JP2014104468A - Draw-up continuous casting apparatus and draw-up type continuous casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a draw-up type continuous casting apparatus and a draw-up type continuous casting method which achieve a higher casting speed and excellent productivity.SOLUTION: A draw-up type continuous casting apparatus comprises a holding furnace 101 holding a molten metal M1, a shape regulation member 102 arranged in the vicinity of the molten metal surface of the molten metal M1 held in the holding furnace 101 and regulating the shape of the cross section of a casting to be casted when the molten metal passes, a cooling part 106 cooling the molten metal M2 passing through the shape regulation member 102 to solidify and a nozzle 107 supplying a high-oxygen gas having an oxygen concentration higher than that of the air to the molten metal M2 passing through the shape regulation member 102.

Description

  The present invention relates to an up-drawing continuous casting apparatus and an up-drawing continuous casting method.

  Patent Document 1 proposes a free casting method as an innovative pull-up type continuous casting method that does not require a mold. As shown in Patent Document 1, after the starter is immersed in the surface of the molten metal (molten metal) (that is, the molten metal surface), when the starter is pulled up, the molten metal follows the starter by the surface film or surface tension of the molten metal. Derived. Here, a casting having a desired cross-sectional shape can be continuously cast by deriving and cooling the molten metal through a shape determining member installed in the vicinity of the molten metal surface.

In a normal continuous casting method, the shape in the longitudinal direction is defined along with the cross-sectional shape by the mold. In particular, in the continuous casting method, since the solidified metal (that is, the casting) needs to pass through the mold, the cast casting has a shape extending linearly in the longitudinal direction.
On the other hand, the shape defining member in the free casting method defines only the cross-sectional shape of the casting, and does not define the shape in the longitudinal direction. And since a shape prescription | regulation member can move to the direction (namely, horizontal direction) parallel to a molten metal surface, the casting in which the shape of a longitudinal direction is various is obtained. For example, Patent Document 1 discloses a hollow casting (that is, a pipe) that is formed in a zigzag shape or a spiral shape instead of being linear in the longitudinal direction.

JP 2012-61518 A

The inventor has found the following problems.
In the free casting method described in Patent Document 1, when the casting speed is increased, the dimensional variation of the casting increases. Therefore, there was a problem that the casting speed could not be increased and the productivity was inferior.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pulling-up-type continuous casting apparatus and pull-up-type continuous casting method which are faster in casting speed and excellent in productivity.

The up-drawing continuous casting apparatus according to one aspect of the present invention is as follows.
A shape determining member that is installed in the vicinity of the molten metal surface of the molten metal held in the holding furnace and that defines the cross-sectional shape of a casting to be cast by passing the molten metal,
A cooling unit for cooling and solidifying the molten metal that has passed through the shape determining member;
A nozzle for supplying a high oxygen gas having an oxygen concentration higher than that of air to the molten metal that has passed through the shape determining member. With such a configuration, the casting speed can be increased and the productivity can be improved.

It is preferable that a plurality of nozzles are provided around the molten metal that has passed through the shape determining member. Thereby, the casting speed can be increased more reliably.
Moreover, it is preferable that the said nozzle is provided with the on-off valve for stopping supply of the said high oxygen gas.

The up-drawing continuous casting method according to one aspect of the present invention is as follows.
Deriving the molten metal held in the holding furnace from the surface of the molten metal with a starter, and pulling up through a shape defining member that defines the cross-sectional shape of the casting to be cast;
Cooling and solidifying the molten metal that has been pulled up through the shape determining member,
A high oxygen gas having a higher oxygen concentration than air is supplied to the molten metal that has passed through the shape determining member. With such a configuration, the casting speed can be increased and the productivity can be improved.

  When the casting is finished, it is preferable that after the supply of the high oxygen gas is stopped, the molten metal that has passed through the shape defining member is separated from the casting. Alternatively, when the casting is finished, after switching from the high oxygen gas to the supply of the non-oxidizing gas, it is preferable to separate the molten metal that has passed through the shape determining member and the casting.

  According to the present invention, it is possible to provide a pulling-up-type continuous casting apparatus and a pulling-up-type continuous casting method that are faster in casting speed and excellent in productivity.

1 is a cross-sectional view of a free casting apparatus according to Embodiment 1. FIG. It is a top view of the internal shape defining member 102a and the external shape defining member 102b. 5 is a plan view showing an example of a planar arrangement relationship between an external cooling gas nozzle 106 and an external oxidizing gas nozzle 107. FIG. It is a graph which compares and shows the dispersion | variation in the thickness in an Example and a comparative example.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment. In addition, for clarity of explanation, the following description and drawings are simplified as appropriate.

