JPH02200732A - Manufacture of grain-oriented silicon steel sheet having excellent magnetic properties - Google Patents

Abstract

PURPOSE:To improve the magnetic properties of the grain-oriented silicon steel sheet by reducing or removing an oxidizing layer on the surface of a silicon steel slab having specified C, Si, Mn, S, Al and N after subjected to decarburization annealing before finish annealing and executing short time nitriding in the state of a strip. CONSTITUTION:The silicon steel constituted of, by weight, 0.025 to 0.095% C, 2 to 4% Si, 0.08 to 0.45% Mn, <=0.015% S, 0.01 to 0.06% Al, 0.003 to 0.013% N and the balance Fe is refined. The slab of the silicon steel is hot-rolled at <1280 deg.C and is left as hot-rolled or is subjected to hot rolled sheet annealing. Then, cold rolling is executed for one time or >=2 times with interposed process annealing. Next, an oxidizing layer on the surface of the steel sheet is reduced or removed. After that, the strip is run and is subjected to nitriding treatment at 500 to 900 deg.C for <2 min. Then, the steel sheet is coated with an annealing and separation agent and is subjected to finish annealing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing grain-oriented electrical steel sheets with excellent magnetic properties.

(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 iron monomerity. It is also important to have a good coating.

Grain-oriented electrical steel sheets use the secondary recrystallization phenomenon to form (
It is obtained by developing crystal grains having a so-called Goss orientation, which has a (110) plane and a (001) axis in the rolling direction.

As is well known, this secondary recrystallization occurs during finish annealing, but in order to achieve the occurrence of secondary recrystallization within 11 minutes, 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 N, MnS, and MnSe, present.

For this purpose, the Tl magnetic steel slab is heated to a high temperature of about 1350 to 1400°C to completely dissolve the components forming the inhibitor, such as AZ + Mn + S4e, N, etc., and then hot-rolled. Annealing is performed to finely precipitate the inhibitor in the plate or in the intermediate stage before the final cold rolling.

By applying this kind of treatment, grain-oriented electrical steel sheets with high magnetic flux density can be manufactured, but as mentioned above, the heating of electrical steel slabs is carried out at high temperatures, so the amount of molten scale generated becomes large. ,, it 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 JP-A-5224116, in addition to AI, Zr, Tj, B, Nb+Ta, V,
Cr.

A manufacturing method is disclosed in which a nitride-forming element such as Mo is contained in the steel and the slab is heated at 1110 to 1260°C. In JP-A-59-190324, an electromagnetic steel slab with a low carbon content of 0.01% or less and selectively containing S, Se, and M and B is used as a material,
A manufacturing method is disclosed in which the slab heating temperature is reduced to 1 300 '' C or less by performing pulse annealing in which the surface of the steel sheet is repeatedly heated at high temperature for a short time during temporary recrystallization annealing after cold rolling. In Publication No. 5956522, M
n 0.08 to 0.45%, S ri. 007% or less, lower the (Mn) (S) product, and further M.

We have proposed a manufacturing method in which the slab heating temperature is 1280°C or less by using an electromagnetic steel slab containing P and N as the material.

(Problems to be Solved by the Invention) As described above, methods using low-temperature slab heating have been studied in the production of grain-oriented electrical steel sheets, and some effects have been achieved. It is difficult to form an effective inhibitor in a stable manner, so it is difficult to formulate an inhibitor with excellent magnetic properties for JI industry.

For stable production, further inspection δ・1 is required゛(′
There is J.

The present invention heats an electromagnetic fil slab to 1280'f:
As a low-grade product (lower than 7), it has the advantages of preventing the occurrence of molten sgale 1, preventing scratches, and reducing heating energy, while suppressing the appearance of gonium-order recrystallization before annealing. All the inhibitors on the steel plate (,,: Neta 4, C
Form 5. The first objective is to obtain a directional electromagnetic sheet with excellent magnetic stability.

(The problem is ``one piece for treachery 4'') The gist of the present invention is 11% by weight C; 0.025・-0.09
5% SiH2,O"・4.0% Mr+; 0.0B"0.4.5% S; 0.015% or more 1.Af: 0.010 to .060%.

N: 0.0030-0.0130%.

4 included, and depending on the heart j -ko, P+0.005-・0
404 scarcity)%.

