JPH04341518A - Production of extra thin grain-oriented silicon steel sheet having high magnetic flux density and reduced in iron loss - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet extremely reduced in sheet thickness, having high magnetic flux density, and reduced in iron loss by hot-rolling a low carbon steel slab under specific temp. conditions to form a hot coil and then subjecting this slab to cold rolling to the final extra thin sheet thickness at specific cold rolling rate. CONSTITUTION:A slab of a low carbon steel having a composition containing, by weight, 0.025-0.085% C, 2.5-4.5% Si, 0.01-0.10% Mn, 0.01-0.04% Si, 0.010-0.065% Sol.Al, 0.005-0.0100% N, 0.03-0.5% Cu, and 0.03-0.5% Sn is heated uniformly up to 1300-1450 deg.C in an electric nitrogen-atmosphere furnace and hot-rolled under the conditions of 1150-1250 deg.C surface temp. before finishing, 950-1100 deg.C surface temp. after finishing, and 400-600 deg.C coiling temp. into a hot coil of <=2.5mm or <=1.9mm thickness. This hot coil is subjected to cold rolling at >=83% cold rolling rate twice or once, by which the grain-oriented silicon steel sheet having an extra thin final sheet thickness of 0.23mm, having high magnetic flux density, and reduced in iron loss can be produced.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is an ultra-thin high magnetic flux density
The present invention relates to a method for industrially stably manufacturing a unidirectional electrical steel sheet with low core loss.

0002

[Prior Art] Unidirectional electrical steel sheets are mainly used as core materials for transformers and generators, and have the characteristics of low core loss and high magnetic flux density. something is demanded by the market. In order to obtain low iron loss, two methods are generally used: one method is to increase the Si content as much as possible to increase the specific resistance of the material to reduce eddy current loss, and the other is to reduce the eddy current loss by reducing the thickness of the finished product as much as possible. However, with the method of reducing the thickness of the finished product, secondary recrystallization during final annealing becomes unstable, and with conventional methods, it is difficult to stably obtain products with excellent magnetic properties with a thickness of 0.23 mm or less industrially. be. In order to stably perform secondary recrystallization, it is necessary to create a fine and uniform precipitated dispersed phase in the steel before finishing annealing, and to segregate grain boundary elements at the grain boundaries. It is important to suppress recrystallization as much as possible and selectively grow secondary recrystallization in the (110)[001] orientation in the subsequent final annealing. As a means of suppressing primary recrystallization, the pinning effect of the grain boundaries by the precipitated dispersed phase and the drag effect of the grain boundaries by the grain boundary segregated elements have been considered.
, MnSe, and AlN, and the grain boundary segregation elements are generally Sn, Sb, Bi, Te, Se, and the like.

[0003] From the above-mentioned viewpoint, it has been proposed to use MnS and AlN as the precipitated dispersed phase and Sn as the grain boundary segregation element to produce thin product sheets with a thickness of 0.30 mm or less, particularly 0.23 mm or less. A method for producing a high magnetic flux density unidirectional electrical steel sheet has already been proposed in Japanese Patent Publication No. 48725/1983. The gist of this proposed invention is as follows. C: 0.025-0.085%, Si: 2.5-4
．． 5%, Mn: 0.01~0.10%, S: 0.01~
0.04%, solAl: 0.010-0.065%
, N: 0.005~0.0100%, Cu: 0.03~
A slab containing 0.5%, Sn: 0.03 to 0.5%, balance iron and unavoidable impurities is heated to a high temperature and then hot rolled,
In a predetermined method for manufacturing a high magnetic flux density unidirectional electrical steel sheet that includes a cold rolling process with a final cold rolling rate of 83% or more, the finishing front surface temperature in the hot rolling is 1150 to 1250°C, and the finishing rear temperature is 950 to 1050°C. ℃, and the winding temperature is 500-60
The temperature is controlled within the 0°C temperature range.

