Free-cutting copper-based nickel-silicon alloy and preparation method thereof

Abstract

The invention relates to the technical field of functional copper alloys, in particular to a free-cutting copper-based nickel-silicon alloy and a preparation method thereof. The invention relates to a free-cutting copper-based nickel-silicon alloy, which comprises the following elements in percentage by mass: 3.5 to 5.5 percent of Ni, 0.7 to 1.5 percent of Si, 0.03 to 0.06 percent of Mg, 0.04 to 0.08 percent of P, 0.01 to 0.03 percent of Sb and the balance of copper and inevitable impurities. Mg, Sb and P are added in the form of an Mg-Sb-P solid solution. The free-cutting copper-based nickel-silicon alloy disclosed by the invention has excellent cutting performance and mechanical performance.

Description

Technical Field

[0001] The present application relates to the technical field of functional copper alloys, and more specifically, to a free-cutting copper-based nickel-silicon alloy and a preparation method thereof. Background Art

[0002] Copper-based nickel-silicon alloy is an alloy material with copper, nickel and silicon as its main components. It has superior mechanical properties and is widely used in electronics, aerospace, automobiles and other fields. Its design principle is that during the high-temperature solid solution process, nickel and silicon form dispersed δ-Ni2Si particles and precipitate in the solid solution aging alloy heat treatment matrix, thereby greatly improving the mechanical properties of the material.

[0003] The main grades of copper-based nickel-silicon alloys include C70250, C70260, C19010, C19005, etc. Among them, the C70250 series has a higher nickel-silicon content, and the nickel-silicon mass ratio is controlled at around 4:1. Therefore, under the same process conditions, the C70250 series precipitates a larger number of δ-Ni2Si particles, thereby obtaining better mechanical properties.

[0004] However, copper-based nickel-silicon alloys all have the defect of poor cutting performance. In order to improve their cutting performance, a certain amount of cutting elements are usually added. Pb is a common cutting element, but Pb is harmful to the environment and human body. Therefore, as people pay more attention to health, the trend of Pb-free materials is becoming more and more obvious. At the same time, the addition of cutting elements will lead to a significant decrease in the mechanical properties of the material. Therefore, there is an urgent need for a Pb-free copper-based nickel-silicon alloy with both excellent mechanical properties and cutting performance. Summary of the Invention

[0005] In order to improve the defect that conventional Pb-free copper-based nickel-silicon alloys are difficult to have both excellent mechanical properties and cutting performance, the present application provides a free-cutting copper-based nickel-silicon alloy and a preparation method thereof.

[0006] In a first aspect, the present application provides a free-cutting copper-based nickel-silicon alloy, which adopts the following technical solution: A free-cutting copper-based nickel-silicon alloy comprises the following elements in percentage by mass: 3.5-5.5% Ni, 0.7-1.5% Si, 0.03-0.06% Mg, 0.04-0.08% P, and 0.01-0.03% Sb, with the remainder being copper and unavoidable impurities; the Mg, Sb, and P are added in the form of a Mg-Sb-P solid solution.

[0007] The reason why the cutting performance of copper-based nickel-silicon alloy is poor is that when the Si content is high, the microstructure of copper-based nickel-silicon alloy will gradually change from α+β dual phase to β+γ dual phase. Since the γ phase is hard and brittle, when the γ phase is too much, the cutting performance of copper-based nickel-silicon alloy will be reduced.

[0008] To improve the problem of reduced cutting performance caused by the γ phase, Mg and P are added in this application. The addition of Mg and P makes the structure of the copper-based nickel-silicon alloy finer and more uniform, thereby greatly improving the mechanical properties and cutting performance of the copper-based nickel-silicon alloy. Moreover, P can also form a NiP compound with Ni, effectively improving the mechanical properties of the copper-based nickel-silicon alloy.

[0009] In addition, Mg can react with Cu to form Cu2Mg, a brittle but not hard intermetallic compound, and Sb can react with Cu to form Cu2Sb, an intermetallic compound that improves the cutting performance of copper-based nickel-silicon alloys. P can form Cu3P particles, which destroy the continuity of the matrix, thereby facilitating chip breaking during cutting and further improving the cutting performance of copper-based nickel-silicon alloys.

