A single-phase brass with easy breaking chips and a method for producing the same

Abstract

The application discloses a single-phase brass with easy-to-break chips, which is characterized by comprising the following components in percentage by weight: Cu 64-70wt%, Pb 0.003-0.06wt%, Ce 0.005-0.15wt%, P 0.005-0.1wt%, As 0.01-0.15wt%, and the rest being Zn and inevitable impurities. The application also discloses a preparation method of the single-phase brass with easy-to-break chips. Compared with the prior art, the single-phase brass with easy-to-break chips has good cutting machinability.

Description

Technical Field

[0001] This invention relates to the field of metallurgical materials, specifically to a brittle single-phase brass and its preparation method. Background Technology

[0002] In the machining of metal materials using CNC machine tools, the chip breaking process is particularly important due to the large number of cutting tools and the close connection between the tool holder and the tools. If even one tool fails to break chips reliably, it can disrupt the machine tool's automatic cycle or even the normal operation of the entire automated production line. Therefore, the ease of chip breaking is often used as an indicator of a material's machinability. Materials that break chips easily during cutting have good machinability, while those that break chips more easily have poor machinability.

[0003] For CNC machine tools, it's crucial to avoid both coiled or long spiral copper chips, as these shapes easily become entangled in the workpiece and cutting tool. It's also essential to avoid excessively fine copper chips, as these can easily embed themselves in critical areas of the machine tool guideways and cutting tool assembly (such as reference surfaces). This not only necessitates additional protective devices but also makes chip removal more difficult. C-shaped chips are a better type of chip, as they are neither harmful to workers nor prone to becoming entangled in the workpiece or cutting tool.

[0004] Brass is an alloy composed of Cu and Zn, and its Zn content varies widely, resulting in significant differences in its room temperature microstructure. According to the Cu-Zn binary phase diagram, there are three types of room temperature microstructures for brass: brass with a Zn content below 35% has a microstructure consisting only of the α phase at room temperature, called α brass (single-phase brass); brass with a Zn content in the range of 36-46% has a microstructure consisting of two phases (α+β) at room temperature, called (α+β) brass, also known as two-phase brass.

[0005] The α phase is a solid solution of Zn dissolved in Cu, possessing the same crystal structure as Cu. Therefore, the α phase is soft and has good plasticity. Single-phase brass has good strength, plasticity, electrical conductivity, and electroplating properties, making it suitable for machining deep-drawn parts with complex shapes. It is widely used in industries such as electronics, digital mobile communications, automobiles, medical devices, and instrumentation. For details, please refer to the invention patent "A Brass Alloy and Its Preparation Method" with patent application number CN202210162683.5 (publication number CN114540662A).

[0006] Alpha single-phase brass has excellent overall performance, but it is difficult to break chips during machining. The copper chips are spring-like or long spiral chips, which are very easy to wrap around the cutting tool, making single-phase brass difficult to use for CNC machine tool machining. Summary of the Invention

[0007] The first technical problem to be solved by the present invention is to provide a single-phase brass with good machinability and easy chip breaking, in light of the current state of the prior art.

[0008] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned easily breakable single-phase brass.

[0009] The technical solution adopted by the present invention to solve the first technical problem is: a single-phase brass that is easy to break, characterized in that, by weight percentage, it is composed of the following components: Cu 64-70wt%, Pb 0.003-0.06wt%, Ce 0.005-0.15wt%, P 0.005-0.1wt%, As 0.01-0.15wt%, with the balance being Zn and unavoidable impurities.

[0010] The functions of each component in brass are as follows:

[0011] Pb: Pb has extremely low solubility in α-brass, with a limiting solubility of only 0.03 wt%. When the Pb content in α-brass exceeds 0.03 wt%, cracking is likely to occur during hot working. When the Pb content in α-brass is less than 0.003 wt%, Pb can be completely dissolved in α-brass at room temperature. Pb does not exist in a free state and therefore cannot play a chip-breaking role.

[0012] Ce: Ce can form Pb2Ce compound with Pb, which can not only eliminate the hot brittleness of low melting point Pb, but also avoid the problem of hot working cracking of α brass after the Pb content exceeds 0.03wt%. Pb2Ce is a brittle compound that can play a chip-breaking role. When the Pb content exceeds 0.06wt%, although brass is easier to break chips, the added Ce element cannot completely eliminate the hot brittleness of Pb.

[0013] P: P is rarely dissolved in brass. In α-brass, if the P content exceeds 0.005 wt%, the brittle phase Cu3P appears. Although it can slightly reduce the plasticity of α-brass, it can improve the machinability of α-brass. However, as the P content continues to increase, the amount of Cu3P brittle phase gradually increases. During casting, it is easy for it to aggregate due to poor cooling. Brass is prone to cracking during casting and cold deformation. Therefore, the amount of P added cannot be too high. In this application, the upper limit is not more than 0.1 wt%.

[0014] As: At room temperature, the solubility of As in brass is less than 0.1 wt%. As forms a brittle compound CuZnAs with Cu, which is distributed on the grain boundaries and plays a role in chip breaking. If the As content is less than 0.01 wt%, it cannot form compounds with Cu and Zn. If it exceeds 0.15 wt%, the improvement effect on brass cutting will actually be worse.

