JPS59190325A - Production of grain-oriented silicon steel plate having excellent iron loss for which continuous casting method is applied - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel plate having an excellent magnetic characteristic by subjecting a continuous casting slag for a grain-oriented silicon steel plate contg. a small amt. of S and an adequate amt. of Mn, P and Cr to hot rolling, continuous annealing for a short time, cold rolling and continuous decarburization annealing then to high temp. finish annealing under specific conditions. CONSTITUTION:A continuous casting slag for a grain-oriented silicon steel plate contg. 0.025-0.075% C, 3.0-4.5% Si and 0.010-0.060 SolAl, contg. S as little as <0.007% and contg. 0.08-0.45% Mn, 0.015-0.045% P and 0.07-0.25% Cr is heated to <=1,280 deg.C without cooling or to >=1,280 deg.C in the case of requiring a high magnetic flux density and is hot rolled to a plate material. The plate material is continuously annealed for a short time at 850-1,200 deg.C and is cold rolled under strong rolling down of >=80% draft to a final plate thickness. The plate material is subjected to continuous decarburization annealing in a wet hydrogen atmosphere and finally an annealing releasing agent is coated thereon and is heated at a heating rate of <=15 deg.C/hr between 700-1,100 deg.C, by which the high temp. finish annealing is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a unidirectional silicon-lead plate with excellent magnetic properties, in which crystal grains in a body-centered cubic lattice constituting a steel plate kFJ are oriented as (110)〈001〉 in terms of Miller index. The present invention relates to a manufacturing method using a hot rolled sheet (jN band) made by continuous casting and one hot rolling process.

Unidirectional silicon steel sheets are used as soft magnetic materials for the cores of transformers and generators, and must have good magnetic properties such as magnetization properties and iron loss properties.

The quality of the magnetization characteristics is determined by the magnitude of the magnetic flux density If (represented by B8) induced within the iron core by a constant applied magnetic field. Materials with high magnetic flux density are desirable because electrical equipment can be made smaller. Iron loss (represented by W1715o) is the power loss consumed as thermal energy when a predetermined alternating current magnetic field is applied to the iron core. It is known that the quality of iron loss is influenced by magnetic flux density, plate thickness, amount of impurities, resistivity, and crystal grain size. Recently, the demand for unidirectional silicon steel sheets with low iron loss has been increasing, reflecting the energy saving trend.

By the way, unidirectional silicon steel sheets are produced by finishing high-temperature annealing of furnace plates that have reached their final thickness through hot rolling and cold rolling.
It is obtained by so-called secondary recrystallization, in which primary recrystallized grains having a 0) <001) orientation selectively grow. In order to cause secondary recrystallization, fine precipitates such as MnS and ALN must be present in the copper plate before final high temperature annealing (inhibitor effect), and (110) during final high temperature annealing.
001) It is necessary to suppress primary recrystallized grain growth other than orientation. By controlling such secondary recrystallization, the magnetic flux density can be increased by increasing the proportion of grains with accurate (110) (001) orientation. Since products with high magnetic flux density can reduce the size of electrical equipment and improve core loss, it is important to establish manufacturing conditions for grain-oriented silicon steel sheets with high magnetic flux density. Representative techniques include methods described in Japanese Patent Publication No. 40-15644 by Satoru Taguchi et al. and Japanese Patent Publication No. 5]-13469 by Taku Imanaka et al. recent years,
The industrialization of the continuous gun method is progressing at a rapid pace, and even for unidirectional silicon steel sheets, it is possible to reduce manufacturing costs by saving labor and improving yields, and to achieve uniform magnetic properties in the longitudinal direction of the finished product by making the chemical composition uniform. The continuous casting process is being applied with the expectation that it will become more effective.

However, products obtained using a copper plate manufactured by hot rolling after heating a continuously cast slab to 1280°C or higher as a starting material often have linear secondary recrystallization imperfections and may have poor magnetic properties. there were. As these countermeasures, M, F,
Littman, in Japanese Patent Application Laid-Open No. 48-53919, proposes a technique for producing a hot-rolled sheet from a multi-continuously cast slab through seven hot rolling steps. Furthermore, Akira Sakakura and others
No. 370'09 proposes a technique for producing a hot-rolled plate through seven hot-rolling steps from a continuously cast slab during the production of a high magnetic flux density unidirectional silicon furnace plate. However, due to technical limitations, all of these prior art techniques produce hot-rolled sheets through seven hot-rolling processes, and cannot be said to be technologies that fully utilize the advantages of continuous casting. Later, as a manufacturing method using continuous casting slabs, Morio Shiozaki et al.
Publication No. 913, Japanese Patent Publication No. 54-120214 by Tsuyoshi Matsumoto et al.
The technology shown in the publication was proposed.

