DE2040870A1 - Continuous wire resistance annealing process - Google Patents

Description

Richard Fox

VelishCd.Heim 157

• Sudc: cnstrc! 3e 2

OUTOKUMPU Oy, Outokumpu, Pinnland

Continuous wire resistance annealing process

The invention relates to a continuous wire resistance annealing process to enlarge the grain structure, or a continuous nuierlicheü wire resistance annealing process in which the wire * brought to recrystallization temperature with the help of electric current using its electrical resistance in order to obtain a coarser grain size.

■ In practice, a number of wire annealing processes are known, which can be divided into two groups:

1. Batch annealing processes in which the wire is in bundles or wound on reels in ovens of various types, such as e.g. bell furnaces, salt bath furnaces, roller hearth furnaces, muffle furnaces ™ and the like is annealed. The heat transfer takes place in the process by radiation and / or convection.

2. Continuous annealing process in which the wire is through an externally heated tube is guided or directly inductively or resistively heated. ·

Characteristic of the batch annealing process is the long annealing time to get the compact wire spools to a uniform one

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Bring temperature. The long annealing time and the high temperatures in this furnace can also result in this method sticking of the wire windings may occur. Furthermore, the cleanliness of the wire after the Annealing process, caused e.g. by changes in the furnace atmosphere, due to evaporation of the drawing grease adhering to the wire or of wire components such as zinc, not properly can be achieved. On the other hand, however, thanks to the long annealing time and the relatively accurate controllable temperatures the structural properties regulate the material relatively effortlessly within wide limits.

In the case of continuous annealing processes, the capacity of the pull-through ovens remains due to the low throughput speed of the Wire, and this makes these processes expensive. Will the capacity be increased by extending the furnace or by Increasing the number of wires to be drawn through the furnace at one time increases only one very much awkward and complicated furnace construction. With the inductive method, the capacity remains extremely low, so that this method is seldom used for wire in general and not at all for thin wire. As for the continuous Process concerns, one is increasingly to the resistance annealing process (resistive annealing process) passed because it is characterized by very high speed and, compared to the other annealing furnaces, by small dimensions the required glow device. Especially

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Special one uses this process today together with wire drawing machines, whereby the wire hardened in the drawing process is passed directly into the annealing device. As a disadvantage of the resistance annealing process must, however, be determined that the extremely fast annealing, which takes place in fractions of a second, often does not allow the wire to die to give desired properties.

In the German patent specification Mr. 1 186 223 is an anti-j standing annealing process described in which the annealing ^ es Wire is done by means of current pulses; it should thereby the irregularities of the wire, e.g. by, varying Drawing speed arise and be eliminated. Since the Wire is heated by current impulses, some places are annealed twice, but this does not cause any damage, since no appreciable grain growth is caused by such rapid annealing occurs. The properties of the wire annealed in this way correspond on average the properties of wire that has been resistance annealed in a conventional manner, " In resistance annealing, attempts were also made to enlarge the grain size by initially setting the temperature relatively increases rapidly and further heating is then prevented by inserting the wire into a cooling liquid. Although the Wire goes through several checks to get the conditions here to create a grain growth, but is because of the large -.... ' Inertia of grain growth either requires an inconveniently long annealing section or the advantage obtained remains very low.

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The conventional resistance glow process is predominantly used Annealed copper, and for the oea material the process is also well suited, since the softening already occurs at relatively low Temperatures occurs and the grain size generally increases, because the alloy constituents that prevent grain growth and impurities are absent.

For this reason, the desired properties can be achieved relatively easily with copper. However, if one strives for a structure with large crystals, which can only be achieved in the known processes by means of a grain waohatum, one easily obtains an uneven structure that causes fluctuations in the properties of the wire. In general, however, it is impossible at all to produce coarse grain sizes with the known resistance annealing processes.

