JPH0465369A - Formed body for detective heat history - Google Patents

Abstract

PURPOSE:To improve the precision in detecting an indicated temp. by using the unsintered formed body of the ceramic Al2O3 having a specified content of SiO2 as the formed body by detecting the heat history in the sintering of ceramic, etc. CONSTITUTION:This formed body 10 for detecting a heat history contains >99.7 wt.% Al2O3 and < 0.2 wt.% SiO2 and is obtained by press forming, and the grain diameter of the raw powder, green density of the formed body, etc., are strictly controlled. The sintering temp, is changed under given conditions, the size of the sintered formed body 10 is measured, and the relation between the size and sintering temp. is prepared as a conversion table. When a formed body is sintered under different conditions, the formed body 10 is sintered along with a body to be sintered, the size of the sintered body is measured, and the indicated temp. is obtained from the table.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is for detecting the thermal history in the firing process of ceramics, etc., and in particular for detecting the thermal history of alumina, zirconia, etc. in an oxidizing atmosphere. The present invention relates to a molded body for detecting thermal history during firing in a temperature range of C.

[Conventional technology] In the firing process of ceramics, the temperature profile,
The thermal history of the object to be fired varies depending on the type of firing furnace, the settings within the furnace, etc. That is, even if the firing temperature is the same, the thermal H history will be different if other conditions are different, and it is necessary to detect this thermal history correctly.

For example, a Seegel cone disclosed in Japanese Utility Model Application No. 56-29441 has been used to detect the thermal history of an object to be fired. A Zegel cone is equipped with a plurality of triangular pyramids having different melting temperatures on a support base, and after firing this Zegel cone together with the object to be fired,
Thermal history was detected by the way each triangular pyramid fell.

However, since this method cannot provide accurate detection, it is now rarely used.

Therefore, as shown in, for example, Japanese Patent Application Laid-Open No. 1-184388, an unfired molded ceramic body is used, and after firing this molded body together with an object to be fired, the dimensional change due to shrinkage is measured. , detecting thermal history was also being done.

For example, a ring-shaped molded body 20 as shown in FIG. 2 or a sheet-shaped molded body 30 as shown in FIG. 3 have been used.

When measuring dimensional changes due to firing shrinkage, the dimensional changes are conveniently converted to temperature, but this temperature is not a measurement of the actual temperature, but represents the thermal history, and is not the actual temperature. In the invention, this will be referred to as the indicated temperature.

[Problems with conventional technology] However, the above-mentioned ceramic molded body for thermal history detection has
Since some were made of natural raw materials containing A1□03 or SiO□ as a main component and containing a large amount of impurities, the firing shrinkage rate varied and the accuracy of the detected indicated temperature was poor.

In addition, the ring-shaped one shown in Figure 2 has a large area and requires a large space in the firing furnace, and the sheet-shaped one shown in Figure 3 causes warping, making it impossible to measure dimensions correctly. There was a problem with that.

[Means for Solving the Problems] Therefore, the present invention provides Al2O399.7% by weight or more, S
A ceramic green molded body containing 0.2% by weight or less of iO is used as a molded body for thermal history detection.

In the present invention, the reason why AI, Os is 99.7% by weight or more is to reduce the amount of impurities, reduce the variation in firing shrinkage rate, and improve the accuracy of the detected indicated temperature.
This is to set the temperature at 2°C. Also, 5in20.2% by weight
The following is the case when SiO2 is more than 0.2% by weight.
This is because the material is completely sintered and becomes dense at a temperature of 1750° C. or lower, making it impossible to detect thermal history.

[Example] The present invention will be explained in detail below.

As shown in FIGS. 1(a) and 1(b), the molded body 10 for detecting thermal history of the present invention has arcuate portions 12 and 12 parallel to the disk body, and the remaining arcuate portions are The measurement surface 11.11 has excellent roundness. Further, a recess 13 for distinguishing between the front and back is formed on one side, and chamfers 14 are provided at the corners of the upper and lower surfaces.

Furthermore, this molded body 1O has a weight of 99.7 Al2O399.7
It is an unfired molded body having a composition of 6% or more and 0.2% by weight or less of SiO□, and is press-molded by extremely strictly controlling the particle size of the raw powder, the green density of the molded body, etc.

Then, as will be described later, the dimensions of the molded body IO after firing are measured while changing the firing temperature under certain conditions, and a conversion table of the relationship between the dimensions and the firing temperature is prepared. Thereafter, when firing is performed under different conditions, the indicated temperature can be determined from the above conversion table by firing this molded body 10 together with the object to be fired and measuring the dimensions after firing.

