EP4438199A1 - Method for producing an electric strip or sheet and electric strip or sheet produced therefrom - Google Patents

Abstract

A method for producing an electrical strip or sheet (15), in particular one that is not grain-oriented, is shown. In order to create an electrical strip or sheet (15) with a high level of flatness, it is proposed that during casting in a continuous casting plant (1), the melt (3) in the mold (2) is first stirred with a first electromagnetic stirrer (EMRS) (12) and a non-solidified part of the slab strand (7) is secondly stirred in the region of the strand guide (6) with a second electromagnetic stirrer (SEMS) (14).

Description

The invention relates to a method for producing an electrical strip or sheet, in particular a non-grain-oriented one, and to an electrical strip or sheet produced thereby.

To produce a slab strand with a larger core zone with fine-grained and globular solidification structure, it is EP3134220B1 It is known to provide an electromagnetic stirrer after the mold in a continuous casting plant. This mold also has an electromagnetic brake (EMBr) to slow down the flow rate of the metallic melt in the mold.

In order to produce a flat electrical strip or sheet, it is known to further process a slab from a slab strand by hot rolling, hot strip annealing and subsequent cold rolling and, if necessary, straightening. A wide variety of measures are known to reduce the product tolerances of the electrical strip or sheet - for example, to achieve a high degree of flatness on the electrical strip or sheet, which flatness has a direct effect on the degree of lamination of a sheet stack made up of sheet metal parts of the electrical strip or sheet.

The invention therefore has the task of improving a method for producing an electrical strip or sheet based on the prior art so that a comparatively high level of flatness can be achieved on the electrical strip or sheet in a reproducible manner. In addition, the electrical strip or sheet produced should be versatile.

The invention solves the problem by the features of claim 1.

Surprisingly, it was found that casting a melt to form a slab strand can have a significant effect on the flatness of an electrical strip or sheet. This also applies after subsequent rolling of a slab of the slab strand. According to the invention, stirring takes place twice during casting - namely a first stirring of the melt in the mold with a first electromagnetic stirrer (EMRS) and a second stirring of a non-solidified part of the slab strand in the area of the strand guide with a second electromagnetic stirrer (SEMS). Investigations on the solidified slab strand showed that due to the interaction of the two electromagnetic stirrers, a structure with a particularly high globulitic content is established in the slab strand and thus in the slab. The slab is therefore particularly suitable for subsequent rolling in order to enable a comparatively low product tolerance, particularly with regard to flatness, in the electrical strip or sheet produced with it. According to the invention, a versatile electrical strip or sheet can be created, which also includes the use for laminated cores with a high degree of lamination. This includes, for example, a laminated core for a rotor or stator of an electrical machine, such as electric motors or generators.

It can be particularly advantageous if the first electromagnetic stirrer (EMRS = Electromagnetic Rotating Stirrer) generates a circulating flow in the melt around the central longitudinal axis of the mold. For example, this can also improve globulitic solidification.

Preferably, the first electromagnetic stirrer generates a circulating flow in the melt around the central longitudinal axis of the mold. This can further improve the homogenization of the melt and further increase the globulitic portion of the solidification structure of the slab strand.

The above, for example, can be further improved if the melt is stirred close to the solidifying region in the mold, in which the circulating flow generated is essentially formed in the peripheral region of the mold.

The stirring of the first electromagnetic stirrer (EMRS) can be made more uniform, for example, if it is designed as a rotary stirrer. This makes it possible to achieve temperature homogenization, for example, but also to reduce overheating more quickly.

Preferably, the first electromagnetic stirrer (EMRS) stirs the melt in a longitudinal section of the mold with a magnetic field, which longitudinal section extends from a bath level of the mold to at most the end of an immersion tube immersed in the melt bath of the mold. This allows, for example, the melt to be prepared before or at the beginning of its solidification to form the uniform structure according to the invention.

