JP2007169755A - Grain-oriented electromagnetic steel sheet in coiled form and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grain-oriented electromagnetic steel sheet having uniform and adequate magnetic properties over a full length of a coil. <P>SOLUTION: The grain-oriented electromagnetic steel sheet in a coiled form includes 1.0-5.0 mass% Si; has a forsterite coating film as an undercoating film; has a glassy inorganic coating film on the surface; has the total concentration of Ti, Mo, W, Ta, V, Nb and Zr controlled to 150 ppm or lower in the ends of the matrix in a coil width direction; has the concentration of C in the matrix and the coating film controlled to 30 ppm or lower in the ends in the coil width direction; has a difference of the C concentration in the matrix and the coating film between a central area and the ends in the coil width direction controlled to 20 ppm or lower; and thereby has a ratio of a core loss before and after stress relief annealing controlled to 1.2 or less over the full width of the coil. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a grain-oriented electrical steel sheet coil and a method for manufacturing the same, and in particular, by effectively suppressing the formation of carbides that are a cause of deterioration of iron loss at the end of the coil, it prevents deterioration of magnetic properties and is good over the entire width of the coil. It is intended to obtain excellent magnetic characteristics.

  A grain-oriented electrical steel sheet used as a core material for transformers and generators is required to have a high magnetic flux density and a low iron loss. For that purpose, it is important to highly accumulate the crystal orientation of the steel sheet after the final finish annealing in the {110} <001> orientation called the Goss orientation. This is because the crystal orientation <001>, which is the easy axis direction of the iron crystal, is highly accumulated in the rolling direction, so that the magnetizing force required for magnetization in the rolling direction is reduced and the coercive force is lowered, resulting in hysteresis. This is because the loss is reduced and the iron loss is reduced.

  Such a Goss orientation is formed by utilizing a phenomenon called “secondary recrystallization” during the final finish annealing, in which the Goss orientation preferentially grows by eroding the orientation of the matrix. Since this finish annealing is usually performed at a high temperature for a long time, it is heat-treated in a batch furnace in a coiled state. In addition, an annealing separator mainly composed of magnesium oxide (magnesia) is applied to prevent fusion at high temperatures.

However, in the above manufacturing method, since the coil is heat-treated in a batch furnace, the problem that the quality of the steel sheet becomes uneven at each position of the coil is likely to occur. For example, deformation occurs due to buckling at the lower end of the coil, and film defects and magnetic characteristics are defective at the outermost winding portion.
Possible causes include temperature variations between the coil surface and inside, and oxidation and nitridation due to differences in exposure to the annealing atmosphere between the coil surface and inside, and other element behavior changes. Various countermeasures have been taken against these problems.

For preventing the buckling deformation of the coil lower end, for example, Patent Document 1 discloses a method of suppressing deformation by speeding up secondary recrystallization during finish annealing by introducing strain to the end before finish annealing. Further, in Patent Document 2, when annealing is performed by placing the coil winding axis direction vertically on the coil cradle in the inner cover, the outer peripheral end surface of the coil cradle is coated with a heat insulating material and annealed. Has been proposed.
As for prevention of coating defects at the top of the coil furnace, for example, Patent Document 3 proposes a method of reducing the amount of electrodeposited Si after electrolytic degreasing at the edge portion and the central portion.
Furthermore, regarding the uniformity of the magnetic properties, Patent Document 4 discloses that the inhibitory power of the inhibitor is increased by continuously or stepwise increasing the amount of oxygen in the decarburization annealing from the outer winding portion to the inner winding portion of the coil. A method of making the magnetic properties uniform by causing uniform secondary recrystallization while keeping the coil full length constant is disclosed.
JP 10-204542 Annual Report JP-A-5-51643 Japanese Patent Laid-Open No. 2002-266027 JP-A-5-117756

  By the way, regarding magnetic characteristics, not only the degree of integration in the Goss direction by secondary recrystallization, but also the presence of fine precipitates prevents domain wall movement when magnetizing a steel sheet, thereby increasing iron loss. There is also a problem. Such precipitates are removed to some extent by the subsequent purification annealing after the secondary recrystallization annealing.However, the precipitates are formed again when the product is assembled into a transformer and then subjected to strain relief annealing. Therefore, the problem that the magnetic characteristics deteriorated has been pointed out.

For this problem, Patent Document 5 discloses a method for suppressing the precipitation of TiN and TiC by specifying the relationship between the amount of titanium compound separating agent additive and the finish annealing cooling rate, and Patent Document 6 discloses an annealing separator and A method for suppressing the precipitation of carbide by reducing the amount of C in steel is disclosed. Further, Patent Document 7 discloses a method in which a Ti compound is added to an annealing separator and N ₂ is contained in a finish annealing atmosphere. Patent Document 8 describes a forsterite film of a directional silicon steel product. Methods for specifying the included Ti concentration and N concentration are disclosed.
JP-A 63-162814 Japanese Patent Laid-Open No. 2-93021 Japanese Patent No. 2574607 JP-A-6-179977

These various methods have improved both the longitudinal and width non-uniformity of the coil due to finish annealing and the deterioration of iron loss due to strain relief annealing.
However, none of these are sufficient, and the problem that iron loss deteriorates at the end in the coil width direction after strain relief annealing has occurred sporadically. Such deterioration is often found after the transformer is manufactured on the user side, and is often a big problem.

