316 Nb Steel

Steel name: 316 Nb
Diagram No.: 8180
Type of diagram: TTP
AISI/SAE designation: ~316
Chemical composition in weight %: <0.10% C, <0.50% Si, <2.00% Mn, 16.50-19.50% Cr, 2.25-2.75% Mo, 11.00-14.50% Ni, 8xC-1.00% Nb, <0.05% N
Steel group: Austenitic stainless steels
Note: TTT curves of initial and final precipitation stages of sigma phase in delta-ferrite of 316 Nb steel. The TTT diagram of s phase precipitation in 316 Nb steel is presented in figure. It is found that the precipitation occurs between 700 and 1000°C when the treatment time does not exceed 120 minutes. For each annealing temperature, the transformation begins in the d-ferrite islands. At 1000°C, the transformation begins after 120 minutes of annealing and it stops before all the d-ferrite is transformed. Between 750 and 950°C, d-ferrite islands are totally transformed in less than 120 minutes. The precipitation rate is particularly high between 800 and 900°C where the transformation begins after about 1 minute of annealing and ends after 10 to 12 minutes. A longer isothermal hold of 93 hours at 875°C shows that the sigma phase appears also in austenitic matrix after the d-ferrite islands are totally transformed.
Reference: Not shown in this demo version.
Xavier Ledoux, et al., KINETICS OF SIGMA PHASE PRECIPITATION IN NIOBIUM-STABILIZED AUSTENITIC STAINLESS STEEL AND EFFECT ON THE MECHANICAL PROPERTIES, Materials Science Forum Vols. 783-786 (2014) pp 848-853, doi:10.4028/www.scientific.net/MSF.783-786.848

Transformation Diagram


Click the image to enlarge the diagram.

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