JPH0222421A - Production of unidirectional type silicon steel sheet having superlow iron loss - Google Patents

Abstract

PURPOSE:To attain stable superlow iron loss by subjecting a silicon steel sheet with a specific composition to decarburizing annealing, secondary recrystallization, and purification annealing, removing surface oxides, and then forming an extra thin high-tensile film of the oxide or nitride of a specific metal by a CVD method, etc. CONSTITUTION:A slab of a silicon steel which has a composition containing, by weight, 0.01-0.08% C, 2.0-4.0% St, 0.01-0.2% Mn, 0.001-0.007% S, 0.005-0.06% Al, and 0.001-0.010% N as essential components and having the balance Fe with inevitable impurities is heated to 1000-1250 deg.C and hot-rolled. The hot rolled plate is cold-rolled in an atmosphere capable of nitriding, while process-annealed between the cold rolling stages, so as to be formed into the final sheet thickness. The resulting sheet is subjected to decarburizing annealing in warm hydrogen, and a separation agent at annealing for inhibiting forsterite formation is applied to the above sheet, and then, secondary recrystallization and purification annealing are carried out. Then, oxides on the surface of this finish-annealed sheet are removed, and polishing treatment is applied. Subsequently, an extra thin high-tensile film of at least one kind selected from the nitrides and carbides of Ti, Zr, Hf, V, Nb, Ta, etc., is formed on the above sheet by means of CVD, ion plating, etc. By this method, an unidirectional type silicon steel sheet having superlow iron loss can be stably produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing an ultra-low iron loss unidirectional silicon steel plate.

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 product is used as an iron core, and the product is required to have high magnetic flux density (B, represented by the value) and low iron loss (WIT/S, represented by the value) as electrical and magnetic properties.

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 a product with a thickness of 0.30 mm has magnetic properties of 8.
,. Value of 1.90T or more, 1,7. . The value is 1.05W/
The magnetic properties of products weighing less than 1 kg and having a plate thickness of 0.23 mm are B.
10 value 1.89T or more, Gai, 7. . The value is 0.90W,
Unidirectional silicon steel sheets with low iron loss of less than /kg are now 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, Japanese Patent Publication No. 5224499
In the publication, ultra-low iron loss is achieved by mirror-finishing the surface of a unidirectional silicon steel sheet after finish annealing, or applying thin metal plating on the mirror-finished surface or coating and baking an insulating film on top of it. A method for manufacturing unidirectional silicon steel sheets has been proposed.

However, this method of improving iron loss through mirror finishing cannot be adopted from a process perspective because it does not contribute enough to reducing iron loss despite the significant increase in cost. Due to problems with subsequent 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
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.

On the other hand, recently, Japanese Unexamined Patent Publication No. 62-40315 discloses that a silicon steel slab is heated to a high temperature and a component that serves as an inhibitor is dissolved in the final product without going through the process of heating a silicon steel slab to a solid solution, as in the conventional manufacturing method of silicon steel sheet. During secondary recrystallization during annealing (
Although a method has been disclosed in which Si, Al)N is present in a steel sheet and used as an inhibitor, it is still impossible to perform secondary recrystallization in a stable process and to obtain sufficiently low iron loss. It's hard to say what the manufacturing method is.

(Problem to be Solved by the Invention) In order to take advantage of the improved iron loss effect achieved by the above-mentioned mirror finish, the inventors have found that, in particular, from the viewpoint of the development of energy-saving materials today, the above-mentioned disadvantages of increased costs can be avoided. We believe that it is important to overcome the problems of insulating layer adhesion and durability without deteriorating properties, and based on this basic understanding, we have developed finish-annealed grain-oriented silicon steel sheets. By applying a special steel plate surface treatment after removing oxides on the surface and polishing, especially when nitride is used as an inhibitor, we aim to achieve not only advantageous but also stable ultra-low iron loss. It is something.

(Means for Solving the Problem) The inventors removed the drawbacks of the above-mentioned conventional technology, and
As a result of various studies in order to achieve ultra-low iron loss in a stable manufacturing process, we found that the weight percentage is simply %: C0.01-0.08%, Si 2.0-4.0
%, Mn 0.01-0.2%, S
0.001-0.007%, A1 0.00
5~0.06%, N 0.001~0.010%, balance Fe and unavoidable impurities.
After heating at a temperature of 0 to 1250°C, hot rolling is performed to obtain a hot rolled plate, and after intermediate annealing in an atmosphere with nitriding ability, cold rolling is performed for two passes to obtain the final plate thickness, Next, after decarburizing annealing in wet hydrogen, a compound with nitriding ability is added and an annealing separator for suppressing forsterite formation is applied, and the finished annealed plate is further subjected to secondary recrystallization and purification annealing. Tll Zr, llf, v, Nb, Ta,
Cr, Mo, w, Mn, Co.

