JPH03104823A - Production of grain-oriented silicon steel sheet with superlow iron loss - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet reduced in iron loss by applying hot rolling and cold rolling to a slab of a high silicon steel to form a steel sheet of the final sheet thickness, performing decarburizing and primary recrystallization annealing, irradiating the steel sheet surface with an electron beam under specific conditions, if necessary, and then applying secondary recrystallization annealing and purification annealing to the above steel sheet. CONSTITUTION:A slab of a low-carbon high-silicon steel containing 2.0-4.5% Si is hot-rolled, and the resulting hot rolled plate is cold-rolled once or is cold-rolled twice while process- annealed between the cold rolling stages so as to be formed into a cold rolled steel sheet of the final sheet thickness. Subsequently, after decarburizing and primary recrystallization annealing in warm hydrogen, a slurry of a separation agent at annealing composed essentially of MgO is applied to the steel sheet to carry out secondary recrystallization annealing and purification annealing, or, after decarburizing and primary recrystallization annealing, the steel sheet surface is irradiated with an electron beam so that this electron beam reaches a position at a depth of 1/10 of sheet thickness from the surface of the steel sheet 1, that is, a region 2 where Goss orientation secondary recrystallized grains are preferentially generated, and then, a separation agent at annealing is applied to the above surface to carry out secondary recrystallization annealing and purification annealing. By this method, the grain- oriented silicon steel sheet free from deterioration in iron loss characteristics even if subjected to stress relief annealing treatment can be produced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a unidirectional silicon steel sheet with low iron loss, and in particular, the present invention relates to a unidirectional silicon steel sheet with low iron loss, and in particular, to improve the iron forming process by controlling the nuclei of Goss-oriented grains at the positions where secondary recrystallization occurs. The aim is to reduce the

(Prior art) In unidirectional silicon steel sheets, secondary recrystallized grains of the product are highly concentrated in the Goss orientation, and a forsterite film is formed on the surface of the steel sheet. It is a breakthrough in small insulating coatings, and is complex and requires strict control.
It is manufactured through a wide variety of processes.

Such unidirectional silicon steel sheets are mainly used as iron cores for transformers and other electrical equipment, and their magnetic properties include high magnetic flux density (represented by B. value) and iron loss (W+7/ It is required to have a low S. value) and an insulating film with good surface properties.

Particularly in the wake of the energy crisis, the need to prioritize reducing power loss has become significantly stronger, and the need for unidirectional silicon 'iFI' with lower iron chain strength as a core material for transformers has become increasingly important. .

Now, the history of iron loss improvement of unidirectional silicon steel sheets is based on Goss direction 2.
It is no exaggeration to say that this is a history of improvements in the secondary recrystallization texture. As a method for controlling such secondary recrystallized grains, AIN. MnS. A method of preferentially elongating secondary recrystallized grains in the Goss orientation using a so-called inhibitor, which suppresses the length of primary recrystallized grains such as MnSe and sb, has been implemented.

On the other hand, there is a completely different method to control the secondary recrystallization texture, namely laser irradiation on the steel plate surface {Ichiyama
Correct: Tetsu to Hagane, 69 (1983), P. 895, Special Publication No. 57-2252, No. 57-53419, No. 58-2
4605, 58-24606} or plasma irradiation {JP-A-62-96617, JP-A-62-15
No. 1511, No. 62-151516 and No. 62-1
No. 51517] proposed an innovative method of introducing local microstrain to subdivide the magnetic domain and thereby reduce the iron loss.

However, all of these methods increase costs and, in addition, the effect of magnetic domain refining disappears when strain relief annealing is performed. For this reason, there was a problem that it could only be used for stacked iron cores.

(Problems to be Solved by the Invention) The present invention is intended to achieve magnetic domain refining by a method different from the conventional method, which can solve the above problems, and the effect of strain relief annealing is The purpose of this study is to propose a method for producing unidirectional silicon steel sheets that do not lose their properties.

(Means for Solving the Problems) This invention hot-rolls a silicon-containing steel slab, then cold-rolls it once or twice with intermediate annealing to give it a final thickness, and then decarburizes it.・In the manufacturing method of unidirectional silicon steel sheet, which consists of a series of steps of performing primary recrystallization annealing, subsequently applying an annealing separator to the surface of the steel sheet, and then performing secondary recrystallization annealing and purification annealing. For copper plates before annealing, 1 of the plate thickness from the surface
A method for producing an ultra-low iron loss unidirectional silicon plate, which comprises irradiating the surface of a forged plate in dots or lines with an electron beam having a depth of 710 mm, followed by secondary recrystallization annealing. It is.

