SU1574370A1 - Method and apparatus for moulding blanks from powder in casing - Google Patents

Abstract

The invention relates to powder metallurgy, in particular, to methods and devices for forming blanks by extrusion. The purpose of the invention is to expand the technological capabilities of the method by pressing abrasive and pyrophoric powders. When molding core blanks with a diameter of 40 mm and a length of 500 mm from magnesium-based powder, mylar tracing paper with a thickness of 0.2 mm was used as a shell in the form of ribbons 24 mm wide. The tapes were overlapped with an overlap of 2 mm in a matrix container with a diameter of 49 mm and a 20 ° angle of the funnel matrix. The total number of ribbons is 7. The working surfaces of the device feeding the ribbon (guides) had a radius of 100 mm with an arc length of 90 mm. The force on the punch 160 kN, the deformation rate of 2.2 m / min. Density after pressing is 95 - 98%. In order to feed the tapes into the cavity of the matrix, the device, in addition to the guides, also contains a washer of elastic material at the end of the punch and clamps with ribs. The distance between the guides and the ribs is equidistant. 2 sec. and, 3 z. p. f-ly, 3 ill.

Description

The invention relates to powder metallurgy, in particular, to methods and devices for forming blanks by extrusion.

The purpose of the invention is to expand the technological capabilities of the method by pressing abrasive and pyrophoric powders.

According to the mold forming method. of the powder in the shell, the latter is formed from the tapes by laying them without a gap, and the material of the shell is chosen to be a material whose compressive stress is not

less stress compressing powder. Tapes can be placed or overlapped, and as a material, lavsan tracing paper, brass or steel can be used.

In a device for forming blanks from a powder in a shell containing a matrix and coaxially mounted in it with the ability to move along its axis a punch with a washer made of elastic material fixed to its end, in the upper part of the matrix container are mounted radial guides having a curvilinear working surface one

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with a rectilinear generatrix, and a clamp, on the outer surface of which there are ribs with working surfaces, equidistant working surfaces of the guides, and flanges are made on the working surface of the guides or edges,

FIG. 1 shows a device for carrying out the method, vertical section; in fig. 2 - the same, top view; in fig. 3 - finished. Product with a different pattern of packing tape sheath, cross section.

The device contains a matrix 1 with a profiled internal cavity, including a container, a conical part and calibrating the juice, inside which is coaxially positioned with the possibility of reciprocating movement along the axis of the punch 2 with a stepped washer 3 of elastic material, for example polyurethane, radial but installed

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dies in the direction of pressing, the powder 10 is formed. In this case, the tapes also move in the direction of pressing, since the coefficient of friction between the powder and the tapes is higher than at the contact of the tapes with the die. If necessary, the coefficient of friction of the tape against the walls of the matrix is reduced by applying a lubricant. Thereafter, the punch is removed from the matrix container, the empty cavity of which is filled with powder, and the process is repeated in the previous sequence. At the exit from the matrix calibrator, the ribbons 8 are easily separated from the molded preform. After using up the stock of tapes in the cassettes, they are joined to the tapes of other cassettes by any known means, or after editing, tapes of the previous cassettes are used.

Change the width of the tape and, respectively, guides, tape in the container

on the matrix, guides 4 with flanges 25 and neRe matrices are placed end-to-end on the boom of the working cylindrical surface, clamps 5 form a funnel; the guides and cavity of the matrix, formed into the shell 9, the number of guides and radial ribs 6 corresponding to the number of simultaneously fed tapes into the cavity of the matrix, and the distance between the flanges of each of the guides is Irina tape.

A device for carrying out the proposed method works as follows.

The tapes 8 are tucked under the ribs 6 of the clamp 5 and passed through the cavity of the matrix 1. After that, a plug of plastic material (not shown) is inserted into the matrix container and, by force of the punch 2 with a fixed washer 3, the plug is pressed into the conical part of the matrix, whereby the tapes are pressed against the walls of the container. Then, the powder 10 being formed is poured into the funnel-shaped cavity, the punch 2 is removed from the container of the matrix 1, after which the powder under the action of gravity fills the free flow. container lodge. Then punch 2 working vcHJraeM move along the axis

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forged ends or overlapped. In the case of butt-and-splitting ribbons, they provide good direction to each other, but at the same time, strict requirements are imposed on the dimensional accuracy of their width, so that the total is equal to

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the circumference of the cross section of the cavity of the matrix container. As a result, crimping tape in the conical part. the matrix widths are reduced, and when reused, in addition to straightening, one of the tapes must be replaced with a wider one and, accordingly, a guide so that the container cavity is completely covered with the shell material.

