JPS6263407A - Production of low iron loss unidirectional silicon steel plate - Google Patents

Abstract

PURPOSE:To obtain both super low iron loss and excellent film adhesion property, by forming a hybrid thin film composed of carbide, nitride, and carbon- nitride compound on the surface of a steel plate. CONSTITUTION:On an unidirectional silicon steel plate which is finished in decarbonization and the primary recrystallization annealing to obtain a composition containing C:0.001-0.01wt% and N:0.0005-0.01wt%, a surface thin layer is stuck and formed which is made of at least one kind of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Ni, Al, B and Si. After that, the secondary recrystallization annealing and then purification annealing are performed in the non-oxidizing atmosphere to form a hybrid thin film composed of carbide, nitride and carbonnitride compound on the surface of steel plate. Vapoer deposition, iron plating, sputtering, and CVD method match suitably to coating means of surface thin layer, and such a lamination layer is preferable to be about 0.1-2.0mum thick.

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 (B,.

(represented by the value of W+7150) and low iron loss (represented by the value of W+7150).

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.
．． , 1.90T or more, W+t/so 1.05W/kg
Below, the magnetic properties of a product with a plate thickness of 0.23+n+n are 8
Unidirectional silicon steel sheets with ultra-low iron loss of 101, 89T or more and Ltzso 0.90W/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).

This magnetic domain refining technology is effective for transformer materials with stacked cores that are not subjected to strain relief annealing, but for transformer materials that are wound with main seams and subjected to strain relief annealing, laser irradiation is difficult. The introduced local microstrain is released by annealing and the magnetic domain width becomes wider.
The disadvantage is that the laser irradiation effect is lost.

On the other hand, earlier than this, in Japanese Patent Publication No. 52-24499, the surface of the unidirectional silicon steel sheet after annealing was mirror-finished, or the mirror-finished surface was coated with thin metal plating or the like. 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 sheet.

However, this method of improving iron loss through mirror finishing cannot be adopted from a process perspective, as it does not make a sufficient contribution to reducing iron loss, although it increases the cost significantly. 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 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 properties that outweigh the disadvantage of increased cost as described above, especially those that do not suffer from property deterioration during high-temperature treatment. We believe that it is important to overcome the problems of adhesion and durability of the insulating layer, and based on this basic understanding, we have developed a particularly advantageous ultra-low iron loss through drastic improvements in the processing method of grain-oriented silicon steel sheets. It is an object of this invention to achieve the following.

(Means to Solve the Problem) As a result of various studies to achieve the above object, the inventors found that C: 0.001 to 0.01 wt% (hereinafter simply expressed as %) and N : 0.0005~0.01
Ti, Zr, Hf,
V, Nb, Ta.

Cr, Mo, W, Mn, Co, Ni, Al
After forming a surface thin layer of at least one of B and Si, secondary recrystallization annealing and purification annealing are performed in a non-oxidizing atmosphere to form a mixture of carbides, nitrides and carbonitrides on the surface of the steel sheet. First of all, this invention was completed after obtaining the knowledge that forming a thin film is extremely effective in achieving the desired purpose.

In this invention, the means for forming the surface thin layer include vacuum evaporation, ion blasting, sputtering and CV
The D method is advantageously suitable, and the j9: of such a thin layer is from 0.1 to
The thickness is preferably about 2.0 .mu.m.13 In addition, in the present invention, the following non-oxidizing atmosphere is particularly advantageously suitable for use in the secondary recrystallization annealing and purification annealing.

1) H2 gas or Ar gas By performing annealing in an open atmosphere of these gases, diffusion of C and N in the steel sheet to the surface is promoted, and a mixed thin film is advantageously formed.

11) Carbonizing gas and/or nitriding gas Carbonizing gases include hydrocarbon gases such as C11 and C2H6, CO gas, and mixed gases of these gases with H2 gas and ^r gas. , - As a gas that can form a blade chamber,
N2 gas, NH3 gas, and mixed gases of these gases and H2 gas or back gas are advantageously compatible, and by performing annealing in such a gas atmosphere, C and N in the steel can be diffused to the surface and A mixed thin film is effectively formed by carburizing and/or nitriding from an atmospheric gas.

This invention will be explained in detail below.

First, the experimental results that formed the basis of this invention will be explained.

