JP6692317B2 - High corrosion resistance leadless brass alloy - Google Patents

Description

  The present invention relates to a brass alloy, and more particularly to a material applied to a water supply member used for a water supply route or the like, particularly a water supply member having erosion-corrosion resistance.

  A copper alloy containing 20 to 40 mass% of zinc is called brass or brass and is used for various purposes. Among them, Cu-Zn-Pb type brass casting type 3 "CAC203" specified in JIS H5120 has excellent tensile strength, proof stress and elongation, and has been used for parts of water supply equipment such as valves and parts of water supply devices. It was However, since CAC203 contains 0.5 to 3.0% by weight of Pb, it is difficult to comply with the recent lead regulations that have advanced all over the world. Therefore, brass alloys having a reduced lead content are being studied so as to reduce the Pb leaching amount while maintaining the excellent tensile strength, yield strength and elongation of JIS H5120 CAC203.

  Further, the brass alloy has a problem different from that of lead. When a brass alloy is used for a water supply member such as a valve, it is induced by dezincification corrosion in which zinc is selectively eluted into water in a stationary state and a rapid flow of water called erosion-corrosion that occurs in running water. Exposed to corrosion. When the brass alloy is in contact with static water, the surface of the metal material is gently covered with an oxide film to counter the dezincification corrosion to some extent. Due to the effect of shearing force and turbulent flow, the oxide film is destroyed and corrosion progresses. This corrosion is called erosion-corrosion. If any of these corrosions progresses, the strength of water supply equipment and materials will inevitably decrease and water will leak from the corroded portions. Therefore, brass alloys having corrosion resistance against these corrosions are desired.

  For example, in patent document 1, Cu: 62.3-65.0 mass%, Sn: 1.0-3.5 mass%, Bi: 0.5-2.0 mass%, Al: 0.005-0. 0.5% by mass, Pb: 0.1% by mass or less, Fe: 0.1% by mass or less, Si: 0.1% by mass or less, Mn: 0.03% by mass or less, and the balance Zn and unavoidable impurities It is described that the copper-based alloy for die casting is excellent in dezincing resistance and erosion-corrosion resistance.

  Note that Patent Document 1 describes that Pb, which has been conventionally added to improve the machinability in accordance with the revision of the Pb elution standard, is replaced with Bi or Si (paragraph [0003]. ]).

  Moreover, in patent document 2, Zn: 25-40 wt%, P: 0.005-0.070 wt%, Sn: 0.05-1.0 wt%, Al: 0.05-1.0 wt%, and also Fe. : 0.005-1.0 wt%, Pb: 0.005-0.3 wt%, one or two kinds in total of 0.005-1.3 wt%, with the balance being copper and inevitable impurities It is described that the copper alloy consisting of is excellent in dezincification corrosion resistance.

Furthermore, Patent Document 3 describes an example in which the effects of individual elements are unified by the zinc equivalent (Zneq), and an alloy has been found that satisfies the required physical properties by satisfying the inequality of the zinc equivalent Zneq. There is. Specifically, Al: 0.4 to 2.5 mass%, P: 0.001 to 0.3 mass%, Bi: 0.1 to 4.5 mass% and Ni: 0 to 5 are contained. 0.5% by mass, the contents of Mn, Fe, Pb, Sn, Si, Mg, and Cd are each 0 to 0.5% by mass, Zn is contained, and the balance is Cu and unavoidable impurities. The condition is that the Zneq and Al contents satisfy the following equations (1) and (2).
Zneq + 1.7 × Al ≧ 35.0 (1)
Zneq-0.45 x Al ≤ 37.0 (2)

Japanese Patent No. 4522736 Japanese Patent Publication No. 61-39387 Patent No. 5522582

  However, none of the alloys has particularly sufficient erosion-corrosion resistance, and while maintaining the tensile strength and proof stress required as a brass alloy for water supply members, while suppressing the elution of Pb, it is possible to achieve higher corrosion resistance. was difficult.

  That is, although brass alloys having these properties individually existed in the past, a brass alloy having a good balance of safety, durability and convenience could not be achieved. Therefore, an object of the present invention is to obtain a brass alloy having these three elements in a well-balanced manner, and to make the water supply member highly practical.

This invention limits Pb to 0.25 mass% or less,
Zn is 22 mass% or more and 32.0 mass% or less, Sn is 0.50 mass% or more and 2.2 mass% or less, Al is 0.40 mass% or more and 1.6 mass% or less, and P is 0.001 mass%. Not less than 0.200 mass% and not more than 0.1 mass% and not more than 1.2 mass% Bi,
Further, the above problem was solved by using a brass alloy in which the total of Al, Sn, and Bi was set to 3.40 mass% or less and the balance was copper and inevitable impurities.

