JP2579717C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decarburizing annealing a grain-oriented electrical steel sheet used as an iron core material of a transformer. [0002] The most necessary characteristic of grain-oriented electrical steel sheets is that they have low iron loss. In recent years, in order to reduce the iron loss, the surface of the steel sheet after the secondary recrystallization is subjected to a magnetic domain refining technique, that is, a treatment such as laser irradiation, so that the iron loss has been greatly improved. At this time, the iron loss value after the magnetic domain refinement is governed by the magnetic flux density of the product. That is, the higher the magnetic flux density, the better the iron loss after the magnetic domain refinement. Therefore, the higher the magnetic flux density has become increasingly important. At present, a grain-oriented electrical steel sheet having a magnetic flux density B ₈ of about 1.92 T is put on the market using AlN as an inhibitor, but further improvement in the magnetic flux density is required.
On the other hand, as a film property, the film may be peeled off at the time of bending by the customer,
Film adhesion is also an important property. Conventionally, as means for improving magnetic properties and film adhesion, for example, Japanese Patent Publication No. 54-24
No. 686 and Japanese Patent Publication No. 57-1575 disclose that the heat treatment cycle of decarburizing annealing is two stages. In Japanese Patent Publication No. 57-1575, the temperature in the front region of the decarburizing annealing process is set to 750 to 880 ° C., the PH ₂ O / P H ₂ in the atmosphere is set to 0.15 to 0.75, and the temperature in the subsequent rear region is set. A method for decarburizing and annealing a grain-oriented electrical steel sheet at a temperature of 750 to 1200 ° C. and a PH ₂ O / P H ₂ in the atmosphere of 0.15 or less is disclosed. Further, Japanese Patent Application Laid-Open No. 2-240215 discloses a three-stage heat treatment cycle. Although the magnetic properties and the adhesion of the product film were greatly improved by these methods, coils having poor magnetic properties, particularly poor magnetic flux density and poor adhesion of the film, often occurred, and were problematic. In other words, a product that sufficiently satisfies both the magnetic properties and the film adhesion at the same time could not be obtained industrially stably. SUMMARY OF THE INVENTION The present invention provides a technique for manufacturing a grain-oriented electrical steel sheet that simultaneously improves both magnetic properties, particularly magnetic flux density and film adhesion. [0007] The gist of the present invention is as follows. (1) By weight%, C: 0.01 to 0.10%, Si: 2 to 4%, Mn: 0.05 to 0.10 %, S + Se: 0.01 to 0.03%, Sol Al: 0.01 to 0.04%, N: 0.003 to 0.01%, Sn + Sb: 0.01 to 0.3%, Cu ≦ 0.3%, Mo ≦ 0.2%, and the balance Fe When decarburizing and annealing a cold rolled sheet made of unavoidable impurities, the temperature in the front region of the decarburizing annealing step is 750 to 880 ° C., and the PH ₂ O / P H ₂ in the atmosphere is 0.15 to 0. and 75, the decarburization annealing process oriented electrical steel sheet to a P H ₂ O / P H ₂ in the atmosphere and 0.15 the temperature of the subsequent back region at from 750 to 1200 ° C., MgO after decarburization annealing treatment Coated and dried
A method for decarburizing annealing a grain-oriented electrical steel sheet, comprising controlling oxygen in steel to a weight ratio of 0.03 to 0.07% after the step . (2) The directivity according to (1), wherein the front region is divided into two stages, the front stage is performed at 750 to 850 ° C., and the rear stage is performed at a temperature higher than the front stage at 800 to 880 ° C. Decarburization annealing method for electrical steel sheets. The present invention consists of three findings. That is, first, the oxide layer formed on the steel sheet surface by the decarburizing annealing is mainly composed of SiO _{2 and} is thin, thereby improving the magnetic flux density. Second
On the other hand, the thicker the oxidized layer on the steel sheet surface generated by the decarburizing annealing, the better the product film tends to be. Third, these characteristically opposite phenomena include MgO after decarburizing annealing.
