JP4455507B2 - Valve for drinking water - Google Patents

Description

  The present invention relates to a valve for drinking water using a bronze alloy that improves mechanical properties such as tensile strength while ensuring a predetermined machinability, and further improves castability, and in particular, Pb. The present invention relates to a valve for drinking water which uses a bronze alloy which is applied to a mass production valve containing a rare element as an alternative component and which is improved in terms of tensile strength.

  Among the alloys, in particular, the bronze casting (CAC406) is excellent in castability, corrosion resistance, machinability, and pressure resistance, has a good hot water flow at the time of melting, and is suitable for casting parts having a somewhat complicated shape. Conventionally, it has been widely used for general piping equipment such as valves, cocks and joints.

  Since this CAC406 is easy to obtain a sound casting and contains about 5% Pb in mass ratio, it is particularly good in machinability, so it is often used for water fittings for this type of piping equipment. Has been.

  When this bronze alloy is used as a material for water-contact fittings such as valves, lead contained in the bronze casting is hardly dissolved, resulting in deterioration of water quality. This phenomenon becomes prominent particularly when water stays in the water-contact fitting. Therefore, at present, so-called lead-less copper alloys are actively developed, and several new alloys have been proposed. A typical example will be described below.

For example, a lead-less copper alloy has been proposed in which Bi is added instead of lead in a bronze alloy to improve machinability and prevent dezincing (for example, see Patent Document 1). Moreover, lead-free bronze with improved machinability by adding Ca to BC6 (CAC406) or the like to mainly form a compound with P (CaP, Ca ₃ P ₂ ) to obtain a function of reducing cutting waste. Has been proposed (see, for example, Patent Document 2). Although it is characterized in that an intermetallic compound of CaP is precipitated, the addition of Ca into a copper alloy is difficult to use practically because Ca is an active metal, and thus the oxidation is intense and the yield is remarkably low. Moreover, the lead-free bronze which suppressed generation | occurrence | production of the porosity at the time of casting by Bi addition for machinability improvement by addition of Sb, and raised mechanical strength is proposed (for example, refer patent document 3). Further, Ni is added for the purpose of strengthening the matrix and preventing segregation. A bronze casting material has been proposed in which Ti is added to refine the crystal as a substitutional intermetallic compound and B is added to reinforce the grain boundary strength as an interstitial intermetallic compound (for example, Patent Document 4). reference.). Further, a lead-free free-cutting bronze alloy in which Bi is added to improve machinability and seizure resistance and Sn, Ni, and P are added to ensure dezincing resistance and mechanical properties has been proposed ( For example, see Patent Document 5.) Further, a bronze alloy in which Se—Zn compound is precipitated in particular by addition of Se and Bi and mechanical properties and machinability are equivalent to those of CAC406 has been proposed (for example, see Patent Document 6).
In addition, there is a report submitted as a report on the results of research on lead-free copper alloy castings (see Non-Patent Document 7).
Japanese Patent Publication No. 5-63536 (page 2-3) Japanese Patent No. 2949061 (page 2-3, FIG. 2) Japanese Patent No. 2889829 (pages 3-6) Japanese Patent No. 2723817 (page 2-10) JP 2000-336442 A (page 3-4) US Pat. No. 5,614,038 (page 1-4) Published by Japan Nonferrous Metal Casting Association, etc., 2001 Development Report on Leadless Copper Alloy Castings, February 28, 2002

As described above, all the lead-free bronze alloy materials that have been proposed ensure the specified values of JIS H5120 bronze alloy (CAC406) (tensile strength of 195 N / mm ² or more, elongation of 15% or more). However, the above-mentioned characteristics of the CAC406 material distributed in the market have a tensile strength of around 240 N / mm ² and an elongation of around 33%, which are significantly higher than the JIS standard values. At present, no alloy has been developed that can ensure equivalent mechanical properties and machinability. The lead-less bronze alloy contains Se, Bi, etc. as an alternative component of Pb, but these elements are expensive rare elements. There has been a demand for the development of an alloy that secures the above-mentioned characteristics equivalent to the material CAC406. Furthermore, the leadless bronze alloy has been proposed with an eye to improving mechanical properties and machinability, but Pb is a component that contributes to the soundness of castings. However, how to ensure the soundness of castings was not clarified.

