CA2889124C - Inoculant alloy for thick cast-iron parts - Google Patents

Abstract

The invention relates to an inoculant alloy for the treatment of thick cast-iron parts, based on ferrosilicon and containing between 0.005 and 3 wt. % of rare earths, and characterised in that it also contains between 0.2 and 2 wt. % of antimony.

Description

Inoculating alloy for thick castings The present invention relates to an inoculating alloy for processing of cast iron.
Cast iron is a well-known and widely used iron-carbon alloy for the manufacture of mechanical parts. Cast iron is obtained by mixing constituents of the alloy in the liquid state at a temperature of Between 1320 and 1450 C before casting in a mold and cooling of the alloy got.
During cooling, carbon can adopt several physico-chemical structures depending on several parameters.
When carbon combines with iron and forms iron carbide Fe3C (also called cementite), the resulting melt is called cast iron white. White cast iron has the characteristic of being hard and brittle, which is not desirable for certain applications.
If the carbon appears as graphite, the resulting cast iron is called gray cast iron. Gray cast iron is softer and can be worked.
To obtain cast iron parts with good properties mechanical, it is therefore necessary to obtain a structure of the cast iron comprising the maximum carbon in graphite form and limit as much as possible formation of these iron carbides which harden and weaken the alloy.
In the absence of any specific inoculation treatment, the carbon however tends to combine with iron to form iron carbide. It is therefore necessary to treat cast iron in the liquid state so as to modify the carbon association parameters and obtain the desired structure.
To this end, liquid iron undergoes an inoculation treatment aimed at introduce graphitizing components or supports to the cast iron graphitization commonly called germs which will promote, during the cooling of the cast iron in the mold, the appearance of graphite rather than of iron carbide.
In general, therefore, the components of an inoculant are elements favoring the formation of graphite and the decomposition of carbon iron during solidification of the cast iron. We can cite, by way of example, the carbon, silicon, calcium, aluminum, ...
Of course, an inoculant can be designed to fill other functions and to this end include other components presenting a

2 particular effect. Cast iron can also undergo additional treatments prior or subsequent.
It is thus possible in particular, depending on the properties sought, whether the graphite formed is spheroidal, vermicular or lamellar.
Either graphite form can be obtained in such a way preferential by a particular treatment of the cast iron using components specific.
Thus, for example the formation of spheroidal graphite can be favored by a so-called nodulizing treatment aimed mainly at providing the melting of magnesium in sufficient quantity for graphite to grow so as to form round particles (spheroids or nodules).
These nodulizing components are usually added under specific alloy form (nodulizing alloy) prior to treatment inoculating cast iron during a particular treatment.
Thus, the nodulizing alloy essentially makes it possible to influence the forms graphite nodules, while the inoculant aims to increase the number of these nodules and homogenize the structures graphitics.
Mention may also be made of the addition of desulfurizing products, or of products allowing specific treatment of certain defects in cast iron depending on the initial composition of the liquid iron bath, such as microphone-sink marks and pitting, which may appear during cooling.
These treatments can be carried out on one or more occasions and different times in the production of cast iron.
Most inoculants are conventionally made from a FeSi45, FeSi65 or FeSi75 type ferro-silicon alloy with adjustment of the chemistry depending on the intended composition of the inoculant. It can also be of mixtures of several alloys.
It should be noted that the inoculation efficiency of the cast iron part also depends on its thickness (or the rate of solidification).
In areas of low thickness, cooling faster, we will note a higher risk of carbide formation.
Conversely, in areas of greater thickness, the cooling will be slower (2 to 4 hours) and will favor the formation of graphite.

