JP5560923B2 - Method for producing non-oriented electrical steel sheet with excellent magnetic properties in rolling direction - Google Patents

Description

  The present invention relates to a manufacturing method for manufacturing a non-oriented electrical steel sheet suitable for a core such as a split core in which magnetic properties in the rolling direction are important.

  In recent years, split cores, which have been increasing in the automotive field as motor stator cores, can align the direction of good magnetic properties of steel sheets with the direction in which the magnetic flux of the core concentrates, for example, the teeth direction, which is expected to improve motor efficiency. it can. Therefore, it can be said that the electrical steel sheet having excellent magnetic properties in the rolling direction is one of the materials suitable for the split core.

  However, the unidirectional electrical steel sheet produced by the secondary recrystallization method is generally difficult to use as a steel sheet for motors because of its high cost and the glass coating deteriorates the punchability of the core. .

  As a method for producing a non-oriented electrical steel sheet having excellent magnetic properties in the rolling direction, for example, in Patent Document 1, Si is 2.0 mass% or less, Al is 1.0 mass% or more, and the rolling reduction after finish annealing. A technique is disclosed in which 3-10% skin pass rolling is performed, followed by strain relief annealing.

  Moreover, in patent document 2, it is a manufacturing method which performs the cold rolling of 2 times or more on both sides of intermediate annealing, C content at the time of final cold rolling is 0.005-0.05 mass%, in final cold rolling A manufacturing technique in which the rolling reduction is 30 to 80% is disclosed. In this technique, since the C content is large, magnetic aging is likely to occur, and in some cases, a decarburization step is required.

JP 2006-265720 A JP 2009-203520 A

  An object of the present invention is to stably provide an electrical steel sheet that is excellent in magnetic properties in the rolling direction and that can reduce deterioration of iron loss properties due to magnetic aging.

  The steel composition and the crystal grain size before cold rolling are appropriately adjusted, and cold rolling is performed twice or more with intermediate annealing in between, the rolling reduction rate in final cold rolling is appropriately adjusted, and the final In cold rolling, by performing an aging treatment for each pass, a non-oriented electrical steel sheet having extremely excellent magnetic properties in the rolling direction can be produced. In the present invention, the aging treatment between passes appropriately controls the temperature and time. The gist of the present invention is as follows.

(1) In mass%,
C: 0.001 to 0.005%,
N: 0.001 to 0.005%
Si: 2.0-4.0%,
Mn: 0.05 to 1.0%
Al: 0.1 to 2.0%
Containing
C + N: 0.002 to 0.008%
And
S: 0.005% or less,
Ti: 0.005% or less,
O: 0.005% or less,
The slab composed of the remaining Fe and unavoidable impurities is hot-rolled, and if necessary, hot-rolled sheet annealing is performed, and then cold-rolling is performed twice or more sandwiching the intermediate annealing, followed by finish annealing. Then, if necessary, in the method for producing a non-oriented electrical steel sheet comprising an insulating coating treatment, the crystal grain size before the final cold rolling is set to 100 μm or more, and the rolling reduction is performed in the final cold rolling. The magnetic properties in the rolling direction are characterized by performing cold rolling at 40 to 75% and performing aging treatment for 1 to 10 minutes in the temperature range of 50 to 300 ° C. between the final cold rolling passes. A method for producing an excellent non-oriented electrical steel sheet.

  (2) The slab contains one or two of Sn and Sb in a total amount of 0.01 to 0.2% by mass, and is excellent in magnetic properties in the rolling direction according to claim 1. Method for producing an electrical steel sheet.

  ADVANTAGE OF THE INVENTION According to this invention, the non-oriented electrical steel plate which was extremely excellent in the magnetic characteristic of the rolling direction can be manufactured, and the high efficiency of the motor using a split core can be achieved.

It is a figure which shows the relationship between the aging temperature in the aging time of 3 minutes of the aging between passes at the time of the 2nd cold rolling, and the magnetic flux density B50 of a rolling direction. It is a figure which shows the relationship between the time in the aging temperature of 200 degreeC of the aging between passes at the time of the 2nd cold rolling, and the magnetic flux density B50 of a rolling direction. It is a figure which shows the relationship between the average crystal grain diameter of the intermediate annealing board before the second cold rolling, and the magnetic flux density B50 of a rolling direction. It is a figure which shows the relationship between the rolling reduction at the time of the second cold rolling, and the magnetic flux density B50 of a rolling direction.

