EP0586197A2 - Gut zerspannbare bleifreie und Kupfer enthaltende schmiedbare Legierungen - Google Patents

Gut zerspannbare bleifreie und Kupfer enthaltende schmiedbare Legierungen Download PDF

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Publication number
EP0586197A2
EP0586197A2 EP93306792A EP93306792A EP0586197A2 EP 0586197 A2 EP0586197 A2 EP 0586197A2 EP 93306792 A EP93306792 A EP 93306792A EP 93306792 A EP93306792 A EP 93306792A EP 0586197 A2 EP0586197 A2 EP 0586197A2
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Prior art keywords
lead
phase
composition
fabrication
maximum
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EP93306792A
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English (en)
French (fr)
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EP0586197A3 (de
Inventor
John Travis Plewes
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AT&T Corp
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American Telephone and Telegraph Co Inc
AT&T Corp
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Publication of EP0586197A2 publication Critical patent/EP0586197A2/de
Publication of EP0586197A3 publication Critical patent/EP0586197A3/de
Withdrawn legal-status Critical Current

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    • 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
    • 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

Definitions

  • the invention relates to copper-containing, lead-free alloys which retain the properties associated with the prototypical lead-containing "forging brasses" and/or "architectural bronzes". Of particular importance, alloys of the invention evidence the freedom from embrittlement sufficient to permit hot working at the low pressures characteristic of the prototype materials.
  • compositions for serving various uses are based on long experience, and are set forth, for example, in C opper D evelopment A ssociation Handbook, 8th ed., Part 2-Alloy Data (1985).
  • Bismuth an element next to lead in the periodic table, shares many of the properties of lead, and does impart machinability to copper-containing alloys. See, Copper , A. Butts, ed., p. 704 (1954). Significantly, a variety of studies lead to the conclusion that bismuth shares none of the toxicity problems of lead. Consultation with EPA indicates that bismuth, in amounts likely encountered, is no problem in drinking water, nor generally in inhalation or ingestion. Bismuth has not been found to have any harmful effect on the human nervous system, or on health in general. In fact, a common indigestion remedy contains bismuth as a major ingredient.
  • the invention is directed to retention of hot working properties of lead-free, two-phase copper-containing alloys including the "forging brasses" and "architectural bronzes". Included compositions may be substituted for lead-containing materials without altering processing conditions - most importantly without constraint on hot rolling or other contemplated hot working.
  • alloys of the invention depend for workability only upon phosphorus and/or indium inclusion together with lead-replacing bismuth. Required concentrations of the third elements, phosphorus and indium are quite small. Further, qualities resulting in needed machinability are often attained with lower bismuth content - perhaps half that of lead. Accordingly, desired characteristics are attained at reasonable cost. The same cost consideration leads to a pronounced preference for phosphorus over relatively expensive indium.
  • Required ingredients are typically: 0.5-2.0 Bi together with as little as 0.1 P, 0.25 In or appropriate lesser amounts of both if included in combination.
  • the inventive teaching relies on avoidance of the now-observed bismuth-associated embrittlement - on attainment of noted hot working characteristics - and, accordingly, description as well as claims are in terms of processing requiring such characteristics. These characteristics are, in the following description, referred to as “forging” characteristics.
  • a class of alloy compositions of concern are variously designated, as “forging brasses” or “architectural bronzes”.
  • Use of the term, "forging” has reference to hot working properties as retained in accordance with the inventive teaching, and is not to be considered limiting with respect to alloys, however designated, which otherwise meet stated compositional and workability properties.
  • FIG. 1 A first figure.
  • This figure is a plot on coordinates of temperature and composition in terms of weight percent zinc as based on the binary alloy of copper and zinc (without regard either to lead in the prototypical material or to bismuth plus third element addition in the lead-free material). Plotted lines constitute the conventional phase diagram, e.g. as shown in Constitution of Binary Alloys , M. Hansen, p. 650 (1958).
  • the consequential portion of the phase diagram is that showing: the single-phase, ⁇ -phase, copper-rich material, in region 1, to the left of phase boundary 2-3; the single-phase, ⁇ -phase - material in region 4 on the zinc-rich side of phase boundary 5-6, and the two-phase - ⁇ + ⁇ -phase - material in region 7 as bounded by boundaries 2-3 and 5-6.
  • the three blocked regions 8, 9 and 10 designate those compositions, which, for the leaded materials, are the regions of primary consequence with regard to the invention. These three regions identify the ⁇ + ⁇ , two-phase regions of CDA-designated leaded compositions 360, 377 and 385, respectively (corresponding in that order with regions 8, 9, 10).
  • composition regions in which lead is replaced by bismuth plus third element addition, identify, as well, primary regions of consequence in the present context. Variation to result in selection of compositions outside these regions is, at least initially, unlikely if only by reason of familiarity with the working properties of the prototypical compositions.
  • the blocked regions are nominal in that they both encompass minor areas corresponding with single-phase composition not meeting the inventive requirements and exclude minor areas of two-phase composition meeting the inventive requirements.
  • compositional range of consequence - that defining equilibrium two-phase structure over the designated 600-825°C - is that encompassed within broken line 11.
  • the broken line traces the portion of the composition shown as bounded by isothermal lines at 600°C and 825°C, and by phase boundaries 2-3 and 5-6.