[0010] Compared with adding Mg, P and Sb separately, when Mg, Sb and P are added in the form of solid solution, Mg3P2 compound can be pre-formed between Mg and P, and Mg3Sb2 compound can be pre-formed between Mg and Sb. The above compounds are dispersed in the alloy matrix, thereby further improving the cutting performance of copper-based nickel-silicon alloy.

[0011] Preferably, the preparation method of the Mg-Sb-P solid solution is: First, Mg, Sb and P are mixed, and then the mixed powder is placed in a mold and pressed into shape on a press. It is then sintered under the coverage of graphite paper at a sintering temperature of 600-800°C, and finally crushed and ground to obtain a Mg-Sb-P solid solution.

[0012] Preferably, the free-cutting copper-based nickel-silicon alloy further includes Bi 0.1-3.0%.

[0013] Preferably, the mass percentage of Bi is 0.1-1.5%.

[0014] Although the addition of Mg, Sb and P can effectively improve the cutting performance of copper-based nickel-silicon alloy, the improvement effect is still insufficient. Bi is a relatively brittle and hard metal with a low melting point and is not dissolved in copper. Its uniform distribution in the copper matrix can further improve the cutting performance of copper-based nickel-silicon alloy.

[0015] As for the addition amount of Bi, when the mass percentage of Bi is less than 0.1, the actual cutting performance improvement effect is not obvious due to the small amount of addition. However, at the same time, when the mass percentage of Bi exceeds 1.5%, a small amount of Bi will be stored in the copper-based nickel-silicon alloy matrix in the form of a thin film, which will instead cause the cutting performance of the copper-based nickel-silicon alloy to decrease. Therefore, the mass percentage of Bi is preferably 0.1-1.5%.

[0016] Preferably, the free-cutting copper-based nickel-silicon alloy further includes Sn0.02-0.06% and Tl0.02-0.06%.

[0017] Although controlling the amount of Bi can effectively improve the generation of thin-film Bi, it is difficult to completely avoid it. The main method to further reduce the Bi content in the film is to increase the dihedral angle, that is, to reduce the surface tension of copper or increase the surface tension of Bi.

[0018] Tl is insoluble in copper but soluble in Bi, and can effectively increase the surface tension of Bi. Sn has a large solid solubility in copper but is insoluble in Bi, and the surface energy of Sn is lower than that of copper. Therefore, Sn can effectively reduce the surface tension of copper, and then through the synergistic effect of Bi modification and copper modification, the possibility of Bi appearing in a thin film is effectively reduced, thereby improving the cutting performance of copper-based nickel-silicon alloy.

[0019] Preferably, the Bi, Sn and Tl are added in the form of Bi-Sn-Tl-Cu solid solution.

[0020] Compared with adding Bi, Sn and Tl separately, adding them in the form of Bi-Sn-Tl-Cu solid solution can promote Tl to pre-wet Bi and Sn to pre-wet Cu, further reducing the possibility of Bi appearing in a thin film and improving the cutting performance of Cu-based NiSi alloy.

[0021] Preferably, the preparation method of the Bi-Sn-Tl-Cu solid solution comprises the following steps: Preparation of Tl-Bi solid solution: First, Tl and Bi are mixed, and then the mixed powder is placed in a mold, pressed on a press, and then sintered under the cover of graphite paper at a sintering temperature of 300-400°C. Finally, it is crushed and ground to obtain Tl-Bi solid solution; Preparation of Sn-Cu solid solution: First, Sn and Cu are mixed, with the amount of Cu added being 2-4 times that of Sn. The mixed powder is then placed in a mold and pressed into shape on a press. It is then sintered under the cover of graphite paper at a sintering temperature of 1000-1200°C. Finally, it is crushed and ground to obtain a Sn-Cu solid solution. Bi-Sn-Tl-Cu solid solution: First, Tl-Bi solid solution and Sn-Cu solid solution are mixed, and then the mixed powder is loaded into a mold, pressed into shape on a press, and then sintered under the coverage of graphite paper at a sintering temperature of 1000-1200℃. Finally, the Bi-Sn-Tl-Cu solid solution is crushed and ground.

