A copper-tin alloy target and a preparation method thereof

Abstract

The present invention discloses a copper-tin alloy target and a preparation method thereof, relating to the field of alloy target preparation, aiming to prepare a CuSn alloy target with uniform structure, fine grain size and high density. The key points of the technical solution are as follows: A preparation method of a copper-tin alloy target includes the following steps: S1. Select Cu ingots and Sn ingots as raw materials and conduct weighing and proportioning; S2. Add the weighed Cu ingots and Sn ingots into a melting furnace equipment for melting; S3. Spray-form the molten liquid after melting; S4. Perform hot extrusion on the pre-treated blank; S5. Conduct machining to form. The CuSn alloy target prepared by the copper-tin alloy target and the preparation method thereof of the present invention has uniform structure, fine grains and high density.

Description

Technical Field

[0001] The present invention relates to the field of alloy target preparation, and more specifically, to a copper-tin alloy target and a preparation method thereof. Background Art

[0002] Among copper alloys, copper-tin alloys have high strength, excellent elasticity, good thermal conductivity, corrosion resistance, wear resistance, etc., and are widely used in the fields of electronics and electrical appliances. Copper-tin alloys with different Sn contents are applied in different fields. Copper-tin alloys with Sn content between 3-4wt.% are mainly used for elastic components, wear-resistant parts and anti-magnetic parts. Copper-tin alloys with Sn content between 5-11wt.% are mainly used for bearings, bushings and turbines, etc. At present, Sn-Cu (bronze) deposition materials are of great significance in aspects such as anti-corrosion, decorative surfaces, electronics and tribology. In addition, copper-tin alloys are also applied in fields such as semiconductor lead frames, cable connectors, relays, junction boxes and contact wires. In the Cu-Sn alloy binary phase diagram, there are several phases such as α, β, γ, δ. The α phase is a substitutional solid solution of Sn dissolved in pure copper, belonging to the face-centered cubic structure. The β phase is a solid solution based on the electron compound Cu3Sn. The γ phase is a solid solution based on CuSn. The δ phase is a solid solution based on the electron compound Cu 31 Sn8. According to the Cu-Sn phase diagram, they will form a variety of metal compounds, such as Cu5Sn, Cu3Sn, Cu31Sn8, etc. These compounds are all produced by peritectic reactions and are all incongruently melting compound phases. The liquid structure of the Cu-Sn alloy has obvious micro-inhomogeneity due to Cu3Sn and Cu3Sn-like atomic clusters. According to the equilibrium phase diagram, another phase ε-Cu3Sn existing in the smelted Cu-Sn alloy has a tin content as high as 25at.%; and at a temperature of 500-600°C, the solid solubility limit of Sn in Cu can reach 9.1at.%.

[0003] The Cu-Sn alloy has a wide solid-liquid two-phase region. Using traditional casting methods, it is easy to form segregation, and the alloy composition is uneven. Especially on the bottom and side surfaces of the casting, "tin sweat" increases with the increase of the hydrogen absorption amount. Studies have pointed out that the reverse segregation of tin is actually the movement of tin-rich substances between dendrites, which has a great relationship with the solidification speed of the casting. At the same time, the plasticity and electrical conductivity of the alloy are poor. Traditional cast tin bronzes have a large crystallization temperature range and a slow solidification speed, so they are prone to shrinkage porosity, thus affecting their application in industrial production.

[0004] With the development of heat treatment processes, many preparation methods have emerged, such as vacuum hot pressing sintering, SPS sintering, self-propagating method, etc. However, for two elements with a large difference in melting points, there will always be various problems such as segregation, microstructural inhomogeneity, abnormal grain growth, etc.

[0005] Solving the problems of composition segregation, non-uniform microstructure, and abnormal grain growth in CuSn alloy targets is the key to preparing high-quality CuSn alloy targets. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a copper-tin alloy target and its preparation method, which can solve the problems of composition segregation, non-uniform microstructure, and abnormal grain growth in CuSn alloy targets, so as to prepare a CuSn alloy target with uniform structure, fine grain size, and high density.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions: A preparation method of a copper-tin alloy target, comprising the following steps:

[0008] S1. Select Cu ingots and Sn ingots as raw materials and weigh and proportion them;

[0009] S2. Add the weighed Cu ingots and Sn ingots to a melting furnace equipment for melting;

[0010] S3. Spray-form the molten liquid after melting;

[0011] S4. Hot-extrude the pre-treated blank;

[0012] S5. Perform machining to form.

[0013] The present invention is further configured as: In step S1, weigh and proportion according to a mass ratio of Cu:Sn = 40:60 - 70:30.

[0014] The present invention is further configured as: In step S2, the melting equipment is a vacuum melting furnace.

