JP3588414B2 - Electrical steel sheet horizontal continuous heat treatment furnace - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a horizontal heat treatment furnace for an electromagnetic steel sheet that continuously performs heating, soaking, and cooling treatments.
[0002]
[Prior art]
Regarding the method of laying a hearth roll in a conventional electromagnetic steel sheet continuous continuous annealing furnace, since the iron loss of the product increases when strain is given in the annealing process, the pitch of the hearth roll is generally constant and set to be small. However, the number of hearth rolls has increased, causing an increase in equipment costs. On the other hand, for example, Japanese Patent No. 2505503 discloses a diameter and a laying pitch of a hearth roll which does not increase iron loss of a silicon steel sheet for each processing zone having a different temperature in a horizontal annealing furnace for a silicon steel sheet. I have.
[0003]
That is, in the horizontal heat treatment furnace for a silicon steel sheet, the furnace body is divided into three stages: a front stage, a middle stage, and a rear stage from the entry side, and the roll diameter is 120 in the front stage and the rear stage where the temperature of the material to be annealed is less than 800 ° C. In the middle stage where the hearth roll of up to 300 mm exceeds 1500 mm and the laying pitch is 3000 mm or less and the temperature of the material to be annealed is in the region of 800 ° C. or higher, the hearth roll having a roll diameter of 120 to 300 mm exceeds 500 mm and 1500 mm It has been proposed to reduce the equipment cost without increasing the iron loss of the silicon steel sheet by arranging at the following laying pitch.
[0004]
[Problems to be solved by the invention]
However, as the processing capacity increases, the furnace length of the horizontal annealing furnace increases, and even with the laying pitch as in the conventional technology, the number of hearth rolls to be installed becomes considerably large, so that an increase in equipment costs is inevitable. There has been a strong demand for hearth rolls in high-temperature sections of 800 ° C. or higher, which require regular replacement, to significantly reduce equipment costs, especially by reducing the number of installations.
[0005]
FIG. 5 is a conceptual diagram showing a conventional chain drive system, showing a plane inside the furnace in cross section and showing a drive device outside the furnace.
Conventionally, a carbon sleeve type roll is used as a hearth roll, and a drive system of a hearth roll group is such that a plurality of five to ten hearth rolls 2 are connected by a drive chain 6 into one group, and one hearth roll is formed. The drive motor 3 drives the group of hearth rolls 2 collectively, that is, a so-called chain drive system, so that a peripheral speed difference between the hearth rolls 2 due to inertia easily occurs in one drive groove, and the hearth roll 2 However, the uniformity of the material to be annealed deteriorates, the wear of the carbon sleeve caused by the slip between the material to be annealed 10 and the hearth roll 2 increases, and the carbon roll must be replaced frequently. Was.
[0006]
In particular, in a high-temperature portion where the furnace temperature exceeds 800 ° C., there is a concern that an increase in the slip between the hearth roll 2 and the material to be annealed due to an increase in thermal deformation of the hearth roll 2 at a high temperature. To increase the installation pitch means to increase the supporting load of the material to be annealed to be borne by one hearth roll 2, that is, the contact surface pressure between the hearth roll 2 and the material to be annealed increases, and the carbon sleeve roll The wear pitch of the hearth roll 2 was limited to 1500 mm because the wear amount of the hearth roll 2 became large.
[0007]
When the surface of the carbon sleeve hearth roll is damaged or the surface of the carbon sleeve becomes rough, the surface is polished and reused. That is, in the conventional chain drive system, there is a problem that hearth rolls having different roll diameters cannot be installed in the same drive group, so that a reproduction roll cannot be installed at an arbitrary location.
[0008]
[Means for Solving the Problems]
The present invention has been made to solve such a problem and to reduce the number of hearth rolls to be installed in a high temperature portion where the furnace temperature is 800 ° C. or higher. That is, in the horizontal continuous heat treatment furnace for electrical steel sheets, the diameter of the hearth roll provided in the zone for heat-treating the material to be annealed at a furnace temperature of 800 ° C. or more is 150 to 300 mm, and the arrangement pitch is more than 1500 mm and 4500 mm or less. An object of the present invention is to provide a horizontal continuous heat treatment furnace for an electromagnetic steel sheet, comprising: a drive motor for driving a hearth roll via a joint for each hearth roll; and a drive control device for the drive motor.
