EP0049373B1 - Surface hardened sintered iron workpiece and method of manufacturing this workpiece - Google Patents
Surface hardened sintered iron workpiece and method of manufacturing this workpiece Download PDFInfo
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- EP0049373B1 EP0049373B1 EP81106947A EP81106947A EP0049373B1 EP 0049373 B1 EP0049373 B1 EP 0049373B1 EP 81106947 A EP81106947 A EP 81106947A EP 81106947 A EP81106947 A EP 81106947A EP 0049373 B1 EP0049373 B1 EP 0049373B1
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- Prior art keywords
- sintered iron
- sintered
- workpiece
- hardening
- parts
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 40
- 238000004519 manufacturing process Methods 0.000 title claims description 3
- 229910052742 iron Inorganic materials 0.000 title description 2
- 238000000034 method Methods 0.000 claims abstract description 17
- 229910052910 alkali metal silicate Inorganic materials 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 12
- 239000004115 Sodium Silicate Substances 0.000 claims description 5
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 5
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 5
- 239000011148 porous material Substances 0.000 abstract description 4
- 239000002184 metal Substances 0.000 description 9
- 229910052751 metal Inorganic materials 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 238000005255 carburizing Methods 0.000 description 6
- 238000005256 carbonitriding Methods 0.000 description 5
- 238000005470 impregnation Methods 0.000 description 5
- 239000003795 chemical substances by application Substances 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 238000011049 filling Methods 0.000 description 4
- 238000005121 nitriding Methods 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 238000010791 quenching Methods 0.000 description 4
- 230000000171 quenching effect Effects 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 238000004663 powder metallurgy Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000009965 odorless effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000000256 polyoxyethylene sorbitan monolaurate Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 231100000563 toxic property Toxicity 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/02—Pretreatment of the material to be coated
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
Definitions
- the invention relates to a method for producing a surface-hardened sintered iron part, a sintered iron part being produced by powder metallurgy and the sintered iron part being subjected to a heat treatment suitable for hardening iron parts.
- Sintered iron parts can be significantly improved in their properties by a subsequent heat treatment.
- Such heat treatment processes to achieve greater hardness are carburizing or carbonitriding as a preliminary stage, as well as hardening, case hardening, nitriding and oxidizing as the actual hardening process.
- the carburization of sintered iron parts in carbon-donating agents is preferably carried out in the gas atmosphere at temperatures between 820 and 930 ° C.
- the hardening takes place by subsequent quenching, preferably in an oil bath.
- Carburizing or carbonitriding with subsequent quenching is referred to as case hardness.
- Carbonitriding which uses both carbon and nitrogen-releasing media, is carried out at temperatures from 720 to 950 ° C. This process enables surfaces with high wear resistance to be achieved.
- heat treatment process in this document therefore corresponds to the definition as it appears from the material data sheet "Heat treatment of sintered metal parts” published by the Powder Metallurgy Association; Sint 06, edition Nov. 1979, Beuth Verlag GmbH, Berlin 30 and Cologne 1 was given and includes all the procedures specified there in section 3.
- these are impregnated with an alkali silicate at least on the surface according to DE-OS 19 47 963 and the silicate is cured.
- the impregnation of sintered metal parts with alkali silicate is known from DE-PS 20 50 576 as pretreatment of sintered metal bodies to which a metal layer is to be applied using metal salt baths.
- the object of the invention is to provide a method which makes it possible to create a surface-hardened sintered iron part with a defined hardening depth, regardless of its space filling or sintering density.
- the invention is achieved in that the sintered iron part is impregnated with an alkali silicate solution before the heat treatment is carried out, that the alkali silicate solution adhering to the surface of the sintered iron part is rinsed off and that the impregnated sintered iron part is dried at an elevated temperature.
- a sodium silicate solution is preferably used as the alkali silicate solution.
- the advantages of the present invention lie in the fact that relatively porous sintered iron parts can now be provided with a very wear-resistant surface layer by normal heat treatment for the purpose of hardening, without the properties of the core of the sintered iron part being changed thereby.
- Another decisive advantage lies in the fact that, by preventing the penetration of carbon, nitrogen or oxygen inside the body, the increase in volume of the sintered iron material associated with the absorption of foreign atoms is prevented. This makes it possible, even with surface-hardened sintered iron parts, to comply with the tolerances of IT 6 and IT 7 that are usually to be observed with sintered iron parts. However, due to the case hardening that was previously possible, only tolerance ranges of IT 9 are possible.
