In modern electronic design and industrial manufacturing, selecting the optimal copper alloy is a critical step in ensuring long-term product reliability, conductivity, and mechanical strength. UNS C51100 (commonly referred to as 4% Tin Phosphor Bronze or CuSn4 under European standards) stands out as one of the most versatile copper-tin-phosphorus alloys. With its unique combination of mechanical toughness, excellent fatigue resistance, and superior formability, C51100 is widely chosen for applications requiring spring components, electrical terminals, and high-wear structural parts.
As a leading high-tech manufacturer specializing in advanced strategic metal materials, Sichuan Kepai New Material Co., Ltd. provides bespoke casting, extrusion, drawing, and precision processing for UNS C51100 phosphor bronze. By leveraging our state-of-the-art smelting and quality analysis facilities, we ensure that every batch of C51100 conforms to strict international tolerances, optimizing the chemical balance to offer our customers a competitive edge in product design and performance.
The fundamental characteristics of C51100 are governed by its precise chemistry. Standard specifications require a Tin (Sn) concentration of 3.5% to 4.5% and a Phosphorus (P) addition of 0.03% to 0.35%, with the remainder being pure Copper (Cu). The tin content acts as a solid-solution strengthener, significantly increasing the alloy’s tensile yield point and resistance to cyclic fatigue. Phosphorus acts primarily as a powerful deoxidizing agent during smelting, which eliminates the formation of brittle cuprous oxides. This results in a cleaner microstructure, enhancing the metal's ductility, weldability, and resistance to atmospheric corrosion.
C51100 exhibits exceptional springback capability, making it the material of choice for contact terminals in automotive relays and high-density connectors. It possesses an electrical conductivity of approximately 20% IACS (International Annealed Copper Standard), which offers a balanced compromise between electrical transmission and high mechanical spring tension. Additionally, the alloy shows resistance to stress relaxation at elevated temperatures, ensuring that springs and connectors maintain constant contact pressure over years of continuous deployment.
The table below provides a comprehensive overview of the chemical composition thresholds and the key mechanical properties of C51100 phosphor bronze across different tempers. Understanding these properties allows design engineers to choose the correct temper for bending, stamping, and deep-drawing processes.
| Element / Property | Composition Limits (%) / Value | Reference Temper (O60 - Soft) | Reference Temper (H02 - Half Hard) | Reference Temper (H08 - Spring) |
|---|---|---|---|---|
| Copper (Cu) | Remainder (approx. 95.5%) | Matched | Matched | Matched |
| Tin (Sn) | 3.50% - 4.50% | 4.00% Nominal | 4.00% Nominal | 4.00% Nominal |
| Phosphorus (P) | 0.03% - 0.35% | 0.15% Nominal | 0.15% Nominal | 0.15% Nominal |
| Tensile Strength (MPa) | 310 - 680 MPa | 310 - 380 MPa | 410 - 495 MPa | 620 - 680 MPa |
| Yield Strength (0.2% offset, MPa) | 110 - 580 MPa | 130 MPa | 330 MPa | 560 MPa |
| Elongation in 50mm (%) | 4% - 45% | 45% | 20% | 4% |
| Electrical Conductivity (% IACS) | 20% IACS | 20% IACS | 20% IACS | 20% IACS |
*Note: The actual mechanical properties can be customized according to specific cold-rolling ratios, stress-relief annealing cycles, and strict dimensions requested by global OEMs.
At Sichuan Kepai, our state-of-the-art factory is fully equipped to handle specialized custom requests. Our core engineering workflow integrates modern smelting technologies and advanced testing protocols to guarantee consistent grain structure and defect-free alloy delivery.
Using vacuum-induction melting and continuous horizontal casting systems, we prevent oxygen entry and maintain precise control over tin segregation. By stabilizing elemental distribution at the molecular level, we achieve uniform properties across the entire length of the phosphor bronze rod or wire.
Achieving target mechanical tempers (such as H02, H04, or H08) requires precise cold reduction. Through multi-pass drawing and intermediate, atmosphere-controlled annealing, we regulate grain size distribution, preventing surface cracking and optimizing bend formability.
Our dedicated chemical composition laboratories, metallographic polishing stations, and microcomputer-controlled universal testing machines enable thorough evaluation. Every order undergoes non-destructive eddy-current conductance tests to verify physical specifications before packaging.
Navigating the complex landscape of raw metal procurement requires a reliable supply chain partner. Sourcing UNS C51100 from Sichuan Kepai New Materials provides distinct operational advantages for global enterprises:
Strategically located in the Western area of the Sichuan Guanghan Industrial Development Zone, adjacent to National Highway 108, our facility offers streamlined transportation links. This facilitates efficient movement of raw inputs and enables rapid container shipping to major domestic and international shipping ports.
Spanning over 9,000 square meters of production area, Sichuan Kepai controls the entire production cycle. By managing everything from primary melting and drawing to final quality inspection, we maintain direct control over quality and minimize reliance on external intermediaries, reducing lead times.
We ensure compliance with international environmental standards, including RoHS Directive 2011/65/EU and REACH Regulation (EC) No 1907/2006. Our products are shipped with detailed material test reports (MTRs) and mill test certifications to facilitate seamless customs clearance and regulatory compliance in North American, European, and Asian markets.
The rapid advancement of electric vehicles (EVs), 5G telecommunication networks, and industrial automation has generated strong demand for high-reliability copper alloys. The structural resilience and electrical characteristics of C51100 make it well-suited to meet these demands.
The high vibrational environments of automotive drivetrains require connector materials that resist stress relaxation. C51100 phosphor bronze maintains contact pressure over a wide temperature range, preventing connection degradation in EV battery packs and electronic control units.
Signal integrity in high-frequency 5G networks relies on precise tolerances in spring contacts. The clean microstructure and isotropic bending properties of our custom C51100 sheet and wire allow for high-volume stamping of micro-connectors without micro-cracking.
Our experience in manufacturing high-purity copper derivatives informs our production of C51100. This alloy serves as an ideal base for welding tips and wire guides that require thermal stability and wear resistance in high-temperature environments.
For wear-resistant sleeves, slide bearings, and stamped diaphragms, the low friction coefficient and high fatigue limit of C51100 ensure extended operating life for industrial machinery, minimizing maintenance downtime.
Sichuan Kepai New Materials Co., Ltd., established in 2017, is a high-tech enterprise integrating research and development, production, and sales. Currently, the factory covers an area of approximately 9,000 square meters, with an office space of about 1,000 square meters. The company primarily engages in the production of strategic emerging new materials for the national 13th Five-Year Plan, including special copper alloys such as tellurium copper, high-conductivity oxygen-free copper, silver copper, and dispersion copper, while also focusing on the research and development of high-conductivity, easy-to-machine, high-strength copper alloys. Our products are mainly applied in high-tech fields such as new energy vehicles, 5G technology, laser cutting, and lithium battery relays.
The company is located in the western area of the Sichuan Guanghan Industrial Development Zone, adjacent to National Highway 108, boasting a superior geographical location and convenient transportation, which lays a solid foundation for the rapid development of the enterprise. Since its establishment, Kepai has adhered to the business philosophy of "innovation-driven development, quality wins the market," committed to providing customers with the highest quality high-end copper alloy materials, and promoting industrial upgrading and sustainable development.
Technological innovation is the core competitiveness of Sichuan Kepai New Materials Co., Ltd. The company has a research and development and production team composed of senior industry experts who keep pace with international cutting-edge technology trends and continuously explore the unknown boundaries in the field of new copper alloy materials. Through a combination of independent research and development and industry-university-research collaboration, Kepai has made breakthrough progress in several areas, including high-performance tellurium copper, lead copper, and sulfur copper. Many of its technological achievements have reached international advanced levels and have been successfully applied in various industries such as new energy vehicles, precision machining parts, plasma cutting, relays, and energy storage, earning widespread recognition and praise in the market.
Kepai's product line is rich and diverse, covering a comprehensive range of solutions from basic materials to high-end customization. We focus on providing customers with high-performance, high-quality high-end copper alloy products, including but not limited to pure copper, oxygen-free copper, oxygen-free high-conductivity tellurium copper, nickel tellurium copper, tin bronze, beryllium copper, lead bronze, sulfur copper, and chromium zirconium copper. These products play an important role in reducing production costs and enhancing product performance due to their excellent physical and chemical properties and environmental friendliness, creating significant economic and social benefits for customers.
In the face of global market competition, Sichuan Kepai New Materials adheres to the development strategy of "rooted in Sichuan, radiating nationwide, and moving towards the world." By continuously optimizing market layout and improving the sales network, we have established a stable customer base in multiple provinces and cities across the country and have formed long-term cooperative relationships with several internationally renowned enterprises. At the same time, the company actively expands into overseas markets, participates in international competition and cooperation, and strives to promote Kepai's brand influence on the global stage.
We understand that the long-term development of an enterprise is inseparable from an excellent corporate culture. We advocate the corporate spirit of "integrity, innovation, collaboration, and win-win," encouraging employees to explore boldly and innovate courageously, while also emphasizing teamwork and talent cultivation, striving to create a harmonious, open, and inclusive work atmosphere. We believe that only by continuously pursuing excellence and creating value can we win the trust of customers and the respect of society.
Our facility features state-of-the-art production systems and analytical instruments to ensure that our custom C51100 phosphor bronze and other special copper alloys are produced to exact specifications.
Smelting
laying-off
extrusion
drawing
straightening
package
Conductance Instrument
Composition Test Room
Polishing Machine
Servo Testing Machine
Universal Tester
Hardness Tester
Sichuan Kepai operates in accordance with standard global quality management practices, ensuring compliance and reliability for industrial supply partnerships.
Browse answers to common questions about UNS C51100 chemistry, tempers, customization capabilities, and global procurement.
Looking ahead, Sichuan Kepai New Materials Co., Ltd. will continue to uphold its original intention, with even greater enthusiasm and determination, to engage in research and application in the field of new materials, contributing to the development of the new copper alloy materials industry in China and globally. We look forward to working hand in hand with partners from all walks of life to create a brilliant future together!
Kepai
