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High-strength blackened gasket
High-strength blackened gasket is a gasket that forms a black Fe₃O₄ oxide film on the surface of alloy steel through chemical oxidation (blackening treatment), with a film thickness of about 0.5-1.5μm. Its base material is usually 65 manganese steel or 42CrMo alloy steel, and after quenching + tempering treatment, the hardness can reach HRC35-45.
Description
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Product definition and core process
High-strength blackened gasket is a gasket that forms a black Fe₃O₄ oxide film on the surface of alloy steel through chemical oxidation (blackening treatment), with a film thickness of about 0.5-1.5μm. Its base material is usually 65 manganese steel or 42CrMo alloy steel, and after quenching + tempering treatment, the hardness can reach HRC35-45.
Core material and characteristics
Material:
65 manganese steel (good elasticity, used for spring gaskets);
42CrMo alloy steel (high strength, used for flat gaskets).
Features:
High mechanical properties: tensile strength ≥1000MPa, suitable for high load scenarios;
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 electroplating hydrogen embrittlement, suitable for precision equipment.
Function and applicable scenarios
Function:
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:
Regularly check the integrity of the oxide film, 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: 65 manganese steel is suitable for elastic requirements, 42CrMo is suitable for static high loads;
In high-temperature scenarios (>300℃), ceramic coatings or stainless steel gaskets need to be used instead.
Comparison and selection guide of three major gaskets
| Type | Electroplated galvanized gasket | Colored galvanized gasket | High-strength blackened gasket |
| Core advantages | Low cost, strong versatility | High corrosion resistance, color identification | High strength, high temperature resistance |
| Salt spray test | 24-72 hours without white rust | 72-120 hours without white rust | 48 hours without red rust |
| Applicable temperature | -20℃~80℃ | -20℃~100℃ | -40℃~200℃ |
| Typical scenarios | Ordinary machinery, indoor environment | Outdoor equipment, humid environment | Engine, vibration equipment |
| Environmental protection | Cyanide-free process complies with RoHS | Hexavalent chromium must comply with REACH, trivalent chromium is more environmentally friendly | No heavy metal pollution |
Selection suggestions:
Economic needs: Electroplated galvanized gaskets, suitable for ordinary industrial scenarios;
High corrosion environment: Colored galvanized gaskets, give priority to chromium-free passivation process;
High load/high temperature scenario: High-strength blackened gaskets, matching bolt strength grade (such as 42CrMo for 10.9 grade bolts gasket).
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