[0009]
Further, the drive control device calculates a rotation speed obtained by adding a hearth roll diameter correction for each hearth roll to a hearth roll reference speed command corresponding to the line speed, and controls the rotation speed for each hearth roll. It is characterized by being constituted. The hearth roll diameter is usually 150 mm or more in order to reduce the deflection due to the weight of the hearth roll to a certain value or less, and is often used within a range not exceeding 300 mm for economic reasons. And the hearth roll diameter was 150 to 300 mm.
[0010]
【Example】
In order to reduce the number of hearth rolls to be installed in the high-temperature part, reducing the number of hearth rolls increases the weight of the material to be annealed, which is shared by one hearth roll. It is important that the material does not become shorter, that the material to be annealed does not meander in the furnace, and that the increase in iron loss of the material to be annealed during the annealing process does not exceed an allowable value.
[0011]
FIG. 1 is a conceptual diagram showing an example of equipment of the present invention. In the horizontal continuous heat treatment furnace 1, the material to be annealed 10 is heated to a predetermined heating temperature in the heating zone, and then enters the soaking zone. In the soaking zone, the temperature is kept at a soaking temperature of 800 ° C. or more for a certain period of time by an electric heater or the like, and then cooled to near normal temperature in a subsequent cooling zone. The diameter D of the hearth roll 2 provided in the soaking zone where the material to be annealed 10 is soaked in a temperature range of 800 ° C. or more is 150 to 300 mm, and the arrangement pitches P ₁ , P ₂ , P _3. ··· _{Pn is set} to a value exceeding the conventional limit of 1500 mm and not more than 4500 mm. Further, in the present invention, in order not to promote wear of the hearth roll, instead of the conventional chain drive system, one drive motor is connected to each hearth roll via a joint, and each hearth roll is connected to each other. The system was driven independently.
[0012]
FIG. 4 shows a method of independently driving each hearth roll. Each of the hearth rolls 2 is connected to the drive motor 3 via a joint 7. Each drive motor 3 is controlled by a drive control device 9. In controlling the hearth roll rotation speed, first, in response to the hearth roll reference speed command 8 corresponding to the line speed, the hearth roll speed calculator 4 controls the speed so that the material to be processed maintains the tension set for each section. Controlled.
[0013]
Further, when setting the hearth roll, the hearth roll diameter correction calculator 5 calculates the hearth roll rotation speed according to the diameter of each hearth roll. The drive control device 9 controls the rotation speed of the hearth roll for each hearth roll based on the speed calculation command transmitted through these calculators. The hearth roll speed calculator 4 used here controls the speed of the hearth roll by a method of controlling the tension of the material to be annealed over the entire line including the horizontal continuous heat treatment furnace, and the tension of the material to be annealed in each section of the line. Is detected, the torque or speed of the drive motor for each section is corrected, and control is performed so that the tension of the material to be annealed for each section becomes a predetermined set value.
In the apparatus as described above, the wear amount of the carbon sleeve, the meandering of the material to be annealed, and the iron loss of the material to be annealed were confirmed.
[0014]
In the single drive system shown in FIG. 4, first, the wear amount of the carbon sleeve of the hearth roll and the arrangement pitch were examined, and the result of FIG. 2 was obtained.
FIG. 2 shows a comparison of the wear amount of the hearth roll when the arrangement pitch is set to two cases of 1500 mm and 4500 mm for three types of D ₁ , D ₂ , and D ₃ within the range of the hearth roll diameter of 150 to 300 mm. This shows the results of passing a sheet through 0.26 to 0.35 mm and a sheet width of 970 to 1000 mm for about 6 months. The hearth roll uses a carbon sleeve roll in which a carbon sleeve is fitted to an iron core, and the wear amount of the hearth roll, that is, the wear amount of the carbon sleeve is the case where the arrangement pitch of the hearth roll is 1500 mm and 4500 mm. It can also be seen that there is almost no difference and that the values are within the allowable limit.
