A copper alloy and a method for producing the same

Abstract

The application discloses a copper alloy and a preparation method thereof. The copper alloy comprises the following components in mass percentage: Cu: 61.5-63.5 wt%, Fe < 0.005 wt%, Pb < 0.005 wt%, Sb < 0.005 wt%, Bi < 0.002 wt%, P < 0.0025 wt%, and Zn as the balance; and the proportion of beta phase in the copper alloy is less than 8%. The proportion of beta phase in the copper alloy is reduced by controlling the temperature, time and cooling speed in the hot rolling and annealing process, and finally the copper alloy product meeting the requirements of modern high-speed stamping technology is obtained, which has the mechanical property requirements, the proportion of beta phase is less than 8%, and the grain size of alpha phase organization is between 20-40 mu m. The copper alloy product can be applied to the manufacture of conductive and heat-conducting elements, corrosion-resistant structural parts, elastic elements, daily hardware and decorative materials and the like.

Description

Technical Field

[0001] This invention relates to the field of copper alloys, and more specifically to a copper alloy and its preparation method. Background Technology

[0002] High-speed precision stamping technology integrates high-speed precision press technology, high-precision variable stamping die technology, high-quality product material technology, intelligent control technology, and green environmental protection into a modern advanced stamping manufacturing technology. It has the advantages of high production efficiency, high quality, high consistency, and energy saving and consumption reduction. It is widely used in electronic components, IC integrated circuit lead frames, electronic iron cores, automotive parts, heat exchanger fins, and home appliance parts, and is used to produce connecting devices, connectors, brushes, electrical terminals, and elastic parts.

[0003] Common copper alloys such as H62, H65, H68, and H70 possess excellent mechanical and cold-working properties, and are widely used in various structural parts, shallow-drawn parts, deep-drawn parts, and hardware. Among them, H62, as an inexpensive and common (α+β) duplex alloy, is also used in stamping production.

[0004] Studies have shown that when the Zn content reaches 36% or more, a β solid solution based on the electron-containing compound CuZn will appear in the alloy microstructure dominated by the α phase. On the one hand, the β phase is more susceptible to corrosion than the α phase, resulting in surface dezincification; on the other hand, the β phase has poorer plasticity at room temperature than the α phase, and as a hard and brittle phase, it is prone to localized low plasticity during high-speed stamping, leading to copper powder shedding. The Zn content in H62 brass, as required by national standards, is around 38%, and the β phase ratio is generally above 25%. Compared to other stamping alloys such as H65 and H68 with α phase, it exhibits significant copper powder shedding during high-speed stamping, which adheres to the mold and press surface, increasing equipment maintenance frequency, reducing equipment lifespan, and severely impacting production efficiency and product quality.

[0005] Patent document CN1590569A discloses a brass alloy with superior corrosion resistance and dezincification resistance, and its manufacturing method. This invention increases the α-phase ratio in the copper alloy by adding small amounts of tin and silicon to the brass material. Patent document CN102433461A discloses a dezincification-resistant brass alloy. This invention improves the dezincification corrosion resistance of the copper alloy by adding small amounts of antimony, silicon, nickel, etc. to the brass material.

[0006] However, the aforementioned copper alloy materials have a complex composition and a wide heat treatment temperature range, resulting in unstable resistance to dezincification corrosion. This makes them prone to copper powder shedding during subsequent production processes, which is detrimental to the manufacturing of copper alloy products. Furthermore, the presence of arsenic or lead in these copper alloys poses health risks and causes environmental pollution.

[0007] Therefore, it is of great significance to find a processing technology for H62 copper alloy that can control the β phase ratio, improve the dezincification layer, and meet the high-speed stamping performance requirements, so as to produce copper alloys that can meet the requirements of modern high-speed precision stamping. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention provides a copper alloy that can meet the requirements of modern high-speed precision stamping and effectively avoid the phenomenon of copper powder falling off after stamping.

