JP3364096B2 - Electric heating method of metal heated strip - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electrically heating a metal heating strip. More specifically, the present invention relates to a method for electrically heating a metal strip to be heated, in which a metal strip to be heated, such as a strip steel sheet, is continuously heated for heat treatment.

[0002]

2. Description of the Related Art Conventionally, as a heating method for continuously heat-treating a metal strip to be heated such as a strip steel sheet, the metal strip to be heated is directly energized through an energizing roll. There is a method of heating by the Joule heat of the tropical wood itself.

When the above heating method is adopted, while the metal heated strip is being conveyed from the low temperature side current-carrying roll to the high temperature side current-carrying roll, a wave is generated in the metal heated band material. The generated waves were caught between the high-temperature-side energizing roll and the pressing roll, and the metal-made heated belt material carried out from the high-temperature-side energizing roll sometimes had a defective shape such as wrinkles.

Therefore, as a method for solving the above problem,
A method for electrically heating a metal strip, in which one pressing roll that can move up and down is provided between two sets of energizing rolls, and the metal strip is passed through while pressing the pressing roll (JP-A-6-2876).
No. 44), when the thin steel sheet is electrically heated, the expander roll is heated until the temperature becomes substantially the same as the temperature of the thin steel sheet, and the thin steel sheet is prevented from being drawn by pressing the expander roll against the thin steel sheet (JP-A-6- (279870 publication)
Have been proposed.

The above-mentioned method can suppress the occurrence of a defective shape of the metal strip or the thin steel plate to some extent, but the wave generated while being conveyed from the low-temperature side energizing roll to the high-temperature side energizing roll can be sufficiently suppressed. It could not be reduced, and the metal plate or thin steel plate sometimes had a defective shape such as wrinkles.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, in which a metal band to be heated is conveyed while being electrically heated from a low temperature side energizing roll to a high temperature side energizing roll. While removing the wave generated in the metal heated strip during heating, it is possible to eliminate the occurrence of wrinkles and other shape defects in the metal heated strip carried out from the high temperature side energizing roll. An object of the present invention is to provide a method for electrically heating a heated strip.

[0007]

DISCLOSURE OF THE INVENTION According to the present invention, an electric current is passed through a metal heated band to heat the metal heated band by Joule heat. The method is a pair of pinch rolls from above and below the metal heated strip between the energizing rolls.
The rolling reduction between the pinch rolls is 0.05 to 0.
The present invention relates to a method for electrically heating a metal strip to be heated, which is characterized in that the strip is passed through while being sandwiched so as to be 5 kg / mm .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the method for electrically heating a metal strip to be heated of the present invention is such that an electric current is passed through the metal strip to be heated between energizing rolls and the metal strip is heated by Joule heat. It is a method of heating a tropical material, in which the metal band to be heated is pressed between the energizing rolls by a pair of pinch rolls from above and below.
It is characterized in that it is passed through while sandwiching it so as to be 0.05 to 0.5 kg / mm .

In the method for electrically heating a metal band to be heated of the present invention, one of the major points is that the metal band to be heated is sandwiched between the current rolls by pinch rolls from above and below. There are features.

As described above, according to the present invention, the means for passing the metal heated strip between the energizing rolls while sandwiching it between the energizing rolls from above and below with the pinch rolls is adopted. While the metal heated strip is being energized and heated from the roll to the energized roll on the high temperature side, waves are prevented from being generated on the metal heated strip, and the metal heated strip is carried out from the energized roll on the high temperature side. It is possible to eliminate the occurrence of shape defects such as wrinkles in the heated metal band material. The reason why it is possible to eliminate the occurrence of wrinkles and other shape defects in the metal heated strip carried out from the high-temperature side energizing roll is not clear, but is probably based on the following reasons. That is, as it is conveyed from the low-temperature side energizing roll to the high-temperature side energizing roll, the metal heated strip is heated, but with this heating, the metal heated strip is thermally expanded. Become. in this way,
When the metal heated band material thermally expands, a wavy phenomenon occurs in the metal heated band material. In the present invention, since the metal heated strip is sandwiched by the pinch rolls from above and below, the generated waves spread in the plate width direction of the metal heated strip, and in this state the high temperature side It is considered that the heated metal strip carried out from the high-temperature side energizing roll does not suffer from shape defects such as harmful wrinkles.

