JPH06207220A - Production of grain-oriented silicon steel sheet with high magnetic flux density - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet with high magnetic flux density by performing preliminary cold rolling at a specific draft. CONSTITUTION:A continuously cast slab, having a composition consisting of, by weight, 0.15-0.100% C, 2.0-4.0% Si, 0.03-0.12% Mn, 0.010-0.065% Sol.Al, 0.0040-0.0100% N, 0.005-0.050%, in total, of S and/or Se, further 0.003-0.3% of one or >=2 elements selected from the group consisting of Sb, Sn, Cu, Mo, Ge, B, Te, As, and Bi, and the balance essentially Fe, is subjected to a slab heating and hot-rolled. The resulting plate is subjected to-hot rolled plate annealing, to preliminary cold rolling, to precipitation annealing, and then to final high- degree cold rolling at 81-89% draft to <=0.25mm final sheet thickness. Subsequently, the resulting sheet is subjected to decarburizing and primary recrystallization annealing, to final finish annealing, and to application of coating, by which the grain oriented silicon steel sheet with high magnetic flux density is produced. At this time, preliminary cold rolling is performed at 5-50% draft by using work rolls of cold rolling mill where (work roll diameter)/(hot rolled plate thickness)<=90 is satisfied. Thus, the grain-oriented silicon steel sheet with high magnetic flux density can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high magnetic flux density unidirectional electrical steel sheet used for an iron core of a transformer or the like.

[0002]

2. Description of the Related Art Unidirectional electrical steel sheets are mainly used as iron core materials for transformers and generators, but with the recent demand for energy saving, steel sheets with higher magnetic flux density and less iron loss are available from the market. Is required. To achieve low iron loss,
There are known a method of reducing the eddy current loss by increasing the Si content of the steel sheet as much as possible to increase the specific resistance of the material, and a method of reducing the eddy current loss by reducing the product sheet thickness as much as possible. In addition, recently, magnetic domain control technologies such as laser irradiation on the steel sheet surface of products and forming grooves on the steel sheet surface by tooth profile rolls have been developed and put into practical use, and it is possible to significantly reduce iron loss. ing. In this case, it is known that the iron loss after magnetic domain control decreases as the magnetic flux density before magnetic domain control increases, and it is very important to manufacture a steel sheet with a high magnetic flux density.

In order to obtain a grain-oriented electrical steel sheet having a high magnetic flux density, it is necessary to obtain a secondary recrystallized structure highly integrated in the {110} <001> orientation, the so-called Goss orientation. Two
It is known that the inhibitor and the primary recrystallization texture have a great influence on the secondary recrystallization. As for the inhibitor, it is necessary to allow the precipitation-dispersed phase of about 100 to 1000 angstroms to exist uniformly and finely in the steel before finish annealing, and AlN, MnS, MnSe and the like are generally known. Furthermore, Sb, Sn, Cu, Mo, Ge, B, Te, As, Bi of grain boundary segregation elements are present at the grain boundaries.
It is useful to segregate such as. On the other hand, the primary recrystallization texture has been conventionally controlled by appropriately combining the process conditions of hot rolling, cold rolling and annealing.

However, if the Si content is increased and the product sheet thickness is reduced, it becomes difficult to control the secondary recrystallization orientation in the finish annealing, and it is difficult to obtain a product having a high magnetic flux density and a sheet thickness of 0.25 mm or less. It wasn't easy. 2 when the product plate thickness becomes thin
One of the reasons why it is difficult to control the secondary recrystallization direction is that a larger cold rolling reduction is applied to obtain a thinner product from the same hot-rolled sheet, which causes a disadvantage in texture. Further, a method of reducing the thickness of the hot-rolled sheet according to the product sheet thickness can be considered, but thinning the hot-rolled sheet inevitably lowers the hot-rolling finish temperature, and the precipitation state of MnS, MnSe, etc. Inappropriate, the disadvantage that the magnetic characteristics deteriorate will occur,
This method has limitations.

As a solution to such a problem, there is a method in which a hot rolled sheet is annealed and then pre-cold rolled. By the way, in the cold rolling process, it is known that the cold rolling rate, the work roll diameter, the roughness of the work roll and the like affect the magnetic properties. Regarding the influence of the work roll diameter in the pre-cold rolling, in particular, JP-A-4-289121 discloses that a hot rolled sheet is rolled at a rolling ratio of (roll diameter) / (sheet thickness) ≧ 50 at a rolling reduction of 0.5 to 15%. After that, a hot-rolled sheet is annealed in the temperature range of 700 to 1100 ° C., and the final sheet thickness is finished by cold rolling two or more times with intermediate annealing sandwiched therebetween.

