continuous casting is performed.

  In this continuous casting, as a method of controlling the flow rate when the molten metal is introduced from the trough into the mold as the ingot descends, as shown in FIG. 16, with the control method (FIG. 16 (a)) using the spout 100 / float 101, There is a control method (FIG. 16 (b)) using the stopper 102 and the float 103 (Light Metal Basic Technology Course Fifth Edition (Japan Society of Light Metals: Issued in August 2006, published in FIG. 12)).

  The control method using the stopper 102 and the float 103 has a quality problem that the molten metal poured into the float part is likely to entrain oxide when it gets into the float part. It was necessary to make it smaller. For this reason, when manufacturing a large slab, the control method by the stopper 102 and the float 103 is mainly used.

In the control method using the stopper 102 and the float 103, the molten metal amount is controlled by adjusting the opening degree by the stopper 102 processed into a columnar shape in a state where the molten metal having a predetermined depth is accumulated in the trough 104.
However, the molten metal in the trough 104 flows even when the molten metal of a predetermined depth is accumulated, and therefore, the molten liquid downstream of the stopper 102 has a flow when the flowing liquid is blocked by a cylindrical object. In addition, Karman vortices generated on the downstream side are generated, and the Karman vortices sometimes involve oxides on the surface of the melt. The oxides involved were scattered inside the ingot and became inclusions in the final product, causing deterioration of product characteristics.

  The oxide involved at this time is in the form of a film, and its size is 5 to 20 mm, which is almost the same as the size of the Karman vortex. Moreover, the inclusions entrained are floating in the molten metal, and the size is approximately 10 μm to 1000 μm.

  This Karman vortex is normally generated on the downstream side in the flow direction when the molten metal surface depth is small, and when the Karman vortex reaches the spout, an oxide film on the surface of the molten metal is engulfed as an inclusion. Therefore, as a countermeasure, it is necessary to prevent the generation of Karman vortex and the entrainment of the oxide film due to this by maintaining a predetermined amount of the molten metal surface depth.

  However, even if it is easy to maintain a predetermined amount of the molten metal surface depth in the steady state, it is possible for the operator to maintain the molten metal surface depth in the unsteady state (at the start or at the end) at the predetermined depth. It was necessary to be ready to operate with constant monitoring, and the load on the workers was heavy.

  In Patent Document 1, a stopper body that opens and closes a molten metal outlet formed on the bottom surface of the trough by a vertical movement is rotatably supported, and a stirring blade is attached to the downstream portion, and the molten metal follows the stopper body by the rotation of the stopper body. There has been disclosed a long stopper for continuous casting that can generate an upward flow and prevent inclusions on the surface of the Dandy surface due to the upward flow around the long stopper even when the height of the surface of the tundish decreases.

JP 2002-11565 A

However, the countermeasure of Patent Document 1 is to stir the molten metal. Therefore, the continuous casting apparatus is complicated and the cost is inevitably increased. Also, the dynamic energy is added to the molten metal by stirring, so that the activity of the molten metal can be controlled. There is a problem that it increases.
Therefore, a means for preventing Karman vortices generated on the downstream side when the stopper is blocked by a cylindrical object by making it an integral streamline is also conceivable. However, it is expensive to process the stopper shape into a streamline shape, and there are drawbacks such as easy breakage in handling.

  The present invention has been made in view of the above-described problems in the prior art, and an object of the present invention is to provide a continuous casting apparatus and a continuous casting method capable of achieving both reduction of inclusions in a continuously cast product and control of a stopper / spout flow rate.

  The inventors of the present invention have studied in detail the occurrence of the Karman vortex and the state of entrainment of the cylindrical stopper on the downstream side of the molten metal flow direction in the trough, and at least on the downstream side of the molten metal flow direction in the trough It is clear that by forming a molten metal flow in a direction parallel to the flow direction of the steel, generation of Karman vortices can be suppressed and entrainment of various nonmetallic inclusions floating in the oxide film on the molten metal surface and in the molten metal can be suppressed. I made it.