  The present invention will be described in detail for each component.

  The reason for limiting the composition of steel is as follows.

<C: 0.001 to 0.005 mass%>
C exhibits an effect of increasing iron loss and causes magnetic aging. Therefore, C is 0.005 mass% or less. However, if the amount is too small, the effect of improving the texture due to aging between passes during cold rolling does not appear, so C is set to 0.001% by mass or more. Preferably, it is 0.002-0.005 mass%.

<Si: 2.0 to 4.0% by mass>
Si increases the specific resistance of steel and also has the effect of reducing iron loss. In order to acquire this effect | action, 2 mass% or more is required. On the other hand, when Si exceeds 4 mass%, steel becomes embrittled and rollability falls. Therefore, Si is set to 2.0 to 4.0 mass%. Preferably, it is 2.0-3.5 mass%.

<Mn: 0.05 to 1.0% by mass>
Mn increases the specific resistance of the steel, and also acts to coarsen the sulfide and render it harmless. In order to obtain this action, 0.05% by mass or more is necessary. On the other hand, if Mn exceeds 1.0% by mass, the magnetic flux density is reduced and the cost is increased, and cracking is easily caused during cold rolling. Therefore, Mn is set to 0.05 to 1.0% by mass. Preferably, it is 0.1-0.5 mass%.

<Al: 0.1 to 2.0% by mass>
Al is effective as a deoxidizing material, and it can also be rendered harmless by coarsening the nitride. Moreover, like Si, the specific resistance of steel is increased and the iron loss is reduced. In order to obtain these actions, 0.1% by mass or more is necessary. However, if it exceeds 2.0 mass%, the steel becomes brittle and the rollability deteriorates. Therefore, Al is 0.1 to 2.0% by mass. Preferably, it is 0.2-2.0 mass%.

<N: 0.001 to 0.005 mass%>
N forms fine precipitates and hinders crystal grain growth during annealing. Therefore, N is set to 0.005 mass% or less. However, if the amount is too small, the effect of improving the texture due to aging between passes during cold rolling does not appear, so N is 0.001% by mass or more. Preferably, it is 0.001-0.004 mass%.

<C + N: 0.002 to 0.008 mass%>
C and N are important elements for expressing the texture improving effect by aging between passes during cold rolling. In order to obtain a texture improving effect, C + N needs to be 0.002% by mass or more. On the other hand, when C + N exceeds 0.008 mass%, magnetism deteriorates due to precipitates. Therefore, C + N is 0.002 to 0.008 mass%. A preferable range is 0.02 to 0.07% by mass, and a more preferable range is 0.02 to 0.06% by mass.

<Impurity>
S, Ti, and O form precipitates, hinder grain growth during annealing, and deteriorate magnetism. Therefore, any element is made 0.005 mass% or less. Preferably, both are 0.003 mass% or less.

<Sn and Sb: 1 type or 2 types in total 0.01 to 0.2% by mass>
Sn and Sb are effective in improving the texture and suppressing nitriding and oxidation during annealing. In order to acquire the effect, it is necessary to contain 1 type or 2 types in total 0.01 mass% or more. If the amount is too large, the effect is saturated, and further, it has an adverse effect on the embrittlement of steel and the suppression of crystal grain growth. Preferably, it is 0.03-0.15 mass%.

<Other additive elements>
Although not stipulated, Ni is 0.5 to 5 mass% for improving the texture, Cr is 0.5 to 5 mass% for increasing the specific resistance, and rare earth is 0.001 for the purpose of suppressing impurity precipitation. In order to increase the hardness by 0.05 mass%, P may be appropriately added in an amount of 0.005 to 0.1 mass% and Cu may be 0.1 to 3 mass%.

  The present invention includes other inevitable elements that are not specified, and the balance is Fe.

  Next, a manufacturing method will be described.

  In the present invention, the slab having the component composition described above is hot-rolled, and if necessary, hot-rolled sheet annealing is performed, and then cold rolling is performed twice or more sandwiching the intermediate annealing, followed by finishing. In the method for producing a non-oriented electrical steel sheet comprising annealing and then applying an insulating coating, if necessary, the crystal grain size before the final cold rolling is set to 100 μm or more, and the final cold rolling is performed. The split core is characterized by being subjected to cold rolling at a rolling reduction of 40 to 75% and aging treatment at a temperature range of 50 to 300 ° C. for 1 to 10 minutes between the final cold rolling passes. It is a manufacturing method which manufactures the non-oriented electrical steel sheet for use.

