JPH07188760A - Production of low core loss grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To suppress the growth of secondarily recrystallized grains deviated from the Goss direction, simultaneously to form grain boundaries on the Sn deposited parts and to attain low core loss, at the time of forming linear grooves on the surface of a steel sheet and producing a grain-oriented silicon steel sheet by a magnetic domain fractionating method, by applying Sn plating to groove parts and regulating the temp. rising rate of final finish annealing. CONSTITUTION:A silicon-contg. slab is subjected to hot rolling and is thereafter subjected to cold rolling for one time or for >=two times including process annealing to regulate its sheet thickness to a final one, which is subjected to decarburizing annealing and is then subjected to final finish annealing to form a grain-oriented silicon steel sheet. After the final cold rolling in this producing process, continuous or noncontinuous linear grooves are formed on the surface of the steel sheet, and the groove parts are applied with Sn plating. Moreover, in the temp. rising stage in the subsequent final finish annealing, the temp. rising rate between 850 to 1050 deg.C is regulated to 5 to 25 deg.C/hr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a low iron loss grain oriented electrical steel sheet suitable for use as an iron core of a transformer or other electric equipment.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are mainly used as core materials for transformers, and are required to have good magnetic properties. Particularly when used as an iron core, it is important that the energy loss is low, that is, the iron loss is low. As one of conventional measures for reducing iron loss, there is a technique of forming a groove portion in a direction intersecting with the rolling direction. For example, in Japanese Patent Laid-Open No. 59-197520, a linear flaw is introduced in a direction substantially perpendicular to the rolling direction before the final finish annealing to generate a magnetic pole there, thereby subdividing a magnetic domain and eventually reducing iron loss. A technique for achieving the above is disclosed.

Similarly, fine secondary recrystallized grains are linearly generated by a local chemical treatment in a direction intersecting the rolling direction, and iron loss is caused by a magnetic domain subdivision effect by magnetic pole generation of a magnetic field. Techniques for reducing it have been proposed. That is, in JP-A-60-114522, a steel sheet obtained by subjecting a hot-rolled sheet obtained by hot rolling an slab for Al-containing silicon steel to necessary heat treatment and then cold rolling according to a conventional method It has been proposed that a dilute solution containing a decarburization retarder such as Sn or a compound thereof be locally adhered to the surface, and the action of the decarburization retarder causes the coated area to be fine secondary recrystallization. . Similarly, as a technique for reducing iron loss by a magnetic domain refining effect by a local chemical treatment, Japanese Patent Laid-Open No. 60-96720 discloses that a steel sheet before final finishing annealing is locally worked and Sn
Techniques for attaching compounds to the area are disclosed.

[0004]

SUMMARY OF THE INVENTION In order to further reduce the iron loss, the inventors of the present invention use the above-mentioned two techniques for reducing the iron loss of grain-oriented electrical steel sheets, namely, linear groove formation and local groove formation. By combining chemical treatment and forming grooves on the surface of the final cold rolled sheet by etching, and then depositing Sn or Sn compound on the grooves, a fine grain boundary is formed at the bottom of the grooves after final finishing annealing, and the amount of magnetic pole is increased. Tried to increase. However, although the secondary grain boundary can be formed in the adhered portion only by simply depositing Sn and the Sn compound in the groove portion, the crystal orientation of the secondary grain itself is largely deviated from the so-called Goss orientation, resulting in the magnetic flux. The density characteristic B ₈ is lowered,
Since the hysteresis loss was significantly increased, the iron loss was rather deteriorated.

The present invention advantageously suppresses the formation of secondary recrystallized grains deviated from the Goth orientation and exerts the effect of forming secondary recrystallized grain boundaries by depositing Sn and its compound on the groove. An object of the present invention is to propose a method for producing a low iron loss grain-oriented electrical steel sheet, which is capable of further reducing iron loss in addition to the effect of reducing iron loss by forming grooves.

