A copper-nickel-tin-phosphorus-copper alloy resistant to high-temperature softening and its preparation process

Abstract

The invention discloses a copper-nickel-tin-phosphorus-copper alloy resistant to high-temperature softening and a preparation process thereof, relating to the technical field of alloy preparation. The invention comprises the following steps: placing various raw materials in a melting furnace for smelting and then casting; then placing the raw materials in a vacuum aging furnace after rolling treatment, and applying an electric field to perform dynamic aging treatment while performing the aging treatment; then placing the raw materials in an annealing furnace, and placing an electric field applying device in the annealing furnace, first preheating the alloy in the annealing furnace, then activating and controlling the electric field to perform auxiliary annealing, then cooling the alloy and turning off the electric field during the cooling process to achieve migration of tin ions and phosphorus ions along electric field lines in the electric field, forming and retaining a composite precipitated phase, and then performing electrolytic polishing and vacuum coating to obtain the copper-nickel-tin-phosphorus-copper alloy resistant to high-temperature softening; applying different electric field assistances during the aging treatment and annealing treatment respectively, so as to reduce the time required for preparation while improving the high-temperature softening resistance of the copper-nickel-tin-phosphorus-copper alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy preparation, in particular to a high-temperature softening-resistant copper-nickel-tin-phosphorus-copper alloy and a preparation process thereof. Background Art

[0002] Copper-nickel-tin-phosphorus alloy has many advantages such as high strength, high hardness, high elasticity, strong resistance to thermal stress relaxation, stable conductivity, solderability, plateability, and non-toxicity and environmental protection. It is widely used in the manufacture of large lead frame materials and connector materials for electronic appliances.

[0003] In recent years, with the development of the electronics industry, various electronic devices have been moving towards miniaturization, thinning, and lightweighting. The reduction in weight and the high degree of integration of the devices used in them have led to the miniaturization, lightweighting, and high performance of electronic components. At the same time, higher requirements have been placed on the performance of structural parts, requiring the materials used to manufacture parts to meet performance requirements such as strength, conductivity, and bending. More importantly, with the miniaturization and centralization of electronic components, the accompanying heat generation problem cannot be ignored. Therefore, improving the resistance to high-temperature softening is of great significance to the future development of electronic devices. Summary of the Invention

[0004] The object of the present invention is to provide a copper-nickel-tin-phosphorus-copper alloy resistant to high-temperature softening and a preparation process to at least partially solve the above-mentioned problems.

[0005] To achieve the above object, the present invention provides the following technical solution: a copper-nickel-tin-phosphorus-copper alloy resistant to high temperature softening and a preparation process thereof, comprising the following steps:

[0006] Copper, nickel, tin, phosphorus and trace additives are placed in a furnace for smelting and then cast to obtain an alloy ingot;

[0007] The alloy ingot is placed in a vacuum aging furnace after rolling, and a pulse generator is set to apply an electric field to perform dynamic aging treatment while performing aging treatment to obtain a pre-annealed alloy;

[0008] The pre-annealed alloy is placed in an annealing furnace, and an electric field applying device is placed in the annealing furnace. The alloy is first preheated in the annealing furnace, and then the electric field is activated and controlled to perform auxiliary annealing. The alloy is then cooled and the electric field is turned off during the cooling process, so that tin ions and phosphorus ions migrate along the electric field lines in the electric field, are enriched at the grain boundaries, and a composite precipitate phase is formed and retained, thereby obtaining a pre-finished alloy.

[0009] The pre-finished alloy is electrolytically polished and vacuum-coated to obtain a high-temperature softening-resistant copper-nickel-tin-phosphorus-copper alloy.

[0010] Furthermore, the dynamic aging treatment is carried out at a temperature of 360-400° C., an electric field strength of 800-1200 V / cm, an electric field frequency of 20-50 Hz, and an aging treatment time of 30-60 min.

[0011] Furthermore, the electric field applying device uses a DC pulse with a pulse width of 10 ms. The electric field applying device uses a parallel plate electrode, the electrode is in direct contact with the alloy ingot, and the surface of the electrode is coated with a graphite layer.

[0012] Furthermore, after the pre-annealed alloy is placed in an annealing furnace, vacuum treatment and mixed gas are sequentially performed, and then the annealing furnace is preheated at a rate of 10°C / s. When the temperature in the annealing furnace rises to 550-600°C, the electric field applying device is activated and the electric field is controlled to perform auxiliary annealing.

