CA2718613A1 - Dezincification resistant brass alloy - Google Patents
Dezincification resistant brass alloy Download PDFInfo
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- CA2718613A1 CA2718613A1 CA 2718613 CA2718613A CA2718613A1 CA 2718613 A1 CA2718613 A1 CA 2718613A1 CA 2718613 CA2718613 CA 2718613 CA 2718613 A CA2718613 A CA 2718613A CA 2718613 A1 CA2718613 A1 CA 2718613A1
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C9/00—Alloys based on copper
- C22C9/04—Alloys based on copper with zinc as the next major constituent
Abstract
A dezincification resistant brass alloy is provided. The dezincification resistant brass alloy includes 0.5 to 1.2 wt% of silicon; 0.01 to 0.2 wt% of antimony; 0.02 to 0.25 wt%
of arsenic; 0.4 to 0.8 wt% of aluminum; and more than 95.8 wt% of copper and zinc.
The dezincification resistant brass alloy of the present invention has excellent casting properties, great cutting property and corrosion resistance
of arsenic; 0.4 to 0.8 wt% of aluminum; and more than 95.8 wt% of copper and zinc.
The dezincification resistant brass alloy of the present invention has excellent casting properties, great cutting property and corrosion resistance
Description
DEZINCIFICATION RESISTANT BRASS ALLOY
BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to dezincification resistant copper alloys, and more particularly, to a dezincification resistant brass alloy.
Description of Related Art Brass alloy includes copper and zinc as major ingredients usually at a ratio of about 7:3 or 6:4. Dezincification corrosion is a selective corrosion of brass alloys. When a copper-zinc alloy is in an aqueous solution (such as sea water or fresh water), some corrosion occurs on a surface of the alloy, and zinc on the surface of the alloy is dissolved. However, copper residue still remains on the surface of the alloys, resulting in red porous sponge-like copper, i.e. dezincification corrosion phenomenon.
Generally, if the zinc content is less than 15 wt%, dezincification is not likely to occur. However, as the zinc content increases, the sensitivity to dezincification is increased. If the zinc content exceeds 30 wt%, dezincification corrosion is more severe.
It has been reported in literatures that dezincification corrosion is associated with alloy compositions and environmental factors. In the context of alloy compositions, dezincification of brass alloy with a single a phase and zinc content higher than 20 wt% gives porous copper, whereas dezincification of brass alloy with double a+O phases begins initially in 0 phase and later expands to a phase when 0 phase is completely converted into loosely-structured copper (see Kuaiji Wang et al., Chinese Journal of Materials Research, Vol.13, pages 1-8).
Since dezincification of brass alloy severely damages the structures of brass alloys, the surface intensities of brass products produced from brass alloys are decreased and porosity thus occurs on brass pipes. This significantly decreases the lifetimes of the brass products, and causes application problems. Therefore, standards like AS 2345 and ISO 6509 are established for testing the dezincification resistance of a brass product, i.e.
the depth of a dezincification layer formed on the surface of a brass product shall not exceed 100 lAm.
Regarding the formulations of dezincification resistant brass alloys, except for copper and zinc which are major ingredients, patents such as US
Patent No. 4,417,929 discloses a formulation comprising iron, aluminum and silicon, US Patent Nos. 5,507,885 and US 6,395,110 disclose formulations comprising phosphorus, tin and nickel, US Patent No. 5,653,827 discloses a formulation comprising iron, nickel and bismuth, US Patent No. 6,974,509 discloses a formulation comprising tin, bismuth, iron, nickel and phosphorus, US Patent No. 6,787,101 discloses a formulation comprising phosphorus, tin, nickel, iron, aluminum, silicon and arsenic, and US Patent Nos. 6,599,378 and US 5,637,160 disclose adding selenium and phosphorus in a brass alloy to achieve a dezincifying effect. Alternatively, please refer to Kuaiji Wang et at., Chinese Journal of Materials Research, Vol.13, pages 1-8, wherein a dezincification effect is achieved by adding boron and selenium into a brass alloy.
Conventional dezincification resistant brass alloys usually have higher lead contents (most in the range from 1 to 3 wt%) for facilitating subsequent processing of brass materials. However, as the awareness of environmental protection increases and the impacts of heavy metals on human health and issues like environmental pollutions become major focuses, it is a trend to restrict the usage of lead-containing alloys. Various countries, such as Japan and the United States of America, have sequentially amended relevant regulations and put intensive efforts to lower lead contents in the environment by particularly demanding that no molten lead shall leak from the lead-containing alloy materials used in products such as household electronic appliances, automobiles and water systems to drinking water and lead contamination shall be avoided during processing. Thus, there exists an urgent need in the industry to develop a brass material having dezincification resistance and possessing desirable properties like good casting properties, machinability, corrosion resistance and mechanical properties.
In order to eliminate damages to human bodies and environment, the present invention provides a free cutting brass alloy including silicon and antimony instead of lead, and further including arsenic for improving dezincification resistance.
SUMMARY OF THE INVENTION
The present invention provides a dezincification resistant brass alloy, including 0.5 to 1.2 wt% of silicon (Si); 0.01 to 0.2 wt% of antimony (Sb);
0.02 to 0.25 wt% of arsenic (As); 0.4 to 0.8 wt% of aluminum (Al); and more than 95.8 wt% of copper (Cu) and zinc (Zn).
In the present invention, the brass alloy has effects of solid solution strengthening due to the addition of silicon and aluminum. Further, the addition of zinc influences mechanical strength and elongation rate of the brass alloy. In the present invention, silicon has the zinc equivalent coefficient as about 10 to 12, and aluminum has the zinc equivalent coefficient as about 4 to 6. The amount of silicon is 0.5 to 1.2 wt% of the brass alloy, and the amount of aluminum is 0.4 to 0.8 wt% of the brass alloy.
Once the zinc equivalent is controlled to be lower than 45%, the tensile strength of the brass alloy is about 320 MPa, the elongation rate is about 10.8%, and the hardness is about HRB 76. Apparently, the brass alloy of the present invention has great mechanical strength and elongation rate.
In the present invention, the addition of silicon makes inter-metallic compounds being separated out, so as to improve the cutting property of the brass alloy. The cutting property and fluidity of the alloy melt are improved as long as the amount of silicon is increased. However, when the amount of silicon is more than 1.2 wt% and the zinc equivalent is more than 45%, the brass alloy turns to be brittle and has decreased mechanical strength and elongation rate. For example, when the zinc equivalent is 48%, the brass alloy has the tensile strength as about 55 MPa, elongation rate as about 2%
and hardness as about HRC 30, and thus the brass alloy fails to have good casting property. In addition, the brass alloy of the present invention preferably includes 0.5 to 0.8 wt% of silicon.
In the present invention, the addition of aluminum improves the effect of solid solution strengthening, increases the strength and hardness of the brass alloy, and decreases the specific weight of the brass alloy. Moreover, due to the addition of silicon, when the zinc equivalent is no more than 45% and the amount of aluminum is more than 0.8 wt%, the elongation of the brass alloy is decreased, the metal melt is easily oxidized to form slag and the m fluidity of the brass alloy is lowered, such that the casting product of the brass alloy may have some flow marking, entrapped slag and less compact.
Preferably, the brass alloy of the present invention includes 0.5 to 0.8 wt%
of aluminum.
The divacancy occurs on the surface of the brass alloy during corrosion, and then the divacancy diffuses toward the interior of the brass alloy due to the concentration gradient, and zinc atoms diffuse toward the surface of the brass alloy, such that zinc is dissolved first.
