JP2003027139A - Method for manufacturing grain-oriented electrical steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively solve the problem of coil set being an obstacle to magnetic properties, punching and coating when manufacturing a product of grain- oriented electrical steel sheet which is free from undercoat film composed essentially of forsterite and has excellent magnetic properties and punchability by means of low-temperature final finish annealing at <=1,050 deg.C using a stock having inhibitor-free high-purity components. SOLUTION: The inside diameter of a coil at coiling before finish annealing is made to >=150 mm radius, and the coil after the finish annealing is continuously annealed at 800-1,000 deg.C to undergo flattening.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet mainly used as an iron core material for a small motor or a generator, and in particular, in the flattening annealing, the winding tendency of the coil is advantageously eliminated, and It is used to prevent deterioration of characteristics and punchability.

[0002]

2. Description of the Related Art An EI type core as shown in FIG. 1 is widely used as a typical shape of a small transformer used by laminating electromagnetic steel sheets. This EI type core is known as an efficient processing method in which the amount of scrap generated during punching is small. The flow of magnetic flux in the EI core is about 20% in the area perpendicular to the rolling direction, but about 80% is in the rolling direction. Therefore, using the grain-oriented electrical steel sheet is far better than using the non-oriented electrical steel sheet. Good magnetic properties can be obtained.
For this reason, grain-oriented electrical steel sheets are used in many cases where iron loss is important.

On the surface of the grain-oriented electrical steel sheet, an undercoat (glass coating) mainly composed of forsterite (Mg ₂ SiO ₄ ) is usually formed. Since this forsterite coating is significantly harder than the semi-organic / resin-based coating applied to the non-oriented electrical steel sheet, the die for punching is greatly worn. For this reason, re-polishing or replacement of the mold becomes frequent, resulting in a decrease in work efficiency and a cost increase at the time of processing a core by a customer. Further, the slitting property and the shearing property are similarly deteriorated due to the presence of the forsterite coating.

As a method of improving the punching workability of the grain-oriented electrical steel sheet, it is possible to remove the undercoat by pickling or a mechanical method, but not only the cost becomes high, but also the surface quality deteriorates. There is a big problem that the magnetic characteristics are also deteriorated. Further, Japanese Patent Publication No. 6-49948 and Japanese Patent Publication No. 6-
Japanese Patent No. 49949 discloses a technique for suppressing the formation of forsterite by compounding an annealing separator mainly composed of MgO, and Japanese Patent Application Laid-Open No. 8-134542 discloses silica containing Mn as a material. , A technique for suppressing the formation of forsterite by applying an annealing separator mainly composed of alumina has been proposed. However, in these methods, forsterite is often partially formed due to the change in the finish annealing atmosphere between the layers of the coil, and it is extremely difficult to obtain a product plate in which the formation of the undercoat is completely suppressed. .

In view of this point, the inventors of the present invention previously disclosed a technique for expressing secondary recrystallization in a high-purity material containing no inhibitor component by utilizing the effect of suppressing the grain boundary migration of solid solution N. -129356. In addition,
2001-32021 has proposed a technique for suppressing the formation of an oxide film by making the atmosphere in the recrystallization annealing low oxidative by using a C-reduced component. With these techniques, it has become possible to inexpensively manufacture a grain-oriented electrical steel sheet that does not form forsterite.
Since such a grain-oriented electrical steel sheet does not have a hard undercoat on the surface, it is advantageously suitable for a small electric device such as an EI type core that emphasizes punching workability.

[0006]

However, in the above technique, although there is no hard undercoat on the surface of the plate after final finish annealing for the purpose of secondary recrystallization, it is generated by annealing in the coil shape. In the flattening annealing that corrects the winding tendency, it was revealed that the flexibility was extremely poor.
Flattening annealing is generally annealed for a short period of time continuously, and at the same time, an insulating coating is applied, but if the curl is insufficiently corrected, not only the deterioration of magnetic properties but also
It causes serious troubles such as uneven coating at the time of coating and defective threading in the punching process.

Various improvements have been made to the flattening annealing technique. For example, in Japanese Patent Laid-Open No. 4-83825, there is a method of setting the tension during annealing to 0.35 kg / mm ² or more.
Japanese Patent Laid-Open No. 19 proposes a method of setting the tension to 0.35 kg / mm ² or less by equipping a special hearth roll facility. However, all of the conventional methods are intended for materials having an undercoat that has been annealed at high temperature in final finish annealing,
Subjected to secondary recrystallization annealing at 1050 ° C or less as in the present invention,
The technical scope of the material is completely different from that of a material having no undercoat.

The present invention has been developed in view of the above-mentioned current situation, and by advantageously improving the flexibility of a material having no undercoat after the final finish annealing for the purpose of secondary recrystallization. An object of the present invention is to propose an advantageous method for producing a grain-oriented electrical steel sheet capable of effectively correcting a curl in flattening annealing for a short time.

[0009]

[MEANS FOR SOLVING THE PROBLEMS] The clarification process of the present invention will be described below. Mass%, C: 0.0020%, Si: 3.4
%, Mn: 0.07%, Sb: 0.04%, sol.Al: 50ppm, N: 15
ppm, other components: A steel material containing no inhibitor component reduced to 30 ppm or less was heated to 1100 ° C and then hot-rolled to form a hot-rolled sheet having a thickness of 2.5 mm. Then, this hot rolled sheet was soaked in a nitrogen atmosphere at 900 ° C. for 1 minute and then rapidly cooled, and cold rolled to a final sheet thickness of 0.30 mm. The obtained steel sheet was sheared to an Epstein size of length: 280 mm, width: 30 mm, and further hydrogen: 50 vol%, nitrogen:
Primary recrystallization annealing was performed at 950 ° C for 30 seconds in an atmosphere of 50 vol% and dew point: -30 ° C. In the final finish annealing, the sample is sandwiched between dies with various radii of curvature for the purpose of intentionally giving curl, and the holding temperature: 900 ℃ in a nitrogen atmosphere with a dew point of -20 ℃. Up to 30 ℃ / h
After holding at 900 ° C for 50 hours, the furnace was cooled at a rate of 30 ° C / h.
As a comparative material, after holding at 900 ° C for 50 hours,
The material was heated to 1200 ° C., held at this temperature for 5 hours, and then furnace-cooled to prepare a material. At this time, a material having a forsterite coating was inserted between the samples in order to prevent fusion of the samples. The thus obtained sample with curl was soaked at a temperature corresponding to flattening annealing for 2 minutes and flattened by its own weight.
The measurement of the plate warp due to the curl was performed according to the curl measuring method of JIS C 2550.

FIG. 2 shows the results of an examination of the relationship between the flattening temperature of the 900 ° C. holding material and the radius of curvature of the mold. In addition,
In this test, if the warp of the plate due to the curl exceeds 5 mm, it was considered that the shape correction was insufficient. By the way, the certainty of the tendency was confirmed by identifying the condition that the warp exceeds 10 mm. As shown in the figure, if the radius of curvature of the mold is small, a high flattening temperature is required to correct the curl,
It can be seen that the flattening temperature can be lowered as the radius of curvature of the mold is increased. Incidentally, in the case of the comparative material which was finally heated to 1200 ° C, the warpage was 5 mm or less at 700 ° C or higher regardless of the radius of curvature of the mold.

The reason why the result as shown in FIG. 2 is obtained is not clear, but it is different from the case of annealing at a high temperature exceeding 1050 ° C. after secondary recrystallization like a normal grain-oriented electrical steel sheet. Differently, it is considered that the flexibility was poor due to the high dislocation density in the steel sheet. That is, when the secondary recrystallized crystal grains are flattened with a steel plate having a curvature,
The crystal orientation gradually changes within the same crystal grain. At this time, dislocations are introduced or moved and rearranged in order to mitigate the change in crystal orientation within the same grain. However, when the dislocation density in the steel sheet before flattening annealing is high,
It is presumed that the above-mentioned dislocation introduction and migration rearrangement are incomplete during the flattening annealing, resulting in insufficient shape correction.

Therefore, in the manufacturing method in which the high temperature finish annealing exceeding 1050 ° C. is not performed, the final finish annealing in the coil shape is at least 150 mm at the inner diameter portion having the smallest coil curvature in consideration of the subsequent flattening annealing. It is necessary to have the above curvature. Further, it is preferable to set the temperature to at least 800 ° C. or more in the flattening annealing for a short time within about 2 minutes.

