Note: Descriptions are shown in the official language in which they were submitted.
I 13~8~40
1¦ B~CKGROUND OF THE INVENTION
21
3 The present invention relates to a copper alloy as well
4 as to the making of a copper alloy in preparation of the
making, and to be used within the process of making, a mold
6 for continuous casting, such as a mold for continuous
7 casting of high melting metals, such as steel.
9 In the past molds to be used for this purpose were
made of copper of the type SF-Cu, which, owing to its
11 particularly high thermal conductivity is capable of
12 extracting rapidly a large amount of heat from the molten
13 metal being cast. The walls of the mold are (or can be
14 made) sufficiently thick so that they can take up the
expected mechanical load and wear. In order to increase the
16 hot strength of such a mold, it has been proposed to use an
17 alloy that includes at least 85X copper and at least one
18 alloying element which causes precipitation hardening. Here
19 then, one may use up to 3% chromium, silicon, silver, and
beryllium. However, a mold made of this particular alloy
21 was not completely satlsfactory, because, unfortunately the
22 particular components silicon and beryllium reduced its
23 thermal conductivity of the resulting product rather
24 drastically (3ee AT-Patent 234,930).
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DESCRIPTION OF TH~ INVENTION
3 It is an object of the present invention to provide a
4 new and improved copper alloy with a very high thermal
conductivity and a high mechanical strength, particularly in
6 temperatures above 300 centigrade, and having a high, hot
7 plasticity. The material is to be used, or useable,
8 primarily for the making of molds for continuous casting.
In accordance with the preferred embodiment of the
11 present invention, a copper alloy is suggested, wherein the
12 alloying components are, from 0.05% to 0.4% zinc; from 0.02%
13 to 0.3% magnesium; from- 0.02% to 0.2% phosphorus; all
14 percentages by weight; the remainder being copper, and
inevitable impurities resulting from the manufacturing.
16
17 Generally, it is known that the addition of zinc or
18 magnesium reduces the conductivity of copper. However, the
19 reduction is not very large, while phosphorus when added to
copper, produces a drastic reduction in thermal
21 conductivity. The strength, however, is increased by the
22 addition of zinc-magnesium or phosphorus. It is quite
23 surprising that by using all three of these elements within
24 the stated ranges the thermal conductivity of copper as
compared with the commercially useable SF-copper is hardly
26 reduced at all. Owing to the mixed crystal hardening,
27 augmented by supplemental hardening through phosphide
28
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l formation, the strength is considerably higher as compared
2 with the SF-copper, bearing in mind that phosphide is
3 amenable to precipitation. Particularly the hot strength is
4 considerably better than the hot strength of SF-copper. It
was found that an alloy being comprised from 0.1 to 0.25%
6 zinc, from 0.05 to 0.15% magnesium, and from 0.05 to 0.1%
7 phosphorus, all percentages by weight, the remainder copper
8 and inevitable impurities, is of particular advantage.
The addition of silicon up to 0.~%, preferably about
ll only 0.1% by weight, has a positive effect on the hardness
12 and, therefore, improves the wear proofing. Adding up to
13 0.15% zirconium increases the hot plasticity. Moreover,
14 these additions in combination with a particularly
controlled heat treatment, improves the softening aspects of
16 the material. Both additions, silicon and zirconium, in the
17 stated concentrations, will not reduce to any noticeable
18 extent the thermal conductivity.
19
A8- far as the making of such an alloy of the type
21 described above, i8 concerned, it is an inventive
22 contribution to proceed as follows. In accordance with the
23 preferred embodiment of making the inventive alloy, it is
24 proposed to cast the alloy in the stated composition and,
251 subsequently to hot work the casting following which the
26¦ alloy is annealed from 1 to 5 hours at 300 to 550
271 centigrade, and finally cold worked at a degree of
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1 1;~38~ 0
1 deformation of at least 10%. An additional lOX minimum cold
2 deformation in between the hot working, on one hand, and the
3 precipi~ation annealing at 300 to 550 centigrade on the
4 other hand has a very positive effect on the homogenization
and on the combination of features and desirable
6 characteristics. However, it is essential that there be a
7 minimal 10% cold working to succeed any respective last
8 annealing.
