HU181438B - Process for preparing sheets of borian silicone iron alloys - Google Patents

Description

A process for the production of boron-containing silicon-iron alloy plates

2

The present invention relates to the production of electro-steel. More particularly, the present invention relates to a novel process for the production of single-oriented silicon-iron alloy sheets using an insulating coating containing a small amount of skin, which is critical for the skin and nitrogen content of the base board.

The products which can be formed by the process of the invention are commonly referred to in the literature as "silicon-containing electro-steels" or, more specifically, "silicon-iron alloy plates". These alloys contain iron as the parent metal to which alloy is associated with about 2.2-4.5% by weight of silicon together with a relatively small amount of other impurities and very little carbon. These products have a cube edge oriented structure; the crystal structure of the products is more than 70% crystalline in orientation [110] [001] (indicated by Miller indices).

This type of grain-oriented silicon-iron alloy sheet is currently commercially produced by the following operations: hot rolling, heat treatment, cold rolling, heat treatment, re-cold rolling, desulphurization, desulfurization and recrystallization.

The ingots are usually first formed by hot rolling to form a strip or plate narrower than 0.40 cm; this product (the so-called "hot rolled strip") is rolled to the final thickness by cold rolling, using appropriate intermediate softening treatments (usually reducing the sheet thickness by at least 50%), and finally the product is structured in the final heat treatment step.

No. 3,905,842. According to U.S. Patent No. 4,123,121, the magnetic properties of this type of material can be greatly improved by adding a predetermined amount of skin to the metal material relative to the nitrogen content of the final structuring heat treatment step. Improvements in magnetic properties can be achieved by adding very small amounts of skin; however, in order to achieve the desired results, the boron / nitrogen ratio must be kept within strict limits.

No. 3,905,843. According to U.S. Pat. No. 4,677,121, the magnetic properties of silicon-iron alloy plates produced by the use of a two-step cold rolling process interrupted by an intermediate heat treatment step can be improved to the same degree by providing a predetermined ratio of boron and nitrogen their ratio to each other is less than 2.1: 1.

It is known to produce hot rolled silicon-iron alloy sheets in which the sheet is brought directly to the final size by cold rolling without intermediate heat treatment. According to the method described there, a very small amount of skin is added to the metallic material and the ratio of metallic material to manganese sulfur is kept below 1.8: 1.

The present invention is based on the discovery that, under certain conditions, boron present in a conventional electrically insulating coating on silicon-iron alloy plates has a beneficial effect on secondary recrystallization of the metal and promotes the formation of a crystal structure and associated special magnetic property. . Specifically, we found that if the ultimate

-1181438 heat treatment is carried out on coated silicon-iron alloy plates with a very small amount of skin to obtain products with significantly better magnetic properties than expected. This phenomenon is probably due to secondary recrystallization of the metal in the presence of boron, whereas otherwise this process does not take place. In further studies, it has been found that it is not sufficient to perform the final heat treatment on a boron-containing silicon-iron alloy in order to obtain adequate magnetic properties; after all, the desired results can only be achieved if the metal to be subjected to the final heat treatment itself contains a small amount of skin. The process according to the invention can significantly reduce the amount of skin to be added to the pouring pan compared to the above-cited publications, without, however, diminishing the favorable magnetic properties attributable to boron in the final heat treatment.

It has also been found that end products with reproducibly advantageous properties are obtained when the content of boron in cold-rolled and de-carbonated silicon-iron alloy is at a predetermined low value, while in the electrically insulating coating applied to the sheet it is also maintained at a predetermined value. It has further been found that the best results are obtained when the boron content, measured together in the alloy and the coating, does not exceed a predetermined maximum value. Advantageous magnetic properties can be easily, reproducibly, and regularly obtained if the nitrogen content of the alloy is proportionally determined to the middle-upper value of the total boron content of the alloy and the coating.

Specifically, it has been found that in the final heat treatment of silicon-iron alloys, secondary recrystallization can always be achieved even if the alloy contains 1.5 parts per million and the electrically insulating coating on them contains 6.0 parts per million skin. Even in the case of boron contents above the above-mentioned limits, excellent magnetic properties can be provided, provided that the total boron content of the system does not exceed 90 parts per million and within that the alloy plate has less than about 50 parts per million boron. It has further been found that when the total amount of boron present in the alloy and the coating is greater than about 40 parts per million, the nitrogen content of the alloy should be greater than about 70 parts per million, preferably between about 80 parts per million and about 90 parts per million. ensure the appropriate magnetic properties of the silicon alloy plates.

