KR20120042483A - Brass alloy with corrosion resistance containing little lead - Google Patents

Abstract

PURPOSE: Anti-corrosive brass alloy with a low content of lead is provided to prevent lead extraction and corrosion resulting from dezincification. CONSTITUTION: Anti-corrosive brass alloy with a low content of lead comprises copper(Cu) of 61.5-62.5 weight%, lead(Pb) of 0.01-0.15 weight%, iron(Fe) of 0.01-0.1 weight%, tin(Sn) of 0.3-1.0 weight%, aluminum(Al) of 0.55-0.7 weight%, nickel(Ni) of 0.01-0.1 weight%, bismuth(Bi) of 0.6-1.0 weight%, arsenic(As) of 0.10-0.15 weight%, and zinc(Zn) alloy components of the remaining amount. The content of aluminum is not over 0.5% in order to improve the mobility and castability of the brass alloy.

Description

Brass alloy with corrosion resistance containing little lead

The present invention relates to a brass alloy, and more particularly, to a brass alloy for casting containing copper (Cu) and zinc (Zn) as a main component.

Casting brass alloys have a wide variety of uses, from mechanical, electronic, electrical, automotive and architectural components to everyday goods. Casting brass alloys are added with various elements to design the alloy to obtain the mechanical properties and the properties suitable for the various applications.

One of the most required physical properties is workability, 1.0-4.5% by weight of lead (Pb) is added to improve processability, and lead (Pb) is distributed in the tissue in the form of particles with little solid solubility in brass. As a result, the chip is crushed during processing. In addition, because the relatively low melting point (Pb) by the heat generated during the processing of the brass alloy serves as a lubricant, it has the effect of reducing the processing resistance, and also has the effect of extending the life of the cutting tool. Accordingly, lead (Pb) has been treated as an essential additive for producing free cutting brass. However, lead (Pb) is absorbed into the human body through food and drinking water, as well as breathing, contact with the body from the atmosphere and accumulates in the bone. Accumulated lead (Pn) in the human body causes developmental symptoms in children during growth, osteoporosis in adults, jaundice in the skin and eyes, vomiting, digestive disorders, lethargy, black lines in the gums, high blood pressure, vision Diseases such as disorders and the brain can cause cramps and shock. Therefore, the use of brass alloy in which lead (Pb) component is eluted is strictly regulated.

In order to solve the above problems, much research has been conducted on brass alloys in which bismuth (Bi) is added instead of lead (Pb). As a result, related technologies such as US Patent No. 5,288,458, Japanese Laid-Open Patent Publication No. 5-255778, Japanese Laid-Open Patent Publication No. 54-135618, International Publication No. 93-24670, International Publication No. 94-243325, and the like have been published. There is a bar.

U.S. Patent No. 5,288,458 adds 1.8-5.0 wt.% Bismuth (Bi) to a copper (Cu) -zinc (Zn) binary brass alloy having a mixed phase of alpha + beta (α + β) two phases, Cold workability was greatly improved by using aluminum (Al), tin (Sn), silicon (Si), magnesium (Mg), and lead (Pb) as impurities. However, US Pat. No. 5,288,458 is disadvantageous in terms of economics as a lot of relatively expensive bismuth (Bi) is added, there is a problem that the mechanical properties are weak due to the excessive addition of bismuth (Bi).

In Japanese Patent Laid-Open No. 5-255778, 0.5 to 4.0% by weight of bismuth (Bi) is contained in a brass alloy composed of 57 to 61% by weight of copper (Cu), 0 to 0.9% by weight of mischmetal and zinc (Zn). ) Or the total content of bismuth (Bi) and lead (Pb) in a brass alloy composed of 57 to 61% by weight of copper (Cu), 0.1 to 0.5% mismetal and zinc (Zn). The present invention relates to a brass alloy having excellent workability by adding 3.0% by weight. In this alloy, a small amount of bismuth (Bi) is added, which has an economically advantageous effect, but it can fundamentally prevent elution of lead (Pb). There is no problem.

In Japanese Patent Application Laid-Open No. 54-135618, copper (Cu) is contained in a copper (Cu) -zinc (Zn) -based brass having a content of 58 to 66% by weight, and an amount of lead (Pb) of 0.1% or less by weight as an unavoidable impurity. The addition of 0.5-1.5% by weight of bismuth (Bi) to the alloy has revealed a brass alloy excellent in workability and forging.However, in this case, the content of lead (Pb) managed as impurities is less than 0.1% by weight. If you are trying to manufacture this alloy using a brass scrap of the operation to lower the content of lead (Pb) is difficult to increase the manufacturing cost.

