U.S. patent application number 10/608488 was filed with the patent office on 2004-12-30 for strip material used for shadow mask having improved post-etching shape.
Invention is credited to Hatano, Takaaki, Kawahara, Tetsuo, Kondo, Yuko, Yamagata, Ryo.
Application Number | 20040261911 10/608488 |
Document ID | / |
Family ID | 33540594 |
Filed Date | 2004-12-30 |
United States Patent
Application |
20040261911 |
Kind Code |
A1 |
Kondo, Yuko ; et
al. |
December 30, 2004 |
Strip material used for shadow mask having improved post-etching
shape
Abstract
A mild steel or Fe--Ni alloy used for a shadow mask has TS/0.2%
YS .ltoreq.1.03. The cross sections S.sub.1 and S.sub.2 of a strip
parallel and perpendicular to the rolling direction (RD),
respectively, are subjected to the residual stress, which vary in
the thickness direction. The maximum tensile residual stress
(.sigma..sub.t) generated on a central portion of the cross
sections S.sub.1 and S.sub.2 is adjusted to 50N/mm.sup.2 or less. A
rectangle specimen elongated in the rolling direction (RD) is
sampled from a rolled strip 1 shown at a central portion as seen in
the width direction. Another rectangle specimen elongated in a
direction perpendicular to the rolling direction (RD) is sampled
from a rolled strip at a central portion as seen in the width
direction. The rectangle specimens are clamped at one of the ends
and are suspended downwards in a direction of the long sides
thereof. Warp of the other non-clamped ends is 10 mm or less.
Inventors: |
Kondo, Yuko; (Kanagawa,
JP) ; Kawahara, Tetsuo; (Kanagawa, JP) ;
Yamagata, Ryo; (Kanagawa, JP) ; Hatano, Takaaki;
(Kanagawa, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
33540594 |
Appl. No.: |
10/608488 |
Filed: |
June 30, 2003 |
Current U.S.
Class: |
148/336 |
Current CPC
Class: |
C22C 38/105
20130101 |
Class at
Publication: |
148/336 |
International
Class: |
C22C 038/08 |
Claims
1. A mild steel rolled strip used for a shadow mask, which consists
of Al-killed steel having 1.03 or less of TS (tensile
strength)/0.2% YS (yield strength) measured in a direction parallel
to a rolling direction (RD), wherein said strip may have cross
sections S.sub.1 and S.sub.2 parallel and perpendicular to the
rolling direction respectively, wherein tensile residual stress
(.sigma..sub.t) is generated on a central portion of the cross
sections S.sub.1 and S.sub.2, in the rolling direction (RD) and a
direction perpendicular to the rolling direction (RD),
respectively, characterized in that said tensile residual stress
(.sigma..sub.t) is 50N/mm.sup.2 or less at the highest; and further
warp of said strip is 10 mm or less, when measured by the following
method: a first rectangle specimen elongated in the rolling
direction (RD) and having long and short sides is sampled from the
strip, such that the long sides are 500 mm long and the short sides
50 mm wide, a second rectangle specimen elongated in a direction
perpendicular to the rolling direction (RD) and having long sides
and short sides is sampled from the strip, such that the long sides
are 500 mm long and short sides are 50 mm wide, and the first and
second rectangle specimens are clamped at one of the ends on a flat
sheet fixed horizontally and are suspended downwards in the
direction of the long sides thereof, and warp of the other
non-clamped ends is measured.
2. A mild steel according to claim 1, wherein said Al-killed steel
consists of: 0.010 mass % or less of C; 0.04 mass % of Si; 0.08
mass % or less of Al; from 0.10 to 0.60 mass % of Mn; 0.040 mass %
or less of S; and, 0.035 mass % or less of P, the balance being Fe
and unavoidable impurities.
