JPH0864341A - Energizing roll - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a current-carrying roll capable of sufficiently transferring heat input from a material to be heated in the width direction and causing almost no thermal crown. A current-carrying roll, which is in continuous contact with a material to be heated in a high temperature region, has a heat pipe embedded in a metal shell and has a diameter of 20 to 20 mm.
An energizing roll having a length of 30 mm.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a current-carrying roll.
More specifically, the present invention relates to a current-carrying roll used when heat-treating a band-shaped steel plate or the like such as quenching or annealing.

[0002]

2. Description of the Related Art Conventionally, a strip-shaped steel sheet to be continuously fed has been arranged at predetermined intervals along its feeding path as an electric heating device for performing heat treatment such as quenching and annealing on a strip-shaped steel sheet. An energization heating device is known for contacting the energizing rolls and applying a voltage between the energizing rolls to energize and heat the strip steel sheet.

In the above-mentioned electric heating device, the electric current roll on the heating outlet side is heated by the strip-shaped steel plate which has been heated to a high temperature by the electric current heating. At this time, the axial length of the electric current roll is larger than the width of the strip-shaped steel plate. Since it is long, the contact portion near the center of the energizing roll is directly and intensively heated, and the non-contact portions near both ends of the energizing roll are not heated so much. Therefore, even if the energizing roll has a perfect diametrical dimension at the time of manufacture, a temperature deviation occurs in the axial direction during operation, and a diameter deviation (hereinafter referred to as a thermal crown) occurs.

As described above, when a thermal crown is generated on the energizing roll, a contact failure occurs between the energizing roll and the strip-shaped steel sheet, particularly at the edge portion of the strip-shaped steel sheet where the gap between the energization roll and the strip-shaped steel sheet becomes large. There is a problem that sparks are generated and spark flaws are formed on the surface of the energizing roll and the surface of the strip-shaped steel sheet, and in particular, the spark flaw of the energizing roll continuously causes transfer flaws on the strip-shaped steel sheet thereafter.
As a result, the life of the current-carrying roll and the quality of the strip-shaped steel sheet are deteriorated.

Therefore, in order to prevent the generation of sparks between the current-carrying roll and the material to be heated due to the thermal crown of the current-carrying roll, a soaking roll having a heat pipe installed therein is used. Another electric heating device has been proposed (JP-A-5-62762).

However, when conducting an energization test using the temperature equalizing roll, the heat input from the material to be heated into the temperature equalizing roll exceeds the heat transfer capacity of the heat pipe, and the temperature equalizing in the width direction of the temperature equalizing roll is performed. However, there is still a problem that a thermal crown is generated and a spark may occur between the temperature-equalizing roll and the material to be heated.

[0007]

Therefore, in view of the above-mentioned prior art, the present inventors can sufficiently transfer the heat input from the material to be heated in the width direction and generate a small amount of thermal crown. As a result of earnest studies for the purpose of providing a current-carrying roll, the diameter of the heat pipe was made larger than that of the conventional product (10 to 15 mm) and was adjusted to be within a specific range. They have found that they can be suppressed almost, and have completed the present invention.

[0008]

That is, the present invention relates to a current-carrying roll which is brought into contact with a material to be heated continuously fed in a high temperature region, in which a heat pipe is embedded in a metal shell, The present invention relates to a current-carrying roll, wherein the heat pipe has a diameter of 20 to 30 mm.

[0009]

OPERATION AND EXAMPLES As described above, the current-carrying roll of the present invention is a current-carrying roll that comes into contact with a continuously heated material to be heated in a high temperature region, in which a heat pipe is embedded in a metal shell. And the diameter of the heat pipe is 20 to 3
It is characterized by being 0 mm.

In the present invention, since the heat pipe has a built-in heat shell in the metal shell of the energizing roll, when the contact portion of the energizing roll is directly and intensively heated by the high temperature material to be heated, Also, the heat is substantially transferred by the heat pipe to the non-contact portion of the energizing roll, the temperature deviation in the axial direction of the energizing roll is suppressed, and as a result, the generation of the thermal crown of the energizing roll is effectively prevented. .

Further, in the present invention, since the diameter of the heat pipe is set within a specific range, the heat input from the material to be heated to the energizing roll is within the heat transfer capacity of the heat pipe. The temperature distribution in the width direction of the energizing roll can be reduced.

