Wrought copper-zinc alloy, semi-finished product made from a wrought copper-zinc alloy, and method for producing such a semi-finished product

Abstract

The invention relates to a wrought copper-zinc alloy for producing a wire-shaped, tubular or rod-shaped semi-finished product with the following composition in wt.%: Cu: 58.0 to 63.0%; Si: 0.04 to 0.32%; P: 0.05 to 0.20%; Sn: optionally up to 0.25%; Al: optionally up to 0.10%; Fe: optionally up to 0.30%; Ni: optionally up to 0.30%; Pb: optionally up to 0.25%; Te, Se, In: optionally up to 0.10% each; Bi: maximum 0.009%; and the remainder Zn and unavoidable impurities, wherein the proportion of unavoidable impurities is less than 0.2 wt.%. The ratio of the weight proportions of P and AI is at least 1.0. The alloy has a microstructure consisting of a globular α phase, a ß phase, and phosphide particles. The proportion of ß phase in relation to the total of α phase and ß phase is at least 20 vol.% and at most 70 vol.%. Si is present both in the α phase and in the ß phase. In an area of 21000 μm2, there are 7 to 200 phosphide particles with an equivalent diameter of 0.5 to 1 μm, 4 to 150 phosphide particles with an equivalent diameter of 1 to 2 μm, and a maximum of 30 phosphide particles with an equivalent diameter of more than 2 μm.

Description

[0001] Wieland-Werke AG

[0002] Description

[0003] Copper-zinc wrought alloy, semi-finished product made of a copper-zinc wrought alloy and process for producing such a semi-finished product

[0004] The invention relates to a wrought copper-zinc alloy for the production of wire-, tubular-, or rod-shaped semi-finished products, to semi-finished products made from a wrought copper-zinc alloy, and to a method for producing such a semi-finished product. A wrought copper-zinc alloy is generally understood to mean a wrought material made from a copper-zinc alloy.

[0005] Copper-zinc alloys with 3 to 5 wt.% lead are excellently machinable and also very suitable for hot and cold forming. Lead-containing copper-zinc alloys are therefore used in a wide variety of applications, for example, for connections and components in the automotive industry, building technology, mechanical engineering, electrical appliances and electronic components, telecommunications, and as fittings in water installations.

[0006] The positive effect of lead in wrought copper-zinc alloys is based on the fact that lead is present in elemental form as particles in the structure, and these particles act as chip breakers. During machining, lead is present in the liquid phase due to the strong local deformation in the workpiece and the resulting local temperature increase. Since lead cannot absorb stresses in its liquid state, this leads to a stress concentration in the load-bearing, weakened matrix and thus to easier chip breakage. In addition, lead is incorporated into the tribological layer between the material and the tool during machining, thus leading to effective lubrication and thus a reduction in friction and wear. Furthermore, due to its low solubility, lead has little effect on electrical conductivity. This is particularly advantageous for materials used in electrical applications.Furthermore, lead is known to significantly refine the grain of copper-zinc alloys. This is beneficial for the straightness and dimensional accuracy of semi-finished products, especially rod-shaped ones. High dimensional accuracy is also required when crimping electronic wires. Furthermore, lead is inexpensive.

[0007] However, lead is harmful to the environment. Even the smallest amounts of lead accumulate in the human body and can cause health problems. Therefore, the EU, the USA, China, and other countries have continually reduced the limits for copper alloys and are striving to replace lead-containing brass with lead-reduced or lead-free machinable copper alloys. Limit values ​​are set by EU directives such as RoHS (Directive 2011 / 65 / EU), which stipulates a maximum of 1000 ppm (0.1 wt%) lead. To ensure good machinability of the material even at such low lead levels, various alloying elements are proposed as alternatives to lead.

[0008] Numerous publications have described the use of bismuth (Bi) as an alternative to lead to improve machinability. To mitigate the problem of Bi film formation along grain boundaries and the associated susceptibility to stress cracking and hot cracking, alloying with other elements is proposed. Reference is made in particular to publications KR 10 0 555 854 B1, KR 10 2006 096 877 A, JP 2005 290475 A, JP 2014 122 427 A, and JP 2006 083443 A. Nevertheless, Bi is undesirable because, on the one hand, it is a scarce, limited-abundance metal and, on the other hand, it leads to hot brittleness within the material cycles of copper materials.

[0009] Furthermore, copper-zinc alloys are known from the document EP 2 194 150 B1 which contain 0.1 to 1.5 wt.% Si, 0.03 to 0.4 wt.% Al, 0.01 to 0.36 wt.% P, 0.05 to 0.5 wt.% Sn and 0.001 to 0.05 wt.% rare earths. The alloys are easy to machine due to the formation of an α, β and possibly γ microstructure. Al phosphides are formed due to the Al content. The Y phase and Al phosphides improve chip formation but reduce the service life of the tool. In addition, the content of rare earths probably leads to embrittlement of the microstructure. The alloys are used for castings and hot-pressed parts.

