EP1263993B1 - Method for producing non grain-oriented electric sheets - Google Patents

Abstract

The invention relates to a method for producing non-grain-oriented hot-rolled magnetic steel sheet in which from a raw material such as cast slabs, strip, roughed strip or thin slabs produced from a steel comprising (in weight %) C: 0.0001-0.05 %; Si: <=1.5 %; Al: <=0.5 %, wherein [% Si]+2[% Al]<=1.8; Mn: 0.1-1.2 %; if necessary up to a total of 1.5 % of alloying additions such as P, Sn, Sb, Zr, V, Ti, N, Ni, Co, Nb and/or B, with the remainder being iron and the usual impurities, in a finishing roll line at temperatures above the Ar1 temperature, a hot strip with a thickness <=1.5 mm is rolled, wherein at least the last forming pass of hot rolling is carried out in the mixed region austenite/ferrite and wherein the total deformation epsilH achieved during rolling in the mixed region austenite/ferrite is <35 %. With the method according to the invention, it is possible in particular to economically produce thicker magnetic steel sheet which is not grain-oriented and which has good magnetic properties.

Description

The invention relates to a method for producing non-grain oriented electrical sheet. Under the term "Non-grain oriented electrical steel" are listed here the DIN EN 10106 ("final annealed electrical sheet") and DIN EN 10165 ("non-final annealed electrical steel sheet") covered electrical sheets understood. Beyond that also more anisotropic varieties included as long as they not to be considered grain-oriented electrical sheets.

Non-grain oriented electrical sheets in the thickness range of 0.65 to 1 mm, for example, use in the Production of engines, each only for short Operating times are turned on. typically, Such engines are in the field of home appliances or used as auxiliary drives in motor vehicles. Such engines should deliver high performance, whereas energy consumption is a subordinate one Role play.

A first method for producing Non-grain oriented hot rolled electrical steel is out DE 198 07 122 A1. In the known method becomes one (in mass%) 0.001 to 0.1% C, 0.05 to 3.0% Si, to 0.85% A1, where% Si + 2A1 ≤ 3.0%, and 0.5 - 2.0% Mn and the remainder iron and usual Impurities containing starting material directly from the Pouring heat or after reheating to one hot rolled at least 900 ° C. in the As part of the hot rolling are targeted two or more Forming stitches in the two-phase area austenite / ferrite carried out. In this way can be saved of time and energy if necessary cold-rolled and finally treated electrical steel produce, which compared to conventional sheets of this Kind has improved magnetic properties.

In the conventional production of Non-grain oriented electrical sheet, like her For example, in EP 0 897 993 A1, usually one is made of a steel Composition cast slab or thin slab to one Vorband pre-rolled. This prelude is then in hot-rolled several stitches. If necessary, will the hot-rolled strip annealed. Then it will coiled. After the reeling is usually a Pickling and further annealing of the hot strip, which finally in one step or in several steps Cold rolled with intermediate annealing to final thickness becomes. If necessary, a supplementary Temper rolling performed. Unless the final processor this calls for, the cold-rolled band eventually too still final annealed.

Instead of pre-rolling a Vorbandes from a cast slab can also be thin slabs or direct used, cast pre-bands for generating Electrical sheets are used. When using Cast tapes also have the option of To cast extremely thin tapes, the dimensions of which Approximated dimensions of the hot strip to be produced are. By the casting of such a Vorbands and the Hot rolling this strip into a continuous process can be integrated, technological and cost Benefits are achieved.

The magnetic properties of the final product become through each of the individual in the making influenced processing steps. Therefore For example, when hot rolling the stitch sequence and the condition of each rolling pass in the hot strip existing structure depending on the Steel composition determined conversion behavior of the Steel above the temperature at the beginning of rolling and which was carried out between the individual rolling passes Cooling adjusted so that the desired magnetic Properties of the final product can be achieved. As well the properties of the final product are determined by the Annealing temperatures, the reel temperature and the Deformations in the course of cold rolling determined.

