KR20240011531A - Method for manufacturing non-oriented electrical steel sheet - Google Patents

Abstract

A method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes the steps of (a) providing a steel material for a non-oriented electrical steel sheet; (b) hot rolling the steel to form a hot rolled steel sheet; (c) measuring the temperature distribution of the hot rolled steel sheet; and (d) in the temperature distribution, i) within the temperature range of the ideal region of ferrite and austenite, but ii) at a temperature at an arbitrary point and at another point within a radius having a first set value centered on the point. If the temperature deviation exceeds the second set value, changing the hot rolling conditions.

Description

Method for manufacturing non-oriented electrical steel sheet {METHOD FOR MANUFACTURING NON-ORIENTED ELECTRICAL STEEL SHEET}

The present invention relates to a method of manufacturing a non-oriented electrical steel sheet, and more specifically, to a method of manufacturing a non-oriented electrical steel sheet that can prevent the generation of defects.

Electrical steel sheets can be divided into oriented electrical steel sheets and non-oriented electrical steel sheets depending on their magnetic properties. Oriented electrical steel sheet is manufactured to facilitate magnetization in the rolling direction of the steel sheet and has particularly excellent magnetic properties in the rolling direction, so it is mainly used as the iron core of large, small and medium-sized transformers that require low core loss and high magnetic permeability. . In contrast, non-oriented electrical steel sheets have uniform magnetic properties regardless of the direction of the steel sheet, so they are widely used as iron core materials for small electric motors, small power transformers, and stabilizers.

Republic of Korea Patent Publication No. 2015-0001467A

The technical problem to be achieved by the present invention is to provide a method of manufacturing a non-oriented electrical steel sheet that can prevent the generation of defects.

However, these tasks are illustrative and do not limit the scope of the present invention.

A method of manufacturing a non-oriented electrical steel sheet according to one aspect of the present invention for solving the above problems includes the steps of (a) providing a steel material for a non-oriented electrical steel sheet; (b) hot rolling the steel to form a hot rolled steel sheet; (c) measuring the temperature distribution of the hot rolled steel sheet; and (d) in the temperature distribution, i) within the temperature range of the ideal region of ferrite and austenite, but ii) at a temperature at an arbitrary point and at another point within a radius having a first set value centered on the point. determining whether the temperature deviation exceeds a second set value; Includes.

In the method of manufacturing the non-oriented electrical steel sheet, step (d) is i) within the temperature range of the ideal region of ferrite and austenite, and ii) the temperature at an arbitrary point and a first set value centered on the point. If the temperature deviation of other points within the radius exceeds the second set value, it may include determining that the scap is defective.

The method of manufacturing the non-oriented electrical steel sheet, in the temperature distribution, i) falls within the temperature range of the ideal region of ferrite and austenite, and ii) sets the temperature at an arbitrary point and a first set value centered on the point. The method may further include changing the hot rolling conditions when the temperature difference at other points within the branch radius exceeds the second set value.

In the method of manufacturing the non-oriented electrical steel sheet, the hot rolling conditions may include hot rolling rough rolling temperature, hot rolling finishing rolling temperature, slab edge temperature, or descaling conditions.

In the method of manufacturing the non-oriented electrical steel sheet, the first set value may be 100 mm, and the second set value may be 40°C.

In the method of manufacturing the non-oriented electrical steel sheet, the step of measuring the temperature distribution of the hot rolled steel sheet may include measuring the temperature distribution over the full length and full width of the hot rolled steel sheet.

The non-oriented electrical steel sheet according to another aspect of the present invention to solve the above problems includes silicon (Si): 0.1 to 4.0 wt%, manganese (Mn): 0.1 to 0.5 wt%, and aluminum (Al): 0.3 to 0.9 wt%. , Carbon (C): more than 0 and less than 0.004% by weight, phosphorus (P): more than 0 and less than 0.015% by weight, sulfur (S): more than 0 and less than 0.004% by weight, nitrogen (N): more than 0 and less than 0.004% by weight, titanium (Ti): It is a non-oriented electrical steel sheet made by sequentially applying hot rolling, hot rolling annealing, cold rolling, and cold rolling annealing processes to steel consisting of iron (Fe) and other inevitable impurities in an amount exceeding 0.004% by weight and the remainder. In the temperature distribution of a hot-rolled steel sheet obtained by hot-rolling steel, i) it falls within the temperature range of the ideal region of ferrite and austenite, and ii) the temperature at any one point and the other within a radius having a first set value centered on the one point. The temperature deviation of each point is all less than or equal to a second set value, the first set value is 100 mm, and the second set value is 40°C.

