JP2016036824A - Plasma heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma heating device capable of preventing a torch from being immersed in molten metal under an operation condition of being not constant in a molten metal surface height in plasma heating time.SOLUTION: A plasma heating device is provided for heating molten metal in continuous casting by a plasma, and comprises a stopper receiver 8 for moving together with lifting of a torch 12, and a torch falling preventive stopper 9 is arranged by (n) pieces (n≥2) in a movable range of the stopper receiver 8, at least (n-1) pieces among these are a movable type stopper 9a, and the movable type stopper 9a can change a position between an advance position 21 and a retreat position 22. In plasma heating, the movable type stopper 9a existing under the stopper receiver 8 is set in the advance position 21, and the movable type stopper 9a existing above the stopper receiver 8 is set in the retreat position 22. When the torch descends since abnormality of a torch driving control system is caused, trouble of immersing the torch 12 in the molten metal, can be prevented.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a plasma heating apparatus for plasma heating molten metal during continuous casting.

  In the continuous casting method in which the molten metal stored in the pan is poured into the tundish and then supplied to the continuous casting mold, the molten metal in the pan and the tundish is always in a heat radiating state, and the temperature of the molten metal along with the progress of casting. Will go down. Due to this drop in temperature, the bottom of the tundish obstructs the immersion nozzle installed for supplying molten steel to the mold and impedes the separation of impurities (inclusions) in the tundish and mold. Triggers a drop in quality and troubles in stopping casting operations. For this reason, a technique for heating the molten metal in the tundish has been introduced, and a plasma heating apparatus or an induction heating apparatus is generally used as the technique. Among them, the plasma heating device has an advantage that it can be applied without significant modification to the tundish as compared with the induction heating device.

  Since the heating torch of the plasma heating apparatus is exposed to the radiant heat of the molten metal and the arc, the inside is water-cooled to prevent damage to the torch (for example, Patent Document 1). The torch can be moved up and down by an elevating mechanism (for example, Patent Document 2). When performing plasma heating of the molten metal, the torch is lowered, approaches the molten metal surface, maintains a predetermined interval, and starts heating.

  Since the distance between the torch and the molten metal in the plasma heating apparatus is very close, an event that the tip of the torch is immersed in the molten metal can occur. In particular, when a torch drop occurs due to a failure of the torch lifting device, the torch is damaged by immersion in molten metal. As mentioned above, since the cooling water constantly circulates inside the torch, when the tip of the torch is immersed in the molten metal, a large amount of cooling water flows out into the molten metal and the molten metal scatters due to a vapor explosion. There is a concern that will occur. When this trouble occurs, there is a possibility of developing into a large-scale trouble such as casting interruption or equipment damage. Therefore, a method for preventing the torch from being immersed in the molten metal is desired.

  The plasma control apparatus described in Patent Document 3 proposes a method for detecting an abnormal approach between a torch and a molten metal surface based on an impedance determination circuit signal of a pilot arc circuit or a current detection signal of a pilot arc.

  In the plasma heating apparatus described in Patent Document 4, in order to protect the plasma torch tip by lifting it from the tundish in the event of a power failure, a clutch is provided in the drive system of the torch lifting device so that the torch support arm can always be raised. Counter weights are connected to enable the upper limit to be withdrawn during power outages.

  The plasma torch drive device described in Patent Document 5 has a fixed frame, a moving frame, and an internal moving body, and the plasma torch is suspended and supported by the internal moving body. The position where the moving frame descends to the moving frame lower limit stopper and the internal moving body descends to the lower wall of the moving frame is the plasma torch lower limit position. In this state, the molten steel in the tundish is heated by the plasma torch. Since the lower limit stopper for the moving frame and the lower wall of the moving frame are provided, the trouble that the plasma torch further descends from the lower limit position of the plasma torch is prevented.