Further, since the metal heated strip is heated to a higher temperature in the vicinity of the high-temperature energizing roll than in the vicinity of the low-temperature energizing roll, the generation of waves in the vicinity of the high-temperature side energizing roll becomes remarkable. However, in the present invention, when the metal heated band material is sandwiched between the pinch rolls from above and below in the vicinity of the high-temperature-side current-carrying roll and passed through, the high-temperature-side current-carrying roll is carried out. Occurrence of shape defects such as wrinkles on the metal heated strip is further suppressed.

Further, in the present invention, when the metal heated strip between the energizing rolls is pushed up by the pinch rolls or pushed down to pass the strips, the strips are carried out from the energizing rolls on the high temperature side. It is further suppressed that a defective shape such as a wrinkle is generated in the metal heated band material.

A method for electrically heating a metal heated strip according to the present invention will be described below with reference to the drawings.

1 to 4 are schematic explanatory views each showing one embodiment of a method for electrically heating a metal band to be heated according to the present invention.

In FIGS. 1 to 4, 1 is a metal heated strip such as a strip steel plate, 2a and 2b are low temperature side energizing rolls and pressing rolls, 3a and 3b are high temperature side energizing rolls and pressing rolls, respectively. Reference numerals 4a and 4b are an upper pinch roll 4a and a lower pinch roll 4b, respectively, for sandwiching the metallic heated strip 1 from above and below.

When the metal heated strip 1 is passed through in the direction of arrow A, for example, a low frequency heating power source connected between the low temperature side energizing roll 2a and the high temperature side energizing roll 3a. The metal heated strip 1 is heated between the energizing roll 2a and the energizing roll 3a by applying electricity from the power source 5. The heating temperature of the metal heated strip 1 cannot be unconditionally determined depending on the type of the metal heated strip 1 or the like, and usually depends on the type of the metal heated strip 1 or the like. It is set appropriately.

The distance between the current-carrying roll 2a and the current-carrying roll 3a cannot be unconditionally determined because it varies depending on the scale of the threading line of the metal heated strip 1.
Usually, the distance may be about 2 to 50 m.

Since the upper pinch roll 4a and the lower pinch roll 4b are in direct contact with the metal heated strip 1 through which an electric current flows, they are made of a non-conductive material having heat resistance. A representative example of such a non-conductive material is a roll obtained by spraying a non-conductive ceramic such as zirconia onto a roll made of a material such as iron or carbon. Upper pinch roll 4a and lower pinch roll 4
The diameter of b is not particularly limited, but is 50 to 100 m so that it can be brought as close as possible to the pressing roll 3b and the energizing roll 3a on the high temperature side.
It is preferably about m. The roll widths of the upper pinch roll 4a and the lower pinch roll 4b are the widths of the portions through which the metal heated strip 1 passes in order to sufficiently remove the waves generated in the metal heated strip 1. It is preferable to be the same as or more than.

The reduction between the upper pinch roll 4a and the lower pinch roll 4b allows the waves generated in the metal heated strip 1 to be sufficiently removed.
0.05kg / mm or more, especially 0.1kg / mm
It is preferable to set the above, but if the reduction is too large, the upper pinch roll 4a and the lower pinch roll 4b
The amount of heat removed by will increase and a new wave will be generated,
Since there is a tendency for the metal heating strip 1 to oscillate due to the unbalance in the reduction, it is preferably 0.5 kg / mm or less, especially 0.2 kg / mm or less.

The energizing roll 2a and the energizing roll 3a are usually provided in a parallel state in order to heat the metal band 1 to be heated uniformly and maintain a constant tension between them. Has been. The upper pinch roll 4a and the lower pinch roll 4b are also usually installed so as to be parallel to the energizing roll 2a and the energizing roll 3a in order to sufficiently eliminate the waves generated in the metal heated strip 1. Is preferred. In addition, as long as the object of the present invention is not impaired, the upper pinch roll 4a and the lower pinch roll 4 are
b is for the energizing roll 2a and the energizing roll 3a,
It may be installed at a slight angle.

In FIG. 1, the metal heated strip 1 conveyed in the direction of arrow A from the low-temperature side energizing roll 2a to the high-temperature side energizing roll 3a is passed through an upper pinch roll 4a and a lower pinch roll 4b in a so-called horizontal pass. FIG. 3 is a schematic explanatory view showing an embodiment when conducting heating by energization in the state, that is, in a state in which the metal heated strip 1 is not pushed down or pushed up by the upper pinch roll 4a or the lower pinch roll 4b.

