CA1083017A - Method of producing a continuously processed copper rod - Google Patents
Method of producing a continuously processed copper rodInfo
- Publication number
- CA1083017A CA1083017A CA280,685A CA280685A CA1083017A CA 1083017 A CA1083017 A CA 1083017A CA 280685 A CA280685 A CA 280685A CA 1083017 A CA1083017 A CA 1083017A
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- CA
- Canada
- Prior art keywords
- rod
- temperature
- hot
- coiled
- coiling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Metallurgy (AREA)
- Crystallography & Structural Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- Physics & Mathematics (AREA)
- Continuous Casting (AREA)
- Metal Rolling (AREA)
- Metal Extraction Processes (AREA)
- Heat Treatment Of Nonferrous Metals Or Alloys (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
- Winding, Rewinding, Material Storage Devices (AREA)
- Conductive Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In a continuous casting system where molten copper is cast into a bar and then rolled into a rod, the copper rod is immediately hot-coiled before being subjected to any quenching or cooling operation. The hot-coiling of the rod is carried out at a temperature of from 700°F. to 1200°F. and preferably within a range of from 950°F. to 1150°F., so that the rod is hot-coiled at a high enough temperature to permit sufficient thermal vacancy diffusion to occur within the rod material, and thereafter gradually cooled to room temperature to thereby impart certain im-proved mechanical properties to the resultant rod product.
A copper or copper alloy rod which is processed in this fashion has a lower yield tensile strength, lower ultimate tensile strength, lower recrystallization temperature, lower hardness and is much more ductile and hence easier to draw into wire than a corresponding rod which is quenched or cooled prior to coiling.
In a continuous casting system where molten copper is cast into a bar and then rolled into a rod, the copper rod is immediately hot-coiled before being subjected to any quenching or cooling operation. The hot-coiling of the rod is carried out at a temperature of from 700°F. to 1200°F. and preferably within a range of from 950°F. to 1150°F., so that the rod is hot-coiled at a high enough temperature to permit sufficient thermal vacancy diffusion to occur within the rod material, and thereafter gradually cooled to room temperature to thereby impart certain im-proved mechanical properties to the resultant rod product.
A copper or copper alloy rod which is processed in this fashion has a lower yield tensile strength, lower ultimate tensile strength, lower recrystallization temperature, lower hardness and is much more ductile and hence easier to draw into wire than a corresponding rod which is quenched or cooled prior to coiling.
Description
BACKGROUND OF THE INVENTION
_ . .
In recent years, much effort has been expended in the metallurgical field to develop techniques for con-tinuously casting molten metal into continuous metal rod.
The advantages of continuous casting over batch casting are well known in the art and include the elimination of such prior art batch casting operations as initially casting individual bars of the metal, cooling the bars and casting molds, stripping the bars from the casting molds, an~ then reheating the bars to a sufficient temperature so that they may be rolled into lengths of rod.
For example, the prior art production of copper rod from cast copper wire bars, typically weighing 250 pounds, included reheating the cast bars to 1700F in order .
to homogenize the metal and condition it for the subsequent ~ `
hot-forming operation, and thereafter rolling the bars i~ a so-called "looping mill" which was a long, slow operation that permitted the rod to completely recrystallize between rolling passe.s. After rolling, the copper rod would be . ~:
completely co~ered with a black oxide coating, and no cold work (stored energy) would remain in the rod as it exited the mill at 1000F. The 250 pound length of rod emitting from the looping mill was taken-up on a coiling device and immediately quenched to facilitate subsequent handling~ .
Inasmuch as no stored energy remained in the rod as it :
exited the mill, the quenching operation did not affect its metallurgical properties.
In the continuous production of-metal rod ~;~
according to present practice, on the other hand, molten ~
_ . .
In recent years, much effort has been expended in the metallurgical field to develop techniques for con-tinuously casting molten metal into continuous metal rod.
The advantages of continuous casting over batch casting are well known in the art and include the elimination of such prior art batch casting operations as initially casting individual bars of the metal, cooling the bars and casting molds, stripping the bars from the casting molds, an~ then reheating the bars to a sufficient temperature so that they may be rolled into lengths of rod.
For example, the prior art production of copper rod from cast copper wire bars, typically weighing 250 pounds, included reheating the cast bars to 1700F in order .
to homogenize the metal and condition it for the subsequent ~ `
hot-forming operation, and thereafter rolling the bars i~ a so-called "looping mill" which was a long, slow operation that permitted the rod to completely recrystallize between rolling passe.s. After rolling, the copper rod would be . ~:
completely co~ered with a black oxide coating, and no cold work (stored energy) would remain in the rod as it exited the mill at 1000F. The 250 pound length of rod emitting from the looping mill was taken-up on a coiling device and immediately quenched to facilitate subsequent handling~ .
Inasmuch as no stored energy remained in the rod as it :
exited the mill, the quenching operation did not affect its metallurgical properties.
In the continuous production of-metal rod ~;~
according to present practice, on the other hand, molten ~
- 2 - - ?
