ES2634000T3 - Method of manufacturing magnetic parts of a differential relay comprising a microgranallado surface treatment - Google Patents

Abstract

Method of manufacturing a magnetic part (15.17) of a differential relay (5) of high sensitivity, said manufacturing process being characterized in that it comprises a microgranallado surface treatment step of at least a portion of a surface of said magnetic piece (15.17), said microgranallado surface treatment step comprising a projection of microspheres under pressure on said surface portion.

Description

DESCRIPTION

Method of manufacturing magnetic parts of a differential relay comprising a microgranallado surface treatment.

[0001] The present invention relates to a method of manufacturing a magnetic part of a high sensitivity differential relay.

[0002] It applies in particular to the manufacture of switches or circuit breakers of differential protection.

10

[0003] Such differential switches or circuit breakers are intended to ensure the safety of people by quickly cutting off a main electrical circuit when a defect appears in this circuit. In particular, differential circuit breakers of the so-called "own current" type are constituted by a fault current detector, a high sensitivity differential relay, and a circuit opening mechanism.

15 main electric.

[0004] The differential relay comprises a magnetic circuit that has two magnetic pieces, which are a mobile vane and a fixed armor.

20 [0005] When a defect appears in the main circuit, the fault current detector is suitable for

Send an electrical signal to the differential relay. In response to said electrical signal, the differential relay opens, by pivoting the vane in relation to the armature, which causes the movement of the opening mechanism of the main electrical circuit.

[0006] The magnetic parts of the differential relay of the differential relay consist of an alloy

soft magnetic, characterized by an induction to high saturation, a weak coercive field and a relatively high electrical resistivity. These characteristics ensure a good functioning of the differential relay.

[0007] In order to satisfy the conditions of desirable magnetic characteristics, it is known that

30 manufacture the magnetic parts of the magnetic circuit in magnetic alloy of the iron-nickel type, for example an alloy comprising, by weight, from 46% to 49% nickel, mainly 48%, the rest is iron and impurities resulting from The elaboration. Said alloy has the advantage of having a saturation induction Bs of 1.5 Tesla and an Hc coercive field of 4 A / m.

[0008] EP 0 889 488 A1 describes a magnetic alloy of the iron-nickel type, with a bearing

light parts to normalize the contact surfaces of an armature and a trowel.

[0009] Magnetic parts manufactured in this way are, however, susceptible to being subjected to

humid atmospheric conditions, which implies a risk of corrosion between iron and nickel

40 alloys that form oxides and iron hydroxides that carry either untimely drives of the differential relay, or on the contrary to a sticking of the paddle on the armature.

[0010] In addition, successive contacts between the vane and the armature are likely to lead to local wear and deformation of these parts, which leads to a malfunction of the differential relay.

Four. Five

[0011] Generally, the nickel-based magnetic alloys used have a weak hardness (of the order of 120 HV) and a weak wear resistance. In addition, these nickel alloys are not stainless and their corrosion resistance under the conditions of use of the relay is insufficient.

[0012] Therefore we have proposed to improve the hardness and wear resistance of the surfaces of

contact of the magnetic parts of the relays, making metallic coatings on these surfaces that also increase the corrosion resistance of the contact surfaces. Said metallic coatings are, for example, gold, chromium or diamond carbon deposits.

55 [0013] However, this technique is very expensive.

[0014] On the other hand, it has been proposed to condition differential relays in plastic boxes

waterproof, suitable to protect the magnetic circuit from corrosion. However, this technique does not allow to solve the problems related to the wear of the magnetic circuit.

[0015] An objective of the invention is to remedy these drawbacks and provide a method of manufacturing magnetic parts of a differential relay that has good wear resistance, and is less expensive to implement than the procedures according to the state of the technique.

5

[0016] To this end, the invention has as its object a procedure of the type mentioned above, said manufacturing process comprising a micrograndalized surface treatment step of at least a portion of a surface of said magnetic piece, said step of surface treatment by microgranallado comprising a projection of microspheres under pressure on said surface portion.