For example, it can be provided that the first electromagnetic stirrer in the melt at the solidification front generates a flow rate in the range of 0.02 to 0.5 m/s (meters/second) in order to adequately prepare the melt for solidification with a more uniform structure. This can also be beneficial for improved globulitic solidification. This can be improved if the flow rate is, for example, in the range of 0.2 to 0.4 m/s (meters/second). For example, a stirring frequency of 1 Hz (Hertz) can be advantageous here.

Preferably, the second electromagnetic stirrer generates two flows in the non-solidified part of the slab strand, which are arranged one after the other in the longitudinal direction of the slab strand and circulate in opposite directions across the width of the slab strand. This can improve the homogenization of the melt. It can also further homogenize the temperature of the melt across the width of the strand.

If the second electromagnetic stirrer is arranged in the bending zone of the strand guide, for example, a comparatively large volume part of the slab strand can be prepared for solidification.

Preferably, the second electromagnetic stirrer is arranged at a distance in the range of 1.5 to 7 m (meters) from the end of the mold in order to be able to exert sufficient influence on the melt in the non-solidified part of the slab strand. This can be further improved if the second electromagnetic stirrer is arranged at a distance in the range of 4 to 5 m (meters) from the end of the mold.

Preferably, the second electromagnetic stirrer generates a flow rate in the melt in the range of 0.2 to 0.9 m/s. Particularly preferably, the second electromagnetic stirrer generates a flow rate in the melt in the range of 0.4 to 0.7 m/s. This can improve the homogenization of the melt. It is also possible to further homogenize the temperature of the melt across the strand width in this way.

Preferably, the slab has a solidification structure with a globulitic content of > 90%, as this has a particularly beneficial effect on the flatness of the electrical strip or sheet. This is even more so if the slab has a solidification structure with a globulitic content of > 99%. In general, it is mentioned that globulitic grains are those grains whose ratio of grain length to grain width is ≤ 3.

As is well known, the slab is further processed by hot rolling, possibly hot strip annealing, and then cold rolling to create an electrical strip or sheet.

The electrical strip or sheet is preferably coated over the entire surface on at least one flat side with a thermosetting hot-melt adhesive varnish, in particular a baking varnish layer. The electrical strip or sheet can also be coated on both of its flat sides with a hot-melt adhesive varnish. The hot-melt adhesive varnish is then converted to the B-state. The hot-melt adhesive varnish is preferably converted to the B-state in order to adequately prepare the electrical strip or sheet for a packaging process.

Alternatively, it is conceivable that the electrical strip or sheet is fully coated on at least one flat side, in particular on both flat sides, with an insulating varnish, which is then hardened.

The coating can be applied to one or both flat sides of the electrical strip or sheet.

• 1,5 bis 3,5 Silizium (Si),
• 0,1 bis 2, insbesondere 0,1 bis 1,5, Aluminium (Al),
• 0,1 bis 1 Mangan (Mn),
• 0,01 bis 0,2 Phosphor (P)

und als Rest Eisen (Fe) sowie herstellungsbedingt unvermeidbare Verunreinigungen auf. Dies Legierungszusammensetzung kann
optional einzeln oder in Kombination aus der Gruppe:

• < 0,01 Schwefel (S)
• < 0,01 Kohlenstoff (C)
• < 1,0, insbesondere < 0,3, Nickel (Ni)
• < 1,0, insbesondere < 0,3, Chrom (Cr)
• < 1,0, insbesondere < 0,3, Titan (Ti)
• < 1,0, insbesondere < 0,3, Niob (Nb)
• < 1,0, insbesondere < 0,3, Vanadium (V)
• < 1,0, insbesondere < 0,3, Kupfer (Cu)

und als Rest Eisen (Fe) sowie herstellungsbedingt unvermeidbare Verunreinigungen aufweist. Vorzugsweise ist der gemeinsame Gehalt in Gew.-% von Ni+Cr+Ti+Nb+V+Cu < 1,0, insbesondere < 0,3.Preferably, the electrical strip or sheet has an alloy composition with in each case in wt.%

