KR20230150728A - Materials of tools usale for burning - Google Patents

Abstract

(Problem) To provide a tool material for firing that prevents surface silica from rising even when repeatedly used in firing, has less impact on the quality of the product after firing, and can be fired under higher speed conditions than before.
(Solution) The present invention provides a base material made of silicon carbide, and at least a portion of the surface of the base material where the object to be fired has a total content of an oxide film and alumina mainly composed of mullite of 65% by mass or more and 95% by mass. A base layer of alumina-siliceous material with a thickness of 1㎛ or more and 30㎛ or less, a middle layer of 95% by mass or more of 99.9% by mass of alumina and a thickness of 1㎛ or more and 30㎛ or less, and composed of stabilized zirconia with calcia or yttria as a stabilizer. Surface layers with a thickness of 1 μm to 30 μm are sequentially formed, and all of the base layer, the middle layer, and the surface layer are firing tool materials with a porosity of 5% or less.

Description

{MATERIALS OF TOOLS USALE FOR BURNING}

The present invention relates to tool materials for firing, for example, setters, shelf boards, and sagbags.

Conventionally, it has been practiced to place a fired object in a firing tool and then bake and heat treat the fired object. For this firing tool material, ceramic materials with excellent heat resistance, such as alumina-silica material, alumina-silica-magnesia material, magnesia-alumina-zirconia material, and silicon carbide material, are used. In particular, ceramics made of silicon carbide have excellent heat resistance strength and creep resistance, making them a suitable material.

Additionally, a technique is also known in which the base material of the tool material for firing is made of silicon carbide, and an alumina layer or zirconia layer is formed on the surface of the base material.

For example, in Patent Document 1, the silicon carbide-based substrate has an apparent porosity of 20% or more and an apparent specific gravity of 3.20 or less, a silicon dioxide layer is formed on the surface of the silicon carbide crystals in the surface layer of the silicon carbide-based substrate, and the carbonization A tool material for firing silicon carbide material is disclosed in which at least one of ZrO ₂ and Al ₂ O ₃ is coated on at least the portion of the silicon substrate where the object to be fired is placed.

As described above, the firing tool material based on silicon carbide with a multilayer structure on the surface has excellent mechanical and thermal properties and can achieve increased body thickness and longer life. In addition, by forming a silicon dioxide layer on the surface of the substrate, problems such as oxidation reaction of the silicon carbide substrate, etc. on the atmosphere in the furnace, peeling of the coating layer, and sintering abnormalities such as discoloration of the fired object are also improved. .

However, if a silicon dioxide layer is formed on the surface of the silicon carbide substrate, silicon and oxygen from the silicon dioxide layer gradually rise to the surface of the zirconia coating layer through repeated use and are soon exposed. In addition, there was a risk that the silicon or oxygen would react with the fired object placed on the tool material, causing a problem of lowering the yield in firing electronic components. Therefore, in the tool material made of silicon carbide as described above, the levitation of silicon and oxygen from the base material (silicon dioxide layer) is suppressed even during repeated use, and the structure is such that no reaction occurs with the object to be fired. It is desirable.

In this regard, in Patent Document 2, a base layer with a thickness of 30 to 300 μm containing mullite as a main component is formed on the surface of a silicon carbide base material on which an oxide film (silica layer) is formed, and a surface layer made of stabilized zirconia is formed on the surface. It is described that by forming this, the levitation of silicon and oxygen from the silicon carbide base (silica layer) to the zirconia surface layer is suppressed, and the lifespan is improved even with repeated use.

In addition, Patent Document 3 describes a tool material for firing that is placed in a firing furnace and is accommodated in a firing furnace together with the object to be fired, wherein the tool material for firing is made of a silicon carbide sintered body, and silicon carbide at least in the portion where the object to be fired is placed. It is described that in addition to the SiO ₂ layer on the surface of the sintered body, layers of mullite, alumina, and zirconia are formed by plasma spraying or the like.