[0006]

[Patent Document 1] Japanese Patent Application Laid-Open No. 4-28912
The method proposed in No. 1 is a method of performing cold rolling twice or more in addition to pre-cold rolling and hot-rolled sheet annealing, resulting in high manufacturing cost and complicated process control. There's a problem. In addition, AlN is not used as an inhibitor, and it relates to a manufacturing process in which the rolling reduction of the final strong cold rolling is less than 80%, and the magnetic flux density B ₈ is about 1.92T and is not obtained. The present invention uses AlN as an inhibitor, hot-rolls annealed hot-rolled sheets, pre-cold-rolls, precipitation-anneals, and finally cold-rolls with a reduction ratio of 81 to 88%. It proposes a method in which a cold rolling machine having a work roll diameter / hot rolled sheet thickness ≦ 90 and a rolling reduction of 5 to 50% is used.
It is intended to provide a method for producing a high magnetic flux density unidirectional electrical steel sheet which has a high magnetic flux density, a low production cost, and is not complicated in process control.

[0007]

The present invention, in% by weight, comprises C:
0.015-0.100%, Si: 2.0-4.0%,
Mn: 0.03 to 0.12%, Sol. Al: 0.01
0-0.065%, N: 0.0040-0.0100
%, A total of one or two selected from S and Se: 0.005 to 0.050%, and further Sb, Sn, C
A slab in a continuously cast slab containing 0.003 to 0.3% of one or more selected from u, Mo, Ge, B, Te, As, and Bi, and the balance being substantially Fe. After heating, hot rolling, hot-rolled sheet annealing, preliminary cold rolling, precipitation annealing, final strong cold rolling with a rolling reduction of 81 to 89% to a final sheet thickness of 0.25 mm or less, and decarburization -In the method for producing a high magnetic flux density unidirectional electrical steel sheet by primary recrystallization annealing, final finishing annealing, and coating application,
A method for producing a high magnetic flux density unidirectional electrical steel sheet, characterized in that preliminary cold rolling is performed by a cold rolling machine having a work roll diameter / hot rolled sheet thickness ≦ 90 at a rolling reduction of 5 to 50%.

The present inventor has studied a method for producing a high magnetic flux density grain-oriented electrical steel sheet having excellent magnetic properties. As a result, the work roll diameter for pre-cold rolling is defined as work roll diameter / hot rolled sheet thickness ≦
It has been found that setting 90 is very effective. FIG. 1 shows an example of the result of an experiment conducted by the present inventor. In the composition range according to the invention C: 0.069%, Si: 3.
09%, Mn: 0.068%, S: 0.029%, So
l. Al: 0.035%, N: 0.0087%, Sn:
A slab containing 0.10% was continuously cast, and after heating the slab, the plate thickness was hot rolled to 2.30 mm. Then, the hot-rolled sheet was annealed at 1150 ° C. for 2 minutes, pre-cold-rolled at a reduction ratio of 22% to 1.80 mm by cold-rolling machines with various work roll diameters, and 10
Precipitation annealing is carried out by soaking at 00 ° C for 2 minutes and then rapidly cooling, 100 mmφ
With a cold rolling machine having a work roll diameter of 0.22 mm, final strong cold rolling was performed at a reduction rate of 87.8% to obtain a product sheet thickness. Then, the cold-rolled sheet was subjected to decarburization / primary recrystallization annealing, final finishing annealing, and coating to obtain a product. The relationship between the work roll diameter of the pre-cold rolling / the thickness of the hot rolled sheet and the magnetic flux density at this time is shown in FIG. From this, it can be seen that particularly high magnetic flux density can be obtained when the work roll diameter / hot rolled sheet thickness is ≦ 90.

The conditions and the reasons for limitation of the present invention are as follows. If the lower limit of C is less than 0.015%, the secondary recrystallization becomes unstable, and the upper limit of 0.100% is economically disadvantageous because the time required for decarburization becomes longer when C is higher than this. Limited If Si is less than the lower limit of 2%, good iron loss cannot be obtained, and if it exceeds the upper limit of 4%, cold ductility is significantly deteriorated. If the lower limit of Mn is less than 0.03%, hot embrittlement occurs, and if it exceeds the upper limit of 0.12%, magnetic failure occurs. S and Se are elements necessary for forming MnS and MnSe, and the total of one or two of these is lower than 0.
If it is less than 005%, the absolute amounts of MnS and MnSe are insufficient,
If the upper limit of 0.050% is exceeded, hot cracking occurs, and purification in final finish annealing becomes difficult.

Sol. Al is an element necessary for forming AlN, and if the lower limit is less than 0.010%, the absolute amount of AlN is insufficient, and if it exceeds the upper limit of 0.065%, a proper dispersed state of AlN cannot be obtained. N is an element necessary for forming AlN. If the lower limit is less than 0.0040%, the absolute amount of AlN is insufficient, and if the upper limit is more than 0.0100%, AlN is insufficient.
The proper dispersion state of can not be obtained. Sb, Sn, Cu, M
o, Ge, B, Te, As, and Bi segregate at the grain boundaries to stabilize secondary recrystallization, but if the content of one or more selected from these is less than the lower limit of 0.03%. The segregation amount is insufficient, and the upper limit of 0.3% is due to economic reasons and deterioration of decarburization.

