JPH07268489A - Method for manufacturing abrasion resistant carbon roll - Google Patents

Abstract

(57) [Summary] [Purpose] To produce a carbon roll which is less likely to have a non-uniform temperature distribution on the roll surface, can prevent the generation of a thermal crown, and is also abrasion resistant. [Structure] In a carbon roll having a long body made of carbon, a metal layer having a thickness of 10 to 50 μm is provided on a base material carbon, and a ceramics or cermet layer is sprayed thereon. The metal layer is preferably made of one or more of Ni, Cr, Co, Al and Y. [Effect] A high quality and dense ceramic sprayed layer can be obtained on the surface of the carbon roll, and the manufactured carbon roll has excellent wear resistance and thermal shock resistance. Further, since the base material is carbon, the temperature distribution is unlikely to occur and the coefficient of thermal expansion is small, so that the generation of thermal crown can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a heat treatment furnace for transportation,
Manufacturing method of abrasion-resistant carbon roll used for roll cooling or electric heating, particularly, production of carbon roll excellent in abrasion resistance without causing thermal crown based on temperature distribution even when contacted with high temperature metal material Regarding the method.

[0002]

2. Description of the Related Art A hearth roll in a furnace used for annealing a metal, for example, continuous annealing of a cold-rolled steel sheet, has a high temperature in the furnace. Is low and the edge of the roll has a higher temperature, resulting in a temperature distribution. Depending on this temperature distribution, thermal expansion causes a concave crown in the center with high indentations and high edges in the profile. On the contrary, when it comes into contact with a steel plate whose temperature is higher than the ambient temperature of the furnace, or when it is used to cool a heated steel plate, the cooling roll, or the energizing roll or pressing roll used for energizing heating has a roll temperature higher than that of the steel plate. The temperature is low in the part that is in contact with the high temperature steel plate, but the temperature is low in the part that is not in contact with the steel plate, and a convex crown is generated. In such a state, the steel sheet is likely to have a temperature distribution and a tension distribution, and the shape of the steel sheet is deteriorated, so that an ear wave or a diaphragm is likely to occur. Further, when the width of the steel sheet changes, the profile of the roll changes, the shape of the steel sheet is likely to become unstable, and there is a problem that it is necessary to operate at a low speed until the profile of the roll becomes stable.

Further, when a crown is formed on the current-carrying roll or the pressing roll, the contact pressure on the steel plate is partially reduced, and as a result, sparks are generated between the steel plate and the current-carrying roll,
There is a problem in that melting marks are generated on both of the current-carrying rolls, resulting in deterioration of product quality and roll life.

[0004]

Therefore, in order to prevent the temperature distribution from being generated in the roll due to contact with a metal material or the ambient temperature, the roll is designed not to expand even if the temperature distribution is generated. Focusing on the material of the body, when considering a material that easily diffuses heat and does not expand, carbon is a material that has both the properties of good thermal conductivity and difficulty in thermal expansion. Among carbon, extruded graphite has a property that its thermal conductivity becomes higher as crystallization progresses. In particular, since the crystal is oriented in the extrusion direction, the heat conduction is particularly high in this direction, and the heat conductivity is 2 to 3 times that of iron that is usually used. Therefore, if the extrusion direction is the roll cylinder length direction, heat tends to diffuse in the cylinder length direction, and the temperature distribution is unlikely to occur even when contacting with high temperature metal. On the other hand, graphite has a small coefficient of linear expansion and is 1/2 to 1/1 / the size of iron.
Since there is only 10 elongations, even if a temperature distribution is attached, the amount of thermal expansion is small and the profile is unlikely to change. In addition to carbon materials, many carbon materials having similar properties are also used for CIP molding and molding. Hereinafter, these carbons are used as sleeves in the long body portion and are fixed to the metal shaft, and are referred to as carbon rolls.

Although such a carbon roll has properties effective for preventing a thermal crown, it is soft on the other hand, and its wear resistance becomes a problem when it is used as a roll.

In order to improve the wear resistance of carbon,
For example, JP-A-4-280865 discloses that carbon is mixed with metal fibers and / or metal powders, and further metal wires and / or wire nets are arranged. However, this is mainly for use in a rail pantograph sliding plate, and is not sufficient for improving the wear resistance of the carbon roll.

An object of the present invention is to provide a method for producing a carbon roll which is less likely to have a non-uniform temperature distribution on the roll surface, which can prevent the generation of a thermal crown, and also has abrasion resistance.

[0008]

According to the present invention, in a carbon roll having a long body made of carbon, a metal layer having a thickness of 10 to 50 μm is provided on carbon as a base material, and a ceramic or cermet layer is sprayed thereon. And a method for manufacturing an abrasion resistant carbon roll. The metal layer is N
It is preferable that i, Cr, Co, Al, and Y are made of one kind or two or more kinds.

[0009]

In order to improve wear resistance, it is effective to form a hard layer on the surface layer of soft carbon. Therefore, in the present invention, the coating layer is formed by spraying ceramics on the surface of the carbon roll. Since the ceramic coating layer has high hardness and excellent wear resistance, it eliminates the drawback of the carbon roll that it is easily worn.

However, in order to obtain a dense thermal spray coating, it is necessary to spray ceramic powder onto the surface of the carbon roll at a high speed, which may cause the surface layer of the carbon roll to be scraped off. For this reason, it is difficult to obtain a good coating film, and the ceramics hardly penetrate into the carbon of the base material, so that the ceramic sprayed layer is easily peeled off.

Therefore, in the present invention, instead of directly spraying ceramics on the base material carbon, a metal layer of 50 μm or less is first provided by thermal spraying or plating, and then ceramics is sprayed on the metal layer. . Since the thickness that can be practically formed by thermal spraying or plating is 10 μm, the lower limit was set to 10 μm. When spraying a metal, it is not necessary to spray it at a higher speed than ceramics, and therefore there is no fear that the surface layer of carbon will be scraped off. Moreover, since the melting point of metal is lower than that of ceramics and it is easily melted, a metal layer that enters the gap from the surface of the base material carbon and is in close contact with the base material carbon can be obtained. After that, if ceramics or a cermet composed of metal and ceramics is sprayed on the metal layer, the metal layer acts as a protective film and prevents the base material carbon from being scraped off. Further, in the case of plating, a dense film can be easily obtained.

The thickness of the metal layer is 50 μm or less. Since the coefficient of thermal expansion of metal is larger than that of ceramics, when the thickness of the metal layer becomes thicker, the metal layer thermally expands and breaks the ceramic layer, or the ceramic layer easily peels off, resulting in poor thermal shock resistance. It was confirmed by an experiment that the range where such a problem does not occur is 50 μm or less.
Regarding the lower limit, a layer of about 20 μm is usually formed by thermal spraying in one pass, and the thickness remaining after polishing is 10 μm or more for practical use. Therefore, the lower limit is 1.
It was set to 0 μm.

If the metal layer is easily oxidized, the ceramic layer is easily peeled off. Therefore, it is preferable to spray a metal which is difficult to be oxidized, such as Ni, Cr, Co, Al or Y. NiCr and MCrAlY (M:
Ni, CoNi, Co) or the like may be used. These may be used alone or in combination of two or more. There is no particular limitation on these compositions. The surface layer may be made of ceramics alone, but when cracks due to the difference in thermal expansion occur, a cermet formed by mixing metal and ceramics is less likely to crack and a stable coating film can be obtained.

Since the carbon roll manufactured as described above has a ceramic sprayed coating layer having a very high hardness on the surface of the roll body, the drawback of the carbon roll, that is, the problem of poor wear resistance due to its softness is solved. To be done.
The problem of thermal crown generation due to the temperature distribution of the roll can be solved by the characteristics of the base material carbon, which has good thermal conductivity and is less likely to thermally expand. In this way, according to the present invention, a carbon roll which does not generate a thermal crown and has excellent wear resistance can be obtained.

[0015]

EXAMPLE WC-12% Co (cermet) and ZrO ₂ -8% Y ₂ O ₃ (ceramic) were directly sprayed on the base material carbon by 150 μm each, and the NiCr alloy (80
% Ni20% Cr) and CoNiCrAlY (49: 2)
2: 21: 7.5: 0.5 wt%) by spraying 25,5
Table 1 shows the results of evaluation of thermal spraying workability, releasability, wear resistance, and thermal shock resistance of a metal layer having a thickness of 0, 75, 100, 150 μm, on which the cermet and ceramics were thermally sprayed.

[0016]

[Table 1]

The thermal spraying was performed by using a plasma gun in air after preheating a carbon roll having a surface roughness of Ra of about 10 μm by subjecting carbon to shot blasting in advance to 400 ° C. As the thermal spraying material, one having an average particle size adjusted to 40 μm is used, and after the thermal spraying is cooled, the surface roughness is Ra1 by polishing.
It was adjusted to μm or less.

It can be seen from Table 1 that the metal layer has a thickness of 50 μm or less and is excellent in all of thermal spraying workability, releasability, wear resistance and thermal shock resistance.

[0019]

Industrial Applicability According to the present invention, it is possible to obtain a high-quality and dense ceramics sprayed layer without carving the base material carbon, and the manufactured carbon roll has a hard ceramics sprayed layer on the surface layer, which is a drawback of carbon. It also solves the problem of wear and has excellent thermal shock resistance, so it can be used stably for a long time. Further, since the base material is carbon, the temperature distribution is unlikely to occur even when it comes into contact with the material to be heated or the atmosphere, and the coefficient of thermal expansion is small, so that the generation of thermal crown can be suppressed.

Claims (2)

[Claims] 1. A wear-resistant carbon characterized in that, in a carbon roll having a long body made of carbon, a metal layer having a thickness of 10 to 50 μm is provided on carbon as a base material, and a ceramics or cermet layer is sprayed thereon. Roll manufacturing method. 2. The metal layer comprises Ni, Cr, Co, Al,
The method for producing an abrasion-resistant carbon roll according to claim 1, comprising any one or more of Y.