JPH06188116A - Oriented silicon steel plate for low core loss and high flux density and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an oriented silicon steel plate for low core loss and high flux density. CONSTITUTION:An oriented silicon steel plate for low core loss and high flux density contains 1-7% Si, 0.03-0.15% P, and, if necessary, 0.02-0.20% Sn. On the surface of the steel plate, grooves whose average maximum depth is 2-50mum and which have forsterite left behind on parts of the bottom are made at intervals of 45-90 deg. from the longitudinal direction of the steel plate. This silicon steel plate has a primary film mainly composed of forsterite of the average thickness of 0.3mum or smaller and whose core loss W17/50 is 0.70Watt/kg or lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high magnetic flux density grain-oriented silicon steel sheet having extremely excellent iron loss and a method for producing the same.

[0002]

2. Description of the Related Art 1-7% with excellent magnetic properties for transformers, etc.
When manufacturing a grain-oriented silicon steel sheet containing Si, a primary coating that secures insulation properties and imparts tension to the steel sheet surface to improve the magnetic characteristics necessary for improving the performance of the transformer and that has good adhesion to the steel sheet is formed. Forming has been one of the important problems of grain oriented silicon steel sheets in the prior art. That is, in the usual technique, after the primary annealing accompanied by decarburization, a steel sheet is coated with a slurry of magnesium oxide (MgO) fine powder called magnesia dissolved in water, dried if necessary, and then the secondary re-treatment is performed. burned by recrystallization annealing step, forsterite reaction with SiO ₂ and Si in the steel sheet (Mg
A ceramic-like insulating coating called ₂ SiO ₄ ) is formed. This is effective in giving tension to the steel sheet and improving the magnetic property, especially the characteristic value called iron loss, which governs the efficiency of the transformer. Moreover, the state of formation of this forsterite is called the GOSS orientation of the steel sheet in the secondary recrystallization, and is {110 relative to the steel sheet longitudinal direction (rolling direction), which is essential for improving the magnetic permeability and the magnetic flux density. } <0
It is well known that it also plays an important role in growing slightly coarse secondary recrystallized grains having a crystal orientation of 01>. On the contrary, during the secondary recrystallization annealing temperature rising process, even if it is attempted to perform secondary recrystallization without forming a sufficiently dense film, fine nitrides and sulfides called inhibitors in the steel sheet remain as they are, or It disassembles and quickly escapes from the steel plate. For this reason, the inhibitor effect of growing the GOSS-oriented grains preferentially during the temperature rise and suppressing the growth of other oriented grains cannot be exhibited, and it is commonly called fine grain. This results in a steel sheet with extremely poor magnetic properties, in which crystal grains do not grow partially or entirely. It should be noted that titanium oxide (TiO ₂ or the like) or another compound may be added to this MgO to form a denser primary coating.

However, there is a great demand for iron loss reduction of magnetic steel sheets, which has a great influence on the energy conversion efficiency of the transformer for energy saving as seen in the advent of amorphous materials in recent years, and the extension of the above-mentioned prior art meets this demand. Things have become difficult. In the conventional technique, in addition to the above method, a so-called product steel sheet surface after secondary recrystallization is intentionally imparted with a groove or some damage by a method of energy irradiation such as mechanical or laser to perform magnetic domain subdivision,
Methods are being taken to improve iron loss. However, even with this method, it was still difficult to realize a low iron loss that can counter Almorphus. On the other hand, since the primary coating containing forsterite as a main component is a hard solid substance, there is a problem in workability such as shearing of the product, resulting in a shortened tool life.

[0004]

SUMMARY OF THE INVENTION The present invention solves these problems and, based on the technical knowledge shown in the skeleton below, forms a solid substance containing forsterite as a main component called a primary film. In order to obtain a high magnetic flux density grain-oriented silicon steel sheet with extremely low iron loss while suppressing it as much as possible, a new product development technology was discovered.

[0005]

The gist of the present invention is as follows. (1) Si: 1 to 7% and P: 0.03 to 0.15% are included, and the average of the maximum depths on the steel plate surface is 2 to 50 μm.
Then, the grooves in which forsterite partially remains at the bottom are provided at intervals in the direction of 45 to 90 degrees from the longitudinal direction of the steel sheet, and the average thickness of the primary coating mainly composed of forsterite is 0.3 μm. in the following, the iron loss at W _17/50 0.7
A high magnetic flux density grain-oriented silicon steel sheet having an extremely excellent iron loss, which is characterized in that it is 0 Watt / kg or less.

