JP2003201522A - Method for preventing edge strain in grain-oriented magnetic steel sheet in finish-annealing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively reduce the occurrence of an edge strain without needing a special member, an extra process and troublesome treatment, etc. <P>SOLUTION: At the point of time when the concentration of impurity gas component in an annealing atmosphere is reduced to the extent that the 70% or more of the impurity concentration at the initial period in the steel is judged to be removed from the steel by continuously measuring the impurity gas component in the steel gasified in the atmosphere with purification of the steel sheet during finish-annealing with a box-type annealing furnace, the finish-annealing is completed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing ear distortion in finish annealing of grain-oriented electrical steel sheets, and more particularly, to accurately determine the purification time of the steel sheet in finish annealing to minimize the finish annealing time. Thus, it is intended to effectively prevent the occurrence of ear strain at the coil end portion on the side in contact with the coil pedestal, which has been a concern during finish annealing in the conventional box-type annealing furnace.

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet is obtained by subjecting a hot-rolled sheet adjusted to a predetermined composition to one or two or more cold rolling steps with an intermediate anneal, followed by decarburization annealing and an annealing separator. Is applied and dried, and then wound into a coil while applying a winding tension, and then finish annealing is performed in a predetermined atmosphere gas. In the above finish annealing, the coil is placed in an annealing furnace with its winding axis perpendicular to the upper surface of the coil pedestal and is annealed at a high temperature for a long time. Distortion called "ear distortion" occurs at the coil end on the contact side. This tendency is particularly remarkable in thin materials with a plate thickness of 0.30 mm or less. Such distortion of the coil side edge portion is a major obstacle in terms of both magnetic characteristics and workability since the grain-oriented electrical steel sheets are laminated and used. Therefore, it is necessary to reduce the occurrence of such ear strain as much as possible.

[0003] Conventionally, as a measure for reducing such ear distortion, for example, in Japanese Unexamined Patent Publication No. 5-179353, a steel material containing 0.2 mass% or more C between the coil and the coil pedestal and having a transformation point is used. We have proposed a method of performing high-temperature finish annealing in the state of being inserted as a floor plate. Although this method shows a considerable strain reducing effect, it was not very effective when applied to a steel coil of a component design that causes secondary recrystallization at high temperature.

Further, in Japanese Unexamined Patent Publication No. 10-204542, prior to finish annealing, the coil end portion on the side in contact with the coil pedestal is subjected to finish annealing by finish annealing at the same time as or earlier than the center portion in the coil width direction. It proposes a method of adding a means, specifically, a pre-strain of 0.1 to 0.5% to the end of the decarburized annealed plate on the side in contact with the coil pedestal. However, as described above, this method requires an extra step of applying a pre-strain to the end portion of the decarburized annealed plate prior to the finish annealing.

Further, in Japanese Patent Laid-Open No. 11-246913,
Inner winding part of the coil (T₁), Middle winding part
(T₂) And the outer winding part (T₃) About the winding tension
₃ ≧ T ₁ ≧ T₂ Satisfying the relationship of
Inner winding part (W₁), Middle winding part (W₂) And the outer winding part (W
₃), The coating amount in₃ ≤W₁ ≤W₂ Satisfy the relationship
It is proposed that the amount be set to a certain amount. However, this
The method is to adjust the coating amount of the annealing separator before coiling
In addition to having to adjust by hand, wind it up in a coil
When it is necessary to control the tension in the coil longitudinal direction,
It requires complicated processing.

[0006]

However, if the occurrence of ear distortion can be effectively prevented without the need for the above-mentioned special members, extra steps, and complicated treatments, the effect is not achieved. Extremely large. The present invention has been developed in view of the above situation, and can effectively reduce the occurrence of ear strain without the need for a special member, an extra step, a complicated process, etc. as in the conventional case. The purpose is to propose a method for preventing ear distortion in finish annealing of grain-oriented electrical steel sheets.

