EP2170551A1

EP2170551A1 - Method for producing a wire from copper or from a copper alloy by means of extrusion

Info

Publication number: EP2170551A1
Application number: EP08786062A
Authority: EP
Inventors: Thomas Pfeffer; Reinhold Czieslick; Karl Goertz
Original assignee: Umicore AG and Co KG
Current assignee: Umicore AG and Co KG
Priority date: 2007-07-21
Filing date: 2008-07-11
Publication date: 2010-04-07
Also published as: DE102007034093A1; ZA201000757B; CA2692344A1; CN101778694A; US20100192370A1; BRPI0814270A2; MX2010000701A; AU2008280307A1; PE20090673A1; EA201000160A1; AR067624A1; CL2008002091A1; KR20100042626A; JP2010534138A; WO2009013150A1; DE102007034093B4

Abstract

The invention describes a continuous method for producing wires from copper or from a copper alloy, wherein the copper or copper alloy is in the form of a cast billet (1) and is drawn at a temperature above 500°C into one or more finished wires with the aid of an extruder (2), in which a female die (4) and corresponding drawing dies are located, characterized by the following steps, a) protecting the hot wires (5) emerging from the female die (4) in a stretching zone (I) from oxidation by means of a shielding gas, b) cooling the wires in a cooling zone (II) in a temperature-controlled water bath (6) at a temperature greater than 60°C, c) measuring the cross-sectional dimensions of the wires after they leave the water bath and exerting a controlled tensile force on the wires, so that the deviations of the cross-sectional dimensions of the wires from a desired cross section are minimized by stretching the wires in the stretching zone (I), and d) placing the wires into a divided drawing die (14) without prior swaging, closing the drawing die and drawing the wires to the finished dimensions continuously until the cast billet is used up.

Description

Method for producing a wire made of copper or of a copper alloy

description

The invention relates to a method for producing wires made of copper or of a copper alloy according to the preamble of claim 1. The suitable for this purpose

Copper alloys, for example, are standardized in the standard DIN EN 1044. In addition to copper as alloying additives, they contain cadmium, zinc, silicon, tin, manganese, nickel,

Silver, phosphorus and other non-ferrous metals. From these alloys usually wires are made with diameters of 1 to 5 mm. The main field of application of this invention is in the field of the production of brazing wires based on copper alloys.

Methods and devices for producing wires and rods made of copper or copper alloys are described, for example, in German Offenlegungsschriften DE 39 29 287 A1 and DE 196 02 054 A1 as well as in US Pat. Nos. 2,290,684 and 2,795,520. Starting point for the production of the wires are usually cylindrical ingots, which are heated to 550 to 600 ⁰ C and extruded with an extruder to one or more wires. The resulting raw wires must usually be brought by further drawing or rolling processes to the desired final diameter.

The extrusion methods described can be used to produce wires or rods with different cross-sectional shapes. Round or square cross sections are preferred. The extruded wires are usually made to size by one or more cold drawing. In the case of alloys, only cold forming with a degree of deformation of between 25 and 30% is possible with each drawing process. The degree of deformation depends on the alloy chosen. With pure copper, a higher degree of deformation is achievable. The degree of deformation is defined as the ratio of the change in cross section relative to the initial cross section.

Copper or copper alloys form a dark oxide skin of Cu (IΙ) oxide at the surface at high temperatures and tend to embrittle at large changes in shape during the drawing or rolling processes. Without further precautions to avoid these problems, the raw wires emerging from the extruder to remove the oxide skin in dilute sulfuric acid must be pickled and then with To be rinsed with water. The embrittlement can be reversed by annealing. The cited patent documents avoid the formation of the oxide skin by spraying the hot wires emerging from the extruder with water from suitable spray nozzles to obtain "bright metallic" wires.

The extrusion methods described can be used to produce wires or rods with different cross-sectional shapes. Round or square cross sections are preferred. The extruded wires are usually made to size by one or more cold drawing. With each drawing process, depending on the material, only cold forming with a degree of deformation between 25 and 50% is possible. The degree of deformation is defined here as the change in cross section relative to the initial cross section.

