R. Taillard et al., EFFECT OF SILICON ON CGHAZ TOUGHNESS AND MICROSTRUCTURE OF MICROALLOYED STEELS, Metallurgical and materials transactions. A, Physical metallurgy andmaterials science, 26(2), 1995, pp. 447-457
The aim of this article is to present the beneficial effect of a reduc
tion of silicon content on coarse-grained heat-affected zone (CGHAZ) t
oughness. This study was achieved with experimental and industrial E35
5 structural steels. These 0.09 wt pet C steels were Ti-microalloyed w
ith silicon contents ranging from 0.05 to 0.5 wt pet. First, we demons
trate that the CGHAZ toughness is predominantly affected by the volume
fraction of retained austenite (gamma r). Second, we show that the ex
istence of retained austenite pertains only to its carbon enrichment.
This enrichment is promoted essentially by an increase of the silicon
level due to the retarding action of silicon on the formation of carbi
des in ferrite as well as in austenite. In the same way, the increase
of silicon content slows down the decomposition of retained austenite
into pearlite. The reduction of the silicon content of the steel great
ly increases the ductility of the CGHAZ through the decrease of the vo
lume fraction of retained austenite.