.316 L Stainless Steel Hot Electron Theory Of Aging Research

For the thermal aging occurring in the stainless steel 316L used for the sand-control expandable screen in the high temperature environment of deep wells and ultra-deep wells, the atomic configuration probabilities of stainless steel 316L were calculated. Based on Empirical Electron Theory of Solid and Molecules (EET), the valence electron structure parameters of the stainless steel 316L were calculated in the different temperatures of 25℃, 100℃,200℃,300℃,400℃by using Bond Length Difference method (BLD). Dynamical tensile test on 316L was proceeded in the temperatures of 25℃,100℃,150℃,200℃,300℃, 350℃. After dynamical tensile test, the datum of stress-strain curves and mechanical properties were analyzed, as well as microstructure organization and fracture morphology.The atomic configuration probabilities and valence electron structure parameters show that the atomic configuration probability of unit cell with C in 316L is more 3 orders than the unit without C. So the thermal aging is mainly decided by the valence electron structures of unit cell without C. When the C/at%>0.32%, the formula for the calculated lattice constant ac of Fe-C unit cell is adaptive. When the temperature increases from 25℃to 400℃, s increases gradually, but n'a decreases gradually and Nl decreases in various degree, which indicate that in this temperature range, the phase stability of the material increases gradually, while the strength, hardness, bonding force, strength of phase combination and elongation decrease. When the temperature increases from 25℃to 200℃, solid solution strengthening coefficient Sc decreases gradually. When the temperature rises to 300℃, Sc increases significantly. Afterwards, when the temperature rises to about 400℃, Sc decreases gradually. It shows that the strength and hardness of the material decreases gradually form 25 to 200℃. while the temperature rises to about 300℃, the strength rebounds. When the temperature increases from 25℃to 250℃, elongation decreased greatly, while the temperature rises to 350℃, the elongation is almost unchanged. This is a solid solution strengthening effect reflected in the valence electron structure. From the strengthening effect of C in alloy, it can be concluded that C atoms dissolved in the phase structure unit of alloy have strong interactions with the alloying elements, which not only increases appropriately the material strength and hardness, but also increases the solid solution strengthening effect of C atom and alloying elements on the matrix. On the whole, in addition toσof y-Fe is smaller than s of y-Fe-C, s of unit cell without C is much greater than s with C, which indicates that the stability of phase structure of unit cell without C is stronger than the unit cell with C.The datum of mechanical properties from the tensile test, the results of analyzing the microstructures and fracture morphologies show that the parameters, such asσ,n'a,Sc Nl, based on the valence electron calculation are consistent fully the dynamic tensile test datum and analyzing results, which reveals the underlying reasons of stainless steel 316L thermal aging phenomenon from the microscopic electronic structure calculation.