JPH11173965A - Evaluation method for compaction characteristic of granular substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluation method for the compaction characteristic of a granular substrate, in which a process for changing individual granular substances into a compactly molded body from the state of the granular substances in their compaction, can be evaluated microscopically. SOLUTION: When granular substances 1 are compacted, a fundamental operation in which a pressing member 3 is pressed in for a set time at a constant displacement speed so as to be stopped for a set time is repeated. A change in a load acting on the pressure member 3 is measured in every fundamental operation. The relationship between the pressing time of the pressing member 3 and the load is found. The yield behavior of a granular substance layer 2 in every fundamental operation is investigated. Thereby, the compaction characteristic such as the deformation characteristic, the breakdown characteristic or the like of the granular substances 1 is evaluated microscopically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for evaluating the properties of granules during compaction, such as the flow properties or filling properties of the granules.

[0002]

2. Description of the Related Art Conventionally, evaluation of compaction characteristics of granules is performed, for example, in order to judge the formability of fine ceramics or the like. That is, at present, intelligent materials have been developed, and fine ceramics having high functionality and high reliability have received particular attention.
The manufacturing process of fine ceramics can be roughly divided into a raw material adjustment process, a molding process, and a firing process.
This will be further emphasized in the subsequent firing step. For this reason, in order to obtain fine ceramics having high functionality and the like, it is essential to improve the homogeneity of the molded body. And it is thought that the press molding process of the compact most affects the homogeneity of the compact. It is considered that the process of compacting granules proceeds in the order of rearrangement of granules, destructive deformation of granules, and rearrangement of primary particles. When evaluating the compaction properties of granules, not only grasping the change points of these compaction mechanisms as macroscopic evaluations, but also microscopic evaluation of the properties of the granules affecting each compaction mechanism is an important factor. Conventionally, when evaluating the compaction properties of granules, for example, in order to evaluate the strength of the granules in the press forming step of the granules, compress the powder layer and measure its pressure and relative density In order to obtain a compaction response diagram showing the change in relative density, and to evaluate the deformation and fracture characteristics of a single granule, conduct a fracture strength test on one granule using a micro compression tester Methods have been used.

[0003]

However, in the method for obtaining a compaction response diagram as described above, the granules are rearranged with respect to three states of the granules, that is, the pressing force from the compaction response diagram. It is possible to grasp the state, the state in which the granules are deformed and broken, and the state in which the granules are rearranged at the primary particle level. However, this method could not evaluate the microscopic compaction characteristics of the granules and the heterogeneity of the packed bed. In the above-mentioned micro compression test, the granules are compressed using a flat indenter. However, since the shapes of the granules are different from each other, the test results vary for each compression test. In addition, in the micro-compression test, the granules are only compressed in one specific direction,
The conditions are different from the case where the packed bed of granules is actually compacted. Therefore, the results obtained by the micro-compression test do not always correspond to the characteristics when compacting the actual granules. That is, in view of the necessity of evaluating both the microscopic viewpoint and the macroscopic viewpoint in order to evaluate the compaction characteristics of the granules, it is not possible to sufficiently evaluate the compaction characteristics of the granules in the above-described conventional method. could not.

[0004] An object of the present invention is to overcome the drawbacks of the prior art, and to provide a granule capable of microscopically evaluating the process of individual granules from the state of the granules to the compacted compact during compaction. An object of the present invention is to provide a method for evaluating consolidation characteristics.

[0005]

Means of the present invention for achieving this object will be described with reference to the examples shown in FIGS.

(Means 1) In the method for evaluating the compaction characteristics of granules 1 according to the present invention, as described in claim 1, a mold 4 for compacting the granules 1 is filled with the granules 1 and a pressing member is provided. 3
When pressurizing the granule 1 by using the method, after pressing the pressing member 3 against the granule 1 at a constant displacement speed for a predetermined time, an operation of stopping the pressing of the pressing member 3 for a predetermined time is performed. As a basic operation, in the basic operation, a change in the load acting on the pressing member 3 or the mold 4 is measured, and the relationship between the pressing time of the pressing member 3 and the load is obtained. A region where the rate of increase in the load with respect to the increase in the pushing time is constant is defined as a first region A, and a region immediately before the end of pressing where the ratio of the increase in the load with respect to the increase in the pushing time is constant is a second region. B, the relationship between the indentation time and the load in the first area A and the second area B is obtained as a first function and a second function, respectively, at the end point of the first area. The load with the Py, the load at the common point between the second function and said first function and Pb, at the time when the basic operation ends,

[0007]

(Equation 3)

The filling rate of the granular material layer 2 is obtained from the relationship represented by the following formula, and the filling rate is compared with the Py and Pb.
It is characterized in that the correlation with Pb / Py obtained from the above is obtained, and the basic operation is repeated, whereby the correlation is sequentially obtained, and the deformation / fracture characteristics of the granule 1 are evaluated. (Operation / Effect) Each item specified by this means has the following meaning. The first region is a region where the granular layer is mainly elastically deformed and compacted, and the load Py at the end point of the first region is considered to indicate a yield point of the granular layer. On the other hand, the second region is a region that is plastically deformed or broken and compacted after the granule layer has yielded, but the mode of transition from the first region to the second region is not necessarily constant. The load at the common point between the first function and the second function is defined as Pb, and the load Pb is regarded as the load immediately after the granule layer yields. In the method of the present invention, Pb / Py evaluates the compaction characteristics of the granules by grasping the behavior of the granules at the time of yield depending on which of Py and Pb is larger. That is, Pb is greater than Py
Is larger, that is, if the transition from the first function to the second function is performed gently without a decrease in the load when the granules yield, the granules are sequentially rearranged mainly by the flow of the granules. Is considered to be caused. In other words, the tendency that Pb becomes larger than Py is a phenomenon observed in the early stage of consolidation. However, when the granules are destroyed in the later stage of compaction and compact the granule layer in which the primary particles are generated, the granules are replaced with the primary particles, and the load required for compaction is high. But
Pb is larger than Py as in the case of the granules. That is, the tendency that Pb becomes larger than Py is a phenomenon that is also observed in the later stage of consolidation.

