JPH06228724A - Hot dip galvanizing roll and its production - Google Patents

Abstract

PURPOSE:To easily obtain a hot dip galvanizing roll excellent in durability and handling property by forming an Si3N4 film or a film prepared by substituting Si and N in the above film by Al and O, respectively, and allowing them to enter into solid solution on the surface of a roll body. CONSTITUTION:An alloy film consisting of Co, Ni, Cr, Al, and Y or a cermet film composed essentially of WC is formed, as necessary, by means of thermal spraying on the surface of a body 2 of a roll used in a hot dip galvanizing bath for steel sheet. An Si3N4 film or a film 1 where Si and N in the film are substituted by Al and O, respectively, and glassy structure is removed is formed thereon. At the time of forming the film 1, the surface of the roll body 2 is coated, by thermal spraying, with an SiO2 film of 5-20mu, to which 1-10% Al2O3 and 5-20% ZrO2 are added as necessary, or a metallic Si film. Subsequently, this film is heated to 800-1400 deg.C under an N2 or NH3 gas atmosphere of 80-100% concentration and (1 to 10)kg/cm<2> absolute pressure, and, in the case of SiO2 film, O in it is reduced by C and removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot dip galvanizing roll and a method for producing the same.

[0002]

2. Description of the Related Art In a facility where a cold-rolled steel sheet is reduced in a heat treatment furnace and then immersed in a molten zinc bath to plate zinc on the surface of the steel sheet, while supporting the steel sheet in the molten zinc bath, the sheet passing direction of the steel sheet is changed. In order to prevent wear of the hot-dip galvanized roll used to change from downward to upward due to the steel plate, either a self-fluxing alloy containing nickel, cobalt, etc. or a tungsten carbide coating containing cobalt is applied to the roll surface by thermal spraying. (Japanese Patent Laid-Open Nos. 04-254571 and 03-9
4048, JP 01-79356).

Further, various oxide-based ceramics can be applied as a sprayed coating which can prevent alteration of a self-fluxing alloy spray containing nickel, cobalt and others and tungsten carbide containing cobalt in a molten zinc bath and have extremely small wettability. There are possible ways to do this.

[0004]

However, the above-mentioned prior art has the following problems.

(I) In the case of a cermet containing cobalt or nickel, the sprayed coating comes in contact with zinc in a molten state to deteriorate. In particular, cobalt does not form a carbide or the like during thermal spraying and is not stabilized, so that it is dispersed in the coating in a metallic state, and substitutes with zinc to fall off.

[0006] Cobalt, nickel and the like are dispersed as a paste material in the cermet, and if they fall off, peeling in the coating film is induced and the original performance of the coating film is deteriorated.

(II) In various ceramics or cermets, silicon nitride is a ceramic having an extremely strong covalent bond and is excellent in film strength, thermal shock resistance and mechanical properties, and has low reactivity with metals. Since the wettability with the molten metal is small, it is effective as a method of forming a film surface of silicon nitride on the surface of the hot dip galvanizing roll to prevent the roll from being consumed due to the reaction between the metal of the roll base and zinc.

Conventionally, a thermal spraying method has been widely used as a method for forming a ceramic or cermet coating on a roll base.

However, in the case of silicon nitride, since it decomposes and sublimes in a high temperature range of 1900 ° C. or higher, it is extremely difficult to form a film by thermal spraying. As a special method, there is also a method in which other low melting point ceramics or cermet is previously attached to the periphery of the sprayed raw material powder of silicon nitride, and only the periphery is melted without being melted, but the coating by this method is used. Contains a lot of bubbles, has low film strength, and is easily peeled off.

Further, since the bonding force is weak, there are inherent defects such as poor wear resistance.

As described above, the coating films of tungsten carbide and silicon nitride by the conventional thermal spraying technique have not been sufficient in terms of performance.

[0012]

The present invention has been made to solve the above problems, and its gist is as follows.

(1) Steel plate On the surface of the body of the roll used to convey or support the steel plate in the hot dip galvanizing bath,
A hot dip galvanizing roll, characterized in that a silicon nitride film or a silicon nitride film silicon is replaced by aluminum and nitrogen is replaced by oxygen to form a solid solution film.