[0015] The present invention is further configured as: In step S2, the melting parameters are: temperature 700 - 900 °C, heating rate 20 - 50 °C / min, vacuum degree < 10 -2 Pa, stirring speed 30 - 100 r / min, melting time 0.5 - 2 h.

[0016] The present invention is further configured as: In step S3, the spray-forming parameters are: spray atmosphere N2 / Ar gas, spray pressure 2 - 6 MPa, spray nozzle size 0.5 - 4 mm, deposition disk descent speed 0.5 - 2 mm / min, deposition speed 5 - 30 kg / min.

[0017] The present invention is further configured as: In step S4, the hot-extrusion parameters are: blank temperature 350 - 500 °C, extrusion cylinder temperature 300 - 450 °C, extrusion speed 8 - 20 mm / min, extrusion ratio 2:1 - 8:1.

[0018] The present invention is further configured such that: the material of the extrusion cylinder is one of tungsten steel, molybdenum steel or chromium steel.

[0019] The present invention is further configured such that: during the hot extrusion process, a lubricant is used to lubricate the die, reducing the friction between the product and the die.

[0020] The present invention is further configured such that: the lubricant is talcum powder, cubic boron nitride powder or carbon black.

[0021] The present invention also provides a copper-tin alloy target prepared by the above process.

[0022] In summary, the present invention has the following beneficial effects:

[0023] ① The CuSn alloy is prepared by spray forming; compared with the CuSn materials prepared by traditional casting or deformation processes, the CuSn alloy prepared by the present invention has small grains, fine and uniformly distributed precipitated phases, and the chemical composition and structure of the product are effectively controlled macroscopically and microscopically. Therefore, the mechanical properties of the product can be kept isotropic, and the overall performance is significantly improved; compared with the traditional powder metallurgy process, since multiple processes including powder making, powder mixing, pressing and sintering are omitted, the oxygen content and purity in the material can be effectively controlled.

[0024] ② Hot extrusion is used to further densify the spray-formed blank, eliminate the closed pores inside the product, discharge the gas, and further refine the grains of the product and eliminate abnormally grown grains; in addition, the grain arrangement can be made consistent macroscopically, improving the mechanical properties of the product.

[0025] ③ The copper-tin alloy target prepared by the present invention has simple, controllable and highly stable process operation, low cost, and the obtained product has high purity, high density, low gas content, uniform microstructure and fine grain size, and is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a process flow schematic diagram of the present invention;

[0027] Figure 2 is a phase diagram of the spray-formed CuSn alloy;

[0028] Figure 3 is a SEM microstructural morphology diagram of Example 1;

[0029] Figure 4 is a SEM microstructural morphology diagram of Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention will be described in detail below with reference to the drawings and embodiments.

[0031] The present invention provides a spray-formed fine-grained copper-tin alloy target and a preparation method thereof.

[0032] First, select a Cu ingot with a purity of 99.99% and a Sn ingot with a purity of 99.99% as raw materials, and weigh and mix them according to the mass ratio of Cu:Sn = 40:60 - 70:30.

[0033] Then add them to a vacuum melting furnace on the spray forming equipment for melting; the melting parameters are: temperature 700 - 900 °C, heating rate 20 - 50 °C / min, vacuum degree < 10 -2 Pa, stirring speed 30 - 100 r / min, melting time 0.5 - 2 h.

[0034] Perform spray forming on the molten liquid, and the spray forming parameters are: spray atmosphere N2 / Ar gas, spray pressure 2 - 6 MPa, nozzle size 0.5 - 4 mm, deposition disk lowering speed 0.5 - 2 mm / min, deposition speed 5 - 30 kg / min.

[0035] The selected melting equipment is a vacuum melting furnace, and the purposes of using a vacuum melting furnace are: 1) reducing the gas content of the product, especially the O content; 2) not requiring slag skimming, reducing material waste; 3) reducing the introduction of impurities.

[0036] The as-sprayed blank has a density of 95% - 99%. Perform surface pretreatment on the blank to remove the adhered powder on the surface.

[0037] Perform hot extrusion on the pretreated blank to further improve the density of the product, eliminate micro-defects, refine the grain size and make it isotropic. The hot extrusion parameters are: blank temperature 350 - 500 °C, extrusion cylinder temperature 300 - 450 °C, extrusion speed 8 - 20 mm / min, extrusion ratio 2:1 - 8:1.