Further, in recent years, with the increase in demand for grain-oriented electrical steel sheets, the production capacity has been increased and the coil capacity has increased. Degradation has recurred again. In recent years, in particular, there has been an increasing demand for improvement of iron loss due to increased interest in energy saving, and slight deterioration of iron loss has become unacceptable.
Therefore, there is an urgent need to obtain uniform characteristics over the entire coil width without deterioration of iron loss after strain relief annealing.

  The present invention advantageously solves the above-described problem of magnetic characteristics in the width direction of the coil, in particular, iron loss is deteriorated by strain relief annealing, and provides a directional electromagnetic having uniform and good magnetic characteristics over the entire length of the coil. The object is to propose a steel sheet together with its advantageous manufacturing method.

That is, the gist configuration of the present invention is as follows.
(1) A grain-oriented electrical steel sheet coil having a glassy inorganic coating on the surface of a forsterite undercoating, containing 1.0 to 5.0 mass% of Si, and further, A total concentration of Mo, W, Ta, V, Nb and Zr is 150 ppm or less, and a C concentration including a coating at the end in the coil width direction is 30 ppm or less, and a coating is applied to the center in the width direction at the end in the coil width direction. A grain-oriented electrical steel sheet coil characterized in that the difference in C concentration included is within 20 ppm, and the ratio of iron loss before and after strain relief annealing is 1.2 or less over the entire width of the coil.

(2) A silicon steel slab containing 1.0 to 5.0 mass% of Si is hot-rolled and then subjected to primary recrystallization annealing after the final sheet thickness is obtained by one or more cold rollings including annealing treatment. In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of applying a final finish annealing after applying an annealing separator to the steel sheet surface,
As the main ingredient of the annealing separator, use a titanic acid compound containing at least 50% magnesia and containing the following composition as a trace amount of magnesia: 1 to 10 parts by mass with respect to 100 parts by mass. A method for producing a grain-oriented electrical steel sheet coil characterized by the following.
Record
(M ⁺ _a , M2 ⁺ _b , M3 ⁺ _c ) Ti _x O _y
However, 0 ≦ a ≦ 4, 0 ≦ b ≦ 2, 0 ≦ c ≦ 2
1 ≦ x ≦ 4, 2 ≦ y ≦ 9
M ⁺ : Any one selected from Li, Na, K M ²⁺ : Any one selected from Mg, Ca, Sr, Ba, Cr, Co, Mn, Zn, Fe M ³⁺ : Any one selected from Fe, Al, Cr, Mn

(3) A silicon steel slab containing 1.0 to 5.0 mass% of Si is hot-rolled and then subjected to primary recrystallization annealing after the final plate thickness is obtained by one or more cold rollings including annealing treatment. In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of applying a final finish annealing after applying an annealing separator to the steel sheet surface,
The coil cradle or coil top, or both before final annealing, directional, characterized in that the titanic acid compound composed of a following composition, spraying 0.02 kg / m ² or more per coil surface area 0.7 kg / m ² or less A method for manufacturing electrical steel sheet coils.
Record
(M ⁺ _a , M2 ⁺ _b , M3 ⁺ _c ) Ti _x O _y
However, 0 ≦ a ≦ 4, 0 ≦ b ≦ 2, 0 ≦ c ≦ 2
1 ≦ x ≦ 4, 2 ≦ y ≦ 9
M ⁺ : Any one selected from Li, Na, K M ²⁺ : Any one selected from Mg, Ca, Sr, Ba, Cr, Co, Mn, Zn, Fe M ³⁺ : Any one selected from Fe, Al, Cr, Mn

  According to the present invention, it is possible to prevent the deterioration of the magnetic characteristics at the end by suppressing the generation of carbide, which is a cause of deterioration of the iron loss at the end of the coil, and to obtain good magnetic characteristics over the entire width of the coil. it can.

Now, as a result of investigating the cause of the deterioration of the iron loss due to strain relief annealing at the position in the width direction, the inventors have found that the C concentration increases at the end in the width direction. It has been newly found that it occurs even under conditions where the amount of C in the agent is reduced.
The following is a description of how this knowledge was obtained.
C: 0.06 mass% (hereinafter simply expressed as%), Si: 3.25%, Mn: 0.07%, Al: 0.023%, Se: 0.018%, Cu: 0.05%, N: 0.0070% and Sb: 0.035% A plurality of silicon steel slabs having the balance of Fe and inevitable impurities were heated at 1400 ° C. for 30 minutes, and then hot-rolled. Then, hot-rolled sheet annealing is performed at 1000 ° C for 1 minute, and after pickling, primary cold rolling is performed to obtain an intermediate thickness of 1.6 mm, followed by intermediate annealing at 1000 ° C for 1 minute. After pickling, the final thickness was 0.23 mm by secondary cold rolling. Next, after decarburization annealing was performed at 850 ° C. for 100 seconds in an atmosphere having an atmospheric oxidation property (P [H ₂ 0] / P [H ₂ ]) of 0.45, TiO was added to 100 parts by mass of MgO. An annealing separator containing 7 parts by mass of ₂ and 3 parts by mass of strontium hydroxide was applied at a coating amount of 14 g / m ² per both sides of the steel sheet, and wound around a coil. At this time, MgO used for the annealing separator was selected and used with a C content of 0.1 mass% or less, and the C content of the decarburized annealing plate was 8 ppm or less. Therefore, when the whole is converted into the steel plate content, it becomes 15 ppm or less. After this is kept in the coil yard for 1 to several days, 1 kg of MgO is sprayed on the coil cradle to finish and annealed, and then the unreacted separating agent is removed, and then the tension coating is applied. After baking, it was flattened and wound on a coil.
At the position 100m from the outer winding part of the product coil obtained, (1) From the coil center part (plate width center part) and (2) From the part (plate width end part) where the outermost part was dropped 10mm, A sample of × 100 mm was taken and subjected to strain relief annealing at 800 ° C. for 3 hours in an N ₂ atmosphere.

