Steel P1 CARB-HQ
Heat-treated state
AISI/SAE P1 · UNS T51601
CARB-HQ = carburized & quenched
Carburize at 900–925 °C and oil quench after cavity machining for a 0.5–1.5 mm case at 60–64 HRC; low-temperature tempering must follow immediately to avoid cracking.
Values for the CARB-HQ condition
Other P1 tempers and conditions
P1 is listed in 6 conditions; see the grade overview at P1.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Order this ≤130 HB soft state for cold hobbing cavities or for rough and finish machining, then carburize and quench; at 240 MPa yield it is not a service condition. | 240 | 380 | 35 | 120 HB | — |
Normalized | Normalize at 900–925 °C with air cooling after forging or heavy deformation to remove coarse, uneven structure before carburizing; treat it as a preparation step only. | 280 | 420 | 32 | 135 HB | 11 % IACS |
Carburized, quenched & tempered 230–260 °C | Pick the 230–260 °C temper (case 55–58 HRC) for cavities with sharp corners or impact loading, trading a little hardness for higher case toughness and lower residual stress. | 430 | 620 | 20 | 56 HRC | 10 % IACS |
Carburized, quenched & tempered 150–200 °C | Choose carburizing plus a 150–200 °C temper (case 58–62 HRC) as the usual final production state, pairing a wear-resistant case with a tough core for medium-volume cavities. | 460 | 650 | 18 | 60 HRC | — |
CARB-HQThis page Carburized & quenched | Carburize at 900–925 °C and oil quench after cavity machining for a 0.5–1.5 mm case at 60–64 HRC; low-temperature tempering must follow immediately to avoid cracking. | 500 | 700 | 15 | 62 HRC | 9 % IACS |
Cold hobbed | Expect this work-hardened state (190 HB, 10% elongation) after cold-pressing the cavity; follow with recrystallization annealing or feed the part directly into carburizing. | 520 | 620 | 10 | 190 HB | 11 % IACS |
What is P1 CARB-HQ?
P1 CARB-HQ is P1 heat treated to CARB-HQ — carburize at 900–925 °C and oil quench after cavity machining for a 0.5–1.5 mm case at 60–64 HRC; low-temperature tempering must follow immediately to avoid cracking. P1 CARB-HQ has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 63% of steel grades. Elongation at break is 15% and the elastic modulus is 207 GPa (30 Msi). P1 CARB-HQ 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; CARB-HQ is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 75/100, better than 94% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Difficult to machine — 8/100, worse than 100% of steel grades
- Limited service temperature — 150°C (302 °F), worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Low fracture toughness — 28 MPa·√m (25.5 ksi·√in), worse than 97% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
P1 CARB-HQ properties
Typical room-temperature values for P1 CARB-HQ; 22 are specific to this condition. Other listed values are P1 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P1 CARB-HQ 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
P1 CARB-HQ has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 63% of steel grades. Elongation at break is 15% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
P1 CARB-HQ is rated for continuous service to 150°C (302 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
P1 CARB-HQ conducts electricity at 9 % IACS, better than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of P1 CARB-HQ takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
P1 CARB-HQ's machinability is not recommended (8/100, worse than 100% of steel grades); weldability poor (15/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with P1 CARB-HQ
Is P1 easy to machine?
In the annealed condition the steel is very soft and prone to built-up edge, so use sharp tools with large positive rake, high surface speed and plenty of coolant. Once carburized and quenched, the part can only be ground or EDM'd.
Can P1 be welded?
Carbon content is very low, so weldability is good; repair with low-hydrogen electrodes or TIG. On carburized areas, grind away the case layer before welding and re-carburize the part afterwards.
Can P1 be formed, bent or molded?
Cold hobbing is the core process for this grade: the soft cavity blank is pressed to shape by a hardened master hob in one or several strokes, with recrystallization annealing between passes.
What surface finishes work on P1?
After carburizing and quenching, finish grind and polish the cavity. Hard chrome or electroless nickel is common for rust protection and release; nitriding can be used to strengthen surfaces that were not carburized.
P1 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 |
|---|---|---|
| CASTM A681 P1: 0.10 % max | ≤ 0.1 | 0.08 |
| Mn | 0.1 – 0.4 | 0.25 |
| Si | 0.1 – 0.4 | 0.2 |
| Pimpurity limit | ≤ 0.03 | — |
| Simpurity limit | ≤ 0.03 | — |
| Febalance; no intentional Cr/Ni/Mo additions — hardness comes from carburizing | balance | — |
P1 CARB-HQ — frequently asked
What is P1 CARB-HQ used for?
P1 CARB-HQ is typically used for plastic injection mould cavities, die-casting inserts, cold-hobbed cavity blocks, carburized mould inserts and wear faces, compression and transfer moulding dies and rubber and shoe-sole moulds. In short: hobbable mould steel; case-hardening P-series grade; softest mould steel supplied.
What is the yield strength of P1 CARB-HQ?
P1 CARB-HQ has a typical yield strength of 500 MPa (72.5 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 63% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is P1 CARB-HQ easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 100% of steel grades). In the annealed condition the steel is very soft and prone to built-up edge, so use sharp tools with large positive rake, high surface speed and plenty of coolant. Once carburized and quenched, the part can only be ground or EDM'd.
Can P1 CARB-HQ be welded?
Not readily — weldability is rated poor (15/100). Carbon content is very low, so weldability is good; repair with low-hydrogen electrodes or TIG. On carburized areas, grind away the case layer before welding and re-carburize the part afterwards.
What surface finishes work on P1 CARB-HQ?
After carburizing and quenching, finish grind and polish the cavity. Hard chrome or electroless nickel is common for rust protection and release; nitriding can be used to strengthen surfaces that were not carburized.
Can P1 CARB-HQ be formed, bent or molded?
Cold hobbing is the core process for this grade: the soft cavity blank is pressed to shape by a hardened master hob in one or several strokes, with recrystallization annealing between passes.
What is the maximum service temperature of P1 CARB-HQ?
P1 CARB-HQ is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between P1-ANN and P1-HOB?
ANN is the default condition — order this ≤130 HB soft state for cold hobbing cavities or for rough and finish machining, then carburize and quench; at 240 MPa yield it is not a service condition. HOB: expect this work-hardened state (190 HB, 10% elongation) after cold-pressing the cavity; follow with recrystallization annealing or feed the part directly into carburizing. Yield strength is 240 MPa in ANN versus 520 MPa in HOB.
Sources
- ASTM A681 — Standard Specification for Tool Steels Alloy — ASTM International (2022)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Mold Steels) — ASM International (1990)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
- ASM Handbook Vol.4 — Heat Treating (Carburizing) — ASM International (1991)
- UNS T51601 alloy designation record — SAE/ASTM Unified Numbering System (2020)
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.