HK1193849B - Non-oriented electromagnetic steel sheet, method for producing same, laminate for motor iron core, and method for producing said laminate - Google Patents

Description

Non-oriented electromagnetic steel sheet, method for producing same, laminate for motor core, and method for producing same

Technical Field

The present invention relates to a non-oriented electrical steel sheet suitable for an iron core material of an electrical device, a method for manufacturing the same, and the like.

Background

In recent years, motors that rotate at high speed and have a relatively large capacity have been increasing as drive motors for electric vehicles, hybrid vehicles, and the like. Therefore, the core material used for the drive motor is required to have a low core loss in the range of several 100Hz to several kHz, which is higher than the commercial frequency. The core used for the rotor is also required to have a required mechanical strength so as to be able to withstand centrifugal force and stress fluctuation. Such a demand may be for a core material used for a member other than a drive motor of an automobile.

Conventionally, techniques have been proposed to reduce iron loss and/or improve strength (patent documents 1 to 12).

However, these techniques have difficulty in achieving both of reduction of iron loss and improvement of strength. In addition, it is practically difficult to manufacture a non-oriented electrical steel sheet.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. H02-008346

Patent document 2: japanese laid-open patent publication No. H06-330255

Patent document 3: japanese patent laid-open publication No. 2006 and 009048

Patent document 4: japanese patent laid-open publication No. 2006-070269

Patent document 5: japanese laid-open patent publication No. 10-018005

Patent document 6: japanese laid-open patent publication No. 2004-084053

Patent document 7: japanese laid-open patent publication No. 2004-183066

Patent document 8: japanese patent laid-open publication No. 2007-039754

Patent document 9: japanese laid-open patent publication No. 10-88298

Patent document 10: international publication No. 2009/128428

Patent document 11: japanese patent laid-open publication No. 2003-105508

Patent document 12: japanese laid-open patent publication No. 11-229094

Disclosure of Invention

Problems to be solved by the invention

The invention aims to: provided are a non-oriented electrical steel sheet and a method for manufacturing the same, which can achieve both reduction of iron loss and improvement of strength.

Means for solving the problems

The present invention has been made to solve the above problems, and the gist thereof is as follows.

(1) A non-oriented electrical steel sheet characterized by: it comprises, in mass%

C: more than 0.01% and not more than 0.05%,

Si：2.0%～4.0%、

Mn: 0.05% to 0.5%, and

Al：0.01%～3.0%，

and further contains at least one selected from the group consisting of Ti, V, Zr and Nb,

the remainder being made up of Fe and unavoidable impurities;

when the contents (% by mass) of Ti, V, Zr, Nb and C are represented by [ Ti ], [ V ], [ Zr ], [ Nb ], [ C ], respectively, the value of parameter Q represented by "Q ═ ([ Ti ]/48+ V ]/51+ Zr ]/91+ Nb ]/93)/([ C ]/12)" is 0.9 to 1.1;

the parent phase of the metallic structure is a ferrite phase;

the metal structure does not contain an unrecrystallized structure;

the average grain diameter of ferrite grains constituting the ferrite phase is 10 to 200 μm;

in the ferrite grains, precipitates containing at least one element selected from the group consisting of Ti, V, Zr and Nb are contained at 10 particles/μm³The above density exists;

the precipitates have an average particle diameter of 0.002 to 0.2. mu.m.

(2) The non-oriented electrical steel sheet according to item (1) above, characterized in that: further contains at mass% a component selected from

N：0.001%～0.004%、

Cu: 0.5% to 1.5%, and

sn: 0.05-0.5% of at least one.

(3) The non-oriented electrical steel sheet according to the above (1) or (2), characterized in that: the precipitates are at least one selected from the group consisting of carbides, nitrides and carbonitrides.

(4) A method for manufacturing a non-oriented electrical steel sheet, comprising:

a step of hot rolling the slab heated to 1100 to 1330 ℃ to obtain a hot-rolled steel sheet,

a step of cold-rolling the hot-rolled steel sheet to obtain a cold-rolled steel sheet, and

a step of subjecting the cold-rolled steel sheet to final annealing at a temperature of 850 to 1100 ℃;

the slab comprises, in mass%

C: more than 0.01% and not more than 0.05%,

Si：2.0%～4.0%、

Mn: 0.05% to 0.5%, and

Al：0.01%～3.0%，

and further contains at least one selected from the group consisting of Ti, V, Zr and Nb,

the remainder being made up of Fe and unavoidable impurities;

when the contents (% by mass) of Ti, V, Zr, Nb and C are represented by [ Ti ], [ V ], [ Zr ], [ Nb ], [ C ], respectively, the value of parameter Q represented by "Q ([ Ti ]/48 < V >/51 < Zr ]/91 < Nb ]/93)/([ C ]/12)" is 0.9 to 1.1.

(5) The method for producing a non-oriented electrical steel sheet according to item (4), wherein: the slab further contains a component selected from the group consisting of

N：0.001%～0.004%、

Cu: 0.5% to 1.5%, and

sn: 0.05-0.5% of at least one.