It is of a particular advantage to hot work the alloy
11 above the temperature of maximum solvability of the alloying
12 components, and then to quench by about 750 centigrade.
13 This feature establishes an additional hardening; a solution
14 annealing (homogenization) may be carried out separately
from the hot working. Rowever, quenching from a
16 homogenization annealing and/or hot working at a temperature
17 above 750 degrees C may be only down to the 300 to 550
18 degrees C of subsequent annealing. Quenching to room
19 temperature may be advisable if the final annealing is
deferred for some reason or lf the additional cold working
21 step is interposed.
22
23 The invention is explained more fully with reference to
24 a specific example. It is assumed that an alloy is made,
having a composition of O.l9X zinc, 0.09% magnesium, 0.07%
26 phosphorus, the remainder copper, and inevitable impurities,
27 all percentages by weight. Following casting, this material
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1 ¦ was hot worked through extrusion, and the extruded product
2 ¦ was then drawn (cold) following cooling for the degree a
3 ¦ deformation of 20%. This alloy was then annealed for five
4 ¦ hours, and at about 500 centigrade. Samples were produced,
5 ¦ which were respectively cold worked at 10%, 20% and 40%.
6 ¦ Tables A, B, and C show the properties of these samples, and
71 compare the same to SF-copper, as well as to a copper-
8¦ chromium-zirconium alloy.
Comparing, from an overall point of view, the new
11 materials with the properties of SF-copper, as it was
12 usually used for making molds for continuous casting,
13 illustrates very clearly that for comparable degrees of
14 deformation the strength values of the metal alloy are
higher by about 10-50%. The thermal conductivity is
16 li~ewise considerably higher. Very important, however, is
17 that the softening at higher temperature is like much more
18 favorable with the novel alloy. This alloy, for example,
19 softens for comparable conductivity only at a temperature of
above S00 centigrade. In addition, there is a considerably
21 lower creepage extension at higher temperatures, which
22 guarantees a better tendency to maintain dimensions and
23 contour. Particularly, distortion is avoided.
24
From an overall point of view, it can be expected that
26 the novel copper alloy in accordance with the invention, is
27 a very good material for making molds for continuous
28
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1 casting. If one compares such an alloy with the copper
2 chromium allows, the inventive alloy has better properties.
3 The inventive alloy can be made much easier and simpler, and
4 the alloying elements as used are more economical. Thus,
from an overall point of view, molds to be used for
6 continuous casting and made from the new material, other
7 conditions being equal, are considerably more economical.
8 Somewhat better are the technological properties of the
9 alloy, if the hot working is carried out at a solution
annealing temperature, whereupon the material is quenched,
11 and then the various steps outlined above will follow.
12 Through precipitation of intermediate phases from the copper
13 matrix, one can obtain still more favorable strength and
14 values as well as values for the thermal conductivity.
16
18
19
21
221
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TABLE A
_. -
2 MATERIAL- SF-Cu CuZn 0.2 Mg 0.09 P 0.075 CuCrZr
.. _.
3 X DEFORMATION: 25 10 20 40 cold
4 def.&
hard-
ened.
Rm: 2~7 3~5 385 420 448
7 (-tensile strength in N/mm )
(3-sample average)
9 R 0.2: 2~5 356 378 400 329
(~0.2% 2stretch limit
in N/mm ;3-sample average)
11
A5 1~ 13.5 12.5 12.0 27
12 ( 10) (Alo)
(=% expansion at rupture;
13 3-sample average)
14
Z: --82 ~4 74 70 65
(= % cross sectional
16 constriction at fracture;
3-sample average)
17
18 HB 2.5/6.25: 91 104 112 115 140
(=2.5/6.25 Brinell hardness;
l9 3-sample average)
.
