EP0015819B1 - Method for the production of articles mainly consisting of spheroidal graphite cast iron - Google Patents
Method for the production of articles mainly consisting of spheroidal graphite cast iron Download PDFInfo
- Publication number
- EP0015819B1 EP0015819B1 EP80400260A EP80400260A EP0015819B1 EP 0015819 B1 EP0015819 B1 EP 0015819B1 EP 80400260 A EP80400260 A EP 80400260A EP 80400260 A EP80400260 A EP 80400260A EP 0015819 B1 EP0015819 B1 EP 0015819B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- cast iron
- mould
- molten metal
- hydrogen
- pouring
- 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.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/08—Manufacture of cast-iron
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/10—Making spheroidal graphite cast-iron
Definitions
- the present invention relates to a process for producing cast iron parts, in particular spheroidal graphite cast iron, of the type in which molten metal is poured from a preparation bag into a mold.
- Hydrogen pits generally form under the skin of parts in a solidified area and this formation occurs with a certain delay on solidification, so that these defects do not appear immediately after demolding. In fact, it is at the time of the finishing operations, such as machining of the molded parts, that the hydrogen pits appear to the eye and one is then constrained to discard the parts thus molded and almost completely machined. It follows high losses due not only to the molding, but to the subsequent operations of demasselotage, grinding, deburring, heat treatments, etc ...
- the subject of the present invention is a process for the production of cast iron parts, in particular spheroidal graphite cast iron, which makes it possible to avoid the formation of hydrogen pits for sure and this invention is characterized by the imperative joint use of two measurements each known per se: on the one hand, it is ensured that the magnesium content of the cast iron being between 0.03 and 0.07%, the aluminum content is at least equal to 0.1% and on the other hand, the known technique of casting in a mold inerted by liquid nitrogen previously poured into the bottom of the mold is applied to said cast iron during casting.
- the invention makes it possible to combine two measurements in a particularly efficient manner; in fact, it had been observed that by increasing the aluminum content in a pig iron beyond the usual values, the quantity of hydrogen included went through a maximum, then decreased regularly for practically canceling out, for aluminum contents of 0.1% and more. But we had not gone further than this observation, because the tests which had been made with such aluminum contents had led to other disadvantages consisting of inclusions of alumina. Indeed, the relatively large amounts of aluminum included in the cast iron, whether in the oven or during ladle casting for example, react with the oxygen in the air to form alumina.
- this alumina which has a lower density than cast iron, settles easily at the various stages of production in the oven, in a ladle, and can thus be easily eliminated.
- this settling cannot be ensured, because both the shape of the supply duct and that of the cavity or the vents, is always such that it is created within the metal. during casting, significant turbulence which therefore prevents any settling.
- the alumina therefore remains in the cast iron in the course of solidification in the form of inclusions generally close to the surface. These inclusions or "dross" have no adhesion or resistance and their presence therefore reduces the mechanical resistance on the surface of the parts thus molded.
- the joint intervention of the second measure recommended by the invention which consists in avoiding any presence of air in the molding cavity, it can be sure that during the molding operation at least, no formation of alumina can not occur and as we have seen that the dross that had formed prior to the molding operation could be easily removed, so we manage, thanks to the combination of the two measures recommended by the invention to ensure that no inclusion of alumina remains in the molded parts, therefore to avoid, in addition, the undesirable hydrogen pitting.
- the invention applies essentially to the casting of spheroidal graphite cast iron.
Abstract
Description
La présente invention concerne un procédé d'elaboration de pièces en fonte notamment en fonte à graphite sphéroïdal, du genre où l'on coule le métal en fusion d'une poche de préparation dans un moule.The present invention relates to a process for producing cast iron parts, in particular spheroidal graphite cast iron, of the type in which molten metal is poured from a preparation bag into a mold.
Généralement, ce procédé de moulage de fonte à graphite sphéroïdal et, à un moindre titre, de fonte dite lamellaire et de fonte dite alliée, est souvent sujet à des défauts que l'on dénomme généralement "piqûres" d'hydrogène.Generally, this process of casting spheroidal graphite cast iron and, to a lesser extent, of so-called lamellar cast iron and of so-called alloyed cast iron, is often subject to defects which are generally called "pits" of hydrogen.
