Is 303 stainless food grade?

swellwelder · Jun 16, 2011

I spent a half hour googling this and didn't find anything useful about this question. I have to make a stainless transition out of 2&3/4" solid, and all I have in that size is 303. It is easy to say 304 is food safe, but does the sulfer added knock 303 out of the food safe category?

Dale Nelson

JRIowa · Jun 16, 2011

The Europeans are the only ones that have written specs on food grade stainless. Usually the stainless steels specified for food grade are 304, 316, 420, & 430. Ask your customer if they will OK a 303 substitution.
JR

SchneiderMachine · Jun 16, 2011

Yeah, I'd ask the customer but, I still do know why it would matter at all. You have to think, is your aluminum pot and pans food grade, how about your cast iron skillet? Are any of those "food grade"???

Dave

swellwelder · Jun 16, 2011

My guess is that the only one who really cares would be the USDA inspector who comes around to see that everything is bright shiny metal. Whether he knows anything about different grades of stainless is debatable. Or how he could tell that it was 303 instead of 304!

Dale

David J. · Jun 16, 2011

The very few "food grade" stainless projects were with customer
supplied 304 material. That said, I think the whole food grade thing
for the parts I did specified smoothly ground welds and radius
with no place to trap food/debris and allow easy cleaning.
Not sure if the material was a issue.
David

greenbuggy · Jun 16, 2011

SchneiderMachine said:
Yeah, I'd ask the customer but, I still do know why it would matter at all. You have to think, is your aluminum pot and pans food grade, how about your cast iron skillet? Are any of those "food grade"???

Dave

I suspect finish means more for trapped food particles/bacteria/fungi than the base material, but thats just a suspicion.

"aircraft grade aluminum is a crock. They don't machine the cheapo food tray from quality grade billet. Nobody brags about "sewage grade stainless" now do they?"

jhruska · Jun 16, 2011

304 and 316 stainless may be alloyed with Sulfur and Selenium to enhance machinability.

' Type 302 uses are kitchen equipment, utensils, dairy installations, and food processing equipment.
This is an austenitic grade "18-8" with 0.15% max carbon, 8-10% nickel, and 17-19% chromium.
Excellent corrosion resistance and because of the austenitic structure it has very good ductility and may be deep drawn and severely formed. It may be welded if the heat zones are cooled rapidly. Otherwise the weld zones are susceptible to intergrannular corrosion. Correct this problem by annealing above 1900 degrees followed by rapid cooling to trap the carbides in situ.

Type 304 has a lower carbon content and is not as likely to cause trouble after welding with respect to carbide precipatation and the resulting corrosion.'

*The Making and Shaping of Steel United States Steel

Regards,
John

John

Ries · Jun 16, 2011

304 L does NOT have lead in it.
The L stands for "low carbon", not lead.

The L in steel can mean lead, but, in stainless, it means low carbon, and although recipes vary a bit from mill to mill, a representative 304L stainless is something like this-

COMPOSITION
Type 304 % Type 304L %
Carbon 0.08 max. 0.03 max
Manganese 2.00 max. 2.00 max.
Phosphorus .045 max. .045 max.
Sulfur .030 MAX. .030 max.
Silicon .075 max. .075 max.
Chromium 18.00- 20.00 18.00- 20.00
Nickel 8.00-12.00 8.0-12.00
Nitrogen 0.10 max. 0.10 max.
Iron Balance Balance

no lead, no selenium.

316L is very similar, except it has around 2% Molybdenum in it.

Ox · Jun 16, 2011

Just call it 18-8 and drive on.

Pretty sure that some of the 303 products that we make here have to pass food grade apps.

...

The "L" in 304 and 316 indicated lower MAX level of carbon.
304/316 = .08 max C
304/316L = .03 max C

L labeled material is known to be for welding purposes.
Seems like a welder would know this?*

Has nothing to doo with lead in this case.
But easilly cornfused with carbon steel grades with lead added.

(Looks like Riese beet me to it.)

*After reading it aggin - and noting the mis-information - I guess that middle part was cut/pasted, and maybe he is not a welder?

-------------------

Think Snow Eh!
Ox

tmt · Jun 16, 2011

Others have already defined the L in 304L and 316L. 303 will machine a bit better than 304, however it is not suitable for welding. So if the part needs to be welded into place, find something better for that purpose like 304. As has been mentioned, check with the customer first.

jhruska · Jun 16, 2011

I stand corrected and smarter!
John

wildwestpat · Jun 16, 2011

Take a look at the web site for the British Stainless Steel Association:-

http://www.bssa.org.uk/topics.php?article=45

It gives a bit of good background on the grades of stainless and the characteristics for food processing machinery. Corrosion with common cleaning chemicals as well as the welding, bending, spinning properties of the various grades.

Regards - Pat

SchneiderMachine · Jun 16, 2011

????? I weld 303 all the time, never had a problem. I do use 304 filler though. 304 defiantly welds much better though.

Machining 303 is a night and day difference than 304, to me anyway, and I do a fair share of it.

Dave

tmt said:
Others have already defined the L in 304L and 316L. 303 will machine a bit better than 304, however it is not suitable for welding. So if the part needs to be welded into place, find something better for that purpose like 304. As has been mentioned, check with the customer first.

Chris Figgatt · Jun 16, 2011

greenbuggy said:
....Nobody brags about "sewage grade stainless" now do they?"

Lol! Now that's a good one!

wesg · Jun 16, 2011

Yeah, I like that too. I'll have to remember that next time somebody asks what I made something out of: "Certified sewage grade ...'

swellwelder · Jun 16, 2011

This part is entirely a machining job, no welding required. 303's machinability is a definite reason for wanting to use it. This will start out at about 5# and be about 2# when finished, so the faster and better I can machine it the better!

Thanks for the info. Will check with the customer, but have a feeling he has no idea there are even different classes of stainless!

Dale

tmt · Jun 16, 2011

SchneiderMachine said:
????? I weld 303 all the time, never had a problem. I do use 304 filler though. 304 defiantly welds much better though.

Machining 303 is a night and day difference than 304, to me anyway, and I do a fair share of it.

Dave

Sorry, I didn't mean to imply that it was not weldable. Due to the higher carbon content it is more suscepticle to intergranular corrosion. 303 wouldn't be my first choice if it had to be welded.

JRIowa · Jun 16, 2011

Unless you're buying mill quantity, it's hard to find 304 or 316 only. Almost all of the stainless we buy (it's in the tons) is dual certified now. The stainless is really 304L/316L. We have customers that specify 316 on the contract. They won't listen to the fact that we can't buy 316 and won't accept a dual material certification. So...we have the material re-certified as 316.
JR

Ox · Jun 17, 2011

Yeah, anything that pases "L" requirements gits grandfathered in on the non-L label as well.

I haven't seen anything that wasn't dual cert in many yrs either.

------------------

Think Snow Eh!
Ox

metlmunchr · Jun 17, 2011

No one but the customer can answer the question of 303 suitability. For example, if they're complying with 3A standards, most contact surfaces have to be 316, 304 can only be used for things like drain lines, and the use of 303 is restricted. 3A standards are widely used in the dairy industry.

If they're complying with NSF standards then 304 is more widely used. Not sure about NSF's stand on 303, but I wouldn't be surprised if they restrict it too since the sulfur addition has a fairly large effect on corrosion resistance. Anything that makes the surface more prone to deterioration is going to make the surface more difficult to clean and more likely to trap food residue.

Ask 'em and see what they want.

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