[0015] For the same material, hardness also affects chip breaking during machining. Generally, high hardness makes chip breaking easier, but the cutting force is large and the tool wears quickly. If the hardness is low, chip breaking is not easy, and copper chips will curl and wrap around the tool. Preferably, the hardness HV5 of the chip-breaking single-phase brass in this application should be controlled between 140 and 170. When the length of the copper chips is in the range of 10 to 50 mm, they can fall off freely during machining and are not easy to wrap around the tool and workpiece.

[0016] Generally, the better the plasticity of an alloy, the less likely it is to break chips during machining, and the easier it is to obtain a good machined surface. If the plasticity of the material is very low, it becomes a brittle material, and the strength of the material deteriorates, making it unsuitable for load-bearing components. The plasticity index of a material is usually expressed by elongation. Preferably, the elongation A50 of the easily breakable single-phase brass rod and wire of this application should be controlled within 12-20%.

[0017] The chip-breaking single-phase brass of this application consists of a matrix α phase and a trace amount of a second phase. The second phase is mainly composed of brittle phases such as Pb2Ce, Cu3P, and CuZnAs, and is dispersed. The area ratio of the second phase needs to be controlled between 0.1% and 1.5%. If it is below 0.1%, the second phase will not play a chip-breaking role. If it exceeds 1.5%, since the melting point of these brittle phases is higher than that of brass, they tend to accumulate at the grain boundaries during solidification, which weakens the grain boundary strength of the alloy and makes it prone to cracking during cold deformation.

[0018] Since the brass of this application mainly relies on a variety of brittle phases to achieve easy chip breaking, and these brittle phases are distributed within the grains or on the grain boundaries, increasing the grain boundary area can further improve the chip breaking effect. The smaller the grain size, the more grains per unit area, and the larger the total grain boundary area. The more uniform the distribution of the brittle phases Pb2Ce, Cu3P, and CuZnAs, the better the chip breaking effect. However, if the grain size is too small, more grains with different orientations need to be coordinated, the resistance to plastic deformation of the metal is higher, which will lead to greater tool wear during alloy cutting and a worsening of cutting performance. Therefore, preferably, the grain size of the brass of this application should be controlled between 8 and 25 μm.

[0019] Furthermore, as a preferred embodiment, the average size of the Pb2Ce, Cu3P, and CuZnAs phases is below 800 nm. The purpose is twofold: first, to increase the number of brittle phases; and second, to reduce the negative impact of large-sized brittle phases at grain boundaries on the hot and cold working of the alloy.

[0020] The technical solution adopted by the present invention to solve the second technical problem is: a method for preparing the above-mentioned brittle single-phase brass, characterized in that the process flow of the brittle single-phase brass is: smelting → horizontal continuous casting → extrusion → peeling → stretching → annealing → finished product stretching → low temperature annealing.

[0021] Preferably, it includes the following steps:

[0022] 1) Smelting: Prepare the required ingredients and smelt them in a smelting furnace at a temperature of 950-1150℃. After all the metal has melted and the composition has been tested and found to be qualified, the metal is transferred to a holding furnace at a temperature of 1010-1130℃, which is also the casting temperature.

[0023] 2) Horizontal continuous casting: Ingot specifications Φ80~300mm, traction time 1~7s, traction pitch 1~10mm, pause time 0.1~3s, reverse push time 0.1~3s, reverse pull pitch 0.5~4mm, pull stop time 0.1~3s, ingot sawing length 300~1600mm;

[0024] 3) Extrusion: As can be seen from the Cu-Zn binary alloy phase diagram, the lower limit of Cu content in the brass of this application is 64wt%. At this temperature, the temperature for the transformation of the α phase to the β phase is around 720℃. This temperature increases with the increase of Cu content. Above this temperature, the β phase begins to appear in the α phase matrix. Since the β phase has better high-temperature plasticity than the α phase, the difference in the difficulty of deformation between the α and β phases leads to the appearance of microcracks inside the extruded billet. The subsequent extension of these cracks leads to processing cracking. Below the lower limit of the extrusion temperature range, not only will the extrusion not be able to proceed, but it will also result in… Since Cu3P and CuZnAs phases cannot be completely dissolved in the brass matrix, the extrusion temperature of the brass in this application needs to be determined according to the Cu content: when the Cu content is 64-66 wt%, the extrusion temperature is set at 640-700℃; when the Cu content is 66-68 wt%, the extrusion temperature is set at 680-740℃; when the Cu content is 68-70 wt%, the extrusion temperature is set at 720-780℃; the extrusion flow rate is 1-3, the extrusion ratio is 30-500, the extrusion speed is 2-18 mm / s, and the winding method is coiled or straight.

[0025] 4) Peeling: The purpose of peeling is to eliminate defects such as peeling and sand holes on the surface of the bar. Before peeling, the extruded blank is stretched once, and the processing rate is controlled at 5-30%. The purpose is to harden the extruded blank with large fluctuations in diameter and to harden the surface of the extruded blank. This is beneficial to ensure the quality of peeling and also facilitates the control of the amount of peeling.

