JPH0336242A - Nonoriented silicon steel sheet excellent in magnetic property and its production - Google Patents

Abstract

PURPOSE:To produce a nonoriented silicon steel sheet in which the composition in a surface layer part is different from that in an internal layer part and which has low iron loss and high magnetic flux density by subjecting a slab of silicon steel with a specific composition to hot rolling and to pickling treatment, applying, e.g. an aqueous solution containing specific elements to the resulting steel plate, subjecting the above steel sheet to drying and then to annealing in a nonoxidizing atmosphere, and successively carrying out cold rolling and final annealing. CONSTITUTION:A slab of a dead-soft carbon steel having a composition containing, by weight, <=0.0050% C, 1.0-4.0% Si, 0.1-2.0% Al, <=0.0030% N, and <=0.003%, in total, of one or >=2 elements among Se, Te, Sb, Bi, Pb, Sn, and As is hot-rolled, coiled at <=700 deg.C, and subjected to pickling treatment. Subsequently, an aqueous solution containing one or >=2 elements among the above-mentioned Se, etc., is applied to the resulting plate, and, after drying, the plate is annealed in a nonoxidizing atmosphere, cold-rolled, and subjected to final annealing so as to be formed into a sheet metal material, by which the nonoriented silicon steel sheet consisting of both surface layer parts which total surface thickness is <=20% of the total sheet thickness and in which the thickness per side is regulated to >=2mum and both surface layer and an internal layer part, having a composition containing <=0.0050% C, 1-4% Si, 0.1-2.0% Al, and <=0.0030% N and also containing Se, Te, and other components by >=0.02% in both surface layer parts and by <=0.003% in the internal layer part, and excellent in magnetic properties can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a non-oriented electrical steel sheet, particularly a non-oriented electrical steel sheet having low core loss and high magnetic flux density, and a method for manufacturing the same.

[Prior art and its problems]

In recent years, there has been a demand for higher efficiency and smaller motors from the perspective of energy conservation, and it has become increasingly important to improve the magnetic properties of non-oriented electrical steel sheets, which are used as paulownia wood cores, through lower iron loss and higher magnetic flux density. It's coming.

In order to reduce iron loss in non-oriented electrical steel sheets, it is common to reduce flow loss by increasing electrical resistance by adding Si. However, steel [4J S
As the number of particles increases, recrystallization of ferrite becomes difficult to occur after hot-rolling and winding, and if the ferrite recrystallization zone in the hot-rolled sheet is low, then the magnetic flux density of the cold-rolled and annealed steel sheet becomes low. 11 minutes. In order to overcome these drawbacks associated with Si addition, a method has been disclosed in which a hot-rolled sheet is annealed to sufficiently recrystallize the ferrite, and then cold-rolled and annealed.

Additionally, when elements such as Sn and Sb are added to steel, these elements segregate at the ferrite grain boundaries during hot-rolled sheet annealing.
In the annealing step after cold pressing, the 111
) By suppressing the recrystallization of components near the grain boundaries,
Furthermore, a technique for improving the magnetic flux density has been disclosed (for example, Japanese Patent Laid-Open No. 5735027). However, if these elements segregate uniformly on the grain boundaries in the thickness direction of the hot-rolled sheet, the growth of ferrite grains during the annealing stage after cold rolling is suppressed, which leads to the problem of suppressing the decrease in iron loss. There is.

On the other hand, when nitrogen is present in the atmosphere gas during hot rolling calcination i1i or final annealing II;', nitrogen diffuses from the surface of the steel sheet and reacts with nitride-forming elements in the steel such as . Nitrides such as A and QN are precipitated on the surface. If nitrides precipitate during annealing of a hot rolled sheet in this way, the growth of ferrite grains near the surface of the steel sheet will be significantly reduced in the final annealing step after cold rolling, and the magnetic properties will not improve. In addition, the precipitation of nitrides due to nitriding in the final annealing stage
Similarly, it reduces the growth of ferrite grains near the surface of the steel sheet, inhibiting improvement in magnetic properties.

In order to prevent such deterioration of magnetic properties due to nitridation during annealing, a conventional technique (Japanese Unexamined Patent Publication No. 51-48707) in which an anti-nitriding agent is applied at the slab stage and diffused into the slab, and the final annealing after cold pressing is applied. Previously, a technique of applying an anti-nitriding agent such as No. 80 (Japanese Patent Publication No. 48567/1983) has been proposed.