According to an embodiment of the present invention, a method for manufacturing a non-oriented electrical steel sheet that can prevent the generation of defects can be provided.

Of course, the scope of the present invention is not limited by this effect.

1 is a flowchart showing a method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention.
Figure 2 is a diagram showing the strength of the non-oriented electrical steel sheet at different temperatures in the method of manufacturing the non-oriented electrical steel sheet according to an embodiment of the present invention.
Figures 3 and 4 are diagrams matching the temperature distribution and scap defect distribution of a hot rolled steel sheet in the method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the invention.
Figure 5 is a photograph of a scap defect on the surface of a non-oriented electrical steel sheet.
Figure 6 is a photograph of a scap defect in the cross section of a non-oriented electrical steel sheet.

A method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention will be described in detail. The terms described below are terms appropriately selected in consideration of their functions in the present invention, and definitions of these terms should be made based on the content throughout the present specification.

Generally, electrical steel is divided into oriented electrical steel and non-oriented electrical steel. Grain-oriented electrical steel sheets are mainly used in stationary equipment such as transformers, while non-oriented electrical steel sheets are mainly used in rotating equipment such as motors and generators. Due to policies to reduce _CO2 emissions to prevent global warming, existing internal combustion engine vehicles are rapidly being replaced by eco-friendly vehicles (hybrid vehicles (HEV), electric vehicles (EV)). In particular, electric vehicles (EVs) must produce large torque at low speeds or when accelerating, and rotate at high speeds (over 200 Hz) when driving at constant or high speeds, so non-oriented electrical steel, which is the iron core material of the motor, has high magnetic flux density and low low speed. The iron loss must be satisfied at the same time. The characteristics of electrical steel material can be evaluated by magnetic flux density and iron loss. The magnetic flux density is B ₅₀ , and iron loss is generally evaluated at W _15/50 , but in cases where high frequency characteristics are required, such as in electric vehicles, W _10/400 iron loss is used. Evaluating. B ₅₀ represents the magnetic flux density at 5000A/m, W _15/50 represents the iron loss at 50Hz and 1.5T, and W _10/400 represents the iron loss at 400Hz and 1.0T.

Factors that affect the magnetic properties of non-oriented electrical steel sheets include chemical composition, size and distribution of inclusions and precipitates, thickness of the steel sheet, microstructure, insulating coating layer, and texture.

These various factors are influenced by the non-oriented electrical steel manufacturing process conditions. Non-oriented electrical steel sheets are manufactured through the following process: steelmaking/rolling → hot rolling → heat treatment → cold rolling → heat treatment and coating. By optimizing each process condition, electrical steel sheets with excellent magnetic properties can be manufactured.

There is a problem in that the amount of scab defects increases during hot rolling in the manufacturing method of non-oriented electrical steel sheet. Scap defects are scab-shaped defects that have different shapes depending on the causative factors, and may cause additional problems because they deteriorate the surface quality of the plate.

The technical idea of the present invention is to reduce scab by avoiding the occurrence of abnormal temperature ranges and temperature deviations during hot rolling, rough rolling, and finishing rolling processes.

Figure 1 is a flowchart showing a method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention, and Figure 2 is a flowchart showing the strength of the non-oriented electrical steel sheet by temperature in the method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention. This is a drawing showing .

Referring to Figure 1, a method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes (a) providing a steel material for a non-oriented electrical steel sheet (S10); (b) hot rolling the steel to form a hot rolled steel sheet (S20); (c) measuring the temperature distribution of the hot rolled steel sheet (S30); and (d) in the temperature distribution, i) within the temperature range of the ideal region of ferrite and austenite, but ii) at a temperature at an arbitrary point and at another point within a radius having a first set value centered on the point. Determining whether the temperature deviation exceeds the second set value (S40); Includes.