[0013] Furthermore, after the electric field applying device is activated, the intensity of the applied alternating electric field is 500 V / cm, the frequency of the alternating electric field is 1000 Hz, the auxiliary annealing time is 10-15 minutes, and the switching period of the electric field direction is 30 seconds.

[0014] Furthermore, after the auxiliary annealing is completed, the surface is cooled to 300° C. at a rate of 5-10° C. / s, the electric field applying device is turned off, and then the surface is water-cooled to room temperature.

[0015] Furthermore, the electrolyte in the electrolytic polishing is a phosphoric acid-ethanol solution, the voltage during the electrolysis process is 12V, and the electrolysis time is 3min;

[0016] After electrolysis, a titanium nitride protective layer is coated on the surface of the alloy by vacuum coating, and the thickness of the protective layer is 1-2 μm.

[0017] Furthermore, the mass percentages of copper, nickel, tin, phosphorus and trace additives are: ≥96.1% copper, 0.7-0.9% nickel, 1.0-1.5% tin, 0.03-0.06% phosphorus and ≤0.06% trace additives

[0018] The trace additives include silicon and iron, and the mass percentages thereof are respectively: less than 0.01% silicon and less than 0.05% iron.

[0019] Furthermore, during the smelting process, copper and nickel are first melted, and after the temperature reaches 1150° C., tin and phosphorus elements are added, and then the melt is electromagnetically stirred at a frequency of 50 Hz for 10 minutes.

[0020] On the other hand, the present invention also provides a copper-nickel-tin-phosphorus-copper alloy resistant to high-temperature softening, which is prepared according to the above preparation method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention applies different electric field assistance during the aging treatment and annealing treatment, thereby reducing the time required for preparation and improving the high-temperature softening resistance of the copper-nickel-tin-phosphorus-copper alloy. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0024] An embodiment of the present invention provides a high-temperature softening-resistant copper-nickel-tin-phosphorus-copper alloy and a preparation process thereof, comprising the following steps:

[0025] Copper, nickel, tin, phosphorus and trace additives are placed in a furnace for smelting and then cast to obtain an alloy ingot;

[0026] The alloy ingot is placed in a vacuum aging furnace after rolling, and a pulse generator is set to apply an electric field to perform dynamic aging treatment while performing aging treatment to obtain a pre-annealed alloy;

[0027] The pre-annealed alloy is placed in an annealing furnace, and an electric field applying device is placed in the annealing furnace. The alloy is first preheated in the annealing furnace, and then the electric field is activated and controlled to perform auxiliary annealing. The alloy is then cooled and the electric field is turned off during the cooling process, so that tin ions and phosphorus ions migrate along the electric field lines in the electric field, are enriched at the grain boundaries, and a composite precipitate phase is formed and retained, thereby obtaining a pre-finished alloy.

[0028] The pre-finished alloy is electrolytically polished and vacuum-coated to obtain a high-temperature softening-resistant copper-nickel-tin-phosphorus-copper alloy.

[0029] It should be noted that the above-mentioned rolling treatment includes hot rolling, cold rolling and intermediate annealing. The heating temperature in the hot rolling process is 900°C, the holding time is 2h, and the total deformation is ≥85% through multiple rolling passes. The final rolling temperature is ≥600°C to obtain a hot-rolled plate with a thickness of 2-3mm. Hot rolling is dominated by dynamic recrystallization at high temperature. The coarse cast structure is broken by multiple rolling passes to form uniform recrystallized grains; the cold rolling process is completed in 4-6 passes, and the deformation of each pass is ≤25%. The total deformation of cold rolling to 0.5mm thickness is 75-80%. Cold rolling introduces high-density dislocations and deformation twins, and the stored deformation energy provides driving force for subsequent aging precipitation; intermediate annealing is carried out between hot rolling and cold rolling. During the intermediate annealing process, the temperature is 450°C and nitrogen protection annealing is performed for 1h to eliminate work hardening.