[0026] 5) Stretching: The extruded billet after peeling is stretched to the specified size in 1 to 4 passes; α brass has excellent plasticity, and the single-pass processing rate is controlled at 10 to 25%, and the total processing rate is controlled at 35 to 50%. The reason for controlling the total processing rate within this range is that the extrusion structure is fully deformed, the original grains are completely broken, the number of recrystallization nuclei increases significantly, and the annealed recrystallized grains are fine.

[0027] 6) Annealing: After stretching, annealing at a relatively low temperature is required. One purpose is to eliminate work hardening and promote the precipitation of Cu3P and CuZnAs phases from the grain boundaries. Another purpose is to avoid excessively high annealing temperatures that could lead to grain growth and a grain size exceeding 25 μm. The peak precipitation temperature of Cu3P phase is 270℃. If annealing exceeds this temperature, the size of Cu3P phase tends to become coarser. The dissolution temperature of Cu3P phase in brass is around 400℃. The peak precipitation temperature of CuZnAs is 420℃. If annealing exceeds this temperature, the size of CuZnAs phase tends to become coarser. The recrystallization temperature range of α-phase brass is 350–450℃. Therefore, the annealing temperature of brass in this application should be controlled between 390 and 450℃. The time to rise from room temperature to this temperature should be controlled between 15 and 90 minutes. After reaching the set temperature, the holding time should be between 120 and 300 minutes.

[0028] 7) Finished product stretching: According to the mechanical property requirements of the finished product, the processing rate is controlled between 8% and 20%. If the finished product processing rate is less than 8%, the material strength and hardness are too low, the chip breaking effect is poor, and the processed parts are easy to deform under stress. If the finished product processing rate exceeds 20%, the material hardness is too high, and the parts are easy to crack during cold deformation processing.

[0029] 8) Low-temperature annealing: The precipitation temperature of Cu3P phase is 260-350℃. The purpose of low-temperature annealing is twofold: first, to fully precipitate the Cu3P phase, further improving the chip breaking effect during brass machining; second, α-brass contains the ordered compound Cu3Zn, which transforms into the ordered compound Cu9Zn in the 200-300℃ range. Cu9Zn is a brittle compound, which can improve the machinability of α-single-phase brass. Therefore, considering both effects, the annealing temperature is set at 250-300℃, the time to rise from room temperature to this temperature is controlled at 20-60 min, and the holding time is 120-360 min.

[0030] 9) Inspection and packaging.

[0031] Furthermore, in step 3), the extruded billet flows directly into a water-sealed tank for cooling after exiting the mold. The water temperature does not exceed 40°C. The purpose is twofold: first, to ensure that the Cu3P and CuZnAs phases are completely dissolved in the brass matrix; and second, to control the grain size of the extruded billet through rapid cooling, thus avoiding grain growth caused by natural cooling of the high-temperature extruded billet in the air.

[0032] Furthermore, in step 4), the sizing band of the stripping die is removed to make the annular cutting edge sharper and avoid the situation where the copper sticking to the sizing band scratches the surface of the wire blank, thus obtaining a brighter bar wire surface. The stripping amount is controlled between 0.10 and 0.30 mm. If the stripping amount is too large, pitting is easily generated on the surface of the billet. If the stripping amount is too small, it will not play a role in eliminating surface defects of the extruded bar.

[0033] Furthermore, in step 6), the heating time is controlled between 15 and 40 minutes. This is because if the heating rate is very slow during heat treatment, the deformed metal will recover during the heating process, which will reduce the distortion energy, reduce the number of recrystallization nuclei, and make the grains coarser. Conversely, if the heating rate is too fast, the recovery and atomic diffusion will not have time to proceed, and recrystallization will begin, which will have the effect of refining the grains.

[0034] Furthermore, in step 6), the furnace cooling method is water cooling, the purpose of which is to promote the dissolution of the Cu3P phase into the matrix at 390-450℃, in preparation for the low-temperature annealing of the finished product to precipitate again.

[0035] Compared with the prior art, the advantages of the present invention are as follows: without changing the overall properties of brass, by adding trace amounts of Pb, Ce, P, and As elements and by using a processing technology different from that of single-phase brass, a certain proportion and size of brittle phases of Pb2Ce, Cu3P, and CuZnAs are formed in the α-phase brass matrix, making the copper chips of α single-phase brass easy to break and not entangle the tool during the cutting process, so that single-phase brass can be used for CNC machine tool cutting. Attached Figure Description

[0036] Figure 1 The image shows the metallographic structure of the brass in Example 1.

[0037] Figure 2 Metallographic diagram of brass in Comparative Example 11;

[0038] Figure 3 Photographs showing the morphology of copper shavings from the brass in Example 1;

[0039] Figure 4 Photographs showing the morphology of copper shavings from brass in Comparative Example 11. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0041] Example 1:

[0042] One specification is The preparation method of easily breakable single-phase brass rods is as follows:

[0043] 1) Smelting: Prepare the raw materials according to the required composition in Table 1. The smelting temperature is 970-1100℃. After all the metal has melted, test the composition and then pour it into the industrial frequency furnace for heat preservation at a temperature of 1045-1065℃.

