JP2002105537A - Method for manufacturing grain oriented silicon steel sheet hardly causing edge crack and having satisfactory film characteristic, excellent magnetic property and high magnetic flux density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent edge cracking which is liable to occur at hot rolling in the case of manufacturing a grain oriented silicon steel sheet containing Bi in combination with Cr together with known inhibitors and to manufacture a grain oriented silicon steel sheet having high magnetic flux density, satisfactory film characteristics and excellent magnetic properties in high production yield. SOLUTION: Prior to the initiation of roughing in hot rolling in the process for manufacturing the grain oriented silicon steel sheet, a steel slab is heated to <1,300 deg.C in an atmosphere of 0.01-15 vol.% average oxygen concentration, subjected to horizontal reduction at 1-20% draft and/or edging at 1-20% draft, and further heated to >=1,350 deg.C in an atmosphere of 0.01-2 vol.% average oxygen concentration while regulating temperature-rise rate at >=1,300 deg.C to <=10 deg.C/min.

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 high magnetic flux density grain-oriented electrical steel sheet used as an iron core of a transformer, a generator, and the like. It is intended to effectively prevent the occurrence of cracks.

[0002]

2. Description of the Related Art A product containing Si and having a crystal orientation of $ 1
Oriented electrical steel sheets oriented in the 10 ° <001> orientation, the so-called Goss orientation, have excellent soft magnetic properties and are therefore frequently used as iron cores for transformers and generators. What is fundamentally important as a characteristic of such an electromagnetic steel sheet is that the iron loss value is low. In particular, recently, the demand for energy saving has been further increased, and the demand for improving the properties of grain-oriented electrical steel sheets has been increasing more and more.

Generally, in order to reduce the iron loss of an electromagnetic steel sheet, a method of increasing the Si content effective for reducing the eddy current loss to increase the electric resistance, a method of reducing the thickness of the steel sheet, and a method of reducing the grain size of the product Are known, and furthermore, a method of increasing the degree of integration of crystal orientation to improve the magnetic flux density is known. However, at present, the method of increasing the Si content is at a limit since excessively containing Si causes deterioration in rollability and workability. Is also limited because of the extreme increase in manufacturing costs.

[0004] Methods for improving the remaining magnetic flux density have been well studied so far, and the degree of integration of Goss orientation in secondary recrystallized grains can be controlled by selecting the type of precipitate called an inhibitor and controlling its morphology. The main thing is to increase the quality. Here, inhibitors include sulfides, selenides, and nitrides such as Cu _2-x S, MnS, Cu _2-x Se, MnSe, AlN, and BN, which are substances that generally have extremely low solubility in steel. Is used. Recently, for the purpose of further enhancing the inhibitor function, for example, Japanese Patent Publication No. 60-48886 discloses that Cu or Sn is contained in steel.
Is added, and JP-A-2-115319 discloses Sb.
And methods for adding Mo have been proposed. As the form of the inhibitor, it is important to uniformly and finely disperse it. For this reason, conventionally, slab heating before hot rolling was heated to high temperature to completely dissolve the inhibitor,
A method is employed in which the inhibitor is finely dispersed and precipitated in the process from the hot rolling step to the secondary recrystallization.

As disclosed in Japanese Patent Application Laid-Open No. 51-41624, Bi has long been known as an element that is extremely effective in enhancing the function of an inhibitor.
Bi has an excellent effect as an inhibitory element of the inhibitor function, but has a defect that it inhibits formation of a forsterite film unique to grain-oriented electrical steel sheets. As a method for improving such coating defects, it is effective to add Cr to steel as described in JP-A-2000-96149, and it is possible to improve coating characteristics by this method. became.

However, when Cr is contained in the Bi-containing steel, not only the edge cracks in hot rolling are extremely increased, but also a new problem that stable and good magnetic properties cannot be obtained arises. Was. As for grain-oriented electrical steel sheets, not only magnetic properties but also inexpensive supply are strongly desired, and it is also an important issue to manufacture them with good production yield. From the viewpoint of improving the production yield, it is an important issue how to prevent the occurrence of edge cracks at the plate edge in hot rolling.

As a technique for reducing edge cracks in a grain-oriented electrical steel sheet to which Bi is added, for example, there are methods described in JP-A-6-179918 and JP-A-8-246055. JP-A-6-179918 is characterized in that the amount of S is reduced and the slab heating temperature is set to 1280 ° C. or less.
In this method, as described in JP-A-8-246055, the adjustment of the inhibitor becomes inappropriate, and excellent magnetic characteristics cannot be obtained. Japanese Patent Application Laid-Open No. Hei 8-246055 discloses a method of increasing the rate of temperature rise in a temperature range of 1250 ° C. or more in slab heating to reduce edge cracks by suppressing abnormal grain growth. According to the method, although some effect of reducing ear cracks was recognized, a sufficiently satisfactory effect could not be obtained. In addition, all of these technologies are those in which Cr is not added.
When Cr and Cr were added in combination, no effect of reducing ear cracking was observed.

[0008]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems. In the case of manufacturing a grain-oriented electrical steel sheet containing both Bi and Cr together with a known inhibitor, hot rolling is performed. An object of the present invention is to propose a method of effectively preventing the occurrence of edge cracks, which is sometimes concerned, and manufacturing a high magnetic flux density grain-oriented electrical steel sheet having good coating properties and excellent magnetic properties with a high production yield.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, to prevent the occurrence of edge cracks in a steel slab containing a complex of Bi and Cr, Before heating the slab to 1300 ° C or higher, the slab should be strained, and the rate of temperature rise in the high temperature range of 1300 ° C or higher should be reduced. We have found that lowering is effective. The present invention is based on the above findings.

