JP2008156741A - Method for manufacturing non-oriented electromagnetic steel sheet with high magnetic flux density - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a non-oriented electromagnetic steel sheet having high magnetic flux density at a low cost. <P>SOLUTION: A steel slab includes 0.1% to 2.0% Si, 1.0% or less Al, while satisfying the expression of 0.1%≤Si+2Al≤2.0%, less than 0.004% C, 0.003% or less S, 0.003% or less N, and the balance Fe with unavoidable impurities. The method for manufacturing the non-oriented electromagnetic steel sheet comprises the steps of: hot-rolling the steel slab into a hot-rolled plate through a rough rolling step and a subsequent finish hot rolling step; pickling the plate; cold-rolling the plate once with a rolling ratio of 85 to 97%; and then finish-annealing the sheet. In the above finish hot rolling step, a heating temperature ST for the slab, a starting temperature F0T of the finish rolling, and an ending temperature FT of the finish hot rolling are set as in the expression (1), the expression (2) and the expression (3) respectively: Expression (1) 850°C≤ST≤1,150°C; Expression (2) 850°C≤F0T≤1,150°C; and Expression (3) 3,750°C≤FT≤850°C, and a rolling reduction ratio of at least one or more passes in an area α is set at 15% or higher. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a non-oriented electrical steel sheet having a high magnetic flux density, which is used as an iron core material for electrical equipment.

  In recent years, in the fields of electrical machinery, especially rotating machines where non-oriented electrical steel sheets are used as iron core materials, and in the fields of medium and small transformers, global power conservation, energy conservation, and global environmental conservation such as CFC regulations Among these trends, the trend toward higher efficiency is spreading rapidly. For this reason, there is an increasing demand for non-oriented electrical steel sheets to improve their characteristics, that is, to achieve high magnetic flux density and low iron loss.

  The reduction of iron loss in non-oriented electrical steel sheets has been achieved mainly by reducing the Joule heat loss due to eddy current loss flowing in each steel sheet forming the iron core during use by increasing the electrical resistivity by adding Si and Al. It was.

  On the other hand, as energy loss of the entire device including the rotating machine and the iron core, the contribution of copper loss, which is Joule heat loss caused by current flowing through the coil wound around the iron core, cannot be ignored. In order to reduce the copper loss, it is effective to reduce the current density necessary for exciting the same magnetic field strength, and it is indispensable to develop a material that expresses a higher magnetic flux density with the same exciting current. That is, development of a high magnetic flux density non-oriented electrical steel sheet is essential. By increasing the magnetic flux density to be excited, there is an advantage that the size of the iron core of an electrical device using a non-oriented electrical steel sheet such as a rotating machine or a small transformer can be reduced in size and weight.

  In the prior art, in the non-oriented electrical steel sheet that has been developed for the purpose of low iron loss, elements having high electrical resistivity such as Si and Al have been mainly added, but when the content of these elements increases, Because the saturation magnetic flux density of non-oriented electrical steel sheets decreases, in order to increase the operating magnetic flux density when actually used as an electrical device, the excitation current must be increased and the copper loss will increase. There were difficulties. Therefore, the non-oriented electrical steel sheet containing many elements with high electrical resistivity such as Si and Al has to reduce the operating magnetic flux density. As a result, for example, in a rotating machine, a high torque should be exhibited. There was a problem that became difficult.

  On the other hand, by realizing the high magnetic flux density non-oriented electrical steel sheet that discloses the manufacturing method in the present invention, it is possible to reduce the size of both the rotating machine and the iron core. Has the advantage that energy loss during operation can be reduced by reducing the weight of the entire system.

  Further, in the rotating machine, the torque increases, and a more compact and high-output rotating machine is realized.

  Thus, the realization of a high magnetic flux density non-oriented electrical steel sheet not only can reduce the energy loss during the operation of the iron core and the rotating machine, but also has a ripple effect on the entire system including it. There is nothing.

  Patent Document 1 (JP-A-58-204126) contains C ≦ 0.02%, the total amount of Si or Si and Al is 1.5% or less, Mn: 1.0% or less, and P: 0.20% or less. The balance is finished at a finish rolling temperature of steel consisting of inevitable impurities at a low temperature of 600 to 700 ° C., wound up at a temperature of 500 ° C. or less, and this steel strip is at a temperature of A 3 transformation point or less for 30 seconds to 15 minutes. A method for producing a non-oriented electrical steel sheet characterized by annealing is disclosed.

  However, in the manufacturing method in this prior application, there is a problem that the hot-rolled steel strip after hot-rolling is subjected to a hot-rolled sheet annealing step, and there is a problem that the cost is increased. There was a problem that consumers of electrical steel sheets could not be accepted in reality.

  In the examples, the C content is 0.004% or more in mass%, and in the non-oriented electrical steel sheet manufacturing method of the single cold rolling method that omits the hot-rolled sheet annealing found in the present invention, By limiting the content to a certain value or less, there is no technical idea that the effect of improving the magnetic flux density of the product can be enhanced through texture control by controlling the integrated process starting from hot rolling.

  In Patent Document 2 (Japanese Patent Application Laid-Open No. 59-104429), in the finish hot rolling of steel in which the total amount of Si and Al is 1.5% or less, the hot rolling end temperature is finished to 600 ° C. or more and 700 ° C. or less A manufacturing method is disclosed in which finish rolling is performed after cold rolling at a rolling reduction of 75% to 85%.

  However, since the finish hot rolling end temperature is too low at 700 ° C. or lower, the rolling reaction force of the finish hot rolling becomes excessively high, which may significantly impair the productivity and make the finish hot rolling impossible. In addition, in order to stably perform finish hot rolling while keeping the finish hot rolling finish temperature low, it is necessary to reduce the finish hot rolling speed, and as a result, productivity is inferior, resulting in an increase in cost. There is. It was also found that the effect of improving the magnetic flux density of the product cannot be obtained sufficiently at the finish hot rolling finish temperature in the above range.

  Moreover, also in C content, in the high concentration of 0.006% and 0.005% of C content shown in the examples, not only finish hot rolling conditions but also finish hot rolling conditions disclosed in the present application. It was also revealed that the effect of improving the magnetic flux density is not sufficient.

  Furthermore, as a method for improving the magnetic properties of the non-oriented electrical steel sheet by improving the primary recrystallization texture, Sn addition, as disclosed in Japanese Patent Application Laid-Open No. 55-158252, Non-oriented electrical steel sheets with excellent magnetic properties due to the improvement of the texture by adding Sn and Cu as in Kaikai 62-180014 or Sb as in Patent Document 5 (Japanese Patent Laid-Open No. 59-100217) A manufacturing method is disclosed. However, even with the addition of these texture control elements such as Sn, Cu, or Sb, it is possible to meet the demands of today's customers to supply high magnetic flux density low iron loss non-oriented electrical steel sheets at low cost. I couldn't do it enough.

  In addition, the manufacturing process such as the finishing annealing cycle described in Patent Document 6 (Japanese Patent Application Laid-Open No. 57-35626) has been taken, but all of them have a low iron loss. However, the magnetic flux density was not sufficiently effective.

  Thus, in the prior art, it has not been possible to manufacture a high magnetic flux density non-oriented electrical steel sheet that is advantageous for downsizing of iron cores, which is strongly demanded by recent customers. I couldn't respond.

  In the present invention, the re-rolling texture after cold rolling and finish annealing is obtained by pre-building the texture of the hot-rolled sheet by setting the finish hot-rolling process of the non-oriented electrical steel sheet to a specific condition. It is a technical idea to control, and further, when performing this production method, the content of carbon contained in the steel significantly affects the effect of the finish hot rolling method disclosed in the present invention. Newly found. This provides a technique for producing a non-oriented electrical steel sheet having a high magnetic flux density by a method that is cheaper than the prior art.

JP 58-204126 A JP 59-104429 A JP-A-55-158252 Japanese Patent Laid-Open No. 62-180014 JP 59-100217 JP-A-57-35265

  An object of the present invention is to solve such problems in the prior art and to provide a high magnetic flux density non-oriented electrical steel sheet.