It has also been found that increasing the boron content of the coating significantly reduces the iron loss of the finished product and (although to a lesser extent) improves the magnetic permeability of the finished product. However, it is emphasized that the boron content can only be increased up to the critical upper concentration limits given above.

It has also been found in our experiments that the ratio of manganese to sulfur in the alloys can be up to 2.5: 1 in the process according to the invention without degrading the magnetic properties of the final product.

The above-mentioned findings are very surprising, especially considering that the results obtained according to the invention are very different when

No. 676,227 U.S. Pat. No. 4,123,119 discloses a boron-based coating for the final heat treatment of boron-free silicon-iron alloy plates. According to the cited patent, while treating boron-free base plates, secondary crystalline particles are formed which are smaller than average, but the permeability of the final product is not improved; while the process of the invention does not reduce the particle size, but at the same time significantly increases the permeability of the final product.

It has further been found that, while the process according to the invention must maintain a relatively low and well-defined content of boron in the coating, this boron content can be easily adjusted to the desired value. For example, the skin may be applied in the form of a suspension together with magnesium hydroxide or other similar electrically insulating material on the surface of the sheet to be treated; however, U.S. Patent No. 3,054,732 may be used. and a coating method as described in U.S. Pat. In the latter step, the plate may be immersed in an aqueous solution of the boron compound, or rubbed or sprayed on the surface of the plate with an aqueous solution of the boron compound.

It further found that the present method can be used very advantageously bórforrásként boric acid (H3BO3), and / or sodium tetraborate (Na ₂ B ₄ O _7). It will be appreciated by those skilled in the art that other compounds which may have the desired effect under the final heat treatment conditions may be used as the boron source for coating treatment. The basic requirement for the boron source to be incorporated into the coating is that the boron source undergoes decomposition in the final heat treatment step and diffuses the released boron into the surface of the alloy.

It will be apparent from the foregoing that the novel process of the present invention also provides new products. The products of the present invention are fine-grained, primary-recrystallized, final-sized magnetic-silicon-iron alloy plates having a boron-containing coating (e. G., A coating comprising a skin formed by the reaction of silicon with magnesium hydroxide or the like). Due to the presence of boron, nitrogen, manganese and sulfur in the alloy plate and the boron in the coating, the silicon-iron alloy plate can be transformed into a mono-oriented final product which has extremely valuable magnetic properties and at the same time contains little or no skin of this origin.

Further, the products of the present invention may be de-carbonized, coated, cold rolled strips or sheets containing a predetermined proportion of the coating and base alloy relative to the nitrogen content of the alloy. The presence of boron in the final heat treatment results in secondary recrystallization of the plates, resulting in final products with excellent magnetic properties.

Specifically, the products of the present invention are fine-grained, primary recrystallized magnetic silicon-iron alloy plates with an electrically insulating layer, containing 3 to 50 parts per million of skin, and having a thin, highly adherent, water-insoluble calcium, magnesium, has a skin coating made of aluminum hydroxide. The coating is preferably for the silicon-iron alloy sheet.

-2181438 contains 25 to 150 parts per million of skin; the boron content of the coating, when calculated on the same basis, is preferably from 50 to 80 parts per million, in order to minimize iron losses. The ranges listed are independent of the boron content of the silicon-iron alloy plate as long as the boron content of the base plate remains within the range of 3 to 50 parts per million previously reported.

Further, the products of the present invention are electrically insulated, fine-grained, primary-recrystallized magnetic-silicon-iron alloy plates containing from about 1.5 to about 50 parts per million by weight of skin and about 30 to about 90 parts per million by weight of nitrogen. This layer contains from about 6 to about 90 parts per million of skin relative to the alloy sheet, and the total amount of boron in the coated sheet is between about 7.5 parts per million and about 90 parts per million.

The novel process of the present invention provides the above novel products and then undergoes a final heat treatment step. In this final heat treatment step, a secondary recrystallization process leading to the formation of a cube-oriented crystal structure in the plates is induced.

Plates formed according to the invention were carried out ^and several sets of experiments. The results of some experiments are shown in Figures 1-6. 4A.

