Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper
  • C22C9/04—Alloys based on copper with zinc as the next major constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
  • B22D11/004—Copper alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
  • B22D11/049—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds for direct chill casting, e.g. electromagnetic casting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/02—Casting exceedingly oxidisable non-ferrous metals, e.g. in inert atmosphere
  • B22D21/025—Casting heavy metals with high melting point, i.e. 1000 - 1600 degrees C, e.g. Co 1490 degrees C, Ni 1450 degrees C, Mn 1240 degrees C, Cu 1083 degrees C
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon

Definitions

• the invention relates to a wrought copper-zinc alloy for production of a semifinished product in wire, pipe or bar form, to a semifinished product produced from a wrought copper-zinc alloy, and to a process for production of such a semifinished product.
• a wrought copper-zinc alloy generally means a wrought material composed of a copper-zinc alloy.
• Copper-zinc alloys with 3% to 5% by weight of lead have excellent machinability and additionally very good hot and cold formability.
• Lead-containing copper-zinc alloys are therefore used in a multitude of applications, for example for connections and components in the automotive industry, in building technology, in mechanical engineering, in electrical appliances and in electronic components, in telecommunications and as fittings in water installations.
• lead in elemental form as particles in the microstructure, and these particles act as chip breakers.
• lead In the course of machining, lead is in the form of a liquid phase as a result of the significant local deformation in the workpiece and the resultant local increase in temperature. Since the lead is not able to absorb stresses in the liquid state, this leads to a concentration of stress in the load-bearing, weakened matrix and hence to easier chip breakage.
• lead is also incorporated into the tribological layer between material and workpiece in the course of machining and hence leads to effective lubrication and hence to a reduction in friction and wear. Moreover, because of its low solubility, lead barely makes any contribution to electrical conductivity.
• document EP 2 194 150 B1 discloses copper-zinc alloys containing 0.1% to 1.5% by weight of Si, 0.03% to 0.4% by weight of Al, 0.01% to 0.36% by weight of P, 0.05% to 0.5% by weight of Sn, and 0.001% to 0.05% by weight of rare earths.
• the alloys Owing to the formation of an ⁇ , ⁇ and possibly ⁇ microstructure, the alloys have good machinability.
• the Al content results in formation of Al phosphides, which are unwanted.
• the ⁇ phase and aluminum phosphides improve chip formation, they worsen the service life of the tool.
• the proportion of rare earths is likely to lead to embrittlement of the microstructure.
• the alloys are used for castings and hot pressings.
• the invention relates to a wrought copper-zinc alloy for production of a semifinished product in wire, tube or bar form, having the following composition in % by weight:
• the invention proceeds from the consideration of reducing the proportions of Pb in the copper-zinc alloy as far as possible without worsening the machinability of the alloy.
• Si and P are specifically added to the alloy, and the proportion of the ⁇ phase is adjusted so as to give favorable machining properties on the one hand, and on the other hand not to worsen the hot and cold formability of the alloy, and such that the semifinished product produced from the alloy has excellent straightness.
• the process regime, especially in the casting and hot forming operations, is chosen so as to result in the desired properties.
• a globular ⁇ phase is a prerequisite for good straightness and trueness to scale of the semifinished product.
• ⁇ phase forms from the ⁇ phase after hot forming. Therefore, the ⁇ phase must be in fine-grain form in the cast state.
• P content distinct grain refining of the cast microstructure of the original base matrix composed of ⁇ phase occurs.
• the addition of at least 0.20% by weight of P is necessary. This is similar to the effect of 2% to 3% by weight of Pb on the grain refining of ⁇ - ⁇ -brass.
• the residual melt becomes enriched with P and hence leads to a subdivision of the ⁇ phase.
• Solidification forms a eutectic composed of phosphide and ⁇ phase.
• grain refining of the a crystallites is observed.
• This grain refining of the cast microstructure by P facilitates hot forming, continues into the microstructure after hot forming, and consequently leads to grain refining in the final state.
• phosphide particles are present both in the ⁇ phase and in the B phase in the final state.
• the alloy preferably contains at least 0.22% by weight of P.
• coarse phosphides are formed in the cast state in that individual phosphites coagulate and form long network-like forms. These coarse phosphides wet the grain boundaries, melt during hot forming and lead to cracks in the material. In addition, ductility is reduced.
• the cooling rate has to be at least 30° C. per minute (° C./min), preferably at least 40° C. per minute, and at most 60° C. per minute, preferably at most 50° C. per minute.
• the uniformly finely distributed phosphides that accompany a fine-grain ⁇ phase in the cast state dissolve in the matrix during the hot forming and then reform during the cooling operation in the course of hot forming. In this way, the characteristic distribution of the phosphides in the cast state is ultimately mapped onto the microstructure in the final state.
• the distribution of the phosphides in the final state and the globular form of the a phase are therefore determined not only by the chemical composition of the alloy but also by the process regime in the casting and in the hot forming.
