KR0180865B1 - Method for manufacturing magnetic shielding steel plate - Google Patents

Abstract

The present invention is C: 0.02-0.08% by weight, Si: 0.02% by weight or less, Mn: 0.1-0.3% by weight, S: 0.03% by weight or less, P: 0.03% by weight or less, Al: 0.01-0.06% by weight, residue Fe And low carbon steel hot rolled steel sheets of 1.6 mm-2.3 mm pickled low carbon steel composed of impurities inadequately mixed during steelmaking, and cold rolled low carbon steel hot rolled steel sheets with a high pressure reduction rate of not less than 85% by 0.20 mm- After making 0.15 ㎜ cold rolled steel sheet, spherical annealing is performed in a batch furnace, the furnace is cooled to 80-120 ° C with the outer cover of the batch furnace peeled off, and secondary cold rolling is carried out at a low rolling rate of 5-25% or less. After carrying out to obtain a target thickness value of 0.10 mm-0.15 mm, secondary spheroidizing annealing is carried out, and is slowly cooled to 450 ° C-550 ° C with the outer cover of the batch furnace covered, and the outer cover is removed to remove 80 ° C-120 ° C. The furnace is cooled to ℃, and the cold rolled steel sheet is removed from the batch furnace. W is one of the CRT magnetic shield plate manufacturing method using a low carbon steel to carry out the temper rolling at% or less. The self-shielding steel sheet using the low carbon steel has improved self-shielding effect by supplementing the self-shielding effect reduction factor by C by coarsening than the grains of Ti-added ultra-low carbon steel which usually use microstructured grains of low carbon steel. In addition, the low carbon steel has the advantages of low price, convenient supply, and smooth delivery time.

Description

Manufacturing method of self shielding steel sheet for CRT using low carbon steel

The present invention relates to a method of manufacturing a magnetic shield steel sheet, and more particularly, to a method of manufacturing a magnetic shield steel sheet for CRT using low carbon steel.

The electrons emitted from the CRT or the gun of the computer monitor cannot reach the exact position of the fluorescent surface due to the influence of the geomagnetism. The magnetic shield steel sheet blocks the effects of the geomagnetism and can reach the exact position of the fluorescent plane. To be installed. As such a magnetic shielding material, various kinds are known in the art, and various methods of manufacturing magnetic shielding steel sheets are also known.

The magnetic shielding material to be used for this is required to have a high permeability material that blocks magnetic well. As the material of the high permeability, ferromagnetic metals such as nickel, iron, and cobalt may be used. Among them, iron is the most inexpensive and easy to supply, so all the iron is used in the form of iron or iron alloy.

Such conventional self-shielding steel sheet products have a thickness of 0.3 mm or more, and the batch furnace is heat treated for 40 hours at a temperature of about 620 ° C. for spherical annealing. In this case, the reduction ratio was about 85%, so that the heat treatment was not good, and the crystal grains were not sufficiently formed, so the actual permeability was maintained at about 1300.

Currently, ultra low carbon steel and Ti-added ultra low carbon steel which have undergone decarburization annealing in an open coil furnace are used as the magnetic shielding material. The ultra low carbon steel, which has undergone the decarburization annealing process, has a high permeability and is preferable as a magnetic shielding material. However, the decarburization annealing process requires a high temperature, and in terms of productivity, compared to a general batch furnace, the manufacturing cost becomes expensive. Have Therefore, the ultra low carbon steel which has undergone the decarburization annealing process is used only as a magnetic shielding material for computer monitors requiring a high magnetic shielding effect, and the magnetic permeability for general CRTs that does not require a high magnetic shielding effect is not sufficient. Although it is lower than the ultra low carbon steel which has undergone the decarburization annealing process, the Ti-added ultra low carbon steel which is cheaper in manufacturing cost is mainly used because the decarburization process is performed in a large amount in the steelmaking process.

However, since Ti is added to the ultra-low carbon strength steelmaking process, expensive Ti is added, and thus, the raw material is more expensive than low carbon steel, and the supply and demand of raw materials is not excellent. If manufacturing a shielding material for CRT using low carbon steel, the manufacturing cost will be lower, and since the hot rolled steel which is most commonly used as a raw material for cold rolled steel is low carbon steel, supply of raw materials will be smooth and the delivery time will be accurate. This has the advantage of being.