International Publication No. 93-24670 discloses brass containing 57 to 62% by weight of copper (Cu), 3.0% by weight of other alloying components and melt management impurities, additives for improving machinability, and zinc (Zn) as a residual component. Bismuth (Bi) is added to the alloy, and additives and impurities for improving machinability include aluminum (Al), boron (B), lead (Pb), tin (Sn), iron (Fe), antimony (Sb), and silicon. (Si), manganese (Mn), nickel (Ni), etc. are listed. This alloy solves most of the above-mentioned shortcomings and has excellent processability and main component. However, in order to manage lead (Pb), which is an impurity, the production cost is increased due to the problem of using copper (Cu) and zinc (Zn).

Brass alloys coastal areas, that is, chlorine ion (Cl ^-) Brass generated in accordance with the ionization gap between the case used in the inclusion area and the ambient air is contaminated industrial areas, the hot atmosphere of product using that, the alloy components The electrochemical corrosion of the alloy causes a corrosion phenomenon called de-zinc phenomenon by dissolving zinc (Zn).

This corrosion phenomenon degrades the mechanical properties of brass, and in particular, metals such as lead (Pb), which are eluted with zinc (Zn), are harmful to the environment and the human body. Therefore, in recent years, the regulation of corrosion is seriously emerging in relation to the environmental problems in the world.

Therefore, research on active alloys having good mechanical processability and corrosion resistance and no elution of harmful components such as lead has been actively conducted.

In order to solve the problem of de-zinc corrosion, research on brass alloys has been actively conducted. Conventional technologies in this field include US Patent No. 3,963,526, Japanese Patent Application Laid-Open No. 60-194035, Korean Patent No. 141858, Japanese Patent Application Laid-Open No. 6-108184, Japanese Patent Application Laid-open No. 3-170646, and the like.

U.S. Patent No. 3,963,526 discloses 61-66% by weight of copper (Cu), with the addition of more than 0.02% by weight of arsenic (As), antimony (Sb) or phosphorus (P) as zinc anti-zinc to the brass alloy. Discloses a technique for improving the corrosion resistance by annealing heat treatment at a temperature of 450 ~ 600 ℃.

Japanese Patent Laid-Open No. 60-194035 discloses 63 to 66% by weight of copper (Cu), 1.0 to 2.5% by weight of lead (Pb), 0.7 to 1.2% by weight of tin (Sn), 0.1 to 0.7% by weight of nickel (Ni), iron A brass alloy having excellent corrosion resistance having 0.1 to 1.0% by weight of Fe, 0.01 to 0.1% by weight of antimony (Sb), 0.01 to 0.2% by weight of phosphorus (P) and zinc (Zn) as the remaining components is introduced.

Japanese Patent Laid-Open No. 6-108184 discloses 61.0-65.0 wt% of copper (Cu), 1.0-3.5 wt% of lead (Pb), 0.7-1.2 wt% of tin (Sn), 0.2-0.7 wt% of nickel (Ni), 0.04% to 0.4% by weight of iron (Fe), 0.02% to 0.1% by weight of antimony (Sb), 0.04% to 0.15% by weight of phosphorus (P), and 0.08% to 0.2% by weight of zinc (Zn) as the remaining components. Introduces brass alloy with excellent corrosion resistance after annealing at 500 ℃ ~ 600 ℃.

In addition, the Republic of Korea Patent No. 141858 is 59.5 ~ 62.5% by weight of copper (Cu), 1.7 ~ 2.5% by weight of lead (Pb), 0.16 ~ 0.22% by weight of arsenic (As), 0.8 ~ 1.2% by weight of tin (Sn), nickel (Ni ) 0.05 ~ 0.3% by weight, iron (Fe) 0.05 ~ 0.2% by weight, zinc (Zn) as the remaining components, and introduced a brass alloy with excellent corrosion resistance after annealing heat treatment at a temperature of 700 ~ 750 ℃ have.

Referring to the conventional patent literature published as above, the research so far has been conducted in the direction of adding a substitute metal by developing a substitute for lead (Pb), and as a result the published corrosion-resistant brass alloys are de-zinc Although it shows a good effect on the corrosion resistance by, but it contains at least 1.0% by weight of lead (Pb) for cutting workability, it has not yet solved the lead (Pb) dissolution problem. .

