Copper-zinc wrought alloys, semi-finished products made from copper-zinc wrought alloys, and methods for manufacturing such semi-finished products

Abstract

The present invention relates to a copper-zinc wrought alloy for producing semi-finished products in wire, tube, or rod form, having the following composition by weight: Cu: 58.0-63.0%, Si: 0.04-0.32%, P: 0.05-0.20%, 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, and In: optionally up to 0.10% each, Bi: max. 0.009%, and the balance being Zn and unavoidable impurities, with the proportion of unavoidable impurities being less than 0.2% by weight. The ratio of the weight fractions of P and Al is at least 1.0. The alloy has a microstructure consisting of spherical α-phase, β-phase, and phosphide particles. The proportion of the β-phase relative to the total of the α-phase and β-phase is at least 20% by volume and at most 70% by volume. Si exists in both the α and β phases. 2 In this area, 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 up to 30 phosphide particles with an equivalent diameter greater than 2 μm.

Description

Technical Field

[0001] The present invention relates to an alloy for copper-zinc forging for manufacturing wire-shaped, tube-shaped, or bar-shaped semi-finished products, a semi-finished product made of an alloy for copper-zinc forging, and a method for manufacturing such a semi-finished product. The alloy for copper-zinc forging generally means a forging material made of a copper-zinc alloy.

Background Art

[0002] A copper-zinc alloy containing 3 to 5% by weight of lead has excellent machinability and is very suitable for hot forming and cold forming. Therefore, lead-containing copper-zinc alloys are used in many applications, for example, for the automotive industry, construction technology, machinery manufacturing, electronic devices and components, connections and components in communications, and also as joints for plumbing facilities.

[0003] The positive effect of lead in the copper-zinc forging alloy is based on the fact that lead exists as fine particles alone in the structure, and these particles act as chip breakers. During machining, lead exists as a liquid phase due to the strong local deformation of the member and the accompanying local temperature rise. Since liquid lead cannot absorb stress, stress concentrates on the fragile matrix that transmits the load, which makes chip breaking more likely to occur. In addition, during machining, lead is incorporated into the tribology layer between the material and the tool, which leads to effective lubrication and thus a reduction in friction and wear. Furthermore, since lead has low solubility, it has no effect on conductivity. This is particularly advantageous for materials used in electrical applications. It is also known that lead in copper-zinc alloys causes obvious grain refinement. This is particularly advantageous for the straightness and dimensional accuracy of bar-shaped semi-finished products. High dimensional accuracy is also required when crimping electronic wires. Furthermore, lead is also inexpensive.

[0004] However, lead is harmful to the environment. Even small amounts of lead can accumulate in the human body if ingested, potentially causing health problems. Therefore, in the EU, the US, China, and other countries, regulatory limits for copper alloys are constantly being lowered, and efforts are being made to use lead-reduced or lead-free machinable copper alloys instead of leaded brass. Regulatory limits, for example, are set at an upper limit of 1000 ppm (0.1 wt%) of Pb in EU directives such as RoHS (Directive 2011 / 65 / EU). To ensure good machinability of materials even with such low lead content, various alloying elements are proposed as substitutes for lead.

[0005] Numerous documents have shown that using bismuth (Bi) as a substitute for lead improves machinability. Further elemental additions have been proposed to mitigate the formation of Bi films along grain boundaries and the resulting vulnerability to stress and hot cracks. This is particularly relevant to Patent Documents 1, 2, 3, 4, and 5. However, Bi is undesirable because it is a rare metal that is difficult to obtain, and it causes high-temperature brittleness within the material cycle of copper materials.

[0006] Furthermore, as documented in Patent Document 6, copper-zinc alloys containing 0.1-1.5 wt% Si, 0.03-0.4 wt% Al, 0.01-0.36 wt% P, 0.05-0.5 wt% Sn, and 0.001-0.05 wt% rare earth elements are well known. This alloy is easily machinable by forming α, β, and sometimes γ structures. The presence of Al leads to the formation of Al phosphides. While the γ phase and Al phosphides improve chip formation, they worsen tool life. Furthermore, the inclusion of rare earth elements is thought to lead to embrittlement of the structure. re These alloys are used in cast and hot-forged parts.

[0007] The use of phosphorus, which forms brittle phosphides within alloys, as a substitute for lead is further described in Patent Document 7 for a material containing 58.5-63.5 wt% Cu, 0.4-1.0 wt% Si, 0.005-0.19 wt% P, 0.003-0.25 wt% Pb, the remainder being zinc, and other arbitrary elements. Adding 0.005-0.19 wt% P to form phosphides and adding 0.4-1.0 wt% Si to strengthen the α and β phases results in a material that is easy to machine. However, due to the high proportion of Si, the conductivity is reduced compared to leaded brass. This is disadvantageous for applications as electronic components, and on the other hand, especially when the temperature rises, such as during drilling, the phosphides lose their brittleness, resulting in a loss of chip-breaking function. This effect becomes more pronounced as the thermal conductivity of the material deteriorates, and consequently, the conductivity deteriorates. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Korean Patent Publication No. 10-0555854 [Patent Document 2] Korean Published Patent Publication No. 10-2006-096877 [Patent Document 3] Japanese Patent Publication No. 2005-290475 [Patent Document 4] Japanese Patent Publication No. 2014-122427 [Patent Document 5] Japanese Patent Publication No. 2006-083443 [Patent Document 6] European Patent No. 2194150 [Patent Document 7] International Publication No. 2020 / 261604 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The present invention is based on the problem of providing a copper-zinc alloy for forging, which has excellent machinability and good electrical conductivity especially during drilling, and contains alloy components with environmental concerns as little as possible, for manufacturing semi-finished products in wire, tube or rod shape. Furthermore, this alloy must be easily processable on an industrial scale. For this reason, it is necessary that this alloy can be easily hot-formed by extrusion or the like, can be easily cold-formed by drawing or crimping or the like, and that the semi-finished products manufactured from this alloy have excellent straightness and very good dimensional stability. Furthermore, the present invention is also based on the problem of providing a method for manufacturing semi-finished products in wire, tube or rod shape from such an alloy.

Means for Solving the Problems

[0010] The present invention A copper-zinc forging alloy for manufacturing wire-shaped, tubular, or rod-shaped semi-finished products, having the following composition in weight percent, namely: Cu: 58.0~63.0%, Si: 0.04~0.32%, P:0.05~0.20%、 Sn: Optional, up to 0.25% Al: 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: each can be set to a maximum of 0.10%. Bi: Maximum 0.009%, The remainder consists of Zn and unavoidable impurities. The proportion of the aforementioned unavoidable impurities is less than 0.2% by weight. The ratio of the weight fractions of P and Al is at least 1.0. The alloy has a structure consisting of spherical α-phase, β-phase, and phosphide particles, and the proportion of the β-phase to the sum of the α-phase and β-phase is at least 20% by volume and at most 70% by volume. Si is present in both the α phase and the β phase. 21000 μm 2 The area contains 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 up to 30 phosphide particles with an equivalent diameter greater than 2 μm. 。

Embodiments for Carrying Out the Invention

[0011] The present invention relates to a copper-zinc forging alloy for producing wire-shaped, tubular, or rod-shaped semi-finished products, wherein the alloy has the following composition in weight percent, namely: Cu: 58.0~63.0%, Si: 0.04~0.32%, P:0.05~0.20%、 Sn: Optional, up to 0.25% Al: Optionally up to 0.10%, preferably up to 0.05%. Fe: optionally up to 0.30%, preferably up to 0.10%. Ni: Optional, up to 0.30% Pb: Optionally up to 0.25%, preferably up to 0.10%. Te, Se, In: each can be set to a maximum of 0.10%. Bi: Maximum 0.009%, The remainder consists of Zn and unavoidable impurities. The proportion of unavoidable impurities is less than 0.2% by weight. The weight fraction ratio of P to Al is at least 1.0. This alloy has a structure consisting of spherical α-phase, β-phase, and phosphide particles. The proportion of the β-phase to the sum of the α-phase and β-phase is at least 20% by volume, preferably at least 30% by volume, at most 70% by volume, and preferably at most 50% by volume. Silicon is present in both the α-phase and the β-phase. 21000 μm 2 The area contains 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 up to 30 phosphide particles with an equivalent diameter greater than 2 μm.

[0012] In this context, the present invention is based on the idea of ​​reducing the proportion of Pb in the copper-zinc alloy as much as possible without impairing the machinability of the alloy. To this end, Si and P are appropriately added to the alloy, and the proportion of the β phase is adjusted so that, on the one hand, advantageous machinability properties and high conductivity are obtained, particularly during drilling, on the other hand, the hot and cold forming of the alloy is not impaired, and the semi-finished products produced from the alloy have excellent straightness. Furthermore, process control, particularly during casting and hot forming, is selected so that the desired properties are ultimately obtained.