That is, the gist of the present invention is as follows. 1. C: 0.03 to 0.10 mass%, Si: 2.5 to 4.5 mass%, B
i: 0.005 to 0.100 mass%, Cr: 0.010 to 0.500 mass
%, A steel slab having a composition containing other known inhibitor elements is subjected to a series of steps combining hot rolling, cold rolling and heat treatment. Before the start of rough rolling in the steel slab, the average oxygen concentration was 0.01 to 15 vol%
After heating in an atmosphere of less than 1300 ° C., a horizontal reduction with a reduction ratio of 1 to 20% and / or a width reduction with a reduction ratio of 1 to 20% are performed, and then an average oxygen concentration of 0.01 to 2 vol% High magnetic flux directionality with less edge cracks and good film properties, characterized by heating to 1350 ° C or more at a rate of temperature rise of 1300 ° C or less in atmosphere at a rate of 10 ° C / min or less. Manufacturing method of electrical steel sheet.

2. C: 0.03 to 0.10 mass%, Si: 2.5 to 4.
5 mass%, Mn: 0.05 to 1.5 mass%, Bi: 0.005 to 0.100
mass% and Cr: 0.010 to 0.500 mass%, and further, as an inhibitor element, S and / or Se: 0.01
0 to 0.040 mass%, sol.Al: 0.015 to 0.050 mass%,
B: 0.001 to 0.01 mass% and N: 0.005 to 0.015 mass
%, And as an inhibitor reinforcing element, Ni: 0.05-0.
5 mass%, Cu: 0.05-0.5 mass%, Sn: 0.05-0.5 mass
%, Sb: 0.005 to 0.10mass%, As: 0.005 to 0.10mass
%, Mo: 0.005 to 0.10mass%, Te: 0.005 to 0.10mass%
And P: a steel slab having a composition containing one or more selected from 0.005 to 0.10 mass% is hot-rolled, and if necessary, is subjected to hot-rolled sheet annealing; After performing cold rolling twice or more including intermediate annealing and finishing to the final sheet thickness, decarburizing annealing combined with primary recrystallization is performed, and then an annealing separator mainly composed of MgO is applied. Then, in a method for producing a grain-oriented electrical steel sheet comprising a series of steps of performing a final finish annealing consisting of a secondary recrystallization annealing and a purification annealing, the steel slab has an average oxygen concentration of 0.01% before starting rough rolling in hot rolling. 1300 ℃ in atmosphere of ~ 15 vol%
After heating to less than 1%, the horizontal reduction with a reduction rate of 1 to 20% and / or the width reduction with a reduction rate of 1 to 20% is performed, and then, in an atmosphere having an average oxygen concentration of 0.01 to 2 vol%, 1300 ° C or more. A method of producing a high magnetic flux density grain-oriented electrical steel sheet having a small edge crack and excellent coating properties and excellent magnetic properties, characterized by heating at a temperature of 1350 ° C. or more at a heating rate of 10 ° C./min or less.

3. C: 0.03 to 0.10 mass%, Si: 2.5 to 4.
5 mass%, Mn: 0.05 to 1.5 mass%, Bi: 0.005 to 0.100
mass% and Cr: 0.010 to 0.500 mass%, and further, as an inhibitor element, S and / or Se: 0.01
0 to 0.040 mass%, sol.Al: 0.015 to 0.050 mass% and N: 0.005 to 0.015 mass%, and as inhibitor reinforcing elements Ni: 0.05 to 0.5 mass%, Cu: 0.05 to 0.5 mass
s%, Sn: 0.05 to 0.5 mass%, Sb: 0.005 to 0.10 mass
%, As: 0.005 to 0.10mass%, Mo: 0.005 to 0.10mass
%, Te: 0.005 to 0.10 mass% and P: 0.005 to 0.10 ma
A steel slab having a composition containing one or more selected from ss% is hot-rolled, subjected to hot-rolled sheet annealing if necessary, pickled, and includes one or intermediate annealing After performing cold rolling two or more times to finish the final sheet thickness, decarburizing annealing also serving as primary recrystallization is performed, and then an annealing separator containing MgO as a main component is applied. In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of performing a final finish annealing consisting of crystal annealing and purification annealing, before starting rough rolling in hot rolling, the steel slab has an average oxygen concentration of 0.01 to 15%.
After heating to less than 1300 ° C in a vol% atmosphere, the rolling reduction is
After applying a horizontal reduction of 20% and / or a width reduction of a reduction ratio of 1 to 20%, an average oxygen concentration of 0.01 to 2 vol%
High flux density direction with less edge cracks and excellent coating properties, characterized by heating to a temperature of 1350 ° C or higher with a temperature rise rate of 1300 ° C or higher in an atmosphere of 1300 ° C or higher and 10 ° C / min or lower Manufacturing method of conductive electrical steel sheet.

4. C: 0.03 to 0.10 mass%, Si: 2.5 to 4.
5 mass%, Mn: 0.05 to 1.5 mass%, Bi: 0.005 to 0.100
mass% and Cr: 0.010 to 0.500 mass%, and further, as an inhibitor element, S and / or Se: 0.01
0 to 0.040 mass%, B: 0.001 to 0.01 mass% and N:
0.005 to 0.015 mass%, and as inhibitor inhibitor elements, Ni: 0.05 to 0.5 mass%, Cu: 0.05 to 0.5 mass%,
Sn: 0.05-0.5 mass%, Sb: 0.005-0.10 mass%, As:
0.005 to 0.10 mass%, Mo: 0.005 to 0.10 mass%, Te: 0.
A steel slab having a composition containing one or more selected from 005 to 0.10 mass% and P: 0.005 to 0.10 mass% is hot-rolled, and if necessary, hot-rolled sheet annealing is performed. After pickling, cold rolling is performed once or twice or more including intermediate annealing to finish the final sheet thickness, then decarburizing annealing also serving as primary recrystallization, and then annealing mainly containing MgO In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of applying a separating agent and then performing a final finish annealing consisting of a secondary recrystallization annealing and a purification annealing, the steel slab is subjected to hot rolling before starting rough rolling. After heating in an atmosphere having an average oxygen concentration of 0.01 to 15 vol% to less than 1300 ° C., a horizontal reduction with a reduction ratio of 1 to 20% and / or a width reduction with a reduction ratio of 1 to 20% are performed. In an atmosphere with an oxygen concentration of 0.01 to 2 vol%, the temperature rise rate at 1300 ° C or higher is 10 ° C / min. As below
A method for producing a high magnetic flux density grain-oriented electrical steel sheet, characterized by being heated to a temperature of 1350 ° C or higher and having small edge cracks and excellent coating properties and excellent magnetic properties.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an experiment on which the present invention is based and its results will be described. Experiment 1 First, the following experiment was conducted to clarify the effect of slab heating conditions on edge cracking in a hot rolling step of a steel slab containing Bi and Cr. Hereinafter, “%” used to indicate the content of each element indicates a mass percentage (mass%) unless otherwise specified. C: 0.08%, Si: 3.40%, Mn: 0.06%, Cu: 0.10%, S
e: 0.02%, N: 0.0090%, sol. Al: 0.027%, Cr: 0.2
A continuous cast slab of 220 mm thickness containing 0% and Bi: 0.030% was heated in a gas heating furnace at 1200 ° C for 60 minutes, and then a part of the slab was subjected to horizontal reduction at various reduction rates (normal (Pressure reduction in the thickness direction), and then charged into an induction heating furnace. Next, the temperature was raised to 1360 ° C. while changing the heating rate at 1300 ° C. or more in various ways. Then, rough rolling thickness: 45mm
Then, the occurrence of edge cracks was observed for a hot-rolled sheet having a thickness of 2.5 mm by finish rolling.

