Low-bismuth graphite brass alloy and preparation method and application thereof

Abstract

The invention belongs to the technical field of copper alloys, and particularly relates to a low-bismuth graphite brass alloy and a preparation method and application thereof. The preparation method comprises the following steps: smelting preparation raw materials according to the composition of elements in the low-bismuth graphite brass alloy to obtain a melt; the preparation raw materials comprise a Cu raw material, nodular cast iron, a Zn raw material, a Bi raw material and a Sn raw material; and the melt is cast, and the low-bismuth graphite brass alloy is obtained. Spheroidal graphite is introduced by using nodular cast iron, the problem that graphite and copper are immiscible is solved, meanwhile, the cutting performance of the low-bismuth graphite brass alloy is supplemented, on one hand, use of precious metal bismuth is reduced, and therefore the production cost is reduced; and on the other hand, the spheroidal graphite is beneficial to improving the mechanical property of the brass alloy, so that the brass alloy with high mechanical property and good cutting property is obtained, and the brass alloy is beneficial to being used in water conveying and distribution equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of copper alloys, and in particular relates to a low-bismuth graphite brass alloy and a preparation method and application thereof. Background Art

[0002] Brass alloys are widely used in water supply and distribution equipment such as faucets, valves, and pipe fittings because of their special antibacterial and bactericidal properties, good corrosion resistance, hot and cold forming, and regeneration and recycling. Among the many brass alloys, lead brass is the most widely used because of its excellent machinability. However, lead is neither soluble in copper nor forms intermetallic compounds with copper. During production or use, it is easy to precipitate metallic lead in the form of solid or gaseous state. The lead dissolved in the brass matrix enters the water body, causing excessive lead in drinking water. Lead is a harmful element. The harm it causes to the human body includes: damage to the brain center and peripheral nervous system; damage to the hematopoietic system, hindering the synthesis of hemoglobin, leading to anemia; affecting the function of the digestive system; inhibiting the function of the immune system, etc.

[0003] At present, most reports on lead-free brass are about replacing lead with bismuth. Bismuth (Bi) is close to lead in the periodic table, and they have many similar properties. Bismuth can play a lubricating and chip-breaking role like lead. And the surface tension of bismuth is smaller than that of lead, and its wettability is better than that of lead. However, in the late stage of alloy solidification, copper and bismuth are easy to form a low-melting point eutectic and exist in a liquid state on the grain boundary of copper grains. At the same time, bismuth is also easy to segregate in the grain boundary of copper alloy in the form of a single atomic layer in the form of a network or film, which will cause the brass alloy to be hot and cold brittle, causing copper to fracture brittlely from a metal with good plasticity. It can be seen that the brittle effect of bismuth on copper is very harmful, and the brittle grain boundary caused by its segregation at the grain boundary will seriously damage the processing performance of copper alloys. In addition, the production cost of bismuth brass is much higher than that of lead brass, and bismuth resources are relatively scarce, which limits its scope of application and is not conducive to actual promotion and application.

[0004] Graphite is a commonly used solid lubricant because it is cheap and non-toxic. If graphite can be dispersed in the matrix of difficult-to-cut metal materials, it will produce easy-to-cut properties similar to those of adding lead. The presence of an appropriate amount of graphite particles in the copper alloy matrix significantly reduces its friction coefficient and greatly improves its wear resistance. Graphite particles improve the cutting performance of the alloy and reduce cutting and feed forces. Therefore, graphite brass can completely replace lead-containing brass.

[0005] However, graphite has low strength and small specific gravity, so it is easy to float. At the same time, it has a high melting point (3850°C) and is not mutually soluble with copper, so it is difficult to melt graphite into the copper matrix. In summary, graphite brass cannot be industrially produced and promoted at present because it is impossible to evenly disperse graphite particles in the copper alloy matrix. Summary of the invention

[0006] The object of the present invention is to provide a low-bismuth graphite brass alloy and a preparation method and application thereof. The low-bismuth graphite brass alloy provided by the present invention has excellent cutting performance, mechanical properties and corrosion resistance, and has low production cost, and can be promoted and applied in water supply and distribution equipment.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a low-bismuth graphite brass alloy, comprising the following steps:

[0009] According to the composition of the elements in the low-bismuth graphite brass alloy, the raw materials are smelted to obtain a melt; the raw materials include Cu raw material, ductile iron, Zn raw material, Bi raw material and Sn raw material; the low-bismuth graphite brass alloy includes the following components in percentage by weight: Cu 57-70wt%, Fe 4.5-9.2wt%, C 0.18-0.4wt%, Si 0.1-0.3wt%, Sn 0.09-1wt%, Bi 0.2-0.5wt%, Mn 0.02-0.08wt%, and the balance is Zn and unavoidable impurities; the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite;

[0010] The melt is cast to obtain the low-bismuth graphite brass alloy.