In addition, Patent Document 3 states that it is preferable to make each layer of mullite, alumina, and zirconia as thin as possible because the thinner the layer, the smaller the effect of thermal expansion, and the film thickness of the zirconia film is about 10㎛ to 200㎛, and the mullite film is It is described that the thickness is about 10 μm to 200 μm, and the thickness of the alumina film is about 10 μm to 200 μm.

Patent Document 1: Japanese Patent Publication No. 2006-117472 Patent Document 2: Japanese Patent Publication No. 2009-234817 Patent Document 3: Japanese Patent Publication No. 2019-11238

However, in the invention described in Patent Document 1, as described above, when a silicon dioxide layer (silica layer) is formed on the surface of a silicon carbide substrate, silicon or oxygen from the silicon dioxide layer (silica layer) is removed through repeated use. It gradually rises toward the surface of the zirconia coating layer and is soon exposed to the surface. Additionally, there was a problem in that the silicon or oxygen reacted with the fired object placed on the tool material, reducing the yield of the fired object.

In addition, in the invention described in Patent Document 2, the thickness of the film formed on the substrate is 30 to 300 μm and the heat capacity is large, so there is a problem that it is not suitable for a faster firing process.

In addition, as in the invention described in Patent Document 3, even in a firing tool material having an oxide film, an intermediate layer (base layer), and a surface layer sequentially formed on the surface of the substrate, silicon or oxygen passes through the intermediate layer or the surface layer and is deposited thereon. There was a problem in that it reacted with the fired product and lowered the yield. That is, if the thickness of the various layers laminated on the substrate is thinned, temperature followability is improved, but there is a problem that it is difficult to obtain the effect of suppressing the levitation of silicon and oxygen from the SiO ₂ layer formed on the substrate.

The present invention has been made in view of the above, and its purpose is to provide a tool material for firing made of silicon carbide, which has excellent temperature followability and in which levitation of silicon and oxygen is sufficiently suppressed.

The present invention relates to an oxide film formed on at least a portion of the surface of a substrate made of silicon carbide on which a fired object is placed, and a total content of alumina formed on the surface of the oxide film with mullite as a main component of 65% by mass or more and 95% by mass or less. an alumina-siliceous base layer having a thickness of 1 µm to 30 µm, an intermediate layer formed on the surface of the base layer containing 95% by mass to 99.9% by mass of alumina and having a thickness of 1 µm to 30 µm, and the intermediate layer. It has a surface layer formed on the surface of stabilized zirconia with calcia or yttria as a stabilizer and has a thickness of 1 ㎛ or more and 30 ㎛ or less, and all of the base layer, the intermediate layer, and the surface layer have a porosity of 5% or less. It is characterized by

Here, it is preferable that the oxide film is a SiO ₂ layer. Additionally, it is preferable that the thickness of the base material at least in the portion where the object to be fired is placed is 1.5 mm or more and 4 mm or less.

By having this structure, it is possible to make a tool material for firing made of silicon carbide, which has excellent temperature followability and sufficiently suppresses levitation of silicon and oxygen.

According to the present invention, compared to the prior art, it is possible to provide a tool material for firing made of silicon carbide, which has excellent temperature followability without employing a very complicated structure or manufacturing method, and in which levitation of silicon and oxygen is sufficiently suppressed. You can.

Figure 1 is a cross-sectional view (middle layer and surface layer omitted) for explaining the recessed portion.
Fig. 2 is a cross-sectional view showing a state in which recessed portions are formed in the base layer and the middle layer (surface layer omitted).
Figure 3 is a cross-sectional view (surface layer omitted) for explaining the penetration part.
Figure 4 is a cross-sectional view for explaining the penetration portion where the surface layer penetrates into the middle layer.

Hereinafter, embodiments of the present invention will be described.