Therefore, in the present invention, the dezincification resistant brass alloy includes arsenic for inhibiting the re-deposition of copper.
Furthermore, the arsenic atoms form a protection layer at the crystal boundary, so as to occupy or diffuse into the divacancy for interrupting the dissolution of zinc, and thus achieve dezincification resistance. Preferably, the brass alloy of the present invention includes 0.07 to 0.17 wt% of arsenic. The proper addition amount of arsenic significantly improves the dezincification resistance of the brass alloy; however, if the addition of arsenic is more than 0.17 wt%, no relative improvement can be obtained.
In addition to improve mechanical properties for processing, such as cutting property, antimony is added in the dezincification resistant brass alloy, wherein antimony and copper form inter-metallic compounds as brittle granules dispersed in S phase and phase boundary of 3 phase for improving cutting property and filling the divacancy so as to decrease corrosion of the brass alloy. Further, when the amount of antimony is more than 0.2 wt%, the brittleness of the alloy is significantly increased and the strength of the alloy is further limited. Moreover, since antimony atoms aggregate at the crystal CA 02718613 2010-10-20 _...___...__.._r boundary of the alloy to form deflection, resulting hot embrittlement of the casting product. Hence, the amount of antimony added in the brass alloy of the present invention is 0.01 to 0.12 wt%.
In the present invention, as the addition of silicon increases, precipitation of arsenic and antimony in aqueous solution is decreased (NSF 61-2007a SPAC). When the amount of arsenic is more than 0.25 wt% and the amount of antimony is more than 0.2 wt%, precipitation amount of arsenic and antimony exceed the standard established in regulations, and cannot be decreased even though the amount of silicon is increased. Based on the about illustrations, the present invention provides a dezincification resistant brass alloy, including 0.5 to 1.2 wt% of silicon (Si); 0.01 to 0.2 wt% of antimony (Sb); 0.02 to 0.25 wt% of arsenic (As); 0.4 to 0.8 wt% of aluminum (Al); and more than 95.8 wt% of copper (Cu) and zinc (Zn).
In the present invention, the dezincification resistant brass alloy further includes one or more selected from the group consisting of nickel, tin, boron and lead. For example, the dezincification resistant brass alloy includes nickel, tin, boron or lead. For example, the dezincification resistant brass alloy includes 0.2 to 1.25 wt% of nickel and tin.
In one embodiment, the dezincification resistant brass alloy includes 0.1 to 1 wt% of tin. In another embodiment, the dezincification resistant brass alloy includes 0.1 to 0.25 wt% of nickel. In addition, the dezincification resistant brass alloy includes boron in a range from 1 to 20 ppm, and preferably in a range from 5 to 15 ppm. The proper amount of nickel and tin are added to improve corrosion resistance, and to increase the strength of the brass alloy.
The suitable amount of boron is added alloy material, which the process can to reduce grain size and improve the property of the brass alloy.
In another embodiment, the dezincification resistant brass alloy includes 0.05 to 0.18 wt% of lead. The proper amount of lead is added to improve cutting property of the brass alloy.
The alloy can contain unavoidable impurities in an amount less than 0.2 wt%.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a metallographic structural distribution of a specimen of a dezincification resistant brass copper alloy of the present invention;
FIG. 1B is a metallographic structural distribution of a specimen of a CW602N brass specimen;
FIG. 1C is a metallographic structural distribution showing a specimen of C85700 brass alloy;
FIG. 2A is diagram showing the fluidity of the dezincification resistant brass alloy of the present invention;
FIG. 2B is diagram showing the fluidity of CW602N brass alloy;
FIG. 2C is diagram showing the fluidity of C85700 brass alloy;
FIG. 3A is a diagram showing the turning characteristic of the dezincification resistant brass alloy of the present invention;
FIG. 3B is a diagram showing the turning characteristic of CW602N
brass alloy;
FIG. 3C is a diagram showing the turning characteristic of C85700 brass alloy;
FIG. 4A is a metallographic structural distribution showing the specimen of the dezincification resistant brass alloy of the present invention after performing a test of dezincification corrosion resistance;
FIG. 4B is a metallographic structural distribution showing the specimen of CW602N brass alloy after performing a test of dezincification corrosion resistance; and FIG. 4C is a metallographic structural distribution showing the specimen of C85700 brass alloy after performing a test of dezincification corrosion resistance.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The detailed description of the present invention is illustrated by the following specific examples. Persons skilled in the art can conceive the other advantages and effects of the present invention based on the disclosure contained in the specification of the present invention.
In the specification of the present invention, the term "dezincification resistant copper alloy/dezincification resistant brass alloy" is a commonly used technological term in the field, and means an alloy having surfaces that are tolerant to corroding conditions in the environment and not likely to dezincify. AS 2345 regulations (Dezincification resistance of copper alloys) are used as a basis to define that the depth of the dezincification layer formed on the surface of a brass alloy product shall not exceed 100 pm.
Unless otherwise specified, the ingredients comprised in the dezincification resistant brass alloy of the present invention, as discussed herein, are all based on the total weight of the alloy, and are expressed in weight percentages (wt%).
The composition of the dezincification resistant brass alloy in the present invention meets the requirement as set forth in California Bill AB 1953, in which the materials of bathroom products contacting water must have lead less than 0.25 wt%. Further, NSF 61 requires that lead leach much be less than 5 ppb. The dezincification resistant brass alloy of the present invention meets the above regulations and is applicable to faucets, water pipes, water supply systems, and etc.
In accordance with inventor's research, the dezincification resistant brass alloy includes specific amounts of silicon, antimony and arsenic to have characteristics as those of the conventional lead brass. Specifically, the dezincification resistant brass alloy of the present invention includes only 0.5 to 1.2 wt% of silicon, 0.01 to 0.2 wt% of antimony and 0.02 to 0.25 wt%
of arsenic to have characteristics (such as cutting property) as those of the conventional lead brass, is not prone to generate product defects like cracks and slag inclusions, and complies with the dezincification requirement set forth in AS-2345.. In addition, the dezincification resistant brass alloy of the present invention effectively reduces the cost of production, and is extremely advantageous to commercial-scale productions and applications.
In an embodiment, the dezincification resistant brass alloy of the present invention includes 58 to 65 wt% of copper, 0.5 to 1.2 wt% of silicon, 0.01 to 0.2 wt% of antimony, 0.02 to 0.25 wt% of arsenic, 0.4 to 0.8 wt% of aluminum, less than 0.2 wt% of unavoidable impurities, and zinc in balance.
In another embodiment, the dezincification resistant brass alloy of the present invention includes 59 to 63 wt% of copper, 0.5 to 0.8 wt% of silicon, 0.01 to 0.12 wt% of antimony, 0.07 to 0.17 wt% of arsenic, 0.5 to 0.8 wt% of aluminum, less than 0.2 wt% of unavoidable impurities, and zinc in balance.
In another embodiment, the dezincification resistant brass alloy of the present invention includes 59 to 63 wt% of copper, 0.5 to 0.8 wt% of silicon, 0.01 to 0.12 wt% of antimony, 0.07 to 0.17 wt% of arsenic, 0.5 to 0.8 wt% of aluminum, less than 5 to 15 ppm of boron, 0.1 to 1 wt% of tin, 0.1 to 0.25 wt% of nickel, less than 0.2 wt% of unavoidable impurities, and zinc in balance.
