The Harvey process of making armor plate is an important recent development in cementation and case hardening, and is covered by his United States patents No. 376,194, January 10, 1888, and No. 460,262, September 29, 1891. It consists, see [Fig. 260], in embedding the face of the plate in carbon, protecting the back and sides with sand, heating to about the melting point of cast iron, and subsequently hardening the face. The Krupp armor plate, now rated as the best, is made under the patent to Schmitz and Ehrenzberger, No. 534,178, February 12, 1895.
In coating with metals, the so-called “galvanizing” of iron is an important art. This was introduced by Craufurd (British patent No. 7,355, of April 29, 1837), and consisted in plunging the iron into a bath of melted zinc covered with sal ammoniac. In more recent years the tinning of iron has become an important industry, and machines have been made for automatically coating the plates and dispensing with hand labor, examples of which are found in patents No. 220,768, October 21, 1879, Morewood; No. 329,240, October 27, 1885, Taylor, et al., and No. 426,962, April 29, 1890, Rogers and Player.
In metal founding the employment of chill moulds is an important step. Where any portion of a casting is subjected to unusual wear, the mould is formed, opposite that part of the casting, out of metal, instead of sand, and this metal surface, by rapidly extracting the heat at that point by virtue of its own conductivity, hardens the metal of the casting at such point. The casting of car wheels by chill moulds, by which the tread portion of the wheel was hardened and increased in wearing qualities, is a good illustration. Important types are found in patents to Wilmington, No. 85,046, December 15, 1868; Barr, No. 207,794, September 10, 1878, and Whitney, re-issue patent, No. 10,804, February 1, 1887.
In wire-working great advances have been made in machines for making barbed wire fences. The French patent to Grassin & Baledans, in 1861, is the first disclosure of a barbed wire fence. This art began practically, however, with the United States patent to Glidden and Vaughan for a barbed wire machine, No. 157,508, December 8, 1874, re-issued March 20, 1877, No. 7,566, and has assumed great proportions. A machine for making wire net is shown in patent to Scarles, No. 380,664, April 3, 1888, and wire picket fence machines are shown in patents to Fultz, No. 298,368, May 13, 1884, and Kitselman, No. 356,322, January 18, 1887. Machines for making wire nails were invented at an early period, but the product found but little favor until about 1880, when they began to be extensively used, and have almost entirely supplanted cut nails for certain classes of work, since their round cross section and lack of taper give great holding power and avoid cutting the grain of the wood. In 1897 the wire nails produced in the United States amounted to 8,997,245 kegs of 100 pounds each, which nearly doubled the output of 1896. The output of cut nails for the same year was 2,106,799 kegs.
The bending of wire to form chains without welding the links has long been done for watch chains, etc., but in late years the method has extended to many varieties of heavy chains. The patents to Breul, No. 359,054, March 8, 1887, and No. 467,331, January 19, 1892, are good examples.
An interesting class of machines, but one impossible of illustration on account of their complication, are machines for making pins. In earlier times pins had their heads applied in a separate operation. Making pins from wire and forming the heads out of the cut sections began in the Nineteenth Century with Hunt’s British patent No. 4,129, of 1817. This art received its greatest impetus, however, under Wright’s British patent No. 4,955, of 1824. A paper of pins containing a pin for every day in the year, and costing but a few cents, gives no idea to the purchaser of the time, thought and capital expended in machines for making them, and yet were it not for such machines, rapidly cutting coils of wire into lengths, pointing and heading the pins, and sticking them into papers, the world would be deprived of one of its most ubiquitous and useful articles. Many tons of pins are made in the United States weekly, and it is said that 20,000,000 pins a day are required to meet the demand.
In the metal working art the making of [firearms] and projectiles has grown to wonderful proportions. Cutlery and builders’ hardware is an enormous branch; wire-drawing, sheet metal-making, forging, and the making of tools, springs, tin cans, needles, hooks and eyes, nails and tacks, and a thousand minor articles, have grown to such proportions that only a bird’s-eye view of the art is possible.
In the making of shot, the old method was to pour the melted metal through a sieve, and allow it to drop from a tower 180 feet or more in height. David Smith’s patent, No. 6,460, May 22, 1849, provided an ascending current of air through which the metal dropped, and which, by cooling the shot by retarding its fall and bringing a greater number of air particles in contact with them, avoided the necessity of such high towers. In 1868, Glasgow and Wood patented a process of dropping the shot through a column of glycerine or oil. Still another method is to allow the melted metal to fall on a revolving disk, which divides it into drops by centrifugal action.
Alloys.—Over 300 United States patents have been granted for various alloys of metals. The so-called babbit metal was patented in the United States by Isaac Babbit, July 17, 1839, and in England, May 15, 1843, No. 9,724. This consists of an antifriction compound of tin, 10 parts, copper, 1 part, and antimony, 1 part, and is specially adapted for the lubricated bearings of machinery. Phosphor bronze, introduced in 1871, combines 80 to 92 parts copper, 7 of tin, and 1 of phosphorus (see United States patents to Lavroff, No. 118,372, August 22, 1871, and Levi and Kunzel, No. 115,220, May 23, 1871). The addition of phosphorus promotes the fluidity of the metal and makes very clean, fine and strong castings. In alloys of iron, chromium steel is covered by patents to Baur, No. 49,495, August 22, 1865; No. 99,624, February 8, 1870, and No. 123,443, February 6, 1872; manganese steel, by Hadfield’s patent, No. 303,150, August 5, 1884; aluminum steel, by Wittenström’s patent, No. 333,373, December 29, 1885, and phosphorus steel, by Kunkel’s patent, No. 182,371, September 19, 1876. The most recent and perhaps most important, however, is nickel steel, used in making armor for battleships. This is covered by Schneider’s patents, Nos. 415,655, and 415,657, November 19, 1889.
In 1878 England led the world in the iron industry with a production of 6,381,051 tons of pig iron, as compared with 2,301,215 tons by the United States. In 1897 the United States leads the world in the following ratios: