JP7092655B2 - Heat resistant material - Google Patents

Description

The present disclosure relates to heat resistant members.

Products that are supposed to be used at high temperatures, such as heaters used for heating the interior of automobiles, use heat-resistant members that are unlikely to be damaged even when used at a temperature of about 600 ° C.

Here, as the material of the heat-resistant member, alumina ceramics which are difficult to oxidize even at a temperature of about 600 ° C. and can be used for a long period of time in an atmospheric environment are widely adopted (for example, Patent Documents). See 1).

Japanese Unexamined Patent Publication No. 2001-2464

In recent years, products having an operating temperature of about 1000 ° C. are assumed, and the heat-resistant members used in such products are required to have excellent heat-resistant impact resistance.

In addition, when a heat-resistant member is used in an automobile or the like, an impact such as vibration is applied to the heat-resistant member, so that it has not only excellent heat-resistant impact resistance but also excellent mechanical strength so as not to be damaged by the impact. Is required.

The present disclosure has been devised in view of such circumstances, and an object of the present disclosure is to provide a heat-resistant member having both excellent mechanical strength and heat-resistant impact resistance.

The heat-resistant member of the present disclosure contains alumina crystals, glass, and _murite crystals, and contains 70% by mass or more and 89% by mass or less of Al in terms of _Al2O3 among 100% by mass of all the constituents, and is made of Si. It is made of alumina ceramics in which the total of the content in terms of SiO ₂ , the content of Ca in terms of CaO, and the content of Mg in terms of MgO is 11% by mass or more and 30% by mass or less. In the values obtained by Rietveld analysis, the alumina crystals are 80% by mass or more, and the mullite crystals are 4% by mass or more.

The heat-resistant member of the present disclosure has excellent mechanical strength and heat-impact resistance.

The heat-resistant member of the present disclosure will be described in detail below.

The heat-resistant member of the present disclosure contains alumina crystals, glass, and _murite crystals, and contains 70% by mass or more and 89% by mass or less of Al in terms of _Al2O3 among 100% by mass of all the constituents, and is made of Si. It is made of alumina ceramics in which the total of the content in terms of SiO ₂ , the content of Ca in terms of CaO, and the content of Mg in terms of MgO is 11% by mass or more and 30% by mass or less.

Further, the glass is a mixed glass containing calcium oxide (CaO) and magnesium oxide (MgO) in silicon oxide (SiO ₂ ).

Further, the mullite crystal is a compound of alumina (Al ₂ O ₃ ) and silicon oxide (SiO ₂ ), and the composition formula is expressed as Al ₆ O ₁₃ Si ₂ .

The heat-resistant member of the present disclosure has an alumina crystal of 80% by mass or more and a mullite crystal of 4% by mass or more in the values obtained by Rietveld analysis. Here, since the glass and mullite crystals are superior in heat-resistant impact resistance as compared with the alumina crystals and have the above-mentioned composition ratio and contain the above-mentioned amount of mullite crystals, the heat-resistant member of the present disclosure has excellent heat-resistant impact resistance. Has sex. Further, since the heat-resistant member of the present disclosure contains the above-mentioned amount of alumina crystals which is superior in mechanical strength to glass, the heat-resistant member of the present disclosure has excellent mechanical strength. Therefore, the heat-resistant member of the present disclosure has excellent mechanical strength and heat-impact resistance.

Here, the excellent mechanical strength means that the value of the three-point bending strength at room temperature (25 ° C.) according to JIS R 1601-2008 is 280 MPa or more. Further, excellent thermal shock resistance means that the thermal resistance temperature in the underwater drop test is 230 ° C. or higher. Here, the heat resistant temperature in the underwater dropping test is when a test piece heated to T2 (° C.) and having a diameter of 10 mm and a length of 20 mm is dropped into water at T1 (° C.), which is a temperature lower than T2. It is the maximum value of the temperature difference T2-T1 (° C.) at which cracks or chips do not occur in the test piece.