[0010] The replacement of lead with phosphorus, which forms brittle phosphides in the alloy, is further described in the document WO 2020 / 261604 A1 for a material with Cu from 58.5 to 63.5 wt.%, Si from 0.4 to 1.0 wt.%, P from 0.005 to 0.19 wt.%, Pb from 0.003 to 0.25 wt.%, the remainder zinc and other optional elements. The addition of 0.005 to 0.19 wt.% P to form phosphides and 0.4 to 1.0 wt.% Si to strengthen the α and β phases results in a material that is easy to machine. However, due to the high Si content, the conductivity is reduced compared to lead-containing brass. On the one hand, this is disadvantageous for use as an electronic component, and on the other hand, the phosphides lose their brittleness and thus their chip-breaking function, particularly at elevated temperatures, which occur, for example, during drilling.This effect is all the more pronounced the poorer the thermal conductivity and thus the electrical conductivity of the material. The object of the invention is to provide a copper-zinc wrought alloy for the production of wire, tube, or rod-shaped semi-finished products that exhibits excellent machinability, particularly when drilling, good electrical conductivity, and the lowest possible content of environmentally harmful alloy components. Furthermore, the alloy should be easy to process on an industrial scale. This requires that it can be easily hot-formed, for example by extrusion, that it can be easily cold-formed, for example by drawing or crimping, and that semi-finished products made from the alloy exhibit excellent straightness and very good dimensional stability.Furthermore, the invention is based on the object of specifying a method for producing a wire-, tube- or rod-shaped semi-finished product from such an alloy.

[0011] The invention is represented with respect to a copper-zinc wrought alloy by the features of claim 1 and with respect to a manufacturing method by the features of claim 16. The further dependent claims relate to advantageous embodiments and developments of the invention.

[0012] The invention relates to a copper-zinc wrought alloy for the production of wire, tube or rod-shaped semi-finished products with the following composition in weight %:

[0013] Cu: 58.0 to 63.0%,

[0014] Si: 0.04 to 0.32%,

[0015] P: 0.05 to 0.20%,

[0016] Sn: optional up to 0.25%,

[0017] AI: optionally up to 0.10%, preferably up to 0.05%

[0018] Fe: optionally up to 0.30%, preferably up to 0.10%

[0019] Ni: optional up to 0.30%,

[0020] Pb: optionally up to 0.25%, preferably up to 0.10%

[0021] Te, Se, In optionally up to 0.10% each, Bi: maximum 0.009%

[0022] The remainder is Zn and unavoidable impurities, with the proportion of unavoidable impurities being less than 0.2 wt.%. The ratio of the weight fractions of P and Al is at least 1.0. The alloy has a microstructure consisting of globular α-phase, β-phase, and phosphide particles. The proportion of the β-phase in the sum of α-phase and β-phase is at least 20 vol.%, preferably at least 30 vol.%, and at most 70 vol.%, preferably at most 50 vol.%. Silicon is present in both the α-phase and the β-phase. In an area of ​​21,000 pm 27 to 200 phosphide particles with an equivalent diameter of 0.5 to 1 pm, 4 to 150 phosphide particles with an equivalent diameter of 1 to 2 pm and a maximum of 30 phosphide particles with an equivalent diameter of more than 2 pm are present.

[0023] The invention is based on the idea of ​​reducing the proportion of Pb in the copper-zinc alloy as much as possible without impairing the alloy's machinability. To this end, Si and P are deliberately added to the alloy, and the proportion of the ß-phase is adjusted so that, on the one hand, favorable machinability, particularly during drilling, and high conductivity are achieved, while, on the other hand, the hot and cold formability of the alloy is not impaired, and the semi-finished product made from the alloy exhibits excellent straightness. Furthermore, the process control, particularly during casting and hot forming, is selected to achieve the desired properties.

[0024] A globular α-phase is a prerequisite for good straightness and dimensional stability of the semi-finished product. The α-phase forms from the β-phase after hot forming. Therefore, the β-phase must be fine-grained in the as-cast state. Surprisingly, it has been shown that a fine-grained β-phase in the as-cast state is favored by evenly distributed copper- and / or zinc-containing phosphides. During primary crystallization of the β-crystallites, the residual melt becomes enriched with P, thereby leading to a subdivision of the β-phase. During solidification, a eutectic of phosphide and β-phase forms. In addition to the grain refinement of the basic matrix of β-phase, grain refinement of the α-crystallites is observed. This grain refinement of the cast structure by P facilitates hot forming, continues into the structure after hot forming, and consequently leads to grain refinement in the final state. With a P content of at least 0.05 wt.%, phosphide particles are present in the ß-phase in the final state.At a P content of more than 0.20 wt.%, the ductility of the alloy is low.

