JPH10195547A - Hearth roll excellent in wear resistance, and build-up resistance, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a hearth roll excellent in wear resistance and build-up resistance and having a long service life. SOLUTION: The surface of a roll base metal 2 in the outer circumference of a hearth roll 1 is applied with a roll surface coating layer having wear resistance and build-up resistance. This roll surface coating layer is composed of two layers of a surface layer 7 having a microstructure in which TiN grains 4 coated with a metallic oxide (except iron oxide) layer 6 stable at 1400 deg.C are dispersed into a metallic except iron and iron alloys) matrix 5 composed of heat resistance metal heated at 900 deg.C and a metallic layer 3 for bonding as the substrate of the surface layer 7. Preferably, the volume ratio of the TiN grains 4 in the surface layer 7 is regulated to 40 to 90%, and the balance matrix metal 5 and the coated metallic oxide 6 of the TiN grains 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hearth roll provided in a continuous heat treatment furnace for conveying steel sheets, and in particular, a hearth roll excellent in wear resistance and build-up resistance, and It relates to a manufacturing method.

[0002]

2. Description of the Related Art A hearth roll disposed in a continuous heat treatment furnace for steel sheets is used, for example, in an oxidizing or reducing atmosphere at a temperature of 600 to 1300 ° C. to convey a material to be heat treated continuously for a long time. Is subjected to abrasion, and the deposited oxide and iron powder of the material to be heat-treated adhere to and accumulate on the roll surface to form a so-called build-up.

If irregularities due to wear or build-up occur on the hearth roll, the steel sheet as a material to be heat-treated will be scratched while being conveyed, causing a deterioration in the surface quality of the steel sheet product.

In order to prevent such deterioration in the quality of the steel sheet, the operation is periodically interrupted to cool the inside of the heat treatment furnace.
An operator enters the furnace, grinds and cleans the surface of the hearth roll, or replaces the roll itself.

As a technique for preventing such abrasion and build-up, Japanese Patent Application Laid-Open No. 63-250449 discloses a roll-up resistant ceramic having a ceramic coating made of Ti-based nitride or Ti-based carbide. A heat treatment furnace roll (hearth roll) having excellent wear resistance is disclosed.

Japanese Unexamined Patent Publication (Kokai) No. 6-116703 discloses that a sprayed material in which the surface of a chromium carbide is coated with a nickel-chromium alloy or the like as a binding metal is used to eliminate the influence of the atmosphere during the spraying, so There is disclosed a hearth roll excellent in heat resistance and abrasion resistance, in which a dense and high hardness coating (cermet material sprayed layer) in which a metal bond exists in a network between chromium carbides is applied to the roll surface.

[0007]

However, in the hearth roll disclosed in Japanese Patent Application Laid-Open No. 63-250449, the T
When a ceramic coating made of i-based nitride or Ti-based carbide is formed by thermal spraying, Ti-based nitride or T
The i-based carbide is oxidized during thermal spraying to become brittle Ti-Oxide and falls off from the coating, so that there is a problem that many pores are generated in the coating and excellent build-up resistance cannot be obtained.

The hearth roll disclosed in JP-A-6-116703 has excellent heat resistance and wear resistance when a chromium carbide cermet film is laminated on the surface of the hearth roll, and has poor build-up resistance in a short period of time. However, there is a problem that the chromium carbide reacts with the adhered oxide or iron powder of the material to be heat-treated over a long period of time to cause build-up. Further, once build-up occurs, there is a problem that the build-up does not fall off and the operation must be interrupted because the coating is dense and has excellent wear resistance. That is, even if the chromium carbide cermet coating was laminated, the life of the roll for transporting the steel sheet was still short.

Accordingly, the present invention has been made to advantageously solve the above-described problems, and can suppress the occurrence of wear and build-up of a roll for transporting a steel sheet, and provide a long-life wear-resistant. It is an object of the present invention to provide a hearth roll excellent in heat resistance and build-up resistance and a method for manufacturing the same.