(2) Si: 1 to 7%, P: 0.03 to
0.15%, Sn: 0.02 to 0.20%, the average depth of the maximum part is 2 to 50 μm on the surface of the steel plate, and the groove in which forsterite partially remains at the bottom is the longitudinal direction of the steel plate. From 45 to 90 degrees, and the average thickness of the primary coating mainly composed of forsterite is 0.3 μm or less and the iron loss is _{0.70 Watt} at W _17/50 .
/ Kg or less, a high magnetic flux density grain-oriented silicon steel sheet having an extremely excellent iron loss.

(3) A high magnetic flux density grain-oriented silicon steel sheet having extremely excellent iron loss as set forth in the above item 1 or 2, wherein the groove interval is 2 to 20 mm. (4) Si: 1 to 7%, P: more than 0.045% to 0.2
Steel containing 0% is melted and cold rolled in hot rolling, cold rolling, primary recrystallization annealing, application of an annealing separator, and secondary recrystallization annealing in the production of grain-oriented silicon steel sheets. After medium or cold rolling, the average maximum depth of the steel sheet surface is 2
~ 50 μm grooves are provided at intervals from the longitudinal direction of the steel sheet in the direction of 45 to 90 degrees, and then the steps from the primary recrystallization annealing are performed, and the steel sheet is removed from the primary recrystallization annealing to the secondary recrystallization annealing. The surface is coated with a substance containing at least one kind of chloride and sulfide, and the average thickness of the insulative primary coating mainly composed of forsterite produced during the secondary recrystallization annealing is 0.3 μm or less. A method for producing a high magnetic flux density grain-oriented silicon steel sheet having extremely excellent iron loss, which is characterized by the following.

(5) Si: 1 to 7%, P: 0.045
% Steel to 0.20%, Sn: 0.02 to 0.20%, and then hot-rolling, cold-rolling, primary recrystallization annealing, applying an annealing separator, and secondary recrystallization annealing. In the production of the grain-oriented silicon steel sheet, which is a basic step, the average maximum depth of the steel sheet surface during cold rolling or after cold rolling is 2 to 50 μm.
Grooves are provided in the direction of 45 to 90 degrees from the longitudinal direction of the steel sheet at intervals, then the steps from the primary recrystallization annealing are performed, and the steel sheet surface is subjected from the primary recrystallization annealing to the secondary recrystallization annealing. A material containing at least one kind of chloride and sulfide is applied to, and the average thickness of the insulative primary coating mainly composed of forsterite formed during secondary recrystallization annealing is 0.3 μm or less. And a method for producing a high magnetic flux density grain-oriented silicon steel sheet having excellent iron loss.

(6) The interval between grooves provided after cold rolling is 2
-20 mm, The method for producing a high magnetic flux density grain-oriented silicon steel sheet having extremely excellent iron loss according to item 4 or 5 above. (7) The method for producing a high magnetic flux density grain-oriented silicon steel sheet having extremely excellent iron loss as described in any one of the above items 4 to 6, wherein nitriding is performed during the primary recrystallization annealing. (8) Calcium chloride is added as a chloride contained in the annealing separator, and potassium sulfide is added as a sulfide. The high magnetic flux density with extremely excellent iron loss according to any one of items 4 to 7 above. Manufacturing method of grain-oriented silicon steel sheet.

(9) Any one of the above 4 to 8 characterized in that the temperature rising rate during the secondary recrystallization annealing is 30 ° C. or less per hour, and the nitrogen partial pressure in the atmosphere gas is 30% or more. The method for producing a high magnetic flux density grain-oriented silicon steel sheet having extremely excellent iron loss described in 1. The present invention will be described in detail below. Secondary recrystallization of grain-oriented silicon steel sheet is called GOSS orientation {110} <001>
It is important to grow grains of orientation sufficiently during secondary recrystallization annealing (also called finish annealing). This is to coarsely recrystallize only certain specific grains in the primary recrystallization annealing (hereinafter referred to as primary annealing).
It is well known in the art that it is technically necessary to prepare fine precipitates such as AlN called "hibitor)" before finish annealing. Then, nitrogen necessary for this purpose is added during steel melting, after primary annealing, or during other steps. For the purpose of the present invention, it was also found that the method of adding nitrogen after the primary annealing is the optimum method of adding nitrogen. If nitrogen is added during or immediately after the primary annealing, the equipment for nitriding reaction is usually installed inside or close to a part of the equipment for the primary annealing that also functions as a decarburizing reaction, and after or after the primary annealing. A method of nitriding reaction in parallel is also effective. In the case of steel that has been sufficiently carbonized during the melting of steel, it is rather important to change the oxide layer of the surface layer after primary annealing so that it has an advantageous shape for the coating reaction, rather than the decarburizing function.

