High Strength 12.9 Grade Black Oxide Allen Head Socket Cap Screws - China Supplier & Factory

Manufacturing Process
Quality Control System
Flexible Customization
Technical Service
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.
Application Scenarios





High-Quality 12.9 Grade Socket Cap Screw Display
Frequently Asked Questions
Grade 12.9 is one of the highest strengths available for bolts, providing a tensile strength of 1200MPa. It is ideal for heavy-duty applications where safety and high clamping force are critical, such as in automotive engines and industrial machinery.
Yes, black oxide provides a layer of protection against mild corrosive environments and humidity. It is best suited for indoor use or applications where the part is protected by oil or grease. Its main advantage is providing protection without the risk of hydrogen embrittlement.
Absolutely. We offer flexible customization for head shapes, slot types, extra-long specifications, and various surface treatments to meet your unique engineering requirements.
We implement a full traceability system using furnace numbers, source-locked raw materials, and micron-level thread rolling processes. Every batch undergoes optical sorting and mechanical testing in our joint laboratory.
We provide comprehensive technical services including selection calculations, BOM optimization, on-site failure analysis, and guidance on installation tool selection to ensure the best performance for your assembly.
Yes, we provide free sample making and testing services to ensure our high-strength fasteners meet your specific application standards before proceeding with full production.
















