JPH02282422A - Production of high-flux-density thin grain-oriented magnetic steel sheet - Google Patents

Abstract

PURPOSE:To produce the thin grain-oriented magnetic steel sheet having a high magnetic flux density ad a low iron loss by hot-rolling a magnetic steel slab consisting of C, Si, Al, Mn, S, N and Fe and having a specified composition, annealing, quenching and then cold-rolling the hot-rolled sheet at a specified high draft. CONSTITUTION:A magnetic steel slab contg., by weight, 0.025-0.85% C, 2.5-4.5% Si, 0.010-0.065% acid-soluble Al, 0.03-0.15% Mn, 0.010-0.050% S, 0.0030-0.0120% N, <=1.5% of >=1 kind amount Cu, Sn, Cr and Mo, as required, the balance Fe and inevitable impurities is hot-rolled. The hot-rolled sheet is continuously annealed at 950-1200 deg.C and then quenching to deposit AlN. The steel sheet is reduced to the final thickness of 0.15-0.23mm by the cold rollings including >=1-times final strong rollings at the draft of 81-95%, decarburized and finish-annealed. In this case, the rollings are performed by using a roll having 30-100mm diameter at the high rolling tension of 10-35kg/mm<2>, the preceding pass is carried out at the high draft of >=30%, and the average sheet temp. in the succeeding pass to <=0.40mm sheet thickness is controlled to 150-230 deg.C. By this method, a high-flux-density low-iron-loss thin grain-oriented magnetic steel sheet excellent in a magnetic domain refining effect is obtained.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to the production of a thin, unidirectional electrical steel sheet with high magnetic flux density and excellent magnetic properties, which has an easy axis of magnetization <100> in the rolling direction of the steel sheet. It is about law.

(Prior Art) Unidirectional electrical steel sheets are mainly used as core materials for transformers and other electrical equipment, and as magnetic properties, they must have good excitation properties and iron loss properties.

As a numerical value representing this excitation characteristic, for example, the strength of the magnetic field is 10
Using the magnetic flux density B1° at 00^/ro, the iron loss characteristics are as follows: 50 hertz (Hz) AC magnetic flux density 1.7 Tesla (
Iron loss WIT/S at T). is used.

Recently, there has been a strong demand for lower iron loss due to the current situation where energy conservation is an urgent issue.

Unidirectional electrical steel sheets are manufactured by finishing annealing (1
10) Manufactured by growing a so-called Goss structure with <001> orientation using a secondary recrystallization phenomenon.

In order to improve magnetic properties, it is important to stably develop secondary recrystallized grains whose <001> axes are highly aligned in the rolling direction and whose (110) planes are parallel to the surface of the steel sheet. Further, magnetic domain refining technology is a method for significantly reducing iron loss, but in order to maximize this iron loss improvement effect, it is important to increase the crystal grain size after secondary recrystallization.

For this purpose, it is said that it is necessary to optimize the cold rolling reduction rate and perform warm rolling during the final strong cold rolling.

Various studies have been made regarding this method of cold rolling under heavy rolling. For example, the method described in Japanese Patent Publication No. 50-26493 proposes a method for cold rolling electrical steel sheets containing small amounts of C and AI. This means that the final hard cold rolling reduction is 81
~95%, the material temperature is in the range of 50 to 350°C, and the thermal effect duration changes depending on the material temperature, thereby improving the slip mechanism during cold rolling (SLip S
A slight change in the crystal orientation of the primary recrystallized grains (system) causes a change in the crystal orientation of the primary recrystallized grains. It is said to encourage growth. As a result, high magnetic flux density and low core loss can be obtained.

By the way, ways to reduce iron loss include increasing the St content, reducing the thickness of the steel plate, applying tension to the steel plate, and refining magnetic domains by applying strain externally. There is. However, increasing the St content causes the steel to deteriorate,
This causes problems in actual manufacturing because the cold rollability deteriorates significantly. On the other hand, if the thickness of the steel plate is reduced, for example, to 0.18 mm, the secondary recrystallization during final annealing may become unstable and the magnetic properties may deteriorate. In addition, tension addition is
Since there is a limit to the tension effect of the coated insulating film, it cannot be expected to significantly reduce iron loss. Furthermore, since magnetic domain refinement is greatly influenced by the size of the secondary recrystallized grains of the material, a technique for increasing the secondary recrystallized grain size of the material is required.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for producing a thin unidirectional electrical steel sheet that has a high magnetic flux density, significantly reduces iron loss, and has an excellent magnetic domain refining effect. .

