WO2023230694A1 - Cast iron comprising niobium particles and method for producing cast iron - Google Patents

Abstract

The present invention pertains to the fields of material engineering and nanotechnology. More specifically, the invention discloses an improved cast iron and a method for producing cast iron. The method according to the invention comprises incorporating niobium particles in the step preceding the solidification of cast iron, providing various advantages in known industrial processes. Besides being applicable to existing cast iron plants, without structural modifications, the method according to the invention allows producing a great variety of products in the same plant, which is a very desirable result in this field which is not achieved by conventional processes. The product according to the invention has remarkable properties. In one embodiment, the product according to the invention is called Steeron, because it exhibits steel characteristics, while being a cast iron. This product comprises cast iron with niobium particles, has a defined composition, exhibits improved characteristics and is useful in a variety of applications.

Description

Invention Patent Descriptive Report

CAST IRON COMPRISING NIOBIUM PARTICLES AND PROCESS FOR OBTAINING A CAST IRON

Field of Invention

[0001] The present invention lies in the field of materials engineering and nanotechnology. More specifically, the invention discloses an improved cast iron and a process for obtaining it. The process of the invention comprises the incorporation of Niobium particles in a stage prior to the solidification of cast iron, providing several advantages in the respective known industrial process, being applicable to existing casting plants, without structural modifications. The product of the invention has remarkable properties. In one embodiment, the product of the invention is called Steeron, as it has steel characteristics even though it is cast iron. Said product comprises cast iron equipped with Niobium particles, has a defined composition, presents improved characteristics and is useful in a variety of applications.

Background of the Invention

[0002] The incorporation of particles into molten metals is a technical difficulty that has not yet been satisfactorily resolved, and is the subject of intense studies.

[0003] In the specific field of cast iron, various approaches have been studied and tried to improve the properties of the final product. One approach is to try to incorporate nanoparticles from different materials. However, the use of nanoparticles on a large scale still faces multiple limitations, starting with the unavailability of nanoparticle preparations with high concentration, purity, precise particle size profile or even simple availability in large quantities. In addition, there are several other technical problems that limit the industrial use of nanoparticles, including the tendency to aggregation, the difficulty of dispersion, the risks associated with possible dispersion in the air/environment and the still little-known effects resulting from human or animal contact with nanoparticles.

[0004] The problem of difficulty in mixing/dispersing/homogenizing additives, particularly those containing nanoparticles, in the processing of metals and special steels has been known for some time, and there are different approaches to trying to resolve it.

[0005] In the search for the state of the art in scientific and patent literature, the following documents were found that relate to the topic:

[0006] Document CN105414497 goes into detail about the technical difficulties of dispersing additives in the manufacture of special steels. Said document discloses a device developed specifically to solve this problem, and includes a pipe, a feeder with a valve welded to the side of an opening and a thin sealed and welded pipe, with the end directed towards the center of the opening of the other pipe, so to enable the insufflation of air or argon to form negative pressure and then allow the addition of fine powders of the additive into the liquid steel medium (molten). The device provides adjustment for uniform additive addition. It does not disclose or anticipate the present invention.

[0007] Document JP3321491, entitled “Method for adding rare earth element to molten steel and additive", discloses a safe way of adding an additive to molten steel. Said additive is prepared by filling a container with a powder of an alloy containing rare earths, copper and aluminum. The container is made of a hollow bar of carbon steel or stainless steel. The method of adding the additive consists of continuously adding said additive to the molten steel in the casting phase. It does not reveal or anticipate the present invention.

[0008] Document US4892580 discloses an additive in the form of lead-containing filaments for obtaining modified steels. Said additive is presented in the form of filaments consisting of a metallic coating and a finely divided material, which comprises metallic lead or lead alloys, in addition to a material that releases CO2 at the temperature of molten steel. It does not disclose or anticipate the present invention.

[0009] Document RU2569621 discloses a method for producing steel containing niobium. Said method includes a step of melting the steel and forming a 200mm thick layer in a receptacle. During the treatment of the metal outside the furnace, ferroniobium is added at a rate of 0.01 to 1 kg per ton of metal. It does not disclose or anticipate the present invention.

[0010] Document US 3860777 discloses a process for welding low alloy steels containing niobium. In said document, weld deposits of improved strength and hardness are obtained, when compared with hitherto known congeners. The process involves adding controlled amounts of vanadium and/or titanium to the molten metal, together with other alloying elements in order to provide the formation of a deposit whose concentration is controlled in comparison to the concentration of niobium present. It does not disclose or anticipate the present invention.

[0011] Document WO 92226675 discloses a ferroniobium alloy and a niobium additive for steel, cast iron and other metallic alloys. The ferroniobium alloy has a microstructure comprising a eutectic matrix (E) and a primary constituent (N) as a niobium-rich solid solution, which requires the chemical composition to be 75 to 95% niobium, 5 to 25% iron , with the maximum impurities defined below: tantalum 0.1%, silicon 3%, aluminum 1% and tin 0.15%. This additive is useful for adding niobium to steel, cast iron, and other materials. It does not disclose or anticipate the present invention.

[0012] The co-pending patent application BR 102021016247-3, still confidential and with inventors in common with the present invention, reveals a preparation of niobium nanoparticles obtained by a top down approach. Said preparation concomitantly includes the following technical characteristics: particles entirely in the particle size range of nanometers; high purity; on an industrial scale, with an adequate cost for economic viability. Referred prepared in nanometric powder has very high purity, since the process does not add impurities or lead to the formation of reaction products, as is the case with state-of-the-art bottom-up (or synthesis) processes. It does not disclose or anticipate the present invention.

[0013] The co-pending patent application BR 102022002639-4, filed by IHR in Feb 2022 with the same inventors and still confidential, reveals a useful premix for the use of nanoparticle preparations from various materials. In the aforementioned document, incorporated herein by reference, a premix of nanoparticles with peculiar composition, purity and granulometric profile is described, being useful in a variety of applications and solving several technical problems, including facilitating dispersion in other substances, facilitating use in industrial processes. It does not disclose or anticipate the present invention.

[0014] The dissertation by Luiz, T.M. (2019) (Synthesis of Nb2Ü5 nanoparticles for application in materials hardened by oxide dispersion presents a material formed from pure Fe (i.e. purity of 99.6%) comprising a reinforcement of Nb2Ü5 nanoparticles in concentrations of 0.25, 0.5, 1.0, 5.0 and 10.0 wt%. The matrix used in the dissertation was pure iron, substantially differentiating from the composition of cast iron, as well as completely differentiating from the process of the present invention that is applied to irons melted.

[0015] The article by Bedolla-Jacuinde A. and Hernandez B.X. (2003) (Effect of niobium in medium alloyed ductile cast irons) discloses a process for obtaining a ductile nodular cast iron comprising the addition of niobium particles. However, unlike the present project, the Fe-Nb particles are already added to the molten iron before molding in green sand. Additionally, the aluminum mentioned in this document is used to deoxidize the alloy, which use differs from the approach used in the present invention.

[0016] From what can be seen from the researched literature, no documents were found anticipating or suggesting the teachings of the present invention. Summary of the Invention

[0017] The present invention provides a new molten metallic material, which provides solutions to several prior art problems. The invention also discloses a process that provides substantial improvements over its counterparts.

[0018] It is one of the objects of the invention to provide cast iron with improved mechanical properties.

[0019] In one embodiment, the present invention presents a cast iron comprising Niobium particles in a concentration of 0.01 to 1% by mass. In one embodiment, the cast iron comprises niobium pentoxide nanoparticles.

[0020] In one embodiment the improved cast iron of the invention is a Nodular cast iron and in another embodiment it is a Gray cast iron. In both cases, the product of the invention has improved physicochemical and mechanical properties.

[0021] In one embodiment, the product of the invention reaches the same levels of tensile strength limit or yield limit using less metallic material in the respective part, delivering the same mechanical performance with lower relative weight (mass) .

[0022] In one embodiment, the product of the invention is in the form of ingots, billets or other massive cast iron structures with improved thermal properties.

[0023] Another object of the invention is to provide an industrial process for manufacturing cast iron doped with niobium particles, said process providing greater ease of dispersion of nanoparticles in the metal, greater safety in the industrial process and ease of use on a large scale. In one embodiment, said process provides the obtaining of an improved cast iron through in situ reaction, providing more safety and more flexibility in the industrial process, in addition to ease of large-scale employment.

[0024] An additional object of the present invention is a process for obtaining cast iron comprising the addition of Niobium particles in a concentration of 0.01 to 1% by weight prior to casting the molten matrix.

[0025] In some embodiments, the process of the invention provides reduction of shrinkage, better homogenization of particles in the melt, standardization of metallic alloys (baseline), and/or the production of parts with complex geometries.

[0026] These and other objects of the invention will be immediately valued by those skilled in the art and will be described in detail below.

Brief Description of Figures

[0027] The following figures are displayed:

[0028] Figure 1 illustrates the zeta potential of aluminum particles as a function of pH. The zeta potential modulus (mV) is an indication of particle stability. The greater the zeta potential modulus, the more stable the particles. [0029] Figure 2 illustrates the zeta potential of Niobium Pentoxide particles as a function of pH.

[0030] Figure 3 illustrates the granulometry results for aluminum particles using the Cilas equipment.

[0031] Figure 4 illustrates a MeV result (scanning electron microscopy) for the metallic mixture after 5h of mixing, with a magnification of 3.11 kx and 2.01 kx at 10.0 kV, in which the field of viewing is 89.1 pm and 138 pm in BSE mode, WD of 9.63 mm results obtained on VEGA3 TESCAN equipment.