(6) The method for producing a non-oriented electrical steel sheet according to the item (4) or (5), wherein: the cold rolling method includes a step of hot-rolling and annealing the hot-rolled steel sheet before the step of cold rolling.

(7) A laminated body for a motor core, characterized in that:

a plurality of non-oriented magnetic steel sheets laminated to each other;

the non-oriented electrical steel sheet contains, in mass%

C: more than 0.01% and not more than 0.05%,

Si：2.0%～4.0%、

Mn: 0.05% to 0.5%, and

Al：0.01%～3.0%，

and further contains at least one selected from the group consisting of Ti, V, Zr and Nb,

the remainder being made up of Fe and unavoidable impurities;

when the contents (% by mass) of Ti, V, Zr, Nb and C are represented by [ Ti ], [ V ], [ Zr ], [ Nb ], [ C ], respectively, the value of parameter Q represented by "Q ═ ([ Ti ]/48+ V ]/51+ Zr ]/91+ Nb ]/93)/([ C ]/12)" is 0.9 to 1.1;

the parent phase of the metallic structure is a ferrite phase;

the metal structure does not contain an unrecrystallized structure;

the average grain diameter of ferrite grains constituting the ferrite phase is 10 to 200 μm;

in the ferrite grains, precipitates containing at least one element selected from the group consisting of Ti, V, Zr and Nb are contained at 10 particles/μm³The above density exists;

the precipitates have an average particle diameter of 0.002 to 0.2. mu.m.

(8) The laminated body for a motor core according to the above (7), characterized in that: the non-oriented electrical steel sheet further contains, in mass%, a material selected from the group consisting of

N：0.001%～0.004%、

Cu: 0.5% to 1.5%, and

sn: 0.05-0.5% of at least one.

(9) The laminated body for a motor core according to the above (7) or (8), wherein: the precipitates are at least one selected from the group consisting of carbides, nitrides and carbonitrides.

(10) A method for manufacturing a laminated body for a motor core, comprising:

a step of laminating a plurality of non-oriented electromagnetic steel sheets to each other to obtain a laminate, and

annealing the laminate under the conditions that the soaking temperature is 400-800 ℃, the soaking time is 2 minutes-10 hours, and the average cooling rate from the soaking temperature to 300 ℃ is 0.0001 ℃/s-0.1 ℃/s;

the non-oriented electrical steel sheet contains, in mass%

C: more than 0.01% and not more than 0.05%,

Si：2.0%～4.0%、

Mn: 0.05% to 0.5%, and

Al：0.01%～3.0%，

and further contains at least one selected from the group consisting of Ti, V, Zr and Nb,

the remainder being made up of Fe and unavoidable impurities;

when the contents (% by mass) of Ti, V, Zr, Nb and C are represented by [ Ti ], [ V ], [ Zr ], [ Nb ], [ C ], respectively, the value of parameter Q represented by "Q ═ ([ Ti ]/48+ V ]/51+ Zr ]/91+ Nb ]/93)/([ C ]/12)" is 0.9 to 1.1;

the parent phase of the metallic structure is a ferrite phase;

the metal structure does not contain an unrecrystallized structure;

the average grain diameter of ferrite grains constituting the ferrite phase is 10 to 200 μm;

in the ferrite grains, precipitates containing at least one element selected from the group consisting of Ti, V, Zr and Nb are contained at 10 particles/μm³The above density exists;

the precipitates have an average particle diameter of 0.002 to 0.2. mu.m.

(11) The method for manufacturing a laminated body for a motor core according to the above (10), characterized in that: the non-oriented electrical steel sheet further contains, in mass%, a material selected from the group consisting of

N：0.001%～0.004%、

Cu: 0.5% to 1.5%, and

sn: 0.05-0.5% of at least one.

(12) The method for manufacturing a laminated body for a motor core according to the above (10) or (11), wherein: the precipitates are at least one selected from the group consisting of carbides, nitrides and carbonitrides.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the composition and structure of the non-oriented electrical steel sheet are appropriately defined, and thus both reduction of iron loss and improvement of strength can be achieved.

Detailed Description

First, a non-oriented electrical steel sheet and a method for manufacturing the same according to an embodiment of the present invention will be described.

The non-oriented electrical steel sheet of the present embodiment has a predetermined composition, the matrix phase of the metallic structure is a ferrite phase, and the metallic structure does not contain a non-recrystallized structure. The ferrite grains constituting the ferrite phase have an average grain size of 10 to 200 [ mu ] m, and precipitates containing at least one element selected from the group consisting of Ti, V, Zr and Nb are contained in the ferrite grains at 10 particles/[ mu ] m³The precipitates have the above density, and the average grain size of the precipitates is 0.002 to 0.2. mu.m. With this configuration, both reduction of iron loss and improvement of strength can be achieved. As a result, the efficiency of the motor can be greatly improved.