A method for manufacturing an ultra-low iron loss unidirectional silicon steel sheet comprising coating an ultra-thin tensile coating consisting of a small amount (both of them) selected from nitrides and/or carbides of Ni, , Al + B, and Si. In addition to the above-mentioned components, this silicon steel slab also contains Sn.
0.005-0.5%, Cu 0.01-1.0
%, or/and Mo + a small amount of Sb, B (both of which are contained in a total of 0.005 to 0.5%). This led to the completion of the invention.

The following will be explained in accordance with specific experiments that led to the success of this invention.

■ C0.053%, S43.35%, Mn 0.
085%S 0.026%, ,Al 0.025%
, silicon steel slab containing N 0.0072% (normal unidirectional silicon steel material composition), C 0.055%, Si 3.35%, Mn 0.07
5%.

S 0.003%, Al 0.026%, N
0.0066%, C0.054%, Si3.36%,
Mn 0.078%.

S 0.003%, At 0.027%, N 0
．． 0069%.

Cu 0.1%, Sn 0.05%, ■ C0.
055%, Si3.34%, Mn 0.077%S
0.00wt%, , Al 0.024%, N
0.0073%.

■ ■ Cu 0.1%, Sn 0.05%, M
o 0.021%, ■ C0,052%, Si 3
．． 36%, Mn 0.079%.

S 0.00wt%, Al 0.028%,
N 0.0071%.

Cu 0.09%, Sn 0.0wt%,
Mo 0.015%.

Silicon steel slabs each containing 0.023% Sb and the remainder substantially Fe (■ to ■ are silicon steels with material components targeted by the present invention) were heated at A 1380°C for 5 hours and B 1100°C (normal A hot rolled sheet was obtained by heating for 2 hours at a heating temperature for hot rolling, not at a heating temperature that dissolves the inhibitor into solid solution.

Thereafter, rolling was performed twice with intermediate annealing for 1 minute at 1050°C to obtain a final cold-rolled plate with a thickness of 0.20 mm. During this intermediate annealing, (a) NH3 (5%) + 11□ nitridation was performed. Atmosphere (conditions of the present invention).

Q)) Each was treated in a normal atmosphere of NZ (50%) + 11□ (50%). After that, after performing primary recrystallization annealing in wet hydrogen at 840°C, which also serves as decarburization, the annealing separator Mg, which suppresses the forsterite formation reaction, is applied on the steel plate surface.
O (30%), Al2O3 (65%), and ferromanganese nitride (5%) were applied.

After that, the temperature was raised from 850°C to 1150°C at 10°C/hr to develop Goss-oriented secondary recrystallized grains.
Purification annealing was performed in dry H2 at 0°C for 8 hours.

Thereafter, oxides on the surface of the steel plate were removed by pickling, and the surface was electrolytically polished to a mirror-like state Ra=0.08 μm (center line average roughness). Thereafter, a tension film of TiN was formed on the surface of the steel plate by an ion plating method (HCD method) (ICD conditions at this time were an acceleration voltage of 50 V, an acceleration current of 500 A, and a film thickness of 0.8 μm).

Table 1 summarizes the magnetic properties of the products after these treatments.

As is clear from Table 1, in the case of ordinary unidirectional silicon steel material compositions such as (■), the properties do not change significantly depending on the processing conditions.
1.93T, enemy 1,7. . Direct power is 0.72 to 0.77W
/kg.

On the other hand, in the silicon steel material components ■ to ■, which are the subject of the present invention,
The magnetic properties are extremely different depending on the experimental conditions, and the best conditions for the magnetic properties are heating conditions such as low-temperature heating of B, and for intermediate annealing conditions, treatment in a nitriding atmosphere (a) is suitable. The magnetic properties of the tl+o value are 1.93~
1.94T, WI7150 value is 0.58-0.5
It is noteworthy that the iron loss is extremely low at 9 W/kg.

(Function) As described above, using the material components of the steel slab according to the present invention,
When treated in a nitriding atmosphere during intermediate annealing under low-temperature heating, a rapid improvement in magnetic properties, especially for iron, has been brought about after the subsequent Ti coating has been formed.

Although the reason for this has not been clearly elucidated, it is thought to be due to the following reasons.