[0010]

Means for Solving the Problems The present invention provides the following (1)-
It is as (10).

(1) On the surface of the roll base material around the roll,
In a hearth roll having an abrasion-resistant, build-up-resistant roll surface coating layer, the roll surface coating layer comprises
A surface layer having a microstructure in which TiN particles covered with a metal oxide (excluding iron oxide) layer stable at 400 ° C. are dispersed in a metal (except iron and iron alloy) matrix made of a refractory metal at 900 ° C. A hearth roll excellent in abrasion resistance and build-up resistance, comprising two layers of a bonding metal layer as a base of the surface layer.

(2) The resistance to (1), wherein the ratio of TiN particles in the surface layer is 40 to 90% by volume, and the remainder is a matrix metal and a coating metal oxide of TiN particles. Hearth roll with excellent wear and build-up resistance.

(3) The coating metal oxide of the TiN particles in the surface layer is Al or CoCrAlY or CoNi.
(1) characterized in that it is an oxide of CrAlY.
Or (2) Hearth roll excellent in wear resistance and build-up resistance.

(4) The matrix metal in the surface layer is CoCrAlY, CoNiCrAlY or NiC
r, a hearth roll excellent in abrasion resistance and build-up resistance according to any one of the above (1) to (3).

(5) The abrasion resistance and build-up resistance of any of (1) to (4), wherein the thickness of the bonding metal layer and the thickness of the surface layer are each 50 to 300 μm. Excellent hearth roll.

(6) On the surface of the roll base material around the roll,
In a method for manufacturing a hearth roll having a wear-resistant, build-up-resistant roll surface coating layer, a bonding metal layer is laminated by a thermal spraying method on a roll base material surface around a hearth roll, and then the bonding metal layer is formed. The oxide is 1400 ° C
Coated with a stable metal (except iron and iron alloys)
By spraying the thermal spray raw material powder composed of N particles and a powder for a metal (except iron and iron alloy) matrix of a refractory metal at 900 ° C., 14 produced during thermal spraying is deposited.
A surface layer having a microstructure in which TiN particles covered with a metal oxide (except iron oxide) layer stable at 00 ° C. are dispersed in a metal (except iron and iron alloy) matrix made of a refractory metal at 900 ° C. A method of manufacturing a hearth roll excellent in wear resistance and build-up resistance, comprising forming a roll surface coating layer composed of two layers of a bonding metal layer as a base of the surface layer.

(7) By adjusting the composition of the thermal spraying raw material powder, Ti in the surface layer of the roll surface coating layer after thermal spraying is adjusted.
(6) The wear resistance of (6), wherein the ratio of the N particles is 40 to 90% by volume, and the remainder is a coating metal oxide of the matrix metal and the TiN particles.
A method of manufacturing hearth rolls with excellent build-up resistance.

(8) The metal coating the TiN particles is Al or CoCrAlY or CoNiCrAl.
(6) or (7), wherein the hearth roll is excellent in wear resistance and build-up resistance.

(9) The matrix metal is CoC
The method for producing a hearth roll excellent in abrasion resistance and build-up resistance according to any one of the above (6) to (8), which is rAlY, CoNiCrAlY or NiCr.

(10) The abrasion resistance and build-up resistance according to any one of (6) to (9), wherein the lamination thickness of each of the bonding metal layer and the surface layer is 50 to 300 μm. Method for manufacturing hearth rolls with excellent quality.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic view showing a cross-sectional structure of a hearth roll according to the present invention, which has excellent wear resistance and build-up resistance. As shown, the hearth roll 1 comprises a matrix metal 5 and a Ti coated with a metal oxide layer 6.
The surface layer 7 composed of the N particles 4 is laminated on the surface of the base material 2 with the bonding metal layer 3 interposed therebetween.

