EP2083428A1 - Fe-Co alloy for highly dynamic electromagnetic actuator - Google Patents

Abstract

Iron-cobalt alloy comprises (e.g.): cobalt (>= 6 wt.%) and nickel (= 30 wt.%); silicon (>= 0.2); chromium (0.5-8 wt.%); nickel (= 4 wt.%); manganese (= 4 wt.%); aluminum (= 4 w.%); titanium (= 1 wt.%); carbon (= 1 wt.%); molybdenum (= 3 wt.%); vanadium and tungsten (= 3 wt.%); niobium and tantalum (= 1 wt.%); silicon and aluminum (= 6 wt.%); cobalt and silicon to chromium (less than 27 wt.%); aluminum and molybdenum, and silicon, chromium and vanadium (>= 1.3 wt.%); aluminum and chromium, vanadium and molybdenum, and silicon (>= 50 wt.%); and iron and inevitable impurities (balance). Iron-cobalt alloy comprises: cobalt (>= 6 wt.%) and nickel (= 30 wt.%); silicon (>= 0.2); chromium (0.5-8 wt.%); nickel (= 4 wt.%); manganese (= 4 wt.%); aluminum (= 4 w.%); titanium (= 1 wt.%); carbon (= 1 wt.%); molybdenum (= 3 wt.%); vanadium and tungsten (= 3 wt.%); niobium and tantalum (= 1 wt.%); silicon and aluminum (= 6 wt.%); oxygen, nitrogen, sulfur, phosphorus and boron (= 0.1); cobalt and silicon to chromium (less than 27 wt.%); silicon, aluminum chromium, vanadium, molybdenum and titanium (>= 3.5 wt.%); 1.23 wt.% of aluminum and molybdenum, and 0.84 wt.% of silicon, chromium and vanadium (>= 1.3 wt.%); 14.5 wt.% of aluminum and chromium, 21 wt.% of vanadium and molybdenum, and 25 wt.% of silicon (>= 50 wt.%); and iron and inevitable impurities (balance).

Description

The present invention relates to a Fe-Co alloy more particularly intended for the manufacture of electromagnetic actuator with high dynamics, without being limited thereto.

An electromagnetic actuator is an electromagnetic device that converts electrical energy into mechanical energy with an electromagnetic conversion mode. Some of these actuators are called linear because they convert the received electrical energy into a rectilinear movement of a moving part. Such actuators are found in solenoid valves and electro-injectors.

A preferred application of such electro-injectors is the direct injection of fuel into combustion engines, especially diesel engines. Another preferred application relates to a particular type of solenoid valve used for the electromagnetic control of valves of internal combustion engines (gasoline or diesel).

In these actuators, the electrical energy is supplied in a winding by a series of current pulses, creating a magnetic field that magnetizes a non-closed magnetic yoke, thus having a gap. The geometric characteristics of the cylinder head make it possible to direct most of the magnetic field lines axially vis-à-vis the gap zone. Under the effect of the electric pulse, the air gap is subjected to a magnetic potential difference. The actuator also comprises a core made mobile by the action of the electric current in the coil. Indeed, the magnetic potential difference introduced into the coil between the movable core resting on one of the poles of the cylinder head and the opposite pole of the cylinder head creates an electromagnetic force on the magnetized core, via a magnetic field gradient. The magnetized core is thus set in motion. The rest position can also be located in the middle of the air gap, thanks to two symmetrical springs, promoting by their stiffness the dynamics of the moving part, in particular for electromagnetically controlled valves.

The setting in motion of the mobile core occurs with a phase shift with respect to the moment of generation of the electrical pulses. For an optimal operation of the actuator, it is shown that it is necessary for the metal to have an electrical resistivity at 20 ° C ρ _el high, and in particular greater than 50 μΩ.cm and a coercive field Hc low, it is to say less than 32 Oe and preferably less than 8 Oe. These conditions make it possible to obtain an excellent magnetization dynamic by the generation of weak currents induced in the yoke and the magnetic core, making it possible to quickly reach the minimum magnetization of the core generating its movement. This excellent dynamics thus makes it possible to reduce the actuation times and the electrical consumption of the actuator.

