Stainless Steel Composition

Stainless steel refers to a wide variety of grades of metal which contain an alloy that has at least 10.5% of chromium with low carbon content, other elements are added to make each of grade having unique characteristics.

Stainless Steel Composition

The chemical compositions for some commonly used austenitic, ferritic, martensitic and duplex stainless steels are provided in the following tables based on ASTM standard.

Austenitic Stainless Steel Grades

Stainless steel grades Chemical composition % by mass max
UNS No AISI No. C Si Mn P S Cr Mo Ni Others
S30100 301 0.15 1.00 2.00 0.045 0.030 16.0/18.0 6.0/8.0 N 0.10
S30400 304 0.07 0.75 2.00 0.045 0.030 17.5/19.5 8.0/10.5 N 0.10
S30403 304L 0.030 0.75 2.00 0.045 0.030 17.5/19.5 8.0/12.0 N 0.10
S30453 304LN 0.030 0.75 2.00 0.045 0.030 18.0/20.0 8.0/12.0 N 0.10/0.16
S30500 305 0.12 0.75 2.00 0.045 0.030 17.0/19.0 10.5/13.0
S31600 316 0.08 0.75 2.00 0.045 0.030 16.0/18.0 2.00/3.00 10.0/14.0 N 0.10
S31603 316L 0.030 0.75 2.00 0.045 0.030 16.0/18.0 2.00/3.00 10.0/14.0 N 0.10
S31635 316Ti 0.08 0.75 2.00 0.045 0.030 16.0/18.0 2.00/3.00 10.0/14.0 Ti 5x (C+N) / 0.70 N 0.10
S31653 316LN 0.030 0.75 2.00 0.045 0.030 16.0/18.0 2.00/3.00 10.0/14.0 N 0.10/0.16
S31700 317 0.08 0.75 2.00 0.045 0.030 18.0/20.0 3.0/4.0 11.0/15.0 N 0.10
S31703 317L 0.030 0.75 2.00 0.045 0.030 18.0/20.0 3.00/4.00 11.0/15.0 N 0.10
S31753 317LN 0.030 0.75 2.00 0.045 0.030 18.0/20.0 3.0/4.0 11.0/15.0 N 0.10/0.22
S32100 321 0.08 0.75 2.00 0.045 0.030 17.0/19.0 9.0/12.0 Ti 5 x C min/0.70 N 0.10
S34700 347 0.08 0.75 2.00 0.045 0.030 17.0/19.0 9.0/13.0 Nb+Ta 10 x C min/1.0

Super Austenitic Grades

Stainless steel grades Chemical composition % by
UNS No AISI No. C Si Mn P S Cr Mo Ni Others
N08904 904L 0.020 1.00 2.00 0.045 0.035 19.0/23.0 4.0/5.0 23.0/28.0 Cu 1.0/2.0 N 0.10

Duplex Grades

Stainless steel grades Chemical composition % by mass max
UNS No AISI No. C Si Mn P S Cr Mo Ni Others
S31803 2205 0.030 1.00 2.00 0.030 0.020 21.0/23.0 2.5/3.5 4.5/6.5 N 0.08/0.20
S32304 2304 0.030 1.00 2.50 0.040 0.030 21.5/24.5 0.05/0.60 3.0/5.5 N 0.05/0.20; Cu 0.05/0.60
S32750 2507 0.030 0.80 1.20 0.035 0.020 24.0/26.0 3.0/5.0 6.0/8.0 N 0.24/0.32; Cu 0.50

Ferritic Stainless Steel Grades

Stainless steel grades Chemical composition % by mass max
UNS No AISI No. C Si Mn P S Cr Mo Ni Others
S40300 403 0.15 0.50 1.00 0.040 0.030 11.5/13.0
S40500 405 0.08 1.00 1.00 0.040 0.030 11.5/14.5 Al 0.10./0.30
S40800 0.08 1.00 1.00 0.045 0.045 11.5/13.0 0.50 Ti 12xC/1.10
S40900 409 This well known grade is replaced by S40910 S40920 and S40930
S41008 410S 0.08 1.00 1.00 0.040 0.030 11.5/13.5 0.60
S43000 430 0.12 1.00 1.00 0.040 0.030 16.0/18.0
S43400 434 0.12 1.00 1.00 0.040 0.030 16.0/18.0 0.75/1.25
S43600 436 0.12 1.00 1.00 0.040 0.030 16.0/18.0 0.75/1.25 Nb+Ta 5xC/0.80
S44200 442 0.20 1.00 1.00 0.040 0.035 18.0/23.0 0.60

