High-strength high-plasticity lead-tin bronze alloy and preparation method thereof

Abstract

The application discloses a high-strength and high-plasticity lead-tin bronze alloy and a preparation method thereof, and belongs to the technical field of copper alloy preparation. The application comprises the following steps: (1) the lead-tin bronze alloy is subjected to induction heating smelting and deoxidation, degassing and deslagging treatment, and after the alloy melt surface is pushed away to be mirror-like, the alloy melt is uniformly placed; (2) the alloy melt uniformly placed in the step (1) is subjected to quenching modification treatment, and a semi-solid slurry is obtained; (3) the semi-solid slurry obtained in the step (2) is poured into a preheated mold and extruded, the castings after extrusion forming are kept in the mold for a certain time and then rapidly oil-cooled to room temperature, and lead-tin bronze castings are obtained; and (4) the lead-tin bronze castings are subjected to solid solution and aging treatment, and the high-strength and high-plasticity lead-tin bronze alloy is obtained. The lead-tin bronze alloy prepared by the application has high strength and plasticity, and can meet higher use requirements.

Description

Technical Field

[0001] This invention belongs to the field of copper alloy preparation technology, specifically relating to a high-strength, high-ductility lead-tin bronze alloy and its preparation method. Background Technology

[0002] Lead-tin bronze alloys have many advantages such as good friction reduction, high thermal conductivity, fatigue resistance and anti-galling properties. They are often used to make wear-resistant parts such as bearings, bushings, pistons and bearing shells, and are widely used in high-speed rail, shipbuilding, aviation and other fields.

[0003] Lead-tin bronze alloys are made by adding lead to tin bronze, resulting in granular lead phases distributed in the matrix as soft particles that provide good lubrication, thus achieving a low coefficient of friction and good wear resistance. However, the addition of lead leads to grain boundary embrittlement, severely reducing the alloy's ductility. Lead-tin bronze alloys produced using traditional lead-tin alloy component manufacturing processes exhibit significant Pb gravity segregation and Sn anti-segregation, and are prone to defects such as porosity and cracks, leading to a severe reduction in the strength and plasticity of lead-tin bronze alloys, especially the CuSn10Pb2Ni3 alloy.

[0004] CuSn10Pb2Ni3 alloy is one of the important materials for hydraulic machinery in aero-engines, and is usually used in combination with steel to form piston pump rotors and slippers. With the development of society, the strength and plasticity of this alloy produced by traditional processes can no longer meet current service conditions.

[0005] Therefore, it is necessary to provide a high-strength and high-ductility lead-tin bronze alloy and its preparation method to improve the strength and ductility of lead-tin bronze alloys, especially for CuSn10Pb2Ni3 alloys, so as to make the performance of lead-tin bronze alloys more suitable and meet the requirements of current service conditions. Summary of the Invention

[0006] To overcome the problems in the prior art, this invention prepares a semi-solid slurry, forming a primary α-phase within it, which inhibits dendrite formation in the subsequent solidification structure, transforming the structure into equiaxed crystals. Simultaneously, by controlling the preheating temperature of the die, the cooling rate of the alloy melt during extrusion is reduced, allowing solute elements enriched at the solid / liquid interface during solidification to fully diffuse into the remaining liquid phase. Combined with rapid oil cooling to suppress Sn precipitation from the matrix, the solidified structure is uniformly distributed, reducing the content of hard and brittle intergranular phases, thereby improving the strength and plasticity of the lead-tin bronze alloy.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] This invention provides a method for preparing a high-strength, high-ductility lead-tin bronze alloy, the method comprising the following steps:

[0009] (1) The lead-tin bronze alloy is induction heated and melted, and then deoxidized, degassed and slag removed. After the surface of the alloy melt is peeled open to a mirror-like state, the alloy melt is allowed to stand still to homogenize.

[0010] (2) The alloy melt after static homogenization in step (1) is subjected to quenching modification treatment to obtain a semi-solid slurry;

[0011] (3) The semi-solid slurry obtained in step (2) is poured into a preheated mold and extruded into shape. After extrusion, the casting is kept in the mold for a certain period of time and then quickly oil-cooled to room temperature to obtain lead-tin bronze casting.