The gist of the present invention is as follows.
(1)
In mass% in steel
0.1% ≦ Si ≦ 2.0%
Al ≦ 1.0%
And 0.1% ≦ Si + 2Al ≦ 2.0% is satisfied,
C <0.004%
S ≦ 0.003%
N ≦ 0.003%
As a steel slab consisting of Fe and the inevitable impurities in the balance, hot rolling is used to perform rough rolling and subsequent hot rolling to obtain a hot rolled sheet, pickling and a single cold rolling step, followed by finishing. In the manufacturing method of the non-oriented electrical steel sheet to be annealed, the slab heating temperature ST, the finishing rolling start temperature F0T, and the finishing hot rolling end temperature FT of the finish hot rolling are respectively determined as follows, and in the finishing hot rolling, the α region A method for producing a non-oriented electrical steel sheet having a high magnetic flux density, wherein the rolling reduction of at least one pass is 15% or more.

850 ° C ≤ ST ≤ 1150 ° C
850 ° C ≤ F0T ≤ 1150 ° C
750 ° C ≦ FT ≦ 850 ° C
(2)
In the method for producing a non-oriented electrical steel sheet according to (1), a method for producing a non-oriented electrical steel sheet characterized in that a rolling rate in the cold rolling step is 85% or more and 97% or less. As a result of intensive investigations on inexpensive manufacturing methods for non-oriented electrical steel sheets that achieve high magnetic flux density, the texture of hot-rolled sheets can be reduced by making the finish hot rolling process of non-oriented electrical steel sheets a specific condition. Pre-fabrication makes it possible to control the recrystallized texture after cold rolling and finish annealing, and the prior art has added costly processes such as hot-rolled sheet annealing to obtain high magnetic flux density. The present invention provides a method for producing a non-oriented electrical steel sheet having a low cost and a high magnetic flux density, particularly when performing this production method. To properly control However, it has been found that the effect of the finish hot rolling method disclosed in the present invention is remarkably enhanced, and an appropriate content of carbon is also disclosed at the same time.

  According to the present invention, a non-oriented electrical steel sheet having a high magnetic flux density can be produced at a low cost.

  First, components will be described.

  In the present invention, excessive addition of Si reduces the magnetic flux density of the product and is harmful, so its content is limited to 2.0% or less. On the other hand, an addition amount of 0.1% or more is required for the purpose of ensuring electric resistivity within a range not hindering improvement in magnetic flux density and reducing eddy current loss.

  Al may be added for the purpose of securing electrical resistivity in the same manner as Si. In the present invention, since addition of Al is not essential, the lower limit is not determined. On the other hand, like Si, excessive addition reduces the magnetic flux density of the product and is harmful, so its content is limited to 1.0% or less.

  Since Si and Al are added to ensure electrical resistivity, the total amount of (Si + 2Al) needs to be 0.1% or more. On the other hand, if the total amount of (Si + 2Al) exceeds 2.0%, the magnetic flux density of the product is reduced, which is harmful. Therefore, the total amount of (Si + 2Al) is limited to 2.0% or less.

  Controlling the C content to a certain level or less is a novel finding that is important for sufficiently expressing the effect of texture control in an integrated process from finish hot rolling to finish annealing in the present invention. If it is only a viewpoint which prevents the increase in the loss by the magnetic aging in use as a non-oriented electrical steel sheet like the past, it is enough if the content is 0.005% or less.

  However, in the present invention, if the C content is 0.004% or more, the recrystallization texture of the product after finish annealing cannot be controlled successfully, and a high magnetic flux density cannot be obtained. Therefore, in the present invention, the C content is set to less than 0.004%. Furthermore, in order to increase the magnetic flux density of the non-oriented electrical steel sheet by texture control in a series of processes in the present invention, the C content is preferably 0.003% or less.

  In the present invention, a high magnetic flux density can be achieved by reducing S and N.

  S and N are partly re-dissolved during slab heating in the hot rolling process, and fine precipitates of MnS and AlN are reprecipitated during hot rolling to suppress grain growth during finish annealing. It causes the loss to worsen. For this reason, both the contents must be 0.003% or less.

  Next, process conditions will be described.

  The steel slab composed of the above components is melted in a converter and manufactured by continuous casting or ingot-bundling rolling. The steel slab is heated by a known method. The slab is hot rolled to a predetermined thickness.

