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 the form of wire, tube, or rod, having the following composition by weight: Cu: 58.0-66.0%, Si: 0.15-1.2%, P: 0.20-0.38%, Sn: optionally up to 0.5%, Al: optionally up to 0.05%, Fe: optionally up to 0.3%, Ni: optionally up to 0.3%, Pb: optionally up to 0.25%, Bi: optionally up to 0.1%, Te, Se, and In: optionally up to 0.1%, each up to 0.01%, B: optionally up to 0.01%, with the balance being Zn and unavoidable impurities, the proportion of which is less than 0.20% by weight. 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 60% by volume. Si is present in both the α-phase and the β-phase. In an area of 21000 μm2, there are 50 to 700 phosphide particles with an equivalent diameter of 0.5 to 1 μm, 10 to 300 phosphide particles with an equivalent diameter of 1 to 2 μm, and 3 to 45 phosphide particles with an equivalent diameter of 2 to 5 μm. The proportions of beta phase and Si, P, and Pb were selected so that the alloy satisfied the following condition: 107.378 - 2.25255·[Beta] - 64.1438·[Si] - 115.18·[P] - 30.7071·[Pb] + 0.017965·[Beta]·[Beta] + 24.6217·[Si]·[Si] + 66.7257·[P]·[P] + 0.542512·[Beta]·[Si] + 1.36208·[Beta]·[P] + 43.4012·[Si]·[P] < 37, where [Beta] is the proportion of beta phase in volume percent, [Si] is the proportion of silicon in weight percent, [P] is the proportion of phosphorus in weight percent, and [Pb] is the proportion of lead in weight percent.

Description

Technical Field

[0001] The present invention relates to an alloy for copper-zinc forging for manufacturing wire-shaped, tube-shaped, or rod-shaped semi-finished products, a semi-finished product made of the 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] Copper-zinc alloys containing 3 to 5% by weight of lead are excellent in machinability and are also 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, connectors and components in communications, and also as joints for plumbing facilities.

[0003] The positive action 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, making 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 rod-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 are set at an upper limit of 1000 ppm (0.1%) Pb in EU directives such as RoHS (Directive 2011 / 65 / EU). Various alloying elements are proposed as lead substitutes to ensure good machinability of materials even at such low lead content levels.

[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 undesirable 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 the alloy, 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 leads to a material that is easily machinable in this case. However, a maximum P content of 0.19 wt% is too low to achieve the grain refinement effect on the microstructure that lead provides. [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 forging alloy for producing wire-shaped, tube-shaped, or rod-shaped semi-finished products, which has excellent machinability and good mechanical properties and contains alloy components with environmental concerns as little as possible. Furthermore, this alloy must be easily processable on an industrial scale. This requires that the 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 produced 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 producing wire-shaped, tube-shaped, or rod-shaped semi-finished products 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: 58.0~66.0%, Si: 0.15~1.2%, P:0.20~0.38%、 Sn: Optional, up to 0.5% Al: Optional, up to 0.05% Fe: up to 0.3% (optional) Ni: Optional, up to 0.3% Pb: Optional, up to 0.25% Bi: Optional, up to 0.1% Te, Se, In: Each can be set to a maximum of 0.1%. B: Optional, up to 0.01% The remainder consists of Zn and unavoidable impurities. The proportion of the aforementioned unavoidable impurities is less than 0.20% by weight. 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 60% by volume. Si is present in both the α phase and the β phase. 21000 μm 2 The area contains 50 to 700 phosphide particles with an equivalent diameter of 0.5 to 1 μm, 10 to 300 phosphide particles with an equivalent diameter of 1 to 2 μm, and 3 to 45 phosphide particles with an equivalent diameter of 2 to 5 μm. The proportion of the β phase and the proportions of Si, P, and Pb are such that the alloy meets the following conditions, namely, 107.378-2.25255·[Beta]-64.1438·[Si]-115.18·[P]-30.7071·[Pb]+0.017965·[Beta]·[Beta]+24.62 17·[Si]·[Si]+66.7257·[P]·[P]+0.542512·[Beta]·[Si]+1.36208·[Beta]·[P]+43.4012·[Si]·[P]<37 The following conditions are met: [Beta] represents the proportion of the β phase in volume percent, [Si] represents the proportion of silicon in weight percent, [P] represents the proportion of phosphorus in weight percent, and [Pb] represents the proportion of lead in weight percent. 。

