RU224664U1 - Device for electric pulse pressing of tablets with a hole made of electrically conductive powders - Google Patents

Abstract

The utility model relates to the field of powder metallurgy, in particular to a device for electric pulse pressing of pellets with a hole from electrically conductive powders; it can be used in the production of products from powder materials, in particular fuel pellets with a hole in the center for nuclear reactors, chemical and other industries. The device contains a pulsed energy source, a metal cage with a ceramic matrix made of insulating material, upper and lower supports made in the form of cups, an upper movable punch inserted into the bottom of the upper support and located under the rod, a lower fixed punch inserted into the bottom of the lower support located on the lower base connected to the lower plate. Guides are installed on the bottom plate, onto which two bushings are mounted with the possibility of vertical sliding. Connected to the mentioned bushings is a plate on which a holder with a matrix is fixed. On the side parts of the upper and lower supports, the rod and the lower base there are through coaxial holes for installing a fixing rod through them during the pressing process, and in the side parts of the bushings there are bolts for fastening the matrix with a metal cage on guides made with a rectangular groove. At the end of the lower punch there is a central hole 3 mm deep, into which a ceramic sleeve with a metal rod inside it is inserted, the length is 2 times the thickness of the tablet and the diameter is equal to the hole in the resulting tablet. At the end of the upper punch there is also a central hole with a diameter similar to that in the lower punch and a depth exceeding the thickness of the tablet. It is ensured that tablets with a central hole are obtained with the specified characteristics and the same density throughout the entire volume of the tablet. 5 ill.

Description

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

A device for electric pulse pressing of powder is known, described in utility model patent No. 216267, published on June 20, 2022, “Device for electric pulse pressing of powders.” This device includes a pulsed energy source, a metal cage with a ceramic matrix made of insulating material, located under the pneumatic press rod, an upper movable punch with an upper support, a lower fixed punch with a lower support installed on the lower base, two guides installed on the lower plate, a plate with two bushings made with the possibility of vertical sliding along the guides and a holder with a matrix fixed on the said plate, while the upper support is put on the pneumatic press rod and is made in the form of a glass, into the bottom of which the upper punch is inserted, and on its side parts and the rod there are through coaxial holes for installing a fixing rod, installed on the bottom plate, two guides are made with rectangular grooves, bolts are installed in the side parts of the bushings for fastening the matrix with a metal clip on the mentioned guides, and the height of the working part of the upper punch is equal to the height of the matrix.

This improved design of the device allows, after the electric pulse pressing process, to lift up the punches with the matrix using a rod, and not manually, to fix the matrix with the holder on the guides in the upper position, and then with the upper punch and squeeze out the resulting sample with the lower punch without removing the lower support. However, this device does not allow the production of tablets with a hole.

The solution closest to the one proposed in terms of technical essence and achieved effect is a device for electric pulse pressing of powder materials (utility model patent No. 220034, published 08/21/2023, “Device for electric pulse pressing of tablets with a hole made of electrically conductive powders”). This device includes a pulsed energy source, a metal holder with a ceramic matrix made of insulating material, an upper movable punch with an upper support located under the rod, a lower stationary punch with a lower support installed on the lower base, a plate with two bushings on which the holder with matrix, and the bushings are able to slide vertically along the guides installed on the lower plate, while the upper support is made in the form of a glass, into the bottom of which the upper punch is inserted, and on its side parts and the rod there are through coaxial holes for installing a fixing rod through them in during the pressing process, in addition, bolts are installed in the side parts of the bushings for fastening the matrix with a metal cage on guides, additionally made with a rectangular groove, while the height of the working part of the upper punch is equal to the height of the matrix, in addition, the lower punch is made with a central hole in which it is fixed a rod made of refractory material with a diameter equal to the hole in the resulting tablet; in addition, a ceramic bushing with an outer diameter equal to the diameter of the punch is put on this rod, and a metal bushing made of refractory material is put on it, and the upper punch is made with a diameter equal to the outer diameter of the metal bushing and with a recess into which another ceramic bushing with the same dimensions as on the lower punch is inserted, and the upper punch has a through hole for extruding the ceramic bushing.

This improved design of the device allows, after the electric pulse pressing process, to lift the matrix with the upper punch to the top using a rod. In this case, a rod made of refractory material in the lower punch is pulled out from the resulting tablet and remains in the lower support on the lower base, which does not subsequently interfere with the removal of this tablet. After this, fix the matrix with the holder on the guides in the upper position, and then use the upper punch to squeeze out the resulting tablet with a hole. However, this device makes it possible to obtain tablets with a hole of only different densities by volume; near the side surface the density will be slightly lower than in the central zone. This is due to the fact that the current pulse here passes between the center and the side surface, and since the side surface has a larger area than the central zone, the current pulse density in the central zone will be slightly higher than in the side. This leads to the fact that the heat release near the central zone will be higher, which ensures greater heating of the powder in this zone. In this regard, it becomes more plastic and compacts better.

