IRON AND STEEL Pure iron is a silvery-white metal having a mild but brilliant luster. It is rarely seen in a pure state. Com mercial iron and steel comprise a se ries of alloys of iron with carbon, man ganese, chrome, nickel, tungsten, and other metals. These alloys have vari ous names, depending in some cases upon the added metal, as nickel steel, and in other cases upon the process of manufacture, as pig iron, wrought iron, steel, etc.
The qualities of iron vary in its different forms. The more carbon it contains, the darker it becomes. Wrought iron is in fibers and can be bent and welded. Steel and cast iron are in crystals, and are hard and brit tle. Iron is seven or eight times as heavy as water, according to condi tion. It transmits heat in comparison with silver about as 12 to 100. It is one of the hardest of metals, and also among the most difficult to melt, but varies from hardened steel, which is the hardest of metals, to wrought iron and pure iron, which are nearly as soft as copper. Ordinary cast iron is about three to five times as hard as copper. Iron wire of an inch in diameter may be drawn to a length of 49,000 feet without breaking.
Pig Iron.—This is an alloy of iron with from 1.5 to 7 per cent of car bon. It is produced in a blast fur nace, and shaped by casting it into molds. It is brittle and much easier to melt than wrought iron or steel. This is the crude product, usually first made from the ore and worked up into other forms by various proc esses of manufacture.
Wrought Iron. — This consists of crystals of an alloy of iron with a very little carbon held together by melted cinder or silicate added in the process of manufacture. It is very difficult to melt, but before melting becomes pasty, in which condition two pieces may be welded together. It does not harden. While plastic it may be hammered or rolled to any desired shape, which it will retain on cooling.
Steel.—This is a compound of iron obtained by casting in a fluid state, so as to give a malleable product. The
distinguishing properties of steel are that it can be fused, welded, and hardened by tempering. It contains from .075 to 1.5 per cent of carbon.
The addition of more carbon makes steel easier to melt, but harder to weld.
Compounds of Iron.—Among well known compounds of iron are cya nides of iron with potassium, known as red and yellow prussiate of potash and Prussian blue. Also the mixture of sulphur with iron known as green vitriol or copperas, used in dyeing, in the manufacture of inks, as a deodo rizer, etc.
To Temper Iron and Steel. — The alloys of iron and steel containing .05 per cent or more of carbon are capa ble of being hardened or tempered by heating to redness and plunging into some cooling liquid. The carbon which was formerly mixed mechanically with the iron is chemically dissolved in the iron by this process. Temper may af terwards be withdrawn by reheating.
To Caseharden Iron or Steel.—Mix in powdered form equal parts of prus siate of potash, sal ammoniac, and saltpeter. Heat the iron to redness, roll it in this mixture, and quench it in a bath of cold water containing 2 ounces of prussiate of potash and 4 ounces of sal ammoniac to each gallon.
Or dissolve in 30 gallons of water 1 bushel of salt, pound of prussiate of potash, pound of cyanide of pot ash, and pint of oil of vitriol; heat the iron to redness and quench in this mixture.
To Soften Iron or Steel.—To drill hard iron or steel, dissolve 1 ounce of gum camphor in 1 pint of alcohol and add 1 pint of turpentine. Pour from a can as you would oil.
Or, if the iron can be heated with out damage, as in sled runners, heat it to a cherry red and lay on the spot to be drilled a small piece of sulphur, and let it stand until cool. This sof tens the iron, which can then be drilled without difficulty.
To Draw the Temper of Iron or Steel.—Cover the metal with tallow, heat it slowly in a charcoal fire, and let it cool of itself.