Tin bronze strip
Tin bronze strip is an alloy strip with a copper base and 3-14% tin. Elements such as phosphorus, zinc, and lead may be added to improve performance. It offers excellent wear resistance, corrosion resistance, elasticity, and fatigue resistance, and is widely used in machinery manufacturing, automotive, and instrumentation. Common grades include QSn4-3 (4% tin, 3% zinc) and QSn6.5-0.1 (6.5% tin, 0.1% phosphorus). QSn4-3 offers high strength (tensile strength ≥400 MPa) and is suitable for heavy loads. QSn6.5-0.1 offers excellent elasticity (elastic limit ≥250 MPa) and is primarily used in precision springs. Strip thickness ranges from 0.1-3 mm, widths from 50-600 mm, a surface finish of Ra ≤ 0.8 μm, and a dimensional tolerance of ±0.005 mm, meeting complex forming requirements.
The production process for tin bronze strip requires a balance between alloy composition uniformity and processability. First, electrolytic copper and tin ingots are charged into a medium-frequency induction furnace in appropriate proportions at a melting temperature of 1100-1200°C. Phosphor copper (0.1-0.3%) is added for deoxidation and grain refinement. Elements such as lead and zinc are added later in the melting process to prevent burnout. The melt is then cast in a continuous casting machine into strip with a thickness of 10-20 mm. The strip undergoes homogenization annealing (600-700°C for 4-6 hours) to eliminate segregation. Hot rolling is suitable for strip ≥3 mm thick, heating at 700-800°C and reducing by 20-30% per pass. Cold rolling is used for thin-walled strip, using multiple passes to reach the target thickness. Intermediate annealing is performed at 400-500°C, with a controlled hardness of HB80-120. After tension straightening, cleaning and polishing, the finished belts pass the bending test (180° without cracks) and the wear test (wear ≤ 0.01mm/1000 times) to ensure quality.
In the machinery manufacturing sector, tin bronze strip is the preferred material for wear-resistant components. Machine tool spindle bearings utilize 0.5-1mm thick QSn6.5-0.1 strip, stamped and inlaid with graphite, reducing the friction coefficient to 0.08. This has extended the spindle life of a precision machine tool to 15,000 hours. Hydraulic pump valve plates utilize QSn4-3 strip, with oil grooves etched to withstand pressures of 30 MPa or higher. This has reduced the leakage rate of a hydraulic equipment manufacturer’s products to below 0.01%. Roller bearings in textile machinery are wound with tin bronze strip, which can withstand continuous vibration and exhibit excellent wear resistance. This has reduced the wire breakage rate at a textile mill by 40%.
In the automotive industry, the application of tin bronze strip is focused on high-reliability components. Synchronizing rings in automotive transmissions utilize 1-2mm thick QSn6.5-0.1 strip. After phosphating, the surface stabilizes the friction coefficient, resulting in a 25% improvement in gearshift smoothness for one automaker. Brake shoe rivet strips in the braking system utilize QSn4-3, which boasts a tensile strength of ≥450MPa and maintains connection strength even at high temperatures (200°C). This has reduced the brake system failure rate of a commercial vehicle by 30%. Motor brush holders in new energy vehicles are stamped from tin bronze strip, offering both excellent conductivity and elasticity. This has reduced the operating noise of the motors of one electric vehicle brand to below 65 decibels.
As high-end equipment demands higher material performance, innovation in tin bronze strip continues to advance. Manufacturers have developed high-strength tin bronze strip (QSn8-0.3) with a tensile strength exceeding 500 MPa. This strip, used in bearing retainers for wind turbine equipment, has a lifespan of up to 20 years. FDA-certified lead-free tin bronze strip (lead content ≤ 0.01%) has been developed for food machinery, reducing the corrosion rate of equipment on a canned food production line by 50%. Using asynchronous rolling technology, the strip thickness tolerance is controlled to ±0.002mm, improving the dimensional consistency of precision springs at an instrument manufacturer to 99.5%. In the future, with the advancement of intelligent and green manufacturing, tin bronze strip will evolve towards higher strength, lower lead content, and more complex functions, expanding its application in high-end equipment and medical devices.
