Copper alloy for low-lead pressure reducing valve body and preparation method of copper alloy

Abstract

The invention discloses a copper alloy for a low-lead pressure reducing valve body and a preparation method of the copper alloy, and relates to the technical field of alloys, the copper alloy comprises 0.5-1 wt% of tin, 0.01-0.05 wt% of phosphorus, 0.4-0.8 wt% of lead, 0.1-0.5 wt% of manganese, 0.05-0.5 wt% of iron, 1-1.4 wt% of molybdenum, 0.5-1.5 wt% of bismuth, 0.1-0.4 wt% of silicon, and the balance inevitable impurity elements and copper; molybdenum powder modified by sulfydryl is coordinated with lead in the melt, free lead is stably adsorbed on the surfaces of molybdenum powder particles and then is uniformly distributed in the copper alloy, and the molybdenum powder is kept in a solid state in the copper alloy mixed melt, so that the lead cannot be extruded to generate segregation migration in the solidification process of the copper alloy mixed melt, and the copper alloy mixed melt is solidified. The formation of a lead-rich area on the inner wall of the valve body is obviously reduced, the uniformity of lead in a copper alloy mixed melt is ensured, and the risk of dissolving and separating out lead in a water medium in the service process of the valve body is further reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of alloys, in particular to a copper alloy for low-lead pressure reducing valve body and a preparation method thereof. BACKGROUND

[0002] Lead brass is a very important and widely used complex brass, which has excellent cutting performance and wear resistance, and is often used as valve body material. On the one hand, lead is almost insoluble in copper alloy and is distributed in the form of dispersed particles, which plays a self-lubricating and chip-breaking role during machining, thereby significantly improving the cutting performance and casting performance of the alloy. On the other hand, lead particles can provide lubrication at the friction interface, which helps to improve the wear resistance and sealing performance of the valve body during opening and closing. Traditional lead copper alloy has been widely used in the valve manufacturing industry for a long time. However, lead is toxic, and for the preparation of low-lead pressure reducing valve body from lead copper alloy, the content of lead needs to be controlled below 0.8% to be suitable for pressure reducing valve in water.

[0003] For low-lead pressure reducing valve, on the one hand, the standard electrode potential of lead in copper alloy is lower than that of copper, which often exists as an anode in the copper matrix, and is easy to form a micro-battery with the copper matrix. When in contact with water, lead will first dissolve and precipitate, and lead ions entering the water will cause drinking water pollution, which may cause serious health hazards in the long term. On the other hand, the melting point of lead is 327℃, and the low melting point of lead migrates to the surface during the casting process, resulting in a much higher lead concentration on the inner wall of the valve body than in the interior. After the valve body is in contact with water, the water flow will erode the inner wall of the valve body, further causing a large amount of lead to come into contact with water.

[0004] Therefore, it is necessary to design a copper alloy for low-lead pressure reducing valve body and a preparation method thereof to solve the above technical problems. SUMMARY

[0005] The present application overcomes the shortcomings of the prior art and provides a copper alloy for low-lead pressure reducing valve body and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a preparation method of a copper alloy for low-lead pressure reducing valve body, comprising the following steps: Step S1, heat the copper to a molten state, add tin, phosphorus, lead, manganese, iron, bismuth and silicon in proportion and mix uniformly to obtain a copper alloy mixed melt; Step S2, take molybdenum powder and treat it with mercapto modification to obtain mercapto-modified molybdenum powder, and then perform sulfidation treatment; Step S3, gradually cool the copper alloy mixed melt to a semi-solid state, and add the sulfidation-treated molybdenum powder in proportion and mix uniformly to adsorb the lead in the copper alloy mixed melt; Step S4, pouring and cooling the copper alloy mixed melt in step S3 to obtain the valve body.

[0007] In a preferred embodiment of the present application, the components of the copper alloy mixed melt include: 0.5-1wt% of tin, 0.01-0.05wt% of phosphorus, 0.4-0.8wt% of lead, 0.1-0.5wt% of manganese, 0.05-0.5wt% of iron, 1-1.4wt% of molybdenum, 0.5-1.5wt% of bismuth, 0.1-0.4wt% of silicon, and the balance of inevitable impurity elements and copper. The content of the impurity elements is 0-1wt%.

[0008] In the step S1, the following sub-steps are included in a preferred embodiment of the present application. Step S11, heating the copper to 1050-1150℃ at a rate of 10-15℃ / min, and keeping the temperature for 10-15min until the copper is completely liquefied. Step S12, adding tin, phosphorus, lead, manganese and iron into the melted copper solution in sequence, and magnetically stirring for 20-30min.

[0009] In the step S2, the particle size of the molybdenum powder is 1-5μm in a preferred embodiment of the present application.

