JPH02200731A - Manufacture of grain oriented silicon steel sheet having excellent magnetic properties and film properties - Google Patents

Abstract

PURPOSE:To improve the magnetic and film properties of the steel sheet by subjecting a slab of a silicon steel having specified C, Si, Mn, S, etc., to rolling, finish annealing under prescribed conditions, subjecting it to nitriding before secondary recrystallization and forming an inhibitor constituted of (Al-Si)N. CONSTITUTION:A silicon steel constituted of, by weight, 0.025 to 0.095% C, 2 to 4% Si, 0.08 to 0.45% Mn, <=0.015% Si, 0.01 to 0.06% Al, 0.003 to 0.013% N and the balance Fe is refined. The slab constituted of the silicon steel is hot-rolled at <1280 deg.C, is thereafter cold-rolled and is subjected to decarburization annealing. Next, at the time of coating the slab with an annealing and separation agent and subjecting it to finish annealing, NH3 is introduced therein at 500 to 900 deg.C, which is subjected to nitriding before secondary recrystallization to form an inhibitor contg. (Al-Si)N as main compsn.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to a directional electrode 65f with excellent magnetic properties and coating properties.
This invention relates to a method for manufacturing steel plates.

(Prior Art) Grain-oriented electrical steel sheets are mainly used as core materials for transformers, generators, and other electrical equipment, and must have good magnetic properties such as excitation properties and ironability. It is also important to have a good coating. A grain-oriented electrical steel sheet is obtained by utilizing a secondary recrystallization phenomenon to develop crystal grains having a so-called Goss orientation with a (110) plane on the rolling surface and a (001) axis in the rolling direction.

As is well known, this secondary recrystallization occurs during finish annealing, but in order to reduce the occurrence of secondary recrystallization to 1 minute, the growth of primary recrystallized grains must be suppressed to the secondary recrystallization temperature range during finish annealing. It is necessary to have so-called inhibitors, which are fine precipitates such as AfN + MnS and MnSe, present.

For this reason, the electromagnetic steel slab is heated to a high temperature of about 1350-1400°C, and the components that form inhibitors, such as N, are heated.
, Mn) S + Se I N, etc., are completely dissolved in solid solution, and annealing is performed to finely precipitate the inhibitor in a hot-rolled sheet or an intermediate sheet before final cold rolling.

Grain-oriented electrical steel sheets with high magnetic flux density are now manufactured through such treatments, but as mentioned above, heating of electrical steel slabs is carried out at high temperatures, resulting in a large amount of molten scale. This will interfere with the operation of the heating furnace. There are also problems such as high energy consumption of the heating furnace.

On the other hand, methods for producing grain-oriented electrical steel sheets are being considered by lowering the slab heating temperature. For example, in Japanese Patent Application Laid-open No. 5224116, in addition to AI, Zr, Ti IB, Nb
.

By incorporating nitride-forming elements such as Ta, V, Cr, Mo, etc. into the steel, slab heating can be improved to 11
A manufacturing method carried out at 10 to 1260°C is disclosed. In JP-A-59190324, the C content is 0.01%.
With the following low carbon S, Se and AN,! : Using an electromagnetic steel slab that selectively contains B as a material, during the primary recrystallization annealing after cold rolling, the slab heating temperature is increased to 130℃ by performing pulse annealing in which the steel plate surface is repeatedly heated at high temperature for a short period of time.
A manufacturing method in which the temperature is 0° C. or lower is disclosed. Furthermore, in Japanese Patent Application Laid-Open No. 59-56522, Mn is set to 0.08 to 0.0.
60.

By setting the S content to 0.007% or less, lowering the (Mri3 (S) product), and using an electromagnetic steel slab containing 8i, P, and N, the slab heating temperature can be increased to 1280"
The company employs manufacturing methods that produce grades C or F.

(Problem to be solved by the invention) As described above, in the production of grain-oriented electrical steel sheets, a method using low-temperature slab heating has been studied, and although it may have certain effects, it is still difficult to manufacture materials with excellent magnetic properties by industrial production. However, it cannot be said that it has reached the point where it can be manufactured in a sufficiently stable manner, and further study is required.

