JP4283687B2 - Method for producing non-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a non-oriented electrical steel sheet that is used as an iron core material for motors and transformers, has excellent iron loss and magnetic flux density, and has extremely small magnetic property anisotropy in the plate surface, and a method for producing the same. is there.

  Non-oriented electrical steel sheets are widely used as iron core materials for various motors, transformers, ballasts and the like for heavy electrical equipment and home appliances. Generally, low iron loss is required from the viewpoint of energy saving, and further higher magnetic flux density is required from the viewpoint of miniaturization of electrical equipment. To date, the aim is to improve iron loss and magnetic flux density. Many techniques have been disclosed, and optimization of components, addition of special elements, application of hot-rolled sheet annealing, higher temperature of finish annealing, and the like have been put into practical use.

  On the other hand, especially when used in rotating machines, the development of steel sheets with low magnetic property anisotropy in the steel sheet surface is strong from the viewpoint of smoothness of rotation, motor efficiency, and effects of stress when incorporated as motor members. Although requested, technical development in this respect is not sufficient. That is, the magnetic properties of non-oriented electrical steel sheets are generally evaluated by the average value in the rolling direction (coil longitudinal direction, L direction) and the vertical direction (coil width direction, C direction) of the steel sheet. Because. The reason for using the characteristics in the L direction and the C direction is to consider the in-plane anisotropy of the steel sheet, but the characteristics of the steel sheet are the direction of rolling and 45 ° (coil diagonal) compared to these two directions. In many cases, the characteristic value of the direction (D direction) is unique, and the anisotropy becomes very large in the D direction. In addition, the magnetic properties of the steel sheet may be evaluated with a test piece cut into a circle called a ring as the average value of the magnetic properties in the plate surface. In this evaluation, the smoothness of rotation when used as a motor Since the effect of stress applied to the member cannot be estimated, it is unsuitable for evaluation including anisotropy, and even if this property is high, the anisotropy in the plate surface is large, resulting in practical inconvenience. Has been pointed out. Strictly speaking, the characteristics in the 22.5 ° and 67.5 ° directions from the coil rolling direction may be considered, but generally the characteristics of these orientations show a large difference compared to the L, C, or D directions. However, the evaluation in the L, D, and C directions is considered to be a necessary and sufficient condition, and the characteristics in the D direction in addition to the conventional L and C directions are considered in the evaluation of the steel sheet including in-plane anisotropy. It is essential.

  It is well known that such in-plane anisotropy is mainly due to the crystal orientation anisotropy and texture of the steel sheet. For this reason, many attempts have been made to control the texture of steel sheets. Basically, efforts have been made to orient the crystal so that the orientation of the crystal is random in each direction within the plate surface.

  In particular, it is well known that in order to reduce the in-plane anisotropy, it is advantageous to increase the accumulation in the {100} orientation rather than the {110} orientation as the crystal orientation. Technology development is underway. In particular, many developments have focused on the fact that the accumulation in the {100} direction is increased by lowering the hot rolling temperature, lowering the Ar3 temperature or lower in materials having transformation points, and performing hot rolling in the α region. .

  For example, Patent Literature 1 discloses a technique for causing the crystal rotation corresponding to a very high cold rolling rate to develop the {100} orientation by adding up the strain due to cold rolling using the accumulation of strain due to α-region hot rolling. Is disclosed. However, with this technology, the hot rolling temperature for obtaining an effective effect is limited to a narrow range, so that not only hot rolling becomes difficult, but also the inclusion of important elements essential for electrical steel sheets such as Si and Al. If the amount of the material is high, the effect disappears and the use is limited, which impedes practical use. Furthermore, it has been pointed out that ridging occurs when applied to non-transformed steels with high Si and Al, which have no transformation point, and general high-grade electrical steel sheets. In this technique, the average in-plane characteristics are improved to some extent, but the reduction in in-plane anisotropy is insufficient.

  Patent Document 2 is technically considered to be the same technology as Patent Document 1, but by clarifying the grain size before hot rolling of α region, the amount of hot rolling reduction, and the lubrication effect. A technique for further developing the {100} orientation and extending the applicable range of the hot rolling temperature is disclosed. However, even with this technique, the effect of the material having a high content of Si, Mn, and Al disappears, and the problem of ridging in the high Si and Al steel pointed out in Patent Document 1 has not been solved. Furthermore, since the crystal grain size before α-region hot rolling is made coarse, surface defects of the steel plate called ridging or crystal pattern may occur even in low Si steel, making it difficult to obtain a stable effect. Yes. Also in this technique, if the characteristics in the D direction are also taken into consideration, the reduction of the in-plane anisotropy is insufficient as in Patent Document 1, and the merit in practical use is hardly clarified, and the practical application has not progressed.

  Patent Document 3 discloses an electrical steel sheet having a high accumulation in the {100} orientation by allowing the {100} orientation resulting from a columnar solidified structure generally formed during casting to remain after hot rolling, cold rolling, and annealing. Obtaining techniques are disclosed. However, in this technique, since the {100} orientation of the slab is not lost, the hot rolling conditions, in particular, the upper limit of the hot rolling reduction ratio is limited to a very low value, so that the slab thickness needs to be very thin as 50 mm or less. Since the productivity in the continuous casting process, which is usually manufactured with a thickness of 200 to 250 mm, is reduced to a fraction, the practical application is hindered.

