US3315349A

US3315349A - Method of producing hot-formed copper-base products

Info

Publication number: US3315349A
Application number: US498774A
Authority: US
Inventors: Daniel B Cofer
Original assignee: Southwire Co LLC
Current assignee: Southwire Co LLC
Priority date: 1965-10-20
Filing date: 1965-10-20
Publication date: 1967-04-25
Anticipated expiration: 1984-04-25
Also published as: NL6614846A; ES371038A3; JPS5141584B1; GB1100416A; BE688612A; DE1558807B2; SE318238B; DE1558807A1

Description

April 25, 1967 D. B. COFER Filed Oct. 20, 1965 2 Sheets-Sheet 1 Vi Z M i a GQQQQOGOOG GQUQUOOQQQQQ INVENTOR. Daniel B Co/r dur i i g BY:

A TTORNEYS D. B. COFER April 25, 1967 METHOD OF PRODUCING HOT-FORMED COPPER-BASE PRODUCTS 2 Sheets-Sheet 2 Filed Oct.

Q2121?! B Cofer ATTORNEYS BY: 1 m 1" United States Patent 3,315,349 METHOD OF PRODUCING HOT-FORMED COPPER-BASE PRODUCTS Daniel B. Cofer, Carrollton, Ga., assignor to Southwire Company, Carrollton, Ga., a corporation of Georgia Filed Oct. 20, 1965, Ser. No. 498,774 9 Claims. (Cl. 29-528) This invention relates generally to the production of copper-base products and, more particularly to a method of producing hot-formed copper-base products from molten metal.

In the production of hot-formed copper-base products such as products hot-formed of pure or commercially pure copper or various copper alloys, it is generally desirable that the products exhibit a grain structure characterized by fine equi-axed grains having a minimum of grain alignment. This is because copper-base products having a grain structure with these characteristics have the best tensile strength, ductility, electrical and thermal conductivity, and other properties for the commercial use of the product.

It is to the production of hot-formed copper-base products having fine equi-axed grains with no grain alignment that the invention disclosed herein is admirably suited. This is because the invention provides hot-formed copper-base products having a grain structure characterized by equi-axed grains of uniformly finer grain size and with less grain alignment than has been previously attainable in the prior art.

This grain structure is obtained by solidifying molten metal to obtain cast metal and by hot-forming the cast metal in substantially the condition in which it solidified and in a manner which imparts substantial movement to the cast metal along a plurality of angularly disposed axes of deformation. Since the cast metal solidified from molten metal at a temperature above its hot-forming temperature, the hot-forming of the cast metal in substantially the condition in which it solidified permits the heating of the cast metal prior to hot-forming to be completely eliminated or to be used simply to adjust the hot-forming temperature of the cast metal immediately prior to hot-forming.

It is by its unique combination of solidifying molten metal to obtain cast metal and of hot-forming the cast metal in a particular condition and in a particular manner that the invention disclosed herein provides hot-formed copper-base products having uniformly distributed equiaxed grains of finer grain size and with less grain alignment than has been previously attainable in the prior art. These and other features and advantages of the invention will be more clearly understood from the following description and the accompanying drawings in which like characters of reference designate corresponding parts throughout and in which:

FIG. 1 schematically shows one example of apparatus .suitable to practice the invention, this apparatus comprising a casting machine and a rolling mill having a plurality of roll stands;

FIG. 2 shows the transverse cross-sectional shapes of cast metal as it is hot-formed in a manner in accordance with the invention;

FIG. 3 shows the transverse cross-sectional shapes of cast metal as it is hot-formed in a manner not in accordance with the invention;

FIG. 4 is a photomicrograph of a portion of a transverse cross-sectional surface of a cast copper bar solidified in a continuous casting means such as the casting machine shown in FIG. 1 and cooled by quenching to cold forming temperature;

FIG. 5 is a photomicrograph of a portion of a trans- ICC verse cross-sectional surface of a copper rod produced by the invention;

FIG. 6 is a photomicrograph of a portion of a transverse cross-sectional surface of a copper rod produced by solidifying molten metal in a continuous casting means such as the casting machine shown in FIG. 1 to obtain cast metal and hot-forming the cast metal in substantially the condition in which it solidified and in a manner generally represented by the transverse cross-sectional shapes of FIG. 3 and using a number of deformations equal to the number used in the hot-forming of the copper rod of FIG. 5;

FIG. 7 is a photomicrograph of a portion of a transverse cross-secti-onal surface of the copper rod of FIG. 6 after four additional deformations during hot-forming.

