ES2362241A1 - Manufacturing process of castings with spheroidal graphite - Google Patents

Abstract

The present invention relates to a process for manufacturing spheroidal castings by using metal or permanent molds. The resulting mechanical properties of the new parts are considered of great interest due to, among other reasons, the large number of graphite spheroids obtained in the parts.

Description

Manufacturing procedure for parts of spheroidal cast iron.

The present invention relates to a spheroidal castings manufacturing process through the use of metal or permanent molds. The properties mechanics resulting from the new parts, are considered of great interest due, among other aspects, to the large number of spheroids graphite obtained in the pieces.

Prior art

The manufacture of iron castings It is mainly aimed at obtaining materials economically competitive metallic and with adequate properties to the functionality of the designed components. On this last case, part of the current research efforts are geared towards obtaining graphite smelters with optimized properties. The objective of these "new foundry materials" focuses in offering a cheaper alternative to the use of steels or other special alloys for the manufacture of parts With high performance.

Within the field of iron foundries with precipitated graphite, the spheroidal cast iron constitutes one of the materials with more travel since its discovery in the 1950s. Compared to lamellar or gray cast iron, the formation and subsequent growth of graphites in the form spheroid causes significant increases in breaking loads, elastic limits and, especially, in the lengthening of the material. An appropriate combination of these three properties mechanical means obtaining materials with an extensive field of technological application

Additionally, the massive formation of graphite spheroids within the metal matrix has even more interesting consequences. Under these conditions, diffusion of carbon atoms is favored [ M. Wessén, I. Svensson, Metall. Mat. Trans. A, A27, 1996 , 2209-2220 ] towards the numerous spheroids available during the period of austenite cooling (Fe-γ). Consequently, suitable conditions are obtained for the formation and growth of ferrite (Fe-?) In the solid-solid transformation [ J. Sertucha, R. Suárez, J. Izaga, LA Hurtado, J. Legazpi, Int. J. Cast Met. Res., 2006 , 19, 315-322 ]. This structural phase gives the material a high degree of ductility and impact resistance, except those cases in which the contents of Si and / or P are high [ LE Björkegren, K. Hamberg, Proc. Keith Millis Symposium on Ductile Cast Iron, 2003 , I. Riposan, M. Chisamera, S. Stan, Int. J. Cast Met. Res., 20, 2007 , 64-67 ].

On the other hand, the influence of the cooling conditions on the structural characteristics and, therefore, the mechanical properties of iron foundries with spheroidal graphite is well known [ GM Goodrich, RW Lobenhofer, AFS Trans., 2007 , 115, work No. 07-045; BV Kovacs, AFS Trans., 1981 , 89, 79-96 ].

In the vast majority of the processes of current manufacturing molds are used configured with mixtures that contain silica sand (SiO2) as constituent controlling.

This refractory material is characterized by have a comparatively low thermal conductivity, which greatly limits the cooling rate of the alloy casting inside this type of mold.

This type of technique has the following inconvenience

- molding operations are more difficult, the demolding and obtaining of pieces is slow.

- presence of sand inclusions.

- low spheroid density per unit of volume of material (lower homogeneity in the properties of the material).

- due to the low speed of solidification, major additions of magnesium are necessary in treatments to ensure a correct spheroidization index in the material.

- high risk of metal contraction.

- low yields in molds (ratio between the metal of the pieces and the metal cast in the mold).

- there is the possibility of deformations in the mold footprints due to metastatic pressure (lower dimensional accuracies in the pieces).

- need for subsequent operations of finish (burrs) in the pieces.

- low thermal conductivity of the material and poor machinability

That is why it is necessary develop new methodologies for obtaining pieces of foundry that improve the disadvantages mentioned above.