  In particular, Non-Patent Document 7 only reports the results of research on lead-free copper alloys, and alloys that have the same characteristics as CAC406 while reducing the amount of rare elements such as Se and Bi. The fact is that the development of

  The present invention has been developed as a result of earnest research, and its purpose is to accurately capture the true characteristics of rare elements (Bi or Bi and Se) that are alternative components of Pb. By this, even if the content of rare elements (Bi or Bi and Se) in the alloy is reduced, while maintaining the same machinability as the bronze alloy (CAC406) that has been conventionally used in general, it is equivalent to or better than CAC406. It is possible to reduce the occurrence of casting defects by elucidating the influence of the decrease in Pb substitute components (Bi, or Bi and Se) on the soundness of castings, as well as mechanical properties such as tensile properties. It is another object of the present invention to provide a drinking water valve processed and formed using a bronze alloy which can be suppressed and can be manufactured at low cost by reducing rare elements.

In order to achieve the above object, the invention according to claim 1 includes Zn 5.54 to 10.0 (mass%), Sn 2.8 to 5.0 (mass%), Bi 0.4 to 3.0 (mass). %), 0 ≦ Se ≦ 0.35 (mass%), a bronze alloy composed of the balance Cu and inevitable impurities, and calculated as 0.93 Bi (mass%) + 2.86 Se (mass%) A bronze alloy with a physical quantity in the range of 1.20 (Vol%) to 4.90 (Vol%) and a tensile strength of not less than 215 N / mm ^2. It is a valve for drinking water that is used to process and mold a valve for drinking water.

According to the present invention, the content of rare elements (Bi, or Bi and Se) in the alloy can be reduced by accurately capturing the true characteristics of rare elements (Bi, or Bi and Se) that are substitute components of Pb. Even if it is reduced, it becomes possible to obtain a valve for drinking water having mechanical properties equivalent to or better than those of CAC406, while ensuring the same machinability as bronze alloy (CAC406) that has been conventionally used. In addition, it is possible to provide a valve used for drinking water, which is remarkably improved in terms of tensile strength.

  The present invention can produce a valve for drinking water using a bronze alloy containing rare elements (Bi, or Bi and Se) at a low cost by reducing rare elements (Bi or Bi and Se). It became.

  The bronze alloy of the present invention accurately captures the true characteristics of each element such as rare elements (Bi or Bi and Se) which are substitute components of Pb, and based on the true characteristics of each element, the bronze alloy of the present invention This bronze alloy was developed as a composition range of the following, and is composed of the most suitable composition range for improving mechanical properties while ensuring a predetermined machinability and soundness of castings. One Embodiment of the valve | bulb for drinking water using the bronze alloy in invention is described. The bronze alloy in the present invention is Zn 5.0-10.0 mass%, Sn: 2.8-5.0 mass%, Bi: 0.4-3.0 mass%, 0 ≦ Se ≦ 0.35 mass, And the form which consists of remainder Cu and an unavoidable impurity is employ | adopted. A preferable embodiment of the bronze alloy in the present invention is Sn: 2.8 to 5.0 mass%, Bi: 0.4 to 3.0 mass%, 0 ≦ Se ≦ 0.35 mass, Zn: 5.0 to A bronze alloy composed of 10.0% by mass, Ni: 3.0% by mass or less, 0 <P <0.5% by mass, Pb: less than 0.2% by mass, and the balance Cu. The Se content is preferably 0.2% by mass or less, and the Sn content is preferably 3.5 to 4.5% by mass.