Ces défauts sont provoqués par une baisse brutale de la solubilité de l'hydrogène dans le métal en cours de solidification; ils se produisent surtout dans des conditions de dif- fusibilité réduites, comme c'est le cas de pièces minces ou d'épaisseur moyenne.These defects are caused by a sudden drop in the solubility of hydrogen in the metal being solidified; they occur especially under conditions of reduced diffusibility, as is the case with thin or medium thickness parts.
Les piqûres d'hydrogène se forment généralement sous la peau de pièces dans une zone solidifiée et cette formation intervient avec un certain retard sur la solidification, si bein que ces défauts n'apparaissent pas immédiatement après démoulage. En fait, c'est au moment où les opérations de parachèvement, telles qu'usinage des pièces moulées, que les piqûres d'hydrogène apparaissent à l'oeil et l'on est constraint alors à mettre au rebut les pièces ainsi moulées et presque complètement usinées. Il s'ensuit de fortes pertes dues non seulement au moulage, mais aux opérations ultérieures de démasselotage, de meulage, d'ébarbage, de traitements thermiques, etc....Hydrogen pits generally form under the skin of parts in a solidified area and this formation occurs with a certain delay on solidification, so that these defects do not appear immediately after demolding. In fact, it is at the time of the finishing operations, such as machining of the molded parts, that the hydrogen pits appear to the eye and one is then constrained to discard the parts thus molded and almost completely machined. It follows high losses due not only to the molding, but to the subsequent operations of demasselotage, grinding, deburring, heat treatments, etc ...
De nombreuses études ont été menées pour déterminer les causes de la présence de l'hydrogène dans le métal et l'on sait maintenant que cet hydrogène provient de la décomposition de l'eau contact du métal à haute température, cette eau pouvant être absorbée à différents stades du processus d'élaboration, par exemple l'humidité de l'air ou des réfractaires constituant la paroi du four, du chenal conduisant à la poche et enfin dans le moule lui-même, et l'on a pu également constater que la cause essentielle de la présence d'hydrogène est précisément l'absorption d'hydrogène juste avant solidification, c'est-à-dire d'hydrogène qui se manifeste dans les moules de coulée.Numerous studies have been carried out to determine the causes of the presence of hydrogen in the metal and it is now known that this hydrogen comes from the decomposition of the contact water of the metal at high temperature, this water being able to be absorbed at different stages of the production process, for example the humidity of the air or of the refractories constituting the wall of the oven, of the channel leading to the ladle and finally into the mold itself, and it has also been observed that the essential cause of the presence of hydrogen is precisely the absorption of hydrogen just before solidification, that is to say of hydrogen which is manifested in the casting molds.
C'est donc bien entendu les moules dits en sable à vert qui causent le plus de défauts de piqûres d'hydrogène, puisque le sable qui les constitue présente une certaine humidité.It is therefore of course the so-called green sand molds which cause the most hydrogen stinging defects, since the sand which constitutes them has a certain humidity.
On a constaté également que ce défaut était accentué en fonction de la longueur du parcours d'alimentation de la pièce moulée et que les pièces situées en bout de la grappe en étaient les plus affectées.It was also found that this defect was accentuated as a function of the length of the feed path of the molded part and that the parts located at the end of the cluster were the most affected.
Pour remédier à ce défaut, en tout cas l'atténuer, on a bien proposé d'augmenter la température de coulée, ce qui, en reportant dans le temps la solidification de la pièce coulée, favorise donc le dégazage et par là même évite dans une grande mesure la formation de piqûres dues à l'hydrogène. Mais ce remède n'est pas toujours applicable, car il dépend de l'organisation de l'installation de moulage, des synchronisations dans les processus de fusion et de moulage, etc.... et en outre, cette façon de faire occasionne une dépense énergétique supplémentaire non négligeable.To remedy this defect, in any case attenuate it, it has been proposed to increase the casting temperature, which, by postponing the solidification of the cast part over time, therefore promotes degassing and thereby avoids in to a great extent the formation of pitting due to hydrogen. But this remedy is not always applicable, because it depends on the organization of the molding installation, synchronizations in the melting and molding processes, etc ... and in addition, this way of doing causes significant additional energy expenditure.