In the method for producing a non-oriented electrical steel sheet according to the present embodiment, a slab heated to 1100 to 1330 ℃ and having a predetermined composition is hot-rolled to obtain a hot-rolled steel sheet. Subsequently, the hot-rolled steel sheet is cold-rolled to obtain a cold-rolled steel sheet. Subsequently, the cold-rolled steel sheet is subjected to final annealing.

Here, the composition of the non-oriented electrical steel sheet will be described. Hereinafter, "%" as a content unit means "% by mass". Further, regarding the composition of the slab, since the non-oriented electrical steel sheet follows the slab, the composition of the non-oriented electrical steel sheet described here is the composition of the slab used in the production thereof. The non-oriented electrical steel sheet according to the present embodiment includes, for example, C: more than 0.01% and less than 0.05%, Si: 2.0% -4.0%, Mn: 0.05 to 0.5% and Al: 0.01 to 3.0% by weight, and further contains at least one selected from Ti, V, Zr and Nb. The balance of the non-oriented electrical steel sheet is composed of Fe and unavoidable impurities, and when the contents (% by mass) of Ti, V, Zr, Nb, and C are represented by [ Ti ], [ V ], [ Zr ], [ Nb ], [ C ], respectively, the value of parameter Q represented by "Q ═ ([ Ti ]/48+ V ]/51+ Zr ]/91+ Nb ]/93)/([ C ]/12)" is 0.9 to 1.1.

< C: more than 0.01% and not more than 0.05% >

C forms fine precipitates with Ti, V, Zr and Nb. The fine precipitates contribute to the improvement of the steel strength. If the C content is 0.01% or less, precipitates of such an amount that the strength is sufficiently improved cannot be obtained. If the C content exceeds 0.05%, precipitates tend to be coarse. Coarse precipitates hardly contribute to the improvement of strength. Further, if the precipitates are precipitated in a coarse manner, the iron loss is likely to deteriorate. Therefore, the C content is set to be more than 0.01% and 0.05% or less. The C content is preferably 0.02% or more, and also preferably 0.04% or less.

＜Si：2.0%～4.0%＞

Si increases the resistivity of steel and reduces the core loss. If the Si content is less than 2.0%, the effect cannot be sufficiently obtained. If the Si content exceeds 4.0%, the steel is embrittled and rolling becomes difficult. Therefore, the Si content is set to 2.0% to 4.0%. The Si content is preferably 3.5% or less.

＜Mn：0.05%～0.5%＞

Like Si, Mn increases the resistivity of steel to reduce the iron loss. In addition, Mn coarsens sulfides to make them harmless. If the Mn content is less than 0.05%, these effects cannot be sufficiently obtained. If the Mn content exceeds 0.5%, the magnetic flux density decreases, and cracks are likely to occur during cold rolling. In addition, the cost increase becomes significant. Therefore, the Mn content is set to 0.05% to 0.5%. The Mn content is preferably 0.1% or more, and also preferably 0.3% or less.

＜Al：0.01%～3.0%＞

Like Si, Al increases the resistivity of steel and reduces the iron loss. In addition, Al also functions as a deoxidizing material. If the Al content is less than 0.01%, these effects cannot be sufficiently obtained. If the Al content exceeds 3.0%, the steel is embrittled and rolling becomes difficult. Therefore, the Al content is set to 0.01% to 3.0%. The Al content is preferably 0.3% or more, and also preferably 2.0% or less.

＜Ti、V、Zr、Nb＞

Ti, V, Zr and Nb form fine precipitates with C and/or N. The precipitates contribute to the improvement of the strength of the steel. If the value of the parameter Q is less than 0.9, C is excessive relative to Ti, V, Zr, and Nb, and thus the tendency of C to exist in a solid solution state in the steel sheet after the final annealing is increased. If C is present in a solid solution state, magnetic aging is likely to occur. If the value of parameter Q exceeds 1.1, C is insufficient for Ti, V, Zr and Nb, so that it is difficult to obtain fine precipitates and a desired strength cannot be obtained. Therefore, the value of the parameter Q is set to 0.9 to 1.1. The value of the parameter Q is preferably 0.95 or more, and also preferably 1.05 or less.

The non-oriented electrical steel sheet according to the present embodiment may further include a metal selected from the group consisting of N: 0.001-0.004%, Cu: 0.5% -1.5% and Sn: 0.05-0.5% of at least one.

＜N：0.001%～0.004%＞

N and C form fine precipitates in the same manner as Ti, V, Zr and Nb. The fine precipitates contribute to the improvement of the steel strength. If the N content is less than 0.001%, precipitates cannot be obtained in such an amount that further improvement in strength is sufficient. Therefore, the N content is preferably 0.001% or more. If the N content exceeds 0.004%, the precipitates tend to be coarse. Therefore, the N content is set to 0.004% or less.

＜Cu：0.5%～1.5%＞

The inventor finds that: when Cu is contained in the steel, precipitates containing at least one element selected from Ti, V, Zr and Nb are likely to be finely precipitated. The fine precipitates contribute to the improvement of the steel strength. If the Cu content is less than 0.5%, the effect cannot be sufficiently obtained. Therefore, the Cu content is preferably 0.5% or more. Further, the Cu content is more preferably 0.8% or more. If the Cu content exceeds 1.5%, the steel is easily embrittled. Therefore, the Cu content is set to 1.5% or less. The Cu content is also preferably 1.2% or less.

The reason why the precipitates are finely precipitated in the case where Cu is contained in steel is not clearly understood, but the present inventors presume that the reason is: a local concentration distribution of Cu is generated in the matrix, and this becomes a precipitation site of carbide. Therefore, Cu may not be precipitated when the above-mentioned precipitates are precipitated. On the other hand, the precipitates of Cu contribute to the improvement of the strength of the non-oriented electrical steel sheet. Therefore, Cu can be precipitated.

＜Sn：0.05%～0.5%＞

The inventors have also found that: if Sn is contained in the steel, precipitates containing at least one element selected from Ti, V, Zr and Nb are likely to be finely precipitated. The fine precipitates contribute to the improvement of the steel strength. If the Sn content is less than 0.05%, the effect cannot be sufficiently obtained. Therefore, the Sn content is preferably 0.05% or more. Further, the Sn content is more preferably 0.08% or more. If the Sn content exceeds 0.5%, the steel is easily embrittled. Therefore, the Sn content is set to 0.5% or less. The Sn content is also preferably 0.2% or less.

< other ingredients >

Ni may be contained in an amount of 0.5 to 5% and P may be contained in an amount of 0.005 to 0.1%. Ni and P contribute to solid solution hardening of the steel sheet and the like.

Next, the metal structure of the non-oriented electrical steel sheet will be described.

As described above, the matrix phase (matrix) of the metal structure of the non-oriented electrical steel sheet according to the present embodiment is a ferrite phase, and the non-recrystallized structure is not included in the metal structure. Since the unrecrystallized structure on the one hand increases the strength and on the other hand significantly deteriorates the iron loss. In addition, if the average grain size of ferrite grains constituting the ferrite phase is less than 10 μm, the hysteresis loss increases. If the average grain size of ferrite grains exceeds 200 μm, the effect of fine grain hardening is significantly reduced. Therefore, the average grain size of the ferrite grains is set to 10 μm to 200 μm. The average grain size of the ferrite grains is preferably 30 μm or more, and also preferably 100 μm or less. The average grain size of ferrite grains is more preferably 60 μm or less.

In the present embodiment, precipitates containing at least one element selected from Ti, V, Zr, and Nb exist in ferrite grains. The smaller the precipitates are, and the higher the number density of the precipitates is, the higher the strength can be obtained. Further, the size of the precipitates is also important from the viewpoint of magnetic properties. For example, when the diameter of the precipitates is smaller than the thickness of the magnetic domain wall, deterioration (increase) of hysteresis loss due to pinning in moving the magnetic domain wall can be prevented. If the average grain size of the precipitates exceeds 0.2. mu.m, these effects cannot be sufficiently obtained. Therefore, the average grain size of the precipitates is set to 0.2 μm or less. The average particle diameter is preferably 0.1 μm or less, more preferably 0.05 μm or less, and still more preferably 0.01 μm or less.

The theoretical thickness of a magnetic domain wall of pure iron is estimated from exchange energy and anisotropy energy to be about 0.1 μm, but the actual thickness of a magnetic domain wall varies due to changes in the orientation in which the magnetic domain wall is formed. In addition, when an element other than Fe is contained, as in the non-oriented electrical steel sheet, the thickness of the magnetic domain wall is also affected by the type, amount, and the like of the element. From this viewpoint, it is considered that the average grain size of precipitates of 0.2 μm or less is appropriate.

If the average grain size of the precipitates is less than 0.002 μm (2 nm), the effect of increasing the mechanical strength is saturated. Further, it is difficult to control the average grain size of the precipitates to be less than 0.002. mu.m. Therefore, the average grain size of the precipitates is set to 0.002 μm or more.

Further, the higher the number density of precipitates, the higher the strength can be obtained, and if the number density of precipitates in ferrite grains is less than 10 precipitates/μm³It is difficult to obtain a desired strength. Therefore, the number density of precipitates was set to 10 precipitates/μm³The above. The number density is preferably 1000 pieces/. mu.m³More preferably 10000/mum³Above, it is more preferably 100000 pieces/. mu.m³Above, it is more preferably 1000000 pieces/. mu.m³The above.

Next, a method for producing a non-oriented electrical steel sheet will be described. In the present embodiment, a hot-rolled steel sheet is obtained by hot-rolling a slab heated to a temperature of 1100 to 1330 ℃ as described above. Subsequently, the hot-rolled steel sheet is cold-rolled to obtain a cold-rolled steel sheet. Subsequently, the cold-rolled steel sheet is subjected to final annealing.

