In the world of overhead lifting, there is no room for error. A suspended load is not just material; it is a potential hazard. This is why the quality of a lifting chain—whether Grade 80 (G80) or the higher-tensile Grade 100 (G100)—can never be overstated. For engineers and rigging professionals, a chain is a safety device, and its manufacturing process must be held to the most exacting standards.
At SCIC (www.scic-chain.com) , we understand that the integrity of a lifting chain is the sum of its parts. From the chemistry of the raw steel to the final surface coating, every step in the production line determines the chain's ability to perform safely under load.
Here are the critical elements that define world-class lifting chain quality.
1. The Foundation: Steel Material Selection
The journey to a safe lifting chain begins not in the factory, but in the steel mill. G80 and G100 chains require specialized alloy steels—typically containing elements like chromium, molybdenum, and boron.
- G80 Chains: Require a fine-grained, low-alloy steel that responds predictably to heat treatment, e.g., 20Mn2 or 22MnCrNi
- G100 Chains: Demand even more advanced metallurgy. To achieve the higher tensile strength (1000 N/mm²) without becoming brittle, the steel must be cleaner (with fewer non-metallic inclusions) and alloyed with precision, e.g., SAE8620D
Using substandard steel to save costs is a recipe for catastrophic, brittle failure.
2. The Weld: The Strongest Link
A chain is only as strong as its weakest point, and for round link chains, that point is the weld. Modern lifting chains utilize flash butt welding.
- Process Control: The welding current, upset pressure, and temperature must be meticulously controlled to create a weld that is metallurgically indistinguishable from the parent material.
- Consistency: The weld zone must be free of oxide inclusions and cracks. At SCIC, we ensure the weld flash is cleanly removed, but more importantly, that the grain structure of the steel is continuous across the joint.
3. The Heart of Performance: Heat Treatment
Heat treatment is what transforms a bent piece of steel into a high-performance Grade 80 or 100 chain. This is typically a three-stage process:
- Hardening: The chain is heated to a critical temperature and then quenched (rapidly cooled) to create a martensitic structure—the source of its high strength.
- Tempering: This is the most delicate step. The chain is reheated to a specific lower temperature. This reduces the internal stresses from quenching and "tempers" the steel, trading a tiny amount of hardness for a massive increase in toughness. A properly tempered chain will stretch (elongate) before it breaks, providing a visible warning before failure.
4. Verification: Force and Break Testing
You cannot inspect quality into a chain; you must prove it. Every single meter of lifting chain produced must meet international standards (like ISO or DIN).
- Proof Force Testing: Every chain is subjected to a proof load (typically 2.5 times the working load limit for G80). This stretches the chain elastically, verifying the integrity of the material and the welds.
- Breaking Force Testing: Destructive samples from every production batch are pulled to destruction. The breaking force must significantly exceed the minimum specified by the standard (e.g., 4 times the WLL). This isn't just about hitting a number; it is about ensuring the failure mode is ductile (showing a "necking down" of the link) rather than brittle.
5. Surface Finish: Protection and Performance
The final step is protection. The environment dictates the finish:
- Black Oxide / Oiled: The standard finish. It provides a base level of rust resistance for indoor use and allows the chain to be easily inspected for cracks.
- Painting (e.g., Grade Color Coding): Often used for identification (e.g., G80 is often black, G100 is often blue). It offers moderate corrosion protection.
- Galvanizing: Provides excellent corrosion resistance for marine or chemical environments. However, this requires extreme caution. If not performed correctly (e.g., acid pickling), galvanizing can introduce hydrogen embrittlement, making a high-strength chain dangerously brittle. Special post-baking processes are mandatory. For Hot Dip Galvanizing finish, the chain’s working load limit and breaking force shall be reduced by 20-25%.
- E-Coating (Electrophoretic Deposition): An increasingly popular choice for G100 chains. It provides a very uniform, durable, and corrosion-resistant coating without the risk of hydrogen embrittlement associated with hot-dip galvanizing.
For the rigging professional, a chain is a tool of trust. At SCIC, we believe that trust is earned through meticulous attention to every element of production: the steel, the weld, the heat treatment, and the testing. When you choose a G80 or G100 chain from SCIC (www.scic-chain.com), you are choosing a product engineered for safety, reliability, and performance under the most demanding conditions.
Post time: Feb-25-2026