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: 58.0~66.0%, Si: 0.15~1.2%, P:0.20~0.38%、 Sn: Optionally up to 0.5%, preferably up to 0.3%. Al: Optional, up to 0.05% Fe: up to 0.3% (optional) Ni: Optional, up to 0.3% Pb: Optionally up to 0.25%, preferably up to 0.10%. Bi: Optional, up to 0.1% Te, Se, In: Each can be set to a maximum of 0.1%. B: Optional, up to 0.01% The remainder consists of Zn and unavoidable impurities. The proportion of unavoidable impurities is less than 0.2% by weight. This alloy has a structure consisting of spherical α-phase, β-phase, and phosphide particles. The phosphide particles preferably contain copper and / or zinc-containing phosphides, or are copper and / or zinc-containing phosphides. 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 22% by volume, at most 60% by volume, and preferably at most 40% by volume. Silicon is present in both the α-phase and the β-phase. 21000 μm 2 The area contains 50 to 700 phosphide particles with an equivalent diameter of 0.5 to 1 μm, 10 to 300 phosphide particles with an equivalent diameter of 1 to 2 μm, and 3 to 45 phosphide particles with an equivalent diameter of 2 to 5 μm. The proportion of the β phase and the proportions of Si, P, and Pb are such that this alloy meets the following conditions, namely, 107.378-2.25255·[Beta]-64.1438·[Si]-115.18·[P]-30.7071·[Pb]+0.017965·[Beta]·[Beta]+24.62 17·[Si]·[Si]+66.7257·[P]·[P]+0.542512·[Beta]·[Si]+1.36208·[Beta]·[P]+43.4012·[Si]·[P]<37 The following conditions are met: [Beta] represents the proportion of the β phase in volume%, [Si] represents the proportion of silicon in weight%, [P] represents the proportion of phosphorus in weight%, and [Pb] represents the proportion of lead in weight%.

[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, favorable machinability is produced, 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 produced.

[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 shown that as the P content increases, a clear grain refinement occurs in the cast microstructure of the original basic matrix consisting of the β-phase. To achieve sufficient grain refinement in the cast microstructure and the subsequent formed microstructure, it is necessary to add at least 0.20 wt% of P. This is similar to the effect of 2-3 wt% of Pb on grain refinement in α-β brass. During the primary crystallization of the β-crystal, P accumulates in the residual molten material, 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 microstructure by P facilitates hot forming and continues in the microstructure after hot forming, resulting in grain refinement in the final state. When the proportion of P is at least 0.20 wt%, phosphide particles are present in both the α and β phases in the final state. Preferably, this alloy contains at least 0.22 wt% P. At P content exceeding 0.38 wt%, coarse phosphides are formed in the cast state as individual phosphides solidify to form long, network-like structures. These coarse phosphides wet the grain boundaries and melt during hot forming, causing cracks in the material. In addition, ductility is reduced.

[0014] However, if the cooling rate during alloy casting is too low, for example in casting with a fixed mold (Standkokille), this type of undesirable effect can occur even if the phosphorus content is less than 0.38 wt%. The necessary high cooling rate can be achieved, for example, by continuous casting with a water-cooled mold. In this way, when the phosphorus content is 0.20 to 0.38 wt%, the phosphide particles are already spherical in the cast state and are finely dispersed within the microstructure. Such cast products can then be successfully hot forged at temperatures of 620 to 700°C, preferably 630 to 680°C, without cracking of the material.

[0015] Furthermore, for the spherical α-phase to be formed, controlled cooling of the material after hot forming is necessary. Within the temperature range of 550°C to 350°C, the cooling rate must be at least 30°C / min, preferably at least 40°C / min, at most 60°C / min, and preferably at most 50°C / min. 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. Thus, the characteristic distribution of phosphides in the casting state is ultimately reflected in the final microstructure. 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 process control during casting and hot forming. Thus, the characteristics of the phosphides in the final state are like a fingerprint left on the product by specific process control. The dispersion of phosphides in the final state can be characterized as follows: 21000 μm 2 The area contains 50 to 700 phosphide particles with an equivalent diameter of 0.5 to 1 μm, 10 to 300 phosphide particles with an equivalent diameter of 1 to 2 μm, and 3 to 45 phosphide particles with an equivalent diameter of 2 to 5 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 80%. Furthermore, it is advantageous if at least 40%, preferably at least 60%, 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 or with an equivalent diameter larger than 5 μm in the alloy is not ruled out. In this case, the number of phosphide particles with an equivalent diameter larger than 5 μm is at most 30%, preferably at most 15%, of the number of phosphide particles with an equivalent diameter of 2 to 5 μm.

