A high-strength flat guide copper alloy and its preparation method

Abstract

A high-strength flat-guide copper alloy and its preparation method. The present invention relates to a copper alloy and its preparation method. The purpose of the present invention is to develop a copper alloy with good strength and electrical conductivity by reasonably regulating alloying elements and heat treatment processes. The present invention includes: 75% - 79% of copper, 0.3 - 0.7 of tin, 0.5 - 0.9 of aluminum, 0.05 - 0.15 of nickel, <0.15 of phosphorus, and the balance is zinc. The present invention has successfully prepared a brass alloy with high strength and relatively ideal electrical conductivity by reasonably selecting alloy components and further regulating the heat treatment process. Deformation processes such as hot forging, hot rolling, and cold rolling used in material forming are mature in technology and easy to control in the process, and the preparation process has general applicability. The present invention belongs to the technical field of metal materials.

Description

Technical Field

[0001] The present invention relates to a copper alloy, and specifically to a high-strength flat-guide copper alloy and a preparation method thereof. The present invention belongs to the technical field of metal materials. Background Art

[0002] As an important alloy material, high-strength copper alloys are widely used in aerospace, core electronic devices, integrated circuits, etc. due to their good mechanical properties and workability. At present, in the research and development of high-performance copper alloys, on the one hand, the types and contents of alloying elements are adjusted; on the other hand, the heat treatment process is improved to optimize the structure and properties of the alloy. However, the strength and conductivity of copper alloys are contradictory to each other and usually cannot be taken into account simultaneously. Therefore, how to further improve the conductivity on the premise of increasing the strength of copper alloys has become a current research hotspot.

[0003] The types of copper alloys that are widely studied and produced at present are: Cu-Be series alloys, Cu-Cr series alloys, Cu-Ni-Sn series alloys. However, the Be element in Cu-Be series alloys is highly toxic and has low environmental affinity. The second phase of Cu-Cr series alloys has poor stability, so the heat treatment processing conditions are harsh. In Cu-Ni-Sn series alloys, the Ni and Sn elements are expensive, and the comprehensive cost is high. Many problems limit the further commercialization and large-scale application of the above alloys. Brass is composed of Cu and Zn, and adding various alloying elements is called complex brass. Brass has good corrosion resistance and workability, and the Zn element in brass is inexpensive, non-toxic and environmentally friendly. However, at present, the research on brass mainly focuses on corrosion resistance and wear resistance, and the research on its conductivity is less. There is also a lack of brass grades with matching strength and conductivity in the market.

[0004] Therefore, taking brass as the raw material, by reasonably regulating the alloying elements and heat treatment process, developing a copper alloy with good strength and conductivity has important scientific research significance and market application value. Summary of the Invention

[0005] The purpose of the present invention is to take brass as the raw material, and by reasonably regulating the alloying elements and heat treatment process, to develop a copper alloy with good strength and conductivity, and then to propose a high-strength flat-guide copper alloy and a preparation method thereof.

[0006] The technical solution adopted by the present invention to solve the above problems is:

[0007] The high-strength flat-guide copper alloy described in the present invention includes: 75% - 79% of copper, 0.3 - 0.7 of tin, 0.5 - 0.9 of aluminum, 0.05 - 0.15 of nickel, <0.15 of phosphorus, and the balance is zinc.

[0008] The preparation method of the high-strength flat-guide copper alloy described in the present invention includes the following steps:

[0009] Step 1: Batching: Select 75% - 79% copper, 0.3 - 0.7 tin, 0.5 - 0.9 aluminum, 0.05 - 0.15 nickel, and <0.15 phosphorus by mass percentage, with the balance being zinc;

[0010] Step 2: Melting: The alloy is melted in an intermediate frequency induction melting furnace. Charcoal is used for covering during melting. A graphite crucible is used, and cryolite is used as a flux. The melting temperature is 1100 - 1400°C. After melting pure copper, alloying elements such as nickel, boron, and phosphorus are added, held for a period of time and stirred. After cooling, aluminum, zinc, and tin are added, cryolite is added and stirred to remove slag. After heating up, it is held for a period of time, and the alloy needs to be stirred during the holding process, then taken out of the furnace.

[0011] Step 3: Casting: An iron mold is used. Before casting, it is placed in an electric furnace for drying and dehydration treatment. Then, zinc oxide is applied to the inner wall of the iron mold. The melted alloy is poured into the mold and air-cooled. After complete cooling, the as-cast part of the alloy is obtained.