[0030] In a further embodiment of this embodiment, the dynamic aging treatment is as follows: the temperature is 360-400 ° C, the electric field strength is 800-1200 V / cm, the electric field frequency is 20-50 Hz, and the aging treatment time is 30-60 min; at 360-400 ° C, the Ni, Sn, and P atoms in the supersaturated solid solution form GP zones through short-range diffusion, which serve as precipitation phase precursors; the electric field drives the solute atoms (such as Sn 2+ 、P 3- ) migrate along the direction of the electric field, inducing the precipitated phase (such as Cu3P, Ni3Sn) to migrate along the <110> The crystal directions are preferentially arranged to form a directional strengthening network; the periodic electric field changes break the stability of the solute atomic clusters and promote the uniform nucleation of the nano-precipitated phase; if the electric field intensity is too high, it will lead to excessive local current density, causing arc discharge, ablating the alloy surface, and forming a stress concentration source.

[0031] In a further implementation of this embodiment, the electric field applying device uses a DC pulse with a pulse width of 10ms, and the electric field applying device uses a parallel plate electrode. The electrode is in direct contact with the alloy ingot, and the surface of the electrode is coated with a graphite layer; wherein the direction of the electric field is parallel to the rolling direction, and the induced precipitated phase is preferentially arranged along the grain boundary, and the electrode contact surface is coated with a graphite layer with a thickness of 0.1mm to prevent oxidation of the alloy surface and arc discharge.

[0032] In a further implementation of this embodiment, after the pre-annealed alloy is placed in an annealing furnace, vacuum treatment and mixed gas are sequentially performed, and then the annealing furnace is preheated at 10°C / s. When the temperature in the annealing furnace rises to 550-600°C, the electric field applying device is activated and the electric field is controlled to perform auxiliary annealing; at 550-600°C, the stored energy is released, dislocations are rearranged to form recrystallized nuclei, and the alternating electric field reduces the activation energy of grain boundary migration, thereby promoting rapid grain growth to 5-10μm.

[0033] In a further implementation of this embodiment, after the electric field applying device is activated, the intensity of the applied alternating electric field is 500 V / cm, the frequency of the alternating electric field is 1000 Hz, the auxiliary annealing time is 10-15 min, and the switching period of the electric field direction is 30 s; by periodically reversing the direction of the electric field, the diffusion barrier of Sn / P atoms at the grain boundary is broken, the grain boundary composition is homogenized, and the Sn segregation degree is reduced from 8 at.% to 5 at.%.

[0034] Through electric field induction, the proportion of large-angle grain boundaries >15° is increased to 70%. Large-angle grain boundaries can effectively pin dislocations and inhibit grain boundary sliding at high temperatures. The electric field directional control makes the precipitated phases distributed in chains along the grain boundaries with a spacing of 20-50nm. Dislocations need to cut multiple precipitated phases at the same time, and the strengthening effect is improved by 40%.

[0035] In a further implementation of this embodiment, after the auxiliary annealing is completed, the material is cooled to 300°C at a rate of 5-10°C / s, the electric field application device is turned off, and then water-cooled to room temperature; the coarsening of the precipitated phase is suppressed and the nano-scale strengthening phase is retained. If the cooling rate is insufficient during the water cooling process, the Cu3P phase may coarsen to >100nm, the dislocation bypass mechanism will dominate, and the anti-softening temperature will be reduced to below 400°C.

[0036] In a further embodiment of this example, the electrolyte in the electrolytic polishing is a phosphoric acid-ethanol solution, the voltage during the electrolysis process is 12 V, and the electrolysis time is 3 min;

[0037] After electrolysis, a titanium nitride protective layer is coated on the alloy surface by vacuum coating, and the thickness of the protective layer is 1-2μm; the surface oxide is selectively dissolved by electrolysis, and the dissolution rate of Cu is greater than Sn when the voltage is 12V, obtaining a smooth surface with Ra<0.1μm and improving the adhesion of the coating; a 1-2μm thick TiN layer is formed by physical vapor deposition, and a dense TiO2 oxide film is generated at high temperature to block oxygen diffusion. The coating thickness should not be too thick, otherwise the internal stress accumulation will cause the coating to peel off and the high-temperature oxidation resistance will fail. Correspondingly, if it is too thin, it cannot achieve the purpose of blocking oxygen diffusion.

[0038] In a further embodiment of this embodiment, the mass percentages of copper, nickel, tin, phosphorus and trace additives are: ≥96.1% copper, 0.7-0.9% nickel, 1.0-1.5% tin, 0.03-0.06% phosphorus and ≤0.06% trace additives

[0039] The trace additives include silicon and iron, and the mass percentages thereof are respectively: less than 0.01% silicon and less than 0.05% iron.