[0016] Brittle microstructure components that act as separation points during machining, thereby assisting chip breaking, are advantageous for the machinability of the alloy. 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, as well as by finely dispersed phosphides in the α phase. Therefore, the Si content in the alloy must be at least 0.15 wt%. The aforementioned phosphide particles act as separation points during machining, becoming particles that are advantageous for chip breaking. If the P content is less than 0.20 wt%, unfavorable chips are produced and the grains become coarser. Furthermore, any low Pb content is advantageous for machinability.

[0017] Therefore, the machinability of the alloy is determined by the selection of a combination of parameters: β phase, Si, P, and optionally a small amount of Pb. In the proposed copper-zinc forging alloy, the proportion of the β phase to the sum of the α and β phases is at least 20 vol%, preferably at least 22 vol%. A high proportion of the β phase is detrimental to cold forming. Therefore, the proportion of the β phase is at most 60 vol%, preferably at most 40 vol%. The Si content of the alloy is 0.15 to 1.2 wt%, and the P content is 0.20 to 0.38 wt%. Furthermore, up to 0.25 wt% of Pb, preferably up to 0.10 wt% of Pb, can also be added. In this case, the proportion of the β phase and the proportions of Si, P, and Pb are such that this alloy meets the following conditions, namely: 107.378-2.25255·[Beta]-64.1438·[Si]-115.18·[P]-30.7071·[Pb]+0.017965·[Beta]·[Beta]+24.62 17·[Si]·[Si]+66.7257·[P]·[P]+0.542512·[Beta]·[Si]+1.36208·[Beta]·[P]+43.4012·[Si]·[P]<37 The alloy is selected to satisfy the following conditions: Here, [Beta] represents the proportion of the β phase in volume percent, [Si] represents the proportion of silicon in weight percent, [P] represents the proportion of phosphorus in weight percent, and [Pb] represents the proportion of lead in weight percent. This relationship quantitatively describes the influence of the β phase, Si, P, and Pb parameters on the machinability of the alloy, as well as the interaction of these parameters. For example, if the proportion of the β phase is small, this can be corrected by increasing the proportion of silicon and / or phosphorus in the alloy composition specification, and vice versa.

[0018] The copper content of the alloy is between 58.0 and 66.0% by weight. If the copper content is less than 58.0% by weight, the ductility of the alloy is too low. If the copper content is more than 66.0% by weight, the zinc content of the alloy is too low to achieve good machinability.

[0019] Furthermore, the alloy composition can be selected such that the Si / P ratio is preferably at least 0.6, and particularly preferably at least 0.9. In a further preferred embodiment, the alloy composition can be selected such that the total Si and P is at least 0.58% by weight, and particularly preferably at least 0.64% by weight. The two measures described above, either independently or in combination, contribute to satisfying the aforementioned ratios and thus contribute to achieving favorable machinability properties.

[0020] Any elements, Sn and Al, support the formation of the β phase. If the proportion of Sn exceeds 0.5% by weight, a further tin-containing phase may form, potentially adversely affecting the properties of the alloy. Preferably, the proportion of tin should be at most 0.3% by weight, and particularly preferably at most 0.2% by weight. Furthermore, aluminum, along with phosphorus, forms aluminum phosphides. However, these are undesirable, so the proportion of Al should not exceed 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 0.3% by weight, and particularly preferably at most 0.1% by weight.

[0022] Nickel supports the formation of the α phase. Furthermore, nickel forms phosphides, but this does not have a favorable effect on machinability. Therefore, the proportion of nickel should be at most 0.3% by weight, and particularly preferably at most 0.1% 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. At a maximum amount of 0.1% by weight, Bi does not adversely affect the alloy. Therefore, a maximum of 0.1% by weight of Bi is acceptable in this alloy. Preferably, the proportion of Bi is less than 0.015% by weight.

[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] Bor, in any arbitrary proportion up to 0.01% by weight, contributes to grain refinement.

[0026] 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 0.05% by weight, because these elements can form phosphides that can compete with copper-containing and / or zinc-containing phosphides.

[0027] 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.

[0028] Advantageously, the ratio of the weight fraction of P to the total weight fraction of Fe and Ni can be greater than 2.0, i.e., P / (Fe+Ni) > 2.0. This results in the formation of mainly copper-containing and / or zinc-containing phosphides, which are advantageous for machinability. The formation of iron phosphides or nickel phosphides is suppressed.

