U.S. patent application number 10/361660 was filed with the patent office on 2003-08-28 for age-hardenable copper alloy.
Invention is credited to Helmenkamp, Thomas, Rode, Dirk.
Application Number | 20030159763 10/361660 |
Document ID | / |
Family ID | 27635063 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030159763 |
Kind Code |
A1 |
Helmenkamp, Thomas ; et
al. |
August 28, 2003 |
Age-hardenable copper alloy
Abstract
An age-hardenable copper alloy made of 1.2 to 2.7% cobalt, which
is able to be partially replaced by nickel, 0.3 to 0.7% beryllium,
0.01 to 0.5% zirconium, optionally 0.005 to 0.1% magnesium and/or
iron and in some instances up to a maximum of 0.15% of at least one
element from the group including niobium, tantalum, vanadium,
hafnium, chromium, manganese, titanium and cerium. The remainder is
copper and includes production-conditioned impurities and usual
processing additives. This copper alloy is used as the material for
producing mold blocks for the side dams of continuous strip-casting
installations.
Inventors: |
Helmenkamp, Thomas;
(Osnabruck, DE) ; Rode, Dirk; (Osnabruck,
DE) |
Correspondence
Address: |
KENYON & KENYON
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
27635063 |
Appl. No.: |
10/361660 |
Filed: |
February 10, 2003 |
Current U.S.
Class: |
148/411 ;
420/488; 420/492; 420/494; 420/496 |
Current CPC
Class: |
C22C 9/06 20130101; B22D
11/066 20130101 |
Class at
Publication: |
148/411 ;
420/488; 420/492; 420/494; 420/496 |
International
Class: |
C22C 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2002 |
DE |
102 06 597.7 |
Claims
What is claimed is:
1. An age-hardenable copper alloy suitable as a material for
producing block for the side dams of strip-casting installations,
comprising: 1.2 to 2.7% cobalt, 0.3 to 0.7% beryllium, 0.01 to 0.5%
zirconium, and a balance of copper.
2. The copper alloy according to claim 1, further comprising 0.005
to 0.2% magnesium.
3. The copper alloy according to claim 1, further comprising 0.005
to 0.2% iron.
4. The copper alloy according to claim 2, further comprising 0.005
to 0.2% iron.
5. The copper alloy according to claim 1, further comprising up to
a maximum of 0.15% of at least one element selected from the group
consisting of niobium, tantalum, vanadium, hafnium, chromium,
manganese, titanium and cerium.
6. The copper alloy according to claim 2, further comprising up to
a maximum of 0.15% of at least one element selected from the group
consisting of niobium, tantalum, vanadium, hafnium, chromium,
manganese, titanium and cerium.
7. The copper alloy according to claim 3, further comprising up to
a maximum of 0.15% of at least one element selected from the group
consisting of niobium, tantalum, vanadium, hafnium, chromium,
manganese, titanium and cerium.
8. The copper alloy according to claim 4, further comprising up to
a maximum of 0.15% of at least one element selected from the group
consisting of niobium, tantalum, vanadium, hafnium, chromium,
manganese, titanium and cerium.
9. The copper alloy according to claim 4, comprising: 1.8 to 2.4%
cobalt, 0.45 to 0.65% beryllium, 0.15 to 0.3% zirconium, up to
0.05% magnesium, up to 0.1% iron, and a balance of copper.
10. The copper alloy according to claim 1, wherein up to 80% of the
cobalt content is replaced by nickel.
11. The copper alloy according to claim 2, wherein up to 80% of the
cobalt content is replaced by nickel.
12. The copper alloy according to claim 1, wherein a part of the
zirconium content is replaced by up to 0.15 wt. % of at least one
element selected from the group consisting of cerium, hafnium,
niobium, tantalum, chromium, manganese, titanium and vanadium.
13. The copper alloy according to claim 2, wherein a part of the
zirconium content is replaced by up to 0.15 wt. % of at least one
element selected from the group consisting of cerium, hafnium,
niobium, tantalum, chromium, manganese, titanium and vanadium.