Next, whether or not the heat-resistant member of the present disclosure contains alumina crystals, glass, and mullite crystals may be confirmed by the following method. First, the heat-resistant member of the present disclosure is pulverized and then measured using an X-ray diffractometer (XRD). Then, the presence of alumina crystals and mullite crystals can be confirmed by performing identification using a JCPDS card from the obtained values of 2θ (2θ is a diffraction angle). In addition, the presence or absence of glass can be confirmed by the presence of the halo pattern on the low angle side.

As another method for confirming the presence or absence of glass, a heat-resistant member is cut and a mirror-polished cross section is observed. Next, this observation surface is observed with a scanning electron microscope (SEM), and if an amorphous part other than the crystal is confirmed by the energy dispersion type analyzer (EDS) attached to the SEM, that part is glass. By irradiating the portion with X-rays, it can be confirmed whether or not the glass contains silicon, calcium, magnesium and oxygen.

In the heat-resistant member of the present disclosure, the alumina crystal is the main crystal containing the largest amount among the crystals, and is relatively larger than the mullite crystal. Therefore, if a relatively large crystal is irradiated with X-rays in the observation region in the SEM and aluminum and oxygen appear as large peaks, the crystal is an alumina crystal.

Further, the mullite crystal is smaller than the alumina crystal and exists in a region other than the alumina crystal, for example, in glass. Therefore, if a crystal that is clearly smaller than the alumina crystal existing in the glass is irradiated with X-rays and the presence of silicon, aluminum, and oxygen is confirmed in the crystal, the crystal is a mullite crystal.

In addition, the content of the components constituting the heat-resistant member of the present disclosure may be confirmed by the following method. First, a quantitative analysis of the components contained in the heat-resistant member is performed using an ICP emission spectroscopic analyzer (ICP). Then, each of them may be calculated by converting them into oxides from the contents of aluminum (Al), silicon (Si), calcium (Ca), and magnesium (Mg) measured by ICP. Although aluminum is contained in both alumina crystals and mullite crystals, it is possible to confirm the amount of aluminum corresponding to the alumina crystals and the amount of aluminum corresponding to the mullite crystals from the values obtained by the Rietbelt analysis. can.

Further, silicon is contained in both mullite crystals and glass, and the amount of silicon corresponding to mullite crystals can be confirmed from the stoichiometric composition from the amount of aluminum corresponding to mullite crystals. Of the total 100% by mass of the constituent components, the total of Si in terms of SiO ₂ , Ca in terms of CaO, and Mg in terms of MgO is 11% by mass. Although it is 30% by mass or less, the content of Si in terms of SiO ₂ is 7% by mass or more and 20% by mass or less, the content of Ca in terms of CaO is 1% by mass or more and 8% by mass or less, and Mg is converted to MgO. The content in the above may be 1% by mass or more and 5% by mass or less.

Further, the contents of alumina crystals and mullite crystals in the heat-resistant member of the present disclosure may be confirmed by the following method. first. After pulverizing the heat-resistant member of the present disclosure, the diffraction peak is measured by powder X-ray diffraction. This diffraction peak includes a peak based on the crystal structure of each of the alumina crystal and the mullite crystal. Therefore, by analyzing the diffraction peak by Rietveld analysis, it is possible to calculate the content of each of the alumina crystal and the mullite crystal when the total content of the alumina crystal and the mullite crystal is 100% by mass.

Further, the heat-resistant member of the present disclosure may contain 12% by mass or less of mullite crystals in the value obtained by Rietveld analysis. If such a configuration is satisfied, the heat-resistant member of the present disclosure can improve the heat-resistant impact resistance while maintaining the mechanical strength.

Further, the average value of the equivalent circle diameters of the mullite crystals in the heat-resistant member of the present disclosure may be 0.1 μm or more and 0.5 μm or less. Here, the diameter equivalent to a circle means the diameter of the circle when it is replaced with a circle equal to the area when the mullite crystal is observed. If such a configuration is satisfied, the mullite crystal has a size that does not easily generate internal stress, and the mullite crystal has a size that easily suppresses the growth of cracks. , Mechanical strength and thermal shock resistance can be improved.

