Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ ~7~i5
3 ~ACI~GROU~D OF THE :~:NyENTION
4 The present invention relates to the making of
pass-through molds for machines for continuous casting using
6 tubular ~lanks which have been made by extrusion and~or
7 drawing andJor forging of age-hardening copper alloys
8 whereby these blanks are at first solution annealed followed
9 by quenching and actual hot age-hardening.
German printed patent application 26 35 454
11 proposes a material for molds for continuous casting which
12 includes age-hardening copper alloys whereby a suitable
13 selection of the allo~ing components have been made to
14 include for example chromium and zirconium so as to obtain
high thermal conductivity, hot strength values as well as
16 strength against creapage and hot plasticity. Such alloys
17 are used for making mold plates to be used in the assembly
18 of molds and they will be solution annealed at 1030 degrees
19 C, quenched in water and age-hardened at a temperature of
475 degrees C. Cutting and milling is carried Ollt on the
21 plate therea~ter in order to obtain the final dimensions.
22 These steps as outlined can also be used for the malcing of
23 thiclc wall tubular single piece molds provided that after
24 the tubular blank has been made through press working,
drawing or the like one immediately provides for the
26 hardening treatment following which cutting or milling is
27 carried out to obtain the final dimensions. However these
28
1 2
2 method steps are not applicable if in case of straight as
3 well as curved, conical or partial conical molcls a mandrel
4 with the final dimensions is introduced in the copper based
tubular blank and forced onto the mandrel in a final cold
6 working step as shown and described in German patent 18 09
7 633.
10 DESCRIPTION OF THE INVENTION
~1 It is an object of the present invention to
12 provide a new and improved method for making tubular molds
13 of age-hardening copper material so as to satisfy
14 requirements as to quality~
It is a particular object of the present invention to
16 provide a new and improved method for making a mold ~or
17 continuous casting using a tubular blank made through
18 extrusion, drawing or forging or any combination thereof and
19 using furthermore an age-hardening copper alloy, also the
steps of solution annealing, quenching and hot or warm age-
22~ ardening of these parts \re to be retained in the process.
27
~ 5
2 In accordance with the preferred embodiment Oe the
3 present invention it is suggested that prior to warm age-
4 hardening, a cold forming and sizing of the blank is carried
out to obtain the wall dimensions under utiliæation of an
6 inserted mandrel. It has been found that this cold working7 and sizing step carried out under utilization of a mandrel
8 having the final dimensions and contour; any distorting of
9 the mold during use is no longer to be expected,
particularly when subsequently a warm working step is used
11 for purposes of warm age-hardening of the copper material.
12 Rather, molds made in this manner have a very long life, and
13 even after extensive use they retain the dimensions at
14 minimum wear.
Cold working and sizing by means of a mandrel can
16 be carried out in different ways. Mandrel and blank are
17 together moved through a die. Re~erence is made here to
18 German patent 18 09 633 wherein a straight tubular blank is
19 forced upon a curved mandrel having final dimensions and the
shape of the mold to be made whereby the outer dimensions of
21 the mandrel are slightly different from the internal
22 dimensions o~ the blanlc being processed so that the blank
23 has to be pre-shaped corresponding to the actual mandrel
24 dimensions.
As per the inventionr the blank and inserted mandrel
26 are together drawn through a die in order to firmly force
27 the inner surfaces of the tubular blank upon the mandrel.
~ 7~
2 Subsequently the mandrel is forced out o~ the now cold
3 hardened blank.
4 Another advantageous mode of procedure is to provide
cold working and sizing by applying a force upon the outer
6 wall of the blank e.g~ through forging or rolling. Other
7 methods for shaping in this regard are explosion methods or
8 hydrostatic and electrodynamic methods. In special cases it
9 was found suitable to combine two or more of these various
ways of cold working. By way of example the tubular blank
11 together with inserted mandrel may be drawn through a die
12 while at the same time additional cold working is carried
13 out through rolling or forging and a final application of
14 force is carried out through detonation of an explosive.
Solution annealing o~ the blank prior to cold working
16 or sizing may be carried out in air requiring subsequently
17 that the surface of the blank be cleaned or smoothed through
18 grinding or polishing. In some cases it may be of advantage
19 if the solution annealing does encompass the entire tubular
blank while in other cases it may suffice to solution anneal
21 just the interior space of the tubular blank but in a
22 reducing atmosphere. This latter method can be carried out
23 with advantage by filling dry charcoal into the interior of
24 the tubular blank and closing the ends of this tubular blank
on both ends with partially perforated sheet metal caps.
26 In carrying out the invention it is believed that
27 ractically all hardenible copper and copper bared raterials
~ 7 ~
2 can be used whereby particular on account o~ these steps,
3 annealinr cold working, and age-hardening one obtains
4 properties and characteristics which render the molds thus
made to be very suitable for that purpose. Particular alloys
6 envisioned here are alloys on the basis of CuCr, CuCrZr,
7 CuCoBe, CuCoNiBe, CoCoNiBeCr, CuNiSi and others. Copper
8 based material in which the invention can be applied with
9 advantage ar for example alloys having from 0~2 to 1.2 % Cr,
from 0.05 to 0.4 % Zr, up to 0~04 ~ Li, Ca, Mg, Si and/or Br
11 as deoxidizing material; all percentages are by weight and
12 the remainder being copper and the usual impurities.