[0032] Figure 5 illustrates the EDS (Energy Dispersive Spectroscopy) result for the metallic mixture after 5h of mixing. The EDS shows the proportion of each element in the metallic mixture.

[0033] Figure 1 shows a photo of “Bunches” of Al aluminum foil and A4 as detailed in Tables 1 and 2.

[0034] Figure 2 shows illustrative photos of an embodiment of the process for obtaining the FoFo of the invention in green sand: in A) the addition of a “bundle” is shown in a mold before casting the melt; in B) the casting of the casting into the mold containing the “bundles” is shown.

[0035] Figure 3 shows a combined photo of the casting cast in three green sand molds.

[0036] Figure 4 shows photos illustrating an embodiment of the process for obtaining the FoFo of the invention in cold-box, manual line: in A) a mold is shown to which a “bundle” was added, before casting; in B) a panoramic photo of the production line with several molds is shown; In C) the detail of the casting casting over a mold containing “bundles” is shown.

[0037] Figure 5 shows photos of cold-box molds in two conditions. In A) the experimental condition P1 base (left) is shown; in B) the experimental condition P1 lateral (right) is shown.

[0038] Figure 6 shows photos of two conditions for adding niobium pentoxide nanoparticles to cold-box molds. In A) the condition P1 chopped (left) is shown; in B) condition P1 in 9 (right) is shown.

[0039] Figure 7 shows photomicrographs of samples with and without attack. In A) the condition of B1 without attack is shown (left); in B) the condition with attack is shown (right).

[0040] Figure 8 shows photomicrographs of samples with and without attack. In A) the condition of B2 without attack is shown (left); in B) the condition with attack is shown (right).

[0041] Figure 9 shows photomicrographs of samples with and without attack. In A) the condition of B3 without attack is shown (left); in B) the condition with attack is shown (right).

[0042] Figure 10 shows photomicrographs of samples with and without attack. In A) the condition of P1 without attack is shown (left); in B) the condition with attack (right).

[0043] Figure 11 shows a graph of the tensile strength results in Mpa for the different conditions tested.

[0044] Figure 12 shows photos of another embodiment of an improved FoFo production process, in green sand molds. In A) and B) views of “bundles” placed in the green sand mold prior to casting the casting are shown.

[0045] Figure 13 shows a photo of another embodiment of improved FoFo production process, showing a view of the action of chopped Nb2Ü5 + Al nanoparticles.

[0046] Figure 14 shows a photo of an embodiment of the process for obtaining Gray FoFo after casting and inoculation.

[0047] Figure 15 shows a photo of a cross-section of a Gray FoFo ingot obtained by the process of the invention. The highlighted area shows details of the macroporosities.

[0048] Figure 16 shows three photos of Gray FoFo test specimens (CP) prepared by the process of the invention, for tensile testing.

[0049] Figure 17 shows a graph of the Brinell hardness of the Gray FoFo samples tested.

[0050] Figure 18 shows photomicrographs of the Gray FoFo samples obtained by the process of the invention, magnified by 100x. Sample identification is visible in each of the five images.

[0051] Figure 19 shows photomicrographs of the Gray FoFo samples obtained by the process of the invention, magnified 100x and etched with 3-4% Nital. Sample identification is visible in each of the five images.

[0052] Figure 20 shows etched photomicrographs of samples P6-P and B. The identification of the samples is visible in each of the two images.

[0053] Figure 21 shows, in A) the dimensions of the CPs; in B) a photo of the Nodular FoFo CPs prepared for tensile testing is shown.

[0054] Figure 22 shows a graph with yield limit data and tensile strength of FoFo Nodular samples.

[0055] Figure 23 shows a graph with the stretching data of the FoFo Nodular samples.

[0056] Figure 24 shows photomicrographs of the parts with and without attack. Sample identification is visible in each of the four images.

[0057] Figure 25 shows a graph with the tensile strength limit and yield limit data for two of the experimental conditions tested (B and P6-P).

[0058] Figure 26 illustrates the zeta potential of aluminum particles as a function of pH. The zeta potential modulus (mV) is an indication of particle stability. The greater the zeta potential modulus, the more stable the particles. [0059] Figure 27 illustrates the zeta potential of Niobium Pentoxide particles as a function of pH.

[0060] Figure 28 illustrates the granulometry results for aluminum particles using the Cilas equipment.

[0061] Figure 29 illustrates a MeV result (scanning electron microscopy) for the metallic mixture after 5h of mixing, with magnification of 3.11 kx and 2.01 kx at 10.0 kV.

[0062] Figure 30 illustrates the EDS (Energy Dispersive Spectroscopy) result for the metallic mixture after 5h of mixing. The EDS shows the proportion of each element in the metallic mixture.

[0063] Figure 31 illustrates a graph that compares the results of the average tensile strength limits (LRT) for fusions from 0 to 19 illustrated in table 24.

Detailed Description of the Invention

[0064] The product of the invention is a cast iron with improved properties due to the addition of niobium particles.

[0065] In the context of the present invention, the expression “Niobium particles” covers various chemical entities containing Niobium, including Niobium metallic, oxides, hydrates, hydrides, carbides, or nitrides of Niobium, iron Niobium or Niobium linked to other metals or transition metals, or combinations thereof. It also includes Niobium pentoxide (Nb20s), NbC, NbO and FeNb. These can be microparticles, submicroparticles or nanoparticles.

[0066] In one embodiment, the product of the invention is in the form of ingots, billets or other massive structures with a more refined and homogeneous structure, without presenting macroporosity or shrinkage.

[0067] In one embodiment, the product of the invention is in the form of ingots, billets or other massive cast iron structures with an increased tensile strength limit, without reducing other mechanical properties (e.g., yield limit, elongation) and ductility.

[0068] In one embodiment, the product of the invention is in the form of ingots, billets or other massive cast iron structures with increased yield strength, without reducing other mechanical properties.

[0069] The surprising increase in tensile strength without decreasing ductility is a notable technical effect of the invention that can be recognized by a person skilled in the art.

[0070] In one embodiment, the product of the invention is in the form of ingots, billets or other massive cast iron structures with improved thermal properties.

[0071] In a first aspect, the present invention presents a cast iron comprising Niobium particles in a concentration of 0.01 to 1% by mass. [0072] In one embodiment, the Niobium particles are in a concentration of 0.01 to 0.5% by mass. In one embodiment, the Niobium particles are in concentration of 0.02 to 0.4% by mass. In one embodiment, the Niobium particles are in a concentration of 0.03 to 0.3% by mass. In one embodiment, the Niobium particles are in concentration of 0.04 to 0.2% by mass. In one embodiment, the Niobium particles are in a concentration of 0.05 to 0.2% by mass. In one embodiment, the Niobium particles are in concentration of 0.07 to 0.14% by mass. [0073] In one embodiment, said Niobium particles are composed of Niobium pentoxide, Niobium, FeNb or combinations thereof. In one embodiment, said Niobium particles are composed of Niobium pentoxide.

[0074] In one embodiment, the cast iron of the present invention additionally comprises aluminum in a concentration of 0.01 to 1% by mass. [0075] In one embodiment, aluminum is in a concentration of 0.01 to 0.5% by mass. In one embodiment, the aluminum is in a concentration of 0.01 to 0.044% by mass. In one embodiment, the aluminum is in a concentration of 0.01 to 0.037% by mass. In one embodiment, the aluminum is in a concentration of 0.02 to 0.037% by mass. In one embodiment, the aluminum is at a concentration of 0.02% by mass.

[0076] In an embodiment of the present invention, said Niobium particles are particles having a particle size profile in the nanometer range. In one embodiment, said Niobium particles are particles having a particle size profile d90 in the particle size range of hundreds of nanometers.

[0077] In one embodiment, said Niobium particles are Niobium pentoxide nanoparticles or FeNb nanoparticles.

[0078] In one embodiment, said cast iron is nodular cast iron or gray cast iron.

[0079] In one embodiment, the cast iron of the present invention presents at least a 7% increase in yield strength when compared to the original cast iron; and/or at least 11% increase in tensile strength when compared to original cast iron.

[0080] In one embodiment, the cast iron of the present invention is selected from:

- a gray cast iron with the addition of 0.1% Nb2Ü5, graphite with thinner and shorter forms, pearlite matrix 95% and ferrite 5%; or

- a nodular FoFo with addition of 0.1% (wt) Nb2Ü5, graphite with forms VI (78%) and V (22%), 45 nodules /mm2, sizes 5 and 6, modularity in 100%. Pearlite matrix 89% and ferrite 11%.

[0081] In the present invention, an arrangement of stoichiometric balances is implemented in the premix composition, so that alloys with customized properties can be obtained as can be seen from the non-limiting examples below.

[0082] The process of the invention provides for the in situ reaction of niobium particles and other ingredients with cast iron, providing the formation of other forms of niobium within the microstructure of the cast iron.

[0083] In one embodiment, the process of the invention minimizes or eliminates the formation of shrinkage and solidification voids in the preparation of ingots, billets or other massive cast iron structures.

[0084] In one embodiment, the process of the invention provides the formation of ingots, billets or other massive structures with a more refined and homogeneous structure.

[0085] In one embodiment, the process of the invention provides modification of the chemical profile of the part into which the particles are incorporated.

[0086] In a second aspect, the present invention presents a process for obtaining cast iron comprising the addition of Niobium particles in a concentration of 0.01 to 1% by weight prior to casting the molten matrix.