On a également proposé d'accroître la dose de noir minéral ou de brai dans le sable de moulage, de façon à modifier les conditions de contact du métal avec la paroi des moules et de ralentir l'oxydation du métal par l'oxygène provenant de la décomposition de l'humidité. Le "mouillage" du sable par la fonte qui suppose la présence d'un film oxydé est ainsi évité. Bien que cette façon de faire ait également pour effet de diminuer la présence d'hydrogène, elle augmente également, et de façon non négligeable, le coût du moulage.It has also been proposed to increase the dose of mineral black or pitch in the molding sand, so as to modify the conditions of contact of the metal with the wall of the molds and to slow down the oxidation of the metal by the oxygen coming from decomposition of moisture. The "wetting" of the sand by the cast iron which supposes the presence of an oxidized film is thus avoided. Although this procedure also has the effect of reducing the presence of hydrogen, it also increases, and not insignificantly, the cost of molding.
On a bien constaté le rôle de la teneur en aluminium des fontes dans la formation des piqûres d'hydrogène et on a pu établir que, pour les teneurs en magnésium habituelles de 0,03 à 0,07%, l'absorption d'hydrogène tend à augmenter avec la teneur en aluminium et le risque de piqûre intervient dès que la teneur en pourcentage des fontes en aluminium dépasse quelques millièmes. (Par teneur, on entend ici le pourcentage en poids d'une addition ou impureté par rapport à la masse total de métal). Cette situation est d'autant plus génante que généralement, la teneur en aluminium dans la fonte coulée est difficilement maîtrisable. En effet, que la fonte de base contienne ou non de l'aluminium, l'obtention de fonte à graphite sphéroïdal nécessite l'introduction de produits d'addition et de traitements tels que nodulisants, inoculants, qui contiennent de l'aluminium, si bien qu'en général, on ne peut prédéterminer à l'avance s'il y aura des piqûres d'hydrogène et quelle en sera l'importance.The role of the aluminum content of the cast irons in the formation of hydrogen pitting has been clearly observed and it has been established that, for the usual magnesium contents of 0.03 to 0.07%, the absorption of hydrogen tends to increase with aluminum content and the risk of stinging occurs as soon as the percentage content of aluminum cast irons exceeds a few thousandths. (By content, here is meant the percentage by weight of an addition or impurity relative to the total mass of metal). This situation is all the more annoying as generally the aluminum content in the cast iron is difficult to control. In fact, whether the basic cast iron contains aluminum or not, obtaining spheroidal graphite cast iron requires the introduction of additives and treatments such as nodulizers, inoculants, which contain aluminum, if although, in general, you cannot predetermine in advance whether or not hydrogen will be injected.
La présente invention a pour objet un procédé d'élaboration de pièces en fonte, notamment en fonte à graphite sphéroïdal, qui permet d'éviter à coup sûr la formation de piqûres d'hydrogène et cette invention est caractérisée par l'utilisation impérativement conjointe de deux mesures chacune connue en soi: d'une part, on fait en sorte que la teneur de la fonte en magnésium étant comprise entre 0,03 et 0,07%, la teneur en aluminium soit au moins égale à 0,1% et d'autre part, l'on applique à ladite fonte en cours de coulée, la technique connue en soi de coulée en moule inerté par de l'azote liquide préalablement déversé en fond de moule. Ainsi, l'invention permet de combiner deux mesures d'une façon particulièrement performante; en effet, on avait bien constaté qu'en augmentant au-delà des valeurs usuelles la teneur en aluminium dans une fonte, la quantité de l'hydrogène incluse passait par un maximum, puis décroissait régulièrement pour pratiquement s'annuler, pour des teneurs d'aluminium de 0,1% et plus. Mais on n'avait pas été plus loin que cette constatation, car les essais qui avaient été faits avec de telles teneurs en aluminium avaient conduit à d'autres inconvénients consistant en des inclusions d'alumine. En effet, les quantités d'aluminium relativement importantes incluses dans la fonte, que ce soit au four ou lors de la coulée en poche par exemple, réagissent avec l'oxygène de l'air pour former de l'alumine. Dans las majorité des cas, cette alumine, qui présente une densité plus faible que la fonte, décante facilement aux différents stades d'élaboration dans le four, en poche, et peut être ainsi aisément éliminée. Au contraire, lors d'une coulée en moule, on ne peut assurer cette décantation, car aussi bien la forme du conduit d'alimentation que celle de l'empreinte ou des évents, est toujours telle qu'il se crée au sein du métal en cours de coulée, d'importantes turbulences qui interdisent donc toute décantation. L'alumine reste donc dans la fonte en cours de solidification sous forme d'inclusions généralement près de la surface. Ces