Inorganic powder cold isostatic pressing forming process

Abstract

The invention discloses an inorganic powder cold isostatic pressing forming process, and relates to the technical field of inorganic powder processing forming, and the inorganic powder cold isostatic pressing forming process comprises n times of pressurization-pressure maintaining-pressure reducing processes, compared with the prior art, the inorganic powder cold isostatic pressing forming process provided by the invention has the advantages that the density of the green body can reach a larger value under the conditions that the maximum forming pressure is the same and the pressure maintaining time is the same, so that a cold isostatic pressing machine with a lower pressure upper limit can be selected when cold isostatic pressing equipment is selected, and the equipment cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic powder processing and forming, and particularly relates to a cold isostatic pressing process for inorganic powder. Background Art

[0002] Cold Isostatic Pressing (CIP) is a process in which elastic materials such as rubber or plastic are used as the die material of the jacket at room temperature. The powder is loaded into the die, and liquid or gas is used as the pressure medium in the cylinder of the isostatic press to form the powder material, providing a regular or approximately regular green body for further sintering, forging or hot isostatic pressing processes.

[0003] In the cold isostatic pressing process, the forming pressure is an important factor affecting the properties of the green body. For powders, as the forming pressure increases, the density and strength of the green body increase. However, the greater the forming pressure, the higher the requirements for the equipment and the higher the equipment cost. Therefore, how to obtain a dense green body with a lower pressure to avoid high equipment investment has become a problem that those skilled in the art need to overcome. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a cold isostatic pressing process for inorganic powder, which uses an oscillating pressure (multiple pressurization-holding pressure-depressurization processes) during the cold isostatic pressing process. Compared with the one-time pressurization forming, under the same maximum pressure, the density of the obtained green body is greater.

[0005] The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] The object of the present invention is to provide a cold isostatic pressing process for inorganic powder, including n pressurization-holding pressure-depressurization processes.

[0007] Further, the inorganic powder includes but is not limited to at least one of silicon, silicon nitride, aluminum nitride, boron nitride, and alumina powder. Other types of inorganic powders can also be applied to the cold isostatic pressing process of the present invention.

[0008] Further, n>1. Regarding the value of n, as n increases, the density of the green body will not increase infinitely, but it will lead to an increase in energy consumption. Therefore, the value of n needs to be selected according to the actual situation.

[0009] Further, the specific steps of the pressurization-holding pressure-depressurization process are as follows:

[0010] Step 1: Increase the pressure to the first pressure at the first pressure increase rate, hold the pressure, and then decrease the pressure at the first pressure decrease rate;

[0011] Step 2: Increase the pressure to the second pressure at the second pressure increasing rate, hold the pressure, and then decrease the pressure at the second pressure decreasing rate;

[0012] ……

[0013] Step n - 1: Increase the pressure to the (n - 1)th pressure at the (n - 1)th pressure increasing rate, hold the pressure, and then decrease the pressure at the (n - 1)th pressure decreasing rate;

[0014] Step n: Increase the pressure to the nth pressure at the nth pressure increasing rate, hold the pressure, and then decrease the pressure at the nth pressure decreasing rate to obtain a green body.

[0015] Further, the first pressure ≤ the second pressure ≤... ≤ the (n - 1)th pressure ≤ the nth pressure.

[0016] In the present invention, the first (n - 1) pressure decreases can be to reduce the pressure to atmospheric pressure or to reduce the pressure to some other value; the nth pressure decrease is to reduce the pressure to atmospheric pressure.

[0017] Further, the first pressure increasing rate, the second pressure increasing rate... the (n - 1)th pressure increasing rate, the nth pressure increasing rate are 0.1 - 5 MPa / s.

[0018] Further, the pressure holding time is 1 - 5 min.

[0019] Further, the first pressure decreasing rate, the second pressure decreasing rate... the (n - 1)th pressure decreasing rate, the nth pressure decreasing rate are 0.1 - 5 MPa / s.

