JPH073425A - Two-melting-point heat-resistant thermal spray material and heat-resistant member subjected to thermal spray processing - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a thermal spray material and a hearth roll obtained by spraying the thermal spray material, which has excellent high-temperature wear resistance and build-up resistance. [Composition] As a structure stabilizing material for zirconium oxide, C
Contains 50% by weight or more of a high melting point stabilized ZrO ₂ part containing 35% by weight or less of one or more of aO, MgO, a rare earth oxide, Y ₂ O ₃ and HfO ₂ , and the balance is other than ZrO ₂ -SiO ₂ system. A heat-resistant thermal spray material composed of a SiO ₂ -based low-melting point composite oxide, a low-melting point eutectic ceramics or a peritectic type ceramics, and unavoidable impurities, and a high-melting point ceramics part and a low-melting point ceramics part. Hearth roll with a sprayed layer. [Effect] High-quality, long-life as a hearth roll by forming a coating layer consisting of high-melting-point ceramics part and low-melting-point ceramics part with excellent build-up resistance, peeling resistance, and abrasion resistance on the roll surface. Can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant thermal spray material and a heat-resistant member having a thermal spray layer formed from the thermal spray material, and particularly to a heat treatment furnace roll (excellent in high temperature wear resistance and build-up resistance). Hereinafter referred to as Hearth Roll).

[0002]

2. Description of the Related Art A hearth roll anneals and conveys a heat-treated steel material at an oxidizing or reducing atmosphere temperature of 500 to 1100 ° C., so that the surface thereof is subject to abrasion, oxides and iron adhered to the heat-treated steel material and iron. Powders often adhere and deposit on the roll surface to form so-called build-ups.

If such unevenness due to wear or build-up occurs on the hearth roll, the steel sheet, which is the material to be heat-treated, is flawed during transportation, which causes deterioration in quality. In order to avoid this, the operation of the heat treatment furnace is periodically interrupted to clean the hearth roll surface and replace it with a spare part.

[0004]

For this reason, conventionally, a heat-resistant alloy of high chromium and high nickel was used as the material of the hearth roll, and the heat-resistant alloy cermet or ceramics was sprayed on the roll surface. Was still not enough.

The present invention solves the above-mentioned conventional problems and is a coating layer having excellent build-up resistance, peeling resistance and abrasion resistance against a hearth roll used in an oxidizing or reducing atmosphere. Is formed on the roll surface to provide a high-quality, long-life hearth roll.

[0006]

In order to achieve the above object, the inventors of the present invention have conducted extensive studies and as a result, it is effective to specify the component composition as a constituent material of the thermal spray layer formed on the roll surface. Based on this finding, the present invention has been completed.

That is, in the present invention, CaO, MgO, rare earth oxides, Y
₂ 0 _3, a high melting point stabilizing ZrO ₂ parts of the HfO ₂ 1 or more contained than 35 wt% includes 50 wt% or more, the remainder Z
SiO ₂ -based low melting point composite oxides other than rO ₂ —SiO ₂ -based oxides,
The gist is a heat-resistant thermal spray material, which comprises a low melting point eutectic ceramics or a peritectic type ceramics and unavoidable impurities, and is composed of a high melting point ceramics portion and a low melting point ceramics portion. _{, CaO · SiO 2, 3CaO ·} 2SiO 2, 2CaO
_{· SiO 2, 2MgO · SiO 2} , MgO · SiO 2, 3
Al ₂ O ₃・ 2SiO ₂ , CaO ・ Al ₂ O ₃・ 2SiO ₂ ,
2CaO ・ Al ₂ O ₃・ SiO ₂ composite oxide, Al ₂ O ₃
-SiO ₂ KyoAkiraiki component, MgO-SiO ₂ KyoAkiraiki component, CaO · SiO ₂ KyoAkiraiki component, ZrO ₂ -Al ₂ O ₃
It is composed of a SiO ₂ -based low melting point component system. In addition to the above, at least one of Co and Ni is the main component, and further 10 to
40% by weight of one or more of alloys or carbides and borides having a composition of 30% Cr and 15% or less Al, and optionally 1% or less Y, Hf or more.
The gist of the heat-resistant thermal spray material added is as follows. Further, the present invention, the heat-sprayed layer composed of the heat-resistant spraying material is formed on the surface of the hearth roll and the sprayed layer is treated with a sealing agent containing a ceramic-forming component, and further heat-treated to form a coating film. The gist is a hearth roll that has been sealed and densified.

