JPS6210215A - Ultra-low iron loss grain oriented silicon steel sheet and its production - Google Patents

Abstract

PURPOSE:To produce a grain oriented silicon steel sheet having an extremely small iron loss by finishing the surface of a finish-annealed steel sheet from which surface oxides are removed near the center line thereof to a specular surface then forming microstrains thereto to form a mixed phase in which fine crystal grain groups mixedly exist and further forming an insulating film consisting of a specific material. CONSTITUTION:After a silicon steel contg. 2-4% Si is hot rolled, the steel is subjected to homogenization annealing, then to cold rolling to form the steel sheet having the final sheet thickness. The sheet is subjected to a decarburization primary recrystallization annealing treatment in succession of the above; thereafter, a separating agent for annealing essentially consisting of MgO is coated thereon and the sheet is subjected to secondary recrystallization annealing and further to purification annealing in dry hydrogen. The surface is finished to a specular surface having <=0.4mum center line average height by polishing and thereafter the local microstrains are formed thereto. The ultra-thin tensile film which has <=1.0mm fine crystal grain groups mixedly existing in the secondary recrystal groups and consists of the nitride, carbide, boride, etc. of various metals is successively formed at >=500 deg.C by a CVD method, etc. and finally the insulating film essentially consisting of a phosphate and colloidal silica is coated thereon and is baked, by which the silicon steel sheet having the extremely small iron loss is produced.

Description

[Detailed Description of the Invention] (Industrial Application Field) Remarkable developments have been made in recent years in an effort to meet the ultimate requirements 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 steel sheets, after processing and assembly, so-called strain relief annealing is applied. However, it has been pointed out that the disadvantage is that it inevitably causes characteristic deterioration, and that its usage is limited.

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

As is well known, unidirectional silicon steel sheets are products in which secondary recrystallized grains are highly concentrated in the (11,0) [001), that is, Goss orientation, and are mainly used in transformers and other electrical appliances. The magnetic flux density (B+) of the product is used as the iron core of equipment and has electrical and magnetic properties.

It is required that the iron loss (WIT/S, represented by the value) is high and the iron loss (WIT/S, represented by the value) is 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 mm has magnetic properties of 8.
. 1.90T or more, WIwaysa 1.05W/Kg or less, and the magnetic properties of products with a plate thickness of 0.23mm are B161
．． 89T or more, 1,7. . The production of unidirectional silicon steel sheets with a low core loss of about 0.90 W/Kg or less is rather becoming 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 at 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. 58-2
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 cannot be adopted from a process perspective, as it does not contribute enough to reducing iron loss despite the significant increase in cost. Due to problems with adhesion, it has not 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
If high-temperature annealing is performed at a temperature of 0° C. or higher, the steel sheet and the ceramic layer will 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, microstrains are formed in a steel plate after final annealing by mechanical introduction or traces of laser irradiation, and then heated at a high temperature of 500°C or higher to form microrecrystallized grains in the strain introduction region. A method of manufacturing an ultra-low core loss unidirectional silicon steel sheet, which does not deteriorate in properties even when subjected to high-temperature annealing, has been proposed by producing a group of unidirectional silicon steel sheets. These manufacturing methods differ from the above-mentioned case of magnetic domain refining 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 more advantageously take advantage of the above-mentioned improvement in iron loss due to the mirror finish, the inventors have decided to reduce the above-mentioned costs, especially from the perspective of today's development of energy-saving materials. 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 degrading the properties during high-temperature treatment, and in particular, without deteriorating the properties during high-temperature treatment. However, when the oxides on the surface of a grain-oriented silicon steel sheet that has been finish annealed are removed and then polished to a mirror-like state,
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, An ultra-low iron loss unidirectional silicon steel sheet having an ultra-thin tensile coating strongly adhered through a mixed phase (first invention), a super-low core loss unidirectional silicon steel plate having an ultra-thin tensile coating of the first invention, which mainly contains phosphate and colloidal silica on the ultra-thin tensile coating of the first invention. An ultra-low core loss unidirectional silicon steel sheet (second invention) further provided with a coating film as a component, and oxides on the surface of the finish annealed steel sheet are removed, and then polished to a center line average roughness of 0.4 μm. The following mirror-finished steel plate was subjected to carbon dioxide treatment at a temperature of 500°C or higher after introducing artificial minute strain to local positions on its surface.
1.0 in the secondary recrystallized grains near the steel sheet surface by VO, ion plating or ion implantation.
Forms a mixed phase in which microcrystal grain groups of mm or less are mixed together, and at the same time, Tj, Zr, Hf, V, Nb, Ta + Mn, Cr, Mo adhere firmly on the steel plate surface via the mixed phase.
, W, Co, Ni, Al, B and Si nitrides and/or carbides.