However, in the former method, since the diffusion layer of the nitriding element is oxidized during slab heating or hot rolling, there is a disadvantage that it must be used in combination with the oxidation preventive l1 agent. On the other hand, in the latter method, an anti-nitriding agent such as Se is applied after cold pressing, so nitriding can be prevented at the final annealing stage, but nitriding at the hot-rolled sheet annealing stage cannot be prevented. , Se in the antinitriding agent in the final annealing step.

Because elements such as Sn and Sb rapidly diffuse and permeate from the surface of the steel sheet, the grain growth of Ferrite 1 grains is significantly reduced.
On the contrary, it causes deterioration of magnetic properties.

In view of these conventional problems, the present invention is capable of preventing nitridation during hot-rolled sheet annealing and final annealing, and provides a high magnetic flux density non-oriented electrical steel sheet having a texture with good magnetic properties and the like. The purpose is to provide a method suitable for manufacturing.

[Means to solve the problem]

For this reason, the present invention provides a surface layer of a steel plate with a specified thickness.
Se, Te, Sb, Bi, Pb, Sn.
It is a multi-layer structure silicon-containing steel sheet having a shell layer rich in S, etc., and has a 1-layer structure so as to achieve low core loss and high magnetic flux density through interaction between the inner and outer layers.

That is, the non-oriented electrical steel sheet of the present invention has an alloy composition in a limited surface layer where the thickness is 20% or less in total on both sides of the steel sheet and 21 or more on one side with respect to the total thickness of the steel sheet. C2
0.0050wt%, Si: ], O ~4.0wt%,
A. 9+0.1 ~2.0wt%, N≦0.0030w
[1,02v
L% or more, the balance consists of Fe and unavoidable impurities,
Alloy composition in the remaining inner layer in the plate thickness direction, C≦0.0
050wt%, Si:1. O~4. Ov1. %, /l:
0. l ~2.0wt%, N≦0.0030w
t%, Se, Te, Sb, BPb, Sn, A
One or more elements in s is 0.003 per unit
Its basic feature is that it has a multilayer structure composed of wt% or less, the balance being Fe and unavoidable impurities.

Moreover, in order to suitably manufacture such a non-oriented electrical steel sheet, the present invention provides C≦0.005Dwt%, Si: 1. O~
4, Ovt%, A, 9:0.1-2.0wt%, N≦0
．． 0030wt%, 50Tc, Sb, Bi, Pb, Sn
, II or two or more elements of As are O, D in total
An electromagnetic steel slab consisting of O3vt% or less, the balance Pc and unavoidable impurities is hot-rolled, then coiled at 700°C or less, and the hot-rolled plate is pickled, followed by Se, TeSb, Bi, P.
After applying an aqueous solution or a 7!13 solution of a compound containing one or more of B, Sn, and As and drying it, the sheet is hot-rolled in a non-oxidizing atmosphere, and then cold-rolled. Another basic feature is that the final annealing is performed after the final plate thickness is achieved.

The present invention will be explained in detail below.

The present invention basically consists of making the alloy composition of the extremely limited surface layer of the steel plate richer than that of the inner layer.
In addition to improving the magnetic flux density, the aim is to improve iron loss by preventing nitridation. In particular, in the manufacturing method of the present invention, S is applied to the #A plate surface before hot-rolled plate annealing.
By coating elements such as e, Te, Sb, Bi, Pb, Sn, As, etc., it is possible to prevent the decrease in iron loss due to nitridation that occurs in each subsequent annealing step 1, and to prevent the concentration of these elements. This promotes the formation of a texture with good magnetic properties.

Unexploded lν] The steel plate has an alloy composition of C≦0.0050w
t%, Si: 1.0~4.0wt%, A, Q: 0.1~
2.0wt%, N≦0.0030wt,%, and S
The total of one or more elements of c, Tc, Sb, Bi, Pl), Sn, and S is added to the total thickness of the steel plate Jv.
In contrast, the content is specified as 20% or less at the abutment on both sides of the steel plate, 0.02wt% or more in the 2 or more surface layer portion on one side, and 0.003w1% or less in the inner layer portion of the remaining portion in the thickness direction.

First, the reasons for limiting the thickness of the surface layer and alloying elements such as Sl] and Te will be explained.

When a hot rolled sheet after pickling is coated with a compound containing the element to be diffused and then annealed, followed by cold pressing and final annealing, the concentration profile of the diffusing element in the thickness direction of the steel sheet is the first.
It is shown schematically as shown in the figure. Here, the concentration C of the diffusion element in the diffusion region is the element concentration on the steel plate surface and the plate thickness [-1
``If the elemental concentration of 6 parts is c, , co, then. - The diffusion region of the element is defined as the distance g from the steel plate surface of the portion C in the element concentration profile.

