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Associate

Join Date: Nov 2007
Posts: 26

How to tell different grade of stainless steel?

12/02/2007 8:53 AM

Hi..all

i often see two types of marking on a stainless stell pipe.. its marked as 304/304L. 1. Aren't they two different grade? If so, what does one with "L" and without "L" differs? Differs in composition? why marked both on the same pipe?

2. Also by visual inspection, one cannot tells a plate is 304/304L grade or 316/316L grade.. whats instrument can i use to test it.

3. Also stainless steel will not magnet right? tks..

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Anonymous Poster
#1

Re: How to tell different grade of stainless steel?

12/02/2007 12:02 PM

These are 2 different steels of same grade , but cost wise totally different .

SS 304 L is a low Carbon steel ( % C < 0.03 ) and is very good for higher temperature applications as it is resistant to intergranualr corrossion due to non- forming of garin boundry carbides.

SS304 is normal for normal temperature application is OK , and cheaper than SS304L.

SK Hegde

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#2

Re: How to tell different grade of stainless steel?

12/02/2007 2:01 PM

The "L" designates only a lower carbon modification of the basic grade. In your example both 304 and 304L are also commonly called 18-8 Austenitic stainless steels. (The 18-8 designates the nominal Chromium-Nickel composition). The basic or general purpose 18-8 is 302 with a nominal Carbon content of 0.15% max. 304 is actually a lower carbon modification of 302 with nominal C contend reduced to 0.08% maximum for restriction of carbide precipitation during welding. 304L then is a modification of 304 further reducing the nominal C content to 0.03% maximum.

Same thing applies to 316 and 316L (which has 16.00/18.00 Cr and 10.00/14.00 Ni along with 2.00/3.00 Mo) for higher corrosion resistance and creep strength than 302 and 304.

The dual marking indicates that the carbon content meets the "L" version requirements which means it also meets the requirements of the non-"L" version (because the required C limits are maximum).

As noted above, this family of SST is Austenitic which means it is not hardenable by heat treatment. It can be annealed (softened) by heat treatment but it is only hardenable by cold-working. The other two types are Martensitic (hardenable by heat treatment) and Ferritic (which is not hardenable by heat treatment nor cold working).

Martensitic and Ferritic grades are strongly magnetic whereas Austenitic grades are non-magnetic in general. However, they can be slightly magnetic, depending upon the degree of cold-working and the temperatures to which they have been exposed.

There are some chemical spot tests that will allow one to differentiate between say 304 and 316 but will not detect the differences in carbon content between 304 and 304L, for example. One might play around a bit with grinding wheel spark testing, comparing 302 with 304 and 304L to see if the carbon content changes either the color or shape of the sparks.

Otherwise, chemistry, arc emission spectrometry or energy dispersive x-ray would be required to measure the carbon content.

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Participant

Join Date: Jan 2008
Posts: 1
#11
In reply to #2

Re: How to tell different grade of stainless steel?

01/19/2008 5:01 PM

Hello, My name is Scott Waterman and I was reading Bluestone's reply regarding telling the difference between 304 and 304L or 316 and 316L Stainless Steel.

I noticed Bluestone mentioned there is some sort of chemical spot tests one can perform to help differentiate 304 from 316.

How does one acquire information regarding this spot testing?

Any info you may be able to provide will be greatly appreciated.

Sincerely,

Scott Waterman

swaterman@cleanair-usa.com

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#12
In reply to #11

Re: How to tell different grade of stainless steel?

01/19/2008 5:38 PM

The major difference between 304 and 316 is the 2 per cent moly in 316.

So you need a moly spot test.

Are you a chemist?

To make the test solution you will need 3 parts of 5% potasssium thiocyanate sol. added to one part stannous chloride solution (prepared by dissolving 25g of stannous chloride in 20 ml of conc HCL and diluting to 100ml ). make a puddle of this test solution on the metal, connect the positive terminal of a six volt 'Hot shot' battery to the stainless metal to be tested (Alligator clip) and the negative lead to a carbon rod held just touching against the top of the drop of solution (NOT THE METAL!!!) for 2 or 3 seconds.the solution will turn pink. if moly is present (ie 316) the spot will stay pink or rose colored. If no moly is present the spot will fade quickly to light green or clear.

Eye protection, hand protection, proper disposal of chemicals, adult supervision, good luck finding an MSDS for the solution, etc. etc. etc.

This is a qualitative, semiquantitative methodology. as such, having known standards to assure test solution is still working is a good practice.

not much use in shops with sodium lights and when used by color blind heavy fisted shop techs.

milo

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Anonymous Poster
#19
In reply to #12

Re: How to tell different grade of stainless steel?

10/31/2010 5:26 PM

YA THANKS DEAR

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Participant

Join Date: Feb 2010
Posts: 1
#16
In reply to #11

Re: How to tell different grade of stainless steel?

