Preparation method of beryllium copper alloy

Abstract

The invention relates to a preparation method of beryllium-copper alloy. The preparation method comprises the following steps: (S1) accurately weighing the following raw materials by mass: copper, beryllium, copper-yttrium alloy, copper-titanium alloy, copper-manganese alloy and nano ytterbium powder; (S2) the raw materials are added into a vacuum induction furnace, the temperature is increased to 1400-1600 DEG C under the inert atmosphere, after the raw materials are completely molten, a covering agent is spread on the melt, smelting, standing and slagging-off are conducted under the stirring condition, the melt is poured into a mold under the condition of 1100-1200 DEG C, and a beryllium copper alloy ingot is obtained; and (S3) the beryllium-copper alloy ingot is subjected to face milling treatment, solution treatment, cold machining deformation treatment and aging treatment in sequence, and the product beryllium-copper alloy is obtained. A small amount of metal elements are added, aging treatment is carried out under the microwave condition, and then slow cooling is carried out at the constant cooling rate, so that the overaging phenomenon can be remarkably inhibited, the hardness of the alloy is improved, and meanwhile, the mechanical property, especially the stress relaxation resistance, is also improved.

Description

Technical Field

[0001] The invention belongs to the technical field of copper alloys, and in particular relates to a preparation method of beryllium copper alloy. Background Art

[0002] Beryllium copper alloys can be divided into high beryllium alloys (beryllium content 1.5-3%) and low beryllium alloys (beryllium content 0.2-1%) according to the content of metallic beryllium. Among them, beryllium copper alloys with high beryllium content play an important role in many fields, especially in high-tech fields such as instrumentation, electronics, and aerospace, due to their excellent comprehensive properties such as high strength, high hardness, high elasticity, high thermal conductivity, corrosion resistance, wear resistance, and fatigue resistance. Beryllium copper alloys with high beryllium content have high strength and elasticity, as well as excellent machinability, easy casting, easy welding, and easy electroplating. They are widely used in elastic sensitive and conductive devices, such as switches, reeds, plug-ins and other components in electronic instruments. However, due to the limitations of equipment and process, the performance of the head, tail, middle, surface and interior of large-sized beryllium copper alloys is inconsistent, especially the grain size is inconsistent, resulting in inconsistent performance, wide distribution of hardness and mechanical properties, and therefore unstable performance. Beryllium exists in the alloy in the form of solid solution, but the current process of solid solution treatment is not sufficient, the phase change occurs very quickly, the grains tend to grow when heated, there is a large volume change during the heat treatment process, and weak defects such as cracks and bubbles are formed. Local decomposition is prone to occur during the solid solution process, which can easily lead to over-aging. As a result, the grain size dispersion is wide after aging, and the mechanical properties cannot reach the same level as foreign alloys with the same beryllium content.

[0003] CN112760521A discloses a preparation method of beryllium copper alloy, comprising the following steps: S1: taking a copper raw material accounting for 85% to 90% of the total mass of Cu, cleaning the surface, treating it in dilute sulfuric acid to remove the oxide scale, and putting the peeled Cu into a vacuum melting furnace for melting treatment, and the vacuum melting treatment is carried out in the following manner: evacuating the furnace to a pressure of 0.005 to 0.010Pa, then filling argon gas to 0.15 to 0.20MPa, adding the peeled Cu, Ni, Nb, and Cr in an argon protective atmosphere, and the order of adding the materials is Cu, Ni, Cr, and Nb, and after all the materials are melted, TiB2, Sn, Si, and Zn are added, and the melting is continued until all the materials are melted and maintained for 3 to 8 hours, and after the melting is completed, a primary ingot is cast; S2: forging the primary ingot obtained by step S1, and controlling the deformation amount to 60 to 75% during the forging process; S3: The primary ingot forged in step S2 is put into a vacuum melting furnace for melting treatment, and the melting conditions are controlled according to the operation mode of step S1 for secondary melting. During the melting process, the remaining copper raw material is added, and the melting is continued until all the materials are melted, and then the arc is turned off to cool the melt to complete solidification, and the solidified melt is turned over, and the melting, cooling and turning steps are repeated 3 to 4 times. After the melting is completed, a secondary ingot is cast; S4 forging the secondary ingot obtained in step S3, and the deformation is controlled to be 80 to 90% during the forging process, and then solution quenching is performed; S5 cold plastic processing is performed on the secondary ingot after the processing in step S4, and the single processing rate is controlled to be 60 to 70%, and a finished product of the material is obtained after the cold plastic processing is completed; S6 aging treatment is performed on the finished product of the material after the cold plastic processing, and the aging temperature is controlled to be 350 to 380° C. During the treatment, the finished product is obtained by air cooling or furnace cooling after keeping warm for 3 to 8 hours. This patent changes the traditional method of large deformation and large plastic processing at one time, and adopts repeated melting and cooling operations to improve the uniformity of grain distribution, ensure that alloy elements in the copper matrix will not precipitate, avoid uneven grain size, and strengthen the mechanical strength enhancement effect of fine grains. However, this patent requires multiple melting, which is time-consuming and labor-intensive, and is not applicable in industrial large-scale production.