FIG. 1 shows the relationship between the slab heating conditions and the edge cracks of the hot-rolled sheet. As shown in the figure, the maximum depth of ear cracks when horizontal reduction was performed at a rolling reduction of 20% or less before high-temperature heating by an induction heating furnace and the heating rate at high temperatures of 1300 ° C or more was reduced. Was found to be smaller.

The mechanism for reducing the ear cracks is considered as follows. The edge cracks are generated by applying a tensile tension in the longitudinal direction to the edge of the sheet during hot rolling. At this time, it is considered that precipitates, crystal grain boundaries, and the like are the starting points of the cracks. By the way, when the slab is heated to a high temperature close to the melting point, if the temperature rising rate is high, the temperature becomes high in a state where inclusions and precipitates are not sufficiently dissolved in the matrix. As a result, the portion where the inclusions and precipitates are present and the periphery thereof locally have a composition different from that of the parent phase, and accordingly have a different melting point.
At this time, if the melting point is low, liquefaction occurs locally. As described above, when the rate of raising the temperature to a high temperature is high, liquefaction occurs locally, and the liquefaction is a starting point of the ear cracks, which easily causes ear cracks.

Particularly, in Bi-containing steel, Bi hardly forms a solid solution with iron, so that Bi is precipitated, and it is considered that other elements are easily precipitated with this Bi as a nucleus. Further, since Bi is an element that is easily segregated at the grain boundary, it is conceivable that Bi segregates at the interface between the precipitate and the mother phase, and the precipitate is hardly dissociated into a solid solution. Further, when Cr is added, the edge cracks are extremely deteriorated, and it is considered that this phenomenon becomes remarkable especially for Cr-based precipitates. For this reason, it is considered that liquefaction is apt to occur locally in steel containing Bi and Cr, and ear cracks are extremely deteriorated when the heating rate is high. Therefore, Cr and
For Bi-containing steel, improvement in ear cracking can be expected by slowing the rate of temperature rise at high temperatures.

However, as shown in the result of Experiment 1, this effect does not appear unless the slab is strained before high-temperature heating. This is because when the slab is heated to a high temperature without distortion, the crystal grains become coarse, the toughness is impaired and ear cracks are likely to occur, and large ear cracks occur even when the heating rate is slow. Conceivable. Therefore, in order to improve edge cracking, it is important to reduce the rate of temperature rise in a high temperature range while suppressing distortion by giving strain to the slab and suppressing crystal grain coarsening. However, if the amount of strain before heating at a high temperature is too large, ear cracks will also worsen. This is considered to be because a large amount of strain causes cracks on the end face, which tends to cause ear cracks.

Incidentally, the magnetic properties of the product sheet obtained by using the hot rolled sheet of the present experiment were almost deteriorated under the condition of a low heating rate. However, some materials showed good magnetic properties. Therefore, in order to elucidate the cause, a more detailed investigation was conducted on the heating conditions. As a result, it has been found that when the oxygen concentration in the heating atmosphere is low, good magnetic properties are exhibited. Then, the relationship between the heating atmosphere and the magnetic properties was investigated next.

Experiment 2 C: 0.08%, Si: 3.40%, Mn: 0.08%, Cu: 0.10%, S
e: 0.02%, N: 0.0085%, sol. Al: 0.027%, Cr: 0.2
Containing 5% and Bi: 0.040% Thickness: 210mm, Width: 12
A continuous casting slab of 00 mm is heated in a gas heating furnace at 1150 ° C for 80 minutes, and then subjected to a horizontal reduction at a reduction rate of 10%.
It was charged in an induction heating furnace. Then, it was heated to 1420 ° C. under two conditions of a heating rate of 1300 ° C. or more, 3 ° C./min and 15 ° C./min.
At this time, the oxygen concentration in the atmosphere of the heating furnace was variously changed. Thereafter, a sheet bar having a thickness of 35 mm was formed by rough rolling, and then a 2.3 mm hot-rolled sheet was formed by finish rolling. Investigation of the occurrence of edge cracks in the hot-rolled sheet obtained in this way showed that when the heating rate was 3 ° C / min, the maximum depth of the edge cracks was as good as 5 mm or less, whereas the heating rate was Is 15 ℃ / m
In the case of in, the maximum depth of the ear cracks was extremely bad at 40 mm or more.

Then, hot-rolled sheet annealing is performed at 1000 ° C. for 50 seconds, and after pickling, cold-rolled to an intermediate thickness of 1.7 mm, and then intermediate annealing at 1125 ° C. for 120 seconds and cooling at 35 ° C./s. After quenching at a high speed, a cold-rolled sheet having a final thickness of 0.22 mm was finished by cold rolling including warm rolling at 210 ° C. Thereafter, after decarburizing annealing at 840 ° C. for 120 seconds, an annealing separator containing MgO as a main component is applied at 7 g / m ² per side, and then heated to 850 ° C. at a rate of 8 ° C./h in a nitrogen atmosphere. And then at 10 ° C / h in an atmosphere of 25 vol% nitrogen and 75 vol% hydrogen
Was heated to 1200 ° C. at a heating rate of 5 ° C., and purification annealing was performed at 1200 ° C. for 5 hours in a hydrogen atmosphere.