The microstructure in which TiN particles are dispersed in a metal (excluding iron and iron alloy) matrix in the surface layer in the surface coating layer of the hearth roll of the present invention is based on Ti
N is easily oxidized, but the oxidized and generated Ti oxide has an abradable property of falling off relatively easily, so that the build-up resistance of the hearth roll is extremely excellent.
Furthermore, since only TiN exposed on the surface of the hearth roll is oxidized during use in the heat treatment furnace, excellent wear resistance and build-up resistance as the hearth roll can be obtained.

Ti in the surface layer in the hearth roll surface coating layer
The ratio of the N particles is between 40% and 90% by volume. If it is less than 40%, the metal component is too large and the build-up resistance is inferior.

The metal oxide (excluding iron oxide) layer covering the TiN particles prevents oxidation of the TiN particles during thermal spraying so that the TiN particles work effectively during use of the hearth roll in the heat treatment furnace. As a result, the TiN particles are not oxidized during thermal spraying, which contributes to the formation of a dense coating. Furthermore, the metal oxide layer itself also contributes to improving the wear resistance of the hearth roll used in the heat treatment furnace. Since iron oxide is an oxide of the same kind of metal as the steel sheet to be conveyed, it has poor buildup resistance and cannot be used.

As a method for forming a metal oxide (excluding iron oxide) layer that coats TiN particles, a TiN particle coated with a metal (except iron and iron alloy) is coated with a surface coating layer of a hearth roll by thermal spraying. For example, a method of producing the coating metal by oxidizing the coating metal can be exemplified.

The metal (excluding iron and iron alloy) coating the TiN particles is oxidized during thermal spraying to form a metal oxide (excluding iron oxide) that functions as an oxidation protection film, and thus is treated in a heat treatment furnace. Stable at 1400 ° C. (the vapor pressure at 1400 ° C. is 1 Ton) which can prevent oxidation of TiN particles during thermal spraying so that the TiN particles work effectively during use of the hearth roll.
rr or less) can be arbitrarily selected from metals to be metal oxides. Since iron and iron alloys are the same kind of metal as the steel sheet to be conveyed, they have poor buildup resistance and cannot be used. Specifically, Al, Ti, Cr, Co, N
i, Zr and the like can be exemplified. Among them, since Al ₂ O ₃ generated by oxidation during thermal spraying has excellent properties as an oxidation protective film, A is a metal that can form an Al ₂ O ₃ film that prevents oxidation of TiN particles during thermal spraying.
It is a preferred embodiment to select 1, CoCrAlY, or CoNiCrAlY.

As a method of coating a metal on TiN particles,
Methods such as electrolytic plating, electroless plating, PVD, CVD, and mechanical alloying can be employed. According to these methods, the surface of the TiN particles can be densely covered with the metal.

For example, in the mechanical alloying method, T
Metal powder finer than iN particles (for example, CoCrAl
Y powder) and an organic binder are prepared, mixed in a predetermined ratio, and sufficiently stirred under reduced pressure or an inert gas atmosphere to bond a metal to the surface of the TiN particles. In addition, any suitable coating method may be used as long as there is an appropriate method capable of dense metal coating.

The matrix metal does not soften at a hearth roll operating temperature of 900 ° C. and has a melting point of 1400 other than iron alloy.
Any heat-resistant metal (including an alloy) having a temperature of at least ° C may be used. In addition,
Since iron and iron alloys are the same kind of metal as the steel sheet to be conveyed, they have poor buildup resistance and cannot be used. It has excellent oxidation resistance and is stable in a high temperature atmosphere such as in a heat treatment furnace.
A heat-resistant alloy of oNiCrAlY or NiCr is a preferable alloy as the matrix metal.

First, a metal layer for bonding is provided on the surface of the hearth roll base material by thermal spraying. This is because, compared to simply roughening the base material surface by a blasting method or the like, the surface roughness of the bonding metal layer by the thermal spraying method is large, and the adhesion of the surface layer is increased by the mechanical bonding force. .

