Lead bronze alloy and preparation method thereof

Abstract

The present invention discloses a lead-bronze alloy comprising the following components by weight: Pb: 0.4-0.7%, Si: 0.1-0.2%, Ce: 0.4-0.7%, with the balance being Cu. The microstructure of the lead-bronze alloy consists of α, CePb3, Ce5Pb3, and Si phases. The lead-bronze alloy bar exhibits excellent mechanical properties, electrical conductivity, and machinability, as well as a high softening temperature and a low friction coefficient. The present invention also discloses a method for preparing the lead-bronze alloy.

Description

Technical Field

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

[0002] Lead bronze C18700 is a high-conductivity, free-cutting copper alloy with high electrical conductivity, excellent machinability, good hot and cold workability, easy welding, and corrosion resistance. Lead bronze C18700 is a copper alloy containing lead, with a lead content of 0.7-1.5%. It is primarily produced through semi-continuous casting and hot extrusion. Because lead has a melting point of only 327°C, while the extrusion temperature is much higher, the lead (Pb) melts and dissociates at the grain boundaries during the extrusion process, creating pores in the material and reducing its surface strength. Excessive extrusion temperatures and speeds generate significant friction between the material surface and the guide rails. When this friction exceeds the surface strength, the material cracks. Therefore, existing techniques have attempted to reduce scrap rates by lowering the extrusion temperature and speed. However, this significantly reduces production efficiency, hindering mass production.

[0003] In terms of application, lead bronze C18700 is primarily used in welding and cutting nozzles. Its primary processing method is turning, and its operating environment is characterized by high temperatures, high currents, and abrasion resistance. Therefore, high requirements are placed on the material's turning, electrical conductivity, resistance to high-temperature softening, and friction and wear properties. Although lead bronze C18700 has high electrical conductivity and good turning performance, its resistance to high-temperature softening and friction and wear is poor, similar to that of red copper, resulting in a short service life. This is especially true when lead bronze C18700 is used in the welding and cutting nozzle industry, where nozzles need to be replaced 10-15 times a day, resulting in a service life of only about 30 minutes per nozzle. Therefore, the material's service life needs to be increased.

[0004] Chinese patent number CN116334441A discloses a free-cutting, highly conductive, oxygen-free lead-copper alloy and its preparation method. The alloy's mass percentage composition is P: 0.003% to 0.012%, Pb: 0.8% to 1.2%, O: 1 to 10 ppm, with the remainder being Cu and unavoidable impurities. Impurity element contents of Fe and Si are controlled to be ≤ 0.005%, Al, Sb, Mn, and Ni ≤ 0.02%, and the total amount of impurities is ≤ 0.05%. The alloy is prepared using bottom-blowing refining technology, charcoal covering, reduced annealing times, and increased cold working deformation. The process is: smelting → casting → extrusion → pickling → cold drawing and annealing → straightening and sawing.

[0005] The above patent only solves the welding and hydrogen embrittlement problems, but does not solve the problem of cracking of products in mass production at higher extrusion speeds. In addition, its resistance to high-temperature softening is low and cannot meet the higher temperature requirements of the welding and cutting nozzle industry. Summary of the Invention

[0006] The invention provides a lead-bronze alloy. The lead-bronze alloy bar has good mechanical properties, electrical conductivity and turning performance, as well as a high softening temperature and a low friction coefficient.

[0007] The present invention provides a lead bronze alloy, wherein the weight percentages of the components of the lead bronze alloy are as follows: Pb: 0.4-0.7%, Si: 0.1-0.2%, Ce: 0.4-0.7%, and the balance is Cu;

[0008] The microstructure of the lead bronze alloy consists of α, CePb3, Ce5Pb3 and Si phases.

[0009] The present invention introduces appropriate amounts of Ce and Pb to form high-melting-point compounds CePb3 and Ce5Pb3 with melting points of 1000-1200°C, thereby solving the problem of surface cracking caused by the low melting point of Pb during high-temperature extrusion and improving the material's strength, resistance to high-temperature softening, and wear resistance. Introducing an appropriate amount of Si further improves the material's strength, resistance to high-temperature softening, and wear resistance by forming Si hard points.

[0010] The rare earth elements Ce and Pb provided by the present invention form CePb3 and Ce5Pb3 in the material. These are dispersion-strengthened phases that are evenly distributed on grain boundaries, have a high melting point, and do not melt during the extrusion process, thus resolving the cracking problem caused by high extrusion temperatures and fast extrusion speeds. Furthermore, they hinder the slippage of dislocations, creating dislocation pileups at the locations of the CePb3 and Ce5Pb3 phases, resulting in a dispersion strengthening effect and improving the material's strength and high-temperature softening resistance. Furthermore, the CePb3 and Ce5Pb3 phases form a solid lubricating film during friction and wear, reducing shedding of the copper matrix and increasing the material's wear resistance.

[0011] The present invention provides a Pb content of 0.4-0.7%. If the Pb content is higher than 0.7%, free lead is more likely to form, and the material will crack due to the high extrusion temperature and fast speed. When the Pb content is lower than 0.4%, the material's turning performance is poor due to the small amount of CePb3 and Ce5Pb3 formed. When the Ce content is between 0.4-0.7%, when the Ce content is greater than 0.7%, the copper liquid is more viscous during smelting, which is not conducive to the pulling of the ingot. When the Ce content is less than 0.4%, more free Pb particles remain in the matrix, increasing the risk of extrusion cracking, reducing the amount of CePb3 and Ce5Pb3, weakening the dispersion strengthening effect, and reducing the material's strength, resistance to high-temperature softening, and wear resistance. Furthermore, the weight ratio of Ce to Pb is 1:1 to 1:1.2, the orientation of the CePb3 phase is {221}, the orientation of the Ce5Pb3 phase is {193}, the size of the CePb3 phase is 0.5 to 1.5 μm, and the size of the Ce3Pb5 phase is 1 to 3 μm. The appropriately sized Ce5Pb3 and CePb3 phases act as dispersion strengthening, thereby improving the mechanical properties of the lead-bronze alloy provided by the present invention.

[0012] The Si element provided by the present invention can produce dispersion strengthening, uniformly distributed in the matrix as individual particles. These hard particles act as a barrier to dislocation slip, enhancing the material's strength and resistance to high-temperature softening. In actual use, the Si, along with the lubricating film of CePb3 and Ce3Pb5, contribute to wear resistance, reducing shedding of the copper matrix during friction and wear. Regarding turning performance, the Si particles, CePb3 phase, and Ce3Pb5 phase all act as chip breakers, improving the material's turning performance. When the Si content exceeds 0.2%, its electron scattering effect is enhanced, significantly decreasing conductivity and making it unsuitable for use in high-current connectors. When the Si content is less than 0.1%, the number of dispersed Si particles decreases dramatically, reducing the material's strength, resistance to high-temperature softening, wear resistance, and turning performance, making it unsuitable for use in welding and cutting nozzle materials. Specifically, the Si phase has a {111} orientation, a close-packed plane. The internal atomic structure transitions from crystalline to amorphous in a short time, minimizing cutting forces, ensuring easy cutting and high-temperature resistance. The number of Si+CePb3+Ce3Pb5 phases is 17000-25000 / mm 2 The size of the Si phase is 2-4 μm. Too much Si will affect the electrical conductivity of lead bronze.

[0013] Furthermore, the lead bronze alloy has a tensile strength of 460-490 MPa, an electrical conductivity of 84-85% IACS, a softening temperature of 420-440° C., a friction coefficient of 0.08-0.12, and a turning performance of 85-87% C36000.

[0014] The present invention also provides a method for preparing a lead bronze alloy, comprising:

[0015] (1) batching, smelting, and semi-continuously casting the lead bronze alloy according to the weight percentage of each component to obtain an ingot;

[0016] (2) extruding the ingot to obtain an extruded billet, wherein the extrusion process is as follows: the extrusion temperature is 700-900° C., and the extrusion speed is 7-10 mm / s;

[0017] (3) The extruded billet is drawn to obtain a lead bronze alloy.

[0018] Furthermore, in step (1), the smelting temperature is 1200-1250°C.

[0019] Furthermore, in step (1), the pulling speed of the semi-continuous casting is 50-60 mm / min, and the cooling water flow rate is 14-17 m 3 / h, cooling water temperature is 20-25℃.

[0020] Furthermore, in step (2), the extrusion ratio is 8-488, and the specification of the extruded billet is Φ8-90 mm.

[0021] Furthermore, before drawing the extruded billet, the billet is pickled to remove the oxide scale produced on the extruded surface, thereby preventing the oxide scale from being pressed into the surface due to excessive wire drawing in the subsequent process, resulting in peeling of the material after processing.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention forms high-melting-point post-metallic compounds CePb3 and Ce5Pb3 by adding appropriate amounts of Pb and Ce, thereby minimizing free Pb and avoiding cracking of the material edge due to the low melting point of Pb during high-temperature extrusion, thereby improving the strength, high-temperature softening resistance and wear resistance of the material; the present invention forms hard points by adding an appropriate amount of Si element, which not only improves the strength of the material, but also combines with the CePb3 phase and Ce5Pb3 phase to enable the prepared lead bronze alloy to have higher wear resistance during use and avoid Cu separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the crystal phase organization diagram of the lead bronze alloy prepared in Example 1. DETAILED DESCRIPTION

[0025] The present invention provides a lead bronze material for high-temperature resistant welding and cutting nozzles through composition adjustment and organizational optimization. The material has excellent turning, high-temperature softening resistance and wear resistance, a long service life, solves the problems of easy cracking during extrusion and low production efficiency, and is beneficial to mass production in enterprises.

[0026] Example 1

[0027] (1) Semi-continuous casting: 2961 kg of cathode copper, 15 kg of Cu-Si (Si 20%), 12 kg of elemental Pb, and 12 kg of rare earth Ce were mixed and then smelted and semi-continuously cast to obtain an ingot. The semi-continuous casting specification was Φ245 mm. The specific melting and semi-continuous casting parameters are shown in Table 1.

[0028] (2) Extrusion: A 3150t large-tonnage extruder is used to extrude the ingot obtained in step (1) to obtain an extruded billet. The extrusion billet specification is Φ20mm, the extrusion temperature is 720°C, the extrusion speed is 10mm / s, and the extrusion ratio is 78.

[0029] (3) Pickling: The Φ20 mm extruded billet obtained in step (2) was pickled and soaked for 3 min.

[0030] (4) Drawing: Use an 8t combined drawing machine to draw the pickled extruded billet to Φ17mm to obtain lead bronze alloy bars. Figure 1 As shown, the microstructure of the prepared lead bronze alloy rod consists of α, CePb3, Ce5Pb3 and Si phases.

[0031] Performance test: The performance test of the prepared lead bronze rod was carried out, as shown in Table 2.

[0032] Example 2

[0033] (1) Semi-continuous casting: 2955 kg of cathode copper, 15 kg of Cu-Si (Si 20%), 15 kg of elemental Pb, and 15 kg of rare earth Ce were mixed and then smelted and semi-continuously cast to obtain an ingot. The semi-continuous casting specification was Φ245 mm. The specific melting and semi-continuous casting parameters are shown in Table 1.

[0034] (2) Extrusion: A 3150t large-tonnage extruder is used to extrude the ingot obtained in step (1) to obtain an extruded billet. The extrusion billet specification is Φ20mm, the extrusion temperature is 730°C, the extrusion speed is 9mm / s, and the extrusion ratio is 78.

[0035] (3) Pickling: The Φ20 mm extruded billet obtained in step (2) was pickled and soaked for 3 min.

[0036] (4) Drawing: An 8t combined drawing machine is used to draw the pickled extruded billet to Φ17mm to obtain lead bronze rods.

[0037] Performance test: The performance test of the prepared lead bronze rod was carried out, as shown in Table 2.

[0038] Example 3

[0039] (1) Semi-continuous casting: 2934 kg of cathode copper, 30 kg of Cu-Si (Si 20%), 18 kg of elemental Pb, and 18 kg of rare earth Ce were mixed and then smelted and semi-continuously cast to obtain an ingot. The semi-continuous casting specification was Φ245 mm. The specific melting and semi-continuous casting parameters are shown in Table 1.

[0040] (2) Extrusion: The ingot obtained in step (1) was extruded using a 3150t large-tonnage extruder to obtain an extruded billet. The extruded billet had a diameter of 20 mm, an extrusion temperature of 740°C, an extrusion speed of 9 mm / s, and an extrusion ratio of 78.

[0041] (3) Pickling: The Φ20 mm extruded billet obtained in step (2) was pickled and soaked for 3 min.

[0042] (4) Drawing: An 8t combined drawing machine is used to draw the pickled extruded billet to Φ17mm to obtain lead bronze rods.

[0043] Performance test: The performance test of the prepared lead bronze rod was carried out, as shown in Table 2.

[0044] Comparative Example 1

[0045] American Standard C18700, samples Φ17mm were purchased from the market and then tested. The specific test results are shown in Table 2.

[0046] Table 1 shows the melting and semi-continuous casting parameters of Examples 1 to 3

[0047]

[0048] Performance Analysis:

[0049] The electrical conductivity is tested by the bridge method and the implementation standard is GB / T351-2019.

[0050] The tensile strength is tested by a tensile testing machine and the standard GB / T228.1-2021 is implemented.

[0051] The elongation is tested by a tensile testing machine and the standard GB / T228.1-2021 is implemented.

[0052] The softening temperature is determined by placing the sample in a muffle furnace at a certain temperature for 1 hour and then air cooling it. The hardness drops by 15%, and this temperature is called the softening temperature of the material.

[0053] The friction coefficient was measured by using a large-load friction and wear testing machine under the conditions of a load of 100 kN, a temperature of 25°C, a friction speed of 200 r / min, and a dry friction mode.

[0054] Turning performance = cutting force F of C36000 / cutting force of tested alloy * 100% As shown in Table 2, the lead bronze alloys prepared in Examples 1-3 have good mechanical properties and electrical conductivity, as well as a high softening temperature, a low friction coefficient, and high turning performance.

[0055] Table 2 Performance parameters of Examples 1-3 and Comparative Example 1

[0056]

Claims

1. A lead bronze alloy, characterized in that The weight percentages of the components of the lead bronze alloy are: Pb: 0.4-0.7%, Si: 0.1-0.2%, Ce: 0.4-0.7%, and the balance is Cu; The microstructure of the lead bronze alloy consists of α, CePb3, Ce5Pb3 and Si phases.

2. The lead bronze alloy according to claim 1, characterized in that The weight ratio of Ce to Pb is 1:1-1:1.

2.

3. The lead bronze alloy according to claim 1, characterized in that The size of the CePb3 phase is 0.5-1.5 μm, and the size of the Ce3Pb5 phase is 1-3 μm.

4. The lead bronze alloy according to claim 1, characterized in that The orientation of the Si phase is {111}.

5. The lead bronze alloy according to claim 1, characterized in that The number of Si+CePb3+Ce3Pb5 phases is 17,000-25,000 per mm 2 .

6. The lead bronze alloy according to claim 1, characterized in that The size of the Si phase is 2-4 μm.

7. The lead bronze alloy according to claim 1, characterized in that The lead bronze alloy has a tensile strength of 460-490 MPa, an electrical conductivity of 84-85% IACS, a softening temperature of 420-440° C., a friction coefficient of 0.08-0.12, and a turning performance of 85-87% C36000.

8. A method for preparing a lead bronze alloy according to any one of claims 1 to 7, characterized in that: include: (1) batching, smelting, and semi-continuously casting the lead bronze alloy according to the weight percentage of each component according to any one of claims 1 to 7 to obtain an ingot; (2) extruding the ingot to obtain an extruded billet, wherein the extrusion process is as follows: the extrusion temperature is 700-900° C., and the extrusion speed is 7-10 mm / s; (3) The extruded billet is drawn to obtain a lead bronze alloy.

9. The method for preparing a lead bronze alloy according to claim 8, wherein: In step (1), the smelting temperature is 1200-1250°C.

10. The method for preparing a lead bronze alloy according to claim 8, wherein: In step (2), the extrusion ratio is 8-488, and the specification of the extruded billet is Φ8-90mm.

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