EP0968068A1

EP0968068A1 - Compacting auxiliary agent for producing sinterable shaped parts from a metal powder

Info

Publication number: EP0968068A1
Application number: EP98964406A
Authority: EP
Inventors: René LINDENAU; Klaus Dollmeier; Wieland Kynast; Jens Wahnschaffe
Original assignee: GKN Sinter Metals GmbH and Co KG; GKN Sinter Metals GmbH
Current assignee: GKN Sinter Metals GmbH
Priority date: 1997-11-28
Filing date: 1998-11-18
Publication date: 2000-01-05
Anticipated expiration: 2018-11-18
Also published as: TW434064B; ATE214988T1; DE19752993A1; AR009920A1; EP0968068B1; WO1999028069A1; BR9807116A; KR20000070202A; CA2279275C; JP3386078B2; ES2173662T3; JP2000517004A; DE59803513D1; KR100341359B1; US6224823B1; CA2279275A1

Abstract

The invention relates to a method for producing sinterable shaped metallic parts from a metal powder to which a compacting auxiliary agent has been added. Said compacting auxiliary agent contains at least partially components from the family of polyalkylene glycols. The metal powder is placed in the mould and compacted under pressure before being discharged from the mould in the form of a shaped compacted part.

Description

Description: PRESSING AID FOR THE PRODUCTION OF SINTERABLE MOLDED PARTS FROM METAL POWDER

description

One problem with the production of metallic molded parts using the powder metallurgy process is to produce the molded parts with the highest possible density, since the metallic powders are first filled into a press die and then via a single or multi-axis press using hydraulic or mechanical pressing devices with high pressure need to be compressed. A shaped body obtained in this way, generally referred to as green compact, is then usually subjected to a thermal process

Protective atmosphere sintered, so that there is a solid and precisely shaped metal molding.

The density of the finished sintered molded part essentially depends on the green density achieved, and unlike in the compression of ceramic powders, the metal powder particles undergo plastic deformation due to their different crystalline structure and the associated number of movable lattice construction defects. Due to the particle geometry - also different from ceramic powders - the lubricity of the individual powder particles against each other is reduced in metallic powders, so that even the loose bed in the mold has a pore volume that is almost completely eliminated when pressing only with very high pressing pressures can be. However, high pressing pressures result in high wear on the pressing tool during the compression process and also lead to increased sliding friction of the finished green body in the pressing die, so that here too higher discharge forces with correspondingly increased wear have to be applied. However, high ejection forces harbor the risk of undesired local recompaction and cracking of the green compact. To avoid these disadvantages, EP-A-0 375 627 proposed a method in which the metal powder to be pressed is mixed with a lubricant liquefied by a liquid solvent. Metal stearates, in particular lithium or zinc stearates, and paraffins, waxes, natural or synthetic fat derivatives are proposed as lubricants for this purpose, which are first liquefied, for example, with organic paraffin solvents as the liquid solvent. The disadvantage of this method is, on the one hand, that the dry metal powders first have to be mixed with a two-component lubricant system, namely the stearates and the solvent, this premixing having to be largely homogeneous. Another disadvantage is that this powder mixture must be preheated to a relatively high level up to the softening point of the lubricant used before the mold is filled. As a result, there is also a risk of hooking in the feed devices for the press mold. After completing the pressing process and ejecting the green body, the lubricant must be evaporated in a separate process before the green body can then be heated to the actual sintering temperature. It cannot be avoided here that the remaining portions of the lubricant remain in the sintered body, which, depending on the intended use and the type of pure or alloyed Metc-.ll powder used, can also lead to disadvantages.

From EP 0 559 987 a metallurgical powder composition based on iron is known which contains an organic binder for the iron-based powder components and the alloy powder components. To improve the pressing behavior, the organic binder contains a proportion of polyalkylene oxide, which should have a molecular weight of at least 7000 g / mol, but much higher molecular weights are preferred.