C: 0.042%, Si: 3.36%, Mn: 0.
066%, Se: 0.021%, Mo: 0.025
% and Sb: 0°025% and N: 0,001~0
．． A silicon steel slab with a composition containing 0.02% was hot rolled to form a hot rolled sheet with a thickness of 2.4 mm, and then heated at 900°C.
, uniform annealing for 3 minutes, followed by cold rolling twice with intermediate annealing at 950°C for 3 minutes, resulting in a plate thickness of 0.
A final cold-rolled sheet of 23 mm was obtained.

Afterwards, the dew point was varied in the range of 50 to 10°C8.
Primary recrystallization annealing, which also serves as decarburization, was performed in wet hydrogen at 20°C.

Then, a 0.8 μm thick TI vapor deposited layer was formed on the surface of the decarburized and primary recrystallized annealed plate using a vacuum vapor deposition apparatus.

Thereafter, secondary recrystallization annealing was performed at 850°C for 50 hours in a 50% N2-H□ atmosphere, followed by purification annealing at 1200°C for 3 hours in H2. An insulating film coating treatment was applied.

The magnetic properties of the product thus obtained and the amount of C1N in the steel,
Table 1 also shows the amounts of C and N in the decarburized and primary recrystallized plates.

As is clear from the results shown in Table 1, Ti was vapor-deposited on the sample in which the amount of C and N at the time of decarburization and primary recrystallization was 1100 pp or less, and then secondary recrystallization annealing was performed in a non-oxidizing atmosphere. Magnetic flux density when subjected to purification annealing (hereinafter referred to as finish annealing when both are expressed together). is 1.89 or more and iron loss Wlff/S.

Excellent properties were obtained, with a value of 0.83 W/kg or less.

It is also noteworthy that the amounts of C and N in the steel at this time are 25 ppm or less, which is significantly lower than the C and Nl in the steel at the time of decarburization and primary recrystallization.

Furthermore, all products with good magnetic properties also had excellent adhesion.

(Function) The above-mentioned improvements in magnetic properties and adhesion can be achieved by depositing T1 after decarburization and primary recrystallization annealing, and then performing finish annealing in a non-oxide atmosphere to reduce C in the steel. , N diffuses onto the surface of the steel sheet, forming TiC, TiN$ and Ti(C,
A mixed thin film consisting of N) is formed, and this surface thin film effectively applies tension to the steel plate.

Furthermore, since the diffusion of C and N in the steel is utilized in forming the mixed thin film, the degree of bonding between the film and the steel plate is increased, and therefore, the adhesion of the film can also be improved.

Next, the manufacturing process of the unidirectional silicon steel sheet will be explained in more detail, including a further explanation. First, the starting material is a conventionally known unidirectional silicon steel material, such as ■C: 0.03 to 0. 050%, S+: 2.50~4
．． 5%, Mn: 0.01-0.2%, Mo:
Q, 003~0.1%, Sb: 0.005~0
．． 2%, N: 0.0005-0.005%, one or both of S and Se in total, 0.005-0.
Composition containing 0.05%, ■c: o, oa ~ 0.08%, Si: 2.0 ~ 4.0
%, S: 0.005-0.05%, N: 0.
001 to 0.01%, Sn: 0.01 to 0.5
%, Cu: 0.01-0.3%, Mn: 0
．． Composition containing 01 to 0.2%, ■c: o, oa to 0
．． 06%, Si:2.0~4.0%, S20.00
5 ~ 0.05%, B: 0.0003 ~ 0.0
040%, N: 0.001-0.01%, Mn
: Composition containing 0.01-0.2%, ■C: 0.03-0.05%, Si: 2.0-4.0%
, Sb: 0.005-0.2%, N: 0.
0005-0.005%, composition containing any one or both of S and Se = 0, 005-0.05%, ■C: 0.03-0.05%, Si: 2.0 ~4
．． 0%, N: 0.0005-0.01%, any one or two of S and Se: 0.005-0
．． It is applicable in compositions containing 0.05%.

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

After finishing the final cold rolling 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 iron loss as much as possible, and as mentioned above, in the present invention, a mixed thin film is formed by utilizing the diffusion of C and N in the steel in the subsequent final annealing. Due to the necessity of forming carbon, excessive decarbonization is not preferable, and 0.001. ~0.
It is essential that 0.1% C be present. This is because if the amount of C in the decarburized/first recrystallized annealed plate is less than 0.001%, it is difficult to obtain a good mixed thin film; This is because if the former percentage is exceeded, the development of Goss-oriented grains becomes poor in the secondary recrystallization treatment, resulting in deterioration of magnetic properties, which is not preferable.

