EP0926251B1 - Process for making and using a copper-tin-titanium alloy - Google Patents

Description

The invention relates to the use of a semi-finished product in strip, wire, tube or profile form made of a Cu-Sn-Ti alloy. The CuSnTi alloy consists of Sn 12-20% by weight, Ti 0.002-1.0 % By weight remainder CU, optionally further elements and usual impurities. Such an alloy can Sufficiently rapid cooling from the molten state Room temperature can be obtained in such a structural state that that for the Semi-finished product production preform (casting tape, casting block, casting bolt) is technically free from coarse, brittle phases and therefore in a special way for the Manufacture of semi-finished products as strips, profiles, wires, hollow profiles or tubes by kneading is suitable. Such semi-finished products are ideal for Production of various everyday objects and items Functional parts of precision mechanics and electromechanics as well as general ones Mechanical engineering. Because of their chemical composition and the Such an alloy has a particularly favorable method of manufacture Combination of high mechanical strength with excellent ductility combined with good corrosion resistance.

According to the current state of the art, the requirements for modern ones arise Semi-finished products both from the use and environmental properties as well as after Cost aspects. Because of the competitive pressure, those appear Attractive materials that enable rational, waste-free production. In this way, especially kneading materials appear in many cases Casting materials for Cu alloys are particularly advantageous when it comes to Production of complex functional parts goes. The kneadability of Cu materials however limits the use of highly valued properties of the Cast materials in which the Cu-Sn materials play a particularly important role play. You excel e.g. due to very high strength and hardness at very good corrosion properties and a general excellent suitability for tribological requirements. In the literature (e.g. K. Dies, Kupfer and Copper alloy in technology, Berlin 1967 page 504ff.) Is treatment and The composition of the tin bronzes is explained very comprehensively. There is also on the achievability of homogeneous structures even with cast bronze up to about 15% by weight Sn received by heat treatment. It explains there that Homogenization annealing leads to pores (see above pp. 514-516) and on the other hand mechanical properties can be improved by homogenization, without pointing out any cold deformation that is possible as a result (p. 545 ff). Classically manufactured bronzes are high in tin therefore homogenize for forming and therefore contains pores. The specialist it is known that pores are undesirable for most technical applications. They are weak points when subjected to mechanical loads and interfere with the forming themselves or usually prevent the formation of a faultless one after forming Surface. According to the prior art, the use of cast bronze as Kneading materials not given. So far the contrast between kneading and Cast materials are considered insurmountable, the availability of a kneading material considered as desirable with the properties of a cast material become.

It was therefore the task of the present invention, a material and to propose a process for its production which contrasts the overcomes the CuSn kneading materials and the CuSn casting materials. The The material is said to have the chemical and mechanical properties of the cast bronze Combine with the processing properties of the kneading materials for what especially the adjustment of the cold deformability and at the same time securing one high mechanical strength and hardness is necessary.

The object is achieved by the use of a semi-finished product made of a Cu-Sn-Ti alloy after the process steps according to claim 1 or 3 was produced. The Cu-Sn-Ti alloy is made from the molten state cooled down so quickly that the castings The usual segregation does not occur and that the structure is free of Macroscopic segregations is among macroscopic segregations understood structural components that are present in the cast structure and one Take a share of more than 10 vol .-% and one as individual phase fields Have dimensions of more than 1 mm. A sufficiently high one Cooling rate between liquidus and solidus temperature to avoid Such macro-increases can be achieved by various techniques. This includes band casting (see for example: Vaught, C.F .: Apparatus of and Apparatus for Continuous Casting of a Metal Strip, patent USA WO 87/02285 (1987); Wünnenberg, K., Frommann, K., Voss-Spilker, P .: Device for continuous casting of wide strip, published application DE 3601338 A1 (1987)) and spray compacting (see for example: GB-PS 1 379 261, Reginald Gwyn Brooks, (1972), GB-PS 1 599 392, Osprey Metals Ltd., (1978), European Patent 0 225 732, Osprey Metals Ltd., (1986)). The one with these Processed preforms differ from e.g. B. by usual Continuous casting produced preforms clearly in their structural state. Your Machinability through hot and cold forming are excellent as for example in DE 4126 079 "strip casting process for separating and / or copper alloys sensitive to stress and / or susceptible to segregation "and DE 4201065 "Application of the spray compacting process to improve the Flexural fatigue strength of semi-finished products made of copper alloys " However, the compositions cited there do not refer to typical ones Cast alloys. Surprisingly, it has now been found that the vulnerability of e.g. cast-tin bronzes defined in DIN for imperfections and pores but also for segregation by adding titanium or zirconium as well as Iron can be reduced to such an extent that the technical use of the so preforms produced by kneading is possible. More to be explained later Embodiments with the addition of further alloy components also allow important for mechanical function and corrosion resistance Set properties appropriately.

For classic cast-tin bronzes, both the warping and the Cold forming is not possible or only possible to a very limited extent. In contrast, allow Alloys produced according to the invention in the cold state Cross-sectional changes in the cast condition of at least 20% or Comparative degrees of deformation of at least ϕ = 0.25 (ϕ: in A0 / A1; A0: cross section before cold working; A1: cross section after cold working).

The use of classic cast alloys is prohibited for the Hot forming due to the melting at the process temperature Phases of segregation, which lead to the destruction of the workpiece or because of low process temperature then brittle phases that either the Drive the forming resistance so high that the forming is done mechanically is no longer possible or lead to shearing and destruction of the workpiece. In contrast, the preforms produced according to the invention allow their use of hot forming processes with a large change in cross-section. Are Processes with dominant compressive stress such as presses and round rolls highly recommended.

So are the alloy compositions of the type to be used according to the invention provided technically as a preform, they are suitable for kneading in the Heat from rolling, pressing and forging and from these basic shapes derived forming process. At room temperature they can be warm beforehand formed castings, but also the castings themselves, by rolling, drawing, Hammering, embossing, deep drawing and forming processes derived from such as Pilgrims, flanging, knurling and bending are formed

1. Herstellung der Vorform

1.1 Dünnbandgießen Zur Herstellung von dünnen Bändern 2 bis 25 mm Dicke

1.2 Sprühkompaktieren

1.2.1 Zur Herstellung von Flachformen oder Bändern bis 250 mm Dicke

1.2.2 Zur Herstellung von Rohren mit Wanddicken bis zu 100 mm

1.2.3 Zur Herstellung zylindrischer Körper bis 600 mm, die z.B. als Bolzen zum Strangpressen dienen können.

1.3 Spangebende Bearbeitung der Vorform

2. Weiterverarbeitung der Vorform

2.1 Warmumformung Für Walzverfahren wird die Warmumformung im Temperaturbereich von 600 - 800 °C,
für Pressverfahren im Temperaturbereich von 550 - 800 °C empfohlen.

2.2 Kaltverformung Bezogene Querschnittsänderungen bis 95 % und Vergleichsumformgrade bis ϕ = 3 sind möglich. Für die Vorform werden typischerweise bezogene Querschnittsänderungen von mindestens 20 % bzw. Vergleichsumformgrade von mindestens ϕ = 0,25 ertragen.

2.3 Zwischenglühungen zum Rekristallisieren und zur Erholung des Formänderungsvermögens Hierfür sind Glühungen im Temperaturbereich zwischen 400 und 700 °C für 1 Minute bis 10 Stunden Dauer geeignet.

2.4 Abschließende Kaltumformung Für eine abschließende Kaltumformung sind bezogene Querschnittsänderungen typischerweise bis 95 % nach einer vorangehenden Zwischenglühung möglich.

2.5 Abschließende Wärmebehandlung Eine Abschließende Wärmebehandlung wird durchgeführt, um den Eigenspannungszustand durch thermische Behandlung günstig zu beeinflussen oder um die mechanischen Eigenschaften in zweckmäßiger Weise durch Anlass- oder Weichglühbehandlung zu beeinflussen oder um durch gezielte Einstellung heterogener Phasen z.B. notwendige tribologische oder Zerspanungseigenschaften zusätzlich einzustellen.