• the characteristics of the phosphides in the final state are thus like a fingerprint left on the product by the particular process regime.
• the distribution of the phosphides in the final state can be characterized as follows: In an area of 21 000 ⁇ m 2 , there are 50 to 700 phosphide particles having an equivalent diameter of 0.5 to 1 ⁇ m, 10 to 300 phosphide particles having an equivalent diameter of 1 to 2 ⁇ m, and 3 to 45 phosphide particles having an equivalent diameter of 2 to 5 ⁇ m.
• the equivalent diameter of a phosphide particle means the diameter of a circle of equal area to the phosphide particle.
• the predominant portion of the phosphide particles having an equivalent diameter of at least 0.5 ⁇ m has an equivalent diameter of not more than 2 ⁇ m.
• the proportion of the phosphide particles having an equivalent diameter of 0.5 ⁇ m to 2 ⁇ m is preferably at least 70% of the number of all phosphide particles having an equivalent diameter of at least 0.5 ⁇ m. This proportion is more preferably at least 80%.
• phosphides having an equivalent diameter of less than 0.5 ⁇ m or more than 5 ⁇ m will be present in the alloy.
• the number of phosphide particles having an equivalent diameter of more than 5 ⁇ m is at most 30%, preferably at least 15%, of the number of phosphide particles having an equivalent diameter of 2 to 5 ⁇ m.
• Brittle microstructure constituents are advantageous for machinability of the alloy that act as separation sites in the machining operation and hence promote chip breaking.
• the ⁇ phase is brittle and promotes machinability.
• An increase in the proportion of ⁇ phase can be achieved by an increase in the Zn content and/or by inclusion of silicon in the alloy, since silicon stabilizes the ⁇ phase.
• the above-described phosphide particles are particles that act as separation sites on machining and promote chip breaking. A P content of less than 0.20% by weight leads to unfavorable chips and relatively coarse grains. In addition, a small optional fraction of Pb has an advantageous effect on machinability.
• the machinability of the alloy is consequently determined by the combined selection of the parameters of ⁇ phase, Si and P, and an optionally present small proportion of Pb.
• the proportion of the ⁇ phase in the sum total of ⁇ phase and ⁇ phase is at least 20% by volume, preferably at least 22% by volume.
• a high proportion of the ⁇ phase has an adverse effect on cold formability. Therefore, the proportion of the ⁇ phase is not more than 60% by volume, preferably not more than 40% by volume.
• the Si content of the alloy is 0.15% to 1.2% by weight, the P content 0.20% to 0.38% by weight.
• the proportion of the ⁇ phase and the proportions of Si, P and Pb are chosen such that the alloy meets the condition
• [beta] denotes the proportion of the ⁇ phase in % by volume
• [Si] the proportion of silicon in % by weight
• [P] the proportion of phosphorus in % by weight
• [Pb] the proportion of lead in % by weight.
• the Cu content of the alloy is 58.0% to 66.0% by weight. In the case of a Cu content of less than 58.0% by weight, ductility of the alloy is too low. In the case of a Cu content of more than 66.0%, the zinc content in the alloy is too small to achieve good machinability.
• the composition of the alloy may preferably be chosen such that the Si/P ratio is at least 0.6, more preferably at least 0.9. In a further preferred embodiment, the composition of the alloy may be chosen such that the sum total of Si and P is at least 0.58% by weight, more preferably at least 0.64% by weight. Both the aforementioned measures contribute both independently and in combination to fulfilment of the above-described relations and hence to achievement of favorable machining properties.
• the optional Sn and Al elements promote formation of the B phase.
• further tin-containing phases may form, which can have an adverse effect on the properties of the alloy.
• the proportion of tin should preferably be not more than 0.3% by weight, more preferably not more than 0.2% by weight.
• aluminum forms aluminum phosphides with phosphorus. However, these are unwanted, and therefore the Al content should not exceed 0.05% by weight.
• Nickel promotes the formation of the ⁇ phase. Moreover, nickel forms phosphides, which do not have an advantageous effect on machinability. Therefore, the proportion of nickel must be not more than 0.3% by weight, preferably not more than 0.1% by weight.
• the element Bi is present as an impurity in secondary raw materials, for example scrap. It is capable of improving the machinability of the alloy. In amounts of not more than 0.1% by weight, Bi has no adverse effect on the alloy. Therefore, up to 0.1% by weight of Bi in the alloy is tolerated. Preferably, the proportion of Bi is less than 0.015% by weight.
• Te, Se and In can have an advantageous effect on the machinability of the alloy. In amounts of not more than 0.1% by weight each, they have no adverse effect on the alloy. Therefore, up to 0.1% by weight each of Te, Se and In in the alloy is tolerated.
• An optional proportion of up to 0.01% by weight of boron contributes to grain refining.
• the balance of the alloy composition consists of zinc and unavoidable impurities.
• the proportion of these impurities is not more than 0.2% by weight.
• the proportions of Mn and Mg should each be not more than 0.1% by weight, more preferably each not more than 0.05% by weight, because these elements can form phosphides that can compete with the copper-and/or zinc-containing phosphides.
• the Pb content in the alloy may be at least 0.02% by weight. Even such a small proportion of Pb improves the machining properties and has a positive effect on grain refining.