[0009] A copper alloy comprising the following components by mass percentage: Cu: 61.5-63.5 wt%, Fe < 0.005 wt%, Pb < 0.005 wt%, Sb < 0.005 wt%, Bi < 0.002 wt%, P < 0.0025 wt%, and Zn as the balance; wherein the proportion of the β phase in the copper alloy is less than 8%.

[0010] This invention controls the lower limit of Cu content to 61.5 wt% and optimizes the control of impurity elements, which can reduce the "Zn equivalent coefficient", causing the α / (α+β) phase boundary to shift towards the Zn side, increasing the α phase region and reducing the β phase.

[0011] Preferably, the proportion of the β phase in the copper alloy is controlled to be below 8%.

[0012] Preferably, the α-phase grain size of the copper alloy is controlled between 20-40 μm. The grain size affects the machinability of H62 brass under high-speed stamping. When the grain size exceeds 40 μm, the alloy will develop severe orange peel defects after stamping, and the surface roughness will increase rapidly; when the grain size is less than 20 μm, the alloy is harder, making stamping more difficult and increasing the risk of stamping cracks.

[0013] This invention also discloses a method for preparing the copper alloy, which can produce H62 copper alloy products that meet mechanical performance requirements, have a β phase ratio of less than 8%, and an α phase grain size of 20-40 μm, thus meeting the requirements of modern high-speed stamping technology.

[0014] A method for preparing a copper alloy includes the following steps: batching and casting → hot rolling → rough rolling → annealing → medium / finish rolling → cleaning;

[0015] The melting temperature is controlled at 1080-1350℃; during casting, the casting speed is controlled at 100-140 mm / min, and the primary cooling water flow rate is controlled at 30-50 mm / min. 3 / h, the inlet water pressure is controlled at 0.3-0.6MPa, the cooling water temperature is controlled at 20-35℃, and the crystallizer vibration frequency is 40-60 times / minute. To ensure that there are no defects such as shrinkage cavities and cracks in the head and tail of the ingot, the head of the ingot is sawn ≤150mm and the tail is sawn ≤50mm.

[0016] Preferably, in the hot rolling process, the initial rolling temperature is controlled between 650-680℃, the final rolling temperature is controlled between 460-500℃, and the cooling method combines air cooling and water cooling. The temperature is first reduced to 410-450℃ in an air cooling zone, and the cooling water flow rate is controlled at 25-35 mm. 3 / h, reducing the temperature to 100-150℃.

[0017] In H62 alloy, the β solid solution, which is a high-temperature phase, begins to gradually precipitate into α solid solution around 750℃. Using an initial rolling temperature of 650-680℃ can reduce the formation of β phase solid solution in H62 alloy, while retaining a portion of the α phase can suppress the formation and growth of the β phase. Furthermore, in the Cu-Zn binary phase diagram, the proportion of α solid solution is highest and the proportion of β phase is lowest around 460℃. Therefore, controlling the final rolling temperature at 460-500℃, combined with slower air cooling and a 25-35mm rolling mill... 3 The low-flow-rate water cooling process can promote the transformation of the β phase into the α phase and reduce the solid solubility of the α supersaturated solid solution, preventing excessive solid solubility from causing a large amount of β phase to precipitate during subsequent processing. Ultimately, the β phase ratio of the hot-rolled billet is controlled between 18-24%.

[0018] Preferably, to ensure the surface quality of the billet, the hot-rolled copper alloy is milled. The milling process requires removing 0.5-0.6 mm from both the upper and lower surfaces.

[0019] Preferably, the roughing blank thickness is 10.8-11.4 mm, and the roughing rate is ≥70%.

[0020] Preferably, the annealing process uses an annealing temperature of 460-500℃ and a holding time of 6-8 hours. Providing sufficient holding time at this temperature promotes the full transformation of the β phase into the α phase, further reducing the proportion of the β phase in the alloy and controlling it below 8%. On the other hand, controlling the grain size of the α phase within 20-40 μm prevents excessively large grains due to excessively high temperature or long holding time. The cooling rate after annealing is controlled at 50-65℃ / h to reduce the supersaturated solid solubility of the α phase and improve the processing stability of the alloy structure at room temperature.

