JPH06212261A - Production of high magnetic flux density silicon steel sheet excellent in magnetic property and film property - Google Patents

Abstract

PURPOSE:To improve the surface film and magnetic properties of a steel sheet by specifying the oxygen content and nitrogen content after nitriding in a sheet subjected to primary recrystallization annealing. CONSTITUTION:Molten steel contg. 1 to 7% Si and >0.045 to 0.20% P is subjected to hot rolling and cold rolling, and primary recrystallization annealing is executed. Next, at the time of adding N required for an inhibitor, the oxygen content by a chemical analysis method in the sheet subjected to the primary recrystallization annealing is regulated to 25 to 900ppm. The nitrogen content after the subsequent nitriding is regulated to 120 to 400ppm. The nitrided steel sheet is coated with a separation agent for annealing, and secondary recrystallization annealing is executed. Since N required for an inhibitor is efficiently added after the primary recrystallization annealing and a primary film is stably formed on the surface of the silicon steel in the case of the secondary recrystallization annealing, the grain-oriented silicon steel sheet having high magnetic flux density and low iron loss can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silicon steel sheet having excellent surface coating and magnetic properties.

[0002]

2. Description of the Related Art In manufacturing a silicon steel sheet having excellent magnetic properties for a transformer or the like, the insulating property and the magnetic property required for improving the performance of the transformer are improved by applying tension to the surface of the steel plate, and the adhesion with the steel plate is improved. It is very important to form a good primary coating. In the usual technology, after the primary annealing accompanied by decarburization, magnesium steel called magnesia (M
gO) fine powder of water is applied in a slurry form,
After drying if necessary, it is fired in the secondary recrystallization annealing step, and forsterite (M
A ceramic-like insulating film called g 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.

In addition, this state of forsterite formation is called the GOSS orientation of the steel sheet in the secondary recrystallization, which is generally called the GOSS orientation, with respect to the steel sheet longitudinal direction (rolling direction) which is essential for improving the magnetic permeability and the magnetic flux density. It is also well known that it plays an important role also in growing slightly coarser secondary recrystallized grains having a crystal orientation of {110} [001].
That is, even when trying to carry out secondary recrystallization without forming a sufficiently dense film during the secondary recrystallization annealing temperature rising process, fine nitrides and sulfides called inhibitors in the steel sheet remain as they are, or It disassembles and falls out of the steel plate quickly. For this reason, the inhibitory effect of preferentially growing GOSS-oriented grains during the temperature rise and suppressing the growth of other oriented grains cannot be exerted, and is commonly called fine grains.
This results in a steel sheet having extremely poor magnetic properties, in which secondary recrystallized grains of OSS oriented grains are not partially or entirely grown. In addition, titanium oxide (T
(iO ₂ etc.) and other compounds may be added to form a denser primary coating.

In practice, however, it is not easy to stably produce a sufficient primary coating film and secondary recrystallization structure even with the above technical knowledge. Especially, various secondary recrystallization annealing conditions are required due to industrial necessity. Although it may be changed, it is not easy in this case to form a sufficient primary film and to generate secondary recrystallization having a sufficiently proper orientation. One of the reasons for this is that the elucidation in the manufacturing process regarding the formation of the primary film and the formation of an appropriate additive in the secondary recrystallization process called an inhibitor is not yet sufficient.

In particular, in the inhibitor control technique for adding N after the primary recrystallization annealing, it is not detailed in detail how to optimally add the optimum amount of N, so that it depends on individual experience. However, the actual situation is that the stable primary coating and the secondary recrystallization have not been freely controlled as described above.

[0006]

The present invention solves the problems in the prior art, efficiently adds N necessary for an inhibitor after primary recrystallization annealing, and further stabilizes the primary coating during secondary recrystallization. Stable GOS formed on the surface of silicon steel
The present invention provides a method for producing a grain-oriented silicon steel sheet having S-oriented secondary recrystallized grains.

