JP2005298935A - Method for producing non-oriented silicon steel sheet excellent in whole peripheral magnetic characteristic and punch-out workability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-oriented silicon steel sheet excellent in the whole peripheral magnetic characteristic on the surface of the steel sheet and punch-out workability. <P>SOLUTION: In order to improve the whole peripheral magnetic characteristic on the steel surface and the punch-out workability, the alloy components to be added (Si: 0.1% to < 0.8%, Al:0.1%-0.6%, Mn: 0.1%-1.5%, if necessary, P: ≤0.15%) and impurity elements (C, S, N, Ti, V, Zr, Nb, As) are regulated and further, hot-rolled sheet annealing temperature is made to be at ≥Ac<SB>3</SB>transformation temperature and rolling-reduction ratio of cold-rolling is made to be 80%-90%, and the finish annealing is applied at 700°C-850°C for 10 sec to 1 min. In this way, after finish-annealing, ä100} series texture is developed and thus, the magnetic characteristic excellent in the whole periphery on the steel surface can be obtained and the punch-out workability is secured by making ≥0.65 yield ratio after finish-annealing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent magnetic properties used as an iron core material for electrical equipment. The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent workability.

  In recent years, in the fields of electrical machinery, especially rotating machines, medium- and small-sized transformers, electrical components, etc., in which non-oriented electrical steel sheets are used as iron core materials, global power and energy savings and global environmental conservation movements In particular, the demand for higher efficiency and smaller size is increasing. Under such a social environment, naturally, improvement of the performance of non-oriented electrical steel sheets is strongly demanded as an urgent issue. As is well known, many measures have been taken to improve the performance of non-oriented electrical steel sheets.

In terms of iron loss reduction, in general, from the viewpoint of reducing eddy current loss due to an increase in electrical resistance, a method of increasing the content of Si or Al has been taken.
However, this method has a problem that a decrease in magnetic flux density is inevitable. In addition to simply increasing the content of Si or Al, harmless impurities due to high-purity steel such as C, S, N, and chemical treatment such as Ca addition as described in Patent Document 1 Iron loss has also been reduced due to conversion.
Furthermore, measures on the manufacturing process such as a device for finishing annealing as described in Patent Document 2 have been taken.

On the other hand, with regard to increasing the magnetic flux density, treatments in the manufacturing process such as a hot-rolled sheet annealing condition and a cold rolling condition as described in Patent Document 3, and Sn as described in Patent Document 4 A treatment by improving the primary recrystallization texture by adding an alloying element such as Cu or the like has been performed.
However, even if the magnetic properties of the non-oriented electrical steel sheet are improved by the above-described treatment, the steel sheet normally specified in JIS C 2552 is used when used in an electrical device as an iron core of a rotating machine or the like. It is necessary to consider not only the average magnetic characteristics in the rolling direction and the direction perpendicular to the surface of the steel sheet, but also the overall magnetic characteristics in the plate surface of the steel sheet, that is, the average magnetic characteristics in the entire plate surface.
For this purpose, a {100} <0vw> texture is developed in a non-oriented electrical steel sheet, and it has excellent magnetic properties uniformly in all directions from the rolling direction to the vertical direction in the plate surface. It is desirable.
In order to develop such a {100} <0vw> texture in a non-oriented electrical steel sheet, as described in Patent Document 5, the reduction ratio of cold rolling is 85% or more, desirably 90% or more. In addition, there is a method in which the finish annealing is performed for a long time of 2 minutes to 1 hour at 700 to 1200 ° C., and such a high pressure cold rolling and long-time finish annealing are performed. This has resulted in a decrease in production, an increase in manufacturing costs, and problems with equipment constraints, and it has not been put into practical use.
In addition, as described in Patent Document 6 and Patent Document 7, a special manufacturing method such as a rapid solidification method in which molten steel is solidified by a moving and renewed cooling body surface to form a thin strip has also been proposed. Due to equipment constraints and stable productivity, it has not been put into practical use.