  In the finish hot rolling in the present invention, when the slab heating temperature ST is less than 850 ° C., the rolling reaction force at the time of rough hot rolling and finish hot rolling becomes too large and rolling becomes difficult, so the slab heating temperature is set to 850 ° C. or more. . On the other hand, when the slab heating temperature exceeds 1150 ° C., impurities such as S in the steel re-dissolve and reprecipitates finely during finish hot rolling, preventing crystal grain growth during finish annealing, resulting in significant iron loss. As it deteriorates and recrystallization control during finish annealing is hindered and the magnetic flux density is lowered, the slab heating temperature is set to 1150 ° C. or lower.

  When the finish hot rolling start temperature F0T is less than 850 ° C., the rolling reaction force during finish hot rolling increases and rolling becomes difficult, so the finish hot rolling start temperature is set to 850 ° C. or more. On the other hand, when the finish hot rolling start temperature exceeds 1150 ° C., the recrystallization progress rate during finish hot rolling becomes too high, and the effect of the present invention for controlling the texture of the hot rolled steel strip while performing finish hot rolling is effective. As a result, the magnetic flux density of the product is significantly lowered, so the finish hot rolling start temperature is set to 1150 or less.

  When the finishing hot rolling finish temperature FT is less than 750 ° C., the rolling reaction force during finishing hot rolling increases, finishing hot rolling becomes difficult, the shape of the hot rolled sheet deteriorates, and the thickness control becomes difficult, and the product Therefore, the finish hot rolling finish temperature is set to 750 ° C. or higher. When the finish hot rolling finish temperature exceeds 850 ° C., the recrystallization progress rate during finish hot rolling becomes too high, and the effect of the present invention for controlling the texture of the hot rolled steel strip while performing finish hot rolling is impaired. As a result, the magnetic flux density of the product is remarkably lowered, so the finish hot rolling finish temperature is set to 850 ° C. or lower.

  In the present invention, since it is necessary to control the texture of the hot-rolled steel strip during finish hot rolling, it is necessary to set the reduction ratio of at least one pass or more in the α region to 15% or more in the finish hot rolling. . In the finish hot rolling, if at least one pass is not rolled at 15% or more in the α region, the recrystallization texture during cold rolling and subsequent finish annealing is controlled by the texture control of the hot rolled steel strip intended by the present invention. Since the effect of increasing the magnetic flux density by controlling the above cannot be obtained, it is determined that the rolling reduction of at least one pass or more in the α region is 15% or more in the finish hot rolling. As described in the explanation of the components, the texture control of the hot-rolled steel strip is performed by securing the reduction amount of at least one pass in the α region at 15% or more in the finish hot rolling while controlling the C content. It is possible to improve the recrystallized texture of the product after cold rolling and finish annealing of the hot-rolled steel strip, and to increase the magnetic flux density.

  The reason why low iron loss can be achieved by this technical idea is currently being elucidated, but by improving the rolling rate above a certain level in the α region, the texture of the hot-rolled steel strip should be improved. Therefore, among the crystal grains in the recrystallized texture of the product after cold rolling and recrystallization, it is possible to enrich the crystal grains having the {100} plane in parallel with the plate surface. I guess that is the mechanism of.

  The inventors have found that when the hot rolling end temperature becomes too high, the texture of the hot rolled steel strip formed by finishing hot rolling in the α phase region disappears due to the progress of recrystallization and grain growth.

  From this point of view, the hot-rolled sheet annealing, which has been used in the prior art to improve the magnetic flux density of non-oriented electrical steel sheets, is a hot-rolled steel strip that is built in the present invention and is useful for improving the magnetic flux density of products. It is thought that the magnetic flux density of the product could not be sufficiently improved because the texture of the steel sheet was offset by recrystallization and grain growth that proceeded in the hot-rolled steel strip during hot-rolled sheet annealing.

  The technical idea by this conventional manufacturing method is to increase the crystal grain size before cold rolling, thereby inhibiting the development of crystal grains having {111} planes parallel to the plate surface, which hinder the improvement of magnetic flux density, The object was to increase the abundance of crystal grains having a small amount of {110} <001> orientation. For this reason, the method which has the technical idea of this invention of improving the magnetic flux density of a product by improving the texture of the hot-rolled steel strip which just finished finishing hot rolling was not disclosed.

  Moreover, even if the hot rolling end temperature for achieving this purpose is too low, a texture unfavorable for improving the magnetic flux density of the product develops in the hot rolled steel strip, resulting in a decrease in the magnetic flux density of the product. They revealed.

