Stainless steel type 316 and type 304 are raw material grades for stainless steel. Stainless steel fasteners are sometimes referred to and ordered as their raw material grades (such as SS 316 and SS304) and sometimes referred to and ordered as their ASTM specification. The common ASTM specifications that cover stainless steel bolts are A193, A320 and F593. Type 316 stainless has a unique chemical composition which includes 16% chromium, 10% nickel and 2% molybdenum. Type 304 stainless has 18% chromium, 8% nickel and no molybdenum (this is where the “18-8” designation comes from). Stainless steel 316 is more resistant to chlorides than stainless steel 304, making it the preferred material for marine construction.
Sometimes, a type “SS316L” or type “SS304L” bolt will be specified in a particular application. The “L” at the end of these designations refers to the low carbon content of the steel. Stainless steel certified to 316L or 304L will have a maximum of 0.03% carbon, versus the 0.08% maximum that regular 316 and 304 can have. Low-carbon stainless steel bolts are used to avoid corrosion problems that are caused by welding, as the lower carbon content reduces the “sensitization effect” (the precipitation of chromium carbides at grain boundaries) caused by the high temperatures involved in welding. Since carbon is the principal hardening element in steel, low-carbon bolts have reduced hardness but are easier to weld.
The difference in carbon content does not affect the overall corrosion resistance of the steel, and low-carbon stainless steel bolts can be ordered to each of the A193, A320 and F593 specifications. When you order a low-carbon stainless steel bolt, just let us know about this requirement and our expert estimators will be sure to provide you with the correct material.
Hi,
Can you provide the comparison for SS410 & SS316 in terms of strength and corrosion resistance?
I am looking for material which is high strength and good corrosion resistance. Thanks.
@Young- Typically speaking, ss410 is stronger than ss316, and ss316 is more corrosion resistant than ss410. However, there are manufacturing processes and heat treatment options that can drastically increase or decrease both strength and corrosion resistance. We would need to know many more specifics in order to answer your question.
Hi,
Could you please let me know what is hardness of SS316 and SS304 which i need to know for selecting the material for our application in paper factory.
Thanks,
Manu
@Manu- The only hardness required by A193 is a maximum of 223 HBN, there is no mimimum. Otherwise both 304 and 316 have identical tensile and yield values, 75ksi minimum tensile, 30ksi minimum yield.
thanks for this information Kailey
Hi,
Can you give me the similar comparison or differences between SS 321 and SS 304 also SS 321 and SS 316.
Thanks in advance for your reply.
Regards,
Virupaksh
@Virupaksh- Mechanically, 321/304/316 are identical, unless subsequent processing has been done. Chemically, 321 has titanium added to it, and has similar other elements to 316. 304 has slightly less Nickel than both 316 and 321. A complete comparison can be done by looking at the ASTM A276 standard.
Hi,
Could you direct me to the appropriate ASTM specification for a 3/4 inch countersunk stainless steel bolt?
Regards,
Jyotirmoy
@Jyortirmoy – Most of the off the shelf countersunk stainless bolts will not be manufactured to an ASTM standard, simply to 304/316 chemistry. If you require an ASTM standard, F593 is the general purpose ASTM standard, but they would need to made special in order to be certified to F593, as the industry has been slow to adopt the F593 standard.