JPH1046259A - Manufacturing method of oriented silicon steel sheet with excellent coating properties - Google Patents

Abstract

(57) [Problem] To improve magnetic properties and film properties by improving an annealing separator. SOLUTION: The main component of the annealing separator is MgO having a volume of pores having a circle equivalent diameter of 0.001 μm or more and 0.1 μm or less that is 0.03 ml / g or more and 0.2 ml / g or less. The hydrated water content of MgO after coating and drying on the steel sheet surface is adjusted to 1.0 wt% or more and 3.9 wt% or less based on MgO. More preferably, such that the CAA value becomes a predetermined value according to the pore volume
Use MgO.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented silicon steel sheet used for iron cores of transformers and other electric equipment, and more particularly to an improvement in an annealing separator applied before finish annealing. Thus, it is intended to propose a method capable of improving the magnetic characteristics and the film characteristics.

[0002]

2. Description of the Related Art The process of manufacturing a grain-oriented silicon steel sheet is performed by subjecting a steel slab to hot rolling, cold rolling, and then decarburizing annealing, followed by final finishing annealing for secondary recrystallization. Is common. Of these, secondary recrystallization occurs in the final finish annealing, and coarse crystal grains having a uniform axis of easy magnetization in the rolling direction are generated. Since such finish annealing is performed for a long time, an annealing separator mainly composed of MgO is usually applied before annealing for the purpose of preventing the steel sheet from seizing.

[0003] In addition to its role as an annealing separator, MgO has a function of forming a forsterite film by reacting with an oxide layer mainly composed of SiO ₂ generated on the steel sheet surface during decarburization annealing. The forsterite film has a function as a kind of binder for bringing the insulating coating into close contact with the base iron part, a function as an insulating material, and a function of improving magnetic properties by applying tension to a steel sheet. Therefore, it is necessary to form a forsterite film having a uniform thickness and good adhesion to a steel sheet, and therefore, the characteristics of MgO as a raw material are important.

[0004] In addition, the function of the annealing separator also has an effect of changing the generation and growth behavior of precipitates and the growth behavior of crystal grains of a steel sheet to affect magnetic properties. For example, MgO
If too much water is brought into the slurry when it is converted into a slurry, the steel sheet will be oxidized, deteriorating its magnetic properties and generating point-like defects in the coating. Alternatively, it is also known that secondary recrystallization behavior is changed by impurities contained in MgO entering steel during annealing. Therefore, the quality of the components and powder properties of the annealing separator are important factors that influence the magnetic properties and coating properties of the grain-oriented silicon steel.

Therefore, various methods for improving the quality of the annealing separator have been disclosed. For example, Japanese Patent Publication No. 54-14
No. 566 discloses a method for forming a good forsterite film by specifying the impurity concentration, hydration amount, and sieve permeability of magnesia fired in a muffle furnace at a high temperature. Also, Japanese Patent Application Laid-Open No. 58-193
No. 373 discloses a method of improving the magnetic characteristics by specifying the particle size of MgO measured from the X-ray diffraction width spread.

[0006]

Although the above-mentioned techniques have improved the film properties and magnetic properties to some extent, they have led to an increase in cost and the inability to produce products stably even if the product properties are improved, resulting in a low yield. Many things to lower,
It was difficult to say that a sufficient effect had been obtained. In particular, in recent years, a method of lowering the slab heating temperature has been studied to reduce the cost of silicon steel production.However, this method involves changes in the component system and primary recrystallization annealing conditions, resulting in unstable coating quality. Thus, problems such as insufficient film formation, film defects, and poor adhesion are likely to occur. Therefore, there is a high need to improve the annealing separator to stabilize the film formation in order to improve these problems.

[0007] The present invention has been made in view of the above circumstances, and by improving the annealing separator, the magnetic properties,
It is intended to propose a method for stably improving the film properties.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a hot rolled silicon steel sheet is subjected to one or more cold rolling operations including intermediate annealing to finish to a final thickness and then subjected to primary recrystallization annealing. , Then slurried the annealing separator with water and applied to the steel sheet surface,
In a method for producing a grain-oriented silicon steel sheet comprising a series of steps of drying and then performing final finish annealing, the volume of pores in the range of 0.001 μm or more and 0.1 μm or less in circle-equivalent diameter as MgO as the main component of the annealing separator is MgO. After using 0.03 ml / g or more and 0.2 ml / g or less, and after coating and drying on the steel plate surface,
The hydration water content of MgO is 1.0 wt% or more and 3.9 wt% based on MgO.
A method for producing a grain-oriented silicon steel having excellent coating properties, characterized by the following. Here, the pore volume is 0.03 ml / g
When the pore volume is 0.07 ml / g or less and CAA40% or less, the CAA40% value is 35 seconds or more and 75 seconds or less when the pore volume is 0.07 ml / g or more and 0.1 ml / g or less.
% Value is 65 seconds or more and 90 seconds or less, pore volume is 0.1 ml / g or more and 0.2
MgO with a CAA 40% value of 75 seconds or more and 100 seconds or less at ml / g or less
It is more preferable to use