However, all of these technologies require new measures to be taken for equipment. Furthermore, even with these countermeasures, the occurrence of linear secondary recrystallization defects has not been completely solved. In other words, recently there has been an increasing demand for low core loss unidirectional silicon steel sheets for the purpose of high-quality craftsmanship.
In order to meet this demand, it is important to increase the magnetic flux density and increase the Si content. In particular, special public relations
Since the technology disclosed in Publication No. 44 is a one-time rolling method, the manufacturing cost is low and a unidirectional silicon steel sheet with a high magnetic flux density can be obtained. Therefore, if it becomes possible to increase the St, the iron loss can be greatly improved. However, when the Si content is increased, the occurrence of secondary recrystallization defects rapidly increases, and especially in the case of such a height of 81, the linear secondary recrystallization defects that occur when using a continuous casting slab further increase. Therefore, if the St content exceeds 30%, stable industrial production becomes extremely difficult. This is because, as stated in Japanese Unexamined Patent Publication No. 48-51852 by Akira Sakakura et al., increasing the Si content makes it difficult to secure AtN suitable for secondary recrystallization, especially in continuous casting slabs. It is thought that this is because the failure of secondary recrystallization due to this inappropriate fi AIH becomes more noticeable when using .

As described above, the biggest problem in producing high magnetic flux density unidirectional silicon steel sheets by the -rolling method is that secondary recrystallization becomes unstable as the S1 content increases.

The basic metallurgical idea of this method is to create an appropriate AIN state by utilizing the α→T transformation 1e during annealing.
It is thought that increasing the Si dramatically changes the α→γ transformation behavior, making it difficult to control it to an appropriate AIN state, and this corresponds to the fact that the higher the St, the more secondary recrystallization defects occur.

The inventors of the present invention have completely prevented the secondary recrystallization defects that occur when using continuous casting slabs, and in particular, have achieved high yielding by a single rolling method that completely reduces the secondary recrystallization defects that increase as the St content increases. We have developed a method for stably manufacturing silicon flanges with unidirectional magnetic flux density. What is even more revolutionary is that, according to this method, the slab heating temperature exceeds 1280°C prior to hot rolling, which has traditionally been considered essential in the production of unidirectional silicon-lead sheets. It has been discovered that heating is not necessarily necessary, and that even better core loss can be obtained by heating the slab at a lower temperature. In the method for producing a high magnetic flux density unidirectional silica plate based on Japanese Patent Publication No. 40-1564.4, MnS and AAN, which are precipitated dispersed phases necessary for the occurrence of secondary recrystallization, are used.
f Because of the need to achieve an appropriate dispersion state, the heating temperature of the slab during hot rolling has been varied. Especially in the 4th year of special public service
As in the method described in JP-A No. 48-51'852 by Akira Sakakura et al., which is an improvement of the method described in No. 0-15'644, when the Si content increases, A7N precipitation during hot rolling occurs at a high temperature. In order to start trenching from the ground, it is necessary to heat the slab to a high temperature.

For example, for 2.8 inch SL, 1250℃ or more, 3.05 inch S
At t, the temperature is 1350°C. In this way, 8
If the amount is increased by 1, it will be necessary to increase the slab heating temperature.
There have been problems with high manufacturing costs due to increased energy used when heating the slab, decreased yield due to the generation of slag during heating, and increased repair costs.

According to the present invention, even when Si is as high as 3.0 or more,
Secondary recrystallization is carried out in a sufficiently stable manner at a low slab heating temperature that does not exceed 1280°C.

In fact, the obtained iron loss is better than that of high-temperature slab heating materials, and its value is the current highest grade Japanese Industrial Standard (
, JIS) G6 H (0,30-thickness
1W17150 is 1.05 w/kg or less) or more.

As described above, according to the present invention, the highest grade high magnetic flux density unidirectional silicon steel sheet can be stably manufactured using a high St-containing continuously cast slab regardless of the high or low slab heating temperature during hot rolling. . That is, in the present invention, C: 0.025 to 0.0
75%, Si: 3.0-4.5%, acid-soluble At: 0.
010-0.06'O section, N: 0.0030-0.
0130%, S: 0.007% or less, Mn: 0.08
~0.45%, P: 0.015~0.045%, C
r: 007 to 0.25% A continuously cast slab for a unidirectional silicon flange plate consisting of the balance Fe and unavoidable impurities is heated without preliminary hot rolling, and then hot rolled to form a hot rolled plate; The hot-rolled sheet was then continuously annealed for a short period of time in the range of 850 to 1200°C, and then subjected to strong reduction cold rolling at a reduction rate of 80% or more to obtain the final thickness. The gist of this invention is a method for producing a unidirectional silicon-lead plate with excellent iron loss, which is characterized by continuous decarburization annealing, followed by coating with an annealing separator and final high-temperature annealing.

The present invention will be explained in detail below.

First, the reasons for limiting the number of ingredients used in the present invention will be described. The molten lead used in the present invention can be produced using a converter furnace, an electric furnace,
Any method such as open hearth may be used, but the component content must fall within the following range.

If C is less than 0.025%, secondary recrystallization becomes unstable, and even if secondary recrystallization occurs, the magnetic flux density is poor (only 1.80 T or less can be obtained with Blo), so 0.02
If it's more than 5%, it's not a woman. On the other hand, if C is too large, the decarburization annealing time will be long and it is not economical, so 0.0
It was set to 75% or less.