The magnetic properties of the grain-oriented electrical steel sheet thus obtained and the amount of scale loss due to slab heating were investigated. The magnetic properties are as follows: magnetic flux density B ₈ (T) when magnetized at 800 A / m, frequency: 50 Hz, magnetic flux density: 1.7 T
_Was evaluated by the iron loss W _17/50 (W / kg). The scale loss was evaluated by the following formula (slab weight before heating the gas furnace-slab weight after induction heating) ス slab weight before heating the gas furnace × 100. The weight of the slab after induction heating was calculated from the sum of the weight of the hot rolled sheet and the weight of the portion cut during hot rolling by a crop shear or the like. The relationship between the oxygen concentration in the atmosphere in the heating furnace and the magnetic properties was determined by measuring the temperature rise
2 and 3 separately for the cases of / min and 15 ° C./min. Similarly, the scale loss ratio due to slab heating is shown in FIGS.

As shown in FIGS. 2 and 3, it can be seen that the magnetic properties deteriorate when the oxygen concentration in the heating atmosphere is high. In particular, when the heating rate is as low as 3 ° C./min, the magnetic properties are deteriorated even when the oxygen concentration in the induction heating furnace is 3 vol%. 4 and 5 that the scale loss rate is as high as 1% or more under the condition where the magnetic characteristics are deteriorated. In addition, as a result of analyzing the scale of the slab surface after induction heating under the condition where magnetic deterioration occurred, Bi and Cr
Was detected.

From the above, the causes of the deterioration of the magnetic characteristics are as follows.
It is considered as follows. During heating of the slab, Bi on the surface layer is removed together with the scale, and when the oxygen concentration in the atmosphere is high, Bi is removed.
The amount of decrease increases. In particular, when Cr is added, it is considered that the amount of scale generation increases due to the change in the scale composition of the surface layer, and the amount of Bi removed increases. As a result, it is considered that when the oxygen concentration in the atmosphere is high, the inhibitor strength is weakened and the magnetic properties are degraded. Also,
Even if the oxygen concentration in the atmosphere is the same, especially when the heating rate is low in a high temperature range of 1300 ° C or more, Bi is removed because the heating time becomes longer or the growth rate and structure of the scale change. It is considered that the amount increases, and as a result, the magnetic properties deteriorate.

Next, preferred conditions for manufacturing a grain-oriented electrical steel sheet which is the subject of the present invention will be described. First, the typical component composition ranges are as follows. Si: 2.5 to 4.5% Si is an effective component for increasing the specific resistance of steel sheet and reducing iron loss. However, if it exceeds 4.5%, the cold-rolling property is impaired, whereas if it is less than 2.5%, the specific resistance is reduced. Not only decreases, but also in the final finish annealing performed for secondary recrystallization and purification, α → γ transformation causes randomization of the crystal orientation, and a sufficient iron loss reduction effect cannot be obtained. Is 2.5-4.
Limited to the 5% range.

C: 0.03 to 0.10% The feature of the present invention is that the C content is 0.10% or less.
That is, if the C content exceeds 0.10%, the γ transformation amount becomes excessive, and the uniformity of the distribution of inhibitors such as MnSe and MnS precipitated during hot rolling is impaired. Further, the load of decarburization annealing increases, and poor decarburization easily occurs. On the other hand, if it is less than 0.03%, the effect of improving the structure cannot be obtained, and the secondary recrystallization is incomplete, and the magnetic properties are similarly deteriorated. Therefore, the C content is 0.03-0.10
%.

Bi: 0.005 to 0.100% In the Bi addition, which is one of the features of the present invention, Bi is 0.0
If it is less than 05%, the expected effect cannot be obtained, while if it exceeds 0.100%, uniform dispersion becomes difficult. Therefore, Bi is 0.005 ~
It is to be contained in the range of 0.100%.

Cr: 0.010 to 0.500% Since the Bi additive material inhibits the formation of a forsterite film, Cr is added for improvement. The effect is 0.010
% Is not sufficient. On the other hand, if the content exceeds 0.500%, the effect is saturated and the cost is increased.
Limited to the range of 0.500%.

Mn: 0.05 to 1.5% Mn needs to be at least about 0.05% in order to prevent hot brittleness. However, if the amount of Mn is too large, the magnetic properties deteriorate, so the upper limit is 1.5%. It is desirable to be about.

The inhibitor elements are as follows. S and / or Se: 0.010 to 0.040% Se or S can be contained alone or in combination as an inhibitor component. These components precipitate as Mn compounds or Cu compounds in steel, but a total content of 0.010% or more is required to maintain the suppression effect. on the other hand
If it exceeds 0.040%, even if the slab is heated at a high temperature, the solid solution cannot be completely formed and coarse precipitates are formed, which is rather harmful. Therefore, S and / or Se are 0.010 to 0.040.
% Range. At this time, if Mn / (Se + S) is smaller than 2.5, grain boundary cracks and edge roughness increase significantly during hot rolling, so that it is practically necessary to satisfy Mn / (Se + S) ≧ 2.5.

Sol.Al: 0.015 to 0.050% and / or B: 0.001 to 0.01% When the final cold rolling reduction is 80% or more, the secondary recrystallization temperature becomes extremely high. In addition to the elements, it is necessary to contain an inhibitor component that is stable at high temperatures, and Al, B, and N are suitable as such inhibitor components. Of these, Al needs to be contained as 0.015 to 0.050% as sol.Al (acid-soluble Al). Where the sol.Al content is
If the amount is less than 0.015%, it is difficult to uniformly disperse AIN in a size that functions as an inhibitor, which is not preferable. Further, it is necessary that B be contained in an amount of 0.001 to 0.01%. Here, when the content of B is less than 0.001%, the amount of precipitated BN is insufficient, so that a good secondary recrystallization cannot be obtained. Conversely, if it exceeds 0.010%, it is difficult to uniformly disperse the particles in a size that functions as an inhibitor, which is not preferable.