In the present invention, it is important to regularly provide grooves having an average maximum depth of 2 to 50 μm on the surface of the steel sheet after or during cold rolling. This is because the grooves can make the magnetic domains of the product finer and contribute to the reduction of iron loss. The method of providing the groove is a grooved roll, a mechanical method such as a grooved or blade type press, an energy irradiation method such as laser and plasma,
Basically, any method such as a method of spraying water, oil, etc. at high pressure, a method of chemical corrosion by acid, etc., a method of electrical corrosion, or a combination thereof is essential. If the effect is recognized. But,
This alone cannot obtain the low iron loss targeted by the present invention.

The most important technical requirement in the present invention is the combination with the average thickness of the primary coating mainly composed of forsterite on the surface of the steel sheet. It has been found that when the thickness is 0.3 μm or less, the magnetic characteristics are remarkably improved in combination with the above. Further, when a groove is formed before finish annealing, some of the forsterite remains at the bottom of the groove, which is also supposed to promote the iron loss improving effect. The reason for this is not always clear, but if this primary coating is thick, it obstructs the flow of magnetic flux in the steel sheet, especially if the coating has many irregularities, or if oxides such as spinel (MgO.Al ₂ O ₃ ) are formed directly under forsterite. It can be easily imagined that the tendency is large when there are many. Therefore, if the primary coating on the surface is reduced as much as possible to be thin or completely eliminated, and if regular grooves are formed instead, the magnetic flux flows smoothly and regularly.
As a result, iron loss can be sufficiently reduced. Of course, there will be restrictions on the depth and pitch of the grooves.

The important findings of the present invention are as follows. In the prior art, a method is used in which a so-called primary product after forming a so-called primary coating is provided with grooves to subdivide magnetic domains. This is because the magnetic domain control effect is larger than that of the prior art method in which a groove is formed in the intermediate step. However, what has been made clear by the present invention is that a method of forming a groove after cold rolling or during cold rolling, which is inexpensive in terms of cost, is also sufficient when the primary coating thickness is extremely small or there is no coating. The key point is the fact that the magnetic domain subdivision effect is exerted.

A grain-oriented silicon steel sheet having the chemical composition shown in Table 1 (however, the amount of N in S1 is the value after primary annealing and nitriding) is hot-rolled, and after hot-rolled sheet annealing, cold-rolled to 0.23 mm. After making a groove having a depth of 15 μm and a pitch of 5 mm with a roll, primary annealing is performed, and then a steel sheet is coated with an annealing separating agent in which various additives are added to MgO powder, and finish annealing is performed.
FIG. 1 shows the results of examining the iron loss of the samples to which the insulating coating having tension was applied while changing the average thickness of the primary coating. As can be seen from this, the iron loss is reduced (improved) as the thickness of the primary coating becomes smaller, and it can be seen that it is particularly remarkable at 0.3 μm or less. This is because the groove is attached in an intermediate step after cold rolling, so even if forsterite etc. is clogged in the groove in the post step and the magnetic domain control effect deteriorates, the average thickness of the primary coating on the steel plate surface is small, or It is shown that the magnetic domains are sufficiently subdivided when there is no coating.

[0015]

[Table 1]

Next, when Al is added for secondary recrystallization, AlN or Si ₃ N ₄ is mainly used as an inhibitor. Here, one of the methods of the present invention is during primary annealing, or It was found that the method of nitriding thereafter is more preferable for the purpose of the present invention. This is for the following reason. Unlike adding a large amount of nitrogen during steel melting,
It is easier to control the optimal amounts of AlN and Si ₃ N ₄ by nitriding later, and even if the primary coating such as forsterite becomes thin or disappears as in the present invention during the secondary recrystallization annealing, the amount of AlN and Si ₃ N _{4 in} the atmosphere is reduced. It is considered that this is because it is easy to secure the optimum nitrogen amount by controlling the nitrogen partial pressure (P _N2 ).