It is also necessary that the core has a saturation magnetization Js high, ie greater than 1.75 T and preferably greater than 1.9 T, so as to allow a maximum force at the end of this high pulse as possible. It is indeed this force which guarantees the maintenance of the open or closed position of the actuator, which is particularly important when it is necessary to totally interrupt the flow of a fluid at high pressure or to compensate the return force of one or more springs. Such saturation magnetization level thus provides a compact actuator having a high strength and power density.

These magnetic cores have various shapes that can be made from wires, bars, plates or rolled sheets. They must therefore have good heat-formability, and preferably good cold-forming ability when necessary.

Once manufactured and put into service, these cores can be subjected to a slightly oxidizing working environment and must therefore have a good resistance to corrosion to resist this type of premature wear.

They are also subjected to multiple shocks when they terminate abruptly in their abutment races and must therefore have good mechanical characteristics, that is to say, in practice, a tensile strength Rm greater than 500 MPa and preferably, an elastic limit R _{0,2 of} greater than 250 MPa in the hot-rolled state at a thickness of at least 2 mm.

Ferrocell (Fe-Co) alloys such as those described in US Pat. EP 715,320 . The materials described have 6 to 30% cobalt, 3 to 8% of one or more elements selected from chromium, molybdenum, vanadium and / or tungsten, the balance being iron. These alloys, however, have insufficient dynamics.

The present invention aims to provide a material suitable for the manufacture, economically, of cores for compact electromagnetic actuators with high dynamics and high saturation. This material must also allow implementation hot, and preferably, cold, improved.

• 6 ≤ Co + Ni ≤ 30
• Si ≥ 0,2
• 0,5 ≤ Cr ≤ 8
• Ni ≤ 4
• Mn ≤ 4
• Al ≤ 4
• Ti ≤ 1
• C ≤ 1
• Mo ≤ 3
• V + W ≤ 3
• Nb + Ta ≤ 1
• Si + Al ≤ 6
• O + N + S + P + B ≤ 0.1

le reste de la composition étant constitué de fer et d'impuretés inévitables dues à l'élaboration,
étant entendu en outre que les teneurs en respectent les relations suivantes :

• Co + Si -Cr ≤ 27
• Si + Al + Cr + V +Mo + Ti ≥ 3,5
• 1,23(Al + Mo) + 0,84(Si + Cr + V) ≥ 1,3
• 14,5(Al + Cr) +12(V+Mo) + 25Si ≥ 50

A first object of the invention thus consists of a Fe-Co alloy whose composition comprises in% by weight:

• 6 ≤ Co + Ni ≤ 30
• If ≥ 0.2
• 0.5 ≤ Cr ≤ 8
• Ni ≤ 4
• Mn ≤ 4
• Al ≤ 4
• Ti ≤ 1
• C ≤ 1
• Mo ≤ 3
• V + W ≤ 3
• Nb + Ta ≤ 1
• If + Al ≤ 6
• O + N + S + P + B ≤ 0.1

the remainder of the composition consisting of iron and unavoidable impurities due to the preparation,
it being further understood that the contents respect the following relations:

• Co + Si -Cr ≤ 27
• Si + Al + Cr + V + Mo + Ti ≥ 3.5
• 1.23 (Al + Mo) + 0.84 (Si + Cr + V) ≥ 1.3
• 14.5 (Al + Cr) +12 (V + Mo) + 25Si ≥ 50

• l'alliage Fe-Co est tel que : 10 ≤ %Co + %Ni ≤ 22
• l'alliage Fe-Co est tel que : 1 ≤ Cr ≤ 5,5
• l'alliage Fe-Co est tel que : Ni ≤ 1
• l'alliage Fe-Co est tel que : 0,1 ≤ Mn ≤ 1
• l'alliage Fe-Co est tel que : Al ≤ 2

In particular embodiments, considered alone or in combination, the alloy may further comprise the following additional features:

• the Fe-Co alloy is such that: 10 ≤% Co +% Ni ≤ 22
• the Fe-Co alloy is such that: 1 ≤ Cr ≤ 5.5
• the Fe-Co alloy is such that: Ni ≤ 1
• the Fe-Co alloy is such that: 0.1 ≤ Mn ≤ 1
• the Fe-Co alloy is such that: Al ≤ 2

