Cast component made of a copper casting alloy and casting process

Abstract

Cast component made of a copper casting alloy with the following composition: P: 50 - 190 ppm by weight Mg: 20 - 350 ppm by weight Cu: Rest and unavoidable impurities, where the material of the cast component is in the as-cast state.

Description

[0001] The invention relates to a cast component made of a copper cast alloy and a casting method for producing cast components made of a copper alloy.

[0002] There is a need for highly electrically conductive components with complex geometric shapes. Due to its high electrical conductivity, pure or low-alloy copper is the preferred material for such components. In principle, such components can be manufactured from semi-finished products by machining and, if necessary, by joining. The semi-finished product itself is produced from a cast format through forming steps. Alternatively, the components can be manufactured by casting. The components essentially receive their shape during the casting process. The components are no longer formed after casting. Machining steps, such as drilling holes, or surface treatment steps such as grinding, polishing, or coating, can follow the casting process in special cases.For the purposes of this invention, the production of a component by a casting process means that the shape of the component is essentially already achieved by the casting process. The component is thus produced to a near-net-shape by the casting process. In particular, the component is not subjected to any forming or heat treatment after the casting process. The material of the finished component is therefore in the as-cast state.

[0003] Whether it is more advantageous to produce a component using a casting process or by machining from a semi-finished product depends on various factors. One of these factors is the size of the component. The larger the component, the more advantageous it will be to produce it using a casting process. For copper materials, it may be more advantageous to produce the component using a casting process if the component dimensions are 50 mm or larger or if the component weight is 100 g or more. The shape of the component also plays a role: the more complex the shape of the component, the more effort is required to produce such a component using machining. For complex components, casting processes are a promising manufacturing method.

[0004] Producing components from virtually pure copper using casting processes is challenging. The production of such components using the lost foam process is particularly challenging. This is due, among other things, to the fact that copper can release large amounts of gas in its molten state. In the lost foam process, a positive model made of hydrocarbon-containing polymer foam is decomposed by the melt. This creates a large volume of gas and results in turbulent melt flow. As a result, the problem of pore formation is more critical in components produced using the lost foam process than in components produced using other casting processes.

[0005] Deoxidizers are added to reduce the oxygen content in copper melts. For pure copper grades, the elements P, Li, Zn, Sn, Be, Cd, Ca, Al, and Mn, as well as boron copper (CuB2), calcium boride, and boron carbide, are mentioned in the literature. In practice, phosphorus has become the preferred deoxidizer for copper. However, it should be noted that dissolved phosphorus significantly reduces the electrical conductivity of the alloy: additions of less than 0.05 wt.% P are sufficient to reduce the electrical conductivity from 100% IACS to values ​​below 65% IACS. For components with high electrical conductivity requirements, wrought copper materials with a P content of less than 50 wt. ppm are used if these components are manufactured from a semi-finished product.

[0006] A Mg-containing copper alloy for wires is known from JP 57089448 A. The Mg content ranges between 5 and 100 ppm, and the P content is a maximum of 1 ppm. Magnesium lowers the alloy's recrystallization temperature, thus preventing the problem of wires sticking together during annealing by lowering the annealing temperature.

[0007] From the document JP S63-310 929 A a thin rolled strip made of a copper alloy with 0.0001 to 0.5 wt.% Mg and optionally P is known.

[0008] JP H02-153 051 A discloses a material for a wire. The material, which may contain small amounts of Mg and P, is drawn and annealed.

[0009] Furthermore, the document US 2012 / 0 273 097 A1 discloses a method for producing sputter targets from a copper material that may contain Mg and P. The method comprises the steps of hot forming and quenching.

[0010] The invention is based on the object of providing an improved cast component made of a copper casting alloy and an improved casting process for producing cast components. In particular, the cast component should have an electrical conductivity of at least 49 MS / m (corresponding to 85% IACS) and a porosity of less than 1.5 vol.%.