[0012] Step 4: Hot forging: Before forging, the oxide film and defects on the surface of the casting are trimmed using a milling machine. It is heated using an electric furnace. The inside of the electric furnace is cleaned before heating. The forging temperature is 780 - 850°C. After multiple times of reheating and holding and forging, a cuboid forging is obtained.

[0013] Step 5: Hot rolling: Before hot rolling, the surface of the workpiece needs to be polished smoothly. The hot rolling temperature is between 780 - 850°C. During hot rolling, the second phase AlP with a size of only 3 - 5 nm will precipitate, and this second phase will greatly improve the strength of the alloy. The rolling is carried out in multiple passes, with a single pass reduction rate of 15 - 20%, and a total deformation of 70 - 90%. A hot-rolled sheet with a thickness of 2 - 4 mm can be obtained.

[0014] Step 6: Cold rolling: Before cold rolling, the workpiece also needs to be polished. To prevent cracking during rolling, it is rolled in multiple passes, with a single pass deformation of 3 - 5% and a total deformation of 60 - 90%. Finally, a cold-rolled sheet with a thickness of 0.5 - 1.5 mm can be obtained.

[0015] The beneficial effects of the present invention are:

[0016] The invention successfully prepared a brass alloy with high strength and relatively ideal conductivity by reasonably selecting alloy components and further regulating the heat treatment process. It was first discovered that a second-phase AlP with a size of 3-5 nm would precipitate after hot rolling of the alloy, which would greatly improve the strength of the material and maintain the conductivity unchanged. According to the stress-strain curve, the engineering stress-strain strength of the alloy after hot rolling is 675 MPa (true stress-strain strength 802 MPa), and the conductivity is 22.7% IACS; after annealing the hot-rolled sheet, the strength reaches 528 MPa (true stress-strain strength 775.2 MPa), and the conductivity is 23.01% IACS, while the strength of the cold-rolled state can reach 905 MPa (true stress-strain strength 1023 MPa), and the conductivity is 22.6% IACS. The deformation processes such as hot forging, hot rolling, and cold rolling used in material forming are mature and the processes are easy to control, and the preparation process has general applicability. Brief Description of the Drawings

[0017] Figure 1 is the engineering stress-strain tensile curve of the copper alloy in different states;

[0018] Figure 2 is Figure 1 the true stress-strain tensile curve in different states obtained by

[0019] Figure 3 is the XRD pattern of the copper alloy in different states; the as-cast phase is α-Cu, and the hot-rolled state and hot-rolled & annealed phases are composed of α-Cu and AlP;

[0020] Figure 4 is the transmission picture of the hot-rolled state; (a) is the bright-field image with a scale bar of 50 nm, and the black dots are the precipitated phase AlP with a size of 3-5 nm, (b) is the high-resolution picture, and (c) is the overall Fourier transform picture corresponding to (b), confirming that the matrix structure of the copper alloy is α-Cu, and there is a dispersed two-phase AlP in the matrix;

[0021] Figure 5 is the scanning picture of the hot-rolled & annealed state, and AlP is granular in the matrix;

[0022] Figure 6 is Figure 5 the EDS of the corresponding element P;

[0023] Figure 7 is Figure 5 the EDS of the corresponding element Al.

[0024] The above phase, composition, morphology, and element characterizations fully confirm the existence of AlP and illustrate its morphology, size, and distribution in the matrix. Detailed Description of the Invention

[0025] Specific Embodiment 1: A high-strength flat-guide copper alloy described in this embodiment includes: 75% - 79% copper, 0.3 - 0.7 tin, 0.5 - 0.9 aluminum, 0.05 - 0.15 nickel, phosphorus < 0.15, and the balance is zinc.