[0011] Preferably, the graphite spheroidization rate of the ductile iron is ≥80%; and the particle size of the spheroidal graphite particles in the ductile iron is 15 to 30 μm.

[0012] Preferably, the average particle size of the spherical graphite in the low-bismuth graphite brass alloy is 8 to 20 μm.

[0013] Preferably, the raw materials for preparation further include a magnesium spheroidizer, and the mass of the magnesium spheroidizer accounts for 1.6-2% of the mass of the ductile iron.

[0014] Preferably, the grade of the magnesium spheroidizer is QRMg8HRE3.

[0015] Preferably, the grade of the ductile iron is QT500-7.

[0016] Preferably, the copper raw material is electrolytic copper, the Zn raw material is a Zn ingot, the Bi raw material is a Bi ingot, and the Sn raw material is a Sn ingot;

[0017] The smelting comprises the following steps:

[0018] S1, performing a first smelting on the Cu raw material to obtain a first melt;

[0019] S2, adding ductile iron to the first melt for a second smelting to obtain a second melt;

[0020] S3. Adding Zn raw material, Bi raw material and Sn raw material to the second melt for third smelting to obtain the melt.

[0021] Preferably, the temperature of the first smelting is 1050-1100°C; the temperature of the second smelting is 1300-1350°C; the temperature of the third smelting is 950-1050°C;

[0022] When the raw material preparation further includes a magnesium spheroidizer, after obtaining the first melt, step S2 is replaced by: adding ductile iron and a magnesium spheroidizer to the first melt for a second smelting to obtain the second melt.

[0023] The present invention provides a low-bismuth graphite brass alloy prepared by the preparation method described in the above technical scheme, comprising the following components in percentage by weight: Cu 57-70wt%, Fe 4.5-9.2wt%, C 0.18-0.4wt%, Si 0.1-0.3wt%, Sn 0.09-1wt%, Bi 0.2-0.5wt%, Mn 0.02-0.08wt%, and the balance is Zn and unavoidable impurities; the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite.

[0024] The present invention provides application of the low-bismuth graphite brass alloy described in the above technical solution in water delivery and distribution equipment.

[0025] The invention provides a preparation method of a low-bismuth graphite brass alloy, comprising the following steps: smelting raw materials according to the composition of elements in the low-bismuth graphite brass alloy to obtain a melt; the raw materials include a Cu raw material, ductile iron, a Zn raw material, a Bi raw material and a Sn raw material; the low-bismuth graphite brass alloy includes the following components in percentage by weight: Cu 57-70wt%, Fe 4.5-9.2wt%, C 0.18-0.4wt%, Si 0.1-0.3wt%, Sn 0.09-1wt%, Bi 0.2-0.5wt%, Mn 0.02-0.08wt%, and the balance is Zn and inevitable impurities; the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite; and the melt is cast to obtain the low-bismuth graphite brass alloy. The present invention uses ductile iron as the raw material for preparing copper alloy. Ductile iron melts during the smelting process to form liquid Fe and spherical graphite, wherein the spherical graphite is directly and evenly dispersed in the melt of the copper alloy, and directly used as the initial raw material of graphite particles in the copper alloy, solving the problem that graphite and brass are not miscible; at the same time, graphite presents a spherical form in the copper alloy matrix, further improving the cutting performance and mechanical properties of brass; the present invention uses ductile iron as the raw material of the copper alloy, introduces evenly dispersed spherical graphite in the copper alloy matrix, and replaces part of the Bi element with spherical graphite, thereby reducing the amount of bismuth used in the copper alloy and improving the corrosion resistance of brass. Thus, the low-bismuth graphite brass alloy of the present invention is non-toxic and corrosion-resistant, meets the requirements of water distribution equipment for molding and processing, and has a low content of precious metals, and has a good application scenario.

[0026] In summary, the preparation method of the low-bismuth graphite brass alloy provided by the present invention has the following beneficial effects:

[0027] The present invention introduces ductile iron as the raw material of the copper alloy, and supplements the cutting performance of brass by graphite dispersed in the copper matrix. The present invention preferably uses ductile iron with a spheroidization rate of ≥80%. On the one hand, the use of Bi raw materials can be reduced, thereby reducing production costs. On the other hand, the spheroidal ductile iron is beneficial to improving the mechanical properties of the brass alloy, thereby obtaining a brass alloy with high mechanical properties and good cutting performance.

[0028] At the same time, the preparation method provided by the present invention uses Bi raw material. The Bi element itself can improve the cutting performance, and can cooperate with the graphite in the copper alloy. As a surface active element of graphite, it helps to increase the number of graphite nodules in the copper alloy, refine the size of the graphite nodules, reduce graphite distortion, and promote the formation of spherical graphite.

