JP2540946B2 - Non-oriented electrical steel sheet with excellent magnetic properties and method of manufacturing the same - Google Patents

Description

The present invention relates to a non-oriented electrical steel sheet, particularly a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density, and a method for producing the same.

[Prior art and its problems]

In recent years, from the viewpoint of energy saving, high efficiency of motors,
With respect to the non-oriented electrical steel sheet used as an iron core material, which is required to be downsized, it is becoming more and more important to improve the magnetic characteristics by reducing the iron loss and increasing the magnetic flux density.

In order to reduce the iron loss in a non-oriented electrical steel sheet, it is common to reduce the eddy current loss by increasing the electrical resistance by adding Si. However, when the amount of Si in the steel increases, recrystallization of ferrite after hot rolling and winding hardly occurs, and when the ferrite recrystallization rate in the hot rolled sheet is low as described above, the cold rolled-annealed steel sheet is subsequently used. The magnetic flux density of will decrease. Therefore, in order to compensate for such drawbacks caused by the addition of Si, a method of annealing a hot-rolled sheet to sufficiently recrystallize the ferrite and then cold-annealing is disclosed. However, only such hot-rolled sheet annealing cannot sufficiently reduce the iron loss and the high magnetic flux density of the steel sheet.

When elements such as Sn and Sb are added to the steel, these elements segregate at the ferrite grain boundaries during hot-rolled sheet annealing and, in the annealing stage after cold pressing, grains of the (111) component harmful to magnetic properties are A technique for further improving the magnetic flux density by suppressing recrystallization from the vicinity of the boundary has been disclosed (for example, JP-A-57-35627). However, if these elements are segregated uniformly on the grain boundaries in the thickness direction of the hot-rolled sheet, the ferrite grain growth property in the post-cold-pressure annealing step is suppressed, and the decrease in iron loss is suppressed. There is.

On the other hand, when nitrogen is present in the atmosphere gas at the time of final annealing, nitrogen diffuses and permeates from the steel plate surface, and nitrides such as AlN precipitate in the vicinity of the steel plate surface due to reaction with nitride forming elements in the steel such as Al. To do. Such a nitride significantly reduces the ferrite grain growth property in the vicinity of the steel sheet surface and hinders the improvement of magnetic properties. Conventionally, in order to prevent deterioration of magnetic properties due to nitriding during such annealing, a technique of applying a nitriding inhibitor at the slab stage and diffusing and permeating (JP-A-51-48707),
In addition, a technology (Japanese Patent Publication No. 56-48567) of applying a nitriding inhibitor such as Se after cold pressing and before final annealing has been proposed.

However, of these, in the former method, since the diffusion layer of the nitriding preventing element is oxidized during slab heating or hot rolling, not only is there a disadvantage that it must be used as a mixture with an antioxidant, Magnetic properties (iron loss, magnetic flux density) are not sufficiently improved. On the other hand, in the latter method, although some effect can be obtained in terms of nitriding prevention in the final annealing stage, elements such as Se, Sn, and Sb in the nitriding inhibitor during final annealing rapidly diffuse and penetrate from the steel sheet surface. Therefore, the grain growth property of the ferrite grains is remarkably reduced, and rather the magnetic properties (iron loss, magnetic flux density) are deteriorated.

As described above, the conventional technology using Se, Sb, Sn, etc. as an additive element in steel or as a nitriding inhibitor cannot satisfy both low iron loss and high magnetic flux density of a non-oriented electrical steel sheet at the same time. It was

Therefore, an object of the present invention is to solve the problems of the prior art and to provide a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density, and a manufacturing method thereof.

[Means for solving problems]

In order to solve such a problem, the present invention, after hot rolling and pickling, Se, Te, Sb, Bi, Pb, S on the steel sheet surface layer portion before cold rolling.
One or more elements of n and As are diffused and permeated,
And by using a silicon steel sheet having a multilayer structure in which the penetration depth and concentration of the above Se to As in the steel sheet surface layer part are specified conditions, it is found that low iron loss and high magnetic flux density can be achieved at the same time, It has been completed.