[0010] In the step S2, the following sub-steps are included in a preferred embodiment of the present application. Step S21, immersing the molybdenum powder into the pickling solution at a liquid-solid ratio of 10-12:1, and treating with ultrasonic waves at 60-80℃ for 25-30min. Step S22, taking a mixed solution of 3-mercaptopropyltrimethoxysilane and ethanol, and adding acetic acid to adjust the pH to 4-4.5. Step S23, drying the pickled molybdenum powder, and adding the mixed solution, and reacting at 60-70℃ for 5-6h to immobilize the mercapto group on the surface of the molybdenum powder. Step S24, vacuum drying the reacted molybdenum powder at 75-80℃ for 10-15min to obtain the mercapto-modified molybdenum powder. Step S25, passing the mercapto-modified molybdenum powder into argon, and heat-treating at 500-800℃ for 30-120min to form a molybdenum sulfide coating on the surface of the molybdenum powder, thereby obtaining the molybdenum sulfide powder.

[0011] In the step S21, the pickling solution includes: H2SO4 with a concentration of 96-98%, HNO3 with a concentration of 60-68% and H2O, wherein the mass ratio among H2SO4, HNO3 and H2O is 3-4:1:1 in a preferred embodiment of the present application.

[0012] In a preferred embodiment of the present application, the 3-mercaptopropyltrimethoxysilane is mixed with ethanol in a mass ratio of 1:9-10. The mass ratio of the molybdenum powder to the mixed solution is 1:5-7.

[0013] In a preferred embodiment of the present application, in the step S3, the copper alloy mixed melt is cooled at a rate of 5-10℃ / min to 800-900℃ to be in a semi-solid state. The molybdenum sulfide powder is added to the copper alloy mixed melt, stirred at 100-200rpm for 10-15min, and kept at a temperature of 800-900℃, and left for 5-8min.

[0014] In a preferred embodiment of the present application, in the step S4, after pouring is completed, the temperature is cooled to room temperature at a rate of 10-15℃ / min.

[0015] A copper alloy for a low-lead pressure reducing valve body, comprising: 0.5-1wt% of tin, 0.01-0.05wt% of phosphorus, 0.4-0.8wt% of lead, 0.1-0.5wt% of manganese, 0.05-0.5wt% of iron, 1-1.4wt% of molybdenum, 0.5-1.5wt% of bismuth, 0.1-0.4wt% of silicon, and the balance being inevitable impurity elements and copper.

[0016] The present application solves the defects in the background art, and has the following beneficial effects: (1) The present application provides a preparation method of a copper alloy for a low-lead pressure reducing valve body, which utilizes molybdenum sulfide powder to coordinate with lead elements in the melt, to stably adsorb free lead on the surface of molybdenum powder particles, and then uniformly distribute lead in the copper alloy, and through the solid state of the molybdenum powder in the copper alloy mixed melt, lead will not be extruded to cause segregation migration during the solidification of the copper alloy mixed melt, significantly reducing the formation of a lead-rich area in the valve body inner wall, ensuring the uniformity of lead in the copper alloy mixed melt, and further reducing the risk of lead dissolution and precipitation in water medium during the service of the valve body.

[0017] (2) The present invention provides a method for preparing a copper alloy for a low-lead pressure reducing valve body, by cooling the melt to a semi-solidified state, causing the liquid lead to be squeezed into the interdendritic region to form a flaky structure, reacting with the surface of the molybdenum powder forming a molybdenum sulfide coating to form a Pb-S / Pb-Mo-S complex state and chemically fixing the free lead on the surface of the molybdenum powder, significantly reducing the chemical freeness of lead, so that the free lead in the copper alloy melt can be captured in time and exist in a complex / bonded form, reducing the dissolution risk caused by the lead entering the mother phase or surface in a soluble form from the source. The present invention directly changes the chemical form of lead by forming chemical bonds, significantly reducing the lead dissolution rate during the service life of the valve body, improving the environmental safety of the water supply system, and eliminating its harm to water quality while retaining the lead to improve the processing and lubrication properties.

[0018] (3) The present invention provides a method for preparing a copper alloy for a low-lead pressure reducing valve body, which uses high-melting-point molybdenum as a carrier to keep the molybdenum in a solid state in the melt and act as an anchoring phase for lead, thereby adsorbing and fixing free lead. The solid and dispersed molybdenum particles will not be squeezed out by the liquid phase or migrate with the low-melting-point phase during the solidification process, so that the adsorbed lead is embedded in the parent phase along with the molybdenum particles instead of aggregating at the grain boundaries or the surface of the casting, thereby avoiding the segregation of lead in the late solidification stage and the enrichment of the lead in the inner cavity and the surface, resulting in the formation of a high-concentration lead peak on the inner wall. This solution uses molybdenum as a carrier to ensure that the lead is evenly dispersed in the matrix, thereby improving the uniformity and surface density of the copper alloy material, reducing the risk of embrittlement, porosity and early failure caused by local lead enrichment, and thus improving the mechanical stability and service life of the valve body. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments described in the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive efforts. Figure 1 The present invention is a flowchart of a method for preparing a copper alloy for a low-lead pressure reducing valve body according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0022] like Figure 1 As shown, a method for preparing a copper alloy for a low-lead pressure reducing valve body comprises the following steps: Step S1, heating copper to a molten state, adding tin, phosphorus, lead, manganese, iron, bismuth, and silicon in proportion and mixing them uniformly to obtain a copper alloy mixed melt; Step S2, taking molybdenum powder and subjecting it to thiol modification treatment to obtain thiol-modified molybdenum powder, and then performing a sulfurization treatment; Step S3, gradually cooling the copper alloy mixed melt to a semi-solidified state, and adding sulfurized molybdenum powder in proportion and uniformly mixing, so as to absorb lead in the copper alloy mixed melt; wherein, a large amount of copper solid phase skeleton has been precipitated in the semi-solidified melt, and the remaining liquid phase is rich in low melting point elements such as lead and fills the dendrite gaps; Step S4: pouring and cooling the copper alloy mixed melt in step S3 to obtain a valve body.

