JPH08165520A - Nonoriented silicon steel sheet excellent in workability and production thereof - Google Patents

Abstract

PURPOSE: To provided a high silicon-containing nonoriented steel sheet excellent in workability and magnetic characteristic by annealing the silicon steel having a specific composition composed on the inner and the outer layers different in Si content after cold-rolling to make the sheet. CONSTITUTION: After forming the surface layer part by casting and solidifying molten steel having <3.0% Si into the inner surface part of a vertical mold, the inner layer part is formed by casting and solidifying the molten steel having 4.0-8.0% Si, and after casting the inner and the outer duplex layer steel ingot, the annealing is executed at >=1000 deg.C to diffuse Si. This steel ingot is hot-rolled to make the hot-rolled steel sheet having the low Si-containing surface layer part at >=5% thickness to one side in both sides and the mixed layer of 0.05-0.5% between the low Si-containing surface layer part and the high Si-containing inner layer part. The C content in the surface layer part and the inner layer part of this hot-rolled steel sheet is <=0.10% and S and N contents are <=0.0040%, respectively and the total content of Al and Ti is 0.0100% in the composition of the steel sheet. The high silicon nonoriented steel sheet composed of the surface layer, mixed layer and inner layer and excellent in the workability and the magnetic characteristic, is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a low surface layer Si and an inner layer high S.
i, a method for producing a non-oriented electrical steel sheet having a mixed layer at a boundary portion and having excellent workability and magnetic properties, which is used for a rotating machine.

[0002]

2. Description of the Related Art Generally, when manufacturing a magnetic steel sheet, an increase in the amount of material Si increases the electrical resistance and reduces the eddy current loss of the product, but it is well known that the workability deteriorates. By the way, what is currently industrialized as a general-purpose product is that the Si content is less than 3.5%.

Therefore, various attempts have been made as means for improving the workability. One of them is a method of covering the surface of a high Si material with a low Si material having good workability. In this method, the surface layer Si is 3% or less, and the inner layer Si is 3.2 to 10.
Japanese Patent Application Laid-Open No. 51-51 describes that a good cold-rolling property / low iron loss non-oriented electrical steel sheet is produced as a starting material for a hot-rolled steel sheet.
No. 77521 gazette, or a high silicon steel sheet having excellent surface properties such as cold rollability and scale layer formation using a steel ingot material having a surface layer Si of less than 1% and an inner layer Si of 1.0 to 7.0%. , And Japanese Patent Application Laid-Open No. 63-114940 relating to the production thereof, and one direction with good magnetic properties using a material in which the silicon concentration in a steel ingot continuously or discontinuously increases from the outer layer to the inner layer. Japanese Patent Application Laid-Open No. 54-127829, which describes a method for producing a magnetic electrical steel sheet, and a surface layer S
i ≦ 3%, inner layer 3% <Si ≦ 7%, and crystal grains <100
> There is a disclosure regarding a silicon steel sheet having excellent magnetic properties in which axes are integrated in a direction perpendicular to the plate surface and a method for manufacturing the same.
No. 140442 is publicly known. However, when the difference in the amount of Si (workability) in the inner surface layer is large, cracks are likely to occur from the boundary portion during cold rolling. This problem is not mentioned in any of the above cases.

On the other hand, as a known example having a mixed region of Si, during the continuous casting, Si or Fe-Si powder is added to the center of the mold by a wire so that the surface layer has low Si and the inner layer has high Si. Japanese Patent Publication Sho 58-3 for manufacturing non-oriented electrical steel sheets
No. 7367 and Japanese Patent Application Laid-Open No. 57-75274 are disclosed, but in both of these methods, the mixing region has a total plate thickness of 1
It is too large as 0% or more, and there is a problem that component separation is insufficient.

In order to solve this problem, the inventors of the present invention, in Japanese Patent Application No. 4-65384, have a mixed region of the inner surface layer Si to prevent cracks that tend to occur from the boundary portion during cold rolling. Provided are a high-silicon-containing non-oriented electrical steel sheet having excellent magnetic properties and good magnetic properties, and a method for producing the same. However, this method is still another step in improving the bending workability of the hot-rolled sheet, and there remains a problem in workability of continuous pickling line threading and reel winding in cold rolling.