For the product coil thus obtained, the iron loss before and after strain relief annealing was measured and the ratio (after strain relief annealing / before strain relief annealing) was calculated. Further, after magnetically measuring the sample after strain relief annealing, the amount of C including the coating and the amount of trace added elements in the base iron part were measured.
The obtained results are shown in Table 1.
The magnetic characteristics of the samples before strain relief annealing were all constant within the ranges of B ₈ = 1.915 to 1.925 T and W _17/50 = 0.80 to 0.85 W / kg. In addition, the total of Ti, Mo, W, Ta, V, Nb and Zr concentration in the iron core at the end in the coil width direction after strain relief annealing is less than 150ppm, especially the amount of Ti is 50-80ppm. It was constant within the range.

As apparent from the table, before the finish annealing, both the central portion and the end portion of the plate width of the steel sheet are within 15 ppm in terms of C, and a satisfactory amount of C as described in Patent Document 6 has been achieved. Nevertheless, some end samples of the product plate have an abnormally high C concentration. In this case, the iron loss after the stress relief annealing is also deteriorated.
On the other hand, after the strain relief annealing, there is no deterioration of iron loss in the sample having a low C concentration in the plate width central portion and the plate width end portion, and a uniform iron loss is obtained from the plate width end portion to the central portion. .

Thus, even if the C content in the steel sheet and the annealing separator is decreased, a new phenomenon that has not been found in the past is that the C content of the final product plate increases at the end, and the iron loss decreases accordingly. It was found.
Therefore, the inventors have clarified this cause and have conducted intensive studies on a method for reducing the C content at the time of the final product. The results of this study are described below.

From the results of the previous experiment, the reason why the C concentration at the end of the plate width increased despite the fact that the plurality of coils were subjected to substantially the same processing was the coil yard after the decarburization annealing until the finish annealing. We paid attention to the fact that the time spent in the coil differs for each coil. Then, the annealing separator was scraped off from the coil kept in the coil yard for several days, and this was subjected to chemical analysis, and gas mass analysis (method of mass analyzing the gas generated at that time while heating the sample) was performed.
Table 2 shows the results of chemical analysis.

  As shown in the table, it can be seen that the C content of the powder collected from the coil retained in the coil yard for 7 days is significantly increased as compared with immediately after winding. From this, it can be seen that the annealing separator absorbed C during residence.

FIG. 1 shows a comparison of the results of gas mass analysis of the above two samples. Both samples have CO ₂ peaks at around 300 ° C and around 600 ° C.
These two temperature ranges correspond to the decomposition temperatures of Mg (OH) ₂ and MgCO ₃ , respectively. Of these peaks, there is not much difference between the samples at around 600 ° C. The sample retained for a long time in the yard has a significantly larger peak than the sample immediately after winding.

From the above results, the inventors inferred the phenomenon that carburization occurs only at the coil end as follows.
It is known that MgO, an annealing separator, is hydrated by slurrying with water and applying and drying. Since this is a rapid hydration reaction, the hydrated product is not completely magnesium hydroxide crystals, but is a chemically active substance in the state of a decomposition intermediate. When such substances are exposed to the atmosphere, they absorb carbon dioxide in the atmosphere and
Mg (OH) ₂ + xCO ₂ → Mg (CO ₃ ) _x・ (OH) _2-2x + xH ₂ O
It is considered that magnesium carbonate hydroxide was generated by the reaction of
It is considered that this magnesium carbonate hydroxide is thermally decomposed again during the finish annealing, and C 2 enters the steel by generating CO ₂ gas. Such reaction to magnesium carbonate hydroxide occurs at the outermost inner winding of the coil and the upper and lower plate width end faces that are directly exposed to the outside air, and the generation and carburization of CO ₂ gas during finish annealing are also in contact with this outside air. Therefore, it is considered that the C concentration increased at the end portion in the coil width direction and the C amount did not increase at the central portion.

From the above points, it became clear that carburization occurs when the annealing separator absorbs CO ₂ gas during the residence time of the coil in the coil yard. investigated.
In simple terms, carbon dioxide absorption occurs during the coil residence time, so it may be necessary to shorten the residence time. However, this method is for convenience and trouble-shooting due to the operating conditions of the finish annealing equipment. It is not easy due to problems such as securing inventory.
In addition, it is conceivable to manage the humidity and CO ₂ concentration in the entire coil yard, but it is not practical because of the huge cost of capital investment.

Therefore, the inventors examined a method for absorbing CO ₂ generated by this production rather than suppressing the production of magnesium carbonate hydroxide. As a result, it was determined that the use of a titanic acid compound is extremely effective.
Hereinafter, the background of obtaining the above knowledge will be described.

