JPS5846547A - Manufacture of internal magnetic shield for color picture tube - Google Patents

Abstract

PURPOSE:To eliminate the necessity for a magnetic annealing process after molding and obtain an internal magnetic shield provided with good mechanical strength and blackening film quality while fully holding a magnetic shielding effect, by fixing N as a compound of AlN to a cold rolled steel belt, in composition mainly composed with Fe and contained with C, Mn, SolAl, N and impurities, press molding the cold rolled steel belt and then applying surface blackening treatment. CONSTITUTION:An ultra-low carbon steel belt, fixed as a compound of AlN by precipitation treatment, in composition mainly composed with Fe and contained with 0.01wt% C or less, 0.1-0.3wt% Mn, Al and N, where Al and N are 0.01- 0.06wt% and 0.02-0.1wt% respectively in a solid solution state, is press molded and then heated for 10-30min in a wet atmosphere at 550-600 deg.C, thus surface blackening treatment is applied to obtain specific permeability at least 600 in crystal grain size ASTM8. A crystal grain is not formed large in the crystal grain size ASTM8, and a magnetic shield, with good press molding and a fine blackening film also with sufficient mechanical strength, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an internal magnetic shield for a color picture tube having excellent magnetic properties and a dense blackened surface film.

In general, a color picture tube VCSR has an internal tube or two
, , By providing a funnel-shaped magnetic shield outside the tube, the electron beam is prevented from being bent by the earth's magnetism. In particular, the internal magnetic shield enclosed in the tube has high magnetic permeability and mechanical strength, as well as high thermal emissivity and is made of gas-released carbon cold-rolled steel strip. By applying magnetic annealing treatment at 700 to 860°C, the crystal grains were made coarser than those of MuSTM6, and the magnetic permeability was increased. Heat treatment is carried out at a temperature of .

For this reason, heat treatment is required twice, which is not only extremely uneconomical, but also has the disadvantage that mechanical strength decreases due to coarsening of crystal grains, and deformation problems are likely to occur during handling. there were. Further, the blackened film grown from such coarse grains tends to have a coarse structure, and there is also the problem that the film is likely to fall off.

- The present invention has been made to eliminate the above-mentioned conventional drawbacks, and will be described in detail below along with examples.

The rectangular cylindrical internal magnetic shield 1 shown in the drawing has a flange portion 2 projecting like a brim around the periphery of a large-diameter opening, and the flange portion 2 is coupled to a frame (not shown) of a shadow mask.

Earth's magnetism is less than 1 Gauss, but in the case of a 20-inch color picture tube not equipped with a magnetic shield, it causes a deviation of more than 1 ωμm in the electron beam projection point on the fluorescent surface. In order to improve the shielding effect of the magnetic shield, the structure of the magnetic shield is important, but it is even more important to increase the magnetic permeability of the material used. Practical materials have a relative magnetic permeability μ of 600 or more.

In order to increase magnetic permeability, carbon (C
) and d Nitrogen (N) must be minimized, the number of grain boundaries must be reduced, and the grain size must be increased. The present invention aims to obtain high magnetic permeability while keeping the crystal grain size relatively small by reducing the amount of C and fixing the free K with a magnet.

C needs to be 0.01% by weight or less in order to improve press formability and magnetic permeability and to reduce gas release. If 0 is 0.01% by weight or less, 0 is 0-1
2% by weight low cast iron steel material in a hot atmosphere at 660-76
It can be obtained by decarburizing at 0°C. On the other hand, M
When n is less than 0.1% by weight, hot brittleness occurs and hot rolling becomes difficult, and when it is more than 0.3% by weight, the copper strip hardens,
Press formability deteriorates.

Go nomuno means the amount of go nomuno dissolved in steel, and it is sufficient if there is an amount necessary to fix N in the steel to muno H. Although it is related to the amount of N described later, the So value is 0.0.
If it is less than 1% by weight, free N remains and reduces magnetic permeability and press formability.

Moreover, when the So value exceeds 0.06% by weight, it is a harmful non-metallic inclusion. The amount of muno2o3 produced increases and press formability deteriorates.

If N is less than 0.02% by weight, the amount of muno-N that prevents crystal grain coarsening will be insufficient, and if it exceeds 0.1% by weight,
Free N increases, reducing magnetic permeability and press formability. - Precipitation and fixation of Muno-N can be carried out as follows. That is, after hot rolling, the copper strip is wound into a coil at a temperature of 600'C or lower, cooled to fix A and N, and then annealed at a temperature higher than the recrystallization temperature. However, this annealing can be performed concurrently with the decarburization treatment described above.

An example of the present invention is shown in which Fe is the main component and GO,00
5% by weight, MnO, 18% by weight, SO! Muno 0D44
A cold-rolled steel strip with a thickness of 0.151111 mm is press-formed to a composition containing 0.46 wt. % NO, 0.46 wt. % impurities, and an internal magnetic shield as shown in the figure. Then,
In order to perform surface blackening treatment, this molded article is heated in a humid atmosphere at a temperature of 676°C for 16 minutes.As in the past, Fe is the main component, CO0αχwt%, Mn0.26wt%, SoJ Muj! When a copper strip with a composition containing 0.001% by weight, NO, 032% by weight and impurities is press-formed and the surface blackened, the grain size becomes smaller.
The relative magnetic permeability of TMs was only about 460.

When the crystal grain size is s'rMs, since the crystal grains are not coarsened, press formability is good, the blackened film is dense, and a magnetic shield with sufficient mechanical strength can be obtained. Incidentally, at a temperature comparable to that of blackening treatment, there is almost no growth in crystal grain size.

As described above, according to the method for manufacturing an internal magnetic shield of the present invention, the main component is Fe, co, 0.01% by weight or less,
Mn0.1-0.3% by weight, goJmuj! 0.01～
A cold rolled steel strip with a composition containing O, 0.6% by weight, N, 0.02 to 0.1% by weight and impurities is press-formed and then subjected to surface blackening treatment. This makes it possible to omit the post-forming magnetic annealing step, which has conventionally been considered indispensable, thereby making it possible to obtain an internal magnetic shield with good mechanical strength and blackened film quality while maintaining a sufficient magnetic shielding effect.

[Brief explanation of the drawing]

The drawing is a perspective view of the internal magnetic shield. 1... Internal magnetic shield, 2... Flange.

Claims (1)

[Claims] The ultra-low carbon steel strip, which is fixed as a compound called Muno-N by the starting ring, is pressed in a humid atmosphere for 10 to 30 minutes after press forming.
The surface is blackened by heating at 650 to 600'C for 0 minutes, and the relative magnetic permeability at crystal grain size 8TM8 is reduced to 60.
A method for producing an internal magnetic shield for a color picture tube, characterized in that the internal magnetic shield is 0 or more.