The large number of production steps makes the Production of electrical sheets technically complex and expensive. This proves especially with larger ones Sheet thicknesses as disadvantageous.

The object of the invention is a method specify with which in particular thicker Non-grain oriented electrical sheets cost-effective produce good magnetic properties have.

C:

0,0001 - 0,05 %,

Si:

≤ 1,5 %,

Al :

≤ 0,5 %, wobei [%Si] + 2[%Al] ≤ 1,8,

Mn:

0,1 - 1,2 %,

wahlweise bis insgesamt 1,5 % an Legierungszusätzen von P, Sn, Sb, Zr, V, Ti, N, Ni, Co, Nb und / oder B
Rest Eisen sowie übliche Verunreinigungen,
hergestellt ist, in einer Fertigwalzstaffel bei oberhalb der Ar₁-Temperatur liegenden Temperaturen ein Warmband mit einer Dicke ≤ 1,5 mm gewalzt wird, wobei mindestens der letzte Umformstich des Warmwalzens im Mischgebiet Austenit / Ferrit durchgeführt wird und die gesamte im Zuge des Walzens im Mischgebiet Austenit / Ferrit erreichte Formänderung ε_H < 35 % ist.This object is achieved by a method of producing non-oriented hot-rolled electrical steel sheet comprising: a starting material, such as cast slabs, strips, slivers or thin slabs, made of a steel having (in% by weight)

C:

0.0001 - 0.05%,

Si:

≤ 1.5%,

Al:

≤ 0.5%, where [% Si] + 2 [% Al] ≤ 1.8,

Mn:

0.1 - 1.2%,

optionally up to a total of 1.5% of alloying additions of P, Sn, Sb, Zr, V, Ti, N, Ni, Co, Nb and / or B.
Remainder iron as well as usual impurities,
a hot strip having a thickness ≤ 1.5 mm is rolled in a finishing roll at temperatures above the Ar ₁ temperature, at least the last hot stamping pass in the austenite / ferrite mixing zone being carried out, and the entire during the rolling in the Mixed region austenite / ferrite reached strain ε _H <35%.

According to the invention, an austenite-forming Steel cast strip from the casting heat used directly rolled to a hot strip. The rolling conditions are during hot rolling chosen so that the complete Ferrite transformation not until the end of rolling is completed. Instead, at least the last stitch in the mixed area austenite / ferrite performed while all other stitches in austenite to be rolled.

By producing the primary material and hot rolling the electric sheet in a process according to the invention can be performed non-grain oriented Electro-plate tapes are produced whose thickness is so low is that she, without again to the thickness reduction cold rolled, delivered to the end user can be. Particularly good results can be achieved achieve a method according to the invention, if the Starting material as a cast thin slab or cast strip is produced and the hot rolling continuously on the Production of the starting material follows. So have hot tapes, in accordance with the invention from a on a Casting mill produced and continuously processed starting material are manufactured, excellent features.

It has been found that in compliance with the According to the invention provided operating conditions hot rolled non-grain oriented electrical sheets which have in their properties those Electrical sheets are at least equal, in conventionally following hot striping cold rolled. The inventive method thus makes it possible, while saving more costly and time-consuming steps that in the state of Technology has always been considered necessary, high quality electric sheets with good magnetic Produce properties cost-effectively.

Usually, the finished hot rolled and if necessary, cooled hot rolled strip. there the reel temperature is preferably at least 700 ° C. Experience has shown that in compliance with this Reel temperature a hot strip annealing all or at least be saved to a substantial extent. The hot strip is already softened in the coil, with his Characteristics determining characteristics, such as grain size, Texture and excretions are positively affected. It is particularly advantageous in this context, if the band using the coil heat of a passive Annealing is subjected. Such from the coil heat "in-line" annealing performed at high temperature coiled, not significantly cooled in the coil Hot strip may otherwise fail completely replace required hot band bake annealing. Thus, annealed hot strips with particularly good magnetic and technological properties produce. The required time and Energy expenditure is considerably lower than with the conventionally for improving the properties of Electric sheet performed hot strip annealing.