3. An Fe--Ni alloy rolled strip used for a shadow mask, which
consists of Fe--Ni alloy containing from 34 to 38 mass % of Ni and
having 1.03 or less of TS (tensile strength)/0.2% YS yield
strength) measured in a direction parallel to a rolling direction
(RD), wherein said strip may have cross sections S.sub.1 and
S.sub.2 parallel and perpendicular to the rolling direction (RD),
respectively, wherein tensile residual stress (.sigma..sub.t) is
generated on a central portion of the cross sections S.sub.1 and
S.sub.2, in the rolling direction (RD) and a direction
perpendicular to the rolling direction (RD), respectively,
characterized in that said residual stress tensile (.sigma..sub.t)
is adjusted to 50N/mm.sup.2 or less at the highest; and further
warp of said strip is 10 mm or less, when measured by the
follow-ing method: a first rectangle specimen elongated in the
rolling direction (RD) and having long sides and short sides, is
sampled from the strip, such that the long sides are 500 mm long
and the short sides 50 mm wide, a second rectangle specimen
elongated in a direction perpendicular to the rolling direction and
having long sides and a short sides is 50 mm wide, and the first
and second rectangle specimens are clamped at one of the ends on a
flat sheet fixed horizontally and are suspended downwards in a
direction of the long sides thereof, and warp of the other
non-clamped ends is measured.
4. An Fe--Ni alloy rolled strip according to claim 3, wherein said
Fe--Ni alloy contains from 2 to 8 mass % of Co.
5. An Fe--Ni alloy rolled strip according to claim 4, wherein said
Fe--Ni alloy contains from 0.05 to 0.8 mass % of at least one
element selected from the group consisting of Nb, Ta, Hf, Ti and
Zr.
6. An Fe--Ni alloy rolled strip according to claim 3, 4 or 5,
wherein said Fe--Ni alloy further contains 0.10 mass % or less of C
and 0.1 mass % or less of Si, 0.05 mass % or less of Al; 0.5 mass %
or less of Mn; 0.005 mass % or less Si; and 0.005 mass % or less of
P.
7. An Fe--Ni alloy rolled strip according to claim 6, wherein the
Si content is 0.05 mass % or less.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates to a mild-steel strip or an
Fe--Ni alloy strip used for a shadow mask having improved
post-etching shape.
[0003] 2. Description of Related Art
[0004] A strip for a shadow mask of a Braun tube is usually
produced by rolling. The strip for the shadow mask is degreased and
then subjected to application of photo-resist on both surfaces. A
pattern of through holes is delineated on the photo-resist layer
which is then developed. Ferric chloride solution is sprayed on
both surfaces of the strip to form through holes. The strip is then
cut into shadow-mask segments (c.f. Materia (Journal of Japan
Institute for Metals), Vol. 36 (1977), No. 11, pages 1070-1074).
The shadow-mask segments are conveyed by an automatic conveying
line during the etching process or the manufacturing process of a
Braun tube. The etched shadow masks should not be caught on the
conveyer so as to avoid conveying failure. The flatness of the
etched shadow mask is, therefore, important.
[0005] Residual stress of a strip for a shadow mask is
schematically illustrated in FIG. 1. The direction across the major
surfaces of a strip 1 is hereinafter referred to as the thickness
direction. The direction of a strip 1 across the sides of a strip
is hereinafter referred to as the width direction. The thickness of
a strip 1 is denoted in FIG. 1 as "t". FIG. 1 illustrates that: the
residual stress (.sigma.) on the cross-sections, S.sub.1, and
S.sub.2 parallel and perpendicular to the rolling direction (RD),
respectively, distributes along the thickness direction. An example
of actual measurement of residual stress (.sigma.) is shown in FIG.
2.
[0006] As shown in FIG. 1, in a post-rolling strip for the shadow
mask, the residual stress (.sigma.) generated in the surface
portions of a strip 1 as seen in the thickness direction is such
that such portion is subjected to compression residual stress
denoted as .sigma..sub.c. Such compression residual stress
(.sigma..sub.c) is generated on both cross-sections, S.sub.1 and
S.sub.2, parallel and perpendicular to the rolling directions (RD).
respectively. Meanwhile, the residual stress (.sigma.) generated in
the central position of a strip as seen in the thickness direction
is such that such portion is subjected to tension denoted as
.rho..sub.t. Such tensile residual stress (.sigma..sub.t) is
generated on both cross-sections. S.sub.1 and S.sub.2 parallel and
perpendicular to the rolling direction (RD), respectively.
