Tin-lead bronze and preparation method and application thereof

Abstract

The invention discloses tin-lead bronze and a preparation method and application thereof.The tin-lead bronze comprises, by weight, 5%-11% of Sn, 2%-6% of Pb, 0.09%-4% of Ni, 0.05%-0.3% of P, 0.01%-1% of Zn and the balance Cu and inevitable impurities, the alloy structure of the tin-lead bronze comprises an alpha phase, an alpha + delta eutectoid and elemental Pb particles dispersed and distributed in the alpha phase, the area ratio of the alpha + delta eutectoid is smaller than or equal to 12%, and the area ratio of the elemental Pb particles is smaller than or equal to 10%. The as-cast average grain size of the tin-lead bronze is 20-70 microns, and the difference value delta D between the minimum grain size and the maximum grain size is smaller than or equal to 20 microns. Through improved design of alloy components and microstructures, a cast ingot with a specified structure is obtained by adopting a centrifugal casting process, meanwhile, the problem of dendritic segregation existing in a traditional casting method is solved, and the prepared material meets high requirements of special industries such as aerospace, ships and large engineering machinery.

Description

Technical Field

[0001] This invention relates to the field of copper alloy technology, and more specifically, to a tin-lead bronze, its preparation method, and its application. Background Technology

[0002] Tin-lead bronze, as an important copper-based alloy, is widely used in industry due to its excellent comprehensive properties. The existence form of Pb in copper-tin alloys and its influence mechanism on alloy properties have been well studied. Pb is almost insoluble in copper-tin alloys, and is uniformly distributed in the matrix in a free state. This unique microstructure endows the alloy with good self-lubricating and friction-reducing properties.

[0003] In industrial applications, tin-lead bronze is often bonded to a steel substrate using diffusion welding technology to form a bimetallic composite material. This composite structure fully leverages the advantages of both materials: the steel substrate provides structural strength, while the tin-lead bronze surface layer provides wear resistance. This composite material is particularly suitable for critical components such as hydraulic pump cylinders, bearing bushings, and bearing shells. These components withstand extreme conditions such as high speed and heavy loads in aerospace, shipbuilding, and large-scale engineering machinery, placing stringent requirements on material properties.

[0004] However, the casting characteristics of tin-lead bronze present challenges to material preparation. This alloy has a wide crystallization temperature range and exhibits typical pasty solidification characteristics. This solidification characteristic leads to difficulties in feeding and easily results in dendritic segregation and micro-shrinkage defects. Simultaneously, in the later stages of solidification, when the grain boundaries still contain a liquid phase or when solidification has just been completed, the alloy's high-temperature strength is low, making it prone to hot cracking. Traditional sand casting and metal mold casting processes struggle to overcome these inherent defects, often leading to problems such as Pb density segregation, shrinkage cavities, micro-shrinkage, and Sn reverse segregation.

[0005] Tin-lead bronze materials prepared using traditional casting methods, when diffuse-welded to a steel substrate, exhibit internal defects such as micro-shrinkage porosity and cracks, which significantly reduce the bonding quality of the composite interface. These defects easily become crack initiation points under heavy-load conditions, leading to premature failure of the composite material. With the ever-increasing reliability requirements of modern industry, tin-lead bronze materials prepared using traditional processes are no longer sufficient to meet the performance requirements of critical components such as hydraulic pumps and bearings in aerospace, shipbuilding, and large-scale engineering machinery industries.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a tin-lead bronze, its preparation method, and its application, so as to improve the above-mentioned technical problems.

[0008] This invention is implemented as follows: In a first aspect, the present invention provides a tin-lead bronze, the chemical composition of which includes: Sn: 5~11wt%, Pb: 2~6wt%, Ni: 0.09~4wt%, P: 0.05~0.3wt%, Zn: 0.01~1.0wt%, with the balance being Cu and unavoidable impurities. The alloy structure of the tin-lead bronze includes an α phase, an α+δ eutectoid, and elemental Pb particles dispersed in the α phase. The area ratio of the α+δ eutectoid is ≤12%. The average grain size of the tin-lead bronze in the as-cast state is 20μm~70μm, and the difference between the smallest and largest grain size ΔD is ≤20μm.

[0009] In an optional embodiment, the chemical composition contains 8-11 wt% Sn; and / or 2-3.5 wt% Pb; and / or 2-4 wt% Ni; and / or 0.05-0.15 wt% P; and / or 0.01-0.5 wt% Zn.

[0010] In an optional implementation, the area ratio of the α+δ eutectoid is ≤8%.

[0011] In an optional embodiment, the average grain size of the tin-lead bronze in its as-cast state is 30 μm to 60 μm.

[0012] In an optional embodiment, the difference between the minimum and maximum grain size ΔD ≤ 15 μm, preferably ΔD ≤ 8 μm.

[0013] In an optional embodiment, the average particle size of the elemental Pb particles is 0.1~8 μm.

[0014] In an optional embodiment, the average particle size of the elemental Pb particles is 1~6 μm.

[0015] In an optional embodiment, the elemental Pb particles with a particle size of 1~6μm account for more than 40%.

[0016] In an optional embodiment, the oxygen content in the tin-lead bronze is ≤60ppm.

[0017] In an optional embodiment, the as-cast alloy microstructure of the tin-lead bronze is an equiaxed, recrystallization-like structure, free of dendrites.

[0018] In an optional embodiment, the tin-lead bronze and H13 steel are diffusion welded in the range of 800~900℃, and the copper-steel bonding strength Rm≥300MPa.

[0019] Secondly, the present invention provides a method for preparing tin-lead bronze as described in any of the foregoing embodiments, wherein the process flow of the preparation method includes: smelting → centrifugal casting.

