TWI390057B - Dezincification resistant and low lead brass alloy - Google Patents

Description

Low lead anti-dezincification copper alloy

This invention relates to a dezincification resistant copper alloy, and more particularly to a low lead anti-dezincification brass alloy.

The main components of brass are copper and zinc, the ratio of which is usually about 7:3 or 6:4, and when the zinc content in brass exceeds 20% by weight, dezincification is prone to corrosion, such as When the brass alloy article is applied to the environment, the zinc on the surface of the alloy is preferentially dissolved, and the copper contained in the alloy remains on the base material to form a corrosive phenomenon of brittle copper in the porous hole. In general, when the zinc content is less than 15% by weight, dezincification is less likely to occur, but as the zinc content increases, the sensitivity of dezincification is increased; when zinc is more than 30% by weight, the dezincification corrosion phenomenon is more pronounced.

It has been reported in the literature that the alloy composition and environmental factors will affect the dezincification corrosion phenomenon. The composition of the alloy is such that the single-phase α-brass containing more than 20% of zinc has decopied copper leaving porous copper, while α+β double The dezincification corrosion of phase brass begins with the β phase. When the β phase is completely transformed into loose copper, it is extended to the α phase (see Wang Jihui et al., 1999, Journal of Materials Research, No. 13, pp. 1-8). page).

Since the dezincification of brass 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. Therefore, for the anti-zinc removal ability of brass products, the international standards such as AS 2345, ISO 6509, etc. are generally accepted, that is, the depth of the dezincification layer on the surface of the brass product should not exceed 100 μm.

In addition to the essential components of copper and zinc, US 4,417,929 discloses iron, aluminum and antimony components, and US 5,507,885 and US 6,395,110 disclose compositions containing phosphorus, tin and nickel; 5,653,827 discloses compositions comprising iron, nickel and antimony; US 6,974,509 discloses compositions comprising tin, antimony, iron, nickel and phosphorus; US 6,787,101 discloses phosphorus, tin, nickel, iron, aluminum, antimony and arsenic; and US 6,599,378 and US 5,637,160 and other patents disclose the addition of selenium and phosphorus to brass alloys to achieve dezincification resistance; or see Wang Jihui et al., 1999, Journal of Materials Research, No. 13, pp. 1-8, revealing boron and Arsenic and the like are added to the brass alloy to achieve the anti-zinc removal effect.

However, the anti-dezincification brass has a high lead content (mostly 1-3wt%), which is beneficial to the cold/hot processing of brass materials, but with the rise of environmental awareness, the impact of heavy metals on human health and The problem of environmental pollution is gradually being taken seriously. Therefore, restricting the use of lead-containing alloys is the current trend. Japan, the United States and other countries have successively revised relevant regulations, and strive to reduce the lead content in the environment, covering home appliances, automobiles, and water. Lead-containing alloy materials for peripheral products, in particular, require that lead is not eluted from the product to drinking water, and lead contamination must be avoided during processing. Therefore, the industry continues to develop brass materials to find alloy formulations that can replace lead-containing anti-dezincification brass, but still take into account casting and machining properties and resistance to dezincification.

To achieve the above and other objects, the present invention provides a low lead dezincification resistant brass alloy comprising: 0.3% by weight or less of lead (Pb); 0.02 to 0.15% by weight of bismuth (Sb) 0.02 to 0.25 wt% arsenic (As); 0.4 to 0.8 wt% aluminum (Al); 1 to 20 ppm boron (B); and 97 wt% or more copper (Cu) and zinc (Zn), wherein The copper is contained in the anti-dezincification copper alloy in an amount of 58 to 70% by weight.

The anti-dezincification copper alloy of the invention is a brass alloy, and the total content of copper and zinc can be more than 97% by weight. In the embodiment, the content of the copper is 58-70% by weight, and the copper in the range can provide good toughness of the alloy, which is beneficial to the subsequent processing of the alloy material. In a preferred embodiment, the copper content is from 61 to 65% by weight.