FIG. 2 is a schematic explanatory view showing one embodiment of the electric heating method of the present invention shown in FIG. 1, in which the metal band 1 to be heated is placed in the upper pinch roll near the high temperature side electric roll 3a. 4a and a lower pinch roll 4b are schematic explanatory views showing one embodiment when they are passed through while being sandwiched.

In FIG. 2, the upper pinch roll 4a and the lower pinch roll 4b are provided at positions where the high-temperature side energizing roll 3a and the pressing roll 3b are disposed in order to sufficiently remove the waves generated in the metal heated strip 1. It is preferable to be as close to these rolls as possible within a range that does not hinder the operation of.

FIG. 3 is a schematic explanatory view showing one embodiment of the electric heating method of the present invention shown in FIG. 2, in which the metal heated strip 1 is pushed upward by the lower pinch roll 4b. It is a schematic explanatory drawing which shows one embodiment at the time.

In the embodiment shown in FIG. 3, the upper pinch roll 4a and the lower pinch roll 4b are provided in the vicinity of the high temperature side energizing roll 3a, and the metal heated strip 1 is the lower pinch roll 4b. Has been pushed upwards. As described above, when the metal heated strip 1 is pushed upward by the lower pinch roll 4b, the effect of removing the wave generated in the metal heated strip 1 is further improved.

The metal heated strip 1 is attached to the lower pinch roll 4
The pushing width when pushing upward with b is the roll distance (heating length) between the energizing roll 2a and the energizing roll 3a,
It cannot be unconditionally determined because it depends on the type of the metal heated strip 1 and the like. Normally, the pushing width is sufficient to remove the waves generated in the metal heated strip 1;
Further, the contact area between the lower pinch roll 4b and the metal heated strip 1 is increased, and the amount of heat removed from the metal heated strip 1 is increased, so that the metal heated strip 1 is deformed. In order to prevent this, the distance between the rolls is 1.5 to
When it is 2.5 m, it is preferably about 10 to 20 mm.

FIG. 4 is a schematic explanatory view showing an embodiment of the electric heating method of the present invention shown in FIG. 2, in which the metal band material 1 to be heated is pushed downward by the upper pinch roll 4a. It is a schematic explanatory drawing which shows one embodiment at the time.

In the embodiment shown in FIG. 4, the upper pinch roll 4a and the lower pinch roll 4b are provided in the vicinity of the high temperature side energizing roll 3a, and the metal heated strip 1 is heated to the upper pinch roll 4a. It is pushed down by. Thus, when the metal heated strip 1 is pushed down by the upper pinch roll 4a, the effect of removing the waves generated in the metal heated strip 1 is shown in FIG. It is further improved as compared with the embodiment.

The heated metal strip 1 is placed on the upper pinch roll 4
The pushing width when pushing downward with a is the same as in the embodiment shown in FIG.
Since it depends on the distance between the rolls (heating length) and the type of the metal heated strip 1 and the like, it cannot be determined unconditionally. Usually, the pressing width is sufficient to remove the wave generated in the metal heated strip 1, and the upper pinch roll 4a
In order to prevent the deformation of the metal heated strip 1 from occurring because the contact area between the metal heated strip 1 becomes large and the amount of heat removed from the metal heated strip 1 increases. When the distance between the rolls is 1.5 to 2.5 m, 10 to 20
It is preferably about mm.

Each of the schematic explanatory views of the method for electrically heating the metal heating strip shown in FIGS. 1 to 4 is one embodiment of the present invention, and the present invention is limited to such embodiment. Not a thing.

It should be noted that the method for electrically heating the metal strip to be heated according to the present invention may be carried out by any of the methods generally used except that the upper pinch roll and the lower pinch roll are used.

That is, as shown in FIGS. 1 to 4, when a voltage is applied from the power source 5 to the energizing rolls 2a and 3a and the metal heating strip 1 is passed over the energizing rolls 2a and 3a, The heated metal strip 1 itself is heated by Joule heat. The heating temperature of the metal heated strip 1 is determined by the voltage applied from the power source 5, the plate passing speed, the energizing roll 2a,
It can be appropriately adjusted by adjusting the distance between the rolls of 3a and the like. Since the tension of the metal heated strip 1 running between the current-carrying rolls 2a, 3a varies depending on the type, heating temperature, size, etc. of the metal heated strip 1,
It cannot be determined unconditionally, but usually 0.5-4
It may be about kg / mm ² . The energizing roll 2
The upper surface of the metal-made heated strip 1 that is passed over a and 3a is pressed by the pressing rolls 2b and 3b.