  It is well known in the above-mentioned patent documents and the like that the magnetic flux density higher than that in the case of one cold rolling can be obtained by performing cold rolling twice or more with intermediate annealing. Satisfying everything will dramatically improve the magnetic flux density.

<Aging treatment between passes in final cold rolling: 1 to 10 minutes in a temperature range of 50 to 300 ° C.>
(Experiment 1) Inter-aging aging treatment An ingot having the composition shown in Table 1 was melted by vacuum melting, heated at 1100 ° C. for 1 hour, and then heated to 2.5 mm in thickness by hot rolling. It was a sheet. This hot-rolled sheet was subjected to hot-rolled sheet annealing at 1000 ° C. for 1 minute to obtain a hot-rolled annealed sheet. After pickling the hot-rolled annealed plate, an intermediate cold-rolled plate having a thickness of 0.8 mm is obtained by the first cold rolling. An annealing plate was used.

  The obtained intermediate annealed plate is subjected to the second cold rolling while being subjected to an aging treatment at 50 ° C. to 400 ° C. for 1 to 60 minutes between passes, and a final cold rolled plate having a thickness of 0.35 mm is obtained. Obtained. At the same time, a final cold-rolled sheet without aging treatment between passes was also produced. Subsequently, the final cold-rolled sheet was subjected to finish annealing at 1000 ° C. for 30 seconds to obtain a final annealed sheet.

  A single-sheet test piece was cut out from the final annealed plate, and the magnetic flux density B50 was measured. FIG. 1 shows the relationship between the aging temperature and the magnetic flux density B50 in the rolling direction at an aging time of 3 minutes between passes during the final cold rolling. It was found that when the aging temperature is 50 ° C. or more and 300 ° C. or less, the B50 in the rolling direction rises with respect to the material that has not been subjected to the aging treatment.

  FIG. 2 shows the relationship between aging time and magnetic flux density at an aging temperature of 200 ° C. Even with aging for 1 minute, the magnetic flux density was improved as compared with the case without aging treatment. Further, when the finish annealed plate was treated at 200 ° C. for 100 hours, the deterioration of the iron loss W15 / 50 was within 3%. Therefore, decarburization was not necessary.

  From the above, the non-oriented electrical steel sheet having a high magnetic flux density in the rolling direction can be obtained by applying an aging treatment between passes during the final cold rolling even if the C content is low and does not require decarburization. It has been found that it can be manufactured. The mechanism is not necessarily clear, but it is presumed that the texture after the final annealing has been improved to include the orientation in the vicinity of {110} <001> that contributes to the improvement of magnetism in the rolling direction by aging treatment between passes. .

  It is presumed that the transformation introduced by processing and the interaction of solute carbon contribute to the improvement of the texture. Therefore, the magnetic flux density in the rolling direction can be improved by appropriately containing an aging treatment containing a certain amount of solute carbon.

  From the above, the temperature range of the pass aging treatment of the final cold rolling of the present invention is set to 50 to 300 ° C. at which an increase in magnetic flux density in the rolling direction is observed in FIG. Preferably, it is 150-300 degreeC. As is apparent from FIG. 2, the aging time has an effect of improving the magnetic flux density in the rolling direction even for 1 minute, and since the improvement effect is saturated after 10 minutes or more, it is set to 1 to 10 minutes.

<Average crystal grain size before final cold rolling: 100 μm or more>
(Experiment 2) Average crystal grain size before final cold rolling The first cold rolling was applied to the 2.5 mm thick hot rolled annealed plate used in Experiment 1 to obtain an 0.8 mm intermediate cold rolled plate. . Then, 900-1050 degreeC and the intermediate annealing for 1 minute were given, and it was set as the intermediate annealing board. The average crystal grain size of the intermediate annealed plate was changed in the range of 60 to 250 μm.

  Then, the 2nd cold rolling was implemented, performing the aging treatment at 200 degreeC for 3 minutes between passes, and obtained the final cold-rolled sheet of thickness 0.35mm. The final cold rolled sheet was subjected to finish annealing at 1000 ° C. for 30 seconds to obtain a final annealed sheet. A single plate test piece was cut out from the final annealed sheet, and the magnetic flux density B50 was measured.

