SK285293B6 - Soft magnetic nickel-iron alloy with low coercive field strength, high permeability and improved resistance to corrosion - Google Patents

Abstract

The invention relates to a soft magnetic nickel-iron alloy containing 35-65 mass % nickel, one or several of the rare earths cerium, lanthanum, praseodymium or neodymium and the impurities introduced during smelting, the sum of the rare earths being between 0.003 and 0.05 mass %.

Description

Technical field

The invention relates to a magnetically soft iron-nickel alloy.

BACKGROUND OF THE INVENTION

From Carl Heck: "Magnetische Werkstoffe und ihre Technische Anwendung", Huting Verlag, Heidelberg 1975, p. 349 et seq., It is known to use magnetically soft materials for anchor and yoke relays.

The main material requirements are high saturation flux density to achieve high magnetic holding force at low energy, high permeability so that low magnetic field density, i.e. low field current and high flux density in the air gap can be generated, and the armature acts high pulling force. The low coercive intensities allow easy opening of the relays when the excitation current is reversed.

Table 1: Relay materials according to DIN 17405

In addition to the magnetic requirements, the relay material also requires corrosion resistance in an alternating climate test, since the correct function of the relay is essential in all weather conditions. In case of insufficiently corrosion-resistant materials, this requirement can only be met by additional coatings of the finished parts with a corrosion-resistant layer.

The anchor and yoke contact surfaces must have as little gap as possible to achieve high permeability of the yoke and anchor magnetic circuit. They must not be damaged by switching the relay on, since then the starting current of the relay changes.

Similar magnetic requirements are also imposed on other moldings and die-cut parts of magnetically soft materials.

The magnetic requirements for relay material are given in DIN 17405 "Weichmagnetische Werkstoffe fur Gleichstrom relais". The following table 1 shows the lift from DIN 17405.

material Coercive intensity Min. magnetic induction (T) Essential alloy components Mark. Material number Max. Hc (A / m) at coercive intensity H in A / m Weight. % 20 50 100 300 500 4000 RNÍ24 1.3911 24 0.20 0.45 0.70 0.90 1.00 1.18 36 Ni RNi 12 1.3926 12 0.50 0.90 1.10 1.25 1.35 1.45 50 Ni RNi 8 1.3927 8 0.50 0.90 1.10 1.25 1.35 1.45 50 Ni RNi 5 2.4596 5 0.50 0.65 0.70 0.75 70 to 80 Ni, small quantities Cu, Cr, Mo RNi 2 2.4595 2.5 0.50 0.65 0.70 0.75

DIN 17745 “Nickel and Eisen Knetlegierungen aus Nickel and Iron” describes Ni 48 (material numbers 1.3926 and 1.3927) as starting materials for types RNi 12 and RNi 8 (see Table 2). Ni 36 alloy (material number 1.3911) is the starting material for RNi 24 types.

Table 2: Extract from DIN 17745

označe- not Material number Composition in wt. % Alloy components Admissible ingredients Ni 48 1.3926 1.3927 Ni min. 46, Fe 49-53 C 0.05, Mn 0.5, Si 0.3 Ni 36 1.3911 about 36

In melting the iron-nickel alloys, in addition to the required alloy components, deoxidizing and / or desulfurizing elements such as manganese, silicon and aluminum are also necessary. Moreover, it is not possible to exclude certain minimum admixtures of oxygen, sulfur, phosphorus, carbon, potassium, magnesium, chromium, molybdenum, copper and cobalt when these mixtures are produced, due to the favorable production costs, by conventional steelmaking technology. Conventional steelmaking technology is understood to mean melting in an open arc furnace followed by ladle metallurgy and / or VOD treatment for deoxidation, desulphurisation and degassing. Thereafter, the block or slab is hot-faced to about 4 mm in one or two steps and then cold-cooled to a final thickness, optionally with inter-firing. Magnetic properties deteriorate as described e.g. in DE 19612556 Al, admixtures of carbon, nitrogen, oxygen, sulfur and non-metallic exudates. Non-metallic impurities result from the necessary deoxidizing and / or desulfurizing treatment of the melt before casting. Depending on the deoxidizing and / or desulfurizing agent, these are e.g. potassium, magnesium or aluminum oxides.

