DE3049424A1 - Hot isostatic pressing of metal parts with complex shape - where metal powder is placed in inner capsule located in outer capsule filled with compactable refractory and evacuated - Google Patents

Abstract

A metal capsule/corresp. with the complex shape required for the compact is filled with metal powder and placed in a vacuum-tight outer capsule(II), which completely surrounds capsule(I) and is filled with a homogeneous and compactable refractory which is used as a pressure transfer mediom. Capsule(I) pref. has a non-symmetrical shape whereas capsule (II) has a simple shape and is made of steel sheet.Capsule (II) is pref. annealed 1 h at 1000 deg.C. to remove gases, oxides and impurities such as grease; and pref. has an outer pipe which can be used to evacuate both capsules and is then sealed. The refractory is esp. Al2O3 powder. Used for example, mfr. of components used in aircraft or space vehicles. Prevents the fracture of the inner capsule.(I).

Description

Device and method for hot isostatic pressing

geometrically complex, powder metallurgical pressed pieces die The invention relates to a device and a method for hot isostatic pressing (often abbreviated HIP) geometry n complicated, powder metallurgical pressed pieces according to the preamble of claims 1 and 11 and the pressed pieces thus produced self.

Hot isostatic pressing has been known for a long time (See, for example, DE-AS 23 63 141 with further references): A thin-walled one Press capsule, manufactured e.g. B. by electroplating nickel onto a core made of wax (or low-melting alloy) and subsequent melting of the Kerns, an inlet pipe is filled with metal powder, then evacuated and closed, which is followed by the hot isostatic pressing of the metal powder in the press capsule then to produce the desired workpiece as a pressed piece.

The metal used as the press capsule should be as thin-walled as possible (e.g. for nickel only approx. 1 mm thick) in order to then manufacture accordingly Remove the metal layer adhering to the pressed piece with as little effort as possible, z. B. by machining, sandblasting or chemically.

Further requirements for the press capsule are: - Uniformity of the Wall thickness over the entire surface, - vacuum tightness and - ductility high pressure and high temperature.

In practice, these requirements may not be sufficient if the pressed piece is geometrically complicated, because then the press capsule is also geometrically complicated.

In particular, embrittlement of the press capsule leads to leaks, which prevent compression of the metal powder in the press capsule.

Such geometrically complex pressed pieces come in particular as components of aerospace equipment. So you can't so far can be produced by hot isostatic pressing, but only in conventional Way by forging and subsequent machining on all sides, the Losses of the order of 50% of the forged blank caused what This is all the more disadvantageous as it is usually extremely expensive alloys.

It is therefore the object of the invention to provide a method and a device to create for hot isostatic pressing of the type mentioned, which with essential lower demands on the press capsule manage without affecting the quality of the finished product Pressing is impaired.

According to the invention, this problem is solved by the teaching. according to the characterizing part of claims 1 and 11, respectively.

The agents according to the invention are obviously extremely simple: - an easy-to-build auxiliary capsule and - a passive pressure transmission medium, that only forwards the pressure supplied from the outside, i.e. not independently pressure must generate.

The invention allows the use of metallic compression capsules, the advantages over the previously known Xind through the admissibility of: - different Wall thickness, - generally less wall thickness, - vacuum leaks.

The practical testing of the method according to the invention has densities of the metal powder in the metallic press capsule to 100%.

Material tests carried out on pressed pieces produced according to the invention have shown that the static property values are the minimum values of forged material and exceed the dynamic property values at least in the scatter range for Forging material lie.

In contrast, an auxiliary capsule for (allegedly) hot isostatic presses of highly stressed and intricately shaped Workpieces for turbo machines have become known (see. DE-AS 30 10 299), - however deliberately no press capsule is provided there, because the one with a galvanic Deposition produced press capsule pressed workpieces again and again a rework what would have needed in terms of the material properties hot isostatic pressed workpieces would have been very expensive (see column 1, line 39 - 52); - Instead there is a ceramic core open on one side with the negative contour of the workpiece is enclosed by a sheet metal outer skin as an auxiliary capsule, although the the open side of the ceramic core from this distance, at the bottom and at the Sides of the ceramic core, however, rests; this distance must (disadvantageously) must be precisely matched to the expected compression (cf. there column 2, line 63 - 67); - after all, there is a departure from the (real) i s o static pressing, because the pressurization of the metallurgical powder from the Hifs capsule is anisotropic takes place, namely a greater anisotropy is caused by the ceramic core.

In the teaching according to the invention of claim 11 is of particular importance Interest of method step f), since in this way in particular a removal of more molecular water layers in the pressure transfer medium, which are previously attached to air when the pressure transmission medium was stored, such as ceramic powder to have; These multi-molecular water layers would namely be in the actual hot isostatic Pressing in water vapor with a volume that has been increased many times over, resulting in a extraordinarily high overpressure in the auxiliary capsule, which is then closed in a vacuum-tight manner with all undesirable consequences.

