The Working of Steel | Page 5

as just explained; but unfortunately, a 53-point steel (containing 0.53 per cent carbon) may locally be called something like "No. 3 temper."
A widely used method of classifying steels was originated by the Society of Automotive Engineers. Each specification is represented by a number of 4 digits, the first figure indicating the class, the second figure the approximate percentage of predominant alloying element, and the last two the average carbon content in points. Plain carbon steels are class 1, nickel steels are class 2, nickel-chromium steels are class 3, chromium steels are class 5, chromium-vanadium steels are class 6, and silico-manganese steels are class 9. Thus by this system, steel 2340 would be a 3 per cent nickel steel with 0.40 per cent carbon; or steel 1025 would be a 0.25 plain carbon steel.
Steel makers have no uniform classification for the various kinds of steel or steels used for different purposes. The following list shows the names used by some of the well-known makers:
Air-hardening steel Chrome-vanadium steel Alloy steel Circular saw plates Automobile steel Coal auger steel Awl steel Coal mining pick or cutter steel Axe and hatchet steel Coal wedge steel Band knife steel Cone steel Band saw steel Crucible cast steel Butcher saw steel Crucible machinery steel Chisel steel Cutlery steel Chrome-nickel steel Drawing die steel (Wortle)
Drill rod steel Patent, bush or hammer steel Facing and welding steel Pick steel Fork steel Pivot steel Gin saw steel Plane bit steel Granite wedge steel Quarry steel Gun barrel steel Razor steel Hack saw steel Roll turning steel High-speed tool steel Saw steel Hot-rolled sheet steel Scythe steel Lathe spindle steel Shear knife steel Lawn mower knife steel Silico-manganese steel Machine knife steel Spindle steel Magnet steel Spring steel Mining drill steel Tool holder steel Nail die shapes Vanadium tool steel Nickel-chrome steel Vanadium-chrome steel Paper knife steel Wortle steel
Passing to the tonnage specifications, the following table from Tiemann's excellent pocket book on "Iron and Steel," will give an approximate idea of the ordinary designations now in use:
Approximate Grades carbon range Common uses
Extra soft 0.08-0.18 Pipe, chain and other welding purposes; (dead soft) case-hardening purposes; rivets; pressing and stamping purposes. Structural (soft) 0.15-0.25 Structural plates, shapes and bars for (medium) bridges, buildings, cars, locomotives; boiler (flange) steel; drop forgings; bolts. Medium 0.20-0.35 Structural purposes (ships); shafting; automobile parts; drop forgings. Medium hard 0.35-0.60 Locomotive and similar large forgings; car axles; rails. Hard 0.60-0.85 Wrought steel wheels for steam and electric railway service; locomotive tires; rails; tools, such as sledges, hammers, pick points, crowbars, etc. Spring 0.85-1.05 Automobile and other vehicle springs; tools, such as hot and cold chisels, rock drills and shear blades. Spring 0.90-1.15 Railway springs; general machine shop tools.
CHAPTER II
COMPOSITION AND PROPERTIES OF STEEL
It is a remarkable fact that one can look through a dozen text books on metallurgy and not find a definition of the word "steel." Some of them describe the properties of many other irons and then allow you to guess that everything else is steel. If it was difficult a hundred years ago to give a good definition of the term when the metal was made by only one or two processes, it is doubly difficult now, since the introduction of so many new operations and furnaces.
We are in better shape to know what steel is than our forefathers. They went through certain operations and they got a soft malleable, weldable metal which would not harden; this they called iron. Certain other operations gave them something which looked very much like iron, but which would harden after quenching from a red heat. This was steel. Not knowing the essential difference between the two, they must distinguish by the process of manufacture. To-day we can make either variety by several methods, and can convert either into the other at will, back and forth as often as we wish; so we are able to distinguish between the two more logically.
We know that iron is a chemical element--the chemists write it Fe for short, after the Latin word "ferrum," meaning iron--it is one of those substances which cannot be separated into anything else but itself. It can be made to join with other elements; for instance, it joins with the oxygen in the air and forms scale or rust, substances known to the chemist as iron oxide. But the same metal iron can be recovered from that rust by abstracting the oxygen; having recovered the iron nothing else can be extracted but iron; iron is elemental.
We can get relatively pure iron from various minerals and artificial substances, and when we get it we always have a magnetic metal, almost infusible, ductile, fairly strong, tough, something which can be hardened slightly by hammering but which cannot be hardened by quenching. It has certain chemical properties, which need not be