JPH0629461B2 - Method for producing silicon steel sheet having good magnetic properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for producing a grain-oriented silicon steel sheet having a (110) <001> orientation as a main orientation.

<Prior Art> A technology for producing a grain-oriented silicon steel sheet from a continuously cast slab is known. Generally, when the continuous cast slab becomes thicker,
If it exceeds 80 mm, the solidification time at the time of casting becomes long, and the center segregation becomes large, and the inhibitor (MnS, MnSe
Others) are coarsely precipitated, which hinders the fine dispersion of the entire inhibitor and makes secondary recrystallization unstable. Furthermore, if the slab thickness is thick, the outer portion will be heated more than necessary if the inhibitor is completely dissolved into the vicinity of the center during heating before hot rolling, and the crystal grains will grow too much or the surface condition will deteriorate. There are also drawbacks.

By the way, a technique for improving the characteristics by slab-rolling a continuous cast slab of grain-oriented silicon steel is disclosed in Japanese Examined Patent Publication No. 50-37009 and Japanese Examined Patent Publication No. 53-9694.
mm continuous cast slab is slab-rolled at a temperature of 1250 to 1300 with a reduction rate of 30 to 70%. In addition, the thickness of 1
A 00-300 mm silicon steel slab is hot-rolled at a temperature of 750-1200 ° C with a reduction rate of 5-50%, and then reheated to 1260-1400 ° C for the final hot rolling.

However, in these conventional techniques, when the slabbing of the continuous cast slab is performed under high pressure, the finishing slab thickness becomes thin, and it is not possible to secure an appropriate amount of reduction in rough rolling, and the structure is not sufficiently improved. On the contrary, there is a problem that the effect of slabbing is reduced. Further, even when the thickness of the continuous casting slab is small, there is a problem in that an appropriate amount of reduction ratio in rough rolling cannot be secured, the structure improvement in rough rolling is insufficient, and the characteristics deteriorate. On the other hand, when the slab thickness is large, even if slabbing is performed, a suitable reduction ratio in rough rolling can be secured, but there are drawbacks such as central segregation as described above, and deterioration of properties cannot be avoided. It was

<Problems to be Solved by the Invention> The present invention uses a continuous casting slab as a raw material of grain-oriented silicon steel sheet to complete solid solution of an inhibitor and to secure an appropriate amount of reduction in rough rolling to obtain magnetic properties. A method for manufacturing a grain-oriented silicon steel sheet is proposed.

<Means for Solving Problems> In the present invention, steel containing C: 0.01 to 0.08% and Si: 2.0 to 4.0% is formed into a slab by continuous casting, the slab is formed into a hot rolled sheet by hot rolling, and then 1 2 times or intermediate annealing
Manufactured grain oriented silicon steel sheet with (110) <001> orientation as the main orientation consisting of a series of steps in which cold rolling is performed once to obtain the final thickness, and then decarburization annealing and subsequent high temperature final finishing annealing are performed. In the method, a slab having a thickness of 180 to 280 mm is continuously cast, the slab is heated to a temperature range of 1000 to 1250 ° C., rolling is performed to increase the thickness by 5% or more, and then the slab surface temperature is increased by induction heating. Heating to a temperature range of 1350 to 1500, holding in the temperature range for 1 to 60 minutes, and subsequently hot rolling, or continuously casting a slab having a thickness of 180 to 280 mm, and then an induction slab of 1000 to 1250 ° C. The temperature is increased to 5% or more and rolling is performed to increase the thickness, and then slab rolling is performed to reduce the slab thickness to 200 mm.
After the above, slab surface temperature of 1350 ~ by induction heating
Heating to a temperature range of 1500, holding in that temperature range for 1 to 60 minutes, and subsequently hot rolling, or thickness 180 to 280
mm slab is continuously cast, then the slab is heated to a temperature range of 1350 to 1500 by induction heating and held at the temperature range for 1 to 60 minutes, and then rolled to increase the thickness by 5% or more. Is carried out, and then hot rolling is carried out, which is a method for producing a grain-oriented silicon steel sheet having good magnetic properties.