Cy; 0.07-0.25% of one type or 21a, M
o, V, Nb, Sfi.

One or more types of SnHTl 1 Te'l B in total, 5
An electromagnetic material containing not less than 1% of f-1 and the remainder consisting of iron and iron (avoidable impurities) is heated to a temperature of less than 1280"C to form hot-rolled, as-hot-rolled or hot-rolled sheets. After annealing, cold rolling once or twice or more with intermediate annealing, and decarburizing annealing to reduce or remove the oxide layer on the copper plate Table 7rB,
Strike:・Pig running condition 1・500・~q
o o A patented excellent method for manufacturing grain-oriented electrical steel sheets characterized by nitriding for a short time of less than 2 minutes at a temperature of ``C:'', coating with an annealing separation layer, and annealing with ``-''. be.

The present invention will be explained in detail below.

The present inventors have applied low l1 slab heating, which heats an electrical steel slab to a temperature below 1280'C, to produce a grain-oriented electrical steel sheet with excellent magnetic properties of 1 to 17 with a stable property of 2. We considered manufacturing it. As a result, the slab heating stage}5.
Then, the components forming the inhibitor, for example, M I N
I M n +S etc. are completely dissolved in steel,
After decarburization annealing, the oxidized layer on the surface of the steel sheet is reduced or removed, and a state H in which the small string is made to run
If nitrided for a short time, it has a strong inhibitory effect (AI
, S i ) It has been found that an inhibitor mainly composed of N can be evenly formed on a steel sheet, and a grain-oriented electrical steel sheet with excellent magnetic properties can be obtained.

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 C content is set to 0.025% or more. On the other hand, if the content is too large, the decarburization annealing time will become longer, so the content should be 0.095% or less.

Si is a necessary component for the formation of inhibitors in iron mines, and for this reason, the higher the content, the higher the content, the more it is present during cold rolling. Since occurrence occurs frequently, the rate should be set at 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 of F is required to achieve this effect. On the other hand, if the content increases, the magnetic flux density deteriorates, so it is set at 0.45% or more. Furthermore, in the present invention, the slab is heated at a temperature lower than 1280"C, so that, for example, a compound with S, MnS, is completely dissolved in solid solution, and MnS as a 4" inhibitor.
Since s is not used, the first limit is as described above.

The S content should be 0.015% or less, as it may prevent the normal growth of secondary crystal grains.
.

Af is combined with A or Si (Af, Si) N
Form 2,! It is necessary for stabilizing the primary recrystallization, and for this purpose it is necessary to contain 0.010% or more. On the other hand, since the slab heating temperature in the present invention is less than 1280"C and Af is incompletely deposited and □' solid-cooled, when the Wit content of Af increases, an inappropriate ΔIN is formed at the hot rolling stage. Therefore, 0.060% or more is set as 1.

N is contained in an amount of 0.0030% or more in order to combine with the above-mentioned AI, St, etc. and exert a stabilizing effect on primary recrystallization.

However, when its content increases, the number of surface defects increases to 1.
0. . 0130% or more "■・Zuru.

In addition to the above elements, if necessary! ', 1 type 1t or 2 types of Cr or/and M+i, V, Nb
, Sb, Sn, Ti.

Te, Bf: 01 or more may be contained. At this time, P has the effect of increasing the magnetic flux density during heat combination after heating the low-temperature slab, and in order to achieve this effect, P must be 0.00
5% or more is required. - If its content increases, cold rollability deteriorates, so the content should be 0.045% or less.

Cr has the effect of increasing magnetic properties by expanding the range of IV amount at which high magnetic flux density can be obtained;
,07% or more is required. On the other hand, if the oil content increases, the decarburization performance deteriorates, so the content should be 0.25% or less.

Mo, Jb, Sb, Sn, Ti, Te, and B are each contained within 0.30% in order to improve magnetic properties, but the upper limit of their total is 1.5%.

Electromagnetic 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, the AN in the electromagnetic steel slab is not completely dissolved in solid solution and is in an incompletely dissolved state. Furthermore, MrS having a higher solid solution temperature is naturally 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 an intermediate annealing in between, and cold rolling is performed twice to obtain the final plate thickness.

However, in the present invention, the electrical steel slab is heated to a low temperature of less than 280°C.

