EP1051714B1 - 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 soft magnetic nickel-iron alloy.

From the book "Magnetic materials and their technical application" by Carl Heck, Hütig Verlag, Heidelberg 1975, p. 349ff is known for the material of armature and yoke are used in relays with soft magnetic materials.

The main requirements for the material are a high saturation flux density in order to to achieve high magnetic holding forces with low energy, high permeability, thus a small magnetic field strength, i.e. a low excitation current and a high flux density can be generated in the air gap and so one great attraction to the anchor. Allow low coercivity easy opening of the relay when the excitation current drops.

In addition to the magnetic requirements for a relay material the requirement of corrosion resistance in an alternating climate test, since a correct operation of the relay in any weather condition is required This requirement in the case of insufficiently corrosion-resistant materials, only by additional The finished parts are coated with a corrosion-resistant layer become.

The contact surfaces of anchor and yoke must have the smallest possible gap have to a high permeability of the magnetic circuit from yoke and Reach anchor. They must not be damaged by switching the relay as the trigger current of the relay changes.

Similar requirements also exist for other molded and stamped parts soft magnetic materials.

The magnetic requirements for a relay material are described in DIN 17405 "Soft magnetic materials for DC relays". The following Table 1 shows an extract from DIN 17405. Relay materials according to DIN 17405 material Coercive field strength min. magnetic induction in T Characteristic alloy components Nickname Material number Max. Hc in A / m at a field strength H in A / m Mass fraction in% 20th 50 100 300 500 4000 RNi 24 1.3911 24th 0.20 0.45 0.70 0.90 1.00 1.18 36 Ni RNi 12 1.3926 12th 0.50 0.90 1.10 1.25 1.35 1.45 50 Ni RNi 8 1.3927 8th 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 amounts of Cu, Cr, Mo RNi 2 2.4595 2.5 0.50 0.65 0.70 0.75

DIN 17745 "Wrought alloys made of nickel and iron describes the alloy Ni 48 (material numbers 1.3926 and 1.3927) as the starting materials for the grades RNi 12 and RNi 8 (see table 2). The alloy Ni 36 (material number 1.3911) is the starting material for the grades RNi 24. Extract from DIN 17745 Nickname Material number Composition in mass% Alloy components Permissible admixtures Ni 48 1.3926
1.3927 Ni min. 46, Fe 49 to 53 C 0.05, Mn 0.5, Si 0.3 Ni 36 1.3911 approx. 36

When melting nickel-iron alloys are in addition to the desired Alloy elements or deoxidation and / or desulfurization elements like manganese, silicon and aluminum. In addition, certain minimal additions of oxygen, sulfur, phosphorus, carbon, Do not avoid calcium, magnesium, chromium, molybdenum, copper and cobalt, if you compare these alloys with usual because of the cheap cost Wants to manufacture steel mill technology. Under common steel mill technology this involves melting in an open arc furnace with subsequent ladle metallurgy and / or VOD treatment for deoxidation, desulfurization and Degassing understood. Then the block or the continuous casting slab is in one or two steps thermoformed to a thickness of about 4 mm and then Cold-formed to its final thickness, if necessary with intermediate annealing. The magnetic Properties deteriorate, as z. B. described in DE 19612556 A1 by adding carbon, nitrogen, oxygen, Sulfur and on non-metallic inclusions. Non-metallic contaminants arise due to the required deoxidation and / or desulfurization treatment the melt before pouring. Depending on the deoxidation and / or Desulfurizing agents are e.g. Oxides of calcium, magnesium or aluminum.

To avoid this difficulty, soft magnetic materials are therefore used with the highest requirements according to the state of the art selected clean feed materials manufactured using vacuum technology, as expressly stated in DE-A 3910147 and in DE-C 1259367 becomes. Another possibility known from the literature is that in DE-A 4105507 described very complex and expensive electroslag remelting process under vacuum or inert gas from previously under vacuum or inert gas melted blocks.

