Alloy Steel
Steel AISI/SAESteel alloyed with elements like chromium, molybdenum, or vanadium to enhance strength, hardness, or toughness beyond plain carbon steel.
Alloy steels contain intentional additions of chromium, molybdenum, nickel, vanadium, or boron beyond carbon steel limits to achieve specific mechanical properties through heat treatment. They bridge the gap between plain carbon steels and specialty steels, offering higher hardenability, strength, and toughness for demanding structural and machine components.
Designation Guide
AISI/SAE 41xx series (Cr-Mo) includes 4140 and 4130, workhorses of the alloy steel world. The 43xx series adds nickel (Ni-Cr-Mo), while 86xx (Ni-Cr-Mo, lower alloy) provides economical hardenability. 52100 (high-carbon chromium) is the premier bearing steel. The 9260 (silicon-manganese) grade excels as spring steel.
Selection Tips
4140 is the default choice for general-purpose shafts, gears, and structural components requiring through-hardening. 4130 (lower carbon) offers better weldability for aircraft tubing and structural fabrication. For bearing applications, specify 52100 with controlled oxygen content. Always match heat treatment to section size — thicker sections may need higher-alloy grades (4340, 8640) for uniform hardness distribution.