In this invention, it is important to use an electron beam that extends from the surface of the steel plate to a depth of 1710 mm, specifically IIc
Those generated using a small current and high voltage using the D method are advantageously suitable.

(for production) Next, this invention will be described in detail based on experimental examples.

C: 0.063 wt% (hereinafter simply referred to as %) +
si: 3.39%, Mn: 0.072%,
Al7 0.025%, Se: 0.026%,
A silicon steel slab containing Sn: 0.015% and Mo: 0.013% was heated at 1420°C, hot-rolled into a hot-rolled sheet with a thickness of 1.8 mm, and then heated at 1050°C for 3 minutes. Cold rolling was performed twice with intermediate annealing of 0.2
A final cold-rolled sheet with a thickness of 0 mm was obtained. After that, the following (8) to (
The treatment shown in C) was performed.

(A) EB generated at a high voltage of 150 kV, 1.2 mA and low current and deflected at a wide angle of 300 mm.
After irradiating the steel plate surface with an interval of 1000 μm and a width of 8 mm,
Decarburization and primary recrystallization annealing were performed in wet hydrogen at 840°C.

(B) After decarburizing primary recrystallization annealing in wet hydrogen at 840'C, EB generated at a high voltage of 150 kV, 1.2 mA and low current and deflected at a wide angle of 300 mm was The surface of the steel plate was irradiated with a beam of 1000 μm and a width of 8 IIlm.

(C) Primary recrystallization annealing for decarburization was performed in wet hydrogen at 840°C.

The magnetic properties of the obtained product are shown in Table 1.

As is clear from Table I, the product treated according to the conditions of (A) and (B) above is B1. The value is 1.94T, which is about the same as the product that underwent normal processing (C), but WI? /
50 is significantly improved to 0.09 to 0.11 W/kg.

The reason why the iron loss of the samples treated according to the conditions (A) and (B) is significantly improved compared to other samples is that the thickness of the steel plate increases from the surface of the steel plate 1 as shown in Figure 1. 1710
This is because the lengthening of the Goss grains can be promoted by irradiating the EB that extends to the depth position, that is, the region 2 where the Goss-oriented secondary recrystallized grains preferentially grow.

E extends from the steel plate surface to a depth of 1/10 of the plate thickness
B can be obtained by setting the acceleration conditions to high voltage and small current. That is, the beam diameter of EB generated at high voltage and small current can be narrowed down compared to the conventional EB generated at about 60 kV, so that the beam can penetrate to the location where Goss grains are generated.

In addition, in order to apply EB irradiation uniformly over a large area of the steel sheet surface (for example, a range of 3501 in the width direction of the sheet), there is a dynako single focus that automatically controls the accelerating current in the EB scanning direction, and a dynako double focus that automatically controls the accelerating current in the EB scanning direction. It is desirable to apply a stingmatol that automatically adjusts the beam focus at the end of the scanning direction, which occurs depending on the implementation. In other words, by infiltrating EB to the position where Goss-oriented secondary recrystallized grains preferentially grow to generate Goss nuclei, and by applying this treatment uniformly over a wide range in the sheet width direction, a large amount of Goss grains can be destroyed. This is to control the Goss nucleus with high precision.

Note that the above-mentioned treatment is performed at a high voltage of 100 kV or more and at a voltage of 0.
Narrowly narrowed E generated with a small current of 05 to 10mA
It is preferable to uniformly irradiate the surface of the steel plate with B at intervals of 0.5 to 10 mm.

As the silicon-containing steel that is the material of this invention, any conventionally known steel with a certain composition is suitable, but representative compositions are as follows.

C: 0.01-0.10% C is an element useful for the development of Goss orientation, which results in uniform refinement of the structure during hot rolling and cold rolling, and addition of at least 0.01% or more. is preferred. However, 0.1
If the content exceeds 0%, the Goss orientation will be disturbed, so the upper limit is 0. About 10% is preferable.

Si:2. O~4.5% Si increases the specific resistance of the steel sheet and effectively contributes to reducing iron loss, but if it exceeds 4.5%, cold rollability is impaired;
If it is less than 0%, not only will the resistivity decrease, but also randomization of crystal orientation will occur due to α-γ transformation during the final high-temperature annealing performed for secondary recrystallization and purification, resulting in sufficient iron loss improvement. Since no effect can be obtained, the amount of Si is preferably about 2.0 to 4.5%.