02/03/2010 3:54 AM

1.First check for magnetic response.Response will be more for 304(A2)
2.Take 65% Nitric acid and put few drops on the item.You can see the reaction on 304(A2)
3.Wash and wipe the water.Now add Molybdnem(REAGENZPATE D304-316 ATZEND 9%) drops on the item.wait for 3 minutes.If it is 316(A4),this area will become blackish in colour.

Good Luck

THANDASSERY DINESH

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#3

Re: How to tell different grade of stainless steel?

12/02/2007 10:42 PM

3. Also stainless steel will not magnet right? Wrong it will on 304 / 316 but not on 304L/316 L and thats how u check - layman term.

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Join Date: Nov 2006
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#5
In reply to #3

Re: How to tell different grade of stainless steel?

12/03/2007 2:53 AM

Most of the austenite grade SS materials have 0.15 C% in addition to Mn, SI, Cr, Ni and Mo ( in certain types like 316, 317, 309 Mo) etc. In all above austenite grades low carbon version is also available with maximum carbon percentage of 0.03 and identified with suffix L, i.e., 304L, 316L, 309L, etc. It requires use of same type/similar filler wire like E/ER 304L, E/ER 316L etc. to optimize the applications.

All austenite SS materials will have more or less same Silvery finish and can not be identified as such and only spectrometry (a economical, faster, easy available in portable models) and similar methods for its chemical composition. The austenite materials does not attract magnet in general compared to other two grades.

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Guru

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#8
In reply to #3

Re: How to tell different grade of stainless steel?

12/04/2007 2:11 PM

I wonder if it's from where you are getting your stainless steel.

We use almost exclusively 304 stainless steel. I have come across some that was magnetic but the majority of the time it has been non-magnetic at least not enough to detect it.

Pump shaft on the other hand is also stainless steel and it is magnetic enough to hold a magnet.

I don't know about 316.

416 however would be magnetic because it is layered mild steel between two layers of stainless.

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#4

Re: How to tell different grade of stainless steel?

12/03/2007 2:23 AM

Your 1st question was answered by Mr.Bluestone.

For 2nd, it may be your customer's requirement. And you have to ask your customer or refer to your product standard e.g. JIS or BS or DIN,.......

You can not distinguish 304/304L from 316/316L by visual inspection. You can use chemical method: "Molibdenum detector" for your purpose.

3rd, There are too much kind of stainless steel e.g.201, 301, 303, 304,..... with magnet property or not in them.

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Guru

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#6

Re: How to tell different grade of stainless steel?

12/03/2007 10:31 AM

Some stainless is magnetic. It depends on the grade.

You can usually tell the grade because it is marked on the material. I don't know if any tool to test it.

I know that 416 grade is mirror reflective. It also has a layer if mild steel sandwiched between two layers of stainless steel making it a type that is best to not apply welding too.

The stainless steel that is on the outside of kitchen appliances is 201 stainless steel. It has a low nickel content to it.

There is some color variations to it, just like gold of different purities has a different color to each.

When you work around stainless steel enough you could probably tell the difference by sight.

Sometimes you might see stainless steel with rust in it. That is mostly caused by coming in contact with another metal that is capable of rusting and leaving impurities on the surface.

I've looked up stainless steel before trying to find out the properties of 201 when looking for a cheaper alternative to 304 SS, because the unstable pricing of nickel drives the price of stainless steel up and I don't recall seeing anything noting the differences of having the "L" attached to the grade. That just means that I was not looking for that particular piece of information.

You can google it. The information is there.

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#7

Re: How to tell different grade of stainless steel?

12/04/2007 1:56 PM

Good afternoon waterlucky.

304 is .08 maximum carbon; 304 L is.03 max carbon; In stainless steels in the western countries (where my experience is) the L designates low carbon.

316 is .08 max carbon; 316L is .03 max carbon. no other chemical differences.

Since 304 is .08 maximum, the 304L at .03 Carbon is acceptable for the .08 max Carbon of the 304 grade (304 L meets 304, but not vice versa). Same for the 316L.

It can conceivably help a steelmaker reduce his inventory cost of possession if he makes a heat -Say 180 ton or so, or perhaps a multiple heat string- of this steel and he can apply that heat to orders for either grade. If not, then he has to carry double inventory, increasing his costs, and the possibility that he will not have the right grade for your eventual order;

See the following website for a portable instrument that can qualitatively determine the difference between different metallic materials: http://www.niton.com/

Not all stainless steel grades are "not magnetic." Martensitic and ferritic Stainless steels have magnetic properties, while the huge amount of nickel in the austenitics make them non magnetic. you would do well to look at a web page such as : http://www.azom.com/details.asp?ArticleID=470 , and in particular table 1 to get a better understanding for the stainless steels.

For your information, both the 304/304L and the316/316L grades are austenitic, so no, you could not sort them by using a response to a magnet. they would be permeability of mu= 1.008;magnetic stainless grades mu inthe range of 400-1000.

Hope that this information helps.

milo

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#9

Re: How to tell different grade of stainless steel?

12/04/2007 7:38 PM

May I sugest you, how to distinguish them in production process.