In the method of manufacturing the non-oriented electrical steel sheet, the step (d) (S40) is i) within the temperature range of the ideal region of ferrite and austenite, but ii) at the temperature of an arbitrary point and centered on the point. If the temperature deviation of other points within the radius having the set value of 1 exceeds the second set value, it may include determining that the scap is defective.

The method of manufacturing the non-oriented electrical steel sheet, in the temperature distribution, i) falls within the temperature range of the ideal region of ferrite and austenite, and ii) sets the temperature at an arbitrary point and a first set value centered on the point. If the temperature deviation of other points within the branch radius exceeds the second set value, a step (S50) of changing the hot rolling conditions may be further included. If either the condition i) or the condition ii) is not satisfied, a step S60 of determining that the problem resulting from the occurrence of a scap defect is negligible and performing a subsequent process can be performed. The subsequent process may include hot rolling annealing, cold rolling, and cold rolling annealing processes. Below, the subsequent process will be briefly described.

Hot rolled annealing : A step of first annealing heat treatment can be performed on hot rolled steel. The first annealing heat treatment is an APL (Annealing and Pickling Line) step of annealing and pickling a hot-rolled sheet and can be understood as a preliminary annealing treatment or a hot-rolling annealing treatment. The first annealing heat treatment step includes, for example, an annealing process in which the temperature is raised at a temperature increase rate of 20°C/s or higher, and then annealing is started at a temperature of 950 to 1100°C and maintained for 30 to 120 seconds. After annealing, the steel may be cooled at a cooling rate of 30° C./s or more. The step of pickling after cooling may be further included. After hot rolling, a hot rolled sheet annealing process is performed to ensure microstructure uniformity and cold rolling properties. The first annealing temperature is adjusted at 950 to 1100°C to form a uniform microstructure from which the stretched cast structure is removed. If the first annealing temperature is too low (less than 950℃), the stretched cast structure remaining after hot rolling may remain, causing microstructure unevenness, and grain growth may not be sufficient, resulting in small grains that may act as an obstacle to cold rolling. there is. On the other hand, if the first annealing temperature is too high, exceeding 1100°C, grains grow excessively, causing texture imbalance in the final product, causing anisotropy in properties. Pickling may be performed after the hot rolled sheet annealing process. The oxidation layer formed on the surface is removed through pickling solution and is performed before cold rolling.

Cold rolling : A step of cold rolling the first annealed heat-treated steel material is performed. The reduction rate of cold rolling is 80 to 90%, and the thickness of the steel after cold rolling may be 0.35 mm or less (strictly, 0.25 mm or less). In order to provide rolling properties, warm rolling can be performed by raising the plate temperature to 150 to 200°C.

Cold rolled annealing : The cold rolled steel may be subjected to a second annealing heat treatment. The second annealing heat treatment is the ACL (Annealing and Coating Line) step of final annealing the cold rolled sheet and can be understood as a cold rolled annealing treatment. For example, the second annealing heat treatment step includes annealing under the conditions of temperature increase rate: 10°C/s or more, annealing temperature: 850 to 1000°C, holding time: 5 to 70 seconds, and cooling rate: 20°C/s. It may include cooling under conditions above. The second annealing heat treatment is performed with the cold rolled sheet obtained after cold rolling. The temperature that derives the optimal grain size is applied considering the improvement of iron loss and mechanical properties. In cold rolling annealing, heating is performed under mixed atmosphere conditions to prevent surface oxidation and nitriding. The surface condition becomes smoother through a mixed atmosphere of nitrogen and hydrogen. If the cold rolling annealing temperature is less than 850°C, the grain size may be fine and hysteresis loss may increase, and if the cold rolling annealing temperature exceeds 1000°C, the grain size may become coarse and eddy current loss may increase. Therefore, the appropriate grain size is 90 to 160㎛.

