JP5729009B2 - Annealing separator - Google Patents

Description

  The present invention relates to an annealing separator, and more particularly to an annealing separator that is effective in suppressing the occurrence of buckling of a coil inner diameter portion that occurs when a grain-oriented electrical steel sheet is wound into a coil shape. is there.

  For example, the production process of grain-oriented electrical steel sheets is generally performed by subjecting a steel slab adjusted to a predetermined composition to hot rolling, annealing and cold rolling, and performing recrystallization annealing, finish annealing, and flattening annealing. Is. Of these steps, in recrystallization annealing, it is customary to apply an annealing separator to the surface of the steel sheet in order to prevent the steel sheet coil from fusing during subsequent finish annealing.

  Many of these annealing separators are mainly composed of magnesia (MgO) in order to react with silica formed on the steel sheet surface to form a forsterite film on the steel sheet surface. The steel sheet coated with the annealing separator is then wound into a coil. At that time, if the coil is wound at a winding tension equivalent to that of a normal cold-rolled steel sheet, the lower part of the coil will be deformed by its own weight during finish annealing in the vertical state (up-end state). It is common to wind up with a tension | tensile_strength higher than a cold-rolled steel plate.

  However, since the coil is wound with a high tension, when the coil is loosened, there has been a problem that buckling occurs in the inner diameter portion of the coil. That is, since it is necessary to scrape the portion where buckling has occurred, the yield is reduced, and when the coil is inserted into the payoff reel in the horizontal state (down-end state) during flattening annealing, the buckling portion is Another problem was the need to remove it in advance.

  With respect to these problems, in Patent Document 1, the coil winding tension is optimized, the linear shrinkage rate of the annealing separator is optimized so that the coil does not loosen, and the annealed separator after slurrying is used. A technique for preventing crushing and buckling by reducing particles having a particle size of 40 μm or more is proposed.

Japanese Patent No. 3885463

However, although the shape defect is greatly reduced and the yield is improved by the technique of Patent Document 1, the property of the steel sheet surface changes due to fluctuations in rolling conditions and the friction coefficient at the interface between the steel sheet and the annealing separator changes. However, there was a problem in that buckling still occurred.
Then, the objective of this invention is related with the annealing separation agent which suppresses generation | occurrence | production of the buckling of the coil internal-diameter part at the time of winding up a steel plate in a coil shape.

  As a result of diligent investigations on how to solve the above problems, the inventors have included a proper amount of coarse grains having an appropriate range diameter in the annealing separator, thereby providing a grip effect between the steel sheets wound up in a roll shape. It has been found that buckling can be prevented by mechanically suppressing slippage between steel plates, and the present invention has been completed.

That is, the summary and construction of the present invention is the following passage Ride.
(1) An annealing separator containing magnesia, the magnesia having a particle size of 25 μm or more and less than 75 μm: magnesia containing at least 0.05% by mass to 20% by mass and having a particle size of 75 μm or more suppressed to 0.01 mass% or less state, and are volumetric shrinkage less 80% 20%, annealing separator which total content of the magnesia is characterized der Rukoto least 60 wt%.
(2) The annealing separator according to (1), wherein the total content of magnesia is 80% by mass or more.

  According to the present invention, it is possible to prevent buckling that occurs at the inner diameter of the coil that occurs when the coil is wound. As a result, since the generation of scrap coils is prevented, the product yield is improved, and line troubles such as failure to pull out the coils can be prevented.

It is a figure which shows the time change of a drawing load with respect to the case where a coarse grain is included in an annealing separation agent, and the case where it does not contain.

Hereinafter, the present invention will be specifically described.
The problem that buckling occurs at the inner diameter portion of the coil when the steel sheet is wound in a coil shape is not limited to the electromagnetic steel sheet but also occurs in the cold-rolled steel sheet. The cause of buckling in the coil inner diameter portion is that the coil inner diameter portion cannot withstand compressive stress when the coil is loosened because the winding tension when winding the coil is excessive. It is known that this buckling is likely to occur when the coefficient of friction between the steel plates is small, when the roundness of the coil is low, or when the steel plate is thin. Therefore, conventionally, as described in, for example, Patent Document 1, an annealing separator having a maximum static friction coefficient increased by reducing coarse particles contained has been proposed.

  However, the inventors do not necessarily determine whether or not buckling occurs depending on the maximum coefficient of static friction between the steel sheets, and buckling occurs even though the maximum coefficient of static friction including coarse grains is small. It has been found that there is an annealing separator that does not. The experimental results that led to this knowledge will be described below.