As an invention in which the inner diameter of the coil is limited, Japanese Patent Application Laid-Open No. 49-27421 has already disclosed a method of making the diameter 600 mm or more (radius 300 mm or more).
However, this proposal is a method aimed at improving the orientation of the secondary recrystallized grains, relates to a conventional manufacturing technique for forming an undercoat by high temperature annealing, and the new problem raised by the present invention is The technical scope is completely different.

Further, from the viewpoint of cost reduction and energy saving, it was considered effective to apply tension to lower the flattening temperature. Therefore, a mold having a radius of curvature of 150 mm was used. A sample having a curl was prepared by an experiment, and tension was applied to one end of the sample to perform soaking for 2 minutes at a temperature corresponding to flattening annealing. FIG. 3 shows the results of the investigation on the effect of tension on the plate warp. As shown in the figure, it is understood that the flattening temperature can be lowered by applying a tension of 1 MPa or more to the sample.

Further, the inclusion of Sb or Sn in the material is effective in suppressing the fusion of the steel sheets during finish annealing and preventing defects such as defects caused by the fusion. It has been found that there is an advantage that it can be omitted or used in a small amount. Moreover, it was also effective in suppressing the surface oxidation and nitriding during the finish annealing and stabilizing the secondary recrystallization. The present invention is based on the above findings.

That is, the gist of the present invention is as follows. 1. A steel material for grain-oriented electrical steel, which contains Si in the range of 2.0 to 8.0 mass% and does not contain an inhibitor component, is hot-rolled, cold-rolled to a final thickness, and then subjected to primary recrystallization annealing. Then, after winding it into a coil, 800 ~
It is excellent in magnetic properties and punching workability because it has no undercoating (glass coating) mainly composed of forsterite (Mg ₂ SiO ₄ ) by subjecting to secondary recrystallization after finishing annealing at 1050 ° C for 5 hours or more. When manufacturing a grain-oriented electrical steel sheet, the coil inner diameter before winding into a coil before finish annealing should be ≥150 mm, and the coil after finish annealing should be
A method for producing a grain-oriented electrical steel sheet, which comprises flattening by continuous annealing in a temperature range of 800 to 1000 ° C.

2. A steel material for grain-oriented electrical steel, which contains Si in the range of 2.0 to 8.0 mass% and does not contain an inhibitor component, is hot-rolled, cold-rolled to a final thickness, and then subjected to primary recrystallization annealing. Then, after winding it into a coil, it is subjected to final annealing at 800 to 1050 ° C for 5 hours or more and secondary recrystallization to give forsterite (Mg
_{2 When} manufacturing a grain-oriented electrical steel sheet that does not have an underlying coating (glass coating) mainly composed of SiO ₄ ) and has excellent magnetic properties and punching workability, before finishing annealing, coil inner diameter when wound into a coil A grain-oriented electrical steel sheet characterized in that the coil after finish annealing is flattened by continuous annealing in a temperature range of 700 to 1000 ° C and a tension applied to the steel sheet of 1 to 15 MPa, while making it ≥150 mm. Manufacturing method.

3. In the above 1 or 2, the steel material is
A method for producing a grain-oriented electrical steel sheet, which further comprises a composition containing Sb and / or Sn: 0.01 to 0.50 mass%.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION First, the reason why the composition of the steel material is limited to the above range in the present invention will be explained. In addition, unless otherwise indicated, "%" display regarding components means mass% (mass%). Si: 2.0 to 8.0% Si is an element useful for increasing the electric resistance of steel and improving iron loss, so it is contained at 2.0% or more. However, if the content exceeds 8.0%, the workability is remarkably reduced and cold rolling becomes difficult. Therefore, the Si content is limited to the range of 2.0 to 8.0%.

In the present invention, it is only necessary for Si to be contained within the above range, and an inhibitor component is not required. The term "inhibitor component" as used herein refers to Se, S, Mn, Al, N, etc. used for forming dispersed precipitates called so-called main inhibitors such as MnSe, MnS, AlN.