[0029] At the same time, the preparation method provided by the present invention uses a reasonable amount of raw material addition, which will not affect the morphology of graphite in the copper alloy, maintain the spheroidization rate of graphite in the copper alloy, further improve the cutting performance, mechanical properties and corrosion resistance, and is conducive to the application of the low-bismuth graphite brass alloy prepared by the present invention in water transportation and distribution products.

[0030] In summary, the preparation method of the low-bismuth graphite brass alloy provided by the present invention has a simple operation method and reduces material costs, and is expected to improve production efficiency and reduce costs, which is conducive to the promotion and application of the material in water distribution products.

[0031] Furthermore, in the present invention, the raw material further comprises a magnesium spheroidizer, and the mass of the magnesium spheroidizer accounts for 1.6-2% of the mass of the ductile iron. The present invention further adds a small amount of magnesium spheroidizer to further promote the formation of spheroidal graphite in the low-bismuth graphite brass alloy. DETAILED DESCRIPTION

[0032] The present invention provides a method for preparing a low-bismuth graphite brass alloy, comprising the following steps:

[0033] According to the composition of the elements in the low-bismuth graphite brass alloy, the raw materials are smelted to obtain a melt; the raw materials include Cu raw material, ductile iron, Zn raw material, Bi raw material and Sn raw material; the low-bismuth graphite brass alloy includes the following components in percentage by weight: Cu 57-70wt%, Fe 4.5-9.2wt%, C 0.18-0.4wt%, Si 0.1-0.3wt%, Sn 0.09-1wt%, Bi 0.2-0.5wt%, Mn 0.02-0.08wt%, and the balance is Zn and unavoidable impurities; the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite;

[0034] The melt is cast to obtain the low-bismuth graphite brass alloy.

[0035] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0036] The invention melts raw materials according to the composition of elements in the low-bismuth graphite brass alloy to obtain a melt; the raw materials include a Cu raw material, ductile iron, a Zn raw material, a Bi raw material and a Sn raw material; the low-bismuth graphite brass alloy includes the following components in percentage by weight: Cu 57-70wt%, Fe 4.5-9.2wt%, C 0.18-0.4wt%, Si 0.1-0.3wt%, Sn 0.09-1wt%, Bi 0.2-0.5wt%, Mn 0.02-0.08wt%, and the balance is Zn and unavoidable impurities; the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite.

[0037] In the present invention, the Cu raw material is specifically electrolytic copper, and the purity of the electrolytic copper is ≥99.95%. The Cu raw material used in the embodiment may be 1# electrolytic copper. The Zn raw material is specifically a Zn ingot, and the purity of the Zn ingot is ≥99.99%. The Zn raw material used in the embodiment may be a 0# zinc ingot. The Bi raw material is specifically a Bi ingot, and the purity of the Bi ingot is ≥99.99%. The Bi raw material used in the embodiment may be Bi9999. The Sn raw material is specifically a Sn ingot, and the purity of the Sn ingot is ≥99.9%. The Sn ingot used in the embodiment may be Sn99.90.

[0038] The ductile iron refers to the national standard GBT9441-2021, and the graphite spheroidization rate of the ductile iron is preferably ≥80%, more preferably 80-90% (spheroidization rate level 3). The particle size of the graphite particles in the ductile iron is level 7+level 8, that is, the particle size of the spheroidal graphite particles in the ductile iron is 15-30μm. In a specific embodiment of the present invention, the grade of the ductile iron is preferably QT500-7. The mass percentage of each element in the ductile iron with the grade QT500-7 specifically includes: C 3.6-3.8wt%, Si 2.2-2.8wt%, Mn0.5-0.8wt%, P<0.08wt%, S<0.02wt%, and the balance is Fe.

[0039] In the present invention, the spherical graphite in the copper alloy is conducive to improving the interface bonding between copper and graphite, and has a lubricating effect on brass while further improving the mechanical properties, thereby replacing precious metals to a certain extent; and, C and Fe are abundant in source, which can reduce the production cost of brass alloys, and is therefore more conducive to promotion and application. The use of ductile iron can directly introduce spherical graphite, avoiding subsequent annealing steps, thereby simplifying the preparation process.

[0040] In the present invention, the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite, and the average particle size of the spherical graphite in the low-bismuth graphite brass alloy is preferably 8 to 20 μm, and specifically preferably 8 to 16 μm or 12 to 20 μm. In the present invention, the smaller the particle size of the spherical graphite in the low-bismuth graphite brass alloy, the better it is to reduce the friction coefficient of copper-graphite, form a complete friction film on the sliding contact surface, and correspondingly improve the cutting ability of brass; but the reduction of the particle size of the spherical graphite in the low-bismuth graphite brass alloy weakens the overall strength of the copper alloy. Therefore, the average particle size of the spherical graphite in the low-bismuth graphite brass alloy provided by the present invention is maintained in the range of 8 to 16 μm, which can enable the low-bismuth graphite brass alloy to obtain the best cutting ability and mechanical strength.

