JP5025942B2 - Method for producing non-oriented electrical steel sheet - Google Patents

Description

  The present invention provides a method for producing a non-oriented electrical steel sheet that is desirable as a rotating machine core material and has excellent in-plane magnetic properties within the plate surface of the steel sheet.

  Non-oriented electrical steel sheets are used for small stationary devices such as large generators, motors, acoustic equipment and ballasts. There is a strong need for energy and resource saving in recent years, and compressor motors such as air conditioners and refrigerators, as well as drive motors for electric vehicles, are particularly aimed at higher efficiency. These have a magnetic flux density of 1.9% or more of Si + Al. High efficiency non-oriented electrical steel sheets with high iron loss and low iron loss are often used.

  When used in electrical equipment as an iron core such as a rotating machine, the rolling direction (hereinafter referred to as “L direction”) of steel sheets and the perpendicular direction (hereinafter referred to as “C direction”), which are normally specified by JIS, etc. In addition to the average magnetic properties of the steel sheet, it is required to have excellent all-round magnetic properties in the steel plate surface. For this purpose, the {111} orientation grains that do not include the iron easy axis in the steel plate surface are reduced as much as possible, and the {100} orientation grains that include the iron easy axis in the steel plate surface are as much as possible. It is desirable to develop.

  Class non-oriented electrical steel sheets with Si + Al of 1.9% or more are generally applied with hot-rolled sheet annealing, and are trying to reduce {111} orientation grains, but there are still many {111} orientation grains. is the current situation. It is important to reduce {111} -oriented grains, increase {100} -oriented grains, further increase the magnetic flux density of the entire circumference, and reduce iron loss.

The following has been proposed as a method for producing a steel sheet with increased {100} oriented grains.
In Patent Document 1 (Japanese Patent Laid-Open No. 3-294422), hot-rolled sheet annealing is performed at a temperature of 1000 ° C. or higher and 1200 ° C. or lower for 30 seconds to 5 minutes, and cold rolling is performed at a cold rolling rate of 80% or higher and 90% or lower, There has been proposed a method characterized in that finish annealing is performed at 850 ° C. or higher and 1000 ° C. or lower for 15 seconds to 2 minutes.

  In Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-197217), the average grain size after hot-rolled sheet annealing is set to 400 μm or more, cold rolling is performed at a reduction rate of 80% to 90%, and finish annealing is performed at 800 ° C. or more. There has been proposed a method characterized by performing the treatment at 950 ° C. or lower for 10 seconds to 1 minute.

ここで、ｎ：冷延パス回数、Ｈ_i：ｉパス目の入り側板厚、Ｈ_i+1：ｉパス目の出側板厚（ｉ＋１パス目の入り側板厚）、Ｒ_i：ｉパス目の圧延ロール径 Patent Document 3 (Japanese Patent Application Laid-Open No. Hei 8-100205) proposes a method of setting the M value of the following formula (1) to 0.1 to 7 regarding the relationship between the sheet thickness during cold rolling and the diameter of the rolling roll. Yes.

Here, n: number of cold rolling passes, H _i : entry thickness of the _i- th pass, H _{i + 1} : exit thickness of the i-th pass (i + 1-th entry thickness), R _i : i-th pass Roll diameter

  Non-Patent Document 1 discloses that a recrystallization treatment following cold rolling is performed when the M value of the above formula (1) is small under the conditions of 0.26% Si component system, no hot-rolled sheet annealing, and a cold rolling rate of 82%. It has been reported that {111} oriented grains in 1/5 layer of later steel plates are suppressed and cube oriented grains increase.