[0013] The spherical α-phase is a prerequisite for good straightness and dimensional stability of the semi-finished product. The α-phase arises from the β-phase after hot forming. Therefore, the β-phase must be fine in the cast state. Surprisingly, it has been found that uniformly finely dispersed copper and / or zinc-containing phosphides act favorably on the fine β-phase in the cast state. During the primary crystallization of the β-crystal, the residual molten material is concentrated with P, thereby causing the refinement of the β-phase. During solidification, a eutectic mixture consisting of phosphides and the β-phase is formed. In addition to grain refinement of the basic matrix consisting of the β-phase, grain refinement of the α-crystal is also observed. This grain refinement of the cast structure by P facilitates hot forming and continues in the structure after hot forming, resulting in grain refinement in the final state. When the proportion of P is at least 0.05 wt%, phosphide particles are present in the β-phase in the final state. When the proportion of P is greater than 0.20 wt%, the ductility of the alloy is low.

[0014] Furthermore, a high proportion of P combined with Si is detrimental to conductivity. Therefore, in a preferred embodiment of the present invention, the sum of the proportions of Si and P is preferably at most 0.45% by weight.

[0015] Furthermore, for the spherical α-phase to be formed, controlled cooling of the material after hot forming is necessary. In the 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, at most 60°C per minute, and preferably at most 50°C per minute. The uniformly finely dispersed phosphides, accompanied by a fine β-phase in the casting state, dissolve in the matrix during hot forming and are then newly formed during the cooling process of hot forming. In this way, the characteristic distribution of phosphides in the casting state is ultimately reflected in the final structure. Therefore, the distribution of phosphides and the spherical shape of the α-phase in the final state are determined not only by the chemical composition of the alloy but also by the process control during casting and hot forming. Thus, the characteristics of the phosphides in the final state are like a fingerprint that specific process control leaves on the product. The dispersion of phosphides in the final state can be characterized as follows: In an area of ​​21,000 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 up to 30 phosphide particles with an equivalent diameter greater than 2 μm. 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 phosphide particles with an equivalent diameter of at least 0.5 μm have an equivalent diameter of at most 2 μm. Preferably, the proportion of phosphide particles with an equivalent diameter of 0.5 to 2 μm is at least 70% of the total number of phosphide particles with an equivalent diameter of at least 0.5 μm. 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 μm have an equivalent diameter of at most 1 μm. The presence of phosphide particles with an equivalent diameter smaller than 0.5 μm within the alloy has not been ruled out.

[0016] Brittle microstructure components that act as separation points during machining, thereby assisting chip breaking, are advantageous for the machinability of alloys. The β phase is brittle and advantageous for machinability. Increasing the proportion of the β phase can be achieved by increasing the Zn content and / or by adding silicon, because silicon stabilizes the β phase. Furthermore, it has been proven that reducing the ductility of the α phase is advantageous for good machinability. This is achieved by adding and embedding silicon in the α phase. Therefore, the Si proportion in the alloy must be at least 0.04 wt%. If the Si proportion is greater than 0.32 wt%, the conductivity will be less than 12 MS / m and is therefore insufficient. When the P proportion is at least 0.05 wt%, favorable chip formation occurs during drilling. Furthermore, any low Pb proportion is advantageous for machinability.

[0017] The Cu content of the alloy is 58.0–63.0% by weight. If the Cu content is less than 58.0% by weight, the ductility of the alloy is too low. If the Cu content is more than 63.0% by weight, the zinc content of the alloy is too low to achieve good machinability.

[0018] The weight fraction ratio of P to Al is at least 1.0. Aluminum forms aluminum phosphides with phosphorus. However, these are undesirable because they do not improve machinability. The weight fraction ratio of P to Al in the alloy must be at least 1.0 in order to allow for sufficient excess P to form copper and / or lead-containing phosphides.

[0019] Any elements, Sn and Al, support the formation of the β phase. If the proportion of Sn exceeds 0.20 wt%, the machinability of the alloy deteriorates. However, this deterioration can be corrected by heat treatment if the proportion of Sn is 0.25 wt% or less. Preferably, the proportion of tin should be at most 0.20 wt%, and particularly preferably at most 0.10 wt%.

[0020] Aluminum forms aluminum phosphides with phosphorus. However, these are undesirable, so the proportion of Al should not exceed 0.10% by weight, preferably 0.05% by weight.

[0021] Iron contributes to the refinement of the crystal grain in the microstructure. Furthermore, iron forms hard phosphides, which negatively affect tool life during machining. Therefore, the proportion of iron should be at most 0.30% by weight, and particularly preferably at most 0.10% by weight.

