KR100940593B1 - Lead-free cutting bronze alloy and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A lead-free cutting bronze alloy for casting, and a manufacturing method thereof are provided to restrain brittleness, and to remarkably increase strength and processability. CONSTITUTION: A lead-free cutting bronze alloy for casting comprises Zn 3.5~13 wt%, Sn 2.0~6.0 wt%, Fe 0.03~0.3 wt%, P 0.03 wt% or less, and Pb 0.2 wt% or less. And the lead-free cutting bronze alloy for casting comprises Bi 0.5~4.0 wt%, B 5~100 ppm, and one of Mg 0.01~0.1 wt%, Ni 0.8 wt% or less, and the rest comprises Cu and a small amount of inevitable impurities.

Description

Lead-free cutting bronze alloy and manufacturing method thereof

The present invention relates to an alloy for bronze casting containing little lead harmful to the human body and a manufacturing method thereof.

Generally, bronze in the broad sense means all copper alloys other than brass, and bronze in the narrow meaning means copper (Cu) -tin (Sn) alloy. In particular, the latter is called tin bronze. Tin bronze is commercially called Phosphor bronze because phosphorus (P) is added as a deoxidizer when casting tin bronze. Tin bronze has excellent properties such as high strength, good abrasion resistance, and good corrosion resistance to seawater. Tin bronze is a metal material first discovered and used by mankind after the Neolithic period. Therefore, tin bronze has been developed many kinds of alloys according to the purpose of use. Tin bronze is still widely used as an industrial material today because of its relatively high mechanical properties, excellent corrosion resistance (especially excellent corrosion resistance to seawater), good castability and good machinability. However, the price is high because of limited resources for manufacturing tin bronze. Therefore, tin bronze has been replaced by other materials for use as daily necessities or mechanical materials.

Bronze is an alloy of copper (Cu) and tin (Sn). On the other hand, bronze may contain a small amount of zinc (Zn) or lead (Pb). Bronze is the most representative copper alloy after brass. Bronze has better corrosion resistance and mechanical properties than brass, but is expensive. Bronze is commonly used as a cast and is also known as tin bronze. Bronze is often added with phosphorus (P) and zinc (Zn) to improve deoxidation and plasticity. Bronze is widely used in equipment, arts and crafts, daily necessities, money, bells and statues. Bronze is classified variously according to the content and use of tin (Sn). That is, the gun metal contains 86 to 90 wt% of copper (Cu), 15 to 25 wt% of tin (Sn), and a small amount of zinc (Zn). Bell bronze contains 75 to 85 wt% of copper (Cu) and 15 to 25 wt% of tin (Sn). Kyungcheong-dong contains 65-70wt% of copper (Cu) and 30-35wt% of tin (Sn). Bronze Bronze contains about 95 wt% of copper, about 5w% of tin, and a small amount of zinc (Zn). On the other hand, bearing bronze contains lead (Pb)). In addition, phosphor bronze, aluminum bronze, manganese bronze, etc., are called special bronze. Bronze color is reddish brown when the tin content is less than 5wt%, but becomes yellowish with increasing tin (Sn) content and becomes yellowish when tin becomes 15wt%. In particular, BC1 (1 bronze casting) is used for valves, water dispensers, bearings, nameplates, and general mechanical parts due to its good fluidity and cutting ability. BC6 is used for valves, pump bodies, impellers, hydrants, bearings, sleeves, bushes and general mechanical parts because of its high pressure resistance, abrasion resistance, machinability and castability. These bronze alloys are composed mainly of copper, tin, and zinc, and are composed of several wt% lead and residual components. In the alloy constituting bronze, copper (Cu) accounts for most of the content. Tin (Sn) is an element added for suppressing elution of lead by improving not only castability but also corrosion resistance. Tin (Sn) forms an alloy with copper (Cu) and serves to raise the hardness. Zinc (Zn) provides a similar effect to tin (Sn), lowers the melting point and serves to reduce the melt. In bronze, zinc (Zn) and tin (Sn) are contained in a ratio of several wt% to several tens wt%, respectively. On the other hand, lead (Pb) is added in order to improve the machinability of bronze.

However, with increasing interest in environmental protection and health damage in recent years, elution of lead (Zn) in water, including tap water, has become a problem. That is, the lead Pb is eluted in the water because several wt% lead Pb is contained in the components such as the water supply, the pipe, and the pump using the bronze alloy as described above. If lead (Pb) eluted water is used as a beverage or the like, there is a risk of harm to human health. Lead (Pb) added to bronze may be absorbed into the human body through food or drinking water as well as breathing from the atmosphere and body contact, and may be accumulated in bone. Lead (Pb) causes developmental phenomena in children during growth, osteoporosis in adults, jaundice in the skin and eyes, vomiting, digestive disorders, lethargy, black lines in the gums, hypertension, and vision disorders. It can affect the brain and cause cramps and shock. Because of these problems, the use of bronze and brass alloys in which lead (Pb) components are eluted is increasingly regulated.