In the low-lead anti-dezincification brass of the present invention, the content of the cerium is 0.02 to 0.15% by weight. In a preferred embodiment, the cerium content is from 0.04 to 0.12% by weight. According to the alloy formulation of the present invention, an element such as copper and bismuth forms an intermetallic compound, which improves the machinability of the alloy material without causing casting defects.

In the low lead anti-dezincification brass of the present invention, the aluminum content is from 0.4 to 0.8% by weight. In a preferred embodiment, the aluminum content is from 0.5 to 0.7% 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 anti-dezincification copper alloy of the present invention, the arsenic content is 0.02 to 0.25 wt%. In a preferred embodiment, the arsenic content is from 0.13 to 0.17 wt%. Adding an appropriate amount of arsenic can significantly improve the resistance of brass to dezincification corrosion.

In the anti-dezincification copper alloy of the present invention, the boron content is from 1 to 20 ppm. In a preferred embodiment, the boron content is from 8 to 14 ppm. Adding an appropriate amount of boron can refine the grain of the alloy material and improve the properties of the alloy material.

The anti-dezincification-resistant copper alloy of the present invention comprises 0.2 to 1.25 wt% of at least one element selected from the group consisting of nickel and tin. In an embodiment, the anti-dezincification copper alloy may include both nickel and tin. In a preferred embodiment, the tin content is from 0.1 to 1% by weight. In a preferred embodiment, the nickel is present in an amount from 0.1 to 0.25% by weight.

The anti-zinc-free copper alloy of the present invention contains an extremely low lead content of 0.3% by weight or less. In an embodiment, the lead content is from 0.05 to 0.3% by weight. The alloy may also have impurities, and the unavoidable impurity content is 0.1% by weight or less.

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, "dezincification-resistant copper alloy/dezincification-resistant brass alloy" is a term commonly used in the art, meaning that the surface of the alloy is resistant to environmental corrosion conditions and is not prone to dezincification. Here, AS 2345 Australia The Dezincification resistance of copper alloys shall prevail that the depth of the dezincification layer on the surface of the product defining the brass alloy shall not exceed 100 μm.

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

According to the low lead anti-dezincification copper alloy of the present invention, it is only necessary to use 0.02-0.15 wt% of bismuth and 0.02-0.25 wt% of arsenic to achieve the material properties (such as machinability, etc.) of the conventional lead brass. And such low-lead anti-dezincification copper alloy material is less prone to cracks or inclusions and other product defects, and meets the anti-zinc removal requirements of Australia AS-2345. Moreover, the brass alloy formulation of the present invention effectively reduces the production cost of the low lead anti-dezincification copper alloy, and has great advantages for commercial mass production and application.

In addition, the anti-dezincification copper alloy formulation of the present invention can make the lead content as low as 0.3 wt% or less, or even 0.2 wt% or less, thereby facilitating the manufacture of faucets and bathroom components, water pipes, water supply systems and the like.

In one embodiment, the low lead anti-dezincification copper alloy of the present invention comprises: 58-70% by weight of copper; 0.02 to 0.15% by weight of bismuth; 0.02 to 0.25 wt% of arsenic; 0.4 to 0.8% by weight of aluminum; 1 to 20 ppm of boron; 0.05 to 0.3% by weight of lead; 0.1% by weight or less of unavoidable impurities; and the balance of zinc.

In another embodiment, the low lead anti-dezincification copper alloy of the present invention comprises: 58-70 wt% copper; 0.02 to 0.15 wt% bismuth; 0.02 to 0.25 wt% arsenic; 0.4 to 0.8 wt% aluminum 1 to 20 ppm of boron; 0.2 to 1.25 wt% of nickel and/or tin; and 0.05 to 0.3% by weight of lead; 0.1% by weight or less of unavoidable impurities; and the balance of zinc.

In still another embodiment, the low lead anti-dezincification copper alloy of the present invention comprises: 61-65 wt% copper; 0.04-0.12 wt% bismuth; 0.13-0.17 wt% arsenic; 0.5-0.7 wt% aluminum 8-14 ppm boron; 0.1-1 wt% tin; 0.1-0.25 wt% nickel; 0.05 to 0.3 wt% lead; 0.1 wt% or less unavoidable impurities; and the balance zinc.