[0025] Furthermore, a high P content in combination with Si has a detrimental effect on electrical conductivity. Therefore, in a preferred embodiment of the invention, the sum of the Si and P contents is preferably at most 0.45 wt.%.

[0026] Furthermore, to achieve a globular α-phase, it is necessary that the cooling of the material after hot forming is controlled: In a temperature range of 550 °C to 350 °C, the cooling rate must be at least 30 °C per minute (30 °C / min), preferably at least 40 °C per minute, and at most 60 °C per minute, preferably at most 50 °C per minute. The evenly finely distributed phosphides, which are associated with a fine-grained β-phase in the as-cast state, dissolve in the matrix during hot forming and then reform during the cooling process during hot forming. In this way, the characteristic distribution of the phosphides in the as-cast state is ultimately reflected in the microstructure in the final state. The distribution of the phosphides in the final state and the globular shape of the α-phase are therefore determined not only by the chemical composition of the alloy, but also by the process control during casting and hot forming.The characteristics of the phosphides in the final state are thus like a fingerprint left on the product by the specific process. The distribution of the phosphides in the final state can be characterized as follows: In an area of ​​21,000 pm. 27 to 200 phosphide particles with an equivalent diameter of 0.5 to 1 pm, 4 to 150 phosphide particles with an equivalent diameter of 1 to 2 pm and a maximum of 30 phosphide particles with an equivalent diameter of more than 2 pm are present. The equivalent diameter of a phosphide particle is understood to be the diameter of a circle with the same area as the phosphide particle. The majority of the phosphide particles with an equivalent diameter of at least 0.5 pm have an equivalent diameter of at most 2 pm. Preferably, the proportion of phosphide particles with an equivalent diameter of 0.5 to 2 pm is at least 70% of the number of all phosphide particles with an equivalent diameter of at least 0.5 pm. Particularly preferably, this proportion is at least 75%.Furthermore, it is advantageous if at least 30%, preferably at least 50%, of all phosphide particles with an equivalent diameter of at least 0.5 pm have an equivalent diameter of at most 1 pm. It is not excluded that phosphides with an equivalent diameter of less than 0.5 pm may be present in the alloy.

[0027] Brittle structural components are advantageous for the machinability of the alloy, acting as separation points during machining and thus promoting chip breaking. The ß-phase is brittle and promotes machinability. An increase in the proportion of ß-phase can be achieved by increasing the Zn content and / or by alloying with silicon, because silicon stabilizes the ß-phase. For good machinability, it has also proven advantageous to reduce the ductility of the α-phase. This is achieved by alloying and intercalating silicon in the α-phase. Therefore, the Si content in the alloy must be at least 0.04 wt.%. With a Si content of more than 0.32 wt.%, the electrical conductivity is less than 12 MS / m and thus insufficient. A P content of at least 0.05 wt.% leads to favorable chips when drilling. Furthermore, a small optional proportion of Pb has a beneficial effect on machinability.

[0028] The Cu content of the alloy is 58.0 to 63.0 wt.%. At a Cu content of less than 58.0 wt.%, the ductility of the alloy is too low. At a Cu content of more than 63.0 wt.%, the zinc content in the alloy is too low to achieve good machinability.

[0029] The weight ratio of P to Al is at least 1.0. Aluminum reacts with phosphorus to form aluminum phosphides. However, these are undesirable because they do not improve machining performance. To ensure a sufficient excess of P for the formation of copper- and / or zinc-containing phosphides, the weight ratio of P to Al in the alloy must be at least 1.0.

[0030] The optional elements Sn and Al support the formation of the ß-phase. At a Sn content of more than 0.20 wt.%, the machining properties of the alloy deteriorate. However, this deterioration can be compensated for by heat treatment up to a Sn content of 0.25 wt.%. The tin content should preferably be no more than 0.20 wt.%, and particularly preferably no more than 0.10 wt.%.

[0031] Aluminum forms aluminum phosphides with phosphorus. However, these are undesirable, so the Al content should not exceed 0.10 wt.%, preferably 0.05 wt.%.

[0032] Iron leads to grain refinement of the microstructure. Furthermore, iron forms hard phosphides, which adversely affect tool life during machining. Therefore, the iron content may not exceed 0.30 wt.%, preferably 0.10 wt.%. Nickel promotes the formation of the α-phase and thus improves cold formability. Furthermore, nickel forms phosphides, which have no beneficial effect on machinability. Therefore, the nickel content may not exceed 0.30 wt.%, preferably 0.10 wt.%.