[0038] The extrusion cylinder is made of one of high-strength steels such as tungsten steel, molybdenum steel or chromium steel. During the extrusion process, a lubricant needs to be used to lubricate the die, reduce the friction between the product and the die, and avoid the risks of die sticking, product cracking and die damage. The lubricant can be substances with high hardness or self-lubricating properties such as talc powder, cubic boron nitride powder, carbon black, etc. Perform various machining operations on the extruded product to the required shape and size. Example 1

[0039] After weighing a Cu ingot with a weight percentage of 60% and a tin ingot with a mass percentage of 40%, add them to a vacuum melting furnace. First, evacuate to 10 -2Pa, and then raise the temperature to 800°C at a heating rate of 30°C / min. After the metal ingot is completely melted to form an alloy solution, start the pneumatic stirring device and stir at a rate of 50 r / min for 1.5 h to fully mix the two metal melts.

[0040] Set the nozzle size of gas atomization to 2 mm, the injection gas pressure to 4 MPa, the deposition disk to descend at 1 mm / min, and the injection atmosphere to Ar gas. Open the feed port below the vacuum melting furnace to allow the molten liquid to flow into the injection equipment, and break up the molten liquid into fine droplets by high-pressure Ar and deposit them on the deposition disk.

[0041] After performing appearance pretreatment on the as-sprayed CuSn blank to remove the particle adhesions on the surface, conduct hot extrusion. First, place the blank in a heating furnace and heat it to 450°C, heat the extrusion cylinder to 400°C, apply a lubricant to the inner cavity surface of the extrusion cylinder, set the extrusion ratio to 5:1, and the extrusion speed to 10 mm / min. Perform appropriate machining on the extruded blank to the required shape and size. Example 2

[0042] After weighing a Cu ingot with a weight percentage of 40% and a tin ingot with a mass percentage of 60%, add them to the vacuum melting furnace. First, evacuate to 10 -2 Pa, and then raise the temperature to 750°C at a heating rate of 20°C / min. After the metal ingot is completely melted to form an alloy solution, start the pneumatic stirring device and stir at a rate of 50 r / min for 1 h to fully mix the two metal melts.

[0043] Set the nozzle size of gas atomization to 3 mm, the injection gas pressure to 6 MPa, the deposition disk to descend at 3 mm / min, and the injection atmosphere to Ar. Open the feed port below the vacuum melting furnace to allow the molten liquid to flow into the injection equipment, and break up the molten liquid into fine droplets by high-pressure Ar and deposit them on the deposition disk.

[0044] After performing appearance pretreatment on the as-sprayed CuSn blank to remove the particle adhesions on the surface, conduct hot extrusion. First, place the blank in a heating furnace and heat it to 400°C, heat the extrusion cylinder to 300°C, apply a lubricant to the inner cavity surface of the extrusion cylinder, set the extrusion ratio to 7:1, and the extrusion speed to 20 mm / min. Perform appropriate machining on the extruded blank to the required shape and size. Example 3

[0045] Example 3 is basically the same as Example 1, except that the mass fraction of Cu is 50% and the mass fraction of Sn is 50%.

[0046] Comparative Example 1

[0047] A CuSn alloy target was prepared by a melting and casting method using a 4N Cu ingot with a mass fraction of 60% and a 4N Sn ingot with a mass fraction of 40%. First, the Cu ingot was heated to 1150 °C in an intermediate frequency melting furnace to form a copper melt, then the tin ingot was gradually added to the molten Cu liquid and continuously stirred for about 30 min. The uniformly stirred molten liquid was cast into a mold, and the blank was taken out after cooling to room temperature.

[0048] Comparative Example 2

[0049] Weighed Cu powder (D50 = 10 μm) with a mass fraction of 60% and Sn powder (D50 = 10 μm) with a mass fraction of 40% were added to a tungsten steel pot, and 1% stearic acid was added as a process control agent. The ball milling parameters were: ball-to-material ratio of 8:1, total loading of 1 / 2, ball milling time of 8 h, the pot was evacuated to a vacuum degree of 150 Pa, and the ball milling speed was 500 / 700 r / min one-minute alternating speed. The milled powder was sieved through an 80-mesh sieve.

[0050] The sieved powder was weighed according to the product size and then loaded into a hot-pressing graphite mold. When loading the mold, first place graphite paper at the bottom and around the inside, add the powder to the graphite cavity in portions, and level the powder each time a layer is added. Then place graphite paper again, and both the graphite mold and the graphite paper need to be evenly sprayed with a high-temperature resistant mold release agent.

[0051] The graphite mold was placed directly below the press head of a vacuum hot-pressing furnace, and the mold was pre-pressed at 2.5 MPa, and the sintering parameters were set. First, evacuate the furnace body to below 10 -2 Pa, first heat up to 120 °C at a rate of 2 °C / min and hold for 2 h; then heat up to 350 °C at a rate of 2 °C / min and hold for 3 h; then heat up to 550 °C at a rate of 4 °C / min, and simultaneously pressurize to 20 MPa at a pressure increasing rate of 1 MPa / min during the heating process. After holding for 2 h, cool down with the furnace and release the pressure. After the temperature drops to room temperature, open the furnace chamber, take out the mold for demoulding, and machine the CuSn alloy to the required size.

