JPH06346134A - Hearth roll for continuous heat treatment furnace - Google Patents

Abstract

PURPOSE:To always keep the crown of a roll during operation to a suitable state even if the size of a band metal or the operational condition changes by fitting a sleeve having lower thermal expansion coefficient and the same or higher regidity than the barrel part of the roll on the inner peripheral surface at a position of the barrel part of the hearth roll contacting with the band metal. CONSTITUTION:In a continuous heat treatment furnace for band metal 3, the hollow hearth roll arranged at the position having the atmospheric temp. higher than the temp. of the band metal 3 is fitted with the sleeve 2 composed of a material having the lower thermal expansion coefficient and the same or higher rigidity than the constituting material of the roll barrel part 1, on the inner peripheral surface at the position of the roll barrel part 1 contacting with the band metal 3. Then the sleeves 2 can be fitted and joined on two positions in the inner peripheral surface of the roll barrel part 1 contacting with the both edges of the band metal. By this method, the crown is always kept to the suitabile state during the operation and the development of meandering and heat buckling of the band metal 3 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hearth roll used when heat treatment such as annealing is performed by continuously passing a strip plate such as a steel plate through a heating furnace.

[0002]

2. Description of the Related Art When a strip such as a steel sheet is passed through a continuous heat treatment furnace, the strip is supported and conveyed by a hearth roll provided in the furnace. At this time, a crown is provided on the body of the hearth roll so that the strip does not meander in the axial direction of the hearth roll. If the crown is small, the strip will meander, and it will not be able to perform proper heat treatment as it will be displaced from the predetermined position in the furnace.
It also causes troubles such as contact with the furnace wall. If the crown is too large, a wrinkle called a heat buckle occurs on the strip. Therefore, the crown of the roll body must always be maintained at an appropriate value during operation.

By the way, when the set temperature of the heating furnace is changed, or the size (width, thickness) of the strip to be stripped and the stripping speed are changed even if the temperature is constant, the inlet side and outlet side of the heating zone and In places such as the cooling zone entrance side where the difference between the ambient temperature and the strip plate temperature is large, the crown of the roll body may change, and meandering or heat buckling may occur. That is, while the temperature of the hearth roll is the ambient temperature, the strip plate temperature is lower than the ambient temperature on the heating zone entrance side.
As shown in the partial cross-sectional view of (a), the portion of the roll body 1 in contact with the strip 3 is cooled and contracts, the crown becomes smaller, and the strip 3 becomes more likely to meander. Further, since the strip plate temperature is higher than the ambient temperature on the heating zone outlet side and the cooling zone inlet side,
As shown in (b), the portion of the roll body 1 in contact with the strip plate 3 expands and the crown becomes large, and a heat buckle is likely to occur on the strip plate 3. In FIG. 3, 4 is a roll shaft and 5 is an end plate.

As a means for solving such a problem, the present applicant has heretofore provided a layer of a metal having high thermal conductivity on the inner peripheral surface of the body of a hollow hearth roll made of heat-resistant steel to form a temperature distribution in the axial direction of the roll. Japanese Patent Laid-Open No. 2-163326 proposes to make uniform and maintain an appropriate crown, but the sufficient effect has not been obtained. Further, a large number of slits continuous in the axial direction and penetrating the hollow portion are provided on the outer periphery of the body portion of the hearth roll to absorb the strain in the circumferential direction of the roll to prevent the crown from varying.
Although proposed by Japanese Patent No. 1328, there is a problem that the sprayed film is easily peeled off when the roll surface is coated with the sprayed film. Furthermore, Japanese Patent Publication No. 58-43454 proposes a control method for maintaining a proper crown by spraying a refrigerant whose temperature and flow rate are adjusted from inside or outside the hollow hearth roll. In addition to this, as cooling methods from the inside, there are JP-A-58-56826 and JP-A-4-202716, and as external cooling methods, JP-A-62-253734 and JP-A-63-263.
There is a publication of 38532. However, the internal cooling method has a problem that the structure is complicated and the burden of maintenance is heavy, and the external cooling method has a problem that a countermeasure considering the influence on the atmosphere in the furnace and the strip is required.

[0005]

DISCLOSURE OF THE INVENTION The present invention, in a continuous heat treatment furnace for strips such as steel sheets, maintains an appropriate crown during operation even if the size of strips or operating conditions are changed.
It is an object of the present invention to provide a hearth roll that does not generate meandering or heat buckle of a strip, has a simple structure, is effective, and has no adverse effect on the atmosphere or the strip.

