T.O. 1-1A-9
2-250. Plain Carbon Steels BSA 1016 through 1030. This group of steels is commonly known as the carburizing or case
hardening grades. The addition of manganese improves machining qualities but reduces the cold formability
characteristics. This group is widely used for forged sock.
2-251. Plain Carbon Steels 1030 through 1050. This group (medium carbon types) is used where higher mechanical
properties are required. The lower carbon and m2ngpnese types are used for most cold formed parts. Alloys 1030 1035
are used for wire and rod for cold upsetting applications, such as bolts. The higher carbon groups, such as 1040 are
often cold drawn to required physical properties for use without heat treatment.
2-252. Alloy Steels 1055 through 1095. Thin alloy group is used where wear resistance resulting from high carbon
content is needed, and is heat treated before use in particularly every application..
2-253. 1100 Series Steel. Steels in this group are generally used where easy machining is the primary requirement.
The main use of these steels is for screw stock.
2-254. 1300 Series Alloy Steel. The basic advantages of this group is high strength coupled with fair ductility and
abrasion resistance. The major use is in the manufacture of forging.
2-255. 2300 Series Nickel Alloy Steels. The addition of nickel has very little effect on machinability and greatly
increases elasticity and strength. This material is normally machined in the forged, annealed, and normalized condition,
and heat treated after fabrication.
NOTE
These grades not currently being produced. Listed for reference only.
2-256. 2500 Series Nickel Steel. This series almost without exception, is a carburizing grade with extremely high
strength core. However, the case is not as hard as obtained with other carburizing steels. This steel is used for parts
requiring a high strength core and good wear resistance.
NOTE
These grades not currently being produced.
2-257. 3100, 3200, and 3300 Series Nickel Chromium steels. This series of steels is characterized by good wear
resistance and tough core and surface. The 3300 series is used primarily in the form of forgings and bare which are
required to meet rigid mechanical properties. This steel is more difficult to handle in fabrication and beat treatment than
lower nickel chromium alloys.
2-258. 4000 Series Molybdestm Steels. This group of steels have good impact strength and require close control of heat
treatment practices to obtain the required strength and ductility.
2-259. 4100 Series Chromium Molybdemim Steels. This series has good working properties, response to heat
treatment, and high wear resistance. This group is easily fabricated by forging and rolling. After welding and cold
forming, internal stresses produced should be relieved and loss in strength regained by normalizing.
2-260. 4130 Grade Steel. This grade is used extensively in aircraft construction in the form of sheet, bar, rod and
tubing. This grade has very good cold forming characteristics. Forming and welding operations are accomplished
utilizing annealed material, and heat treated or normalized after these operations are completed. 4130 sheet (MIL-8-
18729 can be cold bent in the annealed condition to an angle of 1800 with a radius equal to the thickness of the sheet. In
the normalized condition, a radius equal to 3 times the thickness is recommended.
2-261. 4140 Series Steel. This steel is used for structural, machined and forged parts over 1/2 inch thick. It is usually
obtained in the normalized condition. Forgings are always normalized or heat treated after fabrication.
2-262. 4300 Series Nickel -Chromium Molybdenum Steels. These steels are used to meet conditions in which other
alloy steels have insufficient strength. Preparation for machining or forming must be by a suitable annealing cycle.
2-263. 8000 Series Molybdemum Steels. These steels are characterized by their high impact strength and resistance to
fatigue. They are easy to forge and machine, and are stable at high temperatures.
2-264. 8600, 8700, 9300, 9700, 9800, and 0900Series Steels. These steels have approximately the same
characteristics as the 4300 series steels.
2-265. CORROSION RESISTANT (STAINLESS) AND HEAT RESMITANT 8TEELB.
2-266. The fabrication of stainless steel requires the use of modified procedures in comparison to those used for carbon
steels.
2-267. Forming Sheet Stock. The corrosion resdstlng series, i.e., types 301, 302, 304, 305, 316, 321, 347, 410, 430,
431, etc., generally have good forming and drawing qualities. Some types (302, 304 and 305) have forming
characteristics superior to plain carbon steel because of the wide spread between tensile and yield strength, and higher
elongation. However, more power is required to form these types than is required for carbon steel because of higher
tensile strength and the fact that yield strength increases rapidly during forming or bending.
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