JP2007056303A - Method for producing non-oriented silicon steel sheet excellent in magnetic characteristic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a non-oriented silicon steel sheet excellent in a magnetic flux density. <P>SOLUTION: When the non-oriented silicon steel sheet is produced, a part or all processes for cold-rolling before a finish annealing are performed in a pack rolling. by which two or more steel sheets are laminated. In this case, the pack rolling is performed in conditions of ≥200°C rolling temperature and ≥30% rolling reduction ratio. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a non-oriented electrical steel sheet suitable for use as an iron core material for a transformer or a rotary machine, and in particular, so-called lap rolling in which two or more steel sheets are stacked and rolled during cold rolling. By using this, the magnetic flux density is further improved.

  In recent years, environmental problems have attracted a great deal of attention, and from the viewpoint of energy saving, improvement of characteristics and efficiency of transformers and motors has become an urgent task. Electrical steel sheets are widely used as iron cores for motors, transformers, and the like, and it is considered that the improvement in magnetic properties of the electrical steel sheets greatly contributes to energy saving.

The magnetic properties of the electrical steel sheet are strongly influenced by the texture of the steel sheet. For example, in a grain-oriented electrical steel sheet, the magnetic properties in the rolling direction are improved by aligning the <100> axis, which is the easy axis of magnetization, with the rolling direction. On the other hand, non-oriented electrical steel sheets have excellent magnetic properties in the plate surface by accumulating {100} planes parallel to the steel plate surface.
It is no exaggeration to say that the main magnetic characteristics of the electrical steel sheet are iron loss and magnetic flux density, and the magnetic flux density is determined by the texture of the steel sheet.

As a method for improving the magnetic flux density of the steel sheet, a method of coarsening the crystal grain size of the hot-rolled sheet as disclosed in Patent Document 1 or Patent Document 2, or a technique disclosed in Patent Document 3 is disclosed. There is known a method for improving the texture of a finish-annealed plate by adding a trace amount of elements such as Sb and Sn.
Patent Document 4 discloses that steel containing 0.03 to 0.2% P contains one or more selected from Sn, Sb, Cu and Ni in small amounts at the same time, and A method of obtaining a steel sheet having a high magnetic flux density and a low iron loss by controlling the annealing and subsequent cooling conditions, or the hot rolling finishing temperature and the subsequent cooling conditions is proposed. However, even if these techniques are used in combination, it is difficult to say that the allowance for improving the magnetic flux density is sufficient.

JP-A-56-98420 JP-A-3-211258 Japanese Patent Publication No.57-59293 JP-A-6-271996

  The current manufacturing method is almost optimized as a manufacturing method for non-oriented electrical steel sheets to obtain good magnetic properties. By simply improving general manufacturing conditions, non-directional electromagnetic steel sheets can be dramatically improved. It was difficult to improve the magnetic flux density of the steel sheet.

  The present invention has been developed in view of the above-mentioned present situation, and the cold rolling process uses a so-called lap rolling in which steel sheets are stacked in a laminated state, thereby further improving the magnetic flux density. It aims at proposing the advantageous manufacturing method of a grain-oriented electrical steel sheet.

  That is, in producing the non-oriented electrical steel sheet, the present invention is to perform part or all of the cold rolling process before finish annealing by lap rolling in which two or more steel sheets are laminated. It is a method for producing a non-oriented electrical steel sheet having excellent magnetic properties, characterized by performing lap rolling under conditions of temperature: 200 ° C. or higher and rolling reduction: 30% or more.

  ADVANTAGE OF THE INVENTION According to this invention, the non-oriented electrical steel sheet excellent in magnetic flux density can be obtained by performing cold rolling of the non-oriented electrical steel sheet by lap rolling under a predetermined condition.

Hereinafter, the present invention will be specifically described.
First, the experimental results on which the present invention is based will be described. Unless otherwise specified, “%” in relation to ingredients means mass%.
<Experiment 1>
A steel slab containing Si: 2.74%, Mn: 0.16% and Al: 0.30% was hot rolled into a 1.6 mm thick hot rolled sheet, and then annealed at 1000 ° C for 60 seconds, followed by cold rolling. To a thickness of 0.20-1.4 mm. Thereafter, after degreasing treatment, two steel plates having the same thickness were stacked and cold-rolled at a temperature of 200 ° C. to obtain a thickness of 0.35 mm. Thereafter, finish annealing was performed at 920 ° C. for 10 seconds.
The sample thus obtained was magnetically measured.

