KR100328032B1 - A Method for Manufacturing Non-Oriented Ultra-Thin Gauge Sillicon Steel Sheet - Google Patents

Abstract

PURPOSE: A method for manufacturing grain oriented super thin silicon steel sheets with superior magnetic properties is provided. CONSTITUTION: In a method for manufacturing grain oriented super thin silicon steel sheet where silicon steel ingot comprising Si 0.5 to 3.0 wt.%, 0.010 wt.% or less of C, 0.002 wt.% or less of Mn, S 0.005 to 0.03 wt.%, 0.01 wt.% or less of N, 0.01 wt.% or less of Al, a balance of Fe and incidental impurities is subject to hot rolling, pickling, first cold rolling, first process annealing, second cold rolling, second process annealing, third cold rolling and final annealing, the method is characterized in that the reduction ratio in each pass in cold rolling processes is 20 to 40 %.

Description

A Method for Manufacturing Non-Oriented Ultra-Thin Gauge Sillicon Steel Sheet}

The present invention relates to a method for producing non-oriented silicon steel sheet used as an iron core material such as a generator, an electric motor, and more particularly, to a method for producing an ultra-thin non-oriented silicon steel sheet having a thickness of 150 µm or less with excellent magnetic properties.

Non-oriented silicon steel sheets mainly used as iron cores in rotating machines such as large turbine generators and electric motors have a decisive influence on the characteristics of these devices. Therefore, the development of non-oriented silicon steel sheet having excellent magnetic properties is important not only in improving the characteristics of these devices but also in terms of energy saving.

As the non-oriented silicon steel sheet is used as the iron core material of the rotor, the direction of the magnetic field applied during use is changed. Therefore, it is important that the non-oriented silicon steel sheet having excellent magnetic properties not only have low iron loss but also have as little magnetic properties as possible in the rolling direction and the rolling vertical direction.

As a method of improving the magnetic properties of non-oriented silicon steel sheet, Japanese Laid-Open Patent Publication No. Hei 1-19171 discloses that a hot rolled sheet is annealed at a reheating temperature of more than 700 ° C. and then cold rolled at a rate of 3-15%. After annealing again, annealing at 700-800 ℃ and cold rolling. Then, the cold rolled sheet is annealed again at a temperature of reheating temperature of more than 800 ℃ and then subjected to 3-15% skin pass to increase the size of the recrystallized grain to improve the magnetic properties. However, this method is disadvantageous in that the reheating annealing and skin pass process are imposed compared to the existing manufacturing process, resulting in higher production cost, and only applied to silicon steel having a Si content of less than 2.0%.

Further, in Japanese Patent Publication No. 58-34531, the hot rolled plate is annealed at 900-1000 ° C. for 1-7 minutes, followed by pickling and cold rolling. Thereafter, annealing at 950-1100 ° C. for 1-5 minutes has been suggested to improve the magnetic properties by lowering the contents of impurities, particularly carbon, nitrogen and sulfur, in the steel. However, this method also has a disadvantage in that the manufacturing cost increases as the annealing process is imposed.

In addition, Japanese Patent Laid-Open No. 5-299261 discloses a method of improving the magnetic properties by thinning the thickness of a silicon steel sheet to 20-50 µm. In other words, the existing oriented and non-oriented silicon steel sheet is used as a starting material, and after removing the insulating film on the surface, ultra-thin non-oriented silicon steel having excellent magnetic properties with a thickness of 20-50 μm by the process of rolling, recrystallization annealing, and coating the insulating film. Prepared. However, the ultra-thin non-oriented silicon steel sheet manufactured by this method has excellent magnetic properties, but it is manufactured by repeating the process of removing the insulating film and applying it again as a starting material using expensive finished oriented and non-oriented silicon steel sheet. Has the disadvantage of being high.

In addition, Japanese Laid-Open Patent Application No. 5-186829 and the method for producing ultra-thin silicon steel sheets having a thickness of 150 µm or less through a sequential process of hot rolling, cold rolling, intermediate annealing, and final annealing using slabs made of the melt casting method as starting materials. Japanese Patent Application Laid-Open No. 5-186830. In Japanese Patent Laid-Open No. 5-186829, the hot rolled sheet is first cold rolled at 30-85% rolling rate, intermediately annealed, second cold rolled at 40-80% rolling rate, and 50-75% rolled rate after intermediate annealed 3 Three-stage cold rolling method for cold rolling is applied, and in Japanese Patent Laid-Open No. 5-186830, the first hot rolling of the hot rolled sheet at a rolling rate of 40% or more, and the second cold rolling at 50-80% rolling rate after the intermediate annealing. The two-stage cold rolling method is applied. However, these two methods cannot be applied to non-oriented ultra-thin silicon steel as a method for producing oriented ultra-thin silicon steel sheet.