The present invention lowers the heating temperature of the electromagnetic steel slab to a low temperature of less than 1,280°C, thereby obtaining advantages such as reducing the occurrence of melted scale, preventing the occurrence of surface flaws, and reducing heating energy, while maintaining both magnetic properties and coating properties within 1 minute. The purpose of this study is to provide a manufacturing method for obtaining an excellent directional electromagnetic plate.

(Means for Solving the Problems) The gist of the present invention is that C: 0.025% by weight
~0. ．． 095%, Si:2.0~4.0%, Hn
: 0.08~0.45%1 S≦0°015%,
AN: 0.010 to 0.060%, N: 0
．． 0,005 to 0.045%, Cr: 0.07
~0.25% of one species or 211. Or Mo,
V, Nb, Sb, 5nTi, Te,
An electrical steel slab containing 1.5% or less of one or more types of B in total is heated to a temperature below 128Q'C to completely dissolve the nitride-forming elements, and then hot-rolled to form the necessary Depending on the case, annealing is performed twice or more times with an intermediate annealing.
cold rolled, decarburized annealed, coated with an annealing separator,
During final annealing, the temperature is increased to 500℃ or higher, l: 900'
A nitrogen compound gas with nitriding ability is introduced into the annealing atmosphere at a temperature below C and nitrided before secondary recrystallization to form (AN, 5i)N.
The patented method for producing a tropic electrical & i steel sheet is characterized by forming an inhibitor whose main composition is , and performing high-temperature finish annealing.

The present invention will be explained in detail below.

The present inventors applied low-temperature slab heating in which electromagnetic steel slabs are heated to a temperature of less than 1280'C to produce a directional electromagnetic grain plate with excellent magnetic properties and coating properties, and to produce it industrially and stably. I passed the test as soon as possible. As a result, inhibitor-forming elements such as AI, N, Mri, and S are not completely dissolved in the steel during the slab heating stage, and a nitrogen compound gas with nitriding ability is introduced into the annealing atmosphere during the temperature raising process of final annealing. As a result, it was found that an inhibitor whose main composition is (AI, Si)N, which has a strong inhibitory effect, is stably formed, and a grain-oriented electrical steel sheet with excellent magnetic properties can be obtained. In addition, since nitriding with nitrogen compound gas is performed on steel sheets with very high activity, the oxide layer containing Si02 formed on the steel sheet surface during decarburization annealing is only slightly reduced, and the oxidized layer containing SiO2 is It was found that □ remained sufficiently and the glass coating formed by final annealing was good.

The composition of the electromagnetic steel slab to which the present invention is applied is as follows.

If the C content decreases, secondary recrystallization becomes unstable, so the content should be 0.025% or more. On the other hand, if the content is too large, the decarburization annealing time will become long, so the content should be 0.095% or less.

St is a necessary component for reducing iron loss and forming an inhibitor, and is therefore contained in an amount of 2.0% or more.

On the other hand, if the content increases, cracks will occur frequently during cold rolling, so the content should be 4.0% or less.

Mn has the effect of preventing hot brittleness and improving the quality of the glass coating, and 0.08% or more is required to achieve this effect. On the other hand, when the content increases, the magnetic flux density deteriorates, so it is set to 0.45% or less. Furthermore, in the present invention, since the slab is heated at less than 1280"C, a compound with S, MnS, for example, is not completely solid-dissolved, and MnS is not used as an inhibitor, so that I-fllJ is as described above.

S tends to cause segregation and hinders the normal growth of secondary recrystallized grains, so it should be kept at 0.01.5% or less.

Al is necessary for stabilizing secondary recrystallization by combining with N or Si to form (A7,St.)N, and for this purpose, it is contained in an amount of 0.010% or more. On the other hand, since the slab heating temperature in the present invention is less than 1280°C, M is completely dissolved in solid solution, so if the AI content increases, inappropriate AIN will be formed at the hot rolling stage. 060% or less.

N is contained in an amount of 0.0030% or more in order to combine with the above-mentioned /V, Si, etc. and have a stabilizing effect on secondary recrystallization.

However, if its content increases, surface defects will occur, so the content should be 0.0130% or less.

Furthermore, if necessary, in addition to the above elements, one or two of P, Cr, or/and Mo, V, Nb, S
b.

Contains one or more of Sn i Ti, Te, and B.

