Difference between Austenitic and Ferritic Stainless Steel

 

What Is The Difference Between Austenitic And Ferritic Stainless Steel

Ferritic stainless steels contain little to no nickel in the composition. They have chromium in high amounts, in some cases up to 27% but the lack of nickel makes them prone to corrosion of all sorts. However, the strength is higher than or equal to their austenitic counterparts. The austenitic stainless steels have chromium and nickel in the composition with some grades having molybdenum in the content. This provides the materials with good strength and added corrosion resistance.

Why Ferritic And Austenitic Stainless Steels Are Not Heat Treatable

The heat treatment methods involve heating up to a higher temperature and cooling of the materials. Since the ferritic and austenitic steels have carbon in their composition, heating up to elevated temperatures would result in the formation of chromium carbide grains which would reduce the corrosion resistance dramatically. Also, the heat treatment procedures doe not change the austenitic grain structure in a way to improve the strength. Even after compromising the corrosion resistance, the heat treatment doesn’t result in high strength. Therefore bot the austenitic and ferritic steels are not heat treated.


Austenitic And Austenitic-ferritic Stainless Steel Forgings

Forging is the process hammering the heated steel with high pressures to shape them into the desired forms. Austenitic and ferritic steels can be forged to make the different products made in these steels. The forging allows to reduce the surface porosity which also provides a fine grain structure to the product. The forging process improves the tensile strength, fatigue strength and the lifespan of the products. With forging, the products also become ductile. For these advanced properties, the forged products are preferred in most applications.

Annealing Of Austenitic And Ferritic Steels

Both these steels could not be heat treated. Heat treatment is a process that involves heating up the product after manufacture. Instead, these materials could be annealed, a heating and cooling process that is employed during manufacturing. The annealing does not improve the strength, but it improves the hardness of the material. The austenitic stainless steels are the ones that are mostly annealed to retain the corrosion resistance and improve the hardness. The ferritic steel types generally don’t require annealing.


Irradiated Austenitic And Ferritic Steels

Irradiation is a process of removing neutrons from the nuclei of an atom. The irradiation processes take place in high temperature applications, especially in the nuclear power generation and other nuclear related activities. When steels are exposed to irradiation temperatures and environments, they get irradiated and the yield strength decreases greatly. To avoid the irradiation effect, the steels have to be kept at optimum temperatures. The materials do not irradiate faster under a range of temperature. The different grades of steels would have different optimum temperatures.


Austenitic And Ferritic Microstructure

The grain structure in the metallurgic microstructure defines the ferritic, austenitic, martensitic and duplex steel types. The austenite or gamma phase iron is the forming particle of the austenitic stainless steel. It is a non-magnetic particle structure. The ferrite on the other hand has high magnetic properties in the microstructure. The selection of these materials for various applications consider these magnetic properties in addition to the strength and corrosion resistance.

 

Most Frequently used grades of Ferritic Stainless Steel
  • 405
  • 409L
  • 410L
  • 430
  • 439
  • 430Ti
  • 441
  • 434
  • 436
  • 444
  • 447

 