N: 0.005 to 0.015% N is a component constituting AlN and / or BN as a main inhibitor component, and must be contained at 0.005% or more. However, if the content exceeds 0.015%, it gasifies in the steel and causes defects such as blisters.
0.005 to 0.015% is to be contained.

Further, the inhibitor reinforcing elements are as follows. That is, Ni, Cu, Sn, Sb, Mo, As,
Since Te, P, and the like have an auxiliary function of enhancing the inhibitory power of known inhibitors, it is preferable to include them in steel as needed. About the suitable addition amount required for this,
Ni, Cu, Sn 0.05-0.50%, Sb, Mo, Te, As, P 0.0
It is between 0.05 and 0.10%. As for other additional elements, for example, Ge, Co, etc. are preferably contained as appropriate because they have an effect of improving the surface properties of the steel sheet.

Next, the manufacturing conditions according to the present invention will be specifically described. The molten steel adjusted to the preferable components described above is usually made into a steel slab by a continuous casting method or an ingot-bulking method. Then, after this steel slab is heated,
The hot-rolled coil is formed by hot rolling. At this time, it is important that the slab heating temperature be 1350 ° C. or higher. This is because if the slab heating temperature is lower than 1350 ° C., the solid solution of the inhibitor component is not sufficient, and fine uniform dispersion of the inhibitor such as Mn (Se, S), AlN cannot be obtained.

In this slab heating step, as described above, in order to prevent the Bi in the slab from decreasing during heating and to prevent the magnetic properties from deteriorating, the oxygen concentration must be 0.01 to 15 vol. Slab heating is performed in an atmosphere having an oxygen concentration of 0.01 to 2 vol. Here, the lower limit of the oxygen concentration in the atmosphere is set to 0.01 vol% because it is difficult to industrially realize it to be less than 0.01 vol%.

Further, in order to prevent edge cracks, before starting the rough rolling, after heating to less than 1300 ° C., a horizontal reduction with a reduction ratio of 1 to 20% and / or a width reduction with a reduction ratio of 1 to 20% are performed. After that, the heating rate at 1300 ° C or more is set to 10 ° C / min or less.
Heat above 1350 ° C. Here, if the rolling reduction under the horizontal reduction or the width reduction is less than 1%, the effect of preventing ear cracks is low.
These rolling reductions need to be 1% or more. Note that 13
The lower limit of the heating rate at 00 ° C or higher is not particularly specified, but long-time annealing increases the cost, so from the economical point of view it is 0.2 ° C.
/ min or more is preferable. Heating prior to horizontal or width reduction is 1000-
The temperature is preferably in the range of 1250 ° C. Thus, it is possible to effectively prevent the occurrence of edge cracks in hot rolling, which is a concern when adding Bi and Cr, and also to prevent the magnetic properties from deteriorating due to a decrease in the Bi content.

In the cold-rolling step, after the hot-rolled sheet is annealed, the sheet is subjected to a single cold-rolling method to make the final sheet thickness by one cold rolling, or, if necessary, to hot-rolled sheet annealing, followed by intermediate annealing. A cold rolling twice method of performing cold rolling two or more times between them can be adopted. As for the rolling reduction in the cold rolling, it is preferable that the first rolling in the two-time cold rolling method is about 15 to 60% as conventionally known. This is because when the rolling reduction is less than 15%, the mechanism of rolling recrystallization does not work and the crystal structure cannot be homogenized, whereas when it exceeds 60%, the texture is integrated and the second rolling This is because the effect cannot be obtained. Further, it is preferable that the rolling reduction of the final rolling is about 80 to 90%. This is because when the rolling reduction exceeds 90%, secondary recrystallization becomes difficult, while when the rolling reduction is less than 80%, good secondary recrystallized grain orientation cannot be obtained and the magnetic flux density of the product decreases. .

When the annealing temperature is excessively low in hot-rolled sheet annealing and intermediate annealing, the frequency of (110) grains serving as nuclei for secondary recrystallization in the recrystallized structure after rolling is insufficient, and good orientation is obtained. Cannot be obtained.
In order to obtain the strength of (110) grains, it is necessary to coarsen the crystal structure after annealing of the hot-rolled sheet to a certain size or more. For this purpose, it is essential to raise the temperature to 800 ° C. or more. On the other hand, as for the upper limit of the annealing temperature,
Since it is important that the inhibitors such as (Se, S) and AlN do not re-dissolve or grow Ostwald, annealing at 1200 ° C. or lower is preferable.

The cooling process of such annealing is not particularly limited, but a quenching treatment is performed to increase the solute C in the steel after annealing, or fine carbide is added to the steel. It is effective to perform a low-temperature holding treatment at about 300 ° C. after quenching in order to cause precipitation, in order to improve the magnetic properties of the product. A known means for increasing the oxidizing property of the annealing atmosphere and decarburizing the surface layer of the steel sheet is also effective. Also, the final cold rolling is performed at 100-350 ° C.
In addition, the texture of the primary recrystallization can be further improved by warm rolling at 100 ° C. or by adding an inter-pass aging treatment at 100 to 350 ° C. for 10 to 60 minutes. Furthermore, after the final cold rolling, it is also possible to perform a process of providing a linear groove on the surface of the steel sheet for magnetic domain refinement as is known.

Next, the steel sheet having the final thickness is subjected to decarburization annealing by a known method, and then an annealing separator containing MgO as a main component is applied to the surface of the steel sheet, and then subjected to final finish annealing. At this time, it is preferable to add a Ti compound or to include Ca or B in the annealing separator, since it has the effect of further improving the magnetic properties. In the final finish annealing, heated middle least 1050 ° C. or higher, for preferably at a temperature range of not lower than 900 ° C., it is necessary to raise the temperature in an atmosphere containing H _2. In other words, the H ₂ atmosphere has an important effect on the formation of oxides and nitrides in the film formed during the final annealing, and it is necessary to enhance the reducibility especially in the middle to late stages of annealing at 900 ° C or higher. Is valid. After the final finish annealing, after removing the unreacted annealing separator, an insulating coating is applied to the steel sheet surface to form a product, but if necessary, the steel sheet surface may be mirror-finished before coating, or A tension coating may be used as the insulating coating. Further, the coating and baking treatment of the coating may also serve as the flattening treatment. In addition, in order to obtain a further iron loss reduction effect on the steel sheet after the secondary recrystallization, a known domain refining treatment, that is, plasma jet or laser irradiation is applied to a linear region, or a linear dent due to a projection roll is formed. Processing for providing an area can also be performed.

