DE2006066A1 - Process for sintering powder bodies and furnace for carrying out the process - Google Patents

Description

Allmänna Svenska Elektriska Aktiebolaget Västeras / Sweden -

Process for sintering powder cores and furnace for the implementation of the procedure

The invention relates to a method for sintering powder bodies and a furnace for carrying out the ' Procedure ♦,

High density and freedom from pores in powder metallurgy manufactured carbide bodies for tool purposes means high quality. In the case of cutting tools, high density means, among other things, increased wear and tear » and lower risk of cutting edge breakage when rolling and the like means freedom from pores; it increases pest severity

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and better surface fineness, which in turn means = that one can obtain a greater surface fineness in a rolled product. Also in the production of electrical resistance bodies, for example from MoSi _2, a very high density and freedom from pores mean significant advantages. The strength increases and the risk of local overheating and subsequent burns is reduced. The advantages in the form of high density and pore freedom are just as great for kermets of various kinds.

004-0667 T32-2. ORIGINAL (NSPSCTED

Great density and freedom from pores have been achieved so far by enclosing a pressed powder body in a gas-tight, heat-resistant envelope made of a suitable metal, after which the envelope was evacuated, sealed and placed in a furnace in which the material was sintered under the simultaneous action of high pressure . Temperatures and pressures were up to 1BOO ⁰ C and 2000 bar used. Attaching an envelope to a compression molded body, especially if it has a complicated shape, evacuating and sealing the envelope, as well as removing the envelope after pressure sintering, results in high costs. Particularly in the production of small cutting elements, encapsulation means a considerable increase in costs in relative terms. The problem is how to do the sintering and hot pressing under conditions such that the desired quality can be obtained without costly encapsulation.

The invention relates to a method according to which sintered powder bodies with high density by fining powder bodies, preferably under vacuum, which have been shaped in the usual way by pressing powder and the bodies are hot-pressed after sintering under the direct action of a pressure medium. The sintering the body and the subsequent pressing will thus executed without the body in a gas-tight

009886/1322

Hü.-le are encapsulated. According to the invention made from an iuiver or a powder mixture Body uei Atmarenaruok or lower pressure and sintered at such a temperature that powder grains made of cenis-iiben material are connected or that a binder other powder grains contained in the powder mixture connects, according to which aie body under the direct action of a pressure medium such as argon, helium, nitrogen oaer hydrogen * are isostatically hot-pressed. "

I-ine aen.cable explanation for the fact that the density of Gesinlenen iroauriten is increased by isostatic;: hes hot pressing who .it ι: can advertise, although the bodies are not enclosed by tesonized envelopes, is that the pressure medium prevents us from doing so. 1, to fill in the voids created between the bound powder grains. The Binaemittel bi-Viet aabei a closed Karsei around each cavity and prevents the Iiruckmittei because sudringen like in this one. In the nachfo. ^ End Varmpressen the cavities in the same manner veraoiiwinden as in hot pressing materi- which is enclosed in an envelope, if pressure and temperature are selected so that the Bindemittei is sufficiently easy ieformierbar so that iie bonded powder grains slide against each other and fill in the empty spaces.

? ί; ΐ ^Λ ias procedure is a special furnace of: er Art

009886/1322

BATH ORIGINAL

used, which has an insulated furnace chamber enclosed in a pressure chamber. The pressing is done immediately after carried out after sintering and begins at sintering temperature. During pressing, the temperature must be at least set such a value that the binder is so easily deformable that the trees closed are pressed together. Temperature and pressure are of one another and depending on the powder composition.

The method is applicable to powder bodies of various Kind, especially for carbide products that include WC, TaC, TiC, or VC or a mixture of two or more of these Substances, as well as a binding agent consisting of Co and / or Ni and possibly Pe, contain · In the usual way, every powder Shaped bodies are only sintered at atmospheric pressure or lower pressure, preferably under vacuum, see above that the carbide grains of the substances contained are added together. Binder amount and temperature will be like this chosen that most of the remaining cavities or pores between the powder grains are completely closed, after which the sintered body is placed in a furnace with an in a pressure chamber enclosed furnace space is isostatically pressed. This pressing is advantageously carried out at the sintering temperature executed, i.e. a temperature at which the binder can be plastically deformed relatively easily or possibly fluent or at least almost fluent,

