JPS6240317A - Manufacture of grain-oriented silicon steel sheet with extremely small iron loss - Google Patents

Abstract

PURPOSE:To enhance the adhesion of a film as well as to improve the iron loss characteristics of annealed grain-oriented silicon steel sheet by forming a Ti surface layer on the surface of the steel sheet and carbonizing and nitriding the surface layer to form a very thin tension film. CONSTITUTION:A Ti surface layer formed on the surface of a grain-oriented silicon steel sheet contg. 0.001-0.010wt% C and 0.0005-0.0100wt% N after finish annealing is carbonized and nitrided to form a very thin tension film of TiC, TiN or Ti(C, N). An insulating film contg. phosphate and colloidal silica as essential components is further formed. By this method, the adhesion of the films are enhanced and the magnetic characteristics, especially the iron loss characteristics, can be improved.

Description

[Detailed Description of the Invention] (Field of Industrial Application) In recent years, 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. The remarkable development efforts are gradually bearing fruit, but one serious drawback to their implementation is that after processing and assembly when using unidirectional silicon steel sheets,
It has been pointed out that when so-called strain-relief annealing is applied, it inevitably causes characteristic deterioration and is disadvantageous in 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 (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 (W+tzs, represented by the value) be high and the iron loss (W+tzs, represented by the value) be low.

This unidirectional silicon steel sheet is manufactured through a wide variety of complicated processes, but numerous inventions and improvements have been made so far, and today products with a thickness of 0.30+m have magnetic properties of B.
oo 1.90T or more, Lt/so 1.05W 8g or less, and a product with a plate thickness of 0.23m has a magnetic property of B.

Unidirectional silicon steel sheets with ultra-low iron loss of 1.89T or more, W+t/so O, and 90W/kg or less 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 "evaluation" (iron loss evaluation) system is becoming widespread.

(Prior Art) Under these circumstances, recently, the surface of a unidirectional silicon steel sheet after final annealing is irradiated with a laser in a direction approximately perpendicular to the rolling direction to introduce local microstrain to subdivide the magnetic domains. It has been proposed to reduce the iron loss (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).

Although this magnetic domain refining technology is effective for transformer materials for laminated iron cores that are not subjected to strain relief annealing, it is difficult to introduce them by laser irradiation when applying strain relief annealing, mainly for wound core transformer materials. The local minute strain caused by the annealing process is released and the magnetic domain width becomes wider.
The disadvantage is that the laser irradiation effect is lost.

On the other hand, earlier than this, Japanese Patent Publication No. 52-24499 (in this case, the surface of a unidirectional silicon steel sheet after finish annealing is mirror-finished, or the mirror-finished surface is coated with metal thin plating or further A method for producing ultra-low core loss unidirectional silicon steel sheets has been proposed by applying and baking an insulating film on the steel.

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, although it increases the cost significantly, and especially after applying and baking the insulating film that is essential after mirror finishing. 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 cannot be used in actual manufacturing processes because the steel sheet and the ceramic layer will separate when subjected to high-temperature annealing at 600° C. or higher.

(Problems to be Solved by the Invention) In particular, from the perspective of today's energy-saving material development, the inventors have developed characteristics that outweigh the disadvantages of cost amplifiers as described above.
We believe that it is important to overcome the problems of adhesion and durability of the insulating layer without deterioration of properties during high-temperature treatment, and based on this basic understanding, we have developed a steel plate on the surface of a grain-oriented silicon steel plate that has been finish annealed. It is an object of the present invention to achieve a particularly advantageous ultra-low iron loss by radically improving the processing method.

(Means for Solving the Problems) Now, as a result of various studies to achieve the above object, the inventors have found that preferably 0.1 to 2 .0μm thick Deer Ti
After forming the Fii layer, the Ti surface layer is carbonized and/or
Or, by nitriding, TiC, T
Forming an ultra-thin tensile film of iN or Ti (C,N) (first invention), and further forming an insulating film mainly composed of phosphate and colloidal silica (second invention) We have obtained knowledge that this method is extremely effective in achieving the intended purpose.

