Steel - SAE AISI 1010|1015|1020|1025|1045|1018|1117|1035|1040|1050|1215|4140|4150

Steel is a term used for iron to which between 0.02 to 1.7% carbon has been added. The old definition of steel used to be something like "it rusts and it sinks in water." This material comprises the most diverse group of alloys and applications in the metals world. If there is something that needs to be made, there probably is a steel alloy that it can be made of. Steel does, of course, have poor corrosion resistance, but its relatively low cost and ease of painting make it a common choice.

The numbering system for steel is actually one of the few things in the metals industry that seems to make sense. You can determine the alloying ingredients by the first two digits of the alloy number, and the carbon content by the last two digits. For instance, 1018 mild steel is simply iron with a carbon content of 0.18%. Generally speaking, as the carbon content goes up, strength increases, but machinability and weldability decrease.

Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and the form of their presence in the steel controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron.

1010 - General purpose steel. Good weldability and forming and extruding chrematistics. Often used for general structural and automotive bodies.

1015 - General purpose low carbon plate with predictable qualities. Has excellent welding and bending properties. Structural applications.

1020 - Good general purpose low carbon plate. Good machinability and formability. Used in automotive camshafts and similar applications.

1025 - Plate. Higher carbon plate for greater strength. Has optimal combination of strength, weldability and good form retaining after machining.

1045 Medium carbon steel. often used for bolts, studs and shaft parts. High strength and hardness.

1018, 1020 (HR,CF) - Low carbon steel. Has good hardening properties, fair machinability. Readily brazed and welded.

1117 (HR,CF) - Low carbon, high manganese steel. Good machinability, case hardening is deep and uniform. Good for bending, broaching and most deforming without cracking.

1035 (HR) - Intermediate carbon higher in strength and hardness than low carbon steel. Used for studs, bolts etc.

1040, 1045 (HR,CF) - Used when greater strength and hardness is desired in the as rolled condition. Good for hammer forge processes. Uses include gears, shafts, axles, bolts sand studs.

1050 (CF) - Strain hardened, stress relieved material typically 100 KSI yield strength.

1141 (HR,CF) - Improved machinability and better heat treatment response (surface hardness is deeper and more uniform) than plain carbon steels. Uses include gears, shafts, axles, bolts, studs, pins, etc.

1215 (HR,CF) - Fast cutting steel is considered the standard screw stock. Cutting speeds and machining characteristics are excellent.

4140/4150 - Widely used general purpose alloys, low in cost. A broad range of strength and toughness is attainable through variations in heat treatment. Used for forgings, tubing and fittings

4340 - Highly alloyed steel, nominally 1.8% Ni, .80% chromium and .25% molybdenum. High strength characteristics. Used for heavily stressed parts operating in fatigue and other duty conditions.