• the ratio of the proportions by weight of P and the sum total of Fe and Ni may be more than 2.0, i.e. P/(Fe+Ni)>2.0. This achieves the effect that predominantly the copper- and/or zinc-containing phosphides that are favorable for machining properties are formed. The formation of iron phosphides or nickel phosphides is suppressed.
• the proportions of Fe and Ni add up to not more than 0.1% by weight. This restriction also inhibits the formation of iron phosphides and nickel phosphides compared to the formation of the copper- and/or zinc-containing phosphides.
• the P content may be at least 0.26% by weight and at most 0.33% by weight. If the P content is at least 0.26% by weight, a sufficiently large amount of phosphide particles is formed, in order to achieve a particularly fine grain, a globular ⁇ phase and very good machinability. If the P content in the alloy is not more than 0.33% by weight, it is highly likely that cracking will be avoided on hot forming.
• the Si content may be at most 0.35% by weight.
• a wrought copper-zinc alloy having this relatively low Si content is notable for high electrical conductivity. The electrical conductivity is then at least 12 MS/m.
• the Si content may be at least 0.25% by weight, preferably at least 0.30% by weight. This achieves very good machinability with simultaneously good surface quality.
• the Cu content may be at least 60.0% by weight and at most 61.5% by weight.
• An alloy having particularly advantageous properties is obtained with the following composition: Cu 60.0% to 61.5% by weight, Si 0.25% to 0.35% by weight and P 0.26% to 0.33% by weight, balance: Zn and unavoidable impurities.
• the Si content may be at least 0.50% by weight and at most 1.0% by weight.
• a wrought copper-zinc alloy having a Si content within this range is notable for excellent machine properties coupled with good ductility.
• the wrought copper-tin alloy may have a hardness of at least 170 HV10, preferably at least 180 HV10.
• the wrought copper-tin alloy may have a tensile strength R m of at least 520 MPa, preferably at least 560 MPa.
• the wrought copper-tin alloy may have an ⁇ grain size of at most 21 ⁇ m, preferably at most 17 ⁇ m.
• the wrought copper-zinc alloy may have an electrical conductivity of at least 12 MS/m.
• the invention further provides a semifinished product in wire, pipe or bar form, made from an above-described wrought copper-zinc alloy, and a component produced from such a semifinished product by machining and optional further processing steps.
• the semifinished product may also take the form of a profile.
• a further aspect of the invention relates to a method of producing a semifinished product in wire, pipe or bar form.
• the process comprises the following steps:
• the alloy can be melted using Cu cathodes, Zn blocks, brass scrap, Cu—P prealloys and Cu—Si prealloys.
• the melting is preferably effected in an induction kiln.
• the melt is cast in a water-cooled mold to a tubular or bolt-shaped cast format.
• the cast format may optionally be milled and is then hot-pressed at a temperature of 620 to 700° C. Subsequently, the hot-pressed intermediate product is cooled, where the cooling is effected within the temperature range from 550 to 350° C. at a cooling rate of 30 to 60° C. per minute, preferably 40 to 50° C. per minute.
• the defined cooling establishes a favorable ratio of the proportions of ⁇ phase and ⁇ phase, and a favorable particle distribution of copper- and/or zinc-containing phosphides.
• the hot pressing operation may optionally be preceded by a heat treatment for homogenization of the cast product.
• the hot pressing operation may be followed, without further intermediate steps, by pickling and then a cold forming operation.
• the degree of forming is preferably between 3% and 30%. What is meant here by degree of forming is the relative decrease in the cross-sectional area of the product. Because there are no further steps between the hot pressing and cold forming operations except for the pickling operation, this first production process is very favorable.
• the hot pressing operation is followed by a heat treatment between 525 and 625° C., preferably between 550 and 600°° C., for a period of 1 to 5 hours, with subsequent cooling at a cooling rate of 20 to 40° C. per minute within a temperature range from 500 to 350° C.
• a heat treatment between 525 and 625° C., preferably between 550 and 600°° C., for a period of 1 to 5 hours, with subsequent cooling at a cooling rate of 20 to 40° C. per minute within a temperature range from 500 to 350° C.
• the heat treatment should be effected at about 550° C.
• the heat treatment may be followed by the steps of pickling and cold forming, as in the first production process.
• Samples No. 1 to No. 45 were melted in an induction kiln and then cast.
• the composition of the samples is documented in tables 1 to 4.
• Sample No. 16 represents the lead-containing reference alloy CuZn39Pb3.
• the samples were milled, homogenized at 650° C. for 1 hour and then hot-formed. In the cooling that follows after the hot forming, the cooling rate within the temperature range between 550 and 350° C. was about 40° C. per minute.
• tensile strength R m and elongation at break were each determined from the tensile test, as were hardness (Vickers hardness HV10) and electrical conductivity.
• the longitudinal sections of the samples were examined by light microscopy.
• the area proportions of the ⁇ phase and of the ⁇ phase corresponding to the proportions by volume, and the ⁇ grain size were determined therefrom.
• the light microscope images of the unetched samples were used for quantitative determination of the size distribution of the phosphide particles. Image details of dimensions 167 ⁇ m ⁇ 126 ⁇ m (corresponding to an area of 21 000 ⁇ m 2 ) were chosen, and these were evaluated in 1000-fold magnification by means of the ImageJ software.
