JP2015027689A - Pull up type continuous casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pull up type continuous casting method excellent in productivity.SOLUTION: The pull up type continuous casting method according to an aspect is configured to pull up a molten metal M1 held in a holding furnace 101 in an acceleration section by using a starter ST. When the starter ST is accelerated to predetermined pull up speed during start of casting, there are provided a first acceleration section for accelerating from a stopped state to first speed by first acceleration, a second acceleration section for accelerating from the first speed to second speed by second acceleration, and a constant speed section for pulling up the starter by the first speed between the first acceleration section and the second acceleration section.

Description

  The present invention relates to a pull-up type 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, a molten gas is indirectly cooled by spraying a cooling gas onto a casting immediately after solidification connected to a starter. Here, it is necessary to advance the casting in a state where the solidification speed (hereinafter referred to as the solidification speed) progressing from top to bottom is substantially balanced with the pulling speed. For example, the cooling capacity for the pulled molten metal remains constant (that is, the solidification rate remains constant), and even if only the pulling speed is increased, the solidification interface rises and the pulled molten metal is broken. That is, when the cooling capacity is determined, an appropriate pulling speed corresponding to the cooling capacity is determined. In order to increase the pulling speed and improve the productivity, it is necessary to increase the cooling capacity described above.

  At the start of casting, acceleration is performed from a stopped state to a desired pulling speed (that is, an appropriate pulling speed commensurate with the above-described cooling capacity). However, if the pulling acceleration is too large, there is a problem that the molten metal pulled up by the starter is broken before the desired pulling speed is reached, and even casting cannot be performed. On the other hand, if the pulling acceleration is reduced in order to prevent the molten metal from being broken during the acceleration, it takes time to reach a desired pulling speed, resulting in poor productivity.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pull-up-type continuous casting method which is excellent in productivity, suppressing the tearing of the molten metal pulled up at the time of acceleration.

The up-drawing continuous casting method according to one aspect of the present invention is as follows.
It is a pulling-up-type continuous casting method for pulling up the molten metal held in the holding furnace using a starter,
When accelerating the starter to a predetermined pulling speed at the start of casting,
A first acceleration section accelerating at a first acceleration from a stopped state to a first speed;
A second acceleration section accelerating at a second acceleration from the first speed to the second speed;
And a constant speed section in which the starter is pulled up at the first speed between the first acceleration section and the second acceleration section.
With such a configuration, it is possible to provide a pulling-up-type continuous casting method that is excellent in productivity while suppressing tearing of the drawn molten metal during acceleration.

  The first acceleration is an acceleration at which the molten metal pulled up by the starter is broken before reaching the predetermined pulling speed when accelerating from a stopped state, and the first acceleration The acceleration of 2 is preferably an acceleration at which the molten metal pulled up by the starter is broken before reaching the predetermined pulling speed when the acceleration is continued from the stop state. Productivity can be increased.

Further, it is preferable that the first acceleration and the second acceleration are equal. In this case, it is particularly preferable that the first acceleration and the second acceleration be the maximum acceleration that can be exhibited by the pulling machine that pulls up the starter.
Further, the starter is moved between the second acceleration section and the third acceleration section, the third acceleration section accelerating at the third acceleration from the second speed to the third speed, and the second acceleration section and the third acceleration section. And a constant speed section that is pulled up at the second speed.

  On the other hand, the second acceleration may be larger than the first acceleration. In this case, it is particularly preferable that the second acceleration is the maximum acceleration that can be exhibited by the pulling machine that pulls up the starter.

  According to the present invention, it is possible to provide a pulling-up-type continuous casting method that is excellent in productivity while suppressing tearing of the drawn molten metal during acceleration.

1 is a schematic cross-sectional view of a free casting apparatus according to Embodiment 1. FIG. 3 is a plan view of a shape defining member 102 according to Embodiment 1. FIG. 3 is a schematic graph showing a method for accelerating the pulling speed according to the first embodiment. 6 is a schematic graph showing a pulling speed acceleration method according to Modification 1 of Embodiment 1. 10 is a schematic graph showing a pulling speed acceleration method according to Modification 2 of Embodiment 1. 6 is a plan view of a shape defining member 102 according to Embodiment 2. FIG. 6 is a side view of a shape defining member 102 according to Embodiment 2. FIG.

