US20090220375A1 - Bronze-based alloy of low lead content - Google Patents

Bronze-based alloy of low lead content Download PDF

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US20090220375A1
US20090220375A1 US11/919,997 US91999706A US2009220375A1 US 20090220375 A1 US20090220375 A1 US 20090220375A1 US 91999706 A US91999706 A US 91999706A US 2009220375 A1 US2009220375 A1 US 2009220375A1
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mass
tensile strength
bal
alloy
casting
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Tomoyuki Ozasa
Hisanori Terui
Hidenobu Tameda
Teruhiko Horigome
Kazuhito Kurose
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Kitz Corp
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    • 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
    • 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
    • C22C9/02—Alloys based on copper with tin as the next major constituent

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  • the present invention relates to a bronze-based alloy of low lead content suitable as a material for plumbing instruments, such as valves or joints for water supply, hot water supply or steam emission, pressure instruments, such as cylinders or casings, or structural members and particularly to a bronze-based alloy of low lead content improved in tensile strength at high temperatures and capable of contributing to the soundness of a casting.
  • a bronze casting (JIS H5120 CAC406) is generally excellent in castability, corrosion resistance, machinability and pressure resistance and has numerously been used for plumbing instruments for water supply, hot water supply and steam emission, such as valves, cocks and joints.
  • the bronze casting (CAC406) contains several % of Pb (lead) and contributes particularly to the enhancement of machinability and pressure resistance.
  • Pb lead
  • JP-B HEI 5-63536 discloses a leadless copper alloy substituting Bi for lead to enable the enhancement of cuttability and the prevention of dezincification.
  • Patent Document 2 discloses a leadless bronze to which Sb is added to enable the suppression of the generation of porosities during the course of casting in consequence of the addition of Pb for enhancing the cuttability, thereby achieving the enhancement thereof in mechanical strength.
  • Patent Document 3 discloses a bronze alloy having Se and Bi added thereto to particularly deposit a Zn—Se compound thereon, thereby making the mechanical properties, cuttability and castability thereof substantially identical with those of CAC406.
  • Patent Document 1 JP-B HEI 5-63536
  • Patent Document 2 Japanese Patent No. 2889829
  • leadless copper alloys are produced using recycled materials, such as scraps, or ingots comprising such recycled materials and since these materials contain Pb mixed therein as an unavoidable impurity, even when the casting equipment exclusive for producing leadless copper alloys is used, it is unavoidable that Pb be mixed in the leadless copper alloys. Under the present set of circumstances, therefore, the content of Pb up to 0.25 mass % is allowable (for leadless bronze valves prescribed under JIS B 2011). Thus, the technique of super reduction making the Pb content approximate to zero is impractical from the standpoints of mass-production and manufacturing cost.
  • the present invention has been developed as the result of keep studies made in view of the aforementioned problems and has as its object to first improve the tensile strength of a bronze-base alloy of low lead content at high temperatures, secondly provide a bronze-based alloy of low lead content excellent in mass production while avoiding the adverse effect of lead on human bodies owing to the reduction in the amount of lead and contributing to the promotion of the environmental conservation including recycling and further to secure the soundness of castings.
  • the invention set forth in claim 1 is directed to a bronze-based alloy of low lead content, comprising 2.0 to 6.0 mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % ⁇ P ⁇ 0.6 mass % and the remainder of Cu and unavoidable impurities, whereby the P increases grain boundary strength in the alloy to improve tensile strength thereof at high temperatures.
  • the invention set forth in claim 2 is directed to a bronze-based alloy of low lead, comprising 2.0 to 6.0 mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % ⁇ P ⁇ 0.6 mass %, 0.0 mass % ⁇ Ni ⁇ 3.0 mass % and the remainder of Cu and unavoidable impurities to improve tensile strength thereof at high temperatures and secure soundness of a casting.
  • the invention set forth in claim 3 is directed to a bronze-based alloy of low lead content, comprising 2.0 to 6.0 mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % ⁇ P ⁇ 0.6 mass %, 0.0 mass % ⁇ Se ⁇ 1.3 mass % and the remainder of Cu and unavoidable impurities to improve tensile strength thereof at high temperatures and secure soundness of a casting.
  • the invention set forth in claim 4 is directed to a bronze-based alloy of low lead content, comprising 2.0 to 6.0 mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % ⁇ P ⁇ 0.6 mass %, 0.0 mass % ⁇ Ni ⁇ 3.0 mass %, 0.0 mass % ⁇ Se ⁇ 1.3 mass % and the remainder of Cu and unavoidable impurities to improve tensile strength thereof at high temperatures and secure soundness of a casting.
  • the invention set forth in claim 5 or claim 6 is directed to a bronze-based alloy of low lead content, further comprising 0.005 to 2.0 mass % of Pb to secure a tensile strength of at least 152 MPa at a temperature of 180° C. in an alloy region having a secondary dendrite spacing of 14 ⁇ m or more.