In addition, the disclosed lead-free brass alloys have a low lead (Pb) content and add bismuth (Bi), which is an element for improving machinability, thereby showing good machinability but no lead (Pb) elution. However, the above-mentioned conventional lead-free brass alloys still do not solve the problems caused by de-zinc corrosion, and also have to manage lead (Pb) content at 0.05% by weight or 0.1% by weight or less. Phosphorus brass scrap cannot be reused and cost increases due to the use of raw materials mixed with high purity copper and zinc.

An object of the present invention is to devise to solve the above problems, and basically, the amount of lead (Pb) to be less than 1ppm prescribed by the Ministry of Health and Welfare, while excellent in machinability, castability and corrosion resistance, It is to provide a brass alloy that can be produced at low cost by using brass scrap as a material.

Corrosion-resistant brass alloy with a low lead content according to the present invention to achieve the above object, copper (Cu) 61.5 ~ 62.5% by weight, lead (Pb) 0.01 ~ 0.15% by weight, iron (Fe) 0.01 ~ 0.1% by weight, tin (Sn) 0.3-1.0 wt%, Aluminum (Al) 0.55-0.7 wt%, Nickel (Ni) 0.01-0.1 wt%, Bismuth (Bi) 0.6-1.0 wt%, Arsenic (As) 0.10-0.15 wt%, remainder The alloy component is characterized by being zinc (Zn).

The brass alloy according to the present invention has recently become a concern for environmental protection or health damage, the lead elution of water, including tap water is a problem, while solving this problem, corrosion-resistant brass alloy that can prevent the de-zinc phenomenon By providing, lead dissolution and corrosion can be prevented, and the effect of greatly improving machinability (processability) is provided. The brass alloy according to the present invention has the effect of reducing the production cost by allowing the domestic brass production companies to import the lead-free corrosion-resistant brass, thereby increasing the product competitiveness in the world market.

1 shows zinc equivalents of various alloying elements by the study of Guillet.
Figure 2 is a table showing the chemical composition of the brass alloy according to an embodiment of the present invention, and the brass alloy components of Comparative Example 1, Comparative Example 2.
Figure 3 is a photograph showing the corrosion characteristics test results.
Figure 4 is a table comparing the corrosion depth obtained from the corrosion test results of FIG.
5 is a photograph comparing the chip shape photograph formed as a result of the cutting test.
6 is a table comparing physical values measured from the cutting test results.
7 is a report showing the lead dissolution test results of the corrosion-resistant brass alloy according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows zinc equivalents of various alloying elements by the study of Guillet. Figure 2 is a table showing the chemical composition of the brass alloy according to an embodiment of the present invention, and the brass alloy components of Comparative Example 1, Comparative Example 2. Figure 3 is a photograph showing the corrosion characteristics test results. Figure 4 is a table comparing the corrosion depth obtained from the corrosion test results of FIG. 5 is a photograph comparing the chip shape photograph formed as a result of the cutting test. 6 is a table comparing physical values measured from the cutting test results.

1 to 6 will be described a corrosion-resistant brass alloy less lead content with a dense microstructure according to an embodiment of the present invention.

Corrosion-resistant brass alloy with a low lead content according to the present invention, copper (Cu) 61.5 ~ 62.5% by weight, lead (Pb) 0.01 ~ 0.15% by weight, iron (Fe) 0.01 ~ 0.1% by weight, tin (Sn) 0.3 ~ 1.0 Weight%, Aluminum (Al) 0.55-0.7 weight%, Nickel (Ni) 0.01-0.1 weight%, Bismuth (Bi) 0.6-1.0 weight%, Arsenic (As) 0.10-0.15 weight%, The remaining alloy components are zinc (Zn) It is characterized by the).

Hereinafter, the background and reason for selecting the range of the alloy composition as described above will be described in detail.

In general, it is preferable that the lead (Pb) is essentially not contained in the brass alloy. However, lead (Pb) is an impurity introduced together with other metals in the manufacturing process of the brass alloy, and when using conventional brass scrap, it is very difficult to exclude this, and the processing cost is excessive, the Ministry of Health and Welfare In order to release below the prescribed value, it is preferable to adjust the amount to 0.2% by weight or less by preliminary analysis. In the present invention, the lead content is limited to a range that can be practically minimized in the range of 0.2% by weight or less. Accordingly, in the present invention, the content of lead is limited to the lower limit of 0.01 wt%, which is the minimum content that can be introduced into the impurities when scrap is used. In addition, the upper limit was limited to 0.15% by weight as the maximum allowable value in the range of less than 0.2% by weight of lead, which is substantially referred to as lead-free brass.