Patent Document 4 (Patent No. 2578074) proposes a method of rolling the non-oriented electrical steel sheet in the temperature range of 150 ° C. to 470 ° C. during cold rolling.
JP-A-3-294422 JP 2004-197217 A Japanese Patent Laid-Open No. 8-110085 Japanese Patent No. 2578074 R. Kawamata, T. Kubota and K. Yamada: JMEPEG, 6 (1997), p.701

  However, the methods disclosed in Japanese Patent Laid-Open Nos. 3-294422 and 8-11005 are techniques for increasing the magnetic flux density in the L and C directions. In addition, the method disclosed in Japanese Patent Laid-Open No. 8-100185 has little improvement in magnetic flux density when Si + Al is 1.9% or more. Although the method of Non-Patent Document 1 also describes B50 in the measurement example, the non-oriented electrical steel sheet is regulated by JIS C2550 to measure with a sample in the L and C directions. It is considered that the density is evaluated, and it is understood that the magnetic flux density in the L and C directions is increased.

  As described in the specification, the method of Japanese Patent Application Laid-Open No. 2004-197217 is a technique aimed at the development of {100} texture, but particularly when the cold rolling rate is increased to over 90%, There was a drawback that the reduction of the magnetic flux density around the periphery due to the development of {111} oriented grains. The present invention provides a non-oriented electrical steel sheet that solves the above-described problems of the prior art and has a high magnetic flux density on the entire circumference even when the cold rolling rate exceeds 90%.

  In Japanese Patent No. 2578074, it is specified in claim 1 that rolling is performed at a plate temperature of 150 ° C. to 470 ° C. This is because Si: 4.5 wt% to 7.1 wt% is contained and is brittle. As a countermeasure against cracking during rolling, rolling is performed at a higher temperature, and the purpose is different from that of the present invention, and the components are also different.

ここで、ｎ：冷延パス回数、Ｈ_ｉ：ｉパス目の入り側板厚、Ｈ_ｉ＋１：ｉパス目の出側板厚（ｉ＋１パス目の入り側板厚）、Ｒ_ｉ：ｉパス目の圧延ロール径 That is, the present invention
(1) In mass%,
C: 0.004% or less, Si: 3.04 % to 3.5%,
Al: 0.2% to 3.0%, 3.24 % ≦ (% Si +% Al),
Mn: 0.02 to 1.0%, S: 0.0030% or less,
N: 0.0030% or less,
In the manufacturing method of the non-oriented electrical steel sheet in which the slab composed of the remaining Fe and the inevitable impurities is slab-heated, hot-rolled, hot-rolled sheet annealed, cold-rolled, and finish-annealed, A non-oriented electrical steel sheet characterized by having an average crystal grain size of 300 μm or more, an M value represented by the following formula in cold rolling of 0.1 to 5 and a cold rolling rate of 85% to 93% Production method.

Here, n: number of cold rolling passes, H _i : entry side plate thickness of _i- th pass, H _{i + 1} : exit side plate thickness of i-th pass (i + 1-th pass entry plate thickness), R _i : rolling roll of i-th pass Diameter

(2) The non-oriented electrical steel sheet according to (1), wherein one or two of Sn and Sb is contained in an amount of 0.02 to 0.4% in terms of mass%. Production method.

(3) The above (1) or (2), characterized by containing 0.0005% to 0.020% of each of REM, Mg, and Ca in a content of 1% by mass The manufacturing method of the non-oriented electrical steel sheet described in 1 .

  According to the present invention, when the cold rolling rate is as high as 85% to 93%, the average crystal grain size after hot-rolled sheet annealing is 300 μm or more, and the M value of the formula (1) is 0.1 or more and 5 By controlling the following, a non-oriented electrical steel sheet having excellent magnetic properties with a much higher magnetic flux density than the conventional method due to the reduction of {111} orientation grains and the development of {100} orientation grains. A method of manufacturing can be provided. It fully meets the demand for non-oriented electrical steel sheets with a 1.9% or higher Si + Al class used in the cores of high-efficiency motors such as compressor motors for air conditioners and refrigerators, and drive motors for electric vehicles. , Its industrial value is extremely high.