That is, by lowering the slab heating in (2), the hot rolling finishing temperature can be lowered, so it is possible to increase the frequency of Goss-oriented secondary recrystallization nuclei generated near the surface of the steel sheet. ■The inhibitor used at this time is not the conventional method in which the inhibitor must be made into a solid solution by high-temperature heating (AlN + Mn5), but the inhibitor used in JP-A-62-4
It is believed to be (Si, Al)N disclosed in Publication No. 0315, but Goss generated during hot rolling at that time
In order to effectively carry over the nuclei to the secondary recrystallization process, the inhibitor function of (Si, Al)N is strengthened by creating a nitriding atmosphere during intermediate annealing as disclosed in the present invention. (For the mechanism of Goss nuclear generation and inheritance, please refer to the following inventor's explanation or paper: Yukio Iro, Tetsu to Hagane, 70 (1984), P, 2033
．． Yukio Iguchi et al. 9 Journal of the Japan Institute of Metals, 50 (1986)
, P, 874. Y, InokuLi et.

al,, Trans, l5IJ, 27 (198
7), P, 139, and Met, Trans
, 16A (1985), P, 1613) In addition, the present inventors have already shown that ultra-low iron loss can be achieved by forming a tensile thin film of nitrides and carbides without forming the current forsterite film. JP-A-62-1820, 1982-1821, and 1982 disclosed by
This is clear from JP-A No. 2-1822 or JP-A No. 62-69502, and it is thought that ultra-low iron loss can be effectively achieved by combining these.

The above-mentioned reasons (1) to (2) have made it possible to manufacture a grain-oriented silicon steel sheet with ultra-core loss.Next, the manufacturing process of a grain-oriented silicon steel sheet according to the present invention will be described in more detail, including a general explanation.

First, the reason why the component composition of the material is limited to the above range in this invention will be explained.

c o, oi ~ 0.08% C is an essential element for improving the hot rolling texture,
If C is less than 0.01%, texture control becomes weak and a large band structure is formed, inhibiting the development of secondary recrystallized grains.

Furthermore, if C exceeds 0.08%, it will have a negative effect on the hot rolling texture, and decarburization will take a long time, so C should be 0.01% or more.
It should be limited to a range of ~0.08%.

Si 2.0 to 4.0% When Si is less than 2.0%, the electrical resistance is low and the iron loss value increases due to increased eddy current loss. On the other hand, when it is more than 4.0%, it is difficult to 2. Because brittle cracks are more likely to occur.
It was limited to a range of 0 to 4.0%.

Mn 0.01-0.2% Mn is present as a precipitated dispersed phase in unidirectional silicon steel sheets.
When nS or MnSe is used, it contributes as an inhibitor-forming element, but in the present invention, since MnS or MnSe is not used as an inhibitor, the role of Mn is only to improve processability, and for that purpose, Mn is 0.01 to 0.2 It was decided to add in a range of %.

s o, ooi ~ 0.007% S is 0.0% in the conventional general unidirectional silicon steel material component.
It contains about 15 to 0.035%, but from what was shown in Table 1, at least 0.001% is required, but 0.
If S exceeds 0.007%, the desired effect can no longer be achieved, so S is limited to 0.001 to 0.007%.

sol Al 0.005 to 0.06% Al is as disclosed in Japanese Patent Application Laid-Open No. 62-40315,
(Si, Al) It is an important element because it is used as an inhibitor of N, and it needs to be added in a range of 0.005 to 0.06% to effectively suppress primary grain growth.

N 0.001-0.01% N is an important element used in the use of (Si, Al)H inhibitors, and in consideration of the above
The content was set to be in the range of 0.01 to 0.01%.

Other Cu commonly used as inhibitors
, When adding one or two of Sn, the amount of CuO is 0.01 to 1.0%, and the amount of Sn is 0.005 to 0.5.
%, Cu is less than 0.01% and Sn is less than 0.005%, and Cu exceeds 1.0% and Sn exceeds 0.5%.

Furthermore, in addition to these, it is advantageous to add a total of 0.005 to 0.5% of at least one of Mo, Sb, and B to the silicon steel material in terms of suppressing grain growth of primary recrystallized grains. If it is less than 0.005%, the force to effectively exert the suppressing force is small, and if it exceeds 0.5%, it will not be possible because it will cause plate cracking during cold rolling and require a long time for degreasing, making it uneconomical. be.

Next, a series of manufacturing steps according to the present invention will be specifically explained.

First, to melt the material, it is possible to use an LD converter, an electric furnace, an open hearth or other known steelmaking furnaces, and it is also possible to perform vacuum treatment or vacuum melting.

Next, the molten silicon steel produced in this manner is made into a slab by a continuous casting method or an ingot-blowing method.