009886/1322

and with one. Pressure medium that acts directly on the body- '. ' surface works. This eliminates the costly encapsulation of the powder body, which was previously the case with pressure sintering or hot isostatic pressing was deemed necessary. The hard metal bodies usually contain. 0 - 99 # WG and / or TiG, 0 - 30 # TaC, NbO and / or VC as hard particles and 1 - 30 j £ Co and / or NC as well possibly iron as a binding agent. Most common are bodies with 0 --99 '$ WC and / or TiG, 1 - 30 # Co and / or Ni as well as other substances in small quantities, mainly as impurities. The sintering itself can usually take place at a slightly lower temperature than normal sintering at atmospheric pressure or under vacuum, because an equally good filling of the gaps between the grains as was previously no longer required during sintering itself. It is only important that the cavities and pores are well closed, so that isostatic pressing without special Hül ^ -e can be carried out with good results. ; Somewhat smaller binders can possibly be produced from the same five-round be used. Lower temperature also means there is a risk of binding agents during the Sintering, which runs down the body, becomes less. You can possibly be satisfied with the powder-'body before isostatic pressing only on the surface

. ■ '■■' ■ · = -. · '■■' ■■ - '-! ■ ■ "■ '■". "■. ■ · ■'. ■■ - ^: too sintein. The sintering temperature is usually '

- 1200 - 16Ö0 ° C * The following isostatic pressing is ^ in most cases zweokmäsaigerweise at 800-1500 ⁰ O

¹ ^ ORlQlNALlNOf ¹ ECTED ^ ^!

O0dÖ8S7ia22

and 100 - 2000 bar. As a general rule, that an increase in pressure means that a lower! temperature can be applied to the same To achieve sight. The sintering and the following. Pressing leads to the best result when both are in one and the same furnace can be run. If the sintering takes place under vacuum, a pressure chamber is one separate vacuum valve with large flow cross-section necessary to achieve the required pressure reduction. The grain size of the powder used is expedient 1 - ^ yum.

The process is also suitable for the production of electrical radiators, for example from MoSip and glass. Powder prepared from the body at a temperature of 900 - 1 400 ⁰ C sintered, after which the body under the direct action of a pressure medium at 100 - be hot pressed isostatically 1400 ⁰ G - 2000 bars and the 800th The grain size of the powder used is usually 1 - 75 / um

A third group of products for which the process can be used are kermets of various types. A kermet made from 90 - 99 i> Al ₂ O and 1 - 10 56 Ag is produced by pressing a powder with a grain size of 1 - 50 µm into bodies which are sintered under vacuum, usually at 10 "Torr or lower and leaving 900 - HOO ⁰ G, so that closed pores or voids are created.

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ORlQtNAL INSPECTED ^

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after which the body is isostatically hot-pressed under the direct action of a pressure medium at TOO - 2000 bar and 800 - 14-0O ^{0 C *}

A fourth product, which may be prepared, billets are made from uranium dioxide powder of uranium dioxide is sintered in hydrogen gas atmosphere or under vacuum at a temperature of at least 155o ⁰ C and then at * a pressure of IVX) - 2000 bars and a temperature of 15 'V - IsOu ⁰ C warra-pressed. A number of other products should be able to be manufactured using the process.

As an example of the technical port step that this method represents, it can be mentioned that sintered bodies that are manufactured according to the usual method generally contain 130-500 times as many cavities per unit of volume as bodies that are manufactured according to the method according to of the invention are made. When comparing I with the previous method for -'Drucksintern ".- of fulcrum bodies which are enclosed in an evacuated, heat-resistant cover, one gains the advantage that a 'time-consuming and costly operation is omitted. The method enables sintering without a cover , without cooling the body between sintering and hot pressing, and without complicated transport arrangements with sluices that prevent the hot bodies from coming into contact with air. When pressing uranium dioxide UO ₂ , a density of 99.5 £ of the theoretically achievable density seems to be possible.

009086/1 ^ 22. -3-

The invention also relates to a furnace in which both sintering and hot pressing can be carried out and which is therefore particularly suitable for carrying out the method. 5 oven of the invention consists of one cylindrical pressure chamber with a high pressure cylinder, in this cylinder protruding end closures, una arrangements for the absorption of axial forces, which from an in the pressure chamber enclosed pressure medium on the end closures be exercised. The furnace space and the heating arrangements are enclosed in an insulating sheath Form of a jacket surrounded by an insulating lid and base. The furnace is characterized in that the one End closure, usually the lower one, with an annular part with a member sealing against the cylinder is provided, as well as with a valve disk covering the opening of the annular part, a sealing member between the ring-shaped part and the valve disk, a vacuum line that can be connected to the ring-shaped part in a sealing manner, as well as a member for separating the valve disk from the annular part, so that when vacuum sintering an opening with a relatively large flow cross-section can get.

