DE1458973C3 - Process for the production of electrical steel sheets with a Goss texture from silicon steel - Google Patents

Description

The invention relates to a method for producing electrical steel sheets with a cast texture from silicon steel, that of 2 to 3.5% silicon, up to 0.15% manganese and the remainder of iron with the usual production-related There is contamination from hot rolling, descaling of hot sheets, 1-, 2- or 3-stage cold rolling to the final thickness and a final annealing in the form of a primary and one attached to it subsequent secondary recrystallization stage, with during the primary recrystallization stage Sulfur or decomposable sulfur compounds are brought into the vicinity of the annealing material and the Sulfur as a grain growth inhibitor in the grain interfaces of the material during the primary Recrystallization is diffused, as described in the main patent 14 58 970.9.

In "Archiv für das Eisenhüttenwesen", 35 (1964), Issue 1, pp. 75 to 83, is the production of silicon steel sheets outlined with Goss texture. The silicon steel sheets described therein contain silicon and manganese within the amount ranges given above. On p. 80 of the cited reference is stated that these silicon steel sheets contain sulfide inclusions which impede grain growth. On p. 82 in column 2 there is a description of sulphide inclusions in connection with the processing of materials talked about with Goss texture. The one used in these electrical steel sheets as a grain growth inhibitor However, sulfur always comes from the melt and is from the introduction of sulfur from the outside not mentioned in it.

ίο It has been known for a long time that sulfur plays an important role in achieving a Goss texture. It is believed that the sulfur in Form of sulfides during the primary grain growth stage of the final anneal as an inhibitor for normal grain growth acts, so that the grains of the primary grain structure are prevented from to grow as would be the case with a subsequent grain growth. The for Existing time of primary grain growth

However, the amount of sulfur depended on the previous information in the literature depends solely on the sulfur in the melt.

Other factors have also been viewed as critical in processing so far. For example the degree of cold rolling as well as the number of cold rolling stages are considered critical. One took so far also that excellent permeabilities can only be achieved in silicon steel sheets, when silicon steel slabs are hot-rolled at a high temperature to a medium thickness. All of these factors shut down the manufacture of Goss-textured electrical steel sheet from silicon steel a complex and difficult operation. It was also not previously known which treatment would be used the material after rolling to its final thickness had to be subjected to the development of a to ensure secondary grain growth with Goss texture during the final annealing.

From US Pat. No. 31 30 095 it was already known that by adding sulfur from the outside during the recrystallization of sheet metal, the grain growth can be favorably influenced, this However, the patent is concerned exclusively with the production of cube texture, the sulfur crsl after the primary recrystallization has elapsed, it diffuses into the surface zone of the block.

The object of the invention is therefore to provide an improved method for producing electrical steel sheets with Specify Goss texture made of silicon steel, which is technically easy to carry out and the production of thin electrical sheets made of a silicon steel! with Goss texture that allows for different usual manganese contents have excellent magnetic properties.

While this problem is solved for the first time according to the main patent 14 58 970.9 that from outside sulfur is added as a grain growth inhibitor, according to the invention, the amounts of grain growth inhibitor added to the

first ma! on those contained in the silicon steel Manganese amount and the final thickness of the silicon steel sheet Voted.

The invention is based on a method for producing electrical steel sheets with a Goss texture

Silicon steel of the type described above according to the main patent 14 58 970.9 and is thereby characterized in that a silicon steel with at least 0.03% manganese is assumed and that

the content of sulfur in elemental or bound form in that used during the final annealing refractory annealing separator, the manganese content in the silicon steel and the final thickness of the sheet metal The diagrams of FIGS. 2 to 5 are coordinated in such a way that the manganese content depending on the final thickness in the hatched field of the respective sulfur content of 1, 2, 4 and 8% assigned diagram.

According to the method according to the invention, it is first maize possible in a technically simple way using a magnetic sheet made of silicon steel with a Goss texture produce excellent magnetic properties with different manganese contents.

According to a preferred embodiment of the ¹ S process of the invention, the hot-rolled silicon steel is rolled to the final thickness in a cold-rolling stage with a degree of deformation of 65 to 85%, preferably 70 to 80%.

According to a further preferred embodiment of the method of the invention, the hot-rolled Silicon steel in two or three cold rolling stages with one or two intermediate anneals and rolled to the final thickness with a degree of deformation in the last cold rolling stage of 60 to 80%.

