JP2000096196A - Nonoriented silicon steel sheet with low iron loss, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented silicon steel sheet having high magnetic flux density and low iron loss. SOLUTION: The steel sheet has a composition which consists of, by weight, 0.1-3.5% Si, 0.1-1.5% Mn, 0.0010-0.0025% C, <=0.002% N, <=0.002% S, <=0.003%,Pi, <=0.003% Nb, <=0.005% V, <=0.003% Zr, <=0.003% Ca, <=0.003% As, <=0.05% Cr, <=0.01% Sn, <=0.05% Cu, <=0.02% O, and the balance Fe with inevitable impurities and in which the value of Q, determined by equation Q=log ([Ti%]+[Nb%]+[V%]+[Zr%]+[Ca%])×[C%]), is regulated to -4.70. In the equation, [Ti%], [Nb%], [V%], [Zr%], [Ca%], and [C%] represent respective weight concentrations of Ti, Nb, V, Zr, Ca, and C in a product, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-oriented electrical steel sheet having a low iron loss, which is used as an iron core material of electric equipment, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, in the field of electric machines, particularly rotating machines and medium- and small-sized transformers in which non-oriented electrical steel sheets are used as an iron core material thereof, global electric power and energy savings as well as chlorofluorocarbon gas regulations. Among the movements for global environmental conservation, such as the above, the movement for higher efficiency is rapidly spreading. For this reason, there is an increasing demand for non-oriented electrical steel sheets to improve their properties, that is, reduce iron loss.

[0003] On the other hand, in order to reduce iron loss, it is not merely necessary to increase the content of Si or Al.
No. 80169, Mn and S
A method is disclosed in which a precipitate is made harmless by making the steel highly pure by reducing the amount of the steel. However, when the contents of Mn and S are simultaneously reduced, the amount of the precipitates is reduced, but the size of the precipitates is reduced, and there is a problem that the expected iron loss reduction effect cannot be obtained.

Japanese Patent Application Laid-Open No. 6-248398 describes that S
In a high-grade non-oriented electrical steel sheet in which i: 1.5 to 4.0% and Al: 1.0 to 3.0%, S ≦ 0.0020
%, N ≦ 0.0030% and O ≦ 0.0030% to improve iron loss.

Japanese Unexamined Patent Publication (Kokai) No. 9-195011 discloses a non-oriented electrical steel sheet having a Si content of 1.0% or less.
A technology that satisfies log (V (%) · N (%)) ≦ −5.29 is disclosed.

[0006]

In order to respond to the recent demands for higher efficiency by customers, the present inventors have conducted intensive research and development, and have disclosed in Japanese Patent Application Laid-Open No. 5-140649 the use of non-oriented electrical steel sheets. A method has been provided for eliminating the adverse effects of the harmful element Ti on magnetic properties. That is, Si: 1.0 to 4.0%,
Al: 0.001 to 2.0%, N: ≦ 0.0020%,
S: ≦ 0.0020%, C: ≦ 0.0030%, Mn:
0.1-2.0%, Ti: 0.003-0.010%,
Zr: ≦ 0.0050%, Nb: ≦ 0.0050%,
A technique for improving magnetic properties using a slab consisting of V: ≤0.0050%, P: ≤0.2%, and the balance Fe and unavoidable impurities has been proposed.

However, in the purification of steel in these technologies, when steel sheets of non-oriented electrical steel sheets are continuously produced, variations are likely to occur for each charge, although the individual conditions are satisfied. From the viewpoint of stably obtaining a non-oriented electrical steel sheet having a low iron loss, some problems remain.

As a result of detailed analysis on this point, the present inventors have found that if the product of the total amount of harmful elements and carbon is equal to or less than a certain value, a non-oriented electrical steel sheet with low iron loss can be stably manufactured. We found a new finding that we could.

On the other hand, in the conventional invention relating to high-purity steel, it has been considered that the smaller the C content, the better from the viewpoint of magnetic aging. However, by applying advanced steelmaking technology, the C content becomes zero. When the content is less than 0.001%, the problem that the iron loss is improved in the high-purity steel, but the magnetic flux density is lowered is clarified.