[0008]

The structure and operation of the present invention will be described. It is presumed that the sprayed layer of the hearth roll of the present invention exhibits properties by the mechanism described in detail below. That is, Fe ₂ O ₃ or Fe ₂ O ₃ or Fe was analyzed based on the analysis of the welding phenomenon when the ceramics layer is formed by thermal spraying on the steel material surface and the build-up generation phenomenon.
Oxides with low reactivity with O should be selected. Therefore, oxides with high melting point and thermodynamically low standard energy of formation (large absolute value) should be used. From the viewpoint of bonding force, the thermal spray material should be formed of a high-stability ceramic part having a high melting point and a high-bonding ceramic part having a relatively low melting point, and the low-melting part should also be Fe.
_A composite oxide system, which is a ceramic that has low reactivity with ₂ O _3, etc., is preferable, the bonding part ceramics should have a fine grain structure due to the structure of the thermal spray coating, and the eutectic low melting point ceramics are also effective. It is excellent in adhesion to the base material of the coating that induces very fine microcracks in it. For this reason, when the high melting point oxide and the low melting point oxide are mixed and sprayed, the phase diagram shows a liquidus line. Extending between solidus lines to facilitate the formation of fine solidification cracks in ceramics. A film without high-temperature microcracks causes cold cracking at low temperatures (for example, glass cracking at room temperature) and penetrates the film. The present invention was completed by recognizing that cracks are generated and easily propagated throughout the coating, and that the coating structure should be a relatively stable material that does not change in crystal form after solidification until room temperature. , Conventional ceramics thermal spray material It is built with a new technological concept that is not found in

The reason why the component composition is limited in the present invention will be described. Zirconium oxide has a high melting point and is selected as an oxide having a low reactivity with Fe ₂ O ₃ or the like, and is used as a stabilizer of tetragonal or cubic at room temperature, which includes CaO, MgO and Ce.
One or more kinds of O ₂ , Y ₂ O ₃ and HfO ₂ are added in an amount of 35% by weight or less. That is, 35% by weight is selected as the upper limit of the necessary and sufficient amount of the stabilizer added. Stabilized ZrO _{2 is set} to 50% by weight or more because it has reactivity with Fe ₂ O ₃ as a whole structure of the coating, micro-cracking of the structure and cracking resistance and peeling resistance due to thermal shock closely related thereto. , Selected according to the impact resistance of the coating. If it is less than 50% by weight, the structure ratio of the high melting point portion and the low melting point portion becomes unsuitable.

Remaining CaO ・ SiO ₂ , 3CaO ・ 2S
_{iO 2, 2CaO · SiO 2,} 2MgO · SiO 2, Mg
O ・ SiO ₂ , 3Al ₂ O ₃・ 2SiO ₂ , CaO ・ Al _{2
O 3 · 2SiO 2, 2CaO ·} Al 2 O 3 · SiO 2 , etc. S
The iO ₂ -based low melting point oxide is selected based on its low melting point and reactivity with Fe ₂ O ₃ .

That is, these complex oxides are composed of a single C
It has been found that aO, SiO ₂ , MgO and the like have reactivity with Fe ₂ O ₃ , but when the above composite oxide is used, the reactivity becomes extremely small. Moreover, these melts remain up to about 2150 ° C. or lower, and act as a binder for high melting point ceramics. In addition, it partially dissolves the high melting point ceramics portion and effectively acts to generate solidification microcracks.

Si having a low melting point and a eutectic refining effect
As an O ₂ -based eutectic component, CaO-SiO ₂ -based (SiO ₂
45 wt% etc.), Al ₂ O ₃ —SiO ₂ system (Al ₂ O ₃
9 wt%), MgO-SiO ₂ system (SiO ₂ 38 wt
%, 65 wt%), etc., and Al ₂ O ₃ —ZrO ₂ —Si
There seems to be an O ₂ system.

Therefore, the present invention also includes the case where the high-coupling-force ceramics utilizing the eutectic refining or the peritectic refining are used to bond the high-melting point low-reactivity ceramics as an aggregate. In particular, although these low melting point fine ceramics structures are reactive with Fe ₂ O ₃ etc. as a single component, it is acknowledged that it is difficult to form buildup because the structure is fine. It is considered that even if one crystal grain peels off and adheres to the steel sheet, it has no adverse effect because it is a fine grain.

Further, in the second aspect, when the low melting point ceramic part is a ternary system, ZrO ₂ --Al ₂ O _3-
The low melting point component system of SiO ₂ is also specified. This is because the melting point of this component system can be lowered to 1800 ° C. or lower.

In addition to the cermet formation by the MCrAlY-based alloy, the third aspect of the present invention is to add carbides and borides, which have a low reactivity with the above-mentioned ceramics, to the above-mentioned ceramics structure, and utilize the high hardness of these additives to form the structure. It is intended to disperse and strengthen the whole. Therefore, in some cases, nitride may be the target. The carbide may partially react with the O _{2 component} in the oxide or the ceramics, but in the present invention, it is added in the range of 40% by weight or less so that the dispersion strengthening of the structure is appropriately performed.

