DE3210075A1 - PROCESS FOR PRODUCING GRAIN ORIENTED SILICONE STEEL - Google Patents

Description

Process for producing grain-oriented silicon steel

Grain-oriented silicon steel in the form of sheet metal is known for a wide variety of uses in electrical engineering facilities, including the manufacture of transformer cores. This steel is produced by casting blocks and heating the blocks, typically in gas-fired soaking pits, to a temperature that is suitable for rolling either onto a semi-finished product such as billet or directly into hot strip. After annealing and pickling, the hot strip is cold-rolled in one or more passes with intermediate annealing. The steel is then normalized, causing decarburization. The steel is then subjected to a final texture annealing, during which the desired crystal orientation is achieved. Conventionally, the block temperature is at the direct rolling of blocks to form hot strip in about 1345 ⁰ C.

During the final texture anneal, the silicon steel passes through a secondary recrystallization, during which the grain aggregates grow and a cube-edge texture or

(110) has 1J3O1.J orientation. These are great grains arranged with their fooi] axes parallel to the rolling direction

and extend with their (1-10) -surfaces, parallel to the 5

Rolling plane. As a result, that which is rolled out to sheet metal has Material has a preferred direction of easy magnetizability, namely the rolling direction. When using this material, and especially when used for the manufacture of transformer cores, is before. the material A lower core loss is required, because decreasing core losses go hand in hand with decreasing consumption of thermal energy. In addition, in the interests of easy magnetizability, the material should have good magnetic properties , g have permeability.

In order to achieve these desired magnetic properties, ie in order to obtain favorable values for the core loss and the magnetic permeability, it has been necessary to hot-roll at an ingot temperature in the range of 13-5 ° C. Thus, the traditional way of working is, “starting from the block or. down to about ⁰ C TlOO hot roll of semi-finished product to hot strip at temperatures in excess of 126o C to ^0. However, these extremely high temperatures are difficult to achieve and in particular create problems because of the slagging (scaling) that occurs during the heating of the blocks to these high temperatures in the soaking furnaces. Furthermore, the high amounts of heat required also have an impact on the generation costs, in addition to the increased costs for the refractory lining of the heating devices.

The invention thus primarily pursues the goal of a Specify a process for the production of grain-oriented silicon steels, which is achieved by hot rolling temperatures characterized, which are lower than the conventionally used hot rolling temperatures, without thereby unfavorable Influences on the magnetic properties

of the steel, in particular the core losses and the magnetic permeability would have to be accepted.

Further advantages and details of the invention result from the following description based on preferred exemplary embodiments.

In the broadest sense, according to the invention, a grain-oriented silicon steel with an otherwise conventional composition can be hot-rolled directly from the ingot to hot strip, this hot strip typically having a thickness of about. 2.54 mm or less, provided the steel has a manganese / sulfur ratio of less than about 2.5, and preferably a manganese / sulfur ratio within the range of about 1 to less than about 2.5. Preferably, the hot rolling is carried out on a steel whose manganese / sulfur ratio corresponding to the above block and its temperature between 1204 ⁰ C and less than ⁰ 126o C. It has been found, as will be demonstrated later by means of examples, that these temperatures, which are below the usual hot-rolling temperatures, do not have any subsequent influence on the core losses and the magnetic ones

25 result in the permeability of the steel, provided that the

low manganese / sulfur ratios are guaranteed. Furthermore, according to the invention, the core losses can go even further be reduced by processing steels having effective amounts of copper up to about 0.4

30% by weight, and preferably about 0.2 to less than about

Is 0.58 wt%. Consequently, in direct hot rolling optimal core and magnetic losses from ingot to hot strip. Permeabilities reached when the processed Steel both the low manganese / sulfur ratios mentioned above as well as contains copper within the specified amounts. .Will this invention. ■ conditions are met, the remaining

ir 6-

equally high hot rolling temperatures, which in the state of Technology needed to have good magnetic properties

to ensure. 5

Consequently, by using lower rolling temperatures than usual in the prior art, those already mentioned Disadvantages with regard to the implementation of the process and with regard to costs are avoided. Consequently creates the Invention of a mode of operation by means of which a grain-oriented silicon steel with good magnetic properties can be produced with considerable cost advantages compared to • conventional working methods.

As preferred exemplary embodiments and to explain the significance of the manganese / sulfur ratios in the context of the invention and their influence on the magnetic properties of the steel, the Si steel compositions compiled in Table 1 below were melted and the steel materials produced from them in the range from 1204 to 126O ⁰ C hot rolled.