• the phosphide particles were classified by their equivalent diameter into the categories of 0.5 to 1 ⁇ m, 1 to 2 ⁇ m, 2 to 5 ⁇ m and—if present—greater than 5 ⁇ m.
• Machinability was determined by means of a plane test. This was done using an insert with a contour that promotes chip breaking. The machining depth was 125 ⁇ m and the plane speed 35 m/min. During the planing operation, the bending moment that acts on the tool was measured, and this was used to determine the average bending moment. The resultant chips were visually assessed and categorised by chip form. The chip form was assigned a chip form number according to the following list:
• Chip form number Chip form 0 torn chips, helical chips 0.5 coiled chips with 1 to 2 turns 0.75 coiled chips with an arc that forms an angle of 270° to 360° 1 coiled chips with an arc that forms an angle of 180° to 270° 1.25 coiled chips with an arc that forms an angle of less than 180°
• Chip form number 1 corresponds to the lead-containing reference alloy CuZn39Pb3 (sample No. 16).
• the results of the studies are documented in tables 1 to 4.
• the unannealed samples No. 1 to No. 15 (table 1) and the annealed samples No. 27 to 34 (table 3) are inventive samples.
• the unannealed samples No. 16 to No. 26 (table 2) and the annealed samples No. 35 to 45 (table 4) are comparative samples and are identified by (*).
• Machinability of the samples was assessed using the bending moment ascertained in the planing and the shape of the chips.
• An average bending moment of not more than 36 Nm and chips that correspond to chip form number 1 or 1.25 were considered to be very favorable.
• Samples No. 1 to No. 15 are inventive samples in the unannealed state.
• the proportion by volume of the ⁇ phase is at least 20% and at most 38%.
• ⁇ grain size is not more than 15 ⁇ m.
• Hardness is at least 180 HV10, and tensile strength R m at least 560 MPa.
• Elongation at break is at least 4.7%.
• the measured bending moment is not more than 35.7 Nm.
• the form of the chips for all samples corresponds to chip form number 1 or 1.25.
• Samples No. 16 to No. 26 are comparative samples in the unannealed state.
• the reference sample No. 16 contains 3.3% by weight of lead and shows very good machining properties.
• Sample No. 17 shows that machining properties are very poor without lead and without further alloy elements.
• the bending moment is good, but the chip form is poor, which can be attributed to the absence of phosphide particles as chip breakers.
• the same finding is made for sample No. 21, containing 0.53% by weight of Si.
• Samples No. 19, 20 and 22 have 0.05% to 0.1% by weight of phosphorus, which has a favourable effect on chip form and, at least in the case of sample No. 19 and in the case of sample No. 22, on bending moment as well.
• hardness and tensile strength R m are well below the values for samples No. 1 to No. 15.
• samples No. 18 to No. 22 having an Si content of 0.58% by weight shows only slightly improved hardness and tensile strength.
• samples No. 18 to No. 22 show a much greater ⁇ grain size at 19 to 25 ⁇ m than samples No. 1 to No. 15.
• the coarser ⁇ grain leads to drawbacks in terms of straightness and trueness to scale.
• the high P content is reflected in a large number of phosphide particles having an equivalent diameter of 2 to 5 ⁇ m. It is thus a sign of poor hot formability and additionally of brittle material characteristics at room temperature if the alloy, in an area of 21 000 ⁇ m 2 , has more than 45 phosphide particles having an equivalent diameter of 2 to 5 ⁇ m.
• Samples No. 27 to No. 34 are inventive samples in the annealed state.
• the proportion by volume of the B phase is at least 22% and at most 39%.
• ⁇ grain size is 21 ⁇ m. This can be attributed to the annealing temperature of 600° C.
• ⁇ grain size is not more than 16 ⁇ m.
• samples No. 27 to No. 34 have a somewhat lower hardness of at least 170 HV10 and a somewhat lower tensile strength R m of at least 520 HV10.
• annealing improved elongation at break. Consequently, a more ductile material state can be established. Bending moment and chip form are very good to excellent.
• Samples No. 35 to No. 45 are comparative samples in the annealed state.
• the silicon-containing but phosphorus-free samples No. 35 and No. 38 are characterized by an unfavorably high bending moment and poor chip form.
• Samples No. 36, 37 and 39 having a small P content have a distinct improvement in machine properties compared to samples No. 19, 20 and 22, but hardness and tensile strength are unsatisfactory.
• samples No. 25 to No. 39 show a much greater ⁇ grain size at 31 to 39 ⁇ m than samples No. 1 to No. 15. The coarser ⁇ grain leads to drawbacks in terms of straightness and trueness to scale.
• the phosphorus-containing but silicon-free samples No. 40 and 41 give a very good chip form, but bending moment is an unfavorably high-level.
• the annealed samples No. 42, 43 and 44 which correspond to the unannealed samples No. 3, 4 and 5 in terms of composition, show a higher bending moment and poorer chip form than the unannealed variants.
• the annealing reduced the proportion by volume of the ⁇ phase to values below 20% and shifted the distribution of the phosphide particles toward coarser particles. These two effects together lead to a deterioration in machining properties.
• Sample No. 45 having a P content of 0.65% by weight is characterized by a high bending moment. This is caused by a very small proportion of ⁇ phase of only 9% by volume.
• the sample has a very high density of phosphides having an equivalent diameter of 2 to 5 ⁇ m.
• Alloys having an above-described composition can also be used as casting alloys for castings.