Description of the invention

The present invention relates to a new manufacturing process of spheroidal castings, which resolves all the aforementioned problems, when use molds configured with mixtures containing silica sand (SiO 2) as a majority constituent. This is done using metal or "permanent" molds. The use of this new type of molds, makes the following advantages:

- Better surface finish and minimal interaction metal mold. Greater ease in the process of surface cleaning of the pieces.

- Ease in molding operations (only It is necessary to open and close the coquillas in addition to making your adequate maintenance).

- Fast demolding and obtaining pieces.

- Absence of sand inclusions (the defect more common in foundries that use sand molds).

- High spheroid density per unit of volume of material (greater homogeneity in the properties of the material).

- Due to the higher speed of solidification, Minor additions of magnesium are necessary in treatments to ensure a correct spheroidization index in the material.

- Low risk of metal contraction (minimization of rechupes and microrechupes).

- High yields in the molds (relation between the metal of the pieces and the metal cast in the mold).

- There is no possibility of deformations in mold footprints due to metastatic pressure (greater dimensional precision in the pieces).

- If there is a good adjustment of the molds, just subsequent finishing operations (burrs) are necessary in the pieces.

- Such an important increase in the number of spheroids per unit volume translates into an increase in the thermal conductivity of the material and an improvement in its machinability

This new technique can be used for manufacture of castings for the automotive sector, hydraulic components, metal molds for the industry glass, centrifuged tubes, etc ... The use of metal molds greatly accelerates the speed of solidification and subsequent material cooling, generating important changes in the structures obtained in the raw state of casting.

Therefore, a first aspect of the present invention is a manufacturing process of castings spheroid comprising the following stages:

to)

fusion of metal charges to a temperature between 1400 and 1600 ° C. More preferable between 1430 and 1450 ° C.

b)

adjustment of metal loads for achievement of the required composition;

C)

spheroidization treatment with temperatures below 1148 ° C; Y

d)

casting process in metal molds or "permanent"

According to a preferred embodiment, the charges Metallic are selected from the group consisting of high ingots carbon, casting chip briquettes, cast iron, scrap metal, steel from the automotive sector, returns or any combination thereof. Preferably, metal charges are selected among high carbon ingots, returns, briquettes of foundry shavings, steel from the automotive sector or any combination thereof.

According to another preferred embodiment, the composition of the metallic charges is:

-

between 25 and 90% high carbon ingot

-

between 0 and 30% steel from the automotive sector

-

between 0 and 50% of casting chip briquettes

-

between 1 and 50% returns.

Always keeping in mind that the sum of all The components must be 100%.

Preferably, the composition of the metal loads is:

-

between 30 and 80% high carbon ingot

-

between 0 and 25% steel from the automotive sector

-

between 0% and 35% of casting chip briquettes

-

between 1 and 35% returns.

Always keeping in mind that the sum of all The components must be 100%.

Even more preferably, the composition of The charges is:

-

75% of high carbon ingot

-

20 of steel from the automotive sector

-

0% of casting chip briquettes

-

5 of returns.

or

-

33.33% high carbon ingot

-

0% of steel from the automotive sector

-

33.33% of casting chip briquettes

-

33.33% of returns.

Always keeping in mind that the sum of all The components must be 100%.

According to a preferred embodiment, after adjustment The following composition is obtained from metal charges:

-

C: from 3.95 to 4.05% by weight.

-

Yes: from 1.00 to 2.60% by weight.

-

Mn: from 0.40 to 0.80% by weight.

-

S: from 0.00 to 0.20% by weight.

-

Others:

More preferably, after adjusting the Metal loads the following composition is obtained:

-

C: from 3.60 to 4.05% by weight.

-

Yes: from 1.90 to 2.60% by weight.

-

Mn: from 0.50 to 0.80% by weight.

-

S: from 0.00 to 0.10% by weight.

-

Others:

Always keeping in mind that the sum of all The components must be 100%.

All these percentages by weight are with respect to total fade.

According to another preferred embodiment, the process of Fusing of metal loads is done in rotary kilns. By on the other hand the melting time and stay of said metallic load is 60 to 80 minutes (hours), preferably 70 minutes.

