EP1318529A2 - Surface hardened soft magnetic actuator part and fabrication process - Google Patents

Abstract

Soft magnetic actuator part has a surface hardness of at least 150 HV 0.01 increased by nitriding. The N concentration has the following deep profile: a top value of maximum N concentration of at least 0.2 wt.% in the depth region of up to 1 mu m, an N-concentration of at least 0.25 wt.% in the depth region of 1 mu m, an N-concentration of at least 0.1 wt.% in the depth region of 2 mu m and an N-concentration of at least 0.05 wt.% in the depth region of 5 mu m. <??>An Independent claim is also included for a process for the surface treatment of an electromagnetic actuator part comprising nitriding at 380-480 degrees C at a nitriding number KN of approximately 10, preferably in an oxygen atmosphere (oxynitriding) at an oxidation number KO of approximately 0.20.

Description

The invention relates to a surface-hardened soft magnetic Actuator part and a method for its production.

When using relay parts, RCD switches, electromagnetic Injectors, electromagnetic valve adjusters in motor vehicles, textile machines and others In addition to high corrosion resistance, actuators and a high hardness at the same time very good soft magnetic Properties of the individual soft magnetic actuator parts required.

It has been around for a long time to meet these requirements known, the actuator parts used on their surfaces to be provided with a treatment, in particular this Nitriding. However, the known nitriding processes Disadvantage that the surfaces are chemically strong be changed, i.e. usually nitride deposits in have the surface layer. This solid-state chemical Change takes into account changes in solid state physics themselves, leading to a deterioration in soft magnetic Properties on the surfaces of the treated parts and thus deterioration of the soft magnetic parts overall lead.

The plasma nitriding of relay parts is known from the literature, with the aim of improving the corrosion resistance and reducing the abrasion of the functional surfaces]. This is done according to T. Satoshi, Electromagnetic Relay and its Manufacture, Jap. Patent application 10-92286, published April 10, 1998, filed September 13, 1996 by the company Nippon Koshuha Gijutsu KK by plasma nitriding at 480 to 590 ° C creating a connection layer of iron nitride Fe ₄ N on the surface, corresponding to a phase proportion of Fe ₄ N of 100% in the surface layer. The presence of a plasma with nitrogen ions and the relatively high treatment temperatures ensure the formation of this connection layer. This application states that even with a layer thickness of 1.5 μm, neither surface hardness nor corrosion resistance are sufficient, so that layer thicknesses of iron nitride of 2 to 20 μm are ultimately proposed.

However, such large layer thicknesses are not acceptable for particularly sensitive relays, such as residual current circuit breaker relays, or other electromagnetic actuators with a high effective permeability of the magnetic circuit composed of different parts. On the one hand, these layers, magnetically speaking, lead to an enlargement of the air gap and thus considerably reduce the effective permeability of the magnetic circuit. In addition, it is known that tensions which inevitably arise when such a connection layer grows and which are also unavoidable later in operation due to different thermal expansion in comparison with the base material, lead to a deterioration in the magnetic properties, which are manifested, for example, in a significant increase in the coercive field strength. For sensitive relays and other applications with high permeability of the magnetic circuit, a method should therefore be sought which largely avoids the formation of a connection layer. This is achieved by keeping the N content in the surface layer below 5% by weight, if possible, and the formation of a surface connection layer being hardly detectable by practical means, ie with layer thicknesses well below 0.5 µm and a phase proportion of Fe ₄ N in the depth range up to 1 µm below the surface below a practical detection limit of 10% by weight. In addition, this method must also be suitable for effectively nitriding soft magnetic alloys with higher Ni or Co contents.

The object of the present invention is therefore to provide new surface-treated to provide soft magnetic actuator parts, which has a higher surface hardness at the same time compared to slight losses in the soft magnetic properties have the state of the art.

According to the invention, this object is achieved by an actuator part solved according to claim 1. Refinements and training of the inventive concept are the subject of the dependent claims.

According to the invention, a soft magnetic actuator part made of soft magnetic alloy with a surface hardness increased by nitriding of at least 150 HV0.01 is provided, which has the following depth profile of the N concentration: Depth range up to 1 µm Peak value of the maximum N concentration of at least 0.2%, at a depth of 1 µm an N concentration of at least 0.25%, at a depth of 2 µm an N concentration of at least 0.1%, at a depth of 5 µm an N concentration of at least 0.05%.

In the invention, a degradation is achieved the solid-state chemical and thus the solid-state physical Surface properties changed by the Nitriding process is minimized as far as possible.

Usually at temperatures of 510 ° C or 570 ° C and nitriding indices K _N ≤1, the susceptibility to corrosion of the alloys due to nitriding increases considerably and the usual climatic tests are no longer passed by the nitrided actuator parts. To prevent this, the present invention works in a lower temperature range between 380 ° C and 480 ° C. It is thus achieved to reduce the penetration depth in order to keep the tension of the surface layer securely connected with the nitriding as low as possible in order to optimize the magnetic properties of the parts. At these temperatures, a nitriding process can only be achieved with exceptionally high nitriding parameters.

In all cases the method of oxynitriding was chosen. The nitriding index K _{N is} used to describe the nitriding conditions. The thermodynamic equilibrium of the NH ₃ decomposition reaction NH ₃ ½ N ₂ + 1.5 H ₂

is far from being achieved under the usual nitriding conditions. The presence of atomic nitrogen from the NH ₃ decomposition reaction is decisive for the nitriding process. It is therefore expedient and customary for the process to use the nitriding index K N = P (NH 3 ) / P (H 2 ) 1.5 . to describe the ratio of undecomposed to decomposed NH ₃ . The treatment is typically carried out with a nitriding index of approximately 10. The oxygen _{activity is also} described via the oxidation number K _O : K O = P (H 2 O) / P (H 2 ).

For the result, since the low temperatures act far from the thermodynamic equilibrium, it makes a difference whether K _{O is set} by adding air or by moistening or injecting water. The nitriding is typically carried out at an oxidation number of approximately 0.2. The measurement is carried out using a ZrO ₂ probe, which is typically operated at a higher temperature, in this case at 825 ° C. The thermodynamic equilibrium is established there - that is, no difference between the addition of air or H ₂ O. However, there is no balance in the colder nitriding atmosphere. You then have a much higher oxygen potential when K _{O is set} via air - the samples start up. With H ₂ O addition, the actual oxygen potential is much lower - the samples remain blank.

The investigations were carried out on a total of 4 different soft magnetic alloys, the nominal composition (in% by weight) of which is shown in the following table. alloy Ni Co Cr Mo Mn Si Ti Fe PERMENORM 5000V5 47.5 <0.3 <0.1 <0.2 0.5 0.2 <0.01 rest CHRONOPERM 50 47.5 <0.3 2.0 <0.1 0.45 0.15 <0.01 rest RECOVAC 50 48.0 <0.3 <0.1 <0.2 0.5 0.2 1.7 rest VACOFLUX 17 <0.1 17.0 2.0 0.8 <0.1 <0.1 <0.01 rest The composition of the alloys near the surface was analyzed by means of the optical glow discharge spectroscopy GDOS. Tables 1 to 4 contain selected N and O concentrations, which were taken from the diagrams.