For this reason, developed countries and domestic companies have already begun developing lead-free brass for brass used for water supply, and recently added bismuth (Bi), selenium (Se) and silicon (Si) instead of lead (Pb). Produce products. However, in the case of bronze, alloys that do not contain lead (Pb) has not yet been developed. This is because the domestic copper castings are used for industrial purposes rather than for water supply, and are more expensive than brass. On the other hand, recently developed corrosion resistant brass in Korea shows corrosion depth of less than 100㎛. In 1998, the industry standard on KS B 2308 Ball Valve was revised. , Lead-free brass) and bronze materials', which resulted in neglecting the lead elution problem in the bronze materials. In general, lead-free (lead-free) in the processing brass means that the lead (Pb) content is less than 0.2wt%. The content of lead (Pb) is not intentionally added, but is an amount unavoidable as lead (Pb) flowing in recycle scrap. At this time, according to the request of the bronze valve industry, as a ball valve material, it was revised together to be used as a bronze with excellent corrosion resistance. However, it did not solve the problem of dissolution of lead contained in bronze material.

The lead-free free-cut bronze casting alloy having a fine microstructure according to the present invention and a method for manufacturing the same have been devised to solve the above problems, and do not elute substantially harmful lead in water. The composition, processability, and mechanical properties are aimed at developing a new lead-free bronze that is inferior to the conventional bronze, and pioneering the domestic and overseas market.

In order to achieve the above object, the alloy for lead-free free-cut bronze casting with a dense microstructure according to the present invention, zinc (Zn) 3.5 ~ 13wt%, tin (Sn) 2.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 0.5 ~ 4.0wt%, magnesium (Mg) 0.01 ~ 0.1wt%, boron (B) It contains 5 to 100ppm and the rest is characterized by copper (Cu) and trace amounts of unavoidable impurities.

In order to achieve the above object, the alloy for lead-free free-cut bronze casting with a dense microstructure according to the present invention, zinc (Zn) 6 ~ 13wt%, tin (Sn) 2.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 0.5 ~ 2.0wt%, magnesium (Mg) 0.01 ~ 0.1wt%, boron (B) 5 to 100ppm, nickel (Ni) 0.8wt% or less, aluminum (Al) 0.005wt% or less, and the rest is characterized by copper (Cu) and trace amounts of unavoidable impurities.

In order to achieve the above object, the alloy for lead-free free-cut bronze casting with a dense microstructure according to the present invention, zinc (Zn) 3.5 ~ 8wt%, tin (Sn) 4.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 0.7 ~ 2.5wt%, magnesium (Mg) 0.01 ~ 0.1wt%, boron (B ) 5 to 100ppm, nickel (Ni) 0.8wt% or less, aluminum (Al) 0.005wt% or less, and the rest is characterized by copper (Cu) and trace amounts of unavoidable impurities.

In order to achieve the above object, the alloy for lead-free free-cut bronze casting with a dense microstructure according to the present invention, zinc (Zn) 3.5 ~ 8wt%, tin (Sn) 4.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, containing lead (Pb) 0.2wt% or less, bismuth (Bi) 2.0 ~ 4.0wt%, magnesium (Mg) 0.01 ~ 0.1wt%, boron (B) 5 to 100ppm, nickel (Ni) 0.8wt% or less, aluminum (Al) 0.005wt% or less, and the rest is characterized by copper (Cu) and trace amounts of unavoidable impurities.

In order to achieve the above object, the alloy for lead-free free-cut bronze casting with a dense microstructure according to the present invention, zinc (Zn) 6 ~ 13wt%, tin (Sn) 2.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 0.5 ~ 2.0wt%, magnesium (Mg) 0.01 ~ 0.1wt%, boron (B) 5 to 100ppm, nickel (Ni) 0.8wt% or less, aluminum (Al) 0.005wt% or less, and the rest is characterized by copper (Cu) and trace amounts of unavoidable impurities.

In order to achieve the above object, the alloy for lead-free free-cut bronze casting with a dense microstructure according to the present invention, zinc (Zn) 3.5 ~ 8wt%, tin (Sn) 4.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 0.7 ~ 2.5wt%, boron (B) 5 ~ 100ppm, nickel (Ni) It is characterized by including 0.8 wt% or less, aluminum (Al) 0.005 wt% or less, and the rest are copper (Cu) and trace amounts of unavoidable impurities.