At this time, according to the present invention, as described above, while the metal heated strip 1 is being passed through, as shown in FIGS.
As shown in FIG. 4, the metal heated strip 1 is sandwiched between the upper pinch roll 4a and the lower pinch roll 4b from above and below, and is passed through. The wave generated in 1 is removed,
It is possible to prevent a defective shape such as a wrinkle from occurring in the metal heated strip 1 carried out from the high temperature side energizing roll 3a.

[0034]

EXAMPLES Next, the method for electrically heating the metal heating strip of the present invention will be described in more detail with reference to Examples.
The invention is not limited to only such embodiments.

Example 1 An electric heating device (heating length 1.9 m) for heating a metal band material shown in FIG. 3 was used. As the upper pinch roll 4a and the lower pinch roll 4b, rolls (diameter 120 mm, roll width 1300 mm) obtained by spraying zirconia on carbon rolls were used, respectively, and the upper pinch roll 4a and the lower pinch roll 4b during passing were set between Is 0.
The pressure was adjusted to 1 kg / mm, and the push-up width was set to 10 mm at a position of 350 mm, 450 mm or 550 mm from the high temperature side energizing roll 3a.

Next, as the metal heated strip 1, a normal steel plate having a thickness of 0.2 mm and a width of 850 mm is passed from the low-temperature side energizing roll 2a in the direction of arrow A at a speed of 20 m / min to form the energizing roll 2a. The tension between 3a is adjusted to 4 kg / mm ^2, and the voltage in the power source 5 is adjusted so that the metal heated strip 1 is heated to 850 ° C. in the vicinity of the energizing roll 3a on the high temperature side. did.

The intensity of the average streak pattern of the ordinary steel sheet carried out from the high temperature side energizing roll 3a was examined according to the following method. The results are shown in Table 1.

(Average Stripe Intensity) An ordinary steel plate to be measured is placed on a surface plate, and the distance to the ordinary steel plate is measured from above by a laser distance meter to obtain the wavelengths and amplitudes of all waves. After that, the formula: [Steepness (%)] = [amplitude (mm)] / [wavelength (m
m)] × 100, the steepness for each wave is obtained, and the average value is used as the average streak intensity.

COMPARATIVE EXAMPLE 1 In the same manner as in Example 1, except that the upper pinch roll 4a and the lower pinch roll 4b were not used, the ordinary steel plate was passed through in the same manner as in Example 1, and the high temperature side energizing roll 3 was used.
The intensity of the average streak pattern of the ordinary steel sheet carried out from a was examined in the same manner as in Example 1. The results are shown in Table 1.

[0040]

[Table 1]

From the results shown in Table 1, in Example 1, the upper pinch roll 4a and the lower pinch roll 4 were
It can be seen that since the metal heated strip 1 is sandwiched by b, the wrinkles (striated pattern) generated in the ordinary steel plate after the electric heating is significantly suppressed. Particularly, in Example 1, the upper pinch roll 4a and the lower pinch roll 4b
It can be seen that, the shorter the distance from the energizing roll 3a on the high temperature side is, the more the generation of wrinkles (streak patterns) is suppressed.

Examples 2 to 3 The electric heating device (heating length 1.9 m) for heating the metallic band material shown in FIG. 3 was used. As the upper pinch roll 4a and the lower pinch roll 4b, rolls (diameter 120 mm, roll width 1300 mm) obtained by spraying zirconia on carbon rolls were used, respectively, and the upper pinch roll 4a and the lower pinch roll 4b during passing were set between Is 0.
Adjusted to be 1 kg / mm, and a push-up width of 10 mm (Example 2) or a push-up width of 0 mm (flat pass) (Example 3) at a position of 350 mm, 450 mm or 550 mm from the high temperature side energizing roll 3a. It was installed so that

Next, as the metal heated strip 1, a normal steel plate having a thickness of 0.2 mm and a width of 850 mm was passed from the low-temperature side energizing roll 2a in the direction of arrow A at a speed of 20 m / min to form the energizing roll 2a. Adjust the tension between 3a to be 4 kg / mm ² and adjust the voltage in the power source 5 so that the metal heated strip 1 is heated to 800 ° C. near the high temperature side energizing roll 3a. did.

