JPH04187721A - Production of grain-oriented silicon steel sheet having superior magnetic property - Google Patents

Abstract

PURPOSE:To obtain superior magnetic properties by controlling temp. rise rate and annealing atmosphere, respectively, at the time of applying final finish annealing to a cold rolled sheet of grain-oriented silicon steel containing Al and Se. CONSTITUTION:A hot rolled plate of a grain-oriented silicon steel where Al and Se are incorporated as inhibitor forming elements for superiorly exerting secondary recrystallization is cold-rolled by the conventional method, and, at the time of final finish annealing, temp. rise rate is regulated to >=20 deg.C/hr until an arbitrary prescribed temp. between 700 and 875 deg.C is reached. Subsequently, temp. rise rate is regulated to 5 deg.C/hr to <15 deg.C/hr from the above prescribed temp. until a temp. in the region of 1100-1300 deg.C is reached, and further, the partial pressure of N2 in an H2, N2 annealing atmosphere in the course of temp. rise 15 regulated to >=80% until an arbitrary temp. between 700 and 875 deg.C is reached and also to >=50% from the above temp. until an arbitrary temp. between 920 and 980 deg.C is reached. Then, annealing is performed while further regulating the partial pressure of N2 to <=50% from the arbitrary temp. between 920 and 980 deg.C until a temp. in the region of 1100-1300 deg.C is reached.

Description

[Detailed Description of the Invention] Industrial Application Fields The present invention relates to a method for producing grain-oriented silicon steel sheets with good magnetic properties, and in particular, to further improve the magnetic properties by adding innovation to the final annealing process. It was planned.

<Conventional technology> Grain-oriented silicon steel sheets are soft magnetic materials that are mainly used as iron core materials for transformers and other electrical equipment. A magnetic flux density is required.

In order to obtain a grain-oriented silicon steel sheet with excellent magnetic properties, secondary recrystallization must be completely performed in the final annealing process (110).
It is necessary to preferentially grow the (001) orientation. In order to stably perform secondary recrystallization, MnS, MnSe, and IP! which suppress the growth of primary recrystallized grains are required. A primary recrystallized grain growth inhibitor such as N is required.

Therefore, in order to perform secondary recrystallization well in final annealing, it is necessary to allow the inhibitor to function normally at the temperature at which secondary recrystallization occurs and to suppress the growth of crystal grains other than Goss-oriented grains. To achieve this, it is necessary to maintain fine dispersion of the inhibitor. In conventional finish annealing, inhibitors grow during temperature rise and prevent loss of inhibitory effect8.
Japanese Patent Laid-Open No. 134917 discloses a method in which the heating time to a temperature range of 00 to 1150°C is 35 hours or less.
Alternatively, the temperature range from 700 to 900"c is averaged 15 to 1
A method of rapidly heating at 00°C/hr and removing heat at 2-10°C/hr from an arbitrary temperature between 900 to 1000°C to a temperature at which at least 50% of secondary recrystallization progresses is disclosed in JP-A No. 5.
This method is proposed in Japanese Patent No. 4-40227.

However, when these methods are used to actually manufacture Q-shaped magnets, the problem is that the magnetic properties are unstable and deteriorate due to the influence of the process conditions before the final annealing and the delicate process conditions during the final annealing. It has been difficult to stably obtain products with high magnetic flux density.

In view of this situation, the present inventors proposed a method for imparting an extremely high magnetic flux density by devising the heating rate of final annealing to fully demonstrate the function of the inhibitor contained in the patent application No. 1999. - Proposed in No. 148313.

However, grain-oriented silicon steel sheets containing AffiN as the main inhibitor have a problem in that stable magnetic properties are difficult to obtain due to the subtle influence of the annealing atmosphere.

That is, since AffiN decomposes or becomes coarse due to the influence of the final annealing atmosphere, it is important to control the atmosphere, particularly the N2 partial pressure. For example, JP-A-52-786
No. 15 discloses a nitrogen content of 20 to 70 νo1. % nitrogen-hydrogen atmosphere at 700-1000°C, then recrystallization at 1000-1200°C in a hydrogen atmosphere.
Denitrification treatment is performed by heating and soaking at a temperature of 2 hours or more.
In addition, Japanese Patent Application Laid-Open No. 55-47324 discloses that 850
N2 in an annealing atmosphere at any temperature up to ~950”C
A method in which the partial pressure is set to 20% or less and the N2 partial pressure is set to 3% or more in the temperature range from the start to the end of secondary recrystallization is
Furthermore, Japanese Patent Application Laid-Open No. 185726/1983 discloses a method using a mixed atmosphere of lh and Ar as the final annealing atmosphere gas.

<Problems to be Solved by the Invention> In these conventional techniques, the main focus is on controlling the final annealing atmosphere to maintain an appropriate dispersion of AIN at the start of secondary recrystallization. However, it is difficult to control the dispersion state of u2N only by the annealing atmosphere, and it varies greatly depending on the material components, hot rolling conditions, and annealing conditions. Therefore,
Conventional atmosphere control alone was insufficient to achieve sufficient improvement in magnetic properties.

Therefore, it is an object of the present invention to provide a method for manufacturing grain-oriented silicon steel sheets that suppresses fluctuations in magnetic properties caused by instability of the initial dispersed state of AlN as much as possible and obtains good magnetic properties. It is.

<Means for Solving the Problems> The present invention provides a method of hot rolling a grain-oriented silicon steel slab, subjecting it to cold rolling once or twice or more including intermediate annealing to obtain the final plate thickness, and then decarburizing the slab. In the method for producing a grain-oriented silicon steel sheet, which comprises a series of steps of applying an annealing separator and final annealing, the hot-rolled sheet contains Al and Se as inhibitor constituent elements, and during the final annealing. 2 to increase the heating rate to any predetermined temperature between 700 and 875°C.
0°C/hr or higher, and then 1100°C from the predetermined temperature.
5℃/hr or more 15℃/in the temperature range from ℃ to 1300℃
hr, and during heating up to 11 □, the N2 partial pressure in the N2 annealing atmosphere to any temperature between 700 and 875"C is 8
0% or more, then 50% or more from that temperature to any temperature between 920 to 980°C, then 50% or less from the arbitrary temperature between 920 to 980°C to a temperature range of 1100 to 1300°C. This is a patented manufacturing method characterized by the following: Desirably, the temperature can be maintained at a temperature of 700 to 840°C during final annealing for 20 hours or more.

<Function> In order to obtain an appropriate final annealing method for producing a grain-oriented silicon steel sheet containing HeP, the present inventors conducted the following experiments and obtained knowledge that led to the present invention.

The experimental results will be explained below.

Si as a material containing AP and Se: 3.23wt%
(Hereinafter, single % indicates) C: 0.069%, 5o
j2. Aff: 0.025%, N: 0.0
085%, Mn: 0.075%, Se:
A steel ingot containing 0.021% and the remainder substantially having a composition of Fe.Si: 3.19
%, C: 0.067%.

sol, AP, +0.026%, N: 0.00
88%, Mn: 0.076%, S: 0.
A steel ingot B having a composition of 0.022% and the remainder being essentially Fe was prepared. After heating these steel ingots to 1360°C, 2.
It was made into a hot-rolled plate with a thickness of 4 mm, and then cold-rolled in Step 1 to finish it with a thickness of 1.5 mm.

Then, after further intermediate annealing at 1075°C 12O seconds, it was cooled.
It was cold rolled to a thickness of 0.23 mm and decarburized annealed at 850°C. For final annealing, heat up to 800°C at a rate of 50°C/hr, then remove heat from 800°C at a rate of 10°C/hr and raise the temperature to 1200°C. The annealing atmosphere was set to N2.
112 in a mixed atmosphere from room temperature to 800℃
Divide into three categories: c to 950℃ and 950℃ to 1200℃, and change the partial pressure in 14□ as shown in Table 1.1
-2.

Table 1 does not show the magnetic properties of the obtained products. Steel ingot A containing An and Se had very good characteristics under the condition that the partial pressure of nitrogen in the atmosphere was reduced as the temperature rose. On the other hand, AP
Ingot B containing S and S had good characteristics under the condition that the nitrogen partial pressure in the atmosphere was increased as the temperature rose, but steel ingot A
This value was lower than the magnetic flux density value obtained in .

Based on these experimental facts, the present inventors determined that with a composition containing Aff and 5(!), during final annealing, the temperature range from 700 to 875°C was changed from heat to heat removal, and the nitrogen partial pressure in the final annealing atmosphere was We have newly discovered that products with high magnetic flux density can be obtained by increasing the magnetic flux density as the temperature rises.

In addition, the present inventors investigated the inhibitor composition in the decarburized annealed plates of steel ingots A and B.

