JPH0337846B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) In recent years, remarkable development efforts have been made to improve the electrical and magnetic properties of grain-oriented silicon steel sheets, and in particular to meet the extreme requirements of reducing iron loss. However, a serious problem associated with its implementation is that when unidirectional silicon steel sheets are subjected to so-called strain relief annealing after processing and assembly, the accompanying deterioration of properties may occur. It has been pointed out that there are disadvantages in that this inevitably occurs and restrictions are placed 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 satisfy the above requirements, regardless of whether or not it undergoes a high-temperature thermal history such as strain relief annealing. I will explain. 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 (B ₁₀
(represented by the W 17/50 value) and low iron loss (represented by the W _17/50 value). 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 mm have magnetic properties of B ₁₀ 1.90T or more, W _{17 /50} 1.50W/Kg or less, and the magnetic properties of products with a plate thickness of 0.23mm are B ₁₀ 1.89T
As described above, ultra-low core loss unidirectional silicon steel sheets with W _17/50 0.90W/Kg or less are being manufactured. In particular, recently there has been a marked increase in the demand for reducing power loss as a top priority from the standpoint of energy conservation.・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 was proposed to reduce iron loss (Special Publication No. 57-2252, Special Publication No. 57-53419, Special Publication No. 58-26405, and Special Publication No. 58-1982).
-Refer to each publication No. 26406). This magnetic domain refining technology is effective for transformer materials for laminated cores that are not subjected to strain relief annealing, but it is difficult to introduce it by laser irradiation for transformer materials for rolled cores that are subjected to strain relief annealing. There is a drawback that the laser irradiation effect is lost because the localized microstrain is released by the annealing treatment and the magnetic domain width becomes wider. On the other hand, in Japanese Patent Publication No. 52-24499, the surface of the unidirectional silicon steel plate after finish annealing is mirror-finished, or the mirror-finished surface is coated with metal thinning or an insulating coating is further applied on the mirror-finished surface. A method for manufacturing ultra-low core loss unidirectional silicon steel sheets has been proposed by coating and baking. 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 at the cost of a significant increase in costs. 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 thin film of oxide ceramics is deposited after mirror-finishing the surface of a steel plate. 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 an insulating layer that has properties that outweigh the disadvantage of increased cost as described above, in particular, without deterioration of properties due to high temperature treatment. We believe that it is important to overcome the problems of adhesion and durability, and based on this basic understanding, we have developed a drastic treatment method for steel sheets after removing oxides on the surface of grain-oriented silicon steel sheets that have been finish annealed. It is an object of the present invention to achieve particularly advantageous ultra-low iron loss through improvement. (Means for Solving the Problems) As a result of various studies to achieve the above object, the inventors have found that, for example, on the surface of a grain-oriented silicon steel sheet from which oxides have been removed, After forming a thin Ti layer with a thickness of preferably about 0.1 to 0.2 μm by vapor deposition, the Ti surface layer is carbonized and/or
or by nitriding on the steel plate surface.
This method of forming an ultra-thin tensile film of TiC, TiN or Ti(C,N) (first invention), and furthermore, forming an insulating film mainly composed of phosphate and colloidal silica (second invention) We have obtained the 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: is added to the unidirectional silicon steel sheet after final annealing.
0.001 to 0.010 wt% (hereinafter simply expressed as %) and N: 0.0005 to 0.0100%, a Ti surface layer is formed on the surface of the steel sheet from which oxides have been removed, and then non-oxidizing To promote the purification of C and N in the steel sheet by annealing in an atmosphere (third and fourth inventions), and also to prepare a finish-annealed unidirectional silicon steel sheet containing a predetermined amount of C and N. After removing surface oxides, a Ti surface layer is formed, and then annealing is performed in a carbonizing gas and/or nitriding gas atmosphere to promote purification of C and N in the steel sheet and remove it from the atmosphere. Carburizing and/or nitriding (fifth and sixth inventions), and after removing surface oxides of a finish-annealed unidirectional silicon steel sheet containing a predetermined amount of C and N, a Ti surface layer is removed. After that, annealing is performed in a non-oxidizing atmosphere to promote the purification of C and N in the steel sheet, and then annealing is performed in a carbonizing and/or nitriding gas atmosphere to remove carburization from the atmosphere. They also discovered that adding nitriding action and/or nitriding action (seventh and eighth inventions) are 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: 0.042%, Si: 3.36%, Mn: 0.066%, Se:
Various silicon steel slabs containing N: 0.021%, Mo: 0.025% and Sb: 0.025%, and N: 0.001 to 0.015% were hot rolled.