In the present invention, in manufacturing non-oriented silicon steel sheet, the third cold rolling method or the second cold rolling method for producing the oriented ultra-thin silicon steel sheet is applied, and in this case, all cold rolling conditions in the third cold rolling method or the second cold rolling method are appropriately controlled. It is an object of the present invention to provide a method for producing a non-oriented silicon steel sheet having excellent magnetic properties and having an ultra-thin thickness of 150 μm or less.

The present inventors made the slab by melt casting method, followed by the hot rolling, cold rolling and intermediate annealing, the final cold rolling, and the final annealing to manufacture the ultrathin non-oriented silicon steel sheet having a thickness of 150 μm or less in terms of process cost. In addition, in the three-stage cold rolling method and the two-stage cold rolling method, which are methods for manufacturing the grain-oriented ultra-thin silicon steel sheet, by appropriately adjusting the rolling rate per pass (hereinafter referred to as "rolling speed") during cold rolling It has been found that non-oriented silicon steel sheet having excellent magnetic properties can be produced.

Starting from the above point of view, the present invention is Si: 0.5-3.0% by weight, C: 0.010% or less, Mn: 0.002% or less, S: 0.005-0.03% or less, N: 0.01% or less, Al: 0.01 Silicon steel ingots consisting of% or less, balance Fe and other unavoidable impurities are hot rolled, pickled, primary cold rolled, primary intermediate annealing, secondary cold rolling, secondary intermediate annealing, tertiary cold rolling and final annealing. To produce ultra-thin silicon steel sheet by performing the continuous process by the secondary cold rolling method followed by the third cold rolling method followed by hot rolling, pickling, the first cold rolling, the first intermediate annealing, the second cold rolling and the final annealing. The method relates to a method for producing a non-oriented ultrathin silicon steel sheet having a rolling ratio (rolling speed) per pass during the first, second and third cold rolling in the range of 20-40%.

Hereinafter, the present invention will be described in more detail.

The present invention in terms of weight percent Si: 0.5-3.0%, C: 0.010% or less, Mn: 0.002% or less, S: 0.005- 0.03%, N: 0.01% or less, Al: 0.01% or less, residual Fe and other unavoidable impurities Hot-rolled, pickled silicon steel consisting of hot rolling, primary cold rolling, primary intermediate annealing, secondary cold rolling, secondary intermediate annealing, tertiary cold rolling and final annealing The primary cold rolling, primary intermediate annealing, secondary cold rolling and final annealing are applied.

At this time, all the cold rolling is carried out at a rolling rate (rolling speed) per pass of 20-40% to obtain excellent magnetic properties. In the specimen with a low rolling speed, the magnetic properties deteriorate, and rolling at too high a rolling speed requires a special rolling machine, which increases production costs. This phenomenon can be explained as follows. In other words, in the cold rolling, the tensile stress is applied in the cold rolling direction, and the compressive stress is applied in the direction perpendicular to the surface of the specimen. Therefore, if the rolling speed is lower than 20%, it can be seen that the compressive stress is lowered in the direction perpendicular to the surface of the specimen. By the way, the silicon steel having a body-centered cubic structure has a series structure in which the (100) surface is parallel to the rolling surface and the direction is parallel to the rolling direction when the cold rolling is performed, and the surface is rotated about an axis. This means that cold rolling will gradually eliminate the existing (110) [001] tissue. In other words, if the rolling speed is lower than 20%, the compressive stress component becomes smaller, and accordingly, the (110) [001] nucleus remains in the steel, so that the characteristics of the non-oriented silicon steel are rather developed due to the development of the final annealing (110) [001]. It seems to be worse. Therefore, in the present invention, by rolling at a rolling speed of 20-40% during cold rolling, excellent magnetic properties are obtained in terms of non-oriented silicon steel sheet.

Hereinafter, an Example is given and this invention is demonstrated in detail.

Example

Invention Example 1

Si: 2.93% by weight, C: 0.007%, Mn: 0.001%, S: 0.001%, N: 0.001%, Al: 0.001% After rolling, a hot rolled sheet having a thickness of 2.5 mm was made, followed by pickling to remove surface oxides. Thereafter, primary cold rolling was performed at a rolling rate of 75% and a rolling rate (rolling speed) of 20% per pass, followed by a first intermediate annealing treatment at 800 ° C. for 30 minutes at a vacuum atmosphere of 5 × 10 ⁴ torr. Secondary cold rolling was performed at a rolling rate of 60% and a rolling rate per roll (rolling speed) of 20%, followed by secondary intermediate annealing for 30 minutes at 800 ° C. in a vacuum atmosphere of 5 × 10 ⁴ torr. Thereafter, cold rolling was performed at a rolling rate of 60% and a rolling rate (rolling speed) of 20% per third pass. The third cold rolled sheet was subjected to a final annealing treatment at 1200 ° C. for 1 hour in a vacuum atmosphere of 5 × 10 ⁴ torr to prepare an ultrathin silicon steel sheet having a thickness of 100 μm. Fragment to a magnetic measurement using a measuring instrument ₅₀ and the B W _15/50 of a very thin silicon steel plate, and obtaining a ratio (B _50⊥ / B _50∥) in the rolling direction and rolling in the vertical direction B _50, a result table 1 is shown.

Invention Example 2

Si: 2.04% by weight, C: 0.007%, Mn: 0.001%, S: 0.001%, N ₂ : 0.001%, Al: 0.001%, after the silicon steel ingot having the balance of Fe was maintained at 1200 ° C for 1 hour. After hot rolling, a hot rolled sheet having a thickness of 2.4 mm was made and then pickled to remove surface oxides. Thereafter, primary cold rolling was performed at a rolling rate of 50% and a rolling rate (rolling speed) of 30% per pass, followed by a first intermediate annealing treatment at 800 ° C. for 30 minutes at a vacuum atmosphere of 5 × 10 ⁴ torr. After cold rolling at 60% of rolling rate and 30% of rolling rate (rolling speed) per pass, secondary intermediate annealing was performed for 30 minutes at 800 ° C. in a vacuum atmosphere of 5 × 10 ⁴ torr. After the third cold rolling at 79% of rolling rate and 30% of rolling rate per pass (rolling speed), ultra-thin silicon having a thickness of 100 μm by vacuum annealing at 5 × 10 ⁴ torr and final annealing at 1200 ° C. for 1 hour. Steel sheet was prepared. Measure the B ₅₀ and W _15/50 of this ultra-thin silicon steel sheet using a fragment _magnetometer , calculate the _ratio of B ₅₀ (B _{50 과} / B _{50 ∥} ) between the rolling direction and the rolling vertical direction. Indicated.

Invention Example 3

Si: 0.52%, C: 0.007%, Mn: 0.001%, S: 0.001%, N: 0.001%, Al: 0.001% by weight in a silicon steel ingot having a composition of the balance Fe held at 1200 ° C. for 1 hour and then hot After rolling, a 1.5 mm thick hot rolled sheet was made, followed by pickling to remove surface oxides. Thereafter, primary cold rolling was performed at a rolling rate of 80% and a rolling rate (rolling speed) of 30% per pass, followed by a first intermediate annealing treatment at 800 ° C. for 30 minutes at a vacuum atmosphere of 5 × 10 ⁴ torr. After the second cold rolling at 67% of rolling rate and 30% of rolling rate per pass (rolling speed), ultra-thin silicon having a thickness of 100 μm by vacuum annealing at 5 × 10 ^-4 torr and final annealing at 1200 ° C. for 1 hour. Steel sheet was prepared. Using short magnetic measuring devices measure the B ₅₀ and W _15/50 of the ultra-thin silicon steel plate, and obtaining a ratio of a rolling direction and rolling in the vertical direction B _50, it is shown in Table 1. The results.