Alternatively or in addition to the "passive" annealing in the coil if the properties to be set can do this necessitate the tape following the reeling be subjected to an annealing. Regardless, in which form the hot strip annealing is performed can It may be beneficial to the annealing in a conventional manner under an oxygen-reduced atmosphere perform.

According to another, especially for processing a steel with a Si content of at least 0.7 wt .-% particularly suitable embodiment of Invention, the hot strip after rolling in the Finishing scale at a reel temperature of less than 600 ° C, in particular less than 550 ° C, reeled. The Reeling at these temperatures leads to the to a solidified alloy Hot strip state. Thereby further improvements of the Properties of such a strung and alloyed Electrical sheets are achieved by the reeled Hot strip immediately after the coiling in the coil is cooled accelerated.

Practical experiments have shown that hot-rolled electrical steel strip can be produced with particularly good properties if the center of gravity of the deformation during hot rolling is clearly in the austenite region. Therefore, a further embodiment of the invention, which takes into account this result, characterized in that the deformation achieved in the course of rolling austenite / ferrite ε _{h is} limited to 10% - 15%.

Regardless of how strong the hot strip in the mixed area γ / α can be deformed by a suitable choice of Ratio of degree of deformation and deformation rate, i.e. Utilization of the heat generated during forming, an optimal temperature control in the sense of avoidance a cooling of the rolling stock and thus a complete Conversion to ferrite can be avoided.

In this context, the term "total change in shape ε _h " is understood to mean the ratio of the decrease in thickness during rolling in the respective phase region to the thickness of the strip when it enters the relevant phase region. According to this definition, a hot strip produced according to the invention has, for example, a thickness h ₀ after rolling in the austenite region. In the course of the subsequent rolling in the two-phase mixing zone, the thickness of the hot strip is reduced to h ₁ . By definition, this results in the total change in shape ε _h achieved during mixing rolling, for example, to (h ₀ -h ₁ ) / h ₀ with h ₀ = thickness when entering the first austenite / ferrite mixed stand and h ₁ = thickness when leaving the last one Rolling mill passed in the mixed state.

To improve the condition of the strip surface and the further processability, it is favorable if the hot strip is pickled after reeling.

Demands the end user a final annealed Electrical sheet, so it is appropriate, the hot strip after the Pickling at an annealing temperature of at least 740 ° C to anneal a final annealed electrical steel strip. Will against it the final annealing after pickling at one lower annealing temperature of at least 650 ° C carried out, so is a non-annealed Get electrical tape, which if necessary one Final annealing can be subjected to the end user. Both annealing treatments can, depending on the Peculiarities of the respective alloy, the desired Properties of the electric sheet and the available standing facilities, either in the hood furnace or in the Continuous furnace be performed.

A further improvement of the processability of the produced and delivered according to the invention Elektro Wristband can be achieved in that the pickled hot strip at a degree of deformation of up to 3% is smoothed. In this rolling become bumps the surface of the strip smoothed, without it to a Significant influence of in the course of hot rolling created structural state comes.

Alternatively or in addition to a pure smoothing stitch the above-explained type, the dimensional stability and Surface texture of the invention produced, Hot rolled strip can be improved by that the pickled hot strip at a degree of deformation of more than 3% to 15% temper rolling. Also this Nachwalzen does not lead to structural changes that would be comparable with the changes that occur during cold rolling because of This achieved high degrees of deformation usually targeted be brought about.

A further advantageous embodiment of the invention is characterized in that the hot rolling in the mixing area done with lubrication. By hot rolling with Lubrication occur on the one hand lower shear deformations so that the rolled strip results in a more homogeneous Structure over the cross section receives. On the other hand reduced by the lubrication, the rolling forces, so that over the respective Walzstich a higher thickness decrease is possible.

Preferably, the final thickness of the hot strip is 0.65 mm up to 1 mm. At low cost and consequently produced inexpensively marketable bands of this thickness a high demand.

The process according to the invention is particularly suitable for Processing of such steels, which has a Si content of have at most 1 wt .-%. Such steels have a pronounced austenite phase, so that the transition from the austenite to the mixed phase austenite / ferrite can be controlled very precisely.

