JPS5855211B2 - (h,k,o) Manufacturing method for unidirectional electrical steel sheet with crystals in [001] orientation and excellent iron loss - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a unidirectional electrical steel sheet having crystals in the (h, ni, o) [001, 1 orientation and excellent core loss.

Electrical steel sheets are used as core materials for transformers and the like.

Such electromagnetic steel sheets are generally required to have magnetic properties such as being able to obtain a large magnetic flux density with a small excitation current and having a small iron loss value so that the supplied excitation current can be efficiently converted into magnetization energy.

They are broadly classified into non-oriented electrical steel sheets, which are mainly used for rotating machines, and unidirectional electrical steel sheets, which are mainly used in transformers, although they are also used in some large-scale rotating machines.

Unidirectional electrical steel sheets can be said to be more advanced than non-oriented electrical steel sheets in that they have significantly superior magnetic properties and a high degree of directivity.

By the way, the unidirectional electrical steel sheet is disclosed in U.S. Patent No. 196555.
As described in specification No. 9, N.P. Goss (N, P, G
Since the basic manufacturing method was provided by Mr. O8S), it has been industrially manufactured in large quantities up to the present day.

After this manufacturing method was invented, other researchers revealed that the excellent magnetic properties of such steel sheets were due to the crystal grain orientation being so high that it was incomparably more advanced than conventional materials. Ta.

In other words, if expressed in terms of Miller index, the rolling direction coincides with the axis of easy magnetization <001>, and the steel plate surface is composed of oriented grains that can be expressed as (110) <001> parallel to the (110) plane.

Such an orientation is commonly known as the Goss orientation, specifically named after the inventor.

Subsequent inventions and discoveries regarding the grain orientation of unidirectional electrical steel sheets, with the exception of a few examples, focused on how to bring the orientation of each grain closer to the (110) Goss ideal orientation in the rolling direction. This was a solution to the proposition of improving the magnetic flux density of the steel sheet and, in turn, creating a steel plate with a small iron loss value.

In particular, as revealed in the invention by Mr. Taguchi et al. (Japanese Patent Publication No. 15644/1973), the orientation of most crystal grains is (110) by a process that is simpler than the conventional manufacturing process by Mr. Goss. OOl〉A method for manufacturing unidirectional steel plates with extremely high magnetic flux density within 3 degrees of the ideal orientation has been provided, and it has already been mass-produced industrially and is replacing the conventional Goss method. .

In this way, for the past several decades since the invention of unidirectional electrical steel sheets by Mr. Goss up to the present, with a few exceptions, (110)<001>G as shown in Figure 1 has been produced.
It has been thought that bringing the orientation closer to the ideal O8S direction is a way to improve the magnetic properties.

The present invention breaks away from the conventional idea of increasing the degree of integration of the GO8S ideal orientation, and by dispersing it in other orientations and adding tension to the steel plate, the number of The present invention provides a unidirectional electrical steel sheet with excellent magnetic properties having the above advantages.

In the process of manufacturing a steel sheet containing 4.5% or less silicon, the present invention is characterized in that the <001> axis of each crystal grain coincides with the rolling direction of the steel sheet, and the index of the consolidation crystal plane parallel to the steel sheet surface is In order to obtain a steel plate with a structure consisting of (h, ni, o) planes that are rotationally dispersed around the rolling direction, cold rolling is performed by rolling with special grooved rolls and then rolling with smooth rolls. At the same time, the iron loss in the rolling direction is improved by
The present invention provides a method for manufacturing a grain-oriented electrical steel sheet that also improves magnetic properties in other directions within the sheet surface.

The present invention will be explained in detail below.

First, the silicon content is limited to 4.5% or less.

As is well known, silicon increases the electrical resistance value of a steel sheet and significantly improves the iron loss value, so it is usually contained in an amount of about 3%, with an upper limit of 4 or 5% at which workability becomes a problem.

Furthermore, grain-oriented electrical steel sheets for specific uses may contain no silicon at all or have a very low silicon content, and the present invention aims to reduce the silicon content contained in such conventional grain-oriented electrical steel sheets. Since it can be applied in exactly the same way to other cases, the lower limit is set to substantially 0%.

