DD201808A5 - TWO-STAGE COLD-ROLLED AND INTERMEDIATE STEEL PLATE FOR THE PRODUCTION OF ELECTRO-LEADS, METHOD FOR THE PRODUCTION THEREOF, AND METHOD FOR PRODUCING FINISHED, NON-ORIENTED ELECTRO-LEAVES - Google Patents

Abstract

In order to keep the required strip thickness of a two-stage cold-rolled and zwischengegluehten steel sheet for the production of electrical steel sheets after the first cold rolling low u. In this way, the necessary duration of the decarburizing final annealing can be shortened and in order to produce electrical steel sheets with reasonable core losses with simultaneously high values of magnetic induction also from unalloyed or tempered steel with an Si content of less than 0.15%, it is ensured according to the method that the crystallites forming the sheet after the intermediate annealing have an average grain diameter of less than 0.07 mm, preferably of 0.005 to 0.05 mm.

Description

Two-stage cold-rolled and intermediate-annealed steel sheet for the production of electrical steel sheets, process for its production and process for the production of finish-annealed, non-oriented electrical steel sheets

Field of application of the invention

The invention relates to a two-stage cold-rolled and intermediate-annealed steel sheet for producing low-core-loss, high-induction magnetic steel sheets and a method for producing such steel sheets, which are referred to as "semi-finished" products. Furthermore, an embodiment of the invention also relates to the production of finished final annealed electrical sheets

 Characteristic of the known technical solutions

According to Euronorm 126-77 or 106-71, respectively, electrical sheet grades are averaged over the guaranteed maximum value for the magnetization loss P, expressed in watts / kg, with alternating field magnetization of 50 Hz for a conventional peak value of the sinusoidal induction of 1 or 1.5 Tesla at room temperature and divided according to their nominal thickness. The aim is generally to obtain the highest possible values for the magnetic induction (magnetic flux density) B, measured in Tesla at certain strengths (A / m) of an alternating magnetic field H 'of the products, with the lowest possible loss of magnetization reversal. Minimum values of B are prescribed for the individual types of electrical steel.

The magnetic properties are tested in the 25 cm Epstein frame according to Euronorm 118.

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It is known that by alloying additives such as silicon and aluminum, the Ummagnetisier- ungsverluste steel. Although the plates are lowered, however, the values: magnetic induction are thereby likewise reduced. For these reasons, and also for reasons of processability (for example with regard to the service life of the punching tools) and for cost reasons, it is therefore desirable to keep the Si content as low as possible for a given type of electrical steel steel. Since it is further known that the Ummagne- tisierungsverluste are higher in fine-grained material than coarse-grained, hot-rolled starting * electr band is twice annealed and cold rolled two stages (DE-OS 26 27 532 and DE-OS 27 47 660) by known methods , ·

From recrystallization images it is known that for an extreme coarse grain formation in the course of the final annealing not only the chemical composition, the .Verformungsgrad and the final annealing conditions are decisive, but also the nature of the preceding processing steps .. The grain after final annealing is greater, the coarser this Band was already after the first glow. The grain size after the first annealing can be controlled to some extent by both the temperature and the annealing time. It is therefore generally endeavored to create a relatively coarse-grained structure already at the first annealing. ,

These known methods for the production of electrical steel have the disadvantage that the strip thickness after the first cold rolling due to the required high degree of deformation in the last cold rolling (DE-OSs 26-27 532 and 27 47 660) must be relatively large. For example, to produce a 0.50 mm thick electrical steel, must at the first cold rolling a. Thickness of 0.9 to 1.7 mm can be maintained. Such a thick strip is hardly decarburized during the first annealing, a reduction in C content

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but is indispensable for the required aging resistance of electrical steel sheets; The final annealing must therefore be carried out very slowly. In particular, Si-alloyed electrical sheets are today almost exclusively continuous, d. H. in a continuous furnace, annealed. It is therefore necessary in the known methods to start from extremely low carbon steel.

Furthermore, it has not been possible to produce electric sheets of unrefined or tempered steel having a silicon content of less than 0.15% with reasonable magnetization losses and simultaneously high levels of magnetic induction.