[0012] (4) Solution treatment and aging treatment are performed on lead-tin bronze castings to obtain high-strength and high-plasticity lead-tin bronze alloy.

[0013] Preferably, in step (1), the melting temperature of the lead-tin bronze alloy is 1200℃~1250℃.

[0014] Preferably, in step (1), 1% CuP14 by mass of the alloy melt is added to the alloy melt for deoxidation, degassing and slag removal treatment.

[0015] Preferably, in step (1), the static homogenization temperature is 1065℃~1085℃, and the holding time is 25~30min.

[0016] Preferably, in step (2), the cooling rate of the quenching is ≥500℃ / s.

[0017] Preferably, in step (3), the forming pressure of the extrusion molding is 110MPa to 150MPa, and the extrusion speed is 20mm / s to 24mm / s.

[0018] Preferably, in step (3), the mold preheating temperature is 550℃~600℃.

[0019] Preferably, in step (3), after extrusion molding, the casting is kept at 550℃~600℃ in a mold for 1~3 minutes, and the oil cooling time to room temperature is 5-6 minutes.

[0020] Preferably, in step (4), the solution treatment temperature is 580℃~650℃, the solution treatment time is 16~20h, and after the solution treatment is completed, an aging treatment is performed at a temperature of 160~200℃ for a time of 6-8h.

[0021] In another aspect, the present invention provides a lead-tin bronze alloy, which is prepared by the above-described preparation method.

[0022] The poor performance of lead-tin bronze alloys is due to several factors. Firstly, with increasing tin content, especially when it exceeds 8%, the solid solution strengthening effect of the α-solid solution formed by tin in the copper matrix increases, but so does the number of intergranular phases. The hard and brittle tin-rich phases lead to increased hardness, strength, and wear resistance, but decreased ductility and increased brittleness. Secondly, high-tin-content lead-tin bronze alloys exhibit severe macroscopic and microscopic dendritic segregation during gravity casting. The presence of heavy lead also contributes to gravity segregation, which negatively impacts alloy performance. Thirdly, the paste-like solidification process of lead-tin bronze alloys makes them highly susceptible to casting defects such as hot cracks, porosity, and shrinkage cavities, resulting in poor overall mechanical properties. This invention addresses the aforementioned problems through a two-pronged approach: First, a semi-solid slurry is prepared using rapid chilling modification. By forming a certain amount of primary α-phase in the slurry, dendrite formation in the subsequent solidification is suppressed, transforming the microstructure into equiaxed crystals. Second, by controlling the preheating temperature of the die, a high die temperature reduces the cooling rate of the alloy melt during extrusion forming. This allows solute elements enriched at the solid / liquid interface during solidification to diffuse fully into the remaining liquid phase. Combined with subsequent rapid oil cooling to suppress Sn precipitation from the matrix, the solidified microstructure is uniformly distributed, reducing the content of hard and brittle intergranular phases. Through the synergistic control of rapid chilling modification and die preheating, an alloy with a small, uniformly distributed microstructure of hard and brittle intergranular phases is prepared. Finally, solution treatment and aging are employed to further improve elemental segregation and microstructure uniformity, resulting in a high-strength, high-ductility lead-tin bronze alloy.

[0023] The beneficial effects of this invention are:

[0024] 1. The lead-tin bronze alloy prepared by this invention has excellent strength and plasticity, and better comprehensive mechanical properties, which can meet higher application requirements.

[0025] 2. This invention differs from existing technologies that improve alloy performance by adding alloying elements. For the first time, it utilizes a semi-solid rheological extrusion method in lead-tin bronze alloys, combining rapid melt cooling modification technology with high die temperature technology to synergistically control the microstructure of the alloy and prepare high-strength, high-ductility lead-tin bronze alloys. This lays a solid foundation for expanding into fields such as the preparation of lead-tin bronze / steel dissimilar bimetallic composite materials.