2.5.1 Anlassen Das Anlassen wird im Temperaturbereich 150 - 300 °C mit Dauern zwischen 1 Minute und 10 Stunden durchgeführt.

2.5.2 Erholung und Rekristallisationsglühungen werden im Temperaturbereich von 300 - 700 °C mit Glühdauem von 1 Minute bis zu 10 Stunden durchgeführt.

2.5.3 Heterogenisierung Heterogenisierungsbehandlungen werden zum Einstellen der Gleichgewichtsphasen im Temperaturbereich von 700 - 900 °C mit Glühdauern von wenigstens 1 Minute bis zu 10 Stunden durchgeführt. Sie dienen besonders zur Einstellung hoher Härten oder zur Gefügedifferenzierung, die vorwiegend zur Optimierung tribologischer Eigenschaften dient.

This results in the following individual elements for the application of the methods according to the invention to the alloys according to the invention:

1. Production of the preform

1.1 Thin strip casting For the production of thin strips 2 to 25 mm thick

1.2 Spray compacting

1.2.1 For the production of flat forms or strips up to 250 mm thick

1.2.2 For the production of pipes with wall thicknesses up to 100 mm

1.2.3 For the production of cylindrical bodies up to 600 mm, which can serve as bolts for extrusion, for example.

1.3 Machining the preform

2. Further processing of the preform

2.1 Hot stamping For rolling processes, hot stamping is carried out in the temperature range of 600 - 800 ° C,
recommended for pressing processes in the temperature range of 550 - 800 ° C.

2.2 Cold forming Related cross-sectional changes up to 95% and comparative degrees of deformation up to ϕ = 3 are possible. For the preform, typically related cross-sectional changes of at least 20% or comparative degrees of deformation of at least ϕ = 0.25 are endured.

2.3 Intermediate annealing for recrystallization and for the recovery of the shape changing ability. Annealing in the temperature range between 400 and 700 ° C for 1 minute to 10 hours is suitable.

2.4 Final cold forming For a final cold forming, related cross-sectional changes are typically possible up to 95% after a previous intermediate annealing.

2.5 Final heat treatment A final heat treatment is carried out in order to favorably influence the residual stress state through thermal treatment or to suitably influence the mechanical properties by tempering or soft annealing treatment or to additionally adjust the necessary tribological or machining properties by targeted adjustment of heterogeneous phases.

2.5.1 Starting Starting is carried out in the temperature range 150 - 300 ° C with a duration between 1 minute and 10 hours.

2.5.2 Recovery and recrystallization annealing are carried out in the temperature range of 300 - 700 ° C with annealing times from 1 minute to 10 hours.

2.5.3 Heterogenization Heterogenization treatments are carried out to set the equilibrium phases in the temperature range of 700 - 900 ° C with annealing times of at least 1 minute to 10 hours. They are particularly used for setting high hardnesses or for differentiating the structure, which is mainly used to optimize tribological properties.

The choice of the preform and the subsequent combination of the manufacturing steps, such as listed, happens according to expediency and economy.

Preforms according to 1.1 are preferably without a hot forming stage further processed. For the other preforms is expediently used faster and larger cross-section reduction a hot forming stage intended.

The sequence of cold working and intermediate annealing according to 2.2 and 2.3 serves the production of the desired semi-finished products and their dimensions - and can be used for Repeat as needed. The cold forming and final treatments serve the manufacture of semi-finished products, the targeted adjustment of geometric and mechanical Properties for the direct use of the semi-finished product or its further processing e.g. by coating, plating or manufacturing composite materials.

In addition to the procedural approaches, the following approaches are also available Note the selection of the composition:

The range of cast bronzes suitable for use in the present invention Representing a worthwhile range ranges from about 12 to 20% by weight of Sn. The higher the Tin content, the higher mechanical properties can be achieved.