[0004] When preparing beryllium copper alloy, in order to improve the strength of the alloy, the material after solution and quenching treatment needs to be aged. Proper aging treatment can give the alloy material better elasticity, plasticity and fatigue resistance and other properties. The parameters of aging treatment are crucial, and the temperature and time of aging treatment need to be reasonably regulated. However, due to the instability of the heat treatment process, over-aging phenomenon is easily produced, that is, the grain boundary reaction is serious, which affects the alloy performance. This is an important problem that domestic beryllium copper alloy has not fundamentally solved. CN118006948A discloses a method for preparing a high-strength, high-conductivity and high-plasticity beryllium copper alloy, wherein the aging treatment is carried out until the first strengthening peak of the alloy appears. The aging treatment has a first strengthening peak and a second strengthening peak. The traditional aging treatment generally corresponds to the second strengthening peak. The patent aging treatment ends at the first strengthening peak, which improves the comprehensive performance of the alloy and shortens the aging treatment time. However, due to insufficient aging time, the strength and hardness performance are insufficient. CN102719699B discloses a method for preparing a low-beryllium copper alloy, wherein cobalt, nickel, yttrium, or tin are added. Cobalt and nickel can form a strengthening phase with beryllium, inhibit grain growth, and improve alloy strength; yttrium can inhibit the discontinuous reaction of the alloy and improve the aging hardening effect of the alloy. The patent performs two aging treatments, the first aging treatment temperature is 300-400℃ for 1-16h, air cooling; the second aging treatment temperature is 450-550℃ for 1-16h, air cooling. However, the alloy obtained in the patent has insufficient stress relaxation resistance and elastic modulus performance. Summary of the invention

[0005] In order to solve the shortcomings of the existing beryllium copper alloy preparation process, the problem of over-aging is easy to occur, and the performance of the obtained alloy product needs to be improved. The present invention proposes a preparation method of beryllium copper alloy, which avoids the over-aging phenomenon by adding specific metal elements and performing microwave treatment with specific parameters during the aging process. Specifically, the present invention provides the following technical solutions to solve the above technical problems:

[0006] A method for preparing a beryllium copper alloy comprises the following steps:

[0007] (S1) accurately weighing raw materials according to mass: copper, beryllium, copper-yttrium alloy, copper-titanium alloy, copper-manganese alloy, and nano-ytterbium powder; the raw materials are used in an amount such that beryllium accounts for 1.8-2.6wt% of the raw materials, yttrium accounts for 0.3-0.5wt%, titanium accounts for 1.1-1.8wt%, manganese accounts for 0.2-0.4wt%, and ytterbium accounts for 0.12-0.17wt%;

[0008] (S2) adding the raw materials into a vacuum induction furnace, heating to 1400-1600° C. under an inert atmosphere, spreading a covering agent on the melt after all the raw materials are melted, smelting under stirring conditions, standing, slagging, and pouring the melt into a mold at 1100-1200° C. to obtain a beryllium copper alloy ingot;

[0009] (S3) The beryllium copper alloy ingot is subjected to milling treatment, solution treatment, cold working deformation treatment, and aging treatment in sequence to obtain a product beryllium copper alloy.

[0010] The present invention prepares beryllium copper alloy by adding yttrium, titanium, manganese and ytterbium in specific proportions. The combination of the elements improves the comprehensive performance of the product beryllium copper alloy. In particular, the addition of ytterbium gives the beryllium copper alloy high yield strength and high stress relaxation resistance. However, the amount of ytterbium added needs to be strictly controlled. When the amount added is too much or too little, the alloy performance cannot be effectively improved.

[0011] Furthermore, in step (S1), the purity of each raw material is ≥99.9%, especially the content of phosphorus, arsenic and lead is ≤5ppm. Phosphorus impurities will promote abnormal grain growth of beryllium copper alloy, resulting in large grains, accelerating the decomposition of solid solution, generating fusible materials distributed at the grain boundaries, and reducing the strength of the alloy. Lead and arsenic impurities will promote alloy grain boundary reactions, accelerate aging softening, and be detrimental to the mechanical properties of the alloy.

[0012] Furthermore, in step (S1), the yttrium content in the copper-yttrium alloy is 3-5wt%, the titanium content in the copper-titanium alloy is 6-10wt%, and the manganese content in the copper-manganese alloy is 6-10wt%.

[0013] Furthermore, in step (S1), the particle size D90 of the nano ytterbium powder is 60-100 nm.