The coating properties were also good when metal Zr was added and ZrO ₂ was produced during thermal spraying as in Example 20 described later. Therefore, the addition of the metal component which finally becomes the oxide of the present invention is also included in the technical scope of the present invention. A fourth aspect relates to a heat resistant member having a thermal spray layer formed of the thermal spray material, for example, a hearth roll.

According to a fifth aspect of the present invention, the pores of the micro-cracked coating of the thermal sprayed layer are sealed and the ceramics are sealed by low temperature firing. Therefore, as a sealing liquid, an aqueous solution containing chromic acid as a main component (Cr ₂ O ₃ generation), a metal alkoxide-containing alcohol solution or a water addition solution thereof (sol-gel method) is impregnated and baked to produce various metal oxides ( SiO ₂ , CeO ₂ ,
ZrO ₂ etc.) can be used for sealing. Therefore, methods similar to these are also possible, and it goes without saying that they can be used as long as they form ceramics as the sealing method. It seems that the firing temperature should be 300 ° C. or higher.

The melting point of the high melting point ceramic portion of the present invention is preferably 2200 ° C. or higher, and the lower limit temperature at which the low melting point ceramics melt remains is preferably 2150 ° C. or lower. Apparent liquidus line and solid phase Line temperature difference is at least 5
It has been found that it is better to set the temperature above 0 ° C. Therefore, combinations of ceramics that meet these conditions are also possible.

As the thermal spraying method, a high-speed gas thermal spraying method, an explosive thermal spraying method, a plasma thermal spraying method or the like can be applied, but in any case, the heating time at the time of thermal spraying is extremely short, and the portions having different melting point differences are uniformly melted and melted. Seems too short. As shown in the schematic diagram of FIG. 1, the thermal spraying structure is clearly divided into two phases and exhibits the effects as described above. Further, it is the same as the ordinary ceramics spraying that the application of the metal-based or cermet-based underlaying spraying and the application of the gradient spraying method are effective under the ceramics spraying.

[0020]

EXAMPLES The present invention will be specifically described with reference to Examples.
This does not limit the invention. Example 1 A thermal spraying powder having two melting points shown in Table 1 was prepared by a granulation method in such a manner that a high melting point material was surrounded by a low melting point material in a particle size range of 30 to 100 μm. In addition, Table 1
In the figures, the number before the chemical component symbol indicates% by weight, and the one without a number indicates that the rest is the component. However, the number of the composite oxide indicates the number of moles.

[0021]

[Table 1]

A thermal spray test piece was prepared using this thermal spray powder and subjected to various tests shown in Table 2. As an undercoat, 50 μm of CoNiCrAlY or the like was plasma sprayed, and then 200 μm of a topcoat was plasma sprayed. The thermal spray materials (No. 1 to No. 28) of the present invention are comparative examples (No. 2).
9-No. Compared to 31), it has excellent build-up resistance, abrasion resistance, and peeling resistance. It has been confirmed that, in addition to the granulation and encapsulation method, a method for producing a thermal spray material, a method for mixing electro-melting powder, or a combination of these methods can achieve good results.

[0023]

[Table 2]

Table 3 shows the characteristics of the sprayed layer subjected to the sealing treatment.
Shown in. The sealing material Cr ₂ O ₃ was baked at 450 ° C. for 30 minutes after applying the chromic acid main component aqueous solution, and the other oxide sealing materials were metal component-containing alkoxide alcohol solution (10%
After adding water), it was baked at 450 ° C. for 30 minutes.

[0025]

[Table 3]

The build-up occurrence ratio is determined by the evaluation equipment devised by the present inventors. As the test equipment, five rolls having a diameter of 250 mm and a body length of 400 mm are arranged in an electric furnace with the steel plate wrapped around as shown in FIG. 2, and the steel plate is run. When the steel plate is run, slip is applied to the steel plate and the test roll only for the roll to be evaluated based on the running speed of the steel plate, and the degree of build-up that adheres to the roll surface is evaluated.

The test conditions are annealed cold-rolled steel sheet having a steel sheet thickness of 0.7 mm and a width of 300 mm, and the atmosphere is one hour during the heating up to 800 ° C. after the steel sheet starts running in the electric furnace. An oxide film is formed in advance. After that, the nitrogen in which 2% of hydrogen has been mixed in advance is charged for 0.5 hour while heating the steel plate to 900 ° C. while the steel is running, and the air in the electric furnace is replaced.