[0040] In a further embodiment of this embodiment, during the smelting process, copper and nickel are first melted, tin and phosphorus are added after the temperature reaches 1150°C, and then the melt is electromagnetically stirred at a frequency of 50 Hz for 10 minutes; it should be noted that the entire smelting is in a vacuum environment, and in a vacuum (≤10 -3 Smelting in a low-pressure (Pa) environment prevents active metals such as Cu and Sn from reacting with oxygen to form oxides (such as Cu2O and SnO2), ensuring alloy purity. The alternating magnetic field can induce eddy currents inside the melt, generating Lorentz force to drive the melt flow and eliminate component segregation. Rapid cooling can inhibit dendrite growth, form fine equiaxed crystals (grain size ≤ 50μm), and reduce casting defects.

[0041] Example 1

[0042] The raw materials are weighed to have a mass percentage of ≥96.1% copper, 0.8% nickel, 1.3% tin, 0.05% phosphorus, <0.01% silicon and <0.05% iron.

[0043] Copper and nickel are added to a vacuum induction furnace, first vacuumed and then heated to melt. After the temperature reaches 1150°C, tin and phosphorus are added. Electromagnetic stirring is performed at a frequency of 50 Hz for 10 minutes. After smelting, the ingots are cast into water-cooled copper molds at a cooling rate of 100°C / s to suppress tin segregation.

[0044] The alloy ingot is heated to 900°C and kept warm for 2 hours for multiple rolling passes with a total rolling deformation of 88%. The final rolling temperature is 650°C to obtain a 3mm thick hot-rolled plate. The hot-rolled plate is placed under nitrogen protection at 450°C for 1 hour to eliminate work hardening; then 5 cold rolling passes are performed with a deformation of ≤25% in each pass to obtain a 0.5mm thick rolled plate, whose total deformation relative to the hot-rolled plate is 78%.

[0045] The rolled plate was placed in vacuum aging at a temperature of 380°C, an electric field strength of 800V / cm, and an electric field frequency of 50Hz for 40min.

[0046] The rolled plate after aging treatment is placed in an air cushion continuous annealing furnace, and the air cushion continuous annealing furnace is equipped with an optional superconducting magnet and an integrated electric field application module. The electrode spacing is adjustable (50-200mm), and vacuum treatment is carried out and a 95% N2+5% H2 mixed gas is introduced to inhibit oxidation. The temperature is raised to 560°C at a rate of 10°C / s in the preheating stage to activate the electric field. An alternating electric field is applied with a frequency of 1kHz and a field strength of 500V / cm for 10 minutes. The direction of the electric field is switched periodically every 30 seconds to break the grain boundary diffusion barrier; the plate is cooled to 300°C at a rate of 8°C / s, the electric field is turned off, and the plate is subsequently water-cooled with a cooling rate of >100°C / s to retain the nano-precipitated phase.

[0047] The surface oxide layer was removed by electrolysis with a phosphoric acid-ethanol solution at a voltage of 12V for 3 minutes, and then a 1μm thick titanium nitride protective film was vacuum-plated to improve high-temperature oxidation resistance.

[0048] Example 2

[0049] The difference from Example 1 is that the rolled plate is placed in vacuum aging and treated for 40 minutes at a temperature of 380° C., an electric field strength of 900 V / cm, and an electric field frequency of 50 Hz.

[0050] Example 3

[0051] The difference from Example 1 is that the rolled plate is placed in vacuum aging and treated for 40 minutes at a temperature of 380° C., an electric field strength of 1000 V / cm, and an electric field frequency of 50 Hz.

[0052] Example 4

[0053] The difference from Example 1 is that the rolled plate is placed in vacuum aging and treated for 40 minutes at a temperature of 380° C., an electric field strength of 1100 V / cm, and an electric field frequency of 50 Hz.

[0054] Example 5

[0055] The difference from Example 1 is that the rolled plate is placed in vacuum aging and treated for 40 minutes at a temperature of 380° C., an electric field strength of 1200 V / cm, and an electric field frequency of 50 Hz.

[0056] Example 6

[0057] The difference from Example 3 is that the temperature is raised to 560° C. at a rate of 10° C. / s during the preheating stage to activate the electric field, and an alternating electric field is applied with a frequency of 1 kHz and a field strength of 500 V / cm for 11 minutes.