(Embodiment 1)
First, with reference to FIG. 1, the free casting apparatus (pull-up type continuous casting apparatus) according to Embodiment 1 will be described. 1 is a cross-sectional view of a free casting apparatus according to Embodiment 1. FIG. As shown in FIG. 1, a free casting apparatus according to Embodiment 1 includes a molten metal holding furnace 101, an internal shape defining member 102a, an external shape defining member 102b, a double gas nozzle 103, a support rod 104, an actuator 105, and an external cooling gas nozzle. 106, an external oxidizing gas nozzle 107 is provided. Here, the double gas nozzle 103 includes an internal cooling gas nozzle 103a and an internal oxidizing gas nozzle 103b.

  The molten metal holding furnace 101 accommodates a molten metal M1 such as aluminum or an alloy thereof and holds it at a predetermined temperature. In the example of FIG. 1, since the molten metal is not replenished to the molten metal holding furnace 101 during casting, the surface of the molten metal M1 (that is, the molten metal surface) decreases as the casting progresses. On the other hand, the molten metal may be replenished to the molten metal holding furnace 101 at any time during casting to keep the molten metal surface constant. As a matter of course, the molten metal M1 may be another metal or alloy other than aluminum.

  The internal shape defining member 102a and the external shape defining member 102b are made of, for example, ceramics or stainless steel, and are disposed in the vicinity of the molten metal surface. In the example of FIG. 1, the inner shape defining member 102a and the outer shape defining member 102b are arranged so as to contact the molten metal surface. The internal shape defining member 102a defines the internal shape of the casting M3 to be cast, and the external shape defining member 102b defines the external shape of the cast M3 to be cast. Further, the external shape determining member 102b prevents the oxide film formed on the surface of the molten metal M1 and foreign matters floating on the surface of the molten metal M1 from being mixed into the casting M3.

  The casting M3 shown in FIG. 1 is a hollow casting (that is, a pipe) having a horizontal cross section (hereinafter referred to as a transverse section) having a tubular shape. Specifically, the inner shape defining member 102a defines the inner diameter of the cross section of the casting M3, and the outer shape defining member 102b defines the outer diameter of the cross section of the casting M3.

  FIG. 2 is a plan view of the inner shape defining member 102a and the outer shape defining member 102b. Here, the cross-sectional views of the internal shape determining member 102a and the external shape determining member 102b in FIG. 1 correspond to the II cross-sectional view in FIG. As shown in FIG. 2, the external shape defining member 102b has, for example, a rectangular planar shape, and has a circular opening at the center. The internal shape defining member 102a has a circular planar shape and is disposed at the center of the opening of the external shape defining member 102b. A gap between the inner shape determining member 102a and the outer shape determining member 102b becomes a molten metal passage portion 102c through which the molten metal passes. As described above, the shape defining member 102 includes the inner shape defining member 102a, the external shape defining member 102b, and the molten metal passage portion 102c. A double gas nozzle 103 is disposed at the center of the internal shape defining member 102a.

  As shown in FIG. 1, the molten metal M <b> 1 is pulled up following the casting M <b> 3 by its surface film and surface tension, and passes through the molten metal passage portion 102 c of the shape defining member 102. That is, when the molten metal M1 passes through the molten metal passage portion 103 of the shape defining member 102, an external force is applied to the molten metal M1 from the shape defining member 102 (the internal shape defining member 102a and the external shape defining member 102b), and the casting M3 A cross-sectional shape is defined. Here, the molten metal pulled up from the molten metal surface following the casting M3 by the surface film or surface tension of the molten metal is referred to as a retained molten metal M2. Further, the interface between the casting M3 and the retained molten metal M2 is a solidification interface.

  The double gas nozzle 103 is connected to the central portion of the internal shape defining member 102a and supports the internal shape defining member 102a. Here, the small-diameter internal cooling gas nozzle 103a provided inside the double gas nozzle 103 sprays a cooling gas (air, nitrogen, argon, etc.) from the center of the casting M3 to the casting M3, and cools the casting M3 from the inside. ing.

  On the other hand, a large-diameter internal oxidizing gas nozzle 103b provided outside the double gas nozzle 103 introduces a gas having a higher oxygen concentration than air (hereinafter also simply referred to as “high oxygen gas”) at a low flow rate. Thereby, formation of the oxide film on the surface of the retained molten metal M2 inside the casting M3 is promoted, and the force for retaining the retained molten metal M2 is increased. Therefore, the dimensional accuracy of the casting M3 when the casting speed is increased is improved. That is, the casting speed can be increased and productivity is improved. The high oxygen gas is not intended for cooling.