[0020] Exemplarily, when n = 4, the following pressure increasing - pressure holding - pressure decreasing process can be adopted:

[0021] Step 1: Increase the pressure to 30 - 50 MPa at a pressure increasing rate of 0.1 - 5 MPa / s, hold the pressure for 1 - 5 min, and decrease the pressure to atmospheric pressure at a pressure decreasing rate of 0.1 - 5 MPa / s;

[0022] Step 2: Increase the pressure to 80 - 100 MPa at a pressure increasing rate of 0.1 - 5 MPa / s, hold the pressure for 1 - 5 min, and decrease the pressure to atmospheric pressure at a pressure decreasing rate of 0.1 - 5 MPa / s;

[0023] Step 3: Increase the pressure to 130 - 150 MPa at a pressure increasing rate of 0.1 - 5 MPa / s, hold the pressure for 1 - 5 min, and decrease the pressure to atmospheric pressure at a pressure decreasing rate of 0.1 - 5 MPa / s;

[0024] Step 4: Finally, increase the pressure to 180 - 200 MPa at a pressure increasing rate of 0.1 - 5 MPa / s, hold the pressure for 1 - 5 min, and decrease the pressure to atmospheric pressure at a pressure decreasing rate of 0.1 - 5 MPa / s to obtain a green body.

[0025] Further, the inorganic powder is made into agglomerates and then cold isostatically pressed. The inorganic powder can be made into large-particle-size agglomerates by means of spray granulation or the like, aiming to improve the fluidity of the inorganic powder so as to better fill the inorganic powder into the molding die.

[0026] Further, the inorganic powder is filled into the molding die under the action of vibration. The inorganic powder in the die is evenly distributed by vibration, and electromagnetic vibration can be adopted.

[0027] The beneficial effects of the present invention are as follows: Compared with the prior art, the cold isostatic pressing process of the inorganic powder provided by the present invention can make the density of the green body reach a larger value under the condition that the maximum molding pressure is the same and the pressure holding time is the same. Furthermore, when selecting a cold isostatic pressing device, a cold isostatic press with a lower upper pressure limit can be selected, thereby reducing the equipment cost. Description of the Drawings

[0028] Figure 1 SEM diagrams of the granulated silicon powder agglomerates in the examples and the comparative examples;

[0029] Figure 2 SEM diagrams of the granulated silicon nitride powder agglomerates in the examples and the comparative examples;

[0030] Figure 3 Graph of the relationship between pressure and time during the cold isostatic pressing process of Example 1;

[0031] Figure 4 Graph of the relationship between pressure and time during the cold isostatic pressing process of Example 2;

[0032] Figure 5 Graph of the relationship between pressure and time during the cold isostatic pressing process of Example 3;

[0033] Figure 6 Graph of the relationship between pressure and time during the cold isostatic pressing process of Example 4;

[0034] Figure 7 Graph of the relationship between pressure and time during the cold isostatic pressing process of Example 5;

[0035] Figure 8 Graph of the relationship between pressure and time during the cold isostatic pressing process of Example 6;

[0036] Figure 9 Graph of the relationship between pressure and time during the cold isostatic pressing process of Example 7;

[0037] Figure 10 Graph of the relationship between pressure and time during the cold isostatic pressing process of Comparative Example 1;

[0038] Figure 11Graph of the relationship between pressure and time during cold isostatic pressing for Comparative Example 2;

[0039] Figure 12 Graph of the relationship between pressure and time during cold isostatic pressing for Comparative Example 3;

[0040] Figure 13 Graph of the relationship between pressure and time during cold isostatic pressing for Comparative Example 4;

[0041] Figure 14 Graph of the relationship between pressure and time during cold isostatic pressing for Comparative Example 5. Detailed Implementation Modes

[0042] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments and diagrams.

[0043] The raw materials in the following examples and comparative examples are described as follows:

[0044] The D50 particle size of the silicon powder agglomerates is 40 μm, which is obtained by spray granulation of silicon powder.

[0045] The D50 particle size of the silicon nitride powder agglomerates is 50 μm, which is obtained by spray granulation of silicon nitride powder.

[0046] Example 1

[0047] (1) Load the silicon powder agglomerates into a rubber mold, seal the mold, and place it in the pressure chamber of a cold isostatic press.