10

[0017] According to other aspects of the invention, the manufacturing process comprises one or more of the following characteristics:

- said magnetic piece is an armature or a vane of a magnetic circuit;

15 - said piece is a Fe-Ni alloy comprising, by weight, from 46% to 49% nickel, the rest is iron and impurities resulting from the elaboration;

- said microspheres are glass, ceramic or steel microspheres;

- said microspheres are projected onto said surface portion with a pressure between 1 and 5 bars;

- the manufacturing process further comprises an intermediate polishing stage of said magnetic piece, 20 carried out before the microgranulation surface treatment stage;

- the manufacturing process also comprises a final stage of polishing said magnetic piece, carried out after the microgranulation surface treatment stage.

[0018] The invention also aims at a method of manufacturing a magnetic circuit 25 of a high sensitivity differential relay, said magnetic circuit comprising two magnetic parts that

they form an armor and a trowel, said procedure comprising:

- the manufacture of said magnetic parts, and

- the assembly of said magnetic parts to form said magnetic circuit, in which the manufacture of at least one of said parts is carried out by a method of manufacturing a magnetic part

according to the invention.

[0019] The invention also aims at a magnetic part of a magnetic circuit of a high sensitivity differential relay, characterized in that it is obtained by a method of manufacturing a

35 magnetic piece according to the invention.

[0020] The invention also aims at a magnetic circuit of a high sensitivity differential relay, said magnetic circuit comprising two magnetic pieces that form an armature and a vane, characterized in that at least one of said magnetic pieces is a magnetic piece according to

40 invention

[0021] The invention will be better understood after reading the following description, presented only by way of example and made by referring to the attached figures, among which:

Figure 1 is a schematic view of a circuit breaker that has a high sensitivity differential relay according to the invention,

Figure 1 is a schematic view of a device for performing a method according to an embodiment of the invention,

Figure 3 is an electrical assembly scheme for determining the impedance of magnetic circuits 50 according to the invention.

[0022] A circuit breaker 1 interposed on a main electrical supply circuit of an electrical apparatus 2, for the detection of a leakage current in this main electrical circuit has been illustrated on FIG.

[0023] The circuit breaker 1 comprises a magnetic nozzle 3, a high sensitivity differential relay 5, and a

opening mechanism 7 of the electric circuit.

[0024] Magnetic nozzle 3 is suitable for detecting a current defect in the main circuit.

[0025] The differential relay 5 comprises a magnetic circuit 9, a permanent magnet 11 and a recovery spring 13.

[0026] The magnetic circuit 9 has two magnetic relay pieces, which are a mobile vane 15 and a fixed U-shaped armor 17.

[0027] The armor 17 comprises a base 18, and a first and second branches 19 and 20, the branches 19 and 20 each end with a flat polar surface 19a, 20a.

[0028] The vane 15 is mounted in comparison with polar surfaces 19a, 20a of the armature 17. The

vane 15 comprises a substantially flat polar surface 15a, suitable to be in contact with the polar surfaces 19a, 20a of the armature 17.

[0029] The vane 15 is pivotally mounted around an axis corresponding to an edge 21 of a first

15 branch 19 of the armature 17, between a resting position, shown in Figure 1, in which the polar surface 15a of the vane 15 is in contact against the polar surfaces 19a, 20a of the armature 17, and a pivoted position, in which the vane 15, which pivots around the edge 21, is no longer in contact with the polar surface 20a of the second branch 20.

[0030] The polar surface 15a of the vane 15 and the polar surfaces 19a, 20a of the armor 17 are

contact areas intended to be in contact with each other.

[0031] Paddle 15 and armor are made in a Fe-Ni alloy. The Fe-Ni alloy is for example an alloy comprising, by weight, from 46% to 49% nickel, the rest is iron and impurities resulting from the

25 elaboration. This is, for example, an alloy of the Supra50 ® type.

[0032] Permanent magnet 11 has a parallel bar shape. The permanent magnet 11 is placed between the branches 19 and 20 of the armature 17, one of the poles of the magnet 11 is coupled to the base 18 of the armor 17, and the other pole is placed in comparison with the vane 15.

30

[0033] The permanent magnet 11 is suitable for exerting a magnetic force on the vane 15 to keep it in the rest position.

[0034] On the other hand, the recovery spring 13 is suitable for exerting a force on the vane 5, 35 antagonistic to the force exerted by the permanent magnet 11, to bring it towards the pivoted position.