Object of the invention

The invention aims to overcome these drawbacks and to provide electric sheets as "semi-finished" products or as finished final annealed electrical sheets, which are manufactured in an energy-saving manner and using existing equipment.

Explanation of the essence of the invention

The invention has for its object to produce electrical steel sheets with relatively low re-magnetization losses higher magnetic induction than such comparable composition «

The invention is based on the recognition that in order to achieve this goal, a certain small grain size of the crystallites forming the sheet after the intermediate annealing of the starting material is authoritative, .while, as previously stated, in this stage of processing a relatively large average grain size in the range of 0 , 1 to 0.2 mm was sought (DE-OS 27 47 660).

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Accordingly, the invention consists in that in two-stage cold-rolled and annealed steel sheet for the production of electrical steel sheets with low loss of magnetic reversal and high magnetic induction, the sheet-forming crystallites after Zwischenglühung

I b-2b b

have an average grain diameter of less than 0.07 mm, preferably from 0.005 to 0.05 mm.

According to further embodiments of the invention, the crystallites in sheet metal of silicon-alloyed 'steel with a

, Content of 1 to 3.2% silicon has an average grain diameter of 0.02 to 0.04 mm, in the case of tempered steel sheet containing 0.05 to 0.08% carbon, 0.55 to 0.73% manganese , .0.05 to 0.10%. SiIicium, 0.02 to 0.06% aluminum, 0.09 to 0.11% phosphorus and 0.020 to 0.024% sulfur have an average grain diameter of 0.005 to 0.02 mm and unalloyed steel sheet containing less than 0 , 02% carbon, 0.50-0.70% manganese, 0.09-0.16% phosphorus and 0.017-0.026% sulfur have an average grain diameter of 0.03-0.05 mm. ,

The method for the production of electrical sheets with low loss of magnetization and high magnetic.

Induction from a steel sheet with the above-mentioned average grain diameters of the crystallites, wherein hot rolled steel sheet is rolled to final strength in an intermediate annealing with an intermediate annealing, is characterized in that: a steel sheet containing 1 to 3.2% silicon, which either at a temperature of 820 to 85O ° C for a time of 1 to 3 minutes in the course of en or, was annealed at a temperature of 620 to 700 ° C for 10 to 14 hours in the annealing furnace, and which in the second cold rolling in a Walzstich was reduced by 4 to 10%, a final annealing, advantageously at a temperature of 920 to 9 80 ° C wan oven is subjected ..

from 920 to 98o C during 2 to. 5 minutes in continuous

According to a further embodiment of the method according to the invention is a sheet of ungeuhigtem or calmed

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Steel with a silicon content of less than 0.15% at a temperature of 620 to 690 C for 11 to 13 hours in the annealing annealing annealed intermediate and the second cold rolling in one. Walzstich by 6 to 10% .reduziert, whereupon optionally after intermediate storage of the obtained "semi-finished" product, the final annealing at a "temperature of 760 to 800 ° C for 90'to .120 minutes is performed.

The Elektrobleehe produced according to the invention also have

after possible intermediate storage in the "semi finished" () stage, very good magnetic properties were achieved, while at the same time being highly economical to produce. For many uses, the processing of "semi-finished" products is very advantageous, since, for example, ready-made electro-alloys of carbon steel with an Si-content of less than 0.15% are extremely soft. In order to produce burr-free moldings, in these cases, a non-final annealed steel sheet is punched, for example, and only subsequently subjected to the moldings of a final annealing. '

In the second cold rolling according to the invention a relatively low degree of reduction is maintained, which is why '.---' 25 steels with relatively high starting carbon content one. ' can be set. The once cold-rolled steel strips are already decarburized due to their low strength during the intermediate annealing to a greater extent. ,

Another advantage is that the first annealing (intermediate annealing) can be performed without special precautions in a Haubenglühofen (base annealing). In this type of annealing, which is known .Economic than an annealing in a continuous furnace, 5 is a wound coil annealed.