[0007]

Means for Solving the Problems The clarification process of the present invention will be described below. Conventionally, the annealing time in finish annealing of electromagnetic steel sheets has been set by estimating a sufficient time for achieving purification of the steel sheet. However, the occurrence of ear strain increases in proportion to the length of the finish annealing time. Therefore, if the finish annealing time can be effectively shortened, the occurrence of ear strain can be advantageously prevented.

Therefore, the present inventors have examined an effective method for shortening the finish annealing time. As a result, for each electromagnetic steel sheet coil, if it is possible to accurately grasp the point at which the steel sheet has been purified to a satisfactory degree, it is not necessary to perform additional finishing annealing after that, so the finishing annealing time I came to have the idea that the shortening of

[0009] Then, next, research was repeated on a method of grasping the time when the purification of the steel sheet was achieved to a satisfactory degree. As a result, as an index for judging the purification of the steel sheet, during finish annealing, the impurity gas component in the steel gasified in the atmosphere by the purification of the steel sheet is suitable, and when this impurity gas component reaches a predetermined concentration Is judged as the end of purification,
It was found that by finishing the finish annealing, the finish annealing time can be significantly shortened as compared with the conventional one, and the occurrence of ear strain can be remarkably reduced. The present invention is based on the above findings.

That is, according to the present invention, the silicon-containing steel slab is hot-rolled, then cold-rolled once or twice or more with intermediate annealing, and then decarburized and annealed in a box-type annealing furnace. When manufacturing a grain-oriented electrical steel sheet by a series of processes for applying finish annealing, during finish annealing in a box-type annealing furnace, impurity gas components in steel gasified in the atmosphere due to purification of the steel sheet are continuously measured, The concentration of the impurity gas component in the annealing atmosphere is characterized by terminating the finish annealing at a time when it is determined that 70% or more of the initial impurity concentration in the steel has been determined to have been removed from the steel, This is a method for preventing ear distortion during finish annealing of grain-oriented electrical steel.

In the present invention, impurities in the atmosphere
H as a gas component₂Se, H₂S, N ₂And NH₃ etc
Fits in an advantageous way.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. According to the findings of the inventors, it has been found that the magnetic characteristics of the electromagnetic steel sheet vary depending on the degree of purification in finish annealing, but the characteristics hardly change when the degree of purification exceeds a certain level. That is, in the past, since the magnetic properties were improved as the purification was improved, S and S
In order to remove impurities such as e and Al from the steel as much as possible, the annealing time was set with the aim of specifically removing 95% or more of the initial impurity concentration in the steel. Further, the annealing time was set to a constant value on the assumption of a coil in which the addition amount of the impurity component was the maximum, as a time for sufficiently purifying regardless of the difference in individual coil components.

Therefore, the inventors have reexamined the above points. As a result, (1) Although the magnetic properties are improved as the steel plate is refined, the change in properties becomes extremely small when the purification is over a certain level.In other words, even if purification is not performed for a long time as in the conventional case, Satisfactory magnetic properties are obtained, (2) Purification progresses rapidly from the start of finish annealing to a certain point, but then becomes gentle, (3) And after the purification progresses rapidly, it becomes gentle. Although the absolute time differs depending on the individual coil, it is generally the time when about 70% of the initial concentration of impurity components in the steel is removed from the steel, and after this time, the magnetic properties are improved. Was determined to be minor.

1 (a) and 1 (b) respectively show H ₂ of the impurity gas components in the atmosphere as an index for judging the purification of the steel sheet.
The results obtained by examining the relationship between the annealing time and the impurity gas concentration in the atmosphere when Se and NH ₃ are used are shown below. The impurity gas concentration here is a value obtained by integrating the average concentration per unit time with the annealing time. In both (a) and (b) of the figure, the concentration of the impurity gas component in the atmosphere rises sharply from the start of annealing to a certain point, and thereafter becomes gentle. Then, the concentration of each gas component was measured at the time when the gas concentration in the atmosphere suddenly increased and then became gentle. All of them corresponded to the case where about 70% of the initial impurity concentration in the steel was removed from the steel. It was found to be the concentration.

