JP2001073028A - Hearth roll for heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an inner water-cooling type hearth roll for conveying a sheet material, such as a steel plate, charged in a heating furnace, and particularly, to improve build-up resistance and also, synthetic heat efficiency of the furnace by restraining a takeout calory to out of the furnace caused by cooling water. SOLUTION: This hearth roll has a structure arranging an intermediate layer 2 composed of a heat insulating material around a heat resistant steel- made roll base body 1 and fitting a sleeve having the heat resistance and the built-up resistance as an outermost layer member 3. The sleeve 3 is a sintered body composed of Al2O3, Al2O3-SiO2, SiC, Si3N4 or the like. The intermediate layer 2 is formed as the low density filling layer (e.g. 0.2 g/cm3) of ceramic fibers. This heat conductivity is desirable to be <=0.5 W/m.K. If necessary, on the outer peripheral surface of the sleeve 3, a thermal-spraying coated layer 4 composed of Al2O3, Al2O3-SiO2, ZrSiO4 or the like, is arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace equipment for continuously heat-treating a sheet-like material such as a steel sheet, for example, an internal part provided in a furnace of another heating furnace such as an annealing furnace in a continuous steel sheet hot-dip coating line. In connection with the improvement of hearth rolls with a water-cooled structure, in particular, the build-up resistance has been increased to extend the life of the rolls and maintain long-term stable operation, and the amount of cooling heat exchange accompanying forced cooling of the rolls has been reduced as much as possible. Suppression,
The purpose is to improve the thermal efficiency of the entire heating furnace.

[0002]

2. Description of the Related Art A hearth roll in a furnace for supporting and guiding a sheet material such as a steel sheet to be charged into a heating furnace must be capable of stably maintaining a smooth roll surface state. If the surface is rough, uneven, or other surface pattern is generated, it is transferred to the product surface, which impairs the quality of the product. For this reason, for example, in a continuous steel sheet galvanizing line, in an annealing furnace or a non-oxidizing furnace that heat-treats a cold-rolled steel sheet serving as a plating base sheet, as a hearth roll, a metal-based or ceramic-based sprayed coating layer is formed on the roll surface. Alternatively, a material having a structure in which a sleeve made of a ceramic sintered body is fitted and fixed as an outermost layer member of the roll is used.

[0003] In a hearth roll installed in a furnace where the ambient temperature exceeds 1000 ° C, build-up (the surface scale of the material to be treated is not sufficient) only by providing a normal sprayed coating layer on the roll surface. The protective effect of the phenomenon of adhesion and deposition on the surface is insufficient. For such a high-temperature atmosphere, a roll having an internal water-cooled structure is generally used. 2, (11) the roll body member (12) is a shaft member for supporting the body member, the shaft member _{(1 2),} the screw shaft (13) (and its peripheral cylindrical support 13 ₁ consisting helical fins 13 ₂ provided on the surface) is supported. The cooling water is supplied to the cooling water flow path defined by the body member and the support (b), circulates in the roll axis direction along the helical fins (13 _2). In the case of a roll using a ceramic sleeve, such an internal water-cooled structure is usually adopted for the purpose of protecting the roll and suppressing build-up.

[0004]

The hearth roll has an internal water-cooled structure, and the outermost layer of the roll is forcibly cooled by conduction heat transfer, so that the heat effect on the roll in the high-temperature furnace atmosphere is reduced and reduced, and the temperature of the roll surface is lowered. As a result, thermal damage to the surface and generation of build-up can be prevented and the useful life of the roll can be improved. However, on the other hand, the heat taken out of the furnace increases as the heat inside the furnace and the material to be heated is taken away by the cooling water, increasing the heating energy required to maintain the atmosphere temperature in the furnace and increasing the thermal efficiency of the entire furnace. A drastic drop is forced.

[0005] As a measure for improving the thermal efficiency, for example, it has been proposed to adopt a roll structure in which the outer periphery of the roll is covered with a heat insulating material such as asbestos or silica / alumina fiber (Japanese Patent Application Laid-Open Nos. 1-290712 and 1-1990). No. 301818). However, the wear resistance and build-up resistance of the heat insulating material to be coated often pose a problem, and it is particularly difficult to apply it to an annealing furnace or the like in a production line of a surface-treated steel sheet requiring high quality. In view of the above, the present invention suppresses an excessive amount of heat exchange, which is the biggest drawback of the internal water cooling structure, improves the heat efficiency of the heating furnace by minimizing the cooling of the rolls and minimizes the build-up of the roll surface. An object of the present invention is to provide a hearth roll capable of maintaining stable furnace operation for a long period of time by improving the properties.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an internal water-cooled hearth roll which is provided in a heating furnace and carries and conveys a sheet-like material to be continuously charged into the furnace. A layer made of a heat insulating material is provided around the body of the roll base having the path at the center of the axis to form an intermediate layer. As the outermost layer member that comes in contact with the material to be heated, ceramic sintering with excellent heat resistance and build-up resistance It has a laminated structure in which a sleeve made of a body is mounted.