JP 2009-266428 A JP-A-3-285746 JP-A-10-22095 JP-A-9-122849 JP-A-9-115688

  The trouble that the torch of the plasma heating device is immersed in the molten metal can be caused not only by a power failure but also by an abnormality in the torch drive control system. In the method described in Patent Document 3, it is difficult to prevent the torch from being immersed in the molten metal both during a power failure and when the torch drive control system is abnormal. Although the method described in Patent Document 4 can cope with a power failure, it cannot cope with an abnormality in the torch drive control system. In addition, in the method described in Patent Document 4, when the gap between the torch and the molten metal is small at the time of ignition, in order to prevent the torch from being immersed in the molten metal, switching from the drive system to the counterweight is extremely performed. It needs to be done in a short time. Furthermore, since the counterweight requires a weight that is greater than that of the torch components, there is a problem that a large load is applied to the base portion, and the amount of capital investment such as deterioration of the base portion and structural reinforcement is increased.

  When the molten metal in the tundish is plasma heated, the molten metal surface height in the tundish also changes due to fluctuations in operating conditions and individual differences in the tundish shape (such as refractory construction). The position of is not constant. In the apparatus described in Patent Document 5, since the plasma torch lower limit position determined by the stopper position is fixed, in a situation where the molten metal surface height is not constant, the torch is moved by the stopper when the molten metal surface height increases. Cannot be immersed in molten metal.

  The present invention is a plasma capable of preventing the torch from being immersed in the molten metal even when there is an abnormality in the torch drive control system in the operating condition where the molten metal surface height during plasma heating is not constant, even during a power failure. An object is to provide a heating device.

That is, the gist of the present invention is as follows.
(1) A plasma heating apparatus that plasma-heats molten metal during continuous casting, wherein the plasma heating torch can be raised and lowered, and has a stopper receiver that moves along with the raising and lowering of the torch.
N stoppers (n ≧ 2) for preventing torch dropping are arranged in the movement range of the stopper receiver, and at least n−1 of the n stoppers are movable stoppers, and the movable stoppers move forward. The position can be changed between the position and the retracted position. When the stopper is in the advanced position, the stopper receiver is blocked by the stopper and cannot move below the stopper. When the stopper is in the retracted position, the stopper Is a plasma heating device characterized by not obstructing the movement of the stopper receiver.
(2) the distance between the molten metal surface and the torch tip in the plasma heating and T _g, the distance between the i-th and (i-1) th stopper from the top P _i-1 and (i = 2- through n) Then, the plasma heating apparatus according to (1) above, wherein the following expression (1) is satisfied.
20 mm ≦ P _i-1 ≦ T _g / cos θ (1)
However, (theta) is an angle between a torch raising / lowering path | route and a perpendicular direction.
(3) the distance between the receiving i-th stopper and the stopper from the top and D _i, a D _i is a positive value when the stopper receiving is above the stopper, previously a predetermined threshold value C _T for the distance D _i Set
When the distance D _i is smaller than C _{T when the} torch is lowered, the i-th stopper is moved backward, and when the distance D _i is larger than C _{T when the} distance D _i is raised, the i-th stopper is moved backward. The plasma heating apparatus according to (1), wherein the stopper is moved forward.
(4) plasma heating apparatus according to (3), characterized in that the 10~30mm the predetermined threshold C _T.
(5) the distance between the molten metal surface and the torch tip in the plasma heating and T _g, the distance between the i-th and (i-1) th stopper from the top P _i-1 and (i = 2- through n) The plasma heating apparatus according to (3) or (4) above, wherein the following expression (2) is satisfied.
20 mm ≦ (P _i-1 + C _T ) ≦ T _g / cos θ (2)
However, (theta) is an angle between a torch raising / lowering path | route and a perpendicular direction.
(6) The plasma heating apparatus as described in (2) or (5) above, wherein T _g is determined using a torch tip position during steady heating as a torch tip position during plasma heating.
(7) The plasma heating apparatus as described in (2) or (5) above, wherein T _g is determined using a torch tip position at the time of ignition as a torch tip position during plasma heating.
(8) In the above (1) or (2), during the plasma heating, the movable stopper below the stopper receiver is set to the forward position, and the movable stopper above the stopper receiver is set to the reverse position. A method of using the plasma heating apparatus described.

  In the plasma heating apparatus of the present invention, n stopper stoppers (n ≧ 2) are disposed as stopper receivers that move as the torch moves up and down, and at least n−1 are movable stoppers. The position can be changed between the forward position and the reverse position. During plasma heating, the movable stopper below the stopper receiver is set to the forward position, and the movable stopper above the stopper receiver is set to the reverse position. Even if the position of the molten metal surface in the tundish is higher than the lowest molten metal surface, when the torch drive control system malfunctions and the torch descends, the trouble of the torch being immersed in the molten metal is prevented It becomes possible to do.

