TWI392752B - Low-lead copper alloy - Google Patents

Description

Low lead copper alloy

This invention relates to a copper alloy, and more particularly to a low lead copper alloy.

The main components of brass are copper and zinc, which are usually about 7:3 or 6:4, and usually contain small amounts of impurities. In order to improve the properties of brass, conventional brass is lead-containing (up to 1-3% by weight) to achieve the desired mechanical properties of the industry, and thus has become an important industrial material, which is widely used in pipelines, faucets, water supply/drainage systems. Products such as metal devices or metal valves.

However, with the rise of environmental awareness, the impact of heavy metals on human health and the problem of environmental pollution are gradually being taken seriously. Therefore, limiting the use of lead-containing alloys is the current trend, and countries such as Japan and the United States have successively revised relevant regulations to promote Reducing the lead content in the environment, including lead-containing alloy materials used in household appliances, automobiles, and water peripheral products, in particular, it is not allowed to dissolve lead to drinking water from the product, and lead pollution must be avoided in the processing.

In addition, when the zinc content in the brass exceeds 20% by weight, dezincification corrosion is likely to occur, especially when the brass is exposed to a high chloride ion environment, such as a seawater environment, the dezincification corrosion phenomenon is accelerated. occur. Since dezincification can seriously damage the structure of the brass alloy, the surface strength of the brass product is lowered, or even the brass tube is perforated, the service life of the brass product is greatly shortened, and the application problem is caused.

In view of the above-mentioned problems of high lead content and dezincification, the industry continues to develop copper alloy formulations, in addition to the necessary components of copper and zinc, such as TW421674, US7354489, US20070062615, US20060078458, US2004023441, US2002069942, etc. The lead-free copper alloy formulation of the element, but the disadvantage of the above alloy is poor machinability. CN10144045 discloses a lead-free copper alloy formulation containing aluminum, bismuth and phosphorus as main alloying elements. Although it can be used for casting, the machinability is poor, the processing efficiency is much lower than that of lead brass, and it is not suitable for mass production. CN101285138 and CN101285137 disclose a lead-free copper alloy formulation using phosphorus as a main alloying element, but it is prone to cracks, slag inclusions and the like when used for casting. For example, US Pat. No. 7,729, 215, US 6,974, 509, US Pat. No. 6,955, 378, US Pat. No. 6,149, 739, US Pat. No. 5, 092, 056, US Pat. No. 5, 565, 827, US Pat. No. 5, 487, 867, US Pat. No. 5, 306, 072, US Pat. The range of high bismuth content is prone to cracks, slag inclusions, etc., and the cost is too high, which is not conducive to commercialization. US6413330 discloses a lead-free copper alloy formulation containing bismuth, bismuth and the like, and CN101440444 discloses a high-zinc bismuth-free brass alloy, which has a high strontium content but a low copper content, and the melt flow of the alloy is poor, and is compared in a metal mold. Difficult to refill the cavity, it is easy to produce casting defects such as insufficient pouring. CN101403056 discloses a lead-free brass alloy containing bismuth and manganese, but the strontium content is liable to cause defects such as cracks and slag inclusions, while the bismuth-low manganese is high in hardness, is not easy to be broken, and has poor machinability. The brass alloy formulations described above still have disadvantages such as poor casting properties and material embrittlement.

In addition, in addition to the necessary components of copper and zinc, US Pat. No. 4,417,929 discloses the inclusion of iron, aluminum and bismuth, and US Pat. No. 5,507,885 and US Pat. No. 6,395,110 disclose compositions containing phosphorus, tin and nickel. Compositions of nickel and ruthenium; U 6974509 discloses components comprising tin, antimony, iron, nickel and phosphorus; U.S. Patent 6,787,101 discloses phosphorus, tin, nickel, iron, aluminum, bismuth and arsenic; and US 6,599,378 and US Pat. No. 5,637,160 disclose selenium and Phosphorus and other ingredients are added to the brass alloy to achieve dezincification resistance. However, conventional anti-dezincification brass has a high lead content (mostly 1-3wt%), which is beneficial to the cold/hot processing of brass materials, but does not meet environmental requirements, high lead dissolution, and is easy to process. Lead pollution is produced.

Therefore, the industry is eager to develop new brass materials, to find alternatives to lead-containing brass, and to achieve dezincification resistance, but still have to consider the casting properties, machinability, corrosion resistance, and mechanical properties of the alloy formulation.

