JPS63227722A - Manufacture of grain-oriented magnetic steel sheet having very small iron loss - Google Patents

Abstract

PURPOSE:To obtain a grain-oriented magnetic steel sheet having a very small iron loss by mirror-finishing the surface of a finish-annealed grain-oriented magnetic steel sheet, partially producing small strain, forming a mixed phase contg. a group of fine grains and further forming a very thin tension film of a specified metallic compd. CONSTITUTION:A silicon steel sheet subjected to final cold rolling is finished- annealed, the surface oxide is removed and the surface of the steel sheet is mirror-finished to <=0.4mum central average roughness by chemical polishing, buffing or other method. The surface is then processed to locally produce small stain and recrystallization is caused at the strain produced positions at a high temp. of >=500 deg.C by CVD, ion plating or other method to form a mixed phase contg. a group of fine grains of <=1.0mm grain size in secondary recrystallized grains near the surface of the steel sheet. A very thin tension film of at lest one of the nitrides, carbides, oxides, borides, silicides, phosphides or sulfides of specified elements having 0.1-2mum thickness is further formed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] Remarkable developments have been made in recent years in an effort to meet the ultimate demands for improving the electrical and magnetic properties of unidirectional silicon steel sheets, particularly for reducing iron loss. Even though efforts are being made and the efforts are beginning to be effective, a serious problem associated with implementation is that when using unidirectional silicon TLJ plates, after processing and assembly, so-called strain relief annealing is applied. However, it has been pointed out that there is a disadvantage in that it inevitably causes deterioration of characteristics and limits its usage.

In this specification, the following is related to the results of research and development to open up a new method that can advantageously meet the above requirements, regardless of whether or not it undergoes a high-temperature thermal history such as strain relief annealing. state

By the way, unidirectional silicon steel sheets are products in which secondary recrystallized grains are highly concentrated in the (110) (001), or Goss orientation, and are mainly used in transformers and other electrical equipment. The magnetic flux density (Bo.

It is required that the iron loss (WI4/S, represented by the value) be high and the iron loss (WI4/S, represented by the value) be low.

This unidirectional silicon steel plate is manufactured through a wide variety of complicated processes, but numerous inventions and improvements have been made so far, and today a product with a thickness of 0.30 m + W has magnetic properties of 8.
1゜1.90T or more, /,. The magnetic properties of the product are 1.05W/Kg or less and the plate thickness is 0.23m+W.

1.89T or more, W+? The production of unidirectional silicon steel sheets with a low core loss of about 15° 0.90 m/kg or less is becoming rather common.

Particularly recently, there has been a marked increase in demand for power loss reduction features from an energy-saving perspective, and in Europe and the United States, when creating a transformer with low loss, the reduction in iron loss is converted into a monetary value and added to the transformer price.・The ``evaluation'' (iron loss evaluation) system has become widespread, and this is nothing but the ultimate requirement mentioned in the beginning.

(Prior art) Under these circumstances, recently, the surface of a unidirectional silicon steel plate after finish annealing is irradiated with a laser in a direction approximately perpendicular to the rolling direction to introduce local microstrain to subdivide the magnetic domains. Proposal to reduce iron loss
No. 252, Special Publication No. 57-53419, Special Publication No. 5B-2
6405 and Special Publication No. 58-26406)
However, this magnetic domain refining technology does not apply strain relief annealing, and even though stacked iron core orientation is effective as a transformer material,
The disadvantage of mainly wound core transformer materials that undergo strain relief annealing is that the laser irradiation effect is lost because the annealing process releases the local minute strain introduced by laser irradiation and widens the magnetic domain width. be.

On the other hand, earlier in Japanese Patent Publication No. 52-24499, the surface of the unidirectional silicon steel plate after finish annealing was mirror-finished, or the mirror-finished surface was coated with thin metal plating, and furthermore, insulation was applied on the mirror-finished surface. A method of manufacturing an ultra-low core loss unidirectional silicon steel sheet by applying and baking a film has been proposed.

