JPH01176033A - Production of grain-oriented magnetic steel sheet having excellent magnetic characteristic - Google Patents

Abstract

PURPOSE:To provide a magnetic characteristic which is not deteriorated even by stress-relief annealing by incorporating a stage for imparting local strains to a steel sheet and a stage for welding a secondary recrystallization nucleus forming material to the edge of the steel sheet prior to the final finish annealing of the grain-oriented magnetic steel sheet. CONSTITUTION:A silicon-contg. steel slab is hot-rolled, and annealing and cold rolling are applied respectively at least once. Local strains are imparted to the steel sheet, and then the secondary recrystallization nucleus forming material such as the single crystal substance and polycrystal substance having high Goss azimuth collectivity is welded to the edge of the steel sheet. The steel sheet is then finally finish-annealed. As a result, the secondary grain boundary is increased, namely, the secondary grains are refined, and a grain-oriented magnetic steel sheet with a reduced iron loss is obtained.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing unidirectional electrical steel sheets with excellent magnetic properties, and in particular, the present invention relates to a method for manufacturing unidirectional electrical steel sheets with excellent magnetic properties, and in particular, to effectively control the growth process from the nucleation of Goss-oriented secondary recrystallized grains. The aim is to make the secondary grains finer by controlling the magnetic properties, thereby achieving an advantageous improvement in magnetic properties.

(Prior art) As is well known, unidirectional silicon steel sheets are mainly used in transformers,
This unidirectional silicon steel sheet is used as the iron core of other electrical equipment, and has excellent magnetic properties in the rolling direction, that is, B1 in terms of magnetic properties (excitation properties). The magnetic flux density represented by the value (magnetic flux density in the rolling direction generated when the magnetic field strength is 1000 A/m) is high, and -IT/SI value (magnetic flux density when magnetized at 1.7 T and frequency 50 Hz) is high. The iron loss represented by iron loss is required to be low.

In order to improve the magnetic properties of the unidirectional silicon steel sheet as described above, it is necessary to align the <001> axes of the secondary recrystallized grains in the steel sheet to a high degree in the rolling direction. For this purpose, M
In addition to fine precipitates such as nS and MnSe,
1-13469, a small amount of s
b, as well as As, Bi, Pb and Sn as disclosed in Japanese Patent Publication No. 54-32412, and a small amount of Mo etc. as disclosed in Japanese Patent Publication No. 57-14737. At the same time, by appropriately combining the processing conditions of hot rolling and cold rolling in order to form a suitable primary recrystallization texture, it has recently been possible to achieve a magnetic flux density B10 value of 1 at a plate thickness of 0.30 tm. High magnetic flux density exceeding .90T and iron loss -1,/. The value is 1.05W
/kg or less unidirectional silicon steel sheets are now being manufactured.

(Problems to be Solved by the Invention) However, the following problems still remain in actual production on an industrial scale.

In other words, if the <001> axes of the secondary recrystallized grains of the product are highly aligned in the rolling direction in order to improve the 81° value of the product, the secondary grains will inevitably become coarser and the 81° value will improve. The corresponding iron loss improvement cannot be obtained. Therefore, the special public official
In Publication No. 8, a method for improving iron loss by introducing strain using a laser or the like was proposed, but this method has the disadvantage that the effect of improving iron loss is lost especially by the strain relief annealing required for wound cores. was there.

On the other hand, if the secondary grains are made finer in order to improve the iron loss so as not to be lost even in such stress relief annealing, B.

The problem remained that the iron loss could not be improved commensurate with the refinement of the secondary grains.

This invention advantageously solves the above problems, and B1
In addition to stably obtaining a material with a high zero value, it is possible to effectively control the nucleation and growth process of Goss-oriented secondary recrystallized grains to obtain fine secondary grains that are suitably controlled. The purpose of the present invention is to propose an advantageous manufacturing method for a grain-oriented electrical steel sheet that has excellent magnetic properties that do not deteriorate even during pre-annealing.

(Means for solving the problem) In order to highly align the <001> axes of the secondary recrystallized grains in the finished product in the rolling direction, the steel sheet before secondary recrystallization must have a crystal structure, texture, inhibitors, etc. As mentioned above, it is necessary to maintain the proper conditions, and in order to achieve these conditions, it is necessary to strictly control the complex and wide-ranging processing conditions, starting from the material composition to steel manufacturing, hot rolling, cold rolling, and heat treatment. That's right.

