JPH025820B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing grain-oriented electrical steel sheets with excellent iron loss. (Prior Art) Grain-oriented electrical steel sheets are mainly used as iron cores for transformers and other electrical equipment, and must have good magnetic properties such as excitation properties and iron loss properties. Grain-oriented electrical steel sheets are produced by utilizing the secondary recrystallization phenomenon to develop a secondary recrystallization called the Goss structure, which has a (110) plane on the rolled surface and a <001> axis in the rolling direction. can get. In order to develop this secondary recrystallization, a so-called inhibitor is required to suppress the primary recrystallized grain growth up to the secondary recrystallization temperature range in the final annealing heating process.
There are MnSe, BN, etc., and it is important that these inhibitors are finely precipitated and dispersed, do not melt up to a certain temperature range, and do not cause size changes. Normally, the manufacturing method for grain-oriented electrical steel sheets is as follows:
A silicon steel material containing Si4wt% (hereinafter abbreviated as %) or less is hot-rolled, and if necessary, the hot-rolled sheet is annealed.
A cold-rolled sheet with the final finish thickness is obtained through one or two cold rolling processes, and then decarburized annealed, coated with an annealing separator containing MgO as the main component, and subjected to final finish annealing. It is manufactured through a series of steps in which secondary recrystallized grains with the Goss orientation are developed, impurities such as S and N are removed, and a glass-like insulating film is formed. In recent years, when there is a strong demand for energy conservation, various studies have been made to reduce the iron loss of grain-oriented electrical steel sheets, and in addition to additive components that form inhibitors, annealing separators that are involved in the formation of insulation films have been proposed. For example, Tokusekki Publication No. 56-75577 states that in an annealing separator mainly composed of MgO, S or an S compound that decomposes at temperatures below 1000°C should be added in an amount of 0.4 to 2% in terms of S, and an Sr compound should be added in an amount of 0.2% in terms of Sr. ~10% and, if necessary, a Ti compound, and apply the annealing separator to the plate surface on which an oxide layer containing SiO ₂ is formed by decarburization annealing, and then final finish annealing. A method is disclosed. Furthermore, JP-A-58-107417 discloses that Sb or an Sb compound having a particle size distribution of 70% or less of 20μ or less is added to an annealing separator mainly composed of MgO.
%, and the annealing separator is applied and final annealing is performed. In the former, iron loss is lowered by containing S in the annealing separator, and by containing Sr, point defects in the film caused by the S content are prevented. In the latter case, Sb is included in the annealing separator to reduce the secondary recrystallized grain size and reduce core loss. Although such proposals have been made, there are few that can be said to be sufficient, and the current situation is that various considerations must be made in the future. [Object of the Invention] The present invention was created through detailed study of the film formation process, with the aim of producing grain-oriented electrical steel sheets with excellent iron loss. (Structure and operation of the invention) The present invention will be described in detail below. In the production of grain-oriented electrical steel sheets, annealing separator is used in final annealing.
The glass-like film formed on the plate surface through the reaction between MgO and SiO ₂ in the oxide film formed on the plate surface during decarburization annealing is 2MgO + SiO ₂ .
→Formed by the reaction of Mg ₂ SiO ₄ . For this reason,
The oxide film formed on the plate surface during decarburization annealing requires the presence of a certain amount of SiO ₂ or more.
It is desirable to perform decarburization annealing for a long time at a low dew point in the SiO ₂ forming region. However, due to decarburization and productivity issues, in terms of thermochemical equilibrium, it is common to perform annealing at a high dew point and for a short time in the Fayalite formation region. Therefore, the oxide film of the decarburization plate is an oxide film mainly composed of Fe ₂ SiO ₄ huayalite or Fe ₂ SiO ₂ +SiO ₂ and may contain a very small amount of FeO. Fe like this
Oxides act as a source of oxygen on the surface of the steel sheet, making the annealing area oxidizing during the final finish annealing process, and are therefore unfavorable from the standpoint of improving magnetic properties. Therefore, in order to improve the magnetic properties, the present inventors destabilized the inhibitor due to the annealing atmosphere gas during the temperature rising process in final finish annealing, and developed an annealing separation method to minimize the effect on the oxidized layer on the surface of the steel sheet. As a result of various studies on the composition of the agent,
Even among chlorine compounds, which were conventionally considered harmful when included in annealing separators, we have newly discovered that certain compounds have very effective effects. The present invention was made based on this knowledge, and its technical gist is that in the production of _grain -oriented electrical steel sheets, Sb, Sr, Ti, Zr chloride 1
By applying an annealing separator containing 0.02 to 1.5 parts by weight of one or more seeds per 100 parts by weight of magnesium oxide and performing final annealing, iron loss can be significantly reduced. According to this particular chloride-containing annealing separator, since these chlorides have a low melting point (for example, SbCl ₃ is about 80°C), the annealing separator coating and drying process,
Alternatively, in the temperature raising process of final finish annealing, it becomes a solution or molten state on the oxide film formed during decarburization annealing and reacts with Fe oxide in the oxide film to reduce FeO in the annealed surface oxide layer, By enriching the surface with SiO ₂ and making it dense, it is advantageous for glass film formation. Also, by etching FeO,
It has the effect of reducing the amount of oxygen in the oxide film of the steel sheet and suppressing the atmosphere between the sheets from becoming oxidizing during final finish annealing. Furthermore, since Sb, Sr, Zn, and Ti used as chlorides form a dense thin film on the steel sheet surface,
It has the effect of protecting the SiO ₂ -based oxide film during temperature rise during final annealing, and also protecting the surface from oxidation by atmospheric gas due to hydrated moisture of the annealing separator MgO. These new findings and effects will reduce iron loss. The details will be described below. The method of the present invention is widely used for producing grain-oriented electrical steel sheets. First, the steel components of the applied hot-rolled sheet for grain-oriented electrical steel sheet (hereinafter referred to as hot-rolled sheet) will be described. If the C content is less than 0.03%, secondary recrystallization will be poor;
% is unfavorable in terms of decarburization and magnetic properties, so it is set at 0.03 to 0.100%. Si is an important component that controls iron loss, and if it is less than 2.5%, good iron loss cannot be obtained. On the other hand, if its content exceeds 4.0%, the cold rollability will deteriorate significantly, so it should be reduced to 2.5 to 4.0%.
shall be. In addition, Mn, S, Cu,
Contains Al, N, etc. There is no need for special regulations regarding this content, but Mn is 0.03 to 0.20%, S: 0.01
~0.05%, Al is 0.01~0.06% as acid-soluble Al, N
is 0.003 to 0.012%, and Cu is 0.05 to 0.030%. One or both of sulfides and nitrides may be included. Furthermore, if necessary, Sn, Sb, Se, Cr, Ni, Mo
There is no problem even if one or more of the following elements are contained. A hot-rolled sheet is manufactured by hot-rolling a steel billet obtained by continuous casting or ingot-blushing rolling. Thereafter, the hot-rolled sheet is annealed if necessary, and then cold-rolled once or twice or more with intermediate annealing to give the sheet a final thickness of, for example, 0.15 to 0.35 mm. After that, decarburization annealing is performed in an infiltrated hydrogen + nitrogen atmosphere, and an oxide layer containing SiO ₂ is formed on the plate surface.
Apply the annealing separator of the present invention. The annealing separator contains Sb, Sr,
One or more types of Ti, Zr chloride, 0.02~
It contained 1.5 parts by weight. The reason for limiting the chloride content to 0.02 to 1.5 parts by weight is that if it is less than 0.02 parts by weight, the aforementioned etching and sealing effects will be small, and if it is more than 1.5 parts by weight, the etching action will be too strong and the steel plate surface will be damaged. This is because excess Cl remains in the high-temperature part of the final annealing temperature increase process and prevents glass film formation. The magnesium oxide is a light compound that is easily soluble in water.
MgO may be used, or a water-insoluble MgO clinker may be used, but low-activity MgO with a hydration moisture of 4% or less may be used.
It is effective to use Also, if necessary
TiO ₂ and B compound may be added. The steel plate coated with the slurry liquid of the annealing separator is dried at 200 to 300°C, and then heated in an H ₂ or N ₂ + H ₂ atmosphere.
The final annealing is then recrystallized and purified by annealing in H ₂ at 1200°C for 20 hours. Example 1 Si: 3.25%, Al: 0.028%, Cu: 0.08%, Sn:
0.10%, Mn: 0.080%, N: 0.008%, S: 0.024
%, C: 0.065% component was hot rolled, hot rolled plate annealed, pickled and cold rolled by a known method.
The thickness was 0.225mm. This steel plate was heated to 840℃ for 2 minutes.
After decarburization annealing in _N2 + _H2 infiltrated atmosphere,
When an annealing separator mixed with varying amounts of antimony chloride (SbCl ₃ ) was applied to 100 parts by weight of MgO and 5 parts by weight of TiO ₂ , and final annealing was performed at 1200°C for 20 hours, the following results were obtained. was gotten.

