SAE 304 stainless steelis the most commonstainless steel.It is an alloy ofiron,carbon,chromiumandnickel.It is anaustenitic stainless steel,and is therefore not magnetic. It is less electrically and thermallyconductivethancarbon steel.It has a highercorrosionresistance than regular steel and is widely used because of the ease in which it is formed into various shapes.[1]
The composition was developed byW. H. HatfieldatFirth Brownin 1924 and was marketed under the trade name "Staybrite 18/8".[2]
It is specified bySAE Internationalas part of itsSAE steel grades.It is also known as:[3]
- 4301-304-00-IandX5CrNi18-9,the ISO 15510 name and designation.
- UNS S30400in theunified numbering system.
- A2 stainless steeloutside the US, in accordance withISO 3506forfasteners.[4]
- 18/8and18/10stainless steel (also written 18-8 and 18-10) in the commercialtablewareand fastener industries.
- SUS304the Japanese JIS G4303 equivalent grade.
- 1.4301,theEN10088 equivalent.[5]
- 06Cr19Ni10andISC S30408,the equivalent in Chinese GB/T 20878 and GB/T 17616 nomenclature.
- 08Kh18N10and03Kh18N11,the equivalents for 403 and 403L inGOSTnomenclature.
Chemical composition
edit| Standard | AISI(UNS) | C,≤ | Si,≤ | Mn,≤ | P,≤ | S,≤ | Cr | Ni |
|---|---|---|---|---|---|---|---|---|
| ASTM A276/A276M | 304 (S30400) | 0.08 | 1.00 | 2.00 | 0.045 | 0.030 | 18.0–20.0 | 8.0–11.0 |
Corrosion resistance
edit304 stainless steel has excellent resistance to a wide range of atmospheric environments and many corrosive media. It is subject to pitting and crevice corrosion in warmchlorideenvironments and tostress corrosion crackingabove about 60 °C (140 °F). It is considered resistant to pitting corrosion in water with up to about 400 mg/L chlorides at ambient temperatures, reducing to about 150 mg/L at 60 °C.
304 stainless steel is also very sensitive at room temperature to thethiosulfateanions released by theoxidationofpyrite(as encountered inacid mine drainage) and can undergo severepitting corrosionproblems when in close contact withpyrite- orsulfide-richclaymaterials exposed to oxidation.[citation needed]
For more severe corrosion conditions, when 304 stainless steel is too sensitive to pitting or crevice corrosion by chlorides or general corrosion in acidic applications, it is commonly replaced by316stainless steel. 304 and 302 stainless steels are subject to chloride stress fracture failure when used in tropical salt water conditions such as oil or gas rigs. 316 stainless steel is the preferred alloy for these conditions.
Mechanical properties
edit304 stainless steel cannot be heat treated—instead it can be strengthened by cold working. It is weakest in the annealed condition, and is strongest in the full-hard condition. The tensile yield strength ranges from 210 to 1,050 MPa (30,000 to 153,000 psi).
The density is 7,900 kg/m3(0.286 lb/cu in), and its modulus of elasticity ranges from 183 to 200 GPa (26.6×106to 29.0×106psi).[7]
Applications
edit
304 stainless steel is used for a variety of household and industrial applications such as food handling and processing equipment, screws,[4]machinery parts, utensils, andexhaust manifolds.304 stainless steel is also used in the architectural field for exterior accents such as water and fire features. It is also a common coil material for vaporizers.
EarlySpaceX StarshipsusedSAE 301 stainless steelin their construction,[8]before moving over to SAE 304L for theSN7 test tank[broken anchor][9]andStarship SN8in 2020.[10]
304 stainless steel was used to clad theGateway Archin St. Louis, Missouri.[11][12]
Carbon content
edit304, 304H, and 304L all possess the same nominal chromium and nickel content and also possess the same corrosion resistance, ease of fabrication, and weldability. The difference between 304, 304H, and 304L is the carbon content which is < 0.08, < 0.1, and < 0.035% respectively (also see UNS designations S30400, S30409, & S30403 respectively). 304 has both the H=High and the L=Low carbon variants.
