JPS6059044A - Grain-oriented silicon steel sheet having low iron loss value and its production - Google Patents

Abstract

PURPOSE:To produce a grain-oriented electrical steel sheet having a high magnetic flux density and small iron loss by subjecting a hot rolled steel sheet having a specific compsn. contg. Si, C, Sn, etc. to an adequate heat treatment and final cold rolling then applying tension coating thereon after decarburization and finish annealing. CONSTITUTION:A hot rolled steel sheet contg. 2.5-4.5% Si, 0.02-0.10% C, 0.04- 0.4% Sn, 0.015-0.040% sol Al, 0.0040-0.0100% N, 0.030-0.150% Mn, 0.015- 0.040% S, <=0.04% Se and <=0.4%>=1 kind among Sb, Cu, As and Bi is held for 10-600sec at 900-1,200 deg.C or <=100sec at 1,050-1,200 deg.C and is then held for 30- 500sec at 800-1,000 deg.C and is then cooled down to 100 deg.C in 3-50sec. The steel sheet is rolled at 81-93% draft in the final cold rolling, thereafter and the steel sheet is heated for 30sec at 150-300 deg.C at least twice and is made into 0.15-0.23mm. final thickness between rolling passes. The steel sheet is subjected to decarburization annealing and finish annealing in an atmosphere consisting of >=50% H2 and N2 and is then subjected to tension coating, by which the grain- oriented electrical steel sheet having W17/50<=0.90W/kg is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a thin, high magnetic flux density unidirectional electrical steel sheet with excellent iron loss characteristics used for iron cores of transformers, etc., and a method for manufacturing the same. .

(Prior art) A unidirectional electrical steel sheet has crystal grains whose easy axis of magnetization <ooi> coincides with the rolling direction and whose (110) plane is almost aligned in an orientation parallel to the steel sheet surface (so-called Goss orientation). A steel sheet with crystal orientation consisting of Unidirectional electrical steel sheets are known to have good magnetic properties such as magnetization properties and core loss properties. As is well known, iron loss consists of hysteresis loss and eddy current loss.The physical factors of H hysteresis loss include the crystal orientation, purity, and internal strain of the steel plate, and eddy current loss includes the electrical resistance of the steel plate, These include plate thickness, magnetic domain size, crystal grain size, and tension applied to the steel plate.

Efforts have been made to bring the orientation of crystal grains closer to perfect Goss orientation in order to improve iron loss. Also,
Focusing on the influence of crystal grain size, specific resistance, surface coating, etc. on iron loss characteristics, attempts have been made to improve iron loss characteristics from this perspective.

However, at present, the iron loss W per 1 kg when magnetized to 1.7 T at 50 Hz is 171 at 715o.
5o〈1. There are few ways to obtain iron loss values as low as ow/yu. Even if there were, there would be difficulties in industrialization or use of the product. For example, there is a method of increasing St to increase the specific resistance, but as the amount of St increases, workability deteriorates, so an upper limit occurs. In addition, there are methods for improving iron loss characteristics by imparting tension to steel sheets, such as improving the forsterite film (Japanese Patent Publication No. 51-12451) and using top coating (Japanese Patent Publication No. 53-28375). If an attempt is made to increase the tension effect by increasing the thickness of the coating, there will be disadvantages such as lowering the load capacity of the transformer core, so there is an upper limit to the tension effect of the coating. Recently, methods for improving core loss characteristics by subdividing magnetic domains include marking (Japanese Patent Publication No. 58-5968) and laser irradiation (% Publication No. 58-26405), but when going through a strain relief annealing process, Since it is no longer effective, it must be limited to applications that do not require stress relief annealing. In addition, as is well known, there are many methods to reduce iron loss by refining crystal grains, especially for thin materials (%
326), but generally speaking, there is a phenomenon in which it becomes difficult to secure a high magnetic flux density when measures are taken to reduce the size of crystal grains, so there is a limit to the iron loss value that can be achieved.

(Object of the Invention) The present invention discovers and utilizes a new influencing factor regarding iron loss, and provides a highly practical low iron loss product and a method for manufacturing the same. That is, the present inventors have regulated the impurity elements to a predetermined amount or less, and at 0°1 where a predetermined amount of tension exists.
B1o≧1.90 with a plate thickness of 5 to 0.23 mrn
It is a high magnetic flux density steel sheet of T, and by regulating the degree of unevenness of grain boundaries, the conventional level W ≧1.00 W/1
W Yoshi and more than 10% are also 17/s.

