A high-strength, corrosion-resistant copper alloy rod and its preparation method

Abstract

This invention discloses a high-strength, corrosion-resistant copper alloy rod. The mass percentages of the components in the high-strength, corrosion-resistant copper alloy rod are as follows: Sn: 3-5 wt%, Al: 1-3 wt%, Fe: 0.8-2 wt%, Ni: 1-2 wt%, P: 0.05-0.3 wt%, Zn: 0.001-0.3 wt%, Mn: 0.001-0.3 wt%, with the balance being Cu and unavoidable impurities. The mass ratio of Ni to Fe is 0.95-1.05. This high-strength, corrosion-resistant copper alloy rod exhibits high strength, high corrosion resistance, and low cost. This invention also discloses a method for preparing the high-strength, corrosion-resistant copper alloy rod.

Description

Technical Field

[0001] This invention belongs to the field of copper alloy technology, specifically relating to a high-strength corrosion-resistant copper alloy rod and its preparation method. Background Technology

[0002] Tin bronze is a type of bronze with Sn as the main alloying element, typically containing 3% to 14% tin. It is primarily used to manufacture elastic components and wear-resistant parts. Wrought tin bronze contains no more than 8% tin and can also contain elements such as phosphorus, lead, and zinc. This alloy possesses high mechanical properties, anti-friction properties, and corrosion resistance. It is easy to machine, has good brazing and welding performance, a low shrinkage coefficient, and is non-magnetic. It can be used to prepare coatings for bronze bushings, sleeves, and antimagnetic components using wire flame spraying and arc spraying. It exhibits high strength, corrosion resistance, and excellent casting properties, and has long been widely used in various industrial sectors.

[0003] QSn6.5-0.1 is a representative grade of tin bronze, possessing high strength, corrosion resistance, and excellent cold and hot working properties. It is commonly used in the manufacture of electronic connectors, springs, and other corrosion-resistant components. The chemical composition of QSn6.5-0.1 is: Sn: 6-7wt%, P: 0.10-0.25wt%, Zn≤0.3wt%, Fe≤0.05wt%, Pb≤0.02wt%, Al≤0.002wt%, with the balance being Cu and unavoidable impurities. QSn6.5-0.1 exhibits excellent mechanical properties and corrosion resistance, with a hard-state tensile strength Rm≥470MPa and elongation A≥13%. These mechanical properties make QSn6.5-0.1 widely used in industrial manufacturing, such as in electronics, aerospace, automotive, shipbuilding, and petrochemical industries.

[0004] The ability of a metallic material to resist corrosion and damage from the surrounding medium is called corrosion resistance, which is determined by the material's composition, chemical properties, and microstructure.

[0005] The strength and corrosion resistance of QSn6.5-0.1 cannot fully meet the mechanical strength and corrosion resistance requirements of special components such as ships, chemical equipment, and seawater treatment equipment. QSn6.5-0.1 alloy exhibits hot brittleness, making it prone to cracking during hot working, resulting in a low yield. While simply increasing the Sn content can improve the alloy's strength to some extent, it still does not meet the high strength requirements. Furthermore, since Sn is a precious metal element, increasing the Sn content leads to an increase in the cost of alloy raw materials.

[0006] Chinese Patent Publication No. CN102304642A discloses a cast wear-resistant tin bronze alloy and its preparation method. This cast wear-resistant tin bronze alloy is composed of the following components by weight percentage: Sn 10-14%, Pb 2-5%, Ni 1-4%, with the total content of impurities Fe, Sb, Al, Zn, P, Si, and Bi ≤0.25%, and the balance being Cu. The preparation method involves sequentially melting electrolytic copper plates, pure nickel plates, pure tin ingots, and pure lead ingots. A refining agent is then added to the melt, followed by casting and cooling to obtain a cast wear-resistant tin bronze alloy ingot. The alloy ingot undergoes homogenization annealing treatment to obtain the cast wear-resistant tin bronze alloy product. The tin bronze alloy disclosed in this patent has room for further improvement in corrosion resistance and mechanical properties, and a higher tin content increases the success rate.

[0007] In view of the defects or deficiencies in the existing technology, there is an urgent need to design a copper alloy that not only has high strength but also excellent corrosion resistance. Summary of the Invention

[0008] This invention provides a copper alloy rod with high strength, high corrosion resistance and low cost.

