The Carbon Question: 316, 316L and 316Ti Compared

September 21, 2026

Three names, one alloy family, and a difference that only appears when heat does. This is the short version of a decision that stops a lot of drawings.

The actual difference

All three are the molybdenum bearing austenitic grade, roughly 16 to 18 percent chromium, 10 to 14 percent nickel and 2 to 3 percent molybdenum. The PREN of all three sits near 24, calculated from nominal composition. In a corrosion test on an unwelded sample they behave the same.

What separates them is carbon and what carbon does when the material is held between about 450 C and 850 C.

	Carbon	Strength	Welding	Typical use
316	up to 0.08 percent	highest of the three	risk of sensitisation	Unwelded parts, higher temperature service
316L	up to 0.03 percent	slightly lower	the normal choice	Welded parts, most machined parts
316Ti	up to 0.08 percent, stabilised with titanium	like 316	good, keeps strength hot	Sustained service above 400 C

Sensitisation, in plain terms

Chromium is what makes stainless stainless. It sits dissolved in the metal and feeds the passive film on the surface.

Carbon has an appetite for chromium. Hold 316 in the sensitising range and chromium carbides form at the grain boundaries. The chromium that went into those carbides is no longer available at the boundary, so a thin band either side of each boundary is locally low in chromium and corrodes faster than the metal around it. In service the attack runs along the grain boundaries and the part can fail without ever looking corroded.

The temperature range matters because welding puts a band of material either side of the bead through it. This is the failure mode called weld decay, and it is why the L grades exist.

316L solves it by starving the reaction. Below about 0.03 percent carbon there is not enough to form meaningful carbide, so the chromium stays where it is useful.

316Ti solves it differently. Titanium is added to grab the carbon first, forming titanium carbide instead. The chromium stays in solution and the part keeps the higher strength of standard 316. This matters when the part will sit hot for a long time, because the low carbon trick only protects during a short excursion such as a weld. In sustained service above roughly 400 C, carbide can still form in 316L over months.

What this means for a machined part

Unwelded, room temperature, no downstream heat. The choice is academic. Write 316L and move on. Most bar and plate is dual certified to both 316 and 316L, which means one heat meets the chemistry of the L grade and the mechanical minimums of the standard grade. You will very likely receive the same steel whichever you specify.

Welded, at any point in its life. 316L, without exception. That includes a part machined from bar that someone will later weld a fitting onto. It also includes weld repair, which happens more often than drawings admit. There is more on this in machining stainless weldments.

Sustained service above 400 C. This is the only place 316Ti earns its keep. Exhaust components, furnace hardware, some chemical process parts. Sourcing is harder outside Europe and lead times reflect that.

Polished or cosmetic surfaces. Avoid 316Ti. The titanium carbides are hard particles in a soft matrix and they show up as streaks and comet tails when the surface is polished or electropolished.

The trap: assuming L means weaker

316L has a slightly lower minimum yield and tensile strength than 316 on paper. In practice the difference is small, most dual certified stock clears the 316 minimums comfortably and the certificate will say so. Do not design around the paper difference without reading a real certificate.

The other trap runs the other way. Some buyers specify 316 believing they are getting a stronger part, then have it welded. That combination is exactly the case the L grade exists to prevent.

A note on 316LVM and 316LS

For implant and surgical work you will meet 316LVM, vacuum melted to ASTM F138 with tighter inclusion control. It is a different specification, not just a cleaner 316L, and it costs considerably more. Do not write it on a drawing for a non implant part, because the sourcing burden lands on the shop and on your lead time. If your part touches the body, say so in the RFQ and let the grade follow from the requirement. See ISO 13485 against ISO 9001 for the quality system side of the same question.

What to write

For nearly every machined part, this line is enough:

Material: 316L stainless steel, ASTM A276 or A479, dual certified 316/316L acceptable. Mill certificate with heat number required.

Add a condition only when you have a reason. If the part runs hot, say the temperature in the RFQ rather than jumping to 316Ti, because a shop that machines these grades regularly may know a cheaper route. The buyer guide covers what else belongs on the print, and the grade table puts these next to the rest of the family.

Frequently asked questions

Figures in this guide are published specification limits or published typical values for the alloy, not measurements of any part. Machinability is rated against free-machining carbon steel B1112 at 100 and PREN is chromium plus 3.3 times molybdenum plus 16 times nitrogen. The conventions are set out in thereference section and the editorial standards.

Keep reading

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