According to the invention, the coarsening of the grain structure in a continuous wire resistance annealing process is achieved in that the annealing is started in two phases, whereby in the first phase at an empirically determined temperature, which depends, among other things, on the drawing speed, the protective gas used, the cooling, the wire thickness, the annealing stretch length and the target nozzle temperature of the wire is also determined, a controllable amount of nuclei is generated , whereupon the actual annealing is carried out in the second phase so that the wire is completely recrystallized after the end of the phase.

Original

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With resistance annealing, the metal is softened duroh recrystallization takes place. There are three phases in recrystallization; Recovery, primary recrystallization and grain growth. The primary recrystallization takes place in such a way that germs form in the deformed structure, which then au like grains bsw. Crystals grow.

In the growth of the Kora, part of the "in the primary" grows; Recrystallization resulting crystals at the expense of the other crystals. The properties of the soft wire are depends on the grain size. With increasing grain size, strength and hardness decrease, while toughness increases The grain size is regulated by the annealing temperature in such a way that the desired properties are obtained. With resistance annealing Because of the short glow time, there is hardly anything worth mentioning Kristallwaohstum before. The grain size of the resistance annealed The wire essentially stops at the level that is in primary recrystallization is achieved} i.e. the number ^ of the crystals is the same as that of the resulting crystal nuclei.

The wind speed in the formation is strongly dependent on the temperature addicted. With; The appearance rises as the temperature increases! the germ®. The following therefore applies to resistance annealing: The higher the temperature at nucleation, the lower remains the grain size. With the conventional resistance glow @ B Dl © nucleation occurs at a very high temperature, since the The temperature is increased very quickly because of the short glow time,

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so that wire annealed in this way generally has a small grain size. If a coarser grain size is desired, the rhyme formation should be as small as possible Temperature happen. Duron the present invention solves this problem advantageously so that the glow in two Phases is executed. In the first phase a suitable number of nuclei are formed, and 'was through one Adjustment of the temperature so that an exactly desired amount of germs arises in the time available. In the second phase, the germs formed then grow, until complete recrystallization has taken place. This second phase has a higher temperature than the first phase because of the short period of time that is available for it to take place. If only an insufficient number of germs develop in the first phase, it follows that in the Deformed structure in the second phase many new germs arise, which result in an uneven grain structure, and the wire does not acquire the desired properties. If, on the other hand, too many crystal nuclei are formed in the first nose, this results in a small grain size, which is advantageous the nucleation and glow are lost. In practice, this annealing process is accomplished using three or four Contact rollers and one or more power sources.

The invention is described in detail below with reference to the accompanying drawings, in which two embodiments, which are only intended as examples, are shown. _{ßAD 0R / Q / NAL}

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Flg. 1 shows the system for a dual-phase annealing process at that the wire is not cooled between the first and the second!

Fig. 2 shows the system for a two-phase annealing process, at which the wire is cooled between the rhyme formation and growth phases will.

In Flg. 1 the wire runs over the contact rollers 1 and 2, where ^ preheating takes place. In this generally customary prewarning phase, temperatures are used that are so low that the wire does not oxidize and in no case do the recrystallization germs form. This goal warming serves only as an auxiliary phase, after which it can also be declared. The nucleation annealing according to the invention takes place between the contact rollers 2 and 3 , in which the current is selected so that at the end of this phase, precisely the appropriate amount of crystal nuclei is present in the wire. Immediately after this phase, “without the wire being cooled in the meantime,” follows between the contact rollers 3 and 5 the phase of occurrence in which the complete crystals are formed. After this second phase, the structure has been completely re-crystallized. The wire is cooled down on the contact roller 5 to such an extent that the wire no longer oxidizes. The cooling is usually done according to the conventional method by means of water, water emulsion or the like, whereby the contact roller 5 is located in the coolant and the wire runs through it. In order to report an oxidation, the distances between the contact

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roll 2-3 and 3 - 5 generally with a Schutegas coat Mistake. On the path between the contact rollers 5 and 6, the wire is subjected to a slight drying process, which is carried out at such low temperatures that no oxidation occurs on the wire and in no case does it occur Grain growth can occur.