ELECTRICAL
21 CONDUCTIVITY: 472 49 5 49'5 49'5 49'5
(Siemens.meter/mm )
2~
23 SEMI-HARD SOFTENING
TEMPERATURE: 400 5~5 565 550 500
24 (0.5 hours annealing
in dearees C)
____ __ __
26 SEMI-HARD ANNEALING
TIME: 2-3 64 64 64 ---
27 (at 350 degrees C
in hours)
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TABLE B
MATERIAL: SF-Cu CuZn 0. 2 Mg 0 .1 P 0. 08 CuCrZr
% DEFORMATION: 25 10 20 40 10
CREEP EXTENSIONS
7 AT A LOAD OF
150 N/mm2, AT
8 200 degrees C,
FOR A TOTAL OF
9 6 HOURS IN %: 0.035 0.023 0.014 0.02~ 0.006
CREEP EXTENSIONS
ll AT A LOA2D OF
150 N/mm AT
12 200 degreés C,
FOR A TOTAL OF
13 24 HOURS IN %: 0.05 0:035 0.04~ 0.059 0.008
14
CREEP EXTENSIONS
AT A LOAD OF
150 N/mm2, AT
16 200 degrees C,
FOR A TOTAL OF
17 72 HOURS IN %: 0.07 0.041 0.055 0.064 0.012
18
CREEP EXTENSIONS
l9 AT A LOA~ OF
150 N/mm , AT
200 degrees C,
FOR A TOTAL OF
21 216 HOURS IN %:0.10 0.049 0.0~8 0.086 0.014
22
CREEP EXTENSIONS
23 AT A LOA~ OF
150 N/mm , AT
24 200 degrees C,
FOR A TOTAL OF
500 HOURS IN %:0.14 0.086 0.080 0.100 0.014
26
27
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CREEP EXTENSIONS
AT A LOAD OF
2 150 N/mm2, AT
200 degrees C,
3 FOR A TOTAL OF
4 1000 HOURS IN %:0.20 0.096 0.082 0.107 0.014
CREEP EXTENSIONS
AT A LOA~ OF
6 150 N/mm~, AT
I 200 degrees C,
7 FOR A TOTAL OF
8 2000 HOURS IN %:0.320 0.110 0.100 0.120 0.014
TABLE C
MATERIAL: SF-Cu CuZn 0.2 Mg 0.1 P 0.08 CuCrZr
11
12 % DEFORMATION: 25 10 20 40 10
13
CREEP EXTENSIONS
14 AT A LOAD OF
150 N/mm2 AT
250 degreés C,
FOR A TOTAL OF
16 6 HOURS IN %: 0.11 0.053 0.036 0.030 0.012
17 __
CREEP EXTENSIONS
18 AT A LOA~D OF
150 N/mm , AT
l9 250 degrees C,
FOR A TOTAL OF
20 - 24 HOURS IN %: 0.31 0.055 0.053 0.047 0.014
21 _
CREEP EXTENSIONS
22 AT A LOAD OF
150 N/mm2, AT
23 250 degrees C,
FOR A TOTAL OF
24 72 HOURS IN X: 0.58 0.073 0.093 0.079 0.014
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-l CREEP EXTENSIONS
l AT A LOAD OF
2¦ 150 N~mm2, AT
250 degrees C,
3 FOR A TOTAL OF
216 HOURS IN %:1.27 0.120 0.140 0.130 0.014
CREEP EXTENSIONS
AT A LOAD OF
6 150 N/mm2, AT
250 degrees C,
7 FOR A TOTAL OF
8 500 HOURS IN %:4.57 0.140 0.180 0.160 0.014
9 CREEP EXTENSIONS
AT A LOAD OF
150 N/mm2, AT
250 degrees C,
ll FOR A TOTAL OF
1000 HOURS IN %:* 0.210 0.310 0.260 0.014
12
13 CREEP EXTENSIONS
AT A LOAD OF
14 150 N/mm2, AT
250 degrees C,
FOR A TOTAL OF
16 2000 HOURS IN %:* * * 0.600 0.014
17 * = premature fracture
18
19
The invention is not limited to the embodiments
described above, but all changes and modifications thereof
21
not constituting departures from the spirit and scope of the
22
23 invention, are intended to be included.
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