Three stainless grades cover almost everything that comes through a fabrication shop in Tamil Nadu: 304, 316 and 430. They look nearly identical on the rack and behave very differently in service.

Choosing wrongly is expensive in both directions — 430 that rusts within a year on a coastal site, or 316 specified for an indoor bracket at three times the necessary cost.

The Short Version

304: the Default

If nobody has specified a grade, 304 is almost certainly what is meant. Around 18% chromium and 8% nickel give it a self-healing passive oxide layer, good formability and excellent weldability.

It handles rain, humidity and most food and domestic environments without trouble. Railings, gates, kitchen equipment, structural brackets, planters, signage — 304 does all of it.

Its weakness is chlorides. Salt attacks the passive layer locally and causes pitting: small deep holes rather than general rust. That is a real consideration in Chennai, and a serious one within a couple of kilometres of the coast.

316: When There Is Salt or Chemistry

316 adds roughly 2% molybdenum, which stabilises the passive layer against chloride attack. Everything else about it is broadly similar to 304 — same look, same weldability, same fabrication behaviour.

Use it when the part will live near the sea, in a swimming pool environment, in chemical processing, or anywhere it will be washed down with chlorinated water. In those conditions the price difference buys years of service life.

430: the Budget Grade, With Conditions

430 is ferritic. It contains chromium but essentially no nickel, which is why it costs the least of the three — nickel is the expensive ingredient in stainless.

It gives a bright finish and resists indoor humidity perfectly well, which makes it a sensible choice for decorative panels, pooja room screens, wall art and interior trim that will never be rained on.

It is magnetic, unlike 304 and 316, which is occasionally useful and occasionally a surprise. It is less weldable and less formable, and it will develop surface rust outdoors, particularly in coastal air.

Choosing in Practice

1. Will the part live outdoors? If no, 430 is worth considering. If yes, start at 304.
2. Is it within a few kilometres of the sea, or exposed to pool water, brine or chlorinated washdown? If yes, 316.
3. Does it need welding into an assembly? Prefer 304 or 316; 430 is harder to weld well.
4. Is appearance the whole point and the environment dry? 430 gives the same brightness for less.
5. Is it structural or safety-critical? Do not economise on grade.

How the Three Cut

All three cut cleanly on a fiber laser, and we cut all of them up to 45 mm. The practical differences are about finish rather than capability:

• Nitrogen assist gas gives a bright, oxide-free edge that can be left as-cut or polished. It is the normal choice for visible stainless work.
• Oxygen cuts faster and cheaper but leaves an oxidised edge, which is fine for parts that will be painted or hidden.
• Stainless conducts heat less readily than mild steel, so it holds a crisp edge well but needs sensible nesting on thin decorative work to avoid heat build-up.

Which gas is right for your job affects both finish and price, as covered in what laser cutting costs.

Common Mistakes

• Specifying 316 for everything "to be safe". It is a real cost increase with no benefit indoors.
• Assuming a magnet test proves quality. Magnetism distinguishes 430 from 304 and 316, but heavily cold-worked 304 can become slightly magnetic too.
• Mixing grades in one assembly without thinking about galvanic contact.
• Ordering "SS" with no grade. It is the single most common cause of a job being quoted twice.

For where stainless sits among the other metals we cut, see materials that can be laser cut.