[0087] In one embodiment, the Niobium particles are in a concentration of 0.01 to 0.5% by mass. In one embodiment, the Niobium particles are in concentration of 0.02 to 0.4% by mass. In one embodiment, the Niobium particles are in a concentration of 0.03 to 0.3% by mass. In one embodiment, the Niobium particles are in concentration of 0.04 to 0.2% by mass. In one embodiment, the Niobium particles are in a concentration of 0.05 to 0.2% by mass. In one embodiment, the Niobium particles are in concentration of 0.07 to 0.14% by mass.

[0088] In one embodiment, said Niobium particles are particles having a particle size profile in the nanometer range. In one embodiment, said Niobium particles are particles with a particle size profile of d90 in the particle size range of hundreds of nanometers.

[0089] In one embodiment of the process of the present invention, the step of adding Niobium particles is done by adding a premix comprising Niobium and aluminum particles.

[0090] In one embodiment, aluminum is in a concentration of 0.01 to 1% by mass. In one embodiment, the aluminum is in a concentration of 0.01 to 0.1% by mass. In one embodiment, the aluminum is in a concentration of 0.01 to 0.044% by mass. In one embodiment, the aluminum is in a concentration of 0.01 to 0.041% by mass. In one embodiment, the aluminum is in a concentration of 0.01 to 0.037% by mass. In one embodiment, the aluminum is in concentration from 0.01 to 0.034% by mass. In one embodiment, the aluminum is in concentration from 0.02 to 0.037% by mass. In one embodiment, the aluminum is in a concentration of 0.02 to 0.034% by mass. In one embodiment, the aluminum is in a concentration of 0.02% by mass.

[0091] In an embodiment of the process of the present invention, said aluminum is powdered, crushed, ground or chopped.

[0092] In one embodiment of the process of the present invention, the premix comprising niobium and aluminum particles is added in at least one of the following ways:

- to the mold before casting the melt;

- in the transfer pan before pouring the melt;

- at the entrance to the mold feed channel before casting the casting;

- in the furnace before casting the melt; or

- in the jet together with the inoculant.

[0093] The premix addition point is chosen according to the process approach, eg, mold size, geometry complexity, etc. Additionally, as these are extremely small fractions of material, the addition point is also determined by the dispersion capacity, considering the parameters mentioned above. There is a combination of factors to determine the best addition point depending on the process approach.

[0094] To better illustrate the point described above, in an embodiment in which the premix is added to the mold before casting the melt, this approach may be more suitable when the part to be molded is in a vertical position and has sufficient mass to ensure the dispersion of the premix.

[0095] In an embodiment in which the premix is added to the transfer pan before pouring the melt, this approach may be more suitable when the process allows it.

[0096] In an embodiment in which the premix is added at the entrance to the mold feed channel before casting the melt, this approach may be more suitable when the mold box is only for one part.

[0097] In an embodiment in which the premix is added to the furnace before pouring the melt, this approach may be more suitable when process temperatures allow.

[0098] In an embodiment in which the premix is added to the jet together with the inoculant, this approach may be more suitable when the factory process allows it.

[0099] In an embodiment of the process of the present invention, said aluminum has a particle size profile in the range of nanometers or micrometers. In one embodiment, said aluminum is in the form of particles having a particle size profile d90 in the particle size range of hundreds of nanometers to tens of micrometers.

[0100] In one embodiment of the process of the present invention, the premix comprises Nb2Ü5 and a molar ratio of AI/Nb20s of 1 to 5, to provide an in situ reaction between aluminum and niobium pentoxide. In one embodiment, the premix comprises AI/Nb20s molar ratio of 1 to 4.33. In In one embodiment, the premix comprises AI/Nb20s molar ratio of 2 to 4. In one embodiment, the premix comprises AI/Nb20s molar ratio of 3 to 3.67. In one embodiment, the premix comprises an AI/Nb20s molar ratio of 3.33.

[0101] In one embodiment, the process of the invention additionally comprises a step of adding FeSiCaBa or FeSiCaBaZr inoculant in a proportion of 0.1 to 1% by mass. In one embodiment, the inoculant is FeSiCaBa and is added in a proportion of 0.2 to 0.6% by mass. In one embodiment the inoculant is FeSiCaBaZr and is added in a proportion of 0.2 to 0.4% by mass.

[0102] In one embodiment, the process of the invention additionally comprises a step of adding fuel to the melt charge. In one embodiment, the fuel is natural or synthetic graphite.

[0103] In one embodiment, the process of the invention additionally comprises a step of adding scrap to the melt charge.

[0104] Examples

[0105] The examples shown here are only intended to exemplify some of the various ways of carrying out the invention, however without limiting its scope.

[0106] Example 1 - Preparation of Y-shaped Gray Fluffy ingots.

[0107] In this embodiment, Y-shaped ingots with a mass of 5.5 kg each were prepared with Gray FoFo in green sand and cold-box according to the conditions described in Tables 1 and 2.

[0108] Table 1: number of pieces in Y in each experimental condition.

[0109] Table 2: number of pieces in Y in each experimental condition.

[0110] The concentrations of each material used in the experiment are detailed in tables 3 to 5 below.

[0111] Table 3: Scheme of the ^1st inoculation (0.1%m) Nb2Ü5 - Variation in the content of the dispersing medium.

[0112] Table 4: 2nd inoculation scheme (0.01 to 0.5%m) Nb2Ü5 - Variation in nanoparticle content.

[0113] Table 5: Scheme of the ^3rd inoculation (0.1%m) Nb2Ü5 - Variation in nanoparticle content.

[0114] When fusing the base materials, 0.3% m of the FeSiCaBa inoculant was added to the pan. In both processes, niobium pentoxide nanoparticles wrapped in aluminum film in the form of a bundle were added directly to the molds, as shown in figures 1 to 3. The amount of niobium pentoxide and aluminum were as defined in the tables 3 to 5 above.

[0115] Each pan has a capacity of 200 kg, with approximately 35 ingots being produced per process. Cast iron casting temperatures at the beginning of the ladle corresponded to 1410 ^s C in green sand and 1415 ^s C in cold-box, which corresponded to the production of 35 ingots. The pouring temperature at the end of the ladle corresponded to 1353 ^S C in cold-box, production of the remainder. Pouring times are between 5-7 seconds for both processes.

[0116] After casting the cast iron over the niobium pentoxide, the cooling times corresponded to approximately 1 hour in green sand and 4 hours in a cold-box. Under these processing conditions, it was observed that the added aluminum films floated in both processes (Figure 3), indicating that this form of addition is not the most suitable.

[0117] Example 2 - Preparation of Y-shaped ingots - changing the way of adding nanoparticles

[0118] In this embodiment, the conditions for adding the nanoparticles were changed to obtain Y-shaped ingots with a mass of 5.5 kg each.

[0119] The concentrations of each material used in the experiment are detailed in tables 3 to 5 of the previous example.

[0120] The ingots were prepared with FoFo Nodular in a cold-box according to the conditions described in Table 6.

[0121 ] Table 6: number of pieces in Y in each experimental condition.

[0122] In the experiment with notation B1, there was no addition of niobium pentoxide nor aluminum nanoparticles.

[0123] In the experiment with notation B2, only aluminum film (0.0372 %m) was added.

[0124] In the experiment with the notation P1, niobium pentoxide nanoparticles were added to aluminum film (AI/Nb20s = 3.7 molar), under different conditions, all making up the total amount of the experiment in example 1.

[0125] 1) P1 base: aluminum films and nanoparticles were divided into 7 equal parts and placed on the bottom of the mold in layers. Niobium pentoxide nanoparticles were added to each layer of aluminum film (Figure 5A).

[0126] 2) Side P1: aluminum foil covering the internal part of the mold and nanoparticles added on top (Figure 5B).

[0127] 3) Chopped P1: aluminum foil manually chopped into the smallest possible size with the help of scissors and mixed with the nanoparticles at the bottom of the mold (Figure 6).

[0128] 4) P1 in 9: 9 bundles of identical masses were separated and weighed and added to the bottom of the mold (Figure 6A and B).

[0129] 5) P1 manual feeding in 8 times: 1 bundle was separated and weighed according to the process carried out in example 1. “8 times” corresponds to the number of “shells” used in the process. [0130] 6) P1 repetition example 1: addition of bundles as used in the example, as control (Figure 4).

[0131] When melting the base materials, there was an addition of 0.3%m. of the FeSiCaBa inoculant in the pan, similarly to example 1.

[0132] In the present example, 7 pieces were produced. The pouring temperature at the beginning of the ladle corresponded to 1420 ^s C. The temperature at the end of the ladle was not measured; estimates indicate that the temperature did not vary much at the end of production. Pouring times are around 5-7 seconds for both processes. After pouring over the pans, the cooling time was approximately 4 hours under all conditions tested.

[0133] The results indicate substantial improvement in relation to the products obtained in example 1.

[0134] Metallography tests with and without etching show different visual profiles, as shown in figures 7-10.

[0135] Furthermore, mechanical property tests revealed substantially different properties. Table 7 summarizes the results of the tensile test tests.

[0136] Table 7 - test results in tensile strength test (in Mpa).

[0137] The data in table 7 are best visualized in figure 11, which shows the tensile strength in Mpa.

[0138] Example 3 - Preparation of Gray FoFo ingots [0139] In this embodiment, loaf-shaped ingots with a mass of 30 kg each were prepared. The ingots were prepared with Gray FoFo in sand molds according to the conditions described in Table 8.