C: 0.07%, Si: 3.5%, Mn: 0.06%, solAl: 50ppm, N: 25ppm, S: 10ppm, Se: 0.1ppm, O: 10ppm, Sb: 0.02%, Sn: 0.02% and Cu: 0.15% A steel slab containing Fe and an inevitable impurity composition was heated to 1150 ° C. and hot rolled to form a hot rolled sheet having a thickness of 2.0 mm. Next, after hot-rolled sheet annealing at 1000 ° C. for 30 seconds, after finishing to a final sheet thickness of 0.30 mm by cold rolling, the oxidation of the atmosphere (P [H ₂ 0] / P [H ₂ ]) is 0.45 In the atmosphere, decarburization annealing was performed at 850 ° C. for 100 seconds. Subsequently, MgO: 100 parts by mass, TiO ₂ : 2 parts by mass, strontium hydroxide: 3 parts by mass, and Ba ₂ TiO _{4 in an amount} of 0 to 20 An annealing separator containing part by mass was applied in an amount of 14 g / m ² per both sides of the steel sheet, and then wound around a coil. At this time, the C concentration in the steel plate after the annealing separator was applied and the separator was 10 to 15 ppm in terms of steel plate.
After that, this coil is allowed to stay in the coil yard for several days, and then 1 kg of MgO is applied to the coil cradle to prevent fusion, followed by finish annealing, and after removing the unreacted separating agent, a tension coating is applied. After baking, it was flattened and wound on a coil.
At the position 100m from the outer winding part of the product coil obtained, (1) From the coil center part (plate width center part) and (2) From the part (plate width end part) where the outermost part was dropped 10mm, A sample of × 100 mm was taken and subjected to strain relief annealing at 800 ° C. for 3 hours in an N ₂ atmosphere.

For the product coil thus obtained, the iron loss before and after strain relief annealing was measured and the ratio (after strain relief annealing / before strain relief annealing) was calculated. Further, after magnetically measuring the sample after strain relief annealing, the amount of C including the coating and the amount of trace added elements in the base iron part were measured.
The obtained results are shown in Table 3.
The magnetic characteristics of the samples before strain relief annealing were all constant within the ranges of B ₈ = 1.895 to 1.905 T and W _17/50 = 0.98 to 1.03 W / kg. In addition, the total of Ti, Mo, W, Ta, V, Nb, and Zr concentration in the base iron part at the end in the coil width direction after strain relief annealing is 150 ppm or less, and especially the Ti amount is 50 to 70 ppm. It was constant within the range.

As is clear from the table, it can be seen that by appropriately adding Ba ₂ TiO ₄ , the C concentration at the end of the plate width is significantly reduced, and the magnetic properties are improved accordingly. However, when the addition amount of Ba ₂ TiO ₄ was increased to 20 parts by mass, the C concentration at the end of the plate width increased, and the deterioration of iron loss due to strain relief annealing also increased.

Regarding the carbon dioxide absorption effect of such titanic acid compounds, in this example of Ba ₂ TiO ₄
Ba ₂ TiO ₄ + CO ₂ → BaCO ₃ + BaTiO ₃
This is thought to be because Ba ions absorb CO ₂ to form carbonates.
However, if the addition amount is too large, the MgO content is relatively lowered, so that the coating is deteriorated, and oxygen or nitrogen other than C penetrates to facilitate the formation of precipitates. It is thought that iron loss deteriorates instead.
In any case, by using titanates such as Ba ₂ TiO ₄ , carburization is remarkably suppressed, and uniform and good magnetic properties in the plate width direction can be obtained even after strain relief annealing.

Hereinafter, with respect to the component composition and manufacturing method of the grain-oriented electrical steel sheet according to the present invention, the requirements for obtaining the effects of the present invention, the range thereof, and the operation thereof will be described.
First, the grain-oriented electrical steel sheet coil targeted by the present invention is a grain-oriented electrical steel sheet coil with a vitreous inorganic coating and a forsterite base coat.
The total concentration of Ti, Mo, W, Ta, V, Nb and Zr in the iron core at the coil end is 150 ppm or less. This is because when these concentrations exceed 150 ppm, carbides precipitate and iron loss deterioration due to strain relief annealing is likely to occur.

Next, the C concentration including the coating at the end portion in the coil width direction is suppressed to 30 ppm or less, and the difference in C concentration including the coating with respect to the central portion in the width direction at the end portion in the coil width direction is within 20 ppm. To control. About C, even if it is in a film, since it may penetrate | invade in steel during strain relief annealing, it is inadequate only with a base metal component, and it is necessary to reduce C density | concentration including a film. When the C concentration including this film exceeds 30 ppm, the deterioration becomes remarkable. Therefore, the C concentration at the end in the width direction is set to 30 ppm or less. Also, if the C concentration difference between the coil width direction end and the width direction center exceeds 20 ppm, the magnetic characteristics start to deteriorate and uniform magnetic characteristics cannot be achieved in the width direction. The difference in C concentration is 20 ppm or less.
As described above, by adjusting the components, a uniform grain-oriented electrical steel sheet coil in which the ratio of iron loss before and after strain relief annealing is 1.2 or less over the entire width of the coil can be obtained.