[0014] Furthermore, in step (S2), the inert atmosphere is argon, and the covering agent is at least one of graphite flakes, borax, and calcium fluoride. The smelting is to mix the melt evenly under stirring conditions with a graphite stirring rod, and the smelting time is 3-5 hours.

[0015] Furthermore, in step (S2), the covering agent is a composite mixture of graphite flakes, borax and calcium fluoride in a mass ratio of 3-5:2-3:3-5. After the covering agent is ground and sieved, the particle size is 20-100 μm.

[0016] Furthermore, in step (S3), the milling treatment is to mill off 1-2 mm of the surface; the solution treatment temperature is 850-930°C, and the treatment time is 1-3h; the deformation amount of the cold working deformation treatment is ≥50-80%, such as 60%, 65%, 70%, 75%.

[0017] Furthermore, in step (S3), the aging treatment is carried out at 300-400°C for 1-3h under microwave conditions with a power of 200-500W and a frequency of 600-1500MHz, and then the temperature is slowly reduced at a cooling rate of 1-5°C / min.

[0018] Furthermore, the aging treatment is carried out at 320-380°C for 1-2h under microwave conditions with a power of 200-450W and a frequency of 600-1000MHz, followed by slow cooling at a cooling rate of 1-4°C / min.

[0019] In a preferred technical solution of the present invention, the aging treatment is carried out at 330-350°C for 1-1.5h under microwave conditions with a power of 300-400W and a frequency of 600-800MHz, followed by slow cooling at a cooling rate of 2-3°C / min.

[0020] Beryllium copper alloy is sensitive to heat treatment process, especially aging treatment, and is very prone to over-aging, which causes serious grain boundary reaction and leads to strength reduction. The present invention performs aging treatment under specific microwave conditions, and then cools the temperature at a cooling rate instead of conventional air cooling, which can significantly inhibit the occurrence of over-aging phenomenon, improve the hardness of the alloy, and improve the mechanical properties, especially the stress relaxation resistance. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further explained and illustrated by specific embodiments below.

[0022] The yttrium content of the copper-yttrium alloy used in the embodiment of the present invention is 4.1wt%, the titanium content of the copper-titanium alloy is 7.6wt%, and the manganese content of the copper-manganese alloy is 8.2wt%.

[0023] Example 1

[0024] (S1) accurately weighing raw materials according to mass: copper, beryllium, copper-yttrium alloy, copper-titanium alloy, copper-manganese alloy, and nano ytterbium powder (D90=60nm); the raw materials are used in an amount such that beryllium accounts for 2.2wt% of the raw materials, yttrium accounts for 0.42wt%, titanium accounts for 1.33wt%, manganese accounts for 0.28wt%, and ytterbium accounts for 0.14wt%;

[0025] (S2) adding each raw material into a vacuum induction furnace, heating to 1580° C. under an argon atmosphere, and spreading a covering agent (a mixture of graphite flakes, borax, and calcium fluoride in a mass ratio of 5:2:4, with a particle size of 30-60 μm) on the melt after all the raw materials are melted, smelting for 5 h under stirring conditions with a graphite rod, standing, skimming, and pouring the melt into a mold at 1150° C., and obtaining a beryllium copper alloy ingot after cooling;

[0026] (S3) The beryllium copper alloy ingot is subjected to surface milling treatment, with the upper and lower milling depths being 1 mm respectively; then, it is subjected to solid solution treatment at 900°C for 1 h, with the deformation amount of the cold working deformation treatment being 70%, and then, it is subjected to aging treatment at 330°C for 1.5 h under microwave conditions of 300 W power and 800 MHz frequency, and then, it is cooled to room temperature at a cooling rate of 2°C / min to obtain the product beryllium copper alloy.

[0027] Examples 2-5, Comparative Examples 1-5

[0028] The preparation processes of Examples 2-5 and Comparative Examples 1-5 are the same as those of Example 1, except that the proportions of the raw materials in step S1 are different, as shown in Table 1. Comparative Examples 1-5 are based on Example 1, but do not contain changes in the contents of metal Y, Ti, Mn, and Yb.

[0029] Table 1 Alloy raw material metal content (wt%)

[0030]

[0031]

[0032] Example 6

[0033] The preparation process is the same as that of Example 1, except that in step (S1), the D90 of the raw material nano ytterbium powder is 100 nm.

[0034] Example 7

[0035] The preparation process is the same as that in Example 1, except that in step (S3), the aging treatment is carried out at 350°C for 1.5h under microwave conditions with a power of 400W and a frequency of 600MHz, and then the temperature is cooled to room temperature at a cooling rate of 3°C / min.

[0036] Example 8

[0037] The preparation process is the same as that in Example 1, except that in step (S3), the aging treatment temperature is 370° C. and the aging treatment time is 1.5 h.