Details of the present invention will be described below.
As a result of earnestly examining the method for producing a non-oriented electrical steel sheet having a high total magnetic flux density in a class of Si + Al of 1.9% or more, the present inventors have determined that the average grain size after hot-rolled sheet annealing is 300 μm or more, In cold rolling, it is very effective that the constant M represented by the formula (1) is 0.1 to 5 and the cold rolling rate is 85% to 93%. I found it more effective when done.

Table 1 is an example of experimental results conducted by the present inventors. A slab containing C: 0.0025%, Si: 2.1%, Al: 0.3%, Mn: 0.23%, S: 0.0017%, N: 0.0015%, and the balance inevitable impurities Slab heated, hot rolled to 3.90 mm thickness and 1.40 mm thickness (sheet thickness before cold rolling t: 3.90 mm, 1.40 mm), hot-rolled sheet annealed at 1100 ° C x 1 minute, hot-rolled sheet The average crystal grain size of the annealed plate was 352 μm. And the diameter of the cold-rolled work roll was 200 mmφ, cold rolled to 0.35 mm at 75% and 91% reduction ratios in 5 passes, finish annealing at 850 ° C. for 1 minute, and magnetically measured. The total circumferential magnetic flux density y _−R was obtained by the following equation, where y _{−X represents} the value of the magnetic flux density in the X degree direction from the rolling direction.
y _−R = {y ₋₀ + y ₋₉₀ + 2 × (y _−22.5 + y ₋₄₅ + y _−67.5 )} / 8
Table 1 shows the relationship between the rolling reduction of the cold rolling, the rolling schedule, the M value, and the total magnetic flux density. FIG. 1 shows the relationship between the angle from the rolling direction and the magnetic flux density.

  In the example of the present invention with a cold rolling rate of 91% and an M value of 4.71, a high magnetic flux density can be obtained in both the 0 degree and 90 degree directions, and the 45 degree direction is also higher than the comparative examples, compared with the comparative examples 1-3 It can be seen that the total magnetic flux density is very high.

  Next, the influence of the average crystal grain size of the hot-rolled sheet annealed sheet was examined. Same as the experiment of Table 1 C: 0.0025%, Si: 2.1%, Al: 0.3%, Mn: 0.23%, S: 0.0017%, N: 0.0015%, the remainder is inevitable A slab containing a typical impurity was slab heated, hot-rolled to a thickness of 3.90 mm (sheet thickness t before cold rolling: 3.90 mm), and annealed at various temperatures to change the average crystal grain size. Then, cold rolled work roll diameter: 200 mmφ, 5 passes, Table 1 of the present invention, M: 4.71, Comparative Example 1, M: 6.75 Rolling schedule to 0.35 mm with a cold rolling rate of 91% It was hot rolled, subjected to a final annealing at 850 ° C. for 1 minute, and magnetically measured. FIG. 2 shows the relationship between the average grain size of the hot-rolled sheet annealed plate and the total magnetic flux density. This shows that a remarkably high magnetic flux density can be obtained when the M value is 4.71 and the hot-rolled sheet annealed plate average crystal grain size is 300 μm or more.

The reason for limitation of the present invention will be described below.
C is 0.004% or less in order to make it a ferrite one phase, not an austenite or ferrite two phase region.

  Si: 1.5% to 3.5%, Al: 0.2% to 3.0%, 1.9% ≦ (% Si +% Al): C is 0.004% or less, and 1.9% ≦ If (% Si +% Al), the austenite and ferrite do not become the two-phase region, but the ferrite one-phase, so 1.9% ≦ (% Si +% Al). Since Si and Al increase the electric resistance and decrease the eddy current loss, the lower limits are set to 1.5% and 0.2%, respectively. When Si and Al are added in excess of 3.5% and 3.0%, respectively, the workability is remarkably deteriorated.

  Mn is made 0.02% or more in order to improve brittleness. When the upper limit of 1% is added, the magnetic flux density deteriorates.