To avoid this problem, magnetically soft materials which are subject to the highest prior art requirements so far have been manufactured from selected pure starting materials by means of vacuum technology, as disclosed in DE-A 3910147 and DE-C 1259367. Another known option in the literature it is a very demanding and expensive electroslag melting under vacuum or under the protective atmosphere of blocks pre-melted under vacuum or under the protective atmosphere described in DE-A 410507.

Japanese document JP-A 07166281 relates to a magnetic alloy for magnetic heads consisting of Mi and Fe with additives Nd, Pr or Sm. The amount of Ni is greater than 78% by weight.

SUMMARY OF THE INVENTION

The problem solved by the invention resides in the smelting of a magnetically soft iron-nickel alloy which meets the described requirements for magnetic properties and corrosion and wear resistance, and which finds a number of preferred applications for magnetically soft components.

This problem is solved by a magnetically soft iron-nickel alloy with a nickel content of 35 to 65% by weight, with one or more cerium rare earths, lanthanum, pig-iron or neodymium, and with melting impurities, with a total amount of rare earths between 0.003 and

SK 285293 Β6

0.05% by weight, the total rare earth content of cerium, lanthanum, praseodymium and neodymium in% by weight. is at least

4.4 times the sulfur content in wt.

Preferred embodiments of the invention are apparent from the respective dependent claims.

The alloy according to the invention is preferably produced by steel technology, i.e. by melting in an open arc furnace followed by ladle metallurgy and / or VOD treatment (vacuum oxidative decarburization) for deoxidation, desulphurisation and degassing. Thereafter, the block or slab is hot-faced to a thickness of about 4 mm in one or two steps and then cold-cooled to a final thickness, optionally with inter-firing, to adjust the hardness required to manufacture the components from the strip. Following the production of the alloy components and the firing of these components at temperatures between 800 and 1150 ° C, coercive intensities of less than 8 A / m can be achieved with these components.

Preferred cases of use of the alloy according to the invention are, inter alia, relay components such as yokes and anchors.

In addition, the ferro-nickel alloy according to the invention can be conveniently used for the following other applications:

- Solenoid valve caps and housings

-arms or poles, or pole extensions, resp. pole plates and anchors of holding magnets, resp. electromagnets

- coil cores and stators of stepper switching motors as well as rotors and stators of electric motors,

- molded and die-cut parts of sensors, transmitters and position sensors,

- magnetic heads and shielding of magnetic heads,

- screening, such as motor screening, shielding for measuring instruments and cathode ray tube screening.

Flat specimens were punched from a 1.2 mm thick strip produced by steel technology, cleaned, baked at 1080 ° C for 4 hours under a hydrogen atmosphere, and then cooled in an oven at 300 ° C. These samples were subjected to the climate test described in DIN 50017 with 28 cycles of 8 hours at 55 ° C and 90 to 96% air humidity and 16 hours at 25 ° C and 95 to 99% air humidity. Alloys with a nickel content of 36 to 81% by weight were investigated. and partly with additives such as chromium, copper and / or molybdenum (see Table 3). Alloys with a nickel content of less than 55% by weight. have, after completion of this alternating climatic test, all the more severe surface corrosion effects than alloys with more than 75% nickel (B. Gehrmann, H. Hattendorf, A. Kolb-Telieps, W. Kramer, W. Mottgen: Material and Corrosion 48, 535-541 (1997)) and thus do not, without additional anti-corrosion measures, meet the aforementioned requirements for relay material in terms of corrosion resistance. The magnetic properties required by DIN 17405, on the other hand, were met, as shown by the coercive intensities Hc shown in Table 3 (prior art).