These figures and the following detailed description disclose a specific embodiment of the invention. However, it will be understood that the present invention is not limited to the details disclosed herein since it may be embodied in other equivalent forms without departing from the inventive concept.

The method of producing hot-formed copper-base products disclosed herein is best understood in terms of means suitable to its practice such as the apparatus schematically shown in FIG. 1 and which comprises a continuous casting machine 10 and a rolling mill 11. The continuous casting machine 10 serves as a means for solidifying molten metal 9 to provide a cast bar 12 that is conveyed in substantially the condition in which it solidified from the continuous casting machine 10 to the rolling mill 11 which serves as a means for rot-forming the cast bar 12 into rod 16 or another hot-formed product in a manner which imparts substantial movement to the cast bar 12 along a plurality of angularly disposed axes.

The continuous casting machine 10 is of conventional casting wheel type having a casting wheel 13 with a casting groove (not shown) partially closed by an endless belt 14 supported by the casting wheel 13 and an idler pulley 15. The casting wheel 13 and the endless belt 14 cooperate to provide a mold (not shown) into one end of which molten metal 9 is poured to solidify and from the other end of which the cast bar 12 is emitted in substantially that condition in which it solidified.

The rolling mill 11 is of conventional type having a plurality of roll stands 17 arranged to hot-form the cast bar 12 by a series of deformations. The continuous casting machine 10 and the rolling mill 11 are positioned relative to each other so that the cast bar 12 enters the rolling mill 11 substantially immediately after solidification and in substantially that condition in which it solidified. In this condition, the cast bar 12 is at a hot-forming temperature within the range of temperatures for hotforming the cast bar 12 at the initiation of hot-forming without heating between the casting machine 10 and the rolling mill 11. In the event that it is desired to closely control the hot-forming temperature of the cast bar 12 within the conventional range of hot-forming temperatures, means for adjusting the temperature of the cast bar 12 (not shown) may be placed between the continuous casting machine 10 and the rolling mill 11 without departing from the inventive concept disclosed herein.

It will be understood that with the apparatus of FIG. 1, the cast metal may be of any one of a plurality of lengths determined by the lengths of time the molten metal is solidified and may extend between the continuous casting machine 10 and the rolling mill 11. Thus, the steps of solidifying molten metal to obtain cast metal and of hot-forming the cast metal are performed simultaneously. However, the apparatus of FIG. 1 is shown only schematically because each'component of the apparatus is known to those skilled in the art and because once the invention is understood, it will be apparent to Patented Apr. 25, 1967 -fied from molten metal.

those skilled in the art that a direct chill casting machine or any one of many other known devices may be substituted for the continuous casting machine 10 shown in FIG. 1 and that a continuous forging machine or any one of many other known devices may be substituted for the rolling mill 11 shown in FIG. 1. This is because the invention requires only means for solidifying molten metal to provide cast metal and means for hot-forming the cast metal in the condition and in the manner disclosed herein.

The manner in which the means for hot-forming cast metal must hot-form the cast metal is best illustrated by reference to FIG. 2. From FIG. 2, it will be seen that as cast metal, such as the cast bar 12, is elongated into a hot-formed product such as rod 16, the cast metal has a plurality of transverse cross-sectional shapes which are alternately substantially flattened and substantially round.

Roll stands 17 of a rolling mill 11 having roll passes (not shown) which hot-form cast metal in a manner which results in these transverse cross-sectional shapes are well known to those skilled in the art and those skilled in the art will understand that this manner of hot-forming cast metal results in substantial movement of the cast metal not only along an axis of elongation but also along axes angularly disposed to the axis of elongation. It will also be understood that the hot-forming of a cast metal in a manner which imparts substantial movement to the cast metal along a plurality of angularly disposed axes may be accomplished by techniques of hot-forming other than that represented by the transverse cross-sectional shapes of FIG. 2.