3 It follows that the parts with areas of different thickness may have different physico-chemical structures from one area to another the other, which is not desirable.
In addition, the control of germination in areas of strong thickness remains difficult and can lead to obtaining a non-uniform.
For thick parts, when the process inoculation is not controlled, the formation of degenerate graphite and / or Chunky graphite can reduce the mechanical properties of cast iron. For solve these defects, the founder generally proceeds to the addition of Antimony pure in liquid metal.
Adding pure antimony to liquid metal causes problems precision because the rate of introduction is very low (of the order of 10 to 30g per ton of liquid iron). The addition yield of pure antimony is understood between 50 and 80% and the useful quantity introduced is therefore difficult controllable.
If the quantity is not sufficient, degraded graphite may be train in the structure.
Conversely, if the quantity introduced exceeds the objective, antimony will tend to strongly increase the proportion of perlite, unwanted phase in ferritic structures.
In the case of adding pure antimony, the smelter must also associate Rare Earths (abbreviated as TR or RE for Rare Earths) in order to to obtain maximum improvement in the shape of the graphite. Likewise, if the quantity of Rare Earths is insufficient, the part will have a spiky type graphite. Conversely, if the amount of Rare Earths is too strongly dosed, the graphite defect will be rather chunky, this which mainly occurs when the raw materials used are relatively pure These graphite defects, of the spiky or chunky type degrade the mechanical properties of the cast iron, and in particular the resistance to traction and the impact resistance of the formed part.
The introduction of pure antimony into the liquid iron causes in in addition to its vaporization and thus leads to a strong release of gas. He was measured that with the addition of pure antimony, the threshold of antimony release in the working environment was greater than 0.5 mg / m3, limit value WO 2014/07640

4 PCT / FR2013 / 052710 exposure (ELV set by regulations). Operators must therefore work with a particulate respirator type N95 or higher.
The treatment of thin parts has already been the subject of development of specific inoculants. Documents FR2511044A1, FR2855186A1 and EP0816522A1 describe such an inoculant for thin parts.
Such an inoculant according to these documents for thin parts comprises in particular an inoculant alloy based on ferro-silicon and comprising between 0.005 and 3% by mass of Rare Earths, in particular Lanthanum, as well as between 0.005 and 3% by mass of bismuth, lead or antimony in a Rare Earth / (Bismuth + Lead + Antimony) ratio included between 0.9 and 2.2; bismuth being particularly preferred, the descriptions of these documents relate only to bismuth.
It should be noted that these documents do not disclose the use antimony only generally but does not contain any specific example or no particular value relating to this element.
Among other documents mentioning the use of antimony, the following documents can be cited.
Document WO2006 / 068487A1 describes an inoculant comprising a phase modifier component (inoculant function) associated with an agent modification of the structure of graphite which may be antimony. he should be noted that this structural modifier is used in mixture with the inoculating compound (ferrosilicon) and not in alloyed form.
Antimony is further clearly mentioned as being a promoter of perlite, a phase which, as mentioned earlier, is usually not desired. The amount of antimony used is between 3 and 15%, this who corresponds to a large quantity probably at the origin of the proportion of perlite formed.
JP2200718A describes an inoculant consisting of a mixture of ferrosilicon, antimony, calcium silicide and rare earths.
Antimony is not used in an alloy form.
Document JP57067146A describes an alloy based on ferrosilicon comprising between 5 and 50% by mass of antimony and up to 10% of earth rare. Besides the high proportion of antimony, this alloy is used as perlite inhibitor, not as an inoculant.
There are also several articles and documents dealing with nodulizing function (form of graphite) of antimony, which is not the goal

