HAVE ANY MATERIAL TESTS BEEN FORGOTTEN?

摘要

Basic tests on a material used in the construction of pressure vessels and pipes close to the yieldpoint temperature, namely with? The tensile test specimen to determine the yield point, tensile strength, necking down andelongation,? The impact test specimen to determine the energy absorbed at defined temperatures (notchedbar test),? The CT specimen to determine KIC or JI values, and? Other metallographic and corrosive analyses of materialsprovide an overview of the behaviour of the components manufactured with the tested material underspecified operating conditions. Tests on notched specimens supplementary to the above-mentionedtests deliver information about the notch sensitivity in the tested material.In the past, long-term tests on notched material specimens under constant load at temperaturesbetween 300 and 350 °C have always been disregarded.The tests described here, which are conducted over a total period of up to 25,000 hours on finegrainedstructural steel (WB36) using CT specimens under a constant load, confirm the occurrence oftime-dependent creep at temperatures from 340 to 350°C in the vicinity of the crack tips, accompaniedby crack growth. The fractographic and metallographic findings on the fracture surfaces formed underconstant load are explained.Reference is made to the potential consequences as well as to counter-measures that can beincorporated in the pressure component design in this temperature range.