(2) C on the surface of the body of the roll used to convey or support the steel sheet in the hot dip galvanizing bath
Forming a coating formed by spraying an alloy consisting of o, Ni, Cr, Al and Y, and forming a silicon nitride coating or a silicon nitride coating on the upper layer of which aluminum is aluminum and nitrogen is oxygen to form a solid solution. A hot-dip galvanized roll characterized by.

(3) Steel plate A cermet film containing tungsten carbide as a main component is formed on the surface of the body of a roll used to convey or support a steel plate in a hot dip galvanizing bath, and a silicon nitride film or silicon nitride film is formed on the cermet film. A hot dip galvanizing roll, characterized in that a film is formed by replacing aluminum in the film with aluminum and replacing nitrogen with oxygen to form a solid solution.

(4) Steel plate 5 is formed on the surface of the body of the roll used to convey or support the steel plate in the hot dip galvanizing bath.
After coating a silicon oxide film or a metal silicon film having a thickness of up to 20 microns by a thermal spraying method, heating it to a temperature of 800 to 1400 ° C. in an atmosphere of nitrogen gas or ammonia gas having a concentration of 80 to 100% and an absolute pressure of 1 to 10 kg / cm ^2. However, in the case of a silicon oxide film, oxygen in the film is reduced by carbon,
A method for producing a hot-dip galvanized roll, which comprises removing the hot-dip galvanized roll.

(5) Steel plate 5 is formed on the surface of the body of the roll used to convey or support the steel plate in the hot dip galvanizing bath.
After coating a silicon oxide coating or a metal silicon coating with 1 to 10 percent alumina of -20 microns by spraying, the concentration is 80 to 100 percent, the absolute pressure is 1 to 10
A hot dip galvanizing roll characterized by heating to a temperature of 800 to 1400 ° C. in an atmosphere of nitrogen gas or ammonia gas of kg / cm ² and reducing and removing oxygen in the film with carbon in the case of a silicon oxide film. Production method.

(6) Steel plate 5 is formed on the surface of the body of the roll used for transporting or supporting the steel plate in the hot dip galvanizing bath.
~ 50 micron 1 to 10 percent alumina and 5
After coating a silicon oxide film or a metal silicon film to which zirconia of 20% is added by a thermal spraying method, the concentration is 80-
Temperature 800 in an atmosphere of 100% absolute pressure 1-10 kg / cm ² nitrogen gas or ammonia gas.
A method for manufacturing a hot dip galvanizing roll, which comprises heating to ˜1400 ° C., and reducing and removing oxygen in the film with carbon in the case of a silicon oxide film.

[0019]

[Action]

1) In the case of an alloy containing cobalt or cermet, the sprayed coating comes into contact with molten zinc and deteriorates. The alteration is caused by the mutual diffusion of ternary compounds of cobalt, zinc, iron and aluminum at the interface of the sprayed coating. In order to prevent this, it is necessary to block the contact between the ternary compound of zinc, iron and aluminum and cobalt. In the case of an alloy containing cobalt or cermet, it is effective to form a barrier layer on the surface layer.

2) It is necessary to select a material having a low reactivity with the ternary compound of zinc, iron and aluminum in the molten zinc as the material of the barrier layer. Silicon nitride and silicon nitride produced by the present inventors should be used as the first material. The ceramic or cermet film as one component is the best.

3) When the roll is dipped in molten zinc,
As a measure against peeling or cracking of the thermal spray coating due to thermal stress, silicon nitride and ceramics containing silicon nitride as the first component have a high thermal conductivity, but a low coefficient of linear expansion, resulting in extremely excellent thermal shock resistance and It is effective because even if it is immersed in molten zinc, trouble such as cracking does not occur.

In the case of other ceramics, 250 to 3 in advance
After preheating to 00 ° C., it is immersed in zinc, but if preheating is partially incomplete, problems such as cracking occur.