14. The copper alloy according to claim 1, which, after hot forming
of the cast blank, is cold formed up to 40%, is then solution
treated at a temperature lying in the temperature range of 850 to
970.degree. C., and is subsequently submitted to a 0.5 to 16-hour
age-hardening treatment at 400 to 550.degree. C.
15. The copper alloy according to claim 14, which, after the hot
forming, is cold formed by 5 to 30%.
16. The copper alloy according to claim 14, which, after hot
forming, is cold formed by 10 to 15%.
17. The copper alloy according to claim 1, which, in the
age-hardened state, has a tensile strength of at least 650 Mpa, a
Vickers hardness of at least 210 HV, an electrical conductivity of
at least 40% IACS, a hot tensile strength at 500.degree. C. of at
least 400 Mpa, a minimum hardness of 160 HV after 500 hours of
constant ageing at 500.degree. C. and a maximum grain size
according to ASTM E112 of 0.5 mm.
18. The copper alloy according to claim 1, which, in the
age-hardened state, has a tensile strength of at least 700 to 900
Mpa, a Vickers hardness of 230 to 280 HV, an electrical
conductivity of 45 to 60% IACS, a hot tensile strength at
500.degree. C. of at least 450 Mpa and a minimum hardness of 160 HV
after 500 hours of constant ageing at 500.degree. C.
19. The copper alloy according to claim 1, which has a grain size
between 30 and 90 .mu.m, ascertained according to ASTM E112.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to an age-hardenable copper alloy as
material for producing blocks for the side dams of continuous
strip-casting installations.
[0003] 2. Description of Related Art
[0004] The worldwide aim, especially in the steel and copper
industries, to cast semifinished material to as close to the final
dimensions as possible, in order to save hot forming and/or cold
forming steps, led even before 1970 to the development of the
so-called Hazelett strip-casting installations, in which the molten
metal solidifies in the gap between two bands guided in parallel.
The side dams in, for example, the strip-casting installation known
from U.S. Pat. No. 3,865,176, are made of metallic mold blocks or
dam blocks having a T groove, which are lined up on a flexible
continuous band such as one made of steel, and which move in the
longitudinal direction, synchronously with the casting bands. In
this context, the dam blocks bound the casting mold cavity formed
by the casting bands.
[0005] Also known, from EP 0 974 413 A1 are dam block chains for
continuous strip-casting, formed by blocks having a slot and key.
The advantage of these further developed mold blocks having a slot
and key comes about due to a more exact alignment and guidance of
the blocks during the casting process, and leads to an improvement
of the surface quality of the cast strip. In order to prevent
premature wear of the side edges of the blocks by plastic
deformation and the formation of cracks, a suitable material has to
have great hardness and strength, a fine-grained microstructure and
a good long-term resistance to softening. In order to remove the
heat of solidification from the liquid molten material, a high
thermal conductivity of the mold block material is additionally
required.
[0006] Finally, optimum fatigue behavior of the material is of the
most decisive significance, which will ensure that, after leaving
the casting segment, the thermal stresses appearing during the
cooling off of the blocks do not lead to cracking of the blocks at
the corners of the T groove incorporated for the accommodation of
the steel band. In this context, particularly great thermal
stresses are to be expected in dam blocks having the design using
slot and key, on account of the unfavorable geometry and mass
distribution.
[0007] If such cracks caused by thermal shock appear, the
respective mold block will fall out of the dam block chain of the
continuous strip-casting machine after even a short period, molten
metal being able to run uncontrollably from the casting mold cavity
and to damage parts of the installation. For the purpose of
exchanging the damaged mold blocks, the entire strip-casting
installation has to be stopped and the casting process has to be
interrupted.
[0008] A testing method has proven itself for checking the tendency
to crack, in which the mold blocks are submitted to heat treatment
for two hours at 500.degree. C. and are subsequently quenched in
water at 20 to 25.degree. C. Even if this thermal shock test is
repeated several times, in the case of a suitable material no
cracks may appear in the T groove surface.
