JP6583614B2 - Electrode breakage prevention device for arc furnace - Google Patents

Description

  The present invention relates to an electrode breakage prevention device for an arc furnace, and more particularly to an electrode breakage prevention device that can reliably prevent electrode breakage without causing malfunction.

  An example of an electrode breakage prevention device is described in Patent Document 1, and in this device, a load of a wire for operating an electrode support for supporting an electrode to be raised and lowered is detected by a load cell, and the detected load of the load cell is an upper limit value. And when either of the lower limit values is exceeded, the raising / lowering of the electrode is stopped because there is a possibility of electrode breakage.

Real Kaihei 7-8996

  However, graphite electrodes used in arc furnaces gradually wear out during operation and lighten their weight, so the lower limit may be exceeded due to relatively small fluctuations in wire load. There is a problem that the operation efficiency is lowered because the raising and lowering of the electrode is stopped each time when the fear of the above is erroneously detected.

  Therefore, the present invention solves such a problem, and it is possible to reliably determine the risk of electrode breakage and avoid this without causing erroneous detection due to electrode wear, and an arc furnace that does not cause a decrease in operation efficiency. An object of the present invention is to provide an electrode breakage prevention device.

In order to achieve the above object, according to the first aspect of the present invention, a consumable electrode (3) that can be moved up and down in the furnace body (1) of an arc furnace by an electrode lifting device (4), a consumable electrode (3), and the same The load detection means (5) for detecting the load of the lifting / lowering part of the electrode lifting / lowering device (4) that moves up and down, and the load detected by the load detection means (5) when the consumable electrode (3) is raised to a predetermined position The reset means (6) for resetting the value, and the consumable electrode (3) is lowered by the electrode lifting / lowering device (4) as there is a risk of electrode breakage when the reset load value exceeds the predetermined value and changes upward or downward. First descending limiting means (6) for stopping, calculating means (6) for calculating the length of the consumable electrode, and changing means (6) for changing the value of the predetermined value according to the calculated length value. .

In the first invention, since the load value is reset before energizing the consumable electrode, even if the graphite electrode is gradually consumed during operation and its weight is lightened, it is not affected, and is always The risk of electrode breakage can be determined appropriately. As a result, the useless lifting operation of the electrode is avoided and the reduction of the operation efficiency is prevented. In addition, in view of the fact that electrode breakage is the result of moment force acting on the consumable electrode, by changing the predetermined value for determining electrode breakage according to the length of the consumable electrode, it is possible to cancel useless electrode elevation. And the operational efficiency can be further improved.

  In the second invention, the detection range of the load detection means (6) is set in correspondence with the load change range expected upward or downward with respect to the reset load value.

  According to the second aspect of the present invention, the detection range can be set to correspond to the load change range, so that the resolution of detection can be increased, and the possibility of electrode breakage can be more reliably determined.

In the third aspect of the invention , the change rate calculating means (6) for calculating the change rate of the load detected by the load detecting means (5), and when the calculated change rate exceeds the other predetermined value and changes upward. Second descent restriction means (6) is further provided for stopping the descent of the consumable electrode (3) by the electrode elevating device (4) as there is a possibility of electrode breakage.

According to the third aspect of the present invention , it is possible to effectively prevent breakage of the electrode due to the fine scrap that has fallen gradually leaning against the graphite electrode.

  In addition, the code | symbol in the said parenthesis shows the correspondence with the specific means as described in embodiment mentioned later as an example.

  As described above, according to the electrode breakage prevention apparatus for an arc furnace of the present invention, it is possible to reliably determine the risk of electrode breakage and avoid this without causing erroneous detection due to electrode wear, resulting in a decrease in operation efficiency. There is nothing.

It is a figure which shows the whole arc furnace structure which attached the electrode breakage prevention apparatus in 1st Embodiment of this invention. It is a figure which shows the setting range of a detection span in 2nd Embodiment of this invention. It is a figure which shows the whole arc furnace structure which attached the electrode breakage prevention apparatus in 5th Embodiment of this invention.

  The embodiment described below is merely an example, and various design improvements made by those skilled in the art without departing from the gist of the present invention are also included in the scope of the present invention.