4) In the case of silicon nitride, since it decomposes and sublimes in a high temperature range of 1900 ° C. or higher, the raw material powder of silicon nitride is directly melted by thermal spraying and deposited on a roll to form a thermal spray coating. However, there is also a method in which other low melting point ceramics or cermet is attached in advance around the sprayed raw material powder of silicon nitride, and only the surroundings are melted without melting the silicon nitride itself. Contains a lot of bubbles, has low film strength, and is easily peeled off. Also, since the binding force is weak, the wear resistance is poor. Therefore, silicon nitride or a ceramic film containing silicon nitride as the first component is formed on the surface of the roll by the method described below.

After coating the surface of the body of the roll with an extremely thin film of silicon oxide or metallic silicon of 5 to 20 microns by using a thermal spraying method, the coated surface is ground to the required flatness accuracy,
Concentration 80-100%, absolute pressure 1-10kg /
Temperature of 500 to 1400 ° C. in a nitrogen gas atmosphere of cm ²
In the case of a silicon oxide film, oxygen is reduced and removed with carbon.

The reaction of the film at that time is shown in formula 1 for a silicon oxide film and in formula 2 for a metal silicon film.

3SiO ₂ + 6C + 2N ₂ → Si ₃ N ₄ + 6CO 1 formula 3Si + 2N ₂ → Si ₃ N ₄ 2 formula Silicon nitride formed by this method has a part of the silicon oxide remaining, which is a factor that reduces the strength. Therefore, after coating the surface of the roll body with 5 to 20 micron of silicon oxide or metallic silicon with 1 to 10% of alumina by thermal spraying, the coated surface is ground to the required flatness accuracy. In the case of a silicon oxide film, the oxygen in the film is reduced and removed by carbon in the case of heating the film at a temperature of 500 to 1400 ° C. in an atmosphere of nitrogen gas having a concentration of 80 to 100% and an absolute pressure of 1 to 10 kg / cm ^2. A silicon nitride film is formed, and the silicon in the vitreous structure in the film is solid-solution replaced with aluminum and nitrogen is dissolved with oxygen, so that the vitreous structure does not exist in the grain boundaries of the structure. So as to.

Further, in order to increase the strength of the silicon nitride, the surface of the body of the roll is partially stabilized with 5 to 20 micron of alumina and 1 to 10% of alumina and yttria.
After coating a silicon oxide film or a metal silicon film to which a percentage of zirconia is added by a thermal spraying method, the coated surface is ground to the required flatness accuracy, and the concentration of nitrogen is 80 to 100% and the absolute pressure is 1 to 10 kg / cm ² of nitrogen. In the case of a silicon oxide film, by heating in a gas atmosphere at a temperature of 800 to 1400 ° C., the oxygen in the film is reduced and removed by carbon, and the silicon in the vitreous structure in the film is made of aluminum and nitrogen is made of oxygen. By performing solid solution substitution, a glass-like structure does not exist in the grain boundaries of the structure, and a film strengthened by dispersion with zirconia can be formed.

Effect of Spraying Rolls with Silicon Nitride or Ceramics Having Silicon Nitride as First Component as Barrier Layer Silicon nitride and silicon nitride are used as materials for the barrier layer formed between zinc and the thermal spray coating on the roll surface. The ceramic as one component is used because silicon nitride is a hexagonal ceramic having a very strong covalent bond and the reactivity to molten zinc is extremely low.

That is, in the case of silicon nitride, two of silicon and nitrogen are used.
When individual atoms approach each other, the individual atomic orbitals strongly overlap, and the bond between each electron of the atoms of silicon and nitrogen of this bond orbital is stronger than other ceramics, and the covalent bond is extremely strong. This is because zinc and other atoms at the contact interface are less likely to diffuse between crystal lattices, and a reaction due to diffusion caused by the exchange of interstitial atoms is less likely to occur.

5) The thermal spraying of an alloy of Co, Ni, Cr, Al, Y or tungsten carbide on the lower layer is made by applying fine particles to the surface of the upper layer of silicon nitride and ceramics having silicon nitride as the first component. When cracks occur, molten zinc penetrates the cracks, reaches the roll matrix, and corrodes the metal of the matrix, which is the purpose of preventing this.