There are no particular regulations regarding other contained components in the present invention, and they are necessary for manufacturing ordinary grain-oriented electrical steel sheets, such as Mn, S, A/, N, Ti, V, Nb, etc.
It also includes cases where Se, Sb, etc. are contained singly or in combination.

However, steel making methods, melting methods, which are already known technologies,
A steel slab obtained by an agglomeration method can be used as the material.

Such a material is made into a hot rolled coil by hot rolling.

After hot rolling, precipitation annealing is performed at a temperature of 9500C to 1200C, if necessary.

Cold rolling may be performed by either a one-stage method or a two-stage method including intermediate annealing, but one-stage strong cold rolling at a rolling reduction of 81 to 95% is preferred.

The basis of this invention is to perform rolling with grooved rolls for at least one pass during this cold rolling.

That is, during cold rolling, at least one initial pass of cold rolling is performed using rolls having grooves parallel to the rolling direction, and the other passes are performed using ordinary smooth rolls.

In this rolling process, the rolling temperature is 50 to 350.
It is preferred that at least one pass of rolling is carried out at a temperature in the range of °C.

After this cold rolling, decarburization annealing is performed, MgO is applied, and final finish annealing is performed at 1200° C. in a hydrogen atmosphere.

The resulting product contains crystal grains in the (h, ni, o)[001,1 orientation in addition to the (110) COOL, 1 orientation, and such crystal grains with the same magnetic flux density do not coexist. Shows significantly lower iron loss compared to products.

The grooves of the cold rolling roll must have a pitch of 1 mm or more, less than 10 grooves, and a depth of 0.05 or more and 1 mTt or less.

If the pitch is less than 1 pitch, the groove will not be effective, and if the pitch is more than 10 pitches, it will be effective, but the effect will be significantly reduced.

Also, if the depth of the groove is less than 0.05 mounds, the effect is slight and 1
If you go too far, there is a risk of damaging the shape of the steel plate.

The shape of the groove is not particularly limited, but it is desirable that it be shaped so that it will not be damaged by wear.

If all passes of cold rolling are performed using grooved rolls, the surface shape of the steel sheet will become uneven, which is not preferable.

Furthermore, if the product is rolled with grooved rolls at a rolling rate of 60% or more, the orientation dispersion of the product will increase, so it is better to carry out rolling at a rolling rate within this range and at the beginning of cold rolling.

It is better to make the grooves exactly parallel to the rolling direction (perpendicular to the roll axis), but an inclination within a few degrees is acceptable.

This effect during cold rolling is thought to be caused by two reasons.

One is that rolling with grooved rolls causes dispersion of crystal orientation.

In the present invention, rolls having grooves parallel to the rolling direction are used.

A crystal grain having an orientation of (h, ni, o) [001:], which is (110) (001) rotated around the [001) axis, is produced by the effect of this groove.

In other words, the grooves parallel to the rolling direction create unevenness parallel to the rolling direction on the steel sheet, and when it is rolled by the next smooth roll, stress is generated in the direction perpendicular to the rolling direction, changing the crystal orientation to [001, nuclei rotated around one axis. It is thought that it gives rise to

Another reason is the promotion of work hardening due to the induction of many slip systems.

Japanese Patent Publication No. 5413846 shows that aging treatment during cold rolling is effective as a method for producing grain-oriented silicon steel sheets.

According to the explanation, solid solute N. It is said that carbon is formed during cold rolling and gathers in defective areas, which changes the deformation mechanism during subsequent cold rolling and changes the texture.

In short, it is said that facilitating processing is effective.

In the case of cold rolling with grooved rolls, the slip system caused by rolling becomes complicated, and combined with the rolling temperature, it is thought that work hardening occurs easily.

In the case of grooves in a direction other than the rolling direction, the effect of work hardening is considered to be large, but the influence of orientation dispersion becomes large.

As for rolling using grooved rolls, there are two.

Three inventions have been proposed.