[0007] Through-holes of a shadow mask shown in FIG. 4 have on
either side of the shadow mask an aperture in the form of a true
circle having, for example, 130 .mu.m of diameter. This aperture is
hereinafter referred to as the small aperture 2. The through-holes
have on the other side an aperture in the form of a true circle and
having, for example, 220 .mu.m of diameter. This aperture is
hereinafter referred to as the large aperture 3. FIG. 4 also
schematically illustrates how at shadow mask warps under the
influence of the residual stress (.sigma.). The apertures 2, 3 of a
through-hole are non-symmetrical to and of different diameter from
one another. This is because when the through holes are formed on a
shadow mask, the etching amount of material in the side, where the
large aperture 3 is formed, is greater than that on the other side,
where the small aperture 2 is formed. The residual stress (.sigma.)
on both sides becomes therefore un-balanced, with the result that
warp occurs.
[0008] The compressive stress (.sigma..sub.c) in the surface
portion, where the small apertures 2 are formed, can be treated as
the internal stress of a compressed spring. On the other hand, the
tensile stress in the central region can be treated as the internal
stress of a extended spring. These springs exert mutual influence
to balance the stresses. The warp occurs, therefore, after etching
in such a manner that a convex shape is formed on a side of the
small aperture 2.
[0009] Conventionally, the shadow masks for civilian use have only
slightly non-symmetrical apertures, and slight warp generates under
the influence of the residual stress. However, in a highly precise
shadow mask, since the non-symmetry mentioned above is
considerable, large warp occurs under the influence of the residual
stress.
[0010] Generally speaking, the residual stress can be relieved by
means of stress-relief annealing at a temperature lower than the
recrystallization temperature. The warp after etching can thus be
prevented. However, the stress-relief annealing increases the
production cost. In addition, the stress-relief annealing does not
greatly decrease the tensile strength (TS) but seriously decreases
the 0.2% yield strength (YS). When the 0.2% YS becomes low, serious
wrinkle is liable to occur in the subsequent etching process.
SUMMARY OF INVENTION
[0011] It is an object of the present invention to provide an
Al-killed-steel rolled strip or an Fe--Ni based-alloy rolled strip
produced by straightening, but not stress-relief annealing,
enabling reduction of residual stress and the post-etching
warp.
[0012] The present inventors discovered that the etching warp of an
Al-killed steel rolled strip and an Fe--Ni alloy rolled strip can
be suppressed by the straightening process carried out after the
final rolling under the following conditions (1) and (2) described
below. As a result of elimination of the stress relief annealing,
the production cost can be saved. In addition, the 0.2% YS of the
same level as TS could be attained, that is, TS/0.2%
YS.ltoreq.1.03.
[0013] (1) Residual stress distributes along the thickness
direction on the cross sections S.sub.1 and S.sub.2 of a strip
parallel and perpendicular to the rolling direction (RD),
respectively, as described hereinabove. In other words, the cross
sections S.sub.1 and S.sub.2 of a strip parallel and perpendicular
to the rolling direction (RD), respectively, are subjected to the
residual stress, which varies in the thickness direction. The
maximum tensile residual stress (.sigma..sub.t) generated on a
central portion of the cross sections S.sub.1 and S.sub.2 mentioned
above is adjusted to 50N/mm.sup.2 or less.
[0014] (2) A rectangle specimen 10(1) elongated in the rolling
direction (RD) is sampled from a rolled strip 1 shown in FIG. 3 at
a central portion as seen in the width direction. The long sides of
a rectangle specimen 10(1) are 500 mm long, while the short sides
of a rectangle specimen 10(1) are 50 mm wide. Another rectangle
specimen 10(2) elongated in a direction perpendicular to the
rolling direction (RD) is sampled from a rolled strip 1 shown in
FIG. 3 at a central portion as seen in the width direction. The
long sides of a rectangle specimen 10(2) are 500 mm long, while the
short sides of a rectangle specimen 10(2) are 50 mm wide. As shown
in the right-half of FIG. 3, the rectangle specimens 10(1) and
10(2) are clamped at one of the ends and are suspended downwards in
the direction of the long sides thereof. Warp of the other
non-clamped ends is measured. The rectangle specimen 10(1) warps in
the rolling direction (RD). This warp is hereinafter referred to as
the curl warp (Wc). The rectangle specimen 10(2) warps in a
direction perpendicular to the rolling direction (RD) and this warp
is hereinafter referred to as the gutter warp (Wg). The curl warp
(Wc) and the gutter warp (Wg) are adjusted to 10 mm or less by
means of straightening described hereinbelow.