Next, in order to reduce or eliminate the primary coating film during finish annealing as much as possible, according to the present invention, chlorides and sulfides are added to the surface of the steel sheet after the primary annealing by ordinary magnesia (Mg).
O) It was found to be effective to add it by mixing it in the powder. Among these, calcium chloride (CaCl ₂ ) and potassium sulfide (K ₂ S) are particularly effective. Even in the conventional method, in addition to MgO, TiO ₂ and antimony compounds (Sb ₂ (SO ₄ ) ₃ ), boron compounds (Na ₂ B ₄ O ₇ ), strontium and barium compounds,
Although the reaction is facilitated by adding a charcoal / nitride system or the like, the effects of these additives are exerted also in the present invention, and therefore the addition does not change the essence of the present invention.

A very important point in the present invention is the behavior of P. Table 2 shows the {111} plane index strength of the crystal orientation by X-ray after primary recrystallization of 3% Si steel in which only the amount of P was changed. The magnetic flux densities of the steel sheets obtained by primary recrystallization, nitriding and secondary recrystallization are shown in the same table. Obviously, these values change with the amount of P. On the other hand, when Sn is added in coexistence with P, iron loss is also significantly reduced as shown in FIG. 2 of the example of 0.06% P-3% Si steel, which is preferable. This is considered to be the effect of Sn grain refinement.

[0019]

[Table 2]

Now, it is necessary to touch on the method of manufacturing the grain-oriented silicon steel sheet. As described above, the grain-oriented silicon steel sheet according to the present invention contains Al as necessary in addition to Si, and Si
₃ N ₄ or AlN, and M when there is a large amount of S in steel
Limited to steels with nS as the primary inhibitor. Of course, in addition to Si, Al, P, Sn, Se, Sb, Cu,
The addition of other additive elements such as B, Nb, Ti, V, Ni and Cr to improve the magnetic characteristics does not change the basics of the present invention.

By the way, AlN or Si ₃ N ₄ , Mn
Steel containing S as an inhibitor is known, and the technique of the present invention can be applied to any of the cases. However, the following production method is most suitable for further exerting the characteristics of the present invention. That is, it is a steel containing 1 to 7% of Si, containing 0.1% or less of Al when steel is melted, if necessary, and during or after decarburization annealing during primary annealing after cold rolling in the grain-oriented silicon steel sheet manufacturing process. In addition, N is contained in an amount of 30 to 600 ppm before secondary recrystallization annealing by a method of forcibly adding N to the steel sheet directly through a nitriding reaction.

In the present invention, Si is used as a source as described above.
A minimum of 1% is required for the formation of rusterite. one
On the other hand, if it exceeds 7%, the workability is extremely deteriorated, and it is suitable for industrial production.
Not suitable. Al is effective in forming AlN inhibitor
It However, if it exceeds 0.1%, Al ₂O₃Large amount of production
It impairs the cleanliness of sound steel, which in turn impairs magnetic properties.
Bring an impact.

N is indispensable for forming the Si ₃ N ₄ inhibitor, and in the present invention, a minimum of 30 ppm is required after the primary annealing, that is, before the secondary recrystallization of the finish annealing is started. On the other hand, when Al is intentionally used, 60 ppm or more is necessary to secure the amount of AlN. However, 600
If it exceeds ppm, Al and Si are eaten too much, which is not preferable.

P is extremely important in the present invention. When steel is melted, if it is less than 0.045%, the effect of increasing the magnetic flux density is small, while if it exceeds 0.20%, the brittleness becomes large and cold rolling is difficult. The amount of P in the product is important in the present invention. P is present as a solid solution in iron and partly exists as a precipitate, but it is extremely effective in reducing iron loss in the product, and its effect cannot be exhibited unless it is present at least 0.03%. On the other hand, the presence of more than 0.15% causes embrittlement of the product,
For example, the workability and punchability of the product are impaired and the product cannot be used.

When S is positively used, at least 0.01% of S is necessary for effectively using MnS as an inhibitor. On the other hand, if it exceeds 0.05%, aggregation is not preferable. In the present invention, the other elements are not particularly characteristic as compared with the conventional steel, but the following restrictions are preferable.

C must be sufficiently low during steel melting or sufficiently low during decarburization annealing of primary annealing, and is preferably 0.03% or less at the start of secondary recrystallization annealing. If Mn is 0.5% or less, it reacts with S to form a MnS inhibitor. If it is 0.15% or less, it is preferable for further improving the magnetic flux density. O is Al if 0.05% or less after steel is melted
_It is preferable for cleanliness without making too much ₂ O ₃ .