Next, a manufacturing method for obtaining the above-described coil will be described.
First, Si is contained as a component by 1.0 to 5.0%. This Si is an element necessary for increasing the electric resistance and reducing the iron loss and stabilizing the α phase of iron to enable high-temperature heat treatment, and requires at least 1.0%. If it exceeds%, cold rolling becomes difficult, so the Si content is limited to a range of 1.0 to 5.0 mass%.
Next, C is preferably C: 0.01 to 0.10%. This C is not only an element useful for improving the hot-rolled structure using transformation, but also an element useful for the generation of goth-oriented crystal grains, and needs to contain 0.01% or more. If it exceeds 0.10%, the effect becomes too strong, and the texture deteriorates. Therefore, C is preferably in the range of 0.01 to 0.10%.

In addition to C and Si, an inhibitor component has been conventionally added, but recently, a method not using an inhibitor has been carried out, and the present invention is advantageously adapted to any method.
In the case of using an inhibitor, AlN, BN, MnS, MnSe and the like are well known as the inhibitor, but any of these may be used, or two or more of these may be used in combination. When MnS and / or MnSe is used as an inhibitor, it is preferable to set Mn: 0.03 to 0.10% and the total amount of S and Se: 0.01 to 0.00.03%. When AlN is used as an inhibitor, Al: 0.01 to 0.04%, N: 30 to 120 ppm, and when BN is used as an inhibitor, B: 0.001 to 00.015%, N: 30 to 120 ppm. preferable. In any case, if it is lower than these ranges, the effect as an inhibitor is poor, while if it is higher, secondary recrystallization becomes unstable.

  In addition to the main inhibitor described above, Ni is 0.01 to 1.50%, Sn: 0.01 to 0.50%, Sb: 0.005 to 0.50%, P: 0.005 to 0.50%, Cr: 0.02 to 1.50%, Te : 0.003 to 1.50%, Bi: 0.003 to 1.50%, Pb: 0.003 to 1.50%, and Cu: 0.01 to 0.10%, or one or more selected from them can also be used. These concentrate preferentially at the grain boundaries of the primary recrystallized grains, and have the effect of increasing the secondary recrystallization start temperature and improving the magnetic flux density by reducing the difference in grain boundary movement during annealing. Further, these are further contributed to the improvement of the magnetic properties by being present in the steel simultaneously with the precipitation dispersion type inhibitors such as MnSe, MnS, CuxS, CuxSe, AlN and BN.

  On the other hand, when an inhibitor is not used, it is preferable to reduce Al to 100 ppm or less and N, S, and Se to 50 ppm or less for satisfactory secondary recrystallization. In addition, reducing carbide-forming elements such as Ti, Mo, W, Ta, V, Nb, and Zr to 50 ppm or less prevents deterioration of iron loss after stress relief annealing and ensures good workability. It is effective in doing.

Next, preferred manufacturing conditions according to the present invention will be described.
The silicon steel slab adjusted to the above components is hot-rolled and then subjected to primary recrystallization annealing after the final plate thickness is obtained by one or more cold rolling processes including annealing. In this primary recrystallization annealing, the temperature in the soaking area is preferably 750 to 950 ° C. This is because when the temperature exceeds 950 ° C., the primary recrystallized grains grow too much, resulting in poor secondary recrystallization. This is because the grain orientation becomes unstable. The temperature increase rate in the primary recrystallization annealing is preferably 5 to 80 ° C./s from room temperature to 700 ° C. This is because if the rate of temperature rise is lower than 5 ° C / s, decarburization proceeds too much in the heating region and a desired texture cannot be obtained, whereas if it is faster than 80 ° C / s, the initial oxidation becomes unstable and good. This is because no film is formed. The soaking time is preferably 20 to 240 s. This is because when the soaking time is less than 20 s, primary recrystallization failure occurs, and when it exceeds 240 s, primary recrystallization grain growth proceeds, both of which cause deterioration of magnetic properties. Furthermore, it is preferable that the atmospheric oxidation property (P [H ₂ 0] / P [H ₂ ]) at the time of annealing is 0.05 to 0.85. This is because if the atmospheric oxidation property (P [H ₂ 0] / P [H ₂ ]) is less than 0.05, a good oxide film cannot be obtained and the coating deteriorates. This is because an oxide film is formed, and the film is deteriorated.

In the present invention, by using a titanic acid compound, decarburization during finish annealing can be performed, so that the constraint conditions during primary recrystallization annealing can be reduced. For example, the soaking time conventionally required 50s or more for decarburization, but this technology has made it possible to decarburize even under 50s. For this reason, even with a steel type that has had to extend the annealing time for decarburization with a thick plate material, the use of this technology makes it possible to anneal in a short time, thereby improving productivity. it can. In addition, atmospheric oxidation (P [H ₂ 0] / P [H ₂ ]) has conventionally required 0.20 or more for decarburization, but this technology enables annealing even at 0.20 or less. As a result, there is no short-circuit of the annealing furnace heater due to the occurrence of pick-up due to the oxide or peeling of the oxide, which can contribute to quality improvement and reduction of production loss. Furthermore, C can also be used as a restraining force by performing finish annealing without intentionally decarburizing.