However, in actual production on an industrial scale, it is easy to deviate from the overall appropriate conditions mentioned above, and if there is even a slight deviation, the orientation of the <001> axis in the rolling direction becomes poor. In response to the problem, the inventors
We conducted research on the secondary recrystallization phenomenon that determines the orientation of the 001 > axis, focusing on the generation and growth of secondary recrystallization nuclei, which is the basis thereof.

As a result, it was found that the material properties of the steel sheet before secondary recrystallization, such as crystal structure, texture, and inhibitors, deviated somewhat from the conventional overall appropriate conditions due to actual variations or simplifications in the manufacturing process conditions. By welding a material that is known to be able to stably obtain good magnetism as the core of the secondary grains, it is possible to weld the material that is known to be able to stably obtain good magnetism as the core of the secondary grains. It was found that oriented secondary grains can be stably obtained, and as a result, excellent magnetic properties are exhibited.

Further, as a result of repeated studies on the growth rate of secondary grains, it was found that the introduction of grain boundaries or dislocations increases the driving force for grain boundary movement, and as a result, the growth rate of secondary grains increases significantly.

This invention is based on the above knowledge.

That is, the gist of the present invention is as follows.

(1) A silicon-containing steel slab is hot rolled, then annealed and cold rolled at least once, and then final annealed to produce a grain-oriented electrical steel sheet. , a unidirectional electrical steel sheet with excellent magnetic properties, which includes a step of imparting a localized amount to the steel sheet before annealing, and a step of welding a material for forming secondary recrystallization nuclei to the edge of the steel sheet. Production method.

Hereinafter, this invention will be specifically explained based on the basic experimental results that led to this invention.

C: 0.065 wt% (hereinafter simply expressed as %), Si
: 3.25%, Mn: 0.075%, S: 0.
002%, Al: 0.020%, Mo: 0.012
% and N: A steel slab containing 0.0090% was heated at 1350'C for 2 hours and then hot rolled to a plate width of 10.
0■, the thickness was 2.3 mm. Then 1 at 1050°C
Annealed for minutes and water cooled in mist. Next, the scale on the surface of the steel plate was removed, and after flattening and rolling, a liquid mixture of mineral oil and graphite was applied to the entire surface of the steel plate, and the output was increased to 600.
The beam diameter of the W carbon dioxide laser is 0.311III
Laser irradiation was carried out to penetrate the plate thickness at three wheel intervals in a direction perpendicular to the rolling direction with a focus on φ.

At this time, a shielding plate was installed in half of the steel plate in the width direction to block half of the laser beam in a direction perpendicular to the rolling direction.

On the other hand, C: 0.053%, Si: 3.00%,
Mn: 0.080%.

A steel slab containing S: 0.020%, Af: 0.026% and N: 0.0070% was
After heating at 50"C for 2 hours, hot rolling to a thickness of 2.3cm, annealing at 1050°C for 1 minute, and cooling with water in mist. A shielding plate of the above steel plate was installed. After removing the shielding plate and welding to the edge of the steel plate on the side where it was applied, and removing the coating liquid,
A cold-rolled plate with a thickness of 0.30 mm was finished by cold rolling. Next, decarburization annealing was performed at 820°C for 15 minutes in wet hydrogen, and after applying an annealing separator, R =
1 at 1200°C with a curvature of 500 values.
Finish annealing was performed for 5 hours.

Furthermore, after applying an insulating coating mainly composed of phosphate, strain relief annealing was performed at 800°C for 3 hours.

The magnetic property results at this time were B1°~1.951 (T), 78, corresponding to the area where the laser beam was shielded. ~1.12 w/kg, whereas the area corresponding to the area irradiated with the laser beam was Bl(1
”1.950 (T), W+tzso=1.03 w
/kg, which was a significant improvement.

The reason for this is the melting of the laser beam irradiation area.

Due to the carburizing and quenching effects, the introduction of strain due to rolling is enhanced, resulting in changes in the structure of the primary grains and the state of the inhibitor, resulting in two differences between the laser beam irradiated area and the non-irradiated area.
This is thought to be due to the difference in the growth rate of secondary recrystallized grains, which led to the formation of new secondary grain boundaries in these boundary areas, and as a result, the secondary grains became finer than in the laser beam shielding area. .

Regarding the method of refining coarse secondary grains, a method by forming a secondary grain growth inhibiting region is proposed in JP-A-50-137819, but this method simply inhibits the growth of secondary recrystallized grains. It merely introduces a region where secondary grains grow in a localized region within the steel sheet, and by introducing a grain boundary in the boundary region where this speed difference occurs, the secondary grains are made finer. This invention is fundamentally different from this invention.

