US3717745A - Continuous resistance annealing method for wires - Google Patents

Continuous resistance annealing method for wires Download PDF

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Publication number
US3717745A
US3717745A US00116193A US3717745DA US3717745A US 3717745 A US3717745 A US 3717745A US 00116193 A US00116193 A US 00116193A US 3717745D A US3717745D A US 3717745DA US 3717745 A US3717745 A US 3717745A
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Prior art keywords
wire
annealing
heating
temperature
resistance
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US00116193A
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English (en)
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A Kosonen
S Nieminen
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Outokumpu Oyj
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Outokumpu Oyj
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/62—Continuous furnaces for strip or wire with direct resistance heating
    • 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

Definitions

  • ABSTRACT A wire running through contact wheels is resistance heated by a current set to heat the wire in a first step to a relatively low temperature which has been determined experimentally and which is dependent upon, e.g., the drawing rate, the protective gas used, cooling, the thickness of the wire, the length of the annealing distances, and the solidus temperature of the wire to create a controlled number of crystal nuclei in the wire and then the actual annealing is effected in a second step by a current heating the wire to a high temperature to recrystallize the wire completely.
  • the invention relates to the field of continuous resistance annealing of wires.
  • the batch annealing or tempering methods are characterized by long heating periods as it takes a long time to obtain an even temperature in massive spools.
  • a further disadvantage is the possible sticking together of the loops of wire because of the long annealing period and the high temperature.
  • the degree of purity of the wires may remain unsatisfactory after the annealing because of, for example, the wire drawing greases evaporating from the wires, or the vaporization of components present in the wires themselves, such as zinc.
  • the structural properties of the material can be regulated with relative facility and within a wide range because of the long annealing period and the relatively precise control of the temperature.
  • the annealing capacity remains low because of the slow movement of the wires, which is the reason why the method is expensive. If the annealing capacity is increased either by lengthening the furnace or by increasing the number of wires to be drawn through it, the furnace becomes very impractical structurally. In the inductive method the annealing level remains very low; therefore, it is very seldom used for wires and never for thin wires.
  • resistance annealing is gaining ground because it is very rapid and because the required annealing unit is small compared with the other furnace types mentioned above.
  • the method is used especially in connection with wiredrawing machines, in which case the wire hardened during the drawing process is immediately conducted into the annealing unit. It can, however, be noted that the resistance annealing method has the disadvantage that, owing to the very rapid annealing which takes place in a fraction of a second, the qualities required of annealed wire cannot always be obtained.
  • German Pat. No. 1,186,223 introduces a resistance annealing method in which wire is annealed with current impulses, and its purpose is to eliminate the unevenness of wire due to, for example, a changing drawing rate.
  • current impulses When current impulses are used for the annealing, some parts of the wire will be annealed twice, but it will not cause any harm as no noteworthy crystal growth takes place in such a rapid annealing. Nevertheless, the properties of the wire thus annealed are, on the average, similar to those of wire that has undergone a normal resistance annealing process.
  • Attempts have been made to increase the crystal size by resistance annealing or tempering also by first raising the temperature relatively fast and then stopping the rising of the temperature by directing the wire into cooling liquid. In spite of the fact that the wire may run over several contact wheels the purpose is to create conditions for crystal growth but, because of its slowness, either the annealing distance becomes impractically long or the gained advantage remains quite insignificant.
  • the wire is first heated to a low temperature experimentally determined to create a controlled member of crystal nuclei and then the wire is heated to a high temperature to crystallize the metal wire completely.
  • recrystallization In resistance annealing the softening of the metal occurs through recrystallization.
  • the recrystallization comprises three phases: recovery, primary recrystallization, and crystal growth.
  • Primary recrystallization takes place so that crystal nuclei are born in the treated structure and they grow into crystals.
  • Crystal growth takes place so that some of the crystals formed in primary recrystallization grow larger at the expense of other crystals.
  • the properties of soft wire depend upon the crystal size so that when the crystal size enlarges, the strength and hardness decrease and the tenacity, (or, more accurately in the language of metallury, tensility), increases.