'~`
metal passes from a holding furnace into the mold of a casting wheel where it is cast into a ~etal bar. The solidified metal bar is removed from the casting wheel and directed into a rolling mill where it is rolled into con-tinuous rod. Depending upon the intended end use of the metal rod product, the rod may be subjected to cooling during rolling or the rod may be cooled or quenched immediately upon exiting from the rolling mill to impart thereto the desired mechanical properties. As disclosed in U.S. Patent 3,395,560 to Cofer et al, a continuously-processed rod is preferably cool~d as it exits the rolling mill and prior to being coiled. Because the continuous casting and rolling oparation does not include the inter-vening homogenizing step of the prior art batch casting of wire bars, and because the rolling operation is relatively rapid as compared with the prior art looping mill, the continuous rod emitting from the rolling mill will have a substantial amount of cold work retained therein and thus the immediate quenching operation will serve to retain the same and freeze impurities in solid solution thus improving the tensile strength of the product~
Conventional cooling techniques include immers-ing the rod in a coolant, and spray-cooling the rod with coo ant. In all cases, however, it is standard practice to cool or quench the continuously produced rod prior to its coiling and rods ormed in this manner are hereinafter referred to as cold-coiled rods in contrast to the hot-coiled rods of the present invention.
-~33~
In some instances, it is desirable to have uniformly dispersed copper oxide inclusions throughout the rod product whereas in other instances, it is neceqsary to remove such oxide by shaving or scalping operations. The oxide and other surface scale may be removed from the rod product by pickling the surface of the rod in a liquid such as sulfuric, nitric or other acids. The pickling operation aLso performs a cooling function so that it is possible to both cool and pickle the rod in one operation ancl one example of such a system for quench-pickling cast rod is shown in U.S. Patent 3,623,532 to Cofer et al. Rods formed in this manner are also cooled, due to the pickling operation, prior to their delivery to a coiling apparatus and therefore are cold-coiled.
One disadvantage of the prior art systems for continuous production of metal rod is that due to the ;
cooling operation, the rod becomes harder and hence more difficult to coil. This is particularly disadvantageous with large diameter rod. Another disadvantage of quenching the high temperature rod prior to coiling is that the retained vacancies and lattice defects which are present after quenching remain in the rod since the temperature of the quenched rod is too low to enable these defects to be rectiied through thermal vacancy diffusion. For many applications, such as wire drawing, rod which is quenched prior tc coiling becomes too hard and will have too high a yield tensile streng~hand too high a de~ree of residual !
stress to be commercially suitable.
~8~7 Additionally, rod quenched at high temperatures as it exits the rolling mill will exhibit a high recrystal-lization temperature because impurities contained in the metal will be trapped or frozen in solid solution. Conse-quently, the rod will have a high annealing temperature which obviously necessita~es appropriate process equipment and energy requirements capable of effecting the high temperature anneal. Moreover, when the rod is drawn into wire intended to be subsequently fabricated into magnet wire by coating the same with enameling composition in an annealing tower, a high temperature anneal ~e.g., greater than 500F) will cause the enamel to blister on the surface of the wire. Consequently, under these circumstances the annealing and enameling would have to be effected in separate operations.
STATEMENT OF THE INVENTION
, According to the present invention, a continuous length of copper or copper alloy rod is coiled as it exits from a rolling mill and prior to any quenching or cooling operations, and thereafter gradually cooled to room tempera-ture. The rod is hot-coiled under temperature-controlled conditions to selectively impart desired characteristics to the rod before the rod has had an opportunity to cool. By coiling the rod in this manner, a much lesser degree of vacancies and lattice defects are ultimately retained in the final rod product, the ductility of the rod is improved, the recrystallization temperature is lowered, the yield tensile strengthis lowered and the rod has a lesser degree 8~ 7 of residual stress than rods of similar composition which are cold-coiled.
More particularly, there is provided in accordance with this invention a methocl of producing a con-tinuously processed copper rod comprising the steps of:
a) continuously casting molten copper con-taining normal impurities into a cast bar at a rate at which said impurities are trapped in solid solution;
b) substantially immediately hot-rollin~ the cast bar in the as-cast condition into continuous rod at a rate at which said impurities are retained in solid solu-tion;
c) cooling the rod after rolling; and d) coiling the rod;
characterized in that in order to improve the ductility of the rod and to lower the residual stresses therein the rod is hot-coiled prior to any substantial cooling thereof from the hot-rolling temperature, and thereafter gradually cooled to room temperature to permit precipitation of substantially all of said impurities thereby lowering the recrystalliza-tion termperature of the rod.
In addition, another aspect of this invention concerns the production of enamel-coated magnet wire.
Because the method ~f this invention yields a rod having a lower recrystallization temperature than cold-coiled rod, it is possible to simultaneously anneal wire drawn down rom the rod while coating the wire wi~h an enameling composition at a temperature of approximately 500F.