After descaling a hot-rolled sheet with a thickness of 2 mm consisting of the composition of 5teel A in Table 1 by pickling, SbC was added to the surface of the steel sheet.
, h was applied, the hot-rolled plate was annealed at 850°C, cold-pressed to 0.5 m, and final annealed at 950°C. Figure 2 shows the difference in magnetic properties between the a-skin and a steel sheet obtained in the same process without applying SbC, Q3. According to the figure, the range of the sb diffusion region (steel plate surface layer) (
Thickness), its Sb concentration, and magnetic properties have the following relationship.

(A) The concentration of Sb in the diffusion region is Sb<0.0
In the case of 2wt%, nitridation cannot be prevented in each annealing process in the manufacturing stage, so nitrides appear in the □□□ part of the table), and as a result, the grain growth of ferrite grains is suppressed in the final annealing stage, and the iron loss value The amount of decrease is small. Furthermore, since the sb concentration is low, there is no major change in the texture, and the magnetic flux density is also almost unchanged.

(B) Concentration of Sb in the diffusion region or Sl, )20
．． 02w1% and sb diffusion area <21un, the Sba degree in the surface layer is high, so nitriding in each firing i=b can be suppressed, and as a result, fine ferrite grains in the surface layer disappear, and iron Loss value decreases. However, 17, the magnetic flux density is hardly tabulated.

(C) 31) The concentration in the diffusion region is Sb≧0,
fl 2 w 1% and sb diffusion area ≧2 μm
In the case of 0, the magnetic flux density improves. There is a close relationship between magnetic flux density and texture, and increasing the degree of integration of the (1,00) or (110) component containing the easy axis of magnetization leads to higher magnetic flux density. As mentioned above, when elements such as Sn and Sb are present in steel, these elements suppress the nucleation of (II+) components harmful to magnetic flux density in the final annealing stage after cold pressing, and ( This has the effect of preferentially nucleating the 1,00) and (110) components. In addition, in the recrystallization reaction at the final annealing stage, when viewed in the thickness direction, the area near the surface of the steel sheet is where nucleation occurs fastest and grains grow. Therefore, Sn is present near the surface of the steel sheet.

When sb is present in an amount of 0.02 wt% or more, the magnetic flux density improves due to the nucleation of the (↓00) and (↑10) components in the surface layer.

(D) Sb diffusion region 1.1: Case 7:, Sba degree > 0.1 wt%, or sb diffusion region > 100 μm (
(20% or more of the plate thickness), elements such as sb have the effect of suppressing grain boundary movement by segregating on the grain tips during ferrite grain growth. This is disadvantageous for reducing iron loss,
When it exists at a low concentration in a limited area near the surface layer, its effect is negligibly small, and on the contrary, the iron loss decreases due to the decrease in hysteresis loss accompanying the improvement of the texture. 17 But in the diffusion area? If the degree of a is high or the diffusion region is wide, the effect of suppressing grain growth by these elements will appear, and the iron loss will not decrease. Therefore, the element diffusion region must be 20% or less of the product board thickness. In addition, the optimum grain size to minimize the iron loss value is 5if
It varies depending on fi, or approximately 60 for 1% Si steel.
μm, preferably l[)[)trm or more for 3% Si steel.

Such results are similar to other Tc, Sc, Bi, Pb, Sn
, As, and the same applies when two or more of these elements including sb are used.

Based on the above-mentioned theory, in the present invention, the thickness of the surface layer is determined to be 20% or less of the total thickness of the steel plate in terms of i+ on both sides of the steel plate, and 2 μm or more on one side. S contained in
e, Te, Sb, Bi, PI), S11. The total of one or two elements of AS is defined as 0.02wt, 1 or more.

On the other hand, in the inner layer part, Sc, Tc, Sb, Bi, Pb,
IF among Sn and As! r! Alternatively, if the total amount of two or more elements exceeds 0.003 wt%, grain growth will decrease and iron loss will deteriorate. The following shall apply.

Further, the limiting widths of other components are as follows.

C: If it exceeds 0.0050wt%, the magnetic properties will deteriorate,
Further, problems arise in terms of magnetic aging.

N: If it exceeds 0.0030 wt%, a large amount of fine AρN will precipitate by reacting with AR in the steel, resulting in a decrease in grain growth and a deterioration in iron loss.

Si: When it is less than 1.0 wt%, eddy current loss increases due to a decrease in specific resistance, and improvement in iron loss value is small.

On the other hand, if it exceeds 4.0 wt%, cold rollability will deteriorate.