Therefore, AZ, Mn, S, etc. in the steel are in an incomplete solid solution state, and if this continues, inhibitors such as (^I, 5i)N, MnS, etc. will be present in the steel sheet to cause secondary recrystallization. not exist. Therefore, - fJJ, which infiltrates N into the steel and functions as an inhibitor before the appearance of medical crystals;
5i) It is necessary to form N.

Nitriding of steel sheets is promoted in a dry atmosphere (low dew point gas).

Conventionally, steel sheets have been nitrided by coating them with an annealing separator containing a nitrogen compound, and in the form of a thin strip coil with a space factor of about 90%. In such a thin strip coil state, the gap between the plates is as narrow as 10 μm or less, resulting in very poor air permeability.

Therefore, not only does it take a long time to replace the atmosphere between the plates with a dry atmosphere, but it also takes a long time for N2 as a nitriding source to enter and diffuse between the plates. As a means of dispersing this, attempts have been made to nitride the mesh plate as a loose strip coil.
Although the non-uniformity of nitriding caused by the non-uniformity of the temperature inside the coil, which is a problem when nitriding a steel plate in the form of a strip coil, is reduced, it is still not enough.

In the past, the present invention had a strong inhibitory effect (AJ, 5t)N
In order to stably form the nitriding treatment after decarburization annealing, various studies were conducted. As a result, it was found that nitriding of a steel plate for the formation of (AJ, 5i)H largely depends on the surface properties of the steel plate. As a result of further investigation of this knowledge, when nitriding using a nitriding gas such as N111 gas,
N! After h is first dissociated and adsorbed on the steel sheet surface, active atomic N is trapped in the steel sheet, but Fe-3i, which has a thickness of about 100 to 200 atoms formed during the decarburization annealing process,
When system oxides exist on the surface of a copper plate, they act as a barrier to nitrogen intrusion, and by reducing them with a reducing gas containing UZ before nitriding or removing them by pickling, etc., nitriding can be done in an extremely short time. It has been found that (Δ/, 5i)N can be formed in a “ζ-like” shape throughout the steel sheet.

Figure 1 plots the relationship between the nitriding time and the amount of nitrogen in the steel in the nitriding process after reduction, using the reduction time as a parameter when the steel plate surface is reduced with a gas containing 11□ prior to the nitriding process. be. Note 1: The nitriding treatment is 650
The steel plate was passed in strip form at ~850°C.

From FIG. 1, it can be seen that by carrying out the reduction treatment for 10 seconds or more, nitriding of the steel sheet occurs in a short time. After that, an annealing separator was applied, and 1-annealing was performed at 1200°C, and the magnetic properties were measured. The results are shown in FIG. 3, and the magnetic flux density of the steel sheet in which the oxidized layer was reduced and nitrided for a short time after decarburization annealing was B. is high, iron loss Wl/811 is low, and magnetic properties are excellent. This is thought to be due to the formation of (^7,5i)N, which has a high inhibitor function, when reduced and nitrided for a short time. The composition of the steel slab used in the test is in weight%: C: 0.05%, Sl: 3.2%, M
n: 0.12%, S: 0.007%, 8N 80.03% N2 0.008%, the balance is iron and inevitable impurities, and the slab heating temperature is 1200
“It is C.

In addition, Figure 2 shows the nitriding time and the nitriding time in the nitriding process after the nitriding process, using a 10% hydrochloric acid solution to remove oxidized debris from one piece of steel after decarburization annealing, and using the treatment time at 7 pm as a parameter, prior to the nitriding process. This is a plot of the relationship with the amount of nitrogen in button 1. The nitriding treatment was carried out by passing the steel plate in strip form at a temperature of 750°C.

It can be seen that the pickling treatment causes nitriding to occur in a short period of time during subsequent strip running. Thereafter, an annealing separator was applied for 4 hours, and final annealing was performed at 1200° C., and the magnetic properties were measured. In this case too, the oxide layer is removed and the nitrided one is the magnetic flux density opening. , iron loss W+'? 150 was also excellent. This is considered to be because the inhibitor (AJ, 5i)N was stably formed.

Thus, prior to nitriding, the steel plate surface is reduced with a reducing gas containing, for example, II, or hydrochloric acid and sulfuric acid.