Table 3

Composition in% wt. hc (A / m) max. Hc according to DIN 17405 alloy fe Ni Mo Cr Cu Mn Are you Fe-36Ni 62.90 36.50 0.01 0.03 0.03 0.27 0.18 4.2 24 Fe-40Ni 58.35 40.75 0.02 0.05 0.04 0.50 0.18 4.7 Fe-41Ni 58.50 40,65 0.01 <0.01 0.04 0.47 0.21 3.2 Fe-45Ni 54.25 44.70 0.02 0.02 0.02 0.58 0.28 2.5 Fe-47Ni-6Cr 45,85 47.30 <0.01 6.04 0.01 0.21 0.26 3.8 Fe-48Ni 51.70 47.50 0.04 0.03 0.02 0.41 0.20 2.4 8 Fe-50Ni 48,85 50,70 0.01 0.04 0.03 0.21 0.05 3.5 8 Fe-55Ni 43.70 55.45 0.06 0.06 0.05 0.42 0.14 12.5 Fe-76NiCrCu 16.05 75.95 0.10 2.00 4.96 0.60 0.22 0.87 2.5 Fe-77 Ni-Ti, Nb 14.80 77.30 0.01 0.10 4.50 0.49 0.24 2.4 2.5 Fe-77 Ni-Mo, Cu 13.85 77.15 3.45 0.10 4.47 0.53 0.33 0.85 2.5 Fc-80Ni-Mo 13.95 80.10 4.75 0.05 0.09 0.50 0.33 0.44 2.5 Fe-81Ni-Mo 12.45 81.50 5.27 0.03 0.05 0.43 0.13 1.23 2.5

Sulfur was found at the corroded sites of these samples after the alternating climate tests by REM / EDX.

Surprisingly, the improvement of the corrosion behavior according to the invention is achieved by means of desulfurization for the corrosion of susceptible iron-nickel alloys with a nickel content of 35 to 65% by weight. cerium. This is preferably done with a mixed metal of the group by the chemical behavior of very similar rare earth cereals and / or lanthanum and / or prime and / or neodymium. Sufficient rare earth atoms must be present to reliably bind all sulfur. Starting from, for example, the formation of cerium sulphide with the largest proportion of CeS, this is the case when more cerium atoms are present in the alloy than sulfur atoms.

Accordingly, the cerium content in wt. at least

4.4 times greater than the sulfur content in% by weight in order to achieve complete binding of the sulfur by the cerium. The corresponding condition applies to other rare earths lanthanum, praseodine and / or neodymium and to the total rare earth content.

As already mentioned, the addition of a strong deoxidizing and desulfurizing agent such as cerium as a result of reaction products in the material can affect the magnetic properties (A. Hoffmann, Uber den Einfluss von verschiedenen Desoxidationselementen auf die Verformung und die Anfangspermeabilitat von Ni-Fe-Legierung (Z. Angew. Physik 32: 236-241). Surprisingly, the addition of rare earths can be dosed such that the magnetic values of permeability and coercive intensity lie within the limits of the variations of the batches fused according to the prior art.

It is known that deoxidizing residues from the relay contact surfaces break off, remaining between these surfaces and, for example in the case of oxide residues, higher hardness can destroy finely ground contact surfaces when the relay is switched again. Therefore, relay materials can have only a very low content of non-metallic inclusions according to DIN

50602 (method M). Therefore, also in the case of deoxidation with cerium, or a rare earth mixed metal of cerium, lanthanum, praseodymium and neodymium, the maximum values of sulfide inclusions in the fibrous form of SS must be less than 0.1 resp. 1.1, maximum values of oxidic inclusions in dissolved form of OA (alumina) less than 2.2 and 3.2, respectively. 4.2, maximum values of oxidic inclusions in the fibrous form of OS (silicates) less than 5.2 resp. 6,2 resp. 7.2 and maximum values of oxidic inclusions in globular form of OG less than 8.2, resp. 9.2.