That is, the continuous casting apparatus of the present invention includes a trough to which molten metal from a ladle, a melting furnace or a holding furnace is supplied, a spout having a molten metal injection hole disposed between the trough and the mold, and a molten metal injection hole. And a stopper for adjusting the amount of molten metal passing through the spout by attaching and detaching to the opening, and having a through hole passing through the axial position of the stopper along the molten metal flow direction in the trough. Features.

Further, the continuous casting method of the present invention supplies molten metal from a ladle, a melting furnace or a holding furnace to a trough, and attaches / detaches a stopper to a molten metal injection hole of a spout disposed between the trough and the mold, thereby passing the spout through molten metal. In the continuous casting method in which the amount is adjusted, the stopper is provided with a through-hole passing through the axial center position of the stopper along the molten metal flow direction in the trough.

  The width of the through hole is preferably 5 mm or more.

  It is desirable that the lower end of the through hole is 50 to 100 mm from the trough bottom surface, and the upper end is 200 mm or more from the trough bottom surface.

  The molten metal may be aluminum or an aluminum alloy.

[Action]
As shown in FIG. 1, the Karman vortex coupled with the negative pressure effect due to the high-speed molten metal flowing into the spout 10 triggered by the generation of the Karman vortex 3 behind the stopper 2 perpendicular to the fluid flow in the fluid flow 1. The yarn 4 is generated, and the molten oxide film and inclusions present on the trough surface 1a are drawn into the spout 10 and the inclusions are mixed into the final product.

According to the results of the examination by the inventors, the occurrence point of harmful Karman vortex 3 that entraps various non-metallic inclusions floating in the molten oxide surface or molten metal is the molten metal flow velocity, the molten metal surface height and the stopper. 2 is most prominent in the region α shown in FIG. 2, and this region α is defined by the following equations (i) and (ii) on the downstream side of the stopper 2 when the diameter of the stopper 2 is 2r. It was an area.
(I) Distance L from the center of the stopper 2 in the molten metal flow direction
r <L ≦ 2r
(Ii) The distance w from the center of the stopper 2 in the direction perpendicular to the molten metal flow direction
−0.5r ≦ w ≦ 0.5r

According to the continuous casting apparatus and the continuous casting method of the present invention, an appropriate flow of the molten metal flow can be formed on the downstream side of the stopper by the through hole provided so as to penetrate the position passing through the axial core portion of the stopper, Even if the vortex is generated, a harmful vortex that involves the oxide film on the surface of the molten metal is not reached, and the Karman vortex reaches the spout and the oxide film on the surface of the molten metal can be prevented from being involved as an inclusion.
Therefore, according to the continuous casting apparatus and the continuous casting method of the present invention, not only the steady state in which inclusion inclusion is suppressed by setting the molten metal surface depth to a predetermined depth, but also the flow direction when the molten metal surface depth is small. Karman vortex reaches the spout and the oxide film on the surface of the melt as inclusions even in the unsteady state such as casting start and end when casting surface depth is less than 150mm where Karman vortex is significantly generated downstream of Involvement can be prevented.

  According to the continuous casting apparatus and the continuous casting method of the present invention, the entrainment of the oxide film can be suppressed, so that the ingot quality is improved and the product quality after processing is also improved.

Hereinafter, the best mode for carrying out the continuous casting apparatus of the present invention will be described in detail.
As shown in FIG. 3, in the continuous casting apparatus 5 of the present invention, the molten metal is first supplied to the trough 6 from a ladle (not shown), a melting furnace or a holding furnace.

  Next, the molten metal contacting the water-cooled mold 7 immediately below the trough 6 at the exit of the trough 6 is rapidly cooled and solidified. Is continuously drawn through the mold 7 while solidifying. A spout 10 having an injection hole 9 is disposed between the trough 6 and the mold 7, and the amount of molten metal passing through the spout 10 is adjusted by the stopper 2.

  In the continuous casting apparatus 5 according to this embodiment, the stopper 2 has a circular cross section, and a through hole 11 is provided that passes through the position of the stopper 2 passing through the stopper 2 axial core portion along the molten metal flow direction. Thus, the molten metal flow is caused to flow through the through-hole 11, and the flow in the direction parallel to the molten metal flow direction is forced along the molten metal flow direction in the region α on the downstream side of the stopper 2 having a diameter of 2r. By making it, the generation of harmful vortices is suppressed and the oxide film on the surface of the molten metal is prevented from being involved.

  When the size of the through-hole 11 is small, it becomes easy to entrain the oxide film due to the adhesion or blockage of the oxide film in the through-hole 11, the pressure loss when passing through the through-hole 11 is increased, and the melt flow rate is reduced, Since the vortex is not eliminated, the width of the through hole 11 is preferably 5 mm or more, more preferably 10 mm or more, and further preferably 15 mm or more. On the other hand, if the through hole 11 is too large, the substantial strength of the stopper 2 is reduced, and the stopper 2 is easily damaged during handling. Therefore, the width of the through hole 11 is 50% or less, more preferably 40% or less with respect to the stopper 2 diameter. good.

Although there is no restriction | limiting in particular as a shape of the through-hole 11, You may open the through-hole 11 continuously in a molten metal depth direction with a circular drill, and may process an inner surface into a rectangle or an ellipse after that.

FIG. 4 shows an appropriate position of the through hole 11, the through hole 11 a shows a mode in which a space of 50 mm is provided between the lower end and the bottom surface 6 a of the trough 6, and the through hole 11 b has the lower end and the bottom surface of the trough 6. 6a shows a mode in which a distance of 50 to 200 mm is provided, and the through hole 11c shows a mode in which a 200 mm gap is provided between the lower end of the trough 6 and the bottom surface 6a of the trough 6.

When the molten metal surface height is not sufficiently high, the through-hole 11 needs to be provided to reach a height position corresponding to the molten metal surface position in the trough 6. However, at a position exceeding 200 mm from the bottom surface 6a of the trough 6, the molten metal surface height is sufficiently high so that no oxide film or inclusions are involved. Therefore, as shown in FIG. 4, the through hole 11 in the stopper 2 does not necessarily have to reach a height position corresponding to the molten metal surface position. Further, when the through hole 11 is provided so as to reach a position close to the tip of the stopper 2, an oxide film and inclusions can be easily caught through the through hole 11, and the reverse effect is obtained.

From the above, the position of the through hole 11 is preferably located in the range of 50 to 200 mm as the height position measured from the bottom surface 6a of the trough 6, and more preferably in the range of 100 to 200 mm.
In addition, when the through hole 11 is provided at a position away from the stopper 2 axis, non-uniform flow occurs on the downstream side of the stopper 2 and a desired effect cannot be obtained.

  The molten metal to be cast is particularly preferably aluminum or an aluminum alloy, but may be other metals or alloys such as steel.

FIG. 5 schematically shows an aspect of the through hole 11 included in the stopper 2 in the continuous casting apparatus according to the embodiment of the present invention.
In this embodiment, the through hole 11 of the stopper 2 has a rectangular shape as viewed from the side of the stopper 2, and the through position of the through hole 11 in the stopper 2 is the center of the stopper 2 along the molten metal flow in the trough 6. It is considered as a passing position.

FIG. 6 shows an aspect of the through hole 11 of the stopper 2 in the continuous casting apparatus according to another embodiment of the present invention.
In this embodiment, the through hole 11 of the stopper 2 has a true circular shape as viewed from the side of the stopper 2, and the through position of the through hole 11 in the stopper 2 is the axial center of the stopper 2 along the molten metal flow in the trough 6. It is a position that passes through.