(First embodiment)
FIG. 1 shows a schematic cross section of an arc furnace provided with an electrode breakage prevention device. In the figure, a graphite electrode 3 as a consumable electrode is inserted into a furnace body 1 of an arc furnace through a lid body 2 covered with an upper opening, and is inserted into the tip and the bottom of the furnace body 1. A discharge occurs between the scrap S and the scrap S is heated and melted. A plurality of graphite electrodes 3 are provided in a three-phase AC arc furnace, but the same applies to other graphite electrodes.

  The outer periphery of the graphite electrode 3 is gripped by a gripper 41 that constitutes the electrode lifting device 4, and the gripper 41 is provided at one end of a support arm 42 that extends horizontally. An intermediate portion of the support arm 42 is supported by an upright column 43, and guide rollers 431 are in contact with both sides of the column 43 to guide the vertical movement of the column 43.

  A wire 45 is suspended on the lower outer periphery of the pulley 441 provided at the lower end of the column 43, and one end of the wire 45 extending upward is coupled to one end of the load cell 5 serving as load detecting means. The other end of the load cell 5 is coupled to the fixed side. A load signal 5 a output from the load cell 5 is input to the control device 6.

  The other end of the wire 45 extending upward is turned downward through an idle pulley 442 and then wound around a winding drum 461 provided in the lifting mechanism 46. The take-up drum 461 is driven to rotate forward and backward by a drive motor 462 of the elevating mechanism 46, winds up the wire 45 during forward rotation and moves up the support 43 (and hence the graphite electrode 3), and feeds out the wire 45 during reverse rotation and feeds the support Therefore, the graphite electrode 3 is moved downward.

  The forward / reverse rotation and stop of the drive motor 462 are controlled by the output of the control device 6. The control device 6 always takes the load signal 5a of the load cell 5, but when the graphite electrode 3 is raised to a predetermined position (usually the upper limit position), the load value of the load signal 5a is internally reset (usually zero). Reset. The upper limit position can be known by detecting the operation of a limit switch (not shown). The graphite electrode 3 is usually raised to the upper limit position at the start of operation when the lid body 2 is opened or when the scrap S is added. At this time, the graphite electrode 3 is not energized.

  When starting energization of the graphite electrode 3, the control device 6 lowers the graphite electrode 3 by the drive motor 462, and then detects the current and voltage energized to the graphite electrode 3 via the water-cooled cable 31. Then, the graphite electrode 3 is moved up and down appropriately so that these become desired values, and the discharge between the scrap S and the scrap S is heated and melted.

  At this time, even if the weight of the graphite electrode 3 is reduced due to consumption during the previous energization, the load value of the load signal 5a of the load cell 5 is reset to zero before the start of new energization as described above. The absolute decrease of the load due to the consumption of the graphite electrode 3 is cancelled.

  In this state, when the graphite electrode 3 rides on the non-conductive scrap S, the load on the graphite electrode 3 apparently decreases greatly, and the load value detected by the load cell 5 changes below a predetermined lower limit value. Therefore, in this case, it is assumed that there is a possibility of electrode breakage, so that the lowering of the electrode 3 is stopped or the electrode 3 is pulled up by a predetermined amount to prevent the electrode breakage.

  Further, when the scrap S that has melted leans against the graphite electrode 3 and the load value detected by the load cell 5 changes upward beyond a predetermined upper limit value, it is considered that there is a risk of electrode breakage. The descent is stopped or the electrode 3 is pulled up by a predetermined amount to prevent electrode breakage.

  In this case as well, the graphite electrode 3 is gradually consumed by energization and its load (weight) is reduced. However, since the load decrease due to this consumption is small, the reset load value changes below the lower limit value. Never do. Therefore, unlike the conventional case, there is no problem that the risk of electrode breakage is erroneously detected and the electrode elevation is stopped and operation is hindered.

(Second Embodiment)
In the first embodiment, the detected span (range) X in the control device 6 for the load signal 5a of the load cell 5 is predicted upward or downward with respect to the reset load value R as shown in FIG. It is set corresponding to the load change range A, and the upper limit value and the lower limit value are set in the detection span X, respectively. In this way, it is possible to detect the load change of the load cell 5 with higher resolution, and thus it is possible to reliably prevent the electrode from being broken. The detection span indicated by Y in FIG. 2 is conventional, E is the tare load value, and M is the allowable load value of the load cell 5.

