A leaded brass and its preparation method

Abstract

A leaded brass, characterized in that it comprises components in the following weight percentages: Cu: 57.5-58.5 wt%, Pb: 1.8-2.6 wt%, Fe: 0.06-0.18 wt%, P: 0.002-0.012 wt%, Sn ≤ 0.08 wt%, and the balance is Zn and unavoidable impurities; the microstructure of the brass is α+β+Pb phase, wherein the morphology of the Pb phase is spherical, so that the leaded brass has excellent comprehensive properties and lower cost. The present invention also relates to a preparation method of the foregoing leaded brass.

Description

Technical Field

[0001] The present invention relates to the processing of copper alloys, in particular to a leaded brass, and also to a preparation method of the foregoing leaded brass. Background Art

[0002] Brass is a general term for alloys mainly composed of copper and zinc. C3604 is a brass grade in Japanese standards, with its content usually being Cu: 57 - 61, Pb: 1.8 - 3.7, Fe < 0.5, Sn + Fe < 1, and the balance being Zn. It has the characteristics of high strength, excellent machining properties such as turning and drilling, and smooth machining surfaces. It is widely used in electronics and electrical connectors, and is generally machined into connectors by turning. However, a small part of the coil products need to cold upset the material, and the cold deformation rate reaches more than 60%. During the cold upsetting process, cracking often occurs, with an occurrence ratio of about 10%. Increasing the Cu content and reducing the contents of impurity elements such as Fe, Al, and Sn can reduce the ratio of cold upsetting cracking, but there is still about 3% of cracking. The cracking occurs at the end of the connector, which is also the part with the largest cold upsetting deformation degree.

[0003] The above problems make the existing C3604 leaded brass not suitable for terminal connectors that require cold upsetting. In view of the above problems, it is necessary to improve the composition and processing technology of the existing C3604 leaded brass to prepare a leaded brass suitable for cold upsetting. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a leaded brass suitable for cold upsetting, so that the leaded brass with low copper content can be made into terminal connectors through cold upsetting.

[0005] The second technical problem to be solved by the present invention is to provide a preparation method of the above leaded brass in view of the above technical status.

[0006] The technical solution adopted by the present invention to solve the above first technical problem is as follows: A leaded brass, characterized by comprising the following components in weight percentages: Cu: 57.5 - 58.5 wt%, Pb: 1.8 - 2.6 wt%, Fe: 0.06 - 0.18 wt%, P: 0.002 - 0.012 wt%, Sn ≤ 0.08 wt%, and the balance being Zn and unavoidable impurities; the microstructure of the brass is α + β + Pb phase, wherein the morphology of the Pb phase is spherical.

[0007] Cu: The content of Cu affects the proportion of α-phase and β-phase in the brass microstructure. When the Cu content is less than 57.5 wt%, the proportion of β-phase increases, which increases the brittleness of the brass. However, when the Cu content exceeds 58.5 wt%, the proportion of β-phase is too small, and the ingot needs to be heated to a higher temperature during hot extrusion. The problem with high-temperature extrusion is that copper skin adheres to the extrusion cylinder wall and the die, and the copper skin is easily carried into the extruded blank, causing cold heading cracking.

[0008] Pb: Pb exists as an independent phase in the brass, distributed as free particles at the grain boundaries or within the grains. While improving the cutting performance of the brass, it reduces the plasticity of the brass. The morphology, quantity, and distribution ratio of the Pb phase also affect the cold heading performance of the brass.

[0009] P: The addition of trace amounts of P increases the surface tension of the Pb phase, reduces the wettability between the Pb phase and the brass grain boundaries and matrix, making the irregular Pb phase spherical, and improving the influence of the Pb phase morphology on the cold heading performance. When the P content is less than 0.002 wt%, the effect on the Pb phase is negligible. When the P content exceeds 0.012 wt%, the influence of P on the cold deformation performance of the brass is more obvious, and it may even cause cold heading cracking.

[0010] Fe: The solubility of Fe in the brass is very low, and it basically exists in the form of hard particles, playing a role in nucleation. Therefore, an appropriate amount of Fe can control the grain size of the brass. When the Fe content is below 0.06% in the alloy of the present invention, the influence on the grain size is small. However, when the Fe content exceeds 0.18 wt%, the grains are overly refined, increasing the cold heading deformation resistance of the material.