1.0% by mass of coarse magnesia particles having a particle size of 390 mesh or more and less than 330 mesh (that is, 38 μm or more and less than 45 μm) with a standard sieve, and the balance is less than 500 mesh (that is, less than 25 μm) with a standard sieve Prepare three steel plates each having a size of 150 mm x 80 mm x 0.27 mm, each coated with an annealing separator made of magnesia and an annealing separator of the same composition that does not contain the coarse particles. Then, a surface pressure of 2.9 × 10 ⁵ N / m ² (3.0 kgf / cm ² ) was applied, and the second (that is, the middle) steel plate was pulled out at a speed of 0.2 mm / s. FIG. 1 shows the time variation of the drawing load at that time.

  As is apparent from this figure, the maximum value of the drawing load is 400 N when coarse particles are not included, but is 390 N when coarse particles are included. This indicates that the maximum coefficient of static friction is smaller when coarse particles are included. However, the buckling of the coiled steel sheet occurred when the annealing separator did not contain coarse grains, and did not occur when the coarse steel grains contained coarse grains.

  The reason for this is not clear, but is probably due to the following mechanism. That is, with an annealing separator that does not contain coarse particles, the frictional force is decreasing when a stress exceeding the maximum static frictional force is applied. On the other hand, when coarse particles are present, the maximum static friction force is smaller than when no coarse particles are included, but slippage occurs gradually when stress exceeding the maximum static friction force is applied. This is considered to be due to the fact that the coarse effect causes a grip effect between the steel plates while the stress is relieved, and the dynamic friction force increases and the slippage stops.

  As a result of earnestly examining the above experimental results and the particle size range and content of coarse particles, the inventors have found that the appropriate amount of coarse particles having an appropriate range diameter is used in order to prevent buckling occurring in the inner diameter portion of the coil. It has been found that it is effective to contain it in an annealing separator.

Below, the reason for limitation of each structural requirement is demonstrated about this invention.
First, the content of magnesia in the annealing separator is arbitrary, but it is preferably 60% or more from the viewpoint of obtaining excellent film properties. This is because by setting the content of magnesia to 60% or more, it becomes easy to react with silica on the surface of the steel sheet to form a forsterite film. More preferably, it is 80% or more.

  Further, as magnesia, magnesia having a particle size of 25 μm or more and less than 75 μm: at least 0.05 mass% or more and 20 mass% or less is contained. Here, the reason why the particle size is limited to the above range is that when the magnesia particle size is smaller than 25 μm, the grip effect between the steel plates is small because the particle size is small. On the other hand, when it is larger than 75 μm, coarse grains become rollers and the reduction of the maximum static frictional force is increased, and conversely, buckling is likely to occur. Hereinafter, particles having a particle size of 25 μm or more are referred to as “coarse particles”.

  The content of magnesia having the above range diameter is 0.05% by mass or more and 20% by mass or less. That is, if it is less than 0.05% by mass, the grip effect between the steel plates due to coarse grains is small, and if it is more than 20% by mass, the surface of the forsterite film formed on the steel plate surface is rough. This is because it becomes easier.

On the other hand, magnesia having a particle size of 75 μm or more is suppressed to 0.01% by mass or less. This is because if the content exceeds 0.01% by mass, creases are likely to occur on the steel sheet surface.
Note that it is difficult to control the particle size accurately with a general laser scattering type particle size distribution measuring apparatus. Therefore, in the present invention, the particle size of magnesia is defined by the sieve residue.
Specifically, the particle size of particles that do not pass through 200 mesh with a standard sieve is defined as 75 μm or more, and the particle size of particles that pass through is defined as less than 75 μm. In addition, the particle size of particles that do not pass through 500 mesh and 635 mesh with the standard sieve is specified as 25 μm or more and 20 μm or more, respectively, and the particle size of particles that pass through 500 mesh and 635 mesh with the standard sieve is less than 25 μm and less than 20 μm, respectively. It prescribes. In the present invention, the content of magnesia having a predetermined particle size is controlled by adding an appropriate amount of magnesia sieved by the above method to an annealing separator whose particle size is adjusted to less than 25 μm. .

  Moreover, it is preferable that the volumetric shrinkage rate of the annealing separator is 20% or more and 80% or less. This is because if the volumetric shrinkage is 80% or less, it is easy to insert the payoff reel during the next sheet passing, and if it is 20% or more, the atmospheric gas between the coil layers during annealing is reduced. This is because the flowability is good and the appearance of the forsterite film is good.

Here, the volume shrinkage (%) of the annealing separator is
(Volume before firing−volume after firing) ÷ (volume before firing) × 100
Calculate with
Moreover, when calculating | requiring a volume contraction | shrinkage rate, what was press-molded by the pressure 200kgf / cm < ² > (19.6MPa) to the outer diameter 20mm was used for the measurement. The firing was performed at 1200 ° C. × 20 h in a nitrogen atmosphere.

There are various methods for adjusting the volumetric shrinkage of the annealing separator. For example, when magnesia is mainly used, the ceramic industry magazine 70 [2] 1962 P335 “Reaction of MgO and Fe ₂ O ₃ and as is described in its effect on the sintering of magnesia "can be adjusted by controlling the content of Fe ₂ O _3, it can be similarly adjusted by the content control of trace elements other than Fe ₂ O _3.
Further, the higher the magnesia firing temperature, the lower the volumetric shrinkage in annealing after coating the steel sheet.

