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Differences between 303 and 303s stainless steel?


(2007)

Q. I WOULD LIKE TO KNOW JUST WHAT IS THE DIFFERENCE BETWEEN 303 AND 303S STAINLESS STEEL. 303 S IS AVAILABLE IN A MUCH WIDER VARIETY OF SIZES THAN ORDINARY 303 WHICH WOULD BE OF MUCH BENEFIT TO MY BUSINESS.

DAVID YORK
MANAGER MACHINE SHOP - WEST PALM BEACH, FLORIDA, USA


(2007)

A. '303S' isn't defined by AISI, ASTM, SAE or QQ-S-746B. Perhaps vendorspeak for 303 to remind salespeople and customers that it contains additional sulfur? Or, confusion with the selenium-containing free-machining 303Se grade?

To avoid ambiguity, order by UNS designation and an appropriate ASTM specification.
ASTM A582/A582A, 'Standard Specification for Free-Machining Stainless Steel Bars' includes the following austenitic grades, by UNS designation and (Type):
S20300 (XM-1) Contains higher S, Mn & Cu, lower Ni (relative to 304).
S30300 (303) higher S, C & P.
S30310 (XM-5) higher S, C, P & Mn, slightly lower Ni.
S30323 (303Se) higher Se, C & P, slightly higher S.
S30345 (XM-2) higher S & C. Also added Al for better formability and Mo for pitting corrosion resistance.

The free-machining grades are poorer than traditional '18-8' stainless grades such as S30400 (304) for corrosion resistance, welding, cold-forming and hot-forming. Passivation is thus even more essential for corrosion resistance.

Ken Vlach
- Goleta, California
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October 2, 2012

Q. As I understand the "Difference between 303 and 303s stainless steel" sheet (Letter 46234), ASTM A582/A582A is the specification for the UNS grades listed. I have interest in 303S and 303Se. The list defines 303Se for ASTM A582/A582A, but says nothing about 303S. Does ASTM A582/A582A cover both 303S and 303Se? If not, what is the spec for 303S?

Dan Walter
- Painesville, Ohio, USA


October 24, 2012

A. I'm checking my big alloy book, and unless this is something more recent than my copy, I see no 303S. There's a "303S31" that is apparently the same as plain old 303, and a 303Se of course, but no 303S.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois



thumbs up signThank you for your response. What started all of this was an upgrade to one of our drawings that had 303S and 303Se as the two possible materials to use for the resulting part. If there is no such thing as 303S, I will remove it, and just leave the 303Se. Thanks again for your help.

Dan Walter [returning]
- Painesville, Ohio, USA



Effect of Sulphur in AISI 303

November 6, 2016

Q. First I have fundamental question, how to review/read Mill Test Report where it is written Max or Min in Chemical composition?

Second question, S is Min 0.15 by weight. If it is less than 0.15 than what will be effect?

Malik Asif Mumtaz
- Sialkot, PAKISTAN


November 2016

A. Hi Malik. It seems to me that if it is lower in sulfur than the specification for 303, then it is not 303. Perhaps it's 304?

I would expect, but don't know, that it will not machine as well as it is supposed to because my understanding is that the purpose of the sulfur is to improve machinability. Good luck.

Regards,

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Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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