Mn: 0.02-0. 12% Mn is at least 0.02% to prevent hot embrittlement
It is preferable to set the upper limit at about 0.12%, since too much content deteriorates the magnetic properties.

Inhibitors include so-called MnS, MnSe and AIN inhibitors. In the case of MnS, MnSe,
At least one selected from Se, S: 0.0
05 to 0.06% Se and S are both effective elements as inhibitors that control secondary recrystallization of grain-oriented silicon steel sheets. From the perspective of ensuring suppressive power, at least 0.005% is required, but if it exceeds 0.06%, the effect will be impaired, so the lower and upper limits are 0.01% and 0, respectively.
．． It is preferable to set it to about 0.06%.

In the case of A1{4 system, AI: 0.005-0.10% N: 0.0
Regarding the range of 0.04 to 0.015% AI and N, for the same reasons as in the case of the MnSe system mentioned above,
It is set within the above range. Here, the above-mentioned MnS, MnS
The e system and the AIN system can each be used in combination.

The inhibitor precepts are S, Se, AI mentioned above.
In addition to Cu, Sn, Cr, Ge, Sb, Mo
．． Te, Bi, and P are also advantageously compatible, so
They can also be contained together in small amounts. Here, the preferred addition ranges of the above precepts are Cu, Sn. C
r: 0.01-0.15%, Ge, Sb, Mo
, Te, Bi: 0.005-0.1%, P: 0
．． 01 to 0.2%, and each of these inhibitors can be used alone or in combination.

(Example) Practical profit group (1) C: 0.043%, Si: 3.36%
, Se: 0.022%, Sb: 0.025%
and a 2.2 mm thick hot-rolled plate obtained by heating and hot rolling a silicon steel slab containing 0.013% of C: 0 and the remainder substantially consisting of Fe, or (2) C: 0
．． 069%, Si: 3.49%, Aj2:
0.023%, Se: 0.025%, Cu:
0.05%, Sn: 0.1% and Mo: 0.
After heating a silicon steel slab containing 0.13% and the remainder substantially consisting of Fe, it was hot rolled and then heated to 1100°C.
A final cold-rolled sheet with a thickness of 0.20 mm obtained by cold rolling twice with an intermediate annealing of 2 minutes in between was subjected to the following treatments (a) to (C), respectively.

(aH75kV, 1.0mA (7) After irradiating the steel plate surface with EB with a wide angle deflection of 300mm width using a high voltage, small current generating susseter, at 10mm width at 800μm intervals,
Decarburization and primary recrystallization annealing were performed in wet hydrogen at 30'C.

Cb) After decarburization and primary recrystallization annealing in wet hydrogen at 830"C, a 300mm wide wide-angle deflection EB generated with a high voltage of 175kL 1.0mA and a small current was applied to the steel plate. The surface was irradiated with a width of 10 mm at intervals of 800 am.

(C) Decarburization and primary recrystallization annealing were performed in wet hydrogen at 830°C.

Next, after applying a slurry of an annealing separator mainly containing MgO to the surface of the steel plate that has undergone the above treatment, the material of (1) above is subjected to secondary recrystallization annealing at 850"C for 50 hours,
105 at 10'C/h from 850°C to the above (2) material
After raising the temperature to 0°C to develop Goss-oriented secondary recrystallized grains, purification annealing was performed in dry hydrogen at 1230″C for 8 hours.

As shown in Table 2, the results of an investigation of the magnetic properties of the products thus obtained show that the products obtained according to the present invention have a particularly remarkable improvement in core loss.

Table 2 (Effects of the Invention) According to the present invention, it is possible to provide a method for stably manufacturing a unidirectional silicon steel plate in which iron loss does not deteriorate even when subjected to strain relief annealing.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a steel plate showing the mechanism of improving magnetic properties of the present invention. 1. Unidirectional silicon steel plate 2. Preferential formation of primary recrystallized grains in -Goss orientation Figure 1

Claims (1)

[Claims] 1. After hot rolling a silicon-containing steel slab and then cold rolling once or twice with intermediate annealing to obtain the final thickness, decarburization and primary recrystallization. In a method for manufacturing a unidirectional silicon steel sheet, which consists of a series of steps of annealing, subsequently applying an annealing separator to the surface of the steel sheet, and then performing secondary recrystallization annealing and purification annealing, for the steel sheet before secondary recrystallization annealing. , 1 of the plate thickness from the surface
1. A method for producing an ultra-low core loss unidirectional silicon steel sheet, which comprises irradiating the surface of the steel sheet in dots or lines with an electron beam having a depth of /10, followed by secondary recrystallization annealing.