[0044] 2) Horizontal continuous casting: Ingot specifications: Φ195mm, traction time: 2.8s, traction pitch: 5.5mm, pause time: 1.0s, reverse push time: 1.2s, reverse pull pitch: 2.0mm, pull stop time: 0.7s, ingot sawing length: 650mm;

[0045] 3) Extrusion: Extrusion temperature: 670℃, Extruded billet specifications: Extrusion flow rate: 2, extrusion ratio: 132, extrusion speed: 3~9mm / s, the extruded billet flows directly into the water seal tank for cooling after exiting the die, water temperature: 30-35℃, and the winding method is coiling;

[0046] 4) Peeling: Before peeling, the extruded blank is first stretched to... Processing rate: 15.97%, peeling die without sizing belt, peeling amount: 0.16mm, post-peeling specifications:

[0047] 5) Stretching: The extruded billet after peeling undergoes three stretching passes to the specified dimensions. Single-pass processing rate: 10-25%, total processing rate: 48.42%;

[0048] 6) Annealing: Annealing temperature: 420℃, time to rise from room temperature to this temperature: 25min, holding time after reaching the set temperature: 180min, cooling method after exiting the furnace is water cooling;

[0049] 7) Finished product stretching: Finished product specifications: Processing rate: 16.94%;

[0050] 8) Low-temperature annealing: Annealing temperature: 270℃, time to rise from room temperature to this temperature: 30min, holding time: 180min;

[0051] 9) Inspection and packaging.

[0052] Example 2:

[0053] One specification is The preparation method of easily breakable single-phase brass wire is as follows:

[0054] 1) Smelting: Prepare the raw materials according to the required composition in Table 1. The smelting temperature is 990~1120℃. After all the metal has melted, test the composition and then pour it into the induction furnace for heat preservation at a temperature of 1050~1070℃.

[0055] 2) Horizontal continuous casting: Ingot specifications: Φ145mm, traction time: 2.5s, traction pitch: 3.6mm, pause time: 1.1s, reverse push time: 1.0s, reverse pull pitch: 2.0mm, pull stop time: 0.35s, ingot sawing length: 500mm;

[0056] 3) Extrusion: Extrusion temperature: 690℃, Extruded billet specifications: Extrusion flow rate: 2, extrusion ratio: 145.5, extrusion speed: 2~8mm / s, the extruded billet flows directly into the water seal tank for cooling after exiting the die, water temperature: 32-36℃, and the winding method is coiling;

[0057] 4) Peeling: Before peeling, the extruded blank is first stretched to... Processing rate: 22.14%, peeling die without sizing belt, peeling amount: 0.13mm, post-peeling specifications:

[0058] 5) Stretching: The extruded billet after peeling undergoes three stretching passes to the specified dimensions. Single-pass processing rate: 10-25%, total processing rate: 46.32%;

[0059] 6) Annealing: Annealing temperature should be 400℃, time to rise from room temperature to this temperature should be 20 minutes, holding time after reaching the set temperature should be 210 minutes, and water cooling should be used when removing from the furnace.

[0060] 7) Finished product stretching: Finished product specifications: Processing rate: 17.36%;

[0061] 8) Low-temperature annealing: Annealing temperature: 270℃, time to rise from room temperature to this temperature: 30min, holding time: 180min;

[0062] 9) Inspection and packaging.

[0063] Example 3:

[0064] One specification is The preparation method of easily breakable single-phase brass wire is as follows:

[0065] 1) Smelting: Prepare the raw materials according to the required composition in Table 1. The smelting temperature is 1000~1120℃. After all the metal has melted, test the composition and then pour it into the induction furnace for heat preservation at a temperature of 1060~1080℃.

[0066] 2) Horizontal continuous casting: Ingot specifications: Φ254mm, traction time: 5.0s, traction pitch: 4.2mm, pause time: 2.6s, reverse push time: 1.0s, reverse pull pitch: 2.0mm, pull stop time: 1.0s, ingot sawing length: 1100mm;

[0067] 3) Extrusion: Extrusion temperature: 720℃, Extruded billet specifications: Extrusion flow rate: 1, extrusion ratio: 161, extrusion speed: 2~10mm / s, the extruded billet flows directly into the water seal tank for cooling after exiting the die, water temperature: 34-40℃, and the winding method is coiling.

[0068] 4) Peeling: Before peeling, the extruded blank is first stretched to... Processing rate: 8.88%, peeling die without sizing belt, peeling amount: 0.20mm, post-peeling specifications:

[0069] 5) Stretching: The extruded billet after peeling undergoes two stretching passes to achieve the specified final dimensions. Single-pass processing rate: 10-25%, total processing rate: 39.34%;

[0070] 6) Annealing: Annealing temperature: 420℃, time to rise from room temperature to this temperature: 25min, holding time after reaching the set temperature: 240min, cooling method after exiting the furnace is water cooling;

[0071] 7) Finished product stretching: Finished product specifications: Processing rate: 13.12%;

[0072] 8) Low-temperature annealing: Annealing temperature: 280℃, time to rise from room temperature to this temperature: 30min, holding time: 270min;

[0073] 9) Inspection and packaging.