That is, the above-mentioned prior invention is characterized by heating the raw material slab at a temperature of 1250° C. or higher to completely dissolve MnS and AlN, which will become the precipitated dispersed phase, and finishing it in the subsequent hot rolling process. Front temperature 1150-125
By controlling the temperature to 0°C, MnS is precipitated uniformly and finely during the transition from rough rolling to finishing rolling, and then by controlling the temperature after finishing to 950 to 1050°C, precipitation of MnS in the finishing stand is suppressed. . Furthermore, by winding up the hot coil with a thickness of 2.5 mm or less that exits the finished surface at a temperature of 500 to 600°C, precipitation of AlN from the finishing stand to winding is controlled, and the precipitation of Sn to the grain boundaries is controlled. The purpose is to obtain high-quality hot coils for use in unidirectional electrical steel sheets with high magnetic flux density by performing active precipitation. In Example 1 of the above-mentioned prior patent, a hot coil thickness of 2.3 mm to 0.0 An example of obtaining a product with a thickness of .23 mm is disclosed, while in Example 2, a product with a thickness of 0.23 mm is obtained from a hot coil thickness of 2.0 mm by a single cold rolling method.
．． An example of obtaining a product with a thickness of 23 mm is disclosed.

[0005]

[Problems to be Solved by the Invention] According to the above-mentioned prior invention, the precipitated dispersed phase and the grain boundary segregated elements are effectively utilized, and a thin grain-oriented electrical steel sheet having a high magnetic flux density that cannot be obtained by conventional methods can be obtained. However, it is an object of the present invention to provide a thin unidirectional electrical steel sheet which has a higher magnetic flux density and a lower iron loss by a one-time cold rolling method that is inexpensive to manufacture.

On the other hand, as the market demand for ultra-low core loss unidirectional electrical steel sheets has increased in recent years, laser irradiation treatment has been applied to the surface of the product, or streaks have been created on the surface of the product under a predetermined load. Techniques for improving iron loss through so-called magnetic domain refining treatment, such as post-heat treatment, have been developed and are being put into practice. The former magnetic domain subdivision process is, for example,
-2252 publication, 58-36051 publication, 58
The latter magnetic domain subdivision process has been proposed in, for example, Japanese Patent Laid-Open No. 117218/1983. It is known that the higher the magnetic flux density of these unidirectional electrical steel sheets subjected to magnetic domain refining treatment, the greater the iron loss improvement margin after magnetic domain refining treatment. Another object of the present invention is to provide a grain-oriented electrical steel sheet that has a high magnetic flux density that is optimal for magnetic domain refining treatment and has a low iron loss by using the two-time cold rolling method.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration.

(1) C: 0.025-0.085%
, Si: 2.5-4.5%, Mn: 0.01-0.10
%, S: 0.01-0.04%, solA
l: 0.010~0.065%, N: 0.005~
0.0100%, Cu: 0.03-0.5%,
When hot rolling a slab containing Sn: 0.03 to 0.5%, balance iron and unavoidable impurities after high temperature heating, the finishing front temperature is 1150 to 1250°C, the finishing rear temperature is 950 to 1100°C, and winding temperature 400-60
A hot coil is obtained at 0°C, and this hot coil is processed into an ultra-thin high magnetic flux density unidirectional electrical steel sheet with a finished plate thickness of 0.23 mm or less by a predetermined manufacturing process including a single cold rolling process of 83% or more. In the manufacturing method, the slab is uniformly heated at a high temperature of 1300 to 1450°C in an electric atmosphere heating furnace, and the thickness of the hot coil after hot rolling is 1.
A method for producing an ultra-thin, high magnetic flux density, low iron loss unidirectional electrical steel sheet, characterized in that the thickness is 9 mm or less.