In this regard, the most important task is to develop a new device that makes it possible to produce tablets with a central hole of equal density throughout the entire volume of the tablet.

The technical result of the claimed device is the creation of a new product that, using electric pulse pressing, produces tablets with a central hole with the necessary characteristics and the same density throughout the entire volume of the tablet.

The specified technical result is achieved by the fact that in a device for electric pulse pressing of tablets with a hole made of electrically conductive powders, containing a pulsed energy source, a metal cage with a ceramic matrix made of insulating material, upper and lower supports made in the form of glasses, an upper movable punch inserted into the bottom of the upper supports and located under the rod, a lower stationary punch inserted into the bottom of the lower support, located on the lower base connected to the lower plate, guides installed on the lower plate, on which two bushings are mounted with the possibility of vertical sliding, a plate connected to the said bushings, on which a holder with a matrix is fixed, while on the side parts of the upper and lower supports, the rod and the lower base there are through coaxial holes for installing a fixing rod through them during the pressing process, and bolts are installed in the side parts of the bushings for fastening the matrix with a metal holder on the guides, made with a rectangular groove, according to the utility model, at the end of the lower punch there is a central hole 3 mm deep, into which a ceramic sleeve with a metal rod inside it is inserted, with a length 2 times greater than the thickness of the tablet and a diameter equal to the hole in the resulting tablet, and at the end of the upper The punch also has a central hole with a diameter similar to the lower punch and a depth 3 times greater than the thickness of the tablet.

This improved design of the device allows, after the electric pulse pressing process, to lift up the matrix with the upper punch using a rod. In this case, the ceramic sleeve with a metal rod is pulled out of the lower punch. Then fix the matrix with the cage on the guides in the upper position, and the upper punch, and squeeze out the resulting tablet with a hole of equal density throughout the entire volume and a ceramic sleeve with a metal rod. After this, you need to move the resulting tablet into a hand press and squeeze out a ceramic sleeve with a metal rod. A central hole 3 mm deep in the end of the lower punch is necessary for centering the ceramic sleeve with the metal rod. And its length is 2 times greater than the thickness of the tablet, allowing you to pour in a sufficient amount of powder to create a hole in the resulting tablet. The central hole at the end of the upper punch, with a depth 3 times greater than the thickness of the tablet, allows the ceramic sleeve with a metal rod to enter inside the upper punch during the pressing process and not interfere with the compaction of the powder. These settings are optimal. It should also be noted that the current pulse here passes between the ends of the punches, which have an equal area, which in turn ensures equal heat generation throughout the entire volume of the resulting tablet.

In fig. Figure 1 shows a device for electric pulse pressing of tablets with a hole made of electrically conductive powders.

In fig. Figure 2 shows a lower support with a lower punch with a ceramic bushing and a metal rod inside it, an upper support with an upper punch, bushings and a cage with a matrix when powder is poured into it.

In fig. Figure 3 shows the device when raising the matrix to the upper position to press out the resulting tablet with a hole.

In fig. Figure 4 shows a device for pressing out the resulting tablet with a hole.

In fig. 5 shows a device for extruding a ceramic tube from the center of a tablet.

The essence of the utility model is illustrated in Fig. 1, which shows a device for electric pulse pressing of tablets with a hole made of electrically conductive powders. 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, connected to the lower plate 6 by a threaded connection. The upper movable punch 2 is inserted into the upper support 7 in the form of a hollow cylinder with a bottom and is electrically insulated from the lower punch 3 by insulating bushings 8, mounted on the mount 9. Pressure P is applied to the upper punch 2 from the loading device 10 (pneumatic press) through the rod 11, which are isolated from each other by a non-conductive gasket 12. The electrically conductive powder 13 is placed in a ceramic matrix 14, clamped into a metal cage 15. On the bottom plate 6 there are two guides 16 and 17 with elastic rings 18 and 19, on which bushings 20 and 21 are mounted, connected with plate 22. This plate is connected to a metal holder 15. The upper support 7 is put on the end of the rod 11 and secured to it using a rod with a head 23, passing through the coaxial holes in the rod and the upper support. The lower support 4 is put on the lower base 5 and secured to it using a rod with a head 24 passing through coaxial holes in the lower base and the lower support. Bolts 25 and 26 are screwed into bushings 20 and 21, which allow the matrix with powder to be fixed on the guides at the required height. The upper movable punch 2 and the lower fixed punch 3 are secured in the lower and upper supports with locking screws 27 and 28, respectively.

