CA1308940C

CA1308940C - Copper alloy and method

Info

Publication number: CA1308940C
Application number: CA000542572A
Authority: CA
Inventors: Horst Gravemann
Original assignee: KM Kabelmetal AG
Current assignee: KM Kabelmetal AG
Priority date: 1986-06-20
Filing date: 1987-07-21
Publication date: 1992-10-20
Anticipated expiration: 2009-10-20
Also published as: EP0250001A3; JP2530657B2; DE3620654A1; EP0250001A2; FI872760L; EP0250001B1; IN168226B; ES2038620T3; ZA874542B; DE3775474D1; FI872760A0; FI88623B; JPS648236A; ATE70858T1; FI88623C

Abstract

COPPER ALLOY AND METHOD

ABSTRACT OF THE DISCLOSURE

Method of making a copper alloy to be used as a mold for continuous casting and comprising from 0.05% to 0.4% zinc; from 0.02% to 0.3% magnesium; from 0.02% to 0.2%
phosphorus; all percentages by weight; the remainder being copper, and inevitable impurities: the alloy is cast and hot worked possibly followed by quenching and cold working with at least 10% deformation; the alloy is then annealed from 1 to 6 hours at a temperature from 300 to 550° centigrade; and finally cold worked with at least 10% deformation.

Description

I 13~8~40 1¦ B~CKGROUND OF THE INVENTION

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).

Z ~ ~

;~08~0 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.

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 ~3~

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.

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 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.

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 ~ ~3~ 0 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.

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 ~ o 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.

l ~ o 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) A5 1~ 13.5 12.5 12.0 27 12 ( 10) (Alo) (=% expansion at rupture;
13 3-sample average) Z: --82 ~4 74 70 65 (= % cross sectional 16 constriction at fracture;
3-sample average) 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~

TEMPERATURE: 400 5~5 565 550 500 24 (0.5 hours annealing in dearees C) ____ __ __ TIME: 2-3 64 64 64 ---27 (at 350 degrees C
in hours) ~ 1~08~

TABLE B
MATERIAL: SF-Cu CuZn 0. 2 Mg 0 .1 P 0. 08 CuCrZr % DEFORMATION: 25 10 20 40 10 CREEP EXTENSIONS

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 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 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 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 13~ 0 CREEP EXTENSIONS
AT A LOAD OF
2 150 N/mm2, AT
200 degrees C, 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, 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 12 % DEFORMATION: 25 10 20 40 10 CREEP EXTENSIONS

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

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 ~ '~ :~08~0 -l CREEP EXTENSIONS
l AT A LOAD OF
2¦ 150 N~mm2, AT
250 degrees C, 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, 8 500 HOURS IN %:4.57 0.140 0.180 0.160 0.014 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 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 The invention is not limited to the embodiments described above, but all changes and modifications thereof not constituting departures from the spirit and scope of the 23 invention, are intended to be included.

Claims

1. Copper alloy comprising from 0.05% to 0.4% zinc; from 0.02% to 0.3% magnesium; from 0.02% to 0.2% phosphorus; from 0 to 0.2% silicon; and from 0 to 0.15% zirconium; all percentages by weight; the remainder being copper, and inevitable impurities.

2. Copper alloy as in claim 1, comprising from 0.1% to 0.25% zinc; from 0.05% to 0.15% magnesium; from 0.05% to 0.1%
phosphorus; from 0 to 0.2% silicon; all percentages by weight; the remainder copper, and inevitable impurities.

3. Copper alloy as in claim 1, comprising not more than 0.2% silicon.

4. Copper alloy as in claim 2, comprising not more than 0.1% silicon.

5. Copper alloy as in claim l, comprising not more than 0.15% zirconium.

6. Method of making the copper alloy as defined in claim 1, 2, 3, 4 or 5, comprising the step of:

casting and hot working the alloy:

annealing the alloy from 1 to 6 hours at a temperature from 300 to 550° centigrade; and cold working the annealed alloy with at least 10%
deformation.

Claim 7. Method as in claim 6, including additionally cold working the alloy with at least a 10% deformation and following hot working and prior to annealing.

Claim 8. Method as in claim 6, wherein said hot working is carried out at a temperature above the maximum solution temperature, the alloy being quenched from at least 750° centigrade.

Claim 9. Method as in claim 8, wherein the quenching is carried out down to annealing temperature.

Claim 10. Method as in claim 8 wherein the quenching is carried out down to room temperature.

Claim 11. Method as in claim 6 including a homogenizing annealing above 750 degrees C following the hot working.