Here, as a means for carbonizing and/or nitriding the Ti surface layer, C: 0°001 is added to the unidirectional silicon steel sheet after final annealing.
~0.010wt? ! (hereinafter shown as single %) and N
:0.0005 to 0.000%, a Ti surface layer is formed on the surface of the steel sheet, and then annealed in a non-oxidizing atmosphere to purify C and N in the steel sheet. (3rd and 4th inventions) Also, after forming a surface layer of Ti on the surface of a finish-annealed unidirectional silicon steel sheet containing a predetermined amount of C and N, carbonization is performed. Annealing is carried out in a carbonaceous gas and/or nitriding gas atmosphere to promote the purification of C and N in the steel sheet and to carry out carburizing and/or nitriding from the atmosphere (fifth. sixth invention)
Furthermore, a surface layer of Ti is formed on the surface of a finish-annealed unidirectional silicon steel sheet containing a predetermined amount of C and N, and then annealing is performed in a non-oxidizing atmosphere to improve the content of the steel sheet. Promote purification of C and N, and continue to improve carbonization and/or
Alternatively, annealing is performed in a nitriding gas atmosphere to take into account carburizing and/or nitriding effects from the atmosphere (7th.
It was also discovered that the eighth invention) is particularly effective, leading to the completion of this invention.

The following explanation will be given in accordance with specific experiments that led to the success of each of the above inventions.

C: 0.042χ, Si: 3.36χ, Mn:
0.066X, Se: 0021χ, Mo: 0
．． 025χ and Sb: Various silicon steel slabs containing 0.025χ and N in the range of 0.001 to 0.015χ were hot rolled into 2.4 m thick hot rolled sheets, and then Uniform annealing was performed at 900° C. for 3 minutes, and then cold rolling was performed twice with intermediate annealing at 950° C. for 3 minutes, to obtain a cold rolled sheet with a final thickness of 0.23 m. After that, primary recrystallization annealing, which also serves as decarburization, is performed in wet hydrogen at 820°C with the dew point varied in the range of 50 to 10°C, and then AIz03:60χ, Mg
O: 25χ, Zrf)z: 10χ and Tt(h:
After applying an annealing separator with a blending ratio of 5%,
Secondary recrystallization annealing at 0°C for 50 hours, followed by 1 hour in saturated hydrogen.
Purification annealing was performed at 200°C for 8 hours.

Thereafter, a 0.7 μm film was deposited on the surface of this steel plate using a vapor deposition device.
After depositing a thick Ti layer, heat treatment at 750°C in H2 gas.
, and was annealed for 3 hours.

Table 1 shows the results of an investigation into the relationship between C and Ni in the steel and the magnetic properties at the final annealing stage during the above manufacturing process, and the relationship between the C and N amounts and the magnetic properties of the final product.

Table 1 also shows that after annealing in +12 gas,
11□Gas, N2+^r s CHa + 112,
The results of investigating the amount of C and N in the steel and the magnetic properties after annealing at 750° C. for 5 hours in a CH4+R and N2+CIL+H gas atmosphere are also listed.

Table 1 also shows the results of examining the adhesion of each product board.

As is clear from the results shown in Table 1, samples in which C and Nl are each 100 ppm or less during final annealing are either annealed in H2 gas after depositing Ti, or
Alternatively, when annealing is further performed in a carbonizing and/or nitriding gas atmosphere, the magnetic flux density Boo is 1.89T.
Above, and iron loss W177. Excellent characteristics were obtained in which the resistance was 0.87 W/kg or less.

It is noteworthy that both C and Ni in the final product are significantly reduced compared to after final annealing.

All products with good magnetic properties also had excellent adhesion.

Next, N2+lh, N, +^r, CH was applied to a steel plate coated with a Ti vapor deposition layer in the same manner as in the manufacturing process described above.
.

+lI2, CI+4 +Ar and N2+CH, +H2
Table 2 shows the results of investigating the C, Nl and magnetic properties in the steel of the product obtained by annealing at 800° C. for 15 hours in a gas atmosphere, together with the results of the investigation of adhesion.

As is clear from Table 2, the samples with C1Ni1 of 100 ppm or less after final annealing were evaluated for carbonization and/or
Or, when annealed in a nitriding gas atmosphere, magnetic flux density is applied. is 1.89T or more, and the iron loss is /,.

Excellent characteristics were obtained in which the resistance was 0.87 W/kg or less.

Furthermore, all of the above-mentioned C and N content materials also had excellent adhesion.

(Function) The above-mentioned improvement in magnetic properties can be achieved by applying carbonization and/or nitriding treatment after forming the Ti surface layer to form an ultra-thin coating made of TiC, TiN or Ti(C,N) on the surface of the steel sheet. is formed, and this coating effectively applies tension to the steel plate.