The system shown in Fig. 2 differs from that System in Fig. 1 in that after the nucleation phase (between the contact rollers 2 and 3) in the same way as on the contact roller 5 of the example described above the contact roller 3 is cooled. Between the contact rollers 3 and 4 takes place, as on the route of the contact rollers 1 - 2, the wire is preheated, but this can also be dispensed with if necessary. Duroh this arrangement is achieved that the contact roller 3 neither through Oxidation is still damaged by contamination, as is easily the case with the system shown in FIG. 1 can. The subsequent annealing takes place in the manner shown in FIG. 1.

With the method according to the invention, fabric wires (Fourdrinier wire) were annealed with success. When annealing Qewebe weft wires (80 i » Cu, 20 $> Zn), a wire diameter of 0.23 mm and a drawing speed of 8.8ra / e according to the conventional process, ie with a single-phase process, was used for the 0.2 grense Maximum value of 16.5 kp / r " and a maximum value of about 0.008 mm for the grain size

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aims. Kit the two-phase process according to the invention was under the same conditions for the 0.2 limit the value

12.8 kp / nua and the value 0.025 mm for the grain size is achieved. In the single-phase process, the length of the annealing line was about 800 mm; in the two-phase process, the germinal path was about 1400 mm long. The temperature was about at the end of the first phase, 400 to 500 ⁰ C, at the end of the second phase is about 850 - 95O ⁰ C.

In simulation tests, two current pulses of suitable strength and duration were fed into the wire and the wire was cooled in between. The length of the wire in the device used was about 250 mm, the duration of the current pulses was 50-300 ma and a hydrogen gas stream was used as the coolant. Pure nickel wire (diameter 0.17 ram) resulted at a temperature of approx. 300 ^° C. in the first phase and approx. 1000 ^° C. in the second phase, a 0.2 limit value of

15.9 kg / mm. 19.0 kgf / mm obtained - the temperature remained in the first phase (germ, etc. formation) is lower or higher than it rose said W WET, so were the same HauptglUhphase for 0.2 Grease-values of 18.1. In experiments with pure copper wire (diameter 00:15 ram) (25O ⁰ C ca.) the value of 6.9 kgf / mm, it "has been after suitable preheating for C.2-Grenz® hold while he otherwise at about 7 * 5 kgf / mm lay. to about 95O ⁰ C increased lsi the second glow phase the Versuohe Kupfardraht.wurde with the temperature. The effect is with Cu wire, as also due to the explanations made zp. expect is relatively low. : ..'- ■ .: =; ■ '«

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The specified temperatures are only to be regarded as guidelines, because they are influenced by a large number of factors, such as the drawing speed, the protective gas, the cooling, the wire thickness, the length of the annealing section, the Solidus temperature etc.

The method according to the invention can also be used in connection use with inductive heating, which, however, should not yet come into question with the current state of the art, because inductive heating is only used when the working speed is low or the temperature is low acts.

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Claims (3)

- ii - Claims 1. Continuous wire resistance annealing process for coarsening der ICorngeftlge, characterized in that the Annealing is carried out in two phases, being in the ereten Phase (2 - 3) at an empirically determined temperature, the a.o. * from the pulling speed, the shutagas used, the cooling, the turntable, the glow stretching length and the solidus temperature of the wire is taken, a controllable kenge germs are generated, whereupon the actual annealing is carried out in the avsiten phase (4 - 5) is that the wire is completely re » is crystallized. 2. The method according to claim 1, characterized in that the Wire between the first (2 - 3) and second phase (4-5) is cooled. - | 3. The method according to claim 1, characterized in that a wire made of copper or a copper alloy is used. BATH ORIGINAL 109838/1032