Steel T12A
GB T12A
T12A is the highest-carbon member of the T7–T13 carbon tool steel family at about 1.2 % C, giving the maximum attainable hardness in the series at the cost of brittleness.
Reference datasheet — T12A 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
T12A tempers and conditions
T12A is supplied in 10 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard stock condition: globular carbides in ferrite, ≤207 HB, machine or cold-form now and harden afterwards. | 420 | 720 | 20 | 200 HB | — |
Cold rolled strip, annealed | Thin soft strip (0.1–3 mm) for blanking saw blades, springs, shims and small cutters that are hardened after forming. | 420 | 700 | 18 | 12 HRC | 9.5 % IACS |
Precision ground / silver steel, annealed | Ground round or flat stock held to h9/h11 tolerance in the soft state — for punches, gauge pins and reamer blanks finished by grinding after hardening. | 420 | 720 | 20 | 13 HRC | 9.5 % IACS |
Hot rolled | Cheapest mill condition for bar and plate that will be fully machined and heat treated by the user; hard, coarse pearlitic structure. | 480 | 850 | 10 | 25 HRC | 9.5 % IACS |
Cold drawn | Choose for close-tolerance small bar, wire and drill-rod blanks where some extra strength and a bright surface help before hardening. | 700 | 880 | 8 | 24 HRC | 9.5 % IACS |
Water quenched + tempered 300–400 °C | Tough/spring-like condition for shock-loaded parts and light springs where full file hardness is not needed. | 1,450 | 1,700 | 4 | 52 HRC | 8.6 % IACS |
Water quenched + tempered 230–280 °C | Use where some impact is unavoidable — cold chisels, light punches, woodworking blades. | 1,650 | 1,900 | 2 | 58 HRC | 8.2 % IACS |
Water quenched, untempered | Maximum hardness reference state only; must be tempered promptly — untempered T12A cracks readily. | 1,750 | 2,100 | 0.5 | 65 HRC | 7.5 % IACS |
Water quenched + tempered 180–220 °C | Slight toughness gain for reamers, taps, gauges and small cutting tools with a little bending load. | 1,800 | 2,050 | 1 | 61 HRC | 7.8 % IACS |
Water quenched + tempered 150–180 °C | Standard file/scraper/hand-tool treatment: maximum wear resistance and edge holding, minimum toughness. | 1,900 | 2,200 | 1 | 64 HRC | — |
What is T12A?
T12A is the highest-carbon member of the T7–T13 carbon tool steel family at about 1.2 % C, giving the maximum attainable hardness in the series at the cost of brittleness. Annealed material is roughly 420 MPa yield, 720 MPa tensile, 20 % elongation and 200 HB (93 HRB), and stock is available hot-rolled, annealed, cold-drawn, cold-rolled annealed, precision-ground annealed, quenched and tempered (QT150–QT350) for files, scrapers and light cutting edges. Hardening depth is only a few millimetres, impact resistance is poor and corrosion resistance is nil, with service capped near 400 °C; T10A is the tougher choice where edge chipping is a risk. T12A has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,300°C (2,372 °F). T12A has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 720 MPa (104 ksi) — weaker than 53% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
What is T12A used for?
- files
- scrapers
- reamers
- razor-type blades
Advantages
- Polishes to a fine finish — 70/100, better than 87% 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
- Low fracture toughness — 50 MPa·√m (45.5 ksi·√in), worse than 86% of steel grades
T12A properties
Typical room-temperature values for T12A-A; bars are the position among steel grades.
Physical3
T12A has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,300°C (2,372 °F).
Mechanical16
T12A has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 720 MPa (104 ksi) — weaker than 53% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
T12A is rated for continuous service to 400°C (752 °F). It conducts heat at 47 W/m·K (27.2 BTU/hr·ft·°F), better than 75% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
T12A conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (9/100), worse than 98% of steel grades.