The invention has for its object to improve the methods described above. This object is achieved with a method for producing sinterable metallic molded parts from a metal powder which has been mixed with a pressing aid which at least partially contains components from the family of the polyalkylene oxides and which is filled into a mold and after compression under pressure is ejected from the mold as a pressed molding. The use of pressing aids which contain at least portions from the family of the polyalkylene oxides, in particular the polyalkylene glycols, preferably the polyethylene oxides, in particular in the form of polyethylene glycols, has surprisingly shown that in order to achieve high densities and high green strengths, much lower compression pressures than are to be used with other pressing aids and that the forces necessary for ejecting the pressed molded part from the pressing mold are significantly reduced, so that the disadvantages of the previously known methods mentioned above are avoided. A special binder in the powder mixture is not required, since, due to the "lubrication" of the powder particles moving relative to one another during the pressing process, not only a high density but also a high strength of the green body due to the much higher "packing density" of the powder particles and thus an increase direct contacts between the metal particles in the powder can be achieved. A high green strength is always desirable if the green body is to be processed before sintering. "Metal powder" in the sense of the invention refers to the powder mixture intended for the production of the molded part with all alloy and acid additives, with the exception of pressing aids.

A particular advantage of the pressing aids selected from the family of polyethylene oxides, in particular when they are used in the form of polyethylene glycols, is that an appropriate selection of the molecular weight can influence the pressing parameters, both with regard to the flow behavior when mixing and when filling the form, as well as in terms of softening point and thus the temperature control and the material flow during the pressing process. It is particularly advantageous if the pressing aid proposed according to the invention lies with its softening point between 40 ° C and 80 ° C, so that, for example, in series production, the tool temperature that arises during continuous pressing is usually sufficient to ensure that the powder mixture flows properly Filling into the mold as well as during pressing. Accordingly, the metal powder mixed with the molding aid can be filled into the mold at room temperature. In series production in particular, it may be expedient to heat the pressing tool accordingly in order to compensate for any interruptions in the series run. Controlled heating of the pressing tools to about 55 ° C. is expedient, so that both heating due to the frictional heat and cooling due to work interruptions are taken into account and constant pressing conditions can thus be specified. This considerably simplifies the handling of the metal powder, in particular the filling process, since it is possible to work with "cold" powder, that is to say with powder at room temperature. Caking, lump formation or the like cannot occur since the heating of the metal powder mixed with the pressing aid takes place only in the press mold. For extremely large parts, additional powder preheating can be useful.

The further advantage of the low softening temperature is that immediately after the filling, the pressing aid portions in the amounts of metal powder in contact with the heated mold walls are theirs

Preserve softening temperature, so that during the subsequent pressing process the relative movements occurring on the tool walls between the powder filling and the pressing tool are already "lubricated" and so the friction in these areas is reduced. At the subsequent full

When pressurized, the entire powder filling is heated above the softening point as a result of the pressing pressure, so that the internal, as a result of the particle geometry

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3 P ¹ P φ Φ GP P- <! tr P φ et G 1 φ HN P- Pi tr P rt P- P- cn

P Hi G P- Φ p: Φ 0 P- rt G φ o GPCZ rt P Φ cn cn Q) tö P ^J cn GG g rt Pi P Φ GZGG: G Φ a P 53 G Ω 3 o cn 3 • Φ rt cn p. PP a tr H XI Φ P a P rt tr GP »tr rt

P- s: cn Φ Z a Hl G Φ Φ ~ -J P- P- P a Φ cn Φ P- rt • »Φ 3

^ Φ rt tö Φ P- "« • Φ Φ <G = a GP LΠ • X! • X! N Φ PGP ¹ Φ NG o

Φ P- rt •! Ω P- 3 o tr φ P- G <-. P P Ui H rt G Φ P rt tr cn cn P P G tö Φ <n G C: Φ •• G Φ cn cn cπ Φ tr P "o G φ cn • J G G c P- t cn tr P P H 3 Ω J o X

^ cn P ^J Φ a tr P- φ G a P ¹ G -j Ω φ φ Ω z P P- tr ^^ o G

1 Φ Φ t <PPG: G cn • XJ <Φ tr PG tr φ s: et P- Ω P ¹ tr P- cn rt cn P- tr et Ω a φ σ P a cn G Φ et Φ 3 tr P

