hardness. A malleable cast iron is produced through a easily as the low-carbon steels. They are used for crane prolonged  annealing  process. hooks, axles, shafts, setscrews, and so on. INGOT IRON.— Ingot iron is a commercially pure iron  (99.85%  iron)  that  is  easily  formed  and  possesses good ductility and corrosion resistance. The chemical analysis and properties of this iron and the lowest carbon steel are practically the same. The lowest carbon steel, known as dead-soft, has about 0.06% more carbon than ingot iron. In iron the carbon content is considered an impurity and in steel it is considered an alloying ele- ment. The primary use for ingot iron is for galvanized and  enameled  sheet. Steel Of all the different metals and materials that we use in our trade, steel is by far the most important. When steel was developed, it revolutionized the American iron industry.  With  it  came  skyscrapers,  stronger  and  longer bridges, and railroad tracks that did not collapse. Steel is manufactured from pig iron by decreasing the amount of  carbon  and  other  impurities  and  adding  specific amounts of alloying elements. Do not confuse steel with the two general classes of iron: cast iron (greater than 2% carbon) and pure iron (less than 0.15% carbon). In steel manufacturing, con- trolled amounts of alloying elements are added during the molten stage to produce the desired composition. The composition of a steel is determined by its applica- tion and the specifications that were developed by the following:  American  Society  for  Testing  and  Materials (ASTM), the American Society of Mechanical Engi- neers (ASME), the Society of Automotive Engineers (SAE), and the American Iron and Steel Institute (AISI). Carbon steel is  a term applied to a broad range of steel that falls between the commercially pure ingot iron and the cast irons. This range of carbon steel may be classified into four groups: HIGH-CARBON   STEEL/VERY   HIGH-CAR- BON STEEL.— Steel in these classes respond well to heat treatment and can be welded. When welding, spe- cial electrodes must be used along with preheating and stress-relieving procedures to prevent cracks in the weld areas. These steels are used for dies, cutting tools, mill tools, railroad car wheels, chisels, knives, and so on. LOW-ALLOY,   HIGH-STRENGTH,   TEM- PERED  STRUCTURAL  STEEL.—  A special low- carbon  steel,  containing  specific  small  amounts  of alloying elements, that is quenched and tempered to get a yield strength of greater than 50,000 psi and tensile strengths of 70,000 to 120,000 psi. Structural members made  from  these  high-strength  steels  may  have  smaller cross-sectional areas than common structural steels and  still  have  equal  or  greater  strength.  Additionally, these steels are normally more corrosion- and abrasion- resistant. High-strength steels are covered by ASTM specifications. NOTE: This type of steel is much tougher than low-carbon steels. Shearing machines for this type of steel must have twice the capacity than that required for low-carbon  steels. STAINLESS STEEL.— This type of steel is clas- sified by the American Iron and Steel Institute (AISI) into  two  general  series  named  the  200-300  series  and 400  series.  Each  series  includes  several  types  of  steel with  different  characteristics. The 200-300 series of stainless steel is known as AUSTENITIC. This type of steel is very tough and ductile in the as-welded condition; therefore, it is ideal for welding and requires no annealing under normal atmospheric  conditions.  The  most  well-known  types  of steel in this series are the 302 and 304. They are com- monly called 18-8 because they are composed of 18% chromium  and  8%  nickel.  The  chromium  nickel  steels Low-Carbon Steel . . . . . . . . 0.05% to 0.30% carbon are the most widely used and are normally nonmagnetic. Medium-Carbon Steel . . . . . . 0.30% to 0.45% carbon The 400 series of steel is subdivided according to High-Carbon Steel . . . . . . . . 0.45% to 0.75% carbon their  crystalline  structure  into  two  general  groups.  One Very High-Carbon Steel . . . . . 0.75% to 1.70% carbon group is known as FERRITIC CHROMIUM and the other  group  as  MARTENSITIC  CHROMIUM. LOW-CARBON STEEL.— Steel in this classifi- Ferritic Chromium.— This type of steel contains cation is tough and ductile, easily machined, formed, 12% to 27% chromium and 0.08% to 0.20% carbon. and welded. It does not respond to any form of heat These alloys are the straight chromium grades of stain- treating,  except  case  hardening. less steel since they contain no nickel. They are nonhar- MEDIUM-CARBON STEEL.—  These  steels  are denable by heat treatment and are normally used in the strong and hard but cannot be welded or worked as annealed or soft condition. Ferritic steels are magnetic 1-5