Here, the average value of the equivalent circle diameters of the mullite crystals may be confirmed by the following method. First, the heat-resistant member is cut and the cross section polished to a mirror surface is used as the observation surface. Next, this observation surface is photographed by SEM. Then, in the photograph taken, the part of the murite crystal is traced and painted in black, and the image analysis software "A image-kun" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.) is referred to as the image analysis software "A image-kun". In the case of the above, it is assumed that the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd. is used. good. As the analysis conditions for "A image-kun", the brightness of the particles may be "dark", the binarization method may be "automatic", and the shading may be "yes".

Further, in the heat-resistant member of the present disclosure, the number of mullite crystals having an aspect ratio of 5 or more may be 10 or more and 200 or less in the range of an area of 200 μm ² . Here, the aspect ratio of the mullite crystal is a value when the major axis of the mullite crystal is divided by the minor axis. The major axis of the mullite crystal is the maximum length in the cross section of the mullite crystal. The minor axis of the mullite crystal is the length of a straight line orthogonal to the major axis segment at the center of the major axis segment.

If such a configuration is satisfied, the mullite crystal having an aspect ratio of 5 or more can suppress the growth of cracks, and the mullite crystal having an aspect ratio of 5 or more can be cracked due to expansion when heated. The heat-resistant member of the present disclosure has further improved mechanical strength and heat-impact resistance.

The number of Murite crystals having an aspect ratio of 5 or more is the same as that of measuring the average value of the circle-equivalent diameters of the Murite crystals described above. It may be calculated by applying it to a range of 200 μm ² for image analysis and using the obtained “maximum / minimum” as the aspect ratio.

Further, as described above, the heat-resistant member of the present disclosure has excellent mechanical strength and heat-impact resistance. It can be widely used in various technical fields such as a flow path member for flowing a gas or the like and a protective member for protecting a human body or the like from an ultra-high-speed flying object.

Next, a method for manufacturing the heat-resistant member of the present disclosure will be described below.

First, alumina (Al ₂ O ₃ ) powder, silicon oxide (SiO ₂ ) powder, calcium carbonate (CaCO ₃ ) powder and magnesium carbonate (MgCO ₃ ) powder are prepared.

Next, after firing, the calcined powder A to be glass is produced by the following procedure. First, alumina powder, silicon oxide powder, calcium carbonate powder, magnesium carbonate powder, alumina powder is 5% by mass or more and 10% by mass or less, silicon oxide powder is 40% by mass or more and 60% by mass or less, and calcium carbonate powder is calcium oxide ( Weigh and mix so that the CaO) equivalent is 20% by mass or more and 30% by mass or less, and the magnesium carbonate powder is 10% by mass or more and 20% by mass or less in terms of magnesium oxide (MgO). Next, the mixed powder is pulverized by dry or wet pulverization, dried, and then heated at 1000 ° C. or higher and 1200 ° C. or lower to obtain a calcined powder A.

Next, after firing, calcined powder B to be mullite crystals is produced by the following procedure. First, the alumina powder is weighed to 71.8% by mass and the silicon oxide powder is 28.2% by mass, and the mixture is mixed. Next, the mixed powder is heated at 1100 ° C. or higher and 1400 ° C. or lower to obtain a calcined powder B.

Next, the content of Al in terms of Al ₂ O ₃ is 70% by mass or more and 89% by mass or less, the content of Si in terms of SiO ₂ and Ca in terms of CaO, and the content of Mg in terms of MgO. The total content in the above is 11% by mass or more and 30% by mass or less, and the amount of the calcined powder B is 4% by mass or more with respect to the total of 100% by mass of the alumina powder and the calcined powder B. Alumina powder, calcined powder A, and calcined powder B are weighed and mixed.

Next, the mixed powder is granulated by a known method such as a spray drying method, and then pressure-molded by a known method to obtain a molded product having a desired shape. Next, the obtained molded body is fired at a temperature of 1300 ° C. or higher and 1500 ° C. or lower in an atmospheric atmosphere to obtain the heat-resistant member of the present disclosure.

