DE1091409B - Method and device for the production of powder metallurgical objects provided with channels - Google Patents

Description

GERMAN

The invention relates to a method for producing channels provided with powder metallurgy Objects, the powder mass with channel cores embedded in predetermined positions compacted by compression molding and then post-treated to remove the channel cores will. Such channels are used for. B. too much for the supply of liquid or gaseous coolants Machine parts subjected to high temperatures, such as gas turbine blades.

The channels can serve to circulate a coolant, but advantageously can also be used by the The possibility of making use of the porosity of the powder metallurgical objects, to allow the coolant supplied inside to exit the pores and a so-called To effect sweat cooling.

Each channel is generally formed by a very fine bore to allow both the flow of the To control coolant in the desired amount as well as to inadmissible material weakening of the blades avoid. The formation and the exact location of such a channel in a powder metallurgical shovel involves considerable difficulties. These difficulties are increased when the in the channels required for a shovel are numerous.

It is customary to create the channels by inserting a core of required cross-section and necessary To provide a shape as a material that will be used in the subsequent heat treatment, i. H. during sintering of the condensed object, divides or disappears. Are used as cores wires, for example made of cadmium or other substances, they evaporate and leave empty spaces, which form the desired channels. If polystyrene is used as the channel core material, the same goes for it gaseous monomer, while when using waxes these volatilize. The thin one Cross-section of such materials, however, has an unfavorable effect in terms of their rapid and accurate storage during the filling of the powder and also on maintaining their position during compaction of the powder.

In known methods for producing channels provided with powder metallurgical articles the procedure is such that first a layer of powder is introduced into the die cavity and leveled, after which the channel cores are placed on the powder layer in order to then pass it through to cover another layer of powder introduced and leveled into the cavity, whereupon further canal cores arranged and covered with more powder until the cavity is filled in this way is. However, this method is, in particular, a method and an apparatus

for making with channels

provided, powder metallurgical

Objects

Applicant:

The Birmingham

Small Arms Company Limited,

Birmingham (Great Britain)

Representative: Dr.-Ing. A. van der Werth, patent attorney,
Hamburg-Harburg 1, Wilstorfer Str. 32

Claimed priority:
Great Britain 31 May 1955

troublesome and time-consuming where the objects to be deformed are a plurality of fine, in one channels arranged in a predetermined position to ensure that fine and small channel cores arranged in an exact position and by the following covering with the next layer of powder in their Location remain unchanged.

Since the powder volume is greatly reduced by the compaction, the canal cores can be used In the known method, wires do not occupy the same position after compaction as they did before held the compaction. The wires can bend, especially at high temperatures to break. Uniform results can neither be achieved nor expected.

The aim of the invention is to make the filling of the powder together with the channel cores in essential Shorter time, considerably more precisely and with less effort than with previous methods perform.

According to the invention, the powder mass is approximated to one of the initial shapes for pressing Corresponding cavity penetrating, outside the cavity supported cores filled with soaked in a freezable liquid and frozen, whereupon the supports of the cores are removed are exposed, the frozen block and after cutting or shortening the protruding

009 628/222

Core ends inserted into the mold, thawed, dried and pressed. In this way they lie canal cores supported outside the powder uniformly and in the foreseen position in the compacted Dimensions. A very considerable saving of time and effort is achieved, which is decisive there is where an ongoing manufacturing operation is being performed because all of the channel cores are in the Preform boxes are housed even before any powdery material is added, and because the entire powdery substance is thus at once, supported for example by what is known per se Shaking the box, can be added. Influences that move the channel cores out of their position could thus be avoided. The channel cores can be arranged in any direction to the direction of compaction be because the storage takes place outside of the mold.

Pushing the channel cores through the holes is easy. If the channel cores are straight, ao they are quickly plugged in and then attached by soldering or gluing, for example. Instead, they can by wedges, clamping plates or the like. Be set.

A disassemblable preform box is preferably used to hold the solidified contents of the box after the freezing process can be removed more easily. Those carrying the canal cores Walls can be arranged removably from the side walls in the same way. The one through the hole punch Pieces of the cores going in the opposite walls must be severed in order to be severed allow these walls from the block; the protruding core parts can close to the Surfaces of the then exposed block are supported.

The addition of impregnating liquids to the block does not affect the powder, if done carefully has been condensed.

The dimensions of the solidified block can be less than the corresponding dimensions of the die cavity be which receives the block, the difference preferably being kept small will.

When the amount of solidified block is less than the corresponding amount of die cavity by more than a tolerance of, for example, 0.025 to 0.050 mm, to make the block more comfortable Way can be brought into the mold, then the one created in the mold cavity Space to be filled with metal powder to prevent the block from collapsing when the frozen liquid is removed prior to compaction and / or sintering. Will powder at the ends of the Block where the duct cores protrude, so the clogged end pieces can be removed, after the block is sintered to allow admission to the channels.

If it is desired that channels run only part of the length of the finished article, so the clogged end piece can only be removed at one end in order to expose only one end of the channels.

The liquid that can be frozen is used which is the powder or the material of the channel-forming Parts do not corrode or react with them; the box and the molding material should be in the same way of the liquid cannot be attacked.

Liquids with freezing points between -20 and + 15O ⁰ C and corresponding boiling points between +20 and + 300 ° C are generally suitable; however, liquids with high vapor pressures are preferred. Benzene has been found to be particularly suitable; but water, naphthalene and paradichlorobenzene can also be used.