P G Φ P 3 Φ Φ tr P Φ P <Φ i φ φ rt a P- Φ a P- X)

Φ p: Φ P- PP r- ¹ GP Φ 1 et P- G Φ Φ 1 P- H cn φ

P- • XI P Φ G P P Φ G 1 rt P- 1

G 1 1 1 1 1 G φ φ 1

P- <υ σ tr ω P P- Φ rt Φ Φ P- to cn cn <«Ό

Ω Φ G P- tr P P Φ

O Hl <P ^J

GP Φ cn tr Z

Φ P t φ

P- Φ P-

G G N cn

Φ cn Φ Φ

P- a G J W

Φ P rt rt

G Ω tr rt tr a "<

P

P- a cn Φ

Ω Φ G tr 3 H Ό φ P P-

P XJ n

<G Φ cn φ • X) tr c +

P Φ G Φ tr X3 P- P

Φ φ cn P cn tr O cn Φ tr •

Φ G Φ P ^J

P Φ P- P

C G 3

G a P- J Φ a rt P •

N P c G a G φ

P a z Φ

X Φ G φ P a

G G

G ι-3 G

Φ φ • P

G Ω

• tr a

G Φ ta P- cn

P- X

Φ 33

P P tr ta

Φ P-

P- Φ 1

P

however, the disadvantages described must be accepted.

Finally, curve 3 shows the result when using the method according to the invention, which leads to a clear increase in the final density.

The green densities and green strengths that can be achieved depending on the baling pressure are shown in the tables below. The results are compared here, which result from different mixing processes for the metal powder mixed with pressing aid and different pressing pressures.

Compression pressure Mixing Density Green strength in Mpa g / cm ³ 3-point bending test N / mm ²

Table 1

Table 3

Table 4

Table 5

tö Ω Φ G a a H Ό y 33 a a a σ cn g Z G o a et X 3 3 H et Z X X Ό ι-3

P- P Φ P- P P- PG φ • P P- P- P P- rt φ φ G Φ GP φ rt P- P- G P- GPOGP φ = a G tr Ω cn P φ cn Φ Ω cn Φ P- et X! a cn P y cn Φ cn et O P y y y tr

XI G o Φ Φ tr t-3 P rt tr • XJ PC Φ et rt P- Ω a G a et <Φ φ Ω cn N rt 53 P rt tr a Ω et Z t-3 et y G a G ^t ö P- P- XI tr X) Φ P Φ " _^ 3 φ y

<Φ tr G Φ P tr G P- P Φ PP y «XI cn P 3 XJ X) Φ rt y P y • p- P y φ cn 3 P φ P y φ G = P σ et Φ 3 P- Φ Φ XP Φ Φ a rt Φ

P rt tr P a N 3 y φ G Φ 3 Φ φ G P- Ω to t 3 Φ GP P- H Ö • 3 cn P- P- cn H- G y G: G ≤ G y P- rt tr tr φ P- P- G σ Ω P P- Φ p-

G J φ cn Φ <Φ tr XJ φ Φ rt <y y a et P- P cn et XJ φ tr tr> φ tr P- et

Ω X P P- <Φ P y Ω cn cn φ φ Ω Φ Φ y y φ Ω P Φ Φ G. G N

G ^* Φ tr <rt Φ PG •. tr rt Ό P tr P P- p- P- tr • XI a P y cn Pi Φ Φ φ

P- φ Φ tr P Ό GX cn P- P • Ö φ G Ω cn Ω rt Φ φ X y et P tr 3 P- P- tr rt P- G Φ NP P- X3 o φ J Φ PG tö tr 3 tr Φ XJ PP ISl φ Φ tr Φ G XI

Φ o Φ Φ cn - "y X Ω φ NG a P- G Φ y C P- Φ P- g Φ rt cn ^• ga WP P- 53 rt tr cn Z Φ tr to Φ G y G: φ rt a G Ω et cn t X) P "o 3 rt G Φ P- Φ Ω rt φ P- P- φ rt P- G <G p- rt Φ tö G = PQ) φ y tö y tr

P- PP cn rt tr a P- 3 P et G XJ a Φ GG Φ PG tr G: <3 p- G φ P 1 Ω P- a Φ P- GZP 3 P- XZ rt P Φ Φ yy Φ G Φ 3 cn G Ω Φ φ

3 Φ z G cn Φ o G et G Φ a P- P- et P cn o <P a P φ et a N 3 Φ tr P rt φ ω Ω G P G ö G P- φ P a tr Φ Φ tr -. tr Φ P- Ό

• G Φ Φ rt ZP tr a P- tr • «a PGJGG a P- P P- P Φ Φ P a Ω P cn a P P- Φ P- y φ c rt φ Φ Φ P- Φ • Φ φ y cn o P ω φ tr φ Φ PX! 3 Ω et P- σ P Φ h j z G G = cn Φ N <Ω cn a Φ • G rt 53 rt cn Ω rt Ό tr

P- Ω P P P o P cn a Z a o σ ≤ a tr i φ Φ G Φ rt N P Φ et <

Φ tr Φ Φ O: tr P- Φ P P- φ P P- φ P φ Ω P P σ 33 C M c-- Φ P o C:

P- 53 Φ cn Φ G P- cn G cn Φ P a G g- φ Ω G φ Φ Z G P G P- P P- G P

P Φ> Ω rt P- et P- • XI Ω rt rt rt G 3 P P P P P- G XJ XJ a G rt 3

G P- G tr 3 G Φ Φ tr y Φ Φ Φ P G P- <G Φ Ω rt G P Φ P- G o a

<X) G cn et O: tr P 3 φ P- tr P Ω G Φ φ Ω G tr Φ Φ a a tr Ω N P to "• P

Φ Φ rt X) Φ Φ ZXG Ω Φ N tr a PP tr NG Φ PG tr G Φ σs cn JG P- Z y P- P- P Φ g tr G P- G: 3 rt φ aa • P P- et 3 XJ P

Φ Φ P- P- GPG oa φ a Φ P 3 a P- Φ φ P σ Φ X) cn Φ Φ φ Ω <tr cn JP Ω Φ 3 G P- ^■ φ y O: Q) rt P- rt a cn Φ G ta Φ ö 3 p- Φ o

Φ 0 a tr P- Z Φ Φ P cn • P tr Φ XJ 3 rt y z Φ P- rt P- cn G P P- Ω Z P

G j a • φ G Φ XI G X rt Φ P P- y P- Φ G P P g y Φ rt G- G φ cn tr p- cn

Φ Φ Φ Φ P- Φ G> φ G P G P- rt P "G cn P- X p- P Φ P a 5o Ω Ω rt

GGP tö σ 3 et 3 yy P P- P Φ Ω XJ w cn P Ω 1— ^• a tr <tr Φ

P Φ P- Φ P- p: P rt J G G X tr a P- a P Ω y tr N y Φ a P et o rt tr

≤ G Ω cn Ω P) P cn to P φ GP φ P- y P- P z tr et φ φ et P- Φ GG cn Φ φ GP 0 tr P Φ Ω rt xj a P et 3 • 3 y φ 3_ GP φ φ Φ P- - GP Ω G 1 G

P rt G: G et Φ P tr. φ φ G Φ Φ et = G = P- G 3 cn XJ XG Φ o \ ° a rt Φ G a φ 53 et 3 cn GGP <; _^ a tr Ω rt rt a Ω a rt

Φ G φ a> Φ P- J rt X) φ w Φ φ tr tr <Φ P G P Ό Z P P

Φ PGPG cn Ω Φ 33 Φ Φ P 0 a PPG Φ φ P- cn cn cn: PPPGG tr ω cn cn PG cn tr P- Φ Φ 3 XG Φ G P- P XJ P- XI GP c • P φ 1 et tr Ω et g et GPP P- P rt P ^t ö X, Ό Φ Ω PX Ω <_n ^t ö φ

N tö P- P Φ X P- Φ ιP X t + G = cn PPG φ cn Φ PP tr φ G φ rt tr o 0 XJ φ G XJ C Φ rt C Φ Φ Φ P Ω y X ay P rt P- φ G a XJ cn P- oy φ

