The Effect of Simulated Welding Conditions on Austenite Decomposition Kinetics.
Abstract
The polished surface technique weld simulator was used to obtain quantitative information on the phase transformations taking place in the weld heat affected zone (HAZ) of a Fe-0.6C steel. The progress of the ferrite to austenite and austenite to pearlite transformations were determined by quantitative metallography and related to the thermal history, as measured by microthermocouples, throughout the specimen. The alpha yields gamma transformation is observed to be complete at 780 C under a heating of 50 C/s while the pearlite in the HAZ coarsens and dissolves to form an austenite initially inhomogeneous; both these processes initiate at internal 'faults' in the pearlite colonies. On cooling a pearlitic type morphology with an interlamellar spacing not resolved by optical microscopy is formed from this austenite. Inflections were observed in the cooling curves measured in the weld simulator which did not correspond exactly to the pearlite transformation temperature at that point but were a reflection of the recalescence effect caused by the latent heat evolved by a transformation occurring at some nearby point. By comparing the weld simulator and continuous cooling transformation data it was concluded that inhomogeneous austenite favors the nucleation of a non-conventional pearlite. Cooling rates between 625 C and 525 C and between 525 C and 425 C were found to characterize well the fraction of pearlite present in the microstructure which, due to the rapid cooling experienced, does not contain the equilibrium carbon content.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1981
- Accession Number
- ADA111189
Entities
People
- A. J. Criado
- B. G. Mellor
- F. A. Calvo
Organizations
- Complutense University of Madrid