13
14
DESCRIPTION OF THE DRAWINGS
16 While the specification concludes with claims
17 particularly pointing out and distinctly claiming the
18 subject matter which is regarded as the invention, it is
19 believed that the invention, the objects and ~eatures of the
invention and further objects, features and advantages
21 thereof will be better understood from the following
22 description taken in connection with the accompanying
23 drawings in which:
24 Figs. 1 - 5 illustrate schematically a sequence of
steps to be carried out for practicing the preferred
26 embodiment of the present invention in accordance with the
27 best mode thereof;
28
~ 75~
2 Fig. 6 is a alternative blank shown ln a
3 perspective view; and
4 Fig. 7 shows a complex shape to be made under
utilization of the method in accordance with the preferred
6 embodiment of the present invention.
7 Proceeding now to the detailed description of the
8 drawings, Fig. l illustrates a tubular blank of any kind of
9 cross section including the cross sections shown in Figs. 6
and 7 and others. This tubular blank is made by means of
11 extrusion and/or drawing and/or forging. It is assumed that
12 the blank l is made of an age-hardening Cu alloy having 0.5
13 % Cr, 0.12~ zr, 0 015% Boron, the remainder being Cu and the
14 usual impurities, all percentages by weight. This tubular
blank is solution annealed, preferably in a reducing
16 atmosphere at a temperature between a 1000 and 1020 degrees
17 C for about l/2 hour. Subsequently the thus annealed tube is
18 quenched in water.
19 It can be seen from Fig. l that the tubular blank l is
assumed to be straight. Now as per the next step a hard Cr
21 plated mandrel 2 is forced into this tubular blank l. The
22 mandrel 2 is of a curved configuration. The end result is
23 shown in Fig~ 3 in that the curved mandrel 2 has forced a
24 curved contour upon the tube l. Subsequently and by means of
external force application by, the mandrel plus tube
26 configuration is ~orced through an annular drawing a die, or
27 by one or several forging or rolling procedures the tube l
28
~1 ~7~75~
2 is brought into intimate contact with the mandrel all
3 through the interior so that the interior of blanks so that
4 the interior of the tube 1 assumes the outer dimensions of
the mandrel 2. Cold working of the copper piece 1 is
6 selected so that the original hardness o 55 H~ is increased
7 from 80 to 100 HB .
8 As shown, mandrel 2 has a curved configuration so as to
9 match the ~esired curved contour of the mold to be made
because such curving approximating a circle is desirable for
11 purposes of ease o~ withdrawing an ingot from a mold. In
12 addition, there may be superimposed a conical or
13 frustoconical contour upon the interior o the mold. The
14 mandrel will have to have a corresponding conical taper~
Upon forcing the mandrel into the straight tube a certain
16 deformation occurs inherently thus forcing the tube 1 to
17 assume a curved contour. The tube 1 may initially be
18 prepared to have a somewhat curved configuration which
19 facilitates the introduction and insertion of the curved
mandrel. Following the removal of the mandrel ~rom the tube
21 which is shown in Fig~ 4 and 5, the now very accurately
22 dimensioned mold tube 1` is warm age-hardened for about 3 to
23 4 hours at a temperature between 460 to 480 degrees C. This
24 warm aye hardening treatment is preferably carried out in a
protective gas atmosphere.
26 The particular Cu alloy used for the tube 1 as
27 mentioned above was provided with the following
28
1~ lZ'7d,755
2 characteristic data on account o~ the process a9 carried
3 out:
4 The.rmal conductivity: 324(W~m.K)
Recri~talisation Temperature: ~00 degrees C
Softening Temperature: 500 degrees C
7 HB hardness 2.5~62.5: 142
8 Tensile strength: 445 N/square mm
9 0.2 yield strength limit: 360 N/square mm
Elongation at fracture: 18%
11 Hot strength at 200 degrees C: 416 N/square mm
12 Elongation at fracture at 200 degrees C: 17%
13 Hot strength at 350 degrees C: 352 N/square m~
14 Elongation at :eracture at 350 degrees C: 15
16 These values should be compared with data o~ a
17 non-callibrated mold which has not been provided and
18 subjected to the inventive process but has the same alloying
19 consistency:
21 Thermal conductivity: 315 W/m.K
22 Recristallization temperature: ~00 degrees C
23 Softening temperature: 500 deyrees C
24 HB hardness 2.5/62.5: 115
Tensile stren~th: 3'15 N/~quare mm
26 0.2 yield strength limit: 282 N/square mm
27 Elongation at ~racture: 19
28
~ 7 5 ~ .
2 Hot strength at 200 degrees C: 345 N~s~uare mm
3 Elongation at ~racture at 200 degrees C: 16%
4 Hot strength at 350 degrees C: 28S N/square mm
Elongation at fracture at 350 degrees C: 14%
7 The example for practicing the invention left open
8 the particular cross section of the mold. Aside from a
9 round, a s~uare shaped, a rectangular or a polygonal cross
section of a known variety~ one may encounter have more
11 complex cross sections such as T or or double T or I shaped
12 cross section. The I-shaped cross section is shown in Fig.
13 7. In all these cases a mandrel to be inserted has to have
14 the corresponding cross section for the process to be used
with advantage.
16 The invention is not limited to the embodiments
17 described above but all changes and modifications thereof,
18 not constituting departures from the spirit and scope oE the
~ invention, are intended to be included.
24
26
27
28
