RU2812071C1 - Device for pulsed electric pressing of powder materials - Google Patents

Abstract

FIELD: powder metallurgy.

SUBSTANCE: devices for pulsed electric pressing of powder materials. It can be used in the production of products from powder materials, in particular fuel pellets for nuclear reactors, chemical and other industries. The electric pressing device contains a pulsed energy source, a loading device, a metal cage with a ceramic matrix made of an insulating material, an upper floating die with an upper support located under the rod, a lower fixed die with a lower support mounted on the lower base, a plate with two bushings, on which the clip is fixed with a matrix. The bushings are able to slide vertically along guides mounted on the bottom plate. In the side parts of the bushings, bolts are installed for fastening the matrix with a metal clip on the guides, which are additionally made with a rectangular groove. The upper and lower punches, which have cylindrical shanks, are pressed to the end of the rod and to the end of the lower base with union nuts. On the lower part of the rod, a rectangular detachable plate is fixed and tightened with bolts, on which two traction rods are fixed with threads at the lower ends equal to the height of the matrix, and which are electrically isolated from the rod by textolite bushings, and the rods pass through the plate and are fixed to it from top to bottom using lock nuts.

EFFECT: it is possible to obtain products with specified characteristics, expand the range of their sizes and reduce the labour intensity of manufacturing press equipment.

1 cl, 4 dwg

Description

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

A device for electric pulse pressing of powder is known, described in the utility model patent No. 196265, publ. 12/06/2019, “Device for electric pulse pressing of powder materials.” 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 spring-loaded and have the ability to slide vertically along guides installed on the bottom plate. In addition, on one of the two guides, a bushing is inserted with a hollow metal cylinder with a wall thickness of 5÷8 mm fixed on it with an inverted base with a slot in it and a side part for the passage of the lower punch, while the metal cylinder can be installed on the lower base, and the height of the cylinder h is equal to 0.91<h<1.51, where 1 is the height of the matrix, the outer diameter of the cylinder D is equal to the diameter of the base, and the width of the slot b is equal to 1.1d<b<l.5d, where d is the diameter of the punch.

The device works as follows. A powder of electrically conductive material, enclosed in a ceramic matrix and clamped into a metal cage, is pressed by punches from above and below. Pressure P is applied to the upper punch from the loading device through the rod. After that, a current pulse is applied from a pulsed current source to the powder filling. The discharge current pulse, flowing through the pressed powder, heats it up. Due to the applied pressure, the backfill is compacted and a dense sample is obtained. This design of the device allows, after the electric pulse pressing process, to bring a cylinder under the matrix with the upper punch and squeeze out the resulting sample with the lower punch.

However, to extrude the resulting sample, it is necessary to first lift up the punches with the matrix in order to bring the cylinder under it, since this process is carried out manually, which is very difficult. After that, remove the lower support from the lower punch, which causes significant effort due to the tight fit of the punch shank in the support.

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 (patent for invention No. 2797226, dated 08.24.2022, “Device for electric pulse pressing of powder materials”). This device includes a pulsed energy source, a loading device, a metal cage 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 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 plate, and the upper and lower supports are made in the form of glasses, into the bottom of which the upper and lower punches are inserted, respectively, with a chamfer on the side surface of the shank for fixing them with locking screws located in the side parts of the supports, and the upper support is put on the end of the rod and secured to it using a rod passing through the coaxial holes in the rod and the upper support, and the lower support is put on the lower base and secured to it using a rod passing through coaxial holes in the lower base and lower support, in the side parts of the bushings there are bolts for fastening the matrix with a metal frame on the 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, and it is put on the upper support and the plate with bushings U-shaped bracket with semicircular cut-outs for a holder for the matrix on one side and the upper support on the other side on the end parts of the bracket, a height equal to the sum of the height of the matrix and the length of the upper punch, ensuring its fastening to the upper support and the plate with the matrix.

