JP3076888B2 - 2 melting point heat-resistant sprayed material and heat-resistant member processed by thermal spraying - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Hearth rolls are used to anneal and convey a steel material to be heat-treated at an oxidizing or reducing atmosphere temperature of 500 to 1100 ° C., so that the surface thereof is subject to wear, and oxides or iron adhering to the heat-treated steel material. The powder often adheres and accumulates on the roll surface to form a so-called build-up.

[0003] If such irregularities due to wear or build-up occur on the hearth roll, flaws are formed while the steel sheet as the material to be heat-treated is being conveyed, which causes quality deterioration. In order to avoid this, the operation of the heat treatment furnace is periodically interrupted to grind and clean the surface of the hearth roll, or to replace it with a spare part.

[0004]

For this reason, conventionally, heat-resistant alloys of high chromium and high nickel have been used for the material of the hearth roll, and further, heat-resistant alloy cermets and ceramics have been sprayed on the roll surface. Was still not enough.

The present invention solves the above-mentioned conventional problems, and provides a coating layer having excellent build-up resistance, peel 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]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies, and as a result, it is effective to specify the composition of components as a constituent material of a sprayed layer formed on the roll surface. This led to the completion of the present invention.

That is, according to the present invention, CaO, MgO, rare earth oxide, 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,
The gist of the present invention is a heat-resistant sprayed material comprising low-melting eutectic ceramic or peritectic ceramic and unavoidable impurities, comprising a high-melting ceramic part and a low-melting ceramic part. _{, 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 ,
Composite oxides of _{2CaO · Al 2 O 3 · SiO} 2, Al 2 O 3
—SiO ₂ eutectic zone component system, MgO—SiO ₂ eutectic zone component system, CaO · SiO ₂ eutectic zone component system, ZrO ₂ —Al ₂ O ₃
It is composed of -SiO ₂ based low-melting component. In addition to the above, one or more of Co and Ni as main components,
40% by weight of an alloy or a carbide or boride having a composition to which 30% of Cr and 15% or less of Al, and if necessary, 1% or less of one or more of Y and Hf are added.
The gist is the heat-resistant sprayed material added below. In addition, the present invention provides a thermal spraying layer composed of the heat-resistant thermal spraying material, the hearth roll formed on the surface and the thermal spraying layer are treated with a sealing agent containing a ceramic-forming component, and further heat-treated to form a coating. 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 characteristics by a mechanism described in detail below. That is, based on the analysis of the welding phenomenon when a ceramics layer is formed by thermal spraying on the surface of a steel material and the build-up generation phenomenon, Fe ₂ O ₃ or Fe ₂ O ₃
It is necessary to select an oxide having low reactivity with O. Therefore, it is necessary to use an oxide having a high melting point and a thermodynamically low standard formation energy (having a large absolute value). From the viewpoint of bonding strength, the thermal spray material should be formed of a high melting point high stability ceramic part and a relatively low melting point high bonding ceramic part, and the low melting point part is also made of Fe.
_A composite oxide system, which is a ceramic with low reactivity with ₂ O ₃ etc., should be good. The bonding ceramics should have a fine-grained structure based on the structure of the sprayed film, and a eutectic low melting point ceramic is also effective. Inducing very fine micro cracks in the film is excellent in adhesion to the base material of the coating. For this reason, when high-melting oxide and low-melting oxide are mixed and sprayed, the phase diagram shows a liquidus line. Spreads between solidus lines to facilitate the generation of micro-solidification cracks in ceramics. Coatings without high-temperature micro-cracking cause cold cracking at low temperatures (eg, cracking of glass at room temperature) and penetrate the coating. The present invention has been completed by recognizing that cracks are generated and easily propagated throughout the film, and that the film structure should be a relatively stable material with no change in crystal form up to room temperature after solidification. , Conventional ceramic spray material It is built on new technical ideas that are not available.

The reason for limiting the component composition in the present invention will be described. Zirconium oxide has a high melting point and is selected as a low-reactivity oxide for Fe ₂ O _{3 and the} like. CaO, MgO, Ce is used as a tetragonal or cubic stabilizer at room temperature.
One or more 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 to be added. The reason why the stabilized ZrO _{2 is set} to 50% by weight or more is the reactivity with Fe ₂ O ₃ as the whole structure of the film, the micro-cracking of the structure, and the 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 inappropriate.

The 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 oxide is selected based on its low-melting property and reactivity with Fe ₂ O ₃ .

That is, these composite 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-mentioned composite oxide is used, the reactivity becomes very small. In addition, these melts remain at about 2150 ° C. or lower and function as binders for high melting point ceramics. In addition, it partially dissolves the high melting point ceramic part and effectively works to generate solidification microcracks.