However, this method of improving iron loss through mirror finishing is
In order to adopt it in terms of process, it would result in a significant cost increase and its contribution to iron loss reduction would not be sufficient, and (after mirror finishing, an indispensable insulating film was applied and baked, and there would be problems with adhesion.) It has not yet been adopted in current manufacturing processes.

Japanese Patent Publication No. 56-4150 also proposes a method in which a steel plate surface is mirror-finished and then an oxide-based ceramic thin film is vapor-deposited. However, this method also has 60
High-temperature annealing at 0°C or higher causes the steel plate and the ceramic layer to separate, so it cannot be used in actual manufacturing processes.

Furthermore, Japanese Patent Publication No. 14827/1982, Japanese Patent Application Publication No. 59/1983
In Publication No. 23822, micro-strains are formed in a steel plate after finish annealing by mechanical introduction or traces of laser irradiation, and then heated at a high temperature of 500°C or higher to form micro-recrystallized grain groups in the strain-introduced region. A method of manufacturing an ultra-low core loss unidirectional silicon steel sheet that does not cause property deterioration even after high-temperature annealing has been proposed. These manufacturing methods differ from the above-mentioned case of magnetic domain refining and formation by introducing local minute strain by laser irradiation after final annealing.
Although high-temperature annealing has the advantage that the effect of improving properties does not disappear, it is still difficult to say that sufficient ultra-low iron loss has been achieved due to the use of a forsterite coating.

(Problems to be Solved by the Invention) In order to take advantage of the above-mentioned effectiveness of improving iron loss through mirror finishing, the inventors have found that, especially from the perspective of today's development of energy-saving materials, the above-mentioned cost increase has been avoided. Based on this basic understanding, we believe that it is important to more advantageously overcome the problems of adhesion and durability of ultra-thin tensile coatings without deteriorating their properties during high-temperature treatment. , when polishing to a mirror-like state after removing oxides on the surface of a grain-oriented silicon steel sheet that has been finish annealed,
It is an object of the invention to particularly advantageously achieve ultra-high iron loss by radically improving the steel sheet processing method after removing the oxides.

(Means for Solving the Problems) The above problems can be effectively satisfied by a configuration based on the following matters.

Contains a group of fine crystal grains of 1.0 mm or less mixed with secondary recrystallized grains near the surface of a steel sheet that has been mirror-finished to a centerline average roughness of 0.4 μm or less through final annealing, and on the surface of the steel sheet, An ultra-low iron loss unidirectional silicon steel sheet having an ultra-thin tensile coating strongly adhered via the mixed phase (first invention), phosphate and colloidal silica are applied on the ultra-thin tensile coating of the first invention. An ultra-low iron loss unidirectional silicon steel sheet (second invention) further provided with a coating film as a main component, and oxides on the surface of the finish annealed steel sheet are removed and then polished to a center line average roughness of 0. A steel plate made into a specular state of 4μ steel or less is subjected to artificial microstrain at local positions on its surface, and then subjected to carbon dioxide treatment at a temperature of 500℃ or higher.
By VD, ion plating or ion implantation, 1.0
Forms a mixed phase in which microcrystal grain groups of mm or less are mixed, and at the same time, Ti, Zr1HflV, Nb1Ta, Mn, Cr, MO are firmly adhered on the steel plate surface via the mixed phase.
, WICO, Ni, A f IB and St nitride and/or carbide.

Affi, oxides of St, Ti, Sn+Fe, Zr, Ta and Ce.

5irTi, Nb+ Ta, A J! lZr+H
f t L and Ka boride.

Silicides of Mo, W, Ti, Zr and V.

An ultra-low core loss unidirectional silicon film comprising the step of forming an ultra-thin tensile coating made of at least one member selected from the group consisting of B and St phosphides and Fe and Zn sulfides. This is a method for manufacturing a steel plate (third invention).