Usually the vacuum line is connected to the oven in such a way that it protrudes into the annular opening of the end closure. The connection line can be used to connect the valve disc in relation to the

009886/1322 "9"

200606 «

ring-shaped part to worship. To move or shake to avoid the batch in the furnace, the line is introduced, If it comes into contact with the valve disk, after which the 'annular' of the end closure is lowered, see above that there is an opening between the furnace chamber and the vacuum pump receives. To reduce the stress on the valve head, / especially if it has a large diameter or has a small thickness, it can be marked with an outstanding Be provided with part that, when the valve * opening is closed, supports the organ that acts on the end closure Absorbs forces.

The furnace according to the invention is illustrated below with reference to FIG Drawing described; in this show

Fig. 1 shows a furnace, partially in section, with a

trans-por-t aiii en J press frame that has a , High pressure chamber with a furnace chamber pushed

and absorbs the forces acting on the terminations when the oven is under pressure , is set, '

Pig. 2 and 5 a section through the lower part of the pressure chamber during hot pressing or vacuum sintering,

Fig. 4 is a section through the upper part of the pressure - * - chamber and .... ·, -

5 and 6 sections through an end connection along "lines AX baw # SB inJU", 3rd.

;; , .-. . ; '■■; ";. -.10.«.; -000886/1322

In the drawing, 1 denotes a press frame, aas between the position shown in the figure uni a La ₁ J '' * in which the high-pressure chamber 'L umgibö, movable-icr · is arranged. The frame consists of yokes 3 and 4, inserts between them and a band jacket 6. The frame is supported by rags ₍ which run on rails G. The high-pressure chamber 2 is supported by a column 9 and contains a high-pressure cylinder consisting of a inner tube 10 and a surrounding band jacket 11 as well as end rings 12, which hold the band jacket axially together and serve as fastening for brackets with which the high pressure chamber is fastened to the column. Chamber 2 has an upper end closure 13 »in, the pipe A sealing ring 14 is located between the pipe and the end closure. The actual furnace space 15, in which the charge 16 is located, is surrounded by an insulating jacket 1? Layer 21 and 22 consists of insulating material and two end rings 23 and 24. The jacket 1ν is a central ring on the upper end closure 13a hung up and connected to it in a gastight manner. In the upper part of Hanteis 17, an insulating cover 25 is inserted, the sleeve consists of a sheet 26 which is filled with insulation material 27 and provided with passages 28 for electrical lines to the heating element 47th The casing 26 is fastened to a fastening ring 29 which is clamped between the ring 24 and the upper end tube 11. Yes the ring

009886/1322 - ri -

BATH

ϊΐίηϊ Itu-u-ii for the! O-rings 3 ^ uni 31 · Between the: ^:) 3cke :. <ö .Una the upper end closure 13 forms a. ^ '■ • Scji'ivöscr Haue 5 ^, outside mix den: Oven space 15 only through t \ lne) ru3icau3t :. sici.s. opening; '; ^: connected stent. In aem ivauia 1-2 iiann a heating element ui ;. a supply line angcorln «t v.-rüen, which iedcv-U is not shown. In the egg closure there is a duct 34 with a duct 5- for a supply line 35. In the closure there is also a duct 5- for the supply von Jruekinittel and an urn iür den .Sealing ring 14 arranged. The channel 3 opens in the column 39 between. the inner V.and of the tube U and the outer tube 10 into the 'jacket. 17 · The heating elements 4 <are carried by a pipe 40 which surrounds the furnace chamber 15. The elements are fastened to the outside of the tube 40 with the aid of slotted rails 41 'through which the heating elements can be inserted. The tube 40 is suspended in the cover 25 by means of protective rails 43 located on the inside of the tube. Between the cover 25 ″ and the pipe 40 there is a gap 44, so that openings are formed through which the connecting parts of the heating elements of the gap 46 can run between the pipe 20 of the jacket 1 / and the pipe 40 a! pressure plate 45- with -a hat for the electrical line

. The pressure chamber has a lower end closure consisting of an annular part 5P with a seal 51,

009886/1322

As opposed to the inner surface of the tube 10, there is a flat valve part 52, which forms the smaller eyehole 55 on its saddle and the larger bore 54 on its inner one * In the ring-shaped part 50, there is a valve disk with an internal pinholing 5, which seals the synthetic surface 52. The valve disk 55 has a pin 57 protruding closer to the bottom with such a length, diiss