[0041]

EXAMPLES Example 1 C: 0.07%, Si: 3.25%, Mn: 0.08%, Cu: 0.10%, S
e: 0.02%, N: 0.0088%, sol.Al: 0.027%, Cr: 0.0
2%, Sb: 0.03% and Bi: 0.03%, the balance being Fe
And the composition of unavoidable impurities thickness: 220 mm, width:
A continuous casting slab of 1200 mm was placed in a gas heating furnace and heated at 1200 ° C. for 70 minutes in an atmosphere having an oxygen concentration of 5 vol%. Then, after a width reduction was performed by a press machine, a horizontal reduction was performed by a horizontal roll, and then heating was performed to 1400 ° C. in an atmosphere having an oxygen concentration of 0.5 vol% in an induction heating furnace. At this time, the width reduction, the horizontal reduction, and the heating rate from 1300 ° C. to 1400 ° C. were variously changed. Then, rough rolling to a thickness of 40
mm and then finish rolling to 2.2 mm
A thick hot rolled sheet was used. Table 1 shows the results of observations on the occurrence of edge cracks in each of these hot-rolled sheet coils.

[0042]

[Table 1]

As shown in Table 1, according to the present invention, prior to the high-temperature heating in the induction heating furnace, a rolling reduction of 1% to 20% or a horizontal reduction was performed, and the temperature was raised from 1300 ° C. to 1400 ° C. The edge cracks of the hot-rolled sheet obtained at a temperature rate of 10 ° C./min or less were all slight.

Then, these hot rolled sheets were annealed at 1110 ° C. for 50 seconds, rapidly cooled at a rate of 30 ° C./s, pickled, and finished in a first cold rolling to a thickness of 1.5 mm. Then at 1130 ° C 70
After performing intermediate annealing for 2 seconds and quenching at a rate of 30 ° C / s,
It was finished to a thickness of 0.22 mm by warm rolling at 230 ° C. Thereafter, after degreasing, decarburization annealing was performed at 830 ° C. for 2 minutes in an atmosphere having a dew point of 58 ° C., a hydrogen concentration of 50 vol%, and a nitrogen concentration of 50 vol%. Then, MgO in Sr (OH) ₂ 2%, the TiO ₂ 5% on both sides of the steel sheet with an annealing separator agent added SrSO ₄ 2% was applied to one side of the coating amount as 6 g / m ^2, the final finishing As annealing, up to 850 ° C in N ₂ gas at a rate of 30 ° C / h, and from 850 ° C to 1050 ° C, N ₂ : 25 vol%, H ₂ : 75 vol%
Mixing at a rate of 12.0 ° C. / h in the gas, thereafter the of H ₂ gas
The temperature is raised to 1200 ° C at a rate of 25 ° C / h, maintained at 1200 ° C for 8 hours, and then lowered to 600 ° C in H ₂ gas.
The temperature dropped in Ar gas. After the final annealing as described above, the unreacted annealing separator is removed, and magnesium phosphate containing 50% colloidal silica is applied by tension coating, baked at 840 ° C for 30 seconds, and then magnetic domain refinement. A laser was irradiated at intervals of 7.5 mm as a treatment to obtain a product plate. As a result of examining the magnetic properties and coating properties of the product sheet thus obtained, both the magnetic properties and the coating properties were extremely good.

Example 2 C: 0.06%, Si: 3.3%, Mn: 0.08%, Cu: 0.15%, S
e: 0.02%, N: 0.0080%, sol. Al: 0.027%, Cr: 0.0
A continuous casting slab containing 2% and Bi: 0.03%, with the balance being Fe and inevitable impurities, having a thickness of 210 mm and a width of 1300 mm, was charged into a gas heating furnace at 1150 ° C for 80 minutes. After heating, the slab width is reduced to 1100mm under width pressure by a press
I made it. Next, the mixture was heated to 1400 ° C. in an induction heating furnace at a rate of 1300 ° C. or higher at 4 ° C./min. At this time, the oxygen concentration in the atmosphere of the gas heating furnace and the induction heating furnace was variously changed. Thereafter, a sheet bar having a thickness of 40 mm was obtained by rough rolling, and subsequently a hot-rolled sheet having a thickness of 2.0 mm was obtained by finish rolling. Then, these hot-rolled sheets were annealed at 1140 ° C for 80 seconds,
After quenching at a rate of ° C./s, it was pickled and finished to a thickness of 0.22 mm by a combination of cold rolling and warm rolling at 220 ° C. Then, after degreasing, decarburization annealing was performed at 850 ° C. for 3 minutes.

Then, 2% of SrSO ₄ and 5% of TiO ₂ were added to MgO.
Apply the added annealing separator to both sides of the steel sheet, and apply 8
g / m ^{2, and} as final finish annealing, up to 850 ° C. in N ₂ gas at a rate of 30 ° C./h, and from 850 ° C. to 1050 ° C .: N ₂ : 25 vol%, H ₂ : 75 vol. 12.5 ° C in a gas mixture of 1%
/ h, then 1200 ° C at a rate of 25 ° C / h in H ₂ gas
Until the temperature was raised, it was held 8 hours at 1200 ° C., H ₂ up to 600 ° C.
The temperature was lowered in the gas, and from 600 ° C., the temperature was lowered in the Ar gas. After the final annealing as described above, the unreacted annealing separator is removed, and magnesium phosphate containing 50% colloidal silica is applied by tension coating and then applied at 840 ° C.
Bake for 30 seconds to make a product plate. Table 2 shows the results obtained by examining the magnetic properties of the product sheet thus obtained.