,~
1~83~:~7 Having in mind the above and othex objects, features and advantages of the invention that will be evident from an understanding of this disclosure, the present invention comprises the method and resultant product as illustrated in the presently preferred embodiment o~ the invention which is hereina~ter set forth in suf~i-cient detail to enable those persons skilled in the art to clearly understand the function, operation, and advan-tages of it when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram depicting the major operations of a continuous casting system employing the method of the present invention; and Figure 2 is a schematic view of a continuous casting system arranged to carry out the method of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
According to one aspect of the present invention and with reference to Figure 1, the method of the invention comprises the steps of continuously casting 5 molten metal into a cast metal bar, rolling 6 the cast bar while at high temperature into a metal rod, and coiling 7 the metal rod be~ore subjecting the same to any quenching or cooling operations. In ~his fashion, the metal rod is hot-coiled immed~ately after being rolled and while at the high temper-ature at which it was rolled. The coiled rod may then be ;
gradually cooled 8 to room temperature.
- ' ~
'~`
metal passes from a holding furnace into the mold of a casting wheel where it is cast into a ~etal bar. The solidified metal bar is removed from the casting wheel and directed into a rolling mill where it is rolled into con-tinuous rod. Depending upon the intended end use of the metal rod product, the rod may be subjected to cooling during rolling or the rod may be cooled or quenched immediately upon exiting from the rolling mill to impart thereto the desired mechanical properties. As disclosed in U.S. Patent 3,395,560 to Cofer et al, a continuously-processed rod is preferably cool~d as it exits the rolling mill and prior to being coiled. Because the continuous casting and rolling oparation does not include the inter-vening homogenizing step of the prior art batch casting of wire bars, and because the rolling operation is relatively rapid as compared with the prior art looping mill, the continuous rod emitting from the rolling mill will have a substantial amount of cold work retained therein and thus the immediate quenching operation will serve to retain the same and freeze impurities in solid solution thus improving the tensile strength of the product~
Conventional cooling techniques include immers-ing the rod in a coolant, and spray-cooling the rod with coo ant. In all cases, however, it is standard practice to cool or quench the continuously produced rod prior to its coiling and rods ormed in this manner are hereinafter referred to as cold-coiled rods in contrast to the hot-coiled rods of the present invention.
-~33~
In some instances, it is desirable to have uniformly dispersed copper oxide inclusions throughout the rod product whereas in other instances, it is neceqsary to remove such oxide by shaving or scalping operations. The oxide and other surface scale may be removed from the rod product by pickling the surface of the rod in a liquid such as sulfuric, nitric or other acids. The pickling operation aLso performs a cooling function so that it is possible to both cool and pickle the rod in one operation ancl one example of such a system for quench-pickling cast rod is shown in U.S. Patent 3,623,532 to Cofer et al. Rods formed in this manner are also cooled, due to the pickling operation, prior to their delivery to a coiling apparatus and therefore are cold-coiled.
One disadvantage of the prior art systems for continuous production of metal rod is that due to the ;
cooling operation, the rod becomes harder and hence more difficult to coil. This is particularly disadvantageous with large diameter rod. Another disadvantage of quenching the high temperature rod prior to coiling is that the retained vacancies and lattice defects which are present after quenching remain in the rod since the temperature of the quenched rod is too low to enable these defects to be rectiied through thermal vacancy diffusion. For many applications, such as wire drawing, rod which is quenched prior tc coiling becomes too hard and will have too high a yield tensile streng~hand too high a de~ree of residual !
stress to be commercially suitable.
~8~7 Additionally, rod quenched at high temperatures as it exits the rolling mill will exhibit a high recrystal-lization temperature because impurities contained in the metal will be trapped or frozen in solid solution. Conse-quently, the rod will have a high annealing temperature which obviously necessita~es appropriate process equipment and energy requirements capable of effecting the high temperature anneal. Moreover, when the rod is drawn into wire intended to be subsequently fabricated into magnet wire by coating the same with enameling composition in an annealing tower, a high temperature anneal ~e.g., greater than 500F) will cause the enamel to blister on the surface of the wire. Consequently, under these circumstances the annealing and enameling would have to be effected in separate operations.
STATEMENT OF THE INVENTION
, According to the present invention, a continuous length of copper or copper alloy rod is coiled as it exits from a rolling mill and prior to any quenching or cooling operations, and thereafter gradually cooled to room tempera-ture. The rod is hot-coiled under temperature-controlled conditions to selectively impart desired characteristics to the rod before the rod has had an opportunity to cool. By coiling the rod in this manner, a much lesser degree of vacancies and lattice defects are ultimately retained in the final rod product, the ductility of the rod is improved, the recrystallization temperature is lowered, the yield tensile strengthis lowered and the rod has a lesser degree 8~ 7 of residual stress than rods of similar composition which are cold-coiled.
More particularly, there is provided in accordance with this invention a methocl of producing a con-tinuously processed copper rod comprising the steps of:
a) continuously casting molten copper con-taining normal impurities into a cast bar at a rate at which said impurities are trapped in solid solution;
b) substantially immediately hot-rollin~ the cast bar in the as-cast condition into continuous rod at a rate at which said impurities are retained in solid solu-tion;
c) cooling the rod after rolling; and d) coiling the rod;
characterized in that in order to improve the ductility of the rod and to lower the residual stresses therein the rod is hot-coiled prior to any substantial cooling thereof from the hot-rolling temperature, and thereafter gradually cooled to room temperature to permit precipitation of substantially all of said impurities thereby lowering the recrystalliza-tion termperature of the rod.