As a result, A1. In the steel ingot A containing Se, many MnSe+ to NN composite precipitates were observed in the form of a MnSe precipitate as a core and An overlying it. On the other hand, in steel ingot B containing Af and S, MnS and A ff +1 often precipitate separately (the ratio of double autoprecipitates of MnS and Δl was extremely small. In this way, Ai and Se
Steel ingots A and AN contain S, and steel ingot B contains MnSe and M.
It was observed that there were differences not only in the type of precipitate called nS but also in the form of the precipitation.

As estimated by the inventors below, steel ingot A containing 4E and Se
The composite precipitate of MnSe and Ill in MnSe is AI! , H, it can be said to be more stable than the MnS and ArN precipitates in steel ingot B containing i and S. In the case of materials with MnS and AfN as inhibitors, there are many inhibitors of MnS alone, and in order to generate good orientation by secondary recrystallization, Japanese Patent Application Laid-Open No. 55-47
As described in the specification of the No. 324 publication, in the first half of the secondary recrystallization, N2 in the atmosphere is absorbed into the steel sheet and A1. It is desirable that the nitrogen partial pressure in the first half of annealing be low so that N does not become coarse and lose its ability to suppress grain growth.

In the experimental results of the present inventors, steel ingot B containing Ai and S
In this case, the lower the N2 partial pressure in the annealing atmosphere up to 950° C., which corresponds to the initial stage of secondary recrystallization, the higher the magnetic flux density becomes.

On the other hand, in the case of a steel ingot containing i and Se, the higher the N2 partial pressure in the annealing atmosphere up to 950°C, the higher the magnetic flux density. This is because the ratio of composite precipitates is high in MnSe and AIN, and the precipitates of AfN alone are small, so when the nitrogen force is exhausted in the early stage of secondary recrystallization, precipitates of AfN alone are newly formed. Although this often happens, it is difficult for the composite compound to become coarse.In fact, when the N2 partial pressure in the annealing atmosphere is lowered, the 80 decomposes, and the MnSe wrapped in AIN becomes exposed. This seems to have the negative effect of accelerating the growth of MnSe. The annealing atmosphere from 950°C, which is the latter stage of secondary recrystallization, is as described in JP-A-55-47.
According to the specification of Japanese Patent No. 324, it is necessary to use an atmosphere with a high N2 partial pressure to prevent coarsening of surface crystal grains.

On the other hand, in the case of steel ingots containing AN and Se, lowering the N2 partial pressure in the latter half of annealing increases the magnetic flux density, but this is because the composite compound of An and MnSe is stable and the N2 partial pressure is increased. If the temperature continues to rise, secondary recrystallization will occur at the center of the plate thickness, rather than near the surface layer where a good Goss orientation exists. Therefore, the N2 partial pressure in the latter stage of secondary recrystallization is kept low, and 80% and Mn
It is thought that the magnetic flux density will be higher if the decomposition of the Se complex is promoted and secondary recrystallized grains grow from the surface layer.

As explained in detail above, the present invention achieves an improvement in magnetic flux density by applying completely new knowledge of the precipitation form of an inhibitor in a steel ingot containing AA and Se to the setting of a final annealing atmosphere.

Further, the present invention will be explained in detail below.

In manufacturing the unidirectional itmi plate which is the object of the present invention, molten steel obtained by conventional steel manufacturing methods is cast by continuous casting method or ingot making method, and if necessary, a blooming step is performed. A slab is obtained by sandwiching the slab, followed by hot rolling and, if necessary, hot-rolled plate annealing, followed by cold rolling once or twice or more with intermediate annealing in between to obtain a cold-rolled plate of the final thickness. . If the final cold rolling reduction is less than 80%, the orientation of the secondary recrystallized grains is bad. If it exceeds 95%, secondary recrystallization is difficult;
More than 95% is preferred. Decarburization annealing is then performed in a conventional manner. The chemical composition of the hot rolled sheet is si: 2.5 to 4.
0%, C: 0.03-0.10%, m Soluble Af
:0.010~0.065%, N:0.0010
-0.0150%, gate n: 0.02-0.30%,
Se: 0.005 to 0.040% is preferably contained, and other elements known as inhibitor constituent elements include sb: 0.01 to 0.20%, Cu: 0
．． 02-0.20%, Sn: 0.02-0.30%
, Ge: 0.01-0.30%, Ni: 0
．． 02-0, 20% and Mo: 0.0I-0,05
% may be added singly or in combination. Si is 4.
If it exceeds 0%, cold rolling is difficult, and if it is less than 2.5%, the electric resistance is low and good iron loss cannot be obtained, so it is 2.5 to 4.
．． 0% is preferred. If C is less than 0.03, a good primary recrystallized structure cannot be obtained, and if it exceeds 0.10%, decarburization will be insufficient and the magnetic properties will deteriorate, so 0.03 to 0.10% is preferable.

