JPH06306450A - Carbon roll - Google Patents

Abstract

PURPOSE:To prevent the generation of a thermal crown and to improve the wear resistance of a carbon roll by forming a metal carbide layer on the roll surface. CONSTITUTION:This roll consisting essentially of carbon is brought into contact with a material heated to high temp. and used to transport, energize and cool the material, and a metal carbide layer is formed on the roll surface. Otherwise, a metal layer is provided on the carbon as an intermediate layer, and a metal carbide layer is formed thereon as the outermost surface layer. A graphite with high heat conductivity and low thermal expansion is utilized for the roll main body, and a metal carbide highly resistant to wear and having a linear expansion coefficient almost identical to that of the carbon main body is used as the surface layer. Consequently, a nonuniform temp. distribution is hardly generated on the roll surface, a thermal crown is not formed, and the wear resistance is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier roll used in a heat treatment furnace and a current-carrying roll used for cooling or energizing a roll, and more particularly to a thermal crown based on the temperature distribution even when contacting with a high temperature metal material. The present invention relates to a carbon roll that suppresses heat and has excellent wear resistance.

[0002]

2. Description of the Related Art In a hearth roll in a furnace used for annealing metal, for example, continuous annealing of cold-rolled steel sheet, when the atmosphere temperature of the furnace is high and the steel sheet in contact is lower than the ambient temperature, the temperature at the center of the roll is It is low and the roll edge has a higher temperature, resulting in a temperature distribution. Depending on this temperature distribution, the profile of the roll results in a concave crown with a centrally depressed and high edge due to thermal expansion. On the contrary, when it comes into contact with a steel plate having a temperature higher than the ambient temperature of the furnace, a cooling roll used to cool the heated steel plate, or an energizing roll used for electric heating, the roll temperature is higher than that of the steel plate. The parts that come in contact with the low and high temperature steel plates are heated to high temperatures,
The temperature of the portion that does not come into contact with the steel plate becomes low and a convex crown is formed. In such a state, the steel sheet is likely to have a temperature distribution and a tension distribution, the shape is deteriorated, and an ear wave or a diaphragm is likely to occur. In addition, when the width of the steel plate changes, the profile of the roll changes, the shape of the steel plate becomes defective, and meandering easily occurs, and it is necessary to operate at low speed until the profile of the roll stabilizes. There was.

Further, in the case of a current-carrying roll, when the roll is crowned, the contact pressure on the steel plate is partially reduced, and as a result, a spark is generated between the steel plate and the current-carrying roll, and melting marks are generated on both the steel plate and the current-carrying roll. There is a problem that product quality is deteriorated and roll life is shortened.

As described above, the change of the roll profile causes various inconveniences. Therefore, in order to make the roll surface temperature uniform, JP-A-57-13679 is used.
Japanese Patent Publication No. 3 discloses that a conductive magnetic film is formed on the surface of the roll so that the resistance value of the portion where the magnetic flux density is high becomes large, and a uniform temperature distribution is obtained when induction heating is performed. ing. Further, Japanese Patent Application Laid-Open No. 61-79733 describes a conveying roll in which the surface of the roll body is made of a conductive ceramic so that it can be electrically heated. It is described that this roll can make the temperature distribution in the width direction of the roll uniform by conducting electricity through a conductive ceramic and heating the roll.

[0005]

However, even if these conventional techniques try to make only the roll surface temperature uniform, if a substance different from the roll surface temperature comes into contact with the roll, the roll surface temperature distribution also becomes non-uniform. Since heat is transferred to each part from the bearing to the roll, it is difficult to make the temperature uniform inside the roll, and it is difficult to make the roll profile uniform.

It is an object of the present invention to provide a roll which is less likely to have a non-uniform temperature distribution on the roll surface, thus preventing the generation of a thermal crown and also having abrasion resistance.

[0007]

In order to solve the above-mentioned problems, the present invention provides (1) a carbon-based roll which is brought into contact with a material heated to a high temperature to carry, carry, or cool. A layer made of metal carbide is formed on the roll surface. (2) In a roll mainly composed of carbon which is brought into contact with a material heated to a high temperature to carry, carry, or cool, a metal layer is provided as an intermediate layer on the carbon, and a metal carbide is formed on the outermost layer. Is provided.