<Operation> The inventors performed the following experiment. That is, several continuous cast slabs with thicknesses between 180 and 300 mm were made, and each was heated to 1150 ° C in a gas heating furnace, then placed in an induction heating furnace and heated to 1400 ° C and held for 10 minutes before hot working. 30 in rough rolling
After making a sheet bar having a thickness of mm, finish rolling was performed to form a coil having a thickness of 2.0 mm and a product thickness of 0.23 mm was obtained by a normal two-time cold rolling method. The continuous cast slabs with thicknesses of 280 mm and 250 mm were first heated to 1050 ° C and slab-rolled at different rolling reductions, and then heated similarly to hot rough rolling, finish rolling, and cold rolling to obtain product sheets.

The results of this experiment are shown in Fig. 1. Without slabbing, the iron loss of the product made from a slab with a thickness of 250 mm is minimal. When the slab thickness is thicker than 280 mm and 300 mm, the center segregation is large, and when the slab thickness is thin, especially when it is 180 mm, the iron loss is large because a sufficient rolling reduction cannot be secured in rough rolling. It is thought that it has become.

It can be said that the slab thickness of the original slab of 250 mm is slab-rolled, and the iron loss is always low compared to the one without slab-rolling of the same thickness, but the slab-rolling effect is improved, but slab-rolling is performed. No, about the same as the iron loss of a 250 mm thick slab, or 180
It is rather worse in the thin area of mm. It is considered that this is because it is not possible to secure a sufficient reduction ratio in rough rolling.

On the other hand, when the original slab thickness is 280 mm, the center segregation of the slab is large, so even if slabbing to 250 mm and 230 mm is performed, the iron loss is higher than that of the same thickness without slabbing. It was Those that have been slab-rolled to 180 mm,
After all, the rolling reduction in the rough rolling was reduced, and the characteristics were further deteriorated accordingly.

The knowledge obtained from the following experiments, that is, when the reduction rate at the time of slabbing is increased, and when the continuous casting slab thickness is thin,
Based on the fact that a sufficient reduction ratio in rough rolling cannot be secured and the effect of improving the magnetism by improving the structure is insufficient, and conversely when the continuous casting slab is thick, the communication segregation of the slab impairs the effect of improving the magnetism. It is an idea of the present invention.

Next, the reasons for limiting the constituent features of the present invention will be described.

If the C content exceeds 0.08, it cannot be completely removed by decarburization annealing and the magnetic properties are deteriorated. On the other hand, if the C content is less than 0.01, γ transformation does not occur and the structure improvement in hot rolling is insufficient.
Limited to the range of%.

If Si exceeds 4%, rolling is impossible and 2.0
%, The electric resistance is small and the iron loss is large.
Limited to 4.0%.

Furthermore, there are no particular restrictions on the other components contained in the present invention, and the elements necessary for producing a normal grain-oriented silicon steel sheet can be appropriately contained. For example, Mn, Se, Al, N, or S, Ni, Zn, Cu, Mo, Sb, Sn, etc., which are elements necessary for stably causing secondary recrystallization, can be contained alone or in combination.

The thickness of continuous cast slab is limited to 180-280mm. 280 mm
This is because if it exceeds the value, the center segregation of the continuous casting slab will be large and the magnetic properties will deteriorate, while if it is less than 180 mm, the productivity will be poor with the current continuous casting technology.

The temperature when heating these slabs before thickening and rolling
The reason for limiting the temperature to 1000 ° C to 1250 ° C is that the strain recovers dynamically at 1250 ° C or higher and sufficient microstructure improvement cannot be performed.
This is because if the temperature is less than 1000 ° C, thickening rolling and slab rolling cannot be performed.

In thickening rolling, if it is less than 5%, the amount of increase in thickness is small, so the amount of increase in rolling reduction in rough rolling is small and the effect of improving the magnetism is insufficient. Therefore, the increased thickness in thickening rolling must be 5% or more. . Rolling to increase the thickness is carried out by using a large rolling roll with a large reduction load attached in the lateral direction of the slab, by attaching pushers on both sides of the slab and thereby compressing in the width direction, or by using both. At that time, the number of passes, the direction of rolls and the direction of charging slabs are not particularly limited.

The finished thickness of the slabs subjected to slabbing is limited to 200 mm or more, but if it is less than 200 mm, the necessary reduction rate cannot be secured during rough rolling and the structure cannot be improved.