[0033] The element Bi is present as an impurity in secondary raw materials, such as scrap. It can improve the machinability of the alloy. However, amounts above 0.009 wt.% can adversely affect hot formability. Therefore, up to 0.009 wt.% Bi is tolerated in the alloy.

[0034] The elements Te, Se, and In can have a beneficial effect on the machinability of the alloy. In amounts up to 0.1 wt.% each, they have no negative impact on the alloy. Therefore, up to 0.1 wt.% each of Te, Se, and In is tolerated in the alloy.

[0035] The remainder of the alloy composition consists of zinc and unavoidable impurities. To avoid uncontrollable influences of these impurities on the alloy's properties, the maximum content of these impurities is 0.2 wt.%. Preferably, the Mn and Mg contents should each be no more than 0.1 wt.%, and particularly preferably no more than 0.07 wt.%, because these elements can form phosphides that can compete with the copper- and / or zinc-containing phosphides.

[0036] In a preferred embodiment of the invention, the Pb content in the alloy can be at least 0.02 wt.%. Even such a low Pb content improves machining properties and has a positive effect on grain refinement.

[0037] Advantageously, the P content can be at most 0.15 wt.%, particularly preferably at most 0.12 wt.%. This has a positive effect on the hot formability of the alloy.

[0038] In an advantageous embodiment of the invention, the P / Fe ratio can be at least 1.0. Iron forms hard iron phosphides with phosphorus. However, these are undesirable because they reduce the service life of the tools. To ensure a sufficient excess of P in the alloy to form copper- and / or zinc-containing phosphides, the weight ratio of P to Fe should be at least 1.0.

[0039] Within the scope of a preferred embodiment of the invention, the Fe content can be less than 0.10 wt.% and the Ni content can be at most 0.07 wt.%. This restriction inhibits the formation of iron phosphides and nickel phosphides compared to the formation of copper- and / or zinc-containing phosphides, which are advantageous for machining. Particularly favorable properties are achieved if the condition that the P / Fe ratio is at least 1.0 is simultaneously met. Furthermore, it is particularly preferred if the Fe content is at most 0.05 wt.% and / or the Ni content is at most 0.04 wt.%.

[0040] In an advantageous embodiment of the invention, the Si content can be at least 0.23 wt.%. This favors the machining properties of the alloy. Furthermore, a Si content of at least 0.23 wt.% has a positive effect on the surface quality of the product.

[0041] In an alternative embodiment of the invention, the Si content can be at most 0.15 wt.%, preferably at most 0.12 wt.%, particularly preferably at most 0.08 wt.%. Such a limitation of the Si content has a beneficial effect on the electrical conductivity of the alloy.

[0042] In this alternative embodiment of the invention, the P content can advantageously be at most 0.10 wt.%. This particularly favors the electrical conductivity of the alloy.

[0043] Furthermore, in this alternative embodiment of the invention, the Cu content can be a maximum of 59.5 wt.%. This upper limit for the Cu content results in particularly favorable combinations of conductivity, machinability, mechanical properties, and processability.

[0044] In a further embodiment of the invention, the proportions of the elements Cu, Zn, Si, P and Pb can total at least 99.75 wt.%. This ensures that the properties of the alloy are essentially determined by the alloying elements Cu, Zn, Si, P and Pb, while the influence of other elements plays only a very minor role. Alternatively or additionally, it can be advantageous to select the composition of the alloy so that the proportions of the elements Cu, Zn, Si, P, Sn and Pb total at least 99.85 wt.%. Because no tin phosphides are formed, it is a less critical alloying component than, for example, Fe, Ni or Al.

[0045] Advantageously, the copper-zinc wrought alloy can have a hardness of at least 120 HV10, preferably at least 150 HV10.

[0046] Advantageously, the copper-zinc wrought alloy can have a tensile strength R mof at least 500 MPa, preferably at least 530 MPa.

[0047] Advantageously, the copper-zinc wrought alloy can have an electrical conductivity of at least 12.5 MS / m, preferably at least 12.7 MS / m, particularly preferably at least 13.0 MS / m.

[0048] An alloy with a particularly advantageous combination of properties has the following composition in wt.%:

[0049] Cu: 58.5 to 59.0%

[0050] Si: 0.04 to 0.09%

[0051] P: 0.05 to 0.10%

[0052] Pb: 0.04 to 0.08%

[0053] Fe: optional up to a maximum of 0.10%

[0054] Ni: optional up to a maximum of 0.07%

[0055] Sn: optional up to a maximum of 0.20%

[0056] AI: optional up to 0.05%

[0057] The remainder is zinc and unavoidable impurities, with the proportion of unavoidable impurities being less than 0.1 wt.%. The low proportion of alloying elements Si and P achieves a particularly high electrical conductivity of at least 14 MS / m, preferably at least 15 MS / m. Machinability is supported by the Pb content of 0.04 to 0.08 wt.%.

