EP0926251A1 - Copper-Tin-Titanium alloy - Google Patents

Abstract

A titanium-containing tin-bronze, of specific composition, is new. new copper-tin-titanium alloy has the composition (by wt.) 12-20% Sn, 0.002-1% Ti, balance Cu and impurities. ADDITIONALLY CLAIMED ARE: (i) a casting produced from the above alloy and exhibiting a segregated coarse phase content of less than 10 vol. , an undetectable content of segregated particles of greater than 50 microns cross-sectional size, a cold deformability of ≥ 20% (w.r.t. cross-sectional change) and up to 10 vol. micro-segregation with a typical linear distribution of less than 20 microns width; and (ii) production of strip, wire, profile or tubular semifinished products of the above alloy by thin strip casting or spray compacting, followed by hot and/or cold working optionally with intermediate anneals.

Description

The invention relates to a Cu-Sn-Ti alloy, its production and its Use. The CuSnTi alloy consists of Sn 12-20% by weight, Ti 0.002-1.0 % By weight of rest Cu and usual impurities. Such an alloy can sufficiently quick cooling from the molten state Room temperature can be obtained in such a structural state that that for the Semi-finished product 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 considerations. 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 generally 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 that cold forming becomes 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 under mechanical stress 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 manufacture which contrasts the overcomes the CuSn kneading materials and the CuSn casting materials. Of 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 a Cu-Sn-Ti alloy, which consists of the molten state is cooled down so quickly that the castings The usual segregation does not occur and that the structure is free of is macroscopic segregation. Under 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 Casting 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 it then 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 hot forming and 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 there Processes with dominant compressive stress such as presses and round rolls highly recommended.

Are the alloy compositions of the type of this type 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 Walzerfahren 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 Glühdauern 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 shapes 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, for example, as bolts for extrusion.

1.3 Machining the preform

2. Further processing of the preform

2.1 Hot forming For rolling operations, hot forming 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 Tempering The tempering 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 of 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 step processed further. 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 manufacture 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 setting 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 bronze designed for use by 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 refinement significantly affect.

Iron at levels of is also used to support the homogeneous structure formation 0.005 to 2% by weight, but it also contributes through the formation of a connection 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.

Depending on which manufacturing facilities are available, phosphorus can necessary for pre-deoxidation of the melt or through interaction contribute to the thermal stabilization of the material with Fe and Ti. Residual salaries after pre-deoxidation of less than 0.001% by weight are regularly insufficient, while levels above 0.4% neither for deoxidation nor for thermal Stabilization offer further advantages.

Levels up to 5% by weight appear to improve the Strength properties and increased corrosion resistance where necessary recommendable. 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 Phosphorous can also be used. Regarding the content restriction 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 for temper hardening 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, especially when interacting with titanium and magnesium 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 galvanizing 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 but can also be used to increase the mechanical workability, since Manganese contents are suitable, especially the plastic formability continues to be positive influence.

Chip breaking additives of lead and / or carbon in the form of graphite with up to 3% by volume are indicated for setting the cutting properties. Continue but comes to ensure emergency running properties sliding components are of great importance. Content over 3 vol .-% lead to disadvantages in terms of plastic formability and mechanical resilience, so that they are within the scope of the presented invention be disregarded.

The invention is illustrated by the following example:

In electromechanics, springs or e.g. in precision engineering for highly stressed temples are as strong as possible, but ductile material in wire form wanted. 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 oven 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 Verfahrensschritte

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 thus produced was machined on all sides in order 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 pre-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 was only successful up to the degree of deformation mentioned. The pre-wires were then through the process 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 dimension and then lay as a round wire with 2.3mm
Diameter hard as drawn, for example, for electromechanical components and after a final recrystallizing final annealing in a hydrogen atmosphere with subsequent shine pickling as a round wire with a diameter of 2.3 mm, soft for the production z. B. for the aforementioned glasses parts.

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 adjusted seat shape for the user.

Two other advantages become apparent after short-term heat exposure, as is quite common, for example, in connection work by soldering or welding. In order to demonstrate this, a CuSn14 alloy with 13.8% by weight of tin, the rest of copper and usual impurities according to the procedure of the invention was also produced to a 2.3 mm thick wire using the procedure described above. 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 60µm CuSn6 (kneading material) 185HV10 90HV10 70µm CuSn8 (kneading material) 195HV10 95HV10 60µm 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 application of the method according to the invention) 210HV10 100HV10 125µm CuSn16Ti (application of the method to the alloy according to the invention) 240HV10 140HV10 40µm

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 falls 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 according to the invention is favorable after Process according to the invention always produced if after The highest possible strengths should be maintained and the Suitability for use due to coarse grain formation with regard to mechanical loads or questions of surface processing must not be restricted.

Based on 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 due to cold forming, great variability in the dimensions of the semi-finished products thermomechanical treatability. The object of the invention is accordingly solved.

Claims (17)

Copper-tin-titanium alloy, characterized in that it is made of
12 to 20% by weight of tin,
0.002 to 1% by weight of titanium,
Remainder copper and usual impurities. Copper alloy according to claim 1, characterized in that the titanium is completely or partially replaced by zircon is. Copper alloy according to claim 1 or 2, characterized in that
that it additionally contains 0.005 to 2% by weight of iron. Copper alloy according to claim 3, characterized in that the iron is completely or partially replaced by cobalt is. Copper alloy according to one or more of claims 1 to 4, characterized in
that it additionally contains 0.001 to 0.4 wt .-% phosphorus. Copper alloy according to one or more of claims 1 to 5, characterized in
that it additionally contains up to 5% by weight of nickel. Copper alloy according to one or more of claims 1 to 6, characterized in
that it additionally contains up to 1% by weight of magnesium. Copper alloy according to one or more of claims 1 to 7, characterized in
that it additionally contains up to 2% by weight of aluminum. Copper alloy according to one or more of claims 1 to 8, characterized in
that it additionally contains manganese and zinc individually or together up to a maximum of 5% by weight. Copper alloy according to one or more of claims 1 to 9, characterized in that
that it additionally contains up to 3% by volume of lead and / or carbon as a chip breaker. Casting made from the copper alloy according to one or more of claims 1 to 10, characterized in that that the proportion of coarse phases resulting from segregation is less than 10% by volume, that segregation particles larger than 50 µm in cross-section cannot be detected, that a cold deformation of at least 20% related cross-sectional change is endured in the as-cast state and that micro segregations up to a volume fraction of 10% can be present, typically occurring line-shaped distributions of these micro segregations having a width of less than 20 μm. Process for the production of semi-finished products in strip, wire, profile or tube form, made of a copper alloy according to claims 1-10, characterized in that that a preform is produced by thin strip casting or spray compacting, which is then subjected to hot and / or cold forming steps, possibly with intermediate annealing. Use of the semi-finished product produced according to claim 12 for the production of everyday objects, such as jewelry, clothing accessories, temples, hinges, Eye edge profiles, parts for bracelets of wristwatches or cases of wristwatches. Use of the semi-finished product produced according to claim 12 for the production of electromechanical components, that is especially relay springs, switching elements, contacts, Connectors, semiconductor carriers, commutators. Use of the semi-finished product produced according to claim 12 for the production of functional elements of mechanical engineering, in particular levers, gears, worm gears, Rollers, spindle nuts, springs. Use of the semi-finished product produced according to claim 12 for the production of plain bearings, coupling pieces and Friction discs from vehicle and mechanical engineering. Use of the semi-finished product produced according to claim 12 for the production of fittings for solid, liquid and gaseous media.