  • the invention set forth in claim 7 is directed to a bronze-based alloy of low lead content used as a material for a valve, water faucet clasp or water meter.
  • the invention of claim 1 it has been made possible to provide a bronze-based alloy of low lead content, improved in tensile strength at high temperatures, contributing to the promotion of the environmental conservation including recycling and excellent from the standpoints of mass-productivity and manufacturing cost.
  • the application of the conventional leadless copper alloys has been limited to implements for the supply of water or hot water having a principal temperature of 100° C. or less in use.
  • the copper alloy of the present invention improved in tensile strength at high temperatures can be developed to appropriate use of the conventional bronze alloys over the general application, with no restriction made on its application, and can enlarge the range of its application as recycled materials and exhibits its effects from the viewpoints of the manufacturing cost, not to mention the environmental conservation.
  • it is preferably applicable to alloys low in cooling velocity during the course of casting, such as sand castings, and optimum for alloys requiring a tensile strength of 152 MPa at a high temperature (about 180° C.).
  • a bronze-based alloy of low lead content suppressing a decrease in tensile strength at high temperatures, contributing to the promotion of the environmental conservation including recycling and excellent from the standpoint of mass-productivity.
  • it contains Ni as a principal component to obtain P—Ni interaction, thereby suppressing the content of P therein, enabling the tensile strength thereof to be 152 MPa at a high temperature (about 180° C.) and obtaining the action of enhancing the tensile strength thereof by means of the Ni using the content of 0 mass % ⁇ P ⁇ 0.6 mass %.
  • the fundamental allowable stress of CAC 406-2 at 200° C.
  • the present invention makes it possible to secure even at high temperatures 152 MPa that is four times the prescribed value. While the excess content of P in a casting has a tendency to lowering the soundness of the casting, the P—Ni interaction enables the tensile strength at high temperatures to be secured even in a small content of P, thereby also securing the soundness of the casting to a satisfactory extent. Thus, it is possible to obtain an alloy suitably usable for a pressure-resistant container, such as a valve.
  • a bronze-based alloy of low lead content containing Se as a principal component, suppressing the content of Bi and exhibiting its tensile strength of 152 MPa at a high temperature (about 180° C.). Since Se is present in the alloy in the form of intermetallic compounds of Se—Zn and Cu—Se, it is effective for securing the tensile strength and soundness of a casting while suppressing the content of Bi. Thus, it is possible to obtain an alloy suitably usable for a pressure-resistant container, such as a valve.
  • the invention of claim 5 it is made possible to provide a bronze-based alloy of low lead content, which can secure an excellent tensile strength even at high temperatures without being affected by the content of Pb.
  • the tensile strength at high temperatures can be secured without being affected by Pb interfused from a furnace and a ladle in the case where the conventional casting equipment for producing CAC406 is used concurrently for the mass-production of the alloys of the present invention and without being affected by Pb interfused as an unavoidable impurity in the case where the alloys of the present invention are produced using recycled materials, such as scraps or ingots comprising such scraps.
  • FIG. 1 It is a graph showing the relationship between the content of P of the copper alloy of the present invention and the tensile strength thereof at 180° C.
  • FIG. 2 It is a schematic view of a dendrite.
  • FIG. 3 It is a micrograph showing the typical microstructure of CAC406.
  • FIG. 4 It is an explanatory view showing the measurement method for secondary dendrite arm spacing.
  • FIG. 5 It is a graph showing the relationship between the secondary dendrite spacing of alloys and the tensile strengths thereof at normal room temperature.
  • FIG. 6 It is a graph showing the relationship between the secondary dendrite spacing of alloys and the tensile strengths thereof at 180° C.
  • FIG. 7 It is a photograph showing the cut surface of a barrel part of a small valve (a general-purpose gate valve of leadless bronze having a nominal pressure of 10 K and a nominal diameter of 1 ⁇ 2).
  • FIG. 8 It is a photograph showing the cut surface of the barrel part in FIG. 7 that has been subjected to etching treatment with nitric acid.
  • FIG. 9 It is a graph showing the relationship between the content of Pb of the alloys and the tensile strength thereof at 180° C.
  • FIG. 10 It is a graph showing the relationship between the content of Ni of the copper alloy of the present invention and the tensile strength thereof at 180° C.
  • FIG. 11 It is a graph showing the relationship between the contents of Ni and P of the copper alloys of the present invention and the tensile strengths thereof at 180° C.
  • FIG. 12 It is a graph showing the influence of the Sb content on a leadless copper alloy.
  • FIG. 13 It is an explanatory view showing a casting method scheme for stepwise cast test pieces.
  • FIG. 14 It is an explanatory view showing the surface observed in the visible dye penetrant testing for each stepwise cast test piece.
  • FIG. 15 It is a conceptual diagram showing the P—Ni interaction.
  • FIG. 16 It is a SEM photograph showing the alloy of the present invention.
  • FIG. 17( a ) is an SEM photograph showing the alloy of the present invention and ( b ) a photograph showing the texture of the fracture surface of the same alloy.