After making a hot-rolled plate with a thickness of 2.4 mm, it was uniformly annealed at 900°C for 3 minutes, then cold-rolled twice at 950°C with an intermediate annealing of 3 minutes in between, resulting in a final plate thickness of 0.23.
It was made into a cold-rolled sheet of mm. After that, primary recrystallization annealing, which also serves as decarburization, is performed in wet hydrogen at 820℃ with the dew point varied in the range of 50 to 10℃.
_Al2O3 : 60% _, MgO: 25%, _ZrO2 : 10% and
After applying an annealing separator with a TiO ₂ ratio of 5%, secondary recrystallization annealing was performed at 850°C for 50 hours, and then purification annealing was performed in dry hydrogen at 1200°C for 8 hours. After that, the oxides on the surface of each steel plate were removed by pickling, and then a 0.7 μm thick Ti vapor deposition layer was formed on the surface after the oxides were removed using a vapor deposition device.
Annealing was performed at 750° C. for 3 hours in H ₂ gas. Table 1 shows the results of an investigation into the relationship between the amount of C and N in the steel and the magnetic properties at the final annealing stage during the above manufacturing process, and the relationship between the amount of C and N and the magnetic properties of the final product. Table 1 also shows that after annealing in _H2 gas,
The amount of C _and N in the steel and its magnetic properties were investigated after annealing at 750° _C for 5 hours in a N ₂ + H ₂ gas, N ₂ + Ar, CH _{4 +} H ₂ , CH + Ar, and N 2 + CH 4 + H 2 gas atmosphere. The results are also listed. Table 1 also shows the results of examining the adhesion of each product board.

【table】

[Table] As is clear from the results shown in Table 1, the amount of C and N during final annealing was 100 ppm each.
After removing the oxide from the following sample, depositing Ti,
When annealing is performed in _H2 gas or in a carbonizing and/or nitriding gas atmosphere, the magnetic flux density B ₁₀ is 1.90T or more and the iron loss W _17/50 is 0.85W/ Excellent properties of less than Kg were obtained. It is noteworthy that the amounts of C and N in the final product are both significantly reduced compared to after final annealing. All products with good magnetic properties also had excellent adhesion. Next, a steel plate coated with a vapor-deposited layer of Ti in the same manner as in the manufacturing process described above was heated with N ₂ +H ₂ , N ₂ +Al,
The results of an investigation of the amount of C and N in _the steel and the magnetic properties of products obtained by annealing at 800°C for 5 hours in a CH ₄ + H ₂ , CH _{4 +} Al, and N ₂ + CH 4 + H 2 gas atmosphere are shown below. Table 2 shows the results of the gender investigation.

[Table] As is clear from Table 2, C after finish annealing,
When a sample with a N content of 100 ppm or less is annealed in a carbonizing and/or nitriding gas atmosphere, the magnetic flux density B ₁₀ is 1.90 T or more and the iron loss W _17/50
Excellent characteristics were obtained, with a value of 0.87W/Kg or less. In addition, 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 carbonizing and/or nitriding the surface layer of TiC, TiN or Ti(C,N) on the surface of the steel sheet.
