US20240093327A1

US20240093327A1 - Continuous annealer for wire

Info

Publication number: US20240093327A1
Application number: US18/264,099
Authority: US
Inventors: Stefan Nixdorf; Jürgen Kohl
Original assignee: Maschinenfabrik Niehoff GmbH and Co KG
Current assignee: Maschinenfabrik Niehoff GmbH and Co KG
Priority date: 2021-02-05
Filing date: 2022-02-01
Publication date: 2024-03-21
Also published as: JP2024505690A; EP4288573A1; DE102021201104A1; WO2022167424A1; MX2023009173A; CN116848270A

Abstract

A continuous annealer for wire is disclosed, and specifically for annealing and recrystallizing a wire in a continuous process. The continuous annealer for wire comprises: two contact discs for contacting a first wire portion extending therebetween; an annealing zone situated between the two contact discs; and annealing means for annealing the first wire portion in the annealing zone, as a result of which a first partial recrystallisation process in the first wire portion takes place in the annealing zone. A recrystallisation zone is situated downstream of the second contact disc, wherein, downstream of the annealing zone, the first wire portion passes through the recrystallisation zone as the second wire portion, and a second partial recrystallisation process takes place in the second wire portion. The wire has the opportunity to recrystallize further after leaving the annealing zone without further heating. By extending the recrystallisation time, the recrystallisation temperature can be reduced accordingly. As a result, the same degree of recrystallisation can be achieved overall with a significantly lower input of energy than when the wire is cooled immediately after leaving the annealing zone.

Description

The entire content of priority application DE 10 2021 201 104.7 is hereby incorporated into the present application by reference.
The invention relates to a continuous annealer for wire for annealing and recrystallizing a wire in a continuous process. The wire is in particular a metallic wire, preferably of copper or aluminum or of an alloy of multiple metals.
Manufacturing wire generally entails drawing the wire in multiple stages so as to reduce the cross section; i.e. respectively directing it through a drawing die having an opening of slightly smaller diameter than the diameter of the wire directed through it. In doing so, the material of the wire is deformed and the diameter of the wire thereby reduced to the diameter of the drawing die opening. Since the wire's cross section can only be slightly reduced in such a drawing process, multiple such drawing processes are performed successively in which the diameter of the wire is successively reduced until the desired wire diameter is reached.
However, in addition to the reduction in the diameter of the wire, simultaneous strain hardening of the wire material also occurs during the drawing process due to the deformation of the wire material. This leads to the wire's lower ductility and lower residual strain; i.e. after being drawn, the wire breaks or respectively splits faster upon strain/extension than it does prior to being drawn.
For this reason, the wire is recrystallized after drawing by the addition of heat; i.e. the crystal lattice of the wire material, which exhibits lattice imperfections in the form of lattice structure dislocations as a result of drawing, is regenerated and thereby “repaired.”
Three parameters substantially determine the recrystallization, namely degree of deformation, temperature and dwell time:

- A higher degree of deformation results in a more effective recrystallization.
- A higher temperature results in a more effective recrystallization, whereby specific material-dependent limit values must not be exceeded.
- A longer dwell at temperature time results in a more effective recrystallization.