That is, the non-oriented electrical steel sheet of the present invention, after hot rolling and pickling, Se, Te, Sb, Bi, Pb, in the steel sheet surface layer portion before cold rolling,
Steel sheet in which one or more elements of Sn and As are diffused and permeated, and the total thickness of the steel sheet is 20% or less in total on both sides and 2 μm or more on one side. The alloy composition in the limited surface layer portion is C ≦ 0.0050 wt%, Si: 1.0
~ 4.0wt%, Al: 0.1 ~ 2.0wt%, N≤0.0030wt%, Se, T
One or two or more of e, Sb, Bi, Pb, Sn, and As are added in a total amount of 0.02 wt% or more, the balance Fe and inevitable impurities, and the alloy composition in the inner layer portion of the balance thickness direction , C ≦ 0.0050 wt%, Si: 1.0 to 4.0 wt%, Al: 0.1 to 2.0 wt
%, N ≦ 0.0030 wt%, one or more of Se, Te, Sb, Bi, Pb, Sn and As elements total 0.003 wt% or less,
The basic feature is that it has a multi-layer structure composed of the balance Fe and unavoidable impurities.

Further, in order to preferably manufacture such a non-oriented electrical steel sheet according to the present invention, C ≦ 0.0050 wt%, Si: 1.0 to 4.0 wt%, Al:
0.1 ~ 2.0wt%, N≤0.0030wt%, Se, Te, Sb, Bi, Pb,
0.003w in total of one or more elements of Sn and As
After hot rolling an electromagnetic steel slab consisting of t% or less and the balance Fe and unavoidable impurities, it is wound at 700 ° C. or less, pickled the hot rolled sheet, and then Se, Te, Sb, Bi, Pb, Sn, An aqueous solution or suspension of a compound containing one or more of As is applied and dried, and then hot-rolled sheet annealing is performed in a non-oxidizing atmosphere to obtain the above Se, Te, Sb, Bi, 1 out of Pb, Sn, As
Or two or more elements are diffused and permeated into the surface layer of the steel plate,
Another basic feature is that final annealing is performed after the final thickness is obtained by cold rolling.

 Hereinafter, the details of the present invention will be described.

The non-oriented electrical steel sheet of the present invention is an alloy component such as Se in the surface layer portion having a specific thickness of the steel sheet (one or more elements among Se, Te, Sb, Bi, Pb, Sn and As). The condition is to be richer than the inner layer portion, alloy components such as Se of the surface layer portion, after hot rolling and pickling, diffused and permeated into the steel sheet surface layer portion before cold rolling. That is, the alloy components such as Se must have diffused into the surface layer of the steel sheet before the final annealing. In a steel sheet obtained by applying a nitriding inhibitor such as Se after cold pressing and before final annealing as in the prior art, since Se and the like diffusely permeate into the steel sheet surface layer portion during final annealing, the present invention is based on the reason described below. The desired excellent magnetic properties (low iron loss, high magnetic flux density) cannot be obtained.

Further, in the present invention, the alloy composition is C ≦ 0.0050 wt%,
Si: 1.0-4.0wt%, Al: 0.1-2.0wt%, N0.0030wt%, and the total of one or more elements of Se, Te, Sb, Bi, Pb, Sn, As. The total thickness of the steel sheet is 20% or less on both sides of the steel sheet, and 0.02 on the surface layer of 2 μm or more on one side.
It is specified to be not less than wt% and not more than 0.003 wt% in the remaining inner layer portion in the plate thickness direction.

First, the reasons for limiting the thickness of the surface layer and alloy elements such as Sb and Te will be described.

The hot-rolled sheet after pickling is coated with a compound containing an element to be diffused, then annealed, then cold pressed and finally annealed, and the concentration profile of the diffusing element in the steel sheet thickness direction is as shown in Fig. 1. Indicated. Here, the concentration C of the diffusion element of the diffusion region, when the elemental concentration and the concentration of element thickness center portion of the steel sheet surface and C _1, C _0, And On the other hand, the diffusion region of the element is the distance l from the surface of the steel sheet at the portion that becomes C in the concentration profile of the element.

After descaling a hot-rolled steel sheet having a composition of Steel A shown in Table 1 and having a thickness of 2 mm by pickling, a suspension of SbCl ₃ was applied to the surface of the steel sheet, and the hot-rolled steel sheet was annealed at 850 ° C. , 0.5 mm, and further subjected to final annealing at 950 ° C. for the steel sheet obtained, the diffusion region and concentration of Sb and the magnetic property values of the steel sheet obtained without applying SbCl ₃ in the same process The difference is shown in FIG. According to this figure, the range (thickness) of the Sb diffusion region (steel plate surface layer portion) and its Sb concentration and the magnetic properties have the following relationship.

(A) When the concentration of Sb in the diffusion region is Sb <0.02 wt% Since nitriding cannot be prevented in each annealing step in the manufacturing stage, nitride precipitates on the surface layer, resulting in grain growth of ferrite grains in the final annealing stage. Property is suppressed, and the amount of decrease in iron loss value is small. Moreover, since the Sb concentration is low, the texture does not change significantly, and the magnetic flux density hardly changes.