In order to achieve the above object, the alloy for lead-free free-cut bronze casting with a dense microstructure according to the present invention, zinc (Zn) 3.5 ~ 8wt%, tin (Sn) 4.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, containing lead (Pb) 0.2wt% or less, bismuth (Bi) 2.0 ~ 4.0wt%, boron (B) 5 ~ 100ppm, nickel (Ni) 0.8wt % Or less, aluminum (Al) 0.005 wt% or less, and the rest is characterized by copper (Cu) and trace amounts of unavoidable impurities.

In order to achieve the above object, the method for producing an alloy for lead-free free-cut bronze casting with a dense microstructure according to the present invention, bronze scrap, zinc (Zn) ingot, tin (Sn) ingot (ingot) Charging the bismuth (Bi) ingot and the remaining alloying elements to charge the melting furnace;

A melting step of heating and melting for 1 hour and 30 minutes while stirring while maintaining the temperature of the melting furnace at 1050 ° C to 1100 ° C;

An impurity removal step of removing the non-metallic inclusions floating in the slag state by maintaining the temperature of the melting furnace at 1120 ° C. to 1180 ° C. after the melting step; And

The casting step of casting the molten alloy in which the non-metallic inclusions have been removed are formed in an ingot form.

An alloy for lead-free free-cut bronze casting with a fine microstructure according to the present invention and a method for preparing the same, by providing an alloy in which bismuth (B) and phosphorus (P) and boron (B) are optimally added, lead (Pb) There is an effect of providing an alloy for lead-free free-cut bronze casting with a fine microstructure that suppresses the brittleness of bismuth (Bi) added as an alternative element of) and significantly improves workability. In addition, the lead-free free-cut bronze casting alloy having a fine microstructure according to the present invention provides an effect of significantly increasing the strength by adding magnesium (Mg). The lead-free free-cut bronze casting alloy with a fine microstructure according to the present invention is different from the lead-free bronze and its components conventionally developed overseas to provide an import substitution effect to reduce the cost of the product to improve the international competitiveness of related industries You can. In addition, the lead-free free-cut bronze casting alloy with a dense microstructure according to the present invention provides the effect of expanding the spread of environmentally friendly materials.

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

1 is a table showing the components of the bronze alloy and the conventional bronze alloy according to the preferred embodiments of the present invention. FIG. 2 is a table showing cutting resistance test results of the bronze alloys shown in FIG. 1. 3 is a photograph showing the shape of a cut chip of the bronze alloys shown in FIG. 4 is an optical micrograph showing the size of the grains of the bronze alloys shown in FIG. 5 is a table comparing the hardness of the alloys shown in FIG. 6 is a process chart for explaining a method for producing an alloy for lead-free free cutting bronze casting with a dense microstructure according to the present invention.

With reference to Figures 1 to 6 will be described a lead-free free-cut bronze casting alloy with a dense microstructure according to various embodiments of the present invention and a method of manufacturing the same.

In general, the machinability of the bronze alloy can be significantly improved by adding 0.5 to 3.0 wt% of lead (Pb). By the way, lead (Pb) is hardly soluble in copper (Cu) in the solid state, but has a significant solubility in the liquid state. In the solidification process of the bronze alloy, lead is precipitated and dispersed as second phase particles, which are uniformly distributed along the grains and grain boundaries. During the cutting of bronze alloys, these lead (Pb) particles break the cut chips to prevent sticking of the tool and the workpiece. Many plumbing fittings are made of this bronze alloy. About 500,000 tons of Pb-containing copper alloys are used annually in the United States alone. On the other hand, medical research shows that lead (Pb) is toxic, and in Europe and the United States, the content of lead in drinking water is strictly regulated. Therefore, there is a need to find other components to replace lead (Pb) in the free cutting bronze alloy, and the present invention has begun by finding an alloying element capable of replacing lead (Pb) according to such a necessity.