The so-called degree of deformation is the extent of the change in the crystalline structure as a result of the drawing process, in particular the extent of the wire's cross-sectional reduction.
In addition to the recrystallization, the addition of heat also effects regeneration of the wire material's granular structure. A longer heating thereby results in increased grain growth. Larger grains in turn lead to better residual strain of the wire, thus greater wire ductility until break.
Since recrystallization ensues at high temperatures (e.g. 550° C.) and the wire thereby anneals, the associated systems are also referred to as “wire annealers.”
On the one hand, there can be an “offline” application of heat to effect the recrystallization; i.e. drawn and solidified wire is heated in a stationary heat-treating apparatus. particularly a recrystallization furnace, and thereby recrystallized. The recrystallization process is thereby in particular determined by the temperature curve over time, particularly by process parameters such as the ramp-up time, dwell time, dwell temperature and cooling time.
On the other hand, the wire can be recrystallized in a continuous process; i.e. as the wire passes through the drawing system at undiminished speed. Although this is more difficult to implement technically, it leads to higher efficiency and productivity since the recrystallization is not occurring in a separate downstream work step in the drawing process entailing removing the wire from the machine, winding it onto spools and possibly needing to thread it back into the drawing machine for further processing.
In the continuous process, recrystallization takes place in fractions of a second as the feed rate of the wire can be up to 50 meters per second.
After recrystallization, the wire needs to be cooled down again, this likewise ensuing in a continuous process and one integrated into a single system, a continuous wire annealer. This also transpires in fractions of a second.
The cooling generally takes place immediately after recrystallization by submerging the wire in a cooling medium, in particular in an emulsion or in oil. Directly submerging the wire in the cooling medium also prevents surface tarnishing.
Disadvantageous with this method is that immediately submerging the wire in the cooling medium following the recrystallization of the wire draws the thermal energy introduced into the wire out again. This thereby reduces the dwell at temperature time, which in turn requires being compensated for by a higher input of heat. This leads to high energy consumption of the continuous wire annealer.
The present invention is thus based on the task of reducing the continuous wire annealer's consumption of energy.
This task is solved by a continuous annealer for wire according to claim 1 or, respectively, a method for annealing and recrystallizing a wire according to claim 11. Further advantageous developments of the invention are set forth in the dependent claims.
The invention is based on a continuous annealer for wire for annealing and recrystallizing a wire, particularly a metallic wire, in a continuous process, which comprises:

- at least two contact disks configured such that a first contact disk contacts a rear end, as seen in the wire's direction of travel, and a second contact disk contacts a front end, as seen in the wire's direction of travel, of a first wire portion extending between the first contact disk and the second contact disk,
- an annealing zone situated between the first contact disk and the second contact disk and configured such that the first wire portion passes through the annealing zone, as well as
- annealing means for annealing the first wire portion in the annealing zone, whereby a first partial recrystallization process takes place in the first wire portion in the annealing zone.