- the sintered iron parts are evacuated in a container to which a pump and a storage vessel with alkali silicate solution is connected until a vacuum of 5.33-10 to 2.66. 10 - 2 bar (4 to 20 torr) is reached.
- a vacuum of 5.33-10 to 2.66. 10 - 2 bar (4 to 20 torr) is reached.
- the tap to the pump is closed and the tap to the storage vessel is opened so that the alkali silicate solution can flow in in a strong jet.
- the impregnation liquid is about 5 cm above the sintered parts, the impregnation solution is interrupted and the vacuum in the container is slowly released.
- the sintered iron parts then remain in the alkali silicate solution for about 30 minutes under atmospheric pressure.
- the sintered parts are now removed from the solution.
- the parts are allowed to drain and finally rinsed with cold water.
- the rinsing is carried out either by repeated dipping in water or the parts are then dried in air or with oil-free compressed air and heated and dried in stages in a drying cabinet from 50 to 180 ° C.
- the drying temperature can optionally be further increased without disadvantages, which will be the case if the drying takes place in the same oven in which the curing is carried out.
- alkali silicate solution over other impregnating solutions are the extremely low cost of the impregnating agent itself, as well as its low viscosity, which allows easy handling.
- the alkali silicate solution is non-flammable, is odorless and has no toxic properties. In closed storage containers it shows no signs of aging or hardening.
- the above-mentioned heat treatment methods can be used to harden iron parts. Since the pore walls are largely protected from the ingress of carbon, nitrogen or oxygen by the alkali silicate, carburization, carbonitriding, nitriding or oxidation only occur via the surface. The penetration of these elements into the sintered iron part is thus controlled, as with solid iron parts, only from the surface by the rate of diffusion of the foreign atoms in the metal. It follows from this that the foreign atoms are only embedded in a surface layer and thus surface hardening with a specific hardening depth is achieved.
- a sintered iron part was produced from a standard iron powder without further additions by pressing the sintered powder and annealing the compact in a non-oxidizing atmosphere.
- the density was 6.6 g / cm 3 , the space filling was 84%.
- Some of the sintered iron parts were impregnated with sodium silicate solution, rinsed and dried at 180 ° C. using the process described above. This treatment was not carried out on the other part of the sintered iron parts.
- Both the impregnated and the non-impregnated sintered iron parts were subjected to the same carburizing treatment was 2 hours at a temperature of 870 ° C. Endogas with a dew point - 2 "C was used as the carburizing medium.
- the hardening was carried out by subsequent quenching in an oil bath. The parts were then cut open and the Vickers hardness HV 0.3 measured at various distances from the surface. The measurement result is shown in Fig. 1. The curves show the hardness depending on the distance to the surface.
- curve (A) which was measured for parts without sodium silicate impregnation, it follows that the hardness is practically constant up to a depth of 1.5 mm from the surface.
- curve (B) drops steeply for the part with a sodium silicate treatment and already reaches the value of the starting material before hardening at a depth of about 0.5 mm.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Organic Chemistry (AREA)
- Powder Metallurgy (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
- Electromagnets (AREA)
- Turning (AREA)
Abstract
Description
Die Erfindung betrifft ein Verfahren zur Herstellung eines oberflächengehärteten Sintereisenteiles, wobei ein Sintereisenteil pulvermetallurgisch gefertigt und das Sintereisenteil einer zur Härtung von Eisenteilen geeigneten Wärmebehandlung unterzogen wird.The invention relates to a method for producing a surface-hardened sintered iron part, a sintered iron part being produced by powder metallurgy and the sintered iron part being subjected to a heat treatment suitable for hardening iron parts.
Sintereisenteile können durch eine nachfolgende Wärmebehandlung in ihren Eigenschaften wesentlich verbessert werden. Derartige Wärmebehandlungsverfahren zur Erzielung einer größeren Härte sind Aufkohlen oder Carbonitrieren als Vorstufe, sowie Härten, Einsatzhärten, Nitrieren und Oxidieren als eigentliche Härteverfahren.Sintered iron parts can be significantly improved in their properties by a subsequent heat treatment. Such heat treatment processes to achieve greater hardness are carburizing or carbonitriding as a preliminary stage, as well as hardening, case hardening, nitriding and oxidizing as the actual hardening process.