  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 schematic cross-sectional view of a free casting apparatus according to Embodiment 1. FIG. As shown in FIG. 1, the free casting apparatus according to Embodiment 1 includes a molten metal holding furnace 101, a shape defining member 102, a support rod 104, an actuator 105, a cooling gas nozzle 106, and a pulling machine 108. The xy plane in FIG. 1 constitutes a horizontal plane, and the z-axis direction is the vertical direction. More specifically, the positive direction of the z axis is vertically upward.

  The molten metal holding furnace 101 accommodates a molten metal M1 such as aluminum or an alloy thereof, and holds the molten metal M at a predetermined temperature having fluidity. 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. Here, when the set temperature of the holding furnace is raised, the position of the solidification interface SIF can be raised, and when the set temperature of the holding furnace is lowered, the position of the solidification interface SIF can be lowered. As a matter of course, the molten metal M1 may be another metal or alloy other than aluminum.

  The shape defining member 102 is made of, for example, ceramics or stainless steel, and is disposed in the vicinity of the molten metal surface. In the example of FIG. 1, the main surface (lower surface) on the lower side of the shape defining member 102 is disposed so as to contact the molten metal surface. The shape defining member 102 defines the cross-sectional shape of the casting M3 to be cast, and 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 entering the casting M3. The casting M3 shown in FIG. 1 is a solid casting in which the shape of a horizontal cross section (hereinafter referred to as a transverse cross section) is a plate shape. Of course, the cross-sectional shape of the casting M3 is not particularly limited. The casting M3 may be a hollow casting such as a round pipe or a square pipe.

FIG. 2 is a plan view of the shape defining member 102 according to the first embodiment. Here, the cross-sectional view of the shape determining member 102 in FIG. 1 corresponds to the II cross-sectional view in FIG. 2. As shown in FIG. 2, the shape defining member 102 has, for example, a rectangular planar shape, and has a rectangular opening portion (a molten metal passage portion 103) having a thickness t <b> 1 × a width w <b> 1 for allowing the molten metal to pass through a central portion. have.
Note that the xyz coordinates in FIG. 2 coincide with those in FIG.

  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 103 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 from the shape defining member 102 to the molten metal M1, and the cross-sectional shape of the casting M3 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 boundary between the casting M3 and the retained molten metal M2 is a solidification interface SIF.

The support rod 104 supports the shape defining member 102.
A support rod 104 is connected to the actuator 105. The shape defining member 102 can be moved in the vertical direction (vertical direction) and the horizontal direction by the actuator 105 via the support rod 104. With such a configuration, the shape determining member 102 can be moved downward as the molten metal surface is lowered due to the progress of casting. Further, since the shape defining member 102 can be moved in the horizontal direction, the shape of the casting M3 in the longitudinal direction can be changed.

  The cooling gas nozzle (cooling unit) 106 is a cooling unit that blows cooling gas (air, nitrogen, argon, etc.) supplied from a cooling gas supply unit (not shown) onto the casting M3 and cools it. Increasing the flow rate of the cooling gas can lower the position of the solidification interface SIF, and decreasing the flow rate of the cooling gas can increase the position of the solidification interface SIF. Although not shown, the cooling gas nozzle (cooling unit) 106 can also move in the horizontal direction and the vertical direction in accordance with the movement of the shape defining member 102.

  While the casting M3 is pulled up by the puller 108 connected to the starter ST and the casting M3 is cooled by the cooling gas, the retained molten metal M2 in the vicinity of the solidification interface SIF is sequentially solidified to form the casting M3. Increasing the pulling speed by the pulling machine 108 can raise the position of the solidification interface SIF, and decreasing the pulling speed can lower the position of the solidification interface SIF.

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 103 of the shape defining member 102.

  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 M <b> 2 is formed in the molten metal passage portion 103 of the shape defining member 102. That is, the shape defining member 102 imparts a shape to the retained molten metal M2.

  Next, since the starter ST is cooled by the cooling gas blown from the 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.

  Here, at the start of casting, the pulling speed is accelerated from the stopped state to a desired pulling speed (that is, an appropriate pulling speed commensurate with the cooling ability of the cooling gas nozzle 106). The free casting method according to Embodiment 1 has one feature in the method of accelerating the pulling speed at the start of casting. Hereinafter, a method for accelerating the pulling speed at the start of casting will be described with reference to FIG.