[0026] 3. The preparation process of this invention is relatively simple, low-cost, and highly efficient. It can continuously prepare semi-solid slurry and can be achieved using existing extrusion, die casting, and other forming equipment, making it suitable for industrial application. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the process flow of the preparation method of the present invention;

[0028] Figure 2 This is a microstructure diagram of the high-strength, high-ductility lead-tin bronze alloy prepared in Example 1 of the present invention;

[0029] Figure 3 This is a microstructure diagram of the high-strength, high-ductility lead-tin bronze alloy prepared in Example 2 of the present invention;

[0030] Figure 4 This is a microstructure diagram of the high-strength, high-ductility lead-tin bronze alloy prepared in Example 3 of the present invention;

[0031] Figure 5 This is a microstructure diagram of the high-strength, high-ductility lead-tin bronze alloy prepared in Example 4 of the present invention;

[0032] Figure 6 The microstructure of the lead-tin bronze alloy prepared in comparison is shown in the figure.

[0033] Figure 7 The stress-strain curves of the lead-tin bronze alloys prepared in Examples 1-4 and the comparative examples of the present invention are shown. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0035] In the embodiments and comparative examples of this invention, unless otherwise specified, commercially available analytical grade chemical reagents were used in the experiments.

[0036] In both the embodiments and comparative examples of this invention, CuSn10Pb2Ni3 alloy was used as the initial raw material.

[0037] Example 1

[0038] This embodiment prepares a high-strength, high-ductility lead-tin bronze alloy using the following method:

[0039] (1) Weigh 3 kg of CuSn10Pb2Ni3 alloy block and heat it in a medium frequency induction furnace at a melting temperature of 1250℃. At the same time, add 0.03 kg of CuP14 to the melt for deoxidation, degassing and slag removal until the surface of the melt is smooth and mirror-like. After the temperature of the alloy melt drops to 1085℃, let it stand for 25 minutes to homogenize.

[0040] (2) The alloy melt after static homogenization is subjected to rapid cooling modification treatment by a rapid cooling device at a cooling rate of 500℃ / s, and the resulting semi-solid slurry is collected in a crucible preheated to 1020℃.

[0041] (3) The semi-solid slurry is poured into a mold at a temperature of 550℃ and directly extruded by a forming pressure of 110MPa and an extrusion rate of 22mm / s. After being kept in the mold for 2 minutes, it is taken out and quickly oil-cooled for 5-6 minutes to obtain a lead-tin bronze casting.

[0042] (4) The lead-tin bronze casting was solution treated at 600℃ for 20h, and then aged at 200℃ for 6h to obtain a high-strength and high-plasticity CuSn10Pb2Ni3 alloy.

[0043] The CuSn10Pb2Ni3 alloy prepared in this embodiment was observed, and the results are as follows: Figure 2 As shown. The stress-strain curve of the alloy prepared in this embodiment was obtained by testing as follows. Figure 7 As shown.

[0044] pass Figure 2 It can be seen that the lead-tin bronze alloy prepared in this embodiment has fine grains, the microstructure is transformed into equiaxed crystals, and the intergranular phases are significantly reduced, which is beneficial to improving the plasticity of the alloy.

[0045] Example 2

[0046] (1) Weigh 3 kg of CuSn10Pb2Ni3 alloy block and heat it in a medium frequency induction furnace at a melting temperature of 1240℃. At the same time, add 0.03 kg of CuP14 to the melt for deoxidation, degassing and slag removal until the surface of the melt is smooth and mirror-like. After the temperature of the alloy melt drops to 1075℃, let it stand for 30 min to homogenize.

[0047] (2) The alloy melt after static homogenization is subjected to rapid cooling modification treatment by a rapid cooling device at a cooling rate of 550℃ / s, and the resulting semi-solid slurry is collected in a crucible preheated to 1020℃.

[0048] (3) The semi-solid slurry is poured into a mold at a temperature of 570℃ and directly extruded by a forming pressure of 130MPa and an extrusion rate of 20mm / s. After being kept in the mold for 3 minutes, it is taken out and quickly oil-cooled for 5-6 minutes to obtain a lead-tin bronze casting.

[0049] (4) The lead-tin bronze casting was solution treated at 600℃ for 16h, and then aged at 160℃ for 8h to obtain a high-strength and high-plasticity CuSn10Pb2Ni3 alloy.