Die Aufkohlung von Sintereisenteilen in kohlenstoffabgebenden Mitteln erfolgt vorzugsweise in der Gasatmosphäre bei Temperaturen zwischen 820 und 930° C. Die Härtung erfolgt durch nachfolgendes Abschrecken, vorzugsweise in einem Ölbad.The carburization of sintered iron parts in carbon-donating agents is preferably carried out in the gas atmosphere at temperatures between 820 and 930 ° C. The hardening takes place by subsequent quenching, preferably in an oil bath.
Als Einsatzhärte wird ein Aufkohlen oder Carbonitrieren mit direkt anschließendem Abschrecken bezeichnet. Das Carbonitrieren, bei dem gleichzeitig neben kohlenstoff- auch stickstoffabgebende Medien verwendet werden, wird bei Temperaturen von 720 bis 950°C durchgeführt. Durch dieses Verfahren lassen sich Oberflächen von hohem Verschleißwiderstand erzielen.Carburizing or carbonitriding with subsequent quenching is referred to as case hardness. Carbonitriding, which uses both carbon and nitrogen-releasing media, is carried out at temperatures from 720 to 950 ° C. This process enables surfaces with high wear resistance to be achieved.
Auch durch eine Wärmebehandlung in ausschließlich stickstoffabgebenden Medien, dem Nitrieren bei Temperaturen von 480 bis 580° C werden harte verschleißfeste Oberflächen erzeugt. Schließlich ist noch die Behandlung von Sintereisenteilen in überhitztem Wasserdampf zu erwähnen, wodurch ebenfalls eine Steigerung der Härte und Verschleißfestigkeit neben der Erhöhung der Korrosionsbeständigkeit zu erzielen ist. Bei diesem Verfahren wird eine Eisenoxidschicht, und zwar Magnetit (Fe304) gebildet.Heat treatment in exclusively nitrogen-releasing media, nitriding at temperatures from 480 to 580 ° C also creates hard, wear-resistant surfaces. Finally, the treatment of sintered iron parts in superheated steam should also be mentioned, which also leads to an increase in hardness and wear resistance as well as an increase in corrosion resistance. In this process, an iron oxide layer, namely magnetite (Fe 3 0 4 ) is formed.
Der Begriff Wärmebehandlungsverfahren in dieser Schrift entspricht somit der Definition, wie sie aus dem vom Fachverband Pulvermetallurgie herausgegebenen Werkstoffleistungsblatt »Wärmebehandlung von Sintermetallteiten«; Sint 06, Ausgabe Nov. 1979, Beuth Verlag GmbH, Berlin 30 und Köln 1 gegeben wurde und umfaßt sämtliche Verfahren die dort in Abschnitt 3 angegeben wurden.The term heat treatment process in this document therefore corresponds to the definition as it appears from the material data sheet "Heat treatment of sintered metal parts" published by the Powder Metallurgy Association; Sint 06, edition Nov. 1979, Beuth Verlag GmbH, Berlin 30 and Cologne 1 was given and includes all the procedures specified there in section 3.
Im Gegensatz zu Massiveisenteilen, bei denen durch Härten nach einem Aufkohlen, Carbonitrieren oder Nitrieren eine definierte Oberflächenhärtung leicht zu erzielen ist, ist dies bei Sintereisenteilen ohne besondere Maßnahmen nicht möglich. Durch die offenen, von der Oberfläche zugänglichen Poren können gasförmige oder flüssige Behandlungsmedien in das Sintermetallteil eindringen. Freilich ist dieser Vorgang von der Raumerfüllung bzw. der Sinterdichte abhängig. So wird angegeben (a. a. O.), daß bei einer Raumerfüllung von etwa 85%, was einer Sinterdichte von ca. 6,6 g/cm3 entspricht, beim Aufkohlen stets mit einer Durchkohlung zu rechnen ist, d. h. nach dem Abschrecken zu einer Durchhärtung führt.In contrast to solid iron parts, in which a defined surface hardening can be easily achieved by hardening after carburizing, carbonitriding or nitriding, this is not possible with sintered iron parts without special measures. The open pores accessible from the surface allow gaseous or liquid treatment media to penetrate into the sintered metal part. Of course, this process depends on the space filling or the sintering density. It is stated (loc. Cit.) That if the space is filled to around 85%, which corresponds to a sintered density of approximately 6.6 g / cm 3 , carburization is always to be expected when carburizing, ie after quenching to harden leads.
