KR20010062883A - A method for manufacturing grain oriented steel sheet with high magnetic induction - Google Patents

Abstract

The present invention relates to a method for producing a grain-oriented electrical steel sheet, by controlling the amount of nitrogen after the simultaneous decarbonation treatment method for producing a high magnetic flux density grain-oriented electrical steel sheet with a magnetic flux density of 1.92 Tesla or more, iron loss 1.05 W / Kg or less The purpose is to provide.

In the present invention, C: 0.06 to 0.07%, Si: 3.10 to 3.25%, Mn: 0.074 to 0.087%, S: 0.013 to 0.024%, Sol.Al: 0.025 to 0.030%, N: 0.0075 to 0.0090%, In the method of manufacturing a grain-oriented electrical steel sheet comprising re-heating the silicon steel slab consisting of the balance Fe and unavoidable impurities at 1370 ℃ or more, followed by hot rolling, hot roll annealing, and then cold rolling, decarbon annealing and final high temperature annealing. ,

The weight ratio of [Al] / [N] is at least 3.4; and

In the decarbonization annealing process, a high magnetic flux density oriented electrical steel sheet manufacturing method characterized by simultaneous decarbonation treatment so that the amount of nitrogen after annealing is 110 to 120 ppm is a technical gist of the present invention.

Description

Method of manufacturing high magnetic flux density oriented electrical steel sheet {A METHOD FOR MANUFACTURING GRAIN ORIENTED STEEL SHEET WITH HIGH MAGNETIC INDUCTION}

The present invention relates to a method for producing a grain-oriented electrical steel sheet used as a core material of transformers, generators and other electrical appliances, and more particularly, to a high magnetic flux density oriented electrical steel sheet by strengthening the inhibitor in the simultaneous annealing and intermediate annealing process It relates to a method of manufacturing.

Oriented electrical steel is mainly used as iron core material for transformers, generators and other electrical appliances, and should have good magnetic properties, especially iron loss characteristics.

A grain-oriented electrical steel sheet is a material having a so-called "Goss orientation" having a [001] axis on the (110) plane in the rolling direction. Typically, a grain-oriented electrical steel sheet is a (110) [001] primary recrystallized grain through a rolling process. By selectively growing the to secure a goth organization effective for magnetism.

In this manufacturing technique, precipitates (hereinafter referred to as Inhobitor) are finely and uniformly dispersed in the cavity to suppress coarse growth of primary recrystallized grains before the start of secondary recrystallization, and selectively grow only (110) [001]. It is very important.

Conventionally, the Goss structure is secured mainly by adding S to MnS precipitates. In recent years, Al is newly added to increase the degree of integration of the Goss structure. Al combines with N in the steel sheet to form a dispersed phase with AlN and suppresses the growth of primary recrystallization, and plays a role of making secondary recrystallization with high density. A oriented electrical steel sheet which obtains a high density of goth orientation using AlN and MnS is generally referred to as a high magnetic flux density oriented electrical steel sheet.

This technology was first disclosed by US Patent Nos. 3287183 and 3636579, after which a number of techniques for manufacturing high magnetic flux density oriented electrical steel were published. Although some Al is not added, such as a technique of adding Se and adding Sb to it, or a technique in which Cu, Sn, etc. are contained in steel, it is common to use Al and Mn coexisting in the actual industry. .

The normal action in the case of using Al and Mn as inhibitors is as follows. Al and Mn, respectively, are AlN and MnS, which precipitate at the grain boundaries of the primary recrystallization and suppress the movement of the grain boundaries until the start of the secondary recrystallization during the high temperature annealing process, thereby enabling the secondary recrystallization to be appropriately sized. This precipitated particle needs to be as small as possible in order to effectively suppress primary recrystallization. Therefore, slabs made in steelmaking should be heated for a long time at high temperature of 1370 ℃ in order to solidify AlN and MnS in the furnace of hot rolling process, and finish rolling in high temperature for a short time so as not to precipitate as much as possible during rolling. In the subsequent hot-rolled sheet annealing process, it is necessary to precipitate MnS and AlN to form an effective precipitated dispersed phase. However, if this condition is deviated, for example, if the reheating temperature is too low, the incompletely employed inhibitor will coarsen with hot rolling, or a significant amount of inhibitor will precipitate and grow before finishing the rolling, and thus, In the case of abnormal growth of the material or an inappropriate amount of inhibitor, the restraining force is weakened, and the secondary recrystallization is inferior, and thus, it is impossible to manufacture a oriented electrical steel sheet having high magnetic flux density, especially iron loss.