Meanwhile, after the final cold rolling annealing, a coating process may be performed to form an insulating coating layer. By forming an insulating coating layer, punchability can be improved and insulation properties can be secured. The thickness of the insulating coating layer formed on the top and bottom of the cold rolled material may be about 1 to 2 μm.

Referring again to FIG. 1, in the method of manufacturing the non-oriented electrical steel sheet, the hot rolling conditions in the hot rolling condition changing step (S50) include hot rolling rough rolling temperature, hot rolling finishing rolling temperature, slab edge temperature, or descaling pattern conditions. can do.

Hot rolling rough rolling temperature and hot rolling finishing rolling temperature can be changed by adjusting heater arrangement, heat source intensity, coolant injection amount and spray pattern, etc. The slab edge temperature can be changed by adjusting the placement of edge heaters adjacent to the slab edge area, where the cooling rate is faster than the slab center, or the intensity of the heat source. The descaling pattern can be changed by adjusting the spray pattern or amount of high-pressure water supplied to remove scale formed on the hot-rolled steel sheet.

In the method of manufacturing the non-oriented electrical steel sheet, the first set value may be 100 mm, and the second set value may be 40°C.

In the method of manufacturing the non-oriented electrical steel sheet, the step of measuring the temperature distribution of the hot rolled steel sheet may include measuring the temperature distribution over the full length and full width of the hot rolled steel sheet.

Referring to Figure 2, the strength of a non-oriented electrical steel sheet with a high amount of silicon changes depending on the temperature. At high and low temperatures, a single phase of austenite (γ) and a single phase of ferrite (α) appear, showing the typical behavior of metallic materials in which strength increases as temperature decreases. However, in the ideal region consisting of ferrite and austenite, a unique behavior occurs in which strength decreases as temperature decreases.

In the abnormal region, a local thickening occurs at the edge of the steel plate, which coincides with the local elastic deformation region of the roll. In this state, if additional rolling is performed, it may develop into scap, etc. In the present invention, it was confirmed that scap defects were caused when rolling was performed in an abnormal area. Furthermore, it was confirmed that the greater the temperature deviation within the ideal region, the greater the intensity deviation, which increases the number and area of scabs.

The technical elements constituting the method of manufacturing a non-oriented electrical steel sheet according to the technical idea of the present invention to prevent the generation of defects are as follows.

First, avoid the abnormal temperature range. The ideal region temperature range varies depending on the composition of the steel type, and the ideal region can be confirmed through thermodynamic calculations and high-temperature physical property experiments. It is desirable to avoid abnormal areas during hot rolling as much as possible.

Second, the degree of temperature deviation during rolling is reduced. If the abnormal area section cannot be avoided, the difference between the temperature of one point of the hot rolled steel sheet and the temperature of another point within a radius of the first set value (e.g., 100 mm) centered on the one point is the second set value. It was confirmed that when the temperature exceeds (for example, 40°C), the number of scaps significantly increases and the length of scaps increases rapidly.

Table 1 measures the deviation between the temperature of one point of the hot rolled steel sheet in the area including the ideal temperature range and the temperature of other points within a radius of 100 mm centered on the one point, and shows the number of scaps and the average scap length accordingly. .

Temperature deviation (℃) Number of scabs Average scap length (mm) 0~10 - - 10~20 One 0.4 20~30 2 0.8 30~40 4 1.1 40~50 16 2 50~60 27 2.6 60~70 33 4.4 70~80 40 3.9

Referring to Table 1, when the temperature deviation was 0 to 10℃, no scap was observed, and when the temperature deviation was 10 to 20℃, the number of scaps was 1 and the average scap length was observed to be 0.4mm, and the temperature deviation was 0.4mm. When the temperature was 20 to 30℃, the number of scaps was 2 and the average scap length was observed to be 0.8mm. When the temperature deviation was 30 to 40℃, the number of scaps was 4 and the average scap length was observed to be 1.1mm. The temperature deviation was observed to be 4 and the average scap length was 1.1mm. When the temperature was 40 to 50℃, the number of scaps was 16 and the average scap length was observed to be 2mm. When the temperature deviation was 50 to 60℃, the number of scaps was 27 and the average scap length was observed to be 2.6mm, and the temperature deviation was 60. When the temperature was ~70℃, the number of scaps was 33 and the average scap length was observed to be 4.4mm. When the temperature deviation was 70~80℃, the number of scaps was 40 and the average scap length was observed to be 3.9mm.