Further, in the present invention, when the heat pipe is provided at a specific depth from the surface of the current-carrying roll, it withstands the surface pressure required for current-carrying and, moreover, the temperature of the current-carrying roll is uniform. There is an advantage that it can be realized.

The energizing roll of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic explanatory view in a radial cross section showing an embodiment of the energizing roll of the present invention.

In FIG. 1, a current-carrying roll 3 is brought into contact with a material to be heated in a high temperature region such as a strip-shaped steel plate, and has a metal shell 1 containing a heat pipe 2 and a hollow portion 4. Have.

In the energizing roll 3, a plurality of heat pipes 2 built in the metal shell 1 are provided along the axial direction of the metal shell 1.

The heat pipe 2 is one in which a heat medium is enclosed in a closed pipe body, the heat medium is evaporated on the high temperature side of the closed pipe body, and the generated vapor is cooled on the low temperature side of the closed pipe body. It has a function of condensing and returning to a liquid, and the condensate returns to a high temperature side by a capillary action or a centrifugal force.
At this time, the latent heat necessary for evaporation is supplied to the heat medium on the high temperature side, and the heat is released on the low temperature side.

The heat medium used in the heat pipe 2 varies depending on the target heating temperature of the material to be heated such as the strip steel plate. Specific examples of such a heat medium include water, naphthalene, sodium and the like. The heat medium has an optimum operating temperature range, for example, in the case of water, up to about 300 ° C., and in the case of naphthalene, 300 to 300 ° C.
Up to about 400 ° C, and in the case of sodium, up to about 1000 ° C.

According to the research conducted by the present inventors, it has been found from experimental results that the heat transfer capacity of the heat pipe 2 is proportional to the cube of the diameter of the heat pipe 2. Therefore, like the energizing roll 3, it has good contact with the material to be heated,
When the heat input is large, the heat pipe 2 with a small diameter
If you just increase the number of
A thermal crown will be generated.

On the other hand, in the present invention, the diameter (inner diameter) d of the heat pipe 2 is within a specific range, that is, 20.
Since it is set within the range of up to 30 mm, the effect of effectively suppressing the generation of the thermal crown is exhibited.

The number of heat pipes 2 provided on the metal shell 1 is 16 in FIG. 1, but in reality, it depends on the outer diameter of the metal shell 1 and the like, so it can be determined in a general manner. Although not possible, normally, for the current-carrying roll 3 having a diameter of the metal shell 1 of 300 to 600 mm,
From the viewpoint of sufficiently reducing the amount of thermal crown generation and ensuring the roll strength to withstand the surface pressure required for energization, the number is preferably 30 to 50.

If the embedding depth t from the surface of the metal shell 1 of the heat pipe 2 is too shallow,
The surface of the metal shell 1 is plastically deformed by the contact pressure between the current-carrying roll 3 and the material to be heated, which is necessary for the current flow, and when it is too deep, the temperature-equalizing effect in the width direction is significantly increased. As a result, the thermal crown and the sparks are generated.
It is preferably about the same.

In the present invention, the length of the heat pipe 2 is the same as the width of the metal shell 1 or equal to the width of the metal shell 1 in order to effectively prevent the generation of the thermal crown. It is preferable that the lengths are close to each other.

The diameter of the metal shell 1 cannot be unconditionally determined because it depends on the intended use of the energizing roll 3 or the like. For example, when the energizing roll 3 is heat-treated at about 750 to 900 ° C. on a strip steel sheet. When used for, it is preferable that the thickness is about 300 to 600 mm.

A cavity 4 is provided in the metal shell 1, and a heating temperature of the heat pipe 2 is set to a predetermined operating temperature by introducing a coolant such as water into the cavity 4 if necessary. It can be adjusted to fall within the range.

The diameter of the hollow portion 4 is not particularly limited and is usually about 30 to 100 mm.

The outer diameter of the shaft (not shown) of the current-carrying roll 3 has sufficient mechanical strength, and the shaft is deflected by the pressure-reduction force necessary for energization, and the distribution of the force in the axial direction is distributed. Is not uniform, and particularly in the vicinity of the center, the rolling force is preferably about 200 to 400 mm so as not to be insufficient.

