JP6528992B2 - Casting equipment - Google Patents

Description

  The present invention relates to a casting apparatus, and more particularly to a casting apparatus for continuously producing an ingot from a molten alloy in which a slag layer is formed on the upper surface of a molten metal.

  Conventionally, as a casting method for obtaining an ingot from molten alloy, there are vacuum arc remelting (VAR) and electroslag remelting (ESR). In these methods, a molten metal pool is formed and solidified in a solidified space surrounded by a water-cooled mold wall, and since it is solidified so as to be piled up, it becomes a solidified form generally called laminated solidification. This lamination solidification can alleviate the occurrence of segregation such as central segregation and reverse V segregation which occur in ingot casting due to the small solidification space, and increase the cooling rate by using a water-cooled mold Because of the ability to do so, there is also the advantage that the tissue becomes finely uniform.

  However, since it is necessary to manufacture the electrode for re-dissolution, these VARs and ESRs also have the problem of requiring many man-hours for that and energy for re-dissolution. On the other hand, as a technique for solving this problem, Japanese Patent Application Laid-Open No. 2007-111760 directly injects molten alloy at a predetermined injection rate into a solidification space surrounded by a water-cooled mold wall without using a remelting electrode. There is disclosed a technique in which a molten metal pool in which a slag layer is disposed is formed and solidified, and the ingot is drawn vertically from the lower portion of the water-cooled mold according to the injection rate of the molten alloy.

Japanese Patent Application Publication No. 2007-111760

  In JP 2007-111760 A, in order to solve the problem that a non-uniform slag layer is formed on the surface of the drawn ingot, a plurality of heating electrodes are placed in the slag in the water-cooled mold, By controlling for each specific heating electrode according to the slag temperature, the uneven heating state of the slag in the water-cooled mold is improved and the slag state is uniformed, so that a smooth ingot skin can be obtained. It describes what can be done.

  In the technique disclosed in the above-mentioned publication, a power supply is arranged to apply a voltage between each heating electrode and the ingot drawn out from the lower part of the water-cooled mold. For this reason, control of energization can be performed for every heating electrode by operation of the switch provided for every heating electrode, and the molten state of the whole slag can be equalized. However, when the ingot drawn out from the lower part of the water-cooled mold reaches a certain length, an operation occurs to cut the elongated ingot. When cutting this ingot, it is necessary to change the connection back to the ingot left on the water-cooled mold side since one of the power supply wires is connected to the ingot. There is a problem that the heating process can not be performed by the heating electrode and the casting process itself temporarily stops.

  Therefore, in view of the above problems, according to the present invention, even if a long ingot is cut, casting can be continuously performed without temporarily stopping the heating of the slag by the heating electrode, and the inside of the cooling mold It is an object of the present invention to provide a casting apparatus capable of uniformly maintaining the molten state of slag.

  In order to achieve the above object, the casting apparatus according to the present invention is a casting apparatus for continuously producing an ingot from a molten alloy, and cooling the molten alloy in which a slag layer is formed on the upper surface of the molten metal. A cooling mold for solidifying and extracting the ingot obtained from the lower part from the lower part, and a heating means for heating the slag layer in the cooling mold, the heating means containing at least the slag layer in the slag layer A power supply for applying a voltage between a plurality of heating electrodes partially immersed, an in-mold electrode partially exposed on the inner surface of the cooling mold, and each of the plurality of heating electrodes and the in-mold electrode And further comprising The molten alloy may be appropriately supplied from a tundish holding the molten alloy in order to continuously produce an ingot.

  The casting apparatus according to the present invention may further include a control device that controls each of the plurality of heating electrodes in accordance with the temperature of the slag layer. In this case, a temperature detector or a current detector may be provided for each of the plurality of heating electrodes, and a detection signal of the temperature detector or the current detector is input to the control device. You may

  Thus, in addition to the plurality of heating electrodes immersed in the slag layer, an in-mold electrode partially exposed on the inner surface of the cooling mold is further provided, and between each of the plurality of heating electrodes and the in-mold electrode Since the power supply wiring of the heating electrode has no effect even if the ingot extending from the lower part of the cooling mold is cut by installing the power supply so as to apply the voltage to the heating electrode, heating of the slag by the heating electrode is temporarily performed. Casting can be performed continuously without stopping. Further, since heating can be controlled for each of the plurality of heating electrodes, the molten state of the slag in the cooling mold can be uniformly maintained. In particular, since a current path is formed between the heating electrode in the slag layer and the in-mold electrode provided on the inner surface of the cooling mold, sufficient heating of the slag in the meniscus portion generated on the inner surface of the cooling mold may be achieved. Since it is possible, smooth ingot skin can be obtained more stably and continuously.