[0048] (2) As Figure 3 shown, increase the pressure from atmospheric pressure to 200 MPa in 2 min, hold the pressure for 2.5 min, and then decrease the pressure to atmospheric pressure in 2 min; increase the pressure from atmospheric pressure to 200 MPa in 2.5 min, hold the pressure for 2.5 min, and then decrease the pressure to atmospheric pressure in 2 min; increase the pressure from atmospheric pressure to 200 MPa in 2 min, hold the pressure for 2.5 min, and then decrease the pressure to atmospheric pressure in 2 min; increase the pressure from atmospheric pressure to 200 MPa in 2 min, hold the pressure for 2.5 min, and then decrease the pressure to atmospheric pressure in 2 min to obtain a green body.

[0049] The density of the green body prepared in this example is 1.323 g / cm 3 .

[0050] Example 2

[0051] (1) Load the silicon powder agglomerates into a rubber mold, seal the mold, and place it in the pressure chamber of a cold isostatic press.

[0052] (2) As Figure 4As shown, the pressure is increased from atmospheric pressure to 50 MPa in 0.5 min, held for 2.5 min, and then decreased to atmospheric pressure in 0.5 min; the pressure is increased from atmospheric pressure to 100 MPa in 1 min, held for 2.5 min, and then decreased to atmospheric pressure in 1 min; the pressure is increased from atmospheric pressure to 150 MPa in 1.5 min, held for 2.5 min, and then decreased to atmospheric pressure in 1.5 min; the pressure is increased from atmospheric pressure to 200 MPa in 2 min, held for 2.5 min, and then decreased to atmospheric pressure in 2 min, obtaining a green body.

[0053] The density of the green body prepared in this example is 1.430 g / cm 3 。

[0054] Example 3

[0055] (1) Load the silicon powder agglomerates into a rubber mold, seal it, and place the mold in the pressure chamber of a cold isostatic press.

[0056] (2) As Figure 5 shown, the pressure is increased from atmospheric pressure to 100 MPa in 1 min, held for 2.5 min, and then decreased to atmospheric pressure in 1 min; the pressure is increased from atmospheric pressure to 100 MPa in 1 min, held for 2.5 min, and then decreased to atmospheric pressure in 1 min; the pressure is increased from atmospheric pressure to 200 MPa in 2.5 min, held for 2.5 min, and then decreased to atmospheric pressure in 2 min; the pressure is increased from atmospheric pressure to 200 MPa in 2 min, held for 2.5 min, and then decreased to atmospheric pressure in 2 min, obtaining a green body.

[0057] The density of the cold green body prepared in this example is 1.407 g / cm 3 。

[0058] Example 4

[0059] (1) Load the silicon powder agglomerates into a rubber mold, seal it, and place the mold in the pressure chamber of a cold isostatic press.

[0060] (2) As Figure 6 shown, the pressure is increased from atmospheric pressure to 200 MPa in 2 min, held for 3 min, and then decreased to 100 MPa in 1 min; the pressure is increased from 100 MPa to 200 MPa in 1 min, held for 3 min, and then decreased to 100 MPa in 1 min; the pressure is increased from 100 MPa to 200 MPa in 1 min, held for 4 min, and then decreased to atmospheric pressure in 2 min, obtaining a green body.

[0061] The density of the green body prepared in this example is 1.326 g / cm 3 。

[0062] Example 5

[0063] (1) Load the silicon powder agglomerates into a rubber mold, seal it, and place the mold in the pressure chamber of a cold isostatic press.

[0064] (2) As Figure 7 shown, increase the pressure from atmospheric pressure to 200 MPa in 2 min, hold the pressure for 2 min, decrease the pressure to 100 MPa in 1 min, and hold the pressure for 2 min; increase the pressure from 100 MPa to 200 MPa in 1 min, hold the pressure for 2 min, decrease the pressure to 100 MPa in 1 min, and hold the pressure for 2 min; increase the pressure from 100 MPa to 200 MPa in 1 min, hold the pressure for 2 min, and decrease the pressure to atmospheric pressure in 2 min to obtain a green body.

[0065] The density of the green body prepared in this example is 1.369 g / cm 3 .

[0066] Example 6

[0067] (1) Load the silicon nitride powder agglomerates into a rubber mold, seal it, and place the mold in the pressure chamber of a cold isostatic press.