The manufacturing process of the unidirectional silicon steel sheet according to the present invention will be described in more detail, including a general explanation.

First, the starting materials are conventionally known unidirectional silicon steel sheet material components,
For example, ■c: o, oas~0.050χ, St: 2.
50~4.5χ, Mn: 0.01~0.2χ, Mo
: 0.003~0.1χ, Sb: 0.005~
0.2χ, the total of one or two types of S or Se,
Composition containing 0.005 to 0.05χ ■C: 0.0
03~0.08χ, Si: 2.0~4.0χ, S
: 0.005~0.05χ, N: 0.001~
0. O1χ, Sn: 0.01~0.5χ, Cu:
0.01~0.3χ, Mn: 0.01~0.2χ
Composition containing ■C: 0.003 to 0.06χ, St
: 2.0~4.0χ, s: 0.005~0.0
5X, B: 0.0003-0.0040χ, N
: 0.001~0.01χ, Mn: 0.01~
It is applicable to compositions containing 0.2χ.

Next, the hot-rolled sheet is either uniformly annealed at 800 to 1100°C and then cold-rolled once to reach the final thickness, or it is usually subjected to intermediate annealing at 850" to 1050°C. In the second cold rolling method, the initial rolling reduction is about 50% to 80%, and the final rolling reduction is about 50% to 85%.
The final cold-rolled plate thickness is from 0.15 mm to 0.35 mm+ thickness in terms of %.

After finishing the final cold rolling, the steel plate finished to the product thickness is surface degreased and then subjected to decarburization primary recrystallization annealing treatment in wet hydrogen at 750°C to 850°C.

After that, an annealing separator containing MgO as a main component is usually applied to the surface of the steel sheet. At this time, it is effective to avoid the formation of forsterite, which is generally essential to form after finish annealing, in order to simplify the subsequent mirror finishing of the steel sheet, so A2□Oa + Zr is used as an annealing separator.
It is preferable to use MgO mixed with 50% or more of 0g + Ti1t, etc.

After that, secondary recrystallization annealing is performed, but this step is (110)
This is done to sufficiently develop secondary recrystallized grains with <001> orientation, and is usually box annealed to immediately
This is done by raising the temperature above ℃ and maintaining it at that temperature.

In this case, in order to develop a highly uniform secondary recrystallized grain structure in the (100) <001> orientation, it is advantageous to perform holding annealing at a low temperature of 820°C to 900″C; Heat-removal annealing at a heating rate of 5 to 15°C/h may also be used.

Purification annealing after secondary recrystallization annealing is carried out at 1100°C in water and hydrogen.
It is necessary to perform annealing for 1 to 20 hours to achieve purification of the steel plate.

After this purification annealing, the oxide film on the surface of the steel sheet is removed by known chemical removal methods such as pickling, mechanical removal methods such as cutting and grinding, or a combination thereof.

After this oxide removal treatment, the steel plate surface is polished to a mirror-like state, that is, with a center line average roughness of 0.4 μm, using conventional methods such as chemical polishing such as chemical polishing and electrolytic polishing, mechanical polishing such as puff polishing, or a combination thereof. Finish as below.

Next, a local microstrain is introduced onto the surface of the mirror-finished steel plate using a conventionally known method, such as the method of pressing a rigid piece against the steel plate and scratching it (Japanese Patent Publication No. 50
(Refer to Publication No. 35699), moving or scratching the surface of a steel plate with the edge of a knife or razor, diamond sand, a metal scrubber, etc.

■A method in which a rigid body with a sharp linear tip is pressed against a steel plate.

■A method in which liquid or hard powder or a mixture thereof is injected onto the steel plate at high pressure and scratched as necessary.

(2) A method of scanning finely focused dot or line laser irradiation or high-energy electron beams may also be used.