(B) The concentration of Sb in the diffusion region is 0.02 wt% Sb,
In the case of Sb diffusion region <2 μm, the Sb concentration in the surface layer portion is high, so that nitriding in each annealing step can be suppressed, so that fine ferrite grains in the surface layer portion are eliminated, and the iron loss value is reduced accordingly. However, the magnetic flux density hardly changes.

(C) When the concentration in the Sb diffusion region is Sb 0.02 wt% and the Sb diffusion region is μm, the magnetic flux density is improved. There is a close relationship between the magnetic flux density and the texture, including the (100) or (1
10) Increasing the degree of component integration leads to higher magnetic flux density. As described above, when elements such as Sn and Sb are present in the steel, these elements suppress the nucleation of the (111) component harmful to the magnetic flux density in the final annealing stage after cold pressing,
It has the effect of preferentially nucleating the (100) and (110) components. Further, in the recrystallization reaction in the final annealing stage, when viewed in the plate thickness direction, the vicinity of the surface of the steel sheet is the location where nucleation occurs first and grain growth occurs. Therefore, the presence of 0.02 wt% or more of Sn and Sb near the surface of the steel sheet improves the magnetic flux density with the nucleation of the (100) and (110) components in the surface layer.

(D) Sb concentration in the Sb diffusion region> 0.1 wt% and S
When b diffusion region ≧ 2 μm, or when Sb concentration ≧ 0.02 wt% in Sb diffusion region and Sb diffusion region> 50 μm (over 20% of the total thickness of both sides of the steel plate), elements such as Sb are Segregation on the grain boundaries during ferrite grain growth has the effect of suppressing grain boundary movement. This is disadvantageous for the reduction of iron loss, and when it is present at a low concentration in a limited area near the surface layer, its effect is negligibly small, and conversely the hysteresis loss associated with texture improvement is The iron loss decreases due to the decrease of. However, if the concentration of the diffusion region is high or the diffusion region is wide, the effect of suppressing grain growth by these elements appears, and iron loss does not decrease. Therefore, the diffusion area of elements must be 20% or less of the product plate thickness. The optimum grain size for minimizing the iron loss value depends on the amount of Si, but it is desirable that it is approximately 60 μm for 1% Si steel and 100 μm or more for 3% Si steel.

Such an effect is the same with other elements such as Te, Se, Bi, Pb, Sn, and As, and also when two or more of these elements containing Sb are used.

And for the above reasons, in the present invention, the thickness of the surface layer portion is specified to be 20% or less in total on both sides of the steel sheet with respect to the total thickness of the steel sheet, 2 μm or more on one side, and Se contained in the surface layer portion, Te,
0.02wt of the total of one or two elements of Sb, Bi, Pb, Sn, As
Specify as% or more.

On the other hand, in the inner layer, one of Se, Te, Sb, Bi, Pb, Sn, As
If the total amount of one kind or two or more kinds of elements exceeds 0.003 wt%, the grain growth property deteriorates and the iron loss deteriorates. Therefore, in the inner layer portion, the total amount of the above alloy elements is 0.003 wt%.
The following is assumed.

 The reasons for limiting the other components are as follows.

If the C content exceeds 0.0050 wt%, the magnetic properties deteriorate and the magnetic aging also causes a problem.

N: When it exceeds 0.0030wt%, it reacts with Al in steel and becomes fine AlN.
Are deposited in large amounts, which reduces the grain growth property and deteriorates the iron loss.

When Si is less than 1.0 wt%, the eddy current loss increases due to the decrease in specific resistance, and the improvement in iron loss value is small. On the other hand, if it exceeds 40 wt%, cold rolling property deteriorates.

If Al: less than 0.1 wt%, AlN finely precipitates by reacting with N in the steel, and thus ferrite grain growth property is deteriorated and magnetic properties are deteriorated. On the other hand, Al, like Si, lowers the specific resistance and iron loss, but if it exceeds 2 wt%, the cold rolling property deteriorates.

 Next, the manufacturing method of the present invention is described.

In the method of the present invention, C 0.005 wt%, Si: 1.0 to 4.0 wt%, A
l: 0.1-2.0wt%, N0.0030wt%, Sb, Se, Te, Bi, Pb, Sn,
One or more elements of As are 0.003wt in total
%, The magnetic steel slab consisting of the balance Fe and unavoidable impurities is hot-rolled and then wound at 700 ° C. or less, and then the hot-rolled sheet is pickled.