DETAILED DESCRIPTION OF THE INVENTION

By way of example, a steel-alloy technology in a 30-ton arc furnace was made of an iron-nickel alloy containing about 48% nickel and small manganese and silicon additives (batches E5407 and E0545) and compared to batches of very similar composition but without the rare earth additions corresponding to the state of the art (batch T4392) , T5405 and T5406). The exact compositions are given in Table 4.

Table 4: Composition of Batches of the Prior Art (T) and Batches of the Invention (E). All data are in wt.

element State of the art Composition according to the invention Limit values Batch T2536 T5477 T5488 T4392 T4505 T5406 E5407 E0545 Ni 47.45 47.5 47.85 47.7 47.45 47.9 47.65 47.65 Mn 0.40 0.40 0.36 0.38 0.40 0.38 0.39 0.41 max. 0.5 Are you 0.19 0.19 0.22 0.20 0.14 0.15 0.14 0.22 max. 0.3 A1 0,005 0,005 0,007 0,009 0,007 0,008 0,005 0,005 max. 0,010 mg 0,001 0.0003 0.0008 0.0001 0.0001 0.0002 0.0006 0.0008 max. 0,002 ca 0.0004 0.0004 0.0003 0.0001 0.0002 0.0002 0.0003 max. 0,002 cerium 0,014 0,011 la 0,008 0,005 pr 0,001 0,001 nd 0,003 0,003 Rare soils total 0,026 0,020 max. 0,050 WITH 0.0020 0.0012 0.0007 0.0012 0.0008 0.0010 0.0010 0.0022 max. 0.0040 4.4 * S 0.0044 0.0088 ABOUT 0.0020 0.0010 0.0015 0.0020 0.0020 0.0020 0.0025 max. 0.0040 N 0.0010 0.0010 0,001 0.0010 0.0010 C 0,011 0,009 0,004 0,013 0,012 0,009 0,007 0,016 max. 0.05 P 0,002 0,002 0,002 0,002 0,002 0,002 0,002 0,003 Cr 0.03 0.03 0.03 0.04 0.04 0.04 0.05 0.02 Mo 0.05 0.09 0.13 0.10 0.14 0.05 0.04 0.08 Cu 0.06 0.06 0.04 0.10 0.05 0.05 0.05 0.15 What 0.04 0.02 0.01 0.04 0.02 0.02 0.02 0.03 B 0,001 0,001 0,001 0,001

Small amounts of boron can be added to improve stampability, such as batches T4392, T5405, T5406 and E5407. Boron content in wt. in batches according to the invention E5407 and E0545 is more than 4.4 times greater than the sulfur content in wt.

After melting, block rolling was carried out, followed by hot rolling the strip to about 4 mm, and then cold forming to a final thickness of 1.0 mm.

Circular samples with a diameter of 25.5 mm were punched out of this. This five for all lots except E0545. Here a piece of about 15 mm x 15 mm x 5 mm cast sample was used, the surfaces of which were smoothly ground. All samples were cleaned and a portion of the samples was fired at 970 ° C for 6 hours under a hydrogen atmosphere and then cooled to below 300 ^° C in an oven. The other sample was fired at 1030 ° C for 2 hours under a hydrogen atmosphere cooled below 300 ° C. All samples were subjected to a shortened climatic test for 2 days with a temperature / humidity rhythm of 3 hours from 25 ° C and 55% humidity to 55 ° C and 98% humidity. The samples lay flat on the glass pans, so that even more severe crevice corrosion conditions prevailed on the underside. The result is shown in Table 5.

Table 5: Results of climate tests

Batch After shortened climatic test: Corrosion samples / total number of samples tested notes 970 ° C / 6 hours 1030 ° C72 hours T5405 10/10 10/10 on both sides, several distinct points on the sample T5406 10/10 10/10 on both sides, several distinct points on the sample E5407 0/10 0/10 E0545 0/1

No corrosion was observed in batches E5407 and E0545 according to the invention, whereas in both comparative batches T5405 and T5406, there were corrosion points on both sides in each sample.