Figure 1 shows the change in permeability in the. depending on the boron content of the cold rolled alloy strip. The three curves in the figure show the effect of the wine added to the magnesium oxide coating.

Figure 2 shows the rate of loss of iron loss as a function of the boron content of the cold rolled alloy strip. The magnesium oxide coating on the test alloy strips was rubbed with dilute boric acid solution before the final heat treatment step.

Figure 3 shows the permeability and iron loss of the final product as a function of the maximum amount of boron available for the base plate from the coating.

Examination of the three curves shows that permeability is relatively small, but with increasing boron content of the coating, while decreasing iron loss is more favorable in the same boron interval.

Figure 4 shows the permeability of the final product as a function of the maximum amount of boron available to the base plate from the coating. The four curves in the figure represent the values determined from 42 to 84 parts by weight of an alloy sample with variable nitrogen content; on one curve the boron content of the base alloy

We also present the results obtained by increasing it from 9 parts per million to 50 parts per million.

Figure 5 illustrates a change in the parameters shown in Figure 4 for base alloys with 40% sulfur content.

Figure 6 illustrates a change in the parameters shown in Figures 4 and 5 for base alloys processed in accordance with the invention but containing higher amounts of sulfur.

In carrying out the process of the present invention, the novel types of intermediates may be formed as follows: In the first step, a suitable silicon iron melt is formed, then the melt is cast and hot rolled to the intermediate size. The melt to be poured contains 2.2 to 4.5% silicon, less than 2.3: 1 relative to manganese and sulfur, about 3 to 50 parts per million skin, about 15 to 95 parts per million (based on the amount of skin). 1 part by weight) of nitrogen and the remainder of iron and trace amounts of possible contaminants such as carbon, aluminum, copper and oxygen. The melt to be cast may also contain the following components: 2.2 to 4.5% silicon, about 1.5 to 50 parts per million skin, about 30 to 90 parts per million (1 to 15: 1 parts by weight of skin) nitrogen, up to 0 , 10% manganese, sulfur (up to 2.5: 1 manganese: sulfur by weight) and the remainder iron and other contaminants listed above. In both cases, after the heat treatment, the hot strip or sheet is optionally cold rolled to the final size with an intermediate heat treatment and then de-carbonized.

Any of the above-prepared, fine-grained, primary recrystallized silicon-iron alloy plates are coated with a boron-containing coating according to the invention prior to the final structuring heat treatment. The coating is preferably carried out electrolytically (see, for example, U.S. Patent No. 3,054,732); in this step, a 5.08 to 10.7 μm thick Mg (OH) ₂ coating is preferably applied to the plate. The coated sheet is then immersed in an aqueous solution of boric acid, sodium borate or other water-soluble boron compound. Preferably, the bath is diluted with an aqueous solution of about 5 to about 10 g of boron compound per liter.

As a final step in the process of the invention, the coated sheet as described above is heated in a hydrogen gas or a nitrogen-hydrogen gas mixture. Secondary crystal nucleus growth begins at about 950 ° C. The temperature is raised at about 50 ° C / hour to 1000 ° C, during which time the secondary recrystallization process takes place. If desired, the plate is heated to a final temperature of 1175 ° C to completely remove residual carbon, sulfur and nitrogen.

According to the invention, the boron content of the coating is adjusted to 15 parts per million of the alloy plate with a boron content of 1.5 to 6.9 parts per million.

It is also advantageous to adjust the boron content of the coating to 10 to 70 parts per million for a sheet containing 10 parts per million skin and 30 parts per million nitrogen.

Further, the process of the invention is advantageously carried out by adjusting the boron content of the coating to 10 to 40 parts per million of the sheet, in the case of a skin containing 50 parts per million skin, 80 to 90 parts per million nitrogen.

The invention is further illustrated by the following non-limiting examples.

Example 1

No. 3,905,843. U.S. Pat.

carbon 0.030% manganese 0.035% sulfur 0.031% Skin 0.0010% nitrogen 0.0050% copper 0.24% aluminum 0.005% iron ad 100.0%

-3181438

From the above melt composition, prepare the sheets of 274.3 μ and 345.4 μ thickness, respectively, by rolling the hot melt and then pickling and curing the intermediate thickness plate (about 2540 μ thickness). The plates are then cold-rolled to a thickness of 1524 μ, and the plates are reheated and brought to the final thickness by cold-rolling. Finally, the plates are decarbonised in a stream of hydrogen (dew point of gas stream at room temperature) for 8 minutes at 800C.