According to another preferred embodiment in the step of Carbon and silicon content adjustment are added depending on its content in the molten metal (metal fillers) obtained in stage a) to optimize the next stage c) of spheroidization, such that molten metal charges are transfer to at least 1 induction furnace (1000 Hz), preferably to 3 induction furnaces. On the other hand the temperature is maintained of the base metal in a temperature range between 1400 and 1500 ° C, preferably between 1400 and 1450 ° C.

In another preferred embodiment, the treatment of Spheroidization comprises the following stages:

to.

addition to a treatment spoon, FeSiMg in a proportion of 0.7 to 1.0% by weight with respect to metal loads to be treated.

b.

adding an inoculant on the FeSiMg in a proportion of 0.15 to 0.20% by weight with respect to metal loads to be treated.

C.

addition of steel cuts so that these cover the FeSiMg and the inoculant beforehand introduced into a reaction chamber;

d.

filling of metal loads from stage b) up to 20 to 30% by volume of the spoon, orienting the fall of the metal towards the area opposite a reaction chamber;

and.

complete the spoon filling with metal charges; Y

F.

derail the treated metal.

According to a preferred embodiment the alloy FeSiMg, comprises the following composition:

-

Yes: from 30 to 60% by weight;

-

Mg: from 1 to 30% by weight;

-

AC: from 0.1 to 4% by weight;

-

To the: from 0.1 to 3% by weight;

-

Rare earth: from 0 to 3% in weight; Y

-

Faith: from 30 to 60% by weight;

Even more preferably, the FeSiMg alloy, It comprises the following composition:

-

Yes: from 40 to 48% by weight;

-

Mg: from 4 to 10% by weight;

-

AC: from 0.5 to 1.5% by weight;

-

To the: from 0.3 to 1.2% by weight;

-

Rare earth: from 0 to 1.3% in weight; Y

-

Faith: from 35 to 50% by weight;

According to another preferred embodiment, the inoculant It comprises the following composition:

-

Yes: from 50 to 90% by weight;

-

AC: from 0.1 to 5.5% by weight;

-

To the: from 0.1 to 5% by weight;

-

Ba: from 0 to 15% by weight;

-

Bi: from 0 to 5% by weight;

-

Rare earth: from 0 to 4.5% in weight;

-

Faith: from 15 to 35% by weight;

Even more preferably, the inoculant It comprises the following composition:

-

Yes: from 68 to 78% by weight;

-

AC: from 0.3 to 1.9% by weight;

-

To the: from 0.3 to 1.5% by weight;

-

Ba: from 0 to 9.5% by weight;

-

Bi: from 0 to 1.2% by weight;

-

Rare earth: from 0 to 1% in weight;

-

Faith: from 20 to 30% by weight;

According to another preferred embodiment, they are added stamping steel cuts until it covers the FeSiMg.

In another preferred embodiment, after the stage of spheroidization, a mold casting stage is carried out metallic or "permanent". This stage includes the following sub-stages:

to.

metal transfer from the spheroidization stage to a pouring spoon equipped with a siphon exit;

b.

derail the treated metal from the previous stage;

C.

filling of metal molds or permanent through the siphon, ensuring that the cup of the laundry remains full throughout the filling process of the molds;

d.

vein addition (entry addition of the mold or shell) of an inoculant to the casting metal, in a weight percentage of 0.15% with respect to the metal treated in the spoon, whose composition is:

-

C: 3.70 to 3.85% by weight;

-

Yes: 2.55 to 2.67% by weight;

-

Mn: 0.6 to 0.7% by weight;

-

P: 0.035 to 0.07% by weight;

-

S: 0.010 to 0.014% by weight;

-

Mg: 0.023 to 0.036% by weight; Y

-

Cu: 0.01 to 0.02% by weight.

and.

unmold the metal parts obtained; Y

F.

shot blast the pieces obtained in the previous stage

In the present invention it is understood by spheroidization to a method to relieve residual efforts in a high carbon steel, consisting of heating for a long time time at the lowest temperature of its transformation, followed by Slow cooling until it reaches room temperature.

