The Metallographic Method of Classification
By aid of the microscope it is possible actually to look into the structure of these materials.
TABLE A
IRON AND STEEL PRODUCTION OF THE UNITED STATES FOR 1912
Part of a Chemical Laboratory Where 6,000 Samples a Year Are Analyzed
By cutting in any direction through a piece of metal or alloy, polishing the surface exposed very clean and smooth and then etching (corroding) slightly with acid, the exposed grains of the metal may be seen when sufficiently magnified. Not only may the grains of metal be seen, but certain of the other constituents which are present are visible. Photographs, also, can be taken by attaching a camera to the microscope. This method of analysis, which is known as “metallography,” has proved as valuable an aid to the metallurgist as it proved to the geologist when applied to the study of rocks and geological specimens.
Machine for Determining Strength of Iron and Steel Bars
The metallography of wrought iron, cast iron, malleable iron and steel differentiates them to us with considerable accuracy, as is shown by a glance at the accompanying photomicrographs, as photographs taken through the microscope are called.