Further, the sample is held at a temperature of 900 ° C. for 1 hour in a nitrogen atmosphere containing hydrogen. The steel plate is continuously run even during the retention, so that the slip ratio between the sprayed evaluation roll and the steel plate is 1%. After the restraint is completed, the running of the steel plate and the power supply of the electric heater are stopped, and the steel is naturally cooled in a nitrogen atmosphere containing hydrogen. The evaluation is the buildup occurrence rate, that is, the area of the buildup that has occurred is measured using an image processing method, and then the value obtained by dividing the area of the buildup by the roll surface area is the occurrence rate of the buildup,
The unit is%, and the lower the generation ratio value, the more the build-up is less likely to occur and the thermal spray coating is evaluated.

As shown in FIG. 3, the laboratory test method for abrasion resistance is as follows. A spray coating of a test piece having a square shape of 50 mm square and a thickness of 10 mm, which has a spray coating formed in advance, has an outer diameter of 4 mm.
Is evaluated by the amount of wear of the thermal spray coating when the ordinary steel pin is pressed with a load of 5 kg and the circular orbit of 50 mm diameter is drawn and slid. That is, wear volume / mileage / pin load is calculated and evaluated.

The thermal shock test was carried out according to the heat peeling test method of the JIS H 8666 ceramics thermal spray test method. After heating the sprayed coating of a test piece having a shape of 50 mm square and a thickness of 10 mm to 900 ° C., the step of dropping in water is repeated, and evaluation is made by the number of repetitions until cracks or peeling occur in the surface layer of the sprayed coating. It is a thing.

[0031]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, a hearth roll having a coating layer excellent in build-up resistance, peeling resistance and abrasion resistance is formed on the surface of the roll to obtain high quality, It has excellent effects such as long life and is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional explanatory view showing the structure of a coating formed by spraying a ceramic sprayed material of the present invention.

FIG. 2 is a schematic explanatory view of equipment for testing build-up resistance of a member spray-coated with a ceramic spray-coated material of the present invention.

FIG. 3 is a schematic explanatory view of equipment for testing the wear resistance of a member spray-coated with a ceramic spray-coated material of the present invention.

[Explanation of symbols]

 1 High melting point part 2 Low melting point part 3 Micro crack 4 Dispersed phase 5 Ceramics film 6 Bond coat film 7 Base material 20 Electric furnace 21 Test roll 22 Steel plate 23 Heater 31 Thermal spray coating 32 4mm diameter ordinary steel pin 33 Wear part

Front Page Continuation (72) Inventor Masaru Kawazoe 1-3-8 Yaesu Chuo-ku, Tokyo Nittetsu Hard Co., Ltd. (72) Inventor Muneto Hiroshige 1-3-8 Yaesu Chuo-ku, Tokyo Nippon Steel Hard Co., Ltd. In the company

Claims (5)

[Claims] 1. A structure stabilizing material for zirconium oxide, including CaO, MgO, a rare earth oxide, Y ₂ O ₃ and HfO _2.
High melting point stabilized Zr containing 35% by weight or less of one or more of
The content of O ₂ is 50 wt% or more, and the balance is ZrO ₂ —SiO ₂
-Resistant thermal spraying characterized by being composed of a high melting point ceramics part and a low melting point ceramics part, which are composed of SiO ₂ -based low melting point composite oxides other than material. 2. The low melting point ceramic part is CaO.Si.
O ₂ , 3CaO · 2SiO ₂ , 2CaO · SiO ₂ , 2M
gO ・ SiO ₂ , MgO ・ SiO ₂ , 3Al ₂ O ₃・ 2Si
O ₂ , CaO ・ Al ₂ O ₃・ 2SiO ₂ , 2CaO ・ Al ₂
O ₃ · SiO ₂ composite oxide, Al ₂ O ₃ —SiO ₂ eutectic region component system, MgO—SiO ₂ eutectic region component system, CaO · Si
The heat-resistant thermal spray material according to claim 1, which is composed of an O ₂ eutectic region component system and a ZrO ₂ —Al ₂ O ₃ —SiO ₂ system low melting point component system. 3. A composition containing at least one of Co and Ni as main components, and further containing 10 to 30% of Cr and 15% or less of Al, and optionally 1% or less of one of Y and Hf. The heat-resistant thermal spray material according to claim 1 or 2, wherein 40% by weight or less of one or more of alloys, carbides and borides is added. 4. A heat resistant member having a sprayed layer formed of any of the heat resistant sprayed materials according to claim 1. 5. The heat-resistant member according to claim 4, wherein the thermal sprayed layer is treated with a sealing agent containing a ceramic-forming component, and further heat-treated to seal and densify the coating.