EP0246162A1 - Process for sintering pulverulent material in a continuous furnace - Google Patents

Process for sintering pulverulent material in a continuous furnace Download PDF

Info

Publication number
EP0246162A1
EP0246162A1 EP87401098A EP87401098A EP0246162A1 EP 0246162 A1 EP0246162 A1 EP 0246162A1 EP 87401098 A EP87401098 A EP 87401098A EP 87401098 A EP87401098 A EP 87401098A EP 0246162 A1 EP0246162 A1 EP 0246162A1
Authority
EP
European Patent Office
Prior art keywords
sintering
powder
furnace
hydrogen
atmosphere
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP87401098A
Other languages
German (de)
French (fr)
Other versions
EP0246162B1 (en
Inventor
Michel Madsac
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Original Assignee
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Air Liquide SA, LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude filed Critical Air Liquide SA
Priority to AT87401098T priority Critical patent/ATE50936T1/en
Publication of EP0246162A1 publication Critical patent/EP0246162A1/en
Application granted granted Critical
Publication of EP0246162B1 publication Critical patent/EP0246162B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • 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
    • B22F3/10—Sintering only
    • B22F3/1003—Use of special medium during sintering, e.g. sintering aid
    • B22F3/1007—Atmosphere
    • 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
    • B22F3/001—Starting from powder comprising reducible metal compounds
    • 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
    • B22F3/10—Sintering only
    • B22F3/11—Making porous workpieces or articles
    • B22F3/1143—Making porous workpieces or articles involving an oxidation, reduction or reaction step
    • 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
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • the present invention relates to a sintering process in a continuous furnace of a powder material containing oxygen in the form of oxide and / or in adsorbed form, in which the oxygen present is reduced during a first step pre-sintering, and then ensures the cohesion of the material during a second sintering step.
  • Sintering operations are generally carried out in continuous ovens under a controlled atmosphere. More and more nitrogen-based atmospheres are used in these sintering furnaces to replace the atmospheres generated by exothermic generators or by ammonia crackers, on the one hand because the flow control of synthetic atmospheres is more easy and on the other hand, because their composition can be modified according to the characteristics of the process. Furthermore, the exothermic generators have a very variable dew point and it is necessary to have a large quantity of hydrogen in the atmosphere of the furnace, in order to maintain the reducing nature of this atmosphere and avoid the oxidation of the powder. or the support on which it is sintered.
  • a commonly used protective atmosphere contains inert gases such as nitrogen and reactive gases capable of reducing oxides, such as hydrogen and / or carbon monoxide.
  • the purpose of the pre-sintering step in particular in the absence of a binder between the different grains of powder, is intended to reduce the oxides present in the powder and generally, to reduce the oxygen present in the layer of powder. It is therefore necessary that the atmosphere contains the reducing qualities required.
  • the purpose of the sintering step is in particular to increase intergranular cohesion as well as the diffusion at the interface of the grains and of the support when the sintering is carried out on a separate support.
  • This sintering step also requires an atmosphere of a reducing nature, avoiding the entry of air into the hot zone and the oxidation of the powder which would slow down the sintering of the latter.
  • the pre-sintering step was the step of the process on which the productivity of a production line depended, for a determined quality of sintering.
  • the method according to the invention makes it possible to determine the total flow rate of synthetic gas in the pre-sintering oven as a function of the speed of advance of the material in the oven, this speed being the same in the pre-sintering oven and in the sintering oven.
  • the parameter P (H2) f is the lowest value measured at a point in the furnace corresponding to the total reduction of the oxides, the flow of atmosphere being sufficient to ensure the complete reduction of the oxides as well as a sintering and an adhesion corresponding to a predetermined value.
  • the parameter X (O2) i is measured according to the usual techniques for assaying oxygen in a pulverulent mixture.
  • the coefficient ⁇ is determined in the following manner: a nitrogen and hydrogen atmosphere is injected in the usual manner into the sintering furnace, for example in the manner usually carried out with an exothermic generator. Is added to the injected gas, for example 5%, by volume of a "tracer" gas such as helium, during a determined time interval, for example 10 minutes. The evolution of the rate of helium in the gas escaping from the oven as a function of time is recorded at the inlet and at the outlet of the oven. This helium level is integrated as a function of the time at the inlet and at the outlet of the furnace, respectively (He) i and (He) o . The coefficient ⁇ is equal to (He) i / ((He) i + (He) o ).
  • S P represents the mean section of the parts in the plane perpendicular to the oven mat.
  • a layer of 0.9 mm of powder is deposited containing 73% copper, 23% lead and 4% tin.
  • the width of the support on which the powder is deposited is 200 mm, the density of the powder is 5.2 T / M3 and the percentage of oxygen in the powder is 0.28%.
  • the ribbon advances at speed V S in the oven, consisting of a 30-meter long pre-sintering oven at a temperature of 820 ° C, at the outlet of which the ribbon and the powder are laminated between two steel cylinders, then introduced into the sintering oven (30 meters in length - 820 ° C), each pre-sintering and sintering oven has a cooling zone of 10 meters in length ("water-jacket" type) .
  • the atmosphere is injected into the pre-sintering and sintering furnaces near the junction of the hot and cooling zones.
  • the flow rate of 30m3 / h of atmosphere containing 10% of H2 by volume is maintained by 90% of N2 by volume.
  • By placing slightly below this speed (around 160 m / h), it is verified that a material is obtained having the predetermined sintering qualities identical to those obtained using an exothermic generator generating an atmosphere containing 10% of hydrogen. , 8% CO, 6% CO2 and 76% N2, at a flow rate of 30 m3 / hour, both at the pre-sintering oven and at the sintering oven, but with a feed rate of material about 110 m / h.
  • the gain in speed of the process according to the invention is therefore around 50%.
  • the method according to the invention makes it possible to accelerate the speed (at constant speed) or to reduce the flow (at constant speed) in the pre-sintering furnace, but also makes it possible to reduce the gas flow in the sintering furnace with an atmosphere containing less hydrogen, which overall results in a significant reduction in production costs.
  • Such tapes can be used as self-lubricating pads.
  • the width of the support on which the powder is deposited is 150 mm, the density of the powder is 0.8 T / M3 and the percentage of oxygen in the powder is 0.18%.
  • the ribbon advances at speed V S in the oven, consisting of a hot zone at the temperature of 1040 ° C, 4 m in length, followed by a cold zone of the "water-jacket" type.
  • the atmosphere is injected into the oven at the junction between the hot zone and the cold zone as well as at the end of the cold zone. It consists of 10% hydrogen and 90% nitrogen.
  • the coefficient ⁇ is determined as indicated above: the measured value is 20%.
  • the flow rate of 6 m3 / h of atmosphere containing 10% of H2 by volume is maintained by 90% of N2 by volume.
  • a material is obtained having the predetermined sintering qualities identical to those obtained using an ammonia cracker-burner. generating an atmosphere containing 10% hydrogen, and 90% nitrogen at a flow rate of 6 m3 / hour, but with a material advance speed of approximately 80 m / h.
  • Such tapes can be used as porous electrodes for alkaline batteries.

