EP1063310B1 - Use of a tin rich copper-tin-iron alloy - Google Patents

Abstract

Use of a copper-based alloy containing (in wt.%) 12-20 tin, 0.2-5 iron and a balance of copper for the manufacture of components of vehicles and general machines is new.

Description

The invention relates to the use of a Cu-Sn-Fe alloy for mechanical stressed components of machine or vehicle construction. The Cu-Sn-Fe alloy consists of Sn 12 - 20 wt .-%, Fe 0.2 - 5.0 wt .-%, balance Cu and the usual Impurities. The alloy is cooled down sufficiently quickly from the molten state at room temperature in one Get structural condition that the preform available for the semi-finished product (Cast strip, cast block, cast bolt) is technically free of coarse, brittle phases and therefore in a special way for the production of semi-finished products Bands, profiles, wires, hollow profiles or pipes - suitable for kneading. This Semi-finished products are ideal for the production of various mechanical Functional parts of precision engineering, vehicle or general mechanical engineering. Because of their chemical composition and manufacturing method draws the above Alloy high mechanical strength or high wear resistance with excellent ductility. She also has one good corrosion resistance and thermal conductivity.

CuSn materials are because of their high mechanical strength, their large Resistance to sliding stress or wear and their corrosion resistance for various mechanical components of the general Mechanical engineering used. CuSn wrought alloys with typically 8% by weight Sn are very easy to form and are therefore also suitable for the production of complex ones Functional parts. For example, in plain bearings and gears, as springs and for parts exposed to sea water such as chains, fittings, etc. used. For components that are subjected to very high mechanical loads are, for example, for gears, CuSn cast alloys are preferred with Sn contents above 10% by weight. Reach through the increased tin content the cast bronze has the required strength, but it is also bad formable. For this there are essentially brittle phases in the primary structure of such Cast bronze responsible for the common casting process during the Torpor arise. These phases can also be followed by a thermal aftertreatment cannot be removed without pores or imperfections in the material remain, which in turn affect the deformation.

For mechanically stressed components of general machine or vehicle construction So there is a desire for a material that is the contrast between the CuSn kneading materials and the CuSn casting materials overcomes: The Material is said to be the chemical and mechanical properties of the cast bronze combine with the processing properties of the kneading materials, which is why the setting of the cold deformability and at the same time securing a high mechanical strength and hardness is necessary.

JP-A-04 017 635 offers a sintered alloy that acts as a sliding element to be used.

In the recent past, a material and a method for its production have been presented ¹ with which the solution of the task should be possible in principle. The material is a tin-rich CuSn alloy with about 12-20% by weight Sn, the rest Cu. The high Sn content ensures the strength of the material.

Spray compacting ^{2 is a} suitable method for the primary shaping of this alloy or strip casting ³ , The material cools so quickly from the molten state that the segregation that is customary in castings is suppressed. The primary structure of this alloy is therefore free of macroscopic segregation at room temperature ⁴ , The preforms produced using these processes can be shaped very well either warm or cold.

The material so produced is mainly due to its excellent mechanical Properties versatile in the field of mechanical engineering. Yet some shortcomings can be identified.

The process of master shaping is difficult for the following reasons: As with conventional, comparatively low tin wrought wrought alloys also in the present case the need to deoxidize the melt. at The conventional alloys are therefore more oxygen-sensitive to the melt Elements such as B. phosphorus added. These additions are usually like this selected that in addition to melt deoxidation also the material properties (e.g. strength) can be influenced favorably. Because of the high affinity for oxygen the added elements tend to burn off when they melt and pour and slagging. As a result, complex process control is required for compliance of defined concentrations necessary. Generally affect the oxides The deoxidizer in the melt also sensitive to the melt viscosity and thus the procedural boundary conditions of the master molding process of spray compacting. Ideally, therefore, a vacuum oven comes for the Melting process used so that oxidation of the additives is largely prevented can be. However, the process engineering effort required is not always expedient and economical.

Oxides from admixtures with an affinity for oxygen can also be used in hot forming of the tin-rich CuSn alloys. They deteriorate the surface quality of the formed material and lead to tool contamination and as a result for a shorter tool life. When cutting or cutting these oxides are also undesirable in the volume of materials because they are due to their Hardness promote increased tool wear.

JP-A-63235455 is a phosphorus-containing copper alloy for electrical engineering Known components that have good fatigue properties. The melt is produced with high cooling rate in the form of thin preforms and then rolled into 0.3 mm thick strips.