Throughout the description and the claims the word "comprises" and its variants not they intend to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be partly detached of the description and in part of the practice of the invention. The following examples and drawings are provided by way of illustration, and are not intended to be limiting of the present invention.

Description of the figures

Figure 1. Figure 1 shows the configuration of the half-molds designed to manufacture jaws intended for railway sector

Figure 2. Heat treatment applied on jaws to remove carbides. The evolution of temperature in One of the pieces during the treatment application.

Examples

In the embodiment example, they are studied comparatively the implications derived from using molds of silica or metallic sand to manufacture castings nodular with high requirements (wind sector). On the other hand, it determine the advantages and disadvantages of using molds permanent in a productive process.

The process of fusion of materials is performed in rotary kilns with capacity for 5500 kg. Charges Metals used were made up of 75% ingot High carbon, 20% steel from the automotive sector and 5% returns. After the fusion of these charges, the metal resulting moves to three induction furnaces (1000 Hz) with capacity for 1800 kg in order to adjust the contents of Carbon and Silicon (chemical composition by weight, graphite:% C ≥ 98; FeSi:% Si = 74.6; % Al = 0.8; % Fe = 24.6) and raise the temperature of the base metal up to 1400-1450 ° C. Table 1 shows the chemical composition intervals used in the base metal preparation.

TABLE 1 Chemical compositions of metal base

one

The spheroidization treatments of the base metal were carried out by transferring 70-75 kg from the electric furnaces to a spoon with a maximum capacity of 90 kg and equipped with an exit siphon for the metal. Before carrying out this operation, 0.8% of the FeSiMg621 alloy (2-10 mm granulometry and chemical composition by weight:% were introduced inside the reaction chamber belonging to this treatment spoon): Si = 44.1;% Mg = 6.8;% Ca = 2.2;% Al = 0.6;% TR = 1.2 and% Fe = 45.1), 0.15% of a commercial inoculant (0.5-3 mm particle size and chemical composition by weight:% Si = 64.3;% Ca = 1.3;% Al = 0.9;% Ba = 9.3 and% Fe = 24.2) and stamping steel cuts as covering material. The pouring of the metal from the electric furnace is carried out so that the metal falls on the side opposite to that occupied by the reaction chamber at the bottom of the treatment spoon. The weight control of transferred metal was carried out with the help of a dynamometer located above the
spoon.

After finishing the treatment reaction with magnesium, the metal was descrambled conveniently and moved quickly to a pouring spoon with a capacity of about 80 kg and endowed with exit siphon. The purpose of this device is avoid the introduction of slags formed inside the molds during laundry. The metal contained in the spoon of Casting was occasionally defoiled for the same purpose. Laundry of the molds was done manually and through the siphon, ensuring that the pouring cup was kept full throughout The mold filling process. A post-inoculation of the casting metal, adding in vein 0.15% of a commercial inoculant (0.2-0.7 mm of particle size and chemical composition by weight:% Si = 73.5; % Ca = 1.7; % Al = 1.0; % Bi = 0.9 and% Fe = 22.9).

TABLE 2 Chemical compositions of metal treated with Mg

2

Silica sand molds were manufactured with support of a high pressure vertical molding line (12 kp / cm2) and mixtures consisting of: 80.8% silica sand reused, 9.3% activated sodium bentonite, 4.5% material carbonaceous, 3.6% water and 1.8% new silica sand. Mixes They were sent to the molding machine with a compactability of 38-41%

Permanent molds were manufactured by machining a cast iron, previously cast in a mold prepared for this effect The material used to prepare this crude is casting with laminar graphite belonging to quality EN-GJL-200.