  S forms 0.0030% or less in order to produce a fine sulfide and to play a harmful effect on iron loss.

  N forms fine nitrides such as AlN and exerts a harmful effect on iron loss, so 0.0030% or less.

  The average crystal grain size after hot-rolled sheet annealing is set to 300 μm or more. As shown in FIG. 2, when it is less than 300 μm, a high magnetic flux density cannot be obtained.

If it is desired to further improve the magnetic characteristics, the following means can be employed.
One or two of Sn and Sb are contained in an amount of 0.02 to 0.4%. If it is 0.02% or more, the magnetic flux density B50 can be increased. The upper limit of 0.4% is because the effect is saturated.

  When one or more of REM, Mg, and Ca are contained in each content of 0.0005% or more, S in the steel generates REM sulfide, Mg sulfide, and Ca sulfide coarsely and is fine. Sulfide is reduced and good magnetic properties can be obtained. If the upper limit of 0.020% is contained, the magnetic properties deteriorate.

ここで、ｎ：冷延パス回数、Ｈ_i：ｉパス目の入り側板厚、Ｈ_i+1：ｉパス目の出側板厚（ｉ＋１パス目の入り側板厚）、Ｒ_i：ｉパス目の圧延ロール径 The M value of the following formula is 0.1-5. If it exceeds 5, a high magnetic flux density cannot be obtained, and if it is less than 0.1, the production load such as too many cold rolling passes or too small cold rolling work roll diameter becomes too large.

Here, n: number of cold rolling passes, H _i : entry thickness of the _i- th pass, H _{i + 1} : exit thickness of the i-th pass (i + 1-th entry thickness), R _i : i-th pass Roll diameter

  The cold rolling rate is 85% to 93%. If it is less than 85% or exceeds 93%, it is impossible to obtain a high magnetic flux density.

  The temperature of cold rolling shall be 180-350 degreeC. This is because if the temperature is lower than 180 ° C. or higher than 350 ° C., a good effect of improving magnetic characteristics cannot be obtained as shown in the examples.

A slab containing C: 0.0014%, Si: 2.21%, Mn: 0.19%, Al: 0.30%, S: 0.0012%, N: 0.0019% is heated at 1150 ° C. And hot rolled to a thickness of 2.70 mm. Hot rolled sheet annealing was performed at 1050 ° C. for 120 seconds, and the average crystal grain size of the hot rolled sheet annealed sheet was set to 321 μm. Then, the M value was changed under various conditions, cold-rolled to 0.35 mm, continuously annealed at 980 ° C. for 60 seconds, and an insulating film was applied to obtain a product. At this time, the cold rolling rate is 87%. The total magnetic flux density or the total iron loss was determined by the following equation, where y− _R was the total value and y− _X was the actual measurement in the X degree direction.
_{y -R = {y -0 + y} -90 + 2 × (y -22.5 + y -45 + y -67.5)} / 8
Table 2 shows the relationship between the cold rolling conditions and the magnetic properties at this time.
From this, it can be seen that good magnetic properties can be obtained in the reference example .

A slab containing C: 0.0012%, Si: 2.19%, Mn: 0.17%, Al: 0.33%, S: 0.0020%, N: 0.0012% is heated at 1150 ° C. And hot rolled to a thickness of 2.70 mm. Hot-rolled sheet annealing was performed at various temperatures for 120 seconds to change the average crystal grain size of the hot-rolled sheet annealed sheet. And No. 1 of Example 1. The product was cold-rolled to 0.35 mm according to the cold-rolling schedule of No. 2, continuously annealed at 980 ° C. for 60 seconds, and an insulating film was applied to obtain a product.
Table 3 shows the relationship between the hot-rolled sheet annealing temperature, the hot-rolled sheet annealed plate average crystal grain size, and the magnetic properties at this time. The total magnetic flux density or the total iron loss was determined by the following equation, where y− _R was the total value and y− _X was the actual measurement in the X degree direction.
_{y -R = {y -0 + y} -90 + 2 × (y -22.5 + y -45 + y -67.5)} / 8
From this, it can be seen that good magnetic properties can be obtained in the reference example .