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

The components of the low-lead anti-dezincification 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: 61.95 wt% Al: 0.469 wt%

Sb: 0.0415wt% B: 13ppm

As: 0.151wt% Ni: 0.143wt%

Pb: 0.141wt% Sn: 0.294wt%

Zn: balance.

Example 2:

Cu: 62.05 wt% Al: 0.557 wt%

Sb: 0.0763wt% B: 8ppm

As: 0.162wt% Ni: 0.231wt%

Pb: 0.173wt% Sn: 0.546wt%

Zn: balance.

Example 3:

Cu: 62.6 wt% Al: 0.671 wt%

Sb: 0.1137wt% B: 11ppm

As: 0.147wt% Ni: 0.187wt%

Pb: 0.159wt% Sn: 0.741wt%

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 anti-dezincification brass alloy and the reclaimed material of the present invention are preheated for 15 minutes to make the temperature reach 400 ° C or higher, and then the two are smelted in an induction furnace at a weight ratio of 7:1, and 0.2 wt is added. % of the refining and slag-removing agent, until the brass alloy reaches a certain molten state (hereinafter referred to as melting copper liquid), and is cast by a metal gravity casting machine with a sand core and a recasting mold, and is controlled by a temperature monitoring system to make a casting The temperature is maintained between 1010-1060 °C. The casting amount is preferably 1-2kg per casting, and the casting time is controlled within 3-8 seconds.

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.

In addition, the conventional CW602N anti-dezincification brass (sometimes referred to as DR brass, which is ASZ345-2006 certified anti-dezincification brass) and the conventional 59 lead brass are used as comparative examples to prepare the same process as above. object. The composition, processing characteristics and total production yield of each alloy are shown in Table 1.

It can be seen from Table 1 that the yield of the test group of the low lead anti-dezincification copper alloy according to the present invention is more than 90%, which is equivalent to the conventional 59 lead brass and DR brass (CW602N), and can be used as an alternative. Brass material. The low-lead anti-dezincification copper alloy of the invention can greatly reduce the lead content in the alloy, effectively avoid lead pollution generated in the process, and reduce the amount of lead released when the cast object is used, while taking into consideration material properties. Can meet environmental requirements.

Test Example 2:

The test piece of the low lead anti-dezincification copper alloy (Example 3), CW602N brass (Comparative Example 1) and 59 lead brass (Comparative Example 4) of the present invention was examined under an optical metallographic microscope for the microstructure distribution. The result of magnifying 100 times is shown in Fig. 1A-1C, respectively.

The measured values of the main components of the alloy of Example 3 were: Cu: 62.6%, Zn: 36.43%, Pb: 0.159%, Sb: 0.1137%, Al: 0.627%, and As: 0.147%, and the tissue distribution was as shown in Fig. 1A. Show.

As shown in Figure 1A-1C, the α phase structure of the metallographic phase of CW602N brass (Fig. 1B) is coarser, indicating that the machinability of the material is poor; and the low lead anti-dezincification copper alloy of the present invention and 59 lead brass The metallographic phase is similar, forming a dendritic phase structure which will form uniform particles, but the α phase of the low lead anti-dezincification copper alloy of the present invention has finer crystal grains and more compact structure, indicating that the material has good mechanical properties. performance.

Test Example 3:

Dezincification tests were carried out on the brass alloys of Example 3, Comparative Example 1, and Comparative Example 4 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 metallographic electron microscope. The result was as follows. The figure shows.

The average dezincification depth of the low lead anti-dezincification brass of the present invention of Example 3 was 77.6 μm as shown in Fig. 2A. The average dezincification depth of the CW602N brass of Comparative Example 1 was 82.28 μm as shown in Fig. 2B. The average dezincification depth of the lead brass of Comparative Example 4 was 336.72 μm as shown in Fig. 2C.