  Patent Document 4 discloses a technique for integrating in the {100} orientation by applying a double cold rolling annealing method in addition to low temperature hot rolling, but the cost of the double cold rolling annealing has not been put into practical use due to the bottleneck. .

  Patent Document 5 is considered to be the same technique as Patent Document 3, and discloses a technique for integrating in the {100} orientation by setting the hot-rolled sheet thickness to 1 mm or less, but as in Patent Document 3, {100} High lubrication in hot rolling is necessary to avoid excessive strain in hot rolling that causes the orientation to disappear, especially distortion due to shear deformation on the surface of the steel sheet. It has not been put into practical use due to a significant increase in cost and pickling cost.

JP 60-125325 A JP-A-2-104619 JP-A-3-260017 JP-A-4-107216 JP-A-11-189850

  The present invention has been made in view of such a situation, and in particular, by further developing the conventional techniques of Patent Document 1 and Patent Document 2, the thinning and hot rolling of the hot-rolled slab that hinders the productivity of the casting process. High Si without hot rolling lubrication that hinders process productivity, ultrathin hot rolling that also hinders productivity in pickling processes, and double cold rolling annealing that hinders productivity in cold rolling annealing processes , Which provides technology applicable to all ordinary electromagnetic steel sheets including Al steel, and has excellent magnetic properties as the average in-plane properties, but extremely small magnetic properties that could not be achieved with conventional technology A method for stably producing a non-oriented electrical steel sheet having in-plane anisotropy is provided.

  The present inventors have studied the optimum manufacturing conditions (especially hot rolling conditions) in order to find a manufacturing method of non-oriented electrical steel sheets with small in-plane anisotropy of magnetic properties, and applied hot rolling technology at low temperature and high pressure. In addition to not only static amount but also dynamic consideration of the strain applied hot, not only the average in-plane characteristics of magnetic properties are greatly improved, but also the in-plane variation of magnetic flux density. In addition to the extremely low isotropic, it is possible to obtain a very favorable effect even when applied to high-Si, Al steel, which has been a wall in the conventional hot rolling technology at low temperature and high pressure. It was found that defects such as ridging can also be suppressed in the transformation steel. Further, the present invention has been completed by clarifying that the average magnetic property in the plate surface can be controlled more preferably by controlling the slab heating conditions in such a material.

In the present invention, not only is the hot rolling temperature lowered to provide a large reduction at a low temperature, but also the strain rate, the amount of strain applied in passes, and the time between passes are adjusted according to the hot rolling temperature range. It is characterized by optimization in consideration of accumulation and crystal rotation. The gist of the present invention is as follows.
(1) In mass%, C: 0.040% or less, Si: 0.05 to 3.5%, Mn: 3.0% or less, Al: 3.5% or less, S: 0.015% or less, Molten steel containing P: 0.25% or less and N: 0.040% or less is solidified by casting into a steel piece having a thickness of 50 mm or more, and logarithmic strain is 1.0 or more in a temperature range of 500 ° C. or more and 850 ° C. or less. For rolling in a temperature range of 850 ° C. or lower in hot rolling, the average strain rate of each rolling pass is 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more , and between each rolling pass A method for producing a non-oriented electrical steel sheet characterized by performing cold rolling at a rolling reduction of 50% or more after pickling for a time of 4.0 seconds or less. Here, the logarithmic strain is a natural logarithm of (sheet thickness before rolling) / (sheet thickness after rolling).
(2) have contact to the hot rolling of the steel plate (1), the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, each rolling pass in a temperature range of 850 ° C. or less The average strain rate is 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more, the time between each rolling pass is 4.0 seconds or less, and rolling in a temperature range of 900 ° C. or more is logarithmic strain. A method for producing a non-oriented electrical steel sheet, characterized by having a logarithmic strain or less by rolling in a temperature range of 0 ° C. or lower and 500 ° C. or higher and 850 ° C. or lower.
(3) (1) or (2) have contact to the hot rolling of steel, the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the temperature range at 850 ° C. or less The average strain rate of each rolling pass is 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more, the time between each rolling pass is 4.0 seconds or less, and the temperature range is 850 ° C. or more and 900 ° C. or less. A method for producing a non-oriented electrical steel sheet, wherein rolling is logarithmic strain of 0.5 or less.
(4) (1) to (3) have contact to the hot rolling of steel, the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the temperature range at 850 ° C. or less The average strain rate of each rolling pass is 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more, the time between each rolling pass is 4.0 seconds or less, and rolling in a temperature range of 900 ° C. or more A method for producing a non-oriented electrical steel sheet, wherein an average strain rate of a rolling pass is 10 / s or less.
(5) (1) to (4) have contact to the hot rolling of steel, the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the temperature range at 850 ° C. or less Each rolling pass has an average strain rate of 30 / s or more, each log pass has an average logarithmic strain of 0.2 or more, and each rolling pass has a time of 4.0 seconds or less. A method for producing a non-oriented electrical steel sheet, wherein an average logarithmic strain of a rolling pass is 0.5 or less.
(6) (1) to (5) have contact to the hot rolling of steel, the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the temperature range at 850 ° C. or less Each rolling pass has an average strain rate of 30 / s or more, each log pass has an average logarithmic strain of 0.2 or more, and each rolling pass has a time of 4.0 seconds or less. The method for producing a non-oriented electrical steel sheet, wherein a time between rolling passes is 10.0 seconds or more.
(7) (1) to have contact to the hot rolling of the steel plate (6), the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the temperature range at 850 ° C. or less Rolling in a temperature range of 900 ° C. or more is completed by setting the average strain rate of each rolling pass to 30 / s or more, the average logarithmic strain of each rolling pass to 0.2 or more, and the time between each rolling pass to 4.0 seconds or less. A method for producing a non-oriented electrical steel sheet, characterized in that the time until starting rolling in a temperature range of 850 ° C. or lower is 10 seconds or longer.
(8) A method for producing a non-oriented electrical steel sheet, wherein the slab heating temperature in hot rolling is 1100 ° C. or lower among the steel sheets of (1) to (7).

