Comparison of Types304SS and 316/316LSS
Comparison of Types304SS and 316/316LSS
(OP)
Can anybody point to a decent practical comparison of 304 to 316/316l? I can find the metallurgical comparison charts I need. I work in an industry where these materials are used quite often in the products we make. Our standard product is made from 304. Some customers request 316/316l. These are usually Chem/Pharma folks. My question comes from the practical point of view. Why would I prefer 316 over 304? What are some of the applications for 316 where 304 will NOT survive? How would I describe the differences to a salesman who is technically disfunctional?





RE: Comparison of Types304SS and 316/316LSS
There is an FAQ above which gives the relationship that determines the resistance of a stainless steel to pitting and another one which gives the things in the environment which promote corrosive attack on stainless, which most often takes the form of pitting corrosion.
316 is seldom used in food service applications, but it is common is corrosive environments(seaside or chemical plants) or applications where no corrosion can be tolerated,e.g.pharmaceuticals.
RE: Comparison of Types304SS and 316/316LSS
RE: Comparison of Types304SS and 316/316LSS
RE: Comparison of Types304SS and 316/316LSS
Gerald Austin
RE: Comparison of Types304SS and 316/316LSS
The lower carbon does not impart better corrosion resistance in austenitics per se. What it does is to keep welds from precipitating chrome carbides which would deplete the matrix of vital chromium. This precipitation can also be prevented by quenching or post-weld annealing.
The 316 thus treated is equal to 316L in corrosion resistance.
The book price of 316L is $1.98/lb vs $1.40 for 304 and $1.50 for 304L. The bargain grade is 201 at $1.28/lb, and it doesn't require low carbon to prevent sensitization.
RE: Comparison of Types304SS and 316/316LSS
as Chromium is less in 316 would this decrease its oxidation resisitance ?
and why we increse Ni percentage in 316, also please can you tell me why Ni is good austenite former i mean what its influence on austenite ?
RE: Comparison of Types304SS and 316/316LSS
RE: Comparison of Types304SS and 316/316LSS
1) ASM had a study that Chlorine deteriorates
316 stainless Steel. I cannot remember the cause but
they had alot of failures when companies that used
Chlorine as a chemical and 316 Stainless Steel as a
metal.
2) 304 Stainless Steel becomes magnetic in a
cryogenic environmnet where as 316 does not.
FSU did a study on different materials in a cryogenic
environment.
Other than that, cost?
Cobalt can also be used to ensure an FCC structure
adding Nickel will increase workability also.
RE: Comparison of Types304SS and 316/316LSS
The extra Ni in 316 stabilizes the austenite--it's much more stable than 304.
RE: Comparison of Types304SS and 316/316LSS
You have made the comment that "There are no corrosion environments in which 304 is better than 316."
I have read some papers that conclude 304L is superior to 316L in kraft liquor pulping because of the higher chrome and no moly. Similar discussions regarding 2205 and 2304 (most don't spec 2304 due to lack of availability and fabrication/welding experience compared to 2205).
Have you, or anyone else, ever seen these results and care to comment?
RE: Comparison of Types304SS and 316/316LSS
I will double check my facts and respond. There is no doubt that higher chrome is a plus, regardless of what other changes occur in composition, but moly, to my knowledge, is never a negative except for high temperature oxidation.
I'll be back.
RE: Comparison of Types304SS and 316/316LSS
RE: Comparison of Types304SS and 316/316LSS
For clarification discussions are not related to SCC. A couple of references:
"In-Situ Coupon Immersion Study of Stainless Steels in Kraft Cooking", Nadezhdin & McDonald, 9th International Symposium on Corrosion in the Pulp and Paper Industry
"Corrosion Phenonmena in Black Liquor Evaporators", Klarin, 10th International Symposium on Corrosion in the Pulp and Paper Industry.
There are some other articles in the 10th ISCPP which show similar results in kraft liquor.
RE: Comparison of Types304SS and 316/316LSS
Because of the lower chromium content in 316SS, there are, as others have pointed out, exceptions to this rule. These exceptions are highly oxidizing environments such as high temperature (>1500F) air, hot concentrated nitric acid, and some ranges of oleum. I believe, but am not certain, that 304SS may also outperform 316SS in concentrated chromic acid and sulfuric acid (>98%).
The "L" designation for stainless steel has been explained by others. But it may interest you to know that 'dual certified' materials are in wide use in North America. Dual certified materials are those that meet the requirements of both the standard grade and the "L" grade.
RE: Comparison of Types304SS and 316/316LSS