  That is, the inventors have clarified that there is an optimum hot rolling end temperature range in order to control the texture of the hot rolled steel strip intended by the present invention.

  In addition, if the amount of C in the steel exceeds the range specified in the present invention, the formation of a texture suitable for improving the magnetic flux density of the product by hot rolling in the α phase region is significantly hindered, The inventors have also revealed that the magnetic flux density of the product is significantly reduced.

  The hot-rolled steel strip after finishing hot rolling is pickled and cold-rolled to the final thickness. The cold-rolled steel strip after cold rolling is recrystallized by finish annealing to obtain a finished product. This product may be used without being subjected to strain relief annealing, or may be used after being subjected to strain relief annealing after being shaped through a process such as punching into an appropriate shape.

  As a method of further promoting the effect of improving the magnetic properties of the non-oriented electrical steel sheet according to the present invention, it is preferable to control the cold rolling rate to 85% during cold rolling. Thereby, magnetic flux density further improves. Although the upper limit of the cold rolling rate is not defined, the manufacturing cost increases by increasing the cold rolling rate, and therefore the cold rolling rate is preferably 97% or less from the viewpoint of productivity. The reason why the magnetic flux density is improved by increasing the cold rolling rate is currently under intensive investigation, but by improving the cold rolling rate to 85% or more, the texture improved by the manufacturing method defined in the present invention. It is presumed that the magnetic properties are improved by promoting the cold rolling of the hot-rolled steel strip having a texture and improving the texture after recrystallization.

  The temperature range of finish annealing must be performed in the α phase range because it is necessary to form an appropriate recrystallized texture to increase the magnetic flux density during finish annealing from the texture created from the hot-rolled steel strip. There is. That is, when the finish annealing temperature exceeds the Ac1 point, which is the upper limit of the α phase region, the magnetic flux density of the product is lowered. Therefore, the finish annealing temperature needs to be performed at the Ac1 point or less within the α phase.

  If the final annealing time is less than 15 seconds, recrystallization is insufficient and a high magnetic flux density cannot be obtained. On the other hand, if the finish annealing time exceeds 3 minutes, productivity deteriorates and costs increase, so the finish annealing time should be within 3 minutes.

  Thereby, it becomes possible to manufacture a non-oriented electrical steel sheet having a high magnetic flux density at a lower cost than before. In addition, the high magnetic flux density non-oriented electrical steel sheet obtained by the present invention is most suitable for electrical equipment that is required to be small and light, iron cores of rotating machines, and small transformers. Suitable for iron core applications such as required motors for electric vehicles.

  Next, examples of the present invention will be described.

  A slab for non-oriented electrical steel having the components shown in Table 1 was heated by a normal method at 1100 ° C. for 1 hour and finished to 2.5 mm by hot rolling. The finish hot rolling start temperature was 1000 ° C., and the finish hot rolling finish temperature was changed from 700 ° C. to 865 ° C. by controlling the rolling rate and the cooling rate between the hot rolling stands.

Since the Ar ₁ transformation point of this steel is 880 ° C., at the finishing hot rolling machine consisting of 7 stands, at least 3 passes of reduction on the outlet side are carried out in the α region of 880 ° C. or less, and the reduction rate is 5th pass Is controlled to 19.5%, the sixth pass is 15.2%, the seventh pass is 10.7%, and the reduction amount in the α phase region is 15% in at least the second pass and the fifth pass. Control hot rolling was performed to ensure the above.

  Subsequently, pickling was performed, and the product was finished to 0.5 mm by cold rolling, and this was subjected to finish annealing at 750 ° C. for 30 seconds in a continuous annealing furnace. Then, it cut | disconnected to the Epstein sample and measured the magnetic characteristic.

  Table 1 shows the components of the present invention and the comparative example, and Table 2 shows the measurement results of the relationship between the finish hot rolling end temperature and the magnetic properties.

  From Table 2, it is possible to manufacture high-flux-density non-oriented electrical steel sheets by appropriately controlling the finish hot-rolling finish temperature and reduction conditions, omitting costly processes such as hot-rolled sheet annealing. It is.