So there is an urge for materials that, on the one hand, in terms of strength, Formability and corrosion resistance of those described above CuSn alloy at least equal, but on the other hand a simplified handling enable in manufacturing and processing.

The object thereby achieved is achieved by the present invention according to claim 1 solved that for mechanical components of machine or vehicle construction an alloy is used, which in addition to copper has a tin content of 12 to 20% Sn and a Contains 0.2 to 5% Fe and / or Co. To achieve good formability, the primary shaping of the alloy should be carried out again using a casting process, at which prevents the formation of brittle phases by a high cooling rate. It is surprising that when casting the alloy according to the invention with a such processes to a large extent on the complex vacuum or protective gas technology can be dispensed with.

By setting the above. The alloy particularly achieves Fe and Sn contents good mechanical properties. On the one hand, they express themselves in a high degree of firmness or hardness, in a high creep or softening resistance and in one high wear resistance.

On the other hand, the materials have a sufficiently high toughness which enables a related shape change through cold forming of more than 20%.

Sn also ensures the corrosion resistance of the material. The Sn content should not exceed 20% because then - even with an unconventional casting process - The increased occurrence of brittle phases cannot be prevented.

When setting the above Fe contents have been found to be suitable for the above-mentioned. Use relevant material properties of the alloy according to the invention that of the known CuSn alloys. Surprisingly, the Fe contents an additional melt deoxidation, which in the conventional CuSn alloys are usually made using P additives, not necessary. In addition, iron apparently complicates the formation of stubborn layers of scale the surfaces of heated or hot-formed components. To achieve this Effects and for the formation of a homogeneous, even structure is a minimum salary necessary on Fe. Large iron concentrations should be avoided since there are agglomerations of Fe particles in the structure, which It is difficult to machine the material.

Preferred embodiments of the invention are the subject of the further claims 2 to 6.

Due to its metal-related relationship, iron can go through in whole or in part Cobalt to be replaced.

Additions of manganese and / or zinc up to 5 wt .-% are possible to the metal value to reduce the alloy.

The setting of certain cutting properties is determined by the addition of Lead or graphite up to 3 vol .-% completed. In addition, these additives ensure improved Emergency running properties in components subject to friction or sliding. The salaries must be restricted, since lead or graphite additives adversely affect the forming impact.

In order to further increase the strength values, aluminum can contain up to 2% by weight. be added. Higher levels are not useful as they are surface processing or impair the joining of the material.

Nickel additives up to 5 wt .-% improve the strength properties and Corrosion resistance. Higher levels promote curing mechanisms, which means the further processing of the alloy is difficult.

Depending on the type and mode of operation of the available manufacturing facility phosphorus can be used to deoxidize the melt. A significant one Effect occurs from 0.01% P. To avoid coarse iron phosphide particles the structure of the phosphorus should be matched to the iron concentration, the Fe content / P content> 2. P contents above 0.5% by weight should be avoided because thereby reducing the ductility of the material on the one hand and in Loose layers of heat adhere to the heat, especially during hot forming to disturb.

The invention is illustrated by the following example.

Example:

Sliding stresses occur in worm gear transmissions as well as with highly loaded sliding elements between material pairings under very high surface pressures on. Materials with very high strength and sufficient tribological properties are required Characteristics. The CuSnFe according to the invention is suitable for these applications.

Alloy particularly suitable.

To produce a semi-finished product suitable for worm gear production a bolt CuSn15Fe0.8 manufactured by spray compacting. As an atomizing gas nitrogen was used. Those for the alloys deoxidized by suitable additives typical phenomena of slag formation, burning and Viscosity increase in the melt due to oxide formation could in the inventive Alloy complete despite atmospheric melting conditions be avoided. A slight Fe erosion of 0.85% by weight was observed 0.75% by weight in the sprayed bolt, but for production and function of the component remained irrelevant.

The structure in the sprayed state was uniform and metallographically free from Segregations. After the bolt had been machined, it was hot-worked by extrusion into a rod with a diameter of 20 mm. The temperature the material was 650 ° C. The bar stock was straightened.

The material was in the soft state after hot forming. The mechanical properties were determined with A ₁₀ = 53%, R _p0.2 = 253 MPa, R _m = 548 MPa, HV = 133.

The bars were pickled for surface leveling. The further processing was carried out using cold drawing processes to increase the strength properties. The Forming was carried out in two steps. In the first forming step, the rods were drawn to a diameter of 17.9 mm, corresponding to one Area reduction of 20% ( = 0.22). The second was carried out without intermediate annealing Forming step on diameter 15.5 mm. The total forming thus corresponded an area reduction of 40% ( = 0.51). The bars were subsequently straightened.

