Black Oxide High Strength Hexagon Structural Bolts

Black Oxide High Strength Hexagon Structural Bolts are heavy-duty connection fasteners tailored for high-load steel construction joints. Medium carbon alloy steel serves as the base raw material of the structural bolts, processed via complete quenching and tempering heat treatment to achieve uniform internal metal grain structure. The finished structural bolts deliver a minimum tensile strength of 1040MPa, which satisfies the long-term bearing load demand of large-span steel frame buildings, industrial factory frameworks, highway bridge main supports and heavy mechanical installation bases. The black oxide finish creates a thin, dense oxidation film covering the entire bolt surface. This protective layer blocks minor moisture erosion and reduces surface friction abrasion when structural bolts are assembled and fastened repeatedly outdoors. The thread of each structural bolt adopts precise rolling forming technology to guarantee consistent thread pitch, smooth assembly and reliable anti-loosening performance under dynamic vibration load. Ningbo Gangtong Zheli Fastener Co., Ltd adopts standardized production flow for all manufacturing steps of the structural bolts.

Production Strength & Quality Control

Every batch of metal raw material for structural fastener production undergoes third-party chemical composition analysis to eliminate unqualified alloy raw materials in advance. After forging and heat treatment, semi-finished structural bolts will go through three core mechanical tests including tensile resistance, yield strength and surface hardness detection. Black Oxide High Strength Hexagon Structural Bolts follow a strict three-stage inspection system: random sampling inspection of semi-finished bolts, full dimensional measurement of finished bolts and secondary mechanical performance verification of finished bolts. The annual factory pass rate of the structural bolts steadily stays above 99.6%, avoiding dimensional deviation or strength defects during mass production. The universal material testing machine can pull test finished structural bolts until fracture to record real tensile limit data, while hardness testers check surface hardness to confirm effective heat treatment effect. Thread gauges match each specification structural bolt to eliminate unqualified threads that cannot fit standard nuts. Mass stock of regular-size structural bolts is stored to meet large-volume purchase needs from global construction buyers.

Application & Global Supply Advantage

The heavy-duty structural fastener series fits multiple heavy-load connection scenarios including industrial steel frames, highway bridge bearing supports, heavy mechanical equipment racks and new energy photovoltaic steel brackets. Different working environments put forward diverse customized demands for structural bolts.Black Oxide High Strength Hexagon Structural Bolts support personalized modification on bolt effective length, thread pitch, surface anti-rust thickness and assembly matching accessories according to clients’ engineering construction drawings. For coastal high-humidity projects, extra thickened black oxide anti-rust layers can be added on structural bolt surfaces to extend service life in corrosive atmosphere. All batches of structural bolts come with full official mechanical inspection documents covering tensile, yield and hardness indexes. These standardized test records fully comply with international construction acceptance norms and help overseas clients finish local engineering inspection procedures without obstacles. Ningbo Gangtong Zheli Fastener Co., Ltd provides complete formal technical supporting documents for every order of structural bolts.