Molybdenum and its applications
Ferritic stainless steel
The ferritic family includes stainless steels with a broad range of corrosion resistance. The most widely used ferritic grade is Type 430, which has a corrosion resistance just below that of Type 304 austenitic stainless steel. At the lower end of corrosion resistance is Type 409, which is commonly used in automotive exhaust systems. The most corrosion resistant ferritic grades are the super ferritic stainless steels such as UNS S44660 and S44735, which have a corrosion resistance in many environments that is equal to that of the 6% Mo super austenitic grades.
Ferritic grades are commonly used in appliances, tube applications and automotive exhaust systems. Because of their very low nickel content, ferritic stainless steels are less costly on a weight basis than the austenitic grades with a similar corrosion resistance. However, their lower toughness and less favourable fabrication properties limit their use. Ferritic grades that contain more than about 12% chromium are also susceptible to a loss of ductility due to alpha prime precipitation that occurs when heated to temperatures of 315 to 525°C (600 to 950°F). Because of this, the higher alloyed ferritic grades typically have a maximum service temperature of 315°C (600°F).
Chemical Composition* (weight%) and PREN of some common ferritic stainless steels**
| Grade |
No. |
UNS |
EN No. |
C |
N |
Cr |
Ni |
Mo |
Cu |
Other |
PREN*** |
| 403 |
S40300 |
--- |
0.15 |
1.0 |
0.5 |
11.5
13.0
|
0.60 |
… |
… |
|
11.5-12.5 |
| 405 |
S40500 |
--- |
0.08 |
1.0 |
1.0 |
11.5
14.5
|
0.60 |
… |
… |
Al 0.10-0.30 |
11.5-13 |
| 409 |
S40910 |
1.4512 |
0.030 |
1.0 |
1.0 |
10.5
11.7
|
0.50 |
… |
0.030 |
Ti 6x(C=N) min.,
0.50 max., Nb 0.17
|
10.5-12 |
| 430 |
S43000 |
1.4016 |
0.12 |
1.0 |
1.0 |
16.0
18.0
|
0.75 |
… |
… |
|
16-17 |
| 439 |
S43035 |
--- |
0.03 |
1.0 |
1.0 |
17.0
19.0
|
0.50 |
… |
0.030 |
Ti [0.2+4(C+N)] min.,
1.10 max., Al 0.15
|
17-18 |
| 434 |
S43400 |
1.4113 |
0.12 |
1.0 |
1.0 |
16.0
18.0
|
… |
0.75
1.25
|
… |
|
18.5-20 |
| 436 |
S43600 |
1.4526 |
0.12 |
1.0 |
1.0 |
16.0
18.0
|
… |
0.75
1.25
|
… |
Nb 5xC min.,
0.80 max.
|
18.5- 20 |
| 444 |
S44400 |
1.4521 |
0.025 |
1.0 |
1.0 |
17.5
19.5
|
1.0 |
1.75
2.50
|
0.035 |
(Ti+Nb) [0.20+4(C=N)]min.,
0.80 max.
|
23.5-25 |
| XM-27 |
S44660 |
--- |
0.030 |
1.0 |
1.0 |
25.0-
28.0
|
1.0
1.35
|
3.0
4.0
|
0.040 |
(Ti+Nb) 0.20-1.0,
Ti + Nb 6x(C=N) min
|
36-40 |
| --- |
S44735 |
--- |
0.030 |
1.0 |
1.0 |
28.0
30.0
|
1.0 |
3.6
4.2
|
0.045 |
(Ti+Nb) 0.20-1.00,
(Ti +Nb) 6x (C+N) min.
|
40-43 |
Notes:
