JPH08188855A - Ferritic stainless steel excellent in demagnetization characteristic and workability - Google Patents

Abstract

PURPOSE: To produce a ferritic stainless steel excellent in demagnetization characteristic and workability. CONSTITUTION: This ferritic stainless steel has a composition which contains 10-15% Cr, <=1.0% Si, <=0.1% Al, and <=1.0% Mn and in which the contents of C, Ni, Cu, N, Mo, Nb, and Ti are limited to <=0.05%, <=0.30%, <=0.10%, <=0.02%, <=0.10%, <=0.10%, and <=0.10%, respectively, and also the H value represented by equation H=14×[45×(C%+N%)--5×(Ti%+Nb%+Al%)+Ni%+Cu%+Mn%-Cr%-∫i%-Mo%+20] is regulated to 120-135.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferritic stainless steel suitable as a cathode ray tube shadow mask frame or the like which is required to have good demagnetizing characteristics and workability.

[0002]

2. Description of the Related Art A shadow mask for a cathode ray tube is fixed to a mask frame with a uniform tension applied in each direction. Mild steel has been conventionally used as a mask material and a frame material. However, when mild steel is used, distortion is likely to occur on the mask surface due to the difference in cooling rate between the mask material and the frame material during manufacturing. The distortion causes a problem such as color shift. Although the distortion of the mask material can be relaxed by controlling the tension at the time of manufacturing, it requires a complicated work and is not sufficiently effective in suppressing the distortion. Therefore, the use of a material having a coefficient of thermal expansion smaller than that of mild steel as the frame material has been studied. For example, in JP-A-1-239736 and JP-A-3-297035, the use of stainless steel as the frame material prevents distortion on the mask surface during manufacturing. Further, when the frame material is magnetized due to the influence of the earth magnetism or the like, a color shift occurs.
Normally, a TV has a degaussing mechanism built in, but if the degaussing characteristics of the material are poor, the power required for degaussing increases. In this regard, Japanese Patent Laid-Open No. 397035/1993 examines the shielding property of geomagnetism and the demagnetizing property of the material, and introduces a material having a high maximum magnetic permeability from the viewpoint of the shielding performance.

[0003]

However, in a weak magnetic field of the order of the earth's magnetism, the higher the permeability, the greater the residual magnetization of the material. As a result, the coercive force also increases, and the demagnetization characteristic is rather poor. A high Ni alloy such as permalloy having a maximum magnetic permeability of more than 100,000 is used for the shield of a weak magnetic field such as that of the earth's magnetism, and a large effect cannot be expected with stainless steel. Further, although stainless steel is an advantageous material in terms of strain suppression, its workability is greatly inferior to that of mild steel. Therefore, in order to be used as a mask material or a frame material formed on a complicated curved surface, stainless steel having further excellent workability is desired. The present invention has been devised to solve such a problem, and by adopting a component design in which demagnetization characteristics are prioritized over the shielding effect of geomagnetism, good workability is maintained, and excellent It is an object of the present invention to provide stainless steel suitable for applications such as an inexpensive cathode ray tube shadow mask frame exhibiting demagnetization characteristics.

[0004]

In order to achieve the object, the ferritic stainless steel of the present invention has a Cr content of 10 to 10.
A ferritic stainless steel containing 15% by weight, Si: 1.0% by weight or less, Al: 0.1% by weight or less and Mn: 1.0% by weight or less, C: 0.05% by weight or less, Ni: 0.30% by weight or less, Cu: 0.10% by weight
Below, N: 0.02 wt% or less, Mo: 0.10 wt%
Hereinafter, Nb: 0.10% by weight or less, Ti: 0.10% by weight or less, and the H value represented by the following formula (1) is 12
It is maintained in the range of 0 to 135. H = 14 * {45 * (C% + N%)-5 * (Ti% + Nb% + Al%) + Ni% + Cu% + Mn% -Cr% -Si% -Mo% + 20} ... (1)

[0005]

As a result of repeated studies on the workability and degaussing characteristics of stainless steel strips, the present inventors have found that the material hardness affects the workability and degaussing characteristics. That is, the lower the material hardness, the better the workability, but the worse the demagnetization property. On the contrary, when the material hardness is high, the demagnetizing property is excellent, but the workability is poor. The present invention has been completed on the basis of such knowledge. In order to reduce the influence of impurities on the material hardness, the impurities are regulated, and the H value represented by the formula (1) is 120 to 120%.
By adjusting to 135, the demagnetizing characteristics and workability of stainless steel are balanced. The action of each component contained in the stainless steel of the present invention is as follows. Cr is 1
When the content is 0% by weight or more, the coefficient of thermal expansion is effectively reduced, but when the content is more than 15% by weight, problems such as an increase in material price and hardening are caused. Si, Al, Mn and the like are essential elements as a deoxidizing agent and a desulfurizing agent at the time of melting, but Si = 1.0% by weight, Al = 0.1% by weight and Mn = 1.0% by weight. If it exceeds, non-metallic inclusions are formed in the steel and the surface properties of the product are deteriorated.

