JP7202235B2 - Low lead copper alloy - Google Patents

Description

The present invention relates to lead-containing bronze alloys with reduced lead content.

Bronze castings (JIS H5120 CAC406), which have been conventionally used for water supply equipment and parts of water supply equipment, are excellent in castability, corrosion resistance, machinability, and pressure resistance, and are used in valves, pump parts, water supply equipment, and water supply equipment. It is used in various fields such as materials and equipment, bearings, and general machine parts. This bronze casting (CAC406) contains 4.0 to 6.0% by weight of lead, so that it has high machinability and is easy to process. However, in recent years, there are concerns about the effects of lead on the human body and the environment. Therefore, environmental regulations such as water quality regulations, RoHS, and REACH directives are being developed, and usage environments are being restricted. For this reason, lead-free copper alloys with reduced lead content or no lead are being studied with the goal of reducing the amount of lead leaching.

For example, in Patent Document 1, Cu is 71.5 to 78.5% by mass, Si is 2.0 to 4.5% by mass, and lead is contained in a range of 0.005% by mass to less than 0.02% by mass. and a free-cutting copper alloy with a balance of Zn. In this copper alloy, the required performance is exhibited by further satisfying the following conditions within the above range. First, Cu, Si, and Pb satisfy the inequality of 61-50Pb≤Cu-4Si≤66+50Pb in mass% units, and form an alloy composition containing Fe as an impurity not exceeding 0.5 mass%. In addition, the γ phase and/or the κ phase are uniformly dispersed in the matrix composed of the α phase, and the total phase area is α phase ≥ 30%, 0% ≤ β phase ≤ 5%, 0% ≤ μ phase ≤ 20% and 18-500(Pb)%≦κ phase+γ phase+0.3μ phase−β phase≦56+500(Pb)%. This results in a free-cutting copper alloy containing an ultra-low amount of lead.

Further, in Patent Document 2, Sn: 0.8 to 8.0 wt%, Bi: 0.2 to 7.0 wt%, Ni 0.2 to 3.0 wt%, and the balance Cu , discloses a lead-free copper alloy suitable for ingots and welding in which a Cu--Sn--Ni compound is precipitated in the alloy to improve machinability. The content of Pb is about 0.02 to 0.03% by weight, which can be included as an impurity. Further, it is disclosed that the alloy contains Se: 0.1 to less than 3.0% by weight and P: less than 0.5% by weight.

Furthermore, in Patent Document 3, 0.5 to 15 mass% Sn, 0.001 to 0.049 mass% Zr, 0.01 to 0.35 mass% P, and 0.01 to 15 mass% Pb , one or more elements selected from 0.01 to 15 mass% of Bi, 0.01 to 1.2 mass% of Se and 0.05 to 1.2 mass% of Te, and the balance of 73 mass% or more Cu and Fe and/or Ni are contained as inevitable impurities, and when either of them is contained, the content of Fe or Ni is 0.2 mass% or less, and Fe and Ni are contained, their total content is limited to 0.25 mass% or less, respectively, f1 = [P] / [Zr] = 0.5 to 100, f2 = 3 [Sn] / [ Zr] = 300 to 15000, f3 = 3 [Sn] / [P] = 40 to 2500, f4 = [Zn] + 3 [Sn] = 10 to 43 and f5 = [Cu] - 0.5 [Sn] - 3 [P] + 0.5 ([Pb] + [Bi] + [Se] + [Te]) - 0.5 ([As] + [Sb]) - 1.8 [Al] + [Mn] + [Mg ] = 60 to 90 (the content of element a is [a] mass%, and [a] = 0 for element a that is not contained), and the total content of α phase, γ phase, and δ phase is the area It describes a copper alloy casting with excellent machinability, strength, wear resistance and corrosion resistance, characterized by having a ratio of 95% or more and an average crystal grain size in the macrostructure at the time of melting and solidification of 300 μm or less. It is

Japanese Patent No. 4951623 JP 2003-193157 A Japanese Patent No. 5111853

However, with the lead-free copper alloys described in Patent Documents 1 and 2, the points to be noted when handling at actual casting sites are significantly different from those of conventional CAC406, so casting and processing processes using conventional CAC406 It is difficult to make a smooth transition from manufacturing procedures such as In addition, there was a concern that contamination could occur with the site where lead-containing copper alloys are manufactured, resulting in an increase in defects.