While trying to solve the above problems, the present inventors reinforce the precipitates in the appropriate place during the manufacturing process to stabilize the high-strength oriented electrical steel sheets with a magnetic flux density of 1.92 Tesla or more and iron loss of 1.05 W / Kg or less even in the existing abnormal materials. I came to realize that it can be produced with This method is performed by nitriding treatment as shown in Japanese Patent Laid-Open No. Hei 1-230721 and Japanese Patent Laid-Open No. Hei 1-283324. The nitriding method includes applying an annealing separator containing a nitriding compound to a steel sheet, incorporating a nitriding gas into the atmosphere gas during the elevated temperature of the high temperature annealing process, or applying the steel sheet in a gas atmosphere capable of nitriding in a decarburization process. There is nitriding.

All the above methods use a method of diffusing nitrogen generated by ammonia decomposition at about 500 ° C. or more by nitriding with ammonia gas into the steel sheet. This is because the nitride formed by reacting with nitrogen, which is already present in the steel, enters the steel sheet and serves as an inhibitor.

However, when the nitriding treatment is usually performed on a high temperature material heating material, the magnetic tends to be inferior. This is because the precipitates, which are already stably formed, act in the direction of weakening the inhibitor's inhibitory power such as being coarse in a nitrogen atmosphere generated by decomposition in ammonia.

Accordingly, the present inventors have conducted research and experiments to solve the above problems, and when the abnormal material having a low content of calcined nitrogen is nitrided under specific conditions, it is found that the magnetic properties are rather improved, contrary to the general tendency, and the present invention. The present invention provides a high magnetic flux density oriented electrical steel sheet having a magnetic flux density of 1.92 Tesla or more and an iron loss of 1.05 W / Kg or less by controlling the weight ratio of [Al] / [N] and the amount of nitrogen after co-denitrification. It is an object of the present invention to provide a method which can be manufactured.

In the present invention, C: 0.06 to 0.07%, Si: 3.10 to 3.25%, Mn: 0.074 to 0.087%, S: 0.013 to 0.024%, Sol.Al: 0.025 to 0.030%, N: 0.0075 to 0.0090%, In the method of manufacturing a grain-oriented electrical steel sheet comprising re-heating the silicon steel slab consisting of the balance Fe and unavoidable impurities at 1370 ℃ or more, followed by hot rolling, hot roll annealing, and then cold rolling, decarbon annealing and final high temperature annealing. ,

The weight ratio of [Al] / [N] is 3.4 or more; and

The decarbonization annealing process relates to a high magnetic flux density oriented electrical steel sheet manufacturing method characterized by simultaneous decarbonation treatment so that the nitrogen after the annealing is 110 ~ 120ppm.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the present invention, the above-described conventional steel components are characterized in that N≤0.0090%, the sol.Al/N ratio is controlled to 0.34 or more, and decarbonized annealing is carried out so that the nitrogen content is 110 to 120 ppm after annealing.

In other words, in order to have an appropriate inhibitory strength, an inhibitor such as AlN or MnS should be precipitated in an appropriate size and amount. For proper precipitation of AlN, Al and N should be uniformly distributed in the steel in an appropriate amount and ratio. If the amount of Al to precipitate an appropriate amount of AlN is sufficient, but the amount of Al is relatively insufficient, the amount of AlN precipitation is insufficient, and thus the inhibitory power is weakened, resulting in magnetic inferiority. As a result, in order to precipitate sufficient inhibitor, N must be replenished in steel so that residual Al can precipitate with AlN. In the present invention, nitrogen generated by decomposition of ammonia introduced into the furnace at high temperature was used.

In the decarbonization annealing step, 0.2 to 0.5% NH ₃ is preferably 0.3 to 0.4 Nm ₃ / Hr, and the simultaneous decarbonation treatment is performed such that the nitrogen content is 110 to 120 ppm after annealing.

In addition, the reason why the denitration of the decarbonized plate is 110 to 120 ppm is appropriate. If the amount of nitriding is too small, the supplementary role of the inhibitor cannot be expected. Because you will not be able to.

Hereinafter, the present invention will be described in detail through examples.

Example 1

After reheating the silicon steel slab prepared as shown in Table 1 at 1370 ℃ hot rolled to 2.3mm thickness, the hot rolled sheet was pre-annealed at 1115 ℃ and cold rolled to 0.30mm thickness.

The produced cold rolled plate was subjected to co-denitrification in an atmosphere containing 0.6 Nm ₃ / Hr of a mixed gas of 25% H ₂ + 75% N _{2 having} a dew point of 48 ° C. and a dry 0.5% NH ₃ in a furnace maintained at 845 ° C.

Thereafter, MgO, an annealing separator, was applied to the steel sheet for final high temperature annealing. The hot annealing was heated to 1,195 ° C. at a temperature of 15 ° C./Hr at a rate of 15 ° C./Hr at 25% N ₂ + 75% H ₂ , and reached 100% after 1,195 ° C. It was kept for 25 hours in a% H ₂ atmosphere.

Then, the magnetic properties of the steel sheet according to the change of the steel component and the amount of nitride were investigated, and the results are shown in Table 1 below.

Magnetic properties were measured for the iron loss value (W _17/50) was measured under a magnetic flux density (B ₁₀₎ and 1.7Tesla, 50Hz induced in the specimen under a magnetic field of 1,000A / m.

division Sting Nitriding amount (ppm) Chemical composition (wt%) Al / N Magnetic properties C Si Mn S sol.Al N Magnetic flux density (Tesla) Iron loss (W / kg) Comparative Material 1 × － 0.062 3.22 0.078 0.016 0.027 0.0075 3.6 1.851 1.178 Comparative Material 2 0.062 3.19 0.076 0.014 0.028 0.0078 3.6 1.860 1.165 Comparative Material 3 0.060 3.24 0.074 0.014 0.028 0.0076 3.7 1.840 1.275 Comparative Material 4 － 0.067 3.21 0.080 0.016 0.028 0.0080 3.5 1.890 1.066 Comparative Material 5 ○ 117 0.063 3.24 0.074 0.024 0.024 0.0090 2.6 1.860 1.255 Comparative Material 6 151 0.060 3.24 0.074 0.013 0.028 0.0076 3.7 1.885 1.090 Comparative Material7 131 0.063 3.16 0.084 0.014 0.027 0.0075 3.6 1.875 1.220 Invention 1 114 0.062 3.19 0.076 0.028 0.0078 3.6 1.930 1.010 Invention 2 110 0.062 3.19 0.076 0.0078 3.6 1.940 0.995 Invention 3 120 0.060 3.24 0.074 0.0076 3.7 1.921 1.030 Invention 4 120 0.067 3.21 0.080 0.016 0.0080 3.5 1.930 1.025

As shown in Table 1, the comparative materials (6), (7) is a case of excessive nitriding resulted in a significant decrease in iron loss, and the result of measuring the crystal grains of the final hot-annealed plate is also coarse grain size of about 2cm It was confirmed that it is. In other words, the over-loaded nitrides are clustered, which results in the loss of their ability as inhibitors, resulting in secondary recrystallization in the initial stages of high temperature annealing, whereby grains have grown beyond their proper size.

Although the comparative material 5 was nitrided in an appropriate amount, the Al / N ratio was small, indicating that the magnetism was deteriorated due to the adverse effect as described above because the inhibitor had already been formed in the AP plate.

On the other hand, in the case of the invention materials (1) to (4), N contained 80 ppm, and the steel was low in nitrogen. Therefore, under normal conditions, the secondary recrystallization was unstable because an adequate amount of precipitates could not be produced. Unable to obtain a satisfactory magnetic quality, the application of the present invention was confirmed to significantly improve the magnetism.

As described above, according to the present invention, by appropriately controlling the amount of nitrogen during the decarbonization annealing, the magnetic flux density of 1.92 Tesla or more and iron loss of 1.05 W / Kg or less have the effect of producing a high magnetic flux density oriented electrical steel sheet having excellent magnetic properties. .

Claims (1)

C: 0.06 to 0.07%, Si: 3.10 to 3.25%, Mn: 0.074 to 0.087%, S: 0.013 to 0.024%, Sol.Al: 0.025 to 0.030%, N: 0.0075 to 0.0090%, balance Fe and In the method for producing a grain-oriented electrical steel sheet comprising re-heating a silicon steel slab made of unavoidable impurities at 1370 ℃ or more, followed by hot rolling and hot roll annealing, followed by cold rolling, decarbonization annealing and final high temperature annealing. The weight ratio of [Al] / [N] is at least 3.4; and In the decarbonization annealing process, a high magnetic flux density oriented electrical steel sheet manufacturing method characterized by simultaneous decarbonation treatment so that the nitrogen content is 110 to 120 ppm after annealing.