Häufig ist jedoch erwünscht, ausschließlich eine Oberflächenhärtung zu erhalten. Die Beschränkung der Aufkohlung auf eine Randschicht gelingt bisher erst ab einer Raumerfüllung von mehr als etwa 90%, was einer Sinterdichte von 7,0 g/cm3 entspricht. Die Forderung nach einem Sintereisenteil mit einer geringeren Raumerfüllung und gleichzeitiger Oberflächenhärtung konnte bisher nicht erfüllt werden.However, it is often desirable to obtain only surface hardening. So far, the carburization has only been limited to one surface layer when more than about 90% of the space has been filled, which corresponds to a sintered density of 7.0 g / cm 3 . The demand for a sintered iron part with less space filling and simultaneous surface hardening could not be met so far.
Als Vorbehandlungsverfahren vor der Wärmebehandlung sind verschiedene Entfettungsverfahren bekannt.Various degreasing processes are known as pretreatment processes prior to heat treatment.
Zu einem anderen Zweck, nämlich der Erhöhung der Korrosionsbeständigkeit von Sintermetallteilen werden diese nach der DE-OS 19 47 963 wenigstens an der Oberfläche mit einem Alkalisilikat imprägniert und das Silikat ausgehärtet.For another purpose, namely to increase the corrosion resistance of sintered metal parts, these are impregnated with an alkali silicate at least on the surface according to DE-OS 19 47 963 and the silicate is cured.
Die Imprägnierung von Sintermetallteilen mit Alkalisilikat ist aus der DE-PS 20 50 576 als Vorbehandlung von Sintermetallkörpern, auf die eine Metallschicht unter Verwendung von Metallsalzbädern aufgebracht werden soll, bekannt.The impregnation of sintered metal parts with alkali silicate is known from DE-PS 20 50 576 as pretreatment of sintered metal bodies to which a metal layer is to be applied using metal salt baths.
Aufgabe der Erfindung ist es, ein Verfahren anzugeben, das es erlaubt, ein oberflächengehärtetes Sintereisenteil mit einer definierten Einhärtetiefe zu schaffen, unabhängig von seiner Raumerfüllung bzw. Sinterdichte.The object of the invention is to provide a method which makes it possible to create a surface-hardened sintered iron part with a defined hardening depth, regardless of its space filling or sintering density.
Die Erfindung wird dadurch gelöst, daß das Sintereisenteil vor Durchführung der Wärmebehandlung mit einer Alkalisilikatlösung imprägniert wird, daß die an der Oberfläche des Sintereisenteils anhaftende Alkalisilikatlösung abgespült wird und daß das imprägnierte Sintereisenteil bei erhöhter Temperatur getrocknet wird. Vorzugsweise als Alkalisilikatlösung eine Natriumsilikatlösung verwendet.The invention is achieved in that the sintered iron part is impregnated with an alkali silicate solution before the heat treatment is carried out, that the alkali silicate solution adhering to the surface of the sintered iron part is rinsed off and that the impregnated sintered iron part is dried at an elevated temperature. A sodium silicate solution is preferably used as the alkali silicate solution.
Die Vorteile der vorliegenden Erfindung liegen darin, daß nunmehr auch relativ poröse Sintereisenteile durch eine normale Wärmebehandlung zum Zweck der Härtung mit einer sehr verschleißfesten Oberflächenschicht versehen werden können, ohne daß dadurch die Eigenschaften des Kernes des Sintereisenteiles verändert werden.The advantages of the present invention lie in the fact that relatively porous sintered iron parts can now be provided with a very wear-resistant surface layer by normal heat treatment for the purpose of hardening, without the properties of the core of the sintered iron part being changed thereby.
Ein weiterer entscheidender Vorteil liegt in der Tatsache, daß mit der Verhinderung des Eindringens des Kohlenstoffs, Stickstoffs oder Sauerstoffs im Innern des Körpers die mit der Aufnahme von Fremdatomen verbundene Volumenzunahme des Sintereisenwerkstoffes verhindert wird. Hierdurch ist es möglich, auch bei oberflächengehärteten Sintereisenteilen, die üblicherweise bei Sintereisenteilen einzuhaltenden Toleranzen von IT 6 und IT 7 einzuhalten. Durch die bisher mögliche Einsatzhärtung sind dagegen nur Toleranzbereiche von IT 9 möglich.Another decisive advantage lies in the fact that, by preventing the penetration of carbon, nitrogen or oxygen inside the body, the increase in volume of the sintered iron material associated with the absorption of foreign atoms is prevented. This makes it possible, even with surface-hardened sintered iron parts, to comply with the tolerances of IT 6 and IT 7 that are usually to be observed with sintered iron parts. However, due to the case hardening that was previously possible, only tolerance ranges of IT 9 are possible.