The present invention relates to an oxide film formed on at least a portion of the surface of a substrate made of silicon carbide on which a fired object is placed, and a total content of alumina formed on the surface of the oxide film with mullite as a main component of 65% by mass or more and 95% by mass or less. an alumina-siliceous base layer having a thickness of 1 µm to 30 µm, an intermediate layer formed on the surface of the base layer containing 95% by mass to 99.9% by mass of alumina and having a thickness of 1 µm to 30 µm, and the intermediate layer. It has a surface layer formed on the surface of stabilized zirconia with calcia or yttria as a stabilizer and has a thickness of 1 ㎛ or more and 30 ㎛ or less, and all of the base layer, the intermediate layer, and the surface layer have a porosity of 5% or less. It is characterized by

First, the base material of the present invention is made of silicon carbide. Examples of the base material of the present invention include sintered bodies containing silicon carbide and unavoidable impurities (unavoidable impurities) described in Patent Documents 1 to 3.

In addition, in the description of the present invention, any silicon carbide that can be used as a firing tool material is sufficient, and it is not necessary that it is silicon carbide that meets special conditions, etc.

In the present invention, an oxide film (a film made of SiO ₂ ) is formed on the surface of the silicon carbide sintered body at least in the portion where the object to be fired is placed.

In this way, by forming an oxide film (a film made of SiO ₂ ) on the surface of the silicon carbide sintered body, oxidation of the base material (silicon carbide) can be suppressed, and further, the oxidation associated with the oxidation of the base material (silicon carbide) can be suppressed. , it is possible to suppress changes in oxygen concentration within the kiln. Additionally, by interposing an oxide film (a film made of SiO ₂ ), the adhesion between the surface of the silicon carbide sintered body and the base layer is also improved.

Here, the portion where the fired object is placed includes the location where the fired object directly contacts and the surrounding area. The point where this fired object directly contacts and the surrounding area mean a part of one main surface of the sintered body for firing, but are not limited to this and may be the entire one main surface. Additionally, if there is no particular problem, an oxide film may be formed on the entire surface of the firing tool material.

This oxide film is a film made of SiO ₂ and can be formed by oxidizing the surface of the substrate by heating it to 800°C or more and 1600°C or less in a gas atmosphere of air, oxygen, or a mixed gas containing oxygen. there is.

A method of forming the oxide film other than the above may be applied as long as the required film thickness and density can be obtained.

Additionally, the thickness of the oxide film is not particularly limited, but is preferably in the range of 0.5 μm to 1.5 μm. If the thickness of the oxide film is less than 0.5 μm, the effect of suppressing oxidation of the base material (silicon carbide) is not obtained. On the other hand, even if the thickness of the oxide film exceeds 1.5 μm, the effect does not change much, and there is a risk of cracks occurring due to stress arising from the difference in thermal expansion rate.

On the oxide film, an alumina-siliceous base layer having a total content of alumina containing mullite as a main component of 65% by mass to 95% by mass and having a thickness of 1 μm to 30 μm, and alumina 95 formed on the surface of the base layer. an intermediate layer of not less than 99.9% by mass and not more than 1 μm and not more than 30 μm thick, and a surface layer formed on the surface of the intermediate layer made of stabilized zirconia with calcia or yttria as a stabilizer and having a thickness of not less than 1 μm but not more than 30 μm. It is available.

In the present invention, the above-described base layer suppresses the levitation of silicon or oxygen from the substrate made of silicon carbide, and the middle layer relieves stress caused by the difference in thermal expansion between the substrate made of silicon carbide and the surface layer made of zirconia. And the surface layer is made of a material (zirconia) with low reactivity with the object to be fired.

The first feature of the present invention is that the thickness of each layer of the base layer, intermediate layer, and surface layer is 1 μm or more and 30 μm or less. This is particularly different from Patent Document 2 in that each layer thickness is set to be thinner than 30 μm and 300 μm or less (preferably 50 μm or more and 250 μm or less).

Since the layer thickness of the base layer, intermediate layer, and surface layer formed on the substrate is thinner than the film thickness of the prior art, the heat capacity of each of these layers decreases, and when the temperature is raised by putting it into the kiln, the temperature increase rate Even if it is made higher than before, it becomes difficult for cracks to occur. The higher temperature increase rate than before referred to herein preferably refers to 1100°C/min or more.