In particular, by utilizing the diffusion of C and H in the steel sheet during the carbonization and/or nitriding treatment of the Ti surface film, the degree of bonding between the steel sheet and the film is increased, further improving the adhesion of the film. It is possible.

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 material, such as ■C: 0.03 to 0.050χ, Si: 2.
50~4.5χ, Mn: 0.01~0.2Z,
Mo: 0.003-0.1χ, Sb: 0.0
05~0.2χ, N: 0.0005~0.01χ
, the total of one or both of S and Se is 0.005
Composition containing ~0.05%, ■C: 0.03~0.08χ, Si: 2.0~
4.0χ, S: 0.005-0.05χ, N:
0.001~0.01χ, AI: 0.01~0.0
6χ, Sn: 0.01~0.5χ, Cu: 0
．． 01~0.3χ, Mn: 0.01~0.2χ
A composition containing: ■C: 0.03~0.062 XSi: 2.0~
4.0! , S: 0.005-0.05χ, B:
0.0003~0.0040χ, N: 0.001~
Composition containing 0.01χ, Mn: 0.01 to 0.2χ, ■C: 0.03 to 0.05χ, Si: 2.0 to 4
．． 0! .

sb: o, oos~0.2χ, N: 0.00
05 to 0.01χ, a composition containing any one or both of S and Se, and 0.005 to 0.05χ;
C70,03~0.05χ, Si: 2.0~4.
0χ, N: 0.0005-0.01χ, S and S
Any one or two of e: 0.005 to 0.
05! It is applicable to compositions containing .

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 reduction rate is about 50% to 85%, and from 0.151 m to 0.35 m. The final cold-rolled sheet thickness is the thickness of the board.

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

Here, the decarburization treatment usually develops secondary recrystallized grains that are strongly accumulated in the Goss orientation in the subsequent secondary recrystallization annealing, and also reduces the amount of C in the steel in order to further reduce C in the steel in the purification annealing. This is done in order to reduce the iron loss as much as possible, and as mentioned above, in this invention, since the annealing after depositing Ti promotes the purification of C along with N, At this decarburization annealing stage, there is no need to carry out severe decarburization as in the past, and 0.01%
A level below (preferably o, ooi% or more) is sufficient.

After that, an annealing separator mainly composed of MgO is usually applied to the surface of the steel sheet, but in this invention, it is better not to form forsterite, which is generally required to be formed after finish annealing. Since it is effective for simplifying mirror finishing, 8'20s is used as an annealing separator.
+ Z r 021 T r Oz etc. at 50% or more M
It is preferable to use it by mixing it with gO.

After that, secondary recrystallization annealing is performed, but this process is! 1101
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 (11o), in order to develop a highly uniform secondary recrystallized grain structure in the <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 is then performed in dry hydrogen, but in order to further improve the film adhesion of the product sheet, C:0.
001-0.01% and N: 0.0005-0.
It is important that 0.1% remain. For this purpose, appropriate annealing conditions may be selected from among the conditions of 1100° C. or higher and 1 to 20 hours in purification annealing.

Thereafter, a surface layer of Ti is formed on the surface of the steel sheet, and the thickness of the Ti surface layer at this time is preferably about 0.1 to 2.0 μm.

Further, the method for forming the Ti surface layer may be, in addition to the vapor deposition described above, a method such as a CVD method, an ion blasting method, or an ion implantation method.

The grain-oriented silicon steel sheet with a Ti surface layer is then annealed in a non-oxidizing atmosphere, a carbonizing and/or nitriding atmosphere, and further annealing in a non-oxidizing atmosphere and then a carbonizing and/or nitriding atmosphere. However, these annealing treatments are performed in the following manner.

i) As the atmosphere gas for annealing in a non-oxidizing atmosphere, 11□ gas or Ar gas is particularly advantageously suitable, and annealing is performed in such an atmosphere at a temperature of 500°C or higher to remove C and H surfaces in the steel sheet. This promotes the spread of the virus. At this time, if the amount of C in the steel is greater than the amount of N, an extremely thin film consisting mainly of TiC will be formed on the surface of the steel sheet, whereas in the opposite case, an extremely thin coating mainly consisting of TiN will be formed. .

ii) Annealing in a carbonizing and/or nitriding gas atmosphere Carbonizing gases include hydrocarbon gases such as CH, C, and I+6, and CO gas, and furthermore, these gases and H
2 and meter gas, and as a nitriding gas,
N2 gas, NH, gas and these gases and H2 and A
By carrying out the annealing in such an atmosphere at a temperature of 500° C. or higher, a gas mixture with r gas is advantageously suitable.
By promoting the purification of C and N in steel and carburizing and/or nitriding from atmospheric gas, a mixed thin film of carbides and/or nitrides is formed on the surface of the steel sheet.