(2) C: 0.025-0.085%
, Si: 2.5-4.5%, Mn: 0.01-0.10
%, S: 0.01-0.04%, solA
l: 0.010~0.065%, N: 0.005~
0.0100%, Cu: 0.03-0.5%,
When hot rolling a slab containing Sn: 0.03 to 0.5%, balance iron and unavoidable impurities after high temperature heating, the finishing front temperature is 1150 to 1250°C, the finishing rear temperature is 950 to 1100°C, and winding temperature 400-60
A hot coil is obtained at 0°C, and this hot coil is subjected to a predetermined manufacturing process including preliminary cold rolling and a final cold rolling process with a final cold rolling rate of 83% or more to produce an ultra-thin high magnetic flux density unidirectional product with a thickness of 0.23 mm or less. In the method for manufacturing electrical steel sheets, the slab is heated at a high temperature of 1300 to 1
A method for producing an ultra-thin, high magnetic flux density, low core loss, unidirectional electrical steel sheet, characterized by uniformly heating to 450° C. and setting the thickness of the hot coil after hot rolling to 2.5 mm or less.

[0010] The contents of the present invention will be explained in detail below. The present inventors have discovered the above-mentioned prior art in Japanese Patent Publication No. 62-4872.
Regarding the invention described in Publication No. 5, the hot rolling process was examined in detail. As a result, when heating slabs at high temperatures using a commonly used gas heating furnace, uniform heating is difficult.
It was found that there were large variations in the width and longitudinal direction of the finishing front temperature and finishing finishing temperature within the coil. This tendency becomes remarkable when the plate thickness of the hot coil becomes 2.5 mm or less, and especially when the plate thickness of the hot coil becomes 1.9 mm or less, the temperature at the end of the coil decreases significantly. Incidentally, in the case of a 1.9 mm hot coil, the finished front temperature varies from 1050 to 1200°C, and the finished finished temperature varies from 850 to 1100°C. As a result, the finishing front temperature of 1150 to 1250°C and the Mn in the finishing stand required to precipitate MnS uniformly and finely between rough rolling and finishing rolling.
The finishing surface temperature required to suppress S precipitation is 950~
As a result, the lower limit temperature of 1100° C. is exceeded, and the magnetic flux density and iron loss of the product deteriorate, and variations in iron loss values occur.

[0011] In addition, in the case of a 1.6 mm hot coil, it is difficult to uniformly heat the slab in a gas heating furnace, and the center temperature in the thickness direction of the slab is lower than the surface temperature, so it is difficult to heat the slab from rough rolling. The amount of temperature drop during and during finishing rolling was large, and it was not possible to maintain a finishing front temperature of 1150°C and a finishing finishing temperature of 950°C over the entire length in the longitudinal direction. The finishing front temperature of 1150 to 1250°C and Mn in the finishing stand required to uniformly and finely precipitate MnS.
The finishing surface temperature required to suppress S precipitation is 950~
It was found that the lower limit temperature of 1100° C. was exceeded, resulting in deterioration of the magnetic flux density and iron loss of the product.

[0012] Therefore, the inventors of the present invention determined the lower limits of the finished front temperature and the finished finished surface temperature, which are caused by uneven heating of the slab in the longitudinal and width directions by the gas heating furnace and the center temperature in the thickness direction being lower than the surface temperature. Resolving the deviation is
Considering that it is essential to improve the magnetic flux density and iron loss of the product and to stabilize the iron loss value, uniform heating in the longitudinal and width directions of the slab, heating in which the center temperature in the thickness direction of the slab is higher than the surface temperature (thickness direction As a result of examining the central high-temperature heating method, it was found that an electric heating method represented by induction heating was the most suitable. That is, unlike the external heat input method of gas heating, induction heating uses an internal heat input method, so that it is possible to uniformly heat the slab in the longitudinal direction and width direction, and to heat the slab at a high temperature in the thickness direction. Therefore, by heating the slab to a predetermined temperature range by induction heating and supplying it to hot rolling, a predetermined finishing front surface temperature of 1150 to 1250°C and finishing back surface temperature of 95° C.
0~1100℃ can be stably and reliably secured,
As a result, more complete utilization of the precipitated dispersed phase is possible.