[0023] By utilizing the coordination effect between molybdenum sulfide powder and lead in the melt, free lead is stably adsorbed on the surface of molybdenum powder particles and then evenly distributed in the copper alloy; By keeping the molybdenum powder in a solid state in the copper alloy mixed melt, the lead will not be squeezed and segregated during the solidification of the copper alloy mixed melt, which significantly reduces the formation of lead-rich areas on the inner wall of the valve body, ensures the uniformity of lead in the copper alloy mixed melt, and further reduces the risk of lead dissolution and precipitation in the aqueous medium during the service life of the valve body.

[0024] In the present invention, the components of the copper alloy mixed melt include: 0.5-1wt% tin, 0.01-0.05wt% phosphorus, 0.4-0.8wt% lead, 0.1-0.5wt% manganese, 0.05-0.5wt% iron, 1-1.4wt% molybdenum, 0.5-1.5wt% bismuth, 0.1-0.4wt% silicon, and the remainder are unavoidable impurity elements and copper; The content of impurity elements is 0 to 1 wt%.

[0025] By adding bismuth and silicon to a copper alloy melt, bismuth tends to segregate at grain boundaries, forming localized atomic clusters. Since the bismuth atomic radius is significantly larger than that of iron or copper, its presence at grain boundaries can cause lattice distortion, increase the grain boundary energy barrier, and hinder grain boundary migration. Silicon can form a high-melting-point compound to pin the grain boundaries, achieving a pinning effect. This is mainly because grain boundary migration requires overcoming an energy barrier, and the segregation of bismuth increases the barrier height, inhibiting grain boundary movement. Lead easily diffuses along grain boundaries at high temperatures, so the addition of bismuth inhibits the migration of lead.

[0026] In the present invention, step S1 includes the following sub-steps: Step S11, heating the copper to 1050-1150°C at a rate of 10-15°C / min, and keeping the temperature for 10-15 minutes until the copper is completely liquefied; Step S12: Add tin, phosphorus, lead, manganese and iron to the molten copper solution in sequence, and stir the mixture with electromagnetic stirring for 20 to 30 minutes.

[0027] In step S1, the copper is heated at a rate of 10-15°C / min until the entire metal is liquid and reaches 1050-1150°C, and the temperature is kept at this temperature for 10-15 minutes; Add tin which is easily soluble and has little effect on the melt in sequence, then add the phosphorus-containing master alloy Cu-P main alloy, then add lead, and finally add the iron-manganese main alloy.

[0028] Tin is easily soluble in copper and contributes to fluidity and lubrication. Adding it first can improve the melt viscosity / lubricity and facilitate the dispersion of subsequent elements. Phosphorus is easily oxidized and forms intermetallic compounds with copper. To prevent the loss of phosphorus and the generation of free phosphorus gas, the Cu-P main alloy is added in small batches and stirred rapidly to allow phosphorus to enter the melt in the form of a stable main alloy. Lead has a low melting point, is volatile, and easily splashes. It should be added in the form of small particles, strips, or lead balls under conditions where the mother liquor temperature is stable and stirring is good. The cover should be sealed or covered with a covering agent as soon as possible after addition. Finally the main iron-manganese alloy is added.

[0029] Considering that lead is insoluble in copper alloys and the surface energy of lead is usually lower than that of the copper matrix, when the temperature rises, the lead atoms obtain sufficient kinetic energy to overcome the lattice constraints and transform from a solid state to a quasi-liquid or high-mobility state. At this time, the vibration of the lead atoms intensifies and the vacancy defects increase, providing channels for diffusion. In order to avoid uneven distribution of lead in the copper alloy due to its own migration, molybdenum powder needs to be sulfurized so that it can adsorb lead in the copper alloy melt. Specifically: In step S2, the following sub-steps are included: Step S21, immersing molybdenum powder in an acid wash solution at a liquid-to-solid ratio of 10 to 12:1, and ultrasonically treating the solution at 60 to 80° C. for 25 to 30 minutes, wherein the particle size of the molybdenum powder is 1 to 5 μm; The pickling solution comprises: H2SO4 with a concentration of 96-98%, HNO3 with a concentration of 60-68%, and H2O, wherein the mass ratio of H2SO4, HNO3 and H2O is 3-4:1:1; The molybdenum powder is treated by using an acid washing solution, so as to remove the oxide layer and impurities on the surface of the molybdenum powder, expose the fresh metal surface, and promote the surface activation through ultrasonic waves to generate a large number of reactive sites, thereby laying a foundation for subsequent functional modification; In step S22, a mixed solution of 3-mercaptopropyl trimethoxysilane and ethanol is taken, wherein the 3-mercaptopropyl trimethoxysilane and ethanol are mixed in a mass ratio of 1:9-10, and acetic acid is added to adjust the pH to 4-4.5. In step S23, the molybdenum powder after acid washing is dried and added into the mixed solution, and reacted at 60-70°C for 5-6h to load mercapto groups on the surface of the molybdenum powder. In step S24, the reacted molybdenum powder is vacuum dried at 75-80°C for 10-15min to obtain mercapto-modified molybdenum powder. In step S25, the mercapto-modified molybdenum powder is introduced into argon and heat-treated at 500-800°C for 30-120min to form a molybdenum sulfide coating on the surface of the molybdenum powder, thereby obtaining molybdenum sulfide powder.