[0074] Example 4:

[0075] One specification is The preparation method of easily breakable single-phase brass rods is as follows:

[0076] 1) Smelting: Prepare the ingredients according to the required composition in Table 1. The smelting temperature is 1010~1120℃. After all the metal has melted, test the composition and pour it into the induction furnace for heat preservation at a temperature of 1060~1080℃.

[0077] 2) Horizontal continuous casting: Ingot specifications: Φ245mm, traction time: 4.0s, traction pitch: 3.8mm, pause time: 1.5s, reverse push time: 1.3s, reverse pull pitch: 2.0mm, pull stop time: 0.8s, ingot sawing length: 800mm;

[0078] 3) Extrusion: Extrusion temperature: 680℃, Extruded billet specifications: Extrusion flow rate: 1, extrusion ratio: 31.5, extrusion speed: 2~6mm / s, the extruded billet flows directly into the water seal tank for cooling after exiting the die, water temperature: 30-40℃, and the winding method is straight strip;

[0079] 4) Peeling: Before peeling, the extruded blank is first stretched to... Processing rate: 13.47%, peeling die without sizing belt, peeling amount: 0.30mm, post-peeling specifications:

[0080] 5) Stretching: The extruded billet after peeling undergoes three stretching passes to the specified dimensions. Single-pass processing rate: 10-25%, total processing rate: 0.90%;

[0081] 6) Annealing: Annealing temperature: 450℃, time to rise from room temperature to this temperature: 30min, holding time after reaching the set temperature: 270min, cooling method after exiting the furnace is water cooling;

[0082] 7) Finished product stretching: Finished product specifications: Processing rate: 17.35%;

[0083] 8) Low-temperature annealing: Annealing temperature: 300℃, time to rise from room temperature to this temperature: 30min, holding time: 240min;

[0084] 9) Inspection and packaging.

[0085] Example 5:

[0086] One specification is The preparation method of easily breakable single-phase brass wire is as follows:

[0087] 1) Smelting: Prepare the ingredients according to the required composition in Table 1. The smelting temperature is 1000~1120℃. After all the metal has melted, test the composition and pour it into the industrial frequency furnace for heat preservation. The heat preservation temperature is 1070~1090℃.

[0088] 2) Horizontal continuous casting: Ingot specifications: Φ254mm, traction time: 6.0s, traction pitch: 3.8mm, pause time: 1.8s, reverse push time: 1.5s, reverse pull pitch: 1.0mm, pull stop time: 0.50s, ingot sawing length: 750mm;

[0089] 3) Extrusion: Extrusion temperature: 740℃, Extruded billet specifications: Extrusion flow rate: 3, extrusion ratio: 465, extrusion speed: 3~9mm / s, the extruded billet flows directly into the water seal tank for cooling after exiting the die, water temperature: 32-39℃, and the winding method is coiling;

[0090] 4) Peeling: Before peeling, the extruded blank is first stretched to... Processing rate: 15.97%, peeling die without sizing belt, peeling amount: 0.12mm, post-peeling specifications:

[0091] 5) Stretching: The extruded billet after peeling undergoes three stretching passes to the specified dimensions. Single-pass processing rate: 10-25%, total processing rate: 47.36%;

[0092] 6) Annealing: Annealing temperature: 380℃, time to rise from room temperature to this temperature: 30min, holding time after reaching the set temperature: 210min, cooling method after exiting the furnace is water cooling;

[0093] 7) Finished product stretching: Finished product specifications: Processing rate: 17.35%;

[0094] 8) Low-temperature annealing: Annealing temperature: 270℃, time to rise from room temperature to this temperature: 30min, holding time: 180min;

[0095] 9) Inspection and packaging.

[0096] Example 6:

[0097] One specification is The preparation method of easily breakable single-phase brass rods is as follows:

[0098] 1) Smelting: Prepare the ingredients according to the required composition in Table 1. The smelting temperature is 1010~1120℃. After all the metal has melted, test the composition and pour it into the induction furnace for heat preservation at a temperature of 1060~1080℃.

