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Vol.8, No1, 2008,
pp. 55-64 |
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SIGNIFICANCE OF CRACKS IN THE HEAT-AFFECTED-ZONE OF STEELS FOR ELEVATED TEMPERATURE APPLICATION Ljubica Milović Faculty of Technology and Metallurgy, University of Belgrade |
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Abstract Damage and failure of welded joints are classified according to the crack position. Type IV cracking occurs in welded joints in creep-resistant steels, due to enhanced rate of creep void formation in the presence of coarse grained carbide particles in fine-grained and intercritically annealed regions of the heat-affected zone. Creep damage accumulation causes premature failure. So, the evaluation of residual service life of equipment operating at elevated temperatures in power plants and in process industry requires analysis of material behaviour in subcritical and in creep regime. The occurrence of type IV cracks is observed in 9–12% chromium steels. The problem can be solved by reaustenitisation and tempering heat treatment, but this is a rare practical option, and components have to be designed taking into account reduced creep strength and life. Keywords: type IV cracks, P91 steel, HAZ regions, creep |
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full article (1.27 MB)
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