[0041] In the present invention, the raw material preferably further comprises a magnesium spheroidizer, and the mass of the magnesium spheroidizer accounts for 1.6-2% of the mass of the ductile iron. In the present invention, the grade of the magnesium spheroidizer is preferably QRMg8HRE3. The mass percentage of each element in the magnesium spheroidizer with the grade QRMg8HRE3 includes: 5.5-6.5wt% of Mg, 1.5-2.5wt% of RE, 4.0-5.0wt% of Si and other elements.

[0042] In the present invention, the raw material for preparing the low-bismuth graphite brass alloy preferably also includes a magnesium spheroidizer, which can promote the graphite spheroidization reaction in the melt during the casting process of the copper alloy, forming spheroidal graphite with a smaller particle size and more uniformity, and maintaining the stability of the morphology of the spheroidized graphite during the casting process. Excessive magnesium spheroidizers can cause defects such as deformation and shrinkage cavities of the castings. Therefore, the mass of the magnesium spheroidizer in the raw material for preparing the low-bismuth graphite brass alloy provided by the present invention preferably accounts for 1.6-2% of the mass of the ductile iron. The mass percentage of Mg element in the obtained low-bismuth graphite brass alloy is 0.004-0.01wt%. The quality and performance of the low-bismuth graphite brass alloy castings are guaranteed.

[0043] In the present invention, the smelting is preferably carried out in an induction furnace. The smelting preferably comprises the following steps:

[0044] S1, performing a first smelting on the Cu raw material to obtain a first melt;

[0045] S2, adding ductile iron to the first melt for a second smelting to obtain a second melt;

[0046] S3. Adding Zn raw material, Bi raw material and Sn raw material to the second melt for third smelting to obtain the melt.

[0047] The present invention performs a first smelting of the Cu raw material to obtain a first melt. In the present invention, the temperature of the first smelting is preferably 1050-1100°C. The first smelting preferably includes sequentially performing a first melting and a first slag removal. The first melting is preferably to obtain a Cu melt by subjecting the Cu raw material to the first smelting temperature. The first slag removal is preferably to filter out the scum on the surface of the Cu melt to obtain the first melt,

[0048] After obtaining the first melt, the present invention adds ductile iron to the first melt for second smelting to obtain a second melt. In the present invention, when the preparation of the raw materials preferably also includes a magnesium spheroidizer, after obtaining the first melt, the present invention preferably replaces the step of second smelting with: adding ductile iron and a magnesium spheroidizer to the first melt for second smelting to obtain the second melt. In the present invention, the temperature of the second smelting is preferably 1300-1350°C. The second smelting is preferably carried out under stirring.

[0049] After obtaining the second melt, the present invention adds Zn raw material, Bi raw material and Sn raw material to the second melt for third smelting to obtain the melt. In the present invention, after obtaining the second melt, the present invention preferably turns off the power of the induction furnace, cools down to the temperature of the third smelting, and then adds Zn ingots, Bi ingots, and Sn ingots in sequence. The temperature of the third smelting is 950-1050°C, and the third smelting preferably includes: stirring and melting the Zn ingots, Bi ingots, and Sn ingots, and then standing and keeping them warm. The standing and keeping time is preferably 5-10 minutes. The standing and keeping makes the alloy homogenized and removes slag and impurities. The temperature of the third smelting is preferably 950-1050°C, which can effectively avoid the burning of Zn ingots, Bi ingots, and Sn ingots.

[0050] After obtaining the melt, the present invention casts the melt to obtain the low-bismuth graphite brass alloy.

[0051] The present invention has no special requirements on the specific implementation process of the casting.

[0052] The present invention provides a low-bismuth graphite brass alloy prepared by the preparation method described in the above technical scheme, comprising the following components in percentage by weight: Cu 57-70wt%, Fe 4.5-9.2wt%, C 0.18-0.4wt%, Si 0.1-0.3wt%, Sn 0.09-1wt%, Bi 0.2-0.5wt%, Mn 0.02-0.08wt%, and the balance is Zn and unavoidable impurities; the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite.

[0053] In terms of mass percentage, the low-bismuth graphite brass alloy provided by the present invention comprises 57-70wt% Cu, preferably 60-68wt%, and more preferably 57%, 65% or 70%.