This design of the device allows, after the electric pulse pressing process, to lift up the matrix with the upper punch using a rod and a U-shaped bracket, and not manually. The lower punch is pulled out of the matrix and remains in the lower support on the lower base and does not subsequently interfere with the removal of the resulting sample. After this, it is necessary to fix the matrix with the holder on the guides in the upper position, and then use the upper punch to squeeze out the resulting sample. However, the fixed height of the U-shaped bracket limits its use at different heights of powder filling into the matrix (it is impossible to attach it to the upper support and the plate with the matrix) and, as a result, narrows the range of heights of manufactured tablets. In addition, the manufacture of locking screws for the side part of the supports and the conical shanks of the punches for the supports is quite labor-intensive.

In this regard, the most important task is to develop a new device that makes it possible to produce products with a larger range of sizes and reduce the labor intensity of manufacturing punch shanks and supports for them.

The technical result of the claimed device is the creation of a new product that, using electric pulse pressing, provides samples with the necessary characteristics, expanding their size range and significantly reducing the labor intensity of manufacturing press equipment.

The specified technical result is achieved by the fact that in a device for electric pulse pressing of powder materials, including a pulsed energy source, a loading device, a metal cage with a ceramic matrix made of insulating material, an upper movable punch with an upper support located under the rod, a lower fixed punch with a lower support installed on the lower base, a plate with two bushings, on which a holder with a matrix is fixed, and the bushings are able to slide vertically along the guides installed on the lower plate, and on the side parts of the bushings there are bolts for fastening the matrix with a metal holder on the guides, additionally made with a rectangular groove, according to the invention, the upper and lower punches having cylindrical shanks are pressed to the end of the rod and to the end of the lower base with union nuts, and on the lower part of the rod a rectangular detachable plate is fixed and tightened with bolts, on which two traction rods with threads on the lower ends equal to the height of the matrix, and which are electrically isolated from the rod by textolite bushings, and these rods pass through the plate and are fixed to it in height using lock nuts.

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 and traction rods mounted on a rectangular split plate. The lower punch is pulled out of the matrix and remains in the lower support on the lower base and does not subsequently interfere with the removal of the resulting sample. After this, it is necessary to fix the matrix with the holder on the guides in the upper position, and then use the upper punch to squeeze out the resulting sample. The thickness of the rectangular split plate is 10÷12 mm, the diameter of the traction rods is 10÷12 mm with a thread of 8÷10 mm and its length on the lower part is equal to the height of the matrix, these are the optimal dimensions that ensure reliable and strong fastening of the split plate on the lower part of the rod, and traction rods on a plate with a matrix. Union nuts on the lower base and the end of the rod ensure that the punches with supports are tightly pressed to the end of the rod and to the end of the lower base. The thread on the lower part of the traction rods, equal to the height of the matrix, ensures fastening of the plate with the matrix at the required height depending on the height of the backfill and thereby makes it possible to obtain samples with different heights.

In fig. Figure 1 shows a device for electric pulse pressing of powder materials.

In fig. Figure 2 shows a rectangular split plate and a plate for a metal cage with holes for traction rods.

In fig. Figure 3 shows a device for electric pulse pressing of powder materials when raising the matrix to the upper position to press out the resulting sample.

In fig. Figure 4 shows a device for electric pulse pressing of powder materials when pressing out the resulting sample.

The essence of the invention is illustrated in Fig. 1, which shows a device for electric pulse 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, connected to the lower plate 6 by a threaded connection. The upper movable punch 2 is inserted into the upper support 7 and is electrically isolated from the lower punch 3 by insulating bushings 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. 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 to plate 22. This plate connected to a metal holder 15. Bolts 23 and 24 are screwed into bushings 20 and 21, which allow the matrix with powder to be fixed on the guides at the required height. The lower end of the rod 11 is made with a thread onto which the upper union nut 25 with a central hole for the punch is screwed, and on the upper part of the lower base 5 there is also a thread for screwing onto it another lower union nut 26 with a central hole for the punch. The upper support 7, together with the upper punch 2 inserted into it, having a cylindrical shank, is pressed against the end of the rod 11 using a union nut 25. The lower support 4, together with the lower punch 3 inserted into it, having a cylindrical shank, is pressed against the end of the lower base 5 s using a union nut 26. On the lower part of the rod 11, a rectangular split plate 27 is fixed and tightened using bolts 28 and 29 (Fig. 2). Two traction rods 30 and 31 are attached to this bracket with threads at the lower ends equal to the height of the matrix, and which are electrically isolated from the rod by textolite bushings 32 and 33. These rods pass through the plate 22 and are adjusted in height using nuts 34 and 35 .