[Table] Example 2 Si: 3.18%, Al: 0.026%, Mn: 0.080%, N:
A slab containing 0.008%, S: 0.023%, and C: 0.060% was hot-rolled, hot-rolled plate annealed, pickled, and cold-rolled to a thickness of 0.29 mm by a known method. This steel plate is heated to 840℃
After decarburizing annealing in an N ₂ + H ₂ infiltration atmosphere for 2.5 minutes, strontium chloride SrCl ₂ and zirconium chloride ZrCl ₄ were added to 100 parts by weight of MgO and 5 parts by weight of TiO ₂ .
Apply an annealing separator mixed with varying amounts of
When final annealing was performed at 1200°C for 20 hours, the following results were obtained.

[Table] Example 3 The steel plate after decarburization annealing used in Example 1 was
An annealing separator containing antimony chloride (SbCl ₃ ) and strotium chloride (SrCl ₂ ) in varying ratios was applied to 100 parts by weight of MgO, 5 parts by weight of TiO ₂ , and 0.2 parts by weight of NaBO ₂ . When finishing annealing was performed, the following results were obtained.

【table】

[Table] Example 4 C: 0.045%, Si: 3.15%, Mn: 0.068%, S:
Hot-rolled silicon steel ingot containing 0.023% to 2.15mm
And so. After pickling, it was cold-rolled to 0.68mm and heated to 980°C.
After annealing, it was cold rolled to a final thickness of 0.29 mm. Decarburization annealing was then performed at 840° C. for 2 minutes in an N ₂ +H ₂ infiltration atmosphere. After applying SbCl ₃ and ZrCl ₄ as an annealing separator to the steel sheet in varying amounts from 0.05 to 1.0 parts by weight based on 100 parts by weight of MgO, final annealing was performed.
Table 4 shows the magnetism and appearance of the glass film after annealing.

[Table] As described above, according to the present invention, a grain-oriented electrical steel sheet with low iron loss and a good film is manufactured.

Claims (1)

[Claims] 1 A hot rolled sheet containing C: 0.030 to 0.100 wt%, Si: 2.5 to 4.0 wt%, and at least one of sulfide and nitride as a primary recrystallized grain suppressor is annealed as necessary, After achieving the final plate thickness by cold rolling once or twice or more with intermediate annealing in between, decarburization annealing is performed to form an oxide layer containing SiO ₂ on the plate surface,
In the method for producing a grain-oriented electrical steel sheet, in which a final annealing is performed after applying an annealing separator containing magnesium oxide as a main component on the oxide layer, Sb, Sr,
A grain-oriented electrical steel sheet with excellent iron loss characterized by using an annealing separator containing one or more chlorides of Ti and Zr in an amount of 0.02 to 1.5 parts by weight per 100 parts by weight of magnesium oxide. manufacturing method.