[0008]

In the present invention, the roll comes into contact with a high temperature metal,
The purpose of the roll is to prevent the temperature distribution from being generated due to the ambient temperature and prevent the roll from expanding even if the temperature distribution is generated. That is, focusing on the material of the long length of the roll, a material that easily diffuses heat and does not expand thermally was examined. Materials with high thermal conductivity include copper and silver, and materials with low expansion have non-conductive materials such as ceramics. Generally, materials with high thermal conductivity have large expansion and conversely materials that do not easily expand. It has the property of poor heat conduction. However, extruded graphite is a peculiar material that has both properties of good thermal conductivity and low expansion. Extruded graphite has a property that its thermal conductivity becomes higher as the crystallization progresses. In particular, since the crystals are oriented in the extrusion direction, the heat conduction is particularly high in this direction, and the heat conduction is extremely good in the extrusion direction, and the heat conductivity is 2 to 3 times that of iron which is usually used. Therefore, when the extrusion direction is the roll cylinder length, the heat easily diffuses in the cylinder length direction, and the temperature distribution does not easily occur even when contacting with a high temperature metal. Further, graphite has a small coefficient of linear expansion and has an elongation of only 1/2 to 1/10 that of iron. Especially in graphite, the elongation in the direction perpendicular to the extrusion direction is particularly small,
Even if there is a temperature distribution, the amount of expansion is small and the profile is unlikely to change.

As described above, graphite has extremely good characteristics in terms of shape stability with respect to temperature, but has the property of being semi-soft, and wear resistance becomes a problem when used as a roll. Therefore, as a method of imparting the wear resistance of the roll while fully utilizing the properties of graphite, it was considered to form a thin wear resistant coating on the roll surface.
It is difficult to form a film because carbon is generally poor in reactivity, but since certain metals form carbides at high temperatures, a compound that reacts with these carbons is mixed with a binder, etc. Alternatively, there is a method of applying the material by spraying or the like and then raising the temperature to a temperature at which carbide is formed and firing it, or a method of directly forming the carbide on carbon by thermal spraying. Carbide has a high hardness and usually has a Vickers hardness of 500 kg / mm ² or more and a linear expansion coefficient of 3
~ 7 × 10 ^-6 [1 / ° C] and the coefficient of linear expansion of carbon is also 1 ~
Since a material having an expansion coefficient substantially equal to 10 × 10 ⁻⁶ [1 / ° C.] can be selected, a stable wear resistant coating can be obtained even at a high temperature.

Such a stable carbide coating need only be present at least at the portion in contact with the conveying material or the current-carrying material. However, the entire length of the roll cylinder provides higher processing accuracy and a stable coating. Since it is easy to do so, it is desirable that a coating be present on the entire long part of the body. Carbides include W, Ti,
Ta, Zr, Cr, Hf, Si and the like are preferable.

[0011]

EXAMPLES The effects of the present invention will be described below based on examples. (Example 1) FIG. 1A is a side sectional view of a roll according to the present invention, and FIG. 1B is a sectional view taken along the line AA of FIG.

The carbon used was fired at 3000 ° C., had a thermal conductivity of 140 [W / m ² K] and a linear expansion coefficient of 1.
× 10 ^-6 [1 / ° C] diameter 230 mm, length 1000 m
A sleeve 1 having a wall thickness of 40 mm and a thickness of 40 mm is placed in an iron shaft 3, and both ends of the sleeve are fixed by fixing rings 2. The surface of this roll is plasma sprayed with 150 μm of WC-12% Co 4. Although not shown, the carbon sleeve 1 has a diameter of 10 m in four places at both ends at 90 ° C in the longitudinal direction.
Make a hole with a depth of m and a depth of 30 mm, and insert a bolt from the end face side of the fixing ring 2 here to prevent rotation of the sleeve. There is. A cold-rolled steel sheet having a plate width of 500 mm and a thickness of 0.3 mm was heated to 750 ° C. and brought into contact with this roll for 1 hour, and the profile of the roll was measured by a displacement gauge with a stylus cooled. The result of comparison between the roll according to the present invention and an iron roll of the same size as the present invention is shown in FIG. In the roll according to the present invention, the difference between the center of contact of the steel plate and the edge of the steel plate is 4 μm, which is about 1/10 of that of the iron roll of 50 μm.
Therefore, the thermal crown can be suppressed significantly.