FIG. 1 shows the results of examining the relationship between the rolling reduction in lap rolling and the magnetic properties B _{50 of the} steel sheet (magnetizing force: magnetic flux density when magnetized at 5000 A / m).
As shown in the figure, it can be seen that B ₅₀ is significantly improved when the rolling reduction in the lap rolling is 30% or more.

As described above, the reason why the magnetic properties are improved by using the cold rolling as the lap rolling has not yet been clearly clarified, but the inventors speculate as follows.
When rolling with steel sheets stacked, the overlapped portion does not deform until it exceeds the boundary, and it is considered that this portion is constrained in deformation. Due to this constraint, the deformation mode is different from that of normal rolling, and the change in the rolling structure or recrystallization nucleation at this part is presumed to have led to a recrystallization texture that is advantageous to the final magnetic properties after finish annealing. Is done. In this respect, when the rolling reduction of the lap rolling is less than 30%, this effect is exhibited only in the very vicinity of the overlapped portion, and as a result, it is considered that there is almost no change in the magnetic characteristics as a whole. .

Hereinafter, the production method of the present invention will be specifically described.
There is no restriction | limiting in particular about the component composition of the non-oriented electrical steel sheet made into object by this invention, All the conventionally well-known component systems are suitable.
The molten steel adjusted to a predetermined component composition is made into a slab by a normal ingot-making method, a continuous casting method or the like. In addition, a thin cast piece having a thickness of 100 mm or less may be manufactured by a direct casting method.
The slab is heated by a normal method and then hot-rolled, but may be hot-rolled immediately without being heated after casting. In the case of a thin slab, hot rolling may be performed, or hot rolling may be omitted and the subsequent process may be performed as it is.

  Then, hot-rolled sheet annealing is performed as necessary. In order to obtain good magnetic properties, it is desirable to perform this hot-rolled sheet annealing. The hot-rolled sheet annealing temperature is preferably 800 ° C. or higher and 1100 ° C. or lower. When the hot-rolled sheet annealing temperature is less than 800 ° C., a band structure in hot rolling remains, and it becomes difficult to realize a primary recrystallized structure of sized particles. On the other hand, when the temperature exceeds 1100 ° C., the grain size after the hot-rolled sheet annealing is too coarse, which is disadvantageous for realizing a primary recrystallized structure of sized particles.

After hot-rolled sheet annealing, at least one cold rolling is performed with intermediate annealing as necessary.
In the present invention, this cold rolling process is important, and it is necessary to perform cold rolling by lap rolling in which two or more steel plates are laminated. In addition, the rolling reduction at that time needs to be 30% or more. This is because, if the rolling reduction is less than 30%, the satisfactory improvement in the magnetic property B ₅₀ is not achieved as shown in FIG.
In addition, this lap rolling may pass through all the processes of cold rolling, and may be a one part process. In addition, the lap rolling may be reduced to a target reduction rate in one pass or may be set as a target reduction rate by multiple passes.

  Furthermore, in the present invention, the rolling temperature in the above lap rolling needs to be 200 ° C. or higher. This is because if the rolling temperature in the lap rolling is less than 200 ° C., a satisfactory improvement in magnetic properties cannot be expected. The upper limit of the rolling temperature is preferably about 700 ° C. This is because when the rolling temperature exceeds 700 ° C., so-called dynamic recrystallization occurs, and recrystallization occurs during rolling, and the texture may change drastically and the magnetic properties may deteriorate.

In the above lap rolling, it is desirable to keep the surface where the steel plates are in close contact with each other by degreasing and pickling before the steel plates are stacked. You may apply | coat or insert different materials, such as an adhesive agent and a separator, in this contact surface. When stacking steel plates, they may simply be brought into contact, but if there is a risk that the two plates will be misaligned during rolling, they may be partially welded before rolling or partially using a solvent. It may be glued.
In addition, it is effective for improving the magnetic properties to perform the aging treatment in the range of 100 to 400 ° C. once or a plurality of times during the cold rolling.