If the thickness of each layer exceeds 30 μm, the heat capacity of each layer increases, and cracks or cracks occur due to repetition at the temperature increase rate in the present invention, making it unbearable for use. Speaking only from the perspective of heat capacity, the thinner the thickness of each layer, the better, but anything less than 1㎛ fundamentally lacks strength and durability, and performing uniform film formation with this thinness increases manufacturing costs. It is not desirable for reasons such as: The layer thickness of the base layer, intermediate layer, and surface layer of the present invention is more preferably 5 μm or more and 25 μm or less.

In addition, in Patent Document 2, “If the thickness of the base layer is less than 30 μm, the effect of suppressing the levitation of silicon or oxygen to the zirconia surface layer cannot be sufficiently obtained, while even if the thickness exceeds 300 μm, the effect is not achieved. “There is no further improvement, and it also hinders the overall thickness of the tool material, and has major disadvantages such as high weight and high cost.”

However, in Patent Document 2, the heat capacity as a tool material is not mentioned, and there is no specific proposal for a solution to this problem.

Additionally, Patent Document 2 states that if the thickness of each layer is too thin, the effect of suppressing the levitation of silicon and oxygen from the silicon carbide substrate (a film made of an oxide film (SiO ₂ )) cannot be sufficiently obtained. This point is the same in the present invention, and the same problem occurs simply by making each layer thin.

Therefore, as a second feature of the present invention, each layer, that is, the base layer, the middle layer, and the surface layer, are all set to have a porosity of 5% or less.

The inventors of the present invention have discovered that by setting the porosity below a predetermined value, it is possible to sufficiently suppress the levitation of silicon and oxygen from a substrate made of silicon carbide.

If many pores exist in each layer, the silica component concentration becomes relatively high, and the diffusion rate increases due to an increase in the concentration gradient between the silica component concentration in each layer and the silica component concentration in the surface layer (contact surface with the firing atmosphere). It is thought that this accelerates the rise of silicon and oxygen.

As mentioned above, from the viewpoint of suppressing the levitation of silicon and oxygen, a smaller porosity is preferable, but a porosity of less than 1% is a high-cost manufacturing condition, including ensuring in-plane uniformity, so it cannot be said to be preferable. I can't. More preferably, it is 3% or more and 5% or less.

In the present invention, each layer (base layer, middle layer, and surface layer) can be formed by plasma spraying. Also, at that time, if the powder used as the raw material for each layer has a small particle size, a layer with a porosity of 5% or less as described above is formed.

As an example, as the particle size range of the raw material, standardized products of 10 ㎛ or more and 45 ㎛ or less are preferable.

In addition, in Patent Document 3, the thickness of each layer is 10 to 200 μm, and as an example, the thickness of the zirconia layer and the mullite layer is 30 μm. On the other hand, Patent Document 3 shows that by setting the porosity of the base material itself to be as large as 15 to 60% and reducing the thickness of the base material to 0.2 to 1 mm, weight reduction and low heat capacity can be achieved, and the firing tool material can be reduced in weight and heat capacity. The goal is to ensure that the temperature can quickly follow the temperature inside the furnace.

In contrast, the present invention does not place any particular restrictions on the substrate itself, that is, it can be made thicker than the substrate described in Patent Document 3 or made excellent in temperature followability even if the substrate has a small porosity.

In addition, by doing this, compared to the tool material described in Patent Document 3, the base material can be made thicker and thus less likely to crack. Alternatively, it can be used as a tool material with improved strength by increasing density by having a small porosity.

Specifically, the present invention further provides a firing tool that has excellent strength and durability even when the thickness of the base material at least at the portion where the object to be fired is placed is 1.5 mm or more and 4 mm or less, and has temperature followability and surface flotation of silica is suppressed. It is extremely excellent as a material and can be said to be more desirable.

Here, in the present invention, in an arbitrary cut surface of a tool material for firing, a location where at least one of the base layer, the intermediate layer, and the surface layer is dug into the base material is defined as the dug-out portion, and the depth of the dug-in portion is D, and the When the width of the recessed portion is W, it is more preferable if W ≤ 30 μm and D/W ≥ 1.