[0011] The invention is represented with respect to a cast component by the features of claim 1 and with respect to a casting method by the features of claim 7. The further dependent claims relate to advantageous embodiments and developments of the invention.

[0012] The invention includes a cast component made of a copper cast alloy with the following composition: P: 50 - 190 ppm by weight Mg: 20 - 350 ppm by weight Cu: Rest and unavoidable impurities, where the material of the cast component is in the as-cast state.

[0013] The invention is based on the consideration that small amounts of deoxidizers added to the copper alloy affect the electrical conductivity of the alloy as well as the mold filling and porosity of the cast product. Phosphorus has a positive effect on the casting behavior of the alloy and thus on the mold filling of the cast product. Therefore, the alloy should contain at least 50 ppm by weight of phosphorus. As the phosphorus content increases, the porosity of the cast product decreases. On the other hand, phosphorus significantly reduces the electrical conductivity of the alloy. To achieve an electrical conductivity of at least 49 MS / m (equivalent to 85% IACS), the phosphorus content in the alloy must not exceed 190 ppm by weight. Tests show that a further improvement in the porosity of the cast product can be achieved by adding even small amounts of magnesium.To achieve a significant improvement in the porosity of the cast product, at least 20 wt. ppm of magnesium must be added to the alloy. The addition of magnesium affects the electrical conductivity of the alloy significantly less than the addition of phosphorus, so the magnesium content can be varied within a relatively wide range. If more than 350 wt. ppm of magnesium is added to the alloy, the electrical conductivity drops to values ​​below 49 MS / m. Therefore, a maximum of 350 wt. ppm of magnesium should be added to the alloy.

[0014] The particular advantage of the inventive cast component made of a copper cast alloy is that the special combination of phosphorus and magnesium allows for the production of a cast product with good mold filling, low porosity, and high electrical conductivity. Phosphorus generally ensures good casting behavior and thus good mold filling. The phosphorus content is limited to maintain high electrical conductivity. The addition of magnesium ensures low porosity in the cast material, even with a relatively low phosphorus content. The electrical conductivity is at least 49 MS / m, and the porosity is below 1.5 vol.%.

[0015] The cast alloy may contain unavoidable impurities. These impurities can influence the properties of the alloy. In particular, impurities can reduce the alloy's electrical conductivity. The amount of impurities should be such that the copper content in the alloy is at least 99.92 wt.%, preferably at least 99.95 wt.%. With large P and Mg contents, the total content of all impurities must be smaller than with small P and Mg contents. The sum of all impurities should preferably not exceed 150 wt. ppm, particularly preferably not exceed 90 wt. ppm.

[0016] In a preferred embodiment of the invention, the weight proportions of phosphorus P and magnesium Mg can be such that the following relationship applies to them: P+0.15⋅Mg≤220 wt. ppm.

[0017] The sum of the phosphorus content and 0.15 times the magnesium content should therefore preferably not exceed 220 ppm by weight. This additional limitation allows an electrical conductivity of at least 49 MS / m to be achieved with greater reliability. Particularly preferably, the weight proportions of phosphorus (P) and magnesium (Mg) can be calculated such that the sum of the phosphorus content and 0.15 times the magnesium content does not exceed 175 ppm by weight. This can achieve an electrical conductivity of the alloy of at least 52 MS / m.

[0018] Advantageously, the P content of the alloy can be at least 80 ppm by weight. This ensures very good castability of the alloy and excellent mold filling, even with complex cast component shapes.

[0019] Furthermore, in an advantageous embodiment of the invention, the Mg content can be at least 40 ppm by weight. This achieves a reduction in porosity to 1 vol.% or less. In a particularly preferred combination of such a Mg content with a P content of at least 80 ppm by weight, a copper casting alloy with particularly good mold filling properties can be achieved.

[0020] In an advantageous embodiment of the invention, the P content can be a maximum of 170 ppm by weight. This allows the electrical conductivity to be increased to 52 MS / m.