In addition, another aspect of this invention concerns the production of enamel-coated magnet wire.
Because the method ~f this invention yields a rod having a lower recrystallization temperature than cold-coiled rod, it is possible to simultaneously anneal wire drawn down rom the rod while coating the wire wi~h an enameling composition at a temperature of approximately 500F.
,~
1~83~:~7 Having in mind the above and othex objects, features and advantages of the invention that will be evident from an understanding of this disclosure, the present invention comprises the method and resultant product as illustrated in the presently preferred embodiment o~ the invention which is hereina~ter set forth in suf~i-cient detail to enable those persons skilled in the art to clearly understand the function, operation, and advan-tages of it when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram depicting the major operations of a continuous casting system employing the method of the present invention; and Figure 2 is a schematic view of a continuous casting system arranged to carry out the method of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
According to one aspect of the present invention and with reference to Figure 1, the method of the invention comprises the steps of continuously casting 5 molten metal into a cast metal bar, rolling 6 the cast bar while at high temperature into a metal rod, and coiling 7 the metal rod be~ore subjecting the same to any quenching or cooling operations. In ~his fashion, the metal rod is hot-coiled immed~ately after being rolled and while at the high temper-ature at which it was rolled. The coiled rod may then be ;
gradually cooled 8 to room temperature.
- ' ~
3~
One type of apparatus which may be used to carry out the method of the inven~ion is shown schematically in Figure 2. The apparatus comprises a continuous casting system comprising a delivery device 10 which receives molten copper metal containing normal impurities and delivers the metal to a pouring spout 11. The pouring spout 11 directs the molten metal to a peripheral groove contained on a rotarv mold ring 13. ~n endless flexible metal band 14 encircles both a portion of the mold ring 13 as well as a portion of a set of band-positioning rollers 15 such that a continuous casting mold is defined by the groove in the mold ring 13 and the overlying metal band 14 between the points A and B. A cooling system is provided ~or cooling the apparatus and effecting controlled solidification of the molten metal during its transport on the rotary mold ring 13. The cooling system includes a plurality of side headers 17, 18, and 19 disposed on the side of the mold -ring 13 and inner and outer band headers 21 and 22, respec-tively, disposed on the inner and outer sides of the metal band 14 at a loca~ion where it encircles the mold ring. ~
A conduit network 2~ having suitable valving is connected ~;
to supply and exhaust coolant to the various headers so ;
as to control the cooling of the apparatus and the rate of solidification of the molten metal. For a more detailed showing and explanation of this type of apparatus, reference may be had to U.S. Patent 3,596,702 to Ward et al. ~ `
By such a construction, molten copper metal containing normal impurities is fed from the pouring spout 11 into the casting mold at the point A and is solidified .. ,; - . . ~
~3`{1~7 and partially cool~d during its transport between the points A and s by circulation of coolant through the cooling sys~
tem. Thus by the time the cast bar reaches the point ~, it is in the form of a solid cast bar 25. The solid cast bar 25 is withdrawn from the casting wheel and fed to a conveyor 27 which conveys the cast bar to a rolling mill 28. It should be noted that at the point B, the cast bar 25 has only been cooled an amount sufficient to solidify the bar and the bar remains at an elevated temperature to allow an immediate rolling operation to be performed thereon.
The rolling mill 28 comprises a tandem array of rolling stands which successively roll the bar into a continuous length of wire rod 30 which has a substantially uniform, circular cross-section.
In accordance with the invention, the wire rod 30 is not quenched or cooled after its formation but rather is immediately fed to a coiler 31. The coiler in the em-bodiment shown comprises a coiling basket which receives the wire rod 30 and coils the same into extremely long lengths of coiled rod. The coiling operation occurs immedi-ately downstream from the rolling operation without any intervening quenching or cooling. After the rod is coiled, it is delivered to a subsequent cooling station for gradual cooling to room temperature to permit precipitation of sub-stantially all of the impurities from solid solution thereby lowering the recrystallization temperature of the rod.
It is a metallurgical postulate that impurities in solid solution will raise the recrystallization tempera-ture of the product. Moreover, the impurlties in copper (e.g., iron, silver, tin and lead) are additive in in-creasing the recrystallization temperature. Consequently, by permitting precipitation of substantially all -the impurities from solid solution as above-described, the recrystallization temperature of the copper rod will be substantially lowered as compared with the recrystalli~a-tion temperature of rod produced by prior art processes wherein the rod is immediately quenched upon exit from the rolling mill. As a result of the lowered recrystallization temperature, the continuously-produced rod may be annealed at lower temperatures in order to achieve minimum elongation requirements. It should be apparent that the low tempera-ture anneal is desirable in order to reduce oxidation and also to conserve energy and increase the life of process equipment. Moreover, in the production of ma~net wire having an enameled coating thereon, it is advantageous if the annealing and enameling can be effectuated simultaneous-ly in the annealing tower. If annealing at temperatures greater than 500F is required, the enamel will blister on the surface of the rod. On the other hand, if the annealing can be accomplished at temperatures lower than 500F, enameling and annealing can be effectuated simultan-eously in an annealing tower at about 500F.
