Black Steel Washers

In addition to the blackening process, Black Steel Washers can also use phosphate treatment to obtain a dark gray to black surface. The porous structure of the phosphate film has excellent oil storage capacity and can significantly reduce the friction coefficient during assembly. According to ISO 9717 regulations for phosphate conversion coatings, the surface density of the phosphate coating shall not be less than five grams per square meter, and the surface density of the phosphate conversion coating shall not be less than five grams per square meter. According to the 946 friction coefficient test, after coating with anti-rust oil, the friction coefficient of the bearing surface dropped from 0.16 to 0.10, a decrease of about 37%. When the tightening torque of the M12 bolt is 100 Nm, based on the friction coefficient and preload force conversion formula, the axial preload force can be calculated to be about 42,000 N, which is about 20% higher than the unoiled state. At the same time, the phosphating treatment temperature is low, which has minimal impact on the dimensional accuracy of the gasket. According to the ISO 4759-1 tolerance standard, the outer diameter deviation is still maintained within plus or minus 0.3 mm. It is suitable for use as a leveling gasket for hydraulic pipeline flanges and heavy equipment bases.

 

 

The anti-oxidation ability of black steel washers in high-temperature environments mainly depends on the stability of its surface oxide layer. When the operating temperature exceeds 300 degrees Celsius, the blackened film may decompose and appear dark red, but the mechanical properties of the matrix remain stable. According to the ASTM E8 high-temperature tensile test method, the yield strength of the gasket matrix drops to about 85% of the room temperature value at 350 degrees Celsius, which is about 190 MPa. At this time, according to the ASME PCC-1 evaluation method for high-temperature bolt connections, the creep rate in the thickness direction of the gasket is less than 0.001 mm per hour, which is enough to maintain the bolt pretightening force attenuation by no more than 5% after one hundred hours of continuous operation.

 

 

In vacuum or clean environments where lubricants cannot be used, black steel washers rely on their surface microporous structure to provide a certain degree of dry friction damping. According to the transverse vibration test according to DIN 267 Part 26, after 10,000 vibrations at a frequency of 20 Hz and an amplitude of 1 mm, the residual preload force retention rate is approximately 73% of the initial value, which is approximately 12% higher than ordinary uncoated steel washers with smooth surfaces. Therefore, it is suitable for connection nodes in internal combustion engine exhaust pipes and high-temperature steam pipelines that require moderate loosening and avoid lubricating oil contamination.

 

 

 

 

 

 

 

 

Obtain drawings from clients or produce drawings based on their samples or specifications.

The drawings, product raw materials, surface treatment, and other details are attested to by both parties.

 

 

 

 

Provide a quote, ensure that the order quantity is accurate, and include all relevant details,

such as the terms of payment, the terms of trade, the type of packaging, etc.

 

 

 

Follow the original drawings and samples exactly when producing the goods.

It was carefully packaged and delivered to the clients following a final inspection.

 

 

 

 

 

 

 

 

 

 

 

 

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