Accordingly, an object of the present invention is to improve the reduction ratio of cold rolling and annealing conditions in a batch by a two-stage heat treatment method for spheroidization, and brown using low carbon steel having improved self-shielding effect than conventional Ti-added ultra low carbon steel. The present invention provides a method for manufacturing a conventional self-shielding steel sheet.

1 shows a spheroidizing heat treatment cycle according to the invention.

2 shows an arrangement used in the present invention.

3 is a view showing the grain size with heat treatment temperature and time according to the present invention.

In order to achieve the above object, a method for manufacturing a magnetic shielding steel sheet for a CRT using low carbon steel according to the present invention is C: 0.02 to 0.08 wt%, Si: 0.02 wt% or less, Mn: 0.1 to 0.3 wt%, S: 0.03 wt This low carbon steel is made of a low carbon steel hot rolled steel sheet composed of% or less, P: 0.03 wt% or less, Al: 0.01 to 0.06 wt% or less, residual Fe and unavoidable impurities, and having a thickness of 1.6 mm to 2.3 mm. Primary cold rolling of the hot rolled steel sheet at a high pressure reduction rate of 85% or more to form a cold steel sheet having a thickness of 0.15 mm to 0.20 mm, and the first spheroidized annealing in the batch furnace shown in FIG. 2 at 650 ° C to 700 ° C. After 5 hours to 10 hours, the step of cooling the furnace to 80 ℃ ~ 120 ℃ in the state of removing the outer cover of the batch, and performing a second cold rolling at a low pressure reduction rate of less than 5 to 25% by a target thickness value of 0.10 Obtaining the thickness of 0.1 mm to 0.15 mm, and the secondary spheroidization pool in the batch furnace. Is carried out at 700 ℃ to 800 ℃ for 10 hours to 20 hours, while slowly cooling to 450 ℃ to 550 ℃ with the outer cover of the batch furnace, and remove the outer cover to cold-rolled steel sheet to 80 ℃ ~ 120 ℃ The furnace cooling step, and the step of removing the cold rolled steel sheet in a batch furnace to perform a rough rolling of 1% or less. The heat treatment cycle of this manufacturing process is shown in FIG.

An embodiment of the present invention made as described above is as shown in the grain size according to the heat treatment temperature and time shown in FIG.

Example 1

In the first heat treatment for spherical annealing, the annealing temperature was performed at 650 ° C. for 5 hours. At this time, the growth of the crystal grains was hardly achieved, and the result was obtained when the grains were sufficiently grown for 10 hours. In addition, at a temperature of 700 ℃, the crystal grains are sufficiently grown in 5 hours, the permeability was more than 2000, but there was a problem of longer working time. Therefore, in consideration of the secondary heat treatment, it was examined to take the heat treatment time shorter while lowering the temperature.

Example 2

The annealing temperature for spheroidizing annealing was performed at 680 degreeC for 7 hours. At this time, the grain growth was adequate and the permeability was about 1700.

Example 3

After the first heat treatment for spheroidizing annealing and cooling, the second heat treatment temperature section was set again. At this time, since the section to be baked is almost disappeared during the first cooling, the temperature was changed from 700 to 10 hours and 20 hours. The proceed was divided. As a result, a sufficient permeability could be obtained in about 20 hours, but it had a long time in view of productivity.

Example 4

After the first heat treatment for spheroidizing annealing and cooling, and again the second heat treatment temperature at 800 ℃ to investigate the permeability over time, it was concluded that 10 hours is sufficient, but the burnt problem began to occur, As a result of performing it again at 750 degreeC, it turned out that 12 hours or more is enough.

Example 5

In view of the productivity and workability after Example 4 above, the results of experiments by time at the secondary heat treatment temperature of 750 ° C. for spherical annealing resulted in a good permeability over 12 hours but no significant linear effect, showing a gentle increase. there was.

Example 6

The most stable crystal grains and permeability were obtained for 7 hours at the first heat treatment temperature of 680 ℃ and 12 hours at the second heat treatment temperature of 750 ℃. The longer the heating time, the longer the grain size did not significantly progress, the heating time was only a factor of the cost increase, there was also a problem that the firing phenomenon between the coil and the coil. Of course, if the illumination is large, there is no swelling phenomenon, but stable production was difficult.

As can be seen in the above embodiment, a suitable heat treatment method is 5 to 10 hours at 650 ℃ ~ 700 ℃ for the first heat treatment for spherical annealing, and 10 to 20 at 700 ℃ ~ 800 ℃ for the second heat treatment The conclusion is that time is appropriate.