P- G X Hi a <J P G cn G G tr y rt P- <J Φ G cn G G 0 cn et cn <o • ^ tr

Ω X Φ Hi Φ 0 P- 'a φ G _^ a et G a Φ φ P- 3 Φ cn J φ Ω 3 P- Ω Φ φ φ tr rt P- p: PG ay et Φ P- Φ G P- P σ Ό P Φ tr tr P XI tr PJ rt G

G 1 rt y φ Ό a NGZ Φ cn XJ Ω Ω 3 rt Φ G a Φ rt X Ό ~ - _^ tr φ φ »y ö 00 PC Φ et p: tr P * PP Pl φ GZ Φ φ T3 P 3 ^

G P- P- oy P Φ y tr Ω tö et φ rt cn P Φ Φ PPP P- P Φ O yg σ X) Ω o Ω <G p: PPG tr φ P- P P- rt 3 P- Φ P P- rt o 5o y φ φ ι_J. P- tr P Φ PI to Φ G: y Φ rt P- Ω G Ό G Ω P- 3 P • Ό rt - G rt φ Φ P- et g C: P φ rt GG <• XJ tr X tr P φ Φ PG yo X! P

1 cn φ Ό G _^ 3 O «a 1 φ G: a φ P cn G: Φ XJ P ayy rt P 1 1 1 PG Φ 1 PGP φ 1 P y 1 P 1 1 1 cn 1 1

LO ω> to y y ι o LΠ o LΠ o UI

o G -d σ cn Φ Ui 23 tö P 33 rt H ir ¹ 3 H rt ir <rt P- cn 3 a G Ω cn a W gaa α MZ

P P- y P- P- G et P c φ P- Φ G φ P- P- Φ p: φ Φ 3 Ω P- Φ Φ tr φ Φ G o C: Φ P- P φ

G φ P- Φ Ω rt P P y G Φ P rt XJ cn cn P rt «P G tr cn G P φ P- et y P P Φ G P-

Ω a φ tr 3 G <Φ 3 P- Ω Φ cn • _^ P- <Φ Ω • GG cn cn φ P Ω y

XP 53 cn P- a Φ P a G P- φ tr G φ tr Φ G tr cn • _^ rt Ω X rt Ω P tr cn

P- <rt a cn rt P- P G P- cn P et Ό Φ a P y P a et σ Φ a Φ tr G Φ P G

G • X) φ Φ φ Ω Φ cn 3 Pi Φ> Ω G G G P- c Φ J φ φ P- tr a: P- φ y G: cn a a

G Φ P P- P tr P- Ω P- P tr G G y rt Φ G P- y G Φ P P- P • X! P- P P G Φ P- a G tr «P tr y tr cn a <tr φ J G <cn • X) tr φ« cn φ Pi φ a P C a a cn φ

P φ <P Φ Ω P- Φ Φ G cn a φ ^• T) a cn rt P- o tö a rt P φ • XJ Hi P- φ pi g P * POP φ tr Φ P P- JPP Φ rt • Ω tr G P- C: w Φ GG Φ Ω G «XI 3 φ 0 rt GPG: PG cn rt <G a P- P Φ tr P" P- cn G c G a Z a tr PP

3 H Φ G rt 3 tr i G Φ G cn φ y P- G Ω P- w Φ rt G Ό XJ P- P- et <G: X

• 6 φ GJ Φ P- Φ P • XJ G Ω cn <Φ G tr tc y P- N ^• T! Φ Φ PI a P- Ω Φ Φ o G P-

Φ X P- rt P tr Φ tr Ω 3 φ a rt o Φ G G G P cn G Φ P a cn tr - «P Φ 3

P G a a y P <! P φ tr P- P g - 3 φ 3 y Ω P to φ et et <cn G P

PP ^J Φ Φ ιQ a φ Φ JP φ P- ao «<a tr cn rt P Φ P- rt y rt P cn P a GPGP P- N P- a P cn P- PX) G tö X Φ Φ O Ω Φ tr tr <PG Φ tö φ