[0054] In terms of mass percentage, the low-bismuth graphite brass alloy provided by the present invention includes Fe 4.5-9.2wt%, preferably 5-9wt%, more preferably 5.5-8.5wt%, and specifically preferably 4.64%, 7.44% or 9.31%.

[0055] In terms of mass percentage, the low-bismuth graphite brass alloy provided by the present invention includes 0.18-0.4wt% C, preferably 0.2-0.35wt%, and specifically preferably 0.19%, 0.29%, 0.38% or 0.3%. In the present invention, the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite, so the destructive and splitting effect on the copper matrix is ​​very small, and the degree of stress concentration caused is also small, the effect of the matrix can be fully exerted, and the spherical graphite is conducive to improving the bonding of the copper / graphite interface, so the mechanical properties of the brass alloy can be improved.

[0056] In the present invention, the graphite spheroidization rate of the spheroidized graphite in the low-bismuth graphite brass alloy is preferably ≥80%. The C element in the low-bismuth graphite brass alloy exists in the form of spheroidal graphite, and the average particle size of the spheroidal graphite in the low-bismuth graphite brass alloy is preferably 8 to 20 μm, specifically preferably 8 to 16 μm or 12 to 20 μm.

[0057] In terms of mass percentage, the low-bismuth graphite brass alloy provided by the present invention comprises Si in an amount of 0.1-0.3wt%, preferably 0.15-0.2wt%, and more preferably 0.13%, 0.2% or 0.28%.

[0058] In terms of mass percentage, the low-bismuth graphite brass alloy provided by the present invention includes 0.09-1wt% Sn, preferably 0.1-0.8wt%, and specifically preferably 0.09% or 1%. In the present invention, the Sn element can improve the cold and hot processing properties of bismuth brass, enhance the effect of bismuth on improving the cutting performance of brass, and improve the corrosion resistance of the material; on the other hand, the low melting point element Sn is adsorbed on the graphite / metal interface to form a thin layer that hinders the diffusion of carbon atoms into graphite nodules, thereby preventing the generation of ferrite. In the present invention, excessive Sn segregates in the last solidified liquid to form intergranular compounds, resulting in a decrease in strength and toughness, and anti-spheroidization occurs at the same time.

[0059] The low-bismuth graphite brass alloy provided by the present invention comprises Bi in an amount of 0.2-0.5wt%, preferably 0.3-0.4wt%, and more preferably 0.2% or 0.5% by weight. In the present invention, the Bi element can improve the cutting performance of brass. In addition, the addition amount of bismuth has a direct effect on the formation and stability of the graphite morphology, thereby affecting the performance of the alloy.

[0060] In terms of mass percentage, the low-bismuth graphite brass alloy provided by the present invention includes Mn 0.02-0.08wt%, and is preferably 0.032%, 0.051%, 0.058% or 0.049%.

[0061] The low-bismuth graphite brass alloy provided by the present invention comprises, in terms of mass percentage, the balance of Zn and inevitable impurities, wherein the inevitable impurities are impurities remaining in the raw materials after smelting and inevitable impurities introduced during the preparation process.

[0062] In the present invention, when the raw material for preparing the low-bismuth graphite brass alloy preferably further includes a magnesium spheroidizer, the low-bismuth graphite brass alloy provided by the present invention preferably further includes Mg0.004-0.01wt%, specifically preferably 0.004%, 0.008% or 0.01%, in terms of mass percentage. In the present invention, the magnesium spheroidizer maintains the spheroidization rate of graphite during processing, while improving the corrosion resistance and hot working properties of the material; at the same time, the magnesium spheroidizer provides magnesium elements to the low-bismuth graphite brass alloy, which can refine the copper matrix grains, improve the uniformity of the alloy structure, and improve the strength and toughness of the alloy.

[0063] The present invention provides application of the low-bismuth graphite brass alloy described in the above technical solution in water delivery and distribution equipment.

[0064] In the present invention, the water supply and distribution equipment is preferably a faucet, a water valve or a pipe connector.

[0065] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0066] Example 1

[0067] This embodiment provides a low-bismuth graphite brass alloy, the components of which are shown in Table 1. The low-bismuth graphite brass alloy of this embodiment is prepared by the following method:

[0068] According to the components, electrolytic copper, Zn ingot, Bi ingot and Sn ingot are weighed; electrolytic copper is placed on the bottom of an induction furnace, heated to 1100°C until all the materials are melted, and the surface scum is filtered off; the temperature is raised to 1300-1350°C, and ductile iron (QT500-7, spheroidization rate 3, size 7+8) with graphite spheroidization rate 3 and size 7+8 and Mg spheroidizer (the grade of magnesium spheroidizer is QRMg8HRE3) are added, wherein the mass of ductile iron accounts for 5% of the total mass of the raw materials. wt% (the mass of the ductile iron is consistent with the mass content of the C element and the Fe element of the low-bismuth graphite brass alloy in Table 1), and the mass of the Mg spheroidizer is 1.6wt% of the mass of the ductile iron; turn off the power of the induction furnace, cool it to 950-1050° C., add the Zn ingot, the Bi ingot, and the Sn ingot in sequence, and stir them thoroughly; heat it to 1000-1050° C. and keep it still for 5-10 minutes to homogenize the alloy and remove the slag and impurities; take it out of the furnace for casting, and cool it to obtain the low-bismuth graphite brass alloy.

