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Views: 0 Author: Site Editor Publish Time: 2026-11-07 Origin: Site
In substations, subway tunnels, high-speed railway catenary systems, and trackside enclosures, grounding and equipotential bonding serve as an invisible safety lifeline. Investigations into many engineering failures reveal that the root cause often lies not in the main cables or copper busbars, but in a seemingly insignificant connecting bolt—whether due to corrosion, rising contact resistance, loosening from vibration, or galvanic corrosion between dissimilar metals—ultimately leading to overheating, arcing, and the failure of the grounding system. While the industry traditionally relied on galvanized carbon steel or standard stainless steel bolts—treating them merely as "fasteners"—high-end power and rail transit projects now classify them as **integral components of the conductive path**. In this context, silicon bronze fasteners have emerged as the preferred solution.
The core challenges in grounding and equipotential bonding—ensuring a stable conductive path, long-term corrosion resistance, and sustained contact pressure—are requirements that ordinary steel cannot simultaneously satisfy.
First, a grounding connection is not merely a mechanical fixture; it serves as a vital conduit for electrical current. Lightning strikes, fault-induced short circuits, and stray induced currents must be rapidly dissipated through these connection points. Carbon steel and stainless steel possess relatively low electrical conductivity. Once their interfaces oxidize, contact resistance rises steadily; under high-current conditions, this leads to localized overheating—creating "hot spots" that pose risks of arcing or fire. In contrast, copper-based alloys offer inherently stable conductivity. Their surface oxide films are far more conductive than those of iron-based materials, resulting in minimal resistance drift over long periods of operation.
Second, environments such as rail transit systems and outdoor power substations are exceptionally demanding. Factors like high humidity and condensation in tunnels, coastal salt spray, acid rain, trackside dust, and stray currents in metro systems frequently trigger galvanic corrosion. When copper busbars or terminals are fastened with steel bolts, the significant potential difference between the two metals accelerates electrochemical corrosion in humid conditions. This can cause bolts to seize due to rust and contact surfaces to degrade into powder, effectively rendering the grounding path useless after only a few years. Silicon bronze, however, shares a similar electrical potential with copper busbars and terminals, which **suppresses galvanic corrosion**. This ensures that the entire connection system ages uniformly, avoiding the "weak link" scenario where bolts fail prematurely while the copper components remain intact.
Third, rail transit infrastructure is subject to constant vibration and the cyclical effects of thermal expansion and contraction. Standard brass lacks sufficient strength and is prone to creep, while pure copper is too soft, leading to a loss of preload. Stainless steel threads, meanwhile, are susceptible to galling or seizing, which complicates maintenance and disassembly. Silicon bronze utilizes solid-solution strengthening—achieved through the addition of silicon—to enhance mechanical strength and resistance to stress relaxation, all while maintaining excellent conductivity. Furthermore, it is less prone to thread galling. Consequently, it can sustain the necessary preload over long periods, even under conditions of continuous vibration and fluctuating temperatures, thereby ensuring the long-term reliability of the conductive interface. In short: Carbon steel bolts serve as "fasteners," whereas silicon bronze bolts function as **conductive connecting components**—they are part of the grounding circuit and determine the full-lifecycle reliability of the entire grounding system.
1. Catenary system grounding for metros/high-speed railways: support structure grounding, grounding of embedded channels in tunnels, return conductors, equipotential bonding, and connection bolts for copper grounding busbars.
2. Rolling stock grounding: equipotential bonding of the vehicle body, axle-end grounding devices, bogie grounding terminals, and grounding connections for onboard high-voltage cabinets.
3. Trackside equipment: signaling enclosures, communication cabinets, trackside grounding for traction substations, bonding of cable trays, and connection points for stray current protection.
1. Substation grounding grids: copper bars, grounding busbars, grounding down-conductors, and bolts for connecting grounding electrodes;
2. Switchgear, ring main units (RMUs), and box-type substations: equipotential bonding for enclosures, securing of copper grounding bars, and grounding terminals for high-voltage equipment;
3. Outdoor wind and photovoltaic (PV) power plants, and energy storage containers: outdoor grounding connections (preferred for use in coastal or highly corrosive environments);
4. Conductive connections for cable terminations, copper grounding lugs, and grounding busbars.
We primarily offer two mainstream grades, tailored to meet various engineering and technical specifications. All items can be supplied as complete assemblies—including nuts, flat washers, and spring washers—and we support production according to Chinese national standards (GB), American standards (ASTM), or custom specifications based on your technical drawings.
Positioning: A grade prioritized for grounding and electrical conductivity. Offering superior conductivity, it is suitable for the vast majority of grounding, equipotential bonding, and copper busbar connection applications. It is the most frequently specified grade for grounding projects in metro systems and substations, striking an optimal balance between corrosion resistance, electrical conductivity, and moderate mechanical strength. It remains stable even in salt-spray conditions or the humid environments found in tunnels.
Application: High mechanical load conditions. Featuring higher silicon and manganese content, this material offers superior tensile strength, enhanced vibration resistance, and greater creep resistance. It is well-suited for use in bogies, axle-end grounding components, and heavy-duty, high-vibration locations. While its electrical conductivity is slightly lower than that of C65100, it is prioritized for its ability to maintain preload even under vibration.