It is a typical sectional view showing one embodiment of a casting device concerning the present invention. FIG. 2 is a cross-sectional view of the casting apparatus along line II-II shown in FIG. It is a longitudinal cross-sectional view of the casting apparatus along line III-III shown in FIG. FIG. 4 is a cross-sectional view of the casting apparatus along line IV-IV shown in FIG. 3;

  Hereinafter, an embodiment of a casting apparatus according to the present invention will be described with reference to the attached drawings. It is to be noted that the drawings are drawn with some deformation or omission of the configuration in order to give priority to the understanding of the present invention, and are not to scale.

  As shown in FIG. 1, the casting apparatus of the present embodiment includes a cooling mold 20 for solidifying the molten alloy supplied from the tundish 10 holding the molten alloy 1 to obtain an ingot 6.

  The tundish 10 mainly includes a tundish main body 11 for containing the molten alloy 1 and a nozzle 12 for discharging the molten alloy provided at the bottom thereof. The nozzle 12 is provided with a valve (not shown) capable of adjusting the speed at which the molten alloy is injected into the cooling mold 20. Between the tundish 10 and the cooling mold 20, a shield 14 for blocking the molten alloy and the outside air is disposed.

  The cooling mold 20 includes a mold body 21 extending in the vertical direction in order to make the molten alloy injected from the tundish 10 into an ingot. The inner diameter and the length (height) of the mold body 21 vary depending on the desired size of the ingot, and for example, in the case of a cylindrical shape, the inner diameter is 200 to 1000 mm, the length 200 to 800 mm, and a prismatic shape If it is, one piece may be 200 to 1000 mm, and the length may be 200 to 800 mm. In addition, the cooling mold 20 is provided with a heating electrode 30 for controlling the slag 3 to a predetermined temperature at the upper opening where the molten alloy is injected. Furthermore, at the lower opening where the ingot 6 of the cooling mold 20 is discharged, a lifting device (not shown) for extracting the solidified ingot, and secondary cooling for further cooling the extracted ingot For example, a mist injector 40 is provided.

  The more detailed structure of the mold main body 21 and the heating electrode 30 in this Embodiment is demonstrated using FIG.2 and FIG.3. As shown in FIGS. 2 and 3, the mold body 21 is disposed so that the molten metal flow 2 is injected from the nozzle 12 of the tundish 10 at the center of the upper opening of the cylindrical shape. In addition, the nozzle 12 can also use the immersion nozzle made to immerse in the slag 3 and a molten metal.

  Further, at the upper opening, a plurality of heating electrodes 30 are uniformly arranged so that the temperature can be controlled with respect to the entire slag 3. Specifically, eight round rod-like heating electrodes 30a to 30h are annularly arranged at equal intervals around the position where the molten metal flow 2 of the mold main body 21 is injected, but the present invention Is not limited to this configuration. For example, the shape of the heating electrode may be a flat or curved plate, or a plurality of heating electrodes may be arranged in a ring of two or more.

  The plurality of heating electrodes 30 are disposed so as to extend in parallel with the longitudinal direction of the mold body 21. The upper ends (proximal ends) of these heating electrodes 30 are respectively fixed to the support member 33 via the insulator 34. Further, lower ends (tips) of these heating electrodes 30 are located at a depth sufficient to immerse in the slag 3 and, for example, located at the lower end (bottom end) of the in-mold electrode 23 It is also good.

  The mold body 21 includes a water cooling unit 22 for cooling the molten alloy injected into the inside, an in-mold electrode 23 connected to the heating electrode 30 via a power supply 32, and a graphite sleeve 25 for keeping the slag warm. Equipped with Each of these is provided facing the inner side of the mold body 21. The in-mold electrode 23 is provided in the mold main body 21 via the insulator 24.

  The lower end of the in-mold electrode 23 is preferably disposed at the same depth position as the lower end of the heating electrode 30, but is not particularly limited thereto. Further, the upper end of the in-mold electrode 23 may be at a position where the area of the in-mold electrode 23 on the inner side surface of the mold main body 21 can be secured such that the in-mold electrode 23 can be sufficiently energized with the heating electrode 30.