After machining and subsequent operations adjustment, the molds were coated internally with a layer of refractory paint and mounted on a carousel with capacity for 12 molds, all equipped with a cooling system Internal by water. At each turn of the carousel, a system of burners fed with acetylene was responsible for providing a layer of charcoal on the refractory paint that covers the inner face of metal molds. The addition of this carbonaceous layer can Be regulated in each case. The temperature control of the Molds were made manually.

The parts used to carry out the This study is: a component of the brakes used in wind turbines and a clamping jaw for rail rails. The weight of the brake caliper is 7.2 kg, showing sections between 5 and 43 mm. In the case of the jaw, the weight is 0.35 kg and the sections vary between 5 and 12 mm. In this way, it is possible evaluate the effect of different cooling rates on The same component. Figure 1 shows the configuration of the semi-molds designed to manufacture jaws for the sector railway

The pieces manufactured both in the molds permanent as in those made with sand mixtures of silica correspond to the brake caliper. The gag is only manufactured using metal molds. After manufacturing, the pieces were demoulded and subsequently shot blasting.

The materials of these pieces were subjected to a metallographic study to determine the rate of spheroidization (IE), the density of nodules (N) and the composition of The metal matrix in different sections. The values of these parameters were obtained by analyzing 5 observation fields different in each sample and comparing them with standard patterns [15, 16]. On the other hand, the mechanical properties were determined on mechanized specimens directly on the pieces. The dimensions of these specimens depended on the area of the piece of Where they were obtained.

Results and Discussion

The structural characterizations took carried out in a narrow and a massive section, belonging to three brake calipers made of silica sand molds, three jaws and three brake calipers manufactured using molds Metallic, all of them in raw casting. The results obtained from these studies are included in Table 3.

TABLE 3 Results of the metallographic characterizations (casting blanks) where IE represents the nodularity and N represents the number of nodules per mm2

3

The comparative analysis of the data contained Table 3 clearly shows the strong increase in the number of graphite spheroids when the cooling of the material has place inside the metal molds. This fact may Check when comparing brake calipers manufactured using silica sand molds with those obtained from permanent molds. In the case of the clamping jaw, it is of a smaller piece and with narrower sections. Without However, for a similar cooling section, they are not obtained very important increases in parameter N with respect to the clamps brake. This fact reveals the strong influence of the speed of solidification in the values of parameter N obtained.

Another aspect to consider is the ferrite content observed in each case. The tweezers manufactured in the metal mold are mostly or totally ferritic, however, those that come from the sand molds do not exceed 30-35% of this phase in any of the inspected sections (the manganese content in the casting metal is 0.60-0.70%). This behavior should be assigned mainly to the presence of a greater number of graphite nodules per unit volume in materials cooled in the metal mold. In this way, the distance between spheroids decreases considerably and the effective diffusion of carbon atoms from the austenite during cooling in the solid state is favored, even when it is probably faster than in the parts manufactured inside the molds of sand. It is necessary to take into account that the moment of demolding when permanent molds are used usually occurs 50-60 seconds after the mold is completed. In the case of fabrications made with sand molds, this period of time may exceed 10
min.

When comparing the matrix structures in similar sections of brake calipers and jaws, both made with metal molds, it is observed that the speed of austenite cooling does influence the formation of ferrite during eutectoid transformation. Even with older values of parameter N, the jaws show lower contents of this phase than the tweezers (Table 3). This fact may be related to the size of the pieces and the influence that this parameter has in the material cooling rate when these pieces are demoulded and remain in contact with the air.

Another structural phase detected and which reveals the behavior described above are iron carbides. This type of compound is formed only in the jaws of clamping, that is, in the narrowest sections with kinetics of more critical cooling. It is logical to verify that the largest carbide concentration has been observed in the areas of periphery belonging to the narrowest sections in this piece. The fastest cooling originating in these areas in contact with the metal mold favors the appearance of the phases carburic. In these cases, effective temperature control of the molds and the guarantee of an effective inoculation in the metal of laundry acquires an even greater relevance.