The device works as follows. The lower punch 3, installed in the lower support 4 with a union nut 26, is inserted into the matrix 14, clamped into the holder 15, from below, and the powder of the electrically conductive material 13 is poured in (Fig. 1). Then the upper punch 2 with the upper support 7 and the union nut 25 is inserted into it. This entire assembly is inserted into the plate 22 and placed on the lower base 5 and the powder is pressed. Pressure P is applied to the upper punch 2 from the pneumatic press 10 through the rod 11. After which, the union nuts 25 and 26 are screwed onto the lower end of the rod 11 and the base 5, respectively. The upper punch 2, together with the support 7, is tightly pressed to the end of the rod 11, and the lower punch 3, together with the support 4, is tightly pressed to the end of the base 5. 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 downwards. 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 the traction rods 30 and 31 freely pass through the holes in the plate 22 and do not interfere with the powder compaction process.

Now you need to extract the resulting sample from the matrix. To do this, screw the nuts 34 and 35 onto the traction rods 30 and 31 until they touch the plate 22. Using a pneumatic press 10, lift the rod 9 up (Fig. 3). The matrix 14, together with the resulting sample in the holder 15 along the guides 16 and 17, also rises upward due to the action of the traction rods 30 and 31. 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 23 and 24, 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. To do this, we begin to lower the rod 11 down, the upper punch 2 also goes down and squeezes out the resulting sample 13 (Fig. 4) from the matrix 14. It should be noted that the traction rods 30 and 31 freely pass through the holes in the plate 22 and do not interfere with the removal of the resulting product .

This design of the proposed installation allows the lower punch to be removed from the matrix before pressing out. In addition, the traction rods 30 and 31, by adjusting the nuts 34 and 35 on them, make it possible to produce tablets with a height from 2 to 25 mm. In addition, the use of union nuts 25 and 26 allows you to reliably and tightly press the punches together with the supports to the end of the rod and the lower base, respectively. This makes it possible to avoid the complex and labor-intensive production of locking screws for the side of the supports and conical shanks of the punches for the supports.

The proposed device was tested in obtaining tablets from various materials of the required density. For zirconium nitride this is about 95÷98% of the theoretical density. For Cu+0.45% Al ₂ O ₃ this is about 97÷98% of the theoretical density. For tungsten pseudo alloys VNZh, VNZhK this is about 95÷99% of the theoretical density. Samples were obtained in the form of tablets in the amount of 17÷21 pieces in one hour and with a height of 2 to 25 mm. At the same time, using a well-known installation, it was possible to produce products with a height of about 7 mm. For other sample sizes, it would be necessary to produce a U-shaped bracket with a modified height.

Thus, this expands the range of manufacturing samples with the required density and reduces the labor intensity of manufacturing punch shanks and supports for them.

Claims (1)

A device for electric pulse pressing of powder materials, containing a pulsed energy source, a loading device, a metal cage 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 mounted on the lower base, a plate with two bushings on which the holder with the matrix is fixed, and the bushings are able to slide vertically along the guides installed on the bottom plate, and on the side parts of the bushings there are bolts for fastening the matrix with a metal holder on the guides, additionally made with a rectangular groove, characterized in that the upper and the lower punches, having cylindrical shanks, are pressed to the end of the rod and to the end of the lower base with union nuts, and on the lower part of the rod, a rectangular detachable plate is fixed and tightened with bolts, on which two traction rods are fixed with threads at the lower ends equal to the height of the matrix , and which are electrically isolated from the rod by textolite bushings, and these rods pass through the plate and are fixed to it in height using lock nuts.