Gradient annular groove ball milling tank

Abstract

The utility model belongs to the technical field of powder metallurgy powder preparation, and particularly relates to a gradient annular groove ball milling tank which is applied to development and research of novel composite materials and metallurgical technologies. When a traditional ball milling tank with a smooth inner wall is used for preparing flaky metal powder, the consumed time is long, the powder loss is large, impurity elements are easy to introduce, and particularly, hard metal powder (such as titanium and tungsten) is difficult to mill into flaky metal powder. According to the gradient annular groove ball-milling tank provided by the utility model, the gradient annular inner groove is formed in the inner wall of the ball-milling tank, so that the stress condition and the collision mode of metal powder and the ball-milling tank under the action of ball-milling beads can be optimized, and the metal powder is converted into a sheet shape with high efficiency and low loss. The inner molded surface of the gradient annular groove ball milling tank is a cylindrical surface, and a plurality of annular grooves are distributed in the inner molded surface in the height direction; wherein the section of the annular groove is in a semi-elliptical arc shape, and the ellipticity of the annular groove from the top to the bottom is gradually reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of powder metallurgy powder preparation, in particular to a gradient annular groove ball milling jar, which is applied to the development and research of new composite materials and metallurgical technology. Background Art

[0002] Flake powder metallurgy is a new type of powder metallurgy method that has received widespread attention in recent years. Compared with conventional spherical or irregular shaped metal powders, flake metal powders have a larger surface area, higher reinforcement adsorption capacity, better composite material interface bonding level, and stronger crystal preferential orientation. The sintered metal block exhibits better mechanical properties. Therefore, flake metal powder technology is widely used in the development and research of new composite materials and metallurgical technology.

[0003] However, the traditional ball mill with smooth inner wall has the disadvantages of long time consumption, large powder loss, and easy introduction of impurity elements when preparing flaky metal powders. Especially for harder metal powders (such as titanium, tungsten, etc.), it is difficult to grind them into flakes. Utility Model Content

[0004] The utility model provides a ball mill with gradient annular grooves. By machining the gradient annular inner grooves on the inner wall of the ball mill, the force conditions and collision mode of metal powder with the ball mill under the action of ball mill beads can be optimized, so that the metal powder can be converted into flakes with high efficiency and low loss.

[0005] The inner surface of the gradient annular groove ball mill is a cylindrical surface, and a plurality of annular grooves are arranged on the inner surface along the height direction; wherein the cross section of the annular groove is a semi-elliptical arc, and the ellipticity of the annular groove decreases from the top to the bottom.

[0006] Preferably, the depth of the annular groove is not greater than the radius of the largest ball milling bead used in the ball milling process, and is not less than the radius of the smallest ball milling bead used.

[0007] Preferably, the height of the annular groove is greater than the diameter of the largest ball milling bead used in the ball milling process.

[0008] Preferably, there are eight annular grooves distributed along the height direction on the inner surface of the ball mill; the ellipticity of the annular grooves from top to bottom is 1.6-1.4, 1.4-1.2, 1.2-1.1, 1.1-1.08, 1.08-1.06, 1.06-1.04, 1.04-1.02, and 1.02-1.00 respectively.

[0009] Preferably, the surface roughness of the annular groove is Ra=0.8-3.2.

[0010] Preferably, the number of the annular grooves on the inner surface of the ball mill is M.

[0011] Wherein, V is the volume of the ball mill, R is the radius of the inner circumference of the ball mill, and L is the major axis length of the elliptic arc with the largest ellipticity of the annular groove.

[0012] Preferably, two adjacent annular grooves are transitioned by a smooth rounded corner.

[0013] Preferably, the radius r of the transition fillet between two adjacent annular grooves is 1-5 mm.

[0014] Preferably, M≤8.

[0015] Preferably, the ball mill is made of nylon, stainless steel, hard alloy steel, polyurethane or ceramic.

[0016] Beneficial Effects

[0017] (i) The inner wall of the ball mill described in the utility model is processed with a gradient annular groove (i.e., an annular groove whose ellipticity decreases from the top to the bottom). During the ball milling process, the metal powder and the ball milling beads will be distributed inside the gradient annular groove under the action of centrifugal force, thereby increasing the contact probability and contact area between the metal powder and the ball milling beads. The metal powder will be subjected to greater friction, shear force and pressure, so that the metal powder will be quickly flakes.

[0018] (ii) Due to the gradient annular groove design, metal powders of different sizes can come into contact with matching ball milling beads in grooves of different sizes and be subjected to forces in different directions, thereby increasing the uniformity of metal powder flakes and reducing raw material loss.

[0019] (3) Because the ball milling time is reduced, the contact time between the metal powder and the gas, medium, and ball mill itself is reduced, which reduces the process of the metal powder absorbing oxygen, nitrogen, carbon and other impurity elements, and reduces the introduction of impurities during the ball milling process.

[0020] The content of impurity elements in the flaky metal powder is reduced.

[0021] (iv) The ball mill can be made of nylon, stainless steel, carbide steel, polyurethane or ceramic to meet the needs of powder metallurgy preparation of different properties.