[0058] The invention further relates to a wire-, tube-, or rod-shaped semi-finished product made of a wrought copper-zinc alloy described above, as well as a component manufactured from such a semi-finished product by machining and optionally further processing steps. The semi-finished product can also be in the form of a profile.

[0059] A further aspect of the invention relates to a method for producing a wire-, tube-, or rod-shaped semi-finished product. The method comprises the following steps: a) melting a copper alloy with a composition as described above, b) continuously casting a tube- or bolt-shaped casting format using a water-cooled mold, c) hot pressing the casting format at a temperature of 620 to 700 °C followed by cooling at a cooling rate of 30 to 60 °C per minute in a temperature range of 550 to 350 °C, d) optionally heat treatment in a temperature range of 525 to 625 °C for 1 to 5 hours followed by cooling at a cooling rate of 20 to 40 °C per minute in a temperature range of 500 to 350 °C, e) optionally cold forming.

[0060] Cu cathodes, Zn ingots, brass scrap, Cu-P master alloys, and Cu-Si master alloys can be used to melt the alloy. Melting is preferably carried out in an induction furnace. The melt is poured into a tubular or billet-shaped casting format in a water-cooled mold.

[0061] The cast format can optionally be milled and then hot-pressed at a temperature of 620 to 700 °C. The hot-pressed intermediate product is then cooled, with cooling occurring in the temperature range of 550 to 350 °C at a cooling rate of 30 to 60 °C per minute, preferably 40 to 50 °C per minute. This controlled cooling process establishes a favorable ratio of the α-phase to β-phase components, as well as a favorable particle distribution of copper and / or zinc-containing phosphides. Optionally, a heat treatment can be performed prior to hot pressing to homogenize the cast product.

[0062] In a first manufacturing process, pickling and then cold forming can follow hot pressing without any further intermediate steps. In cold forming, the degree of deformation is preferably between 3 and 30%. The degree of deformation is defined as the relative reduction in the cross-sectional area of ​​the product. Because no further steps take place between hot pressing and cold forming, apart from the pickling process, this first manufacturing process is very advantageous.

[0063] In a second manufacturing process, hot pressing is followed by heat treatment at between 525 and 625 °C, preferably between 550 and 600 °C, for a period of 1 to 5 hours, followed by cooling at a cooling rate of 20 to 40 °C per minute within a temperature range of 500 to 350 °C. By selecting the heat treatment conditions in combination with the defined cooling after heat treatment, a favorable ratio of the proportions of α-phase and β-phase as well as a favorable particle distribution of copper and / or zinc-containing phosphides can be achieved. If an increase in the proportion of the β-phase is desired, heat treatment should be carried out at approximately 600 °C. If an increase in the proportion of the α-phase is desired, heat treatment should be carried out at approximately 550 °C.Heat treatment allows the ratio of the α-phase to β-phase, as well as the particle distribution of the phosphides, to be adjusted and optimized. In particular, ductility can be improved. After heat treatment, the pickling and cold forming steps follow, as in the first manufacturing process.

[0064] With regard to further technical features and advantages of the method according to the invention, reference is hereby explicitly made to the explanations in connection with the copper-zinc wrought alloy according to the invention and to the exemplary embodiments.

[0065] The invention is explained in more detail using exemplary embodiments.

[0066] Samples No. 1 to No. 44 were melted in an induction furnace and then cast. The composition of the samples is documented in Tables 1 to 4. Sample No. 10 represents the lead-containing reference alloy CuZn39Pb3. The samples were milled, homogenized for 1 hour, and then hot-formed. Samples No. 8 and No. 9 were hot-formed by pressing at 630 °C, and the remaining samples were hot-formed by rolling at 650 °C. During cooling after hot-forming, in the temperature range between 550 and 350 °C, the cooling rate was approximately 40 °C per minute for the rolled samples and approximately 30 °C per minute for the pressed samples.

[0067] Samples No. 1 to No. 7 and No. 10 to No. 23 were milled after hot forming and then cold formed to a deformation degree of 20%. Samples No. 8 and No. 9 were pickled after hot forming and then cold formed to a deformation degree of 7%.

[0068] Samples No. 24 to No. 44 were annealed for 3 hours after hot forming. The annealing temperature for samples No. 26, No. 27, and No. 38 to No. 41 was approximately 550 °C, while for samples No. 24, No. 25, No. 28 to No. 37, and No. 42 to No. 44, it was approximately 600 °C. After annealing, cooling took place in the temperature range between 500 and 350 °C at a cooling rate of approximately 25 °C per minute. Samples No. 24 to No. 44 were then milled and cold formed to a deformation degree of 20%.