  Further, it is preferable to stop the supply of the high oxygen gas at the end of casting because the formation of an oxide film on the surface of the retained molten metal M2 is not promoted, and the retained molten metal M2 and the casting M3 are easily separated. An open / close valve may be provided in the internal oxidizing gas nozzle 103b. Alternatively, when the high oxygen gas is switched to a non-oxidizing gas (for example, nitrogen, argon, etc.) immediately before the end of casting, the formation of the oxide film on the surface of the retained molten metal M2 is suppressed, and the retained molten metal M2 and the casting M3 are Furthermore, it becomes easy to separate.

  The support rod 104 supports the external shape defining member 102b. The positional relationship between the internal shape defining member 102a and the external shape defining member 102b can be maintained by the double gas nozzle 103 and the support rod 104.

  A double gas nozzle 103 and a support rod 104 are connected to the actuator 105. The actuator 105 allows the double gas nozzle 103 and the support rod 104 to move in the vertical direction (vertical direction) and the horizontal direction while maintaining the positional relationship between the internal shape defining member 102a and the external shape defining member 102b. With such a configuration, the inner shape defining member 102a and the outer shape defining member 102b can be moved downward as the molten metal surface is lowered due to the progress of casting. Further, since the inner shape defining member 102a and the outer shape defining member 102b can be moved in the horizontal direction, the shape of the casting M3 in the longitudinal direction can be freely changed.

  The external cooling gas nozzle (external cooling part) 106 is for blowing and cooling cooling gas (air, nitrogen, argon, etc.) on the casting M3 from the outside of the casting M3. While the casting M3 is pulled up by a pulling machine (not shown) connected to the starter ST and the casting M3 is cooled by the cooling gas, the retained molten metal M2 near the solidification interface is sequentially solidified to form the casting M3. .

  The external oxidizing gas nozzle 107 introduces high oxygen gas at a low flow rate. Thereby, formation of the oxide film on the surface of the retained molten metal M2 outside the casting M3 is promoted, and the force for retaining the retained molten metal M2 is increased. Therefore, the dimensional accuracy of the casting M3 when the casting speed is increased is improved. That is, the casting speed can be increased and productivity is improved. The high oxygen gas is not intended for cooling.

  Further, it is preferable to stop the supply of the high oxygen gas immediately before the end of casting because the formation of an oxide film on the surface of the retained molten metal M2 is not promoted, and the retained molten metal M2 and the casting M3 are easily separated. An open / close valve may be provided in the external oxidizing gas nozzle 107. Alternatively, when the high oxygen gas is switched to a non-oxidizing gas (for example, nitrogen, argon, etc.) immediately before the end of casting, the formation of the oxide film on the surface of the retained molten metal M2 is suppressed, and the retained molten metal M2 and the casting M3 are Furthermore, it becomes easy to separate.

  FIG. 3 is a plan view showing an example of a planar arrangement relationship between the external cooling gas nozzle 106 and the external oxidizing gas nozzle 107. In the example of FIG. 3, eight external cooling gas nozzles 106 are arranged so as to surround the periphery of the casting M3 radially at 45 ° intervals. Further, the eight external oxidizing gas nozzles 107 are also arranged so as to surround the casting M3 radially at intervals of 45 °. As a whole, eight external cooling gas nozzles 106 and eight external oxidizing gas nozzles 107 are alternately arranged radially at substantially equal intervals (22.5 ° intervals).

Next, the free casting method according to Embodiment 1 will be described with reference to FIG.
First, the starter ST is lowered, and the tip of the starter ST is immersed in the molten metal M1 through the molten metal passage portion 102c between the internal shape defining member 102a and the external shape defining member 102b. It is preferable to use a starter ST having the same cross-sectional shape as the casting M3 and extending linearly in the longitudinal direction.

  Next, the starter ST is started to be pulled up at a predetermined speed. Here, even if the starter ST is separated from the molten metal surface, the retained molten metal M2 pulled up from the molten metal surface following the starter ST is formed by the surface film or surface tension. As shown in FIG. 1, the retained molten metal M2 is formed in the molten metal passage portion 102c between the inner shape defining member 102a and the outer shape defining member 102b. That is, the shape is imparted to the retained molten metal M2 by the inner shape defining member 102a and the outer shape defining member 102b. In the free casting method according to the first embodiment, high oxygen gas is introduced at a low flow rate by the internal oxidizing gas nozzle 103b and the external oxidizing gas nozzle 107. Therefore, the formation of an oxide film on the surface of the retained molten metal M2 is promoted, and the force for retaining the retained molten metal M2 is increased.