  The circumferential arrangement of the in-mold electrode 23 is shown in FIG. As shown in FIG. 4, the plurality of in-mold electrodes 23 a to 23 h are arranged at equal intervals along the circumferential direction of the mold body 21. Specifically, eight in-mold electrodes 23a to 23h are arranged between the eight heating electrodes 30a to 30h, that is, alternately arranged, but the present invention is limited to this configuration. It is not a thing. For example, unlike the configuration of FIG. 4, the in-mold electrode 23 may be integrally disposed over the entire circumferential direction of the mold body 21 without being divided and disposed.

  The power supply 32 is connected in parallel to the plurality of heating electrodes 30 a to 30 h through the wiring 31 and is also connected in parallel to the plurality of in-mold electrodes 23 a to 23 h. Furthermore, in the wiring 31, the branch lines 31a to 31h between the plurality of heating electrodes 30a to 30h and the power supply 32 are turned on / off so that heating of the plurality of heating electrodes 30a to 30h can be controlled individually. A switch (not shown) for turning off is provided. In the present invention, by providing a plurality of power supplies 32, heating of each of the heating electrodes 30a to 30h can be controlled individually or for each of several heating electrodes.

  Moreover, in order to detect the temperature of the slag 3 in the mold main body 21, multiple temperature detectors (illustration omitted) are arrange | positioned. For example, a temperature detector may be provided at the tip of each heating electrode 30. Furthermore, each heating electrode 30 is provided with a current detector (not shown) for measuring the current of the electrode. Then, detection signals from the temperature detector and the current detector are input, and the switch of the power supply 32 and the heating electrode 30 is controlled so as to keep the state of the slag 3 uniform according to the information obtained from these signals. A controller (not shown) is provided.

The material of the heating electrode 30 is not particularly limited as long as it can withstand oxidation and a predetermined temperature of slag, and for example, a cermet refractory using pure iron, Mo (molybdenum), or ZrO ₂ (zirconia) is adopted. can do. Further, the material of the in-mold electrode 23 is not particularly limited as long as the material can withstand a predetermined temperature of oxidation or slag, and, for example, a cermet refractory using pure iron, Mo (molybdenum) or ZrO ₂ (zirconia) Etc. can be adopted.

  The graphite sleeve 25 is a heat retaining member, and is preferably disposed at a position where the slag 3 is formed in the mold main body 21 and a formation position of the solidified shell. When the graphite sleeve 25 is adjacent to the in-mold electrode 23, the graphite sleeve 25 is disposed via the insulator 24.

  The water cooling unit 22 is configured so that water circulates and flows therein in order to cool and solidify the molten metal pool formed inside. The water cooling section 22 is disposed from the lower end of the graphite sleeve 25 to the lower opening from which the ingot of the mold body 21 is discharged.

  According to the casting apparatus of the present embodiment having the above configuration, first, the molten alloy melt 1 having, for example, about 1500 ° C. in the tundish 10 is cooled as the molten metal flow 2 from the nozzle 12 at the bottom thereof. Inject into 20. The injection speed of the molten alloy 1 is preferably 0.3 m / min or less. In addition, although the slag 3 will be described in detail later, a voltage is applied between the plurality of heating electrodes 30 and the in-mold electrode 23 by the power supply 32, whereby a uniform molten state can be maintained.

  The molten metal injected from the nozzle 12 forms a molten metal pool 4 whose upper surface is positioned above the lower end of the graphite sleeve 25 of the cooling mold 20. A meniscus 4m is formed at the interface between the molten metal pool 4 and the inner surface of the graphite sleeve 25, and the upper surface of the molten metal pool 4 is lowered at this portion. Then, the molten metal pool 4 is cooled by the water cooling unit 22 to form the shell 5 on the water cooling unit 22 side, and the cooling proceeds further and is solidified to form the ingot 6. By pulling out the ingot 6 downward from the cooling mold 20 by a lifting device (not shown) in accordance with the injection rate of the molten alloy 1, it is possible to continuously carry out lamination solidification. Moreover, the ingot 6 which came out from this downward direction can also inject and cool the mist 41 from the mist injector 40. FIG.

  The control device sets the target slag temperature range to, for example, 1350 ° C. to 1400 ° C. in consideration of the melting point of the molten steel, and the values of the current detectors of the plurality of heating electrodes 30 are equal. Control the switch so that That is, in the portion where the temperature of the slag 3 is high, the electric resistance is low and the current is preferentially supplied since the current is preferentially supplied. Therefore, slag heating of the part with high temperature is stopped by turning off electricity supply of the heating electrode with a high value of an electric current detector by a switch. Then, when the value of the current detector of the heating electrode becomes equal to the values of the other current detectors, energization is started by the switch. By repeating such control, the temperature distribution of the slag 3 in the cooling mold 20 can be controlled to be uniform. In addition, the control device may control the energization of the heating electrode by the switch instead of or in addition to the detection signal from the current detector by the detection signal from the temperature detector.