• 6 ≤ Co + Ni ≤ 22
• Si ≥ 0,2
• 0,5 ≤ Cr ≤ 6
• Ni ≤ 1
• Mn ≤ 4
• Al ≤ 4
• Ti ≤ 0,1
• C ≤ 0,1
• Mo ≤ 3
• V + W ≤ 3
• Nb + Ta ≤ 1
• Si + Al ≤ 6
• O + N + S + P + B ≤ 0.1

le reste de la composition étant constitué de fer et d'impuretés dues à l'élaboration,
étant entendu en outre que les teneurs en silicium, aluminium, cobalt, chrome, vanadium, molybdène, titane et nickel respectent les relations suivantes :

• Co + Si -Cr ≤ 27
• Si + Al + Cr + V + Mo + Ti > 3,5
• 1,23(Al + Mo) + 0,84(Si + Cr + V) ≥ 1,3
• 14,5(Al + Cr) +12(V+Mo) + 25Si ≥ 50

In a more particularly preferred embodiment, the alloy according to the invention has a composition in% by weight which comprises:

• 6 ≤ Co + Ni ≤ 22
• If ≥ 0.2
• 0.5 ≤ Cr ≤ 6
• Ni ≤ 1
• Mn ≤ 4
• Al ≤ 4
• Ti ≤ 0.1
• C ≤ 0.1
• Mo ≤ 3
• V + W ≤ 3
• Nb + Ta ≤ 1
• If + Al ≤ 6
• O + N + S + P + B ≤ 0.1

the rest of the composition consisting of iron and impurities due to the preparation,
it being further understood that the contents of silicon, aluminum, cobalt, chromium, vanadium, molybdenum, titanium and nickel respect the following relations:

• Co + Si -Cr ≤ 27
• Si + Al + Cr + V + Mo + Ti> 3.5
• 1.23 (Al + Mo) + 0.84 (Si + Cr + V) ≥ 1.3
• 14.5 (Al + Cr) +12 (V + Mo) + 25Si ≥ 50

The alloy according to the invention can be formed into a bar, wire, plate or rolled sheet.

It can in particular be used for manufacturing electromagnetic actuator movable core manufactured from a bar or a wire or a plate or a rolled sheet.

Such an electromagnetic actuator comprising a movable core of Fe-Co alloy according to the invention can in particular be used in an injector for an electronically controlled combustion engine or even as an internal combustion engine valve actuator. electronic control.

As has been seen previously, the alloy according to the invention is an iron-cobalt alloy with a low cobalt content having moderate levels of addition elements.

The cobalt content, optionally partially substituted with nickel, is between 6 and 30% by weight in order to obtain a good saturation magnetization while maintaining a high resistivity. It is preferably less than 22% by weight to reduce the amount of expensive additive elements while maintaining good saturation.

The nickel content, which may partially substitute cobalt, is, however, maintained at less than 4% because its presence considerably increases the coercive field of the alloy.

The silicon content of the alloy according to the invention is greater than or equal to 0.2% by weight. Such a minimum content makes it possible to obtain a good mechanical resistance Rm. Moreover, this element makes it possible to very effectively increase the coercive field of the alloy by lowering it significantly. However, the joint addition of aluminum and 6% silicon is limited to preserve the alloy good heat-transformability. It is furthermore preferred to limit this cumulative content to less than 4% by weight in order to keep the alloy good cold processability.

The aluminum content of the alloy according to the invention is less than or equal to 4% by weight. This element has a role similar to that of silicon by favoring the obtaining of a weak coercive field. We limit its addition to 4% because otherwise Js would become too weak. However, it does not improve the mechanical properties of the alloy.

The chromium content of the alloy according to the invention is between 0.5 and 8% by weight. This essential element of the alloy makes it possible to extend the silicon addition range with respect to hot and cold transformation, while maintaining the good resistivity and saturation properties. However, it is limited because it increases the coercive force of the alloy.