In the present invention, Sn is remarkably effective in reducing iron loss when coexisting with P. If it is less than 0.02%, the effect is not obtained. On the other hand, if it exceeds 0.20%, nitriding is not sufficient and the inhibitor becomes weak, while the primary coating cannot be sufficiently formed, resulting in deterioration of characteristics. Next, the production method of the present invention other than the chemical components will be described. Steel is melted in a converter or electric furnace, etc.
The molten steel, whose composition has been adjusted by adding a refining process as necessary, has a thickness of 30 to 400 m by a continuous casting method, an ingot slab rolling method, or a thin slab continuous casting method for omitting the hot rolling step.
The slab has a thickness of m (50 mm or less in the thin slab continuous casting method). Here, 30 mm is a lower limit for ensuring productivity, and 400 mm is an upper limit for preventing abnormal distribution of Al ₂ O ₃ etc. due to center segregation. Further, the thickness of 50 mm in the thin slab continuous casting method is the upper limit for suppressing the generation of coarse particles due to the low cooling rate.

The slab is reheated to 1000 to 1400 ° C. by gas heating, electric heating, etc., and then hot rolled to obtain a hot coil having a thickness of 10 mm or less.
Here, 1000 ° C. is the lower limit of AlN melting,
C is the upper limit for preventing surface roughness and material deterioration. Further, the plate thickness of 10 mm is the upper limit for obtaining a cold speed at which an appropriate precipitate is formed. In the thin slab continuous casting method, it is also possible to directly form a coil, and for that purpose, 10 mm or less is preferable.

The hot coil made in this way is reapplied to 80
Annealing at 0 to 1250 ° C. is often performed to improve magnetism. Here, 800 ° C. is the lower limit for remelting AlN, and 1250 ° C. is the upper limit for preventing AlN coarsening. After such a treatment step, the hot coil is pickled directly or batchwise and then cold rolled. Cold rolling has a reduction rate of 60 to 95.
%, But 60% is the limit at which recrystallization is possible in the present invention, and preferably 70% or more by primary annealing {111} <1.
12> GOSS with a large number of oriented grains during secondary recrystallization annealing
This is the lower limit for promoting the production of oriented grains, while 95
If more than 100%, G is referred to as swinging GOSS grains in secondary recrystallization annealing
When the OSS-oriented grains rotate in the plane of the plate, grains that are not favorable for the magnetic properties are generated.

The above is the case of manufacturing by the so-called single cold rolling method, but in the case of cold rolling-annealing-cold rolling called the double cold rolling method, the first rolling reduction is 10 to 80%, and the second rolling is The rolling reduction is 50 to 95%. Here, 10% is the minimum reduction ratio necessary for recrystallization, 80% and 95% are the upper limit reduction ratios for producing proper GOSS-oriented grains during secondary recrystallization, respectively, and 50% in the double cold rolling method. Is {11 at the time of primary annealing
1} <112> It is the lower limit of the reduction ratio that appropriately leaves grains.

It is also commonly called "interpass aging", and heating the steel sheet in the range of 100 to 400 ° C by an appropriate method during the cold rolling is also effective for improving the magnetic properties. 10
Below 0 ℃, there is no effect of aging, while at 400 ℃
If it exceeds the limit, dislocations will be recovered. Now, an important requirement in the present invention is groove formation during or after cold rolling. This remains after finishing annealing, and a low iron loss, which cannot be seen in the past, can be obtained in combination with a method of reducing the primary coating containing forsterite as the main component to an average of 0.3 μm or less. The method of forming the groove is as described above, but if the average depth of the maximum part of the groove is less than 2 μm, there is no magnetic domain subdivision effect.
On the other hand, if it exceeds 50 μm, it is too deep and the smooth flow of the magnetic flux is hindered, and the iron loss deteriorates. It is preferably 5 to 30 μm. The grooves should be regularly arranged. this is,
This is because the magnetic domain is subdivided regularly. Usually, it is preferable to be engraved at a substantially constant pitch having an angle of 45 degrees to a right angle with respect to the longitudinal direction of the steel sheet. If it is less than 45 degrees, the direction of magnetic domain subdivision does not match the crystallographic orientation preferred for magnetism. The groove pitch is preferably 2 to 10 mm. If it is less than 2 mm, the magnetic domain is subdivided too much and 90
° Magnetic domains increase, iron loss and magnetostriction are bad. On the other hand, if it exceeds 10 mm, the effect of subdividing the magnetic domain is not obtained. Needless to say, in the double cold rolling method, it is preferable to form the groove after or during the second rolling. After that, primary annealing is performed, and at this time, nitriding is performed if necessary. Both the single cold rolling method and the double cold rolling method perform primary annealing, but it is effective to perform decarburization by this annealing. As mentioned above, C
Is not preferable for the growth of secondary recrystallized grains, and if it remains as an impurity, iron loss is deteriorated. When melting steel, C
Not only will the decarburization process be shortened by lowering {11
1} <112> oriented grains are also increased, which is preferable. By setting an appropriate dew point in this decarburization annealing step, the oxide layer necessary for the subsequent formation of the primary coating can be secured.