Tab. 1 shows the nitrogen concentration in% by weight at different penetration depths t in µm. Nitriervariante N (% by weight) t = 1 micron t = 2 .mu.m t = 5 .mu.m CHRONOPERM 50 8h / 570 ° C / K _N = 1.0 / + H ₂ O 0.87 0.61 0.50 8h / 570 ° C / K _N = 0.5 / + H ₂ O 0.65 0.51 0.42 8h / 570 ° C / K _N = 0.25 / + H ₂ O 1.00 0.72 0.49 8h / 570 ° C / K _N = 0.18 / + H ₂ O 0.46 0.38 0.26 8h / 510 ° C / K _N = 0.5 / + H ₂ O 0.94 0.39 0.12 24h / 380 ° C / + air 1.56 1.08 0.21 24h / 410 ° C / + air 0.93 0.72 0.18 24h / 380 ° C / + H ₂ O 0.41 0.12 0.06 24h / 440 ° C / + H ₂ O 1.24 0.90 0.53 12h / 460 ° C / + H ₂ O 1.05 0.80 0.40 8h / 480 ° C / + H ₂ O 1.68 1.30 0.78 18h / 450 ° C / + H ₂ O 1.23 0.86 0.45 PERMENORM 5000V5 8h / 570 ° C / K _N = 1.0 / + H ₂ O 0.26 0.20 0.21 8h / 570 ° C / K _N = 0.5 / + H ₂ O 0.23 0.18 0.17 8h / 570 ° C / K _N = 0.25 / + H ₂ O 0.13 0.11 0.10 8h / 570 ° C / K _N = 0.18 / + H ₂ O 0.16 0.13 0.11 8h / 510 ° C / K _N = 0.5 / + H ₂ O 0.16 0.13 0.09 24 h / 380 ° C / air + 1.32 0.90 0.18 24h / 410 ° C / + air 0.69 0.60 0.21 24h / 380 ° C / + H ₂ O 0.24 0.12 0.06 24h / 440 ° C / + H ₂ O 0.68 0.50 0.31 12h / 460 ° C / + H ₂ O 0.87 0.62 0.37 8h / 480 ° C / + H ₂ O 1.12 0.81 0.56 18h / 450 ° C / + H ₂ O 0.77 0.60 0.37 VACOFLUX 17 8h / 570 ° C / K _N = 1.0 / + H ₂ O 1.32 0.88 0.72 8h / 570 ° C / K _N = 0.5 / + H ₂ O 0.74 0.62 0.57 8h / 570 ° C / K _N = 0.25 / + H ₂ O 0.66 0.54 0.49 8h / 570 ° C / K _N = 0.18 / + H ₂ O 0.68 0.58 0.52 8h / 510 ° C / K _N = 0.5 / + H ₂ O 0.10 0.08 0.06 24h / 380 ° C / + air 0.36 0.18 0.12 24h / 410 ° C / + air 0.90 0.66 0.30 24h / 380 ° C / + H ₂ O 0.12 0.10 0.09 24h / 440 ° C / + H ₂ O 1.18 0.87 0.62 12h / 460 ° C / + H ₂ O 0.93 0.74 0.67 8h / 480 ° C / + H ₂ O 8.76 6.56 5.02 18h / 450 ° C / + H ₂ O 1.53 1.20 1.03

The following Table 2 shows the nitrogen concentration in% by weight at different penetration depths in µm. The maximum N concentration N _max , half and 10% of the maximum N concentration are given, each determined from the GDOS profile. In addition, the depth in µm. alloy N _max (%) N _max / 2 (%) N _max / 10 CHRONOPERM 50 24h / 380 ° C / + air 1.67 at 0.62µm 0.84 at 2.5µm At 5.38 µm 24h / 410 ° C / + air 0.99 at 0.67µm 0.50 at 2.87 µm At ≈20µm 24h / 380 ° C / + H ₂ O 0.53 at 0.54µm 0.27 at 1.36 µm > ≈10μm 24h / 440 ° C / + H ₂ O 1.30 at 0.51 µm 0.65 at 3.85 µm At 8.46 µm 12h / 460 ° C / + H ₂ O 1.18 at 0.62µm 0.59 at 3.44 µm At 9.23 µm 8h / 480 ° C / + H ₂ O 1.74 at 0.64µm 0.87 at 4.49 µm At 12.5 µm 18h / 450 ° C / + H ₂ O 1.60 at 0.51 µm 0.80 at 2.28µm At 8.0 µm PERMENORM 5000V5 24h / 380 ° C / + air 1.53 at 0.67µm 0.76 at 2.46 µm At 5.44 µm 24 h / 410 ° C / air + 0.72 at 0.62µm 0.36 at 3.59µm At ≈13µm 24h / 380 ° C / + H ₂ O 0.28 at 0.64 µm 0.14 at 1.69 µm At »10µm 24h / 440 ° C / + H ₂ O 0.87 at 0.26µm 0.44 at 2.92 µm At 10.56 µm 12h / 460 ° C / + H ₂ O 0.93 at 0.77µm 0.47 at 3.54 µm At 11.49 µm 8h / 480 ° C / + H ₂ O 1.30 at 0.45µm 0.65 at 3.33 µm At 13.33µm 18h / 450 ° C / + H ₂ O 0.85 at 0.66µm 0.43 at 4.16µm At 12.74 µm VACOFLUX 17 24h / 380 ° C / + air 1.08 at 0.26µm 0.54 at 0.77µm At ≈20µm 24h / 410 ° C / + air 1.68 at 0µm 0.84 at 1.59 µm At> 20µm 24h / 380 ° C / + H ₂ O 0.15 at 0.41 µm 0.08 at >> 10µm At >>> 10µm 24h / 440 ° C / + H ₂ O 1.39 at 0.51 µm 0.70 at 3.85 µm At ≈48µm 12h / 460 ° C / + H ₂ O 1.05 at 0.62µm 0.50 at ≈14µm At >> 20µm 8h / 480 ° C / + H ₂ O 8.76 at 1.00µm 4.38 at ≈8µm At >> 80µm 18h / 450 ° C / + H ₂ O 1.77 at 0.38µm 0.89 at 12.72 µm At >> 30µm

It applies to all 3 alloys that the maximum concentration N _max and the depth of penetration decrease with decreasing temperature. This trend can be compensated for by an extended nitriding time or a higher nitriding index. The N uptake is lowest for PERMENORM 5000V5. VACOFLUX 17 absorbs the most at high temperatures. At the lower temperatures, CHRONOPERM 50 absorbs the most nitrogen.

Nitriding tests were also undertaken on anchors made of RECOVAC 50. In addition to the results for RECOVAC 50, it should be noted that unpolished areas that still had the TiO ₂ tarnish layer from the final annealing showed no hardening effect. The TiO2 layer obviously acts as a very efficient diffusion barrier.

Tab. 3 shows the oxygen concentration in% by weight at different penetration depths t in µm. Nitriervariante 0 (% by weight) t = 1 micron t = 2 .mu.m t = 5 .mu.m CHRONOPERM 50 8h / 570 ° C / K _N = 1.0 / + H ₂ O 0.71 0.31 ≤ 0.08 8h / 570 ° C / K _N = 0.5 / + H ₂ O 0.70 0.19 0 8h / 570 ° C / K _N = 0.25 / + H ₂ O 1.89 0.63 0.31 8h / 570 ° C / K _N = 0.18 / + H ₂ O 0.71 0.20 <0.08 8h / 510 ° C / K _N = 0.5 / + H ₂ O 0.70 0.24 0 24h / 380 ° C / + air 0.54 0.21 ≤ 0.06 24h / 410 ° C / + air 0.78 0.30 0.18 24h / 380 ° C / + H ₂ O 0.62 0.25 0.12 24h / 440 ° C / + H ₂ O 0.46 0.19 0.06 12h / 460 ° C / + H ₂ O 0.62 0.19 <0.06 8h / 480 ° C / + H ₂ O 0.78 0.19 <0.06 18h / 450 ° C / + H ₂ O 0.71 0.21 0 PERMENORM 5000V5 8h / 570 ° C / K _N = 1.0 / + H ₂ O 0.55 0.20 0 8h / 570 ° C / K _N = 0.5 / + H ₂ O 0.62 0.16 0 8h / 570 ° C / K _N = 0.251 + H ₂ O 0.78 0.27 0.08 8h / 570 ° C / K _N = 0.18 / + H ₂ O 0.79 0.28 0.08 8h / 510 ° C / K _N = 0.5 / + H ₂ O 0.47 0.16 0 24 h / 380 ° C / air + 0.75 0.30 ≤ 0.12 24h / 410 ° C / + air 0.63 0.30 0.12 24h / 380 ° C / + H ₂ O 0.74 0.25 0.12 24h / 440 ° C / + H ₂ O 0.50 0.25 <0.06 12h / 460 ° C / + H ₂ O 0.77 0.28 0.06 8h / 480 ° C / + H ₂ O 0.75 0.31 <0.06 18h / 450 ° C / + H ₂ O 0.61 0.21 0 VACOFLUX 17 8h / 570 ° C / K _N = 1.0 / + H ₂ O 0.82 0.35 0.12 8h / 570 ° C / K _N = 0.5 / + H ₂ O 0.39 0.08 0 8h / 570 ° C / K _N = 0.25 / + H ₂ O 0.87 0.28 ≈ 0.08 8h / 570 ° C / K _N = 0.18 / + H ₂ O 0.71 0.31 ≈ 0.08 8h / 510 ° C / K _N = 0.5 / + H ₂ O 0.60 0.16 ≤ 0.08 24h / 380 ° C / + air 0.66 0.24 ≤ 0.18 24h / 410 ° C / + air 0.54 0.30 0.18 24h / 380 ° C / + H ₂ O 0.50 0.25 0.15 24h / 440 ° C / + H ₂ O 0.62 0.25 0.12 12h / 460 ° C / + H ₂ O 0.62 0.22 0.15 8h / 480 ° C / + H ₂ O 1.86 0.93 0.25 18h / 450 ° C / + H ₂ O 1.10 0.31 0.18