[0030] The trimethoxysilane group in the 3-mercaptopropyl trimethoxysilane molecule can react with the hydroxyl groups on the surface of the molybdenum powder after hydrolysis to form a stable -Si-O-Mo- bond, and the -SH mercapto group at the other end is exposed on the surface of the particle to obtain mercapto-modified molybdenum powder.

[0031] Considering that the organic mercapto functional group cannot survive at the high temperature of copper alloy smelting, but it is the best precursor for achieving molecular-level uniform dispersion of sulfur on the surface of the molybdenum powder, in order to improve the dispersion uniformity of sulfur on the surface of the molybdenum powder, the molybdenum powder is modified by mercapto, and the modified molybdenum powder is sulfidized.

[0032] In the process, since the molybdenum powder is directly sulfidized, the sulfur element mainly exists in the form of physical adsorption or local reaction, and is distributed extremely unevenly, which is easy to agglomerate, thereby greatly reducing the effective reaction area. The one end of the 3-mercaptopropyl trimethoxysilane molecule is a siloxane group capable of forming a covalent bond with the oxide on the surface of the molybdenum powder, and the other end is a mercapto group (-SH). Through molecular self-assembly, the sulfur atom is accurately nailed on the surface with a molecular spacing density, which ensures that the active sites of the formed molybdenum sulfide are extremely uniformly distributed without any agglomeration dead angle. The 3-mercaptopropyl trimethoxysilane is used to modify the molybdenum powder, which avoids the problem that the sulfur powder is easy to fall off and improves the bonding strength between the sulfur and the molybdenum powder.

[0033] When heated to 500-800°C in an inert atmosphere (such as argon), the organic thiol chain will decompose and carbonize, but its sulfur atoms will undergo a solid-phase reaction with the molybdenum substrate to form a strong, stable, high-temperature resistant molybdenum sulfide coating, which can then fully react with lead and has a high melting point. It can remain in a solid state in the copper alloy melt, and can then combine with lead in the subsequent process and make it evenly distributed.

[0034] In the present invention, the mass ratio of the molybdenum powder to the mixed solution is 1:5-7.

[0035] In step S3, the copper alloy mixed melt is cooled to 800-900° C. at a rate of 5-10° C. / min to form a semi-solidified state; Add molybdenum sulfide powder to the copper alloy mixed melt, stir at 100-200 rpm for 10-15 minutes, maintain the temperature at 800-900° C., and let it stand for 5-8 minutes.

[0036] By slowly cooling the melt to 800-900°C, at this temperature, the copper dendrites that solidify first form a skeleton, and the liquid lead is squeezed into the inter-dendritic area. Due to the modification effect of Bi / Si on the grain boundaries, the lead cannot shrink into a ball and can only be forced to spread along the grain boundaries, eventually forming a continuous or semi-continuous sheet-like or reticular structure.

[0037] Flake lead has a larger specific surface area, providing more contact sites for the sulfur vacancies of molybdenum sulfide, promoting the formation of Pb-S-Mo bonds, enhancing the bonding density, and thus enhancing the strength of the Pb-S-Mo bonds, effectively inhibiting the migration and dissolution of lead. At the same time, it enables the lead to be evenly dispersed along with the molybdenum sulfide powder to achieve the purpose of uniform dispersion.

[0038] It should be noted that a large number of unsaturated sulfur atoms are exposed in the layered structure of molybdenum sulfide powder, forming highly active sulfur vacancies. The ionic radius of lead is highly consistent with the lattice size of sulfur vacancies, and it can be embedded in the vacancies to form strong covalent bonds. However, copper and iron have smaller sizes or lower charge densities, and their bonding stability is significantly weaker than that of lead. Under the high temperature environment of the melt, the sulfur on the surface of molybdenum sulfide powder and lead form a stable cyclic complex Pb-Mo-S through chelation. Other metals are difficult to form similar stable structures due to differences in their electronic layer structures. Therefore, when molybdenum sulfide powder is added to the copper alloy melt, it will preferentially combine with lead.

[0039] When molybdenum sulfide powder is added to the copper alloy melt, the free lead in the melt will be preferentially anchored by the mercapto groups on the surface of the molybdenum powder, forming a Pb-Mo-S coordination bond and firmly binding it. As a result, the lead no longer migrates and segregates freely in the form of droplets or particles, but instead adheres to the surface of the molybdenum powder and is evenly distributed in the melt with the molybdenum powder.