Table 1 shows the results of a wear test using a pin-on-disk to prepare a test material of 50 mm square and 10 mm thickness in order to investigate the wear resistance of the carbon of the present invention. A pin made of SUS304 having a size of 3 mm × 4 mm was pressed against the pin, and an experiment was conducted for 120 minutes at a pressure of 5 kg / mm ² and a sliding speed of 5 mpm. The relative wear amount in the table is wear depth ÷ (sliding distance × load). As a result of the wear test, samples A to P according to the present invention
Did not wear at all. On the other hand, untreated graphite U not subjected to the above treatment is 32 [μm · mm ² / km · kg], which is a cold isotropic compression molding (C
The IP) material V has 16 [μm · mm ² / km · kg] and the molding material W has 22 [μm · mm ² / km · kg], and the carbon of the present invention is extremely excellent in wear resistance.

[0014]

[Table 1]

(Embodiment 2) FIG. 2 (a) is a side sectional view of a roll according to the present invention provided with a metal intermediate layer, and FIG. 2 (b) is a sectional view taken along the line AA of FIG. 2 (a). . The metal intermediate layer 5 is N
iCrAlY layer with a plate width of 500 m as in Example 1.
A cold-rolled steel sheet having a thickness of 0.3 mm and a thickness of 0.3 mm was heated to 750 ° C. and kept in contact for 1 hour, and the profile of the roll was measured with a displacement gauge in which a stylus was cooled. As a result, as in Example 1,
In the roll according to the present invention, the difference between the center of contact of the steel sheet and the edge of the steel sheet is 4 μm, which is about 1 / m compared to 50 μm of the iron roll.
It was 10, and the thermal crown could be suppressed significantly.

The wear resistance of carbon according to the present invention in which an intermediate layer of NiCrAlY was provided and a carbide layer of 100 μm was provided thereon was evaluated by the same pin-on-disk as in Example 1. Table 2 shows the results, which are AP
Shows no abrasion at all, and the carbon of the present invention has extremely excellent abrasion resistance.

When the intermediate layer is provided as in the second embodiment, the surface pores peculiar to graphite can be contained, a sound spray structure free of pinholes can be obtained, and kinetic energy such as jet coating and explosive spraying can be obtained. Even if a large-scale thermal spraying method for scooping the surface layer is used, it is excellent in that fine thermal spraying is possible without damaging the surface.

[0018]

[Table 2]

[0019]

EFFECTS OF THE INVENTION When the carbon roll of the present invention is used, even if it comes into contact with a material to be heated at a high temperature, the temperature distribution is not so much and the expansion coefficient is small. The contact failure can be avoided, and the deformation of the strip heated to a high temperature and the uneven temperature distribution can be prevented. Therefore, for example, when it is used in a continuous annealing furnace for steel plates, the profile of the roll is stable even if the plate width is changed, so that the deterioration of the plate shape can be prevented and the occurrence of meandering can be prevented. Therefore, production can be performed without reducing the line speed, and high-speed transportation is also possible. Further, when used for roll cooling or the like, since the heat conduction of carbon is good, cooling can be performed efficiently and without causing a defective shape.

Even when applied to a current-carrying roll, the profile is stable even when it comes into contact with a metal which has been heated to a high temperature, so that the occurrence of sparks due to poor contact can be prevented.

Even with respect to wear, which is a drawback of carbon,
Since this roll has a hard coating on the surface, it can be used stably for a long time. Further, even if the wear advances, the base material can be used any number of times by reprocessing only the surface layer, which is economical.

[Brief description of drawings]

FIG. 1 (a) shows a side cross section of a carbon roll of the present invention. (B) The AA cross section of Fig.1 (a) is shown.

FIG. 2 (a) shows a side cross section of another example of the carbon roll of the present invention. (B) The AA cross section of Fig.2 (a) is shown.

FIG. 3 shows a comparison of thermal crowns of a carbon roll according to the present invention and a conventional roll.

[Explanation of symbols]

 1 Carbon sleeve 2 Fixing ring 3 Shaft 4 Carbide 5 Metal intermediate layer

Claims (2)

[Claims] 1. Contact with a material heated to a high temperature, conveyance,
A carbon roll which is mainly composed of carbon which is either energized or cooled, characterized in that a layer made of a metal carbide is formed on the roll surface. 2. Contact with a material heated to a high temperature, conveyance,
A carbon roll which mainly conducts electricity or cools, characterized in that a metal layer is provided as an intermediate layer on the carbon and a layer made of metal carbide is provided on the outermost layer.