It is about adding nucleating elements of the very active graphite (Ca, Si, Ba, Bi, etc.), which can counteract the effect exerted by the high speed of solidification to form carbides. In the process methodology Two inoculations were used in this work: in FeSiMg treatment and post-inoculation in the pouring vein However, it has not been possible to avoid training of carbides in the most critical sections belonging to the jaws The usefulness of carbides formed in the periphery areas as an effective measure to prevent wear in parts with certain applications. In any case, a proper inoculation of the casting metal also contributes to minimize the formation of contraction defects and increase the number of nodules, especially in the narrowest sections, such and as it has been verified in the present work. Although it has not been detected the presence of contraction defects, in the bibliography works have been published that deal with the appearance of rechupes and / or microrechupes in parts manufactured in molds metallic

In order to eliminate the presence of carbides in the jaws, another three pieces were selected for subject them to a normalized heat treatment. The evolution of the temperature in one of these parts during the application of this Treatment is shown in Figure 2. The treated parts are inspected metallographically to confirm the total decomposition of carbides and the presence of structures fully ferritic matrices in all sections previously analyzed and specified in Table 3.

In relation to the surface finish of the pieces, after demolding and subsequent cooling until reaching the room temperature, those manufactured using the molds permanent ones show a surface covered only by a thin dark layer of iron oxides. This layer can easily be eliminated with a short period of shot blasting. Comparatively speaking, the surface quality of the pieces made with molds Metallic is superior to that obtained with sand molds. By on the other hand, the dimensional accuracy obtained using the molds Metallic is also older and more repetitive.

Superficial defects that may be observed in certain pieces and more frequently they are: slags and wrinkles or folds. In the first case, given the speed with which the solidification period elapses, it is very important to ensure the cleanliness of the casting metal and the effectiveness of the filling systems when avoiding slag entry into the cavities that make up the pieces. With respect to surface wrinkles in castings spheroidal, it has been observed that these are favored when used extended casting times and / or, mainly, temperatures of the metal molds are higher.

All the pieces selected in this study were inspected by x-ray fluoroscopy in order to determine the presence of internal defects caused by the contraction of the metal during the solidification stage. Baking tin Metals prepared to manufacture both the brake caliper and the clamping jaw does not include any type of system feeding (Figure 1).

Therefore, it is necessary to evaluate the presence of rechupes and / or microrechupes in the manufactured parts to obtain information on the behavior of the balance of expansion-contraction of the metal inside The metal molds. In no case detected the presence of contraction defects in the selected and manufactured parts in metal molds The absence of such porosities must be related to the cooling kinetics applied when Use this type of mold. On the contrary, the brake calipers made in sand molds do show micro-size plugs variable mainly in section changes close to more massive sections of the piece.

Table 4 shows the load values maximum breakage (R), elastic limit (LE) and elongation (A) obtained from tensile tests carried out for the purpose to determine the mechanical properties of the selected parts. In the case of clamping jaws, mechanical tests have been made only on the three pieces undergoing treatment thermal fermentation described in Figure 2. In the clamps of brake, all materials were tested in the raw casting state. Tensile specimens are machined from two zones in each piece. In brake calipers, these areas correspond to space intended for the hydraulic system (pot) and the central body (center). In the jaws, the specimens are obtained from the wedge of support and the support area of the piece.

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TABLE 4 Mechanical properties obtained on piece

4

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When comparing the mechanical properties of brake calipers made of metal and sand molds obtain results consistent with the structural characteristics shown in Table 3. An increase in the speed of solidification of the piece inside the metal mold originated a strong increase in parameter N and a significant increase in Ferrite content

These characteristics give rise to materials that comfortably exceed 500 MPa breaking load, with limits surprisingly high elastics (approximately 400 MPa) and elongation that can reach 20%. When moving the piece to molds made of silica sand, materials with higher load, similar elastic limit and elongations clearly less than 12%.

