Heat-resistant coating for anisotropic electro-technical steel

FIELD: metallurgy.

SUBSTANCE: coating includes following components, wt %: dispersed silica 75-89; magnesium oxide 10-20; colloid silica 1-3.

EFFECT: high electric resistance and maintaining magnetic properties of steel at acceptable level due to elimination of zone enriched with non-metallic inclusions in under-surface layers.

2 dwg, 2 tbl

 

The invention relates to the production of electrical steel, more precisely to the transformer steel and heat-resistant coating on it.

Electricity losses during magnetization reversal is determined by the degree of perfection of the crystal texture, the dispersion of domain structure and, not least, the structure of the subsurface zone (1-3).

If subsurface area full of non-metallic inclusions (of the type shown in figure 1), alternating magnetization difficult. Magnetic losses increase in proportion to the depth of degraded areas and the development of superficiality interface between metal and ceramic surface layer (ground layer). The main cause of degradation of the subsurface layer is unmanaged interaction of heat-resistant magnesia coating with metal, as evidenced by the composition of the inclusions, mainly represented by posterita (Mg2SO4). Therefore, improving the structure of the subsurface zone is determined by the ability to control the process of interaction between metal and magnesium coatings.

Partially this problem was solved by the introduction of steel components, passivating the metal surface (Sb, Cu). More efficient removal from the surface of steel fayalite (Fe2SiO4formed when Bezuglova is Tige and act as a catalyst in the interaction of the metal with a heat-resistant coating. However, the removal of fayalite is realized due to etching of the surface, which increases costs.

The closest analogue of the proposed invention is a heat-resistant coating for anisotropic electrical steel, obtained from a composition containing the following components, wt.%: phosphoric acid 45,3 is 48.5, magnesium oxide 3,9-4,4, aluminum hydroxide 2,0-2,6, boric acid 0.3 to 0.4, liquid complex fertilizers 5-10, water - other (4).

The primary object of the present invention is the selection of the composition of the heat-resistant coating, in which the process of protobranchia is implemented only on the metal surface, which prevents the degradation of the subsurface layer. This object is achieved in that the heat-resistant coating for anisotropic electrical steel contains the following components, wt.%: powdered silica 75-89, magnesium oxide 10-20, colloidal silica 1-3 in terms of SiO2.

Provided by the invention the technical result consists in increasing the quality of heat-resistant coating by eliminating zone enriched non-metallic inclusions in the subsurface layers, which allows to obtain a coating having a high electrical resistance, allowing to preserve the magnetic properties of steel at an acceptable level.

The main component offers the suggested coating composition - powdered silica, which is inert to the metal, colloidal silica (silica Sol) is added to stabilize the suspension, i.e. prevent stratification, and magnesium oxide to form a thin soil layer does not penetrate into the metal.

The following experimental results confirm the efficiency of heat-resistant coating of the proposed structure.

The metal for the experiments was smelted in the BOF (composition, wt.%: Si 3,10-3,30; C 0,03-0,004; Mn 0,28-0,33; S 0.003 to 0.004 percent; Cu 0,5-0,55; Al 0,015-0,018; N20,01-0,012; the rest is iron and inevitable impurities) and poured into slabs by continuous casting machines. The cast slabs were heated in the reheating furnaces to a temperature 1240-1260C, rolled on broadband mill stripes 2.5 mm thick hot-Rolled strip was processed according to the following scheme: etching, the first cold rolling to a thickness of 0.7 mm, obezuglerozhivajushchego annealing, the second cold rolling to a thickness of 0.27 mm, degreasing, coating the heat-resistant coating, high-temperature annealing, straightening annealing with application of a magnetic insulating coating.

As heat-resistant coatings used in the composition of the following composition (table 1).

/tr>
Table 1
Variant coverContent, wt.%
magnesium oxide,
MgO
disperse powdered silicathe colloidal silica in terms of SiCO2
1100--
23070-
32080-
4 (corresponding to the claimed composition)
20773
5 (corresponding to the claimed composition)
15832
6 (corresponding to the claimed composition)
10891
75932

Table 2 illustrates the differences in magnetic properties and quality of coverage by using different compositions of heat-resistant coating.

Table 2
Qualitative indicators were using heat-resistant coatings of different composition.
Variant of the coating composition (table 1)Magnetic propertiesThe characteristic quality of a soil layer
B800, TP1,7/50In W/kg
11,871,11Grun the new layer high quality
21,871,09a soil layer uneven
31,871,08suspension stratified, clay layer poor
41,881,04a soil layer high quality
51,881,03a soil layer of satisfactory quality
61,891,02-,,-
71,871,02a soil layer uneven

From the data (table 2), it follows that the use of heat-resistant coatings recommended composition (options 4-6) allows to reduce the specific magnetic losses of P1,7/505-7% while maintaining the quality of the soil layer at an acceptable level, it is sufficient to obtain high electrical resistance in the finished metal. A positive effect in improving MAGN is the shaft properties achieved by removing the degraded layer in the subsurface zone of the bands (figure 2).

Thus, the introduction of the heat-resistant coating of silica in the form of dispersed powder and colloid (sols) silica can improve the quality of the finished metal at minimal cost.

Sources of information

1. JP 2000-038615, IPC C21D 8/12, 08.02.2000.

2. US 6733599 B2, IPC C21D/70, 09.10.2003.

3. JP 11-302731 A, 02.11.1999.

4. EN 2108634 C1 IPC H01B 3/02, 10.04.1998 (prototype).

Heat-resistant coating for anisotropic electrical steel, containing magnesium oxide, characterized in that it further comprises a dispersion of powdered silica and colloidal silica in the following ratio, wt.%:

disperse powdered silica7589
magnesium oxide1020
colloidal silica13



 

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SUBSTANCE: coating includes following components, wt %: dispersed silica 75-89; magnesium oxide 10-20; colloid silica 1-3.

EFFECT: high electric resistance and maintaining magnetic properties of steel at acceptable level due to elimination of zone enriched with non-metallic inclusions in under-surface layers.

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