  FIG. 3 shows the relationship between the average grain size before the second cold rolling and the magnetic flux density B50 in the rolling direction. It was observed that B50 in the rolling direction increased as the average grain size before the second cold rolling increased.

  As can be seen from FIG. 3, the magnetic flux density B50 in the rolling direction starts to increase significantly when the average crystal grain size before the final cold rolling is 100 μm or more, and continues to increase with the average crystal grain size thereafter. If it is 100 μm or less, the {110} <001> texture effective for improving the magnetic properties in the rolling direction is not sufficiently developed after the final annealing, so it is presumed that the magnetic flux density is not improved.

  In order to sufficiently develop the {100} <001> texture, in the present invention, the average grain size before the final cold rolling is set to 100 μm or more. Preferably, it is 150 μm or more, more preferably 2000 μm or more.

<Draft ratio of final cold rolling: 40 to 75%>
(Experiment 3) Reduction ratio of final cold rolling The first cold rolling was applied to the 2.5 mm thick hot-rolled annealing plate used in Experiment 1 with a reduction ratio of 0.45 to 2.3 mm. The intermediate cold-rolled sheet was used. The intermediate cold-rolled sheet is subjected to an intermediate annealing at 1000 ° C. for 1 minute, and then a second cold rolling is performed while performing an aging treatment at 200 ° C. for 3 minutes between passes. A 35 mm final cold rolled sheet was obtained.

  The reduction ratio of the final cold rolling was changed in the range of 30 to 85%. Thereafter, the final cold-rolled sheet was subjected to finish annealing at 1000 ° C. for 30 seconds to obtain a final annealed sheet, a single-sheet test piece was cut out from the final annealed sheet, and the magnetic flux density B50 was measured.

  FIG. 4 shows the relationship between the rolling reduction during the second cold rolling and the magnetic flux density B50 in the extending direction. An increase in B50 in the rolling direction was observed when the rolling reduction was between 40 and 70%.

  The rolling reduction of the final cold rolling is 40 to 75% from FIG. In order to develop a {110} <001> texture effective in improving the magnetic flux density in the rolling direction, the rolling reduction needs to be 40% or more. On the other hand, when the rolling reduction is larger than 75%, it is presumed that the {111} // ND texture that reduces the magnetic flux density develops and the phenomenon shown in FIG. 4 is observed. Preferably, the rolling reduction is 45 to 70%, more preferably 55 to 70%.

<Other manufacturing methods>
A general steel plate manufacturing method can be applied. That is, the molten steel blown in the converter is degassed to adjust to a predetermined component composition, and subsequently cast and hot rolled to obtain a hot rolled sheet. The slab heating temperature, processing temperature, winding temperature and the like in hot rolling are not particularly limited.

  Although hot-rolled sheet annealing is not always necessary, the development of {110} <001> can be strongly promoted in the texture of the final annealed sheet by performing, so in order to obtain excellent magnetic properties, It is desirable to implement. Next, two or more cold rollings with intermediate annealing are performed to obtain a predetermined plate thickness, followed by final finish annealing, and if necessary, an insulating coating is applied to obtain a product plate.

  In addition, by increasing the number of cold rolling sandwiching the intermediate annealing, the development of {110} <001> can be strongly promoted in the texture after the final annealing, so that the magnetic flux density can be further improved. .

  Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on this one example of conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

<Example 1>
Steel with the component composition shown in Table 2 was hot rolled into a 2.5 mm hot rolled sheet, and then subjected to hot rolled sheet annealing at 1000 ° C. for 1 minute to obtain a hot rolled annealed sheet. After the pickling, the first cold rolling was performed to obtain an intermediate cold-rolled sheet having a thickness of 0.8 mm. Further, the intermediate cold-rolled sheet was subjected to intermediate annealing at 1000 ° C. for 1 minute to obtain an intermediate-annealed sheet.

  The obtained intermediate annealed plate was subjected to the second cold rolling while being subjected to an aging treatment at 200 ° C. for 3 minutes between passes to obtain a final cold-rolled plate having a thickness of 0.35 mm. Subsequently, the final cold-rolled sheet was subjected to finish annealing at 1000 ° C. for 30 seconds to obtain a final annealed sheet. A single plate test piece was cut out from the final annealed plate, and the magnetic flux density B50 and iron loss W10 / 400 in the rolling direction were measured.

