CS218567B2 - Fire-proof oxide coating for electromagnetic silicon steel - Google Patents

Abstract

SILICON STEEL AND PROCESSING THEREFORE A process for producing electromagnetic silicon steel having a cube-on-edge orientation and a permeability of at least 1870 (G/Oe) at 10 oersteds, The process includes the steps of: preparing a melt of silicon steel containing from 0.02 to 0.06% carbon, from 0.0006 to 0.0080% boron, up to 0.0100% nitrogen, no more than 0.008% aluminum and from 2.5 to 4.0% silicon; casting said steel; hot rolling said steel; cold rolling said steel; decarburizing said steel; applying a refractory oxide coating containing both boron and SiO2; and final texture annealing said steel.

Description

The invention relates to a refractory oxide coating for electromagnetic silicon steels having a cube orientation at the edge and a permeability of at least 2,350. ΙΌ ^-3 H. . m ^-1 at 795 A. m ^_1 .

U.S. Patent Nos. 3,873,381, 3,905,842,

905 843 and 3 957 546 disclose the production of grain-oriented electromagnetic silicon steel and inhibited by boron. The methods described relate to the production of high magnetic quality steel from a boron-containing melt of silicon steel.

Conventional refractory oxide coatings, although suitable for achieving the desired electrical insulating properties, may have a detrimental effect on the magnetic properties of the steel, particularly in terms of permeability and core losses.

These drawbacks are largely overcome by the inventive refractory oxygen coating for electromagnetic silicon steel having a cube orientation at the edge and a permeability of at least 2,350 '. ΙΟ ^1-3 H.. m ^-1 at 795 A. m ^-1 and containing, in a concentration by weight of 0.0-2 to 0.0-6% carbon, 0.0006 to 0.0080%, preferably at least 0.0008% boron, up to 0.0100% nitrogen, 0.008 percent aluminum and 2.5-4.0% silicon, which coating is applied after decarburization of the steel and before annealing to the final structure.

SUMMARY OF THE INVENTION The refractory oxygen coating comprises a composition comprising boron in a concentration of 0.1 to 2% by weight, and further comprising 100 parts by weight of at least one of magnesium, calcium, aluminum and titanium oxides, hydroxides and carbonates. and boron compounds with magnesium, calcium, aluminum and titanium and 0.5 to 40 parts by weight of silica.

The coating may further comprise 0.01 to 100 parts by weight of at least one other boron-containing substance and its compounds. It may also contain from 0.01 to 20 parts by weight of inhibitors of the group comprising sulfur, sulfur compounds, nitrogen compounds, selenium, and selenium compounds. It may further comprise 0.01 to 10 parts by weight of fluxes.

For the purposes of the definition, "one part" is equal to the total mass of the above substance from the group consisting of magnesium, calcium, aluminum and titanium oxides, hydroxides and carbonates and boron - magnesium - calcium - aluminum - titanium compounds, divided by 1IC (O.

The refractory oxide coating of the present invention is intended for silicon steels of the above type and not only achieves the desired electrical insulation when the steels are used in electrical engineering, for example for the production of transformer cores, but its new effect is primarily to improve the magnetic properties of steel permeability and reduction of core losses.

The steel to which the invention relates is processed according to conventional methods, i.e. casting, hot rolling, one or more cold rolling and normalizing, decarburizing, dehumidifying and applying a refractory oxygen coating in accordance with the cold rolling process. The invention is then annealed to the final structure.

The processing of the steel itself is not critical and any of the procedures set forth in numerous publications may be used, including U.S. Patent No. 2,867,557 and the other patents mentioned above. The term casting includes continuous casting. Heat treatment of the strip during hot rolling is also included in the present invention. However, it is preferable to roll cold steel to a thickness of not more than 0.5 mm, without intermediate annealing between the individual passes when it is rolled from a hot-rolled strip of about 1.22 thickness. up to 3 mm. Melts containing by weight 0,0'2 to 0,06% of carbon, 0,0'15 to C.15% of magnane, 0,01 to 0,05% of a sulfur and selenium substance, Ο, Ο'Οόβ to 0 0080% boron, up to 0,0100% nitrogen,

2.5 to 4.0% silicon, up to 1.0% copper, up to 0.008% aluminum, the remainder iron, are most preferred for the subject invention. Boron values are usually above 0.0008%. The steel produced according to the invention has a permeability of at least 2,350. H ³ O ³ H. m ^-1 at 795 A. m ^_1 . Preferably, the steel has a permeability of at least 2,390,10 ^-3 H. m ^-1 at 795 A. m ^-1 and core loss up to • 1.544 W. kg ^-1 at 1.7 T.

The coating according to the invention can be carried out in any manner. The coating may be mixed with water and applied as a slurry, or may be electrolytically applied. Likewise, the constituents of the coating can be applied together or in individual layers. Preferably, the coating comprises 0.2 wt% boron and / or at least 3 parts by weight. S1O2. The boron content is usually not more than 15%. It is usually below 5%. The silica content is usually not more than 20% by weight. parts. The other inhibitors contained in the coating are usually selected from the group consisting of sulfur, sulfur compounds, nitrogen compounds, selenium and its compounds. Typical boron sources are boric acid, sintered boric acid (B2O3J, ammonium pentaborate, and sodium borate. Typical fluxes include lithium oxide, nitric oxide, and other known oxides. Silicon dioxide is added in known ways. Colloidal silica is preferred.

The following are some examples of specific embodiments.

Example I

Samples from three fusions (fusing A, V, and C) of silicon steel were cast and processed into silicon steel having a cube orientation at the edge. The composition of the melts is shown in Tab. AND.

