The previous report has shown the rupture characteristics of mild steel at 450°C under the stress conditions of a relatively small pulsating stress being superimposed on the static tensile stress which is sufficient to produce a creep rupture.
The work described in this paper is concerned with the rupture properties of 1Cr-1/2 Mo steel and their welds at 550°C under the similar conditions of stress to those mentioned above.
The amplitude-to-mean stress ratios A (σ
a/σ
m) selected for this experiment were 0(static), 10, 20 and 40%.
The results ogtained are summarized as follows:
1. The mean stress versus time for rupture diagram in log-log plots showed that the rupture life decreased with an increasing stress amplitude ratio A and the static stress rupture had the longest life.
2. The stress-rupture diagram plotted on the basis of maximum (crest) stress in the stress cycle in view of fatigue behavior showed that the rupture life increased with an increasing stress ratio A and the static stress rupture had the shortest life, being incompatible with fatigue behavior.
3. Rupture characteristics under pulsating stress were investigated from creep behavior by the same method of analysis as reported in previous paper. The superposition of alternating stress resulted in a decline of rupture strength, supposedly due to the dynamic effect, for the base metal but in no decline in the welded joint except for the shot-life tests.
4. Ductilities of test specimen, determined by true strain at the fractured section, did not show remarkable difference in static and pulsating stress rupture between base metal and welded joint.
Welded joint showed lower ductilities than base metal.
5. There was no remarkable difference in situation of fracture in welded specimens between static and pulsating stress rupture. Most of their fractures occured at the base metal adjoining the heat affected zone in short-life test and approached the deposit metal with an increase of rupture life.
抄録全体を表示