A significant feature of the present invention resides in the discovery that rolled rods which are first quenched and then coiled are at too low a temperature to , permit vacancy difusion to occur and therefore such rods possess certain mechanical properties which are undesirable.
-- 1 0 - ' ' ~
~3~'7 From an examlnation of cold-coiled rods, it was learned that they possessed a hi~h degree of vacancies and lattice defects which were quenched in the rods and since vacancy concentrations in most metals increase with increasing temperature, the high degree of vacancies is believed to be due to the fact that the temperature of the quenched rods is too low to permit these defects to be rectified through .
thermal vacancy diffusion or thermal recovery of the exist-ing high dislocation density material. When the metal is hot rolled, the last 2 or 3 rolls produce a high dislocation density in the metal matrix due to the act that a great portion of this deEormation is "warm rolling" which produces a high p~rcentage o~ cold work to the matrix. This cold work is produced by the ~eneration of dislocations and defects which would be held-in by a quick water quench. As a result, the rod is hard and not easily bendable and as a consequence, it is difficult to coil such rods, especially those o larger diameter~ The present i.nvention allows thermal recovery of these defects to a certain degree so as to provide improved mechanical properties in the coiled rod.
By way of example only, the results of two comparative tests will be given so that the advantages of the invention will be more readily apparent. In both exam-ples, the chemical composition of the copper alloy rod, in paxts per million, is as follows:
Pb Sn Ag Sb Fe Mn As Bi 1 1 1 1 1 < 1 < 1 X~PLE~ COI.D-C'OIL13D RO
A length of copper alloy rod having the fore-going chemical composition was formed by continuous casting of molten metal into cast bar followed by rolling the bar into metal rod of 3/8 inch diame-ter. The metal rod was then quenched and cooled to room temperature, between 80-100F., after which the cooled rod was coiled in a coiling apparatus. The following mechanical properties of the rod were measured:
Ultimate tensile strength 31-32 KSI
Yield tensile strength 16.5-17.5 KSI
Elongation (10") 40-4~1%
Rockwell F. Hardness 50 EXA~IPLE 2 HOT-COILED ROD
A copper alloy rod was formed by casting and rolling in the same manner as described above in Example 1 only in this case, the rolled rod was in~ediately fed to the coiling apparatus and coiled in a hot condition before any quenching or cooling operation. The copper alloy rod was delivered directly from the rolling mill and coiled while at a temperature of 1110F. and after the rod was gradually cooled to room temperature, the following mechanical properties were measured: , Ultimate tensile strenyth 30-31 KSI
Yield tensile strength 12-13 KSI
~ .:
Elongation (10") 43-44~ ;~
Rockwell F. Hardness 42 .
- . - - .
.. . .
~83~.7 From a comparison of the two Examples, the improved results obtained Erom hot-coiling the copper alloy rod as oRposed to cold-coiling the copper alloy rod are readily seen. One significant result is that the yield tensile strength decreased from the 16,000 psi range to the 12,000 p~i range. This lower yield tensile strength results in a more ductile rod which is easier to process, especially easier to draw into wire.
Another significant result is that the Rockwell F Hardness decreased from about 50 to about 40 with the attendant result that the ductility of the rod was increased thereby making the rod easier to cold form, such as by drawing. This is evidenced by the increase in elongation of the hot-coiled rod as opposed to the cold-coiled rod.
The Examples given above are representative only and similar ~-result3 are obtained using any copper and copper alloy mat:erials which are currently employed in the art and com-paring thP mechanical properties of col,d-coiled versus hot-coiled rods made from those materials.
In accordance with the present invention, it has been found that the rod-coiling temperature should lie within 700F. to 1200F. in order to permit adequate thermal vacancy diffusion to occur since the vacancies are not quenched at this temperature range and recovery of the re idual cold working imparted during rolling of the rod will therefore nccur. This temperature ran~e is suitable particularly ~or copper and copper alloy rods. ~lso, the region within 950F. to 1150F. has been found to be especi-ally effeative in impartinq the foregoing desirable - 13 ~
.
~3(~L7 mechanical properties to the rod and therefore the preferred temperature range ~or the rod-coiling is ~rom 950F. to 1150F.
It has also been found in accordance with the invention that the hot-coiled rod should be gradually cooled to room temperature at a cooling rate not exceeding 300F. per minute in order to permit precipitation of sub~
stantially all of the impurities from the copper rod. ~ -Thus it will be seen that in accordance with the present invention, a copper rod is produced which hascertain predetermined mechanical properties which were not hereto-fore obtainable by coiling the rod in the conventional manner. The rod product formed in accordance with the method of the invention is annealable at a lower temperature than a cold-coiled rod and has a low~r yield tensile strength and lower hardness than corresponding rod which is cold-coiled.
While the invention has been disclosed with reference to one preferrea embodiment, it is understood that ~ ~;
many modifications and changes will become apparent to those ordinarily skilled in the art and the present invention is ;~
intended to cover all such obvious modifications and changes ~ ;
which fall within the spirit and scope of the invention as deined in the appended claims.