Conventionally extruded wires have, according to experience, a fluctuation range of their cross-sectional dimensions of ± 5%. For copper alloys according to DIN EN 1044, however, the required limit dimensions for wires are ± 3%. In order to comply with the limiting dimensions, a so-called calibration train is first made prior to the finishing in order to reduce the tolerance of the cross-sectional dimensions. In this case, wire sections with a larger cross section are deformed more strongly than thinner wire sections. This leads to different elongation at break, tensile strength and hardness along the wires. In general, hardness and tensile strength increase with increasing degree of deformation, while the elongation at break decreases. Therefore, before the finishing, the wires must be annealed in order to eliminate the work hardening during forming by annealing above the recrystallization temperature.

The quality of the extrusion thus has a decisive influence on the subsequent operations.

Furthermore, it has been found that the prior art spraying of the extruded solder wires with cold water sometimes results in spotty surfaces of the wires. In addition, the wires thus produced are brittle and can not be processed without prior annealing in subsequent drawing processes.

For pulling to finished dimension, drawing equipment is available, the heart of which are so-called diamond or carbide dies. They have a pull opening through which the wire is pulled. Since the pull opening is smaller than the wire diameter, the wire must be sharpened in a suitable device, before he can be threaded through the drawing opening. This process is time consuming and prevents continuous production of the ingot to the solder wire with finished size.

Object of the present invention is therefore to provide a continuous process for producing a wire made of copper or a copper alloy, being produced without interruption, starting from the extrusion of a Gußblocks in only one subsequent drawing process, a bare metal wire with finished size.

This object is achieved by the method specified in the main claim. Preferred embodiments of the method are described in the subclaims.

The process according to the invention is based on the extrusion processes known from the prior art. Copper or copper alloy are placed in the form of a cast pin (1) in an extruder (2) and pressed at a temperature above 500 ⁰ C by a die (4) with one or more Matrizenöffhungen and then cooled in a cooling zone. The raw wire (s) (5) emerging from the matrix are drawn to finished dimensions in just one subsequent drawing process. The method comprises the following steps:

a) protecting the hot wires (5) emerging from the die (4) in a stretching zone (I) with a protective gas against oxidation, b) cooling the wires in a cooling zone (II) in a tempered water bath (6) with a temperature greater as 60 ⁰ C, c) measuring the cross-sectional dimensions of the wires after exiting the water bath and applying a controlled tensile force to the wires so that the deviations of the cross-sectional dimensions of the wires from a desired cross-section are minimized by stretching the wires in the stretch zone and d ) Inserting the wires without prior sharpening in a split die (14), closing the die and pulling the wires to finished dimension without interruption until the cast bolt (1) is used up.

The process allows multiple wires to be manufactured in parallel. The die of the extruder must have this many corresponding Extrusionsöffungen. Preferably, the die is equipped with two extrusion ports. For the sake of simplicity, the following explanations relate only to the production of a wire. When making multiple wires, the procedures for each wire must be made independently. With the method, wires with different cross-sectional shapes can be produced, preferably wires with a round cross-section are produced.

According to the invention, a stretching zone is arranged between the die and the cooling zone. In the

Stretching zone is the temperature of the wire just behind the exit from the Matrize still so high that the wire has a plastic nature and can be drawn with relatively little effort in the length. Here are the

Cross-sectional dimensions of the wire starting from the cross-sectional dimensions of the die opening reduced to a desired cross-section. This process is with a

Manufacturing tolerance of about ± 5% afflicted. It has been found that by controlling the tensile force acting on the wire, the tolerance of the cross-sectional dimensions on

± 3% can be reduced.

In the case of round wires, it has proven useful if the diameter of the die opening is larger by a factor of 1.4 to 2, preferably by a factor of 1.5 to 1.8, than the desired wire diameter after leaving the stretching zone. A larger die diameter reduces the requirements for the extrusion pressure of the extruder.

The drawing speed for the wires behind the stretching zone is preferably between 0.5 and 1.5, in particular between 0.7 and 1.0 m / s.

The tensile force for the stretching process can be introduced through a arranged behind the cooling zone stretching drive in the wire. To control the tensile force of the actual cross-section is measured after the exit of the wire from the water and before the stretch drive and compared with the desired cross-section. The actual cross section forms the controlled variable whose deviation from the nominal cross section is determined in a controller and used to determine the necessary change in the tractive force of the stretching drive. The desired cross-section of the wire can be determined, for example, with an optical wire thickness gauge.