[0021] Preferably, in the hot rolling process, the initial rolling temperature is 650℃, the final rolling temperature is 462℃, and the cooling water flow rate is 25mm. 3 / h; In the annealing process, the annealing temperature is controlled at 460℃, the holding time is 6h, and the cooling rate is 50℃ / h. These process conditions can significantly reduce the proportion of the β phase, and the proportion of the β phase in the resulting copper alloy product is only 1.05.

[0022] The present invention allows for the selection of intermediate rolling or finishing rolling processes based on product thickness requirements, tolerance requirements, and performance requirements of the manufactured products.

[0023] Preferably, the cleaning process is degreasing → water washing → acid washing → hot water washing → grinding → passivation → drying.

[0024] Preferably, the degreasing agent is an aqueous solution of sodium hydroxide with a pH range of 7-9 and a solution temperature of 60-70℃.

[0025] Preferably, the pickling is performed using sulfuric acid, with the sulfuric acid concentration controlled at 100-130 g / L and the temperature at 70-85℃.

[0026] Preferably, the grinding brush used in the grinding process is made of non-woven fabric + silicon carbide, with a mesh size of 800-2000 mesh, a brush radius of 300-500 mm, a reduction of 20-50%, and a rotation speed of 400-2000 r / min. The purpose of using a relatively hard grinding brush is to remove the 3-6 μm dezincification layer from the surface, preventing the loose surface layer caused by dezincification from falling off and forming copper powder during high-speed stamping.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) Based on the national standard, this invention optimizes the composition ratio of H62 copper alloy, increases the Cu content ratio, reduces the interference of impurity elements such as Fe and Pb, reduces the "Zn equivalent coefficient", causes the α / (α+β) phase boundary to shift towards the Zn side, increases the α phase region, and reduces the β phase ratio;

[0029] (2) This invention reduces the proportion of β phase in H62 by controlling the hot rolling temperature and using air cooling and water cooling, thereby improving the grain size and further enhancing its high-speed stamping performance and avoiding subsequent copper powder shedding; by controlling the annealing temperature, holding time and cooling rate, the β phase is transformed into the α phase.

[0030] (3) The present invention uses an 800-2000 mesh non-woven fabric + silicon carbide grinding brush, combined with a cleaning process, to achieve the effect of removing a 3-6μm dezincification layer on the surface, thereby improving the problems of surface dezincification porosity, cracking, and copper powder loss during high-speed stamping.

[0031] (4) The process described in this invention can produce H62 copper alloy products with a grain size of approximately 20-40 μm, a β phase ratio of ≤8%, physical properties that meet product requirements, and excellent deep-drawing performance, which can satisfy the requirements of modern high-speed stamping technology. The produced H62 copper alloy can be used to manufacture conductive and thermally conductive components, corrosion-resistant structural parts, elastic components, daily hardware, and decorative materials, etc. Attached Figure Description

[0032] Figure 1 The image shows the metallographic structure of the copper alloy obtained after hot rolling in Example 1.

[0033] Figure 2 The image shows the metallographic structure of the copper alloy obtained after annealing in Example 1.

[0034] Figure 3 The image shows the metallographic structure of the finished copper alloy from Example 1. Detailed Implementation

[0035] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0036] The preparation steps of Example 1 are as follows:

[0037] 1) Batching and casting: Batching is carried out according to the optimized H62 composition table. The melting temperature is controlled at 1250℃. After adding the materials, the mixture is stirred continuously until all the raw materials are melted. Samples are taken for spectral analysis. The materials are diluted and replenished in time according to the raw material ratio requirements.