G P Φ rt cn N φ Φ rt Φ G Ω Φ y Φ T3 P P P P G tr P- Φ Ω P- O z cn tr P

P XJ tö Ω P Φ J P- P P- et G tr cn G n G: P ¹ P- y P- P Φ G φ tr Φ G = cn φ PPP tö φ Ω G ιP a G Ό P- Φ PI rt GP a Ω Ω 3 G = PG φ G Ό

N z Φ C: w P y tr Pi Φ a z Φ G G φ rt P G P- G P tr tr G tr C a tn a y Φ

G P- to G P ta φ P- et Z G P P- 3 XJ y P- p: G xj Ω XJ P et φ ≤ Pi Φ G c O Φ P- • M

P Ω tr Hi Pi o 53 G Φ Φ cn P <G rt C 3 Φ tr Φ PGP Φ P- et GGGG P-: tr P- Φ P- 3 tr ιp et G aw rt φ φ G 3 et XI G a P cn Φ J a X) Hi

Ω rt P- cn G O P- rt a X tS) • P- tr P 3 Φ a a P- Φ cn φ G 3 rt a P Φ.-3 cn P-

X P rt a • XI y Z P- P G cn Φ Hl P- Φ cn Ui tr cn G P- P- φ P P cn

N P- cn P- c φ H Φ • XI G 3 H Φ P O: g G «P Ω et Φ P a P-« P Φ -0 P- Φ tr φ Ω

G G 3 xi G G cn a P φ G P- P G 3 P Φ Φ 0 tr P G tr tö cn X o G Φ P- tr

Pi P- X xa P- 3 P- a cn cn Ό P- 3 rt cn tr <et G Φ N P a Ω Φ tr o φ P y G φ

G = a rt Φ. et P- Φ Φ et tr Ω rt G cn P- P y Φ Φ tr GG φ P- tr P- Φ o cn tr y rt tr φ et P- p: et G tr φ tr y Ω J ya φ PG rt y to Φ rt P- Φ φ P>

P P Φ rt rt et Ό φ P- φ a <tr φ y P- G rt t i φ tr o - «3 XJ tö P G P- c

Φ y Φ c P 3 G P φ G> υ Hi cn Φ tö G G cn P- w P o rt Pi

G g Ui P- N yya 3 GP <G Hi et P- GG cn φ yo «P a ≤ 3 ^" y PP rt y

" _^ Φ cn G <P P- φ a P o P ¹ yc O y P * a QJ G Hi tr P P- P o ^ G tr • P ι + 3 rt P Φ cn P Φ Ω PP Φ <cn Pi G 3 _^ cn y G Φ PP "φ Ω N tn a P P- tr GP Φ Ω Hl cn tr G tr XJ φ P- Hl G Φ tr 3 3 φ J 3 rt tr G rt

PP "rt z P- Pi cn tr P- N Φ P- PO XJ P φ φ a P- G a N tr y - _^ y OG a O: φ G tö φ G tr Φ • _^ G φ P- GP rt cn a P P- C ^• ^ a φ

N Ό a tr a P- P P- a P P y P P cn P a G cn 53 rt rt P- P cn P y Φ cn tr

C Φ y Φ Φ 3 G <G Φ Pi P G G tr y XJ φ P- φ Φ Φ 0 φ P Ω C: φ P Φ Φ

3 y 3 G P- cn o G 53 o • XI a G Φ Φ P P Ω P- rt tr y Hi G tr Ω G G P-

P • w • X) tr P X3 tr y φ Φ XJ P- xi tr tr GN Φ i Hi M Hi φ X ιp Ω a φ Φ <G P- φ Φ tr cn P- • JP y cn P- Ό rt φ G P- rt P- GN y P Φ a

P- Φ Hl cn G cn Φ «XI y rt G et tr a Φ Φ G P G C: Φ cn N C ^ G-- Φ

G P G φ O tr φ Hl φ Φ P P- y DJ XJ Φ tr P- φ G N Pi X G <P

Φ P tr a Ω G tr ¹ GP 3 cn P- Z cn 3 et G <3 = P- Φ y GPCC: o Hi Φ

G rt p: P tr et Φ a G p: 3 G cn P- rt Φ Φ Φ t ^ l a G P Ω Ό G = tr - φ P a

P y cn Φ «P φ a 53 P- OPPNGP P- P Φ tsi tr G Ω <P cn cn tr P a P- et a P- P- P y Φ rt φ a GG ta Hl P- G cn 3 O φ y X Φ φ et Φ G c XG σ P y Φ φ GG et P- a • _^ a G go O: G XJ JG <NPG 3 P- cn G