[0006]

SUMMARY OF THE INVENTION The present invention is a hollow hearth roll installed in a continuous heat treatment furnace for strips, which has a coefficient of thermal expansion different from that of the constituent material of the roll body. A sleeve made of a material having rigidity equal to or higher than that of the
By providing it on the inner peripheral surface at a specific position in the roll axis direction, local thermal expansion and contraction of the roll body is suppressed, and an appropriate crown is maintained.

FIG. 1 (a) shows a hearth roll of the present invention which is installed at a location where the ambient temperature of the continuous heat treatment furnace is higher than the temperature of the strip plate 3. The hearth roll of FIG. A sleeve 2 made of a material having a low coefficient of thermal expansion and rigidity equal to or higher than that of the roll body 1 is fitted to the inner peripheral surface of the portion of the roll body 1 in contact with the strip plate 3. At a place where the ambient temperature is higher than the strip plate temperature, such as the heating zone entrance side of the continuous heat treatment furnace, the portion of the roll body 1 in contact with the strip plate 3 is cooled and contracts to have a small crown as shown in FIG. 3 (a). However, in the hearth roll of the present invention, as shown in FIG. 1 (a), the sleeve 2 is fitted on the inner peripheral surface of the roll body 1 at the portion in contact with the strip 3, and the sleeve 2 is a roll. Body 1
Since it has a lower coefficient of thermal expansion, it does not easily shrink even when cooled, and is made of a material having rigidity equal to or higher than that of the roll body 1, so that the roll body 1 is prevented from shrinking, A proper crown is maintained.

FIG. 1 (b) also shows a hearth roll of the present invention installed at a location where the ambient temperature of the continuous heat treatment furnace is higher than the temperature of the strip plate 3, and the coefficient of thermal expansion of the constituent material of the roll body 1 A sleeve 2 made of a material having a high coefficient of thermal expansion and a rigidity equal to or higher than that of the roll body 1 is joined to the inner peripheral surface of the roll body 1 at two portions in contact with both edges of the band plate 3. There is. Also in this case, as shown in FIG. 3 (a), the portion of the roll body 1 in contact with the strip 3 is cooled and shrinks, and the crown tends to become smaller. The sleeve 2 is joined to the inner peripheral surface of the roll body 1 at the two portions that contact the edges of the strip 3 as shown in FIG.
The sleeve 2 has a coefficient of thermal expansion higher than that of the roll body 1, so that the sleeve 2 is made of a material having a larger shrinkage amount due to cooling than the roll body 1 and a rigidity equal to or higher than that of the roll body 1. Therefore, the roll body 1 is uniformly contracted up to both edges of the strip 3 and the proper crown is maintained.

FIG. 1 (a) shows a hearth roll of the present invention which is installed at a place where the ambient temperature of the continuous heat treatment furnace is lower than the temperature of the strip 3, and the coefficient of thermal expansion of the constituent material of the roll body 1. A sleeve 2 made of a material having a lower coefficient of thermal expansion and a rigidity equal to or higher than that of the roll body 1 is fitted and joined to the inner peripheral surface of the portion of the roll body 1 in contact with the strip plate 3. ing. Since the strip plate temperature is higher than the ambient temperature on the heating zone outlet side and the cooling zone inlet side of the continuous heat treatment furnace, the portion of the roll body 1 in contact with the strip plate 3 has a crown due to thermal expansion as shown in FIG. 3B. Although the hearth roll of the present invention tends to become large, as shown in FIG. 1A, the sleeve 2 is fitted and joined to the inner peripheral surface of the roll body 1 at the portion in contact with the strip plate 3. Since the sleeve 2 has a coefficient of thermal expansion lower than that of the roll body 1, it does not easily expand even when heated, and is made of a material having rigidity equal to or higher than that of the roll body 1. The thermal expansion of No. 1 is suppressed and an appropriate crown is maintained.

FIG. 1 (b) also shows the hearth roll of the present invention installed at a place where the ambient temperature of the continuous heat treatment furnace is lower than the temperature of the strip plate 3, and the coefficient of thermal expansion of the constituent material of the roll body 1. A sleeve 2 made of a material having a higher coefficient of thermal expansion and a rigidity equal to or higher than that of the roll body 1 is fitted to the inner peripheral surfaces of the two portions of the roll body 1 in contact with both edges of the band plate 3. Has been done. Also in this case, as shown in FIG. 3 (b), the portion of the roll body 1 in contact with the strip 3 tends to have a large crown due to thermal expansion, but the hearth roll of the present invention is as shown in FIG. 1 (b). The sleeve 2 is joined to the inner peripheral surface of the roll body portion 1 at two portions in contact with both edges of the strip plate 3,
Since the sleeve 2 has a higher coefficient of thermal expansion than the roll body 1, the amount of expansion due to heating is large, and the sleeve 2 is made of a material having rigidity equal to or higher than that of the roll body 1. Expands evenly to both edges of the strip 3,
A proper crown is maintained.

