Strip with gradient properties by annealing in reactive atmospheres

Interstitial Free (IF) steels have excellent deep drawing capabilities and non-ageing properties. These steel grades still have some disadvantages such as a generally weak mechanical strength and high reactivity in the grain boundaries during galvannealing, which produces brittle Fe-Zn-intermetallic compounds. Furthermore the resistance to secondary work embrittlement is rather low due to the absence of soluble interstitials in grain boundaries. A good remedy is the insertion of a defined amount of carbon into the surface after recrystallization started. The possibilities and limits of a change in surface properties of Ti-IF sheet steel by a short time annealing in reactive atmospheres (CO, H2, N2) were evaluated: The introduction of carbon interstitials during continuous annealing increases mechanical strength associated with bake hardening and moderate age hardening and a good formability. However, to achieve fully recrystallized grains with a favourable (111)-texture the carburizing treatment should start after new grains have nucleated. A short carburizing treatment during continuous annealing can significantly improve the resistance of Ti-IF and P-Ti/Nb-IF steel against secondary work embrittlement (SWE). The r-value was slightly influenced by the added carbon atoms, the r-values were in the range between 3 and 2. The higher the carbon potential of a carburizing atmosphere, the higher is the carbon pickup. This could lead to the formation of an austenite layer which has a much higher solubility for carbon than the ferrite.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2000

Author dc:creator

• Ahrens, Michael Kurt

Contributors dc:contributor

• Bleck, Wolfgang

• info:eu-repo/classification/ddc/660
• Technische Chemie
• IF-Stahl
• Mikrolegierter Stahl
• Titan
• Einsatzhärten
• Mechanische Eigenschaft

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123100%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:61437