As described above, according to the present invention, Si is 2.0 to 8.0.
%, And any conventionally known one is suitable as long as it does not contain an inhibitor component in an amount that requires high temperature finish annealing, but the representative compositions are as follows. C: 0.10% or less When the C content exceeds 0.10%, magnetic aging does not occur 0.005
It takes a long time to reduce the content to 0.1% or less, and productivity is impaired. Therefore, the content is preferably 0.10% or less. In particular, in order to omit decarburization annealing and obtain a smooth product surface, it is necessary to reduce it to 0.005% or less at the material stage.

Mn: 0.01-2.0% Mn is required for stable and good secondary recrystallization.
Addition of 0.01% or more is desirable, but if it exceeds 2.0%, the magnetic flux density decreases, so the amount of Mn is preferably 0.01 to 2.0%.

S, Se: 0.010% or less Since S and Se combine with Mn to form Mn (S, Se),
In the method of omitting high temperature finish annealing as in the present invention, the smaller the number, the more preferable. Therefore, it is desirable that the content of each is 0.010% or less, preferably 0.005% or less.

Sol.Al: 0.001 to 0.02% sol.Al allows a slight amount of Al to remain as an excess of Al used for adjusting oxygen in steel during refining to 0.005% or less. Since it has a function of suppressing the formation of Si nitride and preventing nitriding in the final finish annealing at 0.
You may contain 001% or more, preferably 0.002% or more. However, if it exceeds 0.02%, the final finish annealing temperature for causing secondary recrystallization becomes high, so the upper limit is made 0.02% or less, preferably 0.015% or less.

N: 0.005% or less N, like C, causes magnetic aging and deteriorates iron loss, so it is necessary to set it to 0.005% or less, but it is possible to increase it by the equivalent amount depending on the amount of sol.Al. Is. For example, sol.Al
The equivalent N of 0.010% is 0.005%, so at this time N
Can be increased to 0.010%.

Sb and / or Sn: 0.01 to 0.50 mass% In the present invention, Sb or Sn can be added as a means for suppressing nitriding during finish annealing. Both are 0.
The content of 01% or more has the effect of suppressing surface oxidation and nitridation during final refining and stabilizing secondary recrystallization, but if it exceeds 0.50%, it tends to become brittle, so 0.01-0.50% It is preferably within the range. The surface oxidation suppressing effect of Sb, Sn is effective in suppressing fusion of the steel sheets during finish annealing, and is also effective in preventing defects such as flaws due to fusion, so whether or not a pure separation agent is used, Alternatively, there is an advantage that the amount used is small.

In addition, Ti, Nb, which are nitride forming elements,
Reducing each of B, Ta and V to 0.005% or less is also effective in preventing iron loss deterioration and ensuring workability. Further, Ni can be added in order to improve the structure of the hot rolled sheet and improve the magnetic properties. However, if the addition amount is less than 0.005%, the effect of improving the magnetic properties is small, while if it exceeds 1.50%, secondary recrystallization becomes unstable and the magnetic properties deteriorate, so the Ni content should be about 0.005 to 1.50%. Is preferred. Furthermore, for the purpose of improving iron loss,
Cu: 0.01 to 1.50%, P: 0.005 to 0.50%, Cr: 0.01 to 1.
One kind or two kinds or more selected from 5% may be appropriately added.

Next, the manufacturing method of the present invention will be described. Molten steel adjusted to the above-mentioned preferred component composition is smelted by a known method using a converter, an electric furnace, etc., and if necessary subjected to vacuum treatment, etc., then using a usual ingot making method or continuous casting method. Manufacture slabs. Also, using direct casting method, 100
You may directly manufacture the thin slab with a thickness of less than mm. The slab is heated by a usual method and hot-rolled, but it may be directly subjected to hot rolling without heating after casting. Further, in the case of a thin cast piece, hot rolling may be performed, or hot rolling may be omitted and the process may be directly performed.