  Next, since the starter ST is cooled by the cooling gas blown from the internal cooling gas nozzle 103a and the external cooling gas nozzle 106, the retained molten metal M2 is solidified in order from the upper side to the lower side, and the casting M3 grows. Go. In this way, the casting M3 can be continuously cast. Moreover, a bending part can be provided to the casting M3 by moving the internal shape defining member 102a and the external shape defining member 102b in the horizontal direction. Instead of moving the inner shape defining member 102a and the outer shape defining member 102b in the horizontal direction, the starter ST fixed to the pulling machine may be moved in the horizontal direction. Alternatively, the inner shape defining member 102a, the outer shape defining member 102b, and the starter ST may be moved in opposite directions within the horizontal plane.

(Example)
Next, specific examples according to the first embodiment will be described.
A pipe made of aluminum alloy A6063 having a design size of an outer diameter of 30 mmφ, an inner diameter of 24 mmφ, and a thickness of 3 mm was cast using the free casting apparatus shown in FIG. The molten metal temperature was 705 ± 5 ° C. The cooling gas (air) flow rate in the internal cooling gas nozzle 103a was 2 L / min, and the cooling gas flow rates in the eight external cooling gas nozzles 106 were 8 L / min in total. The oxygen gas flow rate in the internal oxidizing gas nozzle 103b was 0.5 L / min, and the oxygen gas flow rates in the eight external oxidizing gas nozzles 107 were 0.5 L / min in total. The height H1 of the front end portion of the external cooling gas nozzle 106 from the external shape determining member 102b was 30 mm, and the distance L1 from the casting M3 was 10 mm. The height H2 = 5 mm from the external shape determining member 102b at the tip of the external oxidizing gas nozzle 107 and the distance L2 = 20 mm from the retained molten metal M2. Two pulling speeds, 50 mm / min and 100 mm / min, were used. For 200 mm long pipes cast at two different pulling speeds, the variation in thickness at 4 locations in the circumferential direction × 20 locations in the longitudinal direction = 80 locations was investigated.

(Comparative example)
The pipes cast under the same conditions as in the example except that the oxygen gas was not passed through the internal oxidizing gas nozzle 103b and the eight external oxidizing gas nozzles 107 were examined for thickness variations.

  FIG. 4 is a graph showing a comparison of thickness variations in the example and the comparative example. As shown in FIG. 4, the variation in pipe thickness was smaller in the example than in the comparative example at both pulling speeds of 50 mm / min and 100 mm / min. In particular, when the pulling speed is 100 mm / min, the pipe thickness variation in the comparative example is large (particularly thinning), whereas in the example, the pulling speed is 50 mm / min in the comparative example. Values and variability. Thus, by setting the surroundings of the retained molten metal M2 as an oxidizing atmosphere, the casting speed can be increased and the productivity can be improved.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.

101 Molten metal holding furnace 102 Shape defining member 102a Internal shape defining member 102b External shape defining member 102c Molten metal passage 103 Double gas nozzle 103a Internal cooling gas nozzle 103b Internal oxidation gas nozzle 104 Support rod 105 Actuator 106 External cooling gas nozzle 107 External oxidation gas nozzle M1 Molten metal M2 Holding molten metal M3 casting ST starter

Claims (6)

A holding furnace for holding molten metal;
A shape determining member that is installed in the vicinity of the molten metal surface of the molten metal held in the holding furnace and that defines the cross-sectional shape of a casting to be cast by passing the molten metal,
A cooling unit for cooling and solidifying the molten metal that has passed through the shape determining member;
A pulling-up-type continuous casting apparatus, comprising: a nozzle that supplies high oxygen gas having an oxygen concentration higher than air to the molten metal that has passed through the shape defining member. A plurality of the nozzles are provided around the molten metal that has passed through the shape defining member.
The up-drawing continuous casting apparatus according to claim 1. The nozzle includes an on-off valve for stopping the supply of the high oxygen gas.
The up-drawing continuous casting apparatus according to claim 1 or 2. Deriving the molten metal held in the holding furnace from the surface of the molten metal with a starter, and pulling up through a shape defining member that defines the cross-sectional shape of the casting to be cast;
Cooling and solidifying the molten metal that has been pulled up through the shape determining member,
A pulling-up-type continuous casting method, wherein high oxygen gas having an oxygen concentration higher than air is supplied to the molten metal that has passed through the shape determining member. When ending casting, after the supply of the high oxygen gas is stopped, the molten metal that has passed through the shape determining member and the casting are separated.
The pulling-up-type continuous casting method according to claim 4. When ending casting, after switching from the high oxygen gas to the supply of non-oxidizing gas, the molten metal that has passed through the shape determining member and the casting are separated,
The pulling-up-type continuous casting method according to claim 4.

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