FIG. 7 shows an aspect of the through hole 11 provided in the stopper 2 in the continuous casting apparatus according to still another embodiment of the present invention.
In this embodiment, the through hole 11 of the stopper 2 has an elliptical shape as viewed from the side of the stopper 2, and the through position of the through hole 11 in the stopper 2 is the axial center of the stopper 2 along the molten metal flow in the trough 6. It is a position that passes through.

FIG. 8 shows an aspect of the through hole 11 of the stopper 2 in the continuous casting apparatus according to another embodiment of the present invention.
In this embodiment, the through hole 11 of the stopper 2 has a substantially diamond shape as viewed from the side of the stopper 2, and the through position of the through hole 11 in the stopper 2 is the axial center of the stopper 2 along the molten metal flow in the trough 6. It is a position that passes through.

FIG. 9 shows an aspect of the through hole 11 provided in the stopper 2 in the continuous casting apparatus according to still another embodiment of the present invention.
In this embodiment, the through hole 11 of the stopper 2 has a trapezoidal shape viewed from the side of the stopper 2, and the through position of the through hole 11 in the stopper 2 is the axis of the stopper 2 along the molten metal flow in the trough 6. It is considered as a passing position.

FIG. 10 shows an aspect of the through hole 11 provided in the stopper 2 in the continuous casting apparatus according to still another embodiment of the present invention.
In this embodiment, the stopper 2 has a pair of through-holes 11 arranged in a row. The shape of each through-hole 11 viewed from the side surface of the stopper 2 is circular, and the through-position of each through-hole 11 in the stopper 2 is the trough 6. The position passes through the axis of the stopper 2 along the molten metal flow.

FIG. 11 shows a continuous casting apparatus according to still another embodiment of the present invention.
In each of the embodiments described above, the flow rate control at the inlet of the spout 10 was performed. In this embodiment, the through hole provided in the stopper 2 downstream of the stopper 2 in the flow rate control at the outlet of the spout 10. Eleven aspects are shown.
Also in this embodiment, the through-hole 11 passing through the position passing through the stopper 2 axial core portion in the trough 6 is set to an appropriate position corresponding to the Karman vortex generation location on the downstream side of the stopper 2 in the same manner as each of the above-described embodiments. By disposing, the generation of Karman vortex (Kalman flow) is suppressed around the stopper 2, and the molten oxide film and inclusions existing on the molten metal surface of the trough 6 are prevented from being drawn into the spout 10. Appropriate stopper 2 and spout flow rate control is performed.

Example Using a continuous casting apparatus according to the embodiment of the present invention shown in FIG. 5, an ingot (400 mm thickness × 1600 mm width) of 5182 alloy was cast by a continuous casting machine as an example of the continuous casting method of the present invention. At this time, the hot water surface depth in the trough 6 was 130 mm. After casting, the bottom 300 mm and the head 200 mm are cut, then the long side surface is shaved 10 mm on one side, and after soaking, cold rolling is performed after hot rolling to obtain a 1.6 mm thick plate. . A 30 cm × 30 cm sample was cut from the coil plate, and heated at 450 ° C. × 1 H in a steam atmosphere to investigate the number of blister defects.
In addition, the other conditions were the same as in the example, and the continuous casting method of each comparative example shown below was performed, and the number of defects was investigated in the same manner as in the example. Table 1 shows the results of the above examples and comparative examples.

FIG. 12 shows Comparative Example 1 and was cast without forming the through hole 11 in the stopper 2.
FIG. 13 shows Comparative Example 2 in which the through-hole 11 provided in the circular stopper 2 has a quadrangular width of 3 mm, and the lower end to the upper end of the through-hole 11 position measured from the bottom of the trough are 100 to 200 (mm).
FIG. 14 shows Comparative Example 3 in which the circular stopper 2 has a through-hole 11 having a rectangular shape with a width of 20 mm, and the lower end to the upper end of the through-hole 11 position measured from the bottom of the trough are 20 to 50 (mm).
FIG. 15 shows Comparative Example 4 in which the circular stopper 2 has a through-hole 11 having a square shape with a width of 20 mm, and the bottom-to-top end of the through-hole 11 measured from the bottom of the trough is 100 to 200 (mm). Casting was performed along the molten metal flow in a position opposite to the axis of the stopper 2.