Note that, as described above, the indicated temperature is not an actual temperature, but a convenient representation of the thermal history. That is,
By using the molded article for detecting thermal history of the present invention, it becomes possible to manage the thermal history itself by determining the indicated temperature even if the firing conditions are different.

Moreover, since the molded body 10 of the present invention has the arc portion 12.1.2, it has a smaller area than the conventional example shown in FIG. 2, and does not require a large space in the firing furnace. Note that the arc portions 12.12 do not have to be parallel to each other,
- It may be formed only in the following locations. Furthermore, since the molded product 10 of the present invention is a press-formed product with a certain degree of wall thickness, warpage does not occur, and when measuring dimensions, as shown in FIG. Measurement surface 11.
11 with a low constant pressure micrometer, the same diameter can be accurately measured even if the measurement position is shifted.

Example 1 SiO□ was added as a sintering aid to a purified alumina raw material with a purity of 99.9% or more, wet-pulverized with an alumina ball, and particle size analysis was performed using a laser light scattering method to obtain an average particle size of 4. , 0±0.1 μm.

Granules with good fluidity are obtained by adding 6% by weight of a wax binder to this raw material powder, mixing, and spray drying. The granules are press-molded in an air-conditioned molding room into the shapes shown in FIGS.
A molded article for thermal history detection of the present invention was obtained within the range of No. 3.

When the amount of 8102 in the above raw materials was varied and fired,
As shown in Table 1, SiO2 with more than 0.2% by weight becomes densified at 1720°C and does not shrink at higher temperatures, so it cannot be used at temperatures above 1720°C. I couldn't come. In the case of a normal alumina firing furnace, it is necessary to measure the temperature at about 1750°C, so the amount of 5iO7 had to be 0.2% by weight or less.

Table Example 2 Same as Example 1, SiL amount was 0.10% by weight.
A molded body 1 for thermal history detection with a diameter of 22.300 mm
I prepared 0. This compact IO was heated at a heating rate of 20'C in an oxidizing atmosphere using a strictly calibrated firing furnace.
/hour, held at maximum firing temperature for 2 hours, cooling rate 300'C
/Occasionally calcined and degreased at 350°C for 1 hour. The dimensions of the compact IO after firing were measured at 20°C using a low constant pressure micrometer.

Firing of 20 molded bodies 10 was repeated three times while varying the firing temperature (indicated temperature).

The results are shown in Table 2 and FIG.

In addition, the detection accuracy (3σ) of the indicated temperature was calculated from the dimensional variation (3σ) at each temperature and the amount of dimensional change (slope of the tangent) per I''C at that temperature.

As shown in Table 2, the results showed that the accuracy of detecting the indicated temperature was within ±2°C within the range of 1400°C to 1750°C.

Furthermore, although Table 2 shows the dimensions of the molded object for each indicated temperature of 50'C, by measuring the dimensions for each indicated temperature in more detail, it is possible to convert the dimensions of the molded object and the indicated temperature. It can be done.

(Margin below) Table In addition, in the above example, in order to obtain a molded body JO for thermal history detection, the particle size of the raw material was 4.0±0.1 μm, and the green density of the molded body was 2.300±0.005 g. /cm3, but the value is not limited to this value and can be changed in various ways. In that case, the particle size is usually ±
It is managed to be within the range of 0.2 μm. On the other hand, controlling the green density is important, and if the variation is suppressed within the range of ±o, oig/cm3, the detection accuracy of the indicated temperature can be increased by ±2°C.
It was possible to do so.

[Effects of the Invention] As described above, according to the present invention, by using a ceramic unfired molded body containing A1□0399.7% by weight or more and SiO20 = 2% by weight or less as a molded body for thermal history detection, it is possible to Since the temperature detection accuracy is extremely high at ±2°C, the firing process can be strictly controlled even if the firing conditions change, making it possible to obtain an excellent sintered body.

[Brief explanation of drawings]

FIG. 1(a) is a plan view showing a molded body for detecting thermal history according to an embodiment of the present invention, and FIG. 1(b) is a sectional view taken along the line X--X in FIG. 1(a). FIGS. 2 and 3 are perspective views showing conventional molded bodies for detecting thermal history, respectively. FIG. 4 is a graph showing the relationship between the firing shrinkage rate and the indicated temperature in the molded article for thermal history detection of the present invention. 1 Molded body for detecting discharged heat history 11: Measurement surface 12, arc portion 13, recessed portion 14: Chamfer

Claims (1)

[Claims] Al_2O_3 99.7% by weight or more, SiO_2
A molded body for detecting thermal history, characterized in that it is composed of an unfired ceramic molded body containing 0.2% by weight or less.