ES2169597T5 - NICKEL-IRON MAGNETIC LOW ENERGY ALLOY WITH LOW INTENSITY OF THE COERCIVO FIELD, HIGH PERMEABILITY AND IMPROVED CORROSION RESISTANCE. - Google Patents

Abstract

Low-energy hypomagnetic alloy of iron-nickel composed of a nickel weight content of between 35% and 65%, of one or more of the lanthanides cerium, lanthanum, praesodymium or neodymium, as well as the inevitable impurities of the casting process . In this alloy the sum of the lanthanides is between 0.003% and 0.05% by weight and the total proportion of cerium, lanthanum, praesodimium and neodymium in% by weight is at least 4.4 times greater than the percentage by weight of sulfur.

Description

Nickel-iron alloy Low energy magnetic with low coercive field intensity, high permeability and improved corrosion resistance.

The invention relates to a magnetic alloy Low energy nickel-iron.

As mentioned in the book Magnetische Werkstoffe und ihre technische Anwendung by Carl Heck, Hütig Verlag, Heidelberg, 1975, p. 349 et seq., The possibility of using low energy magnetic materials is known in the manufacture of relay armor and cylinder heads.

These materials are mainly required a high saturation flux density, in order to obtain with low energies a great magnetic retention force, a high permeability so that a low can be generated in the air gap magnetic field strength, that is, a low current of excitation, as well as a high flow density, thus acting a great force of attraction in the armor. Field strengths Reduced coercive allow a simple opening of the relay in case of reduction of the excitation current.

Together with these magnetic requirements, of a relay material is expected to demonstrate in a cycle test its resistance against corrosion, since it is a correct operation of the relay is necessary in any weather situation Low resistance materials against to corrosion can only be protected from it by additional coating of finished parts with a layer anticorrosive

In order to achieve high permeability of the magnetic circuit between cylinder head and armor, the space between their Contact surfaces should be as small as possible. Likewise, the operation of the relay itself must not damage these surfaces, since the excitation current of the relay itself would look altered

Also other components manufactured with low energy magnetic materials, such as die cut pieces  and profiles must meet similar requirements.

DIN 17405, Low Energy Magnetic Materials for DC Current Relays [ Weichmagnetische Werkstoffe für Gleichstromrelais] , describes the magnetic requirements that materials for relay manufacturing must meet. The following table 1 shows an extract of DIN 17405.

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TABLE 1 Materials for the manufacture of relays according to DIN 17405

one

DIN 17745 nickel alloys and iron mass [Knetlegierungen und Eisen aus Nickel] Ni alloy described 48 (no. 1.3926 and 1.3927 material) as a base material for RNi 12 and RNi 8 ranges (see Table 2). Ni 36 alloy (material number 1.3911) is the base material for the RNi 24 range.

TABLE 2 Excerpt from DIN 17745

2

Apart from the desired alloy elements in nickel-iron alloy casting, also Deoxidizing and desulfurizing elements, such as manganese, silicon and aluminum. On the other hand, they can't avoid minimum additions of oxygen, sulfur, phosphorus, carbon, calcium, magnesium, chromium, molybdenum, copper and cobalt, if desired produce these alloys with a usual steel technology to Cause of the low cost. In this case, by steel technology usual it is understood the melting in arc melting furnaces with the subsequent metallurgical procedure in spoon and / or treatment deoxidant, desulfurizing and degassing VOD. Then, the block or roughing is hot formed in one or two stages, until reaching a thickness of 4 mm and then cold the final thickness is given, if necessary, by annealing intermediate As described, for example, in the document DE 19612556 A1, the additions of carbon, nitrogen, oxygen, Sulfur and other non-metallic elements deteriorate the properties magnetic materials. Because of the treatments Deoxidants and / or desulfurizers needed involved in the pre-casting casting produces non-metallic impurities. Depending on what are the deoxidizing media and / or desulfurizers used, these impurities will be, for example, oxides of calcium, magnesium or aluminum.