If St exceeds 4.5%, cracking during cold rolling becomes significant, so it was set to 4.5'fi or less. In addition, if it is less than 3.0%, the highest grade iron loss of W1715o of 1.05 WA9 or less cannot be obtained when the thickness of the oyster is 0.30 mm, so it is set to be 3.0% or more.

Desirably it is 32% or more.

In the present invention, AtN is used as a precipitate necessary for secondary recrystallization. Therefore, in order to secure the minimum necessary amount of AIN, acid-soluble At is 0.010% or more and N is 0.0%.
0.030% or more is required. Acid soluble AA is 0.060
If it exceeds 0.060%, the AIN of the hot rolled sheet will be inappropriate and the secondary recrystallization will become unstable. Regarding N, if Olo exceeds 130 qb, a "bulge on the surface of the steel plate" called Telister will occur (1,013 qb).
It was set to 0° or less.

One of the features of the present invention is to reduce the S content to 0.007 or less. When manufacturing a high magnetic flux density unidirectional silicon steel sheet by a single rolling method using AtN as an inhibitor, S is an essential element to obtain magnetism, as disclosed in Japanese Patent Publication No. 156.44/1983. be. Mata Tokko Sho 4
As shown in Japanese Patent No. 7-25250, S is necessary to form MnS, which is a precipitate effective in causing secondary recrystallization. In these known techniques, S is defined as being effective for secondary recrystallization.

However, it was not known that the inclusion of S was harmful to secondary recrystallization. The present inventors have discovered that when producing a high magnetic flux density unidirectional silicon copper plate by a single rolling method using AtN as an inhibitor, continuous casting slabs can be produced by reducing the S content to 0.007 or less. Linear secondary recrystallization defects that occur when used as a raw material and secondary recrystallization defects that occur when a high SL content slab is used as a prime phase (this occurs particularly when the slab heating temperature during hot rolling is low) However, we found that

Figure 1 shows C: 0.058%, 81: 3.35%, Mn
: 0.23, P: 0.036, acid-soluble At: 0.
03]%, N:O, (1085%, Cr:0.13%'
After heating to 11410°C, a continuous a &# J slab containing r and S of 0.002 to 0.033 is hot-rolled.
, 3 myn, was continuously annealed at 1150°C x 2ml, then cold rolled to a thickness of 0.30mm, decarburized at 850°C x 2ml in wet hydrogen, and the annealing separator was Mg0i? Cloth 12. Secondary rectification of diverticulate product obtained by finishing high-temperature annealing at 1200°C for 20 hours.
Indicates the incidence of defects. It can be seen that as the S content decreases, the occurrence of powdery secondary recrystallization defects decreases, and when the S content is less than 0.007, no defects occur at all.

121g is C: 0.050%, Si: 3.45
%, Mn: 0.25, P: 0.040, acid-soluble At: 0.027, N: 0.0080%, Cr
: Contains 0.1.8%, and S is 0.002~
Small specimen 40mm thick containing 0.035%-1120
The slab was heated to 0°C, then cooled to 1000°C in the air, kept in a 1000°C furnace for 30 sec, and then heated to 1000°C for 30 seconds.
It was hot-rolled to 2.3 m with A steel, continuously annealed at 1120°C x 2 m1n, further cold-rolled to 0.30 mm, film charcoal annealed at 850°C x 2 min in a wet hydrogen atmosphere, and sealed with a furnace needle 1 separating agent. - shows the incidence of secondary recrystallization failures of products subjected to finishing high-temperature annealing at 200° C. for 20 hours after coating with MgO. As can be seen from Fig. 2, secondary P crystal defects are most likely to occur in cases where the S content is 0.007% or less. S is 0007
If 3f is less in the range of φ or less, the secondary recrystallization is somewhat stabilized.Also, lowering S at the clear nail stage is desirable because it facilitates the 113.8 treatment during high-finish firing. In the current Melt 11 technology, the range in which S can be easily lowered without increasing the cost i is generally 0001 or more.

The second feature of the present invention lies in Mn and P. In the present invention, the fourth goal is to reduce the S content in the material, so there is no MnS and the magnetic flux density of the external product is poor. However, even in the case of such PS materials, the glue in the material,
The present inventors have found that the magnetic flux density can be improved by adjusting the in and P content to an appropriate amount.

Figure 3 shows C: 0,060chi, Si: 3.33%, S: 0
．． Section 004, acid-soluble At: 0.032%, N: 0.0
A continuously cast slab containing 090% Cr: 0.15qb was heated to 1350°C, then hot-rolled into a hot-rolled plate with a thickness of 2.3 mm, and after continuous annealing at 1150°C x 2m1n, it was cold-rolled. .30 m and 850 m in a wet hydrogen atmosphere.
℃×2mlnO decarburization annealing, M was used as an annealing separator
The effects of the Mn and P contents in the slab on the magnetic flux density (B, .) of the product obtained by applying gO and performing final high-temperature annealing at 1200° C. for 20 hours are shown.

