A description and study of high-temperature oxidation of steel articles

A study of the durability and destruction of metal construction elements under high-temperature oxidation

“…Taking account of the fact that the stresses on the interior surface of the pipe due to oxidation (the uneven distribution of oxide in the metal and the formation of an oxide film) increase monotonically as the oxide film grows, while the mfiximal levels of thermal stresses (from thermocycling) decrease, we obtain Thus, formulas (4)- (7), together with the expressions for the thermal [7] and concentration [1,7] stresses (caused by oxidation) make it possible to compute the useful life of an armature in the shape of a cylindrical pipe when it is subject to oxidation and thermocycling. Here the shape of a cycle is determined by the parameters [7] x h~, X c~, t=~, that characterize the heating, cooling, and maximal drop in temperature on the time interval A'c ~.…”

“…In the computations the time interval of oxidation was partitioned into segments of length at most 2.5 years. If the circumferential concentration of stresses on the inner surface of the pipe [1,7] exceeds the conditional yield limit of the material of the armature from some time on during the oxidation, the values of these stresses are replaced by the yield limitcr0a in relations (6) and (7), which determine the durability of the armature under isothermal oxidation starting from that instant of time. …”

“…To estimate the damage to the metal resulting from both creep due to tensile stresses and fatigue due to periodic loading we chose the crit~5;on of extended durability and its refinement in the case of tensile equivalent loads and thermocycle shapes that vary in time in the oxidation process, We compute the working lifetime and exhib# the regularities of destructioa of steel pipes with a mass-isolated internal surface in a high-temperature oxidizing environment.The authors [1,7] have proposed a mathematical model of high-temperature oxidation of metals. In the original relations the results of experimental studies are taken into account more fully, in particular, the presence of a rather thick transition region between the oxidized film and the pure metal.…”

“…Quantitative studies of durability were carried out for an armature made of X18H10T steel of thickness r~ -r 2 = 10 -3 , 2.10 -3 , 25-10 -3 m. The armature was oxidized at a constant temperature of 700~ for which the resistaace to tear is S = 9.024.108 Pa; the mechanodiffusion characteristics that are applied in the formulas of [1,7] The method of experimentally determining the conditional limit of durability Cr(r is given in [2,3]. The results of experiments for determining Crlr for the type of nonrusting austenitic steels under consideration are described in [6,10,12].…”