In general, aluminum (Al) is a metal added to improve the castability as well as the mechanical strength of the brass alloy, when less than 0.1% by weight of the fluidity in the molten state becomes poor. Meanwhile, when aluminum (Al) is contained in an amount of more than 0.5% by weight, the fluidity may be increased to improve castability, but aluminum oxide (Al ₂ O ₃ ) may be formed in the molten metal to adversely affect the formation of an alloy. Crazy

Tin (Sn) is an element added not only for castability but also for improving corrosion resistance and suppressing elution of lead (Pb). When the content of tin (Sn) is 0.2% by weight or less, it is difficult to obtain a great effect in improving castability. When the content of tin (Sn) is added in excess of 0.6% by weight, there is a problem in that a weak gamma (γ) phase is formed and mechanical properties deteriorate. Therefore, the content of tin (Sn) is preferably buried about 0.2 to 0.6% by weight.

Nickel (Ni) is added as an assistant for improving the corrosion resistance of tin (Sn) and is preferably added less than tin (Sn).

Iron (Fe) may be added to increase the mechanical strength, if the content is increased to increase the mechanical strength. In general, the content of iron (Fe) should be added at least 0.1% by weight, and when the content exceeds 0.5% by weight, there is a problem in that the alloy is weakened by forming an intermetallic compound with another metal.

In addition to the above components, bismuth (Bi) may be added in order to prevent a decrease in the mechanical processability caused by insufficient content of lead (Pb) according to the nature of the product to be manufactured. However, since bismuth (Bi) is a relatively expensive metal and occupies an important position for the cost increase of the product, it is preferable to add it so as to be 0.1 to 0.5% by weight in accordance with the composition of the composition.

In general, alloys in which other elements are added to brass to improve color, wear resistance, corrosion resistance, and mechanical properties are called special brass. Alloy elements are mainly tin (Sn), aluminum (Al), silicon (Si), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb) and the like. These alloying elements are dissolved in the α phase or β phase of the brass of brass, and in the solid solution range, there is usually no significant difference from the structure of the brass and only a change in the ratio of the amounts of the α phase and the β phase is obtained.

 The addition of such a third element has the same effect as increasing or decreasing the amount of zinc in brass. In this sense, when the content of alloying element 1 corresponds to the content of zinc X, this X is called the zinc equivalent of the alloying element. 1 shows zinc equivalents of various alloying elements by the study of Guillet. Nickel is a copper and electrolytic solution, so the zinc equivalent is negative.

The zinc equivalent (Zn _eq ) of the alloy can be obtained by the following equation (1). Where q is the percentage of each element added and t is the zinc equivalent of each element. It is common that the zinc equivalent of the utility alloy is not more than 40% at room temperature processed materials and not more than 45% at others. Among practical alloys, zinc equivalent should be less than 39% to improve corrosion resistance. That is, the β phase fraction having poor corrosion resistance should be reduced.

Zn _eq = (Zn% + t * q) / (Cu% + Zn% + t * q) * 100% ------ Equation (1)

Take the case of 62% Cu, 2% Pb, 1% Al, 35% Zn, which is the chemical composition of the alloy. The equivalent weight at this time is 59% according to the above formula. The alloy having a copper content of 62.0% is α phase at room temperature in the Cu-Zn state diagram, but substantially equivalent copper is 59%, suggesting that the α phase is 70% and the rest is β phase. Alloy elements with high zinc equivalents, such as silicon (Si), aluminum (Al), tin (Sn), etc., are strong β-phase accelerating elements or stabilizing elements, while nickel (Ni) with zinc equivalents of 1 or less (-valued) It is an alpha phase stabilizing element. Arsenic (As) and antimony (Sb) have a zinc equivalent of 3, but are known as α-phase stabilizing elements that do not affect the β-phase.

The corrosion resistant brass will now be described in more detail.

Brass is generally used in corrosive conditions because it is superior in corrosion resistance to other metals. However, in recent years, the use conditions of brass are becoming more severe. Corrosion occurs in brass products that are superior in corrosion resistance due to water quality and environmental pollution in which brass is used. Among the many corrosions that occur in brass, selective corrosion is the most typical of de-zinc corrosion.