On the other hand, when Py is larger than Pb, that is, when the yield is accompanied by a decrease in the load of the granules,
For example, a certain granule is destroyed due to an increase in the stress acting between the granules, so that a space is created between the granules, and the load is reduced due to a loss of the contact force between the granules. It is considered something. Since such behavior can occur when a space is still left inside the granular layer, it can be considered to be a phenomenon often observed in the middle stage of compaction of the granular layer. As described above, according to the method of the present invention, the compaction of the granules is in the initial state by measuring the value of Pb / Py for each packing ratio of the granule layer and grasping the change in Pb / Py. Or the degree of consolidation in the middle or late stage. By paying attention to whether the degree of consolidation shifts to the higher side or the lower side of the filling rate, it is possible to evaluate the superiority of the filling property of the granules.

(Means 2) In the method for evaluating the compaction characteristics of the granules 1 according to the present invention, as described in claim 2, the granules 1 flow from the filling rate determined by the first basic operation. It can be evaluated whether it is easy or not. (Operation / Effect) In the present method, since the pressing amount per pressing of the pressing member can be set small, the first pressing of the granule layer is performed without breaking the granules in the granule layer so much. It is possible. In this case, the packing ratio of the granules obtained by the first indentation is considered to be due to only the rearrangement of the granules, and the higher the packing ratio is, the more easily the granules are rearranged. That is, the fact that the particles are easily rearranged means that the flow characteristics of the granules are excellent. Therefore, the flow characteristics of the granules can be evaluated from the filling ratio obtained by the first indentation.

(Means 3) In the method for evaluating the compaction characteristics of the granules 1 according to the present invention, as described in claim 3, when the basic operation is repeated, if Pb / Py> 1, the granules 1 or the granules are Primary particles 1a produced by the destruction of
Is determined to be in a rearranged state, and if Pb / Py ≒ 1, it is determined that the granule 1 is in a plastic deformation state, that is, the granule 1 is in a state of being plastically deformed by receiving a pressing force, Pb
If / Py <1, it can be determined that the granule 1 is in a deformed and broken state, that is, the granule 1 itself is deformed with breaking. (Operation and Effect) As described in the operation and effect of the means 1, Py
When Pb is larger, that is, when Pb / Py> 1, the granule or 1 caused by the destruction of the granule is generated.
If it is determined that the next particle is in a rearranged state and Py is smaller than Pb, that is, if Pb / Py <1, the particle is in a deformed / broken state, that is, the particle itself is deformed with destruction. It can be determined that it is in the state. Then, the reason why Pb / Py = 1 is satisfied is that the transition from the first region to the second region is performed without a decrease in load,
This is the case where the contact between both areas is clear. In other words, when substantially the entire granule layer is rearranged, and furthermore, when the yielding of the granules is performed by rapidly shifting to a predetermined compaction state without destruction of the granules, for example, It is conceivable that each granule is plastically deformed and compacted. Since the plastic deformation is considered to occur when the stress on each granule acts uniformly from all directions around the granule, the arrangement of the granules is relatively dense due to the occurrence of the plastic deformation. It is possible to determine that. If the granules are not broken as described above, a space that will later become a defect of the molded body is not generated inside the granule layer, and ideal compaction can be performed. Considering that the granules are eventually broken and become primary particles, the range of the filling rate at which such plastic deformation occurs is limited. However, the better the filling of the granules, the earlier the plastic deformation due to the indentation. Causes
In addition, it can be assumed that if the state of filling is good, plastic deformation is possible even after several indentations, so that granules that can maintain the state of Pb / Py ≒ 1 for a longer time have better filling properties. It can be determined that there is. As described above, in the case of the present means, the initial area where Pb / Py> 1
an intermediate region in which the value of b / Py changes in the vicinity of 1;
By paying attention to three regions, that is, the terminal region where / Py> 1, the compacted state of the granules can be evaluated.
In particular, by paying attention to a region where the value of Pb / Py is close to 1, the filling property of the granules can be evaluated.

(Means 4) In the method for evaluating compaction characteristics of granules according to the present invention, as described in claim 4, instead of obtaining the correlation between the filling ratio and the Pb / Py, the first method is used. The pushing time until reaching the end point of the area A is Ty
And the pushing time until the load reaches the point Pb is Tb, the load at the end point of the second area B is Pp, and the pushing time until the end point of the second area B is reached. Is defined as Tp, and the filling rate and Py /
Ty, and the filling rate and (Pp-P
b) / (Tp−Tb), and the Py
From the difference between / Ty and (Pp-Pb) / (Tp-Tb),
The degree to which the compaction of the granules 1 has progressed can be determined. (Action / Effect) Py / Ty indicates the slope of the load change before the granule layer yields, that is, the slope of the first function related to the first region. On the other hand, (Pp-Pb) / (Tp-Tb)
Indicates the slope of the load change after the granule layer yields, that is, the slope of the second function related to the second region. The difference between these two inclinations is considered to represent the difference between the compacted state before the granular layer yields and the compacted state after the granular layer yields. That is, in the first region, the respective granules are mainly elastically deformed, whereas in the second region, the granules are decomposed in addition to being plastically deformed or broken. The rearrangement of the primary particles and the like generated is also performed.
For this reason, the slope of the first function is larger than the slope of the second function. And, in the state where the filling rate is low, that is, in the state where the number of times of pressing of the pressing member is small, the ratio of the granules that have been plastically deformed or broken is small, and the existence ratio of the granules that can be elastically deformed is high. The difference between the slope of the first function and the slope of the second function appears clearly. On the other hand, as the filling rate increases, the granules have already yielded and plastic deformation or destruction has progressed, so that the abundance of the elastically deformable granules decreases. Therefore, as the filling rate increases, the difference between the slope of the first function and the slope of the second function decreases. As described above, the difference between Py / Ty and (Pp-Pb) / (Tp-Tb) indicates the degree to which the compaction of the granules has progressed.