The composition range of the bronze alloy in the present invention and the reason thereof will be described.
Bi: 0.4-3.0 mass%
It is effective for improving the machinability. In order to prevent the occurrence of casting defects such as shrinkage cavities by entering the porosity generated in the casting solidification process and ensure the soundness of the casting, Bi is contained in an amount of 0.2% by mass or less , and Bi. It is effective to contain 0.4% by mass or more. On the other hand, in order to ensure the required mechanical properties, it is effective to be 3.0% by mass or less, and in particular, it is 1.7% by mass or less while suppressing the content while reducing the mechanical properties. It is effective to ensure sufficient. Practically, it is preferable to contain 0.8 to 1.7% by mass of Bi together with the content of Se, and considering the optimal content of Se, about 1.3% by mass is optimal.

Se: 0 <Se ≦ 0.35 mass%
It exists as an intermetallic compound of Bi—Se, Se—Zn, and Cu—Se in the bronze alloy, and is a component that contributes to ensuring the machinability and the soundness of the casting, similarly to Bi. Therefore, the inclusion of Se is effective for ensuring the mechanical properties and the soundness of the casting described later while suppressing the Bi content. Here, the mechanical property values such as the tensile strength of the bronze alloy at the mass production level vary within a range of about 20% depending on the casting conditions even if the component values of the casting are substantially the same. It has been found by experience. In order to satisfy the JIS standard value even when the tensile strength becomes the lowest value due to this variation, the tensile strength is one of the characteristics that tend to decrease with increasing Se content. Therefore, it is necessary to secure a tensile strength of about 97% of the maximum value (about 250), so 0.35 mass% was made the upper limit. Further, Se contributes to ensuring the soundness of castings even if contained in a small amount, but in order to reliably obtain its action, inclusion of 0.1% by mass or more is effective, and this value is set as a preferred lower limit value. I did .

Sn: 2.8 to 5.0 mass%
It is contained in order to improve the wear resistance and corrosion resistance by solid solution in the α phase and improving the strength and hardness and forming a protective film of SnO ₂ . Sn is an element that linearly decreases the machinability as the content increases in the practical component range. Therefore, it is necessary to ensure the mechanical properties within a range that does not decrease the corrosion resistance while suppressing the content. As a more preferable range, paying attention to the elongation characteristics that are easily affected by the Sn content, the elongation at the maximum value (Sn = 4.0% by mass) can be reliably obtained even if the casting conditions and the like slightly change. 3.5-4.5% by mass was found. Conventionally, Sn has been known as a component that reinforces the matrix and improves mechanical properties as the content increases, but as a result of intensive research, the relationship between Sn content and tensile strength In the low region, the tensile strength is improved as the Sn content is increased. However, the tensile strength is peaked around 4.4% by mass, and the tensile strength is lowered when the content is higher than that. In addition, the relationship between the Sn content and the elongation was obtained so as to exhibit substantially the same tendency as the tensile strength property.

Zn: 5.0-10.0 mass%
It is effective as an element that improves hardness and mechanical properties, particularly elongation, without affecting the machinability. In addition, Zn suppresses the formation of Sn oxides due to gas absorption into the molten metal and is also effective for the soundness of the molten metal. Therefore, the inclusion of 5.0% by mass or more is effective for exerting this action. is there. More practically, the content is preferably 7.0% by mass or more from the viewpoint of compensating for the suppression of Bi and Se. On the other hand, since Zn has a high vapor pressure, it is preferably contained in an amount of 10.0% by mass or less in consideration of ensuring the working environment and castability. Considering the economic efficiency, about 8.0% by mass is particularly optimal.

Ni: 3.0% by mass or less Even when Ni is not contained at all, necessary mechanical properties such as tensile strength can be obtained, but it is added when the mechanical properties of the alloy are more effectively improved. Ni dissolves in the α solid solution up to a certain amount, strengthens the matrix, and improves the mechanical properties. Inclusion of more than that forms an intermetallic compound with Cu and Sn, and improves the machinability while lowering the mechanical properties. In order to improve the mechanical strength, the content of Ni of 0.2% by mass or more is effective, but the peak of mechanical strength exists at about 0.6% by mass. Therefore, the preferable Ni content is set to 0.2 to 0.75% by mass.

