JPS62280329A - Manufacture of inner shielding material for cathode-ray tube excellent in formability and electromagnetic wave-shielding characteristic - Google Patents

Abstract

PURPOSE:To efficiently manufacture an inner shielding material for cathode-ray tube excellent in formability and electromagnetic wave-shielding characteristic, by subjecting a slab in which respective contents of C, Al, and N are limited to hot rolling, to cold rolling, and then to annealing under specific conditions. CONSTITUTION:The slab containing, by weight, <=0.02% C, 0.005-0.06% Al, and <=0.0030% N is hot-rolled under the conditions of soaking temp. Ts and winding temp. Tc satisfying Ts<=1.1Tc+409.5 and of a finishing temp. of Ar3-900 deg.C. Subsequently, the hot-rolled plate is subjected to cold rolling at >=60% draft, to decarburizing annealing to <=0.0030% C by an open annealing method, and further to cold rolling at <=60% draft so as to improve magnetic permeability. After that, the cold-rolled sheet is subjected to final annealing at >=650 deg.C to undergo acceleration of grain growth. In this way, the inner shielding material for cathode-ray tube combining superior electromagnetic wave-shielding characteristic with excellent formability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an inner shield material for a cathode ray tube.

[Conventional technology and its problems]

An inner shield material with a thickness of about 150 μm is attached to the inner wall of the cathode ray tube built into the CR'r device of a television receiver or each computer in order to shield the electron beam emitted from the electron gun from the influence of external electromagnetic fields. has been done. Recently, in particular, there has been a demand for higher-definition cathode ray tubes, and excellent properties are also required for the material of this ellipse. However, the inner shield material for cathode ray tubes not only has good electromagnetic and wave shielding properties, but also has to be thin to reduce weight. However, reducing the plate thickness is disadvantageous in terms of shielding properties as shown in equation (1) below, and in order to compensate for this, it is necessary to increase the soft magnetic properties of the material, particularly the magnetic permeability μ.

Absorption loss A=KttJT5...Scream...(1) However, f
Double layer wave number G: ratio 1! To the rate! : Two constants Thickness μ : Magnetic permeability In order to increase the magnetic permeability μ, it is effective to purify the copper component, secure the ferrite grain size, and perform strain relief annealing. The ferrite grain size is ensured.

However, in order to increase the grain size, high-temperature annealing is effective. There is a major problem in that steel has no choice but to be used, and improvement in magnetic properties cannot be expected.

Rimmed steel also has the disadvantage of inferior formability compared to killed steel, and in addition to not being able to obtain large magnetic properties, the magnetic properties of the shield material deteriorate due to processing, so it cannot be assembled by mating or relatively light processing. This results in a shielding material that requires the following, which increases the number of man-hours required for assembly and construction.

The present invention was made in view of such conventional problems,
It is an object of the present invention to provide a method for producing an inner shield material for cathode ray tubes that has excellent electromagnetic shielding properties and excellent moldability.

Therefore, in the present invention, C: 0.02 wt% or less, α: O
,005~0.06 wt%, N:0.0030wt%
A slab containing: T8≦1. Soaking temperature TS and coiling temperature Tc satisfying I Tc +409.5, Ar+ or below 9 fl After hot rolling at a finishing temperature of 0°C or below, cold rolling at a rolling reduction of 60 or higher, then open. By performing decarburization annealing using the annealing method, the C content can be reduced to O or Q.
The basic characteristics are that the O content is 30 wt% or less, and further, after cold rolling at a reduction rate of 60% or less, final annealing is performed at 650° C. or higher.

The details of the present invention will be explained below along with the reasons for its limitations.

In the present invention, At killed steel is used in place of the conventionally used rimmed steel, and manufacturing conditions are specified in order to improve the magnetic shielding properties of this At killed steel. In other words, as mentioned above, in order to improve the electromagnetic shielding characteristics, it is effective to purify the steel components, ensure the grain size, and annealing to remove strain. From these viewpoints, the components and manufacturing conditions of At-killed steel are determined as follows. It was stipulated as follows.

In the present invention, the steel composition is C: 0.02wtS or less, kl
: 0.005~0.06wt%
, N 2 o, oo 3 owt% or less.

When At-killed steel is annealed after cold rolling, AtN precipitates and suppresses ferrite grain growth.

Therefore, if the annealing temperature is not high enough, it will have a finer grain structure compared to rimmed steel. Therefore, in the present invention, N is set to 0.0030 wt% or less in order to suppress the amount of ALH precipitation as much as possible.

Furthermore, in order to prevent deterioration of the shielding properties due to magnetic aging of N, which is an interstitial element, the lower limit was set at 0.005 wt% in order to completely fix N as AtN. However, adding too much kA impairs economic efficiency and deteriorates shielding properties, so the upper limit is set at 0.06 wt%.

The less C there is, the higher the magnetic permeability μ is, and as shown in FIG. 2, the magnetic permeability significantly increases by 1.7 at 0.0030 wt % and below. Therefore, in the present invention, the Ct in the steel is reduced to 0.02wt or less in the l14 degassing process, and open annealing is performed before the final annealing to reduce the final content to 0.0030%.
It should be less than wt%.

In the present invention, a slab having the above composition is used.

TS < 1.1 Tc + 409.5 However, TS:
Soaking temperature Tc: Soaking temperature TS that satisfies the coiling temperature and coiling temperature Tc, Ar, hot rolling is carried out at a finishing temperature of 900° C. or less.

As mentioned above, the present invention suppresses N-i as much as possible, but as for N, which is present in a small amount.

Precipitating it as AIR before cold rolling is an effective means for improving grain growth. Therefore, during the hot rolling stage, low-temperature heating is used to minimize the dissolution of IN in the slab, and high-temperature winding is used to precipitate as much AtN as possible. I tried to let them do it. The present inventors set AΔ to a particle size of 7ooX or more.

Without suppressing ferrite grain growth due to AtN,
It was discovered that a sufficient grain size could be obtained, and the hot rolling temperature conditions for this purpose were investigated. As a result, the soaking temperature TS and the winding temperature Tc are as shown in FIG.

TS≦1. By performing hot rolling to satisfy I TC+ 409.5, A
It was found that the particle size of Δ could be increased to 700A or more.

In order to ensure grain growth, in addition to the above conditions, soaking temperature T8≦1150°C and winding temperature T
It is preferable that c≧650°CG).

In order to improve the soft magnetic properties, <io
It is desirable to increase the degree of integration of crystals having the o> orientation. However, the present inventors' studies have shown that if sufficient ferrite grain size and component purification are achieved in the At-killed steel inner shield material, no special component design or manufacturing process for the purpose of texture control is required. It has been found that sufficient magnetic permeability can be obtained as a shield material, that as an inner shield material there is little deterioration of soft magnetic properties due to processing, and that homogenization of the structure is an important factor in construction.

In the present invention, from the viewpoint of uniformity of the structure, the finishing temperature is set to Ar.
Must be 3 or more. This is because when finished at an Ar point of 3 or less, abnormally coarse grains grow due to secondary recrystallization during winding, impairing the uniformity of the structure. On the other hand, if the finishing temperature is too high, the ferrite grains become abnormally coarse due to the coarsening of the austenite grains, so the upper limit was set at 900°C.

After hot rolling as described above, cold rolling at a reduction rate of 60% or more, and then decarburization annealing using an open annealing method,
Furthermore, in the present invention, cold rolling is carried out at a reduction rate of 60% or less,
It is said that cold rolling is performed twice after decarburization annealing, and if the reduction ratio is large in one cold rolling, the grain size becomes fine and it becomes impossible to obtain the large ferrite grain size that is the aim of the present invention. Although there is a problem, such a problem can be avoided by performing cold compression in two steps.

In addition, in decarburization annealing, as mentioned above, C is 0.0030
wt% or less to improve magnetic permeability.

After the second cold pressing, annealing at 600'C or higher is performed.

The higher the annealing temperature, the better the grain growth, which contributes to improving the magnetic permeability μ. FIG. 3 shows the relationship between annealing temperature, grain growth, and magnetic permeability, and shows that good grain growth and magnetic permeability improvement effects were obtained at an annealing temperature of 650° C. or higher.

However, in the case of batch annealing, if annealing is performed at too high a temperature, there is a risk of seizure in the steel, so the upper limit temperature is inevitably regulated.

Therefore, in the method of the present invention, it is preferable to perform annealing in a gas floating type continuous heat treatment equipment.

The shielding material of the present invention manufactured as described above has a lower N and A compared to shielding materials manufactured using conventional rimmed steel.
Since it is completely fixed as tN and the C content in the steel is reduced to an extremely low level, it has extremely excellent properties such as magnetic aging, which causes almost no problem, and no deterioration in shielding properties.