[0010] As described above, a new finding that the C content in high-purity steel, which has not been regarded as a problem in the prior art, is controlled to a specific range, has not been omitted at all in the conventional invention relating to high-purity steel. As a result, it becomes possible to stably produce a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss, thereby completing the invention.

[0011]

The gist of the present invention is as follows. (1) By weight%, 0.1% ≦ Si ≦ 3.5%, 0.1% ≦ Mn ≦ 1.5%, C ≦ 0.004%, N ≦ 0.002%, S ≦ 0.002 %, Ti ≦ 0.003%, Nb ≦ 0.003%, V ≦ 0.005%, Zr ≦ 0.003%, Ca ≦ 0.003%, As ≦ 0.003% Cr ≦ 0.05%, It contains Sn ≦ 0.01%, Cu ≦ 0.05%, O ≦ 0.02%, and the Q value defined by the following formula satisfies −4.70 or less, with the balance being Fe and inevitable impurities. Non-oriented electrical steel sheet with low iron loss. Q = log
{([Ti%] + [Nb%] + [V%] + [Zr%] + [Ca%]) × [C%]}
... Equation (1) where [Ti%], [Nb%], [V%],
[Zr%], [Ca%] and [C%] are Ti, Nb,
Weight concentration of V, Zr, Ca, C in the product.

(2) By weight, as an alloy component,
The non-oriented electrical steel sheet with low iron loss according to the above (1), wherein 0.10% ≦ Al ≦ 2.00%.

(3) By weight%, 0.1% ≦ Si ≦ 3.5%, 0.1% ≦ Mn ≦ 1.5%, C ≦ 0.004%, N ≦ 0.002%, S ≦ 0.002%, Ti ≦ 0.003%, Nb ≦ 0.003%, V ≦ 0.005%, Zr ≦ 0.003%, Ca ≦ 0.003%, As ≦ 0.003% Cr ≦ 0. 0.05%, Sn ≦ 0.01%, Cu ≦ 0.05%, O ≦ 0.02%, and the Q value defined by the following formula satisfies -4.70 or less, with the balance being Fe and inevitable A slab made of impurities is hot-rolled into a hot-rolled sheet, then subjected to a single cold rolling, followed by finish annealing, and then further subjected to skin pass rolling or not to give a product. A method for manufacturing non-oriented electrical steel sheets with low iron loss. Q = log {([Ti%] + [Nb%] + [V%] + [Zr%] + [Ca%]) × [C%]} Formula (1) where [Ti%], [Nb%], [V%], [Zr%], [Ca
%] And [C%] are Ti, Nb, V, Zr, Ca,
Weight concentration of C in product.

(4) As an alloy component, further,
Wherein a slab containing 0.10% ≦ Al ≦ 2.00% is used.
A method for producing a non-oriented electrical steel sheet having a low iron loss as described above.

(5) 0.0010% ≦ C ≦ 0.002
(1), (2), or 5%.
(3) or (4) The manufacturing method of the non-oriented electrical steel sheet with low iron loss.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The present inventors have conducted intensive studies on the problems in the prior art in order to simultaneously achieve a low iron loss and a high magnetic flux density. As a result, in a non-oriented electrical steel sheet having a transformation, Si was reduced to 0.1%.
10 to 3.50%, 0.10 to 2.00% Al, Mn
In a steel containing 0.10 to 1.50%, the content of C, S and N is reduced, and Ti, V, Nb, Ca,
The Zr, As, Cr, Sn, Cu, and O contents are reduced after satisfying a specific relational expression, and a high purity steel is obtained. A method of manufacturing a grain-oriented electrical steel sheet, or a non-oriented electrical steel sheet manufacturing method to make the final thickness by cold rolling two or more times with intermediate annealing, hot-rolled sheet annealing or high-temperature finishing, and controlled hot rolling by high-temperature winding The present inventors have found that a non-oriented electrical steel sheet with low iron loss can be produced also in the above process, and have reached the present invention. Furthermore, it has been found that the magnetic flux density is increased by setting the C content in a specific range.

The magnetic properties of the non-oriented electrical steel sheet can be improved by enlarging the crystal structure before cold rolling.
For this reason, conventionally, in the finish hot rolling, the hot rolling end temperature is raised, or the hot rolled sheet is annealed, or the crystal structure before cold rolling is coarsened by high-temperature winding to increase the magnetic flux density of the product and reduce iron loss. Things have been done. Also, in order to maximize the effect of the above technology, inventions related to various high-purity steels have been made.

However, as the steelmaking technology of high-purity steel advances and the C content decreases, there is a problem that the high magnetic flux density that has been obtained by increasing the crystal grain size before cold rolling cannot be obtained. It was revealed. The present inventors have analyzed this point, and found that there is an optimal range for the C content, which was considered to be better as the content was smaller because the iron loss deteriorated due to magnetic aging in the prior art. Heading, the invention was completed.

First, the components will be described. Si is added to increase the specific resistance of the steel sheet, reduce the eddy current loss, and improve the iron loss value. If the Si content is less than 0.10%, sufficient resistivity cannot be obtained, so it is necessary to add 0.10% or more. On the other hand, the Si content is 3.50%
Exceeds 3.50%, cold rolling becomes difficult.

Mn, like Si, has the effect of increasing the specific resistance of the steel sheet and reducing eddy current loss. For this reason,
The Mn content needs to be 0.10% or more, while
If the Mn content exceeds 1.50%, the deformation resistance during hot rolling increases and hot rolling becomes difficult, and the crystal structure before cold rolling tends to become finer, which deteriorates the magnetic properties of the product.
The n content needs to be 1.50% or less.

Al, like Si and Mn, has the effect of increasing the specific resistance of the steel sheet and reducing eddy current loss. A
In order to obtain such an effect by 1, 0.10%
It is necessary to add above. On the other hand, when the Al content is 2.00
%, The magnetic flux density is reduced and the cost is increased. Further, even if the Al content in the steel is less than 0.10%, the effect of the present invention is not impaired at all.

In order to improve the mechanical properties, magnetic properties and rust resistance of the product or for other purposes, P,
Even if one or more of B, Ni and Sb are contained in steel, the effect of the present invention is not impaired.

If the C content exceeds 0.004%, magnetic aging occurs during use of the product, and iron loss deteriorates.
It is necessary to make it 04% or less. From the viewpoint of preventing magnetic aging and improving magnetic flux density, it is preferable to control C to 0.0025% or less and 0.0010% or more.

S and N partially re-dissolve during slab heating in the hot rolling step, and sulfides such as MnS and A
A nitride such as 1N is formed. Due to the presence of these, at the time of transformation from the γ phase to the α phase after hot rolling, it provides the nucleus of the α phase and hinders the grain growth of the α phase crystal structure after the transformation,
Its content must be 0.002% or less.

The Ti content, Nb content, V content, Zr content, Ca content, and Cr content are 0.003%, 0.003%, 0.005%, and 0.005%, respectively.
If it exceeds 3%, 0.003% or 0.05%, Ti, V,
Precipitation of carbides of Nb, Zr, Ca, Cr becomes remarkable,
The coarsening of the hot-rolled crystal structure is hindered, and the crystal grain growth in the finish annealing step is hindered, deteriorating the magnetic properties. Therefore, the Ti content, Nb content, V content, Zr content, Ca content, and Cr content are 0.003% or less, 0.003% or less, 0.005% or less, and 0.003% or less, respectively.
%, 0.003% or less, and 0.05% or less.

In the present invention, each of Ti, V, Nb,
In addition to the content of Zr and Ca alone, a specific relationship needs to be established between the total content including the whole and the C content. That is, in the Q value determined by the equation (1), Q = log {([Ti%] + [Nb%] + [V%] + [Zr%] + [Ca%]) × [C%]} Equation (1) where [Ti%], [Nb%], [V%], [Zr%], [Ca
%] And [C%] are Ti, Nb, V, Zr, Ca,
Weight concentration of C in product. When the Q value of the formula (1) exceeds -4.70, it is not possible to obtain the low iron loss non-oriented electrical steel sheet intended by the present invention. Therefore, the Q value of equation (1) is -4.7.
Must be 0 or less.

Further, as a factor affecting the formation of precipitates that inhibit crystal grain growth, it is necessary to suppress the As content. As is itself, in steel within the component range of the present invention, No precipitates such as sulfides and nitrides are formed. However, if a certain amount or more of As is contained in the steel, the sulfide size becomes fine, so that the coarsening of the hot-rolled crystal structure is significantly inhibited. From such a viewpoint, A
The s content needs to be 0.0030% or less.

Since Sn and Cu segregate at the crystal grain boundaries of steel and hinder grain growth and worsen product iron loss, their contents must be 0.01% or less and 0.05% or less, respectively. is there.

If the O content exceeds 0.02%, Si
Precipitation of oxide-based inclusions such as O ₂ and Al ₂ O ₃ becomes remarkable, hindering crystal grain growth and exacerbating the iron loss of the product. Therefore, the content needs to be 0.02% or less.

P is added in a range of up to 0.1% in order to improve the punchability of the product. P ≦
If it is 0.2%, there is no problem from the viewpoint of the magnetic properties of the product. B is added in order to form BN at the time of hot rolling, to prevent fine precipitation of AlN, and to render N harmless.

The B content needs to be balanced with the amount of N, and the content of B is 0.5 to 1.
Preferably, the range of 5 is satisfied.

Next, the reasons for defining the component range of the present invention will be described. The present inventors have conducted intensive studies and found that C, N,
S, Ti, V, Nb, As, Ca, Cr,
By controlling the content of impurities such as Sn, Cu, and O, it has been discovered that both magnetic properties, namely, iron loss and magnetic flux density, in a product can be significantly improved, and the present invention has been completed.

The following experiment was conducted in order to confirm the constituent requirements of the present invention. Steel having the components shown in Tables 1 and 2 was melted and subjected to finish hot rolling to finish to a thickness of 2.5 mm. At this time, while changing the hot-rolling termination temperature, the hot-rolled sheet after hot-rolling is subjected to hot-rolling sheet annealing, and hot-rolled sheets having various crystal grain sizes before cold rolling are pickled and cold-rolled to 0.5 mm. After thickening and degreasing, 72
After annealing at 0 ° C. for 30 seconds, the Epstein sample was cut and its magnetic properties were measured.

[0034]

[Table 1]

[0035]

[Table 2]

FIG. 1 shows the relationship between the crystal grain size before cold rolling and the magnetic flux density. It can be seen that the material of the present invention has a higher magnetic flux density than the material of the comparative example. Furthermore, in the material of the comparative example, when the crystal grain size before cold rolling is 100 μm or more, the increase in the magnetic flux density reaches a plateau, but it can be seen that the material of the present invention has a high magnetic flux density.

Next, steels having the components shown in Tables 3 and 4 were melted and subjected to finish hot rolling to finish to a thickness of 2.5 mm. At this time, while changing the hot-rolling termination temperature, the hot-rolled sheet after hot-rolling is subjected to hot-rolling sheet annealing, and hot-rolled sheets having various crystal grain sizes before cold rolling are pickled and cold-rolled to 0.5 mm. After thickening and degreasing, 720 ° C
For 30 seconds at 750 ° C. to cut the Epstein sample.
After performing a strain relief annealing corresponding to a customer for 2 hours, magnetic properties were measured.

[0038]

[Table 3]

[0039]

[Table 4]

FIG. 2 shows the relationship between the crystal grain size before cold rolling and iron loss. It can be seen that the material of the present invention has lower iron loss than the material of the comparative example. By using a high-purity steel having a C content in a specific range as described above, it is possible to reduce iron loss in a product, increase a magnetic flux density, and produce a non-oriented electrical steel sheet having excellent magnetic properties. is there.

The steel slab composed of the above components is produced in a converter and is produced by continuous casting or ingot-bulking rolling. The steel slab is heated by a known method. In the present invention, hot rolled sheet annealing is performed or not, and a product is formed by one cold rolling and continuous annealing. Further, a skin pass rolling step may be added to obtain a product.

Further, the final thickness may be obtained by performing cold rolling two or more times with intermediate annealing. Further, a skin pass may be performed thereafter to obtain a final thickness. If the skin pass rolling is less than 2%, the effect cannot be obtained, and if it is more than 20%, the magnetic properties deteriorate, so the content is set to 2% to 20%.

