JP2960262B2 - Roll for heat treatment furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is provided in a heat treatment furnace,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll for heat treatment furnace (hereinafter, hearth roll) which is excellent in build-up prevention, high-temperature peeling resistance and high-temperature abrasion resistance.

[0002]

2. Description of the Related Art For example, a hearth roll disposed in a continuous annealing furnace has a surface which is to be continuously annealed and conveyed for a long time in an oxidizing or reducing atmosphere at 600 to 1300 ° C. to convey the material. Abrasion occurs, and oxides and iron powder adhering to the material to be heat-treated adhere and accumulate on the roll surface to form a so-called build-up.

When such irregularities due to abrasion or build-up occur on the hearth roll, they are flawed while the steel sheet as the material to be heat-treated is being conveyed, causing deterioration in quality. In order to prevent such steel sheet quality deterioration,
After the operation is periodically interrupted to cool the inside of the heat treatment furnace, an operator enters the furnace to grind the surface of the hearth roll or replace the roll itself.

Conventionally, in order to prevent such abrasion and build-up, as described in, for example, Japanese Patent Publication No. 57-29549, a roll surface is spray-coated with ceramics such as zirconia and alumina. Had been proposed.

However, the coating obtained by spraying alumina has a volume change in a high-temperature atmosphere and deteriorates intergranular strength. The coating obtained by spraying zirconia has a high melting point of zirconia and is not dense. There is a disadvantage that the oxide is easily bitten and the build-up resistance is poor.

[0006]

The present inventors have a large build-up prevention effect to be applied to hearth rolls used in these oxidizing or reducing atmospheres, and have excellent high-temperature peeling resistance and abrasion resistance. As a result of various studies on a coating material and a coating means, a coating roll having excellent build-up resistance and excellent peeling resistance and abrasion resistance was found, and the present invention was completed.

That is, according to the present invention, a coating layer having a large build-up prevention effect and having excellent high-temperature peeling resistance and abrasion resistance is formed on the roll surface when used in an oxide or reducing atmosphere. The purpose is to provide a hearth roll.

[0008]

According to the present invention, a Zr-based silicide (hereinafter, referred to as ZrSi ₂ ) is contained in an amount of 10 to 70 vol%, and the balance is at least one of MgO, CaO, and Y ₂ O ₃ by 5% by weight. Zr-based oxides containing up to 20% (hereinafter referred to as stabilized ZrO
₂ ) is a roll for a heat treatment furnace having a thermal sprayed coating consisting of:

Hereinafter, the present invention will be described in detail. The substrate of the hearth roll is made of heat-resistant cast steel. On these substrates, a ceramic powder film is formed by spraying a material powder comprising ZrSi ₂ and stabilized ZrO _{2 on} the surface thereof.

In the present invention, the material for thermal spraying is MgO, Ca
O, were used Y ₂ O ₃ stabilized ZrO ₂ containing 5-20% by one or more wt%, low reactivity with iron oxides, are stable without causing transformation at a high temperature atmosphere That's why. However, stabilized ZrO ₂ has a disadvantage that the melting point is high and a dense coating cannot be obtained by thermal spraying, iron oxide is easily bitten into the coating, and the build-up resistance is poor.

Therefore, in the present invention, the stabilized ZrO ₂ raw material powder has a relatively low reactivity with iron oxide and a low melting point.
An rSi ₂ powder is added to form a dense film having excellent build-up resistance, high-temperature peel resistance, and high-temperature wear resistance.

[0012] ZrSi ₂ addition amount from the test results of ZrO ₂
If the amount is less than 10 vol%, the effect of densification of the film cannot be obtained, and the amount of ZrSi ₂ added is 70 v to the amount of ZrO _2.
It was found that the build-up resistance of the coating deteriorated due to the influence of ZrSi _{2 when} the content exceeded ol%. From this, ZrS
i The ₂ amount should be about 10 to 70 vol%.

[0013]

The test contents and results are described in detail below. The ceramic coating of the present invention was tested for build-up resistance, peel resistance, and abrasion resistance. Among them, 50 × 50 × 10mm SUS was used for peeling resistance and abrasion resistance test.
50 × 30 × 5mm S for base material and build-up resistance test
The sample sprayed as shown in Table 1 on a US substrate was used.
Table 2 shows the physical property values of the raw material powders used in forming the thermal spray coating.