JP-A 07166281 relates to a magnetic alloy for magnetic heads made of Ni and Fe with additions of Nd, Pr or Sm. Here is the amount of Ni over 78% by weight.

The object underlying the invention is a soft magnetic Melt iron-nickel alloy that meets the requirements described magnetic properties, corrosion and wear resistance suffices and for a number of preferred applications finds soft magnetic components.

This task is solved by a soft magnetic iron-nickel alloy with a nickel content of 35 - 65% by mass and one or more of the sides Earth cerium, lanthanum, praseodymium or neodymium as well as melting-related Impurities, the sum of rare earths between 0.003 and 0.05 mass% and the total proportion of rare earths cerium, Lanthanum, praseodymium and neodymium in mass% at least by a factor of 4.4 is greater than the sulfur content in mass%.

Advantageous developments of the subject matter of the invention are the associated See subclaims.

The alloy according to the invention is preferably produced by steelwork technology, ie by melting in an open arc with subsequent ladle metallurgy and / or VOD treatment (vacuum oxidation-decarburization) for deoxidation, desulfurization and degassing. Thereafter, the block or the continuous casting slab is thermoformed in one or two steps up to a thickness of about 4 mm and then cold-formed to final thickness, if necessary with intermediate annealing to adjust the hardness required for the production of parts from this strip.
Following the production of parts from this alloy and the annealing of these parts at temperatures between 800 and 1150 ° C., these parts can achieve coercive field strengths of less than 8 A / m.

Preferred applications of the alloy according to the invention include Relay parts, like yokes and anchors.

• Ventildeckel und Ventiltöpfe von Magnetventilen
• Joche bzw. Polstücke bzw. Polschuhe bzw. Polbleche und Anker von Halteund Elektromagneten
• Spulenkerne und Statoren von Schrittschaltmotoren sowie Rotoren und Statoren von Elektromotoren
• Form- und Stanzteile von Sensoren, Positionsgebem und -aufnehmem
• Magnetköpfe und Magnetkopfabschirmungen
• Abschirmungen, wie z. B. Motorabschirmungen, Abschirmbecher für Anzeigeinstrumente und Abschirmungen für Kathodenstrahlröhren.

In addition, the iron-nickel alloy according to the invention can also be usefully used for the following further applications:

• Valve covers and valve pots of solenoid valves
• Yokes or pole pieces or pole shoes or pole sheets and armatures of holding and electromagnets
• Coil cores and stators of stepper motors as well as rotors and stators of electric motors
• Molded and stamped parts from sensors, position sensors and sensors
• Magnetic heads and magnetic head shields
• Shields such as B. motor shields, shield cups for display instruments and shields for cathode ray tubes.

Flat samples were punched out of a 1.2 mm thick band produced with steelwork technology, cleaned, subjected to an annealing treatment of 1080 ° C./4 hours under hydrogen and then cooled to 300 ° C. in an oven. The climate test described in DIN 50017 was carried out on these samples with 28 cycles of 8 hours at 55 ° C / 90 to 96% humidity and 16 hours at 25 ° C and 95 to 99% humidity. Alloys with nickel contents of 36 mass% to 81 mass% and some additives such as chromium, copper and / or molybdenum were examined (see table 3). Alloys with a nickel content of less than or equal to 55% by mass all show significantly stronger signs of corrosion on the surface after the end of this alternating climate test than the alloys with nickel contents of more than 75%. (B. Gehrmann, H. Hattendorf, A. Kolb-Telieps, W. Kramer, W. Möttgen, in Material and Corrosion 48, 535-541 (1997)) and thus do not meet the above-described requirements for a relay material in terms of corrosion resistance without additional corrosion-improving measures. The magnetic properties required by DIN 17405, on the other hand, were met, as the coercive field strengths Hc given in Table 3 demonstrate (prior art). Composition in mass% Hc in A / m Max. Hc according to DIN 17405 alloy Fe Ni Mon Cr Cu Mn Si Fe-36Ni 62.90 36.50 0.01 0.03 0.03 0.27 0.18 4.2 24th 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 8th Fe-50Ni 48.85 50.70 0.01 0.04 0.03 0.21 0.05 3.5 8th Fe-55Ni 43.70 55.45 0.06 0.06 0.05 0.42 0.14 12.5 Fe-76Ni Cr Cu 16.05 75.95 0.10 2.00 4.96 0.60 0.22 0.87 2.5 Fe77Ni-Ti, Nb 14.80 77.30 0.01 0.10 4.50 0.49 0.24 2.4 2.5 Fe-77Ni-Mo, 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-81Ni-Mo 12.45 81.50 5.27 0.03 0.05 0.43 0.13 1.23 2.5

In the corroded areas of these samples was after the end of the alternating climate test found sulfur using REM / EDX.

The improvement in corrosion behavior according to the invention is surprisingly by desulfurizing the more corrosion-prone nickel-iron alloys with a nickel content of 35 mass% to 65 mass% Cer reached. This is preferably done with a mixed metal from the chemical behavior of very similar rare earths cerium and / or lanthanum and / or praseodymium and / or neodymium. For all the sulfur to bind securely, sufficient rare earth atoms must be present. If you start with education e.g. cerium sulfide with the largest cerium content CeS out, this is the case if there are more cerium atoms than sulfur atoms in the alloy available.

The cerium content in mass% must then be at least a factor of 4.4 higher be than the sulfur content in% by mass in order to completely bind the To reach sulfur through cerium. The same applies to the other rare ones Earth lanthanum, praseodymium and / or neodymium and for the total content Rare Earth.

As previously mentioned, the addition of such a strong deoxidation and Desulfurizing agents such as cerium by those remaining in the material Reaction products that impair magnetic properties (A. Hoffmann, About the influence of different deoxidation elements on the deformation and the initial permeability of Ni-Fe alloys, Z. Appl. Physik 32, page 236 to 241). Surprisingly, the addition of rare earths can be done in this way dose that the magnetic values of permeability and coercive force within the usual range of fluctuation according to the prior art melted batches.

It is known that deoxidation residues from the contact surfaces of the relay break out, stay between these surfaces and through their z. B. at oxidic residues greater hardness when switching the relay further can destroy finely ground contact surfaces. Therefore the relay materials are allowed only a very low content of non-metallic inclusions DIN 50602 (method M). That is why deoxidation also has to be done with cerium or a mixed metal from the rare earths cerium, lanthanum, praseodymium, Neodymium the maximum size values of the sulfidic inclusions in line form SS less than 0.1 or 1.1, the maximum size values of the oxide inclusions in dissolved form OA (aluminum oxides) less than 2.2 or 3.2 or 4.2, the maximum size values of the oxide inclusions in line form OS (silicates) less than 5.2 or 6.2 or 7.2 and the maximum size values of the oxidic Inclusions in globular form OG less than 8.2 or 9.2.

As an example, a nickel-iron alloy with approx. 48% nickel and minor additions of manganese and silicon was melted using steelwork technology in a 30-ton arc furnace (batches E5407 and E0545) and with batches of a very similar composition, but without the addition of rare earths which correspond to the prior art (batches T4392, T5405 and T5406) compared. The exact compositions are shown in Table 4.

Small amounts of boron can be added to improve punchability as with batches T4392, T5405, T5406 and E5407. The amount of the cerium content in mass% in the batch according to the invention E5407 and E0545 is more than the factor 4.4 larger than the sulfur content in Dimensions %.

After the melting, block and then hot strip rolling followed about 4 mm and a subsequent cold forming to final thickness 1.0 mm.

