JPS61235511A - Production of ultra-low iron loss grain oriented silicon steel sheet having thermal stability - Google Patents

Abstract

PURPOSE:To provide thermal stability to a grain oriented silicon steel sheet and to decrease the iron loss thereof to an ultra-low level by subjecting said steel sheet to primary annealing then coating a separating agent for annealing consisting of MgO mixed with Al2O3, ZrO2, TiO2, etc., on said steel sheet and subjecting such steel sheet to secondary recrystallization annealing then to purification annealing in a Ti-contg. atmosphere. CONSTITUTION:The grain oriented silicon steel sheet having the prescribed compsn. is subjected to decarburization and primary recrystallization annealing. The separating agent for annealing which consists essentially of MgO and is incorporated therein with >=50wt.%>=1 kinds among Al2O3, ZrO2 and TiO2 is coated thereon and the steel sheet is subjected to the secondary recrystallization annealing. The steel sheet is thereafter subjected to the purification annealing in the gaseous atmosphere contg. Ti or the gaseous atmosphere mixed further with a non-oxidative gas. The extra-thin tensile film consisting of TiN, TiC or Ti(C, N) is formed on the surface of the steel sheet by such treatment. The film has excellent adhesiveness and the grain oriented silicon steel sheet having the excellent thermal stability and magnetic characteristic and the ultra-low iron loss is thus obtd.

Description

[Detailed Description of the Invention] (Field of Industrial Application) In recent years, remarkable efforts have been made to improve the electrical and magnetic properties of unidirectional silicon steel sheets, and in particular to meet the extreme demands of reducing iron loss. Our development efforts are gradually bearing fruit, but one serious problem associated with their implementation is that when using unidirectional silicon steel sheets, when so-called strain relief annealing is applied after processing and assembly, there is a risk of property deterioration. It has been pointed out that there are disadvantages in that it unavoidably involves accompaniment and restrictions on how it can be used.

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 (110) (001), or Goss, orientation, and are mainly used in transformers and other electrical equipment. When used as an iron core, the product is required to have a high magnetic flux density (represented by the value e+) and a low iron loss (represented by the value Wit/S) as electrical and magnetic properties.

This unidirectional silicon steel sheet is manufactured through a wide variety of complicated processes, and numerous inventions and improvements have been made to date.
Today, the magnetic properties of products with a plate thickness of 0.30 mm are B+o1.
．． The magnetic properties of the product are 90T or more, Ltzsol, 05W/kg or less, and a plate thickness of 0.23auo. 1.8
9T or more, WB7soO, 90W/kg or less ultra-low iron 1
1. Unidirectional silicon steel sheets are being manufactured.

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 "Eva IJ, Nijo" (iron loss evaluation) system is becoming widespread.

(Prior art) Under these circumstances, recently, a method has been developed to subdivide the magnetic domains by introducing local minute strain to the surface of a unidirectional silicon steel sheet after final annealing by laser irradiation in a direction approximately perpendicular to the rolling direction. (See Japanese Patent Publication No. 57-2252, Japanese Patent Publication No. 57-53419, Japanese Patent Publication No. 58-26405, and Japanese Patent Publication No. 58-26406).

This magnetic domain refining technology is effective for transformer materials for laminated core transformers that are not subjected to strain relief annealing, but for material for wound core transformers that are subjected to strain relief annealing,
There is a drawback that the local minute strain introduced by laser irradiation is released by annealing and the magnetic domain width becomes wider, so that the laser irradiation effect is lost.

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

However, this method of improving iron loss through mirror finishing cannot be adopted from a process perspective because it does not make a sufficient contribution 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.

(Problems to be Solved by the Invention) Improving iron loss through mirror finishing as described above involves a significant increase in cost. It is an object of the invention to obtain advantageously.

(Means for solving problems) The above purpose is precisely fulfilled by the following steps.

A hot-rolled plate obtained by hot-rolling a unidirectional silicon steel slab is subjected to the necessary heat treatment and then cold-rolled once or twice with intermediate annealing to obtain the final plate thickness, Next, decarburization and primary recrystallization annealing are performed, then an annealing separator mainly composed of MgO is applied to the surface of the steel sheet, and then secondary recrystallization annealing and purification annealing are performed.A series of manufacturing methods for unidirectional silicon steel sheets. In,
In addition to mixing at least one selected from ^1□Os, 2r02 and Tie into the annealing separator in an amount of 50% by weight or more, a gas atmosphere containing Ti or a non-oxidizing gas atmosphere is added after the secondary recrystallization annealing. By performing purification annealing in a mixed gas atmosphere with a reactive gas, TiN, Ti
A method for producing a thermally stable, ultra-low core loss unidirectional silicon steel sheet (first invention), characterized by forming an ultra-thin tensile coating made of C or Ti (C,N).

A hot-rolled plate obtained by hot-rolling a unidirectional silicon steel slab is subjected to the necessary heat treatment and then cold-rolled once or twice with intermediate annealing to obtain the final plate thickness, Next, decarburization and primary recrystallization annealing are performed, then an annealing separator mainly composed of MgO is applied to the surface of the steel sheet, and then secondary recrystallization annealing and purification annealing are performed.A series of manufacturing methods for unidirectional silicon steel sheets. Wipe it,
In addition to mixing 50% by weight or more of at least one selected from Al2O3, 2r02 and TiO□ into the annealing separator, a gas atmosphere containing Ti or a non-oxidizing gas is added after the secondary recrystallization annealing. By performing purification annealing in a mixed gas atmosphere of
or Ti (C,N), forming an ultra-thin tension film, and then further applying laser irradiation in a direction transverse to the rolling direction to introduce local strain, and then applying a low-temperature coating film treatment. A method for producing a thermally stable, ultra-low core loss unidirectional silicon steel sheet (second invention).

The inventors conducted many trial experiments to develop ways to improve the thermal stability of magnetic properties.

As a result, Al2O3, ZrO, etc. are included in the annealing separator applied after decarburization and primary recrystallization annealing of unidirectional silicon steel sheets.

Tie2 or the like is mixed with MgO at a concentration of 50% or more, applied to the surface of the steel sheet, and subjected to secondary recrystallization annealing, and then heated at high temperature in a reactive gas atmosphere containing Ti or in a mixed gas atmosphere with a non-oxidizing gas. By performing purification annealing, an extremely thin layer of TiN, TiC or Ti (C
, N), it has been discovered that it is possible to produce a unidirectional silicon steel sheet with thermal stability and ultra-low core loss.

Here, the reactive gas containing Ti, with Ticls as a typical example, reacts with N and/or C in the heat treatment environment under the above heat treatment conditions or in the steel of grain-oriented silicon steel sheet,
TiN, TiC, or Ti (C,N) refers to a gas that is a component useful in forming an insulating film,
In addition to the above-mentioned TiCl4, TiCl, TiCl2, etc. are also included.

In addition, non-oxidizing gases include CL, N2.82, etc., and Ar as long as it does not inhibit the above reaction at least.

NH3 and CO gas are also suitable.

The explanation will proceed according to specific experiments that led to the success of each of the above inventions.

C0,048% by weight (hereinafter simply expressed as %), Si 3
．． 38%, Mn 0.062%, SeO, 022%,
SbO, 025% and M.

Continuously cast silicon steel slab containing 25% O, 1340
After heating at ℃ for 4 hours, it was hot rolled to obtain a hot rolled sheet with a thickness of 2.0 mm.

After that, after homogenization annealing at 900℃ for 3 minutes, at 950℃ 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 surface of the steel plate is coated with inert A1203 (80%).
and MgO (20%), followed by secondary recrystallization annealing at 850°C for 50 hours and 1200°C.
Purification annealing was performed for 5 hours.

Purification annealing after this secondary recrystallization annealing is performed in an atmosphere of ■'l'1c14 gas and N2, ■TlC14
In an atmosphere of gas, N2 and N3, ■TlC14 gas and CH
, in an atmosphere of N2, ■TiCl4 gas, N2 and C)1
When heat treatment was performed in an atmosphere of 4 and N2, a film thickness of 0.3. um TiN, Tic
Alternatively, an ultra-thin tensile coating layer made of Ti(C,N) was formed.

Thereafter, each was coated with a coating liquid containing phosphate and colloidal silica as main components.

In addition, for comparison with these, according to the conventional known technology, 1.
After performing purification annealing at 200° C. for 5 hours in hydrogen hydroxide, coating treatment was also performed with a coating liquid containing phosphate and colloidal silica as main components. Furthermore, after using a conventional annealing separator mainly composed of MgO and performing purification annealing in a hydrogen atmosphere at 1200°C for 5 hours, the main components were also phosphate and colloidal silica. Coating treatment was performed using a coating solution.

Table 1 summarizes the experimental results of the magnetic properties and adhesion of the product thus obtained.