When the amount of Mn decreases, secondary recrystallization becomes unstable, and when it increases, B10 increases, but there is no difference in the improvement effect even if it is added above a certain level, and the amount of added alloy is large. As for P, if the content is low, the B10 will be poor, while if the content is high, the frequency of cracking during cold rolling will increase, and the incidence of secondary recrystallization failure will increase. The above results indicate a range in which Blo is high, secondary recrystallization is stable, and there are few cracking problems.Mn: 0.08 to 0.45%, P
: The range of the present invention is 0.015 to 0.045. (In Figure 3, × is B, .<1.80, △ is 1.8
0≦B. (1, 89, ○ is],, 89≦B1o<
L 92.0 is 1. "92 <,,Blori193,■
is 1.93〈Blo. Unit Teala) M4 diagram is C: 0.045%, St: 3.35%, s20,
002'%, acid-soluble At: 0.028%, N: 0.0
A small specimen with a thickness of 4 o, containing 075%, cr:o, is%, was heated to 1150°C, and after slab extraction, it was hot-rolled in 3 passes.
．． A hot-rolled plate with a thickness of 3 mm (the hot-rolling completion temperature at this time is approximately 8
The temperature was 20°C. ) 11" Continuously annealed at 20°C for 2 min, further cold rolled to 0.30°C, decarburized annealed in a wet hydrogen atmosphere, and coated with MgOi as an annealing separator.
The influence of Mn and P on the magnetic flux density (Blo) of a product subjected to final high-temperature annealing at ℃×20 hr is shown. Compared to the 1410℃ slab heating material shown in Figure 3, B10 is lower by 0:01~0.03T overall, but Mn and P
The influence trend is the same as in Figure 3. (In Figure 4, × is Blo<1.80, Δ is 1.80≦B1o<
iys g,○ha1.89<B,. <1.91. Q
is 1.91<B. There is. The third feature of the present invention is that magnetism is stabilized by containing Cr only in an appropriate amount.

Although the technique disclosed in Japanese Patent Publication No. 4,045,644 can obtain a high magnetic flux density, it is necessary to control the acid-soluble No. 11 in steel within a narrow range, which poses a problem for stable industrial production. Since the production method based on the present invention also uses ANO as an inhibitor, it is necessary to strictly control the acid-soluble ANO in the steel in order to obtain a high magnetic flux density. As a result of further research, the present inventors found that by containing an appropriate amount of Cr in steel, acid-soluble A
,! It was found that the range of quantities can be expanded. Furthermore, it has been found that a product manufactured from a Cr-containing material has an iron loss of 456 at the same magnetic flux density.

Figure 5 shows C: 0.06%, Si: 3.33%
, Mn: 0.30%, P: 0.035%, acid soluble A
l: 0.029 section, N: (continuous @ including 10090 chi gold)
The whole slab was heated to 1350°C with a heating plate and hot rolled to a thickness of 2.
It was made into a hot rolled sheet of 3 parts, continuously annealed at 1120°C for 2 min, further cold rolled to 0.30mg, decarburized annealed in a wet hydrogen atmosphere, coated with MgO'i as an annealing separator,
The influence of Cr on the relationship between magnetic flux density (Blo) and iron loss (W17150) of a product obtained by final annealing at 0°C for 20 hours is shown. It can be seen that as the amount of Cr increases, the iron loss improves under the same magnetic flux density.

Even if the amount of Cr is further increased, the effect will not particularly increase, but rather the problem will arise that the decarburization rate during decarburization annealing will be delayed, so it is unsuitable to add more than 0.25% of Cr.

Molten steel containing the above-mentioned components is continuously cast to form a slab 7, and hot rolled to form a hot-rolled plate. Continuously cast slabs are of limited scope since one of the objects of the present invention is to apply the advantages of using continuously cast slabs. However, if continuous casting equipment is not available, there are no particular problems when using slabs produced by the blooming method.

Next, we will discuss the slab heating temperature. In the case of the component range limited in the present invention, the higher the slab heating temperature, the higher the magnetic flux density. However, as shown in FIG. 6, it has been found that according to the present invention, in order to obtain a high magnetic flux density, it is no longer necessary to heat the slab at a high temperature exceeding 1300° C., which was conventionally considered essential. Moreover, when compared under the same magnetic flux density, it was found that the iron loss was significantly better when the slab heating temperature was changed. When the slab heating temperature is high, the magnetic flux density is high and the highest grade G6H or higher can be obtained, and if the finished product is subjected to magnetic domain control treatment (for example, laser irradiation), the iron loss is further improved. When the slab heating temperature is low, the iron loss under the same magnetic flux density is good and the highest grade G6H or higher can be obtained, so for the purpose of reducing manufacturing costs, the present invention is heated to a temperature of 1280°C or lower without generating slag during slab heating. Adopt and get.