The plates thus obtained were cut with Epstein tapes and stripped according to U.S. Pat. No. 3,054,732. A coating (5.08 μm) of Mg (OH) _{2 was} applied by the method described in U.S. Pat.

The experiments were performed on 3 to 3 strips of 274.3 μ and 345.4 μ, respectively. Each tape is retained as a control, i.e. in this case no skin is applied to the magnesium oxide coating. One additional tape is immersed in 5 g / l aqueous sodium borate for 15 seconds, and one additional tape is immersed in 10 g / l aqueous sodium borate for 15 seconds. The six sample strips were then heated at 1160 ° C under a hydrogen stream for 4 hours. The magnetic properties of the resulting tapes are shown in Table 1.

Table 1

Sample sign Concentration of Na ₂ B ₄ O ₇ solution in g / ml Iron loss of coated sample, W / kg 15 kGauss for 17kGauss The permeability of the coated sample at 10 Oe 11 1H 0 0 1,318 1.98 1799 11-1H 5 5 1,515 2,143 1806 11-1H 10 10 1.31 1.852 1881 14-1H 0 0 1.565 2.315 1743 14-1H 5 5 1.905 2.734 1707 14-1H 10 10 1.632 2.31 1801 11-1B 0 0 1,457 2,205 1729 11-1B 5 5 1.424 2.00 1834 11-1B 10 10 1,462 2,205 1747 14-1B 0 0 1,467 2,179 1767 14-1B 5 5 1,599 2,337 1797 14-1B 10 10 1,676 2,390 1778

Example 2

Two Epstein batches were made from 212 μ and 213.5 μ thickness, respectively. The tapes were prepared as described in Example 1 and electrolytically coated as described in Example 1. The strips were then immersed in 7.5 g / l aqueous sodium tetraborate for 15 seconds. The resulting strips were made into Epstein bundles and subjected to the final heat treatment described in Example 1. The results observed are shown in Table 2.

Table 2

Sample sign Iron loss, W / kg 15 kGauss for 16.3 kGauss For 17 kGauss permeability Nei-Looe 1H Feet Ann. 1,288 1.574 1,782 1842 1H Feet Ann. 1,281 1.574 1,782 1834

Example 3

No. 3,905,843. A commercially available casting is prepared using BOF silicon-iron alloy as described in U.S. Pat. The composition of the melt is as follows:

silicon 3.10% copper 0.26% manganese 0.032% sulfur 0.014% carbon 0.024% boron 0.0015% nitrogen _ 0.0035% iron 100.0%

The melt is prepared by hot rolling and direct cold rolling into sheets having a final thickness of about 220 μ. The cold-rolled sheets are decarbonated, and the corresponding rolls are disclosed in U.S. Patent No. 3,054,732. U.S. Pat. Plates were immersed in a solution containing 5,361 water, 12.7 g / l boric acid and 1.91 ammonia to form approximately 50 parts per million skin by weight of the magnesium oxide coating.

Boric acid and ammonia in the aqueous solution are converted to ammonium borate, which, however, decomposes on heat treatment (2150 F to 1177 ° C) and thus no inorganic acid amide is present during the formation of the coating.

The resulting coated plates were then heated for 3 hours at 1177 ° C under anhydrous hydrogen flow.

The plates obtained after the final heat treatment have excellent magnetic properties. Plates have a permeability of 1905 gauss / oersted at 10 oersted and a loss of iron of 1.032 watts / kg at 15 kilos and 1.39 watts at 17 kilos

Example 4

Slabs are prepared from the melt of the following composition as described above:

silicon 3.15% copper 0.26% manganese 0.32% sulfur 0.14% Mn / S = *. 29 carbon 0.26% phosphorus 0.005% chromium 0.06% nickel 0.091% titanium 0.004% tin 0.011% boron 0.0011% nitrogen 0.0035% iron ad 100.0%

The plates are brought to a final thickness of 269.2 μ by hot rolling and direct cold rolling. The plates were normalized and the plates were prepared according to the method described in 3,054,732. U.S. Pat. No. 4,122,119, electrolytically coated with 5.08 μm of magnesium oxide. The plates are then immersed in a 1% boric acid solution prepared as described in Example 3.