[0022] In a second aspect, the present application provides a method for preparing a free-cutting copper-based nickel-silicon alloy, which adopts the following technical solution: A method for preparing a free-cutting copper-based nickel-silicon alloy comprises the following steps in sequence: raw material mixing - melting - casting - extrusion - aging; The melting temperature is 1300-1400°C, the casting temperature is 1200-1300°C, the casting speed is 20-40 mm / min, the ingot crystallization temperature is 600-800°C, the crystallizer cooling water pressure is 0.4-0.8 MPa, the water inlet temperature is 15-25°C, and the water outlet temperature is 30-40°C; In the extrusion process, the ingot heating temperature is 850-950℃, the holding time is 1-4h, the extrusion ratio is 30-100, the extrusion speed is 8-12mm / s, the extrusion is in-line solution, the solution temperature is 800-900℃, and the cooling rate is 300-400℃ / s; During the aging process, ammonia protection is used, the aging temperature is 380-450℃, the time from room temperature to aging temperature is 60-120min, and the holding time is 120-200min.

[0023] In summary, this application has the following beneficial effects: 1. The addition of Mg and P makes the structure of copper-based nickel-silicon alloy fine and uniform, thereby greatly improving the mechanical properties and cutting performance of copper-based nickel-silicon alloy. In addition, P can also form NiP compounds with Ni, thereby effectively improving the mechanical properties of copper-based nickel-silicon alloy.

[0024] 2. Mg can react with Cu to form a brittle but not hard intermetallic compound Cu2Mg, and Sb can react with Cu to form an intermetallic compound Cu2Sb, which improves the cutting performance of the copper-based nickel-silicon alloy. P can form Cu3P particles, which destroy the continuity of the matrix, thereby facilitating chip breaking during the cutting process, thereby further improving the cutting performance of the copper-based nickel-silicon alloy.

[0025] 3. Compared with adding Mg, P and Sb separately, when Mg, Sb and P are added in the form of solid solution, Mg3P2 compound can be pre-formed between Mg and P, and Mg3Sb2 compound can be pre-formed between Mg and Sb. The above compounds are dispersed in the alloy matrix, thereby further improving the cutting performance of copper-based nickel-silicon alloy.

[0026] 4. Bi is a relatively brittle and hard metal with a low melting point. It is not dissolved in copper. Its uniform distribution in the copper matrix can further improve the cutting performance of the copper-based nickel-silicon alloy. As for the amount of Bi added, when the mass percentage of Bi is less than 0.1, the actual cutting performance improvement effect is not obvious due to the small amount of Bi added. However, at the same time, when the mass percentage of Bi exceeds 1.5%, a small amount of Bi will be stored in the copper-based nickel-silicon alloy matrix in the form of a thin film, which will cause the cutting performance of the copper-based nickel-silicon alloy to decline. Therefore, the mass percentage of Bi is preferably 0.1-1.5%.

[0027] 5. Although controlling the amount of Bi can effectively improve the formation of thin-film Bi, it is difficult to completely avoid it. The main method to further reduce the Bi content in the film is to increase the dihedral angle, that is, to reduce the surface tension of copper or increase the surface tension of Bi; Tl is insoluble in copper but soluble in Bi, and can effectively increase the surface tension of Bi. Sn has a large solid solubility in copper but is insoluble in Bi, and the surface energy of Sn is lower than that of copper. Therefore, Sn can effectively reduce the surface tension of copper, and then through the synergistic effect of Bi modification and copper modification, the possibility of Bi appearing in a thin film is effectively reduced, thereby improving the cutting performance of copper-based nickel-silicon alloy. DETAILED DESCRIPTION

[0028] The present application is further described in detail below in conjunction with Examples 1-13 and Comparative Example 1.

