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What is Stainless steel?

  • 100 Series—austenitic chromium-nickel-manganese alloys
  •     Type 101—austenitic that is hardenable through cold working for furniture
  •     Type 102—austenitic general purpose stainless steel working for furniture
  • 200 Series—austenitic chromium-nickel-manganese alloys
  •     Type 201—austenitic that is hardenable through cold working
  •     Type 202—austenitic general purpose stainless steel
  • 300 Series—austenitic chromium-nickel alloys
  •     Type 301—highly ductile, for formed products. Also hardens rapidly during mechanical working. Good weldability. Better wear resistance and fatigue strength than 304.
  •     Type 302—same corrosion resistance as 304, with slightly higher strength due to additional carbon.
  •     Type 303—free machining version of 304 via addition of sulfur and phosphorus. Also referred to as "A1" in accordance with ISO 3506.
  •     Type 304—the most common grade; the classic 18/8 stainless steel. Also referred to as "A2" in accordance with ISO 3506.
  •     Type 304L—same as the 304 grade but contains less carbon to increase weldability. Is slightly weaker than 304.
  •     Type 304LN—same as 304L, but also nitrogen is added to obtain a much higher yield and tensile strength than 304L.
  •     Type 308—used as the filler metal when welding 304
  •     Type 309—better temperature resistance than 304, also sometimes used as filler metal when welding dissimilar steels, along with inconel.
  •     Type 316—the second most common grade (after 304); for food and surgical stainless steel uses; alloy addition of molybdenum prevents specific forms of corrosion. It is also known as marine grade
        stainless steel due to its increased resistance to chloride corrosion compared to type 304. 316 is often used for building nuclear reprocessing plants. 316L is an extra low carbon grade of 316, generally
        used in stainless steel watches and marine applications, as well exclusively in the fabrication of reactor pressure vessels for boiling water reactors, due to its high resistance to corrosion. Also referred
        to as "A4" in accordance with ISO 3506. 316Ti includes titanium for heat resistance, therefore it is used in flexible chimney liners.
  •     Type 321—similar to 304 but lower risk of weld decay due to addition of titanium. See also 347 with addition of niobium for desensitization during welding.
  • 400 Series—ferritic and martensitic chromium alloys
  •     Type 405—ferritic for welding applications
  •     Type 408—heat-resistant; poor corrosion resistance; 11% chromium, 8% nickel.
  •     Type 409—cheapest type; used for automobile exhausts; ferritic (iron/chromium only).
  •     Type 410—martensitic (high-strength iron/chromium). Wear-resistant, but less corrosion-resistant.
  •     Type 416—easy to machine due to additional sulfur
  •     Type 420—Cutlery Grade martensitic; similar to the Brearley's original rustless steel. Excellent polishability.
  •     Type 430—decorative, e.g., for automotive trim; ferritic. Good formability, but with reduced temperature and corrosion resistance.
  •     Type 439—ferritic grade, a higher grade version of 409 used for catalytic converter exhaust sections. Increased chromium for improved high temperature corrosion/oxidation resistance.
  •     Type 440—a higher grade of cutlery steel, with more carbon, allowing for much better edge retention when properly heat-treated. It can be hardened to approximately Rockwell 58 hardness, making it
        one of the hardest stainless steels. Due to its toughness and relatively low cost, most display-only and replica swords or knives are made of 440 stainless. Available in four grades: 440A, 440B, 440C,
        and the uncommon 440F (free machinable). 440A, having the least amount of carbon in it, is the most stain-resistant; 440C, having the most, is the strongest and is usually considered more desirable
        in knifemaking than 440A, except for diving or other salt-water applications.
  •     Type 446—For elevated temperature service
  • 500 Series—heat-resisting chromium alloys
  • 600 Series—martensitic precipitation hardening alloys
  •     601 through 604: Martensitic low-alloy steels.
  •     610 through 613: Martensitic secondary hardening steels.
  •     614 through 619: Martensitic chromium steels.
  •     630 through 635: Semiaustenitic and martensitic precipitation-hardening stainless steels.
  •     Type 630 is most common PH stainless, better known as 17-4; 17% chromium, 4% nickel.
  •     650 through 653: Austenitic steels strengthened by hot/cold work.
  •     660 through 665: Austenitic superalloys; all grades except alloy 661 are strengthened by second-phase precipitation.
  • Type 2205—the most widely used duplex (ferritic/austenitic) stainless steel grade. It has both excellent corrosion resistance and high strength.
Stainless steel designations
SAE designationUNS designation % Cr % Ni % C % Mn % Si % P % S % NOther
254S3125420180.02 max----0.206 Mo; 0.75 Cu; "Super austenitic"; All values nominal
303S3030017–198–100.15210.20.15 min-Mo 0.60 (optional)
303SeS3032317–198–100.15210.20.06-0.15 Se min
304CuS3043017–198–100.0820.750.0450.03-3–4 Cu
316S3160016–1810–140.0820.750.0450.030.102.0–3.0 Mo
316LS3160316–1810–140.0320.750.0450.030.102.0–3.0 Mo
316FS3162016–1810–140.08210.20.10 min-1.75–2.50 Mo
316NS3165116–1810–140.0820.750.0450.030.10–0.162.0–3.0 Mo
317S3170018–2011–150.0820.750.0450.030.10 max3.0–4.0 Mo
317LS3170318–2011–150.0320.750.0450.030.10 max3.0–4.0 Mo
321S3210017–199–120.0820.750.0450.030.10 maxTi 5(C+N) min, 0.70 max
329S3290023–282.5–50.0820.750.040.03-1–2 Mo
347S3470017–199–130.0820.750.0450.030-Nb + Ta, 10 x C min, 1 max
348S3480017–199–130.0820.750.0450.030-Nb + Ta, 10 x C min, 1 max, but 0.10 Ta max; 0.20 Ca
405S4050011.5–14.5-0.08110.040.03-0.1–0.3 Al, 0.60 max
409S4090010.5–11.750.050.08110.0450.03-Ti 6 x C, but 0.75 max
430FS4302016–18-0.121.2510.060.15 min-0.60 Mo (optional)
430FSeS4302316–18-0.121.2510.060.06-0.15 Se min
434S4340016–18-0.12110.040.03-0.75–1.25 Mo
436S4360016–18-0.12110.040.03-0.75–1.25 Mo; Nb+Ta 5 x C min, 0.70 max
416S4160012–14-0.151.2510.060.15 min-0.060 Mo (optional)
416SeS4162312–14-0.151.2510.060.06-0.15 Se min
420S4200012–14-0.15 min110.040.03--
420FS4202012–14-0.15 min1.2510.060.15 min-0.60 Mo max (optional)
422S4220011.0–12.50.50–1.00.20–0.250.5––1.25 Mo; 0.20–0.30 V; 0.90–1.25 W
440AS4400216–18-0.60–0.75110.040.03-0.75 Mo
440BS4400316–18-0.75–0.95110.040.03-0.75 Mo
440CS4400416–18-0.95–1.20110.040.03-0.75 Mo
Heat resisting
501S501004–6-0.10 min110.040.03-0.40–0.65 Mo
502S502004–6-0.1110.040.03-0.40–0.65 Mo
2250.03 max----0.153 Mo; All values nominal
Super duplex
2507S327502570.03 max----0.284 Mo; All values nominal