When laying overlapping tapes, there are no high requirements for dimensional accuracy across their width, since during compression in the conical part of the matrix they have the opportunity to shift one relative to another in the circumferential direction, which practically does not cause a change in the initial width of the tapes. After straightening, these tapes can be reused without replacing guides, since there is no need to change the distance between the flanges of the latter. However, with such a laying pattern, longitudinal grooves in the zones of overlap of the tapes remain on the outer surface of the moldable billet equal to the thickness of the tapes themselves. The amount of overlapping tapes

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forged ends or overlapped. In the case of butt-and-splitting ribbons, they provide good direction to each other, but at the same time, strict requirements are imposed on the dimensional accuracy of their width, so that the total is equal to

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the circumference of the cross section of the cavity of the matrix container. As a result, crimping tape in the conical part. the matrix widths are reduced, and when reused, in addition to straightening, one of the tapes must be replaced with a wider one and, accordingly, a guide so that the container cavity is completely covered with the shell material.

When laying overlapping tapes, there are no high requirements for dimensional accuracy across their width, since during compression in the conical part of the matrix they have the opportunity to shift one relative to another in the circumferential direction, which practically does not cause a change in the initial width of the tapes. After straightening, these tapes can be reused without replacing guides, since there is no need to change the distance between the flanges of the latter. However, with such a laying pattern, longitudinal grooves in the zones of overlap of the tapes remain on the outer surface of the molded workpiece, equal to the thickness of the strips themselves.

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The width is 0.05–0.10. When the overlap value is less than 0.05 of the width of the tapes, due to possible distortions of the latter during the formation of the shell, gaps between them are formed, since when laying overlapped, the ends of the adjacent tapes do not support each other. When the amount of overlap is greater than 0.1 of the width of the tapes, the shell material is wasted.

The thickness of the tape is chosen in the range of 0.1 - 0.3 mm. When the thickness is less than 0.1 mm, the carrying capacity of the casing is lost, and when the thickness is greater than 0.3 mm, the material of the tapes is wasted.

When forming face profiles, the number of tapes fed simultaneously to the deformation zone is equal to the number of faces. In the case of extrusion of blanks with a circular cross section, the number of ribbons simultaneously fed into the matrix is chosen in the range of 6-10 pieces. When the number of simultaneously fed tapes is less than 6, corrugations may occur in the zone of transition from the matrix container to the walls of the container. In the case of simultaneous use of more than 10 tapes, the processability of the process is reduced, since a greater number of them will need to be loaded into the device and subjected to subsequent editing for reuse.

The implementation of guide inserts with a cylindrical working surface formed by the movement of a rectilinear generatrix on a curved guideway ensures a smooth transition of the ribbon from the flat to the part of the tubular casing. With any other working surface of these inserts (conical, face), at the entrance to the matrix container, ribbons are formed in the ribbons, since the chute formed from the belt will need to be bent relative to the edge of the matrix container formed under the feeder-clamp. The presence of corrugations in the tapes at the container entrance leads to a decrease in the surface quality of the required blanks and even to rupture of the shells.

Example 1. Rod type blanks with a diameter of 40 mm, a length of 600 mm, and a relative density of 0.92 - 0.98 were made from aluminum APW powder without the use of binders and a lubricant. As a shell is1574370

use cold-rolled tapes from brass L68 0.2 mm thick and. wide

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stacked end to end

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Zam in the matrix container with a cavity diameter of 49 mm and a corner of a matrix funnel 20 °. The number of simultaneously laid tapes and, accordingly, the guide inserts and the radial ribs on the feeder-clamp is 7. The working surfaces of the guide inserts and the radial ribs on the feeder-clamp are parts of a circular cylinder with a radius of 100 mm and arc lengths of 90 mm. - The extrusion force at a given density of the obtained blanks is 460 kN. The application of consistent graphite grease GOST 3333-80) on the surface of the tapes in contact with the walls of the container, reduces the technological effort to 120 kN. The surface roughness is formed - HbDc blanks in both cases corresponds to the roughness of the tapes themselves

5 without the presence of zadirb. When extruding without the use of the shell, the technological force reaches 650 kN, the sticking of the formable material on the walls of the matrix container and in

The scoring on the surface of the resulting blanks to a depth of 1.5 mm. An attempt to use a tubular sheath made of polyethylene with a wall thickness of 0.3 mm does not give a positive effect due to a local rupture of the wall of the shell, as a result of which the powder adheres to the walls of the container, and the technological force increases to 610 kP. The relative density of the molded blanks 0.92 - 0.94.