[0021] In a further advantageous embodiment of the invention, the Mg content can be a maximum of 200 ppm by weight. Surprisingly, at Mg contents above 200 ppm by weight, no further improvement in the porosity of the cast material occurs. At Mg contents above 200 ppm by weight, the porosity remains at a level between 1.0 and 1.5 vol.%. In contrast, a decrease in porosity to values ​​below 1.0 vol.% is even observed when the Mg content is reduced from 200 ppm by weight to approximately 100 ppm by weight. Therefore, the Mg content can preferably be a maximum of 150 ppm by weight, particularly preferably a maximum of 120 ppm by weight, and in particular a maximum of 80 ppm by weight. Furthermore, if the P content of the alloy is simultaneously increased to 170 ppm by weight with an Mg content of a maximum of 80 ppm by weight.-ppm, the alloy's properties are particularly favorable: At approximately 53 MS / m, a very high electrical conductivity can be achieved, while the porosity of the cast material is below 0.75 vol.%. Preferably, the Mg content of the alloy can be at least 40 wt. ppm and the P content at least 80 wt. ppm.

[0022] A further aspect of the invention includes a casting method for producing a cast component from a copper alloy. The copper alloy has a composition as described above. According to the invention, a lost mold is used to shape the cast component.

[0023] The inventive casting process includes the use of a copper alloy with the following composition: P: 50 - 190 ppm by weight Mg: 20 - 350 ppm by weight Cu: Residue and unavoidable impurities.

[0024] By using such a copper alloy, a casting process can be used to produce a cast component of good quality and high electrical conductivity. The cast component has a porosity of less than 1.5 vol.%. The electrical conductivity is at least 49 MS / m.

[0025] In a preferred embodiment of the invention, the weight proportions of phosphorus P and magnesium Mg in the alloy used in the casting process can be such that the following relationship applies to them: P+0.15⋅Mg≤220 wt. ppm.

[0026] In a particularly preferred embodiment of the invention, the weight proportions of phosphorus P and magnesium Mg in the alloy used in the casting process can be such that the following relationship applies to them: P+0.15⋅Mg≤175 wt. ppm.

[0027] Advantageously, the P content of the alloy used in the casting process can be at least 80 ppm by weight. Furthermore, in an advantageous embodiment of the invention, the Mg content of the alloy used in the casting process can be at least 40 ppm by weight. Particularly preferred is the combination of such a Mg content with a P content of at least 80 ppm by weight. This achieves a porosity in the cast component of less than 0.75 vol.%.

[0028] In an advantageous embodiment of the invention, the P content of the alloy used in the casting process can be at most 170 wt. ppm. In a further advantageous embodiment of the invention, the Mg content of the alloy used in the casting process can be at most 200 wt. ppm. Preferably, the Mg content can be at most 150 wt. ppm, particularly preferably at most 120 wt. ppm, and in particular at most 80 wt. ppm. An extremely high electrical conductivity of at least 53 MS / m can be achieved if the Mg content of the alloy is limited to a maximum of 80 wt. ppm and, at the same time, the P content of the alloy is limited to 170 wt. ppm.

[0029] In the inventive casting process, a lost-molding mold is used to shape the cast component. Both sand molds and ceramic molds can be used. Cast components with complex shapes are often produced using such casting processes. The good mold-filling properties of the described copper alloy are therefore particularly suitable for these casting processes.

[0030] Advantageously, an inventive lost-mold casting process can use a lost-mold pattern as a model for the cast component. Lost-mold casting processes include the lost-wax casting process, full-mold casting, and the lost-foam process. Components produced using these casting processes are subject to stringent requirements regarding pore-freeness. Therefore, the copper alloys described above are particularly suitable for the production of cast components using such casting processes.

