EP0059864A1 - Process for manufacturing amorphous metal alloys based on iron, phosphorus, carbon and chromium - Google Patents

Abstract

The present invention relates to a process for the preparation of amorphous metal alloys based on iron, phosphorus, carbon and chromium, of the type according to which a metal alloy is cooled very quickly in the liquid phase so as to obtain a structure vitreous, characterized in that the liquid phase is prepared from cast iron, phosphorus and chromium. This process makes it possible to obtain an amorphous alloy of a low cost comparable to that of crystalline products and yet having improved properties. The invention also relates to the amorphous alloy obtained having the following composition in atomic percentage: Cr: 1.5 to 8; C: 8 to 16; P: 4 to 12; If: up to 3.5; the rest being iron and the P / C ratio being less than 1.

Description

The present invention relates to a process for the preparation of amorphous, or vitreous, metallic alloys based on iron, phosphorus, carbon and chromium, as well as to an alloy composition resulting therefrom.

We know, since the work directed in 1958 by Pol Duwez at the California Institute of Technology, amorphous metal alloys, which are obtained by very rapid cooling of a liquid phase, thus allowing to keep its disordered structure, or non-crystalline. Indeed, the material is thus brought directly to a temperature below a certain threshold, called the vitrification temperature, itself located at a temperature much lower than that of solidification at which crystallization begins.

A technique for manufacturing amorphous metal alloys, called hyperhardening, involves sending a jet of molten metal onto the surface of a rotating disc or cylinder, the temperature of which is kept below or equal to ambient temperature. The liquid then spreads over the disc in a thick film of only a few microns. As the film is extremely thin and in close contact with a heat sink of much larger volume and the metals have a high thermal conductivity, the metal cools and solidifies very quickly, at a speed of the order of 10 ° C / second.

In a particular embodiment, the jet of molten metal strikes the internal surface of a rapidly rotating hollow cylinder (POND and MADDIN, Trans of Met. Soc., AIME, Vol. 245, p. 2475, 1969).

The films or ribbons thus prepared have remarkable properties, both mechanically and magnetically. Thus, the alloys have a very high tensile strength and their ductility is characterized by excellent bending resistance, making it possible to achieve curvatures around a radius of the order of the thickness of the ribbon; they also have properties of soft magnetism, that is to say that they are magnetized and demagnetized with a very weak field.

The first compositions of amorphous alloys were binary, based on gold and silicon; many metallic compositions have been tried since, but those likely to lead to an amorphous alloy by hyper quenching generally consist of a metal or a alloy of transition metals (iron, cobalt, nickel) or of a noble metal (gold, palladium, platinum) and a metaloid of small atomic radius (boron, silicon, phosphorus, carbon).

Patent FR 2 211 536 describes a composition of the MYZ type, in which M is a metal chosen from iron, nickel, chromium, cobalt or vanadium or a mixture of these elements, Y is a metalloid chosen from phosphorus, carbon or boron and Z is an element chosen from the group consisting of aluminum, silicon, tin, antimony, germanium, indium or beryllium. However, the various iron-based compositions are made from elements of high purity. Similarly, the iron-phosphorus-carbon alloy developed according to the technique described in Journal of non-crist. Solid. n ° 5, 1970, p. l, by Pol DUWEZ, is obtained by the fusion of an iron powder with 99.99% purity, pure red phosphorus, graphite-quality carbon of powder electrode, this mixture undergoing sintering to form ingots.

The processes for preparing these amorphous metal alloys are therefore expensive since they require the use of the elemental metals constituting the alloy in the pure state.

The Applicant has found that, surprisingly, an amorphous metal alloy can be prepared from extremely common materials.

The subject of the invention is therefore a process for the preparation of amorphous metal alloys based on iron, of phosphorus, carbon and chromium, of the type according to which a metallic alloy is very rapidly cooled in the liquid phase so as to obtain a vitreous structure, characterized in that the liquid phase is prepared from cast iron, phosphorus and chromium.

According to a first embodiment of the process of the present invention, the liquid phase is obtained by adding phosphorus, in an amount of 3.8 to 11.5 _% by weight and of chromium, in an amount of 0 to 12% by weight, to of cast iron in a liquid state, the above percentages being counted in relation to cast iron.

Unless otherwise indicated, the percentages given in the remainder of this specification for the proportions of the various elements are by weight.

According to a first variant, it is possible to carry out a simultaneous addition of phosphorus and chromium.

According to a second preferred variant, the phosphorus is first added to the liquid cast iron, the resulting cast iron mixture is scoured and then the chromium is added.

In a third variant, the chromium is first added to the liquid iron, then the phosphorus is then added.

According to a second embodiment of the process of the present invention, the liquid phase is prepared by simultaneous remelting of cast iron in the solid state and from 0 to 12; by weight of chromium in the solid state, relative to the cast iron, then 3.8 to 11.5% by weight of phosphorus in the solid state, relative to the cast iron, are added.