[0009] This invention provides a high-strength, corrosion-resistant copper alloy rod. The mass percentages of the components in the high-strength, corrosion-resistant copper alloy rod are as follows: Sn: 3-5 wt%, Al: 1-3 wt%, Fe: 0.8-2 wt%, Ni: 1-2 wt%, P: 0.05-0.3 wt%, Zn: 0.001-0.3 wt%, Mn: 0.001-0.3 wt%, with the balance being Cu and unavoidable impurities. The mass ratio of Ni to Fe is W. Ni / W Fe The value is 0.95-1.05. The properties of this high-strength copper alloy are as follows: tensile strength Rm≥850MPa, yield strength Rp0.2≥720MPa, hardness HV5≥220, and elongation A50≥5%.

[0010] The functions of each element are as follows:

[0011] The optimal mass ratio of Ni to Fe should be controlled between 0.95 and 1.05. This is because when the Ni content is approximately equal to the Fe content, the K phase is uniformly dispersed in fine granules, which is conducive to obtaining good comprehensive mechanical properties. When the Ni content is less than the Fe content, the K phase precipitates in a layered manner, and when the Fe content is greater than the Ni content, the K phase precipitates in a blocky manner. The strengthening effect of the layered and blocky K phases is far less than that of the fine-grained K phase.

[0012] Sn: Sn has a strong solid solution strengthening effect in Cu, and the strength of tin-phosphor bronze increases with increasing Sn content. When the Sn content is below 3 wt%, the solid solution strengthening effect of Sn contributes little to improving the alloy strength, and thus fails to pin dislocations, resulting in dislocation fixation. As the Sn content increases to above 5 wt%, Cu and Sn form a hard and brittle δ phase, which negatively impacts the strength of tin-phosphor bronze. Sn can further improve the alloy's resistance to corrosion in steam and slightly acidic atmospheres.

[0013] Al plays a role in solid solution strengthening in the alloy of this invention. With the increase of Al content, the tensile strength and yield strength of the alloy are significantly improved. Al element forms a dense layer of Cu2O and Al2O3 mixed corrosion-resistant oxide film on the surface of the copper alloy, which inhibits the corrosion of the alloy matrix and significantly improves the corrosion resistance of the alloy. When the Al content is less than 1%, the protective oxide film formed on the alloy surface is not dense enough and cannot effectively block the corrosion of the alloy matrix by corrosive media. Therefore, the Al content of the alloy of this invention is in the range of 1-3 wt%.

[0014] Fe: Fe can delay the recrystallization process of copper, thus refining the microstructure and improving strength. When the Fe content reaches 0.8 wt% or more, a Fe-rich K phase will be formed in the alloy, which will improve the strength and hardness of the alloy. However, as the Fe content continues to increase, the plasticity of the alloy will decrease. When the Fe content exceeds 2 wt%, the improvement in the strength of the alloy is not significant, but the plasticity of the alloy decreases significantly. Therefore, the Fe content range of the alloy in this invention is 0.8-2 wt%.

[0015] Ni: Ni can alter the morphology of the α phase in the alloy's microstructure. Without Ni, the α phase is needle-like; as the Ni content increases, it transforms from needle-like to blocky. Ni forms a Ni-rich K phase in the alloy, which improves the alloy's strength, hardness, and corrosion resistance. Ni works synergistically with Fe, improving the alloy's strength while mitigating the problem of reduced plasticity due to increased strength from Fe alone. The Ni content in the alloy of this invention is 1-2 wt%.

[0016] P: P readily forms a coherently ordered compound Cu3P with Cu. When the P content is below 0.1%, it is difficult for P to form sufficient Cu3P and Fe3P reinforcing phases with Cu and Fe to enhance the strength of the alloy through second-phase precipitation. When the P content exceeds 0.3%, Cu3P forms eutectics with the α and δ phases, causing hot brittleness of the alloy and making it prone to cracking during hot working. Therefore, the P content in the copper alloy of this invention does not exceed 0.3%.

[0017] Zn: Trace amounts of Zn can improve the casting properties of the alloy, but its resistance to discoloration is poor, so its content should be limited to no more than 0.3 wt%.