This is because an ultra-thin coating is formed, and this coating effectively applies tension to the steel plate. In particular, by utilizing the diffusion of C and N 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, and the adhesion of the film is improved. obtain. Furthermore, by removing surface oxides, the surface of the steel sheet becomes rough with appropriate roughness, resulting in further improvement in adhesion. 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 sheet material, such as C: 0.03 to 0.05%, Si: 2.50 to 4.5%, Mn:
0.01~0.2%, Mo: 0.003~0.1%, Sb: 0.005~
Composition containing 0.2%, N: 0.0005-0.01%, one or both of S and Se in total of 0.005-0.05% C: 0.03-0.08%, Si: 2.0-4.0%, S:
0.005~0.05%, N: 0.001~0.01%, Al: 0.01~
0.06%, Sn: 0.01~0.5%, Cu: 0.01~0.3%,
Composition containing Mn: 0.01-0.2%, C: 0.03-0.06%, Si: 2.0-4.0%, S:
0.005~0.05%, B: 0.0003~0.0040%, N:
Composition containing 0.001-0.01%, Mn: 0.01-0.2%, C: 0.03-0.05%, Si: 2.0-4.0%, Sb:
0.005-0.2%, N: 0.0005-0.01%, S and
Any one or two of Se: 0.005~
Composition containing 0.05%, C: 0.03-0.05%, Si: 2.0-4.0%, N:
0.0005-0.01%, any one of S and Se
It is applicable in compositions containing 0.005 to 0.05% of one species or two species. Next, the hot-rolled sheet is either uniformly annealed at 800-1100℃ and then cold-rolled once to reach the final thickness, or it is usually subjected to intermediate annealing at 850-1050℃ and further processed. In the two-step cold rolling method, in the latter case, the initial rolling reduction is about 50% to 80%, and the final rolling reduction is 50%.
The final cold-rolled plate thickness is between 0.15mm and 0.35mm at a rate of about 85%. After the final cold rolling, the steel plate finished to the product thickness is surface degreased and then decarburized and primary recrystallized annealed 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, but as already mentioned in this invention,
Since the purification of C as well as N is promoted in the annealing after Ti is deposited, there is no need to carry out decarburization as harshly as in the past at this decarburization annealing stage.
A content of about 0.01% or less (preferably 0.001% 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. Al ₂ O ₃ , ZrO ₂ , TiO _{2 ,} etc. are used as annealing separators because they are effective in simplifying mirror finishing.
It is preferable to use 50% or more of MgO mixed with MgO. After that, secondary recrystallization annealing is performed, but this step is carried out to sufficiently develop secondary recrystallized grains with {110}<001> orientation, and is usually box annealed to immediately raise the temperature to 1000℃ or higher. This is done by heating and holding at that temperature. In this case, in order to develop a highly uniform secondary recrystallized grain structure in the {110}<001> orientation, it is advantageous to perform retention annealing at a low temperature of 820°C to 900°C.
In addition, slow heat annealing at a heating rate of 0.5 to 15° C./h may also 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: 0.0005-0.01% are added to the steel sheet.
It is essential that these remain. For this purpose, an appropriate upper limit of annealing may be selected from the conditions of 1100° C. or higher and 1 to 20 hours in purification annealing. Thereafter, the oxide film on the surface of the steel plate is removed by known chemical removal methods such as pickling, mechanical removal methods such as cutting and grinding, or a combination thereof. After that, a Ti surface layer is formed on the steel sheet surface from which oxides have been removed, and the Ti surface layer thickness at this time is 0.1
It is preferable to set it to about 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 plating 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. () Annealing in a non-oxidizing atmosphere As the atmospheric gas, H ₂ gas and Ar gas are particularly effective.
Annealing is performed at a temperature of 500℃ or higher to remove C,
This promotes the diffusion of N to the surface. At this time, if the amount of C in the steel is larger than the amount of N, an ultra-thin film mainly made of TiC will form on the steel plate surface.
On the other hand, in the opposite case, an extremely thin film consisting mainly of TiN will be formed. () Annealing in a carbonizing and/or nitriding gas atmosphere Carbonizing gases include hydrocarbon gases such as CH ₄ and C ₂ H ₆ and CO gas, as well as combinations of these gases with H ₂ and Ar gas. Also, as the nitriding gas, N ₂ gas, NH ₃ gas, and a mixture of these gases with H ₂ or Ar gas are advantageously suitable.
By annealing at the above temperature, purification of C and N in the steel and carburizing and/or nitriding from atmospheric gas are achieved, thereby forming a mixed thin film of carbides and/or nitrides on the surface of the steel sheet. Let it form. 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. The formation of this insulating coating and baking layer is as follows:
Conventionally known methods may be used as they are. (Example) (A) C: 0.041%, Si: 3.48%, Mn: 0.062%,
Mo: 0.025%, Se: 0.022%, Sb: 0.025% and N: 0.0038% (B) C: 0.053%, Si: 3.32%, Mn: 0.072%,
S: 0.018%, Al: 0.025% and N: 0.0066% (C) C: 0.039%, Si: 3.31%, Mn: 0.059%,
S: 0.030%, B: 0.0019%, N: 0.0068% and Cn: 0.15% (D) C: 0.046%, Si: 3.09%, Mn: 0.063%,
A silicon steel hot rolled sheet having a composition containing Se: 0.019% and Sb: 0.025% (E) C: 0.038%, Si: 3.08%, Mn: 0.071% and S: 0.019% was used.
