Fracture toughness characteristics of jumbo size rolled steel angles

To study the effect of temperature, heat-treatment, and rate of loading on the energy absorption characteristics of the steel used in the rolling of ultra-large size angles (300 x 300 x 35 and 350 x 350 x 35 mm size), tests were carried out on Charpy V-notch specimens machined from as-supplied and heat-treated (470°C for 400 seconds) coupons. Three different loading rates -- dynamic (impact), intermediate (50 mm/min. crosshead speed), and slow (0.5 mm/min. crosshead speed) -- and five different temperatures — 20°C, 0°C, -20°C, -40°C, -65°C — were included in the investigation. From the test data, critical plane-strain stress-intensity factors were estimated for each combination of specimen condition, loading rate, and service temperature, and the possibility of brittle fracture type of failure investigated. From the experimental and analytical study, it is concluded that these angles can be used in as-supplied condition, under slow rate of loading, at temperatures as low as -65°C, without any possible brittle fracture type of failure.