  Preferably, a brass alloy containing 0.3 mass% or more of Bi is used.

  Further, in addition to the composition of the brass alloy, a brass alloy containing one or more of the following additional elements can also solve the above problems. First, B may be contained in the range of 0.02 mass% or less. Further, Sb may be contained in the range of 0.10 mass% or less. Further, Ni may be contained in the range of 1.0 mass% or less.

  According to the present invention, while suppressing the elution of Pb by suppressing the content of Pb, while ensuring tensile strength and proof stress, it also has dezincification corrosion resistance and erosion-corrosion resistance, safety, durability and convenience. It is possible to manufacture a brass alloy water supply member that secures a good balance of properties.

Schematic diagram of tensile test evaluation method Erosion-corrosion test equipment conceptual diagram

Hereinafter, the present invention will be described in detail.
The present invention is a brass alloy for water supply members containing at least Zn, Sn, Al, P and Bi.

  The Zn content of the brass alloy needs to be 22% by mass or more. If it is less than 22% by mass, the tensile strength will be insufficient and problems will occur in mechanical properties. Further, when the content is 24% by mass or more, 0.2% proof stress can be sufficiently ensured, and the brass alloy has excellent strength. On the other hand, it needs to be 32.0% by mass or less, and preferably 30% by mass or less. When Zn exceeds 32.0 mass%, dezincification corrosion and erosion-corrosion become too large.

  The Al content of the brass alloy needs to be 0.40 mass% or more. If it is less than 0.40% by mass, the 0.2% proof stress will be insufficient, resulting in a problem in mechanical properties. On the other hand, it needs to be 1.6% by mass or less, and preferably 1.10% by mass or less. If it exceeds 1.6 mass%, the elongation may be too low.

  The Bi content of the brass alloy needs to be 0.1% by mass or more, and is preferably 0.3% by mass or more. If the amount is less than 0.1% by mass, the occurrence of defects in the metal structure cannot be ignored, and the presence of the defects in the metal structure causes the elongation to decrease too much. Also, dezincification corrosion becomes significant. By containing Bi, the machinability can also be improved. On the other hand, it must be 1.2% by mass or less, and preferably 0.8% by mass or less. If it exceeds 1.2% by mass, the elongation may be too low.

  The Sn content of the brass alloy needs to be 0.50 mass% or more. If it is less than 0.50% by mass, resistance to erosion-corrosion and yield strength become insufficient. On the other hand, it needs to be 2.2 mass% or less, and is preferably 1.6 mass% or less. This is because if Sn is too much, the elongation will be too low.

  The P content of the brass alloy needs to be 0.001 mass% or more, and is preferably 0.003 mass% or more. P contributes to the machinability and exerts a deoxidizing effect. If it is too small, the deoxidizing effect at the time of casting is lowered, so that gas defects are increased and the molten metal is oxidized to lower the flowability of the molten metal. There is a risk that Furthermore, if P is less than 0.003 mass%, there is concern about the resistance to dezincification corrosion, and if it is less than 0.001 mass%, the lack of resistance cannot be ignored. On the other hand, it must be 0.200 mass% or less, preferably 0.15 mass% or less. If the amount of P is too large, the amount of hard Al-P compound and the like will increase too much, and the elongation will decrease.

  Further, the total content of Al, Bi and Sn in the brass alloy needs to be 3.40 mass% or less. The elongation may not satisfy the sufficient condition only by satisfying the above condition for each element. These three elements are closely related, and this condition is necessary for the brass alloy to achieve the balance between strength and corrosion resistance while reducing Pb and ensuring safety.

  The Pb content of the brass alloy needs to be 0.25 mass% or less. If it exceeds 0.25% by mass, it will be difficult to satisfy the leaching standard as an alloy for water supply members in some regions, so the content must be at most 0.25% by mass. However, the above brass alloy satisfies the range of the individual elements as described above and the conditions that combine the above three elements, so that even if the content of Pb, which was conventionally required, is reduced, the brass alloy has a balanced practicability. It can be a high alloy.

  The above brass alloy may contain, in addition to Cu, an element other than the above-mentioned as an unavoidable impurity that is inevitably contained in view of raw materials and manufacturing problems. However, the contents of these elements must be kept within a range that does not impair the effects of the present invention. This is because if there are too many unexpected elements, the physical properties may be impaired even within the above range. The total amount of these unavoidable impurities is preferably less than 1.0% by mass, and more preferably less than 0.5% by mass.

