2026-08-27
High‑strength bolts serve as key fasteners connecting components within photovoltaic mounting systems. Their quality directly determines the safety and stability of the entire mounting structure. As an integrated manufacturer of photovoltaic mounting structures and fasteners, Zhongtang Group has established a comprehensive quality inspection system for high‑strength bolts. Strict controls are implemented across the full workflow from incoming raw materials to finished‑product delivery, ensuring every bolt complies with international standards.
Quality inspection for high‑strength bolts commences with raw‑material screening. The Grade 8.8, 10.9 and 12.9 high‑strength bolts sourced by Zhongtang Group adopt premium alloy steel. Upon material arrival, material certificates are verified, and each steel batch undergoes spectroscopic analysis and hardness testing to confirm compliance of chemical composition and mechanical properties. Non‑conforming raw materials are rejected outright to guarantee bolt quality at the source.
During production, Zhongtang Group exercises focused monitoring over critical processes for high‑strength bolts. Thread rolling technology is applied for thread machining to achieve 6‑g thread precision with smooth, defect‑free surfaces. Quenching temperature and tempering duration are precisely controlled in heat treatment to meet grade‑specific requirements for tensile strength, yield strength and impact toughness. Equipped with an automatic temperature‑control system, the Group’s heat‑treatment workshop keeps traceable temperature records for every production batch.
Prior to delivery, finished high‑strength bolts undergo a series of rigorous tests. First, torque‑coefficient testing is performed with professional testers to maintain torque‑coefficient values within 0.11‑0.15, enabling accurate pre‑tensioning torque during on‑site installation. Second, hardness testing is carried out: Grade 8.8 bolts register HRC 22‑32, Grade 10.9 bolts HRC 32‑39, and Grade 12.9 bolts HRC 39‑44. Third, tensile strength and proof‑load tests are completed via universal material testing machines to validate mechanical performance. Fourth, anti‑corrosion surface inspection is conducted. For photovoltaic mounting bolts finished with Dacromet or hot‑dip galvanizing, salt‑spray testing and zinc‑coating thickness gauges are used to assess coating quality.
Furthermore, Zhongtang Group can provide third‑party test reports upon client request, covering international certifications including SGS, CE and GOST. Our high‑strength bolts are widely deployed in domestic and global photovoltaic mounting projects, earning customer recognition for consistent quality and reliable performance. Zhongtang Group commits that all dispatched high‑strength bolts pass 100 % visual inspection plus batch‑sampled mechanical‑property testing. Non‑conforming goods are prevented from reaching the market, delivering solid assurance for the structural safety of photovoltaic mounting systems.