[0020] In an optional embodiment, the smelting includes: first adding copper and nickel raw materials to an electric furnace for melting according to their chemical composition, then adding lead, tin and zinc raw materials. After the composition is qualified, the temperature of the copper liquid is adjusted, a slag remover is added and stirred to remove slag, then phosphorus copper master alloy is added for deoxidation. After the composition is qualified, argon gas is blown into the copper liquid for refining, then copper-wrapped RE is added and fully mixed with the copper liquid before slag removal. In an optional embodiment, the centrifugal casting includes: casting the molten copper obtained after melting into a mold using a centrifugal casting process, wherein the rotational speed of the mold during centrifugal casting is based on the Konstantinov formula. The calculation is dynamic, where R is the inner surface radius of the casting in meters, and β is an adjustment coefficient, which is 1.4 to 1.5.

[0021] In optional implementations, it further includes at least one of the following features: A. During the smelting process, lead, tin and zinc raw materials are added. After the composition is tested and found to be qualified, the temperature of the copper liquid is adjusted to 1200℃~1250℃. B. The argon blowing refining time is 10 min to 60 min; C. Add the copper-wrapped RE, mix it thoroughly with the molten copper, adjust the furnace temperature to 1180℃~1240℃, and then remove the slag; D. The amount of RE added, based on the mass of the tin-lead bronze, is 0.01wt%~0.05wt%; E. The inner wall of the mold is coated with a release agent; F. Before pouring the molten copper into the mold, the mold is baked to 300~400℃ for 30min~60min, and then cooled to 50~150℃ before pouring begins; G. The casting temperature is controlled at 1080~1150℃; H. The casting speed should be controlled between 120s and 720s; I. After casting is completed, the mold continues to rotate for 180s~600s.

[0022] In an optional embodiment, the method for preparing the tin-lead bronze further includes turning and / or penetrant testing.

[0023] Thirdly, the present invention provides the application of tin-lead bronze as described in any of the foregoing embodiments in forming a bimetallic composite material with steel by diffusion welding technology.

[0024] This invention offers the following advantages: by optimizing the chemical composition of tin-lead bronze and controlling its microstructure, it effectively improves upon existing technologies that suffer from casting defects and insufficient adaptability to high-temperature environments during welding. The prepared bimetallic composite tin-lead bronze material exhibits significantly improved microstructure, performance, and process stability, meeting the stringent performance requirements of high-end fields such as aerospace, shipbuilding, and large-scale engineering machinery. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a transmissive imaging photograph of the cross-section of the ingot in Embodiment 1 of the present invention; Figure 2 This is a transmissive imaging photograph of the cross-section of the ingot of Comparative Example 1 of the present invention; Figure 3 This is a photograph of the copper layer after diffusion welding of copper sheet and steel in ingot processing according to Embodiment 1 of the present invention; Figure 4 This is a penetrant development photograph of the copper layer after diffusion welding of a copper sheet and steel in the ingot of Comparative Example 1 of the present invention. Figure 5 Photograph of the copper layer cracking after diffusion welding of copper sheet and steel in ingot processing according to Comparative Example 1 of the present invention. Figure 6 This is a metallographic diagram of the ingot of Embodiment 1 of the present invention; Figure 7 This is a metallographic diagram of the ingot of Comparative Example 1 of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0028] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0029] In the description of this invention, the terms "comprising," "including," etc., mean "including but not limited to." In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or multiple.

[0030] Some embodiments of the present invention provide a tin-lead bronze, the chemical composition of which includes: Sn: 5~11wt%, Pb: 2~6wt%, Ni: 0.09~4wt%, P: 0.05~0.3wt%, Zn: 0.01~1.0wt%, with the balance being Cu and unavoidable impurities. The alloy structure of the tin-lead bronze includes an α phase, an α+δ eutectoid, and elemental Pb particles dispersed in the α phase, wherein the area ratio of the α+δ eutectoid is ≤12%, the average grain size of the as-cast tin-lead bronze is 20μm~70μm, and the difference between the smallest and largest grain size ΔD is ≤20μm.

[0031] Specifically, in the chemical composition, Sn can improve the strength and corrosion resistance of copper alloys. In the copper alloy of this invention, when the Sn content is below 5 wt%, the hardness and strength of the copper alloy are low, and the corrosion resistance is poor. Since the intermetallic compound δ phase formed by Sn and Cu is a hard and brittle phase, when the Sn content exceeds 11 wt%, the amount of δ phase is too large, and the anti-segregation of Sn is more serious.

[0032] Pb is distributed in the alloy matrix in elemental form, playing a role in lubrication and friction reduction, and improving the wear resistance of the alloy. When the Pb content is less than 2wt%, the friction reduction effect of Pb particles is poor; when the Pb content exceeds 6wt%, the Pb particles in the as-cast alloy are large in size.

[0033] Ni helps accelerate the solidification and crystallization rate of the melt, acts as a crystal skeleton to prevent segregation and refine the microstructure.

[0034] The main function of P is deoxidation during smelting. The P2O5 bubbles generated by the oxidation reaction have the functions of degassing and removing inclusions.

[0035] Among them, the α phase is a solid solution of Sn dissolved in Cu, which has the same face-centered cubic lattice as Cu and allows the alloy to retain good plasticity; the δ phase is an intermediate compound (Cu 31 Sn8-based solid solutions are hard and brittle. The area ratio of α+δ eutectoid is controlled to ≤8% because the δ phase is hard and brittle. When the eutectoid ratio exceeds 8%, the δ phase particles or lamellar structures will form a continuous or semi-continuous "brittle network" inside the alloy. During high-temperature welding, the δ phase itself does not undergo plastic deformation, while the α phase will undergo significant thermal expansion and plastic flow when heated. Due to the uncoordinated deformation between the two phases, huge internal stress is generated. When the stress exceeds the fracture strength of the δ phase, microcracks will immediately be generated at the phase interface.