[0022] Nickel supports the formation of the α phase, thereby improving cold forming. Furthermore, nickel forms phosphides, but this does not have a favorable effect on machinability. Therefore, the proportion of nickel should be at most 0.30% by weight, and particularly preferably at most 0.10% by weight.

[0023] The element Bi (bicarbonate) is present as an impurity in secondary raw materials, such as scrap. This can improve the machinability of the alloy. However, if the proportion exceeds 0.009% by weight, it may negatively affect the hot formability. Therefore, a maximum of 0.009% by weight of Bi is permitted in this alloy.

[0024] The elements Te, Se, and In can, advantageously, have a beneficial effect on the machinability of the alloy. Up to a maximum of 0.1% by weight of each, they do not have an adverse effect on the alloy. Therefore, up to 0.1% by weight of Te, Se, and In is permissible in this alloy.

[0025] The remainder of the alloy composition consists of zinc and unavoidable impurities. To avoid the uncontrollable influence of impurities on the alloy properties, the proportion of these impurities is a maximum of 0.2% by weight. Preferably, the proportions of Mn and Mg in particular should be at most 0.1% by weight, and especially preferably at most 0.07% by weight, because these elements can form phosphides that can compete with copper-containing and / or zinc-containing phosphides.

[0026] In a preferred embodiment of the present invention, the Pb content of the alloy can be at least 0.02% by weight. Even such a small Pb content improves machinability and has a positive effect on grain refinement.

[0027] Advantageously, the proportion of P can be at most 0.15% by weight, and particularly preferably at most 0.12% by weight. This has a favorable effect on the hot formability of the alloy.

[0028] In an advantageous embodiment of the present invention, the P / Fe ratio can be at least 1.0. Iron, together with phosphorus, forms hard iron phosphides. However, these iron phosphides are undesirable because they reduce tool life. For there to be a sufficient surplus of P in the alloy to form copper-containing and / or lead-containing phosphides, the weight fraction ratio of P to Fe must be at least 1.0.

[0029] In a preferred embodiment of the present invention, the proportion of Fe can be less than 0.10 wt%, and the proportion of Ni can be at most 0.07 wt%. This limitation suppresses the formation of iron phosphides and nickel phosphides compared to the formation of copper-containing and / or zinc-containing phosphides, which are advantageous for machining. Particularly advantageous properties are achieved when the condition that the P / Fe ratio is at least 1.0 is simultaneously met. Furthermore, it is particularly preferable that the proportion of Fe is at most 0.05 wt%, and / or the proportion of Ni is at most 0.04 wt%.

[0030] In an advantageous embodiment of the present invention, the Si content can be at least 0.23% by weight. This is advantageous for the machinability of the alloy. Furthermore, when the Si content is at least 0.23% by weight, it has a favorable effect on the surface quality of the product.

[0031] In an alternative embodiment of the present invention, the proportion of Si can be at most 0.15% by weight, preferably at most 0.12% by weight, and particularly preferably at most 0.08% by weight. Such limitation of the Si proportion has a favorable effect on the conductivity of the alloy.

[0032] In this alternative embodiment of the present invention, the proportion of P can preferably be at most 0.10% by weight. This is particularly advantageous for the electrical conductivity of the alloy.

[0033] Furthermore, in this alternative embodiment of the present invention, the proportion of Cu can be at most 59.5% by weight. This upper limit on the Cu proportion provides a particularly advantageous combination of conductivity, machinability, mechanical properties, and processability.

[0034] In a further embodiment of the present invention, the proportions of the elements Cu, Zn, Si, P, and Pb can be at least 99.75% by weight in total. This ensures that the properties of the alloy are determined primarily by the alloying elements Cu, Zn, Si, P, and Pb, with the influence of other elements playing only a very secondary role. Alternatively or additionally, it may be advantageous to select the alloy composition such that the proportions of the elements Cu, Zn, Si, P, Sn, and Pb are at least 99.85% by weight in total. Since tin phosphides are not formed, tin is less important as an alloying component than, for example, Fe, Ni, or Al.

[0035] Advantageously, the copper-zinc alloy for forging can have a hardness of at least 120 HV10, preferably at least 150 HV10.

[0036] Advantageously, the copper-zinc forging alloy can have a tensile strength Rm of at least 500 MPa, preferably at least 530 MPa.

[0037] Advantageously, the copper-zinc forging alloy can have an electrical conductivity of at least 12.5 MS / m, preferably at least 12.7 MS / m, and particularly preferably at least 13.0 MS / m.