The invention is explained in more detail below with reference to the accompanying drawings.

FIGS. 2 to 5 show the relationship between the amount of sulfur from an external source, the manganese content and the thickness of the finished product. From these graphs it can be seen that an end product with a thickness of less than 50.8 μm can be obtained if 2 to 8% sulfur are supplied from an external source and the manganese content is between about 0.06 and 0.13%.

2 to 5 inclusive show diagrams which areas with a satisfactory secondary Show grain growth. In them are increasing percentages of manganese against the thickness of the Sheet metal material in μηι with constant sulfur contents applied.

6 shows a diagram in which the permeability at H = IO Oersted versus the degree of deformation of a hot-rolled sheet in a single-stage Cold rolling is applied. This figure also shows pole figures, which indicate the degree of orientation, which is available at the three points on the curve of the diagram.

The various two-dimensional diagrams illustrated in Figures 1-5 are herein Fall clearer than three-dimensional diagrams showing both the manganese and the Relate the sulfur content to the material thickness.

As already mentioned, when carrying out the method according to the invention, a silicon steel sheet, which contains predetermined amounts of manganese, treated with sulfur or sulfur compounds, when it has been brought to the final thickness during the primary grain growth at the Final glow. This can be done in a number of ways. The invention can be with the addition of Ferrous sulfide or other sulfur compounds that occur at the temperatures of primary grain growth dissociate or decompose to the annealing separator used in the final heat treatment To run. However, elemental sulfur can also be added to the separator.

6o The amount of elemental sulfur or sulfur in the form of a sulfur-containing compound added to the annealing separator is generally from about 0.0025 to about 0.05 percent of the metal charge, or about 0.02 to 0.5 kg of sulfur per ton of metal charge. Based on the annealing separator, the sulfur content is 1 to 8%, the range from 1 to 5%, based on 5 kg of MgO per ton, being preferred. Useful results can also be achieved if the sulfur content in the annealing separator is reduced to about 0.5% or increased to about 10%. The amount of sulfur contained in the silicon steel can exceed the solubility of sulfur in the region of the grain boundaries. Some sulfur is lost during drying of a coating applied from a slurry and in handling the dried coating. In order to compensate for this loss, it is therefore necessary to add a sufficient excess and the values given above relate in all cases to the amount of sulfur or sulfide present during the heat treatment when the silicon steel contains the prescribed amounts of manganese given below.

Silicon steel is generally an iron-silicon alloy to understand, which contains 2 to 3.5% silicon and 0.03 to 0.15% manganese. Usually a as-cast carbon content of about 0.025% in the material is preferred, although not is limited to this, but the product should be subjected to a decarburization treatment before final annealing will. Under "normal" manganese, an amount of manganese in silicon steel is of the order of magnitude of about 0.10%.

It has been found that previously unknown factors influence the diffusion of sulfur. Here it was found that there was a relationship between the manganese content of the silicon steel and the amount of sulfur or sulfur compound, which is necessary to promote secondary recrystallization is. It was also found that a relationship between the amount of sulfur added and the Cold rolling of the material, especially cold rolling, that of the subsequent primary recrystallization immediately preceding exists.

The term "addition of sulfur" used above refers to the use of sulfur or a sulfur-containing compound in the annealing separator. However, such addition is also effective when it is contained in the decarburization or in the annealing atmosphere. In all of these cases the sulfur becomes actually absorbed by the sheet metal and appears to be concentrated in the grain boundaries.

In FIGS. 2 to 5, the percentage of manganese is plotted against the sheet metal thickness in μπι after a two-stage Cold rolling applied for different sulfur contents of the annealing separator. These diagrams also apply for a material that has been subjected to one or three-stage cold rolling.

If no sulfur is added, it is generally - regardless of the manganese content - not possible to obtain a satisfactory secondary recrystallization in a material that is thinner than about 203 μΐη. This is illustrated by FIG. 1.

Fig. 2 shows that the hatched area of the satisfactory secondary grain growth is at Addition of 1% sulfur compared to the manganese value

of 0.05% sharply increases. The thinnest material in which secondary grain growth can take place is about 76 μm thick. The manganese content of Materials is critically low. In the higher thickness ranges from 203 to 406 μίτι delivers a considerable Manganese area good results.