P: Less than 0.5% by mass Less than 0.5% by mass is added for the purpose of promoting deoxidation of the molten bronze alloy and producing sound castings and continuous cast ingots. If the content is excessive, the solidus line is lowered and segregation is likely to occur, and a P compound is formed and weakened. Therefore, in the case of die casting, the content is preferably 200 to 300 ppm, and in the case of continuous casting, the content is preferably 0.1 to 0.2% by mass.

Pb: Less than 0.2% by mass The range of inevitable impurities not actively containing Pb was set to less than 0.2% by mass.

  The bronze alloy in the present invention described above is applied to a wetted part as a material. In particular, this wetted part is applied to a drinking water valve.

  Below, the test example and Example of the bronze alloy which is a material which processes and shape | molds the valve | bulb for drinking water in this invention are demonstrated. The components shown in Tables 1 and 2 are the results of actual analysis of tensile test pieces and machinability test pieces. In particular, the Pb component is at an impurity level (0.02% by mass or less), and the Sb component is also an impurity. Level (less than 0.2% by mass).

(Tensile test)
Tensile test pieces were cast and cast at a temperature of 1130 ° C. and tested with an Amsler tester. Table 3 shows the results of the tensile test.

(Machinability test)
For the machinability test piece, a cylindrical workpiece was turned with a lathe, and the cutting resistance applied to the cutting tool was evaluated by a machinability index with the cutting resistance of the bronze casting CAC406 as 100. The test conditions were as follows: casting temperature 1180 ° C. (CO ₂ mold), workpiece shape φ31 × 260 mm, surface roughness R _A 3.2, depth of cut 3.0 mm, lathe speed 1800 rpm, feed rate 0. 2 mm / rev, no oil used. Table 3 shows the test results of the machinability test.

Next, the castability of the bronze alloy, which is a material for processing and forming the drinking water valve in the present invention, is analyzed.
Since the bronze casting has a wide solidification temperature range, it becomes a Massy-type solidification mode and generates a fine shrinkage nest in the dendrite gap. As a result, the pressure resistance performance (castability) of the casting tends to deteriorate significantly. In the bronze, Pb aggregates in the dendrite gap and has a role of filling a fine shrinkage nest. In the alloy of the present invention not containing Pb, the role of Pb is supplemented by the inclusion of Bi and Se. However, the effect of the content and content of Bi and Se on the pressure resistance performance of the casting is not well known, and Bi and Se are added unnecessarily, increasing the material cost and reducing the mechanical properties. There is a possibility. Therefore, the influence of Bi and Se on the castability of the casting is investigated, the optimum blending amount of Bi and Se is determined, and the significance of the Se content is clarified.

  As described above, the bronze alloy is likely to generate fine shrinkage in the casting, but this tendency is particularly remarkable in the thick part of the casting that is gradually cooled. This is called a mass effect. In order to evaluate the degree of mass effect, a step-like casting test piece was prepared, and this was cut and subjected to a dye penetration test. Further, the volume ratio of the amount of non-solid solution (Bi phase, Se—Zn phase) was also measured.

  First, the test method of the dye penetration test and the test results will be described. FIG. 1 shows a casting method for a stepped mold. In the casting method of the stepped casting, it is common to attach a hot water supply of φ70 × 120 to the runway. However, as shown in FIG. 1, the hot water supply was intentionally removed in this test. This is because the actual production of bronze castings is taken into account. In actual production, it is difficult to attach an effective feeder due to problems such as the number of molds installed in one frame, the complexity of the casting shape, and the yield. is there.

Casting conditions for the stepped cast specimen were as follows. Melting was performed in a 15 kg high-frequency experimental furnace, the melting amount was 12 kg, the casting temperature was 1180 ° C., the casting time was 7 seconds, the mold was a CO ₂ mold, and the deoxidation treatment was P270 ppm added. In the dye penetrant flaw detection test, a penetrating solution is sprayed on the cut surface of the test piece, left to stand for 10 minutes, and then the penetrating solution is wiped off. This is a test for judging. Table 4 shows the chemical component values of each specimen.