  The content of each of the above-mentioned elements that become unavoidable impurities is preferably less than 0.4% by mass, more preferably less than 0.2% by mass, and even more preferably less than the detection limit. Examples of such impurities include Si, Fe, Mn, Cr, Zr, Mg, Ti, Te, Se, Cd, and the like. Among them, Se, Cd, and Te, which have known toxicity, are preferably less than 0.1% by mass, and more preferably less than the detection limit. Further, Zr that increases shrinkage cavity defects is preferably less than 0.1% by mass, and more preferably less than the detection limit.

  On the other hand, when the brass alloy contains 0.005 mass% or more of B as an additional element intentionally contained in addition to the unavoidable impurities, the dezincification corrosion resistance is greatly improved. This is because the crystal grains are refined by B and are less susceptible to dezincification corrosion. When B is contained in an amount of 0.007 mass% or more, dezincification corrosion resistance is further improved, which is preferable. On the other hand, it needs to be 0.020 mass% or less. If it is contained in excess of 0.020 mass%, a large amount of hard compound may be generated in the tissue, which may adversely affect machinability and elongation.

  In addition to the unavoidable impurities, the brass alloy may contain Ni as an additional element to be intentionally included. When Ni is contained in an amount of 0.1% by mass or more, the dezincification corrosion resistance of the brass alloy is improved. This effect can be overlapped with the effect of the inclusion of B. On the other hand, it is necessary to be 1.0% by mass or less, and more preferably 0.5% by mass or less. If Ni is added excessively, the phase containing a large amount of Sn increases, and the elongation and the machinability are likely to decrease.

  Further, the brass alloy may contain Sb as an additional element to be intentionally included in addition to the unavoidable impurities. By containing Sb in an amount of 0.02 mass% or more, the effect of improving erosion-corrosion resistance can be obtained. On the other hand, it must be 0.10 mass% or less. This is because if the content exceeds 0.10% by mass, a problem occurs in elongation.

  In addition, as the element to be intentionally contained in the brass alloy, a plurality or all of B, Ni, and Sb may be added within the above content range.

  The value of the content in the present invention does not represent the ratio in the raw material but the content at the time of producing the alloy by casting, forging, or the like.

  The balance of the brass alloy is Cu. The brass alloy according to the present invention can be obtained by a general copper alloy manufacturing method, and when manufacturing a water supply member using this brass alloy, a general manufacturing method (for example, casting, wrought copper, forging, etc.) Can be manufactured by. For example, a method of melting the alloy using a heavy oil furnace, a gas furnace, a high-frequency induction melting furnace, etc., and casting in a mold of each shape can be mentioned.

  Hereinafter, an example of actually producing the brass alloy according to the present invention will be reported. First, a test method performed on a brass alloy will be described.

<Tensile test method>
A sample cast in a φ28 mm × 200 mm mold was processed into a No. 14A test piece specified by JIS Z2241. The specific shape is as shown in FIG. This is a proportional test piece in which the original cross-sectional area S ₀ of the parallel portion and the original gauge point distance L ₀ have a relationship of L ₀ = 5.65 × S ₀ ^ (1/2). The diameter d _{0 of the} rod-shaped portion was 4 mm, the original gauge length L ₀ was 20 mm, the length L _c of the parallel portion formed into a cylindrical shape was 30 mm, and the radius R of the shoulder portion was 15 mm. (L ₀ = 5.65 × (2 × 2 × π) ^ (1/2) = 20.04)

A tensile test was performed on this test piece in accordance with JIS Z2241, and its tensile strength (MPa), 0.2% proof stress (MPa), and elongation (%) were evaluated as follows. The tensile strength was the maximum stress that the test piece withstood during the test until it showed discontinuous yielding in the test. The 0.2% proof stress is the stress when the plastic elongation becomes equal to 0.2% with respect to the original gauge length L ₀ . Further, the elongation is a value obtained by expressing the permanent elongation of the test piece after testing until it breaks, as a percentage with respect to the original gauge length L ₀ .
The evaluation of 0.2% proof stress was ∘ ... 100 MPa or more and × ... less than 100 MPa.
The tensile strength was evaluated as ∘ ... 300 MPa or more, ◯ ... 245 MPa or more and less than 300 MPa, and X ... less than 245 MPa.
・ Evaluation of elongation was set to ⊚ ... 20% or more, ∘ ... 15% or more and less than 20%, and X ... less than 15%.