Abstract

The powdered material contains oxygen in the oxide and/or adsorbed form and the oxygen present is reduced in a first pre-sintering stage and the cohesion of the material is ensured in a second sintering stage. The pre-sintering stage is carried out under a reducing atmosphere based on hydrogen and neutral gas whose flow rate FG is higher than or equal to: <IMAGE> in which relation: SP=section of the layer of powder to be sintered in sq.m DP=voluminal mass of the powder in kg/cu m X(O2)i=percentage of oxygen mass in the powder before the pre-sintering stage, in the oxide and/or adsorbed form, P(H2)i=voluminal percentage of hydrogen in the gas introduced into the furnace, P(H2)f=the smallest voluminal percentage of hydrogen in the atmosphere in the furnace at a point where the oxides have been completely reduced, vS=speed of feed of the material in the furnace expressed in m/hr, alpha is a constant FG being expressed in cu.m/hr.

Description

La présente invention concerne un procédé de frittage dans un four continu d'un matériau en poudre contenant de l'oxygène sous forme d'oxyde et/ou sous forme adsorbée, dans lequel on réduit l'oxygène présent au cours d'une première étape de pré-frittage, puis on assure la cohésion du matériau au cours d'une seconde étape de frittage.The present invention relates to a sintering process in a continuous furnace of a powder material containing oxygen in the form of oxide and / or in adsorbed form, in which the oxygen present is reduced during a first step pre-sintering, and then ensures the cohesion of the material during a second sintering step.

Les opérations de frittage sont généralement réalisées dans des fours continus sous atmosphère contrôlée.
On utilise de plus en plus des atmosphères à base d'azote dans ces fours de frittage pour remplacer les atmosphères engendrées par les générateurs exothermiques ou par les craqueurs d'ammoniac, d'une part parce que le réglage du débit des atmosphères synthétiques est plus aisé et d'autre part, parce que leur composition peut être modifiée en fonction des caractéristiques du procédé. Par ailleurs, les générateurs exothermiques ont un point de rosée très variable et il est nécessaire d'avoir une quantité d'hydrogène importante dans l'atmosphère du four, afin de maintenir le caractère réducteur de cette atmosphère et éviter l'oxydation de la poudre ou du support sur lequel celle-ci est frittée.Sintering operations are generally carried out in continuous ovens under a controlled atmosphere.
More and more nitrogen-based atmospheres are used in these sintering furnaces to replace the atmospheres generated by exothermic generators or by ammonia crackers, on the one hand because the flow control of synthetic atmospheres is more easy and on the other hand, because their composition can be modified according to the characteristics of the process. Furthermore, the exothermic generators have a very variable dew point and it is necessary to have a large quantity of hydrogen in the atmosphere of the furnace, in order to maintain the reducing nature of this atmosphere and avoid the oxidation of the powder. or the support on which it is sintered.