There are no particular restrictions on the conditions for hot rolling of the slab, and it may be carried out under general conditions, but the range of normal hot rolling, for example, the heating temperature of the slab is about 1000 to 1250 ° C., and the final hot rolling is performed. It is desirable to finish hot rolling at a temperature of 700 to 1000 ° C. Then, hot-rolled sheet annealing is performed if necessary. In order to highly develop a specific structure such as a Goss orientation or a cube orientation and a mixed orientation thereof in a product sheet, the hot rolled sheet annealing temperature is preferably 800 ° C or higher and 1100 ° C or lower. This is because the hot-rolled sheet annealing temperature is 800
Below 100 ℃, band structure remains in hot rolling, while at 1100 ℃
If it exceeds, the grain size of the hot-rolled sheet after refining becomes too coarse and the development of the secondary recrystallized structure of each product sheet decreases, and the magnetic flux density decreases.

After the hot-rolled sheet has been annealed, if necessary, one or more cold-rollings with an intermediate anneal sandwiched therebetween, and then a primary recrystallization anneal,
At the same time, if C content is 0.005% or more, decarburization is performed to 0.005% or less, preferably 0.003% or less, where magnetic aging does not occur. The above-mentioned cold rolling may be performed by raising the rolling temperature to 100 to 300 ° C, or performing the aging treatment in the range of 100 to 300 ° C once or plural times during the cold rolling. It is effective in developing a recrystallized structure. At this time, it is effective that the final cold rolling reduction is 50% or more in order to improve the texture after recrystallization.

After the final cold-rolling, the primary recrystallized net is 8000 to 10
It is suitable to carry out in the temperature range of 00 ° C. Also, the atmosphere of the primary recrystallization annealing is a non-oxidizing atmosphere having a dew point of 0 ° C. or less, and suppressing the generation of surface oxides as much as possible is useful for maintaining a smooth surface and obtaining good iron loss. Is. In addition, after the final cold rolling or after the recrystallization annealing, a technique of increasing the Si content in the steel by a siliconizing method may be used together. After that, the calcined pure fiber agent is applied if necessary, and it is effective to sufficiently dry it for the purpose of suppressing the oxide formation without introducing moisture even when the calcined fiber pure agent is applied. In particular
When Sb or Sn is contained, the application of the calcined pure separating agent can be almost omitted, or only a small amount can be used.

Next, final finishing annealing is carried out. The atmosphere in this final finishing annealing is effective to develop secondary recrystallization due to the effect of suppressing the grain boundary migration of solid solution N as the atmosphere containing nitrogen. Is. Further, in order to suppress oxide formation, it is preferable to introduce a non-oxidizing atmosphere gas having a dew point of 0 ° C. or less into the furnace. Because the dew point is 0
This is because if the temperature exceeds ℃, not only the iron loss is deteriorated due to an increase in the amount of surface oxides generated, but also the punchability is significantly deteriorated. Further, the final finish annealing needs to be performed at 800 ° C. or higher in order to develop the secondary recrystallization, but the heating rate up to 800 ° C. does not have a great influence on the magnetic properties, so any condition may be used. The maximum reached temperature is required to be a temperature at which secondary recrystallization is finished well, but it is necessary to be 1050 ° C. or lower from the viewpoint of suppressing the formation of oxides, and preferably
It is desirable to keep the temperature below 1000 ° C. Further, if the holding time at this temperature is less than 5 hours, an incomplete secondary recrystallized structure may be partially formed. Therefore, it is preferable to hold the material for at least 5 hours. The longer the retention time, the more dislocations may disappear and the flexibility may improve. Therefore, the upper limit is not set. However, considering productivity, the limit is about 200 hours.

Then, after the above-mentioned finish annealing, flattening annealing is performed to correct the shape of the steel sheet. In the conventional technique using the inhibitor, low iron loss could not be obtained unless the inhibitor component was purified by high temperature annealing exceeding 1050 ° C, but in the method not using the inhibitor as in the present invention, the purification was performed at high temperature. Even if secondary recrystallization is completed, low iron loss can be obtained. Further, by suppressing the temperature reached in the finish annealing to 1050 ° C. or less, the undercoat is not formed, which is suitable for improving the workability.