[0036] An as-cast average grain size of 30–60 μm falls within the fine to medium-fine grain range, which balances the alloy's high-temperature plasticity and structural stability. From a plasticity perspective, fine grains have large grain boundary areas, which can hinder dislocation movement. Simultaneously, grain boundaries themselves possess a certain slip capability at high temperatures, releasing thermal stress during welding through grain boundary slip. From a structural stability perspective, the grain size is neither excessively refined nor excessively coarsened, ensuring stable grain morphology during welding and preventing abnormal growth that could lead to sudden property changes. The requirement of ΔD ≤ 15 μm essentially eliminates the "grain size gradient." Grains of different sizes exhibit significant differences in their coefficient of thermal expansion, plastic deformation capacity, and atomic diffusion rate at high temperatures: fine grains have a slightly higher coefficient of thermal expansion and stronger plastic deformation capacity; coarse grains have a lower coefficient of thermal expansion and greater deformation resistance. When the grain size difference exceeds 15 μm, this difference creates a "mechanical property gradient" within the alloy, potentially leading to stress concentration during subsequent welding. If ΔD > 15μm, it indicates that the casting structure is highly uneven, which leads to uneven internal stress distribution and cracks during diffusion welding.

[0037] In some embodiments, the chemical composition of the alloy is further optimized, wherein the content of Sn is 8-11 wt%; and / or, the content of Pb is 2-3.5 wt%; and / or, the content of Ni is 2-4 wt%; and / or, the content of P is 0.05-0.15 wt%; and / or, the content of Zn is 0.05-0.5 wt%.

[0038] In some embodiments, the area ratio of α+δ eutectoid is ≤8%, and the average grain size of the as-cast tin-lead bronze is 30μm~60μm. The difference between the minimum and maximum grain size ΔD is ≤15μm, preferably ΔD ≤8μm.

[0039] Furthermore, in some embodiments, the average particle size of elemental Pb particles is 0.1~8 μm. Pb particles in this size range can ensure that the material has excellent friction-reducing properties, and can also prevent the larger Pb particles from agglomerating and increasing in size under high temperature conditions. During the cooling process, after the Pb particles change from liquid to solid phase, they will generate micro-shrinkage pores due to volume shrinkage.

[0040] Furthermore, to achieve better performance from elemental Pb particles, an average particle size of 1-6 μm is preferred. In some preferred embodiments, elemental Pb particles with a particle size of 1-6 μm account for more than 40% of the total elemental Pb particles.

[0041] In some implementations, the oxygen content in tin-lead bronze is ≤60ppm. O exists in the copper alloy matrix in the form of oxides. If the O content is too high, the oxides will accumulate on the grain boundaries, reducing the strength of the grain boundaries. When the material is subjected to external forces at high temperatures, it is prone to intergranular cracking.

[0042] In some embodiments, the as-cast microstructure of tin-lead bronze is an equiaxed, recrystallization-like structure, free of dendrites. An equiaxed, recrystallization-like structure is a microstructure where grains are approximately uniform in size in three-dimensional space, nearly circular or polyhedral, and their morphology and properties are similar to recrystallized structures, but their formation pathways or some characteristics differ from complete recrystallized structures. Segregation of Sn and Pb elements exists between the dendrite arms and dendrites; this segregation can lead to cracking of the alloy after high-temperature welding.

[0043] In some implementations, tin-lead bronze and H13 steel are diffusion welded in the range of 800~900℃, and the strength of the copper-steel bonding surface Rm≥300MPa.

[0044] Some embodiments of the present invention also provide a method for preparing tin-lead bronze as described in any of the foregoing embodiments, wherein the process flow of the preparation method includes: smelting → centrifugal casting.

[0045] Specifically, in some embodiments, the smelting process includes: first, adding copper and nickel raw materials to an electric furnace for melting according to their chemical composition; then adding lead, tin, and zinc raw materials; after the composition is verified to be qualified, adjusting the temperature of the molten copper; adding a slag remover and stirring to remove slag; then adding a phosphorus copper master alloy for deoxidation; after the composition is verified to be qualified, blowing argon gas into the molten copper for refining; then adding copper-coated RE, mixing it thoroughly with the molten copper, and then removing slag.

[0046] For example, the copper raw material can be selected as electrolytic copper, the nickel raw material can be selected as electrolytic nickel, the lead raw material can be selected as lead ingots, the tin raw material can be selected as tin ingots, and the zinc raw material can be selected as zinc blocks.

[0047] In some implementations, raw materials such as electrolytic copper, tin ingots, lead ingots, and electrolytic nickel, as well as auxiliary materials such as slag removers and refining agents, are first heated in a furnace to 300-600°C for baking, in order to thoroughly remove moisture from the raw materials and auxiliary materials.

[0048] In some implementations, lead, tin, and zinc raw materials are added during the smelting process. After the composition is tested and found to be qualified, the temperature of the molten copper is adjusted to 1200℃~1250℃, such as 1200℃, 1210℃, 1220℃, 1230℃, 1240℃, or 1250℃. At this temperature, the slag remover melts rapidly to form a low-viscosity glassy slag with a surface tension much lower than that of the molten copper. This slag can quickly wet the oxide inclusions in the molten copper, encapsulate the fine inclusions through interfacial adsorption, and simultaneously aggregate to form large slag particles. Due to the density difference, these particles quickly float to the surface, making them easy to retrieve and remove.