The respective first and/or second contact disk is thereby preferably designed as a rotatably mounted deflection roller for the wire. Preferably, such a deflection roller has a recessed track for the wire at its outer perimeter in which the wire makes a partial turn around the deflection roller or one or more full turns.
The invention is based on the idea of extending the active recrystallization time (corresponding to the above-cited dwell time in the “offline method”) by not immediately cooling the wire after it exits the annealing zone but rather giving it the opportunity to recrystallize further without any further heating. Any cooling zone is thereby moved further rearward in the wire's direction of travel.
According to the invention, it is therefore provided for a recrystallization zone to be situated downstream of the second contact disk, as seen in the wire's direction of travel, and configured such that a second wire portion, which has previously passed through the annealing zone as a first wire portion, passes through the recrystallization zone and a second partial recrystallization process takes places in the second wire portion.
The terms “first partial recrystallization process” and “second partial recrystallization process” are thereby not to be understood as the recrystallization ceasing after the first partial recrystallization process and restarting again with the second partial recrystallization process. Rather, the first and the second partial recrystallization process together form a physically continuous uninterrupted crystallization process which is only conceptually divided into two partial processes. In other words, the entire recrystallization process is started via the first partial recrystallization process and extended by the second partial recrystallization process.
The inventive method in particular extends the total distance over which the recrystallization occurs, and thus also the recrystallization time. Any subsequent cooling zone is thereby simultaneously moved further rearward in the wire's direction of travel.
The extended recrystallization time enables lowering the recrystallization temperature while achieving the same residual strain, which results in direct energy savings.
Since the second partial recrystallization process ensues without further heat input, the same degree of recrystallization can generally be achieved with a significantly lower input of energy. According to the applicant's findings, energy savings ranging up to 20% can be realistically expected.
Conversely, it is also possible to not reduce the energy input. By inventively lengthening the recrystallization zone, and thus increasing the recrystallization time, the residual strain of the wire is thereby improved. The inventive method thereby enables achieving an almost equally high strain value here as in a furnace.
When using the present invention, the operator of the continuous wire annealer can thus choose whether he wishes to save energy or improve the residual strain of the wire.
In one preferential embodiment of the invention, the annealing means are means for conductively heating the first wire portion, whereby the first contact disk and the second contact disk are configured to respectively feed or discharge an electric current into or from the first wire portion.
Good efficiency results from conductively heating the first wire portion since the electrical energy is converted directly into thermal energy due to the electrical (ohmic) resistance of the first wire portion.
In a further preferential embodiment of the invention, which is an alternative to the embodiment just described, the annealing means are means for inductively heating the first wire portion.
The first wire portion here is arranged in the form of a loop or coil, its ends electrically connected conductively and thus short-circuited. This wire loop or coil acts as a secondary coil for inductive energy transfer and is situated near a primary coil through which an alternating current flows so that an alternating voltage, and thus an eddy current, is induced in the wire loop or coil by electromagnetic induction which in turn heats the first wire portion via its electrical (ohmic) resistance.
In so doing, the first wire portion is heated in non-contact and thus also non-wearing manner, although the efficiency of the energy transfer is thereby lower than with the conductive heating of the wire.
In a further preferential embodiment of the invention, the recrystallization zone is configured to dispose the second wire portion under a protective gas.
Preferably conceivable examples of protective gas are water vapor, nitrogen, hydrogen or a mixture of nitrogen and hydrogen. Due to displacing the atmospheric oxygen, the protective gas prevents the oxidation of the wire surface and thus its tarnishing.
In a further preferential embodiment of the invention, the continuous annealer for wire has no cooling device for the wire between the annealing zone and the recrystallization zone.
The absence of a cooling device between the annealing and recrystallization zones can increase the energy savings since almost all of the residual heat in the first wire portion upon leaving the annealing zone is still present in the recrystallization zone and can be used for the second partial recrystallization process.
In a further preferential embodiment of the invention, which is an alternative to the embodiment just described, the continuous annealer for wire does have a cooling device for cooling the second contact disk.
A cooling device for the second contact disk may be necessary since the heat of the first wire portion passing out of the annealing zone is continuously introduced into the second contact disk and the second contact disk thus significantly heated. In view of the relatively high temperatures of the first wire portion in the annealing zone (e.g. 550° C.), the absence of such a cooling device could result in a thermal overload of the second contact disk in same.
In one variant of the embodiment of the invention just described, the cooling device for cooling the second contact disk comprises means for spraying the second contact disk with a cooling medium, again particularly an emulsion or oil.
In known cooling devices, the second contact disk together with the wire portion in contact with it is for example fully submerged in a cooling basin filled with cooling medium, whereby not only the second contact disk but also said portion of wire is significantly cooled.
In contrast thereto, cooling the second contact disk with a cooling medium spray cools the second contact disk in targeted manner, yet the wire portion in contact with it only to a lesser extent. Furthermore, the cooling medium can in this way be unproblematically supplied and drawn off again. The amount of cooling medium supplied per unit of time can also be easily controlled and adapted to the amount of heat to be dissipated.
The targeted directing of a cooling medium jet spray onto the second contact disk, in particular onto that part of its outer perimeter contact strip not looped by the wire, can prevent the marked cooling of the wire portion looped around the outer perimeter of the second contact disk.
In a further preferential embodiment of the invention, a cooling zone and/or a cooling basin is/are situated downstream of the recrystallization zone, as seen in the wire's direction of travel, this/these being configured such that a third wire portion, which has previously passed through the recrystallization zone as a second wire portion, passes through the cooling zone and/or the cooling basin and is cooled therein by a cooling medium.
Such a cooling zone or cooling basin respectively may be necessary if the wire is still too warm to be further processed after leaving the recrystallization zone, in particular to be wound onto a spool. Preferably, the cooling zone is designed as a housing filled with the cooling medium, wherein the third wire portion is submerged in and passes through the cooling basin. Preferably, the third wire portion is in contrast only sprayed with the cooling medium—similar to the above-described cooling device for the second contact disk—in the cooling basin.
In one variant of the embodiment of the invention just described, the continuous annealer for wire comprises the cooling zone and the cooling zone has means for spraying the third wire portion with a cooling medium, again particularly an emulsion or oil.
Particularly preferentially, the cooling zone thereby comprises at least one apparatus for regulating the volumetric flow of the cooling medium in the cooling zone. In particular, the apparatus has at least one valve for introducing cooling medium into the cooling zone and the at least one valve is adjustable and in particular designed as a proportional valve.
Using a proportional valve enables precisely regulating the amount of cooling medium introduced into the cooling zone through the valve per unit of time. The cooling effect in the cooling zone can in this way be adapted to the amount of heat to be dissipated. This amount of heat in turn depends particularly on the volume of wire material in the third wire portion and thus on the diameter of the wire there.
Instead of a proportional valve, the apparatus for regulating the volumetric flow can also exhibit, for example, a hand lever valve. Using a frequency-controlled pump is also conceivable in order to improve the cooling effect by means of a higher volumetric flow.
In the inventive method for annealing and recrystallizing an in particular metallic wire in a continuous process in an inventive continuous annealer for wire, a first portion of wire passes through the annealing zone and is annealed there, wherein a first partial recrystallization process takes place in the first wire portion. In addition, a second portion of wire, which has previously passed through the annealing zone as a first wire portion, passes through the recrystallization zone, wherein a second partial recrystallization process takes place in the second wire portion.