The following Table 4 shows the oxygen concentration in% by weight at different penetration depths in µm. The maximum O concentration O _max , half and 10% of the maximum O concentration are given, each determined from the GDOS profile. In addition, the depth in µm. O _max (%) O _max / 2 (%) O _max / 10 CHRONOPERM 50 24h / 380 ° C / + air 3.0 at 0µm 1.5 at 0.10 µm 0.3 at 1.95 µm 24h / 410 ° C / + air 2.5 at 0µm 1.25 at 0.15µm 0.25 at 2.67 µm 24h / 380 ° C / + H ₂ O 4.0 at 0µm 2.0 at 0.05 µm 0.4 at 1.44 µm 24h / 440 ° C / + H ₂ O 1.5 at 0µm 0.75 at 0.72µm 0.15 at 2.05µm 12h / 460 ° C / + H ₂ O 3.0 at 0µm 1.5 at 0.08µm 0.3 at 1.49 µm 8h / 480 ° C / + H ₂ O 2.36 at 0µm 1.18 at 0.58µm 0.24 at 2µm 18h / 450 ° C / + H ₂ O 1.66 at 0.51 µm 0.83 at 0.81µm At 2.84 µm PERMENORM 5000V5 24h / 380 ° C / + air 3.0 at 0µm 1.5 at 0.41 µm 0.3 at 1.90 µm 24h / 410 ° C / + air 5.0 at 0µm 2.5 at 0.1µm 0.5 at 1.23 µm 24h / 380 ° C / + H ₂ O 2.5 at 0µm 1.25 at 0.72µm 0.25 at 1.92 µm 24h / 440 ° C / + H ₂ O 4.0 at 0µm 2.0 at 0.21 µm 0.4 at 1.18 µm 12h / 460 ° C / + H ₂ O 2.5 at 0µm 1.25 at 0.75µm 0.25 at 2.25µm 8h / 480 ° C / + H ₂ O 4.0 at 0µm 2.0 at 0.26µm 0.4 at 1.47 µm 18h / 450 ° C / + H ₂ O 1.66 at 0µm 0.83 at 0.66µm At 2.34 µm VACOFLUX 17 24h / 380 ° C / + air 8.0 at 0µm 4.0 at 0.05 µm 0.8 at 0.82µm 24h / 410 ° C / + air 8.5 at 0µm 4.25 at 0.1µm 0.85 at 0.56µm 24h / 380 ° C / + H ₂ O 4.0 at 0µm 2.0 at 0.13 µm 0.4 at 1.18 µm 24h / 440 ° C / + H ₂ O 2.5 at 0µm 1.25 at 0.51 µm 0.25 at 2.05µm 12h / 460 ° C / + H ₂ O 3.5 at 0µm 1.75 at 0.41 µm 0.35 at 1.38 µm 8h / 480 ° C / + H ₂ O 5.0 at 0µm 2.5 at 0.82 µm 0.5 at 2.87 µm 18h / 450 ° C / + H ₂ O 2.91 at 0.38µm 1.46 at 0.76µm At 1.98 µm

The oxygen content generally increases very quickly with the Depth of penetration. It is not a clear dependency on the nitriding parameters.

Tab. 5 shows the surface hardness of disc samples in the final annealed condition and after various nitriding treatments. alloy VACOFLUX 17 CHRONOPERM 50 PERMENORM 5000V5 Not nitrided 156 HV0.1 102 HV0.1 102 HV0.1 24h / 380 ° C / NH ₃ K _N = 10 / with air 493 HV0.01 252 HV0.01 250 HV0.01 24h / 410 ° C / NH ₃ K _N = 10 / with air 658 HV0.01 238 HV0.01 202 HV0.01 24h / 380 ° C / NH ₃ KN = 10 / with H ₂ O 275 HV0.01 169 HV0.01 170 HV0.01 24h / 440 ° C / NH ₃ K _N = 10 / with H ₂ O 1273 HV0.01 328 HV0.01 248 HV0.01 12h / 460 ° C / NH ₃ K _N = 10 / with H ₂ O 1074 HV0.01 309 HV0.01 252 HV0.01 8h / 480 ° C / NH ₃ K _N = 10 / with H ₂ O 1205 HV0.01 427 HV0.01 250 HV0.01 18h / 450 ° C / NH ₃ K _N = 10 / with H ₂ O 1134 HV0.01 297 HV0.01 237 HV0.01

Due to the grinding of anchors and pole pieces, the hardness increases near the surface. An annealed one and ground surface is therefore less Test load harder than a merely annealed surface. The surface hardness increases further due to nitriding. This effect is less evident at a test load of 0.1 kg, but rather more with a lower test load of 0.01kg. This is due to the small thickness influenced by the nitriding Surface zone conditional. So the hardness values form not only reflect the surface zone, but in the larger one Test load also that of the underlying base material. When comparing the results of hardness measurements these thin surface layers are therefore always on to respect the same conditions, i.e. same test load and same measurement method.

Tab. 6 shows the hardness results for pole pieces. To be noted is that the large spread of readings by the occasional unstable position of the pole pieces with the hardness impression on the pole face. The pole pieces can thereby tilting slightly, which results in lower measurements Hardness values can lead.

Tab. 7 (HV0.1) and Tab. 8 (HV0.01) show the results for anchors. For comparison with, results are shown on thin galvanic coatings (NiPd, hard gold) currently in production on parts made of PERMENORM 5000V5. Tab. 9 shows the hardness values of VACOFLUX 17 on rings for different loads and nitration tests. Table 10 lists the Vickers hardness of Recovac 50 anchors for the nitriding tests at 480 ° C or 450 ° C and the non-nitrided state. It should be noted that Recovac 50 shows no surface hardening due to nitriding in the unpolished state. Due to the Ti content of the alloy, a tarnish layer forms during the final annealing under H ₂ . Despite the good dew point (around -40 ° C) of the dry H _{2 used, it is} unavoidable due to the high thermodynamic stability of the TiO ₂ . This TiO ₂ layer obviously acts as a perfect diffusion barrier and prevents hardening by nitriding. In contrast, a significant hardening effect from nitriding can be observed on a ground surface.

Härte von VACOFLUX 17 an Ringen. Nitrierbehandlung HV 0,01 HV0,1 nicht nitriert 156 24h/380°C/K_N=10/mit Luft 493 366 ± 13 24h/410°C/K_N=10/mit Luft 658 351 ± 82 24h/380°C/K_N=10/mit H₂O 275 233 ± 15 24h/440°C/K_N=10/mit H₂O 1273 654 ± 100 12h/460°C/K_N=10/mit H₂O 1074 644 ± 107 8h/480°C/K_N=10/mit H₂O 1205 1165 ± 111 18h/450°C/K_N=10/mit H₂O 1134 1119 ± 82 570°C/8h/K_N=1/mit H₂O 791 570°C/8h/K_N=0,5/mit H₂O 1065 570°C/8h/K_N=0,25/mit H₂O 980 570°C/8h/K_N=0,18 mit H₂O 952 510°C/8h/K_N=0,5/mit H₂O 165 Oberflächenhärte an Ankern aus Recovac 50 Behandlung HV 0.1 HV 0.01 geschliffen ungeschliffen Geschliffen Geglüht, ausgehärtet Nitriert: 18h/450°C/K_N=10 421 270 686 433 222 660 493 215 551 413 238 571 409 253 772 Mittelwert 434 ± 34 240 ± 22 648 ± 90 Geglüht, ausgehärtet Nitriert: 8h/480°C/K_N=10 572 191 772 433 224 533 394 218 439 514 285 840 519 193 805 Mittelwert 486 ± 72 222 ± 38 678 ± 180 Geglüht, ausgehärtet Nicht nitriert 268 292 283 242 249 Mittelwert 267 ± 21 Vergleich der Härte für FI-Anker nach verschiedenen Oberflächenbehandlungen. geglüht geschliffen nitriert NiPd Hartgold Cr HV 0,1 5000V5 102 167 197 180 168 200 CHR 50 102 149 225 RECOVAC 50 267 434 HV 0,01 5000V5 212 357 280 208 316 CHR 50 198 417 RECOVAC 50 648 Vergleich d. Härte für FI-Polstücke nach verschiedenen Oberflächenbehandlungen. geglüht geschliffen nitriert NiPd Hartgold Cr HV 0,1 5000V5 200 204 189 CHR 50 201 209 HV 0,01 5000V5 247 354 224 CHR 50 231 383 Finally, Tab. 11 shows the comparison of hardness values after optimal nitriding with the results for conventional relay FI-coatings. Hardness HV0.1; HV0.01 v. Functional pole piece surfaces, each nitrided m. K _N = 10 m. H ₂ O. alloy unpolished unground + nitrided polished ground + nitrided 460 ° C / 12h HV0,1 CHRONOPERM 50 111 121 206 216 119 151 192 205 115 205 205 235 138 126 202 218 146 123 201 171 MW: 126 ± 14 MW: 145 ± 32 MW: 201 ± 5 MW: 209 ± 21 PERMENORM 5000V5 164 133 218 196 128 183 203 215 160 135 197 201 132 124 181 199 132 145 201 212 MW: 143 ± 16 MW: 144 ± 21 MW: 200 ± 12 MW: 204 ± 7 HV0.01 CHRONOPERM 50 136 178 219 401 117 206 263 368 145 175 257 401 148 189 189 439 125 182 229 305 MW: 134 ± 12 MW: 186 ± 11 MW: 231 ± 27 MW: 383 ± 45 PERMENORM 5000V5 117 193 245 339 140 168 269 305 159 269 263 368 162 193 214 401 123 229 245 358 MW: 140 ± 18 MW: 211 ± 35 MW: 247 ± 19 MW: 354 ± 32 480 ° C / 8h HV0.1 CHRONOPERM 50 133 ± 21 261 ± 18 PERMENORM 5000V5 168 ± 13 223 ± 16 HV0.01 CHRONOPERM 50 220 ± 40 497 ± 35 PERMENORM 5000V5 202 ± 23 347 ± 60 450 ° C / 18h HV0.1 CHRONOPERM 50 127 ± 4 226 ± 10 PERMENORM 5000V5 166 ± 22 209 ± 11 HV0.01 CHRONOPERM 50 180 ± 30 388 ± 59 PERMENORM 5000V5 214 ± 38 364 ± 41

VACOFLUX 17 hardness on rings. nitriding HV 0.01 HV0,1 not nitrided 156 24h / 380 ° C / K _N = 10 / with air 493 366 ± 13 24h / 410 ° C / K _N = 10 / with air 658 351 ± 82 24h / 380 ° C / K _N = 10 / with H ₂ O 275 233 ± 15 24h / 440 ° C / K _N = 10 / with H ₂ O 1273 654 ± 100 12h / 460 ° C / K _N = 10 / with H ₂ O 1074 644 ± 107 8h / 480 ° C / K _N = 10 / with H ₂ O 1205 1165 ± 111 18h / 450 ° C / K _N = 10 / with H ₂ O 1134 1119 ± 82 570 ° C / 8h / K _N = 1 / with H ₂ O 791 570 ° C / 8h / K _N = 0.5 / with H ₂ O 1065 570 ° C / 8h / K _N = 0.25 / with H ₂ O 980 570 ° C / 8h / K _N = 0.18 with H ₂ O 952 510 ° C / 8h / K _N = 0.5 / with H ₂ O 165 Surface hardness on Recovac 50 anchors treatment HV 0.1 HV 0.01 polished unpolished polished Annealed, hardened Nitrided: 18h / 450 ° C / K _N = 10 421 270 686 433 222 660 493 215 551 413 238 571 409 253 772 Average 434 ± 34 240 ± 22 648 ± 90 Annealed, hardened Nitrided: 8h / 480 ° C / K _N = 10 572 191 772 433 224 533 394 218 439 514 285 840 519 193 805 Average 486 ± 72 222 ± 38 678 ± 180 Annealed, hardened Not nitrided 268 292 283 242 249 Average 267 ± 21 Comparison of the hardness for FI anchors after different surface treatments. annealed polished nitrided NiPd hard gold Cr HV 0.1 5000V5 102 167 197 180 168 200 CHR 50 102 149 225 RECOVAC 50 267 434 HV 0.01 5000V5 212 357 280 208 316 CHR 50 198 417 RECOVAC 50 648 Comparison d. Hardness for FI pole pieces after various surface treatments. annealed polished nitrided NiPd hard gold Cr HV 0.1 5000V5 200 204 189 CHR 50 201 209 HV 0.01 5000V5 247 354 224 CHR 50 231 383

As can be seen from the data in Table 11, one Nitriding treatment of ground anchors with optimized Conditions at the highest hardness values that those of coatings that are common today. This also applies to pole piece surfaces.

Tab. 12 shows the results of a corrosion test on relay parts, at which the temperature and relative humidity be changed cyclically. From this it can be seen that the parts corrode if the nitriding index is small and the temperature is greater than 500 ° C.

On the basis of the experience available, nitriding was carried out in the presence of oxygen, ie oxynitriding. Due to the requirements regarding the safety of the production plant, the oxygen potential was set by adding water vapor. When changing to the low temperatures, an air additive was then initially used, because of the fear that an insufficient oxygen potential could not be set with the addition of H ₂ O due to kinetic inhibition. A reasonable hardening can be achieved, but the parts tarnish and are very susceptible to corrosion. Due to the very high O ₂ partial pressure, a rich oxide layer forms on the surface.

