What is the difference between 316 and 316l?

There are several stainless steel grades, which are classified into four major categories. One of the most important categories is austenitic stainless steel. The austenitic stainless steel alloys are further put into several groups based on their chemical composition. One of the most highlighted stainless steel grades belongs to the 300 series. These grades are very versatile and their utility covers several areas, including shipping, marine engineering, general engineering, the petrochemical industry as well as the pharma and food sectors. This being said, grade 316 is the second most used alloys amongst the 300 series. Like most austenitic stainless steel alloys, grade 316 is modifiable. Modifications for stainless steels tend to be on the basis of their application.

Generally, the modifications are minor additions or subtraction in the elements for the specific chemical composition. For instance, marine grade 316 stainless steel has a higher content of carbon in its alloy. Carbon, at elevated temperatures, forms a carbide precipitate and causes sensitization at the grain boundary precipitates. Because of the sensitization, the metal becomes weak, during welding operations. Welding temperatures are often higher as they need to have some melting of the metal in order to fuse it to the other part or fuse itself to form a complete part. And so the melted part, which is the heat affected weld zone tends to have weaker corrosion resistance properties in comparison to the rest of the surface of the components. Since the other surface area has not been heated by the employment of weld treatments the corrosion resistance remains stable. This is a problem that affects welded components of grade 316 stainless steel. As a solution to this problem manufacturers devised a low carbon version of this particular alloy.

The price difference between 316 and 316l stainless steel

Although there are elemental changes in the alloy the material could be dual certified because the changes tend to be at a very minimal level. And so the dual certified alloy will be labeled as 316/316L. Hence, the price for both these alloys would almost be similar to each other.

316 and 316l comparison

Aside from the fact that the content of carbon in stainless steel grade 316L is lower, manufacturers also add nitrogen to its alloy. There are several reasons for adding nitrogen to the alloy. First, the overall mechanical strength of stainless steel grade 316 sees a dip with the reduction of carbon. Second, its tolerance to heat also sees a decline. However, it is because of the lower quantity of carbon in its chemistry, it is possible for grade 316L to be welded without any susceptibility to intergranular corrosion.

Difference between 316 and 316l corrosion resistance

As mentioned previously, the objective for introducing grade 316 stainless steel in the market is its excellent weldability. Lowering the carbon content effectively reduces the alloys vulnerability to intergranular corrosion, in particular to the heat affected weld zone. Similar to grade 316, the low carbon version of the alloy may also be referred to as marine grade steel because it can resist seawater and brine solutions. Hence, the alloy is also dual certified to cater to the needs of several applications. Furthermore, like grade 316, it can resist atmospheric corrosion or what is also referred to as oxidation resistance. Dual certified alloys are also useful in applications that contain halogenic compounds including chlorine and fluorine and bromine. Because they are resistant to corrosion, they form an integral part of consumer goods industries.

316 stainless steel mechanical properties

SUS 316 Yield Strength 0.2% Proof min. (MPa) 205
Tensile Strength min. (MPa) 515 Elongation min. (% in 50mm) 40
Hardness: Rockwell B (HR B) max. 95 Brinell (HB) max. 217

Stainless steel grade 316 chemical composition

ASTM A312 C Mn Si P S Cr Mo Ni N
316 min. 16.0 2.0 10.0
max. 0.08 2.0 0.75 0.045 0.03 18.0 3.0 14.0 0.10

AISI 316 equivalent material

GERMAN WERKSTOFF NR. 1.4401 / 1.4436 BRITISH BS 316S31 / 316S33
EUROPE EN X5CrNiMo17-12-2 / X3CrNiMo17-13-3

316L stainless steel yield strength & properties

AISI 316 Elongation (% in 50mm) min 40
Tensile Strength (MPa) min 515 Rockwell Hardness B (HR B) max 95
Yield Strength 0.2% Proof (MPa) min 205 Hardness Brinell (HB) max 217

316L stainless steel composition

SS 316L C -Carbon Mn – Manganese Si -Silicon P – Phosphorous S (Sulfur)
max. 0.03 2.0 1.00 0.045 0.015
SS 316L Cr – Chromium Mo- Molybdenum Ni-Nickel Fe – Iron N -Nitrogen
min. 16.50 2.0 10.0 Balance
max. 18.50 2.50 13.0 0.10

AISI 316L stainless steel equivalent

USA UNS S31603 RUSSIAN AFNOR Z3CND17‐11‐02 / Z3CND18‐14‐03
GERMAN WERKSTOFF NR. 1.4404 / 1.4435 BRITISH BS 316S11 / 316S13
RUSSIAN GOST 03Ch17N14M3 / 03Ch17N14M2 EUROPE EN X2CrNiMo17-12-2 / X2CrNiMo18-14-3

ASTM Specification for 316 stainless steel

SS 316 Pipe ASTM A312
SS 316 Tube ASTM A213
SS 316 Sheet ASTM A240
SS 316 Plate ASTM A240
SS 316 Pipe Fittings ASTM A403
SS 316 Tube Fittings ASTM A276/ A479
SS 316 Forged Fittings ASTM A182
SS 316 Flanges ASTM A182
SS 316 Fasteners ASTM A193
SS 316 Forging ASTM A182
SS 316 Valves A351 CF8M
SS 316 Casting A351 CF8M
SS 316 Round Bars ASTM A276/ A479

ASTM Specification for 316L stainless steel

SS 316L Pipe ASTM A312
SS 316L Tube ASTM A213
SS 316L Sheet ASTM A240
SS 316L Plate ASTM A240
SS 316L Pipe Fittings ASTM A403
SS 316L Tube Fittings ASTM A276/ A479
SS 316L Forged Fittings ASTM A182
SS 316L Flanges ASTM A182
SS 316L Fasteners ASTM A193
SS 316L Forging ASTM A182
SS 316L Valves A351 CF3M
SS 316L Casting A351 CF3M
SS 316L Round Bars ASTM A276/ A479

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