  • K factor values are meaningful only for the explicit type of working contemplated. Accordingly, while K values accurately define comparative pressures for explicit working as well as working conditions and measurement techniques, they are in no sense fundamental. Iso-pressure lines 20 through 27 represent mean deformation resistance K values in Newton's per square millimeter quantifying force required for forging. Plotted data, while measured on leaded prototypical material (see, Extrusion , K. Lane and H.
  • Stenger p. 169, ISBN 0-87170-094-8, A.S.M., Metals Park, Ohio
  • the plotted data is included for showing the relative hot working ease realized for two-phase materials. It also shows reduction in needed force for increasing temperature.
  • the invention is directed to retention of properties associated with the two-phase system - with the ⁇ + ⁇ brasses.
  • Properties of particular consequence are concerned with "hot workability" - for purposes of the invention, largely workability within the temperature range of 600-825°C.
  • the temperature relationship of such properties is well-known.
  • workability of the two-phase materials is facilitated for higher temperatures, however, at the expense of loss of workability at lower temperatures.
  • Cold workability is impaired - e.g. usage entailing substantial cold rolling is prohibited.
  • hot workability is improved to the extent that the extrusion of which single-phase material is capable is permitted at substantially decreased pressures for the two-phase materials.
  • An ⁇ + ⁇ brass chosen for use not requiring low temperature working, e.g. cold ductility may permit a given degree of extrusion at a given temperature with a pressure substantially less than that required for another composition which is ⁇ .
  • Figure 1 depicts compositional and temperature ranges of particular consequence with regard to hot working. Ranges corresponding with the CDA-designated 377 and 385 lead-containing alloys, for temperatures of consequence, are clearly within the two-phase range. These compositions may be extruded to much greater extrusion ratios than the ⁇ brasses for given pressure. A measure of the relative pressures required is given by the alloy's "K" factor which is defined as the equilibrium constant which relates pressure to deformation - in the instance of extrusion to relate pressure to extrusion ratio.
  • K factors for the two-phase brasses are generally no more than half that for single-phase materials of the same composition (e.g. for 360 brasses of such composition as to be two-phase only above a specific temperature). On the other hand, for a given hot working temperature, it is seen that K factor is dependent solely on composition.
  • the improved workability for the two-phase materials, as with corresponding lead-containing materials, may serve in attainment of a desired extrusion ratio at decreased pressure, with consequent saving in equipment and/or processing cost.
  • FIG. 2 on coordinates of temperature and composition includes iso-pressure (K-factor) lines - each showing needed temperature and composition for attainment of the indicated pressures (K factors). It is clear from this figure, that at any given temperature, T, the K factor drops rapidly as the zinc content is increased above about 37% (K factor drops as a continuum immediately before, at, and after the onset of the ⁇ -phase boundary).
  • extrusion K values are of the same form as that of the iso-pressure lines for forging as shown on FIG. 2, explicit pressure values will differ.
  • compositions addressed by the invention include these CDA-designated 360 brasses, as worked at temperatures at which the two phases are in equilibrium.
  • Contemplated materials are all ⁇ + ⁇ brasses at working temperatures specified. At such elevated temperatures, generally within the 600-825°C range, materials attain their equilibrium (two-phase) state essentially instantaneously. Hot working characteristics of consequence correspond with two-phase materials containing at least five volume percent ⁇ -phase, the remainder essentially ⁇ -phase.
  • compositions contemplated by the invention correspond with compositions included within the far larger classes of lead-containing materials within the CDA-designated 360, 377 and 385 brass/bronze classes as set forth in the CDA Handbook of Wrought Products, eighth edition, 1985, published by Copper Development Association Inc., Greenwich, Conn. Compositional considerations are largely identical as regards copper/zinc ratio. While bismuth may replace lead on a one-to-one basis, as noted, there is experimental evidence which suggests that this replacement element may be somewhat more effective so that desired machinability may be attained with lesser amounts - perhaps 50% of corresponding lead content. Third element additions, of far lesser content, are: phosphorus - 0.1-0.5 and/or indium - 0.25-1.0 (or in appropriately reduced amounts).
  • Precise compositions in terms of copper and zinc content, are those depicted on FIG. 1. While all inclusive, they may contain tolerable contaminants in accordance with art-accepted practice, as well as additional elements intended to serve specific purposes perhaps unrelated to the thrust of the invention. (Such additional elements whether intentional or merely tolerable are not likely to total as much as 5%.)
  • compositions are best specified in terms of FIG. 1, they may be set forth as: Cu 54-64, Bi 0.5-3, P 0.1-0.5 or In 0.25-1, remainder Zn (or appropriate lesser amounts of P and In if both are included). Narrowing of the indicated range is in accordance with hot working temperature with the constraint that all included materials include at least 5 vol.% of ⁇ -phase at such temperature.
  • compositions as so defined were found to satisfy inventive requirements on the basis of test procedures described.
  • compositional ranges define bismuth-containing compositions having machining as well as forging characteristics similar to those of the corresponding lead-containing compositions.
  • Compositions of the invention like the corresponding lead-containing compositions, evidence a machinability of 40% or greater in accordance with usual criteria.
  • machinability is expressed as a percentage relative to the prototypical CDA series lead-containing C360 alloy. This percentage is referred to as "machinability index”.