5 fundamentally researched and does not solve the problem of inoculation (number and quality of nodules). In addition, it is frequently a use of antimony in a mixed and unalloyed form.
There is therefore a need for an inoculating alloy allowing improve the processing of thick parts.
According to a particular embodiment, the invention relates to an alloy ferro-silicon-based inoculant for the treatment of cast iron for manufacture of parts with parts of thickness greater than 6 mm, said inoculant alloy containing 45-80% by mass of silicon, 0.5-4% by mass of calcium, 0.5-3% by mass of aluminum, 0.2-3% by mass of Rare Earths, 0.2-2% by mass of antimony, and the balance in iron, characterized in that the antimony to rare earth ratio is between 0.9 and 2.2.
According to another particular embodiment, the invention relates to a ferro-silicon-based inoculant alloy for the treatment of cast iron for the manufacture of parts with parts of thickness greater than 6 mm, said inoculating alloy containing, characterized in that said alloy contains 45-80% by mass of silicon, 0.5-8% by mass of calcium, 0.5-3% by mass of aluminum, 0.2-3% by mass of Rare Earths, 0.2-2% by mass of antimony, 2-15% by mass of barium, 2-6% manganese, 2-6% zirconium, and the balance in iron, characterized in that the antimony to rare earth ratio is between 0.9 and 2.2.
Thus, it was indeed unexpectedly found that antimony alloyed with rare earths in a ferrosilicon-based alloy according to the proportions claimed allowed efficient inoculation, and with stabilization of spheroids, thick parts without the disadvantages of the pure antimony mentioned above.
280005.00092 / 107713716.1 5a In particular, the introduction of antimony in the form of an alloy allows to achieve a high efficiency of use of antimony, of the order of 97 at 99%. The useful quantity introduced is therefore much more precisely known.
The increase in efficiency thus saves products and simplifies the management of product additions, including for rare earth.
Thanks to this increase in efficiency and the reduction simultaneous emission of gases into the atmosphere, the conditions of work are also improved for operators responsible for additions.
The use of an alloy according to the invention makes it possible to limit the gas release of antimony between 0.1 and 0.2 mg / m3 and the use of a respirator mask is no longer required.
It should also be noted that the antimony / rare earth association significantly lengthens the fade time of antimony.
The produced effect therefore lasts longer in the foundry process full. Note that the fade time of antimony is even greater than the fade time of bismuth in inoculating alloys for thin parts.
The alloy according to the present application, when added in a ladle or in the oven, can thus make it possible to replace or even eliminate an inoculation additional to the jet or late.

6 The alloy according to the present application also allows particularly to greatly limit or even avoid the formation of defects of chunky or spiky type graphite, but also improve the shape graphite ensuring a nodularity greater than 95% while bringing the spheroids of the perfect sphere.
The alloy according to the present application thus makes it possible to ensure homogeneous ferrite / perlite matrix according to the different thicknesses of the room manufactured, which in particular improves the conditions for subsequent machining of the room.
Preferably, the Antimony on Rare Earths report will be greater than 1.4, preferably 1.6, and less than 2.5; preferably less than 2.
According to a first variant embodiment, the inoculating alloy also includes magnesium. It will then be a nodulizing effect additional inoculant.
In particular, it was unexpectedly found that unlike the bismuth already used, antimony made it possible to obtain a better yield of magnesium introduced into the cast iron.
Regarding bismuth, it is known that the latter accelerates the settling of magnesium in the cast iron and that the latter therefore loses more active magnesium for converting flake graphite into graphite spheroidal. The best assimilation of antimony in the form of a nodulizer according to the invention ensures good stability of the residual magnesium between 1350 C and 1580 C.
According to a second variant embodiment, the inoculating alloy does not does not contain magnesium.
Preferably, the ratio of rare earths to antimony is understood between 0.9 and 2.2.
Preferably, the proportion by mass of antimony is greater than 0.3%, preferably greater than 0.5%, more preferably greater than 0.8%.
Preferably, the proportion by mass of antimony is less than 1.5%, preferably less than 1.3%.
Advantageously, the rare earths comprise Lanthanum, preferably only lanthanum.

7 Preferably, the proportion by mass of rare earths is greater than 0.2%, preferably greater than 0.3%.
Preferably, the proportion by mass of rare earths is less than 1.2%, preferably less than 1%.
The present invention also relates to the use of the inoculant according to the invention.
According to a first variant of use, said inoculant is introduced in powder form.
It should be noted in this respect that the products described in documents FR2511044A1 and EP0816522A1 had the drawback of presenting a degradation of their particle size over time during storage of the inoculant. The inoculant according to the invention showed great stability in the grain size distribution under certain conditions.
According to a second variant embodiment, said inoculant is introduced in the form of a solid insert placed in a casting mold.
Preferably, the use of the inoculant according to the invention is aimed at the manufacture of cast iron parts having parts of thicknesses greater than 6mm, preferably parts with thicknesses greater than 20mm, and even more preferably parts of thicknesses greater than 50mm.
The present invention will be better understood in light of the description and examples which follow.
The inoculant according to the invention will typically be used in the part of an inoculation of a cast iron bath. It can also be used in preconditioning of said cast iron as well as as a nodulating agent where appropriate.
In typical use of an inoculant, the composition of an inoculant alloy according to the invention may comprise by example:
Item Quantity (% mass) If 45 ¨ 80 Ca 0.5 ¨ 4 Al 0.5 ¨ 3 Sb 0.2 ¨ 2 Rare Earth 0.2 ¨ 3

