With the quickening of pace due to these steels, the designer is asked to remodel machine tools so that they may stand up against new pressures and speeds. A lathe thus re-patterned is mentioned by Mr. Gledhill: it absorbs sixty-five horse power as against twelve formerly, and has a belt trebled in width so as to measure twelve inches. Mr. Oberlin Smith expects high-speed steel to have other effects on machine design than the conferring of new strength: he looks for a rivalry keener than ever between rotary and reciprocating tools. In his judgment the milling tool, which can be speeded indefinitely, will encroach more and more on the planer, limited as the planer is by its movement being to and fro.
When work on cast iron must proceed at the utmost pace, a jet of air, delivered to the chips with force enough to clear them off as fast as they are formed, enables the speed to be quickened, while, at the same time, the life of the cutter is lengthened.[18]
[18] The foregoing pages on steel have been revised by Professor Bradley Stoughton, of the School of Mines, Columbia University, New York. He contributes at the end of this chapter a brief [list of books] for the reader who may wish to know something of the literature of iron and steel.
Alloys for Electro-Magnets.
In electrical art the alloy employed for electro-magnets should be permeable by magnetism fully and easily, otherwise dynamos and motors will waste energy as their magnetism is constantly gained, lost, or reversed. Once more the experimenter is Mr. Robert A. Hadfield of Sheffield, who produces an excellent alloy by uniting iron with 2.75 per cent. silicon, .08 per cent. manganese, .03 per cent. sulphur, .03 per cent. phosphorus. This alloy is improved by being heated to between 900° and 1100° C., followed by quick cooling; then being reheated to between 700° to 800° C., and cooled very slowly.
Iron is largely used as an electrical conductor, so that it is well to know how its conductivity is affected by ordinary admixtures. In experiments with sixty-eight specimens, Professor W. F. Barrett alloyed iron separately with carbon, aluminium, silicon, chromium, manganese, nickel, cobalt, and tungsten. In every case there was a loss of conductivity, and usually in a degree proportioned to the atomic weight of the added ingredient. Between one element and another there was often a wide disparity of effect. For example, in admixtures, each of one per cent., tungsten increased the resistance of a conductor by two per cent., while aluminium did seven-fold as much harm.
Magnetic Alloys of Non-Magnetic Ingredients.
We have so long been accustomed to thinking that there must be iron in everything magnetic that we hear with astonishment that metals each insusceptible of magnetism, when united strongly display this property. Such is the discovery of Mr. Fr. Heusler, of Dillenburg, near Wiesbaden. He noticed one day that an alloy of manganese, tin, and copper adhered to a tool which he had accidentally magnetized. In the course of experiments Mr. Heusler found that carbon, silicon, and phosphorus did not confer magnetism; while arsenic, antimony, and bismuth did so, all three metals being diamagnetic, that is, placing themselves at right angles to a common steel magnet above which they are freely suspended. An alloy of remarkable magnetic strength was composed of copper 61.5 per cent., manganese 23.5 per cent., and aluminium 15 per cent. This alloy is brittle and considerable changes of temperature but slightly affect its magnetism. When a little lead is added magnetism disappears between 60° and 70° C. This alloy therefore is magnetic when placed in cold water; when the water is heated the magnetism disappears before the water boils, only to reappear when the water cools. The main interest of these discoveries is that the new alloys bridge the gap betwixt magnetic and diamagnetic bodies, that is, they join the iron, nickel, and cobalt group, which place themselves along the line of a magnetic field, with the diamagnetic elements, bismuth, antimony, zinc, tin, lead, silver, and arsenic, which place themselves at right angles to the lines of a magnetic field. We have been accustomed to suppose that magnetism is a property possessed by only a few elements; these alloys show us that magnetism may arise as a result of grouping atoms, none of which by itself has any magnetism whatever. Indeed it may be possible to make an alloy more magnetic than iron, furnishing the electrician with electro-magnets of new power.
Anti-Friction Alloys.
We have briefly glanced at recent progress in the art of alloying in so far as it has produced steels of new strength, elasticity, or hardness; new ability to resist abrasion or high temperatures, new capacity for magnetism, new indifference to changes of temperature as affecting dimensions. Alloying has of late years conferred other gifts upon industry, of which one example may be cited from among many of equal importance. Friction levies so grievous a tax upon the mechanic and the engineer that they are quick to seize upon any material for bearings which reduces friction. As the result of extensive experiments Dr. C. B. Dudley recommends an alloy of tin, copper, a little phosphorus, with ten to fifteen per cent. of lead. He finds the loss of metal by wear under uniform conditions diminishes as the lead is increased and the tin diminished.