鋼の酸洗脆化並に脆化防止劑に就いて(第1報) (I)

Abstract

By means of the bending and tensile tests together with determination and penetration of hydrogen, the author investigated the acid-brittleness of various steels dipped in HCl or H2SO4 solution where FeS was contained. The results are as follows : (1). The Acid-brittleness is accelerated by S'', As… P… Pb… and Hg… in acid solution. And the S'' ion is the most strong and probable accelerator in the actual pickling procedure. (2). Only in the HCl or H2SO4 solution, the alloy steel does not absorb hydrogen and not be embrittled, but the carbon steel absorbss hydrogen and is embrittled. (3). The acid-brittleness of steels dipped in H2S saturated acid solution is the most typical one to investigate. (a) In the case of embrittled rimmed-steels, the tensile strength increases slightly at the beginning of dipping, but later decreases again, and inspite of the heat-treatment of the samples, granular frocculant defect appears in the fractures and the sample steel cracks along the grain boundary. But in the case of killed steels which was tempered at low temperature, the tensile strength decreases to the great extent, the yield point disappeares, and the frocculant defects, which is very similar to the flake in alloy steel, appear in the fractures. In the case of steels tempered at high temperature, the tensile strength and the yield point are not changed at all and no froccurant defects are seen in the fractures. (b) The higher the pickling temperatures are, the more the acid-brittleness decreasse. This is due to the decrease of the supersaturated hydrogen in the specimen by at high pickling temperature. (4). By standing specimens in the boiling water, the occluded hydrogen removes easily from the specimen's surfaces and the original properties are gradually. restored, but in case of frocculant defective specimens, their original properties are not restored. (5). The acid -brittleness is prevented by the addition of such substances as these which remove S'' from the H2S acid solution by means of changing S'' into insoluble compounds or of oxidising S'' into SO4'' in the pickling solution. The anther found that the results of this work would solve many incoinsitant results of acid-britlleness reported by many investigators.