[0029] In particular, it may be advantageous that the combined proportion of Fe and Ni is at most 0.1% by weight. This restriction also suppresses the formation of iron phosphides and nickel phosphides compared to the formation of copper-containing and / or zinc-containing phosphides.

[0030] In a particularly advantageous embodiment of the present invention, the proportion of P can be at least 0.26% by weight and at most 0.33% by weight. When the proportion of P is at least 0.26% by weight, a sufficient number of phosphide particles are formed, thereby achieving particularly fine grains, spherical α-phase, and very good machinability. When the proportion of P in the alloy is at most 0.33% by weight, crack formation during hot forming is more reliably avoided.

[0031] In a further embodiment of the present invention, the Si content can be at most 0.35% by weight. Copper-zinc forging alloys with a relatively low Si content are characterized by high conductivity, that is, the conductivity is at least 12 MS / m.

[0032] In a further embodiment of the present invention, the Si content can be at least 0.25% by weight, preferably at least 0.30% by weight. This achieves good surface quality and very good machinability at the same time.

[0033] In particular, in the embodiments described above, the proportion of Cu can be at least 60.0 wt% and at most 61.5 wt%. Alloys with particularly advantageous properties can be obtained with a composition of 60.0-61.5 wt% copper, 0.25-0.35 wt% Si, 0.26-0.33 wt% P, and the remainder being Zn and unavoidable impurities.

[0034] In an alternative embodiment of the present invention, the Si content can be at least 0.50% by weight and at most 1.0% by weight. Copper-zinc forging alloys having a Si content within this range are characterized by excellent machinability while maintaining good ductility.

[0035] Advantageously, the copper-zinc alloy for forging can have a hardness of at least 170 HV10, preferably at least 180 HV10.

[0036] Advantageously, the copper-zinc forging alloy can have a tensile strength Rm of at least 520 MPa, preferably at least 560 MPa.

[0037] Advantageously, the copper-zinc forging alloy can have an α grain size of at most 21 μm, preferably at most 17 μm.

[0038] Advantageously, copper-zinc alloys for forging can have a conductivity of at least 12 MS / m.

[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 heat treatment conditions in combination with defined cooling after heat treatment, a favorable ratio of α-phase to β-phase and a favorable particle distribution of phosphides containing copper and / or zinc can be set. To increase the proportion of β-phase, heat treatment at approximately 600°C is required. To increase the proportion of α-phase, heat treatment at approximately 550°C is required. Thus, the ratio of α-phase to β-phase and the particle distribution of phosphides can be adjusted and optimized by heat treatment. In particular, this can improve ductility. After heat treatment, the pickling and cold forming steps can be 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. 45 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. 16 is a lead-containing reference alloy CuZn39Pb3. The sample was machined, homogenized at 650°C for 1 hour, and then hot-formed. The cooling rate after hot-forming was approximately 40°C per minute in the temperature range of 550 to 350°C.

[0048] Samples No. 1 to No. 26 were hot-formed, then machined, and subsequently cold-formed to a 20% degree of formability. Samples No. 27 to No. 45 were hot-formed for 3 hours and then annealed. The annealing temperature was approximately 600°C for samples No. 28 and No. 35 to No. 41, and approximately 550°C for samples No. 27, No. 29 to No. 34, and No. 42 to No. 45. After annealing, the samples were cooled at a cooling rate of approximately 25°C per minute in a temperature range of 500 to 350°C. Subsequently, samples No. 27 to No. 45 were machined, and then cold-formed to a 20% degree of formability.

[0049] In the final state, the tensile strength Rm and elongation at break, hardness (Vickers hardness HV10), and conductivity 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 categories of 0.5-1 μm, 1-2 μm, 2-5 μm, and over 5 μm (if present).

[0050] Machinability was determined by planing tests. Here, a contoured throwaway insert favorable for chip breaking was used. The cutting depth was 125 μm, and the planing speed was 35 m / min. During the planing process, the bending moment acting on the tool was measured, and the average bending moment was determined. The corresponding chips were optically evaluated and classified according to their shape. Chip shapes were assigned chip shape numbers according to the following list.

[0051] [Table 1]

[0052] Chip shape number 1 corresponds to the lead-containing reference alloy CuZn39Pb3 (sample No. 16).

[0053] The test results are recorded in Tables 2-9. Unannealed samples No. 1-15 (Tables 2 and 3) and annealed samples No. 27-34 (Tables 4 and 5) are samples based on the present invention. Unannealed samples No. 16-26 (Tables 6 and 7) and annealed samples No. 35-45 (Tables 8 and 9) are comparative samples and are marked with (*).