[0058] Example 7

[0059] The difference from Example 3 is that the temperature is raised to 560° C. at a rate of 10° C. / s during the preheating stage to activate the electric field, and an alternating electric field is applied with a frequency of 1 kHz and a field strength of 500 V / cm for 12 minutes.

[0060] Example 8

[0061] The difference from Example 3 is that the temperature is raised to 560° C. at a rate of 10° C. / s during the preheating stage to activate the electric field, and an alternating electric field is applied with a frequency of 1 kHz and a field strength of 500 V / cm for 13 minutes.

[0062] Example 9

[0063] The difference from Example 3 is that the temperature is raised to 560° C. at a rate of 10° C. / s during the preheating stage to activate the electric field, and an alternating electric field is applied with a frequency of 1 kHz and a field strength of 500 V / cm for 14 minutes.

[0064] Example 10

[0065] The difference from Example 3 is that the temperature is raised to 560° C. at a rate of 10° C. / s during the preheating stage to activate the electric field, and an alternating electric field is applied with a frequency of 1 kHz and a field strength of 500 V / cm for 15 minutes.

[0066] Comparative Example 1

[0067] The mass percentages are ≥96.1% copper, 0.8% nickel, 1.3% tin, 0.05% phosphorus, <0.01% silicon and <0.05%.

[0068] Copper and nickel are added to a vacuum induction furnace, first vacuumed and then heated to melt. After the temperature reaches 1150°C, tin and phosphorus are added. Electromagnetic stirring is performed at a frequency of 50 Hz for 10 minutes. After smelting, the ingots are cast into water-cooled copper molds at a cooling rate of 100°C / s to suppress tin segregation.

[0069] The alloy ingot is heated to 900°C and kept warm for 2 hours for multiple rolling passes with a total rolling deformation of 88%. The final rolling temperature is 650°C to obtain a 3mm thick hot-rolled plate. The hot-rolled plate is placed under nitrogen protection at 450°C for 1 hour to eliminate work hardening; then 5 cold rolling passes are performed with a deformation of ≤25% in each pass to obtain a 0.5mm thick rolled plate, whose total deformation relative to the hot-rolled plate is 78%.

[0070] The rolled plate was placed in vacuum aging at a temperature of 380°C for 3 hours.

[0071] The treated rolled plate is placed in an air cushion continuous annealing furnace, vacuumed and introduced with a 95% N2+5% H2 mixed gas to inhibit oxidation. The temperature is raised to 560°C at a rate of 10°C / s for 10-15 minutes during the preheating stage; the temperature is cooled to 300°C at a rate of 5-10°C / s, and subsequently water-cooled at a cooling rate of >100°C / s to retain the nano-precipitated phase.

[0072] The surface oxide layer was removed by electrolysis with a phosphoric acid-ethanol solution at a voltage of 12V for 3 minutes, and then a 1μm thick titanium nitride protective film was vacuum-plated to improve high-temperature oxidation resistance.

[0073] Comparative Example 2

[0074] The mass percentages are ≥96.1% copper, 0.8% nickel, 1.3% tin, 0.05% phosphorus, <0.01% silicon and <0.05%.

[0075] Copper and nickel are added to a vacuum induction furnace, first vacuumed and then heated to melt. After the temperature reaches 1150°C, tin and phosphorus are added. Electromagnetic stirring is performed at a frequency of 50 Hz for 10 minutes. After smelting, the ingots are cast into water-cooled copper molds at a cooling rate of 100°C / s to suppress tin segregation.

[0076] The alloy ingot is heated to 900°C and kept warm for 2 hours for multiple rolling passes with a total rolling deformation of 88%. The final rolling temperature is 650°C to obtain a 3mm thick hot-rolled plate. The hot-rolled plate is placed under nitrogen protection at 450°C for 1 hour to eliminate work hardening; then 5 cold rolling passes are performed with a deformation of ≤25% in each pass to obtain a 0.5mm thick rolled plate, whose total deformation relative to the hot-rolled plate is 78%.

[0077] The rolled plate was placed in vacuum aging at a temperature of 380°C, an electric field strength of 1000 V / cm, and an electric field frequency of 50 Hz for 40 minutes.