For this reason, to avoid these difficulties, Low energy magnetic materials with maximum requirements according to the state of the art have been manufactured, up to Now, with a selection of purified materials produced with vacuum technology support, as specified in the DE-A 3910147 and DE-C documents 1259367. Within the procedures known in the literature is the slag electrical refusion procedure, very expensive and expensive mentioned in the document DE-A-4105507, performed under vacuum or under protective gas from previously molten blocks under vacuum or protective gas

JP-A 07166281 is refers to a magnetic alloy for magnetic terminals composed of Ni and Fe with additions of Nd, Pr, or Sm. The percentage Ni weight is always greater than 78%.

The objective on which the invention is based is to provide a procedure for the casting of a nickel-iron low energy magnetic alloy that meets the already described magnetic and resistance requirements against corrosion and deterioration.

This objective is achieved thanks to the characteristics of the first patent claim.

In the subordinate claims corresponding other advantageous improvements can be seen of the object of the invention.

The alloy is preferably produced by steel technology, that is, by melting in the furnace of open arc fusion with the subsequent metallurgical procedure in spoon and / or the deoxidant, desulfurizing and VOD degassing (vacuum-oxidation-decarbonization). Then the block or roughing is hot formed in one or two stages, until reaching a thickness of 4 mm and, act followed, cold, the final thickness is given, where appropriate, by intermediate anneals to regulate the hardness required for manufacture of parts from this tape.

Following the manufacture of parts a from this alloy and after annealing at temperatures between 800ºC and 1150ºC, with these pieces can be reached intensities of coercive field less than 8 A / m.

The application in the manufacture of parts of relay, such as armor and cylinder heads, is one of the utilities main alloy according to the invention.

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Also, the alloy of nickel-iron according to the invention is very helpful application in the following cases:

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Valve covers and drums magnetic

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Cylinder heads or pole pieces or polar shoes or pole plates and magnet armor permanent and electromagnets

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Coil cores and motor stators step by step as well as rotors and stators of electric motors

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Profiles and die cut pieces of sensors, indicators and position detectors.

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Magnetic terminals and shields of magnetic terminals

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Shieldings, such as shields of motors, shield boxes for signaling instruments and shields for cathode ray tubes.

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From a 1.2 mm thick band obtained by steel technology, flat samples were punched and then cleaned and annealed at 1080 ° C / 4 hours in hydrogen before being cooled to 300 ° C in the oven. The climatic test described in DIN 50017 was applied to these samples in 28 alternating cycles of 8 hours at 55ºC with an ambient humidity between 90% and 95% and 16 hours at 25ºC with an ambient humidity between 95% and 99%. Alloys with nickel contents between 36% and 81% by weight and, occasionally, other elements such as chromium, copper and / or molybdenum were tested (see Table 3). After the completion of this climate cycle test, all alloys with nickel content less than or equal to 55% by weight revealed to have corrosion signs of greater magnitude on their surface than those of alloys with nickel content greater than 75% (B Gehrmann, H. Hattendorf, A. Kolb-Telieps, W. Kramer, W. Möttgen, in Material and Corrosion , 48, 535-541 (1997)), therefore, without the application of further anticorrosive measures, failed to comply with the requirements already mentioned for relay materials in relation to corrosion resistance. On the contrary, the magnetic requirements demanded by DIN 17405 were satisfied, as can be seen in the intensities of the Hc coercive field in Table 3 (state of the art).

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TABLE 3

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After the climate cycle test through REM / EDX, sulfur was found in the corroded places of these samples.

It is surprising that the increase according to invention of resistance against corrosion was obtained by applying cerium for desulfurization in those nickel-iron alloys prone to corrosion and with a nickel content between 35% and 65% by weight. Therefore, it is advisable to perform this procedure with lanthanides as cerium and / or lanthanum and / or praesodymium and / or neodymium, all of them Very similar chemical behavior. Sulfur can only be canceled totally and effectively if there is enough provision of atoms of lanthanides Such happens if, considering now the formation of cerium sulfide with the highest proportion of cerium, the CeS, there is more cerium atoms available in the alloy than sulfur atoms.