In another embodiment, the dezincification resistant brass alloy of the present invention includes 59 to 63 wt% of copper, 0.5 to 0.8 wt% of silicon, 0.01 to 0.12 wt% of antimony, 0.07 to 0.17 wt% of arsenic, 0.5 to 0.8 wt% of aluminum, 0.05 to 0.18 wt% of lead, less than 0.2 wt% of unavoidable impurities, and zinc in balance.
The present invention is illustrated by the following exemplary examples.
The ingredients of the dezincification resistant brass alloy of the present invention used in the following test examples are described below, wherein each of the ingredients is added at a proportion based on the total weight of the alloy.
Example 1:
Cu: 61.32 wt% Si: 1.03 wt%
Sb: 0.1283 wt% Al: 0.6452 wt%
As: 0.0852 wt% Zn: in balance Example 2:
Cu: 62.75 wt% Si: 0.653 wt%
Sb: 0.047 wt% Al: 0.78 wt%
As: 0.169 wt% Zn: in balance Example 3:
Cu: 62.63 wt% Si: 0.563 wt%
Sb: 0.052 wt% Al: 0.653 wt%
As: 0.165 wt% Ni: 0.152 wt%
B: 10 ppm Sn: 0.861 wt%
Zn: in balance Example 4:
Cu: 64.47 wt% Si: 0.78 wt%
Sb: 0.015 wt% Al: 0.79 wt%
As: 0.142 wt% Pb: 0.115 wt%
Zn: in balance The dezincification-resistant low lead brass alloy of the present invention and foundry return were preheated for 15 minutes to reach a temperature higher than 400., and the two were mixed at a weight ratio of 7:1, along with addition of 0.2 wt% of refining slag, for melting in an induction furnace until the brass alloy reached a certain molten state (hereinafter referred to as "molten copper liquid"). A metallic gravity casting machine was coupled with the sand core and the gravity casting molds to perform casting, and a temperature monitoring system further controlled temperatures so as to maintain the casting temperature to a range from 1010 to 1060C. In each casting, the feed amount was preferably 1 to 2 kilograms, and the casting time was controlled to a range from 3 to 8 seconds.
After the molds were cooled, the molds were opened and the casting heads were cleaned. The mold temperatures were monitored so as to control the mold temperatures to a range from 200 to 220C to form casting parts.
Then, the casting parts were released from the molds. Then, the molds were cleaned to ensure that the site of the core head were clean. The graphite liquid was spread on the surface of the molds following by cooling with immersion. The temperature of the graphite liquid for cooling the mold was preferably maintained at a range from 30 to 36C, and the specific weight of the graphite liquid ranged from 1.05 to 1.06.
Self-checking was performed on the cooled casting parts, and the casting parts were sent in a sand cleaning drum for cleaning. Then, an as-cast treatment was performed, wherein a thermal treatment for distressing annealing was performed on as-casts to eliminate the internal stress generated by casting. The as-casts were subsequently mechanically processed and polished, so that no sand, metal powder or other impurities adhered to the cavity of the casting parts. A quality inspection analysis was performed and the total non-defectiveness in production was calculated by the following equation.
total non-defectiveness in production = the number of non-defective products/the total number of products x 100%
Total non-defectiveness in production reflects the qualitative stability of production processes. High qualitative stability of production processes ensures normal production.
Table 1. Ingredients, processing characteristics and total non-defectiveness in production of the alloys W602N 59 lead brass ezincification resistant brass alloy of the present invention ompara ompara ompara ompar ompara ompara ve Exampi Example Example Example ive ive ive tive tive [e-.
example xample example example example ample el 2 3 4 (%) 1.39 62.92 62.14 62.39 1.86 62.01 61.32 62.75 62.63 64.47 Cu Sb (%} 0.0010 <0.0010 0.0010 0.0010 0.0010 0.0010 .1283 0.047 0.052 ).015 As (%) .112 0.145 .127 .0014 .0011 .0016 .0852 .169 .165 .142 Si (%) .0161 .0035 1.0026 .028 .024 .021 1.03 .653 .563 ).78 Al (%) .634 .618 .601 .51 .58 .55 .6452 .78 .653 ).79 b (%) 1.83 .67 .12 1.47 1.69 1.871 .0086 .002 .0085 ).115 Sn (%) -- --- -- -- -- --- -- -- .861 ---i (%) -- --- -- -- -- -- -- -- v.152 B (%) -- -- -- -- --- -- -- -- lOppm --Inp ut 150 150 150 150 150 150 150 150 150 150 astin (pcs olishi out g out 140 141 140 140 141 144 140 139 141 141 pcs field 2% 93% 2% 2% 93% 6% 2% 0% 3% 3%
It is known from Table I that the dezincification resistant brass alloy of the present invention gave a yield higher than 90% when it was used a raw material.
In Example 3, tin was added and dissolved into copper solid solution, so as to achieve solid solution strengthening and improve the resistance to seawater corrosion. However, when the amount of tin is more than 2.0 wt%, the brittle y phase occurs in the alloy, which adversely affects the plasticity of the alloy, and no relative corrosion resistance can be obtained. In addition, CA 02718613 2010-10-20 _._......._.._~
in order to have great casting, mechanical processing and yield, the amount of tin in the dezincification of the present invention is in a range from 0.1 to 1.0 wt%.
The addition of nickel makes copper liquid form fine crystals, and cleans the copper substrate and crystal boundaries, so as to improve mechanical property of brass casting products. In the brass alloy, nickel has relatively high melting point. Therefore, the amount of nickel needs to be strictly controlled to prevent nickel and other metal elements from forming brittle inter-metallic compounds with high melting points which adversely affect to thermal processing properties of the alloy and forms pores and cracks.
Accordingly, the amount of nickel in the dezincification resistant brass alloy of the present invention is less than 0.25 wt%.
The addition of boron facilitates refinement of the brass alloy, and increases the strength and hardness of the brass alloy. Further, boron slows down the migration of divacancy, so as to improve dezincification resistance of the brass alloy. However, when the amount of boron is more than 20 ppm, boride slag aggregates, no relative strength and hardness of the brass alloy can be obtained, and furthermore, the dezincification resistance of the brass alloy is decreased. Hence, the amount of boron in the dezincification resistant brass alloy of the present invention is less than 20 ppm which makes the yield more than 93%.
The yield of the dezincification resistant brass alloy of the present invention was comparable to those of conventional 59 lead brass (C85700 brass) and DR brass (CW602N brass), and can indeed be a substitute brass material. The dezincification resistant brass alloy of the present invention can significantly decrease the lead content in the alloy, effectively avoid the lead contamination occurred during processes, and decrease the amount of lead leach during processing. It is clear that the dezincification resistant brass alloy of the present invention has material characteristics to meet the environmental requirements.
Test example 2:
FIGS. 1A to 1C illustrate the structural distributions showing the materials of the dezincification resistant brass alloy of the present invention (Example 2), CW602N brass (Comparative Example 1) and 59 lead brass (Comparative Example 4) when the specimens were examined under an optical metallographic microscope at 100X magnification.
The measured values of the major ingredients of the alloy in Examples 2 are as follows: Cu: 62.75%, Zn: 35.42%, Si: 0.653%, Sb: 0.047%, Al:
0.78% and As: 0.169%.
As shown in FIGS. 1A to 1C, the structure of a phase of the metallography of the CW602N brass (as shown FIG. 1B) was coarse, indicating that the CW602N brass had good plasticity but poor cutting property. The metallography of the 59 lead brass showed dendritic structures with a+(6 phase. The dezincification resistant brass alloy of the present invention had Si and Sb added therein, such that the metallography of the dezincification resistant brass alloy of the present invention showed a phase. In the brass alloy of the present invention, the addition of Si expanded the region of 0 phase, and thus the strength and hardness of the brass alloy were increased.