Furthermore, it is necessary to apply and bake an insulating film mainly composed of phosphate and colloidal silica on the ultra-thin tension film formed 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.

(Example) (8) C: 0.041χ, Si: 3.
48χ, Mn: 0.062%1Mo:
0.025χ, Se: 0.022χ, Sb: 0
．． 025χ and N: 0.0038χ (B) C: 0.053χ, Si: 3.32χ,
Mn: 0.072χ, S: 0.018%, ^1:
0.025χ, and N: 0.0066χ(C)
C: 0.039χ, Si: 3.31ZXMn
: 0.059χ, S: 0.030χ, B: 0.0
019χ, N: 0.0068χ and Cu: 0.1
5χ (D) C: 0.046χ, St: 3.09Z
, Mn: 0.063χ, Se: 0.019χ and Sb: 0.025χ(E)C: 0.038
A silicon steel hot rolled sheet having a composition containing χ, Si: 3.08χ, Mn: 0.071χ, and S: 0.019χ was used.

First, hot rolled sheets (A), (C), (D), (E
>, uniform annealing was performed at 900°C. On the other hand, the hot rolled sheet (B) was homogenized at 1050°C for 3 minutes and then heated to 90°C.
It was rapidly cooled from 0°C.

After that, for (A), (D), and (E), 9
Cold rolling was performed twice with intermediate annealing at 50°C to reduce the temperature to 0.
The final plate thickness is 23 mm, and (B) and (C) are 1
A final cold-rolled sheet with a thickness of 0.23 m was obtained by intense cold rolling, but warm rolling at 300° C. was interposed between the cold rolling steps.

After degreasing the surface of these cold-rolled plates, the dew point was reduced to 25°C.
After decarburization annealing at 830″C in wet hydrogen, 8h03
An annealing separator consisting of near 0x, MgO: 25x, and ZrO□: 5% was applied.

After that, (8), (D) are 2 for 50 hours at 850'C.
After the next recrystallization annealing, 1200℃ in dry hydrogen for 6
Subjected to time purification annealing. On the other hand, (B), (C),
(E) was subjected to secondary recrystallization by raising the temperature from 850°C to 1050°C at 5°C/h, and then heating at 1200°C in dry hydrogen for 8
Subjected to time purification annealing.

Thereafter, a 0.7 μm thick Ti vapor deposition layer was formed on the surface of each steel plate obtained.

After that, for (A), (B), and (C), 1
Annealing was performed at 800° C. for 5 hours in a two-gas atmosphere, and some samples were further annealed at 700° C. for 3 hours in an atmosphere containing N2 and/or CI+4 gas.

In addition, (D) and (E) were immediately annealed at 800° C. for 5 hours in an atmosphere containing N2 and/or C114 gas.

TiC, TiN or Ti(C,N) thus obtained
C of grain-oriented silicon steel plate with an ultra-thin coating consisting of
, the results of investigating the amount of N, magnetic properties and adhesion.
Table 3 shows a comparison of the C and N contents and magnetic properties in the steel after final annealing.

Table 3 also includes the results of a study on the magnetic properties of a product in which the surface of the grain-oriented silicon steel sheet with the ultra-thin coating described above is further coated with a coating film containing phosphate and colloidal silica as the main components. show.

As is clear from the results shown in Table 3, according to the present invention, a thin film of Ti is formed on the surface of a unidirectional silicon steel sheet after finish annealing, and then a thin film of Ti is deposited in a non-oxidizing atmosphere or with carbonizing and/or Alternatively, annealing is performed in a nitriding gas atmosphere, further in a non-oxidizing atmosphere, and then in a carbonizing and/or nitriding gas atmosphere to form an extremely thin film of TiC, TiN or Ti(C,N) on the steel plate surface. By applying this method, a significant improvement in magnetic properties, especially in iron properties, was achieved while maintaining good film adhesion.