[0014]

[Table 1]

[0015]

[Table 2]

The present inventors first conducted the following experiment in order to examine the build-up resistance of the product of the present invention. FIG. 1 shows the test apparatus used for the experiment. SCH22 (25Cr-20
Ni-0.4C) was manufactured, and a half-moon shaped pressure roll 6 having a radius of 35 mm was manufactured and reciprocally slid on each of the two sprayed samples 4, 4 'sprayed as shown in Table 1 to build up. An evaluation device capable of reproducing the occurrence was used. Two sprayed samples 4 and 4 ′ were sprayed on both sides 4 and one sprayed on one side 4 ′, and a build-up material 5 (between the half-moon shaped pressure roll 6 and the two samples 4 and 4 ′) was used. Iron oxide powder Fe ₃
O ₄ : true specific gravity 5.18: particle size distribution of 10 μm or less) and put in tray 3. These devices are arranged in a crucible type electric furnace 2 and reciprocate the pressure roll 6 at a constant temperature of 850 ° C. for 4 hours in a reducing atmosphere of N ₂ -H ₂ 5% to reduce build-up. Wake up. In the drawing, reference numeral 1 denotes an atmosphere gas introducing pipe, 7 denotes a pressure rod, 8 denotes a load material, 9 denotes a counterbalance, 10 denotes a seal plate, and 11 denotes a speed reducer.

In the above reproduction experiment, as shown in FIG.
The surface directly in contact with the half-moon roll 6 is designated as A surface, the back surface is designated as B surface, and the surface facing B surface is designated as C surface, and the build-up resistance after the test is shown in Table 3. Using the index, the respective evaluation points were compared with the total value. The build-up resistance of the thermal sprayed sample was evaluated based on the average value of the area ratio of Fe ₃ O ₄ as a build-up source.

[0018]

[Table 3]

Table 4 shows the results of the build-up resistance test.
It was found that the product of the present invention had a higher build-up resistance index than any of the comparative materials, a small area ratio of Fe ₃ O ₄ powder adhered, and excellent build-up resistance. It is considered that the reason why the build-up resistance of the comparative material is lower than that of the present invention is that the added ZrSi ₂ reacts slightly more with the iron oxide than ZrO ₂ .

[0020]

[Table 4]

Next, in order to examine the high temperature peeling resistance of the product of the present invention, the following experiment was conducted. The peeling resistance test was performed by measuring the number of peelings when the sample was repeatedly subjected to thermal shock of holding at 1000 ° C. for 15 minutes and then holding in water for 15 minutes. As shown in Table 5, it was found that the present invention was slightly superior in peel resistance.

[0022]

[Table 5]

Next, in order to examine the high temperature wear resistance of the product of the present invention, the following experiment was conducted. For the wear resistance test,
Using a sample similar to that used in the peeling resistance test, and using an atmosphere N
A ball of material SUJ2 was slid on the surface of the sample at a load of 2 kg, a sliding speed of 0.2 m / s, and a sliding distance of 720 m at a temperature of 900 ° C. in _2- H ₂ 2%, and the high-temperature wear resistance was examined. Table 6
As shown in the figure, the product of the present invention was found to be slightly superior in abrasion resistance because the film was densified. It is considered that the coating was densified because a large amount of ZrSi ₂ having a low hardness was added to the sample, but the hardness of the coating itself was reduced, resulting in poor wear resistance.

[0024]

[Table 6]

In the product of the present invention, CoCrAlY was used as the bond coat component, but CoNiCrAlY, N
Similar results were obtained with the iCrAlY system. In order to further improve the peeling resistance, a so-called cermet layer in which metal is added to the top layer may be used.

[0026]

As described above, the hearth roll of the present invention is remarkably excellent in build-up resistance, high-temperature peeling resistance and abrasion resistance, and greatly contributes to extending the roll life.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a build-up test evaluation device and method.

FIG. 2 is a partially enlarged view of FIG.

[Explanation of symbols]

 4,4 'thermal spray sample 5 build-up material 6 pressure roll

Claims (1)

(57) [Claims] 1. A Zr-based silicide of 10 to 70 vol% of the whole
At least one by weight contains MgO, CaO, Y ₂ O _3.
Roll for a heat treatment furnace having a thermal spray coating made of a Zr-based oxide containing 5 to 20%.