[0038] 2) Semi-continuous casting: casting temperature 1080℃~1100℃, casting into 230mm*620mm ingots, ingot length 7500mm;

[0039] 3) Hot rolling: The ingot is fed into a walking beam furnace and heated for 4 hours. The initial hot rolling temperature is 650℃, and the rolling speed is 180m / min. The ingot is rolled from 230mm thick to 12.5mm, and the final rolling temperature is 462℃. It first enters the air cooling zone to cool to 450℃, and then enters the water cooling zone. The cooling water flow rate is controlled at 25mm. 3 / h, gradually cool the temperature to 150℃, and then rewind;

[0040] 4) Milling: After the material roll has cooled to room temperature, mill the surface using a milling machine. Mill off 0.5mm from both the top and bottom surfaces, resulting in a material roll thickness of 11.5mm.

[0041] 5) Rough rolling: Rough rolling to 1.5mm;

[0042] 6) Single annealing: Protected by a high-hydrogen mixed gas (25% N2 + 75% H2), annealing temperature: 460℃, holding time: 6h; heating rate: 80℃ / h, cooling rate: 50℃ / h;

[0043] 7) Cleaning: The degreasing agent is an aqueous solution of sodium hydroxide with a pH range of 7-9 and a solution temperature of 65℃; acid washing is performed with a sulfuric acid concentration of 120g / L and a temperature of ≤40℃, and the acid solution contains Cu. 2+ ≤6g / l; clean and dry in an oven at 80℃;

[0044] 8) Finishing rolling: The finishing mill rolls the finished product to a thickness of 1.2mm.

[0045] 9) Degreasing and pickling: The degreasing agent is an aqueous sodium hydroxide solution with a pH range of 7-9 and a solution temperature of 65℃; for pickling, the sulfuric acid concentration is 120g / L, the temperature is ≤40℃, and the Cu in the acid solution is... 2+ ≤6g / l;

[0046] 10) Grinding: Grinding is performed using a 1000-mesh non-woven fabric + silicon carbide grinding brush with a radius of 500mm, a pressure of 40%, and a rotation speed of 1000r / min.

[0047] 12) Passivation, cleaning, and drying;

[0048] 13) Cutting;

[0049] 14) Packaging.

[0050] The metallographic structure of the hot-rolled copper alloy in Example 1 is shown below. Figure 1 The metallographic structure of the copper alloy after one annealing is shown in the figure. Figure 2 The metallographic structure of the finished copper alloy is shown in Figure 3 .

[0051] The preparation steps of Examples 2, 3, 4, and 5 are the same as those of Example 1, and the specific key process parameters are shown in Table 1.

[0052] The difference between Comparative Example 1 and Example 1 is that the proportion of Cu is less than that within the range of the present invention, at 60.8%.

[0053] The difference between Comparative Example 2 and Example 1 is that the hot rolling start temperature is higher than the range of the present invention, which is 750°C.

[0054] The difference between Comparative Example 3 and Example 1 is that the hot rolling cooling water flow rate is greater than the range required by this invention, and the cooling water flow rate is 60 mm. 3 / h.

[0055] The difference between Comparative Example 4 and Example 1 is that the annealing parameters are not within the scope of this invention, the annealing temperature is 600°C, and the cooling rate is 90°C / h.

[0056] The difference between Comparative Example 5 and Example 1 is that the material of the abrasive brush is different from that of the present invention; it is a 1000-mesh non-woven fabric brush.

[0057] The key process parameters in the comparative preparation steps are shown in Table 1.

[0058] The copper alloy strips obtained in the examples and comparative examples were subjected to the following tests. The composition results are shown in Table 2, and the performance results are shown in Table 3.

[0059] Composition analysis: The laboratory direct-reading spectrometer was used to perform composition analysis according to the standard "YS / T 482-2022 Analysis Methods for Copper and Copper Alloys: Spark Discharge Atomic Emission Spectrometry".

[0060] Grain size determination in metallographic structure: The grain size in the photographs acquired by a 100x metallographic microscope was determined using the averaging method in "YS / T 347-2020 Method for Determination of Average Grain Size of Copper and Copper Alloys" with a Leica metallographic microscope. The sample width was 10 mm and the length was 10 mm.

[0061] β-phase ratio test: The β-phase in the alloy photographs acquired using a 100x metallographic microscope was tested according to the β-phase test method in "YS / T 347-2020 Method for Determination of Average Grain Size of Copper and Copper Alloys". The sample width was 10 mm and the length was 10 mm.