^ its lower surface with the valve closed on the same Notch as the lower surface of the ring 50 lies and spmit the Joeh 4 of the frame 1 supports when the pressure reaches the end «- lock against this presses. The valve disc is £ 5 »With a number of axial guides 5d, dip of of the bore 54 and thus the valve disk 55 in relation to the annular part 50 « trier. On the valve plate 55 rests an insulating base protruding into the insulating jacket 17, consisting from a sheet metal attached to the valve disk

'with a thick layer of insulating material o1. On this one rests a plate 62 on which the charge 16 is placed. This plate consists of a material with good thermal conductivity and can be equipped with radial channels l3 and 04 between its perimeter and a central tree o5 be provided. Because the plate 62 is a good Has thermal conductivity, can be the central part of the batch heat can be supplied via this plate. The channels help to circulate gas between the space 65 and the gap

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BATH ORIGINAL

the plate can circulate so that the heat through it ·. the plate are passed to or from the central part. can.

In order to generate a vacuum in the furnace, there is a vacuum pump equipment (not shown) which can be connected to the pressure chamber via the lower end closure shaped as a valve. The connection is made by means of a suction tube / O ^1, that of the ring in the bore 53 | Shaped part 50 is pushed in and sealed against the bore with a sealing ring 71. The tube i'O has slots 72 at its outermost end, between which remaining material forms protruding supports 73, ν In the embodiment shown in the figures, the suction tube is pushed into the bore 53 so that the supports 73 come into contact with the valve disk 55 come, after which the annular part is lowered to the position shown in Figs. 1 and 3 and the valve is opened. There are now free connections between the furnace space in the pressure chamber and the suction pipe, namely via the gap between the valve plate, the bore 54 of the annular part 50 and the valve seat 52 and the gaps 62 between the supports 63 # 618 suction pipe. The valve can also be • opened by the suction lifts the valve plate, '' ■■■ '■■' ■ ''^■;. Ι '·''■ V ·.

. The ring-shaped part .50 is durob; Consoles 80 on one Hills 81 attached to a guiding line 82

009886/13 * 2 _{BAD 0BK3) NAL}

long runs that attach to the pillar 9:; t. THE HUI ^ e
and thus the ring-shaped part 50 with the valve disk 55 and the floor lying on it and the charge can be raised and lowered with a cylinder 53, the actuating rod 84 of which is attached to brackets 55 on the sleeve A.

The equipment works in the following ways. The oven ^ is loaded with material 16 and the press frame in

Relation to the high pressure cylinder as in Pig. 1 shown brought. The charge is placed on the furnace floor when the lower end closure is in the lowered position, after which the cylinder S3 brings the entire end closure with the charge into an upper position, see FIG. 2. Then the suction pipe 70 is inserted into the opening of the end closure
pushed, after which the annular part 50 is in the Pig. 3 lowers the position shown. The valve disk 55 with the batch 16 is thereby supported by the Fxützen 73 of the Faug-
w pipe 70 is carried and a gap is formed between the valve disc 55 and the annular part 50. The charge is sintered under vacuum, after which the annular part 50 is raised and the suction pipe 70 is removed and the press frame is pushed over the pressure chamber. Pressure medium is supplied to the pressure chamber and the sintered material BU ftwuemehter density is hot-pressed.

The invention is not based on what is described and approved Executionifor * limited, many variants are Ib groynes the subsequent A | an | iyijftr ^ ab.e is conceivable. - 15 -

BAD ORIGINAL j

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Claims (5)