 In the binary system diagram of Cu-X alloy (X is any one of tellurium (Te), selenium (Se), thallium (Tl), bismuth (Bi) and sulfur (S)), element X is lead (Pb) Similarly, it is known to have a very limited solubility in copper in the solid state and to play a role similar to that of lead (Pb). Tellurium (Te), selenium (Se), and sulfur (S) form an intermetallic compound and are uniformly dispersed as in the case of lead (Pb), thereby improving cutting ability. Unfortunately, tellurium (Te), thallium (Tl), selenium (Se), and sulfur (S) have serious problems. That is, tellurium (Te), selenium (Se), thallium (Tl) is toxic to the human body and the value is also expensive, there is a problem that is difficult to employ as a replacement element of lead (Pb). In addition, sulfur (S), along with other elements used in copper (Cu) and alloys of copper (Cu), cause harmful reactions. Bismuth (Bi) is non-toxic, but even in small amounts, copper is extremely brittle. Bismuth (Bi) is a good candidate to replace lead (Pb) in bronze alloys if only this problem can be overcome.

Therefore, more detailed examination of bismuth Bi as an alternative raw material of lead Pb is required.

Although the copper (Cu) -lead (Pb) state and the copper (Cu) -bismuth (Bi) state are similar, the dispersion of the secondary phase in these binary alloys is very different. In copper (Cu) -lead (Pb) alloys, lead (Pb) particles are uniformly distributed within and at grain boundaries. Thus, in copper (Pu) -lead (Pb) alloys, lead (Pb) does not compromise the mechanical properties of the alloy. In addition, lead (Pb) is inherently ductile because it is a face centered cubic structure (FCC structure). Therefore, even though the content of lead (Pb) is increased to 30wt% in the copper (Cu) -lead (Pb) alloy, the ductility is very large. Bismuth (Bi) may also exist as particles in the grains and grain boundaries of the copper (Cu) -bismuth (Bi) alloy, and when present in the grains shows desirable properties. However, when bismuth (Bi) particles are present at grain boundaries, bismuth (Bi) is present in the form of a film, not spherical particles. If bismuth (Bi) is present in the form of a film, there is a problem of embrittlement of the alloy. In addition, since the crystal structure of bismuth (Bi) is a tetragonal structure (Rhombohedral structure), the structure itself is originally brittle. Therefore, in order to successfully improve the copper (Cu) -bismuth (Bi) alloy, the particles of bismuth (Bi) present in the grain boundary must be changed to be spherical in the form of a film.

The reason why the bismuth (Bi) particles are formed in the film form at the grain boundaries of the copper (Cu) -bismuth (Bi) alloy is known to be directly related to the difference in the surface tension of copper (Cu) and bismuth (Bi) in the liquid phase. . Therefore, the method of changing the shape of the bismuth (Bi) particles into the spherical grain boundary of the copper (Cu) -bismuth (Bi) alloy is to add an alloying element to lower the surface tension of the copper (Cu) or the surface tension of the bismuth (Bi) Can be solved by increasing Lead (Pb) and thallium (Tl) are the only elements that can be dissolved in bismuth (Bi) without melting in copper (Cu) to increase the surface tension of bismuth (Bi). However, lead (Pb) and thallium (Tl) are both toxic and are therefore not considered. In contrast, phosphorus (P), indium (In), tin (Sn), germanium (Ge), gallium (Ga), zinc (Zn) and aluminum (Al) are dissolved in copper but not in bismuth (Bi). It is known that it can significantly reduce the surface tension of copper (Cu).

On the basis of this point, the alloy for lead-free free-cut bronze castings with a dense microstructure according to the present invention has a bismuth (Bi) spherical shape at grain boundaries by finely adding bismuth (Bi) and adding a small amount of phosphorus (P). In addition, boron (B) and magnesium (Mg) is added to promote the refinement of the crystal grains, which is characterized in that the mechanical properties and the machinability can be improved. In particular, by reducing the content of expensive bismuth (Bi) has an advantage in terms of economics, solve the problem of weakness of the mechanical properties that occur when excessive addition of bismuth (Bi).

In the present invention, while setting the content range to improve the mechanical properties and machinability while minimizing the content of expensive bismuth (Bi). In order to obtain the effect of adding bismuth (Bi), at least 0.5 wt% or more of bismuth (Bi) should be contained. If the content of bismuth (Bi) is less than 0.5wt%, the machinability and mechanical properties may be degraded. On the other hand, when the content of bismuth (Bi) exceeds 5wt%, since bismuth (Bi) is present inside the tissue in the form of a film, there is a possibility that cracking or mechanical defects of the bronze product may occur. For this reason the content of bismuth (Bi) was limited to 0.5wt% ~ 5wt%. In addition, in order to optimally maintain a high content of expensive bismuth (Bi) within this range, various embodiments are in the range of 0.5wt% to 4wt% to find a range that can improve mechanical properties and machinability, from 0.5 to 2.0. Designed by dividing the component range of wt%, 0.7wt% ~ 2.5wt%, 2.0wt% ~ 4.0wt%.