In the case of low-temperature slab heating, P has the effect of increasing the magnetic flux density, and in order to achieve this effect, its content must be 0.0
0.05% or more is required. On the other hand, if the content increases, cold rollability deteriorates, so the content should be 0.045% or less.

Cr has the effect of increasing the magnetic properties by expanding the range of M amount that can obtain high magnetic flux density, and for this purpose 0.
0.7% or more is required. On the other hand, if the content increases, decarburization performance deteriorates, so the content is set to 0.25% or less.

Mo l V I Nb l Sb, Sn l T
i I Te , 8 is contained within 0.30% for each component in order to improve the magnetic properties, but as the total content increases, the magnetic flux density deteriorates, so the upper limit is 1.5%. shall be.

Electrical steel slabs are melted in a melting furnace such as a converter or an electric furnace, subjected to vacuum degassing treatment if necessary, and manufactured by continuous casting or ingot-blowing rolling.

The electromagnetic steel slab is heated prior to hot rolling, and the heating temperature is set to less than 1280°C to save energy. At this heating temperature, M in the electromagnetic steel slab is not completely dissolved in solid solution and becomes in an incomplete solid solution state.

Furthermore, MnS, which has a higher solid solution temperature, is 1. Naturally, it is an incomplete solid solution.

After the slab is heated, it is hot rolled, annealed if necessary, or cold rolled without annealing. Cold rolling is performed once or twice with intermediate annealing in between to obtain a predetermined final plate thickness, and then decarburization annealing is performed.

Decarburization annealing reduces C in the steel sheet and forms an oxide layer containing 5iOz on the surface of the steel sheet. Next, an annealing separator containing MgO as a main component is applied in the form of a slurry, dried and/or adhered to the steel plate by electrostatic coating.

Thereafter, it is wound up as a coil and subjected to final annealing.

By the way, when the slab was heated at less than 1280"C, A/,
Since Mr+, S, etc. are in incomplete solid solution, if left as is, the
There are no inhibitors such as fi, Si)N, and MnS. Therefore, in the final annealing, N
enters into aa aa and has an inhibitory effect (
A7. Si) N must be formed.

Conventional methods for nitriding steel include adding a nitrogen compound to the annealing separator and increasing the N partial pressure in the annealing atmosphere, but these methods do not allow the stable formation of the inhibitor. It's difficult.

Therefore, in the present invention, as a result of studying the mechanism of nitriding with a gas containing N and gas before the appearance of secondary recrystallization during final annealing,
The following findings were obtained. First, nitrogen and hydrogen gas are dissociated and adsorbed on the surface of the coil to synthesize ammonia as shown by N2+3L→2N113, and then the ammonia is re-decomposed on the surface of the steel sheet and absorbed into the steel sheet. As is known, the ammonia synthesis reaction occurs under an iron catalyst, and is difficult to occur under an iron oxide catalyst.

The decarburized plate has an oxidized surface and is coated with hydrated magnesia (Mg(OR)x) as an annealing separator, so the hydrated magnesia pyrolysis occurs at 400-500''C during the annealing process. (Mg(011)z-MgO10HzO)
In order to release moisture, the steel plate undergoes additional oxidation.

For the above reasons, the surface of the steel plate is oxidized, so N
In order to nitridate with a gas containing t, it is necessary to reduce the surface of the steel plate with a gas containing 1]2 at 600 to 800'C for a long time. In addition, when synthesizing N(1), a high concentration of NH3 cannot be obtained under pressure conditions around atmospheric pressure such as in an annealing atmosphere.On the other hand, since the amount of nitridation is proportional to the concentration of Nil, the produced NH3 is low. In this case, nitrogen, which is originally used as an inhibitor, may be depleted and secondary recrystallization may not occur sufficiently.Based on the above findings, when nitriding in the coil before secondary recrystallization in finish annealing, 500 to 900
Direct N11.℃ temperature range. When a gas containing N113 is introduced, N adsorbs and enters the steel sheet, and (AJ, Si) N is reliably formed in a short time.Moreover, by adjusting the concentration of N113, the amount of nitridation in the steel sheet can be freely controlled. I found out. As a result, it becomes possible to fully function the inhibitor whose main composition is (IV, Si)N, the occurrence of secondary recrystallization is sufficiently stabilized, and the magnetic flux density is high and iron A grain-oriented electrical steel sheet with a low grain size can be obtained. In addition, when Nil:l was introduced into the annealing atmosphere, the adhesion and appearance of the glass coating deteriorated. This is probably because there are fine vacancies in the oxide layer, and although SiO□ is adsorbed and penetrated into the steel, SiO□ is not destroyed.