The intensity of the average streak pattern of the ordinary steel sheet discharged from the high temperature side energizing roll 3a was examined in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 2 In Example 2, a plain steel plate was passed through in the same manner as in Example 2 except that the upper pinch roll 4a was not used. The intensity of the average streak pattern was examined in the same manner as in Example 1. The results are shown in Table 2.

[0046]

[Table 2]

Next, based on the results shown in Table 2, the relationship between the distance from the energizing roll on the high temperature side to the pinch roll and the intensity of the average streak pattern was examined. The result is shown in FIG.

From the results shown in FIG. 5, in Example 2 of the present invention, the metal heated strip 1 was sandwiched between the upper pinch roll 4a and the lower pinch roll 4b, and the ordinary steel plate between the current-carrying rolls was at the bottom. It can be seen that wrinkles (striated patterns) generated in the ordinary steel sheet carried out from the high temperature side energizing roll 3a are significantly suppressed by being pushed upward by the pinch roll 4b.

Further, in the third embodiment of the present invention, the ordinary steel plate is the upper pinch roll 4a and the lower pinch roll 4b.
It is sandwiched between the two and there is no push-up width (flat pass), but as is clear by comparison with the case where only the lower pinch roll 4b of Comparative Example 2 is used, the high temperature side energizing roll It can be seen that wrinkles (streaks) generated on the ordinary steel sheet carried out from 3a are suppressed.

[0050]

As described above, according to the method for heating a metal heated strip of the present invention, the metal heated strip is electrically heated from the low temperature side energizing roll to the high temperature side energizing roll. It is possible to eliminate the waves generated in the metal heated band material while being conveyed, and to eliminate the occurrence of shape defects such as wrinkles in the metal heated band material carried out from the high temperature side energizing roll.

Further, in the present invention, when the upper pinch roll and the lower pinch roll are arranged in the vicinity of the high temperature side energizing roll, the wrinkled metal band material carried out from the high temperature side energizing roll is wrinkled. It is possible to further prevent the occurrence of shape defects such as.

In particular, in the present invention, when the metal heated strip material between the energizing rolls is pushed up by the pinch rolls or pushed down to pass the strips, it is carried out from the energizing rolls on the high temperature side. It is possible to further prevent a defective shape such as a wrinkle from occurring in the metal heated band material.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing one embodiment of an electric heating method for heating a metal heated strip according to the present invention.

FIG. 2 is a schematic explanatory view showing an embodiment of a method for electrically conducting heating of a metal band to be heated of the present invention.

FIG. 3 is a schematic explanatory view showing one embodiment of a method for electrically conducting heating of a metal band material to be heated according to the present invention.

FIG. 4 is a schematic explanatory view showing one embodiment of a method for electrically conducting heating of a metal heated strip according to the present invention.

FIG. 5 is a graph showing the relationship between the distance from the current-carrying roll to the pinch roll on the high temperature side of the ordinary steel sheets electrically heated in Examples 2-3 and Comparative Example 2 of the present invention, and the intensity of the average streak pattern. .

[Explanation of symbols]

1 Metal heated strip 2a energizing roll 3a energizing roll 4a Upper pinch roll 4b Lower pinch roll

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-176884 (JP, A) JP-A-8-176683 (JP, A) JP-A-6-287644 (JP, A) Actual Kaihei 5- 23481 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C21D 9/62 101 C21D 1/40

Claims (3)

(57) [Claims] 1. A method for electrically heating a metal band to be heated, which comprises heating the metal band to be heated by Joule heat by passing an electric current through the metal band to be heated between the current rolls. Between the metal heated strips from above and below with a pair of pinch rolls .
A method for energizing and heating metal strips to be heated, which is characterized in that the strips are passed while being sandwiched so that the rolling reduction between them is 0.05 to 0.5 kg / mm . 2. The method for electrically heating a metal band to be heated according to claim 1, wherein the metal band to be heated is passed in the vicinity of the current-carrying roll on the high temperature side while being sandwiched by pinch rolls from above and below. 3. The method for electrically heating a metal heated strip according to claim 1 or 2, wherein the metal heated strip between the energizing rolls is pushed up by a pinch roll or pushed down to pass the strip. .