[0038] Alloys with particularly advantageous combinations of properties have the following compositions in weight percent, namely: Cu: 58.5~59.0% Si: 0.04~0.09% P:0.05~0.10% Pb: 0.04~0.08% Fe: Optional, up to 0.10% Ni: Optional, up to 0.07% Sn: Optional, up to 0.20% Al: Optional, up to 0.05% The remainder consists of zinc and unavoidable impurities, with the proportion of unavoidable impurities being less than 0.1% by weight. The low proportions of alloying elements Si and P result in high conductivity of at least 14 MS / m, preferably at least 15 MS / m. Machinability is supported by a Pb content of 0.04–0.08% by weight.

[0039] The present invention also applies to wire-, tubular, or rod-shaped semi-finished products made of the aforementioned copper-zinc forging alloy, as well as components manufactured from such semi-finished products by machining and any further processing steps. These semi-finished products may also be in the form of profiles.

[0040] A further aspect of the present invention relates to a method for producing wire-shaped, tubular, or rod-shaped semi-finished products. This method comprises the following steps, namely: a) A process of melting a copper alloy having the composition described above, b) A process of continuously casting a tubular or bolt-shaped casting format using a water-cooled mold, c) A process of hot forging the casting format at a temperature of 620-700°C, followed by cooling at a cooling rate of 30-60°C per minute in a temperature range of 550-350°C. d) Optionally, heat treatment at a temperature range of 525-625°C for 1-5 hours, followed by cooling at a temperature range of 500-350°C at a cooling rate of 20-40°C per minute. e) Optionally, includes a cold forming step.

[0041] For melting the alloy, Cu cathodes, Zn blocks, brass scrap, Cu-P master alloys, and Cu-Si master alloys can be used. Melting is preferably carried out in an induction furnace. The molten material is poured into a water-cooled mold to form a tubular or bolt-shaped casting format.

[0042] This casting format can optionally be machined and then hot forged at a temperature of 620-700°C. Subsequently, the hot-forged intermediate product is cooled. During this cooling, the cooling is carried out at a rate of 30-60°C per minute, preferably 40-50°C per minute, in a temperature range of 550-350°C. This defined cooling adjusts the favorable ratio of α-phase to β-phase, as well as the favorable particle distribution of phosphides containing copper and / or zinc. Optionally, heat treatment can be performed before hot forging to homogenize the cast product.

[0043] In the first manufacturing method, after hot forging, pickling can be performed without any further intermediate steps, followed by cold forming. In cold forming, the degree of deformation is preferably 3-30%. In this case, the degree of deformation is understood to be the relative reduction in the cross-sectional area of ​​the product. Since no further work steps are performed between hot forging and cold forming, with the exception of the pickling process, this first manufacturing method is very advantageous.

[0044] In the second manufacturing method, after hot forging, a heat treatment is performed at a temperature range of 525-625°C, preferably 550-600°C, for 1-5 hours, followed by cooling at a rate of 20-40°C per minute in a temperature range of 500-350°C. By selecting the heat treatment conditions in combination with the defined cooling after the heat treatment, it is possible to adjust the favorable ratio of α-phase to β-phase and the favorable particle distribution of phosphides containing copper and / or zinc. To increase the proportion of β-phase, the heat treatment should be performed at approximately 600°C. To increase the proportion of α-phase, the heat treatment should be performed at approximately 550°C. Thus, the ratio of α-phase to β-phase and the particle distribution of phosphides can be adjusted and optimized by the heat treatment. In particular, this can improve ductility. After the heat treatment, the pickling and cold forming steps are continued as in the first manufacturing method.

[0045] Herein, further technical features and advantages of the method according to the present invention are explicitly stated, along with descriptions and examples relating to the copper-zinc forging alloy according to the present invention.

[0046] The present invention will be described in detail using examples.

[0047] Samples No. 1 to No. 44 were melted in an induction furnace and then poured into molds. The composition of the samples is recorded in Tables 1 to 4. Sample No. 10 is a lead-containing reference alloy CuZn39Pb3. The samples were machined, homogenized for 1 hour, and then hot-formed. Samples No. 8 and No. 9 were hot-formed at 630°C by pressing, and the remaining samples were hot-formed at 650°C by rolling. The cooling rate after hot-forming was approximately 40°C per minute for the rolled samples and approximately 30°C per minute for the pressed samples, within the temperature range of 550 to 350°C.

[0048] Samples No. 1 to No. 7 and No. 10 to No. 23 were hot-formed, then machined, and subsequently cold-formed to a degree of formability of 20%. Samples No. 8 and No. 9 were hot-formed, then pickled, and subsequently cold-formed to a degree of formability of 7%.

[0049] Samples No. 24 to No. 44 were hot-formed for 3 hours and then annealed. The annealing temperature was approximately 550°C for samples No. 26, No. 27, and No. 38 to No. 41, and approximately 600°C for samples No. 24, No. 25, No. 28 to No. 37, and No. 42 to No. 44. After annealing, the samples were cooled at a cooling rate of approximately 25°C per minute in the temperature range of 500 to 350°C. Subsequently, samples No. 24 to No. 44 were machined and then cold-formed to a degree of formability of 20%.

[0050] In the final state, the tensile strength Rm and elongation A at break, hardness (Vickers hardness HV10), and conductivity λ were determined from tensile tests. The longitudinal section of the sample was examined with an optical microscope. Subsequently, the area fractions of the α and β phases corresponding to the volume fraction, as well as the α particle size, were calculated. Optical microscope images of the unetched sample were used to quantitatively determine the particle size distribution of the phosphide particles. Dimensions: 167 μm × 126 μm (21000 μm) 2 A portion of the image (corresponding to the area of ​​the particle) was selected and evaluated at 1000x magnification using the software ImageJ. In this way, individual particles could be recognized, and their equivalent diameter and area could be determined. Based on their equivalent diameter, the phosphide particles were classified into three categories: 0.5-1 μm, 1-2 μm, and over 2 μm.

[0051] Machinability was evaluated by drilling tests in the final state. The drilling tests were performed using an instrumented drill head. The drilling tests were conducted using the following parameters. • Twist drill, 5mm diameter • Rotational speed: 3200 U / min Feed rate 0.04mm / U Each sample was drilled five times, using a new drill for each sample. • Drilling depth: 10mm

[0052] Drilling was performed along the forming direction. Torque and normal force acting on the drill bit were measured. Unannealed alloy CuZn39Pb3 was used as a reference. The torque measured for each sample was standardized by relating the torque measured for the reference alloy to the torque measured for each sample. That is, the smaller the torque calculated for one sample, the larger the standardized torque for that sample. Similarly, the normal force measured for each sample was also standardized. Standardized Torque M norm and the standardized normal force F N norm The arithmetic mean of these two values ​​was calculated. Samples in which the arithmetic mean calculated in this way was less than 0.75 did not meet the prerequisites for good machinability.

[0053] Chip shapes were classified according to the publication "Richtwerte fur die spanende Bearbeitung von Kupfer und Kupferlegierungen (Standard Values ​​for Machining of Copper and Copper Alloys)" (Informationsdruck i.18) issued by the German Copper Society. Based on this, chips were evaluated as good (2), average (1), or bad (0). In this case, long, zigzag chips (Faltspane) in particular received an unfavorable evaluation.

[0054] The standardized torque and normal force calculated in the test, and the arithmetic mean calculated from them (at the top of the table (M+F N The values ​​indicated as ) / 2 are listed in Tables 1-8 along with the chip shape and characteristic values ​​from tensile tests and hardness measurements.

[0055] [Table 1]

[0056] [Table 2]

[0057] [Table 3]

[0058] [Table 4]

[0059] [Table 5]

[0060] [Table 6]

[0061] [Table 7]

[0062] [Table 8]

[0063] Samples No. 1 to No. 9 (Tables 1 and 2) are unannealed samples based on the present invention. The volume fraction of the β phase is at least 33% and at most 46%. The α grain size is a maximum of 24 μm for rolled samples and a maximum of 35 μm for pressed samples. The small α grain size of sample No. 5 is thought to be due to the alloying element Fe. The hardness is at least 160 HV10, and the tensile strength Rm is at least 520 MPa. The elongation at break is at least 10%. The conductivity is at least 12.7 MS / m for all samples and at least 13.0 MS / m for most samples. In the case of sample No. 9, the conductivity is greater than 15.5 MS / m. The standardized torque is in the range of 0.85 to 1.08. The standardized normal force is in the range of 0.45 to 0.7. The arithmetic mean of the standardized torque and standardized normal force is always at least 0.75. The chip shape was consistently evaluated as good (2) or average (1).

[0064] Samples No. 10 to No. 23 (Tables 3 and 4) are comparative samples in their unannealed state. Reference sample No. 10 contains 3.3 wt% lead and exhibits very good machinability. Sample No. 11 also exhibits good machinability and contains 2.0 wt% lead. Samples No. 12 and No. 16 contain no lead or other alloying elements, and therefore exhibit very poor machinability.