[0068] (2) As Figure 8 shown, increase the pressure from atmospheric pressure to 200 MPa in 2 min, hold the pressure for 2.5 min, and decrease the pressure to atmospheric pressure in 2 min; increase the pressure from atmospheric pressure to 200 MPa in 2.5 min, hold the pressure for 2.5 min, and decrease the pressure to atmospheric pressure in 2 min; increase the pressure from atmospheric pressure to 200 MPa in 2 min, hold the pressure for 2.5 min, and decrease the pressure to atmospheric pressure in 2 min; increase the pressure from atmospheric pressure to 200 MPa in 2 min, hold the pressure for 2.5 min, and decrease the pressure to atmospheric pressure in 2 min to obtain a green body.

[0069] The density of the green body prepared in this example is 2.133 g / cm 3 .

[0070] Example 7

[0071] (1) Load the silicon nitride powder agglomerates into a rubber mold, seal it, and place the mold in the pressure chamber of a cold isostatic press.

[0072] (2) As Figure 9 shown, increase the pressure from atmospheric pressure to 50 MPa in 0.5 min, hold the pressure for 2.5 min, and decrease the pressure to atmospheric pressure in 0.5 min; increase the pressure from atmospheric pressure to 100 MPa in 1 min, hold the pressure for 2.5 min, and decrease the pressure to atmospheric pressure in 1 min; increase the pressure from atmospheric pressure to 150 MPa in 1.5 min, hold the pressure for 2.5 min, and decrease the pressure to atmospheric pressure in 1.5 min; increase the pressure from atmospheric pressure to 200 MPa in 2 min, hold the pressure for 2.5 min, and decrease the pressure to atmospheric pressure in 2 min to obtain a green body.

[0073] The density of the green body prepared in this example is 2.273 g / cm3 。

[0074] Comparative Example 1

[0075] (1) Load the silicon powder agglomerates into a rubber mold, seal the mold, and place it in the pressure chamber of a cold isostatic press.

[0076] (2) As Figure 10 shown, increase the pressure from atmospheric pressure to 200 MPa in 2 min, hold the pressure for 10 min, and then decrease the pressure to atmospheric pressure in 2 min to obtain a green body.

[0077] The density of the green body prepared in this comparative example is 1.264 g / cm 3 。

[0078] Comparative Example 2

[0079] (1) Load the silicon powder agglomerates into a rubber mold, seal the mold, and place it in the pressure chamber of a cold isostatic press.

[0080] (2) As Figure 11 shown, increase the pressure from atmospheric pressure to 50 MPa in 0.5 min, hold the pressure for 2 min; then increase the pressure to 100 MPa in 0.5 min, hold the pressure for 2 min; then increase the pressure to 150 MPa in 0.5 min, hold the pressure for 2 min; then increase the pressure to 200 MPa in 0.5 min, hold the pressure for 4 min, and then decrease the pressure to atmospheric pressure in 2.0 min to obtain a green body.

[0081] The density of the green body prepared in this comparative example is 1.315 g / cm 3 。

[0082] Comparative Example 3

[0083] (1) Load the silicon powder agglomerates into a rubber mold, seal the mold, and place it in the pressure chamber of a cold isostatic press.

[0084] (2) As Figure 12 shown, increase the pressure from atmospheric pressure to 50 MPa in 0.5 min, hold the pressure for 2 min; then increase the pressure to 100 MPa in 0.5 min, hold the pressure for 2 min; then increase the pressure to 150 MPa in 0.5 min, hold the pressure for 2 min; then increase the pressure to 200 MPa in 0.5 min, hold the pressure for 2 min; then increase the pressure to 250 MPa in 0.5 min, hold the pressure for 2 min, and then decrease the pressure to atmospheric pressure in 2.5 min to obtain a green body.

[0085] The density of the green body prepared in this comparative example is 1.436 g / cm 3 。

[0086] Comparative Example 4

[0087] (1) Load the silicon nitride powder agglomerates into a rubber mold, seal the mold, and place it in the pressure chamber of a cold isostatic press.

[0088] (2) As Figure 13 shown, the pressure is increased from atmospheric pressure to 200 MPa in 2 min, the pressure is held for 10 min, and then the pressure is decreased to atmospheric pressure in 2 min to obtain a green body.