<Dezincification corrosion test method>
A test piece was obtained by cutting a 10 mm square cube from a sample cast in a φ28 mm × 200 mm mold, and the test piece was performed according to ISO6509. That is, the periphery of the test piece was covered with an epoxy resin having a thickness of 15 mm or more, and only one surface of the test piece was exposed from the resin. The exposed surface of 100 mm ² was polished with wet polishing paper, finished with No. 1200 polishing paper, and washed with ethanol immediately before the test. The sample embedded in this epoxy resin and exposed on only one surface was immersed in 250 mL of 12.7 g / L cupric chloride aqueous solution at 75 ± 5 ° C. for 24 hours. After the test was finished, it was washed with water, rinsed with ethanol, and immediately, the dezincification depth of the cross-section was measured using an optical microscope. Specifically, the 10 mm sample was divided into 5 fields of view, and the dezincification depth was measured for each field of view. Of the 10 points in total, the deepest point was evaluated as the maximum dezincification corrosion depth as follows. did. A: Less than 100 μm, A: 100 μm or more and less than 200 μm, ×: 200 μm or more.

<Erosion-corrosion test>
As shown in FIG. 2, a sample cast in a mold of Φ20 × 120 mmL was processed into a cylinder of Φ16 mm as a test piece 12, and a gap of 0.4 mm was made to the test piece 12. A 1.6 mm diameter nozzle 11 was set, and a 1% CuCl ₂ aqueous solution 13 was continuously flowed from the nozzle 11 toward the sample at a forward flow rate of 0.4 L / min for 2 hours to measure the maximum depth of the sample before and after the test. .. The evaluation of the maximum depth of erosion-corrosion was ⊚ ... 75 μm or less, ∘ ... deeper than 75 μm, 200 μm or less, × ... deeper than 200 μm.

<Sample manufacturing method>
The materials constituting the respective elements were mixed, melted in a high-frequency induction melting furnace, and then cast to prepare test materials in each example having the contents described in each table. In addition, all the content values are mass% and are measured values after production. The following tests were conducted on each of the obtained copper alloys. In addition, elements not listed in the table and blanks indicate that the values are below the detection limit. In addition, as a comprehensive evaluation, if all items are ◎, it is “◎”, if there is at least one ○ and there is no x, it is “o”, and if there is at least one x, it is x. did.

  Based on Example 1, changes in mechanical properties, dezincification corrosion and erosion-corrosion resistance when the contents of Zn, Al, Bi, P, Sn and Pb were changed were evaluated. The components and the results are shown in Table 1.

(Examples 2a and 2b, Comparative examples 2a and 2b)
First, an example in which the content of Zn was changed was prepared. Comparative Example 2a in which Zn is less than 22 mass% has a problem in tensile strength. In Example 1 in which the content is 22% by mass or more, the tensile strength can be secured. On the other hand, in Comparative Example 2b in which Zn is too much and exceeds 32.0 mass%, there is a problem in elongation.

(Examples 3a to 3d, Comparative Examples 3a and 3b)
Secondly, an example in which the Al content was changed was prepared. In Comparative Example 3a in which Al was less than 0.40% by mass, the 0.2% proof stress was insufficient. In Examples 3a to 3d in which Al exceeds 0.40 mass%, 0.2% proof stress can be secured to some extent. On the other hand, in Examples 3a to 3d, the elongation was decreased with the increase of Al, and in Comparative Example 3b in which Al was more than 1.6 mass%, the elongation was significantly decreased.

(Examples 4a to 4c, Comparative Examples 4a and 4b)
Thirdly, an example in which the content of Bi was changed was adjusted. In Comparative Example 4a in which Bi was less than 0.1% by mass, the elongation decreased and the dezincification corrosion was remarkable, which was a problem in any point. By containing Bi in an amount of 0.1% by mass or more, elongation was greatly improved and dezincification corrosion resistance was also improved. However, the elongation tends to decrease as the Bi content increases, and in Comparative Example 4b in which Bi is contained too much and exceeds 1.2% by mass, the elongation is excessively decreased.

(Examples 5a and 5b, Comparative examples 5a and 5b)
Fourth, an example in which the P content was changed was prepared. Dezincification corrosion was remarkably observed in Comparative Example 5a in which P was less than the detection limit. It was shown in Example 5a that inclusion of P improves the dezincification corrosion resistance. On the other hand, when the P content increases, the elongation tends to decrease, and in Comparative Example 5b in which P exceeds 0.200 mass%, the elongation is too low.

