Material number G10100: SAE 1010
G10100 is the Unified Numbering System designation for SAE 1010, low-carbon steel for cold forming, welding and case hardening specified in ASTM A29.
What G10100 means
UNS numbers (ASTM E527 / SAE J1086) use a letter for the alloy family and five digits: G = AISI/SAE carbon and alloy steels (G41400 = 4140), S = stainless and heat-resisting steels (S30400 = 304), K = miscellaneous steels (K02600 = A36), T = tool steels, N = nickel alloys. The UNS number identifies a composition, not a product form or property level, so G10100 appears in several ASTM specifications (plate, bar, pipe) with different mechanical requirements.
SAE 1010 at a glance
SAE 1010 sits at the bottom of the plain-carbon ladder, and that is exactly why it is everywhere. With 0.10 % carbon the steel is soft, ductile and completely weldable; it cold heads into bolts, roll forms into tube, draws into wire and takes a carburized case when a hard surface is needed on a soft core. It is not a strength grade and was never meant to be — a hot-rolled 1010 bar yields around 180 MPa, less than structural S235.
The designation comes from the SAE-AISI four-digit system: the first two digits describe the alloy family (10 = plain carbon, no alloying), the last two the nominal carbon content in hundredths of a percent. So 1010 is a plain carbon steel with about 0.10 % C. ASTM A29 is the standard that governs bar; sheet and strip in the same chemistry are ordered against A1011 or A1008 by forming class rather than by the 1010 number, which is a frequent source of confusion in enquiries.
The European equivalent is C10 (1.0301) under EN 10084, a case-hardening standard, and the Japanese equivalent is S10C under JIS G4051. Both are close enough on chemistry to be treated as the same steel; what differs is the surrounding standard's requirements for hardenability and case depth.
Full data sheet for SAE 1010 → · Equivalent grades →