U.S. patent application number 10/332507 was filed with the patent office on 2003-09-04 for fe-ni or fe-ni-co or fe-ni-co-cu alloy strip with improved cuttability.
Invention is credited to Coutu, Lucien, Durieux, Vincent, Giusti, Jerome.
Application Number | 20030164211 10/332507 |
Document ID | / |
Family ID | 8852509 |
Filed Date | 2003-09-04 |
United States Patent
Application |
20030164211 |
Kind Code |
A1 |
Coutu, Lucien ; et
al. |
September 4, 2003 |
Fe-ni or fe-ni-co or fe-ni-co-cu alloy strip with improved
cuttability
Abstract
Strip made of an austenitic Fe--Ni alloy or Fe--Ni--Co alloy or
Fe--Ni--Co--Cu alloy, the chemical composition of the alloy of
which comprises, in % by weight: 30%.ltoreq.Ni.ltoreq.70%;
0%.ltoreq.Cu+2.times.Co.ltoreq.20%; 0%.ltoreq.Mn+Cr<5%;
0%.ltoreq.W+2.times.Mo.ltoreq.2%; 0%.ltoreq.Ti+V+Nb+Al.ltoreq.1%;
0.0005%.ltoreq.B.ltoreq.0.007%; the balance being iron and
impurities such as C, S, P, O and N; the chemical composition being
such that Fe+Ni+Cu+Co.gtoreq.95%. The alloy has a cubic texture
with a cubic texture index D.sub.c.gtoreq.7. Process for
manufacturing a strip. Process for manufacturing a part by
mechanical cutting.
Inventors: |
Coutu, Lucien; (Sauvigny Les
Bois, FR) ; Durieux, Vincent; (Nevers, FR) ;
Giusti, Jerome; (Nevers, FR) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
WASHINGTON
DC
20037
US
|
Family ID: |
8852509 |
Appl. No.: |
10/332507 |
Filed: |
April 7, 2003 |
PCT Filed: |
July 10, 2001 |
PCT NO: |
PCT/FR01/02223 |
Current U.S.
Class: |
148/651 ;
420/94 |
Current CPC
Class: |
C22C 38/004 20130101;
C22C 38/08 20130101; C22C 38/002 20130101; C22C 19/03 20130101;
C22C 38/105 20130101; C21D 6/001 20130101; C21D 8/0205
20130101 |
Class at
Publication: |
148/651 ;
420/94 |
International
Class: |
C22C 038/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 13, 2000 |
FR |
00/09249 |
Claims
1. Strip made of an austenitic Fe--Ni alloy or Fe--Ni--Co alloy or
Fe--Ni--Co--Cu alloy, characterized in that the chemical
composition of the alloy comprises, in % by weight:
30%.ltoreq.Ni.ltoreq.70% 0%.ltoreq.Cu+2.times.Co.ltoreq.20%
0%.ltoreq.Mn+Cr<5% 0%.ltoreq.W+2.times.Mo.ltoreq.2%
0%.ltoreq.Ti+V+Nb+Al.ltoreq.1% 0.0005%.ltoreq.B.ltoreq.0.007% the
balance being iron and impurities such as C, S, P, O and N; the
chemical composition being such that Fe+Ni+Cu+Co.gtoreq.95%, and in
that the alloy has a cubic texture with a cubic texture index
D.sub.c.gtoreq.7.
2. Strip according to claim 1, characterized in that:
0.0007%.ltoreq.B.ltoreq.0.004%.
3. Strip according to claim 1 or claim 2, characterized in that
D.sub.c>10.
4. Strip according to any one of claims 1 to 3, characterized in
that the carbon content of the alloy is less than or equal to
0.05%.
5. Strip according to any one of claims 1 to 4, characterized in
that the sulphur content of the alloy is less than or equal to
0.01%.
6. Strip according to claim 5, characterized in that the sulphur
content of the alloy is less than or equal to 0.007%.
7. Strip according to any one of claims 1 to 6, characterized in
that the oxygen content is less than 0.005%.
8. Process for manufacturing a strip according to any one of claims
1 to 7, characterized in that: a strip made of an alloy whose
composition is defined by claims 1 to 7 is manufactured by
cold-rolling with a deformation ratio of greater than 80%; a
fine-grain recrystallization annealing operation is carried out on
the strip; and, optionally, a complementary cold-rolling operation
is carried out with a deformation ratio of less than 40%.