[0140] 0.1%m of Nb2O5 nanoparticles were inoculated via the T (aluminum bundle) and P (chopped aluminum) routes.

[0141] Table 8: number of ingots per experiment.

[0142] In table 8, B= baseline; P1= AI/Nb2O5 (3.7 molar); P6=AI/Nb2O5 (2 molar); the Al concentration is equivalent to 372 and 203 ppm in P1 and P6, respectively.

[0143] When melting the base materials, the inoculant FeSiCaBa was added to the pan and by jet at 0.6 and 0.2%m, respectively.

[0144] The inoculation route via aluminum “bundles” (route T) was done as follows: before casting, an aluminum “bundle” containing nanoparticles was positioned at the bottom of the mold and each of the other four was fixed internally on each wall of the mold with the help of pieces of clips (Figure 12).

[0145] The inoculation route via chopped aluminum (route P) was done as follows: before casting, the chopped parts of the aluminum foil and the nanoparticles were added to the bottom of the mold (Figure 13).

[0146] The pouring temperature corresponded to 1406°C and the pouring times were 8-9 seconds in all cases. After producing the ingots, cooling took place in air.

[0147] No aluminum flotation was observed in any of the inoculation routes (Figure 14). [0148] The results of these experiments with gray FoFo are described below. A shell, taken directly from the oven, was prepared to control the chemical composition of the Gray FoFo. Table 9 presents the acceptable limits and chemical composition results analyzed by an Optical Emission Spectrometer (OES), Q4 Tasman Series 2.

[0149] Table 9 - Acceptable limits and results of the gray FoFo composition in two runs (top and bottom line, respectively).

[0150] The ingots of FoFo formulations (B, P1 and P6) showed internal macroporosity (Figure 15).

[0151] The CPs obtained with formulations (B, P1 and P6) of Gray FoFo showed macroporosities (Figure 16), making it impossible to carry out tensile tests.

[0152] Brinell hardness is calculated for one Cp of each formulation. 5 measurements were taken per Cp. Average values and respective deviations presented in Figure 17. Formulation P6-P contributed, on average, to increasing the hardness value in 3.4% compared to the base alloy and, the P1 formulation contributed, on average, to a decrease in the hardness value by 5.4% compared to the base alloy.

[0153] Photomicrographs obtained with samples cut, sanded and polished to a grain size of 1 pm were obtained and viewed under an optical microscope, in order to evaluate the microstructures. Figure 18 shows the micrographs for Gray FoFo to 100x and Figure 19 shows the micrographs with 3-4% Nital etching for Gray FoFo to 100x.

[0154] Figure 20 shows the micrographs etched with 3-4% Nital, with a 100x approximation for the sample that obtained the best mechanical property result, P6-P, and for the baseline sample, B. In Figure 20, you can see there is a refinement of graphite and a smaller amount of ferrite for sample P6-P, when compared to sample B. This refinement and smaller amount of ferrite may be related to the gain in the mechanical property of hardness. A tensile test is necessary to assess whether the same behavior follows.

[0155] The results of metallographic analyzes suggest a tendency for microstructural refinement from the inoculation of niobium pentoxide nanoparticles. On the other hand, the results of mechanical hardness tests for Gray FoFo are very promising, strongly recommending the continuation of further studies aimed at improving the technology.

[0156] Example 4 - Preparation of Nodular FoFo ingots

[0157] In this embodiment, loaf-shaped ingots with a mass of 30 kg each were prepared. The ingots were prepared with FoFo Nodular in sand molds according to the conditions described in Table 10.

[0158] 0.1%m of Nb2O5 nanoparticles were inoculated via the T (aluminum bundle) and P (chopped aluminum) routes.

[0159] Table 10: number of ingots per experiment.

[0160] In table 10, B= baseline; P1= AI/Nb2O5 (3.7 molar); P6=AI/Nb2O5 (2 molar); the Al concentration is equivalent to 372 and 203 ppm in P1 and P6, respectively.

[0161] When fusing the base materials, the inoculant FeSiCaBa was added to the pan and by jet at 0.6 and 0.2%m., respectively.

[0162] The inoculation route via aluminum “bundles” (route T) was done as described in example 3.

[0163] The inoculation route via chopped aluminum (route P) was done as described in example 3.

[0164] The pouring temperature corresponded to 1445°C and the pouring times were 9-10 seconds in all cases. After producing the ingots, cooling took place in air.

[0165] No aluminum flotation was observed in any of the inoculation routes.

[0166] The results of these experiments with FoFo Nodular are described below. A shell, taken directly from the oven, was prepared to control the chemical composition of FoFo Nodular. Table 11 presents the acceptable limits and chemical composition results analyzed by an Optical Emission Spectrometer (OES), Q4 Tasman Series 2.

[0167] Table 11 - Acceptable limits and results of nodular FoFo composition.

[0168] Ingots of formulations (B, P1 and P6) did not show internal macroporosity.

[0169] Tensile tests carried out on 4 CPs of each formulation resulted in the average values and respective deviations presented in Figures 22 and 23. Compared to the base alloy, formulation P6-P contributed, on average, to increasing flow and resistance in 5.4 and 12.6%, respectively.

[0170] Table 12 details the characteristics of test specimens. In bold, the specific conditions used in the specimens shown in figure 21 are indicated.

[0171] Table 12 - characteristics of the test specimens.

[0172] The photomicrographs shown in figure 24 show the results of metallography with and without attack in conditions B (baseline), and P6-P. [0173] The results of metallographic analyzes suggest a tendency for microstructural refinement from the inoculation of niobium pentoxide nanoparticles. On the other hand, the results of the mechanical yield stress and tensile strength limit tests for FoFo Nodular are very promising, strongly recommending the continuation of further studies aimed at improving the technology.

[0174] Example 5 - Nanostructured premix comprising

Niobium Pentoxide Nanoparticles.

[0175] To prepare the P6 premix, the following materials were used:

• Aluminum foil (80 g); It is

• Blender;

• Attritor mill with zirconia spheres (d = 200-300 pm, m = 800 g).

[0176] The following procedure was performed:

[0177] 80 g of aluminum foil sheets were crushed in a blender. The crushed leaves (40 g) were subjected to grinding in an Attritor mill at 350 RPM with the aid of zirconia spheres (d = 200-300 pm, m = 800 g) in ethanol for 22h.

[0178] The wet metallic mixture was separated using a 500 pm sieve. An aliquot of the wet metallic mixture was taken below 500 pm to determine the zeta potential and particle size.

[0179] An aliquot of the wet metallic mixture below 500 pm was also taken to determine the particle size on Cilas equipment.

[0180] The wet metallic mixture was dried in an oven at 80 °C to obtain the dry powder.

[0181] For a suspension of NbgOs, the pH was adjusted to 6 (experimentally measured solids content: 26% m., volume: 440 mL) using an aqueous ammonium hydroxide solution (pH 14).

[0182] The Niobium pentoxide nanoparticles used in preparing the premix have a particle size distribution of dio = 0.16 pm, dso = 0.35 pm, dgo = 0.78 pm. [0183] Said Nb2Ü5 suspension was mechanically stirred at 300 RPM and, little by little, 23 g of aluminum powder was added to it. After adding aluminum powder, stirring was maintained at 300 RPM for 5 h under pH monitoring.

[0184] An increase in the pH value was observed after 5 h of mixing. The pH of the final mixture remained at ~7.1.

[0185] After 2, 3, 4 and 5 h of mechanical agitation, aliquots were removed from the mother suspension and dried in a vacuum oven at 80 °C to observe the state of the intimate mixture between the Al and Nb2Ü5 particles in the nanostructured premix .

[0186] Table 13 below describes the mass proportion of Nb2Ü5 and Al nanoparticles:

[0187] Table 13 - Mass proportion of Niobium and aluminum nanoparticles

[0188] In view of the experiments carried out, the preferred mass ratio of nanoparticles: aluminum was from 90.8:9.2 to 69.4:30.6.

[0189] The variation in the nanoparticle content in the premix for application to cast iron was also tested, as can be seen in table 14 below.

[0190] Table 14 - Variation in nanoparticle content

[0191] Example 6 - Characterization of the premix

[0192] An embodiment of the nanostructured premix was characterized. To this end, the wet metallic mixture was separated using a 500 pm sieve. An aliquot of the wet metallic mixture was taken below 500 pm to determine the zeta potential and particle size.

[0193] Figure 26 illustrates the zeta potential of aluminum particles as a function of pH. The zeta potential modulus (mV) is an indication of particle stability. The greater the zeta potential modulus, the more stable the particles. [0194] Figure 27 illustrates the zeta potential of Niobium Pentoxide particles as a function of pH.

[0195] In view of the results of the zeta potential as a function of pH, the pH of the metal mixture was adjusted to 6 at the beginning of the procedure.

[0196] As also mentioned in example 5, an aliquot of the wet metallic mixture below 500 pm was also taken to determine the particle size in Cilas equipment.

[0197] Figure 28 illustrates the granulometry results for aluminum particles using the Cilas equipment.

[0198] The results of the particle size test carried out on the Cilas equipment can be seen in Table 15 below:

[0199] Table 15 - Aluminum Particle Size Data

[0200] Figure 29 illustrates a MeV result (scanning electron microscopy) for the metallic mixture after 5h of mixing, with magnification of 3.11 kx and 2.01 kx at 10.0 kV.