[0054] The machinability of the samples was evaluated using the bending moment and chip shape calculated during planing. Chips with an average bending moment of 36 Nm or less and chip shape numbers corresponding to 1 or 1.25 were evaluated as highly favorable.

[0055] Furthermore, we attempted to parameterize the measured average bending moment as a function of the volume fraction of the β phase and the weight fractions of Si, P, and Pb. The resulting functional relationship can be shown as follows.

[0056] f=107.378-2.25255 [Beta]-64.1438 [Si]-115.18 [P]-30.7071 [Pb]+0.017965 [Beta] [Beta]+24 .6217·[Si]·[Si]+66.7257·[P]·[P]+0.542512·[Beta]·[Si]+1.36208·[Beta]·[P]+43.4012·[Si]·[P] Here, f is an approximate quantification of the measured bending moment in Nm, [Beta] represents the proportion of the β phase in volume percent, [Si] represents the proportion of silicon in weight percent, [P] represents the proportion of phosphorus in weight percent, and [Pb] represents the proportion of lead in weight percent. The value of f calculated according to this formula is recorded in the last column of Tables 1-4. Comparing this value f with the measured bending moment, the two magnitudes are in very good agreement. Samples No. 1-15 and No. 27-34 based on the present invention are characterized in that all measured bending moments are less than 36 Nm and the value of f is less than 37.

[0057] [Table 2]

[0058] [Table 3]

[0059] [Table 4]

[0060] [Table 5]

[0061] [Table 6]

[0062] [Table 7]

[0063] [Table 8]

[0064] [Table 9]

[0065] Samples No. 1 to No. 15 (Tables 2 and 3) are unannealed samples based on the present invention. The volume fraction of the β phase is at least 20% and at most 38%. The α grain size is a maximum of 15 μm. The hardness is at least 180 HV10, and the tensile strength Rm is at least 560 MPa. The elongation at break is at least 4.7%. The measured bending moment is a maximum of 35.7 Nm. The chip shape in all samples corresponds to chip shape number 1 or 1.25.

[0066] Samples No. 16 to No. 26 (Tables 4 and 5) are comparative samples in their unannealed state. Reference sample No. 16 contains 3.3% by weight of lead and exhibits very good machinability. Sample No. 17 contains no lead or other alloying elements, and therefore exhibits very poor machinability.

[0067] Sample No. 18 contains only 0.27 wt% Si in addition to Cu and Zn. While the bending moment is good, the poor chip shape is thought to be due to a lack of phosphide particles acting as chip breakers. The same can be observed in sample No. 21, which contains 0.53 wt% Si. Samples No. 19, 20, and 22 contain 0.05 to 0.1 wt% phosphorus, which has a favorable effect on chip shape and, at least in samples No. 19 and No. 22, also has a favorable effect on the bending moment. However, in samples No. 19 and 20, the hardness and tensile strength Rm are clearly lower than those of samples No. 1 to No. 15. Sample No. 22, with a Si content of 0.58 wt%, shows only a slight improvement in hardness and tensile strength. Furthermore, samples No. 18 to No. 22, with a particle size of 19 to 25 μm, have a clearly larger α-grain size than samples No. 1 to 15. Larger α-grains are disadvantageous in terms of straightness and dimensional stability.

[0068] Silicon-free samples No. 23 and No. 24, with P content of 0.24% and 0.29% by weight, were found to exhibit excellent chip shape, but the bending moment was at a high level. Samples No. 25 and No. 26, with P content of 0.65% by weight, respectively, showed excellent machinability. However, due to the high P content, these samples tended to crack during hot forming. Furthermore, this resulted in low elongation at break at room temperature. A high P content is reflected in a large number of phosphide particles with an equivalent diameter of 2-5 μm. Therefore, if the alloy has more than 45 phosphide particles with an equivalent diameter of 2-5 μm in an area of ​​21,000 μm², the hot formability deteriorates, and the material behavior at room temperature becomes brittle.

[0069] These samples demonstrate that silicon contributes to a reduction in bending moment, while phosphorus is favorable for chip breaking. Overall, the combination of the two elements results in good machinability and leads to a small α-grain size.

