Mn, Si and Ti in cast stainless steel at elevated temperature

ABSTRACT

ACI HH II is an austenitic castable stainless steel for high-temperature applications such as grates in a Grate-Kiln indurator. Eight different alloy compositions have been used to evaluate the oxide formation and the microstructural evolution during an isothermal heat treatment at 800°C with a holding time of 200 h in an atmosphere containing 20% O2–N2. Residual ferrite is transformed into sigma phase during the heat treatment while secondary carbides are precipitated in the austenite. Silicon will form a thinner oxide but will reduce its adherence to the steel. Additions of Ti are beneficial for the properties of the oxide layer as the oxide is well adherent and thinner, while additions of Mn increase the growth rate of the oxide and enhance the risk of growth stresses in the oxide. It is proposed that by combing the beneficial effects of both Ti and Si it is possible to suppress the malign effects of Mn additions.

KEYWORDS:

• Grate-Kiln
• stainless-steel
• high temperature
• microsegregation
• Si
• Mn
• Ti

Acknowledgement

We would like to send our gratitude to Professor Ragnar Tegman, who was indispensable in the discussions regarding the results.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors would like to thank Hjalmar Lundbohm Research Centre (HLRC) and Luossavaara-Kiirunavaara AB (LKAB) for their financial support.