  • FIG. 18( a ) is an SEM photograph showing the alloy in Comparative Example, and ( b ) a photograph showing the texture of the fracture surface of the same alloy.
  • FIG. 19 It is a diagram showing the microstructure of the alloy of the present invention.
  • FIG. 20 ( a ) to ( g ) are photographs each showing the distribution of the components of the alloy in FIG. 19 obtained by the EDX analysis.
  • FIG. 21 It is a graph showing the variation in tensile strength at high temperatures with respect to a conventional continuous cast product.
  • the bronze-based alloy of low lead content according to the present invention is characterized in that a casting material has P contained therein to improve the tensile strength of the alloy at high temperatures.
  • the present invention is characterized in that within an alloy region having a secondary dendrite arm spacing interval of 14 ⁇ m or more in an ordinary leadless bronze alloy containing Bi, the tensile strength is improved at high temperatures exceeding 180° C. and specifically in that the tensile strength of 152 MPa at least at 180° C. can be ensured.
  • the “bronze-based” alloy fundamentally comprises Sn, Zn, Bi, Cu and unavoidable impurities and, as preferable bronze-based alloys of low lead content, Cu—Sn—Zn—Bi-based alloys (hereinafter referred to as “Bi-based” alloys) and Sn—Zn—Se-based alloys (hereinafter referred to as “Bi—Se-based” alloys) can be cited.
  • the alloy of “low lead content” used in the present invention refers to an alloy having a Pb content lower than a bronze alloy containing Pb (CAC406 etc.) and not restricted to the content of Pb (0.25 mass % or less) as the residual component of a lead-free (leadless) copper alloy prescribed by JIS H5120 etc.
  • a “high-concentration P (phosphorus)” that will be used in the present invention refers to P in an amount exceeding 0.1 mass % that is larger than the amount of the residual P in the prior art.
  • the “P—Ni interaction” used in the present invention refers to a synergistic effect enabling the ratio of the effect by an increase in P content (enhancement in tensile strength) to be increased at high temperatures in the presence of Ni.
  • the “tensile strength” used in the present invention refers to that evaluated with the Amsler tensile strength tester using the test piece No. 4 prescribed by JIS Z2201 that will be described later.
  • the “soundness of the casting” used in the present invention refers to the evaluation of the presence or absence of cast defects on the surface observed in the visible dye penetrant testing using a stepwise cast test piece that will be described later, made as acceptance if the evaluation is substantially the same as that for CAC406 or is capable of being judged as being in a state improvable by an amendment of a casting method scheme up to substantially the same as that for CAC 406.
  • a copper alloy contains P in a relatively small amount of 0.01 mass % or more and 0.1 mass % or less.
  • a casting produced by the sand casting contains residual P in an amount of 0.01 mass % or more and less than 0.1 mass %.
  • the content of P as the residual component in CAC406 is 0.05 mass % or less.
  • the content of P even when being positively added to a copper alloy for the purpose of preventing cast cracking, is 200 to 300 ppm (0.02 to 0.03 mass %).
  • the P in these examples is added to the molten metal in a casting furnace or ladle, and the content of the residual P in a casting to be produced is 0.1 mass % or less.
  • the alloy has P contained therein in an amount of 0.01 to 0.5 mass %, preferably 0.05 to 0.1 mass % to improve the tensile strength at 100° C.
  • the amount of P contained in the present invention contributes to the enhancement of the tensile strength at a high temperature (about 180° C.) and belongs to a high-concentration range of P to be positively contained, which range greatly surpasses the amount of P to be added for the purpose of deoxidizing molten metal and preventing cast cracking.
  • the amount of the contained P exceeding 0.1 mass % can heighten the grain boundary strength while suppressing the production of Bi—Pb binary eutectic crystals, thereby contributing to the enhancement of the tensile strength at high temperatures.
  • the upper limit of range in which P is contained and which satisfies the tensile strength of 152 MPa be 0.4 mass % and that the lower limit thereof be 0.2 mass %.
  • the upper limit enables acquisition of the peak value of the tensile strength at 180° C. and, more preferably from the standpoint of const for commercial production, the upper limit is 0.4 mass %.
  • the upper limit is preferably 0.4 mass %.
  • the interaction of the P and Ni enables the lower limit of the P content capable of infallibly acquiring the tensile strength of 152 MPa at 180° C. to be lowered.
  • the lower limit of the P content is set to be preferably 0.12 mass % and more preferably 0.14 mass % and, as a result, it is made possible to acquire the tensile strength of 152 MPa at 180° C. at the upper limit suppressed to 0.33 mass %.
  • the upper limit is preferably 0.2 mass %.
  • Ni 0.0 ⁇ Ni ⁇ 3.0 mass %
  • JP-A 2003-193157 proposes a technique having 0.2 to 3.0 weight % of Ni contained in an alloy to secure the tensile strength at normal room temperature substantially the same as that of CAC406, in which a variation in tensile strength with an increase in Ni content assumes a gentle-mountain-shaped characteristic wherein the tensile strength reaches its peak when the Ni content falls in the range of 0.6 to 0.8 weight % in the exemplified alloy containing 0.01 to 0.02 weight % (130 to 200 ppm) of P (refer to FIG. 1 thereof).