First, hot-rolled sheets (A), (C), (D), and (E) were uniformly annealed at 900°C. On the other hand, the hot rolled sheet (B) was heated to 3 at 1050℃.
After uniform annealing for 1 minute, it was rapidly cooled from 900°C. After that, (A), (D), and (E) were cold rolled twice with intermediate annealing at 950℃ to obtain a final thickness of 0.23 mm, and (B) and (C) were cold rolled once. A final cold-rolled sheet with a thickness of 0.23 mm was obtained by intense cold rolling, but warm rolling at 300°C was interposed during the cold rolling. After degreasing the surface of these cold-rolled sheets, decarburization annealing was performed at 830°C in wet hydrogen with a dew point of 25°C.
An annealing separator consisting of 70% Al ₂ O ₃ , 25% MgO, and 5% ZrO ₂ was applied. Thereafter, (A) and (D) were subjected to secondary recrystallization annealing at 850°C for 50 hours, followed by purification annealing at 1200°C for 6 hours in dry hydrogen. On the other hand, (B), (C), and (E) were heated from 850℃ to 1050℃ at 5℃/h for secondary recrystallization, and then subjected to purification annealing at 1200℃ for 8 hours in dry hydrogen. did. Thereafter, each steel plate obtained was pickled to remove the oxide film on the surface, and a 0.7 μm thick Ti vapor deposited layer was formed on the surface after the oxide was removed. Thereafter, (A), (B), and (C) were annealed for 5 hours at 800°C in an H ₂ gas atmosphere, and some samples were further annealed in an atmosphere containing N ₂ and/or CH ₄ gas. The material was annealed at 700°C for 3 hours. In addition, (D) and (E) were immediately annealed at 800° C. for 5 hours in an atmosphere containing N ₂ and/or CH ₄ gas. TiC, TiN or Ti(C,N) thus obtained
The results of investigating the C and N contents, magnetic properties, and adhesion of grain-oriented silicon plates with ultra-thin coatings are compared with the C and N contents and magnetic properties of steel after final annealing. Shown in 3. Table 3 also includes the results of a study on the magnetic properties of a product in which a coating film containing phosphate and colloidal silica as main components is applied to the surface of the above-mentioned ultra-thin film-coated grain-oriented silicon steel sheet. show.

[Table] As is clear from the results shown in Table 3, according to the present invention, after surface oxides were removed from the unidirectional silicon steel sheet after final annealing, a thin film of Ti was formed on the non-oxidizing silicon steel sheet. Annealing is performed in an atmosphere, a carbonizing and/or nitriding gas atmosphere, a non-oxidizing atmosphere, and a carbonizing and/or nitriding gas atmosphere, and the surface of the steel sheet is annealed.
By forming an extremely thin film of TiC, TiN or Ti(C,N), a remarkable improvement in magnetic properties, particularly iron loss properties, was achieved with good film adhesion. (Effects of the Invention) Thus, according to the present invention, magnetic properties, particularly iron loss properties, can be significantly improved regardless of whether high-temperature treatment such as high-temperature strain relief annealing is applied when used as a transformer material for wound cores. Improvements can be realized in conjunction with improvements in film adhesion.

Claims (1)

[Claims] 1. For a finish annealed unidirectional silicon steel sheet, Ti is applied on the surface of the steel sheet from which surface oxides have been removed.
After forming a surface layer, the Ti surface layer is carbonized and/or nitrided to form an ultra-thin tensile coating of TiC, TiN or Ti(C,N) on the surface of the steel sheet. A method for producing ultra-low core loss unidirectional silicon steel sheets. 2. For finish annealed unidirectional silicon steel sheets, Ti is applied on the surface of the steel sheets from which surface oxides have been removed.
