Material number G10950: 1095
G10950 is the Unified Numbering System designation for 1095, high-carbon steel (spring / knife / blade steel) specified in ASTM A29.
What G10950 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 G10950 appears in several ASTM specifications (plate, bar, pipe) with different mechanical requirements.
1095 at a glance
AISI 1095 is the highest-carbon member of the plain-carbon 10xx series: 0.90–1.03 % carbon with only 0.3–0.5 % manganese, UNS G10950. Above the eutectoid composition it forms excess cementite, which gives excellent edge retention and wear resistance after hardening to 64–66 HRC — the reason 1095 has been the standard American knife, sword, saw-blade and spring-clip steel for a century. Blades are tempered to 56–62 HRC; springs, clock springs and blue-tempered strip to 44–50 HRC.
Because it contains no alloying elements, hardenability is very low: a fast quench (brine or a fast quench oil) and thin sections (< 6 mm) are needed for full hardness, and the steel is unforgiving of slow quenches (pearlite forms in about one second). This makes 1095 easy to differentially harden — a clay-coated back stays soft while the edge hardens — but it also means 1095 is not a through-hardening steel for thick parts. Toughness is modest and corrosion resistance nil (blades rust without oil).
EN C100S (1.1274), JIS SK95 (SK4) and BS CS100 are the same steel; W1 tool steel is the tool-quality version; 1084 and 5160 are the tougher alternatives.
Full data sheet for 1095 → · Equivalent grades →