inclusions ou "crasses" n'ont pas d'adhérence ni de résistance et leur présence diminue donc la tenue mécanique en surface des pièces ainsi moulées.The subject of the present invention is a process for the production of cast iron parts, in particular spheroidal graphite cast iron, which makes it possible to avoid the formation of hydrogen pits for sure and this invention is characterized by the imperative joint use of two measurements each known per se: on the one hand, it is ensured that the magnesium content of the cast iron being between 0.03 and 0.07%, the aluminum content is at least equal to 0.1% and on the other hand, the known technique of casting in a mold inerted by liquid nitrogen previously poured into the bottom of the mold is applied to said cast iron during casting. Thus, the invention makes it possible to combine two measurements in a particularly efficient manner; in fact, it had been observed that by increasing the aluminum content in a pig iron beyond the usual values, the quantity of hydrogen included went through a maximum, then decreased regularly for practically canceling out, for aluminum contents of 0.1% and more. But we had not gone further than this observation, because the tests which had been made with such aluminum contents had led to other disadvantages consisting of inclusions of alumina. Indeed, the relatively large amounts of aluminum included in the cast iron, whether in the oven or during ladle casting for example, react with the oxygen in the air to form alumina. In the majority of cases, this alumina, which has a lower density than cast iron, settles easily at the various stages of production in the oven, in a ladle, and can thus be easily eliminated. On the contrary, during a mold casting, this settling cannot be ensured, because both the shape of the supply duct and that of the cavity or the vents, is always such that it is created within the metal. during casting, significant turbulence which therefore prevents any settling. The alumina therefore remains in the cast iron in the course of solidification in the form of inclusions generally close to the surface. These inclusions or "dross" have no adhesion or resistance and their presence therefore reduces the mechanical resistance on the surface of the parts thus molded.
Grâce à l'intervention conjointe de la seconde mesure préconisée par l'invention, qui consiste à éviter toute présence d'air dans la cavité de moulage, on peut être sûr que lors de l'opération de moulage au moins, aucune formation d'alumine ne peut se produire et comme on a vu que les crasses qui s'étaient formées antérieurement à l'opération de moulage pouvaient être facilement éliminées, on parvient donc, grâce à la conjonction des deux mesures préconisées par l'invention à faire en sorte qu'aucune inclusion d'alumine ne subsiste dans les pièces moulées, donc à éviter, en outre, les indésirables piqûres d'hydrogène. A titre d'exemple, une fonte de base coulée en poche avec addition de 0,1% d'aluminium, nodulisée par traitement par cloche plongeuse avec Fe Si Mg (35% Mg) puis inoculée avec Fe Si, est transportée et coulée en sable à vert. Quelques dizaines de secondes avant la coulée du métal, les;:(noules sont inertés en déversant dans la cavité: de moulage une quantité d'azote liquide dont le volume, à l'état vaporisé, est de 50 à 100 fois le volume de la cavité de moulage. A l'usinage, les défauts de piqûres d'hydrogène constatés précédemment à la mise en oeuvre du procédé selon l'invention et qui pouvaient conduire à des rebuts de 15%, pratiquement avaient disparu, le taux de rebut tombant à 2% et cela pour une consommation d'azote liquide d'environ 20 litres par tonne de pièces moulées.Thanks to the joint intervention of the second measure recommended by the invention, which consists in avoiding any presence of air in the molding cavity, it can be sure that during the molding operation at least, no formation of alumina can not occur and as we have seen that the dross that had formed prior to the molding operation could be easily removed, so we manage, thanks to the combination of the two measures recommended by the invention to ensure that no inclusion of alumina remains in the molded parts, therefore to avoid, in addition, the undesirable hydrogen pitting. For example, a basic cast iron poured into a ladle with the addition of 0.1% aluminum, nodulized by treatment with a diving bell with Fe Si Mg (35% Mg) then inoculated with Fe Si, is transported and cast in sand to green. A few tens of seconds before the metal is poured, the; :( noules are inerted by pouring into the cavity: molding a quantity of liquid nitrogen whose volume, in the vaporized state, is 50 to 100 times the volume of the mold cavity. During machining, the hydrogen pitting defects noted previously when implementing the process according to the invention and which could lead to rejects of 15%, practically disappeared, the reject rate falling at 2% and this for a liquid nitrogen consumption of approximately 20 liters per tonne of molded parts.