For the sake of completeness it should be noted that during the creation of the auxiliary capsule first generally the top surface is left free to the To be able to introduce press capsule and the pressure transmission medium, after which only the Auxiliary capsule is closed with a lid, which is also an outer Port for evacuating the auxiliary and the press capsule carries (cf. also the Claim 7).

Advantageous refinements of the invention are set out in the claims 2 - 9 and 12 ff., Which are particularly characterized by an increase in simplicity and with little effort.

The invention is explained in more detail, for example, with the aid of the drawing. The single figure shows: schematically an embodiment of the invention Device, whereby the depicted press capsule is an eometrically complicated (not rotationally symmetrical) shape corresponding to the pressed piece to be produced.

The device shown has, as is readily apparent is, a metallic press capsule 10 which is filled with a metal powder 12, an outer auxiliary capsule 14, which is provided with a pressure transmission medium 16 such as ceramic powder is filled, and a nozzle 18 for evacuation in the context of degassing in particular of the pressure transmission medium 16 immediately before the known hot isostatic Press.

After degassing or evacuation has taken place, the connector 18 is crimped off and welded vacuum-tight.

Otherwise, because of the individual process steps before the actual hot isostatic pressing referred to the teaching given in claims 11 ff.

The actual hot isostatic pressing, which is known per se, then runs as follows: Evacuate and selenium one (not shown) the one according to the invention Device receiving autoclave, - generation of pre-pressure by means of a compressor at room temperature, - heating and further pressure increase, - Hold at given data, cool down and decompress.

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Claims (17)

Claims 1. Device for hot isostatic pressing (HIP) geometrically more complicated, in particular not rotationally symmetrical, powder metallurgical pressed pieces, - with a powder-absorbing -metallic press capsule according to the pressed piece contour, g e k e n n n z e i c h n e t d u r c h - an auxiliary capsule (14), which - the press capsule (10) surrounds vacuum-tight on all sides and - the pressure can be applied, and - a heat-resistant, compressible, homogeneous pressure transmission medium (16) - in the entire space between the auxiliary capsule (14) and the press capsule (10). 2. Apparatus according to claim 1, characterized in - that the Auxiliary capsule (14) - has a simple geometric shape. 3. Apparatus according to claim 2, characterized in - that the geometric shape - a parallelepiped (14) is. 4. Apparatus according to claim 2, characterized in - that the geometric shape - is a circular cylinder. 5. Device according to one of the preceding claims, characterized in that - That the auxiliary capsule (14) - consists of sheet steel. 6. Device according to one of the preceding claims, characterized in that - That the auxiliary capsule (14) - has been annealed under vacuum for 1 h at 1000 "C. - for degassing (removal of oxide and impurities (e.g. grease)) on their inner surface. 7. Device according to one of the preceding claims, characterized in that - That the auxiliary capsule (14) has: - An outer connector (18) for evacuation the auxiliary (14) and the press capsule (10), which can be closed in a vacuum-tight manner after evacuation is. 8. Device according to one of the preceding claims, characterized in that - That the pressure transmission medium - is a loosely poured powder (16). 9. Apparatus according to claim 8, characterized in - that the Powder (16) - is a ceramic powder. 10. Apparatus according to claim 9, characterized in - that the Ceramic powder - Al 203 is. 11. Method for hot isostatic pressing geometrically more complex, especially not rotationally symmetrical, powder metallurgical pressed pieces, - under Use of the device according to one of the preceding claims, characterized by - the following process steps: a) production of the auxiliary capsule (14), b) Degassing of the auxiliary capsule by annealing under vacuum, c) partial filling of the auxiliary capsule with the pressure transmission means (16), d) introducing the degassed, powder-filled ones metallic press capsule (10) in the auxiliary capsule (14), e) remaining backfilling the spaces between the compression capsule (10) and the auxiliary capsule (14) with the Pressure transmission means (16) f) degassing the auxiliary capsule (14) and the metallic one Press capsule (10) by heating under vacuum, g) vacuum-tight sealing of the Hi3fs capsule (14) and the, metallic press capsule (10) and h) implementation of the actual hot isostatic pressing. 12. The method according to claim 11, characterized in - that the Method step b) - is carried out at 1000 OC for 1 h. 13. The method according to claim 11 or 12, characterized in, - that process step f) - carried out at approx. 350-450 ° C. for> approx. 10 h will. 14. The method according to any one of claims 11-13, characterized in, - That process step h) - carried out at> 1000 Rar,> -900 OC,> 1 h will. 15. The method according to any one of claims 11-14, characterized in that - That process step h) - is carried out with argon as the pressure medium. 16. The method according to any one of claims 11-15, - using of the device according to claim 7, d u r c h e k e n n n z e i chn e t - that the outer connector (18) after evacuation - crimped unA vacuum-tight welded will. 17. Press piece, produced with - the device according to one of the claims 1-10 and / or - the method according to one of claims 11-16, - in particular for aerospace device.