RU1787689C - Apparatus for discrete and continuous forming of elongate tubes from powder - Google Patents

Description

with the possibility of rotation of the matrix and the reference rod, obtaining long tubes of unlimited length with a uniform density distribution due to the flow of powder from the container into the cavity of the matrix, so that each pressing cycle leads to rotation of the matrix and the reference rod by an angle corresponding to the volume of powder loaded into the container, which, in turn, leads to the sequential filling of the matrix cavity with a powder densified to the same degree, uniformly throughout its transverse at the cross section.

The proposed apparatus for discrete-continuous molding of long products of powder is illustrated in the drawing, which schematically shows its general view.

The device consists of a container 1 with a channel, a punch 2, a matrix 3 installed in bearings 4 to the side surface of the container 1 and a reference rod 5 installed in bearings 6 coaxially with a matrix 3 and perpendicular to the punch 2. The outlet of the container channel is located in the matrix at a level its axis.

The angle of inclination of the channel to the axis of the container (axis of the punch) and its length, limited by the strength of the walls of the container, should be minimal. An increase in these values leads to an increase in the force of extrusion of the powder previously compacted in the container into the cavity of the matrix due to additional energy expenditures to overcome the contact and interparticle friction in the powder when its flow direction changes when passing from the container cavity to the channel.

The device operates as follows.

During the working stroke of the punch 2, the powder is compacted in the container 1 and enters the cavity of the matrix along the channel to the periphery of its largest cross section at the level of the axis of the reference rod 5. In this case, the matrix and reference rod are rotated around the axis of rotation in bearings 4 and 6 on a certain angle corresponding to the volume of receipt of the powder pre-compacted in the container during the pressing cycle. During repeated cycles of loading the powder into the container, compacting it and aligning it into the matrix cavity, the matrix cavity is sequentially filled uniformly along its cross section and then the homogeneous mass of the powder is compressed when it passes through the conical

matrix into a long pipe with uniform distribution.

PRI me R. In the proposed device, mounted on a hydraulic press 5 with a force of 2000 kN, BK 2o powder was pressed (tungsten carbide -80%, the rest was cobalt) with the addition of paraffin (10% and 6% by weight) as a plasticizer.

0 The main dimensions of the mold: the diameter of the calibrating part of the matrix DK 50 mm, the diameter of the calibrating part of the reference rod Do 2, mm, the maximum diameter of the matrix D 72 mm, the diameter of the punch

5 dn 15 mm, the taper angle of the working surface of the matrix (10 °, the diameter of the container channel dK 15 mm, the angle of inclination of the channel to the axis of the container (axis of the punch) is 45 °, and its length is 40 mm.

0 In the unsteady phase of the pressing process when filling the matrix with powder, the pressing force gradually increased and reached 70 kN in the steady state phase of the process when extruding

5 pipe billets with a diameter of 50 mm with a hole of 20 mm with a content of 10% paraffin in the mixture and 190 kN at 6% paraffin.

By repeatedly repeating the pressing cycles in the device according to the invention, tube blanks up to 2000 mm long were obtained. The resulting blanks had a smooth, defect-free inner and outer surfaces.

Sintering of billets with a length of 500 mm was carried out in the usual manner for a hard alloy (in an atmosphere of dried hydrogen). Sintered billets had a smooth cylindrical surface without cracks and other visible defects. Axis curvature

0-blanks were not observed.

To obtain blanks of similar sizes using a known device (prototype) used a mold with the dimensions of the diameters of the working surface

5 matrix, punch and reference rod of the proposed device.

Pressing was carried out on the same hydraulic press by successively pouring portions of powder into a container and

0 by subsequent activation of the press stroke.

With a force of 75 kN, a tube billet was extruded with an outer diameter of 50 mm and an inner diameter of 20 mm from VK-20 powder with 10% paraffin by weight.

5 Billets, up to 1500 mm long, did not have. visible defects. After sintering, the billets, 500 mm long, had a smooth cylindrical surface, without cracks. However, they turned out to be curved along the axis - in layers x

 The tube preforms arranged diametrically to the punch experienced greater shrinkage of the material during sintering due to the reduced initial density.

When sintering in a hard shell, which prevents bending of the workpiece, transverse

cracks.

When using this unit

for molding: tube blanks from VK-20 powder with 6% paraffin failed to produce defect blanks. When leaving the calibrating part of the matrix, annular cracks formed on the surface of the tube billet due to an increased density gradient in its cross section.

As can be seen from the above example, the application of the proposed device provides discrete-continuous molding of long pipes of unlimited length having good quality.

due to uniform density distribution.

Claims (1)

SUMMARY OF THE INVENTION A device for discrete-continuous molding of long pipes of powder containing a container with a punch, a matrix with a conical working surface and a reference rod coaxially mounted perpendicular to the punch, characterized in that, in order to improve the quality of the pipes by increasing the uniformity of the density distribution in their cross section, the end surface of the matrix is mated to the side surface of the container, their cavities are connected by a channel, the outlet of which is located in the matrix It is mounted at the level of its axis, while the matrix and the reference rod are rotatably mounted .. „