As described above, since this invention improves iron loss by secondary grain boundaries, the improvement effect disappears by strain relief annealing, like the iron loss improvement by laser irradiation disclosed in Japanese Patent Publication No. 58-5968. Therefore, it is particularly effective as a wound core material.

First, regarding the starting material of this invention, the components of conventionally known unidirectional electrical steel sheets, for example, C: 0.002 to 1.0
%, St: 0.1-7.0% and Mn: 0
．． In addition to containing 0.002 to 0.15%, S: 0.005 to 0.05%, Se as inhibitor forming components.
: 0.005-0.05%.

Te: 0.003-0.03%, Sb: 0.
005-0.05%, Bi: 0.005-0.05%,
Sn: 0.01-0.5%, Cu: 0.0
1-0.3%, Mo: 0.005-0.05%,
B: 0.0003-0.0040%, N:
0.001~0.01%, Al: 0.005~
0.05%, Ti: 0.001-0.05%,
V: 0.001-0.05% and Nb: 0.
Any material containing at least one selected from 0.001 to 0.05% is advantageously suitable.

These materials are manufactured by conventional steel manufacturing methods such as converter furnaces and electric furnaces, and then made into slabs, sheet bars, or directly into thin steel sheets by the ingot-blooming method, continuous casting method, roll quenching method, etc. A silicon-containing steel plate is produced by hot rolling, warm rolling, or cold rolling as necessary. Then, if necessary, uniform annealing and further rolling including intermediate annealing are performed one or more times to achieve the final plate thickness. These homogenizing annealing and intermediate annealing are aimed at recrystallization treatment to homogenize the crystal structure after rolling, and are usually performed at 800 to 1200°C for 3
Hold for 0 seconds to 10 minutes. Also, the finishing thickness is 0.50
mm or less, but the secondary recrystallization becomes unstable at 0,23
This invention is particularly effective for thin finished thicknesses of m+s or less.

Next, C is removed from the steel by annealing in wet hydrogen at 700-900°C for 11-15 minutes. Form a crystal texture.

After that, secondary recrystallization annealing is performed at 800-1000°C for 1-50 hours, and then 850-1250°C for 5-50 hours.
A final finish annealing consisting of linear annealing is performed for about an hour, but in this invention, before the above final finish annealing, a step of imparting local strain to the steel plate and a secondary recrystallization are applied to the edges of the steel plate. This method incorporates a step of welding the material forming the nucleus.

The first possible means of imparting local strain here is to locally heat the steel plate during cold rolling to partially release the strain, thereby reducing the accumulated strain and increasing the level of strain before secondary recrystallization. This is a method of partially enlarging the secondary grain size, that is, reducing the amount of strain at grain boundaries. The second possible means is to carburize the steel plate locally at some stage before annealing (excluding final finish annealing), as in the case of the basic experiment described above, contrary to the above-mentioned process. This is a method of partially introducing strain and increasing accumulated strain, thereby partially reducing the primary grain size before secondary recrystallization, that is, increasing grain boundary strain. A third possible method is to partially release the strain by locally decarburizing the steel plate at some stage before decarburization annealing, contrary to the second method described above, to reduce the accumulated strain. and as a result 2
This is a method of partially increasing the primary grain size before the next recrystallization, that is, reducing grain boundary strain. Furthermore, the fourth possible process
This is a method in which a quantity is directly introduced into the steel sheet before secondary recrystallization by a mechanical method or the like.

Above is the first part. Second. In the third and fourth means, the method, timing, amount, and form of strain release, carburizing, decarburization, and strain introduction are not particularly specified, but in any process, secondary grains are latent during secondary recrystallization. It is preferable to change it appropriately within a range that does not significantly affect the period but significantly changes the growth rate.

Further, welding of the material forming secondary recrystallized nuclei can be performed at any stage up to the final annealing as described above. Further, any conventional welding method such as gas, current, laser, plasma, or electron beam can be used, and any of the welding methods, such as butt and overlapping, are suitable.

Further, as the secondary recrystallization nucleation material to be welded, both single crystals and polycrystals with a high Goss orientation concentration are suitable. Among these, preferred polycrystalline materials include: (1) C: 0.025-0.050%, Si: 0.1-0.050%;
4.0%.

Mn: 0.05-0.07%, S: 0.0
15-0.025%.

■ C: 0.025~0.060%, Si: 0.1~
4.0%.