It is heated to 1350 ° C to 1500 ° C using an induction heating furnace and held at that temperature for 1 to 60 minutes.The reason for induction heating is that even if the slab thickness is large, the temperature can be rapidly raised to the inside, This is because the inhibitor can be completely solid-dissolved with almost no growth of crystal grains. Heating temperature from 1350 ℃
The reason for limiting the temperature to 1500 ° C is that if it exceeds 1500 ° C, the surface appearance of the product deteriorates, and if it is less than 1350 ° C, complete solid solution of inhibitors such as MnS and MnSe cannot be achieved. The lower limit of the heating and holding time is 1 minute, which is the minimum time required for the solid solution of the inhibitor, and the upper limit is 60 minutes, because the holding time is longer than this, coarsening of the crystal grains of the slab occurs.

In order to reduce the heating energy cost, the slab is heated in advance in a gas combustion type heating furnace to, for example, about 1250 ° C. or less, and then induction heating is performed in the induction heating furnace in the range of 1350 to 1500 ° C. It does not impair the effect.

The process after hot rolling for the slab heat-treated under the conditions of the present invention is not different from usual, and is one cold rolling or two cold rolling including intermediate annealing, decarburization annealing and subsequent high temperature box annealing. Thus, a grain-oriented silicon steel sheet having a final product thickness can be manufactured.

<Example> Example 1-1 C: 0.04%, Si: 3.4%, Mn: 0.072%, Se: 0.021
%, Sb: 0.026%, Mo: 0.01%, 11 slabs with a thickness of 200 mm were manufactured. Subsequently, heating was performed under the conditions shown in Table 1, and then rolling for thickening was performed. Then 1, 2, 4, 5,
7, 8, 9, 10, and 11 were heated using an induction heating furnace. Three
Was heated to 1100 ° C in a gas combustion type heating furnace and then heated using an induction heating furnace. 6 uses a gas combustion type heating furnace 1350
After heating to ℃, it was held for 60 minutes. In all of Nos. 1 to 11, after rough rolling, a 30 mm sheet bar was used and finish rolling was performed to obtain a 2.0 mm thick hot rolled coil. And the primary cold rolling is 0.60mm thick and 1000
Intermediate annealing was performed at 4 ° C for 4 minutes, and the product was 0.23 mm thick by secondary cold rolling. Then, decarburization annealing at 800 ° C for 4 minutes was performed in wet hydrogen, and MgO was applied to perform secondary recrystallization annealing at 850 ° C in N _2.
Finishing annealing consisting of purification annealing in H ₂ casting was performed. The electromagnetic characteristics of the final product thus obtained are shown in Table 1.

By increasing the thickness according to the present invention, the magnetic characteristics are improved. In No. 4, the amount of thickness increase is as small as 2.5%, and in No. 5, the thickness is not increased, so the magnetic properties are not improved. 6
Since a gas combustion type heating furnace was used, the soaking after thickening was insufficient and the magnetic properties deteriorated. In No. 7, the heating temperature before the rolling for thickening is as high as 1300 ° C. and the crystal grains of the slab grow, so that the magnetic characteristics are not improved. In No. 8, the soaking time was too short as 30 seconds and the solid solution of the inhibitor was insufficient, and in No. 9 it was too long as 75 minutes and the slab crystal grains grew too much, so that the magnetic properties deteriorate. In No. 10, the soaking temperature was too high at 1510 ° C, and crystal grains of the slab grew too much, resulting in poor magnetic properties and poor surface appearance. No. 11 has a low soaking temperature of 1300 ° C and the solid solution of the inhibitor is insufficient, resulting in poor magnetic properties.

Next, the slab containing the components shown in Table 2
The magnetic characteristics of the product manufactured under the same conditions as the symbol 2 in the table are shown.

Even with the above components, good magnetic properties could be obtained by the manufacturing method of the present invention.

Example 1-2 C: 0.06%, Si: 3.1%, Mn: 0.066%, Se: 0.019
%, Al: 0.025%, N: 0.0085%, three 200 mm thick slabs were manufactured. Then, it was heated up to 1100 ° C. and rolled for thickening. Table 3 shows the thickness after thickness setting.