Acid-soluble AI N is AI! , is the basic component forming N, and in order to obtain good magnetic properties, 8! is 0.010~
0.065%, N is 0.0010-0.0150% required.

If the amount exceeds this, All will become coarse and lose its effect as a suppressive force, and if it is less than this, it will be insufficient as an IN foot.

Mn and Se function by forming and inhibiting the binding bond MnSe, but if the Mn content exceeds 0.30% and the Se content exceeds 0.040%, the slab heating temperature required to dissolve MnSe is too high for practical use. 0.0 as Mn
If it is less than 2%, or less than 0.005% as Se, the amount of MnSe is insufficient to function as an inhibitor. Therefore, Mn is 0.02-0.30% and Se is 0.
．． The range of 0.005% to 0.040% is preferable.

Furthermore, it is possible to add Sb and Cu to improve the magnetic flux density. If Sb exceeds 0.20%, the decarburization property will deteriorate, and if it is less than 0.01%, there will be no effect, so 0.
．． If Cu exceeds 0.20%, the pickling properties will deteriorate, and if it is less than 0.01%, there will be no effect, so Cu is preferably 0 and O1 to 0.20%.

Sn, Ge, and Ni can be added to improve core loss. If Sn exceeds 0.30%, it becomes brittle, and if it is less than 0.01%, it is ineffective, so 0.01 to 0.3
0% is preferred. If Ge exceeds 0.30%, a good primary recrystallized structure cannot be obtained, and if it is less than 0.01%, there is no effect, so 0°O1 to 0.30% is preferable, and Ni is 0.2%.
If it exceeds 0%, the hot strength decreases, and if it is less than 0.01%, there is no effect, so 0.01 to 0.20% is preferable.

Mo can be added to improve surface properties. 0゜05
If it exceeds 0.0%, the decarburization property deteriorates, and if it is less than 0.01%, there is no effect, so 0.01 to 0.05% is preferable.

Note that S is an impurity that is unavoidably mixed in, and to completely reduce it would increase the cost, so the upper limit is set to o, oio%.

After decarburization annealing, an annealing separator containing MgO as a main component is applied and final annealing is performed.

At this time, it is effective to mix a known additive such as Tioz into the annealing separator.The feature of the present invention is this final annealing, but when performing the final annealing, the temperature is 700 to 875°C.
The temperature is raised at a rate of 20°C/hr or more to any predetermined temperature (Tsi) between 1,100 and 1,300°C, and then raised at a rate of 5°C/hr or more from the predetermined temperature (Tsi) to a temperature of 1,100 to 1,300°C.
It is to raise the temperature at a rate of ℃/hr that is suitable for pre-symptomatic patients. Tsi is 8
If Tsi exceeds 75°C, secondary recrystallization will be incomplete, and if Tsi is less than 700°C, the magnetic flux density will decrease even if secondary recrystallization is performed, so Tsi is set at 700 to 875°C. Furthermore, if the temperature increase rate up to Tsi is less than 20° C./hr, the magnetic flux density will decrease, so the temperature increase rate up to Tsi should be 20° C./hr or more.

The temperature increase rate from Tsi to 1100-1300℃ is 15
If the temperature exceeds ℃/hr, secondary recrystallization will be incomplete, and if the temperature exceeds 5℃
If it is less than /hr, the magnetic flux density will decrease even after secondary recrystallization, so it is set to be 5°C/hr or more and less than 15°C/hr.

Further, as a process for generating secondary recrystallized nuclei, the temperature can be maintained at 700 to 840° C. for 20 hours or more during heating up to Tsi. In this case, if the holding temperature is less than 700°C, there will be no nucleation effect, and if it exceeds 840°C, the inhibitor will deteriorate, so it is set at 700 to 840°C.

The final annealing atmosphere is a N2 atmosphere with a partial pressure of 80% or more from room temperature to any predetermined temperature between 700 and 875 degrees Celsius, and then from that temperature to any temperature (Tsc) between 920 and 980"C. N2 partial pressure of 50% or more, then 9
1100 to 13 from said any temperature between 20 and 840°C
N2 partial pressure up to 00℃ temperature range is 50% or less, 7
N2 partial pressure up to any temperature between 00 and 840℃ is 80%
If it is less than 80%, the composite precipitates of MnSe and An will decompose and the magnetic flux density will decrease, so it should be set to 80% or more. Also, if the N0 partial pressure from that temperature to any temperature (Tsc) between 920 and 980°C is less than 50%, it is still MnSe and 71! The decomposition of composite precipitates of N and N progresses too much and the magnetic flux density decreases, so it is set to 50% or more. Also 920~980℃
If the N2 partial pressure exceeds 50% from an arbitrary temperature (Tsc) between The following shall apply.

shall be.