One type of apparatus which may be used to carry out the method of the inven~ion is shown schematically in Figure 2. The apparatus comprises a continuous casting system comprising a delivery device 10 which receives molten copper metal containing normal impurities and delivers the metal to a pouring spout 11. The pouring spout 11 directs the molten metal to a peripheral groove contained on a rotarv mold ring 13. ~n endless flexible metal band 14 encircles both a portion of the mold ring 13 as well as a portion of a set of band-positioning rollers 15 such that a continuous casting mold is defined by the groove in the mold ring 13 and the overlying metal band 14 between the points A and B. A cooling system is provided ~or cooling the apparatus and effecting controlled solidification of the molten metal during its transport on the rotary mold ring 13. The cooling system includes a plurality of side headers 17, 18, and 19 disposed on the side of the mold -ring 13 and inner and outer band headers 21 and 22, respec-tively, disposed on the inner and outer sides of the metal band 14 at a loca~ion where it encircles the mold ring. ~
A conduit network 2~ having suitable valving is connected ~;
to supply and exhaust coolant to the various headers so ;
as to control the cooling of the apparatus and the rate of solidification of the molten metal. For a more detailed showing and explanation of this type of apparatus, reference may be had to U.S. Patent 3,596,702 to Ward et al. ~ `
By such a construction, molten copper metal containing normal impurities is fed from the pouring spout 11 into the casting mold at the point A and is solidified .. ,; - . . ~
~3`{1~7 and partially cool~d during its transport between the points A and s by circulation of coolant through the cooling sys~
tem. Thus by the time the cast bar reaches the point ~, it is in the form of a solid cast bar 25. The solid cast bar 25 is withdrawn from the casting wheel and fed to a conveyor 27 which conveys the cast bar to a rolling mill 28. It should be noted that at the point B, the cast bar 25 has only been cooled an amount sufficient to solidify the bar and the bar remains at an elevated temperature to allow an immediate rolling operation to be performed thereon.
The rolling mill 28 comprises a tandem array of rolling stands which successively roll the bar into a continuous length of wire rod 30 which has a substantially uniform, circular cross-section.
In accordance with the invention, the wire rod 30 is not quenched or cooled after its formation but rather is immediately fed to a coiler 31. The coiler in the em-bodiment shown comprises a coiling basket which receives the wire rod 30 and coils the same into extremely long lengths of coiled rod. The coiling operation occurs immedi-ately downstream from the rolling operation without any intervening quenching or cooling. After the rod is coiled, it is delivered to a subsequent cooling station for gradual cooling to room temperature to permit precipitation of sub-stantially all of the impurities from solid solution thereby lowering the recrystallization temperature of the rod.
It is a metallurgical postulate that impurities in solid solution will raise the recrystallization tempera-ture of the product. Moreover, the impurlties in copper (e.g., iron, silver, tin and lead) are additive in in-creasing the recrystallization temperature. Consequently, by permitting precipitation of substantially all -the impurities from solid solution as above-described, the recrystallization temperature of the copper rod will be substantially lowered as compared with the recrystalli~a-tion temperature of rod produced by prior art processes wherein the rod is immediately quenched upon exit from the rolling mill. As a result of the lowered recrystallization temperature, the continuously-produced rod may be annealed at lower temperatures in order to achieve minimum elongation requirements. It should be apparent that the low tempera-ture anneal is desirable in order to reduce oxidation and also to conserve energy and increase the life of process equipment. Moreover, in the production of ma~net wire having an enameled coating thereon, it is advantageous if the annealing and enameling can be effectuated simultaneous-ly in the annealing tower. If annealing at temperatures greater than 500F is required, the enamel will blister on the surface of the rod. On the other hand, if the annealing can be accomplished at temperatures lower than 500F, enameling and annealing can be effectuated simultan-eously in an annealing tower at about 500F.
A significant feature of the present invention resides in the discovery that rolled rods which are first quenched and then coiled are at too low a temperature to , permit vacancy difusion to occur and therefore such rods possess certain mechanical properties which are undesirable.
-- 1 0 - ' ' ~
~3~'7 From an examlnation of cold-coiled rods, it was learned that they possessed a hi~h degree of vacancies and lattice defects which were quenched in the rods and since vacancy concentrations in most metals increase with increasing temperature, the high degree of vacancies is believed to be due to the fact that the temperature of the quenched rods is too low to permit these defects to be rectified through .
thermal vacancy diffusion or thermal recovery of the exist-ing high dislocation density material. When the metal is hot rolled, the last 2 or 3 rolls produce a high dislocation density in the metal matrix due to the act that a great portion of this deEormation is "warm rolling" which produces a high p~rcentage o~ cold work to the matrix. This cold work is produced by the ~eneration of dislocations and defects which would be held-in by a quick water quench. As a result, the rod is hard and not easily bendable and as a consequence, it is difficult to coil such rods, especially those o larger diameter~ The present i.nvention allows thermal recovery of these defects to a certain degree so as to provide improved mechanical properties in the coiled rod.