  Moreover, about the test piece which performed the aging treatment of 200 degreeC x 100 hours immediately after finishing annealing, the iron loss W15 / 50 was measured, and the thing which deterioration of the iron loss by the aging treatment was 3% or more has magnetic aging. Judged to have occurred.

  The magnetic measurement results are shown in Table 2. In the present invention, the magnetic flux density B50 in the rolling direction is as high as 1.78 T or more, and the iron loss W10 / 400 in the rolling direction is as small as 15 W / kg or less. Furthermore, magnetic aging does not occur.

  On the other hand, a comparative example is as follows.

  Comparative Examples B1 and B3 have the same iron loss but a lower magnetic flux density B50 compared to Invention Example A1 and the like having the same basic components. Since C and N are small, it is presumed that the effect of aging between paths was not obtained. B2 and B4 had a lot of C, magnetic aging, and iron loss deteriorated. Since B5 has a small Si content of 1.5%, the specific resistance is small and the magnetic flux density is high, but the iron loss is large.

  Since B6 has a lot of Si, the steel becomes brittle, and the steel plate was broken by cold rolling. B7 has a large iron loss. Since Mn is small, it is presumed that the sulfide was finely precipitated by hot rolling and hindered crystal grain growth during finish annealing.

  Since B8 has too much Mn, it broke by cold rolling. B9 has a large iron loss. This is presumed to be caused by fine precipitation of nitride due to the small amount of Al. B10 contained too much Al and was broken by cold rolling. B11-B13 have many impurities of S, Ti, and / or O, and have a large iron loss.

<Example 2>
Using the ingot having the component composition shown in Table 1, final cold rolled sheets were obtained by the methods described in Experiments 2 and 3. Along with the crystal grain size before the final cold rolling, the reduction ratio of the final cold rolling, the aging treatment conditions performed between passes during the final cold rolling, the magnetic flux density B50 in the rolling direction and the iron loss W10 / 400 is shown in Table 3.

  According to the invention example, it can be seen that a steel sheet having a high magnetic flux density of 1.81 T or more can be obtained efficiently without taking more time than necessary. The iron loss is 13 W / kg or less.

  On the other hand, a comparative example is as follows.

  In Comparative Example D1, the average crystal grain size before final cold rolling is as small as 75 μm, so the magnetic flux density is low and the iron loss is large compared to the inventive examples. D2 has a small rolling reduction of the final cold rolling, and D3 has a large rolling reduction of the final cold rolling, the magnetic flux density is low, and the iron loss is large.

  D4 has a low temperature for the aging treatment between passes, D5 has a high temperature, and D6 has a short magnetic aging time, so the magnetic flux density is low and the iron loss is large. D7 can obtain a high magnetic flux density and a low iron loss, but has a low productivity because the time for aging between passes is too long.

  As described above, according to the present invention, a non-oriented electrical steel sheet with extremely excellent magnetic properties in the rolling direction can be manufactured, and the efficiency of a motor using a split core can be increased. Therefore, this invention has a high applicability in an electromagnetic steel plate manufacture and utilization industry.

Claims (2)

% By mass
C: 0.001 to 0.005%,
N: 0.001 to 0.005%,
Si: 2.0-4.0%,
Mn: 0.05 to 1.0%
Al: 0.1 to 2.0%
Containing
C + N: 0.002 to 0.008%
And
S: 0.005% or less,
Ti: 0.005% or less,
O: 0.005% or less,
The slab composed of the remaining Fe and unavoidable impurities is hot-rolled, and if necessary, hot-rolled sheet annealing is performed, and then cold-rolling is performed twice or more sandwiching the intermediate annealing, followed by finish annealing. Then, if necessary, in the method for producing a non-oriented electrical steel sheet comprising an insulating coating treatment, the crystal grain size before the final cold rolling is set to 100 μm or more, and the rolling reduction is performed in the final cold rolling. The magnetic properties in the rolling direction are characterized by performing cold rolling at 40 to 75% and performing aging treatment for 1 to 10 minutes in the temperature range of 50 to 300 ° C. between the final cold rolling passes. A method for producing an excellent non-oriented electrical steel sheet.   The non-oriented electrical steel sheet having excellent rolling direction magnetic properties according to claim 1, wherein the slab contains one or two of Sn and Sb in a total amount of 0.01 to 0.2 mass%. Manufacturing method.

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