Is the carbon content of the steel over
0.005 wt .-%, it is advantageous if the hot strip is annealed decarburizing before assembly and delivery.

The invention will be explained in more detail below on the basis of exemplary embodiments:
In the following, "J2500", "J5000" and "J10000" designate the magnetic polarization at magnetic field strengths of 2500 A / m, 5000 A / m and 10000 A / m, respectively.

Under "P 1.0" or "P 1.5" is the Loss of magnetization at a polarization of 1.0 T. or 1.5 T and a frequency of 50 Hz understood.

The given in the following tables Magnetic properties are each on individual strips measured along the rolling direction.

In Table 1, for two steels used for the production of electric steel according to the present invention, the contents of the alloy essential constituents are shown in weight%. stole C Si al Mn A 0,008 0.10 0.12 0.34 B 0,007 1.19 0.13 0.23

As indicated in Table 1
Compositions formed melts have been continuously cast in a continuous casting plant to each a pre-band, which has also been continuously fed into a multi-roll stand comprising hot rolling.

Tables 2a-2c show the magnetic properties J ₂₅₀₀ , J ₅₀₀₀ , J ₁₀₀₀₀ , P _1.0 and P _1.5 for each of three electrical sheets A1-A3 or B1-B3 produced from steels A and B, respectively. During hot rolling of these electrical sheets A1 - A3 and B1 - B3, the center of gravity of the deformation has been placed in each case in the area in which the respective strip was in the austenitic state. In the mixed area austenite / ferrite, however, only one rolling pass has been carried out. The total deformation ε _{H achieved here} was less than 35%, in particular 30%.

Following rolling, the hot-rolled strips were rewound at a coiler temperature of 750 ° C. sheet J ₂₅₀₀ [T] J ₅₀₀₀ [T] J ₁₀₀₀₀ [T] P _1.0 [W / kg] P _1.5 [W / kg] A1 1,623 1,704 1,513 5,494 12.457 B1 1,646 1,717 1,556 4,466 9,593 sheet J ₂₅₀₀ [T] J ₅₀₀₀ [T] J ₁₀₀₀₀ [T] P _1.0 [W / kg] P _1.5 [W / kg] A2 1.651 1,726 1,564 5,354 13,548 B2 1,638 1,716 1,550 3,614 8,554 sheet J ₂₅₀₀ J ₅₀₀₀ J ₁₀₀₀₀ P _1.0 P _1.5 [T] [T] [T] [W / kg] [W / kg] A3 1,658 1,728 1,578 4,892 11.073 B3 1,611 1,690 1,532 3,062 7.641

In the case of Examples A1, B1 (Table 2a), the hot strips after cooling have been assembled directly to commercial electrical steel sheets and delivered to the end user. In the case of Examples A2, B2 (Table 2b), the hot strips were pickled before their delivery to the end user and additionally subjected to a smoothing pass. In this smoothing pass, a deformation ε _H of at most 3% has been achieved. The tapes A3, B3 (Table 2c) have each been tempered before pickling after pickling.

Comparative studies, to 1 mm thick, after the According to the invention produced electric sheets and Electrical sheets have been carried out in conventionally hot and cold rolled, show that the recoverable values of the magnetic Polarization and the achievable values of the specific Loss of magnetization of inventively generated Electric sheets in narrow areas with those values match those for the properties in question conventionally produced electrical sheets are determined could.

In diagram 1 logarithmically for three according to the invention produced electrical sheets a, b, c and a conventional Way produced sheet d the respective course of magnetic polarization over the magnetic field strength were applied. The plate a was used directly Sheet b smoothed and sheet c dressed.

In Diagram 2 is logarithmic for the three According to the invention produced electrical sheets a, b, c and the conventionally produced sheet d of the respective Course of the specific loss of magnetization over the magnetic polarization has been applied.