  • Workability sufficient for intended purposes also varies, but all compositions on which claims are based, permit 5:1 extrusion ratio, or more generally, reduction of some dimension by a minimum of 50% for any form of hot working - e.g. by forging or rolling, as well as by extrusion. Pressures in all instances are those associated - as good or better than - hot working characteristics of the prototypical compositions within the noted range of 600-825°C.
  • compositional ranges are in terms of the inventive advance, one aspect of which, simply stated, permits attainment of copper-containing forging alloy characteristics while replacing lead with a combination of bismuth together with one or both of the third element additions.
  • Experimental results demonstrate bismuth to be more effective than lead in terms of consequent machinability. While composition ranges are as expressed, bismuth inclusion is characteristically less than that of replaced lead for equivalent properties - experimental results suggest that about 50% as much bismuth imparts the same machinability.
  • the inventive contribution translates into a large variety of compositions which often contain elements designed to serve functions unrelated to the inventive thrust - unrelated to machinability or workability. In accordance with the generic inventive teaching, all such alloys containing such additional elements may be rendered lead-free while continuing to serve intended functions with little or no change in processing.
  • All alloys within the inventive scope are classified as two-phase alloys - as " ⁇ + ⁇ " alloys - at the working temperature.
  • Associated properties - in particular forging properties - depend upon this two-phase nature.
  • Contemplated substitution for lead has little effect on the two-phase nature of the alloy, which is primarily dependent upon the binary, copper-lead composition and on processing conditions. Specification of the latter, since essentially unchanged by the inventive substitution, is outside the scope of this description.
  • materials satisfying the inventive requirements must be two-phase within the specified composition/temperature range of working. Not all materials are two-phase within the entirety of the composition or temperature range considered alone, and to the extent they are single-phase - to the extent they are not two-phase at some temperature or composition - they are excluded.
  • the relative hot workability for these alloys was measured by hot upsetting billets, 0.75" diam. x 1" height, to 75% thickness reduction in a 60 ton press.
  • the billets were preheated in air for one hour at temperature, were rapidly transferred to the press, and were reduced in height from 1" to 0.25" (i.e. to result in 75% thickness reduction) at a strain rate of 0.15"/sec. All samples were worked at temperatures within the 600-825°C range.
  • the degree of hot workability was determined by comparing the relative degree of edge cracking observed in the experimental alloys with respect to that observed in CDA 377 leaded forging brass tested under the same conditions.
  • CDA 377 alloys are generally recognized as exhibiting good hot working characteristics - considered exemplary as among the leaded two-phase brasses for forging.
  • compositions of the invention are characterized as manifesting a machinability index of at least 40%. This level, corresponding with lower bismuth substitutions within the specified ranges, is expressed as a percentage relative to CDA 360.
  • Oxygen-free high conductivity copper was melted under a controlled atmosphere - under argon at a pressure of 1 atmosphere. Once molten, appropriate quantity of zinc was added, and after five minutes of homogenization at a temperature of ⁇ 1050°C bismuth and third element addition were introduced. Dissolution was essentially immediate at the melt temperature of ⁇ 1050°C. Molten alloy was poured into a 0.75 inch diameter split steel mold, and castings were air cooled. "OFHC" copper, standard in the industry, is ⁇ 99.99% pure, and while unnecessary for most purposes implicit in this teaching was employed consistent with good experimental procedure.
  • a Cu-41%, Zn-2%, Bi alloy (no third element addition) was melted as previously described and poured into a 0.75 inch split steel mold.
  • a sample of commercial CDA 377, the related leaded composition was melted as above and was cast in the same or an identical mold.
  • the castings were sectioned into one inch length (or height) billets. Billets were heated to a variety of temperatures in the 600-825°C range, were held at such temperature for one hour in air, and were hot upset in a 60 ton press at 0.15 inch/sec to a final thickness (height) of 0.25 inch. The outside diameter was unconstrained during forging.
  • the leaded CDA 377 alloy exhibited good hot workability up to 750°C - minimal edge cracking was observed. At temperatures in excess of 775°C, edge tearing and hot shortness was evident.
  • the Cu-41,Zn-2Bi alloy exhibited significant edge tearing (up to 1/4 inch in depth) over the entire temperature range. While the degree of edge tearing lessened as the temperature was reduced, even at the lowest temperature tested, (625°C) only moderate hot workability was observed.
  • Example 1 The unleaded composition of Example 1 but with third element addition - explicitly an alloy of composition Cu-41%,1Zn-2%Bi-0.15%P was melted and poured into a 0.75 inch diameter split steel mold.
  • a sample of commercial CDA 377 was melted as above and cast into the same dimensioned mold.
  • the castings were sectioned into one inch length billets, billets were heated to a variety of temperatures spaced at 50°C intervals within the temperature range of 625-825°C, and were held at temperature for one hour in air. Billets were hot upset as in Example 1 to a final thickness of 0.25 inch.
  • the Cu-41,Zn-2,Bi-0.15P alloy exhibited hot workability at least equivalent to that of the leaded alloy for samples worked over the entirety of the temperature range. At temperatures below 675 and above 775°C, the experimental alloys were clearly superior to CDA 377 in their hot workability.
  • An 800 lb. melt of Cu-1.8%Bi-0.14%P-39%Zn alloy was prepared from scrap charge. The melt was cast in a six inch diameter steel mold and the casting was air cooled. The casting was sectioned into ten inch length billets which were satisfactorily extruded over a temperature range of 680-825°C. Extrusion ratios of 36-150/1 were achieved. Optimum extrusion temperatures appeared to be in the region of 700-750°C. A variety of strain rates within the 0.5-5 inch/sec range were explored. The alloy did not appear to be strain rate sensitive within this temperature regime.