In this case, the induction heating conditions are 130
It is necessary to heat the slab to 0-1450℃, 13
At temperatures below 00°C, complete solid solution of MnS, AlN, etc. forming the precipitated dispersed phase becomes difficult, making it impossible to obtain desired magnetic properties. On the other hand, if the heating temperature exceeds 1450° C., local melting occurs in the slab, causing cracking defects.

[0014] In the production of unidirectional electrical steel sheets, many proposals have already been made to employ an induction heating method for high-temperature heating of slabs in the hot rolling process. In the present invention,
The high-temperature heating of the slab may be carried out only by induction heating, or it may be carried out by two-stage heating, in which the low-temperature region below 1250°C is carried out by ordinary gas heating, and the final heating in the high-temperature region is carried out by induction heating. . At this time, it is desirable to provide the induction heating device near the rough rolling mill in order to ensure the rolling temperature.

[0015] Thus, according to the present invention, the plate thickness is 2.5 mm.
It is now possible to stably secure the predetermined finishing front temperature, finishing finishing temperature, and winding temperature for the following hot coils, and as a result, a high-quality thin hot coil can be obtained, and this hot coil can be used as a starting material. A unidirectional electrical steel sheet with high magnetic flux density and low iron loss can be manufactured by completing the product through predetermined processes. The present invention firstly provides a method for manufacturing an ultra-thin unidirectional electrical steel sheet with high magnetic flux density and low iron loss by a single cold rolling method that is inexpensive to produce; The object of the present invention is to provide a method for producing an ultra-thin unidirectional electrical steel sheet that is suitable for the above-mentioned magnetic domain control treatment, which has a higher magnetic flux density and lower iron loss through a cold rolling process, that is, can significantly improve iron loss through the magnetic domain control treatment. .

As is well known, in the production of unidirectional electrical steel sheets, the final cold rolling rate before decarburization annealing must be 83% or more, and a cold rolling rate of 83% or less does not provide a high magnetic flux density. The product thickness in the first object of the present invention is 0.23 mm or less, and therefore the plate thickness of the hot coil is 1.9 mm or less.

By the double cold rolling method, an ultra-thin unidirectional electrical steel sheet with even higher magnetic flux density can be obtained. This is because the plate thickness of the hot coil can be made thicker so that temperature differences are less likely to occur during finish rolling, and because of the effect of two-time cold rolling, a magnetic flux density B8 of 1.925 (T) or more can be obtained. The thickness of the finished product according to the second object of the present invention is 0.23 mm or less, and the first cold rolling rate is preferably 15 to 40%, so the thickness of the hot coil is 2.5 mm or less.

Next, the reasons for limiting the conditions will be explained. ■If the component composition C is less than the lower limit of 0.025%, secondary recrystallization will become unstable, and if the C content is higher than the upper limit of 0.085%, the time required for decarburization will be longer and it will be economically disadvantageous. Limited for. If Si is less than the lower limit of 2.5%, good iron loss cannot be obtained, and if it exceeds the upper limit of 4.5%, cold rollability is significantly deteriorated. Mn is an element necessary to form MnS,
If it is less than the lower limit of 0.01%, the absolute amount of MnS is insufficient,
If the upper limit of 0.10% is exceeded, the slab heating temperature for dissolving all MnS in solid solution becomes too high, making industrialization difficult. S is an element necessary to form MnS,
If it is less than the lower limit of 0.01%, the absolute amount of MnS will be insufficient, and if it exceeds the upper limit of 0.03%, hot cracking will occur and desulfurization will become difficult in final annealing. solAl is an element necessary to form AlN, and if the lower limit is less than 0.010%, AlN
If the absolute amount of AlN is insufficient and exceeds the upper limit of 0.065%, AlN
An appropriate dispersion state cannot be obtained. N is an element necessary to form AlN, and if it is less than the lower limit of 0.005%, AlN
The absolute amount of is insufficient. Moreover, if the upper limit of 0.0100% is exceeded, secondary recrystallization becomes unstable and blisters are likely to occur. Cu is an element necessary to control the amount of MnS and improve the properties of the finished film, and the lower limit is 0.03.
If it exceeds the upper limit of 0.5%, the properties of the finished film cannot be improved, and if it exceeds the upper limit of 0.5%, the pickling properties and decarburization properties will deteriorate. Sn
is segregated at grain boundaries and stabilizes secondary recrystallization, but if the lower limit is less than 0.03%, the amount of segregation will be insufficient, and if the upper limit is 0.5%, this will result in poor decarburization due to economic reasons.