Figure 6 shows C: 0.050%, Si: 3.45%, Mn:
025, S: 0.002%, P: 0.040%, acid-soluble At: OO27%, N: 0.0080%, Cr
20. After heating a continuous cast slab containing 18%, it was hot-rolled to form a 2.5 m hot-rolled plate, and after continuous annealing at 1120°C Perform decarburization annealing at 850°C for 2 min in an atmosphere,
Apply MgOi as an annealing separator and heat at 1200°C for 20h.
The influence of the slab heating temperature on the vj density of the product obtained by final annealing of r is shown.

From this figure, it can be seen that the higher the slab heating temperature, the higher the magnetic flux density, and that it becomes particularly high at 1300° C. or higher. However, in order to obtain high magnetic flux density, 13
It can be seen that a hot water temperature exceeding 00°C is not necessarily necessary, and that a relatively low amount of added heat may be sufficient. On the other hand, if the slab heating temperature is too high, the heating furnace cannot withstand the equipment, and 1430° C. is the upper limit for industrial production. There is no particular need to determine the lower limit of the slab heating temperature, but if the temperature drops below 1050°C, the power required during hot rolling will increase and the shape of the steel sheet will deteriorate, so for stable industrial production, a temperature of 1050°C or higher is desirable. .

FIG. 7 shows the magnetism after applying a tension coating containing colloidal silica as a main component to a product obtained under the same conditions as shown in FIG. 3 but with only the slab heating temperature changed to 1150°C. When the slab heating temperature is low, the magnetism is better than when it is high, and the core loss is better under the same magnetic flux density. The reason for this is not clear at all, but it is related to the fact that the grain boundaries of products produced by low-temperature slab heating are irregular, and that microcrystal grains with a diameter of about 2 mm are mixed. it is conceivable that.

As described above, in the present invention, which enables the highest uniform iron loss by heating the slab at a low temperature, a hot rolling method having the following advantages can be easily used.

Due to recent advances in continuous casting technology, the productivity of multi-continuous casting has become comparable to the capacity of continuous hot rolling. The waiting time for hot-rolled materials has been eliminated. Therefore, we have developed a method of directly hot-rolling the slab using the sensible heat of the slab without cooling it after continuous casting, or charging it into a heating furnace if the slab humidity, especially the surface temperature, has dropped slightly. This is a method in which the material is heated in a normal value heating furnace for a period of time and then hot rolled. As described above, hot rolling methods are increasingly being used in the production of ordinary steel for the purpose of saving energy. However, since unidirectional electromagnetic steel sheets require slab heating at high temperatures and for long periods of time, it is necessary to install a high-temperature slab heating furnace exclusively for unidirectional electromagnetic lead plates, and continuous casting and continuous M hot rolling are required. It was not possible to adopt a direct connection process. If it is possible to heat the slab at a low temperature as in the present invention, it becomes easy to adopt a direct connection process, and it becomes possible to hot-roll as efficiently as ordinary steel. Furthermore, in a direct connection process that does not require cooling after casting, silicon steel has the following advantages. That is, S
Since slabs containing i have poor thermal conductivity, the temperature difference between the surface layer and the center increases during cooling of the slab, generating thermal stress, causing internal cracks in the slab, and reducing yield. If the slab is not cooled as in the direct connection process, this problem of internal cracking of the slab will be resolved.

The hot-rolled sheet obtained as described above is subjected to continuous annealing for a short time in the range of 850 to 1200°C. If the annealing temperature is less than 850°C, high magnetic flux density cannot be obtained, and if it exceeds 1200°C, secondary recrystallization will be incomplete.

If the annealing time exceeds 30 minutes, the production efficiency is extremely poor, and if the annealing time is less than 30 gee, the effect of the heat treatment is almost lost.

After continuous annealing of the hot-rolled sheet, the final thickness is obtained by cold rolling. Since the present invention aims to obtain a high magnetic flux density unidirectional silicon steel sheet, a strong cold rolling reduction of 80 coefficients or more is required. Next, decarburization annealing is performed in a humid atmosphere. Decarburization annealing has the role of decarburizing and -second crystallization, and at the same time generating an oxide layer necessary for forming an insulating film on the surface of the product. An annealing separator is applied to the narrow side of the steel plate after decarburization annealing to prevent seizure during final high-temperature annealing and to form an insulating film on the surface of the product. As the annealing separator, MgO is the main component, and other materials such as TlO2#At20.
#CaOr A compound containing an S compound, an S compound, or an N compound can be used. Subsequently, final high-temperature annealing is performed. This annealing is performed for the purpose of secondary recrystallization, purification, and forming an insulating film mainly composed of forsterite, which is a mixture of MgO and 5IO2, on the surface of the product. The test is carried out in a mixed atmosphere containing As the finishing high temperature annealing conditions employed in the present invention, gradual heating in the temperature range where secondary recrystallization is performed is effective for stably obtaining a high magnetic flux density (effective for C%. The metallurgical idea behind the gradual heating operation in the recrystallization temperature range is that secondary recrystallized grains with a small inclination from the (110) (001) orientation occur at a low temperature, as is conventionally known from Chikara et al. In fact, by performing slow heating, the volume ratio of secondary recrystallized grains close to the (110)<001) orientation generated at low temperatures in the product is increased, and the magnetic flux density is increased. In the case of the present invention where the amount is small, i.e.
When MnS has a small inhibitory function on grain growth, grain growth in a low temperature range is relatively large.
By heating slowly! It is particularly effective to increase the volume ratio of secondary recrystallized grains generated at low temperatures close to the D (110)<001) orientation in the product to increase the magnetic flux density.