-f _# y «yfahr # n gur flere $ eUU! | £ of sintered
■ hoof .-. i> ly »rfiirffl ^ j ^ ej» Mfttespial, bei de © pirn 34e.
at * 3intern J2y.i, ein§nier yerpinaen uni a f gstejiL body i4-4fcn _f daiureh marked , iftss made of powder fc? »» ie K-PiPi * (1-) l> ei AtfflQß '> Heren · 34er nledrigeyero Drucii iiiii V ^ J splyx ^ r fempepatur sintered wera ^ n, ias.s gi.sh. 4ie Γ.ί ^ eri: üriig |? connect, WQn ^ en -ie geaintertgn Kärper _v (1c) in a pfgi; with §ince in an iiruefckaiiuner (2) ihl; .- enen yfenraiim (Ii?) less direct influence of a pra
niixeZ.8f Vesteiiend from /.rgon, Heiiiuc ,. st-iekgtpff 9Qsr
sjstoff, i0O0tatiech to be warp-pressed too high direction » 2. The method according to claim 1, characterized in that bodies formed from powder are placed in one and a deodorant oven.
an oven room enclosed in a Druak canoe
Atmospheric or lower pressure sintered and aanaeh
isostatic by direct action of a · «- | guided pressure medium consisting of argon, heliuin, nitrogen or hydrogen, hot-pressed to a high density will. 3. The method according to claim 1 or 2, characterized gekennzeichnex, that the body is sintered under vacuum and then at Sin » temperature are isostatically pressed, 4 * Method according to claim 1 or 2, characterized in that. ''that the powdery material .from a mixture of powder .. 009886/1322: -10- various substances ", of which at least one 'ii ^ _. ·.; ■" is a binder that, during sintering, the powder grains of the; '■ ?. other substances going into the powder mixture to form a solid body. I; '.. " ^: 5. The method according to claim 4, characterized in that ■■■■ - '■': WC, TaC, TiC or VC or a mixture of two or more of these substances as well as mainly Co and / or Ni as well φ possibly hard metal bodies containing Fe as a binder Sintered at atmospheric pressure or below and then iso- <statically hot-pressed. o. The method according to claim 5, characterized in that . Carbide body with a grade of 0-99 $ WC and / or TiC, 0-30 $ TaC, NbC and / or VC and 1-30 $ Co and / or Ni and possibly iron can be sintered at atmospheric pressure or below and then hot isostatically pressed. 7. The method according to claim 5 or 6, characterized in that the bodies are sintered at ^{a temperature of 1200-1600 0} C and then hot isostatically pressed at a pressure of 100-2000 bar and a temperature of 300-1500 C. 6. The method according to claim 4 »characterized in that mainly MoSi ₂ as well as possibly containing glass are electric heat bodies sintered at atmospheric pressure or under 'and then hot isostatically pressed. i322 _BAD0R1GIN - V 9. The method according to claim 8, for the production of electric radiators, characterized in that the bodies are ^{sintered at a temperature of 900 - HOO 0} C and then hot isostatically pressed at a pressure of 100 - 2000 bar and a temperature of 800 - HOO ^{0 C.} weraen » 10. The method according to claim 4 »characterized in that Kermets are sintered at atmospheric pressure or below and then hot isostatically pressed. . TT. Method according to claim 10, characterized in that a Kennet with 90 - 99 # AIoO, and 1 - 10 $ Ag content 0 - 10 ~ ² Torr and then sintered at 800-1500 ⁰ C and 100-2000 Bar'isostatisch is hot-pressed. ; '_' 12. The method according to claim 1 or 2, characterized in that the powdery material consists of uranium dioxide TJO ₂ « 13. The method according to claim 12, characterized in that the urandio ^ yd ^ sintered in hydrogen of fgasatjnosphere or under vacuum at a temperature of at least T550 ° C and then at a pressure of 100-2000 bar and a temperature of 1300-16QO ⁰ C is hot pressed. H. Vacuum sintering and hot isostatic pressing furnace of tulip bodies according to the procedure according to the previous' the claims, consisting of a cylindrical Pressure chamber with a high pressure cylinder, into this - 18 -009886 / 1322 BAD ORIGINAL - 13 - protruding end closures, arrangements for absorbing axial forces which are exerted by a pressure medium on the bonnets, an oven space with a heating arrangement arranged in the pressure chamber, a ¹ "surrounding the oven space, shaped like a dumbbell, insulation bit: isolie; top and bottom, as well as a? Vmku ^ impump- • equipment for the generation of a VftKuumlt ' 3 $. d | » Furnace, characterized in that one of the axles (50, 55) of the pressure chamber (2) is provided with an annular part (50), as well as with an element (51) which diohts against the cylinder (10, 11, 12) ) »A * the opening of the annular part (50) covering valve disk (55), a sealing member (56) between the annular part (50) bM the valve disk (55), and an iea annular part (5Q) of the valve closure can be connected in a sealing manner Vacuum line (70), as well as an organ for "separating the valve disk (55) from the annular ^ fe; ij | (50) of the end closure. " 15. Oven according to claim 14, characterized in that the connection line (70) "of the Vakuumauertistung into the annular opening of the end closure protrudes and the valve disc (55) from the annular part (50) of the End closure keeps separate. - 19 - 009886/1322 BADORiQINAL 16. Oven according to claim 15, characterized in that ... ■ the ring-shaped part (50) of the undver closure is universal and can be closed. after separating this part (50) -from V ", the valve disc (55) is countersunk..: _; 17. Oven according to claim 14, characterized in that the valve plate (55) with a centrally protruding Part (57) is provided, which "supports the OrgarP (1) f during hot pressing, the axial one acting on the end closure
Absorbs power. ■ ß 0 9 8 8 6/1 3 2 2 , 10. Blank page