  FIG. 3 is a schematic graph showing a pulling speed acceleration method according to the first embodiment. The horizontal axis represents time, and the vertical axis represents the pulling speed (mm / s). In FIG. 3, the case where the acceleration is continued at the acceleration a1 is indicated by a one-dot chain line for comparison. In this case, before the maximum pulling speed Vmax, which is an appropriate pulling speed commensurate with the cooling ability of the cooling gas nozzle 106, is reached, the retained molten metal M2 is broken into pieces. Here, the acceleration a1 is, for example, the maximum acceleration that the pulling machine 108 can exhibit. In FIG. 3, when the pulling speed reaches the speed V1, the retained molten metal M2 is broken into pieces.

  Further, in FIG. 3, the case where the acceleration is continued at the acceleration a2 in order to prevent the retained molten metal M2 from being broken is also indicated by a one-dot chain line for comparison. Here, the acceleration a2 is the maximum acceleration that can reach the maximum pull-up speed Vmax without breaking the retained molten metal M2 even if the acceleration is continued from the stopped state. That is, if the acceleration is continued from the stop state at an acceleration larger than the acceleration a2, the retained molten metal M2 is broken before reaching the maximum pulling speed Vmax. On the other hand, if acceleration is continued from the stopped state at an acceleration a2 or less, the retained molten metal M2 can reach the maximum pulling speed Vmax without being broken. As shown in FIG. 3, when the acceleration is continued at the acceleration a2, the time to reach the maximum pulling speed Vmax is time t2, which is inferior in productivity.

  Therefore, in the free casting method according to Embodiment 1, a constant speed operation section is provided between the acceleration operation sections in order to improve productivity while preventing tearing of the retained molten metal M2. Specifically, in FIG. 3, the acceleration operation at the acceleration a1 is switched to the constant speed operation before reaching the speed V1 at which the held molten metal M2 is broken. In FIG. 3, when the pulling speed reaches the speed V11 (<V1), the operation is switched to the constant speed operation. Here, the speed V11 is smaller than the maximum pulling speed Vmax commensurate with the cooling capacity. Therefore, the solidification interface SIF decreases in the constant speed operation section at the speed V11.

  After maintaining the speed V11 for a predetermined period, the operation is switched from the constant speed operation to the acceleration operation at the acceleration a1 again. By providing the constant speed operation section and lowering the solidification interface SIF, it is possible to prevent the retained molten metal M2 from being broken at the speed V1 after the acceleration operation at the acceleration a1 is resumed. The acceleration in the acceleration operation section need not be the same. However, it is preferable from the viewpoint of productivity improvement that the acceleration in any acceleration operation section is larger than the acceleration a2. In other words, the acceleration in the acceleration operation section is such that if the acceleration continues from the stop state at that acceleration, the holding molten metal M2 is accelerated before reaching the maximum pulling speed Vmax, thereby improving productivity. From the viewpoint of

  Further, in the example of FIG. 3, the operation is switched again to the constant speed operation at the speed V12 (> V1). Thereafter, the operation is switched again to the acceleration operation at the acceleration a1, and finally the maximum pulling speed Vmax is reached. That is, the constant speed operation section is provided twice. Here, the number of constant-speed operation sections is preferably as small as possible from the viewpoint of productivity. On the other hand, if the constant speed operation section is only once, the retained molten metal M2 may be broken before the maximum pulling speed Vmax is reached. Thus, in order to prevent the retained molten metal M2 from being broken and to make the pulling speed reach the maximum pulling speed Vmax, the constant speed operation section may be provided a plurality of times.

  Moreover, productivity can be improved, so that the length of each constant speed operation area is short. On the other hand, if the constant speed operation section is too short, the solidification interface SIF is not sufficiently lowered in the constant speed operation section, and when the operation is switched to the acceleration operation, the retained molten metal M2 is easily broken.

  Furthermore, in the free casting method according to the first embodiment, even if acceleration is continued, the retained molten metal M2 is accelerated at an acceleration that is greater than the acceleration a2 at which no tearing occurs. Therefore, as shown in FIG. 3, the time to reach the maximum pulling speed Vmax is time t1 (<t2), which is excellent in productivity.