The current-carrying roll 3 of the present invention constructed as described above is heated by a material to be heated, such as a strip-shaped steel plate, which has been heated to a high temperature during the current-carrying heating.
Since the vicinity of the center is directly and intensively heated, the vicinity of the center corresponds to the high temperature side of the heat pipe 2. Further, the vicinity of both ends of the energizing roll 3 is not heated so much and thus corresponds to the low temperature side of the heat pipe 2.

Here, in the present invention, since the diameter d of the heat pipe 2 is 20 to 30 mm as described above, the heat on the high temperature side is substantially generated by the evaporation and condensation action of the heat medium in the heat pipe 2. In addition, it moves to the low temperature side without over-spec due to heat input of the energizing roll and without causing dryout. Evaporation / condensation of the heat medium is a phase change process that occurs even with a very small temperature difference, and as a result, the temperature deviation in the axial direction of the energizing roll 3 can be suppressed to a very small extent. As a result, the energizing roll 3 has almost no thermal crown.

When the heat pipe 2 is provided at a specific embedding depth (5 to 15 mm) from the surface of the current-carrying roll 3, it withstands the surface pressure required for current-carrying, and the temperature of the current-carrying roll 3 is kept constant. There is an advantage that it can be realized.

Next, the energizing roll of the present invention will be described in detail based on examples, but the present invention is not limited to such examples.

Example 1 A heat pipe having a diameter of 20 mm, a transfer distance of 700 mm, and a heat medium of water was prepared.
A low alloy steel shell with a diameter of 0 mm, an inner diameter of 250 mm and a width of 1500 mm was embedded with 40 pieces at a depth of 15 mm from the surface at equal intervals, and a 900 mm wide steel plate was heated to 750 ° C. while introducing cooling water into the cavity of the shell. 3 for electric heating
When operated for 0 minutes, the temperature deviation in the width direction of the energizing roll was several degrees Celsius or less, and sparkless energization could be performed.

Example 2 In Example 1, the heat pipe has a diameter of 20 m.
When the current-carrying roll was operated for 30 minutes in the same manner as in Example 1 except that the current-carrying roll was changed from 30 m to 30 mm, the temperature deviation in the width direction of the current-carrying roll was several degrees Celsius or less.
I was able to perform sparkless energization.

Comparative Example 1 In Example 1, the heat pipe has a diameter of 20 m.
When the energizing roll was operated for 30 minutes in the same manner as in Example 1 except that the m-thickness was changed to the 15 mm-thickness, a dry-out of the heat pipe occurred and an excessive temperature deviation in the width direction occurred in the energizing roll. Occurred, and a severe spark occurred between the steel plate and the energizing roll.

From the results of Examples 1 and 2 and Comparative Example 1,
When a heat pipe with a diameter of 20 to 30 mm was used, the heat input to the energizing roll was not over-specified, dry out did not occur, and the heat input was extremely uneven. It can be seen that the thermal crown does not occur even in the case.

[0036]

A heat pipe is used in the current-carrying roll of the present invention, and direct and concentrated heat transfer from the material to be heated to the contact part of the current-carrying roll heats the non-contact part of the current-carrying roll. Since it is moved substantially by the pipe, it is possible to suppress the generation of thermal crown of the energizing roll.

Further, since the diameter of the heat pipe used for the energizing roll of the present invention is a specific one (20 to 30 mm), the heat input to the energizing roll does not cause over-spec, and the dryout occurs. There is no effect, and even if there is a remarkably uneven heat input, the effect of not generating a thermal crown is achieved.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view in a radial cross section showing an embodiment of an energizing roll of the present invention.

[Explanation of symbols]

 1 metal shell 2 heat pipe 3 energizing roll

Claims (3)

[Claims] 1. A current-carrying roll that is in continuous contact with a material to be heated in a high-temperature region of the material to be heated, wherein a heat pipe is embedded in a metal shell and has a diameter of 2
A current-carrying roll having a length of 0 to 30 mm. 2. The embedding depth of the heat pipe is 5 to 15
The energizing roll according to claim 1, which has a size of mm. 3. The diameter of the metal shell is 300 to 600 mm.
And the number of heat pipes used is 30 to 50, and the energizing roll according to claim 1 or 2.