The phosphorus is preferably introduced in the form of an alloy such as ferrophosphorus, and the chromium also in the form of an alloy such as ferrochrome.

It is then possible to prepare an amorphous metal alloy from very conventional industrial products, such as cast iron, without being forced to use pure elements or at least 99% purity, or to use techniques of 'elaboration like that of vacuum manufacturing which avoids the formation of oxides, the dissolution of gases or the loss of volatile elements.

The invention also relates to an amorphous alloy of the type containing iron, phosphorus, carbon and chromium, characterized in that it has the following composition in atomic percentage: Cr: 1.5 to 8; C: 8 to 16; P: 4 to 12; If: up to 3.5; the rest being iron and the P / C ratio being less than 1.

The alloy thus obtained is characterized both by its P / C ratio <1, and by the presence of Si.

According to the first embodiment, the method of the invention consists in adding to a pig iron maintained in the liquid state, ferrophosphorus and ferrochrome. By pig iron means a pig iron which has not undergone any particular treatment such as desulphurization or dephosphorization but which is descaled, but it is also possible to use a pig iron which has undergone, in addition to de-scouring, prior desulphurization or dephosphorization. This cast iron can be, for example, a cast iron collected in a conventional manner during the casting of the blast furnace. Cast iron is used as a liquid directly from the blast furnace or a storage mixer, or can also be obtained by remelting ingots. Ferrophosphorus and ferrochrome are added in the form of commercial granules. The cast iron is kept liquid by any suitable means such as induction, oxygen blowing, etc., at a temperature between 1250 and 1450 ° C during the additions, the temperature is then brought back to a value between 1250 and 1350 ° C to avoid excessive phosphorus losses. The yields of these additions vary between 80 and 97%, ie 90 to 97% for the ferrochrome and 80 to 97% for the ferrophosphorus.

• - de 3,8 à 11,5%en poids en phosphore par rapport à la fonte, par exemple sous forme de 15 à 44 % en poids de ferrophosphore ayant une teneur d'environ 26 % en phosphore;
• - de 0 à 12 % en poids de chrome par rapport à la fonte, par exemple sous forme de 0 à 17 % en poids de ferrochrome ayant une teneur d'environ 70 % en chrome;
• --le reste étant de la fonte.

The additions are made in the following proportions:

• - from 3.8 to 11.5% by weight of phosphorus relative to the cast iron, for example in the form of 15 to 44% by weight of ferrophosphorus having a content of approximately 26% of phosphorus;
• - from 0 to 12% by weight of chromium relative to the pig iron, for example in the form of 0 to 17% by weight of ferrochrome having a content of approximately 70% in chromium;
• - the rest being cast iron.

When the second embodiment is implemented, one starts with a cast iron ingot having the same nature as the cast iron defined above, this ingot being remelted in the presence of ferrochrome in the form of commercial granules, in order to '' obtain a liquid mixing phase to which the ferrophosphorus is added.

The alloy thus obtained is either directly hyper-soaked or cooled and then hyper-soaked from remelted ingots at a temperature between 1100 and 1300 ° C, according to any known method, such as cooling on or in a roller, or between two rollers when you want to get a ribbon.

As indicated above, the essential characteristic of the process is that the constituents of the starting mixture do not have a high purity.

Different types of pig iron have been used, the carbon content of which is between 2 and 4.5%, a higher content leading to deposits of free graphite on the amorphous ribbon obtained and a lower content unfavorable to the economic conditions of the process, because it it is then necessary to add ferrophosphorus in larger proportions. The sulfur content is preferably less than 0.45%, a value which already exceeds the levels usually encountered for standard pig iron which has not undergone any desulphurization treatment.

The amount of silicon ranges from trace amounts up to 5%, a limit beyond which obtaining a hyper-soaked product is very difficult, the ribbons obtained becoming more and more brittle. The amount of manganese ranges from purity to 4%. Finally, the use of a very phosphorous cast iron as obtained from a phosphorous ore like. that extracted from the mines of Lorraine is very suitable, this type of pig iron having a phosphorus content of up to 1.65%. We can also use chrome cast iron with a chromium content of up to 14%.

By way of illustration, elementary compositions will be given below for four fonts that have been used.

The ferrophosphorus used as an addition element preferably has the best possible phosphorus content, compatible with commercial requirements, a minimum content of 15% being desirable. The ferrophosphorus preferably does not contain more than 2.5% of titanium, which is a conventional impurity because, beyond this value, the formation of titanium oxide disturbs the quenching. Examples of ferrophosphorus compositions are shown in the following table.

Ferrochrome, which is the other preferred addition element in the process of the present invention, is a commercial product preferably having a minimum chromium content of 50%, for example around 70% and which may contain impurities in the water. 'trace amounts such as manganese and magnesium, these impurities having no harmful consequences since they are already present in the initial melt.

By hyperquenching the mixture defined above, an amorphous alloy is obtained, the composition of which has been given above and which comprises other elements in the form of impurities, in particular manganese.