Further, at this point, the steel sheet for which finish annealing has been completed
(Thickness: 0.23 mm) iron loss and then finish annealing
Continuing, 95% of the initial impurity concentration in the steel was removed from the steel.
The iron loss of the finished steel plate (same as above)
When compared, the difference ΔW _17/50 Is about 0.01 W / kg
It was also found that there was almost no difference between the two.

Therefore, in the present invention, when the finish annealing should be finished, the concentration of the impurity gas component in the annealing atmosphere is determined to be such that 70% or more of the initial impurity concentration in the steel is determined to have been removed from the steel. It was when it became. If this judgment is made at a time when the concentration of the impurity gas component exceeds 80% of the initial impurity concentration in the steel and is removed from the steel, the annealing time is extended although the magnetic properties are good. As a result, the occurrence of ear strain is promoted, so that the time of this determination is preferably 80% or less of the initial impurity concentration in the steel.

Next, the preferred component composition of the grain-oriented electrical steel sheet of the present invention will be described. As a starting material, any of the conventionally known component compositions is suitable as the silicon-containing steel, and the representative compositions are as follows. C: 0.01 to 0.10 mass% C is a component useful not only for making the structure uniform and fine during hot rolling and cold rolling but also for developing goss-oriented grains, and it is desirable to add at least 0.01 mass% or more. However, 0.
If the content exceeds 10 mass%, the Goss orientation is rather disturbed, so the upper limit is preferably set to about 0.10 mass%.

Si: 2.0 to 5.5 mass% Si increases the specific resistance of the steel sheet and effectively contributes to the reduction of iron loss, but if the content exceeds 5.5 mass%, the cold ductility is impaired.
On the other hand, if the content is less than 2.0 mass%, not only the resistivity decreases but also the crystal orientation is randomized due to α-γ transformation during the high temperature final finishing annealing performed for secondary recrystallization and purification, which is sufficient. Since the iron loss improving effect cannot be obtained, the Si content is
It is preferably about 2.0 to 5.5 mass%.

Mn: 0.02 to 2.5 mass% Mn is at least 0.02 mass% in order to prevent hot embrittlement.
Although it is necessary to contain a certain amount, if it is too much, the magnetic properties are deteriorated, so the upper limit is preferably limited to about 2.5 mass%. Further, MnS and MnSe can be precipitated as inhibitors with the content within this range.

In order to highly integrate the crystal grains aligned in the Goss orientation by the secondary recrystallization, it is essential that the inhibitor be uniformly and finely precipitated in the steel prior to the secondary recrystallization. As this inhibitor, so-called MnS, Cu _2-X
Precipitate types such as S, MnSe, Cu _2-X Se and AlN, and Sn, A
There are grain boundary segregation types such as s and Sb.

Among precipitate types, MnS, Cu _2-X S, MnSe, Cu
_In the case of _2-X Se system, one or two kinds of S and Se: 0.005
.About.0.06 mass% S and Se are components useful as inhibitors for controlling the secondary recrystallization of grain-oriented electrical steel sheets. From the viewpoint of securing such suppression power, at least about 0.005 mass% is required, but if it exceeds 0.06 mass%, the effect is impaired, so the lower and upper limits are 0.005 mass% and 0.06 mass%, respectively.
It is desirable to set it to about ss%. When Cu is used as an inhibitor component, the Cu content is 0.005 to 0.50 mass%.
It is desirable to set the degree.

In the case of AlN system, Al: 0.005 to 0.10 mass
%, N: 0.004 to 0.015 mass% Al and N content ranges are also described above.
Cu _2-X S, MnSe, for the same reason as in the case of Cu _2-X Se system, it is preferable ranges described above. Here, the above Mn
It is more desirable to use S, Cu _2-X S, MnSe, Cu _2-X Se system and AlN system together.

