DD299711A7 - ARRANGEMENT FOR HOT-ISOSTATIC PRESSING OF REACTION-ACTIVE POWDERS - Google Patents

Abstract

The invention relates to the field of powder metallurgy and relates to the production of pressed products by hot isostatic pressing. According to the invention, the feed powder is enclosed in a sheet metal capsule surrounded by a powder consisting of the main constituents of the feed powder, but in a modified composition. Said system is enclosed in a sheet metal container consisting of a sheet metal with an attached sheet metal ring and a sheet metal disc for covering, the material of which also corresponds to a main constituent of the feed powder. This Metallblechbehaelter is completely surrounded with a powder that consists of a main ingredient of the powder. The entire system is placed in a steel capsule and sealed. The layer thicknesses or Wandstaerken the individual elements behave in a defined relationship to each other. Fig. 1 {Pressing, heizzi-isostatic; Powder, reactive; Sheet metal capsule; Metallblechbehaelter; Powder; Sheet metal ring; Sheet metal disc; Steel capsule; Coating thickness; Wandstaerken; Relationship}

Description

For this 1 page drawing

Field of application of the invention

The invention relates to the field of powder metallurgy. It relates to an arrangement for the hot isostatic pressing reactive reactive powders, which consists of at least one Preßkapsel, from a pressure transmission medium and means for preventing interference between feed powder and the other components of the arrangement.

Characteristic of the known state of the art The hot isostatic pressing (HIP) of powders, in particular of metal powders, is well known. To prevent the powder to be compressed from reacting with the gaseous compression medium, which is the desired Non-porosity of the compact would not ensure the insert powder with a capsule often consisting of metal

wrapped gas-tight. After the evacuation of the powder via a connection piece, the compression of the powder can be carried out to high-density materials, if in addition to the uniform pressure on the capsule at the same time a corresponding

Heat supply happens. According to «) plants are known. In the pressed capsule, the powder to be compressed is embedded in a pressure transfer valve (DE 3049424). To avoid Reactions' wipe the powder to be pressed and the Druckübert.-agermedium it is known, the latter from the same Material (but without sintering aid) like the powder to be pressed or the shaped body to be pressed (DD 154200)

or even to use two layers of the pressure transfer powder, wherein the inner layer in Hipen does not react with the powder to be compressed (cfi-Ber DKG Wiesbaden 62 (1985) 4/5 p 222-228).

However, all of these methods or arrangements do not yet guarantee high purity requirements (eg 4 N). Furthermore, it can in the application of the usual arrangements in the pre-pressing of difficult to pressable material (W, Mo. Suicides) come to inner states of tension and Schieferungen, which as well as a strong adhesion of the pressed Powder on the capsule material leads to failure of the compact. Object of the invention

The aim of the invention is to find an arrangement for the hot isostatic pressing of reactive active powders, which makes it possible to produce compacts having higher utility value properties, in particular with high purity, than hitherto.

Explanation of the essence of the invention

The object of the invention is to provide an arrangement according to the title of the invention, by the construction of which it is possible to achieve the object of the invention.

The arrangement consists of at least one Preßkapsel, from a pressure transmission medium and means for preventing interference between the powder and the other components of the arrangement.

According to the invention, the feed powder is enclosed in a sheet metal capsule. This capsule is made of a material that is a major constituent of the feed powder. To capsule did a powder, consisting of the main constituents of the feed powder, but in a different composition, arranged.

The previously mentioned system is enclosed in a sheet metal container, consisting of a base plate with an attached sheet metal ring and a olfactory disc to the cover, whose material also corresponds to a main component of the feed powder. This sheet metal container is also completely surrounded by a powder, which consists of a main constituent of the feed powder.

This overall system is placed in a steel capsule, closed and pressable, wherein the layer thicknesses or wall thicknesses of the individual elements are in a defined relationship to each other.

In an embodiment of the invention, the layer thickness of the powder used to the wall thickness of the sheet metal capsule to the thickness of the surrounding powder in the vertical direction to the wall thickness of the sheet metal container in the same direction to the thickness of the overlying powder to the wall thickness of the steel capsule such as 200: 1 to 5:25 to 1p0: 1 to 5:25 to 100: 10 to 100.

A further embodiment of the invention is characterized in that

the feed powder is MoSi _x ,

- The sheet metal capsule and the metal sheet container made of Mo sheet and

- The powder around the sheet metal capsule consists of MoSi _x with Mo excess and

- The arranged around the sheet metal container powder is pure Mo powder.

