High Strength 12.9 Grade Black Oxide Allen Head Socket Cap Screws from China Suppliers & Factory

Black Oxide for Rust & Corrosion Resistance
Made of SCM435/40Cr alloy steel with black oxide finishing, the surface forms a magnetic iron oxide film that effectively blocks humid air and mild corrosive media. Although not as salt-spray resistant as stainless steel, it prevents red rust in dry indoor environments, mechanical assembly, and engine compartments. The oxide layer also increases surface hardness and reduces fretting wear, with no hydrogen embrittlement risk – ideal for high-strength fastening.
Ultra-High Strength Metal for Anti-Loosening
Grade 12.9 offers tensile strength ≥1200MPa and yield strength ≥1080MPa, far exceeding stainless steel or Grade 8.8 bolts. When tightened, the hex socket drive transmits high torque, creating enormous clamping force and significantly increasing thread friction. Even under severe vibration, impact, or cyclic loads (e.g., construction machinery, racing chassis), the bolt remains secure. Metal material never ages, ensuring lasting locking performance.
Long Service Life with High Wear Resistance
The black oxide layer provides self-lubricating properties, reducing thread friction and minimizing galling or cold welding during assembly. The cylindrical head and fine knurling enable hand-tightening without tool slippage or surface damage. Proven in fatigue tests, the head-to-shank fillet and thread root withstand millions of cycles without cracking. Compared to common zinc-plated bolts, this product offers superior wear resistance, longer replacement intervals, and lower maintenance costs.
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