It is a figure which shows an example of the plasma heating apparatus of this invention, (a) shows when a torch is in an upper limit position, (b) shows when a torch is in a plasma heating position. It is a fragmentary figure which shows the plasma heating apparatus of this invention during plasma heating. It is a figure which shows the stopper receiving position and operation | movement of a stopper of the plasma heating apparatus of this invention. It is a figure which shows the stopper receiving position and operation | movement of a stopper of the plasma heating apparatus of this invention. It is a figure which shows the stopper receiving position and operation | movement of a stopper of the plasma heating apparatus of this invention. It is a figure which shows the stopper receiving position and operation | movement of a stopper of the plasma heating apparatus of this invention.

  The present invention is a plasma heating apparatus that plasma-heats molten metal during continuous casting, and a plasma heating torch can be moved up and down. Various mechanisms can be used for the raising and lowering mechanism of the torch. As described in Patent Documents 3 and 5, a mechanism that lifts and lowers a moving body mounted with a torch with a wire, and as described in Patent Document 4, a jack screw is rotated by a motor to move a traveling body of the torch. Any mechanism may be employed, such as a moving mechanism. Hereinafter, the case where an electric cylinder is used as a drive device of the lifting mechanism of the torch will be described as an example (FIG. 1).

  The electric cylinder 3 has an advance / retreat arm 4 therein. The rotation of the electric motor 1 is transmitted to the electric cylinder 3 via the gear box 2, and the advance / retreat arm 4 advances from one end of the electric cylinder 3 or retreats into the electric cylinder 3. An elevating arm 7 is installed on the fixed frame 6 of the plasma heating device so as to be elevable. The upper end of the lifting arm 7 is connected to the tip of the advance / retreat arm 4 of the electric cylinder 3. A plasma heating torch 12 is connected to the lower end of the lifting arm 7. The stopper receiver 8 of the present invention is also preferably connected to the lifting arm 7.

  As the advance / retreat arm 4 of the electric cylinder 3 advances and retracts, the elevating arm 7 is lowered and raised, and accordingly the plasma heating torch 12 is lowered and raised. Since both the torch 12 and the stopper receiver 8 are connected to the lifting arm 7, the stopper receiver 8 moves as the torch 12 moves up and down.

  The elevating path 14 for raising and lowering the torch 12 may be vertical or may be a path inclined from the vertical. As shown in FIG. 2, the angle between the elevating path 14 and the vertical direction is set to θ. If the elevating path 14 is vertical, θ = 0 °.

  In the standby state in which plasma heating is not performed, the torch 12 is raised and is in standby as shown in FIG. When plasma heating is performed, the torch is lowered, and the tip of the torch 12 is disposed at a predetermined position near the molten metal surface 13 in the tundish, as shown in FIG.

  As described above, the height of the molten metal surface in the tundish varies depending on fluctuations in the operation state and individual differences in the tundish shape (such as refractory construction), so the position of the molten metal surface is not constant. Within the normal operating range, the lowest expected molten metal surface is called the “lowest molten metal surface”. However, regarding the position of the molten metal surface during plasma heating during the predetermined charging process, the ladle sliding nozzle opening degree is controlled so that the molten metal injection amount from the ladle matches the molten metal outflow from the tundish. As a result, the position of the molten metal surface is kept constant.

At the start of plasma heating, the torch is lowered from the standby position, and adjustment is performed so that the distance between the molten metal surface and the tip of the torch becomes a predetermined T _g (FIG. 1B). Even when the molten metal surface fluctuates during plasma heating, the torch tip position is adjusted in accordance with the fluctuation of the molten metal surface. For example, the position of the molten metal surface in the tundish is measured at the start of plasma heating, and adjustment is performed so that the distance between the molten metal surface and the torch tip is a predetermined T _g . At the same time, the weight of the tundish and the molten metal are measured, and during plasma heating, the fluctuation of the molten metal surface position can be estimated from the change in the measured weight, and the tip position of the torch can be adjusted.