[0069] At the final state, the tensile strength R mand the elongation at break A from the tensile test, the hardness (Vickers hardness HV10), and the electrical conductivity A were determined. The longitudinal sections of the samples were examined by light microscopy. The area fractions of the α-phase and β-phase corresponding to the volume fractions, as well as the α-grain size, were determined. For the quantitative determination of the size distribution of the phosphide particles, the light microscopy images of the unetched samples were used. Image sections measuring 167 pm x 126 pm (corresponding to an area of ​​21,000 pm) were used. 2 ) and analyzed at 1000x magnification using the ImageJ software. This made it possible to identify individual particles and determine their equivalent diameter and area. The phosphide particles were classified based on their equivalent diameter into the categories 0.5 to 1 pm, 1 to 2 pm, and greater than 2 pm.

[0070] Machinability was assessed on the final state using drilling tests. The drilling tests were conducted using an instrumented drill head. The drilling tests were performed using the following parameters:

[0071] • Twist drill, diameter 5 mm

[0072] • Speed ​​3200 rpm

[0073] • Feed rate 0.04 mm / rev

[0074] • 5 holes per sample, a new drill was used for each sample

[0075] • Drilling depth 10 mm

[0076] The holes were drilled longitudinally to the forming direction. The torque acting on the cutting edge of the drill and the normal force were measured. The alloy CuZn39Pb3 in the unannealed state served as the reference. The torque measured on the individual specimens was standardized by relating the torque measured on the reference alloy to the torque measured on the respective specimen. Therefore, the smaller the torque measured on a specimen, the greater the normalized torque of that specimen. The measured normal force was standardized for each specimen in a similar manner. From the standardized torque M norm and the normalized normal force F N norm the arithmetic mean of these two quantities was calculated.

[0077] Samples for which the arithmetic mean calculated in this way is below 0.75 do not meet the requirements for good machinability.

[0078] Chip shape was classified based on the publication "Guidelines for the machining of copper and copper alloys," Information Print i.18, published by the German Copper Institute. Based on this, the chips were rated as good (2), average (1), and poor (0). Long, folded chips, in particular, resulted in an unfavorable rating.

[0079] The determined standardized torques and normal forces of the tests as well as the arithmetic mean calculated from them, which is designated as (M+FN) / 2 in the header of the tables, are listed in Tables 1 to 4 together with the chip shapes and the characteristic values ​​from the tensile test and the hardness measurement.

[0080] Table 1: samples according to the invention, unannealed

[0081] Table 1 (continued): samples according to the invention, unannealed

[0082] belle 2: Reference samples, unannealed

[0083] belle 2 (continued): Reference samples, unannealed

[0084] Table 3: samples according to the invention, annealed

[0085] Table 3 (continued): samples according to the invention, annealed

[0086] belle 4: Reference samples, annealed

[0087] Table 4 (continued): Reference samples, annealed

[0088] Samples No. 1 to No. 9 (Table 1) are samples according to the invention in the unannealed state. The volume fraction of the ß-phase is at least 33% and at most 46%. The α-grain size is a maximum of 24 μm for the rolled samples and a maximum of 35 μm for the pressed samples. The small α-grain size of sample No. 5 can be attributed to the alloying element Fe. The hardness is at least 160 HV10 and the tensile strength R mat least 520 MPa. The elongation at break is at least 10%. The electrical conductivity is at least 12.7 MS / m for all specimens, and at least 13.0 MS / m for the majority of specimens. For specimen no. 9, the electrical conductivity is more than 15.5 MS / m. The standardized torque is between 0.85 and 1.08. The standardized normal force is between 0.45 and 0.7. The arithmetic mean of the standardized torque and the standardized normal force is always at least 0.75. The chip shape was always rated as good (2) or average (1).

[0089] Samples No. 10 to No. 23 (Table 2) are comparison samples in the unannealed state. Reference sample No. 10 contains 3.3 wt.% lead and exhibits very good machining properties. Sample No. 11, which contains 2.0 wt.% lead, also exhibits good machining properties. Samples No. 12 and No. 16 demonstrate that, without lead and without other alloying elements, the machining properties are very poor.

[0090] Samples No. 13 and No. 17 contain only 0.27 wt.% Si in addition to Cu and Zn. While the forces acting on the drill are within acceptable limits, the chip shape is poor, which can be attributed to the lack of phosphide particles as chip breakers. In sample No. 14, the Cu and Si content were increased compared to sample No. 13. The forces acting on the drill are not within acceptable limits, and the chip shape is poor. Furthermore, the electrical conductivity is low.