Epstein batches were prepared from several rolls and the batches treated once with boric acid were again immersed in a 1% boric acid solution under laboratory conditions. Two additional samples from each roll were repeatedly added to 2% and 3% boron sar, 4M 1438, respectively, under laboratory conditions. The wage content of the coatings so formed and the magnetic properties of the resulting products are listed in Table 3. In the preparation of the final products, the tapes are heat-treated in the form of Epstein bundles for 3 hours in anhydrous hydrogen stream at 1177 ° C.

Table 3

Pattern sign iron Loss W / kg 17 kilos permeability Looe at Coating boron mg / tape * 1. Normalized 1,446 1876 0 Once treated 1,530 1872 0.68 1% 1,486 1909 1.24 2% 1,560 1885 1.72 3% 1,554 1887 2.20 2. Normalized 1.477 1886 0 ' Once treated 1,411 1900 1.57 1% 1,431 1912 2.06 2% 1,453 1921 2.86 3% 1,570 1906 2.88 3. Normalized 1,447 1870 0 Once treated 1,418 1886 0.89 1% 1,440 1909 1.33 2% 1,451 1907 2.13 3% 1,517 1886 2.50

* 1 mg boron / Epstein strip = 50 parts per million by weight of silicon-iron alloy plate

Example 5 A laboratory sample was melted in an induction furnace under argon gas. Electrolyte iron and 98% ferrosilicon were used as starting material. Each sample contained 3.1% silicon, 0.1% copper and 0.03% chromium. To each sample was added the same amount of sulfur (0.024%) as iron sulfide; sulfur analysis results fluctuate between 0.033% and 0.019% with mean values of 0.026%.

From the melt castings, slices of 44.45 mm were cut and the alloy slices were brought to about 2286 μm by hot rolling in 6 runs at a temperature of 1200 ° C. The samples are pickled and then heat-treated at 950 ° C (samples are at about 930 ° C to 950 ° C for about 3 minutes). The hot rolled strips are then brought directly to the final size by cold rolling and analyzed at 214.3 μ. The analytical results are reported in Table 4.

Table 4

Analysis of cold rolled strip samples

Sample number B, ppm N, ppm 0, ppm Mn,% s,% c,% First <1 68 70 0,034 0,025 0,038 Second 1.2 - - 0,036 0,033 0.037 Third 1.6; 1.4 - - 0,035 0,025 0,038 4th 1.8 - - 0,034 0.019 0,040 5th 2.4; 3.1 49 76 0,035 0.029 0,033 6th 5.6 48 90 0,035 0,025 0,044 7th 6.9 46 88 0,036 0,030 0.037 8th 7.4 52 115 0,036 0,021 0,039 9th 14 50 98 0,035 0.031 0,036

Sample number B, ppm N, ppm 0, ppm Mn,% s,% c,% 10th 24 46 96 0,036 0,024 0,038 11th 26; 25 62 70 0,036 0,022 0,040 12th 29 47 69 0,035 0.023 0,038

The cold rolled samples were cut with Epstein strips and the strips were carbonized to about 0.007% carbon by heating in a stream of hydrogen at 21.1 ° C with dew point at 800 ° C. The charcoal strips are rubbed with magnesium oxide milk until a weight gain of about 40 mg / strip is achieved, and some of the magnesium strip coated strips are immersed in 0.5% or 1.0% boric acid solution. With this treatment, 15 mil of 15 parts per million and 30 parts per million of skin per million by weight of metal material are applied to the coating. The coated and optionally boric acid treated samples are heated in an anhydrous hydrogen stream at a rate of 40 ° C / hr from 800 ° C to 1175 ° C in a final heat treatment step and maintained for 3 hours at the latter temperature.

The magnetic properties of the products obtained are shown in Table 5 and Figures 1 and 2.

