Alleima® 353 MA - oxidation and carburization properties

Due to the high silicon content and the addition of rare earth metals (REM), Alleima® 353 MA* has very high resistance to oxidation. The REM addition also contributes to an improved scale adhesion during temperature cycling.

Carburization

The ability to form a dense chromium oxide gives Alleima® 353 MA its very good resistance to carburization. Figure 6 shows results from carburization tests performed at the independent National Physics Laboratory (NPL) London. It illustrates how Alleima® 353 MA compares with other high temperature grades.

In the illustrations below, carburization tests at 1050°C (1922ºF) show that in steam cracking tubes for ethylene production, Alleima® 353 MA is better protected from carburization than other common wrought grades. The Cr number below each illustration indicates the remaining free Cr in the metal matrix. Low numbers indicate a high degree of carburization.

Surface of tube
Alleima® 353 MA 25 Cr-35 Ni* 25 Cr-25 Ni*

Cr=15-18%

Cr=5%

Cr <5%

* Competing material used today

Center of tube
Alleima® 353 MA 25 Cr-35 Ni* 25 Cr-25 Ni*

Cr=22-25%

Cr=20-22%

Cr <5%

* Competing material used today

Test conditions

Surface of tube
Carburization 120 h
Temperature = 1050ºC (1922ºF)

Total test time 1100 h (8 cycles)

Center of tube
Decoking 20 h
Temperature = 1050ºC(1922ºF)

*353 MA is a trademark owned by Outokumpu OY.