Hereinafter, the role of elements other than the above-mentioned bismuth (Bi) among the additional elements which play a key role in the lead-free free-cut bronze casting alloy having the fine microstructure described above will be described.

Boron (B) is the most effective element to refine the structure of the bronze alloy. Boron (B) is higher in the content of zinc (Zn) increases the micronizing effect of the tissue. Boron (B) serves to maximize the effect of the other elements added to increase the strength of the alloy. In the present invention, boron (B) was added 5ppm to 100ppm. If the content of boron (B) is added less than 5ppm it is difficult to expect the micronized effect of the alloy structure, when the content of boron exceeds 100ppm there is a problem in that the formation of a structure that can inhibit the mechanical properties of the alloy .

Magnesium (Mg) is a representative light metal element with a specific gravity of 1.74. Magnesium (Mg) is relatively inexpensive and nontoxic. Magnesium (Mg) does not harm the conductivity even when a small amount is added, and has an effect of increasing the strength by excellent work hardening. Magnesium (Mg) forms a magnesium oxide (MgO) film on the surface of the alloy, which is intrinsic to copper alloys even after hot working. Provides the effect of maintaining color. In addition, magnesium (Mg) can also obtain a sufficient deoxidation effect without deoxidation treatment by phosphoric acid, etc., which has a high affinity with oxygen and tends to impair conductivity during bronze alloy melt casting. Magnesium (Mg) can also obtain the effect of improving the corrosion resistance of the alloy by reducing the amount of oxygen remaining in the alloy. On the other hand, when the bronze alloy is dissolved, magnesium (Mg) is not mixed well due to the large difference in specific gravity with copper (Cu). Therefore, it is not preferable to add more than 0.1 wt% because the alloy is not dissolved when more than 0.1 wt% is added. Meanwhile, magnesium (Mg) is an element that activates the tissue refining role of boron (Bi), when the magnesium (Mg) content of less than 0.01wt% does not activate the tissue refining effect of boron (Bi) There is a problem.

Tin (Sn) is an element added for suppressing elution of lead (Pb) by improving not only castability but also corrosion resistance. If the content of tin (Sn) is less than 0.1wt%, it is difficult to obtain an effect in improving the castability, and less than 10wt% improves the corrosion resistance and wear resistance. Bronze containing 2wt% to 6wt% of tin is improved in pressure resistance, abrasion resistance, machinability, and castability, and thus is widely used in general mechanical parts such as valves, pump bodies, impellers, feeders, bearings, and sleeves. In the present invention, the content of tin (Sn) is in the range of 2wt% to 6wt% in order to maintain the optimum component range for improving the corrosion resistance and wear resistance, machinability, pressure resistance, etc. of the bronze product 2wt% ~ 4wt% and 4wt The alloy was designed by dividing the range of% ~ 6wt%.

Zinc (Zn) is an element which improves the moldability of an alloy and is an element which improves seawater resistance and pressure resistance. However, when the content of zinc (Zn) exceeds 15wt%, there is a problem in that the fluidity of the alloy is lowered and the cyan color peculiar to bronze does not appear. In general, the zinc (Zn) content of the bronze used in valves, pump bodies, impellers, feeders, etc. is at least 3wt%. If the content of zinc (Zn) is less than 3wt%, problems of deterioration in strength and wear resistance may occur.

Phosphorus (P) is used as a deoxidizer. When phosphorus of less than 0.05wt% is left in the molten metal in the alloy, the fluidity, hardness and strength of the alloy are increased, and wear resistance and elasticity are improved. And mechanical properties are deteriorated.

Iron (Fe) is added to improve the mechanical strength, and as the content increases, the mechanical strength may be improved. Therefore, the iron (Fe) should be added at 0.03 wt% or more. There is a problem that the alloy becomes weak by forming a. Iron (Fe) is an element that activates the microstructure of the phenomenon caused by boron (B), magnesium (Mg).

Nickel (Ni) is an element that mainly increases the strength and hardness of the alloy, but when it exceeds 0.8 wt%, the content of nickel (Ni) is preferably limited to 0.8 wt% or less because it lowers the physical properties of the alloy.

Aluminum (Al) is the role of impurities in reducing the mechanical properties of the bronze alloy in the bronze alloy, it is best to suppress as much as possible, but usually up to 0.005wt% at casting, this is the maximum value and the ingredients were limited.