[0009] EP 0 346 645 B1 describes an age-hardenable copper-based
alloy which is made of 1.6 to 2.4% nickel, 0.5 to 0.8% silicon,
0.01 to 0.2% zirconium, optionally up to 0.4% chromium and/or up to
0.2% iron, the remainder being copper including production-caused
impurities. This known copper alloy basically satisfies the
prerequisites for a long service life, if used as the material for
producing standard mold blocks for the side dams of continuous
strip-casting installations. The following combination of
properties is given for this copper alloy:
1 Rm at 20.degree. C.: 635 to 660 MPa Rm at 500.degree. C.: 286 to
372 MPa Brinell hardness: 185 to 191 HB (corresponds to about 195
to 210 HV) Conductivity: 41.4 to 42.4% IACS.
[0010] No cracks are to appear during the thermal shock test. One
advantage compared to beryllium-containing copper-based alloys is
the possibility of being able to regrind the mold blocks manually,
since no beryllium is contained in the grinding dust. The
reprocessing of used dam blocks having slot and key is considerably
more costly and, as a rule, requires machine (wet) cleaning of the
T groove and the casting surfaces (e.g. in closed chambers),
whereby the liberation of grinding dusts is prevented. Thus, using
beryllium-containing alloys would basically be possible under these
circumstances.
[0011] A dam block made of the CuNiSiZr alloy described in EP 0 346
645 81, however, disadvantageously tends to premature wear of the
side edges and casting surfaces, at very high mechanical and
thermal stresses in the casting operation of a continuous
strip-casting installation. As the results of investigations have
shown, this wear may be attributed to a material softening of the
casting edges and surfaces to a value below 160 HV. Furthermore,
the thermal shock resistance of the known CuNiSiZr alloy is not
always sufficient for effectively preventing the formation of
cracks in the T groove during casting use, when the alloy is used
for a dam block having a slot and key.
SUMMARY OF THE INVENTION
[0012] It is an object of the invention to create an age-hardenable
copper alloy as a material for producing dam blocks for continuous
strip-casting installations, especially in a slot and key
embodiment, which is stable to changing temperature stresses even
at high casting speeds, and which has a great resistance to wear
and resistance to softening, as well as great resistance to crack
formation in the T groove.
[0013] These and other objects of the invention are achieved by an
age-hardenable copper alloy made of 1.2 to 2.7% cobalt, 0.3 to 0.7%
beryllium, 0.01 to 0.5% zirconium, optionally 0.005 to 0.2%
magnesium and/or 0.005 to 0.2% iron and, in some instances, up to a
maximum of 0.15% of at least one element from the group including
niobium, tantalum, vanadium, hafnium, chromium, manganese, titanium
and cerium, the remainder being copper including production-caused
impurities and the usual processing additives. This alloy is used
as the material for producing block for the side dams of
strip-casting installations.
DETAILED DESCRIPTION OF THE INVENTION
[0014] By using a copper-based alloy made of 1.2 to 2.7 wt. %
cobalt, 0.3 to 0.7 wt. % beryllium, 0.01 to 0.5 wt. % zirconium,
optionally 0.005 to 0.2 wt. % magnesium and/or iron and of the
remainder copper, including production-caused impurities and the
usual processing additives, on the one hand, a sufficient
age-hardenability of the material for achieving great strength,
hardness and conductivity may be ensured. On the other hand, only a
relatively slight cold working of up to a maximum of 40% is
required for establishing a fine-grained microstructure having a
sufficient plasticity. Because of the deliberately graduated
zirconium content, both the fatigue resistance and the heat
resistance properties are improved.
[0015] A further improvement of the mechanical properties of the
dam blocks, especially an increase in tensile strength, may
advantageously be achieved by having the copper alloy contain 1.8
to 2.4 wt. % cobalt, 0.45 to 0.65 wt. % beryllium, 0.15 to 0.3 wt.