8 (especially Lanthanum) Iron Balance Inoculant alloy - composition 1 Obviously, the inoculant could also include additional elements providing particular effects depending on the sought-after properties. This could be more particularly the case in the part of a pre-conditioning treatment of cast iron.
By way of example, the inoculating alloy may thus have the following composition:
Item Quantity (% mass) Si 45 - 80 Ca 0.5 - 8 Al 0.5 - 3 Sb 0.2 - 2 Rare earth (especially 0.2 - 3 Lanthanum) Ba 2-15 Mn 2 - 6 Zr 2 - 6 Iron Balance Inoculating alloy - composition 2 Inoculation treatment will typically consist of the addition of 0.05 (preferably at least 0.1%) to 0.8% by mass of the inoculant with cast iron bath, in particular under the following conditions given as exnnples:
- at the end of melting in an induction furnace - before a magnesium nodulizing treatment, and more particularly between 1 and 5 minutes before this treatment - to cover subsequent treatment of the Sandwich type or Tundish-cover.

9 - in a casting furnace - during a transfer between two bags (transfer and pouring, especially).
- the preconditioning inoculant may in particular be added in the form of a cored wire.
The particle size of the inoculant according to the invention may be adapted according to its methods of addition.
As examples, we can cite:
- Addition in an induction furnace: grain size up to about 40 mm, - Addition between the induction furnace and the ladle:
particle size between about 10 and about 30 mm.
- Addition in the casting basin: grain size between about 0.4 and about 2 mm.
- Addition before casting in the mold: grain size included between about 0.2 and about 0.5 to 2 mm.
- Addition in the form of an inoculating insert placed in the mold of casting: inserts of 20g, 40g, 60g, 80g, 300g, 800g, 2kg, 5kg, 10kg, 20kg and 50kg, for example.
The inoculating alloy can also be added successfully by as inoculant before filling the casting mold or in inoculation by pocket or late, after adjustment of the alloy chemistry (especially Ba between 1.5 and 5% by mass and Ca between 0.5 and 2% by mass).
Depending on the metallurgical state of the cast iron after treatment with the inoculating alloy according to the present application, it is possible to eliminate the post-inoculation step. Indeed, prolonged maintenance of the effect inoculation in time with the action of antimony allows to reduce in a way treatment of late inoculations or even allow them to be remove. With for example the addition of an inoculant containing the couple Bi /

TR, the inoculation effect loses 30 'Vo over the first 4 minutes. So the addition of an inoculant in the late phase becomes an obligation to recover 100 'Vo of the inoculation effect to be achieved. This is not the case with an inoculant according to the present request.
In the context of use as a nodulizer with function additional inoculant, the composition of the alloy will also include magnesium. By way of example, the composition of such a nodulizing alloy with inoculating function could be as follows:

Item Quantity (% mass) If 30 ¨ 60 Ca 0.2 ¨ 5 Al 0.2 ¨ 3 Sb 0.1 ¨ 2 Rare earth (especially 0.1 -3 Lanthanum) Mg 3-12 Iron Balance Nodulizing alloy with inoculating effect ¨ composition 3 The granulometry of the nodulizer (in particular with 5 inoculant) according to the invention will be adapted according to the size of the pockets of treatment. For example, for pockets of 100 to 500 kg of cast iron, we will favor a particle size between approximately 0.4 and approximately 2mm, see up to 7mm. For pockets of 500 to 1000 kg of cast iron, a particle size between about 2 and about 7mm, or between about 10 and