BRIEF EXPLANATION OF DRAWINGS
[0015] FIG. 1 is a schematic drawing illustrating the residual
stress (.sigma.) generated on the cross sections S.sub.1 and
S.sub.2 of a strip parallel and perpendicular to the rolling
direction (RD) respectively, and the residual stress (.sigma.)
distributed along the thickness direction.
[0016] FIG. 2 is a graph showing an example of the distribution of
residual stress along the thickness direction actually
measured.
[0017] FIG. 3 illustrates a method for sampling of rectangle
specimens and measuring the wrap.
[0018] FIG. 4 schematically illustrates the mechanism of how warp
occurs under the influence of the residual stress (.sigma.).
[0019] FIG. 5 schematically illustrates the warp of the shadow
masks, which are etched and then separated from a strip.
[0020] FIG. 6 illustrates a measuring method of warp by means, of
downward suspension.
[0021] FIG. 7 is a schematic drawing of a straightening
machine.
[0022] FIG. 8 is a graph showing a straightening condition of the
Fe--36 mass % Ni alloy in an example.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0023] Al killed steel and Fe--Ni based alloy having from 34 to 38
mass % of the Ni content are generally used as the strip for a
shadow mask. The Fe--Ni alloy exhibits a low coefficient of thermal
expansion and is hence appropriate for a highly precise shadow
mask. The elements other than the principal elements of these
materials exert detrimental influence upon the coefficient of
thermal expansion, the etching property, the formability and the
like. Preferred elements other than the principal elements of
Al-killed steel are: 0.010 mass % or less of C; 0.04 mass % or less
of Si; 0.08 mass % or less of Al; from 0.10 to 0.60 mass % of Mn;
0.040 mass % or less of S; and, 0.035 mass % or less of P. The
elements other than the principal elements of Fe--Ni alloy are
preferably 0.10 mass % or less of C and 0.1 mass % or less of Si,
and more preferably 0.05 mass % or less of Si; 0.05 mass % or less
of Al; 0.5 mass % or less of Mn; 0.005 mass % or less S; and 0.005
mass % or less of P.
[0024] A high-strength Fe--Ni alloy, in which Ni is replaced with
from 2 to 8 mass % of Co, is also provided for a shadow mask. That
is, the Ni content is reduced to a range of from 30 to 35 mass %,
and the Ni is replaced with from 2 to 8 mass % of Co. Co added in
this range does not increase but rather decreases the coefficient
of thermal expansion. In order to further strengthen the Fe--Ni
alloy, Co and additionally, one or more of Nb, Ta, Hf, Ti and Zr
arc preferably added in an amount of from 0.05 to 0.8 mass %. When
the total amount (if Nh, Ta, Hf, Ti and Zr exceeds 0.8 mass %, the
coefficient of thermal expansion seriously increases. The total
amount of these elements is therefore limited to 0.8 mass % or
less. In a case of adding these elements, the elements other than
the principal elements of Fe--Ni alloy are preferably 0.10 mass %
or less of C and 0.1 mass % or less of Si, and more preferably
0.0.5 mass % or less of Si: 0.05 mass % or less of Al; 0.5 mass %
or less of Mn: 0.005 mass % or less S: and 0.005 mass % or less of
P.
[0025] The residual stress (.sigma.) on the cross-section S.sub.1
parallel to the rolling direction (RD) shown in FIG. 1 distributes
in the thickness direction. Regardless of whether the residual
stress (.sigma.) is compressive or tensile, its principal direction
is the rolling direction (RD). The residual stress (.sigma.) on a
cross-section S.sub.2 perpendicular to the rolling direction (RD)
shown in FIG. 1 distributes in the thickness direction. Regardless
of whether residual stress (.sigma.) is compressive or tensile, its
principal direction is perpendicular to the rolling direction (RD).
In a shadow mask according to the present invention, the tensile
residual stress (.sigma..sub.t) is present on a central portion of
both sections S.sub.1 and S.sub.2. Such distribution of residual
stress (.sigma.) has been conventionally generated in a rolled but
not stress-relief annealed strip. The highest tensile residual
stress of more than 50N/mm.sup.2 at a central portion causes large
post-etching warp as is explained with reference to FIG. 4. Such
residual stress is therefore limited to 50N/mm.sup.2 or less
according to the present invention.
