CM690 76mm Stud Link Anchor Chain

Introduction – A Real Order from Canada 

The manufacturing processes for stud link anchor chains and open link chains are similar, the main difference being the stud insertion and welding step. 

This article walks through the actual production process of a real order: 

- Grade: CM690

- Diameter: 76 mm

- Length: 27.5 meters

- Type: Stud link anchor chain

- Classification Society: ABS (American Bureau of Shipping)

- Destination: Canada 

This 76 mm stud link anchor chain is made of high-quality CM690 grade steel, specifically designed for offshore operations and ABS-certified vessel applications. The raw materials used are 76 mm CM690 grade steel with ABS certification. 

Step 1. Material Cutting

Based on the required quantity (200 links for this order), the process department calculates the cutting length and quantity of raw material according to the anchor chain dimensions (6D x 3.6D). 

Step 2. Heating and Bending 

The steel bar is induction heated to approximately 950°C – 1050°C and then automatically bent into a "C" shape. A 76 mm link requires high-capacity bending equipment to ensure dimensional accuracy. In our factory, 76 mm stud link anchor chains are produced on Production Line No. 7, and this diameter requires professional calibration before production begins. 

Step 3. Flash Welding 

The bent links are flash welded under controlled current and pressure, then deburred. 

For CM690 grade steel, welding parameters are critical. They must achieve the required tensile strength while avoiding weak points in the weld area. Welds must be uniform, and welding time cannot be too short. The entire process requires careful control. 

SMEOCEAN uses fully automated data monitoring, ensuring precise timing down to the second. 

Step 4. Stud Insertion and Welding 

A key step in stud link anchor chain manufacturing is stud insertion. Installation, extrusion, and welding – all three stages require a single weld point. 

The stud prevents the chain from kinking and increases lateral stability, which is especially important for 76 mm large-diameter chains used in deep-water mooring. 

Step 5. Heat Treatment (Quenching and Tempering) 

The finished links undergo quenching and tempering heat treatment to achieve the mechanical properties required for CM690 grade. The heating temperature, holding time, and quenching medium concentration are the key parameters controlling the heat treatment result. 

The performance requirements are as follows: 

- Yield Strength: ≥ 690 MPa

- Tensile Strength: 800 – 960 MPa

- Elongation:** ≥ 12% 

This process ensures uniform hardness and eliminates residual welding stress. 

Step 6. Shot Blasting (Surface Preparation) 

To remove impurities from the welding process and heat-treated surfaces, shot blasting is carried out using specialized equipment. After shot blasting, the anchor chain has a clean, smooth surface. 

Step 7. Proof Load Test – ABS Inspector Required 

Each 76 mm link chain requires a proof load test at **2.5 times the Working Load Limit (WLL). 

For CM690 grade chains, the minimum breaking load for a 76 mm diameter chain typically exceeds 12,000 kN. 

For ABS orders, the following steps must be completed in advance: 

1. Schedule an appointment with an ABS inspector

2. Clarify all inspection items with ABS

3. Lay the chain flat on the ground before the inspector arrives 

For this Canadian order, the ABS inspector witnessed the proof load test on-site and signed off on each test report. This batch of chains then received its identification, stamped with a steel seal, allowing for full online traceability. 

For orders without special requirements, we provide factory certificates, but each batch must undergo mechanical performance testing before leaving the factory. 

Step 8. Surface Protection – Galvanizing / Coating / Natural Finish 

Finished chains are available with three surface treatment options: 

- Hot-dip galvanizing: Provides optimal corrosion resistance in seawater environments

- Black paint coating: For deep-water mooring, providing additional protection

- Natural finish (no coating): Suitable for customers who wish to inspect the true surface quality of the steel 

For this Canadian order, the customer requested a black paint coating. SMEOCEAN uses a highly environmentally friendly water-based paint. 

Conclusion：

For CM690 76 mm stud link anchor chains, or other sizes and diameters of anchor chains, please contact us.

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