The liquid used can be removed from the block in the mold by heating and / or reducing the pressure to evaporate the liquid.

Appropriately, a space above the mold cavity can be evacuated and the block at room temperature be warmed up. No further heating is required when using benzene.

Copper wires can be used as channel cores; instead, the cores can be made of cadmium, Polystyrene or other material.

The method according to the invention and an apparatus for carrying out this method are explained below with reference to the drawing, which is a schematic, perspective view represents a preform box used in carrying out the method.

Around a ducted, powder metallurgical object of rectangular shape with longitudinal ducts pre-forming, a pre-molding box, as shown for example in the drawing, used. The preform box has a base plate 1 and two side plates 3, which in known Way are held together by means of countersunk screws. The box is provided with two end walls 5, each of which has a plurality of holes 8.

The ends of the powder block are delimited by two partition walls 11 which are slidable between the Side plates 3 are fitted. Each intermediate wall 11 is provided with several holes 9.

The holes 8 and 9 in the walls 5 and 11 are aligned so that a channel core 21, e.g. B. a wire, can be pushed through all four holes (one in each wall 5 and 11). The channel cores are put through the four walls so that each hole is occupied by a wire.

The ends of the wires on the outside of the end walls 5 are then bent over and clamping plates 15 fastened over the bent ends by means of screws 17 engaging in threaded holes 13.

The partition walls 11 are then at a sufficient distance from the end walls 5 in a predetermined position set up within the space enclosed by the box.

The channel cores 21 are then screwed into threaded holes 7 using tensioning screws 19 stretched against the ends of the box parts 1 and 3.

The connection points of the cavity between the box parts 1 and 3 and the partition walls 11 are then sealed by painting the spots with paraffin wax, creating the partition walls are kept in their position.

The z. B. filled with metal powder made of stainless steel, the filling of the cavity, as known per se, being assisted by shaking.

The powder in the cavity is then mixed with a freezable liquid, e.g. B. with benzene soaked and freezing the powder mass in the box by placing it in dry ice. That Benzene freezes at about -5.4 ° C, but the block does can be set to a much lower temperature, e.g. B. -40 ° C, must be cooled down in order to perform the necessary operations before the benzene melts.

Then the screws 19 and then the base plate 1 and the side plates 3 are removed. In this way, the frozen block becomes, together with the channel cores 21, the partition walls 11, the end walls 5, the plates 15 and the screws 17 are exposed. The solid block will then be tight Sawn through the inside of the end walls 11 and so the walls 11 and 5 and the plates 15 and the Screws 17 removed. These can then be taken apart for themselves.

Instead, the protruding core ends can also be separated a, n from the outside of the partition walls 11 or abbreviated, leaving any desired length of wire exposed, whereupon the Partitions 11 are deducted.

The frozen block is then inserted into the mold, thawed and pressed, with the benzene Will get removed. Benzene boils at about 80.4 ° C under atmospheric pressure; but by evacuating the Compression molding and thus lowering the pressure can make the liquid at much lower temperatures melt and simmer.

Once the benzene has evaporated in its entirety, which can be seen from the fact that the evacuation pump stops withdrawing benzene, the block is ready to be compressed.

The reduction in spacing of the channel cores in the block can be calculated and when designing the hole arrangement the walls of the preform box are taken into account.

The channel cores themselves can be deformed in cross section by the applied pressure; however, this fact can also be taken into account in advance. For example, it has been found that copper wires 1.22 mm in diameter, ^{compressed in stainless steel powder at 4.7 t / cm 2} , are brought to an oval shape of about 1.02 by 1.27 mm so that the cross-sectional shape is not essential Undergoes change.

Claims (8)

Claims: 40 1. Process for the production of channels provided with powder metallurgical objects, wherein the powder mass with channel cores embedded in predetermined positions by Form-45 S press compacted and then post-treated to remove the channel cores, thereby gekenitzeich.net that the powder mass in one of the initial form for pressing approximately corresponding Cavity around the penetrating through the cavity, supported outside the cavity The kernels are filled in, soaked in a freezable liquid and frozen, whereupon the supports of the cores are removed, the frozen block exposed and after cutting off or shortening the protruding core ends inserted into the mold, thawed, is dried and pressed. 2. The method according to claim 1, characterized in that the filling of the cavity, as on known, is supported by shaking. 3. The method according to claim 1, characterized in that not through the frozen block filled mold parts are filled with powder mass before thawing. 4. Benzene as the soaking liquid for practicing the method according to claim 1. 5. Apparatus for carrying out the method according to claim 1, characterized by a preform box, its walls (5, 11) for supporting the channel cores (21) in a predetermined position within of the space enclosed by the box are set up. 6. Apparatus according to claim 5, characterized in that the preform box can be dismantled is. 7. Apparatus according to claim 5 or 6, characterized in that the walls (5) of the preform box for fastening and tensioning the channel cores (21) are set up. 8. Apparatus according to claim 7, characterized in that the channel cores (21) through Gluing, soldering, wedging or clamping are attached. Considered publications: German Patent Specifications No. 541515, 812 840; British Patent No. 611,466; Franz Skanpy, metal ceramics, 3rd edition, 1943, .78. 1 sheet of drawings © 009 628/222 10.60