According to this, when measuring the temperature distribution over the full length and full width of a hot rolled steel sheet, i) it falls within the temperature range of the ideal region of ferrite and austenite, ii) the temperature at any one point and 100 mm centered on that one point. It can be seen that when the temperature deviation at other points within the radius exceeds 40°C, the number of scaps significantly increases and the average scap length also significantly increases.

Figures 3 and 4 are diagrams matching the temperature distribution and scap defect distribution of a hot rolled steel sheet in the method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the invention. Figures 3 and 4 match the temperature distribution and scap defect distribution of a hot rolled steel sheet when the process conditions are different for the same steel type (see Table 2).

Si Mn Al C P S N Ti Bal. 3.35 0.21 0.8 0.0016 0.006 0.0025 0.0018 0.0039 Fe

Referring to Table 2, the composition of the non-oriented electrical steel sheet according to FIGS. 3 and 4 is silicon (Si): 0.1 to 4.0 wt%, manganese (Mn): 0.1 to 0.5 wt%, aluminum (Al): 0.3 to 0.9. Weight%, carbon (C): more than 0 and less than 0.004% by weight, phosphorus (P): more than 0 and less than 0.015% by weight, sulfur (S): more than 0 and less than 0.004% by weight, nitrogen (N): more than 0 and less than 0.004% by weight , Titanium (Ti): Satisfies more than 0 and less than 0.004% by weight and the remaining iron (Fe).

The method of manufacturing a non-oriented electrical steel sheet according to the technical idea of the present invention is not limited by the composition range of the steel sheet. However, hereinafter, an exemplary composition range will be described for understanding of the present invention.

Steel materials for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention include, for example, silicon (Si): 0.1 to 4.0 wt%, manganese (Mn): 0.1 to 0.5 wt%, aluminum (Al): 0.3 to 0.9% by weight, Carbon (C): more than 0 and less than 0.004% by weight, phosphorus (P): more than 0 and less than 0.015% by weight, sulfur (S): more than 0 and less than 0.004% by weight, nitrogen (N): more than 0 and 0.004% by weight. Weight% or less, titanium (Ti): greater than 0 and less than 0.004% by weight, and the remainder includes iron (Fe) and other unavoidable impurities.

Silicon (Si): 0.1 to 4.0% by weight

Silicon (Si) is a major added element that increases resistivity and lowers iron loss (eddy current loss). If the amount of silicon added is low, less than 0.1% by weight, it becomes difficult to obtain the desired high-frequency low core loss value, and as the amount added, the magnetic permeability and magnetic flux density decrease. Additionally, if the amount of silicon added exceeds 4.0% by weight, brittleness increases, making cold rolling difficult and productivity decreasing.

Manganese (Mn): 0.1 to 0.5% by weight

Manganese (Mn), along with silicon, increases resistivity and improves texture. If manganese is added in excess of 0.5% by weight, coarse MnS precipitates are formed and magnetic properties are deteriorated, such as reducing magnetic flux density. Furthermore, when the manganese content exceeds 0.5% by weight, the reduction in iron loss is small compared to the addition amount, but cold rolling properties are significantly reduced. Furthermore, if the manganese content is less than 0.1% by weight, fine MnS precipitates can be formed to suppress grain growth, so the composition range of manganese can be adjusted to 0.1 to 0.5% by weight.

Aluminum (Al): 0.3 to 0.9% by weight

Aluminum (Al) is a major added element that, along with silicon, increases resistivity and lowers iron loss (eddy current loss). Aluminum plays a role in reducing magnetic deviation by reducing magnetic anisotropy. Aluminum meets nitrogen and induces AlN precipitation. If the aluminum content is less than 0.3% by weight, it is difficult to expect the above-mentioned effect, and fine nitrides may be formed, which may increase the variation in magnetic properties. If the aluminum content exceeds 0.9% by weight, cold rolling properties are deteriorated, and Excessive nitride formation reduces magnetic flux density and deteriorates magnetic properties.