  Table 5 shows the test results of the dye penetration test for each sample. 2 and 3 are photographs showing test results of the dye penetrant flaw detection test, and show that a casting defect exists at a position displayed in black. From the results of the dye penetrant flaw detection test, the specimen No. 6, 7 and 14 are accepted. The pass was defined as (◯), which has the same castability as that of the conventional material CAC406 (JIS) and can be produced by the same casting method. Specimen No. With respect to Nos. 5 and 13, shrinkage can be confirmed, but this is considered to be able to be handled by the same casting method as CAC 406, and is regarded as acceptable (Δ). However, some products have defects depending on the product shape and casting conditions, and it seems that some changes must be made to the casting conditions and the casting method. For other specimens, reject (x). Even for rejected products, it is possible to cast good products by changing the casting method or casting, but it is undeniable that it takes cost and labor.

  Next, a method for measuring the volume ratio of the amount of non-solid solution (Bi phase, Se—Zn phase) and the measurement results will be described. A non-solid solution means an element or a compound that does not form a solid solution in a matrix in an alloy but exists in a grain boundary or in a grain. This non-solid solution penetrates into the microporosity due to the solidification mode peculiar to bronze castings and has the effect of filling it. Can be obtained. Examples of the non-solid solution include Bi and Pb in which the majority exists alone, and Se (Bi-Se, Se-Zn, etc.) that exists as a compound. FIG. 4 is a metallographic photograph (magnification 400 times) showing a non-solid solution (Bi phase, Se—Zn phase). Further, the Bi content and Se content indicate the content of Bi and Se in the alloy as component values (unit: mass%), and the Bi phase precipitation amount and Se—Zn phase precipitation amount 2 shows the content of Se—Zn present as a compound with Bi or Zn in the alloy as a volume ratio (unit: Vol%).

The amount of non-solid solution can be calculated from the composition in the alloy, and the procedure is shown below. First, the type of non-solid solution present in the alloy is specified by X-ray analysis. Then, surface analysis (mapping) is performed using EPMA (electron beam microanalyzer), EDX (energy dispersive X-ray analyzer), etc., and the abundance ratio is calculated for each non-solid solution identified by X-ray analysis To do. Table 5 shows the amount of the non-solid solution of each specimen thus calculated. The shape of the specimen was a JIS No. 4 tensile test piece, and this cross section of the central part of the score was analyzed. Vol% (volume ratio) refers to the volume ratio of the amount of non-solid solution to the whole alloy. Moreover, the actual measurement value of the non-solid solution amount in the table represents the total value of Vol% of the Bi phase and the Se—Zn phase constituting the non-solid solution.

  As the amount of non-solid solution decreased, a tendency for shrinkage to occur was confirmed. Specifically, shrinkage cavities were generated when the amount of non-solid solution was less than 1.4 Vol% as a volume ratio with respect to the entire alloy, and when the amount was less than 0.95 Vol%, many shrinkage cavities were generated. On the other hand, shrinkage nests decreased when the amount of non-solid solution exceeded 0.95 Vol%. Therefore, it is effective to secure the amount of non-solid solution of 1.4 vol% or more in order to obtain 1.20 vol% or more which is greater than 0.95 vol% and more castability equivalent to CAC406.

When the amount of non-solid solution exceeds 4.90 Vol%, it has been found that the tensile strength is less than 215 N / mm ² considering the +20 manufacturing error of the standard value 195 N / mm ² of CAC406. Therefore, the content of non-solid solution that can minimize the Bi content and maximize the Se content and ensure the machinability, the soundness of the casting, and the mechanical properties is 4.90 Vol%. It is desirable to set the upper limit of the amount of non-solid solution and 1.20 Vol% as the lower limit.