Further, as a grain boundary segregation system inhibitor, S
n and Sb are Sn: 0.01 to 0.25 mass% and Sb: 0.005, respectively.
Approximately 0.15 mass% is preferable, and each of these inhibitor components may be used alone or in combination. The upper limit of these is that when added in excess of this value, the saturation magnetic flux density decreases and good magnetic properties cannot be obtained. In addition, conventionally known Cr, Te, Ge, As, B
i, P and the like can be added to improve the magnetic characteristics. The preferable range of these is Cr: 0.01 to 0.15 mass%, Te, A
s, Ge and Bi: 0.005-0.1 mass%, P: 0.01-0.2 m
Ass% is preferable. Each of these inhibitor components may be used alone or in combination.

Next, typical manufacturing conditions for the grain-oriented electrical steel sheet will be described. The silicon-containing steel slab used as a raw material is intended for continuous casting or slab rolling from an ingot, but it goes without saying that slab pre-rolled after continuous casting is also included in the subject.

In the above-mentioned silicon-containing steel slab, it is necessary to heat-treat the slab to solidify the inhibitor. In the present invention, the conditions of solution treatment are not particularly limited, but it is desirable to heat at a temperature not lower than the solubility product of each inhibitor component for 5 minutes or more by a gas furnace or an induction electric heating furnace or a combination of both. . It is also possible to make the slab structure after heating finer by applying a light reduction of 20% or less during or before heating. The slab after heating is subjected to ordinary rough rolling to form a sheet bar, and then subjected to hot finish rolling. Then, hot-rolled sheet annealing is performed if necessary.

When the cold rolling is performed twice after the hot rolled sheet is annealed, the first cold rolling is performed at a rolling reduction of about 5 to 50%. Then, after the intermediate annealing, final cold rolling is performed to obtain the target plate thickness, but the final cold rolling is subjected to warm rolling or pass aging treatment as is known to improve the texture of primary recrystallization. Therefore, it is possible to obtain more preferable results by adopting it as the production method of the present invention. It goes without saying that the strong cold rolling method may be performed once. After the final cold rolling, it is also possible to perform a known process for forming linear grooves on the surface of the steel sheet for subdividing the magnetic domains.
The steel sheet having the final thickness by the above method is subjected to decarburization / primary recrystallization annealing by a known method.

After that, after the annealing separator is applied and dried, the final annealing is carried out in the box-type annealing furnace. In the present invention, the end point of this finishing annealing is the concentration of the impurity gas component in the annealing atmosphere. There is a feature in judging with.
That is, as shown in FIGS. 1 and 2 above, it is determined that the concentration of impurity gas components such as H ₂ Se and NH ₃ sharply increased, and 70% or more of the initial impurity concentration in steel was removed from the steel. When the concentration is reached, the purification is progressing to the point where it is sufficiently satisfactory in terms of magnetic properties, and further annealing further promotes the occurrence of ear strain, so in the present invention, impurities in the annealing atmosphere are used. The concentration of the gas component of the initial impurity concentration in the steel
The finish annealing was terminated when 70% or more (preferably 80% or less) reached a concentration at which it was determined that the steel had been removed.

Here, H ₂ Se, H ₂ S, N ₂ and NH ₃ are used as the impurity gas components as an index for judging the purification of the steel sheet.
Etc. fits advantageously. However, it is difficult to capture all the impurity gas released into the atmosphere. Further, the direct value of the gas concentration during finish annealing and its integrated value, which are obtained by the gas analyzer, change in relation to the volume of the finish annealing furnace, the sampling flow rate, and the like. Therefore, the relationship between the gas concentration integrated value and the reduction amount of impurities in steel at a predetermined furnace volume, sampling flow rate, etc. is obtained in advance, and the measured gas concentration integrated value is obtained in advance. It is preferable to finish the annealing at the time when the gas concentration integrated value at the time when the amount of the medium impurities is reduced by 70% from the initial amount is reached.