Then, put it in an induction heating furnace and heat it to 1400 ℃,
Hold for minutes. After that, rough rolling was performed to make a 30 mm thick sheet bar, and finish rolling was performed to obtain a 2.0 mm thick hot rolled coil. Then, the hot rolled sheet was annealed at 1100 ° C for 3 minutes and then cold rolled to 0.30.
mmO, and decarburization annealing at 800 ℃ for 4 minutes in wet hydrogen.
After coating, secondary recrystallization annealing at 850 ℃ in N ₂ and H ₂
Finishing annealing consisting of refining annealing at 1200 ° C was performed. The electromagnetic characteristics of the final product thus obtained are shown in Table 3 The effect of thickening and rolling is also exhibited in the case of the cold rolling once method.

Example 1-3 C: 0.06%, Si: 3.0%, Mn: 0.068%, S: 0.018
%, Al: 0.028%, N: 0.0010%, and four 200 mm thick slabs were manufactured. Then, it was heated up to 1100 ° C. and rolled for thickening. Table 4 shows the thickness after thickness setting.

Then, put it in an induction heating furnace and heat it to 1400 ℃,
Hold for minutes. After that, it was roughly rolled into a 30 mm thick sheet bar, and then finish rolled to obtain a 2.4 mm thick hot rolled coil. Then, primary cold rolling was performed to a thickness of 1.80 mm, and intermediate annealing was performed at 1100 ° C. for 3 minutes, and secondary cold rolling was performed to a product thickness of 0.23 mm. Then 8
Decarburization annealing was performed at 00 ° C for 4 minutes in wet hydrogen, MgO was applied, and then finish annealing was performed at 1200 ° C for 10 hours in hydrogen. The electromagnetic characteristics of the final product thus obtained are shown in Table 4. As in the case of Example 1, the thicker the slab after being thickened and the higher the reduction ratio in rough rolling, the better the magnetic properties.

Next, the magnetic properties of the products produced under the same conditions as the symbol 2 in Table 4 are shown for the components shown in Table 5.

Even with the above components, good magnetic properties could be obtained by the manufacturing method of the present invention.

Example 2 C: 0.04%, Si: 3.2%, Mn: 0.070%, Se: 0.020
%, Sb: 0.024%, Mo: 0.01%, 6 continuous cast slabs were manufactured. Then, it was heated to 1100 ° C., thickened, and then slab-rolled. Their pass schedule is 6th
It is as shown in the table.

Subsequently, 1, 2, 4, and 5 were heated to 1400 ° C. in an induction heating furnace and kept at that temperature for 10 minutes. In No. 3, a gas combustion type heating furnace was used to heat to 1100 ° C., and then an induction heating furnace was heated to 1400 ° C. and the temperature was maintained for 10 minutes. No. 6 was heated to 1350 ° C. using a gas combustion type heating furnace, and then held at that temperature for 60 minutes. After that, 1 to 6 were roughly rolled into a 30 mm sheet bar and then finish rolled into a 2.0 mm hot rolled coil. Then, primary cold rolling was performed to a thickness of 0.60 mm and intermediate annealing was performed at 1000 ° C for 4 minutes Secondary cold-rolled to 0.23mm product. Then coated with MgO conducted in wet hydrogen decarburization annealing at 800 ° C. 4 minutes in N ₂
A finishing annealing consisting of a secondary recrystallization annealing of 850 and a purification annealing in H ₂ was performed. The electromagnetic characteristics of the final product thus obtained are shown in Table 6.

In Comparative Example 5, the slab thickness is reduced to 180 mm by slabbing, so the rolling reduction in rough rolling is low and the characteristics are poor.