  • the leadless alloy containing P as the residual P exhibits no discernible change in tensile strength at a high temperature (180° C.) with an increase in Ni content.
  • the content of Ni in the present invention contributes to the enhancement of the tensile strength at high temperatures on the premise of the content of P at a high concentration exceeding 0.1 mass % and, as shown in Example 4 that will be described later, this variation in tensile strength assumes a parabolic characteristic (with the axis as an x-axis) wherein the P—Ni interaction greatly enhances the tensile strength in the presence of a small amount of Ni content.
  • a small amount of Ni content makes it possible to suppress the P content to within a high-concentration range (0.1 ⁇ P ⁇ 0.6 mass %) and enhance the tensile strength at high temperatures. This is extremely useful in due consideration of the fact that P is easy to evaporate from molten metal to make it difficult to control the P to a high concentration.
  • a concrete Ni content is only required to exceed 0 mass %.
  • 0.05 or 0.08 mass % of Ni is available. It is preferred to use 0.1 mass % of Ni, thereby enabling the tensile strength of 152 MPa at a high temperature (about 180° C.) while suppressing the P content.
  • the upper limit of the Ni content is set to be 3.0 mass %.
  • P the state of saturation in the enhancement of the tensile strength at the preferable upper limit of P (0.4 mass %), it is better to adopt 2.0 mass % as the upper limit of the Ni content.
  • 0.1 mass % may be adopted as the upper limit of the range effectively enabling acquisition of the tensile strength even in a small amount of Ni content in view of cost reduction.
  • the lower limit of the Ni content be 0.3 mass % and that the upper limit thereof be 0.6 mass %.
  • This component is a substitute for Pb, has a low melting point and enters minute shrinkage cavities called microporosities produced in portions being finally solidified in the dendrite spacing of an alloy (casting) during the course of solidification of the casting, thereby enhancing the alloy soundness (resistance to pressure) and contributing to the ensuring of cuttability. While 0.1 mass % or more of Bi is effective for enhancing the cuttability, an alloy is required to contain 0.25 mass % of Bi in addition to the inclusion of Se in order to reduce the number of microporosities and secure its soundness.
  • the excessive content of Bi induces “inverse segregation” allowing the Bi to be concentrated together with Sn or high-concentration P on the surface of a casting during the course of the solidification of the casting and, in this case, there is a possibility of the number of microporisities in the casting being increased. Therefore, it is effective that the upper limit of Bi be set to be 3.0 mass % to secure the soundness of the alloy.
  • the lower limit of the Bi be 0.4 mass % and that the upper limit thereof be 2.5 mass %. Furthermore, in order to enable the mechanical machining under substantially the same cutting conditions as in the case of CAC406, the lower limit is preferably 1.0 mass %.
  • the upper limit of Bi is preferably 2.6 mass %.
  • This component is for enhancing hardness and other mechanical properties, particularly elongation, without imparting the influence of cuttability to an alloy.
  • the content of Zr in an amount of 3.0 mass % or more promotes deoxidation of the molten metal effectively and enables the soundness of a casting and the flowability of the molten metal to be enhanced. Since Zr is comparatively inexpensive, though it is a component desirably contained in an amount as many as possible, the upper limit thereof is fixed at 10 mass % in view of possible deterioration of the casting environment by a vapor of Zn.
  • the upper limit thereof is preferably 4.0 mass %. Furthermore, in the case of requiring the vapor pressure of Zn to be lowered taking particular note of the filling property of the molten metal in a casting mold, the upper limit thereof is preferably 9.0 mass %. Incidentally, in view of the fact that the optimum lower limit of Sn is 2.8 mass % described later, preferably the lower limit of a range of Sn not allowing the deposition of a 6 phase is 6.0 mass %.
  • This component is for contributing to the enhancement of mechanical properties of an alloy, especially elongation and corrosion resistance, and the effective content thereof is 2.0 mass % or more.
  • the upper limit thereof is fixed at 6.0 mass %.
  • the effective content of Sn is 2.8 mass % or more. Furthermore, in case where it is necessary to suppress the inverse segregation of solutes, such as P, Bi and Sn, even under different casting conditions during commercial production, the upper limit of Sn is preferably fixed at 5.5 mass %. Incidentally, in order to acquire a peak value of the tensile strength taking particular note of the tensile strength, the advantageous upper limit thereof is 4.5 mass %.
  • Se is a substitute for Pb and forms intermetallic compounds, such as Se—Zn and Cu—Se, in accordance with the ratio of contents of Cu and Zn, thereby securing the cuttability of the alloy while suppressing the content of Bi.
  • the deposition of the intermetallic compounds causes the microporosities to be diffused, thereby enhancing the soundness of the alloy and stabilizing the tensile strength thereof.