In hot rolling, precipitates containing Ti, V, Zr, and/or Nb contained in a slab are temporarily dissolved by heating, and in the subsequent cooling process, precipitates containing Ti, V, Zr, and/or Nb are finely precipitated. If the heating temperature is less than 1100 ℃, it is difficult to sufficiently dissolve precipitates containing Ti, V, Zr, and/or Nb. If the heating temperature exceeds 1330 ℃, the slab may be deformed or slag may be generated during heating. Therefore, the heating temperature is set to 1100 ℃ to 1330 ℃. The heating temperature is preferably set to 1150 ℃ or higher, and also preferably 1300 ℃ or lower.

In the hot rolling, for example, rough rolling and finish rolling are performed. The finish temperature (finish rolling temperature) of the finish rolling is preferably set to 750 to 850 ℃, and the temperature (coiling temperature) at coiling after the finish rolling is preferably set to 600 ℃ or less. These are all for precipitating precipitates containing Ti, V, Zr and/or Nb as finely as possible.

The thickness of the hot-rolled steel sheet is not particularly limited. However, it is not easy to make the thickness of the hot rolled steel sheet less than 1.6mm, and there is a reduction in productivity. On the other hand, if the thickness of the hot-rolled steel sheet is 2.7mm, the reduction ratio may need to be excessively increased in the subsequent cold rolling. When the reduction ratio in cold rolling is too high, the texture of the non-oriented electrical steel sheet may deteriorate, and the magnetic properties (magnetic flux density, iron loss) may deteriorate. Therefore, the thickness of the hot-rolled steel sheet is preferably set to 1.6mm to 2.7 mm.

The cold rolling may be performed only 1 time, or may be performed 2 or more times with intermediate annealing interposed therebetween. The final reduction in cold rolling is preferably set to 60% to 90%. This is because the metal structure (texture) of the non-oriented electrical steel sheet after the final annealing is further improved, and a high magnetic flux density and a low iron loss are obtained. When the intermediate annealing is performed, the temperature is preferably set to 900 to 1100 ℃. This is to make the metal structure more favorable. The final reduction ratio is more preferably 65% or more, and still more preferably 82% or less.

The soaking temperature of the final annealing is preferably set to 850 ℃ or higher, and the soaking time is preferably set to 20 seconds or longer. This is because the average grain size of ferrite grains of the non-oriented electrical steel sheet is 10 μm or more, and thus a more preferable average grain size is obtained.

Further, if the soaking temperature of the final annealing exceeds 1100 ℃, the following tendency is enhanced: precipitates containing Ti, V, Zr, and/or Nb which are precipitated finely are dissolved in a cold-rolled steel sheet, and then are precipitated not within crystal grains but in crystal grain boundaries. Therefore, the soaking temperature of the final annealing is preferably set to 1100 ℃. Further, if the soaking time exceeds 2 minutes, the decrease in productivity becomes significant. Therefore, the soaking time is preferably set to 2 minutes or less.

Before cold rolling, hot rolled sheet annealing, which is annealing of hot rolled steel sheet, may be performed. By performing appropriate hot-rolled sheet annealing, the texture of the non-oriented electrical steel sheet is more preferable, and a more excellent magnetic flux density can be obtained. In the case where the soaking temperature of the hot-rolled sheet annealing is less than 850 ℃ and the soaking time is less than 30 seconds, it is difficult to make the texture more preferable. If the soaking temperature exceeds 1100 ℃, the following tendency is enhanced: precipitates containing Ti, V, Zr and/or Nb, which are precipitated in a fine manner, are dissolved in a hot-rolled steel sheet and then precipitated not in the grains but in the grain boundaries. If the soaking time exceeds 5 minutes, the decrease in productivity becomes significant. Therefore, the soaking temperature in the hot-rolled sheet annealing is preferably set to 850 to 1100 ℃, and the soaking time is preferably set to 30 seconds to 5 minutes.

Thus, the non-oriented electrical steel sheet according to the present embodiment can be manufactured. Further, the non-oriented electrical steel sheet thus manufactured has the above-described metal structure, and can achieve high strength and low iron loss. That is, the above precipitates are generated during hot rolling, and recrystallization occurs during final annealing to generate the above ferrite phase. After the final annealing, an insulating film may be formed as necessary.

Next, a laminated body for a motor core, which is formed using the non-oriented electrical steel sheet of the present embodiment, will be described.

The laminated body for a motor core includes a plurality of non-oriented electrical steel sheets according to the present embodiment. The laminated body for a motor core can be obtained, for example, by the following method: a plurality of non-oriented electrical steel sheets are formed into a desired shape by punching or the like, and then fixed by lamination, caulking or the like. Since the non-oriented electrical steel sheet according to the present embodiment is included, the laminated body for a motor core has low iron loss and high mechanical strength.

The laminated body for the motor core may be formed after the fixing is completed. After the fixation, annealing may be performed under conditions of a soaking temperature of 400 to 800 ℃, a soaking time of 2 minutes to 10 hours, and an average cooling rate from the soaking temperature to 300 ℃ of 0.0001 ℃/sec to 0.1 ℃/sec, and the annealing may be completed. By performing such annealing, the strength can be further improved by precipitation of precipitates.