[0201] Figure 30 illustrates the EDS (Energy Dispersive Spectroscopy) result for the metallic mixture after 5h of mixing. The EDS shows the proportion of each element in the metallic mixture.

[0202] Example 7 - Nanostructured premix addition test

[0203] To test the nanostructured premix from the previous example, ingots (“loaf shaped”) of nodular cast iron (alloy F) were produced. The mass of the assembly was approximately 27kg and a green sand process was used.

[0204] The content of Niobium pentoxide (nano, sub-micro and micrometric) in relation to the matrix metal was 0.1% by mass (representing 0.07% by mass of Nb). The Al content in relation to the matrix metal was 0.020% by mass (hypo condition).

[0205] The addition of the premix containing nano, sub-micro and micrometric powder particles was made onto the filter. Each filter was positioned over the entrance of each feed channel of each mold.

[0206] Inoculant was added when transferring the melt to the casting pan (FeSiCaBa 0.6%m) (inoculation in the pan) and when transferring the melt from the casting pan to each mold (FeSiCaBa 0.2%m) (inoculation per jet).

[0207] The pouring temperature (start of the ladle) was 1406 °C. Leak time was 8 to 9 seconds. Billet cooling times were around 45 min.

[0208] In the case of jet inoculation, it was observed that part of the powder was thrown into the air when transferring the melt from the casting pan to each mold. In the samples resulting from the process, it was observed that part of the powder was retained along the respective feeding channels. [0209] Example 8 - Test adding the nanostructured premix to the transfer pan

[0210] Another addition route was tested. Ingots (loaf shaped) of nodular cast iron (G1 alloy) were produced. The mass of the assembly was approximately 27kg and a green sand process was used.

[0211] The content of Niobium pentoxide (nanometric) in relation to the matrix metal was 0.1% by mass (representing 0.07% by mass of Nb). The Al content in relation to the matrix metal was 0.020% by mass (hypo condition).

[0212] The addition of the powder premix with aluminum was made over the filter. Each filter was positioned over the entrance of each feed channel of each mold.

[0213] The nanopowder mixture was added with chopped Al foil and kneaded into “balls” (plus nodularizing FeSiMg 1.3% by mass) in the transfer pan.

[0214] Table 16 - Chemical composition of the G1 alloy (from the shell removed from the pan):

[0215] Inoculant was added when transferring the melt to the casting pan (FeSiCaBa 0.6%m) (inoculation in the pan) and when transferring the melt from the casting pan to each mold (FeSiCaBa 0.2%m) (inoculation per jet).

[0216] The pouring temperature (start of the ladle) was 1406 °C. Leak time was 8 to 9 seconds. The ingot cooling times were around 3 hours for the base sample set and around 45min for the P6 premix sample set in the filter and the P6 premix chopped in the pan. [0217] During the addition of the powdered premix with aluminum over the filter, part of the powder was observed to be thrown into the air during jet inoculation.

[0218] No flotation was observed in the samples resulting from the ladle addition route. Tensile tests were carried out on 15 specimens of each billet (base, premix P6 and chopped P6).

[0219] The results of the mechanical evaluation are described below:

[0220] P6 premix over the filter: on average, the route contributed to increasing LRT by 5.8% (base: 500.6 MPa; P6 premix: 529.8 MPa) and increasing elongation (AL) by 13.4% ( base: 13.4%; P6 premix: 15.2%).

[0221] P6 chopped in the pan: on average, the route contributed to increasing LRT by 54.7% (base: 500.6 MPa; P6 chopped: 774.4 MPa) and reducing AL by 41% (base: 13.4 %; chopped P6: 7.9%).

[0222] Example 9 - Addition test of nanostructured premix to gray cast iron

[0223] Gray cast iron ingots (“loaf shaped”) were produced. The mass of the assembly was approximately 27kg and a green sand process was used.

[0224] The content of Niobium pentoxide (nanometric) in relation to the matrix metal was 0.1% by mass (representing 0.07% by mass of Nb). The Al content in relation to the matrix metal was 0.02% by mass (hypo condition).

[0225] The addition of the powdered premix with aluminum was made over the filter. Each filter was positioned over the entrance of each feed channel of each mold.

[0226] The nanopowder mixture was added with chopped Al foil and crushed into “balls”.

[0227] Inoculant was added when transferring the melt to the casting pan (FeSiCaBa 0.6%m) (inoculation in the pan) and when transferring the melt from the casting pan to each mold (FeSiCaBa 0.2%m) (inoculation per jet). [0228] The pouring temperature (start of the ladle) was 1380 to 1440 °C. Leak time was 8 to 9 seconds. Billet cooling times were around 45 minutes.

[0229] During the addition of the powder premix with aluminum over the filter, part of the powder was observed to be thrown into the air during jet inoculation.

[0230] No flotation was observed in the samples resulting from the process. Tensile tests were carried out on 9 specimens (per alloy). The mechanical evaluation was carried out on an MTS machine.

[0231] The results of the mechanical evaluation are described below:

[0232] P6 premix in the filter did not change LRT (base: 242.3 MPa; P6 premix: 242.9 MPa) and P6 chopped in the pan reduced LRT by 2% (base: 242.3 MPa; P6-chopped pan: 237 .3 MPa). The central region of the ingots presented lower resistance values compared to the base and top regions.

[0233] Example 10 - Test with heat treatment (quenching) on nodular cast iron

[0234] Ingots (“loaf shaped”) of nodular cast iron (G1 alloy) were produced. The mass of the assembly was approximately 27kg and a green sand process was used.

[0235] The content of Niobium pentoxide (nanometric) in relation to the matrix metal was 0.1% by mass (representing 0.07% by mass of Nb). The Al content in relation to the matrix metal was 0.02% by mass (hypo condition).

[0236] The nanopowder mixture was added with chopped Al foil and crushed into “balls”.

[0237] Inoculant was added when transferring the melt to the casting pan (FeSiCaBa 0.6%m) (inoculation in the pan) and when transferring the melt from the casting pan to each mold (FeSiCaBa 0.2%m) (inoculation per jet).

[0238] The pouring temperature (start of the ladle) was 1380 to 1440 °C. Leak time was 8 to 9 seconds. Cooling times for the ingots were about 3 hours for the base sample set and about 45min for the P6 premix sample set in the filter and the chopped P6 premix in the pan.

[0239] Heat treatment was carried out on the samples. The samples were austenized at 900 °C for 1 h and cooled to 260 °C. Mechanical tests were carried out on 1 specimen (per alloy).

[0240] The results of the mechanical evaluation are described below:

[0241] P6-chopped pan austempered increased LRT by 14% (base austempered: 1011 MPa; P6-chopped pan austempered: 1151 MPa), increased LE by 5% (base austempered: 867 MPa; P6-chopped pan austempered: 909 MPa ) and elongation (AL) by 150% (base austempered: 1%; P6-chopped pan austempered: 2.5%).

[0242] Tempering can “correct” the microstructure. The significant differences in the cooling speeds of the raw samples generated matrices with very different % phases, which can result in different speeds of microstructural transformations during quenching and impact mechanical results.

[0243] Example 11 - Test with heat treatment (quenching) on nodular cast iron

[0244] Ingots (“loaf shaped”) of nodular cast iron (alloy F) were produced. The mass of the assembly was approximately 27kg and a green sand process was used.

[0245] The Niobium pentoxide content (sub-micro and micrometric) in relation to the matrix metal was 0.1% by mass (representing 0.07% by mass of Nb). The Al content in relation to the matrix metal was 0.02% by mass (hypo condition). The micrometric FeNb content in relation to the matrix metal was 0.11% by mass (representing 0.07% by mass of Nb).

[0246] Sub-micron and micrometric premixes and FeNb powder on each filter were tested, which were positioned over the inlet of each mold feed channel. [0247] Inoculant was added when transferring the melt to the casting pan (FeSiCaBa 0.6%m) (inoculation in the pan) and when transferring the melt from the casting pan to each mold (FeSiCaBa 0.2%m) (inoculation per jet).

[0248] The pouring temperature (start of the ladle) was approximately 1425 °C. Leak time was 8 to 9 seconds. Billet cooling times were around 45 minutes.

[0249] Heat treatment was carried out on the samples. The samples were austenized at 900 °C for 1 h and cooled to 260 °C. Mechanical tests were carried out on 1 specimen (per alloy).

[0250] When transferring the melt from the casting pan to each mold, it was observed that part of the powder was thrown into the air during jet inoculation. In the samples resulting from the process, it was observed that part of the powder was retained along each feeding channel.

[0251] Example 12 - Test to evaluate incorporation of sub-micro and micrometric particles

[0252] Ingots (“loaf shaped”) of nodular cast iron (G1 alloy) were produced. The mass of the assembly was approximately 27kg and a green sand process was used.

[0253] The Niobium pentoxide content (sub-micro and micrometric) in relation to the matrix metal was 0.1% by mass (representing 0.07% by mass of Nb). The Al content in relation to the matrix metal was 0.020% by mass (hypo condition).

[0254] The preparations were added in the form of a mixture of powders (Nb2Ü5 sub-micro or micro) with Al foil chopped and kneaded into “balls” (plus nodularizing FeSiMg 1.3% by mass) in the transfer pan.

[0255] Table 17 - Chemical composition of the G1 alloy (from the shell removed from the pan):

[0256] Inoculant was added when transferring the melt to the casting pan (FeSiCaBa 0.6%m) (inoculation in the pan) and when transferring the melt from the casting pan to each mold (FeSiCaBa 0.2%m) (inoculation per jet).