To avoid workpiece distortion during machining, internal stresses were reduced by a 4-hour annealing treatment at 300 ° C. The rod material finally showed the following properties: A ₁₀ = 5.8%, R _p0.2 = 709 MPa ⁵ , R _m = 865 MPa, HV10 = 265.

The following table compares the properties achieved with a CuSn15.5 alloy which - apart from melting - was processed in the same way. The melting process for this alloy was carried out in a vacuum, so that deoxidizing additives could be dispensed with. The process engineering effort for the production of the CuSn15.5 material was thus considerably higher than the manufacturing effort for CuSn15.5Fe0.7 CuSn15.5Fe0.7 after cold working with 40% reduction in area R _m = 865 MPa, R _p0.2 = 709 MPa, A ₁₀ = 5.8%, HV10 = 265 CuSn15.5 after cold forming with 40% area reduction R _m = 828 MPa, R _p0.2 = 681 MPa, A ₁₀ = 6.7%, HV10 = 250 (CuSn15.5Fe0.7: according to the invention)

The use according to the invention clearly achieves the use of 0.7% by weight of Fe better mechanical properties than the Fe-free variant and is therefore the known tin arms are also more suitable for mechanically stressed components CuSn alloys. The ductility parameters are for both materials similarly, from which it can be concluded that Fe additions are suitable for the formation of To complicate pores and embrittling oxide lines during the primary shaping. This was not to be expected because of this effect of iron in a CuSn alloy was not known.

An annealing treatment at 650 ° C leads to softening of the materials. After 3 hours of annealing, the properties listed in the table below appeared: CuSn15.5Fe0.7 after cold forming with 40% area reduction and subsequent annealing at 650 ° C / 3h. R _m = 548 MPa, R _p0.2 = 253 MPa, A ₁₀ = 50%, HV10 = 133 CuSn15.5 after cold forming with 40% reduction in area and subsequent annealing at 650 ° C / 3h. R _m = 498 MPa, R _p0.2 = 182 MPa, A ₁₀ = 50%, HV10 = 104 (CuSn15.5Fe0.7: according to the invention)

The low level of softening of the alloys according to the invention is striking: the strength parameters clearly exceed those of a conventionally shaped tin bronze with 8% by weight of Sn ⁶ , which was similarly shaped and heat treated. This leads to the conclusion that the tin-rich alloys have much better mechanical properties at high temperatures (ie softening resistance, relaxation resistance, creep or creep resistance) than the conventional CuSn wrought alloys. This is the invention

Alloy also suitable for use at elevated temperatures.

In a direct comparison of the tin-rich, spray-compacted materials the Fe-containing alloy after heat treatment the higher strength values, which indicates a higher temperature resistance of the mechanical properties is.

Based on these results it can be shown that the process engineering Effort to produce tin-rich CuSn alloys due to an increased Fe content bypassed and an improvement of the application-relevant material shafts can be achieved. The object of the invention is therefore achieved.

Claims (6)

1. Use of a spray-compacted copper-tin-iron alloy, which comprises 12 to 20% by weight of tin, 0.2 to 5 % by weight of iron and/or cobalt, selectively up to 2 % by weight of aluminium, and up to 5% by weight of nickel, selectively manganese and/or zinc up to a total of 5% by weight, selectively also up to 3 % by volume of lead and/or intermetallic phases and/or graphite as splinter-stopper, the remainder being copper and customary impurities, for the manufacture of mechanically stressed components of vehicle construction and general machine construction, the ratio of Fe-content and/or Co-content/P-content being > 2.
2. Use according to claim 1 for the manufacture of functional elements of machine construction, especially for the manufacture of levers, springs, gearwheels, worm wheels, rollers, spindle nuts, bolts and screws.
3. Use according to claim 1 for the manufacture of coupling pieces or friction discs from vehicle or machine construction.
4. Use of a copper alloy according to claim 1 having from 12 to 14 % by weight of tin, 1 to 5 % by weight of iron for the purpose according to one or more of claims 1 to 3.
5. Use of a copper alloy according to claim 1 having from 15 to 17 % by weight of tin, 0.3 to 4 % by weight of iron for the purpose according to one or more of claims 1 to 3.
6. Use of a copper alloy according to claim 1 having from 16 to 20 % by weight of tin, 0.3 to 3 % by weight of iron for the purpose according to one or more of claims 1 to 3.