JPS6033896B2 - Method for forming insulation coating on unidirectional silicon steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an insulating film on a unidirectional silicon steel plate,
In particular, the present invention relates to a method for forming a forstellite insulating film that has a uniform appearance and excellent adhesion.

A method for forming a forsteritic coating on a unidirectional silicon steel sheet is to decarburize a silicon steel strip that has been cold-rolled to a predetermined final thickness in warm hydrogen at a temperature of 700 to 90,000 degrees Celsius, and then remove the carbon from the steel strip. A commonly used method is to generate subscales containing Si02 on the surface of the band, then apply a dull separator containing Mg0 as a main component, wind it into a coil, and subject it to high-temperature finishing annealing. The forsterite coating formed through the series of steps described above determines the final appearance of the product, and its quality greatly influences the product value.
Products with defective coatings are not accepted as products, and the appearance of the coating has an extremely large effect on product yield.

Furthermore, an important property of the forsterite coating is its adhesion to the steel plate. If the adhesion is poor, when the product coils are punched, laminated, and assembled into the transformer core, the coating will peel off at the edges, and this conductive area will cause core loss to increase and deteriorate the characteristics of the actual machine. It turns out. That is, the most important properties required of a forsteritic film are its appearance and adhesion. In order to satisfy these characteristics, a large number of studies have been carried out, and in particular, there have been many studies on Mg0, which has a great influence on the formation of a forsteritic film.
Most of the papers relate to methods for forming an insulating film using Mg○, which is fired at a relatively low temperature of about ○. However, even when Mg(OH)2 is fired at a temperature of around 90,000 ℃, many impurities harmful to film formation are not removed. However, the current situation is that it is not possible to prevent harmful components from remaining. In addition, this low temperature firing M
Since g0 has small particles and high activity, it is preferable for reaction with lotus acid (Si02) formed on the steel plate surface after decarburization and annealing. However, when Mg○ is made into a water slurry and applied to the steel plate and dried, Due to hydration, the Mg○ in the area becomes Mg(OH)2 and is brought into the coil. This introduced Mg(OH)2 is decomposed and generated during annealing, which has a great effect on the formation of the film. This special water content is influenced by the activity of Mg0, the water temperature of the slurry, the residence time of Mg0 in the slurry, etc., and it is extremely difficult to strictly control this, so that a good film can be stably obtained. This was the reason why I was unable to do so. Conventionally, as a method for controlling moisture brought into the coil, as disclosed in Japanese Patent Publication No. 49-19981, Mg○ obtained from raw material Mg(OH)2 by low-temperature firing is completely hydrated in hot water in advance. , a method of mixing this with Mg○ obtained by relatively high temperature calcination with low hydration property and using it as a scorching hammer separating agent, or Mg(OH)2 itself as disclosed in JP-A-55-73823. There are methods such as adding an appropriate amount of.

Although these methods can control the moisture brought into the coil to some extent, they use low-temperature fired Mg○ as a raw material, so the impurities contained in MgO are incompletely purified, resulting in a large amount of impurities being formed. There were problems with the appearance and adhesion of the coated film. An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for stably and economically forming a forsterite insulating coating with good appearance and excellent adhesion on a unidirectional silicon steel plate. The above objectives of the present invention are achieved by the following two inventions.

The gist of the first invention is as follows.