A slab containing C: 0.0019%, Si: 2.00%, Mn: 0.31%, Al: 0.29%, S: 0.0009%, N: 0.0014% is heated at 1150 ° C. And hot rolled to various plate thicknesses. Hot-rolled sheet annealing was performed at 1050 ° C. for 90 seconds, and the average crystal grain size of the hot-rolled sheet annealed sheet was set to 321 μm. And it cold-rolled to 0.35 mm on the conditions of Table 4, 980 degreeC x 60 second continuous annealing, apply | coated the insulating film, and was set as the product. Table 4 shows the relationship between the cold rolling rate, cold rolling conditions, and magnetic properties at this time. The total magnetic flux density or the total iron loss was determined by the following equation, where y− _R was the total value and y− _X was the actual measurement in the X degree direction.
_{y -R = {y -0 + y} -90 + 2 × (y -22.5 + y -45 + y -67.5)} / 8
From this, it can be seen that good magnetic properties can be obtained in the reference example .

C: 0.0011%, Si: 3.04%, Mn: 0.19%, Al: 0.60%, S: 0.0009%, N: 0.0011%, components shown in Table 5 Was heated at 1100 ° C. and hot-rolled to a thickness of 2.70 mm. Hot-rolled sheet annealing was performed at 1100 ° C. for 90 seconds, and the average crystal grain size of the hot-rolled sheet annealed sheet was set to 334 μm. And it cold-rolled to 0.35 mm on the conditions shown in Table 6 by the diameter of 70 mm of cold-rolled rolls, continuously annealed at 1020 ° C. for 60 seconds, and applied an insulating film to obtain a product. Table 5 shows the relationship between components and magnetic characteristics at this time. The total magnetic flux density or total iron loss was determined by the following equation, where y _−R was the total value and y _−X was the measured value in the X-degree direction.
y _−R = {y ₋₀ + y ₋₉₀ + 2 × (y _−22.5 + y ₋₄₅ + y _−67.5 )} / 8
From this, it can be seen that when Sn and Sb are contained, B50 is high, and when REM, Ca and Mg are contained, W15 / 50 is low.

It is a figure which shows the angle characteristic of a cold rolling rate, M value, and B50. It is a figure which shows the relationship between hot rolled sheet annealing board average crystal grain diameter, M value, and perimeter B50.

Claims (3)

% By mass
C: 0.004% or less,
Si: 3.04 % to 3.5%,
Al: 0.2% to 3.0%,
3.24 % ≦ (% Si +% Al),
Mn: 0.02 to 1.0%,
S: 0.0030% or less,
N: 0.0030% or less,
In the manufacturing method of the non-oriented electrical steel sheet in which the slab composed of the remaining Fe and the inevitable impurities is slab-heated, hot-rolled, hot-rolled sheet annealed, cold-rolled, and finish-annealed, A non-oriented electrical steel sheet characterized by having an average crystal grain size of 300 μm or more, an M value represented by the following formula in cold rolling of 0.1 to 5 and a cold rolling rate of 85% to 93% Production method.

Here, n: number of cold rolling passes, H _i : entry side plate thickness of _i- th pass, H _{i + 1} : exit side plate thickness of i-th pass (i + 1-th pass entry plate thickness), R _i : rolling roll of i-th pass Diameter   2. The method for producing a non-oriented electrical steel sheet according to claim 1, wherein 0.02 to 0.4% of each of Sn and Sb is contained in an amount of mass%.   The non-directionality according to claim 1 or 2, wherein 0.0005% to 0.020% of REM, Mg, or Ca is contained in each content by mass%. A method for producing electrical steel sheets.

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