JPS6036349A - Glass composition - Google Patents

Abstract

PURPOSE:The titled composition that is obtained by admixing appropriately the following essential components: SiO2, B2O3, Al2O3 and Cu2O, thus being suitably used as an insulating coat under the load of large tensile stress. CONSTITUTION:The objective glass composition is composed of, as essential components, 30-65mol% of SiO2, 11-45mol% of B2O3, 5-15mol% of Al2O3, and 10-20mol% of Cu2O and, as optional components, less than 5mol% of P2O5, less than 2mol% of V2O5, less than 2mol% of Na2O, less than 5mol% of PbO, less than 3mol% of SnO2 and less than 10mol% of ZnO. The total amounts of the essential components are required to exceed 85mol%. The resultant composition has a softening point of about up to 660 deg.C and a thermal expansion coefficient of less than 40X10<-17>/ deg.C. The composition is suitably used as an insulating coat formed on silicon steel plates.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low thermal expansion glass composition having a low softening point, and particularly to a glass composition suitable as an insulating coating formed on the surface of a silicon steel plate for a transformer core. .

Conventionally, it has been confirmed that adding tensile stress to the core of the transformer is an effective way to improve the energy efficiency of transformers. MgO powder is baked and reacted to generate a film with a thickness of about 5 μm and tensile stress is added, and then it is immersed in a 5i02-H3POif solution, dried, and fired to create a film with a thickness of about 3 μm. A method has been adopted in which tensile stress is applied by applying a tensile stress.

The tensile stress generated in these film-formed silicon steel sheets is 0.3 kg/*: for the former product, and O9b ~ 0 for the latter product.
．． It was about 7 kg/1111, and although the energy efficiency of the transformer was improved in each case, it was not satisfactory.

Therefore, in order to further improve the energy efficiency of the transformer, it has been desired to apply a larger tensile stress than before.

As a result of intensive studies in response to such requests, the inventors have discovered that by forming a coating with glass having a coefficient of thermal expansion of 20 x 10-77"c or less, it is possible to apply a larger tensile stress than before. Patent application 1986-231
In the invention No. 309, Cu1O-B with a thermal expansion coefficient of 20xlO/"c or less, 03 on the steel plate surface
-A low thermal expansion glass mainly composed of AI, 03-3in2 system is applied as a glass frit with an average particle size of 2 μm or less, and baked in a neutral atmosphere at a temperature of 1200°C or less to form a glassy coating with a thickness of 5 μm or less. 0.8~1.0kg/seal on the steel plate by forming! We proposed a method to add tensile stress.

In the above invention, the upper limit of the baking temperature is set at 1200° C. simply because the heat resistance of the steel plate is taken into consideration. Therefore, the temperatures for baking the glasses exemplified in the above specification of the invention were all at a high temperature of 1050° C. or higher. However, in general, the crystalline phase of steel sheets changes when the temperature exceeds 1100℃, and in the case of grain-oriented silicon steel sheets for transformer cores, which have a special crystalline phase, the crystal orientation changes and the iron loss is small. Since the properties tend to deteriorate, in order to prevent this, glass baking on a steel plate must be carried out in a short time at a temperature of 1100° C. or lower, preferably I 000'C or lower. In order to easily bake under such conditions, the softening point should be low, preferably 7.
It is necessary to use a glass that has a low viscosity at temperatures below 00°C, more preferably below 660°C, and above its softening point. Inventors Cu20-B203-A I, O
, -3i If the O2-based glass has an appropriate composition, it can be baked onto the surface of a silicon steel plate at a temperature of 1000°C or less for a holding time of several minutes.
It has been found that it is also possible to apply a tensile stress of mn2 or more.

The present invention was made based on the above findings, and its gist is that SiOz 30 to 65 mo1%,
B O11-45 mo1%, A1. A glass composition characterized by comprising LO35~λ315 mo1% and Cu, 010~20 mo1%.

The reason why the content of each component was limited as mentioned above will be explained below.