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of various studies on the optimum MgO conditions for film formation, the inventors have found that the film quality varies greatly depending on the state of the pores in MgO which is the main agent of the annealing separator. Was newly found. The following describes the experiment that led to this finding. C: 0.045 wt% (hereinafter expressed as%), Si: 3.25%, Al:
0.01%, N: 0.0080%, Mn: 0.07%, Se: 0.02%, Sb:
A silicon steel slab containing 0.03% and Cu: 0.08% with the balance being substantially Fe is heated at 1200 ° C for 30 minutes, and then hot-rolled to 2.2m.
m. Thereafter, after hot-rolled sheet annealing at 900 ° C. for 1 minute, the sheet was cold-rolled at 120 ° C. to a thickness of 0.35 mm by a tandem rolling mill to finish to a final sheet thickness. After decarburizing and annealing the cold-rolled sheet, an annealing separator was applied and dried to perform final finish annealing.

[0010] Here, the annealing separator is composed of MgO having various pore volumes as a main component, and TiO ₂ as an additive with respect to MgO.
wt% and Sr (OH) ₂ added at 2 wt% were used. Here, the pore volume referred to in the present invention is a value measured by a constant-volume gas adsorption method, and MgO is vacuum-treated as a pretreatment.
After heat treatment at 400 ° C. for 2 hours, the adsorption gas was measured by the BET multipoint method with N _{2 as} the adsorption temperature and 77 K, and the adsorption data was evaluated by analyzing by the DH method. The DH method is an abbreviation of the Dollimore-Heal method, and is a method of obtaining the distribution of pores from the relative pressure of the adsorbed gas and the increment of the amount of adsorption, assuming that the pores are cylindrical. In addition, the amount of water adsorbed was varied by changing the hydration temperature when MgO 2 was slurried in the range of 4 ° C. to 45 ° C.

[0011] Thereafter, as finish annealing, heating from 850 ° C to 1150 ° C at a heating rate of 15 ° C / hr, followed by 1200 ° C
Purification annealing was performed at 5 ° C. for 5 hours. The film defect occurrence rate of the steel sheet thus obtained was investigated. The coating defect occurrence rate was evaluated using a laser type surface inspection device. Circle equivalent diameter
FIG. 1 shows the relationship between the pore volume of 0.001 μm or more and 0.1 μm or less and the amount of absorbed water and the incidence of film defects.

As can be seen from FIG. 1, the equivalent circle diameter of MgO is 0.00.
Change the volume of the pore part from 1 μm to 0.1 μm to 0.03 to 0.
A good coating can be obtained by adjusting the water adsorption to 2 ml / g and the water adsorption amount to 1.0 wt% or more and 3.9 wt% or less.

By the way, even if the pore volume and the amount of adsorbed water are within the above-mentioned ranges, the result is that the occurrence rate of the coating defects slightly varies. In order to investigate the cause, the above experimental results were converted to a pore volume of 0.03 ml / g or more and 0.2 ml / g.
Hereinafter, the water adsorption amount is limited to the range of 1.0 wt% to 3.9 wt%, the pore volume is plotted on the horizontal axis, and the citric acid activity C is plotted on the vertical axis.
FIG. 2 shows the result of measuring the coating defect occurrence rate by taking the value of AA 40%. Here, as the CAA 40% value, a value obtained by performing the following measurement was used. (same as below)

28.0 g of citric acid, anhydrous sodium benzoate
0.25g, 2.0 ml of 1% phenolphthalein alcohol solution
Was dissolved in pure water to make a 1000 ml solution in a 200 ml beaker.
Take 100ml, raise the temperature to 30 ± 0.5 ℃, put the magnet rotor of 8mm in diameter and 35mm in length with plastic exterior,
Set in a mag mixer with a high temperature bath adjusted to a temperature of 0.5 ° C, and put the electrode of the pH meter into the citric acid solution. Here, 2.0 g of MgO was put into the liquid, and after 10 seconds, the rotor was turned to 90
Spin at 0 rpm to stir the solution, pour it into the solution,
Measure the time until the value reaches 8.0.

FIG. 2 shows that the pore volume is 0.03 ml / g or more.
The CAA 40% value is 35 seconds or more and 75 seconds or less at 07 ml / g or less, and the CAA 40% value is 65 or less at 0.07 ml / g or more and 0.1 ml / g or less.
When the pore volume is 0.1 ml / g or more and 0.2 ml / g or less, and the CAA 40% value is 75 seconds or more and 100 seconds or less, good coating quality is obtained.

Although the detailed mechanism by which such a result is obtained is not clear, the inventors consider as follows. Usually, the annealing separator is slurried with water and applied to a steel sheet. At this time, moisture is adsorbed on the surface of MgO. This moisture adsorption occurs preferentially from the active parts of the MgO surface. If MgO has pores, water will preferentially adsorb to the pores.

After the annealing separator is applied, finish annealing is performed. At this time, water of hydration of MgO is released and becomes an oxygen source to oxidize the steel sheet. In addition, the moisture adsorbed on the outside of MgO has a weak binding force and is quickly desorbed at a relatively low temperature, so there is not much effect on the steel sheet.However, the moisture adsorbed in the pores has a strong binding force and is released at a high temperature. The effect on the steel sheet is large. Therefore, by limiting the amount of hydrated water and setting the pore volume within a predetermined range, the release in a high temperature range that strongly affects the steel sheet is kept within an appropriate range, and the coating properties are brought to a good level. It is thought that we can do it.

The reason why the preferable range of the citric acid activity is deviated by the value of the pore volume is that the pores have high reactivity during the finish annealing and the Mg ²⁺ It is considered that dissociation and rearrangement of ions and O ²⁻ ions are likely to occur, and that the more pores, the higher the sinterability. Therefore, CAA40 depends on the number of fine pores of MgO.
Values must be set separately. That is, it is presumed that the larger the pore volume, the larger the CAA40, and the smaller the pore volume, the smaller the CAA40, so that an appropriate range of reactivity can be obtained.

Next, the reasons for limitation of the present invention will be described.
The silicon-containing steel that is the material of the present invention is as follows. First, there is a method in which C is lowered at the tapping stage so that decarburization annealing is not performed, and a method in which a certain amount is secured to improve the structure and then removed by decarburization annealing. In the former, 0.01 wt% (hereinafter simply referred to as%
In the latter, the preferred range for tissue improvement is 0.01% or more and 0.10% or less. Si is 2 to 4.5%. If it is less than 2%, the effect of reducing iron loss is weakened, and if it exceeds 4.5%, the cold rolling property is impaired.

In addition to these C and Si, an inhibitor-forming component is added. Al, MnS, MnSe and the like are well known as inhibitors, but any of these may be used.
When MnS and / or MnSe is used as the inhibitor, Mn:
0.03 to 0.10%, S + Se: 0.01 to 0.03%. When AlN is used for the inhibitor, Al: 0.01 to 0.04%, N: 50 to
Set to 120 ppm. If it is less than these ranges, the effect as an inhibitor does not work, and if it is too large, secondary recrystallization becomes unstable.

In addition to the above inhibitor components, Cu, Sn, Cr, Sb, Ge, Mo,
Te, Bi, P, V, etc. can also be used. Concentrations of these components effective as an inhibitor are 0.01% or more and 0.2% or less in total. Each of these inhibitors can be used alone or in combination.

After the material containing the above components is hot-rolled by a known method, the material is subjected to cold rolling once or a plurality of times with intermediate annealing to obtain a final sheet thickness. Further, if necessary, the hot-rolled sheet can be subjected to annealing before cold-rolling. After the above-described treatment, primary recrystallization annealing is performed, and after applying an annealing separating agent, final finish annealing is performed. The atmosphere, temperature, and annealing time of this primary recrystallization annealing are not particularly limited, but usually, the atmosphere is 0.05 to 0 at a steam-hydrogen partial pressure ratio PH ₂ O / PH ₂ .
68 or less. This is to form a good internal oxide layer, and if it is less than 0.05, the oxide layer becomes too thin and 0.68
If it is higher, the oxygen content in the oxide layer becomes too large, and in any case, the oxidation of the inhibitor during the finish annealing becomes intense, and the magnetic properties deteriorate. The annealing temperature is 750 ° C or higher and 900 ° C
Hereinafter, it is desirable that the annealing time be 30 seconds or more and 180 seconds or less. This is because the primary recrystallized grain size falls within a specific range, and the magnetic properties are improved within this range.