JP-A-49-83615 discloses that a cubic structure is obtained by cold rolling with grooved rolls.

The invention described in JP-A No. 54-71028 is a two-stage cold rolling method, and when manufacturing unidirectional silicon steel, rolling with a roll having grooves with an angle of 600 or less with the roll axis results in unidirectional cold rolling with good properties. It is said that silicon steel can be obtained.

However, as in the present invention, the idea of rolling with rolls with grooves parallel to the cold rolling direction to produce crystal grains with the orientation of (h, ni, o) [OO1] and improving iron loss is difficult. Not at all.

By the way, the reason why iron loss is improved when (h, ni, o) [001] orientations are mixed will be explained.

As is generally known, when an external magnetic field is applied to an electromagnetic steel sheet, which is a ferromagnetic material, the magnetic domain wall of the steel sheet moves and the magnetic domain rotates, so that the steel sheet is magnetized.

It is generally well known that, particularly under an alternating magnetic field, such movement and rotation of the domain wall occur continuously, and that iron losses such as so-called hysteresis loss and thin current loss occur accordingly.

The iron loss improvement effect of the present invention is based on the predetermined crystal orientation and the application of tension by a predetermined amount of glass film or insulating film, resulting in the subdivision of magnetic domains, a reduction in the movement distance of each domain wall, and a reduction in eddy current loss. It can be inferred.

That is, in a normal material in which each crystal grain is oriented from the (110)[0O1) Goss ideal orientation or grains with an orientation very close to it, the difference in orientation between adjacent crystal grains on the front, rear, left, and right sides is extremely small.

However, when the crystal grains are separated from the (h, k, o) [001] orientation as in the electrical steel sheet obtained according to the present invention, the difference in orientation between adjacent crystal grains is considerably larger than in the former case.

The fact that the orientations of the adjacent crystal grains are different means that the structures of the grain boundaries are different between the two.

Furthermore, when tension is applied to the steel sheet, grain boundaries formed by lattice defects become stress centers and subdivide the magnetic domains, which may result in a reduction in eddy current loss.

Thus, the reason why the iron loss is improved by the present invention is (
h, k, o) <001> oriented steel sheet has a grain boundary structure suitable for generating stress centers for fragmentation of magnetic domains, which leads to improvement of core loss by moderate steel sheet tension. It can be inferred.

The electrical steel sheet according to the present invention improves iron loss particularly in the rolling direction within the steel sheet plane due to the above-mentioned correlation mechanism between crystal orientation and tension.
It goes without saying that the magnetic properties in directions other than the rolling direction are also improved simply by being h, ni, 0)<001>.

By the way, there are a few prior documents regarding methods for manufacturing steel sheets having (h, ni, o) [001) crystal orientations.

That is, US Patent A2473156 specifies (11
0) [001] A Goss orientation unidirectional electrical steel sheet is rolled and annealed, and the <OO1> axis is parallel to the rolling direction.
Furthermore, there is a description of a method for manufacturing thin electrical steel sheets that rotates around the axis.

Furthermore, Japanese Patent Publication No. 45-17056 describes a method for producing a <001> fiber structure by rolling annealing a flat steel ingot.

Furthermore, in Japanese Patent Publication No. 45-40656, Si, At
, has proposed a method of rolling annealing steel containing Mo to produce a <001> fibrous structure.

Such conventional reports on the <001> fibrous structure have focused on improving the magnetic properties in directions other than the rolling direction, and as in the present invention, the rolling direction itself is the most important for the usage conditions of grain-oriented electrical steel sheets. It was a completely unknown matter to improve the iron loss of the steel.

By the way, the crystal orientation is expressed as (h, ni, o) (001) for generality, but according to more detailed investigation results, it is ±15 centered on the (110) [001] Goss orientation. A dispersion of ˜±200 appears to give the most favorable results.

This can be presumed to be because as the rotational dispersion increases and the number of (100)[001] components increases, the number of 90' magnetic domains increases.

Examples will be described below.