Furthermore, the shielding material manufactured by the method of the present invention has superior formability compared to conventional rimmed steel. Molding also causes deterioration of soft magnetic properties, but since the material of the present invention has excellent initial shielding properties, it can maintain sufficient shielding properties even after being subjected to a certain amount of shaping.

Figure 4 shows the relationship between the deformation amount ε and the initial magnetic permeability 1'o of the shielding material obtained by the present invention in comparison with that of the shielding material made of conventional rimmed steel. Since the initial magnetic permeability as annealed is higher than that of the steel, relatively high properties can be obtained even if the magnetic permeability decreases due to deformation. As shown in the figure, if the amount of deformation is up to 5.0%, the initial magnetic permeability exceeds the unprocessed state of the conventional material. Therefore, with the material of the present invention, not only can the surface quality of the steel strip be made smooth by pressure adjustment, but also it can be easily applied to shield materials that require a complicated shape.

〔Example〕

Example 0 A slab with the components shown in Table 1 (however, C is the value after decarburization annealing) was heated to a thickness of 2.0 at a soaking temperature of 1150°C, a finishing temperature of 890°C, and a winding temperature of 700°C. The plate was hot-rolled to a thickness of 0. Next, the plate was first cold-rolled to a JIL of 0.4, then subjected to decarburization annealing at 700°C by an open annealing method, and then the plate was decarburized to a thickness of 0.
．． It was subjected to secondary cold rolling to a thickness of 15 mm and then subjected to batch annealing at 670°C. Incidentally, the test materials Pigeon No. 1 to No. 3 were subjected to skin pass rolling at a pressure adjustment rate of 0.5% after the above-mentioned dulling. Then, the mechanical properties and magnetic properties of each sample material obtained were investigated.

Table 2 shows the mechanical properties of each sample material.Compared to the comparative material, the material of the present invention elongated even though pressure was adjusted, had a higher ; value and n value, and exhibited excellent moldability. It is clear that it has a sexual nature.

In addition, Table 3 shows the DC magnetic properties, and although the present invention material has been subjected to 0.5% pressure regulation, its magnetic permeability is higher and its coercive force is lower than that of the comparative material that has not been pressure-regulated. It can be seen that it exhibits good electromagnetic shielding characteristics.

0 Example ω) A slab having the components shown in the first column was hot rolled to a thickness of 200 mm under different conditions, then primary cold rolled to a thickness of 0.4 tm, and then annealed at 700°C by an open annealing method. The specimens were subjected to decarburization annealing, followed by secondary cold rolling to a plate thickness of 015 mm, and then batch annealing at 670° C., and the direct current magnetic properties of each of the obtained test materials were investigated. The results are shown in Table 4.

〔Effect of the invention〕

According to the present invention described above, it is possible to efficiently produce an inner shield material for cathode ray tubes that has excellent electromagnetic shielding properties and also has excellent moldability.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the grain size in steel and the heating temperature and rolling temperature in hot rolling. Fig. 2 shows the relationship between the C in steel and the initial magnetic permeability. FIG. 3 shows the relationship between annealing temperature, grain size in steel, and initial magnetic permeability. FIG. 4 shows the relationship between the shielding material deformation amount and the initial magnetic permeability for the present invention material and the conventional material. Patent applicant Nippon Kokan Co., Ltd. Inventor Akihiko Nishimoto
Yoshi Hosoya Butsuma
Shunma Urabe 1st
Illustration removal U1 degree (0C) @Figure 2 C (olo) Figure 3 yR, dull temperature &('C) Figure 4 Support amount ε (%) Procedural amendment (voluntary) 1988? Month G day

Claims (1)

[Claims] C: 0.02 wt% or less, Al: 0.005 to 0.06
wt%, N: A slab containing 0.0030 wt% or less is heated at a soaking temperature T_S and a winding temperature T_C that satisfies T_S<1.1T_C+409.5, Ar
After hot rolling at a finishing temperature of _3 or more and 900°C or less, cold rolling at a rolling reduction of 60% or more, and then decarburizing by open annealing to reduce the C content to 0.0030 wt% or less. A method for producing an inner shield material for a cathode ray tube having excellent formability and electromagnetic shielding properties, further comprising cold rolling at a rolling reduction of 60% or less and final annealing at 650° C. or higher.