On the other hand, even if the magnetic properties of the non-oriented electrical steel sheet are improved by the above-described measures, when used in electrical equipment as an iron core such as a rotating machine, changes in the magnetic properties during processing into the iron core are considered. There is a need to.
In particular, when a non-oriented electrical steel sheet is subjected to punching as an iron core material, the shapes of the punched end face and the crimped part not only affect the core performance, but also affect the laminateability and formability of the iron core.
That is, unless the iron core is formed into a predetermined shape, the material magnetic properties as the non-oriented electrical steel sheet cannot be exhibited.
Japanese Patent Laid-Open No. 03-126845 JP-A-61-231120 Japanese Patent Laid-Open No. 04-325629 Japanese Patent Laid-Open No. 05-140648 Japanese Patent Publication No.51-000942 JP 05-279740 A Japanese Patent Laid-Open No. 05-306438

  SUMMARY OF THE INVENTION In view of the above, the present invention provides a method for obtaining a non-oriented electrical steel sheet having excellent in-plane magnetic properties in a plate surface of a steel sheet, which is desirable as a rotating machine iron core material, and having excellent punchability by a normal manufacturing process. It is.

In the normal manufacturing process of non-oriented electrical steel sheets, the present inventors have obtained a {100} texture, in particular {100} <, by combining hot rolled sheet annealing condition control before cold rolling and cold rolling reduction. 0 vw> The texture was developed, and earnestly researched from the viewpoint of whether a non-oriented electrical steel sheet excellent in all-around magnetic properties of the steel sheet desirable as a rotating machine core material could be obtained.
As a result, a component system having an α-γ transformation is used, and by purifying the steel, hot-rolled sheet annealing is performed at a temperature equal to or higher than the Ac3 transformation point temperature, and a cold rolling reduction rate is appropriately selected. The continuous magnetic annealing can significantly improve the in-plane circumferential magnetic properties of the steel sheet, and by making the yield ratio after finishing annealing 0.65 or more, the punching workability can be improved without impairing the magnetic properties. We have found that it is possible to improve. The present invention has been made based on the above findings, and the gist thereof is as follows.

(1) In mass%,
C: 0.002% or less,
Si: 0.1% or more and less than 0.8%,
Mn: 0.1% or more and 1.5% or less,
S: 0.002% or less,
Al: 0.1% or more and 0.6% or less,
N: 0.002% or less,
Ti: 0.002% or less,
After hot-rolling steel comprising the balance Fe and inevitable impurity elements, hot-rolled sheet annealing is performed at a temperature not lower than the Ac3 transformation point temperature, and the final sheet thickness is obtained by cold rolling with a reduction rate of 80% to 90%. The yield ratio after finish annealing is 0.65 or more by performing finish annealing at 700 ° C or more and 850 ° C or less for 10 seconds or more and 1 minute or less. Non-oriented electrical steel sheet manufacturing method.

(2) The steel is further mass%,
V: 0.003% or less,
Zr: 0.003% or less,
Nb: 0.003% or less,
As: The manufacturing method of the non-oriented electrical steel sheet excellent in the all-around magnetic characteristics and the punching workability according to the above (1), characterized by containing 0.003% or less.

(3) The steel is further excellent in all-round magnetic properties and punching workability according to the above (1) or (2), characterized by containing P: 0.15% or less by mass%. A method for producing a non-oriented electrical steel sheet.

  According to the method of the present invention, it is possible to obtain a non-oriented electrical steel sheet that is excellent in the in-plane circumferential magnetic properties of a steel sheet and excellent in punching workability by a normal manufacturing process. The electrical steel sheet can sufficiently meet the demand in the field of rotating machines and the like in which the magnetic steel sheet is used as its core material, and its industrial value is extremely high.

  Hereinafter, the present invention will be described in detail. First, the reasons for limiting the steel components of the present invention will be described.

  C is a harmful component that increases iron loss and causes magnetic aging, so it is 0.002% or less.