Example I C: 0.052%, Si: 2.95%, Mn: 0.07
5%, S: 0.025%, acid soluble A/1. :0.027
%, N: A continuous cast slab containing 0.0070% was hot-rolled, and 2
．． It was made into a 3 mm hot rolled sheet.

This was annealed at 1100° C. for 2 minutes and pickled.

One of these has a groove width of 2 in the circumferential direction of the cold rolling roll and a depth of 0.
1.5 with a grooved roll with 5 mm and 2 pitch grooves.
Roll to peak, then flat roll to 0.30 mm
Finished.

The other one was rolled to 0.30 mm with a flat roll.

In the cold rolling, aging treatment was performed for 20,000,120 minutes for each pass.

Next, these were decarburized annealed in wet hydrogen at 850°C for 2 minutes,
After applying MgO, final annealing was performed at 1200° C. for 20 hours.

The magnetic properties of these products are shown below.

B 8 ('rl W" 715o (W, 4) a) Flat roll rolling 1.930 1.07b) Grooved roll rolling 1.930 1.02 Also, the (100) pole figure showing these crystal orientations is As shown in the figure.

In FIG. 1, a is a pole figure of an electrical steel sheet rolled by flat rolls, and b is a pole figure of an electrical steel sheet rolled by grooved rolls.

From the figure, the one rolled with a grooved roll is (110) [001
) The number of crystal grains whose orientation is rotated around the <001> axis in the rolling direction is increasing.

Example 2 C: 0.055%, Si: 2.93%, Mn: 0.07
0%, S: 0.023%, acid soluble At: 0.025 atm N
: Hot-rolled continuous casting slab containing 0.0065% 2.3
The hot-rolled plate of the connection.

After annealing this at 1100℃ for 2 minutes and pickling,
Rolling was carried out under the following three conditions.

a) Groove width 31nrIt1 depth 0 over the circumference of the roll
．． It was rolled to a thickness of 12 mm using a roll having grooves with a pitch of 3 mm, and then finished to a thickness of 0.30 mm using a flat roll.

b) It was rolled to a thickness of 1.2 mm using a roll in which a piece of piano wire with a diameter of 1 inch was wrapped tightly around the circumference of the roll, and then finished to 0.30 TrLm using a flat roll.

C) Finished to 0.30 mm using only a flat roll.

In addition, 1.6mm at the time of rolling, L2mrn, 0.8m
vt, 250℃ for each plate thickness of 0.6mm and 0.4m7n
, an aging treatment was performed for 20 minutes.

Next, decarburization annealing was performed at 850°C for 2 minutes in wet hydrogen.
After applying gO, final annealing was performed at 1200°C for 20 hours.

The magnetic properties of these products are shown below.

Rolling conditions B8 (T) W1 fi.

(W/ky) (a) 1.94 0
．． 99(b) 1.93 1.00(
c) 1,94 1.06

[Brief explanation of the drawing]

FIG. 1A is a pole figure showing the crystal orientation of an electrical steel sheet formed by flat roll rolling, and FIG. 1A is a pole figure showing the crystal orientation of an electrical steel sheet formed by grooved roll rolling.

Claims (1)

[Claims] After hot rolling a steel ingot or continuous casting slab containing IC: 0.08% or less, S i: 4.5% or less, and sulfide or nitride as a primary recrystallized grain inhibitor. , and annealing if necessary. The plate is cold-rolled in one or more stages to a predetermined thickness, and during this cold rolling, a grooved roll having grooves with a pinch of 1 or more and 10 mm or less and a depth of 0.05 mm or more and 1 m TIL or less is used. In the method of manufacturing unidirectional electrical steel sheets by rolling at least one pass or more, then flat rolling to obtain the final thickness, and then rough decarburization annealing and finish annealing, cold rolling is performed at a reduction rate of 81 to 95%. (h, ni, 0) (001)
A method for manufacturing unidirectional electrical steel sheets with oriented crystals and excellent iron loss. 2. The method according to claim 1, wherein in the cold rolling step including rolling with grooved rolls, at least one pass of cold rolling is performed in a temperature range of 50 to 350°C.