By way of example only, the results of two comparative tests will be given so that the advantages of the invention will be more readily apparent. In both exam-ples, the chemical composition of the copper alloy rod, in paxts per million, is as follows:
Pb Sn Ag Sb Fe Mn As Bi 1 1 1 1 1 < 1 < 1 X~PLE~ COI.D-C'OIL13D RO
A length of copper alloy rod having the fore-going chemical composition was formed by continuous casting of molten metal into cast bar followed by rolling the bar into metal rod of 3/8 inch diame-ter. The metal rod was then quenched and cooled to room temperature, between 80-100F., after which the cooled rod was coiled in a coiling apparatus. The following mechanical properties of the rod were measured:
Ultimate tensile strength 31-32 KSI
Yield tensile strength 16.5-17.5 KSI
Elongation (10") 40-4~1%
Rockwell F. Hardness 50 EXA~IPLE 2 HOT-COILED ROD
A copper alloy rod was formed by casting and rolling in the same manner as described above in Example 1 only in this case, the rolled rod was in~ediately fed to the coiling apparatus and coiled in a hot condition before any quenching or cooling operation. The copper alloy rod was delivered directly from the rolling mill and coiled while at a temperature of 1110F. and after the rod was gradually cooled to room temperature, the following mechanical properties were measured: , Ultimate tensile strenyth 30-31 KSI
Yield tensile strength 12-13 KSI
~ .:
Elongation (10") 43-44~ ;~
Rockwell F. Hardness 42 .
- . - - .
.. . .
~83~.7 From a comparison of the two Examples, the improved results obtained Erom hot-coiling the copper alloy rod as oRposed to cold-coiling the copper alloy rod are readily seen. One significant result is that the yield tensile strength decreased from the 16,000 psi range to the 12,000 p~i range. This lower yield tensile strength results in a more ductile rod which is easier to process, especially easier to draw into wire.
Another significant result is that the Rockwell F Hardness decreased from about 50 to about 40 with the attendant result that the ductility of the rod was increased thereby making the rod easier to cold form, such as by drawing. This is evidenced by the increase in elongation of the hot-coiled rod as opposed to the cold-coiled rod.
The Examples given above are representative only and similar ~-result3 are obtained using any copper and copper alloy mat:erials which are currently employed in the art and com-paring thP mechanical properties of col,d-coiled versus hot-coiled rods made from those materials.
In accordance with the present invention, it has been found that the rod-coiling temperature should lie within 700F. to 1200F. in order to permit adequate thermal vacancy diffusion to occur since the vacancies are not quenched at this temperature range and recovery of the re idual cold working imparted during rolling of the rod will therefore nccur. This temperature ran~e is suitable particularly ~or copper and copper alloy rods. ~lso, the region within 950F. to 1150F. has been found to be especi-ally effeative in impartinq the foregoing desirable - 13 ~
.
~3(~L7 mechanical properties to the rod and therefore the preferred temperature range ~or the rod-coiling is ~rom 950F. to 1150F.
It has also been found in accordance with the invention that the hot-coiled rod should be gradually cooled to room temperature at a cooling rate not exceeding 300F. per minute in order to permit precipitation of sub~
stantially all of the impurities from the copper rod. ~ -Thus it will be seen that in accordance with the present invention, a copper rod is produced which hascertain predetermined mechanical properties which were not hereto-fore obtainable by coiling the rod in the conventional manner. The rod product formed in accordance with the method of the invention is annealable at a lower temperature than a cold-coiled rod and has a low~r yield tensile strength and lower hardness than corresponding rod which is cold-coiled.
While the invention has been disclosed with reference to one preferrea embodiment, it is understood that ~ ~;
many modifications and changes will become apparent to those ordinarily skilled in the art and the present invention is ;~
intended to cover all such obvious modifications and changes ~ ;
which fall within the spirit and scope of the invention as deined in the appended claims.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of producing a continuously processed copper rod comprising the steps of:
a) continuously casting molten copper con-taining normal impurities into a cast bar at a rate at which said impurities are trapped in solid solution;
b) substantially immediately hot-rolling the cast bar in the as cast condition into continuous rod at a rate at which said impurities are retained in solid solution;
c) cooling the rod after rolling; and d) coiling the rod;
characterized in that in order to improve the ductility of the rod and to lower the residual stresses therein the rod is hot-coiled prior to any substantial cooling thereof from the hot-rolling temperature, and thereafter gradually cooled to room temperature to permit precipitation of substantially all of said impurities thereby lowering the recrystalliza-tion temperature of the rod.
a) continuously casting molten copper con-taining normal impurities into a cast bar at a rate at which said impurities are trapped in solid solution;
b) substantially immediately hot-rolling the cast bar in the as cast condition into continuous rod at a rate at which said impurities are retained in solid solution;
c) cooling the rod after rolling; and d) coiling the rod;
characterized in that in order to improve the ductility of the rod and to lower the residual stresses therein the rod is hot-coiled prior to any substantial cooling thereof from the hot-rolling temperature, and thereafter gradually cooled to room temperature to permit precipitation of substantially all of said impurities thereby lowering the recrystalliza-tion temperature of the rod.