[0035] A control coil 23 is wound on the second branch 20 of the armature 17. The control coil 23 is supplied with electric current through the intermediate of the magnetic coil 3. The control coil 23 is suitable for generating a flow magnetic opposite to the glare of permanent magnet 11 on branch 20 when the

40 control coil 13 is traveled by an excitation current.

[0036] When a current defect is detected by the nozzle 3, an excitation current is generated in the control coil 23, which generates a magnetic flux in the magnetic circuit 9 opposite to the permanent magnet flux 11 and implies a reduction or cancellation of the maintenance force exerted on the pallet 15.

45 The force exerted by the recovery spring 13 exceeds the maintenance force exerted on the vane 15, which implies a pivoting of the vane 15 towards its pivoted position.

[0037] By way of example, the spring is tared so that a fault current greater than or equal to 30 mA implies a pivot of the vane 15 towards its pivoted position.

fifty

[0038] The displacement of the vane 15 from its resting position to the pivoted position allows the opening mechanism 7 of the main electrical circuit to be operated, and therefore to cut off the electrical supply of the apparatus 2.

[0039] The manufacture of a magnetic circuit 9 comprises the manufacture of two magnetic parts of this circuit, that is to say vane 15 and armature 17, and the assembly of these two parts to form the circuit.

[0040] The manufacture of each of the magnetic pieces comprises the manufacture of a rough piece.

[0041] Each roughing piece is manufactured by trimming in a Fe-Ni alloy band, followed by a phase to give the shape by folding, so that each of the pieces is given the desired geometry, the trimming is followed by a high temperature heat treatment (greater than 1000 ° C) intended to give the band the desired mechanical and magnetic properties, in particular a very weak coercive field, for example lower or

5 equal to 15 A / m.

[0042] Said coercive field makes it possible to obtain a strong sensitivity of the relay, for example an electric drive power of less than 250 pVA and preferably between 50 and 150 pVA.

[0043] In a known manner, the alloy band is obtained from an ingot by hot rolling,

followed by cold rolling.

[0044] Each chipped piece is subjected to a microgranallado surface treatment stage, during which the microspheres project over at least a portion of the surface of each piece

15 rough. For each of the magnetic pieces, the surface portion on which the microspheres are projected comprises at least the contact areas of this piece, that is the zones of this piece intended to be in contact with the other piece.

[0045] According to one embodiment, the microspheres are projected on the sides of the magnetic pieces that comprise the contact zones of these pieces, that is, the zones of these pieces intended to be in

contact with each other.

[0046] The microgrannel treatment has the effect of performing a surface deformation tempering that penetrates some hundred millimeters, mainly 0.03 mm to 0.05 mm, on the surface portion

25 treated, and thus increase the hardness of the piece on this surface portion. As an example, the microgranallado treatment allows to increase the Vickers hardness in the surface of the piece in more than 50 HV, the hardness passes for example from 120 HV to more than 170 HV.

[0047] A depth of at least a few hundred millimeters, mainly at least 30 0.03 mm, is sufficient to preserve the possibility of performing, after the microgrannel treatment, a

Laminate operation with a slight elimination of material, while at the same time an increased hardness of at least 170 HV is preserved on the surface of the piece. On the other hand, a depth of at most a few hundred millimeters, mainly at most 0.05 mm, ensures the conservation of the magnetic properties of the piece.

35

[0048] At the end of the microgrannel treatment, each of the pieces is subjected to a finishing treatment intended to give the piece the appearance, roughness and flatness sought by the application.

[0049] In particular, obtaining a roughness Ra at least equal to 0.03 pm and less than 0.5 pm 40 ensures a good quality of contract between the contact areas of the two pieces.

[0050] The vane 15 and the armature 17 manufactured in this way are then assembled to form the magnetic circuit 9.

[0051] In a variant, an intermediate treatment stage can be performed on the roughing pieces

of finishing, before the microgranallado treatment stage.

[0052] The microgrannel treatment step will be described in more detail in reference to Figure 2, which schematically illustrates a device 50 for performing this stage.

fifty

[0053] The device 50 comprises a box 52 having an opening 54 for the introduction of the roughing pieces, suitable to be sealed to seal the box 52 tightly.