The chemical composition of the low carbon steel used in the present invention and that of the Ti-added ultra low carbon steel are compared and shown in Table 1. As can be seen from Table 1, there is no Ti component in the low carbon steel used in the present invention, and the amount of carbon (C) is 0.02 to 0.08% by weight. Therefore, low carbon steel does not require expensive Ti and does not require an additional decarburization process to reduce the amount of carbon, thereby reducing manufacturing costs and supplying raw materials because hot rolled steel, which is most commonly used as a raw material for cold rolled steel, is low carbon steel. This has the advantage of being smooth.

Table 2 shows the mechanical properties and grain sizes of the low carbon steel and the Ti-added ultra low carbon steel used in the present invention. As can be seen from Table 2, it can be seen that the grain size of the low carbon steel is larger than that of the Ti-added ultra low carbon steel.

On the other hand, C is known as a factor for reducing the self-shielding effect, in the present invention using a low carbon steel to have a higher self-shielding effect than the Ti-added ultra-low carbon steel has to compensate for this. If coarse grains of the microstructure of the low carbon steel are coarsened, the reduction of the self-shielding effect by the above-described C can be compensated, and coarse grains than the Ti-added ultra-low carbon steel can provide a better self-shielding effect.

In the present invention, a low reduction ratio of 25% or less is applied in the secondary cold rolling. This is because a certain reduction ratio gives a driving force to grow grains upon annealing, but a reduction ratio of 25% or more becomes a factor that hinders grain growth by making the initial crystals before annealing fine.

In addition, as shown in FIG. 1, in the present invention, grain growth can be promoted by slow cooling to 450 ° C to 550 ° C during the cooling of the secondary spheroidizing annealing. This is also effective in preventing a defect called a sticker caused by high temperature annealing, and removes the lowering factor of permeability by eliminating the residual stress due to the high cooling rate. Therefore, the grain size becomes coarser than that of Ti-added ultra low carbon steel by the application of low pressure drop of 25% or less during secondary cold rolling and slow cooling during secondary spheroidization. As such, by coarsening the grains of the microstructure of the low carbon steel, the self-shielding effect reduction factor by C can be compensated for, thereby improving the self-shielding effect than the Ti-added ultra low carbon steel. Table 3 compares the self-shielding effects of low carbon steels and Ti-added ultra low carbon steels. As can be seen in Table 3, the self-shielding rate of low carbon steels is improved by 1.5%.

In conclusion, in the manufacturing method according to the present invention, by applying a low reduction rate during the secondary cold rolling, and by slow cooling from 450 ℃ to 550 ℃ at the time of secondary spherical annealing, grains of low carbon steel is coarser than Ti-added ultra low carbon steel Talk can improve the self-shielding effect.

While the invention has been described so far, it is not limited thereto, and various modifications and variations can be made without departing from the spirit and scope of the invention.

Claims (1)

In the method of manufacturing a self shielding steel sheet for a CRT, C: 0.02 to 0.08 wt%, Si: 0.02 wt% or less, Mn: 0.1 to 0.3 wt%, S: 0.03 wt% or less, P: 0.03 wt% or less, Al: 0.01 The low carbon steel hot rolled steel sheet, composed of ~ 0.06% by weight, residue Fe and unavoidable impurities, and pickled low carbon steel hot rolled steel sheets having a thickness of 1.6 mm to 2.3 mm, is subjected to primary cold rolling at a high pressure drop rate of 85% or more. To form a cold rolled steel sheet having a thickness of 0.15 mm to 0.20 mm, and the first spheroidized annealing in a batch furnace at 650 ° C. to 700 ° C. for 5 hours to 10 hours, and then, after removing the outer cover of the batch furnace from 80 to 80 ° C. A step of cold-cooling to 120 ° C, secondary cold rolling at a low reduction ratio of 5 to 25% or less to obtain a cold rolled steel sheet having a target thickness of 0.10 mm to 0.15 mm, and a second nodular annealing in the batch furnace. 10 to 20 hours at ℃ ~ 800 ℃, and Cooling the cold rolled steel sheet to a temperature of 450 ° C. to 550 ° C. with the outer cover of the batch furnace and then removing the outer cover to anneal the cold rolled steel sheet to 80 ° C. to 120 ° C., and removing the cold rolled steel sheet from the batch furnace. Method for producing a magnetic shield steel sheet for a CRT, characterized in that the step of performing a temper rolling of less than 1%.