If you’ve ever grabbed a rusty old bicycle chain, hauled a heavy load with a farm chain, or walked past the industrial chains that keep conveyor belts running in a warehouse, you probably haven’t stopped to think about how that small, repetitive loop of metal comes to be. For over a decade, I’ve been supplying industrial and specialty chains to businesses across construction, agriculture, and logistics, and one of the most common questions I get from new clients isn’t just “how strong is this chain?”—it’s “how do you make it, anyway?” It’s a fair question. Most of us take chains for granted until one snaps mid-lift or a bike chain skips gears on a busy commute. Let’s pull back the curtain on the process, break it down step by step, and explain why the way we make chains (and the materials we use) matters more than you might think. Chains
It starts with something almost no one sees: raw material selection. Not all metal is created equal, and for chains, the wrong choice means weak, failure-prone product. We use three primary types of steel for most of our chains, depending on the end use. For general-purpose and lift chains, low-carbon steel works well—it’s malleable enough to shape but strong enough for everyday loads. For heavy industrial and agricultural chains that face constant friction, impact, and exposure to dirt or moisture, we turn to medium-carbon steel, which has a higher tensile strength and holds up better under stress. For specialty applications, like chains used in marine environments or for high-temperature furnace work, we use alloy steels mixed with elements like chromium, nickel, or molybdenum to resist corrosion and heat. The steel arrives at our factory in large, coiled rods—think 500-pound coils that look like giant, messy Slinkies—and the first step is processing that rod into a workable wire.
Wire drawing is the next stage, and it’s all about precision. The steel rod is fed through a series of diamond or carbide dies, each slightly smaller than the last, that pull the metal into uniform, thin wire. This isn’t just squeezing the metal thinner, though—each pass through a die adjusts the wire’s diameter and improves its tensile strength by aligning the steel’s internal grain structure, a process called work hardening. By the time the wire comes out of the final draw, it’s smooth, consistent in thickness, and strong enough to start shaping into links. For most standard chains, the wire is drawn to a diameter between 2mm and 20mm; heavy industrial chains can use wire up to 50mm thick, and that process takes longer, with more die passes, to get right. A single mistake in wire diameter at this stage means every link produced after it will be either too loose or too tight, or worse, weaker than it should be, so we test every coil of wire with a micrometer before it even leaves the loading dock.
Now comes the part that looks deceptively simple: forming the links. The drawn wire is fed into a machine called a chain bender, which cuts it to exact lengths and bends it into the classic U-shape of a chain link. This machine is programmed to hold the same dimensions every single time—even a 0.1mm difference in link height can throw off the entire chain’s fit. Once the links are formed, they’re laid out in a line, ready to be connected. For standard welded chains, the open ends of each U-shaped link are brought together and welded to close the loop. Welding is another critical step; we use either resistance welding or gas metal arc welding (GMAW, sometimes called MIG welding) depending on the wire thickness. For smaller, thinner links, resistance welding uses electric current to heat the ends of the link until they melt and fuse together, creating a strong, uniform weld without extra material buildup. For thicker, heavy-duty links, GMAW uses a continuous wire feed and shielding gas to create a deeper, stronger weld that can handle higher loads. After welding, every single link is inspected visually for gaps, uneven welds, or splatters that could weaken the chain later. It’s tedious, but skipping even one bad link can lead to a catastrophic failure down the line.
Once the individual links are welded, the next step is assembling them into a continuous chain. The formed links are fed into an assembly machine that interlocks them one by one, creating the long, flexible chain we know. But a fresh, assembled straight-off-the-machine chain is far from done—it’s brittle, prone to rust, and nowhere near strong enough for real-world use. That’s where heat treatment comes in, and this is the stage that separates a cheap, disposable chain from one that lasts for years.