  The present invention prevents the torch from being immersed in the molten metal under operating conditions where the molten metal surface height during plasma heating is not constant.

  As described above, the present invention has the stopper receiver 8 that moves as the torch moves up and down, and n stoppers 9 (n ≧ 2) for preventing the fall of the torch are arranged in the movement range of the stopper receiver 8. At least n-1 of the n stoppers 9 can be movable stoppers 9a, and the remaining one can be a fixed stopper 9b. Of the n stoppers, the stopper 9 located at the lowermost end is defined as a fixed stopper 9b. In the example of FIGS. 1 and 2, the number of stoppers n = 2, and both of them are movable stoppers. In the examples of FIGS. 3 to 5, the number of stoppers n = 3, the upper and middle stages are movable stoppers 9a, and the lower stage is an example of fixed stoppers 9b. The position of the movable stopper 9a can be changed between the forward movement position 21 and the backward movement position 22. When the stopper is at the forward movement position 21, the stopper receiver 8 is blocked by the stopper and cannot move below the stopper. When the stopper is in the retracted position 22, the stopper does not hinder the movement of the stopper receiver.

  The stopper receiver 8 moves as the torch 12 moves up and down. When the position of the molten metal surface is the lowest expected molten metal surface, the torch position during plasma heating is the lowest position. Of the stoppers, the fixed stopper disposed at the lowest stage is disposed so as to be lower than the stopper receiving position during plasma heating when the molten metal surface position in the tundish is the lowest molten metal surface. Therefore, even if the molten metal surface at the time of plasma heating is at any height within a normal range, it does not happen that the stopper receiver is blocked by the fixed stopper and cannot be disposed at a predetermined position.

  When the position of the molten metal surface in the tundish is higher than the lowest molten metal surface, the position of the stopper receiver is higher than the position of the lowermost stopper during plasma heating. In this state, when the torch drive control system malfunctions and the torch descends, the lowering of the stopper receiver cannot be stopped until the lowermost stopper position is reached, so that there is a concern that the tip of the torch is immersed in the molten metal.

  As described above, in the present invention, at least n-1 of the n stoppers are movable stoppers, and the movable stoppers are disposed above the fixed stoppers. All n stoppers may be movable stoppers. For movable stoppers where the position of the molten metal surface in the tundish is higher than the lowest molten metal surface and is positioned below the position of the stopper receiver during plasma heating, move the stopper to the forward position. And For the movable stopper positioned above the position of the stopper receiver during plasma heating, the stopper is set to the retracted position. When the torch drive control system malfunctions and the torch descends, the stopper receiver is blocked by the position of the movable stopper that is at the highest position among the movable stoppers in which the stopper is in the forward movement position, and below it. Can't move on. That is, in the present invention, even when the position of the molten metal surface in the tundish is higher than the lowest molten metal surface, when the torch drive control system abnormality occurs and the torch descends, the torch becomes a molten metal. It becomes possible to prevent the trouble of immersion.

It is preferable that the distance P between adjacent stoppers is shorter because the torch abnormality lowering amount when an abnormality in the torch drive control system occurs can be reduced. As for the number n of the stoppers, assuming the highest position and the lowest position as the molten metal surface position in the tundish, the position difference L _D between them, the distance P between adjacent stoppers, the torch lift path and the vertical It can be calculated as follows from the angle θ with the direction.
n-1 = L _D / (P · cos θ) (3)

_{Let Tg} be the distance between the molten metal surface during plasma heating and the tip of the torch. The distance between the i-th and i-1th stoppers from the top is P _i-1 (i = 2 to n).