[0062] Zinc-removed layer thickness test: Metallographic testing was performed using a scanning electron microscope according to the "General Rules for Measurement Methods of Scanning Electron Microscope Lengths in the Micrometer Scale" (GB / T 16594-2008). The sample width was 10 mm and the length was 10 mm.

[0063] Copper powder removal test: A high-speed stamping machine was used to produce copper powder at a stamping speed of 800 times / min. After stamping for ten minutes, the machine was stopped to observe the copper powder adhering to the surface of the stamping die.

[0064] Table 1 Key process parameter control of embodiments and comparative examples of the present invention

[0065]

[0066] Table 2. Composition (wt%) of copper alloy strips prepared in the embodiments and comparative examples of the present invention.

[0067] Case Cu Fe Pb Sb Bi P Zn Example 1 61.5062 0.00324 0.00195 0.00100 0.00020 0.00110 Rm. Example 2 61.5359 0.00425 0.00285 0.00236 0.00030 0.00120 Rm. Example 3 61.6482 0.00413 0.00365 0.00245 0.00010 0.00120 Rm. Example 4 61.5561 0.00395 0.00145 0.00289 0.00020 0.00141 Rm. Example 5 61.5652 0.00468 0.00189 0.00306 0.00020 0.00130 Rm. Comparative Example 1 60.8185 0.00489 0.00145 0.00124 0.00020 0.00100 Rm. Comparative Example 2 61.5423 0.00259 0.00126 0.00120 0.00030 0.00110 Rm. Comparative Example 3 61.5258 0.00230 0.00178 0.00143 0.00020 0.00130 Rm. Comparative Example 4 61.5357 0.00458 0.00120 0.00145 0.00030 0.0010 Rm. Comparative Example 5 61.5842 0.00156 0.00136 0.00160 0.00020 0.00140 Rm.

[0068] Table 3. Performance of copper alloy strips from the embodiments and comparative examples of the present invention.

[0069]

Claims

1. A copper alloy, characterized in that, The copper alloy comprises the following components by mass percentage: Cu: 61.5-63.5 wt%, Fe < 0.005 wt%, Pb < 0.005 wt%, Sb < 0.005 wt%, Bi < 0.002 wt%, P < 0.0025 wt%, and Zn as the balance; the proportion of β phase in the copper alloy is < 8%; and the grain size of the α phase microstructure of the copper alloy is controlled between 20-40 μm.

2. The method for preparing the copper alloy according to claim 1, characterized in that, Includes the following steps: Batching and casting → casting → hot rolling → rough rolling → annealing → intermediate / finish rolling → cleaning; In the hot rolling process, the initial rolling temperature is controlled at 650-680℃, and the final rolling temperature is controlled at 460-500℃. Cooling is achieved using a combination of air cooling and water cooling. Air cooling first lowers the temperature to 410-450℃, followed by water cooling to lower it to 100-150℃. During water cooling, the cooling water flow rate is controlled at 25-35 mm. 3 / h; In the annealing process, the annealing temperature is 440-500℃, the holding time is 6-8h, and the cooling rate is controlled at 50-65℃ / h. The cleaning process includes using a non-woven fabric + silicon carbide abrasive brush to grind the copper alloy and remove the 3-6μm zinc-free layer on the surface of the copper alloy; the abrasive brush has a mesh size of 800-2000 mesh, a radius of 300-500mm, a pressure of 20-50%, and a rotation speed of 400-2000r / min.

3. The preparation method according to claim 2, characterized in that, In the hot rolling process, the initial rolling temperature is 650℃, the final rolling temperature is 462℃, and the cooling water flow rate is 25mm. 3 / h; In the annealing process, the annealing temperature is controlled at 460℃, the holding time is 6h, and the cooling rate is 50℃ / h.

4. The preparation method according to claim 2, characterized in that, The hot rolling processing rate is ≥90%.

5. The preparation method according to claim 2, characterized in that, The roughing rate is ≥70%.

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