[0031] In a particularly preferred embodiment, the lost pattern in the inventive casting process can be a pattern that evaporates during the casting process. Casting processes with an evaporating pattern include full-mold casting and the lost-foam process. In these processes, a positive pattern of the cast component is produced from a thermally decomposable material, usually a hydrocarbon-containing polymer foam. The positive pattern is coated with a coating and, after the coating has dried, embedded in a molding material, such as sand. The molding material is then compacted, thus forming the lost pattern. A gating system enables the supply of molten metal to the embedded positive pattern. During the casting process step, molten metal is brought into contact with the thermally decomposable material, so that this material is decomposed into gaseous products by the introduced heat.The resulting cavity is filled with molten metal. The gases formed must escape through the mold material or against the inflow direction of the molten metal. Compared to other casting processes, casting processes with an evaporating pattern are therefore burdened by the problem of gas formation. When casting copper, an additional problem is that copper can release large quantities of gas in its molten state. The formation of large quantities of gas directly at the front of the molten metal makes it difficult to form a defect-free material. These processes therefore pose an increased risk of pore formation in the cast component. In the casting process according to the invention, the composition of the alloy used ensures that, despite this problem, a largely pore-free cast material is formed. The porosity of the cast component is less than 1.5 vol.%.By using alloys with the preferred compositions described above, porosity can be reduced to below 1.0 vol.% or below 0.75 vol.%. At the same time, the targeted selection of the proportions of the elements phosphorus and magnesium ensures low electrical resistance of the cast component.

[0032] It can be particularly advantageous to apply a coating to the surface of a cast component manufactured using a process described above. The coating can be applied to the entire surface or partially to the component. The coating can serve to improve electrical contact. Tin- or silver-based coatings are particularly suitable for this purpose. Alternatively, the coating can serve to improve the corrosion and / or tarnishing resistance of the component. Coatings made of ceramic or organoceramic materials, such as oxides, sulfides, or carbides, are suitable for this purpose.

[0033] The invention is explained in more detail using the exemplary embodiments listed in Table 1. Test samples were cast using the lost foam process. The samples are designed as components with a complex geometry and weigh approximately 0.6 kg each. The composition of the copper alloys used was varied as documented in Table 1. Sample No. . P-share Mg content Cu content and impurities electrical conductivity porosity ppm by weight ppm by weight ppm by weight MS / m Vol.-% 1 0 0 rest 58 20 2 0 58,6 rest 57,5 4,6 3 164 58,2 rest 57 0,55 4 50 84 rest 56,3 0,9 5 104 48,4 rest 56 0,65 6 105 7,5 rest 55,2 1,3 7 156 74 rest 52,5 0,71 8 114 215 rest 52,4 1,4 9 127 51,8 rest 52 0,49 10 182 200 rest 50,6 0,87 11 167 348 rest 50,1 0,96 12 183 25,6 rest 49 1,05 13 236 506 rest 48 1,05 14 312 47,8 rest 47 0,63 15 265 266 rest 46 1 16 251 393 rest 44,9 1,1 17 214 275 rest 39,2 1,03 18 208 253 rest 39,2 1,03 19 695 < 1 rest 38,4 1,4 20 895 < 1 rest 36,6 1,5

[0034] Table 1: Composition, conductivity, and porosity of the samples. Table 1 shows the chemical composition of 20 test samples, particularly the P and Mg content, as well as the conductivity and porosity values ​​determined for the samples. In the table, the samples are sorted by descending electrical conductivity.

[0035] Sample No. 1 consists of pure copper without the addition of P or Mg. The conductivity is 58 MS / m. The porosity of the component cast from pure copper is unacceptable at 20 vol.%. Sample No. 2 consists of copper with an addition of approximately 60 wt. ppm Mg, but without the addition of P. Compared to pure copper (Sample No. 1), the addition of Mg only slightly reduces the electrical conductivity, but significantly improves the porosity. However, a porosity of almost 5 vol.% is not sufficiently good. The reason for the poor porosity is the lack of phosphorus in the alloy.