Round samples with a diameter of 25.5 mm were punched out of them. This applies to all batches except E0545. Here a piece of approx. 15 mm x15 mm x 5 mm from a cast sample was used, the surfaces of which were ground. All samples were cleaned and part of the samples were subjected to an annealing treatment of 970 ° C / 6 hours under hydrogen and then cooled in the oven to below 300 ° C. The second part of the samples was subjected to an annealing treatment of 1030 ° C / 2 hours under hydrogen and then cooled in the oven to below 300 ° C. All samples were subjected to the shortened climate test of 2 days with a temperature / humidity change every 3 hours from 25 ° C and 55% humidity to 55 ° C and 98% humidity. The samples lay individually flat in glass dishes, so that the more severe conditions of crevice corrosion still prevailed on the underside. The result is shown in Table 5. Climate test results Batch After a shortened climate test: samples with corrosion approaches / total number of samples tested Remarks 970 ° C / 6 hours 1030 ° C / 2 hours T5405 10/10 10/10 On both sides, several unique points per sample T5406 10/10 10/10 On both sides, several unique points per sample E5407 0/10 0/10 E0545 0/1

There was no corrosion to batch E5407 and E0545 according to the invention find, while in the two comparison batches T5405 and T5406 each Sample corrosion spots found on both sides.

The addition of such a strong deoxidizing and desulfurizing agent as cerium can, as previously described, impair the magnetic properties due to the reaction products remaining in the material. Surprisingly, the magnetic values of permeability and coercive field strength, which show the batches E5407 and E0545 according to the invention, are within the usual range of fluctuation of the batches melted according to the prior art, as shown in Table 6. Magnetic values of batches according to the prior art (T) and the batches (E) according to the invention measured on samples of 1 mm thickness after annealing from 1080 ° C. for 4 hours under hydrogen and cooling in the oven to 450 ° C. The composition of the batches is shown in Table 4. material Coercive field strength min. magnetic induction in T Static values Nickname Material number Hc in A / m at a field strength H in A / m µ4 µmax 20th 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 10,000 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

Second, two batches were made with the composition shown in Table 7 according to the prior art in their properties in the block and Hot strip rolling considered.

The only difference between the two batches is the difference in the rare earth content. element Limits Batch T0626 T0624 Ni 36.2 36.45 Mn 0.25 0.26 Max. 0.5 Si 0.20 0.19 Max. 0.3 Al 0.009 0.009 Max. 0.010 Mg 0.0030 0.003 Max. 0.002 Approx Max. 0.002 cerium 0.029 0.001 La 0.017 Pr 0.002 Nd 0.006 Total rare earths 0.054 0.002 Max. 0.050 S 0.002 0.002 Max. 0.0040 O 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 Mon 0.06 0.06 Cu 0.05 0.09 Co 0.05 0.03 B - -

For batch T0626 with a total rare earth content of 0.054% Cracks formed during hot forming and the block was then scrap. Such a high content of rare earths leads to poorer thermoforming behavior. Batch T0624, on the other hand, could be used on both block and Roll hot strip with a thickness of approx. 4 mm. Because the rare earth Behavior chemically similar, according to the invention is the content of the sum of the rare Earth cerium, lanthanum, praseodymium, neodymium to a maximum of 0.05% by mass limit to avoid thermoforming problems.

Table 8 shows the examination of the content of non-metallic inclusions according to DIN 50602 in various batches according to the prior art (T) and the batches (E) according to the invention. material Degree of purity according to DIN 50602: Maximum size value (method M) Batch SS OA OS Upper floor Limits 0.1 or 1.1 2.2 or 3.2 or 4.2 5.2 or 6.2 or 7.2 8.2 or 9.2 E5407 k. B. 2.1 k. B. 8.0 E0545 k. B. 2.2 k. B. 8.1 T4392 k. B. 2.2 k. B. 8.0 T5405 k. B. 2.0 k. B. 8.0 T5406 k. B. 2.2 k. B. 8.0 T5477 k. B. 2.1 k. B. 8.1 T5488 k. B. 2.0 k. B. 8.0 T2536 k. B 2.7 k. B kB

The batch T2536 has a maximum in the form of oxide inclusions in line form Size value of 2.7 (method M). This value is for the use of this Batch too high as material for relay parts. It leads to wear on the Contact surfaces of the relay and has the loss of functionality of the relay result. The content of non-metallic inclusions is therefore according to the invention limited as follows:

The maximum size values according to DIN 50602 of the sulfidic inclusions in Line shapes SS are less than or equal to 0.1 or 1.1, the maximum size values according to DIN 50602 of the oxidized inclusions in dissolved form OA (aluminum oxides) less than or equal to 2.2 or 3.2 or 4.2, the maximum size values according to DIN 50602 the oxide inclusions in line form OS (silicates) less than or equal to 5.2 or 6.2 or 7.2 and the maximum size values according to DIN 50602 of the oxidic inclusions in globular form OG less than or equal to 8.2 or 9.2. All others in table 8 batches listed meet the requirements for the content of non-metallic Inclusions.

Claims (14)

1. Soft magnetic iron-nickel alloy having a nickel content of 35-65 % by mass and comprising one or more of the rare earths cerium, lanthanum, praseodymium, neodymium as well as impurities resulting from the melting process, the sum of the rare earths being between 0.003 and 0.05 % by mass and the total part of the rare earths cerium, lanthanum, praseodymium and neodymium in % by mass being greater by at least factor 4.4 than the sulphur content in % by mass.
2. Soft magnetic alloy according to claim 1,
   characterized in that
   the alloy comprises a cerium content of maximum 0.05 % by mass.
3. Soft magnetic alloy according to claim 1 or 2,
   characterized in that
   the alloy comprises max. 0.5 % by mass manganese, max. 0.5 % by mass silicium and admixtures of max. 0.002 % by mass magnesium, max. 0.002 % by mass calcium, max. 0.010 % by mass aluminium, max. 0.004 % by mass sulphur, max. 0.004 % by mass oxygen and further small quantities of admixtures resulting from the melting process as deoxidation and/or desulphurization additions.
4. Soft magnetic alloy according to one of the claims 1 through 3,
   characterized in that
   the alloy contains up to 0.002 / by mass boron.
5. Method for melting a soft magnetic iron-nickel alloy according to claim 1 through 4,
   characterized in that
   the alloy is molten in the open arc furnace with following ladle metallurgy and/or VOD treatment for deoxidation, desulphurization and degasifying.
6. Method according to claim 5,
   characterized in that
   the following parameters are set in the molten alloy:

   the maximum size values of the sulphured inclusions in line form are beneath 0.1 respectively 1.1

   the maximum size values of the oxidic inclusions in dissolved form OA (aluminium oxide) are beneath 2.2 respectively 3.2 respectively 4.2

   the maximum size values of the oxidic inclusions in line form OS (silicates) are beneath 5.2 respectively 6.2 respectively 7.2

   the maximum size values of the oxidic inclusions in globular form OG are beneath 8.2 respectively 9.2.
7. Method according to claim 5 or 6,
   characterized in that
   after manufacturing parts of this alloy and annealing these parts at temperatures between 800°C and 1150°C, coercive field strengths of less than 8A/m are obtained.
8. Use of a soft magnetic iron-nickel alloy according to one of the claims 1 though 4 as material for relay parts.
9. Use of a soft magnetic iron-nickel alloy according to one of the claims 1 though 4 as material for valve bonnets and pots of solenoid valves.
10. Use of a soft magnetic iron-nickel alloy according to one of the claims 1 though 4 as material for yokes respectively pole pieces respectively pole shoes respectively pole sheets and armatures of no-work magnets and electromagnets.
11. Use of a soft magnetic iron-nickel alloy according to one of the claims 1 though 4 as material for coil cores, stators of step motors and rotors and stators of electromotors.
12. Use of a soft magnetic iron-nickel alloy according to one of the claims 1 though 4 as material for structural and punched parts of sensors, position transmitters and position receivers.
13. Use of a soft magnetic iron-nickel alloy according to one of the claims 1 though 4 as material for magnet heads and magnet head shields.
14. Use of a soft magnetic iron-nickel alloy according to one of the claims 1 though 4 as material for shields.