RU201841U1 - Device for electropulse pressing of powder materials - Google Patents

Abstract

The utility model relates to the field of powder metallurgy and can be used in the production of fuel pellets for nuclear reactors. The device for electropulse pressing of powder materials includes a pulsed energy source, a metal cage with a ceramic matrix made of Sialon, an upper movable punch inserted into the rod, a lower stationary punch installed on the lower base, a plate with two bushings, on which a holder with a matrix is fixed, and the bushings are spring-loaded and have the ability to slide vertically along the guides installed on the lower base. The upper and lower punches are made of tungsten, and the height of the end part is H = 0.8 ÷ 1.2 D, where D is the diameter of the end part, and the diameter of the middle part of the punch d = 0.8 ÷ 0.95 D. The increase in the durability of the punches is provided. and thereby reducing the cost of manufacturing tooling. 2 ill.

Description

The utility model relates to the field of powder metallurgy and can be used in the manufacture of products from powder materials, in particular, fuel pellets for nuclear reactors, chemical and other industries.

Known is a device for electropulse pressing of a powder described in A.S. No. 1139564 published on 08/05/1983, which contains a disposable ceramic matrix of aluminum oxide and punches made of refractory material molybdenum. However, in the manufacture of high-temperature ceramic materials (carbides, metal nitrides), the obtained sample is welded to the end of the punch. This requires cleaning the end of the punch, which causes considerable difficulties.

Known is a device for electro-pulse pressing of a powder, described in patent for invention No. 2470737, published in 2010. In it, punches made of graphite have a head diameter slightly higher than the middle part. This reduces the friction of the punch against the die walls when powder enters between the die walls and the punches. However, the use of graphite punches for electro-pulse pressing of powders is impossible due to their insufficient strength.

The solution closest to the proposed one in terms of the technical essence and the achieved effect is a device for electropulse pressing of powder [utility model patent No. 188873, published on 25.04.2019 "Device for electropulse pressing of powder materials]. This device includes a pulsed energy source, a metal holder with a ceramic matrix made of Sialon insulating material (SiAlON), an upper and lower punch made of molybdenum, a plate with two bushings, on which the holder with a matrix is fixed, the bushings being spring-loaded and able to slide vertically along guides installed on the bottom plate.

The device works as follows. Powder of an electrically conductive material, enclosed in a ceramic matrix and clamped in a metal holder, is pressed by punches from above and below. The pressure P is applied to the upper punch from the loading device through the rod. After that, a current pulse is applied from the pulsed current source to the powder filling. The discharge current pulse, flowing through the compressed powder, heats it up. Due to the applied pressure, the filling is compacted and a dense sample is obtained.

In this device, the matrix makes it possible to repeatedly obtain samples from powder materials. However, in the manufacture of high-temperature ceramic materials (carbides, metal nitrides), the obtained sample is also welded to the punch end, which requires cleaning the punch end. In addition, the simple cylindrical shape of the punches causes significant friction between the walls of the die and the punches and their wear.

In this regard, the most important task is the development of a new device for electropulse pressing of a powder, which makes it possible to produce samples from electrically conductive powders of refractory materials such as metal nitrides and carbides in a stable reusable matrix with a longer durability of punches without their destruction.

The technical effect to be achieved by the invention lies in the creation of a new product that, by means of electric pulse pressing, produces a significant number of samples from powders of refractory materials, such as nitrides and carbides, without destroying the matrix and punches.

The specified technical effect is achieved by the fact that in a device for electropulse pressing of powder materials, including a pulsed energy source, a metal cage with a ceramic matrix made of sialon, an upper movable punch inserted into the rod, a lower fixed punch mounted on the lower base, a plate with two bushings , on which a holder with a matrix is fixed, and the bushings are spring-loaded and have the ability to slide vertically along the guides installed on the lower base, according to the invention, the upper and lower punches are made of tungsten, and the height of the end part H = 0.8 ÷ 1.2 D, where D is the diameter of the end part, and the diameter of the middle part of the punch d = 0.8 ÷ 0.95 D.