[0054] The device 50 further comprises support means 56 of the roughing magnetic pieces 55, and projection means 58 of a flow of microspheres wrapped in a fluid, on the parts

maintained by the support means 56.

[0055] The projection means 58 comprise a nozzle 60 for projecting a flow of microspheres wrapped in a fluid, and feeding means of the nozzle 60 in a fluid under pressure which

Wrap some microspheres.

[0056] The microspheres are glass, ceramic or steel spheres of a micrometric size. For example, the microspheres have a diameter between 20 pm and 200 pm.

5

[0057] By way of example, the microspheres are microspheres of the SS19 type marketed by Rossler France. These microspheres are made of sodocalcic glass with an average diameter of approximately 40 pm.

[0058] The fluid in which the microspheres are wrapped is for example water or air.

10

[0059] For example, the fluid used is water, in which the microspheres are mixed, the mixture comprises 25% by volume of microspheres.

[0060] The nozzle 60 comprises an opening 62 through which the fluid mixed with the microspheres is projected under pressure. The shape and dimensions of the opening 62 are adjustable depending on the extent of the

surface to be treated and the homogeneity of the projection sought. The opening 62 is for example a circular opening, with a diameter between 5 and 12 mm, mainly equal to 10 mm.

[0061] The pressure of the mixed fluid of the microspheres at the outlet of the nozzle 60 is, for example, between 1 and 5 bars.

[0062] The support means 56 are suitable for maintaining a magnetic piece in a predetermined position in front of the opening 62 of the nozzle 60 at the time of the projection of the microspheres on this piece. The support means 56 are on the other hand suitable for modifying the position of the magnetic piece

25 in relation to the projection means 58, mainly the distance d between the piece and the opening 62 and the orientation of the piece in relation to the jet leaving the opening 62, hereinafter referred to as the angle of attack a.

[0063] The distance d is for example between 100 mm and 200 mm.

30

[0064] The angle of attack is for example equal to 90 °, that is to say that the jet leaving the nozzle has an angle of incidence on the piece substantially equal to 90 °. The angle of attack can also be selected to be less than 90 °, for example equal to 75 °.

[0065] The adjustment of the distance d and the angle a allow to control the deformation temper obtained on the

treated piece.

[0066] The support means 56 comprise for example a magnet suitable for exerting a magnetic force on a magnetic piece to keep it in position, the magnet is suitable for being carried in

40 rotation in relation to the nozzle 60 to rotate the magnetic part in relation to the nozzle 60.

[0067] The support means 56 thus allows a sweep of one or more pieces to be carried out by the jet leaving the nozzle 60.

[0068] By way of example, Fe-Ni alloy bands have been manufactured, comprising 48% Ni, the

rest is iron and impurities resulting from the elaboration, from ingots, by hot rolling followed by a cold rolling.

[0069] Afterwards, rough blades and armatures have been manufactured by trimming those 50 bands, followed by a phase to shape by folding, and by a thermal treatment intended to confer on the band

the desired mechanical and magnetic properties.

[0070] Then, an intermediate finishing treatment has been carried out on a first series of rough weave, followed by a microgranal treatment by means of the device described as

55 reference in figure 2. At the end of the microgrannel treatment, a finishing treatment has been applied again on the reinforcements to obtain finished reinforcements.

[0071] Furthermore, a microgrannel treatment, without the intermediate finishing treatment, has been carried out on a second series of rough reinforcement by means of the device described as reference in the

Figure 2. At the end of the microgrannel treatment, a finishing treatment has been applied to the reinforcement to obtain finished reinforcement.

[0072] Likewise, a treatment by 5 microgranals, without intermediate finishing treatment, has been carried out on a series of rough blades, by means of a device described in Figure 2. At the end of the

microgrannel treatment, a finishing treatment has been applied to the pallets to obtain finished pallets.