• 1.5 to 3.5 silicon (Si),
• 0.1 to 2, in particular 0.1 to 1.5, aluminium (Al),
• 0.1 to 1 manganese (Mn),
• 0.01 to 0.2 phosphorus (P)

and the rest iron (Fe) as well as unavoidable impurities due to the manufacturing process. This alloy composition can
optionally individually or in combination from the group:

• < 0.01 sulfur (S)
• < 0.01 carbon (C)
• < 1.0, especially < 0.3, Nickel (Ni)
• < 1.0, especially < 0.3, chromium (Cr)
• < 1.0, especially < 0.3, titanium (Ti)
• < 1.0, especially < 0.3, niobium (Nb)
• < 1.0, especially < 0.3, vanadium (V)
• < 1.0, especially < 0.3, copper (Cu)

and the remainder iron (Fe) and unavoidable impurities resulting from the manufacturing process. Preferably, the combined content in wt.% of Ni+Cr+Ti+Nb+V+Cu is < 1.0, in particular < 0.3.

Preferably, this alloy composition satisfies the condition ((wt.% Si) + 2 * (wt.% Al)) > 2.5.

The invention further aims to provide an electrical strip or sheet which is suitable for producing sheet packages with a high degree of lamination.

The invention solves the problem by the features of claim 16.

The production of the electrical strip or sheet according to the invention makes it possible for the electrical strip or sheet to have a flatness over its entire length which, with a nominal dimension range of 15 cm, measured transversely to the rolling direction over the entire width of the electrical strip or sheet, has a tolerance of ≤ 25 µm. This particularly pronounced flatness can ensure a high degree of lamination on the laminated core and thus a high level of efficiency on the electromechanical converter, such as in electrical machines. This is all the more true if this tolerance is ≤ 20 µm.

Preferably it is a coated electrical strip or sheet.

This is achieved by the electrical strip or sheet having a full-surface, thermo-curable hot-melt adhesive lacquer layer, in particular a baked enamel layer, in the B-state on at least one flat side.

Alternatively, the electrical strip or sheet may have a cured insulating varnish layer as a coating.

The coating can be provided on one or both flat sides.

The electrical strip or sheet preferably has a thickness of 0.1 to 1.5 mm (millimeters). For example, a thickness of 0.2 to 1 mm.

Fig. 1

eine schematische Seitenansicht einer teilweise dargestellten Stranggießanlage,

Fig. 2

eine geschnittene Frontansicht der Fig. 1 in Strangausziehrichtung,

Fig. 3

eine geschnittene Draufsicht auf eine Kokille der Fig. 1,

Fig. 4

eine dreidimensionale Ansicht auf ein Elektroblech mit Längsfalten,

Fig. 5

eine abgerissene Schnittansicht in einem Nennmaßbereich des nach Fig. 4 dargestellten Elektroblechs und

Fig. 6

eine dreidimensionale Ansicht auf ein erfindungsgemäßes Elektroblech ohne Längsfalten.

In the figures, for example, the subject matter of the invention is shown in more detail using an embodiment variant. They show

Fig. 1

a schematic side view of a partially shown continuous casting plant,

Fig. 2

a cut front view of the Fig. 1 in the strand withdrawal direction,

Fig. 3

a sectional view of a mold of the Fig. 1 ,

Fig. 4

a three-dimensional view of an electrical sheet with longitudinal folds,

Fig. 5

a torn-off sectional view in a nominal dimension range of the Fig. 4 electrical sheet shown and

Fig. 6

a three-dimensional view of an electrical steel sheet according to the invention without longitudinal folds.

After Fig. 1 a continuous casting plant 1 for producing a slab, preferably in the thickness range of 180 to 270 mm (millimeters), is partially shown. The continuous casting plant 1 has a vertically aligned mold 2, to which a melt 3, namely molten metal, is fed via a dip pipe 4.

A strand guide 6 is arranged downstream of the mold 2 in the strand withdrawal direction 5, with which the slab strand 7 is removed from the mold 2, which slab strand 7 has a non-solidified part 7a and a solidified part 7b - see also Fig. 2 . The strand guide 6 is divided in the order mentioned into a straight guide 8 arranged in alignment with the mold 2, a bending zone 9, a circular arc guide 10 and a straightening zone 11 with a horizontally tapering straight guide (not shown).