[0065] Samples No. 13 and No. 17 contain 0.27% by weight of Si in addition to Cu and Zn. Although the force acting on the drill is within an acceptable range, the chip shape is poor, which is thought to be due to a lack of phosphide particles acting as a chip breaker. In sample No. 14, the proportions of Cu and Si are increased compared to sample No. 13. The force acting on the drill is outside an acceptable range, and the chip shape is poor. Furthermore, the conductivity is also low.

[0066] In sample No. 15, the Si content was slightly increased compared to sample No. 14, and 0.1 wt% of P was added. Consequently, the force acting on the drill decreased, and the chip shape improved somewhat. However, the elongation at break and conductivity were low. Compared to sample No. 1, sample No. 15 has a similar P content and β-phase volume fraction, but shows a higher Si content. The force acting on the drill is similarly good, but the chip shape of sample No. 15 is unfavorable, and the conductivity is poor.

[0067] Sample No. 18 has a different P content of 0.38 wt% compared to Sample No. 17. This mainly leads to a clear improvement in chip shape. However, the elongation at fracture is very small.

[0068] Sample No. 19 contains 0.11% by weight of P in addition to Cu and Zn. While this is advantageous for chip shape, the force acting on the drill is not satisfactory. In Sample No. 22, the proportion of P increased to 0.29% by weight compared to Sample No. 19, resulting in a deterioration of the normal force.

[0069] Sample No. 20 differs from Sample No. 15 primarily in its slightly lower proportion of phosphorus (P). This leads to improved elongation at break. However, due to its high Si content, its conductivity is not at the required level.

[0070] Sample No. 21 contains 0.27 wt% Si and 0.06 wt% P, in addition to 0.22 wt% Sn. Compared to sample No. 2, which does not contain tin, the addition of tin results in a moderate deterioration of the force acting on the drill. Only 0.5–1 μm in diameter were observed for most phosphide particles. Conductivity was not affected at all by the 0.22 wt% Sn.

[0071] Sample No. 23 contains 0.29 wt% Si and 0.30 wt% P. Similar to sample No. 18, the chip shape is good, but the elongation at break, conductivity, and forces acting during drilling are not satisfactory.

[0072] Samples No. 24 to No. 31 (Tables 5 and 6) are annealed samples based on the present invention. Samples No. 26 and No. 27 were annealed at 550°C, and the other samples in Table 3 were annealed at 600°C. The volume fraction of the β phase is at least 31% and at most 49%. The α grain size is in the range of 25 to 40 μm, with samples No. 26 and No. 27 having the smallest grain size. The hardness is at least 160 HV10, and the tensile strength Rm is at least 510 MPa. The elongation at break is at least 11.5%. The conductivity is at least 12.7 MS / m for all samples, and at least 13.0 MS / m for most samples. The standardized torque is in the range of 0.79 to 1.03. The standardized normal force is in the range of 0.56 to 0.71. The arithmetic mean of the standardized torque and standardized normal force was always at least 0.75. The evaluation of the chip shape was always good (2) or average (1). In the case of sample No. 31, which corresponds to unannealed sample No. 21 in terms of composition, annealing was able to achieve a significant improvement in the force acting during drilling and the chip shape. Furthermore, it can be confirmed that annealing shifted the center of gravity of the phosphide particle distribution to larger particles.

[0073] Samples No. 32 to No. 44 (Tables 7 and 8) are comparative samples in the annealed state. Samples No. 32 and No. 33, which contain lead, exhibit good machinability in the annealed state. 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 state.

[0074] Samples No. 35 and No. 36, which contain silicon but not phosphorus and were annealed at 600°C, generated a torque during drilling that was more than twice the torque calculated for reference sample No. 10. Sample No. 36, due to its higher Si content, showed improved chip shape, but reduced conductivity. Sample No. 39, which contains silicon but not phosphorus and was annealed at 550°C, exhibited a more favorable force during drilling than samples No. 35 and No. 36. This is thought to be due to a significantly higher proportion of the β phase. However, the chip shape was poor.

[0075] Sample No. 37, containing 0.58 wt% Si and 0.10 wt% P and annealed at 600°C, exhibits more advantageous properties in drilling than Sample No. 15, even though its composition is the same as Sample No. 15 in its unannealed state. However, due to the higher proportion of Si, its electrical conductivity is insufficient.

