Steel P6 ANN-HOB
Heat-treated state
AISI/SAE P6 · UNS T51606
ANN-HOB = spheroidize annealed
Pick when cavities are to be cold-hobbed with a master punch; softest achievable structure.
Values for the ANN-HOB condition
Other P6 tempers and conditions
P6 is listed in 5 conditions; see the grade overview at P6.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANN-HOBThis page Spheroidize annealed | Pick when cavities are to be cold-hobbed with a master punch; softest achievable structure. | 350 | 585 | 25 | 165 HB | 6 % IACS |
ANNDefault Annealed | Standard stock condition for machining or cold hobbing of cavities before carburizing. | 415 | 655 | 20 | 195 HB | — |
Normalized | Used to refine grain and homogenize forged or hobbed blanks before carburizing. | 550 | 830 | 17 | 23 HRC | 5.5 % IACS |
Hardened & tempered | Direct oil quench without carburizing for tough holder/backing parts that need strength but not a wear surface. | 900 | 1,100 | 14 | 35 HRC | — |
Carburized, hardened & tempered | Standard service condition: hard wear-resistant case over a tough low-carbon core for impact-loaded mold parts. | 930 | 1,150 | 12 | 60 HRC | 32 W/m·K |
What is P6 ANN-HOB?
P6 ANN-HOB is P6 heat treated to ANN-HOB — pick when cavities are to be cold-hobbed with a master punch; softest achievable structure. P6 ANN-HOB has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 74% of steel grades. Elongation at break is 25% and the elastic modulus is 205 GPa (29.7 Msi). P6 ANN-HOB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). ANN is the default condition FabDigit quotes; ANN-HOB is available on request or by drawing note.
Advantages
- Easy to machine — 65/100, better than 93% of steel grades
- Forms and bends easily — 80/100, better than 93% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Poor heat conductor — 35 W/m·K (20.2 BTU/hr·ft·°F), worse than 75% of steel grades
P6 ANN-HOB properties
Typical room-temperature values for P6 ANN-HOB; 22 are specific to this condition. Other listed values are P6 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P6 ANN-HOB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
P6 ANN-HOB has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 74% of steel grades. Elongation at break is 25% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
P6 ANN-HOB is rated for continuous service to 200°C (392 °F). It conducts heat at 35 W/m·K (20.2 BTU/hr·ft·°F), worse than 75% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical2
P6 ANN-HOB has an electrical resistivity of 2.9×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of P6 ANN-HOB takes about 34 MJ of energy and emits 2.4 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 45%.
Manufacturability8
P6 ANN-HOB's machinability is good (65/100, better than 93% of steel grades); weldability good (60/100); formability very good (80/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with P6 ANN-HOB
Is P6 easy to machine?
Machine fully in the annealed state with sharp, positive-rake carbide or HSS; the soft, gummy low-carbon Ni-Cr matrix smears, so use high feed, flood coolant and finish before carburizing.
Can P6 be welded?
Weld only annealed or normalized material with a low-carbon/low-alloy filler, preheat 200–300 °C, then re-anneal or re-carburize; welding a carburized case invites cracking.
Can P6 be formed, bent or molded?
Its main advantage is cold hobbing — cavity impressions can be pressed into the soft annealed blank, with stress-relief anneals between hobbing passes.
What surface finishes work on P6?
Case-hardened surfaces polish and texture well after tempering; add hard chrome or electroless nickel for corrosion protection since the steel rusts readily.
P6 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 |
|---|---|---|
| Clow carbon for cold hobbability | 0.05 – 0.15 | 0.1 |
| Mn | 0.35 – 0.7 | 0.5 |
| Si | 0.1 – 0.4 | 0.25 |
| Cr | 1 – 1.75 | 1.5 |
| Nicore toughness | 3.25 – 3.75 | 3.5 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
P6 ANN-HOB — frequently asked
What is P6 ANN-HOB used for?
P6 ANN-HOB is typically used for carburized mold cores, impact-resistant mold inserts and die components. In short: hobbable mold steel; tough core, hard case; impact-duty P grade.
What is the yield strength of P6 ANN-HOB?
P6 ANN-HOB has a typical yield strength of 350 MPa (50.8 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 74% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is P6 ANN-HOB easy to machine?
Reasonably — machinability is rated good (65/100, better than 93% of steel grades). Machine fully in the annealed state with sharp, positive-rake carbide or HSS; the soft, gummy low-carbon Ni-Cr matrix smears, so use high feed, flood coolant and finish before carburizing.
Can P6 ANN-HOB be welded?
Yes — weldability is rated good (60/100). Weld only annealed or normalized material with a low-carbon/low-alloy filler, preheat 200–300 °C, then re-anneal or re-carburize; welding a carburized case invites cracking.
What surface finishes work on P6 ANN-HOB?
Case-hardened surfaces polish and texture well after tempering; add hard chrome or electroless nickel for corrosion protection since the steel rusts readily.
Can P6 ANN-HOB be formed, bent or molded?
Its main advantage is cold hobbing — cavity impressions can be pressed into the soft annealed blank, with stress-relief anneals between hobbing passes.
What is the maximum service temperature of P6 ANN-HOB?
P6 ANN-HOB is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between P6-ANN and P6 CARB-58?
ANN is the default condition — standard stock condition for machining or cold hobbing of cavities before carburizing. CARB-58: standard service condition: hard wear-resistant case over a tough low-carbon core for impact-loaded mold parts. Yield strength is 415 MPa in ANN versus 930 MPa in CARB-58.
Sources
- ASTM A681 — Alloy Tool Steels — ASTM International (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)
- UNS T51606 alloy record — SAE/ASTM Unified Numbering System (2017)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.