[0089] The density of the green body prepared in this comparative example is 1.930 g / cm 3 .

[0090] Comparative Example 5

[0091] (1) Load the silicon nitride powder agglomerates into a rubber mold, seal the mold, and place the mold in the pressure chamber of a cold isostatic press.

[0092] (2) As Figure 14 shown, the pressure is increased from atmospheric pressure to 50 MPa in 0.5 min, the pressure is held for 2 min; then the pressure is increased to 100 MPa in 0.5 min, the pressure is held for 2 min; then the pressure is increased to 150 MPa in 0.5 min, the pressure is held for 2 min; then the pressure is increased to 200 MPa in 0.5 min, the pressure is held for 4 min, and then the pressure is decreased to atmospheric pressure in 2 min to obtain a green body.

[0093] The density of the green body prepared in this comparative example is 2.068 g / cm 3 .

[0094] Comparing Examples 1 to 7 with Comparative Examples 1 to 2, 4, and 5 shows that under the conditions of the same maximum forming pressure (200 MPa) and the same pressure holding time (10 min), the densities of the green bodies prepared in Examples 1 to 7 are greater.

[0095] From Example 2 and Comparative Example 3, it can be seen that the maximum forming pressure in Example 2 is 200 MPa, and the maximum forming pressure in Comparative Example 3 is 250 MPa. Under the condition of the same pressure holding time (10 min), the densities of the green bodies prepared in Example 2 and Comparative Example 3 are 1.430 g / cm 3 and 1.435 g / cm 3 . This shows that by adopting the pressure-increasing - pressure-holding - pressure-decreasing process described in the present invention, Example 2 can obtain a green body with a density close to that of Comparative Example 3 at a smaller maximum forming pressure.

[0096] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. An inorganic powder cold isostatic pressing forming process, characterized in that: It includes a pressurization-holding pressure-depressurization process for n times.

2. The cold isostatic pressing forming process for inorganic powder according to claim 1, characterized in that: The inorganic powder includes at least one of silicon, silicon nitride, aluminum nitride, boron nitride, and alumina powder.

3. The cold isostatic pressing forming process for inorganic powder according to claim 1, characterized in that: n>1。 4. The cold isostatic pressing forming process of inorganic powder according to claim 1, characterized in that, The specific steps of the pressurization-holding pressure-depressurization process are as follows: Step 1: Pressurize at the first pressure increase rate to reach the first pressure, hold the pressure, and then depressurize at the first pressure decrease rate; Step 2: Pressurize at the second pressure increase rate to reach the second pressure, hold the pressure, and then depressurize at the second pressure decrease rate; …… Step n-1: Pressurize at the (n-1)th pressure increase rate to reach the (n-1)th pressure, hold the pressure, and then depressurize at the (n-1)th pressure decrease rate; Step n: Pressurize at the nth pressure increase rate to reach the nth pressure, hold the pressure, and then depressurize at the nth pressure decrease rate.

5. The cold isostatic pressing forming process for inorganic powder according to claim 4, characterized in that: The first pressure ≤ the second pressure ≤... ≤ the (n-1)th pressure ≤ the nth pressure.

6. The cold isostatic pressing forming process for inorganic powder according to claim 4, characterized in that: The first pressure increase rate, the second pressure increase rate... the (n-1)th pressure increase rate, and the nth pressure increase rate are 0.1-5 MPa / s.

7. The cold isostatic pressing forming process for inorganic powder according to claim 4, characterized in that: The pressure holding time is 1-5 min.

8. The cold isostatic pressing forming process for inorganic powder according to claim 4, characterized in that: The first pressure decrease rate, the second pressure decrease rate... the (n-1)th pressure decrease rate, and the nth pressure decrease rate are 0.1-5 MPa / s.

9. The cold isostatic pressing forming process of inorganic powder according to any one of claims 1 to 8, characterized in that: The inorganic powder is made into agglomerates and then cold isostatically pressed.

10. The cold isostatic pressing forming process for inorganic powder according to any one of claims 1 to 9, characterized in that: The inorganic powder is filled into the forming die under the action of vibration.

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