[0007]

The gist of the present invention is as follows. (1) Si: 1 to 7%, P: more than 0.045% to 0.20
% In steel, and hot-rolled, cold-rolled, primary recrystallization annealing, annealing separation material application and secondary recrystallization annealing in the production of grain-oriented electrical steel sheets, the secondary recrystallization annealing When N is added after the primary recrystallization annealing for the purpose of imparting the inhibitor function necessary for carrying out the heat treatment, the amount of oxygen (O) in the chemical analysis method of the primary recrystallization annealed plate is 25 to
A method for producing a high magnetic flux density silicon steel sheet having excellent magnetic properties and coating characteristics, which is set to 900 ppm and the amount of nitrogen (N) after nitriding following primary recrystallization annealing is set to 120 to 400 ppm.

(2) Si: 1 to 7%, P: 0.045%
Steel containing super-0.20%, Sn: 0.02-0.20% is smelted, and is basically hot-rolled, cold-rolled, primary recrystallization annealing, annealing separation material coating and secondary recrystallization annealing. In the production of grain-oriented electrical steel sheet as a process, chemical analysis of the primary recrystallization annealed plate when N is added after the primary recrystallization annealing for the purpose of imparting the inhibitor function necessary for performing the secondary recrystallization annealing. Amount of oxygen (O) in the method is 25-900ppm
And the amount of nitrogen (N) after nitriding following the primary recrystallization annealing is 1
A method for producing a high magnetic flux density silicon steel sheet having excellent magnetic properties and coating properties, which is characterized by 20 to 400 ppm.

(3) Before secondary recrystallization annealing, 0.05 to 5.0% of an antimony compound is added to magnesia applied for forming a primary coating mainly composed of forsterite, and secondary magnesia is added. A high magnetic flux density excellent in magnetic properties and coating properties according to (1) or (2), characterized in that an average rate of temperature increase from 800 ° C. to the highest reached temperature in recrystallization annealing is 0.1 to 80 ° C. per hour. Manufacturing method of silicon steel sheet.

(4) Boron-based, strontium-barium-based, magnesia is applied to form a primary coating,
Addition of one or more of carbon / nitride-based, sulfide-based, and chloride-based compounds in a total amount of 0.05 to 5.0%, and an average of maximum temperature reached from 800 ° C in secondary recrystallization annealing The method for producing a high magnetic flux density silicon steel sheet having excellent magnetic properties and coating properties according to (1), (2) or (3), characterized in that the temperature rising rate is 5 to 400 ° C. per hour. (5) The ratio of the partial pressures of nitrogen and hydrogen in the primary annealing atmosphere is set to P N ₂
/ P H ₂ ≦ 0.5, a method for producing a high magnetic flux density silicon steel sheet having excellent magnetic properties and coating properties.

The present invention will be described in detail below. Secondary recrystallization of grain-oriented silicon steel sheet is called GOSS orientation {11
It is essential that grains having a 0} <001> orientation are sufficiently grown 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). At this time, fine precipitates such as AlN called an inhibitor (Inhibitor) are sufficiently formed before finish annealing. It is well known that it is technically necessary to keep. Then, N necessary for this purpose is added during steel melting, after primary annealing, or during other steps.

[0012] One of the constitutions of the present invention is the technical finding concerning the optimum addition method when N is added after the primary annealing. Here, I will supplement what is called after primary annealing, but this is to install equipment for performing a nitriding reaction inside or close to a part of the equipment for primary annealing that also normally functions for decarburization,
This is a method of performing a nitriding reaction after the primary annealing or in parallel with it. In the case of steel having a sufficiently low carbonization during steel melting, it is more important than the decarburizing function to change the oxide layer of the surface layer after the primary annealing so as to form a film advantageous for film formation. Here, the result of the experiment of nitriding after the primary annealing is shown. Table 1 shows the chemical composition of the sample and the manufacturing method. Table 2 shows the amount of oxygen in the primary annealed plate of this material and the amount of N in the plate after nitriding.
This relationship is shown in FIG. What is clear in this figure is that there is a clear positive correlation between the oxygen content and the nitriding content in the steel sheet after the primary annealing.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

[0016]

[Table 4]

The reason why the amount of oxygen changes here is that the surface is oxidized during the primary annealing, which is a result of the following reaction resulting from decarburization in the primary annealing.

C + H ₂ O → CO + H ₂ (1) Fe + H ₂ O → FeO + H ₂ (2)

These reactions usually occur simultaneously, and oxygen in the steel sheet increases as decarburization progresses. Now, the following study was conducted on the nitriding after the primary annealing. The nitriding reaction is expressed by the following equation.