In other words, a silicon steel strip rolled to a predetermined final thickness is
A unidirectional method in which a compound containing g○ or Mg○ as a main component is applied as a hammer separation agent and wound into a coil, followed by overflow annealing in a box furnace to form a forsterite (2Mg○・Si02) insulating coating. In the method for forming an insulating film on a silicon steel sheet, the annealing separator is 40% so that the ignition loss rate at 45,000 or more is in the range of 2.0 to 10%.
A Mg that is forcibly hydrated in hot water of 0.00 or higher for 40 to 19 minutes and fired at a high temperature of 130,000 or higher.
This is a method for forming an insulating film on a unidirectional silicon steel sheet, which is characterized by using a compound containing O or Mg○ as a main component. The gist of the second inventor is as follows. That is, as in the first invention, 45
Tio whose main component is Mg0, which was fired at a high temperature of 130,000 or more and forcibly hydrated in hot water of 4,000 or more for 40 to 190 minutes so that the ignition loss rate was in the range of 2.0 to 10% at 0oo or more. ．． 5-10% by weight and Sro. This is a method for forming an insulating film on a unidirectional silicon steel sheet, characterized in that a compound containing 1 to 1% by weight is used. As a result of a detailed study by the present inventors on the factors that affect the formation of a forsteritic film, we found that the annealing separator is free from impurities in MZ0 and when MZO slurry is applied to a steel plate and dried. It was concluded that the interlayer atmosphere within the coil determined by the amount of water partially hydrated and brought into the coil is the main one. The interlayer atmosphere within the coil is dependent on the oxidizing atmosphere introduced by the hydration of Mg0.

In other words, if the special moisture content is small, a low oxidizing atmosphere will result, and the entire film formed will be whitish and have poor adhesion.On the other hand, if the special moisture content is too large, the film will be too oxidizing. The constituent forsterite particles become coarse, impairing the adhesion of the coating, and furthermore, the steel plate is not completely covered and the base iron is exposed. The present inventors have discovered that the raw material Mg
By firing (OH)2 at a high temperature of 130,000 or higher, impurities in Mg(OH)2 can be easily removed, and the Mg(OH)2 obtained by such high-temperature firing has an extremely low water resistance at room temperature. Poorly hydrated slurry residence time;
Since it is not affected by the slurry water temperature, etc., it has been found that the two problems mentioned above, namely, the problem of controlling the impurity of Mg0 and the problem of controlling the amount of water brought into the coil, can be solved at the same time.

The present invention has been made based on this knowledge. Next, the present invention will be explained by basic experiments.

The raw material Mg(OH)2 of the chemical components shown in Table 1 is 9500
It was fired at 0.0°C, 1300°C and 1500qo, and its chemical composition is also shown in Table 1. From Table 1, S, CI, Na
, K and other impurities cannot be removed by firing at 950°C,
It can be seen that it can be removed by firing at 1300 pm or more.

Therefore, in the present invention, the firing temperature of Mg○ etc. is set to 1300
Limited to 00 or more. Other elements such as Fe, Sj, B, and P remain in the M core regardless of the firing temperature, but CI, Na
, K, etc., the adverse effect on the film is small. As mentioned above, the Mg0 fired at a high temperature of 1300℃ or higher is 900℃ compared to the conventional Mg0.
It has extremely high purity compared to Mg0 fired at a low temperature of about qC. Impurities can be easily removed by high-temperature firing, so even if the purity of the raw material is somewhat low, the obtained M
The purity of g○ is good, and the economic effect of obtaining high purity Mg0 using inexpensive raw materials is also great. Next, a comparison of the hydration properties of Mg◯ in Table 1 is shown in Table 2.

This is the weight loss after immersing the calcined MgO in water at 20°C for 30 minutes, drying it, and then scorching it at 100,000 for 2 hours, and quantifying the reactivity with water, that is, the activity of Mg○. It can be seen that Mg0 fired at a high temperature clearly has poor hydration properties compared to Mg0 of 950 oo. Table 2 If the Mg0 obtained by high-temperature firing as described above is simply used as a hammer separating agent and final annealing is performed as in the past, the sailor 01 property is low, so less water is brought into the coil, resulting in a whitish color and poor adhesion. A bad forsteritic film is formed.

An appropriate amount of moisture is essential to form a good forstellite film, and bringing the appropriate amount of moisture into the coil is a difficult problem to be solved when using high-temperature fired Mg○ as an annealing separator. Ta. As a result of our research on the hydration of high-temperature fired Mg0, the present inventors found that even in high-temperature fired Mg0, the rate is not fast in hot water of 4000 or higher;
It has been found that hydration occurs and a portion of the material is converted to Mg(OH)2, and that even when the water is returned to a normal water temperature of 20 to 30 DEG C., hydration does not proceed any further.

Based on this knowledge, by hydrating and cooling the high-temperature calcined Mg○ in an appropriate flood using distilled water and applying it as a slurry at normal water temperature, or by immediately applying a high-temperature slurry of Mg○ using distilled water, High-purity Mg○ fired at high temperature
The amount of water brought into the coil could be controlled to the desired value because it gradually hydrates when the value is 4,000 or more, and does not hydrate when it is less than 4,000. Therefore, the hot water temperature during forced hydration is 4
4000 since hydration hardly progresses below 0oo.
limited to the above. In addition, the hydration time was controlled so that the ignition loss rate at 450oC or above was within the range of 2.0 to 10%, and as shown in the examples in Tables 3 and 4, a uniform gray coating appearance and good adhesion were achieved. The duration was limited to 40 to 190 minutes, which is the optimum time to form a forsteritic film. High temperature firing M
The forced hydration of g○ can be done by keeping the Mg0 slurry warm in hot water, or by directly putting the Mg0 powder into hot water, but it is better to hydrate the Mg0 slurry than to leave it still. has good hydration efficiency. As mentioned above, the amount of water brought into the coil due to hydration of Mg0 has a great influence on the formation of a forsteritic film, but in the present invention, forced hydration is carried out based on basic experiments and examples described later. High temperature fired Mg○4
It has been found that good results can be obtained by using a material whose ignition loss rate is limited to a range of 2.0 to 10% at a temperature of 5,000 or more. The reason for this limitation is 2.0
If the oxidizing atmosphere is less than 10%, the formed film will be whitish and have poor adhesion, and if it exceeds 10%, the oxidizing atmosphere will be too high and the forsterite particles will become coarse and the adhesion will decrease. Incidentally, the ignition loss rate is the ratio of the ignition loss of Mg○ to the weight before ignition, and is the ratio between Mg0 and Mg(O
H) This is a value indicating the water content of the coexisting substances of 2. Scorching heat treatment 4
The reason for limiting the temperature to 5,000 or higher is that dehydration of Mg(OH)2 is almost completed at 40,000, but in scorching heat treatment at this temperature, a small amount of 20 may remain in Mg○. This is because accurate moisture content cannot be obtained unless the scorching heat treatment is performed. Burning treatment must be carried out until there is no change in weight after reprocessing, but the lower the temperature, the longer the burning time is, and in order to complete the process in a short time, a burning temperature of approximately 1000 qo is required. desirable. As mentioned above, the scorching heat loss rate is 2.0 to 10%.
A forsterite material with a uniform appearance and excellent adhesion is created by using a compound mainly composed of Mg○ or Mza0, which is forcibly hydrated in hot water and fired at a high temperature, as a sintered anchor separating agent. However, in addition to Mg○, Tio. 5-1% by weight and Sro. Even when a compound containing 1 to 10% by weight is used as an annealing separator, the objects of the present invention can be more effectively achieved.

That is, by adding Ti and Sr compounds to a compound mainly composed of Mg○ or Mg0, the adhesion between the steel plate and the coating is further improved, but if Ti and Sr are less than 0.5% and 0.1%, respectively. If the amount is less than 10%, the addition has no effect, and if it exceeds 10%, it will have a negative effect on the magnetic properties. 5-1
Weight % of Sro. It was limited to a range of 1 to 1% by weight.

Example 1C: 0.036%, Si: 2.95%, S:
A cold-rolled silicon steel strip with a thickness of 0.3 skin containing 0.018% was subjected to decarburization annealing in a gas atmosphere consisting of a fog point of 6000, 65% hydrogen, and the balance nitrogen;
After firing at 0000 for 2 hours, pulverizing and passing through a 100-mesh Tyler standard strip was subjected to forced hydration under the conditions shown in Table 3, this Mg○ was applied to a steel strip, and 300o0
It was dried and wound into a coil.

Then, in a box furnace, 120
Final annealing was performed at 0o0 for 5 hours, and the formed forsteritic film was investigated on three samples under one condition. Table 3 shows the worst results among the three samples, and Figure 1 shows the results for all three samples. The appearance and adhesion were shown. The adhesion between the forsterite coating and the steel plate is determined by wrapping the steel plate around a cylindrical steel plate with a fixed diameter at an angle of 180 degrees, observing the peeling state of the coating on the inner surface of the bent steel plate, and indicating the minimum diameter without peeling. did.