The steel sheet after lap rolling is handled as a single steel sheet while being stacked. In addition, it is necessary to set the rolling temperature in the above-described lap rolling to 200 ° C. or higher, and to reduce the number of passes (preferably one pass) and increase the rolling reduction (preferably 50% or more), It is suitable for improving the adhesion of the steel plate.
Further, a plurality of stacked steel plates may be stacked again to perform similar rolling. In this case, it is only necessary to satisfy the condition that the rolling reduction is 30% or more at least once among the multiple lap rollings.

Then, after performing degreasing and pickling treatment as needed, finish annealing is performed. In this finish annealing, when decarburization is required, the atmosphere is a wet atmosphere, but when decarburization is not required, a dry atmosphere may be used.
Further, when the obtained laminated steel sheet is further laminated and used, it is advantageous to apply an insulating coating to the surface of the laminated steel sheet in order to reduce iron loss. In this case, in order to ensure good punchability, an organic coating containing a resin is desirable. On the other hand, when emphasis is placed on weldability, it is desirable to apply a semi-organic or inorganic coating.

Example 1
A steel slab containing Si: 2.74%, Mn: 0.16% and Al: 0.30%, with the balance being Fe and inevitable impurities, was hot rolled into a 2.0 mm thick hot-rolled sheet at 30 ° C at 30 ° C. After hot-rolled sheet annealing for 2 seconds, it was finished to a thickness of 0.3 to 1.8 mm by cold rolling. Subsequently, after degreasing and pickling treatment, two steel plates having the same thickness were stacked and cold-rolled at a temperature of 250 ° C. to finish a thickness of 0.50 mm. Thereafter, finish annealing was performed at 900 ° C. for 10 seconds in a dry nitrogen atmosphere.
Table 1 shows the results of measuring the magnetic properties of the non-oriented electrical steel sheet thus obtained.

  As is clear from the table, it can be seen that any non-oriented electrical steel sheet produced under the rolling reduction of 30% or more (rolling temperature: 250 ° C.) according to the present invention can obtain good magnetic properties.

Example 2
A steel slab containing Si: 0.11%, Mn: 0.23% and P: 0.079%, with the balance being Fe and inevitable impurities, was hot rolled into a 1.6 mm thick hot rolled sheet, Finished by rolling to a thickness of 0.2-1.0 mm. Next, after degreasing and pickling treatment, three steel plates having the same thickness were stacked and cold rolled at the rolling reduction and rolling temperature shown in Table 2 to obtain a thickness of 0.50 mm. afterwards. In a dry nitrogen atmosphere, finish annealing was performed at 800 ° C. for 10 seconds.
The results of measuring the magnetic properties of the non-oriented electrical steel sheet thus obtained are also shown in Table 2.

  As is apparent from the table, it can be seen that any non-oriented electrical steel sheet produced under the conditions of rolling temperature: 200 ° C. or higher and rolling reduction: 30% or more according to the present invention can obtain good magnetic properties.

Example 3
A steel slab containing Si: 1.82%, Mn: 0.22%, and Al: 0.33%, the balance being Fe and inevitable impurities, was hot rolled into a 2.0 mm thick hot-rolled sheet at 25 ° C at 1000 ° C. After hot-rolled sheet annealing for 2 seconds, it was finished to a thickness of 0.20 to 1.4 mm by cold rolling. Next, after degreasing and pickling treatment, two steel plates having the same thickness were stacked and cold-rolled at a temperature of 200 ° C. to obtain the thicknesses shown in Table 3. Then, the obtained steel plates were again stacked with the same thickness, and cold-rolled at a temperature of 400 ° C. to obtain a thickness of 0.50 mm. Then, finish annealing was performed at 900 ° C. for 60 seconds in a wet nitrogen-hydrogen mixed atmosphere.
The results of measuring the magnetic properties of the non-oriented electrical steel sheet thus obtained are also shown in Table 3.

  As is apparent from the table, it can be seen that any non-oriented electrical steel sheet manufactured under the conditions according to the present invention can obtain good magnetic properties.

It is a diagram showing a relationship between magnetic properties B ₅₀ of rolling reduction and the steel sheet in superimposed rolling.

Claims (1)

  In producing non-oriented electrical steel sheets, some or all of the cold rolling process before finish annealing is performed by lap rolling in which two or more steel sheets are laminated. At that time, rolling temperature: 200 ° C. or more, Rolling ratio: A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, characterized by performing lap rolling under a condition of 30% or more.

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