Further, Si having a low melting point and a eutectic refining action
As O ₂ -based eutectic components, CaO-SiO ₂ -based (SiO ₂
45 wt%), Al ₂ O ₃ —SiO ₂ system (Al ₂ O ₃ 9
wt%), MgO-SiO ₂ system (SiO ₂ 38wt%,
65 wt%) and the like, and it seems that there is also an Al ₂ O ₃ —ZrO ₂ —SiO ₂ system.

Accordingly, the present invention also includes a case where high-melting-point and low-reactivity ceramics are bonded as an aggregate with high bonding strength ceramics utilizing these eutectic refinement or peritectic refinement. In particular, it has been recognized that these low-melting-point fine ceramic structures are reactive with Fe ₂ O ₃ or the like as a single component, but are difficult to form build-up because the structure is fine. This is considered that even if one crystal grain peels off and adheres to the steel sheet, it does not adversely affect the fine grain.

Further, in the second aspect, the low melting point ceramic part is a ternary system, and the ZrO ₂ —Al ₂ O ₃ —
It also specifies SiO ₂ -based low melting point components. This is because the melting point of the present component system can be lowered to 1800 ° C. or lower.

In addition to the cermet formation by the MCrAlY-based alloy, a carbide, a boride or the like having a low reactivity with the ceramic is added to the ceramic structure, and the high hardness of the additive material is used. It strengthens the whole dispersion. Therefore, in some cases, nitrides can also be a target. The carbide may partially react with the oxide or the O _{2 component} in the ceramics. However, in the present invention, the carbide is added in an amount of 40% by weight or less for appropriately strengthening the dispersion of the structure.

Also, as in Example 20 to be described later, when ZrO ₂ was generated during thermal spraying by adding metal Zr, the film characteristics were good. Therefore, the addition of the metal component that finally becomes the oxide of the present invention is also included in the technical scope of the present invention. Claim 4 relates to a heat-resistant member having a sprayed layer formed of the above-mentioned sprayed material, for example, a hearth roll.

According to a fifth aspect of the present invention, the pores of the micro-cracked film of the sprayed layer are subjected to a sealing treatment, and the ceramics are sealed by performing low-temperature firing. Therefore, as a sealing liquid, an aqueous solution containing chromic acid as a main component (Cr ₂ O ₃ formation), a metal alkoxide-containing alcohol solution or a water-added liquid thereof (sol-gel method) is impregnated and fired to obtain various metal oxides (sol-gel method). SiO ₂ , CeO ₂ ,
(ZrO ₂ etc.). 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 a sealing method. It seems that the firing temperature should be 300 ° C. or higher.

The melting point of the high melting point ceramic part of the present invention is preferably 2200 ° C. or more, and the lower limit temperature at which the low melting point ceramic melt remains is preferably 2150 ° C. or less. Wire temperature difference is at least 5
It has been found that a temperature of 0 ° C. or higher is good. Therefore, a combination of ceramics meeting these conditions is also possible.

As the thermal spraying method, a high-speed gas thermal spraying method, an explosive thermal spraying method, a plasma thermal spraying method, etc. can be applied. In each case, the heating time at the time of thermal spraying is extremely short, and portions having different melting points are uniformly melted and melted. Seems too short. As shown in the schematic diagram of FIG. 1, the sprayed structure is clearly divided into two phases, and exhibits the effect as described above. Under the ceramic spraying, the application of the metal-based or cermet-based underlay spraying, the application of the inclined spraying method, and the like are effective as in the case of the normal ceramic spraying.

[0020]

EXAMPLES The present invention will be described specifically with reference to Examples.
This does not limit the invention. Example 1 A sprayed powder having two melting points shown in Table 1 was produced by a granulation method so as to surround a high melting point material with a low melting point material in a particle size range of 30 to 100 μm. Table 1
In the figures, the numbers before the chemical component symbols indicate% by weight, and those without numbers indicate that the remainder is all the components. However, the number of the composite oxide indicates the number of moles.

[0021]

[Table 1]

Thermal spray test pieces were prepared using the thermal spray powder and subjected to various tests shown in Table 2. After plasma spraying 50 μm of CoNiCrAlY or the like as an undercoat, a 200 μm top coat was plasma sprayed. The thermal spray material of the present invention (No. 1 to No. 28) is a comparative example (No. 2).
9-No. Excellent in build-up resistance, abrasion resistance, and peeling resistance compared to 31). It has been confirmed that a good result can be obtained by a method of producing a thermal spray material by a method of mixing an electrofused powder or a combination thereof, in addition to a granulation encapsulation method.