The device works as follows. The lower punch 3 is inserted into the lower support 4 and pressed with a locking screw 27 (Fig. 2). Then a ceramic sleeve with a metal rod 29 with a diameter equal to the hole in the resulting tablet is inserted into the central hole of this punch. After that, an elastic ring 30 is put on the lower punch 3. Next, a ceramic matrix 14 with a metal holder 15 is inserted onto it. After this, powder 13 is poured into the resulting cavity between the ceramic sleeve with a metal rod 29 and the ceramic matrix 14. Then the upper punch is inserted into the matrix 14 2, inserted into support 7 and fixed with screw 28, while a ceramic sleeve with a metal rod 29 fits into the end hole on this punch. This entire assembly is inserted into plate 22 and placed on the lower base 5 and fixed with a rod 24. A rod 11 is inserted into the upper support 7, a rod 23 is inserted coaxially with it, and the powder is pressed. Pressure P is applied to the upper punch 2 from the pneumatic press 10 through the rod 11. The pulsed energy source 1 is turned on, and the required amount of energy is accumulated in it, which is determined by the type and mass of the powder being compacted. After this, a current pulse is passed from a pulsed source 1 through the pressed 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 pneumatic press 10, moves downward. The holder 15, together with the matrix 14 and the powder filling 13, also begins to move downwards, and it becomes compacted. It should be noted that in the process of compacting the powder backfill, the ceramic sleeve with the metal rod 29 will penetrate deeper and deeper into the hole on the upper punch, which is facilitated by its sufficient depth.

Now you need to extract the resulting sample from the matrix. Using a pneumatic press 10, we lift up the rod 11 (Fig. 3). The matrix 14, together with the resulting sample and the ceramic bushing with a metal rod 29 in the holder 15 along the guides 16 and 17, also rises upward. In this case, the lower punch comes out of the matrix and remains in the lower support on the lower base and does not interfere with the extrusion of the sample. Using bolts 25 and 26, we clamp the bushings 20 and 21 on the guides 16 and 17 and thereby fix the matrix 14 in the upper position.

Then we press out the resulting product, which occurs in two stages. At the first stage, we begin to lower the rod 11 down, the upper punch 2 also goes down and squeezes out the sample along with a ceramic sleeve with a metal rod 29, obtained from the backfill 13 (Fig. 4). At the second stage, it is necessary to squeeze out a ceramic sleeve with a metal rod 29 from the sample. To do this, we turn it over 180 degrees and place it in a hand press. Using a device (Fig. 5), we squeeze out the ceramic sleeve 29 with a steel rod 30 and obtain a tablet with a central hole.

This design of the proposed installation makes it possible to obtain a tablet with a hole, with the required uniform density throughout its entire volume.

The proposed device was tested in obtaining tablets with a hole with a diameter of 8 mm and a height of 5 to 10 mm, while the hole diameter was 3 mm. Tablets of the indicated sizes were obtained from VNZH 7-3 powder (composition 90W-7Ni-3Fe) with a density of 95÷97% of the theoretical, and from VND powder (composition 94.5W-3.25Ni-2.25Cu) with a density of 94÷97% from theoretical. Measuring the microhardness of these tablets using the Vickers method using an HVS-1000 microhardness tester with automatic indenter loading showed the following. The microhardness of the tablet made from VNZH 7-3 powder was H _ν0.1 =526.76, and for the tablet made from VND powder it was H _ν0.1 =470.12. In this case, the microhardness near the central zone of the tablet was the same as for the zone near the side surface of the tablet. This shows that the density of the tablet will also be the same, both near the center and near the side surface. At the same time, measuring microhardness on tablets obtained using an already known device (prototype) showed different values. Thus, the microhardness of the tablet made from VNZH 7-3 powder near the central zone was H _ν0.1 = 525.17 (which corresponds to a density of 95.9% of the theoretical), and near the side surface H _ν0.1 = 491.94 (which corresponds to a density of 94 .1% of theoretical).

Thus, the use of the described device makes it possible to produce products in the form of tablets with a hole from electrically conductive powders with the necessary characteristics and uniform density throughout the entire volume of the tablet.

Claims (1)

A device for electric pulse pressing of tablets with a hole made of electrically conductive powders, containing a pulsed energy source, a metal cage with a ceramic matrix made of insulating material, upper and lower supports made in the form of glasses, an upper movable punch inserted into the bottom of the upper support and located under the rod, a lower fixed one a punch inserted into the bottom of the lower support located on the lower base connected to the lower plate, guides installed on the lower plate, on which two bushings are mounted with the possibility of vertical sliding, a plate connected to the said bushings, on which a holder with a matrix is fixed, while on The side parts of the upper and lower supports, the rod and the lower base have through coaxial holes for installing a fixing rod through them during the pressing process, and in the side parts of the bushings there are bolts for fastening the matrix with a metal cage on guides made with a rectangular groove, characterized in that that at the end of the lower punch there is a central hole 3 mm deep, into which a ceramic sleeve with a metal rod inside it is inserted, with a length 2 times greater than the thickness of the tablet and a diameter equal to the hole in the resulting tablet, and at the end of the upper punch there is also a central hole with a diameter, as in the lower punch, and with a depth exceeding the thickness of the tablet by 3 times.