Afl: If it is less than 0.1 wt%, it will react with N in the steel and cause A,
QN is finely precipitated, which reduces ferrite grain growth and deteriorates magnetic properties. On the other hand, A, cl are similar to Si and 1111, which lowers the specific resistance and reduces iron loss, but 2w
If it exceeds t%, cold rollability will deteriorate.

3 Next, the driving method of the present invention will be explained.

In the method of the present invention, C20,005wt%, Si: 1.
0-4. Owt%, Ai): 0.1-2.0wt%, N
≦0.0030wt%, Sb, Se, Te, Bi, Pb
, Sn, As, a total of 0.003 vt% or less of one or more elements, the balance being Re and unavoidable impurities, is hot rolled and then coiled at 700 ° C. or less, and then, The hot rolled sheet is pickled.

If a 5c-Asπ9 compound is applied and annealed with scale present on the surface of the steel sheet, it may be possible to prevent nitridation, but the scale will inhibit the diffusion of elements into the steel. Therefore, in the present invention, pickling of the hot rolled sheet is essential. In addition, if the stock temperature after hot rolling exceeds 700°C, the surface scale will become thick and sedentary, resulting in a decrease in pickling properties11 and difficulty in descaling1. It becomes.

After the above pickling, Se, Te, Sb, Bi, Pb, Sn,
A water-soluble compound or suspension of a compound containing one or more of As is applied and dried.

In order for the texture at the time of final annealing to have good magnetic properties due to elements such as 5e-As mentioned above, elements such as 5e-As must already be diffused into the surface layer of the steel sheet before final annealing. It won't happen. That is, after cold pressing 5
When a compound such as e-As is applied and annealed, the diffusion of elements such as 5e-As into the peaks of the steel plate and the recrystallization reaction of ferrite proceed in the same manner as in the final annealing stage, resulting in magnetic It is difficult to form a texture with good properties. Therefore, a compound such as Se-As must be applied to the hot-rolled sheet after pickling, and then diffused into the surface layer of the steel sheet by annealing. The suspension or aqueous solution of these elements may be applied by spraying, dipping, or any other method as long as a surface diffusion layer of these elements is formed uniformly.The method is to apply the suspension or aqueous solution of these elements by spraying, dipping, or any other method. The method is effective. Furthermore, if the hot-rolled sheet is subjected to a skin bath to introduce strain to the surface of the steel sheet and then applied, diffusion can be achieved in a short time.

Examples of compounds from Sc to 8s include KzSeOs, K
cTcO3SbC,h, BiC,h, PbCh
, SnCρ2, AsC, Q3, etc., and an aqueous solution or suspension containing one or more of these is used.

Concerns about the above compounds? After coating with IA liquid, etc. and drying it, the hot-rolled sheet 5 is annealed. In order to obtain a texture with good magnetic properties, the ferrite structure of the hot-rolled sheet before cold rolling must be completely reconsolidated. In the case of a silicon steel sheet containing 1 wt% or more of Si, recrystallization during hot rolling and winding is significantly reduced, so the hot rolled sheet must be annealed to completely recrystallize the ferrite structure. Further, in order to form magnetic properties and good texture in the surface diffusion region of 5e-AsZ'2 during final annealing, a diffusion treatment must be performed after coating a compound such as 5e-As. In order to achieve this effect, baking HL17J at a temperature of 750℃ or higher is required.
<Wanted> 2.

In addition, in order to effectively carry out the diffusion reaction of elements such as 5c-As, the atmosphere during annealing of the hot rolled sheet must be a non-oxidizing atmosphere to prevent the oxidation reaction of these compounds. Preferably, a N2-H2 mixed gas or an Ar atmosphere with a concentration of 5% or more per day is preferred.

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

In addition, as a method for obtaining the steel sheet of the present invention, in addition to coating the hot-rolled sheet with a compound as described above, for example, after pickling the hot-rolled sheet, 5e- It is also possible to deposit an element such as As, in which case the element itself is deposited on the surface of the steel sheet.

7 f'z ] 8 [Examples] Example 1 A non-oriented electrical steel sheet was manufactured from a slab having the composition of 5teel A in Table 1 using the following steps and conditions. The structure and magnetic properties of the obtained steel plate are shown in Table 2 along with the manufacturing conditions.