(2) Slab Heating The reason why slab heating is limited to an electric heating method typified by induction heating is as described above. In this case, if the heating temperature is below 1300°C, MnS, A, which forms a precipitated dispersed phase,
Complete solid solution of lN or the like becomes difficult and predetermined magnetic properties cannot be obtained. On the other hand, if the heating temperature exceeds 1450°C, local melting will occur in the slab, causing cracking defects. For this reason, the heating temperature was limited to 1300 to 1450°C. In this case, it goes without saying that heating can be performed in combination with gas heating.

[0020] Hot rolling First, when the finishing front temperature exceeds 1250°C, the amount of MnS precipitated decreases, and when it becomes lower than 1150°C, the amount of MnS precipitated is too large and the magnetic properties are not good. Next, if the surface temperature after finishing is higher than 1100℃, the amount of MnS precipitated will be insufficient, and 950℃
When the temperature is lower than .degree. C., the amount of MnS precipitated is too large and the magnetic properties deteriorate. Further, for coils whose finished surface temperature is controlled to be 950° C. or higher and whose thickness is 2.5 mm or less, it is desirable to prevent AlN precipitation as much as possible by super-hardening treatment. Next, if the winding temperature exceeds 600°C, the amount of precipitated AlN will be too large and the magnetic properties will not be good.
The winding temperature was limited to 400 to 600°C because it is estimated that if the temperature drops below 00°C, the coiled appearance of the hot coil deteriorates, the amount of Sn grain boundary segregation decreases, and the magnetic properties deteriorate.

■ Plate thickness and final cold rolling ratio of hot coils and products As is well known, in the production of unidirectional electrical steel sheets, the final cold rolling ratio before decarburization annealing must be 83% or higher; A high magnetic flux density cannot be obtained at a cold rolling rate. That is, 0.
In order to produce a product with a thickness of 23 mm or less by a single cold rolling method, a hot coil plate thickness of 1.9 mm or less is required. Also,
In order to manufacture using the two-time cold rolling method, the first cold rolling rate should be 15~15.
40% is desirable, and taking this into consideration, the hot coil plate thickness is required to be 2.5 mm or less.

[0022]

【Example】

[Example 1] C: 0.072%, Si: 3.3 in weight%
5%, Mn: 0.080%, S: 0.025%, so
lAl: 0.026%, N: 0.0081%, Cu: 0
．． A magnetic steel slab containing Sn: 0.7% and Sn: 0.15% was heated in a gas heating furnace at 1180° C. for 3 hours, extracted from the furnace, and then width-reduced to adjust to an appropriate slab size. This slab was heated in an electric N2 atmosphere heating furnace at 1335°C for 50 minutes, and after extraction, it was hot rolled under the hot rolling conditions shown in Table 1.
A hot coil with a thickness of mm was obtained. This hot-rolled plate was heated to 1120°C.
After performing two-stage hot-rolled plate annealing by heating for 30 seconds and soaking at 900°C for 60 seconds, the final cold rolling rate was 86%.
Finished to 3mm. Thereafter, hydrogen 20
%, 840℃ x 3 in an atmosphere of 80% nitrogen and a dew point of 40℃
After performing decarburization annealing for 30 minutes and applying an annealing separation material, final annealing was performed at 1200° C. for 20 hours in a hydrogen atmosphere, and then a final coating was applied to produce a finished product.

