X-rays in Science and Industry

Abstract

X-RAYS are useful to industry in two ways: first, in getting the factory out of manufacturing difficulties, and, second, in the search for new scientific principles which may serve to correlate and explain known facts or be applied to the development of new structural products. (1) Solution of Factory Difficulties Probably the first work to employ X-rays in an effort to solve factory problems was done in the Research Laboratory of the General Electric Company, at Schenectady, New York. While a large steel casting several feet in diameter and about a half-inch thick was being machined to size in the factory, a tiny crack was found in the metal. The casting was taken to the laboratory and X-ray plates were taken, which showed a large hole in the inside of the metal. The spot indicated on the plate was punched out and the hole was thus exposed to view. The use of X-rays in work of this sort was very expensive, so that other methods of testing soon were developed for smooth-faced metal, which were just as good and considerably cheaper. The X-ray inspection of castings was therefore discontinued at the General Electric Company, but it has since been taken up by the United States Government at the Watertown Arsenal, where an investigation has been made of foundry processes. Occasionally, too, the Arsenal has made X-ray plates of special castings where considerations of human safety have justified the high cost of such work. The most outstanding example of this was the X-ray inspection of some steam fittings for a new high pressure steam line of the Boston Edison Company. (2) X-ray Diffraction It is in the discovery of new facts on which to base future factory processes that we find the greatest usefulness of X-rays. Practically all work of this sort depends upon the measurement of interatomic distances, so small that they cannot be measured directly. They are of the order of 10−8 cm. By using X-rays of known frequency it is possible to use an X-ray diffraction apparatus as a micrometer for making these extremely small measurements. The technic has been refined so that such measurements may be made easily, with an accuracy of one part in a thousand. This sort of apparatus, which was developed at the Research Laboratory of the General Electric Company, is now in use in the School of Chemistry and Physics at The Pennsylvania State College in investigating the properties of metals and their alloys. By measuring these minute units, it is already possible to predict some of the mechanical properties of metals, and to tell what happens when they form alloys. It is possible to show why copper is more ductile than iron, and why iron is more ductile than arsenic. Similar measurements on tungsten make it seem that the Coolidge process now in use is the only process by which that material can be made into a ductile wire. A more detailed discussion of some of these points follows.