After the primary recrystallization annealing is completed, an annealing dispersant is applied. At least 50% magnesia is used as the main component of the annealing separator. Preferably it is 80% or more. As an additive for the annealing separator, there are various known additives such as sulfates such as TiO ₂ , Mg, Sr, Sb, Cu and Zn, borates such as Li and Na, other hydroxides and chlorides. Compounds are used. In the present invention, these additives can also be used. However, when using compounds such as TiO ₂ , Mo, W, Ta, Zr, V, Nb, etc., it will form carbides when intruding into the steel and cause deterioration due to strain relief annealing, so MgO: 100 parts by mass On the other hand, it is desirable to keep it to 10 parts by mass or less. In the case of other compounds, the addition amount is suitably about 0.5 to 15 parts by mass with respect to 100 parts by mass of magnesia. In addition, about the application | coating amount and hydration amount of an annealing separation agent, 5-15 g / m < ² > (both sides) and about 0.5-5% may be sufficient as usual.
In addition to magnesia as a main ingredient, various additives, and a titanate compound described later, alumina, calcium oxide, and the like can be contained.

In the present invention, in the annealing separator, in addition to the above components, the following chemical formula
Record
(M ⁺ _a , M2 ⁺ _b , M3 ⁺ _c ) Ti _x O _y
However, 0 ≦ a ≦ 4, 0 ≦ b ≦ 2, 0 ≦ c ≦ 2
1 ≦ x ≦ 4, 2 ≦ y ≦ 9
M ⁺ : Any one selected from Li, Na, K M ²⁺ : Any one selected from Mg, Ca, Sr, Ba, Cr, Co, Mn, Zn, Fe M ³⁺ : It is important to contain 1 to 10 parts by mass of the titanic acid compound represented by any one selected from Fe, Al, Cr and Mn with respect to 100 parts by mass of magnesia.
In the above chemical formula, _x in Ti _x O _y is in the range of 1 to 4 and y is in the range of 2 to 9. If X is greater than 4 and y is greater than 9, carbon dioxide is relatively absorbed. Reduction of elements M ⁺ , M ²⁺ , and M ³⁺ reduces the effect of preventing carbon from entering the steel. On the other hand, if x is less than 1 and y is less than 2, the titanate compound is unstable. This is because before the carbon dioxide is absorbed, it decomposes and becomes another compound, so the effect of absorbing the carbon dioxide is also reduced.

  By including such a titanic acid compound, decarburization during finish annealing can be promoted, and deterioration of magnetic properties during strain relief annealing can be suppressed. Here, if the compounding amount of the titanic acid compound is less than 1 part by mass with respect to 100 parts by mass of magnesia, the effect of addition is poor. On the other hand, if it exceeds 10 parts by mass, the ratio of MgO as the main ingredient is relatively lowered. As a result, the coating deteriorates.

Further, in the present invention, _a titanium oxide inclusion having a composition of (M ⁺ _a , M ²⁺ _b , M ³⁺ _c ) ₄ Ti _x O _y is formed on the coil cradle and / or the coil upper part before finish annealing. per coil surface area, also by spraying 0.02 kg / m ² or more 0.7 kg / m ² or less, it may be mentioned the same effect.
Here, the coil surface area is the sum of the areas of the coil upper end surface, lower end surface and side surface. For example, if the coil has an outer diameter of 1.5 m, an inner diameter of 0.5 m (both diameters), and a height of 1 m, the surface area is π · (0.75 ² −0.25 ² ) × 2 + π × 1.5 × 1 + π × 0.5 × 1 = 9.4 m ²
That is, by doing this, CO ₂ released during finish annealing is effectively absorbed, and iron loss deterioration before and after strain relief annealing can be suppressed.
Here, if the application amount is less than 0.2 kg, the effect of absorbing CO ₂ is poor. On the other hand, if it exceeds 7 kg, the cost increases.
In addition, about the other conditions of finish annealing, a well-known method may be sufficient.

After the above-described finish annealing, if necessary, a tension imparting coating or an insulating coating is formed on the surface of the steel sheet, followed by flattening annealing to obtain a product.
In addition, for the purpose of reducing iron loss due to magnetic domain subdivision, plasma jet or laser irradiation is linearly applied to the steel sheet after flattening annealing, linear dents are provided by protruding rolls, or etching is performed after the final cold rolling, etc. Thus, it is possible to perform a process of forming a groove substantially perpendicular to the rolling direction.
Furthermore, it is also effective to reduce iron loss by combining a technique for forming a tension coating by a known method such as a sol-gel method or TiN deposition after the final finish annealing.

Example 1
Contains C: 0.06%, Si: 3.35%, Mn: 0.07%, S: 0.003%, Al: 0.005%, Cu: 0.1%, N: 0.0035% and Sb: 0.040%, the balance being Fe and inevitable impurities A silicon steel slab having the following composition was charged into a gas heating furnace, heated to 1230 ° C. and held for 60 minutes, and then hot rolled into a hot rolled sheet having a thickness of 2.0 mm. Next, hot-rolled sheet annealing was performed at 1000 ° C. for 1 minute, pickled and finished to a final sheet thickness of 0.30 mm by cold rolling, and then the oxidizing properties of the atmosphere (P [H ₂ 0] / P [H ₂ ]) Was decarburized and annealed at 850 ° C. for 100 seconds in an atmosphere of 0.40, and then an annealing separator of MgO: 100 parts by mass, TiO ₂ : 2 parts by mass, strontium hydroxide: 3 parts by mass was added to the steel plate. The coating amount per side was 14 g / m ² and wound around a coil. Thereafter, finish annealing was performed by spraying 0 to 0.7 kg / m ² of Sr ₂ TiO ₄ on the finish annealing coil cradle and the upper part of the coil. Here, in a condition where Sr ₂ TiO ₄ was not sprayed on the coil cradle, MgO was sprayed at 0.1 kg / m ² to prevent fusion with the coil cradle.
Thereafter, the unreacted separating agent was removed by washing with water, and then an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica was applied and baked, followed by flattening annealing to obtain a product.
At the position 100m from the outer winding part of the product coil obtained, (1) From the coil center part (plate width center part) and (2) From the part (plate width end part) where the outermost part was dropped 10mm, A sample of × 100 mm was taken and subjected to strain relief annealing at 800 ° C. for 3 hours in an N ₂ atmosphere.