[0257] The pouring temperature (start of the pan) was 1402 °C (base test), 1418 (sub-micro mixture test) and 1409 °C (micrometric mixture test). Leak time was 8 to 9 seconds. The cooling time for the ingots was around 45 minutes.

[0258] Mechanical tests were carried out on 9 specimens/ingot. The results of the mechanical evaluation are described below:

[0259] P6 premix over the filter: on average, the route contributed to increasing LRT by 5.8% (base: 500.6 MPa; P6 premix: 529.8 MPa) and increasing elongation (AL) by 13.4% ( base: 13.4%; P6 premix: 15.2%).

[0260] Mechanical evaluation of samples with incorporated sub-micrometer mixture: on average, sub-micrometer particles contributed to reducing LRT by 4% (base: 624 MPa; P6-chopped sub-micro: 600 MPa), reducing LE by 2 % (base: 429 MPa; P6-chopped sub-micro: 421 MPa) and do not change elongation (AL) (base: 9%; P6-chopped sub-micro: 9%).

[0261] Mechanical evaluation of samples with incorporated micrometric mixture: on average, micrometric particles contributed to reducing LRT by 5% (base: 624 MPa; P6-micro chopped: 595 MPa), increase LE by 1% (base: 429 MPa; P6-micro chopped: 434 MPa) and do not change AL (base: 9%; P6- micro chopped: 9%).

[0262] Example 13 - Test adding the nanostructured premix to the transfer pan

[0263] Another addition route was tested. Ingots (loaf shaped) of nodular cast iron (G1 alloy) were produced. The mass of the assembly was approximately 24kg and a green sand process was used.

[0264] The content of Niobium pentoxide (nanometric) in relation to the matrix metal was 0.1% by mass (representing 0.07% by mass of Nb). The Al content in relation to the matrix metal was 0.020% by mass (hypo condition).

[0265] The preparations in the form of nanometric premix powder and FeNb powder (plus nodularizing FeSiMg 1.3% by mass) were added to the transfer pan.

[0266] Table 18 - Chemical composition of the G1 alloy (from the shell removed from the pan):

[0267] Inoculant was added when transferring the melt to the casting pan (FeSiCaBa 0.6%m) (inoculation in the pan) and when transferring the melt from the casting pan to each mold (FeSiCaBa 0.2%m) (inoculation per jet). [0268] The pouring temperature (start of the ladle) was 1380 to 1440 °C. Leak time was 8 to 9 seconds. Billet cooling times were around 45 minutes.

[0269] No flotation was observed in the samples resulting from the ladle addition route. Tensile tests were carried out on 9 specimens per ingot. [0270] The results of the mechanical evaluation are described below:

[0271] Mechanical evaluation of alloy G1 - P6 premix: on average, P6-premix contributed to reducing LRT by 0.4% (base: 651 MPa; P6-premix: 648 MPa), increasing LE by 2.6% (base : 439 MPa; P6-premix: 450 MPa) and reduce AL by 11% (base: 7.3%; P6-chopped: 6.5%).

[0272] Mechanical evaluation of alloy G1 - FeNb: on average, FeNb contributed to increasing LRT by 1.5% (base: 651 MPa; FeNb: 658 MPa), reducing LE by 0.8% (base: 439 MPa; FeNb : 447 MPa) and reduce AL by 0.9% (base: 7.3%; FeNb: 6.4%).

[0273] Example 14 - Variation of Niobium pentoxide content in gray cast iron

[0274] Gray cast iron ingots (“loaf shaped”) were produced. The mass of the assembly was approximately 24kg and a green sand process was used.

[0275] The content of Niobium pentoxide (nanometric) in relation to the matrix metal was 0.1% by mass (representing 0.07% by mass of Nb) and 0.2% by mass (representing 0.14% in mass of Nb). No aluminum was used in this example.

[0276] The nanopowder preparations were added to the transfer pan.

[0277] Table 19 - Chemical composition of the alloy (from the shell removed from the melt in the furnace):

0278] Inoculant was added when transferring the melt to the casting pan (FeSiCaBa 0.6%m) (inoculation in the pan) and when transferring the melt from the casting pan to each mold (FeSiCaBa 0.2%m) (inoculation by jet).

[0279] The pouring temperature (start of the ladle) was 1380 to 1440 °C. Leak time was 8 to 9 seconds. Billet cooling times were around 45 minutes.

[0280] No flotation was observed in the samples resulting from the addition route in the pan. No significant changes in mechanical properties were observed.

[0281] Example 15 - Assessment of the pearlizing potential of Niobium

[0282] Ingots (shaped like a “loaf of bread”) + stepped pieces (mass of the billet set + ladder, mass of the set was approximately 21 kg) and Y-blocks of nodular cast iron (Alloy I) were produced. A green sand process was used.

[0283] The content of Niobium pentoxide (nanometric) in relation to the matrix metal was 0.1% by mass (representing 0.07% by mass of Nb). The aluminum content in relation to the matrix metal was 0.02% by mass (hypo condition).

[0284] Addition of the preparation in premix powder form (with aluminum from Alie) and FeNb powder to the transfer pan.

[0285] Table 20 - Chemical composition of alloy I (from the shell removed from the melt in the ladle):

casting (FeSiCaBa 0.6%m) (inoculation in the ladle) and transferring the melt from the casting ladle to each mold (FeSiCaBa 0.2%m) (jet inoculation).

[0287] The pouring temperature (start of the pan) was 1380 (base), 1408 (P6 premix) and 1400 °C (FeNb). Leak time was 8 to 9 seconds. Billet cooling times were around 45 minutes.

[0288] No flotation was observed in the samples resulting from the addition route in the pan. In the samples cut from the Y blocks, micropores were observed in the fillets of all alloys and macropores in the fillets of those modified with P6 premix and FeNb.

[0289] 3 specimens per ingot were machined (central region).

[0290] The results of the mechanical evaluation are described below:

[0291] Mechanical evaluation of alloy I - P6 premix: on average, P6-premix contributed to reducing LRT by 5.2% (base: 640.3 MPa; P6-premix: 673.7 MPa), increasing LE by 3, 3% (base: 459 MPa; P6-premix: 489 MPa) and increase AL by 1.5% (base: 6.57%; P6-chopped: 6.67%).

[0292] Mechanical evaluation of alloy I - FeNb: on average, FeNb contributed to increasing LRT by 2.1% (base: 640.3 MPa; FeNb: 653.7 MPa), increasing LE by 1.5% (base: 459 MPa; FeNb: 465.7 MPa) and increase AL by 1.5% (base: 6.57%; FeNb: 6.67%). [0293] 2 specimens were machined per Y block.

[0294] The results of the mechanical evaluation are described below:

[0295] Mechanical evaluation of alloy I - P6 premix: on average, P6-premix contributed to increasing LRT by 2% (base: 498 MPa; P6-premix: 507.5 MPa), increasing LE by 2% (base: 320 MPa; P6-premix: 326 MPa) and reduce AL by 10% (base: 18.2%; P6-premix: 16.3%).

[0296] Mechanical evaluation of alloy I - FeNb: on average, FeNb contributed to increasing LRT by 14% (base: 498 MPa; FeNb: 570 MPa), increasing LE by 11% (base: 320 MPa; FeNb: 356 MPa) and reduce AL by 25% (base: 18.2%; FeNb: 13.7%).

[0297] 9 specimens were machined per ingot (“loaf” shape).

[0298] The results of the mechanical evaluation are described below:

[0299] Mechanical evaluation of alloy I - P6 premix: on average, P6 premix contributed to increasing LRT by 17% (base: 654 MPa; P6 premix: 763 MPa), increasing LE by 15% (base: 414 MPa; P6 premix : 477 MPa) and reduce AL by 16% (base: 7.5%; P6 premix: 6.3%).

[0300] Mechanical evaluation of alloy I - FeNb: on average, FeNb contributed to increasing LRT by 10% (base: 654 MPa; FeNb: 718 MPa), increasing LE by 8% (base: 414 MPa; FeNb: 449 MPa) and reduce AL by 17% (base: 7.5%; FeNb: 6.2%).

[0301] Example 16 - Effect of nanostructured premix on gray cast iron (FC 200 alloy)

[0302] Y-blocks were produced in gray cast iron (FC 200 alloy - FUCO FC 200 base). A cold-box process was used.

[0303] 2 tests were carried out: experiment 0 corresponded to the furnace “wash” melting and experiment 1 to the melting with premix (with Al from Alie) added to the load. Samples resulting from fusion 0 were used as a baseline.

[0304] The Niobium pentoxide content (nanometric) was 0.1% by mass in relation to the matrix material (representing 0.07% by mass of Nb). The content of aluminum was 0.02% by mass in relation to the matrix material. The premix content was 0.12% by mass in relation to the matrix material.

[0305] Nanometric powder premix was added with aluminum in the oven. The premix was added from the beginning to the middle of the load.

[0306] Inoculant was added when transferring the melt from the furnace to the casting pan (FeSiCaBaZr 0.16% by mass).

[0307] Fusion load 0: all FUCO FC 200 + all 1020 steel scrap + all fuel (natural graphite).

[0308] Fusion load 1: all FUCO FC 200 + all premix (0.12%m) + all 1020 steel scrap + all fuel (natural graphite).

[0309] The temperature of the bath in the oven was approximately 1450 ± 10 °C. The pouring temperature was approximately 1390 ± 10 °C. The pouring time was approximately 15s. For the cooling times of the blocks, the time was from one day to the next until room temperature. In the samples resulting from the process, no flotation of the premix was observed.