  According to the present invention, it is possible to produce a non-oriented electrical steel sheet having a good iron loss value and average value of magnetic flux density in the plate surface and extremely small in-plane anisotropy.

As a result of examining the method for reducing the in-plane anisotropy of the non-oriented electrical steel sheet,
(1) In mass%, C: 0.040% or less, Si: 0.05 to 3.5%, Mn: 3.0% or less, Al: 3.5% or less, S: 0.015% or less, Molten steel containing P: 0.25% or less and N: 0.040% or less is solidified into a steel piece having a thickness of 50 mm or more by casting.
(2) For rolling in a low temperature range of 500 ° C. or more and 850 ° C. or less, control is performed so that the strain amount to be applied is a high strain amount, the strain rate is a high strain rate, and the interval when strain is applied multiple times is shortened. ,
And preferably further according to the manufacturing method
(3) For rolling in the middle temperature range of 850 ° C. or more and 900 ° C. or less, the amount of strain to be applied is controlled to an extremely low strain amount.
(4) For rolling in a high temperature range of 900 ° C. or higher, control the strain amount to be applied to be a low strain amount, the strain rate to be a low strain rate, and to increase the interval when strain is applied multiple times.
(5) After completion of the rolling in the high temperature region, the time until the rolling in the low temperature region is started is a certain time or more.
(6) Further, it has been found that this can be achieved by a production method in which the slab heating temperature in hot rolling is 1100 ° C. or lower. This will be described in detail below.

  First, the components of the steel of the present invention will be described together with the reasons for limitation. All the contents are mass%.

  C is a material with a low hot rolling temperature as in the present invention, and the effect of improving the magnetic flux density by controlling the crystal orientation is particularly strong. Therefore, it is better to control the characteristics slightly higher than ordinary non-oriented electrical steel sheets. However, excessive C content degrades the magnetic properties, so the content is made 0.040% or less. Preferably it is 0.030-0.0001%, More preferably, it is 0.020-0.0005%, More preferably, it is 0.010-0.0010%, More preferably, it is 0.008-0.0015%.

  Si is well known to increase the electrical resistance of a steel sheet and reduce iron loss, and is an element that is naturally added to electromagnetic steel sheets. Although the upper limit of the Si content has been kept very low in the conventional technology using hot rolling and low temperature, this limitation becomes useless if the optimized hot rolling conditions in the present invention are applied. Application to all electrical steel sheets having a simple Si content is possible. In view of the balance between magnetic properties and sheet passing properties, the content is set to 0.05 to 3.5%. If it is less than 0.05%, good magnetic properties cannot be obtained, and if it exceeds 3.5%, the plate-passability in the production process is significantly deteriorated due to embrittlement. Preferably it is 0.3-3.2%, More preferably, it is 0.5-3.0%, More preferably, it is 0.8-2.5%.

  Mn is an important element in the present invention because it reacts with S to form a sulfide. Usually, when Mn is little in the middle, fine MnS may precipitate during hot rolling, and iron loss and magnetic flux density may be remarkably deteriorated. However, in the present invention, by controlling the hot rolling conditions within a specific range, the effect of avoiding this adverse effect also appears, and therefore there is no particular lower limit for Mn. On the other hand, Mn has the effect of increasing the electric resistance of the steel sheet and reducing the iron loss as a solid solution Mn, but if it is contained too much, the original saturation magnetic flux density is lowered, so the upper limit is 3.0%. To do.

  Al, like Si, is actively added for the purpose of increasing the electrical resistance of the steel sheet and reducing the iron loss. Al, like Si, is limited to a range where the upper limit is low in the prior art, but the present invention does not need to be limited in this respect. When Al becomes high, castability deteriorates remarkably, so 3.5% or less. The lower limit is not particularly required, and Al = 0% may be used. However, if the amount is about 0.01 to 0.05%, fine AlN may be formed to deteriorate magnetic characteristics, particularly iron loss. It is. Preferably it is 0.005% or less and 0.1-3.0%, More preferably, it is 0.003% or less and 0.3-2.5%, More preferably, it is 0.002% or less and 0.5-2. 0%, more preferably 0.001% or less and 0.7 to 1.5%.