[0073] All these microgrannel treatments have been carried out by means of microspheres of type 10 SS19 described above, wrapped in water, the water-microsphere mixture contains 25% by volume of

microspheres

[0074] The nozzle used is a nozzle having a circular opening 62 of diameter equal to 10 mm. On the other hand, the distance between the opening 62 of the nozzle 60 and the vanes and the reinforcements has been set at 150 mm.

fifteen

[0075] Each of the series of armor and vanes has been divided into nine groups, and each armor or pallet of each group has been treated by microgranallado following the parameters of angle of attack a, of pressure P and duration of exposure T listed in table 1 below.

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Table 1: Microgrannel treatment parameters applied to each group

 Serie

 Group N ° a (°) P (bars) T (s)

 First series of armor

 1 90 1 7

 2

 90 1 14

 3

 90 1.5 7

 4

 90 1.5 14

 5

 90 2 7

 6

 90 2 14

 7

 75 2

 7

 8

 90 2.5 7

 9

 90 2.5 14

 Second series of armor

 1 90 1 7

 2

 90 1 14

 3

 90 1.5 7

 4

 90 1.5 14

 5

 90 2 7

 6

 90 2 14

 7

 75 2

 7

 8

 90 2.5 7

 9

 90 2.5 14

 Pallet series

 1 90 1 7

 2

 90 1 14

 3

 90 1.5 7

 4

 90 1.5 14

 5

 90 2 7

 6

 90 2 14

 7

 75 2

 7

 8

 90 2.5 7

 9

 90 2.5 14

[0076] Then the influence of microsphere treatment on the hardness of the surface 25 of the vanes and the reinforcements has been measured.

[0077] For this, the Vickers hardness HV0.025 and HV0.01 of the pallets or reinforcements of each of the groups have been measured.

[0078] In addition, the roughness coefficient Ra of the reinforcements and vanes of each group has been measured.

[0079] The measures obtained, resulting in each group of an average of roughness, broth and

Vickers hardness measured on five pallets or armor of this group, are described in table 2.

5 [0080] On the other hand, the influence of microgrannel treatment on the

electrical properties of a magnetic circuit formed by the treated vanes and armor. In particular, the impedance of a magnetic circuit according to the state of the art, formed by the assembly of a vane and a coated armature but not subjected to microgranulation, is generally between 1.10 Q and 1.75 Q. mode, from the vanes and the reinforcements of each group, magnetic circuits have been formed, and the impedance of the circuits formed in this way, that is to say the resistance of these circuits to the passage of a magnetic flux, has been measured.

[0081] The measurement of the impedance of each circuit has been performed according to the assembly described as reference in Figure 3.

fifteen

[0082] As illustrated in Figure 3, a force F has been applied to the vane 15 by a weight. This force is intended to simulate the force exerted by the permanent magnet 11 when the differential relay 5 is working.

[0083] A first coil 70, comprising N1 turns, has been wound around the branches 19 of the

armor 17, and a second coil 72, comprising N2 turns, has been wound around the other branch 20 of the armor 17.

[0084] The first coil 70 has been coupled to an alternating current generator 74, and the second coil has been coupled to a voltmeter 76.

[0085] An alternating current l has been generated by the generator 74 in the first coil 70, the value of this current is controlled by an ammeter 78.

[0086] The voltage V on the terminals of the second coil 74 has been measured.

[0087] Then, the impedance Z has been determined as the relationship between voltage V and current I.

[0088] In particular, reinforcements of each of the groups of the first series have been assembled by one part with vanes that are not coated and not subjected to microgranulation, on the other hand with some

palettes coated with a chromed coating and not subjected to microgranulation, and finally some pallets obtained by the method according to the invention, therefore not coated and micrograined, of the corresponding group of the pallet series.

[0089] On the other hand we have assembled some reinforcements of each of the groups of the second series by

one part with pallets that are not coated and not subjected to microgranulation, on the other hand with pallets coated with a chromed coating and not subjected to microgranulation, and finally some pallets obtained by the method according to the invention, therefore not coated and subjected to microgranallado, of the corresponding group of the series of palettes.

Four. Five

[0090] Then the electrical impedance was measured, indicated as Z pal. Prod, of the magnetic circuits formed by armatures of each of the groups and some uncoated and non-micrograined blades, the electrical impedance, indicated as Z pal Cr, of the magnetic circuits formed by armor of each of the groups and pallets coated with chrome and not subjected to microgranallado, and the

50 electrical impedance, indicated as Z pal pesf., Of the magnetic circuits formed by armatures of each group and of the vanes according to the invention of the corresponding group.

