SU1323234A1 - Apparatus for extrusion of hollow articles from powder - Google Patents

Abstract

The invention relates to devices for extruding hollow articles from powder. The purpose of the invention is to increase the density of products. The device consists of a housing 1 with a hopper 2, a matrix 3, a hollow screw 4 with a drive and a mandrel bar 6. On the matrix and the rod there are 2 I cylindrical sections and sections bounded by a convex surface 7 on the matrix and a concave surface 8 on the rod. The convex-concave surfaces are related by the relation R4Z) - r (Z) RO-r, and (dR / dZ) 1, (dr / dZ) $ 1, where R is the radius of the internal curvilinear surface of the matrix, r is the radius of the curvilinear surface of the rod , RJ, is the radius of the cylindrical sections of the matrix, Gd is the radius of the cylindrical sections of the rod, 2 is the coordinate, measured along the axis of the rod. At the same time, P (2-4) rf, l (0.2-0.7) "/, where 1 is the length of the convex-concave section, l is its deflection, c / is the size of the gap between the matrix and the rod. When the screw 4 is rotated, the powder enters the matrix 3, in which in the area of the convex-concave section an intensive shift of the powder particles relative to each other occurs, which leads to an increase in the density of the articles. 2 sludge. (L oo 00 co 4: (puf.l

Description

The invention relates to powder metallurgy, in particular to devices for extruding hollow articles from powders.

The aim of the invention is to increase the density of products.

In Fig. 1, a device is shown, a longitudinal section; in Fig. 2, an embodiment of a die and a mandrel bar.

The device consists of a housing 1 with a loading hopper 2 fixed on it. A matrix 3 is attached to the end of the housing; inside: a hollow auger 4 connected via a helm

that wheel 5 with the drive (conventionally not shown). An adjusting rod 6 is placed inside the screw. On the matrix and the mandrel bar there are cylindrical, sections and portions bounded by a convex surface 7 on the matrix and a concave surface 8 on the mandrel rod (a design variant of the device is shown in Fig. 2, where the concave surface 7 made on the matrix, and the convex surface 8 - on the mandrel rod). In both cases, these surfaces are related by

RHZ) - rV (Z) R r,

where R is the radius.internal curvilinear surface of the matrix,

g -, the radius of the curved surface of the mandrel bar,

RC, is the radius of the cylindrical sections of the matrix,

Tjj is the radius of the cylindrical sections of the mandrel bar,

2 - coordinate, measured along the axis of the rod.

The length of the above sections of P and their deflection lie within certain limits.

P (2-4) about

L "(0,2-0,7) with

P is the length of the convex-concave region on the surfaces of the dies and the mandrel bar, measured along the axis of the device,

five

0

five

0

five

0

five

0

о Д - deflection of a convex or concave Section, defined as the shortest distance from the most distant point on the surface of the convex or concave section to the generator of the cylindrical section of the matrix or mandrel bar,

the size of the gap between the sections of the matrix and mandrel bar.

The device works as follows.

The screw 4 receives a rotation from the drive, feeds the powder from the feed hopper 2 into the annular gap between the die 3 and the mandrel 6, and squeezes the tubular-shaped product.

In this case, the concave-concave surfaces on the matrix and the rod form an area in which the powder is subjected to an intense shear. The resulting tangential stresses, together with the normal ones, contribute to a more comfortable styling of the powder particles due to the destruction. In addition, the removal of oxide films, the rearrangement of particles and their rubbing into the interparticle space, as well as cold welding at the point of contact, are observed. In this case, changing the direction of motion of the powder reduces the force required to achieve the same density (as compared with the known device). At the same time, the movement of particles one relative to another leads to the destruction of the joints on the finished products and, consequently, to an increase in the strength of the latter.

To obtain products of the highest possible density, the continuity of the flow of the powder mixture to be extruded must be met (otherwise, the finished product will contain either voids, ruptures, cracks, delamination and other defects, or the powder will be wedged between the convex and concave surfaces and get product is impossible). The continuity of the pockets is provided when the cross-sectional area of the annular gap between the die and the mandrel bar does not change, i.e. S const on the entire length of the matrix, ie:

R (Z) - hp2) Rj-g

It is possible to achieve the maximum possible density of products when the Slip Lines of powder particles relative to each other are inclined to the device axis at an angle not exceeding 45. At the same time, friction losses are minimal. If the condition is not fulfilled, stagnant zones appear in which a fixed powder accumulates, preventing the layers from moving, extruded by the screw. The coefficient of internal friction is much higher than the coefficient of friction of the powder on the surface of the matrix and the mandrel bar. Consequently, there is an increase in unproductive losses of pressing force. Therefore, it is necessary that

 45

or

one

dr

dr 1

5G- 1

Powders 11Ж2М2 and ПМС-1 were used for the manufacture of products. The density of products reaches 95% when choosing the optimal values of I and a.

The optimal length P of the convex and concave portions on the matrix and the reference rod is equal to

G (2-4) d,

that provides a significant (14-20% compared with the known) increase in the density of products. In addition, if the deflection of the convex and concave portion lies within

L (O, 2-0, 7) s /,

an increase in the density of products by 11-22% compared with the known is achieved.

 five

232344

Thus, in order to achieve the maximum possible density using the described device, it is necessary to observe all the conditions guaranteeing the desired location of the surfaces, and the geometrical parameters of the convex-concave portions on the surfaces of the matrix and the reference rod are related to the size of the gap 10 between the latter.

Claims (1)

Invention Formula A device for extruding hollow articles from powder, comprising a housing, a die, a hollow screw, a hopper and an arbor rod, characterized in that, in order to increase the density of the articles, the inner surface of the die and the arbor rod are cylindrical with vyploklo-skunyty and sections placed opposite each other, the surface of rotation, which is limited {e these areas, are interconnected by ) - r4z) r rl thirty with (---) 41, (-) Oi: d one, the length of the convex-concave region P is equal to (2-4) o, and its deflection j is equal to (0.2-0.7) /, Where R g R "g" Z is the radius of the inner curved surface of the matrix, the radius of the curved surface of the mandrel bar, the radius of the cylindrical sections of the matrix, the radius of the cylindrical sections of the rod, coordinate, measured along the axis of the rod, the size of the gap between the matrix and the rod. Editor N.Gorvat Compiled by G, Zagorsk Tehred L. Oliynyk Order 2904/13 Circulation 740 Subscription VNIIPI USSR State Committee for Inventions and Discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 Fig2 Proofreader A.Ilyin