Une autre fonction de l'atmosphère protectrice dans les fours de traitement thermique est la création d'une pression positive dans le four, qui va limiter les entrées d'air dans les zones critiques du four afin d'éviter l'oxydation. Une atmosphère protectrice couramment utilisée contient des gaz inertes tel que l'azote et des gaz réactifs capables de réduire les oxydes, tels que l'hydrogène et/ou le monoxyde de carbone.Another function of the protective atmosphere in heat treatment ovens is the creation of a positive pressure in the oven, which will limit the entry of air into critical areas of the oven in order to avoid oxidation. A commonly used protective atmosphere contains inert gases such as nitrogen and reactive gases capable of reducing oxides, such as hydrogen and / or carbon monoxide.

La plupart des poudres métalliques contiennent des oxydes du fait des conditions de production et de stockage de celles-ci. Les atmosphères de traitement thermique doivent être capables de réduire ces oxydes. Ce facteur est critique puisque les couches d'oxyde freinent le processus de frittage. La composition de l'atmosphère doit donc être adaptée pour la réduction des oxydes de surface et de l' oxygène libre contenus dans la poudre.Most metallic powders contain oxides due to the conditions of production and storage thereof. The heat treatment atmospheres must be capable of reducing these oxides. This factor is critical since the oxide layers slow down the sintering process. The composition of the atmosphere must therefore be adapted for the reduction of the surface oxides and of the free oxygen contained in the powder.

Les avantages bien connus des atmosphères synthétiques par rapport aux atmosphères créées à partir de générateurs exothermiques peuvent cependant s'avérer quelques fois insuffisants compte tenu du coût plus éléve desdites atmosphères synthétiques.
Cependant, la Demanderesse a constaté qu'il n'était pas nécessaire d'utiliser les mêmes atmosphères, et/ou les mêmes débits d'atmosphères pour les opérations de pré-frittage et de frittage, ce qui ne peut être réalisé lorsqu'on utilise un générateur pour engendrer les atmosphères de pré-frittage et de frittage.The well-known advantages of synthetic atmospheres compared to atmospheres created from exothermic generators can however prove to be sometimes insufficient taking into account the higher cost of said synthetic atmospheres.
However, the Applicant has found that it is not necessary to use the same atmospheres, and / or the same flow rates of atmospheres for the pre-sintering and sintering operations, which cannot be achieved when uses a generator to generate the pre-sintering and sintering atmospheres.

L'étape de pré-frittage, en particulier en l'absence de liant entre les différents grains de poudre, a pour but de réduire les oxydes présents dans la poudre et d'une manière générale, réduire l'oxygène présent dans la couche de poudre. Il est donc nécessaire que l'atmosphère comporte les qualités réductrices requises.The purpose of the pre-sintering step, in particular in the absence of a binder between the different grains of powder, is intended to reduce the oxides present in the powder and generally, to reduce the oxygen present in the layer of powder. It is therefore necessary that the atmosphere contains the reducing qualities required.

L'étape de frittage a notamment pour but d'augmenter la cohésion intergranulaire ainsi que la diffusion à l'interface des grains et du support lorsque le frittage est réalisé sur un support distinct. Cette étape de frittage nécessite également une atmosphère à caractère réducteur, évitant les entrées d'air dans la zone chaude et l'oxydation de la poudre qui freinerait le frittage de celle-ci.The purpose of the sintering step is in particular to increase intergranular cohesion as well as the diffusion at the interface of the grains and of the support when the sintering is carried out on a separate support. This sintering step also requires an atmosphere of a reducing nature, avoiding the entry of air into the hot zone and the oxidation of the powder which would slow down the sintering of the latter.

Partant de cette analyse, on a constaté que l'étape de pré-frittage était l'étape du procédé dont dépendait la productivité d'une ligne de fabrication, pour une qualité déterminée du frittage.On the basis of this analysis, it was found that the pre-sintering step was the step of the process on which the productivity of a production line depended, for a determined quality of sintering.

Le procédé selon l'invention permet de déterminer le débit total de gaz synthétique dans le four de pré-frittage en fonction de la vitesse d'avance du matériau dans le four, cette vitesse étant la même dans le four de pré-frittage et dans le four de frittage.The method according to the invention makes it possible to determine the total flow rate of synthetic gas in the pre-sintering oven as a function of the speed of advance of the material in the oven, this speed being the same in the pre-sintering oven and in the sintering oven.

Le procédé selon l'invention est caractérisé en ce que l'étape de pré-frittage s'effectue sous atmosphère réductrice à base d'hydrogène et de gaz neutre dont le débit FG est supérieur ou égal à :