[0018] Mn: Trace amounts of Mn can reduce the tendency of alloys to crack during hot working, and at the same time help to improve the mechanical properties and corrosion resistance of the alloys.

[0019] Preferably, the metallographic structure of the high-strength corrosion-resistant copper alloy rod includes an α phase and a K phase, wherein the K phase is dispersed in the α phase, the size of the α phase is 5-25 μm, the size of the K phase is no more than 1 μm, and the area fraction of the K phase is not less than 1.5%.

[0020] The microstructure of the alloy of the present invention is α phase, the size of which is controlled between 5-25 μm. The K phase is uniformly, finely, and dispersedly distributed on the α phase matrix. The size of the K phase should not exceed 1 μm, and the area fraction of the K phase is 1.5-3.0%. At this point, better strength and plasticity can be obtained. If the area fraction of the K phase is too high, the plasticity of the alloy will be reduced, and the elongation will be less than 5%.

[0021] Preferably, the K phase is fine-grained, and the K phase is either Fe-rich or Ni-rich. The Ni-rich K phase has high hardness and good toughness, while the Fe-rich K phase has good hardness. The synergistic effect of the two allows the alloy to achieve high strength while maintaining a certain degree of plasticity.

[0022] On the other hand, the present invention also provides a method for preparing the high-strength corrosion-resistant copper alloy rod, wherein the process flow of the preparation method is: smelting → semi-continuous casting → extrusion → stretching → annealing → drawing, wherein:

[0023] The high-strength corrosion-resistant copper alloy rod is prepared and smelted according to the mass percentage of each component.

[0024] The total processing rate of the stretching is 40-60%.

[0025] This invention achieves the desired grain size and K-phase volume fraction by controlling the total stretching processing rate. If the total stretching processing rate is below 40%, the alloy exhibits low cold deformation, resulting in uneven microstructure deformation across different parts of the billet. The varying energy storage levels due to lattice distortion in different parts lead to different recrystallization driving forces, resulting in inconsistent recrystallized grain sizes. As the degree of cold deformation increases, once the total stretching processing rate exceeds 60%, the microstructure deformation across different parts of the billet is very thorough. The original grains of the extruded billet are completely broken up, significantly increasing the number of recrystallization nuclei and resulting in finer recrystallized grains. Subsequent annealing may lead to α-phase grain sizes less than 5 μm. The stretching processing rate affects the K-phase distribution after annealing. Increasing the total stretching processing rate promotes K-phase refinement, thereby increasing the K-phase area ratio. Controlling the processing rate within this range aims to coordinate with the subsequent annealing process to obtain the desired grain size and K-phase volume fraction.

[0026] Preferably, the raw materials for smelting are electrolytic copper, zinc ingots, tin ingots, electrolytic nickel, electrolytic manganese, and Cu-Fe master alloy. The raw materials are proportioned according to the mass percentage of each component of the high-strength corrosion-resistant copper alloy rod, and then added to an induction furnace for smelting at a temperature of 1100-1220℃. After the composition is qualified, the slag is removed and the material is allowed to stand for more than 3-10 minutes before tilting the converter head to prepare for casting.

[0027] Preferably, the induction furnace lining material is a neutral material, because Al-containing bronze easily reacts with conventional acidic materials, corroding the lining. More preferably, the neutral material is a dry bridging material composed of 60-80 wt% white corundum, 18-35 wt% aluminum-magnesium spinel powder, and 2-5 wt% sintering agent.

[0028] Preferably, a composite solvent is added to the melt formed after smelting, wherein the amount of composite solvent added is 0.2-1 kg per ton of melt, and the mass fraction of each component of the composite solvent is: cryolite 40-70 wt%, fluorite 15-35 wt%, and sodium fluoride 10-30 wt%.

[0029] Since Al in the melt is easily oxidized to form Al2O3, and the slag formed by Al2O3 or Al2O3 and other oxides will flow into the crystallizer with the melt to form inclusions, composite flux should be selected as a covering agent and refining agent. By controlling the composition and ratio of the composite flux, it not only has a good adsorption capacity for Al2O3, but also dissolves Al2O3 in it, which will be separated from the copper liquid with the float and sink of the flux, thus playing the role of slag removal and slag cleaning. It is added twice, before charging and after smelting, with an addition amount of 0.2-1 kg / T copper liquid. After smelting, the composite flux is added and stirred thoroughly for more than 3-6 minutes before slag is removed.

[0030] Preferably, the casting temperature of the semi-continuous casting is 1170-1230℃, the casting speed is 30-90mm / min, and the primary cooling water flow rate is 10-20m³ / min. 3 / h, secondary cooling water flow rate is 1-8m 3 The cooling water pressure is 0.2-0.6 MPa per hour, and the cooling water inlet temperature is ambient. The ingot sawing specifications are...

[0031] Preferably, a semi-continuous casting method using a crystallizer vibration casting method is employed, wherein the amplitude of the crystallizer is 0.5-4 mm and the vibration frequency is 20-100 times / min.

[0032] The alloy melt provided by this invention has a high viscosity. It adopts crystallizer vibration casting technology, and by controlling the amplitude and vibration frequency, the purpose is to reduce slag inclusion defects on the surface of the ingot.

[0033] More preferably, the height of the crystallizer is 150-200mm, and the equiaxed crystal zone ratio of the ingot obtained by the semi-continuous casting is higher than 85%.

[0034] Because the alloy ingot of this invention is prone to developing a layered structure during extrusion, affecting the mechanical properties of the alloy, the layered structure is caused by inhomogeneous casting structure, particularly an excessively large columnar crystal region. To avoid the formation of a layered structure, a short crystallizer should be used, and the height range of the crystallizer should be controlled. A short crystallizer can reduce the number of ingot-shaped crystal regions and expand the equiaxed crystal region. Macroscopic corrosion testing of ingot slices shows that the equiaxed crystal region area should account for more than 85%; otherwise, layered structure is very likely to form during extrusion.

[0035] Preferably, the preheating temperature of the extrusion is 400-450℃, the extrusion ratio is 20-200, and the extrusion temperature is 840-900℃.

[0036] The alloy of this invention exhibits extremely high resistance to extrusion deformation, classifying it as a difficult-to-extrude alloy. The preheating temperature of the tooling and die should reach 400-450℃, with a preheating time of no less than 2 hours. The extrusion ratio should be controlled within the range of 20-200. This is because when the extrusion ratio is less than 20, the casting structure is easily preserved, and the unevenness of mechanical properties between the center and periphery of the extruded billet intensifies. Extrusion becomes difficult when the extrusion ratio exceeds 200. The extrusion temperature should be 840-900℃. Since the viscosity of the alloy to the extrusion tool increases with temperature, peeling defects easily occur on the surface of the extruded billet. Therefore, the extrusion temperature should not exceed 900℃, and below 840℃, when the extrusion ratio is large, it is easy to encounter situations where extrusion cannot proceed. Furthermore, the extrusion speed should be 4-10 mm / s. If the extrusion speed is too low, the ingot temperature drop will result in incomplete extrusion; if the extrusion speed is too high, and the extrusion temperature is high, the extruded billet is prone to cracking. Natural cooling of the extruded billet after extrusion from the die can prevent brittle cracking.

[0037] Preferably, the annealing temperature is 600-680℃, starting from room temperature and gradually increasing to the set temperature, with a holding time of 120-300 minutes. Higher annealing temperatures result in stronger atomic diffusion, easier grain boundary migration, and faster grain growth. The copper alloy provided by this invention has an annealing temperature below 600℃, which cannot completely eliminate work hardening; when the annealing temperature exceeds 680℃, grains begin to grow easily, with an average grain size exceeding 40μm.

[0038] Preferably, the total processing rate of the drawing is 30-45%. If the processing rate is less than 30%, the work hardening effect is weak and the mechanical properties of the material are low. If the processing rate exceeds 45%, the yield strength is too high, the elongation is less than 5%, and the straightness of the bar is difficult to control.

[0039] More preferably, the stretched hardened wire blank is sequentially cut to length and straightened to obtain copper alloy rods with a length of 2-3m and a straightness of no more than 0.5mm / m.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] This invention improves the overall mechanical and corrosion resistance of the alloy by adding a higher proportion of Al, Fe, and Ni elements, thereby changing the morphology of the α-phase microstructure from needle-like to blocky. Furthermore, by controlling the Ni to Fe mass ratio, a uniform, fine, and dispersed K-phase distribution within the α-phase matrix is ​​achieved. 0.2 ≥720Mpa, hardness HV5≥220, elongation A50≥5%, and corrosion resistance passed the 48h artificial atmosphere corrosion test. Attached Figure Description

[0042] Figure 1 Metallographic photograph of the finished product obtained in Example 1 of this invention;

[0043] Figure 2 Metallographic photograph of the QSn6.5-0.1 bar provided in Comparative Example 1 of this invention. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0045] The present invention provides Examples 1-5 and Comparative Examples 1-7, and the specific components are shown in Table 1.

[0046] Example 1

[0047] This embodiment provides a method for preparing a high-strength, corrosion-resistant bar with dimensions of Ф8.4mm × 2500mm as follows:

[0048] 1) Melting: Prepare the raw materials according to the required composition and melt them in an induction furnace at a temperature of 1120-1200℃. Use a composite flux for covering and refining agents, adding 0.5 kg / T of molten copper. Stir thoroughly for 4 minutes, remove slag, and let stand for 5 minutes before tilting the furnace head to prepare for casting. The mass fractions of the components in the composite flux are: cryolite 52 wt%, fluorite 26 wt%, and sodium fluoride 22 wt%.

[0049] 2) Semi-continuous casting: Casting temperature is 1180-1220℃, casting speed is 50mm / min, and primary cooling water flow rate is 16.3m³. 3 / h, secondary cooling water flow rate is 6.4m³ / h. 3 The cooling water pressure is 0.4 MPa, and the inlet temperature is ambient. The crystallizer height is 170 mm, the vibration amplitude is 2 mm, and the vibration frequency is 45 times / min. The dimensions of the sawn ingot are as follows: The measured area ratio of the equiaxed crystal region in the ingot was 91.6%.

[0050] 3) Extrusion: The preheating temperature of the extrusion tooling and die should reach 420℃ and the preheating time should be 4h; the extrusion billet specification is double-flow Ф16mm, the extrusion ratio is 126, the extrusion temperature is 880℃, and the extrusion speed is 6-8mm / s.

[0051] 4) Stretching: The Ф16mm extruded billet is stretched to Ф11mm, with a total processing rate of 52.7%.

[0052] 5) Annealing: The annealing temperature for Ф11mm billet is 650℃, starting from room temperature and holding for 240 minutes.

[0053] 5) Drawing: The annealed Ф11mm billet is drawn into bars with dimensions of Ф8.4mm×2500mm. The total drawing rate is 41.7%, and the straightness after straightening is 0.15mm / m.

[0054] 6) Finished product inspection.

[0055] like Figure 1 As shown, the α phase morphology is blocky, and the α phase size (grain size) is 12.5 μm, which meets the 5-25 μm range of the α phase grain size requirement of the alloy of the present invention. The microstructure contains 1.94% of the k phase, which meets the requirement that the k phase area ratio of the alloy of the present invention is ≥1.5%, and the k phase size is 0.57 μm, which meets the requirement that the k phase size of the alloy of the present invention is ≤1 μm.

[0056] Example 2

[0057] This embodiment provides a method for preparing a high-strength, corrosion-resistant bar with dimensions of Ф4mm × 2000mm as follows:

[0058] 1) Melting: Prepare the raw materials according to the required composition and melt them in an induction furnace at a temperature of 1130-1200℃. Use a composite flux for covering and refining, adding 0.4 kg / T of molten copper. Stir thoroughly for 3 minutes, remove slag, let stand for 5 minutes, and then tilt the furnace head to prepare for casting. The mass fractions of the components in the composite flux are: cryolite 43 wt%, fluorite 30 wt%, and sodium fluoride 27 wt%.

[0059] 2) Semi-continuous casting: Casting temperature is 1170-1210℃, casting speed is 65mm / min, and primary cooling water flow rate is 14m³ / min. 3 / h, secondary cooling water flow rate is 4.5m³ / h. 3 The cooling water pressure is 0.36 MPa, and the inlet temperature is ambient. The crystallizer height range is 200 mm, the crystallizer vibration amplitude is 0.8 mm, and the vibration frequency is 80 times / min. The dimensions of the sawn ingot are as follows: The measured area ratio of the equiaxed crystal region in the ingot was 89.3%.

[0060] 3) Extrusion: The preheating temperature of the extrusion tooling and die should reach 400℃ and the preheating time should be 3.5h; the extrusion billet specification is double-flow Ф7mm, the extrusion ratio is 186, the extrusion temperature is 890℃, and the extrusion speed is 6-9mm / s.

[0061] 4) Stretching: The Ф7mm extruded billet is stretched to Ф5.2mm, with a total processing rate of 44.8%.

[0062] 5) Annealing: The annealing temperature for Ф5.2mm billet is 600℃, starting from room temperature and holding for 270 minutes.

[0063] 5) Drawing: The annealed Ф5.2mm billet is drawn into bars with dimensions of Ф4mm×2000mm. The total drawing rate is 40.8%, and the straightness after straightening is 0.10mm / m.

[0064] 6) Finished product inspection.

[0065] Example 3

[0066] This embodiment provides a specification of The preparation method of high-strength corrosion-resistant bars is as follows:

[0067] 1) Melting: Prepare the raw materials according to the required composition and melt them in an induction furnace at a temperature of 1160-1220℃. A composite flux is used as the covering agent and refining agent, added at a rate of 0.9 kg / T of molten copper. Stir thoroughly for 6 minutes, remove slag, and let stand for 8 minutes before tilting the furnace head in preparation for casting. The mass fractions of the components in the composite flux are: cryolite 65 wt%, fluorite 20 wt%, and sodium fluoride 15 wt%.

[0068] 2) Semi-continuous casting: Casting temperature is 1180-1220℃, casting speed is 55mm / min, and primary cooling water flow rate is 18.4m³. 3 / h, secondary cooling water flow rate 6m 3 The cooling water pressure is 0.45 MPa, and the inlet temperature is ambient. The crystallizer height range is 180 mm, the crystallizer vibration amplitude is 4 mm, and the vibration frequency is 30 times / min. The dimensions of the sawn ingot are as follows: The measured area ratio of the equiaxed crystal region in the ingot was 92.9%.

[0069] 3) Extrusion: The preheating temperature of the extrusion tooling and die should reach 450℃ and the preheating time should be 2h; the extrusion billet specification is single-flow Ф29mm, the extrusion ratio is 76.7, the extrusion temperature is 850℃, and the extrusion speed is 5-7mm / s.

[0070] 4) Stretching: The Ф29mm extruded billet is stretched to Ф22mm, with a total processing rate of 42.4%.

[0071] 5) Annealing: The annealing temperature for Ф22mm billet is 680℃, starting from room temperature and holding for 210 minutes.

[0072] 5) Drawing: The annealed Ф22mm billet is drawn into bars with dimensions of Ф18mm×3000mm. The total drawing rate is 33%, and the straightness after straightening is 0.32mm / m.

[0073] 6) Finished product inspection.

[0074] Example 4

[0075] This embodiment provides a specification of The preparation method of high-strength corrosion-resistant bars is as follows:

[0076] 1) Melting: Prepare the raw materials according to the required composition and melt them in an induction furnace at a temperature of 1170-1230℃. Use a composite flux for both the covering agent and refining agent, adding 0.72 kg / T of molten copper. Stir thoroughly for 6 minutes, remove slag, and let stand for 8 minutes before tilting the furnace head in preparation for casting. The mass fractions of the components in the composite flux are: cryolite 48 wt%, fluorite 32 wt%, and sodium fluoride 20 wt%.

[0077] 2) Semi-continuous casting: Casting temperature is 1180-1220℃, casting speed is 80mm / min, and primary cooling water flow rate is 20m³ / min. 3 / h, secondary cooling water flow rate 8m 3 The cooling water pressure is 0.5 MPa, and the inlet temperature is ambient. The crystallizer height range is 160 mm, the crystallizer vibration amplitude is 1 mm, and the vibration frequency is 80 times / min. The dimensions of the sawn ingots are as follows: The measured area ratio of the equiaxed crystal region in the ingot was 93.5%.

[0078] 3) Extrusion: The preheating temperature of the extrusion tooling and die should reach 420℃ and the preheating time should be 4h; the extrusion billet specification is single-flow Ф25mm, the extrusion ratio is 60.8, the extrusion temperature is 820℃, and the extrusion speed is 5-7mm / s.

[0079] 4) Stretching: The Ф25mm extruded billet is stretched to Ф17.5mm, with a total processing rate of 51%.

[0080] 5) Annealing: The annealing temperature for Ф17.5mm billet is 660℃, starting from room temperature and holding for 240 minutes.

[0081] 5) Drawing: The annealed Ф17.5mm billet is drawn into bars with dimensions of Ф13.1mm×2500mm. The total drawing rate is 44%, and the straightness after straightening is 0.20mm / m.

[0082] 6) Finished product inspection.

[0083] Example 5

[0084] This embodiment provides a specification of The preparation method of high-strength corrosion-resistant bars is as follows:

[0085] 1) Melting: Prepare the raw materials according to the required composition and melt them in an induction furnace at a temperature of 1170-1230℃. A composite flux is used as the covering agent and refining agent, added at a rate of 0.3 kg / T of molten copper. Stir thoroughly for 10 minutes, remove slag, and let stand for 15 minutes before tilting the furnace head in preparation for casting. The mass fractions of the components in the composite flux are: cryolite 58 wt%, fluorite 19 wt%, and sodium fluoride 23 wt%.

[0086] 2) Semi-continuous casting: Casting temperature is 1175-1210℃, casting speed is 35mm / min, and primary cooling water flow rate is 10m³ / min. 3 / h, secondary cooling water flow rate 2m 3 The cooling water pressure is 0.6 MPa, and the inlet temperature is ambient. The crystallizer height range is 175 mm, the crystallizer vibration amplitude is 3 mm, and the vibration frequency is 50 times / min. The dimensions of the sawn ingot are as follows: The measured area ratio of the equiaxed crystal region in the ingot was 88.7%.

[0087] 3) Extrusion: The preheating temperature of the extrusion tooling and die should reach 400℃ and the preheating time should be 4h; the extrusion billet specification is double-flow Ф11mm, the extrusion ratio is 126.5, the extrusion temperature is 840℃, and the extrusion speed is 6-8mm / s.

[0088] 4) Stretching: The Ф11mm extruded billet is stretched to Ф7mm, with a total processing rate of 59.5%.

[0089] 5) Annealing: The annealing temperature for Ф7mm billet is 620℃, starting from room temperature and holding for 300 minutes.

[0090] 5) Drawing: The annealed Ф7mm billet is drawn into bars with dimensions of Ф5.8mm×2000mm. The total drawing rate is 31.3%, and the straightness after straightening is 0.10mm / m.

[0091] 6) Finished product inspection.

[0092] Comparative Example 1

[0093] The comparative example provided is a QSn6.5-0.1Ф8.4mm×2500mm bar; such as Figure 2 As shown, the α phase morphology is needle-like and blocky, and the α phase size (grain size) is relatively large, reaching 35 μm. The microstructure does not contain the k phase.

[0094] Comparative Example 2

[0095] The difference from Example 1 is that the Fe content is only 0.34%, less than 0.8 wt%.

[0096] Comparative Example 3

[0097] The difference from Example 1 is that the Ni content is only 0.015%, less than 1 wt%.

[0098] Comparative Example 4

[0099] The difference from Example 1 is that: W Ni / W Fe Only 0.70, does not meet W. Ni / W Fe It is in the range of 0.95-1.05.

[0100] Comparative Example 5

[0101] The difference from Example 1 is that the crystallizer height is 230mm, which exceeds 200mm.

[0102] Comparative Example 6

[0103] The difference from Example 1 is that the total stretching rate is 28.6%, which is less than 40%.

[0104] Comparative Example 7

[0105] The difference from Example 1 is that the total drawing rate is 23.9%, which is less than 30%.

[0106] The phase ratios and phase sizes of the obtained examples and comparative examples were observed under a scanning electron microscope, and the results are recorded in Table 4.

[0107] The phase morphology, phase size, and phase area fraction of Examples 1-5 and Comparative Examples 1-7 were tested, and the results are recorded in Table 2.

[0108] The tensile strength, yield strength, elongation, and hardness of Examples 1-5 and Comparative Examples 1-7 were tested, and the results are recorded in Table 3.

[0109] Morphology, size and area fraction: observed under a metallographic microscope.

[0110] Tensile strength, yield strength and elongation: tested in accordance with GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0111] Vickers hardness: Tested according to GB / T4340.1-2009 "Metallic materials - Vickers hardness test - Part 1: Test method".

[0112] Corrosion resistance test: A salt spray comparative test was conducted according to the test method (neutral salt spray test method) of GB / T 10125-2012 (artificial atmosphere corrosion test, salt spray test). The test conditions were: temperature: 35±2℃, pH value: 6.5-7.2, salt spray concentration: 5% NaCl solution, test time: 48h, and sample size: Ф4mm×100mm. Before the test, the sample surface was sanded to 1000# with water sandpaper, ultrasonically cleaned, and then placed in a desiccator for later use. After the test, the sample was taken out, gently rinsed with tap water to remove residual sodium chloride solution and corrosion products from the sample surface, then rinsed with anhydrous alcohol, and dried with cool air. The corrosion resistance effect was judged by visually observing the discoloration of the sample surface. Only slight discoloration of the surface indicates that the material has good corrosion resistance.

[0113] Table 1 Chemical composition of the examples and comparative examples

[0114]

[0115]

[0116] Table 2. Dislocation density, percentage of precipitated phases, size, and quantity of examples and comparative examples.

[0117]

[0118] Table 3 Mechanical properties and corrosion resistance of the examples and comparative examples

[0119]

Claims

1. A high-strength, corrosion-resistant copper alloy rod, characterized in that, The high-strength corrosion-resistant copper alloy rod has the following composition by mass percentage: Sn: 3-5wt%, Al: 1-3wt%, Fe: 0.8-2wt%, Ni: 1-2wt%, P: 0.05-0.3wt%, Zn: 0.001-0.3wt%, Mn: 0.001-0.3wt%, with the balance being Cu and unavoidable impurities. The mass ratio of Ni to Fe is 0.95-1.

05. The metallographic structure of the high-strength corrosion-resistant copper alloy rod includes an α phase and a K phase. The K phase is dispersed in the α phase. The size of the α phase is 5-25 μm, the size of the K phase is no more than 1 μm, the area fraction of the K phase is 1.5-3.0%, and the morphology of the α phase is blocky.

2. The high-strength, corrosion-resistant copper alloy rod according to claim 1, characterized in that, The K phase is fine-grained, and the K phase is either Fe-rich or Ni-rich.

3. A method for preparing a high-strength, corrosion-resistant copper alloy rod according to any one of claims 1-2, characterized in that, The process flow of the preparation method is as follows: smelting → semi-continuous casting → extrusion → stretching → annealing → drawing, wherein: The high-strength corrosion-resistant copper alloy rod is prepared and smelted according to the mass percentage of each component as described in any one of claims 1-2. The total processing rate of the stretching is 40-60%.

4. The method for preparing high-strength corrosion-resistant copper alloy rods according to claim 3, characterized in that, A composite flux is added to the melt formed after smelting. The amount of composite flux added is 0.2-1 kg per ton of melt. The mass fraction of each component of the composite flux is: cryolite 40-70 wt%, fluorite 15-35 wt%, and sodium fluoride 10-30 wt%.

5. The method for preparing high-strength, corrosion-resistant copper alloy rods according to claim 3, characterized in that, Semi-continuous casting is carried out using a crystallizer vibration casting method, wherein the amplitude of the crystallizer is 0.5-4mm and the vibration frequency is 20-100 times / min.

6. The method for preparing high-strength, corrosion-resistant copper alloy rods according to claim 5, characterized in that, The height of the crystallizer is 150-200mm, and the equiaxed crystal zone of the ingot obtained by the semi-continuous casting accounts for more than 85%.

7. The method for preparing high-strength, corrosion-resistant copper alloy rods according to claim 3, characterized in that, The preheating temperature for the extrusion is 400-450℃, the extrusion ratio is 20-200, and the extrusion temperature is 840-900℃.

8. The method for preparing high-strength, corrosion-resistant copper alloy rods according to claim 3, characterized in that, The annealing temperature is 600-680℃.

9. The method for preparing high-strength, corrosion-resistant copper alloy rods according to claim 3, characterized in that, The total machining rate of the drawing process is 30-45%.

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