When a compound such as Se to As is applied and annealed while a scale is present on the surface of the steel sheet, nitriding can be prevented, but the scale suppresses diffusion and penetration of elements into the steel. Therefore, pickling of the hot rolled sheet is essential in the present invention. Further, if the winding temperature after hot rolling exceeds 700 ° C., the surface layer scale is thickly formed, so that the pickling property is deteriorated and descaling becomes difficult.

After the above pickling, an aqueous solution or suspension of a compound containing one or more of Se, Te, Sb, Bi, Pb, Sn and As is applied and dried.

In order to make the texture at the time of final annealing excellent in magnetic properties with the elements such as Se to As, the elements such as Se to As must already be diffused in the surface layer of the steel sheet before the final annealing. . That is, when a compound such as Se to As is applied after cold pressing and annealed, in the final annealing stage, diffusion of elements such as Se to As into the steel sheet and recrystallization reaction of ferrite simultaneously proceed, so that magnetic properties It is difficult to form a good texture, and it is not possible to achieve the low iron loss and high magnetic flux density that are the objectives of the present invention. Therefore, Se ~ As
Such compounds must be applied after pickling the hot rolled sheet and diffused to the surface layer of the steel sheet by subsequent annealing. The method for applying the suspension or the aqueous solution of these elements is spraying, as long as the surface diffusion layer of these elements is uniformly formed.
Immersion or any other method may be used, and the method of dipping in a water washing tank after the pickling line is effective. In addition, if the hot-rolled sheet is skin-passed and applied after introducing strain on the surface of the steel sheet,
It can be diffused in a short time.

Examples of Se to As compounds include K ₂ SeO ₃ , KeTeO ₃ , and SbCl.
₃ , BiCl ₃ , PbCl ₂ , SnCl ₂ , AsCl _{3 and the} like, and an aqueous solution or suspension containing one or more of these is used.

After the above compound is applied with a suspension or the like and dried, the hot rolled sheet is annealed. In order to obtain a texture with good magnetic properties, the ferrite structure of the hot-rolled sheet before cold pressing must be completely recombined. In the case of a silicon steel sheet containing 1 wt% or more of Si, recrystallization during hot rolling is significantly reduced,
The hot rolled sheet must be annealed to completely recrystallize the ferrite structure. Further, in the final annealing, in order to form a magnetic texture and a good texture in the surface diffusion region of Se to As or the like, the compound such as Se to As must be diffused after being applied. In order to exert such an effect, annealing at 750 ° C or higher is desirable. Further, in order to effectively react the diffusion reaction of elements such as Se to As, the atmosphere during hot-rolled sheet annealing must be set to a non-oxidizing atmosphere to prevent the oxidation reaction of these compounds. Desirably, an atmosphere of N ₂ —H ₂ mixed gas or Ar—H ₂ mixed gas of 5% H ₂ or more is preferable.

The penetration depth and concentration of Se and the like in the steel sheet surface layer portion defined by the present invention are the coating amount of the compound on the hot rolled steel sheet surface after pickling and the hot rolled sheet annealing conditions (annealing temperature, time, atmosphere, etc.) And the like are adjusted. Usually, the coating amount of the compound is about 0.5 to 2.0 g / m ² , and the annealing condition for hot-rolled sheet is an annealing temperature of 710 ° C (preferably 750 ° C as described above).
Approximately 850 ℃, the annealing time is about 3 to 10 hours in the case of batch annealing, and by adjusting the coating amount of the compound and the annealing conditions of the hot-rolled sheet within these ranges, the desired penetration depth of Se etc. And concentration can be obtained.

The hot-rolled sheet annealed steel sheet is then cold-rolled to the final sheet thickness and then subjected to the final annealing.

As a method of obtaining the steel sheet of the present invention, other than applying the compound to the hot-rolled sheet as described above, for example, after pickling the hot-rolled sheet, elements such as Se ~ As by the CVD (chemical vapor deposition) method Can also be attached, in which case the element itself is deposited on the steel plate surface.

〔Example〕

Example 1 In Table 1, a non-oriented electrical steel sheet was manufactured from a slab having a composition of Steel A by the following steps and conditions. Table 2 shows the composition and magnetic properties of the obtained steel sheet together with the manufacturing conditions.

Example 2 In Table 1, a non-oriented electrical steel sheet was manufactured from a slab having a composition of Steel B and Steel C by the following steps and conditions. The composition and magnetic properties of the obtained steel sheet are
Shown in the table.