β

Table I

Composition (wt.%)

Tav-C ba Mn with В N Si Cu AI Fe A 0.031 В 0,032 C, 0.03 .0,032 0,0-36 0,035 0.020 0.020 -0.020 0.0011 0,0013 0,0013 0.0047 0,0043 0, -0046 3.15 3.15 3.15 0.32 0,3'5 0.34 0.004 004 0.004 Bal Bal Bal

Sample processing included temperature equalization at elevated temperature for several hours, hot rolling to a nominal thickness of 2 mm, normalization of hot rolled strip at 950 ° C, cold rolling to final thickness, from carbonation, coating according to Tab. II, and final texture annealing at a maximum temperature of 1175 ^Q C in hydrogen. For the camp. II and in particular the identification of the sample, the letter denotes the melt and the number of the sample from the melt. For example, A denotes melt A, sample 1.

Table II

Sample

AiBiCi

A2B2C2

A3B3C3

MgO Parts (Parts, Mass)

100 ALIGN!

100100

H3BO3 (Parts, Mass)

2.3 (0.4% B)

4.6 (0.8% B)

The samples were tested for permeability and core loss. The results are apparent from Tab. III.

Table III

Sample Permeability Loss in core (at 795 A. m ^-1 ) (W. Kg ^-1 at .1.7 T) Ai A2 A ₃ B1 B ₂ з Cl c ₂ 1C3 2,365 1,625 2.380 '-1, -600 2,414 1,473 2,393 1,55.8 2,392 1,558 2.421 1.49 * 3 -1,960 2,8'0 2,379 1,535 2,398 1,493

The significant benefit of boron in the coating is apparent from Table 2. III. An improvement in core permeability and loss is also evident. Furthermore, each of the A, V, and S samples with more than 0.5% boron in the coating reached a permeability of more than 2.3'90. . ΙΟ ^-3 H. m ^_1 at 795 A. m ^-1 and a core loss below 1.544 W. kg ^-1 .

Example II

Another group of samples (group 4 to 8) was treated as sample group 1 to 3, without coating. The coating applied to the samples of groups 4 to 8 is evident from the table below. IV, along with those in Groups 2 and 3.

Table IV

Samples of MgO H3BO3 SiO2 (parts by weight) (parts by weight) (parts by weight)

B2 B2 ₂ 100 ALIGN! .2.3 (0.4% В) О A4 B4 C4 100 ALIGN! 2,3- 4.8 AS B5 C5 1OQ 2.3 3.6 Аз Вз Сз (1-00 4.6 (0.8% V) О Аб Ββ Сб ТОО 4.6 1,8 А7 В7 С7 -1О0 4.6 3.6 Αδ В8 Се 100 ALIGN! 4.6 7.3

The samples were tested for permeability and core loss. The results are shown in Tab. IN.

Table V

Sample Permeability Core Loss (at 795 A. M 1) (W. Kg-1 at 1.7 T)

A2 2,380 1,600 ' Ad 2,387 1,552 A5 2,392 1,546 Ba 2,393 1,558 Bd 2,399 1,554 B5 2,416 1,521 C2 2,379 1,535 'CD 2,380 1,5'58 C5 2,387 1,493 A5 2,414 1,473 Aa 2,430 1,440 A7 2,424 1,423 As 2,419 1,440 Bs 2,422 1,493 Be 2,440 1,435 B7 2,434 1,442 B8 2,423 1,439 <C3 2,398 1,493 C6 2.4015 1,455 C7 2,392 1,430 Ca 2,398 1,442

Γ —..... ''

From tab. A further improvement of the magnetic properties by adding SiO 2 to the base coat is apparent. SIO2 increases permeability and reduces core loss. Further, as is apparent from Tab. VI, S102 improves the insulating performance of the base coat. In tab. The VIs are given Franklin values at 3.1 MPa for samples C2, C4 and C5, C6, C7-C5 and as is known, the perfect insulator has a Franklin value of 0 while the perfect conductor has a Franklin value of 1 amp.

Table VI

Sample Franklin value (at 3.1 MPa)

C2 0.97 C4 0.96 C5 0,90 ' C3 0.93 Ca 0.90 C7 0.90 C8 0.88

It is noteworthy how the Franklin value is decreased by increasing the additive SIO2. Best results are obtained if the coating contains more than 3.0 parts of S1O2.

Claims (3)

CLAIMS 1. A refractory oxide coating for electromagnetic silicon steel having a cube grain edge orientation and a permeability of at least 2,350.10 ^-3 H. m_i at 735 A.. m- ¹ and containing by weight a concentration of 0.02 to 0 '06% carbon, 0.0006 to -0.0% i30 ·% boron, to Ο, ΟιΙΟΟ% nitrogen, to -0.006% aluminum and 2.5 up to 4.0% silicon, which coating is applied after the decarburization of the steel and before its annealing to the final structure, characterized in that it is composed of a composition containing boron in a concentration of 0.1 to 2% by weight and further comprising 10 parts by weight of at least one substances from the group consisting of oxides, hydroxides and carbonates of magnesium, calcium, aluminum and titanium and boron compounds with magnesium, calcium, aluminum and titanium and 0,5 to 5 40 parts by weight of silica. 2. A refractory oxide coating as claimed in claim 1 comprising from about 0.01 to about 10 parts by weight of at least one other boron-containing compound and its compounds. 5. A refractory oxide coating as claimed in claim 1, comprising from 0.01 to 20 parts by weight of inhibitors of the group consisting of sulfur, sulfur compounds, nitrogen compounds, selenium, and selenium compounds. 4. A refractory oxide coating as claimed in claim 1, 2 or 5 comprising 0.01 to 10 parts by weight of a flux.