| Title |
Effect of Cooling Rate kon the Formation of δ - Ferrite in Type 304 Stainless Steel |
| Authors |
김선구(Sun K . Kim); 김낙준(Nack J . Kim); 신건(Geon Shin); 이창희(Chang H . Lee) |
| Abstract |
In order to investigate the effect of cooling rate on the formation of δ-ferrite in type 304 stainless steel. Gleeble experiment. TIG welding and laser surface melting were carried out. The transformation mechnism of δ-ferrite to austenite was studied by interrupted quenching experiment of unidirectional solidification. Transformation of δ-ferrite to austenite in the 1400 and 1160℃ range has the profound effect on δ-ferrite content. δ-ferrite content was about 74% at the final solidification, which decreased to about 8% at room temperature. As the cooling rate increased from 0.5 to 9.7×10³C/s, δ-ferrite content increased from 3 to 20%, but the further increase in cooling rate from 9.7×10³ to 3.3×10⁴C/s decreased δ-ferrite content from 20 to 9.7%. With increasing the cooling rate, δ-ferrite morphology changed from vermicular ferrite, lacy ferrite and to euteetic ferrite with concurrent decrease in the δ-ferrite content. |