Landscapes

• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Materials Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Conductive Materials (AREA)
• Powder Metallurgy (AREA)
• Silicon Compounds (AREA)
• Mold Materials And Core Materials (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=87561125

Family Applications (2)

Family Applications After (1)

Country Status (10)

Families Citing this family (2)

Family Cites Families (10)

• 2022
  • 2022-08-11 DE DE102022002928.6A patent/DE102022002928B4/de active Active
• 2023
  • 2023-05-23 TW TW112119139A patent/TW202407110A/zh unknown
  • 2023-07-20 KR KR1020247043467A patent/KR20250047661A/ko active Pending
  • 2023-07-20 JP JP2025504576A patent/JP2025527197A/ja active Pending
  • 2023-07-20 US US19/102,478 patent/US20260028701A1/en active Pending
  • 2023-07-20 CN CN202380055677.2A patent/CN119630824A/zh active Pending
  • 2023-07-20 WO PCT/EP2023/000048 patent/WO2024032923A1/de not_active Ceased
  • 2023-07-20 EP EP23751540.8A patent/EP4569146A1/de active Pending
  • 2023-07-20 CA CA3261021A patent/CA3261021A1/en active Pending
  • 2023-08-02 US US19/101,410 patent/US20260028700A1/en active Pending
  • 2023-08-02 JP JP2025504575A patent/JP2025527196A/ja active Pending
  • 2023-08-02 CA CA3261007A patent/CA3261007A1/en active Pending
  • 2023-08-02 WO PCT/EP2023/000052 patent/WO2024032925A1/de not_active Ceased
  • 2023-08-02 CN CN202380055678.7A patent/CN119585454A/zh active Pending
  • 2023-08-02 EP EP23764232.7A patent/EP4569148A1/de active Pending
• 2024
  • 2024-12-17 MX MX2024015898A patent/MX2024015898A/es unknown
  • 2024-12-17 MX MX2024015900A patent/MX2024015900A/es unknown

Also Published As

Similar Documents

Legal Events