The magnetic properties of the thus obtained product of the present invention are as shown in Table 1. Materials with the same components were heated in a gas heating furnace at 1400° C. for 6 hours, then hot rolled, and a 1.6 mm thick hot plate was prepared. The magnetic properties are higher than those of the comparative material finished into a coil (hot rolled and then processed under the same conditions as the hot coil in an electric heating furnace), with a magnetic flux density of B8 of 1.92T or more, and iron loss of W17/50. It can be seen that 0.85 W/kg or less can be stably obtained. In addition, each temperature in Table 1 indicates the average value in the longitudinal direction of the center temperature in the width direction of the hot-rolled material, and the magnetic flux density and iron loss are calculated at the top, middle, and center temperatures in the longitudinal direction of the strip.
Shows the average value at the bottom.

[0024]

[Table 1]

[Example 2] C: 0.078%, Si: 3
．． 30%, Mn: 0.079%, S: 0.026%,
solAl: 0.026%, N: 0.0083%, Cu
0.07% and Sn: 0.14% were cut into 10 slabs, of which 5 slabs were heated in a gas heating furnace at 1180°C for 3 hours, extracted from the furnace, and then width-reduced. Adjusted to appropriate slab size. After heating this slab for 50 minutes in an electric N2 atmosphere heating furnace at 1335°C, Table 2
Hot rolling was carried out under each hot rolling condition shown below to obtain a hot coil having a thickness of 2.3 mm. On the other hand, the remaining 5 slabs were directly heated in a gas heating furnace at 1380° C. for 7 hours, extracted from the furnace, and then width-reduced. The slab adjusted to the appropriate slab size was hot rolled under each hot rolling condition shown in Table 2 to obtain a hot coil with a thickness of 2.3 mm. 10 hot-rolled sheets with different slab heating conditions are made into the same lot, and these hot-rolled sheets are cold-rolled at a rolling reduction of 33%, heated at 1120°C for 30 seconds, and then soaked at 900°C for 60 seconds. After performing two stages of intermediate annealing, the final cold rolling rate was 85.
It was finished to 0.23 mm by %. Thereafter, the obtained cold-rolled sheet was subjected to decarburization annealing at 840°C for 3 minutes in an atmosphere of 20% hydrogen, 80% nitrogen, and a dew point of 40°C, and after applying an annealing separation material, the temperature was increased to 1200°C in a hydrogen atmosphere. Finish annealing was performed for 20 hours, followed by a final coating process to obtain a finished product.

The magnetic properties of the thus obtained product are shown in Table 2, and the material of the present invention has a magnetic flux density of B8 of 1.
925T or more, iron loss W17/50, 0.83W/kg
It can be seen that the following can be stably obtained, and better magnetic properties can be obtained than the comparative materials. In addition, each temperature in Table 2 indicates the average value in the longitudinal direction of the center temperature in the width direction of the hot rolled material,
The magnetic flux density and iron loss are the average values of the top, middle, and bottom parts in the longitudinal direction of the strip.

[0027]

[Table 2]

[Example 3] C: 0.070%, Si: 3
．． 45%, Mn: 0.085%, S: 0.027%,
solAl: 0.028%, N: 0.0089%, Cu
0.06% of Sn and 0.13% of Sn were cut into 10 slabs, 5 of which were heated in a gas heating furnace at 1180° C. for 3 hours, extracted from the furnace, and then rolled down across the width. The slab adjusted to the appropriate slab size was heated in an electric N2 atmosphere heating furnace at 1400°C for 50 minutes, and after extraction, it was hot rolled under the hot rolling conditions shown in Table 3 to obtain a hot coil with a thickness of 2.3 mm. Ta.