  • the excessive content of Se produces the deposition of brittle intermetallic compounds in a large amount to lower the tensile strength. The upper limit thereof is therefore fixed at 1.3 mass %.
  • the unavoidable impurities in the copper alloy of the present invention besides the Pb, 0.3 mass % or less of Fe, 0.01 mass % or less of Al, 0.01 mass % or less of Si, 0.25 mass % or less of Mn, 0.3 mass % or less of S, 0.01 mass % or less of Mg, 0.01 mass % or less of Ti, 0.1 mass % of Zr, 0.3 mass % or less of Co, 0.3 mass % or less of Cr and 1.1 mass % or less of Sb can be cited.
  • Example 1 a target value of 152 MPa at a target temperature of 180° C. was determined as the reference value of tensile strength. Why 180° C. was adopted was that the maximum permissible working pressure in the case where a fluid was formed into saturated aqueous vapor in a bronze valve of 10 K nominal pressure or Class 150 was 1.0 MPa and that the saturated temperature corresponding to the working pressure was 180° C. Why 152 MPa was adopted was compliant with the fundamental idea that the target tensile strength value of a material main body in the “pressure container structure” prescribed under JIS B 8270 was four times the basic allowable pressure in consideration of the safety etc.
  • Example 1 the samples in Example 1 were taken from sand castings.
  • Test samples in the tensile test were cast in accordance with JIS-A method scheme at a pour point of 1130° C. using a casting mold of Co 2 and then subjected to cutting work to fabricate the test piece No. 4 prescribed under JIS Z2201.
  • the test pieces were tested using an Amsler tensile strength tester. The conditions of this tensile test were adopted in other Examples taking samples from sand castings.
  • Sample Nos. 1-1 to 8 have the content of P, which is one of the characteristic components of the copper alloy of the present invention, varied in the Bi—Se-based alloys. It is found from the test results that the alloys containing P of a high concentration exceeding 0.10 mass % have been improved in tensile strength at a high temperature of 180° C. It is further found from the graph of FIG. 1 that in order to achieve the target value of 152 MPa in Example 1, P has to be contained in the range of 0.26 to 0.50 mass %.
  • Sample Nos. 1-9 to 16 shown in Appendix Table 4 contain high-concentration P, which is one of the characteristic components of the copper alloy of the present invention, with the contents of Sn, Ze, B and Se, which are principal components in the Bi—Se-based alloys similar to sample Nos. 1-1 to 8, varied.
  • Sample Nos. 1-17 to 24 contain high-concentration P, which is one of the characteristic components of the copper alloy of the present invention, with the contents of Sn, Zn and Bi, which are principal components in the copper alloy (Bi-based alloy) of the present invention, varied.
  • compositions thereof consist of 3.0 to 6.0 (preferably 3.1 to 5.9) mass % of Sn, 4.0 to 9.0 (preferably 8.3) mass % of Zn, 1.0 to 3.0 (preferably 1.3 to 2.2) mass % of Bi, 0.2 to 0.5 mass % of Se, 0.20 (preferably 0.22) to 0.50 mass % of P and the balance of Cu and unavoidable impurities.
  • compositions thereof consist of 3.0 to 6.0 (preferably 5.8) mass % of Sn, 4.0 to 9.0 (preferably 8.4) mass % of Zn, 1.0 to 3.0 (preferably 1.1 to 2.2) mass % of Bi, 0.20 to 0.40 (preferably 0.22 to 0.27) mass % of P and the balance of Cu and unavoidable impurities.
  • FIG. 2 is a schematic view showing the dendrite, in which when the stem is defined as a primary dendrite arm (primary branch) and the branches produced from the primary branch as secondary dendrite arms (secondary branches). It has been known that the dendrite arm spacing has a great influence on the mechanical properties etc. of a casting.
  • FIG. 3 is a micrograph showing the typical microstructure of CAC406, from which it can be observed that the secondary dendrite arms have been well developed and well aligned.
  • the measurement method for secondary dendrite arm spacing is a method for measuring the average spacing in the well-aligned dendrite arms as shown in FIG. 4( a ).
  • a search is made, from the microstructure, for dendrite arms grown as aligned in parallel, then a line of optional length substantially orthogonal to the dendrite arms is drawn, and the length L of the line intersecting the dendrite arms is divided by the number (n ⁇ 1) of the dendrite arms to obtain a quotient ds. That is to say, the size of the secondary dendrite arms is expressed as L/(n ⁇ 1).
  • the microstructures of a test piece casting differ in size from one locality to be observed to another and, since the test piece casting has a polycrystalline structure, the individual crystal grains show different ways to grow the dendrite arms.
  • the methods for measuring the secondary dendrite arm spacing of the test pieces are unified as described below. Furthermore, when failing to observe clear crystal grain boundaries in the actually cast product, item 3 below is applied.
  • the localities in which the secondary dendrite arms are aligned in the individual crystal grains near the center of the axial transverse section of a test piece as shown in FIG. 4( b ) are specified, and three or more crystal grains in total are measured.