De-zinc corrosion occurs in α + β 2 phase, or β single phase alloys, and occurs occasionally and locally. To suppress the zinc corrosion, it is possible to use brass below 30% Zn or to add 0.02 ~ 0.2% As to the alloy above 30% Zn. In addition, corrosion resistance can be improved by phase transformation of weak β phase to α phase through de-zinc corrosion through heat treatment. On the other hand, if the corrosion propagation rate is slowed down, the corrosion resistance is improved. Therefore, if a forging step that can refine the crystal grains is added, more excellent corrosion resistant brass can be obtained. In this way, brass that is suppressed from de-galvanization is referred to as corrosion resistant brass.

Let's take a closer look at the de-zinc corrosion phenomenon.

This is a phenomenon in which the zinc is de-zincerated to the surface of the brass or deep by the action of an aqueous solution containing impure water or corrosive substances, especially in water pipes using water containing chlorine ions (Cl ⁻ ). The de-galvanized part becomes porous and the strength is low. This phenomenon can be seen in high zinc brass, i.e., (α + β) two-phase or β single-phase alloys, which occur both globally and locally. In aqueous solution, copper (Cu) and zinc (Zn) dissolve together as chlorides or other salts, but zinc (Zn) is electrochemically more precious than copper (Cu), so only zinc (Zn) is dissolved and copper (Cu) is to be reprecipitated and remain. De-zinc occurs only when zinc (Zn) is at least 15%, but accelerates with increasing zinc (Zn) content. Manganese (Mn) and iron (Fe) also accelerate de-zinc, arsenic (As), tin (Sn), nickel (Ni), aluminum (Al), antimony (Sb), phosphorus (P), and tungsten (W). ), Lead (Pb), etc. reduce the de-zinc. That is, it is possible to use brass below 30% Zn or to add 0.02 ~ 0.2% As to the alloy above 30% Zn to suppress the de-zinc corrosion.

The zinc oxide corrosion mechanism is described as follows.

The zinc (Zn) component of the alloy components is eluted by the action of an aqueous solution of impurities or corrosive substances, leaving only the copper (Cu) component. The hot zinc-coated surface becomes porous and has low strength and low density copper. (Cu) Only residue is left. At this time, the β phase, which contains more zinc (Zn), which is more electrically than copper (Cu), preferentially causes de-zinc and changes to α phase. When the practical brass alloy of the (α + β) phase is de-zinc, the β phase is first corroded and then the α phase is corroded. De-zinc in the α phase mainly occurs at grain boundaries, particularly in the case of insufficient annealing (annealing), near the zinc (Zn) grain boundaries containing the β crystal microcrystal grains. Even in the absence of β-phase grains, the same phenomenon occurs in a small region in which zinc (Zn) is concentrated. This phenomenon occurs because the α phase coexisting with the β phase to which the selective dissolution of zinc (Zn) proceeds is superior to the β phase. Copper (Cu) is deposited on the remaining β-phase crystal grains. This process occurs between the high concentration of zinc (Zn) and the high concentration of copper (Cu) in brass.

De-zinc corrosion occurs mainly in the 35wt% Zn copper alloy in which the β phase is formed. Therefore, in the present invention, the zinc equivalent is lowered by adding α-phase stabilizing element in 60Cu-40Zn brass alloy, and before the zinc (Zn) component is released, an oxide film is formed on the surface of the brass alloy and de-zinc is generated at the grain boundary. To suppress corrosion. In addition, by lowering the zinc equivalent as much as possible to minimize the proportion of β phase having a low corrosion resistance.

Now, specifically, the reason for limiting the content of the alloying element added in the present invention will be described.

The reason for adding bismuth (Bi) and phosphorus (P) as an alternative element of lead (Pb) is as follows.

From the binary system diagrams of Cu-X alloys (X is one of tellurium (Te), selenium (Se), thallium (Tl), bismuth (Bi), and sulfur (S)), these elements are converted to copper in solid state like lead. It is known to have extremely limited employment and play a role similar to lead. In the case of tellurium (Te), selenium (Se), and sulfur (S), an intermetallic compound is formed and uniformly dispersed as in the case of lead, thereby providing the same effect on machinability. Unfortunately, these elements have serious problems. Tellurium (Te), selenium (Se), and thallium (Tl) are toxic and expensive. Sulfur (S), along with other elements used in copper and its alloys, causes harmful reactions. Bismuth (Bi) is non-toxic but, even in small amounts, makes copper extremely brittle. If only this problem can be overcome, bismuth (Bi) is a good candidate to replace lead (Pb) in free-cut copper alloys.