[0006]

An object of the present invention relates to the workability of continuous pickling line threading and reel winding in cold rolling when the difference in the amount of Si in the inner surface layer (workability) is large.
It is an object of the present invention to provide a method for producing a non-oriented electrical steel sheet containing high silicon, which has excellent bending properties of a hot rolled sheet and good magnetic properties.

[0007]

As a result of various studies to solve the above-mentioned problems, the present inventors have focused on precipitates and oxidized inclusions and found that there is a deep relationship with the hot-rolled sheet bending workability. Revealed. That is, when the workability of the inner surface layer portion is significantly different, it is possible to prevent the occurrence of cracks in the boundary layer during cold rolling by having a mixed region of the inner surface layer Si. Sex is not improved enough. However, it was found that the bending workability of the hot-rolled sheet was significantly improved by reducing the precipitates and oxidized inclusions of the material extremely.

The present invention is based on such knowledge, and the gist of the present invention is Si: 4.
When producing a non-oriented electrical steel sheet consisting of 0 to 8.0% and the rest generally known components, Si: 3.0% or less and a surface layer portion consisting of the rest generally known non-oriented electrical steel components 5% on one side.
Above, and the mixed layer of the inner surface layer component is 0.05 on one side
% Or more and 5% or less, and a high silicon-containing non-oriented electrical steel sheet excellent in workability in which the content of Al + Ti in the inner surface layer is 0.0100% or less, and a manufacturing method thereof.

[0009]

The present invention will be described in detail below. The relationship between the amount of precipitates and oxidized inclusions of the material and the bending workability of the hot rolled sheet, which is a feature of the present invention, will be described. FIG. 1 shows the relationship between bending workability and material components Al and Ti (inner surface layer average value). As is clear from the figure, the content of Al + Ti is 0.
0100% or less, preferably 0.0050% or less, that is, by significantly refining the material, the bending workability of the hot-rolled sheet was significantly improved. This is in the hot-rolled sheet (both inner surface layer)
It is considered that the precipitation hardening was suppressed by the extremely small amount of Al and Ti nitrides and oxides. However, even in this case, the hot-rolled sheet is preheated (preferably 50% or less) at the time of continuous pickling line passing or reel winding in cold rolling.
The workability is better if the temperature is higher than ℃.

Next, the role of the mixed layer of the inner surface layer components will be described. Usually, when the difference in the amount of Si in the inner surface layer portion is large, that is, when the ductility is remarkably different, cracks occur in the boundary layer during cold rolling. However, even with such a material, when the product plate has the component mixture layer of the inner surface layer in an amount of 0.05% or more, excellent cold rolling property is exhibited without cracking. Further, the effect of improving the punching property (cracking) of the product plate is recognized by this component mixed layer. On the other hand, the reason why the thickness of the component mixture layer of the inner surface layer is limited to 5% or less on the product plate is to ensure sufficient component separation of the inner surface layer. The thickness of this component mixture layer is
It is defined in the Si concentration region that satisfies the following relational expression. CS + 0.2 × (CI-CS) ≦ boundary layer Si concentration ≦ CS + 0.8 × (CI-CS) where CI: inner layer Si concentration maximum value CS: surface layer portion Si concentration minimum value

A material before cold rolling is obtained by covering the surface of a high-Si material, which is the starting material, with a low-Si material having good workability and having a mixed layer of the inner and outer surface layer components of 0.05% or more in the product plate. There are the following methods. (1) A static magnetic field is formed on the entire width of the slab perpendicular to the casting direction,
By supplying molten steel with different Si contents with this as a boundary, the mixed layer of the inner surface layer components is 0.05% or more in the product plate, 5
A continuous steel ingot having a content equivalent to or less than% is obtained. (2) First, after solidifying a portion corresponding to the surface layer or the inner layer, the remaining portion is solidified with different component materials to obtain a multi-layer steel ingot. After that, 1000 in the state of steel ingot or hot rolled sheet
Annealed at a temperature of ℃ or more to diffuse Si and 0.0
A mixed layer of 5% or more and 5% or less of an inner surface layer component is formed. (3) A hot-rolled sheet having a two-layer steel composition and three-layer structure is manufactured by a rolling compression bonding method. At this time, the hot-rolled sheet is annealed at a temperature of 1000 ° C. or more to diffuse Si, and the product sheet is 0.05% or more, 5
% Or less to form a mixed layer of inner surface layer components.