[0047]

[Table 2]

As shown in Table 2, according to the present invention, a product plate obtained by reducing the oxygen concentration in the gas heating furnace atmosphere to 15 vol% or less and the oxygen concentration in the induction heating furnace to 2 vol% or less. All had good magnetic properties.

Example 3 Molten steel having the composition shown in Table 3 was formed into a slab having a thickness of 230 mm and a width of 1300 mm by continuous casting. This slab was placed in an atmosphere with an oxygen concentration of 5 vol% in a gas heating furnace at 1120%.
After heating at 90 ° C for 90 minutes, the slab width was reduced to 1100mm under width pressure by a press machine, and then reduced to 210mm thickness by horizontal pressure reduction. Then, in an atmosphere with an oxygen concentration of 0.5vol% in an induction heating furnace.
Heated to 1390 ° C. At this time, 1300 in induction heating furnace
The temperature rising rate from 1 ° C. to 1360 ° C. was 5 ° C./s. afterwards,
A sheet bar having a thickness of 35 mm was obtained by rough rolling, followed by finish rolling to obtain a hot-rolled sheet of 2.4 mm. At this time, the maximum depth of the ear cracks of all the materials was as good as 5 mm or less. Then, the steel sheet was annealed at 1100 ° C. for 50 seconds, rapidly cooled at a rate of 40 ° C./s, pickled, and finished in a first cold rolling to a thickness of 1.7 mm. Then, intermediate annealing is performed at 1120 ° C for 70 seconds,
It was quenched at a rate of 30 ° C./s. Then, at 250 ℃ warm rolling
Finished 0.22mm thick. After degreasing,
Decarburization annealing was performed at 820 ° C. for 3 minutes in an atmosphere having a dew point of 60 ° C., a hydrogen concentration of 60 vol%, and a nitrogen concentration of 40 vol%.

[0050] Next, 2% Sr (OH) ₂ to MgO, the TiO ₂ 5
%, SrSO ₄ 2% added annealing separator on both sides of steel plate
The coating amount was 6 g / m ^{2 on} one side, and the final finishing annealing was performed up to 850 ° C in N ₂ gas at a rate of 30 ° C / h.
From 50 ° C to 1050 ° C, at a rate of 12.0 ° C / h in a mixed gas of N ₂ : 25 vol% and H ₂ : 75 vol%, and then 25 ° C in H ₂ gas
The temperature was raised to 1200 ° C. at a rate of / h, maintained at 1200 ° C. for 8 hours, then lowered to 600 ° C. in H ₂ gas, and from 600 ° C. in Ar gas. After the final annealing as described above, the unreacted annealing separator is removed, and magnesium phosphate containing 50% colloidal silica is applied by tension coating, baked at 840 ° C for 30 seconds, and then magnetic domain refinement. A laser was irradiated at intervals of 7.5 mm as a treatment to obtain a product plate.
Table 4 shows the results obtained by examining the magnetic properties and coating properties of the product sheet thus obtained.

[0051]

[Table 3]

[0052]

[Table 4]

As shown in Table 4, the magnetic properties and the coating properties of the product plate obtained according to the present invention were both very good.

[0054]

As described above, according to the present invention, it is possible to stably produce a high magnetic flux density electromagnetic steel sheet having extremely excellent magnetic properties, having little occurrence of edge cracks in hot rolling, and having good coating properties. Obtainable.

[Brief description of the drawings]

[Fig.1] Horizontal rolling reduction before high temperature heating and 1300 ℃ to 1360 ℃
FIG. 4 is a diagram showing the effect of the temperature raising rate during the period on the edge cracking in hot rolling.

[Figure 2] The rate of temperature rise between 1300 ℃ and 1420 ℃ is 3 ℃ / min
FIG. 4 is a diagram showing the influence of the atmosphere oxidation concentration in a gas heating furnace and the atmosphere oxidation concentration in an induction heating furnace on the magnetic flux density under the conditions described in FIG.

[Figure 3] The heating rate between 1300 ℃ and 1420 ℃ is 15 ℃ / min
FIG. 4 is a diagram showing the influence of the atmosphere oxidation concentration in a gas heating furnace and the atmosphere oxidation concentration in an induction heating furnace on the magnetic flux density under the conditions described in FIG.

Fig. 4 Temperature rise rate between 1300 ℃ and 1420 ℃ is 3 ℃ / min
FIG. 4 is a diagram showing the influence of the atmospheric oxidation concentration in the gas heating furnace and the atmospheric oxidation concentration in the induction heating furnace on the scale loss under the conditions described in FIG.

[Figure 5] The heating rate between 1300 ℃ and 1420 ℃ is 15 ℃ / min
FIG. 3 is a diagram showing the effect of the atmospheric oxidation concentration in a gas heating furnace and the atmospheric oxidation concentration in an induction heating furnace on scale loss under the following conditions.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshito Takamiya 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. 1-chome (without address) Kawasaki Steel Corporation Mizushima Works F-term (reference) 4K033 AA02 BA01 BA02 CA01 CA02 CA03 CA04 CA06 CA07 CA08 FA01 FA05 FA13 HA01 HA02 HA03 HA04 HA06 JA04 LA01 MA03 PA06 PA08 PA09 RA04 SA02 SA03 TA01 TA04 TA06 TA07 5E041 AA02 AA19 BC01 CA02 HB05 HB07 HB11 HB14 NN01 NN17 NN18

Claims (4)