On the other hand, the remaining five slabs were directly heated in a gas heating furnace at 1400° C. for 7 hours, extracted from the furnace, and then reduced widthwise. The slabs adjusted to appropriate slab sizes were hot rolled under the hot rolling conditions shown in Table 3 to obtain hot coils with a thickness of 2.3 mm. Ten hot-rolled plates with different slab heating conditions were made into the same lot, and after cold rolling with a rolling reduction of 33%, 11
After performing two stages of intermediate annealing, heating at 20° C. for 30 seconds and then soaking at 900° C. for 60 seconds, the material was finished to 0.23 mm with a final cold rolling rate of 85%. Thereafter, the obtained cold rolled sheet was heated to 840°C in an atmosphere of 20% hydrogen, 80% nitrogen, and a dew point of 40°C
After decarburizing annealing for 3 minutes at °C and applying an annealing separation material,
Finish annealing was performed at 1200° C. for 20 hours in a hydrogen atmosphere, and then a final coating was applied to produce a finished product.

The magnetic properties of the thus obtained product are shown in Table 3, and the material of the present invention has a magnetic flux density of B8 of 1.
930T or more, iron loss W17/50, 0.80W/kg
It can be seen that the following can be stably obtained, and better magnetic properties can be obtained than the comparative materials. In addition, each temperature in Table 3 indicates the average value in the longitudinal direction of the center temperature in the width direction of the hot rolled material,
The magnetic flux density and iron loss are the average values of the top, middle, and bottom parts in the longitudinal direction of the strip.

[0031]

[Table 3]

[0032]

As described above, according to the method of the present invention, an ultra-thin unidirectional electrical steel sheet with high magnetic flux density and low iron loss can be obtained.

Claims (2)

[Claims] Claim 1: C as weight %: 0.025 to 0.0
85%, Si: 2.5-4.5%, Mn: 0.01-0
．． 10%, S: 0.01-0.04%, s
olAl: 0.010-0.065%, N: 0.0
05-0.0100%, Cu: 0.03-0.5%,
When hot rolling a slab containing Sn: 0.03 to 0.5%, balance iron and unavoidable impurities after high temperature heating, the finishing front temperature is 1150 to 1250°C, the finishing rear temperature is 950 to 1100°C, and the winding temperature to 400
A hot coil is obtained at ~600°C, and this hot coil is processed through a predetermined manufacturing process including a single cold rolling process with a cold rolling rate of 83% or more to produce an ultra-thin high magnetic flux density unidirectional electrical steel sheet with a thickness of 0.23 mm or less. In the method for producing
A method for producing an ultra-thin, high magnetic flux density, low iron loss, unidirectional electrical steel sheet, characterized by uniformly heating the hot coil to 1.9 mm or less after hot rolling. Claim 2: C as weight %: 0.025 to 0.0
85%, Si: 2.5-4.5%, Mn: 0.01-0
．． 10%, S: 0.01-0.04%, s
olAl: 0.010-0.065%, N: 0.0
05-0.0100%, Cu: 0.03-0.5%,
When hot rolling a slab containing Sn: 0.03 to 0.5%, balance iron and unavoidable impurities after high temperature heating, the finishing front temperature is 1150 to 1250°C, the finishing rear temperature is 950 to 1100°C, and the winding temperature to 400
A hot coil is obtained at ~600°C, and this hot coil is processed through a predetermined manufacturing process including preliminary cold rolling and a final cold rolling process with a final cold rolling rate of 83% or more to produce an ultra-thin, high magnetic flux density unidirectional product with a thickness of 0.23 mm or less. In the method for producing magnetic electrical steel sheets, the slab is heated at a high temperature of 130 ml in an electric atmosphere heating furnace.
A method for producing an ultra-thin, high magnetic flux density, low core loss, unidirectional electrical steel sheet, comprising heating uniformly to 0 to 1450° C. and setting the thickness of the hot coil after hot rolling to 2.5 mm or less.