Regardless of the technique of hot-forming used to obtain substantial movement of the cast metal along a plurality of anugularly disposed axes, the cast metal must enter the hot-forming means such as a rolling mill 11 while still in substantially that condition in which it solidi- That is, the cast metal must be substantially in its cast condition and not be cooled to cold working temperature and reheated or homogenized between its solidification from molten metal and the initiation of hot-forming. However, it has been found that varying that temperature of the cast metal which results from the cast metal being delivered to the means for hot-forming in substantially that condition in which it solidified in order to maintain a particular hot-forming temperature does not adversely affect the grain structure of copper rod produced by the invention. It is for this reason that means (not shown) for adjusting the temperature of the cast bar 12 may be placed between the continuous casting machine 10 and the rolling mill 11 and that such temperature adjustments are consistent with the requirement of the invention that the cast metal be in substantially that condition in which it solidified from molten metal.

The copper rod 19 of FIG. is representative of the hot-formed copper-base products produced by the invention. This copper rod 19 was produced by solidifying molten copper-base metal in the continuous casting machine of FIG. 1 to obtain cast metal and.- by hotforming the cast metal in a rolling mill 11 by a series of deformations represented by the transverse cross-sectional shapes of FIG. 2 and in substantially that condition in which it solidified. More specifically, the copper rod 19 was produced by removing a cast bar 12 from the continuous casting machine 10 while its temperature was still in the range of temperatures at which copper is hot-formed and by initiating the hot-forming of the cast bar 12 while its temperature was still in this range and without heating between the casting machine 10 and rolling mill 11.

The copper rod 20 of FIG. 7 was produced by solidifying molten metal in the continuous casting machine 10- of FIG. 1 to obtain cast metal and by hot-forming the cast metal in a rolling mill 11 by a series of deformations represented by the transverse cross-sectioal shapes of FIG. 3 and in substantially that condition in which it solidified. The copper rod 20' of FIG. 6 is identical to the copper rod 20 except that the copper rod 20' was deformed four fewer times in hot working than the copper rod 20 and the same number of times as the copper rod 19.

Those skilled in the art will understand that the hotforming of cast metal by the series of deformations represented by the transverse cross-sectional shapes of FIG. 3 does not result in substantial movement of the cast metal along a plurality of angularly disposed axes. Rather, substantial movement of the cast metal is only along the axis of elongation of the cast metal as it is hot-formed. Thus, it will be understood that both the copper rod 20 and the copper rod 20' differ from the copper rod 19 produced by the invention in that they have not been hotformed'in a manner which imparts substantial movement to the cast metal along a plurality of angularly disposed axes.

The

copper rods

19, 20, and 20 were all produced with tough pitch copper and it will now be understood that the copper rod 19, the copper rod 20, and the copper rod 20' were all produced by solidifying molten metal in the continuous casting machine 10 shown in FIG. 1 to obtain cast metal which was hot-formed in substantially that condition in which it solidified. However, only the copper rod 19 was produced by solidifying molten copper-base metal in the continuous casting machine 10 shown in FIG. 1 to obtain cast metal and by hot-forming the cast metal in substantially that condition in which it solidified and in a manner represented by the transverse cross-sectional shapes of FIG. 2. That the copper rod 19 produced by the invention has a grain structure superior to that obtained by the methods represented by copper rods 20, and 20' is shown when FIGS. 5-7 are examined. When these figures are examined, it will be seen that FIGS. 57 are photomicrographs. The photomicrographs of FIGS. 5-7, as well as the photomicrograph of FIG. 4, were made at a magnification of X by slicing a transverse section from the particular copper rod shown and by mounting, polishing, etching and placing the transverse cross-sectional surface obtained in a metallograph in conventional manner.

When the photomicrograph of FIG. 5 is compared with the photomicrographs of FIGS. 6 and 7, it is readily apparent that both the copper rod 20 and the copper rod 20 have grains 30 of larger size and with more grain alignment as at 31 than the copper rod 19. Thus, it is clear from FIGS. 5-7 that the hot-forming of cast metal in a manner which imparts substantial motion to the cast metal along a plurality of angularly disposed axes provides copper rod 19 having a grain structure superior to the grain structure of

copper rods

20 or 20 which were produced by solidifying molten metal to obtain cast metal and by hot-forming the cast metal in substantially that condition in which it solidified, but in a' manner which did not impart substantial movement to the cast metal along a plurality of angularly disposed axes. In this connection, it should be noted that the invention achieves this superior grain structure with fewer deformations than were used in hot-forming the copper rod 20 even though the as cast grain structure of the cast metal for both the copper rod 19 and the copper rod 20 was substantially as shown in FIG. 4 prior to hot-forming.