NH ₃ → N + (3/2) H ₂ (3)

However, in this reaction equation, the effect of the oxygen content of the steel sheet cannot be seen. Therefore, the amount corresponding to the oxygen content of the steel sheet was considered as the FeO content in the surface layer of the steel sheet from the above equation (2), and the following two cases were considered. 1. When it is assumed that an oxide layer (FeO or the like) does not substantially exist in the surface layer portion. F. It is expressed as follows from the Enrietto formula. N + (3/2) H ₂ ← NH ₃ (4) Equilibrium constant: K = 1.77 × 10 ⁻⁵ exp (19250 / RT) = PNH ₃ / (N · P H ₂ ^3/2 ) (5)

2. When an oxide layer (FeO, etc.) exists on the surface layer At this time, it occurs at the interface between the steel sheet and the external atmosphere (4)
It was thought that how to remove H ₂ in the reaction of the formula as a reaction system affects the nitriding. In this case, we must consider the interface region where the following two reaction systems occur simultaneously.

I. N + (3/2) H ₂ ← NH ₃ (4) K = 1.77 × 10 ⁻⁵ exp (19250 / RT) = PN H ₃ / (N · P H ₂ ^3/2 ) (5) II. FeO + H ₂ → Fe + H ₂ O (6) log K = log (P H ₂ O / P H ₂ ) = 827 / T−0.468 (7) ΔF = −3784 + 2.14T (8) where (7), ( Equation 8) is Sawamura's equation. Note that T is an absolute temperature (° K) and R is a gas constant. 1. And 2. The calculation was performed for the case.

Calculation Results I. If no oxide layer (FeO) ... (5) (case of T = 750 ° C.) formula _{Case1 Case2 Case3 P H 2: 0.60} : 0.50: 0.35 PNH 3: 0.15: 0.35: 0.40 P N ₂ : 0.25: 0.15: 0.25 ↓ ↓ ↓ ↓ N = 1.4ppm N = 4.3ppm N = 8.4ppm

II. In the case where there is an oxide layer (FeO) ... (5) + (7) In this case, the reaction occurs at the interface between Fe and FeO, so that the two reaction systems described above occur, and the existing Gas system is NH ₃ , H 2.
₂ , H ₂ O ternary system can be basically considered (N ₂ is only partial pressure adjustment). Therefore, in addition to the above formula (2), PNH ₃ + P H ₂ + P H ₂ O = 1 (9) must be added (when considering P N ₂ , the partial pressure may be adjusted to some extent). The following is obtained from the equations (5), (7) and (9).

[0026] (T = 750 For _{℃) Case1 Case2 Case3 P H 2} : 0.20: 0.10: 0.05 P H 2 O: 0.44 ((2) expression of constraints): 0.22: _{0.11 PNH 3: 0.36 ((3} ) formula): 0.68: 0.84 ↓ ↓ ↓ N = 18ppm N = 93ppm N = ( the case of T = 850 ℃) 333ppm Case4 Case5 Case6 P H 2: _{0.20: 0.10: 0.05 P H 2} O: 0.37: 0.19: 0.09 PNH 3: 0.43: 0.71: 0.86 ↓ ↓ ↓ N = 49ppm N = 224ppm N = 790 ppm When FeO is present as described above, N (nitriding amount) is extremely large.

When the N ₂ partial pressure is taken into consideration, it is as follows. (T = 750 For _{℃) Case1 Case2 Case3 P H 2} : 0.20: 0.10: 0.05 P H 2 O: 0.44: 0.22: 0.11 P N 2: 0.2: 0.2: 0.2 PNH ₃ : 0.16: 0.48: 0.64 ↓ ↓ ↓ ↓ N = 8ppm N = 66ppm N = 254ppm In other words, if the N ₂ partial pressure increases, the nitriding amount may decrease. Recognize. Thus, theoretically, it has been confirmed that nitriding is easier when the primary annealed plate has an oxide layer (FeO or the like). Further, it is expected that the nitriding amount will increase as the partial pressure ratio P N ₂ / PH ₂ of nitrogen and hydrogen in the atmosphere during the primary annealing and nitriding decreases.