  A slab for non-oriented electrical steel having the components shown in Table 3 was heated by a normal method at 1100 ° C. for 1 hour and finished to 2.5 mm by hot rolling. The finishing hot rolling start temperature was 980 ° C., and the finishing hot rolling end temperature was controlled to 805 ° C. by controlling the rolling speed and the cooling rate between the hot rolling stands.

Since the Ar ₁ transformation point of this steel is 865 ° C., in the finishing hot rolling machine consisting of 7 stands, the reduction of the 3 passes on the outlet side is carried out in the α region of 865 ° C. or less, and the reduction rate is 5th pass 25.0%, 6th pass is 15.2%, 7th pass is controlled to 10.7%, and control heat is ensured to ensure 15% or more reduction in the α phase region at 5th pass and 6th pass I did.

  Subsequently, pickling was performed and the product was finished to 0.5 mm by cold rolling, and this was subjected to finish annealing at 760 ° C. for 30 seconds in a continuous annealing furnace. Then, it cut | disconnected to the Epstein sample and measured the magnetic characteristic.

  Table 3 shows the components of the present invention and comparative examples, and Table 4 shows the measurement results of the magnetic properties of the respective test materials.

  In this way, by controlling the C content to less than 0.004% and appropriately controlling the conditions of the finishing hot rolling conditions, costly processes such as hot-rolled sheet annealing can be omitted, and high magnetic flux density can be reduced. It is possible to manufacture grain-oriented electrical steel sheets. Furthermore, it can be seen from Table 4 that a higher magnetic flux density is obtained particularly when the C content is 0.003% or less. Furthermore, it can be seen that when the C content is 0.002% or less, a higher magnetic flux density of 1.815 T or more is obtained.

  A slab for non-oriented electrical steel having the components shown in Table 5 is heated by a normal method at 1050 ° C. for 1 hour, rough rolled into a 40 mm rough bar, and then finished to 2.5 mm by 7-pass hot rolling. It was. The finishing hot rolling start temperature was 950 ° C., and the finishing hot rolling end temperature was controlled to 800 ° C. by controlling the rolling speed and the cooling rate between the hot rolling stands.

Since the Ar ₁ transformation point of this steel is 861 ° C., in a finishing hot rolling machine consisting of 7 stands, the hot rolling finish plate thickness and finishing hot rolling finish temperature are adjusted by variously adjusting the rolling schedule. Control was performed so as to satisfy the above conditions.

  Subsequently, pickling was performed, and the product was finished to 0.5 mm by cold rolling, and this was subjected to finish annealing at 750 ° C. for 30 seconds in a continuous annealing furnace. Then, it cut | disconnected to the Epstein sample and measured the magnetic characteristic.

  Table 5 shows the components of the present invention and comparative examples, and Table 6 shows the measurement results of the relationship between the finish hot rolling finish temperature and the magnetic properties.

  In the present invention 1 and the present invention 2, in the fifth and sixth passes of finish hot rolling, rolling is performed at a temperature in the α-phase region of 861 ° C. or less, and the rolling reduction reaches 15% or more. In the fifth to seventh passes of finish hot rolling, a reduction ratio of 15% or more is secured in the α phase region of 861 ° C. or less, and as a result, the magnetic flux density B50 value of the product is excellent at 1.810T or more. Magnetic characteristics are obtained.

  On the other hand, in Comparative Example 1 and Comparative Example 2, rolling is performed in the α-phase region of 861 ° C. or lower in the fifth to seventh passes of finish hot rolling, and the reduction ratios in those passes are all less than 15%. As a result, it can be seen that the magnetic flux density of the product is inferior to that of the present invention.

  From Table 6, by appropriately controlling the finish hot rolling conditions and securing at least 15% reduction in one pass in the α phase region of 861 ° C. or lower, which is the Ar1 transformation point of this steel, the product magnetic flux density It can be seen that it is possible to significantly improve.

  As described above, by appropriately controlling the hot-rolling conditions and components, it is possible to produce a non-oriented electrical steel sheet having a high magnetic flux density by omitting costly processes such as hot-rolled sheet annealing. .

  The slab for non-oriented electrical steel having the components shown in Table 7 was heated at 1100 ° C. for 1 hour by a normal method and finished to 2.5 mm by hot rolling. The finish hot rolling start temperature was 1000 ° C., and the finish hot rolling finish temperature was changed from 700 ° C. to 880 ° C. by controlling the rolling rate and the cooling rate between the hot rolling stands.