ω ω

on ο

Batch C Mh- S Si Al

0.038 0.035 3.04 0.005

0.040 0.036 3.05 0.005

0.043 0.035 3.00 0.005

.0.042 0.035 3.00, 0.005

0.042 0.034 2.95 0.005

to bO
O Mn: S cn I-
O cn T AF EL I 1.10 0.27 mm Magnetic steel Cu B. 1.10 Waltz
tempera
ture ( ⁰ C). : w / kg
at
1.7 T Permeability (T .m)
__
at 796 A / m 0.20 0.0004 1.20 1204 • 1.67 0.00233 0.19 0.0004 1.20 1204 1.66 0.00232 0.20 0.0004 1.23 1204 1.70 0.00234 0.20 0.0004 1.60 . 1204 1.66 0.00233 0.20 0.0005 2.40 ^: 1232. 1.68 0.00232 ' 0.1.8 0.0007 3.25 1260 1.55 0.00232 0.18 0.0004 1260 1.55 ■ • 0.00227 ' 0.20 0.0010 1260 1.94- 0.00213

0.049 0.030 3.12 0.004

0.055 0.023 3.10 0.004 0.18 0.0004 2.40 1260 1.55 '0.00227'

0.065 0.020 3.00 0.005

The steels listed in Table I were taken straight from the ingot rolled into hot strip, with the hot strip thickness in the range

ranged from 2.032 to 2.286 mm. The hot strip was at 899 ⁰ C 5

annealed and. Cold rolled to an intermediate thickness of 0.7112 to 0.7620 mm. This tape material on intermediate strength was annealed at 949 ⁰ C before the finished dimension of
0.274 mm was rolled out.

10

As can be seen from table Γ, the steels with manganese / sulfur ratios of less than 2.5 show more favorable core losses (watts per kilogram at 1.7 Tesla) in comparison
with the batch number 616.2, which has a comparatively high manganese / sulfur ratio of 3.25, as is common in the prior art.

The influence of copper with a view to further improvement the core losses can be seen from the batches compiled in Table II.

25 30 35

ω co to to> - * μ

cn ο cn O cn O cn

T A F .E L II

Batch C Mn S Si Al Cu B Mn: S

0.27mm MgO coated

Magnetic steel

6369 0.034 0.039 0.022 3.0 0.005 0.19 0.0006 1.80

637Ο 0.031 0.042 0.022 3.0 0.005 0.42 0.0005 1.90

6364 0.030 0.048 0.026 3.0 0.005 0.58 0.0007 1.85

6433 0.030 0.042 0.022. 3.0 0.005 0.20 0.0014 1.91

6377 0.028 0.042 0.021 3.0 0.005 0.42 0.0009 2.00 1232 1.59 0.00235

6376 0.029 0.047 0.024 3.0 0.005 0.58. 0.0009 1.96 1232 '1.68 0.00231 Q ^' · ,, ·, ·

WaIz-
tempera-r
door ( ⁰ C) W / kg
at
1.7 T permeability
at 796 A / m (Tm)
A. .1232 1.62 0.00234 1232 1.59 ■ 0.00235 1232 1.69 .0.00232 1232 1.57 0.00235

32IuUVb

K.4Q.

The steels listed in Table II were directly from Ingot to hot strip with thicknesses of 2.286 mm v: arm-rolled. That

Hot strip was cold in two passes with intermediate annealing 5

rolled out to finished size. The first heat treatment before cold rolling took place at a temperature of 899 ^° C., after which the material was rolled out to a thickness of 0.7112 mm. Then carried out before a heat treatment at 9'19 ⁰ C and a rolling to a thickness. 0.274 mm. The material was then subjected to a final normalization at a temperature of 800 ° C., during which the decarburization was brought about. Finally, the band entkohl.te material was coated in a conventional manner with MgO and annealed in a hydrogen atmosphere at 1177 ⁰ C.

As can be seen from the core loss values given in Table II (watts per kilogram at 1.7 Tesla), this leads The presence of copper in amounts greater than 0.2%, as based on the lot number 6370 recognizable, to improved core losses compared to the lot number 6369, which one Steel labeled with 0.19% copper. However, the core loss values become less favorable if the copper content is not up a content of less than about 0.58% is limited, as can be seen from the batch number 6364, which is a steel which has a copper content of 0.53% and shows a significant deterioration in core losses.

Claims (5)

PATENT CLAIMS 1. Process for producing grain-oriented Si steel, in which a block is cast and heated for hot rolling, whereupon the block is rolled out to hot strip and this strip material is cold-rolled in one or more passes with intermediate annealing, decarburized to finished dimensions, coated and then subjected to a final high-temperature texture annealing, characterized in that, that the hot rolling of the ingot is carried out at a temperature of less than 126o C ⁰ with a steel whose manganese / sulfur ratio is less than about 2.5. 2. The method according to claim 1, characterized in that a steel with a manganese / sulfur ratio is used in the range of about 1 to less than about 2.5. 3- The method according to claim 1 or 2, characterized in that the hot rolling of the block 20th 25th 30th is carried out at a temperature of 12OiI ⁰ C to less than 126o C ^0. 4. Process according to one of Claims 1, 2 or 3, characterized in that a steel with an effective copper content of up to approximately 0.4% by weight is used will. 10 5. The method according to at least one of claims 1, 2 or 3, characterized in that a steel with a copper content of about 0.2 to less than about 0.58% by weight is used. 15th 35