Carbon (C): greater than 0 and less than or equal to 0.004% by weight

Carbon (C) is an element that increases iron loss by forming carbides such as TiC and NbC. The smaller the carbon, the more desirable it is, and it is limited to 0.004% by weight or less. If the carbon content exceeds 0.004% by weight, self-aging occurs and magnetic properties are reduced, and if the carbon content is less than 0.004% by weight, the self-aging phenomenon is suppressed.

Phosphorus (P): greater than 0 and less than or equal to 0.015% by weight

Phosphorus (P) is a grain boundary segregation element that develops texture. If the phosphorus content exceeds 0.015% by weight, grain growth is suppressed due to the segregation effect, magnetic properties are deteriorated, and cold rolling properties are deteriorated.

Sulfur (S): greater than 0 and less than or equal to 0.004% by weight

Sulfur (S) increases iron loss by forming precipitates such as MnS and CuS, and suppresses grain growth, so its addition is limited to 0.004% by weight or less. If the sulfur content exceeds 0.004% by weight, the problem of increased iron loss occurs.

Nitrogen (N): greater than 0 and less than or equal to 0.004% by weight

Nitrogen (N) increases iron loss by forming precipitates such as AlN, Tin, and NbN, and suppresses grain growth, so its addition is limited to 0.004% by weight or less. If the nitrogen content exceeds 0.004% by weight, the problem of increased iron loss occurs.

Titanium (Ti): More than 0 and less than 0.004% by weight

Titanium (Ti) suppresses grain growth by forming fine precipitates such as TiC and TiN. The magnetic properties deteriorate as titanium is added, so the addition is limited to as low as possible and limited to 0.004% by weight or less. If the titanium content exceeds 0.004% by weight, the problem of magnetic properties deterioration occurs.

Again, referring to Figures 3 and 4, first, a temperature contour map (Map) was created through full-length/full-width temperature measurement. In addition, a defect map (Map) of the scab occurrence location (◆) was created and matched. For reference, in the steel plates of FIGS. 3 and 4, the horizontal direction corresponds to the full width and the vertical direction corresponds to the total length. W/S (Work Side) and D/S (Drive Side) correspond to the sides of the steel plate. The width of the steel plate is, for example, 1100 mm. The ideal range of the non-oriented electrical steel sheet having the above-described composition is 940 to 1030°C.

According to Figures 3 and 4, the sufficient conditions for scap generation according to temperature distribution are as follows.

i) It falls within the temperature range of the abnormal region of ferrite and austenite, but ii) If the difference between the temperature of any one point and the temperature of other points within a radius of 100 mm around the point exceeds 40℃, scap occurs. The possibility increases significantly.

In Figure 3, it can be seen that a large temperature deviation section on the center side occurs, causing scaping in the full-length center area, and in Figure 4, it can be seen that scaping occurs in the full-length edge area due to a rapid temperature deviation including the abnormal temperature section on the edge.

Figure 5 is a photograph taken of a scap defect on the surface of a non-oriented electrical steel sheet, and Figure 6 is a photograph taken of a scap defect on the cross section of a non-oriented electrical steel sheet.

In the conventional case, as shown in Figures 5 and 6, scaps occur widely and in large quantities. This deterioration in surface quality will lead to further decline in coating quality, increasing the possibility of adversely affecting magnetic quality, a key element of non-oriented electrical steel sheets. Through the present invention, the occurrence of scabs can be suppressed by reducing temperature deviation. According to the method for manufacturing a non-oriented electrical steel sheet according to the technical idea of the present invention, product/coating quality and production yield can be improved by reducing the amount of scap generation range.