6) Addition of 5 to 20% of zirconia to the upper layer coating means that silicon nitride and zirconia dispersed in the ceramic coating containing silicon nitride as the first component are subjected to compressive stress due to the winding of the strip and are square. This is because in the process of causing stress-induced transformation from the crystal to the monoclinic crystal, fine cracks accompanied by volume expansion at the time of transformation are generated. The fine cracks absorb the deformation due to excessive stress, and further disperse the propagation of the cracks, which has the effect of enhancing the durability of the film itself.

[0032]

【Example】

Example in which Silicon Nitride Ceramics is Sprayed on a Roll as a Blocking Layer FIG. 1 is a view showing a hot-dip galvanizing roll according to the present invention, in which 1 is a thermal spray coating, 2 is a body of a hot-dip galvanizing roll base, and 3 is End plate of the hot-dip galvanizing roll base, 4 indicates the axis of the hot-dip galvanizing roll base.

FIG. 2 shows the details of the sprayed coating of the hot dip galvanizing roll according to the present invention. In the embodiment, the sprayed coating 1 is a coating of silicon nitride and a ceramic containing silicon nitride as the first component. Film portion of silicon film or metal silicon film that did not undergo nitriding reaction, 1B is cermet of tungsten carbide sprayed on the lower layer or Co, Ni, C
It is an alloy layer composed of r, Al, and Y.

100 μm Co, Ni, Cr, A with a plasma sprayer on the surface of the body of the roll used to convey or support the steel sheet in the hot-dip galvanizing bath.
After coating the alloy consisting of 1 and Y, a 15-micron thin silicon nitride film is coated on the upper layer by a plasma sprayer,
After processing to final finishing accuracy by polishing, the concentration is 100
%, 1 in an electric furnace in a nitrogen atmosphere at a pressure of 5 kg / cm ^2.
It was heated to 000 ° C., and then the residual oxygen was heated under carbon contact to reduce and remove it, and a roll having silicon oxide having a surface of silicon oxide of 5 to 10 μm formed was manufactured and used in a hot dip galvanizing line.

As a method of forming silicon nitride as a barrier layer on the surface of the body, a cermet of tungsten carbide or an alloy of Co, Ni, Cr, Al and Y is sprayed on the lower layer, and a thin layer of about 5 to 15 microns is formed on the upper layer. After the metal silicon film is sprayed and further processed by polishing to a final finishing accuracy, the metal silicon surface is heated to about 1000 ° C. in an electric furnace with a concentration of 80 to 100% and a pressure of 1 to 10 kg / cm ² nitrogen atmosphere. It is also possible to convert silicon nitride to 5 to 10 microns, and the present inventor also produced a hot-dip galvanizing roll by this method and used it in an actual hot-dip galvanizing line.

Since silicon oxide partially remains in the silicon nitride formed by this method and becomes a glass-like structure to lower the strength, 1 to 10% of alumina is added to the coating of silicon oxide or metallic silicon and sprayed. Therefore, a silicon nitride film is formed, and silicon in the glass-like structure in the film is solid-solution replaced with aluminum and nitrogen is dissolved with oxygen so that the glass-like structure does not exist in the grain boundaries of the structure.

Further, the present inventor confirmed through experiments that even a silicon oxide film to which zirconia partially stabilized by alumina and yttria was added by the above method, a high-strength silicon nitride film can be formed by the above-mentioned nitriding treatment. There is.

With the method of the present invention, it has become possible to easily form silicon nitride and a ceramic film containing silicon nitride as the first component, which has been conventionally difficult to form a film, on the base surface of a hot dip galvanizing roll. .

A silicon nitride film is formed on the upper layer of the product of the present invention and tungsten carbide cermet or Co is formed on the lower layer.
As a result of using a hot-dip galvanizing roll sprayed with an alloy consisting of Ni, Cr, Al, and Y in a real line in which the present inventor is engaged, in the case of a conventional cermet containing cobalt or nickel, the sprayed coating is zinc in a molten state. It was possible to solve the problem of contact deterioration and peeling of the coating within a total immersion period of 6 to 12 months.

Further, a phenomenon in which a ternary compound of zinc, iron, and aluminum adheres to the interface that has been altered by cermet spraying containing conventional cobalt or nickel by reaction and the thickness grows and the ternary compound adheres to the strip surface is also significantly I was able to improve.