If nitriding is carried out at temperatures below 500 ° C and with a high nitriding index and setting the oxygen potential by adding H ₂ O, the parts will survive the usual climatic test with FI parts. Only at the highest temperature in this series did some 5000V5 parts show minimal rust formation. shows the proportion of corroded parts (with at least one rust point) in the climate test after 3 days (1 cycle: 3h / 20 ° C / 45% rel.humidity and 3h / 55 ° C / 95% rel.humidity) Nitrierversuch CHRONOPERM 50 PERMENORM 5000V5 pole pieces anchor pole pieces anchor 8h / 570 ° C / K _N = 1.0 / with H ₂ O 60% 100% 80% 100% 8h / 570 ° C / K _N = 0.5 / with H ₂ O 20% 80% 30% 70% 8h / 570 ° C / K _N = 0.25 / with H ₂ O 10% 60% 30% 100% 8h / 570 ° C / K _N = 0.18 / with H ₂ O 20% 30% 30% 50% 8h / 510 ° C / K _N = 0.5 / with H ₂ O 100% 100% 100% 100% 24h / 380 ° C / K _N = 10 / with air 80% 100% 30% 100% 24h / 410 ° C / K _N = 10 / with air 20% 100% 30% 100% 24h / 380 ° C / K _N = 10 / with H ₂ O 0% 0% 0% 0% 24h / 440 ° C / K _N = 10 / with H ₂ O 0% 0% 0% 0% 12h / 460 ° C / K _N = 10 / with H ₂ O 0% 0% 0% 0% 8h / 480 ° C / K _N = 10 / with H ₂ O 0% 0% 0% 20% 18h / 450 ° C / K _N = 10 / with H ₂ O 0% 0% 0% 0%

With regard to a sharper corrosion test, which Differences worked out better, was also a diving test performed in artificial sea water. To avoid from crevice corrosion the anchors are on a cord threaded and immersed in the synthetic sea water. With pole pieces this is not possible and you always have the problem of crevice corrosion under the contact surface. at No room temperature was found on all parts examined Corrosion can be observed. To increase aggressiveness The test temperature was therefore the test temperature raised. This much more aggressive corrosion test with artificial sea water at 50 ° C (Tab. 13) survived quite well, but starts at 80 ° C (Tab. 14 and 15) corrosion after just a few hours. The corroded Pole pieces are mainly due to crevice corrosion on the Support surfaces due to smooth container bottoms.

Tab. 13 shows the proportion of corroded anchors in artificial sea water at 50 ° C after 48 hours. Nitrierversuch CHRONOPERM 50 PERMENORM 5000V5 Not nitrided Not checked 0% 24h / 380 ° C / K _N = 10 / with H ₂ O 20% 20% 24h / 440 ° C / K _N = 10 / with H ₂ O 0% 20% 12h / 460 ° C / K _N = 10 / with H ₂ O 0% 20%

Tab. 14 shows the proportion of corroded parts in artificial seawater at 80 ° C after 5h 45min anchor hung on insulated wires and separated by shrink tubing; Pole pieces placed in smooth plastic shells, only non-nitrided pole pieces made of PERMENORM 5000V5 lay on a rough plastic surface. Nitrierversuch CHRONOPERM 50 PERMENORM 5000V5 pole pieces anchor pole pieces anchor Not nitrided 100% 20% 20% 70% 8h / 570 ° C / K _N = 0.18 / with H ₂ O 100% 100% 100% 100% 24h / 380 ° C / K _N = 10 / with H ₂ O 100% 40% 100% 20% 24h / 410 ° C / K _N = 10 / with air 100% Not checked 100% Not checked 8h / 570 ° C / K _N = 0.25 / with H ₂ O 100% Not checked 100% Not checked

Table 15 shows the proportion of corroded parts in artificial sea water at 80 ° C after 4h 15min. 5 pole pieces each were placed in smooth glass dishes. Nitrierversuch CHRONOPERM 50 PERMENORM 5000V5 Not nitrided 80% Not checked 24h / 380 ° C / K _N = 10 / with H ₂ O 100% 80%

Tab. 16 finally shows the result of a puncture test on the use of the HAST test customary for permanent magnets. CHRONOPERM 50 shows better durability. But this has to be tested even further and above all with larger quantities (result of the HAST test according to DIN IEC 68-2-66 - checking the corrosion of anchors after 135 hours at 130 ° C / 95% relative humidity). Nitrierversuch CHRONOPERM 50 PERMENORM 5000V5 Not nitrided Not corroded Not corroded 18h / 450 ° C / K _N = 10 / with H ₂ O Not corroded corroded

Overall, it can be said that the high nitriding temperatures are absolutely unsuitable because they are too susceptible to corrosion of the nitrided parts. When nitriding at low temperatures below 500 ° is sufficient Corrosion resistance given, according to the present valid alternating climate test. When using more severe corrosion tests (artificial sea water at 50 ° C, HAST test) CHRONOPERM 50 performs better. With further increased The aggressiveness of the test conditions then corrode both Alloys - corrosion resistance in the sense of a stainless steel one can with these alloy compositions also do not expect.

It is clear that of all the magnetic values, the static values react most sharply to tension caused by the nitriding process. The following tables therefore show the H _c values and static µ (H) curves determined on punch rings. The aim of this series of tests at low nitriding temperatures was to keep the nitriding layer as thin as possible in order to impair the magnetics as little as possible.

Tables 17 to 19 therefore show the result for the coercive field strength H _c . It can be seen that H _c is influenced very little by the selected nitriding conditions. With CHRONOPERM 50 and VACOFLUX 17 there is no significant change, with PERMENORM 5000V5 H _c increases somewhat with increasing temperature. Regarding the data of the punching rings from CHRONOPERM 50, it should be noted that the rings for the low temperatures of 380 and 410 ° C were obviously damaged and therefore have high H _c values falling out of line (marked with *) in Table 17). The high H _c values and thus also low permeability values are not reflected in the H _c values on parts or in the impedance results on relays, so that in this case damaged punch rings can be assumed (sometime after the final annealing). The results on these punch rings were therefore omitted in the following figures and results. Coercive field strength H _c of CHRONOPERM 50 on different sample shapes (* = punch rings damaged). H _c / mA / cm nitriding Ground anchor Pole piece ground Core (static) Core (f = 50Hz) FF = 1.111 ± 1% not nitrided 43.4 56.2 30.9 539 24h / 380 ° C / K _N = 10 / with air 45.01 55.21 136 *) 24h / 410 ° C / K _N = 10 / with air 57.55 58,65 110 *) 24h / 380 ° C / K _N = 10 / with H ₂ O 40.4 50.04 145 *) 24h / 440 ° C / K _N = 10 / with H ₂ O 38.2 52.81 31.89 12h / 460 ° C / K _N = 10 / with H ₂ O 40.76 51.48 32.74 8h / 480 ° C / K _N = 10 / with H ₂ O 42.2 48.6 34.58 18h / 450 ° C / K _N = 10 / with H ₂ O 41.4 50.6 33.1

Table 18 shows the coercive field strength H _c of PERMENORM 5000V5 on different sample forms. H _c / mA / cm nitriding Ground anchor Pole piece ground Core (static) Core (f = 50Hz) FF = 1.111 ± 1% not nitrided 41.8 52.9 38.0 1003 24h / 380 ° C / K _N = 10 / with air 42.34 54.77 41.47 24h / 410 ° C / K _N = 10 / with air 43.98 47.36 47.18 24h / 380 ° C / K _N = 10 / with H ₂ O 36.82 38.6 40.55 24h / 440 ° C / K _N = 10 / with H ₂ O 49,15 56.2 44.62 12h / 460 ° C / K _N = 10 / with H ₂ O 51.04 60.57 45.67 8h / 480 ° C / K _N = 10 / with H ₂ O 53.05 60.11 51.44 18h / 450 ° C / K _N = 10 / with H ₂ O 52.3 68.0 46.1

Tab. 19 shows the coercive field strength H _c of VACOFLUX 17 on toroidal cores. H _c / mA / cm nitriding Core (static) not nitrided 1082 24h / 380 ° C / K _N = 10 / with air 921 24h / 410 ° C / K _N = 10 / with air 984 24h / 380 ° C / K _N = 10 / with H ₂ O 984 24h / 440 ° C / K _N = 10 / with H ₂ O 964 12h / 460 ° C / K _N = 10 / with H ₂ O 987 8h / 480 ° C / K _N = 10 / with H ₂ O 963 18h / 450 ° C / K _N = 10 / with H ₂ O 1038 8h / 570 ° C / K _N = 1 / with H ₂ O 2873 8h / 570 ° C / K _N = 0.5 / with H ₂ O 1764 8h / 570 ° C / K _N = 0.25 / with H ₂ O 1107 8h / 570 ° C / K _N = 0.18 with H ₂ O 1056 8h / 510 ° C / K _N = 0.5 / with H ₂ O 1082

Figures 1 to 3 show an example of the result for the dc permeability measured on punch rings. This takes based on the results for all 3 alloys - with -50% for the highest temperature of 480 ° C at PERMENORM 5000V5 most clearly. If you compare this with the data for the higher nitriding temperatures above 500 ° C, the degradation here, however, is significantly less. A complete overview is given below

Tab. 20 based on the data for maximum permeability static magnetization.