[0050] The CuSn10Pb2Ni3 alloy prepared in this embodiment was observed, and the results are as follows: Figure 3 As shown. The stress-strain curve of the alloy prepared in this embodiment was obtained by testing as follows. Figure 7 As shown.

[0051] pass Figure 3It can be seen that, compared with Example 1, the high-strength and high-plasticity CuSn10Pb2Ni3 alloy prepared in this embodiment has a further reduced content of intergranular hard and brittle phases and a more uniform microstructure, which is beneficial to further improving the strength and plasticity of the alloy.

[0052] Example 3

[0053] (1) Weigh 3 kg of CuSn10Pb2Ni3 alloy block and heat it in a medium frequency induction furnace at a melting temperature of 1250℃. At the same time, add 0.03 kg of CuP14 to the melt for deoxidation, degassing and slag removal until the surface of the melt is smooth and mirror-like. After the temperature of the alloy melt drops to 1065℃, let it stand for 30 min to homogenize.

[0054] (2) The alloy melt after static homogenization is subjected to rapid cooling modification treatment by a rapid cooling device at a cooling rate of 600℃ / s, and the resulting semi-solid slurry is collected in a crucible preheated to 1020℃.

[0055] (3) The semi-solid slurry is poured into a mold at a temperature of 580℃ and directly extruded by a forming pressure of 150MPa and an extrusion rate of 22mm / s. After being kept in the mold for 3 minutes, it is taken out and quickly oil-cooled for 5-6 minutes to obtain a lead-tin bronze casting.

[0056] (4) The lead-tin bronze casting was solution treated at 580℃ for 16h, and then aged at 180℃ for 6h to obtain a high-strength and high-plasticity CuSn10Pb2Ni3 alloy.

[0057] The CuSn10Pb2Ni3 alloy prepared in this embodiment was observed, and the results are as follows: Figure 4 As shown. The stress-strain curve of the alloy prepared in this embodiment was obtained by testing as follows. Figure 7 As shown.

[0058] pass Figure 4 It can be seen that the high-strength and high-plasticity CuSn10Pb2Ni3 alloy prepared in this embodiment has fewer and more uniformly distributed intergranular hard and brittle phases, and the grain size is also relatively small, which is conducive to improving the alloy deformation synergy and maximizing the strength and plasticity of the alloy.

[0059] from Figure 4 It can be observed that when the mold preheating temperature is 580℃, there are fewer and more uniformly distributed hard and brittle phases between grains, and the grain size is also relatively small. This is beneficial for improving the alloy's deformation synergy and maximizing its strength and plasticity. At this temperature, the strength and plasticity are optimal. Figure 7 As shown.

[0060] Example 4

[0061] (1) Weigh 3 kg of CuSn10Pb2Ni3 alloy block and heat it in a medium frequency induction furnace at a melting temperature of 1200℃. At the same time, add 0.03 kg of CuP14 to the melt for deoxidation, degassing and slag removal until the surface of the melt is mirror-like. After the temperature of the alloy melt drops to 1065℃, let it stand for 28 minutes to homogenize.

[0062] (2) The alloy melt after static homogenization is subjected to rapid cooling modification treatment by a rapid cooling device at a cooling rate of 600℃ / s, and the resulting semi-solid slurry is collected in a crucible preheated to 1020℃.

[0063] (3) The semi-solid slurry is poured into a mold at a temperature of 600℃ and directly extruded by a forming pressure of 150MPa and an extrusion rate of 24mm / s. After being kept in the mold for 1 minute, it is taken out and quickly oil-cooled for 5-6 minutes to obtain a lead-tin bronze casting.

[0064] (4) The lead-tin bronze casting was solution treated at 650℃ for 18h, and then aged at 180℃ for 7h to obtain a high-strength and high-plasticity CuSn10Pb2Ni3 alloy.

[0065] The CuSn10Pb2Ni3 alloy prepared in this embodiment was observed, and the results are as follows: Figure 5 As shown. The stress-strain curve of the alloy prepared in this embodiment was obtained by testing as follows. Figure 7 As shown.

