---
title: "304 vs 304L and 316 vs 316L Stainless Steel"
source: "https://www.laxconsteels.com/304-vs-304l-and-316-vs-316l/"
description: "304L and 316L against 304 and 316: the 0.03 percent carbon limit, sensitisation after welding, strength, dual certification, and the H and Ti grades."
---
# 304 vs 304L and 316 vs 316L: The Low-Carbon Stainless Grades

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AISI 304L and AISI 316L are the low-carbon versions of the austenitic stainless steels AISI 304 and AISI 316. The suffix L stands for low carbon: the L grades limit carbon to 0.03 percent, against 0.08 percent in the straight grades, and keep the chromium, molybdenum and nitrogen windows of their parents. The lower carbon content prevents chromium carbide from forming at the grain boundaries during an ordinary welding cycle, so a welded L-grade part keeps its corrosion resistance beside the weld without a post-weld anneal. The lower carbon content also lowers the specified strength: ASTM A276 sets the minimum yield strength of annealed 304L and 316L bar at 170 MPa, against 205 MPa for 304 and 316. In the annealed and unwelded condition the straight and L grades corrode alike. The choice between them therefore turns on welding, on the strength the design needs, and on the service temperature.

## Carbon limits of the straight and L grades

The 304 and 316 families each contain a straight grade, a low-carbon L grade, a high-carbon H grade and a low-carbon nitrogen-strengthened LN grade. Molybdenum separates the two families: 2.0 to 3.0 percent in every 316 variant and none specified in 304. Within each family the variants differ mainly in carbon. 304L also allows nickel up to 12.0 percent, against 10.5 percent in 304, which keeps the structure fully austenitic once the carbon, itself an austenite former, has been taken out.

*Carbon, chromium, nickel, molybdenum and nitrogen limits of the 304 and 316 variants, with UNS and EN numbers*

| Grade | UNS | EN | Carbon, percent | Chromium, percent | Nickel, percent | Molybdenum, percent | Nitrogen, percent |
| --- | --- | --- | --- | --- | --- | --- | --- |
| [304](https://www.laxconsteels.com/grades/aisi-304/) | S30400 | 1.4301 | 0.08 max | 18.0 to 20.0 | 8.0 to 10.5 | none specified | 0.10 max |
| [304L](https://www.laxconsteels.com/grades/aisi-304l/) | S30403 | 1.4307 | 0.03 max | 18.0 to 20.0 | 8.0 to 12.0 | none specified | 0.10 max |
| [304H](https://www.laxconsteels.com/grades/aisi-304h/) | S30409 | 1.4948 | 0.04 to 0.10 | 18.0 to 20.0 | 8.0 to 10.5 | none specified | not specified |
| 304LN | S30453 | 1.4311 | 0.03 max | 18.0 to 20.0 | 8.0 to 12.0 | none specified | 0.10 to 0.16 |
| [316](https://www.laxconsteels.com/grades/aisi-316/) | S31600 | 1.4401 | 0.08 max | 16.0 to 18.0 | 10.0 to 14.0 | 2.0 to 3.0 | 0.10 max |
| [316L](https://www.laxconsteels.com/grades/aisi-316l/) | S31603 | 1.4404 | 0.03 max | 16.0 to 18.0 | 10.0 to 14.0 | 2.0 to 3.0 | 0.10 max |
| 316LN | S31653 | 1.4406 | 0.03 max | 16.0 to 18.0 | 10.0 to 14.0 | 2.0 to 3.0 | 0.10 to 0.16 |
| [316Ti](https://www.laxconsteels.com/grades/aisi-316ti/) | S31635 | 1.4571 | 0.08 max | 16.0 to 18.0 | 10.0 to 14.0 | 2.0 to 3.0 | 0.10 max |

The windows are those held in the [grade reference](https://www.laxconsteels.com/grades/); manganese, silicon, phosphorus and sulphur limits are common to all eight rows and are given on each grade page. 316Ti adds titanium at a minimum of five times the combined carbon and nitrogen content, to a maximum of 0.70 percent. The EN numbers are nearest counterparts under EN 10088, not identities, and their carbon limits differ slightly from the ASTM limits.

## Sensitisation and the purpose of the L grades

Sensitisation is the precipitation of chromium carbide at the grain boundaries of an austenitic stainless steel held between roughly 425 and 860 degrees Celsius. Carbon diffuses to the boundaries faster than chromium, so each carbide draws its chromium from a narrow band of the adjacent metal. That band can fall below the roughly 10.5 percent chromium the passive film needs, and in a corrosive liquid it is attacked along the boundaries while the grains stay intact. Next to a weld the attack appears as two corroded bands parallel to the fusion line, a pattern known as weld decay. The bands lie where the peak temperature of the welding cycle fell within the sensitising range; metal nearer the fusion line was heated above the range and cooled through it quickly, and metal farther out stayed below it.