1 shows the static permeability, measured Punching rings, from VACOFLUX 17 at different nitriding temperatures; Nitriding time 24h unless otherwise stated.

Fig. 2 shows the static permeability on punch rings of PERMENORM 5000V5 at different nitriding temperatures; Nitriding time 24h unless otherwise stated.

3 shows the static permeability on punch rings of CHRONOPERM 50; Duration 24h, or as specified.

Another statement about the influence of nitriding is possible by determining the static permeability on Magnetic circuit consisting of pole piece and armature (hereinafter referred to as relay). On the one hand, this measurement reflects a change the permeability of the parts and thus the material but also every air gap change due to the nitriding process. The permeability can be measured on parts as they were taken from the nitriding process, that is without any further cleaning - hereinafter referred to as "rough" designated. But it can also be the usual peeling on paper take place - hereinafter referred to as "smooth". As a general rule a measurement in the "rough" state leads to larger ones Scatter and also to lower values. You have to keep in mind that in addition to the nitriding process further handling of the parts including transport under not in low-dust conditions. A comparison and so the evaluation of the magnetic properties should based on the measurement on parts drawn over paper, the otherwise usual measurement condition.

Fig. 4 shows the static permeability on relays PERMENORM 5000V5.

Fig. 5 shows the static permeability on relays CHRONOPERM 50.

Fig. 6 shows the static permeability on relays CHRONOPERM 50 with changed nitriding conditions compared to FIG. 5.

Looking at the results for PERMENORM 5000V5 (Fig. 4) and CHRONOPERM 50 (FIGS. 5 and 6 - two different nitriding conditions), So the decrease in permeability is in the frame of what was also seen on the punch rings. This would therefore argue that there is no significant change in the air gap would have taken place. That conclusion can be based on the results for the printed paper "smooth" condition. Without peeling off There is a lot of scatter in paper - and it does matter non-nitrided parts (see above).

Tab. 20 shows maximum static permeability on punch rings and on relays for various nitriding conditions. unnitriert 24 h / 380 ° C 24 h / 440 ° C 12h / 460 ° C 8h / 480 ° C 18h / 450 ° C V5 punch ring 93284 94703 67845 55796 46673 56556 V5 relay 17829 16937 14790 14824 12763 13770 CHR50-punching ring 111171 ng 101784 94583 82298 94583 CHR50 relay 11850 10816 12805 11293 11642 12830

Now put the permeability result µ (B) as measured on punch rings and the effective permeability µ *, measured on relays, ie on the magnetic circuit consisting of pole piece and armature, in the shear formula µ * = 1 1 / μ M + l L / l Fe on, you can calculate the air gap. This applies at least to the area of smaller modulation. With larger modulation, the result is falsified due to saturation effects. If you consider the result for the "rough" condition, the result for 410 ° C / air is striking. The parts had tarnished due to the nitriding with the addition of air. The Fe-rich oxide layer naturally leads to a significant enlargement of the air gap. Otherwise the results are scattered by 2 to 3 µm without showing any tendency with regard to the nitriding conditions. For functional surfaces cleaned by peeling off on paper, there is a consistent picture - an air gap change due to the nitriding process cannot be determined, see 8 and 9.

Fig. 7 shows the air gap of a relay made of PERMENORM 5000V5 (rough), determined from static permeability measurement.

8 shows the air gap of a relay made of 5000V5 (smooth), determined from static permeability measurement.

Fig. 9 shows the static air gap of a relay CHRONOPERM 50 (smooth)

Since there are practically no air gap changes when nitriding under these nitriding parameters, the change in the dynamic material permeability is decisive for the relay properties. Results above had shown deterioration in static magnetic properties. Due to the material thickness of just over 1 mm in the case of the anchors and 1.98 mm in the case of the pole pieces, a flattening of this degradation can be expected in this 50 Hz application due to the eddy current effects. Figures 10 to 13 now show an example of the result for the two alloys, each without a DC field overlay and with dc bias of 0.45 T. As can already be seen from the H _c values, CHRONOPERM 50 reacts less than PERMENORM 5000V5. There is a clear tendency to deteriorate the magnetics with increasing nitriding conditions, ie increasing temperature. Overall, however, the degradation is moderate. Based on these results, significantly lower impedance losses are to be expected for measurements at relays than was previously the case with the otherwise more usual nitriding temperatures above 500 ° C. Table 21 shows a complete overview of the results using the data for the dynamic 50 Hz maximum permeability.

10 shows PERMENORM's dynamic permeability 5000V5 on punched rings without constant field.

Tab. 21 shows the 50 Hz maximum permeability on punch rings and on relays for different nitriding conditions. unnitriert 24 h / 380 ° C 24 h / 440 ° C 12h / 460 ° C 8h / 480 ° C 18h / 450 ° C V5 punch ring 20457 19896 16082 15,579 14235 15724 V5 relay 7392 6147 6009 6420 5936 5451 CHR50-punching ring 26845 ng 22775 21833 20415 21716 CHR50 relay 7123 6251 6761 6718 6785 7054

Fig. 11 shows the dynamic permeability of PERMENORM 5000V5 on punched rings with constant field.

Fig. 12 shows the dynamic permeability of CHRONOPERM 50 on punched rings without constant field

13 shows the dynamic permeability of CHRONOPERM 50 on punched rings with constant field.

Tables 22 and 23 summarize the induction voltages at the relay, as they are also measured in production, and the quantities derived from them for the various nitriding tests in the temperature range from 380 ° C to 480 ° C. The results in the non-nitrided state serve as comparative values. The field-generating primary winding has N ₁ = 10 turns, the secondary winding on which the induction voltages were measured has N2 = 200 turns. The average iron path length of the relays is l _Fe = 3.4 cm, the average iron cross section A _Fe = 0.069 cm ² . Index 1 stands for the field strength H and = 270mA / cm, index 2 for H and = 500mA / cm, index DC for constant field overlay of B ₌ = 0.45 Tesla. The current that has to flow through the primary winding results from the following equation: I eff = H · l FE N 1 · 2 The induction values result from the equation assuming a form factor FF = 1.11 B = U avg 4 · ƒ · A FE · N 2 and the relationship U avg = U rms FF The permeabilities µ * result from µ * µ * = B H · μ 0 ,

Tab. 22 shows the induction voltages (effective values) and derived values (peak values) for relay parts made of PERMENORM 5000V5 for different nitriding variants. Nitriding treatment: 24h / K _N = 10 (unless otherwise stated). Average values from several individual measurements are given. means not drawn over paper ("rough") nitriding U ₁ / mV B ₁ / T μ * U _{2 + DC} / mV B _{2 + DC} / T μ * Not nitrided 63.64 0.208 6130 79.84 0.260 4138 380 ° C / with air 410 ° C / with air 380 ° C / with H ₂ O 67.25 0,220 6470 89.48 0.292 4649 440 ° C / with H ₂ O 63.70 0.208 6130 84,60 0.276 4395 12h / 460 ° C / with H ₂ O 45,99 0,150 4425 66.76 0.218 3468 8h / 480 ° C / with H ₂ O 60.86 0,199 5855 81.28 0.265 4223 18h / 450 ° C / with H ₂ O 45.27 0.148 4355 57.41 0,187 2982 means drawn over paper ("smooth") nitriding U ₁ / mV B ₁ / T μ * U _{2 + DC} / mV B _{2 + DC} / T μ * Not nitrided 67.59 0,220 6496 85.69 0.277 4416 380 ° C / with air 68.42 0.223 6583 88,20 0,288 4582 410 ° C / with air 69,90 0.228 6724 91,33 0,298 4745 380 ° C / with H ₂ O 72,80 0,238 7003 95.83 0.313 4978 440 ° C / with H ₂ O 67.40 0,220 6484 89.81 0.293 4666 12h / 460 ° C / with H ₂ O 67.03 0.219 6448 88.86 0,290 4617 8h / 480 ° C / with H ₂ O 65.41 0.213 6292 85.16 0,278 4424 18h / 450 ° C / with H ₂ O 61.28 0,200 5895 78.17 0,255 4061