[0052] Comparative Example 3

[0053] Weighed Cu powder (D50 = 10 μm) with a mass fraction of 60% and Sn powder (D50 = 10 μm) with a mass fraction of 40% were added to a tungsten steel pot, and 1% stearic acid was added as a process control agent. The ball milling parameters were: ball-to-material ratio of 8:1, total loading of 1 / 2, ball milling time of 8 h, the pot was evacuated to a vacuum degree of 150 Pa, and the ball milling speed was 500 / 700 r / min one-minute alternating speed. The milled powder was sieved through an 80-mesh sieve.

[0054] The mixed powder is cold-pressed and formed, and the cold-pressing pressure is 200 MPa and the pressure holding time is 3 min. The green compact after pressing is vacuum sintered. First, the vacuum degree is pumped to below 10 -2 Pa, heated to 120 °C at a heating rate of 2 °C / min and held for 1 h, heated to 350 °C at a heating rate of 2 °C / min and held for 1 h; heated to 600 °C at a heating rate of 1 °C / min, held for 4 h and then cooled with the furnace. After the temperature drops to room temperature, the product is taken out for machining.

[0055] The performance tests were carried out on the above Examples 1-3 and Comparative Examples 1-3, and the following data were obtained:

[0056] Density / % Average grain size / μm Segregation percentage / % Oxygen content / PPM Example 1 99.8 9 ≤2 ≤200 Example 2 99.9 12 ≤2 ≤200 Example 3 99.8 10 ≤2 ≤200 Comparative Example 1 90.1 163 ≥5 ≥1000 Comparative Example 2 99.6 42 ≤2 ≤500 Comparative Example 3 93.7 97 ≤5 ≤800

[0057] Attached Figure 2 is the CuSn alloy phase diagram of the present invention; Attached Figure 3 is the SEM microstructural morphology diagram of Example 1; Figure 4 is the SEM microstructural morphology diagram of Comparative Example 1.

[0058] It can be concluded from the above table and the drawings that the copper-tin alloy target of the present invention has a high density, small and uniform grain size, low gas content and high purity.

[0059] The above are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a copper-tin alloy target, characterized in that It includes the following steps: S1. Select Cu ingots and Sn ingots as raw materials and weigh and mix them according to the mass ratio of Cu:Sn = 40:60 - 70:30; S2. Add the weighed Cu ingots and Sn ingots into the melting furnace equipment for melting. Among them, the melting parameters are as follows: temperature 700 - 900 °C, heating rate 20 - 50 °C / min, vacuum degree < 10 -2 Pa, stirring speed 30 - 100 r / min, melting time 0.5 - 2 h; S3. Spray-form the molten liquid after melting. The spray pressure is 2 - 6 Mpa, the density of the blank obtained by spray forming is 95% - 99%. Perform surface pretreatment on the blank to remove the powder adhered to the surface; S4. Hot-extrude the pretreated blank. The temperature of the blank is 350 - 500 °C, and the extrusion ratio is 2:1 - 8:1; S5. Perform machining to form.

2. The preparation method of a copper-tin alloy target according to claim 1, characterized in that: In step S2, the melting equipment is a vacuum melting furnace.

3. The preparation method of a copper-tin alloy target according to claim 1, characterized in that: In step S3, the spray forming parameters: the spray atmosphere is N2 / Ar gas, the size of the spray nozzle is 0.5 - 4 mm, the descending speed of the deposition disk is 0.5 - 2 mm / min, and the deposition speed is 5 - 30 kg / min.

4. The preparation method of a copper-tin alloy target according to claim 1, wherein: In step S4, the hot extrusion parameters: the temperature of the extrusion cylinder is 300 - 450 °C, and the extrusion speed is 8 - 20 mm / min.

5. The preparation method of a copper-tin alloy target according to claim 4, characterized in that: The material of the extrusion cylinder is one of tungsten steel, molybdenum steel or chromium steel.

6. The preparation method of a copper-tin alloy target according to claim 4, characterized in that: During the hot extrusion process, a lubricant is used to lubricate the die to reduce the friction between the product and the die.

7. The preparation method of a copper-tin alloy target according to claim 6, characterized in that: The lubricant is talcum powder or cubic boron nitride powder or carbon black.

8. A copper-tin alloy target, characterized in that: Prepared by the preparation method according to any one of claims 1 - 6 above.

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