  Also, a control device for adjusting the output current of the power supply 32 to a fixed value (set value) by feeding back the signal of the current detector (not shown) is disposed, and the control device (not shown) is controlled by the signal The temperature of the slag 3 can be kept uniform by adjusting the output current of the power supply 32 with the illustration (not shown).

  By maintaining the slag 3 in a uniform state by the above control, an ingot 6 having a smooth ingot surface can be continuously and stably obtained from the cooling mold 20. In addition, by continuously producing the ingot 6 in this manner, it is necessary to cut the ingot 6 having a certain length halfway along the way, but in the present invention, the power source 32 comprises the heating electrode 30 and the inside of the mold. Unlike the prior art in which a voltage is applied between the heating electrode and the ingot, the wiring is applied to apply a voltage between the electrode 23 and the heating electrode 30 even when the ingot 6 is cut. The heating of the slag 3 by this is not interrupted.

  Furthermore, as shown in FIG. 3, in the prior art in which the plurality of heating electrodes 30a to 30h apply a voltage between the ingot and the ingot, the current flows mainly through the current path 35a. The slag in a portion sunk by the meniscus 4m generated on the wall surface may have a worse heating environment and a different melting state than the other portions. In the present invention, a plurality of heating electrodes 30a to 30h are energized in the vicinity of the meniscus 4m because current flows through the current path 35b between the plurality of heating electrodes 30a to 30h, and the slag sunk here is also sufficiently heated. be able to. Therefore, the whole slag in the mold main body 21 can be maintained in a uniform molten state, and the ingot 6 which has smooth ingot skin can be obtained.

  Production of ingot and heating experiment of slag were conducted using a casting apparatus having the following constitution. As a molten alloy to be held in the tundish, a steel type equivalent to JIS SKD11 was used. The composition of the slag is shown in Table 1.

  The shape of the cooling mold, in which the graphite sleeve is embedded, is a square of 400 mm in one side dimension. Further, the iron in-mold electrode was disposed at a position where the slag layer was formed upward from the lower end of the graphite sleeve. Iron round bar electrodes were arranged at intervals of 50 mm as heating electrodes a to d. The lower end of the heating electrode was disposed at the same position as the lower end of the in-mold electrode.

  Then, draw casting was performed so that the temperature of the molten metal was about 1500 ° C. and the injection speed of the molten metal was 0.03 m / min (30 mm / min). The slag heating at the heating electrode sets the depth of slag to about 80 mm, sets the target slag temperature range to 1350 ° C, sets the current of the power supply to 300 A, and the values of the temperature detectors arranged on each of the electrodes become equal. It did while controlling the current of the power supply. At this time, the temperatures detected by the temperature detectors disposed at each of the electrodes are shown in Table 2.

  As shown in Table 2, in the case of the configuration of the present invention, although the slag temperature difference was about 100 ° C. at the beginning, the difference was reduced by control, and the molten state could be made uniform. In this way, nonuniform slag temperature distribution in the early stage of casting can be corrected by controlling the plurality of heating electrodes, and the slag temperature can be made uniform within the target temperature range, and nonuniform solidification of the slag can be prevented. Was confirmed.

DESCRIPTION OF SYMBOLS 1 alloy molten metal 2 molten metal flow 3 slag 4 molten metal pool 5 shell 6 ingot 10 tundish 12 nozzle 20 cooling mold 22 water cooling part 23 electrode in a mold 24 insulator 25 graphite sleeve 30 heating electrode 31 wiring 32 power supply 33 support member 34 insulator 35 current path 40 mist injector

Claims (3)

A casting apparatus for continuously producing ingots from molten alloy, comprising:
A cooling mold for cooling and solidifying the molten alloy having a slag layer formed on the upper surface of the molten metal, and extracting the ingot obtained thereby from the lower part;
Heating means for heating the slag layer in the cooling mold, the heating means including a plurality of heating electrodes of which at least a part is immersed in the slag layer, and a part of the inner surface of the cooling mold A casting apparatus comprising: a mold in-mold electrode exposed; and a power supply for applying a voltage between each of the plurality of heating electrodes and the mold in-mold electrode.   The casting apparatus according to claim 1, further comprising a control device that controls each of the plurality of heating electrodes according to the temperature of the slag layer. A temperature detector or a current detector is provided for each of the plurality of heating electrodes, and detection signals of the temperature detector or the current detector are configured to be input to the control device. Casting apparatus as described in.

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