  • FIG. ( 4 c ) illustrates an example of the measurement of CAC306. Since the average value of the secondary dendrite arm spacing is converged when the number of the dendrites exceeds 10, the influence caused by the difference in locality to be measured can be eliminated.
  • the “continuously cast casting” is molded by means of “continuous casting” that continuously extracts solidified castings from below while pouring molten metal from above into a hollow and vertical metal mold, for example.
  • the solidification of molten metal is promoted with cooling equipment, such as water-cooling.
  • the “sand casting” is molded by means of “sand casting” that pours molten metal into a casting mold formed of solidified casting sand, leaves the molten metal standing to cool it with air and takes solidified metal part out of the casting mold
  • the “metal mold casting” is molded by means of “metal mold casting” that pours molten metal into a casting mold formed of metal, leaves the molten metal standing to cool it with air and takes solidified metal part out of the casting mold.
  • the cooling rates of castings differs depending on the difference of the methods of casting, size of castings and scheme of casting methods, since the “sand casting” and “metal mold casting” used in the present example adopted slower cooling rates than the “continuously cast casting,” the secondary dendrite arm spacing was further widened to possibly lower the tensile strength.
  • the copper alloys of the present invention are improved in tensile strength at high temperatures so as not to be lowered without being affected by the secondary dendrite arm spacing. That is to say, the copper alloys of the present invention are those improved in tensile strength at high temperatures without being affected by the difference in method of casting (cooling rate). In other words, it is found that these alloys are those improved in tensile strength at high temperatures while permitting the manufacture thereof even through the use of the conventional method of casting (cooling rate). In addition, since the copper alloys of the present invention exhibits a tendency similar to that of CAC406 as shown in FIGS. 5 and 6 , they can secure the tensile strength up to high temperatures as a substitute for CAC406.
  • FIG. 7 is the cut surface of a barrel part
  • FIG. 8 shows the same cut surface after being subjected to etching treatment with nitric acid.
  • Sections (alloy regions) 1, 2 and 3 of different-thickness walls have secondary dendrite arm spacing of 27.9 ⁇ m, 24.7 ⁇ m and 23.4 ⁇ m, respectively. Since any of these has an arm spacing exceeding 14 ⁇ m, ordinary sand cast products can be judged as objects to be improved.
  • a section having an arm spacing of 14 ⁇ m or more may be part (alloy region) of a casting and, in this case, the whole of a casting part constitutes an object to which the copper alloy of the present invention is applied.
  • the method of measurement comprises, as shown in FIG. 8 , etching treatment, use of an electron microscope in a state wherein an understanding of the metal texture is made easy to measure the secondary dendrite arm spacing.
  • etching treatment use of an electron microscope in a state wherein an understanding of the metal texture is made easy to measure the secondary dendrite arm spacing.
  • each sample in Example 4 was obtained from a sand casting.
  • the tensile strengths at 180° C. were verified with respect to the copper alloys of the present invention (Bi-based alloys) containing 0.14 mass %, 0.22 mass %, 0.28 mass % and 0.32 mass %, respectively, of P having added thereto 0, 0.20 mass %, 0.40 mass % and 0.60 mass %, respectively, of Ni.
  • those of the alloys containing 0.02 mass % and 0.10 mass %, respectively of P were measured.
  • the composition of each sample is shown in Table 9 and the test results are shown in the same table and plotted in FIG. 11 .
  • compositions thereof consist of 2.0 to 6.0 (preferably 2.3 to 5.7) mass % of Sn, 6.0 to 10.0 (preferably 6.5 to 9.5) mass % of Zn, 0.1 to 3.0 (preferably 2.6) mass % of Bi, 0.12 to 0.40 (preferably 0.33) mass % of P, 0.1 to 3.0 mass % of Ni and the balance of Cu and unavoidable impurities.
  • Bi—Se-based alloys containing 0.1 to 1.3 mass % of Se in addition to the components of the Bi-based alloy can be applied to the present invention.
  • FIG. 15 is a conceptual diagram showing the P-Ni interaction.
  • the copper alloy of the present invention containing P of high concentration (0.1 ⁇ P ⁇ 0.6) is enhanced in tensile strength at high temperatures (refer to A in FIG. 15 ).
  • the alloy of Comparative Example containing P of low concentration exhibits a slight increase in tensile strength at high temperatures (refer to C in FIG. 15 )
  • the copper alloy of the present invention containing P of high concentration exhibits a large increase in tensile strength at high temperatures to the neighborhood of the tensile strength at normal room temperature (refer to B in FIG. 15 ).
  • the P—Ni interaction implies a synergistic effect (refer to B and C in FIG. 15 ) of increasing an enhancing ratio of the effect with an increase in P content (tensile strength) at high temperatures owing to the presence of Ni.
  • FIG. 13 is an explanatory view showing the casting method scheme for stepwise cast test pieces
  • FIG. 14 an explanatory view showing the location of each test piece measured.