Further advantages, features and possible applications of the present invention yield from the following description in conjunction with the figures. Shown therein:

FIG. 1 a continuous annealer for wire from the prior art without a recrystallization zone;

FIG. 2 an inventive continuous annealer for wire with a recrystallization zone.

FIG. 1 shows a continuous annealer for wire 1 from the prior art which has an annealing zone 8 and a cooling zone 4, although no recrystallization zone.
The wire 12, which was drawn in a drawing machine (not illustrated) to a specific diameter and thereby solidified, is heated in the continuous annealer for wire 1 and thereby recrystallized in order to largely suspend the solidification and thus in particular the residual strain; i.e. to increase the maximum ductility prior to wire breakage.
The wire 12 is inserted into the continuous annealer for wire 1 at the left edge and initially runs around a deflection roller 10. All the contact disks of the continuous annealer for wire 1 according to FIGS. 1 and 2 are likewise designed as deflection rollers. The wire 12 then passes through several other deflection rollers. The throughput speed of the wire 12 through the continuous annealer for wire 1 amounts to, for example, 30 m/s.
The wire 12 thereafter reaches the first contact disk 2, travels around same, and passes into the annealing zone 8 where it is heated. The annealing zone 8 is designed as a closed housing (apart from the inlet and outlet openings for the wire 12) such that the lowest amount of thermal energy possible can escape into the environment from the heated wire. The length of the annealing zone 8 in the continuous annealer for wire 1 according to FIG. 1 amounts to, for example, 2000 mm. The section of the wire 12 which passes through the annealing zone 8 is referred to as the first wire portion. The arrow above the annealing zone 8 indicates the wire's direction of travel in the annealing zone 8.
The heating of the first wire portion ensues by a voltage being applied to the first contact disk 2 and the second contact disk 3, preferably a direct current voltage, however particularly preferentially an alternating current voltage, whereby a direct current or alternating current respectively flows through the first wire portion which heats the first wire portion due to its ohmic resistance. The wire 12 thereby reaches a temperature of e.g. 550° C. as it enters into the inlet cooling nozzle 7 of the cooling basin 9.
Due to being heated, the first wire portion experiences a first partial recrystallization process in the annealing zone 8, whereby the first wire portion's solidification induced by the preceding drawing process is largely suspended.
The wire 12 exits the annealing zone 8 at the entrance to the cooling basin 9 where it enters into the inlet cooling nozzle 7. The wire 12 is sprayed or sprinkled with a cooling medium, which is preferably an emulsion or oil, in the inlet cooling nozzle 7 of the cooling basin 9 so as to already dissipate part of the thermal energy from the wire 12 at this point. The wire 12 is thereafter guided around a second contact disk 3 within the cooling basin 9. The cooling basin 9 is filled with a further cooling medium so that the second contact roller 3 as well as the section of the wire 12 running around it are completely submerged in the cooling medium. The cooling medium in the cooling basin 9 draws the heat off from this wire portion. The heated cooling medium is discharged continuously or at specific time intervals and replaced with cold cooling medium. The wire 12 ultimately exits the cooling basin 9 again through the outlet cooling nozzle 6, in which the wire 12 is again sprayed or sprinkled with a cooling medium.
The wire 12 subsequently passes through a cooling zone 4. This also exhibits a closed housing (apart from the inlet and outlet openings for the wire 12) which is flooded with a further cooling medium and in which the wire 12 is completely submerged. The arrow above the cooling zone 4 indicates the wire's direction of travel in the cooling zone 4.
By way of the cooling basin 9 with cooling nozzles 6 and 7 as well as the cooling zone 4, the wire 12 is cooled to a temperature enabling its further processing, in particular being wound onto a spool. However, only the lowest amount of thermal energy as possible is drawn off from the wire 12 in order to ensure the required final temperature when winding (approximately 50° C.).