Figure imgb0001
relation dans laquelle :
SP = section de la couche de poudre à fritter en m²,
DP = masse volumique de la poudre en kg/m³,
X(O₂)i = pourcentage en masse d'oxygène dans la poudre avant l'étape de pré-frittage, sous forme d'oxyde et/ou adsorbé,
P(H₂)i = pourcentage volumique d'hydrogène dans le gaz introduit dans le four,
P(H₂)f = le plus faible pourcentage volumique d'hydrogène dans l'atmosphère du four en un point où les oxydes ont été complètement réduits,
VS vitesse d'avance du matériau dans le four exprimée en m/h,
α est une constante,
FG étant exprimé en m³/heure.The method according to the invention is characterized in that the pre-sintering step is carried out under a reducing atmosphere based on hydrogen and neutral gas whose flow rate F G is greater than or equal to:
Figure imgb0001
 relationship in which:
S P = section of the sintering powder layer in m²,
D P = density of the powder in kg / m³,
X (O₂) i = percentage by mass of oxygen in the powder before the pre-sintering step, in the form of oxide and / or adsorbed,
P (H₂) i = volume percentage of hydrogen in the gas introduced into the furnace,
P (H₂) f = the lowest volume percentage of hydrogen in the furnace atmosphere at a point where the oxides have been completely reduced,
V S material advance speed in the furnace expressed in m / h,
α is a constant,
F G being expressed in m³ / hour.

Tous les paramètres de cette formule sont déterminés expérimentalement en fonction du four et de la poudre à fritter.All the parameters of this formula are determined experimentally depending on the oven and the sintering powder.

Le paramètre P(H₂)f est la plus faible valeur mesurée en un point du four correspondant à la réduction totale des oxydes, le débit d'atmosphère étant suffisant pour assurer la réduction complète des oxydes ainsi qu'un frittage et une adhérence correspondant à une valeur prédéterminée.The parameter P (H₂) f is the lowest value measured at a point in the furnace corresponding to the total reduction of the oxides, the flow of atmosphere being sufficient to ensure the complete reduction of the oxides as well as a sintering and an adhesion corresponding to a predetermined value.

Le paramètre X(O₂)i est mesuré selon les techniques habituelles de dosage d'oxygène dans un mélange pulvérulent.The parameter X (O₂) i is measured according to the usual techniques for assaying oxygen in a pulverulent mixture.

Le coefficient α est déterminé de la manière suivante : on injecte une atmosphère d'azote et d'hydrogène de manière habituelle dans le four de frittage, par exemple de la manière réalisée habituellement avec un générateur exothermique. On ajoute au gaz injecté, par exemple 5 %, en volume d'un gaz "traceur" tel que l'hélium, pendant un intervalle de temps déterminé, par exemple 10 minutes. On enregistre à l'entrée et à la sortie du four, l'evolution du taux d'hélium dans le gaz s'échappant du four en fonction du temps. On réalise l'intégration de ce taux d'hélium en fonction du temps à l'entrée et à la sortie du four, respectivement (He)i et (He)o. Le coefficient α est égal à (He)i / ( (He)i + (He)o ).The coefficient α is determined in the following manner: a nitrogen and hydrogen atmosphere is injected in the usual manner into the sintering furnace, for example in the manner usually carried out with an exothermic generator. Is added to the injected gas, for example 5%, by volume of a "tracer" gas such as helium, during a determined time interval, for example 10 minutes. The evolution of the rate of helium in the gas escaping from the oven as a function of time is recorded at the inlet and at the outlet of the oven. This helium level is integrated as a function of the time at the inlet and at the outlet of the furnace, respectively (He) i and (He) o . The coefficient α is equal to (He) i / ((He) i + (He) o ).

Lorsque le matériau à fritter est sous forme de pièces juxtaposées les unes à côté des autres sur le tapis du four, SP représente la section moyenne des pièces dans le plan perpendiculaire au tapis du four.When the material to be sintered is in the form of parts juxtaposed one next to the other on the oven mat, S P represents the mean section of the parts in the plane perpendicular to the oven mat.

L'invention sera mieux comprise à l'aide des exemples de réalisation suivants, donnés à titre non limitatif :The invention will be better understood with the aid of the following exemplary embodiments, given without limitation:

EXEMPLE 1 : EXAMPLE 1 :

Sur une feuille d'acier au carbone utilisée comme support, on dépose une couche de 0,9 mm de poudre contenant 73 % de cuivre, 23 % de plomb et 4 % d'étain. La largeur du support sur lequel est déposée la poudre est de 200 mm, la masse volumique de la poudre de 5,2 T/M³ et le pourcentage d'oxygène dans la poudre est de 0.28 %.On a sheet of carbon steel used as a support, a layer of 0.9 mm of powder is deposited containing 73% copper, 23% lead and 4% tin. The width of the support on which the powder is deposited is 200 mm, the density of the powder is 5.2 T / M³ and the percentage of oxygen in the powder is 0.28%.

Le ruban avance à la vitesse VS dans le four, constitué d'un four de pré-frittage de 30 mètres de longueur à la température de 820°C, à la sortie duquel le ruban et la poudre sont laminés entre deux cylindres d'acier, puis introduits dans le four de frittage (30 mètres de longueur - 820°C), chaque four de pré-frittage et de frittage comportent une zône de refroidissement de 10 mètres de longueur (type "water-jacket").The ribbon advances at speed V S in the oven, consisting of a 30-meter long pre-sintering oven at a temperature of 820 ° C, at the outlet of which the ribbon and the powder are laminated between two steel cylinders, then introduced into the sintering oven (30 meters in length - 820 ° C), each pre-sintering and sintering oven has a cooling zone of 10 meters in length ("water-jacket" type) .