To achieve the above and other objects, the present invention provides a low-lead copper alloy comprising: 0.05 to 0.3% by weight of lead; 0.3 to 0.8% by weight of aluminum; 0.01 to 0.3% by weight of bismuth; and 1 to 4% by weight of bismuth 0.1 to 1% by weight of tin; and 99.6% by weight or more of copper and zinc, wherein the copper is contained in the low-lead copper alloy in an amount of 61 to 78% by weight.

In one aspect, the total content of copper and zinc contained in the low-lead copper alloy of the present invention is from 93.6 to 98.54% by weight, preferably 94% by weight or more. In one aspect, the copper is present in the low-lead copper alloy in an amount of from 61 to 78% by weight, preferably from 62 to 74% by weight, more preferably from 66 to 72% by weight. The low-lead copper alloy of the present invention contains a bismuth component, and therefore, the low-lead copper alloy of the present invention must have a high copper content to provide good toughness of the alloy material as compared with the conventional lead-containing brass.

In the low-lead copper alloy of the present invention, the lead content is 0.05 to 0.3% by weight. In a preferred embodiment, the lead content is from 0.1 to 0.25% by weight, more preferably from 0.15 to 0.20% by weight, and the addition of a suitable lead improves the machinability of the brass alloy.

In the low-lead copper alloy of the present invention, the content of the cerium is 0.3% by weight or less. In the embodiment, the content of the ruthenium is from 0.01 to 0.3% by weight, preferably from 0.05 to 0.25% by weight, more preferably from 0.1 to 0.2% by weight. Adding appropriate niobs helps to improve alloy machinability.

In the low-lead copper alloy of the present invention, the aluminum content is from 0.3 to 0.8% by weight. In a preferred embodiment, the aluminum content is from 0.4 to 0.7% by weight, more preferably from 0.5 to 0.65% by weight. Adding an appropriate amount of aluminum increases the fluidity of the copper water and improves the casting properties of the alloy material.

In the low-lead copper alloy of the present invention, the content of the cerium is from 1 to 4% by weight. In a preferred embodiment, the cerium content is from 1.5 to 3.5% by weight, more preferably from 2 to 3% by weight. Adding an appropriate amount of bismuth increases the machinability of the brass and improves the corrosion resistance and stress corrosion resistance of the alloy material in a high chloride environment such as seawater.

In the low-lead copper alloy of the present invention, the tin content is from 0.1 to 1% by weight. In a preferred embodiment, the tin content is from 0.2 to 0.9% by weight, more preferably from 0.4 to 0.8% by weight. The addition of an appropriate amount of tin can significantly improve the corrosion resistance of the alloy material to a high chloride ion environment (such as seawater) and increase the strength of the alloy material.

In addition, the addition of niobium and tantalum to copper alloys maintains the machinability of the alloy material under low lead content while enhancing the corrosion resistance of the alloy material in high chloride content environments such as seawater.

The low-lead copper alloy of the invention can be used as an alternative material for the conventional lead-containing brass, has excellent casting properties, good machinability and mechanical properties, and contains extremely low lead content, and meets environmental protection requirements. At the same time, the low-lead copper alloy of the present invention has good resistance to dezincification corrosion, particularly anti-dezinc corrosion resistance against high chloride ions, and can be applied to environments with high concentrations of chloride ions such as sea water and swimming pools.

The embodiments of the present invention are described by way of specific examples, and those skilled in the art can understand the advantages and advantages of the present invention as disclosed in the present disclosure.

In the present specification, unless otherwise stated, the components contained in the low-lead copper alloy are based on the total weight of the alloy and expressed in weight percent (wt%).