[0099] 2) Horizontal continuous casting: Ingot specifications: Φ254mm, traction time: 5.5s, traction pitch: 4.2mm, pause time: 1.6s, reverse push time: 1.4s, reverse pull pitch: 2.2mm, pull stop time: 0.8s, ingot sawing length: 900mm;

[0100] 3) Extrusion: Extrusion temperature set at 770℃; extruded billet specifications: Extrusion flow rate: 1, extrusion ratio: 82, extrusion speed: 2-6 mm / s, the extruded billet flows directly into the water seal tank for cooling after exiting the die, water temperature: 30-36℃, and the winding method is straight strip;

[0101] 4) Peeling: Before peeling, the extruded blank is first stretched to... Processing rate: 13.77%, peeling die without sizing belt, peeling amount: 0.25mm, post-peeling specifications:

[0102] 5) Stretching: The extruded billet after peeling undergoes three stretching passes to the specified dimensions. Single-pass processing rate: 10-25%, total processing rate: 39.67%;

[0103] 6) Annealing: Annealing temperature: 430℃, time to rise from room temperature to this temperature: 35min, holding time after reaching the set temperature: 300min, cooling method after exiting the furnace is water cooling;

[0104] 7) Finished product stretching: Finished product specifications: Processing rate: 19.0%;

[0105] 8) Low-temperature annealing: Annealing temperature: 280℃, time to rise from room temperature to this temperature: 30min, holding time: 240min;

[0106] 9) Inspection and packaging.

[0107] Comparative Example 1: No Ce was added, and everything else was the same as in Example 1. The purpose was to compare the effect of not adding Ce on chip breaking during the machining of single-phase brass.

[0108] Comparative Example 2: No P was added, and everything else was the same as in Example 1. The purpose was to compare the effect of not adding P on chip breaking during the machining of single-phase brass.

[0109] Comparative Example 3: No As was added, otherwise the same as Example 1. The purpose was to investigate the effect of not adding As on chip breaking during the machining of single-phase brass.

[0110] Comparative Example 4: Ce, P, and As were not added, but the rest was the same as in Example 1. The purpose was to compare the effect of not adding Ce, P, and As on chip breaking during the machining of single-phase brass.

[0111] Comparative Example 5: The extrusion temperature was 600°C, and the rest was the same as in Example 1. The purpose was to compare the effect of extrusion temperature on the mechanical properties of single-phase brass and chip breaking during machining.

[0112] Comparative Example 6: The extruded billet was allowed to cool naturally after flowing out of the die, and the rest was the same as in Example 1. The purpose was to compare the effect of water cooling on the mechanical properties and chip breaking during machining.

[0113] Comparative Example 7: The extruded billet after peeling was stretched to the specified size, with a total machining rate of 15%. The rest was the same as in Example 1. The purpose was to compare the effect of the total machining rate of the billet before annealing on chip breaking during the machining of single-phase brass.

[0114] Comparative Example 8: The under-annealing temperature was 540°C, and the rest was the same as in Example 1. The purpose was to compare the effect of the under-annealing temperature on chip breaking during the machining of single-phase brass.

[0115] Comparative Example 9: The cooling method for bottom-annealing after exiting the furnace was natural cooling, and the rest was the same as in Example 1. The purpose was to compare the effect of bottom-annealing without water cooling on chip breaking during the machining of single-phase brass.

[0116] Comparative Example 10: The finished product was not subjected to low-temperature annealing, but otherwise the same as in Example 1. The purpose was to compare the effect of low-temperature annealing on chip breaking during machining of single-phase brass.

[0117] Comparative Example 11: H65 purchased from the market The purpose of this study was to compare the impact of bar stock on chip breaking during machining of existing single-phase brasses on the market.

[0118] The chemical composition of brass in all the above embodiments and comparative examples is shown in Table 1.

[0119] The grain size, brittle phase ratio, brittle phase size, hardness, elongation, and morphology and size of the copper chips from the cutting process of all the above embodiments and comparative examples were characterized, and the final performance test results are shown in Table 2.

[0120] Specifically, the performance testing steps are as follows:

[0121] (1) Grain size: Metallographic specimens were prepared in accordance with GB / T 13298. Grain size was measured in accordance with the comparative method specified in GB / T 6394-2017 (Method for determination of average grain size of metals), that is, the grain size was evaluated by comparing with the standard rating chart.

[0122] (2) Area ratio and size of brittle phase: observed under a scanning electron microscope;

[0123] (3) Hardness: Tested according to GB / T4340.1-2009 "Metallic materials Vickers hardness test - Part 1: Test method";

[0124] (4) Elongation: Tested in accordance with GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0125] The metallographic structure of the brass in Example 1 above is shown in the figure. Figure 1 As shown.

[0126] The metallographic structure of the brass in Comparative Example 11 above is shown in the figure. Figure 2 As shown.

[0127] The morphology photographs of the brass scraps in Example 1 above are as follows: Figure 3 As shown.

[0128] The photographs of the copper shavings morphology in Comparative Example 11 above are as follows: Figure 4 As shown.

[0129] From Table 2 and Figures 1-4 It can be seen that:

[0130] (1) From Figure 1 It can be clearly seen that the brittle phases of Pb₂Ce, Cu₃P, and CuZnAs in brass are dispersedly distributed. Figure 3 As can be seen from Table 2, the morphology of the brass chips obtained in each embodiment is the desired C-type chip, and the size is all below 100mm, indicating that the brass obtained in each embodiment is easier to break.

[0131] It is evident that, without altering the overall properties of brass, this application, by adding trace amounts of Pb, Ce, P, and As elements and employing a processing technology different from that used for single-phase brass, enables the formation of brittle phases of Pb2Ce, Cu3P, and CuZnAs in the α-phase brass matrix in a certain proportion and size. This results in α-phase brass having easily broken copper chips during machining, preventing them from entangled in the cutting tool, thus enabling single-phase brass to be used in CNC machine tool machining.