Further, in the brass alloy of the present invention, Si and Cu formed inter-metallic compounds so as to increase hardness and improve cutting property; and Si was present at # phase and boundaries of lS phase as inter-metallic compounds to improve the cutting property of the brass alloy.
Accordingly, the dezincification resistant brass alloy of the present invention had excellent mechanical property.
Test example 3:
The test of fluidity was performed on the dezincification resistant brass alloy of the present invention (Example 2), DR brass (CW602N brass) (Comparative Example 2) and 59 lead brass (C85700 brass) (Comparative Example 5), wherein the furnace temperature was 1000C and the mold temperature was 150C. The results were shown in PIGS. 2A to 2C. In the fluidity test, the flow distance of the DR brass (CW602N brass) was about 580 mm, the flow distance of the 59 lead brass was about 600 mm, and the flow distance of the dezincification resistant brass alloy of the present invention was about 700 mm. Accordingly, the dezincification resistant brass alloy of the present invention had great fluidity for casting.
Test example 4:
The turning test was performed on the dezincification resistant brass alloy of the present invention (Example 3), DR brass (CW602N brass) (Comparative Example 3) and 59 lead brass (C85700 brass) (Comparative Example 6), wherein the parameters were set as follows; 610 rpm, feed amount: 2 mm and feed rate: 0.2 mm/rpm. The cutting results were shown in FIGS. 3A to 3C.
The turning length of the DR brass (CW602N brass) was about 2 mm and was shown as a C-shaped or short whirlpool-like sheet; the turning length of the 59 lead brass (C85700 brass) was about 2 mm and was shown as a C-shaped sheet; and the turning length of the dezincification resistant brass alloy of the present invention was about 5 mm and was shown as a C-shaped sheet. Accordingly, the dezincification resistant brass alloy of the present invention had turning characteristics, i.e. great mechanical processing property.
Test example 5:
A dezincification test was performed on the dezincification resistant brass alloy of the present invention (Example 3), DR brass (CW602N brass) (Comparative Example 1) and 59 lead brass (C85700 brass) (Comparative Example 4) to test the corrosion resistance of the brasses. The dezincification test was performed according to the Australian standard AS2345-2006 "Dezincification resistance of copper alloys". Before a corrosion experiment was performed, a novolak resin was used to make the exposed area of each of the specimens be 100 mm2. The specimens were ground flat using a 600# metallographic abrasive paper, following by washing using distilled water. Then, the specimens were baked dry. The test solution was 1% CuC12 solution prepared before use, and the test temperature was 75 2C. The specimens and the CuCI2 solution were placed in a temperature-controlled water bath to react for 24 0.5 hours. The specimens were removed from the water bath, and out along the vertical direction. The cross-sections of the specimens were polished, and then the depths of corrosion of the specimens were measured and observed under a digital metallographic electronic microscope.
As shown in FIG. 4A, the average dezincification depth of dezincification resistant brass alloy of the present invention in Example 3 was 74.81 um. As shown in FIG. 4B, the average dezincification depth of the CW602N brass in Comparative example 1 was 82.28 pm. As shown in FIG. 4C, the average dezincification depth of the 59 lead brass was 336.72 Am.
It is corroborated from the above results that the dezincification resistant brass alloy of the present invention meets the dezincification resistance standard set forth in AS2345-2006 (i.e. the depth of a dezincification layer not exceeding 100 pm).
Test example 6:
A test of mechanical properties was performed on the specimens in the examples according to the standard set forth in IS06998-1998 "Tensile experiments on metallic materials at room temperature". Results are shown in Table 2.
Table 2 Mechanical properties Material Tensile strength QM an Elongation00d 1 2 3 4 5 average 1 2 3 4 5 averag e Example 2 320 315 305 325 308 314.6 10 11 11 10 12 10.8 Comparativ e example 356 337 363 374 367 359.4 12 11 13 13 12 12.2 Comparativ e example 361 387 378 359 383 373.6 11 11 13 11 12 11.6 It is known from Table 2 that the tensile strength and the elongation (%) of dezincification resistant brass alloy in the present invention were comparable to those of the conventional 59 lead brass and CW602N, meaning that the dezincification resistant brass alloy of the present invention had mechanical properties comparable to those of the 59 lead brass and CW602N. Further, the lead content of the dezincification resistant brass alloy of the present invention was less than 0.18 wt%, thereby complying with the environmental requirements. It appears that the dezincification resistant brass alloy of the present invention can indeed replace the 59 lead brass and CW602N brass in product manufacturing.
Test example 7:
The test was performed according to the standard set forth in NSF
61-2007a SPAC for the allowable precipitation amounts of metals in products, to examine the precipitation amounts of the metals of the brass alloys in an aqueous environment. Results are shown in Table 3.
Table 3. Precipitation amounts of the metals in the products Element Upper Comparative Comparative Comparative Comparative Example Example limit example 1 example 1 example 4 example 4 1 4 (ug/L) (by lead (by lead stripping stripping treatment) treatment) Pb 5.0 22.863 1.538 14.835 0.861 0.958 1.2384 Sb 0.6 0.006 0.005 0.013 0.012 0.487 0.125 Al 5.0 0.191 0.162 0.415 0.349 4.572 7.852 As 1 0.061 0.058 0.452 0.398 0.573 0.752 As shown in Table 3, the precipitation amounts of each metal of the dezincification resistant brass alloy of the present invention were lower than the upper limits of the standard values, and therefore, the dezincification resistant brass alloy of the present invention meets the standard set forth in NSF 61-2007a SPAC. The materials of Comparative examples 1 and 4 had lead contents significantly exceeding the standard values when no lead stripping treatments were performed. It appears that only the brass alloys of Example I and Example 4 meet the standard set forth in NSF 61-2007a SPAC without performing a lead stripping treatment. Further, the dezincification resistant brass alloy of the present invention clearly had a significantly lower precipitation amount of the heavy metal, lead, than those of the 59 lead brass (C85700 brass) and the DR brass (CW602N brass).
Thus, the dezincification resistant brass ally of the present invention is more environmentally friendly, and more beneficial to human health.
In conclusion, the dezincification resistant brass alloy of the present invention has excellent casting properties and good toughness and machinability, and it is thus not likely to generate defects like cracks and slag inclusions or casting defects. Therefore, the dezincification resistant brass alloy of the present invention can achieve the material characteristics possessed by lead brasses, and be suitable for applications to subsequent processes. Further, there is no need to perform a lead stripping treatment on the dezincification resistant brass alloy of the present invention. This can lower the production costs, and is extremely advantageous in commercial-scale productions and applications.
The invention has been described using exemplary preferred embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation, so as to encompass all such modifications and similar arrangements.
BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to dezincification resistant copper alloys, and more particularly, to a dezincification resistant brass alloy.
Description of Related Art Brass alloy includes copper and zinc as major ingredients usually at a ratio of about 7:3 or 6:4. Dezincification corrosion is a selective corrosion of brass alloys. When a copper-zinc alloy is in an aqueous solution (such as sea water or fresh water), some corrosion occurs on a surface of the alloy, and zinc on the surface of the alloy is dissolved. However, copper residue still remains on the surface of the alloys, resulting in red porous sponge-like copper, i.e. dezincification corrosion phenomenon.
Generally, if the zinc content is less than 15 wt%, dezincification is not likely to occur. However, as the zinc content increases, the sensitivity to dezincification is increased. If the zinc content exceeds 30 wt%, dezincification corrosion is more severe.