The atmosphere for finish annealing is preferably H ₂ gas or (H ₂ + N ₂ ) mixed gas as usual. When a plurality of coils are processed by one finish annealing, it is important to select and process the coils having the same impurity element concentration.

After the final finishing annealing described above, the unreacted annealing separator is removed, and then an insulating coating is applied to the steel sheet surface to obtain a product. If necessary, a mirror surface of the steel sheet surface may be applied before the insulating coating is applied. Chemical treatment may be applied, or tension coating may be used as the insulating coating. Further, the coating and baking treatment of the coating may be performed together with the flattening treatment. Further, in the steel sheet after secondary recrystallization, in order to obtain an iron loss reduction effect, a known domain refinement treatment, that is, plasma jet or laser irradiation is applied to the linear region, or a linear dent region is formed by a projection roll. It is also possible to perform processing such as providing.

[0031]

Example: C: 0.045 mass%, Si: 3.25 mass%, Mn: 0.
A silicon steel slab containing 067 mass% and Se: 0.021 mass%, the balance of which is Fe and inevitable impurities, is hot-rolled, and then cold-rolled twice with intermediate annealing interposed between the two thicknesses: A cold-rolled plate having a width of 0.23 mm and a plate width of 1000 mm was used. Then,
After decarburization annealing, an annealing separating agent containing MgO as a main component was applied and then wound on a coil. Then, this coil was placed in the furnace with its winding axis perpendicular to the upper surface of the coil pedestal, and the soaking temperature: 12 in a hydrogen atmosphere.
Finish annealing was started under the condition of 00 ° C. H ₂ Se was used as the impurity gas component as an index for judging the purification of the steel sheet. Here, when the amount of Se in the steel is the above value, the H ₂ Se gas concentration integrated value in the atmosphere, which corresponds to the time when the amount of Se removed from the steel becomes 70% of the initial Se concentration, is reached. Finish annealing was completed at the time.

When the depth of ear distortion as shown in FIG. 2 was investigated for the coil thus obtained, a maximum of 30 was found.
It was mm. On the other hand, when the same steel sheet was subjected to finish annealing according to the conventional method, the depth of occurrence of ear strain was 50 mm. Therefore, it can be seen that the present invention reduced the depth of occurrence of ear strain by 20 mm. When the iron loss values of the two were examined, the difference ΔW _17/50 between them was 0.01 W / kg, and there was almost no difference between the two.

[0033]

As described above, according to the present invention, when the grain-oriented electrical steel sheet is finish-annealed in the coil state, the occurrence of the ear strain, which is conventionally concerned at the coil end portion in contact with the coil pedestal, is significantly reduced. can do.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between an annealing time and an impurity gas concentration in an atmosphere.

FIG. 2 is an explanatory diagram of a state of occurrence of ear distortion.

Claims (2)

[Claims] 1. A silicon-containing slab of steel is hot-rolled, cold-rolled once or twice with intermediate annealing, then decarburized and then annealed in a box-type annealing furnace. During the production of grain-oriented electrical steel sheets by a series of processes, the impurity gas components in the steel gasified in the atmosphere during the finish annealing in the box-type annealing furnace are continuously measured in the annealing atmosphere. At the time when the concentration of the impurity gas component in is at a concentration at which 70% or more of the initial impurity concentration in the steel is determined to be removed from the steel, the finish annealing is terminated, the grain-oriented electrical steel sheet. To prevent ear distortion during finish annealing of steel. 2. The finish annealing of a grain-oriented electrical steel sheet according to claim 1, wherein the impurity gas component in the finish annealing atmosphere is at least one selected from H ₂ Se, H ₂ S, N ₂ and NH _3. To prevent ear distortion in children.