The present invention provides a unidirectional electrical steel sheet product having an improved ultra-low core loss value and a method for manufacturing the same.

(Structure and operation of the invention) The present invention will be explained in detail below.

First, we will discuss the conditions that a product should have: W17150≦O, 90W/IJ.

The first condition concerns the ingredients. Damn, there is S in steel.
i: 2.3 to 4.3%, Sn: 0.04 to 0.4%, and C as impurities is 15% or less of O, 0O, and N.

Each S content is controlled to 0.0010% or less, and the remainder consists essentially of "jKFe."

The second condition is that the steel plate thickness is 0.15 to 0.23 mm.

The third condition is that Bl O (magnetic flux density when a magnetic field of i o OA/m is applied) is 1.90 T or more.

The fourth condition is that a tension of 0.2 to 1, OIw/■2 exists in the steel plate.

The fifth condition is the core condition of the present invention. When defining a formula as an index expressing the grain boundary shape characteristics of each crystal in the steel sheet, the average value SF of each SF value for the steel sheet is 5.
It is determined that F(0, fiO).

The reasons for limiting these five conditions will be explained below.

First, the present inventors conducted experiments using not only known methods but also a wide range of conditions regarding component elements and various process conditions.
A large number of unidirectional electrical steel sheet products having a thickness of 0.35 ttrs were obtained. Measure the iron loss and magnetic flux density of such steel plates,
In addition, after measuring the steel plate tension derived from the surface coating,
Surface coatings such as the 7-orsterite coating are removed using nitric acid or the like, and the secondary recrystallized structure (hereinafter referred to as macrostructure) of the steel sheet is obtained.

) was exposed.

Then, we analyzed the components in the product steel and systematically examined the morphology of the macrostructure using a commercially available image analyzer, and determined that the product steel sheet satisfies the above six conditions.Wl 715
It has been found that this is necessary in order to obtain a grain-oriented electrical steel sheet (low core loss of 9 or less when l is 0.90 W/).

The reason for limiting the first condition will be explained.

81 increases the resistivity and thus reduces the eddy current losses. If it is less than 2.3, it will not be possible to obtain good iron loss characteristics, which is the objective of the present invention, and if it exceeds 4.34, problems will arise in workability at the manufacturing stage and use stage, which is undesirable. The amount was limited to 2,3 to 4,3.

sn is added to the molten steel during the manufacturing process and remains in the product without being purified. In the secondary recrystallization stage of final annealing, Sn functions to complicate the number of grain boundaries and is effective in lowering the grain boundary shape index SF, which will be described later. This is presumed to be related to the grain boundary segregation of Sn. If it is less than 0.04%, this effect will be small, and if it is more than 0.4%, the forsterite coating will deteriorate, so it is limited to 0.04 to 0.4%.

C not only causes magnetic aging but also deteriorates the magnetic properties that distort the lattice even if it is in solid solution, so it is 0.001
It is necessary to control it to 5% or less.

Since N and S increase the history loss, it is the object of the present invention that W17/s is equal to or less than o, ooio%.

is necessary to obtain a low core loss of Q, 90 W/kli+.

Second. The reason for limiting the third condition will be explained.

FIG. 1 shows the relationship between the product board thickness and W, 715o for a sample that satisfies the first condition. From this figure, W17150≦0.90 To obtain 9 to W/S
In Sn+ C* In addition to the conditions of No. 8, the second condition is that the steel plate thickness is 0.15 to 0.23 van,
We know that the third condition B ≧1.90σ) is necessary. However, in Figure 1, if only the first to third conditions are satisfied, Wl, 75o<, 0.90 W/kl? This shows that this may not always be the case.

Next is the fourth. The reason for limiting the fifth condition will be explained.

First, the SF value will be explained. The SF value is normalized to 5F=1 when the grain shape is circular on the surface of the steel sheet.The value becomes smaller when the grain boundary shape becomes complicated in the matrix.

For example, when the crystal grain shape is a regular hexagon, the value of QTi''!-tO,
It stands at 88. The inventors found from FIG. 1 that there are factors that affect iron loss in addition to the first to third conditions, so they conducted additional experiments and increased the number of samples. And the first. Third
W1 of the sample that satisfies the conditions and has a product board thickness of 0.20 m.
The relationship between 715o and the tension in the rolling direction of the steel plate was investigated, and the average S of the SF value of the aforementioned crystal grains as a steel plate was determined using an image analyzer.
Figure 2 was obtained by adding the value of F. SF is 0
．． If larger than 60, W17150≦0.90 W
It is difficult to secure +7 for /11) and the correlation with rolling direction tension is not very clear, whereas SF is 0.
．． If it is smaller than 60, the tension in the rolling direction is 0.2 to 1.0.
In the range of kg/1m2, Wl 7150≦0.90
It can be seen that W/ky is easier to obtain and the higher the tension, the better the iron loss is in the supine position. In this figure, the inventors
The fourth condition is 0.2 to 1.0 k17/m2 for the steel plate.
The fifth condition is that SF<
I learned that it is necessary to add two conditions of 0.60 in order to obtain good iron loss. The synergistic effect of the fourth and fifth conditions is a completely new physical factor that affects iron loss. Although it is not necessarily clear how this synergistic effect affects iron loss, it is thought to be as follows.

Each crystal grain of a high magnetic flux density unidirectional electrical steel sheet has an orientation difference of about 4 to 5 degrees at the maximum at the grain boundary. When tension in the rolling direction is applied to such grain boundaries, it is estimated that a strain field is generated at and near the grain boundaries. It is estimated that this strain field becomes even larger when the SF value of the grain boundary shape is small, and has the effect of narrowing the magnetic domain width. As a result, it is thought that this contributes to improving the eddy current loss and, in turn, improving the total iron loss.

Next, a method for manufacturing a unidirectional electrical steel sheet with low iron loss according to the present invention will be described.

The first condition is the composition of the hot-rolled sheet material6.
Si: 2.5-4.5%, Sn: 0.04-0.
4%, C: 0.02-010%, acid soluble A/-: 0
．． 015-0.040%, N: 0.0040-0.
0100%, Mn: 0.030-0.250%, S:
0.015-0.040% is an essential condition, and 0.04%
% or less Se, 0.4T or less Sb+ Cu+As+B
t must be included as necessary.

Next, we will discuss the reasons for limiting these components. Regarding O8i, it is concentrated in the surface film during final annealing, so it is reduced by 0.15 to 0.25 in the product steel than in the hot rolled sheet. The reason for limiting the amount of Si in the product steel was explained earlier, and depending on the range, Si in the hot rolled sheet is 2.5 to 4.
．． 51 restriction ranges are required. Regarding C, a sufficient amount is required to cause γ transformation depending on St.
In addition, in order to be able to decarburize to 0.0015% or less in the final product steel, the content in the hot rolled sheet must be 0.1'0% or less, and in the end it was limited to 0.02 to 0.10%. .

Regarding Sn, as mentioned in the product requirements, 0.0
If it is less than 4%, the SF value will increase, and if it is more than 0.4, the forsterite coating will deteriorate and it will be difficult to secure the coating tension, so it is limited to 0.04 to 0.4%.

Regarding acid-soluble At and N, acid-soluble At is Q, (11
If the amount of N is less than 0.0040%, a predetermined amount of effective AtN inhibitor cannot be secured; conversely, if the amount of acid-soluble At is more than 0.040%, 1. Also, N is 0.
If the amount of 0100%
Concerningly, N is 0.0040 to 0.0040. (Limited to 11El 0%.

Similarly, regarding Mn and S, if Mn is less than 0.030 and S is less than 0.015, it will not be possible to secure a predetermined amount of effective MnS inhibitor; conversely, if Mn is less than 0.15
0, there is a lot of Si, and if it exceeds 875KO,040%, the solutionization will be insufficient, so it is not preferable, so Mn is 0.030 to 0.150% and S is 0.0'15 to 0.0.
It was limited to 11qb.

Regarding the ingredients, in addition to 0.04% or less of So, which is conventionally known as an inhibitor constituent element, and SJ of 0.4% or less.
One or more types of Cu and Al1O are contained. This is because if these upper limits are included in this layer, secondary recrystallization will be inhibited.

The hot rolled sheet having the above components is subjected to annealing and cold rolling as necessary. If the product board thickness is very thin, such as 0.20sn or less, heat-sensing treatment is performed before the final cold rolling, hot-rolled board annealing as necessary, and cold rolling at least once with intermediate annealing in between. You may do so.

The second condition concerns heat treatment conditions before final cold rolling.

As heat treatment before the final cold rolling,
Hold at ℃ for 10-600 seconds or 1050-1200℃
After holding for 100 seconds or less at 800-1000℃ for 30-30 seconds
It is necessary to hold for 500 seconds and then cool at 100° C.t for 5-50 seconds. This step controls the precipitation and dispersion of inhibitors such as AtN and MnS, and has a great influence on the aspect of secondary recrystallization during final annealing. Therefore, the shape of the grain boundary of the secondary recrystallized grains of the product steel sheet should be set to 1) <0.
This is extremely important in order to reach 60. 900-120
In the case of heating to 0°C for 10 to 600 seconds, if the temperature is lower than 900°C or shorter than 10 seconds, the initial precipitation of inhibitors such as AtN and MnS is insufficient, and if the heating is heated to higher than 1200°C or for more than 600 seconds, the inhibitors will precipitate. is undesirable because it becomes excessive and uneven. Generally, when the Si content is more than 3.2%, heat treatment is carried out by holding at 1050-1200°C for 100 seconds or less and then holding at 800-100°C for 30-500 seconds. These temperatures and times are necessary to appropriately precipitate and disperse the composite inhibitor in high-St steel. Such post-annealing cooling rate is also important for stabilizing secondary recrystallization and obtaining good iron loss. When cooled to 100°C for 50 seconds or more, the inhibitor precipitates excessively during that time, resulting in smooth grain boundaries in the product steel plate, and it is difficult to obtain a product with an SF of less than 0.00, as described above. It does not become a product with iron loss.

Cooling to 100° C. in less than 5 seconds is not favorable for the growth of secondary recrystallized grains.

The third condition relates to the final cold rolling and its interpass heat treatment. In the final cold rolling process, the steel plate is rolled to a thickness of 0.15 to 0.23 + nm at a rolling reduction of 81 to 93 inches, and the steel plate is rolled at least twice between passes during the cold rolling process.
It must be heated for at least 30 seconds in a temperature range of 0°C.

It is difficult to reduce the 17 of the product steel sheet to 0.60 or less unless the conditions of this inter-pass heat treatment are carefully considered. In addition, when the rolling reduction rate is 81 inches or less, B, o≧1.90T is not profitable, 93
% or more, secondary recrystallization becomes unstable.

The cold-rolled steel sheet thus obtained is decarburized and annealed by a known method, and an annealing separator containing MgO as a main component is applied to the surface. Then, final annealing is performed in a mixed gas of N2 and N2. At this time, when the thickness of the steel plate becomes as thin as 0.15 to 0.23 m, the atmospheric gas during final annealing has an even greater effect on the magnetic properties of the product. If N2 is higher than 50, the inhibitor AtN suppresses primary recrystallization too much and SF
It is difficult to obtain a product with less than 0.60 p. Therefore, it is necessary to create an atmosphere with N2 of 50 or more and remaining N2. The forsterite-coated product thus obtained is subjected to tension coating by a known method, if necessary.

Note that the hot rolled sheet is obtained by hot rolling a steel sheet obtained by a known technique such as a steel manufacturing method, a continuous casting method, or an ingot blooming method.

(Example) Examples of the present invention will be described below.

Si: 2.5-4.3% C: 0.04-0.09%,
Acid-soluble AL: Q, Q2Q~0.032%, N:
0.0050-0.0100%, Mn: 0.05
0-0.150%, S: 0.014-0.035%
, Cu: 0.08-0.15%, Sn: 0.0
A hot rolled sheet of 2.3111iI containing 5-0.20% was obtained. Then, as hot-rolled plate annealing, it was held at 1150℃ for 30 seconds, then held at 900℃ for 1 minute, and then heated to 100℃ for 20 to 3 seconds.
Two levels of water cooling at 0 seconds and air cooling at 60 to 70 seconds were performed, and then cold rolling was performed at two levels of 0.21 van and 0.18 wn. Cold rolling was carried out in 57 passes, and the steel plate was heated by placing it in a constant temperature bath K at 250°C for 20 minutes three times between passes.
Two levels were set for those without interpass heat treatment. After that, after decarburizing annealing and applying a baking separation agent by a known method, N
21 (1) Final annealing was performed in the atmosphere before secondary recrystallization in two cases: H290% and N280% N20%, and then tension coating was applied using the method proposed in Japanese Patent Publication No. 53-28375. Then, the magnetism of the obtained steel sheet was measured, and the steel sheet tension originating from the surface coating was measured.After that, the steel sheet coating was removed using hydrofluoric acid and nitric acid, and an image analysis machine was used to remove the steel sheet coating. F below the crystal grains of the steel plate, and also St in the steel.

The amounts of Sn, C, N, and S were analyzed. Representative examples of those results are shown in Table 1. Looking at this table, sample numbers 10, 11, and 1.2, whose cooling levels do not fall within the scope of the present invention, all have a value of 0.60 or more, and low iron loss is not obtained. In addition, for sample numbers 2 and 6 whose interpass heat treatment conditions are outside the scope of the present invention, the SF is large and the SF is 0.90 w/17 at W1715°.
It has not reached the following.

Regarding sample number 4, which is outside the scope of the present invention in terms of the atmosphere during final annealing, "〒 is not ensured. Also, residual C (N,
Regarding sample number 7゜9 in which S etc. are outside the scope of the present invention, "1"
etc. are secured, but iron loss is poor. In contrast, sample numbers 1, 3, 5, and 8 according to the present invention all achieved "1715 o' 0.90 W 7 kg.

(Effects of the Invention) As described above, the conventional achieved iron loss value level W17150≧1. OW/, compared to 9.
It is clear that unidirectional electrical steel sheets, which have a 10% low iron loss value, can always save several percent or more of power when incorporated into a transformer, and the effect is enormous. According to the present invention, it is not necessary to particularly significantly reduce the crystal grain size, and as can be seen from the examples, it is easy to obtain a high magnetic flux density. Even better iron loss values can be achieved.

[Brief explanation of drawings]

Figure 1 is B. Plate thickness and W1715 with parameters
Figure 2 is a diagram showing the relationship between rolling direction tension and Wl 7150 with SF as a parameter. 1st Gekihana 22 Tension in the direction of the sword c% - Procedural amendment (spontaneous) November 27, 1980 Manabu Shiga, Commissioner of the Patent Office 1, Indication of the case 1982 Patent Application No. 167266 2, Invention Name: Unidirectional electrical steel sheet with low iron loss and its manufacturing method 3, relationship with 41 amendments Patent applicant: New 1, 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665) Honsei Steel Co., Ltd. Co., Ltd. Representative Comments Takeshi 1) Toyota 4 Agent Address: 2-4-1-6 Marunouchi, Chiyoda-ku, Tokyo 100, Japan. Contents (1) Amend the claims in a separate document. (2) Specification page 4 line 15 “(Special Publication No. 5L-12451)
J is corrected to "(Japanese Patent Publication No. 51-12451)". (3) Same page 6 line 14 [100A/mJerlo00A/
Correct to mJ. (4) Change the two lines from the bottom of page 8, “Magnetic properties that cause distortion” to “
Strain and correct for magnetic properties. (5) On page 9, line 9, “Second condition steel plate” is changed to “Second condition:
Correct to “steel plate”. (6) “Third condition” on page 9, line 10, “Third condition:”
Correct to. (7) Correct the bottom line ro, 88J on page 9 to rO, 91J. (8) 3 lines from the bottom of page 11 [~0.250%J is “~0
Correct to "J50%". (9) On the bottom line of page 11, change “as necessary” to “Type 1 or 2.”
Corrected to ``more than species''. (6) Page 14, line 15 and page 15, line 8, “I don’t like it.”
are corrected to "unfavorable." α, page 15, line 12, “at least” is corrected to “at least”. (b) Correct the phrase ``unless the condition is met'' in negative lines 14-15 of the same 15 to ``unless the condition is met''. (2) Correct "10% t's" to "10% or more" in lines 3 and 4 on page 20. (Claim 1, 1c St in steel: 2.3 to 4.3%, Sn:
Contains 0.04 to 0.4% and 0.0% of C as an impurity.
0015% or less, N. A polycrystalline steel plate in which S is controlled to 40.0010% or less, and the remainder is substantially Fe, and the steel plate thickness is 0.1%.
5 to 0.23 m, B10 ≧ 1.90 T, the rust must be 0.2 to 1.0 kg, a tension of /- exists, and the grain boundary shape of each crystal grain of the steel sheet. When defining the formula % formula % as an index representing the characteristics, the average value SF as a copper plate of each SF value is 5
F(0,60 w1v7sa<
0.90 W/kg iron loss o low fx E 4 oriented N East steel plate. 2.3i: 2.5-4.5%, C: 0.02-0
．． 10%, 3n: 0.04-0.4%, acid-soluble At as inhibitor composition: 0.015-0.015%.
0.040%, N:), 0040-0.0100%, M
n: 0.030-0.150%, s2), 015~
0.040% e is an essential component, and 0.04% or less of Se, 0.4% or less of Sb, Cu, AII
, After the hot-rolled sheet containing one or more types of Bi etc. has been annealed and cold-rolled as necessary, it is subjected to heat treatment in a temperature range of 900-1200°C for 10 to 1200°C as a heat treatment before the final cold rolling.
Hold for 600 seconds or hold for 100 seconds or less in a temperature range of 1050-1200°C, then hold for 30-500 seconds in a temperature range of 800-1000°C, then 5-5 to 1001:
In the final cold rolling process, the steel plate is rolled at a cold rolling reduction rate of 81 to 93%, and the steel plate is rolled at least twice between the rolling passes in a temperature range of 150 to 300°C for 30 seconds. By heating the lit end plate thickness 0.15~
0.23 mist cold-rolled steel sheet, then decarburized and annealed, and the surface is coated with an annealing separator mainly composed of MgO,
After winding into a coil, at least before secondary recrystallization occurs, final annealing is performed in an atmosphere containing 50% or more hydrogen and residual nitrogen, and after excess MgO is washed with water, a tension coating is applied. ';0,90W/
kl? A method for manufacturing unidirectional Usui electrical steel sheets with low iron loss.

Claims (1)

[Claims] 1. Sj: 2.3 to 4.3%, Sn: 0.0 in steel
Contains 4 to 0.4% and 0.0015 C as an impurity
% or less, N and S are each controlled to 0.0O10% or less,
The remainder is substantially (polycrystalline steel plate made of CFe, the steel plate thickness is 0.15 to 0.23 mm, B1o''2
1.90T, 0.2~1.0 kl on the steel plate
? When defining the formula as an index expressing the existence of tension of / + 2 and the characteristics of the grain boundary shape regarding each grain of the steel sheet, the average value of each SF value for the steel sheet ``The bottom is ``
lower (W, 715o characterized by being 0, fi O
Unidirectional electrical steel sheet with low core loss of ≦0.90 W/-. 2, Si: 2.5-4.5, COO102-0.10
ql) Contains Sn: 0804-0.4%, acid-soluble At as inhibitor constituent element: 0.015-0
040 section, N: 0.0040-0.0100%, Mn:
0.030-0.150%, S: 0.015-0.
040 is an essential component, and other Se of 0.04 or less
, 0.4% or less of Sb+Cu+As, Bl, etc., after annealing and cold rolling as necessary, a hot rolled sheet containing 0.4% or less of Sb+Cu+As, Bl, etc. Hold in the temperature range of 1200°C for 10 to 600 seconds or hold in the temperature range of 1050 to 1200°C for 100 seconds or less, then hold in the temperature range of 800 to 1000°C for 30 to 5 seconds.
After being held for 00 seconds, it is cooled to 100°C in 5 to 50 seconds, and in the subsequent final cold rolling process, the cold rolling reduction rate is 81 to 93%.
The steel plate is rolled at least twice between the rolling passes.
A cold-rolled steel plate with a final thickness of 0.15 to 0.23 mm is obtained by heating at a temperature range of 150 to 300 degrees Celsius for 30 seconds or more, and then decarburized and annealed to coat the surface with MgO as the main component. After applying an annealing separator and winding it into a coil, finish annealing is performed in an atmosphere containing at least 50% hydrogen and residual monoxide before secondary recrystallization occurs, and excess MgO is washed with water. W1 characterized by applying a tension coating
A method for producing a unidirectional electrical steel sheet with low core loss of 715o≦0 and 90 W/kll.