[0015]
In addition, in two cases where the arrangement pitch of the hearth roll is 1500 mm and when the arrangement pitch of the hearth roll is 4500 mm, the average wear amount of the carbon sleeve by the conventional chain drive system and the single drive system in the present invention is compared as shown in FIG. The result that the amount of wear of the carbon sleeve was greatly reduced in the single drive system as compared with the conventional chain drive system was obtained.
Next, the influence of the meandering of the material to be annealed when the arrangement pitch of the hearth roll was 150 to 300 mm and the arrangement pitch was 1500 mm and 4500 mm was similarly investigated. In the case of, the meandering amount was below the allowable value, and no significant difference was recognized between the two.
[0016]
Furthermore, the relationship between iron loss and the pitch of the hearth roll was investigated. As is well known, the relationship between iron loss and temperature and strain in the annealing process is such that the higher the temperature of the material to be annealed, and the greater the strain in the annealing process, the greater the iron loss. It is also known that the strain in the annealing process increases as the unit tension increases, the diameter of the hearth roll decreases, and increases as the pitch of the hearth rolls increases.
[0017]
When a certain steel type is treated in a range where the hearth roll diameter is 150 to 300 mm and the unit tension is 0.3 to 0.7 kg / mm ^{2 in} a practically used range, when the soaking temperature is 800 ° C. or more, the hearth is hardened. A comparison was made between the two roll arrangement pitches of 1500 mm and 4500 mm, and it was confirmed that the arrangement pitch of the hearth roll had substantially no effect on iron loss in this range.
However, if the pitch of the hearth rolls exceeds 4500 mm, the work of initially passing the material to be annealed into the furnace, that is, the so-called threading work, becomes difficult. Since the loading operation becomes extremely difficult, it is desirable to set the pitch of the hearth roll to 4500 mm or less.
[0018]
【The invention's effect】
By employing a single drive system in which a drive motor and a drive control device are provided for each hearth roll as in the present invention, slip between the workpiece and the hearth roll is reduced, and wear of the hearth roll is also reduced. Therefore, in the horizontal continuous heat treatment furnace for electrical steel sheets, the arrangement pitch of the hearth rolls can be set larger in the zone at a furnace temperature of 800 ° C. or higher than in the conventional case. This makes it possible to reduce the power consumption by about one-third, thereby greatly reducing the operation and maintenance cost associated with the regular replacement of the hearth roll. It was also confirmed that the arrangement pitch of the hearth roll did not affect meandering and iron loss.
In addition, since the hearth roll drive device controls the speed of each hearth roll by adding a roll diameter correction, the installation position of the carbon sleeve used for reproduction can be freely selected regardless of the diameter after reproduction. Become.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a hearth roll diameter and hearth roll arrangement pitches P ₁ , P ₂ , P ₃ ... _{Pn according} to the present invention.
FIG. 2 is a diagram showing experimental data indicating the arrangement pitch of hearth rolls and the amount of wear of hearth rolls.
FIG. 3 is a view showing a difference in average wear amount of a carbon sleeve roll between a conventional chain drive system and a hearth roll independent drive system according to the present invention.
FIG. 4 is a diagram showing a drive system in which one hearth roll is driven by one drive motor in the present invention.
FIG. 5 is a diagram showing a conventional chain drive system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Horizontal continuous heat treatment furnace main body 2 Hearth roll 3 AC motor 4 Hearth roll speed calculator 5 Hearth roll diameter correction calculator 6 Drive chain 7 Joint 8 Reference speed command 9 Drive control device 10 Material to be annealed

Claims (2)

In the electrical steel sheet horizontal continuous heat treatment furnace, the diameter of the hearth roll provided in the zone where the steel sheet is heat-treated at a furnace temperature of 800 ° C. or more is 150 to 300 mm, and the arrangement pitch is more than 1500 mm and 4500 mm or less. A horizontal continuous heat treatment furnace for an electromagnetic steel sheet, comprising: a drive motor for driving a hearth roll via a motor; and a drive control device for the drive motor. The drive control device is configured to calculate a rotation speed obtained by adding a hearth roll diameter correction for each hearth roll to a hearth roll reference speed command corresponding to the line speed, and to control the rotation speed for each hearth roll. The horizontal type heat treatment furnace according to claim 1, wherein:

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