When the torch is lowered abnormally due to a control system abnormality during plasma heating, in the present invention, the abnormal lowering stops by the stopper receiver coming into contact with the nearest stopper below the stopper receiver. Since between the molten metal surface and the torch tip in the plasma heating is the distance T _g, the vertical component of the abnormal descent amount is equal to or less than T _g, can dispel the concern that the torch is immersed in the molten metal. Since the upper limit of the abnormal descending amount can be calculated from the distances P _i-1 to P _i-1 · cos θ between adjacent stoppers, if P _i-1 ≤T _g / cos θ, the torch is not immersed in the molten metal. . The lower limit of the distance P _i-1 between the adjacent stoppers is desirably 20 mm or more due to the influence of the torch stop accuracy. That is, it is preferable to satisfy the following expression (1).
20 mm ≦ P _i-1 ≦ T _g / cos θ (1)

This will be specifically described with reference to FIG. Hereinafter, the distance between the i-th stopper from the top and the stopper receiver is D _i, and D _i is a positive value when the stopper receiver is above the stopper. In FIG. 3 (a), a value D ₁ is in a high position has positive than the stopper receiving 8 upper movable stopper 9a1, all movable stopper including upper movable stopper 9a1 is at the forward position is there. If the torch abnormal falling occurs during plasma heating in this state, in contact with the upper stopper 9a1 moves the stopper receiving 8 by a distance D ₁ abnormal descent is completed. In FIG. 3B, the stopper receiver 8 is just at the position of the upper movable stopper 9a1, and all the movable stoppers including the upper movable stopper 9a1 are at the advanced position. In this state, if the torch abnormal lowering occurs during the plasma heating, the stopper receiver 8 is already in contact with the upper stopper 9a1, and thus does not actually lower. In FIG. 3C, the stopper receiver 8 is just at the position of the upper movable stopper 9a1, the upper movable stopper 9a1 is in the retracted position, and the middle movable stopper 9a2 is in the advanced position. Since it is the distance P ₁ between the upper and middle stoppers, D ₂ = P ₁ , and if the torch abnormal lowering occurs during plasma heating in this state, the stopper receiver 8 moves by the distance D ₂ = P _1. Then, contact with the middle stopper 9a2 completes the abnormal lowering. As long as the distance P _i-1 between the adjacent stoppers satisfies the above equation (1), the amount of vertical descent caused by the abnormal lowering of the torch does not exceed T _g .

The forward / backward movement of the movable stopper is preferably performed automatically if the control system is operating normally. Here, furthermore, predetermined a predetermined threshold value C _T for the distance D _i. Preferably, in the present invention, for each of i = 1 to n−1th movable stoppers, if the distance D _i is smaller than or smaller than C _{T, the} stopper position is set to the retracted position, and the distance D _i is smaller than C _T. If it is larger, the stopper position is the forward position. Specifically, when the distance D _i becomes smaller than C _T when the torch is lowered, the i-th stopper is moved backward, and when the torch is raised, the distance D _i becomes larger than C _T. Then, the i-th stopper is moved forward. In FIG. 4 (a), the first stopper 9a1 since the distance D ₁ of the the first stopper 9a1 is larger than C _T is in the advanced position 21. The torch is lowered operation, the distance D ₁ in the position of figure descending 4 (b) is equal to C _T, 1 th stopper 9a1 operate retracted. In the state of FIG. 4C, the distance between the tip of the torch and the molten metal surface becomes the target _Tg , and the lowering operation is completed. At this time, the first stopper 9a1 is in the retracted position 22, and since D ₂ > C _T , the second stopper 9a2 remains at the advanced position 21. Thus, when up and down operation of the torch is completed to start the plasma heating, the stopper distance between receiving stopper there below the stopper receiving is not less than C _T becomes to be placed in a forward position . When a control abnormality occurs, the stopper receiver is prevented from descending at the highest stopper among the stoppers at the forward movement position.

Is preferably as the value of the threshold C _T is small, when too small, the possibility of receiving the stopper before the stopper during torch descent is retracted collides to the stopper occurs. By the threshold C _T and 10 to 30 mm, it is possible to perform such a problem without control.

