Products
High-strength blackened nuts
High-strength blackened nuts are nuts that form a black Fe₃O₄ oxide film on the surface of alloy steel through chemical oxidation (blackening treatment). The base material is usually 42CrMo or 65 manganese steel. After quenching + tempering treatment, the hardness can reach HRC35-45.
Description
marker
Product definition and core technology
High-strength blackened nuts are nuts that form a black Fe₃O₄ oxide film on the surface of alloy steel through chemical oxidation (blackening treatment). The base material is usually 42CrMo or 65 manganese steel. After quenching + tempering treatment, the hardness can reach HRC35-45.
Core materials and characteristics
Material:
42CrMo alloy steel (static high load): tensile strength ≥1000MPa;
65 manganese steel (elasticity requirement): hardness HRC40-45, suitable for spring nuts.
Features:
High temperature resistance: The oxide film is stable below 200℃, which is better than the galvanized layer;
No risk of hydrogen embrittlement: The chemical oxidation process avoids hydrogen embrittlement of electroplating, which is suitable for precision equipment;
Wear resistance: The oxide film hardness is HV300-400, which can resist slight friction.
Functions and applicable scenarios
Functions:
Withstand high-frequency vibration or impact loads to prevent bolts from loosening;
Maintain stable performance in high temperature environments (such as engine cylinder block connection).
Scenario:
Automobile engine (cylinder head bolts), mining machinery (crusher connection), wind power equipment (spindle flange).
Installation and maintenance
Installation:
When used with high-strength bolts, tighten strictly according to the torque coefficient (such as 0.11-0.15);
Clean the surface oil before installation to ensure that the oxide film is tightly bonded to the substrate.
Maintenance:
Check the integrity of the oxide film regularly, and the damaged parts need to be re-blackened;
Avoid long-term immersion in electrolyte to prevent the oxide film from being damaged.
Purchase suggestions
Select materials according to load: 42CrMo is suitable for static high load, 65 manganese steel is suitable for elastic requirements;
For high temperature scenarios (>300℃), ceramic coating or stainless steel nuts should be used instead.
Comparison and selection guide of the six major nuts
| Type | Electroplated galvanized flange nut | Electroplated galvanized nut | Colored zinc-plated nut | Anti-loosening nut | High-strength blackened nut | Welding nut |
| Core advantages | Dispersed pressure, anti-loosening | Low cost, strong versatility | High corrosion resistance, color identification | Anti-vibration, removable | High strength, high temperature resistance | Permanent connection, convenient |
| Salt spray test | 24-72 hours | 24-72 hours | 72-120 hours | 48 hours (nylon) | 48 hours without red rust | 48 hours (galvanized) |
| Applicable temperature | -20℃~80℃ | -20℃~80℃ | -20℃~100℃ | -56℃~170℃ (all metal) | -40℃~200℃ | -20℃~200℃ |
| Typical scenarios | Pipe flange, steel structure | General machinery, indoor environment | Outdoor equipment, humid environment | Engine, vibration equipment | High temperature machinery, vibration equipment | Automobile manufacturing, construction machinery |
| Installation method | Torque wrench tightening | Torque wrench tightening | Torque wrench tightening | Torque wrench tightening | Torque wrench tightening | Welding fixation |
| Environmental protection | Cyanide-free process complies with RoHS | Cyanide-free process complies with RoHS | Trivalent chromium is more environmentally friendly | Nylon complies with RoHS | No heavy metal pollution | No special requirements |
Selection suggestions:
High sealing requirements: electroplated zinc flange nut, with gasket to enhance sealing;
High corrosion environment: color-plated zinc nut, chromium-free passivation process is preferred;
Vibration environment: anti-loosening nut, all-metal type is suitable for high temperature scenes;
High temperature and high load: high-strength blackened nut, matched with 10.9 grade bolts;
Permanent connection: welding nut, projection welding or spot welding type is selected according to the process.
contact us
Related popular products
Colored zinc-plated gaskets
Colored zinc-plated gaskets are passivated on the basis of electrogalvanizing to form a rainbow-colored passivation film (containing trivalent chromium or hexavalent chromium) with a film thickness of about 0.5-1μm. Its anti-corrosion performance is significantly better than ordinary electrogalvanizing, and the surface color is bright, with both functionality and decorativeness.