[0132] (2) Comparison and analysis of data from comparative examples and implementation examples show that:

[0133] In Comparative Example 1 without Ce, although the copper chip morphology was C-type, the length reached 72 mm. This indicates that adding Ce can improve the chip breaking of single-phase brass because Ce and Pb form a brittle compound called Pb2Ce, which can play a role in chip breaking.

[0134] In Comparative Example 2 without the addition of P, although the copper chip morphology was C-type, the length reached 80 mm. This indicates that the addition of P can improve the chip breaking of single-phase brass because P forms Cu3P brittle phase with Cu, which can play a chip breaking role.

[0135] In Comparative Example 3 without As, although the copper chip morphology was C-type, the length reached 146 mm. This indicates that adding As can improve the chip breaking of single-phase brass because As forms a brittle compound CuZnAs with Cu, which is distributed on the grain boundaries and plays a chip breaking role.

[0136] Comparative Example 4 shows that no Ce, P, or As elements were added. The copper chip morphology was a long spiral chip with a length of 420 mm, indicating that the addition of Ce, P, and As elements together can have a synergistic effect and significantly improve the chip breaking of single-phase brass.

[0137] Comparative Example 5: When the extrusion temperature is 600℃, although the copper chip morphology is C-shaped, the length reaches 250mm. This indicates that limiting the alloy extrusion temperature can improve chip breaking of single-phase brass. The reason is that this temperature is lower than the lower limit of the extrusion temperature range required by the alloy, which is 640℃. At this temperature, the Cu3P and CuZnAs phases cannot be completely dissolved in the brass matrix, resulting in a decrease in the proportion of brittle Cu3P and CuZnAs precipitates during subsequent annealing, which leads to a deterioration in the machinability of the alloy.

[0138] Comparative Example 6: After the extruded billet flows out of the die and cools naturally, the copper chip morphology is a long spiral chip with a length of 336 mm. This indicates that immediate water cooling of the extruded billet after flowing out of the die can improve chip breaking of single-phase brass. The reasons are: firstly, immediate water cooling of the high-temperature extruded billet can allow the Cu3P and CuZnAs phases to be completely dissolved in the brass matrix, which can increase the proportion of brittle Cu3P and CuZnAs precipitates in subsequent annealing; secondly, it can reduce the alloy grain size.

[0139] Comparative Example 7: After peeling, the extruded billet is stretched to the minimum allowable size. The total machining rate is low, only 15%. Although the copper chip morphology is C-shaped, the length reaches 198mm. This indicates that stretching the extruded billet to the minimum allowable size with a high machining rate can improve chip breaking of single-phase brass. The reason is that high machining stretching can fully deform the extruded structure, completely break the original grains, significantly increase the number of recrystallization nuclei, and make the annealed recrystallized grains fine. Since the brass in this application mainly relies on a variety of brittle phases to achieve easy chip breaking, and these brittle phases are distributed in the grains or on the grain boundaries, increasing the grain boundary area can further improve the chip breaking effect. The smaller the grain size, the more grains per unit area, the larger the total grain boundary area, and the more uniform the distribution of Pb2Ce, Cu3P, and CuZnAs brittle phases, the better the chip breaking effect.

[0140] Comparative Example 8: The bottom annealing temperature is 540℃. Although the copper chip morphology is C-type, the length reaches 300mm. This indicates that using a lower temperature annealing of 390~450℃ can improve the chip breaking of single-phase brass. The reason is that the lower temperature annealing can promote the precipitation of Cu3P and CuZnAs phases from the grain boundaries and avoid grain growth.

[0141] Comparative Example 9: The bottom-leaf annealing and furnace exit cooling method is natural cooling. Although the copper chip morphology is C-type, the length reaches 156mm, indicating that the bottom-leaf annealing and furnace exit cooling method is water cooling, which can improve the chip breakage of single-phase brass. The reason is that water cooling can promote the dissolution of Cu3P phase into the matrix at 390-450℃, and the proportion of subsequent low-temperature annealing of finished products will increase.

[0142] Comparative Example 10: The finished product did not undergo low-temperature annealing. Although the copper chip morphology was C-shaped, the length reached 218 mm. This indicates that low-temperature annealing can improve the chip breaking of single-phase brass. The reasons are as follows: First, the purpose of low-temperature annealing is to allow the Cu3P phase to fully precipitate, further improving the chip breaking effect during brass machining; second, α-brass contains the ordered compound Cu3Zn, which transforms into the ordered compound Cu9Zn in the 200-300℃ range. Cu9Zn is a brittle compound, which can improve the machinability of α-single-phase brass.

[0143] Comparative Example 11: H65 purchased from the market The bar stock, with a common H65 composition and produced using conventional processes, produces copper chips that are spring-like coils with a length of 505 mm. These chips exhibit the worst chip-breaking performance, indicating that the single-phase brass of this invention addresses the shortcomings of existing technologies and achieves easy chip breaking.