(Means for Solving the Problems) In order to meet the recent strong demand for low core loss materials, the present inventors conducted various experiments and studies on reducing the core loss of unidirectional electrical steel sheets. As a result, when manufacturing unidirectional electrical steel sheets with high magnetic flux density using AlN as an inhibitor, the electrical steel material containing acid-soluble M is hot-rolled and the final hard-rolled part is heated at a high temperature in the range of 950 to 1200°C. After continuous annealing, it is rapidly cooled to precipitate AlN, and cold rolled one or more times including final strong cold rolling in a rolling reduction range of 81 to 95% to achieve a final plate thickness of 0.15 to 0.23. In the method for manufacturing a thin unidirectional electrical steel sheet, which is decarburized and finish annealed, the cold rolling is performed at the above-mentioned strong reduction rate using a small diameter roll of 30 to 100 mm, and the rolling tension per unit area is 10 to 35 kg.
/- under high tension, the first pass is carried out at a high reduction rate of 30% or more, and the average plate temperature of the second pass is 150 to 230°C with an intermediate plate thickness of 0.40 m or less, thereby achieving high magnetic flux density. It was confirmed that thin unidirectional electrical steel sheets with significantly reduced core loss and excellent magnetic domain refining effects could be manufactured.

This electromagnetic steel material contains C: 0.025 to 0.085%.

Si: 2.5 to 4.5%, acid soluble A/(hereinafter referred to as so1.
AI): 0.010-0.065%, Mn
:0.03~0.15%, S:0.010~0.050
%, N: 0.0030 to 0.0120%, with the balance consisting of iron and inevitable impurities. In addition to these components, one or more of Cu + Sn + Cr + Mo may be included in a total amount of 1.5% or less.

The present invention will be explained in detail below.

First, the steel components of the electromagnetic steel material of the present invention will be described.

When the electromagnetic steel material is heated, C is required to cause T transformation in at least a portion of the steel, depending on the amount of Si. Therefore, the content of C is required to be 0.025% or more. On the other hand, if the content is too large, a product with high magnetic flux density cannot be obtained, so 0. 085% or less.

In order to reduce iron loss, Si is required to be 2.5% or more, and if it exceeds 4.5%, cold rollability deteriorates, so it is set to 4.5% or less.

sol, AI precipitates NN during annealing of the final strongly cold rolled part,
In order to obtain a product with high magnetic flux density, the content must be 0.010% or more. On the other hand, if the content is too large, it will become brittle and also disadvantageous in terms of cost, so it is set to 0.065% or less.

N is the so1. 0.0030 to 0.012 to bind to kl and form ARN as an inhibitor.
0% content is required.

Mn and S are elements necessary to form MnS, and therefore Mn is contained in an amount of 0.03% or more.

On the other hand, if the content increases, the purification time in final annealing becomes longer, so the content should be 0.15% or less. S is the Mn
For the same reason as above, 0.010% or more is necessary, and o
, oso% or less.

To further improve magnetic properties, Cu + Sn + Cr
＋M.

One or more of these may be included.

At this time, the upper limit of the total content is 1.5%. If this upper limit is exceeded, cold rollability and decarburization properties will deteriorate.

A silicon steel slab containing the above-mentioned components, with the remainder being iron and unavoidable impurities, is manufactured from molten steel melted to predetermined components by continuous casting or by ingot making and blooming rolling.

After this silicon steel slab is heated to a predetermined temperature, or immediately after continuous casting, it is hot rolled. These hot rolling conditions do not need to be special conditions. The obtained hot-rolled sheet may be subjected to hot-rolled sheet annealing and then cold-rolled once, or cold-rolled two or more times with intermediate annealing as required. In order to precipitate AlN, which has a strong inhibitory effect, during annealing before the final cold rolling (hot-rolled sheet annealing in the case of one-time cold rolling),
Continuous annealing is performed by heating to a high temperature of 00°C and then rapidly cooling. Cold rolling is carried out once or twice, including a final strong reduction cold rolling performed at a rolling reduction ratio of 81 to 95%, but the final strong reduction cold rolling is 81 to 95% when the main inhibitor is 7VN.
This is to obtain excellent magnetic properties in the steel plate.