The metal forming the bonding metal layer may be the same heat-resistant alloy as the matrix metal of the surface layer. This is because these alloys have excellent oxidation resistance and are stable in a high temperature atmosphere such as in a heat treatment furnace.

The bonding metal layer and the surface layer can be laminated by a plasma spraying method, an explosive spraying method, or a spraying method such as HVOF.

For example, when the plasma spraying method is adopted, the surface of the base material 2 of the hearth roll is subjected to a shot blast treatment, preheated to 100 to 150 ° C. by a plasma spray gun, and then the sprayed raw material powder of the heat-resistant alloy is removed. Use 50-3
A bonding metal layer 3 having a thickness of 00 μm is laminated. Further, on the bonding metal layer 3, a Ti coated with a metal oxide layer 6 is formed.
A surface layer 7 having a thickness of 50 to 300 μm is laminated using a thermal spray raw material powder composed of N particles 4 and a matrix metal 5.

That is, the lamination thickness of the bonding metal layer 3 and the surface layer 7 is 50 to 300 μm, respectively. 50μ
The reason why the thickness is not less than m is that if the thickness is smaller than this, the bonding metal layer has no effect of improving the adhesion, and the surface metal is exposed due to abrasion when used for a long time. On the other hand, a thickness of 300 μm or less
If the thickness exceeds μm, the residual stress at the time of applying the thermal sprayed layer increases, and the thermal sprayed layer is peeled off.

The material powder for thermal spraying is prepared so that the ratio of TiN particles in the surface layer after thermal spraying is between 40% and 90% by volume.
Adjust the percentage of metal (except iron and iron alloy) coated TiN particles and matrix metal.

The increase in volume due to oxidation of the coating metal is caused by Ti
The volume of the coated metal is calculated from the weight increase before and after the metal coating on the N particles, and in the case of an Al alloy as an example, the volume expansion coefficient (1.28 times) due to oxidation of Al and the coating It can be calculated by multiplying the Al content in the metal. Although the effect on the overall volume ratio by the increased amount of oxidation of the coated metal is small, the above calculation shows that the TiN particles coated with metal so that the ratio of the TiN particles in the surface layer after spraying is between 40% and 90% by volume. The ratio of particles and matrix metal can be adjusted.

[0038]

EXAMPLES In order to confirm the effects of the present invention, SCH-2 was used.
A sample was prepared from two materials (JIS G 5122) (for abrasion resistance test: 50 × 50 × 10 mm, for build-up resistance test: 50 × 30 × 5 mm), and sprayed on the sample surface (plasma spray method, explosion) A bonding metal layer and a surface layer were sequentially laminated by a thermal spraying method, and a wear test and a build-up resistance test were performed.

The wear test was conducted at a temperature of 900 ° C. in an atmosphere N ₂ −
In 2% of H ₂ , material SUJ2 (JIS G480
5 1970) with a load of 2 kg and a sliding speed of 0.2
After sliding about 720 m / s for a sliding distance of 720 m, the sample wear volume (mm ³ ) was changed to the sliding distance (mm) by the applied load (k
g) was multiplied by the value (= specific wear). At that time, the case where the specific wear amount was 1 × 10 ⁻⁶ (mm ² / kg) or less was judged as good (○).

The following experiment was conducted to evaluate the build-up resistance.