It has been reported in literatures that dezincification corrosion is associated with alloy compositions and environmental factors. In the context of alloy compositions, dezincification of brass alloy with a single a phase and zinc content higher than 20 wt% gives porous copper, whereas dezincification of brass alloy with double a+O phases begins initially in 0 phase and later expands to a phase when 0 phase is completely converted into loosely-structured copper (see Kuaiji Wang et al., Chinese Journal of Materials Research, Vol.13, pages 1-8).
Since dezincification of brass alloy severely damages the structures of brass alloys, the surface intensities of brass products produced from brass alloys are decreased and porosity thus occurs on brass pipes. This significantly decreases the lifetimes of the brass products, and causes application problems. Therefore, standards like AS 2345 and ISO 6509 are established for testing the dezincification resistance of a brass product, i.e.
the depth of a dezincification layer formed on the surface of a brass product shall not exceed 100 lAm.
Regarding the formulations of dezincification resistant brass alloys, except for copper and zinc which are major ingredients, patents such as US
Patent No. 4,417,929 discloses a formulation comprising iron, aluminum and silicon, US Patent Nos. 5,507,885 and US 6,395,110 disclose formulations comprising phosphorus, tin and nickel, US Patent No. 5,653,827 discloses a formulation comprising iron, nickel and bismuth, US Patent No. 6,974,509 discloses a formulation comprising tin, bismuth, iron, nickel and phosphorus, US Patent No. 6,787,101 discloses a formulation comprising phosphorus, tin, nickel, iron, aluminum, silicon and arsenic, and US Patent Nos. 6,599,378 and US 5,637,160 disclose adding selenium and phosphorus in a brass alloy to achieve a dezincifying effect. Alternatively, please refer to Kuaiji Wang et at., Chinese Journal of Materials Research, Vol.13, pages 1-8, wherein a dezincification effect is achieved by adding boron and selenium into a brass alloy.
Conventional dezincification resistant brass alloys usually have higher lead contents (most in the range from 1 to 3 wt%) for facilitating subsequent processing of brass materials. However, as the awareness of environmental protection increases and the impacts of heavy metals on human health and issues like environmental pollutions become major focuses, it is a trend to restrict the usage of lead-containing alloys. Various countries, such as Japan and the United States of America, have sequentially amended relevant regulations and put intensive efforts to lower lead contents in the environment by particularly demanding that no molten lead shall leak from the lead-containing alloy materials used in products such as household electronic appliances, automobiles and water systems to drinking water and lead contamination shall be avoided during processing. Thus, there exists an urgent need in the industry to develop a brass material having dezincification resistance and possessing desirable properties like good casting properties, machinability, corrosion resistance and mechanical properties.
In order to eliminate damages to human bodies and environment, the present invention provides a free cutting brass alloy including silicon and antimony instead of lead, and further including arsenic for improving dezincification resistance.
SUMMARY OF THE INVENTION
The present invention provides a dezincification resistant brass alloy, including 0.5 to 1.2 wt% of silicon (Si); 0.01 to 0.2 wt% of antimony (Sb);
0.02 to 0.25 wt% of arsenic (As); 0.4 to 0.8 wt% of aluminum (Al); and more than 95.8 wt% of copper (Cu) and zinc (Zn).
In the present invention, the brass alloy has effects of solid solution strengthening due to the addition of silicon and aluminum. Further, the addition of zinc influences mechanical strength and elongation rate of the brass alloy. In the present invention, silicon has the zinc equivalent coefficient as about 10 to 12, and aluminum has the zinc equivalent coefficient as about 4 to 6. The amount of silicon is 0.5 to 1.2 wt% of the brass alloy, and the amount of aluminum is 0.4 to 0.8 wt% of the brass alloy.
Once the zinc equivalent is controlled to be lower than 45%, the tensile strength of the brass alloy is about 320 MPa, the elongation rate is about 10.8%, and the hardness is about HRB 76. Apparently, the brass alloy of the present invention has great mechanical strength and elongation rate.
In the present invention, the addition of silicon makes inter-metallic compounds being separated out, so as to improve the cutting property of the brass alloy. The cutting property and fluidity of the alloy melt are improved as long as the amount of silicon is increased. However, when the amount of silicon is more than 1.2 wt% and the zinc equivalent is more than 45%, the brass alloy turns to be brittle and has decreased mechanical strength and elongation rate. For example, when the zinc equivalent is 48%, the brass alloy has the tensile strength as about 55 MPa, elongation rate as about 2%
and hardness as about HRC 30, and thus the brass alloy fails to have good casting property. In addition, the brass alloy of the present invention preferably includes 0.5 to 0.8 wt% of silicon.
In the present invention, the addition of aluminum improves the effect of solid solution strengthening, increases the strength and hardness of the brass alloy, and decreases the specific weight of the brass alloy. Moreover, due to the addition of silicon, when the zinc equivalent is no more than 45% and the amount of aluminum is more than 0.8 wt%, the elongation of the brass alloy is decreased, the metal melt is easily oxidized to form slag and the m fluidity of the brass alloy is lowered, such that the casting product of the brass alloy may have some flow marking, entrapped slag and less compact.
Preferably, the brass alloy of the present invention includes 0.5 to 0.8 wt%
of aluminum.
The divacancy occurs on the surface of the brass alloy during corrosion, and then the divacancy diffuses toward the interior of the brass alloy due to the concentration gradient, and zinc atoms diffuse toward the surface of the brass alloy, such that zinc is dissolved first.
Therefore, in the present invention, the dezincification resistant brass alloy includes arsenic for inhibiting the re-deposition of copper.
Furthermore, the arsenic atoms form a protection layer at the crystal boundary, so as to occupy or diffuse into the divacancy for interrupting the dissolution of zinc, and thus achieve dezincification resistance. Preferably, the brass alloy of the present invention includes 0.07 to 0.17 wt% of arsenic. The proper addition amount of arsenic significantly improves the dezincification resistance of the brass alloy; however, if the addition of arsenic is more than 0.17 wt%, no relative improvement can be obtained.
In addition to improve mechanical properties for processing, such as cutting property, antimony is added in the dezincification resistant brass alloy, wherein antimony and copper form inter-metallic compounds as brittle granules dispersed in S phase and phase boundary of 3 phase for improving cutting property and filling the divacancy so as to decrease corrosion of the brass alloy. Further, when the amount of antimony is more than 0.2 wt%, the brittleness of the alloy is significantly increased and the strength of the alloy is further limited. Moreover, since antimony atoms aggregate at the crystal CA 02718613 2010-10-20 _...___...__.._r boundary of the alloy to form deflection, resulting hot embrittlement of the casting product. Hence, the amount of antimony added in the brass alloy of the present invention is 0.01 to 0.12 wt%.
In the present invention, as the addition of silicon increases, precipitation of arsenic and antimony in aqueous solution is decreased (NSF 61-2007a SPAC). When the amount of arsenic is more than 0.25 wt% and the amount of antimony is more than 0.2 wt%, precipitation amount of arsenic and antimony exceed the standard established in regulations, and cannot be decreased even though the amount of silicon is increased. Based on the about illustrations, the present invention provides a dezincification resistant brass alloy, including 0.5 to 1.2 wt% of silicon (Si); 0.01 to 0.2 wt% of antimony (Sb); 0.02 to 0.25 wt% of arsenic (As); 0.4 to 0.8 wt% of aluminum (Al); and more than 95.8 wt% of copper (Cu) and zinc (Zn).