The relationship between the mechanical properties of the brass material and the zinc content of the brass material is shown in Figure 1. For (α+β) duplex brass, the strength of the alloy increases at room temperature as the zinc content increases until the zinc content in the alloy reaches 45%; once the zinc content exceeds 45% Then, since the γ phase appears in the metallographic structure of the alloy, the brittleness of the structure is increased, and the alloy strength is drastically lowered. On the other hand, for a brass alloy formulation containing a complex composition, the zinc content is calculated from the "zinc equivalent" of the element contained in the formulation. Since the copper alloy of the present invention includes cerium, and the zinc equivalent of cerium is 10, That is, 1% of yttrium is added to the Cu-Zn alloy, and the metallographic structure is equivalent to a metallographic structure in which a zinc content of 10% is added to the Cu-Zn alloy. Therefore, yttrium is added to the brass alloy to make Cu The α/(α+β) phase boundary in the -Zn system shifts significantly toward the copper side, strongly narrowing the α phase region. Therefore, the niobium content in the alloy is not more than 4 wt%, and the niobium content is higher than 4 wt%, so that the alloy has a γ phase which increases the brittleness of the structure, and the copper alloy of the present invention must contain a high copper content to maintain the alloy material. Good strength and toughness. In the low-lead copper alloy of the present invention, the zinc equivalent of the component is: the zinc equivalent of 矽 is 10, the zinc equivalent of aluminum is 6, the zinc equivalent of tin is 2, the zinc equivalent of lead is 1, and the zinc equivalent of bismuth. Is 1.

According to the low lead copper alloy formulation of the present invention, the lead content of the alloy can be reduced to 0.05 to 0.3% by weight, in accordance with international regulations for the lead content of pipeline materials in contact with water. Therefore, the low-lead copper alloy according to the present invention is advantageous for the manufacture of faucets and sanitary components, water pipes, water supply systems and the like.

In an embodiment, the low-lead copper alloy of the present invention comprises: 61 to 78% by weight of copper; 0.05 to 0.3% by weight of lead; 0.3 to 0.8% by weight of aluminum; 0.01 to 0.3% by weight of bismuth; % of 矽; 0.1 to 1% by weight of tin; and the balance of zinc.

In one aspect, the low lead copper alloy of the present invention comprises: 62 to 74% by weight of copper; 0.1 to 0.25 % by weight of lead; 0.4 to 0.7% by weight of aluminum; 0.05 to 0.25 % by weight of bismuth;重量% by weight; 0.2 to 0.9% by weight of tin; and the balance zinc; wherein the unavoidable impurities are less than 0.1% by weight.

In one aspect, the low-lead copper alloy of the present invention comprises: 66 to 72% by weight of copper; 0.15 to 0.25 % by weight of lead; 0.5 to 0.65% by weight of aluminum; 0.2 to 0.3% by weight of bismuth;重量% by weight; 0.4 to 0.8% by weight of tin; and the balance zinc; wherein the unavoidable impurities are less than 0.1% by weight.

Hereinafter, the present invention will be described in detail by way of illustrative embodiments.

The components of the low-lead copper alloy of the present invention used in the test examples described later are as follows, wherein the ratio of each component is based on the total weight of the alloy:

Example 1:

Cu: 72.21wt% Al: 0.594wt%

Bi: 0.178 wt% Si: 2.732 wt%

Sn: 0.498 wt% Pb: 0.141 wt%

Zn: balance

Example 2:

Cu: 74.23 wt% Al: 0.451 wt%

Bi: 0.169 wt% Si: 2.941 wt%

Sn: 0.645 wt% Pb: 0.184 wt%

Zn: balance

Example 3:

Cu: 69.91 wt% Al: 0.554 wt%

Bi: 0.183 wt% Si: 2.421 wt%

Sn: 0.762 wt% Pb: 0.136 wt%

Zn: balance

Example 4:

Cu: 62.47 wt% Al: 0.684 wt%

Bi: 0.187 wt% Si: 2.123 wt%

Sn: 0.417 wt% Pb: 0.193 wt%

Zn: balance

Test Example 1:

The sand core was prepared by a core shooting machine using round sand, urine aldehyde resin, furan resin and curing agent as raw materials, and the gas generating amount of the resin was measured by a gas generating tester. The obtained sand core must be used within 5 hours, otherwise it needs to be dried in an oven.

The low-lead brass alloy and the reclaimed material of the present invention are preheated for 15 minutes to bring the temperature to 400 ° C or higher, and then the two are smelted in an induction furnace at a weight ratio of 7:1 at a temperature of 1100-1150 ° C. And adding 0.2wt% of the refining slag agent, the material is fully stirred during the smelting process, until the brass alloy reaches a certain molten state (hereinafter referred to as melting copper liquid), and the metal gravity casting machine is matched with the sand core and the weight The casting mold is cast and controlled by a temperature monitoring system to maintain the casting temperature between 1060-1080 °C. The casting amount is preferably 1-2kg per casting, and the casting time is controlled within 3-8 seconds. By the above-mentioned high-temperature melting and low-temperature rapid casting, the segregation phenomenon in the alloy structure can be effectively avoided.