Further, in order to make the mullite crystal 12% by mass or less in the value obtained by the Rietbelt analysis, in the above-mentioned production method, the calcined powder B is compared with the total 100% by mass of the alumina powder and the calcined powder B. The alumina powder, the calcined powder A, and the calcined powder B may be weighed and mixed so that the amount is 12% by mass or less.

Further, in order to make the average value of the equivalent circle diameter of the Murite crystal 0.1 μm or more and 0.5 μm or less, the average particle size obtained by the laser diffraction method is 0.1 μm by performing pulverization in the above-mentioned production method. The calcined powder B having a diameter of 0.5 μm or less may be obtained and used.

Further, in the range of the area of 200 μm ² , the number of mullite crystals having an aspect ratio of 5 or more is 10 or more and 200 or less when the calcined powder B is produced in the above-mentioned production method. The heating temperature may be 1200 ° C. or higher and 1300 ° C. or lower.

Hereinafter, examples of the present disclosure will be specifically described, but the present disclosure is not limited to these examples.

Samples with different compositions and mullite crystal contents were prepared, and their mechanical strength and thermostable impact resistance were evaluated.

First, alumina powder, silicon oxide powder, calcium carbonate powder and magnesium carbonate powder were prepared.

Next, after firing, the calcined powder A to be glass was produced by the following procedure. First, alumina powder, silicon oxide powder, calcium carbonate powder, magnesium carbonate, alumina powder is 10% by mass, silicon oxide powder is 50% by mass, calcium carbonate powder is 25% by mass in terms of calcium oxide (CaO), magnesium carbonate. The powder was weighed so as to be 15% by mass in terms of magnesium oxide (MgO) and mixed. Next, the mixed powder was dry-pulverized, dried, and then heated at 1100 ° C. to obtain a calcined powder A.

Next, after firing, calcined powder B to be mullite crystals was produced by the following procedure. First, the alumina powder was weighed to 71.8% by mass and the silicon oxide powder was 28.2% by mass, and mixed. Next, the mixed powder was heated at 1100 ° C. and pulverized to obtain a calcined powder B having an average particle size of 1.0 μm determined by a laser diffraction method.

Next, the alumina powder, the calcined powder A, and the calcined powder B were weighed so as to have the values shown in Table 1 and mixed.

Next, the mixed powder was granulated by a spray drying method and then pressure-molded to obtain a molded product. Next, each sample was obtained by firing the obtained molded product at a temperature of 1400 ° C. in an atmospheric atmosphere.

Next, the content of the components constituting each sample was quantitatively analyzed using ICP, and the contents of aluminum (Al), silicon (Si), calcium (Ca), and magnesium (Mg) measured by ICP were measured. It was calculated by converting each of them into oxides from the content.

In addition, the content of mullite crystals in each sample was calculated by analysis by Rietveld analysis.

In addition, the three-point bending strength of each sample was calculated by a method according to JIS R 1601-2008.

In addition, the thermal impact resistance of each sample was evaluated by the thermal temperature in the underwater drop test. Specifically, when each sample heated to T2 (° C.) was dropped into water at 25 ° C., the maximum value of the temperature difference T2-25 (° C.) at which cracks or chips did not occur in each sample was calculated. Here, T2 was measured by starting at 125 ° C and increasing by 10 ° C.

The results are shown in Table 1.

As shown in Table 1, the sample No. In 4 to 10, the three-point bending strength was 280 MPa or more, and the heat resistant temperature was 230 ° C. or more. From this, it contains alumina crystal, glass and mullite crystal, and out of 100% by mass of all the constituents, it contains 70% by mass or more and 89% by mass or less in terms of Al ₂ O ₃ and is converted to SiO ₂ of Si. The total content of Ca in terms of CaO, Mg in terms of MgO, and Mg is 11% by mass or more and 30% by mass or less. It was found that when the alumina crystal was 80% by mass or more and the mulite crystal was 4% by mass or more, the aluminum crystal had excellent mechanical strength and thermal shock resistance.