In addition, when Zr is contained as in the alloy described in Patent Document 3, fine shrinkage cavities are induced in the bronze casting system like Si, making it difficult to produce sound products, and proficiency in CAC406 is difficult. It became difficult to migrate based on the procedures given.

On the other hand, in response to the increasing demand for electric system products necessary for the promotion of EV in the automobile industry in recent years, the amount of copper used, mainly pure copper, is increasing, raising concerns about copper supply shortages and soaring prices. . Therefore, there is an urgent need to reduce the amount of copper used as much as possible.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a bronze alloy that can be handled in a procedure close to CAC406, which has been a standard, while suppressing not only the leaching of lead but also the amount of copper used.

In the present invention, Zn is 13.0% by mass or more and 21.0% by mass or less, Sn is 1.2% by mass or more and 5.7% by mass or less, Pb is 0.30% by mass or more and 4.0% by mass or less, P The above problem has been solved by a copper alloy containing 0.5% by mass or less of and the balance being Cu and inevitable impurities.

Moreover, in addition to the above components, a configuration containing 1.5% by mass or less of Ni can also be selected.

The copper alloy according to the present invention has a lower lead content than CAC406, which contains 4.0 to 6.0% by mass of lead, and can comply with lead regulations. Moreover, the necessary amount of Cu can be reduced by increasing Zn within an appropriate range and adjusting Sn within an appropriate range.

This copper alloy may contain, to a limited extent, elements that can be mixed as other unavoidable impurities. However, the total amount must be kept within a range that does not impair the effects of the present invention, and is preferably less than 0.5% by mass, and the content per element is less than 0.1% by mass. and preferred.

According to the present invention, it is possible to obtain a copper alloy that can secure necessary strength and elongation while suppressing the amount of Pb used and reducing the necessary amount of Cu, and that can be handled close to conventional CAC406. As a result, various copper alloy products, for which CAC406 has been used in the past, can be reduced in lead and can be used to save copper while suppressing the burden of changing procedures at the manufacturing site.

Schematic diagram of No. 14A test piece used for mechanical property test in Examples (a) Photograph showing an example of chips of CAC406, (b) Photograph showing an example of chips of Example 3, (c) Photograph showing an example of chips of Comparative Example 5, (d) Photograph of Example 9 Photo showing an example of chips

The present invention will be described in detail below.
The present invention is a bronze-based copper alloy in which the content of Pb is suppressed and the amount of Cu used is reduced as compared with CAC406.

The Zn content of the copper alloy should be 13.0% by mass or more. If it is less than 13.0% by mass, the tensile strength and elongation are too poor compared to CAC406, making it difficult to handle as before. On the other hand, it must be 21.0% by mass or less, preferably 19.5% by mass or less. If the Zn content exceeds 21.0% by mass, the tensile strength deteriorates.

The Sn content of the copper alloy should be 1.2% by mass or more, preferably 2.0% by mass or more. If it is less than 1.2% by mass, the yield strength will be too low. On the other hand, it must be 5.7% by mass or less, preferably 4.0% by mass or less. If it exceeds 5.7% by mass, the elongation and tensile strength are extremely deteriorated.

The Pb content of the copper alloy should be 0.30% by mass or more, and preferably exceeds 0.50% by mass. If it is less than 0.30% by mass, cutting chips will be helically connected when cutting is performed under the same conditions as CAC406, which tends to cause poor cutting. When the content is 0.30% by mass or more and 0.50% by mass or less, the machinability is slightly improved, and some chips are helically connected. It is available by On the other hand, the Pb content must be 4.0% by mass or less, preferably 3.9% by mass or less, and more preferably 3.5% by mass or less. Above 3.5% by mass, the tensile strength begins to decrease. Furthermore, when it exceeds 4.0% by mass, it becomes impossible to comply with environmental regulations.

The P content of the copper alloy should be 0.5% by mass or less. If P is contained excessively, there is concern about an increase in shrinkage cavities, but up to 0.5% by mass can be contained without any particular problem. When P is contained in the above range, it contributes to the soundness of the molten metal, exhibits a deoxidizing effect, and stabilizes the mechanical properties after casting. When it is contained, it is preferably 0.005% by mass or more, more preferably 0.01% by mass or more. However, since the above-mentioned copper alloy has a relatively high Zn content, it is possible to obtain castings of somewhat stable quality even if the deoxidizing step with P is omitted.