Here, a method of measuring the amount of the oxide layer of the primary annealed plate will be described. Commonly known speed (SPEED: Sel
active Potentiostatic Etc
Hing by Electronic Diss
It is possible to analyze the precipitation morphology of the precipitation phase in the metal material by a method called the “solution method”. In this method, the metal surface is dissolved by a few μm using a non-aqueous solvent-based electrolytic solution, leaving an unstable precipitation phase on the matrix surface as it is, and locally using SEM-EDX, EPMA, AES, etc. This is a method for analyzing the precipitation phase. Also,
The etching surface is peeled off by the replica method, and the composition of the precipitation phase and the like are analyzed. It is possible to apply this method to the primary annealed plate and to perform the composition and quantification of the oxide of the surface layer. By this method, FeO, MnO, Al ₂ O ₃ , S of the oxide layer can be obtained.
Quantification of iO ₂ etc. is also possible.

On the other hand, as can be seen from the data in Table 2, the amount of oxide can be measured by directly measuring the amount of oxygen (O) in the primary annealed plate by a normal chemical analysis method. As described above, the value and the nitriding amount correspond well in the experiment. Therefore, in the present invention, the amount of oxygen (O) in a simple ordinary chemical analysis method is used as a technical index. Then, as shown in the experiment, if the oxygen content of the steel sheet after the primary annealing is 25 ppm or more,
Stable nitriding amount of steel sheet Nitrogen amount required to secure the amount of inhibitors such as AlN and Si ₃ N ₄ during the subsequent finish annealing 12
It is possible to obtain 0 ppm or more with a primary annealed plate.

Now, a so-called MgO powder mainly composed of MgO is applied to the surface of the steel sheet in the form of a slurry on the steel sheet that has undergone primary annealing and is nitrided, and film formation and secondary recrystallization are performed in the next finish annealing step. Here, the technical relationship under these conditions and the primary annealed plate nitrided by the method of the present invention was recognized. Table 3 shows the results of a finish annealing drawing experiment in which the MgO powder was applied in a slurry form to the 3% Si steel sheet after the primary annealing and nitriding and the secondary annealing was performed during the secondary recrystallization annealing.

[Table 5]

Here, the powders are referred to as Sb-based and B-based, respectively, because here, respectively, a trace amount of TiO ₂ is added to MgO powder.
(5%), Sb ₂ (SO ₄ ) ₃ (0.2%), TiO ₂
(5%) and Na ₂ B ₄ O ₇ (0.3%) were added to promote the formation of forsterite. The secondary recrystallization annealing was carried out halfway by the method shown in FIG. 2, and a so-called pull-out experiment was carried out at each temperature.

The steel sheet thus drawn out is subjected to GDS from the surface.
Table 3 shows the results obtained by conducting an analysis to determine from which extraction temperature the forsterite, that is, the Mg peak appears. Here, the temperature in () is determined to have appeared in the middle of the measured temperature. What is clear from the results in Table 3 is that forsterite is formed at a lower temperature in the Sb system than in the B system.

It is generally considered that forsterite is produced by the reaction of MgO and surface-concentrated Si in the steel sheet to cause a reaction of 2MgO + SiO ₂ → Mg ₂ SiO ₄ . By the way, I examined how the manufacturing process of silicon steel sheets and the properties of these steel sheets can be controlled. If the causal relationship between the formation process of the primary coating film and the various properties of the silicon steel sheet is clarified as described above, naturally it can be industrially reflected in the production.

As can be seen from the experimental results in Table 3, when a small amount of Sb-based compound is added to MgO, the melting of MgO is performed at a relatively low temperature, so that the temperature rising rate of the secondary recrystallization annealing is relatively high. The smaller the size, the faster the production of forsterite, and the easier the formation of an excellent primary coating. The antimony (Sb) -based compound is
In addition to Sb ₂ (SO ₄ ) ₃ used in this experiment, other compounds containing Sb are included. On the other hand, even if the B-based compound is added to MgO in a small amount even with the same low-melting-point compound, the MgO is melted at a relatively higher temperature than the Sb-based compound. The larger the target, the faster the production of forsterite. The boron (B) system is not only Na system, but C instead of Na system.
Compounds containing a, Mg, etc., boric acid (H ₃ BO ₃ ) and sodium borate are also included.