  Further, the volume shrinkage can be adjusted by controlling the particle size distribution of magnesia. This is because mixing with particles having a plurality of particle sizes rather than single dispersed particles increases the filling rate and decreases the volumetric shrinkage due to annealing. In this regard, for example, in Chemical Engineering Journal 11,433 (1985), an algorithm for calculating a particle size distribution for obtaining the closest packing is disclosed. When the volume shrinkage cannot be adjusted to an appropriate range only by controlling the particle size distribution of magnesia, it can be adjusted by mixing silica, a silicate compound, alumina, or the like.

C: 0.045% by mass, Si: 3.25% by mass, Mn: 0.070% by mass, Al: 80ppm, N: 40ppm, S: 20ppm, electrical steel sheet consisting of Fe and inevitable impurities The steel slab was heated to a temperature of 1200 ° C. and then hot-rolled to obtain a hot-rolled sheet having a thickness of 2.2 mm. The hot-rolled sheet was subjected to hot-rolled sheet annealing at 1000 ° C. for 30 seconds to remove the scale on the surface of the steel sheet. Next, it cold-rolled with the tandem rolling mill, and the final cold-rolled sheet thickness was 0.30 mm. Thereafter, decarburization annealing is performed for 90 seconds at a soaking temperature of 850 ° C., and an annealing separator in which 10 g of TiO ₂ is added to 90 g of magnesia (MgO) is applied to the surface of the steel plate, and the inner diameter is 500 mm and the outer diameter is 1000 mm. The coil was wound up. This coil was placed vertically (the axis was vertical) and subjected to finish annealing for heating up to 1200 ° C. at 25 ° C./h, followed by planarization annealing. Here, MgO was adjusted to 90 g by adding coarse MgO sieved to the particle sizes shown in Table 1 to MgO having a particle size of less than 20 μm. The volume shrinkage of the annealing separator was 40%. Further, the MgO content in the annealing separator is 90% or more.

From Table 1, the occurrence rate of buckling when particles of 25 μm or more and less than 75 μm are contained in an amount of 0.05% by mass or more and 20% by mass or less and the ratio of the particles of 75 μm or more is 0.01% by mass or less. Is 1% or less, indicating that the appearance of the forsterite film is good.
The appearance of the film was visually observed, and it was determined that a pattern or a defect was non-uniform and a non-uniform one was uniform.

C: 0.06% by mass, Si: 2.95% by mass, Mn: 0.07% by mass, Se: 0.015% by mass and Cr: 0.03% by mass, the balance being Fe and inevitable impurities The silicon steel slab is heated at 1350 ° C. for 40 minutes, hot rolled to a thickness of 2.6 mm, then subjected to hot rolling of 900 ° C. × 60 S, and then 1050 ° C. × 60 S. Cold-rolled with intermediate annealing, finished to a final cold-rolled sheet thickness of 0.23 mm, and then decarburized and annealed at a soaking temperature of 850 ° C. for 90 seconds to produce MgO and TiO with a particle size of less than 20 μm ₂ was coated with an annealing separator mixed in the ratio of Table 2, and wound into a coil having an inner diameter of 1000 mm and an outer diameter of 2000 mm. Here, MgO contained coarse particles in the proportions shown in Table 2, and the remainder was adjusted so that the particle size was less than 25 μm. Subsequently, the coil was placed vertically and subjected to finish annealing for heating up to 1200 ° C. at 25 ° C./h, followed by flattening annealing. At this time, the activity of MgO was changed, and the volumetric shrinkage of the annealing separator was changed as shown in Table 2.

  From Table 2, if the MgO in the annealing separator is 60% or more (that is, mainly MgO), the film uniformity is excellent, and if the volume shrinkage is 20% or more, the film uniformity is excellent, and 80% or less. Then, it turns out that it becomes an annealing separation agent which is very easy to insert into the payoff reel.

  The appearance of the film was visually observed, and it was determined that the pattern and defect were non-uniform and the non-uniform one was uniform. The difficulty determination of the insertion into the payoff reel is judged as easy when the coil inner diameter becomes 980 mm or less due to deformation after the coil is placed in the horizontal state and the deformation is less than 10 minutes. It was judged difficult. However, insertion was possible under either condition.

Claims (2)

An annealing separator containing magnesia, the magnesia having a particle size of 25 μm or more and less than 75 μm: 0.05% by mass or more and 20% by mass or less at least, and magnesia having a particle size of 75 μm or more and 0.01% suppressed below wt% state, and are volumetric shrinkage less 80% 20%, annealing separator which total content of the magnesia is characterized der Rukoto least 60 wt%.   The annealing separator according to claim 1, wherein the total content of magnesia is 80% by mass or more.

Images