1 6 2 a. b

Ausführüngsbeispiel

The invention is illustrated by the following examples and by

the accompanying drawing explains in more detail:

The magnetic properties were determined according to Enronorm 118 by testing in 25 cm Epstein frame, wherein each half of the samples was taken parallel to the rolling direction, the other half perpendicular to the rolling direction of the sheets or strips.

All reported grain sizes were determined according to ASTM E 112-63, Section 6 (Comparison Procedure); the assignment of the micro grain size no. according to ASTM for average grain diameter in ram, Table II of this standard can be found. The number before the parentheses expresses the most commonly represented grain size, the numbers in parentheses indicate the scattering range.

Example 1: .

From 10 melts whose chemical composition, according to casting analysis, within the following ranges defined for the individual elements, namely from 0.010 to 0.020% C, 2.50 to 2.70% Si, 0.20 to 0.50% Mn, 0 , 30 to 0.50% Al, less than 0.020% P and less than 0.020% S, 38 were made about 2 mm thick hot strips and cold rolled to 0.53 mm. The annealing conditions in the subsequent first annealing (intermediate annealing) in a continuous furnace with decarburizing inert gas (DX gas containing '7 to 10% H ₃ , about 12 % CO + CO ₂ , balance N ₂ , dew point about 19 to 22 ° C ) were varied so that different particle sizes of the sheet, or band were achieved. The control of the grain size was primarily on the temperature, but also the residence time was varied at a certain annealing temperature. The resulting average grain diameters are assigned to the annealing conditions in the following table:

Gluhtemperatur Veirweilzeit in the first / min7 Annealing / ~ ° C / 840 2.5 84Ö '3,5 950 2.5 950 3.5 950 5 1000 5

average grain diameter / mm /

0.0224 (0.0224-0.032) 0 ^ 032 (0.0224-0.032)

0.045 (0.032-0.0898)

 0.064 (0.032-0.127) 0.0898 (0.045-0.127) 0.127 (0.045-0.18)

ASTM micro-grain size number.

8 (7-8)

7 (7-8)

6 (4-7),

 5 C3-7)

4 (3-6)

3 (2-6)

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-B-

The annealing conditions given in the first and second place correspond to the method according to the invention.

The annealed strips were then cold rolled to a final thickness of 0.50 mm (reduction rate about 5.7%) and annealed in the continuous furnace in the same furnace atmosphere as the first anneal: the annealing temperature was 950 G, the residence time 2.5 to 3 minutes. The residence time was dependent on. After the first annealing already achieved decarburization selected.

The magnetic properties determined on the finished strip are shown graphically in FIG. 1 as a function of the grain size after the first annealing; on the abscissa is the ASTM micro grain size no., on the ordinate the magnetic properties of the final annealed ribbon are plotted, u.zw. in the lower part of the loss of magnetization, deducted in the upper part of the D-diagram magnetic induction. Each point represents a measuring

20 worth.

In Figs. 2 to 4, the texture of some is representative

Ribbons after the first and after the final annealing in

10X magnification reproduced. Under a) and b) are

25 .. each photomicrographs of parallel to the rolling direction. taken samples, under c) and d) each of such shown perpendicular to the rolling direction. In each of Figures 2 to 4, the images labeled a) and c) show the structure after the intermediate denoted by b) and d)

30 the structure after the final annealing.

The contents of the band output steels on the individual elements are in any case within the range at the beginning of the

Example given limits. 35. ,

2 relates to an inventive tape with 0, OT9% C, -

on -ir, η - \ _ η O Ω ~ 7 QQ Π

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- / ίο -

2.65% Si, 0.43% Mn, 0.320% Al, 0.015% P, 0.005% S according to casting analysis; after the first annealing (840C, 2.5 min residence time) the ASTM micro grain size no. At 8 (7-8); the tape was then cold rolled to a degree of reduction of about 5.0% and then finish annealed at 950C and a residence time of 2.5 minutes; the grain size no. according to ASTM of the finished strip was determined with 1 (1-3).