(Examples 6a to 6d, Comparative Examples 6a to 6c)
Fifthly, an example in which the Sn content was changed was prepared. In Comparative Examples 6a and 6b in which Sn was less than 0.50% by mass, the erosion-corrosion resistance was insufficient. Further, especially in Comparative Example 6a in which Sn was small, 0.2% proof stress was insufficient. On the other hand, in Comparative Example 6c in which Sn is 2.11 mass%, the elongation is too low, but regarding this, it is necessary to consider the relationship with other elements. This is because in Example 8b, which will be described later, the amount of Sn is more than that in Example 8b, which is 2.24% by mass, so that the reduction in elongation is relatively suppressed.

(Example 7a, Comparative Example 7b)
Sixth, an example in which both Al and Sn were varied was adjusted. The elongation of Comparative Example 7a in which both are increased is remarkably reduced. On the other hand, the Sn content of Example 7a is 0.96% by mass, which is almost the same as the value of Example 6b in which the Sn content is changed to 0.98% by mass. However, the two are significantly different in Example 6b in erosion-corrosion resistance. The difference between the two is the content of Al, which suggests that Al and Sn are related to each other.

(Examples 8a to 8c, Comparative Example 8a)
Seventh, an example in which both Bi and Sn are varied was adjusted. Here, in Example 8b, Sn is 2.24% by mass, which exceeds 2.11% by mass of Comparative Example 6c, but the decrease in elongation is suppressed. Comparing these two examples suggests that the difference in Bi content is acting. Taken together with the consideration in Example 7a above, it is suggested that Al, Sn and Bi are related to each other.

  Comparing Example 8a and Comparative Example 6c with the total amount of these three elements, the total amount of the three elements of Al + Sn + Bi is greatly different, whereas the total amount of Example 8b is 3.37% by mass. Comparative Example 6c has reached 3.76% by mass. As described above, it was shown that not only the content of each element can be determined alone, but also the physical properties can be balanced by the components that combine the three elements.

(Examples 9a to 9f, Comparative Example 9a)
Further, in addition to the above essential elements, Examples 9a and 9b containing Ni, Example 9c containing B, Examples 9d containing 9B and Ni, and Example 9f containing Sb were added. Comparative Example 9a was prepared. The contents are shown in Table 2. When the same test was carried out, in Examples 9a and 9b, the improvement of dezincification corrosion resistance was confirmed by the addition of Ni. It was also confirmed that the inclusion of both B and Ni improves both elongation and erosion-corrosion resistance. Further, it was confirmed that the addition of Sb improved the erosion-corrosion resistance. However, it was confirmed that if the amount of Sb is too large, a problem occurs in elongation.

11 Nozzle 12 Test Piece 13 CuCl ₂ Aqueous Solution

Claims (5)

Zn is 22 mass% or more and 32.0 mass% or less, Sn is 0.50 mass% or more and 2.2 mass% or less, Al is 0.40 mass% or more and 1.6 mass% or less, and P is 0.001 mass%. And 0.200 mass% or less, Bi 0.1 mass% or more and 1.2 mass% or less , B 0.005 mass% or more and 0.02 mass% or less ,
The balance consists of copper, Pb of 0.25% by mass or less, and inevitable impurities,
A low lead brass alloy for water supply members having a total content of Al, Sn and Bi of 3.40% by mass or less. Zn is 22 mass% or more and 32.0 mass% or less, Sn is 0.50 mass% or more and 2.2 mass% or less, Al is 0.40 mass% or more and 1.6 mass% or less, and P is 0.001 mass%. Or more 0.200 mass% or less, Bi 0.1 mass% or more 1.2 mass% or less , Sb 0.02 mass% or more 0.10 mass% or less ,
The balance consists of copper, Pb of 0.25% by mass or less, and inevitable impurities,
A low lead brass alloy for water supply members having a total content of Al, Sn and Bi of 3.40% by mass or less. Zn is 22 mass% or more and 32.0 mass% or less, Sn is 0.50 mass% or more and 2.2 mass% or less, Al is 0.40 mass% or more and 1.6 mass% or less, and P is 0.001 mass%. 0.200 mass% or less, Bi 0.1 mass% or more 1.2 mass% or less , Ni 0.1 mass% or more 1.0 mass% or less ,
The balance consists of copper, Pb of 0.25% by mass or less, and inevitable impurities,
A low lead brass alloy for water supply members having a total content of Al, Sn and Bi of 3.40% by mass or less. A low lead brass alloy for water supply members which further contains 0.02 mass% or more and 0.10 mass% or less of Sb in addition to the composition of the low lead brass alloy for water supply members according to claim 1 . A low lead brass alloy for water supply members, which further contains 0.1% by mass or more and 1.0% by mass or less of Ni, in addition to the composition of the copper alloy for water supply members according to claim 1, 2 or 4 .

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