JPH0672061B2 - Molded body for heat history detection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is for detecting the thermal history of a firing process of ceramics or the like, and particularly 1400 to 1750 ° C in an oxidizing atmosphere such as alumina and zirconia. The present invention relates to a molded body for detecting heat history in firing in the temperature range of.

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

For example, the thermal history of the body to be fired has been detected using a Zegel cone as disclosed in Japanese Utility Model Publication No. 56-29441. Zegel cones are provided with a plurality of triangular pyramids having different melting temperatures on a support, and after firing this Zegel cone together with the body to be fired, the thermal history of the triangular pyramids falls, It was supposed to detect. However, since it cannot detect accurately, it is now less used. Therefore, as disclosed in, for example, Japanese Patent Application Laid-Open No. 1-184388, by using an unfired molded body of ceramics, firing this molded body together with a body to be fired, and then measuring the dimensional change due to shrinkage. , Thermal history was being detected.

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 was used.

When measuring a dimensional change due to such firing shrinkage, the dimensional change is appropriately converted into a temperature, but this temperature does not represent an actual temperature but represents a thermal history. In the invention, it is called the indicated temperature.

[Problems of Prior Art] However, the above-mentioned ceramic molded body for thermal history detection is
Since it was made of a natural raw material containing Al ₂ O ₃ or SiO ₂ as the main component and containing a large amount of impurities, the firing shrinkage ratio varied, and the detected temperature accuracy was poor.

Further, the ring-shaped one shown in FIG. 2 requires a large space in the firing furnace because it has a large area, and the sheet-shaped one shown in FIG. There was a problem.

[Means for Solving the Problems] Accordingly, the present invention provides a ceramics unfired molded body containing Al ₂ O _{3 of} 99.7% by weight or more and SiO _{2 of} 0.2% by weight or less as a thermal history detecting molded body.

In the present invention, Al ₂ O _{3 is} 99.7% by weight or more in order to reduce the variation in the firing shrinkage rate by reducing the amount of impurities and to make the accuracy of the detected indicated temperature ± 2 ° C. In addition, SiO ₂ 0.2% by weight or less means that
_{If 2} is more than 0.2% by weight, it will be completely sintered at a temperature of 1750 ° C. or less to be densified, and the thermal history cannot be detected. Further, the present invention is a disk-shaped body made of a ceramics unfired molded body, comprising a linear chord portion on the outer periphery, and a molded body for thermal history detection is configured with the remaining arc portion as a measurement surface. is there.

[Examples] Examples of the present invention will be described below.

As shown in FIGS. 1 (a) and 1 (b), the heat history detecting molded body 10 of the present invention is formed by forming chord portions 12 and 12 parallel to a disk body, and the remaining arc portion is Measuring surface 11 with excellent roundness,
It is as 11. In addition, a recess 13 for distinguishing between the front and back is formed on one surface, and chamfers 14 are applied to the corners of the upper and lower surfaces.

Furthermore, this molded body 10 contains Al ₂ O ₃ 99.7 wt% or more, SiO 2
_{2 An} unfired compact having a composition of 0.2% by weight or less, which is formed by press molding while controlling the particle diameter of the raw material powder, the green density of the compact, and the like very strictly.

Then, as will be described later, the firing temperature is changed under a certain condition, the dimensions of the molded body 10 after firing are measured, and the relationship between the dimensions and the firing temperature is prepared as a conversion table. Then, when firing is performed under different conditions, the molded body 10 is fired together with the body to be fired, and the dimensions after firing are measured, whereby the indicated temperature can be obtained from the conversion table.

As mentioned above, the indicated temperature is not an actual temperature but a thermal history for convenience. That is,
If the heat history detecting molded body of the present invention is used, it is possible to manage the heat history itself by obtaining the indicated temperature even when the firing conditions are different.

Further, since the molded body 10 of the present invention has the string portions 12 and 12, the area is smaller than that of the conventional example shown in FIG.
Does not require a large space in the firing furnace. The string portions 12 and 12 do not have to be parallel to each other and may be formed only at one place. Further, since the molded body 10 of the present invention is a press-molded product having a certain thickness, warpage does not occur, and during dimension measurement, the molded body 10 shown in FIG.
As shown in FIG. 5, it is sufficient to measure between the arc-shaped measurement surfaces 11 with a low constant pressure micrometer, and the same diameter D can be accurately measured even if the measurement position is deviated. Furthermore, the molded article of the present invention
The string 10 can be placed in the furnace with the string portion 12 as the lower surface. By doing so, the effect of preventing warping can be increased in a more space-saving manner. Further, the shape of the concave portion 13 may be engraved with characters such as alphabet in addition to the dot shape as shown in FIG.