In the case of the clamping jaw, the applied heat treatment transformed the structure by ferritizing it completely. Consequently, breakage loads are obtained which they can exceed 450 MPa, elastic limits around 300 MPa and elongations of up to 20%. In this context, it is necessary keep in mind that these are results obtained directly on pieces with a maximum section of 12 mm. Therefore, it is about results of great interest with a direct application in the stages of design and subsequent manufacture of castings nodular.

Conclusions

The results obtained in this work have shown that the use of metal molds is suitable for the manufacture of spheroidal castings with important functional requirements The main implications structural derived from the use of this type of molds are the significant increase in the number of graphite nodules per unit of volume of material and a no less considerable increase in ferrite contents in the metal matrix obtained at temperature ambient.

Both structural features allow manufacture parts with interesting mechanical properties, highlighting the high elongations obtained in alloys with loads of breakage greater than 510 MPa.

For all this, the characteristics of the process of production using metal molds and the results presented in this work should be taken into account when define which is the most appropriate and profitable methodology for the production of spheroidal iron castings. TO The main advantages and disadvantages are summarized below found in this type of process with respect to manufacturing They use sand molds.

Claims (27)

1. Procedure for manufacturing parts of spheroidal cast iron comprising the following stages:

to)

fusion of metal charges to a temperature range between 1400 and 1600 ° C;

b)

carbon content adjustment and silicon of the metal charges fused in step (a);

C)

spheroidization treatment of metal loads obtained in step (b) with temperatures below 1148 ° C; Y

d)

load casting process Metals obtained in step (c) in metal molds.

2. The method according to claim 1, where metal charges are selected from the group consisting of high carbon ingots, casting chip briquettes, cast iron, scrap, steel from the automotive sector, returns or any combination thereof. 3. The method according to claim 2, where metal charges are selected from the group consisting of high carbon ingots, returns, chip briquettes cast iron, steel or any combination thereof. 4. The procedure according to any of the claims 1 to 3, wherein the metal charge has the following composition up to 100%:

-

between 25 and 90% high carbon ingot; Y

-

between 1 and 50% returns.

5. The method according to claim 4, where the metal load additionally comprises:

-

a percentage equal to or less than 30% of steel from the sector of automotive;

-

a percentage equal to or less than 50% of chip briquettes foundry.

6. The method according to claim 4, where the metallic load has the following composition until arriving to 100%:

-

between 30 and 80% high carbon ingot; Y

-

between 1 and 35% returns.

7. The method according to claim 6, where the metal load additionally comprises:

-

a percentage equal to or less than 25% of steel from the sector of automotive; Y

-

a percentage equal to or less than 35% of chip briquettes foundry.

8. The method according to claim 1, where the metallic load has the following composition:

-

75% of high carbon ingot;

-

20 of steel from the automotive sector; Y

-

5 of returns.

9. The method according to claim 1, where the metallic load has the following composition:

-

33.33% high carbon ingot;

-

33.33% of casting chip briquettes; Y

-

33.33% of returns.

10. The procedure according to any of the claims 1 to 9, wherein the process of fusion of the charges Metallic is done in rotary kilns. 11. The procedure according to any of the claims 1 to 10, wherein the melting time and stay of said metal charge is 60 to 80 minutes. 12. The method according to claim 11, where the time of fusion and stay of said metallic load is of 70 minutes 13. The procedure according to any of the claims 1 to 12, wherein the melting temperature of the Metal charges are between 1430 and 1450 ° C. 14. The procedure according to any of the claims 1 to 13, wherein in the step of adjusting the Carbon and silicon contents, molten metal charges from stage a) they are transferred to at least 1 furnace induction. 15. The method according to claim 10, where metal charges are transferred to 3 induction furnaces consecutive. 16. The procedure according to any of the claims 14 or 15, wherein the temperature of the charges metallic is maintained in a temperature range between 1400 and 1500 ° C. 17. The method according to claim 16, where the temperature of the metal charges stays in a range of temperatures between 1400 and 1450 ° C. 18. The procedure according to any of the claims 1 to 17, wherein step c) of treating spheroidization comprises the following sub-stages:

to.