  • Crystal size is regulated by the annealing temperature so that the desired properties are obtained. Due to the short annealing period in the resistance annealing process no noteworthy crystal growth will occur during it. In this case the crystal size of resistance annealed wire remains in general essentially the same as it has been after the primary recrystallization or, in other words, the number of crystals is the same as the number of formed crystal nuclei.
  • the nucleation rate is strongly dependent upon the temperature so that when the temperature rises the number of formed nuclei increases. Consequently, the crystal size created in resistance annealing will be smaller the higher the temperature at which the nucleation occurs. In normal resistance annealing the nucleating takes place at a very high temperature since, owing to the short annealing period, the temperature is raised very rapidly. Therefore, the crystal size of resistance annealed wire tends to remain small. When larger crystal size is desired, the nucleation ought to take place at a temperature as low as possible. This has been made possible by the present invention wherein the annealing is carried out in two phases.
  • a suitable number of crystal nuclei are formed by raising the temperature of the wire so that the desired number of crystal nuclei can be caused to form in the available time.
  • the nuclei born in the previous phase are made to grow so that the structure will be completely recrystallized. This second phase must take place at a temperature lower than the previous phase because of the shortness of the available time. If too few crystal nuclei are formed in the first phase, the result is that a great number of crystal nuclei are formed in the remaining structure to be treated during the second phase and the final result is a mixed crystal structure, and the properties of the wire are not those desired.
  • the result is a small crystal size and, thus, the advantage offered by the nucleating annealing is lost.
  • the annealing process is arranged with the help of three or four contact wheels and using one or more sources of current.
  • FIG. 1 shows a two-phase annealing method in which the wire is not cooled between the nucleating and the nucleus-growing annealing phases
  • FIG. 2 shows a two-phase annealing method in which the wire is cooled between the nucleating and the nucleus-growing annealing phases.
  • FIG. 1 DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • the wire runs through contact wheels 1 and 2, where the wire is preheated.
  • this heating phase which is in accordance with common practice, the temperature used is so low that the wire will not oxidize and in no case will recrystallization nuclei be formed.
  • This heating is a sort of auxiliary phase and it can be left out.
  • the nucleating annealing according to the invention is carried out between contact wheels 2 and 3.
  • the current used for this annealing is chosen so that, at the end of this phase, the wire contains an exactly suitable number of crystal nuclei.
  • the structure is, thus, completely recrystallized.
  • the wire is cooled to such a temperature that the wire will not oxidize after it.
  • the cooling is usually carried out, according to common practice, by water, water emulsion or the like so that contact wheel 5 is in the cooling liquid in question and the wire runs through it.
  • a protective gas system must usually be fitted between contact wheels 2, Sand 5.
  • a mild heating with the purpose of drying is carried out between contact wheels 5 and 6 at so low a temperature that no oxidation of the wire will take place, not to speak of crystal growth.
  • the arrangement shown in FIG. 2 deviates from that shown in FIG. 1 in that a cooling is carried out after the nucleating annealing (between contact wheels 2-3) in a similar manner as above at contact wheel 5.
  • a similar preheating is used between contact wheels 3 and 4 as between 1 and 2, which also can be optionally omitted.
  • This arrangement has the advantage that contact wheel 3 is not damaged by oxidation or contamination, which can easily occur in an arrangement according to FIG. I. The rest of the annealing process takes place in the manner according to FIG. 1.
  • the method according to the invention has been used successfully for the annealing of wires for wire cloth.
  • the term 0.2- margin is used in accordance with generally adopted European practice to represent such a tensile strength value that a lasting elongation of 0.2 percent results after the removal of stress. This definition is commonly used for materials which lack a sharp limit in their stress-strain curves.
  • a value of 12.8 kp/mm was obtained for the 0.2-margin and the crystal size was 0.025 mm.
  • the annealing distance in the one-phase experiment was about 800 mm and the nucleating annealing distance in the two-phase annealing was about 1,400 mm.
  • the temperature was about 400500C at the end of the first phase and about 850-950C at the end of the second phase.
  • temperatures given above are only directive because they are dependent upon many factors such as drawing rate, protective gas, cooling, thickness of the wire, length of the annealing distances, the solidus temperature of the wire, etc.
  • the method according to the invention can also be applied to inductive heating, but with the present technical level it is hardly practical because inductive heating is used at slow velocities only or when the heating temperatures are low.
  • a method of resistance annealing metal wires continuously in two electrical resistance heating steps to increase the size of metal crystals in the wire, and to decrease the strength and hardness while increasing the tensility of the wire comprising:

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
US00116193A 1970-02-25 1971-02-17 Continuous resistance annealing method for wires Expired - Lifetime US3717745A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FI700511A FI47993C (fi) 1970-02-25 1970-02-25 Jatkuva metallilankojen vastushehkutusmenetelmä

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US (1) US3717745A (enExample)
CA (1) CA943842A (enExample)
DE (1) DE2040870B2 (enExample)
FI (1) FI47993C (enExample)
FR (1) FR2078889A5 (enExample)
GB (1) GB1343635A (enExample)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4820896A (en) * 1984-04-24 1989-04-11 Elpatronic, Ag Method and apparatus producing drawn copper wire from an electrical seam welder
US5830583A (en) * 1993-04-19 1998-11-03 Clouser; Sidney J. Copper wire
EP3154735A4 (en) * 2014-06-10 2018-01-17 Global Innovative Products, LLC Piezoelectric wire edm
CN111850248A (zh) * 2020-04-30 2020-10-30 福建南平太阳电缆股份有限公司 一种火焰燃烧法导体退火工艺、装置及系统
JP2024505690A (ja) * 2021-02-05 2024-02-07 マシーネンファブリーク・ニーホフ・ゲーエムベーハー・ウント・コー・カーゲー 連続式ワイヤアニール装置

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1635443A (en) * 1925-06-17 1927-07-12 Smith Willoughby Statham Manufacture of cables loaded with alloys of high-magnetic permeability
US1911023A (en) * 1930-05-01 1933-05-23 Gen Electric Method for preventing embrittlement of copper
US2589283A (en) * 1949-07-29 1952-03-18 Syncro Mach Co Wire annealing machine
US2726971A (en) * 1950-10-03 1955-12-13 Syncro Mach Co Apparatus for drying and annealing wire
US3335260A (en) * 1964-12-18 1967-08-08 Niehoff Kommandit Ges Maschf Annealing apparatus for wire and like conductors

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1635443A (en) * 1925-06-17 1927-07-12 Smith Willoughby Statham Manufacture of cables loaded with alloys of high-magnetic permeability
US1911023A (en) * 1930-05-01 1933-05-23 Gen Electric Method for preventing embrittlement of copper
US2589283A (en) * 1949-07-29 1952-03-18 Syncro Mach Co Wire annealing machine
US2726971A (en) * 1950-10-03 1955-12-13 Syncro Mach Co Apparatus for drying and annealing wire
US3335260A (en) * 1964-12-18 1967-08-08 Niehoff Kommandit Ges Maschf Annealing apparatus for wire and like conductors

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4820896A (en) * 1984-04-24 1989-04-11 Elpatronic, Ag Method and apparatus producing drawn copper wire from an electrical seam welder
US5830583A (en) * 1993-04-19 1998-11-03 Clouser; Sidney J. Copper wire
EP3154735A4 (en) * 2014-06-10 2018-01-17 Global Innovative Products, LLC Piezoelectric wire edm
CN111850248A (zh) * 2020-04-30 2020-10-30 福建南平太阳电缆股份有限公司 一种火焰燃烧法导体退火工艺、装置及系统
JP2024505690A (ja) * 2021-02-05 2024-02-07 マシーネンファブリーク・ニーホフ・ゲーエムベーハー・ウント・コー・カーゲー 連続式ワイヤアニール装置

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Publication number Publication date
FI47993C (fi) 1974-05-10
DE2040870A1 (de) 1971-09-16
FI47993B (enExample) 1974-01-31
DE2040870B2 (de) 1972-03-30
GB1343635A (en) 1974-01-16
CA943842A (en) 1974-03-19
FR2078889A5 (enExample) 1971-11-05

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