The following analysis or treatment data apply to FIG. 3: casting analysis: 0.012% C, 2.63% Si, 0.24% Mn, 0.393% Al,

0.021% P, 0.010% S

The first anneal was performed for comparison at 950 C and 5 min dwell time using ASTM micrograin size no. was then 4 (3-6). , Cold rolling degree at the second rolling: about 6.0% Final annealing: 95 ° C., 2.5 minutes retention time Determined ASTM Micro Grain Size No .: 0 (00-1)

The in'Fig. 4 shows a tape with the same casting analysis as in FIG. 3, but the first annealing was carried out at 1000 C, the residence time was 5 minutes, accordingly the ASTM micro grain size no. with 3 (2-6).

Cold deformation at the second rolling: about. 6.5% The final annealing took place again at 95 ° C. and a residence time of 2.5 minutes, whereupon an ASTM micro grain size no. the crystallite was from 0-00.

It can be seen from Fig. 1 that the grain size after the first annealing, although only a minimal effect on the Ummagnetisierungsverlust P ₁ , but the values of P ₁ 'and E

I, UI, D

depend significantly on the grain size at this time. A comparison with Table 1 of EURONORM 106-71 shows that. only the fine-grained bands after the first annealing in all magnetic properties meet the requirements of the steel grade FeV 150-50 HA

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or exceed them by far. The mentioned electrical steel grade combines a favorable compromise between. P and B on itself and is very often used in practice. '' '.' 'Example 2:

Two strips whose chemical composition was within the range specified in Example 1 were base-annealed before the second cold rolling at 690 ° C. for 14 hours, then cold-rolled at a reduction rate of about 5.5%, and cold-rolled in the continuous furnace (950 ° C.). 3 min residence time), finally annealed; this slightly longer annealing time was required to ensure adequate decarburization.

The following magnetic properties were determined on the finished strip:. , ,

Volume ASTM micrograin P. _Q P ' ₅ B (Ψ) at

sizes no. to / W / kg7 -2500 5000 10000 A / m base annealing "·

A 7 (7-8) '1.43 3.50 1.57 1.66 1.78 B 6 (6-8). 1.43 3.54 1.56. 1.66 1.77

  Even with the strips produced in this way, G-Fee 150-50 HA was achieved, with the induction values exceeding the required minimum values. , ,

Example 3:. ,

From a melt of the composition · 0.040% C, 3.10% Si, 0.22. % Mn, 0.790% Al, Ο, θίθ% P, and 0.002% S cast blocks (cast analysis) were rolled into hot strip in the usual manner and cold rolled to 0.53 mm thickness. The annealing conditions in the continuous furnace during the first annealing were varied as follows to achieve different grain sizes; were subsequently

- Λα, -

the strips are cold-rolled again by about 5.5% and finally annealed in the continuous furnace (950 C, 2.5 'min residence time),

As the results given below show, "here too the invention is of great importance, the best values being measured on the tape C according to the invention.

"10.81-0967930

Intermediate annealing "magnetic properties of the final

• glowed. bands

Band - annealing temperature indwelling ASTM microcor- P ₁ PB / Tjbei "

'/ ~ ° C7 time / min7 size no. to / W / kg / '2500 5000 1000

, intermediate annealing

C 840. 2.57 (7-8) 1.31 3.0β 1.57 1.66 1.77

D 840 5 6 (4-7) 1.32 3.13 1.54 1.64 1.76

E 890 2.5 4 (4-5) 1.32 3.34 1.51 1.60 1.72

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Example 4:

10 hot rolled strips of tempered steel (continuous casting precursor) whose chemical composition, according to casting analysis, is the same as. followed by specified range limits, namely 0.05 to 0.08% C, 0.55 to 0.73% Mn, 0.05 to 0.10% Si, 0.02 to 0.06% Al, 0.09 to 0.11% P and 0.020 to 0.024 S, were cold rolled to 0.71 mm, annealed at different temperatures between 660-690 C for 12 hours in the annealing furnace and with about 9% Ver.