By controlling the oxygen content of the steel sheet after the step of coating and drying the steel sheet anti-fusing agent, it is possible to simultaneously satisfy the magnetic flux density and the film adhesion. Hereinafter, a description will be given based on examples of experimental data. Before the decarburization annealing, the three types of cold-rolled sheets with the composition of the steel sheet of 0.20 mm thickness shown in Table 1
Soaking annealing at 830 ° C. for 2 minutes was performed. Atmosphere gas at this time is H ₂ : 1
0%, and the steam gas is PH ₂ O / P H ₂ : 0.0011 to 0.1480 (dew point 13 to
45 ° C.) and the remainder was mixed with N ₂ . Then, after cooling to room temperature, further soaking annealing at 900 ° C. for 30 seconds is performed on H ₂ : 10%
, N ₂ : 90%, PH ₂ O / P H ₂ : 0.0051 (dew point −30 ° C.). Then, a MgO coating containing TiO ₂ was applied and baked in air at 300 ° C. The O content of this steel sheet was determined by chemical analysis after washing the MgO film with water. Then, a batch / high-temperature finish annealing up to 1200 ° C. at a heating rate of 20 ° C./hr was performed. After washing the excess MgO of the steel sheet with water, a tension film was applied and baked, and flattening annealing of the steel sheet was performed at 800 ° C., and the characteristics were evaluated. The test results are shown in FIGS. [Table 1] The film adhesion shown in FIG. 2 was A when the film was wound around a round bar of 20 mmφ and the film was not peeled at all: A, B was partially peeled, and C was completely peeled. As seen in FIG. 1, when the amount of the steel sheet O increases, the magnetic flux density gradually deteriorates. As shown in FIG. 2, the adhesiveness of the coating tends to be improved, but it is clear that the degradation starts when the content exceeds 900 ppm. There is a range that can simultaneously satisfy both the magnetic flux density and the film adhesion, and it can be seen that the range is such that the O content is 0.03 to 0.07%. Further, it is not necessary to set the steel sheet O amount after the decarburization annealing in an appropriate range which is different for each of these three types of component systems. It can be understood that it can be satisfied. In the experiment, C: 0.01 to 0.10%, Si: 2 to 2
4%, Mn: 0.05 to 0.10%, S + Sc: 0.01 to 0.03%, Sol
Al: 0.01-0.04%, N: 0.003-0.01%, Sn + Sb: 0.
Tested within the component ranges of 01-0.3%, Cu ≦ 0.3%, Mo ≦ 0.2%,
Within this range, results equivalent to those in FIGS. 1 and 2 were obtained. When the amount of steel sheet O after decarburization annealing increases, the magnetic flux density deteriorates because the amount of SiO ₂ or Fe ₂ SiO ₄ oxide layer on the steel sheet surface after decarburization annealing increases, It is thought that the fine precipitates in the steel sheet cause a subtle morphological change through the interface, and the magnetic flux density decreases. When the amount of steel sheet O after decarburizing annealing increases, the film adhesion tends to be improved because the film formed by high-temperature finish annealing has a structure in which the film is intertwined with the base iron layer. This may be because the film hardly peels off at the interface with the film. In the sheet thickness before the decarburizing annealing, that is, in the range of the product sheet thickness of 0.15 to 0.35 mm, the optimum amount of the steel sheet O after the decarburizing annealing does not change depending on the sheet thickness. .0
It was in the range of 3 to 0.07%. As a second experiment, an example will be described in which the extent to which the components contained in the steel sheet affect the amount of steel sheet O after decarburization annealing is investigated. Using the steel sheet components before decarburization annealing shown in Table 2, annealing was performed under constant decarburization annealing conditions, and then the O content of the steel sheet was measured. The thickness of the steel plate used is 0.3 mm. In the decarburizing annealing, first, soaking annealing at 850 ° C. for 5 minutes was performed. At this time, the atmosphere gas was H ₂ : 30%, and PH ₂ O / P
H ₂ : 0.40, the balance being N ₂ . Next, a soaking heat treatment at 870 ° C. for 10 seconds was performed using H _{2.
: 70%, P H 2 O} / P H 2: 0.0284, was balance in an N ₂ atmosphere. Table 2 shows the results. [Table 2] As shown in Table 2, the amount of O after decarburizing annealing varies greatly depending on the amount of the component, that is, the small amount of Cu, Sn, Sb, Mo, or the like. This may be because elements that are easily segregated on the surface affect the formation amount of the surface oxide layer. However, as shown in FIGS.
By controlling the amount of the steel sheet O after the decarburizing annealing, it is possible to secure quality characteristics without depending on the additive component system. That is, instead of the constant control of the H ₂ %, N ₂ %, and H ₂ O% of the atmosphere as in the related art,
First, the components including the O content of the steel sheet after the decarburizing annealing are checked, and the O content is 0.03-0.
It is necessary to control the atmosphere as much as possible to reach 07%. As a specific method of the control, for example, P H ₂ O / P H ₂ , an atmosphere gas input amount, an annealing temperature, a sheet passing speed, and the like are changed. The steel sheet thus obtained is coated with MgO or the like for preventing fusion, dried, then annealed at a high temperature, coated with an insulating film, and dried to form a product. [Example 1] Molten steel whose components were adjusted by a converter and a vacuum degassing apparatus was continuously cast, and a slab was produced at 1420 ° C.
And hot-rolled to produce a hot-rolled sheet. After annealing at 1100 ° C, 0.3mm
And degreased. The chemical analysis values of this steel sheet were as follows: C: 0.065% by weight, Si: 3.1%, Mn
: 0.71%, S: 0.006%, Se: 0.021%, N: 0.0096%,
SolAl: 0.022%, Sb: 0.013%, Mo: 0.02%, 0: 0.