9. Process for manufacturing a part by mechanical cutting or by
mechanical cutting and drawing, characterized in that: a blank is
taken from a strip according to any one of claims 1 to 7; and at
least one mechanical cutting operation and optionally at least one
drawing operation are carried out on the blank, it being possible
for the at least one drawing operation to be carried out before or
after the at least one mechanical cutting operation.
10. Process according to claim 9, characterized in that the part is
an electron-gun part with a hole through which the electrons pass,
or in that the part is a leadframe with connection leads, or in
that the part is a magnetic core of a micromotor or transformer.
Description
[0001] The present invention relates to the manufacture of parts
made of an alloy of the Fe--Ni or Fe--Ni--Co or Fe--Ni--Co--Cu type
obtained by the precision mechanical cutting of blanks, which may
possibly be drawn beforehand. These parts are in general used in
miniature electrical or electronic components.
[0002] Many parts of small size, such as electron-gun parts for
colour display cathode-ray tubes, or integrated-circuit support
frames or leadframes, or parts for micromotors, are manufactured by
the precision mechanical cutting of blanks which are possibly
drawn, made of an alloy of the Fe--Ni or Fe--Ni--Co type containing
about 30% to 70% nickel. The quality of the cutting is very
important for this type of part, particularly in order to prevent
the presence of burrs.
[0003] The blanks from which the parts are cut are taken from
generally isotropic or slightly textured strip obtained by
cold-rolling and annealing. In the case of flat or almost flat
parts, that is to say those obtained without appreciable plastic
deformation of the blank, the strip is often used in the
work-hardened state so as to have a higher hardness and a lower
ductility than strip obtained directly after annealing. This higher
hardness and lower ductility favour mechanical cutting. In
contrast, when the drawing is substantial, the strip is used in the
annealed state so as to have a high ductility and the ability to
undergo extensive plastic deformation. In this case, the cutting
operation, which is the drilling of a hole, is sometimes preceded
by local work-hardening intended to reduce the ductility of the
metal along the cutting line. However, both in the case of slightly
drawn parts and parts which are highly drawn, the quality of the
cutting is often insufficient, and this leads to an appreciable
proportion of the cut parts being scrapped.
[0004] To improve the quality of the cutting, it is known to add
small amounts of alloying elements such as molybdenum or niobium to
the alloy, or to maintain very low amounts of residual elements
such as carbon, sulphur, phosphorus or oxygen which may form
inclusions. However, these means are insufficient and the
mechanical cutting capability of the Fe--Ni or Fe--Ni--Co or
Fe--Ni--Co--Cu alloys is deemed to be very inferior compared with,
for example, that of 305 stainless steel.
[0005] It is an object of the present invention to remedy this
drawback by providing a means for improving the cuttability of
Fe--Ni or Fe--Ni--Co or Fe--Ni--Co--Cu type alloys used in thin
strip form for the manufacture by precision mechanical cutting of
parts used especially in electronic or electrical equipment.
[0006] For this purpose, the subject of the invention is a strip
made of an austenitic Fe--Ni alloy or Fe--Ni--Co alloy or
Fe--Ni--Co--Cu alloy in which the chemical composition of the alloy
comprises, in % by weight:
30%.ltoreq.Ni.ltoreq.70%
0%.ltoreq.Cu+2.times.Co.ltoreq.20%
0%.ltoreq.Mn+Cr.ltoreq.5%
0%.ltoreq.W+2.times.Mo.ltoreq.2%
0%.ltoreq.Ti+V+Nb+Al.ltoreq.1%
0.0005%.ltoreq.B.ltoreq.0.007%
[0007] the balance being iron and impurities such as C, S, P, O and
N; the chemical composition being such that Fe+Ni+Cu+Co.gtoreq.95%.
In addition, the alloy has a cubic texture with a cubic texture
index D.sub.c.gtoreq.7.
[0008] As a preference, separately or in combination, the boron
content is between 0.0007% and 0.004%, the D.sub.c index is greater
than 10, the carbon content is less than or equal to 0.05%, the
sulphur content is less than or equal to 0.01%, and better still
less than or equal to 0.007% and the oxygen content is less than
0.005%.