Mn: 0.05-0.07%, Se: 0.0
15-0.040%.

Sb? 0.020-0.060%, Mo: 0
．． 010-0.025%.

■ C: 0.050~0.090%, Si: 2.5~
4.0%.

Mn: 0.05-0.10%, S: 0.0
15-0.025% or Se: 0.015-0.0
40%, An: o, ots ~0.040%,
N: 0.050-0.100%.

A hot-rolled sheet, etc., obtained by heating a silicon steel slab containing Fe and unavoidable impurities to a temperature of 1250°C or higher and then hot rolling it at a temperature of 800°C or higher. Moreover, the shape may be any shape such as a plate or a line.

Also, the material to be welded is Nide or S.

By containing a relatively large amount of at least one type of finely dispersed phase of Mn compounds such as Se and Te, normal grain growth is suppressed as much as possible, and the Goss component of the primary grains is reduced as much as possible by being de-rolled before hard reduction or rolling. The present invention can be applied more effectively if a material with C or the like is suitable, and in particular, a material that grows but does not generate secondary grains during secondary recrystallization.

During secondary recrystallization annealing, by performing temperature gradient annealing where the temperature gradient at the boundary between secondary recrystallized grains and primary recrystallized grains is 1° (/cm or more), the steel plate surface after final annealing can be After making the steel sheet into a mirror-like state, by dry brating such as CVD or PVD, an ultra-thin film consisting mainly of at least one of metal nitrides, carbides, and oxides is firmly formed on the surface of the steel sheet. Magnetism improves.

(Example) Example I C: 0.075%, Si: 3.30%, Mn
: 0.075%, S: 0.025%, AI! ,
A silicon steel slab containing N: 0.030% and N: 0.0085%, with the remainder consisting of Fe and unavoidable impurities, was hot rolled into a hot rolled plate with a thickness of 1.8 mm. Material A was annealed at 1120°C for 2 minutes and then cooled in a mist. Also C: 0.100%, S
i: 3.45%, Mn: 0.20%, S
A silicon steel slab containing: 0.003%, Affi: 0.025%, and N: 0.0090%, with the remainder consisting of Fe and unavoidable impurities, was hot-rolled to a thickness of 2.3 m. After forming a plate, it was cold rolled to a plate thickness of 1.8 rm. Next, a B material was obtained by performing primary recrystallization by performing plasma irradiation using a plasma arc to penetrate the plate thickness at intervals of 3a+m in a direction perpendicular to the rolling direction.

Match the rolling direction and rolling surface of each of the A and B materials to the end of the B material, butt the A material, apply a mixture of graphite powder and mineral oil to the joint, and then laser weld it to the C material. did. Next, the B and C materials are cold rolled to a thickness of 0.
．． Finished as a 23an cold rolled sheet.

Next, decarburization was performed in wet hydrogen at 840°C for 110 minutes, and M
After coating and drying the gO annealing separator, R =
A curvature of 500 m was applied, the temperature was raised at a rate of 15°C/h, and purification annealing was performed at 1200°CCl2O hours.

Furthermore, after applying an insulating coating mainly composed of phosphate, strain relief annealing was performed at 800''C for 3 hours.

At this time, the magnetic properties of the B material are B1°=1.520(T
), whereas the C material was B. =1.945(T
).

L7/s. = 0.81 (w/kg), which was a significant improvement.

In addition, A material is B. =1.948 (T), W+tz
s. = 0.90 (enemy/kg).

Example 2 A hot-rolled sheet of material B of Example 1 was pickled to remove oxide scale on the surface. Next, a liquid mixture of mineral oil and graphite was applied to the surface of the steel plate, and a laser beam with a diameter of 1 inch was irradiated to penetrate the plate thickness in a direction perpendicular to the rolling direction at intervals of 5 inches in the rolling direction. D material was used.

Next, apply the A material of Example 1 to the end of the D material.
After aligning the rolling direction and rolling surface of each material and butting them together, a mixture of graphite powder and mineral oil was applied to the joint, and then laser welding was performed to obtain E material.

This E material was cold-rolled to produce a cold-rolled plate with a thickness of 0.23 mm. Thereafter, the same treatment as in Example 1 was performed.

The magnetic properties of the E material at this time are: B+o = 1.950 (T), l'l+yzso
-0.80 (w/kg), and a significant improvement in magnetism was achieved.

Example 3 After surface scale was removed from the hot rolled sheet of material B in Example 1 by pickling, the surface of the steel sheet was plated with copper to a thickness of 2 μm.

