الفهرس 
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Abstract
This experimental investigation is based on the study of the behavior of low carbon steel in case of the as received and welded conditions when it is subjected to Stress Corrosion Cracking (SCC) situations. This type of steel has many industrial applications especially in power plant manufacturing. It is used in the production of the fins of the economizer of the power plant and subjected to this condition of corrosive environment when it is subjected to the exhaust gases.
Material is received in the form of 1 mm thickness cold rolled steel sheets. The welding process used is Gas Tungsten Arc Welding (GTAW) which commonly used in power plant fabrication.
For the purpose of static loading Stress Corrosion Cracking testing, a special test rig was constructed and provided with an installation for the testing in a corrosive medium.
Specimens were divided into three categories; base metal, as welded and post weld stress relieved specimens. The notched specimens were V-notched and square notched specimens. The tests were carried out in open air as well as in 30% sodium hydroxide as a corrosive medium.
The results of V-notched specimens for both conditions of open air and corrosive medium testing were represented by plotting the applied load versus enhance and also by plotting the crack intensity factor (K) versus enhance. While the squared notch specimens were represented by plotting the applied load versus the endurance.
The results show that the sharp notch specimens provide good resistance of static loading stress corrosion cracking (SCC), either in open air or in 30% sodium hydroxide as a corrosive medium, compared with the square notched specimen. This may be attributed to the fact that the sharp notch propagates in one direction perpendicular to the specimen geometrical axis while the square notch has two directions of crack propagation inclined 450 to the geometrical axis which is the direction of maximum shear stress.
It is also noticed that the specimens examined in 30% sodium hydroxide as a corrosive medium show lower results than that examined in open air and this may be attributed to the corrosive action of sodium hydroxide.
GTAW specimens examined in both open air and 30% sodium hydroxide give poor resistance to static loading Stress Corrosion Cracking (SCC) compared with the base material.
Examination of fracture surface of some specimens determine the mode of failure due to static loading Stress Corrosion Cracking (SCC) which was transgranular in case of testing in air and both intergranular and transgranular in case of testing in 30% sodium hydroxide.
from this experimental work, it can be concluded that notch configuration affects the resistance of material to SCC. In case of relatively higher loads notch configuration has no significant effect. Crack intensity factor (K) increases as the ratio a/w increases specially in case of lower loads which lead to relatively larger endurance. Notch depth to specimen width ratio (a/w) affects the resistance to SCC either in case of testing in open air or in a corrosive medium. Crack propagation is trans-granular in case of air testing while it exhibits trans-granular as well as inter-granular mode of fracture in case of testing in a corrosive medium. Welded specimens exhibit lower resistance to Scc either in air or in 30% Sodium Hydroxide solution as compared with the base material, although thermal stress relieving improves the welded specimens resistance to SCC.