[0026] Referring to FIG. 5, it is illustrated: how the etched
shadow masks 6 are separated from a strip 1; and, the separated
shadow masks 6 warp. One of the etched shadow masks 6(1) warps in
the form of a curl, while the other etched shadow mask 6(2) warps
in the form of a gutter. The residual stress distribution on the
cross-sections S.sub.1 and S.sub.2 parallel and perpendicular to
the rolling direction (RD), respectively, is the factor determining
the direction of warp of a shadow mask.
[0027] It is known that in a strip rolled by bright rolls almost no
residual stress generates on a cross-section S.sub.2 (c.f. FIG. 1)
perpendicular to the rolling direction (RD). A strip used for a
shadow mask is finishing rolled by means of the special rolls
described hereinafter. High residual stress, therefore, generates
also on a cross-section S.sub.2 perpendicular to the rolling
direction (RD). The strips for a shadow mask are etched and stacked
on one another to face the rolled surfaces with one another. The
stacked strips are then heat-treated. In order to prevent adhesion
of the strips during the heat treatment, the unevenness pattern
referred to as the dull figure is copied from the surfaces of
rolls, which have been shot blasted for example. When the rolling
is carried out by means of rolls having large surface unevenness,
the function force on the surface of a strip is greater than in a
case of rolling with bright rolls. The residual stress (.sigma.) on
a cross-section S.sub.2 perpendicular to the rolling direction
becomes, therefore, high. In a rolled strip, the residual stress
(.sigma.) on the cross-section S.sub.1 in a direction parallel to
the rolling direction (RD) is higher than the residual stress
(.sigma.) on the cross-section S.sub.2 in a direction perpendicular
to the rolling direction (RD). Straightening by means of levelers
can decrease the residual stress (.sigma.) on the cross section
S.sub.1 to a level equal to or less than the stress (.sigma.) on a
cross-section S.sub.2 perpendicular to the rolling direction (RD).
Therefore, the stress distribution on a cross-section S.sub.2
parallel to the rolling direction (RD) mainly determines the curl
warp (Wc), while the stress distribution on a cross section S.sub.2
perpendicular to the rolling direction (RD) mainly determines the
gutter warp (Wg).
[0028] In order to attain small post-etching warp, the highest
tensile residual stress (.sigma..sub.t) in a central portion of the
thickness direction must be 50N/mm.sup.2 or less. Conditions of the
leveler straightening for attaining low residual stress (.sigma.)
depend upon the condition of residual stress. Namely, when the
rolling rolls have large surface unevenness, the friction force on
the surface of a strip and hence the residual stress is large. The
magnitude of residual stress is influenced by not only the surface
roughness of the rolls but also the rolling conditions such as
rolling speed, and viscosity of rolling oil. Factors, which
influence the residual stress, are complicated. It is, therefore,
difficult to precisely analyze the influencing factors. A shadow
mask with low residual stress (.sigma.) can be obtained by means of
test straightening under various conditions and selecting narrow
straightening conditions to reduce the residual strength.
[0029] Flatness of a post-etching shadow mask can be measured by
placing the shadow mask on a horizontally placed flat platen in
such a manner that the concave surface of the shadow mask is
directed upward. The warp amount, i.e., the distance between the
furthest bent side of a mask and the platen, is measured to
determine the warp. This warp should be 2 mm or less. However,
since the amount of absolute value of warp measured by this method
is small, accurate warp may not be disadvantageously measured. The
present inventors consequently conceived and arrived at an idea of
the downward suspension method. That is, as shown in FIG. 6, one of
the sides of the shadow mask 10 is fixed by means of a clamp 5 or
the like on a flat sheet fixed perpendicularly. The other free side
of the shadow mask 10 warps from the flat sheet 4. The distance
between the other free side and the flat sheet 4 is measured to
determine the warp. A shadow mask exhibiting 2 mm of warp according
to the method of placing it on a flat platen exhibits 20 mm of warp
according to the downward suspension method. It is, therefore,
expected that the measurement accuracy is enhanced by as much as
approximately 10 times.