After the mold is cooled and solidified, the mold is unloaded to clean the pouring riser, the mold temperature is monitored, the mold temperature is controlled at 200-220 ° C and a casting is formed, and then the casting is demolded. After each molded part is taken out, the mold is cleaned to ensure that the core position is clean, and the graphite is sprayed on the surface of the mold and then immersed in water for cooling. The temperature of the graphite water used to cool the mold is preferably 30-36 ° C, and the specific gravity is 1.05 to 1.06.

The cooled castings are self-tested and sent to the sander drum for cleaning. Next, the blank processing (heat treatment of the cast blank (clearing stress annealing) is performed to eliminate the internal stress generated by the casting). The blank is subsequently machined and polished so that the interior of the casting is free of sand, metal shavings or other impurities. Conduct quality inspection analysis and calculate total production yield:

Total production yield = number of good products / total number of products × 100%

The total production yield of the process reflects the quality stability of the production process, and the higher the quality stability, the normal production can be guaranteed.

Further, the conventional H59 lead brass was used as a comparative example, and the article was prepared in the same manner as described above. The composition, processing characteristics and total production yield of each alloy are shown in Table 1.

The material of the low-lead brass of the invention is close to the conventional H59 lead brass, has low brittle crack sensitivity, can maintain material machinability, and is not easy to generate cracks and the like, and can certainly meet the needs of the production process.

It can be seen from Table 1 that the test group of the low-lead brass according to the present invention has a yield of more than 80%, and the material fluidity is close to that of the conventional H59 lead brass, and the production yield is also comparable to that of the H59 lead brass. It can be used as an alternative material for H59 lead brass, and it has the advantage of low lead content and meets the requirements of environmental protection.

Test Example 2:

The metallographic structure of the test piece of the brass material was examined under an optical metallographic microscope, and the result of magnification was 100 times as shown in Fig. 2A-2B.

Figure 2A shows the metallographic structure of H59 lead brass (Comparative Example 2). The measured values of the main components are: Cu: 61.1 wt%, Al: 0.589 wt%, Pb: 1.54 wt%, Bi: 0.0089% by weight. , Si: 0.0002% by weight. The alloy has an α phase and the crystal grains have a round granular shape.

The composition of the low lead brass of Example 1 was found to be Cu: 72.21 wt%, Al: 0.594 wt%, Pb: 0.141 wt%, Bi: 0.178 wt%, Si: 2.732 wt%, and Sn: 0.498 wt%. The tissue distribution, as shown in Fig. 2B, forms an equiaxed dendritic phase structure with low embrittlement sensitivity, and because the grains are dendritic and granular, the material is more susceptible to chip breaking and provides good machinability. .

Test Example 3:

Dezincification tests were carried out using the brass alloys of Example 1 and Comparative Example 1 to detect the corrosion resistance of brass. The dezincification test is carried out in accordance with the Australian AS2345-2006 "copper alloy anti-dezincification" standard. Before the corrosion test, the phenolic wax was used to mount ‧ so that the exposed area was 100 mm ² . All the test pieces were ground and smoothed by 600# metallographic sandpaper, and washed and dried with distilled water. The test solution was a 1% CuCl ₂ solution, and the test temperature was 75 ± 2 °C. The test piece and the CuCl ₂ solution were placed in a constant temperature water bath for 24±0.5 hours, and then taken out and cut longitudinally. After the cross section of the test piece was polished, the corrosion depth was measured and observed by a digital phase electron microscope. The result was as follows. -3B is shown.

The average dezincification depth of Comparative Example 1 was 372.54 μm as shown in Fig. 3A. The average dezincification depth of Example 1 was 37.67 μm. As shown in Fig. 3B, it was confirmed that the low-lead brass of the present invention has better resistance to dezincification corrosion.

Test Example 4:

The average corrosion degree of the material was electrochemically measured by the brass alloys of Example 1 and Comparative Example 1 to determine the average corrosion resistance of the brass alloy. The brass test piece was polished and the inlaid sample 1 was prepared with reference to FIG. 4, wherein the brass test piece 11 was exposed to the surface of the inlaid sample 1 to a length of about 10 mm, and the brass test piece 11 was embedded in the resin layer 12. The depth is about 4 mm and the wires 13 are attached.