10 about 30mm. For pockets of more than 1000kg of cast iron, we will favor a particle size of between about 10 and about 30mm.
Examples of use will now be given.
Example 1: foundry A - part 8 mm thick.
Foundry reference (A1) In accordance with the prior art, liquid iron was treated by addition to the induction furnace of pure antimony in a proportion of 30g of antimony for a ton of liquid iron.
The cast iron was then subjected to a nodulation treatment using a FeSiMg type nodulating alloy comprising one third of an FeSiMg alloy comprising 2% of rare earths and two thirds of an FeSiMg alloy not comprising no rare earths.
The cast iron finally underwent an inoculation treatment by addition to the casting basin of 0.1% by mass of an FeSiMnZr alloy and 0.1% of an alloy

11 FeSiAl, the inoculating alloys being added in the form of an inoculating insert in the mold.
Use of an inoculating alloy according to the invention (A2) An inoculating alloy according to composition 2 mentioned above and containing (in mass proportion): Si = 65% Si, Ca = 1.76% Ca, Al =
1.23%, Sb = 0.15%, TR = 0.16%, Ba = 7.9%; was used in a proportion 0.15% by mass of cast iron.
The step of adding pure antimony has been eliminated and the processing nodulating was simplified using only the FeSiMg nodulating alloy born containing no rare earths.
Comparative results Al (Reference) A2 (Request) Graphite nodularity 95% 98%
Cast iron matrix (/ 0 8% 3%
perlite) Elongation 15% 18%
Foundry A treated with an inoculant according to the present application showed an increase in tensile elongation on test specimens of control for a grade EN-GJS-400-15.
Example 2: foundry B - part 200 mm thick.
Foundry reference (B1) In accordance with the prior art, liquid iron was treated by addition to the induction furnace of pure antimony in a proportion of 20g of antimony for a ton of liquid iron.
The cast iron then underwent a nodulation treatment using a FeSiMg type nodulizing alloy comprising 1% by mass of rare earths and introduced into the cast iron in the form of a cored wire.
The cast iron finally underwent an inoculation treatment by addition to the casting basin of 0.15% by mass of an FeSiBiTR alloy.
Use of an inoculating alloy according to demand (B2)

12 An inoculating alloy according to composition 2 mentioned above and containing as above: Si = 65% Si, Ca = 1.76% Ca, Al =
1.23%, Sb = 0.15%, TR = 0.16%, Ba = 7.9%; was used in a proportion 0.15% by mass of cast iron.
The step of adding pure antimony has been eliminated and the processing nodulating has been simplified using only a nodulating alloy FeSiMg not containing rare earths (also introduced as wire thicket).
Comparative results B1 (Reference) B2 (Request) Graphite nodularity 91% 97%
Cast iron matrix (% 4% 3%
perlite) Graphite fault 15% 0%
Chunky Resilience at -20 C 7 J 12 J
On the impact resistance results, cast iron B2 obtained results that meet requirements.
Example 3: foundry C ¨ thin parts (thickness less than 6mm).
Foundry reference (Cl) In accordance with the prior art, liquid iron was treated by addition to the induction furnace of pure antimony in a proportion of 25g of antimony for a ton of liquid iron.
The cast iron was then subjected to a nodulation treatment using a FeSiMg type nodulizing alloy comprising 6.7% by mass of magnesium as well as 1.2% calcium and 0.98% rare earths.
The cast iron finally underwent a late inoculation treatment by addition 0.12% by mass of an FeSiMnZrBa alloy having a particle size between 0.2 and 5mm.

13 Use of an inoculating alloy according to demand with function nodulizing (C2) A nodulizing alloy with inoculating function depending on the composition 3 mentioned above was used.
As for the previous examples, the step of adding antimony pure has been deleted.
The nodulizing treatment was carried out using an alloy of type FeSiMg according to composition 3 of the present application and comprising 6.4%
by mass of magnesium as well as 1.3% calcium, 0.6% antimony and 1.2%
of rare earths.
Further inoculation was carried out according to a method late inoculation with 0.09% of an FeSiAlCa alloy and 0.009% of an alloy FeSiMnZrBa.
Comparative results Cl (Reference) C2 (Request) Graphite nodularity 93% 98%
Cast iron matrix (`) / 0 15% 4/5%
perlite) Graphite fault 4% 0%
Chunky By using a nodulizer according to the present application there is a disappearance of chunky graphite defects on all parts controlled.
Thus, additional inoculation (late inoculation) could be made using a more economical inoculant such as FeSiAlCa.
Example 4: foundry D ¨ massive parts.
Foundry reference (D1) In accordance with the prior art, liquid iron was treated by addition to the induction furnace of pure antimony in a proportion of 30g of antimony for a ton of liquid iron.