[0022] (V) The ball milling beads used in the ball milling process have different sizes. The diameter of the largest ball milling bead used should be smaller than the height of the gradient annular groove (the length of the major axis of the elliptical arc). Since the gradient grooves have different sizes, ball milling beads of different sizes can be used in the same ball milling process, so that metal powders of different properties can be formed into flakes with high efficiency and low loss.

[0023] (6) The ball mill material selection is wide, and it can be made of nylon, stainless steel, carbide steel, polyurethane or ceramic. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a cross-sectional schematic diagram of a ball milling jar with gradient annular grooves processed in Example 1;

[0025] Figure 2 This is a force analysis diagram of metal powder being ball-milled into flakes in a ball mill with gradient annular grooves;

[0026] Figure 3 This is a scanning electron microscope (SEM) image of the Ti6Al4V spherical powder in Example 1 after ball milling in a tank with gradient annular grooves;

[0027] Figure 4 The scanning electron microscope (SEM) image of the Ti6Al4V spherical powder in Comparative Example 1 after ball milling in a conventional ball mill with a smooth inner wall;

[0028] Among them, 1-ball mill jar, 2-annular groove, 3-cover, 4-ball mill beads, 5-metal powder, F1-pressure, F2-shear force 1, F3-shear force 2. DETAILED DESCRIPTION

[0029] The following is combined with Figure 1-4 The utility model is further described with specific implementation modes, wherein the methods are conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified.

[0030] This embodiment provides a gradient annular groove ball mill, such as Figure 1 As shown, the inner surface of the ball mill 1 is a cylindrical surface, and a plurality of annular grooves 2 are distributed on the inner surface along the height direction; wherein, the cross section of the annular groove 2 is a semi-elliptical arc (because the friction and wear curves presented under natural circular motion are all semi-arc-shaped, in the utility model, a part of an ellipse is used to approximate the natural semi-arc, so it is called an elliptical semi-arc. The term semi-ellipse, if accurately defined, is half of an ellipse. In fact, the annular grooves 2 in the utility model do not reach half, and the term elliptical semi-arc is selected for the sake of accuracy).

[0031] The ellipticity (ratio of major and minor axes) of the annular groove 2 decreases from top to bottom, thus presenting a gradient distribution pattern (the concept of gradient refers to the change in the ellipticity of each annular groove 2. The gradient in the utility model is understood as the ellipticity of the annular groove 2 decreasing from top to bottom. Therefore, the depth and width of each groove from top to bottom are different, which conforms to the motion trajectory of the ball milling beads on the inner wall under natural circular motion, and has a decreasing gradient distribution pattern. This is because during the high-speed ball milling process, the ball milling beads rotate centrifugally at high speed in the jar, and the probability, time, and friction behavior of the ball milling beads contacting the inner wall of the ball milling jar decrease from bottom to top, which is inversely related to the gradient distribution of the ellipticity of each annular groove 2). The depth of the annular groove 2 (1 / 2 of the length of the minor axis of the elliptical semi-arc) is not greater than the radius of the largest ball milling bead used in the ball milling process, and is not less than the radius of the smallest ball milling bead used; the height of the annular groove 2 (the length of the major axis of the elliptical semi-arc) is greater than the diameter of the largest ball milling bead used in the ball milling process, and the ball milling beads 4 used can all make circular motion in the annular groove 2.

[0032] The number of the annular grooves 2 on the inner surface of the ball mill 1 is M. Further, M≤8 (Explanation for the limit of the number of annular grooves 2 to no more than 8: through experimental experience, it is recommended that the number of grooves should not exceed 8, because grooves above 8 basically do not play a role in the ball milling process. At the same time, if the number of grooves increases, it will impose many restrictions on the ball milling beads, which is not conducive to the simple manufacturing process and causes unnecessary waste); wherein, V is the volume of the ball mill 1, R is the radius of the inner circumference of the ball mill 1, and L is the major axis length of the elliptical arc with the largest ellipticity of the annular groove 2. Two adjacent annular grooves 2 are transitioned by smooth fillets, and the radius of the transition fillet r=1-5mm.

[0033] In the following embodiments:

[0034] Ti6Al4V spherical powder: particle size 5um~45um, manufacturer AP&C, Quebec, Canada;

[0035] Scanning electron microscope: FSEM, HITACHI S-4800N, Japan.

[0036] Planetary ball mill: QM-3SP04.

[0037] Example 1

[0038] (1) A cylindrical ball mill 1 with an outer diameter of 132 mm, an inner diameter of 108 mm and a smooth inner wall is taken. The total height of the ball mill 1 is 116.5 mm, the height of the inner cavity of the ball mill 1 is 104 mm, and the material of the ball mill 1 is nylon; then, 8 annular grooves 2 are continuously processed from the bottom to the top on the inner circumferential surface of the ball mill 1. The cross section of the annular groove 2 is an elliptical arc. In this embodiment, the ellipticity parameters of the annular groove 2 from the top to the bottom are: 1.555, 1.284, 1.162, 1.088, 1.066, 1.053, 1.032, 1.010; the boundary between two adjacent annular grooves 2 is transitioned by a smooth arc, the radius of the transition arc is 4 mm, and the surface roughness Ra of each annular groove 2 is 3.2, such as Figure 1 As shown;

[0039] (2) 20 g of Ti6Al4V spherical powder was added to the ball mill 1 with the annular groove 2 processed in step (1), and 100 g of zirconia ceramic ball mill beads 4 with diameters of 8 mm and 6 mm were added, and then the ball mill 1 was sealed with a cover 3 and then installed in a planetary ball mill. The power of the planetary ball mill was then turned on and the mill was ball milled at 250 r / min for 60 min to flaky the Ti6Al4V spherical powder.