In the present invention, for example, 200 to 10,000 ppm of NHY is introduced into an atmospheric gas containing as a main component rNz, )'I□ in the temperature range of 500 to 900° C. before secondary recrystallization. The reason for this is that when the introduction temperature is low, the decomposition of N1(i) is insufficient and no nitriding occurs, and when the temperature is higher than 500"C, the decomposed active N adsorbs into the steel, penetrates and diffuses, and (AJ ,
St) N is formed. This inhibitor formation is advantageous in that it is achieved reliably and in a short period of time. On the other hand, if the temperature of introduction exceeds 900°C, the inhibitor effect cannot be obtained, so the upper limit is set at 900'C. The amount of N1(3) introduced into the atmosphere is 200 to 100 as mentioned above.
00 ppm is sufficient and there is no specific need.

On the other hand, in final annealing, secondary recrystallization occurs at a temperature of, for example, 950 to 1050°C, and at the same time, a glass film is formed due to the reaction between the oxidized layer on the surface of the steel sheet and the annealing separator, resulting in an appearance with high magnetic flux density. It becomes possible to manufacture high-quality electrical steel sheets.

(Example) Next, examples of the present invention will be described.

Example-1 C: 0.05%, Si: 3.2%, MrzO, 12%,
S: 0.009%, acid soluble IV: 0.028%,
After heating a slab containing 0.005% N and the balance consisting of iron and unavoidable impurities to 1200°C, 2.3 m + a4
This hot-rolled sheet was subjected to hot-rolled sheet annealing at 1120'C for 3 minutes, and then cold-rolled to give a final sheet J'X of 0.3 m.

Next, after decarburizing annealing at 850°C for 3 minutes in an atmosphere consisting of a dew point of 60°C and Hz of 70%, water was added to the annealing separator,
The slurry was made into a slurry, coated with a roll coater, the temperature of the steel plate was raised to 150° C. in a drying oven, and the attached moisture was removed, followed by winding into a 2-il shape. Next, the coil was placed in a finish annealing furnace and annealed. In order to infiltrate N into the steel sheet and form an inhibitor (81.Si) N before secondary recrystallization, 11□, between 500 and 800"C,
500 ppm of N:13 was added to the gas containing N2. Thereafter, the temperature was increased without adding NH3, and finally annealing was performed at 1150° C. for 30 hours.

Example-2 C-, 0°07%, Si: 3.1%, Mn; i0%, S
;008%, acid soluble Af;,031%, N)0.006
0%, P: 0.02%, Cr: 0.08%,
120 slabs with the balance consisting of iron and unavoidable impurities
After heating to 0"C, hot rolling to 2.3 mm, 1120
After annealing the hot-rolled plate for 3 minutes at 850°C for 3 minutes, it was cold rolled to a final thickness of 0.3M.
After decarburizing annealing in an atmosphere consisting of 0"C3H770%, water was added to the annealing separator to form a slurry, and after coating with a coater, the steel plate temperature was raised to 150℃ in a drying oven. Removed adhering moisture.

The adhesion amount was 5 g/m''.Next, 10 g/m'' of Mg0O powder was electrostatically applied between the coil plates to give an average of 50-
A certain amount was secured. Next, the coil was charged into a secondary annealing furnace and annealed. Inhibitor (8J, 5
i) 650-85 to form N before secondary recrystallization
112. during the heating period at 0°C. N113 in gas containing N2
was added at 350 ppm. In the subsequent heating process, N1
Finally, annealing was performed at 1150'C for 30 hours without adding 1°.

Example-3 C: 0.06%, Si: 3.3%, MRI: 0
．． 11%, S: 0.007%, acid soluble/'J: 0.02
8%, N: 0.005B%, Cr: 0°08%,
A slab containing 0.04% Mo with the balance consisting of iron and unavoidable impurities was used as a raw material, and a pace fan was used for annealing to prevent the penetration of NIl and I gases between the coil plates. It was promoted and equalized at the same time. All other conditions were the same as in Example-2.