[0049] In some implementations, the argon refining time is 10 to 60 minutes, such as 10, 20, 30, 40, 50, or 60 minutes. Argon (Ar), as an inert gas, has extremely low solubility in molten copper. After being blown in, it rises in the molten copper as countless tiny bubbles. On one hand, the bubbles act as "carriers," capturing hydrogen, nitrogen, and tiny inclusions in the molten copper through interfacial adsorption. On the other hand, the turbulence generated during the bubble rise enhances the internal stirring of the molten copper, breaking down the stratification of composition and temperature, thus achieving the triple functions of degassing, impurity removal, and homogenization. If the argon refining time is too short, the degassing and impurity removal effects cannot be achieved effectively. If the argon refining time is too long, the improvement in degassing and impurity removal effects is not significant, but the temperature of the molten copper will continue to drop, requiring additional heating, which increases energy consumption and the risk of element volatilization.

[0050] Furthermore, in some embodiments, copper-coated rare earth elements (RE) are added and thoroughly mixed with the molten copper. The furnace temperature is then adjusted to 1180°C~1240°C before slag removal. The amount of RE added, based on the mass of the tin-lead bronze, is 0.01wt%~0.05wt%. RE forms high-melting-point rare earth compounds with impurities in the molten copper. Under rapid cooling conditions, these rare earth compounds act as nuclei for Pb crystallization. When a certain number of rare earth compounds are present, a continuous network structure can be formed, allowing Pb to crystallize around these nuclei, hindering further Pb movement and thus preventing Pb segregation and refining the grain size. However, when the amount of RE added exceeds 0.04wt%, the fluidity of the molten copper deteriorates, making the ingot more prone to shrinkage porosity.

[0051] It should be noted that after the slag is removed, the furnace needs to be left to stand for 5 to 10 minutes before it is taken out of the furnace to prepare for casting.

[0052] In some embodiments, centrifugal casting includes: pouring molten copper obtained after melting into a mold using a centrifugal casting process, wherein the rotational speed of the mold during centrifugal casting is based on the Konstantinov formula. The rotation speed is calculated and dynamically changes, where R is the radius of the inner surface of the casting in meters, and β is an adjustment coefficient, with β ranging from 1.4 to 1.5. If the casting is a hollow ingot, the rotation speed gradually increases.

[0053] As the casting speed increases, the centrifugal force increases, enhancing convection during metal cooling. This overcomes resistance during the feeding process, strengthening the alloy's feeding effect and facilitating the movement of impurities and gases towards the center. This reduces shrinkage defects in the casting and increases density. However, if the casting speed is too high, the tendency for Pb aggregation increases. This aggregation is because the density of the Pb-rich liquid phase in the alloy is significantly greater than that of the Cu-rich liquid phase (Pb density 11.3 g / cm³). 3 Cu 8.9 g / cm 3 Therefore, before a fixed framework is formed in the copper-rich liquid phase, Pb density segregation easily occurs, causing Pb to locally aggregate into coarse lumps and concentrate in bands. Thus, based on the embodiment of this invention, the alloy contains Sn, Pb, and Ni elements with higher densities than Cu, and β is set to a specific value of 1.4 to 1.5. Furthermore, the optimal rotation speed is obtained based on the Konstantinov formula to ensure the quality of the casting. If the range of 1.2 to 1.4 is used for conventional copper alloys, micro-shrinkage defects are prone to appear near the core of the casting.

[0054] In addition, the following points should be noted during the specific operation of centrifugal casting: (1) Apply a release agent to the inner wall of the mold. The release agent consists of 80% graphite powder and 20% anhydrous ethanol coating.

[0055] (2) Before pouring the molten copper into the mold, the mold is baked to 300~400℃ for 30min~60min to remove the water vapor adsorbed by the mold. Natural gas can be used for baking. Then the baked mold is cooled to 50~150℃ before pouring. This is because tin-lead bronze has a wide crystallization temperature range, poor fluidity and feeding ability of molten copper. Excessively high mold temperature makes it take longer for the solidification shell to form on the surface of the casting, which aggravates the gas absorption of the casting and results in poor surface quality of the casting.

[0056] (3) The casting temperature should be controlled at 1080~1150℃, such as 1080℃, 1090℃, 1100℃, 1110℃, 1120℃, 1130℃, 1140℃ or 1150℃, which is 50~100℃ above the liquidus temperature of the alloy. If the casting temperature is too low, it will reduce the fluidity of the copper liquid, resulting in defects such as interlayers and uneven wall thickness inside the casting; if the casting temperature is too high, it is easy to form porosity and shrinkage defects, and it is easy to cause Pb accumulation.

[0057] (4) The casting speed is controlled between 120s and 720s. Tin-lead bronze tends to solidify into a paste-like consistency, and the temperature field distribution inside the casting is relatively wide. The solid-liquid interface advances slowly, which means that it takes longer to solidify completely after casting. If the casting speed is too fast, it may aggravate the temperature gradient, which is not conducive to uniform solidification. Therefore, the embodiment of the present invention adopts a slow casting process.

[0058] (5) After casting is completed, the mold continues to rotate for 180s to 600s. After the molten copper is poured into the mold, there needs to be enough time for solidification. The entire solidification process takes place during the rotation of the centrifuge. If the machine is stopped too early, copper nodules and non-round inner holes will appear on the inner wall of the casting. The specific time is determined according to the weight of the casting.

[0059] In some implementations, cooling water is sprayed onto the mold shell immediately after the centrifuge stops, in order to cool it quickly and refine the casting structure.