Mechanical Properties Database Of Ferritic stainless steel
EN Grade ASTM Grade UNS Austenitic (A) or Ferritic (F) Stainless Steel Rp 0.2 Rp 1.0 Rm Elongation A Elongation A80 Hardness Hardness
MPa MPa MPa % % HR HB
1.4000 TYPE 410S S41008 F > 240 400 - 600 > 19 > 19
1.4003 S40977 F > 280 450 - 650 > 20 > 20
1.4016 TYPE 430 S43000 F > 260 430 - 600 > 20 > 20
1.4510 TYPE 439 S43035 F
1.4512 TYPE 409 S40900 F > 220 380 - 560 > 25 > 25
1.4520 F
1.4589 F
A
1.4301 TYPE 304 S30400 A > 230 > 260 540 - 750 > 45 > 45
1.4303 TYPE 305 S30500 A > 220 > 250 500 - 650
1.4306 TYPE 304L A > 220 > 250 520 - 700 > 45 > 45
1.4307 TYPE 304L S30403 A > 220 > 250 520 - 700 > 45 > 45
1.4310 TYPE 301 S30100 A > 250 > 280 600 - 950 > 40 > 40
1.4318 TYPE 301LN S30153 A > 350 > 380 650 - 850 > 40 > 35
1.4372 TYPE 201 S20100 A > 350 > 380 680 - 880 > 45 > 45
1.4509 S43940 F > 230 430 - 630 > 18 > 18
1.4513 F
1.4541 TYPE 321 S32100 A > 220 > 250 520 - 720 > 40 > 40
1.4550 TYPE 347H S34709 A
1.4622 S44330 F > 300 430 - 630 > 22
1.4401 TYPE 316H S31609 A > 240 > 270 530 - 680 > 40 > 40
1.4404 TYPE 316L S31603 A > 240 > 270 530 - 680 > 40 > 40
1.4420 S31655 A > 350 > 380 650 - 850 > 35
1.4432 TYPE 316L A > 240 > 270 550 - 700 > 40 > 40
1.4435 TYPE 316L A > 240 > 270 550 - 700 > 40 > 40
1.4436 TYPE 316 A > 240 > 270 550 - 700 > 40 > 40
1.4521 TYPE 444 S44400 F > 300 420 - 640 > 20 > 20
1.4571 TYPE 316Ti S31635 A > 240 > 270 540 - 690 > 40 > 40
1.4462 S32205 D > 500 700 - 950 > 20 > 20
1.4362 S32304 D > 450 650 - 850 > 20 > 20
1.4410 S32750 D > 550 750 - 1000 > 20 > 20
1.4016 TYPE 430 S43000 F > 260 430 - 600 > 20 > 20
1.4301 TYPE 304 S30400 A > 230 > 260 540 - 750 > 45 > 45
1.4307 TYPE 304L S30403 A > 220 > 250 520 - 700 > 45 > 45
1.4310 TYPE 301 S30100 A > 250 > 280 600 - 950 > 40 > 40
1.4318 TYPE 301LN S30153 A > 350 > 380 650 - 850 > 40 > 35
1.4376 A > 400 > 420 600 - 900 > 40 > 40
1.4401 TYPE 316H S31609 A > 240 > 270 530 - 680 > 40 > 40
1.4404 TYPE 316L S31603 A > 240 > 270 530 - 680 > 40 > 40
1.4420 S31655 A > 350 > 380 650 - 850 > 35
1.4501 S32760 D
1.4571 TYPE 316Ti S31635 A > 240 > 270 540 - 690 > 40 > 40
FDX 27 S82031 D
1.4162 S32101 D > 530 700 - 900 > 30 > 20
1.4662 S82441 D > 550 750 - 900 > 25 > 20
1.4547 S31254 A > 320 > 350 650 - 850 > 35 > 35
1.4438 TYPE 317L S31703 A
1.4529 N08926 A
1.4652 S32654 A > 430 > 470 750 - 1000 > 40 > 40
1.4466 S31050 A
1.4539 N08904 A > 240 > 270 530 - 730 > 35 > 35
A
1.4006 TYPE 410 S41000 M < 600 > 20 > 20
1.4021 TYPE 420 M < 700 > 15
1.4024 M < 650 > 20 > 20
1.4031 M < 760 > 12 > 12
1.4034 M < 780 > 12 > 12
1.4110 M < 850 > 12 > 12
1.4116 M < 850 > 12 > 12
1.4122 M < 900 > 12 > 12
PH < 1275 > 5 > 5
1.4568 TYPE 631 PH < 1030 > 19 > 19
1.4835 S30815 A > 310 > 350 650 - 850 > 40 > 37
1.4724 F
1.4828 A > 230 > 270 550 - 750 > 30 > 28
1.4833 TYPE 309S S30908 A > 210 > 250 500 - 700 > 35 > 33
1.4841 TYPE 314 A
1.4845 TYPE 310S S31008 A > 210 > 250 500 - 700 > 33
1.4948 TYPE 304H S30409 A > 230 > 260 530 - 740 > 45 > 45
1.4305 TYPE 303 A
1.4307 TYPE 304L S30403 A > 220 > 250 520 - 700 > 45 > 45
1.4404 TYPE 316L S31603 A > 240 > 270 530 - 680 > 40 > 40
PH < 1275 > 5 > 5

 

Chemical Compatibility Chart of Ferritic stainless steel
GRADE EN WEIGHT %
CR OTHER ELEMENTS
405 1.4000 12.0 - 14.0 -
409L 1.4512 10.5 - 12.5 6(C+N)<Ti<0.65
410L 1.4003 10.5 - 12.5 0.3<Ni<1.0
430 1.4016 16.0 - 18.0 -
439 1.4510 16.0 - 18.0 0.15+4(C+N)<Ti<0.8
430Ti 1.4511 16.0 -18.0 Ti: 0.6
441 1.4509 17.5 - 18.5 0.1<Ti<0.6

0.3+3C<Nb<1.0

434 1.4113 16.0 - 18.0 0.9<Mo<1.4
436 1.4513 16.0 - 18.0 0.9<Mo<1.4

0.3<Ti<0.6

444 1.4521 17.0 - 20.0 1.8<Mo<2.5

0.15+4(C+N)<Ti+Nb<0.8

447 1.4592 28 - 30.0 3.5<Mo<4.5

0.15+4(C+N)<Ti<0.8

 

grade chart of Austenitic stainless steel
  • 301
  • 304
  • 304L
  • 303
  • 321
  • 316
  • 316L
  • 316Ti

 

Chemical Composition Austenitic stainless steel
EURONORM (EN) / WERKSTOFF NUMBER EN DESIGNATION AISI / SS MO C CR NI OTHERS
1.4310 X10CrNi18-8 301 NS 0.10 17.5 8 NS
1.4301 X5CrNi18-10 304 NS < 0.07 18.5 9 NS
1.4307 X2CrNi18-9 304L NS < 0.030 18.5 9 NS
1.4305 X8CrNiS18-9 e 303 NS < 0.10 18 9 0.3
1.4541 X6CrNiTi18-10 321 NS < 0.08 18 10.5 Ti: 5×C ≤ 0.70
1.4401 X5CrNiMo17-12-2 316 2.2 < 0.07 17.5 11.5 NS
1.4404 X2CrNiMo17-12-2 316L 2.25 < 0.030 17.5 11.5 NS
1.4571 X6CrNiMoTi17-12-2 316Ti 2.25 < 0.08 17.5 12 Ti: 5×C ≤ 0.70

 

ferritic stainless steel Welding Process
  • Plasma arc welding (PAW)
  • Laser welding
  • High frequency welding (HF)
  • Gas metal arc welding (MIG, MAG, GMAW)
  • Shielded metal arc welding (MMA, SMAW)
  • Resistance welding
  • Gas tungsten arc welding (GTAW, TIG)