Due to the fact that the melting point of tungsten is much higher than that of molybdenum, the durability and strength of tungsten punches will be higher. When the height of the tungsten end part H is less than 0.8 D, the strength of the punch decreases and its durability decreases, and with a height greater than 1.2 D, the cost of the entire punch increases and all dimensions will not be optimal. With a diameter of the middle part of the punch d <0.8 D, the strength of the punch decreases and its durability decreases. When the diameter of the middle part of the punch d> 0.95 D, the gap between the walls of the die and the punch is significantly reduced and when the powder being compacted gets into it, the friction between the die stack and the punch increases, which leads to wear of the punch and a reduction in its service life.

FIG. 1 shows a device for electropulse pressing of powder materials.

FIG. 2 shows a ceramic matrix in a metal cage with punches.

The essence of the invention is illustrated in FIG. 1, which shows a device for electropulse pressing of powder materials. It includes a pulsed energy source 1, an upper movable punch 2 and a lower fixed punch 3. The lower punch 3 is inserted into the lower support 4, which is placed on the lower base 5, located on the lower plate 6. The upper movable punch 2 is inserted into the upper support 7 and electrically insulated from the lower punch 3 by insulating sleeves 8, put on the mount of the rack 9. Pressure P to the upper punch 2 is applied from the loading device 10 (pneumatic press) through the rod 11, which are isolated from each other by a non-conductive gasket 12. The conductive powder 13 is placed in a ceramic matrix 14 made of sialon and clamped in a metal cage 15. On the bottom plate 6 are two guides 16 and 17 with springs 18 and 19, on which sleeves 20 and 21 are put on, connected to the plate 22. This plate is connected to the metal cage 15. FIG ... 2 shows a ceramic matrix in a metal cage with punches. The end portion of the punch 23 and the middle portion 24 are made of tungsten.

The device works as follows. Powder of electrically conductive material 13 (Fig. 1), enclosed in a matrix 14 and clamped in a cage 15, is pressed by punches 2 and 3. Pressure P is applied to the upper punch 2 from a pneumatic press 10 through a rod 11. A pulsed energy source 1 is switched on, the necessary the amount of energy, which is determined by the type and weight of the compacted powder. After that, a current pulse is passed from a pulse source 1 through the compressed powder 13, which heats it up. During this period of time, the upper movable punch 2, which is a continuation of the rod 9 from the loading device 8, moves downward. The yoke 15, together with the matrix 14 and the powder filling 13, also begin to move downward, and its compaction occurs.

Due to the fact that the punches are made of tungsten, which has higher physicochemical properties (such as melting point, heat resistance) compared to molybdenum, the durability of its repeated use should be higher. This was confirmed by his test.

The proposed device was tested when producing tablets from uranium and titanium nitride with a diameter of 8 ÷ 10 mm and a height of 1.5 ÷ 8 mm. With one set of tungsten punches of the VL (or VI) grade, about a hundred pieces of products were made. At the same time, with molybdenum punches, it was possible to make about fifty items.

Thus, the use of the described device for electropulse pressing of powder materials makes it possible to increase the durability of punches and thereby reduce the cost of manufacturing tooling.

Claims (1)

A device for electropulse pressing of powder materials, including a pulsed energy source, a metal cage with a ceramic matrix made of Sialon, an upper movable punch inserted into the rod, a lower stationary punch installed on the lower base, a plate with two bushings on which a cage with a matrix is fixed, and the bushings are spring-loaded and have the ability to slide vertically along the guides installed on the lower base, characterized in that the upper and lower punches are made of tungsten, and the height of the end part H = 0.8 ÷ 1.2 D, where D is the diameter of the end part, and diameter of the middle part of the punch d = 0.8 ÷ 0.95 D.

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