Abstract
Crack-resistance properties of weldment constituents are required in a safety analysis of highly stressed penstock produced from 700 MPa nominal yield strength high-strength low alloy steel. Small size specimens ( 10 × 10 × 55 mm ) with fatigue pre-crack in base metal (BM), weld metal (WM) and heat-affected zone (HAZ) were used in multi-specimens test method for J Ic evaluation. Tests were performed at room and low temperatures, down to −98°C. A low-temperature cabinet for these tests has been designed based on flow of nitrogen gas, developed by heating liquid nitrogen. Fracture toughness of BM is found to be high at room temperatures (800 kN/m), but ‘pop-in’ effect reduced it at temperatures below −40°C (650 kN/m at −40°C, 300 kN/m at −80°C). Similar behaviour was found for WM and HAZ, but with lower fracture toughness values compared to BM and significant scatter of results.
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