L'atmosphère est injectée dans les fours de pré-frittage et de frittage à proximité de la jonction des zônes chaude et de refroidissement.The atmosphere is injected into the pre-sintering and sintering furnaces near the junction of the hot and cooling zones.

On injecte dans le four de pré-frittage une atmosphère contenant 10 % d'hydrogène et 90 % d'azote.An atmosphere containing 10% hydrogen and 90% nitrogen is injected into the pre-sintering oven.

En utilisant un débit de 30m³/heure dans le four de pré-frittage, on mesure P(H₂)f tel que défini plus haut. La valeur mesurée est de 2,8 %. On mesure un coefficient α d'une valeur de 30 %.Using a flow rate of 30m³ / hour in the pre-sintering oven, we measure P (H₂) f as defined above. The measured value is 2.8%. We measure a coefficient α with a value of 30%.

En appliquant la formule mentionnée plus haut, on détermine ainsi que :

Figure imgb0002
By applying the formula mentioned above, it is thus determined that:
Figure imgb0002

Afin d'augmenter au maximum la vitesse du procédé, on maintient le débit de 30m³/h d'atmosphère contenant 10 % de H₂ en volume de 90 % de N₂ en volume.
On obtient une vitesse de frittage qui doit rester inférieure à 5,9 x 30 = 177 mètres/heure.
En se plaçant légèrement en deça de cette vitesse (environ 160 m/h), on vérifie que l'on obtient un matériau ayant les qualités de frittage prédéterminées identiques à celles obtenues en utilisant un générateur exothermique engendrant une atmosphère contenant 10 % d'hydrogène, 8 % de CO, 6 % de CO₂ et 76 % N₂, sous un débit de 30 m³/heure, tant au niveau du four de pré-frittage qu'au niveau du four de frittage, mais avec une vitesse d'avance du matériau d'environ 110 m/h. Le gain en vitesse du procédé selon l'invention est donc d'environ 50 %.In order to increase the speed of the process as much as possible, the flow rate of 30m³ / h of atmosphere containing 10% of H₂ by volume is maintained by 90% of N₂ by volume.
A sintering speed is obtained which must remain below 5.9 x 30 = 177 meters / hour.
By placing slightly below this speed (around 160 m / h), it is verified that a material is obtained having the predetermined sintering qualities identical to those obtained using an exothermic generator generating an atmosphere containing 10% of hydrogen. , 8% CO, 6% CO₂ and 76% N₂, at a flow rate of 30 m³ / hour, both at the pre-sintering oven and at the sintering oven, but with a feed rate of material about 110 m / h. The gain in speed of the process according to the invention is therefore around 50%.

Mais on a constaté de plus qu'il était possible de réduire le débit de gaz dans le four de frittage jusqu'à une valeur d'environ 15m³/heure à l'aide d'un mélange ne contenant que 5 % de H₂ et 95 % de N₂, tout en obtenant les mêmes qualités prédéterminées de frittage du matériau.However, it has also been found that it is possible to reduce the gas flow rate in the sintering furnace to a value of approximately 15 m³ / hour using a mixture containing only 5% of H₂ and 95 % of N₂, while obtaining the same predetermined sintering qualities of the material.

Le procédé selon l'invention permet d'accélérer la vitesse (à débit constant) ou de réduire le débit (à vitesse constante) dans le four de pré-frittage, mais permet également de réduire le débit de gaz dans le four de frittage avec une atmosphère contenant moins d'hydrogène, ce qui se traduit globalement par une abaissement important des coûts de production.The method according to the invention makes it possible to accelerate the speed (at constant speed) or to reduce the flow (at constant speed) in the pre-sintering furnace, but also makes it possible to reduce the gas flow in the sintering furnace with an atmosphere containing less hydrogen, which overall results in a significant reduction in production costs.

De tels rubans sont utilisables comme coussinets auto-lubrifiants.Such tapes can be used as self-lubricating pads.

EXEMPLE 2: EXAMPLE 2 :

Sur une feuille d'acier au carbone pré-nickelée utilisée comme support, on dépose une couche de 0,7 mm de poudre de Nickel.On a sheet of pre-nickel-plated carbon steel used as support, a layer of 0.7 mm of nickel powder is deposited.

La largeur du support sur lequel est déposée la poudre est de 150 mm, la masse volumique de la poudre de 0,8 T/M³ et le pourcentage d'oxygène dans la poudre est de 0,18 %.The width of the support on which the powder is deposited is 150 mm, the density of the powder is 0.8 T / M³ and the percentage of oxygen in the powder is 0.18%.

Le ruban avance à la vitesse VS dans le four, constitué d'une zône chaude à la température de 1040°C, de 4 m de longueur, suivie d'un zône froide de type "water-jacket".The ribbon advances at speed V S in the oven, consisting of a hot zone at the temperature of 1040 ° C, 4 m in length, followed by a cold zone of the "water-jacket" type.