The carbon content of 304H (UNS S30409) is restricted to 0.04–0.10%, which provides optimal high-temperature strength.
The carbon content of 304L (UNS 30403) is restricted to a maximum of 0.035%, which prevents sensitization during welding. Sensitization is the formation of chromium carbides along grain boundaries when stainless steel is exposed to temperatures in the approximate range of 480–820 °C (900–1,500 °F). The subsequent formation of chromium carbide results in reduced corrosion resistance along the grain boundary leaving the stainless steel susceptible to unanticipated corrosion in an environment where 304 would be expected to be corrosion resistant. This grain boundary corrosive attack is known as intergranular corrosion.[13]
The carbon content of 304 (UNS 30400) is restricted to a maximum of 0.08% and is not useful for corrosive applications where welding is required, such as tanks and pipes where corrosive solutions are involved, and 304L is preferred. Its lack of a minimum carbon content is not ideal for high-temperature applications where optimal strength is required, thus, 304H is usually preferred. Thus 304 is typically restricted to bars that will be machined into components where welding is not required or thin sheets that are formed in articles such as kitchen sinks or cookware that are also not welded.
Carbon content has a strong influence on room temperature strength and thus the specified minimum tensile properties of 304L are 34 MPa (5,000 psi) lower than for 304. However, nitrogen also has a strong influence on room temperature strength and a tiny addition of nitrogen produces 304L with the same tensile strength as 304. Thus, practically all 304L is produced as dual certified 304/304L, meaning it meets the minimum carbon content of 304L and also meets the minimum tensile strength of 304.[14][full citation needed]
See also
editReferences
edit- ^Data sheet on SAE 304 stainless steelArchived2012-07-23 at theWayback Machine.
- ^"Archived copy".Archivedfrom the original on 2016-08-13.Retrieved2016-06-20.
{{cite web}}:CS1 maint: archived copy as title (link) - ^"Stainless steel grades listed in the international standard ISO 15510:2010 Comparative designations of grades with similar composition from other important standards. (listed by type of steel structure and by increasing intermediate 3-digits code of the ISO name)"(PDF).International Stainless Steel Forum.Retrieved10 March2023.
- ^ab"Stainless Steel Fasteners".Australian Stainless Steel Development Association. Archived fromthe originalon 2007-09-29.Retrieved2007-08-13.
- ^"X5CrNi18-10 | 1.4301 – learn more".Materials Processing Europe.
- ^AISI SAE 304 Stainless Steel PropertiesArchived2020-08-20 at theWayback Machine.
- ^MIL-HDBK-5J.United States Department of Defense. 31 January 2003. p. 2-222.
- ^Wall, Mike (2020)."SpaceX's Starship will soon be made of different stuff".space.Archivedfrom the original on 5 June 2020.Retrieved30 May2021.
- ^Greenwood, Matthew (22 August 2020)."SpaceX's Starship Vehicle Aces First Test Flight".engineering.Archivedfrom the original on 9 July 2021.Retrieved30 May2021.
- ^Ali, Areeb (28 October 2020)."The Test Flight of SpaceX's Starship Prototype SN 8 Is Excitement Guaranteed".The Wire.Archivedfrom the original on 2 June 2021.Retrieved30 May2021.
- ^Offer, Dave (May 26, 1968)."Lofty Gateway Arch Dedicated And Hailed by HHH in St. Louis"(PDF).The Hartford Courant.p. 12A. Archived fromthe originalon September 14, 2011.RetrievedJanuary 6,2011.
- ^"The Gateway Arch, St Louis".July 6, 2015.
- ^admin (2021-10-12)."What Does Intergranular Corrosion Mean".Retrieved2021-10-14.
- ^"Easily distinguishing tips between 304, 304H and 304L".September 1, 2017.Archivedfrom the original on April 11, 2018.RetrievedApril 11,2018.