(Effects of the Invention) Thus, according to the present invention, the winding core direction can be adjusted to improve the magnetic properties, especially the iron one-member properties, regardless of whether or not high-temperature treatment such as high-temperature strain relief annealing is applicable when used as a transformer material. Significant improvements can be achieved along with improved film adhesion.

Claims (1)

[Claims] 1. After forming a surface layer of Ti on the surface of a unidirectional silicon steel sheet that has been finish annealed, the surface of the steel sheet is improved by carbonizing and/or nitriding the Ti surface layer. A method for producing an ultra-low iron loss unidirectional silicon steel sheet, which comprises forming an ultra-thin tensile coating of TiC, TiN or Ti(C,N) thereon. 2. After forming a Ti surface layer on the surface of a unidirectional silicon steel sheet that has been finish annealed, the Ti surface layer is carbonized and/or nitrided to form TiC, TiN or TiC on the surface of the steel sheet. Production of an ultra-low iron loss unidirectional silicon steel sheet characterized by forming an ultra-thin tensile coating of Ti (C, N) and then forming an insulating coating mainly composed of phosphate and colloidal silica. Method. 3, C: 0.001 to 0.010 wt% and N: 0.
After forming a Ti surface layer on the surface of a finish-annealed unidirectional silicon steel sheet having a composition containing 0.0005 to 0.0100 wt%, the steel sheet is annealed in a non-oxidizing atmosphere. C and N
By promoting the purification of TiC and T on the steel plate surface,
A method for producing an ultra-low iron loss unidirectional silicon steel sheet, which comprises forming an ultra-thin tensile coating of iN or Ti (C, N). 4, C: 0.001 to 0.010 wt% and N: 0.
After forming a Ti surface layer on the surface of a finish-annealed unidirectional silicon steel sheet having a composition containing 0.0005 to 0.0100 wt%, the steel sheet is annealed in a non-oxidizing atmosphere. C and N
By promoting the purification of TiC and T on the steel plate surface,
An ultra-low iron loss unidirectional silicon steel sheet characterized by forming an ultra-thin tensile coating of iN or Ti (C, N), and forming an insulating coating whose main components are chirophosphate and colloidal silica. manufacturing method. 5, C: 0.001-0.010 wt% and N: 0.
After forming a surface layer of Ti on the surface of a finish-annealed unidirectional silicon steel sheet having a composition containing 0.0005 to 0.0100 wt%, annealing is performed in a carbonizing and/or nitriding gas atmosphere. An ultra-thin tensile coating of TiC, TiN or Ti(C,N) is formed on the surface of the steel plate by promoting the purification of C and N in the steel plate and by carburizing and/or nitriding from the atmosphere. A method for producing an ultra-low core loss unidirectional silicon steel sheet. 6, C: 0.001-0.010 wt% and N: 0.
After forming a surface layer of Ti on the surface of a finish-annealed unidirectional silicon steel sheet having a composition containing 0.0005 to 0.0100 wt%, annealing is performed in a carbonizing and/or nitriding gas atmosphere. to promote purification of C and N in the steel plate and carburizing and/or nitriding from the atmosphere to form an ultra-thin tension film of TiC, TiN or Ti(C,N) on the surface of the steel plate, A method for producing an ultra-low iron loss unidirectional silicon steel sheet, which is characterized by forming an insulating film containing Shikarunochiphosphate and colloidal silica as main components. 7, C: 0.001-0.010 wt% and N: 0.
After forming a Ti surface layer on the surface of a finish-annealed unidirectional silicon steel sheet having a composition containing 0.0005 to 0.0100 wt%, the steel sheet is annealed in a non-oxidizing atmosphere. C and N
By promoting the purification of TiC, TiN or Ti(C , N) A method for producing an ultra-low iron loss unidirectional silicon steel sheet, the method comprising forming an ultra-thin tensile coating of N). 8, C: 0.001-0.010 wt% and N: 0.
After forming a Ti surface layer on the surface of a finish-annealed unidirectional silicon steel sheet having a composition containing 0.0005 to 0.0100 wt%, the steel sheet is annealed in a non-oxidizing atmosphere. C and N
By promoting the purification of TiC, TiN or Ti(C , N), and forming an insulating film containing phosphoric acid salt and colloidal silica as main components.