[0006]

[Means for Solving the Problems] As a result of the inventors' investigations on the behavior of the progress of secondary recrystallization during finish annealing,
In particular, after the final cold rolling, to form a linear groove on the surface of the steel sheet, and then to form Sn in the groove portion by plating,
It has been found that the improvement of the magnetic properties can be achieved only by setting the temperature rising rate in the final temperature rising process within a predetermined range. The present invention is based on the above findings.
That is, the present invention is a series of hot-rolling a silicon steel slab, and then cold rolling one or more times with intermediate annealing to obtain a final plate thickness, followed by decarburization annealing and then final finishing annealing. In the production of the grain-oriented electrical steel sheet by the process of, after the final cold rolling, a continuous or discontinuous linear groove is formed on the surface of the steel sheet, and then Sn is plated on the groove portion and the final finish. In the temperature rising process during annealing, the temperature rising rate between 850 and 1050 ℃ should be 5 ℃ / hr or more and 25 ℃ / h or more.
The method for producing a low iron loss grain-oriented electrical steel sheet is characterized in that

[0007]

The operation of the present invention will be described below.
The inventors of the present invention, in the final cold-rolled sheet obtained by hot rolling and cold rolling a silicon steel slab containing Al as an inhibitor constituent, linearly formed in the groove, and further Sn is attached to the groove. Diffusion behavior of Sn during final finish annealing for
The growth behavior of secondary recrystallized grains was investigated. According to the investigation, if the distribution of Sn in the plate thickness direction is non-uniform when secondary recrystallized grains are generated, the suppressing force of the surface layer by Sn is unnecessarily strengthened, and as a result, the orientation is worse than that of the central layer. It was found that secondary grains were formed. In addition, if the heating rate is lowered in the temperature range where secondary recrystallization occurs, the diffusion distance of Sn with respect to temperature increases, and the progress of secondary recrystallization is delayed at the same time. 2 after becoming uniform
The secondary recrystallization progresses, and grains with bad orientation cannot be generated. Also, in the lower part of the Sn adhesion part, the growth of the secondary recrystallized grains is stopped due to the reduction of the interface energy, and the grain boundaries are reduced. It turned out to generate.

Based on the above findings, the following experiments were conducted to reach the present invention. C: 0.068 wt%, Si: 3.20 wt%,
Mn: 0.080 wt%, P: 0.003 wt%, S: 0.002 wt%, so
l An ingot containing Al: 0.028 wt%, N: 0.008 wt%, Se: 0.024 wt% and Sb: 0.029 wt% was soaked at 1420 ° C for 28 minutes to sufficiently dissolve AlN, MnS, MnSe. After that, hot rolling is applied to obtain a plate thickness of 2.7 mm, which is then wound at 550 ° C and then cold rolled to a thickness of 1.5 mm, and then 1100 ° C, 1
After the intermediate annealing for 1 minute, the material was rapidly cooled and then cold-rolled to a final thickness of 0.23 mm. After that, a resist ink having a linear non-printed portion having a width of 0.15 mm and an interval of 7 mm was printed on the surface of the steel sheet. This linear non-printed area is a direction orthogonal to the steel plate rolling direction. These samples were plated with Sn after forming a groove with a depth of 25 μm on the surface of the steel sheet corresponding to the linear non-printed area by electrolytic etching using NaCl.
Various plating amounts were used.

After that, the resist ink was removed, and after washing and drying, decarburization annealing was performed at 840 ° C. for 2 minutes. And Mg
After applying an annealing separator containing O 2 as a main component, finish annealing was performed. This finish annealing was performed after holding for 30 hours at 850 ° C, then
The temperature was raised up to 50 ° C. at various heating rates. Purification annealing was subsequently performed. The relationship between the magnetic properties of the thus-obtained magnetic steel sheet and the heating rate is shown in FIG. Figure 1
As is clear from the above, good electromagnetic characteristics were exhibited when the heating rate was 5 ° C./hr or more and 25 ° C./hr or less at any plating amount. When the temperature rising rate is less than 5 ° C./hr, secondary recrystallization does not occur and a fine grain structure is formed, so that the magnetic properties are deteriorated. On the other hand, when the temperature exceeded 25 ° C / hr, the magnetic properties deteriorated due to the formation of grains with bad orientation due to Sn plating.

In other words, within the range satisfying the present invention, secondary recrystallized grain boundaries are formed by the Sn adhering effect of the groove portion without deterioration of B ₈ and a magnetic pole is generated there. The addition of the subdivision effect makes it possible to achieve iron loss reduction. Further, the Sn adhesion does not change its effect whether it is continuous or discontinuous.