Example 1 SiO ₂ was added as a sintering aid to a purified alumina raw material having a purity of 99.9% or more, wet-milled with alumina balls, and subjected to particle size analysis by a laser light scattering method to obtain an average particle size of 4.0.
The range is ± 0.1 μm. To this raw material powder, 6 wt% of a wax binder is added, mixed and spray-dried to obtain granules having good fluidity. The granules are press-molded in an air-conditioned molding chamber into the shape shown in FIGS. 1 (a) and (b). At this time, the green density of the molded body is 2.300 ±
A molded article for heat history detection of the present invention was obtained in the range of 0.005 g / cm ³ .

When the amount of SiO ₂ in the above raw material was changed and baked,
As shown in the table, those containing more than 0.2% by weight of SiO ₂ were densified at 1720 ° C. and did not shrink at higher temperatures, so they could not be used at 1720 ° C. or higher.
In the case of an ordinary alumina firing furnace, since it was necessary to measure up to about 1750 ° C, the amount of SiO ₂ had to be 0.2% by weight or less.

Example 2 In exactly the same manner as in Example 1, a thermal history detecting molded body 10 having a SiO ₂ amount of 0.10 wt% and a diameter D of 22.300 mm was prepared. This molded body 10 is rigorously controlled and calibrated in a firing furnace, and the temperature is raised in an oxidizing atmosphere at a temperature of 200 ° C./hour at a maximum firing temperature of 2
Hold for a time, bake at a temperature decrease rate of 300 ° C / hour, and heat at 350 ° C for 1
Degreased for hours. The dimensions of the molded body 10 after firing were measured at 20 ° C. with a low constant pressure micrometer.

The firing temperature (instructed temperature) was variously changed, and the firing of 20 molded bodies 10 was repeated three times. The results are shown in Table 2 and FIG.

Also, from the dimensional variation (3σ) at each temperature and the dimensional change amount per 1 ° C. (tangent slope) at that temperature, Then, the detection accuracy (3σ) of the indicated temperature was calculated. As a result, as shown in Table 2, in the range of 1400 to 1750 ° C, the detection accuracy of the indicated temperature was within ± 2 ° C.

Furthermore, although Table 2 shows the dimensions of the molded body for each indicated temperature of 50 ° C, it is possible to obtain a conversion table for the dimensions of the molded body and the indicated temperature by measuring the dimensions for each of the more detailed indicated temperatures. can do.

Further, in the above embodiment, in order to obtain the heat history detecting molded body 10, the raw material particle size is 4.0 ± 0.1 μm, and the green density of the molded body is 2.300.
Although ± 0.005 g / cm ³ is set, neither is limited to this value and can be variously changed. In that case, the particle size is usually controlled to be within ± 0.2 μm. On the other hand, management of green density is important, ± 0.01
If the variation was suppressed within the range of g / cm ³ , the detection accuracy of the indicated temperature could be ± 2 ° C.

[Advantages of the Invention] As described above, according to the present invention, Al ₂ O ₃ 99.7 wt% or more, S
By using a ceramics unfired compact with 0.2% by weight or less of iO ₂ as the thermal history compact, the detection accuracy of the indicated temperature can be made extremely accurate to ± 2 ° C, so the firing process can be performed even if the firing conditions change. It can be strictly controlled, and an excellent sintered body can be obtained. In addition, according to the present invention, the disk-shaped ceramic green body is provided with linear chords on the outer periphery thereof, and the remaining arc portion is used as the measurement surface to form the thermal history detection molded body. The space to put is small, and the diameter can be measured easily and accurately.

[Brief description of drawings]

FIG. 1 (a) is a plan view showing a heat history detecting molded body according to an embodiment of the present invention, and FIG. 1 (b) is a sectional view taken along line XX in FIG. 1 (a). FIG. 2 and FIG. 3 are perspective views showing a conventional thermal history detecting molded body, respectively. FIG. 4 is a graph showing the relationship between the firing shrinkage rate and the indicated temperature in the heat history detection molded body of the present invention. 10: Molded body for heat history detection 11: Measuring surface, 12: Chord 13: Recess, 14: Chamfer

Claims (2)

[Claims] 1. A molded article for thermal history detection comprising a ceramic unfired molded article containing 99.7% by weight or more of Al ₂ O _{3 and} 0.2% by weight or less of SiO ₂ . 2. A molded article for thermal history detection, which is a disk-shaped unfired ceramic molded article, which is provided with a straight chord portion on the outer periphery and has a remaining arc portion as a measurement surface.