The above results confirmed that the low-lead anti-dezincification brass of the present invention conforms to the Australian AS2345-2006 anti-dezincification standard (the depth of the dezincification layer cannot exceed 100 μm), and has better resistance to dezincification.

Test Example 4:

In this embodiment, the mechanical properties were tested in accordance with the ISO 6998-1998 "Metal Material Room Temperature Tensile Test" standard, and the results are shown in Table 2 below.

As can be seen from Table 2, the tensile strength and elongation of the low-lead anti-dezincification brass of the present invention are comparable to those of the conventional lead-lead brass and CW602N brass, indicating that the low-lead brass alloy of the present invention has the equivalent of 59 lead yellow. The mechanical properties of copper and CW602N brass; however, the low lead anti-dezincification brass of the present invention has a low lead content and meets environmental protection requirements, and can be used to manufacture products by replacing 59 lead brass and CW602N brass.

Test Example 5:

According to NSF 61-2007a SPAC single product metal allowable precipitation standard test, the metal precipitation of brass alloy in the environment of contact with water is tested. The test results are shown in Table 3 below:

As shown in Table 3, the precipitation amount of each metal element of the low-lead anti-dezincification brass of the present invention is lower than the upper limit standard value, and meets the requirements of NSF 61-2007a SPAC. When the materials of Comparative Example 1 and Comparative Example 4 were not subjected to lead washing treatment, the lead content greatly exceeded the standard value, and only Example 1 did not need to be subjected to lead washing treatment, which met the standard, and the low lead anti-dezincification brass of the present invention. The precipitation of heavy metal lead in alloys is still significantly lower than that of lead-lead 59 lead brass and CW602N brass, which is more environmentally friendly and beneficial to human health.

In summary, the low-lead anti-dezincification copper alloy material of the invention has excellent casting properties, good toughness, good machinability, and is free from cracks or inclusions, and does not cause casting defects, and can be achieved by lead brass. Material properties, which are beneficial to the subsequent processing of alloy materials. The low lead anti-dezincification copper alloy of the invention has the effect of low lead precipitation without the need of lead washing treatment, can reduce the production cost of the process, and has great advantages for commercial mass production and application.

The above examples are merely illustrative of the low lead anti-dezincification copper alloy of the present invention and are not intended to limit the 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.

1A is a metallographic structure distribution diagram of a low lead anti-dezincification copper alloy test piece of the present invention;

Figure 1B is a metallographic structure of the CW602N brass test piece;

Figure 1C is a metallographic structure of a 59-lead brass test piece;

2A is a metallographic structure distribution diagram of the anti-dezincification corrosion test of the low lead anti-dezincification copper alloy test piece of the present invention;

Figure 2B is a metallographic structure of the CW602N brass test strip for dezincification corrosion testing;

Figure 2C shows the metallographic structure of the 59-lead brass test strip for dezincification corrosion testing.

Claims (8)

A dezincification resistant copper alloy comprising: 0.3% by weight or less of lead; 0.02 to 0.15% by weight of bismuth; 0.02 to 0.25 wt% of arsenic; 0.4 to 0.8% by weight of aluminum; 1 to 20 ppm of boron; and 97% by weight The above copper and zinc, wherein the copper is contained in the anti-dezincification copper alloy in an amount of 58 to 70% by weight. The anti-dezincification copper alloy according to claim 1, wherein the copper content is from 61 to 65% by weight. The anti-dezincification copper alloy according to claim 1, wherein the content of the cerium is from 0.04 to 0.12% by weight. The anti-dezincification copper alloy according to claim 1, wherein the arsenic content is from 0.13 to 0.17% by weight. The anti-dezincification copper alloy according to claim 1, wherein the boron content is 8 to 14 ppm. The anti-dezincification copper alloy according to Item 1 of the patent application further comprises 0.2 to 1.25 wt% of at least one element selected from the group consisting of nickel and tin. The anti-dezincification copper alloy according to item 6 of the patent application, wherein the tin content is 0.1 to 1% by weight. The anti-dezincification copper alloy according to item 6 of the patent application, wherein the content of the nickel is from 0.1 to 0.25% by weight.