  S is directly related to the amount of sulfide. If the content of S is large, even if the hot rolling conditions are appropriately controlled, the amount of precipitation increases, which inhibits grain growth and particularly deteriorates iron loss. Therefore, the upper limit is made 0.015%. In order to further improve the magnetic properties of the steel sheet, it is preferably 0.005% or less, more preferably 0.003% or less, still more preferably 0.002% or less, and still more preferably 0.001%. It may be 0%.

  P has the effect of increasing the precipitation temperature of Cu or Mn sulfide that precipitates at a relatively low temperature, which is undesirable for the magnetic properties, and therefore can be positively added. On the other hand, since the hardness of the steel sheet is increased and the punchability is strongly affected, the amount of addition is limited by the desired punch hardness. Further, if it is contained excessively, the cold-rollability and the like are remarkably deteriorated, which may hinder the production of the steel sheet, so the upper limit is made 0.25%.

  In the steel containing Al, N is controlled to a low level of about 0.004% or less because a large amount of nitride increases the amount of nitride and hinders crystal grain growth. However, if the Al content is suppressed to about 0.005% or less, this adverse effect does not need to be considered at all. Rather, since it has the effect of favoring the crystal orientation by dissolving in steel as in C, it can also be added positively. However, excessive addition causes a problem of magnetic aging and steel plate defects due to microvoids generated during solidification from molten steel, so the upper limit is made 0.040%. Considering productivity, it is preferably 0.020% or less, more preferably 0.015% or less. From the viewpoint of controlling the crystal orientation, the content is preferably 0.0002% or more, more preferably 0.0005% or more, still more preferably 0.001% or more, still more preferably 0.0015% or more, and still more preferably 0.00. It is 003% or more, more preferably 0.005% or more.

  In addition, Ni, Cr, Cu, Ca, Mg, REM, Sn, Sb, Ti, Nb, V, Mo, and other elements that are considered to be added in conventional non-oriented electrical steel sheets Addition of up to has no effect on the present invention. In addition, the effects of the present invention are not affected at all when these elements inevitably contained, and also various other trace elements are contained. In other words, needless to mention the influence of these elements, a product can be obtained without any problems in the production process disclosed in the present invention.

  Next, manufacturing conditions that are important limiting factors of the present invention will be described.

  The non-oriented electrical steel sheet of the present invention can be obtained by casting molten steel comprising the above-described components into a steel piece, hot rolling, pickling, cold rolling, and recrystallization annealing. The outline of the process is not greatly different from the normal process, but the hot rolling conditions are significantly different from the normal conditions.

  In particular, the temperature range in which strain due to rolling is imparted by hot rolling is an important requirement in the present invention, and the effect of the present invention can be obtained by controlling this within the scope of the invention.

  That is, a large portion of hot rolling needs to be performed in a temperature range of 500 to 850 ° C. This temperature range is referred to as a low temperature range in the following description. In order to sufficiently obtain the effects of the present invention, the strain applied in the low temperature range needs to be 1.0 or more in logarithmic strain. If the temperature range is too low, rolling becomes difficult, and if it is too high, the effect of the present invention is lost. From the viewpoint of rollability, the lower limit of the temperature range is preferably 550 ° C, more preferably 600 ° C, and further preferably 650 ° C. Similarly, from the viewpoint of the effect of the invention, the upper limit of the temperature range is preferably 820 ° C, more preferably 780 ° C, and further preferably 750 ° C. If it is 750 degrees C or less, the effect of this invention can be acquired very notably. If rolling is performed in this temperature range, it is possible to maintain a preferable temperature range by processing heat generation unless it is an extremely low speed and light pressure pass schedule. The strain applied in such a low temperature range is preferably 1.5 or more, more preferably 2.0 or more, more preferably 2.5 or more, more preferably 3.0 or more, and further preferably 3.3 or more. is there. There is no doubt that the effect of strain applied in this low temperature range is roughly due to strain accumulation in hot rolling as disclosed in the prior arts 1 and 2. However, in the present invention, this effect is considered by considering the strain applied in the high temperature and medium temperature ranges described in detail below, the strain rate including the low temperature range, recovery in a continuous pass, the disappearance of strain due to recrystallization, and the like. Is to be obtained more prominently.

  In the present invention, the strain rate of the strain applied in this low temperature range and the time interval when applied multiple times are important. Usually, since distortion is given by continuous multi-pass rolling, this will be described below. For rolling in a low temperature region, the average strain rate of each rolling pass needs to be 30 / s or more. Below this, it is necessary to make the rolling temperature very low, which not only causes problems in rollability, but also increases the total required strain and increases the hot rolling load. Furthermore, for example, when low temperature large pressure reduction is performed at a low strain rate, the in-plane anisotropy of the magnetic properties is not so small, and the effect of the present invention cannot be obtained. Preferably it is 50 / s or more, More preferably, it is 70 / s or more, More preferably, it is 100 / s or more.

  Moreover, the average of the logarithmic distortion of each rolling pass shall be 0.2 or more about rolling in a low temperature range. This is because it is preferable to apply the strain in the low temperature region as quickly as possible in order to reduce the in-plane anisotropy of the characteristics that are the characteristics of the present invention as described above. Preferably it is 0.3 or more, More preferably, it is 0.4 or more, More preferably, it is 0.5 or more.