2. A method according to claim 1, characterized in that said coiling is carried out while the rod is at a temperature of from 700°F. to 1200°F.
3. A method according to claim 1, characterized in that said coiling is carried out while the rod is at a temperature of from 950°F. to 1150°F.
4. A method according to either of claims 1 or 2, characterized in that the coiled rod is gradually cooled to room temperature at a cooling rate not exceeding 300°F.
per minute.
per minute.
5. A method according to claim 1, characterized in that the recrystallization temperature of the rod is sufficiently lowered to permit annealing thereof at 500°F.
6. A method according to claim 5, further characterized in that in order to produce a coated magnet wire the hot-coiled rod is subsequently drawn into wire and passed through an annealing tower containing a molten enameling compound at a temperature of approximately 500°F, and therein simultaneously annealing the wire and coating it with the enameling compound.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US696,801 | 1976-06-16 | ||
| US05/696,801 US4066475A (en) | 1974-09-26 | 1976-06-16 | Method of producing a continuously processed copper rod |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1083017A true CA1083017A (en) | 1980-08-05 |
Family
ID=24798603
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA280,685A Expired CA1083017A (en) | 1976-06-16 | 1977-06-16 | Method of producing a continuously processed copper rod |
Country Status (14)
| Country | Link |
|---|---|
| JP (1) | JPS531669A (en) |
| AU (1) | AU506885B2 (en) |
| BE (1) | BE855712A (en) |
| CA (1) | CA1083017A (en) |
| DE (1) | DE2727055A1 (en) |
| ES (1) | ES459829A1 (en) |
| FR (1) | FR2355085A1 (en) |
| GB (1) | GB1536096A (en) |
| IT (1) | IT1079044B (en) |
| PL (1) | PL198917A1 (en) |
| SE (1) | SE7706949L (en) |
| YU (1) | YU39394B (en) |
| ZA (1) | ZA773464B (en) |
| ZM (1) | ZM4877A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5561510B2 (en) * | 2009-02-12 | 2014-07-30 | 住友電気工業株式会社 | Coiled copper or copper alloy coil |
| JP5396939B2 (en) * | 2009-03-16 | 2014-01-22 | 三菱マテリアル株式会社 | Rough drawn copper wire manufacturing method, rough drawn copper wire manufacturing apparatus, and rough drawn copper wire |
| ITUA20162023A1 (en) * | 2016-03-25 | 2017-09-25 | Giulio Properzi | PROCEDURE FOR TRANSFORMING VERGELLA OF NON-FERROUS METALS AND THEIR ALLOYS IN HIGH-STRETCH WIRE AND IN THE RICOTTO STATE. |
| CN113560513B (en) * | 2021-08-11 | 2022-10-11 | 福州丹文科技有限公司 | Automatic control system for copper rod continuous casting and rolling |
| CN114686697B (en) * | 2022-04-09 | 2023-08-18 | 杭州富通集团有限公司 | Processing method of copper rod |
-
1977
- 1977-06-08 AU AU25956/77A patent/AU506885B2/en not_active Expired
- 1977-06-08 ZA ZA00773464A patent/ZA773464B/en unknown
- 1977-06-13 YU YU1458/77A patent/YU39394B/en unknown
- 1977-06-13 GB GB24512/77A patent/GB1536096A/en not_active Expired
- 1977-06-14 FR FR7718152A patent/FR2355085A1/en active Granted
- 1977-06-14 ZM ZM48/77A patent/ZM4877A1/en unknown
- 1977-06-15 DE DE19772727055 patent/DE2727055A1/en not_active Withdrawn
- 1977-06-15 IT IT49828/77A patent/IT1079044B/en active
- 1977-06-15 BE BE178464A patent/BE855712A/en not_active IP Right Cessation
- 1977-06-15 SE SE7706949A patent/SE7706949L/en not_active Application Discontinuation
- 1977-06-16 ES ES459829A patent/ES459829A1/en not_active Expired
- 1977-06-16 PL PL19891777A patent/PL198917A1/en unknown
- 1977-06-16 JP JP7056677A patent/JPS531669A/en active Granted
- 1977-06-16 CA CA280,685A patent/CA1083017A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| BE855712A (en) | 1977-10-03 |
| ES459829A1 (en) | 1978-04-01 |
| JPS531669A (en) | 1978-01-09 |
| JPS5631870B2 (en) | 1981-07-24 |
| YU145877A (en) | 1982-08-31 |
| DE2727055A1 (en) | 1977-12-29 |
| IT1079044B (en) | 1985-05-08 |
| PL198917A1 (en) | 1978-02-13 |
| AU506885B2 (en) | 1980-01-24 |
| GB1536096A (en) | 1978-12-20 |
| ZM4877A1 (en) | 1978-02-21 |
| AU2595677A (en) | 1978-12-14 |
| ZA773464B (en) | 1978-04-26 |
| FR2355085A1 (en) | 1978-01-13 |
| SE7706949L (en) | 1977-12-17 |
| YU39394B (en) | 1984-12-31 |
| FR2355085B1 (en) | 1980-03-07 |
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