In particular, the sample No. Among 4 to 10, sample No. It was found that the mechanical strength of 4 to 9 was improved when the three-point bending strength was 290 MPa and the mullite crystal was 12% by mass or less in the value obtained by Rietveld analysis.

Next, samples having different equivalent circle diameters of mullite crystals were prepared, and their mechanical strength and thermostable impact resistance were evaluated.

As a method for preparing each sample, the sample Nо. It was the same as the production method of 8. In addition, sample No. No. 11 is the sample No. 11 of Example 1. Same as 8.

Next, the average value of the equivalent circle diameters of Murai crystals in each sample was calculated by the following method. First, each sample was cut and the cross section polished to a mirror surface was used as the observation surface. Next, this observation surface was photographed by SEM. Then, in the photograph taken, the part of the mullite crystal is traced and painted in black, and the image analysis is performed by applying the technique called particle analysis of the image analysis software "A image-kun" to perform the image analysis, and the average of the equivalent circle diameters of the mullite crystals. The value was calculated. As the analysis conditions for "A image-kun", the brightness of the particles was set to "dark", the binarization method was set to "automatic", and the shading was set to "yes".

Next, the three-point bending strength and heat resistant temperature of each sample were evaluated by the same method as in Example 1. The results are shown in Table 2.

As shown in Table 2, the sample No. Compared with 11 and 15, sample No. Since the three-point bending strength of Nos. 12 to 14 is 327 MPa or more and the heat resistant temperature is 270 ° C., if the average value of the equivalent circle diameters of the Murite crystals is 0.1 μm or more and 0.5 μm or less, it is mechanical. It was found that the strength and thermal shock resistance were improved.

Next, samples having different numbers of mullite crystals having an aspect ratio of 5 or more were prepared, and their mechanical strength and thermal impact resistance were evaluated.

As a method for preparing each sample, the sample Nо. It was the same as the manufacturing method of No. 14. In addition, sample No. Reference numeral 16 is sample No. 16 of Example 2. Same as 14.

Next, the number of Murite crystals having an aspect ratio of 5 or more in each sample was measured by the same method of measuring the average value of the equivalent circle diameters of the Murite crystals of Example 2, and the particles of the image analysis software "A image-kun" were used. It was calculated by applying a method called analysis to a range where the area is 200 μm ² and performing image analysis, and using the obtained “maximum / minimum” as the aspect ratio.

Next, the three-point bending strength and heat resistant temperature of each sample were evaluated by the same method as in Example 1. The results are shown in Table 3.

As shown in Table 3, the sample No. Compared with 16 and 21, sample No. Since 17 to 20 have a three-point bending strength of 346 MPa or more and a heat resistant temperature of 290 ° C., the number of mullite crystals having an aspect ratio of 5 or more in an area of 200 μm ² is 10 or more 2.
It was found that if the number is 00 or less, the mechanical strength and the thermal impact resistance are improved.

Claims (4)

Contains alumina crystals, glass and mullite crystals,
Of the 100% by mass of all the constituent components, Al is contained in an Al ₂ O ₃ equivalent of 70% by mass or more and 89% by mass or less, and the Si in SiO ₂ equivalent and the Ca O in terms of CaO. , Composed of alumina ceramics having a total of 11% by mass or more and 30% by mass or less with the MgO content of Mg.
A heat-resistant member in which the alumina crystals are 80% by mass or more and the mullite crystals are 4% by mass or more in the values obtained by Rietveld analysis. The heat-resistant member according to claim 1, wherein the mullite crystal is 12% by mass or less in the value obtained by Rietveld analysis. The heat-resistant member according to claim 1 or 2, wherein the average value of the equivalent circle diameters of the mullite crystals is 0.1 μm or more and 0.5 μm or less. The heat-resistant member according to any one of claims 1 to 3, wherein the number of mullite crystals having an aspect ratio of 5 or more is 10 or more and 200 or less in an area of 200 μm ² .