[0091] In sample no. 15, the Si content was slightly increased compared to sample no. 14, and 0.1 wt.% P was added. The forces acting on the drill were thus reduced and the chip shape was slightly improved. However, the elongation at break and the electrical conductivity are low. Compared to sample no. 1, sample no. 15 shows a higher Si content with a similar P content and similar volume fraction of the ß-phase. The forces acting on the drill are similarly good, but the chip shape is less favorable in sample no. 15 and the conductivity is poorer.

[0092] Sample No. 18 differs from Sample No. 17 by 0.38 wt.% P. This essentially leads to a significant improvement in chip shape. However, the elongation at break is very low.

[0093] Sample No. 19 contains only 0.11 wt.% P in addition to Cu and Zn. While this favors chip formation, the forces acting on the drill are unsatisfactory. In Sample No. 22, the P content was increased to 0.29 wt.% compared to Sample No. 19, resulting in a deterioration in the normal force.

[0094] Sample No. 20 differs from sample No. 15 primarily in its slightly lower P content. This leads to an improvement in elongation at break. However, the electrical conductivity is not at the desired level due to the high Si content.

[0095] Sample No. 21 contains 0.27 wt% Si and 0.06 wt% P, as well as 0.22 wt% Sn. Compared to Sample No. 2, which contains no tin, the addition of tin leads to a moderate deterioration in the forces acting on the drill. Almost exclusively, phosphide particles with a diameter of 0.5 to 1 pm are observed. The electrical conductivity is barely affected by 0.22 wt% Sn. Sample No. 23 contains 0.29 wt% Si and 0.30 wt% P. Similar to Sample No. 18, although the chip shape is good, the elongation at break, conductivity, and the forces acting during drilling are unsatisfactory.

[0096] Samples No. 24 to No. 31 (Table 3) are as-annealed samples according to the invention. Samples No. 26 and No. 27 were annealed at 550 °C, while the other samples in Table 3 were annealed at 600 °C. The volume fraction of the ß-phase is at least 31% and at most 49%. The α-grain size is between 25 and 40 pm, with samples No. 26 and No. 27 having the smallest grain size. The hardness is at least 160 HV10 and the tensile strength R mat least 510 MPa. The elongation at break is at least 11.5%. The electrical conductivity is at least 12.7 MS / m for all samples and at least 13.0 MS / m for the majority of samples. The standardized torque is between 0.79 and 1.03. The standardized normal force is between 0.56 and 0.71. The arithmetic mean of the standardized torque and the standardized normal force is always at least 0.75. The chip shape was always rated as good (2) or average (1). In sample no. 31, which corresponds to the unannealed sample no. 21 in terms of composition, a significant improvement in the forces acting during drilling and the chip shape could be achieved by annealing. Furthermore, it can be seen that annealing shifted the center of gravity of the distribution of the phosphide particles towards larger particles.

[0097] Samples No. 32 to No. 44 (Table 4) are reference samples in the annealed condition. The lead-containing samples No. 32 and No. 33 exhibit good machining properties in the annealed condition. Samples No. 34 (annealed at 600 °C) and No. 38 (annealed at 550 °C), which contain only Cu and Zn, are characterized by poor drilling properties even in the annealed condition.

[0098] The silicon-containing but phosphorus-free specimens No. 35 and No. 36, which were annealed at 600 °C, exhibit a drilling torque more than twice that determined for reference specimen No. 10. The higher Si content in specimen No. 36 improves chip formation but reduces electrical conductivity. The silicon-containing but phosphorus-free specimen No. 39, which was annealed at 550 °C, exhibits more favorable drilling forces than specimens No. 35 and No. 36. This can be attributed to the significantly higher proportion of ß-phase. However, the chip formation is poor.

[0099] Sample No. 37, which contains 0.58 wt% Si and 0.10 wt% P and was annealed at 600 °C, shows more favorable drilling properties than sample No. 15 with the same composition in the unannealed state, but the electrical conductivity is insufficient due to the high Si content.

[0100] For samples No. 40 and No. 41, which were annealed at 550 °C and correspond in composition to samples No. 18 and No. 19, respectively, annealing resulted in an improvement in the forces acting on the drill bit, and in particular in sample No. 40, a significant improvement in ductility. However, sample No. 40 exhibits low electrical conductivity due to the high Si and P content. In sample No. 41, the lack of Si cannot be compensated for by annealing to such an extent that the drilling forces are at an acceptable level.

[0101] Sample No. 42 with a Si content of 0.55 wt% and a P content of 0.075 wt% has too low electrical conductivity due to the high Si content.