[0091] The measured impedances are indicated in Table 2.

55 [0092] Likewise, pallets of each of the groups of the pallet series have been assembled by a

part with the uncoated and non-micrograined armor, on the other hand with a chrome coated and not microgranulated armor, and finally some armor obtained by the method according to the invention, therefore not coated and subjected to microgranallado, of the group corresponding to the first series of armors.

[0093] Then the electrical impedance was measured, indicated as Z arm. Prod, of the magnetic circuits formed by vanes of each one of the groups and some uncoated and non-microarranged armor, the electrical impedance, indicated as Z arm Cr, of the magnetic circuits formed by

5 paddles of each of the groups and chrome-clad and non-microarranged armor, and the electrical impedance, indicated as Z arm pesf., Of the magnetic circuits formed by vanes of each group and armatures according to the invention of the corresponding group of the first series of armor.

[0094] The measured impedances, expressed in Ohms, are described in Table 2.

10

[0095] It should be noted that the electrical impedance Z arm pesf. of a magnetic circuit formed by a vane of a group and an armor according to the invention of the corresponding group of the first series of armor is necessarily identical to the electrical impedance Z pal pesf. of a magnetic circuit formed by an armor of the first series of this group and a vane according to the invention of the corresponding group, such as the one

15 described in table 2.

Table 2: Measures of impedance, hardness and roughness

 Serie

 Group No. Z pal. prod. Z pal. Rev. Z pal. pesf. HV 0.025 HV 0.01 Ra (pm)

 First series of armor

 1 1,732 1,248 1,424 269 253 0.0764

 2

 1,614 1,252 1,458 289 290 0,0406

 3

 1,452 1.16 1,322 273 259 0.0358

 4

 1.6 1,202 1,378 276 298 0.0392

 5

 1,658 1.19 1,292 274 229 0.0388

 6

 1,476 1,174 1,294 297 317 0.0382

 7

 1,572 1,166 1,378 287 234 0.0384

 8

 1,484 1,174 1.36 275 275 0.052

 9

 1,454 1,246 1.32 275 251 0.0356

 Second series of armor

 1 1.74 1.35 1,482 297 255 0.0372

 2

 1,644 1,284 1.32 305 285 0.0412

 3

 1,574 1,276 1,304 271 295 0.0366

 4

 1.62 1,246 1,372 294 276 0,041

 5

 1,532 1,242 1,414 257 287 0.0418

 6

 1,532 1,216 1.32 289 300 0.0394

 7

 1,542 1,282 1,382 281 255 0,0384

 8

 1,462 1,112 1,322 242 270 0.0384

 9

 1,458 1.07 1,226 312 311 0.0456

 Serie

 Group No. Z arm. prod. Z arm Rev. Z arm. pesf. HV 0.025 HV 0.01 Ra (pm)

 Pallet series

 1 1.74 1.218 1.424 240 231 0.0678

 2

 1,498 1,232 1,458 215 213 0,066

 3

 1,274 1,016 1,322 246 238 0.0586

 4

 1,454 1,052 1,378 260 224 0.058

 5

 1,536 1.06 1,292 251 149 0,056

 6

 1,422 1,068 1,294 265 257 0,062

 7

 1,482 1,114 1,378 256 232 0,064

 8

 1,448 1,102 1.36 253 263 0.056

 9

 1,492 1.07 1.32 261 245 0.06

[0096] The results presented in Table 2 show that the manufacturing process of the pallets

and of the reinforcements according to the invention, in particular the microgranallado treatment stage of these pallets and reinforcements, allows to increase the surface hardness of these pieces very satisfactorily. In fact, that the angle of attack is equal to 90 ° or 75 °, and that the pressure of the projected flow at the outlet of the nozzle, between 1 bar and 2.5 bars, the hardness of Vickers HV 0.025 and HV 0, 01 are clearly superior to the initial hardness of the pieces 25 (120 HV), and also clearly superior to the hardnesses generally obtained by coating procedures (170 HV).