[0070] Samples No. 27 to No. 34 (Tables 6 and 7) are samples based on the present invention in an annealed state. The volume fraction of the β phase is at least 22% and at most 39%. In sample No. 28, the α grain size is 21 μm. This is thought to be due to the annealing temperature of 600°C. In the other samples annealed at 550°C, the α grain size is a maximum of 16 μm. Compared to samples No. 1 to No. 15, samples No. 27 to No. 34 have a slightly lower hardness of at least 170 HV10 and a slightly lower tensile strength Rm of at least 520 HV10. Conversely, the elongation at break was improved by annealing. As a result, the ductile material state can be adjusted. The bending moment and chip shape range from very good to excellent.

[0071] Samples No. 35 to No. 45 (Tables 8 and 9) are comparative samples in annealed state. Samples No. 35 and No. 38, which contain silicon but not phosphorus, are characterized by undesirable high bending moment and poor chip shape. Samples No. 36, 37, and 39, which have a low proportion of P, have clearly improved machinability compared to samples No. 19, 20, and 22, but their hardness and tensile strength are not sufficient. Furthermore, samples No. 25 to No. 39, with grain sizes of 31 to 39 μm, have a significantly larger α-grain size than samples No. 1 to 15. Larger α-grain sizes are disadvantageous in terms of straightness and dimensional stability.

[0072] Samples No. 40 and No. 41, which contain phosphorus but not silicon, exhibit very good chip shape, but their bending moment is at an undesirably high level. Annealed samples No. 42, 43, and 44, which are compositionally identical to unannealed samples No. 3, 4, and 5, have higher bending moments and worse chip shape than the unannealed variations. Annealing reduced the volume fraction of the β phase to below 20%, and the distribution of phosphide particles shifted to larger particles. These two effects together lead to a deterioration in machinability. Sample No. 45, with a P content of 0.65 wt%, is characterized by a high bending moment. This is due to the extremely low β phase content of only 9 volume percent. Furthermore, this sample has a very high density of phosphides with an equivalent diameter of 2-5 μm.

[0073] 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 66.0%, Si: 0.15-1.2%, P: 0.20-0.38%, Sn: Optional, up to 0.5% Al: Optional, up to 0.05% Fe: Optional, up to 0.3% Ni: Optional, up to 0.3% Pb: Optional, up to 0.25% Bi: Optional, up to 0.1% Te, Se, In: each can be set to a maximum of 0.1%. B: Optional, up to 0.01% The remainder consists of Zn and unavoidable impurities. The proportion of the aforementioned unavoidable impurities is less than 0.20% by weight. 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 60% by volume. Si is present in both the α phase and the β phase. 21,000 μm ２ The area contains 50 to 700 phosphide particles with an equivalent diameter of 0.5 to 1 μm, 10 to 300 phosphide particles with an equivalent diameter of 1 to 2 μm, and 3 to 45 phosphide particles with an equivalent diameter of 2 to 5 μm. The proportion of the β phase and the proportions of Si, P, and Pb are such that the alloy meets the following conditions, namely, 107.378-2.25255・[Beta]-64.1438・[Si]-115.18・[P]-30.7071・[Pb]+0.017965・[Beta]・[Beta]+24.62 17・[Si]・[Si]+66.7257・[P]・[P]+0.542512・[Beta]・[Si]+1.36208・[Beta]・[P]+43.4012・[Si]・[P]<37 A copper-zinc forging alloy selected to satisfy the following conditions, where [Beta] represents the proportion of the β phase in volume percent, [Si] represents the proportion of silicon in weight percent, [P] represents the proportion of phosphorus in weight percent, and [Pb] represents the proportion of lead in weight percent.

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 ratio of the weight fraction of P to the total weight fraction of Fe and Ni is greater than 2.

0.

4. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the proportion of Fe and Ni is at most 0.1% by weight in total.

5. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the proportion of P is at least 0.26% by weight and at most 0.33% by weight.

6. The copper-zinc forging alloy according to claim 1, characterized in that the proportion of Si is at most 0.35% by weight.

7. The copper-zinc forging alloy according to claim 1, characterized in that the proportion of Si is at least 0.25% by weight.

8. The copper-zinc forging alloy according to claim 6 or 7, characterized in that the proportion of Cu is at least 60.0% by weight and at most 61.5% by weight.

9. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the proportion of Si is at least 0.50% by weight and at most 1.0% by weight.

10. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the alloy has a hardness of at least 170 HV10.

11. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the alloy has a tensile strength Rm of at least 520 MPa.

12. The copper-zinc forging alloy according to claim 1 or 2, characterized in that the alloy has an α grain size of at most 21 μm.

13. The copper-zinc forging alloy according to claim 6 or 7, characterized in that the alloy has an electrical conductivity of at least 12 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) 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) Optional cold forming process A method that includes this.

Images