The non-oriented electrical steel sheet implemented according to the above-described technical idea is a non-oriented electrical steel sheet implemented by sequentially applying hot rolling, hot rolling annealing, cold rolling, and cold rolling annealing processes to steel materials having a predetermined composition range, and the steel materials are hot-rolled. In the temperature distribution of a rolled hot-rolled steel sheet, i) it falls within the temperature range of the ideal region of ferrite and austenite, but ii) the temperature at one point and the temperature at another point within a radius that has a first set value centered on the one point. It is characterized in that all deviations of are less than or equal to the second set value. For example, the first set value may be 100 mm, and the second set value may be 40°C. Meanwhile, the composition range of the steel is, for example, silicon (Si): 0.1 to 4.0% by weight, manganese (Mn): 0.1 to 0.5% by weight, aluminum (Al): 0.3 to 0.9% by weight, carbon (C) : Exceeding 0 and not exceeding 0.004% by weight, Phosphorus (P): Exceeding 0 and not exceeding 0.015% by weight, Sulfur (S): Exceeding 0 and not exceeding 0.004% by weight, Nitrogen (N): Exceeding 0 and not exceeding 0.004% by weight, Titanium (Ti): 0 The composition may be in the range of 0.004% by weight or less, with the remainder consisting of iron (Fe) and other unavoidable impurities.

Although the above description focuses on the embodiments of the present invention, various changes and modifications can be made at the level of those skilled in the art. These changes and modifications can be said to belong to the present invention as long as they do not depart from the scope of the present invention. Therefore, the scope of rights of the present invention should be determined by the claims described below.

Claims (7)

(a) providing steel for non-oriented electrical steel sheets;
(b) hot rolling the steel to form a hot rolled steel sheet;
(c) measuring the temperature distribution of the hot rolled steel sheet; and
(d) In the temperature distribution, i) it falls within the temperature range of the ideal region of ferrite and austenite, but ii) the temperature at one point and the temperature at another point within a radius having a first set value centered on the one point. determining whether the deviation exceeds a second set value; Including,
Method for manufacturing non-oriented electrical steel sheet. According to claim 1,
The step (d) is i) within the temperature range of the ideal region of ferrite and austenite, but ii) the difference between the temperature at one point and the temperature at another point within a radius that has a first set value centered on the one point. If exceeds the second set value, including the step of determining that the scap is defective,
Method for manufacturing non-oriented electrical steel sheet. According to claim 1,
In the temperature distribution, i) it falls within the temperature range of the ideal region of ferrite and austenite, but ii) the difference between the temperature at any one point and the temperature at other points within a radius that has a first set value centered on the one point is Further comprising: changing the hot rolling conditions when the second set value is exceeded,
Method for manufacturing non-oriented electrical steel sheet. According to claim 3,
The hot rolling conditions include hot rolling rough rolling temperature, hot rolling finishing rolling temperature, slab edge temperature, or descaling conditions.
Method for manufacturing non-oriented electrical steel sheet. According to claim 1,
The first set value is 100 mm, and the second set value is 40 ° C.
Method for manufacturing non-oriented electrical steel sheet. According to claim 1,
The step of measuring the temperature distribution of the hot rolled steel sheet includes measuring the temperature distribution over the full length and full width of the hot rolled steel sheet,
Method for manufacturing non-oriented electrical steel sheet. Silicon (Si): 0.1 to 4.0 wt%, Manganese (Mn): 0.1 to 0.5 wt%, Aluminum (Al): 0.3 to 0.9 wt%, Carbon (C): greater than 0 to 0.004 wt% or less, phosphorus (P): Exceeding 0 and not exceeding 0.015% by weight, Sulfur (S): exceeding 0 and not exceeding 0.004% by weight, Nitrogen (N): exceeding 0 and not exceeding 0.004% by weight, Titanium (Ti): exceeding 0 and not exceeding 0.004% by weight, and the remaining iron (Fe) and others It is a non-oriented electrical steel made by sequentially applying hot rolling, hot rolling annealing, cold rolling, and cold rolling annealing processes to steel materials composed of inevitable impurities.
In the temperature distribution of the hot-rolled steel sheet obtained by hot-rolling the steel, i) within the temperature range of the ideal region of ferrite and austenite, but ii) within a radius having the temperature of an arbitrary point and a first set value centered on the point. Characterized in that all temperature deviations at different points are less than or equal to a second set value, the first set value is 100 mm, and the second set value is 40°C.
Non-oriented electrical steel sheet.