On the basis of this point, the alloy for lead-free free-cut bronze casting with a dense microstructure according to the present invention was designed in various combinations. The alloy for lead-free free-cut bronze castings with a fine microstructure according to this is copper (Cu) 80-91 wt%, zinc (Zn) 3.5-13 wt%, tin (Sn) 2.0-6.0 wt%, iron (Fe) 0.03-0.3 wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 0.5 ~ 4.0wt%, magnesium (Mg) 0.01 ~ 0.1wt%, boron (B) 5 ~ It is characterized by including 100ppm.

On the other hand, the alloy for lead-free free-cut bronze casting with a dense microstructure according to the present invention, copper (Cu) 80-91wt%, zinc (Zn) 6-13wt%, tin (Sn) 2.0-6.0wt%, iron (Fe) ) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 0.5-2.0wt%, magnesium (Mg) 0.01-0.1wt%, boron ( B) 5 to 100ppm, nickel (Ni) 0.8wt% or less, aluminum (Al) may include 0.005wt% or less.

On the other hand, the alloy for lead-free free-cut bronze casting with a fine microstructure according to the present invention, copper (Cu) 84-90.5wt%, zinc (Zn) 3.5-8wt%, tin (Sn) 4.0-6.0wt%, iron ( Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 0.7 ~ 2.5wt%, magnesium (Mg) 0.01 ~ 0.1wt%, boron (B) 5 to 100ppm, nickel (Ni) may be 0.8wt% or less, aluminum (Al) 0.005wt% or less.

On the other hand, the alloy for lead-free free-cut bronze castings with a fine microstructure according to the present invention, copper (Cu) 80-91wt%, zinc (Zn) 6-13wt%, tin (Sn) 2.0-6.0wt%, iron (Fe ) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 0.5-2.0wt%, magnesium (Mg) 0.01-0.1wt%, boron ( B) 5 to 100ppm, nickel (Ni) 0.8wt% or less, aluminum (Al) may include 0.005wt% or less.

On the other hand, the alloy for lead-free free-cut bronze casting with a fine microstructure according to the present invention, copper (Cu) 84-90.5wt%, zinc (Zn) 3.5-8wt%, tin (Sn) 4.0-6.0wt%, iron ( Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 0.7 ~ 2.5wt%, boron (B) 5 ~ 100ppm, nickel (Ni ) 0.8 wt% or less, aluminum (Al) may include 0.005 wt% or less.

On the other hand, the alloy for lead-free free-cut bronze castings with a dense microstructure according to the present invention, copper (Cu) 82.5 ~ 89.5 wt%, zinc (Zn) 3.5 ~ 8wt%, tin (Sn) 4.0 ~ 6.0wt%, iron ( Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, bismuth (Bi) 2.0 ~ 4.0wt%, boron (B) 5 ~ 100ppm, nickel (Ni ) 0.8 wt% or less, aluminum (Al) may include 0.005 wt% or less.

On the other hand, the method for producing an alloy for lead-free free cutting bronze casting with a fine microstructure according to the present invention, the charging step (S1), melting step (S2), impurity removal step (S3), casting step (S4) It includes.

In the charging step (S1), bronze scraps, zinc (Zn) ingots, tin (Sn) ingots, bismuth (Bi) ingots and the remaining alloying elements are combined and charged into the melting furnace. In the melting step (S2) is heated by melting for 1 hour 30 minutes while stirring while maintaining the temperature of the melting furnace at 1050 ℃ to 1100 ℃. In the impurity removal step (S3), after the melting step (S2), the temperature of the melting furnace is maintained at 1120 ° C. to 1180 ° C. to remove the non-metallic inclusions floating in the slag state. In the casting step (S4), the molten alloy from which the non-metallic inclusions are removed is cast in an ingot form.

Hereinafter, to prepare an alloy for lead-free free-cut bronze casting with a dense microstructure included in the embodiments according to the present invention described above was compared and analyzed the cutting, hardness and degree of grain refinement.

Referring to Figure 1, the conventional bronze alloy as a comparative example, Examples 1 to 9 are examples of the lead-free free-cut bronze casting alloy with a dense microstructure according to the present invention, respectively, bismuth (Bi), It is prepared by varying the content of magnesium (Mg), boron (B). In Examples 1 to 3, the addition of magnesium (Mg) and boron (B) was the main variable, and relatively low content of bismuth (Bi) was added. Examples 4 to 6 are alloys in which the content of bismuth (Bi) is increased relative to Examples 1 to 3, with magnesium (Mg) and boron (B) added as main variables. On the other hand, Examples 7 to 9 is an alloy that increased the content of bismuth (Bi) relative to 4 to Example 6, the main variable is the addition of magnesium (Mg) and boron (B).