(Means 5) In the method for evaluating the compaction characteristics of the granules 1 according to the present invention, as described in claim 5, a mold 4 for compacting the granules 1 is filled with the granules 1 and a pressing member is provided. 3
When pressurizing the granule 1 by using the method, after pressing the pressing member 3 against the granule 1 at a constant displacement speed for a predetermined time, an operation of stopping the pressing of the pressing member 3 for a predetermined time is performed. As a basic operation, in the basic operation, a change in a load acting on the pressing member 3 or the mold 4 is measured, and a relationship between the pressing time of the pressing member 3 and the load is obtained. At the time when the basic operation is completed, the load in the reached state is defined as Pp, and the load at the time when a predetermined time has elapsed after the pressing member 3 is stopped is defined as Pe,

[0014]

(Equation 4)

The packing ratio of the granular material layer 2 is determined from the relationship represented by the following expression, and the packing ratio and the Pp and Pe are determined.
It is characterized in that the correlation with Pp / Pe obtained from the above is obtained, and the above-mentioned basic operation is repeated, thereby sequentially obtaining the correlation and evaluating whether or not the granules 1 are easy to flow. . (Operation / Effect) Here, Pp is the maximum load of the pressing member according to one basic operation, and Pe is the convergence value of the load acting on the pressing member after the stress is relaxed. In other words, Pp / Pe is obtained after the pressing of the granule layer is stopped.
It represents the degree of relaxation of the stress inside the granular material layer, and indicates that the larger the value of Pp / Pe, the greater the load decrease after stopping the pressing of the pressing member. It is considered that such a decrease in load occurs when the granules or primary particles or the like formed by the decomposition of the granules flow or rearrange inside the granule layer. That is, it can be determined that the larger the value of Pp / Pe, the better the fluidity of the granules and the more excellent the filling properties.

[0016] In the description of the means for solving the above problems, reference is made to the drawings and, in order to facilitate comparison with the drawings, the reference numerals are used, but the invention is limited to the configuration shown in the accompanying drawings. Not something.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The method for evaluating the compaction characteristics of granules 1 according to the present invention comprises intermittently compacting a granule layer 2, ie, a packed layer of granules 1, with a pressing member 3, and the granules in each compaction process. Based on the relationship between the filling factor and the load required for compaction, the compacting properties such as the flow properties or the deformation and fracture properties of the granules 1 are evaluated from a microscopic viewpoint. The filling rate is

[0018]

(Equation 5)

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Consolidation and Stress Relaxation of Granular Layer) Granular Layer 2
Is performed, for example, as follows. That is, as shown in FIG. 1, a granule 1 sized to a predetermined particle size is put into a consolidation mold 4.
And the granular material layer 2 is pressed by the pressing member 3, for example, a piston 3a. In this method, pressing is performed for a predetermined time while the displacement speed of the pressing member 3 is constant, and then the pressing of the pressing member 3 is stopped for a predetermined time. This operation is a basic operation, and the basic operation is repeatedly performed until the load of the pressing member 3 reaches a predetermined value. The load is performed using the load cell L attached to the pressing member.
The reason why the pressing member 3 is stopped for a predetermined time is that the individual granules 1 in the granule layer 2 subjected to a predetermined pressing force undergo rearrangement or plastic deformation, and the stress acting on the granule layer 2 This is for relaxing the granules 1 to shift to a more stable state. At the time of pressing the pressing member 3, mainly, a cumulative pressing time from the start of pressing of the pressing member 3 and a load applied to the pressing member 3 at the time were continuously measured. Since the cumulative time means the amount of displacement of the pressing member 3, the amount of displacement of the pressing member 3 from the start of the pressing was also measured. Further, in order to measure the weight of the granules 1 used for the measurement, the weight of the compact at the time when a series of compaction operations was completed was measured using an electronic balance.

(Relationship between pressurization time and pressure) As described above, the process of consolidation and stress relaxation obtained by one basic operation can be roughly shown in FIGS. 2, 3 and 4. In each figure, the horizontal axis represents the pressing time, and the vertical axis represents the load acting on the pressing member 3. Immediately after the start of pushing, a region X showing a constant load with respect to the pushing displacement of the pressing member 3 is seen. In other words, when filling the mold 1 with the granules 1, it is merely performed while sizing using a sieve.
The granule layer 2 is in a sparsely filled state. In addition, the granules 1 which are simply filled naturally have relatively high fluidity. Therefore, at the time of the initial pushing, the rearrangement of the granules occurs, and the load hardly increases.

As the pushing of the pressing member 3 proceeds, for example, as shown in FIG. 2, the load rapidly rises linearly. FIG. 5A is a schematic diagram showing the state of the granule layer in this state. Generally, in the compaction of the granule layer 2,
It is said that the pressure is not transmitted uniformly to the granule layer 2 but is transmitted along a stress transmission line 5 formed between specific granules 1. That is, in the region where the load is rapidly increased, as described above, the rearrangement of the granules 1 progresses, so that a part of the granule layer 2 is moved from the pressing surface of the pressing member 3 to the lower portion of the granule layer 2. It is considered that the stress transmission line 5 is formed toward the, and the granule 1 located along the stress transmission line 5 is elastically deformed. The first area in which the increasing width of the load acting on the pressing member 3 becomes constant with respect to the increasing width of the pushing time is hereinafter referred to as a first area A.

As shown in FIG. 2, the load acting on the pressing member 3 rises rapidly in the first area A, and when the load reaches a certain level, the rate of increase clearly decreases. this is,
It is considered that the elastic deformation of the granule 1 along the stress transmission line 5 reached the yield point. As a result, the subsequent granule layer 2 is considered to be compacted while causing plastic deformation or destruction. In other words, the granules 1 themselves and the smaller particles generated by the destruction of the granules 1 rearrange while coexisting, so that a new stress transmission line 5 is formed in the granule layer 2 and the destruction of the granules 1 again -An unstable state in which deformation occurs will continue. Also in this case, the increasing width of the load acting on the pressing member 3 becomes substantially constant with respect to the increasing width of the pushing time. Such an area that appears after the first area A is hereinafter referred to as a second area B. As shown in FIG. 2, the gradient of the function relating to the first region A where the elastic deformation of the granule 1 is mainly dominant is mainly smaller than the gradient of the function relating to the second region B where the plastic deformation or the like is dominant. Is also big. The second area B lasted until one basic operation was completed.