Table 5

2 Magnetic characteristics measured after final heat treatment in a hydrogen stream

Sample number B ppm MgO JC ' MgO "B" MgO + 15 "THE" ppm B "B" MgO + 30 "THE" ppm B "B" 30 First <1 - 1383 - 1402 - 1394 Second 1.2 - 1432 2.915 1483 - 1467 Third 1.5 2.505 1664 1.61 1873 2,205 1678 4th 1.8 2,048 1751 1.63 1876 2.412 1655 5th 2.7 1,700 1849 1.60 1881 2.073 1730 35 6th 5.6 1,654 1887 - - 1.634 1856 7th 6.9 1,535 1892 1,495 1908 - - 8th 7.4 1,652 1890 1,548 1898 1.665 1845 9th 14 1,647 1891 1,548 1900 1,918 1768 10th 24 1,793 1844 1,623 1869 2.915 1536 40 11th 26 1,663 1873 1,521 1900 1,771 1805 12th 29 - 1472 - 1423 - 1406

"A": Iron loss W / kg at 17 kilos "B": Permeability at 10 oersted

The data in Table 5 and the curves in Figure 1 show the effect of the coated wine on the permeability. Applying an amount of leather equivalent to 15 parts per million of the total amount of alloy will significantly improve the magnetic properties of the article, particularly in the case of alloys containing only 1.5 or 1.8 parts per million by weight of the base. If the boron content is doubled, the permeability of the final product gradually decreases. The reduction in permeability of high-boron band samples is today due to the fact that the required boron / nitrogen ratio is upset. This fact is confirmed by the results obtained with the high nitrogen (No. 11) sample, which is significantly different.

Figure 1 is a graph of samples of magnesium 6C coated oxide coated with boric acid solution, while curves B and C show samples of magnesium oxide coated with a total of 15 parts per million and 30 parts per million of skin treated with boric acid solution, respectively. The reduction in iron loss due to the use of a boron coating is illustrated in Figure 2.

-5181438. The large improvement in the two lowest boron alloys is largely attributable to the improvement in permeability; whereas in the case of higher boron alloys, with little or no change in permeability, a reduction in iron loss of about 1.11 W / kg is typically found in both laboratory and in-line end products.

Example 6

In a further series of experiments examining the performance limits of the new process of the present invention, U.S. Pat. In the same way as described in U.S. Pat.

silicon 3.10% copper 0.29% manganese 0.033% sulfur 0.019% carbon 0.024% Skin 0.0015% nitrogen 0.0058%

Contains iron in the remainder of the melt.

The melt is disclosed in U.S. Patent No. 3,905,843. U.S. Pat. Cold-rolled and de-carbonized sheets are cut into strips and Epstein bundles are made from the strips. Some of the tapes were coated with a magnesium oxide coating as in Example 5, and the coated tapes were rubbed with boric acid to produce samples of boron containing from about 10 parts per million to about 90 parts per million. The remainder of the tapes are coated with a magnesium oxide coating containing boric acid; the boron content of these samples varies from 10 parts per million to 70 parts per million as shown in Figure 3. Epstein bundles were prepared from the treated and non-skin coated magnesium oxide strip samples, placed in a pre-heated space at 800 ° C for final heat treatment and heated to 1175 ° C at 40 ° C / h. The latter temperature was maintained for 4 hours. The magnetic properties of the samples thus subjected to final heat treatment are examined. The results of the tests are shown in Figure 3. The particle size is also determined for some samples. The control sample (where the boron is not available for the silicon-iron alloy) has a particle size of 9.8 mm, while the samples with boron coating have 11.3 mm for boron and 10.4 mm for 30 parts boron. and 60 parts per million boron content, a grain size of 11.5 mm was observed. These latter data contradict the claim in the literature that the particle size decreases from 12 mm to 4 mm when the iron loss is close to 1.11 W / kg.

It is evident from the curves in Figure 3 that adding skin to the coating of boron-containing silicon-iron alloys results in a significant reduction in iron loss while improving permeability to a lesser extent (i.e., from 5 to 10) to 90 parts per million of boron. base alloy, the permeability is only slightly improved).

Example 7

In a further series of experiments similar to that described in Example 5, 11 samples of melt were produced in an air induction furnace, laboratory size. The melts are prepared in an argon shielding gas and argon is bubbled through the melt before casting, while in other cases nitrogen is used as the shielding gas and / or nitrogen is bubbled through the melt. By using only argon as the gas, cast products with the lowest nitrogen content are obtained, while cast products with the highest nitrogen content are obtained when using only nitrogen as the gas. Each casting sample contains 3.1% silicon, 0.1% copper and 0.03% chromium. Cold rolled strips were prepared from the casting samples as described in Example 1. The composition of the tapes is shown in Table 6.

