Hydrogen attack of steel. Progress report, April 1, 1977--March 31, 1978

Four carbon steels of approximately equivalent carbon content and varying mainly in the method of steelmaking, i.e., semi-killed, fully-killed, REM-treated, and electroslag refined (ESR), are being studied to determine the effect of deoxidation practice and inclusion morphology on the hydrogen attack of carbon steel. To date tests have been run on a cold-rolled steel (to develop experimental techniques), the semi-killed, and REM-treated materials. Heat treatment for the latter two steels consisted of 60 minutes at 890/sup 0/C and air cooling to give an average grain size of ASTM No. 8. Significant results are: (1) hydrogen attack results in substantial (factor of ten) greater growth normal to the rolling plane than in the rolling plane; (2) metallography and fractography show a few areas with many microscopic bubbles in the REM-treated steel indicating high bubble nucleation rates on some boundaries and much lower on most boundaries; (3) incubation times, t/sub i/, are on the order of 4 to 5 times that predicted from Weiner's equation. The anisotropy relatives to the rolling plane occurred in all three steels treated. Thus it would seem reasonable that such variables as inclusions or segregation tend to determine the local extent of hydrogen attack. This anisotropy will be examined further in the next series of experiments by comparing all four steels. Of special interest will bethe results of the ESR steel, in which the inclusion content and solidification segregation is significantly reduced