The hot-rolled sheet annealing is carried out because it has the effect of making the structure of the hot-rolled sheet and the precipitation-dispersed phase uniform and also effective in preventing the generation of linear fine grains. The work roll diameter for pre-cold rolling is defined as work roll diameter / hot rolled sheet thickness ≦ 60. If it is smaller than this, the magnetic flux density cannot be increased. Pre-cold rolling is performed once or twice or more, and the total rolling reduction is 5 to 50%. If it is less than 5%, the amount of rolling reduction adjustment to the subsequent final strong cold rolling is too small. If the pre-cold rolling rate exceeds 50%, the texture is unsuitable and the magnetic flux density is significantly reduced. Regarding the rolling reduction in the final strong cold rolling, the texture becomes inadequate if the rolling reduction is less than 81% or more than 89%, so that the secondary recrystallization becomes unstable. The reason for limiting the product plate thickness to 0.25 mm or less is to obtain a product with low iron loss in response to recent demand needs.

[0012]

【Example】

[Example 1] C: 0.088%, Si: 3.45%, M
n: 0.062%, S: 0.021%, Sol. Al:
0.036%, N: 0.0091%, Sn: 0.14
%, Cu: 0.07%, continuously cast, slab-heated, and hot-rolled to form a hot coil having a thickness of 2.1 mm. Then, hot plate annealing was performed, in which the material was soaked at 1080 ° C for 2 minutes and then rapidly cooled, and various work roll diameters were adjusted to 1.30 mm.
Pre-cold rolling was performed at a reduction rate of 8%. And 1050 ℃ × 2
Precipitation annealing was performed by soaking for a minute and then rapidly cooling, and finally cold-rolled with a cold rolling machine having a work roll diameter of 100 mmφ at a reduction rate of 86.9% to obtain a sheet thickness of 0.17 mm. Then, the cold-rolled sheet was subjected to decarburization / primary recrystallization annealing, final finishing annealing, and final coating to obtain a product.

Table 1 shows the work roll diameter of the pre-cold rolling at this time, the work roll diameter / the hot rolled sheet thickness, and the magnetic flux density B ₈ of the obtained product. From this, it is understood that the inventive example can obtain a higher magnetic flux density than the comparative example.

[0014]

[Table 1]

Example 2 A slab containing various components was continuously cast, slab-heated and then hot-rolled to give a thickness of 1.8 mm.
A thick hot rolled plate was obtained. Hot plate annealing was soaked at 1100 ° C. for 2 minutes and then rapidly cooled, and a work roll diameter / hot rolled sheet thickness = 38.9, a work roll diameter 70 mmφ cold rolling machine, and work roll diameter / hot rolled sheet thickness = Work roll diameter of 333.3 600
Pre-cold rolling to 1.10 mm at a reduction rate of 39% with a mmφ cold rolling machine, and soaking at 1100 ° C. for 2 minutes followed by rapid cooling for precipitation annealing,
8 with a cold rolling machine with a work roll diameter of 70 mmφ from 0.15 mm
The final strong cold rolling was performed at a rolling reduction of 6.4%. Then, the cold-rolled sheet thus obtained was subjected to decarburization / primary recrystallization annealing, final finishing annealing and final coating to obtain a product.

Table 2 shows the composition of the slab, the work roll diameter of the pre-cold rolling and the magnetic flux density B _{8 of the} product at this time. Than this,
It can be seen that the inventive example can obtain a higher magnetic flux density than the comparative example.

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

According to the present invention, a high magnetic flux density unidirectional electrical steel sheet having excellent magnetic properties can be manufactured, and its industrial effect is very large.

[Brief description of drawings]

FIG. 1 is a table showing a relationship between work roll diameter / hot rolled sheet thickness of pre-cold rolling and magnetic flux density B ₈ of a product.

Claims (1)

[Claims] 1. By weight%, C: 0.015 to 0.100%, Si: 2.0 to 4.0%, Mn: 0.03 to 0.12%, Sol. Al: 0.010 to 0.065%, N: 0.0040 to 0.0100%, and a total of one or two selected from S and Se:
0.005-0.050%, Sb, Sn, Cu, Mo, Ge, B, Te, As,
And one or more selected from Bi are 0.00
3 to 0.3%, with the balance being slab heating to a continuously cast slab that is substantially Fe composition, then hot rolled, hot rolled sheet annealed, pre-cold rolled, precipitation annealed, 81-89 In a method for producing a high magnetic flux density unidirectional electrical steel sheet by decarburization / primary recrystallization annealing, final finishing annealing, and coating application, a final sheet thickness of 0.25 mm or less is obtained by final strong cold rolling with a reduction rate of%. Pre-cold rolling with a cold rolling machine with work roll diameter / hot rolled sheet thickness ≤ 90
A method for producing a high magnetic flux density unidirectional electrical steel sheet, which is performed at a reduction rate of 50%.