Further, strontium / barium system, carbon / nitride system, sulfide system, and chloride system are recognized to have the same action as boron system in that they have higher melting point than antimony system. These compounds will be collectively called non-antimony compounds. It should be noted that, usually, an oxide such as TiO ₂ is added to MgO to facilitate the high temperature reaction, but the effects of the above-mentioned additives of the present invention are exhibited regardless of the amount of the oxide added. Therefore, even if an oxide is added to MgO, this is referred to as a plane and is regarded as a part of the base material.
As described above, according to the present invention, the primary coating, which is an important controlling factor for the properties of the silicon steel sheet, can be controlled to some extent freely by elucidating its composition distribution and combining it with a manufacturing method having a correlation therewith.

Table 4 shows the {111} plane index strength of the crystal orientation by X-ray after primary recrystallization of the 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, even iron loss is reduced as shown in FIG. 3 of the example of 0.06% P-3% Si steel, which is preferable. This is considered to be the result of fine graining of the product by Sn.

[0037]

[Table 6]

Now, it is necessary to touch on the method of manufacturing a silicon steel sheet. As described above, the silicon steel sheet which can be used in the present invention is limited to steel containing Al as necessary and AlN or Si ₃ N ₄ as a main inhibitor. Of course S
In addition to i, Al, P and Sn, Mn, S, Se, Sb and C
The addition of other additive elements such as u, B, Nb, Ti, V, Ni and Cr to improve the magnetic characteristics does not change the basis of the present invention. By the way, steels using AlN or Si ₃ N ₄ as an inhibitor are known,
The technique of the present invention can be applied to either case. However, the following production method is most suitable for further exerting the characteristics of the present invention.

That is, in a steel containing 1 to 7% of Si, if necessary, Al is contained in an amount of 0.1% or less when the steel is melted, and N is included in the decarburization annealing during the primary annealing after cold rolling in the silicon steel sheet manufacturing process. By the method of forcibly adding N to the steel sheet through the direct nitriding reaction, N of 120 is added before the secondary recrystallization annealing.
ppm to 400 ppm It is characterized in that it is contained in steel. In the present invention, at least 1% of Si is necessary for forming forsterite as described above. On the other hand, if it exceeds 7%, the workability is extremely deteriorated and it is not suitable for industrial production. Al is effective in forming an AlN inhibitor. However, if it exceeds 0.1%, the amount of Al ₂ O ₃ produced increases, impairing the cleanliness of sound steel, and adversely affecting the magnetic properties.

N is indispensable for forming AlN and Si ₃ N ₄ inhibitors, and in the present invention, a minimum of 120 ppm is required after primary annealing, that is, before finish annealing.
On the other hand, when it exceeds 400 ppm, Al and Si are excessively eaten, which 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 needs to 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.
P is important in the present invention, a high value of magnetic flux density cannot be obtained at 0.045% or less during steel melting, while 0.20%
If it exceeds the range, embrittlement proceeds, and cold rolling property deteriorates significantly.

O is A if it is 0.05% or less after the steel is melted.
It is preferable in terms of cleanliness without making too much l ₂ O ₃ . In the present invention, it is particularly important to perform nitriding after or during primary annealing, but the O content of the steel sheet after primary annealing including this nitriding must be 25 to 900 ppm. 25pp
If it is less than m, the amount of N required for secondary recrystallization for forming AlN and Si ₃ N ₄ is not sufficiently nitrided, while if it exceeds 900 ppm, the amount of N becomes too large, and it is rather difficult to perform a sufficient inhibitor role. Become. In the present invention, Sn is extremely effective in reducing iron loss when it coexists with P. 0.02%
If it is less than 0.20%, the effect is not recognized. On the other hand, if it exceeds 0.20%, nitriding cannot be performed sufficiently, the inhibitor becomes weak, and on the other hand, the primary coating cannot be sufficiently performed and the characteristics deteriorate.

Next, the production method of the present invention other than the chemical components will be described. Continuous casting method, ingot-agglomeration and rolling method, or thin slab continuous method for omitting hot rolling step, in which steel is tapped in a converter or electric furnace, and a refining step is added as necessary to adjust the composition. A slab having a thickness of 30 to 400 mm (50 mm or less in the thin slab continuous casting method) is formed by a casting method or the like. Here, 30 mm is the lower limit of productivity, and 400 mm is the upper limit for preventing abnormal distribution of Al ₂ O ₃ etc. due to center segregation. Further, 50 mm 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, and 1400 ° C.
Is the upper limit of surface roughness and material deterioration. Further, 10 mm is an upper limit for obtaining a cold speed at which an appropriate precipitate is formed. In the thin slab continuous casting method, it is possible to directly form a coil, and for that purpose, it is preferably 10 mm or less. The hot coil thus produced is often annealed again at 800 to 1250 ° C. to improve the magnetism. Here, 800 ° C is the lower limit of remelting of AlN, and 1250 ° C is A
1N is the upper limit for preventing coarsening.

After this treatment step, the hot coil is pickled directly or batchwise and then cold rolled. Cold rolling is performed at a rolling reduction of 60 to 95%, 60% being the limit of recrystallization in the present invention, preferably 70% or more by primary annealing and increasing {111} [112] oriented grains, It is a lower limit for promoting the generation of GOSS oriented grains during secondary recrystallization annealing,
On the other hand, if the content exceeds 95%, secondary recrystallization annealing causes GOSS-oriented grains, which are called swinging GOSS grains, to rotate in the plane of the plate to produce grains unfavorable to the magnetic properties.

The above is the case of manufacturing by the so-called single cold rolling method. However, in the case of performing cold rolling-annealing-cold rolling called the double cold rolling method, the first reduction is 10 to 80%, The second 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 the lower limit of the reduction ratio that appropriately leaves the {111} [112] oriented grains during the primary annealing. It is also commonly referred to as interpass aging, and heating the steel sheet in the range of 100 to 400 ° C. by an appropriate method during cold rolling is also effective for improving the magnetic properties. If it is less than 100 ° C, the effect of aging is not obtained, while if it exceeds 400 ° C, dislocations are recovered.

Thereafter, the primary annealing is carried out by either the single cold rolling method or the double cold rolling method, and it is effective to carry out decarburization by this annealing. As described above, C is not preferable for the growth of secondary recrystallized grains, and if it remains as an impurity, it causes deterioration of iron loss. It is preferable to lower C during the melting of steel because not only the decarburization step is shortened but also {111} [112] oriented grains are increased. By setting an appropriate dew point in this decarburization annealing step, an oxide layer necessary for subsequent primary film formation is secured. Primary annealing temperature is 700-950
C is preferred. Here, 700 ° C. is the lower limit temperature at which recrystallization is possible, and 950 ° C. is the upper limit temperature for suppressing 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 during the primary annealing, the nitriding method is performed with ammonia (NH ₃ ) or the like during or immediately after the above primary annealing. Nitriding is performed. In this case, the temperature of the nitriding method is preferably 600 to 950 ° C. Here, 600 ° C. is the lower limit for causing the nitriding reaction, while 950 ° C. is the upper limit for suppressing the generation of coarse particles. In the present invention, the nitriding is preferably performed after the primary recrystallization annealing, but industrially, a partition is provided on the rear surface in the same furnace and the atmosphere is slightly changed as necessary, or NH ₃ gas is flowed,
Since they are performed in close proximity to each other, they are often nitrided in parallel with primary recrystallization. At this time, as described above, the lower the N ₂ partial pressure is, the larger the nitriding amount is, and the partial pressure ratio P N ₂ / P H ₂ of nitrogen and hydrogen is preferably 0.5% or less.

Primary annealing or the above nitriding method is performed, and then magnesium oxide (MgO is the main component.
The powder is called 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. On this occasion,
For the purpose of facilitating the melting of MgO powder during the subsequent secondary recrystallization annealing and promoting the forsterite formation reaction,
It is also possible to add a trace amount of an appropriate compound. TiO ₂
When adding, 1 to 15% is preferable, but here 1%
Is the lower limit for exerting the effect of promoting the forsterite reaction, and if it exceeds 15%, the amount of MgO decreases and the forsterite reaction does not proceed.