It should be noted that from the first area A to the second area B
The relationship between the pressing time of the pressing member 3 and the load at the time of shifting to (1) is that it can be roughly classified into three types as shown in FIGS. That is, although the load does not decrease as shown in FIG. 2, the first type in which the transition from the first area A to the second area B is unclear, and as shown in FIG. The second where the load decreases when shifting to B
4 and a third type in which the transition to the first region A and the second region B is clear and the load is not particularly reduced as shown in FIG. These differences result from the difference in behavior when the granular material layer 2 yields. For example, FIG. 2 according to the first type shows a granular layer 2
Is obtained by rearrangement of the granules 1, and this can be represented as shown in FIG.
That is, the granules 1 elastically deformed by the pressing member 3
The arrangement of the granules 1 is broken, and the granules 1 are sequentially rearranged in the space existing between the granules, thereby alleviating the pressure by the pressing member 3. When such rearrangement occurs in a minute region in the granular layer 2, the surrounding granular layer 2
Is affected, and the region where rearrangement occurs is sequentially expanded. Therefore, in the case of this type, although the load does not decrease when shifting from the first area A to the second area B, the shift point does not appear clearly. FIG. 3 according to the second type shows a case where the state change that the granule 1 yields and leads to brittle fracture occurs substantially uniformly throughout the granule layer 2, and FIG. ). That is, when the granule 1 undergoes brittle fracture, the existing stress transmission line 5 disappears, so that there is a time lag until a new stress transmission line 5 is formed, which reduces the load. It is thought that it appears as Further, FIG. 4 according to the third type is a case where the packed layer of the granules 1 yields due to the plastic deformation of the granules 1, and the state can be represented as in FIG. 5 (c). . In other words, the granule 1 merely undergoes plastic deformation, and the load does not decrease because the stress transmission line does not instantaneously disappear as described above. In this case, unlike the case where the granule 1 causes brittle fracture, it is considered that the stress transmission line itself does not disappear even after the yield of the granule 1 and the stress transmission line 5 in the granule layer 2 sequentially increases. Can be In the case of this type, the portion that transitions from the first region A to the second region B clearly appears, and
There is no decrease in load when shifting from the first area A to the second area B.

As shown in FIGS. 2 to 4, when the displacement of the pressing member 3 was stopped to stop the compaction of the granule layer 2 in each of the basic operations, stress relaxation of the granule layer 2 was confirmed.
This is because the pressure between the granules 1 is increased by the pressing of the pressing member 3, but even after the pressing of the pressing member 3 is stopped, the rearrangement of the granules 1 and the This is considered to be caused by the occurrence of fracture and plastic deformation of the granules 1 and the rearrangement of the granules 1 and the primary particles 1a generated by the breakage, thereby relaxing the pressure between the granules 1. As a result, the load remaining in the state where the relaxation of the stress is completed is mainly due to the granules 1 remaining in the granule layer 2.
Can be considered to be due to the stress transmission line 5 generated in the elastically deformed portion. Then, when performing the next basic operation, first, the pushing load of the pressing member 3 is transmitted along the stress transmission line, and exhibits the same behavior as any of FIGS. 2 to 4 again.

(Pushing Result) In one basic operation, it has been found that there is a correlation between the pushing time of the pressing member 3 and the load as shown in FIGS.
In order to evaluate the consolidation characteristics of the granule layer 2, predetermined numerical values extracted from the obtained correlation are compared and examined. First, the load Py related to the end point of the first area A was determined. Py indicates the load at the yield point of the granular material layer 2. For example, in any of FIGS. 2 to 4, the first area A passes through the consolidation start point, that is, the start point of the first area A.
Were drawn, and points at which the straight line and the indentation result did not match were arranged as Py. The pushing time up to this point is defined as Ty. On the other hand, the load immediately after the granule layer 2 yielded was defined as Pb. However, the behavior before and after yielding when consolidating the granular material layer 2 varies depending on each basic operation as described above, and the Pb is not always clear from the diagram obtained by consolidation. Identified. That is, while obtaining the function relating to the second area B,
A function relating to the first area A was obtained, and an intersection of the two was obtained, and the load at the intersection was defined as Pb. For example, Pb
Is determined on the drawing, the intersection of the straight line or the extended line of the first region A with the straight line of the second region B or the extended line of the straight line may be obtained. The time required for the load to reach Pb is defined as Tb.

The load at the time when the pressing of the pressing member 3 according to the basic operation is completed is defined as Pp. Pp is the maximum value of the load received by the pressing member 3 in the basic operation.
Then, the Pp coincides with the point where the second area B ends. Note that the time required to reach Pp is defined as Tp.

For a certain period of time after the pressing of the pressing member 3 is stopped, the state where the pressing member 3 is stopped is maintained. During this time, it is considered that the load that has reached Pp gradually decreases and approaches a certain value. However, it is not realistic to stop the pressing of the pressing member 3 until the pressing force reaches a certain value. Therefore, the load is estimated by calculation.
Here, the load is Pe.

(Relationship Between Filling Rate and Pb / Py) FIG. 6 shows an example of a correlation between the filling rate of the granular material layer 2 and Pb / Py. Note that the filling rate on the horizontal axis indicates the filling rate at the time when each basic operation is completed. Here, the results of the first granules 1 having good consolidation properties and the results of the second granules 1 having somewhat poor consolidation properties are shown. In FIG. 6, the value of Pb / Py is approximately Pb / Py =
It is distributed on the large and small sides with 1 as the boundary. In FIG. 6, the first
In each of the granule 1 and the second granule 1, the evaluation is performed by roughly dividing into three regions. That is, an area where the number of times of pressing is 1 or 2, an initial area where Pb / Py> 1, an intermediate area where the value of Pb / Py changes near 1, and an end area where Pb / Py> 1 again. By focusing on these three regions, the compaction characteristics of the granule 1 are evaluated. That is, when Pb / Py> 1, it means that the yield of the granule layer 2 is performed according to the first type.
In this case, it is considered that the yield of the granule layer 2 proceeds with rearrangement of the granules 1 and the like. When Pb / Py <1, it means that the yield of the granule layer 2 is performed according to the second type. In this case, the yield of the granule layer 2 proceeds with brittle fracture, and the load acting on the pressing member 3 temporarily decreases. When Pb / Py = 1, it means that the yield of the granule layer 2 is performed according to the third type. In this case, the yield of the granule layer 2 is promptly performed over the whole, and the granule 1 after the yield is mainly compacted by plastic deformation.