[0078] The treated rolled plate is placed in an air cushion continuous annealing furnace, vacuumed and introduced with a 95% N2+5% H2 mixed gas to inhibit oxidation. The temperature is raised to 560°C at a rate of 10°C / s for 3 hours during the preheating stage; cooled to 300°C at a rate of 5-10°C / s, and subsequently water-cooled at a cooling rate of >100°C / s to retain the nano-precipitated phase.

[0079] The surface oxide layer is removed by electrolysis with phosphoric acid-ethanol solution at a voltage of 12V for 3 minutes, and then a 1μm thick titanium nitride protective film is vacuum-plated to improve high-temperature oxidation resistance.

[0080] Comparative Example 3

[0081] The mass percentages are ≥96.1% copper, 0.8% nickel, 1.3% tin, 0.05% phosphorus, <0.01% silicon and <0.05%.

[0082] Copper and nickel are added to a vacuum induction furnace, first vacuumed and then heated to melt. After the temperature reaches 1150°C, tin and phosphorus are added. Electromagnetic stirring is performed at a frequency of 50 Hz for 10 minutes. After smelting, the ingots are cast into water-cooled copper molds at a cooling rate of 100°C / s to suppress tin segregation.

[0083] The alloy ingot is heated to 900°C and kept warm for 2 hours for multiple rolling passes with a total rolling deformation of 88%. The final rolling temperature is 650°C to obtain a 3mm thick hot-rolled plate. The hot-rolled plate is placed under nitrogen protection at 450°C for 1 hour to eliminate work hardening; then 5 cold rolling passes are performed with a deformation of ≤25% in each pass to obtain a 0.5mm thick rolled plate, whose total deformation relative to the hot-rolled plate is 78%.

[0084] The rolled plate was placed in vacuum aging at a temperature of 380°C for 2 hours.

[0085] The treated rolled plate is placed in an air cushion continuous annealing furnace, and the air cushion continuous annealing furnace is equipped with an optional superconducting magnet and an integrated electric field application module. The electrode spacing is adjustable (50-200mm), and vacuum treatment is carried out and a 95% N2+5% H2 mixed gas is introduced to inhibit oxidation. The temperature is raised to 560°C at a rate of 10°C / s in the preheating stage to activate the electric field. An alternating electric field is applied with a frequency of 1kHz and a field strength of 500V / cm for 10-15 minutes. The direction of the electric field is switched periodically every 30 seconds to break the grain boundary diffusion barrier; the plate is cooled to 300°C at a rate of 5-10°C / s, the electric field is turned off, and the plate is subsequently water-cooled with a cooling rate of >100°C / s to retain the nano-precipitated phase.

[0086] The surface oxide layer was removed by electrolysis with a phosphoric acid-ethanol solution at a voltage of 12V for 3 minutes, and then a 1μm thick titanium nitride protective film was vacuum-plated to improve high-temperature oxidation resistance.

[0087] The copper-nickel-tin-phosphorus alloys prepared in Examples 1 to 10 and the copper-nickel-tin-phosphorus alloys prepared in Comparative Examples 1 to 3 were sampled, and tensile strength, yield strength, elongation, hardness, conductivity, high-temperature softening resistance, and Vickers hardness tests were performed. The samples were heated at 500° C. for 5 minutes and then subjected to a Vickers hardness test. The Vickers hardness measured after heating was compared with the Vickers hardness measured before heating to obtain a hardness retention percentage to indicate the high-temperature softening resistance of the alloy. The test results are shown in Tables 1 to 3 below.

[0088] Table 1

[0089]

[0090] Table 2

[0091]

[0092] Table 3

[0093] Example 8 Comparative Example 1 Comparative Example 2 Comparative Example 3 tensile strength 578MPa 546MPa 549MPa 551MPa Yield strength 553MPa 507MPa 518MPa 523MPa Elongation 8.6％ 6.5％ 7.1％ 7.4％ Electrical conductivity 39.8％ 37.7％ 38.1％ 38.2％ Hardness retention percentage 94％ 83％ 92％ 91％

[0094] It can be seen from Table 1 and Table 2 above that Example 7 and Example 8 are the best implementation methods.

[0095] As can be seen from Table 3 above, by comparing the test results of Example 8 with those of Comparative Example 1, it can be seen that by applying different electric field assistance during the aging treatment and annealing treatment, the high-temperature softening resistance of the alloy can be greatly improved on the basis of improving the basic properties of the alloy. By comparing Comparative Example 1 with Comparative Example 2 and Comparative Example 3, it can be seen that the high-temperature softening resistance of the alloy can be improved by assisting with the corresponding electric field during the aging treatment and the annealing treatment. Compared with the existing technology, the corresponding electric field assistance can greatly save the process time and save a lot of costs.