[0030] It is presumed that the curl and gutter warps of the
rectangle specimens sampled from a square sheet are 10 mm. This
means that the residual stresses (.sigma.) in different directions
exist in the square sheet. Since the residual stresses (.sigma.)
are offset in the square sheet, when the square sheet is suspended
for measuring the warp, almost no warp appears. Therefore, the
rectangle specimens are used in the present invention to measure
the warp of material before etching. In the rectangle specimens the
offsetting effect is supposed and the wrap can be precisely
measured.
[0031] A strip used for a shadow mask having improved shape
according to the present invention is straightened but not
stress-relief annealed. The straightening is carried out under the
conditions that; the residual stress, to which the cross-sections
S.sub.1 and S.sub.2 are parallel and perpendicular to the rolling
direction (RD) are subjected, is 50 N/mm.sup.2 or less: and, the
suspension warp of the rectangle specimens 10(1) and 10(2) is 10 mm
or less.
[0032] The present invention is hereinafter explained with
reference to Examples.
EXAMPLES
[0033] Al-killed steels (Nos. 1 and 2, in Table 1) and Fe--Ni based
alloy (Inventive Nos. 3-9 and Comparative Nos. 1-5 in Table 1) were
melted. Ingots were hot-forged and hot-rolled. The oxide scale on
the surface of hot-rolled sheets was removed. Cold-rolling and
annealing were then repeated, and 0.12 mm thick strips were
produced by the final cold-rolling. A straightening machine
straightened the 0.12 mm thick strips. This machine was a
tension-leveling type schematically shown in FIG. 7 and was
provided with multi levelers. In the straightening. IM (inter-mesh
amount of the straightening rolls) and the tension level of a strip
were variously adjusted. IM at the outlet side was adjusted to such
a minus side that the distance between the upper and lower rolls
was equal to the sheet thickness of a strip. IM at the inlet side
was adjusted to the plus side by means of changing the inclination
angle between the upper and lower roll-arrays. The value of IM is
shown in the ordinate of FIG. S. The tension shown in the abscissa
of FIG. 8 was controlled by means of changing the circumferential
speed of bridle rolls in the inlet side.
[0034] The strip, which has passed the straightening machine, was
then examined by the tensile test, the measurement of residual
stress and the measurement of downward warp. In the tensile test, a
JIS 13B specimen was sampled in the directions parallel and
perpendicular to the rolling direction. Tensile speed was 2
mm/min.
[0035] In the measurement of residual stress, rectangle specimens
20 mm in width and 200 mm in length were etched on one of the
surfaces by using the ferric chloride aqueous solution so as to
warp the specimens. The radius of curvature of the specimens was
measured and the residual stress was calculated. This measurement
was carried out with respect to the front and back surfaces of the
specimens while changing the etching amount. Distribution of stress
in the thickness direction was obtained (c.f. Hajime Sudo "Residual
Strain and Distortion" published by Uchida Rokakuho Sha (1988),
page 46). When the residual stress (.sigma.) on the cross-section
S.sub.1, parallel to the rolling direction (RD) is to be measured
the rectangle specimen is sampled from a strip elongated in the
rolling direction (RD). On the other hand, when the residual stress
(.sigma.) on the cross-section S.sub.2 perpendicular to the rolling
direction (RD) is to be measured, the rectangle specimen is sampled
from a strip elongated in a direction perpendicular to the rolling
direction (RD). These specimens were sampled at a central portion
of a strip as seen in the width direction.
[0036] Strips were cut into a form of a shadow mask 340 mm in
length and 270 mm in width as the size of 17 in. Photo-resist was
applied on both surfaces of the cut sections in the form of a
shadow mask and delineated with a pattern of through holes, which
was then developed. Ferric chloride solution was sprayed onto both
surfaces of the cut sections to produce shadow masks. A cut section
was tested as shown in FIG. 6 by the suspension method. The cut
section was suspended in two directions, that is, the rolling
direction of the cut section vertically or horizontally. The warp
in the former direction is denoted in Table 1 as "Material,
Suspension Warp, Parallel (Curl)". The warp in the latter direction
is denoted in Table 1 as "Material, Suspension Warp, Perpendicular
(Gutter)". When the warp was 20 mm or less, it was judged that the
warp of material was acceptable. The results are shown in Table
1.