  Furthermore, the time between rolling passes is set to 4.0 seconds or less for rolling in a low temperature region. This is because it is preferable to apply the strain in the low temperature region as quickly as possible in order to reduce the in-plane anisotropy of the characteristics that are the characteristics of the present invention as described above. Although it is in a low temperature range, recovery and recrystallization proceed immediately after rolling in this temperature range, so that the accumulation of strain intended by the present invention does not occur efficiently, especially when recrystallization proceeds excessively. The effect is completely lost. Preferably it is 3 seconds or less, More preferably, it is 2 seconds or less, More preferably, it is 1 second or less.

  Although the mechanism regarding the manifestation of the effect of reducing the in-plane anisotropy by controlling the rolling conditions in the low temperature region is not clear, the effect of the strain imparted in the low temperature region is not just the macro strain amount. This suggests that it is necessary to consider microrecovery and recrystallization behavior. In particular, in addition to ultra-low C, N, and S, as in recent materials, high-purity materials including Ti and Cu and other trump elements cause recovery and recrystallization behavior faster than conventional materials. It seems that such consideration has become important.

  In addition, the effect of the present invention becomes more remarkable by imparting an appropriate amount of rolling strain in a high temperature range. That is, it is preferable to lightly reduce in the temperature range of 900 ° C. or higher. This temperature range is referred to as a high temperature range in the following description. This temperature is preferably 950 ° C. or higher, but care should be taken because it may cause problems if it is too high as described later. Preferably it is 1100 degrees C or less, More preferably, it is 1050 degrees C or less.

  The strain applied in this high temperature range is 3.0 or less. However, since the effect of the present invention is manifested only by a large strain in the low temperature region, the strain in the high temperature region must not exceed the strain in the low temperature region. The amount of strain is preferably 2.0 or less, more preferably 1.5 or less, still more preferably 1.0 or less, and still more preferably 0.5 or less. The lower limit is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more in order to reduce the anisotropy of the final product and to suppress ridging that is a problem particularly in non-transformed steel. . However, this preferable range depends on the temperature in the high temperature range, the strain rate described later, the time between passes, and the like. The strain rate is 10 / s or less in average for each rolling pass for rolling applied in a high temperature region. Preferably it is 8 or less. When rolling in multiple passes, the average logarithmic strain of each rolling pass is 0.5 or less. Preferably it is 0.3 or less. Furthermore, it is preferable that the time between passes is 10.0 seconds or more.

  The effect of strain imparted in this high temperature range is to destroy the texture due to the columnar structure formed during casting and reduce the in-plane anisotropy, as well as the surface of ridging and crystal patterns that have been problematic in the prior art It has the effect of avoiding defects. Although this mechanism is not clear, if the columnar structure at the time of casting is simply used as a starting point, or if the crystal grain size before the start of rolling in a low temperature region is increased, the crystal selectivity becomes very narrow {100 } It is considered that an orientation having a specific in-plane orientation appears preferentially among the orientations. Appropriate strain is applied in a high temperature range to cause appropriate crystal rotation and restructuring, and the {111} orientation, which is undesirable for magnetic properties in the final orientation selectivity, is significantly reduced, and random {100 } Grow in large numbers, and it seems that ridging and in-plane anisotropy can be improved. However, if the destruction of the structure becomes excessive, nuclei for generating {100} orientations will disappear after the cold rolling and at the time of final recrystallization during annealing. For this reason, it is necessary to avoid the accumulation of excessive distortion, and it is necessary to limit to the above-described range.

  Qualitatively, it is preferable to apply strain slowly, contrary to rolling in a low temperature region. It should be noted that rapid recrystallization may occur immediately after rolling due to the relationship between the straining temperature, strain rate, and strain. In particular, when the temperature is high, the recrystallization rate rises in a short time, and when the crystal grains of the steel plate are filled with new maximum crystal grains, the final {100} orientation is intended for cold rolling and annealing. In some cases, the effect of the present invention is lost. This phenomenon is also strongly dependent on the steel components that affect the recrystallization behavior, so it is difficult to strictly limit the temperature etc. unconditionally, but those skilled in the art should avoid conditions after several trials. It is not difficult to identify.

  One of the characteristics of the production conditions of the present invention is that there exists a temperature range where rolling should be avoided. Specifically, the strain applied in the temperature range from 850 ° C. to 900 ° C., hereinafter referred to as the intermediate temperature range, needs to be 0.5 or less. The temperature is preferably 800 ° C. or more and 950 ° C. or less, the strain is preferably 0.3 or less, more preferably 0.1 or less, and if possible, the reduction in the middle temperature range should not be performed.

  The reason for this is not clear, but it is considered that this temperature range is a transformation region in a transformation system material having a relatively low Si and Al content, and that it is related to the fact that it is a two-phase region. Further, even in a non-transformed material, as described above, it is a temperature range in which the role of strain imparted in a high temperature range and the role of strain imparted in a low temperature range overlap, and the microstructural change due to strain is complicated, and the present invention It seems that the destruction of the structure of a specific orientation required by the material, the enhancement of the selectivity of recrystallization nuclei, and the accumulation of high strain do not occur effectively, making these controls meaningless. Strictly speaking, this temperature range is affected by steel components and the like, but in the present invention, all the component steels in the present invention are limited to 850 ° C. or higher and 950 ° C. or lower. Since there exists a temperature range in which such processing is not preferable, it is necessary to cool this temperature range in actual production.