Example 2 Non-oriented electrical steel sheets were manufactured from slabs having compositions 5teel B and 5teel C in Table 1 using the following process and conditions. Table 3 shows the structure and magnetic properties of the obtained steel plate.

o 5teel B 1 Hot rolled sheet - Pickling - 8bCj) 3 Coating - Hot rolled sheet annealing → Cold pressing - Annealing (0.8g/proof) B2. sbcρ3 coating on slab 10 g/r
vf (220mm t) Hot rolled sheet - Pickling □ Hot rolled sheet annealing - Rolling - Annealing 3 Hot rolled sheet - Pickling - Hot rolled board annealing - Cold rolling - 5bCh coating - Annealing (0.8g/rd') B4 : Hot-rolled sheet - Pickling □ Cold pressing - 8bC, h coating → Baking ton (0,
8g/rf) B5: Hot rolled sheet - pickling - hot rolling calcined #1li - cold rolling 1 / annealing 2 6 hot rolling sheet - pickling cold pressing - annealing 5teel C 1 hot rolling sheet - pickling 1 Hot rolled plate annealing - cold pressing - annealing hot rolling conditions 1120℃ heating, 830℃ finishing, 6500C8,
2.1) mmt Hot rolled plate annealing conditions: 800°C xioh, furnace cooling, 75% + 12-25% N2 Final annealing conditions: 900°C x 2 ml+, air cooling, 25% xioh? -75
%N2, plate thickness 0.5mm + 3 Table *○: Main failure, △: Comparative example

[Brief explanation of drawings]

FIG. 1 shows a hot-rolled sheet after pickling, coated with a compound containing the element to be diffused, annealed, cold-pressed, and finally annealed. This figure shows the concentration profile of the dispersion source cable in the direction of the steel plate 1 in the case of 1. Figure 2 shows that Sb is present on the surface of a hot-rolled sheet that has been descaled by pickling.
81) of a steel plate obtained by applying hot-rolled plate annealing, cold pressing and final annealing after applying C, h's suspension'/iJJ liquid and applying lfI.
5 in the same process, including the diffusion 4 region and its sb concentration.
This shows the difference in magnetic property values from a steel sheet obtained without bCL+ coating. 5

Claims (2)

[Claims] (1) The total thickness of both sides of the steel plate is 2 compared to the total thickness of the steel plate.
The alloy composition in a limited surface layer part that is 0% or less and 2 μm or more on one side is C≦0.0050wt%, Si:
1.0 to 4.0 wt%, Al: 0.1 to 2.0 wt%,
N≦0.0030wt%, Se, Te, Sb, Bi, P
B, Sn, and As, one or more elements in total are 0.02 wt% or more, the balance being Fe and unavoidable impurities, and the alloy composition in the remaining inner layer in the thickness direction is C≦0. 0050wt%, Si: 1.0-4.0wt
%, Al: 0.1-2.0wt%, N≦0.0030w
t%, one or more elements among Sc, Te, Sb, Bi, Pb, Sn, and As total 0.003 wt%
Hereinafter, a non-oriented electrical steel sheet with a multilayer structure composed of the balance Fe and unavoidable impurities and excellent magnetic properties will be described. (2) C≦0.0050wt%, Si: 1.0 to 4.0
wt%, Al: 0.1-2.0wt%, N≦0.003
0wt%, Se, Te, Sb, Bi, Pb, Sn, As
The total amount of one or more elements is 0.003w
After hot-rolling an electrical steel slab consisting of t% or less, the balance being Fe and unavoidable impurities, it is wound up at 700°C or less, and after pickling the hot-rolled plate, Se, Te, Sb, Bi, Pb, Sn
, After coating and drying an aqueous solution or suspension of a compound containing one or more of As, the hot-rolled plate was annealed in a non-oxidizing atmosphere, and the final plate thickness was obtained by cold rolling. After final annealing, the alloy composition in a limited surface layer where the total thickness of both sides of the steel plate is 20% or less of the total thickness of the steel plate and 2 μm or more on one side is C≦0.0050.
wt%, Si: 1.0 to 4.0 wt%, Al: 0.1 to
2.0wt%, N≦0.0030wt%, Sc, Tc,
One or more elements among Sb, Bi, Pb, Sn, and As are composed of a total of 0.02 wt% or more, the balance being Fe and unavoidable impurities, and the alloy composition in the inner layer portion of the remaining part in the thickness direction is as follows: C≦0.0050wt%, Si:1.
0 to 4.0 wt%, Al: 0.1 to 2.0 wt%, N≦
0.0030wt%, Se, Te, Sb, Bi, Pb,
Total of one or more elements among Sn and As is 0
．． A method for producing a non-oriented electrical steel sheet with excellent magnetic properties, characterized by producing a non-oriented electrical steel sheet with a multilayer structure composed of 0.003 wt% or less, the balance being Fe and unavoidable impurities.