When the soaking temperature of the annealing is less than 400 ℃ and the soaking time is less than 2 minutes, it is difficult to sufficiently precipitate precipitates. When the soaking temperature exceeds 800 ℃ and the soaking time exceeds 10 hours, the energy consumption amount increases, or the accessory equipment is easily damaged, and the increase in cost becomes significant. Further, the precipitates are coarse and difficult to sufficiently increase the strength. Therefore, the soaking temperature is preferably set to 400 to 800 ℃, and the soaking time is preferably set to 2 minutes to 10 hours. The soaking temperature is more preferably 500 ℃ or higher, and the soaking time is more preferably 10 minutes or longer. When the average cooling rate from the soaking temperature to 300 ℃ is less than 0.0001 ℃/sec, carbide is likely to be roughly precipitated. If the average cooling rate exceeds 0.1 ℃/sec, it becomes difficult to sufficiently precipitate precipitates. Therefore, the average cooling rate from the soaking temperature to 300 ℃ is preferably set to 0.0001 ℃/sec to 0.1 ℃/sec.

Examples

Next, experiments performed by the present inventors will be described. The conditions and the like of these experiments are examples employed for confirming the feasibility and the effects of the present invention, and the present invention is not limited to these examples.

(Experimental example 1)

First, steels of various compositions shown in table 1 were melted by a vacuum melting method. Next, the obtained slab was heated at 1250 ℃ for 1 hour. Then, the slab heated to 1250 ℃ is hot-rolled to obtain a hot-rolled steel sheet. The thickness of the hot-rolled steel sheet (hot-rolled sheet) was set to 2.0 mm. Subsequently, the hot-rolled steel sheet is pickled and then cold-rolled to obtain a cold-rolled steel sheet. The thickness of the cold-rolled steel sheet (cold-rolled sheet) was set to 0.35 mm. Subsequently, the cold-rolled steel sheet is subjected to final annealing. In the final annealing, the soaking temperature was set to 1000 ℃ and the soaking time was set to 30 seconds. Thus, various non-oriented electrical steel sheets are produced. Then, the metal structure of each non-oriented electrical steel sheet was observed. In the observation of the metal structure, for example, the particle diameter was measured (JIS G0552) and the precipitates were observed. In addition, test pieces of JIS5 were cut out from each non-oriented electrical steel sheet, and the mechanical properties were measured. Further, a 55mm × 55mm test piece was cut out from each non-oriented electrical steel sheet, and the magnetic properties thereof were measured by a single-plate magnetic property test method (JIS C2556). As the magnetic properties, the iron loss (W10/400) was measured under the conditions of a frequency of 400Hz and a maximum magnetic flux density of 1.0T. In order to observe the influence of magnetic aging, iron loss (W10/400) was also measured after 1-day aging treatment at 200 ℃. That is, the iron loss (W10/400) before and after the aging treatment was measured for each non-oriented electrical steel sheet. These results are shown in table 2.

TABLE 1

As shown in Table 2, under the conditions of Nos. C1 to C19 within the range of the present invention, tensile strength of 550MPa or more and iron loss (W10/400) of 35W/kg or less were obtained. On the other hand, in the conditions No. d1 to No. d8 deviating from the scope of the present invention, it is difficult to achieve both the tensile strength and the iron loss.

(Experimental example 2)

First, slabs of steels No. a11 and No. a17 shown in table 1 were heated at the temperatures shown in table 3 for 1 hour. Next, the slabs heated to the temperatures shown in table 3 were hot-rolled to obtain hot-rolled steel sheets. The thickness of the hot-rolled steel sheet was set to 2.0 mm. Then, a part (condition No. e 4) of the hot rolled steel sheet was annealed (hot rolled sheet annealing) under the conditions shown in table 3. Subsequently, the hot-rolled steel sheet is pickled and then cold-rolled to obtain a cold-rolled steel sheet. The thickness of the cold-rolled steel sheet was set to 0.35 mm. Subsequently, the cold-rolled steel sheet is subjected to final annealing. In the final annealing, the soaking temperature was set to 1000 ℃ and the soaking time was set to 30 seconds. Thus, various non-oriented electrical steel sheets are produced. Then, each non-oriented electrical steel sheet was evaluated in the same manner as in experimental example 1. The results are also shown in Table 3.

As shown in Table 3, under the conditions No. E1 to No. E6 within the range of the present invention, a tensile strength of 550MPa or more and an iron loss (W10/400) of 35W/kg or less were obtained. On the other hand, in the conditions No. f1 to No. f2 deviating from the scope of the present invention, it is difficult to achieve both the tensile strength and the iron loss.

