Abstract
An apparatus has been devised so as to be able to measure quantitatively the rate of hydrogen diffusion through black heart malleable cast iron sheet (3mm thickness).
Operation of the apparatus was as follows:
A sheet of the metal was clamped between a stout glass cylinder with a polished flange at the bottom and a strong glass saucer with a substantial flange, the upper surface of which was grounded.
The base of the saucer was connected with a manometer which served as gastight sealing. The metal sheet (specimen) was exposed to the attack of acid on one side. Through the metal sheet the diffused hydrogen was absorbed in the vacuum of the saucer, and the accumulated hydrogen was measured by the manometer.
The area exposed to acid of the specimen of 9cm in diameter was 36.30cm2, and its chemical compositions was C 2.81%, Si 0.95%, Mn 0.38%, and S 0.08.
The acids used were 1N solution of HCl and 1N-3N of H2SO4, and the temperature was 10°-30°C.
The result is as follows:
The time required for saturating the specimens of metal with diffused hydrogen varies depending on the structure and temper carbons.
(1) It is 1, 620-10, 080min. for the specimens of lamellar pearlite containing small temper carbons of up to 0.025mm in diameter.
(2) It is 420-1, 080min. for the spcimens of bull's eye structure and containing the same small temper carbons as the above.
(3) It is 70-300min, for the specimens of ferrite structure containing small temper carbons of 0.025mm and up to 0.05mm in diameter.
(4) It is 1-45min. for the specimens of ferrite structure containing large temper carbons of 0.075mm and 0.10mm.