Heat Resisting Grades

Stainless steel grades Chemical composition % by mass max
UNS No AISI No. C Si Mn P S Cr Mo Ni Others
S30409 304H 0.04/0.10 0.75 2.00 0.045 0.030 18.0/20.0 8.0/10.5
S30451 304N 0.08 0.75 2.00 0.045 0.030 18.0/20.0 8.0/10.5 N 0.10/0.16
S30900 309 0.20 1.00 2.00 0.045 0.030 22.0/24.0 12.0/15.0
S30908 309S 0.08 0.75 2.00 0.045 0.030 22.0/24.0 12.0/15.0
S30909 309H 0.04/0.10 0.75 2.00 0.045 0.030 22.0/24.0 12.0/15.0
S31000 310 0.25 1.50 2.00 0.045 0.030 24.0/26.0 19.0/22.0
S31008 310S 0.08 1.50 2.00 0.045 0.030 24.0/26.0 19.0/22.0
S31400 314 0.25 1.50/3.00 2.00 0.045 0.030 23.0/26.0 19.0/22.0
S31609 316H 0.04/0.10 0.75 2.00 0.045 0.030 16.0/18.0 2.00/3.00 10.0/14.0
S31651 316N 0.08 0.75 2.00 0.045 0.030 16.0/18.0 2.00/3.00 10.0/14.0 N 0.10/0.16
S32109 321H 0.04/0.10 0.75 2.00 0.045 0.030 17.0/19.0 9.0/12.0 Ti 4x(C+N) / 0.70
S34709 347H 0.04/0.10 0.75 2.00 0.045 0.030 17.0/19.0 9.0/13.0 Nb 8xC /1.00
S44600 446 0.20 1.00 1.50 0.040 0.030 23.0/27.0 0.75 N 0.25
N08800 800 (332) 0.10 1.00 1.50 0.045 0.015 19.0/23.0 30.0/35.0 Fe 39.5 min;
Al 0.15/0.60;
Ti 0.15/0.60
N08810 800H 0.05/0.10 1.00 1.50 0.045 0.015 19.0/23.0 30.0/35.0 30.0/35.0 Cu 0.75;
Fe 39.5 min;
Al 0.15/0.60;
Ti 0.15/0.60

Reading more: Stainless steel equivalent grades

Stainless Steel Chemical Elements

There are various chemical elements playing a important role in stainless steel, each of the different grades of stainless steel contains different alloying elements that contribute to its properties such as resistance to corrosion, strength, and flexibility, several critical elements with explanation are listed below:

Carbon (C)

  • Yield point and tensile strength increased with Carbon content increasing, but ductility and impact resistance decrease.
  • When carbon content exceed 0.23%, welding performance of steel will be not good, Carbon content is generally not more than 0.20%.
  • High carbon content can also affect the corrosion resistance of the steel, and make it easy to rust.
  • In addition, carbon can increase cold brittleness and aging of steel, like 304 and 304L, 304L is low carbon 304.

Silicon (Si)

  • In the process of making steel, silicon as reducing agent and oxidizing agent, containing 0.15 – 0.30% of silicon content
  • If silicon content is more than 0.50-0.60%, silicon significantly improve elastic limit, yield point and tensile strength, so it is widely used in spring steel.
  • Adding 1.0 – 1.2% silicon in the quenched and tempered steel, strength can be increased by 15 – 20%.
  • The combination of Silicon, Molybdenum, Tungsten and Chromium has the effect of improving the corrosion resistance and oxidation resistance.
  • Low carbon steel containing silicon 1 – 4%, with a high permeability, used in electrical industry silicon steel sheet
  • Silicon content increasing, not good for welding.

Manganese (Mn)

  • In the process of making steel, manganese is good agent and desulfurization agent, manganese content in common steel of 0.30 – 0.50%.
  • Carbon steel, adding more than 0.70% manganese, not only enough toughness, and have higher strength and hardness, improve steel quenching and performance of thermal processing
  • Manganese content increased, weakened the corrosion resistance of steel, reduce the welding performance. Manganese can improve the strength of steel.

Phosphorus (P)

In general, phosphorus is a harmful element in steel, increasing the cold brittleness of steel to result in welding performance deterioration, reducing ductility to influence the cold bending performance. It usually requires the phosphorus content in steel is less than 0.045%.

Sulfur (S)

  • Sulfur in the normal circumstances is also harmful elements. generating heat, reduce ductility and toughness
  • Sulfur on the welding performance is also bad, reducing corrosion resistance. So the sulfur content is less than 0.055%
  • Requirement of high quality steel are less than 0.040% of sulfur. The addition of 0.08-0.20% to the steel can improve the machinability, often referred to as free-cutting steel

Chromium (Cr)

  • Chromium can improve oxidation resistance and corrosion resistance, so it is an important alloying element of stainless steel
  • In the structural steel and tool steel, chromium can significantly improve the strength, hardness and wear resistance, but at the same time to reduce ductility and toughness

Nickel (Ni)

  • Nickel element can improve the strength of steel, and maintain a good ductility and toughness. Nickel has a higher corrosion resistance to acid and alkali, and has the ability of anti rust and heat resistance at high temperature
  • Improve toughness, so that the steel has a high strength, but also to maintain a good ductility and toughness
  • Nickel can improve the corrosion resistance and low temperature impact toughness
  • Nickel based alloys have a higher thermal performance

Molybdenum (Mo)

  • Molybdenum can make the grain refinement, improve the quenching and thermal properties
  • Under high temperature to maintain sufficient strength and creep resistance (long-term at high temperature under stress, deformation, said creep)
  • Mechanical properties can be improved with the addition of molybdenum in structural steel

Titanium (Ti)

  • Titanium steel is strong deoxidizing agent, making the internal structure of the steel dense, fine grain size, and reduce the aging sensitivity and cold brittleness
  • Improving the welding performance
  • Adding proper titanium to Austenitic stainless steels, avoiding Intergranular corrosion

Copper (Cu)

  • Copper can improve the strength and toughness, especially to atmospheric corrosion performance
  • Disadvantage is prone to cracking during thermal processing, the copper content more than 0.5% ductility significantly reduced
  • When the copper content is less than 0.50%, no effect on the welding property

Nitrogen (N)

Nitrogen can improve the strength of steel。