Figure 8 shows C: 0.060%, Si: 3.42
%, Mn: 0.25, S: 0.002f)
, P: 0.040 ratio, acid soluble ht: 0.032
%, N: 0.009%, CR: O, T5% was heated to 1410°C, then hot-rolled into a hot-rolled plate with a thickness of 2.3 mm, and then continuously cast at 1150°C x 2rnln. After annealing, it was cold-rolled to a thickness of 0.30 mm, decarburized at 850°C in a wet hydrogen atmosphere at 2mlnO, coated with MgO as an annealing separator, and heated at 1200°C for 20 hours.
The magnetic flux density (B
It is a figure which shows the relationship between heating rate in the temperature range of 700-1100 degreeC at the time of finishing high-temperature annealing. This figure shows that the slower the heating rate, the higher the magnetic flux density, especially at 15 u
It can be seen that the value increases significantly below /hr. When the heating rate is within the □ range of 15°C/hr or less, the magnetic flux density does not change significantly. After completing secondary recrystallization through slow heating in the range of 700 to 1100°C, purification annealing is generally performed in pure H2 at a high temperature of around 1200°C to reduce N and S in the steel as much as possible. It is true.

As described in detail above, the present invention utilizes continuous casting slabs as a starting material, which can be manufactured at low cost and which can be industrially stably produced with uniform magnetic properties due to uniform composition in the longitudinal direction of the finished product. At high temperatures, the occurrence of linear secondary recrystallization defects is prevented (this becomes more noticeable especially in high-Si materials), making it possible to produce products with high magnetic flux density and high core loss. In addition, when the slab heating temperature during hot rolling is low, secondary recrystallization defects do not occur even with the high 81 material, and high iron loss is possible due to the characteristics of the product crystal grains unique to the low temperature slab heating temperature. This solves the extremely difficult restrictions on controlling Atnium in steel in the conventional single-rolling method, and enables stable industrial production.

Example I C: 0.060%, St: 3.38%, M
n 0.20t16. P: 0.040chi, S: 0
．． 005, acid-soluble At: 0.033%, N:
Molten steel containing 0.0085% of Cr and 0.16% of Cr was made into a slab by continuous casting, heated at a temperature of 1400°C, and then hot-rolled to produce hot-rolled sheets of columns 2 and 3.

After annealing the hot rolled plate at 1120°C x 2 mlH, 0.30+
Cold rolled to a final thickness of 850 mm in a wet hydrogen atmosphere.
Decarburization annealing was performed at 2 ml of °C. Furthermore, after applying MgO, finishing high-temperature annealing was performed at 1200°C for 20 hours. The heating rate of this final high-temperature annealing in the range of 700 to 1100°C was 10°C/hr. Furthermore, a film containing chromic anhydride as the main component was baked onto the surface of the steel plate. The magnetism of the finished product in the rolling direction is B. = 1.93 Team.

Wl, 15o = 0.99 wA9. As a result of dotted laser irradiation in the C direction on the surface of this product, B,
.

= 1.93 Te5ta, Wl, 15o = 0.8
Extremely excellent magnetism of 8 W/9 was obtained.

Example 2 C: 0.053%, St: 3.35%, Mn:
0.25%.

P: 0.035%, S: 0.003%, acid soluble kt:
0.029%, N: 0.008096. Cr
: A continuous cast slab containing 0.15% was heated to a temperature of 1150° C. and then hot rolled to make a 2.3 am hot rolled sheet. After annealing the hot-rolled plate at 1080°C for 2 min, 0.3
Cold rolled to the final thickness of 0 tone and heated at 850℃ in a wet hydrogen atmosphere.
X 2 m1nQ decarburization annealing was performed. Furthermore, after coating MgO, finishing high-temperature annealing was performed at 1200° C. for 20 hours. The heating rate of this final high temperature annealing in the range of 700 to 1100°C was 20°C/hr. Furthermore, a film containing chromic anhydride as the main component was baked onto the surface of the steel plate. The magnetism of this product in the rolling direction is B. =1,91 Te5ta p
Wl 775o” 0.97 W/9.

It can be seen that when the slab heating temperature during hot rolling is low, the iron loss is excellent compared to the magnetic flux density.

Example 3 C: 0.053%, Si: 3.45%, M
n: 0.23%.

