On some remarkable properties of the characteristic constituent of Steel

Abstract

The microscopical examination of suitably prepared specimens of iron and steel with moderately high magnifying powers shows that there are two very well marked constituents. One of these is comparatively soft, and is undoubtedly iron free from carbon. The other is intensely hard, and most probably contains combined carbon, since it occurs in white cast iron, blister steel and other varieties known to contain carbon in that state. Independant of these there is obviously another constituent which has microscopical characters entirely unlike those of the others, and gives beautiful colours like mother of pearl. For this reason I have always called it the pearly constituent. Laterly I have made use of very much higher magnifying powers, and find that with an illuminator contrived some years ago by the late Richard Beck, a power of 650 linear can be employed with ease. This shows that the pearly constituent really has a structure closely like that of pearl, being made up of alternating thin plates. After very carefully studying most of the leading varieties of iron and steel, I have come to the conclusion that these plates are alternating layers of soft iron free from carbon, and of the intensely hard compound with carbon, already mentioned. The laminae are often of extreme thinness, those of the soft iron being often about 1/40000th inch in thickness, and those of the hard substance only 1/80000th, so that we have alternating ridges and grooves about 1/60000th inch apart. The only satisfactory explanation for this remarkable ...