Austenite recrystallization and carbonitride precipitation in niobium microalloyed steels

Journal Article · Sat Dec 31 23:00:00 EST 1988 · Metallurgical Transactions, (Section) A: Physical Metallurgy and Materials Science; (USA)

DOI:https://doi.org/10.1007/BF02647491· OSTI ID:5217098

Speer, J G; Hansen, S S ^[1]

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1. Homer Research Labs., Bethlehem Steel Corp., Bethlehem, PA (US)

The response of austenite to thermomechanical treatment is investigated in two series of niobium microalloyed steels. Optical and electron metallographic techniques were used to follow the austenite recystallizaiton and carbonitride precipitation reactions in these steels. The first series of steels contained a constant level of 0.05Nb, with carbon levels varying from 0.008 to 0.25 pct. It was found that a lower carbon concentration results in faster austenite recrystallization due to a smaller carbonitride supersaturation which leads to a reduced precipitate nucleation rate. The second series of steels was designed with a constant carbonitride supersaturation by simultaneously varying the Nb and C concentrations while maintaining a constant solubility product. In these steels, the recrystallization kinetics increase as the volume fraction of Nb(C,N) is reduced and/or as the precipitate coarsening rate is increased. The volume fraction of carbonitrides increases as the Nb:(C + 12/14 N) ratio approaches the stoichiometric ratio of approximately 8:1. An experiment to determine whether Nb atoms dissolved in the austenite could exert a significant solute-drag effect on the recrystallization reaction indicated that 0.20Nb in solution could reduce the rate of recrystallization compared to a Nb-free C-Mn steel.

• OSTI ID: 5217098
• Journal Information: Metallurgical Transactions, (Section) A: Physical Metallurgy and Materials Science; (USA), Journal Name: Metallurgical Transactions, (Section) A: Physical Metallurgy and Materials Science; (USA) Vol. 20A:1; ISSN MTTAB; ISSN 0360-2133
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALLOYS
AUSTENITIC STEELS
CARBON
CHEMICAL REACTION KINETICS
CRYSTAL STRUCTURE
DEFORMATION
ELECTRON MICROSCOPY
ELEMENTS
IRON ALLOYS
IRON BASE ALLOYS
KINETICS
LOW TEMPERATURE
MANGANESE ALLOYS
METALLOGRAPHY
MICROSCOPY
MICROSTRUCTURE
NIOBIUM ALLOYS
NONMETALS
PHASE STUDIES
REACTION KINETICS
RECRYSTALLIZATION
SOLUBILITY
STEELS
STOICHIOMETRY