On the other hand, in the above low temperature finish annealing, since the finish annealing temperature is low, the flexibility is insufficient.
It is necessary to eliminate the winding tendency of the coil by flattening annealing. Here, in order to effectively eliminate the winding tendency of the coil, it is important to optimize the conditions for flattening annealing. That is, when it is subjected to final finish annealing in which a coil shape is subjected to long-term refining, it is necessary to set the inner diameter of the coil to be ≧ 150 mm when wound into a coil. This is because if the coil inner diameter is smaller than this, it is difficult to correct the curl even after the flattening annealing. In addition, the flattening annealing is limited to within a few minutes at most in consideration of productivity, so the annealing temperature is 8
It is necessary to set the temperature to 00 ° C or higher, but if it exceeds 1000 ° C, the magnetic properties deteriorate due to plastic deformation, so the annealing temperature in flattening annealing was limited to the range of 800 to 1000 ° C.

Further, it is more advantageous to apply a tension of 1 MPa or more to the steel sheet during the above flattening annealing in order to promote the flattening. However, the applied tension is 15 M
If it exceeds Pa, the magnetic properties may deteriorate due to plastic deformation, so the upper limit of the applied tension is preferably about 15 MPa. In addition, when performing flattening annealing under application of tension in this way, the lower limit temperature of flattening annealing can be reduced to 700 ° C.

Further, when steel sheets are laminated and used, in order to improve iron loss, it is effective to apply an insulating coating on the steel sheet surface after the flattening annealing. In order to secure good punchability, a semi-organic coating containing a resin is desirable, but when importance is attached to weldability, it is advantageous to apply an inorganic coating. Further, in order to prevent not only the workability after the flattening annealing but also the coating property, it is important to prevent the surface oxidation during the flattening annealing as much as possible. For this reason,
Atmosphere in the furnace during heating, soaking and cooling above 300 ℃ is
It is preferable to use a non-oxidizing gas as the introduction gas.
However, when the flattening annealing and the decarburizing annealing are combined, a weak decarburizing atmosphere can be used.

The use of the electromagnetic steel sheet according to the present invention is E
The present invention is not limited to the I-type core, but can be applied to all uses of grain-oriented electrical steel sheets in which workability is important.
Furthermore, since no inhibitor is used as a material and there is no need to perform high temperature heating, decarburization annealing, and high temperature purification annealing of the slab, there is a great advantage that mass production is possible at low cost.

[0038]

Example 1 C: 0.003%, Si: 3.3%, Mn: 0.08%, Sb: 0.03% and sol.Al: 0.004% are contained, N is reduced to 0.0015%, and other than Fe. A 200 mm thick slab was produced by continuous casting from molten steel with a composition in which all the components were reduced to 0.005% or less. Next, this slab was heated at 1050 ° C. for 30 minutes and then hot-rolled to form a hot-rolled sheet having a thickness of 2.7 mm. Next, the hot-rolled sheet was annealed at 950 ° C. for 30 seconds, pickled, and then cold-rolled to a final sheet thickness of 0.34 mm.
Next, hydrogen: 75 vol%, nitrogen: 25 vol%, dew point: -20
After performing primary recrystallization annealing at 900 ° C for 15 seconds in an annealing atmosphere at 900 ° C, the coil was wound into a coil with a radius of 254 mm without using an annealing separator. For comparison, we also manufactured a coil with a winding radius of 127 mm, a dew point of -20 ° C, and a speed of 50 ° C / h up to 800 ° C in a mixed atmosphere of nitrogen: 50 vol% and Ar: 50 vol%. Temperature rises at 800 ℃ to 925 ℃, 10 ℃ / h
The final finish annealing was performed by raising the temperature at a rate of and holding at this temperature for 75 hours.

Next, hydrogen: 25 vol%, nitrogen: 75 vol
%, Dew point: Flattening annealing was carried out for 30 seconds in a pure atmosphere of −20 ° C. under various conditions of annealing temperature. At this time, the tension in the furnace was 5 MPa. After that, a coating solution in which aluminum dichromate, an epoxy resin and ethylene glycol were mixed was applied and baked at 200 ° C to obtain a product. About the sample obtained by shearing to Epstein size in the rolling direction from the coil inner diameter side of the product plate thus obtained,
Warpage and magnetic properties were measured. The results obtained are shown in Table 1.

[0040]

[Table 1]

As shown in Table 1, the radius of the coil inner winding is
If it is less than 150 mm, the warp exceeds 5 mm, and the flattening and tempering temperature is 10 even if the inner coil radius is 150 mm or more.
When the temperature exceeds 00 ° C, the magnetic properties deteriorate. On the other hand, according to the present invention, the inner coil has a radius of 150 mm or more, and the flattening annealing temperature is in the temperature range of 700 to 1000 ° C.
The warpage was as small as 3 mm or less and the magnetic properties were excellent.