A7! , Si+Ti+Sn, Fe, Zr+Ta and C
oxide of e.

Si, Ti, Nb, Ta, AE, Zr, llf,
V, and - boride.

Mo+W, Ti+Zr and V silicides.

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 Si 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: 0.03~0.050! :, St: 2.
50~4.5X, Mn: 0.01~0.2L Mo
: 0.003~0.1χ, Sb: 0.005~
0.2χ, the total of one or two types of S or Se,
Composition containing o, oos ~ 0.05χ ■C: 0.0
3~0.08χ, St: 2.0~4.0χ, S: 0
．． 005~0.05L N:0.001~0.0mm
Z, Sn: 0. '01~0.5χ, CLI: 0
．． Composition containing 01-0.3χ, Mn: 0.01-0.2χ, C: 0.03-0.06χ, Si: 2
．． 0~4.0χ, S: 0.005~0.05χ,
B: 0.0003-0.0040χ, N: Q,
001-0.01X, Mn: 0.01-0.22.

Next, the hot-rolled sheet undergoes uniform annealing at 800 to 1100°C.
One-time cold rolling method, in which the final plate thickness is obtained by two cold rolling steps, or two-step cold rolling method, in which intermediate annealing is usually performed at 850°C to 1050°C, and then further cold rolling is performed.In the latter case, the first rolling rate is 50
% to about 80%, the final rolling reduction is about 50% to 85%, and the final cold rolled plate thickness is 0.15 mm to 0.35 mm.

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 generally more effective to prevent the formation of forsterite, which is indispensable to be formed after final annealing, in order to simplify the subsequent mirror finishing of the steel sheet, so A7 is used as an annealing separator. zoz + Z
It is preferable to use MgO mixed with 50% or more of r0z, TE01, 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, the
It is more advantageous to carry out holding annealing at a low temperature of 00°C, and in addition, for example, 0.5 to b annealing may be used.

Purification annealing after secondary recrystallization annealing requires annealing in saturated hydrogen at 1100° C. or higher for 1 to 20 hours to achieve purification of the steel sheet.

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, conventional methods such as chemical polishing such as chemical polishing and electrolytic polishing, mechanical polishing such as puff polishing, or a combination thereof are used to polish the steel plate surface to a mirror-like state, that is, to a center line average roughness of 0.4 μm or less. Finish it.

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
- plowing 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.

After that, CVO, ion plating, or ion implantation is performed at a high temperature of 500°C or higher to recrystallize the local strain introduced 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 coatings at this time are Tt, Zr, Hf, V+Nb, T
a+Mn, Cr.

Nitride and/or carbide of Mo, W, Co, Ni, A 1 , B, St.

^(!, SitTi, Sn+Fe+Zr, Ta, Ce
oxide + Sit Ti, Nb.

Ta, A A, Zr,) If, V, H boride +
An ultra-thin material made of at least one selected from silicides of Mo, W, Ti, Zr, and V, phosphides of B, St, and sulfides of Fe and Zn is suitable, especially ultra-thin materials. It is effective that the thin tension coating has a thickness of about 0.1 to 2 μm. Since it is difficult to recrystallize CVO, ion plating, or ion implantation at temperatures below 500°C, the processing temperature is set to 500°C or higher.

Furthermore, it is naturally 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 1,000,000 KVA. However, for the formation of this insulating coated and baked layer, conventionally known methods may be used as they are.

Now, the explanation will proceed according to the progress of specific experiments that led to the success of each of the inventions listed above. C: 0.042 (weight below), 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, hot rolling to 2.0111°C
It was made into a thick hot-rolled plate.

Then, after homogenization annealing at 900°C for 3 minutes, at 950°C for 3 minutes.
Cold rolled twice with intermediate annealing for 0.2 min.
A final cold-rolled sheet with a thickness of 3 mm was obtained.

After that, after decarburization and primary recrystallization annealing in a wet hydrogen atmosphere at 820°C, the steel plate surface was coated with inert A120111 (80
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 for 5 hours in saturated hydrogen at °C.

After that, after removing the oxides on the steel plate surface by pickling, 3χ
HP and I (,0□After chemical polishing in mixed solution (8)
: Microscopic mechanical strain (0.1 mm wide flaws) is locally introduced with a knife at 8 mm intervals in the direction perpendicular to the rolling direction (B); Spacing -2.0mm, spot diameter = 0.5mm φ1 @ radiation energy: μ = 20J/
Each of the two samples treated under two different conditions was exposed to a mixed gas of TiCjl'a, Nt and H2 at 750°C for 20 hours using a CVD apparatus to introduce local microstrains (cm"). CVD treatment is performed in an atmosphere to form a mixed phase in which 0.05 to 0.51 fine crystal grain groups are mixedly generated in the secondary recrystallized grains near the surface of the m plate, and at the same time, the mixed phase is An ultra-thin tension coating (0.6 μm) of TiN strongly adhered to the surface of the intervening steel plate.
thickness) was formed. 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).