Nicht zu unterschützen ist auch die Tatsache, daß die Korrosionsbeständigkeit der Sintereisenteile durch die Auskleidung der Poren mit Alkalisilikat erheblich gesteigert wird.Also not to be underestimated is the fact that the corrosion resistance of the sintered iron parts is considerably increased by lining the pores with alkali silicate.
Im folgenden wird das erfindungsgemäße Verfahren beispielhaft erläutert. Die Sintereisenteile werden nach dem Sinterprozeß in einem Behälter, an dem eine Pumpe und ein Vorratsgefäß mit Alkalisilikatlösung angeschlossen ist, so lange evakuiert, bis ein Vakuum von 5,33 - 10 bis 2,66 . 10 -2 bar (4 bis 20 torr) erreicht ist. Bei noch laufender Vakuumpumpe wird der Hahn zur Pumpe geschlossen und der Hahn zum Vorrats gefäß geöffnet, so daß die Alkalisilikatlösung in starkem Strahl einfließen kann. Wenn die lmprägnierflüssigkeit ca. 5 cm über den Sinterteilen steht, wird die Imprägnierlösungszugabe unterbrochen und das Vakuum im Behälter langsam aufgehoben.The following is the inventive The method is explained by way of example. After the sintering process, the sintered iron parts are evacuated in a container to which a pump and a storage vessel with alkali silicate solution is connected until a vacuum of 5.33-10 to 2.66. 10 - 2 bar (4 to 20 torr) is reached. When the vacuum pump is still running, the tap to the pump is closed and the tap to the storage vessel is opened so that the alkali silicate solution can flow in in a strong jet. When the impregnation liquid is about 5 cm above the sintered parts, the impregnation solution is interrupted and the vacuum in the container is slowly released.
Hierauf bleiben die Sintereisenteile ca. 30 Minuten unter Atmosphärendruck in der Alkalisilikatlösung stehen. Die Sinterteile werden nun aus der Lösung genommen. Man läßt die Teile abtropfen und spült schließlich mit kaltem Wasser. Das Spülen erfolgt entweder durch wiederholtes Tauchen in Wasser oder die Teile werden sodann an Luft oder mit ölfreier Preßluft getrocknet und stufenweise im Trockenschrank von 50 bis zu 180°C erwärmt und getrocknet. Die Trocknungstemperatur kann ohne Nachteile auch wahlweise weiter erhöht werden, was dann der Fall sein wird, wenn die Trocknung im selben Ofen erfolgt, in dem die Härtung durchgeführt wird.The sintered iron parts then remain in the alkali silicate solution for about 30 minutes under atmospheric pressure. The sintered parts are now removed from the solution. The parts are allowed to drain and finally rinsed with cold water. The rinsing is carried out either by repeated dipping in water or the parts are then dried in air or with oil-free compressed air and heated and dried in stages in a drying cabinet from 50 to 180 ° C. The drying temperature can optionally be further increased without disadvantages, which will be the case if the drying takes place in the same oven in which the curing is carried out.
Die besonderen Vorteile bei der Verwendung von Alkalisilikatlösung gegenüber anderen lmprägnierlösungen bestehen in den äußerst geringen Kosten des Imprägniermittels selbst, ferner in seiner niedrigen Viskosität, die eine einfache Handhabung zuläßt. Außerdem ist die Alkalisilikatlösung nicht brennbar, ist geruchslos und hat keine toxischen Eigenschaften. In geschlossenen Vorratsbehältern zeigt sie keine Alterungserscheinungen bzw. Aushärtungen.The particular advantages of using alkali silicate solution over other impregnating solutions are the extremely low cost of the impregnating agent itself, as well as its low viscosity, which allows easy handling. In addition, the alkali silicate solution is non-flammable, is odorless and has no toxic properties. In closed storage containers it shows no signs of aging or hardening.