In the hearth roll of the present invention, the outermost layer in contact with the high-temperature atmosphere in the furnace and the material to be heated is formed by a sleeve made of a ceramic sintered body having excellent heat resistance and build-up resistance. Omitting forced cooling to the outer layer to maintain sound surface properties, and separating the outermost layer member and the roll base with a heat insulating intermediate layer,
By restricting the cooling water to only the roll base, the amount of heat taken out of the furnace system by the cooling water is suppressed, and the strength of the roll base is maintained.

[0008]

FIG. 1 schematically shows a roll structure of a hearth roll according to the present invention. (1) is a roll substrate, (2) is an intermediate layer made of a heat insulating material, (3) is an outermost layer member, and (4) is a thermal spray coating. Roll base body (1) is made from heat resistant steel body member having a hollow hole which is a cooling water flow path (a) a shaft member attached at both ends (1 _2),
An intermediate layer made of heat insulating material around the cylinder member (1 ₁₎ (2)
Is formed, and a sleeve made of a ceramic sintered body is fitted and mounted as the outermost layer member (3). The outer peripheral surface of the sleeve (3) is covered and protected with a thermal spray coating (4) if desired.

The ceramic component constituting the sleeve as the outermost layer member is preferably an oxide type. The oxide has a standard free energy of formation biased to the negative side, and has excellent thermodynamic stability at high temperatures. As a representative example, Al ₂ O
₃ , ZrO ₂ , Y ₂ O ₃ , SiO ₂ , TiO ₂ , Mg
O, Cr ₂ O ₃ , CeO ₂ , CaO and the like can be mentioned. In addition, non-oxide ceramics can also be used. For example, SiC and Si ₃ N ₄ have excellent thermodynamic stability under a low oxygen partial pressure and high temperature environment and are suitable as the sleeve material of the present invention. The sleeve is made of one component arbitrarily selected from these ceramics, or two or more composite components, for example, ZrO ₂ -8 mol% Y ₂ O ₃ , Al ₂ O ₃
Manufactured as a sintered body made of -13 wt% TiO ₂ , Al ₂ O ₃ —MgO or the like.

[0010] The intermediate layer has a role of a heat insulating layer that blocks conductive heat transfer between the sleeve and the roll body. This layer
It is preferable to form a fiber filling layer in which the packing density is adjusted by applying ceramic fibers. Insulation used is 100
Those having heat resistance that does not easily cause alteration and deterioration in a temperature range of 0 ° C. or more are preferable. For example, silica alumina is preferably used. This intermediate layer desirably has a thermal conductivity of 0.5 W / m · K or less in a temperature range up to 1000 ° C. This thermal conductivity can be ensured by selecting the type of ceramic fiber used as the heat insulating material and adjusting the density of the filling.

In the hearth roll of the present invention, a sprayed ceramic film is provided on the outer peripheral surface of the sleeve, which is the outermost layer member, if desired. The thermal spray coating of ceramics has a small contact angle with metal components such as steel so that build-up components do not easily adhere, and the effect of the coating structure (which is a laminate of fine droplet particles) is Therefore, even if an external object (foreign material) such as a build-up component adheres, a part of the coating particles are taken away together with the external object and hardly adhere (deposition / growth). As an effect of the coating properties of this thermal spraying, the build-up resistance of the roll surface can be further enhanced.

As the ceramic material of the thermal spray coating, an oxide-based material is preferably used from the same viewpoint as that of the above-mentioned sleeve so that practically sufficient thermal stability is ensured in a high temperature environment where the hearth roll is used. Is done. For example, Al ₂ O ₃ , Zr
O ₂ , Y ₂ O ₃ , SiO ₂ , TiO ₂ , MgO, Cr ₂
O ₃ , CeO ₂ , CaO and the like can be mentioned. Thermal spray coating
A single composition arbitrarily selected from these various components, or a composite composition of two or more thereof, for example, ZrO ₂ -8 mol% Y
₂ O ₃ , Al ₂ O ₃ -13 wt% TiO ₂ , Al ₂ O ₃ −
Ceramics made of MgO or the like are formed as a thermal spray material. Note that SiC and Si ₃ C ₄ described above as examples of the non-oxide ceramics forming the sleeve have a narrow liquidus temperature range and most of them exhibit a sublimation phenomenon from a solid phase during thermal spraying. Hard to apply.