L'atmosphère est injectée dans le four à la jonction entre la zône chaude et la zône froide ainsi qu'en fin de zône froide. Elle est constituée de 10 % d'hydrogène et 90 % d'azote.The atmosphere is injected into the oven at the junction between the hot zone and the cold zone as well as at the end of the cold zone. It consists of 10% hydrogen and 90% nitrogen.

En utilisant un débit de 6 m³/heure dans le four, on mesure P(H₂)f telle que défini plus haut. La valeur mesurée est de 7,5 %.Using a flow rate of 6 m³ / hour in the oven, we measure P (H₂) f as defined above. The measured value is 7.5%.

On détermine le coefficient α comme indiqué précedemment : la valeur mesurée est de 20 %.The coefficient α is determined as indicated above: the measured value is 20%.

En appliquant la formule mentionnée plus haut, on détermine ainsi que :

Figure imgb0003
By applying the formula mentioned above, it is thus determined that:
Figure imgb0003

Afin d'augmenter au maximum la vitesse du procédé, on maintient le débit de 6 m³/h d'atmosphère contenant 10 % de H₂ en volume de 90 % de N₂ en volume.
On obtient une vitesse de frittage qui doit rester inférieure à 23,6 x 6 = 141 mètres/heure.
En se plaçant légèrement en deça de cette vitesse (environ 120 m/h), on obtient un matériau ayant les qualités de frittage prédéterminées identiques à celles obtenues en utilisant un craqueur-bruleur d'ammoniac engendrant une atmosphère contenant 10 % d'hydrogène, et 90 % d'azote sous un débit de 6 m³/heure, mais avec une vitesse d'avance du matériau d'environ 80 m/h.In order to increase the speed of the process as much as possible, the flow rate of 6 m³ / h of atmosphere containing 10% of H₂ by volume is maintained by 90% of N₂ by volume.
A sintering speed is obtained which must remain below 23.6 x 6 = 141 meters / hour.
By being placed slightly below this speed (about 120 m / h), a material is obtained having the predetermined sintering qualities identical to those obtained using an ammonia cracker-burner. generating an atmosphere containing 10% hydrogen, and 90% nitrogen at a flow rate of 6 m³ / hour, but with a material advance speed of approximately 80 m / h.

De tels rubans sont utilisables comme électrodes poreuses pour batteries alcalines.Such tapes can be used as porous electrodes for alkaline batteries.

Claims (5)

1 - Procédé de frittage dans un four continu d'un matériau en poudre contenant de l'oxygène sous forme d'oxyde et/ou sous forme adsorbée, dans lequel on réduit l'oxygène présent au cours d'une première étape de pré-frittage puis on assure la cohésion du matériau au cours d'une seconde étape de frittage, caractérisé en ce que l'étape de pré-frittage s'effectue sous atmosphère réductrice à base d'hydrogène et de gaz neutre dont le débit un débit FG est supérieur ou égal à :
Figure imgb0004
 relation dans laquelle :
SP = section de la couche de poudre à fritter en m²,
DP = masse volumique de la poudre en kg/m³,
X(O₂)i = pourcentage en masse d'oxygène dans la poudre avant l'étape de pré-frittage, sous forme d'oxyde et/ou adsorbé,
P(H₂)i = pourcentage volumique d'hydrogène dans le gaz introduit dans le four,
P(H₂)f = le plus faible pourcentage volumique d'hydrogène dans l'atmosphère du four en un point où les oxydes ont été complètement réduits,
VS = vitesse d'avance du matériau dans le four exprimée en m/h,
α est une constante,
FG étant exprimé en m³/heure.1 - Method of sintering in a continuous furnace a powder material containing oxygen in the form of oxide and / or in adsorbed form, in which the oxygen present is reduced during a first step of pre- sintering, then cohesion of the material is ensured during a second sintering step, characterized in that the pre-sintering step is carried out under a reducing atmosphere based on hydrogen and neutral gas, the flow rate of which is a flow rate F G is greater than or equal to:
Figure imgb0004
 relationship in which:
S P = section of the sintering powder layer in m²,
D P = density of the powder in kg / m³,
X (O₂) i = percentage by mass of oxygen in the powder before the pre-sintering step, in the form of oxide and / or adsorbed,
P (H₂) i = volume percentage of hydrogen in the gas introduced into the furnace,
P (H₂) f = the lowest volume percentage of hydrogen in the furnace atmosphere at a point where the oxides have been completely reduced,
V S = speed of advance of the material in the furnace expressed in m / h,
α is a constant,
F G being expressed in m³ / hour. 2 - Procédé de frittage selon la revendication 1, caractérisé en ce que le matériau en poudre est constitué d'un ou plusieurs oxydes métalliques.2 - Sintering method according to claim 1, characterized in that the powder material consists of one or more metal oxides. 3 - Procédé de frittage selon la revendication 1, caractérisé en ce que le matériau en poudre est constitué d'un ou plusieurs métaux.3 - Sintering method according to claim 1, characterized in that the powder material consists of one or more metals. 4 - Procédé selon l'une des revendications 1 à 3, caractérisé en ce que le matériau en poudre est fritté sur un support métallique.4 - Method according to one of claims 1 to 3, characterized in that the powder material is sintered on a metal support. 5 - Procédé selon l'une des revendications précédentes, caractérisé en ce que l'atmosphère engendrée dans le four de frittage est une atmosphère contenant également de l'hydrogène et un gaz neutre dont la concentration en hydrogène est inférieuer à celle de l'atmosphère de pré-frittage.5 - Method according to one of the preceding claims, characterized in that the atmosphere generated in the sintering furnace is an atmosphere also containing hydrogen and a neutral gas whose hydrogen concentration is lower than that of the atmosphere pre-sintering.
EP87401098A 1986-05-16 1987-05-15 Process for sintering pulverulent material in a continuous furnace Expired - Lifetime EP0246162B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT87401098T ATE50936T1 (en) 1986-05-16 1987-05-15 PROCESS FOR SINTERING POWDER MATERIAL IN A CONTINUOUS FURNACE.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8607067 1986-05-16
FR8607067A FR2598641B1 (en) 1986-05-16 1986-05-16 SINTERING PROCESS IN A CONTINUOUS OVEN OF POWDER MATERIAL