[0043]

Next, an embodiment of the present invention will be described. [Example 1] A slab for a non-oriented electrical steel sheet having the components shown in Table 5 was heated by a usual method, and was subjected to hot rolling by 2.5 mm.
mm. Then, it pickled and finished to 0.50 mm by cold rolling. This is 730 in a continuous annealing furnace.
Annealed at 30 ° C. for 30 seconds. Thereafter, the sample was cut into Epstein samples, and the magnetic properties were measured. Table 5 also shows the components of the present invention and comparative examples and the results of measuring magnetic properties. By controlling the purity of the steel in this way, it is possible to obtain a non-oriented electrical steel sheet having a low iron loss value and excellent magnetic properties.

[0044]

[Table 5]

Example 2 A slab for a non-oriented electrical steel sheet having the components shown in Table 6 was heated by a usual method and finished to 2.5 mm by hot rolling. Then, it pickled and finished to 0.55 mm by cold rolling. Next, in a continuous annealing furnace,
Annealing was performed at 00 ° C. for 20 seconds, and finished by skin pass rolling at a reduction of 9% to a thickness of 0.50 mm, followed by annealing at 750 ° C. for 2 hours corresponding to a customer. Epstein test pieces were cut out from these samples, and the magnetic properties were measured. Table 6 shows the results.

[0046]

[Table 6]

As described above, it is found that a material having a low iron loss value can be obtained by using a high-purity steel having a C content within a specific range.

[0048]

As described above, according to the present invention, it is possible to manufacture a non-oriented electrical steel sheet having low iron loss and excellent magnetic properties.

[Brief description of the drawings]

FIG. 1 is a table showing the relationship between the crystal grain size before cold rolling and the magnetic flux density.

FIG. 2 is a table showing the relationship between the crystal grain size before cold rolling and iron loss.

Claims (5)

[Claims] 1.% by weight: 0.1% ≦ Si ≦ 3.5%, 0.1% ≦ Mn ≦ 1.5%, C ≦ 0.004%, N ≦ 0.002%, S ≦ 0 0.002%, Ti ≦ 0.003%, Nb ≦ 0.003%, V ≦ 0.005%, Zr ≦ 0.003%, Ca ≦ 0.003%, As ≦ 0.003% Cr ≦ 0.05 %, Sn ≦ 0.01%, Cu ≦ 0.05%, O ≦ 0.02%, and the Q value determined by the following formula (1) is −4.70.
A non-oriented electrical steel sheet having low iron loss, satisfying the following, with the balance being Fe and inevitable impurities. Q = log {([Ti%] + [Nb%] + [V%] + [Zr%] + [Ca%]) × [C%]} Formula (1) where [Ti%], [Nb%], [V%], [Zr%], [Ca
%] And [C%] are Ti, Nb, V, Zr, Ca,
Weight concentration of C in product. 2. The non-oriented electrical steel sheet according to claim 1, further comprising 0.10% ≦ Al ≦ 2.00% by weight as an alloy component. 3.% by weight: 0.1% ≦ Si ≦ 3.5%, 0.1% ≦ Mn ≦ 1.5%, C ≦ 0.004%, N ≦ 0.002%, S ≦ 0 0.002%, Ti ≦ 0.003%, Nb ≦ 0.003%, V ≦ 0.005%, Zr ≦ 0.003%, Ca ≦ 0.003%, As ≦ 0.003% Cr ≦ 0.05 %, Sn ≦ 0.01%, Cu ≦ 0.05%, O ≦ 0.02%, and the Q value determined by the following formula (1) is −4.70.
A slab consisting of Fe and inevitable impurities is hot-rolled to form a hot-rolled sheet, and the steel sheet is subjected to one-time cold rolling, then to finish annealing, and then to skin pass rolling, or A method for producing a non-oriented electrical steel sheet having a low iron loss, wherein the non-oriented electrical steel sheet is manufactured without being subjected to a treatment. Q = log {([Ti%] + [Nb%] + [V%] + [Zr%] + [Ca%]) × [C%]} Expression (1) where [Ti%], [Nb%], [V%], [Zr%], [Ca
%] And [C%] are Ti, Nb, V, Zr, Ca,
Weight concentration of C in product. 4. The non-oriented electrical steel sheet according to claim 3, wherein a slab containing 0.10% ≦ Al ≦ 2.00% by weight is further used as an alloy component. Manufacturing method. 5. The method for producing a non-oriented electrical steel sheet having a low iron loss according to claim 1, wherein 0.0010% ≦ C ≦ 0.0025%.