14 The cast iron was then subjected to a nodulation treatment using a FeSiMg type nodulating alloy comprising 9.1% by mass of magnesium as well as 1.4% calcium and 1.1% rare earths.
Finally, the cast iron underwent an inoculation treatment by adding a insert of 10 kg per tonne of cast iron of an inoculating FeSiMnZr alloy.
Use of an inoculating alloy according to demand (D2) An inoculating alloy according to composition 2 mentioned above and containing: Si = 65% Si, Ca = 1.76% Ca, Al = 1.23%, Sb = 0.15%, TR =
0.16%, Ba = 7.9%; was used as a 10kg insert as for the reference.
As for the previous examples, the step of adding antimony pure has been deleted.
The nodulizing treatment was carried out using the same alloy only for reference, i.e. using a nodulizing alloy of type FeSiMg comprising 9.1% by mass of magnesium as well as 1.4% of calcium and 1.1% rare earths.
Comparative results D1 (Reference) D2 (Request) Graphite nodularity 92% 97%
Cast iron matrix (% 5/10% 0/5%
perlite) Graphite fault 2% 0%
Chunky Tensile strength 370 MPa 420 MPa Elongation 18% 22%
Impact resistance at - 10J 14J

Cast iron D allows to develop a dark shade EN-GJS-400-18-LT used in particular in the wind energy sector. The use of the inoculant according to demand has increased impact resistance in a way important.

Example 5: foundry E ¨ thin parts and treatment nodulizing.
Foundry reference (El) 5 The liquid cast iron has undergone a nodulation treatment using a FeSiMg type nodulating alloy comprising 9.1% by mass of magnesium as well as 0.8% bismuth and 0.7% rare earths.
The cast iron was then subjected to an inoculation treatment according to a late inoculation method by adding 0.18% of an FeSiMnZr alloy 10 having a particle size of between 0.2 and 5 mm.
Use of an inoculating alloy according to demand with function nodulizing (E2) A nodulizing alloy according to composition 3 mentioned above

15 was used. The alloy used is an FeSiMg type alloy comprising 9.1% of magnesium as well as 0.75% antimony and 0.5% rare earths.
The cast iron then underwent an additional inoculation treatment according to a late inoculation method by adding 0.17% of an alloy FeSiMnZr having a particle size between 0.2 and 5mm.
Comparative results El (Reference) E2 (Request) Graphite nodularity 91% 95%
Graphite fault 2% 0%
Chunky Yield Mg 54% 69%
As mentioned previously, we see that the fact of replacing bismuth with antimony increased the yield of magnesium in cast iron E.

16 Example 6: D foundry on massive parts.
The foundry reference (F1) and the test (F2) using an alloy inoculant according to the request were carried out in accordance with Example 4 and the foundry D by inoculating massive pieces.
Comparative results F1 (Reference) F2 (Request) Efficiency Sb 67% 98%
It can be seen that thanks to the high efficiency obtained, it is possible to better control the amount of antimony added. The F2 foundry enabled a significant savings by reducing the doses of antimony to be added by 31.5%.
Example 7: D foundry on massive parts.
The foundry reference (G1) and the test (G2) using an alloy inoculant according to the request were carried out in accordance with Example 4 and the foundry D by inoculating massive pieces.
Comparative results G1 (Reference) G2 (Request) Release of Sb in 8 0.7 ring / m3 0.1 mg / m3 hours It can be seen that thanks to the inoculant according to the present application, the release of antimony is severely limited and far below the threshold regulatory 0.5 mg / m3. The working conditions are improved.
Example 8: foundry H - part 150 mm thick.
Foundry reference (H1)