The length of the stretching zone between die and cooling zone can be between 30 and 500 mm long, preferably it has a length of 50 to 300 mm. Since the freshly extruded wire is still very hot in this zone, it is advisable to prevent the oxidation on the wire surface by infilling or flooding the stretching zone with a protective gas. Suitable shielding gases are argon or nitrogen, nitrogen is preferably used.

The described extrusion with connected controlled stretching of the extruded raw wires leads to wires whose thickness variations are so far reduced that a single downstream drawing process is sufficient to pull the wires to finished size. In order for this drawing process can be connected immediately without interruption after leaving the cooling zone, the wire must leave the cooling zone in a metallic blank. In the context of this invention, "metallic bright" is understood to mean that there is no black Cu (II) oxide on the surface of the solder wires, but only the unavoidable red Cu (I) oxide. Pickling of the wire for the purpose of removing the oxide skin can be done then omitted.

According to the invention, the metallically bright surface of the wire behind the cooling zone is ensured by a plurality of measures:

"In the stretch zone, the wire is infused or flooded with a wire

Inert gas protected against oxidation;

• In the cooling zone, the wire is cooled in a tempered water at a temperature above 60, preferably above 80 ⁰ C below 100 ⁰ C. For this purpose, the wires are preferably pulled through the water bath within 1 to 10 seconds;

• Preferably, the water bath is constantly swirled to prevent gas bubbles forming on the hot wire surface. This can be done, for example, that the wires are flowed across the running direction with hot water.

The above measures lead to solder wires with a metallically bright surface, which still have a sufficient deformability for subsequent drawing processes. It is essential here that the water bath is heated to about 60 to 95 ⁰ C. Temperatures of the water bath below 60 ⁰ C lead to embrittlement of the wire, which in the subsequent finishing has frequent wire breakage.

After cooling the wire in a water bath, it is drawn to finished size in a single drawing process. So that this drawing process can be integrated without interruption into the overall process, a split die was developed. As a result, the usual sharpening of the wire and threading into the die is unnecessary. After starting the extrusion, the beginning of the wire is inserted into the open die, the die is closed and the wire is drawn to finished size. The method is suitable in principle for all extrusion processes in which a continuous profile with reduced tolerances of the cross-sectional dimensions is to be produced. However, the method is preferably used for the production of wires made of copper or copper alloys containing addition of copper alloying additions of silver, cadmium, zinc, silicon, tin, manganese, nickel or phosphorus or combinations of these additives. The method makes it possible to produce a ready-made wire with a metallically bright surface in a continuous operation from a cast block.

In the following the invention will be explained in more detail with reference to examples and figures. Show it:

Figure 1: Basic structure for carrying out the method

Figure 2: Measurement protocol for the diameter of two parallel drawn wires without regulation of the stretch drive

Figure 3: Measurement protocol for the diameter of two parallel drawn wires with regulation of the stretch drive

Figure 4: Structure of the split die

Figure 1 shows the basic structure for carrying out the method. Reference numeral (1) denotes the cast bolt made of copper or a copper alloy. It is located in the extruder (2) and is held by a not shown external heating at a temperature of, for example, 600 ⁰ C. With the punch (3), the cast bolt is pressed through an opening in a die (4). The extruded raw wire is designated by reference numeral (5). To the die (4) includes the stretching zone (I), in which the wire is only moderately cooled. To avoid oxidation of the wire, the stretching zone is filled or flooded, for example, with a protective gas. In the subsequent cooling zone (II), the still hot wire is cooled to a temperature below 100 ⁰ C by passing through a tempered water bath (6), which is maintained at a temperature of at least 60 ⁰ C. The water bath is shown in plan view of the water surface. The arrows directed from opposite sides to the raw wire (5) represent an inflow of the wire with water from a plurality of nozzles arranged along the wire in the water bath. The necessary water is circulated. For this purpose, there is an outlet at the bottom of the water bath, through which a pump sucks water and feeds back to the water bath via the Anströmdüsen. The transverse flow of the wires prevents dert that gas bubbles settle on the wire surfaces and lead to a stained surface.