The use for the same purpose of a dowel tracing tape (TU 6-17-668-80), having a width of 22 mm and a thickness of 0.2 mm, provides high surface quality of the moldable blanks, since no strips of the tapes themselves are observed and the powder sticks to the walls matrices. Technological effort at the same time reaches 140 kN. The relative density of the molded blanks 0.92 - 0.94.

Example 2. Formed cylindrical billet with a diameter of 40 mm and a length of 400 mm with a relative density

5 0.9 - 0.94- from a mixture containing 98% iron powder grade ПЖ2М2 н 2% powder of boron carbide without the use of binders and a lubricant material

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rial As a shell, cold-rolled tapes of thickness O, 1 mm and 24 mm wide, of steel 10, laid overlapped in a matrix container with a cavity diameter of 49 mm and a corner of a matrix funnel 20 °, are used. The number of simultaneously fed tapes and, respectively, of the guide inserts and radial ribs in the feeder-clamp l is equal to 7. The working surfaces of the guides and the ribs are chosen to have a cylindrical radius of 100 mm and an arc length of 90 mm. The surfaces of the tapes in contact with the walls of the matrix container, jr, are lubricated with graphite lubricant with a pre-grease (GOST 3333-80). The technological effort in this case is 380 kN, while in the case of non-shell molding, it JQ reaches 740 kN. The relative density of the workpiece is 0.92 - 0.95.

As a result of the use of a steel tape sheath, the durability of the matrix increased 4 to 5 times. After removing 25 ent from the formed billet and subsequent edits in the rolls, it was possible to reuse them at least three times. Longitudinal grooves form in the places where the tapes overlap, but their depth is less than the depth of marks that appear on the workpiece due to abrasion of the working surface of the matrix with solid inclusions of boron carbide. So, in case of using a shell of 0.1 mm thick tape, the depth of the grooves on the workpiece is mm, while when extruding a bar without using a shell after 40 .Q molding cycles, longitudinal risks O of 14 mm appear on its surface.

P r and I m p 3. Molded steel blanks with a diameter of 40 mm and a length of 500 mm with a relative density of 0.95 - 0.98 of magnesium-based powder steel are formed. As a shell, a tape of mylar tracing paper (TU 6-17-668-80) is used. 0.2 mm and a width of 24 mm. The tapes are overlapped with an overlap of 2 mm in the matrix container with a cavity diameter of 49 mm and the angle of the matrix funnel 20. The number of simultaneously laid tapes is 7. The working surfaces of the guide inserts and the radial ribs on the feeder-clamp are parts of a circular cylinder with a radius of 100 mm and an arc length

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90 mm. The technological effort on the punch to achieve a given density reaches 160 kN. The warping speed is 2.2 m / min. In pro- . During the extrusion process, no shell destruction is observed. Squeezing with the same cuts and the speed of deformation with the use of a polyethylene sheath by a known method or in its absence leads to an increase in the technological force on the punch to 530 kN and to ignite the mixture.

Thus, the proposed method and device for its implementation allows pressing abrasive and pyrophoric powders.

Claims (6)

1. A method of forming blanks from a powder in a shell, including extruding the powder with a punch into the mouth cavity of the matrix successively in portions in the shell of unlimited length covering the surface of the working cavity of the matrix, characterized in that abrasive and pyrophoric powders, the shell is formed from the tapes by laying them without a gap, while the material of the shell is chosen, the material whose compressive stress is not less than voltage to compress the powder. 2. A method according to claim 1, characterized in that the belts are butt-mounted along the side ends. 3. A method according to claim 1, characterized in that the tapes have side ends overlapped. 4. Method according to paragraphs. 1-3, characterized in that the ribbons are made of polyester tracing paper, brass or steel. 5. A device for forming blanks from a powder in a casing, containing a matrix and coaxially mounted in it with the ability to move along its axis a punch, so that, in order to expand technological capabilities by pressing abrasive and pyrophoric powders, it is equipped with a washer of elastic material, guides the feed tape sheaths, made with a curved surface 915 and straight-line generators, and pri-Aim with ribs on its surface, the working surfaces of which are equidistant to the working surfaces of the guides, while the washer is fixed on the end of the punch, and the guides ten Placed on the upper end of the matrix. 6. A device according to claim 5, characterized in that flanges are made on the working surface of the guides or ribs. Fig.Z