  Correspondingly, it is preferable that a time of 10 seconds or more elapses between the strain application in the high temperature range and the low temperature range. Depending on the conditions, it may be possible to complete the cooling in a time shorter than this, but this overlaps in consideration of the difference in the invention effect between the strain applied in the high temperature region and the strain applied in the low temperature region as described above. Is not preferable, and it is preferable to apply the strain in the low temperature region after the strain applied in the high temperature region has sufficiently disappeared. As the time required for this, it is preferable that the time from the end of rolling in the high temperature range to the start of rolling in the low temperature range be 10 seconds or more.

  Moreover, it is preferable that the heating temperature of the slab at the time of hot rolling shall be 1100 degrees C or less. This is because the precipitates, particularly sulfides and nitrides are coarsened to be harmless and effective in reducing iron loss, and the thermal history is favorable for low temperature rolling, which is a feature of the present invention. In other words, if the slab is heated at 1100 ° C. or higher as in normal hot rolling conditions, the slab is removed from the heating furnace to obtain a heat history such that most of the rolling required in the present invention is performed in a low temperature range. This is because it is necessary to perform cooling after taking out, which hinders cost and productivity. Preferably it is 1050 degrees C or less, More preferably, it is 1000 degrees C or less.

  Normally, the coil winding temperature after hot rolling is increased to improve the magnetic characteristics. However, in the present invention, the effect of the present invention can be obtained more preferably even if the winding temperature is lowered. Preferably it is 750 ° C. or lower, more preferably 700 ° C. or lower, more preferably 650 ° C. or lower, more preferably 600 ° C. or lower, more preferably 550 ° C. or lower. is not. In such a low-temperature winding material, the hot-rolled structure becomes a complete processed structure in combination with large-scale rolling at a low temperature, which is a feature of the present invention. In a normal electromagnetic steel sheet, the remaining of the processed structure in such a hot-rolled steel sheet is avoided as a significant deterioration of the magnetic properties. In the present invention, however, such a structure has a very small in-plane anisotropy. To express. Of course, the effect of the invention is not lost even if hot winding, hot-rolled sheet annealing or the like is performed.

  Further, since the occurrence of the above phenomenon depends on the applied strain amount, the thickness of the steel slab before hot rolling is required to some extent. In this invention, the thickness of the steel piece before hot rolling shall be 50 mm or more. Preferably it is 100 mm or more, More preferably, it is 150 mm or more, More preferably, it is 200 mm or more. When the thickness of the steel slab is 50 mm or less, even if hot rolling under low temperature and high pressure within the scope of the present invention is performed, {100} texture resulting from the columnar structure formed with solidification during casting remains. As is well known, although the magnetic flux density in a specific direction is improved, the anisotropy in the plate surface becomes very large. The cause of this is not clear, but the amount of strain in the low temperature range, which is a feature of the present invention, is within the scope of the invention in order to destroy the {100} orientation having very strong in-plane anisotropy caused by the columnar structure. Even if this is not sufficient, it is considered that a large strain is required in the total hot rolling.

  The manufacturing process of the steel slab is not particularly limited, but it is best from the viewpoint of cost that it is manufactured by continuous casting from a normal melting process.

  The manufacturing process after pickling does not need to be special at all, and the effects of the present invention can be obtained in the same manner as in a normal method for manufacturing a non-oriented electrical steel sheet.

  Although the cold rolling conditions are not particularly limited, the normal production process is set to 50% or more. Considering the mechanism, there is a possibility that cold rolling can be an alternative to the hot rolling of the present invention, but it is possible to provide a logarithmic strain of 3.0 (cold rolling ratio of 95%) or more by cold rolling. Therefore, it is considered industrially preferable to impart strain in the hot region as in the present invention. Even if the cold rolling rate is further increased by some method, the logarithmic strain of cold rolling should be kept to 3.0 or less in the steel of the present invention. The reason is that if more cold strain is applied, the {100} orientation is weakened by superimposing on the effect of the hot strain of the present invention, and the randomness within the {100} orientation plate is reduced. This is because it may be damaged. Further, for example, even when all the hot rolling is performed in a high temperature region, it is possible to achieve both high accumulation of {100} orientation and randomness in the plate plane as much as the steel of the present invention only by cold rolling. It has not been achieved within. This seems to be due to the difference in the quality of strain between hot and cold, and this also gives consideration to kinetic considerations such as hot recovery and recrystallization as in the present invention. It is considered reasonable that it became important.

  After cold rolling, recrystallization annealing, film formation, etc. are performed in the same steps as those for ordinary non-oriented electrical steel sheets. These conditions are not particularly limited with respect to the effects of the present invention.

  In addition, the non-oriented electrical steel sheet obtained through finish annealing by the manufacturing method of the present invention retains its excellent iron loss value and magnetic flux density even after performing strain relief annealing.