Steel B B1: Hot rolled sheet → Pickling → SbCl ₃ coating → Hot rolled sheet annealing → Cold pressure → Annealing (0.8g / m ² ) B2: SbCl ₃ coating on slab 10g / m ² (220mm t) Hot rolled sheet → Pickling → hot rolled sheet annealing → cold rolling → annealing B3: hot rolled sheet → pickling → hot rolled sheet annealing → cold pressure → SbCl ₃ coating → annealed (0.8g / m ² ) B4: hot rolled sheet → pickled → Cold pressure → SbCl ₃ coating → Annealing (0.8g / m ² ) B5: Hot rolled sheet → Pickling → Hot rolled sheet annealing → Cold pressure → Annealing B6: Hot rolled sheet → Pickling → Cold pressure → Annealing Steel C C1: Hot rolled sheet → Pickling → Hot rolled sheet annealing → Cold pressure → Annealing ・ Hot rolling condition: 1120 ℃ heating, 830 ℃ finish, 650 ℃ winding, 2.0mm t ・ Hot rolled sheet annealing condition: 800 ℃ × 10h, furnace Cold, 75% H ₂ -25% N ₂・ Final annealing condition: 900 ℃ × 2min, Air cooling, 25% H ₂ −75% N ₂ , Sheet thickness 0.5mmt

[Brief description of drawings]

FIG. 1 shows a concentration profile of diffusing elements in the steel sheet thickness direction when a hot rolled sheet after pickling is coated with a compound containing an element to be diffused, annealed, then cold pressed and finally annealed. It is a thing. Fig. 2 shows that after applying a suspension of SbCl _{3 to} the surface of hot-rolled sheet descaled by pickling,
Shows the difference between the Sb diffusion region and the Sb concentration of the steel sheet obtained by hot-rolled sheet annealing, cold pressing and final annealing, and the magnetic property values of the steel sheet obtained without applying SbCl ₃ in the same process. It is a thing.

Claims (2)

(57) [Claims] 1. After hot rolling and pickling, before cold rolling, one or more elements selected from Se, Te, Sb, Bi, Pb, Sn and As are diffused and permeated into the surface layer of the steel sheet. Steel plate, the total thickness of the steel plate is 20% or less in total on both sides, 2μ on one side
The alloy composition in the limited surface layer portion of m or more is C
≤0.0050wt%, Si: 1.0-4.0wt%, Al: 0.1-2.0wt%, N
≤ 0.0030 wt%, one or more of Se, Te, Sb, Bi, Pb, Sn, and As elements in total is 0.02 wt% or more, the balance is Fe and inevitable impurities, and the balance in the plate thickness direction The alloy composition in the inner layer part of C is 0.0050wt%, Si: 1.0-4.0wt
%, Al: 0.1 to 2.0 wt%, N ≦ 0.0030 wt%, Se, Te, Sb, B
A non-oriented electrical steel sheet excellent in magnetic properties of a multi-layer structure composed of 0.003 wt% or less of one or more elements out of i, Pb, Sn, and As in total, and the balance Fe and inevitable impurities. 2. C≤0.0050 wt%, Si: 1.0-4.0 wt%, Al: 0.
1 ~ 2.0wt%, N≤0.0030wt%, Se, Te, Sb, Bi, Pb, S
One or more of n and As are 0.003wt in total
% Or less, hot rolling an electromagnetic steel slab consisting of balance Fe and unavoidable impurities, winding at 700 ° C. or less, pickling the hot rolled sheet, Se, Te, Sb, Bi, Pb, Sn, As Among these, Se, Te, Sb, Bi and Pb are prepared by applying an aqueous solution or suspension of a compound containing one or more of the above, drying it, and annealing it in a non-oxidizing atmosphere. , Sn, As, one or more elements are diffused and permeated into the surface layer of the steel sheet, and further cold-rolled to a final thickness, and then final annealing is performed.
The total thickness of the steel sheet is 20% or less in total on both sides of the steel sheet, and the alloy composition in the limited surface layer portion is 2 μm or more on one side, C ≦ 0.0050 wt%, Si: 1.0 to 4.0 wt% , Al:
0.1 ~ 2.0wt%, N≤0.0030wt%, Se, Te, Sb, Bi, Pb,
One or more of Sn and As elements total 0.02wt
% Or more, the balance is Fe and inevitable impurities, and the alloy composition in the inner layer part in the balance thickness direction is C ≦ 0.0050 wt.
%, Si: 1.0 to 4.0 wt%, Al: 0.1 to 2.0 wt%, N ≦ 0.0030 wt
%, Se, Te, Sb, Bi, Pb, Sn, As, one or more elements in total 0.003 wt% or less, the balance Fe and unavoidable impurities multilayer non-directional electromagnetic A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, which comprises producing a steel sheet.