The addition of such a strong deoxidizing and desulfurizing agent, such as cerium, may, as stated, adversely affect the magnetic properties due to the presence of reaction products remaining in the material. Surprisingly, the magnetic permeability and coercive intensities values of batches E5407 and E0545 according to the invention lie within the usual variation limits of batches fused according to the state of the art, as shown in Table 6.

Table 6: Magnetic values of prior art batches (T) and batches of the invention (E) measured on samples of 1 mm thickness after firing at 1080 ° C for 4 hours and cooled in an oven at 450 ° C. The batch composition is shown in Table 4.

material Coercive intensity Min. magnetic induction (T) Static values Mark. Material number Hc (A'm) at coercive intensity H in A / m μ4 / xmax 20 50 100 300 500 4000 RNi 24 1.3911 <24 0.20 0.45 0.70 0.90 1.00 1.18 RNi 12 1.3926 <12 0.50 0.90 1.10 1.25 1.35 1.45 RNi 8 1.3927 <8 0.50 0.90 1.10 1.25 1.35 1.45 batch E5407 4.2 1.02 1.12 1.18 1.31 1.50 1.56 10200 97800 E0545 2.6 11690 133770 T2536 1.9 8000 179600 T4392 3.8 1.07 1.16 1.22 1.36 1.44 1.54 5000 154700 T5405 2.5 1.06 1.14 1.20 1.32 1.41 1.57 9200 142100 T5406 2.1 1.06 1.14 1.20 1.33 1.42 1.53 10000 158900 T5477 2.76 1.08 1.17 1.21 1.34 1.42 1.53 8200 135100 T5488 5.21 1.09 1.20 1.35 1.40 1.46 1.54 2600 99850

Further, the block rolling and hot rolling properties of two batches of the prior art composition shown in Table 7 were studied.

The two lots differed basically only with different rare earth contents.

Table 7

element Limit value Batch T0626 T0624 Ni 36.2 36.45 Mn 0.25 0.26 max. 0.5 Are you 0.20 0.19 max. 0.3 Al 0,009 0,009 max 0.010 mg 0.0030 0,003 max. 0,002 ca max. 0,002 cerium 0,029 0,001 la 0,017 pr 0,002 nd 0,006 Total rare earth content 0,054 0,002 max. 0,050 WITH 0,002 0,002 max. 0.0040 ABOUT 0.0050 0.0020 max. 0.0040 N 0.0025 0.0020 C 0,004 0,009 max. 0.05 P 0,002 0,002 Cr 0.04 0.01 Mo 0.06 0.06 Cu 0.05 0.09 What 0.05 0.03 B - -

In the case of batch T06 26 with a total rare earth content of 0.054% cracks formed during hot forming and the block was then scrapped. Such a high rare earth content leads to worse heat-forming properties. Batch T0624, on the other hand, was rolled into both a block and a hot-rolled strip of about 4 mm thickness. Since the rare earths behave chemically in a similar manner, according to the invention, it is necessary to limit the total amount of cerium, lanthanum, praseodymium and neodymium rare earths to a maximum of 0.05% by weight in order to avoid hot forming problems.

Table 8 contains an examination of the content of non-metallic inclusions according to D1N 50602 in different batches according to the prior art (T) and according to the invention (E).

