Abstract
1. The low-cycle strength (N≤104 cycles) of welded joints in steel 09G2S under rigid loading in the range of elevated temperatures (293–873°K) is limited by the strength of the metal of the heat-affected zone in the temperature range of dynamic strain-aging (473–673°K). The difference in endurance at high temperature may attain a factor of 1.5–2 in dependence on the number of load cycles in comparison with the analogous characteristic at normal temperature. 2. Raising the test temperature to 823–873°K causes a doubling of the strain amplitude at failure of the base metal with ea>1% (N<103 cycles) in comparison with the strain amplitude under conditions of normal temperature. 3. The cyclic elastoplastic properties of the metal of welded joints in steel 09G2S depend on the test temperature in the following way: at T=293°K the base metal is cycli-cally stable, the metal of the heat-affected zone and the seam metal are cyclically slightly softening materials; at T=473–673°K (the temperature of dynamic strain-aging) the material of all zones of the welded joint become cyclically hardening; at T>823°K there is recovery of the initial cyclic strain properties of the material. 4. In the investigated range of elevated temperatures the static characteristics of strength and ductility of the metal of welded joints in steel 09G2S-EShP change to a considerable degree (by a factor of two to six) in a complex manner. 5. In the temperature range under consideration the fatigue crack propagates by the mechanism of formation of fatigue grooves. Signs of brittle failure were not detected in the fatigue zone or in the final fracture. 6. In specimens subjected to fatigue tests at 823°K the degree of development of processes of recovery and recrystallization is substantially higher than at 473°K; this is due to the increased rupture strain amplitude of low cycle fatigue.
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