A method of improving the magnetic characteristics by separately controlling the atmosphere during the heating for the temporary recrystallization annealing and the atmosphere during the soaking is known, and this method can also be used in the present invention. Further, when AlN is used as an inhibitor, a method of performing a nitriding treatment before, during, or after the primary recrystallization annealing is known. In the present invention, such a method may be performed simultaneously. However, the slab heating temperature
AlN-based materials that have been reduced in cost to 1300 ° C or less
By reducing the amount of Al added, the primary recrystallization is stabilized by precipitating AlN during the temperature rise process during hot-rolled sheet annealing, so nitriding during the secondary recrystallization during finish annealing does not occur. It is very harmful because it changes the AlN morphology. In this regard, the method according to the present invention promotes the formation of olivine during the finish annealing and accelerates the formation of forsterite, thereby increasing the protection of the steel sheet surface and suppressing nitriding. It is valid.

After the primary recrystallization annealing, an annealing separator mainly composed of MgO is applied to the surface of the steel sheet. At this time, MgO reduces the amount of moisture brought in by slurrying to 1.0% or more.
9% or less. This is to control the reactivity of MgO and to adjust the amount of moisture brought into the atmosphere during the finish annealing.
If it exceeds this range, no good coating is formed. The powder characteristics of the MgO used are as follows:
The volume of pores in the range from 001 μm to 0.1 μm is 0.
Use MgO of not less than 03 ml / g and not more than 0.2 ml / g, and make it a slurry with water, apply it, and dry it. .
More preferably, when the pore volume is 0.03 ml / g or more and 0.07 ml / g or less, CAA 40% is 35 seconds or more and 75 seconds or less, and the pore volume is 0.07 ml or less.
CAA 40% is 65 seconds or more and 90 seconds or less when the pore volume is 0.1 ml / g or more and 0.1 ml / g or less, and CAA4 is used when the pore volume is 0.1 ml / g or more and 0.2 ml / g or less.
The coating is improved by using MgO whose 0% is 75 seconds or more and 100 seconds or less.

In addition, the magnetic properties and the coating can be improved by adding an auxiliary agent to the annealing separator. The auxiliaries that can be used for improving magnetic properties and coatings may be those conventionally known, but are generally Mn, Cu, Nb, Tl, Sr, Bi, F
Oxides, hydroxides, sulfates, and the like of e, Sn, Ti, and Mg are known. When these compounds are added, the total amount should be 0.5% or more and 15% or less. If it is less than 0.5%, there is no effect, and if it exceeds 15%, the ratio of MgO decreases and forsterite formation does not proceed. The final finish annealing may be performed by a conventionally known method. After these series of treatments, an insulating tension coat is applied and flattening annealing is performed to finish the product. By such a treatment step, a grain-oriented silicon steel having excellent magnetic properties can be obtained.

[0026]

【Example】

(Example 1) C: 0.07%, Si: 3.28%, Al: 0.02%, N: 75ppm, M
A silicon steel slab containing n: 0.07%, Se: 0.02%, Cu: 0.06%, with the balance being substantially Fe, was heated to 1400 ° C, and 2.
Hot-rolled to a thickness of 2mm, with intermediate annealing at 1050 ° C for 2 minutes
It was cold rolled to 0.35 mm and finished to the final thickness. After decarburizing annealing, 6% TiO ₂ and 1% SrSO in MgO
₄ was added, applied and dried. At this time, the powder characteristics of MgO were variously changed as shown in Table 1. Thereafter, the temperature was raised from 850 ° C. to 1150 ° C. at a rate of 20 ° C./h as finish annealing, followed by purification annealing at 1200 ° C. for 5 hours in a dry H ₂ atmosphere. Table 2 shows the results obtained by examining the coating properties and magnetic properties of the steel sheet thus obtained. When the hydrated water content, the pore surface area, and the CAA 40% value are within the range of the present invention, not only the coating but also the iron loss and the magnetic density are good.