By employing the above configuration, film peeling (lowering of adhesion of the thermal spray film), which is a problem when a thin sprayed film like the present invention is formed, can be effectively suppressed.

The recessed part of the present invention is defined using an arbitrary cut surface of the tool material for firing. This cut surface can be observed using, for example, an optical microscope. In addition, the observation location and magnification are not particularly limited, but are sufficient as long as the irregularities can be clearly recognized to some extent.

As an example, the observation range is a rectangular area with a side of 300 to 1,200 μm and a magnification of 100 to 400 times, and preferably a rectangular area with a side of 600 μm and a magnification of 200 times. This is because the unevenness of the thermal spray coating is relatively large in the recessed portion relative to the layer thickness, so it is better to obtain this amount of area to determine the size of the recessed portion.

And, in the above-mentioned area, when at least one of the base layer, intermediate layer, and surface layer is dug into the base material as the dug-in area, the depth of the dug-in area is D, and the width of the dug-in area is W, W≤30 ㎛ and D/W≥1.

As shown in FIG. 1, when observing an arbitrary area on an arbitrary cut surface of the firing tool material, the base material Z and the base layer 1 (actually also include a middle layer and a surface layer) Paying attention to the interface (L), a line (X) parallel to the horizontal side of the observation screen is drawn and this is used as a reference. This reference line (X) may be measured visually from the observation screen, or may be measured using known image commentary software. Alternatively, it is also possible to calculate it by a method similar to the arithmetic mean roughness (Ra) (JISB0601:1994).

The recessed portion refers to a location where at least one of the base layer, middle layer, and surface layer enters below the reference line (X) in the direction perpendicular to the reference line (X) shown in FIG. 1. Then, when an arbitrary recessed portion is taken as shown in FIG. 1 based on the reference line It is determined whether is established.

Here, when the base layer 1 is thick, as shown in FIG. 1, a recessed part is formed only with the base layer 1, but when the base layer 1 is thin, as shown in FIG. 2, a recessed portion is formed thereon. In some cases, a portion of the formed intermediate layer 2 is dug in to form a buried part. In addition, it is assumed that the intermediate layer 2 is thin, and the surface layer formed thereon also forms a recessed portion.

In the form of W ≤ 30 ㎛ and D/W ≥ 1, the depth of the concave portion is greater than 1 relative to the diameter of the concave portion. In general, in order to strengthen the penetration of the thermal spray coating, it is considered better to have larger irregularities, that is, to have a deeper depth of the concave part relative to the diameter of the concave part.

However, as in the present invention, when a three-layer structure film is formed, and each layer has a thickness of 1 to 30 μm, it is difficult to form a recess of sufficient depth in the depth direction with only the layers. If the irregularities of the substrate are increased, deep concavities can be achieved, but in that case, unevenness is likely to occur in the thickness of the thermal spray coating layer, which may cause problems in its function as a protective layer.

Therefore, in the present invention, by controlling the diameter and depth of the uneven concave portion to a predetermined range, even if the protective layer is thin and the surface of the substrate is relatively smooth, the anchor effect of the layer can be sufficiently secured. was discovered. If the width W of the recessed portion is too large, there are many areas where the layer thickness cannot be sufficiently secured for the upper limit of the layer thickness of 30 μm, so there is a risk that the durability of the layer may be reduced. If the ratio of the depth (D) of the recessed portion and the width (W) of the recessed portion, D/W, is less than 1, there is a risk that the anchor effect or the effect of suppressing the rise of silicon or oxygen may not be sufficiently obtained.

In order for W ≤ 30 ㎛ and D/W ≥ 1, it can be achieved by appropriately controlling the surface condition of the substrate, the size of the raw material powder used to form the thermal spray film, the thermal spray temperature, etc. As an example, the unevenness of the surface forming the thermal spray coating of the substrate is set to be in the range of 4 to 6 ㎛ in Ra (arithmetic mean roughness) and 25 to 35 ㎛ in Ry (maximum height), and the size of the raw material powder of the base layer is set in the range of 15 to 35 ㎛. It should be within the range of 40㎛.