Similarly, for the above-mentioned annealed plate, the amount of N in the steel was 0,000.
If it is less than 5%, a mixed thin film with good properties cannot be obtained, while if it is less than 0. If it exceeds 1%, preferential formation of nitrides will occur in the steel, resulting in a disadvantage of deterioration of the magnetic properties of the product. Therefore, the amount of N must be limited to a range of 0.0005 to 0.01%.

Next, Ti, Zr, Hf, V, Nb, preferably 0.1 to 2.0 μm thick, are applied to the surface of the decarburized and primary recrystallized annealed plate by vacuum evaporation, ion blating, sputtering or CVD. Ta, Cr
, Mo, IN, Mn, Co.

A surface thin layer of at least one of Ni, B, B and Si is formed.

Thereafter, secondary recrystallization annealing and subsequent purification annealing are performed in a non-oxidizing atmosphere to form a mixed thin film of carbides, nitrides and carbonitrides on the surface of the steel sheet.

Generally, secondary recrystallization annealing is performed to sufficiently develop secondary recrystallized grains with (110) <001> orientation, and is usually performed by immediately raising the temperature to 1000°C or higher by box annealing.
This is done by holding it at that temperature.

In this case, in order to develop a highly uniform secondary recrystallized grain structure in the (110) <[101> orientation, it is advantageous to perform retention annealing at a low temperature of 820°C to 900°C; ~b Annealing may be used.

In addition, the subsequent purification annealing is usually performed at 1100°C or higher for 1
It is carried out under conditions of ~20 hours.

In this invention, the above-mentioned secondary recrystallization annealing and purification annealing are carried out in various non-oxidizing atmospheres as mentioned above, so that C and N in the steel can be diffused to the surface, and sometimes further removed from the atmospheric gas. By carburizing and nitriding,
Although a mixed thin film is formed on the surface of the steel sheet, it goes without saying that the atmosphere during the secondary recrystallization annealing and the purification annealing may be changed if necessary.

Furthermore, it is naturally necessary to apply and bake an insulating film mainly composed of phosphate and colloidal silica on the mixed thin 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 can be used as they are.

(Example) C: 0.043%, Si: 3.42%, Mn: 0.
068%, Se: 0, 020%, Mo: 0.025
% and N: A silicon steel slab containing 0.0026% was hot rolled to obtain a hot rolled plate having a thickness of 2.4+n+o.

Then, after homogenizing annealing at 900℃ for 3 minutes,
Cold rolling was performed twice with intermediate annealing at 50° C. for 3 minutes to obtain a final cold rolled sheet having a thickness of 0.23 mm. Then 820
Various metals or metalloids shown in Table 2 were vapor-deposited to a thickness of 0.8 μm on the surface of a steel sheet that had been subjected to primary recrystallization annealing that also served as decarburization in wet hydrogen at 45° C. (dew point: 45° C.).

After that, 850. t
, secondary recrystallization annealing for 50 hours, then 120 hours in dry H2.
Purification annealing was performed at 0° C. for 8 hours, and a coating treatment with an insulating film mainly composed of phosphate and colloidal silica was performed.

Table 2 summarizes the results of examining the magnetic properties and film adhesion of each product thus obtained.

As is clear from the results shown in Table 2, all of the unidirectional silicon steel sheets obtained according to the present invention have Blo ≧1
．． It exhibited excellent magnetic properties such as 91T and L715a≦0.81W/kg, as well as good adhesion.

(Effects of the Invention) Thus, according to the present invention, the winding core direction has excellent magnetic properties, especially ultra-low core loss, regardless of whether high-temperature treatment such as high-temperature strain relief annealing is applied when used as a transformer material. can be obtained with good film adhesion.

Claims (1)

[Claims] 1. C: 0.001 to 0.01 wt% and N: 0.0
Ti, Zr, Hf, V, Nb on the surface of a unidirectional silicon steel sheet that has been decarburized and annealed for primary recrystallization to have a composition containing 0.005 to 0.01 wt%.
, Ta, Cr, Mo, W, Mn, Co, Ni, Al, B
After forming a surface thin layer of at least one of Si and Si, secondary recrystallization annealing and purification annealing are performed in a non-oxidizing atmosphere to form a mixed thin film of carbides, nitrides and carbonitrides on the surface of the steel sheet. 1. A method for producing a low iron loss unidirectional silicon steel sheet, characterized by forming a unidirectional silicon steel sheet.