[0096] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A process for preparing a copper-nickel-tin-phosphorus-copper alloy resistant to high temperature softening, characterized in that: The following steps are involved: Copper, nickel, tin, phosphorus and trace additives are placed in a furnace for smelting and then cast to obtain an alloy ingot; The alloy ingot is placed in a vacuum aging furnace after rolling, and a pulse generator is set to apply an electric field to perform dynamic aging treatment while performing aging treatment to obtain a pre-annealed alloy; The pre-annealed alloy is placed in an annealing furnace, and an electric field applying device is placed in the annealing furnace. The alloy is first preheated in the annealing furnace, and then the electric field is activated and controlled to perform auxiliary annealing. The alloy is then cooled and the electric field is turned off during the cooling process, so that tin ions and phosphorus ions migrate along the electric field lines in the electric field, are enriched at the grain boundaries, and a composite precipitate phase is formed and retained, thereby obtaining a pre-finished alloy. The pre-finished alloy is electrolytically polished and vacuum-coated to obtain a high-temperature softening-resistant copper-nickel-tin-phosphorus-copper alloy; The dynamic aging treatment is performed at a temperature of 360-400°C, an electric field strength of 800-1200 V / cm, an electric field frequency of 20-50 Hz, and an aging treatment time of 30-60 min. After the electric field applying device is activated, the intensity of the applied alternating electric field is 500 V / cm, the frequency of the alternating electric field is 1000 Hz, the auxiliary annealing time is 10-15 minutes, and the switching period of the electric field direction is 30 seconds.

2. The preparation process of the high temperature softening resistant copper-nickel-tin-phosphorus-copper alloy according to claim 1, characterized in that: The electric field applying device uses a DC pulse with a pulse width of 10ms. The electric field applying device uses a parallel plate electrode. The electrode is in direct contact with the alloy ingot, and a graphite layer is coated on the surface of the electrode.

3. The preparation process of the high temperature softening resistant copper-nickel-tin-phosphorus-copper alloy according to claim 1, characterized in that: After the pre-annealed alloy is placed in the annealing furnace, vacuum treatment and mixed gas are carried out in sequence, and then the annealing furnace is preheated at 10°C / s. When the temperature in the annealing furnace rises to 550-600°C, the electric field application device is activated and the electric field is controlled to perform auxiliary annealing.

4. The preparation process of the high temperature softening resistant copper-nickel-tin-phosphorus-copper alloy according to claim 1, characterized in that: After the auxiliary annealing is completed, the substrate is cooled to 300°C at a rate of 5-10°C / s, the electric field applying device is turned off, and then the substrate is water-cooled to room temperature.

5. The preparation process of the high temperature softening resistant copper-nickel-tin-phosphorus-copper alloy according to claim 1, characterized in that: The electrolyte in the electrolytic polishing is a phosphoric acid-ethanol solution, the voltage during the electrolysis process is 12V, and the electrolysis time is 3min; After electrolysis, a titanium nitride protective layer is coated on the surface of the alloy by vacuum coating, and the thickness of the protective layer is 1-2 μm.

6. The process for preparing the high temperature softening resistant copper-nickel-tin-phosphorus-copper alloy according to claim 1, characterized in that: The mass percentages of the copper, nickel, tin, phosphorus and trace additives are: ≥96.1% copper, 0.7-0.9% nickel, 1.0-1.5% tin, 0.03-0.06% phosphorus and ≤0.06% trace additives The trace additives include silicon and iron, and the mass percentages thereof are respectively: less than 0.01% silicon and less than 0.05% iron.

7. The process for preparing the high temperature softening resistant copper-nickel-tin-phosphorus-copper alloy according to claim 1, characterized in that: During the smelting process, copper and nickel are first melted, and after the temperature reaches 1150° C., tin and phosphorus elements are added, and then the melt is electromagnetically stirred at a frequency of 50 Hz for 10 minutes.

8. A copper-nickel-tin-phosphorus-copper alloy resistant to high temperature softening, characterized in that: A copper-nickel-tin-phosphorus-copper alloy resistant to high temperature softening prepared according to any one of claims 1 to 7.

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