In addition, in order to improve the present invention, a state is formed in which the middle layer penetrates into the back surface of the base layer in an arbitrary cut surface, and when this is used as a penetration portion, a binding point with a penetration width L1 of L1 ≤ 1 μm is formed. It is good to have at least one place on average in the observation range of 600㎛. Figure 3 shows a schematic diagram explaining the mode. Starting from one end S1 of an arbitrary recess existing on the reference line X, the end of the recess advanced in a direction parallel to the reference line This is done at the other end (S2). Then, the distance between one end S1 parallel to the reference line X and the other end S2 is set to L1, and this L1 is set as the sliding part. Additionally, the hook-shaped portion including L1 is called a binding point.

Additionally, a penetration portion where the surface layer penetrates into the back side of the intermediate layer may be formed, and an average of one or more binding points with a penetration width L2 of L2 ≥ 1 μm may be provided in an observation range of 600 μm. Figure 4 shows the mode. The basic definition is the same as L1 in Figure 3.

In this way, when the middle layer penetrates into the back side of the base layer and the surface layer penetrates into the back side of the middle layer, even if the thermal sprayed coating is thin, the peeling suppression effect of the thermal sprayed coating is further strengthened, demonstrating the effect of the present invention. While doing so, it becomes more durable and reliable.

(Example)

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the examples shown below.

To a commercially available silicon carbide powder raw material, a methylcellulose-based binder was added in an amount such that the remaining carbon after sintering would be less than 5.0% by weight, and mixed to obtain a mixture. Next, water was added to the mixture, kneaded, and a porous molded body was obtained by press molding.

Then, the porous molded body was sintered in an Ar atmosphere by changing the firing temperature and firing time to predetermined values, and then oxidized by firing at 1500°C for 3 hours in an atmosphere with an oxygen concentration of 4% and the remainder being nitrogen. Thus, an oxide film containing SiO ₂ as a main component was formed on the surface of the sintered body. The thickness of the oxide film containing SiO ₂ as its main component was 1 μm.

As described above, a plate-shaped substrate measuring 300 mm long x 300 mm wide x 2 mm thick and having an average porosity of 23% was produced.

Then, on one surface of the substrate, by plasma spraying, a mullite film (base layer), an alumina film (middle layer) thereon, and a zirconia film ( coating layers) were sequentially formed to prepare each firing tool material for evaluation.

In addition, the porosity was controlled by a known method, that is, by timely adjusting the temperature during plasma spraying, gas flow rate, raw material supply speed, raw material particle size change, and other conditions. In addition, the raw material particle size of each thermal spray material was all 75 μm or less (or 45 μm or less).

(evaluation)

For each of the above-mentioned firing tool materials, porosity, temperature followability, surface silica amount, and peeling resistance were evaluated by the methods shown below.

(porosity)

Porosity was calculated from a cross-sectional image using a scanning electron microscope (SEM). A test piece cut from the firing tool material was cured with epoxy resin, the cut surface was further polished with diamond paste, and an electron micrograph was taken with an SEM at a magnification of 500 times. The area of pores relative to the area of each sprayed material on the image was calculated as porosity.

(Temperature followability)

Temperature followability is measured by attaching a thermocouple to the surface of the firing tool material, placing it in a continuous conveyance spalling test furnace at a temperature increase rate of 700°C/min, and measuring the difference between the temperature inside the furnace and the product surface temperature. If the difference was within 3°C, it was considered acceptable.

(peeling resistance)

The surface of the firing tool material after the above temperature followability test was observed with the naked eye to confirm the presence or absence of peeling of the thermally sprayed film, and the test that no peeling was recognized was judged to have passed.

(Surface silica amount)

The amount of surface silica was evaluated by a firing test of the ceramic electronic component using the above-mentioned firing tool material and fluorescence X-ray analysis.