  • the “visible dye penetrant testing” comprises the steps of spraying a penetrant onto the cut surface of a test piece, leaving the penetrant standing for 10 minutes, then wiping away the penetrant, further spraying a developer onto the cut surface having the penetrant wiped away to determine the presence or absence of casting defects from red marks having emerged on the cut surface.
  • the casting method scheme for the stepwise test piece comprises the step of pouring molten metal from the side of the stepwise part having a wall thickness of 40 mm via a gate riser measuring 70 mm in diameter ⁇ 160 mm in length starting with a pouring gate having a diameter of 25 mm.
  • the casting conditions include performing resolution in an experimental high-frequency furnace, using a meltage of 12 kg, adopting a pour point of 1180° C. and using a Co 2 casting mold.
  • the samples containing P in a high concentration of 0.31 mass % (Nos. 5-8 and 9) were confirmed to have no defect and obtain good castings. It is found from the present test results that in the examples having the following ranges of components, it is made possible to achieve the target value of tensile strength that is 152 MPa at a high temperature (180° C.) owing to the presence of a high concentration of P and as well secure the casting soundness.
  • compositions thereof consist of 2.5 (preferably 2.9) to 6.0 mass % of Sn, 4.0 (preferably 3.9) to 8.0 mass % of Zn, 0.5 to 3.0 (preferably 2.5 mass % of Bi, 0.15 to 0.40 (preferably 0.36) mass % of P, 0 ⁇ Ni ⁇ 2.0 (preferably 1.9) and the balance of Cu and unavoidable impurities.
  • the pieces subjected to cuttability test were evaluated by machining, with a lathe, cylindrical substances to be machined and using a cuttablity index in the cutting resistance exerted on a turning tool when the cutting resistance of a bronze casing CAC406 was regarded as 100.
  • the test conditions include using the pour point of 1160° C. (in the Co 2 casting mold), the shape of the substance to be cut measuring 31 mm in diameter and 300 mm in length, 3.2 as the surface coarseness R A , 3.0 mm as the cut depth, 1800 rpm as the number of revolutions of the lathe, 0.2 mm/rev as the feeding amount and no oil.
  • Nos. 6-1 to 4 are samples of the copper alloys of the present invention (Bi-based alloys) and by Nos. 6-5 to 11 ate samples of the copper alloys of the present invention (Bi—Se-based alloys).
  • any of these samples satisfies an index of 80% or more processible by processing equipment, with a blade and under cutting conditions for use in processing CAC406 and is found to be proccessible under substantially the same cutting conditions as for CAC406.
  • Erosion and corrosion are evaluated by means of the gap jet-flow corrosion test.
  • the test procedure comprised mirror-polishing a test piece that had been machined to have an exposed area of 64 mm 2 (16 mm in diameter) relative to corrosive liquid, then jetting a test solution (a 1% cupric chloride solution) onto the exposed area part of the test piece at a rate of 0.4 t/min for five hours from a jet nozzle (nozzle diameter: 1.6 mm) disposed at a height of 0.4 mm from the surface of the test piece and measuring the maximum corrosion depth in the corroded surface.
  • a test solution a 1% cupric chloride solution
  • the tensile test was performed in the same manner as in Example 1 (relationship between the P content and the tensile strength at 180° C.) to evaluate the tensile test pieces through the observation of the fracture surface texture, observation of the microstructure and EDX analysis.
  • No. 8-1 is a sample of the copper alloy of the present invention (Bi-based alloy) containing P of high concentration
  • No. 8-2 is a sample of the copper alloy of the present invention (Bi-based alloy) containing Ni to suppress the P content to within the high-concentration range (0.1 ⁇ P ⁇ 0.6 mass %)
  • No. 8-3 is a sample of JIS H5120 CAC911 (Bi—Se-based bronze casting), as Comparative Example, containing P in a low concentration of 0.02 mass %.
  • FIGS. 16 to 18 SEM photographs and texture photographs of the facture surfaces of the alloy samples that underwent the tensile test at 180° C. are shown in FIGS. 16 to 18 .
  • the central portion of the fracture surface has a fibrous texture and the peripheral portion thereof has a radial texture.
  • the SEM photographs show a plurality of microscopic dimples (dents). It can therefore be considered that “ductile fracture” would occur during the tensile test at 180° C.
  • the alloy of Comparative Example as shown in FIG. 18 , assumes “cleavage” along the crystal face (cleavage surface of crystal) and no dimple can be observed from the SEM photograph. It can therefore be considered that “brittle fracture” would occur during the tensile test at 180° C.
  • the strength of the alloy at the crystal grain boundaries is enhanced at a high temperature (180° C.). This indicates that the “bristle fracture” is converted into the “ductile fracture.” This is applicable to the case of containing Ni.
  • FIG. 19 shows the microstructure of the copper alloy of the present invention (No. 8-2), and FIG. 20 shows the distribution of the components of the alloy of FIG. 19 obtained by the EDX analysis.