Tab. 23: Induction voltages (rms values) and derived values (peak values) for relay parts made of CHRONOPERM 50 for different nitriding variants Nitriding treatment: 24h / K _N = 10 (unless otherwise stated). Average values are given in each case. means not drawn over paper ("rough") nitriding U ₁ / mV B ₁ / T μ * U _{2 + DC} / mV B _{2 + DC} / T μ * Not nitrided 73.78 0,241 7091 86.70 0.283 4500 380 ° C / with air 410 ° C / with air 380 ° C / with H ₂ O 65.81 0.215 6331 72,90 0,238 3787 440 ° C / with H ₂ O 60.93 0,199 5861 68,85 0.225 3577 12h / 460 ° C / with H ₂ O 54.49 0,178 5242 67.34 0,220 3499 8h / 480 ° C / with H ₂ O 55.46 0,181 5335 65,99 0.215 3428 18h / 450 ° C / with H ₂ O 55.78 0.182 5366 66.03 0,216 3430 means drawn over paper ("smooth") nitriding U ₁ / mV B ₁ / T μ * U _{2 + DC} / mV B _{2 + DC} / T μ * Not nitrided 78.27 0,255 7522 92.7 0,302 4811 380 ° C / with air 67.89 0.222 6531 77.01 0,251 4001 410 ° C / with air 66.88 0.218 6434 73.04 0,238 3794 380 ° C / with H ₂ O 67.86 0.222 6529 76.82 0,251 3991 440 ° C / with H ₂ O 69.93 0.228 6728 79.12 0,258 4111 12h / 460 ° C / with H ₂ O 72.78 0,238 7001 86.59 0.283 4498 8h / 480 ° C / with H ₂ O 70.83 0.231 6814 81.61 0.266 4239 18h / 450 ° C / with H ₂ O 73.99 0,242 7118 87.68 0.286 4555

The results have to be compared with the state of the art at the time of the production of FI relay parts with an average value for the decisive measured variable U2 _DC of typically just over 80 mV. To make matters worse, the test parts have to be transported twice to nitride and then back again, each with express transport and the additional handling steps for the nitriding process. Against this background, the result is very satisfactory. It is therefore possible to produce relay parts by nitriding, the surface hardness of which exceeds that of previously used methods, and this in contrast to the previously customary methods with a minimal loss of permeability or impedance.

Table 24 lists the induction voltages as measured for a relay. All pole pieces are made of PERMENORM 5000V5, the anchors are made of different Alloys after different treatments.

The Ti-containing RECOVAC 50 was tested in a puncture test investigated by RECOVAC 50 anchors. Was measured each with current pole pieces made of PERMENORM 5000V5 and for comparison also with anchors made of V5. Tab. 24 shows the result. Because of the associated with the NiPd coating Air gap, the impedance level drops significantly. Uncoated RECOVAC 50, however, is better. With RECOVAC 50 the deterioration in impedance due to nitriding is more evident - The increase in hardness was also so strong as by far with no other alloy (see above). The level reached corresponds to the level as it was before installation the new pouring system was common. It should be noted the statement already made above that at RECOVAC 50 a hardening only occurs on ground surfaces.

Tab. 24 shows the result of the impedance measurements on various parts. Measurements were taken with new pole pieces from one lot (manufactured using a new casting machine). U _Z02 (mV) is given in the table. 5000V5, nitrided V5 not nitrided - NiPd RECOVAC 50 not nitrided R50 + 18h / 450 ° C R50 + 8h / 480 ° C 39.4 ± 3.9 25.8 ± 3.9 29.3 ± 3.3 21.8 ± 4.9 22.3 ± 4.2

FIGS. 14 to 17 now show the course by way of example the 50 Hz - µ (H) curve measured on relays. Here too in the application-related measurement with dc preload of 0.45 T for PERMENORM 5000V5 (Fig. 15) as well as for CHRONOPERM 50 (Fig. 17) practically no loss. There are also those determined using the shear formula Air gaps no significant differences from the condition without surface hardening, as in the example of PERMENORM 5000V5 (Fig. 18) and CHRONOPERM 50 (Fig. 19).

14 shows the dynamic permeability at a relay made of PERMENORM 5000V5 without constant field preload.

15 shows the dynamic permeability at a relay made from PERMENORM 5000V5 with DC preload of 0.45 T.

16 shows the dynamic permeability at a relay made of CHRONOPERM 50 without constant field preload.

17 shows the dynamic permeability at a relay made of CHRONOPERM 50 with DC preload of 0.45 T.

Fig. 18 shows an air gap of a PERMENORM relay 5000V5 in the "smooth" state without direct current superimposition determined using the shear formula from the on punched rings certain 50Hz permeability and that determined on relays μ (H) curve.

Fig. 19 shows an air gap of a CHRONOPERM relay 50 determined in the "rough" state without direct current superimposition using the shear formula from the one determined on punched rings 50Hz permeability and that determined on relays µ (H) curve.

To evaluate the various surface treatments can be the result for the surface hardness and on the other hand, the impact on permeability or impedance be used. This result is shown in Fig. 20. It it becomes clear that the surface hardening by nitriding the best possible combination of optimal hardness and highest possible Represents permeability.

20 shows the permeability with dc preload of 0.45 T - the measured variable U2 _dc is plotted - as a function of the surface hardness of the anchors for different states. "Untreated" stands for the ground condition. In the galvanic coatings, only the armature is coated - measured with normal, only ground pole pieces made of 5000V5. In the case of nitrided parts, both the armature and the pole piece have been nitrided.

The results of VACOFLUX 17 at higher nitriding temperatures of 510 to 570 ° C have already been reported. A strong hardening effect could only be determined at 570 ° C, but with considerable losses in terms of magnetics. The VACOFLUX 17 ran alongside as part of the ongoing investigations into the nitriding of FI relay parts. By nitriding at lower temperatures, the magnetic impairment can be completely avoided and comparatively high surface hardness around 1,000 (HV0.1) can be achieved. However, the N concentration as a function of depth usually decreases earlier. However, an extremely high N concentration was achieved for the test K _N = 10 at 480 ° C, combined with a very high hardness and a very large penetration depth.

To characterize the surface-hardening layer carried out various investigations. In particular It was necessary to clarify how the layer is structured, and in what form the nitrogen is in the surface layer. Alloy samples were used for these investigations CHRONOPERM 50 and PERMENORM 5000V5 used which for Oxinitrided at 460 ° C for 12 hours. Tab. 25 gives the Alloy composition. Figures 21a and 21b show the associated GDOS depth profiles. One recognizes for both alloys have an immediate oxygen enrichment Surface area, approximately to a depth of approx. 2 µm. This is due to the selected nitriding process. By oxynitriding with a certain oxygen partial pressure effective surface hardening can be achieved.

Table 25 shows the composition of the alloys examined (% by weight). Ni Cr Mn Si rest PERMENORM 5000V5 47.5 <0.1 0.5 0.2 Fe CHRONOPERM 50 47.5 2.0 0.45 0.15 Fe

Figure 21a shows GDOS depth profile for PERMENORM 5000V5 and Figure 21b: GDOS depth profile for CHRONOPERM 50.

To clarify the question of the occurrence of nitride compounds and / or the formation of a nitride compound layer carried out various investigations. First of all an examination for lateral homogeneity by means of spatially resolved Auger spectroscopy.

In this method, the surface layer is by means of sputtered from an ion beam. From time to time the Sputtering process interrupted and the eye spectrum spatially resolved of the surface. That way information about the lateral distribution of the essential elements contained in the alloy in various Distances from the surface.

The results always showed an enrichment of the surface layer with oxygen, due to the chosen method of oxynitriding .. What is striking is the clear Oxygen signal on the surface, which after sputtering is no longer determined.