SiO□ is indispensable for lowering the thermal expansion coefficient of glass together with Cu2O, which will be described later, but 65
If mo exceeds 1%, the softening point will be 700°C or higher, and 10%
Baking at temperatures below 00°C becomes difficult. On the other hand, 30
If the mo amount is less than 1%, the coefficient of thermal expansion becomes large, making it impossible to obtain the desired tensile stress, and also having an adverse effect on water resistance, so the content is set to 30 to 65 mo1%.

B2O3 has a close relationship with the thermal properties of glass, and as the content increases, the softening point decreases, which in turn makes it easier to bake at low temperatures, but if it exceeds 45 mo1%, the tendency to devitrify increases and water resistance deteriorates. On the other hand, if the content is less than 11 mo1%, the softening point will not easily reach 700°C or less, so the content is set to 11 to 45 mo1%. In particular, the effect of lowering the thermal properties such as the softening point of B process O3 is remarkable up to 25mol1%, and considering water resistance, devitrification resistance, thermal expansion coefficient, etc., the most preferable content is 15 to 25111ol1%. be.

Al2O3 improves devitrification resistance, water resistance, and electrical insulation, but if it is less than 5 mo1%, its effects are poor;
If it exceeds 1% by mo, the softening point becomes high, so the content was set to 5 to 1% by mo.

As mentioned above, Cu and O have the effect of lowering the thermal expansion coefficient like Si02, but if it is less than 10 mo1%, the effect is poor, and if it exceeds 20 mo1%, the tendency to devitrify increases, so the content should be reduced to 10 to 20 mo1. % closed.

Although the glass composition of the present invention exhibits the effects of the present invention even when it consists only of the above-mentioned essential components, other components may be selectively added as necessary. However, the content of essential components is 85m
If the content is less than 1%, the effects of the present invention as a coating material such as low expansion, low softening point, easy wettability, and low viscosity cannot be fully exhibited, so the content of essential components is set to 85 no.1% or more, and the remaining shall be the content of the selected ingredient.

Preferred selective components are Pl 05- , V, '0r
They are XNa, 0PbO, SnO2 and ZnO. P2O
5 lowers the softening point, but when 5 mo1% is exceeded, the tendency to devitrify increases. V,,O, lowers the softening point and promotes a decrease in viscosity at temperatures above the softening point, but when it exceeds 2 mol%, it significantly reduces the electrical insulation properties of the glass.

Na>O also lowers the softening point, but rapidly increases the coefficient of thermal expansion, so if it exceeds 2 mo1%, the coefficient of thermal expansion decreases to 40
It is difficult to suppress the softening point to less than
If it exceeds 1%, there is a marked tendency for devitrification.

S n Oz functions to lower the viscosity at temperatures above the softening point, but when it exceeds 3 mo1%, there is a marked tendency to devitrify. ZnO lowers the softening point by substituting Cuρ, but if the content with Cu2O is less than 15 mo1%, the effect is poor, and if the content exceeds 25 mo1% or ZnO alone exceeds 10 mo1%, the coefficient of thermal expansion decreases. increases.

To apply the glass composition of the present invention to the surface of a silicon steel plate, first, the glass composition of the present invention is melted, rapidly cooled, and then ground into a glass frit, which is then applied to the steel plate surface using a conventional method such as a sedimentation method, a spray method, or a dipping method. .

Here, the sedimentation method is, for example, a method in which glass frit is dispersed in a suitable organic solvent, a steel plate is immersed in it, the glass is precipitated on the surface of the steel plate, and the steel plate is taken out after the solvent has evaporated. The spray method is a method in which a solution in which glass frit is dispersed is sprayed onto a steel plate, and the residue is then evaporated to apply the solution. In the dipping method, a steel plate coated with glass is heated to a temperature of 800 ml.
After holding the steel plate in a neutral atmosphere where it is not oxidized at ~1000°C for several minutes, the glass coating is baked onto the steel plate by allowing it to cool. The steel plate having the glass composition of the present invention applied to its surface in this manner is subjected to a tensile stress of 1 kg/kg or more.