It will now be evident that the failure to hot-form the copper rod 20 and the copper rod 20' in a manner which imparted substantial movement to the cast metal along a plurality of angularly disposed axes caused both the cop- .per rod 20 and the copper rod 20 to have poorer grain structures than the copper rod 19. Thus, it is clear that the production of hot-formed copper-base products having a superior grain structure requires the solidifying of molten metal to obtain cast metal and the hot-forming of the cast metal in substantially that condition in which it solidified and in a manner which imparts substantial movement to the cast metal along a plurality of angularly disposed axes.

It will be understood by those skilled in the art that many variations may be made in the embodiment chosen herein for the purpose of illustrating the present invention without departing from the scope thereof as defined by the appended claims.

What is claimed as the invention is:

1. A method of producing a hot-formed copper-base product having a grain structure characterized by uniformly distributed fine grains with substantially no grain alignment, said method comprising the steps of solidifying a molten copper-base metal to obtain cast metal and of hot-forming said cast metal while said cast metal is in substantially that condition in which it solidified by deforming said cast metal a substantial number of times to cause said cast metal to assume a plurality of successive alternately difierent cross-sections which include several substantially flattened and elongated cross-sections and several substantially round cross-sections so as to impart substantial movement to said cast metal along a plurality of angularly disposed axes, said hot-forming serving to hot-form said product and to provide a grain structure characterized by uniformly distributed fine grains With substantially no grain alignment.

2. The method of claim 1 where said method includes the step of maintaining the temperature of said cast metal within a range of temperatures for hot-forming said cast metal between the solidification of said cast metal from said moltefi' copper-base metal and the initiation of hotforming.

3. The method of claim 2 wherein said method includes the step of varying the said temperature of the said cast metal within said range of temperatures to obtain a particular temperature of said cast metal upon initiation of hot-forming.

4. The method of claim 1 wherein one of said axes is an axis of elongation of said cast metal and another said axes is an axis transverse to said axis of elongation.

5. The method of claim 1 wherein said method includes conveying said cast metal to a means for hot-forming substantially immediately after the solidification of said cast metal from said molten copper-base metal.

6. The method of claim 1 wherein said molten copperbase metal is tough pitch copper.

7. The method of claim 1 wherein the steps of solidifying said molten copper-base metal to obtain cast metal and of hot-forming are performed nearly simultaneously.

8. The method of claim 1 wherein said method includes extending the said cast metal between a means for solidifying said molten copper-base metal and a means for hotforming.

9. The method of claim 1 wherein the step of solidifying the said molten copper-base metal provides cast metal in a plurality of lengths with each length being determined by the amount of said molten copper-base metal solidified.

References Cited by the Examiner UNITED STATES PATENTS 2,019,496 11/1935 Kohlhaas. 3,209,452 10/1965 Schneckenburger 2952 8 FOREIGN PATENTS 4/1937 Great Britain.

OTHER REFERENCES JOHN, F. CAMPBELL, Primary Examiner. R. F. DROPKIN, Assistant Examiner.

Claims

1. A METHOD OF PRODUCING A HOT-FORMED COPPER-BASE PRODUCT HAVING A GRAIN STRUCTURE CHARACTERIZED BY UNIFORMLY DISTRIBUTED FINE GRAINS WITH SUBSTANTIALLY NO GRAIN ALIGNMENT, SAID METHOD COMPRISING THE STEPS OF SOLIDIFYING A MOLTEN COPPER-BASE METAL TO OBTAIN CAST METAL AND OF HOT-FORMING SAID CAST METAL WHILE SAID CAST METAL IS IN SUBSTANTIALLY THAT CONDITION IN WHICH IT SOLIDIFIED BY DEFORMING SAID CAST METAL A SUBSTANTIAL NUMBER OF TIMES TO CAUSE SAID CAST METAL TO ASSUME A PLURALITY OF SUCCESSIVE ALTERNATELY DIFFERENT CROSS-SECTIONS WHICH INCLUDE SEVERAL SUBSTANTIALLY FLATTENED AND ELONGATED CROSS-SECTIONS AND SEVERAL SUBSTANTIALLY ROUND CROSS-SECTIONS SO AS TO IMPART SUBSTANTIAL MOVEMENT TO SAID CAST METAL ALONG A PLU-