The wire 12 still wet with cooling medium ultimately passes through a drying zone 5 in which it is dried, preferably by air blown into said drying zone 5.
The wire 12 is thereafter led out of the continuous annealer for wire 1 at the right edge via several other deflection rollers in order to be further processed there, in particular wound onto a spool (not depicted).
FIG. 2 shows an inventive continuous annealer for wire 1 with a recrystallization zone 11.
The inventive continuous annealer for wire 1 according to FIG. 2 is based on the continuous annealer for wire 1 from the prior art according to FIG. 1 and exhibits some modifications compared thereto. Therefore, there will be no reiterated description of the elements of the two continuous wire annealers 1 which correspond to one another.
The wire 12 is guided to the annealing zone 8 as in FIG. 1 and heated there, whereby the first wire portion experiences a first partial recrystallization process and then likewise enters the cooling basin 9.
Should there be an inlet cooling nozzle at the entrance of the cooling basin 9, it is preferably not utilized. The same applies to any outlet cooling nozzle at the exit of the cooling basin 9. The wire 12 is again guided around a second contact disk 3 (not depicted in FIG. 2 ) within the cooling basin 9.
The wire 12 is only cooled slightly or not at all in the cooling basin 9. Preferably, only the second contact disk 3 is sprayed with a further cooling medium in order to cool it while the wire 12 remains largely uncooled. Preferably, while the cooling basin 9 can also be flooded with the cooling medium, it is preferably just minimally circulated and replaced, or not at all, so that only a small amount of thermal energy is drawn off by the cooling medium. The question of how much cooling medium needs to be in the cooling basin 9; i.e. the fill level of cooling basin 9, can be determined experimentally and can differ depending on environment.
The wire 12 then passes through the recrystallization zone 11 which—like the cooling zone 4 arranged at the corresponding location in FIG. 1 —exhibits a largely closed housing. However, the wire 12 is not cooled in the recrystallization zone 11. The wire 12 is thus still warm enough after leaving the cooling basin 9 that a second partial recrystallization process can take place in the recrystallization zone 11.
The annealing zone—in the sense of the section where recrystallization occurs in the wire 12—is in this way lengthened so to speak, e.g. even doubled, wherein energy input, however, only occurs in the first part—the actual annealing zone 8.
While achieving the same degree of recrystallization, the input of thermal energy into the annealing zone 8 can thus be reduced, leading to the above-cited energy savings of up to 20%.
A protective gas atmosphere preferably prevails in the housing of the recrystallization zone 11, preferentially nitrogen or water vapor, in order to prevent oxidation and thus tarnishing of the surface of the wire 12.
The wire 12 then ultimately also passes through a cooling zone 4 and a cooling basin 13 in order for the temperature of the wire 12 to be lowered to a temperature suitable for the further processing. In the exemplary embodiment according to FIG. 2 , the cooling zone 4 and the cooling basin 13 are, for reasons of space, at least partially arranged in an additional housing 15 which is flanged to the housing 14 of the continuous annealer for wire 1. The cooling zone 4 and the cooling basin 13 can, however, also be integrated into the housing 14 of the continuous annealer for wire 1. Providing only the cooling zone 4 or only the cooling basin 13 is also possible.
The wire 12 is submerged in a cooling medium—similar as in the continuous annealer for wire 1 in FIG. 1 —in cooling zone 4. The volumetric flow of the cooling medium can be regulated in the cooling zone 4, whereby the cooling effect on the wire 12 can also be regulated as a function of the diameter and the feed rate of the wire 12. This is preferably effected by at least one proportional valve (not depicted).
The wire 12 is likewise submerged in a cooling medium or even just sprayed with a cooling medium in the cooling basin 13.