[0038] Example 9

[0039] The preparation process is the same as that of Example 1, except that in step (S3), the aging treatment temperature is 320°C.

[0040] Comparative Example 6

[0041] The preparation process is the same as that of Example 1, except that in step 3, the aging treatment is not performed under microwave conditions.

[0042] Comparative Example 7

[0043] The preparation process is the same as that of Example 1, except that in step 3, after aging treatment, air cooling is used instead of a slow and steady cooling rate of 2°C / min.

[0044] Application Examples

[0045] The beryllium copper alloys obtained in the above examples and comparative examples were tested for their performance, and the results are shown in Table 2 below.

[0046] Tensile strength and yield strength test methods: GB / T 228.1-2021;

[0047] Test method for elongation: GB / T 34505-2017;

[0048] Test method for elastic modulus: GB / T 22315-2008;

[0049] Specific test method for hardness: GB / T 4340.1-2024;

[0050] Test method for stress relaxation resistance: GB / T 39152-2020, after treatment at 200℃ for 500h.

[0051] Table 2 Beryllium copper alloy properties

[0052]

[0053]

[0054] It can be seen from the data in Table 2 that the beryllium copper alloy prepared by the preparation method of the present invention has excellent performance. Through the optimized ratio of each metal component, the aging treatment under microwave-assisted conditions and the steps of slowly cooling after the aging treatment, the various performance indicators of the beryllium copper alloy are improved.

Claims

1. A method for preparing a beryllium copper alloy, characterized in that: The following steps are involved: (S1) accurately weighing raw materials according to mass: copper, beryllium, copper-yttrium alloy, copper-titanium alloy, copper-manganese alloy, and nano-ytterbium powder; the raw materials are used in an amount such that beryllium accounts for 1.8-2.6wt% of the raw materials, yttrium accounts for 0.3-0.5wt%, titanium accounts for 1.1-1.8wt%, manganese accounts for 0.2-0.4wt%, and ytterbium accounts for 0.12-0.17wt%; (S2) adding the raw materials into a vacuum induction furnace, heating to 1400-1600° C. under an inert atmosphere, spreading a covering agent on the melt after all the raw materials are melted, smelting under stirring conditions, standing, slagging, and pouring the melt into a mold at 1100-1200° C. to obtain a beryllium copper alloy ingot; (S3) The beryllium copper alloy ingot is subjected to milling treatment, solution treatment, cold working deformation treatment, and aging treatment in sequence to obtain a product beryllium copper alloy.

2. The preparation method according to claim 1, characterized in that: In step (S1), the purity of each raw material is ≥99.9%, and the content of phosphorus, arsenic and lead elements is ≤5ppm.

3. The preparation method according to claim 1, characterized in that: In step (S1), the yttrium content in the copper-yttrium alloy is 3-5wt%, the titanium content in the copper-titanium alloy is 6-10wt%, and the manganese content in the copper-manganese alloy is 6-10wt%.

4. The preparation method according to claim 1, characterized in that: In step (S1), the particle size D90 of the nano ytterbium powder is 60-100 nm.

5. The preparation method according to claim 1, characterized in that: In step (S2), the inert atmosphere is argon, and the covering agent is at least one of graphite flakes, borax, and calcium fluoride; the smelting is carried out by stirring the melt with a graphite stirring rod to mix the melt evenly, and the smelting time is 3-5 hours.

6. The preparation method according to claim 5, characterized in that: In step (S2), the covering agent is a compound mixture of graphite flakes, borax and calcium fluoride in a mass ratio of 3-5:2-3:3-5; the particle size of the covering agent is 20-100 μm.

7. The preparation method according to claim 1, characterized in that: In step (S3), the milling treatment is to mill off 1-2 mm of the surface; the solution treatment temperature is 850-930° C., and the treatment time is 1-3 hours; and the deformation amount of the cold working deformation treatment is ≥50-80%.

8. The preparation method according to claim 1, characterized in that: In step (S3), the aging treatment is carried out at 300-400°C for 1-3h under microwave conditions with a power of 200-500W and a frequency of 600-1500MHz, and then the temperature is slowly cooled to room temperature at a cooling rate of 1-5°C / min.

9. The preparation method according to claim 8, characterized in that: The aging treatment is carried out at 320-380°C for 1-2h under microwave conditions with a power of 200-450W and a frequency of 600-1000MHz, and then the temperature is slowly reduced to room temperature at a cooling rate of 1-4°C / min.

10. The preparation method according to claim 8, characterized in that: The aging treatment is carried out at 330-350°C for 1-1.5h under microwave conditions with a power of 300-400W and a frequency of 600-800MHz, and then the temperature is slowly reduced to room temperature at a cooling rate of 2-3°C / min.

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