As is clear from Table 1, the magnetic properties, that is, B1°, of the products in the cases of Examples (1) to (2) in which the separation agent according to the present invention was treated in a purified annealing atmosphere were 1.91 to 1.92T.

Lt7s. It is noteworthy that the resistance is as good as 0.83 to 0.87 W/kg, and that the adhesion is also excellent.

On the other hand, under the condition (2), the magnetic properties are worse than the conditions (2) to (3), and the adhesion is also extremely poor.

Further, under the condition (■), the adhesion is better than the condition (■), but the magnetic properties are the worst among the conditions (■) to (■).

As described above, the present invention makes it possible to very effectively reduce iron loss and at the same time provide a product with excellent adhesion. Because C and N react preferentially with Ti, purification is promoted and iron loss can be reduced.At the same time, ultra-thin TiN,
Since a tension film of TiC or Ti (C,N) is formed, it is further effective in reducing iron loss.

(Function) Ultra-low iron loss is extremely effectively achieved by improving the magnetic properties and film adhesion mentioned above, promoting purification of the steel sheet, and improving iron loss by preferentially forming an ultra-thin tension film that gives tension to the steel sheet. Realized.

In particular, in this invention, the conventional 7-orsterite coating is not preferentially formed, but TiN, TiC, or Ti (C,N), which constitutes a coating with higher tension, is formed instead, and the coating is cooled after heat treatment with iron. The strong elastic tension caused by the difference in thermal expansion during the process does not utilize the effect of plastic micro-strain, which is introduced into the steel plate surface by laser treatment, so there is no problem with thermal stability and the strain can be reduced. Even under high temperature thermal history during annealing, the electrical and magnetic properties are unaffected.

The above experimental results show that the tension coating made of TiN, which he himself described, is also made of Ti, Zr, and V.

Nb, Ta, Cr, Mo, Co, Ni, M
Nitride and/or carbide of n, AI, B and AI
, Ni, Cr, W, Si, and Zn oxides, it has almost the same effect as described for TiN, and both of them meet the purpose of the present invention. Compatible with

Next, the manufacturing process of the unidirectional silicon steel sheet will be described in more detail, including a general explanation.

First, the starting material is a conventionally known unidirectional silicon steel composition, such as ■C: 0.04 to 0.05%, Si: 2.50 to
4.5%, Mn=0.01-0.2%, MO: 0.0
03~0.1%, Sb: 0.005~0°0.2X
The total of one or two types of SS or Se is 0,00
Composition containing 5-0.05% ■C: 0.04-0.0
8%, Si: 2.0-4.0%, S+0.005-0.
05%, N: 0.001-0.01%, Sn: 0
．． 01-0.5%, Cu: 0.01-0.3%, M
Composition containing n: 0.01-0.2% ■C: 0.03-0.06%, Si: 0.2-4.0%
, S: 0.005~0.05%, B: O,0O03~
0.0040%, N: 0.001-0.01%, Mn
: Applicable to compositions containing 0.01 to 0.2%.

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 from 0.15 mm+ to OJ5 mm.

After finishing the final cold rolling, the steel plate finished to the product thickness is surface degreased and then subjected to decarburization and primary recrystallization annealing 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, in this invention, it is more advantageous not to form forsterite, which is generally indispensable to be formed after finish annealing, so Al1[1, Zr[12, TiO2, etc. %
In the above manner, it is necessary to use it by mixing it with MgO.

After that, secondary recrystallization annealing is performed, but this step is (100)
This is done to sufficiently develop secondary recrystallized grains with <001> orientation.

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 retention annealing at a low temperature of 0.000C, and in addition, for example, 0.5-b annealing may be used.

Purification annealing after secondary recrystallization annealing is performed at 1100℃ in hydrogen
Purification of the steel sheet is achieved by annealing for 1 to 20 hours as described above, but in this invention, after the secondary recrystallization annealing, annealing is performed in a gas atmosphere containing Ti or a mixed gas atmosphere with a non-oxidizing gas. Required condition. In order to perform such atmosphere annealing, TiCl4. It is common to use TiCl3 or TiCla, and to use H, gas, and other gases such as N, C) I, and NH as a mixed gas. After performing this purification annealing treatment, even if a laser treatment is performed using a conventionally known method to introduce local minute strain, the effects of the present invention will not be hindered. However, the insulating film in this case needs to be coated at a low temperature of 600° C. or lower.

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 KV^. For the formation of this insulating coated and baked layer, conventionally known methods may be used as they are.

