Effects of Tempering and Stress Relieving Heat Treatments on Elevated Temperature Stress of 2.1/4Cr-1Mo Steel
1979 Volume 65 Issue 7 Pages 861-868
Details
1979 Volume 65 Issue 7 Pages 861-868
To clarify the effects of tempering and stress relieving heat treatments on elevated temperature strength of 2.1/4Cr-1Mo steel, teenile test and creep rupture test were carried out. Specimens were normalized and tempered at 640°-760°C or normalized and tempered at 680°C and subsequently stress relieved at 640°-720°C. Change in the substructure of specimens during creep rupture test was examined through electron microscope using extracted replicas. Results obtained are as follows.
1) Elevated temperature tensile strength of stress relieved specimen decreases monotonously with the increase in the tempering parameter (T.P.) of the stress relief treatment. On the contrary, that of tempered specimen becomes independent of T.P. in the range of T.P. beyond about 19.5×103.
2) Larson-Miller's master rupture curves for stress relieved specimens and for tempered (680°C) specimen change monotonously, but those for normalized specimen and for tempered (640°, 720° and 760°C) specimens show a tendency to shift to higher stress in the range of the Larson-Miller's parameter (PL.M.) below about 18.5×103.
3) In high PL.M. range creep rupture stress decreases with the increase in the T.P. subjected to the specimen. At a critical PL.M. which is roughly equal to the T.P. of that specimen master rupture curve converges into the curve for normalized specimen.
4) The change in the density of needle-like carbide during tempering or stress relieving heat treatments and also during creep rupture test roughly corresponds with the change in the master rupture strength of each specimen.