Figure 2 shows the cutting resistance test results of the bronze alloys shown in FIG. In general, when the workability of the bronze alloy is excellent, the cutting resistance is low, and chips tend to be chipped. When the workability of the bronze alloy is not good, the cutting force is high and the chip tends to dry. Therefore, a cutting force test was conducted to determine this. Cutting resistance test method was carried out using a drill. The drill used in the cutting force test was a high-speed steel with a diameter of 3.5 mm, and the cutting speed was performed at 1100 rpm and a cutting depth of 10 mm. It is known that the machinability is excellent when the cutting force is less than 4 kgf · cm under these test conditions. The machinability of the lead-free free-cut bronze casting alloy with the dense microstructure according to the present invention was evaluated by setting the free-cut bronze having excellent machinability as a comparative example. Referring to FIG. 2, the cutting resistance of the free cutting bronze shown in the comparative example and the lead-free free cutting bronze casting alloy having the fine microstructures shown in Examples 1 to 9 are satisfactory as 4 kgf · cm or less. Was evaluated. 3 is a photograph showing the shape of a cut chip of the alloys shown in FIG. Chip form of lead-free free-cut bronze casting alloys with dense microstructures containing boron (B) and magnesium (Mg) tended to be brittle. 3, the lead-free free-cut bronze casting alloy having the fine microstructures shown in Examples 1 to 9 was evaluated as having good workability in the form of cut chips.

4 is an optical micrograph for comparing the size of the grains of the alloys shown in FIG. Referring to FIG. 4, it can be seen that the structure of the lead-free free-cut bronze casting alloy having a dense microstructure to which boron (B) and magnesium (Mg) is added is relatively finer. These results prove that the tissue was refined by the addition of boron (B) and magnesium (Mg). Therefore, it is expected that the alloy containing boron (B) and magnesium (Mg) will have excellent mechanical properties and cutting properties. Referring to FIG. 4, the grains of the general bronze alloy shown as a comparative example show an overall coarse trend. On the other hand, the crystal grains of the lead-free free-cut bronze casting alloys with the dense microstructures shown in Examples 1 to 9 show a relatively small tendency, in particular, the texture of the alloy to which boron (B) or magnesium (Mg) is added. This was found to be fine. In addition, when boron (B) and magnesium (Mg) are added simultaneously than when boron (B) or magnesium (Mg) is added alone (Examples 2, 5, 6, 8, and 9) (Example 1, The tissues of 4 and 7 showed a more tendency.

5 shows the evaluation results of the mechanical properties of the lead-free free-cut bronze casting alloy with a dense microstructure according to the present invention. Alloys with good mechanical properties have a low risk of defects during machining. In the present invention, the Vickers hardness was measured to evaluate the mechanical properties of the alloy. Referring to FIG. 5, in Examples 1 to 6, it was evaluated that the hardness of the lead-free free-cut bronze casting alloy having a dense microstructure to which both boron (B) and magnesium (Mg) were added was large.

As described above, the alloy for lead-free free-cut bronze casting with a fine microstructure according to the present invention and a method for manufacturing the same are provided by providing an alloy in which bismuth (Bi), phosphorus (P) and boron (B) are optimally added. There is an effect of providing an alloy for lead-free free-cut bronze casting with a fine microstructure that suppresses brittleness of bismuth (Bi) added as an alternative to lead (Pb) and remarkably improves workability. In addition, the lead-free free-cut bronze casting alloy having a fine microstructure according to the present invention provides an effect of significantly increasing the strength by adding magnesium (Mg). The lead-free free-cut bronze casting alloy with a fine microstructure according to the present invention is different from the lead-free bronze and its components conventionally developed overseas to provide an import substitution effect to reduce the cost of the product to improve the international competitiveness of related industries You can. In addition, the lead-free free-cut bronze casting alloy with a dense microstructure according to the present invention provides the effect of expanding the spread of environmentally friendly materials.

The present invention has been described above with reference to preferred embodiments, but the present invention is not limited to such an example, and various forms of embodiments may be embodied without departing from the technical spirit of the present invention.

1 is a table showing the components of a bronze alloy and a conventional bronze alloy according to preferred embodiments of the present invention.

FIG. 2 is a table illustrating cutting resistance test results of the bronze alloys illustrated in FIG. 1.

3 is a photograph showing the shape of a cut chip of the bronze alloys shown in FIG.

4 is an optical micrograph showing the size of the grains of the bronze alloys shown in FIG.

5 is a table comparing the hardness of the alloys shown in FIG.

6 is a process chart for explaining a method for producing an alloy for lead-free free cutting bronze casting with a dense microstructure according to the present invention.