LIST OF REFERENCE NUMERALS

- 1 continuous annealer for wire
- 2 first contact disk
- 3 second contact disk
- 4 cooling zone
- 5 drying zone
- 6 outlet cooling nozzle
- 7 inlet cooling nozzle
- 8 annealing zone
- 9 cooling basin
- 10 deflection roller
- 11 recrystallization zone
- 12 wire
- 13 cooling basin
- 14 housing of continuous annealer for wire
- 15 housing of cooling zone and cooling basin

Claims

1. A continuous annealer for wire for annealing and recrystallizing an in particular metallic wire in a continuous process which comprises:

at least two contact disks which are configured such that a first contact disk contacts a rear end, seen in the wire's direction of travel, and a second contact disk contacts a front end, seen in the wire's direction of travel, of a first wire portion extending between the first contact disk and the second contact disk,

an annealing zone situated between the first contact disk and the second contact disk which is configured such that the first wire portion passes through the annealing zone, as well as

annealing means for annealing the first wire portion in the annealing zone, whereby a first partial recrystallization process takes place in the first wire portion in the annealing zone,

wherein

a recrystallization zone is situated downstream of the second contact disk, seen in the wire's direction of travel, which is configured such that a second wire portion, which has previously passed through the annealing zone as a first wire portion, passes through the recrystallization zone and that a second partial recrystallization process takes places in the second wire portion.

2. The continuous annealer for wire according to claim 1, wherein the annealing means are means for conductively heating the first wire portion, wherein the first contact disk and the second contact disk are configured to respectively feed or discharge an electric current into or from the first wire portion.

3. The continuous annealer for wire according to claim 1, wherein the annealing means are means for inductively heating the first wire portion.

4. The continuous annealer for wire according to claim 1, the wherein the crystallization zone is configured to dispose the second wire portion under a protective gas.

5. The continuous annealer for wire according to claim 1, wherein it has no cooling device for the wire between the annealing zone and the recrystallization zone.

6. The continuous annealer for wire according to claim 1, wherein it has a cooling device for cooling the second contact disk.

7. The continuous annealer for wire according to claim 6, wherein the cooling device for cooling the second contact disk comprises means for spraying the second contact disk with a cooling medium, particularly an emulsion or oil.

8. The continuous annealer for wire according to claim 1, wherein a cooling zone and/or a cooling basin is/are situated downstream of the recrystallization zone seen in the wire's direction of travel, and configured such that a third wire portion, which has previously passed through the recrystallization zone as a second wire portion, passes through the cooling zone and/or the cooling basin and is cooled therein by a cooling medium.

9. The continuous annealer for wire according to claim 8, wherein it comprises the cooling zone and that the cooling zone has means for spraying the third wire portion with a cooling medium, particularly an emulsion or oil.

10. The continuous annealer for wire according to claim 9, wherein the cooling zone comprises at least one apparatus for regulating the volumetric flow of the cooling medium in the cooling zone, wherein the apparatus in particular has at least one valve for introducing cooling medium into the cooling zone and the at least one valve is adjustable and in particular designed as a proportional valve.

11. A method for annealing and recrystallizing a wire in a continuous process in a continuous annealer for wire according to claim 1, wherein a first wire portion passes through the annealing zone, is annealed there and a first partial recrystallization process thereby takes place in the first wire portion as well as that a second wire portion, which has previously passed through the annealing zone as a first wire portion, passes through the recrystallization zone and a second partial recrystallization process thereby takes place in the second wire portion.

12. The method of claim 11, wherein the wire is metal.