[0029] raw material Ni CAS: 7440-02-0; Si CAS: 7440-21-3; Mg CAS: 7439-95-4; P CAS: 7723-14-0; SbCAS: 7440-36-0; Bi CAS: 7440-69-9; Sn CAS: 7440-31-5; Tl CAS: 7440-28-0; Cu CAS: 7440-50-8.

[0030] Example Example 1 A free-cutting copper-based nickel-silicon alloy comprising the following elements in percentage by mass: Ni 4.0%, Si 1.1%, Mg 0.05%, P 0.06%, Sb 0.02%, with the remainder being copper and unavoidable impurities; A method for preparing a free-cutting copper-based nickel-silicon alloy comprises the following steps: Raw material mixing - melting - casting - extrusion - aging; Raw material mixing: Ni, Si, Mg, P, Sb, and Cu are mixed, and the particle size of Ni, Si, Mg, P, Sb, and Cu is only 800 mesh; Melting: melting temperature 1350℃, holding time 25min; Casting: casting temperature 1250℃, casting speed 30mm / min, ingot crystallization temperature 700℃, crystallizer cooling water pressure 0.6MPa, water inlet temperature 20℃, water outlet temperature 35℃; Extrusion: ingot heating temperature 900℃, holding time 3h, extrusion ratio 60, extrusion speed 10mm / s, extrusion online solution, solution temperature 850℃, cooling rate 350℃ / s; Aging: Ammonia protection is used, aging temperature is 410℃, the time from room temperature to aging temperature is 100min, and the holding time is 150min.

[0031] Example 2 The difference from Example 1 is that Mg, Sb and P are added in the form of Mg-Sb-P solid solution; The preparation method of Mg-Sb-P solid solution is: First, Mg, Sb and P are mixed, and then the mixed powder is loaded into a mold and pressed into shape on a press. It is then sintered under the coverage of graphite paper at a sintering temperature of 700°C. Finally, it is crushed and ground to obtain a Mg-Sb-P solid solution with a particle size of 800 mesh.

[0032] Example 3 The difference from Example 2 is that the free-cutting copper-based nickel-silicon alloy further includes the element Bi; A free-cutting copper-based nickel-silicon alloy comprises the following elements in percentage by mass: 4.0% Ni, 1.1% Si, 0.05% Mg, 0.06% P, 0.02% Sb, 1.1% Bi, and the balance being copper and unavoidable impurities.

[0033] Examples 4-7 The difference from Example 3 is that the mass percentage of Bi is different, as shown in Table 1.

[0034] Table 1 Mass ratio of Bi in Examples 3-7 Example 3 Example 4 Example 5 Example 6 Example 7 Bi 1.1% 0.1% 1.5% 0.05% 3.0% It should be noted that the increase or decrease in the mass percentage of Bi is compensated by copper.

[0035] Example 8 The difference from Example 3 is that the free-cutting copper-based nickel-silicon alloy further includes the elements Sn and Tl; A free-cutting copper-based nickel-silicon alloy comprises the following elements in percentage by mass: Ni 4.0%, Si 1.1%, Mg 0.05%, P 0.06%, Sb 0.02%, Bi 1.1%, Sn 0.04%, Tl 0.04%, and the balance being copper and unavoidable impurities.

[0036] Example 9 The difference from Example 8 is that Sn is no longer added, and the loss is made up by copper.

[0037] Example 10 The difference from Example 8 is that Tl is no longer added and the loss is made up by copper.

[0038] Example 11 The difference from Example 8 is that Bi, Sn, and Tl are added in the form of Bi-Sn-Tl-Cu solid solution; The preparation method of Bi-Sn-Tl-Cu solid solution comprises the following steps: Preparation of Tl-Bi solid solution: First, Tl and Bi are mixed, and then the mixed powder is placed in a mold and pressed on a press. It is then sintered under the cover of graphite paper at a sintering temperature of 350°C, and finally crushed and ground to obtain Tl-Bi solid solution; Preparation of Sn-Cu solid solution: First, Sn and Cu are mixed, with the amount of Cu added being 2-4 times that of Sn. The mixed powder is then placed in a mold and pressed on a press. It is then sintered under the cover of graphite paper at a sintering temperature of 1100°C. Finally, it is crushed and ground to obtain a Sn-Cu solid solution. Bi-Sn-Tl-Cu solid solution: First, Tl-Bi solid solution and Sn-Cu solid solution are mixed, and then the mixed powder is loaded into a mold, pressed on a press, and then sintered under the coverage of graphite paper at a sintering temperature of 1100°C. Finally, the Bi-Sn-Tl-Cu solid solution is crushed and ground, and the particle size of the Bi-Sn-Tl-Cu solid solution is 800 mesh.