[0069] Example 2

[0070] Example 2 provides a low-bismuth graphite brass alloy, the components of which are shown in Table 1. The low-bismuth graphite brass alloy of this example is prepared by the following method:

[0071] Electrolytic copper, Zn ingot, Bi ingot and Sn ingot are weighed according to the components; electrolytic copper is placed on the bottom of an induction furnace, heated to 1100°C until all the materials are melted, and the surface scum is filtered off; the temperature is raised to 1300-1350°C, and ductile iron (QT500-7, spheroidization rate 3, graphite particle size 7+8) with graphite spheroidization rate 3 and size 7+8 and Mg spheroidizing agent are added, wherein the mass of ductile iron accounts for 8wt% of the total mass ( The mass content of the C element and the Fe element of the low-bismuth graphite brass alloy in Table 1 is consistent), the mass of the Mg spheroidizer is 1.8wt% of the mass of the ductile iron; the temperature is lowered to 950-1050° C., the Zn ingot, the Bi ingot, and the Sn ingot are added in sequence and stirred sufficiently; the temperature is raised to 1000-1050° C. and kept still for 5-10 minutes to homogenize the alloy and remove the slag and impurities; the alloy is taken out of the furnace for casting and cooled to obtain the low-bismuth graphite brass alloy.

[0072] Example 3

[0073] Example 3 provides a low-bismuth graphite brass alloy, the components of which are shown in Table 1. The low-bismuth graphite brass alloy of this embodiment is prepared by the following method:

[0074] Weigh electrolytic copper, Zn ingot, Bi ingot and Sn ingot according to the components; place the electrolytic copper on the bottom of the induction furnace, heat it to 1100°C until all the materials are melted, and filter out the surface scum; heat it to 1300-1350°C, add ductile iron with graphite spheroidization rate 3 and size 7+8 (QT500-7, spheroidization rate 3, graphite particle size 7+8) and Mg spheroidizer, wherein the mass of ductile iron accounts for 10wt% of the total mass (which is consistent with the mass content of C element and Fe element in the low-bismuth graphite brass alloy in Table 1), the mass of Mg spheroidizer is 2wt% of the mass of ductile iron; cooling to 950-1050° C., adding the Zn ingot, Bi ingot and Sn ingot in sequence, and stirring them fully; heating to 1000-1050° C. and keeping it still for 5-10 minutes to homogenize the alloy and remove slag and impurities; taking out of the furnace for casting, and cooling to obtain the low-bismuth graphite brass alloy.

[0075] Example 4

[0076] Example 4 provides a low-bismuth graphite brass alloy, the components of which are shown in Table 1. In this comparative example, no magnesium spheroidizer is added. The bismuth brass alloy of this comparative example is prepared by the following method:

[0077] Weigh electrolytic copper, Zn ingot, Bi ingot and Sn ingot according to the components; place the electrolytic copper at the bottom of an induction furnace, heat it to 1100° C. until all the materials are melted, and filter out the surface scum; heat it to 1300-1350° C., add ductile iron (QT500-7, spheroidization rate 3, particle size of graphite particles is 7+8) with a graphite spheroidization rate of 3 levels and a graphite spheroidization rate of 7+8, wherein the mass of the ductile iron accounts for 8wt% of the total mass (consistent with the mass content of C element, Fe element, etc. of the low-bismuth graphite brass alloy in Table 1); cool it to 950-1050° C., add the Zn ingot, Bi ingot and Sn ingot in sequence, and stir them thoroughly; heat it to 1000-1050° C. and keep it still for 5-10 minutes to homogenize the alloy and remove the scum and impurities; remove it from the furnace for casting, and cool it to obtain the low-bismuth graphite brass alloy.

[0078] Comparative Example 1

[0079] Comparative Example 1 provides a bismuth brass alloy, the components of which are shown in Table 1. No ductile iron (QT500-7) raw material is added to this comparative example. The bismuth brass alloy of this comparative example is prepared by the following method:

[0080] Weigh electrolytic copper, Zn ingot, Bi ingot and Sn ingot according to the components; place the electrolytic copper on the bottom of an induction furnace, heat it to 1100° C. until all the materials are melted, and filter out the surface scum; heat it to 1300-1350° C. and add iron powder; cool it to 950-1050° C., add the Zn ingot, Sn ingot and Bi ingot in sequence, stir them thoroughly, heat it to 1000-1050° C. and keep it still for 5-10 minutes to homogenize the alloy and remove the scum and impurities; homogenize the alloy and remove the scum and impurities; take it out of the furnace, cast it, and cool it to obtain the bismuth brass alloy.