After forming a surface layer, the Ti surface layer is carbonized and/or nitrided to form an ultra-thin tension film of TiC, TiN or Ti(C,N) on the surface of the steel sheet, and then the phosphoric acid A method for producing an ultra-low iron loss unidirectional silicon steel sheet, which is characterized by forming an insulating film containing salt and colloidal silica as main components. 3 For a finish-annealed unidirectional silicon steel sheet having a composition containing C: 0.001 to 0.010 wt% and N: 0.0005 to 0.0100 wt%, a surface layer of Ti was formed on the surface of the steel sheet from which surface oxides had been removed. After TiC is deposited on the surface of the steel sheet, annealing is performed in a non-oxidizing atmosphere to promote the purification of C and N in the steel sheet.
A method for producing an ultra-low core loss unidirectional silicon steel sheet, which comprises forming an ultra-thin tensile coating of TiN or Ti(C,N). 4 For a finish-annealed unidirectional silicon steel sheet having a composition containing C: 0.001 to 0.010 wt% and N: 0.0005 to 0.0100 wt%, a surface layer of Ti was added on the surface of the steel sheet from which surface oxides had been removed. After TiC is deposited on the surface of the steel sheet, annealing is performed in a non-oxidizing atmosphere to promote the purification of C and N in the steel sheet.
An ultra-low iron loss unidirectional silicon steel sheet characterized by forming an ultra-thin tensile coating of TiN or Ti (C, N), and then forming an insulating coating whose main components are phosphate and colloidal silica. manufacturing method. 5 For a finish-annealed unidirectional silicon steel sheet having a composition containing C: 0.001 to 0.010 wt% and N: 0.0005 to 0.0100 wt%, a surface layer of Ti was formed on the surface of the steel sheet from which surface oxides had been removed. After the formation, annealing is performed in a carbonizing and/or nitriding gas atmosphere to promote the purification of C and N in the steel sheet and to cause carburizing and/or nitriding effects from the atmosphere.
A method for producing an ultra-low core loss unidirectional silicon steel sheet, which comprises forming an ultra-thin tensile film of TiC, TiN or Ti(C,N) on the surface of the steel sheet. 6 For a finish-annealed unidirectional silicon steel sheet having a composition containing C: 0.001 to 0.010 wt% and N: 0.0005 to 0.0100 wt%, a surface layer of Ti was added on the surface of the steel sheet from which surface oxides had been removed. After the formation, annealing is performed in a carbonizing and/or nitriding gas atmosphere to promote the purification of C and N in the steel sheet and to cause carburizing and/or nitriding effects from the atmosphere.
Ultra-low iron loss characterized by forming an ultra-thin tensile coating of TiC, TiN or Ti (C, N) on the surface of the steel plate, and then forming an insulating coating whose main components are tiphosphate and colloidal silica. A method for producing unidirectional silicon steel sheets. 7 For a finish-annealed unidirectional silicon steel sheet having a composition containing C: 0.001 to 0.010 wt% and N: 0.0005 to 0.0100 wt%, a surface layer of Ti was added on the surface of the steel sheet from which surface oxides had been removed. After the formation, annealing is performed in a non-oxidizing atmosphere to promote the purification of C and N in the steel sheet, and further annealing is performed in a carbonizing and/or nitriding gas atmosphere to remove carburization and/or carbonization from the atmosphere. Or, by adding nitriding effect, TiC, TiN or Ti(C,N) can be added to the steel plate surface.
A method for producing an ultra-low iron loss unidirectional silicon steel sheet, characterized by forming an ultra-thin tensile film. 8 For a finish-annealed unidirectional silicon steel sheet having a composition containing C: 0.001 to 0.010 wt% and N: 0.0005 to 0.0100 wt%, a surface layer of Ti was formed on the surface of the steel sheet from which surface oxides had been removed. After the formation, annealing is performed in a non-oxidizing atmosphere to promote the purification of C and N in the steel sheet, and further annealing is performed in a carbonizing and/or nitriding gas atmosphere to remove carburization and/or carbonization from the atmosphere. Or, by adding nitriding effect, TiC, TiN or Ti(C,N) can be added to the steel plate surface.
1. A method for producing an ultra-low core loss unidirectional silicon steel sheet, characterized by forming an ultra-thin tensile film of 1, and forming an insulating film mainly composed of phosphate and colloidal silica.