The finished "semi-finished" product was for further processing on electrical steel strip with the grade FeV 330-6 5 HD according to EURONORM 126-77 corresponding or ^: better properties intended. As is usual with such products, Epstein samples were taken from the two-stage cold-rolled, not finally annealed material and this - annealed according to the annealing conditions at the subsequent consumer at 780 C for 90 minutes and allowed to cool slowly. In Fig. 5, the magnetic properties determined on the final annealed Epstein samples are dependent on the ASTM micro grain size no. according to the bases · • glowing analogous to FIG. 1 shown graphically.

Example 5:

14 Hot-rolled strip of unkilled steel (vacuum-carbonised), in which the contents of the individual elements were within the limits specified below, according to the casting analysis, u.zw. below 0.02% C, 0.50-0.70% Mn, 0.09-0.16% P, and 0.017-0.06% S, were cooled to 0.54 mm; rolled, base annealed at different temperatures between 680 and 700 C with hold times of 11 to 14 hours, and cold rolled to a final thickness of 0.5 mm with about 9% elongation.

  The test was carried out as described in Example 4: In Fig. 6, the final annealed

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stone-propelled magnetic properties as a function of the ASTM micro grain size no. graphically shown after the base annealing; the representation . corresponds to that of FIG. 1 . The electrical steel sheet is comparable to 5th grade non-annealed electrical steel sheet FeV 280- 50 HD according to EURONORM 126-77.

By Examples 4 and S is illustrated that the Ef-. It is also of great importance for incompletely annealed El.ektroblechsorten ("semi finished" products), since given the chemical composition with the present invention after the first annealing a certain average grain diameter steel sheets after the final annealing achieved the best magnetic values become.

Claims (6)

invention claim 1. Two-stage cold-rolled and burried steel sheet for the production of electrical sheets with low core loss and high magnetic induction, characterized in that the sheet-forming crystallites after the intermediate annealing an average grain diameter of less than 0.07 mm, preferably from 0.005 to 0.05 mm , respectively· 2. sheet of silicon-alloyed steel according to item 1 with a content of 1 to 3.2% silicon, characterized in that the crystallites have an average grain diameter of _T from 0.02 to 0.04 mm. 3. Sealed steel sheet according to item 1, containing 0.05 to 0.08% carbon, 0.55 to 0.73% manganese, 0.05 to 0.10 % silicon, 0.02 to 0.06 % Aluminum, 0.09 to 0.11 % phosphorus and 0.020 to 0.024 % sulfur, characterized in that the crystallites have an average grain diameter of 0.005 to 0.02 mm. 4. Unalloyed steel sheet according to item 1, containing less than 0,02 % carbon, 0,50 to 0,70 % manganese, 0,09 to 0,16 % phosphorus and 0,017 to 0,026 % sulfur, characterized by the crystallites have an average grain diameter of 0.03 to 0.05 mm. 5. A process for producing low-core-loss, high-induction-magnetic steel sheets from a steel sheet according to items 1 and 2, wherein hot-rolled steel sheet is used in a two-stage cold stage. 231529 5 AP C 21 D / 231 629/5 59 386 27 rolled by an intermediate annealing to final strength, characterized in that a steel sheet containing up to 3.2 % silicon, either at a temperature of 820 to 850 ° for a time of 1 to 3 minutes in a continuous furnace or at a temperature of 620 to 70O ⁰ C was annealed for 10 to 14 hours in the annealing furnace and which was reduced by 4 to 10% in the second cold rolling in a finishing pass, a final annealing, preferably at a temperature of 920 to 98O ⁰ C for 2 to 5 minutes, in a continuous furnace is subjected. 6. A process for the production of low loss of magnetization and high induction magnetic steel sheets from a steel sheet according to items 1, 3 and 4, wherein hot rolled steel sheet is rolled in a two-stage cold rolling with an intermediate annealing to final strength, characterized in that a sheet of ungeuhigtem or calmed steel having a silicon content of less than 0.15% at a temperature of 620 to 700 ⁰ C for 11 to 14 hours in the annealing annealing annealed and in the second cold rolling in a rolling pass by 6 to 10 % is reduced, where appropriate after Interim storage of the obtained "semi-finished" product, the final annealing is carried out at a temperature of up to 800 ⁰ C for 90 to 120 minutes. For this 3 pages drawings / diagrams