In order to ensure the necessary homogeneity of the structure, at least Contents of 0.002% by weight of titanium and / or zircon are necessary. The sum of these Contents should not exceed 1% by weight, since this is a very annoying one Impairment of the surface properties occurs. This manifests itself in the Manufacture and use of semi-finished products with a strong tendency to form oxides Subsequent coating or finishing affect sensitive.

Iron in the content of also serves to support the homogeneous structure formation 0.005 to 2% by weight, but it also contributes solely through the formation of connections Sn and in interaction with aluminum, titanium, zirconium and phosphorus thermal stabilization of the material under thermal stress. Levels above 2% by weight are very high because of the then great risk Avoid iron lines or individual iron particles that are forming flawless surfaces. Common substitute for iron is cobalt, for the same applies.

Levels up to 5% by weight appear to improve the Strength properties and increased corrosion resistance where necessary recommended. Levels above 5% by weight lead to difficult handling of the material, since then the hardenability of the known Cu-Ni-Sn materials becomes permanently noticeable.

Magnesium contents up to 1% by weight can be similar to titanium, zirconium or Phosphorus can also be used. Regarding the limitation of the salaries the considerations made for titanium and zircon apply. In addition, the Compound formation of magnesium and phosphorus and the strong tendency of Magnesium for strengthening the tempering for thermal stabilization of the Material can be used.

Aluminum can be used advantageously up to 2% by weight to harden the temper to strengthen and / or to increase the mechanical parameters. For the Handling the melt proves an aluminum addition to be advantageous if the viscosity must be set to a low level because Residual oxygen levels in interaction with titanium and magnesium in particular Have made the melt viscous. Aluminum contents higher than 2% by weight lead to impairments of later operations for surface finishing, such as for example electroplating and also make soldering or welding difficult, and should therefore be avoided.

Limited levels of manganese and zinc up to 5% by weight may be desirable appear to reduce the metal value of the material. Especially manganese is also an option for increasing the machinability, since Manganese contents are suitable, especially the plastic formability continues to increase positively influence.

The invention is illustrated by the following example:

In precision engineering, for highly stressed temple pieces are as strong as possible, but ductile material in wire form desired. Tin bronzes are very suitable for this. The higher their tin content, the higher the strengths achieved. Common kneading tin bronze included rarely more than 9% by weight and therefore appear unsatisfactory. Tin bronzes with very high levels e.g. 15% by weight are now used as kneading materials of the present invention.

To produce a copper alloy semi-finished product in wire form, a bolt CuSn16Ti with the composition 15.5% by weight Sn, 0.25% by weight Ti, 84.15% by weight Cu (rest usual impurities) was used with a spray compacting system from Mannesmann- Demag sprayed under license from Osprey Metals. The composition was melted in a vacuum furnace to avoid the undesirable slagging of Ti. The gas-metal ratio set during spraying was 0.45 Nm ³ / kg. The dimensions achieved were 480mm in diameter and 1200mm in length.

1. Beizen in Schwefelsäure

2. Kaltumformen durch Walzen mit ϕ=0,5

3. Rekristallisierend Zwischenglühen 560°C für 4 Stunden. Die Arbeitsschritte 1. bis 3. wurden bis zum Vorliegen eines Vordrahtes von 5,2mm Durchmesser wiederholt durchgeführt. Die Beschränkung des Umformgrades ergibt sich aus der starken Verfestigung des Werkstoffes auf Streckgrenzenwerte von über 850 MPa bei höheren Umformgraden. Diese würde zwar der Werkstoff noch ertragen, wie Vorversuche im Labor gezeigt hatten, jedoch gelang die umformtechnische Realisierung auf den benutzten Anlagen nur bis zum genannten Umformgrad. Die Vordrähte wurden dann durch die Verfährensschritte

4. Beizen in Schwefelsäure

5. Kaltumformen durch Ziehen an 3,8 mm Durchmesser

6. Rekristallisierend Zwischenglühen 560°C für 4 Stunden

7. Fertigziehen an 2,3 mm. an die Endabmesung gefertigt und lagen dann als Runddraht mit 2,3mm Durchmesser ziehhart z.B. für elektromechanische Bauteile und nach einem abschließendem rekristallisierenden Schlußglühen unter Wasserstoffatmosphäre mit nachfolgender Glanzbeize als Runddraht mit 2,3mm Durchmesser weich für die Fertigung z. B. für die erwähnten Brillenteile vor.