[0060] In some embodiments, the preparation method of this tin-lead bronze also includes turning and / or penetrant testing. The purpose of turning is to machine the casting blank to the required specifications according to the product specifications. Penetrant testing is required on the inner and outer surfaces and end faces of the casting to check for defects such as shrinkage cavities, cracks, and porosity that are not visible to the naked eye. The penetrant testing steps are as follows: First, remove oil stains from the surface to be tested with a cleaning agent; then, spray the penetrant evenly onto the surface to be tested; after 5-15 minutes, remove the penetrant with a cleaning agent; finally, spray the developer evenly onto the outer surface of the casting; after 1-5 minutes, observe whether defects appear (defects are displayed in red).

[0061] Some embodiments of the present invention also provide the use of tin-lead bronze as described in any of the foregoing embodiments in forming bimetallic composite materials with steel by diffusion welding technology.

[0062] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0063] Example 1 This embodiment provides a method for preparing tin-lead bronze, which is a hollow ingot with dimensions of φ230mm×φ81mm×400mm. The preparation method includes the following steps: (1) Smelting: First, the raw materials such as electrolytic copper, tin ingots, lead ingots, and electrolytic nickel, as well as auxiliary materials such as slag remover and refining agent, are heated to 500°C in a heating furnace. Then, according to the chemical composition, the raw materials such as electrolytic copper, tin ingots, lead ingots, and electrolytic nickel are added to the electric furnace in a certain proportion. The order of adding materials is as follows: first, high-melting-point electrolytic copper and electrolytic nickel blocks are added together to melt, and then lead ingots, tin ingots, and zinc blocks are added. After all the added metals have melted and the composition has been tested and found to be qualified, the temperature of the copper liquid is adjusted to 1232°C, and slag remover (CaF 50wt%, NaCl 30wt%) is added. The copper liquid was stirred and slag was removed (NaCO3 was 20wt%). Then, phosphorus copper intermediate alloy was added for deoxidation. After the composition was found to be qualified, argon gas was continuously blown into the copper liquid for 40 minutes. After the argon gas refining was completed, a sample block was taken for pre-furnace inspection. A cylindrical sample was poured to test the deoxidation effect. If the cylindrical sample block shrank well, the argon gas blowing was stopped. Finally, RE (rare earth) was wrapped with copper sheet, pressed into the bottom of the copper liquid in the electric furnace and stirred thoroughly. After adjusting the electric furnace temperature to 1206℃, the slag was removed. Then, it was left to stand for 8 minutes before being taken out of the furnace for pouring. The amount of RE added was 0.02wt%.

[0064] (2) Centrifugal casting: Before pouring the molten copper into the mold, the mold, which has been coated with a release agent, needs to be baked with natural gas to a high temperature of 350°C for 40 minutes, and then cooled to 80°C before pouring. The actual pouring temperature was 1113°C. According to the Konstantinov formula... (ρ: 8.87 g / cm³) 3 (R: 12→3cm, β: 1.42) The centrifuge speed n is gradually increased from 760r / min at the beginning to 1520r / min at the end of the casting process. The time required for this process is 240s. The centrifuge shutdown time is 300s. The dimensions of the casting blank are φ240mm×φ60mm×410mm.

[0065] (3) Turning: The centrifugally cast blank is turned into finished product size φ230mm×φ81mm×400mm.

[0066] (4) Penetration detection.

[0067] Example 2 This embodiment provides a method for preparing tin-lead bronze, which is a hollow ingot with dimensions of φ160mm×φ54mm×350mm. The preparation method includes the following steps: (1) Smelting: First, the raw materials such as electrolytic copper, tin ingots, lead ingots, and electrolytic nickel, as well as auxiliary materials such as slag remover and refining agent, are heated to 380°C in a heating furnace. Then, according to the chemical composition, the raw materials such as electrolytic copper, tin ingots, lead ingots, and electrolytic nickel are added to the electric furnace in a certain proportion. The order of adding materials is as follows: first, high-melting-point electrolytic copper and electrolytic nickel blocks are added together to melt, and then lead ingots, tin ingots, and zinc blocks are added. After all the added metals have melted and the composition has been tested and found to be qualified, the temperature of the copper liquid is adjusted to 1225°C, and slag remover (CaF 50wt%, NaCl 30wt%) is added. The slag was removed by stirring (10 wt% NaCO3, 20 wt%), and then phosphorus copper intermediate alloy was added for deoxidation. After the composition was found to be qualified, argon gas was continuously blown into the copper liquid for 35 minutes. After the argon gas refining was completed, a sample block was taken for pre-furnace inspection. A cylindrical sample was poured to test the deoxidation effect. If the cylindrical sample block shrank well, the argon gas blowing was stopped. Finally, RE (rare earth) was wrapped in copper sheet, pressed into the bottom of the copper liquid in the electric furnace and stirred thoroughly. After adjusting the electric furnace temperature to 1218℃, the slag was removed, and then it was left to stand for 5 minutes before being taken out of the furnace for pouring. The amount of RE added was 0.016 wt%.

[0068] (2) Centrifugal casting: Before pouring the molten copper into the mold, the mold, which has been coated with a release agent, needs to be baked with natural gas to a high temperature of 330°C for 35 minutes, and then cooled to 100°C before pouring. The actual pouring temperature was 1126°C. According to the Konstantinov formula... (ρ: 8.89 g / cm) 3 (R: 8.75→2cm, β: 1.46) The centrifuge speed n is calculated to gradually increase from 915 r / min at the beginning to 1910 r / min at the end of the casting process. The time required for this process is 180s, the centrifuge shutdown time is 260s, and the casting blank size is φ175mm×φ40mm×360mm.

[0069] (3) Turning: The centrifugally cast blank is turned into finished product size φ160mm×φ54mm×350mm.

[0070] (4) Penetration detection.

