Steel T12
AISI/SAE T12 · GB T12A
T12 is the high-carbon end of the Chinese GB/T 1298 unalloyed carbon tool steel series at about 1.15–1.24 % C, where excess carbide gives the highest hardness and wear resistance of the family.
Reference datasheet — T12 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the A condition
T12 tempers and conditions
T12 is supplied in 9 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
High-grade quality | Same carbon level with tightened phosphorus and sulphur limits and cleaner steel — choose for fine cutting edges and gauges where quench cracking must be minimised. | 420 | 740 | 24 | 13 HRC | 9.5 % IACS |
ADefault Solution annealed | Standard stock condition for bar, plate and drill rod — machine or form now, harden later. | 430 | 750 | 22 | 200 HB | — |
Hot rolled | Mill as-rolled condition; buy only if you will spheroidize-anneal or harden it yourself. | 500 | 900 | 12 | 25 HRC | 9.5 % IACS |
Normalized | Used to break up carbide networks in forgings before spheroidizing; not a delivery condition for finished tools. | 550 | 1,000 | 10 | 30 HRC | 9.3 % IACS |
Cold drawn | Bright cold-drawn rod or hard cold-rolled strip for close tolerance and better finish before hardening. | 700 | 880 | 8 | 25 HRC | 9.5 % IACS |
Water quenched + 300–350 °C temper, 52–56 HRC | Tougher medium-hardness setting for springs, chisels and impact tools; wear resistance drops noticeably. | 1,500 | 1,750 | 5 | 54 HRC | — |
Water quenched + 240–260 °C temper, 57–59 HRC | Trades a little hardness for chipping resistance in punches, shear blades and hand tools with impact loading. | 1,600 | 1,900 | 3 | 58 HRC | — |
Water quenched + 200 °C temper, 60–62 HRC | The usual working condition for taps, reamers, drills and small cutters — near-peak hardness with slightly relieved stresses. | 1,750 | 2,050 | 2 | 61 HRC | — |
Water quenched + 150–180 °C temper, 62–64 HRC | Maximum hardness and wear resistance for files, scrapers, engraving tools and gauges where toughness is secondary. | 1,900 | 2,200 | 1 | 63 HRC | 42 W/m·K |
What is T12?
T12 is the high-carbon end of the Chinese GB/T 1298 unalloyed carbon tool steel series at about 1.15–1.24 % C, where excess carbide gives the highest hardness and wear resistance of the family. It is used for files and precision cutting edges and is supplied as hot-rolled, spheroidize-annealed, normalized and cold-drawn bar and strip, in QT150, QT200, QT250 and QT300 tempered conditions, and as T12A. Annealed values are 430 MPa yield, 750 MPa tensile, 22 % elongation and 200 HB, with service temperature limited to about 350 °C. It is brittle, effectively unweldable and shallow-hardening; alloy tool steels such as 9SiCr or Cr12-class grades suit larger or distortion-sensitive tooling. T12 has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,370°C (2,498 °F). T12 has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 750 MPa (109 ksi) — weaker than 51% of steel grades. Elongation at break is 22% and the elastic modulus is 210 GPa (30.5 Msi).
What is T12 used for?
- files
- reamers
- razor blades
- precision cutting tools
Advantages
- Polishes to a fine finish — 80/100, better than 97% of steel grades
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
Limitations
- Difficult to weld — 12/100, worse than 96% of steel grades
T12 properties
Typical room-temperature values for T12-A; bars are the position among steel grades.
Physical3
T12 has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,370°C (2,498 °F).
Mechanical15
T12 has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 750 MPa (109 ksi) — weaker than 51% of steel grades. Elongation at break is 22% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
T12 is rated for continuous service to 350°C (662 °F). It conducts heat at 47 W/m·K (27.2 BTU/hr·ft·°F), better than 75% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
T12 conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of T12 takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 25%.
Manufacturability7
T12's machinability is fair (45/100, worse than 65% of steel grades); weldability not recommended (12/100); formability fair (35/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. T12 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with T12
Is T12 easy to machine?
Machine only in the spheroidize-annealed state (~200 HB) with sharp HSS or coated carbide and generous coolant; once hardened above 60 HRC it is a grinding/EDM-only material.
Can T12 be welded?
Effectively unweldable for structural joints — very high carbon equivalent; if repair is unavoidable, preheat 300–400 °C, use a low-hydrogen or nickel-based filler and immediately re-temper.
Can T12 be formed, bent or molded?
Cold form only thin annealed strip with generous bend radii; hot work between 1050 °C and 850 °C, then slow-cool and spheroidize to avoid carbide networks and cracking.
T12 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CGB/T 1298 | 1.15 – 1.24 | 1.2 |
| Si | ≤ 0.35 | 0.25 |
| Mn | ≤ 0.4 | 0.3 |
| PT12A ≤0.030 | ≤ 0.04 | |
| ST12A ≤0.020 | ≤ 0.03 | |
| Crresidual | ≤ 0.1 | |
| Niresidual | ≤ 0.12 | |
| Curesidual (T12A ≤0.15) | ≤ 0.2 | |
| Fe | balance |
What surface finishes work on T12?
Takes a very fine ground and lapped finish; protect with oil, black oxide, phosphate or hard chrome because bare surfaces flash-rust — no anodizing (ferrous).
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel T12 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- GB (China)
- T12A
How much does T12 cost?
T12 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
T12 — frequently asked
What is T12 used for?
T12 is typically used for files, reamers, razor blades and precision cutting tools. In short: hardest carbon tool steel; file and reamer grade; grinding-only when hardened.
What is the yield strength of T12?
T12 has a typical yield strength of 430 MPa (62.4 ksi) and a tensile strength of 750 MPa (109 ksi) — weaker than 51% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is T12 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine only in the spheroidize-annealed state (~200 HB) with sharp HSS or coated carbide and generous coolant; once hardened above 60 HRC it is a grinding/EDM-only material.
Can T12 be welded?
Not readily — weldability is rated not recommended (12/100). Effectively unweldable for structural joints — very high carbon equivalent; if repair is unavoidable, preheat 300–400 °C, use a low-hydrogen or nickel-based filler and immediately re-temper.
What surface finishes work on T12?
Takes a very fine ground and lapped finish; protect with oil, black oxide, phosphate or hard chrome because bare surfaces flash-rust — no anodizing (ferrous).
Can T12 be formed, bent or molded?
Cold form only thin annealed strip with generous bend radii; hot work between 1050 °C and 850 °C, then slow-cool and spheroidize to avoid carbide networks and cracking.
What is the maximum service temperature of T12?
T12 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between T12-A and T12-QT150?
A is the default condition — standard stock condition for bar, plate and drill rod — machine or form now, harden later. QT150: maximum hardness and wear resistance for files, scrapers, engraving tools and gauges where toughness is secondary. Yield strength is 430 MPa in A versus 1,900 MPa in QT150.
How much does T12 cost?
T12 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- GB/T 1298 Carbon Tool Steel Bars — SAC (China) (2008)
- GB/T 1299 / JIS G 4401 SK120 (SK2) carbon tool steel — SAC / JISC (2009)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (W1 water-hardening tool steel) — ASM International (1990)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.