L'invention s'applique essentiellement au moulage de fonte à graphite sphéroïdal.The invention applies essentially to the casting of spheroidal graphite cast iron.
Claims (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT80400260T ATE105T1 (en) | 1979-03-05 | 1980-02-25 | PROCESSES FOR THE MANUFACTURE OF OBJECTS, PARTICULARLY IN NODULAR IRON. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7905601 | 1979-03-05 | ||
| FR7905601A FR2450650A1 (en) | 1979-03-05 | 1979-03-05 | PROCESS FOR THE PREPARATION OF PARTS, PARTICULARLY IN CAST IRON WITH SPHEROIDAL GRAPHITE |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0015819A1 EP0015819A1 (en) | 1980-09-17 |
| EP0015819B1 true EP0015819B1 (en) | 1981-07-15 |
Family
ID=9222749
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP80400260A Expired EP0015819B1 (en) | 1979-03-05 | 1980-02-25 | Method for the production of articles mainly consisting of spheroidal graphite cast iron |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0015819B1 (en) |
| JP (1) | JPS55117557A (en) |
| AT (1) | ATE105T1 (en) |
| AU (1) | AU539864B2 (en) |
| BE (1) | BE882029A (en) |
| CA (1) | CA1135475A (en) |
| DE (1) | DE3060003D1 (en) |
| ES (1) | ES489156A1 (en) |
| FR (1) | FR2450650A1 (en) |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2080159A (en) * | 1935-06-05 | 1937-05-11 | Republic Steel Corp | Process of treating steel |
| GB987190A (en) * | 1963-03-14 | 1965-03-24 | British Oxygen Co Ltd | Minimising the contamination of molten metal during casting |
| BE793567A (en) * | 1971-12-30 | 1973-06-29 | Air Liquide | METAL CASTING PROCESS |
-
1979
- 1979-03-05 FR FR7905601A patent/FR2450650A1/en active Pending
-
1980
- 1980-02-15 AU AU55602/80A patent/AU539864B2/en not_active Ceased
- 1980-02-25 DE DE8080400260T patent/DE3060003D1/en not_active Expired
- 1980-02-25 AT AT80400260T patent/ATE105T1/en not_active IP Right Cessation
- 1980-02-25 EP EP80400260A patent/EP0015819B1/en not_active Expired
- 1980-02-28 CA CA000346644A patent/CA1135475A/en not_active Expired
- 1980-03-03 BE BE0/199632A patent/BE882029A/en not_active IP Right Cessation
- 1980-03-04 ES ES489156A patent/ES489156A1/en not_active Expired
- 1980-03-05 JP JP2678680A patent/JPS55117557A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| ATE105T1 (en) | 1981-07-15 |
| AU5560280A (en) | 1980-09-11 |
| EP0015819A1 (en) | 1980-09-17 |
| DE3060003D1 (en) | 1981-10-22 |
| BE882029A (en) | 1980-09-03 |
| ES489156A1 (en) | 1980-08-16 |
| FR2450650A1 (en) | 1980-10-03 |
| AU539864B2 (en) | 1984-10-18 |
| JPS55117557A (en) | 1980-09-09 |
| CA1135475A (en) | 1982-11-16 |
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