It should also be noted that this is also ascertainable Carbon signal due to contamination of the surface Is organic. However, this can only be found on the surface - it disappears after the shortest sputtering time. This C enrichment on the surface is therefore technical not significant. There were no significant lateral ones Inhomogeneities on the scale of the resolution of this method (approx. 0.5 µm) are found, so no indication on the appearance of coarse nitride deposits.

Furthermore, a transmission electron microscopic examination was carried out. Usual 3mm diameter TEM samples were punched out of 0.2mm thick tape. They were then subjected to the usual final annealing at 5h / 1150 ° C / H2. Then one side was electropolished on one side with a commercially available TENUPOL device and then oxinitrided at 450 ° C for 18 h with K _N = 10. The TEM sample was then thinned from the previously unpolished side using TENUPOL until a hole was formed. The penetrable edges of the hole thus contain the area near the surface of the other side of the sample. No evidence of a continuous connection layer was found by means of transmission electron microscopy. In addition, there was no clear evidence of nitride excretion

Finally, using high-resolution scanning electron microscopy demonstrated that the samples are free of any Are connecting cover layer. None were found here either Indications of nitrides in the area near the surface below the surface. With several methods (transmission electron microscopy, high resolution scanning electron microscopy, grazing X-ray diffraction) could not nitrides be detected. It follows that the very large amounts of nitrogen present in the surface layer is essentially interstitial (in the interstitial grid).

• Keine Verbindungsdeckschicht: dies ist auch Vorraussetzung für ein hohes Impedanzniveau der Relais, da die Deckschicht unmagnetisch wäre und als Luftspalt wirken würde.
• Bisher kein Nachweis für das Vorliegen von Nitridausscheidungen im oberflächennahen Bereich unterhalb der Oberfläche: dies deutet darauf hin, dass die Härtesteigerung hier wesentlich durch interstitiell gelösten Stickstoff bewirkt wird.
• Damit liegt der Phasenanteil an Eisennitrid im Tiefenbereich von 1 µm unterhalb der Oberfläche sicher unter einer praktischen Nachweisgrenze von 10 Gew.-%.

The results of the investigations can be summarized as follows:

• No connection cover layer: this is also a prerequisite for a high impedance level of the relays, since the cover layer would be non-magnetic and would act as an air gap.
• So far no evidence for the presence of nitride deposits in the area near the surface below the surface: this indicates that the increase in hardness here is essentially caused by interstitially dissolved nitrogen.
• The phase proportion of iron nitride in the depth range of 1 µm below the surface is therefore below a practical detection limit of 10% by weight.

Attempts to nitride FI relay parts made of NiFe (Cr) alloys have shown a significant increase the surface hardness is feasible. With CHRONOPERM 50 surface hardnesses HV0.01 can be generated from over 400, which is the hardness of today's galvanic or Sputter coatings significantly exceeds. This even succeeds with PERMENORM 5000V5, but at a lower level Level of HV0.01 = 350. The method according to the invention achieved minimal loss of permeability or impedance in the relay. While with the coatings common today 1/3 to half of the impedance due to the air gap loses, the loss in the process developed here very low. Through the process now being developed could the corrosion resistance of nitrided parts in the usual Climate test are made. In the different examined more aggressive tests CHRONOPERM 50 cut mostly better than PERMENORM 5000V5.

• Das Nitrieren muss nach dem Schleifen direkt nach der Reinigung der Teile erfolgen;
• Die Polstücke und Anker sollen geordnet auf geeigneten Glühunterlagen positioniert werden, so dass die Funktionsfläche frei liegt. Dafür werden (schonende) Handhabungssysteme notwendig sein;
• Die Anker müssen eine unterscheidbare Funktionsseite (welche beim Nitrieren frei liegt) und Gegenseite (mit schlechterem Gaszutritt) aufweisen;
• Die Handhabung der Teile beim Positionieren auf die Glühunterlagen, beim Transport etc. muss höchsten Ansprüchen genügen, um keine zusätzliche Degradation und Streuung einzufangen.
• Eine Sichtkontrolle, die Endprüfung und das Verpacken sollten erst nach dem Nitriervorgang erfolgen;.

The following boundary conditions for a preferred type of manufacture of nitrided relay parts can also be specified individually or in combination:

• After grinding, nitriding must be carried out immediately after cleaning the parts;
• The pole pieces and anchors should be positioned on suitable glow pads so that the functional surface is exposed. (Gentle) handling systems will be necessary for this;
• The anchors must have a distinguishable functional side (which is exposed when nitriding) and the opposite side (with poorer gas access);
• The handling of the parts when positioning them on the glow pads, during transport, etc. must meet the highest demands in order to avoid additional degradation and scattering.
• A visual inspection, final inspection and packaging should only be carried out after the nitriding process.

Claims (17)

Soft magnetic actuator part with surface hardness increased by nitriding of at least 150 HV0.01, characterized by the following depth profile of the N concentration: in the depth range Peak value of the maximum N- up to 1 µm Concentration of at least 0.2% by weight, at a depth an N concentration of at least of 1 µm 0.25% by weight, at a depth an N concentration of at least 0.1 of 2 µm Wt%., at a depth an N concentration of at least of 5 µm 0.05% by weight. Soft magnetic actuator part according to claim 1 consisting made of a Ni-based alloy with a Ni content of 35 up to 85% by weight. Soft magnetic actuator part according to claim 1 or 2, characterized by a coercive field strength H _c <200 mA / cm. Soft magnetic actuator part according to claim 3, characterized by a coercive field strength H _c <100 mA / cm. Soft magnetic actuator part according to claim 4, characterized by a coercive field strength H _c <70 mA / cm. Soft magnetic actuator part according to one of the preceding claims, characterized by the following depth profile of the N concentration: in the depth range Peak value of the maximum N- up to 1 µm Concentration of at least 0.5 Wt.%. at a depth an N concentration of at least of 1 µm 0.5% by weight at a depth an N concentration of at least of 2 µm 0.35% by weight at a depth an N concentration of at least of 5 µm 0.2% by weight. Soft magnetic actuator part according to claim 1 consisting made of a soft magnetic Co-containing Fe base alloy Soft magnetic actuator part according to claim 7, characterized in that the Co content is 10 to 50% by weight. Soft magnetic actuator part according to one of claims 7 or 8, characterized by the following depth profile of the N concentration: in the depth range Peak value of the maximum N- up to 1 µm Concentration of at least 0.5 Wt%., at a depth an N concentration of at least of 1 µm 0.5% by weight, at a depth an N concentration of at least of 2 µm 0.2% by weight, at a depth an N concentration of at least of 5 µm 0.1% by weight, Soft magnetic actuator part according to claim 9, characterized by the following depth profile of the N concentration: in the depth range Peak value of the maximum N- up to 1 µm Concentration of at least 1% by weight. at a depth an N concentration of at least of 1 µm 0.7% by weight at a depth an N concentration of at least of 2 µm 0.5% by weight at a depth an N concentration of at least of 5 µm 0.3% by weight Soft magnetic actuator part according to one of Claims 7 to 10, characterized by a coercive field strength Hc <2 A / cm, Soft magnetic actuator part according to claim 11, characterized by a low coercive field strength Hc <1.5 A / cm Use of a soft magnetic actuator part after one of claims 1 to 12 in a relay for residual current circuit breakers. Use according to claim 13, wherein the soft magnetic Actuator part ground and subsequently nitrided functional surfaces with at least a hardness HV0.01 of 220. Use according to claim 13 or 14, characterized in that the relay has a magnetic circuit with a pole piece and armature, with a 50 Hz maximum permeability of at least 4,000 being given on one or both parts. Method for surface treatment of an electromagnetic actuator part according to one of Claims 1 to 12, characterized by nitriding in a temperature range between 380 ° C and 480 ° C and with a nitriding index K _N ≈ 10. A method according to claim 16, characterized in that the nitriding in an oxygen atmosphere (oxynitriding) is carried out with an oxidation number K _O ≈ 0.20.

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