A sample measuring 150 mm long x 50 mm wide x 2 mm thick was cut out, a barium titanate molded body measuring 4 mm in diameter x 3 mm in height was placed, a mixed wet gas of nitrogen and hydrogen (99:1) was introduced, and the oxygen partial pressure was 10 ^-19 to 10 ^- It was set in an electric furnace adjusted to a mildly reducing atmosphere of ²¹ atm, and heat cycles between 600°C and 1350°C were repeated.

After repeating this heat cycle 30 times, the amount of surface silica (mass%) was measured by fluorescence X-ray analysis at four locations (diameter 20 mm) on the surface of the setter sample on which the barium titanate molded body was placed, and the value was 0.3. If it was within %, it was considered passing.

(comprehensive evaluation)

In the comprehensive evaluation, those that passed all three items of temperature followability, surface silica amount, and peeling resistance were rated as pass (○), and those that did not satisfy any of the criteria were rated as failed (×). The conditions and evaluation results of each firing tool material are summarized and shown in Table 1 below.

As is clear from the results in Table 1, those within the scope of the present invention (Examples) had good properties as tool materials for firing.

Specifically, in Example 1, all evaluation items passed.

In Example 2, the layer thickness of each layer is all upper limits. In comparison with Example 1, the test passed although slightly inferior in temperature followability, and passed although the amount of surface silica was near the upper limit. Other evaluation results were also good.

In Example 3, the layer thickness of each layer is all at the lower limit. In comparison with Example 1, the surface silica amount was still close to the upper limit due to the thinness of each layer, but the pass and other evaluation results were also good.

In Example 4, the porosity of each layer is close to the upper limit of 5%. In comparison with Example 1, the surface silica amount was near the upper limit due to the large porosity, but the test passed and other evaluation results were also good.

As a more preferable example, in Example 5, each layer had a thickness of 5 μm, and in Example 6, each layer had a thickness of 25 μm. In both comparisons with Example 1, Example 5 had good temperature followability, and Example 6 had good silica amount.

In Comparative Example 1, the layer thickness of each layer exceeded 30 μm, which is the range of the present invention, and was 40 μm.

In this case, the porosity was less than 5%, which is the range of the present invention, but the amount of surface silica exceeded 0.3% of the pass line, so it was rejected.

In Comparative Example 2, the layer thickness of each layer exceeded 30 μm, which is the range of the present invention, and was 100 μm. For this reason, in terms of temperature followability, the temperature difference exceeded 3°C, and in this respect, it was disqualified. In addition, as a tendency when forming a layer by thermal spraying, if the raw material particle size is the same and the layer thickness is increased, the porosity increases. Therefore, in comparison with Comparative Example 1, the porosity increased and exceeded 4%.

In Comparative Example 3, compared to Comparative Example 2, the porosity of each layer was intentionally increased by increasing the raw material particle size. In this case, temperature followability deteriorated significantly compared to Comparative Example 2.

In Comparative Example 4, compared to Comparative Example 3, the thickness of each layer was further increased. In this case, compared with Comparative Example 3, temperature followability slightly deteriorated.

In Comparative Example 5, compared to Comparative Example 4, the thickness of each layer was further increased. In this case, compared to Comparative Example 4, temperature followability further deteriorated. From this, it can be seen that the thickness of each layer greatly affects temperature followability. In addition, since the raw material particle size is large and the film has a high porosity, the film thickness is too thick, so it may be said that the thermal expansion difference between the base material and the sprayed film increases, causing separation.

In addition, the reason that the amount of surface silica in Comparative Examples 3 and 4 is lower compared to Comparative Example 1 is that the raw material particle size of the latter is larger than that of the former, and the proportion of grain boundaries per unit volume in each layer is relatively small. . As a result, since silica preferentially diffuses through grain boundaries, it is believed that the amount of surface silica in Comparative Examples 3 and 4, which have fewer grain boundaries, is lower.

In Comparative Example 6, the layer thickness of the base layer was less than 1 μm, which is the range of the present invention. In this case, if the layer thickness of any one of the three layers was too thin, the amount of surface silica increased and it was found to be disqualified.