[0310] Mechanical evaluation: on average, P6 premix contributed to increasing LRT by 36.5% (base: «207 MPa; P6 premix: «282 MPa).

[0311] Example 17 - Effect of nanostructured premix on gray cast iron (FC 200 alloy)

[0312] Test bars (ASTM A48 standard) and Y-blocks were produced in gray cast iron (FC 200 alloy - FUCO FC 200 base). A cold-box process was used.

[0313] 2 tests were carried out: experiment 2 corresponded to baseline melting and experiment 3 to melting with premix (with Al) added to the load.

[0314] The Niobium pentoxide content (nanometric) was 0.1% by mass in relation to the matrix material (representing 0.07% by mass of Nb). The aluminum content was 0.02% by mass in relation to the matrix material. The premix content was 0.12% by mass in relation to the matrix material.

[0315] Nanometric powder premix was added with aluminum in the oven. The premix was added 2/3 of the way through the melt, that is, right after adding the scrap. [0316] Inoculant was added to the bottom of the casting pan before transferring the melt from the furnace (FeSiCaBaZr 0.30% by mass).

[0317] Fusion charge 2: 3 ingots of FUCO FC 200 + all fuel (synthetic graphite with incorporation efficiency of 98%) + all sulfur (CaS 0.8%m, which was removed from the thermal analysis crucibles) + all metallic tin in bars (0.07%m Sn) + all 1020 steel scrap + 3 FUCO FC 200 ingots.

[0318] Fusion charge 3: 3 ingots of FUCO FC 200 + all fuel (synthetic graphite with incorporation efficiency of 98%) + all sulfur (CaS 0.8% m, which was removed from the thermal analysis crucibles) + all metallic tin in bars (0.07%m Sn) + all 1020 steel scrap + all premix (0.12%m) + 3 FUCO FC 200 ingots.

[0319] CaS was added after melting the ^1st charge of FUCO (after the first 3 ingots melted).

[0320] The temperature of the bath in the oven was approximately 1500 ± 10 °C. The pouring temperature was approximately 1400 ± 10 °C. The pouring time was approximately 15s. For cooling times, the time was from one day to the next until room temperature. In the samples resulting from the Nb addition process, no flotation of the premix was observed. [0321] Improvement in fluidity during pouring was observed after increasing the bath and pouring temperatures. No fuel was observed at the bottom of the oven.

[0322] A shell was removed after melting 50% of the FUCO charge to measure the chemical composition of the starting FUCO.

[0323] Mechanical evaluation: on average, P6 premix contributed to increasing LRT by 36.5% (base: «207 MPa; P6 premix: «282 MPa).

[0324] Block Y mechanical evaluation: on average, P6 premix contributed to increasing LRT by 12% (base: «276 MPa; P6 premix: «310 Mpa).

[0325] Mechanical evaluation test bars: on average, P6 premix contributed to increasing LRT by 17% (base: «231 MPa; P6 premix: «270 MPa).

[0326] Example 18 - Effect of nanostructured premix on cast iron gray (FC 200 league)

[0327] Test bars (ASTM A48 standard), Y blocks and wedges were produced in gray cast iron (alloy FC 200 - FUCO FC 200 base). A cold-box process was used.

[0328] 4 tests were carried out: experiment 4 corresponded to the baseline fusion, experiment 5 to the fusion with hypostoichiometric premix (with Alie's Al), experiment 6 to the fusion with stoichiometric premix (with Alie's Al) and experiment 7 to the fusion with premix hyperstoichiometric (with Al da Alie), added to the charges.

[0329] The Niobium pentoxide content (nanometric) was 0.1% by mass in relation to the matrix material (representing 0.07% by mass of Nb). The aluminum content was 0.020% by mass in relation to the matrix material (hypo condition), 0.034% (stoichiometric) and 0.041% by mass (hyper condition). The premix content was 0.120% by mass in relation to the matrix material (hypo condition), 0.134% by mass (stoichiometric) and 0.141% by mass (hyper condition).

[0330] Nanometric powder premix was added with aluminum in the oven. The premix was added 2/3 of the way through the melt, that is, right after adding the scrap.

[0331] Inoculant was added when transferring the melt from the furnace to the casting pan (FeSiCaBaZr 0.30% by mass).

[0332] Fusion load 4: 50% ingots of DRUM FC 200 + all fuel (synthetic graphite with incorporation efficiency of 98%) + all sulfur (CaS 0.8%m) + all steel scrap 1020 + 50% TAMBOR FC 200 ingots.

[0333] Fusion charge 5: 50% ingots of TAMBOR FC 200 + all fuel (synthetic graphite with incorporation efficiency of 98%) + all sulfur (CaS 0.8%m) + all 1020 steel scrap + all premix (0.120%m) + 50% TAMBOR FC 200 ingots.

[0334] Fusion charge 6: 50% ingots of TAMBOR FC 200 + all fuel (synthetic graphite with incorporation efficiency of 98%) + all sulfur (CaS 0.8%m) + all 1020 steel scrap + all premix (0.134%m) + 50% TAMBOR FC 200 ingots.

[0335] Fusion charge 7: 50% ingots of TAMBOR FC 200 + all fuel (synthetic graphite with incorporation efficiency of 98%) + all sulfur (CaS 0.8%m) + all 1020 steel scrap + all premix (0.141%m) + 50% TAMBOR FC 200 ingots.

[0336] The temperature of the bath in the oven was approximately 1500 ± 10 °C. The pouring temperature was approximately 1400 ± 10 °C. The pouring time was approximately 15s. For cooling times, the time was from one day to the next until room temperature. In the samples resulting from the Nb addition process, no flotation of the premix was observed. [0337] Improvement in fluidity during pouring was observed after increasing the bath and pouring temperatures. No fuel was observed at the bottom of the oven.

[0338] One shell was removed in the stage of transferring the melt from the oven to the casting pan and another in the stage of transferring the pan to the molds.

[0339] No significant changes in mechanical properties were observed.

[0340] Example 19 - Effect of nanostructured premix on gray cast iron (FC 200 alloy)

[0341] Test bars (ASTM A48 standard) and wedges were produced in gray cast iron (FC 200 alloy - FUCO FC 200 base). A cold-box process was used.

[0342] 4 tests were carried out: experiment 8 corresponded to the baseline fusion, experiment 9 to the fusion with hypostoichiometric premix (with Alie's Al), experiment 10 to the fusion with stoichiometric premix (with Alie's Al) and experiment 11 to the fusion with premix hyperstoichiometric (with Al da Alie), added to the charges. [0343] The Niobium pentoxide content (nanometric) was 0.1% by mass in relation to the matrix material (representing 0.07% by mass of Nb). The aluminum content was 0.020% by mass in relation to the matrix material (hypo condition), 0.034% by mass and 0.041% by mass (hyper condition). The premix content was 0.120% by mass in relation to the matrix material (hypo condition), 0.134% by mass (stoichiometric) and 0.141% by mass (hyper condition).

[0344] Nanometric powder premix was added with aluminum in the oven. The premix was added 2/3 of the way through the melt, that is, right after adding the scrap.

[0345] Inoculant was added when transferring the melt from the furnace to the casting pan (FeSiCaBaZr 0.30% by mass).

[0346] Fusion charge 8: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + 50% FUCO FC 200 ingots.

[0347] Fusion charge 9: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + all premix (0.120% m) + 50% FUCO FC ingots 200.

[0348] Fusion charge 10: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + all premix (0.134%m) + 50% FUCO FC ingots 200.

[0349] Fusion charge 1 1: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + all premix (0.141%m) + 50% FUCO ingots FC 200.

[0350] The temperature of the bath in the oven was approximately 1500 ± 10 °C. The pouring temperature was approximately 1400 ± 10 °C. The pouring time was approximately 15s. For cooling times, the time was from one day to the next until room temperature. In the samples resulting from the Nb addition process, no flotation of the premix was observed. [0351] Improvement in fluidity during pouring was observed after increasing the bath and pouring temperatures. No fuel was observed at the bottom of the oven. [0352] One shell was removed in the stage of transferring the melt from the oven to the casting pan and another in the stage of transferring the pan to the molds.

[0353] No significant changes in mechanical properties were observed.

[0354] Example 20 - Effect of nanostructured premix on gray cast iron (FC 200 alloy)

[0355] Test bars (ASTM A48 standard) and wedges were produced in gray cast iron (FC 200 alloy - FUCO FC 200 base). A cold-box process was used.

[0356] 4 tests were carried out: experiment 12 corresponded to fusion with 0.11 %m micrometer FeNb added (0.1%m Nb), experiment 13 to fusion with 0.33 %m micrometer FeNb added (0.3%m Nb), experiment 14 to fusion with 0.55% micrometer FeNb added (0.5%m Nb) and experiment 15 to fusion with 1.1% micrometric FeNb added (1%m Nb), added to the charges.

[0357] Micrometric FeNb was added in powder form in the oven. The premix was added 2/3 of the way through the melt, that is, right after adding the scrap.

[0358] Inoculant was added when transferring the melt from the furnace to the casting pan (FeSiCaBaZr 0.16% by mass).

[0359] Fusion charge 12: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + 0.11%m FeNb + 50% FUCO FC 200 ingots .

[0360] Fusion charge 13: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + 0.33%m FeNb + 50% FUCO FC 200 ingots .