% zirconium, up to 0.05 wt. % magnesium and/or up to 0.1% iron.
[0016] The invention permits that, in the copper alloy up to 80% of
the cobalt content may be replaced by nickel.
[0017] Further improvements of the mechanical properties of a dam
block may be achieved if the copper alloy contains up to a maximum
of 0.15 wt. % of at least one elements of the group including
niobium, tantalum, vanadium, hafnium, chromium, manganese, titanium
and cerium. Usual deoxidants such as boron, lithium, potassium and
phosphorus may also be added up to a maximum of 0.03 wt. %, without
negatively influencing the mechanical properties of the copper
alloy of the present invention.
[0018] According to another specific embodiment, a part of the
zirconium content may be replaced by up to 0.15 wt. % by at least
one element of the group including cerium, hafnium, niobium,
tantalum, vanadium, chromium, manganese and titanium.
[0019] Advantageously, the blocks for the side dams of double
strip-casting installations are produced using the age-hardenable
copper alloy, by the method steps: casting, hot forming, cold
forming up to 40%, solution treating at a temperature in the range
of 850 to 970.degree. C., as well as a 0.5 to 16-hour age-hardening
treatment at 400 to 550.degree. C.
[0020] As a particular advantage, the copper alloy may be cold
formed by 5 to 30% after hot forming. A cold forming degree of 10
to 15% lying within this range is particularly preferred in this
context.
[0021] It is especially advantageous if the dam blocks in the
age-hardened condition have a tensile strength of at least 650 Mpa,
particularly 700 to 900 Mpa, a Vickers hardness of at least 210 HV,
particularly 230 to 280 HV, an electrical conductivity of at least
40% IACS, particularly 45 to 50% IACS, a hot tensile strength at
500.degree. C. of at least 400 Mpa, particularly of at least 450
Mpa, a minimum hardness of 160 HV after 500-hour ageing at
500.degree. C., and a maximum grain size according to ASTM E 112 of
0.5 mm.
[0022] Particularly preferred are dam blocks made of the copper
alloy, if, in the age-hardened condition they have a grain size,
ascertained according to ASTM E 112, between 30 and 90 .mu.m.
[0023] In a preferred embodiment, the copper alloy, after the hot
forming of the cast blank, is cold formed up to 40%, is then
solution treated at a temperature lying in the temperature range of
850 to 970.degree. C., and is subsequently submitted to a 0.5 to
16-hour age-hardening treatment at 400 to 550.degree. C. In a
surprisingly simple way one may succeed in getting rid of the bad
recrystallization behavior observed in the known CuCoBe alloys
during the hot forming and solution treatment. The bad
recrystallization behavior, in the production of mold blocks made
of CuCoBe alloys, in the hot formed, solution treated and
age-hardened condition leads to a coarse microstructure, that is
not acceptable for the application purpose, having grain sizes up
to more than 1 mm. However, if, between the hot forming and the
solution treatment, the material is submitted to cold forming up to
a maximum of 40%, preferably up to a maximum of 15%, this
additional processing step leads to a considerably more
fine-grained microstructure. Relevant investigative series have
confirmed that materials for mold blocks for the side dams of
strip-casting machines, which are cold formed below the
recrystallization temperature, and are subsequently solution
treated, have a clearly finer microstructure at grain sizes below
0.5 mm, while higher degrees of cold forming, above approximately
40%, lead during subsequent solution treatment to a coarsening of
the grain by secondary recrystallization, at grain sizes above 1
mm.
EXAMPLES
[0024] The invention is explained below in greater detail, with the
aid of exemplary embodiments. The advantages of the copper alloys
are demonstrated using three alloys according to the invention (A,
B and C) and three alloys for reference (D, E and F). The
composition of the copper alloys in wt. % is given below in Table
1.