Example 2 C: 0.028%, Si: 3.4%, Mn: 0.15% and sol.Al:
A slab having a thickness of 200 mm was produced by continuous casting from molten steel having a composition containing 0.005%, N reduced to 0.0030%, and all other components other than Fe reduced to 0.005% or less.
Then, after heating this slab at 1200 ° C for 30 minutes,
A hot rolled sheet with a thickness of 2.5 mm was obtained by hot rolling. Then 1050
The hot-rolled sheet was annealed at 30 ° C. for 30 seconds, pickled, and then warm-rolled at a rolling temperature of 250 ° C. to obtain a final sheet thickness of 0.26 mm. Next, hydrogen: 30 vol%, nitrogen: 70 vol%, dew point:
After performing primary recrystallization annealing at 900 ° C for 15 seconds in an annealing atmosphere of −30 ° C, the coil was wound with a radius of 280 mm. At this time, colloidal silica having an average particle size of 0.1 μm was applied as an annealing separator and dried. For comparison, we also manufactured a coil with a winding radius of 127 mm and a dew point of -20 ° C in a mixed atmosphere of nitrogen: 75 vol% and Ar: 25 vol% up to 800 ° C at 30 ° C / h. Temperature rises from 800 ℃
The final finish annealing was performed by raising the temperature to 950 ° C at a rate of 10 ° C / h and maintaining this temperature for 50 hours.

Next, hydrogen: 50 vol%, nitrogen: 50 vol
%, Dew point: In the annealing atmosphere of 45 ° C., flattening annealing was performed at 800 ° C. for 90 seconds also as decarburization annealing. At that time, the tension in the furnace was changed variously. Then, a coating liquid containing magnesium dichromate, an acrylic resin and ethylene glycol was applied and baked at 300 ° C. to obtain a product.

This product was able to obtain not only the Goss orientation as the secondary recrystallization orientation but also the composite secondary recrystallization texture having a considerable number of cube textures at the same time. Incidentally, the C content after decarburization was 0.003%. From the coil inner diameter side of the product plate thus obtained, about the samples obtained by shearing to the Epstein size in the rolling direction and the direction perpendicular to the rolling, respectively, the warpage and the magnetic properties in the rolling direction, and the magnetic properties in the direction orthogonal to the rolling were obtained. It was measured. The obtained results are shown in Table 2.

[0045]

[Table 2]

As shown in Table 2, the radius of the coil inner winding is
If it is less than 150 mm, the warp exceeds 5 mm, and even if the radius of the coil inner winding is 150 mm or more, if the tension exceeds 15 MPa, the magnetic properties deteriorate. On the other hand, according to the present invention, when the radius of the coil inner winding is 150 mm or more and the applied tension to the steel sheet during flattening annealing is controlled within the range of 5 to 15 MPa, the warpage is as small as 2 mm or less, and It was also excellent in magnetic properties.

Example 3 Steel slabs having various compositional compositions shown in Table 3 were heated to 1100 ° C. and then hot-rolled into hot-rolled sheets having a thickness of 1.6 mm. All components not shown in the table were reduced to 0.005% or less. Then, after baking the hot-rolled sheet for 60 seconds soaking at 1000 ° C,
After pickling, it was finished by cold rolling to a final plate thickness of 0.15 mm. Then, after performing primary recrystallization annealing for 20 seconds at 940 ℃ in an atmosphere of hydrogen: 75vol%, nitrogen: 25vol%, dew point: -25 ℃, without applying an annealing separator, the radius was changed. : The coil was wound at 230 mm. Then up to 850 ℃
The final finishing annealing was performed at a rate of 10 ° C / h and kept at this temperature for 100 hours in a nitrogen atmosphere with a dew point of -40 ° C.