[0066] pass Figure 5 It can be seen that the alloy prepared in this embodiment has an increased content of hard and brittle phases between grains and an increased grain size. Compared with Example 3, the alloy performance will be slightly reduced. Therefore, in the preparation method of the present invention, parameter control affects the alloy performance. The parameter range in the preparation method of the present invention is relatively reasonable and can play a good role in improving the alloy performance.

[0067] Comparative Example

[0068] This comparative example uses the same method as Example 3 to treat the lead-tin bronze alloy, the difference being that: in this comparative example, no rapid cooling modification was performed, and the alloy melt after being allowed to stand and homogenize was directly poured into the mold.

[0069] The CuSn10Pb2Ni3 alloy prepared in this embodiment was observed, and the results are as follows: Figure 6 As shown. The stress-strain curve of the alloy prepared in this embodiment was obtained by testing as follows. Figure 7 As shown.

[0070] pass Figure 6It can be seen that the alloy prepared in this embodiment has a coarse microstructure, mainly dendritic structure, with high content of hard and brittle intergranular phases connected in sheets. During tensile deformation, the hard and brittle phases are prone to cracking, which expands the tendency of crack extension, cuts the matrix, and reduces the strength and plasticity of the alloy.

[0071] pass Figure 7 It can be seen that the alloy prepared in Example 3 of this invention has the best strength and ductility. Furthermore, compared with the comparative alloy, the alloy in Example 3 shows a 40.3% increase in strength and a 228% increase in ductility. Therefore, the preparation method of this invention can significantly improve the strength and ductility of lead-tin bronze alloys.

[0072] In conclusion, rapid quenching modification of the melt, combined with appropriate high mold temperature and reasonable process parameters, can significantly improve the strength and plasticity of lead-tin bronze alloys.

[0073] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a high-strength, high-ductility lead-tin bronze alloy, characterized in that: The preparation method includes the following steps: (1) The lead-tin bronze alloy is induction heated and melted and deoxidized, degassed and slag removed. After the surface of the alloy melt is peeled open and becomes mirror-like, the alloy melt is allowed to stand still to homogenize. (2) The alloy melt after static homogenization in step (1) is subjected to rapid cooling modification treatment to obtain a semi-solid slurry; (3) The semi-solid slurry obtained in step (2) is poured into a preheated mold and extruded into shape. After extrusion, the casting is kept in the mold for a certain period of time and then quickly oil-cooled to room temperature to obtain lead-tin bronze casting. (4) Solution treatment and aging treatment are performed on lead-tin bronze castings to obtain high-strength and high-plasticity lead-tin bronze alloy; In step (4), the solution treatment temperature is 580℃. The solution treatment is carried out at 650℃ for 16-20 hours. After the solution treatment, an aging treatment is performed at 160-200℃ for 6-8 hours.

2. The preparation method according to claim 1, characterized in that: In step (1), the melting temperature of the lead-tin bronze alloy is 1200℃~1250℃.

3. The preparation method according to claim 1, characterized in that: In step (1), 1% CuP14 by mass of the alloy melt is added to the alloy melt for deoxidation, degassing and slag removal treatment.

4. The preparation method according to claim 1, characterized in that: In step (1), the static homogenization temperature is 1065℃~1085℃, and the holding time is 25~30min.

5. The preparation method according to claim 1, characterized in that: In step (2), the cooling rate of the quenching is ≥500℃ / s.

6. The preparation method according to claim 1, characterized in that: In step (3), the forming pressure of extrusion molding is 110MPa~150MPa, and the extrusion speed is 20mm / s~24mm / s.

7. The preparation method according to claim 1, characterized in that: In step (3), the mold preheating temperature is 550℃~600℃.

8. The preparation method according to claim 1, characterized in that: In step (3), after extrusion molding, the casting is kept at 550℃~600℃ in a mold for 1~3 minutes, and then cooled to room temperature in oil for 5-6 minutes.

9. A high-strength, high-ductility lead-tin bronze alloy, characterized in that: The high-strength, high-ductility lead-tin bronze alloy is prepared by the preparation method described in any one of claims 1-8.

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