Antimony compounds such as Sb ₂ (SO ₄ ) ₃ are effective in melting MgO at a relatively low temperature, and when added, 0.05 to 5% is preferable. Here, 0.05% is the lower limit for causing the above-mentioned low-temperature melting, while if it exceeds 5%, it is too much 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- and chloride-based compounds that have similar effects to MgO at a relatively higher temperature than antimony-based compounds. It is effective in melting, and if added, 0.05 to
5% is preferable. Here, 0.05% is the lower limit for exhibiting the above-mentioned effect, while if it exceeds 5%, the original reaction of MgO forsterite is inactivated, which is not preferable.

It should be noted that these compounds can be added in combination with each other. However, when an antimony low-temperature melting type compound and a boron-based or other relatively high-temperature melting type compound are mixed and used, the effect is close to that of the high-temperature melting type compound, but it does not contradict the gist of the present invention. In that case, it is preferable to adopt the high temperature melting type temperature rising rate of the present invention.
The percentage of the compound added here is 10% by weight of MgO.
The weight ratio when 0% is shown in%. The secondary recrystallization annealing is preferably performed at the highest temperature reached of 1100 to 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. Note that, as described above, the nitriding method in which N is additionally added from the atmosphere or the like may be performed at a relatively previous stage during the secondary recrystallization annealing.

Now, the temperature rising rate of the secondary recrystallization annealing is particularly important in the present invention. That is, it is necessary to change the temperature rising rate depending on the type of compound added to MgO. When an antimony-based compound is added to MgO, it is necessary that the average heating rate from 800 ° C. to the highest reached temperature is 0.1 to 80 ° C. per hour, which is relatively small. Here, 0.1 ° C./hour is the lower limit of the industrial heating rate, while MgO melts at a low temperature when an antimony-based compound is added as described above, so that forsterite is formed more quickly and reliably. It is necessary to keep the temperature rise rate to 80 ° C./hour or less.

On the other hand, in the case of boron type, strontium / barium type, carbon / nitride type, sulfide type and chloride type, the average heating rate is preferably 5 to 400 ° C. per hour. That is,
When a high temperature melting type compound is added, melting of MgO takes place at a relatively high temperature, and a high temperature rising rate of 5 ° C./hour or more is required in order to reach a high temperature quickly. That itself is not done well in relation to the inhibitor. The above is an important part in the method for producing a silicon steel sheet of the present invention, but industrially, for the purpose of further improving the insulation characteristics and magnetic characteristics, a secondary coating film (organization method or sol-gel method) made of an organic material or an inorganic material is applied to the steel sheet. ), A magnetic domain control method by a non-contact type method such as mechanical or laser addition, and then several steps such as subsequent formation of a tertiary film for preventing dusting. .

[0053]

EXAMPLE Steels having chemical compositions shown in Table 5 were melted in a converter and manufactured under the conditions shown in Table 6. The hot-rolled sheet was partially annealed under the condition of 1120 ° C. for 30 seconds. A part of aging between passes during cold rolling was carried out under the condition of 250 ° C. The nitriding subsequent to the primary recrystallization annealing, which is particularly important in the present invention, is performed by making the atmosphere dry with the same gas composition in the inner part of the furnace where the partition is provided in the same furnace and flowing a certain amount of NH ₃ gas. It is a thing. The amount of oxygen and the amount of nitriding (nitrogen amount) of the steel sheet after such primary annealing are shown in the same table. Furthermore, powder was applied to this steel sheet. The powder was dissolved in water to form a slurry, and then 350
It was dried at ° C.

The type of powder, plain is MgO +
TiO ₂ (5%) composition, Sb-based is MgO + T
iO ₂ (5%) + Sb ₂ (SO ₄ ) ₃ (0.2%), and B system is MgO + TiO ₂ (5%) +
It shows that it is Na ₂ B ₄ O ₇ (0.3%). 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 reaching speed is 1200 ° C. here. After washing with water, a phosphoric acid-based insulating coating (secondary coating) is applied by heating, and then the plate is removed
Strain relief annealing 850 ° C. × 4 hours (N ₂ 90-H ₂ 10, D
ry), and a film and macro appearance inspection, magnetic measurement, adhesion test, etc. were performed. Table 6 shows the results.

