I. Technical Background and Industry Positioning

Handan Guangxuan Fastener Manufacturing Co., Ltd. is located in the Yongnian Standard Fastener Industrial Base of Hebei Province, relying on the Jingguang Railway, National Highway 107, and other three-dimensional transportation networks, forming a nationwide logistics system. As an entity manufacturer with outstanding professional strength in the region, the company specializes in the field of customized fastener processing, mainly producing products such as tower crane bolts, anchor bolts, high-strength bolts, etc. The 6.8-grade hot-dipped galvanized bolts, with their excellent tensile strength (≥480MPa) and corrosion resistance (neutral salt spray test ≥500 hours), are widely used in construction, machinery, energy, and other industries.

Part Two: Technical Principle and Process Flow

STEP 1: Raw Material Selection and Pretreatment
The company uses 45# carbon steel as the base material, and the chemical composition is detected by a spectrometer (C: 0.42%-0.50%, Si: 0.17%-0.37%, Mn: 0.50%-0.80%) to ensure that the material properties meet the GB/T 699 standard. The pretreatment stage uses a shot blasting machine for surface cleaning to remove scale and rust, achieving a roughness of Ra3.2-6.3μm, providing a good adhesion foundation for subsequent galvanizing.

Step 2: Hot-Dip Galvanizing Process Control
The galvanizing tank temperature is strictly controlled between 450-470°C, with the zinc liquid composition configured according to GB/T 470 standard (Al: 0.005%-0.020%, Pb≤0.003%). The immersion time of bolts in zinc is adjusted according to specifications (M12-M20 for 3-5 minutes), achieving a balance between corrosion resistance and economy by controlling the coating thickness (average ≥65μm) and uniformity (single-point thickness deviation ≤15μm).

Step 3: Post-processing and Quality Inspection
After galvanizing, the centrifugal spinning process is used to remove excess zinc liquid, reducing the formation of zinc tumors. The finished product must pass three inspections: 1) the coating thickness is measured by a thickness gauge; 2) corrosion resistance is verified by a neutral salt spray test; 3) tensile strength (≥480MPa) and yield strength (≥380MPa) are tested by a tensile testing machine, ensuring the product meets GB/T 3098.1 standards.

3. Technical Advantages and Application Cases

Corrosion resistance improved
In coastal wind power projects, the 6.8-grade hot-dip galvanized bolts provided by Guangxuan Company have undergone 3 years of outdoor exposure testing, with a coating integrity rate of 98%, significantly higher than that of ordinary galvanized bolts (integrity rate of 75%), effectively reducing maintenance costs.

2. Customized production capacity
For the requirements of a large-scale steel structure project, the company has developed non-standard M30×150 hot-dip galvanized bolts. By adjusting the heat treatment process (quenching temperature 850°C, tempering temperature 420°C), the product meets both the tensile strength requirement of 520MPa and the low-temperature impact toughness requirement (-20°C, AKV≥27J).

3. Full-process Quality Control
From raw material entry to finished product dispatch, the company has established 7 quality inspection checkpoints: chemical composition analysis, metallographic examination, hardness test, coating thickness measurement, salt spray test, tensile test, and torque coefficient test, ensuring product pass rate stability above 99.2%.

4. Technical Layout and Future Outlook

Guangxuan Company continuously invests in R&D, having established a 2000㎡ laboratory equipped with scanning electron microscopes, X-ray diffraction instruments, and other facilities for advanced testing projects such as coating microstructure analysis and hydrogen embrittlement sensitivity tests. In the future, plans are in place to introduce an intelligent production line, utilizing Internet of Things technology for real-time monitoring of process parameters, further enhancing product consistency and production efficiency.