EXAMPLE 1

By operating according to the first embodiment of the method of the present invention, 70% by weight of liquid iron corresponding to sample 1 defined above was mixed with 23% of solid ferrophosphorus corresponding to sample 1 defined above. above, 'then the mixture was descaled and finally added 7% solid ferrochrome to 70% chromium, the various percentages being given relative to the weight of the mixture. After _h yp _e quenching, the resulting amorphous alloy has the following composition (in atomic%):

EXAMPLE 2

• 

Still operating according to the first embodiment of the process of the invention, 65% by weight of liquid pig iron with a composition corresponding to that of sample 2 defined above was mixed with 26.4% of solid ferrophosphorus corresponding to sample 2 defined above, the mixture was descaled, 8.6% solid ferrochrome with 70% chromium was added, the percentages being given by weight relative to the mixture. The alloy obtained has the following composition (in atomic%):

• 

EXAMPLE 3

By operating according to the second embodiment of the process of the present invention, 65% solid cast iron of composition corresponding to that of sample 2 defined above is remelted, with 8.6% solid ferrochrome containing 70% chromium. , then 26.4% of solid ferrophosphorus corresponding to sample 2 defined above is added to the liquid mixture, the percentages being given by weight relative to the mixture. The alloy obtained has the composition given in Example 2.

In its usual crystalline form, an alloy having a composition as defined above is very hard and brittle and its mechanical properties are obviously poor. The tensile strength at break is less than 200 MPa. On the other hand, the cost price of this material is very low since its production requires only a cast iron which can be untreated to which ferrophosphorus and ferrochrome are added in modest quantities.

When made amorphous, this same alloy makes it possible, for example, to obtain metallic ribbons of theoretically unlimited length, of thickness less than 60 microns and of width between 0.2 and several millimeters, while remaining of a low cost, since it is obtained from the same raw materials.

correspondant au premier exemple de réalisation a été soumis à divers essais. Sa température de recristallisation est de l'ordre de 470°C; il subit, avant recristallisation, une perte de ductilité après un traitement de 6 heures à 220°C.By way of comparison, an amorphous alloy (A) of the following composition (enatomic)

corresponding to the first exemplary embodiment was subjected to various tests. Its recrystallization temperature is around 470 ° C; before recrystallization, it undergoes a loss of ductility after a treatment of 6 hours at 220 ° C.

A comparison of the mechanical characteristics of this alloy of composition (A) in its amorphous form and in its crystalline form is shown in the table below:

Claims (13)

1. Process for the preparation of amorphous metal alloys based on iron, phosphorus, carbon and chromium, of the type according to which a metal alloy is cooled very quickly in the liquid phase so as to obtain a glassy structure, characterized in that that the liquid phase is prepared from cast iron, phosphorus and chromium. 2. Method according to claim 1, characterized in that the liquid phase is obtained by addition of phosphorus, in an amount of 3.8 to 11.5% by weight, and of chromium, in an amount of 0 to 12% by weight, to cast iron in liquid state, the above percentages being counted with respect to cast iron. 3. Method according to claim 2, characterized in that the addition of phosphorus is first carried out, the mixture obtained is scoured and then the chromium is added. 4. Method according to claim 2, characterized in that the addition of chromium is first carried out, then the phosphorus is then added. 5. Method according to claim 1, characterized in that the liquid phase is prepared by simultaneous remelting of cast iron in the solid state and from 0 to 12%. By weight of chromium in the solid state, relative to the cast iron , then from 3.8 to 11.5% by weight of phosphorus in the solid state is added, relative to the cast iron. 6. Method according to any one of the preceding claims, characterized in that the cast iron used is a scoured cast iron directly obtained during the casting of the blast furnace and having not undergone any prior treatment or a cast iron having possibly undergone a prior treatment in particular desulfurization and / or dephosphorization. 7. Method according to any one of the preceding claims, characterized in that the cast iron used has a carbon content of 2 to 4.5%, of sulfur less than 0.45 J, of silicon less than 5%, in manganese less than 4% and which can optionally be combined with chromium up to a content of 14%. 8. Method according to any one of the preceding claims, characterized in that the phosphorus is added in the form of ferrophosphorus. 9. Method according to claim 8, characterized in that the ferrophosphorus has a minimum phosphorus content of 15%. 10. Method according to any one of claims 1 to 7, characterized in that the chromium is added in the form of ferrochrome. 11. Method according to claim 10, characterized in that the ferrochrome preferably has a minimum chromium content of approximately 50%. 12. Method according to any one of the preceding claims, characterized in that the addition of ferrophosphorus and ferrochrome is carried out in the cast iron maintained at a temperature of 1250 to 1450 ° C. 13. Amorphous alloy of the type containing iron, phosphorus, carbon and chromium, characterized in that it has the following composition in atomic percentage: Cr: 1.5 to 8; C: 8 to 16; P: 4 to 12; If: _j only 3.5; the rest being iron and the P / C ratio being less than 1.