(Third embodiment)
In the first embodiment, most of the breakage of the graphite electrode 3 occurs at the electrode connection portion directly below the gripper 41 (the graphite electrode 3 is constituted by connecting a plurality of electrodes). A horizontal force acts on the lower end of the electrode, for example, when the electrode 3 rides on the slanted scrap S, and the moment proportional to the length of the graphite electrode 3 (exactly, the length from the lower end of the electrode to the electrode connecting portion directly below the gripper 41). This is because a force is applied to the electrode connecting portion.

Since the cross section of the graphite electrode 3 is constant, if the load detected by the load cell 5 before resetting is compared with the detected load when the length is known at the start of operation, the load difference (weight difference) ), The length of the graphite electrode 3 that has become shorter as it is consumed can be predicted before energization. Therefore, when the length of the graphite electrode 3 is long, the upper limit value and the lower limit value for preventing electrode breakage are relatively smaller than the upper limit value when the length of the graphite electrode 3 is short. When the length of the graphite electrode 3 is shortened, the upper limit value and the lower limit value are compared with the upper limit value when the graphite electrode 3 is long. The lower limit value is relatively small and relatively small . In this way, the operation efficiency is further improved because the electrode elevation is not stopped in order to prevent electrode breakage especially when the graphite electrode 3 is shortened.

(Fourth embodiment)
In the first embodiment, as another cause of electrode breakage, it is conceivable that the fine scrap S that has been melted down gradually approaches the graphite electrode 3 and a load is applied to the electrode 3. Therefore, in the present embodiment, the control device 6 stops the descent of the graphite electrode 3 because there is a possibility of electrode breakage when the change speed of the detected load of the load cell 5 changes beyond a certain upper limit value, or the electrode 3 is pulled up by a predetermined amount to prevent electrode breakage.

(Fifth embodiment)
The arc furnace which is the subject of the present invention may have a structure as shown in FIG. 3, for example. In FIG. 3, a support column 43 for raising and lowering the graphite electrode 3 is formed in a cylindrical shape, and a hydraulic cylinder 71 is installed therein, and the support column 43 is moved up and down by the hydraulic cylinder 71. Yes. The operation of the hydraulic cylinder 71 is performed from the hydraulic mechanism 7 via the hydraulic pressure supply line 72 by the output signal of the control device 6. The load cell 5 is interposed between the hydraulic cylinder 71 and the floor. The other structure is the same as that of the first embodiment, and electrode breakage is prevented by the same control as that of the first embodiment.

  In this case, as a load detection means, a pressure sensor 73 may be provided in the hydraulic pressure supply line 72 instead of the load cell 5, and the load of the graphite electrode 3 may be converted from the detected pressure of the pressure sensor 73.

DESCRIPTION OF SYMBOLS 1 ... Furnace body, 3 ... Consumable electrode, 4 ... Electrode raising / lowering device, 5 ... Load cell (load detection means), 6 ... Control apparatus (Reset means, 1st descent | fall limitation means, calculation means, change means, change speed calculation means, (Second descending limiting means), 7 ... hydraulic mechanism, 73 ... pressure sensor (load detecting means).

Claims (3)

A consumable electrode that can be moved up and down in the arc furnace by the electrode lifting device, a load detecting means for detecting the load of the consumable electrode and the lifting portion of the electrode lifting device that moves up and down integrally therewith, and the consumable electrode is lifted to a predetermined position Reset means for resetting the load value detected by the load detection means, and there is a risk of electrode breakage when the reset load value changes upward or downward beyond a predetermined value. Electrode breakage prevention of an arc furnace comprising: first descent restriction means for stopping descent; calculation means for calculating the length of the consumable electrode; and changing means for changing the value of the predetermined value in accordance with the calculated length value apparatus. The electrode breakage prevention device for an arc furnace according to claim 1, wherein a detection range of the load detection means is set in correspondence with a load change range expected upward or downward with respect to the reset load value. The change rate calculating means for calculating the rate of change of the load detected by the load detection means, and the electrode lifting / lowering device assuming that there is a possibility of electrode breakage when the calculated change rate exceeds the other predetermined value and changes upward. The apparatus for preventing breakage of an electrode in an arc furnace according to claim 1 or 2, further comprising: a second lowering restricting unit that stops the lowering of the consumable electrode.

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