In the latter powder is as a material with getter effect on gases Ti or Ta powder in a proportion of 0.1 to 5% based on the mass of the feed powder.

Ausführungsbelsplel

The invention will be described below with reference to an embodiment. The accompanying drawing shows the arrangement according to the invention in a sectional view.

Essoll a MoSi _x powder, for example, a MoSi? _e -Pulvor 1, be densified by hot isostatic pressing. For this purpose, the structure according to the invention is realized.

In a steel capsule 6 with an outer diameter of 200 mm, a height of 40 mm and a wall thickness of 2 mm, the following internals are introduced:

First, the bottom of the steel capsule β is filled up to a height of 4 mm with Mo powder 5 for pressure transmission. Then a Mo sheet 4 of 0.2 mm thickness is placed and placed a Mo ring 7 with 0 190mm and 31.6mm height. Thereafter, the space between the steel capsule wall and the Mo ring 7 is filled with Mo powder for pressure transmission. This is followed by the assignment of the inner Mo sheet 4 with a MoSi ^ powder 3 with 4mm height. On this MoSi _1i8 powder now a Mo-sheet capsule 2 with 0 178mm is arranged, which is then filled with MoSi _{2> e} -Powder 1 up to a height of 23 mm (about 1.7 kg). The sheet metal capsule 2 is closed with a Ms sheet metal lid 8. On the closed capsule 2 and in the space between the capsule 2 and Mo-Rin ^ i 7 MoSi ^ powder 3 is introduced or introduced to realize the further structure. Its height on the Mo-tin cover 8 is 4 mm. The MoSi ₁₈ powder acts as a diffusion barrier.

The entire previous structure is now fully covered with a Mo sheet metal disc 9 (0.2mm thick).

The sheet metal container made up of components 3, 7, 9 also acts as a diffusion barrier.

The remaining space of the steel capsule 6 is filled with Mo powder 5 containing 1% Ti powder based on the mass of the feed powder. This addition of Ti achieves a getter effect on still existing gases and therefore has a favorable effect on the purity and tightness of the compact.

The Mo powder 5 also acts as an additional diffusion barrier.

To complete the construction, the steel capsule 6 is closed with a steel cover, which is welded at the edge.

Via a suction tube 10, the capsule 6 is evacuated. The suction tube is then closed by pressure welding.

To achieve the required high compression without Preßfehler and without diffusion of contaminants was found that it is also important if the layer thicknesses or wall thicknesses of the capsule assembly according to the invention are present in defined proportions. The areas to be respected have already been specified. In the present example, the following size ratio is achieved in the order mentioned:

200: 1.74: 34.8: 1.74: 34.8: 17.4.

So filled capsules are hot isostatic pressed at 131O ⁰ C, 30min at a pressure of 85MPa. After completion of the pressing takes place by a mechanical processing, a removal of the casings and a processing of the compact (disc) to size.

MoSi _2e discs produced in this way are characterized by densities of 95 to 99% of the theoretical density. Their composition corresponds to the operational specification. Impurities, eg with Fe or with other alien elements, could not be detected.

Claims (3)

1. An arrangement for Heißisostatischon pressing reactive active powders, which consists of at least one Preßkapsel, from a pressure transmission medium and means for preventing interference between feed powder and the other components of the arrangement, characterized in that the insert powder (1) in a sheet metal capsule (2) is enclosed, which consists of a material which is a main component of the feed powder (1), that around this sheet metal capsule (2) a powder (3), consisting of the main constituents of the feed powder, but in a modified composition, is arranged so far said system in a Motallblechbehälter, consisting of a sheet (4) with an attached sheet metal ring (7) and a shearing machine (9), is included, the material also corresponds to a main component of the feed powder that this sheet metal container with a powder (5) completely surrounded, which consists of a main component of the Use powder (1) and that this overall system in a steel capsule (6) placed, closed and pressed, the layer thicknesses or wall thicknesses of the individual elements behave in a defined relationship to each other. 2. Arrangement according to claim 1, characterized in that the layer thicknesses or wall thicknesses of insert powder (1) to sheet metal capsule (2) to powder (3) to metal sheet container (4, 7.9) to powder (5) to steel capsule (6 ) such as 200: 1 to 5:25 to 100: 1 to 5:25 to 100: 10 to 100 in vertical range. 3. Arrangement according to claims 1 and 2, characterized in that the feed powder (1) is MoSi _x , - The sheet metal capsule (2) and the metal sheet container (4,7,9) made of Mo sheet and - The powder (3) consists of MoSi _x with Mo excess and - The powder (5) is pure Mo powder.