Next, a laser beam with a diameter of 2 mm was irradiated at intervals of 5 [11111] in the direction perpendicular to the rolling direction under conditions that only the copper plating layer was evaporated, and after decarburization in wet hydrogen at 840 ° C for 10 minutes, Material F was obtained by removing the remaining copper plating. The A material of Example 1 is butted against the end of this F material with the rolling direction and rolling surface of each of the materials A and F matching, and after applying a mixture of graphite powder and mineral oil to the joint, laser welding is performed. It was made of C material. C material was cold-rolled to produce a cold-rolled plate with a thickness of 0.23 mm. Next, decarburize in wet hydrogen at 840"C for 10 minutes, coat with MgO annealing separator, and after drying, apply a curvature of R = 500nm in the rolling direction and raise the temperature at a rate of 15°C/h. 120
Purification annealing was performed at 0"C for 20 hours. After applying an insulating coating mainly composed of phosphate, annealing was performed at 800°C.
Strain relief annealing was performed at C for 3 hours. The magnetic properties of the G material at this time are Boo'''1.933 (T), Wtt/s.=
0.86 (w/kg), and a significant improvement in magnetism was achieved.

Example 4 CO, 045%, St 3.25%, Mn O, 0
65%, Mo 0.012%, SeO, 019%
A hot-rolled plate obtained by hot rolling a silicon steel slab containing 0.025% of Sb and 0.025% of Sb, and the balance consisting of Fe and unavoidable impurities to a thickness of 2.3 mm was used as the H material, and Example 10A
Materials A and H were butted against the ends of the hot-rolled sheets with the rolling directions of each material being the same, and a mixture of graphite powder and mineral oil was applied to the joint, followed by laser welding.

This welded material was subjected to homogenization annealing at 900'C for 3 minutes, then subjected to a first cold rolling to give an intermediate plate thickness of 0.601 m, and then subjected to intermediate annealing at 950'C for 3 minutes. After that, a second cold rolling was performed to obtain a cold rolled sheet with a vi thickness of 0.23 mm.Next, it was decarburized in wet hydrogen at 850°C for 25 minutes, and then rolled in the rolling direction using a roll with protrusions. 6m
Strain strips of 1% and having a width of 3 ma+ and intersecting the rolling direction at m intervals were introduced into only half of the A material in the rolling direction.

Next, apply MgO annealing separator, and after drying, R-
After giving a curve with a curvature of 5001 and performing secondary recrystallization annealing at 850°C for 30 hours, the temperature was raised at a rate of 20°C/h and purification annealing was performed at 1200°C for 20 hours. .

Furthermore, after applying an insulating coating mainly composed of phosphate, strain relief annealing was performed at 800"C for 3 hours.The magnetic properties of material A at this time corresponded to the region where no strain was introduced, and =1.925 (T).

Lt/5o = 0.88 (w/kg), whereas B1° = 1.92 for the region where strain was introduced.
5 (T).

Wl? /S. -0.84 (w/kg), and a significant improvement in magnetism was achieved.

(Effects of the Invention) Thus, according to the present invention, artificial differences in the growth rate of secondary recrystallized grains can be eliminated by partitioning the steel sheet before secondary recrystallization into areas where the amount of introduced strain is high and areas where the amount of strain is low. By providing this, it is possible to increase the number of secondary grain boundaries, that is, to subdivide the secondary grains, and in turn, to reduce the magnetic properties, especially the iron loss, which does not deteriorate even during strain relief annealing, and furthermore, it greatly contributes to energy conservation. be.

Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] 1. A unidirectional electrical steel sheet is produced by hot rolling a silicon-containing steel slab, then annealing and cold rolling at least once, and then final finish annealing. For this purpose, a method for manufacturing a steel sheet with excellent magnetic properties, which includes a step of applying local strain to the steel sheet before final annealing, and a step of welding a material for forming secondary recrystallized nuclei to the edge of the steel sheet. A method for producing unidirectional electrical steel sheets. 2. The method according to claim 1, wherein the imparting of local strain involves partially heating the steel plate during cold rolling. 3. The method according to claim 1, wherein the local strain is applied by partially carburizing the steel plate in any step before annealing. 4. The method according to claim 1, wherein the application of local strain involves partially decarburizing the steel plate in any step before annealing. 5. The method according to claim 1, wherein the imparting of local strain involves directly introducing strain into the steel plate by a mechanical method immediately before final finish annealing.