[0023]

[Table 2]

Table 3 shows the properties of the thermal 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 the application of the aqueous solution of the main component of chromic acid, and the other oxide sealing material was a metal component-containing alkoxide alcohol solution (10%
After adding water, the mixture was baked at 450 ° C. for 30 minutes.

[0025]

[Table 3]

The build-up rate was determined by an evaluation facility devised by the present inventors and others. In the test equipment, five rolls each having a diameter of 250 mm and a body length of 400 mm are arranged in an electric furnace with the steel sheet wound thereon as shown in FIG. When the steel sheet is run, slip is applied to the steel sheet and the test roll only for the roll to be evaluated based on the running speed of the steel sheet, and the degree of build-up adhering to the roll surface is evaluated.

The test conditions were an annealed cold-rolled steel sheet having a thickness of 0.7 mm and a width of 300 mm. The atmosphere was an atmosphere for one hour while the steel sheet was running in an electric furnace and heated to 800 ° C. for one hour. To form an oxide film in advance. Then, for 0.5 hour while heating the steel sheet to 900 ° C. with the steel sheet running, nitrogen mixed with 2% hydrogen is sealed in advance to replace the air in the electric furnace.

Further, the temperature is maintained at 900 ° C. for 1 hour in a nitrogen atmosphere containing hydrogen. During the holding, the steel sheet is continuously run so that the slip ratio between the sprayed evaluation roll and the steel sheet is 1%. After the holding is completed, the running of the steel sheet and the power supply of the electric heater are stopped, and the steel sheet is allowed to cool naturally in a nitrogen atmosphere containing hydrogen. Evaluation is the build-up occurrence ratio, that is, the area of the build-up that has occurred is measured using an image processing method, and the value obtained by dividing the build-up area by the roll surface area is the build-up occurrence ratio,
The unit is%, and the lower the value of the generation ratio, the less the build-up is generated.

As shown in FIG. 3, a lab test method for abrasion resistance is as follows: a sprayed coating is formed on a test piece having a square shape of 50 mm square and a thickness of 10 mm, and having an outer diameter of 4 mm.
Was evaluated by the amount of abrasion of the sprayed coating when a common steel pin was pressed with a load of 5 kg and slid along a 50 mm diameter circular orbit. That is, the calculation is evaluated based on the wear volume / running distance / pin load.

The thermal shock test was performed in accordance with the JIS H 8666 ceramic thermal spraying test method for heat peeling. 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 process of dropping it into water is repeated, and the number of repetitions until cracks or peeling occurs on the surface layer of the sprayed coating is evaluated. Things.

[0031]

According to the present invention, as described above, a coating layer having excellent build-up resistance, peeling resistance and abrasion resistance is formed on a roll surface as a hearth roll, and high quality, Excellent effects such as long life can be achieved, and it is industrially extremely useful.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional explanatory view showing a configuration of a film sprayed with 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 the ceramic sprayed material of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High melting point part 2 Low melting point part 3 Micro crack 4 Disperse phase 5 Ceramic 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

Continuing on the front page (72) Inventor Katsura Kawazoe 1-3-8 Yaesu, Chuo-ku, Tokyo Nippon Hard Co., Ltd. (72) Inventor Munetoshi Hiroshi 1-3-8 Yaesu, Chuo-ku, Tokyo Nippon Steel Hard Stock (56) References JP-A-58-144414 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 4/10 C23C 4/18 C21D 1/00

Claims (5)

(57) [Claims] 1. As a structure stabilizing material for zirconium oxide, CaO, MgO, rare earth oxide, Y ₂ O ₃ , HfO ₂
Melting point stabilized Zr containing 35% by weight or less of at least one of
O ₂ parts comprises 50 wt% or more, the balance ZrO ₂ -SiO ₂
SiO ₂ system other than the system low-melting composite oxide consists of low melting point eutectic type ceramics or TsutsumiAkiragata ceramics and unavoidable impurities, the heat resistance spraying, characterized in that it is constructed from a refractory ceramic part and a low melting ceramic portion material. 2. The method according to claim 1, wherein the low melting point ceramic portion 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
Composite oxides of the _{O 3 · SiO 2, Al 2} O 3 -SiO 2 KyoAkiraiki component, MgO-SiO ₂ KyoAkiraiki component, CaO · Si
_2. The heat-resistant sprayed material according to claim 1, comprising 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 adding 10 to 30% of Cr and 15% or less of Al, and optionally 1% or less of Y and Hf. 3. The heat-resistant sprayed material according to claim 1, wherein at least one of alloys, carbides and borides is added in an amount of 40% by weight or less. 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.