(Experimental example 3)

First, slabs of steels nos. 11 and 17 shown in table 1 were heated for 1 hour. At this time, the slab heating temperature of steel No. A11 was 1250 ℃ and the slab heating temperature of steel No. A17 was 1150 ℃. Next, the slab heated to 1250 ℃ or 1150 ℃ is hot-rolled to obtain a hot-rolled steel sheet. The thickness of the hot-rolled steel sheet was set to 2.0 mm. Then, the hot-rolled steel sheet is pickled and then cold-rolled to obtain a cold-rolled steel sheet. The thickness of the cold-rolled steel sheet was set to 0.35 mm. Subsequently, the cold-rolled steel sheet is subjected to final annealing. In the final annealing, the soaking temperature was set to 1000 ℃ and the soaking time was set to 30 seconds. Next, an insulating film is formed on the surface of the cold-rolled steel sheet after the final annealing. Thus, various non-oriented electrical steel sheets are produced.

Then, 30 steel sheets having a rolling direction dimension of 300mm and a direction dimension perpendicular to the rolling direction of 60mm were punched out from each of the non-oriented electrical steel sheets. Steel plates of this shape and size are often used in practical motor cores. Then, 30 steel sheets were stacked on each other to obtain a laminated body. Next, each laminate was annealed under the conditions shown in table 4. Next, a steel sheet for testing was extracted from each laminate, and the same evaluation as in experimental example 1 was performed on the steel sheet. That is, the evaluation was performed assuming a laminated body used for the motor core. The results are also shown in Table 4. Here, the comparative example is set to the case where the annealing conditions deviate from the above-described preferable conditions.

As shown in table 4, the tensile strength can be sufficiently improved under the preferable annealing conditions No. g1 to No. g 7. On the other hand, in the conditions No. h1 to No. h6 in which the annealing conditions are out of the preferable ranges, the tensile strength cannot be sufficiently improved, the productivity is lowered, and the iron loss is increased.

The above embodiments are merely concrete examples for carrying out the present invention, and the technical scope of the present invention is not to be construed as being limited by the above embodiments. That is, the present invention can be implemented in various forms without departing from the technical idea or the main feature thereof.

Industrial applicability

The present invention can be applied to, for example, an electrical steel sheet manufacturing industry and an electrical steel sheet utilization industry such as a motor.

Claims (16)

1. A non-oriented electrical steel sheet characterized by:

it comprises, in mass%

C: more than 0.01% and not more than 0.05%,

Si：2.0％～4.0％、

Mn: 0.05% to 0.5%, and

Al：0.01％～3.0％，

and further contains at least one selected from the group consisting of Ti, V, Zr and Nb,

the remainder being made up of Fe and unavoidable impurities;

when the contents of Ti, V, Zr, Nb, and C in mass% are represented as [ Ti ], [ V ], [ Zr ], [ Nb ], [ C ], respectively, the value of parameter Q represented by "Q ═ ([ Ti ]/48+ [ V ]/51+ [ Zr ]/91+ [ Nb ]/93)/([ C ]/12)" is 0.9 to 1.1;

the parent phase of the metallic structure is a ferrite phase;

the metal structure does not contain an unrecrystallized structure;

the average grain diameter of ferrite grains constituting the ferrite phase is 10 to 200 μm;

in the ferrite grains, precipitates containing at least one element selected from the group consisting of Ti, V, Zr and Nb are contained at 10 particles/μm³The above density exists;

the precipitates have an average particle diameter of 0.002 to 0.2. mu.m.

2. The non-oriented electrical steel sheet according to claim 1, wherein: further contains at mass% a component selected from

N：0.001％～0.004％、

Cu: 0.5% to 1.5%, and

sn: 0.05-0.5% of at least one.

3. The non-oriented electrical steel sheet according to claim 1, wherein: the precipitates are at least one selected from the group consisting of carbides, nitrides and carbonitrides.

4. The non-oriented electrical steel sheet according to claim 2, wherein: the precipitates are at least one selected from the group consisting of carbides, nitrides and carbonitrides.

5. A method for manufacturing a non-oriented electrical steel sheet, comprising:

a step of hot rolling the slab heated to 1100 to 1330 ℃ to obtain a hot-rolled steel sheet,

a step of cold-rolling the hot-rolled steel sheet to obtain a cold-rolled steel sheet, and

a step of subjecting the cold-rolled steel sheet to final annealing at a temperature of 850 to 1100 ℃;

the slab comprises, in mass%

C: more than 0.01% and not more than 0.05%,

Si：2.0％～4.0％、

Mn: 0.05% to 0.5%, and

Al：0.01％～3.0％，

and further contains at least one selected from the group consisting of Ti, V, Zr and Nb,

the remainder being made up of Fe and unavoidable impurities;

when the contents of Ti, V, Zr, Nb, and C in mass% are represented as [ Ti ], [ V ], [ Zr ], [ Nb ], [ C ], respectively, the value of parameter Q represented by "Q ═ ([ Ti ]/48+ [ V ]/51+ [ Zr ]/91+ [ Nb ]/93)/([ C ]/12)" is 0.9 to 1.1;

the parent phase of the metallic structure is a ferrite phase;

the metal structure does not contain an unrecrystallized structure;

the average grain diameter of ferrite grains constituting the ferrite phase is 10 to 200 μm;

in the ferrite grains, precipitates containing at least one element selected from the group consisting of Ti, V, Zr and Nb are contained at 10 particles/μm³The above density exists;

the precipitates have an average particle diameter of 0.002 to 0.2. mu.m.

