Steel T4
AISI/SAE T4 · UNS T12004
T4 is a cobalt-alloyed 18W-4Cr-1V tungsten high-speed steel (T12004, SKH3) that offers better red hardness than base T1.
Reference datasheet — T4 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
T4 tempers and conditions
T4 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 |
|---|---|---|---|---|---|---|
Hardened & tempered | Maximum hardness / red-hardness setting for finishing tools on hard or abrasive work; toughness is minimal. | 0 | 65 HRC | 21 W/m·K | ||
ANNDefault Annealed | Stock condition for machining tool blanks before hardening; max 269 HB. | 580 | 950 | 12 | 255 HB | 24 W/m·K |
Hardened & tempered | Standard working hardness for general cutting tools needing a balance of edge life and toughness. | 1,900 | 2,100 | 0.5 | 63 HRC | 2.7 % IACS |
Supply forms, finishes and certifications
Ways T4 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, tempered and surface treated | Surface finish |
What is T4?
T4 is a cobalt-alloyed 18W-4Cr-1V tungsten high-speed steel (T12004, SKH3) that offers better red hardness than base T1. Annealed bar is about 255 HB with 580 MPa yield, 950 MPa tensile, 215 GPa modulus and 24 W/m·K conductivity; hardened to 62 or 65 HRC, with or without surface treatment, it is used for lathe bits, cutters and drills. Cobalt lowers toughness (12 % elongation), grinding is slower than on M-series steels, the 4 % Cr gives no rust protection, and service tops out at 500 °C; T1 is cheaper and tougher, T15 more wear resistant. T4 has a density of 8.75 g/cm³ (0.316 lb/in³), heavier than 100% of steel grades. It melts at 1,260°C (2,300 °F). T4 has a yield strength of 580 MPa (84.1 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 75% of steel grades. Elongation at break is 12% and the elastic modulus is 215 GPa (31.2 Msi).
What is T4 used for?
- lathe tool bits
- milling cutters
- form tools
- heavy-duty drills
Advantages
- High service temperature — 500°C (932 °F), better than 90% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 580 MPa (84.1 ksi), better than 75% of steel grades
Limitations
- High embodied carbon — 5.5 kg CO₂/kg, worse than 97% of steel grades
- Limited formability — 10/100, worse than 95% of steel grades
- Low electrical conductivity — 3 % IACS, worse than 91% of steel grades
- Poor heat conductor — 24 W/m·K (13.9 BTU/hr·ft·°F), worse than 90% of steel grades
- Difficult to machine — 30/100, worse than 89% of steel grades
T4 properties
Typical room-temperature values for T4-ANN; bars are the position among steel grades.
Physical3
T4 has a density of 8.75 g/cm³ (0.316 lb/in³), heavier than 100% of steel grades. It melts at 1,260°C (2,300 °F).
Mechanical15
T4 has a yield strength of 580 MPa (84.1 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 75% of steel grades. Elongation at break is 12% and the elastic modulus is 215 GPa (31.2 Msi).
Thermal6
T4 is rated for continuous service to 500°C (932 °F). It conducts heat at 24 W/m·K (13.9 BTU/hr·ft·°F), worse than 90% of steel grades. Thermal expansion is 11.2 µm/m·K (6.22 µin/in·°F).
Electrical3
T4 conducts electricity at 3 % IACS, worse than 91% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (18/100), better than 83% of steel grades.
Sustainability4
Producing a kilogram of T4 takes about 75 MJ of energy and emits 5.5 kg of CO₂ — more than 97% of steel grades. Typical recycled content is 35%.
Manufacturability8
T4's machinability is poor (30/100, worse than 89% of steel grades); weldability poor (20/100); formability not recommended (10/100).
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. T4 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with T4
Is T4 easy to machine?
Machine only in the annealed state with rigid setups, sharp cobalt-HSS or coated carbide, low speeds and heavy feeds; after hardening the alloy is grind-only and grinds slower than M-series because of the coarse W/V carbides.
Can T4 be welded?
Structural welding is not practised; repair/build-up by TIG or laser with matched HSS filler at 500–550 °C preheat followed by an immediate full temper cycle.
Can T4 be formed, bent or molded?
Hot work only — forge 1100–1150 °C, stop above 950 °C and slow-cool, then anneal 860–880 °C with controlled cooling to ≤269 HB; no cold forming.
T4 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 | 0.7 – 0.8 | 0.75 |
| Mn | 0.1 – 0.4 | 0.25 |
| Si | 0.2 – 0.4 | 0.3 |
| Cr | 3.75 – 4.5 | 4.1 |
| W | 17.5 – 19 | 18.25 |
| V | 0.8 – 1.2 | 1 |
| Cocobalt addition raises hot hardness vs T1 | 4.25 – 5.75 | 5 |
| Moresidual/optional | ≤ 1 | 0.5 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on T4?
Not anodisable; use steam temper (blue oxide), black oxide, phosphating or PVD TiN/TiAlN for edge life, and keep oiled in storage since the 4 % Cr gives no rust protection.
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 T4 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- T12004
- Similar grades
- SKH3
How much does T4 cost?
T4 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.
T4 — frequently asked
What is T4 used for?
T4 is typically used for lathe tool bits, milling cutters, form tools and heavy-duty drills. In short: cobalt-boosted T1; red hardness to 500 °C; lower toughness than T1.
What is the yield strength of T4?
T4 has a typical yield strength of 580 MPa (84.1 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 75% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is T4 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% of steel grades). Machine only in the annealed state with rigid setups, sharp cobalt-HSS or coated carbide, low speeds and heavy feeds; after hardening the alloy is grind-only and grinds slower than M-series because of the coarse W/V carbides.
Can T4 be welded?
Not readily — weldability is rated poor (20/100). Structural welding is not practised; repair/build-up by TIG or laser with matched HSS filler at 500–550 °C preheat followed by an immediate full temper cycle.
What surface finishes work on T4?
Not anodisable; use steam temper (blue oxide), black oxide, phosphating or PVD TiN/TiAlN for edge life, and keep oiled in storage since the 4 % Cr gives no rust protection.
Can T4 be formed, bent or molded?
Hot work only — forge 1100–1150 °C, stop above 950 °C and slow-cool, then anneal 860–880 °C with controlled cooling to ≤269 HB; no cold forming.
What is the maximum service temperature of T4?
T4 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 T4-ANN and T4-HT62?
ANN is the default condition — stock condition for machining tool blanks before hardening; max 269 HB. HT62: standard working hardness for general cutting tools needing a balance of edge life and toughness. Yield strength is 580 MPa in ANN versus 1,900 MPa in HT62.
How much does T4 cost?
T4 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 — ASTM International (2021)
- GB/T 9943 (W18Cr4VCo5) — SAC / (2008)
- JIS G 4403 (SKH3) — JSA (2015)
- 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)
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.