The primary annealing temperature is preferably 700 to 950 ° C. Here, 700 ° C. is the lower limit temperature at which recrystallization is possible, and
50 ° C. is an upper limit temperature that can suppress the generation of coarse particles. Further, in the present invention in which AlN or N of Si ₃ N ₄ inhibitor is forcibly added by the nitriding method or the like during this primary annealing, the nitriding method is performed with ammonia (NH ₃ ) or the like during or immediately after the above primary annealing. Is done.
In this case, the temperature of the nitriding method is preferably 600 to 950 ° C. Here, 600 ° C. is the lower limit that can cause the nitriding reaction, while 950 ° C. is the upper limit that can suppress the generation of coarse particles.

In the present invention, the nitriding is preferably carried out after the primary recrystallization annealing, but industrially, a partition is provided on the rear surface of the same furnace and the atmosphere is slightly changed according to need, and NH _{3 is used.}
Nitrogen is often nitrided in parallel with the primary recrystallization because the gas is supplied or it is carried out in close proximity. At that time, as described above, the lower the N ₂ partial pressure is, the larger the nitriding amount is, and the partial pressure ratio P _N2 / P _H2 of nitrogen and oxygen is preferably 0.5 or less.

Primary annealing or the above nitriding method is performed, and then magnesium oxide (MgO is the main component.
A powder (referred to as gO) is dissolved in water or an aqueous solution containing water as a main component to form a slurry, which is applied to a steel sheet. At this time, a trace amount of an appropriate compound may be added for the purpose of facilitating the melting of the MgO powder during the subsequent secondary recrystallization annealing and promoting the forsterite formation reaction.

When TiO ₂ is added, 1 to 15% is preferable, but 1% is the lower limit at which the forsterite reaction accelerating effect can be exhibited, and if it exceeds 15%, the amount of MgO decreases and the forsterite reaction is rather reduced. Not proceed. Sb
An antimony-based compound such as ₂ (SO ₄ ) ₃ is effective in melting MgO at a relatively low temperature, and when added, its content is preferably 0.05 to 5%. Here, 0.05% is the lower limit at which the above-mentioned low temperature melting can occur, while on the other hand, when it exceeds 5%, it is too large to inactivate the original reaction of MgO forsterite.

Boron-based compounds such as Na ₂ B ₄ O ₇ and strontium / barium-based, carbon / nitride-based, sulfide-based, and chloride-based compounds having the same action as those of the compounds are relatively hotter than antimony-based compounds. Is effective in melting MgO, and when added, 0.05 to 5% is preferable.
Here, 0.05% is the lower limit at which the above effect can be exhibited, while if it exceeds 5%, the original reaction of MgO forsterite is inactivated, which is not preferable.

It is also possible to add these compounds in combination with each other. The% of the compound added here indicates the weight ratio when the weight of MgO is 100%. In the present invention, if one or more of the above-mentioned chlorides or sulfides is further added to the MgO powder,
The average thickness of the primary coating after finish annealing can be 0.3 μm or less, and sufficient secondary recrystallization orientation can be obtained. Among them, calcium chloride (CaCl ₂ ) and potassium sulfide (K ₂ S) are effective. Is. These are at least 0.5%
(Weight ratio when the weight of MgO is 100) is more effective. If it exceeds 20%, the secondary film formation process becomes rather unstable.