Next, the reasons for limiting the steel components and the manufacturing method after hot rolling will be described. As mentioned above, Al and Ti significantly reduce the precipitates and inclusions, improve the bending workability of the hot-rolled sheet, and have excellent workability in continuous pickling line rolling and reel winding in cold rolling. In order to improve
1 + Ti ≦ 0.010%. The inner layer Si is set to 4.0% or more and 8.0% or less in order to increase the specific resistance and improve the iron loss. The surface layer Si is 3.0% or less in order to prevent cracks on the surface and boundary during cold rolling.

C is preferably 0.1% or less because decarburization annealing may be performed as necessary in the step after cold rolling. However, since C is an element that deteriorates the magnetic properties, if it exceeds 0.005% in the product, magnetic aging occurs and the magnetic properties are significantly deteriorated, so 0.005% or less is more preferable.
Since S and N are elements that generate impurities when the content is high and deteriorate the magnetic characteristics, the upper limit of each is 40 ppm.
Is preferred. It is even better if it is 20 ppm or less.

The steel ingot material as described above is heated and hot rolled. Next, after performing annealing as required, cold rolling is performed once or cold rolling is performed twice or more including intermediate annealing to obtain a product sheet thickness. At this time, in the case of the high-purity steel multi-layer material of the present invention, breakage trouble due to cracking of the hot-rolled sheet during continuous pickling line threading or reel winding during cold rolling is suppressed, and workability is excellent. Then, finish annealing for crystal grain growth is performed at a temperature not higher than the transformation temperature to produce a high silicon-containing non-oriented electrical steel sheet having excellent magnetic properties.

[0015]

【Example】

Example 1 A continuous magnetic field having a multi-layer condition shown in Table 2 was obtained by forming a static magnetic field in the full width of the slab perpendicular to the casting direction and supplying molten steel containing the steel components shown in Table 1 with this as a boundary. Steel ingots A, B, C and D were obtained. Next, these steel ingots are heated and hot-rolled into hot-rolled steel sheets having a thickness of 1.8 mm, and hot-rolled steel sheets are annealed at 950 ° C. for 2 minutes, then preheated to 100 ° C. and cooled to a product thickness of 0.35 mm Rolled. Table 3 shows the evaluation results of the bending workability and cold rollability of the hot rolled sheet.

In the evaluation of the workability, in all of the steel ingots A, B, C and D, there was no cracking during cold rolling, which was good. However, the bending workability of the hot-rolled sheet was good in the case of the steel ingots A, B, and C falling within the scope of the present invention, but the steel ingot D was cracked after a few bending times.

Next, the cold-rolled sheet was subjected to finish annealing at 1050 ° C. for 30 seconds and magnetic measurement was performed. The results, as shown in Table 3, show that the material of the present invention has excellent low iron loss characteristics. The product punchability was good in all cases, with no cracks being observed in the materials of the present invention.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[Example 2] After solidifying a portion corresponding to the surface layer or the inner layer at the casting stage, the remaining portions were solidified with different component materials, and the steel components and the multilayer conditions shown in Tables 4 and 5 were set. Multi-layer steel ingots E, F, G, H-1 and H-2 having the same were obtained. Next, these steel ingots are heated and hot-rolled into a hot-rolled sheet having a thickness of 1.8 mm, and further hot-rolled sheet annealing is performed at 950 ° C. for 2 minutes,
It was preheated to 100 ° C. and cold-rolled to a product thickness of 0.35 mm. Table 6 shows the evaluation results of bending workability and cold rollability of the hot rolled sheet.

In the evaluation of workability, except for steel ingot H-2, E,
In all cases of F, G, and H-1, there was no cracking during cold rolling, which was good. However, the bending workability of the hot-rolled sheet was good in the case of the steel ingots E, F, and G falling within the scope of the present invention, but the steel ingots H-1 and H-2 were cracked at a small number of bendings. I got it.