Table 1 From Table 1, the magnetic properties are [1+o is 1.91 to 1.92T,
W+tzs.

Normal process material (comparison material) with 0.60 to 0.65 匈/Kg
0.02~0.03T, W+tzs at B1° compared to
. It is noteworthy that the ratio is 0.23 to 0.28/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 the CVD process, 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) Cliff group 1 (A) C: 0.041χ, Si: 3.48χ, Mn:
0.062χ, Mo: 0.025χ.

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

A hot rolled sheet containing A 1 :0.025'X and N:0.066% was used. First of all, the hot rolled sheet (A) is 900
After equalization annealing at 950° C. for 3 minutes, cold rolling was performed twice with intermediate annealing at 950° C. to obtain a final cold rolled sheet having a thickness of 0.23 mm.

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 form a final cold-rolled sheet with a thickness of 0.23 mm.

After degreasing the surface of these cold-rolled sheets (A) and (B), the steel sheet surface was decarburized and annealed in wet hydrogen at 830°C.
l zoi (70 ri, MgO (252),
An annealing separator consisting of Zr□z (5χ) was applied.

Thereafter, the sample (8) was subjected to secondary recrystallization annealing at 850°C for 50 hours, and then purified annealing in hydrogen at 1200°C for 6 hours.

In addition, the sample (B) was heated at 1050°C at 5°C/hr from 820°C.
After secondary recrystallization at 1200°C,
Purification annealing was performed in soft hydrogen for an hour.

After that, each sample (8) and (B) was pickled to remove the oxide film, and then chemically polished to a center line average roughness of 0.05 μm.
After forming the following mirror-like state, local microstrains were introduced onto the surface of the steel plate using a knife at intervals of 8 mm in a direction perpendicular to the rolling direction. In addition, local microstrain was introduced into some samples using a YAG laser. The usage conditions are that the energy is 20J/
cm2. Spot diameter 0.2mm.

This was carried out with a spot center spacing of 0.5 to 1 mm 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 to 0
．． 7 μm thick). 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.

(Effect of the invention) According to this invention, an ultra-low iron loss unidirectional silicon steel sheet can be stably and easily obtained, and its iron loss characteristics are independent of high temperature thermal history such as chasing annealing. maintained.

Claims (1)

[Claims] 1. In the vicinity of the surface of a steel plate that has been mirror-finished to a centerline average roughness of 0.4 μm or less through final annealing, fine crystals of 1.0 mm or less are present in secondary recrystallized grains near the surface. An ultra-low core loss unidirectional silicon steel sheet that has a mixed phase in which grain groups are mixed, and has an ultra-thin tensile coating strongly adhered through the mixed phase. 2. Near the surface of a steel plate that has been mirror finished to a center line average roughness of 0.4 μm or less through final annealing, 2.
It has a mixed phase in which fine crystal grain groups of 1.0 mm or less are mixed in the next recrystallized grain, and has an ultra-thin tension coating that is strongly adhered through the mixed phase, and further has an ultra-thin tension coating on this ultra-thin tension coating. An ultra-low core loss unidirectional silicon steel sheet with a coating mainly composed of phosphate and colloidal silica. 3. After removing oxides on the surface of the final annealed steel plate, the steel plate is polished to a mirror-like state with a centerline average roughness of 0.4 μm or less, and artificial micro-strains are applied to local positions on the surface of the steel plate. Then, by CVD, ion plating, or ion implantation at a temperature of 500°C or higher, a mixed phase in which fine grain groups of 1.0 mm or less are mixed and generated in the secondary recrystallized grains near the steel plate surface is created. At the same time, Ti, Zr, Hf, V, Nb, Ta, Mn, Cr, Mo were formed and firmly adhered on the steel plate surface through the mixed phase.
, W, Co, Ni, Al, B and Si nitrides and/or carbides, Al, Si, Ti, Sn, Fe, Zr, Ta and Ce oxides, Si, Ti, Nb, Ta, Al, Zr , Hf,
Borides of V and W, silicides of Mo, W, Ti, Zr and V. An ultra-low iron loss unidirectional silicon film comprising the step of forming an ultra-thin tensile coating made of at least one selected from the group consisting of B and Si phosphides and Fe and Zn sulfides. Method of manufacturing steel plates.