[0026] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the preparation method of a high-strength flat-guide copper alloy described in this embodiment includes the following steps:

[0027] Step 1: Batching: Select 75% - 79% copper, 0.3 - 0.7 tin, 0.5 - 0.9 aluminum, 0.05 - 0.15 nickel, phosphorus < 0.15 by mass percentage, and the balance is zinc;

[0028] Step 2: Melting: The alloy is melted in an intermediate frequency induction melting furnace. The melting is covered with charcoal, a graphite crucible is used, and cryolite is used as a flux. After melting pure copper, alloying elements such as nickel, boron, and phosphorus are added, held for a period of time and stirred. After cooling, aluminum, zinc, and tin are added, cryolite is added and stirred to remove slag, heated and held for a period of time. During the holding process, the alloy needs to be stirred and then taken out of the furnace;

[0029] Step 3: Casting: An iron mold is used for the mold. Before casting, it is placed in an electric furnace for drying and dehydration treatment, and then zinc oxide is applied to the inner wall of the iron mold. The melted alloy is poured into the mold and air-cooled, and the as-cast part of the alloy is obtained after complete cooling;

[0030] Step 4: Hot forging: Before forging, the oxide film and defects on the surface of the casting are trimmed using a milling machine, and it is heated using an electric furnace. The inside of the electric furnace is cleaned before heating. After multiple re-heating and holding and forging, a rectangular forged part is obtained;

[0031] Step 5: Hot rolling: Before hot rolling, the surface of the workpiece needs to be polished smoothly. During hot rolling, the second phase AlP with a size of only 3 - 5 nm will precipitate; The rolling is carried out in multiple passes, and hot-rolled sheets with a thickness of 2 - 4 mm can be obtained;

[0032] Step 6: Cold rolling: Before cold rolling, the workpiece also needs to be polished. Multiple passes of rolling are used, and finally cold-rolled sheets with a thickness of 0.5 - 1.5 mm are obtained. Others are the same as in Specific Embodiment 1.

[0033] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that in Step 2, the melting temperature is 1100°C - 1400°C. Others are the same as in Specific Embodiment 1 or 2.

[0034] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that: in step 4, the forging temperature is 780°C-850°C, the single pressing rate is 15-20%, and the total deformation is 70%-90%. Others are the same as specific embodiments 1 to 3.

[0035] Specific implementation mode 5: This implementation mode is different from specific implementation modes 1 to 4 in that: in step 5, the hot rolling temperature is between 780° C. and 850° C. The rest is the same as specific implementation modes 1 to 4.

[0036] Specific implementation method 6: This implementation method is different from specific implementation methods 1 to 5 in that: in step 6, the single deformation amount is 3%-5%, and the total deformation amount is 60%-90%. Other aspects are the same as specific implementation methods 1 to 5.

[0037] The present invention adopts the following examples to verify the beneficial effects of the present invention:

[0038] Embodiment 1:

[0039] ① Ingredients: The copper alloy is composed of 75% copper, 0.3% tin, 0.5% aluminum, 0.05% nickel, 0.04% phosphorus, and the balance is zinc.

[0040] ② Melting: Use medium frequency induction melting furnace for melting, cover with charcoal, use graphite crucible, use cryolite as flux, and the melting temperature is 1300℃. First, melt pure copper, add alloy elements such as nickel, boron, phosphorus, keep warm for a period of time and stir, add aluminum, zinc, tin at a time after cooling, add cryolite to stir and remove slag, heat up and keep warm for a period of time, stir the alloy during the insulation process, and take it out of the furnace.

[0041] ③Casting: The mold is made of iron. Before casting, it is placed in an electric furnace for drying and dehydration. Then a layer of zinc oxide is applied to the inner wall of the iron mold. The smelted alloy is poured into the mold and air-cooled. After complete cooling, the cast part of the alloy is obtained.

[0042] ④ Hot forging: Before forging, use a milling machine to trim the oxide film and defects on the surface of the casting, and use an electric furnace for heating. Clean the inside of the electric furnace before heating. The forging temperature is 800℃. After multiple re-furnace insulation and forging, a rectangular forging is obtained.

[0043] ⑤Hot rolling: The surface of the forging is polished smooth before hot rolling. The hot rolling temperature is 800℃. The single hot rolling deformation rate is 15%. After multiple hot rolling passes, the total deformation is 80%.

[0044] ⑥ Cold rolling: cold rolling removes the oxide on the sample surface, and adopts multi-pass rolling, with a single-pass deformation rate of 3% and a total deformation rate of 60%. Finally, a 1.2mm thick copper alloy cold-rolled plate can be obtained.

[0045] Example 2:

[0046] ① Ingredients: The copper alloy is composed by weight percentage as follows: copper 76%, tin 0.4%, aluminum 0.6%, nickel 0.08%, phosphorus 0.08%, and the balance is zinc.