Publications (2)

Publication Number Publication Date
EP0246162A1 true EP0246162A1 (en) 1987-11-19
EP0246162B1 EP0246162B1 (en) 1990-03-14

Family

ID=9335326

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87401098A Expired - Lifetime EP0246162B1 (en) 1986-05-16 1987-05-15 Process for sintering pulverulent material in a continuous furnace

Country Status (12)

Country Link
US (1) US4713215A (en)
EP (1) EP0246162B1 (en)
JP (1) JPS62274003A (en)
AT (1) ATE50936T1 (en)
AU (1) AU587757B2 (en)
BR (1) BR8702497A (en)
DE (1) DE3761881D1 (en)
ES (1) ES2013767B3 (en)
FR (1) FR2598641B1 (en)
GR (1) GR3000295T3 (en)
PT (1) PT84873B (en)
ZA (1) ZA873505B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0421084A1 (en) * 1989-09-13 1991-04-10 Asea Brown Boveri Ag Method for making components by powder metallurgy

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3167313B2 (en) * 1990-07-24 2001-05-21 シチズン時計株式会社 Parts manufacturing method
US6655004B2 (en) 2001-10-03 2003-12-02 Delphi Technologies, Inc. Method of making a powder metal rotor for a surface
US6675460B2 (en) 2001-10-03 2004-01-13 Delphi Technologies, Inc. Method of making a powder metal rotor for a synchronous reluctance machine
US6856051B2 (en) * 2001-10-03 2005-02-15 Delphi Technologies, Inc. Manufacturing method and composite powder metal rotor assembly for circumferential type interior permanent magnet machine

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4190440A (en) * 1977-06-24 1980-02-26 American Can Company Process for fabricating steel from ferrous metal particles

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3888663A (en) * 1972-10-27 1975-06-10 Federal Mogul Corp Metal powder sintering process
US3979234A (en) * 1975-09-18 1976-09-07 The United States Of America As Represented By The United States Energy Research And Development Administration Process for fabricating articles of tungsten-nickel-iron alloy
US4137106A (en) * 1976-07-26 1979-01-30 Sumitomo Electric Industries, Ltd. Super hard metal roll assembly and production thereof
JPS5420909A (en) * 1977-07-17 1979-02-16 Sumitomo Electric Ind Ltd Method of apparatus for sintering supper hard alloy
US4139375A (en) * 1978-02-06 1979-02-13 Union Carbide Corporation Process for sintering powder metal parts
CA1190418A (en) * 1980-04-21 1985-07-16 Nobuhito Kuroishi Process for producing sintered ferrous alloys
US4436696A (en) * 1981-05-20 1984-03-13 Air Products And Chemicals, Inc. Process for providing a uniform carbon distribution in ferrous compacts at high temperatures
JPS5839707A (en) * 1981-09-01 1983-03-08 Kobe Steel Ltd High density sintering method for powder molding

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4190440A (en) * 1977-06-24 1980-02-26 American Can Company Process for fabricating steel from ferrous metal particles

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0421084A1 (en) * 1989-09-13 1991-04-10 Asea Brown Boveri Ag Method for making components by powder metallurgy
US5174952A (en) * 1989-09-13 1992-12-29 Asea Brown Boveri Ltd. Process for the powder-metallurgical production of a workpiece
CH681516A5 (en) * 1989-09-13 1993-04-15 Asea Brown Boveri

Also Published As

Publication number Publication date
AU587757B2 (en) 1989-08-24
AU7293787A (en) 1987-11-19
ES2013767B3 (en) 1990-06-01
JPS62274003A (en) 1987-11-28
ATE50936T1 (en) 1990-03-15
EP0246162B1 (en) 1990-03-14
FR2598641A1 (en) 1987-11-20
GR3000295T3 (en) 1991-03-15
ZA873505B (en) 1987-11-09
FR2598641B1 (en) 1988-08-26
BR8702497A (en) 1988-02-23
DE3761881D1 (en) 1990-04-19
PT84873A (en) 1987-06-01
PT84873B (en) 1990-02-08
US4713215A (en) 1987-12-15