Si is a component that has the effect of reducing iron loss by increasing eddy current loss by increasing electrical resistance as described above, and also improves punching workability by increasing the yield ratio. Also have. In order to exhibit these effects, it is necessary to contain 0.1% or more.
On the other hand, when the content is increased, the magnetic flux density is reduced as described above, and the hardness is increased to deteriorate the punching workability. Also, in the manufacturing process of the non-oriented electrical steel sheet, cold rolling is performed. Therefore, the workability is reduced and the cost is increased.

Mn also has an action of reducing iron loss by increasing electric resistance and reducing eddy current loss. For this purpose, it is necessary to contain 0.1% or more.
However, if the content is increased, the crystal grain growth property at the time of hot-rolled sheet annealing is lowered, and the crystal grain refinement occurs at the time of cooling to the Ac3 transformation point temperature or less after the hot-rolled sheet annealing. The following.

  S inhibits recrystallization and grain growth after hot rolling due to fine precipitation of sulfides such as MnS, coarsening of crystal grain size after hot-rolled sheet annealing, and accompanying hot-rolled sheet texture Therefore, it is set to 0.002% or less.

As described above, Al is also a component having an action of reducing iron loss by increasing electric resistance and reducing eddy current loss as in the case of Si. Moreover, it has the effect | action which accelerates | stimulates the crystal grain growth property at the time of hot-rolled sheet annealing, and especially this effect | action is remarkable when Si content is less than 0.8% as mentioned above. In order to exhibit these effects, it is necessary to contain 0.1% or more.
On the other hand, when the content is increased, the magnetic flux density is lowered, and the in-plane magnetic anisotropy of the steel plate is increased, and the in-plane magnetic properties in the plate surface are deteriorated. Furthermore, the yield ratio is reduced, and the punching workability is deteriorated.

  N inhibits recrystallization and grain growth after hot rolling due to fine precipitation of nitrides such as TiN including AlN, and increases the grain size after hot-rolled sheet annealing and accompanying hot-rolled sheet To prevent randomization of the texture, the content is made 0.002% or less.

Ti raises the recrystallization temperature and delays the recrystallization and the subsequent grain growth during annealing in the manufacturing process of the non-oriented electrical steel sheet.
In addition, a {111} texture that is undesirable for the magnetic properties of the non-oriented electrical steel sheet is developed.
Furthermore, in combination with fine precipitation such as TiN and TiC, the grain size of the hot-rolled sheet after coarsening and the accompanying randomization of the hot-rolled sheet texture are hindered. To do.

  V, Zr, and Nb inhibit the recrystallization and grain growth after hot rolling due to the fine precipitation of carbides and nitrides such as VN and VC, and increase the grain size after hot rolling annealing. In order to prevent randomization of the hot-rolled sheet texture that accompanies this, the content is made 0.003% or less.

As itself does not form fine precipitates as described above within the steel component range of the present invention.
However, when As is contained, it promotes fine precipitation of sulfides such as MnS, and inhibits recrystallization and crystal grain growth after hot rolling, and increases the grain size of grains after hot-rolled sheet annealing and In order to prevent randomization of the hot rolled sheet texture accompanying this, the content is made 0.003% or less.

P is a component that has the effect of increasing the yield ratio and improving the punching workability, and is added as necessary. However, as its content increases, the hardness increases excessively, and the steel becomes brittle, and there is no effect. Since the problem arises in the manufacturing process itself of a grain-oriented electrical steel sheet and workability | operativity by a customer, it is 0.15% or less.
Other than the above-described components, Fe and unavoidable impurity elements.

Next, the effect of the combination of the hot-rolled sheet annealing conditions and the cold rolling reduction ratio, which are the features of the present invention, on the magnetic properties will be described.
After hot-rolling the steel slab having the components shown in Table 1 to a thickness of 3.0 mm, it is subjected to hot-rolled sheet annealing under the annealing conditions shown in Table 2, and the cold rolling reduction ratio is changed, at 750 ° C. for 20 seconds. After finishing annealing, Epstein samples were taken at different angles (rolling direction, 22.5 degree direction, 45 degree direction, 67.5 degree direction, perpendicular to the rolling direction), and magnetic properties (magnetic flux density: B50) Was measured. The measurement results are also shown in Table 2.