The mosaic sample was immersed in a sodium chloride (NaCl) solution having a concentration of 5%, and a polarization curve including a polarization potential element and a current density was measured by a linear polarization method, and the polarization resistance R _{p was} calculated as follows . Specifically, the larger the value of the polarization resistance R _p , the better the average corrosion resistance of the material.

R _p =Δ E /Δ I

Wherein R _p represents a polarization resistance, Δ E represents a polarization potential, and Δ I represents an applied current density.

As can be seen from Table 2, the Rp value (16.17 KΩ/cm ² ) of the low-lead brass of the present invention is much higher than that of the H59 lead brass (5.83 K Ω/cm ² ), which proves that the low-lead copper alloy of the present invention has excellent resistance. Average corrosivity, especially in high chloride environments. Thus, the low lead copper alloy of the present invention can be used as a material for articles in contact with a high chloride ion environment, by way of example and not limitation, such as as a pipeline material for a swimming pool, or as a line in contact with the marine environment.

Test Example 5:

The mechanical properties of brass alloys were tested in accordance with ISO 6998-1998 "Standard tensile test of metallic materials at room temperature". The results are shown in Table 3:

As can be seen from Table 3, the tensile strength of the low-lead copper alloy of the present invention is higher than that of the conventional H59 lead brass, and the elongation is substantially equivalent to that of the H59 lead brass, indicating that the low-lead brass alloy of the present invention has the equivalent of H59 lead. The mechanical properties of brass; however, the low-lead brass of the present invention has a low lead content and meets environmental requirements, and can indeed be used to manufacture products by replacing H59 lead brass.

Test Example 6:

According to the NSF 61-2007a SPAC single product metal allowable precipitation standard test, the test results of the metal precipitation of the brass alloy in the environment in contact with water are shown in Table 4:

As shown in Table 4, the precipitation amount of each metal of the low-lead brass of the present invention is lower than the upper limit standard value, and meets the requirements of NSF 61-2007a SPAC. The lead content of the material of Comparative Example 1 was significantly higher than the standard value in the case of no lead washing treatment, and Example 1 did not need to be subjected to lead washing treatment, which met the standard, and the lead precipitation amount of Example 1 was still significantly lower than that of the lead-washing treatment. Comparative Example 1 is more environmentally friendly and beneficial to human health.

In summary, the low-lead copper alloy of the present invention has mechanical processing properties comparable to those of the conventional H59 lead brass, better tensile strength, good production yield of the process, and greatly reduced lead precipitation of the product, which is highly suitable as It is used to manufacture products (such as sanitary products such as faucets, etc.) instead of the alloy materials of conventional lead brass. In addition, the low-lead copper alloy of the present invention has excellent resistance to chloride ion corrosion, and is advantageous for manufacturing a water supply system in a high chloride ion environment or a copper product in contact with the marine environment.

The above examples are merely illustrative of the low lead copper alloy of the present invention and the preparation method thereof, and are not intended to limit the present invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is set forth in the appended claims.

1. . . Mosaic sample

11. . . Brass test piece

12. . . Resin layer

13. . . wire

Figure 1 is a graph showing the relationship between the mechanical properties of copper alloy and the amount of zinc;

Figure 2A is a metallographic structure of the H59 lead brass test piece;

2B is a metallographic structure distribution diagram of the low lead brass test piece of the present invention;

Figure 3A is a metallographic structure map of the anti-dezincification test of the H59 lead brass test piece;

3B is a metallographic structure distribution diagram of the low-lead brass test piece for dezincification corrosion test of the present invention;

Figure 4 is a schematic diagram of a mosaic test specimen for electrochemical testing.

Claims (5)

A low-lead copper alloy composed of the following components: 0.05 to 0.3% by weight of lead; 0.3 to 0.8% by weight of aluminum; 0.01 to 0.3% by weight of bismuth; 1 to 1.5% by weight of bismuth; 0.1 to 0.2% by weight Tin; and more than 93.6% of copper and zinc, wherein the content of the copper in the low-lead copper alloy is between 61 and 69% by weight. The low-lead copper alloy according to claim 1, wherein the lead content is from 0.15 to 0.25% by weight. A low-lead copper alloy according to claim 1, wherein the aluminum content is from 0.5 to 0.65% by weight. The low-lead copper alloy according to claim 1, wherein the content of the bismuth is from 0.1 to 0.2% by weight. The low-lead copper alloy according to claim 1, wherein the copper content is 62 to 66% by weight.