Although the Cu-Pb and Cu-Bi states are similar, the dispersion of the secondary phases in these binary alloys is very different. In Cu-Pb alloys, lead (Pb) particles are uniformly distributed within and at grain boundaries, and therefore not detrimental to the mechanical properties of the alloy. In addition, lead (Pb) is inherently ductile because it is a face-centered cubic (FCC) structure. Therefore, Cu-Pb alloys are considerably ductile up to 30wt% Pb. Bismuth (Bi) is also present as particles inside the grains of the Cu—Bi alloy, which is a preferred aspect. However, bismuth (Bi) is present in the form of a film, not spherical particles, at the grain boundary. The presence of such a film embrittles the alloy. In addition, the crystal structure of bismuth (Bi) is a tetrahedron (Rhombohedral structure) itself is large in itself brittle. Therefore, a successful modification of the Cu-Bi alloy would transform the grain boundary film into particles.

The formation of bismuth (Bi) films at grain boundaries is directly related to the difference in surface tension between copper (Cu) and bismuth (Bi) in the liquid phase. That is, the solution of the problem can be solved by adding an alloying element to lower the surface tension of copper (Cu) or to increase the surface tension of bismuth (Bi). Lead (Pb) and thallium (Tl) alone are elements that can melt the bismuth (Bi) and increase the surface tension of bismuth (Bi) without being dissolved in copper (Cu). However, all of these elements are toxic and are therefore not considered. On the other hand, phosphorus (P), indium (In), tin (Sn), germanium (Ge), gallium (Ga), zinc (Zn), and aluminum (Al) are soluble in copper (Cu) but not in bismuth (Bi). It is known that it can significantly reduce the surface tension of copper (Cu). In addition to lowering the content of expensive Bi not only economically advantageous, but also to reduce the problem of weak mechanical properties due to excessive addition of bismuth (Bi). For this reason, bismuth (Bi) is contained at least 0.5wt% to minimize the amount of bismuth (Bi) and to improve the mechanical properties and cutting properties. When the bismuth (Bi) is added to less than 0.5wt%, since the machinability and mechanical properties may be lowered, the minimum amount was determined to be 0.5wt% or more. In addition, the bismuth (Bi) content of more than 5wt% Bismuth (Bi) when the input is in the form of a film inside the joints may be cracked and mechanical defects of the product. For this reason, the content of bismuth (Bi) was determined to be 0.5 ~ 5wt%. In addition, since bismuth (Bi) is an expensive metal, 0.6 to 1.0 wt% component range was selected to find a range in which mechanical properties and cutting properties can be improved while being added within a range of 0.5 to 5 wt%.

Zinc (Zn) has a high solubility in copper (Cu), and it is 45% Zn or less for industrial brass, so only the α and β phases are a problem. α phase is a phase in which zinc (Zn) is dissolved in copper (Cu), and its crystal form is a face-centered cubic lattice, and the lattice constant increases from 3.60Å to 3.693 따라 as the zinc content is changed from 0 to 38%. . The zinc solid solubility limit in the α phase is 39% Zn at 450 ° C and the solubility decreases with decreasing temperature, resulting in about 35% Zn at 250 ° C. In addition, the α phase is soft and has excellent processability at room temperature, and has a low corrosion rate. β phase has a body-centered cubic lattice crystal and the lattice constant increases to 2.942Å ~ 2.949Å as it changes to 46.2 ~ 49.5% Zn. β phase is strong, and hot workability is high, but corrosion rate is fast. In the present invention, zinc is determined as a remaining metal other than copper (Cu) and additional elements.

Arsenic (As) is the most effective inhibitor against de-zinc corrosion. Arsenic (As) addition of 0.02-0.04 wt% As is a standard of addition amount for de-zinc suppression of (alpha) brass. However, it is known that arsenic (As) exhibits no inhibitory effect on the β phase of industrially important (α + β) brass alloys. This is because arsenic (As) selectively collects in the α phase and does not protect the β phase grains. That is, arsenic (As) acts as a stabilizing element of the α phase. This is contrary to the theory that Muntz metal (Cu-40% Zn alloy) increases the resistance to de-zinc by the addition of arsenic (As). Although the possibility of the presence of an arsenic (As) oxide layer has been studied, it is difficult to form a protective film with an arsenic (As) content that is insufficient to suppress de-zinc. When the redox reaction between arsenic (As) ions and solid arsenic (As) occurs in the tip portion where the corrosion proceeds, the production of copper (Cu) ions is inhibited in α brass. However, in alloys containing many impurities such as iron (Fe), manganese (Mn) and magnesium (Mg), these elements react with arsenic (As) to form compounds. Therefore, when an excessive amount of arsenic (As) is added, the corrosion resistance of the brass alloy Decreases. Arsenic (As) content was limited to 0.10 to 0.15% by weight in order to be able to suppress the reduction of corrosion resistance while preventing the de-zinc phenomenon. If the content of arsenic (As) is less than 0.10wt% there is a problem that does not exhibit the required corrosion resistance. On the other hand, when the content of arsenic (As) exceeds 0.15wt%, there is a problem of reducing the corrosion resistance of brass by forming a compound.