P P- φ P Ω P G Φ G P rt p: Φ 3 P XJ φ Φ 33 φ φ G N P- XJ cn

Ω G cn cn P- tr C tr J <y Φ 53 G Φ Ω et O 3 φ P P- PG 3 P Hl Φ cn et X φ φ tr G 3 cn G φ G Φ Φ i 3 3 P- tr P «P P- P • ö GP P- rt G: P- Φ φ P P- rt p: Φ GJ P- a P. Φ y ω y Φ • XJ P N 3 Z rt Φ tr Ω P- Φ P- G G a Φ 53 P N cn 3 Φ Pi Z P- a Φ et y G φ tr o G Φ P- P tr G P- rt G

P- P P- Φ φ c tr P P φ G P- Ό P- G P σ 3 J P Φ y Φ G • G -. x>

Φ • P P- G φ tr P- Φ xa ac 1 Hl φ P- Φ 1 P- 1 G Φ Φ J 1 1 1 t φ P y 1 1 1 1 G 3 et 1 cn 1 1

very homogeneous mixture of pressing aids and metal powder and on the other hand because of the thin "lubricant film" already achieved during mixing, which is further reduced during hot pressing, there is a much higher frequency of direct contact between metallic surfaces between the individual metal particles, and so the input described plastic deformation and entanglement of the metal powder particles can be achieved.

Surprisingly, somewhat higher values than in Table 2 were also obtained for a molding aid mixture from the amide wax and with a proportion of about 40% of a polyethylene glycol with a molecular weight of more than 6000 g / mol, which was mixed warm into the metal powder, which was then pressed hot has been.

In Table 5, the values for the metal powder are shown as a reference, to which an amide wax was cold mixed as a pressing aid and which was cold pressed.

Claims

Expectations

1. Process for the production of sinterable metallic moldings from a metal powder which has been mixed with a pressing aid which at least partially contains components from the family of the polyalkylene oxides and which is filled into a mold and after compression under pressure as a pressed molded part from the mold is expelled.

2. The method according to claim 1, characterized in that the pressing aid contains at least one polyethylene oxide, in particular at least one polyethylene glycol.

3. The method according to claim 1 or 2, characterized in that the pressing aid is contained in the mixture in an amount of up to 5% by weight, preferably less than 1% by weight, based on the metal powder content.

4. The method according to claim 1 to 3, characterized in that the pressing aid has a softening point between 40 ° C and 80 ° C.

5. The method according to any one of claims 1 to 4, characterized in that the pressing aid has a molecular weight less than 7000 g / mol.

6. The method according to any one of claims 1 to 5, characterized in that the pressing aid has a molecular weight between 100 and 6500 g / mol, preferably 3000 to 6000 g / mol.

7. The method according to any one of claims 1 to 6, characterized in that the polyethylene oxide has a molecular weight of more than 6500 g / mol at a proportion of less than 40% of polyethylene oxide in the pressing aid.

8. The method according to any one of claims 1 to 7, characterized in that the pressing aid has a hydroxyl number from 5 to 700.

9. The method according to any one of claims 1 to 8, characterized in that the pressing aid has a density of 0.9 to 1.25 g / cm ³ .

10. The method according to any one of claims 1 to 9, characterized in that the metal powder mixed with the pressing aid is filled into the mold at a temperature below the softening point of the pressing aid used, so that there is a softening of the pressing aid by energy introduced into the Press form, preferably during compression (hot pressing).

11. The method according to any one of claims 1 to 9, characterized in that the metal powder mixed with the pressing aid is introduced into the mold at a temperature below the softening point of the pressing aid used and is compressed without the supply of energy during pressing (cold pressing).

12. The method according to any one of claims 1 to 11, characterized in that the pressing aid is mixed into the metal powder at a temperature which is at least in the range of the softening point of the pressing aid (warm mixing).