FIG. 2 shows the apparatus used in the experiment. Material is S
A half moon roll 12 having a radius of 35 mm, which is CH-22, is manufactured, and is reciprocally slid on each of the two sprayed samples 16, 16 ′.
A device that can reproduce the occurrence of build-up was used. The two sprayed samples 16, 16 'were a sprayed sample 16 sprayed on both sides of the SCH-22 substrate and a sprayed sample 16' sprayed on one side, and the half moon roll 12 and the two sprayed samples 16, 16 'were used. In between, the build-up raw material 13 (iron oxide powder Fe ₃ O ₄ ) was sprayed and stored in the tray 14. This device was placed in a crucible-type electric furnace 15, and the roll 12 was reciprocated for about 4 hours at a constant temperature of 900 ° C. in a reducing atmosphere of N ₂ -H ₂ 2% to generate build-up. In addition, 1 in the figure
Reference numeral 7 denotes an atmospheric gas introduction pipe, reference numeral 18 denotes a pressure rod, reference numeral 8 denotes a load material, reference numeral 9 denotes a counterbalance, reference numeral 10 denotes a seal plate, and reference numeral 11 denotes a speed reducer.

FIG. 3 is an enlarged view showing the arrangement of the build-up raw material and the sprayed sample portion in FIG.

In the above experiment, as shown in FIG.
The surface directly in contact with the half-moon roll 12 is designated as surface A, the back surface is designated as surface B, and the surface opposite to surface B is designated as surface C. The build-up resistance index as shown in Table 1 shows the build-up occurrence after the test. , The build-up resistance was evaluated by the sum of the respective evaluation points, and a total score of 7 or more was judged as good (（).

[0044]

[Table 1]

Table 2 shows Examples 1 to 5 and Comparative Examples 1 to 3.
Table 3 shows the results of the wear test, the results of the build-up resistance test, and the overall evaluation of Examples 1 to 5 and Comparative Examples 1 to 3.

[0046]

[Table 2]

[0047]

[Table 3]

In Examples 1 to 5, the bonding metal layer and the surface layer were laminated on the sample surface by thermal spraying (plasma thermal spraying, explosive thermal spraying), and the thickness of each layer was in the range of 50 to 300 μm. , TiN volume ratio is 40 ~
It is set in the range of 90%. As shown in Table 3, in Examples 1 to 5, the specific wear amount was 1 × 10 ⁻⁶ (m
m ² / kg) or less, and a good value of 7 or more in the build-up resistance test, and the overall evaluation was good (（).

On the other hand, in Comparative Example 1, the bonding metal layer and the surface layer were laminated on the sample surface by the plasma spraying method, and the thickness of each layer was in the range of 50 to 300 μm, and the volume ratio of Cr ₃ C ₂ was Is set to 80%.
As shown in Table 3, Comparative Example 1 had a good specific wear amount of 1 × 10 ⁻⁶ (mm ² / kg) or less in the wear test.
In the build-up resistance test, Cr ₃ C ₂ reacted with Fe and the build-up resistance was as low as 2 points, and the overall evaluation was poor (×).

In Comparative Example 2, a bonding metal layer and a surface layer were laminated on a sample surface by a plasma spraying method, and the TiN coating metal was Fe. As shown in Table 3, Comparative Example 2 had an inferior value of 4.8 × 10 ⁻⁴ (mm ² / kg) because the coating was not dense in the abrasion test. Points and the build-up resistance were low, and the overall evaluation was poor (x).

In Comparative Example 3, a bonding metal layer and a surface layer were laminated on the sample surface by plasma spraying, and TiN was not coated with a metal. As shown in Table 3, Comparative Example 3 had an inferior value of 1.2 × 10 ⁻⁴ (mm ² / kg) in the abrasion test because of a large number of pores in the coating film, and even in the build-up test. The build-up resistance is as low as 2 points because the film is not dense, and the overall evaluation is poor (×)
Met.

[0052]

According to the present invention, the surface layer formed on the surface of the hearth roll base material via the bonding metal layer has a TiN particle having a metal oxide (excluding iron oxide) coating layer formed of metal (excluding iron oxide). Since it has a microstructure dispersed in a matrix (excluding iron and iron alloys), it has excellent wear resistance and build-up resistance, and can be used continuously for a long time even in a heat treatment furnace.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a cross-sectional structure of a hearth roll of the present invention.

FIG. 2 is a schematic diagram of an experimental device for evaluating build-up resistance.