Invention Example 4

Si: 2.93% by weight, C: 0.007%, Mn: 0.001%, S: 0.001%, N: 0.001%, Al: 0.001% After rolling, a 1.5 mm thick hot rolled sheet was made, followed by pickling to remove surface oxides. Thereafter, primary cold rolling was performed at a rolling rate of 80% and a rolling rate (rolling speed) of 40% per pass, followed by a primary intermediate annealing treatment at 5 × 10 ⁴ torr in a vacuum atmosphere at 800 ° C. for 30 minutes. After the second cold rolling at 67% of rolling rate and 40% of rolling rate per roll (rolling speed), ultra-thin silicon steel sheet having a thickness of 100 μm by vacuum annealing at 5 × 10 ⁴ torr and final annealing at 1200 ° C. for 1 hour Was prepared. Using short magnetic measuring devices measure the B ₅₀ and W _15/50 of the ultra-thin silicon steel plate, and obtaining a ratio of a rolling direction and rolling in the vertical direction B _50, it is shown in Table 1. The results.

(Comparative Example)

Si: 2.93% by weight, C: 0.007% or less, Mn: 0.001% or less, S: 0.001%, N: 0.001%, Al: 0.001% or less, silicon steel ingot having a composition of the balance Fe at 1 hour at 1200 ° C After holding, hot rolling was performed to make a hot rolled sheet having a thickness of 2.5 mm, followed by pickling to remove surface oxides. Thereafter, primary cold rolling was performed at a rolling rate of 75% and a rolling rate (rolling speed) of 10% per pass, followed by a first intermediate annealing treatment at 800 ° C. for 30 minutes at a vacuum atmosphere of 5 × 10 ⁴ torr. Thereafter, secondary cold rolling was performed at a rolling rate of 60% and a rolling rate per roll (rolling speed) of 10%, followed by a secondary intermediate annealing treatment at 5 ° C 10 ⁴ torr in a vacuum atmosphere at 800 ° C for 30 minutes. Thereafter, cold rolling was performed at a rolling rate of 60% and a rolling rate (rolling speed) of 10% per third pass. The third cold rolled sheet was subjected to a final annealing treatment at 1200 ° C. for 1 hour in a vacuum atmosphere of 5 × 10 ⁴ torr to prepare an ultra-thin silicon steel sheet having a thickness of 100 μm. Using short magnetic measuring devices measure the B ₅₀ and W _15/50 of the ultra-thin silicon steel plate, and obtaining a ratio of a rolling direction and rolling in the vertical direction B _50, it is shown in Table 1. The results.

Self-characteristics B ₅₀ (T) W _15/50 (W / kg) B _50⊥ / B _50∥ Inventive Example 1 invention example 2 invention example 3 invention example 4 Comparative Example 1.831.801.911.791.93 2.352.522.742.623.53 0.980.950.960.930.75

As can be seen in Table 1, in the case of Inventive Example (1-4) that satisfies the conditions of the present invention showed excellent magnetic properties, on the contrary, in the case of Comparative Examples outside the conditions of the present invention, the magnetic properties. It fell short of this invention example (1-4).

As described above, according to the present invention, by applying a third cold rolling method or a second cold rolling method, which is a method for producing a grain-oriented silicon steel sheet, by controlling the rolling rate per pass during cold rolling, non-oriented ultra-thin silicon having excellent magnetic properties The effect of obtaining a steel sheet is provided.

Claims (2)

Silicon by weight: Si: 0.5-3.0%, C: 0.010% or less, Mn: 0.002% or less, S: 0.005-0.03%, N: 0.01% or less, Al: 0.01% or less, balance Fe and other unavoidable impurities The steel ingot is subjected to a continuous process by the third cold rolling method followed by hot rolling, pickling, first cold rolling, first intermediate annealing, second cold rolling, second intermediate annealing, third cold rolling and final annealing. In the method for producing ultra-thin silicon steel sheet, Method for producing a non-oriented ultra-thin silicon steel sheet, characterized in that the rolling rate per pass during the first, second and third cold rolling range of 20-40%. Silicon by weight: Si: 0.5-3.0%, C: 0.010% or less, Mn: 0.002% or less, S: 0.005-0.03%, N: 0.01% or less, Al: 0.01% or less, balance Fe and other unavoidable impurities In the method for producing ultra-thin silicon steel sheet by performing a continuous process by the secondary cold rolling method leading to the hot ingot, pickling, primary cold rolling, primary intermediate annealing, secondary cold rolling and final annealing , Method for producing a non-oriented ultra-thin silicon steel sheet, characterized in that the rolling rate per pass during the first and second cold rolling is in the range of 20-40%.