In the case of FIG. 1 (a) of the present invention,
The width of the sleeve 2 is preferably from the length of the parallel portion of the taper roll body 1 to the width of the strip plate 3. If the width is too narrow, a sufficient effect cannot be obtained, and if it is too wide, the weight of the roll as a whole becomes large, so that the rotational inertia becomes large and it becomes impossible to follow the speed change.

In the case of FIG. 1B, the gap between the sleeves 2 is equal to or larger than the parallel length of the taper roll body 1, and the widths of the sleeves 2 are at both edges of the strip 3. Is preferred. If the gap is too narrow and the edge of the strip 3 deviates from the position of the sleeve 2, a sufficient effect cannot be obtained. When there are various kinds of strip widths of the strips to be passed, it is preferable to determine the width and position of the sleeve so that all the strips fall within the above range.

Further, the sleeve 2 in the present invention is required to be made of a material which is not distorted by the thermal expansion and contraction of the roll body portion 1, specifically, a material having a high rigidity at the operating temperature or Use thick ones. Further, the sleeve 2 and the roll body 1 may be joined by welding, brazing or bonding, or the material of the sleeve 2 may be sprayed on the roll body 1 having a required thickness.

[0014]

【Example】

(Invention Example 1) As shown in FIG. 2A, the sleeve 2 was fitted to the inner peripheral surface of the central portion in the axial direction of the roll body 1 of the hollow hearth roll. The sleeve 2 was provided with a protrusion 6 and was fitted into a groove provided on the inner peripheral surface of the roll body 1. Roll body 1 is 8
20% C with a thermal expansion coefficient of 1.64 × 10 ^-5 at 00 ° C
It was made of r-40% Ni-Fe alloy and had a length of 2300 mm, a diameter of 800 mm and a wall thickness of 25 mm. The sleeve 2 is 3% Ni-Cr-M having a thermal expansion coefficient of 1.07 × 10 ^-5 at 800 ° C.
It is made of o alloy and has a length of 1000 mm and a wall thickness of 10 mm. Such a hollow hearth roll is installed in an atmosphere at a furnace temperature of 700 ° C. on the heating zone entrance side of a steel plate continuous annealing furnace, and a material temperature of 400
℃, strip width 855mm, strip thickness 0.8mm steel strip speed 30
As a result of passing the plate at 0 m / min, the crown of the hearth roll was properly maintained throughout the operation, and neither meandering nor heat buckle occurred.

(Inventive Example 2) As shown in FIG. 1 (b), sleeves 2 were fitted and welded to the inner peripheral surfaces of two axial positions of the roll body 1 of the hollow hearth roll. Roll body 1 is 70
20% Cr with thermal expansion coefficient of 1.64 × 10 ^-5 at 0 ° C
Made of -40% Ni-Fe alloy, length 2300mm, diameter 8
The thickness was 00 mm and the wall thickness was 25 mm. The sleeve 2 is made of a 13% Mn-Fe alloy having a coefficient of thermal expansion of 2.19 × 10 ⁻⁵ at 700 ° C., and has a length of 250 mm and a wall thickness of 20 mm, and the gap between both sleeves 2 is 700 mm. Such a hollow hearth roll is installed in an atmosphere at a furnace temperature of 800 ° C on the heating zone entrance side of a steel plate continuous annealing furnace, and a steel strip having a material temperature of 500 ° C, a plate width of 1100 mm, and a plate thickness of 1.0 mm is passed at a strip speed of 270 m. As a result, the hearth roll crown was properly maintained throughout the operation, and neither meandering nor heat buckling occurred.

(Invention Example 3) As shown in FIG. 1 (a), a sleeve 2 was fitted and welded to the inner peripheral surface of the central portion of the roll body 1 of the hollow hearth roll in the axial direction. Roll body 1 is 800
15% Cr-having a thermal expansion coefficient of 1.53 × 10 ^-5 at ℃
Made of 60% Ni-Fe alloy, length 2300mm, diameter 80
The thickness was 0 mm and the thickness was 25 mm. The sleeve 2 is made of a 3% Ni-Cr-Mo alloy having a coefficient of thermal expansion of 1.07 x 10 ^-5 at 800 ° C, and has a length of 1000 mm and a wall thickness of 10 mm. Such a hollow hearth roll is installed in an atmosphere at a furnace temperature of 500 ° C on the cooling zone entrance side of a steel plate continuous annealing furnace, and a steel strip having a material temperature of 800 ° C, a plate width of 950 mm, and a plate thickness of 1.0 mm is passed at a strip speed of 290 m. /
As a result of passing the plate in minutes, the crown of the hearth roll was properly maintained throughout the operation, and neither meandering nor heat buckle occurred.