[0009] The invention also relates to a process for manufacturing a
strip made of an Fe--Ni or Fe--Ni--Co or Fe--Ni--Co--Cu alloy in
which:
[0010] a strip made of an alloy whose chemical composition is
defined above is manufactured by cold-rolling with a deformation
ratio of greater than 80%;
[0011] a fine-grain recrystallization annealing operation is
carried out on the strip;
[0012] and, optionally, a complementary cold-rolling operation is
carried out with a deformation ratio of less than 40%.
[0013] Finally, the invention relates to a process for
manufacturing a part by mechanical cutting or by mechanical cutting
and drawing, in which a blank is taken from a strip according to
the invention and at least one mechanical cutting operation and
optionally at least one drawing operation are carried out on the
blank, it being possible for the at least one drawing operation to
be carried out before or after the at least one mechanical cutting
operation. The part is, for example, an electron-gun part with a
hole through which the electrons pass. The part may also be a
leadframe with connection leads. The part may also be a magnetic
core of a micromotor or transformer. This list of applications is
not limiting.
[0014] The invention will now be described in greater detail with
regard to the appended figure and illustrated by examples.
[0015] FIG. 1-a represents, in schematic cross section, a strip in
which a hole has been drilled by mechanical cutting, showing a cut
surface corresponding to poor cuttability.
[0016] FIG. 1-b represents, in schematic cross section, a strip in
which a hole has been drilled by mechanical cutting, having a cut
surface corresponding to acceptable cuttability.
[0017] FIG. 1-c represents, in schematic cross section, a strip in
which a hole has been drilled by mechanical cutting, having a cut
surface corresponding to good cuttability.
[0018] The strip according to the invention is thin, cold-rolled
strip (with a thickness in general of less than 1.5 mm) made of an
alloy of the Fe--Ni or Fe--Ni--Co or Fe--Ni--Co--Cu type which are
known per se in their most general form. In this type of alloy, the
nickel, or the cobalt, which is a substitute for nickel, allows
properties such as the thermal expansion coefficient or the
magnetic permeability to be adjusted. The nickel content is between
30% and 70%; the copper and cobalt contents are such that the sum
Cu+2Co is less than or equal to 20%, these two elements being
optional. The balance is essentially iron, impurities, such as
carbon, sulphur, phosphorus, oxygen and nitrogen, and possibly
complementary alloying elements, such as manganese, chromium,
tungsten, molybdenum, titanium, vanadium, niobium and aluminium.
However, the iron, nickel, copper and cobalt contents must be such
that: Fe+Ni+Cu+Co.gtoreq.95%. The contents of the alloying elements
must be such that: Mn+Cr<5%, W+2Mo.ltoreq.2% and
Ti+V+Nb+Al.ltoreq.1%. Certain impurities, such as carbon, sulphur
and oxygen which are in the form of inclusions, may be desirable in
small amounts since they have a favourable effect on cuttability.
Nevertheless, the carbon content, must, preferably, remain less
than 0.05%, the sulphur content must preferably remain less than
0.01%, and better still less than 0.007%, and the oxygen content
must, preferably, remain less that 0.005%.
[0019] Furthermore, the alloy contains from 0.0005% to 0.007%, and
preferably from 0.0007% to 0.004%, boron and has a (001)<100>
cubic texture characterized by a cubic texture index D.sub.c of
greater than 7, and preferably greater than 10. This is because the
inventors have found, surprisingly, that an addition of boron
combined with a highly pronounced cubic texture very substantially
improves the mechanical cutting capability of alloys of the Fe--Ni
or Fe--Ni--Co or Fe--Ni--Co--Cu type.
[0020] The cubic texture index D.sub.c is the ratio,
I.sub.cubic/I.sub.isotropic, of the maximum reflected X-ray
intensities, measured on a (111) pole figure at a point located at
54.degree.44' from the centre of the figure and along the line at
45.degree. to the rolling direction for a specimen of the strip to
be characterized on the one hand and for an isotropic specimen on
the other.
[0021] The degree of texture of a strip may also be evaluated
simply but approximately by a drawing test by measuring the drawing
ears. This method can be used only to characterize a sufficiently
ductile metal. To use this test, it is possible, for example, to
start with a 60 mm diameter disc, to draw this disc so as to form a
cup 33 mm in diameter and 19 mm in height on average. The
difference in height between the highest points and the lowest
points of the upper edge is then measured. If this height
difference is less than 0.3 mm, the strip is isotropic or has very
little texture; if this difference is greater than 1.5 mm, the
strip has a highly pronounced texture.
