KR20000039448A - Method for decarbon-annealing cold rolled steel for use of shadow mask - Google Patents

Abstract

PURPOSE: A method for decarbon-annealing a cold rolled steel sheet for use of a shadow mask is provided to effectively operate a decarbonizing annealing by adjusting hydrogen density, a dew point temperature, and an annealing temperature. CONSTITUTION: A cold rolled steel sheet contains carbon for 0.001-0.003wt% of entire weight. The cold rolled steel sheet is low temperature annealed at a temperature of under 750°C while adjusting a dew point temperature for -20°C in a nitrogen and hydrogen atmosphere. Then, the steel sheet is high temperature annealed at the temperature of 750-800°C while adjusting the dew point temperature for 30-50°C in the nitrogen and hydrogen atmosphere. Herein, the hydrogen density is 3-10% for the low temperature annealing and 15-20% for the high temperature annealing.

Description

Decarbonization annealing method of cold rolled steel sheet for shadow mask

The present invention relates to a decarbonization annealing method of a cold rolled steel sheet for a shadow mask used in a brown tube of a TV, and more particularly, a shadow that can prevent oxidation of a material surface and improve decarburization performance. It is related with the decarbonization method of the cold rolled steel sheet for masks.

As shown in FIG. 1, the CRT of the TV is provided with an inner shield 4 and a shadow mask 6 fixed to the deflection coil 3 and the frame 5, and a fluorescent screen 7 mounted on the front surface thereof. In structure, the shadow mask 6 makes the electron beam 2 exiting the electron gun 1 into a uniform round shape so that when the electrons react with Phosphorous on the glass surface of the brown tube fluorescent screen 7, It works to make the image look good.

Due to this action, a shadow mask 6 is provided inside many CRTs currently used.

The CRT manufacturer produces a carbon mask cold rolled steel sheet as a final product by decarbonization annealing, and briefly describes the manufacture and subsequent processes of the cold rolled steel sheet for the shadow mask, as shown in FIG. In the etching industry, cold rolled steel sheets manufactured by hot rolling, pickling and primary cold rolling, electrolytic cleaning, decarbonization annealing, secondary cold rolling, and leveling after temper rolling are degreased, washed, coated with photo-resist, dried, When the material is manufactured through the process of blasting, developing and film hardening, etching, photoresist stripping and inspection, CRT manufacturers decarbonize the material processed by the etching company, roller leveling, press forming, In order to manufacture masks, color CRTs are manufactured by surface blackening, inspection, welding assembly and inspection.

As described above, the final decarbonization method of the cold rolled steel sheet for the shadow mask is currently deposited by a CRT manufacturer in a gas atmosphere containing 25% hydrogen, nitrogen, and vapor (dew point temperature: -15 ° C) in a furnace atmosphere of about 780 ° C. It is carried out by decarburizing by passing through a shadow mask material for about 10 minutes.

In Japanese Patent No. 86-276805, which is a conventionally known technique related to such decarbonization, heat treatment is performed at 650 to 750 ° C. in an atmosphere having a dew point temperature of 30 ° C. or higher, and then adjusted to a maximum of 2000 ppm of carbon monoxide at about 550 ° C. or lower.

Influence of Annealing Atmosphere on Mechanical Properties of Extra Low Carbon Aluminum- In the Japanese paper entitled Killed steel used as Materials of Shadow Mask (Nishin Steel Technical Report, Vol. 48, 1983, June), CO + CO ₂ is 1 ppm, the concentration of hydrogen is 1-5%, Dew point temperature below 0 ℃ shows the possibility of carburization.

However, the technique disclosed in the above-mentioned Japanese patent makes it difficult to effectively heat treatment by setting the maximum value of the heat treatment temperature to 750 ° C., and it is possible to regulate the maximum value of carbon monoxide below 550 ° C., but this is not measured by the general industry.

The Japanese paper does not disclose effective decarburization conditions.

The present invention has been made in order to solve the problems of the prior art described above, and an object thereof is to provide a decarbonization annealing method of a cold rolled steel sheet for a shadow mask which performs decarburization annealing effectively by adjusting hydrogen concentration, dew point temperature, and annealing temperature.

1 is a view schematically showing the structure of a CRT;

Figure 2 is a view showing the manufacturing and post-treatment process of the cold rolled steel sheet for the shadow mask.

<Explanation of symbols for main parts of drawing>

1: electron gun 2: electron beam 3: deflection coil

4: internal shield 5: frame 6: shadow mask

7: fluorescent screen

In the decarburization method of the cold rolled steel sheet for shadow mask of the present invention for achieving the above object, in the final decarbonization to produce a cold rolled steel sheet having a carbon content of 0.001 to 0.003% by weight as a shadow mask, nitrogen at less than 750 ℃ And low temperature annealing at a dew point temperature of -20 ° C in a hydrogen atmosphere, and then high temperature annealing at a nitrogen dew point temperature of 30 to 50 ° C at a temperature of 750 to 800 ° C.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments.

Steel composition of less than 0.003% by weight of carbon is used as the composition of the steel, because the carbon content of longer than the decarburization annealing takes a long time, at a carbon concentration of less than 0.0010% by weight is too much cost in the steelmaking process.

In the iron decarburization reaction, it is important that iron is deoxidized without being oxidized. In order to prevent oxidation, it is necessary to lower the dew point, but in order for decarburization to occur, it is necessary to lower the hydrogen partial pressure and raise the dew point temperature.