Furthermore, the glass composition of the present invention has a 5in2-P surface on the silicon steel surface,
Since O has good wettability and reactivity with the coating, the adhesive strength with silicon steel is high and the possibility of peeling is small. Furthermore, the glass composition of the present invention has electrical insulation properties that are practically satisfactory for use as an insulating coating formed on the surface of a silicon steel plate for a transformer core.

Examples will be shown below, but the present invention is not limited thereto unless it exceeds the gist thereof.

S + OZ, H3B O3, A
(OH) , CII z O, H3P O/IL , V
:b 0゜3・Weigh Na2Co3, PbO, SnO2 and ZnO,
After uniformly mixing in a lightning crusher, it was placed in an alumina crucible and melted at a temperature of 1500°C in the atmosphere for 3 hours. The melt was dropped into water to obtain a glass lump, which was ground in an alumina ball mill to an average particle size of 1 μm. Glass flint was produced by doing this. The thermal expansion coefficient and softening point of the glass frit in the temperature range from room temperature to 400°C are shown in Tables 1 and 2.

Separately, silicon steel that has been decarburized and has a SiO-λ P2O5 coating on its surface and isopropyl alcohol 9
A mixed solution prepared at 0% by weight and 10% by weight in ethyl acetate is prepared, glass frit is dispersed in the mixed solution, and a steel plate is immersed in the solution to precipitate the glass frit on the surface of the steel plate. After the solution evaporated, the steel plate was taken out and dried. The thickness of the glass frit deposited on the surface of the steel plate was approximately 5 μm. Next, the steel plate was heated at a heating rate of 3 in an N2 atmosphere.
00”C/hrte900”C, 950”C or 10
An attempt was made to bake glass onto steel and plates by raising the temperature to 00'C and holding it at the same temperature for 1 minute. Regarding the baking conditions in Tables 1 and 2, the marks ◯ and X represent the ratio of glass coverage and non-adhesion, respectively.

2nd Table Note *1) Frit 11h14. Na15 and Na1
Frit No. 6 has the composition disclosed in Example 2 of ``Glass Composition'' in Japanese Patent Publication No. 49-32646 and Example 1 of ``Production Method'' in JP-A No. 56-6924.0, respectively.

Note *2) Softening point and softening point were measured using a differential thermal analysis needle.

As shown in Tables 1 and 2, all glasses having compositions within the range of the present invention were able to be baked onto the surface of a steel plate at a temperature of 1000° C. or lower. Although the glass composition of the present invention has a slight tendency to devitrify, it was able to be uniformly adhered to silicon steel plates, which is the main application of the present invention, without affecting baking. .

As described above, the glass composition of the present invention has a low softening point and a low coefficient of thermal expansion, and has excellent electrical insulation properties, so it can be used not only as an insulating coating formed on the surface of a silicon steel plate, but also as a bonding material for low thermal expansion materials. It can be used as glass for glass by baking or by incorporating it into various metal pastes.

Claims (3)

[Claims] (1) S+0230-65mo1%, B20.1
1-45 mo1%, AI 2035-15 mo1%
and Cu 2010 to 20 mo1%. (2) S i O2 30-65 mo1%, B20 Yo 11-45 mo1%, Al 2-035-15 m
O1% and Cu 2010~20mo1% are essential components, P2O3-5mo1% or less, V2O5-2mo1%
Below, Na 202 mo1% or less, Pb05 mo1
% or less, 5n023mol or less and Znolomol
% or less is the selected component, and the content of the essential component is 85 mo1%.
A glass composition comprising the above and the remainder one or more selected from the selected components. (3) The glass composition according to claim 1 or 2, which has a softening point of 660°C or less and a thermal expansion coefficient of less than 40xlO/''c in the temperature range from room temperature to 400°C. .