0015%. Next, first, soaking annealing at 830 ° C. for 2 minutes was performed. Atmosphere gas at this time was H ₂ : 40% by vol%, steam was blown to change P H ₂ O / P H ₂ , and the remainder was N ₂ . Subsequently, in the same annealing line, without lowering the temperature of the steel sheet, a second-stage soaking process at 890 ° C. for 20 seconds was performed in H ₂ : 40%, PH ₂ O / P H ₂ : 0.003, and the rest in an N ₂ atmosphere. Went inside. Next, an annealing separator containing 2 parts by weight of Ti oxide and 0.4 part by weight of Sr sulfate was applied to 100 parts of magnesia and baked. This steel sheet was subjected to a chemical analysis of the steel sheet O amount by removing the coating film by washing with water, and the results are shown in Table 3. Then, the substrate was heated to 1200 ° C. at 10 ° C./Hr in an H ₂ atmosphere. The results are as follows. The evaluation of film adhesion was evaluated as ○ when the film was not peeled at all when wound around a round bar of 20 mmφ, evaluated as △ when partially peeled, and evaluated as × when completely peeled. [Table 3] As shown in Table 3, a grain-oriented electrical steel sheet satisfying the range of the present invention and having excellent magnetic flux density and adhesion was obtained. Example 2 Molten steel whose components were adjusted by a converter and a vacuum degassing apparatus was continuously cast, and the slab was heated to 1300 ° C.
And hot-rolled to produce a hot-rolled sheet. After annealing at 1000 ° C., 1.3 mm
After annealing at 1150 ° C., it was cold-rolled to 0.15 mm. The chemical analysis values of this steel sheet after degreasing are as follows: C: 0.055%, Si: 3.0% by weight.
%, Mn: 0.80%, S: 0.025%, N: 0.0076%, SolAl:
0.031%, O: 0.0011%. Then, first at 830 ° C for 1 minute and 8
An isothermal annealing at 50 ° C. for 30 seconds was performed. The atmosphere gas at this time was H ₂ : 20% by vol%, steam was blown to change P H ₂ O / P H ₂ , and the remainder was N ₂ . Subsequently, in the same annealing line, without lowering the temperature of the steel sheet, 2 seconds at 930 ° C. for 10 seconds.
The step heat treatment was performed in an atmosphere of H ₂ : 20%, PH ₂ O / P H ₂ : 0.003, and the balance being N ₂ . Next, 2 parts by weight of Ti oxide and 0.1 part of sulfuric acid Sb were added to 100 parts of magnesia.
An annealing separator containing 1 part by weight was applied and baked. The coating film of the steel sheet was removed by washing with water and the amount of the steel sheet O was chemically analyzed. Then, the substrate was heated to 1200 ° C. at 20 ° C./Hr in an N ₂ + H ₂ atmosphere. Then
Excess MgO was washed with water and a tension film was baked. The results are as follows. The evaluation of film adhesion was evaluated as ○ when the film was not peeled at all when wound around a round bar of 20 mmφ, evaluated as △ when partially peeled, and evaluated as × when completely peeled. [Table 4] As shown in Table 4, a grain-oriented electrical steel sheet satisfying the range of the present invention and having excellent magnetic flux density and adhesion was obtained. According to the present invention, a grain-oriented electrical steel sheet satisfying both the magnetic flux density and the film adhesion can be manufactured.

[Brief description of the drawings]     FIG.   It is a table | surface which shows the relationship between the steel plate O amount and magnetic flux density.     FIG. 2   It is a table | surface which shows the relationship between steel sheet O amount and film adhesion.

Claims (1)

Claims: 1. In weight%, C: 0.01 to 0.10%, Si: 2 to 4%, Mn: 0.05 to 0.10 %, S + Se: 0.01 to 0.03%, Sol Al: 0.01 to 0.04%, N: 0.003 to 0.01%, Sn + Sb: 0.01 to 0.3%, Cu ≦ 0.3%, Mo ≦ 0. When decarburizing and annealing a cold-rolled sheet composed of 2% and the balance Fc and inevitable impurities , the temperature in the front region of the decarburizing annealing step is 750 to 880 ° C., and the PH ₂ O / P H of the atmosphere is ₂ is set to 0.15 to 0.75, and the temperature of the subsequent rear region is set to 750 to 1200 ° C., and the PH ₂ O / P H ₂ of the atmosphere is set to 0.15 or less. , Coated and dried with a steel sheet fusion inhibitor containing MgO after decarburizing annealing
A method for decarburizing annealing a grain-oriented electrical steel sheet, comprising controlling oxygen in steel to a weight ratio of 0.03 to 0.07% after the step . 2. The front region is divided into two stages, and the front region is performed at 750 to 850 ° C.,
The decarburizing annealing method for a grain-oriented electrical steel sheet according to claim 1, wherein the rear part is performed at a temperature higher than that of the front part at 800 to 880C.