[0037] In Comparative Example 1, both curl and gutter warps of
material are 10 mm or less. However, since the residual stress
(.sigma.) on the cross-section S.sub.1 parallel to the rolling
direction (RD) exceeds 50 N/mm.sup.2, the curl warp (Wc), i.e., the
warp in the direction parallel to the rolling direction (RD) of a
rectangle specimen 10(1), is large.
[0038] In Comparative Example 2, both curl and gutter warps of
material exceed 10 mm. In addition, the residual stress (.sigma.)
on the cross-sections S.sub.1 and S.sub.2 parallel and
perpendicular to the rolling direction (RD) exceeds 50 N/mm.sup.2.
The gutter warp (Wg), i.e., the warp in the direction perpendicular
to the rolling direction (RD) of the rectangle specimen 10(2), is
large.
[0039] In Comparative Example 3, the residual stress (.sigma.) on
the cross-sections S.sub.1 and S.sub.2, parallel and perpendicular
to the rolling direction (RD), respectively, is less than 50
N/mm.sup.2. However, both curl and gutter warps of the material
exceed 10 mm. Warp of the rectangle specimen 10(1) is, therefore,
large.
[0040] In Comparative Example les 4 and 5, since the stress-relief
annealing is carried out, the residual stress (a) is less than 50
N/mm.sup.2. The warp of the rectangle specimens 10(1) and (2) is,
therefore, very low. However, 0.2% YS is low as a result of the
stress-relief annealing and TS/0.2% YS>1.0:3
[0041] In the inventive Examples, the post-etching shadow mask
exhibits, slight warp even without stress-relief annealing and 0.2%
YS is at a level close to TS.
[0042] Appropriate tension and IM conditions are dependent upon
various factors, such as rigidity of a straightening machine,
lubricating condition, and thickness, shape, mechanical properties,
surface roughness and residual stress of the rolled material. It
is, therefore, difficult to determine the appropriate tension and
IM in a manner independent of these factors. FIG. 8 illustrates,
however, the tension and IM in the inventive and comparative
examples. It turns out, therefore, that 10 mm or less of warp and
50 Nlmm.sup.2 or less of residual stress can be obtained in a range
of from 50 to 65 MPa of tension and a range of 1.2 to 1.9 mm of IM
in the inventive examples.
1 TABLE 1 Material Shadow Mask Residual Stress Suspension Warp
Suspension Warp (N/mm.sup.2) +UZ,44/51 (mm) (mm) No. Composition
(mass %) TS (N/mm.sup.2) 0.2% YS (N/mm.sup.2) 1 TS 0.2 % YS
Parallel Perpen- dicular Parallel (Curl) Perpendicular (Gutter)
Parallel (Curl) Perpen- dicular (Gutter) Judge- ment Example 1
Al-killed Steel 601 593 1.01 45 40 9 7 12 10 .largecircle. 2
Al-killed Steel 604 597 1.01 42 38 7 6 11 8 .largecircle. 3
Fe-36%Ni 615 610 1.01 35 20 8 7 15 8 .largecircle. 4 Fe-36%Ni 614
611 1.00 40 40 8 6 18 5 .largecircle. 5 Fe-36%Ni 629 624 1.01 20 45
7 3 3 19 .largecircle. 6 Fe-32%Ni-4%Co 665 660 1.01 43 26 8 6 11 13
.largecircle. 7 Fe-32%Ni-4%Co 658 651 1.01 38 33 7 7 7 9
.largecircle. 8 Fe-32%Ni-4%Co- 685 669 1.02 36 36 6 7 16 15
.largecircle. 0.25%Nb 9 Fe-32%Ni-4%Co- 694 688 1.01 41 39 4 5 6 14
.largecircle. 0.25%Nb Comparative 1 Fe-36%Ni 627 622 1.01 70 40 10
10 30 5 X Example 2 Fe-36%Ni 610 602 1.01 40 80 15 18 9 32 X 3
Fe-36%Ni 615 601 1.02 35 28 25 15 34 8 X 4 Fe-36%Ni(Stress 590 560
1.05 10 5 3 8 4 8 .largecircle. ReliefAnnealing) 5 Fe-36%Ni(Stress
584 561 1.04 7 3 4 6 4 7 .largecircle. ReliefAnnealing)
* * * * *