[0071] Example 3 This embodiment provides a method for preparing tin-lead bronze, which is a hollow ingot with dimensions of φ300mm×φ102mm×500mm. The preparation method includes the following steps: (1) Smelting: First, the raw materials such as electrolytic copper, tin ingots, lead ingots, and electrolytic nickel, as well as auxiliary materials such as slag remover and refining agent, are heated to 500°C in a heating furnace. Then, according to the chemical composition, the raw materials such as electrolytic copper, tin ingots, lead ingots, and electrolytic nickel are added to the electric furnace in a certain proportion. The order of adding materials is as follows: first, high-melting-point electrolytic copper and electrolytic nickel blocks are added together to melt, and then lead ingots, tin ingots, and zinc blocks are added. After all the added metals have melted and the composition has been tested and found to be qualified, the temperature of the copper liquid is adjusted to 1240°C, and slag remover (CaF 50wt%, NaCl 30wt%) is added. The copper liquid was stirred and slag was removed (20 wt% NaCO3). Then, a phosphorus copper intermediate alloy was added for deoxidation. After the composition was found to be qualified, argon gas was continuously blown into the copper liquid for 45 minutes. After the argon gas refining was completed, a sample block was taken for pre-furnace inspection. A cylindrical sample was poured to test the deoxidation effect. If the cylindrical sample block shrank well, the argon gas blowing was stopped. Finally, RE (rare earth) was wrapped in copper sheet, pressed into the bottom of the copper liquid in the electric furnace and stirred thoroughly. After adjusting the electric furnace temperature to 1231℃, the slag was removed. Then, it was left to stand for 10 minutes before being taken out of the furnace for pouring. The amount of RE added was 0.027 wt%.

[0072] (2) Centrifugal casting: Before pouring the molten copper into the mold, the mold, which has been coated with a release agent, needs to be baked with natural gas to a high temperature of 400℃ for 50 minutes, and then cooled to 150℃ before pouring. The actual pouring temperature was 1143℃, according to the Konstantinov formula. (ρ: 8.85 g / cm³) 3 (R: 11.5→3cm, β: 1.48) The centrifuge speed n is gradually increased from 800 r / min at the beginning to 1590 r / min at the end of the casting process. The time required for this process is 360s. The centrifuge shutdown time is 400s. The specifications of the casting blank are φ320mm×φ80mm×515mm.

[0073] (3) Turning: The centrifugally cast blank is turned into finished product size φ300mm×φ102mm×500mm.

[0074] (4) Penetration detection.

[0075] Example 4 This embodiment provides a method for preparing tin-lead bronze, which is a hollow ingot with dimensions of φ500mm×φ160mm×600mm. The preparation method includes the following steps: (1) Smelting: First, the raw materials such as electrolytic copper, tin ingots, lead ingots, and electrolytic nickel, as well as auxiliary materials such as slag remover and refining agent, are heated to 560°C in a heating furnace. Then, according to the chemical composition, the raw materials such as electrolytic copper, tin ingots, lead ingots, and electrolytic nickel are added to the electric furnace in a certain proportion. The order of adding materials is as follows: first, high-melting-point electrolytic copper and electrolytic nickel blocks are added together to melt, and then lead ingots, tin ingots, and zinc blocks are added. After all the added metals have melted and the composition has been tested and found to be qualified, the temperature of the copper liquid is adjusted to 1228°C, and slag remover (CaF 50wt%, NaCl 30wt%) is added. The copper liquid was stirred and slag was removed (t%, NaCO3 was 20wt%). Then, phosphorus copper intermediate alloy was added for deoxidation. After the composition was found to be qualified, argon gas was continuously blown into the copper liquid for 60 minutes. After the argon gas refining was completed, a sample block was taken for pre-furnace inspection. A cylindrical sample was poured to test the deoxidation effect. If the cylindrical sample block shrank well, the argon gas blowing was stopped. Finally, RE (rare earth) was wrapped in copper sheet, pressed into the bottom of the copper liquid in the electric furnace and stirred thoroughly. After adjusting the electric furnace temperature to 1219℃, the slag was removed. Then, it was left to stand for 6 minutes before being taken out of the furnace for pouring. The amount of RE added was 0.012wt%.

[0076] (2) Centrifugal casting: Before pouring the molten copper into the mold, the mold, which has been coated with a release agent, needs to be baked with natural gas to a high temperature of 380℃ for 60 minutes, and then cooled to 120℃ before pouring. The actual pouring temperature was 1137℃. According to the Konstantinov formula (ρ: 8.87 g / cm³) 3 (R: 26→9cm, β: 1.45) The centrifuge speed n is gradually increased from 530r / min at the beginning to 900r / min at the end of the casting process. The time required for this process is 520s. The centrifuge shutdown time is 490s. The dimensions of the casting blank are φ520mm×φ180mm×620mm.

[0077] (3) Turning: The centrifugally cast blank is turned into finished product size φ500mm×φ160mm×600mm.

[0078] (4) Penetration detection.

[0079] Comparative Example 1 This comparative example provides a method for preparing tin-lead bronze, which differs from Example 1 in that it uses a semi-continuous casting process to prepare the ingot, as detailed below: (1) Smelting: Then, according to the chemical composition, the raw materials such as electrolytic copper, tin ingot, lead ingot, and electrolytic nickel are added to the electric furnace in a certain proportion to melt. After the alloy composition is adjusted to be qualified, a slag remover is added to remove the slag, and then a refining agent is added to refine it. The temperature of the smelting furnace is adjusted, and the actual temperature is 1292℃. Then the furnace head is tilted to prepare for casting.