As shown in Table 1, in Examples 1 to 3, the number of inclusions (the number of blister defects / 900 cm ² ) is 0, and in Example 4, the number of inclusions is 2, whereas any of the comparative examples In addition, the number of inclusions (the number of blister defects / 900 cm ² ) reaches about 20, and the number of inclusions reaches 11 even in the lowest comparative example 2. According to the continuous casting method of the present invention, the inclusion of the oxide film can be suppressed. It is recognized that the ingot quality is remarkably improved.

(A) Explanatory drawing which shows the Kalman flow around the stopper 2 observed in the water model experiment. (B) It is explanatory drawing which shows the Karman vortex grown from the Karman flow. Explanatory drawing which shows the generation | occurrence | production area | region of harmful Karman vortex which entrains the various nonmetallic inclusions floating in the molten oxide surface and molten metal surface. It is a schematic diagram of the continuous casting apparatus concerning embodiment of this invention. It is a partial expansion schematic diagram of the continuous casting apparatus of this invention. It is a partial expansion schematic diagram of the continuous casting apparatus concerning other embodiment of this invention. It is the elements on larger scale of the continuous casting apparatus concerning other embodiment of this invention. It is the elements on larger scale of the continuous casting apparatus concerning other embodiment of this invention. It is the elements on larger scale of the continuous casting apparatus concerning other embodiment of this invention. It is the elements on larger scale of the continuous casting apparatus concerning other embodiment of this invention. It is the elements on larger scale of the continuous casting apparatus concerning other embodiment of this invention. It is the elements on larger scale of the continuous casting apparatus concerning other embodiment of this invention. It is the partial expansion schematic diagram of the continuous casting apparatus used for the continuous casting performed as the comparative example of this invention. It is the elements on larger scale of the continuous casting apparatus used for the continuous casting performed as another comparative example of this invention. It is the elements on larger scale of the continuous casting apparatus used for the continuous casting performed as another comparative example of this invention. It is the elements on larger scale of the continuous casting apparatus used for the continuous casting performed as another comparative example of this invention. Regarding a molten metal flow rate control method in continuous casting using a general continuous casting apparatus, (a) shows a control method using a spout / float, and (b) shows a control method using a stopper / float.

Explanation of symbols

2 ... stopper, 6 ... trough, 10 ... spout, 9 ... injection hole, 11 ... through hole.

Claims (5)

A trough to which molten metal from a ladle, a melting furnace or a holding furnace is supplied, a spout having a molten metal injection hole disposed between the trough and the mold, and an opening / closing of the molten metal injection hole is closed and opened. A continuous casting apparatus comprising: a stopper that adjusts the amount of molten metal passing through the spout in the process, and the stopper includes a through hole that passes through the axial position of the stopper along the molten metal flow direction in the trough. In the process of supplying molten metal from a ladle, melting furnace or holding furnace to the trough, and closing / opening the opening by attaching a stopper to the opening of the molten metal injection hole of the spout arranged between the trough and the mold. In the continuous casting method for adjusting the amount of molten metal passing, a continuous hole passing through the axial position of the stopper along the direction of molten metal flow in the trough is provided in the stopper. The continuous casting method according to claim 2, wherein a width of the through hole is 5 mm or more. The continuous casting method according to claim 2 or 3, wherein a lower end of the through hole is 50 to 100 mm from a trough bottom surface, and an upper end is 200 mm or more from the trough bottom surface. The continuous casting method according to any one of claims 2 to 4, wherein the molten metal is aluminum or an aluminum alloy.

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