[0036] Samples 19 and 20 contain 700 and 900 wt. ppm phosphorus, respectively, but no detectable Mg content. The addition of phosphorus achieves a porosity of approximately 1.5 vol.%, but the electrical conductivity remains at a level corresponding to approximately 65% ​​IACS. While adding sufficiently large amounts of phosphorus can achieve acceptable porosity, the electrical conductivity then drops to a low level.

[0037] Samples Nos. 3 to 18 contain both phosphorus and magnesium. Samples Nos. 3 to 12 have P contents of 50 to 190 wt. ppm and an electrical conductivity of at least 49 MS / m, while samples Nos. 13 to 18 are characterized by P contents of over 190 wt. ppm and an electrical conductivity of less than 49 MS / m. Samples Nos. 17 and 18 also have a relatively high level of aluminum and silicon impurities, so that the Cu content in the alloy of these two samples is below 99.90 wt.%. In addition to the high doping with P and Mg, the high level of impurities is another reason for the low electrical conductivity of these two samples.

[0038] Within samples 3 to 12, the Mg content varies between 7.5 wt. ppm (sample 6) and 348 wt. ppm (sample 11). In particular, a comparison of samples 11 and 12 shows that, compared to phosphorus, magnesium has a largely indifferent and at most very weak influence on the alloy's electrical conductivity.

[0039] Within samples 3 to 12, the porosity varies between 0.49 and 1.4 vol%. It is striking that the two samples with the lowest Mg content (samples 6 and 12) and the two samples with the highest Mg content (samples 8 and 11) exhibit the highest porosity values ​​within this group of samples. Consequently, there is an optimal range for the Mg content in the alloy.

[0040] The most favorable property combinations are achieved with samples No. 3, No. 5, No. 7, and No. 9. These samples exhibit electrical conductivity between 52 and 57 MS / m and porosity below 0.75 vol.%. It is notable that the P content in these samples is between 100 and 170 wt. ppm and the Mg content between 40 and 80 wt. ppm.

[0041] In addition, Sample No. 4 exhibits excellent electrical conductivity and, at 0.9 vol.%, very good porosity. This good conductivity is due to the very low phosphorus content of 50 wt. ppm. The Mg content was adjusted to 84 wt. ppm, which is favorable for porosity.

[0042] Furthermore, sample no. 14 exhibits very low porosity at 0.63 vol. In this sample, too, the addition of approximately 50 wt. ppm of Mg proves to be beneficial for porosity. The electrical conductivity of this sample is only 47 MS / m, which is due to the relatively high phosphorus content (over 300 wt. ppm).

[0043] The test results show that by carefully selecting the proportions of phosphorus and magnesium, a copper casting material with excellent properties in terms of electrical conductivity, mold filling capacity and porosity in the as-cast state can be achieved.

Claims

[1] Cast component made of a copper casting alloy with the following composition: P: 50 - 190 ppm by weight Mg: 20 - 350 ppm by weight Cu: Rest and unavoidable impurities, where the material of the cast component is in the as-cast state. [2] Cast component according to claim 1, characterized by that the following relation applies to the weight proportions of P and Mg: P+0.15⋅Mg≤220 wt. ppm. [3] Cast component according to claim 1 or 2, characterized by that the P content is at least 80 ppm by weight. [4] Cast component according to one of the preceding claims, characterized by that the Mg content is at least 40 ppm by weight. [5] Cast component according to one of the preceding claims, characterized by that the P content is not more than 170 ppm by weight. [6] Cast component according to one of the preceding claims, characterized by that the Mg content is not more than 200 ppm by weight. [7] Casting method for producing a cast component according to one of the preceding claims, characterized bythat a lost mold is used to shape the cast component. [8] Casting method according to claim 7, characterized by that a lost model is used as the model for the cast component. [9] Casting method according to claim 8, characterized by that the lost model is a model that evaporates during the casting process.