P: 0.037th, S: 0.003th, acid soluble A
T: 0.027%, N: 0.0090%, Cr
: Molten steel containing 0.20% was cast by continuous casting in a 250W thick mold. After the molten steel solidified, it was immediately charged into a trolley-type heat retention furnace without cooling, and when the average slab temperature reached about 1130° C., it was hot rolled to produce a 2.3 mm hot rolled sheet. This hot-rolled sheet was annealed at 1080° C. x 2 ml, then cold rolled to a final thickness of 0.30 ma, and decarburized annealed at 850° C. x 2 ml in a wet hydrogen atmosphere. Furthermore, after applying MgO, finishing high-temperature annealing was performed at 1200° C. for 20 hours. This finishing high temperature annealing is 700-110
The heating rate in the 0°C range was 10°C/hr. Furthermore, a film containing chromic anhydride as the main component was baked onto the surface of the steel plate. The magnetic property of this product in the rolling direction is B1o=1,90
Teala, W2, 75o= 1.01 vr/k
It was g.

There was no occurrence of secondary recrystallization defects.

Example 4 C: 0.053q6. Si: 3.45%, Mn: 0.
23%.

P: 0.037%, Sl: 0.003%, acid-soluble At: 0.027%, N+: 0.0090%, Cr
: Molten steel containing 0.20% was cast by continuous casting in a 250W thick mold. In order to minimize the amount of cooling required after solidification of the molten steel, we kept the continuous casting machine warm and heated the slab end face, which easily gets cold, with gas for a short time. Quickly move the slab to the hot rolling mill entrance until the center of the slab cross section is about 1
Hot rolling was started when the temperature was 200° C. and the surface layer was about 1050° C., and a hot rolled sheet having a thickness of 2.3 mm was obtained.

After annealing this hot-rolled plate at 1080°C
Cold rolled to a final thickness of 0m and heated at 850°C in a wet hydrogen atmosphere.
X 2 mid decarburization annealing was performed. Furthermore, after applying MgO, finishing high temperature annealing was performed at 1200°C for 20 hours. The magnetism of this product in the rolling direction is B. = 1.9
0Testa J W17150 = i, o 3w
/kg is h.

[Brief explanation of the drawing]