[0039] Examples 12-13 The difference from Example 1 is that the mass percentages of the components of the free-cutting copper-based nickel-silicon alloy are different, as shown in Table 2.

[0040] Table 2 Mass percentage of each component in free-cutting copper-based nickel-silicon alloy in Examples 11-13 Example 11 Example 12 Example 13 Ni 4.0% 3.5 4.5 Si 1.1% 1.5 0.7 Mg 0.05% 0.03 0.06 P 0.06% 0.08 0.04 Sb 0.02% 0.03 0.01 Bi 1.1% 1.5 0.1 Sn 0.4% 0.02 0.06 Tl 0.04% 0.06 0.02 Cu margin margin margin Comparative Example Comparative Example 1 The difference from Example 1 is that Mg, P and Sb are no longer added, and the lost part is compensated by copper.

[0041] Performance testing Detection method 1. Tensile strength test Three samples were taken from each of Examples 1-13 and Comparative Example 1, and then the tensile strength of the samples was tested according to GB / T228.1-2010 “Tensile test of metallic materials Part 1: Room temperature tensile test method”, and the average value was taken.

[0042] 2. Cutting index test Three samples were taken from each of Examples 1-13 and Comparative Example 1, and then evaluated according to the cutting formation test method in the appendix of YS-T647-2007 "Copper-Zinc-Bismuth-Tellurium Alloy Rod". Assuming the cutting index of C36000 (HPb63-3) to be 100%, the cutting index of the above samples was calculated and the average value was taken.

[0043] The test data are shown in Table 3.

[0044] Table 3 Test data table of Examples 1-13 and Comparative Example 1 Tensile strength / MPa Cutting index / % Example 1 992 85.2% Example 2 1003 88.6% Example 3 995 90.9% Example 4 998 90.1% Example 5 991 90.5% Example 6 1001 88.9% Example 7 987 89.2% Example 8 994 92.3% Example 9 996 91.4% Example 10 995 91.7% Example 11 995 92.9% Example 12 990 91.5% Example 13 987 91.9% Comparative Example 1 975 30.1% With reference to Example 1 and Comparative Example 1 and in combination with Table 3, it can be seen that, relative to Comparative Example 1, the tensile strength of Example 1 is slightly improved, while the cutting index of Example 1 is significantly improved. This shows that the addition of Mg, P, and Sb can effectively improve the cutting performance of the copper-based nickel-silicon alloy without affecting its mechanical properties.

[0045] The reason is that the cutting performance of copper-based nickel-silicon alloy is poor. When the Si content is high, the microstructure of copper-based nickel-silicon alloy will gradually change from α+β dual phase to β+γ dual phase. Since the γ phase is hard and brittle, when the γ phase is too much, the cutting performance of copper-based nickel-silicon alloy will be reduced.

[0046] The addition of Mg and P makes the structure of the copper-based nickel-silicon alloy finer and more uniform, thereby greatly improving the mechanical properties and cutting performance of the copper-based nickel-silicon alloy. In addition, P can also form NiP compounds with Ni, effectively improving the mechanical properties of the copper-based nickel-silicon alloy and effectively alleviating the problem of reduced cutting performance caused by the γ phase.

[0047] In addition, Mg can react with Cu to form Cu2Mg, a brittle but not hard intermetallic compound, and Sb can react with Cu to form Cu2Sb, an intermetallic compound that improves the cutting performance of copper-based nickel-silicon alloys. P can form Cu3P particles, which destroy the continuity of the matrix, thereby facilitating chip breaking during cutting and further improving the cutting performance of copper-based nickel-silicon alloys.