As the silicon-containing steel slab used as the material of the present invention, any of the conventionally known grain-oriented electrical steel sheets can be applied. One containing Al as an inhibitor constituent and using an AlN inhibitor, or AlN And Mn
The combination of S and MnSe improves the iron loss significantly. The typical composition ranges of the components are as follows.

C: 0.02 to 0.09 wt% C is 0.02 in order to improve the hot rolled structure by utilizing γ transformation.
More than wt% is required. On the other hand, if it exceeds 0.09 wt%, decarburization becomes poor, so the range is 0.02 to 0.09 wt%. Si: 2.5-5.0 wt% Si is 2.5 wt% because it increases electric resistance and improves iron loss.
The above is necessary. On the other hand, if it exceeds 5.0 wt%, embrittlement is severe and cold rolling becomes difficult, so the range is 2.5 to 5.0 wt%.

Al: 0.01 to 0.04 wt% Al is a main inhibitor and is a basic component for AlN precipitation. If it is less than 0.01 wt%, the precipitation amount of AlN is insufficient, and conversely.
If it exceeds 0.04 wt%, the precipitated AlN will be coarsened and the suppressing power will deteriorate, so it is in the range of 0.01 to 0.04 wt%. N: 0.0055 to 0.0100 wt% N is also the main inhibitor for the precipitation of AlN, which is the main inhibitor. If it is less than 0.0055 wt%, the precipitation amount of AlN is insufficient,
On the other hand, if it exceeds 0.0100 wt%, it will be gasified when heating the steel slab and cause problems such as blistering.
The range is 0100wt%.

Mn is useful for preventing cracks during hot rolling, and is also useful as an inhibitor-forming component when using a secondary inhibitor such as MnS or MnSe. For that purpose, 0.02 wt% or more is necessary. However, if it exceeds 0.3 wt%, it becomes difficult to dissolve these MnS and MnSe by slab heating, so the range is preferably 0.02 to 0.3 wt%. S and Se combine with Mn to bind to MnS
It is a useful component because it precipitates MnSe. In order to bring about this effect, 0.005 wt% or more is required. On the other hand, when it exceeds 0.040 wt%, coarsening of precipitates causes deterioration of magnetic properties, so 0.005 to 0.040 wt% is preferable. .

In addition, Sb, Cu, Sn, P, Bi, As, B, Ge, V, Nb, which are known as inhibitor reinforcing components, are also known.
Of course, Cr and the like may be contained. For this purpose, Sb is 0.005-0.060 wt% and Cu, Sn, Cr are 0.03
~ 0.30 wt%, Bi 0.005 ~ 0.020 wt%, P, Ge, V, N
b, As 0.005 to 0.030 wt%, B 0.0005 to 0.0020 wt%
The range of inclusion is preferable. In addition, 0.005 to 0.020 wt% of Mo is added to prevent cracking in hot rolling peculiar to silicon steel.
% Can be included.

Next, the manufacturing method according to the present invention will be described. The silicon steel slab containing the above components is slab-heated by a conventional method and then hot-rolled. The coil of hot rolling is made into the final steel plate thickness by one or two or more cold rolling steps sandwiching intermediate annealing, but the final cold rolling is, as is well known, a reduction rate of 80 to 95%. It is preferable that the pressure is set to a high pressure, and if it deviates from this range, the magnetic flux density decreases on either side.

It is an important requirement of the present invention to form continuous or discontinuous linear grooves on the surface of the steel sheet after the final finish cold rolling and then perform Sn plating. It is desirable to form such continuous or discontinuous linear grooves in a direction substantially orthogonal to the rolling direction. The method for forming the linear groove may be a knife edge, a laser beam, an electric discharge machining, an electron beam method, or the like, but the etching method is more preferable in view of the continuity in the processing step with the plating processing to be formed later. This etching method uses an etching resist on the steel plate surface.
As a non-coating area, a linear area which is continuous or discontinuous in the direction orthogonal to the rolling direction is left to be applied and baked, and then an etching treatment is performed. Groove depth is 5-35μ
About m is preferable. The etching treatment may be any conventionally known etching treatment method such as electrolytic etching.