According to the invention, the melt 3 is repeatedly stirred electromagnetically in the continuous casting plant 1, as described in detail in the Fig. 2 taken to remove.

The melt 3 is first stirred in the mold 2 using a first electromagnetic stirrer 12, namely EMRS (Electromagnetic Rotating Stirrer). This first electromagnetic stirrer 12 generates, for example with a rotating magnetic field, a horizontally circulating flow 13 in the melt 3 around the central longitudinal axis (Lk) of the mold 2 and essentially in this peripheral region of the mold 2.

It has been found to be particularly advantageous for the suitability for rolling if the first electromagnetic stirrer 12 stirs the melt 3 in a longitudinal section of the mold 2, starting from its bath level 17 to the end 18 of the immersion tube 4 immersed in the melt bath 18 of the mold 2.

A second stirring of a non-solidified part 7a of the slab strand 7 takes place in the region of the strand guide 6 with a second electromagnetic stirrer 14, namely SEMS (Strand Electromagnetic Stirrer). The second electromagnetic stirrer 14 is arranged in the bending zone 9 of the strand guide 6, at a distance A of 4.4 m (meters) from the end of the mold 2. The second electromagnetic stirrer 14 generates two vertical circulating flows 15a, 15b across the strand width B of the slab strand 7 in the non-solidified part 7a of the slab strand 7 by means of a traveling field 14a. Of these two vertical circulating flows 15a, 15b, the first flow 15a is located above the second electromagnetic stirrer 14 and the second flow 15b is located below the second electromagnetic stirrer 14 - they circulate in opposite directions, as shown in Fig. 2 to recognize.

Through this inventive interaction of the two electromagnetic stirrers 12, 14, which operate differently, a special structure is formed in the slab strand 7, which is suitable for subsequent rolling with low product tolerances with regard to the flatness of the non-grain-oriented electrical strip or sheet 15 produced thereby. This can be demonstrated by comparing the Figures 4 , 5 with the Figures 6 be recognized.

• t1 = 52 µm (Mikrometer),
• t2 = 70 µm und
• t3 = 68 µm.

Alle gemessenen Toleranzen liegen daher deutlich über 20 µm. Ein derartiges Elektroband 115 ist zur Herstellung eines elektromagnetischen Bauteils, von dem eine hohe Leistungsdichte gefordert wird, nicht geeignet.The after the Figures 4 and 5 The electrical steel strip 115 shown was manufactured according to the state of the art (SdT). This electrical steel strip 115 shows how in Fig. 4 As can be seen, several visually striking longitudinal folds 16 are repeated over the entire length, which extend in the rolling direction W and appear as strips on the electrical steel strip 115. These longitudinal folds 16 mean that the required narrow limit in the flatness of the electrical steel strip 115 is not achieved over the width B of the electrical steel strip 115. As in Fig. 5 As can be seen, with a nominal dimension range N of 15 cm (centimeters), measured transversely, i.e. in the transverse direction Q to the rolling direction W over the entire width B of the electrical strip or sheet, several tolerances result. In Fig. 5 A measurement of flatness in a nominal dimension range N of 15 cm is shown. For simplified illustration, the Figures 4 and 6 Of the measurements carried out in the transverse direction Q over the entire width B of the electrical steel strip or sheet, only three measurements with a nominal dimension range N each are shown. The measurement in the middle nominal dimension range N shows a tolerance of greater than ≥ 70 µm. Of these, the individual tolerances shown are

• t1 = 52 µm (micrometers),
• t2 = 70 µm and
• t3 = 68 µm.

All measured tolerances are therefore significantly above 20 µm. Such an electrical steel strip 115 is not suitable for the production of an electromagnetic component that requires a high power density.

• t1 = 15 µm,
• t2 = 18 µm und
• t3 = 17 µm.