It is readily apparent that the properties of the According to the invention produced sheets a, b, c only slightly from the properties of the conventionally produced Electro sheet deviate. This shows that deals with the According to the invention carried out optimization of the Hot rolling selected rolling strategy while saving the costly cold rolling high quality, marketable Make electrical sheets.

Claims (25)

1. A method for producing non-grain-oriented hot-rolled magnetic steel sheet in which from a raw material such as cast slabs, strip, roughed strip or thin slabs produced from a steel comprising (in weight %)

   C:

   0.0001 - 0.05 %;

   Si:

   ≤ 1.5 %;

   Al:

   ≤ 0.5 %, wherein [%Si] + 2[%Al] ≤ 1.8;

   Mn:

   0.1 - 1.2 %;

   optionally up to a total of 1.5 % alloying additions of P, Sn, Sb, Zr, V, Ti, N, Ni, Co, Nb and / or B; with the remainder being iron and the usual impurities;
   in a finishing roll line at temperatures above the Ar₁ temperature, a hot strip with a thickness ≤ 1.5 mm is rolled, wherein at least the last forming pass of hot rolling is carried out in the mixed region austenite / ferrite and wherein the total deformation ε_H achieved during rolling in the mixed region austenite / ferrite is < 35 %.
2. The method according to claim 1,
   characterised in that the steel comprises up to a total of 1.5 % alloying additions of P, Sn, Sb, Zr, V, Ti, N, Ni, Co, Nb and / or B.
3. The method according to claim 1 or 2, characterised in that the raw material is produced as cast thin slab or cast strip and in that hot rolling follows continuously after the production of the raw material.
4. The method according to one of the preceding claims, characterised in that the hot strip is coiled.
5. The method according to claim 4, characterised in that the coiling temperature is at least 700 °C.
6. The method according to claim 5, characterised in that using the coil heat, the hot strip is subjected to passive annealing.
7. The method according to claim 5, characterised in that after coiling, the hot strip is annealed.
8. The method according to one of claims 4 to 7, characterised in that hot-strip annealing takes place in an oxygen-reduced atmosphere.
9. The method according to claim 4, characterised in that the coiling temperature is ≤ 600 °C.
10. The method according to claim 9, characterised in that the coiled hot strip is cooled in the coil at an accelerated rate immediately following coiling.
11. The method according to one of the preceding claims, characterised in that total deformation ε_H achieved during rolling in the mixed region austenite / ferrite, is 10 % - 15 %. SI/cs 991169EPX
12. The method according to one of the preceding claims, characterised in that the hot strip is pickled following coiling.
13. The method according to one of the preceding claims, characterised in that the hot strip is annealed at an annealing temperature of at least 740 °C to obtain a finally annealed magnetic steel strip.
14. The method according to claim 1 or 12, characterised in that the hot strip is annealed at an annealing temperature of at least 650 °C to obtain a magnetic steel strip which has not been subjected to final annealing.
15. The method according to claim 13 or 14, characterised in that annealing takes place in a hood-type furnace.
16. The method according to claim 13 or 14, characterised in that annealing takes place in a continuous furnace.
17. The method according to one of the preceding claims, characterised in that the hot strip is finished and shipped without having been cold-rolled.
18. The method according to one of claims 1 to 16, characterised in that the hot strip is smooth-rolled at a degree of forming of ≤ 3 %.
19. The method according to claim 18, characterised in that the smooth-rolled strip is finished and shipped.
20. The method according to one of claims 1 to 16, characterised in that the hot strip is skin pass rolled at a degree of forming of > 3 % - 15 %.
21. The method according to claim 20, characterised in that the skin pass rolled strip is finished and shipped.
22. The method according to one of the preceding claims, characterised in that the final thickness of the hot strip is 0.65 to 1 mm.
23. The method according to one of the preceding claims, characterised in that hot rolling in the mixed region is accompanied by lubrication.
24. The method according to one of the preceding claims, characterised in that the Si content of the steel is max. 1 % by weight.
25. The method according to one of claims 17, 19 or 21, characterised in that the C content of the steel exceeds 0.005 weight % and in that the hot strip is annealed in a decarburising medium prior to finishing and shipment.

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