From inspecting material, you can identify 304 and 316 by attached document or name plate, If possible then colour marking e.g. 316 is yellow and 304 don't need to mark,..... And keeping this in your production line.

You can't mark by colour(if there is heat treatment process), please apply identify and traceability control method.

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#10

Re: How to tell different grade of stainless steel?

12/10/2007 10:15 AM

They are slightly different steel grades: 304 has a maximum Carbon content of 0,08% and 304L (L for "Low Carbon") has maximum 0.03% Carbon.

The same occurs with 316/316L. The difference with 304 is that 316 has a small molybdenum content (2%).

All of them are "austenitic" and therefore "non magnetic" that is aren´t attracted by a magnet like plain carbon steels do. Note that this characteristic is due to the austenitic structure and not to the fact they are stainless!!!! There are some other stainless steel grades which have ferritic or martensitic structure and their magnetic behaviour is completely different.

The reason for identifying a pipe as 304/304L or 316/316L is that such pipe complies with both specifications (L grades have slightly different strength). Many steel makers use to simplify their production process by making steels which comply with more than one specification thus reducing the number of different grades to manufacture.

Visual inspection will not reveal if it is 304 series or 316 series. The only way to distinguish them is by spectroscopic analysis (there are portables ones) You can look just for Moly, to note if it´s 304 or 316, because if the pipe is marked with 304/304L (or 316/316L) you don´t need to make any difference.

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#13
In reply to #10

Re: How to tell different grade of stainless steel?

11/26/2008 11:29 PM

If someone was going to make muffler parts out of stainless and going to silver solder them together what would be the best grade to use.

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Anonymous Poster
#14

Re: How to tell different grade of stainless steel?

03/11/2009 9:05 AM

There are stainless steels that are magnectic when you drop the amount of nickel and Cr you raise the iron which causes the SS to be magnetic or even in some cases rust.

The rusting though can be removed by passivating the SS

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#15
In reply to #14

Re: How to tell different grade of stainless steel?

03/11/2009 9:50 AM

Magnetic response is function of microstructure, (austenite), not 'raising the iron.'

please see posts 7 and 10 above.

milo

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Anonymous Poster
#17

Re: How to tell different grade of stainless steel?

02/12/2010 2:00 AM

1.304/304L is the most common grade of s.steel.304L is same as the 304 grade but contains less carbon to increase weldability. Is slightly weaker than 304.

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#18

Re: How to tell different grade of stainless steel?

02/25/2010 1:13 AM

I work in stainless steel supplier company in Indonesia, south east asia. We have a lot of fake stainless steel products here, 201 sold as 304. Both 201 and 304 do not respond to magnet so it is a bit difficult to differentiate.

At first I inquired those portable metal analyzer which is too costly. It is priced at USD 50k above. But they do give you detail chemical composition. By the way, you could rent this device at weekly rate of USD 300-700.

Then, our work partner in Japan introduced me to this chemical test to differentiate: 201 against 304... and 304 against 316. It works by testing Manganese content to differentiate 201 against 300 series. Then we could use Ni and Mo test to differentiate 304 and 316. If you are interested, do email me @ teddy_gunarto@yahoo.com I have a few extra that I do not use and intend to sell.

It is not expensive too. around USD 60 to perform 25 test.

I think the only way to differentiate 304 and 304L is to purchase one of those expensive metal analyzer.

Also, do not buy double specification stainless steel 304/304L.. ask for single specification 304L. Double spec is the same as regular 304 grade. Besides regular 304 is cheaper than 304L so u get ripped if you are trying to purchase 304L, and you are given double spec items!

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Participant

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#20
In reply to #18

Re: How to tell different grade of stainless steel?

11/04/2013 11:07 PM

our local metal recyclers both them class st st that is magnetic as plain steel & I've noticed the all good stainless seems mostly non magnetic. This way they are sure its good quality But much of what I've kept thats is magnetic is sure good stainless. Corrosion wise -most people give their Magnetic st st away as ordinary steel.Recyclers get a bargain from those convinced the recylers know best.

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#21
In reply to #20

Re: How to tell different grade of stainless steel?

11/06/2013 4:55 PM

There are several stainless steels: Austenitic, Ferritic, Martensitic, Duplex, Precipitation hardened, etc.

Some are fully magnetic (those ferritic and martensitic, for example).

As stated previously, the magnetic properties depends on the crystal structure.

Kind regards

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#22
In reply to #21

Re: How to tell different grade of stainless steel?

11/07/2013 12:58 AM

thank you Kwetz I'm from NZ -I sure will not remember the name types. But is the more magnetic types the ones that show the slight rusting? ---which is what most people buying St St would prefer not to have.

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Anonymous Poster (4); Bluestone (1); Curley (2); ducon (1); Janissaries (2); Kwetz (2); Milo (3); nam70 (2); RC Extreme Power (1); SRIDHAR (1); STWCLEANAIR (1); tgunarto (1); THANDASSERY DINESH (1)

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