[0144] Table 1. Chemical composition of brass in all examples and comparative examples.

[0145] serial number Cu Pb Ce P As Zn Example 1 64.63 0.0084 0.0078 0.019 0.073 margin Example 2 65.28 0.055 0.12 0.0080 0.033 margin Example 3 66.51 0.039 0.085 0.073 0.024 margin Example 4 67.10 0.024 0.040 0.035 0.13 margin Example 5 68.80 0.010 0.016 0.0054 0.016 margin Example 6 69.45 0.0038 0.0052 0.022 0.050 margin Comparative Example 1 64.63 0.0084 \ 0.019 0.073 margin Comparative Example 2 64.63 0.0084 0.0078 \ 0.073 margin Comparative Example 3 64.63 0.0084 0.0078 0.019 \ margin Comparative Example 4 64.63 0.0084 \ \ \ margin Comparative Example 5 64.63 0.0084 0.0078 0.019 0.073 margin Comparative Example 6 64.63 0.0084 0.0078 0.019 0.073 margin Comparative Example 7 64.63 0.0084 0.0078 0.019 0.073 margin Comparative Example 8 64.63 0.0084 0.0078 0.019 0.073 margin Comparative Example 9 64.63 0.0084 0.0078 0.019 0.073 margin Comparative Example 10 64.63 0.0084 0.0078 0.019 0.073 margin Comparative Example 11 64.48 0.0076 0.00024 0.0016 0.0013 margin

[0146] Table 2. Performance test results of brass in all examples and comparative examples.

[0147]

Claims

1. A type of easily breakable single-phase brass, characterized in that, It consists of the following components by weight percentage: Cu 64~70wt%, Pb 0.003~0.06wt%, Ce 0.005~0.15wt%, P 0.005~0.1wt%, As 0.01~0.15wt%, with the balance being Zn and unavoidable impurities; The process flow for the easily broken single-phase brass is as follows: smelting → horizontal continuous casting → extrusion → peeling → stretching → annealing → finished product stretching → low-temperature annealing. The method for preparing the easily breakable single-phase brass includes the following steps: 1) Smelting: Prepare the required ingredients and smelt them in a smelting furnace at a temperature of 950~1150℃. After all the metal has melted and the composition has been tested and found to be qualified, the metal is transferred to a holding furnace at a temperature of 1010~1130℃, which is also the casting temperature. 2) Horizontal continuous casting: Ingot specifications Φ80~300mm, traction time 1~7s, traction pitch 1~10mm, pause time 0.1~3s, reverse push time 0.1~3s, reverse pull pitch 0.5~4mm, pull stop time 0.1~3s, ingot sawing length 300~1600mm; 3) Extrusion: The extrusion temperature of brass needs to be determined according to the Cu content: when the Cu content is 64~66wt%, the extrusion temperature is set at 640~700℃; when the Cu content is 66~68wt%, the extrusion temperature is set at 680~740℃; when the Cu content is 68~70wt%, the extrusion temperature is set at 720~780℃; the extrusion flow rate is 1~3, the extrusion ratio is 30~500, the extrusion speed is 2~18mm / s, and the winding method is coiled or straight. 4) Peeling: Before peeling, the extruded billet undergoes one stretching pass, with the processing rate controlled at 5-30%; 5) Stretching: The extruded billet after peeling is stretched to the specified size in 1 to 4 passes, with the single-pass processing rate controlled at 10 to 25% and the total processing rate controlled at 35 to 50%; 6) Annealing: The annealing temperature is controlled at 390~450℃, and the time to rise from room temperature to this temperature is controlled at 15~90min. After reaching the set temperature, the holding time is 120~300min. 7) Finished product stretching: Control the processing rate to 8-20%; 8) Low-temperature annealing: The annealing temperature is set at 250~300℃, the time to rise from room temperature to this temperature is controlled at 20~60min, and the holding time is 120~360min; 9) Inspection and packaging; In step 3), the extruded billet flows directly into the water seal tank for cooling after exiting the mold, and the water temperature does not exceed 40℃; In step 6), the cooling method after exiting the furnace is water cooling.

2. The easily breakable single-phase brass according to claim 1, characterized in that: The easily broken single-phase brass has a hardness (HV5) of 140-170, an elongation (A50) of 12-20%, and a grain size of 8-25 μm.

3. The easily breakable single-phase brass according to claim 1, characterized in that: The easily broken single-phase brass is composed of a matrix phase and a second phase. The matrix phase is an α phase, and the second phase includes Pb2Ce, Cu3P, and CuZnAs phases, which are dispersed and have an area ratio of 0.1-1.5%.

4. The easily breakable single-phase brass according to claim 3, characterized in that: The average size of the second phase is below 800 nm.

5. The easily breakable single-phase brass according to claim 1, characterized in that: In step 4), the sizing belt of the peeling die is removed, and the peeling amount is controlled at 0.10~0.30mm.

6. The easily broken single-phase brass according to claim 1, characterized in that: In step 6), the heating time is controlled between 15 and 40 minutes.

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