Table 6

Analysis of cold rolled strips

Sample number Mn,% s,% C% B, ppm N, ppm 20th 0,025 0.011 0,036 7.8 42 21st 0,027 0,010 0,035 6.2 48 22nd 0,025 0,010 0,033 9.2 84 30th 0,025 0,010 0,033 51.0 84 23rd 0,027 0,013 0,036 6.7 43 24th 0,025 0,014 0.029 7.2 55 25th 0,025 0,013 0,030 7.7 62 26th 0,025 0,013 0,030 8.2 72 27th 0,024 0,017 0,030 6.3 42 28th 0,024 0,018 0.032 5.9 60 29th 0,025 0.019 0.031 6.7 93

The cold-rolled samples were cut with Epstein strips and the strips were de-carbonized in a stream of hydrogen at about 21 ° C with a dew point at 800 ° C to less than 0.01% carbon. The strips are then rubbed with magnesium oxide milk until a weight gain of about 40 mg / strip is achieved and the strips (except for the control samples) are immersed in 0.5% or more aqueous boric acid solution. The boron content of the coatings is analyzed before the final heat treatment. Analytical data show that the increase in the boron content of the treatment solution increases the coating wax content substantially linearly; A 0.5% increase in concentration results in an increase in boron content of about 12 parts per million relative to the total sample weight. During the final heat treatment, Epstein batches were prepared from the samples, heated at a rate of 40 ° C / hr from 800 ° C to 1175 ° C, and kept for 3 hours at the latter temperature.

The permeability data of the final products obtained are shown in Figures 4, 5 and 6; in these figures the samples were grouped according to their sulfur content. The nitrogen content of the final heat treatment strips is also shown in the figures. In addition, Articles 4-6. Figures 3A and 5B show the measured iron loss values at several points. In each case, it has been found that the application of a boron coating improves the magnetic properties of the final product; the greatest improvement is seen in low sulfur, high nitrogen samples. When using a boron-free coating, all four low-sulfur samples exhibit primarily normal particle size increase, whereas when skin is added to the coating, a full secondary recrystallization occurs in the high nitrogen base alloy. It is also clear from the analysis data of the intermediate sulfur-containing samples that high permeability can be achieved with high nitrogen-6181438 content: the data with the lowest nitrogen-containing sample are worse than that of other samples in the same group.

Further, it is found that adverse effects associated with high nitrogen content, such as blistering or cracking (which are well known disadvantages of high nitrogen silicon-iron alloys) do not occur at all in the samples treated according to the invention.

In the specification and in the claims series and in the figures, the boron content of the coating is theoretically expressed as the total amount of skin available for the silicon-iron base alloy. In practice, during the final heat treatment, prior to the completion of the secondary recrystallization, a small amount of this boron content drifts into the base alloy. Depending on the conditions used, the amount of diffused boron in the case of low-boron coatings may be as high as nearly half of the boron content of the coating.

Claims (3)

Claims 2 A process for the production of grain oriented silicon-iron alloy plates comprising 2.2 to 4.5% silicon, 1.5 to 50 parts per million skin, 30 to 90 parts per million (1.0 parts to 15 parts per liter of wine), 0.024- A fine-grained, primarily recrystallized alloy plate containing 0.10% manganese and 0.010% -04% sulfur is deposited on the resulting alloy plate, and a secondary recrystallization step resulting in the final heat treatment operation [110] [001] is applied to the coated plate. characterized in that the sheet is coated, preferably electrolytically, or by rubbing with a 5 to 11 microns thick electrically insulating layer of magnesium hydroxide or magnesium oxide, adhering to the sheet, and in the absence of inorganic acid amide, the coated sheet is 3 to 20 g / l, preferably immersed in an aqueous solution containing boric acid or sodium borate, with a The Mn / S ratio in plate 5 is kept below 2.5, and the resulting alloy plate coated with a 6.0 to 90 parts per million boron layer is heat-treated. 2. The process of claim 1, wherein the amount of boron in the sheet and the amount of boron available in the coating are adjusted to a value of 7.5 to 90 parts per million. 3 drawings (with 6 figures) Director of Economic and Legal Publishing House 85.5134.66-4 Alföldi Nyomda, Debrecen - Chief Executive Officer: István Benkő Director