(Inventive Example 4) As shown in FIG. 2 (b), the sleeve 2 was fitted to the inner peripheral surface at two axial positions of the roll body 1 of the hollow hearth roll. The sleeve 2 was provided with a protrusion 6 and was fitted into a groove provided on the inner peripheral surface of the roll body 1. The roll body 1 has a coefficient of thermal expansion of 1.53 × 1 at 800 ° C.
0 ^-5 made 15% Cr-60% Ni- Fe alloy, length 2
The thickness was 300 mm, the diameter was 800 mm, and the wall thickness was 25 mm. The sleeve 2 has a coefficient of thermal expansion of 1.90 × 10 ⁻⁵ at 800 ° C.
% Cr-8% Ni-Fe alloy, length 250 mm, wall thickness 35 mm, gap between both sleeves 2 700 mm. Such a hollow hearth roll was installed in an atmosphere at a furnace temperature of 700 ° C. on the cooling zone entrance side of a steel sheet continuous annealing furnace, and a material temperature of 800
℃, strip width 1050mm, strip thickness 1.2mm steel strip speed 2
As a result of passing the plate at 90 m / min, the crown of the hearth roll was properly maintained throughout the operation, and neither meandering nor heat buckling occurred.

(Prior Art Example 1) In Example 1 of the present invention, as a result of using a hearth roll without a sleeve, the steel strip meandered and could not be threaded.

(Prior Art Example 2) In the invention example 3, as a result of using the hearth roll without the sleeve, a heat buckle was generated in the steel strip.

[0020]

According to the present invention, in a continuous heat treatment furnace for strips such as steel sheets, even if the size of strips or operating conditions are changed,
The proper crown is always maintained during the operation, and the meandering of the strip and the heat buckle are suppressed. Further, the hearth roll of the present invention is effective with a simple structure, and does not adversely affect the atmosphere in the furnace and the strip.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a hearth roll of the present invention in use.

FIG. 2 is a partial cross-sectional view of a hearth roll showing an embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of a conventional hearth roll during use.

[Explanation of symbols]

 1: Roll body part 4: Roll shaft 2: Sleeve 5: End plate 3: Strip plate 6: Protrusion

Claims (4)

[Claims] 1. A hollow hearth roll installed at a location where the temperature of the atmosphere is higher than the temperature of the strip in a continuous heat treatment furnace for strips, the thermal expansion being lower than the coefficient of thermal expansion of the constituent material of the roll body. For a continuous heat treatment furnace, characterized in that a sleeve made of a material having a high rigidity and a rigidity equal to or higher than that of the body is fitted to an inner peripheral surface of a portion of the body contacting the strip plate. Hearth roll. 2. A hollow hearth roll installed at a location where the temperature of the atmosphere is higher than the temperature of the strip in a continuous heat treatment furnace for strips, the thermal expansion being higher than the coefficient of thermal expansion of the constituent material of the roll body. And a sleeve made of a material having a rigidity equal to or higher than that of the body is fitted and joined to the inner peripheral surfaces of the two portions of the body contacting both edges of the strip. A characteristic hearth roll for continuous heat treatment furnaces. 3. A hollow hearth roll installed at a location where the temperature of the atmosphere is lower than the temperature of the strip in a continuous heat treatment furnace for strips, the thermal expansion being lower than the coefficient of thermal expansion of the constituent material of the roll body. And a sleeve made of a material having a rigidity equal to or higher than that of the body is fitted and joined to an inner peripheral surface of a portion of the body contacting the strip plate. Hearth roll for heat treatment furnace. 4. A hollow hearth roll installed in a continuous heat treatment furnace for strips at a location where the temperature of the atmosphere is lower than the temperature of the strips, the thermal expansion being higher than the coefficient of thermal expansion of the constituent material of the roll body. And a sleeve made of a material having a rigidity equal to or higher than that of the body portion is fitted to the inner peripheral surfaces of the two portions of the body portion in contact with both edges of the strip plate. Hearth roll for continuous heat treatment furnace.