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  • Chemical & Material Sciences (AREA)
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EP19930306792 1992-09-01 1993-08-26 Gut zerspannbare bleifreie und Kupfer enthaltende schmiedbare Legierungen Withdrawn EP0586197A3 (de)

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US93880992A 1992-09-01 1992-09-01
US938809 1992-09-01

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EP0586197A3 EP0586197A3 (de) 1994-05-18

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITUA20163561A1 (it) * 2016-05-18 2017-11-18 Almag Spa Metodo per la realizzazione di una billetta di ottone senza piombo o a basso contenuto di piombo e billetta così ottenuta

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3485502B2 (ja) * 1999-08-24 2004-01-13 日立アロイ株式会社 無鉛快削性銅合金材
JP2003277855A (ja) * 2002-03-22 2003-10-02 San-Etsu Metals Co Ltd 無鉛快削黄銅合金材及びその製造方法
WO2014155692A1 (ja) * 2013-03-29 2014-10-02 株式会社栗本鐵工所 水道部材用黄銅合金

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE848708C (de) * 1944-02-11 1952-09-08 Wieland Werke Ag Verwendung von Kupfer-Zink-Legierungen fuer auf Gleitung beanspruchte Maschinenteile
EP0457478A1 (de) * 1990-05-15 1991-11-21 AT&T Corp. Gut zerspanbare bleifreie Knetlegierungen auf Kupferbasis
US5137685A (en) * 1991-03-01 1992-08-11 Olin Corporation Machinable copper alloys having reduced lead content

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE848708C (de) * 1944-02-11 1952-09-08 Wieland Werke Ag Verwendung von Kupfer-Zink-Legierungen fuer auf Gleitung beanspruchte Maschinenteile
EP0457478A1 (de) * 1990-05-15 1991-11-21 AT&T Corp. Gut zerspanbare bleifreie Knetlegierungen auf Kupferbasis
US5137685A (en) * 1991-03-01 1992-08-11 Olin Corporation Machinable copper alloys having reduced lead content
US5137685B1 (en) * 1991-03-01 1995-09-26 Olin Corp Machinable copper alloys having reduced lead content

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
'CDA Handbook of Wrought Products, 8th edition' 1985 , COPPER DEVELOPMENT ASSOCIATION INC. , GREENWICH, CONN. *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITUA20163561A1 (it) * 2016-05-18 2017-11-18 Almag Spa Metodo per la realizzazione di una billetta di ottone senza piombo o a basso contenuto di piombo e billetta così ottenuta

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MX9305206A (es) 1994-05-31
JPH06200340A (ja) 1994-07-19
EP0586197A3 (de) 1994-05-18

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