(Modification 1 of Embodiment 1)
Next, with reference to FIG. 4, the free casting method which concerns on the modification 1 of Embodiment 1 is demonstrated. FIG. 4 is a schematic graph showing a lifting speed acceleration method according to the first modification of the first embodiment. In FIG. 4, the case where acceleration is continued at an acceleration a3 smaller than the acceleration a1 and larger than the acceleration a2 is also indicated by a one-dot chain line for comparison. Even when the acceleration continues at the acceleration a3, the retained molten metal M2 is broken into pieces before reaching the maximum pulling speed Vmax. However, as shown in FIG. 4, when the pulling speed reaches V2, which is higher than the speed V1, the retained molten metal M2 is broken into pieces.

  Therefore, in the free casting method according to the first modification of the first embodiment, the operation is switched to the constant speed operation when the speed V21 that is larger than the speed V1 and smaller than the speed V2 is reached. That is, in the example of FIG. 4, the acceleration is reduced compared to the example of FIG. 3, while the constant speed operation section is only once. Thus, it is preferable to optimize the number of constant speed operation sections according to the acceleration. Moreover, since the retained molten metal M2 is likely to be broken immediately after the start of casting, it is preferable to start accelerating at an acceleration a3 smaller than the acceleration a1.

(Modification 2 of Embodiment 1)
Next, with reference to FIG. 5, the free casting method which concerns on the modification 2 of Embodiment 1 is demonstrated. FIG. 5 is a schematic graph showing a method for accelerating the pulling speed according to the second modification of the first embodiment. In FIG. 4, the accelerations before and after the constant speed operation section are both acceleration a3. On the other hand, in FIG. 5, the acceleration after the constant speed operation section is set to the acceleration a1 which is larger than the acceleration a3 before the constant speed operation section. Thereby, the arrival time t4 to the maximum pulling speed Vmax in Modification 2 is earlier than the arrival time t3 to the maximum pulling speed Vmax in Modification 1. That is, the free casting method according to Modification 2 is superior in productivity to the free casting method according to Modification 1.

  As described above, in the free casting method according to Embodiment 1, the constant speed operation section is provided during the acceleration at the start of casting. Thereby, when accelerating is continued, it is possible to prevent the retained molten metal M2 from being broken while accelerating at an acceleration at which the retained molten metal M2 is broken. Further, the maximum pulling speed Vmax can be reached in a shorter time than in the past, and the productivity is excellent.

(Embodiment 2)
Next, a free casting apparatus according to Embodiment 2 will be described with reference to FIGS. FIG. 6 is a plan view of the shape defining member 102 according to the second embodiment. FIG. 7 is a side view of the shape defining member 102 according to the second embodiment. Note that the xyz coordinates in FIGS. 6 and 7 also coincide with those in FIG.

  Since the shape defining member 102 according to Embodiment 1 shown in FIG. 2 is composed of a single plate, the thickness t1 and the width w1 of the molten metal passage portion 103 are fixed. On the other hand, the shape defining member 102 according to the second embodiment includes four rectangular shape defining plates 102a, 102b, 102c, and 102d as shown in FIG. That is, the shape defining member 102 according to the second embodiment is divided into a plurality of parts. With such a configuration, the thickness t1 and the width w1 of the molten metal passage portion 103 can be changed. Further, the four rectangular shape defining plates 102a, 102b, 102c, and 102d can move in the z-axis direction in synchronization.

  As shown in FIG. 6, the shape defining plates 102 a and 102 b are arranged to face each other in the x-axis direction. Further, as shown in FIG. 7, the shape defining plates 102a and 102b are arranged at the same height in the z-axis direction. The distance between the shape defining plates 102a and 102b defines the width w1 of the molten metal passage portion 103. Since the shape defining plates 102a and 102b can move independently in the x-axis direction, the width w1 can be changed. In order to measure the width w1 of the molten metal passage portion 103, a laser displacement meter S1 may be provided on the shape defining plate 102a and a laser reflecting plate S2 may be provided on the shape defining plate 102b as shown in FIGS. .

Further, as shown in FIG. 6, the shape defining plates 102c and 102d are arranged to face each other in the y-axis direction. Further, the shape defining plates 102c and 102c are arranged at the same height in the z-axis direction. The distance between the shape defining plates 102c and 102d defines the thickness t1 of the molten metal passage portion 103. Since the shape defining plates 102c and 102d are independently movable in the y-axis direction, the thickness t1 can be changed.
The shape defining plates 102a and 102b are disposed so as to contact the upper side of the shape defining plates 102c and 102d.

