Lead brass alloy and preparation method and application thereof

Abstract

The invention discloses a lead brass alloy which comprises the following components in percentage by mass: 57-60% of Cu, 0.8-1.9% of Pb, less than or equal to 0.2% of Fe, less than or equal to 0.2% of Sn, 0.1-0.2% of Ni, less than or equal to 0.1% of Al, less than or equal to 0.01% of Si and the balance of Zn and inevitable impurities. The structure of the lead brass alloy comprises an alpha phase, a beta phase and a Pb elementary substance phase, the area percentage of the alpha phase is 40-60%, and the area percentage of the beta phase is 35-55%. The lead brass alloy has proper mechanical properties and wear resistance, lower ductile-brittle transition temperature and better low-temperature toughness. The invention further discloses a preparation method of the lead brass alloy, the technological process of the preparation method comprises the steps of smelting, traction continuous casting, extrusion, passage straightening, peeling extension and finished product annealing, and the finished product annealing temperature is 280-450 DEG C. The invention further discloses application of the lead brass alloy in a valve in a low-temperature medium environment.

Description

Technical Field

[0001] This invention belongs to the field of copper alloy technology, specifically relating to a leaded brass alloy, its preparation method, and its application. Background Technology

[0002] Most metals exhibit increased strength but decreased toughness as temperature decreases, resulting in low-temperature brittleness. This makes them unsuitable for transporting cryogenic media such as liquefied natural gas and liquid nitrogen. Copper and copper alloys, however, possess excellent toughness and a low ductile-brittle transition temperature, making them suitable for applications down to liquid helium (-269°C), thus becoming a good choice for cryogenic valves.

[0003] Patent application CN119710358A discloses an ultra-low temperature high-toughness copper alloy material and its preparation method, belonging to the technical field of ultra-low temperature high-toughness non-ferrous metal materials. The material's mass percentage composition includes: nickel (Ni): 15-25%; manganese (Mn): 2-6%; aluminum (Al): 2.5-6.5%; phosphorus (P): 0.2-1.0%, with the balance being copper and unavoidable impurities. The preparation steps include: batching (pure Cu, pure nickel, pure manganese)—melting—holding—cooling—melting of Cu-P master alloy and pure aluminum—holding—casting—forging—solution aging heat treatment.

[0004] Patent application CN106916996B discloses a low-temperature ultra-high toughness and wear-resistant copper alloy and its preparation method, belonging to the field of metallic materials and their preparation technology. The copper alloy has the following mass percentage composition: nickel: 25.0–45.0%, manganese: 2–15%, zinc: 1–8%, titanium: 0.1–5.0%, iron: 0.5–5%, chromium: 0.1–3%, with the balance being copper. The preparation steps are: batching—melting and casting—hot extrusion—hot forging—finished product. This invention improves the alloy's low-temperature comprehensive mechanical properties and wear resistance by adding elements such as manganese, zinc, titanium, iron, and chromium, while ensuring good machinability.

[0005] However, both of the aforementioned patent applications achieved low-temperature toughness by controlling the content of alloying elements in cupronickel alloys, but they still failed to obtain a copper alloy with good low-temperature toughness, a low ductile-brittle transition temperature, suitable mechanical properties and wear resistance, and excellent overall performance. Summary of the Invention

[0006] This invention provides a leaded brass alloy with suitable mechanical properties and wear resistance, a low ductile-brittle transition temperature, and good low-temperature toughness.

[0007] This invention provides a leaded brass alloy whose components comprise, by mass percentage, 57-60% Cu, 0.8-1.9% Pb, ≤0.2% Fe, ≤0.2% Sn, 0.1-0.2% Ni, ≤0.1% Al, and ≤0.01% Si, with the balance being Zn and unavoidable impurities. The microstructure of the lead-brass alloy includes an α phase, a β phase, and a Pb elemental phase, with the α phase having an area percentage of 40-60% and the β phase having an area percentage of 35-55%.

[0008] Preferably, the area percentage of the Pb elemental phase is 1-2%.

[0009] This invention limits the content of Sn, Al, and Si in the alloy. The zinc equivalent is calculated by multiplying the zinc equivalent coefficient of the alloying elements other than Cu and Zn by the content of the alloying elements. The zinc equivalent coefficients of Sn (+2), Al (+8), and Si (+10) are positive, which is equivalent to increasing the total Zn content, reducing the α phase, and increasing the β phase. Since Si is equivalent to 10 zinc equivalents, it is especially important to limit the content of Si in order to control the Zn equivalent within a small range, thereby reducing the β phase.

[0010] By increasing the Ni content, the present invention enables Ni to dissolve better into the matrix. Therefore, the increase in Ni content reduces the amount of dissolved Zn, further reducing the β phase and making the α phase account for a higher volume. As a result, the brass alloy provided by the present invention has better low-temperature toughness.

[0011] The face-centered cubic structure ensures that the α phase does not undergo a low-temperature brittle transition, thus avoiding the risk of brittle fracture at its source. The elongation increases as the temperature decreases. In contrast, the body-centered cubic structure makes the β phase sensitive to low temperatures and poses a risk of ductile-brittle transition. The brass of this invention is placed in a low-temperature environment of -196°C to 0°C, and the risk of β phase embrittlement is within an acceptable range.

[0012] If the Ni content provided by this invention is too high, it will form Ni2Si compound with Si, disrupting the continuity of the matrix phase. This compound will lead to a decrease in toughness and tensile strength. If the contents of Sn, Al, and Si are too high, brittle oxides will also form at room temperature. Under low-temperature pressure conditions, the presence of these oxides will make the brittleness of the brass alloy provided by this invention more significant, affecting its low-temperature toughness.

[0013] This invention controls the Fe content. Fe has extremely low solid solubility in Cu-Zn-Pb, so it precipitates as Fe-rich phase particles. When the Fe content is trace, the Fe-rich phase is distributed at the grain boundaries, refining the grains and hindering the propagation of low-temperature cracks. However, when the Fe content is excessive (>0.2%), the coarse Fe-rich phase agglomerates at the grain boundaries and simultaneously severs the matrix phase, resulting in a sharp decrease in toughness and an increase in brittleness at low temperatures.

[0014] Preferably, the average grain size of the α phase and β phase is less than 20 μm.

[0015] More preferably, the average grain size of the α phase is 10-15 μm.

[0016] More preferably, the average grain size of the β phase is 14-18 μm.

[0017] Preferably, Cu 58-59%, Pb 1.0-1.5%, Fe ≤0.2%, Sn ≤0.2%, Ni 0.1-0.2%.

[0018] More preferably, Fe ≤ 0.1%, Sn ≤ 0.1%, and Si ≤ 0.005%.

[0019] More preferably, Al 0.01-0.05%, Si 0.001-0.005%, Sn 0.01-0.1%.

[0020] More preferably, Fe is 0.01-0.1%.

[0021] More preferably, Fe 0.07-0.09%.

[0022] In the smelting process, this invention controls the copper and zinc ingots to a high grade, strictly controls the content of the above-mentioned elements in the recycled materials, and adds a slag remover. Under the above synergistic effect, the content of Fe, Sn, Al and Si is strictly controlled, ensuring that the brass alloy provided by this invention has good low-temperature toughness.

[0023] Preferably, the average size of the Pb elemental phase is less than 3 μm, and the distribution of the Pb elemental phase is greater than 10,000 phases / mm. 2 .

[0024] More preferably, the average size of the Pb elemental phase is 1-3 μm, and the distribution of the Pb elemental phase is 10,000-14,400 phases / mm. 2 .

[0025] This invention controls the average size and quantity of the Pb elemental phase, ensuring its uniform distribution within the microstructure. This guarantees both good wear resistance and good low-temperature toughness. Pb is insoluble in the brass matrix and exists in granular form. A higher number and smaller particle size results in a more uniform distribution and less impact on mechanical properties. However, a high number of coarse particles can easily become crack initiators, exacerbating low-temperature brittleness. There is no rigid standard for the number of lead particles; a higher number generally indicates better uniformity. Controlling the average diameter of the lead particles to below 3 μm helps prevent large lead particles from becoming crack initiators.

[0026] Preferably, the average grain size of the leaded brass alloy is 5-20 μm; for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm.

[0027] More preferably, the average grain size of the leaded brass alloy is 5-18 μm.

[0028] This invention breaks the as-cast structure into spherical, fine grains by controlling the parameters of the extrusion process, thereby obtaining a suitable grain size and avoiding the damage to toughness caused by the as-cast structure. This results in the brass alloy provided by this invention having good low-temperature toughness, while minimizing the risk of increased strength but decreased toughness due to excessively small grain size.

[0029] Preferably, the tensile strength Rm of the leaded brass alloy is above 440 MPa; The yield strength Rp0.2 of the lead-brass alloy is above 190 MPa; The Vickers hardness of the leaded brass alloy is above 110 HV; The elongation A of the leaded brass alloy is 25% or more.

[0030] Preferably, the tensile strength Rm of the leaded brass alloy is 440-500 MPa.

[0031] Preferably, the yield strength of the leaded brass alloy is 190-250 MPa.

[0032] Preferably, the Vickers hardness of the leaded brass alloy is 110-150 HV.

[0033] Preferably, the elongation A of the leaded brass alloy is 25-45%.

[0034] Preferably, the impact absorption energy of the leaded brass alloy under conditions of -196°C to 0°C is 14-30 J.

[0035] On the other hand, the present invention also provides a method for preparing the leaded brass alloy, wherein the process flow of the preparation method includes: smelting → traction continuous casting → extrusion → straightening in the passage → peeling and stretching → annealing of finished product; The lead-brass alloy is batched and smelted according to the mass percentage of each component. The annealing temperature of the finished product is 280-450℃.

[0036] This invention removes residual stress and increases the proportion of the α phase by controlling the annealing temperature of the finished product, resulting in appropriate grain growth and improved plasticity. However, if the annealing temperature of the finished product is too high, it can easily lead to abnormal grain growth.

[0037] Preferably, the extrusion temperature is 570-650℃, the extrusion speed is 15-25mm / s, and the extrusion ratio is 10-30. This invention, by controlling the extrusion temperature, extrusion speed, and extrusion ratio, breaks the as-cast structure into fine, spherical grains, thereby obtaining a suitable grain size. If the extrusion temperature is too low, the billet hardness is too high, and the toughness decreases; if the extrusion temperature is too high, the grain size is too large, and the toughness also decreases. Under these conditions, extrusion can completely transform the as-cast structure into a processed structure, resulting in fine, uniform grains, further improving the excellent low-temperature toughness of the α phase, and partially compensating for the embrittlement tendency caused by the β phase crystal structure.

[0038] Preferably, the preheating temperature of the extrusion die is 430-470℃. This invention, by controlling the die preheating temperature, prevents the billet temperature from dropping too quickly, ensuring the extrusion temperature remains within a suitable range and avoiding situations where extrusion is impossible, or where excessively hard billets negatively impact the toughness of the alloy material.

[0039] Preferably, the extrusion pressure is 5-18 MPa.

[0040] More preferably, the billet is a round bar with a diameter of 15-40 mm and an extrusion pressure of 8-18 MPa.

[0041] More preferably, when the diameter of the round bar is Φ > 40 mm, the extrusion pressure is 5-10 MPa.

[0042] Furthermore, the billet is a hexagonal bar, S10-20mm, and the extrusion pressure is 12-18MPa.

[0043] More preferably, when the hexagonal bar has a specification of S20-30 mm, the extrusion pressure is 10-18 MPa. More preferably, when the hexagonal bar has a specification of S30-40 mm, the extrusion pressure is 8-18 MPa.

[0044] When extruded under these conditions, the as-cast structure can be completely transformed into the processed structure, resulting in fine and uniform grains, which further improves the excellent low-temperature toughness of the α phase and partially compensates for the embrittlement tendency caused by the β phase crystal structure.

[0045] More preferably, the annealing temperature of the finished product is 280-350℃.

[0046] Preferably, the annealing time of the finished product is 2-4 hours.

[0047] Preferably, the feeding sequence of the smelting includes: copper → leaded brass production recycled material and copper shavings → zinc ingots → stirring → adding slag remover and stirring to remove slag → settling → converter.

[0048] More preferably, the copper grade is Cu≥99.9%, and the zinc ingot purity is Zn>99.95%. The mass percentage of each component of the slag remover is 50~70% potassium fluoroborate, 10~20% potassium fluorotitanate, 1~5% iron powder, 5~10% boron powder, and 5~20% boron gangue.

[0049] This invention controls the content of Fe, Sn, Al, and Si in recycled materials and copper shavings from leaded brass production, as well as the grade of copper and the purity of zinc ingots, at the source. Then, by reacting the slag with a slag remover, the content of the above elements is further reduced, thereby strictly controlling the content of Fe, Sn, Al, and Si, and ensuring the good low-temperature toughness of the brass alloy provided by this invention.

[0050] Preferably, the melting temperature is 1030-1080℃.

[0051] Preferably, the straightening and peeling extension processing rate is 2-5%. By controlling the processing rate, this invention ensures straightening while avoiding excessively high billet hardness, which would affect toughness.

[0052] On the other hand, the present invention also provides the application of the aforementioned leaded brass alloy in valves in temperature media environments ranging from -196°C to 0°C; Preferably, the valve for the -196°C to 0°C temperature medium environment is a valve for transporting liquid nitrogen medium.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention reduces the zinc equivalent by limiting the content of Sn, Al, and Si elements, and further reduces the zinc content by adding an appropriate amount of Ni, thereby minimizing the β phase and obtaining a suitable α phase. At the same time, by controlling the content of Sn, Al, and Si elements, this invention can also minimize the formation of brittle compounds of Sn, Al, and Si, so as to maintain good low-temperature toughness. This invention also controls the Fe content to minimize the formation of Fe-containing compounds, so as to lower the ductile-brittle transition temperature. Attached Figure Description

[0054] Figure 1 This is a microstructure diagram of the lead-brass alloy provided in Embodiment 1 of the present invention; Figure 2 This is a microstructure diagram of the lead-brass alloy provided in Embodiment 2 of the present invention. Detailed Implementation

[0055] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0057] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the invention. The chemical components of Embodiments 1-2 and Comparative Examples 1-4 provided by the present invention are shown in Table 1.

[0058] Example 1 In this embodiment, the lead-brass alloy is prepared as a round bar with a specification of Φ37mm. The specific preparation method includes: (1) The raw materials are prepared according to the mass percentage of each component in Table 1. The raw materials include: No. 2 copper, No. 1 zinc ingot, lead ingot, lead brass production waste and copper powder, GHCTJ-2 brass slag remover. The mass percentage of the lead brass production waste and copper powder is 55%, and the mass percentage of each component of the GHCTJ-2 brass slag remover is 60% potassium fluoroborate, 15% potassium fluorotitanate, 3% iron powder, 6% boron powder, and 14% boron gangue.

[0059] (2) Smelting: copper → leaded brass production recycled material and copper shavings → zinc → stirring → adding slag remover and stirring to remove slag → sampling (smelting furnace) → temperature measurement → settling → converter → sampling (holding furnace).

[0060] The specific steps include: before adding large pieces of copper, small pieces of copper should be added to the smelting furnace to prevent smoke; after adding large pieces of copper, leaded brass production waste and copper shavings are added; after they are completely melted to form molten copper, zinc ingots are added to ensure that the zinc ingots are completely melted into the molten copper. The smelting temperature is 1050℃. The lead ingots provided in this embodiment are used as auxiliary materials. After adding zinc, the composition is tested, and the results are used to determine whether dilution or compensation is needed.

[0061] The specific steps for adding slag remover and stirring to remove slag provided in this embodiment are as follows: After all the raw materials in the furnace have been melted, add 3 kg of GHCTJ-2 brass slag remover, stir and ensure that the slag is removed cleanly.

[0062] Then the converter is used, and the temperature of the converter is 1051℃.

[0063] (3) Traction casting: Molten copper is continuously drawn horizontally from the holding furnace by the crystallizer.

[0064] (4) Extrusion: The parameters of the extrusion process provided in this embodiment are as follows: extrusion temperature: 610℃, extrusion speed: 18mm / s, extrusion pressure: 14Mpa, extrusion ratio: 21, and die preheating temperature: 450℃.

[0065] The specific extrusion process provided in this embodiment is as follows: Before extrusion, a handheld thermometer was used to measure the temperature of the cast ingot coming out of the furnace to confirm that the extrusion temperature was 610℃.

[0066] Before extrusion, set the extrusion die heating furnace to the appropriate temperature to preheat the die for at least 20 minutes, and apply asphalt lubricant to the die.

[0067] The billet is extruded according to the parameters of the extrusion process. The head of the extruded billet is sawn 20cm and the tail is sawn 30cm.

[0068] (5) Straightening and peeling: After extrusion, the blank is straightened, peeled, and stretched. Process parameters: Φ37.8-38.2 → peel Φ37.7 → peel Φ37.5 → stretch Φ37.

[0069] (6) Finished product annealing: The billet is annealed at a temperature of 300℃ and a holding time of 3h.

[0070] Example 2 The mass percentages of each component in the leaded brass alloy provided in this embodiment are shown in Table 1.

[0071] In this embodiment, the lead-brass alloy is prepared as a round bar with a specification of Φ37mm. The specific preparation method includes: (1) The raw materials are prepared according to the mass percentage of each component in Table 1. The raw materials include: No. 2 copper, No. 1 zinc ingot, lead ingot, lead brass production waste and copper powder, GHCTJ-2 brass slag remover. The content of lead brass production waste and copper powder is 55%. The mass percentage of each component of the GHCTJ-2 brass slag remover is 53% potassium fluoroborate, 15% potassium fluorotitanate, 4% iron powder, 7% boron powder, and 10% boron gangue.

[0072] (2) Smelting: copper → leaded brass production recycled material and copper shavings → zinc → stirring → adding slag remover and stirring to remove slag → sampling (smelting furnace) → temperature measurement → settling → converter → sampling (holding furnace).

[0073] The specific steps include: before adding large pieces of copper, small pieces of copper should be added to the smelting furnace to prevent smoke. After adding large pieces of copper, leaded brass production waste and copper shavings are added. After the copper is completely melted and formed, zinc ingots are added to ensure that the zinc ingots are completely melted into the copper. The smelting temperature is 1056℃. The lead ingots provided in this embodiment are used as auxiliary materials. After adding zinc, the composition is tested to see if dilution or compensation is needed.

[0074] The specific steps for adding slag remover and stirring to remove slag provided in this embodiment are as follows: After all the raw materials in the furnace have been melted, add 3 kg of GHCTJ-2 brass slag remover, stir, and remove the slag cleanly.

[0075] Then the converter is used, and the temperature of the converter is 1049℃.

[0076] (3) Traction casting: Molten copper is continuously drawn horizontally from the holding furnace by the crystallizer.

[0077] (4) Extrusion: The parameters of the extrusion process provided in this embodiment are: extrusion temperature: 614℃, extrusion speed: 19mm / s, extrusion pressure: 14Mpa, extrusion ratio: 22, and die preheating temperature: 460℃.

[0078] The specific extrusion process provided in this embodiment is as follows: Before extrusion, a handheld thermometer was used to measure the temperature of the cast ingot coming out of the furnace to confirm that the extrusion temperature was 619℃.

[0079] Before extrusion, set the extrusion die heating furnace to the appropriate temperature to preheat the die for at least 20 minutes, and apply asphalt lubricant to the die.

[0080] The billet is extruded according to the parameters of the extrusion process. The head of the extruded billet is sawn 20cm and the tail is sawn 30cm.

[0081] (5) Straightening and peeling: After extrusion, the blank is straightened, peeled, and stretched. Process parameters: Φ37.8-38.2 → peel Φ37.7 → peel Φ37.5 → stretch Φ37.

[0082] (6) Finished product annealing: The billet is annealed at a temperature of 320℃ and a holding time of 3h.

[0083] Comparative Examples 1-3 The difference between Comparative Examples 1-3 and Example 1 is that the contents of Si, Ni and Fe are too high, as shown in Table 1.

[0084] Comparative Example 4 Unlike Example 1, the annealing temperature of the finished product was 250°C.

[0085] Table 1. Mass percentage (wt%) of each component in the examples and comparative examples

[0086] Table 2 Microstructure of Embodiments and Comparative Examples of the Invention

[0087] Table 3 Mechanical properties of embodiments and comparative examples of the present invention

[0088] Table 4 shows the cutting performance, impact absorption energy at room temperature and -196°C of the embodiments and comparative examples of the present invention.

[0089] The methods for performance testing are as follows: Cutting performance is assessed using a cutting performance index. This is achieved by calculating the cutting force using a cutting force tester and comparing it to the C54400 index, then applying the following formula: The relative cutting index was obtained, and the specific data are shown in Table 2.

[0090] Microstructure testing: The microstructure was observed under a metallographic microscope and measured using metallographic analysis software. The results are recorded in Table 2.

[0091] Mechanical property testing: Tensile strength Rm, yield strength Rp0.2 and elongation after fracture A were tested according to GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature", and the results are recorded in Table 3.

[0092] Low-temperature impact toughness test: The test was conducted in accordance with GB / T229-2020 "Metallic Materials Charpy Pendulum Impact Test Method", and the results are recorded in Table 4.

[0093] like Figure 1 and Figure 2 As shown in Tables 2-4, the leaded brass alloys prepared in Examples 1-2 have a high α-phase area ratio, a suitable β-phase area ratio, and suitable Pb phase distribution data, which makes the prepared leaded brass have extremely high plasticity while maintaining good strength and machinability. Since the leaded brass provided by this invention has extremely high toughness, it has a high ductile-brittle transition temperature and high toughness at low temperatures.

[0094] The lead-brass alloy prepared in Comparative Example 1 had a high Si content and a low α-phase area ratio, resulting in a significant decrease in toughness and low low-temperature impact resistance. The lead-brass alloy prepared in Comparative Example 2 had an excessively high Ni content, forming nickel-silicon intermetallic compounds that disrupted the continuity of the matrix phase, significantly reducing toughness and tensile strength, and failing to meet the requirements for low-temperature impact resistance. The lead-brass alloy provided in Comparative Example 3 had an excessively high Fe content, which formed a coarse Fe-rich phase and simultaneously fractured the matrix phase, causing a sharp decrease in toughness, an increase in brittleness, and low low-temperature impact resistance. The lead-brass alloy prepared in Comparative Example 4 had an excessively low annealing temperature, resulting in a low α-phase area ratio, a significant decrease in toughness, and similarly low low-temperature impact resistance.

Claims

1. A lead-brass alloy, characterized in that, Its components, by mass percentage, include: Cu 57-60%, Pb 0.8-1.9%, Fe ≤0.2%, Sn ≤0.2%, Ni 0.1-0.2%, Al ≤0.1% and Si ≤0.01%, with the balance being Zn and unavoidable impurities; The microstructure of the lead-brass alloy includes an α phase, a β phase, and a Pb elemental phase, with the α phase having an area percentage of 40-60% and the β phase having an area percentage of 35-55%.

2. The lead-brass alloy according to claim 1, characterized in that, The average grain size of the α phase and β phase is less than 20 μm.

3. The lead-brass alloy according to claim 1, characterized in that, The average size of the Pb elemental phase is less than 3 μm, and the distribution of the Pb elemental phase is greater than 10,000 phases / mm. 2 .

4. The lead-brass alloy according to claim 1, characterized in that, The average grain size of the leaded brass alloy is 5-20 μm.

5. The lead-brass alloy according to claim 1, characterized in that, The impact absorption energy of the leaded brass alloy under conditions ranging from -196℃ to 0℃ is 14-30 J.

6. A method for preparing a leaded brass alloy according to any one of claims 1-5, characterized in that, The process flow of the preparation method includes: smelting → traction continuous casting → extrusion → straightening in the passageway → peeling and stretching → annealing of the finished product; The lead-brass alloy is batched and smelted according to the mass percentage of each component. The annealing temperature for the finished product is 280-450℃.

7. The method for preparing the lead-brass alloy according to claim 6, characterized in that, The extrusion temperature is 570-650℃, the extrusion speed is 15-25mm / s, and the extrusion ratio is 10-30.

8. The method for preparing the lead-brass alloy according to claim 6, characterized in that, The extrusion pressure is 5-18 MPa.

9. The method for preparing the lead-brass alloy according to claim 6, characterized in that, The feeding sequence for the smelting process includes: copper → recycled leaded brass production materials and copper shavings → zinc ingots → stirring → adding slag remover and stirring to remove slag → settling → converter.

10. The application of a leaded brass alloy according to any one of claims 1-5, or a copper alloy prepared by the method of preparing a leaded brass alloy according to any one of claims 5-9, in a valve in a temperature medium environment of -196°C to 0°C.

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