Behind the cooling zone (II), a measuring system (7) for determining the cross-sectional dimensions of the wire is arranged. Suitable are mechanical or optical measuring systems. The measured signal is compared in the controller (8) with the value for the nominal cross section and output from the resulting control deviation a manipulated variable to the drive motor of the stretching drive (9). If the measured cross section is greater than the nominal cross section, the tensile force of the stretching drive is increased, resulting in a longitudinal expansion with a corresponding reduction of the cross section. Conversely, if the measured cross section is smaller than the desired cross section, the tensile force of the stretch drive is reduced. With this control, the tolerance of the cross-sectional dimensions of the extruded wire can be reduced from ± 5% to less than ± 3%.

In a subsequent processing station (11), the wire is drawn to finished size. This processing station consists of a press with lower punch (12) and upper punch (13). The heart of this processing station is an arrangement of a die and a socket. Die and socket are split to allow insertion of the extrusion extruded wire while extrusion is in progress. One half of the assembly (14) is attached to lower and upper punch. Before the extrusion of the raw wire, the two punches of the press are moved apart. If the raw wire reaches this press, it is placed in the open die and the beginning of the wire is wound behind the die around the drawing drive (16). Then, the upper punch of the press is lowered onto the lower punch until the two separating surfaces of the drawing die lie one on top of the other. The draw drive pulls the wire through the die to finished size. The finished solder wire is wound on a winder not shown in FIG.

Extrusion speed, stretching and drawing to finished size are matched during the entire duration of the process, so that the cast bolt can be extruded without interruption to an unavoidable rest. Preferably, the pulling speed of the wires behind the cooling zone is between 0.5 and 1.5 m / s.

To facilitate the start of the process is located behind the first winding drive a so-called dancer (10), which can compensate for short-term speed differences between the individual processing stations of the process. Reference numeral 15 denotes a wire guide combined with a lubricating station. Figure 4 shows the arrangement of die and socket. It consists of the die (20) which is fixed in a socket (21). The die has a bore (23) whose axis forms a drawing axis. Die and socket are divided along the drawing axis. During wire drawing, both halves of the arrangement lie on one another with the parting surfaces (24) formed during the division and are positioned exactly to one another with pins in the pin holes (25). The threaded holes (26) in the socket serve to secure the halves of the assembly in the upper and lower punches of the press.

The die may consist of hard metal or of diamond, preferably of a polycrystalline diamond.

So that no striations are generated on the wire by the division of the die during wire drawing, the bore of the die must be made exactly. Preference is given to doing so that first a preform of the die is fixed without drilling in the undivided version. Preferably, the die is soldered into a socket made of steel. After inserting the pin holes in the socket, the arrangement is divided along the later drawing axis and the parting surfaces are smoothed. After staking the two halves of the arrangement, the drawing opening is produced as usual with undivided drawing dies.

Surprisingly, it has been found that on the wires drawn with such a die no grooves due to the division of the die are recognizable. The particular advantage of this die is that the raw wire does not have to be sharpened for threading into the drawing opening. Due to the elimination of the sharpening of the raw wire, it is now possible to build a drawing system, with a raw wire in a drawing station to the finished wire continuously without interruption for the purpose of sharpening the wire can be pulled.

In the following comparative example and example, raw wires were extruded from the copper alloy Ag40Cu30Zn28Sn2 (designation according to DIN EN 1044: AG 105). These raw wires were then finished to a wire diameter of 1.5 mm.

Comparative example

A 40 kg casting bolt of said copper alloy was extruded in an extruder through a die with two round die openings of 2.9 mm diameter each into two parallel wires. In the stretching zone, the wire diameters were reduced to a nominal dimension of 1.8 mm by applying a constant tensile force. The speed of the extruded wires behind the stretch zone was 1 m / s. FIG. 2 shows the diameter values recorded with an optical measuring system over a wire length of 880 m. FIG. 2 shows the upper tolerance limit (TDC) at 1.9 mm and the lower tolerance limit (TDC) at 1.7 mm. These values correspond to a thickness tolerance of about ± 5%.

The nominal dimension of the wire diameter was set to 1.8 mm in this extrusion test, in order to have sufficient change in shape for the calibration pull and finishing pull to a diameter of 1.5 mm even with larger fluctuations in the wire diameter.

