A method for producing a large-size precipitation-strengthened copper alloy

Abstract

This invention discloses a method for preparing large-size precipitation-strengthened copper alloys, comprising the following steps: substrate preparation; surface treatment of the bonding surface; hot pressing bonding: multiple substrates are stacked in a vacuum hot press furnace, the pressure head is lowered to the top of the sample and a pre-pressure is applied, the furnace door is closed and the furnace cavity is evacuated, and then argon gas is introduced into the furnace cavity for protection; heating begins, and after reaching the preset temperature, it is held at that temperature for 1-2 hours to ensure uniform sample temperature, followed by isothermal solution treatment of the sample for 1-6 hours; after solution treatment, pressure is applied to the sample, with an overall deformation of 5%-30%, and hot pressing bonding is performed for 1-3 hours; after the hot pressing bonding process, the sample is removed after cooling with the furnace; plastic processing; precipitation strengthening. By using the hot pressing bonding method, chromium-zirconium-copper alloy billets obtained by continuous casting are solid-state stacked, and interface bonding is achieved under certain process parameters. High-quality large-size chromium-zirconium-copper alloy products can then be prepared through subsequent deformation, heat treatment, and other processes.

Description

Technical Field

[0001] This invention belongs to the field of alloy materials technology, and in particular relates to a method for preparing large-size precipitation-strengthened copper alloys. Background Technology

[0002] Precipitation-strengthened copper alloys are commonly used copper alloys, possessing a range of excellent properties including high strength, superior electrical conductivity, excellent fatigue resistance, radiation resistance, and wear resistance. These superior properties primarily originate from the second-phase particles produced by trace amounts of alloying elements added to the copper matrix. For example, chromium-zirconium copper alloy is a common precipitation-strengthened copper alloy. Trace amounts of chromium and zirconium precipitate nano-sized strengthening phases during heat treatment, giving the alloy high strength and high electrical conductivity. It is currently widely used in industrial fields such as high-speed rail contact lines and lead frames.

[0003] Precipitation-strengthened copper alloys, with a large number of nanoparticles in their matrix, not only achieve a balance between high strength and high toughness, but also possess excellent high-temperature performance and radiation resistance due to the granular phase. Therefore, they are considered a preferred material for high heat flux density components in nuclear fusion reactors. Currently, the manufacturing process of precipitation-strengthened copper alloys is mostly continuous casting, primarily used to produce bars with diameters of 60mm-120mm. Subsequent processes such as extrusion, drawing, and heat treatment are then used to prepare wires; and for applications with cross-sectional areas less than 0.3m². 2 The billet is then rolled and heat-treated to produce thin plates and strips. However, these processes are insufficient to meet the demands of large-sized raw materials required in nuclear fusion. Due to the size effect of large ingots, the cooling rates of different parts of the ingot vary, leading to uneven distribution of alloying elements in the macrostructure during casting. This is particularly true for chromium-zirconium-copper alloys, where the addition of chromium and zirconium is less than 1%. The increased cross-sectional area inevitably affects the uniform distribution of these elements. This also limits the application of precipitation-strengthened copper alloys in many fields. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing large-size precipitation-strengthened copper alloys in order to solve the above-mentioned problems. The method involves preparing large-size chromium-zirconium-copper precipitation-strengthened alloys by hot pressing, stacking chromium-zirconium-copper alloy billets obtained by continuous casting in a solid state, and achieving interface bonding under certain process parameters. High-quality large-size chromium-zirconium-copper alloy products can then be prepared through processes such as deformation and heat treatment.