Then, by CVD, ion plating, or ion implantation, the temperature is raised to 500°C or higher to recrystallize the local strain introduction position to form a mixed phase containing fine crystal grains near the steel sheet surface. An ultra-thin tensile film strongly adhered via the mixed phase is formed.

The tension coating at this time is TitZr+Hf+VtNb+T
a, Mn+CrtMo+ lt+ Co, Ni, A
f, B, St nitride and/or carbide.

Aj! , Si, Ti, Sn, Fe, Zr+Ta+Ce
oxides, Si, Ti, Nb+Ta, Ajl! , Zr
, 1ILV, − boride + Mo, LTLZr, V silicide, B, Si phosphide, and at least one selected from Fe and Zn sulfides. Yes, especially for ultra-thin tension coatings 0.1 to 2
It is effective to have a thickness of approximately μI. CVO, ion plating or ion implantation is difficult to recrystallize at temperatures below 500°C.
The treatment temperature is 500°C or higher.

Furthermore, it is necessary to apply and bake an insulating film mainly composed of phosphate and colloidal silica on the ultra-thin tension film produced in this way when using a large-capacity transformer of up to 1 million KVA. For the formation of this insulating coated and baked layer, conventionally known methods may be used as they are.

Now, we will proceed with the explanation according to the progress of the specific experiments that led to the success of each of the invented inventions. C: 0.042% by weight (hereinafter simply expressed as %), Si: 3.38%, Mn: 0.0
62%, Se: 0.021%, Sb: 0.025% and Mo: 0.026%.
After heating at 360° C. for 4 hours, it was hot rolled to obtain a hot rolled sheet with a thickness of 2.0 mm.

After that, it was subjected to equalization annealing at 900°C for 3 minutes and cold rolling twice, including an intermediate annealing at 950''C for 3 minutes.
A final cold-rolled sheet with a thickness of 23 mm was obtained.

Thereafter, after decarburization and primary recrystallization annealing in a wet hydrogen atmosphere at 820°C, the surface of the steel plate was coated with inert Al go3 (80°C).
Apply an annealing separator consisting of χ) and MgO (20%),
Then, secondary recrystallization annealing was performed at 850°C for 50 hours and
Purification annealing was performed at 0°C in miscellaneous hydrogen for 5 hours.

After that, after removing the oxides on the steel plate surface by pickling, 3χ
After chemical polishing in IF and HtOz mixture (A):
Introducing small mechanical strains (0, In++++ width) locally with a knife at 8IIIl+ intervals in the direction perpendicular to the rolling direction (B): Using a pulsed laser to introduce 8a+s+ intervals (spot center spacing) in the direction perpendicular to the rolling direction. -2,0In1m,
Spot diameter -0.5mmφ, irradiation energy: μm
Two types of samples were treated under two different conditions, each of which introduced a local microstrain at 20 J/cm"), and were treated with TiC24, N2, and H for 20 hours at 750°C using a CVD apparatus. CVD treatment is performed in a mixed gas atmosphere to form a mixed phase in which fine crystal grain groups of 0.05 to 0.511III+ are mixedly generated in secondary recrystallized grains near the surface of the steel sheet, and at the same time, the mixed phase is An ultra-thin tensile coating of TiN (0
, 6 μm thick). For some samples, a coating film containing phosphate and colloidal silica as main components was formed on the tension film. The magnetic properties of the products at that time are summarized in Table 1 together with the normal process material (comparative material).

From Table 1 Table 1, the magnetic properties are B1°: 1.91-1.92T, W
+, /s.

Normal process material (comparison material) with 0.60 to 0.65 W/Kg
Compared to B. at 0.02~0.03T, W+w/s
. It is noteworthy that the performance is 0.23 to 0.28 W/Kg, which is extremely good (in particular, the improvement in iron loss characteristics is remarkable).