Since the Ar ₁ transformation point of this steel is 855 ° C., at the finishing hot rolling machine consisting of 7 stands, at least 3 passes on the outlet side are reduced in the α region of 855 ° C. or less, and the reduction rate is 5th pass. Is controlled to 19.5%, the sixth pass is 15.2%, the seventh pass is 10.7%, and the reduction amount in the α phase region is 15% in at least the second pass and the fifth pass. Control hot rolling was performed to ensure the above.

  Subsequently, pickling was performed, and it was finished to 0.35 mm by cold rolling, and this was subjected to finish annealing at 850 ° C. for 60 seconds in a continuous annealing furnace. Then, it cut | disconnected to the Epstein sample and measured the magnetic characteristic.

  Table 7 shows the components of the present invention and comparative examples, and Table 8 shows the measurement results of the relationship between the finish hot rolling end temperature and the magnetic properties.

  From Table 8, it is possible to manufacture high-flux-density non-oriented electrical steel sheets by appropriately controlling the finish hot-rolling finish temperature and reduction conditions, omitting costly processes such as hot-rolled sheet annealing. It is.

  The slab for non-oriented electrical steel having the components shown in Table 9 was heated at 1100 ° C. for 1 hour by a normal method, and finished to 2.5 mm and 2.0 mm by hot rolling. The finish hot rolling start temperature was 1000 ° C., and the finish hot rolling finish temperature was 760 ° C. by controlling the rolling speed and the cooling rate between the hot rolling stands.

Since the Ar ₁ transformation point of this steel is 858 ° C., in the finishing hot rolling machine consisting of 7 stands, at least 3 passes of reduction on the outlet side were performed in the α region of 858 ° C. or lower. When the thickness of the hot-rolled finished sheet is 2.5 mm, the reduction rate of the third pass is controlled to 25.0% for the fifth pass, 15.2% for the sixth pass, and 10.7% for the seventh pass. When the thickness of the hot-rolled finished sheet is 2.0 mm, the fifth pass is controlled to 22.2%, the sixth pass is 17.9%, the seventh pass is 13.0%, and at least the fifth and sixth passes. In the second pass, controlled hot rolling was performed so that the reduction amount in the α-phase region could be secured at 15% or more.

  Subsequently, pickling was performed, cold rolling was performed, and this was subjected to finish annealing at 750 ° C. for 20 seconds in a continuous annealing furnace. Then, it cut | disconnected to the Epstein sample and measured the magnetic characteristic. In cold rolling, the thickness of the finished sheet was changed, and the relationship between the cold rolling rate and magnetic properties was investigated.

  Table 10 shows the relationship between cold rolling conditions and magnetic properties. It can be seen that the magnetic flux density B50 reaches an excellent value of 1.830 T or more when the cold rolling rate is 85% or more.

  Therefore, from Table 10, it is possible to manufacture a non-oriented electrical steel sheet having a high magnetic flux density while omitting costly processes such as hot-rolled sheet annealing by controlling the cold rolling rate to 85%. .

Claims (2)

In mass% in steel
0.1% ≦ Si ≦ 2.0%
Al ≦ 1.0%
And 0.1% ≦ Si + 2Al ≦ 2.0% is satisfied,
C <0.004%
S ≦ 0.003%
N ≦ 0.003%
As a steel slab consisting of Fe and the inevitable impurities in the balance, hot rolling is used to perform rough rolling and subsequent hot rolling to obtain a hot rolled sheet, pickling and a single cold rolling step, followed by finishing. In the manufacturing method of the non-oriented electrical steel sheet to be annealed,
The slab heating temperature ST, finish rolling start temperature F0T, and finish hot rolling end temperature FT of finish hot rolling are determined as follows, and the reduction ratio of at least one pass or more in the α region in the finish hot rolling is 15% or more. A method for producing a non-oriented electrical steel sheet having a high magnetic flux density.
850 ° C ≤ ST ≤ 1150 ° C
850 ° C ≤ F0T ≤ 1150 ° C
750 ° C ≦ FT ≦ 850 ° C   The method for producing a non-oriented electrical steel sheet according to claim 1, wherein a rolling rate in the cold rolling step is 85% or more and 97% or less.