Similar Documents

Publication Publication Date Title
EP1999287B1 (en) Method for continuously annealing and preparing strip of high-strength steel for the purpose of hot-dip galvanizing it
EP0186800B1 (en) Process for coating carbon and graphite bodies
EP0408511B1 (en) Process and apparatus for thermal or thermochemical treatment of steel
EP0246162B1 (en) Process for sintering pulverulent material in a continuous furnace
EP0467749A1 (en) Method of hot dip aluminium coating of a ferritic stainless steel strip
FR2680505A1 (en) PROCESS FOR MANUFACTURING A GRAPHITE MOLDED BODY.
US3859144A (en) Method for producing nickel alloy bonding foil
EP0125486B1 (en) Method of making silicon or metal compound articles or powders by the reaction of solid state silicon or metal articles or powders with a gas
US5207839A (en) Processes for the production of a controlled atmosphere for heat treatment of metals
FR3038623A1 (en) PROCESS FOR REMOVING OXIDES PRESENT AT THE SURFACE OF NODULES OF A METAL POWDER BEFORE USING THE SAME IN AN INDUSTRIAL PROCESS
EP0734805B1 (en) Method and apparatus for making wire electrodes for electric discharge machining
FR2576916A1 (en) Process for forming protective coatings on articles made of refractory alloys in a constantly renewed gas phase, under reduced pressure, and device for its implementation
EP0686844A1 (en) Method and device for measuring wettability in a controlled atmosphere
EP0549398B1 (en) Process for welding or brazing strongly oxidisable metals
EP0093040A1 (en) Process for increasing the life of gas-permeable refractory elements in the bottoms of metallurgical vessels, especially for steel-basic-oxygen furnaces
CA3193686A1 (en) Device and method for producing metal powders
FR2769983A1 (en) PROCESS FOR HEAT ATTACK IN OXIDIZING CONDITIONS OF A CERAMIC
EP0839599B1 (en) Method and apparatus for controlling the constitution of the atmosphere of an enclosure
FR2995615A1 (en) PROCESS FOR PREPARING A SET OF SINTERED ELEMENTS
FR2656003A1 (en) Process and plant for the heat- or thermochemical treatment of a steel making it possible to control the carbon enrichment of the surface region
EP0030060B1 (en) Process and apparatus for automating a vacuum degassing stage of aluminium alloys
FR2543131A1 (en) PROCESSES FOR PRODUCING SEALED GLASS-METAL WELDINGS, PARTICULARLY IN ELECTRONIC COMPONENTS
FR2511396A1 (en) Pack diffusion aluminising - esp. of austenitic stainless steel to improve resistance to high temp. sulphur
EP0112206A1 (en) Method of coating metallic surfaces with carbides
JP2950390B2 (en) Low spatter solid wire for gas shielded arc welding and method for producing the same.

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19870520

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE ES FR GB GR IT LI LU NL SE

17Q First examination report despatched

Effective date: 19881207

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT BE CH DE ES FR GB GR IT LI LU NL SE

ITF It: translation for a ep patent filed

Owner name: BARZANO' E ZANARDO MILANO S.P.A.

REF Corresponds to:

Ref document number: 50936

Country of ref document: AT

Date of ref document: 19900315

Kind code of ref document: T

REF Corresponds to:

Ref document number: 3761881

Country of ref document: DE

Date of ref document: 19900419

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: LU

Payment date: 19900430

Year of fee payment: 4

GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19900531

REG Reference to a national code

Ref country code: GR

Ref legal event code: FG4A

Free format text: 3000295

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19910410

Year of fee payment: 5

Ref country code: AT

Payment date: 19910410

Year of fee payment: 5

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19910411

Year of fee payment: 5

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 19910415

Year of fee payment: 5

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 19910423

Year of fee payment: 5

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19910426

Year of fee payment: 5

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19910515

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: ES

Payment date: 19910516

Year of fee payment: 5

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GR

Payment date: 19910524

Year of fee payment: 5

ITTA It: last paid annual fee
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19910531

Year of fee payment: 5

GBPC Gb: european patent ceased through non-payment of renewal fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: AT

Effective date: 19920515

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19920516

Ref country code: ES

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 19920516

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19920531

Ref country code: CH

Effective date: 19920531

Ref country code: BE

Effective date: 19920531

BERE Be: lapsed

Owner name: L' AIR LIQUIDE S.A. POUR L'ETUDE ET L'EXPLOITATION

Effective date: 19920531

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GR

Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY

Effective date: 19921130

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19921201

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19930129

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19930202

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

REG Reference to a national code

Ref country code: GR

Ref legal event code: MM2A

Free format text: 3000295

EUG Se: european patent has lapsed

Ref document number: 87401098.6

Effective date: 19921204

REG Reference to a national code

Ref country code: ES

Ref legal event code: FD2A

Effective date: 19990601

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 20050515