[0005] The technical solution adopted in this invention is:

[0006] A method for preparing large-size precipitation-strengthened copper alloys includes the following steps:

[0007] Step 1: Substrate preparation;

[0008] Step 2: Surface treatment of the bonding surface;

[0009] Step 3: Hot Press Bonding: Stack multiple substrates with surface-treated bonding surfaces inside a vacuum hot press furnace. Lower the pressure head to the top of the sample and apply a pre-pressure of 3MPa-10MPa to ensure effective contact of the bonding surfaces. Close the furnace door and evacuate the furnace chamber to a vacuum level of 1×10⁻⁶. -2 Pa-10Pa, and then argon gas is introduced into the furnace cavity for protection to ensure that no oxides are formed at the interface due to atmospheric conditions during the hot pressing process;

[0010] The temperature is initially raised to 900℃-1000℃. After reaching the preset temperature, it is held for 1-2 hours to ensure uniform sample temperature. Then, the sample is subjected to isothermal solution treatment for 1-6 hours to regulate the size and number of the second phase in the tissue.

[0011] After solution treatment, apply a pressure of 10MPa-60MPa to the sample, with an overall deformation of 5%-30%, and perform hot pressing bonding after holding the sample at the temperature and pressure for 1-3 hours.

[0012] After the hot pressing process is completed, the sample is cooled to below 200°C in the furnace and then taken out. After hot pressing, the bonding interface between the samples basically disappears, and good metallurgical bonding is achieved between the interfaces.

[0013] Step 4: Plastic processing;

[0014] Step 5: Precipitation enhancement.

[0015] Specifically, the preparation of the substrate in step one involves: producing a chromium-zirconium-copper slab using a horizontal continuous casting process, cutting the chromium-zirconium-copper slab, and preparing a small-sized substrate that is hot-pressed together.

[0016] The specific steps of the second step, the surface treatment of the bonding surface, are as follows: the bonding surface of the chromium zirconium copper alloy is polished with a grinding wheel and sandpaper to remove the oxide scale and dirt on the outer surface of the ingot after horizontal continuous casting, ensuring that the roughness Ra of the contact surface is ≤3.2μm, which helps to avoid interface defects during bonding.

[0017] Specifically, the plastic processing in step four involves plastic processing the hot-pressed sample to deform it into the required workpiece shape.

[0018] In step four, plastic processing includes, but is not limited to, hot forging and hot rolling, which involves heating the bonded sample to 500℃-700℃ for hot processing. The deformation amount in each pass is no more than 5% of the original height to prevent excessive deformation from causing the sample to crack.

[0019] Specifically, step five involves precipitation strengthening: the deformed sample is solution treated at 1000℃ for 1-8 hours and then water-cooled. After the sample cools, it is aged at 560℃ for 1-12 hours.

[0020] The advantages of this invention are as follows:

[0021] Large-size chromium-zirconium-copper precipitation-strengthened alloys are prepared by hot pressing. Chromium-zirconium-copper alloy billets obtained by continuous casting are solid-state stacked and interface bonding is achieved under certain process parameters. High-quality large-size chromium-zirconium-copper alloy products can be prepared by subsequent deformation, heat treatment and other processes, avoiding the compositional segregation and microstructure inhomogeneity that occur when directly casting large-section ingots. Detailed Implementation

[0022] The present invention will be further described below, but the present invention is not limited to these contents.

[0023] Example 1

[0024] Step 1: C18150 (Cu-1.0Cr-0.10Zr) precipitation-strengthened copper alloy is horizontally continuously cast to obtain a billet with a cross-section of 680mm×220mm. It is then cut into a base material with a cross-section of 680mm×680mm×220mm (length×width×height). The mating surfaces are then polished to ensure that there are no oxides or impurities on the contact surfaces before bonding.

[0025] Step 2: Place the polished surfaces of the three samples together in a vacuum chamber, press the samples against the ground surface with a graphite indenter, apply a pre-pressure of 10 MPa, and evacuate to 1 Pa. Then, introduce argon gas into the furnace chamber for protection, ensuring that the argon atmosphere pressure inside the furnace is maintained at 3 × 10⁻⁶. 2 Pa, heating begins;

[0026] Step 3: Heat the vacuum hot press furnace to 950℃ at a heating rate of 10℃ / min, and keep the sample at this temperature for 1 hour to ensure uniform sample temperature. Then, perform a constant temperature solution treatment on the sample for 4 hours. After the solution treatment is completed, apply a pressure of 45MPa to the sample, with an overall deformation of 15%, and keep it at this temperature and pressure for 3 hours.