The following can be roughly evaluated by examining FIG. 6 more specifically. For example, when focusing on the initial region, Pb / Py> 1, it is preferable that the initial region be shifted to the higher filling rate side. That is, the granules 1 having a high filling rate obtained by the initial indentation means that the flow characteristics of the granules 1 are excellent. It is thought that it is possible to promote. Moreover, since the granular material 1 whose value of Pb / Py quickly approaches 1 is the granular material 1 that is easily rearranged, the granular material 1 having a larger Pb / Py slope is more excellent in the filling property. I can say.

When attention is paid to the above-mentioned medium-term area, it is desirable that Pb / Py = 1 in the medium-term area. That is, Pb / Py = 1 means that the granular material layer 2 yields according to the schematic diagram of FIG. That is, when the granule 1 yields, substantially the entire granule layer is
The granules 1 are immediately shifted to a predetermined consolidation state without destruction or the like of the granules 1, and thereafter, the respective granules 1 undergo plastic deformation and are consolidated. That is, in the case of Pb / Py = 1, it means that it is possible to shift to the ideal consolidation state without causing frequent destruction of the granules 1. Therefore, in FIG. 6, the wider the region where Pb / Py 横 1 is, the better the packing properties of the granule 1 are. In the case of the second granules 1, the second granules 1
In the region B, there is a portion where Pb / Py <1 is clearly established. Here, it is considered that the breakdown has occurred according to the schematic diagram of FIG. That is, it can be considered that the compaction of the granule 1 is being performed while a part of the granule 1 is broken. That is, since the second granule 1 does not cause plastic deformation after yielding, there is almost no region where the value of Pb / Py is constant. As a result, the second granules 1
In this case, minute voids tend to remain in portions where the broken pieces of the granules 1 are compacted. For this reason, for example, when obtaining a sintered body of fine ceramics, a large number of minute voids will remain inside the compacted body obtained by compaction, and the inside of the sintered body obtained as a product Many defects also remain.

Further, focusing on the late region where Pb / Py> 1, it is preferable that the late region be shifted to the higher filling rate side. That is, the high final filling rate of the granule layer 2 means that it has nothing but excellent filling properties. This region is considered to represent a state in which the rearrangement of the granules 1 itself is substantially completed, and subsequently, the primary particles 1a and the like generated by the decomposition of the granules 1 are rearranged.

In addition, in the case of the present method, the filling rate is calculated at the end of each basic operation, so that it is possible to know the number of times the pressing member 3 has been pressed until the predetermined filling rate is reached. . As a result, it is possible to compare the number of times of pressing until a predetermined filling rate is obtained, and it is also possible to evaluate the work efficiency.

(Filling rate, Py / Ty and (Pp-P
b) Correlation between / (Tp-Tb)) Correlation between filling ratio and Py / Ty when a certain granule layer 2 is pressed, and filling ratio and (Pp-Pb) / (Tp-Tb) FIG. 7 also shows the correlation with. Py / Ty is the granular layer 2
Of the load change before yielding, that is, the first area A
2 shows the slope of the first function according to the first embodiment. On the other hand, (Pp-Pb) /
(Tp-Tb) indicates the slope of the load change after the granule layer yields, that is, the slope of the second function related to the second region B. It is considered that the difference between these two inclinations represents the difference between the compacted state before the granular layer 2 yields and the compacted state after the granular layer 2 yields. That is, in the first region A, each of the granules 1 is mainly elastically deformed, whereas in the second region B, the granules 1 are plastically deformed or broken. Rearrangement of primary particles and the like generated by the decomposition of the granules 1 is also performed. Therefore, the slope of the first function is larger than the slope of the second function. And
In the state where the filling rate is low, that is, in the state where the number of times of pressing of the pressing member 3 is small, the ratio of the granules 1 which have been plastically deformed or broken is small, and the presence ratio of the granules 1 which can be elastically deformed is high. The difference between the slope of the first function and the slope of the second function appears clearly. On the other hand, as the filling rate increases,
Since the granules 1 have already yielded and undergo plastic deformation or destruction, the abundance of the elastically deformable granules 1 decreases. Therefore, as the filling rate increases, the difference between the slope of the first function and the slope of the second function decreases. If the granule 1 is completely compacted and reaches the final state, no change in state such as rearrangement can occur inside the granule layer 2 anymore, and the first region A and the second region B and the difference between Py / Ty and (Pp−Pb) / (Tp−T
It is considered that the value of b) becomes equal. As mentioned above,
By knowing the difference between Py / Ty and (Pp-Pb) / (Tp-Tb), it is possible to evaluate how much the compaction of the granules 1 has progressed.

(Correlation between Filling Rate and Pp / Pe) FIG. 8 shows a correlation between the filling rate and Pp / Pe when the two types of granules 1 are compacted. Also in this case, as described above,
The first granules 1 having good consolidation characteristics are compared with the second granules 1 having somewhat poor consolidation characteristics. here,
Pp is the maximum load of the pressing member 3 according to the basic operation, and Pe is a convergence value of the load acting on the pressing member 3 after the stress is relaxed. That is, Pp / Pe represents the degree of relaxation of the stress inside the granular material layer 2 after the pressing on the granular material layer 2 is stopped, and the larger the value of Pp / Pe, the more the pressing member 3 This shows that the load drop after stopping the pushing is large. Such a decrease in load is caused by the granules 1 and the primary particles 1a formed by the decomposition of the granules 1.
It is thought that the fluid flows inside the granular material layer 2 or rearranges. Therefore, the value of Pp / Pe is
As shown in FIG. 8, in any of the granules, there is a tendency that the rearrangement of the granules 1 has a maximum value in a region in the early stage of compaction where the rearrangement is considered to be dominant. In addition, the maximum value of Pp / Pe tends to be larger for granules 1 having a higher initial filling factor. For example, as shown in FIG.
When the second filling rate is higher than the first filling rate of the second granules, the maximum value of Pp / Pe of the first granules 1 is larger than the maximum value of Pp / Pe of the second granules 1. Is often large. As described above, the relationship between the filling rate and Pp / Pe is effective for evaluating the fluidity of the granule 1 or the primary particles 1a or the like formed by the decomposition of the granule 1, and for example, When the relationship between the ratio and Pp / Pe is plotted, the entire graph shifts to the higher filling ratio side, and Pp / Pe
The larger the maximum value of is, the more the granule 1 can be evaluated as having good fluidity.