[0040] In step S3, the specific operation is that the molybdenum sulfide powder is added into the melt in batches and slowly to avoid local temperature fluctuation or powder agglomeration caused by large amount of addition at one time, wherein the addition process of the molybdenum sulfide powder is completed within 1 / 3 to 1 / 2 of the whole stirring period, so that there is sufficient time for mixing and reaction later; After the molybdenum sulfide powder is added into the melt, the melt is stirred to fully disperse the molybdenum powder, prevent settlement or agglomeration, and promote the contact and chemical reaction / coordination of the mercapto surface with the free lead in the melt; It should be noted that the formation of the Pb-Mo-S complex state and the chemical fixation of free lead on the surface of the molybdenum powder significantly reduces the chemical free degree of lead, so that the free lead in the copper alloy melt can be captured in time and exist in the form of complexation / bonding, thereby reducing the risk of lead entering the matrix or the surface in a soluble form from the source; By forming a chemical bond to directly change the chemical form of lead, the dissolution rate of lead during the service of the valve body is significantly reduced, the environmental safety of the water supply system is improved, and the harm of lead to water quality is eliminated while the processing and lubrication performance are improved.

[0041] In the present application, in the step S4, the copper alloy mixed melt in step S3 is poured into a valve body form, and after pouring is completed, the temperature is lowered to room temperature at a rate of 10-15 ℃ / min to obtain a low-lead pressure reducing valve body.

[0042] It is worth mentioning that the high-melting-point molybdenum is used as a carrier, so that the molybdenum remains in a solid state in the melt and acts as an anchoring phase for lead, adsorbing and fixing the free lead. The solid and dispersed molybdenum particles will not be squeezed out by the liquid phase or migrate with the low-melting-point phase during the solidification process, so that the adsorbed lead is embedded with the molybdenum particles in the matrix rather than being concentrated on the grain boundaries or the surface of the casting, avoiding the segregation of lead at the end of solidification and the enrichment of lead in the inner cavity and the surface layer, resulting in the formation of a high-concentration lead peak on the inner wall; By using molybdenum as a carrier to ensure the uniform dispersion of lead in the matrix, the uniformity and surface density of the copper alloy material are improved, the risk of embrittlement, porosity and early failure caused by local lead enrichment is reduced, and the mechanical stability and service life of the valve body are improved.

[0043] In the present application, by adding Cu-P master alloy into the melt, phosphorus is introduced into the melt. During the solidification process of the copper matrix, phosphorus can form small phosphide particles (such as Cu3P) as heterogeneous nuclei. This particle provides a preferential deposition site before the formation of dendrites, accelerates local solidification, thereby increasing the density of crystal nuclei and achieving fine-grain refinement.

[0044] A copper alloy for a low-lead pressure-reducing valve body, comprising: 0.5-1 wt% tin, 0.01-0.05 wt% phosphorus, 0.4-0.8 wt% lead, 0.1-0.5 wt% manganese, 0.05-0.5 wt% iron, 1-1.4 wt% molybdenum, 0.5-1.5 wt% bismuth, 0.1-0.4 wt% silicon, and the balance being inevitable impurity elements and copper.

[0045] Example 1

[0046] A, heat the copper to 1150℃ at a rate of 15℃ / min, and keep it for 10 min until the copper is completely liquefied, then add 1 wt% tin, 0.05 wt% phosphorus, 0.6 wt% lead, 0.5 wt% manganese, 0.5 wt% iron, 1 wt% bismuth, and 0.3 wt% silicon into the molten copper solution in sequence, and stir magnetically for 20 min.

[0047] B, take 1 wt% molybdenum powder with a particle size of 1-5 μm, and immerse the molybdenum powder in an acid pickling solution at a liquid-solid ratio of 10:1, and treat it with ultrasound at 60℃ for 25 min, wherein the acid pickling solution comprises: 98% H2SO4, 68% HNO3, and H2O, and the mass ratio among H2SO4, HNO3, and H2O is 3:1:1; take a mixed solution of 3-mercapto propyl trimethoxysilane and ethanol at a mass ratio of 1:9-10, and add acetic acid to adjust the pH to 4-4.5, dry the molybdenum powder after acid pickling at 80℃, and add the mixed solution, and react at 60℃ for 5 h; vacuum dry the molybdenum powder after the reaction is completed at 80℃ for 15 min to obtain molybdenum powder modified by mercapto groups.

[0048] C, pass the molybdenum powder modified by mercapto groups into argon, and heat treat it at 600℃ for 60 min to form a molybdenum sulfide coating on the surface of the molybdenum powder, and obtain molybdenum sulfide powder, and add it into the copper alloy mixed melt and mix uniformly, and stir at 100 rpm for 15 min, and cool down to 850℃ at a rate of 8℃ / min, and stand for 5 min.

[0049] D, cast the copper alloy mixed melt in step C, and cool down to room temperature at a rate of 10℃ / min to obtain the valve body.