[0081] Comparative Example 2

[0082] Comparative Example 2 provides a bismuth brass alloy, the components of which are shown in Table 1. No ductile iron (QT500-7) raw material is added to this comparative example. The bismuth brass alloy of this comparative example is prepared by the following method:

[0083] Weigh electrolytic copper, Zn ingot, Bi ingot and Sn ingot according to the components; place the electrolytic copper on the bottom of an induction furnace, heat it to 1100° C. until all the materials are melted, and filter out the surface scum; cool it to 950-1050° C., add the Fe powder, Zn ingot, Sn ingot and Bi ingot in sequence, stir them fully, heat it to 1000-1050° C. and keep it still for 5-10 minutes to homogenize the alloy and remove the scum and impurities; homogenize the alloy and remove the scum and impurities; take it out of the furnace, cast it, and cool it to obtain the bismuth brass alloy.

[0084] Comparative Example 3

[0085] Comparative Example 3 provides a low-bismuth graphite brass alloy, the composition of which is shown in Table 1, wherein ordinary cast iron is used, and the mass percentage of each element in the ordinary cast iron is the same as that of the spheroidized cast iron used in Examples 1 to 4, but the graphite spheroidization rate of the ordinary cast iron used in this Comparative Example 1 is 30%, which is relatively low. In addition, the low-bismuth graphite brass alloy of Comparative Example 3 is prepared according to the method of Example 2.

[0086] Comparative Example 4

[0087] Comparative Example 4 provides a graphite brass alloy, the composition of which is shown in Table 1, and the copper alloy product does not add Bi. In addition, the graphite brass alloy of Comparative Example 4 is prepared according to the method of Example 2, and no Bi ingot is added during the preparation process.

[0088] Comparative Example 5

[0089] Comparative Example 5 provides a graphite brass alloy, the composition of which is shown in Table 1, and Sn is not added to the copper alloy product. In addition, the graphite brass alloy of Comparative Example 5 is prepared according to the method of Example 2, and no Sn ingot is added during the preparation process.

[0090] Table 1 Composition and properties of copper alloys prepared in Examples 1 to 4 and Comparative Examples 1 to 5

[0091]

[0092]

[0093] Note: The graphite spheroidization rate in Table 1 is the graphite spheroidization rate of spheroidized graphite in the brass alloy, and the average graphite particle size is the average particle size of the spheroidized graphite particles in the brass alloy.

[0094] The performance test results of the low-bismuth graphite brass alloys of Examples 1 to 4 and the brass of Comparative Examples 1 to 5 in Table 1 are shown in Table 2, where:

[0095] In this embodiment, the cutting performance and mechanical properties of the alloy castings provided in Examples 1 to 4 and Comparative Examples 1 to 5 are tested by the following method:

[0096] Cutting performance: Under the same machining conditions, the cutting resistance of the brass of each embodiment and the comparative example and the cutting resistance of the American standard C36000 lead brass are measured by a cutting force tester, so that the cutting efficiency relative to C36000 can be obtained (in engineering, the cutting performance of C36000 lead brass is usually 100%, and other alloys are compared with it as the standard for evaluating the cutting performance of alloys). The calculation method of relative cutting efficiency is: Relative cutting efficiency = C36000 cutting resistance / cutting resistance of brass of each embodiment and comparative example

[0097] ×100%.

[0098] The Brinell hardness test is used to test the hardness of alloy castings. The Brinell hardness test method implements the standard "GB / T 231.1-2009 Metallic Material Brinell Hardness Test Part 1: Test Method". The higher the hardness, the more severe the wear of the tool during machining.

[0099] The tensile strength of alloy castings was tested using the method provided in the standard "GB / T 228.1-2010 Tensile Test of Metal Materials".

[0100] The dezincification experiment of brass was carried out according to the standard GB / T 10119-2008.

[0101] Table 2 Performance test results of copper alloy products prepared in Examples 1 to 4 and Comparative Examples 1 to 5

[0102]

[0103]

[0104] It can be seen from the data in Table 2 that the low-bismuth graphite brass alloy prepared by the component formulas and preparation methods of Examples 1 to 4 of the present invention has a relative cutting rate of >80%, has excellent comprehensive mechanical properties, is easy to process, and has good anti-dezincification performance, so all performances meet the use requirements of bathroom hardware.