(Effect) According to the method of the present invention, the following compaction properties of the granules 1 can be evaluated.

By determining the correlation between the filling ratio and Pb / Py, the deformation and fracture characteristics of the granule 1 can be evaluated. That is, it can be seen that the granules 1 are more easily rearranged in the early stage of consolidation, particularly, the higher the filling rate by the first pressing is. In the middle stage of consolidation, Pb
It can be said that the closer the value of / Py is to 1, the better the plastic deformation and fracture characteristics. That is, the fact that the value of Pb / Py is close to 1 means that the intersection between the first area A and the second area B that intersect at a predetermined angle as shown in FIG.
In addition, there is no sudden change in load near the intersection. This means that almost all of the granule layer 2 yields at once, and then turns into plastic deformation.
Since it is assumed that the granules 1 yield at the same timing, that is, that the respective granules 1 are densely arranged, it can be considered that such granules 1 are easily compacted. Furthermore, in the late stage of compaction, granules 1
Is decomposed, the rearrangement of the primary particles 1a occurs, and the value of Pb / Py increases again. If the maximum load that can be loaded on the pressing member is limited, the higher the filling rate at the maximum load, the better the consolidation characteristics.

From the results of the consolidation test, the filling rate and Py / Ty
And (Pp−Pb) / (T
The correlation with Py / Ty and (Pp-Tb) is obtained.
By paying attention to the difference between (Pb) / (Tp−Tb), it is possible to evaluate the degree to which the compaction of the granules 1 has progressed. That is, Py / Ty and (Pp-Pb) /
It can be determined that the compaction of the granules 1 is progressing as the difference from (Tp-Tb) approaches.

When the correlation between the filling ratio and Pp / Pe is obtained, it is possible to evaluate the quality of the flow characteristics of the granules 1. For example, the higher the filling rate due to the initial pressing,
Alternatively, it can be said that the larger the maximum value of Pp / Pe, the better the fluidity.

(Example) An example of the method for evaluating the compaction characteristics of the granules 1 according to the present invention will be described below.

<Test Granules> The raw material powder of the granules 1 has an average particle size of 0.4 μm and a density of 3.92 g / cm ^3.
Sinterable low soda alumina was used. This easily sinterable low soda alumina is dispersed in distilled water as a dispersion medium, and further, ammonium polyacrylate as a dispersant,
A wax-based binder as a binder was mixed. The raw material powders were adjusted to produce four types of slurries. That is,
Three types of slurries in which the concentration of the dispersant alone was changed (the dispersant addition amount was 0.35, 0.60, 1.50 g / 100 g)
Al ₂ O ₃ ) and a slurry containing two kinds of binders in addition to the dispersant (dispersant addition amount 0.60 g / 100 g A
l ₂ O ₃ , first binder addition amount 1.388 g / 100 g
Al ₂ O ₃ , second binder added 1.808 g / 100 g
Al ₂ O ₃ ). Hereinafter, the slurry to which only the dispersant is added will be referred to as slurries b1, b2, and b3 in the order of the amount of the added dispersant, and the slurry to which both the dispersant and the binder are added will be referred to as slurry k. Each slurry is
The alumina particles were prepared so that the solid concentration was 35% by volume and the total slurry volume was 700 ml (alumina particles 960.4 g, dispersion medium 455.0 ml). The dispersion medium was prepared by adding a dispersant / binder to distilled water and mixing in an ultrasonic bath for 5 minutes. Further, 1500 g of alumina particles, a dispersion medium, and alumina balls having a diameter of 5 mm were placed in a 2000 ml pot and mixed by a rolling ball mill at 90 rpm for 1 hour to prepare. Thereafter, the slurry and the alumina balls were separated by using a sieve, and the slurry was vacuum defoamed by a rotary pump. FIG. 9 shows the viscosities of these slurries. Among the slurries to which only the dispersant is added, the slurry b2 shows the minimum viscosity,
It became a valley with respect to the amount of the dispersant added. This is presumably because the dispersant affects the state of aggregation and dispersion of the particles in the slurry. That is, in the slurry b1, it is considered that the dispersant causes steric cross-linking between the particles and causes network aggregation because the dispersant is small relative to the particles. In the slurry b2, it is considered that the dispersant is sufficiently coated on the particle surface. In the slurry b3, it is considered that depletion aggregation is caused because the dispersant is excessive with respect to the particles. On the other hand, the slurry k to which the binder was added exhibited a higher viscosity than the slurry b2 in which the amount of the dispersant added was the same. This is thought to be due to the binder contributing to the aggregation of the particles.

The slurry was spray-dried using a small spray drier to produce granules 1. That is,
The slurry is fed to the top of the spray dryer using a rotary pump and the slurry is
After dropping on a disk rotating at 5,000 rpm, the granules 1 are evaporated by circulating water by circulating heating air in a conical drier to evaporate water.
I got The temperature in the spray dryer was 150 ° C. on the inlet side and 95 ± 5 ° C. on the outlet side. Hereinafter, the granules 1 prepared from the respective slurries are referred to as granules B1, B2, and B3 from the one with a small dispersant addition amount,
Granules 1 made from a slurry to which both a dispersant and a binder are added are referred to as granules K.

<Consolidation / Stress Relaxation Test of Granule Layer> The compaction of the granule layer 2 was performed using the granules B1, B2, B3, and K.
The stress relaxation test was performed as follows. Each granule B
1, B2, B3, K are 32 to 65 μm using a sieve
After sizing to 16 mmφ using a 90 μm sieve
And the mold was filled in a scrubbed state. 2m thick packed bed
m. The pressing of the granule layer 2 was performed for 1 minute with the displacement speed of the piston 3a as the pressing member 3 set to 0.1 mm / min, and the piston 3a was stopped for 15 minutes.
This operation was repeated until the load on the piston 3a reached 90 MPa, and the change in the load was continuously measured. For piston displacement, attach a dial gauge 6 to the piston 3a,
It was measured when the displacement of the piston 3a started and when the displacement of the piston 3 was stopped. Further, in order to measure the weight of the granules 1 used in the evaluation test, the weight of the compact after compaction was measured using an electronic balance.