Ordinary unidirectional silicon steel is heated to a high temperature of 1350°C or higher to dissociate and dissolve MnS or MnSe, but in this invention, (Si, Al)N is used as an inhibitor, so there is no need to do so. After heating at a temperature of °C, it is subjected to hot rolling by a known method.

If the heating temperature for hot rolling is less than 1100°C, hot cracking will occur, while if hot rolling is carried out at a high temperature exceeding 1250°C, Goss orientation texture will preferentially form in the surface layer of the hot rolled sheet. It becomes impossible to do so.

The thickness of the hot rolled sheet is controlled by the subsequent cold rolling process, but is usually 1
．． It is advantageous to set the thickness to about 2 to 3.0.

Next, the hot-rolled sheet is subjected to high-temperature uniform annealing at 900 to 1200''C depending on the case, but it is preferable to perform a rapid cooling treatment after this annealing.

Thereafter, the steel plate is cold rolled twice with intermediate annealing in between. The intermediate annealing temperature at this time is preferably in the temperature range of 800-1200"C within the recovery/recrystallization temperature range of the steel plate,
Further, the annealing atmosphere at this time must be a nitriding atmosphere, which is an essential condition of the present invention.

The optimal nitriding atmosphere is to mix 1 to 30% of NH into the H2 or N2 atmosphere, but the main purpose is to enhance the inhibitor function by nitriding from the surface of the steel plate. As the nitriding method, a conventionally known method may be used. In addition, when cold rolling is performed twice, it is desirable that the final rolling reduction is as high as 5° to 85%.
It is optimal to perform interpass aging treatment at ℃. The final cold-rolled sheet thickness at this time is approximately 0.10 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 primary recrystallization annealing at 750°C to 850°C.

After that, normally, an annealing separation mainly composed of MgO is 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 finishing annealing. A1zO is used as an annealing separator because it is effective in simplifying the mirror finishing of steel plates.
Not only is 50% or more of + Zr0z + Ti0z etc. mixed into MgO, but also 2.
It is effective to carry out the nitriding treatment at the initial stage of the next recrystallization.
It is necessary to add N or the like.

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 C and holding it at that temperature.

In this case (110) <2 highly aligned in the OOb direction
In order to develop the next recrystallized grain structure,
It is more advantageous to carry out holding annealing at a low temperature of 0'C, and in addition, heat removal annealing at a heating rate of 0.5 to 15'C/h may also be used.

Purification annealing after secondary recrystallization annealing is performed in soft hydrogen at 11
It is necessary to achieve purification of the steel plate by annealing at temperatures above 00°C for 1 to 20 hours.

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

After this oxide removal treatment, the steel plate surface is polished to a mirror-like state, that is, the centerline average roughness is 0, by conventional known methods such as chemical polishing such as chemical polishing and electrolytic polishing, mechanical polishing such as Huff polishing, or a combination thereof. . Finish to 4μm or less.

After that, Ti,
Zr, Hf, V, Nb+ Tat Cr,
An ultra-thin tensile film made of at least one selected from Mot W+Mn+Co, Ni, At, B, and Si nitride and/or carbide is formed.

It is effective to form this ultra-thin tension film with a thickness of about 0.1 to 2 μm.

Applying an insulating film containing phosphate and colloidal silica as the main components to the ultra-thin tension film produced in this way is of course necessary for use in large-capacity transformers of up to 1 million KVA. This is necessary, and conventional methods such as the formation of this insulating baked layer can be used as they are.

(Example) According to Example 1, a silicon steel slab having the six types of components shown in Table 2 was heated at 1100° C. and then hot rolled into a hot rolled plate having a thickness of 1.6 m. then 1
Cold rolling was performed twice with intermediate annealing for 1 minute at 050''C to obtain a final cold rolled sheet with a thickness of 0.20 mm.

In addition, during intermediate annealing, 5% NH, + 50% H2 + 45%
The test was carried out in a nitriding atmosphere of N2.

After that, after decarburization and primary recrystallization annealing in wet hydrogen at 840°C, MgO (30%) and Ah03 were deposited on the steel plate surface.
After applying an annealing separator containing (60%), Zr0z (5%), and ferromanganese nitride (5%), 85
Gos by increasing the temperature from 0℃ to 1150℃ at 8'C/br
After developing s-oriented secondary recrystallized grains, 10
Purification annealing was performed in time-dry H2.

Thereafter, oxides on the surface of the steel plate were removed by pickling, and then mirror-finished to a center line average roughness Ra of 0.06 am by electrolytic polishing.

After that, HCD method (acceleration voltage 45V, acceleration current 500A
A 5iJ4 film (thickness: 1.0 μm) was formed on the surface of the steel plate under a vacuum degree of 7 Xl0-'Torr). The magnetic properties of the products at that time are summarized in Table 2.