[0361] Fusion charge 14: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with 98% incorporation efficiency) + all 1020 steel scrap + 0.55% m FeNb 50% + FUCO FC 200 ingots . [0362] Fusion charge 15: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + 1.1%m FeNb + 50% FUCO FC 200 ingots .

[0363] The temperature of the bath in the oven was approximately 1500 ± 10 °C. The pouring temperature was approximately 1400 ± 10 °C. The pouring time was approximately 15s. For cooling times, the time was from one day to the next until room temperature. In the samples resulting from the Nb addition process, FeNb flotation was not observed.

[0364] Improvement in fluidity during pouring was observed after increasing the bath and pouring temperatures. No fuel was observed at the bottom of the oven.

[0365] One shell was removed in the stage of transferring the melt from the oven to the casting pan and another in the stage of transferring the pan to the molds.

[0366] There was an improvement in mechanical properties after addition of micrometric FeNb. Load with 0.11% by mass of FeNb: there was a 25.3% increase in the tensile strength limit. Load with 0.33% by mass of FeNb: there was a 45.3% increase in the tensile strength limit. Load with 0.55% by mass of FeNb: there was a 37.7% increase in the tensile strength limit. Load with 1.1% by mass of FeNb: there was a 67.9% increase in the tensile strength limit.

[0367] Example 21 - Effect of nanostructured premix on gray cast iron (FC 200 alloy) - variation in Nb20s content

[0368] Test bars (ASTM A48 standard) and wedges were produced in gray cast iron (FC 200 alloy - FUCO FC 200 base). A cold-box process was used.

[0369] 4 tests were carried out: experiment 16 corresponded to the baseline fusion, experiment 17 to fusion with hyperstoichiometric premix (with Alie's Al) - 0.1%m Nb2Ü5, experiment 18 to fusion with hyperstoichiometric premix (with Alie's Al) - 0.5 %m Nb2Ü5 and experiment 18 to fusion with premix hyperstoichiometric (with Al from Alie) - 1%m Nb20s, added when transferring the melt from the furnace to the casting pan together with the inoculant.

[0370] The nanometric Niobium pentoxide content was 0.1; 0.5 and 1.0% by mass in relation to the matrix material.

[0371] The premix contents were 0.141% by mass (hyper condition), 0.703% by mass (hyper condition) and 1.406% by mass in relation to the matrix material.

[0372] Inoculant was added when transferring the melt from the furnace to the casting pan (FeSiCaBaZr 0.16% by mass).

[0373] Fusion charge 16: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + 50% FUCO FC 200 ingots.

[0374] Fusion charge 17: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + all premix (0.141% m) + 50% FUCO FC ingots 200.

[0375] Fusion charge 18: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + all premix (0.703%m) + FUCO FC 200 ingots.

[0376] Fusion charge 19: 50% FUCO FC 200 ingots + all fuel (synthetic graphite with incorporation efficiency of 98%) + all 1020 steel scrap + all premix (1,406%m) + 50% ingots FUCO FC 200.

[0377] The temperature of the bath in the oven was approximately 1500 ± 10 °C. The pouring temperature was approximately 1400 ± 10 °C. The pouring time was approximately 15s. For cooling times, the time was from one day to the next until room temperature. In the samples resulting from the Nb addition process, premix flotation was observed in the additions with 0.5 and 1.0% of Nb20s. [0378] Improvement in fluidity during pouring was observed after increasing the bath and pouring temperatures. No fuel was observed at the bottom of the oven.

[0379] One shell was removed in the stage of transferring the melt from the oven to the casting pan and another in the stage of transferring the pan to the molds.

[0380] No significant changes in mechanical properties were observed.

[0381] Example 22 - Effect of nanostructured premix on gray cast iron (FC 200 alloy) - variation in Nb20s content

[0382] Test bars (ASTM A48 standard), Y blocks and wedges were produced in gray cast iron (FC 200 alloy - FUCO FC 200 base). A cold-box process was used.

[0383] 4 tests were carried out: experiment 20 corresponded to baseline fusion, experiment 21 to fusion with hypostoichiometric premix (with Al from Alie) - 0.1%m Nb2Ü5 added to the load, experiment 22 to fusion with hypostoichiometric premix (with Al from Alie) - 0.1 %m Nb2Ü5 added in the form of wire and experiment 23 to fusion with hypostoichiometric premix (with Al from Alie) - 0.3 %m Nb2Ü5 added to the load.

[0384] The nanometric Nb2Ü5 content was 0.1%, 0.1% and 0.3% by mass in relation to the matrix material.

[0385] The premix contents were 0.120% by mass (hypo condition), 0.120% by mass (hypo condition) and 0.361% by mass (hypo condition) in relation to the matrix material.

[0386] Inoculant was added when transferring the melt from the furnace to the casting pan (FeSiCaBaZr 0.16% by mass).

[0387] Fusion 20 charge: 50% FUCO FC 200 ingots + all fuel (natural graphite) + all 1020 steel scrap + 50% FUCO FC 200 ingots. [0388] Fusion charge 21: 50% FUCO FC 200 ingots + all fuel (natural graphite) + all 1020 steel scrap + all premix (0.120% m) + 50% FUCO FC 200 ingots.

[0389] Fusion 22 charge: 50% FUCO FC 200 ingots + all fuel (natural graphite) + all 1020 steel scrap + all premix (0.120%m) encapsulated in steel wire + FUCO FC 200 ingots.

[0390] Fusion 23 charge: 50% FUCO FC 200 ingots + all fuel (natural graphite) + all 1020 steel scrap + all premix (0.361%m) + 50% FUCO FC 200 ingots.

[0391] The temperature of the bath in the oven was approximately 1450 ± 10 °C. The pouring temperature was approximately 1390 ± 10 °C. The pouring time was approximately 15s. For cooling times, the time was from one day to the next until room temperature. In the samples resulting from the Nb addition process, no flotation of the premix was observed. [0392] One shell was removed in the stage of transferring the melt from the oven to the casting pan and another in the stage of transferring the pan to the molds.

[0393] Y block mechanical evaluation: on average, hypo premix with 0.1% Nb2Ü5 contributed to reducing LRT by 9% (base: 192 MPa; premix: 175.1 MPa) and hypo premix with 0.3% Nb2Ü5 contributed to increase LRT by 24% (base: 192; premix: 238.5 MPa).

[0394] Mechanical evaluation test bars: on average, hypo premix with 0.1% Nb ₂ O ₅ contributed to reducing LRT by 12% (base: 189.1 MPa; hypo premix: 166.7 MPa) and hypo premix with 0.3% Nb2Ü5 contributed to increasing LRT by 19% (base: 189.1 MPa; premix: 225.6 Mpa).

[0395] Example 23 - Comparison of mergers described in previous examples

[0396] Fusions 0 to 15 were compared, table 21 illustrates the summarized chemical composition of each of the fusions:

[0397] Table 21 - Summary chemical composition of each of the fusions:

[0398] Mergers 0 to 19 were compared, table 22 illustrates the raw materials for each of the mergers:

[0399] Table 22 - raw materials for each of the mergers:

[0400] Fusions 0 to 19 were compared, table 23 illustrates details of the specimens and average tensile strength limit (LRT):

[0401] Table 23 - specimens and average tensile strength limit (LRT):

[0402] Figure 31 illustrates a graph that compares the results of the average tensile strength limits (LRT) for melts 0 to 19 illustrated in table 23.

[0403] Those skilled in the art will value the knowledge presented here and will be able to reproduce the invention in the modalities presented and in other variants and alternatives, covered by the scope of the following claims.

Claims

Claims

1 . Cast iron characterized by comprising Niobium particles in a concentration of 0.01 to 1% by mass.

2. Cast iron according to claim 1, characterized in that it comprises Niobium particles in a concentration of 0.03 to 0.3% by mass.

3. Cast iron according to claim 1, characterized in that it additionally comprises aluminum in a concentration of 0.01 to 1% by weight.

4. Cast iron according to claim 3, characterized in that it comprises aluminum in a concentration of 0.01 to 0.044% by mass.

5. Cast iron according to claim 1, characterized in that said Niobium particles are particles having a particle size profile in the nanometer range.

6. Cast iron according to claim 5, characterized in that said Niobium particles are Niobium pentoxide nanoparticles or FeNb nanoparticles.

7. Cast iron according to claim 1 characterized in that said cast iron is nodular cast iron or gray cast iron.

8. Process for obtaining cast iron characterized by the addition of Niobium particles in a concentration of 0.01 to 1% by weight prior to casting the molten matrix.

9. Process for obtaining cast iron according to claim 8, characterized in that said Niobium particles are particles having a particle size profile in the nanometer range.

10. Process for obtaining cast iron according to claim 8, characterized in that the step of adding niobium particles is carried out by adding a premix comprising niobium and aluminum particles.

11 . Process for obtaining cast iron according to claim 10, characterized in that said aluminum is in the form of powder, crushed, ground or chopped.

12. Process for obtaining cast iron according to claim 10, characterized in that said premix is added in at least one of the following ways:

- to the mold before casting the melt;

- in the transfer pan before pouring the melt;

- at the entrance to the mold feed channel before casting the casting;

- in the furnace before casting the melt; or

- in the jet together with the inoculant.

13. Process for obtaining cast iron according to claim 10, characterized in that the premix comprises Nb2Ü5 and a molar ratio of AI/Nb20s of 1 to 5.

14. Process for obtaining cast iron according to claim 8, characterized in that it additionally comprises an inoculant addition step.

15. Process for obtaining cast iron according to claim 8, characterized in that it additionally comprises a step of adding fuel to the melt charge.