Heat treatment is a multi-step process tailored to the type of chain and its intended use. First, we perform normalizing, which involves heating the entire chain to a specific temperature (usually between 800°C and 900°C, depending on the steel type) and letting it cool slowly in air. This relieves the internal stress that built up during wire drawing and link forming, making the chain less brittle and more uniform in strength. Next comes quenching: heating the chain again to a precise temperature, then plunging it into a bath of water, oil, or polymer solution to cool it rapidly. Quenching hardens the steel, making the links strong enough to resist stretching under load. But hardening alone makes steel too brittle, so we follow quenching with tempering. Tempering involves reheating the chain to a lower temperature (usually between 200°C and 500°C) and letting it cool. This balances hardness and toughness—removing some of the brittleness from quenching while keeping most of the strength. For chains used in high-wear applications, we also add a surface treatment like shot blasting, which bombards the chain with small metal particles to smooth the surface and create a compressive stress layer that resists fatigue and corrosion.
After heat treatment, it’s time for finishing touches that add function and longevity. Most chains get a corrosion-resistant coating; common options include hot-dip galvanizing, where the chain is dipped in molten zinc to create a protective layer, or electroplating, which is better for smaller, more delicate chains. For chains used in heavy industrial settings, we might apply a paint or a wax coating to add an extra layer of protection against dirt and chemicals. We also perform quality control testing at multiple stages here. We test a sample of every batch of chain for tensile strength—pulling it until it breaks to make sure it meets or exceeds our specifications. We check for elongation, how much the chain stretches under load, to ensure it stays within safe limits. And for any chain used for lifting or heavy loads, we do load testing, pulling it with a controlled weight to verify it doesn’t bend, break, or fail unexpectedly.
I’ve seen too many businesses cut corners on quality control to save a few dollars, and it almost always comes back to bite them. A farm client of mine a few years ago bought a cheap chain from a non-specialized supplier to pull an old tractor out of a mud pit. The weld on one link failed mid-pull, the tractor tipped into a ditch, and they ended up paying more for repairs than they would have for a high-quality chain from a reputable supplier. That’s why we don’t take shortcuts at any step of the process—we use the right steel, precision machinery, and rigorous testing to make chains that our clients can trust, whether they’re using them to lift a 10-ton construction beam, haul hay bales across a farm, or keep a conveyor belt moving 24/7 in a warehouse.
What many people don’t realize is that chains are far more versatile than just the ones you see on bikes or in construction sites. We supply specialty chains for everything from amusement park ride restraints (they have to be strong enough to hold dozens of people, flexible enough for ride movements, and compliant with strict safety regulations) to deep-sea mooring chains for oil rigs, which have to resist years of saltwater corrosion and constant heavy loads. Each of these chains uses a slightly modified version of the same core process, adjusted to meet the specific demands of its end use.
Rings If you’ve ever worked with chains, you know that choosing the right one for your job is just as important as its manufacturing quality. A chain designed for light, occasional use will fail under heavy, constant load, and vice versa. That’s why I always encourage new clients to reach out with their specific needs—whether you need a small chain for a garage door, a heavy-duty chain for construction, or a specialty chain for a custom application, we can help you pick the right product, and we can even share details on our manufacturing process if you want to see for yourself how we make our chains. We don’t just sell chains—we supply a reliable solution to a problem that many businesses take for granted until it goes wrong. If you’re in the market for a new chain supplier, or if you’ve had issues with failed chains in the past, don’t hesitate to connect with us to discuss your project. We’ll provide honest advice, transparent information about our products, and a chain that’s built to last.
References
- ASTM International. Standard Specification for Steel Chains, Grade 80, Alloy, Heat-Treated, for Lifting Applications. ASTM A391-21, 2021.
- Metals Handbook, Volume 6: Welding, Brazing, and Soldering, 10th Edition. ASM International, 1993.
- Brandt, R. “Wire Drawing: Principles and Processes.” Metal Forming Science and Practice, Elsevier, 2002, pp. 187–212.
- Groover, M.P. Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, 7th Edition. Wiley, 2020, pp. 562–587.
- International Organization for Standardization. Chain, Chain Links, and Chain Attachments for General Lifting Purposes—Part 1: Grade 8. ISO 2408-1:2017, 2017.
Guangzhou Seal Hardware Products Co., Ltd.
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