  • the primary crystal ⁇ is grown in a dendrite form and, in the gap thereof, a Bi-phase is observed.
  • a Cu—P compound (Cu 3 P) and an Ni—P compound (Ni 3 P) exist in the vicinity of the Bi-phase.
  • the P and Ni assume solid solutions also in the ⁇ -phase, they may possibly enhance the matrix strength.
  • the bronze-based alloy of low lead content according to the present invention is a copper alloy befitting various kinds of parts in a wide range of fields, including a material for plumbing instruments (valves, joints, etc.) for water supply, hot water supply or steam emission, pressure instruments (casings etc.). Since the alloy of the present invention is an alloy enhanced in tensile strength, it befits a material for parts of small wall thickness including structural members as well as the plumbing instruments. It is suitable for the process-formation of electric and mechanical products, such as gas appliances, washing machines, air conditioners, etc.
  • Other parts and members having advantageously adopted the copper alloy of the present invention as a material for them include water contact parts, such as valves, water faucets, etc., namely ball valves, hollow balls for the ball valves, butterfly valves, gate valves, globe valves, check valves, hydrants, clasps for water heaters or warm-water-spray toilet seats, cold- and hot-water supply pipes, pipe joints, parts for electric water heaters (casings, gas nozzles, pump parts, burners, etc.), strainers, parts for water meters, parts for underwater sewer lines, drain plugs, elbow pipes, bellows, connection flanges for closet stools, spindles, joints, headers, corporation cocks, hose nipples, auxiliary clasps for water faucets, stop cocks, water-supplying, -discharging and -distributing faucet supplies, sanitary earthenware clasps, connection clasps for shower hoses, gas appliances, building materials, such as doors, knobs, etc., household electrical goods, adapters for she
  • the copper alloy of the present invention is widely applicable to washing things, kitchen things, bathroom paraphernalia, lavatory supplies materials, furniture parts, family room supplies materials, sprinkler parts, door parts, gate parts, automatic vending machine parts, washing machine parts, air-conditioner parts, gas welding machine parts, heat-exchanger parts, solar collector parts, automobile parts, metal molds and their parts, bearings, gears, construction machine parts, railcar parts, transport equipment parts, fodders, intermediate products, final products, assembled bodies, etc.
  • Structural parts such as burners, gas nozzles, flare nuts, ball taps, thermostat parts, bolts, nuts, spindles and sliding parts (bearings, gears, pushers, sleeves and worm gears).
  • Plumbing instruments and pressure instruments such as heat-exchangers (plates and tubes), gas turbines, atomic furnace parts, industrial furnace parts (plumbing, valves and joints), seawater treating facilities, (plumbing, valves, containers and joints), letdown valves, electromagnetic valves, steam valves, safety valves, steam pipework, water-heating instruments, steam generators, boiler parts (plumbing, pipes, containers and joints), pump parts (casings, covers and impellers), steam traps, drainpipes, valves for steam, floats, air-conditioner parts, (plumbing, valves and joints), strainers for steam, hydraulic pump parts (casings and impellers), air release pipes, electric water heater parts (plumbing, valves and joints), hot-water containers, proportional valves, room heater parts, carburetors, service valves, ball taps, tableware washers, water contact parts for valves or water washing (ball valves, hollow balls for ball valves, butterfly valves, gate valves, globe valves, check valve
  • the copper alloy of the present invention is of significance under the circumferences under which cold water and hot water are alternately used or under which a high temperature of 100° C. or more by hot-air drying in a tableware washing and drying apparatus etc. is used.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Domestic Plumbing Installations (AREA)
  • Continuous Casting (AREA)
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US11/919,997 2005-08-30 2006-08-30 Bronze-based alloy of low lead content Abandoned US20090220375A1 (en)

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JP2005-249624 2005-08-30
JP2005249624 2005-08-30
PCT/JP2006/317132 WO2007026780A1 (fr) 2005-08-30 2006-08-30 Alliage de bronze a tete basse

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US9181606B2 (en) 2010-10-29 2015-11-10 Sloan Valve Company Low lead alloy

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JP4866717B2 (ja) * 2006-12-20 2012-02-01 株式会社栗本鐵工所 銅合金
MX2013004777A (es) * 2010-10-29 2014-02-11 Sloan Valve Co Lingote bajo en plomo.
CN109783869B (zh) * 2018-12-17 2020-08-21 中国原子能科学研究院 一种预测反应堆压力容器焊缝热老化晶界p偏析的方法
CN116083748A (zh) * 2022-12-27 2023-05-09 中北大学 一种高强高耐磨铋锡青铜合金及其制备方法

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EP1921173A4 (fr) 2012-08-08
KR20070119039A (ko) 2007-12-18
KR100976741B1 (ko) 2010-08-19
CN101166839A (zh) 2008-04-23
CA2603811A1 (fr) 2007-03-08
CA2603811C (fr) 2011-08-23
WO2007026780A1 (fr) 2007-03-08

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