The maximum reachievable temperature of the secondary recrystallization annealing is 1100.
It is preferable to carry out at ˜1300 ° C. 1100 ° C. is the lower limit temperature at which the secondary recrystallization is performed, while if it exceeds 1300 ° C., the crystal grains become too coarse, and the iron loss is deteriorated. The important points in this secondary recrystallization annealing are as follows. In the present invention, M
Does the effect of the special additive added to the gO powder significantly reduce the primary coating mainly composed of forsterite?
Since it disappears, nitrogen-type inhibitors (AlN, Si ₃ N _4, etc.) necessary for secondary recrystallization during annealing also tend to escape during the finishing annealing. Therefore, the nitrogen partial pressure in the atmosphere gas during the finishing annealing tends to increase. This can be prevented by setting (P _N2 ) to 30% or more, and stable secondary recrystallization can be obtained. Furthermore, if the rate of temperature rise in the secondary recrystallization annealing is too high, the inhibitor easily escapes before sufficient secondary recrystallization occurs. Therefore, it is rather preferable to keep the rate of temperature rise below 30 ° C. for more stable magnetic properties. Is obtained. Note that, as described above, the nitriding method in which nitrogen is additionally added from the atmosphere or the like may be performed at a relatively previous stage during the secondary recrystallization annealing.

The above is an important part of the method for producing a grain-oriented silicon steel sheet according to the present invention. Industrially, the steel sheet after secondary recrystallization is made of an organic or inorganic material for the purpose of further improving the insulating properties and magnetic properties. It is particularly important to apply a high-strength coating (a coating method or a Zolgel method) having an insulating coating according to (3) in combination with heat treatment or the like. The reason for this is that, in the present invention, the primary coating having high tensile properties such as forsterite is extremely small or absent, and it is effective to apply an insulating coating having high tensile properties to complement it. Because.

[0040]

EXAMPLES Steels having chemical compositions shown in Tables 3 and 6 were melted in a converter, and Table 4 (Continued 1 in Table 3), Table 5 (Continued 2 in Table 3), Table 7 ( It was manufactured under the conditions shown in Table 1 (continued-1) and Table 8 (continued-2 in Table 6). The hot-rolled sheet was partially annealed under the condition of 1120 ° C. for 30 seconds.
In addition, aging between passes during cold rolling was performed except for B, and the condition was 250 ° C. Here, the nitriding subsequent to the primary recrystallization annealing, which is particularly important in the present invention, was performed by making the atmosphere dry with the same gas composition and flowing a certain amount of NH ₃ gas in the inside of the furnace where the partition was provided in the same furnace. It is a thing. The nitriding amount (nitrogen amount) after such primary annealing is shown in Tables 4 and 7. Further, a powder was applied to this steel plate, and the powder was dissolved in water to form a slurry, which was then dried at 350 ° C. Here,% is the weight ratio when the weight of MgO is 100%. After that,
Secondary recrystallization annealing was performed while changing the average heating rate from 800 ° C. to the highest reached temperature variously. The maximum temperature reached here is 120
It is 0 ° C. Furthermore, after applying a phosphoric acid-based high-strength insulating coating (secondary coating) by heating, the plate is removed and strain relief annealing 850 ° C x
4 hours _{(N 2 90% -H 2 10} %, Dry) was carried out to perform magnetic measurements test. The results are shown in Table 5 and Table 8. The maximum depth of the groove, the pitch, and the angle with the rolling direction are all measured with the product after the secondary recrystallization annealing.

For magnetic measurement, a 60 × 300 mm single plate was SS
Measured by T test method, B ₈ (800 A / m magnetic flux density, unit is Tesla) and W _17/50 (iron loss at 50 Tesla at 1.7 Tesla, unit is watt / kg), W _13/50 (50
The iron loss at 1.3 Tesla in Hz) was measured. As shown in Tables 5 and 8, it is understood that those falling within the range of the present invention have a high magnetic flux density and a sufficiently low iron loss, and are within the target range of the present invention.

[0042]

[Table 3]

[0043]

[Table 4]

[0044]

[Table 5]

[0045]

[Table 6]

[0046]

[Table 7]

[0047]

[Table 8]

[0048]

According to the present invention, it is possible to obtain a high magnetic flux density grain-oriented silicon steel sheet having extremely low iron loss.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the average thickness of a primary coating and iron loss.

