Steel T6
AISI/SAE T6 · UNS T12006
T6 is a tungsten high-speed steel (T12006) alloyed with about 12% cobalt, giving the highest red-hardness of the tungsten series for the most severe high-temperature machining.
Reference datasheet — T6 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 ANN condition
T6 tempers and conditions
T6 is supplied in 3 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard mill-supplied bar/blank condition for machining tool blanks before hardening. | 590 | 900 | 12 | 262 HB | 22 W/m·K |
Hardened & tempered | Full working hardness for maximum red hardness in heavy roughing and machining of tough/abrasive materials. | 2,000 | 2,200 | 0.5 | 65 HRC | 20 W/m·K |
Hardened & tempered | Choose when interrupted cuts or large tool sections demand more toughness than absolute peak hardness. | 2,000 | 2,200 | 0.5 | 63 HRC | 2.9 % IACS |
Supply forms, finishes and certifications
Ways T6 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
HT-SURF | Hardened + surface treated | Surface finish |
What is T6?
T6 is a tungsten high-speed steel (T12006) alloyed with about 12% cobalt, giving the highest red-hardness of the tungsten series for the most severe high-temperature machining. It is used for heavy interrupted cuts and high-speed tooling, supplied annealed at 262 HB (900 MPa tensile, 590 MPa yield, 12% elongation, 220 GPa modulus) and hardened to 63 or 65 HRC, with a surface-treated condition on file. The trade-offs are low machinability (score 25), crack sensitivity from the coarse primary carbide network, negligible weldability and no corrosion resistance; listed maximum service temperature is 500 °C and thermal conductivity 22 W/m·K. T5 is the lower-cobalt, easier-to-grind alternative. T6 has a density of 8.89 g/cm³ (0.321 lb/in³), heavier than 100% of steel grades. It melts at 1,400°C (2,552 °F). T6 has a yield strength of 590 MPa (85.6 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 76% of steel grades. Elongation at break is 12% and the elastic modulus is 220 GPa (31.9 Msi).
What is T6 used for?
- heavy interrupted cuts
- high-speed lathe tools
- milling cutters for hard alloys
- hot forming tools
Advantages
- High service temperature — 500°C (932 °F), better than 90% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
- High strength — 590 MPa (85.6 ksi), better than 76% of steel grades
Limitations
- Heavy — 8.89 g/cm³ (0.321 lb/in³), worse than 100% of steel grades
- High embodied carbon — 6.5 kg CO₂/kg, worse than 98% of steel grades
- Difficult to weld — 12/100, worse than 96% of steel grades
- Poor heat conductor — 22 W/m·K (12.7 BTU/hr·ft·°F), worse than 93% of steel grades
- Difficult to machine — 25/100, worse than 93% of steel grades
T6 properties
Typical room-temperature values for T6-ANN; bars are the position among steel grades.
Physical3
T6 has a density of 8.89 g/cm³ (0.321 lb/in³), heavier than 100% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical14
T6 has a yield strength of 590 MPa (85.6 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 76% of steel grades. Elongation at break is 12% and the elastic modulus is 220 GPa (31.9 Msi).
Thermal6
T6 is rated for continuous service to 500°C (932 °F). It conducts heat at 22 W/m·K (12.7 BTU/hr·ft·°F), worse than 93% of steel grades. Thermal expansion is 10.8 µm/m·K (6 µin/in·°F).
Electrical3
T6 conducts electricity at 3.1 % IACS, worse than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of T6 takes about 90 MJ of energy and emits 6.5 kg of CO₂ — more than 98% of steel grades. Typical recycled content is 40%.
Manufacturability8
T6's machinability is poor (25/100, worse than 93% of steel grades); weldability not recommended (12/100); formability poor (20/100).
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. T6 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with T6
Is T6 easy to machine?
Machine only in the annealed condition with rigid setups, sharp carbide or cobalt-HSS tools and generous coolant; hardened T6 must be ground or EDM'd, and grinding requires soft, friable wheels to avoid burn/cracking.
Can T6 be welded?
Not a structural weld grade — repair only, with 500–550 °C preheat, matching HSS filler and immediate re-temper; otherwise cracking is near certain.
Can T6 be formed, bent or molded?
Hot work at 1000–1150 °C with slow, controlled cooling and immediate annealing; no meaningful cold forming, and the coarse tungsten carbide network makes it crack-sensitive.
T6 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 |
|---|---|---|
| C | 0.75 – 0.85 | 0.8 |
| Mn | 0.2 – 0.4 | 0.3 |
| Si | 0.2 – 0.4 | 0.3 |
| Cr | 3.75 – 4.5 | 4.1 |
| Wprimary carbide former, red hardness | 18.5 – 21 | 20 |
| V | 1.5 – 2.1 | 1.8 |
| Cohighest Co of the T-series; maximum hot hardness | 11 – 13 | 12 |
| Mo | 0.4 – 1 | 0.7 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on T6?
Steam oxide, black oxide, nitriding or PVD TiN/TiAlN are standard; the alloy rusts without a coating or oil film, and mirror polishing is limited by primary carbides.
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 T6 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- T12006
How much does T6 cost?
T6 is a high-cost steel ($$$$), pricier than about 78% 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.
T6 — frequently asked
What is T6 used for?
T6 is typically used for heavy interrupted cuts, high-speed lathe tools, milling cutters for hard alloys and hot forming tools. In short: highest red-hardness tungsten HSS; 12% cobalt grade; crack-sensitive, hard to grind.
What is the yield strength of T6?
T6 has a typical yield strength of 590 MPa (85.6 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 76% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is T6 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Machine only in the annealed condition with rigid setups, sharp carbide or cobalt-HSS tools and generous coolant; hardened T6 must be ground or EDM'd, and grinding requires soft, friable wheels to avoid burn/cracking.
Can T6 be welded?
Not readily — weldability is rated not recommended (12/100). Not a structural weld grade — repair only, with 500–550 °C preheat, matching HSS filler and immediate re-temper; otherwise cracking is near certain.
What surface finishes work on T6?
Steam oxide, black oxide, nitriding or PVD TiN/TiAlN are standard; the alloy rusts without a coating or oil film, and mirror polishing is limited by primary carbides.
Can T6 be formed, bent or molded?
Hot work at 1000–1150 °C with slow, controlled cooling and immediate annealing; no meaningful cold forming, and the coarse tungsten carbide network makes it crack-sensitive.
What is the maximum service temperature of T6?
T6 is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between T6-ANN and T6 HT-65?
ANN is the default condition — standard mill-supplied bar/blank condition for machining tool blanks before hardening. HT-65: full working hardness for maximum red hardness in heavy roughing and machining of tough/abrasive materials. Yield strength is 590 MPa in ANN versus 2,000 MPa in HT-65.
How much does T6 cost?
T6 is a high-cost steel ($$$$), pricier than about 78% 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
- ASTM A600 — Tool Steel, High Speed, Tool and Die Steels — ASTM International (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Tool Steels) — ASM International (1990)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
- ASM Handbook Vol.16 — Machining — 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.