The amount of carbide that can form is limited by the carbon available. At 0.03 percent carbon an ordinary welding cycle leaves too little carbide to deplete the boundaries, and the L grade is weldable without a post-weld solution anneal. The protection has a limit in time: hours of exposure within the range, in service or in a slow stress relief, can still sensitise an L grade. A sensitised part is restored by solution annealing at 1,010 to 1,120 degrees Celsius followed by a rapid cool, and ASTM A262 sets out the tests that detect sensitisation on a sample. The [corrosion of stainless steel](https://www.laxconsteels.com/corrosion-of-stainless-steel/) article places intergranular attack among the other forms of corrosion.

## Strength of the L grades

Carbon dissolved in austenite strengthens it, so removing carbon lowers the specified strength. ASTM A276 sets the minimum properties of annealed bar as follows.

*ASTM A276 minimum tensile strength, yield strength and elongation of annealed 304, 304L, 316 and 316L bar*

| Grade | Form and condition | Tensile strength, MPa | 0.2 percent yield strength, MPa | Elongation in 50 mm, percent |
| --- | --- | --- | --- | --- |
| 304 | Hot-finished bar, annealed | 515 | 205 | 40 |
| 304L | Hot-finished bar, annealed | 485 | 170 | 40 |
| 316 | Hot-finished bar, annealed | 515 | 205 | 40 |
| 316L | Hot-finished bar, annealed | 485 | 170 | 40 |
| 304, 304L, 316, 316L | Cold-finished bar to 12.70 mm, annealed | 620 | 310 | 30 |

The L grades are specified 30 MPa lower in tensile strength and 35 MPa lower in yield strength, a reduction of about 17 percent in guaranteed yield. Above 12.70 mm, cold-finished annealed bar returns to the hot-finished strength minima of its grade with 30 percent elongation. The LN grades restore the lost strength in a different way: nitrogen at 0.10 to 0.16 percent strengthens austenite in solid solution without forming grain-boundary carbide, so 304LN and 316LN combine the low carbon of the L grades with a specified strength back at the level of the straight grades. The [yield and tensile strength](https://www.laxconsteels.com/yield-strength-vs-tensile-strength/) article explains how these minima are measured.

## Dual-certified 304/304L and 316/316L

Much 304 and 316 bar and plate is produced as a dual-certified heat. Such a heat meets the 0.03 percent carbon maximum of the L grade and also reaches the 515 MPa tensile and 205 MPa yield minima of the straight grade, so the same material conforms to either specification. A dual-certified heat behaves as an L grade in welding and as a straight grade in a strength calculation at ambient temperature. It does not satisfy a requirement for the elevated-temperature properties of a straight grade, because pressure design codes tie the higher allowable stresses at temperature to the carbon content of 304 or 316, and a heat of 0.03 percent carbon does not carry them.

## The H grades and elevated-temperature service

The H grades move carbon in the opposite direction. 304H and 316H specify 0.04 to 0.10 percent carbon, a minimum as well as a maximum, and 304H requires an ASTM grain size of No 7 or coarser. Carbon in solution and in finely dispersed carbides resists creep above roughly 500 degrees Celsius, where the L grades lose strength fastest; pressure codes therefore assign the L grades lower allowable stresses at temperature and do not use them in sustained service above about 500 degrees Celsius. The H grades sensitise in service, but intergranular corrosion needs a liquid electrolyte and does not proceed at 700 degrees Celsius; the risk returns only if the part meets wet conditions after it cools. The straight grades sit between the two: a 0.08 percent maximum with no minimum covers heats that suit either duty and guarantees neither.

## 316L and 316Ti

316Ti answers the same problem as 316L by a different route. Titanium has a stronger affinity for carbon than chromium and forms titanium carbide inside the grains at high temperature, before chromium carbide can form at the boundaries. The steel keeps a carbon limit of 0.08 percent and the elevated-temperature strength that goes with it, and it stays resistant to intergranular attack through years of service in the sensitising range, where 316L is protected only through the short exposure of a weld. 316L is the grade for welded parts that operate below about 500 degrees Celsius; 316Ti is the grade for welded parts that operate hot and corrosive at once, such as expansion bellows, hot acid ductwork and heat exchangers above the sensitisation threshold.