(Function) This improvement in properties is achieved by making the surface of the steel sheet mirror-like.
A local microstrain is introduced, and then, during CvD processing, fine crystal grains are generated at the microstrain introducing position, and at the same time, T
Due to the formation of an ultra-thin tensile coating of iN, an effective reduction in iron loss is led.

(Example) Back construction (A) C: 0.041χ, St: 3.48χ, Mn:
0.062χ, Mo: 0.025χ.

Hot rolled sheet containing Se: 0.022χ, Sb: 0.025χ and (B) C: 0.053X, Si: 3.32
X, Mn: 0.072X, S: 0.018X.

A hot rolled sheet containing A deficiency: 0.025χ and N: 0.066χ was used. First, hot-rolled sheet (A) was heated to 900℃ for 3
After equalization annealing for 2 minutes, intermediate annealing at 950°C was performed for 2 minutes.
Cold rolling was performed twice to obtain a final cold rolled sheet having a thickness of 0.23+u+.

On the other hand, the hot-rolled sheet (B) was uniformly annealed at 1050° C. for 3 minutes, then rapidly cooled, and then warm-rolled at 300″C to obtain a final cold-rolled sheet with a thickness of O-23 m.

Both of these cold rolled sheets (A) and (B) had their surfaces degreased and then decarburized and annealed in wet hydrogen at 830°C. t'3(70χ), MgO(25χ),
An annealing separator consisting of Zr0t(5χ) was applied.

Thereafter, the sample (A) was subjected to secondary recrystallization annealing at 850°C for 50 hours, and then purified annealing in dry hydrogen at 1200°C for 6 hours.

In addition, the sample (B) was heated at 105°C at 5°C/hr from 820°C.
After raising the temperature to 0°C and performing secondary recrystallization, it was heated to 1200°C.
Purification annealing was performed in dry hydrogen for 8 hours.

After that, each sample in (^) and (B) was pickled to remove the oxide film, and then chemically polished to a mirror-like state with a centerline average roughness of 0.05μ or less. Local minute strain was introduced with a knife at 8 m+ intervals in the direction. In addition, local microstrain was introduced into some samples using a YAG laser. The usage condition is that the energy is 20J.
/cn'', a spot diameter of 0.2++ m, a spot center spacing of 0.5 to l+wm, and a laser scanning trace spacing of 8 mm (laser irradiation in a direction perpendicular to the rolling direction).

Thereafter, various thin films (approximately 0.6~
0.7 μM thick) was formed. Thereafter, a coating film containing colloidal silica and phosphate as main components was formed on one part of the sample. The magnetic properties of the products at that time are summarized in Table 2.

Whistle 9 Back (Effects of the Invention) According to this invention, an ultra-low iron loss unidirectional silicon steel plate can be obtained stably and easily, and its iron loss characteristics are not affected by high-temperature thermal history such as chamfer annealing. is kept irrelevant.

Patent applicant Kawasaki Steel Co., Ltd. Representative patent attorney Akira Sugimura Inquiry patent attorney Sugi
Written by Ko Mura

Claims (1)

[Claims] 1. Local positions on the surface of a steel plate that has been finish annealed to remove oxides and then polished to a mirror-like state with a center line average roughness of 0.4 μm or less CVD at a temperature of 500℃ or higher after introducing microstrain into the
, ion plating or ion implantation to form a mixed phase in which fine crystal grains of 1.0 mm or less are mixedly generated in the secondary recrystallized grains near the surface of the steel sheet, and at the same time, the steel sheet is formed through the mixed phase. Oxides of Al, Si, Ti, Sn, Fe, Zr, Ta and Ce, Si, Ti, Nb, Ta, Al, Zr, Hf, strongly adhered on the surface.
Ultra-thin tension made of at least one member selected from the group consisting of V and borides of W, silicides of Mo, W, Ti, Zr and V, phosphides of B and Si, and sulfides of Fe and Zn. A method for producing an ultra-low iron loss unidirectional silicon steel sheet, the method comprising the step of forming a film.