METHOD OF TESTING PIPE STEELS FOR STRESS CORROSION CRACKING Russian patent published in 2016 - IPC G01N17/00 

FIELD: test equipment.

SUBSTANCE: invention relates to corrosion tests, specifically to methods of testing high-strength steel for susceptibility to corrosion cracking. Method of testing pipe steels for stress corrosion cracking (SCC) comprises first cutting a model pattern of rectangular shape, removing dirt, degreasing and drying. Then on working part of model sample is fixed a sealed cell with corrosion solution and between metal surface of working part of said sample and inner surface of cell with corrosive solution is put a plate made of porous non-metallic material. Further, before performing test, method comprises calibrating model samples by determining correspondence between magnitude of applied force or displacement of grip and value of resulting stress on outer surface of samples. Then model sample is loaded, while setting initial load to σ₀ = σ_t, where σ_t is yield strength of pipe steel. Further, method includes selecting mode of cyclic loading and stepped static loading of model sample, increasing stress in it with a pitch of 30 MPa, without changing stress asymmetry factor and frequency of cycles. Then tests are carried out until crack initiation and based on results of experiments, plotting a curve of displacement of grip (S) of test model sample of pipe steel versus number of load cycles (N), where based on change of inclination (appearance of inflection on S-N line) moment of initiation of cracks is determined. After tests model sample is released from cell with corrosion medium and surface of working part of sample is analysed using optical measuring devices, while resistance of SCC steel is evaluated based on test results on at least two samples.

EFFECT: broader functional capabilities.

1 cl, 6 dwg, 1 tbl