Of the elements mixed in the steel as impurities,
C, Ni, Cu and N increase the H value and increase the material hardness, so that C ≦ 0.05 wt% and Ni ≦
0.30% by weight, Cu ≦ 0.10% by weight, N ≦ 0.02
It is necessary to regulate to weight%. Although Mo, Nb, and Ti have an action of reducing the H value, Mo and Nb deteriorate workability, and Ti increases remanent magnetization and coercive force to deteriorate demagnetization characteristics. Mo ≦ 0.10% by weight, Nb ≦
These adverse effects do not appear when the content is regulated to 0.10% by weight and Ti ≦ 0.10% by weight. The H value represented by the following formula (1) is an empirical formula obtained by the inventors of the present invention by melting a large number of alloys, and is an index indicating the degree of residual magnetization and hardness of the annealed material in the ferrite phase. .

When the H value is less than 120, the residual magnetization sharply increases as shown in FIG. 1 and the degaussing characteristic deteriorates. On the other hand, when the H value exceeds 135, the hardness of the material after finish annealing sharply increases as shown in FIG. 2 and the workability deteriorates. It has been found by the present inventors that the remanent magnetization and the material hardness greatly change depending on the H value, and when the components are adjusted based on the H value using this relationship, the demagnetization characteristics and the workability are improved. A well-balanced ferritic stainless steel is obtained. Specifically, the material used for the cathode ray tube shadow mask frame is required to have a residual magnetization Br of 30 or less from the viewpoint of degaussing characteristics. From the viewpoint of workability, the Vickers hardness is desired to be HV130 or less. Therefore,
When the components are adjusted so that the H value is 120 to 135,
As is clear from the relationship between FIG. 1 and FIG. 2, it can be seen that ferritic stainless steel suitable as a mask frame material can be obtained.

[0008]

EXAMPLES Continuous cast slabs having the compositions shown in Table 1 were hot-rolled by a conventional method and then heated in a bell-type annealing furnace to form a ferrite single-phase structure. After cold rolling, it was annealed under a ferrite structure using a continuous annealing pickling line to obtain an annealed finished material having a plate thickness of 2 mm.

[0009]

[Table 1]

A ring test piece for magnetic measurement was cut out from the annealed material and a DC magnetic field of 0.5 oersted was applied.
After reversing, the residual magnetization and coercive force were measured. Further, a drawing process with a depth of 30 mm was performed, and the workability was investigated by the presence or absence of cracks. The survey results are shown in Table 2. In Table 2, the remanent magnetization is 10 Gauss or less and the coercive force is 0.10 Oersted or less, and the remanent magnetization is 1 or less.
Over 0 gauss and under 30 gauss and coercive force is 0.10
Less than Oersted, ○, remanent magnetization of more than 30 Gauss and less than 40 Gauss and coercive force of less than 0.10 Oersted △, remanent magnetization of more than 40 Gauss or coercive force of more than 0.10 Oersted. The demagnetization characteristics were relatively evaluated as x. The workability is ◎ when cracking and roughening does not occur in the drawn part, and ○ when there is a slight roughening of the surface but no cracking is observed.
The case where a large amount of rough skin was generated and cracks were generated was evaluated as x and evaluated in 3 grades. Further, the residual magnetization and the Vickers hardness are arranged by the H value, and the deviation thereof is shown in FIGS. 1 and 2.

As is clear from Table 2, the stainless steel according to the present invention exhibited good workability and excellent demagnetization characteristics. On the other hand, Comparative Examples B-2 and B-5 were excellent in demagnetization characteristics but inferior in workability. Further, Comparative Examples B-1 and B-3 were good in workability but inferior in demagnetization characteristics. As is clear from this comparison, H
It was confirmed that by setting the value in the range of 120 to 135, a ferritic stainless steel having a well-balanced workability and demagnetization characteristic can be obtained.

[0012]

[Table 2]

[0013]

As described above, since the composition of the ferritic stainless steel of the present invention is adjusted so that the H value is 120 to 135, it is a material having a degaussing property and workability in a balanced manner. Become. This stainless steel is used as an inexpensive cathode ray tube shadow mask frame material and other parts that require excellent demagnetization characteristics.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between H value and remanent magnetization.

FIG. 2 is a graph showing the relationship between H value and workability.

Claims (1)

[Claims] 1. Cr: 10 to 15% by weight, Si: 1.0
Wt% or less, Al: 0.1 wt% or less and Mn: 1.0
A ferritic stainless steel containing less than or equal to 10% by weight, C: 0.05% by weight or less, Ni: 0.30% by weight or less, Cu: 0.10% by weight or less, N: 0.02% by weight or less, Mo: 0.10 wt% or less, Nb: 0.10 wt%
Hereinafter, Ti: a ferritic stainless steel which is restricted to 0.10% by weight or less and has an H value represented by the following formula (1) in the range of 120 to 135 and is excellent in demagnetization characteristics and workability. H = 14 * {45 * (C% + N%)-5 * (Ti% + Nb% + Al%) + Ni% + Cu% + Mn% -Cr% -Si% -Mo% + 20} ... (1)