Electrogalvanized cross countersunk drill thread
The head is a cross-groove countersunk design, which can be hidden in the installation surface to keep the surface flat. The drill bit diameter matches the thread diameter (such as ST4.2 drill bit diameter 4.2mm), which complies with GB/T 15856.1-2002 standard.
Hot-dip galvanized embedded plate
Same as electrogalvanized embedded plate, using Q235 or Q355 carbon steel, steel plate thickness 8-50mm, anchor bar diameter 10-32mm, in line with GB/T 700 standard.
Colored zinc plated hexagonal bolts
Hexagonal bolts are the most common standard bolts with hexagonal heads and are used with nuts (standard GB/T 5780). Common materials are Q235 or 35CrMo, with galvanized or blackened surfaces.
Welded plate anchor (welded plate anchor bolt)
The welded plate anchor consists of a threaded rod, a welded pad and a stiffening rib. The pad is fixed with bolts by welding to form an integrated structure of “bolt + pad”. The pad increases the contact area with the concrete, disperses the load and improves stability.
Hexagon socket hot-dip galvanized bolts
The hexagon socket bolt head has a hexagon socket hole and needs to be tightened with a hexagon socket wrench (standard GB/T 70.1). Common materials are 35CrMo or 42CrMo, and the surface treatment is divided into three types: electrogalvanized, color zinc-plated, and black zinc-plated.
Anti-loosening nut (locking nut)
Anti-loosening nut is a nut that prevents the nut from loosening through special design.
U-bolts
U-bolts are U-shaped with threads at both ends, and are used to fix cylindrical objects such as pipes and plates (standard JB/ZQ 4321). Common specifications are M6-M64, made of carbon steel or stainless steel, with galvanized or blackened surface.
Colored zinc-plated expansion hook
Rainbow chromate passivation (c2C) is performed on the basis of electrogalvanizing to form a colored passivation film with a thickness of about 8-15μm. The salt spray test can last for more than 72 hours without white rust.
Electrogalvanized chemical bolts
Chemical bolts fix the screw in a substrate such as concrete through a chemical anchoring agent, and are composed of a screw, a hose, and a washer (standard GB 50367). Common materials are galvanized steel or stainless steel, and the anchoring depth is ≥8d (d is the bolt diameter).
Colored zinc flange bolts
The head of the flange bolt has a round flange to increase the contact area and disperse the pressure (standard GB/T 5787, GB/T 5789). Common specifications M6-M30, material Q235 or 35CrMo, surface galvanized or blackened.
Hexagon socket colored zinc-plated bolts
The hexagon socket bolt head has a hexagon socket hole and needs to be tightened with a hexagon socket wrench (standard GB/T 70.1). Common materials are 35CrMo or 42CrMo, and the surface treatment is divided into three types: electrogalvanized, color zinc-plated, and black zinc-plated.
7-shaped anchors (7-shaped anchor bolts)
The 7-shaped anchor is named because one end of the bolt is bent in a “7” shape. It is one of the most basic types of anchor bolts. Its structure includes a threaded rod body and an L-shaped hook. The hook part is buried in the concrete foundation and connected to the equipment or steel structure through a nut to achieve a stable fixation.
Black zinc-plated hexagonal drill tail wire
Through the black passivation liquid treatment containing silver salt (c2D), a 10-15μm coating is formed, and the salt spray test is more than 96 hours. Environmentally friendly black zinc plating uses trivalent chromium passivation, does not contain hexavalent chromium, and complies with RoHS standards.
10.9S large hexagon bolts
10.9S large hexagon bolts are the core components of high-strength friction-type connections. They are composed of bolts, nuts, and double washers (standard GB/T 1228). The tensile strength reaches 1000MPa and the yield strength is 900MPa. Its surface treatment adopts Dacromet or multi-alloy co-penetration technology, and the salt spray test exceeds 1000 hours. It is suitable for extreme environments such as oceans and high temperatures.
Welding nails
Welding studs are cylindrical head welding studs fixed to the parent material by arc stud welding (standard GB/T 10433), made of SWRCH15A or ML15, with tensile strength ≥400MPa and yield strength ≥320MPa.
Please leave us a message
-
-
-
WeChat