Next, how much Bi or Se acts to secure the amount of non-solid solution will be described based on the actual measurement and test results in Table 5. In order to contain only Bi as a lead substitute component and ensure a non-solid solution amount of 1.35 Vol% or more, it is necessary to contain Bi of 1.5 mass% or more. On the other hand, in the case of containing Bi and Se as lead substitute components, the content of Bi is reduced to 0.7 to 1.2% by mass by including Se in the range of about 0.1 to 0.25% by mass. In the suppressed state, approximately the same amount of non-solid solution can be secured. This is because, among non-solid solutions, Bi and the like are generally present alone in the structure, and 1 mass% of Bi corresponds to a non-solid solution amount (Bi phase) of about 0.9 Vol%, while Se. Is mainly present as an intermetallic compound such as Se—Zn, so that 1% by mass of Se corresponds to a non-solid solution amount (Se—Zn phase) of about 2.9% by volume. This is because a large volume ratio is secured.

  Furthermore, it demonstrates using a graph. FIG. 5 shows the relationship between Bi content (mass%) and Bi phase precipitation (Vol%), and FIG. 6 shows the relationship between Se content (mass%) and Se—Zn phase precipitation (Vol%). . From the regression line of the graph shown in FIG. 5, it can be seen that the Bi phase occupies a volume 0.93 times the Bi content (% by mass). Moreover, it turns out that the Se-Zn phase occupies 2.86 times the volume with respect to Se content (mass%) from the regression line of the graph shown in FIG.

  Se produces a non-solid solution precipitation amount (Se-Zn phase) three times that of Bi by making Se's own specific gravity light (compared to Bi) and an intermetallic compound with Zn. Therefore, by containing Se, the Bi content can be suppressed, the total content of Pb substitute components, which are rare elements, is suppressed, the material cost is reduced, and the amount of non-solid solution is effectively secured. It is possible to obtain a lead-free copper alloy that suppresses the occurrence of casting defects and has excellent pressure resistance.

  The theoretical value of the non-solid solution amount in Table 5 is obtained by substituting the Bi content (% by mass) into the linear regression equation Y = 0.93X obtained in the graph shown in FIG. 5 and obtained in the graph shown in FIG. This is a theoretical value represented by substituting the Se content (mass%) into the regression equation Y = 2.86X of the straight line and adding the obtained values. That is, the non-solid solution amount theoretical value is expressed by the following equation.

  Non-solid solution amount theoretical value (Vol%) = 0.93 Bi (mass%) + 2.86 Se (mass%)

  As shown in Table 5, the measured values and the theoretical values of the amount of non-solid solution are somewhat open, but they are approximated relatively correctly. By doing so, the amount of non-solid solution at the mass production level of the material can be grasped without performing an experiment each time, the occurrence of casting defects can be suppressed, and a lead-free copper alloy excellent in pressure resistance can be obtained. .

It is explanatory drawing which showed the casting method of the step-like casting test piece. It is the photograph which showed the test result (No.1-No.7) of the dyeing | penetration penetration flaw test. It is the photograph which showed the test result (No.8-No.14) of the dyeing | penetration penetration flaw test. It is the metal structure photograph (400-times multiplication factor) which showed the non-solid solution (Bi phase, Se-Zn phase). It is the graph which showed the relationship between Bi content and Bi phase precipitation amount. It is the graph which showed the relationship between Se content and Se-Zn phase precipitation amount.

Claims (1)

Zn 5.54 to 10.0 (mass%), Sn 2.8 to 5.0 (mass%), Bi 0.4 to 3.0 (mass%), 0 ≦ Se ≦ 0.35 (mass%), It is a bronze alloy composed of the balance Cu and inevitable impurities, and the amount of non-solid solution calculated by 0.93 Bi (mass%) + 2.86 Se (mass%) is 1.20 (Vol%) to 4.90 (Vol%). ), And the tensile strength does not fall below 215 N / mm ² , and the valve for drinking water is processed and molded using this bronze alloy with excellent tensile properties. Characteristic drinking water valve.

Images