When the above control is performed, the maximum value of the distance between the stopper receiver and the stopper is (P _i-1 + C _T ) when the uppermost step among the stoppers at the forward position is the i-th. Accordingly, if a control abnormality occurs in this state and the torch abnormally descends and the i-th stopper prevents the descent, the amount of descent of the torch from the occurrence of the abnormality to the end of descent is (P _i-1 + C _T )・ Cos θ
It becomes. Since a control abnormality occurs during plasma heating, the distance between the molten metal surface and the torch tip is T _g .
(P _i-1 + C _T ) ≦ T _g / cos θ
By satisfy | filling, the molten metal immersion of a torch can be avoided. As described above, the lower limit of P _i-1 is desirably 20 mm or more. Therefore, by satisfying the following formula (2), it is possible to prevent the torch from being immersed in the molten metal.
20 mm ≦ (P _i-1 + C _T ) ≦ T _g / cos θ (2)

This will be specifically described with reference to FIG. 5A and 5B, plasma heating is being performed, and the distance between the torch tip and the molten metal surface is T _g . In FIG. 5 (a), D ₁ has a stopper receiving 8 at a position higher than the movable stoppers 9a1 of the upper is greater than C _T a positive value, all movable stopper including upper movable stopper 9a1 Is in the forward position 21. D ₁ <T _g / cos θ. If the torch abnormal falling occurs during plasma heating in this state, in contact with the upper stopper 9a1 moves the stopper receiving 8 by a distance D ₁ abnormal descent is completed. In FIG. 5 (b), D ₁ is slightly smaller than C _T, the upper movable stopper 9a1 is retracted positions 22, middle movable stopper 9a2 is in the advanced position 21. Since it is the distance P ₁ between the upper and middle stoppers, D ₂ = P ₁ + C _T , and if the torch abnormal drop occurs during the plasma heating in this state, the stopper receiver 8 moves the distance D ₂ = P ₁ + C _It moves by _T and comes into contact with the middle stopper 9a2 to complete the abnormal lowering. As long as the distance P _i-1 between the adjacent stoppers satisfies the above equation (2), the vertical descending amount due to the abnormal descending of the torch does not exceed T _g .

The time of ignition and steady heating, there is a case where the distance T _g of the between the molten metal surface and the torch tip in the plasma heating are different. Generally towards during ignition, T _g is less than the steady state heating. Therefore, when distinguishing the two, the time of steady heating is called T _g1 and the time of ignition is called T _g2 .

If T _g2 at the time of ignition is used as T _g in the above equations (1) and (2), the molten metal of the torch can be used regardless of the timing of the control abnormality at the time of ignition or steady heating. This is preferable because it avoids immersion. However, since T _g2 at the time of ignition is as small as about 100 mm, P _i-1 defined by equation (2) becomes a small value, and it is necessary to install a large number n of stoppers.

On the other hand, the above equation (1), as T _g in (2), if the use of the T _g1 of the steady state heating, T _g1 of steady heating so large as about 330 mm, defined in (2) P _A large value can be used as _i-1 , and the number n of stoppers can be reduced. However, the control abnormality that occurs at the timing of ignition cannot be dealt with.

Upon lowering operation torch, the control method of the distance D _i retracts operate i-th stopper When smaller than C _T is an operation at the time of only the control system is functioning properly. When the torch with the control abnormality is lowered is not retracted operating i-th stopper even smaller than naturally distance D _i is C _T. As a method for determining whether the control system is normal or abnormal, for example, a method for determining by comparing the position command of the torch with the actual position can be used. When controlling the position of the torch, a position measuring device for measuring the current value of the torch position is provided. On the other hand, the control system has a torch position command value so that the actual position by the position measuring device matches the position command value. Perform advanced / reverse control. In this case, since the control if the position command and actual position of the torch coincides can be judged to be normal, upon lowering operating the torch, the distance D _i is retracted i th stopper When smaller than C _T Make it work. On the other hand, if the position command and actual position of the torch is a mismatch, position actual becomes that do not follow the position command, the control abnormality is assumed, i-th even smaller than this distance D _i is C _T Do not move the stopper back.

  The stopper of this invention was installed in the plasma heating apparatus attached to the curved slab continuous casting machine (FIGS. 1 and 3 to 5). The rotation of the electric motor 1 is transmitted to the electric cylinder 3 via the gear box 2, and the advance / retreat arm 4 advances from one end of the electric cylinder 3 or retreats into the electric cylinder 3. An elevating arm 7 is installed on the fixed frame 6 of the plasma heating device so as to be elevable. The upper end of the lifting arm 7 is connected to the tip of the advance / retreat arm 4 of the electric cylinder 3. A plasma heating torch 12 is connected to the lower end of the lifting arm 7. A stopper receiver 8 is also connected to the lifting arm 7. The stopper receiver 8 moves as the torch 12 moves up and down.