The manganese content of the alloy according to the invention is less than or equal to 4% by weight and preferably less than or equal to 1% by weight. This element may be added at least 0.1% by weight to improve the heat-transformability of the alloy. Its content is limited because it is a gamma element and the onset of the phase strongly degrades the magnetic performances.

The titanium content of the alloy according to the invention is less than or equal to 1% by weight and preferably less than 0.1%, because this element easily forms nitrides, either during production or during annealing. under air or under ammonia, nitrides which strongly degrade the magnetic properties and are therefore harmful.

The molybdenum content of the alloy according to the invention is less than or equal to 3% by weight. This element can be added to improve the electrical resistivity of the alloy, in complement or partial substitution of chromium.

The carbon content of the alloy according to the invention is less than or equal to 1% by weight, and preferably less than or equal to 0.1% by weight. The presence of carbon deteriorates the magnetic properties of the alloy and so the content is reduced to avoid such degradation.

The cumulative vanadium and tungsten content of the alloy according to the invention is less than or equal to 3% by weight. These elements can be added to improve the electrical resistivity of the alloy, in complement or partial substitution of chromium.

The cumulative content of niobium and tantalum of the alloy according to the invention is less than or equal to 1% by weight. These elements can be added to improve the ductility of the alloy and thus limit its fragility.

Finally, the cumulative content of oxygen, nitrogen, sulfur, phosphorus and boron is limited to 0.1% by weight, since these elements are oxidants and tend to form precipitates which are very unfavorable to the magnetic properties and to the mechanical ductility of the material. Such a limitation supposes, in particular, that the alloy according to the invention is manufactured from raw materials of good purity.

$$\mathrm{Si}\mathrm{+}\mathrm{Al}\mathrm{+}\mathrm{Cr}\mathrm{+}\mathrm{V}\mathrm{+}\mathrm{Mo}\mathrm{+}\mathrm{Ti}\mathrm{>}\mathrm{3}\mathrm{,}\mathrm{5}$$

$$\mathrm{1}\mathrm{,}\mathrm{23}\left(\mathrm{Al}\mathrm{+}\mathrm{Mo}\right)\mathrm{+}\mathrm{0}\mathrm{,}\mathrm{84}\left(\mathrm{Si}\mathrm{+}\mathrm{Cr}\mathrm{+}\mathrm{V}\right)\mathrm{\ge }\mathrm{1}\mathrm{,}\mathrm{3}$$

$$14,5\left(\mathrm{Al}\mathrm{+}\mathrm{Cr}\right)\mathrm{+}12\left(\mathrm{V}+\mathrm{Mo}\right)+25\mathrm{Si}\mathrm{\ge }\mathrm{50}$$

Moreover, the alloy according to the invention must also respect a number of relationships between some of these elements. Thus the following four equations must be respected: $$\mathrm{Co}+\mathrm{Yes}-\mathrm{Cr}\le 27$$

$$\mathrm{Yes}\mathrm{+}\mathrm{al}\mathrm{+}\mathrm{Cr}\mathrm{+}\mathrm{V}\mathrm{+}\mathrm{MB}\mathrm{+}\mathrm{Ti}\mathrm{>}\mathrm{3}\mathrm{,}\mathrm{5}$$

$$\mathrm{1}\mathrm{,}\mathrm{23}\left(\mathrm{al}\mathrm{+}\mathrm{MB}\right)\mathrm{+}\mathrm{0}\mathrm{,}\mathrm{84}\left(\mathrm{Yes}\mathrm{+}\mathrm{Cr}\mathrm{+}\mathrm{V}\right)\mathrm{\ge }\mathrm{1}\mathrm{,}\mathrm{3}$$

$$14,5\left(\mathrm{al}\mathrm{+}\mathrm{Cr}\right)\mathrm{+}12\left(\mathrm{V}+\mathrm{MB}\right)+25\mathrm{Yes}\mathrm{\ge }\mathrm{50}$$

The equation (1) makes it possible, by equilibrating the silicon and the chromium, to guarantee a good aptitude for hot transformation and thus the absence of cracks or cracks during forging and rolling.

The relation (2), in combination with the relation (4), makes it possible to guarantee an electrical resistivity ρ _el high, and in particular greater than 50 μΩ.cm.