FIG. 2 is a diagram showing the effect of the amount of added Sn on 0.06% P-3% Si steel.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location C23C 22/00 A (72) Inventor Isao Iwanaga No. 1 Hibatacho, Tobata-ku, Kitakyushu, Fukuoka Prefecture New Nippon Steel Co., Ltd., Yawata Works

Claims (9)

[Claims] 1. Si: 1 to 7%, P: 0.03 to 0.1
Including 5%, the average maximum depth of the steel plate surface is 2 to 50
In μm, the groove where some forsterite remained at the bottom,
An average thickness of the primary coating mainly composed of forsterite, which is applied at intervals of 45 to 90 degrees from the longitudinal direction of the steel sheet, is 0.3 μm or less, and iron loss is _{0.70 Watt} at W _17/50 . / Kg or less, a high magnetic flux density grain-oriented silicon steel sheet having an extremely excellent iron loss. 2. Si: 1 to 7%, P: 0.03 to 0.1
5%, Sn: 0.02 to 0.20%, the average depth of the maximum portion was 2 to 50 μm on the surface of the steel sheet, and a groove in which forsterite was partially left at the bottom portion was 45 from the longitudinal direction of the steel sheet.
The average thickness of the primary coating mainly composed of forsterite, which is applied at intervals of 90 degrees, is 0.3 μm.
A high magnetic flux density grain-oriented silicon steel sheet having an extremely excellent iron loss, characterized in that the iron loss at W _17/50 is 0.70 Watt / kg or less at m or less. 3. The high magnetic flux density grain-oriented silicon steel sheet with extremely excellent iron loss according to claim 1 or 2, wherein the intervals between the grooves are 2 to 20 mm. 4. Si: 1 to 7%, P: more than 0.045%
Steel containing 0.20% is melted, and hot rolled, cold rolled, primary recrystallization annealing, application of an annealing separator, and secondary recrystallization annealing are the basic steps in the production of oriented silicon steel sheet. During hot rolling or after cold rolling, a groove having an average maximum depth of 2 to 50 μm is formed on the surface of the steel sheet by 45 to 90 from the longitudinal direction of the steel sheet.
Applied at intervals in the direction of the degree, then the steps after the primary recrystallization annealing are performed, and at least one or more kinds of chloride and sulfide are applied to the surface of the steel sheet between the primary recrystallization annealing and the secondary recrystallization annealing. A high magnetic flux with extremely excellent iron loss, characterized in that the average thickness of the insulative primary coating mainly composed of forsterite produced during secondary recrystallization annealing is 0.3 μm or less after coating with a substance containing Manufacturing method of density-oriented silicon steel sheet. 5. Si: 1 to 7%, P: more than 0.045%
Steel containing 0.20% and Sn: 0.02 to 0.20% is smelted, and hot rolling, cold rolling, primary recrystallization annealing, application of an annealing separator, and secondary recrystallization annealing are basically performed. In the production of a grain-oriented silicon steel sheet as a step, during cold rolling or after cold rolling, a groove having an average maximum depth of 2 to 50 μm is formed on the surface of the steel sheet in a direction of 45 to 90 degrees from the longitudinal direction of the steel sheet. Apply at intervals, then perform the steps after the primary recrystallization annealing, and apply a substance containing at least one of chloride and sulfide to the surface of the steel sheet between the primary recrystallization annealing and the secondary recrystallization annealing. Then, the average thickness of the insulating primary coating mainly composed of forsterite generated during the secondary recrystallization annealing is 0.3 μm.
A method for producing a high magnetic flux density grain-oriented silicon steel sheet having an extremely excellent iron loss, which is characterized in that it is m or less. 6. The interval between grooves provided after cold rolling is 2 to 20.
The method for producing a high magnetic flux density grain-oriented silicon steel sheet having extremely excellent iron loss according to claim 4 or 5, wherein the grain size is mm. 7. The method for producing a high magnetic flux density grain-oriented silicon steel sheet having extremely excellent iron loss according to claim 4, wherein nitriding is performed during the primary recrystallization annealing. 8. An extremely excellent iron loss according to claim 4, wherein calcium chloride is added as a chloride and potassium sulfide is added as a sulfide to be added to the annealing separator. Manufacturing method of high magnetic flux density grain-oriented silicon steel sheet. 9. The temperature rising rate during the secondary recrystallization annealing is 30 per hour.
The production of a high magnetic flux density grain-oriented silicon steel sheet having extremely excellent iron loss according to any one of claims 4 to 8, characterized in that the nitrogen partial pressure in the atmosphere gas is 30% or less and the nitrogen partial pressure is 30% or more. Law.