If hot-rolled sheet annealing is performed at a temperature above the Ac3 transformation temperature and the rolling reduction ratio of the cold rolling is selected appropriately, short-term continuous finishing annealing at 750 ° C for 20 seconds will significantly improve the in-plane magnetic properties of the steel sheet. I understand that I can do it.
In this case, the grain size coarsening and texture randomization after hot-rolled sheet annealing are promoted, and the {100} <0vw> system assembly after finish annealing due to a synergistic effect with the cold rolling reduction control It is presumed that the development of the structure is promoted, and it contributes to the remarkable improvement in the magnetic properties of the entire circumference of the steel sheet.

By the way, even if the in-plane magnetic properties in the plate surface of the non-oriented electrical steel sheet are improved as described above, when used in an electrical device as an iron core of a rotating machine or the like, the magnetic characteristics are deteriorated during processing to the iron core. Cannot exhibit its material properties. In particular, when the end face is drooped at the time of punching, caulking is insufficient when the punched steel sheet is laminated and caulked on the iron core, or caulking itself becomes difficult.
Furthermore, the roundness of the punched steel sheet is impaired, and a problem occurs when the shaft of the rotating machine is inserted. In order to avoid these problems, it is effective to consider the yield ratio as an index for adjusting the elementary process from the start to the completion of plastic working during punching.

For this purpose, the yield ratio needs to be 0.65 or more. When the yield ratio is less than 0.65, during the punching process of the non-oriented electrical steel sheet, the elongation from the start of plastic deformation to the breakage increases, and it is also affected by the anisotropy of the mechanical properties. It becomes easier and causes end face sag and poor roundness during punching.
No. above. Table 3 shows the punching workability and magnetic properties (magnetic flux density: B50) when the yield ratio is changed by changing the finish annealing temperature after cold rolling under the manufacturing conditions of No. 5.
The punching workability was evaluated by punching a ring sample (outer diameter φ125 mm, inner diameter φ100 mm) in which the iron core of the rotating machine was simply formed. It can be seen that when the yield ratio is 0.65 or more, good punching workability can be obtained.

  As described above, the feature of the present invention is that the combination of the hot-rolled sheet annealing conditions before cold rolling and the reduction ratio of cold rolling enables a short-time continuous finish annealing, and the in-plane circumferential magnetic properties and punching of the steel sheet. The object is to produce a non-oriented electrical steel sheet excellent in workability.

The hot-rolled sheet annealing temperature needs to be higher than the Ac3 transformation point temperature. If the hot-rolled sheet annealing temperature is less than the Ac3 transformation temperature, the grain size coarsening and texture randomization are not promoted after the hot-rolled sheet annealing, that is, before cold rolling, and even if the rolling reduction of the cold rolling is controlled. The all-around magnetic properties of the steel sheet cannot be improved.
In addition, if it is impurity element content of the steel prescribed | regulated to this invention, if it is more than hot-rolled sheet annealing conditions, ie, Ac3 transformation point temperature, annealing temperature and time will be in the normal manufacturing-process range of a non-oriented electrical steel sheet. In particular, by selecting appropriately under short-time annealing conditions of less than 2 minutes, it is possible to easily promote the grain size coarsening and texture randomization after the hot-rolled sheet annealing.

  The rolling reduction of cold rolling is 80% or more and 90% or less. If it is less than 80%, the magnetic anisotropy becomes large and the circumferential magnetic characteristics are not improved. On the other hand, if it exceeds 90%, the magnetic anisotropy decreases, but a {111} texture unfavorable for the magnetic properties of the non-oriented electrical steel sheet develops and the magnetic flux density decreases.