When aluminum (Al) is added, the region of alpha brass is reduced. Aluminum (Al) has a solid solution effect without affecting hot workability, resistance to erosion, sliding properties and durability. Aluminum (Al) increases the strength of α and β brass and improves the seawater resistance of α brass. In the case of ordinary castings, the solid solution of aluminum (Al) is about 7 wt%, and the surface state of the casting is very good by adding aluminum (Al). However, when 6wt% or more is added, castability decreases because the casting structure tends to be coarsened and oxide slag is easily produced. In the present invention, aluminum (Al) was limited to the component range of 0.55 ~ 0.70wt% for improving the durability while increasing the strength of the brass alloy.

Iron (Fe) was added to improve the mechanical strength of the brass alloy. When the iron (Fe) content is increased, the mechanical strength of the brass alloy is improved, but it is effective to add more than 0.01wt%. However, when the content of iron (Fe) exceeds 0.1wt%, there is a problem in that the alloy becomes brittle by forming an intermetallic compound with another metal. In the present invention, to improve the mechanical properties, the content of iron (Fe) was limited to 0.01 ~ 0.1wt%.

Nickel (Ni) is an element having a negative value in the calculation of the zinc equivalent, and serves to suppress the corrosion of the α phase as an element promoting the α phase. In addition, since it is easier to form the passivation film when added with tin (Sn), it shows more improved corrosion resistance than when tin (Sn) is added alone. Nickel (Ni) improves strength and formability at room temperature and high temperature and also increases corrosion resistance. In the present invention, in order to improve the corrosion resistance, strength and formability of the brass alloy, the component range was limited to 0.01 to 0.1 wt%. If the nickel (Ni) content is less than 0.01wt, there is a problem in that the strength and formability required by the corrosion resistant brass alloy cannot be obtained. On the other hand, when the content of nickel (Ni) is more than 0.1wt%, there is a problem that the value of zinc equivalent is too low and the strength and formability are lowered.

Tin (Sn) is an element that improves the corrosion resistance of brass and is a β-phase stabilizing element. Tin (Sn) is generally used for admiralty brass (71Cu-28Zn-1Sn) and naval brass (60Cu-39.25Zn-0.75Sn). Β phase is stabilized in naval brass to which tin (Sn) is added. However, if arsenic (As) is not present, it is reported that de-zinc phenomenon occurs. Therefore, tin (Sn) is effective in general corrosion, but less effective in de-zinc. When the amount of tin (Sn) added is less than 0.7wt%, the effect is small, and at 1.2wt% or more, weak phase of γ phase appears, so the amount of tin should be adjusted. On the other hand, when the α phase structure is obtained by heat treatment, the addition amount can be reduced. In the present invention, the amount of tin (Sn) added was limited to 0.30 to 1.0 wt% in order to reduce the de-zinc phenomenon while improving the corrosion resistance.

Hereinafter will be described the results of the corrosion properties and machinability test by producing an embodiment of the corrosion-resistant brass alloy with a low lead content according to the present invention described above.

For convenience, hereinafter, the corrosion resistant brass alloy manufactured according to an embodiment of the present invention will be referred to as an embodiment. In addition, two conventional corrosion-resistant brass alloys are selected for comparison with the examples and will be referred to as Comparative Example 1 and Comparative Example 2, respectively.

Figure 2 shows the brass alloy components of Example, Comparative Example 1 and Comparative Example 2.

The manufacturing method of the brass alloy of the component shown in FIG. 1 is as follows.

In other words, the effect of each component of the brass specification on the mechanical properties and casting properties of the material is varied, so when using scrap, at least copper (Cu), lead (Pb), iron (Fe) and tin (Sn), aluminum Clear control of the content of (Al), arsenic (As) and bismuth (Bi) is required. Melting is carried out in crucible furnaces or channel type induction furnaces. Mold casting activities do not have a special melt treatment.