Associated products include silicon bronze hex bolts, flange bolts, double-end studs, fully threaded rods, matching hex nuts, flat washers, and lock washers. Available in sizes ranging from M6 to M30, with full support for UNC/UNF imperial standards. We also offer custom-manufactured stepped bolts and specialized grounding studs based on your technical drawings.
Our manufacturing process utilizes cold heading followed by precision thread rolling, which eliminates the porosity defects often found in cast components. The threads offer consistent precision and are resistant to galling (seizing) during assembly or disassembly. To ensure optimal electrical conductivity, no harmful coatings are applied to the contact surfaces. We provide comprehensive documentation—including material certificates, salt spray test reports, and spectral analysis reports—to meet the stringent requirements for rail transit (TB/T standards) and power engineering project acceptance.
Specializing in copper alloy fasteners for specialized applications—with deep expertise in grounding and electrical conductivity—we are far more than a typical, general-purpose screw manufacturer.
The silicon bronze market is rife with irregularities, including the mislabeling of brass as silicon bronze, the use of low-purity recycled scrap, and the mixing of different alloy grades. We source our raw materials exclusively from major, established manufacturers; every batch comes with a material certification, and we welcome spectral analysis verification of the supplied stock. Furthermore, we maintain separate production lines for C65100 and C65500 to prevent cross-contamination—ensuring from the very source that our products meet conductivity standards and are not prone to premature failure due to corrosion.
We maintain a ready stock of standard-specification components to meet urgent repair and replenishment needs. For specialized trackside requirements—such as custom-shaped grounding studs, extended double-ended studs, stepped components, or small-batch test samples—we offer solutions combining cold heading with precision machining. We also collaborate with design institutes and general contractors to produce prototypes and provide samples for type testing.
Given the multi-year duration of the project, we maintain a stable supply of materials. This ensures there are no mid-project stockouts or last-minute material substitutions, thereby avoiding the need to re-validate the grounding circuit design due to a change in fastener material.
The original 304 stainless steel grounding bolts had been in service for three years. Due to the high-humidity, salt-spray-laden tunnel environment, galvanic corrosion occurred between the copper busbars and the stainless steel bolts. This resulted in excessive contact resistance at multiple connection points, while the bolts themselves became so severely rusted that they could not be removed. These were replaced with C65100 silicon bronze bolt assemblies. Follow-up measurements at the same locations showed stable contact resistance, and the components exhibited no significant corrosion after 1,000 hours of continuous salt-spray testing. A five-year post-installation review revealed no abnormal grounding resistance alarms, and the threaded components remained free from seizing during maintenance and disassembly.
In this outdoor environment, characterized by significant diurnal temperature fluctuations and frequent thunderstorms, the original hot-dip galvanized bolts used at the connection points of the copper grounding busbars began to exhibit coating delamination and localized heating after just two years. By replacing these with a complete set of C65100 silicon bronze bolts, nuts, and washers, the issue of galvanic (dissimilar metal) corrosion was eliminated. Subsequent testing confirmed stable performance during lightning discharge events, and the requirement for routine maintenance inspections has been reduced.
A: While pure copper offers the best electrical conductivity, it has relatively low mechanical strength and is prone to creep. Under conditions of vibration or thermal cycling, the preload—the force holding the connection tight—drops rapidly; once the contact surfaces loosen, the contact resistance spikes. Silicon bronze provides an optimal balance of electrical conductivity, mechanical strength, and corrosion resistance. For grounding connections, the priority is to ensure long-term, stable contact pressure, rather than simply pursuing the highest possible electrical conductivity.
A: Compared to stainless steel, silicon bronze exhibits superior thread-engagement characteristics and is less susceptible to galling or seizing. However, for applications involving high torque and repeated assembly/disassembly, we provide recommended torque specifications; we advise against tightening beyond these limits.
A: The cost of a grounding failure far outweighs the expense of the fasteners themselves. Many steel bolts require bulk replacement every 3–5 years, necessitating power outages for maintenance. In contrast, a properly installed silicon bronze grounding connection can provide stable operation for over a decade. By reducing the total costs associated with power interruptions, troubleshooting, and subsequent retrofitting, it serves as a one-time investment that provides a vital safety margin.
A: Generally, we do not recommend plating on primary conductive contact surfaces, as it introduces additional contact resistance. If a project has specific anti-corrosion requirements, we will evaluate potential plating options, distinguishing between the treatment for conductive contact surfaces and non-conductive areas.
A: Direct contact between aluminum and silicon bronze is not recommended, as there remains a risk of galvanic corrosion. In applications involving aluminum terminals, transitional shims or sealing/isolation measures are required. We proactively highlight these risks to prevent potential issues with the design.
In the grounding systems used for power and rail transit, safety redundancy resides within every connection interface. While many projects focus heavily on cables and copper busbars, they often overlook the fact that a single bolt can determine the lifespan of the entire grounding circuit. Silicon bronze bolts effectively transform a standard "fastener" into a specialized **conductive connection component**, addressing three persistent challenges: corrosion, vibration, and electrical resistance drift.