Fiber side C0.056%, S13.36%, Mn
0.076%, 8%, , Al 0.033%,
N 0.078%, Cu 0.09%,
M.

A silicon steel slab containing 0.031% of Sb and 0.015% of Sb with the remainder substantially made of Fe was heated at 1150° C. and then hot rolled to obtain a hot rolled sheet with a thickness of 1.8. then 1
After intermediate annealing at 100° C. (the annealing atmosphere at this time was a nitriding mixed gas of 3% NH, +55% H, +48% N2), a final cold-rolled sheet with a thickness of 0.20 mm was obtained. After that, after decarburization and primary recrystallization annealing in a wet water system at 850°C, MgO (3%), ^1zos (60%), Zr
0z (3%), Tie.

(2%) and an annealing separator containing ferromanganese nitride (5%).

Next, the temperature was raised from 850″C to 1050°C at a rate of 8°C/h for secondary recrystallization, and then further recrystallized in soft hydrogen for 12
Purification annealing was performed at 00°C for 18 hours.

After that, oxides on the surface of the steel plate are removed by pickling, and the surface of the steel plate is polished to a mirror finish by electrolytic polishing.
VO (no mark in Table 3), ion plating (O mark in Table 3) and ion implantation (Δ in Table 3)
Various thin films (approximately 0.7 to 0.8 μm thick) were deposited using the following methods. An insulating film was formed by applying and baking a coating treatment liquid containing phosphate and colloidal silica as main components.

Table 3 summarizes the results of investigating the magnetic properties of each product obtained.

Back 3 In addition, in each of the above-mentioned product plates, no deterioration in characteristics was observed even after strain relief annealing at 800° C. for 1120 minutes.

(Effects of the Invention) As described above, it is advantageously possible to manufacture an ultra-low iron loss unidirectional silicon steel plate using a stable process.

Claims (1)

[Claims] 1. C0.01-0.08wt%, Si2.0-4.0wt%, Mn0.01-0.2wt%, S0.001-0.007wt%, Al0.005-0. After heating a silicon steel slab consisting of 0.06wt%, N0.001~0.010wt%, balance Fe and unavoidable impurities at a temperature of 1000~1250°C, and hot rolling it into a hot rolled sheet, it has nitriding ability. An annealing separator for suppressing forsterite formation with the addition of a compound with nitriding ability after cold rolling twice in an atmosphere to obtain the final thickness, followed by decarburization annealing in wet hydrogen. Ti, Ti, Ti, etc. are applied to the finished annealed plate which has been coated with Ti, and further subjected to secondary recrystallization and purification annealing, and then CVD, ion plating or ion implantation is performed on the surface of the steel plate after removal of oxides on the surface and polishing treatment. Zr, Hf, V, Nb, Ta, Cr, Mo, W,
Ultra-low core loss unidirectional silicon coated with an ultra-thin tensile coating made of at least one selected from nitrides and/or carbides of Mn, Co, Ni, Al, B, and Si. Method of manufacturing steel plates. 2. In claim 1, the silicon steel slab contains: C0.01-0.08wt%, Si2.0-4.0wt%, Mn0.01-0.2wt%, S0.001-0.007wt%, Al0. 005~0.06wt%, N0.001~0.010wt%, Sn0.005~0.5wt%, Cu0.01~1.0
A method for producing an ultra-low iron loss unidirectional silicon steel sheet, characterized in that the composition contains one or two of the following wt%, and the remainder is Fe and unavoidable impurities. 3. In claim 1, the silicon steel slab contains: C0.01-0.08wt%, Si2.0-4.0wt%, Mn0.01-0.2wt%, S0.001-0.007wt%, Al0. 005-0.06wt%. N0.001 to 0.010 wt% and at least one of Mo, Sb and B in total 0.0
A method for producing an ultra-low iron loss unidirectional silicon steel sheet, characterized in that the composition contains 0.05 to 0.5 wt%, with the balance consisting of Fe and unavoidable impurities. 4. In claim 1, C0.01-0.08wt%, Si2.0-4.0wt%, Mn0.01-0.2wt%, S0.001-0.007wt%, Al0.005-0.06wt%. %. N0.001-0.010wt%, Sn0.005-0.5wt%, Cu0.01-1.0
One or two of wt% and at least one of Mo, Sb and B in total 0.0
A method for producing an ultra-low iron loss unidirectional silicon steel sheet, characterized in that the composition contains 0.05 to 0.5 wt%, with the balance consisting of Fe and unavoidable impurities.