[0080] (2) Semi-continuous casting: The inner diameter of the crystallizer is φ250mm, and the actual casting temperature is 1245℃; the casting speed is 50mm / min, the casting time is 4s, the pause time is 1s, and the primary cooling water flow rate is 12m³ / min. 3 / h, secondary cooling water flow rate 8m 3 / h, the cooling water temperature difference is controlled at 19℃, and the whole ingot of semi-continuous casting needs to have the parts with macroscopic defects at the head and tail removed.

[0081] (3) Turning: According to the customer’s required specifications, the φ250mm casting blank is turned, sawed and drilled into φ230mm×φ81mm×400mm copper ingot.

[0082] (4) Penetration detection.

[0083] Comparative Example 2 This comparative example provides a method for preparing tin-lead bronze, which differs from Example 1 in that it uses an iron mold casting process to prepare the ingot, as detailed below: (1) Smelting: Then, according to the chemical composition, the raw materials such as electrolytic copper, tin ingot, lead ingot, and electrolytic nickel are added to the electric furnace in a certain proportion to melt. After the alloy composition is adjusted to be qualified, a slag remover is added to remove the slag, and then a refining agent is added to refine it. The temperature of the smelting furnace is adjusted, and the actual temperature is 1244℃, ready for casting.

[0084] (2) Casting with iron mold: The inner diameter of the iron mold is φ260mm, the casting temperature is 1244℃, the ingot is naturally cooled to below 100℃ and demolded, and the parts with macroscopic defects at the head and tail of the ingot are cut off.

[0085] (3) Turning: According to the customer’s required specifications, the φ260mm casting blank is turned, sawed and drilled into φ230mm×φ81mm×400mm copper ingot.

[0086] (4) Penetration detection.

[0087] Comparative Example 3 This comparative example provides a method for preparing tin-lead bronze, which differs from Example 1 in that it is smelted using ordinary processes, without the addition of phosphorus copper alloy for deoxidation, argon gas blowing for degassing, or the addition of rare earth elements.

[0088] Comparative Example 4 This comparative example provides a method for preparing tin-lead bronze, which differs from Example 1 in that no rare earth elements are added during smelting, but the rest are the same.

[0089] Comparative Example 5 This comparative example provides a method for preparing tin-lead bronze, which differs from Example 1 in that the centrifugal casting has a faster pouring speed, completing the pouring in 60 seconds, while the rest are the same.

[0090] Comparative Example 6 This comparative example provides a method for preparing tin-lead bronze, which differs from Example 1 in that the centrifuge speed is kept constant at an initial 760 r / min during centrifugal casting, while the rest are the same.

[0091] Comparative Example 7 This comparative example provides a method for preparing tin-lead bronze, which differs from Example 1 in that the centrifuge speed is kept constant at 1080 r / min during centrifugal casting, while the rest are the same.

[0092] Comparative Example 8 This comparative example provides a method for preparing tin-lead bronze, which differs from Example 1 in that the centrifuge speed adjustment coefficient β is set to 1.25, while the rest are the same.

[0093] The chemical composition of the examples and comparative examples is shown in Table 1.

[0094] Table 1

[0095] The penetrant testing in the above embodiments and comparative examples was conducted according to the following test steps: First, the oil stains on the surface to be tested were removed with a cleaning agent. Then, the penetrant was evenly sprayed onto the surface to be tested. After 10 minutes, the penetrant was removed with a cleaning agent. Finally, the developer was evenly sprayed onto the outer surface of the casting. After 3 minutes, it was observed whether any defects appeared (defects were displayed in red). In addition, the ingots of the above embodiments and comparative examples were processed into copper sheets and then diffusion welded with steel. The specific operation was as follows: After the diffusion welding surfaces of the copper sheet and steel were ground smooth, the welding surfaces were cleaned and then placed in a vacuum diffusion welding furnace. The welding pressure was 5-15 MPa and the welding temperature was 800-900℃. The penetrant and diffusion welding results of the ingots are shown in Table 2. If there are no defects and no red is displayed, it is considered qualified. If there are defects and red is displayed, it is considered unqualified. Among them, defects include micro-shrinkage, micro-porosity, cracks, or pores.

[0096] Table 2

[0097] Figure 1 This is a transmissive imaging photograph of the cross-section of the ingot from Example 1. Figure 1 As can be seen, after penetrant development of the cross-section of the ingot in Example 1, the entire cross-section is white and no red appears, indicating that there are no defects such as shrinkage cavities, micro-shrinkage porosity, cracks, or gas pores inside the ingot. Figure 2 For the cross-sectional penetrant photograph of the ingot in Comparative Example 1, from... Figure 2 It can be seen that after penetrant development of the cross-section of the ingot in Comparative Example 1, the center of the ingot appears red, indicating that there are no micro-shrinkage defects in the area near the center of the ingot. Figure 3The image shows the copper layer after diffusion welding of the copper sheet from the casting of Example 1 to H13 steel. Figure 3 It can be seen that after diffusion soldering copper layer penetration development, the color is all white, that is, the microstructure after diffusion soldering does not show micro-porous defects. Figure 4 This is a penetrant photograph of the copper layer after diffusion welding of a copper sheet machined from a casting to H13 steel, as shown in Comparative Example 1. Figure 4 It can be seen that after diffusion soldering copper layer penetration development, the central part turns red, which means that the internal structure of the copper layer after diffusion soldering has micro-porosity defects. Figure 5 A photograph of the copper layer cracking after diffusion welding of the copper sheet processed from the ingot of Comparative Example 1.

[0098] Microstructure analysis: The obtained examples and comparative examples were analyzed according to the method specified in Clause 4.3.3 (grid cut-off method) of GB / T 15749-2008 (Quantitative Metallographic Determination Methods). The specific test data are shown in Table 3.