The magnetic properties and glass coating properties of the products obtained in Examples 1, 2, and 3 were investigated, and the results shown in Table 1 were obtained.

The comparative material was a steel plate with the same composition as used in Example 1, and was subjected to decarburization annealing in the same manner as in Example 1, and silicon nitride was added to MgO at 0%.
An annealing separator containing 8 parts by weight was applied and annealed in two passes.

Table-=1 Characteristics of grain-oriented electrical steel sheet (effects of the invention) As seen in the results of the examples of the present invention, according to the present invention, the grain-oriented electrical steel sheet has extremely high magnetic properties and a good glass coating. is obtained.

Note) 1. Adhesion: Diameter 2. Coating defects that do not peel off when bent at 180°: Spotted areas with a sparkling metallic luster in areas where there is no glass coating.

Claims (4)

[Claims] (1) C: 0.025-0.095%, Si: 2.0-4.0%, Mn: 0.08-0.45%, S: 0.015% or less, Al: 0 in weight% .010 to 0.060%, N: 0.0030 to 0.0130%, and the remainder is iron and inevitable impurities, heated to a temperature of less than 1280 ° C. and hot rolled,
Cold rolling once or twice or more with intermediate annealing in between, decarburizing annealing, applying an annealing separator, and finishing annealing with NH_
A grain-oriented electrical steel sheet with excellent magnetic properties and film properties, characterized by introducing 3 and performing final annealing to form an inhibitor mainly composed of (Al, Si)N by nitriding before secondary recrystallization. Production method. (2) C: 0.025-0.095%, Si: 2.0-4.0%, Mn: 0.08-0.45%, S: 0.015% or less, Al: 0 in weight% .010 to 0.060%, N; 0.0030 to 0.0130%, and further includes P; 0.005 to 0.045%, Cr
; An electrical steel slab containing 0.07 to 0.25% of one kind or two kinds, with the balance consisting of iron and unavoidable impurities.
Heating to a temperature below 80℃, hot rolling, cold rolling once or twice or more with intermediate annealing, decarburizing annealing, applying an annealing separator, and finishing annealing during the heating process. Introducing NH_3 into the annealing atmosphere at a temperature of 500°C or more and 900°C or less,
A method for producing a grain-oriented electrical steel sheet with excellent magnetic properties and coating properties, characterized by performing final annealing to form an inhibitor mainly composed of (Al, Si)N by nitriding before secondary recrystallization. (3) In weight%, C: 0.025-0.095%, Si: 2.0-4.0%, Mn: 0.08-0.45%, S: 0.015% or less, Al: 0 .010 to 0.060%, N; 0.0030 to 0.0130%, and further contains Mo, V, Nb, Sb, Sn, Ti,
An electrical steel slab containing one or more of Te and B in a total of 1.5% or less, with the balance consisting of iron and unavoidable impurities,
Heating to a temperature below 80℃, hot rolling, cold rolling once or twice or more with intermediate annealing, decarburizing annealing, applying an annealing separator, and finishing annealing during the heating process. Introducing NH_3 into the annealing atmosphere at a temperature of 500°C or more and 900°C or less,
A method for producing a grain-oriented electrical steel sheet with excellent magnetic properties and coating properties, characterized by performing nitriding and final annealing to form an inhibitor mainly composed of (Al, Si)N before secondary recrystallization. (4) In weight%, C: 0.025-0.095%, Si: 2.0-4.0%, Mn: 0.08-0.45%, S: 0.015% or less, Al: 0 .010 to 0.060%, N; 0.0030 to 0.0130%, and further includes P; 0.005 to 0.045%, Cr
; 0.07-0.25% of one or two types, Mo, V, N
A total of one or more of b, Sb, Sn, Ti, Te, and B
．． An electromagnetic steel slab containing 5% or less and the remainder consisting of iron and unavoidable impurities is heated to a temperature below 1280°C, hot rolled, and cold rolled once or twice or more with intermediate annealing in between. , decarburization annealing, applying an annealing separator, and finishing annealing.
NH_3 is introduced into the annealing atmosphere at a temperature of 500°C to 900°C during the heating process, and nitrided (Al,
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties and coating properties, the method comprising performing finish annealing to form an inhibitor whose main composition is Si)N.