[0047] ② Melting: Medium-frequency induction melting furnace is used for melting. Charcoal is used for covering during melting. Graphite crucible is used. Cryolite is used as a flux. The melting temperature is 1300°C. First, pure copper is melted, alloying elements such as nickel, boron, and phosphorus are added, held for a period of time and stirred. After cooling, aluminum, zinc, and tin are added at one time. Cryolite is added and stirred to remove slag. After heating up, it is held for a period of time. The alloy needs to be stirred during the holding process and then taken out of the furnace.

[0048] ③ Casting: Iron mold is used. Before casting, it is placed in an electric furnace for drying and dehydration treatment. Then a layer of zinc oxide is coated on the inner wall of the iron mold. The melted alloy is poured into the mold and air-cooled. After complete cooling, the as-cast part of the alloy is obtained.

[0049] ④ Hot forging: Before forging, the oxide film and defects on the surface of the casting are trimmed using a milling machine. Electric furnace is used for heating. The inside of the electric furnace is cleaned before heating. The forging temperature is 820°C. After multiple times of reheating and holding and forging, a cuboid forging is obtained.

[0050] ⑤ Hot rolling: Before hot rolling, the surface of the forging is polished smoothly. The hot rolling temperature is 820°C. The single-pass hot rolling deformation rate is 20%. After multiple passes of hot rolling, the total deformation is 85%, and a hot-rolled sheet with a thickness of 3 mm can be obtained.

[0051] Example 3:

[0052] ① Ingredients: The copper alloy is composed by weight percentage as follows: copper 77%, tin 0.6%, aluminum 0.8%, nickel 0.12%, phosphorus 0.12%, and the balance is zinc.

[0053] ② Melting: Medium-frequency induction melting furnace is used for melting. Charcoal is used for covering during melting. Graphite crucible is used. Cryolite is used as a flux. The melting temperature is 1300°C. First, pure copper is melted, alloying elements such as nickel, boron, and phosphorus are added, held for a period of time and stirred. After cooling, aluminum, zinc, and tin are added at one time. Cryolite is added and stirred to remove slag. After heating up, it is held for a period of time. The alloy needs to be stirred during the holding process and then taken out of the furnace.

[0054] ③ Casting: Iron mold is used. Before casting, it is placed in an electric furnace for drying and dehydration treatment. Then a layer of zinc oxide is coated on the inner wall of the iron mold. The melted alloy is poured into the mold and air-cooled. After complete cooling, the as-cast part of the alloy is obtained.

[0055] ④ Hot forging: Before forging, use a milling machine to trim the oxide film and defects on the surface of the casting, heat it using an electric furnace. Clean the inside of the electric furnace before heating. The forging temperature is 850 °C. After multiple re-heating and holding and forging, a cuboid forging is obtained.

[0056] ⑤ Hot rolling: Before hot rolling, polish the surface of the forging smoothly. The hot rolling temperature is 850 °C, and the single-pass hot rolling deformation rate is 20%. After multiple passes of hot rolling, the total deformation is 90%.

[0057] ⑥ Annealing: After experiencing severe hot deformation, many defects will be generated inside the material. Therefore, it is necessary to further anneal the material to obtain excellent comprehensive properties. Adopt annealing treatment, the temperature is 450 °C, and the holding time is 6 h, and a brass alloy with matching strength and toughness can be obtained.

[0058] Example 4:

[0059] ① Batching: The copper alloy is composed of the following weight percentages: copper 78%, tin 0.7%, aluminum 0.9%, nickel 0.15%, phosphorus 0.15%, and the balance is zinc.

[0060] ② Melting: Use an intermediate frequency induction melting furnace for melting. Use charcoal for covering during melting, use a graphite crucible, and use cryolite as a flux. The melting temperature is 1300 °C. First, melt pure copper, add alloying elements such as nickel, boron, and phosphorus, hold for a period of time and stir, cool down and then add aluminum, zinc, and tin at one time. Add cryolite and stir to remove slag, heat up and hold for a period of time. During the holding process, it is necessary to stir the alloy and then take it out of the furnace.

[0061] ③ Continuous casting and rolling: Pour the molten copper into the tundish. It is necessary to add a covering agent on the surface to keep warm and isolate the air. The internal temperature is maintained at about 1050 °C, and then it is distributed into the mold for cooling to obtain a billet. Then, send the billet into a continuous rolling mill for rolling, and perform water cooling treatment after continuous rolling is completed.

