PRECIPITATION OF TITANIUM NITRIDE IN LOW-ALLOYED STEEL DURING COOLINGAND DEFORMATION

The precipitation of titanium nitride in undeformed solid carbon-manga nese steel has been investigated by means of metallography and electro n microscopy at in-situ melted samples the cooling of which was interr upted at different temperatures for a defined time. The deformation-in duced precipitation of titanium nitride was studied on samples which w ere in-situ melted in a torsion plastometer, deformed after solidifica tion, re-deformed after a holding time, and quenched. Additionally, 50 mm slabs were investigated after direct rolling in a pilot plant, par tially with a preceding soaking. In the range of delta ferrite fast ho mogenization of segregated titanium takes place. No TIN nuclei were fo rmed. In undeformed austenite some large precipitates were formed indi cating the solidification structure. In the 1200 to 1100 degrees C ran ge particle sizes between 20 and 70 nm were reached. A high density of deformation-induced particles smaller than in nm could be obtained at or below 1050 degrees C. The density of the particles increased with decreasing deformation temperature. After fast cooling, below 1000 deg rees C also in undeformed material finely dispersed precipitates were formed.