[0027]

[Table 1]

[0028]

[Table 2]

Example 2 C: 0.06%, Si: 3.28%, Mn: 0.07%, Se: 0.02%, S
b: 1 slab containing 0.025% and the balance being substantially Fe
The sheet was heated to 400 ° C, hot-rolled to a thickness of 2.2 mm, and subjected to intermediate annealing at 1050 ° C for 2 minutes and cold-rolled to 0.23 mm to finish to a final thickness. After decarburizing annealing, MgO 2% as an annealing separator
1% of TiO ₂ and various auxiliaries were added, coated and dried.
At this time, MgO was No. 2 and No. 5 shown in Table 1.
MgO was used. After that, 50% at 820 ° C as finish annealing
After the retention, the sample was subjected to purification annealing at 1200 ° C. for 5 hours in a dry H ₂ atmosphere. Table 3 shows the results of investigating the magnetic properties of the steel sheet thus obtained. When MgO is within the scope of the present invention, the magnetic properties,
The coating is good.

[0030]

[Table 3]

Example 3 Various silicon steel ingots having different chemical components were heated at 1380 ° C. for 30 minutes, hot-rolled to a sheet thickness of 2.2 mm, and then subjected to an intermediate annealing at 1050 ° C. for 1 minute to obtain 0.22%. It was cold rolled to a thickness of mm and finished to a final thickness. After decarburizing annealing, MgO + 6% Ti as an annealing separator
O ₂ + 1% SrSO ₄ was applied and dried. At this time, MgO of No. 2 and No. 5 shown in Table 1 was used. After that, hold at 800 ° C for 15 hours as finish annealing and then 85
The temperature was raised from 0 ° C. to 1150 ° C. at a rate of 15 ° C./h, followed by purification annealing at 1200 ° C. for 5 hours in a dry H ₂ atmosphere. Table 4 shows the results of investigating the magnetic properties of the steel sheet thus obtained. High magnetic properties are realized within the scope of the present invention.

[0032]

[Table 4]

[0033]

As described above, according to the present invention, MgO is used as a main component of the annealing separator, and as a powder characteristic of the MgO, the volume of pores having an equivalent circle diameter of 0.01 μm to 0.1 μm is 0.03 ml. / Og / g and 0.2ml / g or less, and after slurried with water and coated and dried, the hydrated water content of MgO is from 1.0 wt% to 3.9 wt% based on MgO. By doing so, it becomes possible to stably produce oriented silicon steel having good magnetic properties and coating properties, which can greatly contribute to quality improvement. Also, regarding this MgO, the CAA 40% value is 35 seconds to 75 seconds when the pore volume is 0.03 ml / g or more and 0.07 ml / g or less, and the CAA 40% value when the pore volume is 0.07 ml / g or more and 0.1 ml / g or less. Is 65 to 90 seconds, pore volume is 0.1 ml / g
When the concentration is 0.2 ml / g or less, the characteristics can be further improved by using MgO having a CAA 40% value of 75 seconds to 100 seconds.

[Brief description of the drawings]

FIG. 1 shows the relationship between the volume of pores having an equivalent circle diameter of 0.001 μm or more and 0.1 μm or less, the amount of hydration, and the incidence of film defects.

[Figure 2] Limiting the pore volume to 0.03 ml / g or more and 0.2 ml / g or less, and limiting the water adsorption to 1.0 wt% or more to 3.9 wt% or less, the horizontal axis represents the pore volume, and the vertical axis represents the citric acid activity. This figure shows the results of measuring the coating defect occurrence rate by taking the value of CAA 40%.

Claims (2)

[Claims] 1. A hot rolled silicon steel sheet is cold rolled once or plural times including intermediate annealing to finish to a final sheet thickness, and then subjected to primary recrystallization annealing. A method for manufacturing a grain-oriented silicon steel sheet consisting of a series of steps in which the slurry is applied to the steel sheet surface, dried, and then subjected to final finish annealing, with a circle-equivalent diameter of 0.001 μm or more as MgO as the main agent of the annealing separator
The volume of pores in the range of 0.1 μm or less is 0.03 ml / g or more.
The hydrated water content of MgO after using 2 ml / g or less and coating and drying
A method for producing a grain-oriented silicon steel having excellent coating properties, characterized in that the content of O is 1.0 wt% or more and 3.9 wt% or less. 2. When the pore volume is 0.03 ml / g or more and 0.07 ml / g or less, the CAA 40% value is 35 seconds or more and 75 seconds or less, and the pore volume is 0.07 ml or less.
The CAA 40% value is 65 seconds or more and 90 seconds or less when the pore volume is 0.1 ml / g or more and 0.1 ml / g or less.
2. The method according to claim 1, wherein MgO having a percentage value of 75 seconds or more and 100 seconds or less is used.