The quality of adhesion is indicated by the size of its diameter, and the third
Even if a cylinder with a surface diameter of 2 mm is used, if there is no peeling, the adhesion is very good, but if there is no peeling with a diameter of 30 mm, there is no practical problem.

As is clear from Table 3 and Figure 1, the ignition loss rate is 2.
．． No. of the present invention examples within the range of 0 to 10%. Sample materials 3 to 6 have good appearance and adhesion, but comparative examples outside this range have poor appearance and 15.1% N.
o. In the 8 sample villages, the pond iron was exposed and its adhesion was measured for the coating formed on the edge, but the results were worst.

Example 2C: o. o38%, Sj:3.2%, S:0
．． 004%, Se: 0.017%, Sb: 0.025%
A cold-rolled silicon steel strip with a thickness of 0.3 skin was subjected to decarburization bran anchoring under the same conditions as in Example 1, and Mg(OH)2 was calcined in the same manner as in Example 1, under the conditions shown in Table 4. A compound containing Ti and Sr was added to the MZO, and then applied to a steel strip, dried at 300*°C, and wound into a coil.

Thereafter, after holding the temperature at 85,000 in nitrogen gas for 5 hours in a box furnace, final annealing was carried out by holding at 120,000 in Table 4 for 5 hours while passing hydrogen gas, and the forsterite was formed in the same manner as in Example 1. The quality coating was investigated and the results are shown in Table 4 and Figure 2.

Note that the numbers in Figure 2 indicate the sample material No. It shows. Fourth
As is clear from the table and Figure 2, the ignition loss rate is 2.
Test material No. of the present invention example within the range of 0 to 10.0%.
12-15 and No. Comparative Example No. 17 to 19 have excellent coating appearance and adhesion, but are outside the scope of the present invention. 9 to 11 and No. No. 16 had poor coating appearance and poor adhesion. As is clear from the above embodiments, the present invention is directed to high-temperature fired Mg○ or Mg
The weight loss rate on ignition of compounds whose main component is 0 is 2.0 to 10%.
By performing forced hydration in warm water so that the temperature is within the range of It was possible to economically form a forsterite insulating film with excellent properties.

[Brief explanation of the drawing]

Figures 1 and 2 both show the ignition loss rate of hydrated Mg○ and the appearance and adhesion of a forsterite insulating film formed using a sintered anchor separation agent containing Mg○ as the main component. It is a relationship diagram showing a relationship. Figure 1 Figure 2

Claims (1)

[Claims] 1. A silicon steel strip cold-rolled to a predetermined final thickness is coated with MgO or a compound containing MgO as a main component as an annealing separator, wound into a coil, and then subjected to high-temperature annealing in a box furnace. In the method for forming an insulating coating on a unidirectional silicon steel sheet in which a forsterite (2MgO SiO_2) insulating coating is carried out, the annealing separator has an ignition loss rate of 2.0 to 10% at 450°C or higher. The above MgO or M is forcibly hydrated in hot water of 40°C or higher for 40 to 190 minutes and fired at a high temperature of 1300°C or higher.
A method for forming an insulating film on a unidirectional silicon steel sheet, the method comprising using a compound containing gO as a main component. 2. MgO or a compound mainly composed of MgO is applied as an annealing separator to a silicon steel strip that has been cold-rolled to a predetermined final thickness, and after being wound into a coil, high-temperature annealing is performed in a box furnace to form forsterite (2MgO・In the method for forming an insulation coating on a unidirectional silicon steel sheet in which an SiO_2) insulation coating is formed, the annealing separator is heated at 40℃ or higher so that the ignition loss rate at 450℃ or higher is in the range of 2.0 to 10%. Using a compound containing 0.5 to 10 wt% of Ti and 0.1 to 10 wt% of Sr, the main component of which is MgO, which was forcibly hydrated in hot water for 40 to 190 minutes and fired at a high temperature of 1300°C or higher. A method for forming an insulating film on a unidirectional silicon steel sheet, the method comprising: