JPS61264182A - Production of grain oriented silicon steel sheet having excellent magnetic characteristic - Google Patents

Abstract

PURPOSE:To produce a grain oriented silicon steel sheet having excellent magnetic characteristics by incorporating a slight amt. of Mo into a silicon steel of low carbon and contg. S or Se, subjecting the steel to hot rolling and cold rolling to form a sheet material, subjecting the sheet to decarburization annealing, coating an MgO separating agent for annealing on the surface and subjecting the sheet to final finish annealing thereby forming a uniform thin forsterite film on the surface. CONSTITUTION:The grain oriented silicon steel slab contg., by weight %, <0.06% C, 2.0-4.0% Si and 0.003-0.1% Mo and contg. 1 or 2 kinds of 0.008-0.1% S and 0.003-0.1% Se is hot rolled to form the sheet material. The sheet material is subjected to >=2 passes including intermediate annealing or one pass of cold rolling to the final sheet thickness. The sheet is subjected to decarburization annealing and primary recrystallization annealing and thereafter MgO having 0.08-0.18mu grain size measured by an X-ray diffraction method or the compd. consisting essentially or such MgO is coated on the surface as the separating agent for annealing and the sheet is subjected to the final finish annealing. The extremely thin and uniform forsterite (Mg2SiO4) film is formed on the surface and the grain oriented silicon steel sheet having the extremely high magnetic flux density and less iron loss is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a unidirectional silicon steel sheet with excellent magnetic properties, and particularly to a unidirectional silicon steel sheet with a uniform thin 7-orsterite coating, extremely high magnetic flux density, and low iron loss. The present invention relates to a method of manufacturing a silicon steel sheet.

The characteristics required of unidirectional silicon steel sheets, which are mainly used as core materials for transformers, are that the magnetic flux density obtained at a constant magnetization force is high, and that the iron loss is low when a constant magnetic flux density is applied. That's low. Normally, a representative value of these is the magnetic flux density B at a magnetizing force of 1000 A/m2. tesla, and the iron loss at a magnetic flux density of 1.70 tesla and a frequency of 508, expressed as t,A. In particular, considerable results have been achieved through improvements in the composition of raw materials, hot and cold rolling methods, heat treatment methods, etc.

Conventional unidirectional silicon steel sheets usually have Si: 2,0 to 4.
．． Low carbon steel containing 0% - After hot-rolling a material containing trace amounts of inhibitor-forming elements such as n, S, Se, etc., it is subjected to two or more times including intermediate annealing or one cold rolling process. Finished to a predetermined thickness by rolling, the cold-rolled steel sheet is subjected to primary recrystallization annealing that also serves as decarburization, and MgO is added to the surface of this decarburized steel sheet.
It is manufactured by applying a final annealing process after applying an annealing separator mainly composed of. That is, primary and secondary recrystallization annealing transforms the secondary recrystallized grains into (1
10) It develops in the <001> direction, and impurities in the steel sheet are removed, resulting in good magnetic properties.

At this time, the MgO applied to the surface of the decarburized steel sheet reacts with the oxide layer mainly composed of S io2 generated on the surface of the steel sheet after decarburization annealing during the final finish annealing, forming a forsterite coating called Mg, 5i04. It is well-known that . is formed on the surface of a steel plate. This forsterite coating not only maintains electrical insulation between the steel sheets, but also produces unidirectional silicon steel sheets with high magnetic flux density in which secondary recrystallized grains called Ga55 grains are well aligned in the rolling direction. has the effect of improving iron loss characteristics by narrowing the magnetic domain width within secondary recrystallized grains and reducing eddy current loss, and furthermore, when laminating steel plates and assembling them into a transformer core, unavoidable The properties of this annealing separator have an extremely important effect on the production of grain-oriented silicon steel sheets, since it has the effect of alleviating applied compressive stress and preventing deterioration of magnetostrictive and magnetic properties.

However, forsterite is a non-magnetic substance, and it is known that the presence of a coating of 1 or more of 7 orsterite, which is necessary to induce the above effect, on the surface of a steel sheet deteriorates both magnetic flux density and iron loss.

As long as final annealing is carried out after decarburization in wet hydrogen and MgO is used as an annealing separator, the formation of an orsterite film cannot be avoided, and the above effects are also present. In order to improve magnetic properties, it is essential to form a thin, uniform coating with the minimum amount required. However, in the past, it has been extremely difficult to form a satisfactory thin film as described above, and as a result, it has been extremely difficult to stably produce unidirectional silicon steel sheets having excellent magnetic properties.

An object of the present invention is to overcome the drawbacks of the above-mentioned conventional techniques and to provide a stable method for manufacturing grain-oriented silicon steel sheets having extremely high magnetic flux density and low iron loss.

The gist of the present invention is as follows.

That is, in terms of weight ratio, C: 0.06% or less, Si: 2.
0 to 4.0%, Mo: 0.003 to 0.1%, S: 0.008 to 0.1%, Se: O, OO3
A step of hot rolling a unidirectional silicon steel material containing one or two selected from ~0.1%;
a step of finishing the hot-rolled steel sheet to a predetermined thickness by cold rolling two or more times including intermediate annealing or once; a step of subjecting the cold-rolled steel sheet to primary recrystallization annealing that also serves as decarburization; A method for producing a grain-oriented silicon steel sheet comprising the steps of applying an annealing separator to the surface of a carbon steel sheet, and final annealing the steel sheet coated with the annealing separator, wherein the annealing separator is a powder. M whose particle size is in the range of 0.08 to 0.18μ as measured from the broadening of the diffraction line width by X-ray diffraction method
This is a method for producing a magnetic steel sheet characterized by using a compound containing gO or MgO as a main component.

The present inventors added various ingredients to the material to be subjected to final annealing and repeated experiments to investigate the effects on the formation of a forsterite film. As a result, we added a small amount of MO to the material ingredients, and the amount of water used by MgO was increased. By appropriately selecting MgO, MgO with appropriate activity can be obtained.
It has been found that by using this as an annealing separator, a uniform thin film is formed and the magnetic properties of silicon steel sheets are significantly improved.

As a measure of the activity of MgO, the particle size measured from the broadening of the diffraction line width by powder X-ray diffraction is as shown above.
The present invention was achieved by finding that the best results could be obtained by using MgO with an OS of ~0.18μ.

In general, the formation of a 7-orsterite film is caused by a solid phase reaction between the subscale mainly composed of Sin, which is present on the surface of the steel sheet after decarburization annealing, and MgO, which is an annealing separator.
As already mentioned, i O is formed. The amount of MgO applied is usually considerably larger than the amount required when all 5in2 in the saji scale becomes 7 orsterite, but the amount of film formed is determined by the amount of Sin in the subscale. it is conceivable that. Therefore, a requirement for forming a thin film is to reduce the amount of subscale after decarburization annealing.

However, if there are too few subscales, the forsterite coating formed during final finish annealing will be too thin, resulting in poor adhesion to the steel plate, which is undesirable.

Another point to consider is that when MgO is made into a water slurry and applied to the steel sheet, a portion of the MgO is hydrated and becomes 1g (OH)t, which is carried into the steel sheet coil and decomposed and generated during annealing. A steel plate is oxidized with H and O to generate FeO. When FeO thus generated is further reduced in H2 during final finish annealing, new Sin is generated by H2O, which is expected from the amount of subscale formed by decarburization annealing. It must be noted that the amount of coating after final annealing may be greater than the amount of coating applied during final annealing.

Therefore, the necessary requirements for forming a thin forsterite film are to minimize the amount of water introduced into the MgO, and to minimize the subscale content of the steel sheet without impairing adhesion to fc. , no 2
It is a requirement. However, it has been extremely difficult to control the amount of moisture brought in by MgO in the past, so if it is too little, a whitish film with poor adhesion will be formed, and if it is too much, the film will become excessively thick, and the film will become thinner. Point defects and exposed defects of the base metal occur. In addition, if the subscale amount of the steel plate is too small, the subscale thickness of the steel plate is thin and the effect of preventing oxygen diffusion is insufficient, resulting in weak resistance to additional oxidation during final annealing as described above. This results in the disadvantage that the state of the subscale after decarburization annealing cannot be maintained unchanged until the formation of a film during final annealing.

To form such a thin 7-orsterite film,
It is necessary to control the above-mentioned 2-requirement 2, and for this purpose, it is necessary to control the annealing separator and the steel plate itself, but hitherto no technology has been established to freely control these.

As a result of repeated experiments on specific measures to satisfy the above two requirements, the present inventors found that a trace amount of M was found in the material.

By adding , it is extremely resistant to additional oxidation,
It was found that the subscale state after decarburization annealing could be maintained without major changes until the final annealing to form a film. This shows that it is possible to reduce the thickness of the subscale after forming the forsterite film as long as it does not affect the adhesion to the steel plate or the appearance.

Furthermore, as a result of repeating film formation experiments by applying various types of MgO to the material containing a small amount of MO, we found that instead of the conventional method, that is, mixing inert MgO into the separation agent to reduce the amount of moisture carried in. It was discovered that by using MgO with a considerably high activity and within a certain range, a uniform thin 7-orsterite coating could be formed. As a measure of the activity of MgO, MgO has a particle size of 0.08 to 0.18μ measured from the broadening of the diffraction line width by powder X-ray diffraction method.
By using gO, a unidirectional silicon steel sheet with excellent magnetic properties could be obtained.

The reason why the particle size measured from the broadening of the diffraction line width by powder X-ray diffraction method was used as a measure of the activity of MgO is as follows. In other words, the activity of MgO is mainly determined by the raw material M.
g (determined by OHL firing temperature and firing time, the higher the firing temperature and the longer the firing time, the higher the M
Sintering of the gO single crystal particles progresses and the activity decreases. That is, the size of MgO single crystal particles has a very large effect on the activity of MgO. The particle size also changes due to mechanical pulverization after calcination, but such particle size only controls physical properties and has very little effect on activity. The particle size obtained by the broadening of the X-ray diffraction line width indicates the size of the MgO single crystal particle, and therefore it is reasonable to use this value as a measure to quantitatively measure the activity of MgO. It is.

Next, the reasons for limitations in the present invention will be explained.

First, the reason for limiting the component composition of the material is as follows.

If C exceeds 0.06%, decarburization and annealing will take a long time, reducing productivity, and decarburization will also become insufficient, deteriorating magnetic properties, so it was limited to 0.06% or less. .

Si: When Si is less than 2.0%, the specific resistance as a material is low, and a good core loss value cannot be obtained. Moreover, if the content exceeds 4.0%, the workability during cold rolling will be significantly reduced and defects such as plate cracks will occur, so the content is limited to a range of 2.0 to 4.0%.

Mo: If Mo is less than 0.003%, additional oxidation resistance will be poor and it will be difficult to form a good thin forsterite film.9. Moreover, if it exceeds 0.1%, hot and cold workability will deteriorate and iron loss will also deteriorate, so it is limited to a range of 0.003 to 0.1%. The above additional oxidation resistance is expressed as the ratio of the subscale oxygen content in Table I of the steel sheet after decarburization annealing to the oxygen content of the 7 orsterite coating after final finish annealing, and this ratio exceeds 2. It is believed that there is additional oxidation in the case. This is derived from the fact that a fluorstellite film is formed by the reaction 2M"gO+5102→Mg25in, and the stoichiometric change in oxygen is doubled.

Next, the results of an experiment conducted by the present inventors showing the relationship between the Mo content of the material, additional oxidation resistance, and cold workability will be described, and the effect of MO addition will be clarified.

Materials used are C: 0.043%, Si: 3.20%, M
n: 0.060%, Se: 0.018%, Sb: 0
．． When MO is not added to steel with a basic composition including 0222 and 0.001%, 0.003%, 0.0
08%, 0.020%, 0.051%, 0.10%, 0
．． The material changed to 21% was subjected to hot and cold rolling in a conventional manner, decarburized annealed, and then coated with MgO having a particle size of 0.13μ as determined by X-ray diffraction according to the present invention as an annealing separator, and then final finished. This is the result of measurement on a specimen that has been annealed and has an oxygen content of 1.70 S'101' in the subscale after decarburization annealing. The results are shown in Table 1.

As is clear from Table 1, the cold workability of Sample &1 in Table 1 to which no MO was added and Sample 2 with Mo:O, 001% was good, but the resistance to additional oxidation was poor. However, in the range of MO'0.003 to 0.10%, the additional oxidation property becomes almost constant, showing stable additional oxidation resistance and good cold workability. If MO exceeds 0.10%, hot and cold workability will decrease, and iron loss will also deteriorate, so Q.
A range of 0.003 to 0.1% is optimal, and by adding a small amount within this range, resistance to additional oxidation during decarburization annealing becomes extremely strong, and the subscale state after decarburization annealing is maintained at the final annealing. It is a great effect that the steel plate coating can be maintained without major changes until the coating is formed, and is one of the features of the present invention.

S, Se: s, , se both combine with Mn to form Mn8. It is added to form Mn5ei and act as an inhibitor, so s: o, o o less than s%, Se:
If the amount is less than 0,003%, MnS and MnSe generated
The effect of suppressing primary recrystallized grain growth is weak, and both ' is 0.
．． If it exceeds 1%, hot and cold workability deteriorates significantly, so 820, 008 to 0.1%, 8e: 0.003
It was limited to a range of ~0.1%. These S and Se can be added either alone or in combination within the above-mentioned range to achieve final annealing (1101<0
01> secondary recrystallized grains can be sharply developed.

Next, the reason for limiting the particle size measured from the broadening of the diffraction line width by powder X-ray diffraction method used as a measure of the activity of the annealing separator MgO will be explained.

As already mentioned, the activity of MgO is related to the reaction with the subscale of the steel plate mainly composed of Sin and the water utilization reaction in the water slurry. When using ``f, the coating performance is good, but MgO
A large amount of moisture is carried into the steel plate coil due to hydration, and additional oxidation also occurs, increasing the amount of coating and deteriorating the magnetic properties. In addition, when very fine grained MgO is used, point defects occur in the coating.

However, if the particle size of MgO becomes too large and exceeds 0.18μ, the appearance of the forsterite film becomes uneven, and if coarser MgO is used, the adhesion of the film worsens, resulting in a whitish appearance. This is not desirable because it significantly reduces the product value.

For the above reasons, the particle size of MgO was limited to a range of 0.08 to 0.18 microns.

In addition, when the particle size of MgO is 0.18μ and when the particle size is 0.40μ
To compare the hydration properties of the two cases, the weight loss after leaving calcined MgO in water at 20°C for 30 minutes and then scorching it at 1000°C for 2 hours is 1.50% for the former and 0 for the latter.
．． The value is 57%, and this value also represents the amount of hydration that indicates water availability, and while the former has sufficient activity, the latter shows that the activity has decreased significantly. Therefore, in the present invention, Mg
0.18μ was adopted as the upper limit of the O particle size.

Single crystals of MgO typically aggregate to form larger pseudoparticles. The particle size distribution obtained using an optical microscope or a light transmission type particle size distribution measuring device is a distribution of such pseudo particles. In addition, MgO obtained from the width expansion of the X-ray diffraction line
The particle size represents the average particle size of a large number of MgO single crystals. Therefore, MgO having a particle size determined from the broadening of the X-ray diffraction line should also exhibit a corresponding particle size distribution depending on the state of aggregation. As mentioned above, when the particle size distribution of MgO according to the present invention, whose particle size expressed as the average particle size of the MgO single crystal is in the range of O,OS ~ 0.18μ, is measured using the above-mentioned light transmission type particle size distribution analyzer, The resulting pseudoparticles were measured, and the results showed a particle size distribution in which 65 to 90% of the particles were below 2μ.

Also, when observing MgO from the particle state, the particle size is 0.
．． The MgO of the present invention, which is in the range of 0.08 to 0.18μ, has a high activity that leaves a hexagonal plate-like skeleton of Mg(OH)2, which is the mother salt, and has MgO particles aggregated therein. It is thought that an excellent forsterite coating can be obtained because an appropriate amount of inert material with no hexagonal plate-like structure is observed as the firing progresses.In contrast, conventionally known MgO has a small particle size. Since there is no proper standard for distribution, the mixing ratio of highly active MgO with a hexagonal plate-like shape and inert MgO is naturally inappropriate, and as a result, the particle size is less than 0.08μ or 0.18μ. If there are particles exceeding the above range, it is considered that a good forsterite coating could not be obtained.

As mentioned above, the activity of MgO depends on the firing conditions of the raw material Mg (OH) 2. Hydration reactivity t-20℃ showing the activity of
Table 2 shows the weight loss rate when the sample was left standing in water for 30 minutes and then scorched at 1000°C for 2 hours.

As is clear from Table 2, phosphorus, etc. exceeding 1100℃ 2
Surface formation significantly reduces the water reactivity, ie, the activity, of MgO. According to the inventor's above experimental results, this is MgO with a particle size exceeding 0.18μ, and MgO with such low activity
A good thin forsterite film cannot be formed under these conditions. A thin forsterite film with good appearance and adhesion can be formed within a range where the ignition loss rate is 1.5 to 4 inches.

That is, the weight loss rate under the scorching heat conditions is 1.5%ti.
In the case of [, the amount of forsterite coating does not decrease much, the appearance is non-uniform, and the adhesion to the steel plate is not good.

In addition, when MgO with a weight loss rate exceeding 4% is used, although the appearance and adhesion are good, additional oxidation occurs in the final annealing process, the amount of coating increases, and the magnetic properties deteriorate. The particle size of MgO measured from the broadening of the diffraction line width by powder X-ray diffraction, which is a measure of activity corresponding to the ignition loss rate of MgO of 1.5 to 4 cm, is 0.08 to 0.18.
μ, so in the present invention, the appropriate particle size is 0.08 to 0.08.
It was limited to a range of 18μ.

Example I C: 0.042%, Si: 3.25%, Mn: 0.06
0%, Mo: 01013%, S: 0.018%, including hot rolling, homogenization annealing and one intermediate annealing.
The final plate thickness was 0.311111 after cold rolling.
Next, 820 with a dew point of 60°C and consisting of 65% hydrogen and the balance nitrogen.
Decarburization annealing was performed in a gas atmosphere at ℃. The amount of oxygen in the subscale after decarburization annealing was 1.6017 m''. MgO with the particle size shown in Table 3 was applied to this decarburized steel sheet, dried, and then wound into a coil. from 820℃ to 3℃
The appearance of the coating was observed at a heating rate of 1,000 hrs., and the amount of oxygen in the coating, magnetic properties BIO, and W17150 were measured. The results are shown in Table 3.

Table 3 As is clear from Table 3, the steel of the present invention has an MgO grain size in the range of 0.08 to 0.18μ as measured by the X-ray diffraction method according to the present invention! No. 3 and No. 4.5 had a uniform gray appearance, indicating that the magnetic properties were significantly superior to comparative steels not covered by the scope of the present invention.

Example 2 C: 0.040%, Si: 3.25%, Mn: 0.0
64%, Mo: 0. A slab containing 15'% O and 0.018% Se was treated in the same manner as in Example 1 up to the decarburization annealing step. The amount of oxygen in the subscale after decarburization annealing is 1.65? /m''. Separating agents with various particle sizes shown in Table 4 were applied to this decarburized steel plate, dried, and then wound into a coil.
7) Others iCT io 2 1.5%, 5rS041.
0% was added. After performing secondary recrystallization annealing of this copper strip at 850°C for 50 hours, 11'8
The magnetic properties of unidirectional silicon steel sheets obtained by purification annealing in hydrogen at 0° C. for 5 hours were measured in the same manner as in Example 1, and the results are shown in Table 4.

4 Table r□□ 1. Even when a large material is used and the annealing separator is MgO as the main component and small amounts of TiO2 and SrSO4 are added, the particle size according to the X-ray diffraction method according to the present invention is 0.08 to 0.18μ. It is shown that as long as the temperature is maintained within the range of , it is possible to obtain a unidirectional silicon steel sheet that has a uniform gray appearance, has a much better surface quality than comparative examples outside the scope of the present invention, and has significantly superior magnetic properties. ing.

Example 3 C: 0.043%, Si: 3.20%, Mn: 0.06
0%, Mo: 0.012%, Se: 0.018%
, Sb:0.022H was treated in the same manner as in Example 1 up to the decarburization annealing step. The amount of oxygen in the subscale after decarburization annealing is 1.70? It was /-. This decarburized steel plate is mainly composed of MgO with various grain sizes shown in Table 5, Ti021.5%, SrSO41,0% k
fjs was added, a PC annealing separator was applied, and after drying, it was wound into a coil. A unidirectional silicon steel sheet obtained by performing secondary recrystallization annealing by holding this copper strip at 850°C for 50 hours and then purification annealing by heating and holding in hydrogen at 1180°C for 5 hours was treated in the same manner as in Example 1. The annealing separator properties and magnetic properties were measured. The results are shown in Table 5.

As is clear from Table 5, in this case as well, the product using the annealing separator with the particle size of the present invention is significantly superior to the non-limited comparative examples in terms of appearance and magnetic properties. .

Bay 5 Table In Examples 1 and 2.3 above, M according to the present invention was included in the material components of each sample material of Comparative Example A7.1421.

It does not contain , and is made from materials with the same other ingredients.

As is clear from the above examples, the unidirectional silicon steel sheet according to the present invention has a limited material composition, especially Mo: 0.0
When using MgO or a compound mainly composed of MgO, which is added in an amount of 0.3 to 0.1% and further used as an annealing separator, the particle size is measured from the broadening of the diffraction line width by powder X-ray diffraction method. By controlling the thickness to be within the range of 0.08 to 0.18μ, the following effects could be achieved.

(b) By adding MO, the resistance to additional oxidation during final annealing is strong, and the resulting subscale state can be maintained unchanged until the coating is formed during final annealing, making the insulation coating extremely thin. I was able to do it.

(b) Since the particle size is controlled in a limited manner by X-ray diffraction, which affects the activity of MgO or an annealing separator mainly composed of MgO, the amount of moisture brought in can be properly controlled and a thin forsterite with good adhesion can be produced. A quality film can be stably formed.

(c) As a result of (a) and (b), it has a thin insulating coating with good adhesion that exhibits a uniform gray appearance, and its magnetic flux density is extremely high at 1.88 to 1.93 T. It has become possible to stably produce unidirectional silicon steel sheets with excellent magnetic properties and low iron loss values of 1.02 to 1.12 W/A9.

Claims (1)

[Claims] (1) C: 0.06% or less, Si: 2.0~ by weight ratio
4.0%, Mo: 0.003 to 0.1%, and S
:0.008~0.1%, Se:0.003~0.1%
A step of hot rolling a unidirectional silicon steel material containing one or two selected from the above, and a step of cold rolling the hot rolled steel sheet two or more times including intermediate annealing or once. a step of finishing the plate to a predetermined thickness; a step of subjecting the cold-rolled steel sheet to primary recrystallization annealing that also serves as decarburization; a step of applying an annealing separator to the surface of the decarburized steel sheet; and a step of applying the annealing separator. In the method for producing a unidirectional silicon steel sheet, the annealing separator has a particle size of 0.08 to 0.08 as measured from the broadening of the diffraction line width by powder X-ray diffraction. A method for producing a unidirectional silicon steel sheet with excellent magnetic properties characterized by using MgO or a compound mainly composed of MgO in the range of 0.18μ.