[0062] ④ Annealing: Similar to Embodiment 3, it is necessary to anneal the hot-rolled plate. The temperature is 450 °C and the holding time is 6 h, and a brass alloy with matching strength and toughness can be obtained.

[0063] Table 1. Physical properties of the alloy in different states

[0064]

[0065] From Figure 1Combined with the physical properties of the alloy in different states listed in Table 1, it can be seen that the as-cast alloy has the best plasticity, with an elongation rate reaching 42.8% and a strength of 342 MPa; the hot-rolled state has the best comprehensive properties, with a strength of 677.5 MPa and an elongation rate of 18%; the strength of the alloy after cold rolling reaches 902 MPa and the elongation rate is 2%; the conductivity of the material does not change significantly after undergoing deformation in different states (remaining between 22% - 23% IACS).

[0066] The above description is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art, within the scope of the technical solution of the present invention, can make some changes or modifications to the above-disclosed technical content to obtain equivalent embodiments with equivalent changes. However, as long as it does not depart from the technical solution content of the present invention and is based on the technical essence of the present invention, any simple modification, equivalent replacement, and improvement made to the above embodiments within the spirit and principle of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A high-strength flat copper alloy, characterized in that: The high-strength flat copper alloy comprises, by mass percentage, 75% copper, 0.3% tin, 0.5% aluminum, 0.05% nickel, 0.04% phosphorus, and the remainder zinc. The alloy has a cast plastic elongation of 42.8% and a strength of 342MPa; a hot-rolled strength of 677.5MPa and an elongation of 18%; the alloy strength after cold rolling reaches 902MPa and an elongation of 2%; the electrical conductivity of the material does not change significantly after deformation in different states, and remains between 22% and 23% IACS, and a second phase AlP with a size of only 3-5nm will precipitate during the hot rolling process.

2. A method for preparing a high-strength flat copper alloy according to claim 1, characterized in that: The steps include: Step 1: Ingredients: Select copper 75%, tin 0.3%, aluminum 0.5%, nickel 0.05%, phosphorus 0.04%, and the balance zinc by mass percentage; Step 2: Melting: The alloy is melted in a medium frequency induction melting furnace, covered with charcoal, using a graphite crucible, and using cryolite as a flux. After pure copper is melted, nickel and phosphorus alloy elements are added, and the mixture is kept warm for a period of time and stirred. After cooling down, aluminum, zinc, and tin are added, and cryolite is added to stir and remove the slag. After heating up, the mixture is kept warm for a period of time. The alloy needs to be stirred during the insulation process and then taken out of the furnace; Step 3: Casting: The mold is made of iron and placed in an electric furnace for drying and dehydration before casting. Then zinc oxide is applied to the inner wall of the iron mold. The smelted alloy is poured into the mold and air-cooled. After complete cooling, the cast alloy is obtained. Step 4: Hot forging: Before forging, use a milling machine to trim the oxide film and defects on the surface of the casting, use an electric furnace for heating, clean the inside of the electric furnace before heating, and after multiple reheating and forging, obtain a rectangular forging; Step 5: Hot rolling: The workpiece surface needs to be polished smooth before hot rolling. During the hot rolling process, a second phase AlP with a size of only 3-5nm will be precipitated. The rolling process adopts multiple passes to obtain a hot-rolled plate with a thickness of 2-4mm. Step 6: Cold rolling: The workpiece also needs to be polished before cold rolling, and multiple rolling passes are used to finally obtain a cold-rolled plate with a thickness of 0.5-1.5mm.

3. The method for preparing a high-strength flat copper alloy according to claim 2, characterized in that: In step 2, the smelting temperature is 1100°C-1400°C.

4. The method for preparing a high-strength flat copper alloy according to claim 2, characterized in that: In step 4, the forging temperature is 780°C-850°C; the single pressing rate is 15-20%, and the total deformation is 70%-90%.

5. The method for preparing a high-strength flat copper alloy according to claim 2, characterized in that: In step five, the hot rolling temperature is between 780°C and 850°C.

6. The method for preparing a high-strength flat copper alloy according to claim 2, characterized in that: In step six, the single deformation is between 3% and 5%, and the total deformation is between 60% and 90%.

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