Heavy Duty Steel Screws

The material selection for Heavy Duty Steel Screws usually gives priority to chromium-molybdenum alloy steel such as 42CrMo4. After quenching and tempering treatment, a uniform tempered sorbite structure is obtained, taking into account high strength and sufficient toughness. According to the provisions of ISO 898-1 for grade 10.9 fasteners, the hardness range should be HRC 32 to 39. In actual production, the hardness is often controlled at HRC 36 plus or minus 1. The corresponding tensile strength guarantee value at this hardness exceeds one thousand megapascals. At the same time, according to ASTM In the E23 Charpy impact test, the impact absorbed energy can still reach more than 35 joules at minus 40 degrees Celsius, indicating that the material has excellent low-temperature resistance to brittle fracture and is especially suitable for wind power foundations in cold zones or bolt connections on polar drilling platforms. The root of the thread has been smoothly rolled. According to the stress concentration factor calculation of VDI 2230, the effective stress concentration factor can be reduced from 2.5 to 1.6 for ordinary cutting threads, thus extending the fatigue life by about 50% under the same alternating load, ensuring the safety of long-term service.

 

 

In an environment where corrosion and lubrication work together, surface coating selection and control of installation parameters for heavy-duty steel screws are critical. The thickness of the commonly used zinc-nickel alloy coating is eight to twelve microns. According to the ASTM B117 salt spray test, it can withstand 1,200 hours without red rust, which is better than the 700 hours of hot-dip galvanizing. At the same time, the surface is covered with a sealing layer containing solid lubricant, according to DIN According to the 946 friction coefficient measurement, the total friction coefficient is stable between 0.1 and 0.14, which is significantly lower than the 0.18 to 0.25 of ordinary phosphating treatment, which reduces the pretightening force deviation under the same tightening torque from plus or minus 15% to 7%, improving the connection consistency. According to NASM 1312-7, the lateral vibration test was conducted. Under the conditions of frequency of 30 Hz and amplitude of 2 mm, the residual preload force after 20,000 vibrations still maintained 88% of the initial value, while conventional galvanized screws only had 70% remaining. Therefore, this screw is widely used in key parts such as railway track fasteners and heavy truck chassis that are subject to the alternating effects of continuous impact and corrosion, effectively reducing the frequency of maintenance.

 

 

 

 

 

 

 

 

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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