Relation (3) represents a saturation criterion which makes it possible to ensure that the alloy according to the invention will have saturation magnetization Js of less than 2.2T in a manner consistent with the additions of non-magnetic elements necessary for the need of high dynamics. magnetization.

The relationship (4), in combination with the relation (2), makes it possible to guarantee an electrical resistivity ρ _el high, and in particular greater than 50 μΩ.cm.

The manufacture of the alloy according to the invention can be done conventionally for this type of alloy. Thus, the various elements constituting the alloy can be melted by induction under vacuum, then cast into ingots, billets or slabs. These are then hot forged at temperatures ranging from 1000 to 1200 ° C, and then hot-rolled after reheating to a temperature greater than or equal to 1150 ° C, the end-of-rolling temperature being between 800 and 1050 ° C. .

The plates, bars or hot-rolled strips thus produced can be used as is or cold-rolled after pickling by dipping in one or more acid trays and annealing.

It is also possible, in order to further improve the magnetization dynamics of the alloy according to the invention, to diffuse under the surface of the deposited elements by any method adapted to the surface of the manufactured part. Such elements may for example be aluminum, silicon or chromium.

testing

The raw materials necessary for producing the alloy were melted by vacuum induction and vacuum cast in a 50 kg ingot. The ingots are then hot forged at 1000 to 1200 ° C and hot rolled from heating at 1150 ° C to a thickness of 4 to 5 mm for a hot rolling end temperature of at least 800 ° C. After acidic etching, the strips are either characterized in the hot-rolled state by machining tensile test specimens, washers for magnetic characterization, elongated samples for electrical resistivity measurement, or characterized after cold rolling to completion. at the thickness of 0.6mm for the same type of sampling and characterization.

Depending on the case, these two types of metallurgical state (hot rolled state: LAC and cold rolled: LAF) can be characterized in the state or after annealing at 900 ° C for 4 hours under H2 and rapid cooling. Unless otherwise indicated all the following data were obtained after cold rolling and annealing.

The breaking strength Rm is measured on the tensile test piece after annealing the hot rolled at 900 ° C for 4 hours under H2.

The corrosion resistance Tcor is evaluated on a hot rolled rough surface, ground to have a clean surface with a very low roughness and then left at 20 ° C in a salt spray atmosphere.

The test for suitability for hot or cold processing was carried out by simple observation of non-weakened banks during the rolling operations (hot, cold) of the test ingots.

The compositions of the test castings are shown in Table 1 below, it being understood that the cumulative contents of all the oxygen, nitrogen, sulfur, phosphorus and boron tests are less than 0.1% by weight and that the rest compositions consists of iron. <b><u> Table 1 </ u></b> Trial %Co %Or %Yes % Cr % Mn Al% % Ti % Mo V% % W % Nb %Your 1 18 - - 5 0.2 1 - - - - - - 2 * 18 - 0.5 5 0.2 0.5 0.02 - - - - - 3 * 18 1 0.3 4.7 0.2 - - 0.1 - - - - 4 * 18 2 0.3 4.7 0.2 - - - 0.15 - - - 5 * 18 3 0.3 4.7 0.2 - - - - 0.2 - - 6 18 - 0.5 2.7 0.2 - - - - - - - 7 * 18 - 1 3 0.2 - - - - - 0.03 - 8 * 18 - 2 3 0.2 - - - - - - - 9 * 18 - 3 3 0.2 - - - - - - - * 10 18 - 1 7 0.2 - - - - - - - * 11 18 - 2 7 0.2 - - - - - - - * 12 18 - 3 7 0.2 - - - - - - - * 13 18 - 4 7 0.2 - - - - - - - 14 18 - 3.46 - 0.2 - - - - - - - 15 18 - 3.5 0.2 0.2 - - - - - - - 16 18 - 0.55 2.87 0.2 - - - - - - - 17 18 - 1.04 2.11 0.2 - - - - - - - * 18 18 - 0.99 4.98 0.2 - - - - - - - * 19 18 - 2.05 5.18 0.2 - - - - - - - * 20 18 - 2.99 4.97 0.2 - - - - - - - * 21 18 - 3.96 4.9 0.2 - - - - - - - * 22 18 - 1 4 0.2 - - - 1 - - - * 23 18 - 3 4 0.2 - - - 1 - - - 24 * 18 - 5 4 0.2 - - - 1 - - - 25 18 - 7 4 0.2 - - - 1 - - - 26 * 18 - 4 5 0.2 - - - - - - 0.2 27 27 - - 3 0.2 - - - - - - - * 28 27 - 1 3 0.2 - - - - - - - * 29 27 - 2 3 0.2 - - - - - - - 30 27 - 4 3 0.2 - - - - - - - 31 27 - - 5 0.2 - - - - - - - * 32 27 - 1 5 0.2 - - - - - - - 33 * 27 - 2 5 0.2 - - - - - - - 34 * 27 - 4 5 0.2 - - - - - - - *: tests according to the invention