[0048] Referring to Examples 1-2 and in combination with Table 3, it can be seen that compared with Example 1, the tensile strength and cutting index of Example 2 are further improved, which shows that the addition of Mg, Sb and P in the form of Mg-Sb-P solid solution can further improve the mechanical properties and cutting performance of the copper-based nickel silicon alloy.

[0049] The reason is that compared with adding Mg, P and Sb separately, when Mg, Sb and P are added in the form of a solid solution, Mg3P2 compound can be pre-formed between Mg and P, and Mg3Sb2 compound can be pre-formed between Mg and Sb. The above compounds are dispersed in the alloy matrix, thereby further improving the cutting performance of the copper-based nickel-silicon alloy.

[0050] Referring to Examples 2-3 and in combination with Table 3, it can be seen that, relative to Example 2, the cutting index of Example 3 is further improved, while the tensile strength of Example 3 is slightly reduced. This shows that the addition of Bi can further improve the cutting performance of the copper-based silicon-nickel alloy. The reason is that Bi is a relatively brittle and hard metal with a low melting point and is not dissolved in copper. Its uniform distribution in the copper matrix can further improve the cutting performance of the copper-based nickel-silicon alloy. However, the addition of Bi will also affect the mechanical properties of the copper-based nickel-silicon alloy, but the effect is not significant.

[0051] With reference to Examples 3-7 and in combination with Table 3, it can be seen that, relative to Example 3, the cutting index of Examples 4-5 is slightly reduced, and the cutting index of Examples 6-7 is further reduced. At the same time, the tensile strength of Examples 4-7 fluctuates according to the amount of Bi added. This shows that the addition of Bi can improve the cutting performance of the copper-based nickel-silicon alloy, but excessive Bi addition will reduce the cutting performance of the copper-based nickel-silicon alloy.

[0052] The reason is that when the mass percentage of Bi is less than 0.1, the actual cutting performance improvement effect is not obvious due to the small amount of addition. However, at the same time, when the mass percentage of Bi exceeds 1.5%, a small amount of Bi will be stored in the copper-based nickel-silicon alloy matrix in the form of a thin film, which will instead cause the cutting performance of the copper-based nickel-silicon alloy to decline. Therefore, the mass percentage of Bi is preferably 0.1-1.5%.

[0053] Referring to Example 3 and Examples 8-10 and combining with Table 3, it can be seen that compared with Example 3, the cutting performance of Examples 8-10 is improved, among which the improvement of Example 8 is the largest. At the same time, the tensile strength of Examples 8-10 is similar to that of Example 3. This shows that the addition of element Sn and element Tl can improve the cutting performance of copper-based nickel silicon alloy, but when element Sn and element Tl are added in combination, the cutting performance improvement effect of copper-based nickel silicon alloy is better. The reason is that although controlling the amount of Bi can effectively improve the generation of thin film Bi, it is difficult to completely avoid it. The main method to further reduce the Bi content in the thin film is to increase the dihedral angle, that is, to reduce the surface tension of copper or increase the surface tension of Bi.

[0054] Tl is insoluble in copper but soluble in Bi, and can effectively increase the surface tension of Bi. Sn has a large solid solubility in copper but is insoluble in Bi, and the surface energy of Sn is lower than that of copper. Therefore, Sn can effectively reduce the surface tension of copper, and then through the synergistic effect of Bi modification and copper modification, the possibility of Bi appearing in a thin film is effectively reduced, thereby improving the cutting performance of copper-based nickel-silicon alloy.

[0055] With reference to Example 8 and Example 11 and in combination with Table 3, it can be seen that the cutting performance of Example 11 is further improved compared with Example 8. This shows that the addition of Bi, Sn, and Tl in the form of Bi-Sn-Tl-Cu solid solution can further improve the cutting performance of the copper-based nickel silicon alloy.

[0056] The reason is that, compared with adding Bi, Sn and Tl separately, adding them in the form of Bi-Sn-Tl-Cu solid solution can promote Tl to pre-wet Bi and Sn to pre-wet Cu, further reducing the possibility of Bi appearing in a thin film and improving the cutting performance of Cu-based NiSi alloy.