In the present invention, the dezincification resistant brass alloy further includes one or more selected from the group consisting of nickel, tin, boron and lead. For example, the dezincification resistant brass alloy includes nickel, tin, boron or lead. For example, the dezincification resistant brass alloy includes 0.2 to 1.25 wt% of nickel and tin.
In one embodiment, the dezincification resistant brass alloy includes 0.1 to 1 wt% of tin. In another embodiment, the dezincification resistant brass alloy includes 0.1 to 0.25 wt% of nickel. In addition, the dezincification resistant brass alloy includes boron in a range from 1 to 20 ppm, and preferably in a range from 5 to 15 ppm. The proper amount of nickel and tin are added to improve corrosion resistance, and to increase the strength of the brass alloy.
The suitable amount of boron is added alloy material, which the process can to reduce grain size and improve the property of the brass alloy.
In another embodiment, the dezincification resistant brass alloy includes 0.05 to 0.18 wt% of lead. The proper amount of lead is added to improve cutting property of the brass alloy.
The alloy can contain unavoidable impurities in an amount less than 0.2 wt%.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a metallographic structural distribution of a specimen of a dezincification resistant brass copper alloy of the present invention;
FIG. 1B is a metallographic structural distribution of a specimen of a CW602N brass specimen;
FIG. 1C is a metallographic structural distribution showing a specimen of C85700 brass alloy;
FIG. 2A is diagram showing the fluidity of the dezincification resistant brass alloy of the present invention;
FIG. 2B is diagram showing the fluidity of CW602N brass alloy;
FIG. 2C is diagram showing the fluidity of C85700 brass alloy;
FIG. 3A is a diagram showing the turning characteristic of the dezincification resistant brass alloy of the present invention;
FIG. 3B is a diagram showing the turning characteristic of CW602N
brass alloy;
FIG. 3C is a diagram showing the turning characteristic of C85700 brass alloy;
FIG. 4A is a metallographic structural distribution showing the specimen of the dezincification resistant brass alloy of the present invention after performing a test of dezincification corrosion resistance;
FIG. 4B is a metallographic structural distribution showing the specimen of CW602N brass alloy after performing a test of dezincification corrosion resistance; and FIG. 4C is a metallographic structural distribution showing the specimen of C85700 brass alloy after performing a test of dezincification corrosion resistance.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The detailed description of the present invention is illustrated by the following specific examples. Persons skilled in the art can conceive the other advantages and effects of the present invention based on the disclosure contained in the specification of the present invention.
In the specification of the present invention, the term "dezincification resistant copper alloy/dezincification resistant brass alloy" is a commonly used technological term in the field, and means an alloy having surfaces that are tolerant to corroding conditions in the environment and not likely to dezincify. AS 2345 regulations (Dezincification resistance of copper alloys) are used as a basis to define that the depth of the dezincification layer formed on the surface of a brass alloy product shall not exceed 100 pm.
Unless otherwise specified, the ingredients comprised in the dezincification resistant brass alloy of the present invention, as discussed herein, are all based on the total weight of the alloy, and are expressed in weight percentages (wt%).
The composition of the dezincification resistant brass alloy in the present invention meets the requirement as set forth in California Bill AB 1953, in which the materials of bathroom products contacting water must have lead less than 0.25 wt%. Further, NSF 61 requires that lead leach much be less than 5 ppb. The dezincification resistant brass alloy of the present invention meets the above regulations and is applicable to faucets, water pipes, water supply systems, and etc.
In accordance with inventor's research, the dezincification resistant brass alloy includes specific amounts of silicon, antimony and arsenic to have characteristics as those of the conventional lead brass. Specifically, the dezincification resistant brass alloy of the present invention includes only 0.5 to 1.2 wt% of silicon, 0.01 to 0.2 wt% of antimony and 0.02 to 0.25 wt%
of arsenic to have characteristics (such as cutting property) as those of the conventional lead brass, is not prone to generate product defects like cracks and slag inclusions, and complies with the dezincification requirement set forth in AS-2345.. In addition, the dezincification resistant brass alloy of the present invention effectively reduces the cost of production, and is extremely advantageous to commercial-scale productions and applications.
In an embodiment, the dezincification resistant brass alloy of the present invention includes 58 to 65 wt% of copper, 0.5 to 1.2 wt% of silicon, 0.01 to 0.2 wt% of antimony, 0.02 to 0.25 wt% of arsenic, 0.4 to 0.8 wt% of aluminum, less than 0.2 wt% of unavoidable impurities, and zinc in balance.
In another embodiment, the dezincification resistant brass alloy of the present invention includes 59 to 63 wt% of copper, 0.5 to 0.8 wt% of silicon, 0.01 to 0.12 wt% of antimony, 0.07 to 0.17 wt% of arsenic, 0.5 to 0.8 wt% of aluminum, less than 0.2 wt% of unavoidable impurities, and zinc in balance.
In another embodiment, the dezincification resistant brass alloy of the present invention includes 59 to 63 wt% of copper, 0.5 to 0.8 wt% of silicon, 0.01 to 0.12 wt% of antimony, 0.07 to 0.17 wt% of arsenic, 0.5 to 0.8 wt% of aluminum, less than 5 to 15 ppm of boron, 0.1 to 1 wt% of tin, 0.1 to 0.25 wt% of nickel, less than 0.2 wt% of unavoidable impurities, and zinc in balance.
In another embodiment, the dezincification resistant brass alloy of the present invention includes 59 to 63 wt% of copper, 0.5 to 0.8 wt% of silicon, 0.01 to 0.12 wt% of antimony, 0.07 to 0.17 wt% of arsenic, 0.5 to 0.8 wt% of aluminum, 0.05 to 0.18 wt% of lead, less than 0.2 wt% of unavoidable impurities, and zinc in balance.
The present invention is illustrated by the following exemplary examples.
The ingredients of the dezincification resistant brass alloy of the present invention used in the following test examples are described below, wherein each of the ingredients is added at a proportion based on the total weight of the alloy.
Example 1:
Cu: 61.32 wt% Si: 1.03 wt%
Sb: 0.1283 wt% Al: 0.6452 wt%
As: 0.0852 wt% Zn: in balance Example 2:
Cu: 62.75 wt% Si: 0.653 wt%
Sb: 0.047 wt% Al: 0.78 wt%
As: 0.169 wt% Zn: in balance Example 3:
Cu: 62.63 wt% Si: 0.563 wt%
Sb: 0.052 wt% Al: 0.653 wt%
As: 0.165 wt% Ni: 0.152 wt%
B: 10 ppm Sn: 0.861 wt%
Zn: in balance Example 4:
Cu: 64.47 wt% Si: 0.78 wt%
Sb: 0.015 wt% Al: 0.79 wt%
As: 0.142 wt% Pb: 0.115 wt%
Zn: in balance The dezincification-resistant low lead brass alloy of the present invention and foundry return were preheated for 15 minutes to reach a temperature higher than 400., and the two were mixed at a weight ratio of 7:1, along with addition of 0.2 wt% of refining slag, for melting in an induction furnace until the brass alloy reached a certain molten state (hereinafter referred to as "molten copper liquid"). A metallic gravity casting machine was coupled with the sand core and the gravity casting molds to perform casting, and a temperature monitoring system further controlled temperatures so as to maintain the casting temperature to a range from 1010 to 1060C. In each casting, the feed amount was preferably 1 to 2 kilograms, and the casting time was controlled to a range from 3 to 8 seconds.
