Hebei Kappa Metal Products Co., Ltd. is one of the most reliable manufacturers and suppliers of h.t grade black 8.8 bolt only metric cource din931 in China. Welcome to buy bulk high quality h.t grade black 8.8 bolt only metric cource din931 made in China here from our factory. If you have any enquiry about cooperation, please feel free to email us.
Key Parameters
| Standard | German standard DIN931 (for some threads) |
| Grade | 8.8 grade (High Tensile Strength) |
| Product specifications | Metric M6-M36 (customizable) |
| Surface treatment/Finish | Black oxide |
Material and Strength
This product is made from high-quality medium-carbon steel or alloy steel (e.g., 40Cr, 35K). Through quenching and high-temperature tempering (also known as quench-and-temper treatment), it achieves a property class of 8.8, denoting high strength.
It has a nominal tensile strength of 800 MPa and a yield strength ratio of up to 0.8. Combining excellent tensile performance with outstanding fatigue resistance, it is well-suited for fastening applications in heavy-duty equipment and structural components.
Structural features
This product strictly complies with the DIN 931 standard and features a partial thread (semi-thread) design.
The unthreaded shank portion effectively reduces stress concentration and significantly enhances the bolt's shear load capacity.
This makes it particularly suitable for connection applications that demand high positioning accuracy and shear strength.
Surface treatment
A blackening treatment (black oxide coating) is applied to the surface, producing a compact black oxide layer.
This layer serves as a barrier against rust and corrosion. In addition, it imparts a consistent matte black appearance that combines moderate corrosion resistance with a distinctive industrial look.
All units are treated with a rust-inhibiting oil before shipment to ensure extended storage stability.
Application scenario
It is widely applied in heavy machinery, engineering vehicles, construction steel structures, bridge equipment, mining machinery and high-load transmission systems, etc., in extremely demanding working conditions.
As a high-strength fastener, this product is a key component for steel structure connections and equipment assembly, ensuring the long-term stable operation of equipment under vibration and impact conditions.
Packaging and Service
The product is packaged with anti-rust material. Customization is supported for non-standard orders.
We provide matching high-strength washers and nuts to ensure the strength of the connection pair is compatible and meets the requirements of bulk purchasing.
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