addition to a treatment spoon, FeSiMg in a proportion of 0.7 to 1.0% by weight with respect to weight total metal charges;

b.

adding an inoculant on the FeSiMg in a proportion of 0.15 to 0.20% of the total weight of the metal charges;

C.

addition of steel clippings on the mixture obtained in sub-stage b);

d.

filling up to 20 to 30% by volume of the spoon of the metallic loads obtained in the stage b);

and.

addition of metal charges melts from stage b) until the spoon is filled; Y

F.

de-slag the treated metal obtained in sub-stage e).

19. The method according to claim 18, where the FeSiMg alloy comprises the following composition until The 100%:

-

Yes: from 30 to 60% by weight;

-

Mg: from 1 to 30% by weight;

-

AC: from 0.1 to 4% by weight;

-

To the: from 0.1 to 3% by weight; Y

-

Faith: from 30 to 60% by weight.

20. The method according to claim 19, where additionally the FeSiMg alloy comprises a percentage equal to or less than 3% by weight of rare earths. 21. The method according to claim 19, where the FeSiMg alloy comprises the following composition until The 100%:

-

Yes: from 40 to 48% by weight;

-

Mg: from 4 to 10% by weight;

-

AC: from 0.5 to 1.5% by weight;

-

To the: from 0.3 to 1.2% by weight; Y

-

Faith: from 35 to 50% by weight.

22. The method according to claim 21, where the FeSiMg alloy additionally comprises in a percentage equal to or less than 1.3% by weight of rare earths. 23. The procedure according to any of the claims 18 to 22, wherein the inoculant comprises the following composition up to 100%:

-

Yes: from 50 to 90% by weight;

-

AC: from 0.1 to 5.5% by weight;

-

To the: from 0.1 to 5% by weight; Y

-

Faith: from 15 to 35% by weight.

24. The method according to claim 23, where additionally the inoculant comprises an equal percentage or less than 15% by weight of Ba, a percentage equal to or less than 5% in Bi weight and a percentage equal to or less than 4.5% by weight of land rare 25. The method according to claim 18, where the inoculant comprises the following composition until the 100%:

-

Yes: from 68 to 78% by weight;

-

AC: from 0.3 to 1.9% by weight;

-

To the: from 0.3 to 1.5% by weight; Y

-

Faith: from 20 to 30% by weight.

26. The method according to claim 25, where additionally the inoculant comprises an equal percentage or less than 9.5% by weight of Ba, a percentage equal to or less than 1.2% by weight of Bi and a percentage equal to or less than 1% by weight of rare earths 27. The procedure according to any of the claims 1 to 26, wherein step d) of mold casting Metallic comprises the following sub-stages:

to.

metal transfer from the spheroidization stage to a pouring spoon equipped with a siphon exit;

b.

derail the treated metal from the previous stage;

C.

filling of metal molds or permanent through a siphon;

d.

vein addition of an inoculant to casting metal, in a weight percentage of 0.15% with respect to treated metal in the spoon, whose composition is:

-

C: 3.70 to 3.85% by weight;

-

Yes: 2.55 to 2.67% by weight;

-

Mn: 0.6 to 0.7% by weight;

-

P: 0.035 to 0.07% by weight;

-

S: 0.010 to 0.014% by weight;

-

Mg: 0.023 to 0.036% by weight; Y

-

Cu: 0.01 to 0.02% by weight.

and.

unmold the metal parts obtained; Y

F.

shot blast the pieces obtained in the previous stage