Extruded cadmium bronze rod
Extruded cadmium bronze rod is a copper-based bronze bar with 1.0%-1.5% cadmium added. Produced through an extrusion process, it combines high strength, high conductivity, and good wear resistance. It is widely used in motor commutators, switch contacts, high-strength wire, and other fields. Its diameter typically ranges from 10-150 mm, and its length can be customized (1-6 meters). The material grade is generally QCd1.0. Precise control of cadmium content is critical to ensuring performance. Too high a cadmium content will increase brittleness, while too low a cadmium content will not fully enhance the strengthening effect.
The production process for extruded cadmium bronze rods involves key steps, including alloy smelting, ingot casting, heating, extrusion, heat treatment, and finishing. First, electrolytic copper with a purity of at least 99.95% and high-purity cadmium (99.9%) are selected and smelted in a medium-frequency induction furnace at a controlled temperature of 1100-1150°C. An inert gas atmosphere is used to prevent oxidation. Cadmium is added using an intermediate alloy method (such as a Cu-Cd alloy) to ensure uniform composition and a cadmium content deviation of ≤±0.05%. The ingots are cast using a semi-continuous casting process, resulting in round ingots with a diameter of 120-200 mm. Cooling rates of 80-120°C/minute are used to prevent cadmium segregation. The ingots undergo a homogenization annealing process (600-650°C for 4-6 hours) to eliminate casting stresses. During the extrusion process, the ingot is heated to 700-750°C and extruded into rods using a horizontal extruder. The extrusion ratio is controlled at 8-15, and the extrusion speed is 5-10 m/min. Hot-work die steel is used to ensure a smooth rod surface and a diameter tolerance of ≤±0.5 mm. Heat treatment utilizes a solution-treatment and aging process, with a solution temperature of 850-900°C, a hold time of 1-2 hours, followed by a water quench and an aging temperature of 300-350°C, a hold time of 3-4 hours, to precipitate the cadmium in fine particles and enhance strength. Finally, straightening (straightness ≤1 mm/m), machining, and non-destructive testing are performed to ensure the rods are free of defects such as cracks and inclusions.
The performance advantages of extruded cadmium bronze rods make them uniquely competitive in the field of electrical conductivity and wear resistance. First, the balance between high strength and high conductivity. The tensile strength of QCd1.0 cadmium bronze rods is ≥450MPa and the conductivity is ≥80% IACS, which is much higher than that of ordinary brass (conductivity is 25%-35% IACS). It can simultaneously meet the requirements of structural strength and current conduction. Second, it has excellent wear resistance, with a Brinell hardness of ≥120HB and a friction coefficient of ≤0.3. Under sliding friction conditions (such as contact between motor commutators and brushes), the wear rate is reduced by more than 50% compared to pure copper, and the service life is extended by 2-3 times. Third, it has good corrosion resistance, with a corrosion rate of ≤0.01mm/year in the atmosphere, fresh water and lubricating oil. After surface passivation treatment, the salt spray resistance can reach 300 More than one hour; fourthly, it has excellent processing performance and can be used for turning, milling, drilling and other mechanical processing. The processing efficiency is 30% higher than that of stainless steel, which is suitable for making parts with complex shapes; fifthly, it has good welding performance and can be connected by argon arc welding, brazing and other methods. The weld strength is ≥90% of the parent material strength, which meets the assembly requirements.
Across various applications, extruded cadmium bronze rods are a core material for high-end conductive and wear-resistant components. In motor manufacturing, commutators for large generators and motors utilize QCd1.0 cadmium bronze rods with a diameter of 50-100 mm. These rods are machined into commutator segments, leveraging their high conductivity and wear resistance to ensure stable current commutation. In switchgear, contacts for high-voltage circuit breakers and disconnectors utilize cadmium bronze rods with a diameter of 20-50 mm to withstand arc wear and mechanical stress during switching. In rail transit, pantograph sliders for subways and high-speed trains are machined from cadmium bronze rods with a diameter of 30-60 mm, ensuring reliable electrical connection and wear resistance to the contact network. In precision instrumentation, the conductive shafts of potentiometers and sensors utilize small-diameter (10-20 mm) cadmium bronze rods, balancing conductivity and structural support. In aerospace, brush holders for airborne motors utilize cadmium bronze rods, ensuring stable operation in high-altitude, low-pressure environments.
Industry trends indicate that extruded cadmium bronze rods are moving toward low-cadmium, high-precision, and multifunctional characteristics. Low-cadmium bronze rods (cadmium content 0.5%-0.8%) utilize trace amounts of rare earth elements (such as cerium and lanthanum) to reduce cadmium content (reducing toxicity) while maintaining high strength and conductivity, achieving a tensile strength exceeding 420 MPa. High-precision extrusion technology is being promoted, achieving diameter tolerances within ±0.1 mm to meet the processing requirements of precision parts. Composite coating technologies (such as silver and gold plating) further enhance conductivity and oxidation resistance, reducing contact resistance by over 30%. Furthermore, environmentally friendly production processes, including closed melting and cadmium recovery systems, reduce cadmium volatilization pollution and increase waste recovery rates to over 95%. Intelligent extrusion equipment utilizes online temperature monitoring and pressure regulation to ensure stable product performance. With the development of new energy motors and high-end equipment, demand for high-performance extruded cadmium bronze rods will continue to grow, driving the industry to achieve greater breakthroughs in material optimization and green production.