[0050] Example 2

[0051] The same as example 1, except that the proportion of molybdenum powder is changed; A, heat copper to 1150℃ at a rate of 15℃ / min, keep for 10 min until copper is completely liquefied, add 1wt% tin, 0.05wt% phosphorus, 0.6wt% lead, 0.5wt% manganese, 0.5wt% iron, 1wt% bismuth, 0.3wt% silicon into the molten copper solution in turn, and magnetically stir for 20 min.

[0052] B, take 1.1wt% molybdenum powder with a particle size of 1-5μm, immerse the molybdenum powder into the pickling solution at a liquid-solid ratio of 10:1, and treat with ultrasound at 60℃ for 25 min, wherein the pickling solution comprises: 98% H2SO4, 68% HNO3 and H2O, and the mass ratio among H2SO4, HNO3 and H2O is 3:1:1; Take a mixed solution of 3-mercaptopropyltrimethoxysilane and ethanol at a mass ratio of 1:9-10, and add acetic acid to adjust the pH to 4-4.5, dry the pickled molybdenum powder at 80℃, and add the mixed solution, react at 60℃ for 5h; vacuum dry the reacted molybdenum powder at 80℃ for 15 min to obtain mercapto-modified molybdenum powder.

[0053] C, pass the mercapto-modified molybdenum powder into argon, heat treat at 600℃ for 60 min to form a molybdenum sulfide coating on the surface of the molybdenum powder to obtain molybdenum sulfide powder, and add the copper alloy mixed melt to uniformly mix, stir at 100rpm for 15 min, and cool down to 850℃ at a rate of 8℃ / min, and stand for 5 min.

[0054] D, pour the copper alloy mixed melt in step C, cool down to room temperature at a rate of 10℃ / min to obtain a valve body.

[0055] Example 3:

[0056] The same as example 1, except that the proportion of molybdenum powder is changed. A, heat copper to 1150℃ at a rate of 15℃ / min, keep for 10 min until copper is completely liquefied, add 1wt% tin, 0.05wt% phosphorus, 0.6wt% lead, 0.5wt% manganese, 0.5wt% iron, 1wt% bismuth, 0.3wt% silicon into the molten copper solution in turn, and magnetically stir for 20 min.

[0057] B, take 1.2wt% molybdenum powder with a particle size of 1-5μm, immerse the molybdenum powder into the pickling solution at a liquid-solid ratio of 10:1, and treat with ultrasound at 60℃ for 25 min, wherein the pickling solution comprises: 98% H2SO4, 68% HNO3 and H2O, and the mass ratio among H2SO4, HNO3 and H2O is 3:1:1; A mixture solution of 3-mercaptopropyltrimethoxysilane and ethanol in a mass ratio of 1:9-10 is taken, and acetic acid is added to adjust the pH to 4-4.5. The pickled molybdenum powder is dried at 80°C, and then added into the mixture solution. The reaction is carried out at 60°C for 5 hours. The reacted molybdenum powder is vacuum dried at 80°C for 15 minutes to obtain mercapto-modified molybdenum powder.

[0058] C. The mercapto-modified molybdenum powder is passed through argon and heat treated at 600°C for 60 minutes to form a molybdenum sulfide coating on the surface of the molybdenum powder, thereby obtaining molybdenum sulfide powder. The molybdenum sulfide powder is added into a copper alloy mixed melt and uniformly mixed. The mixture is stirred at 100 rpm for 15 minutes, and then cooled to 850°C at a rate of 8°C / min and left for 5 minutes.

[0059] D. The copper alloy mixed melt in step C is poured and cooled to room temperature at a rate of 10°C / min to obtain a valve body.

[0060] Example 4:

[0061] The same as example 1, except that the proportion of molybdenum powder is changed. A. Copper is heated to 1150°C at a rate of 15°C / min, and kept for 10 minutes until the copper is completely liquefied. 1wt% tin, 0.05wt% phosphorus, 0.6wt% lead, 0.5wt% manganese, 0.5wt% iron, 1wt% bismuth, and 0.3wt% silicon are sequentially added into the molten copper solution, and electromagnetically stirred for 20 minutes.

[0062] B. 1.3wt% molybdenum powder with a particle size of 1-5μm is immersed into a pickling solution in a liquid-solid ratio of 10:1 at 60°C, and ultrasonically treated for 25 minutes. The pickling solution comprises 98% H2SO4, 68% HNO3, and H2O in a mass ratio of 3:1:1. A mixture solution of 3-mercaptopropyltrimethoxysilane and ethanol in a mass ratio of 1:9-10 is taken, and acetic acid is added to adjust the pH to 4-4.5. The pickled molybdenum powder is dried at 80°C, and then added into the mixture solution. The reaction is carried out at 60°C for 5 hours. The reacted molybdenum powder is vacuum dried at 80°C for 15 minutes to obtain mercapto-modified molybdenum powder.

[0063] C. The mercapto-modified molybdenum powder is passed through argon and heat treated at 600°C for 60 minutes to form a molybdenum sulfide coating on the surface of the molybdenum powder, thereby obtaining molybdenum sulfide powder. The molybdenum sulfide powder is added into a copper alloy mixed melt and uniformly mixed. The mixture is stirred at 100 rpm for 15 minutes, and then cooled to 850°C at a rate of 8°C / min and left for 5 minutes.

