SK10832000A3 - 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

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

BACKGROUND OF THE INVENTION

From the book 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 low magnetic pole density, i.e. low excitation current and high flux density in the air gap, can be generated, and the anchor acts high pulling force. The low coercive intensities allow easy opening of the relay when the excitation current is reversed.

In addition to the magnetic requirements, the relay material also requires corrosion resistance in an alternating climate test, since the correct operation of the relay is essential in all weather conditions. In the case of poorly 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 Gleichstromrelais. The following table 1 shows the lift from DIN 17405.

Table 1: Relay materials according to DIN 17405

material Koerci-tive intensity Min. magnetic induction (T) significantly ingredients alloys Mark. material number Max. Hc (A / m) at coercive intensity H in A / m Materials. % 20 50 100 300 500 4000 RNi 24 1.3911 24 0.20 0.45 0.70 0.90 1.00 1.18 36 Ni RNi 12 1.3926 12 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 N i, small amounts Cu, Cr, Mo RNi 2 2.4595 2.5 0.50 0.65 0.70 0.75

DIN 17745 Knetlegierungen aus Nickel und Eisen (forming nickel-iron alloys) describes the Ni 48 alloy (material numbers 1.3926 and 1.3927) as starting materials for types RNi 12 and RNi 8 (see Table 2). The Ni 36 alloy (material number 1.3911) is the starting material for RNi 24 types.

Table 2: Extract from D [N 17745 mark Material number Composition in wt. % Alloy components Permitted admixtures 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. In addition, certain minimum additions of oxygen, sulfur, phosphorus, carbon, potassium, magnesium, chromium, molybdenum, copper and cobalt may not be excluded when these mixtures are produced, due to the favorable manufacturing 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. In each case, the deoxidizing and / or desulfurizing agent stages are e.g. potassium, magnesium or aluminum oxides.

In order to avoid this problem, magnetically soft materials which are subject to the highest prior art requirements have so far been produced from selected pure starting materials by means of vacuum technology, as disclosed in DE-A 3910147 and DE-C 1259367. 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. Here, 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 ferro-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 rare earth cerium, lanthanum, praseodymium or neodymium, and melting impurities, with a total amount of rare mines between 0.003 and 0.05 %, wherein the aggregate rare earth content of cerium, lanthanum, praseodymium and neodymium in wt. is at least 4.4 times greater than the sulfur content in% by weight.

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 a ladle matelurgy and / or VOD treatment (vacuum oxidative decarburization) for deoxidation, desulfurization 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, to adjust the hardness required to produce 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 applications 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 is expediently applicable to the following other applications:

- Solenoid valve caps and housings

- yokes or poles or pole pieces, resp. pole plates and anchors of holding magnets electromagnets coil cores and stators of stepping 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 shielding such as motor shielding, shielding for measuring instruments and shielding of cathode ray tubes.

Flat steel specimens were punched from a 1.2 mm thick steel strip, cleaned, baked at 1080 ° C for 4 hours under a hydrogen atmosphere and then cooled in an oven to 300 C. The climate test described in DIN 50017 was performed on these samples. with 28 cycles of 8 hours at 55 ° C and 90 to 96% humidity and 16 hours at 25 ° C and 95 to 99% humidity.

copper and / or molybdenum (see Table 3). Alloys with a nickel content of less than 55% by weight. exhibit any stronger surface corrosion effects than alloys with a nickel content of more than 75% at the end of this alternating climate test (B. Gehrmann, H. Hattendorf, A. Kolb-Telieps, W. Kramer, W. Mottgen: Material and Corrosion 48, 535-541 (1997)) and thus, without additional anti-corrosion measures, do not meet the above requirements for the relay material in terms of corrosion resistance. The magnetic properties required by DIN 17405, on the other hand, were fulfilled, 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-76Ni CrCu 16.05 75.95 0.10 2.00 4.96 0.60 0.22 0.87 2.5 Fe-77NiTi, Nb 14.80 77.30 0.01 0.10 4.50 0.49 0.24 2.4 2.5 Fe-77NiMo, Cu 13.85 77.15 3.45 0.10 4.47 0.53 0.33 0.85 2.5 Fe-80Ni- Mo 13.95 80.10 4.75 0.05 0.09 0.50 0.33 0.44 2.5 Fe-8INi- Mo 12.45 81.50 5.27 0.03 0.05 0.43 0.13 1.23 2.5

At the corroded sites of these samples, after alternating climatic tests, it was through

REM / EDX sulfur found.

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 praseodymium and / or neodymium. In order for all sulfur to be reliably bound, enough rare earth atoms must be present. Starting from, for example, the formation of cerium sulphide with the highest proportion of CeS, this is the case when more cerium atoms than sulfur atoms are present in the alloy.

Accordingly, the cerium content must be in% by weight. 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, praseodymium 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 Anfangspermeabiliten von Ni-Fe-Legierung, Z. Angew.Physik 32: 236-241). Surprisingly, the addition of rare earths can be dosed such that the megnatic values of permeability and coercive intensity lie within the variation limits of 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, the relay materials can exhibit only a very low content of non-metallic inclusions according to DIN 50602 (method M). Therefore, also in the case of deoxidation with cerium, possibly with rare earth metal cerium, lanthanum, praseodymium and neodymium, the maximum values of sulfide inclusions in the fibrous form of SS must be less than 0.1 or more. 1.1, maximum values of oxidic inclusions in dissolved form of OA (alumina) of less than 2.2, respectively

3,2 resp. 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 the globular form of OG less than 8.2 resp. 9.2.

DETAILED DESCRIPTION OF THE INVENTION

By way of example, a steel-alloy alloy containing about 48% nickel and small manganese and silicon additives (batches E5407 and E0545) was melted by steelworking in a 30t arc furnace and compared to batches of very similar composition but without prior art additives (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 figures are in% by weight.

element State of the art Composition according to the invention Medznc 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 Al 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 Cer 0,014 0,011 la 0,008 0,005 pr 0,001 0,001 nd 0,003 0,003 Rare earth pretty 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 0 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. 00:05 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 the batch according to the invention E5407 and E0545 is more than 4.4 times greater than the sulfur content in% by weight.

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 applies to 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 subjected to evaporation at 970 ° C for 6 hours under a hydrogen atmosphere and then cooled to below 300 ° C in an oven. A second portion of the samples was subjected to baking at 1030 ° C for 2 hours under a hydrogen atmosphere and then cooled to below 300 ° C in an oven. All samples were subjected to a shortened climate 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 a shortened climate test: Samples with corrosion attack / total number of samples tested notes 970 ° C / 6 hours 1030 ° C / 2 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 for both comparative batches T5405 and T5406 no corrosion points were present on both sides in each sample.

The addition of a strong deoxidizing and desulfurizing agent such as cerium can, as mentioned above, adversely affect the magnetic properties due to the presence of reaction products remaining in the material. Surprisingly, the magnetic values of permeability and coercive intensity exhibited by 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 Koerci- tive the intensive sity Min. magnetic induction (T) Static Values} Mark. You have- Riyal number hc (A / m) at coercive intensity H in A / m μ4 μηηΐλ 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 U2 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 the two batches of prior art compositions shown in Table 7 were studied.

The two batches differed essentially only in the different contents of the soils taken.

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 0 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 T0626 with a total rare earth content of 0.054%, hot forming cracks formed and the block then went into scrap. Such a high rare earth content leads to worse thermoforming properties. Batch T0624, on the other hand, was both rolled and hot rolled with a thickness of about 4 mm. Since the rare earths behave chemically similarly, it is necessary according to the invention 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 DIN 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 or 1,1 2.2 or 3.2 resp. 4.2 5,2 resp. 6,2 resp. 7.2 8.2 and 9.2, respectively 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 - -

The batch T2536 has a maximum value of 2.7 (method M) in the case of oxidic inclusions in the fibrous form, this value being 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. Accordingly, the content of non-metallic inclusions according to the invention is limited as follows:

Maximum values according to DIN 50602 sulfide inclusions in fibrous form SS are less than or equal to 0.1 or 1.1, maximum values according to DIN 50602 oxidized inclusions in dissolved form OA (alumina) less than or equal to 2.2 or 3.2 resp. . 4.2, maximum values according to DIN 50602 of oxide inclusions in fiber 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 OG less than or equal to 8.2 or 8.2. 9.2. All of the lots listed in Table 8 meet the conditions for non-metallic inclusions.

Claims (14)

Magnetically soft ferro-nickel alloy containing nickel in an amount of 35 to 65 wt. and one or more cerium, lanthanum, praseodymium and neodymium rare earths, as well as melt impurities, wherein 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 the; % wt. is at least 4.4 times greater than the sulfur content in% by weight. 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. % manganese, max. % silicon and admixtures at most 0.002 wt. % 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. The method of 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 resp. 1.1 - maximum values of oxidic inclusions in dissolved form of OA (alumina) of less than 2,2 or 3,2 resp. 4.2 - maximum values of oxide inclusions in the fibrous form of OS (silicates) less than 5,2 resp. 6,2 resp. 7.2 maximum values of oxidic inclusions in globular form of OG less than 8.2 resp. 9.2. Method according to claim 5 or 6, characterized in that after the production of the alloy parts, 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 iron-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 or poles. pole adapters pole plates and anchors of holding magnets electromagnets. I Use of a magnetically soft ferro-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. and Use of a magnetically soft iron-nickel alloy according to any one of claims 1 to 4 as a 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.