It is well known that applying a coating that adds tension to a steel plate after final annealing reduces iron loss, but if the magnetic domain refining technology is applied to products manufactured according to the present invention, it will result in extremely high magnetic flux density and It is possible to obtain products with even lower iron loss.

<Example> Example I Si: 3.35wt%, C: 0.068gt
%, acid soluble A! : 0.022wt%, N: 0
．． 0098wt%, Mn: 0.071wt%.

Se: 0.020wt%, Sb: 0.028
Plate thickness 2.2 including wt% and the remainder being substantially Fe
After annealing a hot-rolled sheet of 1.m at 1000°C for 2 minutes and rapidly cooling it, 1.
Cold rolled to 80+m++ thickness, then quenched after intermediate annealing at 1100°C for 2 minutes, cold rolled to final thickness of 0.23m, then decarburized to 840"C for 2 minutes, followed by 10% TiO2 The added IgO was applied as an annealing separator, and final annealing was performed using the heat pattern shown in FIG. 1 and the conditions shown in Table 2.

Table 2 shows the magnetic flux density and iron loss of the product thus obtained.

Example 2 Si: 3.36wt%, C: 0.066wt%
, acid-soluble Af: 0.023 wt%, N: 0.
0095wt%, Mn: 0.071wt%.

Se: 0.020wt%, Sb: 0.025
wt%, Cu: 100% of a hot-rolled sheet with a thickness of 2.4 mm containing 0.09 wt% and the remainder being essentially Fe(7).
After annealing at 0°C for 2 minutes and quenching, cold rolling to a thickness of 1.50 mm, then intermediate annealing at 1075°C for 2 minutes, and then quenching.
Cold rolled to a final thickness of 0.230111 then 8
Decarburization annealing was performed at 40°C for 2 minutes, and then TiO□ was added to
MgO containing 3% of 0% and 5rSO was applied as an annealing separator, and final annealing was performed under the conditions shown in Table 3 using the heat pattern shown in FIG.

The magnetic flux density of the product thus obtained.

Iron loss is shown in Table 3.

Example 3 A steel containing the components shown in Table 4 with the remainder essentially having a composition of Fe was treated in the same steps as in Example 1 up to the MgOl cloth step.
The annealing was performed at a heating rate of 12° (/hr) from 850°C at a rate of 12° (/hr. The atmosphere during final annealing was performed with the composition shown in Figure 3. Iron loss is realized.

<Effects of the Invention> As in the present invention, in the manufacturing process of grain-oriented silicon steel sheets, the heating rate and annealing atmosphere of the final finish annealing are adjusted so that the function of the inhibitor contained in the grain-oriented silicon steel sheet is controlled. We were able to obtain magnetic properties.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the heat pattern of finish annealing of Example 1, FIG. 2 is of Example 2, and FIG. 3 is of Example 3. Patent applicant: Kawasaki Steel Corporation Figure 1 Figure 2

Claims (1)

[Claims] 1. After hot rolling a grain-oriented silicon steel slab, it is cold rolled once or twice or more including intermediate annealing to obtain the final thickness;
In a method for producing a grain-oriented silicon steel sheet, which comprises a series of steps of decarburizing annealing, applying an annealing separator, and final annealing, the hot rolled sheet contains Al and Se as inhibitor constituent elements, and the final The temperature increase rate during final annealing is 20℃/20℃ to any predetermined temperature between 700 and 875℃.
hr or more, and then from the predetermined temperature to 1100°C to 1
The temperature range up to 300°C is 5°C/hr or more and less than 15°C/hr, and N_2 in the H_2, N_2 annealing atmosphere during temperature increase.
2 Partial pressure up to any temperature between 700 and 875℃ is 80%
Above, next, from that temperature to an arbitrary temperature between 920 to 980°C is 50% or more, and then from the arbitrary temperature between 920 to 980°C to a temperature range of 1100°C to 1300°C is 50% or less. A method for producing a oriented silicon steel plate with good magnetic properties. 2. Claim 1, characterized in that the temperature is maintained in a temperature range of 700 to 840°C during final annealing for 20 hours or more.
A method for producing the described oriented silicon steel sheet with good magnetic properties.