Example 3 C: 0.04%, Si: 3.4%, Mn: 0.070%, Se: 0.020
%, Sb: 0.026%, Mo: 0.01%, four 200 mm thick continuous cast slabs were manufactured. Next, 1 and 3 are induction heating furnaces.
It was heated to 1400 ° C and held at that temperature for 10 minutes. In No. 2, a gas combustion type heating furnace was used to heat to 1100 ° C., and then an induction heating furnace was heated to 1400 ° C., and the temperature was maintained for 10 minutes. In No. 4, a gas combustion type heating furnace was used to heat to 1350 ° C. and then held at that temperature for 60 minutes. After that, thickening rolling is continued and rough rolling is performed to a 30 mm sheet bar, and then finishing pressure is applied. It was rolled into a hot rolled coil with a thickness of 2.0 mm. Then, primary cold rolling was performed to a thickness of 0.60 mm, and intermediate annealing was performed at 1000 ° C. for 4 minutes, and secondary cold rolling was performed to a product having a thickness of 0.23 mm. Then, decarburization annealing at 800 ° C for 4 minutes is performed in wet hydrogen, and MgO is applied to the substrate for 8 minutes in N _2.
Finishing annealing consisting of secondary recrystallization annealing at 50 ° C and purification annealing in H ₂ was performed. The electromagnetic characteristics of the final product thus obtained are shown in Table 7. The magnetic properties are improved by increasing the rolling reduction in rough rolling by performing thickening rolling.

<Effects of the Invention> As described in detail above, according to the present invention, the continuous casting slab thickness is increased by performing thickening rolling before or after high temperature heating of the slab, and performing high temperature heating of the slab by induction heating. Without doing so, the rolling reduction during slab rolling and rough rolling was increased, the effect of improving the structure was enhanced, and a grain-oriented silicon steel sheet with good magnetic properties could be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of the thickness of the continuous casting slab before hot rolling and the thickness of the slab before hot rolling on iron loss when the thickness of the continuous casting slab is reduced by slabbing.

Claims (3)

[Claims] 1. A steel containing C: 0.01 to 0.08% and Si: 2.0 to 4.0% is formed into a slab by continuous casting, and the slab is hot-rolled to form a hot-rolled sheet, which is then annealed once or 2 Manufactured grain oriented silicon steel sheet with (110) <001> orientation as the main orientation consisting of a series of steps in which cold rolling is performed once to obtain the final thickness, and then decarburization annealing and subsequent high temperature final finishing annealing are performed. In the method, a slab having a thickness of 180 to 280 mm is continuously cast, then the slab is heated to a temperature range of 1000 to 1250 ° C., and rolling is performed to increase the thickness by 5% or more,
Then, the slab surface temperature is heated to a temperature range of 1350 to 1500 ° C. by induction heating, held in the temperature range for 1 to 60 minutes, and continuously hot-rolled. Production method. 2. A steel containing C: 0.01 to 0.08% and Si: 2.0 to 4.0% is formed into a slab by continuous casting, the slab is hot-rolled into a hot-rolled sheet, which is then annealed once or 2 Manufactured grain oriented silicon steel sheet with (110) <001> orientation as the main orientation consisting of a series of steps in which cold rolling is performed once to obtain the final thickness, and then decarburization annealing and subsequent high temperature final finishing annealing are performed. In the method, a slab having a thickness of 180 to 280 mm is continuously cast, then the slab is heated to a temperature range of 1000 to 1250 ° C., and rolling is performed to increase the thickness by 5% or more,
Then, slab rolling is performed to reduce the slab thickness to reduce the thickness to 2
After making it over 00 mm, the slab surface temperature becomes 13 by induction heating.
A method for producing a grain-oriented silicon steel sheet having good magnetic properties, which comprises heating to a temperature range of 50 to 1500 ° C., maintaining the temperature range for 1 to 60 minutes, and then hot rolling. 3. A steel containing C: 0.01 to 0.08% and Si: 2.0 to 4.0% is formed into a slab by continuous casting, the slab is hot-rolled into a hot-rolled sheet, which is then annealed once or 2 Manufactured grain oriented silicon steel sheet with (110) <001> orientation as the main orientation consisting of a series of steps in which cold rolling is performed once to obtain the final thickness, and then decarburization annealing and subsequent high temperature final finishing annealing are performed. In the method, the slab having a thickness of 180 to 280 mm is continuously cast, and then the slab is heated to a temperature range of 1350 to 1500 ° C. by induction heating, and the temperature is maintained for 1 to 60 minutes in the temperature range. A method for producing a grain-oriented silicon steel sheet having good magnetic properties, which comprises rolling to increase the thickness by 5% or more and then hot rolling.