[0064] D. Pouring the copper alloy mixed melt in step C, cooling at a rate of 10°C / min to normal temperature state to obtain the valve body.

[0065] Example 5:

[0066] The same as example 1, except that the proportion of molybdenum powder is changed. A. Heating copper to 1150°C at a rate of 15°C / min, keeping for 10 min until the copper is completely liquefied, adding 1wt% tin, 0.05wt% phosphorus, 0.6wt% lead, 0.5wt% manganese, 0.5wt% iron, 1wt% bismuth, 0.3wt% silicon into the melted copper solution in turn, and electromagnetic stirring for 20 min.

[0067] B. Taking 1.4wt% molybdenum powder with a particle size of 1-5μm, immersing the molybdenum powder into the pickling solution at a liquid-solid ratio of 10:1, ultrasonic treatment at 60°C for 25 min, wherein the pickling solution comprises: 98% H2SO4, 68% HNO3 and H2O, and the mass ratio of H2SO4, HNO3 and H2O is 3:1:1. Taking a mixed solution of 3-mercaptopropyl trimethoxysilane and ethanol at a mass ratio of 1:9-10, and adding acetic acid to adjust the pH to 4-4.5, drying the pickled molybdenum powder at 80°C, and adding the mixed solution, reacting at 60°C for 5h; vacuum drying the reacted molybdenum powder at 80°C for 15 min to obtain mercapto-modified molybdenum powder.

[0068] C. Passing the mercapto-modified molybdenum powder into argon, heat treating at 600°C for 60 min to form a molybdenum sulfide coating on the surface of the molybdenum powder to obtain molybdenum sulfide powder, and adding the copper alloy mixed melt to uniformly mix, stirring at 100rpm for 15 min, and cooling at a rate of 8°C / min to 850°C, standing for 5 min.

[0069] D. Pouring the copper alloy mixed melt in step C, cooling at a rate of 10°C / min to normal temperature state to obtain the valve body.

[0070] Comparative Example 1: The same as example 1, except that the molybdenum powder is not modified. A. Heating copper to 1150°C at a rate of 15°C / min, keeping for 10 min until the copper is completely liquefied, adding 1wt% tin, 0.05wt% phosphorus, 0.6wt% lead, 0.5wt% manganese, 0.5wt% iron, 1.3wt% molybdenum powder, 1wt% bismuth, 0.3wt% silicon into the melted copper solution in turn, and electromagnetic stirring for 20 min to obtain a copper alloy mixed melt.

[0071] B. Pour the copper alloy mixed melt prepared in step A and cool it down to room temperature at a rate of 10°C / min to obtain a valve body.

[0072] Performance testing: 1. Lead distribution uniformity test: Cut the valve body along the axis, drill cuttings from the center layer and inner layer, take 3 points in each area, and determine the lead content using ICP-OES.

[0073] 2. Lead dissolution test: With reference to GB / T 8464-2023 "Iron, copper and stainless steel threaded valves", place the valve body in deionized water with a pH of 7.0±0.2 and maintain the water temperature at 25°C for 19 days. The lead dissolution rate of the valve body is tested on the 3rd, 11th and 19th days.

[0074] The valve bodies obtained in Examples 1 to 5 and Comparative Example 1 were subjected to lead distribution uniformity testing and lead dissolution amount testing, as shown in Table 1.

[0075] Table 1:

[0076] Comparison of Examples 1 to 5 and Comparative Example 1 shows that as the molybdenum powder content increases, the lead is more evenly distributed in the melt. This is mainly because, by adding molybdenum powder with sulfide immobilized on its surface to the melt, the free lead in the melt is preferentially anchored by the -S on the surface of the molybdenum powder, forming a Pb-S / Pb-Mo-S complex state and chemically fixing the free lead on the surface of the molybdenum powder, significantly reducing the chemical freeness of lead. As a result, the free lead in the copper alloy melt can be captured in a timely manner and exist in a complexed / bonded form. In combination with high-melting-point molybdenum as a carrier, the molybdenum remains in a solid state in the melt and acts as an anchoring phase for the lead. The solid and dispersed molybdenum particles will not be squeezed out by the liquid phase or migrate with the low-melting-point phase during the solidification process, thereby ensuring uniform lead distribution. However, when the molybdenum powder content is too high, the uniformity of lead in the melt will be reduced. Excessive molybdenum powder content is more likely to produce local agglomeration or form larger inclusions at high temperatures, causing some adsorbed lead to form aggregates that can be released by mechanical disturbance.

[0077] At the same time, as the molybdenum powder content increases, the amount of lead dissolution decreases. This is mainly because the lead is evenly distributed and is not enriched in the surface of the valve body. The surface is immobilized with molybdenum sulfide powder and added to the melt, which produces a stable coordination with lead in the high-temperature melt, forming a Pb-S / Pb-Mo-S complex state and chemically fixing the free lead on the surface of the molybdenum powder, significantly reducing the chemical freeness of lead, so that the free lead in the copper alloy melt can be captured in time and exist in a complexed / bonded form, reducing the dissolution risk caused by the lead entering the parent phase or surface in a soluble form from the source.