  The effect of the present invention is to suppress the introduction of strain after annealing, which is used as a motor, so-called full-process non-oriented electrical steel sheets, as well as to induce strain in the heat treatment process after assembling to a motor etc. by performing skin pass rolling after annealing. The present invention can also be applied to a so-called semi-processed non-oriented electrical steel sheet in which characteristics are improved by using grain growth.

  Furthermore, Sn, W, for the purpose of further improving the magnetic characteristics, additional functions as members such as strength, corrosion resistance and fatigue characteristics, as well as production in the manufacturing process such as casting, annealing, and scrap use Addition or inevitable mixing of trace elements such as Mo, Sb, Cr, Ni, Co does not impair the effects of the present invention.

0.002% C-0.5% Si-0.5% Mn-0.002% S-0.06% P-0% Al-0.002% N-Fe steel was melted and continuously A steel slab was formed by casting, and hot rolling was performed while changing the hot rolling conditions as shown in Table 1 to obtain a hot rolled plate having a thickness of 2.2 mm. After pickling the hot-rolled sheet, it was cold-rolled to 0.50 mm and then subjected to continuous annealing at 750 ° C. for 30 seconds to obtain a product. A sample for measurement is cut out from this plate, and the magnetic properties of the sample obtained by heat treatment at 750 ° C. for 2 hours as strain relief annealing are shown in FIGS. Here, the magnetic properties were measured in the direction of 0 °, 45 °, and 90 ° from the coil rolling direction with a sample having a size of 55 mm × 55 mm, and for each value X ₀ , X ₄₅ , X ₉₀ , The average in the plane is
(X ₀ + 2 × X ₄₅ + X ₉₀ ) / 4
And the in-plane anisotropy is
(X ₀ -2 × X ₄₅ + X ₉₀ ) / 2
It was evaluated by.

  The remarkable improvement in the average characteristics and reduction in the in-plane anisotropy of the hot-rolled condition material of the present invention are clear.

0.002% C-1.6% Si-0.1% Mn-0.001% S-0.02% P-0.2% Al-0.002% N-Fe steel was melted. Was formed into a steel slab by continuous casting, the slab heating temperature was set to 1150 ° C., and hot rolling was performed while changing the hot rolling temperature range to obtain a hot rolled sheet having a thickness of 2.3 mm. After pickling the hot-rolled sheet, it was cold-rolled to 0.50 mm and then subjected to continuous annealing at 950 ° C. × 30 seconds to obtain a product. A sample for measurement was cut out from this plate, and the magnetic flux density B ₅₀ of the sample obtained by heat treatment at 750 ° C. for 2 hours as strain relief annealing was measured in the same manner as in Example 1, and the plate surface average and plate surface anisotropic were measured. 5 and 6 show the results of arranging the properties by the amount of strain in the low temperature range during hot rolling. The improvement in the in-plane average value and the remarkable reduction in the in-plane anisotropy by the hot rolling conditions of the present invention are clear.

0.002% C-2.1% Si-0.3% Mn-0.001% S-0.06% P-0.3% Al-0.001% N-Fe steel was melted. Was formed into a steel slab by continuous casting, the slab heating temperature was set to 1100 ° C., and hot rolling was performed while changing the hot rolling temperature range to obtain a hot rolled sheet having a thickness of 2.0 mm. After pickling the hot-rolled sheet, it was cold-rolled to 0.35 mm, and then subjected to continuous annealing at 1050 ° C. for 30 seconds to obtain a product. The magnetic flux density B ₁₀ of samples obtained from a plate were measured in the same manner as in Example 1, shows a plate surface anisotropy Results Figure 7 organized with the strain amount in a high temperature range of hot rolling. In the figure, ● represents “low-temperature strain> high-temperature strain”, and ○ represents “low-temperature strain <high-temperature strain”. The remarkable reduction in in-plane anisotropy due to the hot rolling conditions of the present invention is clear.

0.001 to 0.003% C-0.1 to 1.5% Mn-0.0003 to 0.003% S-0.01 to 0.08% P comparable to that of ordinary non-oriented electrical steel sheets About steel having a component in the range of -0.001 to 0.003% N, the slab heating temperature is set to 900 ° C to 1200 ° C, hot rolling is performed under different hot rolling conditions, and the plate thickness is 1.8 to 3.0 mm. A hot rolled sheet was obtained. After this hot-rolled sheet was pickled, it was cold-rolled to 0.50 mm, and then subjected to continuous annealing for 30 seconds at a temperature such that the crystal grain size was in the range of 60 to 100 μm, depending on the components, to give a product. FIG. 8 shows the result of measuring the magnetic flux density B ₁₀ of the sample obtained from this plate in the same manner as in Example 1 and arranging the in-plane anisotropy by the amount of Si + Al. In the figure, ● is the amount of strain in the low temperature range, strain rate, time between passes, amount of strain in each pass, amount of strain in the high temperature range, strain rate, time between passes, amount of strain in each pass, strain amount in the middle temperature range , The ratio of the strain amount between the high temperature region and the low temperature region, and the time between rolling from the high temperature region to the low temperature region are all within the scope of the present invention. It is outside. The effect of the hot rolling conditions of the present invention can be applied to a wide range of materials, and the effect of reducing in-plane anisotropy is clear. Note that “*” in the figure indicates that ridging is severe and the surface state of the steel sheet is not good.