The results of the tests are shown in Table 2 below: <b><u> Table 2 </ u></b> Trial js
(T) ρel
(μΩ.cm) hc
(Oe) Apt
to the lake Apt
at LAF R _m
(MPa) Tcor 1 2.06 63.5 3.79 Yes Yes 480 ++ 2 * 2.07 65 3.6 Yes Yes 522 ++ 3 * 2.11 56.4 16.6 Yes Yes 505 ++ 4 * 2.09 61.1 17.3 Yes Yes 505 ++ 5 * 2.07 61.7 22.2 Yes Yes 506 ++ 6 2.17 46.8 0.91 Yes Yes 520 ++ 7 * 2.13 53.7 1.22 Yes Yes 564 ++ 8 * 2.08 63.4 0.8 Yes Yes 648 ++ 9 * 2.01 68.9 0.6 Yes No 732 ++ * 10 2 71 18.7 Yes Yes 563 ++ * 11 1.94 80.5 20.5 Yes Yes 642 ++ * 12 1.88 90.4 15.7 Yes No 730 ++ * 13 1.82 96.6 12.3 Yes No 798 ++ 14 2.04 48.4 0.5 Yes No 760 0 15 2.02 51 0.4 Yes No 752 0 16 2.14 48 2.6 Yes Yes 522 ++ 17 2.13 47 2.2 Yes Yes 565 + * 18 2.01 68 5.15 Yes Yes 567 ++ * 19 1.92 80.5 4.95 Yes Yes 644 ++ * 20 1.88 86 3.15 Yes Yes 730 ++ * 21 1.80 96.5 2.13 Yes Yes 792 ++ * 22 2.11 52 3.51 Yes Yes 566 ++ * 23 2.06 63.5 3.58 Yes Yes 733 ++ 24 * 2 75.7 2.59 Yes Yes 850 ++ 25 1.85 98 1.7 No BORN BORN BORN 26 * 1.81 88.7 3 Yes No 797 ++ 27 2.21 47.2 6.86 Yes Yes 482 ++ * 28 2.15 56.5 10.2 Yes Yes 563 ++ * 29 2.08 64.4 15 Yes No 642 ++ 30 1.93 82 17.5 NO NO 798 ++ 31 2.14 53.7 21.3 YES YES 480 ++ * 32 2.07 66.5 28.4 YES YES 560 ++ 33 * 2.00 77.4 30.5 YES NO 640 ++ 34 * 1.83 92.1 31.8 YES NO 795 ++ *: tests according to the invention, NE: not evaluated

• un champ coercitif Hc à 20°C modéré à faible sur des états métallurgiques aussi bien massifs (plaque LAC de quelques mm d'épaisseur) que mince (laminé à froid de 0,1 à 2mm d'épaisseur),
• une excellente ductilité en transformation à chaud ou à froid du matériau,
• une résistivité électrique à 20°C élevée, typiquement > 50µΩ.cm, tout en conservant une aimantation à saturation à 20°C élevée à très élevée, typiquement >1,75T et de préférence >1,9T, et ne pouvant excéder 2,2T du fait des additions nécessaires à la grande dynamique d'aimantation de l'alliage.
• une résistance à la traction d'au moins 500MPa dans l'état laminé à chaud à une épaisseur d'au moins 2mm,
• une tenue à la corrosion satisfaisante,
• un coût du matériau limité.