<Results of Consolidation / Stress Relaxation Test for Each Granule> As a result of the above-mentioned compaction / stress relaxation test, the following results of evaluation of compaction characteristics were obtained. First, FIG. 10 shows the correlation between the filling rate and Pb / Py. The test results can be classified into a group of granules B3 and K, and a group of granules B1 and B2. The group of granules B3 and granules K can be divided into the following three regions.
That is, in the initial region, Pb / Py sharply decreases from a value larger than 1. In the intermediate region where consolidation has progressed, Pb /
Py shows a substantially constant value near 1. And Pb / Py increases again in the terminal region where the consolidation has further progressed. On the other hand, in the group of the granules B1 and B2, the region where the value of Pb / Py is constant near 1 as seen in the previous group is not seen, and the region in the first half where Pb / Py decreases And the latter half region where Pb / Py increases again. In this case, a clear minimum value where the value of Pb / Py was much lower than 1 was confirmed. That is, in the group of the granule B1 and the granule 1B2 in which such a minimum value appears, it is considered that the brittle fracture of the granule 1 occurs at the time of the yield of the granule layer 2. On the other hand, in the group of granules B3 and K, Pb /
Since there is a stable region where the minimum value of Py is approximately 1, it is considered that the granule 1 is not brittle but is plastically deformed.

FIG. 11 shows the correlation between the filling rate and Py / Ty, and the filling rate and (Pp-Pb) / (Tp-T
4 shows a correlation with b). Py / Ty and (Pp-Pb)
The difference from / (Tp-Tb) increases rapidly in the early stage of consolidation. However, thereafter, the difference between the two gradually decreased, and after the filling rate reached about 0.55, the difference between the two became substantially constant.

FIG. 12 shows the correlation between the filling rate and Pp / Pe. Here, the graph of the granule B1 has shifted to the lower filling rate side, and the graph of the granule K has shifted to the higher filling rate side. Furthermore, in the comparison of the maximum values of Pp / Pe, the maximum value of granule B1 was the smallest,
Was the largest.

The above results are considered to be due to the influence of the agglomeration / dispersion structure between the particles when the slurry was adjusted to produce the granules 1. For example, the flow characteristics of the granules 1 corresponded well to the amount of the dispersant added in the slurry preparation. Specifically, the granule B3 with the largest amount of the dispersant added showed the highest fluidity, while the granule B1 with the smallest amount of the dispersant added had the lowest fluidity. This is probably because the dispersant present on the surface of the granule 1 acts as a lubricant and reduces the coefficient of friction on the surface of the granule 1. The reason why the fluidity of the granule B1 was inferior was that, in the granule B1, each particle of the dispersant was agglomerated with a strong binding force due to network aggregation due to cross-linking between the particles of the dispersant. Power is granule 1
It is considered that this structure is a result of the fact that this structure contributed to the embrittlement of the granule 1. In addition, even the granules B2 in which the amount of the dispersant was larger than the granules B1 exhibited a brittle fracture behavior. This is because the granule B2 shows a dispersed structure at the time of preparing the slurry, but when the slurry is spray-dried, the dispersant around the granule 1 is rapidly hardened to form a strong outer shell structure. Conceivable.

<Inside Observation of the Molded Body> In order to confirm the actual compaction state inside the granule 1, the internal structure of the compact by the granules B1 and B3 was observed at several stages during the compaction. . The internal structure of the granule layer 2 was observed by using an immersion liquid transmission method in which the material was immersed in a liquid having a refractive index substantially the same as that of the raw material alumina (refractive index: 1.77) to make it transparent. In the immersion liquid, diiodomethane (refractive index: 1.7
5) was used. The granule layer 2 was calcined to maintain the shape after immersion. The calcining was performed using a box-shaped Keramax electric furnace at a rate of 250 ° C./hour up to 1,000 ° C.
After maintaining the temperature at 00 ° C. for 10 minutes, the temperature was lowered at 250 ° C./hour. The calcined body was polished in the radial direction using a # 1200 sandpaper, and then observed using a 600 times optical microscope. The appearance of the granule layer 2 obtained by the method is shown in the photographs of FIG. 13 and FIG.

The photographs according to FIGS. 13 (a), (b) and (c)
The internal structure of the granule B1 after the basic operation is repeated four, seven, and nine times is shown. On the other hand, FIG.
(B) The photographs according to (c) show the internal structure of the granule B3 after the basic operation was repeated four times, five times, and seven times. These are all Pb / Py ≒ 1 in FIG.
It is an observation result in the state which is. That is, FIG.
In each of FIGS. 14A and 14B, the photograph (A) shows Pb / Py ≒ 1
The photograph (c) shows the state immediately after Pb / Py> 1, and the photograph (b) shows the state at the intermediate filling ratio between the photograph (a) and the photograph (c). When these photographs are observed, the broken granule 1 is observed in the photograph (a) of the granule B1, but the photograph (a) of the granule B3 is observed.
In Example 1, no destruction of the granules 1 was observed. This is because the dispersant functions effectively in the granule B3,
The granules 1 rearrange at the stage when the stress acting on the granules has increased to some extent, and the stress can be relieved, whereas the effect of the dispersant is not so obtained in the granules B1, and the internal stress of the granules 1 is reduced. Since the granules 1 are not rearranged even when the height is increased, it is considered that the internal stress is further increased and the granules 1 are broken. Also,
Photos (b) and (c) in FIGS. 13 and 14, respectively.
Compared with the above, in the granule B1, the boundary between the granules 1 gradually disappears because the destruction of the granule 1 proceeds, but in the granule B3, the boundary between the granules 1 does not disappear. The boundary does not disappear in granule B3 because granule 1
In B3, since the fluidity is good and the rearrangement proceeds easily, the magnitude of the stress acting on one of the granules 1 does not reach the level at which the granules 1 themselves are broken, and only the plastic deformation occurs. It can be determined that it is staying. In both photographs (c), the portion observed black inside the molded article is considered to be a defect existing in the molded article.
This is presumably because, even after the molded article was immersed in diiodomethane, the air present in the defect was not replaced with diiodomethane, and as a result, air having a different refractive index from alumina diiodomethane was observed as black. Such defects were frequently observed in the molded product of the granule B1, and were scarcely observed in the molded product of the granule B3.