Therefore, to achieve full cancellation of the sulfur by cerium, the weight percentage of cerium should be, at less, 4.4 times higher than the percentage by weight of sulfur. And the same has to be said of the other lanthanides, lanthanum, praesodymium and / or neodymium and for the total sum of them.

As already mentioned, the use of a deoxidizing and desulfurizing agent as potent as, for example, cerium can reduce, through the reaction products remaining in the material, the magnetic properties thereof (A. Hoffmann, Über den Einflu? Von verschiedenen Deoxidationselementen auf die Verformung und die Anfangspermeabilität von Ni-Fe-Legierungen , Z. angew. Physik, 32, pp. 236-241). Interestingly, the amount of lanthanides can be dosed in such a way that the magnetic values of permeability and intensity of the coercive field remain within the usual fluctuation range of the molten charges according to the state of the
technique.

It is known that during the deoxidation process residues occur on the contact surfaces of the relay that they remain between these surfaces and that, due to their greater hardness, for example, in case of oxidic residues, they can damage the delicate contact surfaces during the operation itself of the relay. Therefore, as indicated by DIN 50602 (procedure M), the Relay making materials must contain the smallest quantity of non-metallic elements. Consequently, in the deoxidization by cerium or a metal composed of lanthanides such as cerium, lanthanum, praesodymium and neodymium, values maximum magnitude of sulfur inclusions in line form SS must be less than 0.1 or 1.1, the magnitude values maximum levels of oxide inclusions in the form of (OA) aluminum) dissolved less than 2.2 or 3.2 or 4.2, the maximum magnitude values of oxide inclusions in the form of OS line (silicates) less than 5.2 or 6.2 or 7.2 and the maximum magnitude values of oxide inclusions in form globular OG less than 8.2 or 9.2.

As an example, alloys of nickel-iron with approximately 48% nickel and insignificant amounts of manganese and silicon (E5407 and E0545), produced by steel technology in furnace arc fusion, with other loads of very similar composition but no additions of lanthanides, as is done in the state of the technique (loads T4392, T5405 and T5406). Table 4 shows the exact compositions.

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TABLE 4 Load composition according to the state of the technique (T) and loads according to the invention (E). All data reflect weight percentages

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Small amounts of boron can be added to improve malleability, as has been done in loads T4392, T5405, T5406 and E5407. The percentage by weight of cerium in E5407 and E0545 loads according to the invention is more than 4.4 times higher than the percentage of sulfur by weight.

After casting, a block rolling and then a hot rolling of about 4 mm which was then cold formed to give a final thickness of 1.0 mm

From this sheet are obtained, by die cutting, round samples of 25.5 mm in diameter. This is done with all charges except with E0545. Here a 15 mm x piece has been used 15 mm x 5 mm of a cast sample, whose surfaces are polish All samples are purified and a series of them is Annealing at 970 ° C / 6 hours in hydrogen and then cooled in the oven until its temperature falls below 300ºC. The Remaining samples are annealed at 1030 ° C / 2 hours in hydrogen and then cooled in the oven until its temperature drops below 300 ° C. All samples are subjected to a 2-day abbreviated climate test with alternate cycles 3 hours at 25 ° C and 55% ambient humidity and 55 ° C and 98% ambient humidity. In these tests, the samples rest on a glass tray of such that its lower face is subject to conditions highly favorable to corrosion inside the cracks. Table 5 shows the results.

TABLE 5 Results of the climatic test

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In loads E5407 and E0545 according to the invention, no signs of corrosion were found, while in both corrosion loads T5405 and T5406 corrosion points were found on Both Sides.

As already mentioned, the use of an agent deoxidant and desulfurizer as potent as, for example, the Cerium can reduce, through the remaining reaction products in the material, the magnetic properties of it. Curiously, as indicated in table 6, the magnetic values of permeability and of intensity of the coercive field, such as those with loads according to the invention E5407 and E0545, remain within the margin of fluctuation of molten loads according to the state of the technique.