[Claims] 1. C: 0.03 to 0.10 mass%, Si: 2.5 to 4.5
mass%, Bi: 0.005 to 0.100 mass%, Cr: 0.010 to 0.50
In a method for producing a grain-oriented electrical steel sheet, a steel slab having a composition containing 0 mass% and other known inhibitor elements is subjected to a series of steps combining hot rolling, cold rolling and heat treatment. Before starting the rough rolling in the hot rolling, the steel slab is heated to less than 1300 ° C. in an atmosphere having an average oxygen concentration of 0.01 to 15 vol%, and then a horizontal reduction of 1 to 20% and / or a reduction of 1 to 20%. After applying a 20% width pressure, it is further heated in an atmosphere with an average oxygen concentration of 0.01 to 2 vol% at a temperature rising rate of 1300 ° C or more at a temperature rising rate of 10 ° C / min or less to 1350 ° C or more. A method for producing a high magnetic flux density grain-oriented electrical steel sheet having excellent edge-to-edge cracking and good magnetic properties. 2. C: 0.03 to 0.10 mass%, Si: 2.5 to 4.5
mass%, Mn: 0.05 to 1.5 mass%, Bi: 0.005 to 0.100 mas
s% and Cr: 0.010 to 0.500 mass%, and as an inhibitor element, S and / or Se: 0.010
-0.040 mass%, sol.Al: 0.015-0.050 mass%, B:
0.001 to 0.01 mass% and N: 0.005 to 0.015 mass%
And as an inhibitor reinforcing element, Ni: 0.05 to 0.5
mass%, Cu: 0.05-0.5 mass%, Sn: 0.05-0.5 mass
%, Sb: 0.005 to 0.10mass%, As: 0.005 to 0.10mass
%, Mo: 0.005 to 0.10mass%, Te: 0.005 to 0.10mass%
And P: a steel slab having a composition containing one or more selected from 0.005 to 0.10 mass% is hot-rolled, and if necessary, is subjected to hot-rolled sheet annealing; After performing cold rolling twice or more including intermediate annealing and finishing to the final sheet thickness, decarburizing annealing combined with primary recrystallization is performed, and then an annealing separator mainly composed of MgO is applied. Then, in a method for producing a grain-oriented electrical steel sheet comprising a series of steps of performing a final finish annealing consisting of a secondary recrystallization annealing and a purification annealing, the steel slab has an average oxygen concentration of 0.01% before starting rough rolling in hot rolling. After heating to less than 1300 ° C. in an atmosphere of vol15 vol%, a horizontal reduction of a reduction rate of 1-20% and / or a width reduction of a reduction rate of 1-20% are performed, and then an average oxygen concentration of 0.01- In a 2 vol% atmosphere, the rate of temperature rise above 1300 ° C was set to 10 ° C / min or less. A method for producing a high magnetic flux density grain-oriented electrical steel sheet, characterized by heating to a temperature of 50 ° C. or higher, having less cracks in the edges and excellent magnetic properties with good coating properties. 3. C: 0.03 to 0.10 mass%, Si: 2.5 to 4.5
mass%, Mn: 0.05 to 1.5 mass%, Bi: 0.005 to 0.100 mas
s% and Cr: 0.010 to 0.500 mass%, and as an inhibitor element, S and / or Se: 0.010
-0.040 mass%, sol.Al: 0.015-0.050 mass% and N: 0.005-0.015 mass%, and Ni: 0.05-0.5 mass%, Cu: 0.05-0.5 mass as an inhibitor reinforcing element.
%, Sn: 0.05-0.5 mass%, Sb: 0.005-0.10mass%,
As: 0.005 to 0.10mass%, Mo: 0.005 to 0.10mass%, T
e: 0.005 to 0.10 mass% and P: 0.005 to 0.10 mass%
A steel slab having a composition containing one or more selected from the above is hot-rolled, subjected to hot-rolled sheet annealing if necessary, pickled, and then once or twice including intermediate annealing After performing the above cold rolling to finish to the final sheet thickness, decarburizing annealing also serving as primary recrystallization is performed, and then an annealing separator containing MgO as a main component is applied, and then secondary recrystallization annealing is performed. And a method of manufacturing a grain-oriented electrical steel sheet comprising a series of steps of performing a final finish annealing including a purification annealing, wherein before starting rough rolling in hot rolling, the steel slab is placed in an atmosphere having an average oxygen concentration of 0.01 to 15 vol%. After heating to a temperature of less than 1300 ° C., a horizontal reduction with a reduction ratio of 1 to 20% and / or a width reduction with a reduction ratio of 1 to 20% are performed. Heat to a temperature of 1350 ° C or more with a temperature rise rate of 10 ° C / min or less at a temperature of 10 ° C or more A method for producing a high magnetic flux density grain-oriented electrical steel sheet, characterized by having small edge cracks and excellent coating properties and excellent magnetic properties. 4. C: 0.03 to 0.10 mass%, Si: 2.5 to 4.5 m
ass%, Mn: 0.05 to 1.5 mass%, Bi: 0.005 to 0.100 mas
s% and Cr: 0.010 to 0.500 mass%, and as an inhibitor element, S and / or Se: 0.010
0.040 mass%, B: 0.001 to 0.01 mass% and N: 0.
005 to 0.015 mass%, and as inhibitor reinforcing elements, Ni: 0.05 to 0.5 mass%, Cu: 0.05 to 0.5 mass%, S
n: 0.05 to 0.5 mass%, Sb: 0.005 to 0.10 mass%, As:
0.005 to 0.10 mass%, Mo: 0.005 to 0.10 mass%, Te: 0.
A steel slab having a composition containing one or more selected from 005 to 0.10 mass% and P: 0.005 to 0.10 mass% is hot-rolled, and if necessary, hot-rolled sheet annealing is performed. After pickling, cold rolling is performed once or twice or more including intermediate annealing to finish the final sheet thickness, then decarburizing annealing also serving as primary recrystallization, and then annealing mainly containing MgO In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of applying a separating agent and then performing a final finish annealing consisting of a secondary recrystallization annealing and a purification annealing, the steel slab is subjected to hot rolling before starting rough rolling. After heating in an atmosphere having an average oxygen concentration of 0.01 to 15 vol% to less than 1300 ° C., a horizontal reduction with a reduction ratio of 1 to 20% and / or a width reduction with a reduction ratio of 1 to 20% are performed. 10 ° C / mi at a temperature rise rate of 1300 ° C or more in an atmosphere with an oxygen concentration of 0.01 to 2 vol% A method for producing a high magnetic flux density grain-oriented electrical steel sheet having small edge cracks and excellent coating properties and excellent magnetic properties, characterized by heating to a temperature of 1350 ° C. or more, where n is not more than n.