As can be seen from these tests, the alloy according to the invention makes it possible to combine a set of properties that were not accessible to the prior art:

• a coercive field Hc at 20 ° C moderate to low on metallurgical states both massive (LAC plate a few mm thick) and thin (cold rolled from 0.1 to 2mm thick),
• excellent ductility in hot or cold transformation of the material,
• an electrical resistivity at 20 ° C high, typically> 50μΩ.cm, while maintaining saturation magnetization at 20 ° C high to very high, typically> 1.75T and preferably> 1.9T, and not exceeding 2, 2T because of the additions necessary for the great dynamics of magnetization of the alloy.
• a tensile strength of at least 500 MPa in the hot-rolled state to a thickness of at least 2 mm,
• a satisfactory resistance to corrosion,
• a limited material cost.

As has been seen above, a preferred application of the alloys according to the invention is the manufacture of cores for electromagnetic actuators, whether linear or rotary. Such compact, dynamic and robust actuators can advantageously be used in injectors of direct injection combustion engines, in particular for diesel engines, and in moving parts of actuators controlling the movement of the valves of internal combustion engines.

Claims (12)

Fe-Co alloy whose composition comprises in% by weight: 6 ≤ Co + Ni ≤ 30 If ≥ 0.2 0.5 ≤ Cr ≤ 8 Ni ≤ 4 Mn ≤ 4 Al ≤ 4 Ti ≤ 1 C ≤ 1 Mo ≤ 3 V + W ≤ 3 Nb + Ta ≤ 1 If + Al ≤ 6 O + N + S + P + B ≤ 0.1 the remainder of the composition consisting of iron and unavoidable impurities due to the preparation,
it being further understood that the contents respect the following relations: Co + Si -Cr ≤ 27 Si + Al + Cr + V + Mo + Ti ≥ 3.5 1.23 (Al + Mo) + 0.84 (Si + Cr + V) ≥ 1.3 14.5 (Al + Cr) +12 (V + Mo) + 25Si ≥ 50 Fe-Co alloy according to claim 1, wherein: $$10\le \%\mathrm{Co}+\%\mathrm{Or}\le 22$$

Fe-Co alloy according to either of Claims 1 or 2, in which: $$1\le \mathrm{Cr}\le 5,5$$

Fe-Co alloy according to any one of claims 1 to 3, wherein: $$\mathrm{Or}\le 1$$

Fe-Co alloy according to any one of claims 1 to 4, wherein: $$0,1\le \mathrm{mn}\le 1$$

Fe-Co alloy according to any one of claims 1 to 5, wherein: $$\mathrm{al}\le 2$$

An alloy according to claim 1, whose composition in% by weight comprises: 6 ≤ Co + Ni ≤ 22 If ≥ 0.2 0.5 ≤ Cr ≤ 6 Ni ≤ 1 Mn ≤ 4 Al ≤ 4 Ti ≤ 0.1 C ≤ 0.1 Mo ≤ 3 V + W ≤ 3 Nb + Ta ≤ 1 If + Al ≤ 6 O + N + S + P + B ≤ 0.1 the rest of the composition consisting of iron and impurities due to the preparation,
it being further understood that the contents of silicon, aluminum, cobalt, chromium, vanadium, molybdenum, titanium and nickel respect the following relations: Co + Si -Cr ≤ 27 Si + Al + Cr + V + Mo + Ti> 3.5 1.23 (Al + Mo) + 0.84 (Si + Cr + V) ≥ 1.3 14.5 (Al + Cr) +12 (V + Mo) + 25Si ≥ 50 A bar, wire, plate or rolled sheet of Fe-Co alloy according to any one of claims 1 to 7. An electromagnetic actuator movable core made from a bar or wire or plate or rolled sheet according to claim 8. An electromagnetic actuator having a mobile Fe-Co alloy core according to claim 9. An electronically controlled combustion engine injector comprising an electromagnetic actuator according to claim 10. An electronically controlled electromagnetic combustion engine valve actuator of the type according to claim 10.