In the case of the conventional cermet containing cobalt or nickel, in the case of the thermal spray coating, the ternary compound adhered to the surface of the roll matrix by 1 mm or more in the immersion period of a total of 6 months. In the case of, the thickness of the ternary compound that has reacted and adhered is 0.1 mm or less, and the ternary compound of zinc, iron, and aluminum that has adhered can be easily peeled off after pulling up the roll from the immersion bath. It was in a state.

Further, when the product of the present invention is immersed in a molten zinc bath, it is possible to omit the strict temperature control and handling for uniform heating as in the conventional product, and crack troubles can be caused even by simple preheating with a gas burner. Since it can be used without causing any trouble, the roll replacement work has been greatly simplified.

[0043]

INDUSTRIAL APPLICABILITY As described above, the hot-dip galvanizing roll of the present invention and the method for producing the hot-rolled galvanizing roll have extremely excellent characteristics in terms of facilitating film formation, improving durability in a hot dip galvanizing bath, and improving ease of handling. is doing.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating the present invention.

FIG. 2 is a perspective view illustrating details of a sprayed coating of the present invention.

[Explanation of symbols]

 1 ... Thermal spray coating 2 ... Body 3 ... End plate 4 ... Shaft

Claims (6)

[Claims] 1. A film in which silicon of a silicon nitride film or a silicon nitride film is replaced with aluminum and nitrogen is replaced with oxygen to form a solid solution on the surface of a body of a roll used for transporting or supporting a steel plate in a hot-dip galvanizing bath for steel plates. A hot-dip galvanized roll characterized by being formed. 2. The surface of the body of a roll used to convey or support a steel sheet in a hot-dip galvanizing bath for steel, Co,
A film formed by spraying an alloy consisting of Ni, Cr, Al, and Y, and a silicon nitride film or a silicon nitride film containing silicon as aluminum and nitrogen as oxygen is formed as a solid solution film on top of the film. Hot dip galvanizing roll. 3. A cermet film containing WC as a main component is formed on the surface of the body of a roll used to convey or support a steel plate in a hot-dip galvanizing steel plate, and a silicon nitride film or a silicon nitride film is formed on top of it. A hot-dip galvanizing roll characterized by forming a film in which silicon is replaced by aluminum and nitrogen is replaced by oxygen to form a solid solution. 4. A roll body used for transporting or supporting a steel sheet in a hot-dip galvanizing bath for a steel sheet, has 5-2 on its surface.
After coating a 0-micron silicon oxide film or a metal silicon film by a thermal spraying method, it is heated to a temperature of 800 to 1400 ° C. in an atmosphere of nitrogen gas or ammonia gas having a concentration of 80 to 100% and an absolute pressure of 1 to 10 kg / cm ^2. In the case of a silicon oxide film, the method for producing a hot dip galvanizing roll is characterized in that oxygen in the film is reduced and removed by carbon. 5. A roll body used for transporting or supporting a steel sheet in a hot-dip galvanizing bath for a steel sheet, has 5-2 on its surface.
After coating a silicon oxide film or a metal silicon film with 0 to 1% of alumina added by a thermal spraying method, the concentration is 80 to 100%, and the absolute pressure is 1 to 10 k.
Manufacture of a hot dip galvanizing roll characterized by heating to a temperature of 800 to 1400 ° C. in an atmosphere of g / cm ² of nitrogen gas or ammonia gas, and in the case of a silicon oxide film, oxygen in the film is reduced and removed by carbon. Method. 6. A roll body used for conveying or supporting a steel sheet in a hot-dip galvanizing bath for a steel sheet has 5 to 5 surfaces.
0 micron 1-10 percent alumina and 5-2
After coating a silicon oxide film or a metal silicon film containing 0% zirconia by a thermal spraying method, the concentration is 80 to 10
Temperature of 800 to 1 in an atmosphere of nitrogen gas or ammonia gas at 0% and an absolute pressure of 1 to 10 kg / cm ^2.
A method for producing a hot-dip galvanizing roll, which comprises heating to 400 ° C. and, in the case of a silicon oxide film, reducing and removing oxygen in the film with carbon.