JPH06248348A - Method for heat-treating high silicon steel sheet in magnetic field - Google Patents

Abstract

PURPOSE:To produce a high silicon steel sheet high in magnetic permeability and low in iron loss by heat treatment in a magnetic field. CONSTITUTION:As for a silicon steel sheet having a compsn. contg. 4 to 10wt.% Si or 4 to 10wt.% Si+Al and, in which preferably, the content of C, Mn, P, S, N, O or the like is regulated to prescribed one and having <=0.5mm sheet thickness and 20mum to 2.0mm average crystal grain size, the impression of a magnetic field of 1.6 to 640A/m effective magnetic field is started in the temp. range of 350 to <650 deg.C, and successively, cooling is executed to <=300 deg.C in the same magnetic field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field heat treatment method for high silicon steel sheets used as iron core materials for motors and transformers, and is intended to produce high silicon steel sheets having high magnetic permeability and low iron loss. is there.

[0002]

2. Description of the Related Art Silicon is usually added to magnetic steel sheets that are widely used as iron core materials for motors and transformers. The reason why silicon is added in this way is that the addition of silicon improves electrical resistance, decreases magnetic anisotropy, is inexpensive as an additional element, and forms a stable phase metallurgically. Is mentioned. Conventionally, silicon has been added to steel plates up to the limit of about 3.5 wt% that allows cold rolling,
It has been rolled to a plate thickness of about 0.5 to 0.1 mm and used as an iron core material. On the other hand, recently, various methods for producing a high-silicon steel sheet having improved magnetic properties by adding more silicon have been proposed, including a melt quenching method (see, for example, Japanese Examined Patent Publication No. 60-3).
2705), a warm rolling method (for example, Japanese Patent Publication No. 3-808).
46), a siliconizing method (for example, Japanese Patent Publication No. 2-60041)
Etc. are established as industrial technology.

By the way, the effect of cooling a high silicon steel sheet containing Si in an amount of 3 wt% or more in a magnetic field has been well known, and the following concrete proposals have been made.
Goertz casts an iron alloy containing Si in an amount of 3 to 11 wt% into a ring shape and conducts it in a magnetic field of 10 Oe (800 A / m).
It is said that the magnetic permeability can be improved by cooling from 00 ° C [J. Appl. Phys., 22, (7), 964, (195
1)]. In Japanese Patent Application Laid-Open No. 57-79120, a super-quenched ribbon is heat treated at high temperature to produce {100} <0kl> or {10}.
0} <001> is developed and heat treatment is performed in a magnetic field in a specific temperature range to reduce the cooling rate during annealing in a magnetic field to 500 ° C.
It proposes a method capable of improving the soft magnetic characteristics in the longitudinal direction even if the speed is increased to more than 1 minute.

In JP-A-62-56527, 100-
It has been proposed to apply a magnetic field of 200 Oe after punching a steel sheet and control the state of precipitates in the steel sheet to improve the magnetic properties. Japanese Patent Laid-Open No. 62-2270
No. 79 and Japanese Patent Laid-Open No. 63-26326 propose a cooling method in a magnetic field in a siliconizing method. These disclose a method of applying a magnetic field in a continuous line and a method of applying a magnetic field multiple times, and it is stated that a soft magnetic material can be economically obtained. Japanese Patent Laid-Open No. 1-3099
No. 22 proposes a method of applying a coating containing metal powder to a grain-oriented silicon steel sheet and then cooling it in a magnetic field to deposit precipitates of the metal powder and improve the magnetic properties.

[0005]

However, each of these proposals has the following problems. First, Goer
Since the classical method by tz is to cool from 700 ° C. in a magnetic field, it is necessary to heat and hold the steel strip in a high temperature state, and the applied magnetic field is also 10 Oe (800 A / 800 A /
m), and in order to apply this magnetic field to the high silicon steel strip, it is necessary to install a long magnetic field applying coil or take a large applied current value, which is a problem in terms of economy. Japanese Patent Application Laid-Open No. 57-79120 discloses a magnetic field cooling method for a ribbon manufactured by the ultra-quenching method. The ribbon manufactured by the ultra-quenching method has a special texture as described above. In addition, it is difficult to obtain a thin strip with a wide sheet width by the ultra-quenching method, and there are problems in terms of sheet thickness accuracy and surface roughness. There are drawbacks that cannot be obtained.

The method of Japanese Patent Laid-Open No. 62-56527 has a drawback that it cannot be applied to high-grade electrical steel sheets containing no precipitate because it controls the precipitation state of the precipitate. In addition, the applied magnetic field is large, and since the magnetic field is applied after punching, it is not economical. Also, JP-A-62-1270
The method of No. 79 and the like has a problem in that the applied magnetic field is large and the economy is poor in terms of equipment. Japanese Patent Laid-Open No. 1-3099
No. 22 controls the precipitation state of precipitates, which also has a problem that it cannot be applied to a steel sheet containing no precipitates, and the applied magnetic field has a large defect of 10 Oe or more. The present invention has been made in view of the problems of the prior art as described above, and is premised on a high silicon steel sheet manufactured by a warm rolling method or a Si infiltration treatment method (siliconizing method) that is inexpensive and has stable magnetic properties. An object of the present invention is to provide a magnetic field heat treatment method capable of economically improving the magnetic properties of a high-silicon steel sheet without a large facility burden.

[0007]

Various methods have been proposed for the heat treatment of a high silicon steel sheet in a magnetic field, as described above. However, regarding the strength of the magnetic field, which is an important requirement for efficiently obtaining the effect of the heat treatment in the magnetic field, JP-A-62-56527 and JP-A-62-1270.
79 and Japanese Patent Laid-Open No. 63-26326, 10O
Only the method of applying a magnetic field of e (800 A / m) or more is disclosed.

The inventors of the present invention conducted a test study on a high silicon steel sheet produced by a warm rolling method or a Si infiltration treatment method in order to find out the optimum heat treatment conditions in a magnetic field, particularly an appropriate applied magnetic field strength. As a result, the magnetic properties of the high silicon steel sheet have an extremely strong applied magnetic field dependency in a region where the applied magnetic field is weaker than conventionally thought, and moreover, in the region where the applied magnetic field is weaker than the effect obtained conventionally. It has been found that remarkably excellent magnetic properties can be obtained. It was also confirmed that this effect is a general phenomenon that can be obtained regardless of the method of manufacturing a high silicon steel sheet, such as the warm rolling method and the Si infiltration treatment method.

The fact that the above-mentioned effects are obtained in a region where the applied magnetic field is weak means not only that a high silicon steel sheet having excellent magnetic characteristics can be manufactured, but also that the magnetizing coil for applying a magnetic field can be simplified. This means that it is extremely advantageous in terms of manufacturing cost. As described above, the inventors of the present invention have an extremely strong influence on the magnetic characteristics depending on the strength of the applied magnetic field under the conditions of the heat treatment in the magnetic field, and have the magnetic characteristics superior to the conventional one in the weaker applied magnetic field than conventionally considered. The inventors have found that it becomes possible to manufacture high silicon steel sheets.
The present invention has been made on the basis of such findings and has the following configurations.

(1) A high silicon steel sheet containing Si: 4 to 10 wt% is applied with an effective magnetic field of 1.6 to 640 A / m in a temperature range of 350 ° C. or higher and lower than 650 ° C. A method of heat treating a high silicon steel sheet in a magnetic field, characterized by cooling to 300 ° C. or less at room temperature. (2) Si: 4 to 10 wt%, C: 0.01 wt% or less, Mn: 0.5 wt% or less, P: 0.01 wt% or less, S: 0.01 wt% or less, Sol. Al: 0.20
wt% or less, N: 0.01 wt% or less, O: 0.02w
t% or less, the balance Fe and unavoidable impurities, and a high silicon steel plate having a plate thickness of 0.5 mm or less and an average crystal grain size of 20 μm to 2.0 mm in an effective magnetic field of 1.6 to A method for heat treating a high silicon steel sheet in a magnetic field, which comprises starting to apply a magnetic field of 640 A / m and subsequently cooling to 300 ° C. or less in the magnetic field. (3) A high silicon steel sheet containing Si + Al: 4 to 10 wt% is applied with a magnetic field of an effective magnetic field of 1.6 to 640 A / m in a temperature range of 350 ° C. or higher and lower than 650 ° C., and subsequently 300 ° C. in the magnetic field. A method for heat treating a high silicon steel sheet in a magnetic field, characterized by cooling to the following. (4) Si + Al: 4-10 wt%, C: 0.01w
t% or less, Mn: 0.5 wt% or less, P: 0.01 wt
% Or less, S: 0.01 wt% or less, Sol. Al: 0.
20 wt% or less, N: 0.01 wt% or less, O: 0.0
2 wt% or less, consisting of balance Fe and unavoidable impurities,
Plate thickness 0.5 mm or less, average crystal grain size 20 μm to 2.0 m
A high silicon steel sheet of m having a high temperature characterized by starting to apply a magnetic field of an effective magnetic field of 1.6 to 640 A / m in a temperature range of 350 ° C. or higher and lower than 650 ° C. and subsequently cooling it to 300 ° C. or lower in the magnetic field. Method for heat treatment of silicon steel sheet in magnetic field.

[0011]

The details of the present invention will be described below together with the reasons for limitation. First, the component composition and the like of the high silicon steel sheet subjected to the heat treatment in the magnetic field will be described. This high silicon steel sheet contains 4 to 10 wt% of Si or 4 to 10 wt% of Si + Al. When Si is added in an amount of about 6.5 wt%, the magnetostriction is zero and Si exhibits the best soft magnetism. Si is 4 wt%
If it is less than the above, the desired magnetic properties as a high silicon steel sheet cannot be obtained. On the other hand, when Si exceeds 10 wt%, the saturation magnetic flux density is remarkably reduced. Therefore, Si is 4 to 10 wt%.

Further, it is possible to replace a part of Si with Al, and in this case, it is necessary to regulate the amount of Si + Al. If Si + Al is less than 4 wt%, the magnetic characteristics aimed at by the present invention cannot be obtained. On the other hand, Si + Al is 1
When it exceeds 0 wt%, the saturation magnetic flux density is significantly reduced. Therefore, when a part of Si is replaced with Al, Si +
Al: 4-10 wt%.

Next, the preferable contents of other elements will be described. C is an element harmful to soft magnetism, and its content is preferably as low as possible. Also, C is 0.01
When the content exceeds wt%, a so-called aging deterioration phenomenon occurs in which soft magnetism deteriorates with time. Therefore, C is preferably 0.01 wt% or less. Mn combines with S to become MnS, which has the effect of improving hot workability in the slab stage. However, when Mn exceeds 0.5 wt%, the saturation magnetic flux density is greatly reduced, which is not suitable. Therefore, Mn is 0.5w
It is preferably t% or less. P is an element that deteriorates soft magnetic properties, and its content is preferably as low as possible. The economic efficiency and the adverse effect can be practically neglected if P is 0.01 wt% or less, so P is 0.
It is preferable to set it to 01 wt% or less.

Since S is an element that increases brittleness during hot rolling and also deteriorates soft magnetic characteristics, its content is preferably as low as possible. It is preferable that the sulfur content be 0.01 wt% or less because the sulfur content is economical and the adverse effect can be substantially ignored if the S content is 0.01 wt% or less. Al has a function of cleaning steel by deoxidation, and also has a function of increasing electric resistance in terms of magnetic characteristics. In steel containing 4 to 10 wt% of Si, Si improves the magnetic properties, and Al only has to perform the deoxidizing action of steel. Al is 0.
It is preferably 20 wt% or less. On the other hand, when replacing a part of Si with Al, as described above, Si + A
1 is 4 to 10 wt%.

N is an element that deteriorates the soft magnetic characteristics,
The content thereof is preferably as low as possible because it also causes a change in the magnetic properties over time due to aging. It is preferable to set N to 0.01 wt% or less because the economical efficiency and the adverse effect thereof can be substantially ignored if N is 0.01 wt% or less. O is an element that deteriorates soft magnetic properties, and the content thereof is preferably as low as possible. If 0.02 wt% or less of O is economical and the adverse effect is practically negligible, O is 0.02%.
It is preferable to set it to wt% or less. In addition to the above ingredients,
Cr, Ni, Cu, Sn, M as unavoidable impurities in steel
o may be included, each of which is 0.05
The effect of the present invention is not impaired even if it is contained within the limit of about wt%.

The high silicon steel sheet having these components may be manufactured by any method such as a warm rolling method and a Si infiltration treatment method. Further, these steel plates preferably have a plate thickness of 0.5 mm or less and an average crystal grain size of 20 μm or more and 2.0 mm or less. If the plate thickness exceeds 0.5 mm, the eddy current loss of the steel plate becomes extremely large. If the average crystal grain size of the average crystal grain size is less than 20 μm, the hysteresis loss increases, so that the iron loss becomes large and it becomes unsuitable for practical use. On the other hand, if the average crystal grain size exceeds 2.0 mm, the workability of the steel sheet such as punchability and bendability deteriorates.

The heat treatment in the magnetic field of the present invention may be carried out during recrystallization annealing of the above-mentioned high silicon steel sheet or during Si permeation diffusion treatment, or during heating / cooling of the steel sheet when coating or slitting the steel sheet. Alternatively, it may be carried out as an independent process. Here, the temperature at which a predetermined magnetic field is started to be applied to the steel sheet, that is, the heat treatment start temperature in the magnetic field is 350 ° C. or higher and lower than 650 ° C. When the heat treatment start temperature in the magnetic field is lower than 350 ° C, the effect of applying the magnetic field cannot be obtained. On the other hand, when the heat treatment temperature is 650 ° C or higher, the magnetic properties are improved by the magnetic field application, but compared with the case where the heat treatment in the magnetic field is started from lower than 650 ° C. And its effect is inferior. Therefore, the heat treatment start temperature in the magnetic field is set to 350 ° C or higher and lower than 650 ° C.
However, the effect is more remarkable when the heat treatment in the magnetic field is started preferably in the temperature range of 400 to 550 ° C.

The magnitude of the applied magnetic field must be 1.6 A / m or more and 640 A / m or less as an effective magnetic field in which the diamagnetic field is corrected. The earth's magnetic field is normally 40A in the north-south direction.
However, the effect of the earth's magnetic field depends on the shape and orientation of the sample. If the magnitude of the magnetic field is less than 1.6 A / m, the effect of applying the magnetic field cannot be obtained as an effective magnetic field in consideration of the earth's magnetic field. On the other hand, if it exceeds 640 A / m, the magnetic characteristics are improved as compared with the case where no magnetic field is applied at all, but the magnetic characteristics are inferior to the case where it is 640 A / m or less.
This is not preferable because it causes the magnetizing coil to become longer and the applied current to increase. Therefore, the magnitude of the applied magnetic field is 1.6 A / m or more and 640 A / m or less. However, if the applied magnetic field is preferably 40 A / m or more and 320 A / m or less, the effect becomes more remarkable.

The steel sheet to which the magnetic field is applied as described above is cooled to 300 ° C. or less in the magnetic field.
If the magnetic field application is terminated in the temperature range exceeding 300 ° C., the effect of improving the magnetic characteristics by the heat treatment in the magnetic field cannot be fully obtained. If the end temperature of the magnetic field application is 300 ° C. or lower, desired magnetic characteristics can be obtained. The atmosphere of the heat treatment in the magnetic field described above is not particularly limited as long as it is a non-oxidizing atmosphere, but the steel sheet has already been coated,
When the method of the present invention is carried out in the heat treatment that also serves as the baking, it is not necessary to be strictly non-oxidizing, and an atmosphere having a slightly high oxygen concentration may be used.

[0020]

【Example】

[Example 1] Plate thickness 0.35 having the chemical composition shown in Table 1
After manufacturing a high-mm steel plate of mm by a rolling method, punching it into a ring shape, forming a coil for applying a magnetic field on the ring, and then annealing it at 1200 ° C. for 1 hour in an N ₂ atmosphere,
A DC magnetic field was applied during the cooling. The cooling rate in the temperature range where the magnetic field was applied was about 100 ° C./min, and the cooling was performed up to 200 ° C. in the magnetic field. Then, the coil was removed and the DC BH loop was measured to determine the maximum magnetic permeability. FIG. 1 shows the case where the applied magnetic field during the heat treatment in the magnetic field was 80 A / m (1 Oe) and 800 A / m (10 Oe), the magnetic field application start temperature was from 900 ° C. to 20 ° C.
The change of the maximum magnetic permeability when changing to 0 degreeC is shown. According to this, when the applied magnetic field is 800 A / m, 400
In the range of ℃ to 900 ℃, the influence of the magnetic field application start temperature on the maximum permeability is small, but the applied magnetic field is 80 A / m
When the value is small, the effect of the magnetic field application start temperature appears strongly,
It is understood that the maximum magnetic permeability can be improved by starting the magnetic field application in the region of 350 ° C. or higher and lower than 650 ° C. In addition, especially the magnetic field application start temperature is 400 to 550 ° C.
It can be seen that a more remarkable improvement effect can be obtained by setting the temperature range to.

Example 2 Using a sample similar to that used in Example 1, magnetic field application was started at 500 ° C. when cooling from 1200 ° C., and the magnitude of the applied magnetic field was 0-80.
It was changed in the range of 0 A / m. In the example of applying a magnetic field,
It cooled to 200 degreeC in the magnetic field. The maximum magnetic permeability of these samples was measured by the same method as in Example 1.
The result is shown in FIG. According to this, the smaller the applied magnetic field is, the higher the maximum magnetic permeability is, and the maximum is around 100 A / m. According to the figure, the applied magnetic field is 1.6 A / m to 64
The maximum magnetic permeability is effectively improved in the range of 0 A / m, and the improving effect is particularly remarkable in the range of 40 A / m to 320 A / m.

Example 3 Using a sample similar to that used in Example 1, application of a magnetic field (applied magnetic field: 80 A / m) was started at 500 ° C. when cooling from 1200 ° C. Was varied in the range of 2000 ° C./min to 20 ° C./min, and cooling was performed to 200 ° C. in a magnetic field. The maximum magnetic permeability of these samples was measured by the same method as in Example 1. The result is shown in FIG. This shows that the cooling rate does not affect the effect of the present invention.

Example 4 Using a sample similar to that used in Example 1, magnetic field application (applied magnetic field: 80 A / m) was started at 500 ° C. when cooling from 1200 ° C., and after holding for 1 minute. Then, it was cooled to 300 ° C. in a magnetic field, and then cooled to 300 ° C. or less in a non-magnetic field. As a result of measuring the maximum magnetic permeability of this sample in the same manner as in Example 1, the same value as the maximum magnetic permeability value obtained in Example 2 was obtained.
From this, it can be seen that even if the temperature is maintained for a certain period of time in the applied magnetic field, the characteristics obtained do not change,
In the following, it was confirmed that it was not necessary to apply a magnetic field.

[Example 5] A high silicon steel strip having a plate thickness of 0.1 mm and manufactured by the Si infiltration treatment method having the composition shown in Table 2 was charged into a continuous line equipped with a magnetizing coil shown in Fig. 4. After applying the insulating film with a coater, baking treatment was performed in the heat cycle shown in FIG. Then, in the cooling process during the baking treatment, an external magnetic field of 160 A / m (2 Oe) and 1600 A / m (20 Oe) was started to be applied from 550 ° C. and cooled to 300 ° C. in the magnetic field. Epstein test pieces were sampled in the magnetic field application direction from the high silicon steel plate coil thus obtained and the high silicon steel plate coil to which the magnetic field was not applied, and the iron loss was measured by an AC magnetization test. The result is shown in FIG. According to this, not only is the iron loss value reduced by heat treatment in a magnetic field, but the effect of the magnetic field strength is clearly shown. From the results of this example, the effect of the present invention could be confirmed even in an actual continuous line.

Example 6 A silicon steel sheet having a composition shown in Table 3 and a thickness of 0.50 mm was prepared by a rolling method.
The average crystal grain size of each of these steel sheets was about 0.7 mm. A ring having an inner diameter of 19 mm and an outer diameter of 41 mm was cut out from these steel plates by electric discharge machining, and the maximum magnetic permeability of DC and the saturation magnetic flux density were measured as magnetic field characteristics. Then
After the heat resistant coil was wound around each of the above rings, it was heated to 500 ° C. and cooled between 500 ° C. and 300 ° C. while applying a magnetic field of 80 A / m. Then, the maximum magnetic permeability of DC and the saturation magnetic flux density were measured as the magnetic characteristics of these samples. The results are shown in Table 4. According to this, in the case of adding Si alone and the case of adding Si + Al composite,
Alternatively, if Si + Al is less than 4%, the effect of cooling in a magnetic field cannot be obtained. Further, even if Si or Si + Al exceeds 10%, there is no cooling effect in the magnetic field, and the saturation magnetic flux density is significantly reduced, which is not preferable.

Example 7 A high silicon steel sheet having the chemical composition shown in Table 5 was produced by a rolling method and adjusted to have the sheet thickness and average crystal grain size shown in Table 6. These steel plates were cooled from 450 ° C. in a magnetic field with an effective magnetic field of 50 A / m to obtain products. The magnetic characteristics of these products are 400Hz, 1T
The iron loss value was measured, and a three-point bending test was performed as a workability test. In this three-point bending test, the push-in distance at which cracking occurs when the punch is pushed at a speed of 2.0 mm / min is used as an index. The results are shown in Table 7. According to this, when the plate thickness exceeds 0.5 mm and the average crystal grain size is less than 20 μm, the iron loss value becomes extremely large, and when the average crystal grain size exceeds 2.0 mm, the workability is extremely deteriorated. I understand.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

[0032]

[Table 6]

[0033]

[Table 7]

[Brief description of drawings]

FIG. 1 is a graph showing the influence of the cooling start temperature in a magnetic field on the maximum magnetic permeability of a high silicon steel sheet when the applied magnetic field is 800 A / m and 80 A / m, respectively.

FIG. 2 is a graph showing the effect of the magnitude of the applied magnetic field on the maximum magnetic permeability of a high silicon steel sheet.

FIG. 3 is a graph showing the relationship between the cooling rate during cooling in a magnetic field and the maximum magnetic permeability of a high silicon steel sheet.

FIG. 4 is an explanatory view showing a continuous line used for carrying out Example 5.

FIG. 5 is a drawing showing a thermal cycle of baking treatment in Example 5;

FIG. 6 is a graph showing the iron loss value of each sample in Example 5.

Claims (4)

[Claims] 1. A high silicon steel sheet containing Si: 4 to 10 wt% is applied with a magnetic field of an effective magnetic field of 1.6 to 640 A / m in a temperature range of 350 ° C. or higher and lower than 650 ° C., and subsequently in the magnetic field. A method of heat treating a high silicon steel sheet in a magnetic field, characterized by cooling to 300 ° C or less. 2. Si: 4 to 10 wt%, C: 0.01 w
t% or less, Mn: 0.5 wt% or less, P: 0.01 wt
% Or less, S: 0.01 wt% or less, Sol. Al: 0.
20 wt% or less, N: 0.01 wt% or less, O: 0.0
2 wt% or less, consisting of balance Fe and unavoidable impurities,
Plate thickness 0.5 mm or less, average crystal grain size 20 μm to 2.0 m
A high silicon steel sheet of m having a high temperature characterized by starting to apply a magnetic field of an effective magnetic field of 1.6 to 640 A / m in a temperature range of 350 ° C. or higher and lower than 650 ° C. and subsequently cooling it to 300 ° C. or lower in the magnetic field. Method for heat treatment of silicon steel sheet in magnetic field. 3. A high silicon steel sheet containing Si + Al: 4 to 10 wt% is applied with a magnetic field of an effective magnetic field of 1.6 to 640 A / m in a temperature range of 350 ° C. or higher and lower than 650 ° C., and subsequently in the magnetic field. A method of heat treating a high silicon steel sheet in a magnetic field, characterized by cooling to 300 ° C or less. 4. Si + Al: 4-10 wt%, C: 0.
01 wt% or less, Mn: 0.5 wt% or less, P: 0.0
1 wt% or less, S: 0.01 wt% or less, Sol. A
l: 0.20 wt% or less, N: 0.01 wt% or less,
O: 0.02 wt% or less, balance Fe and unavoidable impurities, plate thickness 0.5 mm or less, average crystal grain size 20 μm
A high silicon steel sheet having a thickness of up to 2.0 mm is applied with a magnetic field having an effective magnetic field of 1.6 to 640 A / m in a temperature range of 350 ° C. or higher and lower than 650 ° C., and subsequently cooled to 300 ° C. or lower in the magnetic field. And a method of heat treating a high silicon steel sheet in a magnetic field.