The nitriding time can be shortened by removing oxides on the surface of the steel sheet through pickling treatment with a dilute pickling solution such as nitric acid, phosphoric acid, or hydrofluoric acid.
) N can be formed stably.

The nitriding treatment is carried out in the shape B where the strip is run, but 5
．．・Inhibitor... - Short-time nitriding is necessary to form highly functional (8j, 5i)N, so! 500
°ζf'? in less than 2 minutes at a temperature of 900°C or less.
cormorant. At this time, a nitriding gas, preferably Nib, is added to a mixed atmosphere of N2 and N2 or (into an atmosphere of these alone).
It is desirable to supply an atmosphere of .about.00000 pui.

The reason why the temperature of the nitriding treatment is set as described above is that if the temperature is less than 500° C., it becomes difficult to nitridize in a short time, and the formation of (ΔZ, 5i)N becomes insufficient.

On the other hand, when this temperature becomes high, nitriding decreases in this case as well, and also affects the development of secondary recrystallization (AJ, 5N)N.
The F limit is set at 900″C because the formation of
5i) Since N is not formed, the time should be less than 2 minutes.

After that, 2. Apply an annealing separator, and perform 1. annealing.

There is no need for a specific annealing separator to be used, and a known one containing hO as a main component or one containing known additives such as Tie, B, etc. can be used. Further, the coating on the steel plate is performed by a known method such as electromagnetic electrostatic coating in the form of a slurry or in the form of a powder without forming a slurry. Regarding final annealing, 1. There is no need to specify the method.

According to the present invention, excellent magnetic properties can be obtained as described above, but even if the pretreatment described above is performed before the nitriding treatment, only the very surface layer of the coating formed by decarburization annealing is reduced. Alternatively, since a sufficient amount of silica exists even if it is simply removed, a good forsterite coating is formed on the surface of the steel sheet after final annealing.

(Example) Next, the present invention will be explained based on examples.

Example ~ 1 A slab having the composition shown in Table 1 was heated under conditions not specified in the same table, hot rolled to a thickness of 2.3 mm, and was used as a hot rolled sheet or hot rolled sheet annealed 2. As shown in the same table, the plate was cold rolled once or twice with intermediate annealing to give a plate thickness of 7.0.30 m. Then 850'CX 3 minutes, dew point 60
'Cθ month! The steel plate was decarburized and annealed in an atmosphere consisting of 270% carbon, and the oxidized layer was reduced by running the steel plate in a strip state under the conditions shown in the same table, and the nitriding treatment was performed.

Next, an annealing separator is applied to the steel plate in the form of a slurry,
It was dried, wound into a coil, and the coil was annealed to 7+-1=7. Measure the magnetic properties and film properties of the obtained grip,
The results are shown in Table 2.

(Note), Film adhesion iff 8180 degree bending h1 No shift Straight line 2, Film defect; y, ii Dots Sparkling in areas where dotted glass film is present and absent Metallic light translation Example-2 Ingredients shown in Table 3 A slab having the composition was heated under the conditions shown in Table C and hot rolled to a thickness of 2.3 ym.

As shown in the table, the hot-rolled sheet or hot-rolled sheet is annealed.
Cold rolled for 2 times or intermediate annealing 2.0.30
The plate thickness was mm. Then, at 850°C for 3 minutes, with a dew point of 6
Decarburization annealing was carried out in an atmosphere consisting of 11270% at 0°C, and the oxidized layer was removed by running the steel plate in a strip state under the conditions shown in the same table, followed by 4-nitriding treatment.

Next, the annealing separator is applied in slurry form to the steel plate 17
, dried 7, wound into a coil, annealed the coil thoroughly, and measured the magnetic properties and coating properties of the obtained steel plate,
The results are shown in Table 4.