Next, the cold-rolled sheet was subjected to finish annealing at 1050 ° C. for 30 seconds and magnetic measurement was performed. The results, as shown in Table 6, show that the material of the present invention has excellent low iron loss characteristics. The product punchability was good in all cases, with no cracks being observed in the materials of the present invention.

[0024]

[Table 4]

[0025]

[Table 5]

[0026]

[Table 6]

Example 3 Hot-rolled sheets I, J, K, and L having a three-layer structure of two kinds of steel components shown in Tables 7 and 8 and having a thickness of 1.8 mm were manufactured by a rolling press-bonding method. Further, the hot-rolled sheet was annealed at 950 ° C. for 2 minutes, then preheated to 100 ° C. and cold-rolled to a product thickness of 0.35 mm. Table 9 shows the evaluation results of bending workability and cold rollability of the hot rolled sheet.

In the evaluation of workability, except for steel ingot L-2, I,
In all cases of J, K, and L-1, cracking did not occur during cold rolling, which was good. However, the bending workability of the hot-rolled sheet was good in the case of steel ingots I, J, and K that fall within the scope of the present invention, but cracks occurred in steel ingots L-1 and L-2 with a small number of bends. I got it.

Next, the cold-rolled sheet was subjected to finish annealing at 1050 ° C. for 30 seconds and magnetic measurement was performed. The results, as shown in Table 9, show that the material of the present invention has excellent low iron loss characteristics. The product punchability was good in all cases, with no cracks being observed in the materials of the present invention.

[0030]

[Table 7]

[0031]

[Table 8]

[0032]

[Table 9]

[0033]

EFFECTS OF THE INVENTION According to the present invention, by using a high-purity steel multi-layer material, breakage troubles due to cracking of a hot-rolled sheet at the time of reel winding in continuous pickling line threading or cold rolling are suppressed,
Excellent workability and good workability on the surface of high Si material with low S
Cover with i material and mix the inner surface layer components with the product plate at 0.05
% To 5%, it is possible to manufacture a high-silicon non-oriented electrical steel sheet having good cold workability and product punchability (suppression of cracking) and good magnetic properties.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between bending workability of a hot rolled sheet and material components Al and Ti (inner surface layer average value).

Claims (4)

[Claims] 1. The weight ratio of the inner layer is Si: 4.0 to 8.0.
%, The surface layer has a weight ratio of Si: 3.0% or less and the thickness is 5% or more on one side, and the mixed layer of the inner surface layer component is 0.05% or more and 5% or less on one side. Al on both surface
A high silicon content non-oriented electrical steel sheet excellent in workability, characterized in that the content of + Ti is 0.0100% or less. 2. The weight ratio of the inner layer is Si: 4.0 to 8.0.
%, The surface layer has a weight ratio of Si: 3.0% or less and the thickness is 5% or more on one side, and the mixed layer of the inner surface layer component is 0.05% or more and 5% or less on one side. Al on both surface
A method for producing a high silicon-containing non-oriented electrical steel sheet having excellent workability, which comprises cold rolling and annealing a material having a + Ti content of 0.0100% or less. 3. The weight ratio of the inner layer is Si: 4.0 to 8.0.
%, C: 0.100% or less, and the contents of S and N are 0.0040% or less, respectively, and the surface layer has a weight ratio of Si:
3.0% or less, C: 0.100% or less, and the content of each of S and N is 0.0040% or less, and the thickness thereof is one side 5.
% Or more, and the inner surface layer mixed layer is 0.0 on one side.
5% or more and 5% or less, and the inner surface layer is Al + Ti
Content of 0.0100% or less, respectively, and a high silicon content non-oriented electrical steel sheet excellent in workability. 4. The weight ratio of the inner layer is Si: 4.0 to 8.0.
%, C: 0.100% or less, and the contents of S and N are 0.0040% or less, respectively, and the surface layer has a weight ratio of Si:
3.0% or less, C: 0.100% or less, and the content of each of S and N is 0.0040% or less, and the thickness thereof is one side 5.
% Or more, and the mixed layer of the components of the inner surface layer is 0.05% or more and 5% or less on one surface of the material before cold rolling, and the content of Al + Ti is 0.0100% or less on both the inner surface layers. A method for producing a high-silicon-containing non-oriented electrical steel sheet excellent in workability, which comprises cold rolling and annealing.