Strengthening of low-interstitial steels by strain-ageing treatments

Journal Article · Tue Aug 04 04:00:00 EDT 1998 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(98)00226-7· OSTI ID:651142

Starling, J; Saimoto, S; Boyd, J D ^[1]

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1. Queen`s Univ., Kingston, Ontario (Canada). Dept. of Materials and Metallurgical Engineering

Formable low-carbon automotive sheet steels can be designed to achieve a 30--50 MPa strength increment during paint baking. This so-called bake hardening process is a form of static strain ageing, whereby dissolved carbon or nitrogen atoms segregate to the dislocations generated during temper rolling and press forming. In ultra-low carbon interstitial-free steels, the concentration of C and N in solution is determined by the equilibrium partitioning between ferrite and precipitates of Ti- or Nb carbonitrides. Thus, during continuous annealing the concentration of interstitial atoms could increase due to precipitate dissolution. The reverse process could occur during cooling due to NbC precipitation at 800--700 C or Fe{sub 3}C precipitation at 400--300 C. The purpose of the present study was to determine the effects of the annealing process variables (temperature, time and cooling rate) on the solute carbon concentration in a series of interstitial free (IF) steels.

• OSTI ID: 651142
• Report Number(s): CONF-980202--
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 4-5 Vol. 39; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DISLOCATIONS
HEAT TREATMENTS
INTERSTITIALS
LOW ALLOY STEELS
PRECIPITATION
STRAIN AGING
ULTIMATE STRENGTH