FIG. 3 is an enlarged schematic view of a sprayed sample portion of an experimental apparatus for evaluating build-up resistance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hearth roll 2 Base material 3 Bonding metal layer 4 TiN particle 5 Matrix metal 6 Metal oxide layer 7 Surface layer 8 Weighting material 9 Counterbalance 10 Seal plate 11 Reduction gear 12 Half moon roll 13 Buildup material 14 Tray 15 Electric furnace 16 Thermal spray Sample 17 Atmospheric gas introduction pipe 18 Pressure rod

Claims (10)

[Claims] 1. A hearth roll having a wear-resistant and build-up-resistant roll surface coating layer on the surface of a roll base material around the roll, wherein the roll surface coating layer is 1400
A surface layer having a microstructure in which TiN particles covered with a metal oxide (excluding iron oxide) layer stable at 900C are dispersed in a metal (excluding iron and iron alloy) matrix made of a refractory metal at 900 ° C; A hearth roll excellent in abrasion resistance and build-up resistance, comprising two layers of a bonding metal layer as a base of the surface layer. 2. Abrasion resistance according to claim 1, wherein the ratio of TiN particles in the surface layer is 40 to 90% by volume, and the balance is a matrix metal and a coating metal oxide of TiN particles. Hearth roll with excellent properties and build-up resistance. 3. The coating metal oxide of TiN particles in the surface layer is Al or CoCrAlY or CoNiCrA.
3. An oxide of 1Y.
Hearth roll with excellent wear resistance and build-up resistance. 4. The method according to claim 1, wherein the matrix metal in the surface layer is Co
The hearth roll according to any one of claims 1 to 3, which is CrAlY, CoNiCrAlY or NiCr, and has excellent wear resistance and build-up resistance. 5. The thickness of the bonding metal layer and the surface layer is:
The hearth roll according to any one of claims 1 to 4, wherein the hearth roll has excellent wear resistance and build-up resistance. 6. A method of manufacturing a hearth roll having a roll surface coating layer having wear resistance and build-up resistance on a surface of a roll base material on the outer periphery of the roll. After laminating a metal layer for bonding, on the metal layer for bonding, TiN particles coated with a metal whose oxide is stable at 1400 ° C. (excluding iron and iron alloys) and a metal of a refractory metal at 900 ° C. (iron and 1400 produced during thermal spraying by laminating thermal spray raw material powder consisting of matrix powder (excluding iron alloy) by thermal spraying.
A surface layer having a microstructure in which TiN particles covered with a metal oxide (excluding iron oxide) layer stable at 900C are dispersed in a metal (excluding iron and iron alloy) matrix made of a refractory metal at 900 ° C; A method for producing a hearth roll excellent in wear resistance and build-up resistance, comprising forming a roll surface coating layer composed of two layers of a bonding metal layer as a base of the surface layer. 7. The proportion of TiN particles in the surface layer of the roll surface coating layer after thermal spraying is adjusted to 40 to 90% by volume by adjusting the blending of the thermal spraying raw material powder, and the remainder is composed of matrix metal and TiN particles. The method for producing a hearth roll having excellent wear resistance and build-up resistance according to claim 6, wherein the hearth roll is a coated metal oxide. 8. The method according to claim 8, wherein the metal coating the TiN particles is Al.
8. The method for producing a hearth roll excellent in wear resistance and build-up resistance according to claim 6 or 7, wherein the method is CoCrAlY or CoNiCrAlY. 9. The method according to claim 8, wherein the matrix metal is CoCrAl.
The method for producing a hearth roll according to any one of claims 6 to 8, wherein the hearth roll is excellent in abrasion resistance and build-up resistance, being Y, CoNiCrAlY or NiCr. 10. The wear resistance according to claim 6, wherein the lamination thickness of the bonding metal layer and the surface layer is 50 to 300 μm, respectively.
A method of manufacturing hearth rolls with excellent build-up resistance.