After the molds were cooled, the molds were opened and the casting heads were cleaned. The mold temperatures were monitored so as to control the mold temperatures to a range from 200 to 220C to form casting parts.
Then, the casting parts were released from the molds. Then, the molds were cleaned to ensure that the site of the core head were clean. The graphite liquid was spread on the surface of the molds following by cooling with immersion. The temperature of the graphite liquid for cooling the mold was preferably maintained at a range from 30 to 36C, and the specific weight of the graphite liquid ranged from 1.05 to 1.06.
Self-checking was performed on the cooled casting parts, and the casting parts were sent in a sand cleaning drum for cleaning. Then, an as-cast treatment was performed, wherein a thermal treatment for distressing annealing was performed on as-casts to eliminate the internal stress generated by casting. The as-casts were subsequently mechanically processed and polished, so that no sand, metal powder or other impurities adhered to the cavity of the casting parts. A quality inspection analysis was performed and the total non-defectiveness in production was calculated by the following equation.
total non-defectiveness in production = the number of non-defective products/the total number of products x 100%
Total non-defectiveness in production reflects the qualitative stability of production processes. High qualitative stability of production processes ensures normal production.
Table 1. Ingredients, processing characteristics and total non-defectiveness in production of the alloys W602N 59 lead brass ezincification resistant brass alloy of the present invention ompara ompara ompara ompar ompara ompara ve Exampi Example Example Example ive ive ive tive tive [e-.
example xample example example example ample el 2 3 4 (%) 1.39 62.92 62.14 62.39 1.86 62.01 61.32 62.75 62.63 64.47 Cu Sb (%} 0.0010 <0.0010 0.0010 0.0010 0.0010 0.0010 .1283 0.047 0.052 ).015 As (%) .112 0.145 .127 .0014 .0011 .0016 .0852 .169 .165 .142 Si (%) .0161 .0035 1.0026 .028 .024 .021 1.03 .653 .563 ).78 Al (%) .634 .618 .601 .51 .58 .55 .6452 .78 .653 ).79 b (%) 1.83 .67 .12 1.47 1.69 1.871 .0086 .002 .0085 ).115 Sn (%) -- --- -- -- -- --- -- -- .861 ---i (%) -- --- -- -- -- -- -- -- v.152 B (%) -- -- -- -- --- -- -- -- lOppm --Inp ut 150 150 150 150 150 150 150 150 150 150 astin (pcs olishi out g out 140 141 140 140 141 144 140 139 141 141 pcs field 2% 93% 2% 2% 93% 6% 2% 0% 3% 3%
It is known from Table I that the dezincification resistant brass alloy of the present invention gave a yield higher than 90% when it was used a raw material.
In Example 3, tin was added and dissolved into copper solid solution, so as to achieve solid solution strengthening and improve the resistance to seawater corrosion. However, when the amount of tin is more than 2.0 wt%, the brittle y phase occurs in the alloy, which adversely affects the plasticity of the alloy, and no relative corrosion resistance can be obtained. In addition, CA 02718613 2010-10-20 _._......._.._~
in order to have great casting, mechanical processing and yield, the amount of tin in the dezincification of the present invention is in a range from 0.1 to 1.0 wt%.
The addition of nickel makes copper liquid form fine crystals, and cleans the copper substrate and crystal boundaries, so as to improve mechanical property of brass casting products. In the brass alloy, nickel has relatively high melting point. Therefore, the amount of nickel needs to be strictly controlled to prevent nickel and other metal elements from forming brittle inter-metallic compounds with high melting points which adversely affect to thermal processing properties of the alloy and forms pores and cracks.
Accordingly, the amount of nickel in the dezincification resistant brass alloy of the present invention is less than 0.25 wt%.
The addition of boron facilitates refinement of the brass alloy, and increases the strength and hardness of the brass alloy. Further, boron slows down the migration of divacancy, so as to improve dezincification resistance of the brass alloy. However, when the amount of boron is more than 20 ppm, boride slag aggregates, no relative strength and hardness of the brass alloy can be obtained, and furthermore, the dezincification resistance of the brass alloy is decreased. Hence, the amount of boron in the dezincification resistant brass alloy of the present invention is less than 20 ppm which makes the yield more than 93%.
The yield of the dezincification resistant brass alloy of the present invention was comparable to those of conventional 59 lead brass (C85700 brass) and DR brass (CW602N brass), and can indeed be a substitute brass material. The dezincification resistant brass alloy of the present invention can significantly decrease the lead content in the alloy, effectively avoid the lead contamination occurred during processes, and decrease the amount of lead leach during processing. It is clear that the dezincification resistant brass alloy of the present invention has material characteristics to meet the environmental requirements.
Test example 2:
FIGS. 1A to 1C illustrate the structural distributions showing the materials of the dezincification resistant brass alloy of the present invention (Example 2), CW602N brass (Comparative Example 1) and 59 lead brass (Comparative Example 4) when the specimens were examined under an optical metallographic microscope at 100X magnification.
The measured values of the major ingredients of the alloy in Examples 2 are as follows: Cu: 62.75%, Zn: 35.42%, Si: 0.653%, Sb: 0.047%, Al:
0.78% and As: 0.169%.
As shown in FIGS. 1A to 1C, the structure of a phase of the metallography of the CW602N brass (as shown FIG. 1B) was coarse, indicating that the CW602N brass had good plasticity but poor cutting property. The metallography of the 59 lead brass showed dendritic structures with a+(6 phase. The dezincification resistant brass alloy of the present invention had Si and Sb added therein, such that the metallography of the dezincification resistant brass alloy of the present invention showed a phase. In the brass alloy of the present invention, the addition of Si expanded the region of 0 phase, and thus the strength and hardness of the brass alloy were increased.
Further, in the brass alloy of the present invention, Si and Cu formed inter-metallic compounds so as to increase hardness and improve cutting property; and Si was present at # phase and boundaries of lS phase as inter-metallic compounds to improve the cutting property of the brass alloy.
Accordingly, the dezincification resistant brass alloy of the present invention had excellent mechanical property.
Test example 3:
The test of fluidity was performed on the dezincification resistant brass alloy of the present invention (Example 2), DR brass (CW602N brass) (Comparative Example 2) and 59 lead brass (C85700 brass) (Comparative Example 5), wherein the furnace temperature was 1000C and the mold temperature was 150C. The results were shown in PIGS. 2A to 2C. In the fluidity test, the flow distance of the DR brass (CW602N brass) was about 580 mm, the flow distance of the 59 lead brass was about 600 mm, and the flow distance of the dezincification resistant brass alloy of the present invention was about 700 mm. Accordingly, the dezincification resistant brass alloy of the present invention had great fluidity for casting.
Test example 4:
The turning test was performed on the dezincification resistant brass alloy of the present invention (Example 3), DR brass (CW602N brass) (Comparative Example 3) and 59 lead brass (C85700 brass) (Comparative Example 6), wherein the parameters were set as follows; 610 rpm, feed amount: 2 mm and feed rate: 0.2 mm/rpm. The cutting results were shown in FIGS. 3A to 3C.
The turning length of the DR brass (CW602N brass) was about 2 mm and was shown as a C-shaped or short whirlpool-like sheet; the turning length of the 59 lead brass (C85700 brass) was about 2 mm and was shown as a C-shaped sheet; and the turning length of the dezincification resistant brass alloy of the present invention was about 5 mm and was shown as a C-shaped sheet. Accordingly, the dezincification resistant brass alloy of the present invention had turning characteristics, i.e. great mechanical processing property.