From Fig. 3 it can be seen that with 2% addition of sulfur, the hatched area extends in the vertical direction broadened and satisfactory secondary recrystallization in thin silicon steel at such a small one Thickness as about 50 μίτι can be obtained, wherein the manganese contents can be between about 0.07 and about 0.12%. The permissible manganese range widens somewhat with a greater final thickness of the product and above 203 μίτι can be a satisfactory secondary recrystallization with manganese levels between about 0.03% and about Achieve 0.15%.

Figures 4 and 5 show hatched areas which form peaks which approximately oppose the 0.10% manganese value. The tips of the hatched However, areas are much closer to the ordinate, indicating that grain growth is satisfactory can also be obtained with very thin silicon steel containing about 0.10% manganese if "About 4 to 8% sulfur can be added to the annealing separator. The lower limit of the hatched area however, decreases gradually to the right, which indicates that at 203 μm at least about 0.05% manganese is present must be. The minimum manganese value drops slightly when you approach 406 μπι, but the Figures 4 and 5 show that in general the manganese content should not fall below 0.03 to 0.04%. the Sulfur addition, which is economically possible and necessary under all known conditions, can be 8% also exceed and is a maximum of about 10%.

It should be noted that various factors are not taken into account in the figures described above which can shift the surfaces of the secondary growth somewhat. About these factors include changes in the amounts of the elements other than manganese and sulfur and the Conditions under which the anneals are carried out, such as. B. the atmosphere used and their access to the surfaces of the silicon steel. As a result of the aforementioned changes there may be deviations from the exact shape of the curves in these diagrams, the diagrams however, provide an accurate indication of secondary grain growth in terms of impact the variables themselves that determine the graphical representations.

So far, the manufacture of silicon steel sheets with Goss texture has given the best results obtained in processes comprising at least two cold rolling stages. For example, a 3% silicon steel, which has been cold-rolled in one stage to a final thickness of about 355 μίτι, usually none really show true secondary recrystallization and it is expected that a permeability of only around 1650 at H = 10 Oersteds. A few such batches react a little better. but most batches will have low permeabilities, especially when the silicon content is high.

It has now surprisingly been found that when the material to be produced is treated with sulfur and contains manganese in an amount which is related to the sulfur content in the above-mentioned relationship, a single-stage cold rolling is an excellent way of achieving a very high permeability and therefore a high one Degree of Goss texture results.
This is illustrated by FIG. 6, in which the permeability at H = 10 Oersteds is plotted against the degree of deformation of the single-stage cold deformation of the material, based on the thickness of the hot sheet metal. It also shows a typical pole figure for

ίο the structure generated in each specified area. It is clear from Fig. 6 that excellent results are obtained when the silicon steel by cold rolling in one stage of an average hot rolled thickness with a degree of deformation from 65 to 85%, preferably from 70 to 80%, is rolled down. The pole figure for this one Area shows a high degree of goss texture. Virtually all grains in this material exhibit one Orientation within ± 5 ° C of the ideal

so (UO) fOOlJ structure on. The permeability of the final product drops dramatically when the degree of cold deformation is less than about 65% or more than about 85%.
Whether or not the cold working can be carried out in one step depends on the thickness of the hot sheet and the desired final thickness. It has been found that the degree of cold deformation should be in the range of 60 to 80% in the last cold rolling stage when the process comprises 2 or 3 cold rolling stages. The above-mentioned degree of cold deformation is considerably greater than is customary in the prior art, in which degrees of deformation of about 50% have hitherto been regarded as the optimum.

• 15 The invention is illustrated by the following examples explained in more detail.

example 1

1. A winding was hot-rolled from an initial temperature of 1400 ^° C. to 1.93 mm. The hot sheet had the following chemical composition:

as carbon 0.027%

Manganese 0.081%

Sulfur 0.024%

Silicon 3.160%

2. The hot sheet was first strip annealed at 913 ° C. for 2 minutes and then by pickling Hot-rolled scale freed.

3. The annealed hot sheet was down to 0.521 mm

cold rolled.
4. This medium thickness material was strip annealed at 913 ° C for about 1 minute and then pickled.

5. The medium-thick material was cold-worked by more than 70% to a final thickness of 152 μm.

6. The 152 μm thick material was 1.5 minutes long at 815 ° C in hydrogen with a dew point of Strip annealed at 54 ° C.

7. The material was washed with an aqueous slurry of pure MgO containing 2% sulfur had been added, coated and the coating

^ was dried on low heat to follow to serve as an annealing separator.