  In this embodiment, in order to simplify the contents, as shown in FIGS. 4 and 5, n = 3 stoppers are provided, and the movable stoppers are two in the upper stage (i = 1) and the middle stage (i = 2). The lower stage (i = 3) was a fixed stopper. Both movable stoppers are movable by an air cylinder. As described above, the number of stoppers can be determined by the fluctuation width of the tundish molten metal surface height. Therefore, it goes without saying that an arrangement with three or more stages can be adopted if necessary. In this case, the lowermost stage may be fixed or movable.

  In order to confirm the effect of the present invention, the present inventors conducted a pseudo test to generate a torch drop caused by control abnormality on a trial basis.

In the plasma torch lifting path 14 that θ from the vertical direction with an inclination of 15 ° of the torch, the torch and the gap T _g of the inter molten metal assuming a case of 100 mm, upper and middle, as shown in FIGS. 4 and 5 The distance between stoppers P _i-1 (i = 2, 3) of the three (= n) stoppers in the lower stage was satisfied under the conditions satisfying the levels 1, 2 and 3 shown in Table 1 below.

Note that the operation of each stopper during normal control is determined when the distance D _i between the i-th (i = 1, 2) movable stopper 9ai and the stopper receiver 8 is C _T = 10 mm or less when the torch is lowered. stopper 9ai is retracted, during the torch rises, when the distance D _i of the stopper 9ai and the stopper receiving 8 is equal to or greater than C _T = 10 mm, was conducted as a stopper 9ai advances (see FIG. 4) to. When the torch falls due to the control abnormality, the control system determines that the control is abnormal, and the stopper 9ai does not move backward even if the distance D _i between the stopper 9ai and the stopper receiver 8 becomes C _T = 10 mm or less when the torch is dropped.

Substituting θ = 15 °, T _g = 100 mm, and C _T = 10 mm into the equation (2),
T _{g /} cos θ ₌ 103.5 mm
It becomes.

As a result, when the conditions satisfying the present invention are satisfied as in Level 1 of Table 1, that is,
20 mm ≦ (P _i-1 +10) ≦ 103.5 mm (i = 2, 3)
In consideration of the purpose of reducing the equipment cost by reducing the number of stoppers as much as possible and reducing the failure occurrence rate, the present inventors have set the pitch P _i-1 = 80 mm. When implemented, it was confirmed that the torch interferes with the stopper when the torch falls due to control abnormality, and the stopper can physically stop the torch before immersion in the molten steel.

On the other hand, as in level 2, if P _i-1 <20 mm and the present invention is not satisfied, that is, if P _i-1 <20 mm, the stopper continuously retracts when the torch descends during normal control. This hinders the descending operation of the torch, making it impossible to follow the molten metal surface. Another reason is that it is difficult to select an air cylinder that can narrow the space between the cylinder rods in terms of equipment.

Further, as in level 3, when T _g / cos θ <(P _i-1 + C _T ) and the conditions do not satisfy the present invention, that is, when 103.5 mm <(P _i-1 + C _T ), stopper is retracted, a torch in case that the distance D ₂ of the middle stopper 9a2 and the stopper receiving 8 exceeds 103.5Mm, when the torch dropped into the plasma heating occurs, the front stopper receiving interferes with the middle stopper Was immersed in the tundish molten metal surface.

Next, using the apparatus shown in FIG. 3, during the plasma heating, control was performed such that the movable stopper below the stopper receiver was set to the advance position and the movable stopper above the stopper receiver was set to the retract position. In this case, if the stopper arrangement pitch is not set such that (P ₁ , P ₂ , P ₃ ...) Is smaller than T _g / cos θ, the torch is immersed in the molten metal surface at the time of dropping. The schematic diagram in case a stopper is 3 steps | paragraphs is shown. In FIG. 3, the distance between the molten metal surface and the tip of the torch is T _g in any of (a) to (e). From (a) to (e), the state of the molten metal surface is decreasing. 3 (a) is the distance between the stopper receiving 8 and the upper stopper 9a1 is D _1. When the molten metal surface 13 is lowered and the stopper receiver 8 is positioned immediately above the upper stopper Pa1 as shown in FIG. 3B, the upper stopper 9a1 is retracted (FIG. 3C). At this time, the distance P ₂ of the upper stopper 9a1 and middle stopper 9a2, stopper before P ₂ is less than T _g / cos [theta], where even fall torch occurs, the torch is immersed in the molten metal surface The receptacle 8 can contact the middle stopper to prevent the torch from being immersed in the molten steel.