[0097] In addition, the roughness coefficients of the vanes and armor are equally satisfactory, mainly greater than 0.03 pm. In this way, these results show that the surface deformation tempering of the surface of the pieces allows for a satisfactory finishing of the pieces with a removal of matter, while maintaining a high hardness on the surface.

5

[0098] It is further noted that the electrical impedances of magnetic circuits formed by a vane and armature manufactured according to the method according to the invention have a satisfactory electrical impedance, between 1.10 Q and 1.75 Q. These satisfactory values are observed. also for some electrical circuits in which only one of the mechanical parts has been manufactured according to a procedure according to the

10 invention

[0099] These results also show that the microgrannel treatment stage allows to increase the surface hardness of these magnetic pieces without negatively impacting other properties, mainly the impedance of the magnetic circuit or the ability of these pieces to be subjected to a

15 effective finishing treatment.

[0100] The contact surfaces of the magnetic parts according to the invention therefore have

a very satisfactory wear resistance, and significantly superior to the wear resistance of the relays that have coatings of the known type.

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[0101] However, it should be understood that the exemplary embodiment presented above is not limiting.

[0102] Mainly, according to a variant, only the vane or only the armor can be manufactured according to a method according to the invention.

25

Claims (11)

1. Method of manufacturing a magnetic part (15.17) of a high sensitivity differential relay (5), said manufacturing process being characterized in that it comprises a stage of 5 treatment of the surface by microgranallado of at least a portion of a surface of said magnetic piece (15.17), said step of surface treatment by microgranallado consisting of a projection of microspheres under pressure on said surface portion. 2. Method of manufacturing a magnetic piece (15.17) according to claim 1, wherein said magnetic piece is an armature (17) or a vane (15) of a magnetic circuit (9).
3. Procedure for manufacturing a magnetic piece (15, 17) according to any of the claims 1 or 2, wherein said piece is a Fe-Ni alloy comprising, by weight, from 46% to 49% nickel, the rest is iron and impurities resulting from the elaboration. fifteen
4. Procedure for manufacturing a magnetic piece (15, 17) according to any of the claims 1 to 3, wherein said microspheres are glass, ceramic or steel microspheres.
5. Procedure for manufacturing a magnetic piece (15, 17) according to any of the 20 claims 1 to 4, wherein said microspheres are projected onto said surface portion with a pressure between 1 and 5 bars.
6. Procedure for manufacturing a magnetic piece (15, 17) according to any of the claims 1 to 5, further comprising an intermediate polishing stage of said magnetic piece (15.17), 25 performed before the microgranallado surface treatment stage.
7. Procedure for manufacturing a magnetic piece (15, 17) according to any of the claims 1 to 6, further comprising a final stage of rolling of said magnetic piece (15.17), carried out before the microgranallado surface treatment stage. 30 8. Manufacturing process according to any one of claims 1 to 7, characterized in that it comprises, before said surface treatment stage, a manufacturing step of a rough magnetic piece, which comprises a cutting phase of a band obtained by means of a lamination hot followed by a cold rolling, said step of surface treatment being performed on said piece 35 roughing magnetics. 9. Method according to claim 8, characterized in that said manufacturing stage of the roughing magnetic piece also comprises, after the cutting phase, a phase of shaping by folding the cut band. 40 10. Method of manufacturing a magnetic circuit (9) of a high sensitivity differential relay (5), said magnetic circuit (9) comprising two magnetic pieces (15.17) that form an armature (17) and a vane (15 ), said procedure comprising: 45 - the manufacture of said magnetic parts (15.17), and - the assembly of said magnetic parts (15.17) to form said magnetic circuit (9), wherein the manufacture of at least one of said magnetic pieces (15.17) is carried out by a manufacturing process according to any one of claims 1 to 9. fifty 11. A magnetic piece (15.17) of a magnetic circuit (9) of a high sensitivity differential relay (5), characterized in that it has been obtained by a manufacturing process according to any one of claims 1 to 9. 55 12. Magnetic circuit (9) of a high sensitivity differential relay (5), said circuit comprising magnetic (9) two magnetic pieces (15.17) that form an armature (17) and a vane (15), characterized in that at least one of said magnetic pieces is a magnetic piece according to claim 11.