In Comparative Example 7, the layer thickness of the intermediate layer exceeds 30 μm, which is the range of the present invention. In this case, if the layer thickness of any of the three layers was too thick, the temperature followability exceeded 3°C, and it was found that the temperature followability deteriorated and was disqualified. In addition, since the raw material particle size is a small dense film and the film thickness is too thick, it can also be said that separation occurs due to thermal expansion differences between the base material and the sprayed film.

In Comparative Example 8, the porosity of the surface layer exceeds 5%, which is the range of the present invention. In this case, if the porosity of any of the three layers was too high, the amount of surface silica exceeded 0.3%, and it was found to be disqualified in this respect.

However, in Example 1, W was 28 μm and D/W was 1.5. Here, the thermal spraying conditions were changed (spray amount increased) to form a base layer with W of 33 ㎛ and D/W of 1.3, and the rest was made to be as similar to Example 1 as possible, and was used as Example 7. Then, after conducting the temperature followability test 20 times in succession, the peeling resistance was evaluated.

Compared with Example 1, in Example 7, slight peeling was confirmed at one location after the above evaluation. In other words, it can be said that Example 7 is slightly inferior to Example 1 in harsher usage conditions.

Here, by changing the spraying conditions (spray amount or reduction), a base layer with W of 27 ㎛ and D/W of 0.9 was formed, and in other respects, Example 8 was manufactured to be as equivalent to Example 1 as possible. . Then, as in Example 7, the temperature followability test was conducted 20 times in succession, and then the peeling resistance was evaluated.

As a result, compared to Example 1, in Example 8, slight peeling was confirmed at one location after the above evaluation.

In addition, by changing the spraying conditions (changing the spray amount and temperature), a base layer with W of 32㎛ and D/W of 0.85 was formed, and other than that, the product was manufactured to be as equivalent to Example 1 as possible, and is referred to as Example 9. . Then, in the same manner as in Examples 7 and 8, the temperature followability test was conducted 20 times in succession, and then the peeling resistance was evaluated.

As a result, compared with Example 1, slight peeling was confirmed in Example 9 at a total of three locations after the above evaluation. As expected, Example 9, in which both W and D/W were outside the more desirable range, can be said to be slightly inferior compared to Examples 7 and 8.

In addition, in Examples 7 to 9, all passed in terms of temperature followability and silica amount.

As explained above, when the tool material for firing according to the present invention is used, temperature followability is high and surface silica is less likely to float even when used repeatedly for firing, so the quality impact on the product after firing is less than before. It can be fired under high-speed conditions, contributing to improved productivity.

Z description
1 lower floor
2 middle layer
W width
D depth
L1 Infiltration Width
L2 Infiltration Width
X baseline

Claims (4)

oxide film,
A base layer formed on the surface of the oxide film, which is alumina-siliceous with a total content of alumina containing mullite as a main component of 65% by mass or more and 95% by mass or less, and has a thickness of 1 μm or more and 30 μm or less;
An intermediate layer formed on the surface of the base layer, containing 95% by mass or more and 99.9% by mass or less of alumina, and having a thickness of 1 μm or more and 30 μm or less,
A surface layer formed on the surface of the intermediate layer is made of stabilized zirconia with calcia or yttria as a stabilizer and has a thickness of 1 ㎛ or more and 30 ㎛ or less,
A tool material for firing, characterized in that all of the base layer, the intermediate layer, and the surface layer have a porosity of 5% or less. According to paragraph 1,
A tool material for firing, characterized in that the oxide film is a SiO ₂ layer. According to claim 1 or 2,
A tool material for firing, characterized in that the thickness of the base material at least in the portion where the object to be fired is placed is 1.5 mm or more and 4 mm or less. According to paragraph 1,
In an arbitrary cut surface of a tool material for firing, a location where at least one of the base layer, the intermediate layer, and the surface layer penetrates into the base material is defined as a recessed portion, and the depth of the recessed portion is defined as D, and the recessed portion is defined as D. A tool material for firing, characterized in that when the width is W, W ≤ 30 ㎛ and D/W ≥ 1.