As a non-ferrous metal alloy with a long and storied history, bronze occupies an irreplaceable position in the field of modern CNC precision machining. Distinguished by its exceptional wear resistance, corrosion resistance, and electrical conductivity, it is widely utilized across a diverse range of high-end manufacturing applications. Based on the different alloying elements, bronze can be divided into the following five major series:
Features: Its chemical composition consists of 83–92% Cu, 7–12% Sn, and 4–8% Pb; it features a Brinell hardness (HB) of 65–90 and a tensile strength of 310–415 MPa. It possesses excellent self-lubricating properties and resistance to seizing, and its machinability via CNC reaches 70%, allowing for medium-to-high-speed cutting with minimal tool wear. Its drawbacks include poor high-temperature resistance; furthermore, its lead content does not meet environmental regulations, rendering it unsuitable for applications involving food or drinking water.
Applications: Suitable for various general-purpose friction transmission components, such as bearings, bushings, worm gears, sliders, and hydraulic valve blocks.
Features: With a lead content ranging from 10% to 14%—higher than that of C93200—this alloy possesses a Brinell hardness of approximately HB 75 and exhibits excellent ductility. Its standout advantage lies in its exceptional embeddability, allowing it to accommodate foreign particles such as dust and impurities encountered during operation; this effectively prevents scratching of the friction pair, resulting in superior anti-seizing performance compared to C93200. Its machinability via CNC is comparable to that of C93200 (approximately 70%); the resulting chips are fine and easily evacuated, making it well-suited for high-speed cutting processes without the need for specialized cooling treatments.
Applications: Primarily used for high-speed, heavy-load bearings, steam turbine journals, friction components in mining machinery, and transmission components operating in high-dust environments.
Features: With a lead content of ≤0.2%, this material qualifies as a lead-free, eco-friendly alloy. It features a Brinell hardness of HB 80–100 and a tensile strength of 400–500 MPa; it exhibits excellent resistance to corrosion by seawater and weak acids, and its overall strength represents a significant improvement over leaded tin bronzes. However, its machinability via CNC has been reduced to 50%; during cutting, chips tend to be long and prone to adhering to the tool. Consequently, machining requires the use of sharp carbide tools and a high-pressure coolant system to optimize chip-breaking efficiency; dry cutting is strictly prohibited.
Applications: Suitable for wear-resistant components in food machinery, marine seawater piping, heavy-duty worm gears, and various eco-friendly precision structural parts.
Features: Its chemical composition consists of 81–86% Cu, 9–11% Al, 2–4% Fe, and 1–3% Ni. It features a Brinell hardness (HB) of 150–200 and a tensile strength of 550–690 MPa; its overall mechanical properties significantly surpass those of tin bronze. It exhibits excellent resistance to corrosion from seawater, weak acids, and salt spray, as well as superior wear and impact resistance, enabling it to withstand heavy loads and alternating stresses; however, it is prone to work hardening during processing. Its machinability via CNC is rated at only 20–30%, characterized by high cutting forces and rapid tool wear. Dry cutting is strictly prohibited; machining operations require low spindle speeds, shallow depths of cut, and climb milling techniques, utilizing high-pressure through-tool coolant.
Applications: Widely used in marine propellers, seawater pump bodies, valves, heavy-duty gears, cams, and wear-resistant structural components for mining machinery.
Features: With an aluminum content of 11–13% and an iron content of 3–5%, this alloy exhibits a higher degree of strengthening and a Brinell hardness of ≥190. Its wear resistance and impact resistance are further improved compared to C95400; however, work hardening effects are significantly more pronounced. Its CNC machinability is slightly lower (≈22%), and cutting presents greater difficulty; therefore, the use of high-hardness coated carbide tools is required. Additionally, it is necessary to reduce cutting speeds, increase tool replacement frequency, enhance cooling and chip evacuation measures, and avoid repeated cutting of the same area.
Applications: Suitable for rolling mill sliders, thrust bearings, heavy-duty worm gears, and various high-stress friction pair components.
Features: Its chemical composition consists of 80–85% Cu, 8–10% Al, 4–6% Ni, and 3–5% Fe. It features a Brinell hardness (HB) of 170–210 and a tensile strength of ≥620 MPa, demonstrating top-tier resistance to stress corrosion cracking. It exhibits outstanding resistance to corrosion in seawater and chloride-rich environments, making it well-suited for deep-sea applications and highly corrosive chemical processing environments; however, its high hardness results in strong abrasiveness. Its machinability via CNC is rated at only 20%, leading to short tool life. Consequently, cutting parameters must be strictly controlled, utilizing low cutting speeds, shallow depths of cut, and climb milling strategies. Furthermore, high-pressure internal coolant systems should be employed, and wear-resistant coated carbide tools must be selected and replaced promptly once they become dull.
Applications: Primarily used for deep-sea propellers, seawater desalination equipment, nuclear power pumps and valves, and corrosion-resistant precision components for the chemical industry.
Features: Its chemical composition consists of 94–96% Cu, 6–7% Sn, and 0.1–0.25% P, wherein the phosphorus acts as both a deoxidizer and a strengthening agent. It features a Brinell hardness (HB) of 90–120 and a tensile strength of 400–500 MPa; furthermore, it exhibits excellent elastic limits and fatigue properties, stable electrical and thermal conductivity, good corrosion resistance, and superior cold and hot working characteristics. While dimensional accuracy is easily maintained, the material is prone to work hardening during processing. Its CNC machinability rating is 55%; since it tends to produce long chips that easily adhere to cutting tools, the use of sharp tooling is essential. Machining operations should be accompanied by an ample supply of high-pressure coolant and utilize a climb milling strategy, with careful control over cutting speed and feed rate to prevent the exacerbation of work hardening.
Applications: Suitable for the CNC machining of springs, spring clips, electronic connectors, relay contacts, precision structural components for instrumentation, and various types of terminals.
Features: By adding 3–4% lead to the C51000 base alloy, mechanical properties are slightly reduced—specifically, elasticity decreases marginally—yet anti-friction performance is significantly enhanced. CNC machinability is substantially improved to 70%; during cutting, chips fracture easily and evacuate smoothly, eliminating the need for complex process controls. This material is well-suited for the precision milling and tapping of complex structures; standard cooling methods suffice for processing requirements, and tool wear remains minimal.
Applications: Primarily used for precision sliding bearings, electrical sliding contacts, and various wear-resistant elastic composite components.
Features: Its chemical composition consists of 97–98% Cu, 1.8–2.0% Be, and 0.2–0.6% Co. Its mechanical properties vary significantly depending on the processing method; in the solution-treated state, it exhibits low hardness and excellent machinability. Following aging treatment, its tensile strength can reach 1030–1380 MPa, with a Rockwell hardness of HRC 35–42. Its core advantages lie in its elastic limit, fatigue strength, and wear resistance—all of which rank at the forefront of copper alloys—while simultaneously possessing excellent corrosion resistance, electrical conductivity, and non-magnetic properties. However, its machinability via CNC is rated at only 15–25%; due to its extremely high hardness after aging, it causes severe tool wear and is prone to tool chipping. Consequently, a specific process sequence is required: "solution treatment first, followed by machining, and finally aging." During the machining stage—performed after solution treatment (water quenching from 790–820°C) has softened the material—it is necessary to employ low cutting speeds, shallow depths of cut, and high-pressure internal cooling techniques, utilizing coated carbide tools to avoid dry cutting and repetitive cutting passes.
Applications: Suitable for aerospace precision springs, sensor components, high-end mold inserts, medical probes, and explosion-proof tools.
Features: Its chemical composition consists of 96% Cu and 2–4% Si, with small additions of Mn and Zn. Its mechanical properties are moderate, featuring moderate tensile strength and hardness, along with good ductility. Its core strengths lie in its excellent weldability and corrosion resistance, as well as the exceptional surface finish achievable after CNC machining. Its machinability rating is approximately 30%; during cutting, it produces long chips, necessitating optimized cooling and chip-breaking strategies, the use of sharp cutting tools, and careful control of cutting speeds to prevent tool adhesion.
Applications: Primarily used for architectural hardware, marine fasteners, electrical terminals, and precision decorative parts.
| Grade | Material | Machinability Rating | Hardness | Advantages | Applications |
|---|---|---|---|---|---|
| C93200 | High-Lead Tin Bronze | 70% | HB 65~90 | Easy machinability, self-lubricating, low cost | General-purpose friction components, ambient-temperature transmission |
| C93700 | High-Lead Tin Bronze | ≈70% | HB ≈75 | Excellent embeddability, strong anti-seizing properties | High-speed and heavy-load applications, high-dust environments |
| C90300 | Lead-Free Tin Bronze | 50% | HB 80~100 | Lead-free and eco-friendly, good corrosion resistance | Food processing, seawater exposure, and environmental protection scenarios |
| C95400 | Aluminum Bronze | 25% | HB 150~200 | High strength, seawater resistant, impact resistant | Marine vessels, heavy machinery, and offshore operating conditions |
| C95500 | High-Iron, High-Aluminum Bronze | ≈22% | HB 190 | High hardness, wear resistant, impact resistant | High-stress friction pairs, rolling mill components |
| C95800 | Nickel-Aluminum Bronze | 20% | HB 170~210 | Ultra-corrosion resistant, resistant to stress corrosion | Deep-sea environments, nuclear power, and highly corrosive conditions |
| C51000 | Phosphor Bronze | 55% | HB 90~120 | High elasticity, conductive, dimensionally stable | Electronic springs, precision connectors |
| C54400 | Leaded Phosphor Bronze | 70% | HB 90~120 | Easy machinability, excellent friction-reducing properties | Precision sliding bearings, sliding electrical contacts |
| C17200 | Beryllium Bronze | 20% | HRC 35~42 | Ultra-high strength, high elasticity, wear resistant | Aerospace, molds and dies, high-end precision components |
| C65500 | Silicon Bronze | 30% | Medium Hardness | Corrosion resistant, good weldability, smooth surface finish | Architectural hardware, marine fasteners |
| Material | Cutting speed Vc (m/min) | Feed Rate（mm/fz） | Depth of cut in roughing (mm) | Finishing depth of cut (mm) |
| Tin bronze | 180–280 | 0.08–0.15 | 0.5–2 | 0.05–0.2 |
| Aluminum bronze | 120–180 | 0.06–0.12 | 0.5–1.5 | 0.05–0.15 |
| Phosphorus bronze | 160–240 | 0.07–0.14 | 0.4–1.2 | 0.05–0.15 |
| Beryllium bronze | 100–160 | 0.05–0.10 | 0.3–1.0 | 0.03–0.10 |
| Silicon bronze | 130–200 | 0.06–0.12 | 0.4–1.2 | 0.05–0.15 |
| Material | Feature | Cutting | Knives | Adaptations |
| Tin bronze | Easy to cut but prone to tool sticking and chip entanglement; core control focuses on tool sticking and chip removal. | High speed, medium feed, and adequate cooling prevent tool sticking and built-up edge. | Features chip breakers and polished cutting edges; preferably ultra-fine grain cemented carbide, TiN coating optional; positive rake angle 6°–12°, large clearance angle 8°–15°; end mills with chip breakers, turning tools with rounded cutting edges. | Suitable for wear-resistant parts; Ra up to 0.4–1.6μm. |
| Aluminum bronze | High hardness and strong abrasion resistance reduce core tool wear. | Reduced cutting speed, high-pressure, high-flow-rate cooling, vibration control prevents chipping. | Cemented carbide coating; preferably TiAlN coating, ultra-fine grain cemented carbide material; positive rake angle 6°–12°, large clearance angle 8°–15°, polished cutting edge, milling cutters with chip breakers, turning tools with rounded cutting edges. | Suitable for high-strength, wear-resistant parts. |
| Phosphorus bronze | Highly flexible, prone to chip entanglement, and easily scratched surface; core chip control and surface protection are key features. | High-pressure cooling, appropriately increased feed rate, reduced cutting force to prevent deformation, and optimized parameters to prevent chip entanglement. | Tools with chip breakers and positive rake angle; preferably ultra-fine grain cemented carbide, TiN coating optional; positive rake angle 6°–12°, large clearance angle 8°–15°; spiral flute taps/thread end mills for threads, internal coolant drills for deep holes. | Suitable for precision elastic parts. |
| Beryllium bronze | Extremely high hardness, difficult to machine, toxic dust; core safety features include wear control and deformation prevention. | Raw material is machined in a soft state after annealing; minimal machining is required after aging. Sealed cooling and dust extraction ensure safety. | Diamond-coated cutting tools; ultra-fine grain cemented carbide material; positive rake angle 6°–12°, large clearance angle 8°–15°; spiral flute taps/thread end mills for threads, internal coolant drills for deep holes. | Suitable for high-precision parts, tolerance ±0.01–0.03 mm. |
| Silicon bronze | Contains silicon hard points, prone to chipping and surface roughening; core enhancement improves tool rigidity and cutting stability. | High-rigidity equipment, ample oil-based cooling, post-machining polishing. | Sharp, polished cutting edge tools; preferential TiAlN coating, ultra-fine grain cemented carbide material; positive rake angle 6°–12°, large clearance angle 8°–15°; internally cooled drill bits for deep holes. | Suitable for machining structural components. |
CNC Machining of Bronze Worm Gear
CNC Machining of Bronze Parts
CNC Machining of Bronze Worm Gear
CNC Machining of Bronze Parts
A: Strongly alkaline coolants can cause corrosion and discoloration of bronze, affecting the surface quality and machining accuracy of parts. Therefore, their use is strictly prohibited throughout the machining process. Oil-based cutting fluids should be used preferentially.
A: The core solution is through two points: first, optimizing cutting parameters; second, using tools with chip breakers. Simultaneously, prioritize climb milling to improve chip removal efficiency and reduce chip entanglement.
A: Beryllium bronze machining produces toxic dust. Dry cutting is strictly prohibited. A closed cooling and dust extraction system is required, and operators must wear appropriate safety precautions. Additionally, the blank must be annealed to a soft state before machining, and after aging treatment, the machining volume should be minimized.
A: For aluminum bronze and silicon bronze, TiAlN coating is preferred; for tin bronze and phosphor bronze, TiN coating is optional; for beryllium bronze, diamond coating is required, all combined with ultra-fine grain cemented carbide.
A: Reduce clamping force, use multi-point support, and employ layered cutting processes. Strictly control cutting heat to prevent deformation of thin-walled parts due to stress and heat.
A: Aging treatment is a mandatory step in beryllium bronze machining. For the other four bronze materials (tin bronze, aluminum bronze, phosphor bronze, and silicon bronze), the appropriate step can be selected based on machining requirements. After aging treatment, the machining amount should be minimized.