[0011] Sn: Sn has a strong solid solution strengthening effect in copper, and at the same time can increase the proportion of β-phase in the duplex brass microstructure, improving the brittleness of the brass. However, its content should be limited to no more than 0.08 wt%.

[0012] For further design, the average diameter of the Pb phase ≤ 2 μm, and the distribution quantity of the Pb phase ≥ 18000 pieces / mm 2 。

[0013] The α-phase is a solid solution of Zn in Cu, with a face-centered cubic lattice and good plasticity. The β-phase is a solid solution based on the electron compound CuZn, with a body-centered cubic lattice. It has good high-temperature plasticity but poor plasticity at room temperature. The leaded brass used for cold heading processing needs to control the proportion of the β-phase. The morphology of the β-phase is granular, the area ratio of the β-phase is 8-20%, and the size of the β-phase is 10-25 μm. This is because the solubility of Pb in the β-phase is 42 times that in the α-phase. The existence of a certain proportion of the β-phase can play a role in wrapping the Pb-phase and reducing the impact of the Pb-phase on the cold heading performance of brass. Since the maximum diameter of the Pb-phase is 2 μm, when the size of the β-phase < 10 μm, it cannot play a wrapping role. However, when the size of the β-phase exceeds 25 μm, the hard brittleness of the β-phase is likely to cause fine cracks during cold heading. When the area ratio of the β-phase is less than 8%, the number of Pb-phases wrapped is small. When the area ratio of the β-phase exceeds 20%, although the number of Pb-phases that can be wrapped increases, the β-phase itself is a hard and brittle phase, and its negative impact on the cold heading performance of brass exceeds the positive impact brought by wrapping the Pb-phase.

[0014] The cold heading deformation of metals occurs due to the slip of grains and the deformation of the grains themselves. Reducing the grain size will inevitably increase the number of grains. Although the deformation can be more evenly distributed to each grain and it is not easy to form stress concentration, thus the cracking tendency is small. However, the smaller the grains and the more the number of grains, the greater the deformation resistance reflected externally, which will also make the cold heading deformation difficult and increase the risk of cracking. Therefore, the average grain size of the brass is 15-30 μm, and the number of grains is 540-1500 grains / mm 2 。

[0015] Tensile strength, yield strength, and hardness can reflect the mechanical properties of materials, and the magnitudes of yield strength, elongation, and hardness can reflect the quality of the cold heading performance of materials. The lower the yield strength, the higher the elongation, and the lower the hardness, the better the cold heading performance of the materials. For the brass used to prepare connectors, it is necessary to maintain appropriate yield strength and hardness, as well as lower yield strength and higher elongation. Therefore, the tensile strength of the brass is 390-480 MPa, the yield strength is 310-390 MPa, the elongation is 12-20%, and the Vickers hardness is 110-140.

[0016] The technical solution adopted by the present invention to solve the second technical problem described above is as follows: A preparation method of the leaded brass as described above, characterized by successively including the following steps:

[0017] 1) Melting: Weigh the materials according to the required components and their contents, and then carry out melting in an industrial frequency melting furnace. The melting temperature is 1000-1090 °C. After all the metals are melted and the chemical composition is qualified, transfer the molten metal to the industrial frequency furnace for heat preservation;

[0018] 2) Horizontal continuous casting: The casting temperature is 1030 - 1070 °C, the ingot specification is Φ145 - 254 mm, the traction time is 1 - 7 s, the traction pitch is 1 - 10 mm, the pause time is 0.1 - 3 s, the reverse push time is 0.1 - 3 s, the reverse push pitch is 0.5 - 4 mm, the retraction and pause time is 0.1 - 3 s, and the sawing length of the ingot is 550 - 1500 mm;

[0019] 3) Extrusion: Before extrusion, the ingot is first heated to a temperature of 600 - 700 °C, which is also the extrusion temperature. The heated ingot is extruded on a 1250 - 3150 T extrusion press. The specification range of the extruded billet is φ6 - 12 mm. At the same time, the extrusion flow number is 1 - 3, the extrusion ratio is 220 - 600:1, the extrusion speed is 4 - 16 mm / s, and the wire is wound up in a coiling manner;

[0020] 4) Intermediate wire drawing: After pickling the extruded billet, it is drawn to an intermediate specification on a wire drawing machine, and the processing rate is 18 - 35%. If the wire drawing processing rate is lower than 18%, the deformation of the wire billet structure is uneven, and the energy storage generated by lattice distortion at each part is different, and the driving force for recrystallization is not the same, resulting in different sizes of annealing recrystallized grains. As the degree of cold deformation increases, when the wire drawing processing rate exceeds 35%, the deformation of the wire billet structure is very sufficient, the original grains of the extruded billet are completely broken, the number of recrystallization nuclei increases significantly, the annealing recrystallized grains are fine, the cold heading deformation resistance increases, and cracking is likely to occur.

[0021] 5) Intermediate annealing: After wire drawing, annealing at a lower temperature is required to eliminate work hardening. The annealing temperature is 420 - 490 °C. Starting from room temperature and heating up, after reaching the set temperature, the holding time needs to be extended to 4 - 6 h. The purpose is to avoid the easy fusion and growth of the Pb phase during high-temperature annealing. Lower-temperature annealing can keep the Pb phase still in the fine spherical shape of the extrusion structure. If the annealing temperature is below 420 °C, the recrystallized grain size is small, the average grain size is less than 25 μm, and the cold heading deformation resistance is large and cracking is easy to occur; after the annealing temperature exceeds 490 °C, the grain growth rate becomes faster, the average grain size exceeds 30 μm, and orange peel is easily formed on the surface of the product after cold heading. If the holding time is less than 4 h, the uniformity of the recrystallized grains is not good; after the holding time exceeds 6 h, the grains gradually grow and are likely to exceed 30 μm. The wire billet after annealing is pickled to remove the surface oxide scale;

[0022] 6) Final wire drawing: According to the mechanical property requirements of the finished product, control the processing rate at 9 - 20%. If the final processing rate is lower than 9%, the tensile strength and hardness of the material are low, and the connector cannot pass the drop test due to deformation; if the final processing rate exceeds 20%, the material hardness is high, and cold heading is prone to cracking.

[0023] 7) Low-temperature annealing: Annealing is carried out under the protection of a reducing atmosphere to eliminate residual stress and avoid increasing the cracking risk due to the superposition of stress generated by cold heading deformation. Annealing temperature: 230 - 320 °C, holding time: 2 - 6 h, and it is taken out of the furnace after cooling to below 60 °C.

[0024] To further save costs, in step 1), the ingredients include components with the following mass percentages: H62 brass scrap: 30 - 40 wt%; 1# pure copper: 20 - 30 wt%; waste brass ≤ 15 wt%; the balance is 1# zinc ingot. In this way, by using recycled materials as raw materials for preparing brass, the cost can be effectively saved, and the content of waste brass in the ingredients is limited because tin-plated waste is easily mixed in waste brass, thereby enabling the control of the Sn content.

[0025] If the quality of the recycled materials is poor, the iron content is likely to fail to meet the standard. To avoid the brass made from the ingredients not meeting the standard, the said ingredients also include CuFe20 master alloy with a mass percentage of 3 - 9 wt%.

[0026] Further design, in step 3), the extrusion temperature is 600 - 660 °C, the extrusion ratio is 440 - 600:1, and the extrusion speed is 10 - 16 mm / s. The low-temperature heating, large extrusion ratio, and rapid extrusion process are adopted. The purpose is to avoid the aggregation and growth of the Pb phase in the ingot structure by low-temperature heating, the complete fragmentation of the as-cast grains can be achieved by large extrusion ratio deformation, and the purpose of rapid extrusion is, firstly, to make up for the insufficient heat of low-temperature heating of the ingot through the instantaneous intense deformation heat, complete dynamic recrystallization in a short time, avoid coarse recrystallization, and prevent the aggregation and growth of the Pb phase. If the extrusion ratio is below 440, due to the low extrusion deformation degree, the as-cast structure of the ingot is likely to remain in the extruded billet structure, and the cold heading performance of the material becomes poor. However, if the extrusion ratio is too high, exceeding 600, the extrusion recrystallized grains are fine. Since high-temperature annealing is not suitable for the subsequent processing annealing of the present invention, it is difficult to control the finished product grain size within the range suitable for cold heading. Since the alloy of the present invention is extruded at a lower temperature, to avoid the influence of temperature drop, rapid extrusion at 10 - 16 mm / s should be adopted.

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] ① For lead brass, by controlling the Cu content to be 57.5 - 58.5 wt% and the Sn content ≤ 0.08 wt%, the ratio of α-phase and β-phase in the microstructure can be controlled, thereby ensuring the mechanical properties of the brass alloy, reducing the consumption of copper, and lowering the cost of copper raw material consumption;

[0029] ② For lead brass, by controlling the Pb content to be 1.8 - 2.6 wt%, while improving the cutting performance of the brass, the plasticity is prevented from being too low, and the influence of Pb on the cold heading performance of the brass is reduced, thereby improving the processing performance of the brass;

[0030] ③The leaded brass plays a nucleation role by controlling the Fe content to be 0.06 - 0.18 wt%, thereby controlling the brass to have a suitable grain size, so that the cold heading processing deformation can be evenly dispersed into each grain, stress concentration is not easily formed, the cracking tendency is small, and the resistance of the material to cold heading deformation will not be too large to affect the cold heading processing;

[0031] ④The leaded brass refines the size of the Pb phase by adding 0.002 - 0.012 wt% of P element. The smaller the size of the Pb phase, the more the number of Pb phases distributed in the matrix. Moreover, the 0.002 - 0.012 wt% of P element can also change the morphology of the Pb phase to make it spheroidized, thereby reducing the negative impact of the Pb element on cold heading and improving the cold heading performance of the brass.

[0032] ⑤The preparation method of the leaded brass involves two annealings. Among them, intermediate annealing uses a relatively low annealing temperature of 420 - 490 °C to eliminate work hardening. Low-temperature annealing uses a reducing atmosphere for protective annealing, and by controlling the morphology of the Pb phase to be spherical, the average diameter of the Pb phase ≤ 2 μm, and the distribution number of the Pb phase ≥ 18,000 pieces / mm 2 , the grain size is 15 - 30 μm, and the number of grains is 540 - 1500 pieces / mm 2 , the morphology of the β phase is granular, the area ratio of the β phase is 8 - 20%, and the size of the β phase is 10 - 25 μm, so that the tensile strength of the prepared brass connector is 390 - 480 MPa, the yield strength is 310 - 390 MPa, the elongation is 12 - 20%, and the Vickers hardness is 110 - 140, with the comprehensive characteristics of high strength, easy cutting, and easy cold heading processing, and the cost is relatively low. Description of the Drawings

[0033] Figure 1 It is the metallographic microscope image (200 times) of the sample in Example 1 of the present invention;

[0034] Figure 2 It is the metallographic microscope image (200 times) of the sample in Comparative Example 1 of the present invention. Detailed Description of the Embodiment

[0035] The following further describes the embodiments of the present invention in detail.

[0036] The leaded brass in this embodiment is characterized in that it includes the following components by weight percentage: Cu: 57.5 - 58.5 wt%, Pb: 1.8 - 2.6 wt%, Fe: 0.06 - 0.18 wt%, P: 0.002 - 0.012 wt%, Sn ≤ 0.08 wt%, and the balance is Zn and unavoidable impurities; the microstructure of the brass is α + β + Pb phase, and among them, the morphology of the Pb phase is spherical.

[0037] A preparation method of the lead brass as described above, characterized by successively comprising the following steps:

[0038] 1) Melting: Weigh the materials according to the required components and their contents, then carry out melting in an industrial frequency melting furnace. The melting temperature is 1000 - 1090 °C. After all the metals are melted and the chemical composition is qualified through testing, pour them into the industrial frequency furnace for heat preservation by means of a converter.

[0039] 2) Horizontal continuous casting: The casting temperature is 1030 - 1070 °C, the ingot specification is Φ145 - 254 mm, the traction time is 1 - 7 s, the traction pitch is 1 - 10 mm, the pause time is 0.1 - 3 s, the reverse push time is 0.1 - 3 s, the reverse push pitch is 0.5 - 4 mm, the retreat and pause time is 0.1 - 3 s, and the sawing length of the ingot is 550 - 1500 mm.

[0040] 3) Extrusion: Before extrusion, first heat the ingot to a temperature of 600 - 660 °C, which is also the extrusion temperature. The heated ingot is extruded on a 1250 - 3150 T extruder. The extrusion blank specification range is φ6 - 12 mm. At the same time, the extrusion flow number is 1 - 3, the extrusion ratio is 440 - 600:1, the extrusion speed is 10 - 16 mm / s, and the wire is wound up in a coiled form.

[0041] 4) Intermediate wire drawing: After pickling the extrusion blank, draw it to an intermediate specification on a wire drawing machine, and the processing rate is 18 - 35%.

[0042] 5) Intermediate annealing: The annealing temperature is 420 - 490 °C. Start heating from room temperature. After reaching the set temperature, extend the heat preservation time to 4 - 6 h. After annealing, remove the surface oxide scale of the wire blank through pickling.

[0043] 6) Final wire drawing: According to the requirements of the mechanical properties of the finished product, control the processing rate at 9 - 20%.

[0044] 7) Low-temperature annealing: Adopt annealing under a reducing atmosphere protection. The annealing temperature is 230 - 320 °C, the heat preservation time is 2 - 6 h, and cool it to below 60 °C before taking it out of the furnace.

[0045] 8) Final product inspection.

[0046] I. Sample preparation

[0047] The samples of each group of examples are prepared according to the foregoing component weight ratios and preparation methods. The situations of the samples of each group of comparative examples are as follows:

[0048] Comparative example 1 is a commercially available C3604 φ4.85 wire.

[0049] Comparative example 2: A C3604 φ4.85 wire with a Cu content of 57.13 wt%, and the preparation process is the same as that of example 1, aiming to compare the influence of the Cu content on the cold heading performance.

[0050] Comparative Example 3: C3604 φ4.85 wire rod without P element added, with the remaining components and preparation process being the same as those in Example 1, aiming to compare the influence of not adding P element on cold heading performance.

[0051] Comparative Example 4: Extrusion temperature is 730 °C, with the chemical composition and other preparation process parameters being the same as those in Example 1, aiming to compare the influence of increasing the extrusion temperature on cold heading performance.

[0052] Comparative Example 5: Intermediate annealing temperature is 540 °C, holding time is 3 h, with the chemical composition and other preparation process parameters being the same as those in Example 1, aiming to compare the influence of the level of intermediate temperature on cold heading performance.

[0053] Comparative Example 6: Finished product processing rate is 5.5%, with the chemical composition and other preparation process parameters being the same as those in Example 1, aiming to compare the influence of reducing the finished product processing rate on the drop test results of the connector.

[0054] 1. Weigh and mix according to the weight ratios of the components of each sample in Table 1 below.

[0055] Table 1. Components of each sample Unit: wt%

[0056]

[0057]

[0058] 2. Prepare each group of samples according to the process parameters in the following steps.

[0059] Table 2. Parameters of the sample casting process

[0060]

[0061] Table 3. Parameters of the sample extrusion process

[0062]

[0063]

[0064] Table 4. Parameters of the wire drawing, intermediate annealing, and low-temperature annealing processes of the examples

[0065]

[0066] II. Performance testing

[0067] Tensile strength, yield strength, elongation, hardness, cold heading performance, drop test, and metallographic microscopy test were carried out on each sample. The standards and methods for each test are as follows:

[0068] Tensile strength, yield strength Rp0.2, and elongation: Detected in accordance with GB / T 228.1–2021 Metallic materials — Tensile testing — Part 1: Method of test at room temperature.

[0069] Hardness HV5: Detected in accordance with GB / T 4340.1–2009 Metallic materials — Vickers hardness test — Part 1: Test method.

[0070] Cold heading performance: The bars prepared in 6 examples and 6 comparative examples were cold headed into insert blanks, and whether cracks appeared on the insert blanks was observed. If there were no cracks, the cold heading performance was good and met the processing requirements. The results were recorded in Table 6.

[0071] Drop test: The bars prepared in 6 examples and 6 comparative examples were processed into inserts, assembled with electronic components such as a housing and a transformer into a complete machine. According to the drop test method specified in IEC 62368-1:2018 Audio / video, information and communication technology equipment — Part 1: Safety requirements: The installed connector specimen was freely dropped from a height of 1 m onto the surface of hardwood at its most unfavorable position. The specimen should be able to withstand 3 drop impacts. If the connector was bent or even broken, it indicated that its strength did not meet the standard. The results were recorded in Table 6.

[0072] Metallographic microscopy test: The grain size, number of grains, β-phase morphology, size and area ratio, and Pb-phase morphology, size and distribution number of each sample were observed under a microscope. The test results were recorded in Table 5. Figure 1 and Figure 2 。

[0073] The test results are as follows:

[0074] Table 5. Microstructure of samples

[0075]

[0076] Table 6 Comparison of sample properties

[0077]

[0078]

[0079] As can be seen from Table 6 above:

[0080] 1) Compared with Comparative Example 1, the tensile strength, yield strength, and hardness of Example 1 were basically the same as those of Comparative Example 1, but the elongation was higher, indicating that the grain size, number of grains, average diameter of Pb phase, distribution number of Pb phase, area ratio of β phase, and size difference of β phase affected the elongation index of the material, and thus affected the cold heading performance of lead brass.

[0081] 2) The performance data of Example 1 and Comparative Example 2 show that when the Cu content is less than 57.5 wt%, the cold heading of lead brass will crack.

[0082] 3) The performance data of Example 1 and Comparative Example 3 show that after adding 0.002 - 0.012 wt% P element during smelting, the size of the Pb phase is refined and the cold heading performance of lead brass is improved.

[0083] 4) The performance data of Example 1 and Comparative Example 4 show that when the extrusion temperature exceeds 660 °C, Pb aggregates and grows, resulting in the cold heading cracking of lead brass.

[0084] 5) The performance data of Example 1 and Comparative Example 5 show that when the intermediate annealing temperature exceeds 490 °C, the size of the Pb phase increases, the distribution quantity of the Pb phase decreases, the grain size increases, and the number of grains becomes less, resulting in the cold heading cracking of lead brass.

[0085] 6) The performance data of Example 1 and Comparative Example 6 show that when the finished product processing rate is less than 9%, the tensile strength and hardness of the material are relatively low. Although the cold heading does not crack, the electrical connector fails the drop test due to deformation.

[0086] 7) The performance data between Example 1 and each comparative example show that by controlling the Cu content, grain size, number of grains, average diameter of the Pb phase, distribution quantity of the Pb phase, area ratio of the β phase, and size of the β phase of lead brass, lead brass with a low Cu content can be obtained to meet the requirement of non - cracking during cold heading of electrical connectors.

[0087] In summary, the lead brass prepared in this example has more excellent anti - deformation ability, cutting performance and cold heading processing performance, and is a high - performance brass for electrical connectors.

Claims

1. A method for preparing lead brass, It is characterized in that Lead brass comprises the following components in weight percentage: Cu: 57.5-58.5 wt%, Pb: 1.8-2.6 wt%, Fe: 0.06-0.18 wt%, P: 0.002-0.012 wt%, Sn≤0.08 wt%, and the balance is Zn and unavoidable impurities; the microstructure of the lead brass is α+β+Pb phase, wherein the morphology of the Pb phase is spherical; The β phase area accounts for 8~20%; The preparation method of lead brass comprises the following steps in sequence: 1) Melting: Mix the ingredients according to the required components and their contents, and the melting temperature is 1000-1090℃; 2) Horizontal continuous casting: casting temperature is 1030-1070℃, ingot specification is Φ145-254mm, traction time is 1-7s, traction pitch is 1-10mm, pause time is 0.1-3s, reverse push time is 0.1-3s, reverse push pitch is 0.5-4mm, back-stop time is 0.1-3s, ingot sawing length is 550-1500mm; 3) Extrusion: extrusion temperature is 600~700℃, extrusion ratio is 220~600:1, and extrusion speed is 4~16mm / s; 4) Intermediate coil drawing: The extruded billet is drawn to the intermediate specification after pickling, and the coil drawing processing rate is 18~35%; 5) Intermediate annealing: annealing temperature is 420~490℃, holding time is 4~6h; 6) Finished product coil pulling: processing rate is 9~20%; 7) Low temperature annealing: Use reducing atmosphere protection annealing, the annealing temperature is 230~320℃, and the holding time is 2~6h.

2. The preparation method according to claim 1, It is characterized in that The average diameter of the Pb phase is ≤ 2 μm, and the number of Pb phase distributions is ≥ 18,000 / mm 2 .

3. The preparation method according to claim 2, It is characterized in that The β phase has a granular morphology and a size of 10 to 25 μm.

4. The preparation method according to claim 1, It is characterized in that The average grain size of the leaded brass is 15 - 30 μm, and the number of grains is 540 - 1500 grains / mm 2 .

5. The preparation method according to any one of claims 1 to 4, It is characterized in that The lead brass has a tensile strength of 390-480 MPa, a yield strength of 310-390 MPa, an elongation of 12-20%, and a Vickers hardness of 110-140.

6. The preparation method according to any one of claims 1 to 4, Features: In step 3), the extrusion temperature is 600-660° C., the extrusion ratio is 440-600:1, and the extrusion speed is 10-16 mm / s.

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