According to the composition of the present embodiment, the mixture is calculated and charged into the melting furnace, heated for 1 hour and 30 minutes while stirring at 1000 ° C to completely dissolve the chemical composition, and the temperature of the melting furnace is maintained at 1070 ° C for 10 minutes, and then slag state. After removing the non-metallic inclusions, lower the temperature of the melting furnace to 1000 ℃ and tapping with the prepared ingot metal.

Two tests were conducted to compare the properties of the brass alloy thus prepared. That is, the corrosion characteristics and machinability test.

Hereinafter, the corrosion test method and the cutting test method will be described sequentially.

Corrosion characteristics tests were carried out according to the international standard ISO-6509. The corrosion solution was dissolved in distilled water with 12.7 g of CuCl ₂ in 2H ₂ O to make 1000 ± 10ml.The sample to be corroded was exposed by exposing the surface of about 10X10mm2 and polished by polishing table # 1200. Washed with ethyl alcohol. The polished sample was precipitated in 250 + 50-10 ml of corrosion solution per 100 mm 2, and was corroded at 75 ± 5 ° C. for 24 hours. The depth of corrosion was measured in micrometer units using an optical microscope, and the average value was obtained.

Machinability tests are carried out by lathe and drill methods. The drill type is used to evaluate cutting resistance and cutting chip shape.

Experimental conditions are made by cutting speed after 1,100 RPM, feed rate 0.13mm / rev, drill dimension 3.5mm, drill depth 10mm.

The machinability test is carried out in parallel with the measurement and comparison materials. Cutting resistance is calculated as a percentage of the comparative material, and chip shape is calculated as the weight fraction of the sheared chip relative to the total weight of the cutting chip.

Figure 3 is a photograph showing the corrosion characteristics test results. Figure 4 is a table comparing the corrosion depth obtained from the corrosion test results of FIG.

As a result of judging with reference to FIGS. 3 and 4, in comparison with Comparative Example 2, the Example showed an increase in the tin (Sn) content and the corrosion depth was decreased from 93.6 μm to 81.99 μm. This is because tin (Sn) is a corrosion resistance improving element, and it is determined that tin (Sn) affects the corrosion depth.

In addition, as a result of examining the effects of zinc equivalent and the depth of corrosion, it was found that the zinc equivalent should be more than 38.5% to affect the corrosion resistance.

Compared with Comparative Example 2, it can be seen that the example reduces the depth of corrosion even if the lead (Pb) component is reduced to 0.15% by weight or less and the tin (Sn) content is increased to 0.3 to 1.0% by weight. have. In other words, even if lead (Pb) is reduced, the effect on the depth of corrosion was found to be small.

5 is a photograph comparing the chip shape photograph formed as a result of the cutting test. 6 is a table comparing physical values measured from the cutting test results.

5 and 6, although the embodiment reduces the lead (Pb) component, which greatly affects the workability when the reference sample is set to 100, the cutting index and the resistance index are lower than those of Comparative Example 2, It did not seem to have a big impact. It is judged that the alloy of the same composition as in Example 1 does not have a big problem in workability.

In addition, Figure 7 is a report showing the lead dissolution test results of the corrosion-resistant brass alloy according to an embodiment of the present invention. As shown in Figure 3, the corrosion-resistant brass alloy according to the present invention can be seen that it can be used for piping for water supply facilities, so as to meet the lead dissolution standards according to the environmental notice.

Thus, the corrosion-resistant brass alloy according to the present invention, while increasing the interest in environmental protection and health damage in recent years, in view of the tendency that lead elution of water, including tap water and the like is a problem, while solving such a problem, while solving the problem, It provides a preventable effect. The corrosion resistant brass alloy according to the present invention has an effect of providing lead dissolution and anticorrosion effect and greatly improving machinability (processability). This effect will enable domestic companies to use domestic products to import lead-free corrosion-resistant brass alloys. Therefore, it is expected to provide the effect of lowering the manufacturing cost of products and improving international competitiveness.

While the present invention has been described with reference to the preferred embodiments, it is to be understood that the invention is not to be limited by the example, and various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims (1)

61.5-62.5% by weight of copper (Cu), 0.01-0.15% by weight of lead (Pb), 0.01-0.1% by weight of iron (Fe), 0.3-1.0% by weight of tin (Sn), 0.55-0.7% by weight of aluminum (Al), Nickel (Ni) 0.01 to 0.1% by weight, bismuth (Bi) 0.6 to 1.0% by weight, arsenic (As) 0.10 to 0.15% by weight, low-lead corrosion-resistant brass alloy, characterized in that the remaining alloy components are zinc (Zn) .

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