The copper alloy may contain Ni in addition to the above elements. In the above copper alloy, Ni is a solid-solution element and stabilizes strength and elongation. The addition of Ni improves tensile strength and elongation over no addition. On the other hand, it must be 1.5% by mass or less. If it exceeds 1.5% by mass, there is concern that the quality of the molten metal will deteriorate due to increased hydrogen absorption. In addition, there is concern about an increase in the amount of Ni eluted from cast products.

In addition to Cu, the above copper alloy may contain, as a remainder, elements other than those mentioned above that serve as impurities within a range that does not impair the effects of the present invention. However, it is preferable to suppress the content to the extent that it is included as unavoidable impurities that are inevitably included due to problems in raw materials and production. The total amount of elements that become inevitable impurities is preferably less than 0.5% by mass, more preferably less than 0.1% by mass. This is because if there are too many unexpected elements, the physical properties may be impaired even if the elements are within the above range. Also, the content per element is preferably less than 0.1% by mass.

Among the elements that become inevitable impurities that the copper alloy may contain, the content of Bi is preferably less than 0.1% by mass, more preferably less than 0.05% by mass, and is less than the detection limit. Most preferred. Bi disperses in Cu without forming a solid solution, and forms a low melting point (125° C.) eutectic compound with similarly dispersed Pb. If the Bi content is high, the amount of dispersed Pb--Bi eutectic compound increases, which may become a starting point for lowering strength such as tensile strength. In addition, dispersed Bi tends to cause shrinkage cavities during sand mold casting. Furthermore, if the amount of Bi is too large, various disadvantages such as deterioration of mechanical properties caused by the inclusion of Bi in the alloy to be recycled occur when recycling cast products manufactured using the above copper alloy. The product will have to be collected separately.

Among the elements that can be contained as inevitable impurities in the copper alloy, the content of Zr is preferably less than 0.003% by mass, and more preferably less than the detection limit. This is because, in bronze-based alloys containing a large amount of Zn, if even a small amount of Zr is contained, there is a high possibility that the physical properties will be greatly affected.

Among the elements that can be included as inevitable impurities in the copper alloy, the content of Si is preferably less than 0.01% by mass, and more preferably less than 0.005% by mass. Too much Si promotes shrinkage cavities, making it impossible to produce sound castings.

Among the elements that become inevitable impurities that the copper alloy may contain, the content of B is preferably less than 0.02% by mass, and more preferably less than 0.01% by mass. Even a very small amount of B has a large effect on properties, and if it is 0.02% by mass or more, the reduction in machinability and tensile strength cannot be ignored.

Any of the other unavoidable impurity elements that the copper alloy may contain is preferably less than 0.1% by mass, more preferably less than 0.05% by mass, and even more preferably less than the detection limit. Examples of such impurities include Fe, Mn, Cr, Mg, Ti, Te, Se, Cd, and Sb. Among these, Se and Cd, which are known to be toxic, are desirably less than 0.1% by mass, and more desirably less than the detection limit.

In addition, the value of the content in the present invention indicates the content at the time when the product is manufactured by the raw material obtained as an alloy or by casting, forging, etc., not the ratio in the raw material.

The balance of the copper alloy is Cu. The copper alloy according to the present invention can be obtained by a general copper alloy production method, and when producing a product from this copper alloy, it can be produced by a general casting method (for example, sand casting). . For example, a method of melting an alloy using a heavy oil furnace, a gas furnace, a high-frequency induction melting furnace, etc., and casting it into a mold of each shape can be mentioned.

Examples of actual production of copper alloys according to the present invention will be reported below. First, the test method for copper alloys will be described.

<Mechanical property test>
It was cast into a 10t-Y block (10 mm × 70 mm × 100 mm) CO ₂ mold, and the lowest part was cut out at 10 mm from the bottom (10 mm × 70 mm × 10 mm). . The specific shape is as shown in FIG. 1, and the proportional test in which the original cross-sectional area S ₀ of the parallel portion and the original gauge length L ₀ have a relationship of L ₀ = 5.65 × S ₀ ^ (1/2) It's a piece. The diameter _d0 of the rod-shaped portion was 5 mm, the original gauge length _L0 was 25 mm, the length _Lc of the cylindrical parallel portion was 30 mm, and the radius R of the shoulder portion was 15 mm. (L ₀ =5.65×(2.5×2.5×π)^(1/2)=25.03)

The tensile strength, elongation and yield strength of this test piece were measured according to JIS Z2241. Table 1 shows the evaluation criteria for the mechanical properties, and Table 2 shows the component ratios and evaluation results of the produced copper alloys.