For the product coil thus obtained, the iron loss before and after strain relief annealing was measured and the ratio (after strain relief annealing / before strain relief annealing) was calculated. Further, after magnetically measuring the sample after strain relief annealing, the amount of C including the coating and the amount of trace added elements in the base iron part were measured.
Table 4 shows the ratio of the Sr ₂ TiO ₄ application amount, the C concentration, and the iron loss before and after the strain relief annealing.
The magnetic characteristics of the samples before strain relief annealing were all constant within the ranges of B ₈ = 1.895 to 1.905 T and W _17/50 = 0.98 to 1.03 W / kg. In addition, the total of Ti, Mo, W, Ta, V, Nb, and Zr concentration in the iron core at the end in the coil width direction after strain relief annealing is 150 ppm or less, especially the Ti content is 40-60 ppm. It was constant within the range.

As is apparent from the table, it is understood that carburization is effectively suppressed by spreading an appropriate amount of Sr ₂ TiO _4, and the iron loss difference before and after the stress relief annealing is also reduced.

Example 2
C: 0.07%, Si: 3.31%, Mn: 0.07%, P: 0.002%, Se: 0.02%, Al: 0.025%, Cu: 0.10% and N: 0.0082%, and Ti, Mo as secondary inhibitors A silicon steel slab containing W, Ta, V, Nb, and Zr in a range of 0 to 200 ppm with the balance being Fe and inevitable impurities is heated at 1200 ° C. for 60 minutes and then hot rolled to 2.2 mm. A thick hot-rolled sheet was used. Next, hot-rolled sheet annealing was performed at 950 ° C for 1 minute, pickled, and after intermediate cold-rolling to a thickness of 1.5 mm, intermediate annealing was performed at 1050 ° C for 1 minute, and pickling Maximum sheet temperature: Finished to a final sheet thickness of 0.35 mm by secondary cold rolling at 210 ° C. Next, a holding annealing was performed at 850 ° C. for 100 seconds in an atmosphere having an atmosphere oxidizing property (P [H ₂ 0] / P [H ₂ ]) of 0.44. At this time, the C content of the steel sheet after decarburization and purification was 100 ppm. Thereafter, as an annealing separator, MgO: 100 parts by mass of Li ₄ TiO ₄ added by 0 part by mass or 3 parts by mass, hydration at 20 ° C. for 30 minutes, basis weight: 14 g / m per side ² applied. Subsequently, after the finish annealing, the unreacted separating agent was removed by washing with water, and then an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica was applied and baked.
At the position 100m from the outer winding part of the product coil obtained, (1) From the coil center part (plate width center part) and (2) From the part (plate width end part) where the outermost part was dropped 10mm, A sample of × 100 mm was taken and subjected to strain relief annealing at 800 ° C. for 3 hours in an N ₂ atmosphere.

For the product coil thus obtained, the iron loss before and after strain relief annealing was measured and the ratio (after strain relief annealing / before strain relief annealing) was calculated. Further, after magnetically measuring the sample after strain relief annealing, the amount of C including the coating and the amount of trace added elements in the base iron part were measured.
Table 5 shows the trace amount of element added in the steel, Sr ₂ TiO ₄ addition amount, C concentration, and the ratio of iron loss before and after strain relief annealing (plate width end).
Note that the magnetic properties of the samples before strain relief annealing were all constant within the ranges of B ₈ = 1.925 to 1.935 T and W _17/50 = 1.15 to 1.20 W / kg. Further, in the inventive examples, the difference in the concentration of C including the coating at the center portion of the plate width and the end portion of the plate width was 20 ppm or less.

As shown in the table, when steel contains a small amount of carbide-forming elements such as Ti, Mo, W, etc., it is also effective for steel sheets that have been decarburized insufficiently by adding Li ₄ TiO _4. In addition, C can be reduced, and iron loss deterioration due to strain relief annealing is also reduced. In this regard, when the amount of carbide forming elements is large, even if Li ₄ TiO ₄ is added, sufficient decarburization and iron loss deterioration effects are not obtained. Further, when no Li ₄ TiO ₄ is added, almost no decarburization occurs and the iron loss is remarkably deteriorated.
From the above, it can be seen that the total amount of carbide-forming elements such as Ti, Mo, and W needs to be suppressed to 0.015% or less.