In general, the oxidation of iron is oxidized to Fe ₃ O ₄ even at very low oxygen partial pressures below 750 ℃. For effective decarburization, below 750 ℃, the dew point temperature is sufficiently lowered below -20 ℃ (the dew point temperature from general liquid nitrogen). Annealing is carried out by suppressing oxidation at a temperature of, and annealing is performed by adjusting the dew point temperature to 30 to 50 ° C. in the range of 750 to 800 ° C., so that decarburization can be effectively performed without oxidation.

After that, annealing is further performed at 750 ° C. or lower by adjusting the dew point temperature to −20 ° C. or lower.

In the present invention, the decarburization annealing atmosphere is a nitrogen and hydrogen gas atmosphere, and the hydrogen concentration is 3 to 10% when annealing at a temperature of less than 750 ° C, and 15 to 20% when annealing at 750 to 800 ° C. It is preferable.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example

The shadow mask material used in the present invention used was 0.0025 wt% carbon and 0.22 mm thick.

The hydrogen concentration in the decarburization treatment atmosphere was 10% and 20%.

Pretreatment time is 2 minutes up to 750 ℃, decarbonized annealing is maintained for 10 minutes at 750 ~ 800 ℃, then cooled to 750 ℃ or less for 2 minutes to lower to room temperature. As a result, the change in yield point elongation is shown in Table 1.

At this time, in the case of the invention material, the conditions at the time of pretreatment and post-treatment were N ₂ -10% H ₂ , and in the case of the prior art, the gas atmosphere conditions of the pretreatment and the post-treatment were the same as the decarburized atmosphere gas.

Although there is no surface oxidation, the yield point elongation of the invention material is significantly lower than that of the conventional material and the comparative material 1, and the decarburization performance is greatly improved. In the case of the comparative material 2, the yield point elongation is similarly small, but due to the recrystallization of the material. Because of this, the tensile strength decreases to 10 kg / mm 2, which is not suitable.

TABLE 1

division Decarburization Temperature (℃) Hydrogen concentration (%) Dew point temperature (℃) Yield Point Elongation (YP-EL) Surface oxidation Conventional 780 25 -13 12 radish Invention 1 750 15 30 0.5 radish Invention 2 750 20 30 0.3 radish Invention 3 750 15 35 0.4 radish Invention 4 750 20 35 0.2 radish Invention 5 800 15 30 0.4 radish Invention 6 800 20 30 0.5 radish Invention 7 800 15 35 0.4 radish Invention Material 8 800 20 35 0.3 radish Comparative Material 1 700 15 35 7.0 radish Comparative Material 2 850 15 35 0.3 radish

Table 2 shows the effect of surface oxidation according to pretreatment and posttreatment conditions. Decarbonization annealing is performed between pretreatment and posttreatment, which is a dew point temperature of 35% in an atmospheric gas containing 15% hydrogen at 800 ° C. Carried out at

TABLE 2

division Pretreatment (room temperature ~ 750 ℃, 2 minutes) Post-treatment (750 ℃ ~ room temperature, 2 minutes) Yield Elongation (%) Oxidation Atmosphere Dew point temperature (℃) Atmosphere Dew point temperature (℃) Invention 1 N ₂ -10% H ₂ -20 N ₂ -10% H ₂ -20 0.3 radish Invention 2 N ₂ -5% H ₂ -20 N ₂ -5% H ₂ -20 0.4 radish Invention 3 N ₂ -5% H ₂ -20 N ₂ -5% H ₂ -20 0.3 radish Comparative Material 1 N ₂ -1% H ₂ -20 N ₂ -1% H ₂ -20 0.3 Oxidation Comparative Material 2 N ₂ -15% H ₂ 35 N ₂ -15% H ₂ 35 0.2 Oxidation Comparative Material 3 N ₂ -15% H ₂ 35 N ₂ -3% H ₂ -20 0.2 Slightly oxidized

As can be seen from Table 2, in the case of the inventive material, there was no oxidation, but in the case of Comparative Material 1 in which the atmospheric gas was outside the scope of the invention, or in the case of Comparative Materials 2 and 3 in which the atmospheric gas and the dew point temperature were outside the scope of the invention, It can be seen that oxidation has occurred.

Therefore, according to the present invention as described above, decarbonization annealing is performed at a high dew point temperature of 30 to 35 ° C and a low hydrogen partial pressure of 15 to 20% at a high temperature of 750 to 800 ° C in the final decarburization process of the cold rolled material for shadow mask. To improve the performance of decarburization, and effective decarburization can be achieved by preventing oxidation of the steel sheet using an atmosphere that prevents oxidation at a temperature lower than 750 ° C.

Claims (3)

In the final decarbonization of a cold rolled steel sheet having a carbon content of 0.001 to 0.003% by weight to produce a shadow mask, at a temperature below 750 ° C, annealing is performed at a dew point temperature of -20 ° C or lower in a nitrogen and hydrogen atmosphere, and then annealed at 750 ° C. The decarbonization annealing method of the cold rolled steel sheet for shadow masks, characterized by annealing at a temperature of 30 to 50 ° C. in a nitrogen and hydrogen atmosphere at ˜800 ° C. The method for decarbonization annealing a cold rolled steel sheet for a shadow mask according to claim 1, wherein the concentration of hydrogen in the atmosphere gas during annealing at less than 750 ° C is 3 to 10%. The method for decarbonization annealing of a cold rolled steel sheet for a shadow mask according to claim 1, wherein the hydrogen concentration in the atmosphere gas at the time of annealing at 750 to 800 ° C is 15 to 20%.