3D and 3E show a situation where the molten metal surface 13 is further lowered. In FIG. 3D, when the stopper receiver 8 is located immediately above the middle stopper 9a2, the middle stopper 9a2 is retracted (FIG. 3E). At this time, the distance P ₃ between the middle stopper 9a2 and the lower stopper 9b3, stopper before P ₃ is less than T _g / cos [theta], where even fall torch occurs, the torch is immersed in the molten metal surface The receptacle 8 can contact the lower stopper 9b3 to prevent the torch from being immersed in the molten steel.

In the case as described above, with respect to the pitch between the adjacent stoppers, a pitch that can be expected in terms of equipment can be selected from 20 mm ≦ P _i-1 ≦ T _g / cos θ.

  As a result of using the device for preventing torch soaking at the time of dropping the torch according to the present invention as a plasma heating device at the time of normal operation, damage due to the torch soaking at the time of dropping the torch and loss time required for replacement could be eliminated.

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Gear box 3 Electric cylinder 4 Advance / retreat arm 6 Fixed frame 7 Lifting arm 8 Stopper receiver 9 Stopper 9a Moving stopper 9b Fixed stopper 12 Torch 13 Molten metal surface 14 Lifting path 21 Forward position 22 Reverse position

Claims (8)

A plasma heating apparatus that plasma-heats molten metal during continuous casting, and the plasma heating torch can move up and down, and has a stopper receiver that moves along with the raising and lowering of the torch,
N stoppers (n ≧ 2) for preventing torch dropping are arranged in the movement range of the stopper receiver, and at least n−1 of the n stoppers are movable stoppers, and the movable stoppers move forward. The position can be changed between the position and the retracted position. When the stopper is in the advanced position, the stopper receiver is blocked by the stopper and cannot move below the stopper. When the stopper is in the retracted position, the stopper Is a plasma heating device characterized by not obstructing the movement of the stopper receiver. When the distance between the molten metal surface during plasma heating and the torch tip is T _g and the distance between the i-th and i-1th stoppers from the top is P _i-1 (i = 2 to n), The plasma heating apparatus according to claim 1, wherein the following expression (1) is satisfied.
20 mm ≦ P _i-1 ≦ T _g / cos θ (1)
However, (theta) is an angle between a torch raising / lowering path | route and a perpendicular direction. The distance between the receiving i-th stopper and the stopper from above and D _i, a D _i is a positive value when the stopper receiving is above the stopper, a predetermined a predetermined threshold value C _T for the distance D _i,
When the distance D _i is smaller than C _{T when the} torch is lowered, the i-th stopper is moved backward, and when the distance D _i is larger than C _{T when the} distance D _i is raised, the i-th stopper is moved backward. The plasma heating apparatus according to claim 1, wherein the stopper is moved forward. Plasma heating device according to claim 3, characterized in that the 10~30mm the predetermined threshold C _T. When the distance between the molten metal surface during plasma heating and the torch tip is T _g and the distance between the i-th and i-1th stoppers from the top is P _i-1 (i = 2 to n), The plasma heating apparatus according to claim 3 or 4, wherein the following expression (2) is satisfied.
20 mm ≦ (P _i-1 + C _T ) ≦ T _g / cos θ (2)
However, (theta) is an angle between a torch raising / lowering path | route and a perpendicular direction. 6. The plasma heating apparatus according to claim 2, wherein _Tg is determined using a torch tip position during steady heating as a torch tip position during plasma heating. 6. The plasma heating apparatus according to claim 2, wherein _Tg is determined by using a torch tip position at the time of ignition as a torch tip position during plasma heating.   3. The plasma heating apparatus according to claim 1, wherein during the plasma heating, the movable stopper below the stopper receiver is set to the forward position, and the movable stopper above the stopper receiver is set to the reverse position. how to use.

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