[0099] Table 3

[0100] Figure 1 The image shows the metallographic structure of the ingot from Example 1. Figure 1 It can be seen that the ingot structure obtained in Example 1 is an equiaxed recrystallization-like structure with a small average grain size of only 42 μm. The difference between the smallest and largest grain size ΔD is small, only 6.6 μm. The number of α+δ eutectoids is very small, accounting for only 4.45% of the area. The Pb particles are also very small, only 2.6 μm. Figure 2 The metallographic diagram of the ingot in Comparative Example 1 is shown below. Figure 2 It can be seen that the ingot structure prepared in Comparative Example 1 is coarse dendrites. Since grain boundaries cannot be seen within the 100X field of view, the grain size D and the difference between the smallest and largest grain size ΔD cannot be measured. There are a large number of α+δ eutectoids, which account for 14.83% of the area. The Pb particles are large, with an average size of 9.0 μm.

[0101] In summary, the embodiments of the present invention address the casting defects and incompatibility with high-temperature environments in the welding process of existing technologies. Through improved alloy composition and microstructure design, a centrifugal casting process is used to obtain ingots with a specified microstructure. At the same time, the dendritic segregation problem existing in traditional casting methods is eliminated, and the prepared materials meet the high requirements of special industries such as aerospace, shipbuilding, and large-scale engineering machinery.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A tin-lead bronze, characterized in that, Its chemical composition includes: Sn: 5~11wt%, Pb: 2~6wt%, Ni: 0.09~4wt%, P: 0.05~0.3wt%, Zn: 0.01~1.0wt%, with the balance being Cu and unavoidable impurities. The alloy structure of the tin-lead bronze includes an α phase, an α+δ eutectoid, and elemental Pb particles dispersed in the α phase. The area ratio of the α+δ eutectoid is ≤12%. The average grain size of the tin-lead bronze in the as-cast state is 20μm~70μm, and the difference between the smallest and largest grain size ΔD is ≤20μm.

2. The tin-lead bronze according to claim 1, characterized in that, In its chemical composition, the content of Sn is 8~11wt%; and / or, the content of Pb is 2~3.5wt%; and / or, the content of Ni is 2~4wt%; and / or, the content of P is 0.05~0.15wt%; and / or, the content of Zn is 0.01~0.5wt%; and / or, the area ratio of the α+δ eutectoid is ≤8%; and / or, the average grain size of the tin-lead bronze in the as-cast state is 30μm~60μm; and / or, the difference between the minimum and maximum grain size ΔD is ≤15μm, preferably ΔD ≤8μm.

3. The tin-lead bronze according to claim 1, characterized in that, The average particle size of the elemental Pb particles is 0.1~8 μm; Preferably, the average particle size of the elemental Pb particles is 1~6 μm; Preferably, in the elemental Pb particles, elemental Pb particles with a particle size of 1~6μm account for more than 40%.

4. The tin-lead bronze according to claim 1, characterized in that, The oxygen content in the tin-lead bronze is ≤60ppm; And / or, the as-cast alloy microstructure of the tin-lead bronze is an equiaxed, recrystallized-like structure, free of dendrites.

5. The tin-lead bronze according to any one of claims 1 to 4, characterized in that, The tin-lead bronze and H13 steel are diffusion welded in the range of 800~900℃, and the strength of the copper-steel bonding surface Rm≥300MPa.

6. A method for preparing tin-lead bronze as described in any one of claims 1 to 5, characterized in that, The process flow of the preparation method includes: smelting → centrifugal casting.

7. The method for preparing tin-lead bronze according to claim 6, characterized in that, The smelting process includes: first, adding copper and nickel raw materials to an electric furnace for melting according to their chemical composition; then adding lead, tin, and zinc raw materials; after the composition is verified to be qualified, adjusting the temperature of the molten copper; adding a slag remover and stirring to remove slag; then adding a phosphorus copper master alloy for deoxidation; after the composition is verified to be qualified, blowing argon gas into the molten copper for refining; then adding copper-wrapped RE and mixing it thoroughly with the molten copper before removing slag. And / or, the centrifugal casting includes: casting the molten copper obtained after melting into a mold using a centrifugal casting process, wherein, during centrifugal casting, the rotational speed of the mold is based on the Konstantinov formula. The value is calculated and changes dynamically, where n is the casting rotation speed in r / min and ρ is the alloy density in kg / cm³. 3 R is the inner surface radius of the casting in meters, and β is an adjustment coefficient, which is 1.4 to 1.

5.

8. The method for preparing tin-lead bronze according to claim 7, characterized in that, It also includes at least one of the following features: A. During the smelting process, lead, tin and zinc raw materials are added. After the composition is tested and found to be qualified, the temperature of the copper liquid is adjusted to 1200℃~1250℃. B. The argon blowing refining time is 10 min to 60 min; C. Add the copper-wrapped RE, mix it thoroughly with the molten copper, adjust the furnace temperature to 1180℃~1240℃, and then remove the slag; D. The amount of RE added, based on the mass of the tin-lead bronze, is 0.01wt%~0.05wt%; E. The inner wall of the mold is coated with a release agent; F. Before pouring the molten copper into the mold, the mold is baked to 300~400℃ for 30min~60min, and then cooled to 50~150℃ before pouring begins; G. The casting temperature is controlled at 1080~1150℃; H. The casting speed should be controlled between 120s and 720s; I. After casting is completed, the mold continues to rotate for 180s~600s.

9. The method for preparing tin-lead bronze according to claim 6, characterized in that, Following centrifugal casting, machining and / or penetrant testing are also performed.

10. The use of tin-lead bronze as described in any one of claims 1 to 5 in forming a bimetallic composite material with steel by diffusion welding technology.

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