Next, Sn plating is applied to the formed linear groove portion. Compared to the method of applying a diluted solution or a diluted suspension of Sn or Sn compound as described in JP-A-60-114522, Sn plating is easier to control the amount of adhesion and has better adhesion. It has the advantage of being good. The Sn plating is achieved by performing a plating treatment with the etching resist used for forming the groove formed on the surface of the steel sheet, performing Sn plating having a predetermined thickness, and then removing the etching resist. If the plating thickness is less than 1 μm, the effect is small, and if it exceeds 50 μm, Sn overflows from the groove, and Sn is transferred during final finish annealing in a box furnace. Therefore, it is preferably in the range of 1 to 50 μm. As the Sn plating, alloy plating such as Sn-35% Ni plating can also be used.

After the final cold rolling, the coil is degreased and then subjected to decarburization annealing. Decarburization annealing is performed in a known wet hydrogen atmosphere at 750
It is carried out at ~ 900 ℃ and 60 ~ 180 sec. The coil after decarburization annealing is coated with an annealing separating agent, and then wound into a coil and subjected to final finish annealing. In this final finish annealing,
It is one of the features of the present invention that the rate of temperature rise between 850 and 1050 ° C is 5 ° C / hr or more and 25 ° C / hr or less. As described above, the magnetic properties are deteriorated when the heating rate is less than 5 ° C / hr and more than 25 ° C / hr.

After the final annealing, the coil is made into a product by removing the remaining annealing separator and then applying an insulating coating if it is necessary to increase the insulation resistance and performing flattening annealing. In addition, it is possible to apply plasma jet, laser or electron beam irradiation, or magnetic domain subdivision technology such as groove formation to the product.

[0021]

Example: C: 0.062 wt%, Si: 3.3 wt%, Mn: 0.076
A silicon steel slab containing wt%, Se: 0.024 wt%, Al: 0.025 and N: 0.008, the balance being substantially Fe composition,
It was hot-rolled, annealed at 1050 ° C. for 2 minutes, cold-rolled, and rolled to a final plate thickness of 0.20 mm. Gravure offset printing this coil in the direction that makes 80 ° with the rolling direction.
An ink containing an epoxy resin as a main component was applied and formed as a resist so as to have linear non-printed areas having a width of 0.2 mm and a gap of 3.5 mm. The ink thickness is 3 μm.

Then, a groove was formed on the surface of the steel sheet corresponding to the non-printed area by electrolytic etching. The electrolytic etching was carried out in a NaCl electrolytic solution at a current density of 8 A / dm ² for 30 s so that the groove depth was 15 μm. Then, Sn electroplating was performed with the resist still attached. Electroplating is
Current density with a solution containing tin phenol sulfonate as the main component
The groove was formed by etching under conditions of 10 A / dm ² and a bath temperature of 50 ° C. with various amounts of Sn deposition. After that, the resist ink is removed, degreasing and drying are performed, then decarburization annealing is performed, and final finishing annealing is performed at 850 to 1050 ° C.
The heating rate was changed during this period. Table 1 shows the results of examining the magnetic properties of the steel sheet after the secondary recrystallization annealing.

[0023]

[Table 1]

[0024]

EFFECTS OF THE INVENTION According to the present invention, by controlling the rate of temperature increase during final annealing when linearly depositing Sn to the groove portion of the final cold-rolled sheet, the deviation from the Goss orientation due to the Sn deposition 2 By suppressing the growth of the next recrystallized grains and generating the crystal grain boundaries at the Sn adhesion portion, the domain line differentiation can be achieved by the generation of the magnetic poles at the grain boundaries. This can further reduce the iron loss in addition to the effect of subdividing the magnetic domain of the groove.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a Sn deposition amount, a temperature rising rate, and magnetic characteristics.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keiji Sato, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. (72) Masayoshi Ishida, 1 Kawasaki-cho, Chuo-ku, Chiba (72) Inventor Kunihiro Senda 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Iron & Steel Co., Ltd.

Claims (1)

[Claims] 1. After hot rolling a silicon-containing steel slab,
In producing a grain-oriented electrical steel sheet by a series of steps in which final sheet thickness is obtained by performing cold rolling once or two or more times with intermediate annealing sandwiched, then decarburization annealing, and then final finishing annealing. , Forming a continuous or discontinuous linear groove on the surface of the steel sheet, and then forming Sn in the groove portion by plating, and in the temperature rising process at the time of final finish annealing, 850 ~
A method for manufacturing a low iron loss grain-oriented electrical steel sheet, characterized in that a temperature rising rate between 1050 ° C. and 5 ° C./hr or more and 25 ° C./hr or less.