TABLE 6 Magnetic values of charges according to the state of the technique (T) and loads according to the invention (E), measured in samples 1 mm thick after annealing at 1080 ° C / 4 hours in hydrogen and cooling to 450 ° C in the oven. The composition of the loads indicated in Table 4

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Secondly the properties were checked in block and in hot foil of two charges according to the state of the technique, whose composition is referred to in table 7.

It can be said that both charges only differed for its particular content of lanthanide elements.

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TABLE 7

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On load T0626, in which the total weight of lanthanides is 0.054%, fissures appeared that left unusable  the block. Such a high content of lanthanides worsens hot forming possibilities. On the contrary, the Sample T0624, both in block and hot band, does allow laminates about 4 mm thick. Since the lanthanides they have a similar chemical behavior, it must be maintained, according to  the invention, the total content of lanthanides such as cerium, lanthanum, praesodymium, neodymium, below 0.05% by weight, so that No problems with hot forming.

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Table 8 shows the records, according to the standard DIN 50602, of the content of non-metallic elements in different loads according to the state of the art (T) and loads according to the invention (E).

TABLE 8

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Load T2536 has a maximum magnitude value of oxide inclusions in the form of a 2.7 line (procedure M). This value is too high for this material to be used in the manufacture of relays. This causes wear of the contact surfaces that the relay leaves finally unusable. Therefore, the content of non-metallic inclusions is limited as follows according to the invention:

The maximum magnitude values according to the standard DIN 50602 of the sulfur inclusions in the form of the SS line must be equal to or less than 0.1 or 1.1; magnitude values maximum according to DIN 50602 of oxide inclusions in form of dissolved OA (aluminum oxide) must be the same or under 2.2 or 3.2 or 4.2; magnitude values maximum according to DIN 50602 of the oxide inclusions in the form of OS line (silicates) must be equal to or less than 5.2 or 6.2 or 7.2; and the maximum magnitude values according to DIN standard 50602 of the OG globular oxide inclusions must be equal to or less than 8.2 or 9.2. All remaining charges listed in table 8 meet the conditions related to content in non-metallic inclusions.

Claims (3)

1. Procedure for casting a low-energy magnetic iron-nickel alloy with a nickel weight content of between 36% and 65% and one or several of the lanthanides cerium, lanthanum, praesodymium or neodymium, as well as the inevitable impurities of the foundry process by casting the alloy in the arc melting furnace opened with the subsequent metallurgical procedure in spoon and / or VOD treatment for deoxidation, desulfurization and degassing, the sum of the lanthanides being between 0.003% and 0.05% by weight and containing the alloy as additives of deoxidation and / or desulfurization a maximum of 0.5% by weight of manganese, a maximum of 0.6% by weight of silicon and impurities of a maximum of 0.002% by weight of magnesium, a maximum of 0.002% by weight of calcium, a maximum of 0.010% by weight of aluminum, a maximum of 0.004% by weight of sulfur, a maximum of 0.004% by weight of oxygen and other impurities in small quantities of other derived elements of the smelting process and the total proportion of the lanthanides cerium, lanthanum, praesodymium and neodymium in% by weight, at less, 4.4 times greater than the percentage by weight of sulfur. 2. Method according to claim 1, characterized in that the following parameters are adjusted in the molten alloy:

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The maximum magnitude values of sulfur inclusions in the form of line are below 0.1 or 1.1.

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The maximum magnitude values of oxide inclusions in the form of OA (aluminum oxide) dissolved are below 2.2 or 3.2 or good 4.2.

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The maximum magnitude values of oxide inclusions in the form of OS line (silicates) are below 5.2 or 6.2 or 7.2.

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The maximum magnitude values of oxide inclusions in form OG globular are below 8.2 or 9.2.

3. Method according to claim 1 or 2, characterized in that after manufacturing parts from said alloy and annealing them at temperatures between 800 ° C and 1150 ° C, coercive field intensities of less than 8 A / m are achieved.