Metal treatment – Process of modifying or maintaining internal physical... – Utilizing disclosed mathematical formula or relationship
Reexamination Certificate
1999-01-27
2001-05-15
Yee, Deborah (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Utilizing disclosed mathematical formula or relationship
C148S547000, C148S677000
Reexamination Certificate
active
06231694
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for producing Fe—Ni alloys with improved punching properties suitable as materials for electron gun parts, such as electrodes for electron gun parts.
In
FIG. 1
is shown a cross section of a color picture tube of the shadow mask type already known in the art. A panel
1
is coated on the back side with a phosphor film
2
that generates the three primary colors of red, green, and blue. In the neck is housed an electron gun
4
that emits electron beams
3
. The electron beams
3
are deflected in scanning by a deflection yoke
5
. The numeral
6
indicates a shadow mask and the numeral
7
indicates a magnetic shield.
In
FIG. 2
, (
a
) and (
b
) are perspective and cross sectional views, respectively, of an electrode
10
as an example of a punched part to be fitted in the electron gun
4
. The electrode
10
acts to accelerate electrons emitted from a cathode in the electron gun. The electrode has small holes
10
a,
10
b,
and
10
c
made by coining and punching so as to allow red, green, and blue color-generating beams, respectively, to pass through them.
In general, the electron gun parts for use in picture tubes and the like are completed by blanking and press punching (called hereinafter merely punching), with or without coining, a sheet of nonmagnetic stainless steel about 0.05 to 0.5 mm thick. Recently in the case of the electrode
10
that is located in the vicinity of the cathode fitted in the electron gun
4
, more weight has been put on low thermal expansion properties than on the nonmagnetism. With the advent of higher refinement, higher performance picture tubes for computer displays and the like in recent years, it has been noted that subtle dimensional changes with thermal expansion of electrodes influence the picture quality (color purity) on the panel
1
(see FIG.
1
).
To cope with the situation, Fe—Ni alloys having low-expansion properties, notably Fe—42% Ni alloy (42 alloy), have come into use as electrode materials. The 42 alloy of the prior art, however, presents a burr formation problem. That is, as electrode blanks of the 42 alloy are punched with a pattern of small holes
10
a,
10
b,
and
10
c
each, burrs B are formed on the edges
10
e
of the holes where punches have forced slugs down and cut them off from the blank (see FIG.
2
). The burrs that result from the punching have adverse effects upon the control of the electron beams, sometimes prove fatal to the electron guns. The tendency toward picture tubes of even greater refinement is making the requirement for the reduction of burring from electron gun parts more and more exacting.
Improvements in the punching properties of Fe—Ni alloys have hitherto been proposed, for example, in Japanese Patent Application Kokai Nos. 6-184703, 6-122945, 7-3400, and 7-34199.
Of those proposals, Kokai No. 6-184703 specifies the S content in the range of 0.002 to 0.05% and disperses S or S compounds along grain boundaries or within grains in the alloy stock. However, the mere addition of S, a free-cutting element, in a specified percentage cannot be deemed adequate for the control of burrs in the modern punching working to most precise specifications.
The remaining Kokai Nos. 6-122945, 7-3400, and 7-34199 propose adding such strengthening elements as Ti, Nb, V, Ta, W, or/and Zr to the alloy for imparting increased hardness and proper extent of embrittlement to the alloy to suppress burring. These proposals, however, posed problems of shortened punching die life with increased hardness.
This invention has for its object to settle the aforedescribed problems of the prior arts and provide a process for producing Fe—Ni alloys for electron gun parts which is improved in punching properties without attendant shortening of die life.
BRIEF SUMMARY OF THE INVENTION
The inventors have intensively studied on the influence of inclusions upon the punching properties and the influence of process conditions upon distribution of the inclusions. As a result, the inventors have successfully solved the above problems by improving the punching properties of the Fe—Ni alloys used for electron gun parts by restricting the contents of Mn and S within specific ranges, and by hot working at suitable temperatures which depend on the contents of Mn and S.
More specifically, MnS precipitated in the material in a proper amount improves the punching properties by accelerating initiation and propagation of a crack in a punching operation. In accordance with inventors study, it was found that the mere restriction of the S content cannot be sufficient for controlling quantity and distribution of MnS to improve the punching properties, that are more affected by heating temperatures in hot working. Moreover, the inventors have discovered that the proper range of the heating temperatures in hot working varies according to the contents of Mn and S. Therefore, the present invention can provide alloys satisfying the severe requirement with respect to the burrs formed on the electron gun parts for the first time by controlling the heating temperature and the contents of Mn and S in proper ranges. Moreover, according to the present invention, the die life can remain long because MnS which improves punching properties in the present invention does not significantly increase hardness of alloys.
The present invention is completed based on the above mentioned knowledge. That is to say, the invention provides a process for producing Fe—Ni alloys used for electron gun parts consisting of: all by weight, 30 to 55% of Ni; 0.05 to 2.00% of Mn; 0.001% to 0.050 of S; and the balance of Fe and inevitable impurities. The process substantially consists of melting, casting, hot working, cold rolling, and annealing. The Fe—Ni alloy satisfies 0.0005≦((%Mn)*(%S))≦0.100. The hot working is carried out at a temperature T defined by the following equation.
1050
≦
T
°
C
.
≦
9500
3.1
-
log
[
(
(
%
Mn
)
*
(
%
S
)
)
]
-
350
(
1
)
In the following, the reasons of the above numerical limitations will be explained together with the effects of the present invention. In the following explanation, “%” means “weight %”.
(Ni): Ni is an important element that determines thermal expansion characteristic of an Fe—Ni alloy. If its content is less than 30% or more than 55%, the alloy is undesirable with a too high thermal expansion coefficient. Hence the Ni content is restricted within the range of 30 to 55%.
(Mn): Mn forms MnS together with S, and MnS improves the punching properties as mentioned above. If its content is less than 0.05%, sufficient punching properties cannot be obtained. On the other hand, if the Mn content exceeds 2.00%, hardness of the alloy increases, thereby accelerating wear of die. Therefore, the Mn content is restricted within the range of 0.05 to 2.00%. More preferable range of the Mn content is 0.05 to 0.80%.
(S): S forms MnS together with Mn, and MnS improves the punching properties. If its content is less than 0.001%, sufficient punching properties cannot be obtained. On the other hand, if the S content exceeds 0.050%, hot working properties and corrosion resistance are deteriorated. Therefore, the S content is restricted within the range of 0.001 to 0.050%. More preferable range of the S content is 0.003 to 0.020%.
Further elements included in the alloy except for the above elements are Fe and inevitable impurities. The inevitable impurities may be ordinary impurities, C, Si, Al, P and Cr. Such impurities are harmful for thermal expansion characteristic. Therefore, the entire amount of the impurities should be within the range of 0.001 to 0.5%.
(Concentration product of Mn and S ((%Mn)*(%S)): Concentration product ((%Mn)*(%S)) is a parameter noticed by the inventor at the first time with respect to improvement of the punching properties of an Fe—Ni alloy used for electron gun parts. Amount of MnS can be more certainly controlled by restricting the range of the concentration produ
Kita Yoshihisa
Yuki Norio
Nippon Mining & Metals Co., Ltd
Scully Scott Murphy & Presser
Yee Deborah
LandOfFree
Process for producing Fe-Ni alloys used for electron gun parts does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing Fe-Ni alloys used for electron gun parts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing Fe-Ni alloys used for electron gun parts will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2527273