The thickness of the thermal spray coating is suitably about 0.1 to 0.3 mm (after polishing). If the thickness is smaller than this, it is difficult to obtain sufficient durability. On the other hand, even if a film thickness exceeding this is provided, the build-up resistance and the effect of improving the durability are small, and the economy is only impaired. Thermal spraying is performed by applying various methods such as plasma flame, gas flame, and explosion flame (detonation). At the time of thermal spraying, the outer peripheral surface of the sleeve is roughened (shot blasting, etc.) as a pretreatment to increase the adhesion strength at the interface between the sleeve and the thermal spray coating. Smooth surface required as a roll surface (for example, arithmetic average roughness Ra
<0.5 μm) is appropriately polished with a diamond grindstone or the like.

[0014]

[Example 1] As a hearth roll installed in a non-oxidizing heat treatment furnace, which is a pretreatment facility for a coated steel strip in a continuous galvanizing line, a test roll having a roll structure shown in FIG. (The application of a thermal spray coating is omitted) was prepared and subjected to an actual machine use test.

(1) Production of Roll An intermediate layer material was filled into a body member (heat-resistant steel hollow pipe) of a roll base, and a sleeve was fitted and mounted. Next, the outer diameter of the sleeve is grinded with a grindstone to adjust the shape accuracy, and a test roll is obtained. The details of the role configuration are as follows.

Roll base body: Grade SUS 304 stainless steel Outer diameter 60 mm (wall thickness 5 mm) Body length 2343 mm

Intermediate layer: heat insulating material SiO₂-Al₂O₃Porous ceramic fiber packing density 0.2g / cm³  Thermal conductivity 0.40W / m · K (at.1000 ℃) Layer thickness 20mm

Sleeve (ceramic sintered body): Grade Mullite ceramic (SiO ₂ -Al ₂ O ₃ ) Outer diameter 120 mm Wall thickness 10 mm Surface roughness Ra 0.5 μm (after grinding)

(2) Actual machine use test and test results Furnace temperature (roll installation part): 1150 ° C Heated material treatment amount: 1,425 kg / min Coolant flow rate inside the roll: 31 l / min

In the above-mentioned actual furnace test, it was observed that all of the test rolls of the invention exhibited excellent build-up resistance and long-term maintainability of shape accuracy such as roundness and cylindricity. Was. Further, each test roll of the invention example and a conventional hearth roll having the entire cooling structure of FIG. 2 (however,
When the calorific value taken out of the furnace system by the cooling water is compared with the outer diameter of the body part 11: 120 mm and the body length: 2400 mm), the hearth roll of the invention example reaches a level equivalent to 20% of the calorific value taken out by the conventional hearth roll. The reduction was measured.

Example 2 A test roll having the roll structure shown in FIG. 1 was prepared as a hearth roll installed in the same non-oxidizing heat treatment furnace as that of the above-described embodiment, and was subjected to a practical use test.

(1) Production of Roll An intermediate layer material was filled into a body member (heat-resistant steel hollow pipe) of a roll base, and a sleeve was fitted and mounted. Next, the outer diameter of the sleeve was ground with a grindstone to adjust the shape precision, and the outer peripheral surface of the sleeve was subjected to a roughening treatment as a pre-spraying treatment.
Thereafter, a coating (sprayed film thickness: 0.35 to 0.45 mm) was formed on the outer peripheral surface of the sleeve by a plasma spraying apparatus, and the coating surface was ground and finished with an artificial diamond grindstone to obtain a test roll. The role configuration is as follows.

Roll base body: Same as in Example 1 Middle layer: Same as in Example 1 Sleeve: Same as in Example 1 Thermal spray coating: Material Zircon (ZrSiO ₄ ) Film thickness 0.25 ± 0.05 mm (polishing) (After finishing) (Surface roughness Ra ≦ 0.5μm)

In addition to the above-mentioned rolls, Al ₂ O ₃ , Y ₂ O _{3 2 to} 8 mol% (partially stabilized zirconia), Al ₂ O ₃ -13 wt% TiO ₂ , Al ₂ O
A test roll having the same roll configuration as above except that _3- MgO was used was prepared.