<Machinability test>
A 10t-Y block (10 mm x 70 mm x 100 mm) was cast into a CO ₂ mold and the bottom was cut out 10 mm from the bottom (10 mm x 70 mm x 10 mm). A test piece obtained by processing this cut sample into a cylindrical shape of φ8 mm × 70 mm is dry cut using a general-purpose lathe using a carbide brazing bit at a feed of 0.15 mm / rev and a rotation speed of 550 rpm. Chips were evaluated as follows. Table 2 shows the evaluation results.
・×: Chips connected and helically extended ・○: Divided, but helical chips included ・◎: Divided, chips less than double winding

FIG. 2(a) shows a photograph of CAC406 as a reference material cut in the same manner.

<Manufacturing method>
Materials constituting each element were mixed, melted in a high-frequency induction melting furnace, and then cast in a CO ₂ mold to prepare test materials having the contents shown in Table 2 in each example. In addition, all the values of content are the mass %, and are the measured value after manufacture. The above tests were performed on each of the obtained copper alloys. "-" in the table indicates that it is below the detection limit. In addition, in any example, B, Bi, Sb, Si, and Fe were below the detection limit. In addition, Zr was also below the detection limit except for Comparative Example 6. Comprehensive evaluation was evaluated as ⊙ when all the tested items were ⊚, ◯ when even one of the tested items was ◯, and × when even one of the tested items was ×.

First, Comparative Example 1, Examples 1 to 5, and Comparative Example 2 were prepared by varying the Sn content and making the contents of the elements other than Sn as close as possible. In the first item in Table 2, these are arranged in order of Sn content. Comparative Example 2, in which Sn exceeded 5.7% by mass, tended to deteriorate in tensile strength and elongation. On the other hand, Comparative Example 1, in which the Sn content is less than 1.2% by mass, has a problem with yield strength. In addition, the shapes of chips were all good. A photograph of chips of Example 3 is shown as FIG. 2(b).

Next, Comparative Example 3, Examples 6, 7, 8, and Comparative Example 4 were prepared by changing the content of Zn on the basis of Example 3 and making the content of elements other than Zn as close as possible. These are listed in the second item in Table 2 in order of Zn content. Comparative Example 3, in which Zn is less than 13.0% by mass, deteriorated in tensile strength. On the other hand, Example 8, in which Zn exceeds 19.5% by mass, tends to slightly decrease in elongation, and Comparative Example 4, in which Zn exceeds 21.0% by mass, exhibits a further decrease in elongation, and also has problems with tensile strength. has occurred.

Next, Comparative Example 5, Examples 9, 10, 11, 12 and 13 were prepared by changing the content of Pb based on Example 3 and making the content of elements other than Pb as close as possible. These are listed in the third item in Table 2 in order of Pb content. In Comparative Example 5, in which the Pb content was less than 0.30% by mass, chips showed a helical structure, and machinability became a significant problem. The photograph is shown in FIG. 2(c). In Example 9, in which Pb was 0.50% by mass, chips that were slightly helical but divided were obtained. The photograph is shown in FIG. 2(d).

Next, Examples 14, 15 and 16 were prepared by changing the content of P based on Example 3 and making the content of elements other than P as close as possible. All examples showed good results.

Next, Examples 17, 18, and 19 were prepared by adding Ni to the components similar to those of Example 3 as additional elements. When Ni was added, the tensile strength and elongation tended to be better compared to Example 3 where Ni was not added.

Furthermore, when Comparative Example 6 was prepared by adding a small amount of Zr, all of them had serious problems in mechanical properties.

Claims (2)

Zn 13.0% by mass or more and 21.0% by mass or less, Sn 1.2% by mass or more and 5.7% by mass or less, Pb 0.50% by mass or more and 4.0% by mass or less, P 0.5% Containing % by mass or less,
A copper alloy in which the balance is Cu and unavoidable impurities. A copper alloy containing Ni in an amount of 1.5% by mass or less in addition to the constituent elements of claim 1.

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