(Example) Example I C: 0.046%, Sl: 3.38%, Mn:
0.068% MO=0, 025%, Se: 0.02
4%, Sb: 0.020%,
After equalization annealing at 00°C for 3 minutes, cold rolling was performed twice with intermediate annealing at 950°C to obtain a final cold rolled sheet with a thickness of 0.23 mm.

Then, after decarburization annealing in wet hydrogen at 820℃, A1
□03 (80%), after applying an annealing separator mainly composed of MgO (20%) and performing secondary recrystallization annealing at 850°C for 50 hours, 1200°C in a mixed gas atmosphere of TiCl, N2, and N2. After performing purification annealing at ℃ for 8 hours, an insulating coating film containing phosphate and colloidal silica as main components was formed on the surface. The magnetic properties and adhesion of the product at that time were as follows.

Magnetic properties B+o: 1.91T 1m+'l/. : 0.86 W/kg adhesion, and the adhesion was good as it could not be peeled off even when bent by 180 degrees with a bending radius of 25 squares.

Example 2 C: 0.058%, Si: 3.39%, Mn:
0,076%, Al20,024%, S: 0.028%
, N: A hot rolled sheet containing 0.0068% was heated to 115
After equalization annealing for 3 minutes at 0℃, rapid cooling treatment was performed, and then 3 minutes
A final cold-rolled sheet with a thickness of 0.23 mm was obtained by warm rolling at 00°C.

After decarburization annealing in wet hydrogen at 850°C, the surface is coated with Al2.
03 (60%), after applying an annealing separator mainly composed of MgO (40%), from 850°C to 1150°C at 8°C/
After secondary recrystallization by heating for hr, TiCl4 and N
Purification annealing was performed at 1200°C for 10 hours in an atmosphere of 2 and N2.

Thereafter, a method of forming an insulating film mainly composed of phosphate and colloidal silica (hereinafter referred to as (A) method) and a laser treatment in a direction perpendicular to the rolling direction (laser conditions: using a pulsed laser, energy 3,7
5X10-3J, spot diameter 0.15mm, spot center spacing 0.31D [I, laser scanning trace spacing! =
6), followed by a low-temperature coating baking treatment at 500°C (hereinafter referred to as method (B)).

The magnetic properties and adhesion of the products obtained by each method (A) and (B) at this time were as follows.

Magnetic properties (^) method: B1°: 1.93T, W17z
s. :0.85W/kg(B) method: Blo:1.93
T, W+tzso: 0.81W/kg adhesion (A
) method: 30mm book (B) method: 3Qmm book

Claims (1)

[Claims] 1. A hot-rolled plate obtained by hot-rolling a unidirectional silicon steel slab is subjected to necessary heat treatment and then cold-rolled once or cold-rolled twice with intermediate annealing in between. is applied to obtain the final plate thickness, then decarburized and
In a series of manufacturing methods for unidirectional silicon steel sheets, in which primary recrystallization annealing is performed, an annealing separator containing MgO as a main component is applied to the surface of the steel sheet, and then secondary recrystallization annealing and purification annealing are performed. , Al_2O_3, ZrO_2 and TiO
In addition to mixing 50% by weight or more of at least one selected from _2, purification annealing is performed in a gas atmosphere containing Ti or in a mixed gas atmosphere with a non-oxidizing gas after secondary recrystallization annealing. By this, TiN,
A method for producing a thermally stable, ultra-low iron loss unidirectional silicon steel sheet, which is characterized by forming an ultra-thin tensile coating made of TiC or Ti(C,N). 2. A hot-rolled plate obtained by hot-rolling a unidirectional silicon steel slab is subjected to the necessary heat treatment and then cold-rolled once or twice with intermediate annealing to obtain the final plate thickness. Then, decarburization and
In a series of manufacturing methods for unidirectional silicon steel sheets in which primary recrystallization annealing is performed, then an annealing separator containing MgO as a main component is applied to the surface of the steel sheet, and secondary recrystallization annealing and purification annealing are performed. , Al_2O_3, ZrO_2 and TiO
In addition to mixing 50% by weight or more of at least one selected from _2, purification annealing is performed in a gas atmosphere containing Ti or in a mixed gas atmosphere with a non-oxidizing gas after secondary recrystallization annealing. By this, TiN,
The method is characterized by forming an ultra-thin tension film made of TiC or Ti(C,N), and then applying laser irradiation in a direction transverse to the rolling direction to introduce local strain, and then applying a low-temperature coating film treatment. A method for producing thermally stable, ultra-low core loss unidirectional silicon steel sheets.