Diese Toleranzen ergeben sich beispielsweise aus Messdaten von Laser-Abstandssensoren optoNCDT ILD 2300 der Firma MICRO-EPSILON.In contrast, the Figures 6 The electrical strip 15 according to the invention shown has no visually recognizable longitudinal folds 16, even over the entire length L of the electrical strip 15. The stirring according to the invention during the casting of the slab strand 7 causes the structure to solidify to an almost 100% globulitic structure, which considerably facilitates further processing of the slab strand 7 or a slab separated therefrom with hot rolling, hot strip annealing and cold rolling. The electrical strip 15 rolled according to the invention has a maximum tolerance in the range of 10 to 20 µm. Of these, For example, those tolerances in a Fig. 6 nominal dimension range N of 15 cm

• t1 = 15 µm,
• t2 = 18 µm and
• t3 = 17 µm.

These tolerances result, for example, from measurement data from optoNCDT ILD 2300 laser distance sensors from MICRO-EPSILON.

This leads to the results summarized in Table 1 for the state of the art (SdT) and for the invention (ERF): Table 1 example flow velocity [m/s] slab EQ [%] Electrical steel maximum tolerance [µm] SdT EMRS not activated 72 70 SEMS 0.6 ERF EMRS 0.4 100 18 SEMS 0.6

During the tests, a casting speed of 1 m/min and an overheating temperature of 33 Kelvin were set. The cast metal melt (and thus also the electrical steel strip produced from it) has the following alloy composition, each in wt.%: 3.2 silicon (Si), 0.9 aluminum (Al), 0.3 manganese (Mn), 0.01 phosphorus (P), 0.002 sulfur (S), 0.002 carbon (C), and the remainder iron (Fe) and unavoidable manufacturing-related impurities total < 0.1.

According to Table 1, the first electromagnetic stirrer (EMRS) 12 generated a flow velocity of 0.3 m/s in the melt at the solidification front. Its stirring frequency was 1 Hz.

The second electromagnetic stirrer (SEMS) 14 generated a flow velocity of 0.6 m/s in the melt according to Table 1. Its stirring frequency was 3 Hz.

A slab with a thickness of 220 millimeters was produced. This slab was further processed using state-of-the-art technology to produce electrical steel grade 15 (SdT) or 115 (ERF) with a thickness of 0.27 mm.

The test series show that by switching on the first electromagnetic stirrer 12, the globulitic content could be increased from 72% to 100% in the solidification structure of the slab. The electrical steel strip 15 according to the invention shows a maximum tolerance in flatness that is reduced by more than 50 µm in some cases, measured with a nominal dimension range N of 15 cm and measured transversely, i.e. in the transverse direction Q to the rolling direction W, over the entire width of the electrical steel strip 15.

The electrical steel strip 15 according to the invention, which is preferably coated with baking varnish on both flat sides, is therefore excellently suited for producing an electromagnetic component with a high degree of lamination and therefore a high power density. This is also possible in compact construction conditions.

In general, it is noted that "in particular" can be translated into English as "more particularly". A feature preceded by "in particular" is to be considered as an optional feature that can be omitted and thus does not represent a limitation, for example of the claims. The same applies to "vorzugsweise", translated into English as "preferably".

Claims (17)