[0076] Samples No. 40 and No. 41, which correspond to sample No. 18 or No. 19 in terms of composition and were annealed at 550°C, showed improvement in the force acting on the drill after annealing, and in particular, a clear improvement in ductility was confirmed in sample No. 40. However, sample No. 40 has low conductivity due to its high proportion of Si and P. In the case of sample No. 41, the deficiency of Si cannot be corrected by annealing until the force during drilling reaches an acceptable level.

[0077] Sample No. 42, with a Si content of 0.55 wt% and a P content of 0.075 wt%, has excessively low conductivity due to its high Si content.

[0078] Samples No. 43 and No. 44 correspond to the unannealed samples No. 22 and No. 23 in terms of composition, but annealing at 600°C resulted in a clear improvement in ductility. Sample No. 43 still does not have satisfactory machinability even after annealing. In sample No. 44, the combination of 0.3 wt% P and 0.29 wt% Si resulted in low electrical conductivity.

[0079] Samples No. 1 to No. 44 demonstrate that alloys with favorable property combinations can be produced by appropriately selecting the elements Si and P. Si reduces the force acting on the drill, thereby improving machinability. However, when the Si content exceeds 0.32 wt%, the conductivity decreases. A P content of 0.05 to 0.2 wt% is favorable for chip shape. Higher P content, in combination with Si, leads to deterioration of ductility and conductivity. Alloys with favorable combinations of these properties can be produced without annealing. In particular, annealing at 550°C to 600°C allows for improvement of machinability in a considerable number of element combinations by appropriately setting the β phase content and phosphide particles afterward.

[0080] Alloys with the aforementioned composition can also be used as casting alloys for cast parts.

Claims

1. A copper-zinc forging alloy for manufacturing wire-shaped, tubular, or rod-shaped semi-finished products, having the following composition in weight percent, namely: Cu: 58.0 to 63.0%, Si: 0.04-0.32%, P: 0.05-0.20%, Sn: Optional, up to 0.25% Al: 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: each can be set to a maximum of 0.10%. Bi: Maximum 0.009%, The remainder consists of Zn and unavoidable impurities. The proportion of the aforementioned unavoidable impurities is less than 0.2% by weight. The ratio of the weight fractions of P and Al is at least 1.

0. The alloy has a structure consisting of spherical α-phase, β-phase, and phosphide particles, and the proportion of the β-phase to the sum of the α-phase and β-phase is at least 20% by volume and at most 70% by volume. Si is present in both the α phase and the β phase. 21,000 μm ２ A copper-zinc forging alloy in which the surface area contains 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 up to 30 phosphide particles with an equivalent diameter greater than 2 μm.

2. The copper-zinc forging alloy according to claim 1, characterized in that the Pb content is at least 0.02% by weight.

3. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the proportion of P is at most 0.15% by weight.

4. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the P / Fe ratio is at least 1.

0.

5. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the proportion of Fe is less than 0.10% by weight and the proportion of Ni is at most 0.07% by weight.

6. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the proportion of Si is at least 0.23% by weight.

7. The copper-zinc forging alloy according to claim 1, characterized in that the proportion of Si is at most 0.15% by weight.

8. The copper-zinc forging alloy according to claim 7, characterized in that the proportion of P is at most 0.10% by weight.

9. The copper-zinc forging alloy according to claim 7 or 8, characterized in that the proportion of Cu is at most 59.5% by weight.

10. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the proportions of the elements Cu, Zn, Si, P, and Pb total at least 99.75% by weight.

11. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the alloy has a hardness of at least 120 HV10, preferably at least 150 HV10.

12. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the alloy has a tensile strength Rm of at least 500 MPa, preferably at least 530 MPa.

13. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the alloy has an electrical conductivity of at least 12.5 MS / m.

14. A wire-shaped, tubular, or rod-shaped semi-finished product made of the copper-zinc forging alloy according to claim 1 or 2.

15. A component manufactured from a semi-finished product as described in claim 14 by machining and any further processing steps.

16. A method for manufacturing a wire-shaped, tubular, or rod-shaped semi-finished product according to claim 14, comprising the following steps, namely: a) A step of melting a copper alloy having the composition described in claim 1, b) A process of continuously casting a tubular or bolt-shaped casting format using a water-cooled mold, c) A process of hot forging 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 at a temperature range of 525 to 625°C for 1 to 5 hours, followed by cooling at a temperature range of 500 to 350°C at a cooling rate of 20 to 40°C per minute. e) Optionally, a cold forming process, A method that includes this.

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