Then, flattening annealing was carried out at a tension of 3 MPa at 875 ° C. for a soaking time of 10 seconds. However, Steel F was subjected to flattening annealing which was combined with decarburization annealing at 820 ° C for 150 seconds in an annealing atmosphere of hydrogen: 40 vol%, nitrogen: 60 vol% and dew point: 35 ° C. After that, an inorganic coating liquid composed mainly of aluminum dichromate was applied and baked at 250 ° C. to obtain a product. The warp was measured for the sample obtained by shearing the thus obtained product plate from the coil inner diameter side to the Epstein size in the rolling direction. Also, as high frequency magnetic characteristics
The iron loss at 400 Hz and 1000 Hz was measured at 1.0T.
The results obtained are shown in Table 4.

[0049]

[Table 3]

[0050]

[Table 4]

As shown in Table 4, when the content of sol.Al was more than 0.02% (Steel Y), secondary recrystallization did not occur even after holding for 100 hours, and only poor magnetic properties were obtained.

[0052]

As described above, according to the present invention, by using low-temperature final finish annealing up to 1050 ° C. by using a material of a high purity component that does not contain an inhibitor, magnetic properties and a base film mainly composed of forsterite and When manufacturing grain-oriented electrical steel sheet products with excellent punching workability, by optimizing the flattening annealing conditions, it is possible to effectively eliminate the winding characteristics of the coil, which hinders magnetic properties, punching and coating. it can. Further, in the present invention, since no inhibitor is used as a raw material and there is no need to perform high temperature heating of the slab, pure decarburization annealing, high temperature purification annealing, etc., there is a great advantage that mass production is possible at low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a shape of an EI type core.

FIG. 2 is a graph showing the influence of the annealing temperature on the flattening of the sample after the secondary recrystallization annealing using the mold with the curvature changed.

FIG. 3 is a graph showing the effects of annealing temperature and applied tension on the flattening of a sample after secondary recrystallization annealing using a mold having a curvature.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22C 38/60 C22C 38/60 (72) Inventor Seiji Okabe 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama In Kawashima Steel Co., Ltd. Mizushima Steel Works (72) Inventor Takeshi Imamura 1-chome, Mizushima Kawasaki-dori, Mizushima Steel Works, Kurashiki City, Okayama Prefecture (No address) F-term in Mizushima Steel Works, Kawasaki Steel Co., Ltd. (reference) 4K033 CA02 CA03 MA01 MA02 RA04 SA03 SA04 5E041 AA02 CA02 CA04 HB11 NN01 NN18

Claims (3)

[Claims] 1. Containing Si in the range of 2.0 to 8.0 mass%,
A steel material for grain-oriented electrical steel sheets that does not contain inhibitor components is hot-rolled, cold-rolled to a final sheet thickness, subjected to primary recrystallization annealing, and then wound into a coil, then 800- Forsterite (Mg ₂ S) was obtained by performing secondary annealing after finishing annealing at 1050 ℃ for 5 hours or more.
Does not have a base film (glass film) mainly composed of iO ₄ ),
When manufacturing grain-oriented electrical steel sheets with excellent magnetic properties and punching workability, the coil inner diameter before winding into the coil before finish annealing should be ≥150 mm, and the coil after finish annealing should be 800 ~
A method for producing a grain-oriented electrical steel sheet, which comprises flattening by continuous annealing in a temperature range of 1000 ° C. 2. Si is contained in the range of 2.0 to 8.0 mass%,
A steel material for grain-oriented electrical steel sheets that does not contain inhibitor components is hot-rolled, cold-rolled to a final sheet thickness, subjected to primary recrystallization annealing, and then wound into a coil, then 800- Forsterite (Mg ₂ S) was obtained by performing secondary annealing after finishing annealing at 1050 ℃ for 5 hours or more.
Does not have a base film (glass film) mainly composed of iO ₄ ),
When manufacturing grain-oriented electrical steel sheets with excellent magnetic properties and punching workability, the coil inner diameter before winding into the coil before finish annealing should be ≥150 mm, and the coil after finish annealing should be 700 ~
In the temperature range of 1000 ° C, the applied tension to the steel sheet is 1 to
A method for producing a grain-oriented electrical steel sheet, which comprises flattening by continuous annealing under the condition of 15 MPa. 3. The steel material according to claim 1 or 2,
A method for producing a grain-oriented electrical steel sheet, which further comprises a composition containing Sb and / or Sn: 0.01 to 0.50 mass%.