[0105] Comparative Example 1 did not introduce graphite, and the cutting performance was poor, and other properties were reduced to varying degrees; Comparative Example 2 did not introduce graphite, but added a high content of Bi, and the cutting performance was reduced to a certain extent, and the mechanical properties were also reduced; in Comparative Example 3, ordinary cast iron was used, and the graphite spheroidization rate was 50%, the cutting performance was reduced to a certain extent, and the mechanical properties were also significantly reduced. Since the non-spherical graphite has a lamellar crystal structure, relative movement between graphite layers is easy to occur, so it is easier to slip and break under the action of external force; Comparative Example 4 did not add Bi, the cutting performance was reduced to a certain extent, and the anti-dezincification performance was significantly reduced; Comparative Example 5 did not add Sn, and all properties were reduced to a certain extent, among which the tensile strength was significantly reduced.

[0106] From the above embodiments, it can be seen that the present invention provides a low-bismuth graphite brass alloy, comprising the following components: Cu 57-70wt%, Fe 4.5-9.2wt%, C 0.18-0.4wt%, Si 0.1-0.3wt%, Sn 0.09-1wt%, Bi 0.2-0.5wt%, Mn 0.02-0.08wt%, and the balance is Zn and inevitable impurities; the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite. The present invention solves the problem of graphite and copper being immiscible by introducing spherical graphite through ductile iron, and at the same time supplements the cutting performance of low-bismuth graphite brass, on the one hand, reducing the use of precious metal bismuth, thereby reducing production costs; on the other hand, spherical graphite is conducive to improving the mechanical properties of the brass alloy, thereby obtaining a brass alloy with high mechanical properties and good cutting performance, which is conducive to its use in water supply and distribution equipment.

[0107] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a low-bismuth graphite brass alloy, characterized in that: The following steps are involved: According to the composition of the elements in the low-bismuth graphite brass alloy, the raw materials are smelted to obtain a melt; the raw materials include Cu raw material, ductile iron, Zn raw material, Bi raw material and Sn raw material; the low-bismuth graphite brass alloy includes the following components in percentage by weight: Cu 57-70wt%, Fe 4.5-9.2wt%, C 0.18-0.4wt%, Si 0.1-0.3wt%, Sn 0.09-1wt%, Bi 0.2-0.5wt%, Mn 0.02-0.08wt%, and the balance is Zn and unavoidable impurities; the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite; The melt is cast to obtain the low-bismuth graphite brass alloy.

2. The preparation method according to claim 1, characterized in that: The graphite spheroidization rate of the ductile iron is ≥80%; the particle size of the spheroidal graphite particles in the ductile iron is 15-30 μm.

3. The preparation method according to claim 1 or 2, characterized in that: The average particle size of the spherical graphite in the low-bismuth graphite brass alloy is 8 to 20 μm.

4. The preparation method according to claim 1 or 2, characterized in that: The raw materials for preparation also include a magnesium spheroidizer, and the mass of the magnesium spheroidizer accounts for 1.6-2% of the mass of the ductile iron.

5. The preparation method according to claim 4, characterized in that: The grade of the magnesium spheroidizer is QRMg8HRE3.

6. The preparation method according to claim 1 or 2, characterized in that: The grade of the ductile iron is QT500-7.

7. The preparation method according to claim 1, characterized in that: The copper raw material is electrolytic copper, the Zn raw material is a Zn ingot, the Bi raw material is a Bi ingot, and the Sn raw material is a Sn ingot; The smelting comprises the following steps: S1, performing a first smelting on the Cu raw material to obtain a first melt; S2, adding ductile iron to the first melt for a second smelting to obtain a second melt; S3. Adding Zn raw material, Bi raw material and Sn raw material to the second melt for third smelting to obtain the melt.

8. The preparation method according to claim 7, characterized in that: The temperature of the first smelting is 1050-1100°C; the temperature of the second smelting is 1300-1350°C; the temperature of the third smelting is 950-1050°C; When the raw material preparation further includes a magnesium spheroidizer, after obtaining the first melt, step S2 is replaced by: adding ductile iron and a magnesium spheroidizer to the first melt for a second smelting to obtain the second melt.

9. The low-bismuth graphite brass alloy prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The invention comprises the following components in percentage by weight: Cu 57-70wt%, Fe 4.5-9.2wt%, C 0.18-0.4wt%, Si 0.1-0.3wt%, Sn 0.09-1wt%, Bi 0.2-0.5wt%, Mn 0.02-0.08wt%, and the balance is Zn and inevitable impurities; the C element in the low-bismuth graphite brass alloy exists in the form of spherical graphite.

10. Use of the low-bismuth graphite brass alloy according to claim 9 in water delivery and distribution equipment.

Images