JPH0377943B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for measuring the fire resistance of china clay for ceramics,
More specifically, the fire resistance of china clay is measured by determining the temperature at the inflection point where the shrinkage changes to expansion in the thermal expansion measurement of the china clay molded body, which is a simple and accurate method. It concerns the degree measurement method.

Traditionally, the fire resistance of china clay prepared for making everyday foods, tiles, sanitary ware, etc. is usually JIS
Measured according to the method specified in M8512 or JIS R2204. However, these measurement methods have the following problems: (1) JIS
In R2204, the sample is crushed to pass through a standard mesh sieve of 297 μm, but the particle size distribution of the same sample varies significantly depending on the crushing method, so the refractory level may differ by several orders of magnitude.(2) In the above method for measuring fire resistance, the fire resistance is expressed by the number of the standard Segel cone, which indicates the approximate deformation state that the tip of the Segel cone has when it comes into contact with the pedestal, but accurate observation under high temperature conditions is difficult. Therefore, the obtained fire resistance depends significantly on the measurer and the accuracy of the standard Segel cone.(3)
It is difficult to accurately measure the fire resistance of samples such as china clay, which expands at the temperature at which the test cone begins to bend. Comparing the fire resistance with a standard Segel cone using a sample passed through a 297 μm sieve has problems such as being impractical, and is not necessarily satisfactory.

In view of these circumstances, the inventors of the present invention have conducted extensive research on a method for easily and accurately measuring the refractory level of china clay without individual errors, and have created a china clay molded body with a specific shape. The purpose can be achieved by determining the temperature at the inflection point where contraction changes to expansion in thermal expansion measurement, and there is also a good relationship between the fire resistance determined by this method and the JIS method. They discovered that there is a correlation and completed the present invention.

That is, in measuring the fire resistance of china clay, the present invention involves molding china clay powder into a cylinder or cube shape, heating this molded body, and determining the temperature at the inflection point where the contraction changes to the expansion. This article provides a method for measuring the fire resistance of china clay.

In the measurement method of the present invention, first, particle size 74μ
m or less (approximately 80wt% less than 20μm, approximately 60wt% less than 10μm
%, containing about 50 wt% of particles less than 5 μm, and about 25 wt% of particles less than 1 μm) is molded into a cylinder or cube using a pellet molding machine. Regarding the size of this molded body, a cylindrical molded body is usually about 10 mm in diameter and a height of about 3 mm, and a cubic shaped body is usually about 10 mm on each side.

Next, the china clay molded body thus produced is placed in a thermal dilatometer and heated. Due to this heating, the molded body thermally expands up to a certain temperature, but when the temperature exceeds this temperature, it contracts due to sintering. As the temperature is further increased, the molded body begins to melt and vitrify at a certain temperature, so that above this temperature the gas generated inside cannot diffuse to the outside and it begins to expand rapidly.

Figure 1 is a graph showing an example of the relationship between temperature and thickness displacement of a molded object (cylindrical shape with a diameter of 10 mm and a thickness of 3 mm) made using china clay powder obtained from Amakusa pottery stone. be.

As can be seen from this figure, the molded body thermally expands gradually up to about 1000°C, but once this temperature is exceeded, it begins to shrink and expands rapidly at an inflection point of about 1400°C.

The inflection point has a good correlation with the fire resistance according to the JIS method.

In the present invention, a relationship between the fire resistance obtained in advance as described above and the fire resistance determined by the JIS M8512 or JIS R2204 fire resistance test method is created,
From this relational expression, the degree of fire resistance can be expressed by a number corresponding to the degree of fire resistance according to the Seegel cone.

Figure 2 shows the temperature at the inflection point where china clay powder obtained from various Amakusa pottery stones is shaped into a cylinder or cube, and the molded body is heated to change from contraction to expansion.
It is a graph showing an example of the relationship with fire resistance according to JIS method.

The correlation coefficient between the two refractory degrees determined from FIG. 2 is 0.94, which shows that there is a good correlation between the two refractory degrees. In addition, the relational expression between the two calculated using the least squares method based on this figure is A=0.83×B+378...() [However, A is the value obtained by converting the fire resistance according to the JIS method to temperature (℃), B is the temperature (°C) at the inflection point. ] It is expressed as .

The fire resistance according to the method of the present invention can be determined by creating a relational expression as shown in the above formula () in advance, using this formula as a conversion formula, and substituting the temperature at the inflection point into the conversion formula. Obtain the value obtained by converting the refractory degree to temperature, and from this temperature, calculate the refractory degree number according to the JIS method.

According to the method for measuring the fire resistance of china clay of the present invention, the conventional
Compared to the method specified in JIS, the method of the present invention can measure the fire resistance of china clay more easily and accurately, making it extremely practical and an effective method for quality control of china clay.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 0.5 g of dry powder of china clay obtained from Amakusa pottery stone, which can be made into china clay by simply crushing, was reduced and taken, and the inner diameter was 10.
The pellet was molded into a cylindrical shape with a thickness of 3 mm using a 3 mm pellet molding machine, and the pellet was set in a thermal dilatometer, and the temperature-thickness displacement curve of the pellet was determined. Part 1
An example is shown in FIG.

As can be seen from Figure 1, the pellets were heated to about 1000°C.
Until then, it expands thermally due to heating, but when the temperature exceeds this temperature, it begins to shrink due to sintering. Furthermore, since the pellets begin to melt and become vitrified at around 1400°C, the gas generated inside cannot diffuse to the outside at temperatures above this temperature and begin to expand.

Figure 2 also shows the fire resistance measured by the JIS method using china clay obtained from various Amakusa pottery stones, and the fire resistance measured by the JIS method using china clay obtained from the various Amakusa pottery stones mentioned above, which has the same particle size distribution as that used in the JIS method. The graph shows the relationship between the fire resistance and the degree of fire resistance measured using a thermal dilatometer using china clay.

The correlation coefficient between both fire resistance degrees obtained from this Figure 2 is
0.94, which shows that there is a good correlation between the two fire resistance degrees. Further, the relational expression between the two obtained by the least squares method based on this figure is shown below.

A=0.83×B+378 However, A is the value (°C) obtained by converting the fire resistance according to the JIS method into temperature (see JIS R8101), and B is the temperature (°C) at the inflection point measured by a thermal dilatometer.

[Brief explanation of drawings]

Figure 1 is a graph showing an example of the relationship between temperature and thickness displacement in a china clay molded body, and Figure 2 is a graph showing an example of the relationship between the fire resistance of china clay according to the present invention and the fire resistance according to the JIS method. It is a graph.

Claims (1)

[Claims] 1. To measure the fire resistance of china clay, mold the china clay powder into a cylindrical or cubic shape, heat this molded body, and measure the change in temperature from gradual expansion followed by contraction due to sintering to rapid expansion due to foaming. Determine the temperature of the bending point, determine the temperature corresponding to the refractory degree, and from that temperature determine the number of the refractory degree by comparison with the standard Segel cone shown in the JIS M8512 or JIS R2204 fire resistance test method. A method for measuring the fire resistance of china clay.