Example 3
Contains C: 0.06%, Si: 3.35%, Mn: 0.07%, S: 0.003%, Al: 0.005%, Cu: 0.1%, N: 0.0035% and Sb: 0.040%, the balance being Fe and inevitable impurities A silicon steel slab having the following composition was heated to 1230 ° C. and held for 60 minutes, and then hot rolled to form a hot-rolled sheet having a thickness of 2.0 mm. Next, hot-rolled sheet annealing was performed at 1000 ° C. for 1 minute, pickled and finished to a final sheet thickness of 0.30 mm by cold rolling, and then the oxidizing properties of the atmosphere (P [H ₂ 0] / P [H ₂ ]) Was decarburized and annealed at 830 ° C. for 100 seconds in an atmosphere of 0.10. At this time, the C content after decarburization annealing was 120 ppm. Then, as a sinter separating agent, a powder obtained by adding ₂ parts by mass of TiO _2, 2 parts by mass of magnesium sulfate and 0 parts by mass or 3 parts by mass of various titanate compounds to 100 parts by mass of MgO was applied. Then, after finishing annealing and removing the unreacted separating agent by washing with water, an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica was applied and baked.
At the position 100m from the outer winding part of the product coil obtained, (1) From the coil center part (plate width center part) and (2) From the part (plate width end part) where the outermost part was dropped 10mm, A sample of × 100 mm was taken and subjected to strain relief annealing at 800 ° C. for 3 hours in an N ₂ atmosphere.

For the product coil thus obtained, the iron loss before and after strain relief annealing was measured and the ratio (after strain relief annealing / before strain relief annealing) was calculated. Further, after magnetically measuring the sample after strain relief annealing, the amount of C including the coating and the amount of trace added elements in the base iron part were measured.
Table 6 shows the addition amount of various titanate compounds, the C concentration, and the ratio of iron loss before and after strain relief annealing (plate width end).
Note that the magnetic properties of the samples before strain relief annealing are all constant within the range of B ₈ = 1.900 to 1.910 T, W _17/50 = 0.95 to 1.02 W / kg. The difference in the concentration of C including the coating at the edge of the plate width was 20 ppm or less. In addition, the total of Ti, Mo, W, Ta, V, Nb and Zr concentration at the end in the coil width direction after strain relief annealing is all 150 ppm or less. In particular, the Ti amount is 40% as shown in Table 6. It was constant within the range of -80 ppm.

  As shown in Table 6, it can be seen that, when appropriate amounts of various titanate compounds are added according to the present invention, decarburization proceeds and deterioration due to strain relief annealing can be almost suppressed.

It is a figure which shows the thermal-analysis result of the annealing separation agent extract | collected from the coil from which the residence time in a coil yard differs.

Claims (3)

  A grain-oriented electrical steel sheet coil with a glassy inorganic coating on the surface of the forsterite undercoating, containing 1.0 to 5.0 mass% of Si, and Ti, Mo, W of the base iron part at the end of the coil width direction , Ta, V, Nb, and Zr concentration is 150 ppm or less in total, C concentration including the coating at the coil width direction end is 30 ppm or less, and C including the coating for the width direction center of the coil width direction end A grain-oriented electrical steel sheet coil characterized in that the difference in concentration is within 20 ppm and the ratio of iron loss before and after strain relief annealing is 1.2 or less over the entire width of the coil. A silicon steel slab containing 1.0 to 5.0 mass% of Si is hot-rolled, and then subjected to primary recrystallization annealing after the final sheet thickness is obtained by one or more cold rolling processes including annealing. In the method for producing a grain-oriented electrical steel sheet comprising a series of steps in which an annealing separator is applied to the steel sheet surface and then subjected to final finish annealing.
As the main ingredient of the annealing separator, use a titanic acid compound containing at least 50% magnesia and containing the following composition as a trace amount of magnesia: 1 to 10 parts by mass with respect to 100 parts by mass. A method for producing a grain-oriented electrical steel sheet coil characterized by the following.
Record
(M ⁺ _a , M2 ⁺ _b , M3 ⁺ _c ) Ti _x O _y
However, 0 ≦ a ≦ 4, 0 ≦ b ≦ 2, 0 ≦ c ≦ 2
1 ≦ x ≦ 4, 2 ≦ y ≦ 9
M ⁺ : Any one selected from Li, Na, K M ²⁺ : Any one selected from Mg, Ca, Sr, Ba, Cr, Co, Mn, Zn, Fe M ³⁺ : Any one selected from Fe, Al, Cr, Mn A silicon steel slab containing 1.0 to 5.0 mass% of Si is hot-rolled, and then subjected to primary recrystallization annealing after the final sheet thickness is obtained by one or more cold rolling processes including annealing. In the method for producing a grain-oriented electrical steel sheet comprising a series of steps in which an annealing separator is applied to the steel sheet surface and then subjected to final finish annealing.
The coil cradle or coil top, or both before final annealing, directional, characterized in that the titanic acid compound composed of a following composition, spraying 0.02 kg / m ² or more per coil surface area 0.7 kg / m ² or less A method for manufacturing electrical steel sheet coils.
Record
(M ⁺ _a , M2 ⁺ _b , M3 ⁺ _c ) Ti _x O _y
However,
0 ≦ a ≦ 4, 0 ≦ b ≦ 2, 0 ≦ c ≦ 2
1 ≦ x ≦ 4, 2 ≦ y ≦ 9
M ⁺ : Any one selected from Li, Na, K M ²⁺ : Any one selected from Mg, Ca, Sr, Ba, Cr, Co, Mn, Zn, Fe M ³⁺ : Any one selected from Fe, Al, Cr, Mn

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