The two grades also follow regional practice. Material number 1.4571 has long been the default molybdenum grade on drawings in continental Europe, where 316L is the default in British and American practice. 316Ti is not used where a polished or electropolished surface matters, because its hard titanium carbide and nitride particles drag during polishing and leave streaks, and its welds are susceptible to knife-line attack in a narrow band at the fusion line in strong oxidising acids. In chloride service the two grades are equal: both have a pitting resistance equivalent number of 22.6 to 29.5.

## Selection for welded, machined and annealed parts

The suffix is chosen from the part's route through fabrication and service.

- Welded fabrications that will see a corrosive liquid, such as vessels, tanks, process pipework, hygienic equipment and heavy sections that cannot be annealed after welding, are specified in 304L or 316L. Matching filler, 308L for the 304 family and 316L for the 316 family, keeps the weld metal low in carbon as well.
- Machined parts that are not welded, such as shafts, fittings, fasteners and valve components, gain nothing in corrosion resistance from the L grade. The straight grade carries the higher guaranteed strength, and a dual-certified heat carries both.
- Parts solution annealed after fabrication have had any carbide dissolved, so the straight grade serves.
- Welded parts in sustained service above about 500 degrees Celsius take an H grade where strength governs, or a stabilised grade such as 316Ti, [321](https://www.laxconsteels.com/grades/aisi-321/) or [347](https://www.laxconsteels.com/grades/aisi-347/) where wet corrosion is also expected.

Between 304L and 316L the choice is the choice between 304 and 316: molybdenum, and with it chloride resistance. The [304 vs 316](https://www.laxconsteels.com/304-vs-316-stainless-steel/) article sets out the chloride limits of the two families.

## The low-carbon grades as bar

A carbon limit of 0.03 percent is reached in steelmaking, not in later processing. In argon oxygen decarburisation, oxygen blown into the melt is diluted with argon, which lowers the partial pressure of carbon monoxide so that carbon is removed in preference to chromium. Laxcon Steels refines its stainless melts in an argon oxygen decarburisation converter and a vacuum oxygen decarburiser, and supplies [bright bar](https://www.laxconsteels.com/products/bright-bars/) from 5 to 115 mm and [hot rolled round bar](https://www.laxconsteels.com/products/hot-rolled-round-bars/) from 16 to 125 mm in 304, 304L, 316, 316L and the other grades of the [austenitic family](https://www.laxconsteels.com/grades/austenitic/), made to order. The hot rolled bar pages for [304L](https://www.laxconsteels.com/products/hot-rolled-round-bars/aisi-304l/) and [316L](https://www.laxconsteels.com/products/hot-rolled-round-bars/aisi-316l/) give the size range and weight per metre in each grade.

## Frequently asked questions

### What is the difference between 316 and 316L?

316L limits carbon to 0.03 percent, against 0.08 percent in 316; the chromium, nickel and molybdenum windows are the same. The lower carbon keeps 316L free of grain-boundary carbide after welding. 316L has a lower specified strength, 170 MPa minimum yield against 205 MPa for annealed bar under ASTM A276.

### Is 316L better than 316?

316L is better for welded parts that meet a corrosive liquid, because it does not sensitise in an ordinary welding cycle. 316 is better where the design needs the higher guaranteed strength or where the part operates above about 500 degrees Celsius. Unwelded and annealed, the two grades have the same corrosion resistance.

### What does the L mean in 304L and 316L?

L stands for low carbon. The L grades limit carbon to 0.03 percent, against 0.08 percent in 304 and 316, so that welding does not precipitate chromium carbide at the grain boundaries. The H grades, 304H and 316H, are the opposite, with carbon held between 0.04 and 0.10 percent for strength at high temperature.

### Can 304L be used in place of 304?

In corrosion resistance, yes: annealed 304L resists corrosion at least as well as 304. In strength, only if the design allows for the lower minima of 485 MPa tensile and 170 MPa yield. A dual-certified 304/304L heat meets the 304 strength minima and the 304L carbon limit together. Above about 500 degrees Celsius neither 304L nor a dual-certified heat replaces 304 or 304H.

### What is the difference between 304L and 316L?

The difference is molybdenum. 316L contains 2.0 to 3.0 percent molybdenum and more nickel, which raise its resistance to chloride pitting and crevice corrosion; 304L contains none. Both limit carbon to 0.03 percent, both weld without sensitising, and both have the same ASTM A276 strength minima for annealed bar.

## Sources

- ASTM A276/A276M, Standard Specification for Stainless Steel Bars and Shapes: Condition A strength minima of 304, 304L, 316 and 316L bar.
- ASTM A240/A240M, Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip: composition windows and the 304H grain size requirement.
- ASTM A262, Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels.
- EN 10088-1 and EN 10088-3, Stainless steels: EN numbers and names of the counterparts.
- Total Materia, Production of Stainless Steels: the argon oxygen decarburisation process.

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