17 In accordance with the prior art, liquid iron was treated by addition to the induction furnace of pure antimony in a proportion of 15g of antimony for a ton of liquid iron.
The cast iron was then subjected to a nodulation treatment using a nodulizing cored wire (diameter 13 mm, 32% Mg, 1.2% TR, 230 g / m powder) The cast iron finally underwent a late inoculation treatment by addition casting 0.15% by mass of an FeSiMnZr alloy.
Use of an inoculating alloy according to demand (H2) An inoculating alloy according to composition 1 [containing Si = 64% Si, Ca = 1.64% Ca, Al = 1.15%, Sb = 0.5%, TR = 0.3%] mentioned above a was used in a proportion of 0.2% by mass of cast iron.
The step of adding pure antimony has been eliminated and the processing nodulating has been simplified using only a nodulating alloy FeSiMg not containing rare earths (also introduced as wire thicket).
Comparative results i H1 (Reference) H2 (Request) Graphite nodularity 87% 98%
Cast iron matrix (% 3% 3%
perlite) Graphite fault 19% 0%
Chunky Resilience at -20 C 4 J 14 J
On the impact resistance results, the H2 cast iron obtained results that meet requirements.
Although the invention has been described with specific examples realization, it is obvious that it is in no way limited and what includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

Claims (16)

CLAIMS: 1. Inoculating alloy based on ferro-silicon for the treatment of a cast iron for the manufacture of parts with parts of greater thickness at 6 mm, said inoculant alloy containing 45-80% by mass of silicon, 0.5-4% by mass of calcium, 0.5-3% by mass of aluminum, 0.2-3% by mass of Rare Earths, 0.2-2% by mass of antimony, and the balance in iron, characterized in that the antimony to rare earth ratio is between 0.9 and 2.2. 2. Inoculating alloy based on ferro-silicon for the treatment of a cast iron for the manufacture of parts with parts of greater thickness at 6 mm, said inoculating alloy containing, characterized in that said alloy contains 45-80% by mass of silicon, 0.5-8% by mass of calcium, 0.5-3% by mass of aluminum, 0.2-3% by mass of Rare Earths, 0.2-2% by mass of antimony, 2-15% by mass of barium, 2-6% manganese, 2-6% zirconium, and the balance in iron, characterized in that the antimony to rare earth ratio is between 0.9 and 2.2. 3. Inoculating alloy according to claim 1 or 2, characterized in that the mass proportion of antimony is greater than 0.3%. 4. Inoculating alloy according to claim 3, characterized in that the proportion of antimony is greater than 0.5%. 5. Inoculating alloy according to claim 3, characterized in that the proportion of antimony is greater than 0.8%. 6. Inoculating alloy according to any one of claims 1 to 5, characterized in that the proportion by mass of antimony is less than 1.5%. 7. Inoculating alloy according to claim 6, characterized in that the mass proportion of antimony is less than 1.3%. 8. Inoculating alloy according to any one of claims 1 to 7, characterized in that the rare earths include Lanthanum. 9. Inoculating alloy according to claim 8, characterized in that the land rare include only lanthanum. 10. Inoculating alloy according to any one of claims 1 to 9, characterized in that the proportion by mass of rare earths is greater than 0.3%. 11. Inoculating alloy according to any one of claims 1 to 10, characterized in that the proportion by mass of rare earths is less than 1.2%. 12. Inoculating alloy according to claim 11, characterized in that the mass proportion of rare earths is less than 1%. 13. Use of an inoculant as defined in any one of claims 1 to 12 for the manufacture of cast iron parts having parts of thicknesses greater than 6 mm, characterized in that said inoculant is introduced in powder form. 14. Use of an inoculant as defined in any one of claims 1 to 12 for the manufacture of cast iron parts having parts of thicknesses greater than 6 mm, characterized in that said inoculant is introduced in the form of a solid insert placed in a casting mold. 15. Use of an inoculant according to claim 13 or 14 for the manufacture of cast iron parts with parts of greater thickness at 20mm. 16. Use of an inoculant according to any one of claims 8 to for the production of cast iron parts having parts of thicknesses superior at 50mm.