Steels with the components shown in Table 2 are melted and made into continuous cast slabs under the conditions shown in Tables 3 and 4 (continued in Table 3), followed by hot rolling, pickling, cold rolling, and continuous annealing products. The characteristics were evaluated. Steel A was evaluated with B ₅₀ and W _15/50 , Steel B with B ₁₀ and W _10/400 , and Steel C with B ₁₀ and W _10/2000 . From this result, it can be seen that the steel sheet within the scope of the present invention has a good iron loss value and particularly a plate surface average of magnetic flux density and extremely small in-plane anisotropy, and the effectiveness of the control of the present invention conditions is clear. is there.

Graph of magnetic flux density B ₅₀ against hot rolling conditions. Graph of iron loss W _15/50 against hot rolling conditions. Plane graph of anisotropy of the magnetic flux density B ₅₀ with respect to the hot rolling conditions. Graph of in-plane anisotropy of iron loss W _15/50 against hot rolling conditions. A graph of magnetic flux density B ₅₀ against logarithmic strain in a low temperature range. Plane graph of anisotropy of the magnetic flux density B ₅₀ with respect to the logarithm distortion in the low-temperature region. Plane graph of anisotropy of the magnetic flux density B ₁₀ with respect to the logarithm distortion in a high temperature range. Plane graph of anisotropy of the magnetic flux density B ₁₀ with respect to Si + Al content.

Claims (8)

In mass%, C: 0.040% or less, Si: 0.05 to 3.5%, Mn: 3.0% or less, Al: 3.5% or less, S: 0.015% or less, P: 0 Molten steel containing 25% or less and N: 0.040% or less is solidified by casting into a steel piece having a thickness of 50 mm or more, and rolling is performed at a logarithmic strain of 1.0 or more in a temperature range of 500 ° C. or more and 850 ° C. or less. In addition, in rolling in a temperature range of 850 ° C. or less in hot rolling, the average strain rate of each rolling pass is 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more , and the time between each rolling pass is 4 A method for producing a non-oriented electrical steel sheet characterized by performing cold rolling at a reduction rate of 50% or more after pickling for 0.0 second or less and further pickling. Here, the logarithmic strain is a natural logarithm of (sheet thickness before rolling) / (sheet thickness after rolling). And have you hot rolling of the steel sheet according to claim 1, the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the average strain rate of the rolling pass in a temperature range of 850 ° C. or less 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more, the time between each rolling pass is 4.0 seconds or less , rolling in a temperature range of 900 ° C. or more is 3.0 or less in terms of logarithmic strain, and The manufacturing method of the non-oriented electrical steel sheet characterized by being below logarithmic strain by rolling in a temperature range of 500 ° C or higher and 850 ° C or lower. And have you hot rolling of the steel sheet according to claim 1, the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the average of each rolling pass the temperature range at 850 ° C. or less The strain rate is 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more, the time between each rolling pass is 4.0 seconds or less, and rolling in the temperature range of 850 ° C. to 900 ° C. is logarithmic strain. The manufacturing method of the non-oriented electrical steel sheet characterized by being 0.5 or less. And have you hot rolling of the steel sheet of claims 1 to 3, the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the average of each rolling pass the temperature range at 850 ° C. or less The strain rate is 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more, the time between each rolling pass is 4.0 seconds or less, and the strain rate of each rolling pass for rolling in a temperature range of 900 ° C. or more. The method of manufacturing a non-oriented electrical steel sheet, characterized in that the average is 10 / s or less. And have you hot rolling of the steel sheet of claims 1 to 4, the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the average of each rolling pass the temperature range at 850 ° C. or less The strain rate is 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more, the time between each rolling pass is 4.0 seconds or less, and the logarithmic strain of each rolling pass for rolling in a temperature range of 900 ° C. or more. The method of manufacturing a non-oriented electrical steel sheet, characterized in that the average of And have you hot rolling of the steel sheet of claims 1 to 5, the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the average of each rolling pass the temperature range at 850 ° C. or less The strain rate is 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more, the time between each rolling pass is 4.0 seconds or less, and the time between rolling passes for rolling in a temperature range of 900 ° C. or more. Is 10.0 seconds or more, The manufacturing method of the non-oriented electrical steel sheet characterized by the above-mentioned. And have you hot rolling of the steel sheet of claims 1 to 6, the rolling log distortion in the temperature range of 500 ° C. or higher 850 ° C. or less and 1.0 or more, the average of each rolling pass the temperature range at 850 ° C. or less The strain rate is 30 / s or more, the average logarithmic strain of each rolling pass is 0.2 or more, the time between each rolling pass is 4.0 seconds or less, and 850 ° C. or less after rolling in the temperature range of 900 ° C. or more is completed. The method for producing a non-oriented electrical steel sheet, characterized in that the time until rolling in the temperature range of 10 seconds is 10 seconds or longer.   The manufacturing method of the non-oriented electrical steel sheet characterized by the slab heating temperature of hot rolling being 1100 degrees C or less among the steel plates of Claims 1-7.

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