[0027] Step 4: After the hot pressing process is completed, the pressure is released and the temperature is lowered. The sample is cooled to below 200°C with the furnace, and the furnace door is opened to remove the sample after connecting to the atmosphere. After the experiment, the microstructure of the sample is observed by scanning electron microscopy. It is difficult to observe the bonding interface. Statistical analysis of the size of the second phase shows that the solution treatment before bonding effectively reduced the size and number of the second phase. EBSD detection shows that the process generated a large number of recrystallized grains at the interface. At the same time, the reduction in the size and number of the second phase at the interface promoted the interface migration.

[0028] Step 5: Heat the hot-pressed sample to 700℃ and perform hot forging, with a deformation amount of 4% per pass, to process and deform it into a sheet.

[0029] Step 6: Perform solution treatment on the deformed sample at 1000℃ for 6 hours and then rapidly cool it. After the sample has cooled, perform aging treatment on the sample at 560℃ for 10 hours.

[0030] Step 7: Perform performance tests on the aged sample, taking 10 samples at different locations (the sampling area must include the bonding interface). The final average tensile strength is 583 MPa, the plasticity is 15%, and the conductivity is 78% IACS. At the same time, the fracture location is not in the matrix. It can be considered that a large-size chromium-zirconium copper ingot with uniform structure and performance that meets the requirements of use was obtained through hot pressing bonding process.

[0031] Example 2

[0032] Step 1: C18160 (Cu-0.7Cr-0.10Zr) precipitation-strengthened copper alloy is horizontally continuously cast to obtain a billet with a cross-section of 300mm×100mm. It is then cut into a base material of 600mm×300mm×100mm (length×width×height). The mating surfaces are then polished to ensure that there are no oxides or impurities on the contact surfaces before bonding.

[0033] Step 2: Place the polished surfaces of the two samples together, place them in the vacuum chamber, press the samples with a graphite indenter, apply a pre-pressure of 10 MPa, and evacuate to 1 Pa. Then, introduce argon gas into the furnace chamber for protection, ensuring that the argon atmosphere pressure inside the furnace is maintained at 3 × 10⁻⁶. 2 Pa, heating begins;

[0034] Step 3: Heat the vacuum hot press furnace to 900℃ at a heating rate of 10℃ / min, keep the sample at this temperature for 1 hour to ensure thorough heating, and then perform a 3-hour isothermal solution treatment on the sample. After the isothermal solution treatment is completed, apply a pressure of 30MPa to the sample to achieve a deformation of 13%, and keep it at this temperature and pressure for 3 hours.

[0035] Step 4: After the hot pressing process is completed, the pressure is released and the temperature is lowered. The sample is cooled to below 200°C with the furnace, then the furnace door is opened to remove the sample.

[0036] Step 5: Heat the hot-pressed sample to 650℃ and hot-roll it into a sheet;

[0037] Step 6: Perform solution treatment on the deformed sample at 1000℃ for 4 hours and then rapidly cool it. After the sample has cooled, perform aging treatment on the sample at 540℃ for 7 hours.

[0038] Step 7: Perform performance tests on the aged samples, taking 10 samples at different locations (the sampling area must include the bonding interface). The final average tensile strength is 536 MPa, the plasticity is 19%, and the conductivity is 75% IACS.

[0039] Example 3

[0040] Step 1: Using PWHC (Cu-1.5Cr-0.20Zr) precipitation-strengthened copper alloy, a 200mm×120mm cross-section billet is obtained by horizontal continuous casting. The billet is then cut into 200mm×200mm×120mm (length×width×height) base materials. The mating surfaces are then polished to ensure that there are no oxides or impurities on the contact surfaces before bonding.

[0041] Step 2: Place the polished surfaces of three samples with clean surfaces together in a vacuum hot press furnace. Use a graphite indenter to hold the samples in place and apply a pre-pressure of 5 MPa. Evacuate the furnace to 1 Pa, then introduce argon gas into the furnace cavity for protection. After introducing argon gas, maintain the argon atmosphere pressure in the furnace at 3 × 10⁻⁶. 2 Pa, heating begins;

[0042] Step 3: Heat the vacuum hot press furnace to 1000℃ at a heating rate of 10℃ / min, and keep the sample at this temperature for 1 hour to ensure that the sample is thoroughly heated. Then, perform a constant temperature solution treatment on the sample for 3 hours. After the constant temperature solution treatment is completed, apply a pressure of 40MPa to the sample to achieve a deformation of 20%, and keep it at this temperature and pressure for 1 hour.

[0043] Step 4: After the hot pressing process is completed, the pressure is released and the temperature is lowered. The sample is cooled to below 200°C with the furnace, then the furnace door is opened to remove the sample.

[0044] Step 5: Heat the hot-pressed sample to 650℃ and hot forge it to deform it into a copper ring;

[0045] Step 6: Perform solution treatment on the deformed sample at 1000℃ for 8 hours and then water-cool it. After the sample has cooled, perform aging treatment on the sample at 580℃ for 12 hours.

[0046] Step 7: Perform performance tests on the aged samples, taking 10 samples at different locations (the sampling area must include the bonding interface). The final average tensile strength is 600 MPa, the plasticity is 8%, and the conductivity is 72% IACS.

[0047] It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention, and these modifications and improvements are all within the scope of protection of this invention.

Claims

1. A method for preparing a large-size precipitation-strengthened copper alloy, characterized in that: Includes the following steps: Step 1: Substrate preparation; Step 2: Surface treatment of the bonding surface; Step 3: Hot Press Bonding: Stack multiple substrates with surface treatment on the bonding surfaces inside a vacuum hot press furnace. Lower the pressure head to the top of the sample and apply a pre-pressure of 3MPa-10MPa. Close the furnace door and evacuate the furnace chamber to a vacuum level of 1×10⁻⁶. -2 Pa-10Pa, and then argon gas was introduced into the furnace cavity for protection; Start heating up to 900℃-1000℃, and hold the temperature for 1-2 hours after reaching the preset temperature to ensure uniform sample temperature. Then, perform isothermal solution treatment on the sample for 1-6 hours. After solution treatment, apply a pressure of 10MPa-60MPa to the sample, with an overall deformation of 5%-30%, and perform hot pressing bonding after holding the sample at the temperature and pressure for 1-3 hours. After the hot pressing process is completed, the sample is cooled to below 200°C in the furnace and then removed. Step 4: Plastic processing; Step 5: Precipitation enhancement.

2. The method for preparing a large-size precipitation-strengthened copper alloy according to claim 1, characterized in that: The specific content of the substrate preparation in step one is as follows: a chromium-zirconium-copper slab is produced by horizontal continuous casting process, the chromium-zirconium-copper slab is cut, and a hot-pressed substrate is prepared.

3. The method for preparing a large-size precipitation-strengthened copper alloy according to claim 1, characterized in that: The specific content of the surface treatment of the mating surface in step two is as follows: use a grinding wheel and sandpaper to grind the mating surface of the chromium zirconium copper alloy to remove the oxide scale and dirt on the outer surface of the ingot after horizontal continuous casting, and ensure that the roughness Ra of the contact surface is ≤3.2μm.

4. The method for preparing a large-size precipitation-strengthened copper alloy according to claim 1, characterized in that: The plastic processing in step four specifically involves: performing plastic processing on the hot-pressed sample to deform it into the required workpiece shape as needed.

5. The method for preparing a large-size precipitation-strengthened copper alloy according to claim 1, characterized in that: The precipitation strengthening process in step five specifically involves: performing a solution treatment on the deformed sample at 1000℃ for 1-8 hours followed by water cooling; and then aging the sample at 560℃ for 1-12 hours after cooling.

6. A method for preparing a large-size precipitation-strengthened copper alloy according to claim 1 or 4, characterized in that: The plastic processing in step four includes, but is not limited to, hot rolling and hot forging, that is, heating the bonded sample to 500℃-700℃ for hot processing, with the deformation amount in each pass not exceeding 5% of the original height.