Method for producing an electrical strip or sheet (15), in particular a non-grain-oriented one, in which in a continuous casting plant (1) a slab strand (7) is cast from a melt (3), wherein this casting feeding the melt (3) into a mold (2), a first stirring of the melt (3) in the mold (2) with a first electromagnetic stirrer (EMRS) (12), a removal of the partially solidified slab strand (7) from the mold (2) with a strand guide (6) and a second stirring of a non-solidified part of the slab strand (7) in the region of the strand guide (6) with a second electromagnetic stirrer (SEMS) (14), and subsequently a slab of the slab strand (7) is further processed into an electrical strip or sheet (15), wherein this further processing comprises rolling. Method according to claim 1, characterized in that the first electromagnetic stirrer (12) generates a circulating flow (13) in the melt (3) around the central longitudinal axis (Lk) of the mold (2). Method according to claim 2, characterized in that the generated circulating flow (13) is formed essentially in the peripheral region of the mold (2). Method according to one of claims 1 to 3, characterized in that the first electromagnetic stirrer (12) is designed as a rotary stirrer. Method according to one of claims 1 to 4, characterized in that the first electromagnetic stirrer (12) stirs the melt (3) in a longitudinal section of the mold (2) with a magnetic field, which longitudinal section extending from a bath level (17) of the mold (2) to at most the end of an immersion tube (4) immersed in the molten bath of the mold (2). Method according to one of claims 1 to 5, characterized in that the first electromagnetic stirrer (12) generates a flow velocity in the range from 0.02 to 0.5 m/s, in particular from 0.2 to 0.4 m/s, in the melt (3) at the solidification front. Method according to one of claims 1 to 6, characterized in that the second electromagnetic stirrer (14) generates two flows (15a, 15b) in the non-solidified part of the slab strand (7), which are arranged one after the other in the longitudinal direction (Lb) of the slab strand (7) and circulate in opposite directions across the strand width of the slab strand (7). Method according to one of claims 1 to 7, characterized in that the second electromagnetic stirrer (14) is arranged in the bending zone (9) of the strand guide (6). Method according to claim 8, characterized in that the second electromagnetic stirrer (14) is arranged at a distance (A) in the range of 1.5 to 7 m, in particular 4 to 5 m, from the end of the mold (2). Method according to one of claims 1 to 9, characterized in that the second electromagnetic stirrer (14) generates a flow velocity in the range from 0.2 to 0.9 m/s, in particular from 0.4 to 0.7 m/s, in the melt (3). Method according to one of claims 1 to 10, characterized in that the slab has a solidification structure with a globulitic content of > 90%, in particular > 99%. Method according to one of claims 1 to 11, characterized in that the slab is hot rolled during its further processing, optionally hot strip annealed, and then cold rolled. Method according to one of claims 1 to 12, characterized in that the electrical strip or sheet (15) is coated on at least one flat side, in particular on both flat sides, either with a thermo-curable hot-melt adhesive lacquer, in particular with a baked lacquer layer, over the entire surface and this layer is then converted to the B-state, or is coated over the entire surface with an insulating lacquer and then cured. Method according to one of claims 1 to 13, characterized in that the electrical strip or sheet (15) has an alloy composition with in each case in wt.% 1.5 to 3.5 silicon (Si), 0.1 to 2, especially 0.1 to 1.5, aluminum (Al), 0.1 to 1 manganese (Mn), 0.01 to 0.2 phosphorus (P), optionally individually or in combination from the group: < 0.01 sulfur (S) < 0.01 carbon (C) < 1.0, especially < 0.3, Nickel (Ni) < 1.0, especially < 0.3, Chromium (Cr) < 1.0, especially < 0.3, titanium (Ti) < 1.0, especially < 0.3, niobium (Nb) < 1.0, especially < 0.3, Vanadium (V) < 1.0, especially < 0.3, copper (Cu) and the remainder is iron (Fe) and unavoidable impurities resulting from the manufacturing process. Method according to claim 14, characterized in that the alloy composition satisfies the condition $$\left(\left(\mathrm{Gew}\%\mathrm{Si}\right)+2*\left(\mathrm{Gew}\%\mathrm{Al}\right)\right)>2.5$$

fulfilled. Electrical strip or sheet, produced by a method according to one of claims 1 to 15, characterized in that the electrical strip or sheet (15) has a flatness over its entire length which, with a nominal dimension range (N) of 15 cm, measured transversely to the rolling direction (W) over the entire width of the electrical strip or sheet (15), has a tolerance of ≤ 25 µm, in particular ≤ 20 µm. Electrical strip or sheet according to claim 16, characterized in that it has a full-surface and thermo-curable hot-melt adhesive lacquer layer, in particular a baked enamel layer, in the B-state, or a cured insulating lacquer layer on at least one flat side.

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