6. The method for producing a non-oriented electrical steel sheet according to claim 5, wherein: the slab further contains a component selected from the group consisting of

N：0.001％～0.004％、

Cu: 0.5% to 1.5%, and

sn: 0.05-0.5% of at least one.

7. The method for producing a non-oriented electrical steel sheet according to claim 5, wherein: the cold rolling method includes a step of hot-rolling and annealing the hot-rolled steel sheet before the step of cold rolling.

8. The method for producing a non-oriented electrical steel sheet according to claim 6, wherein: the cold rolling method includes a step of hot-rolling and annealing the hot-rolled steel sheet before the step of cold rolling.

9. A laminated body for a motor core, characterized in that:

a plurality of non-oriented magnetic steel sheets laminated to each other;

the non-oriented electrical steel sheet contains, in mass%

C: more than 0.01% and not more than 0.05%,

Si：2.0％～4.0％、

Mn: 0.05% to 0.5%, and

Al：0.01％～3.0％，

and further contains at least one selected from the group consisting of Ti, V, Zr and Nb,

the remainder being made up of Fe and unavoidable impurities;

when the contents of Ti, V, Zr, Nb, and C in mass% are represented as [ Ti ], [ V ], [ Zr ], [ Nb ], [ C ], respectively, the value of parameter Q represented by "Q ═ ([ Ti ]/48+ [ V ]/51+ [ Zr ]/91+ [ Nb ]/93)/([ C ]/12)" is 0.9 to 1.1;

the parent phase of the metallic structure is a ferrite phase;

the metal structure does not contain an unrecrystallized structure;

the average grain diameter of ferrite grains constituting the ferrite phase is 10 to 200 μm;

in the ferrite grains, precipitates containing at least one element selected from the group consisting of Ti, V, Zr and Nb are contained at 10 particles/μm³The above density exists;

the precipitates have an average particle diameter of 0.002 to 0.2. mu.m.

10. The laminated body for a motor core according to claim 9, wherein: the non-oriented electrical steel sheet further contains, in mass%, a material selected from the group consisting of

N：0.001％～0.004％、

Cu: 0.5% to 1.5%, and

sn: 0.05-0.5% of at least one.

11. The laminated body for a motor core according to claim 9, wherein: the precipitates are at least one selected from the group consisting of carbides, nitrides and carbonitrides.

12. The laminated body for a motor core according to claim 10, wherein: the precipitates are at least one selected from the group consisting of carbides, nitrides and carbonitrides.

13. A method for manufacturing a laminated body for a motor core, comprising:

a step of laminating a plurality of non-oriented electromagnetic steel sheets to each other to obtain a laminate, and

annealing the laminate under the conditions that the soaking temperature is 400-800 ℃, the soaking time is 2 minutes-10 hours, and the average cooling rate from the soaking temperature to 300 ℃ is 0.0001 ℃/s-0.1 ℃/s;

the non-oriented electrical steel sheet contains, in mass%

C: more than 0.01% and not more than 0.05%,

Si：2.0％～4.0％、

Mn: 0.05% to 0.5%, and

Al：0.01％～3.0％，

and further contains at least one selected from the group consisting of Ti, V, Zr and Nb,

the remainder being made up of Fe and unavoidable impurities;

when the contents of Ti, V, Zr, Nb, and C in mass% are represented as [ Ti ], [ V ], [ Zr ], [ Nb ], [ C ], respectively, the value of parameter Q represented by "Q ═ ([ Ti ]/48+ [ V ]/51+ [ Zr ]/91+ [ Nb ]/93)/([ C ]/12)" is 0.9 to 1.1;

the parent phase of the metallic structure is a ferrite phase;

the metal structure does not contain an unrecrystallized structure;

the average grain diameter of ferrite grains constituting the ferrite phase is 10 to 200 μm;

in the ferrite grains, precipitates containing at least one element selected from the group consisting of Ti, V, Zr and Nb are contained at 10 particles/μm³The above density exists;

the precipitates have an average particle diameter of 0.002 to 0.2. mu.m.

14. The method of manufacturing a laminated body for a motor core according to claim 13, wherein: the non-oriented electrical steel sheet further contains, in mass%, a material selected from the group consisting of

N：0.001％～0.004％、

Cu: 0.5% to 1.5%, and

sn: 0.05-0.5% of at least one.

15. The method of manufacturing a laminated body for a motor core according to claim 13, wherein: the precipitates are at least one selected from the group consisting of carbides, nitrides and carbonitrides.

16. The method of manufacturing a laminated body for a motor core according to claim 14, wherein: the precipitates are at least one selected from the group consisting of carbides, nitrides and carbonitrides.