(2) Actual Machine Use Test and Test Results Each test roll was subjected to an actual machine use test under the same conditions as in Example 1. It was observed that all of the test rolls of the invention examples exhibited excellent build-up resistance and also had long-term maintainability of shape accuracy such as roundness and cylindricity. The amount of heat taken out of the furnace system by the cooling water can be drastically reduced to a level equivalent to 20% of the amount of heat taken out of the conventional roll shown in FIG. 2 (the roll size is the same as the whole-type cooling structure roll described in Example 1). Measured.

[0026]

The hearth roll of the present invention has a structure in which the outermost layer in contact with the furnace atmosphere and the material to be heated is formed of a ceramic sintered body sleeve having heat resistance, build-up resistance and the like. By having a structure in which a sound roll surface can be stably maintained, and the sleeve and the roll base are separated by a heat insulating intermediate layer,
Effectively restrains the amount of heat inside the furnace due to cooling water from being taken out to the outside of the furnace, and has a significant effect on improving the durability and maintenance of rolls, reducing heating energy, and improving overall thermal efficiency. It is.

[Brief description of the drawings]

FIG. 1 is a front sectional view schematically showing a roll structure of a hearth roll of the present invention.

FIG. 2 is a front sectional view schematically showing a roll structure of a conventional whole-cooling type hearth roll.

[Explanation of symbols]

1: roll base body 1 _1: body member 1 _2: shaft member 2: intermediate layer (heat insulating material layer) 3: Sleeve (ceramic sintered body) 4: spray coating a: hollow hole (cooling water channel)

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shinichi Koga 5 Ishizu Nishimachi, Sakai City, Osaka Prefecture Nisshin Steel Co., Ltd. Sakai Works (72) Inventor Kazumi Tani 4-13-4 Fukae Kita-cho, Higashinada-ku, Kobe Tokaro Inside (72) Inventor Yukihiko Hirooka 4-13-4 Fukae-Kitacho, Higashinada-ku, Kobe City Inside (72) Inventor Hiroyuki Kitaaki 4-13-4, Fukae-Kitacho, Higashinada-ku, Kobe Tokalo Corporation (72) Inventor Shinji Motomura 2-56 Sudacho, Mizuho-ku, Nagoya-shi Japan Insulator Co., Ltd. (72) Inventor Sakai ▲ Yoshi ▼ Member 1-20 Sohara Furumachicho, Kakamigahara-shi, Gifu F-term (reference) 3F033 GA06 GB06 GC08 GC10 GE01 HA01 3F049 CA01 LA15 LB10 4K034 AA06 BA04 CA05 EA12 EB04 EB06 EB07 EB08 EC02 EC07 EC09 EC10 EC12 GA18 4K043 AA01 DA05 EA04 GA07 HA04

Claims (5)

[Claims] 1. An internal water-cooled hearth roll provided in a heating furnace for carrying and transporting a sheet-like material to be heated continuously charged in the furnace, wherein a roll base having a cooling water flow path at an axis thereof. A layer made of heat-insulating material is provided around the body of the above to form an intermediate layer, and a sleeve made of a ceramic sintered body with excellent heat resistance and build-up resistance is attached as the outermost layer member that comes in contact with the material to be heated. Hearth roll for a heating furnace having a laminated structure. 2. The sleeve is made of Al ₂ O ₃ , ZrO ₂ , Y
₂ O ₃ , SiO ₂ , TiO ₂ , MgO, Cr ₂ O ₃ , C
2. The hearth roll for a heating furnace according to claim 1, wherein the hearth roll is a sintered body of ceramics comprising one or more components selected from the group consisting of eO ₂ , CaO, SiC, and Si ₃ N ₄ . 3. The hearth roll for a heating furnace according to claim 1, wherein the intermediate layer is a low-density packed layer of ceramic fibers. 4. The hearth roll for a heating furnace according to claim 3, wherein the intermediate layer has a low thermal conductivity not exceeding 0.5 W / m · K in a temperature range up to 1000 ° C. 5. An outer peripheral surface of a sleeve is provided with Al ₂ O ₃ , Zr
O ₂ , Y ₂ O ₃ , SiO ₂ , TiO ₂ , MgO, Cr ₂
One or two selected from the group consisting of O ₃ , CeO ₂ , and CaO
The hearth roll for a heating furnace according to any one of claims 1 to 4, further comprising a ceramic sprayed coating comprising at least one kind of component.