(Shi) 1゜Coating adhesion 1 180 degree bending C No peeling Diameter 2 Coating defects: Speckled metallic luster that shines in areas where no glass coating exists (Effects of the invention) The present invention has conventionally been performed by finish annealing. By reducing and removing the oxidized layer on the surface of the steel sheet after decarburization annealing before final annealing, and nitriding the steel sheet for a short time in the strip state, grain-oriented electrical steel sheets with excellent magnetic properties can be produced. Obtained stably.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the nitriding time and the amount of nitrogen in rivet 1 in the nitriding process after reduction using a puff meter as the reduction time when the surface of the steel plate was reduced with gas C containing 11□ in 111■ prior to the nitriding process. Figure 2 shows the processing time in pan meters when the oxidized layer of the steel plate was removed after decarburization annealing with a 10% solution of hydrochloric acid prior to the nitriding treatment. Figure 3 shows the relationship between the nitriding time and the amount of nitrogen in the steel during the process.
FIG. 4 is a diagram illustrating the magnetic properties of grain-oriented electrical steel sheets obtained by strip nitriding (without oxide layer reduction treatment) process and strip nitridation (with oxide layer reduction treatment) process. Fig. 1 Fig. 3 P10 - H Mi + - - - - Z 0 1 2 y, 94 y, 96 spring B/ly
(T)

Claims (4)

[Claims] (1) C in weight%; 0.025-0.095%, Si;
2.0 to 4.0%, Mn; 0.08 to 0.45%, S; 0.015% or less Al; 0.010 to 0.060%, N; 0.0030 to 0.0130%, A magnetic steel slab containing iron and unavoidable impurities is heated to a temperature of less than 1280 ° C. and hot rolled,
The steel sheet is annealed as hot-rolled or hot-rolled, cold-rolled once or twice or more with intermediate annealing, decarburized annealed, and the oxidized layer on the surface of the steel sheet is reduced or removed, and then the strip is run. 1. A method for producing grain-oriented electrical steel sheets with excellent magnetic properties, which comprises nitriding for a short time of less than 2 minutes at a temperature of 500 to 900[deg.] C., applying an annealing separator, and final annealing. (2) C in weight%; 0.025-0.095%, Si;
2.0 to 4.0%, Mn; 0.08 to 0.45%, S; 0.015% or less Al; 0.010 to 0.060%, N; 0.0030 to 0.0130%, Contains, furthermore, P; 0.005 to 0.045%, Cr
; 1 electromagnetic steel slab containing 0.07 to 0.25% of one kind or two kinds, the balance being iron and unavoidable impurities;
Heating to a temperature below 200°C, hot rolling, annealing as hot rolled or hot rolled sheet, cold rolling once or twice or more with intermediate annealing, decarburizing annealing, oxidation of the surface of the steel sheet After reducing or removing the layer, the strip is run under conditions of 5
A method for producing a grain-oriented electrical steel sheet with excellent magnetic properties, which comprises nitriding for a short time of less than 2 minutes at a temperature of 00 to 900°C, applying an annealing separator, and final annealing. (3) C in weight%; 0.025-0.095%, Si;
2.0 to 4.0%, Mn; 0.08 to 0.45%, S; 0.015% or less Al; 0.010 to 0.060%, N; 0.0030 to 0.0130%, Contains, furthermore, 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 of less than 80°C, hot rolling, as hot rolling or hot rolled plate annealing, cold rolling once or twice or more with intermediate annealing, decarburization annealing, After reducing or removing the oxide layer, the strip is heated for 50 minutes under running conditions.
A method for producing grain-oriented electrical steel sheets with excellent magnetic properties, which comprises nitriding for a short time of less than 2 minutes at a temperature of 0 to 900°C, applying an annealing separator, and final annealing. (4) C in weight%; 0.025-0.095%, Si;
2.0 to 4.0%, Mn; 0.08 to 0.45%, S; 0.015% or less Al; 0.010 to 0.060%, N; 0.0030 to 0.0130%, Contains, furthermore, P; 0.005 to 0.045%, Cr
; 0.07 to 0.25% of one or two types, Mo, V,
An electrical steel slab containing a total of 1.5% or less of one or more of Nb, Sb, Sn, Ti, Te, and B, with the balance consisting of iron and unavoidable impurities, is heated to a temperature of less than 1280 ° C.
After hot rolling, as hot rolling or hot rolled plate annealing, cold rolling once or two or more times with intermediate annealing, decarburization annealing, and reducing or removing the oxidized layer on the steel plate surface. Production of a grain-oriented electrical steel sheet with excellent magnetic properties, characterized by nitriding for a short time of less than 2 minutes at a temperature of 500 to 900°C under the condition of running the strip, applying an annealing separator, and final annealing. Law.