  Next, the drive mechanism of the shape defining plate 102a will be described with reference to FIGS. As shown in FIGS. 6 and 7, the drive mechanism of the shape defining plate 102a includes slide tables T1, T2, linear guides G11, G12, G21, G22, actuators A1, A2, and rods R1, R2. The shape defining plates 102b, 102c, and 102d also have a drive mechanism similar to the shape defining plate 102a, but are omitted in FIGS.

  As shown in FIGS. 6 and 7, the shape defining plate 102a is placed and fixed on a slide table T1 that can slide in the x-axis direction. The slide table T1 is slidably mounted on a pair of linear guides G11 and G12 extending in parallel with the x-axis direction. The slide table T1 is connected to a rod R1 extending from the actuator A1 in the x-axis direction. With the configuration described above, the shape defining plate 102a can slide in the x-axis direction.

  As shown in FIGS. 6 and 7, the linear guides G11 and G12 and the actuator A1 are mounted and fixed on a slide table T2 that can slide in the z-axis direction. The slide table T2 is slidably placed on a pair of linear guides G21 and G22 extending in parallel with the z-axis direction. The slide table T2 is connected to a rod R2 extending in the z-axis direction from the actuator A2. The linear guides G21 and G22 and the actuator A2 are fixed to a horizontal floor surface or a pedestal (not shown). With the above configuration, the shape defining plate 102a can slide in the z-axis direction. The actuators A1 and A2 can include hydraulic cylinders, air cylinders, motors, and the like.

As described above, in the free casting apparatus according to Embodiment 2, the shape of the molten metal passage portion 103 can be changed. Therefore, the cross-sectional shape of the casting M3 can be changed during casting.
Furthermore, in the acceleration operation section at the start of casting, the shape of the molten metal passage portion 103 may be controlled to be small. By reducing the mass of the retained molten metal M2, the retained molten metal M2 can be further prevented from being broken.

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.
For example, the present invention can be applied to a pulling-up-type continuous casting method that does not use the shape defining member 102 as long as it is a pull-up-type continuous casting method that pulls up the molten metal using the starter ST.

101 Molten metal holding furnace 102 Shape defining member 102a to 102d Shape defining plate 103 Melt passing portion 104 Support rod 105 Actuator 106 Cooling gas nozzle 108 Lifting machine A1, A2 Actuator G11, G12, G21, G22 Linear guide M1 Molten metal M2 Holding molten metal M3 Casting R1, R2 Rod S1 Laser displacement meter S2 Laser reflector SIF Solidification interface ST Starter T1, T2 Slide table

Claims (7)

It is a pulling-up-type continuous casting method for pulling up the molten metal held in the holding furnace using a starter,
When accelerating the starter to a predetermined pulling speed at the start of casting,
A first acceleration section accelerating at a first acceleration from a stopped state to a first speed;
A second acceleration section accelerating at a second acceleration from the first speed to the second speed;
A pulling-up-type continuous casting method comprising: a constant speed section for pulling up the starter at the first speed between the first acceleration section and the second acceleration section. The first acceleration, when continuing to accelerate from a stopped state, is an acceleration at which the molten metal pulled up by the starter is broken before reaching the predetermined pulling speed,
The second acceleration is an acceleration at which the molten metal pulled up by the starter is broken before reaching the predetermined pulling speed when continuing to accelerate from a stopped state.
The pulling-up-type continuous casting method according to claim 1. Making the first acceleration equal to the second acceleration;
The pulling-up-type continuous casting method according to claim 1 or 2. The first acceleration and the second acceleration are the maximum acceleration that can be exhibited by the pulling machine that pulls up the starter.
The pulling-up-type continuous casting method according to claim 3. A third acceleration section accelerating at a third acceleration from the second speed to the third speed;
A constant speed section for raising the starter at the second speed between the second acceleration section and the third acceleration section;
The pulling-up-type continuous casting method according to any one of claims 1 to 4. Making the second acceleration greater than the first acceleration;
The pulling-up-type continuous casting method according to claim 1 or 2. The second acceleration is the maximum acceleration that can be exhibited by the pulling machine that pulls up the starter.
The pulling-up-type continuous casting method according to claim 6.

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