As described above, the granules B3 and K in which the dispersant or the binder is appropriately mixed have better compaction properties than the granules B1 and B2 in which the mixing ratio of the dispersant or the like is small. Thus, the consolidation characteristics of the granules 1 predicted from the measurement results of the load and the like in the consolidation test were in good agreement with the consolidation characteristics of the granules 1 confirmed by actual internal observation. As described above, it was found that the behavior of the granule 1 during compaction, such as the flow characteristics and the filling property, of the granule 1 can be microscopically evaluated by using the method for evaluating the compaction characteristics of the granule 1 according to the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a test method for evaluating the compaction properties of granules.

FIG. 2 shows the relationship between the pressing time of the pressing member and the load during compaction of the granules.

FIG. 3 shows the relationship between the pressing time of the pressing member and the load during compaction of the granules.

FIG. 4 shows the relationship between the pressing time of the pressing member and the load during compaction of the granules.

FIG. 5 is a schematic diagram showing the behavior of the granules during compaction of the granules.

FIG. 6 is an explanatory diagram showing a correlation between a filling factor and Pb / Py.

FIG. 7 is an explanatory diagram showing a correlation between the filling rate and Py / Ty and a correlation between the filling rate and (Pp-Pb) / (Tp-Tb).

FIG. 8 is an explanatory diagram showing a correlation between a filling factor and Pp / Pe.

FIG. 9 is an explanatory diagram showing the viscosity of a slurry for producing granules.

FIG. 10 is a diagram showing a correlation between a filling factor obtained by a consolidation test and Pb / Py.

FIG. 11 shows the correlation between the filling ratio obtained by the consolidation test and Py / Ty, and the filling ratio and (Pp−Pb) / (Tp).
-Tb)

FIG. 12 is a diagram showing a correlation between a filling factor obtained by a consolidation test and Pp / Pe.

FIG. 13 is a micrograph showing the internal structure of granules during the compaction process.

FIG. 14 is a micrograph showing the internal structure of granules during the compaction process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Granule 3 Pressing member A 1st area B 2nd area Py Load at the end point of the 1st area Pb Load at the common point of the 1st function and 2nd function Ty Push time until reaching the end point of the 1st area Tb load Pp Load at the end point of the second area B Tp Push time until reaching the end point of the second area Pp Load at the maximum load Pe Pe Fixed time after the pressing member is stopped Load at the passage of time

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[Procedure amendment]

[Submission date] December 8, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 13

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 14

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Makio Naito, Inventor No. 303 Grace Court Anjo 303, Grace Court 8-2, Ubatumi-cho, Nihongi-cho, Anjo-shi, Aichi Prefecture

Claims (5)

[Claims] When filling a granule into a mold for consolidating the granule and pressing the granule using a pressing member, the pressing member is moved at a constant displacement speed with respect to the granule for a predetermined time. After pressing over, the operation of stopping the pressing of the pressing member for a certain period of time is a basic operation. In the basic operation, a change in the load acting on the pressing member or the mold is measured, and the pressing member is pressed. The relationship between the pressing time and the load is obtained, and a region in which the ratio of the increase in the load to the increase in the pressing time is constant immediately after the start of pressing is defined as a first region. A region where the rate of increase of the load is constant is defined as a second region, and a relationship between the indentation time and the load in the first region and the second region is defined by a first function and a first function, respectively. Determined as a second function, the load at the end point of the first area is Py, and the load at a common point between the first function and the second function is Pb. At the time when the basic operation is completed, (Equation 1) In addition to determining the packing ratio of the granular layer from the relationship represented by
The filling rate and Pb obtained from Py and Pb
A method for evaluating compaction characteristics of granules, wherein a correlation with / Py is determined, and the basic operation is repeated, whereby the correlation is sequentially determined and the deformation / fracture characteristics of the granules are evaluated. 2. The method for evaluating compaction properties of granules according to claim 1, wherein whether or not the granules are easy to flow is evaluated based on the filling rate determined by the first basic operation. 3. When the basic operation is repeated, if Pb / Py> 1, it is determined that the granules or primary particles generated by the destruction of the granules are in a rearranged state, and if Pb / Py ≒ 1, It is determined that the granules are in a plastically deformed state, that is, the granules are in a state of being plastically deformed by receiving a pressing force. If Pb / Py <1, the granules are in a deformed / fractured state, that is, The method for evaluating compaction characteristics of granules according to claim 1, wherein it is determined that the granules themselves are deformed with destruction. 4. The method according to claim 1, wherein, instead of obtaining a correlation between said filling rate and said Pb / Py, said pressing time until reaching an end point of said first region is Ty.
The pushing time until the load reaches the point Pb is Tb, the load at the end point of the second area is Pp, and the pushing time until the end point of the second area is Tp.
The correlation between the filling rate and Py / Ty and the correlation between the filling rate and (Pp-Pb) / (Tp-Tb) are obtained, and these Py / Ty and (Pp-Pb) / ( Tp-T
2. The method for evaluating compaction properties of granules according to claim 1, wherein the degree of compaction of the granules is determined from the difference from b). 5. Filling the granules in a mold for compacting the granules and pressing the granules using a pressing member, the pressing members are displaced with respect to the granules at a constant displacement speed for a certain period of time. After pressing over, the operation of stopping the pressing of the pressing member for a certain period of time is a basic operation. In the basic operation, a change in the load acting on the pressing member or the mold is measured, and the pressing member is pressed. The relationship between the indentation time and the load is obtained, the load in a state where the load reaches the maximum is set to Pp, and the load at a point in time after the pressing member is stopped is set to Pe, and the load is set to Pe. At the end of the operation, In addition to determining the packing ratio of the granular layer from the relationship represented by
The filling rate and Pp obtained from the Pp and the Pe
/ Pe, and further, by repeating the basic operation, sequentially obtaining the correlation, and evaluating whether or not the granules are easy to flow. Evaluation methods.