Test example 5:
A dezincification test was performed on the dezincification resistant brass alloy of the present invention (Example 3), DR brass (CW602N brass) (Comparative Example 1) and 59 lead brass (C85700 brass) (Comparative Example 4) to test the corrosion resistance of the brasses. The dezincification test was performed according to the Australian standard AS2345-2006 "Dezincification resistance of copper alloys". Before a corrosion experiment was performed, a novolak resin was used to make the exposed area of each of the specimens be 100 mm2. The specimens were ground flat using a 600# metallographic abrasive paper, following by washing using distilled water. Then, the specimens were baked dry. The test solution was 1% CuC12 solution prepared before use, and the test temperature was 75 2C. The specimens and the CuCI2 solution were placed in a temperature-controlled water bath to react for 24 0.5 hours. The specimens were removed from the water bath, and out along the vertical direction. The cross-sections of the specimens were polished, and then the depths of corrosion of the specimens were measured and observed under a digital metallographic electronic microscope.
As shown in FIG. 4A, the average dezincification depth of dezincification resistant brass alloy of the present invention in Example 3 was 74.81 um. As shown in FIG. 4B, the average dezincification depth of the CW602N brass in Comparative example 1 was 82.28 pm. As shown in FIG. 4C, the average dezincification depth of the 59 lead brass was 336.72 Am.
It is corroborated from the above results that the dezincification resistant brass alloy of the present invention meets the dezincification resistance standard set forth in AS2345-2006 (i.e. the depth of a dezincification layer not exceeding 100 pm).
Test example 6:
A test of mechanical properties was performed on the specimens in the examples according to the standard set forth in IS06998-1998 "Tensile experiments on metallic materials at room temperature". Results are shown in Table 2.
Table 2 Mechanical properties Material Tensile strength QM an Elongation00d 1 2 3 4 5 average 1 2 3 4 5 averag e Example 2 320 315 305 325 308 314.6 10 11 11 10 12 10.8 Comparativ e example 356 337 363 374 367 359.4 12 11 13 13 12 12.2 Comparativ e example 361 387 378 359 383 373.6 11 11 13 11 12 11.6 It is known from Table 2 that the tensile strength and the elongation (%) of dezincification resistant brass alloy in the present invention were comparable to those of the conventional 59 lead brass and CW602N, meaning that the dezincification resistant brass alloy of the present invention had mechanical properties comparable to those of the 59 lead brass and CW602N. Further, the lead content of the dezincification resistant brass alloy of the present invention was less than 0.18 wt%, thereby complying with the environmental requirements. It appears that the dezincification resistant brass alloy of the present invention can indeed replace the 59 lead brass and CW602N brass in product manufacturing.
Test example 7:
The test was performed according to the standard set forth in NSF
61-2007a SPAC for the allowable precipitation amounts of metals in products, to examine the precipitation amounts of the metals of the brass alloys in an aqueous environment. Results are shown in Table 3.
Table 3. Precipitation amounts of the metals in the products Element Upper Comparative Comparative Comparative Comparative Example Example limit example 1 example 1 example 4 example 4 1 4 (ug/L) (by lead (by lead stripping stripping treatment) treatment) Pb 5.0 22.863 1.538 14.835 0.861 0.958 1.2384 Sb 0.6 0.006 0.005 0.013 0.012 0.487 0.125 Al 5.0 0.191 0.162 0.415 0.349 4.572 7.852 As 1 0.061 0.058 0.452 0.398 0.573 0.752 As shown in Table 3, the precipitation amounts of each metal of the dezincification resistant brass alloy of the present invention were lower than the upper limits of the standard values, and therefore, the dezincification resistant brass alloy of the present invention meets the standard set forth in NSF 61-2007a SPAC. The materials of Comparative examples 1 and 4 had lead contents significantly exceeding the standard values when no lead stripping treatments were performed. It appears that only the brass alloys of Example I and Example 4 meet the standard set forth in NSF 61-2007a SPAC without performing a lead stripping treatment. Further, the dezincification resistant brass alloy of the present invention clearly had a significantly lower precipitation amount of the heavy metal, lead, than those of the 59 lead brass (C85700 brass) and the DR brass (CW602N brass).
Thus, the dezincification resistant brass ally of the present invention is more environmentally friendly, and more beneficial to human health.
In conclusion, the dezincification resistant brass alloy of the present invention has excellent casting properties and good toughness and machinability, and it is thus not likely to generate defects like cracks and slag inclusions or casting defects. Therefore, the dezincification resistant brass alloy of the present invention can achieve the material characteristics possessed by lead brasses, and be suitable for applications to subsequent processes. Further, there is no need to perform a lead stripping treatment on the dezincification resistant brass alloy of the present invention. This can lower the production costs, and is extremely advantageous in commercial-scale productions and applications.
The invention has been described using exemplary preferred embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation, so as to encompass all such modifications and similar arrangements.
Claims (13)
1. A dezincification resistant brass alloy, comprising:
0.5 to 1.2 wt% of silicon;
0.01 to 0.2 wt% of antimony;
0.02 to 0.25 wt% of arsenic;
0.4 to 0.8 wt% of aluminum; and more than 95.8 wt% of copper and zinc.
0.5 to 1.2 wt% of silicon;
0.01 to 0.2 wt% of antimony;
0.02 to 0.25 wt% of arsenic;
0.4 to 0.8 wt% of aluminum; and more than 95.8 wt% of copper and zinc.
2. The dezincification resistant brass alloy of claim 1, comprising 58 to 65 wt% of copper.
3. The dezincification resistant brass alloy of claim 1, comprising 0.5 to 0.8 wt% of silicon.
4. The dezincification resistant brass alloy of claim 1, comprising 0.01 to 0.12 wt% of antimony.
5. The dezincification resistant brass alloy of claim 1, comprising 0.07 to 0.17 wt% of arsenic.
6. The dezincification resistant brass alloy of claim 1, comprising 0.5 to 0.8 wt% of aluminum.
7. The dezincification resistant brass alloy of claim 1, further comprising at least one selected from the group consisting of nickel, tin, boron and lead.
8. The dezincification resistant brass alloy of claim 7, comprising 0.2 to 1.25 wt% of nickel and tin.
9. The dezincification resistant brass alloy of claim 7, comprising 0.1 to 1 wt% of tin.
10. The dezincification resistant brass alloy of claim 7, comprising 0.1 to 0.25 wt% of nickel.
11. The dezincification resistant brass alloy of claim 7, comprising 0.05 to 0.18 wt% of lead.
12. The dezincification resistant brass alloy of claim 7, comprising 1 to 20 ppm of boron.
13. The dezincification resistant brass alloy of claim 12, comprising 5 to 15 ppm of boron.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3405592A4 (en) * | 2016-01-21 | 2019-08-28 | Fortune Mfg. Co. Ltd. | Unleaded free-cutting brass alloys with excellent castability, method for producing the same, and application thereof |
-
2010
- 2010-10-20 CA CA 2718613 patent/CA2718613A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3405592A4 (en) * | 2016-01-21 | 2019-08-28 | Fortune Mfg. Co. Ltd. | Unleaded free-cutting brass alloys with excellent castability, method for producing the same, and application thereof |
| US11028466B2 (en) | 2016-01-21 | 2021-06-08 | Fortune Mfg. Co., Ltd. | Unleaded free-cutting brass alloys with excellent castability, method for producing the same, and application thereof |
| EP4170050A1 (en) * | 2016-01-21 | 2023-04-26 | Fortune Mfg. Co. Ltd. | Unleaded free-cutting brass alloys with excellent castability and application thereof |
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