[0078] In summary, by comparing Example 1 to Example 5 and Comparative Example 1, it can be concluded that Example 4 is the optimal solution of the present application.

[0079] The above is based on the ideal embodiment of the present application, through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the content of the specification, and the technical scope must be determined according to the scope of claims.

Claims

1. A method for preparing a copper alloy for a low-lead pressure reducing valve body, characterized in that: The following steps are involved: Step S1, heating copper to a molten state, adding tin, phosphorus, lead, manganese, iron, bismuth, and silicon in proportion and mixing them uniformly to obtain a copper alloy mixed melt; Step S2, taking molybdenum powder and subjecting it to thiol modification treatment to obtain thiol-modified molybdenum powder, and then performing a sulfurization treatment; Step S3, gradually cooling the copper alloy mixed melt to a semi-solidified state, and adding sulfurized molybdenum powder in proportion and uniformly mixing to absorb lead in the copper alloy mixed melt; Step S4: pouring and cooling the copper alloy mixed melt in step S3 to obtain a valve body.

2. The method for preparing a copper alloy for a low-lead pressure reducing valve body according to claim 1, characterized in that: The copper alloy mixed melt comprises: 0.5-1 wt% of tin, 0.01-0.05 wt% of phosphorus, 0.4-0.8 wt% of lead, 0.1-0.5 wt% of manganese, 0.05-0.5 wt% of iron, 1-1.4 wt% of molybdenum, 0.5-1.5 wt% of bismuth, 0.1-0.4 wt% of silicon, and the remainder being unavoidable impurity elements and copper; The content of impurity elements is 0 to 1 wt%.

3. The method for preparing a copper alloy for a low-lead pressure reducing valve body according to claim 1, characterized in that: In the step S1, the following sub-steps are included: Step S11, heating the copper to 1050-1150°C at a rate of 10-15°C / min, and keeping the temperature for 10-15 minutes until the copper is completely liquefied; Step S12: Add tin, phosphorus, lead, manganese and iron to the molten copper solution in sequence, and stir the mixture with electromagnetic stirring for 20 to 30 minutes.

4. The method for preparing a copper alloy for a low-lead pressure reducing valve body according to claim 1, characterized in that: In step S2, the particle size of the molybdenum powder is 1 to 5 μm.

5. The method for preparing a copper alloy for a low-lead pressure reducing valve body according to claim 1, characterized in that: In step S2, the following sub-steps are included: Step S21, immersing molybdenum powder in an acid cleaning solution at a liquid-to-solid ratio of 10 to 12:1, and ultrasonically treating the solution at 60 to 80° C. for 25 to 30 minutes; Step S22: taking a mixed solution of 3-mercaptopropyltrimethoxysilane and ethanol, and adding acetic acid to adjust the pH to 4-4.5; Step S23, drying the acid-washed molybdenum powder, adding the dried powder to the mixed solution, reacting at 60-70° C. for 5-6 hours, and immobilizing the thiol groups on the surface of the molybdenum powder; Step S24, vacuum drying the reacted molybdenum powder at 75-80° C. for 10-15 min to obtain thiol-modified molybdenum powder; Step S25: introducing argon gas into the mercapto-modified molybdenum powder and heat treating it at 500-800° C. for 30-120 min to form a molybdenum sulfide coating on the surface of the molybdenum powder to obtain molybdenum sulfide powder.

6. The method for preparing a copper alloy for a low-lead pressure reducing valve body according to claim 5, characterized in that: In step S21, the pickling solution includes: H2SO4 with a concentration of 96-98%, HNO3 with a concentration of 60-68%, and H2O, wherein the mass ratio of H2SO4, HNO3 and H2O is 3-4:1:

1.

7. The method for preparing a copper alloy for a low-lead pressure reducing valve body according to claim 5, characterized in that: The 3-mercaptopropyltrimethoxysilane and ethanol are mixed in a mass ratio of 1:9 to 10; The mass ratio of the molybdenum powder to the mixed solution is 1:5-7.

8. The method for preparing a copper alloy for a low-lead pressure reducing valve body according to claim 1, characterized in that: In step S3, the copper alloy mixed melt is cooled to 800-900° C. at a rate of 5-10° C. / min to form a semi-solidified state; Add molybdenum sulfide powder to the copper alloy mixed melt, stir at 100-200 rpm for 10-15 minutes, maintain the temperature at 800-900° C., and let it stand for 5-8 minutes.

9. The method for preparing a copper alloy for a low-lead pressure reducing valve body according to claim 1, characterized in that: In step S4, after pouring is completed, the temperature is lowered to room temperature at a rate of 10-15°C / min.

10. A copper alloy for a low-lead pressure reducing valve body, according to the method for preparing a copper alloy for a low-lead pressure reducing valve body according to any one of claims 1 to 9, characterized in that: include: 0.5-1wt% tin, 0.01-0.05wt% phosphorus, 0.4-0.8wt% lead, 0.1-0.5wt% manganese, 0.05-0.5wt% iron, 1-1.4wt% molybdenum, 0.5-1.5wt% bismuth, 0.1-0.4wt% silicon, and the remainder are unavoidable impurity elements and copper.

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