[0057] With reference to Examples 11-13 and in combination with Table 3, it can be seen that compared with Example 11, the cutting performance and crack resistance of Examples 12-13 are slightly reduced. This shows that when the components of the free-cutting copper-based nickel-silicon alloy adopt the proportions of Example 11, the prepared free-cutting copper-based nickel-silicon alloy will have better cutting performance and mechanical properties.

[0058] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A free-cutting copper-based nickel-silicon alloy, characterized in that: The invention comprises the following elements in percentage by mass: Ni 3.5-5.5%, Si 0.7-1.5%, Mg 0.03-0.06%, P 0.04-0.08%, Sb 0.01-0.03%, and the balance is copper and unavoidable impurities; the Mg, Sb and P are added in the form of Mg-Sb-P solid solution.

2. The free-cutting copper-based nickel-silicon alloy according to claim 1, characterized in that: The preparation method of the Mg-Sb-P solid solution is: First, Mg, Sb and P are mixed, and then the mixed powder is placed in a mold and pressed into shape on a press. It is then sintered under the coverage of graphite paper at a sintering temperature of 600-800°C, and finally crushed and ground to obtain a Mg-Sb-P solid solution.

3. The free-cutting copper-based nickel-silicon alloy according to claim 1, characterized in that: The free-cutting copper-based nickel-silicon alloy further includes Bi 0.1-3.0%.

4. The free-cutting copper-based nickel-silicon alloy according to claim 3, characterized in that: The mass percentage of Bi is 0.1-1.5%.

5. The free-cutting copper-based nickel-silicon alloy according to claim 3, characterized in that: The free-cutting copper-based nickel-silicon alloy further includes Sn0.02-0.06% and Tl0.02-0.06%.

6. The free-cutting copper-based nickel-silicon alloy according to claim 5, characterized in that: The Bi, Sn, and Tl are added in the form of Bi-Sn-Tl-Cu solid solution.

7. The free-cutting copper-based nickel-silicon alloy according to claim 6, characterized in that: The preparation method of the Bi-Sn-Tl-Cu solid solution comprises the following steps: Preparation of Tl-Bi solid solution: First, Tl and Bi are mixed, and then the mixed powder is placed in a mold, pressed on a press, and then sintered under the cover of graphite paper at a sintering temperature of 300-400°C. Finally, it is crushed and ground to obtain Tl-Bi solid solution; Preparation of Sn-Cu solid solution: First, Sn and Cu are mixed, with the amount of Cu added being 2-4 times that of Sn. The mixed powder is then placed in a mold and pressed into shape on a press. It is then sintered under the cover of graphite paper at a sintering temperature of 1000-1200°C. Finally, it is crushed and ground to obtain a Sn-Cu solid solution. Bi-Sn-Tl-Cu solid solution: First, Tl-Bi solid solution and Sn-Cu solid solution are mixed, and then the mixed powder is loaded into a mold, pressed into shape on a press, and then sintered under the coverage of graphite paper at a sintering temperature of 1000-1200℃. Finally, the Bi-Sn-Tl-Cu solid solution is crushed and ground.

8. A method for preparing the free-cutting copper-based nickel-silicon alloy according to any one of claims 1 to 7, characterized in that: The following processes are included in sequence: Raw material mixing - melting - casting - extrusion - aging; Melting temperature 1300-1400℃, casting temperature 1200-1300℃, casting speed 20-40mm / min, ingot crystallization temperature 600-800℃, crystallizer cooling water pressure 0.4-0.8MPa, water inlet temperature 15-25℃, water outlet temperature 30-40℃; In the extrusion process, the ingot heating temperature is 850-950℃, the holding time is 1-4h, the extrusion ratio is 30-100, the extrusion speed is 8-12mm / s, the extrusion is in-line solution, the solution temperature is 800-900℃, and the cooling rate is 300-400℃ / s; In the aging process, ammonia protection is adopted, the aging temperature is 380-450℃, the time from room temperature to aging temperature is 60-120min, and the holding time is 120-200min.