2TABLE 1 Co Alloy (%) Ni (%) Be (%) Zr (%) Si (%) Cr (%) Cu (%) A
2.1 -- 0.54 0.18 -- -- Remainder B 2.2 -- 0.56 0.24 -- -- Remainder
C 1.3 1.0 0.48 0.15 -- -- Remainder D -- 2.0 -- 0.16 0.62 0.34
Remainder E 2.1 -- 0.55 -- -- -- Remainder F 1.0 1.1 0.62 -- -- --
Remainder
[0025] In the case of the composition of alloy D, a known
CuNiSi-based alloy is involved, whereas E and F are normalized
CuCo2Be or CuCoNiBe materials.
[0026] All the copper alloys were smelted in an induction crucible
oven and were cast by the continuous strip-casting method to round
billets having a diameter of 280 mm. The round billets of exemplary
alloy A, B and C were extruded on an extrusion press at a
temperature above 900.degree. C. to flat bar of a dimension
79.times.59 mm, and subsequently were drawn, at a loss in cross
section of 12%, to a dimension of 75.times.55 mm. The blocks of the
reference alloys D, E and F were extruded at the same temperature,
directly to the dimension 75.times.55 mm, and were not submitted to
additional cold forming. The CuCoBe and CuCoNiBe materials were
subsequently solution-treated at 900 to 950.degree. C. and were
age-hardened at a temperature range between 450 and 550.degree. C.
for 0.5 to 16 hours.
[0027] The CuNiSi-based alloy was solution-treated at 800 to
850.degree. C. and age-hardened under the same conditions. In the
age-hardened condition, the tensile strength Rm, the Vickers
hardness HV10, the electrical conductivity (as substitute quantity
for the heat conductivity), the grain size according to ASTM E112,
the heat resistance Rm at 500.degree. C. and the resistance to
softening via Vickers hardness measurement (HV10) after ageing at
500.degree. C. after 500 hours were ascertained.
[0028] The thermal shock behavior was finally tested on mold blocks
(1) of dimensions 70.times.50.times.40 mm and mold blocks (2),
having slot and key, of dimensions 70.times.50.times.47 mm. For
this, the mold blocks were first annealed for two hours at
500.degree. C. and then quenched in water at 20 to 25.degree. C.
The T groove of the blocks were then searched for cracks with the
naked eye and a microscope at 10-fold magnification.
[0029] All the test results are summarized in Table 2 below.
3TABLE 2 Vickers Hardness Tensile Vickers Conductivity Grain
Strength 10 After Ageing at Behavior After Strength Hardness
(electrical) % Size (500.degree. C.) 500.degree. C. over
Thermoshock Test Alloy MPa HV10 IACS .mu.m MPa 500 h Block (1)
Block (2) A 801 254 50 30-90 523 173 crack-free crack-free B 804
245 51.5 45-90 464 175 crack-free crack-free C 812 255 49.5 45-90
485 167 crack-free crack-free D 652 205 43 45-90 387 118 crack-free
cracked E 786 260 50.5 to 5000 423 150 cracked cracked F 807 248
48.5 to 3000 434 152 cracked cracked
[0030] In the mold blocks classified as "cracked", the extension of
determined cracks in the groove was 2 to 5 mm, and in individual
cases, the length of the crack was up to 10 mm. One may see from
the reference that, as compared to materials E and F, only copper
alloys A, B and C, and produced using slight cold working, at
optimum properties, have a surprisingly uniform and fine-grained
microstructure, and have the necessary resistance to the formation
of cracks when used as mold block having slot and key. Even when
used in a usual mold block, the copper alloys in accordance with
the invention have a clearly better resistance to softening
compared to the known CuNiSi alloys D, and a somewhat better
resistance to softening when compared to alloys E and F.
[0031] Therefore, the copper alloy in accordance with the invention
is eminently suitable as the material for producing all mold
blocks, that are submitted to typically changing temperature stress
during the casting process, for the side dams of strip-casting
installations. These are both the mold blocks used up to the
present and the mold blocks embodied with slot and key as in EP 0
974 413 A1.
* * * * *