Table 8

material Degree of purity according to DIN 50602: Maximum value (method M) Batch SS OA OS OG Limit values 0,1 resp. 1.1 22 resp. 32 resp. 4.2 52 resp. 62 resp. 7.2 82 resp. 92 E5407 2.1 8.0 E0545 2.2 8.1 T4392 2.2 8.0 T5405 2.0 8.0 T5406 2.2 8.0 T5477 2.1 8.1 T5488 2.0 8.0 T2536 2.7 -

Batch T2536 has a maximum value of 2.7 in the case of oxidic inclusions in the fibrous form (method M). This value is too high to use this batch on the relay components. It leads to wear on the relay contact surfaces and results in the loss of relay functionality. The content of non-metallic inclusions is therefore limited according to the invention as follows:

The maximum values according to DIN 50602 of sulfide inclusions in fibrous form SS are less than or equal to 0.1 and 1.1, respectively, the maximum values according to DIN 50602 of oxidized inclusions in dissolved form OA (alumina) less than or equal to 2.2 and 3 respectively. , 2, resp. 4.2, maximum values according to DIN 5060 2 oxide inclusions in fibrous form OS (silicates) less than or equal to 5.2, resp. 6.2, resp. 7.2 and maximum values according to DIN 50602 of oxidic inclusions in globular form OG less than or equal to 8.2, resp. 9.2. All of the batches listed in Table 8 meet the conditions for non-metallic inclusions.

Claims (14)

PATENT CLAIMS Magnetically soft ferro-nickel alloy containing nickel in an amount of 35 to 65% by weight. and one or more cerium, lanthanum, praseodymium and neodymium rare earths, as well as melt impurities, characterized in that the total rare earth content is between 0.003 and 0.05% by weight, and the aggregate rare earth content of cerium, lanthanum, praseodymium and neodymium in wt. is at least 4.4 times the sulfur content in wt. Magnetically soft alloy according to claim 1, characterized in that the alloy contains at most 0.05 wt. Cerium. Magnetically soft alloy according to claim 1 or 2, characterized in that the alloy contains, as a deoxidizing and / or desulfurizing agent, a maximum of 0.5% by weight. % of manganese, not more than 0.5% by weight of silicon and impurities of not more than 0.002% by weight; % magnesium, max. % potassium, maximum 0.010 wt. % aluminum, max. % sulfur, maximum 0.004 wt. oxygen and other impurities conditioned by melting. Magnetically soft alloy according to any one of claims 1 to 3, characterized in that the alloy contains up to 0.002 wt. boron. A method for melting a magnetically soft iron-nickel alloy according to claims 1 to 4, characterized in that the melting of the alloy in the arc furnace is carried out in an open arc furnace followed by a ladle metallurgy and / or VOD treatment for deoxidation, desulphurisation and degassing. Method according to claim 5, characterized in that the molten alloy is adjusted to the following parameters: - maximum values of sulphide inclusions in fiber form less than 0,1 and 1.1. - maximum values of oxidic inclusions in dissolved form of OA (alumina) of less than 2.2 and 3.2 respectively. 4.2. - maximum values of oxidic inclusions in the fibrous form of OS (silicates) of less than 5,2 respectively 6.2, resp. 7.2. - maximum levels of oxidic inclusions in the globular form of OG of less than 8,2 resp. 9.2. Method according to claim 5 or 6, characterized in that after the production of the components from this alloy, the components are fired at temperatures between 800 ° C and 1150 ° C to achieve coercive intensities of less than 8 A / m. Use of a magnetically soft iron-nickel alloy according to any one of claims 1 to 4 as a material on a relay component. Use of a magnetically soft ferro-nickel alloy according to any one of claims 1 to 4 as a material for the caps and bodies of the solenoid valves. Use of a magnetically soft ferro-nickel alloy according to any one of claims 1 to 4 as a material for yarns or poles, resp. pole adapters pole plates and anchors of holding magnets, resp. electromagnets. Use of a magnetically soft iron-nickel alloy according to any one of claims 1 to 4 as a material for coil cores, stepper switching motor stators and electric motor rotors and stators. Use of a magnetically soft ferro-nickel alloy according to any one of claims 1 to 4 as material for molded and die-cut parts of sensors, transmitters and position sensors. Use of a magnetically soft iron-nickel alloy according to any one of claims 1 to 4 as a material for magnetic heads and shielding of magnetic heads. Use of a magnetically soft iron-nickel alloy according to any one of claims 1 to 4 as a shielding material.