[0055]

[Table 7]

[0056]

[Table 8]

[0057]

[Table 9]

[0058]

[Table 10]

[0059]

[Table 11]

Here, the film appearance inspection is carried out by: ○: scale,
No shimou defect, △: Some shimmi defect, ×:
It shows that there are many scales and shimofuri and the film is not sufficiently formed. Here, the scale means that the coating is widely peeled off to some extent, and the shimofuri is a point-like peeling defect. Also,
The macroscopic visual inspection shows that ◯: sufficient secondary recrystallization is formed, Δ: fine grains are partially observed, and x: fine grains are observed on the entire surface. The magnetic measurement is made by the SST test method of a single plate of 60 × 300 mm, and is B ₈ (magnetic flux density of 800 A / m, unit is Gauss) and W _17/50 (iron loss at 1.7 Tesla at 50 Hz, unit. Watt / kg). The adhesion test was a bending test in which a steel plate was wound around a cylinder having a diameter of 20 mm, and the judgment was evaluated by ◯: no crack in the coating, Δ: fine cracks in the coating, and x: cracks in almost the entire width. Now, as shown in Table 6, the primary annealing conditions, particularly those in which the oxygen amount is within the range of the present invention, are those in which the nitriding amount (nitrogen amount) is sufficiently within the range of the present invention. The magnetic characteristic values and the like are good when the type and the average temperature rising rate of finish annealing are included in the present invention. The composition of the present invention has extremely high magnetic flux density and low iron loss.

[0061]

According to the present invention, a grain-oriented electrical steel sheet having good magnetic properties and coating properties can be obtained.

[Brief description of drawings]

FIG. 1 is a chart showing the relationship between the oxygen content of a primary annealed sheet and the N content of a nitrided sheet.

FIG. 2 is a chart showing a finish annealing cycle.

FIG. 3 is a table showing the effect of Sn% during molten steel on various properties of 0.06% P-3% Si steel products.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location C22C 38/02 (72) Inventor Hodaka Hodaka 1-1 No. 1 Tobita-cho, Tobata-ku Kitakyushu Nippon Steel Hachiman Co., Ltd. Inside the steelworks

Claims (5)

[Claims] 1. Si: 1 to 7%, P: more than 0.045%
In the production of a grain-oriented electrical steel sheet having the basic steps of smelting steel containing 0.20%, hot rolling, cold rolling, primary recrystallization annealing, annealing separation material application and secondary recrystallization annealing, When N is added after the primary recrystallization annealing for the purpose of imparting an inhibitor function necessary for performing the recrystallization annealing, the oxygen (O) amount in the chemical analysis method of the primary recrystallization annealed plate is set to 25 to 900 ppm. A method for producing a high magnetic flux density silicon steel sheet having excellent magnetic properties and coating properties, wherein the amount of nitrogen (N) after nitriding following primary recrystallization annealing is 120 to 400 ppm. 2. Si: 1 to 7%, P: more than 0.045%
The method for producing a high magnetic flux density silicon steel sheet having excellent magnetic and coating properties according to claim 1, wherein a steel containing 0.20% and Sn: 0.02 to 0.20% is melted. 3. An antimony-based compound is added in an amount of 0.05 to 5.0% to magnesia which is applied to form a primary film mainly composed of forsterite before secondary recrystallization annealing, and the secondary recrystallization is performed. An average heating rate from 800 ° C. to the highest temperature reached in crystal annealing is set to 0.1 to 80 ° C. per hour, and the high magnetic flux density silicon steel sheet having excellent magnetic properties and coating properties according to claim 1 or 2. Manufacturing method. 4. A magnesia applied for forming a primary film contains boron, strontium / barium, charcoal.
Addition of one or more of nitride-based, sulfide-based, and chloride-based compounds in a total amount of 0.05 to 5.0%, and an average temperature rise from 800 ° C to the maximum reached temperature in the secondary recrystallization annealing. The speed is set to 5 to 400 ° C./hour, and the speed is set to 5 ° C./hour.
Alternatively, the method for producing a high magnetic flux density silicon steel sheet having excellent magnetic properties and coating properties as described in 3 above. 5. Production of a high magnetic flux density silicon steel sheet having excellent magnetic properties and coating characteristics, characterized in that the ratio of the partial pressures of nitrogen and hydrogen in the primary annealing atmosphere is P N ₂ / P H ₂ ≤0.5. Law.