Sustainability4
Producing a kilogram of T12A takes about 28 MJ of energy and emits 2.1 kg of CO₂ — less than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
T12A's machinability is fair (45/100, worse than 65% of steel grades); weldability not recommended (12/100); formability fair (40/100).
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. T12A is highlighted; hover a dot for its name, or open the interactive family chart.
Working with T12A
Is T12A easy to machine?
Machine only in the spheroidize-annealed state (≤207 HB) with sharp HSS/carbide and generous coolant; after hardening it is a grinding-only material.
Can T12A be welded?
Essentially unweldable for tool duty — if repair is unavoidable, preheat 300–350 °C, use a matching or low-hydrogen filler, and re-temper immediately to avoid quench cracks.
Can T12A be formed, bent or molded?
Cold bending and blanking only from fully spheroidized strip with generous radii; hot work at 1050–850 °C, cool slowly, then anneal. Harden 760–780 °C in water/brine, temper at once 150–200 °C; hardened depth is only a few mm, so keep sections thin and avoid sharp corners.
T12A 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 |
|---|---|---|
| Chypereutectoid — free cementite gives max hardness | 1.15 – 1.24 | 1.2 |
| Si | ≤ 0.35 | 0.2 |
| Mn | ≤ 0.4 | 0.25 |
| PA-grade (high-quality) restriction | ≤ 0.03 | |
| SA-grade (high-quality) restriction | ≤ 0.02 | |
| Crresidual | ≤ 0.1 | |
| Niresidual | ≤ 0.12 | |
| Curesidual | ≤ 0.2 | |
| Fe | balance |
What surface finishes work on T12A?
No native corrosion resistance — protect with oiling, black oxide, phosphating, or hard chrome; polishes to a fine finish in the hardened state thanks to the low S/P A-grade cleanliness.
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 T12A in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- T12
How much does T12A cost?
T12A 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.
T12A — frequently asked
What is T12A used for?
T12A is typically used for files, scrapers, reamers and razor-type blades. In short: hardest carbon tool steel; file and scraper grade; brittle — light cutting only.
What is the yield strength of T12A?
T12A has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 720 MPa (104 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is T12A easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine only in the spheroidize-annealed state (≤207 HB) with sharp HSS/carbide and generous coolant; after hardening it is a grinding-only material.
Can T12A be welded?
Not readily — weldability is rated not recommended (12/100). Essentially unweldable for tool duty — if repair is unavoidable, preheat 300–350 °C, use a matching or low-hydrogen filler, and re-temper immediately to avoid quench cracks.
What surface finishes work on T12A?
No native corrosion resistance — protect with oiling, black oxide, phosphating, or hard chrome; polishes to a fine finish in the hardened state thanks to the low S/P A-grade cleanliness.
Can T12A be formed, bent or molded?
Cold bending and blanking only from fully spheroidized strip with generous radii; hot work at 1050–850 °C, cool slowly, then anneal. Harden 760–780 °C in water/brine, temper at once 150–200 °C; hardened depth is only a few mm, so keep sections thin and avoid sharp corners.
What is the maximum service temperature of T12A?
T12A is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between T12A-A and T12A-QT150?
A is the default condition — standard stock condition: globular carbides in ferrite, ≤207 HB, machine or cold-form now and harden afterwards. QT150: standard file/scraper/hand-tool treatment: maximum wear resistance and edge holding, minimum toughness. Yield strength is 420 MPa in A versus 1,900 MPa in QT150.
How much does T12A cost?
T12A 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 steels) (2008)
- ASTM A686 Standard Specification for Tool Steel, Carbon (W1 grades) — ASTM (2021)
- JIS G 4401 Carbon tool steels (SK120/SK2) — JSA (2009)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Water-hardening tool steels) — ASM International (1990)
- ASM Handbook Vol. 4 — Heat Treating (Tool steel heat treatment) — ASM International (1991)
- ASM Handbook Vol. 16 — Machining (machinability ratings) — ASM International (1989)
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.