[0102] For samples No. 43 and No. 44, which correspond in composition to the unannealed samples No. 22 and No. 23, a significant improvement in ductility was achieved by annealing at 600 °C. Sample No. 43 exhibits unsatisfactory machining properties even after annealing. In sample No. 44, the P content of 0.3 wt.% in combination with the Si content of 0.29 wt.% leads to low electrical conductivity.

[0103] Samples No. 1 to No. 44 demonstrate that, through the careful selection of the elements Si and P, alloys can be produced with a favorable combination of properties. Si reduces the forces acting on the drill and thus improves machining properties. However, a Si content of over 0.32 wt.% reduces electrical conductivity. A P content of 0.05 to 0.2 wt.% promotes chip formation. A higher P content in combination with Si leads to a deterioration in ductility and electrical conductivity. Alloys with a favorable combination of these properties can be produced without annealing. For some element combinations, annealing, particularly between 550°C and 600°C, can subsequently improve the machining properties by specifically adjusting the ß-phase content and the phosphide particles.

[0104] Alloys with a composition described above can also be used as casting alloys for castings.

Claims

Patent claims Copper-zinc wrought alloy for the production of wire, tube or rod-shaped semi-finished products with the following composition in weight %: Cu: 58.0 to 63.0%, Si: 0.04 to 0.32%, P: 0.05 to 0.20%, Sn: optional up to 0.25%, AI: optional up to 0.10%, Fe: optional up to 0.30%, Ni: optional up to 0.30%, Pb: optional up to 0.25%, Te, Se, In optionally up to 0.10% each Bi: maximum 0.009%, Balance Zn and unavoidable impurities, with the proportion of unavoidable impurities being less than 0.2 wt.%, wherein the ratio of the weight fractions of P and Al is at least 1.0, wherein the alloy has a structure of globular α-phase, β-phase and phosphide particles and the proportion of β-phase in the sum of α-phase and β-phase is at least 20 vol.% and at most 70 vol.%, wherein Si is present in both the α-phase and the β-phase, wherein in an area of ​​21000 pm 2 7 to 200 phosphide particles with a equivalent diameter 0.5 to 1 pm, 4 to 150 phosphide particles with an equivalent diameter 1 to 2 pm and a maximum of 30 phosphide particles with an equivalent diameter of more than 2 pm are present. Copper-zinc wrought alloy according to claim 1, characterized in that the Pb content is at least 0.02 wt.%. Copper-zinc wrought alloy according to one of claims 1 to 2, characterized in that the P content is at most 0.15 wt.%. Copper-zinc wrought alloy according to one of claims 1 to 3, characterized in that the P / Fe ratio is at least 1.

0. Copper-zinc wrought alloy according to one of claims 1 to 4, characterized in that the Fe content is less than 0.10 wt.% and the Ni content is at most 0.07 wt.%. Copper-zinc wrought alloy according to one of claims 1 to 5, characterized in that the Si content is at least 0.23 wt.%.A wrought copper-zinc alloy according to any one of claims 1 to 5, characterized in that the Si content is at most 0.15 wt.%. A wrought copper-zinc alloy according to claim 7, characterized in that the P content is at most 0.10 wt.%. A wrought copper-zinc alloy according to claim 7 or 8, characterized in that the Cu content is at most 59.5 wt.%. Copper-zinc wrought alloy according to one of the preceding claims, characterized in that the proportions of the elements Cu, Zn, Si, P and Pb in total amount to at least 99.75 wt. %. Copper-zinc wrought alloy according to one of the preceding claims, characterized in that the alloy has a hardness of at least 120 HV10, preferably at least 150 HV10. Copper-zinc wrought alloy according to one of the preceding claims, characterized in that the alloy has a tensile strength R mof at least 500 MPa, preferably at least 530 MPa. Copper-zinc wrought alloy according to one of the preceding claims, characterized in that the alloy has an electrical conductivity of at least 12.5 MS / m. Wire-, tubular-, or rod-shaped semi-finished product made of a copper-zinc wrought alloy according to one of the preceding claims. Component produced by machining and optional further processing steps from a semi-finished product according to claim 14. Method for producing a wire-, tubular-, or rod-shaped semi-finished product according to claim 14, wherein the method comprises the following steps: a) melting a copper alloy having a composition according to one of claims 1 to 10, b) continuous casting of a tubular or bolt-shaped casting format using a water-cooled mold, c) hot pressing of the cast shape at a temperature of 620 to 700 °C followed by cooling at a cooling rate of 30 to 60 °C per minute in a temperature range of 550 to 350 °C, d) optionally heat treatment in a temperature range of 525 to 625 °C for 1 to 5 hours followed by cooling at a cooling rate of 20 to 40 °C per minute in a temperature range of 500 to 350 °C, e) optionally cold forming.

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