Part 1: Technical Background and Industry Status

8.8 Grade Carbon Steel External Hex Nuts, as key components in the field of mechanical connections, are widely used in industries such as construction, bridges, and automotive manufacturing. Their performance requirements are stringent, necessitating high strength, corrosion resistance, and fatigue resistance. Handan Guangxuan Fastener Manufacturing Co., Ltd., with over 20 years of industry experience, leveraging the regional advantages of the Hebei Yongnian Standard Fastener Industrial Base, has established a full-process standardized quality management system from raw material procurement to finished product delivery, becoming a benchmark enterprise in the domestic 8.8 grade nut processing field.

II. Technical Principle and Core Parameters

8.8 grade nuts strength grade is according to ISO 898-1 standard, with tensile strength reaching above 800MPa and yield strength not less than 640MPa. Guangxuan Company uses 45# carbon steel as raw material and achieves performance standards through the following process control:

1. Heat treatment processQuenching and tempering process using a continuous belt furnace, quenching temperature 850±10°C, holding time 45 minutes; tempering temperature 450±10°C, holding time 2 hours, ensuring hardness reaches HRC28-32.

2. Thread formingUsing high-speed rolling thread machines for cold heading forming, the thread accuracy meets the GB/T 197-2018 6g grade requirements, with a tooth angle of 60°±15', and a pitch deviation of ±0.05mm.

3. Surface TreatmentWe offer various anti-corrosion solutions such as Dacromet, electroplated zinc, and hot-dip galvanized zinc, with a Dacromet coating thickness of 8-12μm and resistance to salt spray test ≥500 hours.

3. Processing Process and Quality Control

Guangxuan Company establishes a four-stage quality control system:

1. Raw material inspectionChemical composition analysis (C: 0.42-0.50%, Mn: 0.60-0.90%) and mechanical property testing are conducted for each batch of incoming carbon steel.

2. Process MonitoringOnline detection equipment is set up in critical processes such as heat treatment and thread rolling, with real-time monitoring of parameters like temperature and hardness, controlling deviations within ±2%.

3. Finished Product InspectionThe destructive sampling is conducted using a universal material testing machine, with a sampling ratio of not less than 5% per batch to ensure tensile strength ≥830MPa.

4. Packaging ProtectionTriple packaging with moisture-proof paper, plastic bag, and cardboard box, with each item weighing no more than 15kg to prevent damage during transportation.

4. Typical Application Cases

In the tower connection of a large-scale wind power project, Guangxuan Company customizes M36×150mm 8.8-grade nuts for the customer, meeting stringent working conditions through the following technical optimizations:

Material upgrade: Replace 45# steel with 40Cr alloy steel, tensile strength improved to 980MPa.

2. Structural Improvement: Increased the hexagon side dimensions from 55mm to 60mm, enhancing the torque-bearing capacity for installation.

3. Corrosion Strengthening: Triple layer of Dacromet coating (total thickness 15μm), passed 2000-hour salt spray test.

The project has been running for 3 years, and there has been no loosening or corrosion in the nut connection, which has been highly recognized by the customers.

V. Technical Advantages and Industry Prospects

Guangxuan Company's 8.8-grade nut processing technology boasts three core advantages:

1. Flexible production capacityEquipped with 50-200 ton multi-station cold heading machines, it can cover the full specification from M6 to M64, with a minimum order quantity of 500 pieces.

2. Efficient delivery systemRelying on the logistics advantages of the Yongnian Industrial Base, regular orders are shipped within 3 days, and urgent orders are responded to within 24 hours.

3. Cost Optimization PlanMaterial utilization rate improved to 92% through process optimization, 5 percentage points higher than the industry average.

With the rapid development of new energy and rail transit industries, the demand for high-tensile nuts is continuously increasing. Guangxuan Company is stepping up its R&D investment, aiming to achieve mass production of 10.9-grade nuts before 2025, further reinforcing its leading position in technology.