The structure in the sprayed state was found to be free of segregation in the metallographic examination. The preform produced in this way was machined on all sides to remove the layer which was porous on the outside from the spraying and to produce a cylindrical body for pressing. This so-called bolt was then formed at 670 ° C. by means of a direct-acting extrusion press into 2 wires with a diameter of 16.3 mm. The wires were then treated thermomechanically:

1. Pickling in sulfuric acid

2. Cold forming by rolling with ϕ = 0.5

3. Recrystallizing intermediate annealing 560 ° C for 4 hours. Steps 1 to 3 were carried out repeatedly until a 5.2 mm diameter wire was present. The limitation of the degree of deformation results from the strong hardening of the material to yield strength values of over 850 MPa at higher degrees of deformation. The material would still be able to withstand this, as preliminary tests in the laboratory had shown, but the forming technology on the systems used could only be achieved up to the specified degree of forming. The pre-wires were then through the procedural steps

4. Pickling in sulfuric acid

5. Cold forming by pulling on 3.8 mm diameter

6. Recrystallizing intermediate annealing 560 ° C for 4 hours

7. Finish on 2.3 mm. made to the final dimensions and then lay as a round wire with a diameter of 2.3 mm, hard for example for electromechanical components and after a final recrystallizing final annealing in a hydrogen atmosphere with subsequent gloss pickling as a round wire with a diameter of 2.3 mm soft for the production z. B. for the aforementioned glasses parts.

Ziehhart: Zugfestigkeit 930 MPa, Streckgrenze 810 MPa, Bruchdehnung A5 18%, Härte 240HV10, Elastiziätsmodul 80 GPa.

Weich: Zugfestigkeit 490 MPa, Streckgrenze 240 MPa, Bruchdehnung A5 62%, Härte 100HV10, Korngröße40 µm.

The metallographic control showed a structure free of segregation with fine excretions. The wires had the following characteristics:

Hardness: tensile strength 930 MPa, yield strength 810 MPa, elongation at break A5 18%, hardness 240HV10, elastic modulus 80 GPa.

Soft: tensile strength 490 MPa, yield strength 240 MPa, elongation at break A5 62%, hardness 100HV10, grain size 40 µm.

This results in the suitability for use in addition to the very high mechanical Characteristic values an advantage by using the method according to the invention on the alloy according to the invention: the ratio between the yield strength and The modulus of elasticity becomes as large as with conventional wrought copper alloys can hardly be reached. This makes them elastic for resilient loads endured deformations very large, which is immediately positive when maximized of spring travel. For example, this is also true for eyeglass temples of great interest since accidental bend does not immediately result in loss of customized seat shape for the user.

Two other advantages become apparent after brief heat exposure, as is quite common, for example, in connection work by soldering or welding.To demonstrate this, a CuSn14 alloy with 13.8% by weight tin, the rest copper and Common impurities are also made into a 2.3 mm thick wire according to the procedure according to the invention. Wires made of CuSn4, CuSn6 and CuSn8 were manufactured based on classically manufactured primary material for this dimension. The wires were then annealed in a salt bath. For a further comparison, the characteristic values determined on castings were also given for two high-tin DIN casting alloys. material Hardness after cold working with approx. 40% related change in cross-section Hardness after a brief heat load of 700 ° C / 3min Grain size after a brief heat load of 700 ° C / 3min CuSn4 (kneading material) 180HV10 80HV10 60 .mu.m CuSn6 (kneading material) 185HV10 90HV10 70 .mu.m CuSn8 (kneading material) 195HV10 95HV10 60 .mu.m GC-CuSn12Ni (cast material according to DIN1705) Hardness in the as-cast state
100 HB10 100HB10 over 1mm GC-CuSn12Pb (cast material according to DIN1705) Hardness in the as-cast state
95 HB10 95HB10 over 1mm CuSn14 (only using the method according to the invention) 210HV10 100HV10 125 microns CuSn16Ti (application of the method to the alloy according to the invention) 240HV10 140HV10 40 microns

As can now be seen, the hardness remains for the material according to this invention significantly higher level and the grain size is significantly smaller than for not Materials according to the invention, even when using the inventive How to use higher tin contents. At the same time, the Comparison with the casting materials in favor of the invention from: The grain is finer and the hardness higher - even after a brief exposure to 700 ° C.