Claims (9)

Zinc (Zn) 3.5-13wt%, tin (Sn) 2.0-6.0wt%, iron (Fe) 0.03-0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, Bismuth (Bi) 0.5 to 4.0 wt%, magnesium (Mg) 0.01 to 0.1 wt%, boron (B) 5 to 100 ppm, nickel (Ni) 0.8 wt% or less, bismuth and aluminum (Al) 0.005 wt% or less An alloy for lead-free free-cut bronze castings comprising at least three elements, including boron, the remainder being copper (Cu) and trace amounts of unavoidable impurities. The method of claim 1, Zinc (Zn) 3.5-13wt%, tin (Sn) 2.0-6.0wt%, iron (Fe) 0.03-0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, Lead-free free-cut bronze castings containing bismuth (Bi) 0.5-4.0 wt%, magnesium (Mg) 0.01-0.1 wt%, boron (B) 5-100 ppm, the remainder being copper (Cu) and trace inevitable impurities Dragon alloy. Zinc (Zn) 6-13wt%, tin (Sn) 2.0-6.0wt%, iron (Fe) 0.03-0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, Bismuth (Bi) 0.5 ~ 2.0wt%, Magnesium (Mg) 0.01 ~ 0.1wt%, Boron (B) 5 ~ 100ppm, Nickel (Ni) 0.8wt% or less, Aluminum (Al) 0.005wt% or less An alloy for lead-free free-cut bronze castings, characterized by copper and trace amounts of inevitable impurities. The method of claim 1, Zinc (Zn) 3.5 ~ 8wt%, tin (Sn) 4.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, Bismuth (Bi) 0.7 ~ 2.5wt%, Magnesium (Mg) 0.01 ~ 0.1wt%, Boron (B) 5 ~ 100ppm, Nickel (Ni) 0.8wt% or less, Aluminum (Al) 0.005wt% or less An alloy for lead-free free-cut bronze castings, characterized by copper and trace amounts of inevitable impurities. The method of claim 1, Zinc (Zn) 3.5 ~ 8wt%, tin (Sn) 4.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, Bismuth (Bi) 2.0 ~ 4.0wt%, magnesium (Mg) 0.01 ~ 0.1wt%, boron (B) 5 ~ 100ppm, nickel (Ni) 0.8wt% or less, aluminum (Al) 0.005wt% or less An alloy for lead-free free-cut bronze castings, characterized by copper and trace amounts of inevitable impurities. The method of claim 1, Zinc (Zn) 6-13wt%, tin (Sn) 2.0-6.0wt%, iron (Fe) 0.03-0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, Bismuth (Bi) 0.5 ~ 2.0wt%, Boron (B) 5 ~ 100ppm, Nickel (Ni) 0.8wt% or less, Aluminum (Al) 0.005wt% or less, the remainder is copper (Cu) and trace amounts of unavoidable impurities An alloy for lead-free free cutting bronze casting, characterized in that. The method of claim 1, Zinc (Zn) 3.5 ~ 8wt%, tin (Sn) 4.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, Bismuth (Bi) 0.7 ~ 2.5wt%, Boron (B) 5 ~ 100ppm, Nickel (Ni) 0.8wt% or less, Aluminum (Al) 0.005wt% or less, the rest is copper (Cu) and trace amounts of unavoidable impurities An alloy for lead-free free cutting bronze casting, characterized in that. The method of claim 1, Zinc (Zn) 3.5 ~ 8wt%, tin (Sn) 4.0 ~ 6.0wt%, iron (Fe) 0.03 ~ 0.3wt%, phosphorus (P) 0.03wt% or less, lead (Pb) 0.2wt% or less, Bismuth (Bi) 2.0 ~ 4.0wt%, boron (B) 5 ~ 100ppm, nickel (Ni) 0.8wt% or less, aluminum (Al) 0.005wt% or less, the remainder is copper (Cu) and trace amounts of unavoidable impurities An alloy for lead-free free cutting bronze casting, characterized in that. A method of manufacturing an alloy for lead-free free-cut bronze castings having a component ratio of any one of claims 1 to 8, A charging step of compounding the bronze scrap, zinc (Zn) ingot, tin (Sn) ingot, bismuth (Bi) ingot and the remaining alloying elements into a melting furnace; A melting step of heating and melting for 1 hour and 30 minutes while stirring while maintaining the temperature of the melting furnace at 1050 ° C to 1100 ° C; An impurity removal step of removing the non-metallic inclusions floating in the slag state by maintaining the temperature of the melting furnace at 1120 ° C. to 1180 ° C. after the melting step; And And a casting step of casting the molten alloy from which the non-metallic inclusions have been removed in an ingot form.

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