The finish annealing is 700 ° C. or more and 850 ° C. or less and 10 seconds or more and 1 minute or less. If it is less than 700 degreeC, the primary recrystallization after cold rolling will become incomplete, and the perimeter magnetic characteristic of a steel plate will not improve. On the other hand, if it exceeds 850 ° C., the yield ratio becomes less than 0.65, and the punching workability deteriorates.
This is because, when the yield ratio is less than 0.65, when the non-oriented electrical steel sheet is punched, the elongation from the start of the plastic deformation to the fracture increases, and the anisotropy of the mechanical properties This is because it is easily affected and causes end face sag and roundness failure during punching.
Furthermore, although the magnetic anisotropy is reduced, a {111} texture that is undesirable for the magnetic properties of the non-oriented electrical steel sheet is likely to develop, and the magnetic flux density of the steel sheet is reduced.
If it is less than 10 seconds, the grain size is poor and the magnetic flux density of the steel sheet is lowered and the iron loss is increased. On the other hand, if it exceeds 1 minute, the effect is saturated, and the productivity is lowered and the manufacturing cost is increased.

  In addition, the steel having a chemical component characterized by the present invention is melted in a converter or an electric furnace, and is formed into a slab by continuous rolling or ingot rolling after ingot forming, and then after the above hot rolling. Processing is performed.

Steels A and B having the components shown in Table 4 were hot-rolled to 1.3 mm thickness, 2.4 mm thickness, and 4.5 mm thickness, respectively, and then subjected to hot-rolled sheet annealing under the conditions shown in Table 5. After cold rolling to a thickness of 35 mm, finish annealing is performed under the conditions shown in Table 5, and then by angle (rolling direction, 22.5 degree direction, 45 degree direction, 67.5 degree direction, perpendicular to the rolling direction) ) Epstein samples were taken and magnetic properties were measured. The measurement results are shown in Table 6.
In addition, the punching workability evaluated by punching a ring sample (outer diameter φ125 mm, inner diameter φ100 mm) is also shown in Table 6.
By this invention, it turns out that the manufacture of the non-oriented electrical steel sheet excellent in the punching workability while being excellent in the in-plate all-around magnetic property of a steel plate is possible.

Steels having the components shown in Table 7 were hot-rolled to a thickness of 1.5 mm, and then subjected to hot-rolled sheet annealing at 1025 ° C. for 45 seconds (Ac3 transformation point: 1007 ° C.), and then cold-rolled to a thickness of 0.20 mm ( Cold rolling reduction ratio: 86.7%), and then subjected to finish annealing at 730 ° C. for 20 seconds, and then by angle (rolling direction, 22.5 degrees direction, 45 degrees direction, 67.5 degrees direction, An Epstein sample was taken in the direction perpendicular to the rolling direction and the magnetic properties were measured. The measurement results are shown in Table 8.
In addition, the punching workability was also evaluated by punching a ring sample (outer diameter φ125 mm, inner diameter φ100 mm).
No. 21 to No. In all cases 28, the yield ratio after finish annealing was 0.68 or more, and good punching workability was exhibited without end sagging.
According to the present invention, it can be seen that it is possible to produce a non-oriented electrical steel sheet that is excellent in the in-plane circumferential magnetic properties of the steel sheet and also excellent in punching workability.

Claims (3)

% By mass
C: 0.002% or less,
Si: 0.1% or more and less than 0.8%,
Mn: 0.1% or more and 1.5% or less,
S: 0.002% or less,
Al: 0.1% or more and 0.6% or less,
N: 0.002% or less,
Ti: 0.002% or less,
After hot-rolling steel comprising the balance Fe and inevitable impurity elements, hot-rolled sheet annealing is performed at a temperature not lower than the Ac3 transformation point temperature, and the final sheet thickness is obtained by cold rolling with a reduction rate of 80% to 90%. The yield ratio after finish annealing is 0.65 or more by performing finish annealing at 700 ° C or more and 850 ° C or less for 10 seconds or more and 1 minute or less. Non-oriented electrical steel sheet manufacturing method. The steel is further mass%,
V: 0.003% or less,
Zr: 0.003% or less,
Nb: 0.003% or less,
The method for producing a non-oriented electrical steel sheet having excellent all-round magnetic characteristics and punching workability according to claim 1, comprising As: 0.003% or less. The non-oriented electrical steel sheet having excellent all-round magnetic properties and punching workability according to claim 1 or 2, wherein the steel further contains P: 0.15% or less in terms of mass%. Production method.