The behavior of the material to be used according to the invention is favorable, according to the Method according to the invention produced whenever after The highest possible strength should be maintained in connection work and that Suitability for use due to coarse grain formation with regard to mechanical loads or questions of surface processing must not be restricted.

On the basis of these results it can be shown that the combination of proposed method with the proposed compositions Properties that were otherwise only available for cast materials: very high Tin levels, very high strengths even after thermal stress. on the other hand the advantages of kneading materials are realized at the same time: small grain size, high Strength through cold forming, great variability in the dimensions of the semi-finished products thermomechanical treatability. The object of the invention is accordingly solved.

Claims (6)

1. Process for the production and use of a copper-tin-titanium alloy consisting of
   from 12 to 20 % by weight tin,
   from 0.002 to 1 % by weight titanium,
   optionally from 0.005 to 2 % by weight iron and/or cobalt,
   optionally also up to 5 % by weight nickel, up to 1 % by weight magnesium, up to 2 % by weight aluminium,
   up to a maximum of 5 % by weight manganese and/or zinc, remainder copper and usual impurities,
   comprising the following steps:

   a) pre-forming of blocks by spray compacting,

   b) hot forming by extrusion or forging in the temperature range of T = from 550 to 800°C,

   c) forming a semi-finished product by one or more cold forming steps with a total comparative degree of forming ϕ of not more than ϕ = 3,
   each followed by intermediate annealing above the recrystallisation temperature in the temperature range of T = from 400 to 700°C for from 1 minute to 10 hours,

   d) optional cleaning of the surface by physical, mechanical or chemical methods,

   the semi-finished product being used in the manufacture of jewellery, clothing accessories, spectacle arms, spectacle hinges, rims, parts for straps for wrist-watches or cases for wrist-watches.
2. Use of a semi-finished product made of a copper-tin-titanium alloy according to claim 1,
   in which some of the titanium has been replaced by zirconium,
   for the purpose according to claim 1.
3. Use of a semi-finished product in strip form made of a copper-tin-titanium alloy according to claim 1 or 2, in which the product is produced by a process comprising the following steps:

   a) pre-forming of strips having a thickness greater than 2.0 mm and up to 25 mm by thin-strip casting,

   b) hot forming by hot rolling in the temperature range of T = from 600 to 800°C,

   c) forming of the semi-finished product by one or more cold forming steps with a total comparative degree of forming ϕ of not more than ϕ = 3,
   each followed by intermediate annealing above the recrystallisation temperature in the temperature range of T = from 400 to 700°C for from 1 minute to 10 hours,

   d) optional cleaning of the surface by physical, mechanical or chemical methods,

   for the purpose according to claim 1.
4. Use of a semi-finished product according to claim 3, in the production of which
   there is carried out between steps c) and d) as step

   e) a final cold forming operation, for the purpose according to claim 1.
5. Use of a semi-finished product according to claim 4, in the production of which
   there is carried out after step e) as step

   f₁) subsequent heat treatment below the recrystallisation temperature in the temperature range of T = from 150 to 300°C for from 1 minute to 10 hours,

   for the purpose according to claim 1.
6. Use of a semi-finished product according to claim 4, in the production of which
   there is carried out after step e) as step

   f₂) subsequent heat treatment in the temperature range of T = from 700 to 900°C for from 1 minute to 10 hours with subsequent advantageous cooling from that annealing temperature, and a multi-phase structure is thereby achieved,

   for the purpose according to claim 1.