Figure 1 shows C: 0.058%, 81: 3.35%, M
n: 0.23%, P: 0.036%, acid soluble A
t: 0.033%, N: 0.0085%, Cr:
Contains 0.13%, and further S is 0.002 to 0.033
After heating the continuously cast slab to 1410°C, it was hot-rolled into a 1) 2.3M@ hot-rolled plate at 1150°C x 2m1n.
After continuous annealing, it was cold rolled to 0.30m+a, decarburized annealed in wet hydrogen for 850cm x 2min, coated with MgO as an annealing separator, and subjected to final high-temperature annealing at 1200℃ x 20hr. A diagram showing the incidence of linear secondary recrystallization defects in products, Figure 2 shows C: 0.050%, S
l: 3.45chi, Mn: 0.25%, P: 0.04
0%, acid soluble kA: 0.027%, N: 0.0080
%, Cr: 0.18%, and S is 0.002~
1200 small specimens with a thickness of 40cm containing 0.035%
After extracting the slab, it was cooled to 100°C by air cooling, held in a furnace at 1000°C for 30 seconds, then hot-rolled for 3 passes to 2.31 mm, continuously annealed at 1126°C x 2 m1n, and then further annealed at 1000°C. Incidence of secondary recrystallization defects in products cold rolled to 30W++, decarburized annealed at 850°C for 2 min in a wet hydrogen atmosphere, coated with MgO as an annealing separator, and then subjected to final high temperature annealing at 1200°C for 20 hours. Figure 3 shows C: 0.060%, Si: 3.33%, S: 0.
004%, acid soluble M: 0.032%, N: 0.009
A continuous cast slab containing 0%, Cr': 0.15% was heated to 1350°C, then hot rolled into a hot rolled plate with a thickness of 2.3 mm, continuously annealed at 1150C x 2 min, and then cold rolled to p 0.30. tma at 850°C in a wet hydrogen atmosphere.
The influence of Mn and P content in the slab on the magnetic flux density (B1o') of the product obtained by performing X 2 m1nO decarburization annealing, applying MgO as an annealing separator, and performing finishing high temperature annealing at 1200 ° C. The figure shown in Figure 4 is C.
: 0.045%, 81: 3.35%, S: 0.00
2%, acid soluble At: 0.028%, N: 0.0075
%, Cr: 1 small specimen with a thickness of 40 mm containing 0.18 inch
The slab was heated to 1.50'CK, and after the slab was extracted, it was hot-rolled to a thickness of 2.3mm thick at 1120°C x 2m1n.
Continuously annealed, further cold-rolled to 0.30 mm, decarburized annealed in a wet hydrogen atmosphere, and coated with MgO as an annealing separator.
A diagram showing the influence of Mn and P on the magnetic flux density (Blo) of a product subjected to 200'CX20hr final high temperature annealing,
Figure 5 shows C: 0.06%, Si: 3.33%, Mn
: 0.30%, P: 0.035%, acid soluble At:O
, 929%, N: 0.0090% was heated to 1350°C, hot-rolled into a hot-rolled plate with a thickness of 2.3 mm, continuously annealed at 1120°C
．． Cold rolled to a length of 30 m, decarburized annealed in a wet hydrogen atmosphere, coated with MgO as an annealing separator, and heated at 1000°C x 20 hours.
The magnetic flux density (Blo
) and iron loss (W17150), Figure 6 shows the influence of Cr on the relationship between C: 0.050%, Si: 3.45%, Mn: 0.25%, S: 0.002%, P:0
．． 040%, acid soluble At: 0.027%, N: 0.0
After heating a continuous casting slab containing 0.080% and Cr: 0.18%, it is hot-rolled! A 72.5 wnO hot-rolled plate was continuously annealed at 1120°C x 2ml, then cold rolled to a plate thickness of 0.30mm, and then heated at 850°C x 2mm in a wet hydrogen atmosphere.
M1dO decarburization annealing is performed, and MgO is used as an annealing separator.
Figure 7 shows the effect of slab heating temperature on the magnetic flux density of a product obtained by coating and finishing annealing at 1200°C for 20 hours. Figure 8 shows the magnetism after applying a tension coating mainly composed of colloidal silica to the product obtained by changing the temperature to 1150°C.
60%, sl: 3.42%XMn: 0.25%,
S: 0.002%, P: 0.040%, acid soluble ht:
o, 032%, N: 0.0090%, Cr: 0.1
After heating the continuous casting slab containing 5 mm to 1410°C, it was hot-rolled into a hot-rolled plate with a thickness of 2.3 mm, and was heated to 1150°C x 2.
By cold rolling after continuous annealing of m1n, j:l 0.30 t
ran at 850°C for 2 min in a wet hydrogen atmosphere.
The magnetic flux density (Blo) of the product obtained by applying MgO as an annealing separator and finishing high-temperature annealing at 1200°C for 20 hours and the 7o at the time of finishing high-temperature annealing were
It is a figure which shows the relationship of the heating rate in the temperature range of o-1100 degreeC. $/Figure S warehouse * Lid ('/=) Figure 2 S warehouse quantity 6%) Figure 3 Mn (7,) Figure 4 Figure 5 Ball requirement '2g Br6 (Te5la) Figure 6 Slough power 0 Thermal Humidity (r) Figure 7 Figure 8 5 10 15 2θ 25 Karo Inugo Speed Seat (Ka/At-) Procedural Amendment (Voluntary) June 20, 1981 Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, Display of the case 1982 Patent Application No. 062688 2 Title of the invention Method for manufacturing unidirectional silicon steel sheet with excellent iron loss applying continuous casting method 3 Relationship with the amended party Patent applicant Tokyo Metropolitan Government 2-6-3 Otemachi, Chiyoda-ku (665) Nippon Steel Corporation Representative Takeshi 1) Yutaka 4, agent 2-4-1-6 Marunouchi 2-4-1 Chiyoda-ku, Tokyo 100, subject to amendment (1) On page 7 of the specification, line 2, "because of a change in" is amended to "by a change in." (2) The third line from the bottom of page 24, "No big change." was replaced with "No big change, but the fluctuation in magnetic flux density decreases as the heating rate decreases. However, considering economic efficiency, 7℃/hr The degree is the lower limit.''

Claims (5)

[Claims] (1) C2 0.0 2 5-70.0 7 5
%, Si: 3.0 to 4.5%, Acid soluble At: 0.010 to 0.060, N: 0.0030
~ O,0130%, S2 0.00'7
Below, Mn: 0.08-0.45%, p:
0.015~0, 04.5%, Cr: 0.07~0
．． A continuously cast slab for a unidirectional silicon copper plate consisting of 25% Fe and unavoidable impurities is hot-rolled to form a hot-rolled plate, and then the hot-rolled plate is continuously annealed for a short time in the range of 850 to 1200°C. After that, the final plate thickness is obtained by cold rolling with a reduction rate of 80 inches or more, and the obtained cold rolled plate is continuously decarburized annealed in a wet hydrogen atmosphere, and then an annealing separator is applied and finished at a high temperature. A method for manufacturing a unidirectional silicon steel sheet with excellent iron loss, which is characterized by performing annealing. (2) 700 to 110 when heated during finishing high temperature annealing
The method according to claim 1, characterized in that heating is carried out in a range of 0°C at a heating rate of 15°C/hr or less. (3) Continuous iron making slab for unidirectional silica plate 1280
The method according to claim 1, wherein the method is heated to a temperature not exceeding .degree. C. and then hot-rolled into a hot-rolled sheet. (4) 128 continuous casting slabs for unidirectional silicon copper plates
Claim 1. Distributing method 0, which is heated to a temperature of 0° C. or higher and then hot-rolled to obtain a hot-rolled sheet. (5) The method according to claim 1, characterized in that the continuously cast slab is hot rolled directly onto the continuous cast slab by utilizing sensible heat of the slab without cooling the continuous cast slab.