The wires were drawn to a diameter of 1.7 mm with the calibration pull. Because of the large diameter variations of the extruded wires, the calibration train introduced corresponding variations in hardness, tensile strength and elongation at break in the wires. By intermediate annealing above the recrystallization temperature, these different mechanical properties were balanced before the wires were finished to a diameter of 1.5 mm.

example 1

The comparative example was repeated with a second cast bolt. In contrast to the comparative example, the tensile force has now been regulated. The nominal diameter of the wires was 1.7 mm. The measurement results for the diameters of the two wires is shown in FIG. 3 over a length of 980 m. FIG. 3 again shows upper and lower tolerance limits. The upper tolerance limit was 1.75 mm and the lower tolerance was 1.65 mm, corresponding to a diameter tolerance of ± 3%.

The diameter tolerance of the raw wire reduced by the method according to the invention made it possible to reduce the mean diameter of the raw wire from 1.8 to 1.7 mm without loss of sufficient deformation during the final drawing to a diameter of 1.5 mm. Calibration and intermediate annealing as in the comparative example were not necessary here.

Example 2

In the series of experiments described below, raw wires from the copper alloy Ag40Cu30Zn28Sn2 (designation according to DIN EN 1044: AG 105) were drawn with a metallically bright surface. These raw wires were then finished to a wire diameter of 1, 5 mm. A 10 kg casting bolt of said copper alloy was extruded in the extruder through a die with two round die openings of 2.9 mm diameter each into two parallel wires. In the stretch zone, the wire diameters were reduced to a nominal dimension of 1.7 mm by applying a controlled tensile force. The stretching zone was protected from atmospheric oxygen by passing it through with nitrogen. The stretching zone led directly into a tempered water bath. To swirl the water, the bath was equipped with a cross-flow device. The speed of the wires passed through the water bath was 1 m / s.

Several cast bolts were extruded with the described apparatus at different temperatures of the water bath. The bare surface extruded wires were then drawn down to 1.5 mm diameter in a 1.7 mm drawing apparatus and their drawing behavior was qualitatively evaluated. The results are shown in the following table. It was found that at temperatures of the water bath of 60 and 80 ⁰ C, the wires could be pulled without wire breaks to the finished product.

Table: Drawing behavior of the extruded wires as a function of the temperature of the water bath

Claims

claims

1. A continuous process for the production of wires of copper or of a copper alloy, wherein copper or copper alloy in the form of a cast bolt (1) are present and at a temperature above 500 ⁰ C by means of an extruder (2), in which a die (4 ) and corresponding drawing dies are finished into one or more wires, characterized by the following steps: a) protecting the hot wires (5) emerging from the die (4) in a stretching zone (I) with a protective gas against oxidation, b) cooling the wires in a cooling zone (II) in a tempered water bath

(6) having a temperature greater than 60 ^° C., c) measuring the cross-sectional dimensions of the wires after exiting the water bath and applying a controlled tensile force to the wires such that the deviations of the cross-sectional dimensions of the wires from a solitary cross-section are due to stretching of the wires in the stretch zone (I) are minimized; and d) inserting the wires without prior sharpening into a split die (14), closing the die and pulling the wires to final dimension without interruption until the cast bolt is exhausted.

2. The method according to claim 1, characterized in that gas bubbles on the surface of the wires in the tempered water bath (6) are prevented by flowing the wires with water across their longitudinal extent.

3. The method according to claim 1, characterized in that the drawing speed behind the stretching zone (I) is between 0.5 and 1.5 m / s.

4. The method according to claim 1, characterized in that the length of the stretching zone (I) between the die (4) and cooling zone (II) is 30 to 500 mm.

5. The method according to claim 4, characterized in that the stretch zone (I) is filled with a protective gas or flooded to a

To prevent oxidation of the hot wire.

6. The method according to claim 1, characterized in that the tensile force in the wire arranged by a behind the water bath

Stretching drive (9) is introduced.

7. The method according to claim 1, characterized in that the cross section of the wire is round.

8. The method according to claim 7, characterized in that the diameter of the die opening by a factor of 1.4 to 2 is greater than the desired wire diameter after leaving the stretching zone (I).

9. The method according to claim 8, characterized in that by using a die (4) having a plurality of die openings a plurality of wires are extruded simultaneously.

10. The method according to claim 1, characterized in that the copper alloy in addition to copper alloying additives selected from the group consisting of silver cadmium, zinc, silicon, tin, manganese, nickel, phosphorus and combinations thereof.