[0040] Comparative Example 1

[0041] On the basis of Example 1, the ball mill jar 1 with the gradient annular inner groove 2 used in the ball milling process of step (2) is replaced by the ball mill jar 1 with a smooth inner wall before the gradient annular inner groove 2 is processed in step (1), and other ball milling conditions remain unchanged. The Ti6Al4V spherical powder is flaked in the ball mill jar 1 with a smooth inner wall.

[0042] Morphological characterization

[0043] The Ti6Al4V powders after flaking in Example 1 and Comparative Example 1 were characterized by SEM. Figure 3 It can be seen from the SEM photos in that after the Ti6Al4V spherical powder in Example 1 was ball-milled at 250 r / min for 60 min, almost all of the Ti6Al4V spherical powder turned into flaky powder, the smaller spherical powder also had a larger deformation, and there was little powder loss. The thickness of the flaky powder was about 3um to 10um. Figure 4It can be seen from the SEM photos in that the Ti6Al4V spherical powder in Comparative Example 1 did not completely turn into flaky powder after ball milling at 250r / min for 60min, but slightly deformed and turned into elliptical cylindrical powder or irregular powder. The smaller spherical powder had almost no deformation and had obvious powder loss. This phenomenon occurs because in the ball mill 1 with a smooth inner wall, the metal powder 5 is subjected to a small force when in contact with the ball mill 4, and the action form is single, which cannot cause the metal powder 5 to produce sufficient plastic deformation in a short time, and thus cannot be flaked. In the ball milling jar with an annular groove 2 processed on the inner wall, under the action of centrifugal force, the metal powder 5 contacts the ball milling beads 4 of different sizes inside the annular groove 2, which increases the contact area between the metal powder 5 and the ball milling beads 4 and optimizes the force conditions and contact mode; the pressure F1, shear force 1F2, shear force 2F3 and friction force received by the metal powder 5 from the ball milling beads 4 are much greater than the forces received by the metal powder 5 in the ball milling jar 1 with a smooth inner wall, and the force directions are more diverse and the force levels are more uniform, such as Figure 2 As shown, therefore, ball milling in a ball mill 1 having an annular groove 2 can greatly shorten the ball milling time, reduce the powder loss during the ball milling process, and better flaky the metal powder 5.

[0044] In summary, the above are embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A gradient annular groove ball mill, characterized in that: The inner surface of the ball mill (1) is a cylindrical surface, and a plurality of annular grooves (2) are arranged on the inner surface along the height direction; wherein the cross section of the annular groove (2) is a semi-elliptical arc, and the ellipticity of the annular groove (2) decreases from the top to the bottom.

2. The gradient annular groove ball mill according to claim 1, characterized in that: The depth of the annular groove (2) is not greater than the radius of the largest ball milling bead (4) used in the ball milling process, and is not less than the radius of the smallest ball milling bead (4) used.

3. The gradient annular groove ball mill according to claim 1 or 2, characterized in that: The height of the annular groove (2) is greater than the diameter of the largest ball milling bead (4) used in the ball milling process.

4. The gradient annular groove ball mill according to claim 1 or 2, characterized in that: The inner surface of the ball mill (1) is provided with eight annular grooves (2) distributed in the height direction; the ellipticities of the annular grooves (2) from the top to the bottom are 1.6-1.4, 1.4-1.2, 1.2-1.1, 1.1-1.08, 1.08-1.06, 1.06-1.04, 1.04-1.02, and 1.02-1.00, respectively.

5. The gradient annular groove ball mill according to claim 1 or 2, characterized in that: The surface roughness of the annular groove (2) is Ra=0.8-3.

2.

6. The gradient annular groove ball mill according to claim 1 or 2, characterized in that: The number of the annular grooves (2) on the inner surface of the ball mill (1) is M, Wherein, V is the volume of the ball mill (1), R is the radius of the inner circumference of the ball mill (1), and L is the major axis length of the elliptic arc with the maximum ellipticity of the annular groove (2).

7. The gradient annular groove ball mill according to claim 1 or 2, characterized in that: Two adjacent annular grooves (2) are transitioned by smooth rounded corners.

8. The gradient annular groove ball mill according to claim 7, characterized in that: The radius r of the transition fillet between two adjacent annular grooves (2) is 1 to 5 mm.

9. The gradient annular groove ball mill according to claim 6, characterized in that: Said M≤8.

10. The gradient annular groove ball mill according to claim 1 or 2, characterized in that: The ball mill (1) is made of nylon, stainless steel, hard alloy steel, polyurethane or ceramic.

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