Cold rolling will be explained in detail with reference to experimental data.

Hot-rolled annealed samples having the steel components shown in Table 1 were cold-rolled under the following conditions.

Cold rolling conditions Hot rolled sheet (original sheet) thickness: 2.3+um Finished sheet thickness: 0.20mm Total rolling reduction
: 91.3% Rolling mill work roll diameter Near 0 φ Rolling tension: 25 kg/+aj Average plate temperature in the latter pass: A hot rolled plate annealed at 20 to 350°C, with a thickness of 0.40 mm in the middle. Cold rolling was carried out by changing the average plate temperature in the following subsequent passes within the range of 20 to 350°C, and then 85°C
Decarburization annealing was performed at 0°C for 150 seconds, an annealing separator was applied and dried, and final annealing was performed at 1200°C.

The thus obtained unidirectional electrical steel sheet sample 1゜2,3
Iron loss WIT/S. , magnetic flux density B1°, crystal grain size, and laser treatment iron loss improvement rate were measured, and the results are shown in FIGS. 1 to 4.

As is clear from these figures, 0.40
Iron tjl W + -15° is obtained by warm rolling at an average plate temperature of 150 to 230"C in the subsequent pass of less than mm.

The magnetic flux density BIG is significantly improved, the crystal grain size is increased, and the iron loss improvement rate by laser treatment is also excellent.

The reason why the magnetic properties are improved and the grain size becomes larger when warm rolling is performed during the final cold rolling, especially when thin, is considered to be as follows. In order to obtain the high magnetic flux density that is a feature of this component system, the final cold rolling rate exceeds 90%, especially for thin materials with a plate thickness of 0.23 mm or less. On the other hand, in order to improve the magnetism of the final product, it is necessary to add (110
) It is desirable that a large number of grains exist. However, (1
10) Since the amount of grains present rapidly decreases at a cold rolling rate of 80% or more, it is generally difficult to achieve both a high magnetic flux density and the presence of (110) grains. Especially when the work roll diameter is 100
Cold rolling mill smaller than mφ, rolling tension 10 to 35 kg/-
When cold rolling with high tension of
) grains are further reduced. However, the remaining (110) grains are
It is very sharp, and those that have undergone secondary recrystallization tend to have high magnetic flux density, low iron loss, and large crystal grain size.

Especially for thin products, if the thickness of the plate becomes thinner during cold rolling, increasing the plate temperature during cold rolling will cause the above-mentioned (
110) Grain reduction can be prevented or enriched. Therefore, when manufacturing a product with a plate thickness of 0.23 InIn or less, use a cold rolling mill with a work roll (WR) diameter of 100 mm or less and apply a high tension of 10 to 35 kg/1 to thin the plate to the specified thickness. It is difficult to do so. In this case, the number of (110) grains is relatively reduced compared to the conventional rolling method, but the plate temperature during cold rolling, especially in thin sheets, is 150 to 23.
By increasing the temperature to 0℃, it is possible to compensate for the decreasing (110) grains, and therefore sharp (110) grains can exist, resulting in products with high magnetic flux density, low core loss, and large crystal grain size. . If the work roll diameter is smaller than 30a+mφ, iron loss will deteriorate and the roll life will be shortened, so it is set to 3011II11φ or more. In addition, the intermediate board thickness is 0.40
If the average plate temperature in the subsequent pass below 150°C is less than 150°C, the above effects cannot be obtained, and if it exceeds 230°C, the structure will recover and the (100) grains will decrease. , the property improvement effect disappears.

(Example) Example 1 The silicon steel slab shown in Table 2 was hot rolled, and the obtained plate thickness was 2.
A 3 mm hot-rolled plate was cold rolled to a plate thickness of 1.5 mm, and A
It was subjected to precipitation annealing of 1N and final cold rolled under the conditions shown in Table 3. After that, decarburization annealing was performed at 850°C for 120 seconds, and an annealing separator containing MgO as the main component was applied, and after drying,
Finish annealing was performed at 200°C for 20 hours.