Durch die Benetzung des Metalls ist eine nur geringe Imprägnierzeit erforderlich. Die Trocknungszeiten sind im Vergleich zu denjenigen anderer Imprägniermittel relativ kurz. Nach erfolgter Aushärtung des Imprägniermittels können die oben angegebenen Wärmebehandlungsverfahren zur Härtung von Eisenteilen angewendet werden. Da nun die Porenwände durch das Alkalisilikat vor Eindringen von Kohlenstoff, Stickstoff bzw. Sauerstoff weitgehendst geschützt sind, tritt eine Aufkohlung, Carbonitrierung, Nitrierung bzw. Oxidation lediglich über die Oberfläche ein. Das Eindringen dieser Elemente in das Sintereisenteil wird somit ähnlich wie bei massiven Eisenteilen nur von der Oberfläche durch die Diffusionsgeschwindigkeit der Fremdatome im Metall gesteuert. Hieraus folgt, daß die Einlagerung der Fremdatome lediglich in einer Oberflächenschicht erfolgt und es somit eine Oberflächenhärtung mit einer gezielten Einhärtetiefe erreicht wird.Due to the wetting of the metal, only a short impregnation time is required. The drying times are relatively short compared to those of other impregnating agents. After the impregnating agent has hardened, the above-mentioned heat treatment methods can be used to harden iron parts. Since the pore walls are largely protected from the ingress of carbon, nitrogen or oxygen by the alkali silicate, carburization, carbonitriding, nitriding or oxidation only occur via the surface. The penetration of these elements into the sintered iron part is thus controlled, as with solid iron parts, only from the surface by the rate of diffusion of the foreign atoms in the metal. It follows from this that the foreign atoms are only embedded in a surface layer and thus surface hardening with a specific hardening depth is achieved.
Zur näheren Erläuterung der Erfindung wird folgendes Beispiel angegeben.The following example is given to explain the invention in more detail.
Es wurde ein Sintereisenteil aus einem Standardeisenpulver ohne weitere Zusätze durch Pressen des Sinterpulvers und Glühen des Preßlings in nichtoxidierender Atmosphäre hergestellt. Die Dichte betrug 6,6 g/cm3, die Raumerfüllung betrug 84%. Ein Teil der Sintereisenteile wurde nach vorgehend beschriebenen Verfahren mit Natriumsilikatlösung imprägniert, abgespült und bei 180"C getrocknet. Bei dem anderen Teil der Sintereisenteile wurde diese Behandlung nicht durchgeführt. Sowohl die imprägnierten, als auch die nicht imprägnierten Sintereisenteile wurden serselben Aufkohlungsbehandlung unterworfen. Die Aufkohlungszeit betrug 2 Stunden bei einer Temperatur von 870°C; als Aufkohlungsmedium wurde Endogas mit einem Taupunkt - 2" C verwendet.A sintered iron part was produced from a standard iron powder without further additions by pressing the sintered powder and annealing the compact in a non-oxidizing atmosphere. The density was 6.6 g / cm 3 , the space filling was 84%. Some of the sintered iron parts were impregnated with sodium silicate solution, rinsed and dried at 180 ° C. using the process described above. This treatment was not carried out on the other part of the sintered iron parts. Both the impregnated and the non-impregnated sintered iron parts were subjected to the same carburizing treatment was 2 hours at a temperature of 870 ° C. Endogas with a dew point - 2 "C was used as the carburizing medium.
Die Härtung erfolgte durch nachfolgendes Abschrecken in einem Ölbad. Anschließend wurden die Teile aufgeschnitten und die Vickershärte HV 0,3 in verschiedenen Abständen von der Oberfläche gemessen. Das Meßergebnis ist in Fig. 1 dargestellt. Die Kurven zeigen die Härte in Abhängigkeit vom Abstand zur Oberfläche.The hardening was carried out by subsequent quenching in an oil bath. The parts were then cut open and the Vickers hardness HV 0.3 measured at various distances from the surface. The measurement result is shown in Fig. 1. The curves show the hardness depending on the distance to the surface.
Aus der Kurve (A), die bei Teilen ohne Natriumsilikatimprägnierung gemessen wurde, ergibt sich, daß bis zu einer Tiefe von 1,5 mm von der Oberfläche die Härte praktisch konstant ist. Demgegenüber fällt die Kurve (B) für das Teil mit einer Natriumsilikatbehandlung steil ab und erreicht bei etwa 0,5 mm Tiefe bereits den Wert des Ausgangsmaterials vor dem Härten.From curve (A), which was measured for parts without sodium silicate impregnation, it follows that the hardness is practically constant up to a depth of 1.5 mm from the surface. In contrast, curve (B) drops steeply for the part with a sodium silicate treatment and already reaches the value of the starting material before hardening at a depth of about 0.5 mm.