[0022] To obtain a strip of alloy having a pronounced cubic
texture, the alloy is smelted, cast and hot-rolled in a manner
known per se so as to obtain a hot strip of sufficient thickness to
allow a cold strip having the desired thickness to be obtained by
cold-rolling with a reduction ratio of greater than 80%, and better
still greater than 90%. The thickness of the hot-rolled strip may,
for example, be 5 mm. The cold rolling must be carried out without
intermediate annealing, but may be preceded by an annealing step.
This is the case, in particular, when, on account of the thickness
of the hot strip and the intended thickness for the cold strip, it
is necessary to carry out several successive cold-rolling passes.
The final cold-rolling pass (with a reduction ratio of greater than
80%) is followed by a recrystallization annealing step generally
carried out in a tunnel furnace in a protective atmosphere
consisting, for example, of a mixture of hydrogen and nitrogen with
a dew point below -40.degree. C. The temperature of the oven, about
1000.degree. C., must be sufficient to obtain fine-grain
recrystallization, but not too high in order to prevent undesirable
coarse-grain secondary recrystallization. The duration of the
annealing step is in general around one minute. Those skilled in
the art will know how to adapt, on a case-by-case basis, the
precise annealing conditions so as to obtain fine-grain
recrystallization while avoiding secondary recrystallization.
[0023] Optionally, and so as to increase the hardness of the strip,
the recrystallization annealing may be followed by complementary
cold-rolling with a reduction ratio of less than 50.degree. or
better still less than 30.degree., in order not to excessively
degrade the initial cubic texture. When the reduction ratio of the
complementary cold-rolling is less than 10%, a cold strip, softened
or slightly work-hardened, having a pronounced cubic texture is
obtained. When the reduction ratio of the complementary cold
rolling is greater than 10%, a work-hardened cold strip with a
pronounced cubic texture is obtained.
[0024] Given the thickness of the hot strip, the cold-rolled strips
obtained have a thickness generally of less than 0.5 mm.
[0025] To manufacture a part according to the invention from a
strip having a cubic texture index of greater than 7, or better
still, greater than 10, or even better greater than 15, a blank is
cut by mechanical cutting in a manner known per se. The blank may
either be the finished part, which is then flat, or a preform. The
preform may be formed by drawing and then cut again by mechanical
cutting. This cutting may, for example, be a drilling operation.
This cutting operation may be preceded by a local work-hardening
step.
[0026] When the part is flat or slightly deformed by drawing, that
is to say when the deformation ratio produced by the drawing is
less than 20%, the strip can be used after a complementary
cold-rolling operation with a reduction ratio of between 10% and
30%, or even 50%. This is the case, for example, for flat parts for
electron guns of colour display cathode-ray tubes, or for
leadframes having connection leads, or for rotors or stators of
electric micromotors.
[0027] When the part is highly deformed, by drawing or by bending
or by a local thickness reduction, that is to say with deformation
ratios of greater than 20%, the strip is used in the softened or
slightly work-hardened state, that is to say without complementary
cold-rolling or with complementary cold-rolling having a reduction
ratio of less than 10%. This is the case, for example, for certain
electron-gun parts for colour display cathode-ray tubes.
[0028] The quality of the cutting is assessed by the cut surface,
which comprises a sheared region and a torn region. The line of
demarcation between these two regions must be regular and located
at approximately mid-thickness. There must not be any burrs.
[0029] Three cut surfaces are shown in FIGS. 1a, 1b and 1c. These
surfaces are those observed around a hole 1a, 1b and 1c, drilled in
a strip 2a, 2b and 2c by punching. Only one half of each hole is
shown after sectioning the strips in a plane passing through the
axis of the holes. The walls 3a, 3b and 3c of the holes each have a
sheared region 4a, 4b and 4c and a torn region 5a, 5b and 5c.
[0030] FIG. 1a corresponds to a strip of an alloy having poor
cuttability. The sheared region 3a corresponds to most of the
thickness and it terminates near the bottom, in substantial burrs
6a.