8. The material was box annealed in a hydrogen atmosphere at 1177 C for 16 hours.

»5

9. The results of the magnetic investigations were as follows:

Permeability

H = 10 Oersted 1820

Watt losses (P 15: 60) 1.12 W / kg

Watt loss (P 15: 400) 14.4 W / kg

Grain size ASTM 4 at IX

Example 2

1. A coil was hot-rolled from an initial temperature of 1400 ° C. to a thickness of 1.93 mm. the chemical composition was as follows:

Carbon 0.026%

Manganese 0.085%

Sulfur 0.027%

Silicon 3.110%

2. The hot sheet was first at 913 C approximately

Annealed for 2 minutes, then the hot-rolled scale was removed by pickling.

3. The annealed hot sheet was cold worked down to 0.495 mm.

4. The medium thick material was at about 913'C

Strip annealed for 1 min and then pickled.

5. The medium-thick material was cold-worked by about 80% to a final thickness of 113 μm.

6. The 113 μm thick material was at for 1 min 815 "C decarburized in hydrogen with a dew point of 54 C.

7. The material was washed with an aqueous slurry of neat MgO containing 2% sulfur, coated and the coating was dried over low heat.

8. The material was box annealed in a hydrogen atmosphere at 1177 ^{J C for 16 hours.}

9. The results of the magnetic examination were as follows:

Permeability
H = 10 oersteds.

40

1800

Watt loss (P 15: 60) 1.08 W / kg

Watt loss (P15: 400) 13.3 W / kg

Grain size ASTM 5 at IX

Example 3

1. A coil was hot-rolled from an initial temperature of 1400 C up to 1.78 mm. The chemical Composition was as follows:

Carbon 0.025%

Sulfur 0.024%

Manganese 0.071%

Silicon 2.980%

2. The hot sheet was first annealed at 913 C for about 2 minutes, then the Hot-rolled scale removed.

3. The sheet was then cold-formed down to 483 μίτι.

4. The medium-thick material was grazing close annealed at 913 ⁰ C for about 1 minute.

5. The annealed sheet was cold-formed down to 229 μίτι.

6. The 229 μίτι thick material was at 913 ° C about Strip annealed for 1 min and then pickled.

7. The 229 μm thick sheet was about 80% Cold worked to a final thickness of 49 μm.

8. The 48 μm thick material was about 30 seconds decarburized at 815 C in hydrogen with a dew point of 54 ° C.

9. The decarburized material was coated with an aqueous slurry containing 2% sulfur and It contained 99% pure magnesium oxide and the coating was dried over low heat.

10. The panel was in hydrogen for 16 hours Box annealed at 1177 ° C.

11. The magnetic properties were as follows:

Permeability

H = 10 Oersted 1790

Watt loss (P 15: 400) .... 12.5 W / kg
Grain size ASTM 2 at IX

For this purpose 4 sheets of drawings 509 537/130

Claims (3)

Patent claims: 1. A process for the production of electrical steel sheets with Goss texture from silicon steel, consisting of 2 to 3.5% silicon, up to 0.15% manganese and the remainder of iron with the usual production-related Impurities from hot rolling, descaling of hot sheets, 1-, 2- or 3-stage Cold rolling to the final thickness and a final annealing in the form of a primary and one attached to it subsequent secondary recrystallization stage, with during the primary recrystallization stage Sulfur or decomposable sulfur compounds are brought into the vicinity of the annealing material and the sulfur acts as a grain growth inhibitor in the grain interfaces of the material during the primary recrystallization is diffused in, according to patent specification 14 58 970, characterized in that that a silicon steel with at least 0.03% manganese is assumed and that the content of sulfur in elemental or bound form in the refractory annealing separator used during the final annealing, the manganese content in the silicon steel and the final thickness of the sheet according to the diagrams in Fig. 2 to 5 are matched accordingly so that the manganese content as a function of the final thickness in the hatched field of the respective sulfur content of 1, 2, 4 or 8% assigned diagram. 2. The method according to claim 1, characterized in that the hot-rolled silicon steel in a cold rolling stage with a degree of deformation of 65 to 85%, preferably 70 to 80% Final thickness is rolled. 3. The method according to claim I, characterized in that the hot-rolled silicon steel in two or three cold rolling stages with one or two intermediate anneals and with one Degree of deformation in the last cold rolling stage is rolled from 60 to 80% to final thickness.