Iron loss WIT/S for each sample of unidirectional electrical steel sheet manufactured in this way. and the magnetic flux density B1° were measured. The results are shown in Table 4 along with the plate temperature during finish cold rolling.

Table 1 Example 2 A silicon steel slab having the steel components shown in Table 5 was hot rolled into a hot rolled plate having a thickness of 2.4 mm. Next, the hot-rolled sheet was annealed and finished cold-rolled under the conditions shown in Table 6 to 850"C.
Decarburization annealing was performed at x120 seconds, an annealing separator containing MgO as a main component was applied, and after drying, final annealing was performed at 1200°C x 20 hours.

For each sample of the produced unidirectional electrical steel sheet, the iron loss Wl'115°, the magnetic flux density B1°, and the grain size.

The iron loss improvement rate during laser treatment was measured. The results are shown in Table 7.

(Effects of the Invention) As is clear from the results of the above examples, according to the present invention, a unidirectional electrical steel sheet with significantly reduced core loss and excellent laser treatment effects can be manufactured, and therefore it is industrially useful. The contribution is extremely large.

[Brief explanation of drawings]

Figure 1 shows the relationship between the average plate temperature and iron loss when the intermediate plate thickness is 0.40 mm or less during finish cold rolling, and Figure 2 shows the relationship between the average plate temperature and magnetic flux density when the intermediate plate thickness is 0.40 onn or less during finish cold rolling. relationship, 3rd
The figure shows the relationship between average plate temperature and grain size for intermediate plate thicknesses of 0.40 mm or less during finish cold rolling, and Figure 4 shows the relationship between average plate temperature and laser treatment for intermediate plate thicknesses of 0.40 mm or less during finish cold rolling. It is a figure showing the relationship of iron loss improvement rate by. 2nd figure 114040mm>1 lower flat G! ＞ffi ('C) Laser °° - row buried
ASTk4 No, ) fried ÷ return

Claims (2)

[Claims] (1) In weight%, C: 0.025-0.085%, Si
: 2.5-4.5%, acid-soluble Al: 0.010-0.
065%, Mn: 0.03-0.15%, S: 0.01
0-0.050%, N: 0.0030-0.0120%
A magnetic steel slab is hot-rolled and heated to 950-1200°C before final hard rolling.
After continuous annealing in the range of 81~
A thin unidirectional electrical steel sheet that is cold-rolled once or twice or more, including final hard-rolling in a rolling reduction range of 95%, to a final thickness of 0.15 to 0.23 mm, decarburized, and finish annealed. In the manufacturing method, cold rolling performed at the above-mentioned strong reduction rate is
With a small diameter roll of 100 mm diameter, under a high rolling tension of 10 to 35 kg/unit area, 30 first passes are performed.
A method for producing a thin unidirectional electrical steel sheet with a high magnetic flux density, characterized in that the process is carried out at a high rolling reduction rate of % or more, and the average plate temperature in the subsequent pass with an intermediate plate thickness of 0.40 mm or less is 150 to 230°C. (2) In weight%, C: 0.025-0.085%, Si
: 2.5-4.5%, acid-soluble Al: 0.010-0.
065%, Mn: 0.03-0.15%, S: 0.01
0-0.050%, N: 0.0030-0.0120%
and further contains one or two of Cu, Sn, Cr, and Mo.
A magnetic steel slab containing a total of 1.5% or less of carbon dioxide, the balance consisting of iron and unavoidable impurities, is hot rolled, and before the final hard cold rolling, it is continuously annealed in the range of 950 to 1200 ° C. and then rapidly cooled, 0 by precipitating AlN and cold rolling one or more times including final hard rolling in a rolling reduction range of 81 to 95%.
．． In a method for manufacturing a thin grain-oriented electrical steel sheet in which the final plate thickness is 15 to 0.23 mm, decarburized, and finish annealed, cold rolling is carried out at the above-mentioned strong reduction rate using small diameter rolls with a diameter of 30 to 100 mm, and the unit area is Rolling tension per unit is 10-35kg/mm
High magnetic flux characterized by performing the first pass at a high reduction rate of 30% or more under high tension of ^2, and making the average plate temperature of the second pass with an intermediate plate thickness of 0.40 mm or less between 150 and 230°C. A method for producing a thin-density unidirectional electrical steel sheet.