[0031] FIG. 1b corresponds to a strip of an alloy having a
cuttability which is just acceptable. The sheared region 3b
corresponds roughly to half the thickness and terminates, near the
bottom, in a few burrs 6b.
[0032] FIG. 1c corresponds to a strip of an alloy having excellent
cuttability. The sheared region 3c corresponds to roughly half the
thickness and has no burrs.
[0033] These figures are given merely by way of indication. Those
skilled in the art will know how to assess in each case the quality
of the cutting in accordance with more precise criteria than that
which can be deduced directly from these figures.
[0034] Apart from the observation of these cut surfaces, the
quality of the cutting can also be assessed by the geometrical
quality of the parts obtained. When the cutting is the drilling of
a round hole, the assessment of the cutting quality takes into
account how circular the hole is.
[0035] In general, the observations needed to evaluate the quality
of the cut parts are made with a magnification of between .times.10
and .times.50.
[0036] By way of examples and comparisons, hot-rolled strips 4.5 mm
in thickness made of an FeNi42 alloy, the chemical compositions of
which in % by weight are given in Table 1, were manufactured.
1 Ref. Ni Mn Si C S P Al B N O Fe PV408 40.8 0.45 0.07 0.005
<0.0005 0.003 <0.005 <0.0005 0.002 0.0025 Bal. PV588 41.1
0.40 0.10 0.004 <0.0005 0.004 <0.005 0.0038 0.002 0.0025 Bal.
PW075 40.6 0.43 0.12 0.009 0.0032 0.003 <0.005 0.0018 0.002
0.0035 Bal.
[0037] Alloys PV588 and PW075 have compositions in accordance with
the invention while alloy PV408 is given by way of comparison.
[0038] Cold strips were produced from these hot strips according to
6 different manufacturing schemes, denoted A, B, C, D, E and F,
comprising: a first cold-rolling pass with a deformation ratio
DEF1, a tunnel-furnace recrystallization annealing step and a
second cold-rolling pass with a deformation ratio DEF2. The first
deformation was in certain cases preceded by a preliminary
deformation of the hot-rolled strip followed by a recrystallization
annealing step in order to adjust the thickness to the desired
value.
[0039] The deformation ratios for each scheme, together with the
hardnesses Hv and elongations at break A% obtained (which are
identical for the three alloys), are given in Table 2.
2TABLE 2 Scheme A B C D E F DEF1 68% 50% 88% 91% 96% 96% DEF2 60%
23% 23% 20% 20% 44% Hv 230 205 205 205 205 220 A % 1% 5% 5% 5% 5%
2%
[0040] For each of these schemes, the cubic texture indices D.sub.c
obtained for each of the alloys are given in Table 3.
3 TABLE 3 A B C D E F PV408 D.sub.c = 1 D.sub.c = 1 nd nd D.sub.c =
25 nd PV588 D.sub.c = 1 D.sub.c = 1 nd D.sub.c = 10 D.sub.c = 25
D.sub.c = 7 PW075 D.sub.c = 1 D.sub.c = 1 D.sub.c = 10 D.sub.c = 25
D.sub.c = 45 D.sub.c = 12
[0041] To obtain a cubic texture index D.sub.c of greater than 10,
these results show that the deformation ratio DEF1 must be high and
preferably greater than 80% and the deformation ratio DEF2 must not
be too high.
[0042] The cold-rolled strips made of PV588 alloy obtained using
schemes D, E and F and the strips made of PWO75 alloy obtained
using schemes C, D, E and F correspond to the invention. The other
ones are given by way of comparison.
[0043] Leadframes were produced, by mechanical cutting, from the
0.25 mm thick strips corresponding to the three alloys and to
manufacturing scheme D. The PV588 and PW075 alloys, containing
boron in accordance with the invention, gave 100% good parts. On
the other hand, the PV408 alloy gave poor parts with significant
burring.
[0044] Three strips 0.4 mm in thickness were manufactured from the
PW075 alloy (containing boron in accordance with the invention)
using schemes A, B and C respectively, from which batches of flat
parts were cut, these parts having a circular hole 0.5 mm in
diameter obtained by punching.
[0045] In the batch corresponding to scheme A (comparison), only
24% of the parts were good and in the batch corresponding to scheme
B (comparison) only 53% of the parts were good. In contrast, 100%
of the parts of the batch corresponding to scheme C (invention)
were good.
* * * * *