Claims (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT81106947T ATE10070T1 (en) | 1980-09-23 | 1981-09-04 | SURFACE HARDENED SINTERED IRON PART AND PRODUCTION METHOD. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3035772 | 1980-09-23 | ||
| DE3035772A DE3035772C2 (en) | 1980-09-23 | 1980-09-23 | Process for the production of a surface-hardened sintered iron part |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0049373A1 EP0049373A1 (en) | 1982-04-14 |
| EP0049373B1 true EP0049373B1 (en) | 1984-10-31 |
Family
ID=6112598
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP81106947A Expired EP0049373B1 (en) | 1980-09-23 | 1981-09-04 | Surface hardened sintered iron workpiece and method of manufacturing this workpiece |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4508681A (en) |
| EP (1) | EP0049373B1 (en) |
| JP (1) | JPS5785904A (en) |
| AT (1) | ATE10070T1 (en) |
| BR (1) | BR8106065A (en) |
| DE (2) | DE3035772C2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10047645C2 (en) * | 1999-09-28 | 2003-09-11 | Suzuki Motor Co | Process for the hardness treatment of sintered parts |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE446605B (en) * | 1985-02-13 | 1986-09-29 | Ibm Svenska Ab | Vacuum impregnation of sintered materials with dry lubricant |
| AU5146798A (en) * | 1996-10-15 | 1998-05-11 | Zenith Sintered Products, Inc. | Surface densification of machine components made by powder metallurgy |
| DE19738919C1 (en) | 1997-09-05 | 1999-04-29 | Maxon Motor Gmbh | Process for manufacturing a plain bearing and plain bearing |
| US6759087B1 (en) | 2002-04-10 | 2004-07-06 | Conspectus, Inc. | Solution for sealing porous metal substrates and process of applying the solution |
| US20070047857A1 (en) * | 2005-08-26 | 2007-03-01 | Tsutomu Hamada | Sleeve for hydrodynamic bearing device, hydrodynamic bearing device and spindle motor using the same, and method for manufacturing sleeve |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE880448C (en) * | 1943-07-13 | 1953-06-22 | Boehler & Co Ag Geb | Process for covering material parts made of special steel which are to be protected from the effects of the nitriding agent during the nitriding process |
| NO135019C (en) * | 1968-09-26 | 1977-01-26 | Allegheny Ludlum Steel | |
| DE2050576C3 (en) * | 1970-10-15 | 1975-03-13 | Schunk & Ebe Gmbh, 6301 Heuchelheim | Process for surface finishing of sintered metal parts |
| GB1450937A (en) * | 1973-07-03 | 1976-09-29 | British Steel Corp | Production and subsequent carburisation of steel products motor vehicle folding rear seat assembly |
| US4071382A (en) * | 1976-07-22 | 1978-01-31 | Midland-Ross Corporation | Method for case hardening powdered metal parts |
-
1980
- 1980-09-23 DE DE3035772A patent/DE3035772C2/en not_active Expired
-
1981
- 1981-09-04 DE DE8181106947T patent/DE3166981D1/en not_active Expired
- 1981-09-04 AT AT81106947T patent/ATE10070T1/en not_active IP Right Cessation
- 1981-09-04 EP EP81106947A patent/EP0049373B1/en not_active Expired
- 1981-09-22 BR BR8106065A patent/BR8106065A/en unknown
- 1981-09-22 JP JP56148944A patent/JPS5785904A/en active Pending
-
1983
- 1983-12-21 US US06/564,350 patent/US4508681A/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10047645C2 (en) * | 1999-09-28 | 2003-09-11 | Suzuki Motor Co | Process for the hardness treatment of sintered parts |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3035772C2 (en) | 1982-09-30 |
| US4508681A (en) | 1985-04-02 |
| DE3166981D1 (en) | 1984-12-06 |
| DE3035772A1 (en) | 1982-05-13 |
| ATE10070T1 (en) | 1984-11-15 |
| BR8106065A (en) | 1982-06-08 |
| JPS5785904A (en) | 1982-05-28 |
| EP0049373A1 (en) | 1982-04-14 |
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